Restriction of dietary energy and protein induces molecular changes in young porcine skeletal muscles.

Little is known about the molecular changes in response to dietary restriction (energy and/or protein) in young growing skeletal muscles. To profile such changes and to gain insights into the signaling molecules that could mediate the diet effects, a dedicated porcine skeletal muscle cDNA-microarray approach was used to characterize differential muscle gene expression between conventionally fed and diet-restricted (20% less protein and 7% less energy) growing pigs, reared from 9 to 21 wk of age. In both red and white muscles, diet restriction resulted in the accumulation of significantly more intramuscular fat, and in the increased expression of genes involved in substrate (protein, glycogen, and lipid) turnover, in translation and mitochondrial function, and in raising glycolytic and oxidative phosphorylation potentials. The unexpected increase in intramuscular lipids in diet-restricted growing pigs could have important health implications for restricted diets in childhood. Despite reduced circulating insulin, more genes, including several novel growth modulatory genes, had higher expression levels, indicating that the cellular response to dietary restriction is an active process. One such responsive gene, P311, was most highly expressed in striated muscles and had a differentiation-dependent increase of expression in murine C2C12 cells, suggesting a role in differentiation/postdifferentiation phenotype determination.

Postnatal myosin heavy chain isoforms in prenatal porcine skeletal muscles: insights into temporal regulation.

Our knowledge of the temporal expression of postnatal (adult) fast myosin heavy chain (MyHC) isoforms (2a, 2x, and 2b) in prenatal muscles is limited. Using the pig as a target species and large-animal model, we report on the qualitative and quantitative expression of the major post- and prenatal MyHC isoforms during gestation, as determined by TaqMan real-time PCR and immunohistochemistry. We found that postnatal fast MyHC mRNAs and proteins were expressed much earlier in the pig (gestation day 35) than was previously reported in small mammals. There was a high degree of coexpression and colocalisation of pre- and postnatal MyHC mRNAs and proteins in prenatal muscles. During a period of prenatal muscle growth (gestation days 35-77), relative expression of MyHC isoforms (embryonic > 2a > 2x > 2b) correlated with the gene order in the skeletal MyHC cluster, which suggests the possible presence of cis-acting elements on the same side as the MyHC embryonic gene associated with temporal regulation.

Development of a porcine skeletal muscle cDNA microarray: analysis of differential transcript expression in phenotypically distinct muscles.

BACKGROUND: Microarray profiling has the potential to illuminate the molecular processes that govern the phenotypic characteristics of porcine skeletal muscles, such as hypertrophy or atrophy, and the expression of specific fibre types. This information is not only important for understanding basic muscle biology but also provides underpinning knowledge for enhancing the efficiency of livestock production. RESULTS: We report on the de novo development of a composite skeletal muscle cDNA microarray, comprising 5500 clones from two developmentally distinct cDNA libraries (longissimus dorsi of a 50-day porcine foetus and the gastrocnemius of a 3-day-old pig). Clones selected for the microarray assembly were of low to moderate abundance, as indicated by colony hybridisation. We profiled the differential expression of genes between the psoas (red muscle) and the longissimus dorsi (white muscle), by co-hybridisation of Cy3 and Cy5 labelled cDNA derived from these two muscles. Results from seven microarray slides (replicates) correctly identified genes that were expected to be differentially expressed, as well as a number of novel candidate regulatory genes. Quantitative real-time RT-PCR on selected genes was used to confirm the results from the microarray. CONCLUSION: We have developed a porcine skeletal muscle cDNA microarray and have identified a number of candidate genes that could be involved in muscle phenotype determination, including several members of the casein kinase 2 signalling pathway.