Effect of early and chronic hypoinsulinism on adipose tissue cellularity in the rat

The effect of chronic hypoinsulinism on the development of retroperitoneal adipose tissue was studied in rats injected with streptozotocin at birth. The streptozotocin injection induced an acute neonatal diabetes which regressed spontaneously after one week and led to a chronic state of chemical diabetes in the young and in the adult rat. Growth of chemically diabetic rats was normal although the retroperitoneal adipose tissue showed a relative hypoplasia which appeared at two months and evolved with age so that at 10 months the number of adipose cells in the retroperitoneal adipose tissue was largely decreased with respect to control animals (1.34 +/- 0.12 x 10(6) versus 2.23 +/- 0.11 x 10(6)). This relative hypoplasia was still present at 20 months. Whereas the hypoplasia associated with the chemical diabetes was highly reproducible, the mean adipocyte size was modified in a variable manner but was never significantly decreased in chemically diabetic rats. These findings indicate that insulin is involved in the control of retroperitoneal adipose tissue cellularity and suggest that the effect of hypoinsulinism on adipocyte number does not depend on a decrease of the mean adipocyte volume.