生酮饮食对海藻酸致痫大鼠海马突触重建和GLUR_5、GLUR_6 MRNA的影响(英文)

Effect of ketogenic diet on hippocampus synaptic reorganization and GluR_5, GluR_6 mRNA in kainic acid induced model

目的生酮饮食是一种高脂、低蛋白和低糖饮食。它的抗痫作用早已明确,但其抗痫机制至今不明。本研究试图从海马突触重建和GLUR5、GLUR6 MRNA表达两方面初步探讨生酮饮食的可能抗痫机制。方法以海藻酸(KAINIC ACID,KA)点燃的雄性SD大鼠(P28)为研究对象,经正常饮食和生酮饮食喂养8周。通过行为学检测、 TIMM’S染色和尼氏染色,观察经不同饮食处理的动物海马苔藓纤维发芽(MFS)和神经元损伤情况,及其癫痫行为和空间学习、记忆功能的变化;经RT-PCR法检测海马GLUR5、GLUR6 MRNA的表达。结果 KA致痫后生酮饮食组动物自发性反复惊厥的次数为(1．40±1．03)次明显少于正常饮食组(7．36±3．7)次。在水迷宫检测中,各组动物找到平台的潜伏期随着测试进行明显缩短(F=33．93,P<0．001),但各处理组间潜伏期却无显著差异(F= 1．24,P=0．32)。KA致痫大鼠海马齿状回内分子层异常TIMM’S染色颗粒的平均A值均显著高于非致痫组,但生酮饮食组和正常饮食组间则无明显差异;各组动物CA3区锥体细胞层及始层的TIMM’S染色颗粒以及海马门和CA1、CA3区神经元的平均A值未见明显差异。KA致痫后生酮饮食组大鼠海马GLUR6 MRNA(48．16±11.53) 明显高于正常饮食组(30．57±15．57,T=2．40,P<0．05),但两组间GLUR5 MRNA却没有显著性差异。结论生酮饮食对KA致痫幼鼠有显著的抗痫作用,并对发育期大脑的空间学习和记忆能力无明显影响。酮食疗法不能抑制KA致痫幼鼠的MFS,它可能通过特有的神经元保护作用,保持大鼠海马GLUR6 MRNA的高表达,抑制苔藓纤维通路的兴奋性传递进而发挥其抗痫作用。

Objective Ketogenic diet （KD） is a high fat, low protein, low carbohydrate diet. Its antiepileptic effect is certain but the underlying mechanism is unknown. The aim of the study is to reveal the possible antiepileptic mechanism of KD treatment from the view points of synaptic reorganization and GluR5 , GluR6 mRNA in hippocampus. Methods Sprague-Dawley rats were induced by kainic acid （KA） at postnatal day 28 as experimental group, control animals were injected the same volume of saline. Animals from each group were divided into two parts, each of which was fed normal rodent chow or ketogenic diet for 8 weeks. Spontaneous recurrent seizures were recorded. Spatial learning and memory ability was evaluated by Morris water maze. Mossy fiber sprouting and neuron damage in hippocampus were investigated by Timm staining and Nissl staining. RT-PCR method was applied to detect the expression of GluR5 , GluR6 mRNA in hippocampus. Results KD-fed rats had significantly fewer spontaneous recurrent seizures（ 1.40±1.03 ） than control diet-fed rats（7.36±3.75 ）. In water maze testing, all groups demonstrated improvement in water maze performance with significantly decreased escape latencies during the testing days （ F = 33.93 , P 〈 0. 001 ）, but no significant differences were found in the time to platform among the four groups（F = 1.24 , P = 0.32）. The mean A of mossy fiber sprouting in the inner molecular layer of dentate gyms was markedly higher in KA-induced animals than that in saline control animals but it was similar in different diet-fed groups. No differences were found in the mean A of Timm staining in CA3 area and Nissl staining of neurons in hilus, CA3 and CA1 areas. In KA ＋ KD group rats, GluR6mRNA was statistically higher （48.16 ±11.53 ） than that in KA ＋ ND group rats （ 30.57 ± 15.57, t = 2.40, P 〈 0.05 ）, but no significant difference of GluR5 mRNA was found in these two groups （ t＇ = - 0.09, P 〉 0.05 ）. Conclusion KD had prominent antiepileptic effect on KA-induced rats and it had no significant impairment on spatial learning and memory for the developing brain. KD can not prevent the MFS in young KA-induced rats, but it may play its antiepileptic role by keeping the high level expression of GluR6 mRNA in the hippocampus, due to its specific neuroprotective action, to inhibit the excitatory transmission.at the MF pathway.