[Effects of diabetes and obesity on the higher brain functions in rodents]

Metabolic disorders, such as diabetes and obesity, have been indicated to disturb the function of the central nervous system (CNS) as well as several peripheral organs. Clinically, it is well recognized that the prevalence of anxiety and depression is higher in diabetic and obesity patients than in the general population. We have recently indicated that streptozotocin-induced diabetic and diet-induced obesity mice have enhanced fear memory and higher anxiety-like behavior in several tests such as the conditioned fear, tail-suspension, hole-board and elevated open-platform tests. The changes in fear memory and anxiety-like behavior of diabetic and obese mice are due to the dysfunction of central glutamatergic and monoaminergic systems, which is mediated by the changes of intracellular signaling. These results suggest that metabolic disorders strongly affect the function of the CNS and disturb the higher brain functions. These dysfunctions of the CNS in diabetes and obesity are involved in the increased prevalence of anxiety disorders and depression. Normalization of these dysfunctions in the CNS will be a new attractive target to treat the metabolic disorders and their complications.