SUMMARYRecent evidence suggests a key role for the brain in the control of energy metabolism, body fat content and glucose metabolism. Neuronal systems, which regulate energy intake, energy expenditure, and endogenous glucose production, sense and respond to input from hormonal and nutrient-related signals that convey information regarding both body energy stores and current energy availability. In response to this input, adaptive changes occur that promote energy homeostasis and the maintenance of blood glucose levels in the normal range. Defects in this control system are implicated in the link between obesity and type 2 diabetes mellitus. Central nervous system may be considered as the conductor of an orchestra implicating many peripheral organs involved in these homeostatic processes. However, brain is mainly a glucose-dependent organ, which can be damaged by both hypoglycaemia and hyperglycaemia. Hypoglycaemia unawareness is a major problem in clinical practice and is associated with an increased risk of coma. Stroke is another acute complication associated with diabetes mellitus, especially in elderly people, and control of glucose level in this emergency situation remains challenging. The prognosis of stroke is worse in diabetic patients and both the prevention management of at risk patients should be improved. Finally, chronic diabetic encephalopathies, which may lead to cognitive dysfunction and even dementia, are also recognized. They may result from recurrent hypoglycaemia and/or from chronic hyperglycaemia leading to cerebral vascular damages. Functional imaging is of interest to explore diabetes-associated cerebral abnormalities. Thus, the intimate relationship between brain and diabetes is increasingly acknowledged in both research and clinical practice.
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