Association of serum levels of IGF-I and IGFBP-1 with renal function in patients with type 2 diabetes mellitus

Objective: Our aim was to determine whether serum Insulin-like growth factor-I (IGF-I) and Insulin-like growth factor binding protein-1 (IGFBP-1) levels were different between type 2 diabetic patients and non-diabetic control group. We also aimed to establish any relationship that might exist between the serum IGF-I and IGFBP-1 levels with the urinary albumin excretion (UAE), creatinine clearance and urinary N-acetyl-beta-D-glucosaminidase (NAG) excretion (as a marker of renal tubular dysfunction) and other parameters (such as age, duration of diabetes, treatment, etc.) in patients with type 2 diabetes mellitus (DM). Design: Fifty-nine type 2 diabetic patients and thirty-one non-diabetic controls were included in this study. Results: Mean serum IGF-I levels in diabetic patients were lower than the non-diabetic controls (158 +/- 12 vs. 287 +/- 26 mu g/l), (p < 0.001). Serum IGFBP-1 levels were also higher in type 2 diabetic patients compared to the control group (67 +/- 5 vs. 35 +/- 4 mu g/l), (p < 0.001). No relationship was obtained between IGF-I and IGFBP-1 levels with neither UAE nor urinary NAG excretion. A significant negative relationship was observed between creatinine clearance and serum IGFBP-1 level (r = -0.39, p = 0.004). In multiple regression analysis IGF-I was independently and negatively associated with age and insulin treatment. On the other hand, IGFBP-1 was negatively related with creatinine clearance and positively related with the duration of diabetes. Conclusion: These results suggest that type 2 DM leads to a decrease in the IGF-I while elevating the IGFBP-1 levels. Further studies are needed to clarify a potential role of increased levels of IGFBP-1 in decreased creatinine clearance in type 2 DM. (C) 2007 Elsevier Ltd. All rights reserved.