Knockdown of VEGFB/VEGFR1 Signaling Promotes White Adipose Tissue Browning and Skeletal Muscle Development.

It has been demonstrated that vascular endothelial growth factor B (VEGFB) and vascular endothelial growth factor receptor 1 (VEGFR1) play a vital role in regulating vascular biological function. However, the role of VEGFB and VEGFR1 in regulating fat deposition and skeletal muscle growth remains unclear. Therefore, this study was conducted to investigate the effects of VEGFB and VEGFR1 on fat deposition and skeletal muscle growth in mice. Our results showed that knockdown of VEGFB decreased body weight and iWAT index, stimulated the browning of mice iWAT with increased expression of UCP1, decreased the diameters of adipocytes, and elevated energy expenditure. In contrast, knockdown of VEGFB increased gastrocnemius (GAS) muscle index with increased proliferation of GAS muscle by expression of PCNA and Cyclin D1. Meanwhile, knockdown of endothelial VEGFR1 induced the browning of iWAT with increased expression of UCP1 and decreased diameters of adipocytes. By contrast, knockdown of endothelial VEGFR1 inhibited GAS muscle differentiation with decreased expression of MyoD. In conclusion, these results suggested that the loss of VEGFB/VEGFR1 signaling is associated with enhanced browning of inguinal white adipose tissue and skeletal muscle development. These results provided new insights into the regulation of skeletal muscle growth and regeneration, as well as fat deposition, suggesting the potential application of VEGFB/VEGFR1 as an intervention for the restriction of muscle diseases and obesity and related metabolic disorders.

VEGFB Promotes Myoblasts Proliferation and Differentiation through VEGFR1-PI3K/Akt Signaling Pathway.

It has been demonstrated that vascular endothelial growth factor B (VEGFB) plays a vital role in regulating vascular biological function. However, the role of VEGFB in regulating skeletal muscle cell proliferation and differentiation remains unclear. Thus, this study aimed to investigate the effects of VEGFB on C2C12 myoblast proliferation and differentiation and to explore the underlying mechanism. For proliferation, VEGFB significantly promoted the proliferation of C2C12 myoblasts with the upregulating expression of cyclin D1 and PCNA. Meanwhile, VEGFB enhanced vascular endothelial growth factor receptor 1 (VEGFR1) expression and activated the PI3K/Akt signaling pathway in a VEGFR1-dependent manner. In addition, the knockdown of VEGFR1 and inhibition of PI3K/Akt totally abolished the promotion of C2C12 proliferation induced by VEGFB, suggesting that VEGFB promoted C2C12 myoblast proliferation through the VEGFR1-PI3K/Akt signaling pathway. Regarding differentiation, VEGFB significantly stimulated the differentiation of C2C12 myoblasts via VEGFR, with elevated expressions of MyoG and MyHC. Furthermore, the knockdown of VEGFR1 rather than NRP1 eliminated the VEGFB-stimulated C2C12 differentiation. Moreover, VEGFB activated the PI3K/Akt/mTOR signaling pathway in a VEGFR1-dependent manner. However, the inhibition of PI3K/Akt/mTOR blocked the promotion of C2C12 myoblasts differentiation induced by VEGFB, indicating the involvement of the PI3K/Akt pathway. To conclude, these findings showed that VEGFB promoted C2C12 myoblast proliferation and differentiation via the VEGFR1-PI3K/Akt signaling pathway, providing new insights into the regulation of skeletal muscle development.

Hyodeoxycholic acid (HDCA) suppresses intestinal epithelial cell proliferation through FXR-PI3K/AKT pathway, accompanied by alteration of bile acids metabolism profiles induced by gut bacteria.

Bile acids (BAs) have been implicated in regulation of intestinal epithelial signaling and function. This study aimed to investigate the effects of hyodeoxycholic acid (HDCA) on intestinal epithelial cell proliferation and explore the underlying mechanisms. IPEC-J2 cells and weaned piglets were treated with HDCA and the contributions of cellular signaling pathways, BAs metabolism profiles and gut bacteria were assessed. In vitro, HDCA suppressed IPEC-J2 proliferation via the BAs receptor FXR but not TGR5. In addition, HDCA inhibited the PI3K/AKT pathway, while knockdown of FXR or constitutive activation of AKT eliminated the inhibitory effects of HDCA, suggesting that FXR-dependent inhibition of PI3K/AKT pathway was involved in HDCA-suppressed IPEC-J2 proliferation. In vivo, dietary HDCA inhibited intestinal expression of proliferative markers and PI3K/AKT pathway in weaned piglets. Meanwhile, HDCA altered the BAs metabolism profiles, with decrease in primary BA and increase in total and secondary BAs in feces, and reduction of conjugated BAs in serum. Furthermore, HDCA increased abundance of the gut bacteria associated with BAs metabolism, and thereby induced BAs profiles alternation, which might indirectly contribute to HDCA-suppressed cell proliferation. Together, HDCA suppressed intestinal epithelial cell proliferation through FXR-PI3K/AKT signaling pathway, accompanied by alteration of BAs metabolism profiles induced by gut bacteria.

cis 9, trans 11, but not trans 10, cis 12 CLA isomer, impairs intestinal epithelial barrier function in IPEC-J2 cells and mice through activation of GPR120-[Ca2+]i and the MLCK signaling pathway.

This study aimed to investigate the effects of conjugated linoleic acid (CLA) on intestinal epithelial barrier function and explore the underlying mechanisms. IPEC-J2 cells and mice were treated with different CLA isomers. The intestinal epithelial barrier function determined by transepithelial electrical resistance (TEER), the expression of tight junction proteins, and the involvement of G-protein coupled receptor 120 (GPR120), intracellular calcium ([Ca2+]i) and myosin light chain kinase (MLCK) were assessed. In vitro, c9, t11-CLA, but not t10, c12-CLA isomer, impaired epithelial barrier function in IPEC-J2 by downregulating the expression of tight junction proteins. Meanwhile, c9, t11-CLA isomer enhanced GPR120 expression, while knockdown of GPR120 eliminated the impaired epithelial barrier function induced by c9, t11-CLA isomer. In addition, c9, t11-CLA isomer increased [Ca2+]i and activated the MLCK signaling pathway in a GPR120-dependent manner. However, chelation of [Ca2+]i reversed c9, t11-CLA isomer-induced MLCK activation and the epithelial barrier function impairment of IPEC-J2. Furthermore, inhibition of MLCK totally abolished the impairment of epithelial barrier function induced by c9, t11-CLA. In vivo, dietary supplementation of c9, t11-CLA rather than t10, c12-CLA isomer decreased the expression of intestinal tight junction proteins and GPR120, increased intestinal permeability, and activated the MLCK signaling pathway in mice. Taken together, our findings showed that c9, t11-CLA, but not t10, c12-CLA isomer, impaired intestinal epithelial barrier function in IPEC-J2 cells and mice through activation of GPR120-[Ca2+]i and the MLCK signaling pathway. These data provided new insight into the regulation of the intestinal epithelial barrier by different CLA isomers and more references for CLA application in humans and animals.