【作者】 王佳；

【导师】 刘学波；

【作者基本信息】 西北农林科技大学 ， 食品科学， 2019， 博士

【摘要】 以高脂高糖饮食模式为代表的高能量膳食已成为当今世界普遍的饮食结构,由此引发的肥胖、糖尿病、胃肠功能紊乱及认知功能障碍等健康问题日益受到人们重视。高能量膳食诱发认知障碍的分子机制非常复杂,涉及了对机体“肠-肝-脑”轴代谢的系统性影响。近年来,通过膳食补充食品功能活性组分改善糖脂代谢紊乱及认知损伤已成为食品营养领域内的重要研究方向。番茄红素是番茄中的主要类胡萝卜素类食品功能组分,具有抗炎、抗氧化等生物功能,且具有血脑屏障通透性的生物学特点。基于此,本研究以食品功能组分番茄红素为研究对象,以“肠-肝-脑”轴为靶点,通过体内外实验探究了番茄红素对高能量膳食诱导的糖脂代谢紊乱及认知障碍的改善作用,主要研究内容与结果如下:(1)采用高脂肪高果糖饮食(High-fat and high-fructose diet,HFFD)诱导C57BL/6J小鼠肥胖模型,探究膳食补充番茄红素对机体肥胖的干预作用及潜在机制。结果显示膳食补充番茄红素能够降低HFFD引起的小鼠体重增加,平衡肥胖小鼠血清脂质含量,改善小鼠葡萄糖耐受性及胰岛素敏感性,并且能通过降低血液中促炎因子IL-1β,TNFɑ和IL-6含量,减轻HFFD引起的小鼠系统性炎症。(2)利用肥胖小鼠脑组织与SH-SY5Y神经元细胞,探究番茄红素对HFFD诱导小鼠认知障碍,神经元损伤,突触可塑性降低,脑部胰岛素抵抗及神经炎症的干预作用。动物行为学检测结果显示,膳食补充番茄红素可有效减轻HFFD诱导的小鼠记忆损伤;番茄红素可通过增加突触致密物含量及突触蛋白表达,改善小鼠突触可塑性;膳食补充番茄红素有效减轻了HFFD诱导的小鼠脑部胰岛素抵抗及神经炎症;番茄红素预处理可通过调控细胞内氧化还原状态及炎症反应改善葡萄糖诱导SH-SY5Y神经元细胞胰岛素抵抗。(3)选取肥胖小鼠肝脏组织及HepG2肝细胞,探究番茄红素对HFFD诱导的小鼠肝脏脂质积累及胰岛素抵抗的干预作用。结果显示,膳食补充番茄红素可有效减轻HFFD诱导的肝脏重量增加,改善肝脏胰岛素抵抗。同时,番茄红素可通过调控肝脏脂质代谢基因表达,改善肝脏脂质积累。膳食补充番茄红素可通过增加线粒体呼吸链复合物I-IV及线粒体功能基因表达,有效改善HFFD诱导的肝脏线粒体功能损伤。另外,膳食补充番茄红素可通过抑制MAPKs/NFκB通路激活,下调促炎因子iNOS及COX-2表达,改善HFFD诱导的肝脏炎症。此外,番茄红素预处理可通过促进PPARɑ表达,抑制棕榈酸诱导的HepG2肝细胞甘油三酯及总胆固醇积累。番茄红素可通过介导IRS-1/AKT通路,增强线粒体功能改善棕榈酸诱导的HepG2肝细胞胰岛素抵抗。(4)选取小鼠肠道组织,探究番茄红素对小鼠肠道脂质积累及炎症反应的干预作用。结果显示,膳食补充番茄红素可促进HFFD小鼠肠道脂肪酸氧化,降低肠道甘油三酯含量。同时,膳食补充番茄红素增加了肠道紧密连接蛋白Occludin、Zo-1和Claudin-1表达,改善了肠道屏障完整性,减轻了HFFD诱导的肠道炎症,降低了血液循环系统中LPS含量,有效增加了HFFD小鼠短链脂肪酸乙酸含量。(5)选取小鼠脂肪组织及3T3-L1脂肪细胞,探究番茄红素对脂肪组织脂质积累的抑制作用。结果显示,膳食补充番茄红素可通过抑制脂肪合成基因表达,增加脂肪分解基因表达(包括产热基因和线粒体功能基因)有效抑制HFFD诱导的脂肪组织增生及脂质积累。同时,膳食补充番茄红素增强了白色脂肪组织自噬,改善了HFFD诱导的脂肪组织炎症反应。另外,番茄红素可通过调节脂质代谢基因表达,抑制3T3-L1脂肪细胞脂质积累。综上所述,膳食补充番茄红素可能会通过影响肠道屏障功能及肠道微生物产物,调控肝脏糖脂代谢,减轻高能量膳食诱导的机体系统性胰岛素抵抗与炎症反应,最终改善脑部突触可塑性及认知功能。本研究发现的“肠-肝-脑”轴介导番茄红素的功能活性机制研究可为番茄红素作为主要功能成分的营养食品开发提供理论基础,同时为其他食品功能组分干预高能量膳食引起的认知损伤提供新的研究思路。更多还原

【Abstract】 High-fat and high-fructose diet(HFFD)has become more and more popular and HFFD-induced obesity,diabetes,gastrointestinal dysfunction and cognitive impairments seriously affect human health.The underlying molecular mechanisms by which HFFD-induced memory loss were complicated and the glycolipid metabolism in gut-liver-brain axis were closely related to cognitive function.In recent years,the exploration of food functional components that may improve glycolipid metabolism and cognitive function has become an important research direction in food nutrition field.Lycopene(LYC),a major carotenoid present in tomato,has been demonstrated to possess health-beneficial functions,such as anti-inflammatory and anti-oxidant effects and blood-brain barrier permeability.With this background,the aim of the current study was to investigate the inhibitory effect of LYC on HFFD-induced cognitive impairments and the protective effects on HFFD-elicited insulin resistance,lipid metabolism dysfunction in gut-liver-brain axis.The main investigations and results are as follows:(1)To investigate the effect of dietary LYC on HFFD-induced obesity,C57BL/6J mice were treated with HFFD and LYC.The present work revealed that LYC treatment suppressed mice body weight gain compared with the HFFD group;LYC improved lipid contents in plasma of obesity mice;LYC supplementation reversed HFFD-eilicited insulin resistance and glucose intolerance.Moreover,LYC supplementation inhibited systemic inflammation through decreasing circulating IL-1β,TNFɑ and IL6 levels.(2)Mice brain tissues and SH-SY5 Y cells were selected to investigated the protective effects of LYC on HFFD-induced cognitive deficits,neuronal cells damages,decreased synaptic plasticity,insulin resistance and neuroinflammation in mice brain.Results of animal behavior tests indicated that the supplementation of LYC improved HFFD-induced memory impairments.LYC significantly improved the contents of postsynaptic density in the hippocampus and increased the expressions of synaptosomal functional proteins compared to the HFFD group.Moreover,LYC attenuated HFFD-induced insulin resistance and neuroinflammation in mice brain.Furthermore,LYC supplementation improved glucose-induced insulin resistance through mediating neuroinflammation and oxidative stress in SH-SY5 Y cells.(3)Liver tissues and HepG2 cells were selected to examined the effects of LYC on HFFD-induced hepatic lipid accumulation and insulin resistance.Results showed that LYC decreased liver weight and improved hepatic insulin resistance compared with HFFD group.LYC suppressed hepatic lipid accumulation by increasing lipidolysis and blocking lipogenesis.LYC also alleviated hepatic mitochondrial dysfunction through increasing the expressions of mitochondrial respiration complexs I-IV and mitochondrial functional genes.Moreover,LYC alleviated hepatic inflammatory response via suppressing the activation of MAPKs/NFκB pathways and down-regulating the expressions of proinflammatory cytokine iNOS and COX-2.In addition,LYC treatments effectively reduced triglyceride and total cholesterol concentrations in palmitate-treated HepG2 cells in a PPARɑ-dependent manner and LYC improved insulin resistance via mediating IRS-1/AKT pathway and enhancing mitochondrial function in palmitate-treated HepG2 cells.(4)Gut tissues were selected to examined the effects of LYC on HFFD-induced intestinal lipid accumulation and inflammatory responses.Results indicated that LYC supplementation down-regulated intestinal triglyceride levels through improving fatty acid oxidation.Meanwhile,LYC treatment also increased the expressions of Occludin,Zo-1 and Claudin-1 compared to HFFD group,improved intestinal integrity.LYC alleviated HFFD-triggered gut inflammation,decreased circulating LPS level and increased short-chain fatty acid acetic acid contents.(5)Adipose tissues and 3T3-L1 adipocytes were selected to examined the effects of LYC on HFFD-induced lipid accumulation in adipose tissue.Results indicated that LYC blocked HFFD-induced adipocyte hypertrophy and lipid accumulation in adipose tissue by decreasing the expressions of lipogenesis genes and increasing the expressions of lipidolysis genes,including thermogenic and mitochondrial functional genes.Moreover,LYC enhanced autophagy in WATs and improved HFFD-induced inflammation responses in WATs.Furthermore,LYC inhibited lipid accumulation in 3T3-L1 adipocytes by regulating lipid metabolism gene expression.In conclusions,the supplementation of LYC might regulate intestinal barrier function and intestinal microbial products,improved glucose and lipid metabolism in liver and reduced systemic insulin resistance and inflammatory responses induced by high-calorie diets,and ultimately improve synaptic plasticity and cognitive function.The present study could provide a theoretical basis for the development of healthy foods with LYC as a major functional ingredient and could provide new strategies for nutritional intervention studies of other natural functional food components on high-calorie diets induced cognitive impairments.更多还原