The prebiotic inulin modulates gut microbiota but does not ameliorate atherosclerosis in hypercholesterolemic APOE*3-Leiden.CETP mice

The effect and mechanism of inulin on atherosclerosis is mediated by the characteristic intestinal flora and metabolites

BACKGROUND

Inflammation and hyperlipidemia can cause atherosclerosis. Prebiotic inulin has been proven to effectively reduce inflammation and blood lipid levels. Utilizing a mouse model induced by a high-fat diet, this study aimed to explore whether the characteristic intestinal flora and its metabolites mediate the effects of inulin intervention on atherosclerosis and to clarify the specific mechanism.

METHODS

Thirty apolipoprotein E-deficient (ApoE-/-) mice were randomly divided into three groups. They were fed with a normal diet, a high-fat diet or an inulin+high-fat diet for 16 weeks. The total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) in the three groups were compared. The gross aorta and aortic sinus of mice were stained with oil red O, and the area of atherosclerotic plaque was observed and compared. The diversity and structure of the mouse fecal flora were detected by sequencing the V3-V4 region of the 16S rRNA gene, and the levels of metabolites in mouse feces were assessed by gas chromatography-mass spectrometry. The plasma lipopolysaccharide (LPS) levels and aortic inflammatory factors were measured by multi-index flow cytometry (CBA).

RESULTS

ApoE-/- mice fed with the high-fat diet exhibited an increase of approximately 46% in the area of atherosclerotic lesions, and the levels of TC, TG and LDL-C were significantly increased (P < 0.05) compared with levels in the normal diet group. After inulin was added to the high-fat group, the area of atherosclerotic lesions, the level of serum LPS and aortic inflammation were reduced, and the levels of TC, TG and LDL-C were decreased (P < 0.05). Based on 16S rRNA gene detection, we found that the composition of the intestinal microbiota, such as Prevotella, and metabolites, such as L-arginine, changed significantly due to hyperlipidemia, and the dietary inulin intervention partially reversed the relevant changes.

CONCLUSION

Inulin can inhibit the formation of atherosclerotic plaques, which may be related to the changes in lipid metabolism, the composition of the intestinal microbial community and its metabolites, and the inhibition of the expression of related inflammatory factors. Our study identified the relationships among the characteristic intestinal microbiota, metabolites and atherosclerosis, aiming to provide a new direction for future research to delay or treat atherosclerosis by changing the composition and function of the host intestinal microbiota and metabolites.

Therapeutic applications of gut microbes in cardiometabolic diseases: current state and perspectives

Cardiometabolic disease (CMD) encompasses a range of diseases such as hypertension, atherosclerosis, heart failure, obesity, and type 2 diabetes. Recent findings about CMD's interaction with gut microbiota have broadened our understanding of how diet and nutrition drive microbes to influence CMD. However, the translation of basic research into the clinic has not been smooth, and dietary nutrition and probiotic supplementation have yet to show significant evidence of the therapeutic benefits of CMD. In addition, the published reviews do not suggest the core microbiota or metabolite classes that influence CMD, and systematically elucidate the causal relationship between host disease phenotypes-microbiome. The aim of this review is to highlight the complex interaction of the gut microbiota and their metabolites with CMD progression and to further centralize and conceptualize the mechanisms of action between microbial and host disease phenotypes. We also discuss the potential of targeting modulations of gut microbes and metabolites as new targets for prevention and treatment of CMD, including the use of emerging technologies such as fecal microbiota transplantation and nanomedicine. KEY POINTS: • To highlight the complex interaction of the gut microbiota and their metabolites with CMD progression and to further centralize and conceptualize the mechanisms of action between microbial and host disease phenotypes. • We also discuss the potential of targeting modulations of gut microbes and metabolites as new targets for prevention and treatment of CMD, including the use of emerging technologies such as FMT and nanomedicine. • Our study provides insight into identification-specific microbiomes and metabolites involved in CMD, and microbial-host changes and physiological factors as disease phenotypes develop, which will help to map the microbiome individually and capture pathogenic mechanisms as a whole.

Efficacy of an inulin-based treatment on intestinal colonization by multidrug-resistant E. coli: insight into the mechanism of action

Inulin, an increasingly studied dietary fiber, alters intestinal microbiota. The aim of this study was to assess whether inulin decreases intestinal colonization by multidrug resistant E. coli and to investigate its potential mechanisms of action. Mice with amoxicillin-induced intestinal dysbiosis mice were inoculated with extended spectrum beta-lactamase producing E. coli (ESBL-E. coli). The combination of inulin and pantoprazole (IP) significantly reduced ESBL-E. coli fecal titers, whereas pantoprazole alone did not and inulin had a delayed and limited effect. Fecal microbiome was assessed using shotgun metagenomic sequencing and qPCR. The efficacy of IP was predicted by increased abundance of 74 taxa, including two species of Adlercreutzia. Preventive treatments with A. caecimuris or A. muris also reduced ESBL-E. coli fecal titers. Fecal microbiota of mice effectively treated by IP was enriched in genes involved in inulin catabolism, production of propionate and expression of beta-lactamases. They also had increased beta-lactamase activity and decreased amoxicillin concentration. These results suggest that IP act through production of propionate and degradation of amoxicillin by the microbiota. The combination of pantoprazole and inulin is a potential treatment of intestinal colonization by multidrug-resistant E. coli. The ability of prebiotics to promote propionate and/or beta-lactamase producing bacteria may be used as a screening tool to identify potential treatments of intestinal colonization by multidrug resistant Enterobacterales.

Bacterial, short-chain fatty acid and gas profiles of partially hydrolyzed guar gum in vitro fermentation by human fecal microbiota

Carbohydrates with different structures have metabolic differences in the human body, as well as individual differences. The present study aimed to investigate the effects of bacterial, short-chain fatty acids (SCFAs) and gas profiles of partially hydrolyzed guar gum (PHGG) on the fecal microbiota of 41 Chinese individuals by simulated fermentation in vitro. Results showed that PHGG stimulated the growth of Bifidobacterium and Faecalibacterium, inhibited the growth of Escherichia-Shigella, Klebsiella, and Dorea, and induced the production of fermentation gases (CO2, and H2) and SCFAs (acetic acid, butyric acid). Furthermore, Bifidobacterium was significantly increased in the young female and the old male-originated samples, while Klebsiella was significantly decreased in the old female ones after PHGG intervention, and there were also certain differences in gases and SCFAs among different population samples. These findings indicate that PHGG can modulate gut microbiota and metabolism well, whereas its use varies in different populations.

Co-administration of amoxicillin-loaded chitosan nanoparticles and inulin: A novel strategy for mitigating antibiotic resistance and preserving microbiota balance in Helicobacter pylori treatment

Helicobacter pylori (H. pylori) is a causative agent of various gastrointestinal diseases and eradication mainly relies on antibiotic treatment, with (AMX) being a key component. However, rising antibiotic resistance in H. pylori necessitates the use of antibiotics combination therapy, often disrupting gut microbiota equilibrium leading to further health complications. This study investigates a novel strategy utilizing AMX-loaded chitosan nanoparticles (AMX-CS NPs), co-administered with prebiotic inulin to counteract H. pylori infection while preserving microbiota health. Following microbroth dilution method, AMX displayed efficacy against H. pylori, with a MIC50 of 48.34 ± 3.3 ng/mL, albeit with a detrimental impact on Lactobacillus casei (L. casei). The co-administration of inulin (500 μg/mL) with AMX restored L. casei viability while retaining the lethal effect on H. pylori. Encapsulation of AMX in CS-NPs via ionic gelation method, resulted in particles of 157.8 ± 3.85 nm in size and an entrapment efficiency (EE) of 86.44 ± 2.19 %. Moreover, AMX-CS NPs showed a sustained drug release pattern over 72 h with no detectable toxicity on human dermal fibroblasts cell lines. Encapsulation of AMX into CS NPs also reduced its MIC50 against H. pylori, while its co-administration with inulin maintained L. casei viability. Interestingly, treatment with AMX-CS NPs also reduced the expression of the efflux pump gene hefA in H. pylori. This dual treatment strategy offers a promising approach for more selective antimicrobial treatment, minimizing disruption to healthy microbial communities while effectively addressing pathogenic threats.

Gut microbiota and microbiota-derived metabolites in cardiovascular diseases

ABSTRACT

Cardiovascular diseases, including heart failure, coronary artery disease, atherosclerosis, aneurysm, thrombosis, and hypertension, are a great economic burden and threat to human health and are the major cause of death worldwide. Recently, researchers have begun to appreciate the role of microbial ecosystems within the human body in contributing to metabolic and cardiovascular disorders. Accumulating evidence has demonstrated that the gut microbiota is closely associated with the occurrence and development of cardiovascular diseases. The gut microbiota functions as an endocrine organ that secretes bioactive metabolites that participate in the maintenance of cardiovascular homeostasis, and their dysfunction can directly influence the progression of cardiovascular disease. This review summarizes the current literature demonstrating the role of the gut microbiota in the development of cardiovascular diseases. We also highlight the mechanism by which well-documented gut microbiota-derived metabolites, especially trimethylamine N-oxide, short-chain fatty acids, and phenylacetylglutamine, promote or inhibit the pathogenesis of cardiovascular diseases. We also discuss the therapeutic potential of altering the gut microbiota and microbiota-derived metabolites to improve or prevent cardiovascular diseases.

Importance of gut microbiota metabolites in the development of cardiovascular diseases (CVD)

Cardiovascular disease (CVD) remains the most common cause of death worldwide and has become a public health concern. The proven notable risk factors for CVD are atherosclerosis, hypertension, diabetes, dyslipidemia, inflammation, and some genetic defects. However, research has shown a correlation between metabolic health, gut microbiota, and dietary risk factors. The gut microbiota makes an important contribution to human functional metabolic pathways by contributing enzymes that are not encoded by the human genome, for instance, the breakdown of polysaccharides, polyphenols and vitamins synthesis. TMAO and SCFAs, human gut microbiota compounds, have respective immunomodulatory and pro-inflammatory effects. Choline and l-carnitine are abundant in high-fat diets and are transformed into TMA by gut bacteria. The liver's phase of metabolism then changes TMA into TMAO. In turn, TMAO promotes the activation of macrophages, damages vascular endothelium, and results in CVD-however, dysbiosis decreases SCFAs and bile acids, which raises intestinal permeability. Congestion in the portal vein, a drop in cardiac output, a reduction in intestinal perfusion, and intestinal leakage are all caused by heart failure. These factors induce systemic inflammation by increasing intestinal leakage. By raising CRP and pro-inflammatory reactions, human gut dysbiosis and elevated TMAO levels promote the development of arterial plaque, hasten the beginning of atherosclerosis, and raise the risk of CAD. A healthy symbiosis between the gut microbiota and host is a key factor in shaping the biochemical profile of the diet, therefore which are crucial for maintaining the intestinal epithelial barrier, growing mucosa, reducing inflammation, and controlling blood pressure.

Meal-Based Intervention on Health Promotion in Middle-Aged Women: A Pilot Study

Middle-aged women belong to a risk group for metabolic dysregulation and menopausal symptoms, mainly due to a dramatic hormonal shift. Supplementation with functional compounds or a single nutrient has been dominantly explored as a nutritional approach for improving aging-related health parameters. However, a meal-based approach might be another strategy for promoting the overall health of the target population. This pilot study aimed to develop a meal-based intervention for middle-aged women and to evaluate its potential health benefits. Considering the nutrient intake status of Korean middle-aged women, diets enriched with four major nutrients (isoflavone, omega-3, fiber, and calcium) were designed and provided to forty-nine women aged 50 to 65 with mild levels of menopausal symptoms for 8 weeks. In the post-intervention phase, they showed reduced body weight and body fat, and improved biochemical metabolic parameters with decreased levels of cholesterol, low-density lipoprotein-cholesterol, ApoB, and fasting insulin. Moreover, bone resorption markers and menopause symptoms were lower in the post-intervention phase. In conclusion, the meal-based intervention might be a prominent strategy for overall health promotion in relatively healthy middle-aged women and further investigation is needed to test its efficacy with a randomized controlled study.

Protective Effect of Vegan Microbiota on Liver Steatosis Is Conveyed by Dietary Fiber: Implications for Fecal Microbiota Transfer Therapy

Fecal microbiota transfer may serve as a therapeutic tool for treating obesity and related disorders but currently, there is no consensus regarding the optimal donor characteristics. We studied how microbiota from vegan donors, who exhibit a low incidence of non-communicable diseases, impact on metabolic effects of an obesogenic diet and the potential role of dietary inulin in mediating these effects. Ex-germ-free animals were colonized with human vegan microbiota and fed a standard or Western-type diet (WD) with or without inulin supplementation. Despite the colonization with vegan microbiota, WD induced excessive weight gain, impaired glucose metabolism, insulin resistance, and liver steatosis. However, supplementation with inulin reversed steatosis and improved glucose homeostasis. In contrast, inulin did not affect WD-induced metabolic changes in non-humanized conventional mice. In vegan microbiota-colonized mice, inulin supplementation resulted in a significant change in gut microbiota composition and its metabolic performance, inducing the shift from proteolytic towards saccharolytic fermentation (decrease of sulfur-containing compounds, increase of SCFA). We found that (i) vegan microbiota alone does not protect against adverse effects of WD; and (ii) supplementation with inulin reversed steatosis and normalized glucose metabolism. This phenomenon is associated with the shift in microbiota composition and accentuation of saccharolytic fermentation at the expense of proteolytic fermentation.

Inulin increases the beneficial effects of rhubarb supplementation on high-fat high-sugar diet-induced metabolic disorders in mice: impact on energy expenditure, brown adipose tissue activity, and microbiota

Consumption of prebiotics and plant-based compounds have many beneficial health effects through modulation of gut microbiota composition and are considered as promising nutritional strategy for the treatment of metabolic diseases. In the present study, we assessed the separated and combined effects of inulin and rhubarb on diet-induced metabolic disease in mice. We showed that supplementation with both inulin and rhubarb abolished the total body and fat mass gain upon high-fat and high-sucrose diet (HFHS) as well as several obesity-associated metabolic disorders. These effects were associated with increased energy expenditure, lower whitening of the brown adipose tissue, higher mitochondria activity and increased expression of lipolytic markers in white adipose tissue. Despite modifications of intestinal gut microbiota and bile acid compositions by inulin or rhubarb alone, combination of both inulin and rhubarb had minor additional impact on these parameters. However, the combination of inulin and rhubarb increased the expression of several antimicrobial peptides and higher goblet cell numbers, thereby suggesting a reinforcement of the gut barrier. Together, these results suggest that the combination of inulin and rhubarb in mice potentiates beneficial effects of separated rhubarb and inulin on HFHS-related metabolic disease and could be considered as nutritional strategy for the prevention and treatment of obesity and related pathologies.

The role of the gut microbiota in health and cardiovascular diseases

The gut microbiota is critical to human health, such as digesting nutrients, forming the intestinal epithelial barrier, regulating immune function, producing vitamins and hormones, and producing metabolites to interact with the host. Meanwhile, increasing evidence indicates that the gut microbiota has a strong correlation with the occurrence, progression and treatment of cardiovascular diseases (CVDs). In patients with CVDs and corresponding risk factors, the composition and ratio of gut microbiota have significant differences compared with their healthy counterparts. Therefore, gut microbiota dysbiosis, gut microbiota-generated metabolites, and the related signaling pathway may serve as explanations for some of the mechanisms about the occurrence and development of CVDs. Several studies have also demonstrated that many traditional and latest therapeutic treatments of CVDs are associated with the gut microbiota and its generated metabolites and related signaling pathways. Given that information, we summarized the latest advances in the current research regarding the effect of gut microbiota on health, the main cardiovascular risk factors, and CVDs, highlighted the roles and mechanisms of several metabolites, and introduced corresponding promising treatments for CVDs regarding the gut microbiota. Therefore, this review mainly focuses on exploring the role of gut microbiota related metabolites and their therapeutic potential in CVDs, which may eventually provide better solutions in the development of therapeutic treatment as well as the prevention of CVDs.

Evaluation of Full-Length Versus V4-Region 16S rRNA Sequencing for Phylogenetic Analysis of Mouse Intestinal Microbiota After a Dietary Intervention

The composition of microbial communities is commonly determined by sequence analyses of one of the variable (V) regions in the bacterial 16S rRNA gene. We aimed to assess whether sequencing the full-length versus the V4 region of the 16S rRNA gene affected the results and interpretation of an experiment. To test this, mice were fed a diet without and with the prebiotic inulin and from cecum samples, two primary data sets were generated: (1) a 16S rRNA full-length data set generated by the PacBio platform; (2) a 16S rRNA V4 region data set generated by the Illumina MiSeq platform. A third derived data set was generated by in silico extracting the 16S rRNA V4 region data from the 16S rRNA full-length PacBio data set. Analyses of the primary and derived 16S rRNA V4 region data indicated similar bacterial abundances, and α- and β-diversity. However, comparison of the 16S rRNA full-length data with the primary and derived 16S rRNA V4 region data revealed differences in relative bacterial abundances, and α- and β-diversity. We conclude that the sequence length of 16S rRNA gene and not the sequence analysis platform affected the results and may lead to different interpretations of the effect of an intervention that affects the microbiota.

Inulin reduces visceral adipose tissue mass and improves glucose tolerance through altering gut metabolites

AIM

Inulin, a soluble dietary fiber, is a source of energy for the host while the metabolites, such as short-chain fatty acids (SCFAs), produced in the gut through bacterial fermentation exerts the anti-obesity effect. In this study, we aimed to apply a metabolomics approach and clarify the role of this soluble dietary fiber on glucose and lipid metabolism under the calorie-matched condition.

MATERIALS AND METHODS

Eight-week-old male C57BL/6J mice were fed a high-fat/high-sucrose based diet containing maltodextrin or inulin for 12 weeks through calorie-matched pair feeding. We evaluated glucose tolerance, and energy expenditure using indirect calorimetry, comprehensive metabolites in the content of jejunum, feces, and portal vein serum using gas chromatography-mass spectrometry, and histological changes in the adipose tissue.

RESULTS

The inulin group exhibited reduced visceral adipose tissue and smaller size of visceral adipocyte. It also exhibited improved glucose tolerance and an increase in energy expenditure. Reflecting the results of fermentation, the metabolomics analysis revealed an increase in the succinic acid and SCFA contents in both feces and portal vein serum in the inulin group.

CONCLUSIONS

Inulin altered the gut metabolites and reduced visceral adipose tissue, thereby resulting in improved glucose tolerance.

Global, distinctive, and personal changes in molecular and microbial profiles by specific fibers in humans

Dietary fibers act through the microbiome to improve cardiovascular health and prevent metabolic disorders and cancer. To understand the health benefits of dietary fiber supplementation, we investigated two popular purified fibers, arabinoxylan (AX) and long-chain inulin (LCI), and a mixture of five fibers. We present multiomic signatures of metabolomics, lipidomics, proteomics, metagenomics, a cytokine panel, and clinical measurements on healthy and insulin-resistant participants. Each fiber is associated with fiber-dependent biochemical and microbial responses. AX consumption associates with a significant reduction in LDL and an increase in bile acids, contributing to its observed cholesterol reduction. LCI is associated with an increase in Bifidobacterium. However, at the highest LCI dose, there is increased inflammation and elevation in the liver enzyme alanine aminotransferase. This study yields insights into the effects of fiber supplementation and the mechanisms behind fiber-induced cholesterol reduction, and it shows effects of individual, purified fibers on the microbiome.

Effects of Taraxacum mongolicum Hand.-Mazz. (dandelion) on growth performance, expression of genes coding for tight junction protein and mucin, microbiota composition and short chain fatty acids in ileum of broiler chickens

Background

Dandelion is becoming an exploitable alternative to the widely prohibited antibiotics in the poultry production. This research aimed to investigate the effects of dandelion on the growth performance and intestinal barrier function of broiler chickens maintained under standard condition of management. One-hundred and sixty 1-day-old Arbor Acres (AA) male broiler chickens were randomly divided into four groups, with five replicates of eight birds each. The birds were fed a basal diet supplemented without (control group, [CON]) or with 500 (low dose [LD]) or 1000 (high dose [HD]) mg/kg dandelion or with 250 mg/kg chlortetracycline 20% premix (CTC) for 42 days, including the starter phase (d 1 to 21) and the grower phase (d 22 to 42). Body weight (BW) of each bird and feed consumption of each replicate were measured at d 21 and d 42. The ileal tissues were collected on day 21 and 42 to determine expression of genes coding for tight junction protein and mucin as well as ELISA analysis for immune factor. The ileal digesta was collected for microbiota and short chain fatty acids analysis.

Results

Compared with CON group, during day 1–21, the average daily feed intake (ADFI) and feed/gain ratio (F/G) of LD group were lower (P < 0.05); during day 22–42, the F/G of LD and CTC group tended to be lower (P = 0.07); during the overall phase, the ADFI of HD and CTC groups were decreased (P < 0.05), and the F/G of dandelion and CTC groups tended to be decreased (P = 0.07). On day 21, the relative mRNA expression of claudin, occludin-1 and mucin1 in dandelion groups were up-regulated (P < 0.05), and the ZO-1 mRNA expression in CTC group was increased (P < 0.05); on day 42, the claudin and mucin1 transcripts in LD group and ZO-1 transcripts in HD and CTC group were up-regulated (P < 0.05), while the occludin-1 and mucin1 transcripts in CTC group was significantly down-regulated (P < 0.05). In addition, the contents of TNF-α in dandelion groups were lower than that in CTC group (P < 0.05). In the analysis of ileal microbiota, on day 21, decreased α-diversity was observed in HD and CTC groups (P < 0.05). Meanwhile, on day 21, the relative abundance of Firmicutes in dandelion groups tended to be higher (P = 0.09), the relative abundance of Lactobacillus in LD and CTC group were increased (P < 0.05), while Bacteroidete, Bacteroides, and Alistipes relative abundance in dandelion and CTC groups were decreased (P < 0.05). On day 42, the Actinobacteriota relative abundance in CTC group tended to be higher (P = 0.05), and Lysinibacillus relative abundance of CTC group was higher (P = 0.02). Compared with CON group, on day 21, the propionic acid and butyric acid content in CTC group were higher, the butyric acid content in HD group was lower (P < 0.10).

Conclusion

In summary, dietary dandelion supplementation at 500 mg/kg of diet enhanced growth performance of broilers by improving the intestinal barrier function. Dandelion can be supplemented in the diet as an antibiotics alternative to enhance production in poultry industry.

Restorative Effects of Inulin From Codonopsis pilosula on Intestinal Mucosal Immunity, Anti-Inflammatory Activity and Gut Microbiota of Immunosuppressed Mice

An inulin (CPPF), isolated from a traditional Chinese herbal medicine Codonopsis pilosula, was characterized and demonstrated with potential prebiotic activity in vitro before. Based on its non-digested feature, the intestinal mucosa and microbiota modulatory effects in vivo on immunosuppressed mice were investigated after oral administration of 200, 100 and 50 mg/kg of CPPF for 7 days. It was demonstrated that the secretions of sIgA and mucin 2 (Muc2) in ileum were improved by CPPF, and the anti-inflammatory activities in different intestine parts were revealed. The intestine before colon could be the target active position of CPPF. As a potential prebiotic substance, a gut microbiota restorative effect was also presented by mainly modulating the relative abundance of Eubacteriales, including Oscillibacter, unidentified Ruminococcus and Lachnospiraceae after high-throughput pyrosequencing of V4 region of 16S rRNA analysis. All these results indicated that this main bioactive ingredient inulin from C. pilosula was a medicinal prebiotic with enhancing mucosal immune, anti-inflammatory and microbiota modulatory activities.

Therapeutic potential of natural products against atherosclerosis: Targeting on gut microbiota

Gut microbiota (GM) has emerged as an essential and integral factor for maintaining human health and affecting pathological outcomes. Metagenomics and metabolomics characterization have furthered gut metagenome's understanding and unveiled that deviation of specific GM community members and GM-dependent metabolites imbalance orchestrate metabolic or cardiovascular diseases (CVDs). Restoring GM ecosystem with nutraceutical supplements keenly prebiotics and probiotics relatively decreases CVDs incidence and overall mortality. In Atherosclerosis, commensal and pathogenic gut microbes correlate with atherogenesis events. GM-dependent metabolites-trimethylamine N-oxide and short-chain fatty acids regulate atherosclerosis-related metabolic processes in opposite patterns to affect atherosclerosis outcomes. Therefore, GM might be a potential therapeutic target for atherosclerosis. In atherogenic animal models, natural products with cardioprotective properties could modulate the GM ecosystem by revitalizing healthier GM phylotypes and abrogating proatherogenic metabolites, paving future research paths for clinical therapeutics.

Inulin Supplementation Disturbs Hepatic Cholesterol and Bile Acid Metabolism Independent from Housing Temperature

Dietary fibers are fermented by gut bacteria into the major short chain fatty acids (SCFAs) acetate, propionate, and butyrate. Generally, fiber-rich diets are believed to improve metabolic health. However, recent studies suggest that long-term supplementation with fibers causes changes in hepatic bile acid metabolism, hepatocyte damage, and hepatocellular cancer in dysbiotic mice. Alterations in hepatic bile acid metabolism have also been reported after cold-induced activation of brown adipose tissue. Here, we aim to investigate the effects of short-term dietary inulin supplementation on liver cholesterol and bile acid metabolism in control and cold housed specific pathogen free wild type (WT) mice. We found that short-term inulin feeding lowered plasma cholesterol levels and provoked cholestasis and mild liver damage in WT mice. Of note, inulin feeding caused marked perturbations in bile acid metabolism, which were aggravated by cold treatment. Our studies indicate that even relatively short periods of inulin consumption in mice with an intact gut microbiome have detrimental effects on liver metabolism and function.

Health promoting microbial metabolites produced by gut microbiota after prebiotics metabolism

Human gut microbiota (HGM) is a microbial complex where dynamic mutualistic interactions related to digestion and absorption of dietary components take place. The consumption of specific food ingredients, such as prebiotics and dietary fibers, constituted mainly by carbohydrates polymers, can modulate the HGM composition and metabolism serving as a fermentable substrate to produce bacterial metabolites with beneficial effects on host health. Especially, bacterial short-chain fatty acids, tryptophan and organic acids have shown positive effects on pathogenic bacteria control, mineral absorption, weight control and obesity, immune response homeostasis, gut barrier improvement, brain modulation and anticancer activity. Despite the fact that these effects vary between individuals due to personal HGM richness, the information presented in this review contributes to understanding the effects of prebiotics and dietary fibers consumption on the generation of HGM metabolites and the mechanisms by which these metabolites interact with host cells improving host health.

Fermentable Dietary Fiber Promotes Helminth Infection and Exacerbates Host Inflammatory Responses

Fermentable dietary fibers promote the growth of beneficial bacteria, can enhance mucosal barrier integrity, and reduce chronic inflammation. However, effects on intestinal type 2 immune function remain unclear. In this study, we used the murine whipworm Trichuris muris to investigate the effect of the fermentable fiber inulin on host responses to infection regimes that promote distinct Th1 and Th2 responses in C57BL/6 mice. In uninfected mice, dietary inulin stimulated the growth of beneficial bacteria, such as Bifidobacterium (Actinobacteria) and Akkermansia (Verrucomicrobia). Despite this, inulin prevented worm expulsion in normally resistant mice, instead resulting in chronic infection, whereas mice fed an equivalent amount of nonfermentable fiber (cellulose) expelled worms normally. Lack of expulsion in the mice fed inulin was accompanied by a significantly Th1-skewed immune profile characterized by increased T-bet⁺ T cells and IFN-γ production in mesenteric lymph nodes, increased expression of Ido1 in the cecum, and a complete absence of mast cell and IgE production. Furthermore, the combination of dietary inulin and high-dose T. muris infection caused marked dysbiosis, with expansion of the Firmicutes and Proteobacteria phyla, near elimination of Bacteroidetes, and marked reductions in cecal short-chain fatty acids. Neutralization of IFN-γ during infection abrogated Ido1 expression and was sufficient to restore IgE production and worm expulsion in inulin-fed mice. Our results indicate that, whereas inulin promoted gut health in otherwise healthy mice, during T. muris infection, it exacerbated inflammatory responses and dysbiosis. Thus, the positive effects of fermentable fiber on gut inflammation appear to be context dependent, revealing a novel interaction between diet and infection.

Synthetic dietary inulin, Fuji FF, delays development of diet-induced obesity by improving gut microbiota profiles and increasing short-chain fatty acid production

Background

Dietary fiber, including inulin, promotes health via fermentation products, such as short-chain fatty acids (SCFAs), produced from the fiber by gut microbiota. SCFAs exert positive physiological effects on energy metabolism, gut immunity, and the nervous system. Most of the commercial inulin is extracted from plant sources such as chicory roots, but it can also be enzymatically synthesized from sucrose using inulin producing enzymes. Studies conducted on rodents fed with a cafeteria diet have suggested that while increasing plasma propionic acid, synthetic inulin modulates glucose and lipid metabolism in the same manner as natural inulin. Therefore, this study aimed to determine the effects of a synthetic inulin, Fuji FF, on energy metabolism, fecal SCFA production, and microbiota profiles in mice fed with a high-fat/high-sucrose diet.

Methods

Three-week-old male C57BL/6J mice were fed a high-fat/high-sucrose diet containing cellulose or Fuji FF for 12 weeks, and the effects on energy metabolism, SCFA production, and microbiota profiles were evaluated.

Results

Body weight gain was inhibited by Fuji FF supplementation in high-fat/high-sucrose diet-fed C57BL/6J mice by reducing white adipose tissue weight while increasing energy expenditure, compared with the mice supplemented with cellulose. Fuji FF also elevated levels of acetic, propionic and butyric acids in mouse feces and increased plasma propionic acid levels in mice. Moreover, 16S rRNA gene amplicon sequencing of fecal samples revealed an elevated abundance of Bacteroidetes and a reduced abundance of Firmicutes at the phylum level in mice supplemented with Fuji FF compared to those supplemented with cellulose. Fuji FF also resulted in abundance of the family Bacteroidales S24-7 and reduction of Desulfovibrionaceae in the feces.

Conclusion

Long term consumption of Fuji FF improved the gut environment in mice by altering the composition of the microbiota and increasing SCFA production, which might be associated with its anti-obesity effects.

Bioregional Alterations in Gut Microbiome Contribute to the Plasma Metabolomic Changes in Pigs Fed with Inulin

Inulin (INU) is a non-digestible carbohydrate, known for its beneficial properties in metabolic disorders. However, whether and how gut microbiota in its regulation contributes to host metabolism has yet to be investigated. We conduct this study to examine the possible associations between the gut microbiota and circulating gut microbiota-host co-metabolites induced by inulin interventions. Plasma and intestinal site samples were collected from the pigs that have consumed inulin diet for 60 days. High-throughput sequencing was adopted for microbial composition, and the GC-TOF-MS-based metabolomics were used to characterize featured plasma metabolites upon inulin intervention. Integrated multi-omics analyses were carried out to establish microbiota-host interaction. Inulin consumption decreased the total cholesterol (p = 0.04) and glucose (p = 0.03) level in serum. Greater β-diversity was observed in the cecum and colon of inulin-fed versus that of control-fed pigs (p < 0.05). No differences were observed in the ileum. In the cecum, 18 genera were altered by inulin, followed by 17 in the colon and 6 in the ileum. Inulin increased propionate, and isobutyrate concentrations but decreased the ratio of acetate to propionate in the cecum, and increased total short fatty acids, valerate, and isobutyrate concentrations in the colon. Metabolomic analysis reveals that indole-3-propionic acid (IPA) was significantly higher, and the branched-chain amino acids (BCAA), L-valine, L-isoleucine, and L-leucine are significantly lower in the inulin groups. Mantel test and integrative analysis revealed associations between plasma metabolites (e.g., IPA, BCAA, L-tryptophan) and inulin-responsive cecal microbial genera. These results indicate that the inulin has regional effects on the intestine microbiome in pigs, with the most pronounced effects occurring in the cecum. Moreover, cecum microbiota plays a pivotal role in the modulation of circulating host metabolites upon inulin intervention.

Mice Microbiota Composition Changes by Inulin Feeding with a Long Fasting Period under a Two-Meals-Per-Day Schedule

Water-soluble dietary fiber is known to modulate fecal microbiota. Although there are a few reports investigating the effects of fiber intake timing on metabolism, there are none on the effect of intake timing on microbiota. Therefore, in this study, we examined the timing effects of inulin-containing food on fecal microbiota. Mice were housed under conditions with a two-meals-per-day schedule, with a long fasting period in the morning and a short fasting period in the evening. Then, 10-14 days after inulin intake, cecal content and feces were collected, and cecal pH and short-chain fatty acids (SCFAs) were measured. The microbiome was determined using 16S rDNA sequencing. Inulin feeding in the morning rather than the evening decreased the cecal pH, increased SCFAs, and changed the microbiome composition. These data suggest that inulin is more easily digested by fecal microbiota during the active period than the inactive period. Furthermore, to confirm the effect of fasting length, mice were housed under a one-meal-per-day schedule. When the duration of fasting was equal, the difference between morning and evening nearly disappeared. Thus, our study demonstrates that consuming inulin at breakfast, which is generally after a longer fasting period, has a greater effect on the microbiota.