Increased body fat in streptozotocin diabetic rats treated with intensive subcutaneous insulin therapy vs. islet transplantation

Abstract

The continued development of novel insulin treatment is predicated on the hypothesis that strict glycemic control is necessary to prevent the secondary complications of diabetes. Although dramatically successful in reducing selected secondary complications, intensive insulin therapy has consequences. These include hypoglycemia, weight gain, and body fat accumulation. In the present studies we compared a model of intensive insulin therapy in diabetic rats and contrasted weight gain and body fat accumulation with pancreatic islet transplantation. Female Wistar Furth rats (173 g) administered streptozotocin (55 mg·kg-1, iv) remained diabetic (DB) for four or nine weeks. At week three, a third group was transplanted (TRAN) with islets of Langerhans (3519 ± 838 150 µm islets); one week later group four began intensive subcutaneous insulin therapy (ISIT; 4 × 0.5-1.0 U regular insulin·day-1). Within one week ISIT rats had normalized plasma glucose; levels were not different from age matched controls (CN) or TRAN animals (ISIT 10.6 ± 1.7, CN 7.2 ± 0.4, TRAN 7.7 ± 0.8 mmol·L-1, P > 0.05). The cumulative occurrence of one episode of hypoglycemia (< 2.8 mmol·L-1) occurred in 50% of ISIT rats. At study termination, body weight of ISIT and CN rats did not differ (199 ± 4 vs. 207 ± 3, P > 0.05). While carcass protein content was similar for TRAN, ISIT, and CN animals, the body fat of ISIT animals was 24% greater than in CN rats and 21% greater than in TRAN rats (P <<N> 0.05). Correlation of body fat vs. plasma glucose illustrated hypoglycemia contributed to the body fat gain of ISIT rats (n = 8, r = -0.70, P = 0.0535). These studies illustrate a disproportionate gain of body fat from ISIT, an effect not observed with islet transplantation. Thus, the metabolic benefit ascribed to islet transplantation appears related to the absence of hypoglycemia.Key words: diabetes, insulin therapy, islet transplantation, body fat, nutrition.