Is leptin associated with diabetic retinopathy?

OBJECTIVE - In advanced stages of diabetic retinopathy, new blood vessels a re formed based on undefined mechanisms. Recently, leptin was shown to poss ess an angiogenic action in vitro and to induce neovascularization in vivo. The aim of the present study was to investigate the relationship between p lasma leptin levels and the severity of diabetic retinopathy): RESEARCH DESIGN AND METHODS - There were 70 patients with type 2 diabetes ( age 47.9 +/- 9.7 years, BMI 26.4 +/- 3.3 kg/m(2)) who were seen in a retina outpatient clinic recruited and assigned to subgroups according to the sta ge of their diabetic retinopathy. There were 66 healthy volunteer subjects matched with the diabetic patients for age, BMI, and sex who served as cont rol subjects (age 46.0 +/- 8.8 years, BMI 27.1 +/- 2.3 kg/m(2)). Fasting pl asma leptin levels were measured. RESULTS - Plasma leptin level of the diabetic patients was not significantl y different from the control subjects. In patients with proliferative diabe tic retinopathy (n = 17), the mean plasma level of leptin (16.1 +/- 9.2 ng/ ml) was significantly higher than that in patients with nonproliferative re tinopathy (n = 20) (11.5 +/- 3.5 ng/ml, P = 0.039) or patients without reti nopathy (n = 33) (5.8 +/- 3.7 ng/ml, P = 0.001). The mean leptin level in p atients with nonproliferative diabetic retinopathy was also significantly h igher than that in patients without retinopathy (P = 0.002). CONCLUSIONS - Our results show that the more advanced the diabetic retinopa thy, the higher the plasma leptin levels, even after adjusting the leptin l evels for BMI. The presence of such a positive correlation need not imply a causal relationship. Nevertheless, previously observed leptin-induced prom otion of angiogenesis and neovascularization lends support to the possibili ty that leptin may play a role in the progression of human diabetic retinop athy to a proliferative phase. This possibility deserves further investigat ion.