Individual and combined effects of 5-year exposure to hyperandrogenemia and Western-style diet on metabolism and reproduction in female rhesus macaques

STUDY QUESTION: What is the impact of prolonged exposure to hyperandrogenemia (T), Western-style diet (WSD) and the combination on metabolic and reproductive function in female rhesus macaques, particularly in the post-partum period? SUMMARY ANSWER: Combined T + WSD worsened measures of insulin sensitivity and parameters of cyclicity following prolonged (5 years) exposure, but there was no effect on post-partum metabolic function. WHAT IS KNOWN ALREADY: Women with hyperandrogenemia due to polycystic ovary syndrome are at higher risk for gestational diabetes and Type 2 diabetes post-partum, but it is unknown if this is related to hyperandrogenemia. Hyperandrogenemia in the presence of a WSD worsens metabolic function in female nonhuman primates. STUDY DESIGN, SIZE, DURATION: Female rhesus macaques began treatment near menarche (roughly 2.5 years of age) consisting of either cholesterol (control; C) or testosterone (T) implants (average serum levels 1.4 ng/ml) and exposure to standard monkey chow or a WSD (15 vs 36% of calories from fat, respectively). The four groups were maintained on treatment for 3 years, underwent a fertility trial in Year 4 and continued with treatments through Year 5. PARTICIPANTS/MATERIALS, SETTING, METHODS: Metabolic measurements (glucose tolerance tests and double X-ray absorptiometry scans) were performed yearly, and results from 5 years of treatment are reported for all animals. Animals were bled daily for 30 days at 5 years to capture changes in ovarian cycle hormones, and ultrasound measurements were performed during the early follicular and luteal phase. MAIN RESULTS AND THE ROLE OF CHANCE: After 5 years of treatment, WSD exposure moderately increased body weight and body fat, although control animals also had a high body mass index due to ad libitum feeding. Animals in the T + WSD group had increased fasting insulin and insulin secretion during an intravenous glucose tolerance test. WSD exposure also altered ovarian cycles, delaying the time to the E2 surge, decreasing progesterone and anti-Müllerian hormone levels and increasing the number of antral follicles present by ultrasound. Longitudinal assessment of metabolic function for only those animals that became pregnant in Year 4 of treatment revealed no differences in post-partum metabolism between groups, although WSD resulted in overall elevated weights, body fat and measures of insulin resistance. LARGE SCALE DATA: None. LIMITATIONS, REASONS FOR CAUTION: The small sample size and heterogeneity in metabolic effects observed in the T + WSD group are limitations of the current study, with only a subset of animals in this group showing impaired insulin resistance relative to controls. In addition, obesity in the C group prevented comparisons to lean animals. WIDER IMPLICATIONS OF THE FINDINGS: Hyperandrogenemia combined with WSD had a greater impact on insulin sensitivity and ovarian function than either treatment alone. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by NIH grant P50 HD071836 to C.T.R., J.H. and C.T. and P51 OD011092 for support of the Oregon National Primate Research Center. All authors declare no competing interests.