No abstract

A better understanding of the control of body fat distribution and muscle development is of the upmost importance for both human and animal physiology. This requires a better knowledge of the features and physiology of adult stem cells in adipose tissue and skeletal muscle. Thus the objective of the current study was to determine the type and proportion of these cells in growing and adult pigs. The different cell subsets of stromal vascular cells isolated from these tissues were characterized by flow cytometry using cell surface markers (CD11b, CD14, CD31, CD34, CD45, CD56, and CD90). Adipose and muscle cells were predominantly positive for the CD34, CD56, and CD90 markers. The proportion of positive cells changed with age especially in intermuscular adipose tissue and skeletal muscle where the percentage of CD90+ cells markedly increased in adult animals. Further analysis using coimmunostaining indicates that eight populations with proportions ranging from 12 to 30% were identified in at least one tissue at 7 days of age, i.e., CD90+/CD34+, CD90+/CD34−, CD90+/CD56+, CD90+/CD56−, CD90−/CD56+, CD56+/CD34+, CD56+/CD34−, and CD56−/CD34+. Adipose tissues appeared to be a less heterogeneous tissue than skeletal muscle with two main populations (CD90+/CD34− and CD90+/CD56−) compared with five or more in muscle during the studied period. In culture, cells from adipose tissue and muscle differentiated into mature adipocytes in adipogenic medium. In myogenic conditions, only cells from muscle could form mature myofibers. Further studies are now needed to better understand the plasticity of those cell populations throughout life.

Methionine is a rate-limiting amino-acid for protein synthesis but non-proteinogenic roles on lipid metabolism and oxidative stress have been demonstrated. Contrary to rodents where a dietary methionine deficiency led to a lower adiposity, an increased lipid accretion rate has been reported in growing pigs fed a methionine deficient diet. This study aimed to clarify the effects of a dietary methionine deficiency on different aspects of tissue lipid metabolism and anti-oxidant pathways in young pigs. Post-weaned pigs (9.8 kg initial body weight) were restrictively-fed diets providing either an adequate (CTRL) or a deficient methionine supply (MD) during 10 days (n=6 per group). At the end of the feeding trial, pigs fed the MD diet had higher lipid content in subcutaneous adipose tissue. Expression levels of genes involved in glucose uptake, lipogenesis but also lipolysis, and activities of NADPH enzyme suppliers were generally higher in subcutaneous and perirenal adipose tissues of MD pigs, suggesting an increased lipid turnover in those pigs. Activities of the anti-oxidant enzymes superoxide dismutase, catalase and glutathione reductase were increased in adipose tissues and muscle of MD pigs. Expression level and activity of the glutathione peroxidase were also higher in liver of MD pigs, but hepatic contents in the reduced and oxidized forms of glutathione and glutathione reductase activity were lower compared with control pigs. In plasma, superoxide dismutase activity was higher but total anti-oxidant power was lower in MD pigs. These results show that a dietary methionine deficiency resulted in increased levels of lipogenesis and lipolytic indicators in porcine adipose tissues. Decreased glutathione content in the liver and coordinated increase of enzymatic antioxidant activities in adipose tissues altered the cellular redox status of young pigs fed a methionine-deficient diet. These findings illustrate that a rapidly growing animal differently adapts tissue metabolisms when facing an insufficient methionine supply.