Regression of white adipose tissue in diabetic rats

The effects of long-term diabetes (4 wk) on the development of parametrial (PWAT) and retroperitoneal (RWAT) white adipose tissues were studied in young Sprague-Dawley rats (170-200 g) injected with a single dose of streptozotocin (75 mg/kg). Diabetes stopped animal growth and totally abolished the normal increases in the wet weight, total protein content, and cellularity (estimated by DNA content) of PWAT and RWAT. Remarkably, the prolonged lack of insulin induced a progressive decrease of the cellularity of RWAT to levels that were lower than those of the initial controls. It also resulted in a marked reduction of adipocyte size. The tiny adipocytes seen in diabetic animals were characterized by the presence of multilocular triglyceride droplets. In general, the decreases in cell number, cell size, and protein content were more pronounced in RWAT than in PWAT. Quantitative cellular frequency studies revealed that adipocytes, and possibly also endothelial cells, contribute to the decrease in RWAT cellularity. The results demonstrate that 1) diabetes inhibits proliferative activity in adipose tissue, 2) total cell number reduction may occur in adipose depot of young growing rats, 3) this effect is depot dependent, and 4) the turnover of adipocytes and endothelial cells is relatively slow (several weeks).