Resveratrol: therapeutic role in metabolic and reproductive function in obese broodmares

Abstract

Resveratrol, a naturally-occurring phytoestrogenic stilbene derivative, has been shown to elicit shifts in physiology of obese animals consuming a high calorie or ad libitum diet toward that of lean counterparts. This study was designed to evaluate effects of oral resveratrol supplementation on parameters of metabolic health and reproductive cyclicity in obese mares on pasture. Seventeen healthy, mares were matched by age and assigned to obese control (OBC; n=5, mean BCS=7.4±0.3), obese supplemented with 5g/d resveratrol (OBR; n=6, mean BCS=7.4±0.2) or non-obese control (NOC; n=6, mean BCS=5.4±0.1) treatments. Control horses received the resveratrol carrier paste. Across three consecutive estrous cycles, morphometric measurements were collected biweekly and follicular dynamics were evaluated via transrectal ultrasonography every other day. Frequently-sampled intravenous glucose tolerance tests were conducted pre- and post- treatment. Insulin and glucose kinetics were analyzed via minimal model. Resveratrol supplementation had no discernible effect on reproductive parameters (P>0.05), however obese mares had more (6 vs. 0) hemorrhagic anovulatory follicles. Neither resveratrol treatment nor time on study influenced morphometric measurements or minimal model parameters (raw data or data adjusted for animal size). As a whole, horses became more insulin resistant over time (Si value < 0.78 (1/[mU/L"min]). NOC horses had lower (P=0.01) acute insulin response to glucose relative to OBC or OBR. Although resveratrol supplementation did not elicit detectable responses in this study, promising results in other species warrant further investigation of the compound in horses, including exploration of bioavailability and possible effects at the tissue or cellular levels.