INS and type 2 diabetes mellitus: However, cross-sectional analyses of 75-g 3-h oral glucose tolerance test results for a large sample of Caucasians and for populations with an exceptionally high prevalence of type 2 diabetes revealed inverted-U plots of insulin vs. glucose in plasma, implying direct proof of excellent insulin secretion during the pre-diabetic state, and consequently of adequate zinc transfer to the correct sites in the pancreatic islet cells [44-46].