Leptin dependent control of testosterone regulated hepatic lipid metabolism

Results: Array analysis revealed that many hepatic lipogenic genes were increased in male ZDF rat livers treated with TU. Interestingly, SREBP-1c, a key transcriptional activator of lipogenic genes and PGC-1 , an activator of SREBP-1c were induced while small heterodimer partner, a transcriptional inhibitor of lipogenic genes was suppressed by TU treatment. Exploring signaling pathways for these effects, we observed that the hepatic activated forms of STAT3 and AMPK, two known inhibitors of hepatic lipogenesis, were decreased in TU treated rat. Moreover, we observed that DHT could block the induction of STAT3 and AMPK phosphorylation in treated primary human hepatocytes. Preliminarily, in the leptin receptor positive zucker diabetic lean male rats, we observed that TU treatment has an oppose effect on the hepatic lipogenic genes, suggesting that hepatic leptin signaling may influence androgen signaling. Further insight into the relationship between androgen deficiency and the leptin system may help improve treatment of the metabolic syndrome. Population based studies have established that androgen deficiency in males correlates with type 2 diabetes, visceral adiposity, and metabolic syndrome. Androgen therapy has been investigated as a possible treatment regime to combat these disorders. However, the molecular mechanism of androgen effects on these diseases still remain poorly understood. The zucker diabetic fatty (ZDF) rat, containing a mutation in the leptin receptor, is a well-investigated model of obesity and type 2 diabetes. Male rats are characterized as androgen deficient and spontaneously develop obese, hyperlipidemia, hyperglycemia and hyperinsulinemia. In this study, we used ZDF male rats as a model of metabolic syndrome to investigate the effects of testosterone administration on the development of the metabolic conditions.