Zinc and insulin metabolism.

A review of experimental studies of the effect of zinc nutrition on insulin metabolism is presented. In addition to a short introduction to the synthesis, secretion, and action of insulin, the effects of zinc deficiency-specifically on glucose tolerance, insulin secretion, insulin synthesis and storage, and on total insulin-like activity-are dealt with. The concentrations of zinc and chromium in serum, pancreas, and liver are compared to those of zinc-deficient animals and pair-fed controls.In contrast to pair-fed controls, zinc-deficient rats had unaltered proinsulin contents after glucose stimulation, but they showed a diminished glucose tolerance, lowered serum insulin content, and an elevated total insulin-like activity. The serum zinc concentration of the deficient animals was greatly reduced and did not change during glucose stimulation, whereas it rose in the case of the pair-fed controls. The serum chromium concentration increased in both groups in response to glucose stimulation. In the pancreas of the deficient animals, the zinc concentration was reduced 60% and it increased during the glucose tolerance test. In the liver there were no significant differences. The chromium concentrations were elevated in both the pancreas and liver of the zinc-deficient rats by 60 and 100%, respectively, and were not influenced by glucose injection.These studies show clearly that nutritional zinc deficiency influences insulin metabolism and action.