INS and type 2 diabetes mellitus: The mechanism for impaired insulin secretion observed in T2D patients from East Asia can be explained by the result from clinical study in Japan showing that intact level of glucagon-like peptide-1 (GLP-1), a hormone which stimulate insulin secretion under hyperglycemic condition and contribute to nearly 70% of the post-prandial insulin secretion, being considerably low in both healthy and T2D subjects compared to Caucasian [13–15].