ORCID Profile
0000-0002-2114-4789
Current Organisations
North West University Faculty of Health Sciences
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North-West University
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Publisher: Springer Science and Business Media LLC
Date: 2003
Publisher: Informa UK Limited
Date: 2009
DOI: 10.1080/10641960802409838
Abstract: The literature shows an increase in endothelin-1 with increased levels of erythrocytes. There are also indications that inflammation and elevated endothelin-1 levels interact with erythropoiesis. In this study, the association of erythrocytes and endothelin-1 in women of different ethnicities was investigated. Blood pressure, vascular resistance, and C-reactive protein (P = 0.09) were significantly higher in the African women (n = 102) compared to the Caucasian women (n = 115), while arterial compliance was significantly lower in the African women with no significant differences for endothelin-1. In single, partial, and multiple regression analyses, there was a significant positive correlation between the red blood cell count and log endothelin-1 in the Caucasians while in the Africans there was a weak negative correlation. This is an indication that endothelin-1 might interfere with erythrocyte production in Africans with higher levels of inflammation.
Publisher: Elsevier BV
Date: 03-2007
DOI: 10.1016/J.REGPEP.2006.10.006
Abstract: Ghrelin, known for its orexigenic activity, also have functions such as vasodilation and a growth hormone releasing action. It is uncertain whether these functions change with increasing age. This study aimed to determine whether ghrelin levels differ between young and older women with different levels of obesity and secondly whether the associations of ghrelin with metabolic syndrome (MS) components, adipocytokines, coagulation factors, and cortisol change with increasing age. Caucasian women (N=107) were ided into young (19-29 years) and older groups (30-56 years). Fasting ghrelin, leptin, adiponectin, glucose, insulin, cortisol, fibrinogen and plasminogen activator inhibitor-1 (PAI-1) levels were determined. Blood pressure (BP), body mass index and waist circumferences were measured. Older lean women showed lower levels of ghrelin (p<0.05) than young lean women, with no differences regarding BP, obesity, lipids, adipokines or insulin resistance (IR). Ghrelin levels of older women remained constant with increasing obesity, but younger women showed significantly reduced ghrelin levels in obese groups. Only younger women showed significant correlations between ghrelin and leptin, adiponectin, fibrinogen and PAI-1 (adjusted for age, obesity and menstrual phase), whereas both age groups showed significant correlations with IR. In younger women factor analysis grouped ghrelin with coagulation factors and all MS components. In older women ghrelin was absent from the MS cluster, but was associated with lower BP, cortisol and IR. Ghrelin levels were not significantly elevated in lean older women, and did not change with increased obesity in older women--as were observed in younger women. The functions of ghrelin also seem to change with increased age since only in young women ghrelin was associated with obesity, coagulation factors and leptin.
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.NUMECD.2014.02.005
Abstract: Simple, low-cost central obesity measures may help identify in iduals with increased cardiometabolic disease risk, although it is unclear which measures perform best in African adults. We aimed to: 1) cross-sectionally compare the accuracy of existing waist-to-height ratio (WHtR) and waist circumference (WC) thresholds to identify in iduals with hypertension, pre-diabetes, or dyslipidaemia 2) identify optimal WC and WHtR thresholds to detect CVD risk in this African population and 3) assess which measure best predicts 5-year CVD risk. Black South Africans (577 men, 942 women, aged >30years) were recruited by random household selection from four North West Province communities. Demographic and anthropometric measures were taken. Recommended diagnostic thresholds (WC > 80 cm for women, >94 cm for men WHtR > 0.5) were evaluated to predict blood pressure, fasting blood glucose, lipids, and glycated haemoglobin measured at baseline and 5 year follow up. Women were significantly more overweight than men at baseline (mean body mass index (BMI) women 27.3 ± 7.4 kg/m(2), men 20.9 ± 4.3 kg/m(2)) median WC women 81.9 cm (interquartile range 61-103), men 74.7 cm (63-87 cm), all P 0.5 appears to be more consistently supported and may provide a better predictor of future cardiometabolic risk in sub-Saharan Africa.
Publisher: Elsevier BV
Date: 03-2014
DOI: 10.1016/J.ATHEROSCLEROSIS.2013.12.025
Abstract: Insulin-like growth factor-1 (IGF-1) has potent endothelial-protective, anti-platelet and anti-thrombotic activities, and also exerts mitogenic and proliferatory actions on vascular smooth muscle cells. Conflicting reports exist regarding the role of IGF-1 in vascular protection and atherogenesis. We therefore investigated the relationships of ambulatory blood pressure (BP) and carotid intima-media thickness (cIMT) with a range of components of the IGF-1 axis in a bi-ethnic population. We included black (N = 86) and white (N = 101) men and measured growth hormone, total IGF-1, insulin-like growth factor binding protein-3 (IGFBP-3), and pregnancy-associated plasma protein-A (PAPP-A) levels. Ambulatory BP was almost 10 mmHg higher in black men (137/88 mmHg versus 128/80 mmHg both p < 0.001), accompanied by an adverse profile of the IGF-axis for all measured components (all p < 0.01), including reduced bioavailable IGF-1 (IGF-1/IGFBP-3 p = 0.006) and tissue IGF-1 accessibility index as represented by IGF-1.PAPP-A/IGFBP-3 (p < 0.001). Single, partial and multiple regression analyses confirmed an independent inverse association between ambulatory systolic BP and bioavailable IGF-1 in black men (R(2) = 0.24 β = -0.22 p = 0.035). cIMT was similar in the ethnic groups (p = 0.34), and was negatively associated with bioavailable IGF-1 in white men (R(2) = 0.42 β = -0.17 p = 0.039) prior to adjustment for γ-glutamyl transferase (R(2) = 0.45 β = -0.10 p = 0.25). Ambulatory systolic BP is inversely related to bioavailable IGF-1 in black men who displayed low IGF-1 concentrations. An inverse relation was found between cIMT and IGF-1 in white men, which disappeared after correction for γ-glutamyl transferase - opposing reports of a detrimental role of IGF-1 in the early stages of atherogenesis.
Publisher: Springer Science and Business Media LLC
Date: 05-08-2011
DOI: 10.1038/JHH.2010.82
Abstract: The renin-angiotensin-aldosterone system can be activated by sympathetic nervous input and is thought to have an important role in the prevalence of hypertension and cardiovascular risk in black Africans. We examined (1) the association between plasma renin responses to mental stress and a marker of sub-clinical atherosclerosis and (2) associations between resting renin and 24-h ambulatory blood pressure. Participants were 143 urbanized black African men and women (43.1 ± 7.7 years) drawn from a study of Sympathetic Activity and Ambulatory Blood Pressure in Africans (SABPA). After an overnight fast, participants completed the Stroop mental stress task. Blood s les were drawn during baseline and 10 min after the task to assess the concentration of active renin in plasma. Blood pressure assessments included continuous Finometer measures during the stress testing and 24-h ambulatory monitoring. Carotid intima-media thickness (CIMT) was measured using high-resolution ultrasound. Approximately 50% of the s le responded to the task with an increase in renin concentration. Multiple linear regression analysis revealed an association between the renin stress response and CIMT (β = 0.024, 95% confidence interval, 0.004-0.043), after adjustment for conventional risk factors, blood pressure stress responses and basal levels of renin activity (R(2) for model = 0.37). In addition, resting renin was inversely associated with ambulatory blood pressure. In summary, heightened release of renin during a laboratory mental stressor was associated with a marker of sub-clinical atherosclerosis thus, it may be a potential mechanism in explaining the increased burden of cardiovascular disease in urbanized black Africans.
Publisher: Oxford University Press (OUP)
Date: 28-07-2016
Abstract: Inconsistent findings are reported on whether insulin-like growth factor-1 (IGF-1) is protective or harmful in predicting hypertension, carotid wall thickness and mortality. We determined the five-year prognostic value of IGF-1 for these outcomes in a large Black population prone to hypertension and cardiovascular disease. A longitudinal study as part of the PURE (Prospective Urban and Rural Epidemiology) study, North West Province, South Africa. We measured IGF-1 and IGF binding protein-3 (IGFBP-3) in 1038 HIV-uninfected participants (age range 32-94 years) and assessed blood pressure, carotid intima-media thickness and mortality. Over five years 116 deaths occurred. Baseline IGF-1 was similar in survivors and non-survivors (p = 0.50), but tended to be higher in survivors upon adjustment for IGFBP-3 and covariates (p = 0.061). Normotensives and hypertensives (p = 0.072), and those with carotid intima-media thickness < 0.9 mm and ≥ 0.9 mm also displayed similar baseline IGF-1 (p = 0.55). Multivariable-adjusted Cox-regression indicated high IGF-1 predicting lower risk for all-cause mortality (hazard ratio 0.45 0.23-0.88) and cardiovascular mortality (hazard ratio 0.26 0.08-0.83) when also adjusting for IGFBP-3. When including normo- and hypertensives at baseline, high IGF-1 was related to normotension at follow-up (hazard ratio 0.68 0.49-0.95). We found no association with carotid intima-media thickness (hazard ratio 0.59 0.31-1.14). In a Black South African population with low socio-economic status and harmful health behaviours, we found a protective independent association between IGF-1 and hypertension, cardiovascular and all-cause mortality, with no association with carotid wall thickness.
Publisher: Elsevier BV
Date: 06-2006
DOI: 10.1016/J.BIOPSYCHO.2005.11.010
Abstract: Specific coping mechanisms of Africans during urbanization were compared to and correlated with cardiovascular responses and perception of health data. Subjects included men (N=286) and women (N=360). The COPE questionnaire classified subjects as active (AC) or passive (PC) copers and the General Health Questionnaire measured subjective perception of health. The Finapres recorded blood pressure continuously before and during application of a handgrip test. Analyses adjusting for age, body mass index and resting cardiovascular data revealed that AC rural subjects showed predominantly cardiac responses and PC rural subjects predominantly vascular responses. All urbanized African men and women showed higher resting blood pressure, vascular responsiveness and hypertension prevalences than their rural counterparts. All rural AC subjects, especially women, and all urban PC subjects, especially men, reported a poorer perception of health. In conclusion, subjects with a PC style showed a predominantly vascular response in rural and urban areas whereas subjects with an AC style seem to shift from a predominant cardiac output response to a predominant vascular resistance response when moving from a rural to an urban area.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 03-2012
Publisher: Springer Science and Business Media LLC
Date: 24-04-2008
DOI: 10.1038/JHH.2008.35
Abstract: Hypertension is highly prevalent in South Africa, resulting in high stroke mortality rates. Since obesity is very common among South African women, it is likely that obesity contributes to the hypertension prevalence. The aims were to determine whether black African women have higher blood pressures (BPs) than Caucasian women, and whether obesity is related to their cardiovascular risk. African (N=102) and Caucasian (N=115) women, matched for age and body mass index, were included. Correlations between obesity (total body fat, abdominal obesity and peripheral fat) and cardiovascular risk markers (haemodynamic parameters, lipids, inflammatory markers, prothrombotic factors, adipokines, HOMA-IR (homoeostasis model assessment insulin resistance)) were compared between the ethnic groups (adjusted for age, smoking, alcohol and physical activity). Comparisons between low- and high-BP groups were also made for each ethnic group. Results showed that African women had higher BP (P<0.01) with increased peripheral vascular resistance. Surprisingly, African women showed significantly weaker correlations between obesity measures and cardiovascular risk markers when compared to Caucasian women (specifically systolic BP, arterial resistance, cardiac output, fibrinogen, plasminogen activator inhibitor-1, leptin and resistin). Interestingly, the latter risk markers were also not significantly different between low- and high-BP African groups. African women, however, presented significant correlations of obesity with triglycerides, C-reactive protein and HOMA that were comparable to the Caucasian women. Although urban African women have higher BP than Caucasians, their obesity levels are weakly related to traditional cardiovascular risk factors compared to Caucasian women. The results, however, suggest a link with the development of insulin resistance.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2011
Publisher: Springer Science and Business Media LLC
Date: 12-2012
DOI: 10.1038/JHH.2011.103
Abstract: The aetiology for an increasing incidence of hypertensive cardiovascular disease amongst Africans in southern Africa is unclear. Hypertension may be induced by inadequate release of L-arginine-derived nitric oxide impairing vascular tone regulation. In addition, asymmetric dimethylarginine (ADMA) is associated with cardiovascular disease. We compared profiles of L-arginine in African and Caucasian men of similar age with cardiovascular risk factors. We studied 163 Caucasian and 132 African men, respectively, (20 to 70 years) measuring serum L-arginine, ADMA, creatinine, urea, symmetric dimethylarginine (SDMA) and blood pressure. L-arginine levels were significantly lower, whereas blood pressure and pulse wave velocity were significantly higher in African men. Simple linear regression showed ADMA more strongly associated with L-arginine in Caucasians (r=0.59 vs 0.19), whereas association of SDMA with L-arginine was significant only in Caucasians (r=0.43 vs 0.001). The stronger association of L-arginine with ADMA in Caucasian men was confirmed by multiple regression analysis (β=0.46 vs 0.25).Our findings show that the relationship of cardiovascular risk factors with serum L-arginine and some of its catabolites is different in African and Caucasian men and that this may be associated with a relatively higher prevalence of hypertension in African men.
Publisher: Springer Science and Business Media LLC
Date: 22-08-2017
DOI: 10.1007/S00726-017-2483-5
Abstract: The relationship of both asymmetric (ADMA) and symmetric (SDMA) dimethylarginine with carotid wall thickness is inconclusive especially among black populations. We aimed to compare carotid intima media thickness (cIMT) and dimethylarginine levels in 75 black and 91 white men at baseline and after a 3-year follow-up, and to investigate associations of percentage change in cIMT with percentage change in dimethylarginine levels (ADMA and SDMA). Plasma levels of ADMA and SDMA were determined with a liquid chromatography mass spectrometry method and B-mode ultrasonography was used to determine the cIMT at baseline and follow-up. In black men, mean cIMT (p = 0.79) and ADMA levels (p = 0.67) remained the same, but SDMA levels were lower (p < 0.001) when comparing baseline and follow-up. In white men, cIMT increased (p < 0.001), but both mean ADMA and SDMA levels decreased (p < 0.001) over time. In black men, percentage change in cIMT was positively associated with percentage change in ADMA (R
Publisher: Oxford University Press (OUP)
Date: 12-2008
DOI: 10.1038/AJH.2008.287
Abstract: The increasing prevalence of hypertension and vascular-related morbidity and mortality among Africans emphasizes the need to identify markers for the early detection of vascular disease. Caucasian-based studies demonstrate that the von Willebrand factor (vWf) is a useful marker of vascular dysfunction. We investigated whether associations between this marker and markers of cardiovascular function in Caucasian women are comparable with African women. The study consisted of apparently healthy African (n = 99) and Caucasian (n = 114) women (mean age, 31.0 years), in idually matched for age and body mass index. We measured blood pressure and arterial compliance noninvasively, and vWf in serum. We assessed univariate and multivariate-adjusted associations of blood pressure and arterial compliance with vWf. Although no ethnic difference existed for mean vWf levels, Caucasian and African women showed opposite associations of blood pressure and arterial compliance with vWf after single, partial, and multiple regression analyses. In Caucasians, after full adjustment, systolic (beta = +0.179 P < 0.05) and diastolic (beta = +0.190 P < 0.05) blood pressure correlated positively and arterial compliance negatively (beta = -0.197 P 99% power existed, significance disappeared after excluding these subjects (beta = -0.071 P = 0.46). Associations of vWf with blood pressure and arterial compliance were not comparable between Caucasian and African women, suggesting that the vWf may not be a useful marker of vascular alterations in African women.
Publisher: Elsevier BV
Date: 09-2010
DOI: 10.1016/J.REGPEP.2010.06.008
Abstract: Adipokines contribute directly to the coexistence of insulin resistance and endothelial dysfunction. Most studies focus on a single adipokine. We therefore investigated the independent relationships of leptin, adiponectin, tumor necrosis factor-alpha, resistin and visfatin, as well as the gut hormone ghrelin with blood pressure and insulin resistance. Secondly we evaluated the interrelationships of adipokines and ghrelin in concert with various cardiometabolic markers. Caucasian women (N=115) with varying levels of obesity (aged 31.3 + or - 9.18 years) were included. Significant correlations of leptin, adiponectin, ghrelin and visfatin with mean arterial pressure (p<0.05) disappeared after adjustment for age, body mass index and waist circumference. But significant correlations with insulin resistance (HOMA) (for leptin, adiponectin and ghrelin) remained significant after adjustments. Factor analyses yielded five factors, but two main clusters, namely a metabolic syndrome cluster (including leptin, adiponectin and ghrelin) and a vascular atherosclerotic cluster (including tumor necrosis factor-alpha, visfatin and resistin). Factor analyses identified patterns which indicate specific roles of the various adipokines. Leptin, adiponectin and ghrelin were more closely related to insulin resistance and central obesity as core components of the metabolic syndrome. Visfatin, tumor necrosis factor-alpha and resistin seem to direct their effects onto the vascular system possibly by means of mechanisms such as inflammation, vasoconstriction and coagulation.
Publisher: Clinics Cardive Publishing
Date: 02-09-2016
Publisher: Oxford University Press (OUP)
Date: 11-2009
DOI: 10.1038/AJH.2009.158
Abstract: Sub-Saharan Africans face an increasing burden of hypertension and related cardiac and cerebrovascular morbidity and mortality, making the identification of factors leading to early vascular abnormalities imperative. We investigated the possible influence of the antioxidant glutathione (GSH) on early subclinical atherosclerosis in 63 hypertensive (aged 45.2 years) and 34 normotensive (aged 38.9 years P < 0.001) nondiabetic African men. We measured ambulatory daytime systolic and diastolic blood pressure (SBP, DBP) as well as daytime mean arterial pressure (MAP), carotid intima-media thickness (CIMT), and calculated the cross-sectional wall area. We determined the reduced form of GSH in whole blood and blood glucose in serum. Blood glucose (110 vs. 92 mg/dl P < 0.001) and CIMT (0.75 vs. 0.61 mm P < 0.001) were higher in hypertensives compared to normotensives. No significant difference existed for GSH. Associations in normotensives suggested the hypotensive effect of GSH after single (SBP: r = -0.35, P < or = 0.05 DBP: r = -0.37, P < or = 0.05 MAP: r = -0.38, P < or = 0.05) and multiple (SBP: B = -0.015, P < 0.05 DBP: B = -0.011, P < 0.05 MAP: B = -0.012, P < 0.05) regression analyses. In hypertensives, CIMT (B = -0.00027, P < 0.01) and cross-sectional wall area (CSWA) (B = -0.0066, P < 0.05) correlated negatively with GSH. These findings were consistent after excluding 10 human immunodeficiency virus (HIV)-positive hypertensive subjects. In hypertensive African men, CIMT is negatively associated with GSH, suggesting a possible contributory role of attenuated GSH levels in the development of subclinical atherosclerosis.
Publisher: Springer Science and Business Media LLC
Date: 27-01-2011
DOI: 10.1038/JHH.2010.134
Abstract: Many mechanisms, including oxidative stress, contribute to hypertension. This study investigated the possible associations between oxidative stress, blood pressure and arterial stiffness in black South Africans. Ambulatory blood pressure measurements were taken for 101 black South African men and 99 women. The stiffness indices included ambulatory arterial stiffness index (AASI) and pulse pressure (PP). Reactive oxygen species (ROS) levels (P<0.0001) were higher in the African women compared with men. ROS levels were also higher in hypertensive compared with normotensive men. The 24 h systolic blood pressure (SBP P<0.01), 24 h diastolic blood pressure (DBP P<0.0001) and pulse wave velocity (PWV P<0.01) were significantly higher in African men compared with women. There were unadjusted positive associations of 24 h SBP (r=0.33 P=0.001), 24 h DBP (r=0.26 P=0.008) and 24 h PP (r=0.29 P=0.003) with ROS in African men only. A positive association between AASI and ROS existed only in hypertensive men (r=0.27 P=0.035), but became nonsignificant (B=0.0014 P=0.14) after adjustments. Adjusted, positive associations of 24 h SBP (B=0.181 P=0.018) and 24 h PP (B=0.086 P=0.050) with ROS were again only evident in African men. ROS is positively associated with SBP and PP in African men, suggesting that increased ROS levels may contribute to hypertension in this population group.
Publisher: Springer Science and Business Media LLC
Date: 10-03-2005
Abstract: High leptin levels are often observed in human obesity and are implicated in obesity-related hypertension. Leptin levels have been found to be higher in hypertensive obese African-American women compared to normotensive African-American women, but a direct association between leptin and blood pressure could not be obtained. Additionally, increased adiposity has been associated with higher aortic stiffness in obese African-American women, but leptin was not included in the study. The effects of leptin on cardiovascular function in African women have not yet been determined. We hypothesised that leptin is directly associated with blood pressure and decreased arterial compliance and that leptin levels are significantly higher in hypertensive overweight/obese African women compared to normotensive overweight/obese African women. A case-case control study was performed which included 98 African women. The subjects were ided into lean normotensive (lean NT), overweight/obese normotensive (OW/OB NT) and overweight/obese hypertensive (OW/OB HT). The Finometer apparatus was used to obtain a more elaborate cardiovascular profile. Serum leptin and insulin levels as well as the HOMA-IR index were determined. Various anthropometric measures were obtained. Leptin levels were elevated (P < or = 0.05) in the OW/OB NT and HT groups compared to the lean NT group, but were similar in the OW/OB NT and HT groups. After adjusting for obesity, insulin resistance, hyperinsulinaemia and age, a direct positive correlation was obtained between leptin and systolic blood pressure (SBP) (P < or = 0.05 r = 0.68) in the OW/OB HT group. Additionally, leptin also correlated negatively with arterial compliance (P< or = 0.05 r = -0.76) and positively with pulse pressure (P < or = 0.05 r = 0.71) in the OW/OB HT group. In conclusion, even though leptin levels were the same in OW/OB HT and NT African women, leptin was directly and positively associated with SBP and pulse pressure and negatively with C(W) only in OW/OB HT African women, independent of obesity, insulin-resistance, hyperinsulinaemia and age.
Publisher: Springer Science and Business Media LLC
Date: 17-05-2007
Publisher: Springer Science and Business Media LLC
Date: 28-09-2015
DOI: 10.1007/S00408-015-9804-9
Abstract: Reduced lung function is associated with a risk for the development of cardiovascular disease. This association may be due to chronic inflammation which is often present in those with reduced lung function. We investigated the possible role of systemic inflammation as the mediator between lung function and arterial stiffness in 1534 black South Africans. Spirometric data including forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were obtained. C-reactive protein (CRP), interleukin-6 (IL-6), blood pressure (BP) and carotid-radial pulse wave velocity (PWV) were determined. In multivariable-adjusted models, an independent inverse association was found between IL-6 and FEV1 (β = -0.20, p < 0.001) and FVC (β = -0.18, p < 0.001). Similar results were found for CRP. PWV was inversely associated with FEV1 (β = -0.06, p = 0.037). No association was found between inflammatory markers, BP or PWV. Reduced lung function was associated with increased inflammation and arterial stiffness. The lack of association between arterial stiffness and inflammatory markers suggests that inflammation may not be the mediating link between lung and vascular function in this population.
Publisher: Elsevier BV
Date: 07-2005
DOI: 10.1016/J.NUT.2004.12.007
Abstract: Early changes in vascular function could be associated with stunting, which may contribute to the development of cardiovascular diseases in later life. In this study we tested the hypothesis that stunting may be related to changes in cardiovascular function in African children ages 10 to 15 y. In the Transition and Health during Urbanization in South Africa in Children study, the health status of children in the North-West Province of South Africa was studied. It was an epidemiologic, cross-sectional study in which 583 black non-stunted and 192 stunted children (stature below the fifth percentile for age) of both sexes ages 10 to 15 y were recruited from 44 schools. Blood pressure was monitored with the Finapres (finger-arterial pressure) apparatus and by means of the Fast Modelflo software program measurements for systolic and diastolic blood pressure, mean arterial pressure, pulse pressure, heart rate, cardiac output, stroke volume, total peripheral resistance, and arterial compliance were obtained. Dietary intake data were collected with a 24-h dietary recall questionnaire. Nutrient coding was the same for all recalls and macro- and micronutrients were calculated. Anthropometric measurements were done according to standard methods. There were no significant differences in systolic blood pressure and diastolic blood pressure between stunted and non-stunted children after correction for body mass index and heart rate. Stroke volume, arterial compliance, and cardiac output were significantly lower and total peripheral resistance was significantly higher in stunted children than in non-stunted children. No significant differences in dietary intake could be detected, although dietary intakes were slightly lower in the stunted children. We found that compliance, a marker of vascular function, is significantly lower in stunted children. Stunting was related to early changes in cardiovascular function in African children ages 10 to 15 y.
Publisher: Oxford University Press (OUP)
Date: 10-02-2014
DOI: 10.1093/AJH/HPT288
Abstract: Increased urinary albumin excretion reflects general vascular damage and predicts adverse cardiovascular and renal outcomes. Albuminuria can be determined from easily collected spot urine s les, especially in low-resource settings. However, no prognostic evidence exists for Africans. We followed clinical outcomes in 1,061 randomly selected non diabetic, human immunodeficiency virus (HIV)-negative Africans (mean age: 51.5 years 62.0% women). Baseline urinary albumin-to-creatinine ratio was assessed from spot urine s les. Over a median follow-up of 4.52 years, 132 deaths occurred, of which 47 were cardiovascular related. The urinary albumin-to-creatinine ratio averaged 6.1 μg/mg (5th to 95th percentile interval 1.2-70.0). In multivariable-adjusted analyses, urinary albumin excretion predicted all-cause mortality (hazard ratio (HR), 1.26 95% confidence interval (CI), 1.07-1.48 P = 0.006), and a tendency existed for cardiovascular mortality (HR, 1.26 95% CI, 0.97-1.63 P = 0.087), which seemed to be driven by fatal stroke (HR, 1.72 95% CI, 1.17-2.54 P = 0.006) rather than cardiac mortality (HR, 0.67 95% CI, 0.41-1.07 P = 0.094). The predictive value remained in 528 hypertensives for both all-cause (HR, 1.38 95% CI, 1.13-1.69 P = 0.001) and cardiovascular (HR, 1.45 95% CI, 1.07-1.96 P = 0.017) mortality, again driven by stroke. Our findings also remained significant after we excluded participants with macroalbuminuria, those on antihypertensive treatment, as well as participants who died within 1 year after enrollment. In nondiabetic HIV-negative Africans, albuminuria predicts all-cause and stroke mortality.
Publisher: Springer Science and Business Media LLC
Date: 20-07-2006
Abstract: The integrated relationship between inflammation, obesity and cardiovascular disease is currently a subject of much research interest. These specific relationships, however, have not been studied in-depth in South African population groups in order to determine the role of ethnicity. It is known that Africans, compared to Caucasians, suffer from a high prevalence of hypertension. It was therefore hypothesized that the levels of inflammatory markers (high-sensitivity C-reactive protein (hsCRP), fibrinogen and leptin) are higher in Africans compared to Caucasians and are notably associated with cardiovascular dysfunction in Africans. Apparently healthy African (N=102) and Caucasian (N=115) women, matched for age and body mass index (BMI), were recruited. Leptin, hsCRP, fibrinogen and lipid levels, waist circumference (WC), BMI, systolic and diastolic blood pressure, cardiac output (CO), total peripheral resistance (TPR) and Windkessel compliance were measured. Results showed that the levels of leptin, hsCRP and fibrinogen were significantly higher (P<0.05) in the African women. The inflammatory markers correlated strongly with cardiovascular parameters, age and obesity (BMI, WC) in both groups, but after adjusting for age and obesity, none of the correlations were significant anymore. Multiple regression analyses (with leptin, hsCRP or fibrinogen as dependent variable) showed that only leptin levels of African women were explained by cardiovascular parameters (BP, TPR and CO). In conclusion, even though African women had significantly higher leptin, hsCRP, fibrinogen and blood pressure levels than Caucasian women, no cardiovascular parameters explained the variation in the inflammatory markers (except for leptin levels of African women).
Publisher: Springer Science and Business Media LLC
Date: 12-2002
Publisher: Springer Science and Business Media LLC
Date: 28-11-2014
DOI: 10.1038/JHH.2013.124
Abstract: It is known that low testosterone (T) and high cortisol levels are associated with hypertension as well as with chronic stress, linking stress with elevated blood pressure (BP). However, the association between acute stress-, chronic stress responses and BP is not clear in Africans. Therefore, we examined the association between cortisol, psychological distress and BP responses in low- and high-T male subgroups. Beat-to-beat and ambulatory blood pressure (ABPM) and electrocardiogram measures were obtained. Serum s les were collected and analyzed for sex hormones and cortisol. Chronic psychological distress was verified with the General Health Questionnaire and acute stress with the cold pressor test. More chronic psychological distress was observed in both low- and high-T Africans compared with the Caucasians. The low-T Africans tended to have more ischemic events (P=0.06) and ABPM values (P⩽0.01) than any of the other groups. Both chronic distress (cortisol) and acute stress (total peripheral resistance cold pressor responses) were associated with ABPM in the low-T African group. Acute and chronic stress may contribute to increased BP in low-T African men. Their cortisol and vascular responses supported a tendency for ischemia, increasing their risk for coronary artery disease.
Publisher: Georg Thieme Verlag KG
Date: 08-10-2014
Abstract: Severe underweight may be a risk factor for hypertension in developing countries, although the manner whereby this occurs is unknown. Leptin is known to exert both beneficial and detrimental vascular effects, and is predictive of poor cardiovascular outcome at high levels, but also at low levels. We explored the relationship between blood pressure and leptin in black men from South Africa with a body mass index (BMI) in the underweight to normal range. We included 113 African men (BMI≤25 kg/m(2)) and took anthropometric, biochemical and cardiovascular measures. The blood pressure-leptin relationship was then investigated along quintiles of leptin and within BMI stratified median split (20 kg/m(2)) groups. Blood pressure increased across leptin quintiles 1-3 (p for trend≤0.040), whereas no relationship was observed along quintiles 3 to 5 (p for trend≥0.14) (adjusted for age and waist circumference). Blood pressure was similar in the two BMI median split groups (p≥0.083). In the low BMI group only, blood pressure associated positively with leptin following unadjusted, partial, and full adjustment (systolic blood pressure and diastolic blood pressure: R(2)=0.20-0.27, β=0.32-0.34, p≤0.009). Decreasing leptin levels are not likely to contribute to hypertension prevalence in the underweight. Rather, in African men with a BMI≤20 kg/m(2), low leptin levels are positively and independently associated with elevated blood pressure, which is not seen at higher BMI (20-25 kg/m(2)). Our findings suggest a differential concentration dependent vascular effect of leptin in underweight and normal weight African men.
Publisher: Hogrefe Publishing Group
Date: 07-2004
DOI: 10.1024/0300-9831.74.4.285
Abstract: Numerous observational studies showed associations of antioxidants (vitamins C and E) and folate intake with a reduced risk of cardiovascular disease, but randomized controlled clinical trials have generally not supported this hypothesis. The objective of this study was to investigate the effects of a daily dosage of 1000 mg vitamin C, 800 mg vitamin E, and 10 mg folate on markers of vascular function in 31 young healthy male adults. Cardiovascular values after a 12-week vitamin (14 subjects) or placebo (17 subjects) intervention were compared to baseline values. Cardiovascular parameters (blood pressure, stroke volume, heart rate, cardiac output, vascular resistance, arterial compliance) were measured continuously after an overnight fast under controlled circumstances with a Finometer device. Our main finding was a significant decrease (p = 0.03) in systolic blood pressure in the experimental group. No statistically significant changes were observed within other cardiovascular variables of the experimental group, but possible beneficial decreases in diastolic blood pressure and increases in arterial compliance after 12 weeks of vitamin supplementation were indicated. In conclusion, beneficial effects of antioxidants and folate were observed probably because the supplementation was used by young healthy subjects under carefully controlled conditions.
Publisher: Elsevier BV
Date: 08-2011
DOI: 10.1016/J.REGPEP.2011.04.003
Abstract: Ageing is associated with elevated adiponectin levels. Our aim was to assess whether age-related increase in adiponectin is associated with a decrease in renal function. The study comprised African (N=277) and Caucasian (N=326) men and women. Adiponectin levels, estimated creatinine clearance rate and obesity indices were determined. African men revealed significantly higher adiponectin levels compared to Caucasian men (p<0.01), reflecting the lower adiposity levels of the African men. No difference in obesity measures (p=0.92) and adiponectin levels (p=0.27) was observed between African and Caucasian women. A significant increase in adiponectin levels with ageing was observed in both African men and women (p<0.01). To the contrary, progressive ageing seems not to be significantly related to elevated adiponectin levels within Caucasians. Renal impairment decreased significantly within all of the groups (p<0.01). Single regression analyses performed in all specified groups revealed significant associations between adiponectin and estimated creatinine clearance, however a multiple regression model revealed that insulin resistance had the strongest association with adiponectin within all the groups. In conclusion, age-related rise in adiponectin levels observed in Africans may not be due to renal impairment.
Publisher: Informa UK Limited
Date: 2005
DOI: 10.1080/08037050500210724
Abstract: Endothelin-1 (ET-1) has been found to be higher in hypertensive African Americans and obese hypertensive Caucasians compared to normotensive controls with an enhanced ET-1-dependent vasoconstrictor tone. ET-1 levels and the associations thereof with cardiovascular function in overweight/obese normotensive and hypertensive African women have not been investigated. It is therefore hypothesized that ET-1 levels are elevated in overweight/obese hypertensive African women compared to overweight/obese and lean normotensive controls. Additionally, it is hypothesized that these elevated ET-1 levels are associated with increased total peripheral resistance (TPR) and decreased arterial compliance (C(W)). A case-case control study was performed which included 98 African women. The subjects were ided into lean normotensive (lean NT), overweight/obese normotensive (OW/OB NT) and overweight/obese hypertensive (OW/OB HT). The Finometer apparatus was used to obtain a more elaborate cardiovascular profile and plasma immunoreactive ET-1 levels were determined. ET-1 levels were similar for the three groups. Although a decrease in vascular function was observed in the OW/OB HT group, no correlations were obtained between ET-1 and the cardiovascular profile, before and after adjusting for age. In African women, ET-1 levels did not differ between lean and overweight/obese and normotensive and hypertensive subjects. The lack of significant associations between ET-1 and decreased vascular function in the overweight/obese hypertensive group suggests that ET-1 is not implicated in obesity-related hypertension in African women.
Publisher: Elsevier BV
Date: 02-2015
DOI: 10.1016/J.JASH.2014.12.003
Abstract: Evidence of the relationship between left ventricular hypertrophy and urinary albumin excretion is contradictory and limited in black adults in whom hypertensive heart disease is common. We aimed to investigate the relationship between subclinical left ventricular hypertrophy and albuminuria in non-diabetic hypertensive blacks. Urinary albumin-to-creatinine ratio (UACR) was determined from 8-hour overnight urine collection. We recorded ambulatory blood pressure and 12-lead electrocardiogram during a typical working day. Cornell product (P = .002), UACR (P = .042), 24-hour systolic pressure (P < .0001), and 24-hour pulse pressure (P < .0001) were higher in the hypertensive group. Cornell product was associated with UACR in single (r = 0.25 P = .012), partial (P trend = .002), and multiple regression (β = 0.326 P = .0005) analyses in the hypertensive group only, even below the threshold for microalbuminuria and independent of 24-hour systolic pressure. Urinary albumin excretion is associated with subclinical left ventricular hypertrophy in non-diabetic hypertensive blacks and may be a useful marker of early cardiovascular disease in blacks.
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.IJCARD.2012.05.035
Abstract: Vascular calcification is believed to be due to the conversion of vascular smooth muscle cells into osteoblast-like cells and is associated with mortality. Since hypertension and related mortality in Africans is a concern, we investigated associations between a marker of osteoblastic activity, alkaline phosphatase (ALP), and measures of arterial structure and function in hypertensive African men. This study included 79 participants. We conducted 24h ambulatory blood pressure and carotid intima-media thickness (cIMT) measurements. cIMT was obtained with an intra-observer variability of 0.04 mm and the cross-sectional wall area (CSWA) was calculated. ALP was measured in serum. ALP was within its reference range (101.6 vs. 30.0-120.0 U/L), however cIMT was higher when this group was stratified and compared to gender and age-specific reference values. In univariate and partial regressions, and confirmed with multiple regression analyses, 24h systolic blood pressure (β=0.289, p=0.018), 24h pulse pressure (β=0.387, p=0.002), but not 24h diastolic blood pressure (β=0.073, p=0.58), were positively associated with ALP. In addition, mean cIMT (β=0.322, p=0.006) and CSWA (β=0.285, p=0.013) also correlated positively with ALP after adjusting for significant covariates, and after excluding participants with diabetes, renal dysfunction or a HIV positive status. Serum alkaline phosphatase is adversely associated with measures of arterial structure and function in hypertensive African men.
Publisher: Elsevier BV
Date: 06-2015
DOI: 10.1016/J.HLC.2014.12.005
Abstract: In South Africa respiratory diseases are highly prevalent, with cardiovascular disease being a manifestation. However, international reference values for lung function are commonly used, which may not be appropriate to correctly identify reduced lung function. An inverse relationship exists between lung function and blood pressure (BP) but is not investigated extensively in black South Africans. We included 2010 Africans from the PURE (Prospective Urban Rural Epidemiology) study (aged > 35 years) in the North West Province. Spirometry was performed and predicted values for forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) were calculated from South African, European and United States prediction equations. With the exception of the European predicted values, all other predicted mean FEV1 and FVC were above 80%. South African reference values displayed the highest percentages of the predicted values for FEV1 and FVC (87.9 and 99.7%, respectively.) BP increased from quintiles five to one for both FEV1 and FVC, (p for trend <0.001). After adjustment the differences remained (p<0.05). South African reference values yielded higher percentages of predicted FEV1 and FVC values than European and US equations suggesting that South African prediction equations may be more useful when investigating lung function in black South Africans. Elevated BP is related to reduced lung function, highlighting the importance in managing both respiratory- and cardiovascular disease.
Publisher: Springer Science and Business Media LLC
Date: 28-04-2011
DOI: 10.1038/HR.2011.45
Abstract: Recent evidence suggests that low-grade urinary albumin excretion is a marker of early general attenuation of vascular function, but studies are limited to Caucasian population groups. We compared low-grade urinary albumin excretion (<3.5 mg mmol(-1) or 30 μg mg(-1)) between non-diabetic African (aged, 41.7 years n=70) and Caucasian (aged, 44.6 years n=91) men and ethnic-specific associations thereof with arterial stiffness and ambulatory blood pressure. The albumin-to-creatinine ratio (ACR) was determined from an 8 h overnight urine collection. We recorded ambulatory blood pressure over 24 h during a typical workday and the carotid-dorsalis pedis pulse wave velocity measured the next morning after a controlled overnight stay. ACR was higher in Africans compared with Caucasians (P < 0.001), also after adjusting for 24 h systolic blood pressure, diastolic blood pressure and hypertension prevalence (P < 0.001) or when grouped by similar 24 h mean arterial pressures (P < 0.01 for all categories). Daytime (P=0.002) and night time (P < 0.001) systolic and daytime (P < 0.001) and night time (P < 0.001) diastolic blood pressures were higher in Africans compared with Caucasians, but no differences existed for daytime and night time pulse pressure and pulse wave velocity. In African men only, after adjustment for covariates, night time systolic blood pressure (β=0.347 P=0.003), diastolic blood pressure (β=0.298 P=0.010) and mean arterial pressure (β=0.331 P=0.004) correlated positively with ACR. In addition, daytime (β=0.265 P=0.032) and night time (β=0.258 P=0.038) pulse pressure as well as pulse wave velocity (β=0.271 P=0.032) correlated positively with ACR. In conclusion, arterial stiffness and ambulatory blood pressure are already associated with low-grade albuminuria in non-diabetic African men with normal kidney function.
Publisher: Elsevier BV
Date: 12-2017
DOI: 10.1016/J.IJCARD.2017.08.070
Abstract: Pulse pressure lification (PPA), i.e. the lification from central arteries to the periphery, is inversely related to arterial stiffness, organ damage and mortality. It is known that arterial stiffness is higher in black than white populations, but it is unclear if this is due to early vascular aging. We therefore investigated whether PPA declines earlier in young normotensive black South Africans, when compared to their white counterparts. We included 875 black and white men and women from the African-PREDICT study (55% black, 41% men), aged 20-30years, with no prior diagnosis of chronic disease, screened for normotensive clinic blood pressure (BP). We determined supine central PP (cPP), and supine brachial systolic- and diastolic BP, from which brachial PP (bPP) was calculated. PPA was defined as the ratio of the litude of the PP between these distal and proximal locations (bPP/cPP). We found the mean PPA to be lower in black compared to white participants (1.43 vs. 1.46 P=0.013). In black adults PPA declined earlier with increasing age (P-trend<0.001), with a weak trend in whites (P=0.069) after adjustment for sex, socio-economic status, height, heart rate and mean arterial pressure. In multivariable-adjusted regression, we found an independent inverse association between PPA and age only in the black group (β=-0.18, P=0.002). PPA declines earlier with age in normotensive black adults younger than 30years, exemplifying early vascular aging which may predispose black in iduals to future cardiovascular outcomes.
Publisher: Informa UK Limited
Date: 29-09-2011
DOI: 10.3109/10641963.2011.561897
Abstract: In Africans, arterial stiffness progression seems more pronounced compared to Caucasians. We compared the arterial stiffness profiles of different age groups and focused on muscular arteries and two more central arterial segments in African and Caucasian people from South Africa. In African (N = 374) and Caucasian (N = 376) participants (20-70 years), we measured carotid-radial (C-R) and carotid-dorsalis pedis (C-DP) pulse wave velocity (PWV) and aortic characteristic impedance (Zao). Major findings were that normotensive and high-normal/hypertensive (HT) Caucasians indicated increased trends of C-R PWV with aging (P = .029 and P = .067), not seen in the African groups (P = .122 and P = .526). Both ethnic groups showed significant increases of C-DP PWV and Zao with aging. High-normal/hypertensive Africans had significantly stiffer arteries than hypertensive Caucasians for almost all age groups, and for all stiffness measures. African C-R PWV correlated significantly with blood pressure (BP), but not with age. Opposite results were observed for Caucasians. In conclusion, the stiffness of muscular arteries is already elevated in young Africans, in both those with normal or elevated BP. This is possibly due to an earlier deterioration during childhood, or perhaps already present from birth. Also, in Caucasians stiffness seems more age-related, while in Africans it seems to be more pressure-related.
Publisher: Springer Science and Business Media LLC
Date: 26-11-2015
DOI: 10.1038/HR.2015.123
Publisher: Informa UK Limited
Date: 02-09-2014
DOI: 10.3109/10715762.2014.951840
Abstract: Various studies indicate a relationship between increased oxidative stress and hypertension, resulting in increased DNA damage and consequent excretion of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG). The aim of this study was to compare urinary 8-oxodG levels in African and Caucasian men and to investigate the association between ambulatory blood pressure (BP) and pulse pressure (PP) with 8-oxodG in these groups. We included 98 African and 92 Caucasian men in the study and determined their ambulatory BP and PP. Biochemical analyses included, urinary 8-oxodG, reactive oxygen species (ROS) (measured as serum peroxides), ferric reducing antioxidant power (FRAP), total glutathione (GSH), glutathione peroxidase (GPx) and glutathione reductase (GR) activity. The African men had significantly higher systolic (SBP) and diastolic blood pressure (DBP) (both p < 0.001). Assessment of the oxidative stress markers indicated significantly lower 8-oxodG levels (p < 0.001) in the African group. The African men also had significantly higher ROS (p = 0.002) with concomitant lower FRAP (p < 0.001), while their GSH levels (p = 0.013) and GR activity (p < 0.001) were significantly higher. Single and partial regression analyses indicated a negative association between urinary 8-oxodG levels with SBP, DBP and PP only in African men. These associations were confirmed in multiple regression analyses (SBP: R(2) = 0.41 β = -0.25 p = 0.002, DBP: R(2) = 0.30 β = -0.21 p = 0.022, PP: R(2) = 0.30 β = -0.19 p = 0.03). Our results revealed significantly lower urinary 8-oxodG in African men, accompanied by a negative association with BP and PP. We propose that this may indicate a dose-response relationship in which increased oxidative stress may play a central role in the up-regulation of antioxidant defence and DNA repair mechanisms.
Publisher: Public Library of Science (PLoS)
Date: 13-03-2013
Publisher: Oxford University Press (OUP)
Date: 03-2010
DOI: 10.1530/EJE-09-0865
Abstract: Alarming increases in hypertension and type 2 diabetes among Africans accentuate the need to identify factors that could serve as targets for prevention or treatment. In Caucasian populations, asymmetric dimethylarginine (ADMA), the predominant endogenous nitric oxide synthase inhibitor, is associated with cardiovascular disease and insulin resistance (IR). ADMA's counterpart, symmetric dimethylarginine (SDMA), originally thought to be inert, was recently also linked with cardiovascular risk. Since little information regarding ADMA or SDMA is available for Africans, our aim was to explore the relationships of ADMA and SDMA with measures of arterial stiffness and IR in Africans and Caucasians from South Africa. The study consisted of 235 nonsmoking, nondiabetic, nonobese, human immunodeficiency virus-uninfected Africans ( n =64) and Caucasians ( n =171), aged 20–70 years. We measured blood pressure, pulse wave velocity, ADMA, SDMA, and IR (homeostasis model assessment, HOMA). African and Caucasian men had similar ADMA and SDMA, whereas Caucasian women had higher ADMA and SDMA than African women ( P .05). African men and Caucasian women indicated strong correlations of ADMA with arterial stiffness ( r =0.47, P =0.021 r =0.26, P =0.008), confirmed in multivariate analyses. Caucasian participants showed negative associations between SDMA and HOMA, being strongest in the men ( r =−0.41 P =0.002). Our results indicate that ADMA is independently associated with vascular dysfunction in African men and Caucasian women. A strong, independent negative association of SDMA with IR was found only in Caucasian participants. The molecular explanation for this is unclear, but these findings motivate experimental studies that could shed more light on these relationships.
Publisher: Springer Science and Business Media LLC
Date: 11-08-2005
Abstract: The comparison of the associations between chronically elevated leptin levels and cardiovascular function in obese Africans and Caucasians has not yet been determined. Therefore, the aim of this study was to compare leptin's associations with cardiovascular function in obese African and obese Caucasian women to determine whether leptin's associations differ between these two groups. This study consisted of two case-case control studies. The first study included a s le of 102 apparently healthy African women and the second, 115 apparently healthy Caucasian women. All lean and obese subjects were selected from each study. The Finometer apparatus was used to obtain a more elaborate cardiovascular profile. Serum leptin levels, insulin levels and the lipid profile were determined. Stroke volume (SV) and cardiac output (CO) were significantly (P< or =0.01) elevated in both obese African and Caucasian groups compared to their lean controls. Total peripheral resistance (TPR) was significantly decreased and arterial compliance (C(W)) significantly increased in both obese African and Caucasian groups. In the obese Caucasian group, diastolic blood pressure (DBP) was significantly (P< or =0.01) lower, SV and C(W) significantly higher (P< or =0.01) and TPR significantly lower compared to the age, body mass index (BMI), and leptin-matched obese African group. After adjusting for age and BMI, leptin correlated negatively with DBP (P< or =0.05 r=-0.33) and TPR (P< or =0.05 r=-0.36) in the obese Caucasian group, but not in the obese African group. Even though leptin levels were similar in obese African and Caucasian women, leptin is favourably associated with vascular function in obese Caucasians, but not in obese Africans.
Publisher: Wiley
Date: 23-09-2016
DOI: 10.1111/ECI.12674
Abstract: The link between impaired lung function and cardiovascular outcome is well established in European and American populations. It is possible that this association may be driven by a systemic spillover of inflammation occurring within the lungs. As several studies have found an increased level of inflammatory markers in African populations, we aimed to establish the contribution of lung function in predicting all-cause and cardiovascular mortality in Africans, whilst taking inflammatory markers into account. We followed 1442 black South Africans from the North West Province participating in the South African leg of the Prospective Urban and Rural Epidemiology (PURE) study, over a five-year period. Spirometry, cardiovascular and metabolic measures were performed, and cardiovascular mortality as well as all-cause mortality used as endpoints. In univariate Cox regression models, both forced expiratory volume in 1-s (FEV FVC, but not FEV
Publisher: Oxford University Press (OUP)
Date: 06-2006
DOI: 10.1016/J.AMJHYPER.2005.12.014
Abstract: Impaired baroreflex sensitivity (BRS) is associated with cardiovascular diseases and the metabolic syndrome. Because lipid abnormalities have been associated with impaired BRS, this study aimed to determine whether diets known to improve the lipid profile, namely a diet high in polyunsaturated fatty acids (walnuts) or monounsaturated fatty acids (cashew nuts), would improve BRS in subjects with metabolic syndrome (MS). A controlled feeding trial with a randomized, controlled, parallel study design was undertaken, which involved 62 subjects with MS. Subjects were stratified according to gender and age and were randomized into three groups receiving a control diet, or a diet high (20% energy) in walnuts or unsalted cashew nuts for 8 weeks while maintaining body weight. The BRS, C-reactive protein (CRP), and MS components were measured before and after the intervention. After the intervention, BRS in the walnut-fed study group decreased (P = .038) and that in the cashew-fed study group increased (P = .036), but the BRS in the control group did not change (P = .56). The percent change of the walnut versus cashew group differed (P = .019). Body mass index, waist circumference, blood pressure, high-density lipoprotein cholesterol, and triacylglycerol did not change. The fasting glucose concentrations of the cashew group increased (P = .03). The significant improvements in BRS obtained by a diet rich in cashew nuts underline the beneficial cardiovascular effects of nuts. However, the opposite result was obtained with a diet rich in walnuts. These significant changes observed might indicate that BRS is particularly sensitive and influenced by changes in diet without changes in obesity.
Publisher: Wiley
Date: 10-1992
Publisher: Elsevier BV
Date: 07-2007
DOI: 10.1016/J.DIABRES.2006.10.010
Abstract: The present study aimed to reveal racial differences in the metabolic pattern of C-peptide and non-esterified fatty acids (NEFA), and in their associations with cardiovascular measures in healthy urban African (102) and Caucasian women (115) from South Africa. An oral glucose tolerance test was performed with measurements before and at 30, 60, 90 and 120min. Various cardiovascular parameters and blood lipids were assessed. Statistical analyses were done in a sub-s le of pre-menopausal women. Fasting C-peptide and hepatic insulin extraction were significantly higher in lean African women compared to their Caucasian counterparts, with no racial differences between women with abdominal obesity. Postchallenge C-peptide response and hepatic insulin extraction were significantly higher in Caucasians with abdominal obesity. There were no racial differences in insulin sensitivity and resistance. Despite different associations of C-peptide and NEFA with cardiovascular measures between the ethnicities both showed significant positive correlations with triglycerides. Increased fasting C-peptide levels and unfavorable associations of C-peptide and NEFA with triglycerides and cardiovascular measures implicate a higher cardiovascular risk in lean African women only. This may be of importance for the development of hypertension in this population group.
Publisher: South African Medical Association NPC
Date: 20-01-2014
DOI: 10.7196/SAMJ.7739
Abstract: The prevalence of HIV is the highest in sub-Saharan Africa South Africa (SA) is one of the most affected countries with the highest number of adults living with HIV infection in the world. Besides the traditional risk factors for cardiovascular disease (CVD) in the general population, in people living with HIV there are specific factors - chronic inflammation, metabolic changes associated with the infection, therapy, and lipodystrophy - that potentially increase the risk for developing CVD. This study proposes a screening discriminant model to identify the most important risk factors for the development of CVD in a cohort of 140 HIV-infected black Africans from the North West Province, SA. Anthropometric measures, systolic blood pressure, diastolic blood pressure and the carotid-dorsalis pedis pulse wave velocity were determined. Blood was analysed to determine the levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol, triglycerides (TGs) and glucose. Partial least squares discriminant analysis was performed as a supervised pattern recognition method. Independent Student's t-tests were further employed to compare the means of risk factors on interval scales for comparison of categorical risk factors between groups, chi2 tests were used. A TG:HDL-C ratio > or = 1.49, TC:HDL-C ratio > or = 5.4 and an HDL-C level < or = 0.76 mmol/l indicated CVD risk in this cohort of patients living with HIV. The results have important health implications for black Africans living with HIV as these lipid levels may be a useful indicator of the risk for CVD.
Publisher: Elsevier BV
Date: 02-2012
DOI: 10.1016/J.HLC.2011.10.009
Abstract: This study compared NT-proBNP levels and the association with cardiovascular markers between Africans and Caucasians from South Africa. This cross-sectional study involved 201 Africans and 255 Caucasians from the North West province, South Africa. Serum NT-proBNP concentrations, blood pressure, pulse wave velocity and arterial compliance were measured. NT-proBNP levels were significantly higher (P<0.001) in Africans than Caucasians, also after adjusting for gender, body mass index (BMI) and pulse wave velocity (P=0.008). This significant difference became borderline significant after adjusting for systolic blood pressure (SBP) (P=0.060), and non-significant after adjusting for arterial compliance (P=0.35). In single regression, a significant positive correlation of NT-proBNP with SBP (r=0.26 P<0.001) and pulse pressure (PP) (r=0.28 P<0.001) were shown for Africans only. After multiple adjustments, the associations of NT-proBNP with SBP and PP remained significant in Africans (SBP: β=0.187, P<0.01 PP: β=0.234, P<0.001), with no significant associations in Caucasians. NT-proBNP levels were higher in Africans than Caucasians, independently of BMI and gender. This difference was partly driven by higher SBP and lower arterial compliance in Africans. NT-proBNP was persistently associated with SBP and PP in Africans, but not in Caucasians. These associations may suggest early vascular changes contributing to cardiac alterations in Africans.
Publisher: Springer Science and Business Media LLC
Date: 28-02-2013
DOI: 10.1038/JHH.2013.14
Abstract: Hypertension, a major risk factor for cardiovascular disease worldwide, is increasing significantly in urbanised South Africans. Impaired glomerular filtration is a potential contributor to hypertension. Although HIV infection is widespread, little is known regarding its contribution to diminished estimated glomerular filtration rate (eGFR) and, in turn, hypertension in Africans. We compared eGFRs and cardiovascular profiles of newly identified HIV infected African men (N=53) not yet undergoing anti-retroviral therapy, and uninfected African men of similar age and anthropometry. The aim of the study was to determine whether eGFR is diminished in treatment naive HIV infected in iduals and whether eGFR is associated with a potential modulator of hypertension, namely serum L-arginine. Cardiovascular risk factor profiles of HIV infected and uninfected men were similar. In men with healthy eGFRs >90 ml min(-1) per 1.73 m(2), eGFR was significantly lower with HIV infection (114 (90 147)) compared with that in uninfected men: (120 (91 168)), P=0.043. Despite the absence of clinically-diagnosed renal dysfunction, eGFR associated significantly with serum L-arginine only in HIV infected men (R(2)=0.277, β=-0.299, P=0.034), whereas L-arginine did not stay in the model for uninfected men. This difference suggests that the fate of L-arginine as a substrate for nitric oxide generation may be altered in HIV infected in iduals. Subsequently this is likely to escalate endothelial dysfunction, contributing to later hypertension and cardiovascular disease. Our findings show that while glomerular filtration rate is not associated with L-arginine in uninfected men, it is diminished and significantly negatively associated with serum L-arginine in HIV infected men.
Publisher: Springer Science and Business Media LLC
Date: 23-03-2017
DOI: 10.1038/JHH.2017.18
Abstract: Consistent reports indicate that hypertension is a particularly common finding in black populations. Hypertension occurs at younger ages and is often more severe in terms of blood pressure levels and organ damage than in whites, resulting in a higher incidence of cardiovascular disease and mortality. This review provides an outline of recent advances in the pathophysiological understanding of blood pressure elevation and the consequences thereof in black populations in Africa. This is set against the backdrop of populations undergoing demanding and rapid demographic transition, where infection with the human immunodeficiency virus predominates, and where under and over-nutrition coexist. Collectively, recent findings from Africa illustrate an increased lifetime risk to hypertension from foetal life onwards. From young ages black populations display early endothelial dysfunction, increased vascular tone and reactivity, microvascular structural adaptions as well as increased aortic stiffness resulting in elevated central and brachial blood pressures during the day and night, when compared to whites. Together with knowledge on the contributions of sympathetic activation and abnormal renal sodium handling, these pathophysiological adaptations result in subclinical and clinical organ damage at younger ages. This overall enhanced understanding on the determinants of blood pressure elevation in blacks encourages (a) novel approaches to assess and manage hypertension in Africa better, (b) further scientific discovery to develop more effective prevention and treatment strategies and
Publisher: Elsevier BV
Date: 04-2008
DOI: 10.1016/J.ATHEROSCLEROSIS.2007.09.011
Abstract: To assess the risk factor pattern of the metabolic syndrome and its association with insulin resistance and hyperuricaemia in a sub-Saharan African population with different levels of urbanisation. Four hundred forty-eight black South African volunteers, men and women aged 15 years and older were investigated in a cross-sectional, comparative, population-based survey. Subjects were stratified into three groups representing different levels of urbanisation in rural and urban areas. The metabolic syndrome was defined according to IDF criteria. Factor analysis was used to examine the risk factor pattern of the metabolic syndrome. The prevalence of the metabolic syndrome was low and did not differ across the three groups. Factor analysis showed slight differences in the metabolic syndrome pattern between the groups. Hyperuricaemia-hypertriglyceridaemia was identified as distinct component in the rural and semiurban group whereas hyperinsulinaemia was loaded together with other risk factors. In the entire study population, five factors could be identified in the following sequence: obesity, hypertension, hyperuricaemia-hypertriglyceridaemia, hyperglycaemia and hyperinsulinaemia. Subjects with hyperuricaemia but not with insulin resistance exhibited an increased risk to develop the metabolic syndrome. Hyperuricaemia was revealed as additional component of the metabolic syndrome in sub-Saharan Africans and should be given more attention in prevention settings.
Publisher: Wiley
Date: 14-03-2012
DOI: 10.1111/J.1469-8986.2012.01362.X
Abstract: Dissociation between β-adrenergic behavioral and physiological defensive active coping (AC) responses was associated with cardiometabolic risk in urban but not rural African males. Whether this is partly driven by underlying neuroendocrine dysfunction is not certain. We aimed to assess the association between coping style, urbanization, and neuroendocrine function. Blood pressure (BP) and serum stress hormones were assessed across levels of urbanization (rural vs. urban) and coping style (active vs. passive) in 178 Black African men. Urban men demonstrated increased hypertension prevalence, α-adrenergic hemodynamic pattern, lower testosterone levels, and a larger cortisol:testosterone ratio (Cort:Test) compared to their rural counterparts. This was particularly evident in urban AC men where cortisol and Cort:Test explained 36-40% of the variance in BP. Dissociation between behavioral and physiological β-adrenergic neuroendocrine responses in urban AC African men was shown. A stressful urban environment might induce an apparent loss of physiological control, thereby facilitating disturbed neuroendocrine AC responses, which could increase cardiovascular disease risk.
Publisher: Informa UK Limited
Date: 09-12-2012
DOI: 10.3109/10641963.2011.628727
Abstract: Serum γ-glutamyltransferase (GGT) is increasingly regarded as a marker of vascular function. However, the usefulness of this marker is in dispute. Gender and ethnic differences, as well as the serum level range where correlations with vascular function will emerge, may complicate the usefulness of GGT. The aim is to compare correlations with markers of vascular function between African and Caucasian groups. This cross-sectional target population study involved four groups of African and Caucasian men and women of 100 participants each. Fasting lipids, GGT, C-reactive protein (CRP), reactive oxygen species, and glycosylated hemoglobin (HbA1c) were determined as well as blood pressure, carotid intima-media thickness (CIMT), and left ventricular hypertrophy. γ-Glutamyltransferase levels were significantly higher in Africans compared with Caucasians and also higher in men than in women. γ-Glutamyltransferase correlated with triglycerides in all four groups and after adjusting the correlations sustained in the male groups but disappeared in women. Correlations existed between GGT and blood pressure, except for the African women. After adjustments, CIMT correlated with GGT in Caucasian men (r = 0.29 P < .01). Glycosylated hemoglobin was associated with GGT in Caucasian women (r = 0.26 P = .01) as well as CRP (r = 0.36 P < .01). When the groups were ided into low and high GGT groups by median split, most of the correlations disappeared in the high GGT groups. Gender and ethnic-specific associations occurred regarding GGT and variables associated with cardiovascular function. With high levels of GGT the correlations diminished. The usefulness of GGT as a marker of vascular dysfunction seems limited.
Publisher: Elsevier BV
Date: 08-2006
DOI: 10.1016/J.IJPSYCHO.2005.07.015
Abstract: The purpose of this study was to compare active and passive coping strategies of Africans with perception of own health and cardiovascular data. The subjects included 236 apparently healthy Africans (men=109 women=127). The COPE questionnaire was adapted, translated and validated for Africans. Scores on reliable sub-scales were used to classify men and women into more active coping (AC) and more passive coping (PC) subgroups. The General Health Questionnaire measured subjective perception of health. Blood pressure was recorded before and during application of the handgrip test, using the Finapres, a continuous non-invasive blood pressure monitor. Plasma renin activity (PRA) values, measured with radio immuno assay, were compared to blood pressure variables. Analyses of co-variance, adjusted for resting values and age, indicated that PC men responded with a larger increase in total peripheral resistance (TPR) (p=0.006), larger decrease in stroke volume (p=0.07), smaller increase in cardiac output (p=0.09) and larger increases in PRA resting (p=0.04) and reactivity (p< or =0.05) values. PC subjects reported a more negative perception of health than AC subjects. Young PC women presented greater hypertension prevalence rates (p< or =0.01) than AC women. In conclusion, all AC and PC subjects reacted with increased vascular reactivity on the handgrip test. PC men presented enhanced vascular reactivity, PRA and perception of poorer health values.
Publisher: Springer Science and Business Media LLC
Date: 07-05-2010
DOI: 10.1038/HR.2010.65
Abstract: Sub-Saharan Africans face an increasing burden of hypertension. Although controversial, recent experimental evidence strongly suggests that serum calcium contributes to elevated blood pressure through increased vascular resistance. We investigated the associations of 24-h blood pressure and cardiovascular reactivity with serum calcium in African men stratified by age. The study consisted of 50 younger (median age: 38 years) and 49 older (median age: 49 years) participants. We measured 24-h ambulatory blood pressure with a mean successful inflation rate of 72.6%. Total peripheral resistance and stroke volume reactivity were obtained using a Finometer device during application of the Stroop color and word conflict test. Total serum calcium was adjusted for serum albumin. Results showed that serum calcium levels were similar between the younger and older groups. However, in the younger group, 24-h systolic blood pressure, 24-h diastolic blood pressure and total peripheral resistance reactivity correlated positively, whereas stroke volume reactivity correlated negatively with serum calcium in single and multiple regression analyses (systolic blood pressure: B=34.99, P=0.017 diastolic blood pressure: B=34.93, P<0.001 total peripheral resistance reactivity: B=65.44, P=0.048 stroke volume reactivity: B=-45.40, P=0.017). No associations were evident in the older African men. In conclusion, 24-h ambulatory systolic and diastolic blood pressures are positively associated with serum calcium in African men younger than 43 years. The blood pressure-serum calcium relationship seems to be mediated through increased vascular resistance during stress.
Publisher: Informa UK Limited
Date: 20-06-2014
DOI: 10.3109/10641963.2013.789044
Abstract: The purpose of this study was to evaluate whether active renin concentration is associated with markers of end-organ damage in urbanized Africans. This study forms part of the Sympathetic Activity and Ambulatory Blood Pressure in Africans (SABPA) study. For this study, 81 men and 74 women were ided into low- and high-renin groups. Ambulatory blood pressure measurements were conducted. A resting 12-lead ECG was determined in order to determine the gender-specific Cornell voltage. Cardiovascular variables were continuously recorded with the Finometer. Carotid-dorsalis pedis pulse wave velocity was obtained with the Complior acquisition system. The carotid intima-media thickness (CIMT) was obtained with the SonoSite MicroMaxx. Blood s les were collected serum and plasma were stored at -80 °C for analysis. Anthropometric measurements were taken using standard methods. A general health questionnaire was also completed. The urinary creatinine was determined with a calorimetric method and albumin with a turbidimetric method. The serum sodium and potassium were determined by making use of the Konelab TM 20i Sequential Multiple Analyzer Computer (SMAC). The concentration of active renin in the plasma was analyzed by making use of a high-sensitivity radio-immunometric assay. A negative association (r=-0.29, p<0.01) exists between renal function (ACR) and plasma renin in the low-renin group (<6.18 pg/mL), which was not observed in Africans with high-renin levels. It seems evident that low renin in black South Africans may result in sub-clinical renal damage and impaired vascular function in a group of urbanized black South Africans.
Publisher: Springer Science and Business Media LLC
Date: 11-02-2010
DOI: 10.1038/JHH.2010.1
Abstract: The African population is considered a high-risk group for the development of hypertension, and identifying risk factors are therefore essential in preventive actions against cardiovascular disease (CVD). Elevated levels of uric acid (UA) are often associated with CVD. Our first aim was to establish possible ethnic differences in UA levels between African and Caucasian men. Our second aim was to determine any associations between UA levels and cardio-metabolic variables, and also how these correlates differ between the two groups. African (N=87) and Caucasian (N=121) men participated in this cross-sectional study. Our results have shown that African men had significantly lower (353±87.7 vs 401±98.2 P<0.01) UA levels compared with Caucasian men. Waist circumference and triglycerides correlated strongly with UA in both ethnic groups. This was confirmed with a forward stepwise multiple regression analysis. After adjustment for confounders, the correlation between UA and triglycerides remained significant only in the Caucasians (r=0.29 P=0.02), whereas only the African men showed an independent correlation between UA and total peripheral resistance (TPR) (r=0.23 P=0.04). TPR increased significantly across UA tertiles only in the African men (P=0.01 vs P=0.96). In conclusion, despite their lower UA levels, Africans showed an independent relationship between UA and vascular resistance, indicating a possible explanation for their high prevalence of hypertension.
Publisher: Springer Science and Business Media LLC
Date: 28-07-2011
DOI: 10.1038/HR.2011.104
Abstract: The prognostic significance of blood pressure (BP) variability has lately enjoyed considerable attention. The need for early markers of cardiovascular dysfunction is imperative in black South Africans who have a significant risk for cardiovascular disease. We therefore compared 24-h BP variability with various traditional and advanced BP measurements, regarding their association with sub-clinical organ damage in black and white South Africans. The study included 409 African and Caucasian teachers aged 25-60 yrs. We measured office BP, 1-min continuous (finger) BP, ambulatory BP, BP reactivity and determined weighted 24-h BP variability. Albumin-to-creatinine ratio, Cornell product and carotid cross-sectional wall area (CSWA) were measures of organ damage. Africans had higher 24-h BP, BP variability, BP reactivity and sub-clinical organ damage (P<0.001). Correlations of BP variability with organ damage were overall weak when compared with other BP measurements. In normotensive groups, we found an independent association of 24-h systolic BP (SBP) variability with Cornell product only in Africans (r=0.37 P=0.01), confirmed in multiple regression models, with 24-h SBP included in the model. Only in hypertensive Caucasians, a significant correlation between CSWA and 24-h SBP variability was evident (r=0.30 P=0.01), although CSWA indicated stronger correlations with office or 24-h SBP than 24-h SBP variability. To conclude, 24-h SBP variability could potentially be an effective measure for the early detection of normotensive Africans at increased risk for the development of cardiovascular complications. Its usefulness based on associations with target organ damage in hypertensive groups seems to be less than traditional office or 24-h BP measurements.
Publisher: Wiley
Date: 15-12-2015
DOI: 10.1111/JCH.12455
Publisher: Springer Science and Business Media LLC
Date: 05-01-2004
Publisher: Elsevier BV
Date: 03-2011
DOI: 10.1016/J.ATHEROSCLEROSIS.2010.12.015
Abstract: There is an emerging burden of cardiovascular disease among urban black Africans in South Africa, which has been largely explained by the transition from traditional African lifestyles to more westernized behavior. We examined the role of health behaviors in explaining the excess burden of sub clinical vascular disease seen in black Africans compared to Caucasians. This was a cross-sectional study, comprising of urban African teachers (n=192 black, 206 Caucasian) working for one of the four Kenneth Kaunda Education districts in the North West Province, South Africa. Conventional cardiovascular risk factors, 24 h ambulatory blood pressure and objectively measured physical activity (Actical® accelerometers), smoking (confirmed by serum cotinine), and alcohol (serum gamma glutamyl transferase) were assessed. The main outcome was a marker of sub-clinical vascular disease, mean carotid intima media thickness (mCIMT), measured using high resolution ultrasound. Compared with Caucasians, the black Africans demonstrated higher mCIMT (age and sex adjusted β=0.044, 95% CI, 0.024-0.064 mm). The blacks also had higher 24h systolic and diastolic blood pressure, triglycerides, adiposity, and C-reactive protein. In addition, blacks were less physically active (790.0 kcal/d vs 947.3 kcal/d, p<0.001), more likely to smoke (25% vs 16.3%, p=0.002), and demonstrated higher alcohol abuse (gamma glutamyl transferase, 66.6 μ/L vs 27.2 μ/L, p<0.001) compared with Caucasians. The difference in mCIMT between blacks and Caucasians was attenuated by 34% when conventional risk factors were added to the model and a further 18% when health behaviors were included. There is an excess burden of sub clinical vascular disease seen in black Africans compared to Caucasians, which can be largely explained by health behaviors and conventional risk factors.
Publisher: Georg Thieme Verlag KG
Date: 22-12-2009
Abstract: This study was aimed to compare prevalences of the metabolic syndrome in Africans using five definitions as proposed by the World Health Organization (WHO), the European Group for the Study of Insulin Resistance (EGIR), the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults [Adult Treatment Panel (ATPIII)], the American College of Endocrinology (ACE), and the International Diabetes Federation (IDF). A further objective was to identify difficulties in classifying Africans with the metabolic syndrome and to suggest specific areas where criteria adjustments for identifying Africans should be made. A case-case-control cross-sectional study involved 102 urban African women. Except for microalbumin data, all data necessary for classification of the metabolic syndrome were collected, including fasting and 2-h glucose and insulin, anthropometric measurements, blood pressure, and lipids. The metabolic syndrome prevalences ranged from 5.4% (EGIR), 15.7% (ATPIII), >or=19.4% (WHO), 24.8% (IDF) to 25.5% (ACE). Only 2.9% (n=3) had a triglyceride level >or=1.69 mmol/l, but 58.8% (n=60) had a HDL-level or=140/90 or used hypertension medication. It seems as if the classification of hypertension, insulin resistance and hyperglycemia might have been adequate, but body composition and dyslipidemia criteria need adjustment for Africans. Since neither definition seems completely suitable for Africans it is suggested that clinical emphasis should rather be on treating any specific cardiovascular disease risk factor that is present, than on diagnosing a patient with the metabolic syndrome.
Publisher: Elsevier BV
Date: 07-2009
DOI: 10.1016/J.DIABRES.2009.04.014
Abstract: Ageing is associated with increased insulin and C-peptide levels. Due to a lack of data, our first aim was to establish whether this also holds true for Africans from South Africa. Our second aim was to determine whether an association between insulin/C-peptide levels and blood pressure exist within an African and Caucasian population with increasing age, as well as to establish gender differences. African men and women (N=260) and Caucasian men and women (N=369) were recruited and stratified into age groups (18-35 years, 36-45 years and >45 years). ANCOVAs and partial correlations were performed. Results showed opposing changes in insulin/C-peptide levels of African and Caucasian men with increasing age. Insulin/C-peptide tended to decrease in African men, whereas insulin tended to increase and C-peptide increased significantly (p=0.03) in Caucasian men. Despite similar obesity levels, the oldest African women had significantly lower insulin (p<0.01) and C-peptide (p<0.01) levels compared to their Caucasian counterparts. In conclusion, insulin/C-peptide levels tended to decrease in the African population with increasing age. Despite significantly lower levels of insulin, blood pressure levels of African men seems to be affected more detrimentally compared to their Caucasian counterparts, leaving them more vulnerable for the development of cardiovascular diseases.
Publisher: Public Library of Science (PLoS)
Date: 23-01-2013
Publisher: Springer Science and Business Media LLC
Date: 14-01-2016
Publisher: Hindawi Limited
Date: 10-2016
Abstract: The objective of this study was to make use of a quantitative and qualitative approach comparing the systemic renin-angiotensin system (RAS) of hypertensive black and white African men by using RAS equilibrium analysis. This sub-study involved 23 black ( n = 15) and white ( n = 8) hypertensive men aged 39.5–41 years, living in the North West Province of South Africa. The RAS-Fingerprinting was determined with LC-MS/MS quantification of angiotensin peptides. Blood pressure and other variables were determined with known methods. The main finding of this study was the significant lower Ang I ( .0 and 45.1 pg/ml p = 0.005) and Ang II (15.6 and 123.9 pg/ml p ⩽ 0.001) encountered in the hypertensive black African men compared to their white counterparts. Levels of Ang 1-5 (downstream metabolite of Ang 1-7) (1.8 and 3.0 pg/ml), were detected in black and white hypertensive men, respectively. The observed differences between circulating RAS components, which are reflected via equilibrium angiotensin levels, point to a distinctive molecular regulation of the RAAS in the two study cohorts. The increased peripheral resistance observed in hypertensive black in iduals might take over a dominant role in control of blood pressure in this study population. A novel highly sensitive LC-MS/MS method resolved the issue of peptide recovery variations during s le preparation by using internal standards for each in idual angiotensin metabolite.
Publisher: Informa UK Limited
Date: 2003
DOI: 10.1080/08037050310001075
Abstract: To investigate whether associations and differences exist regarding the arterial compliance, dietary intake and anthropometric parameters of children of four different ethnic groups in South Africa. In this study, 1244 children from four ethnic groups, aged 10-15 years, were randomly selected from five regions of the North West Province. Blood pressure was measured with a Finapres apparatus and analysed to obtain systemic arterial compliance. Measurements were done to obtain body mass index (BMI), waist-to-hip ratio and percentage body fat. Dietary intake was determined with a 24-h dietary recall questionnaire. The black and mixed-origin subjects indicated the lowest values (p < or = 0.05) for BMI, percentage body fat, and dietary intake, whereas the white and Indian subjects showed significantly higher values than the other ethnic groups. The white and Indian children had significantly higher arterial compliance than the black and mixed-origin children at all ages from 10 to 15 years. Compliance showed significant correlations with all anthropometric parameters. Since black and mixed-origin children have the highest prevalence of undernutrition and stunted growth, it is suggested that parental undernutrition and inadequate nutrition in early life, associated with lower arterial compliance, may lead to the onset of adult hypertension.
Publisher: Oxford University Press (OUP)
Date: 23-07-2012
DOI: 10.1093/IJE/DYS106
Abstract: Longitudinal cohort studies in sub-Saharan Africa are urgently needed to understand cardiovascular disease development. We, therefore, explored health behaviours and conventional risk factors of African in iduals with optimal blood pressure (BP) (≤ 120/80 mm Hg), and their 5-year prediction for the development of hypertension. The Prospective Urban Rural Epidemiology study in the North West Province, South Africa, started in 2005 and included African volunteers (n = 1994 aged > 30 years) from a s le of 6000 randomly selected households in rural and urban areas. At baseline, 48% of the participants were hypertensive (≥ 140/90 mmHg). Those with optimal BP (n = 478) were followed at a success rate of 70% for 5 years (213 normotensive, 68 hypertensive, 57 deceased). Africans that became hypertensive smoked more than the normotensive in iduals (68.2% vs 49.8%), and they also had a greater waist circumference [ratio of geometric means of 0.94 cm (95% CI: 0.86-0.99)] and greater amount of γ-glutamyltransferase [0.74 U/l (95% CI: 0.62-0.88)] at baseline. The 5-year change in BP was independently explained by baseline γ-glutamyltransferase [R(2) = 0.23, β = 0.13 U/l (95% CI: 0.01-0.19)]. Alcohol intake also predicted central systolic BP and carotid cross-sectional wall area (CSWA) at follow-up. Waist circumference was another predictor of BP changes [β = 0.18 cm (95% CI: 0.05-0.24)] and CSWA. HIV infection was inversely associated with increased BP. During the 5 years, 24% of Africans with optimal BP developed hypertension. The surge in hypertension in Africa is largely explained by modifiable risk factors. Public health strategies should focus aggressively on lifestyle to prevent a catastrophic burden on the national health system.
Publisher: Springer Science and Business Media LLC
Date: 05-2003
Publisher: Elsevier BV
Date: 10-2013
DOI: 10.1016/J.IJCARD.2013.07.191
Abstract: Low testosterone, acute and chronic stress and hypercoagulation are all associated with hypertension and hypertension-related diseases. The interaction between these factors and future risk for coronary artery disease in Africans has not been fully elucidated. In this study, associations of testosterone, acute cardiovascular and coagulation stress responses with fibrinogen and von Willebrand factor in African and Caucasian men in a South African cohort were investigated. Cardiovascular variables were studied by means of beat-to-beat and ambulatory blood pressure monitoring. Fasting serum-, salivary testosterone and citrate coagulation markers were obtained from venous blood s les. Acute mental stress responses were evoked with the Stroop test. The African group demonstrated a higher cardiovascular risk compared to Caucasian men with elevated blood pressure, low-grade inflammation, chronic hyperglycemia (HbA1c), lower testosterone levels, and elevated von Willebrand factor (VWF) and fibrinogen levels. Blunted testosterone acute mental stress responses were demonstrated in African males. In multiple regression analyses, higher circulating levels of fibrinogen and VWF in Africans were associated with a low T environment (R(2) 0.24-0.28 p≤0.01), but only circulating fibrinogen in Caucasians. Regarding endothelial function, a low testosterone environment and a profile of augmented α-adrenergic acute mental stress responses (diastolic BP, D-dimer and testosterone) were associated with circulating VWF levels in Africans (Adj R(2) 0.24 p<0.05). An interdependence between acute mental stress, salivary testosterone, D-dimer and vascular responses existed in African males in their association with circulating VWF but no interdependence of the independent variables occurred with fibrinogen levels.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2012
Publisher: Wiley
Date: 26-10-2012
DOI: 10.1007/S11745-012-3732-8
Abstract: The prevalence of hypertension in sub-Saharan Africa is increasing rapidly, and treatment remains challenging. Although the use of L-carnitine in treatment has received much attention, studies reporting on physiological L-carnitine levels in hypertensives are limited. Our aim was to determine physiological levels of L-carnitine and acylcarnitines in African and Caucasian men, and to investigate associations between ambulatory blood pressure (BP) and carnitine levels. Participants included 101 African and 101 Caucasian teachers. Ambulatory BP measurements were conducted, and L-carnitine and acylcarnitine levels determined. African men showed significantly higher systolic BP (p < 0.001), diastolic BP (p < 0.001) and L-carnitine levels (p = 0.01). In both ethnic groups, partial regression analyses revealed a positive association between BP and L-carnitine, although in Caucasians it was with systolic (r = 0.20, p = 0.045), and in Africans with diastolic BP (r = 0.23, p = 0.023). After adjusting for confounders, an independent positive association between systolic (R(2) = 0.37, β = 0.12, p = 0.041) and diastolic BP (R(2) = 0.39, β = 0.14, p = 0.018) and L-carnitine and long-chain acylcarnitines (R(2) = 0.38, β = 0.17, p = 0.005 and R(2) = 0.39, β = 0.15, p = 0.011) were found, independent of ethnicity. Physiological L-carnitine levels were not only higher in Africans than in Caucasians but also above the expected reference range. Despite promising results on L-carnitine (and its short-chain derivatives) in hypertension treatment regimens, our findings paradoxically show that elevated BP is significantly associated with higher physiological L-carnitine and long-chain acylcarnitine levels.
Publisher: Oxford University Press (OUP)
Date: 13-12-2013
DOI: 10.1093/AJH/HPS007
Abstract: Heart failure in the African population is reaching alarming levels. Increased afterload as a result of increased vasoconstriction during stress may lead to impaired ventricular function and stroke volume (SV) as well as vascular hypertrophy. In this study, we challenged the cardiovascular system in order to evaluate the possible contribution of indicators of α-adrenergic vasoconstriction (i.e., vascular resistance and SV reactivity) on left ventricular mass and carotid intima-media thickness (CIMT) in African and Caucasian men. We evaluated 101 African and 101 Caucasian male schoolteachers. Ambulatory blood pressure measurements were taken. Total peripheral resistance, Windkessel compliance and SV, and resting and reactivity values were obtained using a Finometer device while the Stroop color word conflict test was being applied. The electrocardiogram was recorded to obtain the Cornell product as indication of left ventricular mass. The CIMT was measured and the cross-sectional wall area (CSWA) calculated. African men showed higher total vascular resistance resting values as well as higher positive reactivity values compared with Caucasian men. The SV decreased significantly during stress in African men while resting blood pressure and the Cornell product value increased. SV showed a consistent association with left ventricular mass (β = -0.21 P = 0.04) and CSWA (β = -0.24 P = 0.01) in single and multiple regression analyses. No such associations were evident in the Caucasian men. African men showed a suppressed SV, possibly as a result of an increased ventricular afterload leading to end-organ damage.
Publisher: Informa UK Limited
Date: 23-04-2011
DOI: 10.3109/10641963.2010.531842
Abstract: The aim was to determine whether blood glucose or cholesterol is the more prominent contributor to cardiovascular dysfunction in 101 African men and 99 African women. We measured ambulatory daytime blood pressure (BP), carotid intima-media thickness (CIMT), and determined blood glucose and lipids in serum. High-density lipoprotein cholesterol (HDL) (p = 0.002) and HDL: total cholesterol (HDL:TC) (p ≤ 0.001) were significantly lower, while serum glucose (p ≤ 0.001) was significantly higher in men. In single, partial, and multiple regression analysis, BP correlated positively with blood glucose in men. Furthermore, CIMT (B = -0.50 p = 0.009) correlated negatively with HDL:TC in men. While in women CIMT (B = 0.346 p = 0.015) correlated positively with glucose. In conclusion, subclinical atherosclerosis is significantly related to an unfavorable HDL profile in men, whereas in women, this link is stronger with fasting glucose.
Publisher: Oxford University Press (OUP)
Date: 08-2007
DOI: 10.1530/EJE-07-0044
Abstract: Objective : Concentrations of adiponectin, an adipocytokine with insulin-sensitizing actions, may vary according to ethnic group. This study aimed to determine whether fasting adiponectin levels of Caucasian and African women differ. A second objective was to determine which components of the metabolic syndrome are more closely related to adiponectinemia in both groups. Design : A cross-sectional study including 102 urban African and 115 Caucasian women with a wide range of obesity aged 20–55 years. Methods : Anthropometric measurements were taken, namely weight, height, body mass index, waist circumference, and hip circumference. Cardiovascular measurements included blood pressure and arterial compliance. Fasting blood s les were taken to determine glucose, insulin, C-peptide, leptin, adiponectin, and lipid levels. Results : Mean adiponectin levels of the whole groups did not differ, but normal weight African women ( N = 38) showed marginally lower adiponectin levels than their Caucasian counterparts ( N = 41 P = 0.047). No differences in adiponectin were shown for overweight and obese women. Separate multiple regression analyses for ethnic groups showed that only homeostasis model assessment-insulin resistance (HOMA-IR) significantly contributed to the variance in adiponectin levels of African women, whereas leptin, triacylglycerol levels and HOMA-IR contributed significantly to adiponectin variance in Caucasian women. An additional multiple regression analysis in a combined ethnic group ( N = 217) showed ethnicity to be a significant contributor to variances in adiponectin levels. Conclusions : Even though adiponectin levels of these ethnic groups are similar, different associations of adiponectin with leptin and triacylglycerol levels might indicate that there are ethnic differences regarding the mechanistic functions of adiponectin within the scope of the metabolic syndrome.
Publisher: Elsevier BV
Date: 03-2015
DOI: 10.1016/J.HLC.2014.09.019
Abstract: Fibulin-1 and soluble urokinase-type plasminogen activator receptor (suPAR) emerged as mediators in the development of sclerotic disease. SuPAR along with C-reactive protein (CRP) and albumin delineate inflammatory processes associated with extracellular matrix turnover in atherosclerosis. We explored the independent relationship of fibulin-1 with these inflammatory markers in a bi-ethnic South African population. This study included 290 Africans (men: n=130 and women: n=160) and 343 sex- and age-matched Caucasians (men: n=160 and women: n=183). Serum fibulin-1, suPAR, CRP and albumin levels were measured along with conventional cardiovascular and metabolic variables. In both single and age-adjusted regression analyses, fibulin-1 correlated with both suPAR and albumin in African men and with suPAR in Caucasian men. These findings were absent in women. In multivariate regression analysis, these associations were confirmed in African men (R(2)=0.22 β=0.329 p<0.001) and Caucasian men (R(2)=0.14 β=0.234 p=0.008). Fibulin-1 independently associated positively with suPAR in all men, but inversely with albumin in African men only. These results are indicating the presence of potential subclinical inflammation (suPAR) within the extracellular matrix of endothelial tissue, contributing to the potential onset of cardiac fibrosis or vascular sclerosis among these South African men with lower albumin levels.
Publisher: Informa UK Limited
Date: 20-09-2013
DOI: 10.3109/10641963.2012.721839
Abstract: Hypertension (HT) and the metabolic syndrome are major problems in Africa. The role of sex hormones in the cardiovascular profile of black Africans in South Africa has not been studied. Our objective was to study the association between the sex hormones and ambulatory blood pressure and the heart rate (HR) in black and white South Africans. The 24-hour ambulatory blood pressure measurements were performed and the blood s les were taken between 07:00 and 09:00 hours. A total of 80 black and 98 white South African teachers between 25 and 65 years of age from similar socioeconomic backgrounds from the Sympathetic Activity and Ambulatory Blood Pressure in Africans (SABPA) study were included. As a result, a more vulnerable cardiovascular profile was observed in Africans compared with Caucasians. In the African group, low testosterone (T) explained 19%-36% of the variance in systolic blood pressure (SBP), diastolic blood pressure (DBP), and HR, whereas in the Caucasian group non-sex-hormone-binding globulin (non-SHBG)-bound T explained 27% of the variance in HR. In the African males, inverse associations between blood pressure and T (SBP: P = .08 DBP: P = .02) and non-SHBG-bound T (SBP: P < .001 DBP: P < .01) and HR (P < 0.01) were observed. Ambulatory HR predicted a prediabetic state in Africans. In conclusion, low T levels may predispose or result in impaired cardiovascular function in African men. The possibility exists that a prediabetic state, vagal-impaired HR, and hyperkinetic blood pressure responses may predispose or result in low T levels in African men.
Publisher: Elsevier BV
Date: 05-2012
DOI: 10.1016/J.ATHEROSCLEROSIS.2012.01.045
Abstract: The N-terminal prohormone B-type natriuretic peptide (NT-proBNP) is involved in the regulation of volume load and secreted when systemic cardiac overload occurs. Fibulin-1 on the other hand is a component of many extracellular matrix proteins including those present in atherosclerotic lesions, expressed in elastin-containing fibres of blood vessels, and also in the heart. Due to an alarming prevalence of hypertensive heart disease in black South Africans, we investigated the associations of NT-proBNP with fibulin-1 and markers of arterial stiffness in Africans and Caucasians. We included 231 Africans and 238 Caucasians from South Africa aged 22-77 years. Serum NT-proBNP and fibulin-1 levels were determined, and arterial compliance and pulse wave velocity were measured. Africans had significantly higher blood pressure and NT-proBNP levels than Caucasians and African men had higher fibulin-1 levels than Caucasian men. In single regression analysis, NT-proBNP was significantly associated with fibulin-1 in African men and Caucasian women. NT-proBNP correlated negatively with arterial compliance in all groups except Caucasian women. After partial adjustments, the association between NT-proBNP and fibulin-1 strengthened in African men only. After full adjustment in multiple regression analysis, the association of NT-proBNP with fibulin-1 was confirmed in African men (R(2)=0.41 β=0.26 p<0.01) and also in younger women (R(2)=0.34 β=0.251 p=0.012). Only Africans indicated a significant independent association between NT-proBNP and fibulin-1, suggesting that cardiovascular alterations are already present in this relatively young African population as opposed to Caucasians.
Publisher: The Endocrine Society
Date: 05-2010
DOI: 10.1210/JC.2009-2329
Abstract: Low serum IGF-I is an independent risk factor for diabetes and cardiovascular disease. These noncommunicable diseases are extremely common in urban black South Africans, but their IGF-I concentration is unknown. We aimed to compare serum IGF-I concentrations of African and Caucasian people, investigate their age-related IGF-I decline, and determine whether IGF-I could account, at least in part, for the high prevalence of noncommunicable diseases in black Africans. This cross-sectional study involved 211 African and 316 Caucasian men and women (aged 20-70 yr). Fasting glucose, insulin, lipids, albumin, creatinine, liver enzymes, cotinine, high-sensitivity C-reactive protein, reactive oxygen species, IGF-I, blood pressure (BP), and pulse wave velocity were determined. IGF-I was lower in Africans (P < 0.001) and in both ethnicities declined significantly by age quartiles (P < 0.001). In African men and women, IGF-I declined significantly from age quartile 1 to 2 (r = -0.65, P < 0.001), not seen in young Caucasian men and women (r = -0.08, P = 0.45 r = -0.10, P = 0.34). This was confirmed after adjustment for BP, insulin resistance, high-sensitivity C-reactive protein, cotinine, gamma-glutamyl transferase, and reactive oxygen species. Only young Africans showed significant negative correlations of IGF-I with BP, pulse wave velocity, and high-density lipoprotein cholesterol. Africans presented lower IGF-I levels than Caucasians due to an accelerated decline in serum IGF-I concentration prior to 40 yr of age. Strong associations of low serum IGF-I with blood pressure and arterial stiffness in young Africans suggest that the loss of cardiometabolic protection by IGF-I could predispose them to earlier disease onset.
Publisher: Wiley
Date: 12-2009
DOI: 10.1038/OBY.2009.157
Abstract: Sub-Saharan Africa is afflicted by high hypertension prevalence that is expected to rise even further along with increasing obesity rates. The present study aimed to investigate the role of visfatin in obesity and to explore associations of visfatin with markers of endothelial function and hemodynamics in African women compared to a well-matched white s le. The present study involved urban African (n = 102) and white (n = 115) women from South Africa, in idually matched for age and BMI. We measured blood pressure, cardiac output, and arterial compliance noninvasively, and analyzed visfatin as well as circulating markers of vascular function and inflammation in serum. Serum visfatin concentration did not differ between African and white women. Visfatin was unrelated to obesity in African women but positive associations for total and abdominal obesity were found in white women. Age- and obesity-adjusted univariate and multivariate analyses revealed significant positive associations of visfatin with endothelin-1 and fibrinogen in African women. Identical analyses in white women indicated a positive association of visfatin with C-reactive protein and von Willebrand factor. Our findings suggest a possible role of visfatin in the cardiovascular system that seems to be independent of obesity in the African women.
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.CLNU.2018.05.008
Abstract: The relationship between total body iron and cardiovascular disease remains controversial and information absent in black sub-Saharan Africans in whom alcohol consumption tends to be high. The level of total body iron is tightly regulated, however this regulation is compromised by high alcohol intake causing iron loading. The aim of this study is to investigate total body iron, as represented by serum ferritin, and its interaction with measures of alcohol intake in predicting all-cause and cardiovascular mortality. We followed health outcomes for a median of 9.22 years in 877 randomly selected HIV negative African women (mean age: 50.4 years). One hundred and five deaths occurred of which 40 were cardiovascular related. Ferritin averaged 84.0 (5th to 95th percentile interval, 7.5-533.3) ng/ml and due to the augmenting effect of inflammation, lowered to 75.3 (6.9-523.2) ng/ml after excluding 271 participants with high-sensitivity C-reactive protein (CRP) levels (above 8 mg/l). CRP increased by quartiles of ferritin in the total group (P trend = 0.002), but this relationship was absent after excluding the 271 participants with high CRP values (P trend = 0.10). Ferritin, gamma-glutamyl transferase and carbohydrate deficient transferrin (all P < 0.0001) were higher in drinkers compared to non-drinkers, but CRP was similar (P = 0.77). In multivariable-adjusted analyses, ferritin predicted both all-cause (hazard ratio, 2.08 95% confidence interval, 1.62-2.68 P < 0.0001) and cardiovascular (1.94 1.29-2.92 P = 0.002) mortality. In participants with CRP levels below or equal to 8 mg/l, the significant relationship remained between ferritin and all-cause (2.51 1.81-3.49 P < 0.0001) and cardiovascular mortality (2.34 1.45-3.76 P = 0.0005). In fully adjusted models, interactions existed between ferritin and gamma-glutamyl transferase, self-reported alcohol use and carbohydrate deficient transferrin in predicting all-cause (P ≤ 0.012) and cardiovascular mortality (P ≤ 0.003). Iron loading in African women predicted all-cause and cardiovascular mortality and the intake of alcohol seems mechanistically implicated.
Publisher: Springer Science and Business Media LLC
Date: 11-2013
DOI: 10.1007/S00726-013-1611-0
Abstract: Globally the prevalence of non-communicable diseases, such as hypertension and type 2 diabetes, are escalating. Metabolomic studies indicated that circulating branched chain amino acids (BCAAs) are associated with insulin resistance, coronary artery disease and increased risk for cardiovascular events. We aimed to extend the current understanding of the cardiovascular risk associated with BCAAs. We explored whether BCAAs are related to markers of cardiovascular disease in a bi-ethnic population and whether this relationship was influenced by chronic hyperglycaemia. We included 200 African and 209 Caucasian participants, and determined their ambulatory blood pressure and carotid intima-media thickness (cIMT). We analysed blood s les for glycated haemoglobin (HbA1c) and BCAAs. Participants were stratified into two groups according to their HbA1c value using the median cut-off value of 5.6%. Ambulatory BP, cIMT and BCAAs were significantly higher (all p < 0.001) in the high HbA1c group. Single regression analyses indicated significant positive associations of ambulatory blood pressure and cIMT with BCAAs (all p < 0.05) in both the groups. These associations between ambulatory systolic blood pressure (SBP) (r = 0.16, p = 0.035) and cIMT (r = 0.22, p = 0.004) with BCAAs remained in the high HbA1c group after adjusting for age, gender, ethnicity and body mass index (BMI) and were confirmed in multiple regression analyses (ambulatory SBP: R (2) = 0.17, β = 0.21, p = 0.005 and cIMT: R (2) = 0.30, β = 0.19, p = 0.003). Our results demonstrate that BCAAs are independently related to ambulatory BP and cIMT in in iduals with high HbA1c levels and suggest that potential cardiovascular deterioration accompany the rise in BCAAs in conditions of hyperglycaemia.
Publisher: Elsevier BV
Date: 2015
Location: South Africa
No related grants have been discovered for Hugo Huisman.