Differences between porcine longissimus thoracis and semitendinosus intramuscular fat content and the regulation of their preadipocytes during adipogenic differentiation.

Intramuscular fat (IMF) plays an important role in pork quality. However, differences in the adipogenic regulation of IMF content between pig longissimus thoracis (LT) and semitendinosus (ST) remain unclear. Here, we found that IMF content of 180-day-old pig LT was greater than that of pig ST. Furthermore, lipid accumulation was earlier and greater in LT intramuscular preadipocytes (L-IMA) than in ST intramuscular preadipocytes (S-IMA) during differentiation. Interestingly, glucose consumption was lower in L-IMA than in S-IMA. Moreover, monounsaturated fatty acid content was greater in L-IMA than in S-IMA, whereas polyunsaturated fatty acid content was lower. Levels of the expression of key adipogenic genes were higher in L-IMA than S-IMA. Compared with S-IMA, adipogenic signals were more activated in L-IMA after adipogenic induction. In conclusion, IMF deposition differences between pig LT and ST were due to different glucose consumption, fatty acid composition, expression of key adipogenic genes and level of activating adipogenic signals between S-IMA and L-IMA during adipogenesis.

PDGFRα Regulated by miR-34a and FoxO1 Promotes Adipogenesis in Porcine Intramuscular Preadipocytes through Erk Signaling Pathway.

Suitable intramuscular fat (IMF) content improves porcine meat quality. The vital genes regulating IMF deposition are necessary for the selection and breeding of an IMF trait. However, the effect and mechanism of PDGFRα on IMF deposition are still unclear. Here, PDGFRα is moderately expressed in porcine longissimus dorsi muscle (LD), whereas it highly expressed in white adipose tissue (WAT). Moreover, PDGFRα-positive cells were located in the gaps of LD fibers which there were IMF adipocytes. Compared with 180-day-old and lean-type pigs, the levels of PDGFRα were much higher in one-day-old and fat-type pigs. Meanwhile the levels of PDGFRα gradually decreased during IMF preadipocyte differentiation. Furthermore, PDGFRα promoted adipogenic differentiation through activating Erk signaling pathway. Based on PDGFRα upstream regulation analysis, we found that the knockdown of FoxO1 repressed lipogenesis by downregulating PDGFRα, and miR-34a inhibited adipogenesis through targeting PDGFRα. Collectively, PDGFRα is a positive regulator of IMF deposition. Therefore, we suggest that PDGFRα is a possible target to improve meat quality.