Beta-blockers and diabetes: the bad guys come good

Abstract

Type 2 diabetes is becoming very common and is closely linked to physical inactivity and obesity. It is associated with clustering of coronary risk factors and 60-80% of cases have hypertension. The first therapeutic action is appropriate adjustment of life style. Anti-hypertensive therapies such as diuretics, ACE inhibitors and calcium antagonists have been effective in reducing cardiovascular events in type 2 diabetes, though calcium antagonists may be less effective than older therapies and ACE-inhibitors in reducing the risk of heart attacks and heart failure (but possibly more effective in stroke reduction). Beta-blockers (BBs) have a poor image as a potential therapy due to apparent adverse effects on surrogate end-points such as insulin-resistance. However large, controlled trials have shown BBs to be highly effective in reducing the risk of cardiovascular events and death in post myocardial infarction patients with diabetes. The UKPDS study in type 2 diabetics with hypertension showed first-line beta-blockade to be at least as effective as ACE-inhibition in preventing all primary macrovascular and microvascular end-points. The active ingredient appears to be beta-1 blockade, acting not only to lower blood pressure but also to prevent sudden death and cardiovascular damage stemming from chronic beta-1 stimulation associated with raised noradrenaline activity. By contrast, in the LIFE study atenolol was less effective than the angiotensin receptor antagonist losartan in reducing cardiovascular events and all-cause mortality in mainly elderly hypertensives with diabetes. Thus the best beta-blocker results in reducing hard cardiovascular end-points occur in hypertension studies (including the UKPDS study) involving younger/middle aged (say less than 60-65 years) patients, with relatively high sympathetic activity, relatively compliant/elastic arteries (narrow pulse-pressure) and normally functioning beta-1 receptors. In elderly hypertensive patients beta-blockers may be given as second-line therapy on the back of a low-dose diuretic (but possibly as first line agent in elderly hypertensives with prior myocardial infarction). Thus inappropriate attention to surrogate end-points can lead to faulty prescribing habits. Beta-blockers, currently severely underprescribed, should be considered as a first line therapeutic option for all diabetics with ischaemic heart disease or younger/middle aged diabetics with hypertension (but co-prescribed with low dose diuretic therapy in the elderly). The active ingredient for cardiovascular protection appears to be beta-1 blockade; optimal efficacy in lowering blood pressure and safety e.g. reducing risk of bronchoconstriction, is achieved by choosing an agent with high beta-1 selectivity.