Aqueous Humor and Plasma Adiponectin Levels in Proliferative Diabetic Retinopathy Patients

Purpose: To study whether aqueous humor (AH) and plasma adiponectin (APN) levels were altered in proliferative diabetic retinopathy (PDR). Materials and Methods: After excluding subjects with hypertension, hyperlipidaemia, nephropathy, coronary heart disease, heart and renal failure, 20 consecutive type 2 diabetes mellitus (DM) PDR patients and 20 consecutive age-matched non-diabetic and senile cataract (non-DM) controls were enrolled in this study. AH APN and plasma APN concentrations were determined by enzyme-linked immunosorbent assay (ELISA). The expression of AdipoR1/R2 mRNA in peripheral blood mononuclear cells (PBMCs) was measured by real-time polymerase-chain reaction (PCR). The correlations between two parameters, including plasma and AH APN, AdipoR1/R2, plasma insulin and plasma glucose, were analyzed by Pearson's correlation. Results: In non-DM subjects, the APN concentration in AH was 1.26 +/- 0.56 ng/ml, approximately 1/2500 of that in plasma (3.15 +/- 1.36 mu g/ml). The averaged AH APN concentration in PDR patients was significant higher than that of the non-DM controls (5.29 +/- 4.09 ng/ml vs. 1.26 +/- 0.56 ng/ml, p < 0.001). Plasma total APN was not correlated with AH APN in the PDR patients, controls or all subjects. No significant difference was observed in plasma total APN levels and AdipoR1/R2 mRNA levels in PBMCs between the PDR patients and the controls (p > 0.05). Conclusion: Differences in APN concentration between AH and plasma suggest blood-retinal barrier (BRB) plays a key role in maintaining intraocular APN homeostasis. The high APN level in AH may be associated with PDR.