Rapid Communication: Porcine CRTC3 gene clone, expression pattern, and its regulatory role in intestinal epithelial cells

CRTC3 Regulates the Lipid Metabolism and Adipogenic Differentiation of Porcine Intramuscular and Subcutaneous Adipocytes by Activating the Calcium Pathway

Fat deposition, especially the intramuscular (IM) fat deposition, is directly associated with meat quality. The cyclic adenosine monophosphate (cAMP)-responsive element binding-protein (CREB)-regulated transcription coactivator 3 (CRTC3) plays an important role in energy metabolism and various biological processes. The expression of porcine CRTC3 in skeletal muscle is positively associated with intramuscular fat deposition and possesses the capacity to control the intramuscular (IM) adipocyte morphology. However, the metabolic effects and transcriptional mechanism of CRTC3 in porcine intramuscular (IM) adipocytes as well as the regulatory mechanism of CRTC3 on porcine adipocyte differentiation have not been studied. Here, we utilized metabolomics and RNA sequencing (RNA-seq) to determine the metabolic and transcriptome profiles of CRTC3-overexpressing IM adipocytes. Moreover, the effect and regulation mechanism of CRTC3 on porcine IM and subcutaneous (SC) adipocyte differentiation were also studied. Our results showed that CRTC3 overexpression dramatically altered the metabolites in IM adipocytes. Glycerophospholipid (GP) metabolism and related genes were significantly changed in CRTC3-overexpressing IM adipocytes. Moreover, we demonstrated that CRTC3 overexpression promotes adipogenic differentiation by upregulating the Ca²⁺-cAMP signaling pathway in IM and SC adipocytes. We showed alterations in metabolites and in the expression of genes involved in lipid metabolism in CRTC3-overexpressing adipocytes and demonstrated the regulatory mechanism of CRTC3 on the adipogenic differentiation of porcine adipocytes. These results provide new insights into the regulatory roles of CRTC3 in porcine adipocytes, which could be an important target to regulate fat deposition in animals.

Comprehensive evaluation of the metabolic effects of porcine CRTC3 overexpression on subcutaneous adipocytes with metabolomic and transcriptomic analyses

BACKGROUND

Meat quality is largely driven by fat deposition, which is regulated by several genes and signaling pathways. The cyclic adenosine monophosphate (cAMP) -regulated transcriptional coactivator 3 (CRTC3) is a coactivator of cAMP response element binding protein (CREB) that mediates the function of protein kinase A (PKA) signaling pathway and is involved in various biological processes including lipid and energy metabolism. However, the effects of CRTC3 on the metabolome and transcriptome of porcine subcutaneous adipocytes have not been studied yet. Here, we tested whether porcine CRTC3 expression would be related to fat deposition in Heigai pigs (a local fatty breed in China) and Duroc×Landrace×Yorkshire (DLY, a lean breed) pigs in vivo. The effects of adenovirus-induced CRTC3 overexpression on the metabolomic and transcriptomic profiles of subcutaneous adipocytes were also determined in vitro by performing mass spectrometry-based metabolomics combined with RNA sequencing (RNA-seq).

RESULTS

Porcine CRTC3 expression is associated with fat deposition in vivo. In addition, CRTC3 overexpression increased lipid accumulation and the expression of mature adipocyte-related genes in cultured porcine subcutaneous adipocytes. According to the metabolomic analysis, CRTC3 overexpression induced significant changes in adipocyte lipid, amino acid and nucleotide metabolites in vitro. The RNA-seq analysis suggested that CRTC3 overexpression alters the expression of genes and pathways involved in adipogenesis, fatty acid metabolism and glycerophospholipid metabolism in vitro.

CONCLUSIONS

We identified significant alterations in the metabolite composition and the expression of genes and pathways involved in lipid metabolism in CRTC3-overexpressing adipocytes. Our results suggest that CRTC3 might play an important regulatory role in lipid metabolism and thus affects lipid accumulation in porcine subcutaneous adipocytes.

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.