SymposiumObesity, Hypertension, and the Heart
Section snippets
Pathogenesis of Obesity-Hypertension
A series of endocrine, genetic, and metabolic mechanisms have been linked to the development of obesity-hypertension. These include insulin resistance/ hyperinsulinemia, overactivity of sympathetic nervous system, the renin-angiotensin-aldosterone system, salt retention, genetic predisposition, and leptin levels. A schematic review of these mechanisms and their probable interaction in causation of obesity hypertension is presented in Figure 1, and each mechanism is discussed below.
Obesity-Hypertension and The Heart
Because of the high blood volume in the obese, venous return to the right atrium, preload to the left atrium, left ventricular (LV) filling pressure, LV volume, and cardiac output are all shown to be increased.47 Afterload is also increased because of increased LV wall tension caused by increased LV volume.30 The LV adapts to these changes by increasing muscle mass, thereby producing thickening of the myocardial wall.48 In addition to the echocardiographic evidence cited above, autopsy study
Obesity-Hypertension and The Kidneys
Hall et al studied dogs with diet-induced obesity.58., 59. They demonstrated that sodium retention at the level of loop of Henle that may be caused by insulin resistance and hyperinsulinemia, increased sympathetic activity, activation of renin-angiotensin-aldosterone system, and/or higher renal interstitial fluid hydrostatic pressure. Microscopic examination of the animal kidneys revealed an increase in the interstitial cells and expansion of the extracellular matrix between tubules in the
Weight Reduction
It is well documented that reduction of weight is effective in reducing obesityhypertension. 65., 66. This reduction in blood pressure is seen whether or not salt restriction is instituted at the same time. Modest reduction in weight (5 to 10 kg) was effective in up to 75% of the subjects. In addition to better blood pressure control, weight loss is associated with reduction of insulin levels, sympathetic activity, possibly renin and aldosterone levels, and intracellular sodium levels. Cardiac
Summary
Several epidemiological studies have demonstrated a direct relationship between central obesity and hypertension. A series of endocrine and metabolic mechanisms have been linked to the development of obesity-hypertension. These include insulin resistance, hyperinsulinemia, increased adrenergic activity and aldosterone levels, and increased salt and water retention. Low levels of leptin and genetic predisposition may also be important. Hemodynamically, the cardiac output is increased with
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