Editorial [Hot Topic: Novel Peptides and Proteins in Diabetes Mellitus (Guest Editors: Po Sing Leung and Marc de Gasparo)]

Diabetes mellitus remains a hot research topic. More than 10,000 articles related to it have been published in the last twelve months (PubMed). In the U.S., 1.5 million new cases were diagnosed in 2005 and 6.2% of Americans are diabetic. According to the World Health Organization, approximately 197 million people worldwide have impaired glucose tolerance, most commonly attributed to obesity and metabolic syndrome. This number is expected to increase to an astounding 420 million by 2025. As the incidence of the disease continues to increase, so do the incidences of diabetes-related cardiovascular and renal complications. A great deal of work remains in improving our understanding of diabetes mellitus. A deeper knowledge of the pancreatic and peripheral mechanisms involved in hyperglycemia, insulin resistance and insulin insufficiency should facilitate therapeutic improvements. Therefore in this special issue, we have concentrated on novel peptides and proteins that affect insulin sensitivity and glucose metabolism or pancreatic islet differentiation, growth and function. The growth hormone releasing factor ghrelin is thought to affect energy balance and to regulate appetite and body weight maintenance. The presence of low plasma levels of ghrelin has been linked to metabolic syndrome. Hence ghrelin regulation represents a promising target for the development of new drugs for the treatment of obesity and diabetes. The non-protein sulfur amino acid taurine, which is the most abundant free amino-acid in the body, plays an important role in several essential biological processes and has anti-oxidant properties. Taurine-deficiency during pregnancy can lead to impaired glucose tolerance and vascular dysfunction in the adult offspring. Meanwhile, taurine supplementation can improve glucose metabolism and insulin action and taurine can decrease glycation and thus advanced glycation endproduct formation. The recently discovered hormone resistin is secreted by adipose tissue and strongly associated with insulin resistance. Its effects are counterbalanced by adiponectin. The excess of resistin that accompanies excessive adipose tissue mass underscores the deleterious consequences of visceral obesity and the associated risk of developing cardiometabolic syndrome. Furthermore, the endocannabinoid system is overactive in the presence of abdominal obesity or diabetes, and thus contributes to disturbances of energy balance and metabolism. If improving the effects of insulin is a clear goal for treatment, one should not forget the pancreas, its development and its function. Oxidative stress is a critical factor, not only because of the peripheral dysfunction it causes but also because of its deleterious effects on the pancreas itself. High angiotensin II levels and low heat shock protein concentrations appear to be critically involved in the pathogenesis of diabetes mellitus. An ultimate cure for diabetic patients will require development of therapies to improve pancreatic cell growth and function. Pancreatic function may be improved by pharmacological blockade of the renin-angiotensin system (RAS).