Effects of dietary protein levels and genetic background on growth and carcass performance, serum parameter, enzyme and transcription factor mRNA ezpression in subcutaneous adipose tissues in swine
This study was mainly to investigate the effects of dietary crude protein (CP) levels on growth and carcass performance, serum parameter and the mRNA expression of enzymes and transcription factors in subcutaneous adipose tissues in obese and lean swine. Twenty seven obese-type Ningxiang breed fattening pigs and thirty six lean-type hybrid (Duroc × Landrace × Yorkshire) fattening pigs were randomly allocated to three by two groups, fed low, middle and high CP diets respectively for a 46-day period. The CP levels in the diets were 10.41％ (low), 12.91％ (middle) and 15.43％ (high) for Ningxiang; 12.91％ (low), 15.43％ (middle) and 19.66％ (high) for the hybrid according to their own standard maintenance requirement, respectively. All diets were identical in calories. On day 46, blood samples were collected for analysis of serum lipoprotein, total cholesterol, triglycerides and leptin levels. Following the blood collection, 4 pigs from each group were killed and subcutaneous adipose tissues were collected for the analysis of mRNA expression of lipogenic and lipolytic enzymes and transcription factors. Results indicated that dietary CP levels had no significant effect on growth and carcass performance, serum parameter and mRNA expression of lipogenic and lipolytic key enzymes and transcription factors except leptin and sterol regulatory element-binding protein-1c (SREBP-1c). Increases in dietary CP levels resulted in the increase of leptin and decrease of SREBP-1c mRNA expression in subcutaneous adipose tissues. However, there were marked differences in growth and carcass performance, serum parameter and mRNA expression of lipogenic and lipolytic key enzymes and transcription factors between the two breed. The percentage of fat and feed gain ratio, serum triglycerides, total cholesterol, low density lipoprotein and leptin content and the levels of hormone-sensitive lipase (HSL), lipoprotein lipase (LPL) and peroxisome proliferator-activated receptor-γ (PPARγ) mRNA in subcutaneous adipose tissues were significantly higher in Ningxiang pigs. And the average fat thickness was positively correlated with the abundance of HSL, LPL, leptin, PPARγ and liver X receptor-α (LXRα) mRNA in subcutaneous adipose tissues. Furthermore, leptin was positively correlated with LPL and LXRα, and was negatively correlated with SREBP-1c of mRNA expresstion in subcutaneous adipose tissues. These findings suggest that obese and lean genotype fattening pigs have distinct manners in lipid metabolism, the Ningxiang deposited higher energy than hybrid. And some lipid key enzymes (HSL, LPL) and transcription factors (PPARγ, SREBP-1c, LXRα) may participate in the regulation of lipid metabolism via leptin signaling. Dietary protein may indirectly act on these enzymes and transcription factors to influence the subcutaneous lipid metabolism.
Key Laboratory for Agro-ecological Processes in Subtropical Region,, The Chinese Academy ofSciences, Key Laboratory for Agro-ecological Processes in Subtropical Region,, The Chinese Academy of Sciences Key Laboratory of Animal Nutrition and Feed Science, Wuhan Polytechnic University, Hubei,Wuhan 43002 Key Laboratory for Agro-ecological Processes in Subtropical Region,, The Chinese Academy ofSciences,