Dietary Induction of Liver Glucose-6-Phosphate Dehydrogenase in the Rat. ∗

Abstract

It has recently been reported that the enzyme glucose-6-phosphate dehydrogenase (G-6-P DH) decreases in the liver during starvation and increases to a peak activity several times the level of non-starved controls 72 hours after refeeding a high glucose diet‡ (1,2). The present experiment was designed to determine which dietary ingredient is serving as the inducer of this enzyme.

Materials and methods. 48 Sprague-Dawley rats weighing 365 ± 25 (S.D.) g were used in this experiment. These animals had been previously fed Purina Rat Chow. At zero time, 36 animals were started on total starvation plus water ad libitum while 4 animals were started on the control diet of the following composition: casein 20, methionine 0.5, glucose§ 69.78, corn oil 5.0, salt mix 4164(2) 4.0, vitamin premix in casein (2) 0.5, α-tocopheryl succinate 0.02, vitamins A and D 0.10 (to provide 1500 I.U. vit A and 100 I.U. vit D/100 g diet). After seven days of starvation, 12 starved animals were sacrificed and the remaining 24 were divided into 3 groups of 8 rats each, which were refed ad libitum the following three diets: Group 1 control diet as above, Group 2 the same diet with starch replacing glucose and Group 3 a diet in which all carbohydrate was omitted and replaced by fat (hydrogenated vegetable oil|) at a level to give a diet of essentially the same calorie/ protein ratio as in the carbohydrate containing diets of Groups 1 and 2. The composition of this diet is as follows: casein 31.92, methionine 0.82, hydrogenated vegetable oil| 59.54, salt mix 6.55, vitamin premix in casein 0.82, α-tocopheryl succinate 0.04, vitamins A and D 0.15, choline chloride 0.16.

The food intakes of these animals were such as to give approximately 75 cals per day for Groups 1 and 2 and approximately 90 cals per day for Group 3 and provided approximately 4 g per day proteins for Groups 1 and 2 and approximately 4.5 g per day for Group 3.