The aim of the research was to compare gene transcription profiles of Musculus longissimus dorsi (MLD) between pigs fed diets with high (HED) or low (LED) energy contents. Two groups of 4 Casertana pigs were reared from 3 to 12 months of age in the same environmental conditions and fed HED or LED. In the HED, the ave rage daily gain and back fat thickness were significantly (P < 0.05) higher than in LED pigs. Differential expression of genes in MLD of pigs fed diets with different energy density was assessed by a human high-density complementary DNA (cDNA) muscle microarray consisting of 4670 probes and further confirmed by quantitative real time RT-PCR analysis. Seven of the genes up-regulated in MLD of HED pigs were involved in the glycolytic and oxidative metabolism (phosphoglycerate mutase 2, glyceraldehyde-3-phosphate dehydrogenase, NADH dehydrogenase ubiquinone1 beta 9, muscle pyruvate kinase, enolase 3, muscle creatine kinase, isocitrate dehydrogenase 3 (NAD+) gamma) and four in the contractile apparatus (tropomyosin 1 alpha, troponin C2, fast, fast skeletal myosin light chain 2, troponin T3, skeletal, fast). Instead, HED diet reduced the level of expression of muscle proteins associated with slow fibre type (troponin T1, skeletal, slow, supervillin, myosin binding protein C, slow type, titin, myosin, heavy polypeptide 7, beta, calponin homology-associated smooth muscle) and signal transduction (SH3-binding domain protein 5-like, hypothetical protein FLJ21438, protein kinase cAMP-dependent, catalytic, rho guanine nucleotide exchange factor 15). The down-regulation of CTSB was also observed for HED group. From the results it can be assumed that high energy content of the diet influence physiological processes in the muscle tissue by switching slow fibres into fast reacting fibres and thus enhancing meat quality.
