ORCID Profile
0000-0002-4079-7814
Current Organisation
North-West University
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Publisher: MDPI AG
Date: 09-12-2022
DOI: 10.3390/JCDD9120447
Abstract: Elevated homocysteine (Hcy) increases cardiovascular disease (CVD) risk. Our objective was to emphasize Hcy’s contribution in hypertension and CVD management by determining H-type hypertension (hypertension with Hcy ≥ 10 µmol/L) and associations between Hcy, blood pressure (BP) and estimates of vascular function among Black South Africans. We included 1995 adults (63% female). Plasma Hcy and cardiovascular measures (systolic and diastolic BP (SBP, DBP), pulse pressure, heart rate (HR), carotid-radialis pulse wave velocity (cr-PWV), intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1) were quantified. Five Hcy-related polymorphisms (cystathionine β-synthase (CBS 844ins68, T833C, G9276A) methylenetetrahydrofolate reductase (MTHFR C677T) and methionine synthase (MTR A2756G)) were genotyped. Hcy was µmol/L in 41% (n = 762), and of the 47% (n = 951) hypertensives, 45% (n = 425) presented with H-type. Hcy was higher in hypertensives vs. normotensives (9.86 vs. 8.78 µmol/L, p 0.0001, effect size 0.56) and correlated positively with SBP, DBP, cr-PWV and ICAM-1 (r 0.19, p 0.0001). Over Hcy quartiles, SBP, DBP, HR, cr-PWV and ICAM-1 increased progressively (all p-trends ≤ 0.001). In multiple regression models, Hcy contributed to the variance of SBP, DBP, HR, cr-PWV and ICAM-1. H-type hypertensives also had the lowest MTHFR 677 CC frequency (p = 0.03). Hcy is positively and independently associated with markers of vascular function and raised BP.
Publisher: Springer Science and Business Media LLC
Date: 26-11-2015
DOI: 10.1038/HR.2015.123
Publisher: Springer Science and Business Media LLC
Date: 25-06-2021
DOI: 10.1038/S41371-021-00569-6
Abstract: Exogenous estrogens and progestins may affect the components of the renin-angiotensin-aldosterone system (RAAS). Changes in ventricular blood volume are associated with increased secretion of N-terminal pro-hormone B-type natriuretic peptide (NT-proBNP), which may also be affected by hormonal contraceptives. In this study, we aimed to compare components of the RAAS and NT-proBNP between groups using different hormonal contraceptives, including the combination pill, the injection or implant, and controls (no contraception) in black and white women of fertile age (20 - 30 years). Secondly, we determined whether blood pressure and NT-proBNP are associated with the RAAS components. We included 397 black and white women not using contraceptives, 120 using the combination pill, and 103 receiving an injection/implant. RAAS Triple-A analysis was carried out with LC-MS/MS quantification, and blood pressure measurements (ABPM) taken over 24 h. We found that serum aldosterone was higher (475.7 vs. 249.2 pmol/L p < 0.001) in the combination pill group than in the no contraception group of white women. The aldosterone-angiotensin II ratio (AA2) was higher (5.4 vs. 2.5 p < 0.001) in the combination pill group than in the no contraception group. In the black women using the combination pill, we found a borderline-positive and borderline-negative association between 24-h systolic blood pressure and NT-proBNP with equilibrium (eq) Ang II, respectively. In white women using the combination pill, only CRP contributed positively and independently to NT-proBNP. To conclude, activation of RAAS by different hormonal contraceptives may increase future risk for the development of hypertension in young black and white women.
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: 26-05-2021
Publisher: Elsevier BV
Date: 03-2020
DOI: 10.1016/J.MVR.2019.103937
Abstract: Globally, a detrimental shift in cardiovascular disease risk factors and a higher mortality level are reported in some black populations. The retinal microvasculature provides early insight into the pathogenesis of systemic vascular diseases, but it is unclear whether retinal vessel calibers and acute retinal vessel functional responses differ between young healthy black and white adults. We included 112 black and 143 white healthy normotensive adults (20-30 years). Retinal vessel calibers (central retinal artery and vein equivalent (CRAE and CRVE)) were calculated from retinal images and vessel caliber responses to flicker light induced provocation (FLIP) were determined. Additionally, ambulatory blood pressure (BP), anthropometry and blood s les were collected. The groups displayed similar 24 h BP profiles and anthropometry (all p > .24). Black participants demonstrated a smaller CRAE (158 ± 11 vs. 164 ± 11 MU, p < .001) compared to the white group, whereas CRVE was similar (p = .57). In response to FLIP, artery maximal dilation was greater in the black vs. white group (5.6 ± 2.1 vs. 3.3 ± 1.8% p < .001). Already at a young age, healthy black adults showed narrower retinal arteries relative to the white population. Follow-up studies are underway to show if this will be related to increased risk for hypertension development. The reason for the larger vessel dilation responses to FLIP in the black population is unclear and warrants further investigation.
Publisher: Elsevier BV
Date: 08-2011
DOI: 10.1016/J.DIABRES.2011.05.011
Abstract: To investigate the relationship between nocturnal blood pressure and chronically elevated blood glucose to determine if these elevated blood glucose concentrations contribute to a non-dipping blood pressure, especially in high-risk groups such as Africans. Nocturnal blood pressures and blood glucose levels of 41 non-dipping African and 28 non-dipping Caucasian men were investigated. Ambulatory systolic (SBP) and diastolic blood pressure (DBP) were measured and blood collected in sodium fluoride tubes from the antebrachial vein to determine serum glucose and glycosylated hemoglobin A1c (HbA1c) percentage. The estimated average glucose (eAG) was determined from HbA1c percentage with a regression formula. The African non-dippers had higher blood pressures (p<0.001) and elevated HbA1c (p=0.037) and eAG (p=0.041) levels compared to the Caucasians. In single, partial and multiple regression analyses nighttime (00:00-04:00) SBP correlated positively with HbA1c (p=0.069) and eAG (p<0.001) in the African men. No correlations were found in the Caucasian men. Sensitivity analysis confirmed that the association between nighttime SBP (00:00-04:00) and eAG was independent of carotid intima-media thickness in the African men (R(2)=0.617 β=0.438 p=0.008). The blunted nocturnal decline in SBP during the early morning hours is associated with chronically elevated blood glucose in non-dipper African men.
Publisher: Elsevier BV
Date: 12-2020
Publisher: Informa UK Limited
Date: 28-04-2015
DOI: 10.3109/10641963.2015.1013123
Abstract: Haemostatic- and oxidative stress markers are associated with increased cardiovascular risk. In the black population, evidence exists that both an imbalance in the haemostatic system and oxidative stress link with the development of hypertension. However, it is unclear whether these two risk components function independently or are related, specifically in the black population, who is known to have a high prevalence of stroke. We aimed to investigate associations between the haemostatic system and oxidative stress in black and white South Africans. We performed a cross-sectional study including 181 black (mean age, 44 51.4% women) and 209 white (mean age, 45 51.7% women) teachers. Several markers of the haemostatic- (von Willebrand factor, fibrinogen, plasminogen activator inhibitor-1, d-dimer and clot lysis time) and oxidant-antioxidant (serum peroxides, total glutathione, glutathione peroxidase- and glutathione reductase activities) systems were measured. Along with a worsened cardiovascular profile, the black group had higher haemostatic-, inflammation- and oxidative stress markers as well as decreased glutathione peroxidase activity. In multiple regression analyses, fibrinogen was positively associated with serum peroxides (p < 0.001) in both ethnic groups. In the black population, we found negative associations of von Willebrand factor and clot lysis time with glutathione peroxidase activity (p ≤ 0.008), while a positive association existed between clot lysis time and serum peroxides (p = 0.011) in the white population. We conclude that in the black population, decreased GPx activity accompanies an altered haemostatic profile, while in the white population associations may suggest that serum peroxides impair fibrin clot lysis.
Publisher: Elsevier BV
Date: 06-2014
DOI: 10.1016/J.THROMRES.2014.03.037
Abstract: Hypertension is highly prevalent in black South Africans in which morbidity and mortality from stroke are on the increase. Elevated blood pressure and haemostatic markers can induce changes in blood rheology and endothelial function which could result in a procoagulant state that increases the risk for cerebrovascular disease. Information about the coagulation and fibrinolytic systems of people from African descent are limited. We therefore, investigated the haemostatic profile and its relationships with blood pressure in black South Africans. We measured ambulatory blood pressure and haemostatic markers of 201 black and 208 white school teachers. The haemostatic markers included measurements representing coagulation and fibrinolysis (von Willebrand factor, fibrinogen, plasminogen activator inhibitor-1, fibrin D-dimer and clot lysis time). Black participants displayed significantly higher blood pressure, von Willebrand factor, fibrinogen, plasminogen activator inhibitor-1 and D-dimer levels and longer clot lysis times (p≤0.001). Single, partial and multiple regression analyses showed that systolic (p≤0.011) and diastolic blood pressure (p=0.010) correlated positively with D-dimer in black participants, while systolic (p≤0.001) and daytime diastolic blood pressure (p=0.011) correlated negatively with clot lysis time in white participants. The black population had a more prothrombotic profile, with higher levels of coagulation markers and inhibited fibrinolysis, than the white study participants. The positive association between blood pressure and elevated D-dimer in the blacks may contribute to the high prevalence of hypertension and related increased cardiovascular and cerebrovascular risk in this group.
Publisher: Springer Science and Business Media LLC
Date: 17-06-2020
Publisher: Georg Thieme Verlag KG
Date: 27-11-2018
Abstract: An increasing prevalence of obesity-related hypertension is observed in the youth and may have severe consequences for future cardiovascular disease development. Previous studies portrayed leptin as a potential factor involved in obesity-related hypertension development. In order to understand leptin’s contributions to early cardiovascular deterioration, we investigated leptin and its associations with measures of autonomic activity, endothelial activation, and blood pressure in young healthy black and white men and women. We included 820 participants (aged 20–30 years) and determined serum leptin and endothelial cellular adhesion molecules. We measured 24-h blood pressure, heart rate, and heart rate variability components. In multivariate-adjusted regression analyses, we found consistent associations between markers of autonomic activity (such as 24-h heart rate, day and night-time heart rate as well as heart rate variability total power) and leptin in both white (all p≤0.001) and black men (all p≤0.040). These findings were absent or less prominent in women, despite their almost 10-fold higher leptin levels than men. Only in white men, 24-h diastolic blood pressure was associated with leptin (Std β=0.37 p=0.006). This association was found to be partly mediated by autonomic activity (24-h heart rate variability total power). No independent associations were observed between leptin and markers of endothelial cell activation, irrespective of race or gender. Leptin’s independent association with autonomic neural activity in a young apparently healthy population suggests an early influence of leptin on autonomic function and future blood pressure elevation especially in men.
Publisher: Wiley
Date: 16-11-2019
DOI: 10.1111/ECI.13039
Abstract: Information regarding the effect of leptin on the vasculature in young healthy adults at risk for cardiovascular disease development is limited. We therefore examined the associations between measures of subclinical atherosclerosis (carotid intima-media thickness, carotid cross-sectional wall area), large artery stiffness (pulse wave velocity) and a measure of endothelial dysfunction (von Willebrand factor [vWF]) with leptin in young healthy men and women. In a cross-sectional study in South Africa involving 820 normotensive in iduals (337 men and 483 women) aged 20-30 years, we measured carotid intima-media thickness, carotid cross-sectional wall area, pulse wave velocity, vWF from citrated plasma and leptin from serum. Despite sevenfold higher leptin in women than men (P < 0.001), only in young healthy men, we observed negative, independent associations between measures of carotid wall thickness (carotid intima-media thickness: R In young healthy men, we found a beneficial inverse association between measures of carotid wall thickness and circulating leptin, thereby supporting a potential vascular protective role of leptin.
Publisher: Frontiers Media SA
Date: 29-04-2020
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: 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: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2015
Publisher: Elsevier BV
Date: 07-2021
Publisher: BMJ
Date: 08-2021
DOI: 10.1136/BMJGH-2021-006454
Abstract: Chronic kidney disease (CKD) is a global public health problem, seemingly affecting in iduals from low-income and-middle-income countries (LMICs) disproportionately, especially in sub-Saharan Africa. Despite the growing evidence pointing to an increasing prevalence of CKD across Africa, there has not been an Africa-wide concerted effort to provide reliable estimates that could adequately inform health services planning and policy development to address the consequences of CKD. Therefore, we established the CKD in Africa (CKD-Africa) Collaboration. To date, the network has curated data from 39 studies conducted in 12 African countries, totalling 35 747 participants, of which most are from sub-Saharan Africa. We are, however, continuously seeking further collaborations with other groups who have suitable data to grow the network. Although many successful research consortia exist, few papers have been published (with none from Africa) detailing the challenges faced and lessons learnt in setting up and managing a research consortium. Drawing on our experience, we describe the steps taken and the key factors required to establish a functional collaborative consortium among researchers in Africa. In addition, we present the challenges we encountered in building our network, how we managed those challenges and the benefit of such a collaboration for Africa. Although the CKD-Africa Collaboration is focused primarily on CKD research, many of the lessons learnt can be applied more widely in public health research in LMICs.
Publisher: Oxford University Press (OUP)
Date: 06-01-2019
Abstract: Globally hypertension is stabilising, but in sub-Saharan Africa the incidence of hypertension remains on an increase. Although this might be attributed to poor healthcare and ineffective antihypertensive treatment, there is a limited understanding of population and in idual-specific cardiovascular pathophysiology – necessary for effective prevention and treatment strategies in Africa. As there is a lack of longitudinal studies tracking the early pathophysiological development of hypertension in black populations, the African-PREDICT study was initiated. The purpose of this paper is to describe the detailed methodology and baseline cohort profile of the study. From 2013 to 2017, the study included 1202 black ( N = 606) and white ( N = 596) men and women (aged 20–30 years) from South Africa – screened to be healthy and clinic normotensive. At baseline, and each 5-year follow-up examination, detailed measures of health behaviours, cardiovascular profile and organ damage are taken. Also, comprehensive biological s ling for the ‘omics’ and biomarkers is performed. Overall, the baseline black and white cohort presented with similar ages, clinic and 24-hour blood pressures, but black adults had lower socioeconomic status and higher central systolic blood pressure than white in iduals. The prospective African-PREDICT study in young black and white adults will contribute to a clear understanding of early cardiovascular disease development.
No related grants have been discovered for Leandi Lammertyn.