Obesity and hypertension: from pathophysiology to treatment.

While the prevalence of hypertension is clearly increased among the overweight persons, the pathophysiological mechanisms underlying this frequent association of obesity and hypertension are still poorly understood. The expansion of extracellular volume, inducing hypervolaemia and increased cardiac output, represents the characteristic haemodynamic feature of the obesity-related hypertension. The maintenance of hypervolemia in the face of elevated blood pressure, indicates a resetting of pressor natriuresis toward higher blood pressure. The development of hypertension also indicates an increase in peripheral vascular resistance, thus the lack of physiological adaptation of peripheral resistance to increased cardiac output. The mechanisms underlying these changes in renal function and vascular reactivity can no longer be attributed to hyperinsulinaemia as such, but might be related to insulin resistance responsible for the enhancement in pressor activity of noradrenaline and angiotensin II. This increased reactivity to pressor factors may be due to an inadequate nitric oxide generation by vascular endothelium and to increased sodium and calcium concentration in vascular smooth muscle cells. The role of increased neuropeptide Y (NPY) activity, may also be involved. As to enhancement of tubular sodium reabsorption, it could be related to histological changes within the renal medulla, leading to compression of tubules and vasa recta, hence a more efficient sodium reabsorption. As to the therapeutic approach, the low-energy sodium-restricted diet associated with increased physical activity, represents the cornerstones of treatment for the obesity-related hypertension. If this approach fails, the pharmacological treatment becomes necessary, and the use of the converting enzyme inhibitors seems to be the most appropriate choice of drug therapy for hypertensive obese patients.