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Brian Christopher Prall, Moe Hein Aung, Marissa Gogniat, Rachael S Allen, Curran S Sidhu, Jeffrey H Boatright, P Michael Iuvone, Machelle T Pardue; Aerobic Exercise Sustains Retinal Function and Retinal Dopamine Metabolism in Diabetic Rats. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5816.
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© ARVO (1962-2015); The Authors (2016-present)
Aerobic exercise (AE) has many beneficial effects, including neuroprotection and neuroregeneration. We reported previously that AE protects against light-induced retinal degeneration (Lawson et al., 2013; ARVO E-abstract 1269). The purpose of this study was to examine whether AE protects retinal function in an animal model of type 1 diabetes mellitus.
Wild-type Long Evans rats were assigned to one of four treatment groups: control (CTRL), aerobic exercise (AE), diabetic only (DM) or diabetic with aerobic exercise (DMAE). AE consisted of treadmill training 5 days/week for 30min at a speed of 0m/min (CTRL, DM) or 15m/min (AE, DMAE) for 8 weeks. Hyperglycemia was induced using streptozotocin (STZ; 100 mg/kg) with glucose levels >250 mg/dL considered diabetic. Visual acuity, contrast sensitivity and retinal function were measured biweekly (0, 2, 4, 6, 8wks post-STZ) using an optokinetic tracking system and electroretinography (ERG). Retinal levels of dopamine (DA) and its primary metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), were determined by HPLC analysis from retinas collected after 8 weeks of training.
By 8 weeks post-STZ, decreases were seen in contrast sensitivity (51%) and visual acuity (11%) in the DM versus CTRL group. AE preserved contrast sensitivity by 75% in DMAE animals compared to DM (p < 0.05), but had no preservation of visual acuity. At 8 weeks, ERG oscillatory potentials (OPs) for a dim flash (-2.4 log cd s/m2) were delayed in DM vs. CTRL rats (32%). AE improved OP implicit times such that DMAE rats were statistically indistinguishable to controls. DM groups had significantly lower DA and DOPAC than controls (43%, 22%; p < 0.05). Retinal DOPAC and dopamine levels were preserved in DMAE rats, with DA (46%, p < 0.05) and DOPAC (22%, p < 0.05) levels higher in DMAE rats compared to DM animals. No differences were seen between control and AE groups in any of the tested measures.
AE slowed the progression of early visual dysfunction in diabetic retinopathy. In addition, AE prevented the reduction in retinal DA and DOPAC levels associated with diabetes, suggesting one possible mechanism for visual improvements. AE shows promise for reducing early retinal and visual defects in diabetes.
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