Skeletal muscle metabolism in neonatal lean and obese pigs.

Nine lean and nine obese male pigs were examined at 14 d of age. The biceps femoris muscle of the obese pigs had a greater (P less than .05) percentage dry matter, protein and triglycerides than the muscle of lean pigs. The rate of oxidation of glucose to CO2 by the biceps femoris muscle was not influenced (P greater than .05) by phenotype but the rate was greater (P less than .05) when incubations were conducted in either the presence of leucine or palmitate. Glycolytic flux was lower (P less than .05) in the muscle of the obese pigs than in the muscle of lean pigs. Glycolytic flux was enhanced (P less than .05) by addition of leucine or palmitate to the incubation media. The rate of release of lactate, pyruvate, alanine, glutamine and glutamate into the media was similar between phenotypes and was not influenced by the presence of leucine or palmitate (P greater than .05). The total amount of leucine transaminated was greater (P less than .05) in the muscle of lean pigs than in the muscle of obese pigs. This was because of greater (P less than .05) rates of decarboxylation of leucine and release of alpha-ketoisocaproic acid into the media by the muscle of lean pigs when compared with the muscle of obese pigs. However, the ratio of leucine decarboxylated to alpha-ketoisocaproic acid released was similar (P greater than .05) between the two phenotypes. The ratio of palmitate oxidized (to CO2) to palmitate esterified was greater (P less than .01) in the muscle of the lean pigs than in the muscle of obese pigs. This latter finding may partially explain the greater triglyceride content of obese pig muscle. The generally lower rates of oxidation of substrates and of glycolytic flux in the biceps femoris muscle of obese pigs, when compared with lean pigs, may be associated with differences in body composition that develop during growth of lean and obese pigs.