ORIGINAL ARTICLE Endurance Training Increases Leptin Expression in the Retroperitoneal Adipose Tissue of Rats Fed with a High-Sugar Diet

The Author(s) 2013. This article is published with open access at Springerlink.com Abstract The presence of leptin receptors in white adi-pose tissue (WAT) suggests a type of peripheral control during the development of obesity and other metabolic disorders. Both diet composition and exercise influence serum leptin; however, the effect of their combination on long-term WAT leptin metabolism is unknown. In this study, rats fed with standard or high-sugar diets (HSD) were simultaneously subjected to running training for 4-and 8-week periods, and the retroperitoneal WAT (rWAT) was evaluated for adipocyte cell size, lipid and catechol-amine content, Lep, OB-Rb and Ucp2 mRNA transcription levels, and circulating leptin and non-esterified fatty acids (NEFA). The HSD groups displayed a higher adiposity index and rWAT weight, Lep mRNA and protein upregu-lation, and a period-dependent effect on OB-Rb mRNA expression. Exercise decreased serum leptin and upregu-lated the OB-Rb mRNA levels. However, in rats fed with an HSD, the increase in OB-Rb mRNA and reduction in catecholamine levels resulted in a high level of adiposity and hyperleptinemia. The combination of training and an HSD decreases the NEFA levels and upregulating the Ucp2 mRNA expression in the 4-week period, while downregu-lating the Ucp2 mRNA expression in the 8-week period without changing the NEFA levels. Our results suggest that an HSD induces an increase in leptin expression in rWAT, while reducing adipocytes via leptin-mediated lipolysis after an 8-week period. In exercised rats fed an HSD, TAG synthesis and storage overlaps with lipolysis, promoting fat store development and Lep mRNA and plasma protein upregulation in adult rats