Rat insulin assay kit

COS was obtained from Koyo Chemical Co., Ltd. (Tokyo, Japan). The average molecular weight (MW) and deacetylation degree (DD) of COS were about 719 Da and 100%, respectively. The generally manufacturing process for COS in company was: 100% deacetylated chitosan -- > dissolve in hydrochloric acid -- > decompose with chitosanase -- > adjust pH value -- > inactivation -- > decolorization -- > dry -- > chitosan oligosaccharide. The kits for detection of glucose, uric acid, total cholesterol (TC), and triglyceride (TG) were purchased from Audit Diagnostics (Cork, Ireland). A rat insulin assay kit was obtained from Mercodia AB (Uppsala, Sweden). A creatinine enzymatic assay kit was provided by Eagle Diagnostics (Desoto, TX, USA). The assay kits for blood urea nitrogen (BUN), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) were purchased from Randox (Antrium, UK). The superoxide dismutase (SOD) and glutathione peroxidase (GPx) assay kits were obtained from Cayman Chemical (Ann Arbor, MI, USA). A bicinchoninic acid (BCA) protein assay kit was purchased from Thermo Fisher Scientific (Waltham, MA, USA).

We conducted insulin secretion assay according to the method described previously (23 (link)). We seeded INS-1 cells in 12-well plate and treated the cells with different doses of Aβ for 24 h. After treatment, the cells were glucose starved in the glucose-free RPMI 1640 media for 2 h and then incubated in the glucose-free RPMI 1640 media supplemented with 3 mmol/l or 15 mmol/l glucose for 2 h. After 2 h, the insulin level of supernatant was determined with a rat insulin assay kit (Mercodia, Uppsala, Sweden), and total protein amount was quantified to normalize insulin values.