Interaction between glycaemic control and serum insulin-like growth factor 1 on the risk of retinopathy in type 2 diabetes

Abstract

Background: There is strong experimental evidence that insulin-like growth factor 1 (IGF-1) plays a role in the development of diabetic retinopathy. We carried out this study to determine the association between serum IGF-1 levels and retinopathy in patients with type 2 diabetes and whether this association is modified by the severity of hyperglycaemia.

Materials and methods: A total of 480 consenting patients with type 2 diabetes were enrolled between 1 August 2001 and 31 December 2002. All participants provided a medical history and underwent a physical examination, biochemical assessment and eye fundi examination. These patients were followed up in our clinics according to our national guidelines until 31 December 2009.

Results: Compared with the middle tertile, increased levels of IGF-1 did not increase the risk of mild-to-moderate retinopathy (RR, 1·11; 95% CI, 0·63-1·95) and severe retinopathy (RR, 1·84; 95% CI, 0·79-8·57) at baseline. In the longitudinal analysis, increased levels of IGF-1 showed a nonsignificantly increased hazard ratio (HR) for the progression of retinopathy (HR, 1·61; 95% CI, 0·52-4·96) and severe retinopathy (HR, 1·63; 95% CI, 0·65-4·09). However, in patients with relatively good glycaemic control, there was a significantly increased risk of the progression of retinopathy (HR, 2·21; 95% CI, 1·01-5·91) and a cumulative incidence of severe retinopathy (HR, 4·82; 95% CI, 1·10-18·25) in individuals with the highest serum IGF-1 levels.

Conclusions: Our data suggested serum IGF-1 was a contributing factor in severe diabetic retinopathy and this effect may be masked by poor glycaemic control.