Effects of d-mannoheptulose and d-sedoheptulose on blood glucose and ketone bodies in the rat

¹ Laboratory of Biochemistry and Metabolism and Laboratory of Nutrition and Endocrinology, National Institute of Arthritis and Metabolic Diseases, Bethesda, Maryland

The effects of mannoheptulose and its isomer, sedoheptulose, were studied in fasting rats. Mannoheptulose, 400 mg injected subcutaneously, increased blood glucose to 200 mg/100 ml and ketone bodies to 21 mg/100 ml in 1 hr. These effects began to disappear in 2 hr when the blood concentration of mannoheptulose was less than 40 mg/100 ml. Administration of glucose with the heptulose increased the degree of hyperglycemia. Glucose, given alone, lowered the blood ketone bodies in fasting rats; this effect was delayed by mannoheptulose until the concentration of the latter was less than 40 mg/100 ml. Insulin, 1 unit injected subcutaneously, decreased the amounts of glucose and ketone bodies in the blood of fasting rats. Mannoheptulose did not alter the effects of insulin. Mannoheptulose had no effect on blood glucose or ketone bodies in "totally" pancreatectomized rats. The findings suggest that mannoheptulose may act in the pancreas by blocking or suppressing release of insulin. Sedoheptulose did not have any diabetogenic or ketogenic activity; its effect on lowering blood ketone bodies was similar to that after glucose administration.