Apolipoprotein A-I concentration in tears in diabetic retinopathy

BACKGROUND: Apolipoprotein concentrations in reflex tears from healthy and noninsulin-dependent diabetes mellitus (NIDDM) subjects were measured and correlated with the stage of diabetic retinopathy. METHODS AND RESULTS: The apolipoprotein A-I (apo A-I) concentrations in the tears from NIDDM patients with retinopathy were significantly higher than those from patients with no or negligible retinopathy (P<0.05), and apo A-I was not detected in healthy subjects by Western blotting. No reactive band was detected on apo A-I by Western blotting for nitrotyrosine, a marker for peroxynitrite oxidation of the tear proteins. Apo A-I concentration in tears was significantly correlated with the stage of retinopathy (r= 0.598, n = 59, P < 0.001). No apo A-I gene expression was detected in the conjunctiva by reverse transcription polymerase chain reaction. CONCLUSIONS: We conclude that there is increased secretion of native apo A-I from the main lacrimal gland in patients with advanced diabetic retinopathy.