Gender-Linked Differences in Dietary Induction of Hepatic Glucose-6-Phosphate Dehydrogenase, 6-Phosphogluconate Dehydrogenase and Malic Enzyme in the Rat

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Abstract
The objective of these studies was to determine how alterations in dietary carbohydrate affect hepatic glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH) and malic enzyme (ME) activities in adult female rats. Rats were either 1) starved 2 d and then refed a nonpurified diet or a purified 65% carbohydrate diet (glucose, sucrose, fructose or cornstarch) for 3 d, or 2) switched from nonpurified to purified diets for 3 d. Liver G6PDH, 6PGDH and ME activities were determined. In males, enzyme activities were 8- to 12-fold and 3-fold higher when starved and refed purified diets and nonpurified diets, respectively, whereas in females, activities were 2- to 3-fold higher only when refed purified diets. Both genders had higher enzyme activities when shifted to purified diets. Females responded less dramatically than males. Of the higher enzyme activities observed during starvation-refeeding studies, in females 58–65% of the change is a function of switching rats from nonpurified to purified diets. In contrast, in males only 24–40% of the higher activities could be attributed to diet shifting. Results of these studies indicate that the effects of dietary carbohydrates on hepatic G6PDH, 6PGDH and ME activities are gender dependent.