Effect of Diet on the Glucose Tolerance and Plasma Insulin Levels of the Sand Rat (Psammomys Obesus)

Abstract

When sand rats were switched from their usual all vegetable diet to laboratory chow or to a synthetic diet, most developed glycosuria, a marked decrease in glucose tolerance, and elevated plasma insulin. Some animals (all males) had a fulminating reaction with markedly decreased glucose tolerance, low plasma insulin levels and death within three weeks. Others were more resistant and did not show glycosuria at any time although their glucose tolerance tests were abnormal and their plasma insulin levels were high. Still others had an intermediate reaction with early appearance of glycosuria, decreased glucose tolerance, and elevated plasma insulin; then a gradual decrease in these diabetic signs; and finally a reappearance of abnormal glucose tolerance tests with death from severe diabetes mellitus. Since the plasma insulin level was high in most diabetic animals despite a high blood glucose level and decreased glucose tolerance, it is probable that the basic defect in these animals is not an inability to produce insulin, but rather a decrease in peripheral effectiveness of the hormone. However, the few animals that had a fulminating response were apparently unable to synthesize and release an adequate supply of insulin. Sand rats maintained on an all vegetable diet did not show these same marked signs of diabetes mellitus. However, occasional decreases in glucose tolerance were observed which, in some cases, were apparently precipitated by severe jaw infections. The caloric intake of the sand rats fed laboratory chow or the synthetic diet was significantly higher than that of the animals fed only vegetables, although the weight gained by animals on chow or synthetic food was only slightly greater or no greater than that gained by animals on all vegetables.