Prenatal androgen exposure programs metabolic dysfunction in female mice

Abstract

Polycystic ovary syndrome (PCOS) is a common fertility disorder with metabolic sequelae. Our laboratory previously characterized reproductive phenotypes in a prenatally androgenized (PNA) mouse model for PCOS. PNA mice exhibited elevated testosterone and LH levels, irregular estrous cycles, and neuroendocrine abnormalities suggesting increased central drive to the reproductive system. In this study, we examined metabolic characteristics of female PNA mice. PNA mice exhibited increased fasting glucose and impaired glucose tolerance (IGT) that were independent of age and were not associated with changes in body composition or peripheral insulin sensitivity. IGT was associated with defects in pancreatic islet function leading to an impaired response to high glucose, consistent with impaired insulin secretion. Exposure of isolated pancreatic islets to androgen in vitro demonstrated an impaired response to glucose stimulation similar to that in PNA mice, suggesting androgens may have activational in addition to organizational effects on pancreatic islet function. PNA mice also exhibited increased size of visceral adipocytes, suggesting androgen-programed differences in adipocyte differentiation and/or function. These studies demonstrate that in addition to causing reproductive axis abnormalities, in utero androgen exposure can induce long-term metabolic alterations in female mice.

Figure 1

PNA does not alter body mass or composition in PNA mice at 5 months of age. A. Body mass in CON (open circles, n=8) and PNA mice (closed circles, n=9) (p>0.8). B. Total body fat or abdominal fat (region of interest, ROI, subcutaneous and visceral fat combined) in CON and PNA (p>0.4).

Figure 2

PNA does not alter fat pad mass but increases adipocyte size. A. Fat pad mass in CON (open circles) and PNA mice (closed circles) (n=8 CON, n=11 PNA, p>0.5). B, C. Representative photomicrographs of adipose tissue from control (B) and PNA (C) mice. Scale bar represents 200 μM. D. Mean adipocyte size (n=10 CON, n=12 PNA). E. Mean ± SEM glucose uptake (GU) into CON (gray bars) and PNA (black bars) adipocytes in response to varying concentrations of insulin (n=2 to 5 assays per insulin concentration). Basal uptake was higher in PNA adipocytes, but insulin sensitivity was similar. *p<0.05.

Figure 3

PNA mice exhibit impaired glucose tolerance but not insulin resistance. A. Glucose tolerance was impaired in 5 month-old PNA (closed circles) compared to CON (open circles) mice. B. Area under the curve (AUC) in CON (gray bars) and PNA (black bars) mice examined at different ages illustrates that glucose intolerance develops by 1 month of age. C. PNA mice are not insulin-resistant based on insulin tolerance testing (n=10 per group, p>0.2). *p<0.05.

Figure 4

PNA mice have impaired pancreatic response to elevated glucose. A. Mean±SEM ratios (n=8 CON, n=6 PNA) of fura-2 fluorescence at 260 and 280 nm excitation, demonstrating the impaired response of islets from PNA mice upon an increase in glucose concentration from 3 mM to 11 mM. Shaded area indicates SEM. B. Area under the curve was lower in PNA mice. *p<0.05.

Figure 5

Steroids can act directly at the islet to alter insulin release in response to a glucose challenge. DHT or DHT in combination with oestradiol (DHT+OE) impair the release of insulin in response to a high glucose challenge (n=12 mice) *p<0.05 versus control (C, ethanol vehicle) in 11 mM glucose.