Low testosterone concentrations and risk of ischaemic cardiovascular disease in ageing: not just a problem for older men

Androgen Receptor and Cardiovascular Disease: A Potential Risk for the Abuse of Supplements Containing Selective Androgen Receptor Modulators

The androgen receptor (AR) is a member of the family of ligand-activated transcription factors. Selective androgen receptor modulators (SARMs) exert their biological function through complex interactions with the AR. It has been speculated that overexertion of AR signaling cascades as a result of SARM abuse can be a risk factor for the development of various cardiovascular diseases. The present literature review explores the implications of the interaction between SARMs and the AR on cardiovascular health by focusing on the AR structure, function, and mechanisms of action, as well as the current clinical literature on various SARMs. It is shown that SARMs may increase the risk of cardiovascular diseases through implications on the renin-angiotensin system, smooth muscle cells, sympathetic nervous system, lipid profile, inflammation, platelet activity, and various other factors. More research on this topic is necessary as SARM abuse is becoming increasingly common. There is a noticeable lack of clinical trials and literature on the relationship between SARMs, cardiovascular diseases, and the AR. Future in vivo and in vitro studies within this field are vital to understand the mechanisms that underpin these complex interactions and risk factors.

Sex-specific differences in atherosclerosis, thrombospondin-1, and smooth muscle cell differentiation in metabolic syndrome versus non-metabolic syndrome mice

Introduction

Metabolic syndrome (MetS) amplifies the risks of atherosclerosis. Despite well-known sexual dimorphism in atherosclerosis, underlying mechanisms are poorly understood. Our previous findings highlight a proatherogenic protein, thrombospondin-1 (TSP-1), in hyperglycemia- or hyperleptinemia (mimicking obesity)-induced atherosclerosis. However, the role of TSP-1 in the development of atherosclerosis prompted by co-existing hyperglycemia and obesity, characteristic of MetS, is unknown. The goal of this study was to examine sex-specific differences in lesion progression in a model of combined MetS and atherosclerosis (KKAyApoE) and interrogate how these differences relate to TSP-1 expression.

Methods

Male and female KKAy^+/-ApoE^-/- (with ectopic agouti gene expression) and age-matched non-agouti KKAy^-/-ApoE^-/- littermates were placed on a standard laboratory diet from 4 to 24 weeks age followed by blood and tissue harvests for biochemical, molecular, and aortic root morphometric studies.

Results

Metabolic profiling confirmed MetS phenotype of KKAy^+/-ApoE^-/-; however, only male genotypes were glucose intolerant with elevated VLDL-cholesterol and VLDL-triglyceride levels. Aortic root morphometry demonstrated profound lipid-filled lesions, increased plaque area, and augmented inflammatory and SMC abundance in MetS vs non-MetS males. This increase in lesion burden was accompanied with elevated TSP-1 and attenuated LMOD-1 (SM contractile marker) and SRF (transcriptional activator of SM differentiation) expression in male MetS aortic vessels. In contrast, while lipid burden, plaque area, and TSP-1 expression increased in MetS and non-MetS female mice, there was no significant difference between these genotypes. Increased collagen content was noted in MetS and non-MetS genotypes, specific to female mice. Measurement of plasma testosterone revealed a link between the atherogenic phenotype and abnormally high or low testosterone levels. To interrogate whether TSP-1 plays a direct role in SMC de-differentiation in MetS, we generated KKAy^+/- mice with and without global TSP-1 deletion. Immunoblotting showed increased SM contractile markers in male KKAy^+/-TSP-1^-/- aortic vessels vs male KKAy^+/-TSP-1^{+/ +}. In contrast, TSP-1 deletion had no effect on SM contractile marker expression in female genotypes.

Conclusion

Together, the current study implicates a role of plasma testosterone in sex-specific differences in atherosclerosis and TSP-1 expression in MetS vs non-MetS mice. Our data suggest a sex-dependent differential role of TSP-1 on SMC de-differentiation in MetS. Collectively, these findings underscore a fundamental link between TSP-1 and VSMC phenotypic transformation in MetS.