The Role of Adiponectin, Leptin, and Their Ratio in the Pathogenesis of Obesity and Insulin Resistance in Horses

Metabolic syndrome in horses is a multifactorial pathological condition characterized by abdominal obesity, insulin resistance, hormonal dysfunctions, and chronic low-grade inflammation. A key aspect in the pathogenesis of this syndrome is the imbalance of adipokines, particularly leptin and adiponectin, which may play a crucial role in the development of metabolic disturbances. The aim of this study was to determine the changes in leptin, adiponectin levels, and their ratio (leptin-to-adiponectin ratio, LAR) in horses with varying degrees of body condition and to evaluate their association with insulin resistance development. The study involved 18 clinically healthy horses aged 5–10 years, divided into a control group (n=9; body condition score [BCS] 4–6 according to Henneke scale) and an obese group (n=9; BCS ≥7). Serum concentrations of adiponectin and leptin were measured by enzyme-linked immunosorbent assay (ELISA), along with glucose and insulin levels. Insulin sensitivity index (RISQI) and LAR were calculated. Results demonstrated that obese horses had significantly higher leptin levels (p<0.001) and significantly lower adiponectin concentrations compared to controls. This resulted in more than a threefold increase in LAR (p<0.001), indicating marked disruption of hormonal regulation of adipose tissue. Additionally, elevated glycemia, hyperinsulinemia, and decreased RISQI values were observed, confirming insulin resistance in overweight horses. These findings suggest that LAR can serve as a sensitive early biomarker of metabolic distress and insulin resistance in horses. Its use is recommended for early identification of at-risk animals, monitoring the effectiveness of preventive measures, and substantiating personalized strategies for diet and physical activity modification aimed at preventing complications associated with metabolic syndrome.