A high-fat diet and high-fat and high-cholesterol diet may affect glucose and lipid metabolism differentially through gut microbiota in mice

This study was conducted to investigate the effects of a high-fat diet (HFD) and high-fat and high-cholesterol diet (HFHCD) on glucose and lipid metabolism and on the intestinal microbiota of the host animal. A total of 30 four-week-old female C57BL/6 mice were randomly divided into three groups (n=10) and fed with a normal diet (ND), HFD, or HFHCD for 12 weeks, respectively. The HFD significantly increased body weight and visceral adipose accumulation and partly lowered oral glucose tolerance compared with the ND and HFHCD. The HFHCD increased liver weight, liver fat infiltration, liver triglycerides, and liver total cholesterol compared with the ND and HFD. Moreover, it increased serum high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and total cholesterol compared with the ND and HFD and upregulated alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase significantly. The HFHCD also significantly decreased the α-diversity of the fecal bacteria of the mice, to a greater extent than the HFD. The composition of fecal bacteria among the three groups was apparently different. Compared with the HFHCD-fed mice, the HFD-fed mice had more Oscillospira, Odoribacter, Bacteroides, and [Prevotella], but less [Ruminococcus] and Akkermansia. Cecal short-chain fatty acids were significantly decreased after the mice were fed the HFD or HFHCD for 12 weeks. Our findings indicate that an HFD and HFHCD can alter the glucose and lipid metabolism of the host animal differentially; modifications of intestinal microbiota and their metabolites may be an important underlying mechanism.     

Val-Val-Tyr-Pro protects against non-alcoholic steatohepatitis in mice by modulating the gut microbiota and gut-liver axis activation

Val-Val-Tyr-Pro (VVYP) peptide is one of the main active components of Globin digest (GD). Our previous studies indicated that VVYP could protect against acetaminophen and carbon tetrachloride-induced acute liver failure in mice and decrease blood lipid level. However, the effects and underlying mechanisms of VVYP in the treatment of non-alcoholic steatohepatitis (NASH) have not been discovered. Our present study was designed to investigate the preventive effect of VVYP on NASH and its underlying specific mechanisms. We found that VVYP inhibited the cytotoxicity and lipid accumulation in L-02 cells that were exposed to a mixture of free fatty acid (FFA). VVYP effectively alleviated the liver injury induced by methionine-choline-deficient (MCD) diet, demonstrated by reducing the levels of serum alanine aminotransferase (ALT)/aspartate aminotransferase (AST)/triglycerides (TG)/non-esterified fatty acids (NEFA) and improving liver histology. VVYP decreased expression levels of lipid synthesis-related genes and reduced levels of the proinflammation cytokines in the liver of mice fed by MCD diet. Moreover, VVYP inhibited the increased level of LPS and reversed the liver mitochondria dysfunction induced by MCD diet. Meanwhile, VVYP significantly increased the abundance of beneficial bacteria such as Eubacteriaceae, coriobacteriacease, Desulfovibrionaceae, S24-7 and Bacteroidia in high-fat diet (HFD)-fed mice, however, VVYP reduced the abundance of Lactobacillus. Moreover, VVYP conferred the protective effect of intestinal barrier via promoting the expression of the mucins and tight junction (TJ)-associated genes and inhibited subsequent liver inflammatory responses. These results indicated that the protective role of VVYP on NASH is mediated by modulating gut microbiota imbalance and related gut-liver axis activation. VVYP might be a promising drug candidate for NASH.     

Diet leaves a genetic signature in a keystone member of the gut microbiota

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High-fat diet alters gut microbiota physiology in mice

The intestinal microbiota is known to regulate host energy homeostasis and can be influenced by high-calorie diets. However, changes affecting the ecosystem at the functional level are still not well characterized. We measured shifts in cecal bacterial communities in mice fed a carbohydrate or high-fat (HF) diet for 12 weeks at the level of the following: (i) diversity and taxa distribution by high-throughput 16S ribosomal RNA gene sequencing; (ii) bulk and single-cell chemical composition by Fourier-transform infrared- (FT-IR) and Raman micro-spectroscopy and (iii) metaproteome and metabolome via high-resolution mass spectrometry. High-fat diet caused shifts in the diversity of dominant gut bacteria and altered the proportion of Ruminococcaceae (decrease) and Rikenellaceae (increase). FT-IR spectroscopy revealed that the impact of the diet on cecal chemical fingerprints is greater than the impact of microbiota composition. Diet-driven changes in biochemical fingerprints of members of the Bacteroidales and Lachnospiraceae were also observed at the level of single cells, indicating that there were distinct differences in cellular composition of dominant phylotypes under different diets. Metaproteome and metabolome analyses based on the occurrence of 1760 bacterial proteins and 86 annotated metabolites revealed distinct HF diet-specific profiles. Alteration of hormonal and anti-microbial networks, bile acid and bilirubin metabolism and shifts towards amino acid and simple sugars metabolism were observed. We conclude that a HF diet markedly affects the gut bacterial ecosystem at the functional level.     

Capsaicin suppresses liver fat accumulation in high-fat diet-induced NAFLD mice

ABSTRACT

Dietary capsaicin exhibits anti-steatosis activity in obese mice. High-fat diet (HFD)-induced mice is a highly studied approach to develop non-alcoholic fatty liver disease (NAFLD). In this study, we determined whether the topical application of capsaicin can improve lesions of NAFLD. The HFD-induced mice were treated with daily topical application of capsaicin for 8 weeks. Topical application of capsaicin reduced liver fat in HFD-fed mice. Capsaicin stimulated carnitine palmitoyl transferase (CPT)-1 and CD36 expression, which are associated with β-oxidation and fatty acids influx of liver while it decreased the expression of key enzymes involved in the synthesis of fatty acids, such as acetyl Co-A carboxylase (ACC) and fatty acid synthase (FAS). Immunohistochemical analysis revealed the elevated level of adiponectin in liver tissue of the capsaicin-treated mice. These results suggest that the topical application of capsaicin suppresses liver fat accumulation through the upregulation of β-oxidation and de novo lipogenesis in HFD-induced NAFLD mice.     

Structural resilience of the gut microbiota in adult mice under high-fat dietary perturbations

Disruption of the gut microbiota by high-fat diet (HFD) has been implicated in the development of obesity. It remains to be elucidated whether the HFD-induced shifts occur at the phylum level or whether they can be attributed to specific phylotypes; additionally, it is unclear to what extent the changes are reversible under normal chow (NC) feeding. One group (diet-induced obesity, DIO) of adult C57BL/6J mice was fed a HFD for 12 weeks until significant obesity and insulin resistance were observed, and then these mice were switched to NC feeding for 10 weeks. Upon switching to NC feeding, the metabolic deteriorations observed during HFD consumption were significantly alleviated. The second group (control, CHO) remained healthy under continuous NC feeding. UniFrac analysis of bar-coded pyrosequencing data showed continued structural segregation of DIO from CHO on HFD. At 4 weeks after switching back to NC, the gut microbiota in the DIO group had already moved back to the CHO space, and continued to progress along the same age trajectory and completely converged with CHO after 10 weeks. Redundancy analysis identified 77 key phylotypes responding to the dietary perturbations. HFD-induced shifts of these phylotypes all reverted to CHO levels over time. Some of these phylotypes exhibited robust age-related changes despite the dramatic abundance variations in response to dietary alternations. These findings suggest that HFD-induced structural changes of the gut microbiota can be attributed to reversible elevation or diminution of specific phylotypes, indicating the significant structural resilience of the gut microbiota of adult mice to dietary perturbations.     

去卵巢小鼠肠道菌群和血脂的变化

目的 探讨去卵巢对小鼠肠道菌群和血脂的影响。 方法 12只10周龄C57BL/6小鼠随机分为2组:假手术组(SHAM组)和去卵巢组(OVX组),每组6只,进行12周的喂养。每2周测定小鼠体质量,12周后测肝脏指数、血清三酰甘油水平和游离脂肪酸水平,小肠进行病理学检查,收集小鼠粪便并在Illumina MiSeq测序平台进行16S rRNA基因测序检测。 结果 与SHAM组相比,OVX组小鼠体质量、肝脏指数、血清三酰甘油水平和游离脂肪酸水平明显增加(t=4.745,t=15.090,t=11.140,t=4.038,均P结论 去卵巢小鼠血脂升高和肠道菌群失衡,提示肠道菌群可能是预防和治疗雌激素缺乏后脂质代谢异常的潜在靶点。     

Astragaloside IV alleviates mouse slow transit constipation by modulating gut microbiota profile and promoting butyric acid generation

Gut microbiota and short‐chain fatty acids (SCFAs) are associated with the development of various human diseases. In this study, we examined the role of astragaloside IV in modulating mouse gut microbiota structure and the generation of SCFAs, as well as in slow transit constipation (STC). An STC model was established by treating mice with loperamide, in which the therapeutic effects of astragaloside IV were evaluated. The microbiota community structure and SCFA content were analysed by 16S rRNA gene sequencing and gas chromatography‐mass spectrometry, respectively. The influence of butyrate on STC was assessed using a mouse model and Cajal cells (ICC). Astragaloside IV promoted defecation, improved intestinal mobility, suppressed ICC loss and alleviated colonic lesions in STC mice. Alterations in gut microbiota community structure in STC mice, such as decreased Lactobacillus reuteri diversity, were improved following astragaloside IV treatment. Moreover, astragaloside IV up‐regulated butyric acid and valeric acid, but decreased isovaleric acid, in STC mouse stools. Butyrate promoted defecation, improved intestinal mobility, and enhanced ICC proliferation by regulating the AKT–NF‐κB signalling pathway. Astragaloside IV promoted intestinal transit in STC mice and inhibited ICC loss by regulating the gut microbiota community structure and generating butyric acid.     

口服肝素与小鼠肠道菌群的相互作用

口服肝素药物的开发需要系统地理解口服肝素与肠道菌群之间的互作过程。通过荧光体视镜观察荧光素标记的肝素经小鼠口服后在体内的分布情况,利用高效液相色谱法检测肝素在模拟胃肠液中的稳定性和体外培养肠道菌群模拟肠道菌对肝素的降解作用,发现口服肝素主要分布在小鼠胃肠道内,在体外模拟胃肠液条件下肝素结构稳定,但能够被添加肝素的厌氧培养基培养后的肠道菌群降解。为了进一步揭示口服肝素对健康小鼠肠道菌群的影响,利用Illumina MiSeq高通量测序技术测定口服肝素后C57BL/6J小鼠粪便菌群的16S rRNA序列,与口服生理盐水的小鼠粪便菌群进行对比,发现口服肝素的小鼠粪便菌群的生物多样性降低;在门水平上,菌群结构差异不显著;而在属水平上,别样杆菌属Alistipes、副萨特氏菌属Parasutterella和艾克曼菌属Akkermansia相对丰度增高,而嗜胆菌属Bilophila、肠杆菌属Enterorhabdus、瘤胃梭菌属Ruminiclostridium、普雷沃氏菌科Prevotellaceae_UCG_001、瘤胃梭菌属Ruminiclostridium-9、拟杆菌属Bacteroides、Lachnoclostridium、Candidatus_Saccharimonas、Intestinimonas和Dubosiella的相对丰度减少,表明口服肝素能够影响小鼠肠道菌群结构。此外,实验发现口服肝素对小鼠无明显毒副作用,具有较高安全性。研究结果将为开发肝素口服递送策略提供新的思路,为口服肝素类药物的开发提供参考。     

Collinsella aerofaciens对高脂饮食小鼠糖脂代谢及肠道菌群的影响

从人粪便中分离Collinsella aerofaciens,并给予正常和高脂饮食的C57BL/6J小鼠,观察Collinsella aerofaciens对小鼠糖脂代谢及肠道菌群结构的影响。

将40只C57BL/6J雄性小鼠随机分成正常饮食组（NCD组）、正常饮食+菌液组（NCD+B组）、高脂饮食组（HFD组）和高脂饮食+菌液组（HFD+B组）,每组10只。NCD组和HFD组给予100 μL的生理盐水,其余组给予Collinsella aerofaciens 1×10⁹ CFU/mL,连续灌胃12周。第0、4、8和12周通过试剂盒检测空腹血糖（FBG）、随机血糖（GLU）、总胆固醇（TC）和三酰甘油（TG）水平。第12周,对各组小鼠进行口服糖耐量和胰岛素耐量试验,并检测血浆高、低密度脂蛋白胆固醇（HDL-C、LDL-C）水平。收集小鼠粪便,采用高通量测序技术检测16S rRNA V3‒V4区序列,分析肠道菌群结构变化。

第8和12周4组小鼠间TC水平差异有统计学意义（F = 132.424,P＜0.001;F = 107.601,P＜0.001）,与NCD组相比,NCD+B组小鼠TC水平显著升高（P＜0.050）;与HFD组相比,HFD+B组小鼠TC水平显著升高（P＜0.050）。4组小鼠间HDL-C和LDL-C水平差异有统计学意义（F = 7.809,P＜0.001;F = 41.521,P＜0.001）,与NCD组相比,NCD+B组小鼠HDL-C水平显著降低（P＜0.050）,LDL-C水平显著升高（P＜0.050）;与HFD组相比,HFD+B组小鼠LDL-C水平显著升高（P＜0.050）。Spearman相关性分析发现小鼠肠道中Desulfovibrionaceae丰度与FBG、GLU、TC和LDL-C水平呈正相关（r = 0.512,P = 0.011;r = 0.445,P = 0.029;r = 0.728,P＜0.001;r = 0.758,P＜0.001）。

人粪便中分离的Collinsella aerofaciens可以影响小鼠糖脂代谢,可能与其破坏肠道菌群平衡有关,同时为防治血糖血脂异常代谢提供靶点。

     

肠道微生物与线粒体之间的互作

肠道微生物与肠道细胞线粒体功能之间的关系十分密切。一方面,肠道微生物可直接或通过短链脂肪酸、硫化氢和一氧化氮等代谢产物间接影响与线粒体相关的能量代谢过程,调节线粒体活性氧的产生,调控线粒体甚至整个机体的免疫反应。另一方面,肠道细胞线粒体功能紊乱和基因组的遗传变异也会影响肠道微生物的组成和功能。本文主要介绍了肠道微生物和线粒体之间的互作关系的最新研究进展,为靶向作用于肠道菌群和线粒体以调节肠道健康提供理论依据。     

葛仙米多糖对高脂小鼠血脂和肠道微生物的影响

[目的]研究葛仙米多糖对高脂饲料喂养小鼠血脂和肠道微生物的影响.[方法]将健康的8周龄雄性小鼠分成5组,每组10只:正常组C57/6CNC小鼠(N:灌胃生理盐水,喂饲标准饲料),对照组ApoE-/-小鼠(C:灌胃生理盐水,喂饲标准饲料),模型组ApoE-/-小鼠(M:灌胃生理盐水,喂饲高脂高胆固醇饲料),葛仙米多糖低剂...     

An opportunistic pathogen isolated from the gut of an obese human causes obesity in germfree mice

Lipopolysaccharide endotoxin is the only known bacterial product which, when subcutaneously infused into mice in its purified form, can induce obesity and insulin resistance via an inflammation-mediated pathway. Here we show that one endotoxin-producing bacterium isolated from a morbidly obese human''s gut induced obesity and insulin resistance in germfree mice. The endotoxin-producing Enterobacter decreased in relative abundance from 35% of the volunteer''s gut bacteria to non-detectable, during which time the volunteer lost 51.4 kg of 174.8 kg initial weight and recovered from hyperglycemia and hypertension after 23 weeks on a diet of whole grains, traditional Chinese medicinal foods and prebiotics. A decreased abundance of endotoxin biosynthetic genes in the gut of the volunteer was correlated with a decreased circulating endotoxin load and alleviated inflammation. Mono-association of germfree C57BL/6J mice with strain Enterobacter cloacae B29 isolated from the volunteer''s gut induced fully developed obesity and insulin resistance on a high-fat diet but not on normal chow diet, whereas the germfree control mice on a high-fat diet did not exhibit the same disease phenotypes. The Enterobacter-induced obese mice showed increased serum endotoxin load and aggravated inflammatory conditions. The obesity-inducing capacity of this human-derived endotoxin producer in gnotobiotic mice suggests that it may causatively contribute to the development of obesity in its human host.     

Effects of oral sialic acid on gut development,liver function and gut microbiota in mice

Sialic acid (N-acetylneuraminic acid), a 9-carbon monosaccharide, has been widely studied in immunology, oncology and neurology. However, the effects of sialic acid on organ and intestinal development, liver function and gut microbiota were rarely studied. In this study, we found that oral sialic acid tended to increase the relative weight of liver and decreased the serum aspartate aminotransferase (GPT) activity. In addition, sialic acid treatment markedly reduced gut villus length, depth, the ratio of villus length/depth (L/D), areas, width and the number of goblet cells. Furthermore, gut microbes were changed in response to oral sialic acid, such as Staphylococcus lentus, Corynebacterium stationis, Corynebacterium urealyticum, Jeotgalibaca sp_PTS2502, Ignatzschineria indica, Sporosarcina pasteurii, Sporosarcina sp_HW10C2, Facklamia tabacinasalis, Oblitimonas alkaliphila, Erysipelatoclostridium ramosum, Blautia sp_YL58, Bacteroids thetaiotaomicron, Morganella morganii, Clostridioides difficile, Helicobacter tryphlonius, Clostridium sp_Clone47, Alistipes finegoldii, [pseudomonas]_geniculata and Pseudomonas parafulva at the species level. In conclusion, oral sialic acid altered the intestinal pathological state and microbial compositions, and the effect of sialic acid on host health should be further studied.     

Phylogenetic distribution of three pathways for propionate production within the human gut microbiota

Propionate is produced in the human large intestine by microbial fermentation and may help maintain human health. We have examined the distribution of three different pathways used by bacteria for propionate formation using genomic and metagenomic analysis of the human gut microbiota and by designing degenerate primer sets for the detection of diagnostic genes for these pathways. Degenerate primers for the acrylate pathway (detecting the lcdA gene, encoding lactoyl-CoA dehydratase) together with metagenomic mining revealed that this pathway is restricted to only a few human colonic species within the Lachnospiraceae and Negativicutes. The operation of this pathway for lactate utilisation in Coprococcus catus (Lachnospiraceae) was confirmed using stable isotope labelling. The propanediol pathway that processes deoxy sugars such as fucose and rhamnose was more abundant within the Lachnospiraceae (based on the pduP gene, which encodes propionaldehyde dehydrogenase), occurring in relatives of Ruminococcus obeum and in Roseburia inulinivorans. The dominant source of propionate from hexose sugars, however, was concluded to be the succinate pathway, as indicated by the widespread distribution of the mmdA gene that encodes methylmalonyl-CoA decarboxylase in the Bacteroidetes and in many Negativicutes. In general, the capacity to produce propionate or butyrate from hexose sugars resided in different species, although two species of Lachnospiraceae (C. catus and R. inulinivorans) are now known to be able to switch from butyrate to propionate production on different substrates. A better understanding of the microbial ecology of short-chain fatty acid formation may allow modulation of propionate formation by the human gut microbiota.