The prevalence of diabetes is increasing worldwide due to population growth, aging and increasing frequency of obesity and physical inactivity. Diabetes mellitus is caused by a relative or absolute deficiency of the hormone insulin, which results in the characteristic feature of high blood sugar levels that play a key role in diabetes-associated complications. Inappropriately high levels of the sugar-raising hormone glucagon further aggravate the disease. Therefore, diabetes may be treated by increasing insulin levels and/or action, or inhibiting glucagon production and/or action. In an effort to identify the causes of diabetes, most studies have focused on better understanding the physiology of insulin-secreting beta-cells: despite the importance of glucagon, the counter-regulatory hormone to insulin, little is known about the physiology of pancreatic alpha-cells. Recently, Ms. Eva Tuduri and colleagues established that the hormone leptin controls both the secretion of insulin and glucagon, and thereby regulates blood sugar levels. Leptin is produced by fat cells and the levels of leptin in the blood typically correlate to the total content of fat in the body. Leptin is best known for its effects on feeding centers in the brain, where it regulates both food intake and energy expenditure. Ms. Tuduri’s current research project is focusing on understanding the role of leptin in regulating levels of glucagon, independent of leptin actions on body weight. An inhibitory effect of leptin on the function of alpha-cells could be considered as a potential therapeutic strategy to regulate glucagon levels and to normalize sugar levels in diabetic patients.