Insulin and gliclazide therapies improve liver lipid deposition in type 2 di-abetic rats / 中国病理生理杂志

ABSTRACT

AIM:To investigate the effect of insulin and gliclazide therapies on the liver fat accumulation in type 2 diabetic rats .METHODS:A high-fat diet plus low-dose streptozotocin was implemented to establish a type 2 dia-betic rat model, and the rats were randomly divided into diabetes mellitus (DM) group, diabetic rats treated with insulin ( INS) group, diabetic rats treated with gliclazide per os ( PO) group, and normal control ( NC) group.The diabetic rats in INS group and PO group were given insulin and gliclazide for 3 weeks, respectively.The changes of the liver fatty were evaluated with oil red O staining .Fasting plasma adiponectin concentration was measured by ELISA .The expression of adi-ponectin receptor 1 ( AdipoR1 ) was detected by real-time PCR.The protein levels of AMP-activated protein kinase (AMPK), phosphorylated AMPK on threonine 172 ( Thr172p-AMPK), sterol regulatory element-binding protein 1c (SREBP-1c), phosphorylated SREBP-1c on serine 372 (Ser372p-SREBP-1c), acetyl-CoA carboxylase (ACC), phospho-rylated ACC on serine79 (Ser79p-ACC) and immunoglobulin-binding protein (BiP) in the liver homogenate were deter-mined by Western blotting .RESULTS:Compared with the normal rats , in DM group, the presence of cytoplasmic lipid deposits was confirmed by oil red O staining .In INS group, these changes were significantly lower than those in DM group . Similar results were obtained in PO group .Insulin therapy significantly increased the plasma concentration of diponectin and liver tissue levels of AdipoR1 compared with DM group.At the same time, these 2 indicators returned to normal levels after gliclazide therapy .Thr172p-AMPK/AMPK, Ser372p-SREBP-1c/SREBP-1c and Ser79p-ACC/ACC expression ratios were significantly reduced in DM group compared with control values .The expression of BiP was increased on the contrary . After insulin therapy, Thr172p-AMPK/AMPK and Ser372p-SREBP-1c/SREBP-1c were significantly increased, and Ser79p-ACC/ACC and BiP returned to the normal levels .After gliclazide treatment, Thr172p-AMPK/AMPK and Ser372p-SREBP-1c/SREBP-1c returned to the normal levels , the expression ratio of Ser79p-ACC/ACC had no significant improve-ment compared with DM group , and the expression of BiP significantly declined .CONCLUSION: Both the insulin and gliclazide therapies reduce the lipid deposition in the liver of rats with type 2 diabetes by activating AMPK , but the extent and mechanism are not the same.In insulin therapy, AMPK restrains the expression of SREBP-1c directly, increases the phosphorylation of SREBP-1c, and affects SREBP-1c by inhibiting the endoplasmic reticulum stress .Gliclazide treatment, which has no effect on the lipid oxidation , reduces lipid deposition in the liver only through the phosphorylation of SREBP-1c and the suppression of the endoplasmic reticulum stress .