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

ObjectiveOur 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-β-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).DesignFifty-nine type 2 diabetic patients and thirty-one non-diabetic controls were included in this study.ResultsMean serum IGF-I levels in diabetic patients were lower than the non-diabetic controls (158 ± 12 vs. 287 ± 26 μg/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 μg/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.ConclusionThese 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.