SUN-100 The Local Androgen-Estrogen Environment Differentially Regulates Adipocyte Lipid Metabolism by Fat Depot and Sex

Obesity rates have tripled world-wide in the last 40 years. While estradiol (E2) stimulates lipogenesis and contributes to a gynecoid white adipose tissue (WAT) distribution pattern, the role of testosterone (T) in adipocyte metabolism is less clear. Obese men have low T serum concentrations but have variable E2 serum concentrations and increased risk for type II diabetes mellitus. Conversely, women with high T serum concentrations (polycystic ovary syndrome (PCOS)), are at risk for increased visceral white adipose tissue (VWAT) deposition and insulin resistance irrespective of serum E2 concentrations. Recently, in vivo T administration was shown to increase lipogenesis and decrease lipolysis in WAT of females, but loss of T in males was linked with decreased adipocyte insulin signaling. We hypothesized that local androgens would up-regulate insulin signaling and depress lipolysis in female VWAT adipocytes irrespective of local E2 levels, but would down-regulate insulin signaling and stimulate lipolysis in male VWAT adipocytes dependent on local E2 levels. Sexually mature chow-fed female and male Sprague-Dawley rats were euthanized and inguinal SCWAT and VWAT were collected. WAT from females was collected during proestrus (ie, high E2) based on vaginal cytology. WAT was digested and preadipocytes were plated, grown to confluence, and induced to become adipocytes. Cells were then treated for 48 hours with the following steroid treatments: no steroid, dihydrotestosterone (DHT, 10(-6) M), and estrogen receptor α (ERα) inhibitor, fulvestrant (10(-6) M), with T (10(-6) M). After 48 hours, cells were collected for qPCR (insulin receptor (Insr), insulin receptor substrate 1 (Irs1), protein kinase B 2 (Akt2), forkhead box protein 1 (Foxo1), aromatase A1 (Cyp19A1) and western blotting (phosphorylated AKT (pAKT)/AKT and phosphorylated FOXO1 (pFOXO1)/FOXO1 ratios) and media was collected for T and E2 analysis. Adipocytes collected from female rats cultured in fulvestrant and T (Fulv + T) had increased transcript levels of Insr, Irs1, Akt2 in VWAT and SCWAT. Interestingly, Fulv + T increased protein phosphorylation of AKT and FOXO1 only in VWAT adipocytes from females. In contrast, VWAT adipocytes from males had decreased protein phosphorylation of AKT and FOXO1 in response to Fulv +T but had no response at the transcript level to any androgen treatment. Irrespective of sex, both VWAT and SCWAT adipocytes had decreased glycerol release (i.e., lipolysis) in response to Fulv +T. In a steroid-free environment, the T:E2 ratio was highest for male VWAT and lowest for female SCWAT, indicating that male VWAT had the lowest and female SCWAT had the highest aromatase function. However, Cyp19A1 transcript levels were decreased in DHT and increased in Fulv +T of female VWAT. These sexually dimorphic findings suggest that local androgen control of basal lipogenesis and lipolysis is mediated by E2 and adipose location.