Valine Metabolism Is Altered in Obese Adolescents with Polycystic Ovary Syndrome and Relates to Insulin Sensitivity

Abstract

Polycystic Ovarian Syndrome (PCOS) is common and associated with insulin resistance (IR). The mechanism of IR in PCOS is unclear, likely multifactorial, and may relate to branched-chain amino acids (BCAA) and mitochondrial metabolism. We quantitated differences in BCAA and BCAA breakdown product short chain (C3-C5) acylcarnitines in response to hyperinsulinemia in obese girls with and without PCOS, and assessed the relationship to IR and hyperandrogenism. Obese girls with PCOS [n=15, 14.5 ± 1.6 years, BMI %ile 98.5 ± 1.0] and without PCOS [n=6; 13.2 ± 1.2 years, BMI %ile 98.0 ± 1.1] were studied. Insulin sensitivity was assessed with a hyperinsulinemic-euglycemic clamp and a testosterone panel obtained. Nontargeted metabolomics were performed in plasma samples obtained before and after the clamp. T-tests were used for group comparisons, with the Benjamini-Hochberg procedure (false discovery rate (FDR) set to 0.05) to control for multiple testing. Spearman’s correlation coefficient was calculated for BCAA vs. glucose infusion rate (GIR) and free androgen index (FAI). The groups had similar demographic, physical activity, diet attributes, HbA1c and lipids. Girls with PCOS had higher FAI and worse IR than controls. FAI related negatively to short chain acylcarnitines C4 (r = -0.74, p=0.0002) and C3 (r=-0.60, p =0.007). During hyperinsulinemia, girls with PCOS had higher valine (FDR-adjusted p=0.04) and lower valine breakdown product C4 butyrylcarnitine (FDR-adjusted p=0.01). End-clamp valine correlated with GIR (r= -0.59, p= 0.006) as did C4 butyrylcarnitine (r=0.44, p=0.04). Under hyperinsulinemia, a metabolomic signature was revealed in obese girls with PCOS, distinct from that in uncomplicated obesity. Valine was higher in girls with PCOS, while C4 acylcarnitine, its direct mitochondrial metabolite, was lower. Further work is needed to determine if BCAA metabolism is a modifiable target to improve insulin sensitivity or simply a useful biomarker. Disclosure A. Carreau: None. H. Rahat: None. Y. Garcia Reyes: None. L. Pyle: None. K.J. Nadeau: None. M. Cree-Green: None.