Physiologic Response to D-Mannoheptulose: Gluconeogenesis

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Abstract
This study deals with the source of the excess glucose found in the blood of rats given a single sc injection of 400 mg of D-mannoheptulose. 1. The nonprotein nitrogen (NPN) excretion was increased strikingly by mannoheptulose. 2. The incorporation of serine into glucose and glycogen was enhanced. 3. Adrenalectomized rats did not become hyperglycemic after the injection of mannoheptulose; 0.25mg of hydrocortisone restored the hyperglycemic response. 4. After adrenalectomy, the rise in NPN excretion that occurred after mannoheptulose injection into intact rats did not appear. 5. The adrenalectomized, mannoheptulosetreated rat had a diabetic glucose tolerance curve. It is concluded that mannoheptulose induces increased gluconeogenesis. This increase in gluconeogenesis may be due to a direct effect of mannoheptulose on an adrenalregulated pathway or it may be a secondary consequence of an insulin lack caused by mannoheptulose. In the absence of the adrenals, gluconeogenesis is not stimulated.