Submitted to: Journal of Nutritional Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 1, 2007
Publication Date: April 1, 2008
Citation: Ramsay, T.G., Mitchell, A.D. 2008. Impact of dietary protein content on uncoupling protein mRNA abundance in swine. Comparative Biochemistry and Physiology. 149:562-571. Interpretive Summary: Dietary protein insufficiency has been shown to produce excess fat and to affect body heat production. The uncoupling proteins are thought to be involved in waste heat production, reducing the energy efficiency of growth in animals. Previous studies have demonstrated that uncoupling proteins are affected by dietary protein insufficiency. This study attempted to determine whether the uncoupling proteins 2 and 3 are affected by dietary protein content in finishing swine. The data demonstrate that the uncoupling proteins are responsive to dietary protein in swine. Secondly, uncoupling protein response to dietary protein is highly tissue specific. This uncoupling protein response appears to be the result of changes in serum free fatty acids that produces a cascade of changes in regulatory gene expression, that concludes with changes in uncoupling protein expression. These results suggest that reduction in dietary protein can alter nutrient partitioning, with subsequent downstream regulation of genes that are important for nutrient metabolism and energy production.
Technical Abstract: The present study was designed to determine if dietary protein can alter uncoupling protein (UCP) expression in swine, as has been shown in rats, and attempt to identify the mechanism. Eight pigs (~50 kg body weight) were fed an 18% crude protein (CP) diet while another eight pigs were switched to a diet containing 12% crude protein (CP) and fed these diets until 110 kg body weight. The outer (OSQ) and middle (MSQ) subcutaneous adipose tissues, liver, leaf fat, longissimus (LM), red portion of the semitendinosus (STR) and the white portion of the ST (STW) were analyzed for gene expression by real-time PCR. Feeding of 12% CP did not alter growth or carcass composition, relative to 18% CP (P > 0.05). Serum growth hormone, non-esterified fatty acids and triglycerides were reduced with the feeding of 12% CP (P < 0.05). The UCP2 mRNA abundance was reduced in LM, STR, MSQ and OSQ with feeding of 12% CP (P < 0.05), as was UCP3 mRNA abundance in MSQ and STW (P < 0.01). Peroxisome proliferation activated receptor alpha (PPAR alpha) and PPAR gamma were reduced in MSQ and STR (P < 0.05) with feeding 12% CP as was the PPAR alpha regulated protein, acyl CoA oxidase (ACOX, P < 0.05). These data suggest that feeding 12% CP relative to 18% CP reduces serum NEFA, which reduces PPAR alpha and PPAR gamma expression and consequently reduces UCP2 lipoperoxidation in OSQ and STR and also reduced UCP3 associated fatty acid transport in MSQ and STW.