HYPERINSULINEMIA IS ASSOCIATED WITH STIMULATION OF CHOLESTEROL-SYNTHESIS IN BOTH TYPE-1 AND TYPE-2 DIABETES

The effect of hyperinsulinaemia and hyperglycaemia on cholesterol synt hesis was examined in lymphocytes from diabetic subjects. The first pa rt of the study involved the provocation of hyperinsulinaemia by consu mption of a carbohydrate-rich meal, in obese patients with Type 2 diab etes mellitus. Cholesterol synthesis was measured before and 4 h after completing the meal. Results were compared to groups of obese non-dia betic patients and to control subjects. Analysis of the three groups d emonstrated that the percentage change in cholesterol synthesis was di rectly proportional to the percentage rise in serum insulin (r = 0.49, p < 0.05). This physiological study demonstrated that postprandial hy perinsulinaemia promoted cholesterol synthesis; however, we could not estimate the effect of the meal on cholesterologenesis. To study hyper insulinaemia in isolation, we examined the effects of varying insulin infusion rates for 4 h at either low or high levels of serum glucose u sing the glucose clamp technique in young Type 1 diabetic patients. Ch olesterol synthesis in lymphocytes was again measured before and after the study period. Hyperinsulinaemia stimulated cholesterol synthesis (+28.6%, p < 0.05) but hyperglycaemia alone did not exhibit this effec t (-1.7% NS). The combination of hyperinsulinaemia and hyperglycaemia produced the greatest increase in cholesterol synthesis (+51.4%, p < 0 .05) but this increase was not significantly different from hyperinsul inaemia alone. The percentage increase in serum insulin levels was aga in proportional to the percentage change in cholesterol synthesis (r = 0.46, p < 0.05).