Effects of a high protein diet on the evolution of diabetes in streptozotocin-induced and spontaneously diabetic “BB” wistar rats

Summary Recently, we demonstrated a reduction in the diabetogenic action of streptozotocin (STZ) in rats previously adapted to a high protein (HP) diet. These data suggested that amelioration of diabetes resulted from the combination of two effects of the HP diet: initial protection against the diabetogenic action of the drug at the time of exposure and subsequent improvement of the induced diabetic condition. The present study evaluated the effects of a HP diet on the evolution of the metabolic condition in rats with STZ-induced or spontaneous diabetes (BB Wistar rats). Two days after STZ injection, the animals were given isocaloric HP (70% protein, 8% fat) or control (66% carbohydrate, 16% protein, 8% fat) diets for 15 days. After 13 days, the STZ-treated rats fed HP diet showed an impressive decrease in severity of diabetes, as judged by rate of body weight change, plasma glucose, urine volume and glycosuria, serum and pancreatic insulin. The BB Wistar rats, already diabetic for 5 weeks before being transferred to the HP or control diet, were treated with daily injections of insulin. After 31 days on the HP diet, the BB rats showed reduced insulin requirement, reduced blood and urinary glucose levels, but no difference in body weight gain or pancreatic insulin content. The data show that short-term use of HP diets can greatly improve the diabetic condition in STZ-treated animals, but that the beneficial effects of the diet are much less marked in rats with chronic spontaneous diabetes. These data suggest that the ameliorating effect of HP diet is fully manifested only when the diabetic rats have a sufficient number of residual functioning B-cells.