Breed difference and regulatory role of CRTC3 in porcine intramuscular adipocyte

The cAMP responsive element binding protein (CREB)-regulated transcription coactivator 3 (CRTC3) is a member of the CRTC protein family and plays an important role in energy metabolism. The aim of this study was to determine if the expression of porcine CRTC3 is related to intramuscular fat (IMF) deposition and meat quality in Heigai pigs (a local fatty breed in China) and Duroc × Landrace × Yorkshire (DLY) pigs (a lean crossbred pig widely cultured in China). In addition, the effect of ectopic expression of CRTC3 on gene expression in porcine IMF adipocytes was also examined. Our results showed that Heigai pigs had lower lean percentage, thicker back fat thickness and smaller loin muscle area than DLY pigs. Compared with DLY pigs, Heigai pigs had higher marbling scores, better meat color and higher IMF contents and triglyceride concentrations. Higher levels of oxidative metabolic enzyme and expression of the slow oxidative muscle fiber-related genes were observed in longissimus dorsi muscle and psoas major muscle (P < 0.05) from Heigai pigs. Notably, CRTC3 and adipocyte-specific marker genes were highly expressed in muscle tissues of Heigai pigs. The expression of lipolysis-related genes ATGL and HSL were lower in Heigai muscles. Moreover, forced expression of CRTC3 promoted lipid accumulation and increased the expression of PPARγ, C/EBPα, leptin and FABP4 (P < 0.05), whereas it decreased the expression of ATGL and HSL in IMF adipocytes. These results suggest that CRTC3 expression is associated with lipid accumulation and IMF deposition in pigs.