Obese Mice Fed a Diet Supplemented with Enzyme-Treated Wheat Bran Display Marked Shifts in the Liver Metabolome Concurrent with Altered Gut Bacteria

Infant Microbiota Communities and Human Milk Oligosaccharide Supplementation Independently and Synergistically Shape Metabolite Production and Immune Responses in Healthy Mice

BACKGROUND

Multiple studies have demonstrated associations between the early-life gut microbiome and incidence of inflammatory and autoimmune disease in childhood. Although microbial colonization is necessary for proper immune education, it is not well understood at a mechanistic level how specific communities of bacteria promote immune maturation or drive immune dysfunction in infancy.

OBJECTIVES

In this study, we aimed to assess whether infant microbial communities with different overall structures differentially influence immune and gastrointestinal development in healthy mice.

METHODS

Germ-free mice were inoculated with fecal slurries from Bifidobacterium longum subspecies infantis positive (BIP) or B. longum subspecies infantis negative (BIN) breastfed infants; half of the mice in each group were also supplemented with a pool of human milk oligosaccharides (HMOs) for 14 d. Cecal microbiome composition and metabolite production, systemic and mucosal immune outcomes, and intestinal morphology were assessed at the end of the study.

RESULTS

The results showed that inoculation with a BIP microbiome results in a remarkably distinct microbial community characterized by higher relative abundances of cecal Clostridium senu stricto, Ruminococcus gnavus, Cellulosilyticum sp., and Erysipelatoclostridium sp. The BIP microbiome produced 2-fold higher concentrations of cecal butyrate, promoted branched short-chain fatty acid (SCFA) production, and further modulated serotonin, kynurenine, and indole metabolism relative to BIN mice. Further, the BIP microbiome increased the proportions of innate and adaptive immune cells in spleen, while HMO supplementation increased proliferation of mesenteric lymph node cells to phorbol myristate acetate and lipopolysaccharide and increased serum IgA and IgG concentrations.

CONCLUSIONS

Different microbiome compositions and HMO supplementation can modulate SCFA and tryptophan metabolism and innate and adaptive immunity in young, healthy mice, with potentially important implications for early childhood health.

Inulin Supplementation Modulates the Hepatic Transcriptome, Metabolome, and Ferritin Content in Ovariectomized Rats

SCOPE

Liver is an important metabolic organ regulating whole-body homeostasis. This study aims to investigate how prebiotic-induced changes in the metabolic activity of the gut microbiome (GM) and dietary calcium depletion modulates the hepatic metabolome and transcriptome.

METHODS AND RESULTS

The serum metabolome, liver metabolome, and transcriptome are determined on samples from ovariectomized (OVX) rats fed a control diet (Control, n = 7), a control diet supplemented with 5% w/w inulin (Inulin, n = 7), or a calcium-deficient diet (CaDef, n = 7). Inulin fortification is associated with higher serum concentrations of acetate, 3-hydroxybutyrate, and reduced concentration of dimethyl sulfone, revealing that changes in the metabolic activity of the GM are reflected in circulating metabolites. Metabolomics also reveal that the inulin-fortified diet results in lower concentrations of hepatic glutamate, serine, and hypoxanthine while transcriptomics reveal accompanying effects on the hepatic expression of ferric iron binding-related genes. Inulin fortification also induces effects on the hepatic expression of genes involved in olfactory transduction, suggesting that prebiotics regulate liver function through yet unidentified mechanisms involving olfactory receptors.

CONCLUSION

Inulin ingestion impacts hepatic gene expression and is associated with an upregulation of ferritin synthesis-related genes and liver ferritin content.

The Microbiome, Epigenome, and Diet in Adults with Obesity during Behavioral Weight Loss

Obesity has been linked to the gut microbiome, epigenome, and diet, yet these factors have not been studied together during obesity treatment. Our objective was to evaluate associations among gut microbiota (MB), DNA methylation (DNAme), and diet prior to and during a behavioral weight loss intervention. Adults (n = 47, age 40.9 ± 9.7 years, body mass index (BMI) 33.5 ± 4.5 kg/m2, 77% female) with data collected at baseline (BL) and 3 months (3 m) were included. Fecal MB was assessed via 16S sequencing and whole blood DNAme via the Infinium EPIC array. Food group and nutrient intakes and Healthy Eating Index (HEI) scores were calculated from 7-day diet records. Linear models were used to test for the effect of taxa relative abundance on DNAme and diet cross-sectionally at each time point, adjusting for confounders and a false discovery rate of 5%. Mean weight loss was 6.2 ± 3.9% at 3 m. At BL, one MB taxon, Ruminiclostridium, was associated with DNAme of the genes COL20A1 (r = 0.651, p = 0.029), COL18A1 (r = 0.578, p = 0.044), and NT5E (r = 0.365, p = 0.043). At 3 m, there were 14 unique MB:DNAme associations, such as Akkermansia with DNAme of GUSB (r = -0.585, p = 0.003), CRYL1 (r = -0.419, p = 0.007), C9 (r = -0.439, p = 0.019), and GMDS (r = -0.559, p = 0.046). Among taxa associated with DNAme, no significant relationships were seen with dietary intakes of relevant nutrients, food groups, or HEI scores. Our findings indicate that microbes linked to mucin degradation, short-chain fatty acid production, and body weight are associated with DNAme of phenotypically relevant genes. These relationships offer an initial understanding of the possible routes by which alterations in gut MB may influence metabolism during weight loss.

The effects of dietary fibers from rice bran and wheat bran on gut microbiota: An overview

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The physicochemical properties of DFs are related to their digestive behaviors.

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DFs are degraded in the intestines due to the fermentation of gut microbiota.

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DFs and their metabolites exert beneficial effects on gut microbiota.

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The fermentation of DFs improve gut barrier function and immune function.

Whole grain is the primary food providing abundant dietary fibers (DFs) in the human diet. DFs from rice bran and wheat bran have been well documented in modulating gut microbiota. This review aims to summarize the physicochemical properties and digestive behaviors of DFs from rice bran and wheat bran and their effects on host gut microbiota. The physicochemical properties of DFs are closely related to their fermentability and digestive behaviors. DFs from rice bran and wheat bran modulate specific bacteria and promote SAFCs-producing bacteria to maintain host health. Moreover, their metabolites stimulate the production of mucus-associated bacteria to enhance the intestinal barrier and regulate the immune system. They also reduce the level of related inflammatory cytokines and regulate Tregs activation. Therefore, DFs from rice bran and wheat bran will serve as prebiotics, and diets rich in whole grain will be a biotherapeutic strategy for human health.

Dietary Fibre from Whole Grains and Their Benefits on Metabolic Health

The consumption of whole grain products is often related to beneficial effects on consumer health. Dietary fibre is an important component present in whole grains and is believed to be (at least partially) responsible for these health benefits. The dietary fibre composition of whole grains is very distinct over different grains. Whole grains of cereals and pseudo-cereals are rich in both soluble and insoluble functional dietary fibre that can be largely classified as e.g., cellulose, arabinoxylan, β-glucan, xyloglucan and fructan. However, even though the health benefits associated with the consumption of dietary fibre are well known to scientists, producers and consumers, the consumption of dietary fibre and whole grains around the world is substantially lower than the recommended levels. This review will discuss the types of dietary fibre commonly found in cereals and pseudo-cereals, their nutritional significance and health benefits observed in animal and human studies.

Nørskov N, Knudsen KEB, Hedemann MS, Lærke HN. Effects of dietary fibre and protein content on intestinal fibre degradation, short-chain fatty acid and microbiota composition in a high-fat fructose-rich diet induced obese Göttingen Minipig model

An AX-enriched high DF diet improved the intestinal environment and attenuated protein fermentation, while protein did not show prebiotic effects.

Wheat Germ Supplementation Increases Lactobacillaceae and Promotes an Anti-inflammatory Gut Milieu in C57BL/6 Mice Fed a High-Fat, High-Sucrose Diet

BACKGROUND

A link between high-fat diet consumption and obesity-related diseases is the disruption of the gut bacterial population, which promotes local and systemic inflammation. Wheat germ (WG) is rich in bioactive components with antioxidant and anti-inflammatory properties.

OBJECTIVE

The aim of this study was to investigate the effects of WG supplementation in modulating the gut bacterial population and local and systemic inflammatory markers of mice fed a high-fat, high-sucrose (HFS) diet.

METHODS

Six-week-old male C57BL/6 mice were randomly assigned to 4 groups (n = 12/group) and fed a control (C; 10% kcal fat, 10% kcal sucrose) or HFS (60% kcal fat, 20% kcal sucrose) diet with or without 10% WG (wt:wt) for 12 wk. Cecal bacteria was assessed via 16S rDNA sequencing, fecal short-chain fatty acids by GC, small intestinal CD4+ lymphocytes using flow cytometry, and gut antimicrobial peptide genes and inflammatory markers by quantitative polymerase chain reaction. Statistical analyses included Kruskal-Wallis/Dunn's test and 2-factor ANOVA using HFS and WG as factors.

RESULTS

There was a 4-fold increase (P = 0.007) in the beneficial bacterial family, Lactobacillaceae, in the HFS + WG compared with the HFS group. Fecal propionic and n-butyric acids were elevated at least 2-fold in C + WG compared with the other groups (P < 0.0001). WG tended to increase (≥7%; P-trend = 0.12) small intestinal regulatory T cell:Th17 ratio, indicating a potential to induce an anti-inflammatory gut environment. WG elevated (≥35%) ileal gene expression of the anti-inflammatory cytokine Il10 compared to the unsupplemented groups (P = 0.038). Ileal gene expression of the antimicrobial peptides Reg3b and Reg3g was upregulated (≥95%) in the HFS + WG compared with other groups (P ≤ 0.040). WG reduced serum concentrations of the pro-inflammatory cytokines, interleukin (IL)-1B, IL-6, interferon-γ, and tumor necrosis factor-α (≥17%; P ≤ 0.012).

CONCLUSIONS

WG selectively increased gut Lactobacillaceae, upregulated ileal antimicrobial peptides, and attenuated circulating pro-inflammatory cytokines of C57BL/6 mice fed a HFS diet. These changes may be vital in preventing HFS diet-induced comorbidities.

Unaccounted risk of cardiovascular disease: the role of the microbiome in lipid metabolism

PURPOSE OF REVIEW

Not all of the risk of cardiovascular disease can be explained by diet and genetics, and the human microbiome, which lies at the interface of these two factors, may help explain some of the unaccounted risk. This review examines some of the well established links between the microbiome and cardiovascular health, and proposes relatively unexplored associations.

RECENT FINDINGS

Byproducts of microbial metabolism are associated with health and disease: Trimethylamine N oxide is associated with atherosclerosis; whereas short-chain fatty acids are associated with decreased inflammation and increased energy expenditure. More broadly, a large number of association studies have been conducted to explore the connections between bacterial taxa and metabolic syndrome. In contrast, the relationship between the microbiome and triglycerides levels remains poorly understood.

SUMMARY

We suggest that deeper understanding of the molecular mechanisms that drive linkages between the microbiome and disease can be determined by replacing 16S rRNA gene sequencing with shotgun metagenomic sequencing or other functional approaches. Furthermore, to ensure translatability and reproducibility of research findings, a combination of multiple different complementary '-omic' approaches should be employed.

Monovalerin and trivalerin increase brain acetic acid, decrease liver succinic acid, and alter gut microbiota in rats fed high-fat diets

Purpose

Short-chain fatty acids (SCFA) are known for their anti-inflammatory properties and may also prevent against the development of metabolic diseases. This study investigated possible effects of two valeric acid esters, monovalerin (MV) and trivalerin (TV) in rats fed high-fat diets.

Methods

Four groups of rats were given a low-fat diet (LF) or a high-fat control diet (HFC) with or without supplementation of MV or TV (5 g/kg) for 3 weeks (n = 7/group). SCFA (caecum, blood, liver and brain), succinic acid (liver), microbiota (caecum), lipid profile (liver and blood) and the inflammatory biomarker, lipopolysaccharide-binding protein (blood) were analysed at the end of the experiment.

Results

Supplementation of MV and TV to a high-fat diet increased 1.5-fold the amounts of acetic acid in the brain and 1.7-fold serum concentration of valeric acid, whereas liver succinic acid was reduced by 1.5-fold. Although liver triglyceride levels were higher in both MV and TV groups compared with the LF group, liver LDL/HDL ratio was lower in the MV group (P < 0.05). The caecal microbiota composition was altered, with threefold higher abundance of Bacteroidetes and higher ratio of Bacteroidetes/Firmicutes in the MV group compared with the HFC and LF groups. Acetic acid in the brain was negatively correlated with TM7, family S24-7 and rc4-4, and positively associated to Tenericutes and Anaeroplasma.

Conclusions

The present study shows that MV and TV in the specified dose can affect caecal microbiota composition and, therefore, bacterial metabolites in the liver, serum and brain as well as the lipid profile in the liver.

Electronic supplementary material

The online version of this article (10.1007/s00394-018-1688-z) contains supplementary material, which is available to authorized users.

Balancing Herbal Medicine and Functional Food for Prevention and Treatment of Cardiometabolic Diseases through Modulating Gut Microbiota

It has become apparent that gut microbiota is closely associated with cardiometabolic diseases (CMDs), and alteration in microbiome compositions is also linked to the host environment. Next generation sequencing (NGS) has facilitated in-depth studies on the effects of herbal medicine and functional food on gut microbiota. Both herbal medicine and functional food contain fiber, polyphenols and polysaccharides, exerting prebiotics-like activities in the prevention and treatment of CMDs. The administrations of herbal medicine and functional food lead to increased the abundance of phylum Bacteroidetes, and genus Akkermansia, Bifidobacteria, Lactobacillus, Bacteroides and Prevotella, while reducing phylum Firmicutes and Firmicutes/Bacteroidetes ratio in gut. Both herbal medicine and functional food interact with gut microbiome and alter the microbial metabolites including short-chain fatty acids (SCFAs), bile acids (BAs) and lipopolysaccharides (LPS), which are now correlated with metabolic diseases such as type 2 diabetes (T2D), obesity and non-alcoholic fatty liver disease (NAFLD). In addition, trimethylamine (TMA)-N-oxide (TMAO) is recently linked to atherosclerosis (AS) and cardiovascular disease (CVD) risks. Moreover, gut-organs axes may serve as the potential strategy for treating CMDs with the intervention of herbal medicine and functional food. In summary, a balance between herbal medicine and functional food rich in fiber, polyphenols and polysaccharides plays a vital role in modulating gut microbiota (phylum Bacteroidetes, Firmicutes and Firmicutes/Bacteroidetes ratio, and genus Akkermansia, Bifidobacteria, Lactobacillus, Bacteroides and Prevotella) through SCFAs, BAs, LPS and TMAO signaling regarding CMDs. Targeting gut-organs axes may serve as a new therapeutic strategy for CMDs by herbal medicine and functional food in the future. This review aims to summarize the balance between herbal medicine and functional food utilized for the prevention and treatment of CMDs through modulating gut microbiota.

Spermine and spermidine reversed age-related cardiac deterioration in rats

Aging is the most important risk factor for cardiovascular disease (CVD). Slowing or reversing the physiological impact of heart aging may reduce morbidity and mortality associated with age-related CVD. The polyamines, spermine (SP) and spermidine (SPD) are essential for cell growth, differentiation and apoptosis, and levels of both decline with age. To explore the effects of these polyamines on heart aging, we administered SP or SPD intraperitoneally to 22- to 24-month-old rats for 6 weeks. Both treatments reversed and inhibited age-related myocardial morphology alterations, myocardial fibrosis, and cell apoptosis. Using combined proteomics and metabolomics analyses, we identified proteins and metabolites up- or downregulated by SP and SPD in aging rat hearts. SP upregulated 51 proteins and 28 metabolites while downregulating 80 proteins and 29 metabolites. SPD upregulated 44 proteins and 24 metabolites and downregulated 84 proteins and 176 metabolites. These molecules were mainly associated with immune responses, blood coagulation, lipid metabolism, and glutathione metabolism pathways. Our study provides novel molecular information on the cardioprotective effects of polyamines in the aging heart, and supports the notion that SP and SPD are potential clinical therapeutics targeting heart disease.

Mice Fed a High-Fat Diet Supplemented with Resistant Starch Display Marked Shifts in the Liver Metabolome Concurrent with Altered Gut Bacteria

BACKGROUND

High-amylose-maize resistant starch type 2 (HAMRS2) is a fermentable dietary fiber known to alter the gut milieu, including the gut microbiota, which may explain the reported effects of resistant starch to ameliorate obesity-associated metabolic dysfunction.

OBJECTIVE

Our working hypothesis was that HAMRS2-induced microbiome changes alter gut-derived signals (i.e., xenometabolites) reaching the liver via the portal circulation, in turn altering liver metabolism by regulating gene expression and other pathways.

METHODS

We used a multi-omics systems biology approach to characterize HAMRS2-driven shifts to the cecal microbiome, liver metabolome, and transcriptome, identifying correlates between microbial changes and liver metabolites under obesogenic conditions that, to our knowledge, have not previously been recognized. Five-week-old male C57BL/6J mice were fed an energy-dense 45% lard-based-fat diet for 10 wk supplemented with either 20% HAMRS2 by weight (n = 14) or rapidly digestible starch (control diet; n = 15).

RESULTS

Despite no differences in food intake, body weight, glucose tolerance, fasting plasma insulin, or liver triglycerides, the HAMRS2 mice showed a 15-58% reduction in all measured liver amino acids, except for Gln, compared with control mice. These metabolites were equivalent in the plasma of HAMRS2 mice compared with controls, and transcripts encoding key amino acid transporters were not different in the small intestine or liver, suggesting that HAMRS2 effects were not simply due to lower hepatocyte exposure to systemic amino acids. Instead, alterations in gut microbial metabolism could have affected host nitrogen and amino acid homeostasis: HAMRS2 mice showed a 62% increase (P < 0.0001) in 48-h fecal output and a 41% increase (P < 0.0001) in fecal nitrogen compared with control mice. Beyond amino acid metabolism, liver transcriptomics revealed pathways related to lipid and xenobiotic metabolism; and pathways related to cell proliferation, differentiation, and growth were affected by HAMRS2 feeding.

CONCLUSION

Together, these differences indicate that HAMRS2 dramatically alters hepatic metabolism and gene expression concurrent with shifts in specific gut bacteria in C57BL/6J mice.

Impact of Dietary Fibers on Nutrient Management and Detoxification Organs: Gut, Liver, and Kidneys

Increased dietary fiber (DF) intake elicits a wide range of physiologic effects, not just locally in the gut, but systemically. DFs can greatly alter the gut milieu by affecting the gut microbiome, which in turn influences the gut barrier, gastrointestinal immune and endocrine responses, and nitrogen cycling and microbial metabolism. These gut-associated changes can then alter the physiology and biochemistry of the body's other main nutrient management and detoxification organs, the liver and kidneys. The molecular mechanisms by which DF alters the physiology of the gut, liver, and kidneys is likely through gut-localized events (i.e., bacterial nitrogen metabolism, microbe-microbe, and microbe-host cell interactions) coupled with specific factors that emanate from the gut in response to DF, which signal to or affect the physiology of the liver and kidneys. The latter may include microbe-derived xenometabolites, peptides, or bioactive food components made available by gut microbes, inflammation signals, and gut hormones. The intent of this review is to summarize how DF alters the gut milieu to specifically affect intestinal, liver, and kidney functions and to discuss the potential local and systemic signaling networks that are involved.