Effects of zinc supplementation on diabetes mellitus: a systematic review and meta-analysis

The number of people with diabetes and pre-diabetes are exponentially increasing worldwide due to population growth, aging, urbanization, unhealthy eating habits, increasing prevalence of obesity and physical inactivity [1]. Diabetes mellitus is a leading cause of morbidity and mortality worldwide, with an estimated 346 million adults being affected in year 2011 [2]. The prevalence is expected to double between years 20052030, with the greatest increases expected in low- and middle-income developing countries of the African, Asian, and South American regions [2,3]. At present, 80% of the worlds population with diabetes live in low- and middle-income countries [2,4]. Diabetes is also associated with a host of life threatening and potentially disabling macro- and micro-vascular complications [5]. Hence, there is also a much larger burden in the form of lost productivity as a result of restricted daily activity.Ninety percent of those with diabetes have type-2 diabetes, characterized by insulin resistance, hyper insulinaemia, -cell dysfunction and subsequent cell failure [6]. Insulin, is stored as a hexamer containing two Zinc ions in -cells of the pancreas and released into the portal venous system at the time of -cells de-granulation [7]. The Zn(II) ions which are co-secreted with insulin suppress inherent amyloidogenic properties of monomeric insulin [8]. Zalewski, et al. showed that high concentrations of glucose and other secretagogues decrease the islet cell labile Zinc and video fluorescence analysis showed Zinc concentrated in the islet cells was related to the synthesis, storage and secretion of insulin [9]. In vitro data suggests that insulin binds to isolated liver membranes to a greater extent and that there is less degradation when co-administered with Zinc [10]. Zinc is important in insulin action and carbohydrate metabolism [11]. Oxidative stress plays an important role in the pathogenesis of diabetes and its complications. Zinc is a structural part of k