INS and type 2 diabetes mellitus: In accordance with previous animal studies, two meta-analyses confirmed that lower OC levels were observed in patients with type 2 diabetes than in normal controls (7, 31) and acknowledged that OC was negatively associated with fasting plasma glucose levels, HbA1c, insulin resistance and body mass index (BMI) but positively correlated with improved glycemic control, weight loss and regular exercise (11, 12).