Reduced dietary lysine enhances proportion of oxidative fibers in porcine skeletal muscle

The present study was conducted to elucidate the effects of dietary lysine levels on the proportion of oxidative muscle fibers in porcine muscle. Two 6-week-old barrows from each of five litters were used. Each littermate was assigned to one of two diets, control (lysine content: 1.16%) or low lysine (LL) diet (lysine content: 0.73%). The diets were iso-energetic and iso-protein, and contained all essential amino acids (apart from lysine) in the recommended amounts. The pigs were fed these diets for 3 weeks. Citrate synthase (EC 4.1.3.4) activity in longissimus dorsi and rhomboideus muscles was higher in the LL group (P < 0.05). In both muscles, pigs fed the LL diet had a higher proportion of muscle fiber with activities of reduced nicotinic amide adenine dinucleotide dehydrogenase (EC 1.6.5.3, P < 0.01). The abundance of mRNA of peroxisome proliferator-activated receptor gamma coactivator 1 alpha in rhomboideus muscle was higher in the LL group (P < 0.05), and those of peroxisome proliferator-activated receptor gamma 2 were higher in both longissimus dorsi and rhomboideus muscles in the LL group (P < 0.05). We conclude that reduced intake of dietary lysine enhances proportion of oxidative muscle fiber, and hence oxidative capacity of porcine muscle.