Elevated levels of fasting serum GIP may be protective factors for diabetic retinopathy in type 2 diabetes mellitus

Objective Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone which has been ascribed a positive role in cardiovascular function. However, little is known about the association between GIP and microvascular complications including retina and kidney. In the present study, we conducted a cross-sectional study to investigate the relationship between fasting serum GIP and microvascular complications in type 2 diabetes mellitus (T2DM). Methods A cross-sectional study was performed in 295 T2DM patients in our endocrine ward in order to investigate the relationship between fasting serum GIP and microvascular complications. Results Among the 295 T2DM patients, the levels of median fasting serum GIP of all were 431.36pg/ml, interquartile range of which were 333.26~531.96pg/ml and the prevalence of diabetic retinopathy (DR) and diabetic nephropathy (DN) were 37.63% and 38.64% respectively. Our study observed that the prevalence of DR was significantly higher in low-levels GIP group compared with those in high-levels GIP group ( p =0.007) (46.26% versus 31.08%) and the levels of fasting serum GIP were also higher in T2DM patients without DR than those with DR ( p =0.019) (440.99pg/ml versus 405.90pg/ml). Spearman’s correlation and multiple stepwise regression analysis showed that prevalence of DR was independently and negatively correlated with fasting serum GIP in T2DM ( r =−0.134, p =0.021) (DR, β = −0.279; 95% CI, −0.512~−0.047, p = 0.019). However, there were no differences in fasting serum GIP between non-proliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR) ( p =0.951). Similarly, we did not find any association between fasting serum GIP and prevalence of DN by using various statistical analyses. Conclusions Prevalence of DR was independently and negatively correlated with fasting serum GIP in T2DM, indicating that elevated levels of fasting serum GIP may act as protective factors for DR.