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Robin Roberts, Hongmei Luan, Bruce A. Berkowitz; α-Lipoic Acid Corrects Late-Phase Supernormal Retinal Oxygenation Response in Experimental Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2006;47(9):4077-4082. doi: 10.1167/iovs.06-0464.
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purpose. To test the hypothesis that preventative α-lipoic acid (LPA) treatment corrects an abnormal retinal oxygenation response in experimental diabetic retinopathy.
methods. Retinal oxygenation (ΔPo 2) was measured by MRI before (room air [ra]) and during a 4-minute carbogen inhalation challenge in five groups: control Sprague-Dawley (SD) and Lewis (LEW) rats, 3- to 4-month diabetic SD and LEW rats, and 4-month diabetic LEW rats preventatively treated with a chow LPA admix (400 mg/kg per chow). Comparisons were made between the initial 2 minutes of oxygenation change (measured using ra and first carbogen periods [t 1 − ra]) and the next 2-minute change (assessed with first and second carbogen periods [t 2 − t 1]) for superior and inferior hemiretinal ΔPo 2.
results. In control SD rats, ΔPo 2(t 1 − ra) > ΔPo 2(t 2 − t 1) (P < 0.05) was found panretinally. In diabetic SD rats, the superior, but not the inferior, hemiretina had subnormal ΔPo 2(t 1− ra) (P < 0.05) and supernormal ΔPo 2(t 2 − t 1) (P < 0.05). In control LEW rats, ΔPo 2(t 1 − ra) and ΔPo 2(t 2 − t 1) were not significantly different (P > 0.05). Also, control and diabetic LEW rat panretinal ΔPo 2(t 1 − ra) were lower (P < 0.05) than in the respective SD groups. In diabetic LEW rats, a supernormal (P < 0.05) panretinal ΔPo 2(t 2 − t 1) was found that could be corrected with preventative LPA treatment.
conclusions. These data support the hypothesis and suggest that the influence of strain differences on the interpretation of retinovascular ΔPo 2 as a surrogate of drug treatment efficacy for diabetic retinopathy may be minimized by measuring a late-phase supernormal response. The LPA data raise the possibility that oxidative stress contributes to diabetes-induced supernormal ΔPo 2.
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