[Impact and mechanism of CHL1 in insulin resistant adipocytes and insulin resistant mouse model induced by high glucose and high fat].

Abstract

Objective: To investigate the role and mechanism of cell adhesion molecule L1 like (CHL1) in insulin resistant adipocytes and insulin resistant mouse model induced by high glucose and high fat. Methods: The 3T3-L1 preadipocytes were randomly divided into control group (transfected with empty vector) and CHL1 overexpression group (transfected with CHL1 vector), cells were then induced to mature adipocytes by insulin, and insulin resistance was then induced by high sugar and high fat. The glucose content was measured to determine the glucose consumption of cells from the two groups. Protein expression levels of CHL1 and glucose transporter 4 (GLUT4), serine/threonine protein kinase (AKT) phosphorylation levels were detected by Western blot (WB), the mRNA expression levels of TNF-α and IL-6 were detected by real-time quantitative PCR (RT-qPCR). 24 C57BL/6 adult male mouse were randomly divided into conventional diet group (regular group), high-fat diet group (high-fat group), empty vector overexpression+high-fat group and CHL1 overexpression+high-fat group (n=6 each group). CHL1 overexpression was induced by tail vein injection of lentivirus. Four months later, mice were sacrificed, body weight was determined, and the epididymal white adipose tissue was collect. Hematoxylin-eosin staining (HE) was used to observe the pathology of mouse epididymal white adipose tissue, the expression of CHL1 was evaluated by immunohistochemical staining(IHC), RT-qPCR was used to detect the mRNA expression levels of CHL1, TNF-α and IL-6 in mouse epididymal white adipose tissue. Results: In vitro, glucose consumption was significantly higher in the CHL1 overexpression group than in the control group (P<0.05), and the protein expressions of CHL1 and GLUT4 were higher in the CHL1 overexpression group than those in the control group (P<0.01), and the mRNA expressions levels of TNF-α and IL-6 were lower in the CHL1 overexpression group than those in the control group (P<0.01). In vivo, the body weight and epididymal white adipose tissue of mouse were higher in the high-fat group and the empty vector overexpression+high-fat group than those in the conventional group (P<0.01), which were lower in the CHL1 overexpression+high fat group than in the empty vector overexpression+high fat group (P<0.01). HE results showed that the volume of epididymal white adipocytes was larger in the high-fat group and the overexpression control+high-fat group than that in the conventional group, which was smaller in the CHL1 overexpression+high fat group than in the empty vector overexpression+high fat group (P<0.01). The mRNA expression levels of IL-6 and TNF-α in epididymal white adipose tissue of mice were higher in the high-fat group and the empty vector overexpression+high-fat group than those in the conventional group (P<0.01), which were lower in the CHL1 overexpression+high fat group than in the empty vector overexpression+high fat group (P<0.05). IHC results showed that protein expression of CHL1 in epididymal white adipose tissue was lower in the high-fat group and the empty vector overexpression+high-fat group than in regular group, which was upregulated in the CHL1 overexpression+high fat group than in the empty vector overexpression+high-fat group (P<0.01). RT-qPCR results showed that mRNA expression of CHL1 in epididymal white adipose tissue was lower in the high-fat group and the empty vector overexpression+high-fat group than in regular group (P<0.01), which was higher in the CHL1 overexpression+high fat group than in the empty vector overexpression+high fat group (P<0.01). Conclusion: Overexpression of CHL1 can improve insulin resistance in adipocytes and mouse insulin resistance model induced by high glucose and high fat, and the beneficial effects might be mediated by the inhibition of AKT activation and the reduction of related inflammatory responses.