ORCID Profile
0000-0002-2612-7769
Current Organisations
Baker IDI Heart and Diabetes Institute
,
Deakin University
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Publisher: American Physiological Society
Date: 08-2019
DOI: 10.1152/JAPPLPHYSIOL.00904.2018
Abstract: Noncoding RNAs, including microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs) play roles in the development and homeostasis of nearly every tissue of the body, including the regulation of processes underlying heart growth. Cardiac hypertrophy can be classified as either physiological (beneficial heart growth) or pathological (detrimental heart growth), the latter of which results in impaired cardiac function and heart failure and is predictive of a higher incidence of death due to cardiovascular disease. Several miRNAs have a functional role in exercise-induced cardiac hypertrophy, while both miRNAs and lncRNAs are heavily involved in pathological heart growth and heart failure. The latter have the potential to act as an endogenous sponge RNA and interact with specific miRNAs to control cardiac hypertrophy, adding another level of complexity to our understanding of the regulation of cardiac muscle mass. In addition to tissue-specific effects, ncRNA-mediated tissue cross talk occurs via exosomes. In particular, miRNAs can be internalized in exosomes and secreted from various cardiac and vascular cell types to promote angiogenesis, as well as protection and repair of ischemic tissues. ncRNAs hold promising therapeutic potential to protect the heart against ischemic injury and aid in regeneration. Numerous preclinical studies have demonstrated the therapeutic potential of ncRNAs, specifically miRNAs, for the treatment of cardiovascular disease. Most of these studies employ antisense oligonucleotides to inhibit miRNAs of interest however, off-target effects often limit their potential to be translated to the clinic. In this context, approaches using viral and nonviral delivery tools are promising means to provide targeted delivery in vivo.
Publisher: Informa UK Limited
Date: 18-05-2022
DOI: 10.1080/17461391.2021.1921854
Abstract: Sex steroids, commonly referred to as sex hormones, are integral to the development and maintenance of the human reproductive system. In addition, male (androgens) and female (estrogens and progestogens) sex hormones promote the development of secondary sex characteristics by targeting a range of other tissues, including skeletal muscle. The role of androgens on skeletal muscle mass, function and metabolism has been well described in males, yet female specific studies are scarce in the literature. This narrative review summarises the available evidence around the mechanistic role of androgens, estrogens and progestogens in female skeletal muscle. An analysis of the literature indicates that sex steroids play important roles in the regulation of female skeletal muscle mass and function. The free fractions of testosterone and progesterone in serum were consistently associated with the regulation of muscle mass, while estrogens may be primarily involved in mediating the muscle contractile function in conjunction with other sex hormones. Muscle strength was however not directly associated with any hormone in isolation when at physiological concentrations. Importantly, recent evidence suggests that intramuscular sex hormone concentrations may be more strongly associated with muscle size and function than circulating forms, providing interesting opportunities for future research. By combining cross-sectional, interventional and mechanical studies, this review aims to provide a broad, multidisciplinary picture of the current knowledge of the effects of sex steroids on skeletal muscle in females, with a focus on the regulation of muscle size and function and an insight into their clinical implications. HighlightsFree testosterone, but not total testosterone, is associated with lean mass but not strength in pre- and post-menopausal females.Progesterone and estrogens may regulate muscle mass and strength, respectively, in females.Intra-muscular steroids may be more closely associated to muscle mass and strength, compared to systemic fractions.
Publisher: Wiley
Date: 11-03-2023
DOI: 10.1113/JP284288
Publisher: Wiley
Date: 2021
DOI: 10.14814/PHY2.14660
Publisher: Wiley
Date: 08-2020
DOI: 10.14814/PHY2.14520
Publisher: Society for Transparency, Openness, and Replication in Kinesiology
Date: 02-06-2022
DOI: 10.51224/SRXIV.158
Publisher: Cold Spring Harbor Laboratory
Date: 06-08-2020
DOI: 10.1101/2020.08.04.20168542
Abstract: Testosterone is a naturally occurring hormone that has been positively associated with lean mass and strength in males. Whether endogenous testosterone is related to lean mass and strength in females is unknown. To examine the relationship between endogenous testosterone concentration and lean mass and handgrip strength in healthy, pre-menopausal females. Secondary data from the 2013-2014 National Health and Nutrition Examination Survey (NHANES)were used. Females were aged 18-40 (n=753, age 30 ± 6 yr, mean ± SD) and pre-menopausal. Multivariate linear regression models were used to examine associations between total testosterone, height-adjusted lean mass and handgrip strength. Mean ± SD testosterone concentration was 1.0 ± 0.6 nmol·L -1 and mean free androgen index (FAI) was 0.02 ± 0.02. Mean fat-free mass index (FFMI) was 16.4 ± 3.0 kg·m -2 and mean handgrip strength was 61.7 ± 10.5 kg. In females, testosterone was not associated with FFMI (β=0.08 95%CI: −0.02, 0.18 p=0.11) or handgrip strength (β=0.03 95%CI: −0.11, 0.17 p=0.67) in a statistically significant manner. Conversely, FAI was positively associated with FFMI (β=0.17 95%CI: 0.01, 0.33 p=0.04 ) but not handgrip strength (β=0.19 95%CI: −0.02, 0.21 p=0.10 ). These findings indicate that FAI, but not total testosterone, is associated with FFMI in females. The small coefficients however suggest that FAI only accounts for a minor proportion of the variance in FFMI, highlighting the complexity of the regulation of lean mass in female physiology. FAI nor total testosterone are associated with handgrip strength in females when testosterone concentrations are not altered pharmacologically.
Publisher: American Chemical Society (ACS)
Date: 21-04-2021
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 22-09-2022
DOI: 10.1249/MSS.0000000000003000
Abstract: Female athletes sleep less and report more sleep problems than their male counterparts. Inadequate sleep reduces maximal strength in male athletes however, little is known about the impact of sleep restriction (SR) on the quantity and quality of resistance exercise performed by female athletes. This study investigated the effect of nine nights of moderate SR on repeated resistance exercise performance, hormonal responses, and perceived fatigue in females. Ten healthy, resistance-trained, eumenorrheic females age 18–35 yr underwent nine nights of SR (5-h time in bed) and normal sleep (NS ≥7-h time in bed) in a randomized, crossover fashion with a minimum 6-wk washout. Participants completed four resistance exercise sessions per trial, with blood s les collected before and after exercise. Exercise performance was assessed using volume load, reactive strength index, and mean concentric velocity with rating of perceived exertion recorded after exercise. Participants completed awakening saliva s ling and the Multi-component Training Distress Scale daily. Volume load decreased trivially ( %, P 0.05) with SR. Mean concentric velocity per set was slower during SR for the lower-body (up to 15%, P 0.05), but not the upper-body, compound lifts. Intraset velocity loss was up to 7% greater during SR for back squats ( P 0.05). SR increased salivary cortisol area under the curve (by 42%), total training distress (by 84%), and session perceived exertion (by 11%). Sustained SR reduces markers of resistance exercise quality (bar velocity) more than quantity (volume load) and increases perceived effort at the same relative intensity in resistance-trained females. Markers of exercise quality and internal load may be more sensitive than volume load, to advise coaches to the decline in lifting performance for female athletes experiencing SR.
Publisher: Springer Science and Business Media LLC
Date: 13-05-2021
DOI: 10.1038/S41598-021-89232-1
Abstract: The aim of this study was to examine the relationship between endogenous testosterone concentrations and lean mass and handgrip strength in healthy, pre-menopausal females. Testosterone has been positively associated with lean mass and strength in young and older males. Whether this relationship exists in pre-menopausal females is unknown. Secondary data from the 2013–2014 National Health and Nutrition Examination Survey were used to test this relationship. Females were aged 18–40 (n = 716, age 30 ± 6 years, mean ± SD) and pre-menopausal. Multivariate linear regression models were used to examine associations between total testosterone, lean mass index (LMI) and handgrip strength. Mean ± SD testosterone concentration was 1.0 ± 0.6 nmol L −1 and mean free androgen index (FAI) was 0.02 ± 0.02. In pre-menopausal females, testosterone was not associated with LMI (β = 0.05 95%CI − 0.04, 0.15 p = 0.237) or handgrip strength (β = 0.01 95%CI − 0.11, 0.12 p = 0.926) in a statistically significant manner. Conversely, FAI was associated with LMI (β = − 0.03 95%CI − 0.05, − 0.02 p = 0.000) in a quadratic manner, meaning LMI increases with increasing FAI levels. Handgrip strength was not associated with FAI (β = 0.06 95%CI − 0.02, 0.15 p = 0.137) . These findings indicate that FAI, but not total testosterone, is associated with LMI in pre-menopausal females. Neither FAI nor total testosterone are associated with handgrip strength in pre-menopausal females when testosterone concentrations are not altered pharmacologically.
Publisher: Elsevier BV
Date: 07-2019
No related grants have been discovered for Sarah E. Alexander.