Effects of dietary protein/carbohydrate ratio on fat deposition and gene expression of peroxisome proliferator activated receptor γ and heart fatty acid-binding protein of finishing pigs

The present study was conducted to investigate the effect of dietary protein/carbohydrate (CH2O) ratio on fat deposition and expression of peroxisome proliferator activated receptor γ (PPARγ) and heart fatty acid-binding protein (H-FABP) genes in muscle and subcutaneous adipose tissue in pigs. Twenty pigs (73.9 ± 1.2 kg BW) were used in a single factorial experiment, and allocated by BW and ultrasound backfat thickness to the two treatments: low protein/CH2O ratio (LP; 11.2% CP and 68.2% CH2O for phase I, and 10.1% CP and 69.3% CH2O for phase II) diet, or high protein/CH2O ratio (HP; 22.7% CP and 58.3% CH2O) diet. Pigs were housed individually in pens, and had ad libitum access to feed and water. After 80-d feeding, 6 pigs from each treatment were selected and slaughtered. Dietary protein/CH2O ratio had no effect on growth performance; however, the intramuscular fat (IMF) in longissimus muscle (LM) was increased (P < 0.01) when the LP diet was fed. Correspondingly, Warner-Bratzler sheer force of LM in the LP pigs was lower (P < 0.05) than the HP pigs. The LP increased mRNA levels of PPARγ (P < 0.05) and H-FABP (P = 0.09) in LM but not in subcutaneous fat, although the difference of H-FABP gene expression in LM was not statistically significant. The mRNA abundance of PPARγ in muscle correlated positively with IMF content (P < 0.05). The results indicated that an increase in IMF but not subcutaneous fat in pigs fed the LP diet is related to tissue-specific activation of PPARγ and H-FABP mRNA expression, especially the PPARγ gene.