Relation of Leptin Gene Polymorphism to the Circulating Leptin, Insulin, Estradiol, and Progesterone Hormones in Mares with High Rump Fat

Abstract

Equine metabolic syndrome is a growing concern usually associated with increased insulin and leptin concentrations. To investigate the relations of obesity determined by measuring the rump fat (RF) with ovarian hormones, leptin, and leptin gene polymorphism, cyclic mares (n=36) were categorized based on RF thickness estimated by the ultrasonography and body condition score (BCS) into obese (RF>5mm; BCS >5), moderate (RF>3≤5 mm;BCS >3≤5) and lean animals (RF<3mm; BCS<3). The circulating estradiol, progesterone, insulin, and leptin were analyzed. The polymorphism of the leptin gene was performed and compared for obese, moderate and lean mares. Depending on increased RF, the obesity was associated with increased BCS (P<0.0001) and leptin (P<0.0001), insulin (P<0.01), and P4 (P<0.0001). Obese mares of leptin genotype BB had the highest leptin (1146±420 pg/ml), insulin (7.42±0.89 μU/l) and progesterone (22.69±9.34 ng/ml), but minimum estradiol (101±54 pg/ml) concentrations. Mares of leptin genotype AA had the highest RF (P<0.0001). The interaction of leptin genotype and obesity had affected RF and all hormone concentrations with no significant effect on the BCS. In conclusion, obesity in cyclic mares altered ovarian hormones, insulin and leptin concentrations. The hyperleptinemia, and hyperinsulinemia were associated with the leptin genotype BB but neither to the adiposity (RF) nor BCS.