Effect of beta-blockade on hormone release during hypoglycaemia in insulin-dependent diabetics

Previous studies have shown that non-selective, but not beta 1-selective, beta-blockers prolong the duration of hypoglycaemia. In order to elucidate possible mechanisms key hormones as well as alanine levels were measured following insulin-induced hypoglycaemia in 7 insulin-dependent diabetics. The subjects were treated with placebo, propranolol (a non-selective agent) or metoprolol (a beta 1-selective drug) prior to the hypoglycaemia. Treatment with either beta-blocking agent led to higher levels of adrenaline, glucagon, cortisol and growth hormone during hypoglycaemia as compared to those reached on placebo. The adrenaline levels during placebo treatment in response to hypoglycaemia appeared less in these diabetics than that previously reported for non-diabetics. The plasma alanine levels were similar and decreased following insulin administration irrespective of type of treatment. The data show that the release of key glycogenolytic and gluconeogenic hormones is not inhibited by beta-blockers during hypoglycaemia but is instead augmented or, possibly, hormonal clearance is reduced. It is suggested that the delayed recovery in blood glucose on a non-selective beta-blocker is partly due to lack of gluconeogenic substrates such as lactate and glycerol.