OBESITY AND HYPERTENSION - ROLES OF HYPERINSULINEMIA, SYMPATHETIC NERVOUS-SYSTEM AND INTRARENAL MECHANISMS

Hypertension is a well-recognized complication of obesity. However, th e mechanisms for the development of obesity hypertension are not known . One mechanism proposed Is that the hyperinsulinemia present in obese hypertensive patients causes hypertension via sodium retaining and/or sympathetic nervous system stimulatory effects. However, numerous stu dies in dogs have revealed no evidence for such chronic presser action s of hyperinsulinemia. This is in close agreement with studies in huma n insulinoma patients that show marked hyperinsulinemia and normal blo od pressure. The appropriateness of the dog as an experimental model i s strengthened by reports from our laboratory and others that inducing obesity in dogs reproduces many of the characteristics of obesity in humans, including insulin resistance, hyperinsulinemia, sodium retenti on, hypertriglyceridemia and hypertension. Recent studies in obese dog s have indicated that significant increases in renal medullary cellula rity and intercellular matrix deposition could contribute to the sodiu m retention and hypertension. Additional evidence suggests that sympat hetic nervous system stimulation also may contribute to the elevated b lood pressure. However, the mechanisms through which obesity induces t hese changes and the temporal relationship between these factors and t he development of the hypertension remain to be determined.