Effects of insulin and sulphonylureas on insulin-like growth factor-I levels in streptozotocin-induced diabetic rats

OBJECTIVE: Diabetes Mellitus is associated with decreased insulin-like growth factor-I (IGF-I) levels and also, poor growth in diabetes is related with low circulating levels of IGF-I. Insulin acts via an increase of IGF-I synthesis on growth. We studied the effects of insulin and sulphonylureas on serum IGF-I levels and aimed to evaluate the restoration of IGF-I in different therapeutic strategies. DESIGN AND SETTING: Thirty male rats were used in the study and diabetes was induced by a single intraperitoneal injection of streptozotocin (35 mg/kg body weight). After confirmation of hyperglycemia, rats were divided into three groups. The first group was treated with insulin, and second group with glimepiride, third group was not treated (control group). IGF-I levels were measured at basal, after streptozotocin and at the end of the treatment period. RESULTS: Serum IGF-I levels were found to decrease from 577.2 ng/ml to 253.0 ng/ml after streptozotocin (p<0.005). After 1 month, IGF-1 levels were found 524.0 ng/ml in insulin group, 449.3 ng/ml in sulphonylurea group, and 313.1 ng/ml in control group. The increase in IGF-I was statistically significant in insulin group (p<0.005), and in sulphonylurea group (p<0.05), but it was not significant in control group (p>0.05). CONCLUSIONS: Serum IGF-I levels decrease in diabetes and insulin treatment restores IGF-I depletion significantly. And although less effective, treatment with glimepiride restores IGF-I levels significantly.