DIET-INDUCED INSULIN-RESISTANCE PRECEDES OTHER ASPECTS OF THE METABOLIC SYNDROME

This study was designed to examine the effects of a high-fat refined-s ugar (HFS) or a low-fat complex-carbohydrate (LFCC) diet on insulin-st imulated skeletal muscle glucose transport, plasma insulin, blood pres sure, plasma triglycerides, plasma glycerol, body weight, and body fat in female Fischer rats. Insulin-stimulated glucose transport was sign ificantly reduced in the HFS group at 2 wk, 2 mo, and 2 yr, whereas se rum insulin was significantly elevated at all time points. Blood press ure was not significantly elevated in the HFS group until 12 mo, and a ll HFS animals were hypertensive by 18 mo. Glycerol, triglycerides, an d abdominal fat cell size were not significantly different at 2 wk but were significantly elevated in the HFS rats at 2 and 6 mo. Body weigh t was similar in both groups until 20 wk on the diet, when the HFS rat s started to gain more weight. These results demonstrate that insulin resistance and hyperinsulinemia occur before the other manifestations of the metabolic syndrome and that diet, not obesity, is the underlyin g cause.