GABA as a Novel Predictor of Decreased Visual Psychosocial Performance in Diabetic Patients
abstract
This abstract is available on the publisher's site.
Access this abstract nowVisual impairment is one of the most feared complications of Type 2 Diabetes Mellitus. Here, we aimed to investigate the role of occipital cortex γ-aminobutyric acid (GABA) as a predictor of visual performance in type 2 diabetes. 18 type 2 diabetes patients were included in a longitudinal prospective one-year study, as well as 22 healthy age-matched controls. We collected demographic data, HbA1C and used a novel set of visual psychophysical tests addressing color, achromatic luminance and speed discrimination in both groups. Psychophysical tests underwent dimension reduction with principle component analysis into three synthetic variables: speed, achromatic luminance and color discrimination. A MEGA-PRESS magnetic resonance brain spectroscopy sequence was used to measure occipital GABA levels in the type 2 diabetes group. Retinopathy grading and retinal microaneurysms counting were performed in the type 2 diabetes group for single-armed correlations. Speed discrimination thresholds were significantly higher in the type 2 diabetes group in both visits; mean difference (95% confidence interval), [0.86 (0.32-1.40) in the first visit, 0.74 (0.04-1.44) in the second visit]. GABA from the occipital cortex predicted speed and achromatic luminance discrimination thresholds within the same visit (r = 0.54 and 0.52; p = 0.02 and 0.03, respectively) in type 2 diabetes group. GABA from the occipital cortex also predicted speed discrimination thresholds one year later (r = 0.52; p = 0.03) in the type 2 diabetes group. Our results suggest that speed discrimination is impaired in type 2 diabetes and that occipital cortical GABA is a novel predictor of visual psychophysical performance independently from retinopathy grade, metabolic control or disease duration in the early stages of the disease.
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Diabetic Brain or Retina? Visual Psychophysical Performance in Diabetic Patients in Relation to GABA Levels in Occipital Cortex
Metab Brain Dis 2017 Mar 30;[EPub Ahead of Print], M Sanches, SI Abuhaiba, OC d'Almeida, B Quendera, L Gomes, C Moreno, D Guelho, M Castelo-BrancoFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
This novel study correlates occipital cortical GABA levels and type 2 diabetic patient functioning on psychophysical tests. The authors found abnormalities in these tests independent of diabetic retinopathy grade, metabolic control, or disease duration in the early stages of the disease. This study may provide useful criteria for judging prophylactic treatment of diabetic complications.
This paper reflects a growing trend toward clinical tests that are more indicative of visual brain function beyond visual acuity. Similar to functional amblyopia, psychophysical tests can serve as more sensitive biomarkers regarding impaired visual function. In type 2 diabetes, having more sensitive psychophysical tests such as the novel speed discrimination test used in this study can serve as a more complete visual index of compromised visual function indicative of alteration in occipital GABA/Cr.