The slight but significantly delayed recovery from hyperglycemia observed in the IH group may indicate that the beta cells after IH treatment become dysfunctional, and that is why the levels of insulin in the IH animals are low. Role of zinc in insulin production Disturbance of zinc homeostasis has been accepted as one of the most crucial signs of diabetes because diabetic patients experience an increased urinary excretion of zinc and zinc is involved in the synthesis, secretion as well as function of insulin. The zinc level in serum as well as in the cytoplasm of beta cells in diabetic patients is low compared to normal levels irrespective of types of diabetes. Despite the general congruence in opinions, some clinical study defies a one-to-one relationship between the zinc level in beta cells and the level of insulin secretion. Our current results show that insulin production decreases as the ARRY-142886 intracellular zinc level decreases after IH challenge; however, mRNA production of insulin does not show any change. This result may indicate IH insults do not influence the beta cells at the transcription level of insulin, but may influence the assembly process in the production line. The human body contains 2–4 g of zinc in total, but the mobile amount of zinc in plasma is very small, i.e. approximately 12– 16 mM. Mainly, zinc is bound to proteins such as metallothionein in cytoplasmic compartments of zinc abundant cells like pancreatic beta cells. Zinc accumulated in the ER and Golgi apparatus in pancreatic beta cells plays a dual function, i.e. anti-oxidative function and insulin production/secretion function. This may be why our IH model is extremely prone to be diabetic. The additional ROS accumulation from our IH challenge should have consumed zinc in the insulin containing vesicles, ER, as well as Golgi apparatus. Some recent studies view zinc as an intracellular second messenger augmenting insulin activity via ZIP which plays a role of sensor. In fact, there is ample evidence showing that increased zinc levels can boost insulin production and secretion. Hence, Myers et al. explained that the increased zinc concentration in the cytoplasm would increase numbers of ZIPs as ZIP7 did in another study, then as a result, increase insulin secretion. They also quoted that this is why oral administration of zinc improves symptoms in type 1 and type 2 diabetic patients. However, the anti-diabetic effect of zinc is still controversial due to a weak dose-effect relationship clinically. Since most zinc is bound with ligands in beta cells, whether the signaling process of zinc to alarm the innate defense system in response to a physiologic challenge by immediate ‘buffering and muffling’ is sufficiently effective remains to be answered. We have not performed a rescue experiment yet; however, it would be very interesting to observe whether zinc administration would recover ZIP8 expression, and in turn recover insulin secretion in our animal model as well as in vitro model. In fact, no reports are available as to whether zinc administration increases ZIP8 concentration in beta cells.