Age- and Glucocorticoid-Dependent Leptin Release by Horse Adipose Tissue: In Vitro Study

In mammals, corticosteroids overall play the greatest role in stimulation of leptin synthesis and release from the adipose tissue. Some studies have shown that changes in plasma leptin and cortisol concentrations in horses can occur independently of each other. The aim of our study on horses was to evaluate the effect of different ages on the glucocorticoid-dependent leptin release from isolated adipose tissue samples in primary culture. Subcutaneous adipose tissue samples were collected from 25 cold-blood horses aged 7 months to 11 years. Samples of adipose tissue were incubated (200 mg/mL) under control conditions (Dx0), or treated with one of two doses of dexamethasone (100 ng/mL-Dx100 and 1,000 ng/mL-Dx1000) for 12 hours. Histological examination was also conducted to obtain the mean number of adipocytes in the field of view. The medium leptin concentration was analyzed in relation to the number of adipocytes in the tissue samples. A significantly higher medium leptin concentration in Dx1000 than in Dx0 was observed only in tissue samples from foals (7-12 months of age, n = 6). Significant negative correlations were found between the age of horses and the difference in medium leptin levels Dx1000 − Dx0, as well as (Dx1000 − Dx0)/million adipocytes, and (Dx1000 − Dx100)/million adipocytes. The corticosteroids-induced secretion of leptin decreased with the age of horses.