Variations in Glucose Metabolism and Sensitivity to Insulin of the Rat’s Adipose Tissue, in Relation to Age and Body Weight¹

Abstract

The epididymal adipose tissue’s in vitro pattern of glucose metabolism and sensitivity to insulin were compared in 3 groups of rats; Group A) young lean rats (130–160 g, 6–8 weeks old), fed ad lib.; Group B) older heavier rats (500–600 g,>l yr old), fed ad lib.; Group C) rats of Group B after body weight had been reduced 21% through underfeeding, and during subsequent weight regain through resumption of ad lib. feeding. In addition, glucose conversion to CO2 and the insulin effect on this process were compared at monthly intervals during the first 10 months of life, in rats either fed 10 g of chow/day or fed ad lib. The data show that, during the first year of life of the ad lib. fed rat, the pattern of the adipose tissue’s glucose metabolism changes to one where conversion of glucose to glyceride-glycerol becomes the major pathway and conversion of glucose to glyceride-fatty acid virtually disappears, and that simultaneously the responsiveness of the tissue’s glucose metabolism to insulin declines markedly. These changes can be completely reversed by reducing the 1 yr old ad lib. fed rat’s body weight 21% by underfeeding and can be prevented by limiting the rat’s food intake to 10 g chow daily from the time of weaning. (Endocrinology82: 1133, 1968)