Regulation of hepatic peroxisome proliferator‐activated receptor α expression but not adiponectin by dietary protein in finishing pigs

Soy protein regulates adiponectin and peroxisome proliferator‐activated receptor α (PPARα) in some species, but the effect of dietary soy protein on adiponectin and PPARα in the pig has not been studied. Therefore, the objective of this study was to determine whether soya bean meal reduction or replacement influences serum adiponectin, adiponectin mRNA, serum metabolites and the expression of PPARα and other genes involved in lipid deposition. Thirty‐three pigs (11 pigs per treatment) were subjected to one of three dietary treatments: (i) reduced crude protein (CP) diet containing soya bean meal (RCP‐Soy), (ii) high CP diet containing soya bean meal (HCP‐Soy) or (iii) high CP diet with corn gluten meal replacing soya bean meal (HCP‐CGM) for 35 days. Dietary treatment had no effect on overall growth performance, feed intake or measures of body composition. There was no effect of dietary treatment on serum adiponectin or leptin. Dietary treatment did not affect the abundance of the mRNAs for adiponectin, PPARα, PPARγ2, lipoprotein lipase or fatty acid synthase in adipose tissue. The mRNA expression of PPARα, PPARγ2, lipoprotein lipase or fatty acid synthetase in loin muscle was not affected by dietary treatment. In liver tissue, the relative abundance of PPARα mRNA was greater (p < 0.05) in pigs fed the HCP‐Soy diets when compared to pigs fed RCP‐Soy or HCP‐CGM diets. Hepatic mRNA expression of acyl‐CoA oxidase or fatty acid synthase was not affected by dietary treatment. Western blot analysis indicated that hepatic PPARα protein levels were decreased (p < 0.05) in pigs fed the RCP‐Soy diets when compared to pigs fed the HCP‐Soy diets. These data suggest that increasing the soy protein content of swine diets increases hepatic expression of PPARα without associated changes in body composition.