ABNORMAL KIDNEY-FUNCTION AS A CAUSE AND A CONSEQUENCE OF OBESITY HYPERTENSION

1. Obesity is the most common nutritional disorder in the US and is a major cause of human essential hypertension, Although the precise mech anisms by which obesity raises blood pressure (BP) are not fully under stood, there is clear evidence that abnormal kidney function plays a k ey role in obesity hypertension.2. Obesity increases tubular reabsorpt ion and this shifts pressure natriuresis towards higher BP. The increa sed tubular reabsorption is not directly related to hyperinsulinaemia, but is closely linked to activation of the sympathetic and renin-angi otensin systems, and possible changes in intrarenal physical forces ca used by medullary compression due to accumulation of adipose tissue ar ound the kidney and increased extracellular matrix within the kidney. 3. Obesity is also associated with marked renal vasodilation and incre ased glomerular filtration rate, which are compensatory responses that help overcome the increased tubular reabsorption and maintain sodium balance, However, chronic renal vasodilation causes increased hydrosta tic pressure and wall stress in the glomeruli which, along with increa sed lipids and glucose intolerance, may cause glomerulosclerosis and l oss of nephron function in obese subjects, Because obesity is a primar y cause of essential hypertension as web as type II diabetes, there is good reason to believe that obesity may also be the most frequent cau se of end-stage renal disease. 4. Future research is needed to determi ne the mechanisms by which excess weight gain activates the neurohumor al systems and alters renal structure and function, Because of the hig h prevalence of obesity in most industrialized countries, unravelling these mechanisms will likely provide a better understanding of the pat hophysiology of human essential hypertension and chronic renal failure .