ABSTRACT
Objective To investigate the possible mechanisms of glucagon-like peptide 1 receptor agonists (GLP-1Ra) protection against hyperglycemic induced beta cell apoptosis through depression of NOX2-dependent ROS production. Methods The rat model of type 2 diabetes (T2DM) was established by injecting small doses of streptozotocin (STZ) fol?lowed by 8-week high fat diet. The experimental animals were divided into three groups:normal control (N) group, diabetes (T2DM) group and GLP-1Ra group [treated with liraglutide 200 μg/(kg · d)for 12 weeks]. The blood glucose levels were compared before and after modeling, before treatment and 12-week after treatment with GLP-1Ra. The level of glycosylated hemoglobin (HbA1c) was detected by high-pressure liquid chromatography. Automatic biochemical analyzer was used to de?tect levels of aspertate aminotransferase (AST), creatinine (CR) and urea nitrogen (BUN). The apoptotic rates of islets were determined by TUNEL method and cleaved caspase 3 was detected by immunohistochemistry. DCFH-DA fluorescent probe was used to detect reactive oxygen species (ROS) levels of islets. Levels of NADPH oxidase (NOX) catalytic subunit (NOX 2) in islets were measured by immunohistochemistry. Results At the end of the study, glycemic control (average blood glucose/week and HbA1c) and lipid situation were improved significantly in the GLP-1Ra group than those of N group (P0.05). After application Apocynin for inhibition, there were no significant differences between three groups (P>0.05). The level of NOX2 was significantly lower in GLP-1Ra group compared to that of T2DM group (P<0.05). Conclusion GLP-1Ra can inhibit apoptosis ofβcells in diabetes rat, and the depression of NOX2-dependent ROS may be one of the important underly?ing mechanisms.
ABSTRACT
Objective To investigate the possible mechanisms of glucagon-like peptide 1 receptor agonists (GLP-1Ra) induced weight loss. Methods High fat diet induced obese c57BL/6 mice were divided into normal control group (N, n=8), high fat feeding group (HF, n=32) and GLP-1Ra group treated with GLP-1Ra (liraglutide 200μg/(kg·d) or 400μg/(kg·d) for 8 weeks). Changes of body weight, blood glucose and three acyl glycosides (TG) levels were observed in three groups. HE staining was used to observe the morphological changes. Immunofluorescence staining and real-time PCR were used to mea?sure the expression of UCP-1. Furthermore, the expression of PGC-1αin protein level was observed to explore the possible mechanism of GLP-1Ra induced browning in white fat (WAT). Results After 8-week liraglutide (Lira) administration, the body weights were significantly reduced in obese mice (P<0.05). The levels of blood glucose and TG were significantly high?er in HF group than those in N group, which reduced significantly in Lira (200μg·kg-1) and Lira (400μg·kg-1) administra?tion groups (P<0.05). HE staining showed adipocytes in perirenal and inguinal subcutaneous adipose tissue partly acquired brown-like morphological characteristics. The expression levels of UCP-1 protein and mRNA and PGC-1αprotein were ele?vated in adipse tissues, which increased more in Lira (400) than those in Lira (200, P<0.05). Conclusion GLP-1Ra can induce weight loss through white fat browning by activation of UCP-1.
ABSTRACT
Objective To investigate the mechanism of a dipeptidyl-peptidase-4 (DPP-4) inhibitor, saxagliptin, pro?moting the regeneration of islet beta cells in diabetic rats. Methods The male SD rats were randomly divided into three groups including control group (NC, n=10), diabetes group (DM, n=10) and diabetes treated with saxagliptin group (DM-S, n=10). DM-S group was treated with saxagliptin 1 mg/(kg·d) for twelve weeks. The pancreaticβcell function was analysed by hyperglycemic clamps. Immunohistochemistry with anti-PCNA was performed to observe the proliferation rate of pancreaticβcells. Immunofluorescence double staining with anti-insulin, anti-glucagon, anti-DPP-4 and anti-SDF-1 were performed to observe the expression of insulin, glucagon, DPP-4 and SDF-1 in pancreatic tissue. Western blot assay was performed to test the expression of Akt, p-Akt,β-catenin and free-β-catenin protein, and RT-PCR was performed to test the expressionlevels of c-myc and cyclinD1 mRNA in pancreatic tissue. Results Compared with NC group, there were significantly in?creased blood glucose, decreased islet function andβcell mass in DM group. Compared with DM rats, saxagliptin treatment significantly inhibited the expression of DPP-4, decreased the degradation of SDF-1, stimulated the proliferation ofβcells, and ultimately improved the islet function and histopathological changes of pancreas. Conclusion DPP-4 inhibitor saxa?gliptin can significantly improve islet function, which involved in the inhibition of the expression of DPP-4, the decreased degradation of SDF-1 and the stimulation of the proliferation ofβcells.