Reproduction Abstracts

Polycystic ovary syndrome, a common endocrine condition affecting up to 10% of women of reproductive age, is associated with an increased risk of developing insulin resistance and obesity. Obesity is associated with increased energy intake or reduced energy expenditure. In this context, postprandial thermogenesis (PPT), is an important constituent of energy expenditure.

Our lab utilizes a clinically realistic ovine model of PCOS, where pregnant Scottish Greyface ewes are treated biweekly with either 100 mg of testosterone propionate (TP) or vehicle control (C) from days 62 to 102 of gestation. We measured PPT in adult female offspring (C=11; TP=4) through implantation of datalogger thermometers into subcutaneous fat. Glucose tolerance tests were a second experimental readout.

Prenatally androgenized female sheep had normal birthweight and postnatal growth to adolescence. However, as adults (2.5 years old), TP-exposed animals had increased body weight (P<0.05), increased fasting insulin concentrations (P<0.05), and decreased fasting glucose to insulin ratios (P<0.05). TP exposed animals showed decreased peak postprandial increase in temperature (P<0.05) but this was not primarily a function of increased body weight as a difference in PPT was also observed between a subset of matched obese controls and TP exposed animals. Prenatally androgenized females also demonstrated increased latency from commencement of feeding to maximal postprandial temperature (P<0.05) when compared with controls. The reduction in PPT and increased time to reach maximal temperature post-feeding correlated positively with increased levels of fasting insulin (r=0.56; P<0.05 and r=0.68; P<0.05 respectively).

Prenatally androgenized female sheep are destined to have increased body weight most likely due to a reduction in the capacity for energy expenditure, which is mirrored in women with PCOS. This gives us a unique opportunity to investigate the molecular regulation of PPT to develop new interventions to target obesity in PCOS.