Effect Of Hyperglycemic Memory On The Retina And Optic Nerve Of Diabetic Rats

ObjectiveHyperglycemia induce the uptake of neurotransmitter GABA and Gluin retina of diabetic rat, and also the apoptosis of neurons. The goalof this study was to identify the early pathological changes in the ratretina induced by diabetes that are not normalized by insulin replacementand restoration of euglycemia.Methods60SD rats (male,200–220g body weight) were randomly assignedto three groups: normal group;diabetes group;metabolic memory group.Therats in these groups but normal group received a one-time intraperitonealinjection of60mg/kg streptozotocin (STZ; Sigma) in10mM sodium citratevehicle, pH4.5as previously described, to induce experimental model oftype1diabetes. The tail venous blood was taken after72hours. The bloodsugar value or greater tendency for16.7mmol/L for diabetic rats, namelymodel group.15SD rats were choosed as the normal control group, onlyinjected with sodium citrate vehicle.Normal rats act as NC group; DM group, remained in poor glycemiccontrol for the entire duration of the experiment; DI group, were in poorglycemic control for6weeks followed by good glycemic control for6additional weeks. These rats in DI group received subcutaneous injectionswith insulin in the back or the neck2times daily, and the total amountis6-8iu/D. It was necessary to measure blood glouse in every3day foradjusting the dose of insulin, to make sure blood sugar target under 10mmol/L.15rats from the DM group were sacrificed by an overdose ofpentobarbital at6weeks acked as DM1group, and the eyes were enucleatedimmediately.The eyes were cryopreserved(-80℃) or made into paraffinblocks; The rest of the group called DM2group and other groups weresacrificed at12weeks out. Using High Performance Liquid Chromatography(HPLC) way to detect the amount of Glu and GABA in the rat retina; Theretinal distributions of GAD were detected by immunofluorescence stainingand the mRNA expressions of GAD were quantified by Real-time polymerasechain reaction (RT-PCR) respectively. Cell apoptosis was detected byTdT mediated dUTP nick ending labelling (TUNEL).ResultsDI group have a higher concentration of Glu and GABA than DM1groupand NC group, but less than DM2group. Difference about the concentrationof Glu and GABA between these groups was statistically significant (P <0.05), but the ratio of Glu/GABA between DM2group and DI group has nostatistically significant difference (P＞0.05). The retinaldistributions of GAD were detected by immunofluorescence staining andRT-PCR between these groups was statistically significant (P <0.05), DIgroup with DM1group were significantly lower than NC group (P <0.05),also it has increased significantly than DM1group (P <0.05).Immunohistochemical OD value analysis of GAD is consistent with that trendwith RT-PCR detection. Counting nerve cells apoptosis, four groupsrespectively: each group with the difference was statisticallysignificant (P <0.05), DI group compared with NC group or DM1groupincreased significantly (P <0.05). ConclusionsThe continued activation of neurotransmitter or apoptosis plays amajor role in the resistance of retinopathy to halt after reinstitutionof good glycemic control, and the regulation for them could help retardthe progression of diabetic retinopathy. As it occurs in diabetic patientsreceiving insulin replacement, and are prototypical of metabolic memory.