[The effects of insulin and gliclazide therapy on endoplasmic reticulum stress and insulin sensitivity in liver of type 2 diabetic rats].

To investigate the effect of insulin and gliclazide therapy on endoplasmic reticulum (ER) stress and insulin sensitivity in the liver of type 2 diabetic rats. A high fat diet plus a low-dose of streptozotocin was implemented to create a type 2 diabetic rats which were randomly divided into diabetes mellitus (DM) group, insulin treatment (INS) group and gliclazide treatment (GT) group; and healthy rats were as normal control group. Diabetic rats in INS and GT groups were given neutral protamine hagedorn (NPH) insulin and gliclazide respectively for 3 weeks. Protein expression levels of immunoglobulin binding protein (Bip), spliced X-box binding protein 1 (XBP-1s), phosphorylated c-Jun on serine 73 (p-c-Jun), phosphorylated insulin receptor substrate 1 on serine 307 (p-IRS-1), and glucose-6-phosphatase (G6Pase) in liver homogenate were detected by Western blotting. Compared with the normal rats, Bip and XBP-1s in the DM group were up-regulated (0.28 ± 0.07 vs 0.90 ± 0.10 for Bip; 0.41 ± 0.07 vs 0.95 ± 0.07 for XBP-1s; both P < 0.01); p-c-Jun (0.59 ± 0.18 vs 1.94 ± 0.03), p-IRS-1 (1.73 ± 0.18 vs 5.32 ± 0.22) and G6Pase(0.11 ± 0.01 vs 0.45 ± 0.01) were increased (all P values < 0.01). In the INS group, all of aforementioned changes were reversed (0.90 ± 0.10 vs 0.25 ± 0.04 for Bip; 0.95 ± 0.07 vs 0.47 ± 0.01 for XBP-1s; 1.94 ± 0.03 vs 0.50 ± 0.10 for p-c-Jun; 5.32 ± 0.22 vs 1.59 ± 0.32 for p-IRS-1; 0.45 ± 0.01 vs 0.15 ± 0.02 for G6Pase, all P values < 0.01). In the GT group, all of aforementioned changes were also attenuated (0.90 ± 0.10 vs 0.53 ± 0.02 for Bip; 0.95 ± 0.07 vs 0.78 ± 0.02 for XBP-1s; 1.94 ± 0.03 vs 1.33 ± 0.11 for p-c-Jun; 5.32 ± 0.22 vs 3.13 ± 0.02 for p-IRS-1; 0.45 ± 0.01 vs 0.25 ± 0.01 for G6Pase, all P values < 0.05). Furthermore, all of aforementioned protein levels were down-regulated more obviously in the INS group comparing to the GT group (all P values < 0.01). Both insulin and gliclazide therapy could relieve ER stress and c-Jun N-terminal kinase activity and improved insulin sensitivity. The effect of insulin on Bip, XBP-1s, p-c-Jun, p-IRS-1 and G6Pase protein expressions is more obvious than that of gliclazide, which indicates besides lowering glucose, insulin might have protective effects of anti-inflammation, anti-oxidative stress or stimulation of lipid redistribution.