The effect of infantile nutritional levels on adipose tissue cellularity and metabolism was studied in two groups of Sprague-Dawley rats. Caloric intake was varied during the suckling period by manipulating litter size immediately after birth; however, all animals had free access to food after weaning. The epididymal fat pads of animals raised in small litters were heavier than those of their paired siblings raised in large litters. Initially, the differences in pad weight were accounted for primarily by differences in total cell number; however, at 20 wk both cell number and cell size contributed equally. The rate of glucose incorporation into CO2 and triglyceride during in vitro incubations was the same for both groups if expressed on a per cell basis; therefore total tissue incorporation was greater in animals with more cells. The results support the hypothesis that early nutritional experiences can effect permanent changes in the cell number and size of the epididymal fat depot and that total cell number is important in the total metabolism of this organ. These findings and the fact that extreme human obesity is accompanied by similar alterations in cellularity and metabolism indicate that early nutritional experiences should be studied further as a guide to the etiology of obesity in man.
Jerome L. Knittle, Jules Hirsch