Brain glucose sensing and counterregulatory response to hypoglycaemia.

An important obstacle to achieve optimal glycaemic control in diabetics on intensive insulin therapy is the frequent occurrence of insulin induced hypoglycaemic events. In healthy subjects and in diabetics without autonomic neuropathy hypoglycaemia activates the sympathetic nervous system, resulting in epinephrine and glucagon release. Both hormones increase hepatic glucose production and this counterregulatory response is of key importance of glucose homeostasis. Recent research shed light on the fact that antecedent hypoglycaemic episodes play pivotal role in hypoglycaemia associated autonomic failure (HAAF). In this condition the sympatho-adrenal response to decreased blood glucose level is blunted. The existence of HAAF clearly indicates that the nervous system contributes to glucose homeostasis in a substantial manner. This review outlines the mechanisms of both peripheral and central neuronal glucose sensing and of neural pathways involved in the counterregulatory response.