高脂饮食条件下极长链饱和脂肪酸对大鼠认知功能的影响及相关机制

Effects of very-long-chain saturated fatty acids on cognitive function of rats under high-fat diet and its related mechanisms

目的:探讨高脂饮食条件下极长链饱和脂肪酸(VLCSFA)对大鼠认知功能的影响及相关机制。方法:将50只雄性SD大鼠随机分为5组,每组10只,即空白对照组组(饲喂基础饲料)、低含量对照(L-CON)组(饲喂20%对照用油)、低含量VLCSFA(L-VLC)组(饲喂20%实验用油)、高含量对照(H-CON)组(饲喂30%对照用油)和高含量VLCSFA(H-VLC)组(饲喂30%实验用油),饲喂12周。Morris水迷宫测定大鼠学习记忆能力;气相色谱法检测脑皮质脂肪酸组成及含量;生化法检测脑氧化应激水平;ELISA法检测脑促炎因子水平;Western blot法检测脑中β-分泌酶(BACE1)、α-分泌酶(ADAM10)、磷酸化tau蛋白及细胞凋亡相关蛋白的水平。结果:与L-CON组相比,LVLC组大鼠穿越平台次数显著减少(P<0.05),脑皮质C21:0、C22:0、C23:0、C24:0、C26:0和ΣVLCSFA含量显著增加(P<0.05或P<0.01),ADAM10蛋白水平显著下降(P<0.01),BACE1和p-tau396蛋白水平显著升高(P<0.05),谷胱甘肽过氧化物酶(GSH-Px)活性显著降低(P<0.01),丙二醛(MDA)水平显著升高(P<0.05),白细胞介素6(IL-6)和肿瘤坏死因子(TNF-α)水平显著升高(P<0.01);与H-CON组相比,H-VLC组大鼠逃避潜伏期显著延长(P<0.05),脑皮质C20:0、C21:0、C22:0、C23:0、C24:0、C26:0和ΣVLCSFA含量均显著升高(P<0.05或P<0.01),ADAM10蛋白水平显著下降(P<0.01),BACE1、p-tau396和p-tau404蛋白水平显著升高(P<0.01),超氧化物歧化酶(SOD)和GSHPx活性显著降低(P<0.05或P<0.01),MDA水平显著升高(P<0.05),IL-1β、IL-6和TNF-α水平显著升高(P<0.01),B细胞淋巴瘤/白血病蛋白2(Bcl-2)水平显著降低(P<0.05),Bcl-2相关X蛋白(Bax)和cleaved caspase-3蛋白水平显著升高(P<0.05或P<0.01)。结论:通过高脂饮食大量摄入VLCSFA会损害大脑认知功能,其机制可能与脑组织VLCSFA积累增多、淀粉样前体蛋白代谢、tau蛋白过度磷酸化、氧化应激、神经炎症和细胞凋亡有关。

AIM:To examine the effects of very-long-chain saturated fatty acids(VLCSFA)on cognitive function of rats having high-fat diet and the underlying mechanisms.METHODS:Fifty male SD rats were randomly dividedinto 5 groups(n=10)and had the following feed for 12 weeks:blank control group(basic feed),low control oil(L-CON)group(20%control oil),low VLCSFA(L-VLC)group(20%test oil),high control oil(H-CON)group(30%control oil)and high VLCSFA(H-VLC)group(30%test oil).Morris water maze test was used to evaluate the learning and memory impairment of rats.The composition and content of fatty acids in cerebral cortex were determined by gas chromatography.The levels of oxidative stress and inflammatory factor biomarkers were measured using biochemical assay and ELISA kits,respectively.In addition,Western blot was used to determine the levels ofβ-secretase(beta-site amyloid protein precursor-cleaving enzyme 1,BACE1),α-secretase(a disintegrin and metalloproteinase 10,ADAM10),phosphorylated tau protein and apoptosis factors in brains.RESULTS:Compared with L-CON group,the rats in L-VLC group exhibited fewer platform crossings(P<0.05),and higher levels of C21:0,C22:0,C23:0,C24:0,C26:0 andΣVLCSFA in the cerebral cortex(P<0.05 or P<0.01).The levels of BACE1 and p-tau396 were increased(P<0.05),while the expression of ADAM10 decreased(P<0.01).The activity of antioxidant glutathione peroxidase(GSH-Px)was decreased(P<0.01),while the level of malonaldehyde(MDA)increased(P<0.05).The levels of interleukin-6(IL-6)and tumor necrosis factor-α(TNF-α)were increased(P<0.01).Compared with H-CON group,the rats in H-VLC group had longer escape latency(P<0.05),and higher levels of C20:0,C21:0,C22:0,C24:0,C26:0 andΣVLCSFA in the cerebral cortex(P<0.05 or P<0.01).The levels of BACE1,p-tau396 and p-tau404 were increased(P<0.01),while the expression of ADAM10 decreased(P<0.01).The activity of superoxide dismutase(SOD)and GSH-Px were decreased(P<0.05 or P<0.01),while the level of MDA increased(P<0.05).The levels of IL-1β,IL-6 and TNF-αwere increased(P<0.01).Additionally,the level of B-cell lymphoma/leukemia-2(Bcl-2)was decreased(P<0.05),and the levels of Bcl-2-associated X protein(Bax)and cleaved caspase-3 were increased(P<0.05 or P<0.01).CONCLUSION:Intake of excessive VLCSFA in high-fat diet impairs cognitive function probably through induction of VLCSFA accumulation,amyloid precursor protein metabolism disorders,tau protein hyperphosphorylation,oxidative stress,neuroinflammation,and apoptosis.