Sirtuin 1 (Sirt1) plays an important role in fat metabolism. In the current study, we examined the breed differences in Sirt1 between Jinhua pigs (a fatty breed of China) and Landrace pigs (a leaner breed). In addition, the effect of insulin on the gene expression of Sirt1 and the major lipase, adipose triglyceride lipase (ATGL), and hormone-sensitive lipase (HSL) in fat metabolism was also studied in vitro. Compared with the Landrace pigs, the BW of Jinhua pigs was less (P < 0.01), whereas the body fat content were greater (P < 0.01). The protein content and the mRNA abundance of Sirt1 in Jinhua pigs were less (P < 0.01) in subcutaneous adipose tissues compared with the Landrace pigs. Likewise, the mRNA abundance of ATGL and HSL were also less (P < 0.01) in Jinhua pigs. In vitro, treatment with a different dose of insulin (10, 50 and 100 nM) decreased (P < 0.01) glycerol release and the mRNA abundance of Sirt1, ATGL, and HSL in porcine adipocytes. Likewise, treatment with 50 nM insulin for 24 and 48 h also decreased (P < 0.05) glycerol release and the expression of Sirt1, ATGL, and HSL in porcine adipocytes. Furthermore, insulin and Sirt1-specific small interfering RNA treatment decreased (P < 0.01) the expression of Sirt1, ATGL, and HSL compared with the control or insulin treatment. These results indicate that insulin may regulate transcription of Sirt1, ATGL, and HSL in porcine adipocytes and provide information for manipulating these gene expressions in regulating fat metabolism in pigs.

The forkhead transcription factor FoxO1 has been studied as the most downstream targets of the signaling pathway in mammals, and played a key role in adipogeneic, cell cycle progression, and energy metabolism and so on. The aim of this study was to investigate the tissue-specifi c and weight-dependent expression patterns of FoxO1 gene in porcine omental adipose tissue and its relation to adipose deposition. Sixty female Duroc × Landrace × Yorkshire pigs in 5 groups, each group containing twelve pigs weighing 1, 20, 40, 60, and 90 kg were used to study developmental expression of FoxO1 gene by means of semi-quantitative RT-PCR. The results showed that FoxO1 mRNA was expressed at a higher level in heart, brain, omental adipose tissue, skeletal muscle, liver and spleen, at a moderate level in kidney, lung, and peritoneal adipose tissue, and at a less level in duodenum, subcutaneous adipose tissue and pancreas. In addition, our data also showed that the expression levels of FoxO1 gene was lowest in the pigs at 20 kg, and continuously increased from 20 to 90 kg body weight (P<0.05). Furthermore, a close positive correlation between the expression levels of FoxO1 gene and the adipose deposition rate was found in pigs (r=0.84, P<0.05).