Blood was collected from the left cardiac cavity and centrifuged at 3,000 × g for 10 min at 4°C to isolate the supernatant/plasma. FPG levels were determined using a glucose oxidase kit according to the manufacturer's protocol. The plasma levels of the fasting insulin were measured by INS ELISA kit (Thermo Fisher Scientific, Inc., cat. no. ERINS). Non-esterified free fatty acids assay kit (Nanjing Jiancheng Bioengineering Institute, cat. no. A042-2-1), total cholesterol assay kit (Nanjing Jiancheng Bioengineering Institute, cat. no. F002-1-1) and triglyceride assay kit (Nanjing Jiancheng Bioengineering Institute, cat. no. A110-1-1) were used to measure FFA, TC and TG, respectively. The ISI was defined as follows: ISI=l g (1/FPG × serum insulin). The IR index was defined as follows: IR index=FPG level (mg/dl) × fasting serum insulin level (ng/ml)/22.5 (16 (link)).