The Influence Of The Rising Blood Glucose Level On Brain Injury After Hypoglycemia In Rats

Objective: To explore the influence of the rising blood glucose level on brain injuryin rats after insulin-induced hypoglycemia, put forward the "brain injury induced byglucose-reperfusion":.Methods:30adult male SD rats (weight:300±50g, age:4months) were simplingrandomly divided into three equal groups: experimental group has20rats, both vehiclecontrol group and normal control group have5rats. Experimental group were intravenousinjected with insulin. Hypoglycemia rats were induced by insulin.The blood suger level islower than1mmol/L and sustaining1hour. According to the blood glucose concentrationafter reperfusion,20rats from experimental group were sub-divided into four groups:1＜blood sugar≤3mmol/L,3＜blood sugar≤6mmol/L,6＜blood sugar≤9mmol/L and bloodsugar>9mmol/L.(blood sugar=blood glucose level). The vehicle control group wereprepared by intravenous administration of1.5ml/h of25%glucose simultaneously with1u/h of insulin to maintain a plasma blood level between5.5±0.25mmol/L for5hours.The normal control group were5normal rats. TUNEL staining was used to detect theneurons undergoing apoptosis, Fluoro-Jade (FJB) staining was performed to reveal thedegenerating neuronal cell bodies and axons, and HE staining was used to detect theneurons necrosis. SAS8.0software analysis and processing, staining between the twogroups of measurement data using single factor analysis of variance (data), the differencewas statistically significant (P<0.05). Results Brain damage were detected in all rats.(1) TUNEL staining: the percentageof apoptotic neurons showed an obvious increase from the experimental group(hippocampal CA1:40.2±3.1;38.7±2.4;36.8±2.6and76.4±6.3, hippocampal DG:62.4±4.2;59.8±3.7;68.1±2.8and125.4±5.8) compared to the control group (hippocampal CA1:3.2±1.9;2.8±0.8, hippocampal DG:4.1±2.4;3.4±1.2), the difference was statisticallysignificant (hippocampal CA1: F=13.52, P<0.05, hippocampal DG: F=14.29, P<0.05);among the subgroupsfrom the experimental group, the percentage of apoptotic neuronsfrom blood sugar>9mmol/L group (hippocampal CA1:76.4±6.3, hippocampal DG:125.4±5.8) rose more markedly than the other three groups (hippocampal CA1:40.2±3.1;38.7±2.4;36.8±2.6, hippocampal DG:62.4±4.2;59.8±3.7;68.1±2.8), the difference wasstatistically significant (hippocampal CA1: F=5.08, P<0.05, hippocampal DG: F=6.52,P<0.05);(2) FJB staining: FJB positive cells were nearly undetectable in control group,(hippocampal CA1:4.2±2.1;3.6±1.3, hippocampal DG:4.1±2.4;3.4±1.2), however therewas a larger portion of neurons positive for FJB in hippocampus of experimental group rats,(hippocampal CA1:40.2±3.1;38.7±2.4;36.8±2.6and76.4±6.3, hippocampal DG:62.4±4.2;59.8±3.7;68.1±2.8and125.4±5.8) there was a statistical significance betweencontrol group and experimental group (hippocampal CA1: F=18.49, P<0.05, hippocampalDG: F=11.37, P<0.05); furthermore, compared with the other three experiment group(hippocampal CA1:65.3±2.8;69.7±3.1;71.5±4.1and134.8±5.5, hippocampal DG:62.4±4.2;59.8±3.7;68.1±2.8and125.4±5.8), the percentage of FJB positive cells in bloodsugar>9mmol/L group (hippocampal CA1:134.8±5.5, hippocampal DG:125.4±5.8) wassignificantly increased, the difference was statistically significant (hippocampal CA1:F=7.83, P<0.05, hippocampal DG: F=14.29, P<0.05).(3) HE staining: the necrosisneurons were nearly undetectable in control group,(hippocampal CA1:5.3±1.0;5.1±0.9,hippocampal DG:6.3±2.4;5.4±1.5), however there was a larger portion of the necrosisneurons in hippocampus of experimental group rats,(hippocampal CA1:17.1±3.2;19.0±2.7;19.9±1.8和37.6±2.2, hippocampal DG:31.4±3.2;29.8±2.7;38.1±2.3和55.4±6.2), there was a statistical significance between control group and experimental group (hippocampal CA1: F=20.46, P<0.055, hippocampal DG: F=12.15, P<0.05);furthermore, compared with the other three experiment group, the percentage of thenecrosis neurons in blood sugar>9mmol/L group was significantly increased., thedifference was statistically significant (hippocampal CA1: F=6.97, P<0.05, hippocampalDG: F=17.13, P<0.05).Conclusions: Control the rats on the same level of blood glucose and the sameduration of the hypoglycemia, the severity of brain injury is closely correlated to the risingblood glucose concentration after hypoglycemia: the higher glucose level is, the moreserious imparement brain suffer. The hypoglycemic brain damage was aggravated.Allthese suggest that＂brain injury induced by glucose-reperfusion＂may exist.