Beta-blocking agents in patients with insulin resistance: effects of vasodilating beta-blockers

Essential hypertension is-at least in many subjects-associated with a decre ase in insulin sensitivity, while glycaemic control is (still) normal. It s eems that in hypertensive patients, two major functions of insulin are impa ired: there is insulin resistance of peripheral glucose uptake (primarily s keletal muscle) and insulin resistance of insulin-stimulated vasodilation. In view of some retrospective data and meta-analyses, which showed a less t han expected reduction in coronary events (coronary paradox), the metabolic side effects of the antihypertensive treatment have received more attentio n. Many groups have shown that conventional antihypertensive treatment, bot h with beta-blockers and/or diuretics, decreases insulin sensitivity by var ious mechanisms. While low-dose diuretics seem to be free of these metaboli c effects, there is no evidence for this in the beta-adrenergic blockers. H owever, recent metabolic studies evaluated the effects of vasodilating beta -blockers, such as dilevalol, carvedilol and celiprolol, on insulin sensiti vity and the atherogenic risk factors. None of them decreased insulin sensi tivity, as has been described for the beta-blockers with and without beta(1 ) selectivity. This supports the idea that peripheral vascular resistance a nd peripheral blood flow play a central role in mediating the metabolic sid e effects of the beta-blocking agents, as the vasodilating action (either v ia beta(2) stimulation or alpha 1-blockade) seems to more than offset the d etrimental effects of the blockade of beta (or beta(1)) receptors. Further studies are needed to elucidate the relevance of the radical scavenging pro perties of these agents and their connection to their metabolic effects. Th erefore, the beneficial characteristics of these newer beta-adrenoreceptor blockers suggest that the vasodilating beta-blocking agents could be advant ageous for hypertensive patients with insulin resistance or type 2 diabetes .