Evaluation of the impact of diabetes on retinal metabolites by NMR spectroscopy.
OBJECTIVE
Diabetic retinopathy (DR) is a leading cause of blindness in working age adults in developed countries. Changes in metabolites and in metabolic pathways of the retina caused by hyperglycemia may compromise the physiology of the retina. Using nuclear magnetic resonance (NMR) spectroscopy, we aimed to investigate the effect of diabetes on the levels of intermediate metabolites in rat retinas and the metabolic pathways that could be affected.


METHODS
Diabetes was induced in male Wistar rats with a single injection of streptozotocin (65 mg/Kg, i.p.). Metabolic alterations were analyzed in streptozotocin-induced diabetic rat retinas by (1)H NMR spectroscopy. Glucose uptake was measured with 2-deoxy-D-[1-(3)H]glucose. Lactate production was evaluated by (1)H NMR spectroscopy using [U-(13)C]glucose.


RESULTS
Tissue levels of several metabolic intermediates were quantified, but no significant changes in the levels of most metabolites were detected, with the exceptions of glucose, significantly increased, and lactate, significantly reduced in diabetic rat retinas, as compared to age-matched controls. The cytosolic redox ratio, indirectly evaluated by lactate-to-pyruvate ratio, was significantly reduced in diabetic rat retinas, as well as glucose uptake. Parallel studies demonstrated that lactate production rates were significantly diminished, suggesting a reduction in the glycolytic flux.


CONCLUSIONS
These results suggest that diabetes may significantly decrease glycolysis in the retina since higher intracellular glucose levels do not translate into higher intracellular lactate levels or into higher rates of lactate production. These changes may alter the normal functioning of the retina during diabetes and may contribute for vision loss in DR.
Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal. asantiago@fmed.uc.pt
A R
AR
Santiago
M J
MJ
Garrido
A J
AJ
Cristóvão
J M N
JM
Duarte
R A
RA
Carvalho
A F
AF
Ambrósio
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D003847:Deoxyglucose / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D003930:Diabetic Retinopathy / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D006019:Glycolysis; D019344:Lactic Acid / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012160:Retina / Q000378:metabolism*
D001786:Blood Glucose; D019344:Lactic Acid; D003847:Deoxyglucose; D005947:Glucose