The RolE oF Androgen Excess in MUscle Energy MetaboLism in Women With PolyCystic Ovary Syndrome (REFUEL PCOS) Study 2

Overview

Polycystic ovary syndrome (PCOS) affects 10% of all women, and it usually co-exists with high levels of sex hormones called androgens, such as testosterone. Women with PCOS are at increased risk of metabolic complications such as diabetes, non-alcoholic fatty liver disease, high blood pressure and heart disease. However, very little is understood about how androgen excess may drive the metabolic complications observed in women with PCOS. Skeletal muscle is an important site of energy metabolism; increasingly, it is suspected that skeletal muscle energy balance is adversely impacted by androgens, thereby driving metabolic complications. To take this theory forward, we want to investigate the effects of androgens on muscle energy metabolism. We will perform detailed metabolic testing (including blood tests and muscle biopsies) in women with PCOS before and after taking tablets that block the action of testosterone for 28 days. In addition, we will be using a gold standard technique to see how women with PCOS metabolise fat and other nutrients by measuring markers in blood and breath samples after a breakfast test meal. This clinical research will increase our understanding of the complex relationships between hormonal abnormalities and metabolic disease in women with PCOS.

Background: Polycystic ovary syndrome (PCOS) is a lifelong metabolic disorder affecting 10-13% of all women and is associated with major healthcare and economic burden, estimated at $8 billion annually the US in 2020. Traditionally considered a reproductive disorder only, it is now increasingly clear that PCOS is associated with severe metabolic health consequences across the entire life course of women. There is a two-fold increased risk of type 2 diabetes mellitus (T2DM), nonalcoholic fatty liver disease, and emerging evidence of increased cardiovascular disease (CVD) incidence. There are no disease-specific therapies to mitigate or treat metabolic risk in women with PCOS. This is consistently highlighted as the priority concern amongst PCOS patient advocacy groups. Androgen excess is a cardinal feature of PCOS, and circulating androgen burden is closely correlated with metabolic complications. In women with PCOS, the risk of developing metabolic dysfunction is above that conferred by simple obesity, suggesting that androgen excess is a key player; however, a distinct mechanistic role for androgens in this process remains to be elucidated. Androgen excess is associated with metabolically deleterious visceral fat accumulation and circulating testosterone levels correlate directly with the risk of T2DM and NAFLD. Muscle is a critical metabolic target tissue that plays a central role in energy metabolism through processes such as glucose uptake and oxidation, as well as oxidation of fatty acids to generate ATP in the mitochondria. Recent mechanistic data have shown that androgen excess is associated with changes in the transcriptional profile of skeletal muscle genes linked with metabolism and energy balance. Therefore, skeletal muscle is likely to represent an important site of crosstalk between androgen excess, disturbances in energy metabolism and risk of metabolic disease in PCOS. Defective skeletal muscle glucose uptake is a key early step in the pathogenesis of insulin resistance in PCOS, and an early predictor of progression to overt type 2 diabetes mellitus. Impaired mitochondrial oxidation of free fatty acids in skeletal muscle and other disturbances in skeletal muscle mitochondrial function, such as oxidative phosphorylation, are increasingly implicated in the pathogenesis of metabolic disease such as T2DM. Abnormalities in skeletal muscle mitochondrial function have also been identified in small-scale studies in women with PCOS, and were associated with impaired fatty acid oxidation, weight gain and an increased risk of diabetes. We hypothesise that androgen-mediated disturbances in skeletal muscle energy balance play a major role in the pathogenesis of metabolic disease in women with PCOS. Study description: We propose to test our hypothesis utilising state-of-the-art metabolic phenotyping tools in two study visits. We will examine systemic fatty acid oxidation, muscle proteomics and targeted and non-targeted metabolomics in women with PCOS before and after pharmacological androgen receptor blocade. In addition, a subset of ex vivo muscle biopsies will undergo in vitro experiments to measure skeletal muscle mitochondrial morphology and function. After study visit 1, all recruited participants will receive 50mg of an oral androgen receptor antagonist (bicalutamide), resulting in pharmacological AR blockade, before undertaking an identical study visit for repeat assessment.