Glycolytic and Pentose Phosphate Pathway Enzymes in Jejunal Mucosa, Adaptive Responses to Alloxan-Diabetes and Fasting in the Rat

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Abstract
Glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, malic enzyme, hexokinase, and pyruvate kinase activities were measured in the 105,000 × g supernatant fraction of jejunal mucosa and liver of control, alloxandiabetic, and 72-h fasted rats. Alloxan-diabetes was associated with elevated activities of these enzymes in jejunal mucosa. In contrast, fasting reduced the activities of these enzymes. Hepatic enzyme activities were reduced by both diabetes and fasting. Pair-feeding or a 24-h fast reduced the increased mucosal weight of diabetic rats to that of control animals, but jejunal enzyme activity remained similar to control values suggesting that hyperphagia and mucosal hypertrophy are not the sole cause of the elevated enzyme activity in diabetic jejunum. These studies demonstrate a unique response of jejunal mucosal glycolytic and NADPH-generating enzymes in alloxan-diabetes. The elevated activities of these enzymes in diabetic jejunal mucosa contrasts with the reductions in the activities of these enzymes seen in response to fasting in jejunal mucosa, and in response to both alloxan-diabetes and fasting in liver. The absorption of glucose and amino acids is increased in diabetic intestine and this increase in the transport function and energy requirement of the mucosa may result in maintenance of normal or increased activity of the glycolytic and NADPH-generating pathways. (Endocrinology89: 1178, 1971)

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