Feeding diversified protein sources exacerbates hepatic insulin resistance via increased gut microbial branched-chain fatty acids and mTORC1 signaling in obese mice

Isobutyrate Confers Resistance to Inflammatory Bowel Disease through Host-Microbiota Interactions in Pigs

Supplementation with short-chain fatty acids (SCFAs) is a potential therapeutic approach for inflammatory bowel disease (IBD). However, the therapeutic effects and mechanisms of action of isobutyrate in IBD remain unclear. Clinical data indicate that the fecal levels of isobutyrate are markedly lower in patients with Crohn's disease than in healthy controls. Compared with healthy mice and healthy pigs, mice and pigs with colitis presented significantly lower isobutyrate levels. Furthermore, the level of isobutyrate in pigs was significantly negatively correlated with the disease activity index. We speculate that isobutyrate may play a crucial role in regulating host gut homeostasis. We established a model of dextran sulfate sodium-induced colitis in pigs, which have gastrointestinal structure and function similar to those of humans; we performed multiomic analysis to investigate the therapeutic effects and potential mechanisms of isobutyrate on IBD at both the animal and cellular levels and validated the results. Phenotypically, isobutyrate can significantly alleviate diarrhea, bloody stools, weight loss, and colon shortening caused by colitis in pigs. Mechanistically, isobutyrate can increase the relative abundance of Lactobacillus reuteri, thereby increasing the production of indole-3-lactic acid, regulating aryl hydrocarbon receptor expression and downstream signaling pathways, and regulating Foxp3+ CD4+ T cell recruitment to alleviate colitis. Isobutyrate can directly activate G protein-coupled receptor 109A, promote the expression of Claudin-1, and improve intestinal barrier function. In addition, isobutyrate can increase the production of intestinal SCFAs and 3-hydroxybutyric acid and inhibit the TLR4/MyD88/NF-κB signaling pathway to suppress intestinal inflammation. In conclusion, our findings demonstrate that isobutyrate confers resistance to IBD through host-microbiota interactions, providing a theoretical basis for the use of isobutyrate in alleviating colitis.

Serum metabolomic profiling uncovered metabolic shifts in individuals upon moderate-altitude exposure and identified the potentiality of beta-alanine to ameliorate hyperuricemia

BACKGROUND

High-altitude exposure has been associated with an increased risk of hyperuricemia (HU) and gout, though the underlying mechanisms remain poorly understood.

METHODS

We conducted a comprehensive analysis of the serum metabolome and phenome in both discovery and validation cohorts of Han Chinese individuals who underwent long-term moderate-altitude exposure (∼12 months), as well as in an independent cohort consisting of local Han Chinese and Tibetans residing in Nyingchi (>5 years). Beta-Alanine intervention was applied in hypoxanthine and potassium oxonate-induced in vitro and in vivo experiments.

RESULTS

Individuals exposed to moderate altitude exhibited elevated serum urate and an increase in overall medium-chain fatty acids (MCFAs), coupled with a decrease in overall amino acids (AAs) and short-chain fatty acids (SCFAs). Rmcorr correlation analysis revealed a significant negative association between Beta-Alanine and serum urate, whereas nonanoic acid was in versa, potentially driving lower serum urate in long-term exposed residents. Both in vitro and in vivo experiments demonstrated that Beta-Alanine inhibited xanthine oxidase (XOD) and reversed the HU phenotype in human hepatocytes and mice induced by hypoxanthine (HX) and potassium oxonate (PO), with a urate-lowering effect in mice. Hepatic pathology and transcriptome analysis of HU mice treated with Beta-Alanine indicated that the mechanisms involved the inhibition of XOD, amelioration of the inflammation phenotype in hepatocytes, and promotion of renal urate excretion. Furthermore, the 10-fold cross-validation random forest classification (RFC) predictive modeling based on selected metabolites and phenotypes achieved an area under receiver operating characteristic (ROC) curve (AUC) value of 0.93 (95 % confidence interval (CI): 0.85-1.00) and 0.79 (95 % CI: 0.59-0.98) for distinguishing individuals with high risk of asymptomatic HU (AHU) in the training dataset and validation dataset, respectively.

CONCLUSIONS

This study reveals serum urate and metabolome altered in moderate-altitude exposed individuals and Beta-Alanine intervention could ameliorate hyperuricemia. Our findings suggest that targeting the circulating metabolome may pave novel avenues to counter diseases associated with HU.

Circulating short-chain and branched short-chain fatty acids and the risk of incident type 2 diabetes: findings from the 4C study

Previous studies suggested that fecal short-chain fatty acids (SCFAs) and branched short-chain fatty acids (BCFAs) are associated with glucose regulation. However, the potential relationship between circulating SCFAs and BCFAs with incident diabetes risk in both men and women remains unidentified in prospective cohort studies. In this study, we examined a panel of nine serum SCFAs and BCFAs in 3414 subjects with incident diabetes, and matched normoglycemic controls from the China Cardiometabolic Disease and Cancer Cohort study. In fully adjusted conditional logistic regression models, total SCFAs, total BCFAs, and isovaleric acid were significantly associated with incident type 2 diabetes mellitus (T2DM) (P < 0.05). Interestingly, gender-specific analysis showed that per standard deviation (SD) increment of SCFAs were positively associated with incident T2DM among women, with the odds ratio (95% confidence interval) of 1.16 (1.05-1.29) for total SCFAs and 1.18 (1.07-1.31) for propionate, respectively (P < 0.05, false discovery rate (FDR) < 0.05). No significant associations were observed in men. A significant interaction was detected between men and women for propionate (P interaction < 0.001, FDR < 0.01). After further adjustment of insulin measurements, the associations of serum propionate with diabetes remained significant (P < 0.05, FDR < 0.05). Meanwhile, the associations of total BCFAs and isovaleric acid with diabetes were partially mediated by triglycerides, insulin resistance, and β-cell function in mediation analysis. These findings, for the first time in a large prospective cohort, provide evidence for an association between circulating SCFAs and BCFAs with T2DM risk, and support the potential role of circulating propionate with gender disparities in the early pathogenesis of diabetes.

Associations of Plasma and Fecal Metabolites with Body Mass Index and Body Fat Distribution in Children

CONTEXT

Childhood obesity continues to be a critical public health concern with far-reaching implications for well-being.

OBJECTIVE

This study aimed to investigate the association between metabolites in plasma and feces and indicators including body mass index (BMI), BMI for age Z score (BMIZ), and body fat distribution among children aged 6 to 9 years in China.

METHODS

This cross-sectional study enrolled 424 healthy children, including 186 girls and 238 boys. Dual-energy X-ray absorptiometry was used to determine the body fat content and regional fat distribution. Plasma and fecal metabolites were analyzed using targeted metabolomic technologies.

RESULTS

A total of 200 plasma metabolites and 212 fecal metabolites were accurately quantified via ultra-performance liquid chromatography coupled with tandem mass spectrometry. By using orthogonal projections to latent structures discriminant analysis and random forest model, we discovered that 9 plasma metabolites and 11 fecal metabolites were associated with different weight statuses. After adjusting for potential covariates and false discovery rate correction, multiple linear regression analyses revealed that plasma metabolites (fumaric acid, glycine, l-glutamine, methylmalonic acid, and succinic acid) and fecal metabolites (protocatechuic acid) were negatively associated (β -1.373 to -.016, pFDR < 0.001-0.031; β -1.008 to -.071, pFDR 0.005-0.033), while plasma metabolites (isovaleric acid, isovalerylcarnitine, l-glutamic acid, and pyroglutamic acid) and fecal metabolites (3-aminoisobutanoic acid, butyric acid, N-acetylneuraminic acid, octanoylcarnitine, oleoylcarnitine, palmitoylcarnitine, stearoylcarnitine, taurochenodesoxycholic acid, and taurodeoxycholic acid) exhibited positive associations with BMI, BMIZ, and body fat distribution (β .023-2.396, pFDR < 0.001; β .014-1.736, pFDR < 0.001-0.049).

CONCLUSION

Plasma and fecal metabolites such as glutamine may serve as potential therapeutic targets for the development of obesity.

Dietary protein intake and PM2.5 on ovarian cancer survival: A prospective cohort study

BACKGROUND

Evolving evidence suggests both protein consumption and particulate matter less than 2.5 micrometers (PM2.5) might be related to ovarian cancer (OC) mortality. However, no epidemiological studies have explored their potential interaction.

OBJECTIVE

The objective of this study was to explore the association of dietary protein, PM2.5, and their interaction with the survival of OC patients.

METHODS

A prospective cohort study was carried out, which encompassed 658 newly diagnosed OC patients (18-79 years) residing in China. Dietary protein intakes were collected through a food frequency questionnaire examination, including total protein and protein from diverse sources. Average residential PM2.5 concentrations were evaluated using satellite-derived models. We calculated the hazard ratio (HR) and its 95 % confidence interval (CI) by adjusting for multiple variables using Cox proportional risk models. By assessing the relative excess risk due to interaction (RERI) arising from the interplay between PM2.5 exposure and dietary protein intake, we explored the additive interaction between the two. Multiplicative interaction was assessed through a cross-product interaction term.

RESULTS

During a median follow-up of 37.60 months, 123 deaths were documented. As for all-cause mortality, the multivariate-adjusted HRs (95 % CIs) in the highest vs. the lowest tertile were 0.57 (0.35-0.93), 0.60 (0.36-0.99), and 0.58 (0.37-0.90) for intakes of fish, egg, as well as fruit/vegetable protein, respectively (all P for trend < 0.05). A positive association between PM2.5 exposure and all-cause mortality was observed (HR=1.52; 95 % CI: 1.13-2.05, per interquartile range increment). Notably, dietary fish, egg, and fruit/vegetable protein modified these associations, as patients with lower intakes had significantly higher PM2.5-related mortality in the cohort (all P for interaction < 0.05).

CONCLUSIONS

This study provides evidence linking the potential interactions between dietary fish, egg, and fruit/vegetable protein intake and PM2.5 exposure on all-cause mortality of OC patients. Our study demonstrates the importance of adherence to a certain protein diet in reducing PM2.5-related mortality risk for OC patients.

Protective effect of the branched short-chain fatty acid isobutyrate on intestinal damage in weaned piglets through intestinal microbiota remodeling

BACKGROUND

Postweaning intestinal damage in piglets is a challenging issue in the livestock industry. Short-chain fatty acids (SCFAs) are important metabolic products of the gut microbiota and are widely recognized for their role in maintaining normal colonic function and regulating the intestinal immune system. However, the effects of branched short-chain fatty acid (BSCFA) isobutyrate on intestinal health remain largely unknown. This study aims to explore the potential of isobutyrate for alleviating postweaning intestinal damage.

RESULTS

This study indicates that isobutyrate can alleviate diarrhea in weaned piglets, enhance their growth performance, and optimize the gut microbiota. This is mainly achieved through increasing the relative abundance of probiotic bacteria such as Lactobacillus, Megasphaera, and Prevotellaceae_UCG-003, while concurrently reducing the relative abundance of potentially harmful bacteria such as Clostridium_sensu_stricto-1 and Escherichia-Shigella. It promotes the production of SCFAs, including acetate, isobutyrate, and butyrate. Furthermore, it activates G-protein-coupled receptors (GPR43/109A), inhibits the TLR4/MyD88 signaling pathway, strengthens the intestinal barrier function, and regulates the expression of related cytokines.

CONCLUSION

In summary, exogenous isobutyrate can be considered a promising feed additive for improving the intestinal microbiota and regulating intestinal health in piglets. © 2024 Society of Chemical Industry.

Sucrose-preferring gut microbes prevent host obesity by producing exopolysaccharides

Commensal bacteria affect host health by producing various metabolites from dietary carbohydrates via bacterial glycometabolism; however, the underlying mechanism of action remains unclear. Here, we identified Streptococcus salivarius as a unique anti-obesity commensal bacterium. We found that S. salivarius may prevent host obesity caused by excess sucrose intake via the exopolysaccharide (EPS) -short-chain fatty acid (SCFA) -carbohydrate metabolic axis in male mice. Healthy human donor-derived S. salivarius produced high EPS levels from sucrose but not from other sugars. S. salivarius abundance was significantly decreased in human donors with obesity compared with that in healthy donors, and the EPS-SCFA bacterial carbohydrate metabolic process was attenuated. Our findings reveal an important mechanism by which host-commensal interactions in glycometabolism affect energy regulation, suggesting an approach for preventing lifestyle-related diseases via prebiotics and probiotics by targeting bacteria and EPS metabolites.

One Year of Gluten-Free Diet Impacts Gut Function and Microbiome in Celiac Disease

BACKGROUND & AIMS

Currently, the main treatment for celiac disease (CD) is the gluten-free diet (GFD). This observational cohort study investigated the impact of CD and 1 year of GFD on gut function and microbiome.

METHODS

A total of 36 newly diagnosed patients and 36 healthy volunteers (HVs) were studied at baseline and at 12-month follow-up. Small bowel water content (SBWC), whole gut transit time (WGTT), and colon volumes were measured by magnetic resonance imaging. Stool sample DNA was subjected to shotgun metagenomic sequencing. Species-level abundances and gene functions, including CAZymes (carbohydrate active enzymes) were determined.

RESULTS

SBWC was significantly higher in people with CD (157 ± 15 mL) vs (HVs 100 ± 12 mL) (P = .003). WGTT was delayed in people with CD (68 ± 8 hours) vs HVs (41 ± 5 hours) (P = .002). The differences reduced after 12 months of GFD but not significantly. Well-being in the CD group significantly improved after GFD but did not recover to control values. CD fecal microbiota showed a high abundance of proteolytic gene functions, associated with Escherichia coli, Enterobacter, and Peptostreptococcus. GFD significantly reduced Bifidobacteria and increased Blautia wexlerae. Microbiome composition correlated positively with WGTT, colonic volume, and Akkermansia municphilia but negatively with B wexerelae. Following GFD, the reduction in WGTT and colonic volume was significantly associated with increased abundance of B wexlerae. There were also significant alterations in CAZyme profiles, specifically starch- and arabinoxylan-degrading families.

CONCLUSIONS

CD impacted gut function and microbiota. GFD ameliorated but did not reverse these effects, significantly reducing Bifidobacteria associated with reduced intake of resistant starch and arabinoxylan from wheat.

CLINICALTRIALS

gov, number: NCT02551289.

Models incorporating physical, laboratory and gut metabolite markers can be used to predict severe hepatic steatosis in MAFLD patients

Metabolic-associated fatty liver disease (MAFLD) induced-severe hepatic steatosis poses significant health risks. Early prediction of this condition is crucial for prompt intervention. Short-chain fatty acids (SCFAs) and tryptophan are gut metabolites correlated with MAFLD pathogenesis in the gut-liver axis. This study aims to construct prediction models for severe hepatic steatosis by including SCFAs and tryptophan metabolites. This study enrolled 83 participants from the outpatient department in 2023. Physical measurements, serum metabolic and inflammatory markers, metabolites of serum SCFAs and tryptophan were collected. Severe hepatic steatosis was diagnosed using vibration-controlled transient elastography and abdominal sonography. All 40 (48.2%) participants diagnosed with severe hepatic steatosis had MAFLD, while approximately three-quarters of those without severe hepatic steatosis had MAFLD. In comparison to the non-severe hepatic steatosis group, individuals with severe hepatic steatosis exhibited higher levels of waist and arm circumference, serum triglyceride (TG), and lower levels of serum high-density lipoprotein cholesterol (HDL-C) and AST/ALT ratio. They also had higher serum levels of lipopolysaccharide-binding protein, isovaleric acid, and propionic acid, and lower levels of 3-methylvaleric acid, indole-3-propionic acid, and indoxyl sulfate. Models incorporating these markers predicted severe hepatic steatosis. One model additionally included waist circumference and triglyceride-glucose index, while the other incorporated arm circumference and TG/HDL-C ratio. The area under the curve reached 0.958 and 0.938, respectively (p < 0.001). SCFAs and tryptophan metabolites are valuable in predicting severe hepatic steatosis. Further research is needed to investigate the roles of these metabolites in MAFLD.

Benzoic Acid potentiates intestinal IgA response in broiler chickens against Salmonella enterica Serovar Typhimurium infection

As a feed additive, Benzoic Acid (BA) has been demonstrated to significantly enhance feed conversion efficiency, regulate gastrointestinal pH, and improve overall animal health. Young animals, highly susceptible to S. Typhimurium infection, suffer from high mortality rates and substantial economic losses due to this pathogen. Despite promising indications of BA's immunomodulatory potential in boosting intestinal immunity, its underlying mechanisms remain insufficiently understood. This study investigates how BA strengthens intestinal anti-infection defenses in young animals via immunomodulatory pathways, focusing on its impact on macrophage polarization and IgA-mediated immune responses. Employing in vitro cell experiments and animal models, we examined the macrophage phenotypic alterations following BA treatment. We assessed the expression of immune-related genes in the intestine through immunofluorescence staining, Western blotting, and quantitative real-time PCR. The results demonstrate that BA promotes M2 macrophage polarization by activating the mTOR/PPAR-γ/STAT3 signaling pathways. Furthermore, BA enhances the intestinal expression of the polymeric immunoglobulin receptor (PIgR), B-cell activating factor (BAFF) from the TNF family, and activation-induced cytidine deaminase (AID), thereby enhancing IgA production by B-cells. These results underscore the potential of BA to bolster innate immune functions in young chickens, mitigate intestinal damage caused by S. Typhimurium infection, and ultimately promote both animal health and food safety.

A polysaccharide from edible red seaweed Bangia fusco-purpurea prevents obesity in high-fat diet-induced C57BL/6 mice

The study aimed to investigate the impacts of a polysaccharide (BFP) from Bangia fusco-purpurea on high-fat diet (HFD)-induced obesity in C57BL/6 mice, as well as its underlying mechanisms. Our results showed that orally administrated BFP was more effective than inulin (INU) in reducing body weight and fat accumulation in obese mice, indicating its anti-obesity effect. BFP effectively improved the compositions and metabolites of intestinal microbiota in obese mice, leading to enhanced energy metabolism and lipid metabolism, thus contributing to its anti-obesity effect. Notably, the better anti-obesity effect of BFP compared to INU was attributed to their varying degrees of modulation of specific intestinal microbial taxa, such as Clostridium and Aerococcus, as well as the regulation of differential metabolites (including biotin, piperine, G6P, etc.) also varied. Also, both in vitro (3T3-L1 preadipocytes) and in vivo (HFD-induced obese mice) models confirmed that BFP achieved anti-obesity effect attributed to enhance energy metabolism, promote lipolysis, increase fatty acid oxidation, and inhibit adipogenesis via activating the AMP-activated protein kinase and Acetyl-CoA carboxylase signaling pathways and suppressing the peroxisome proliferator-activated receptor γ expression. Our findings suggest that BFP has the potential to be used as prebiotics, dietary agents, and nutritional supplements against obesity.

Translational approach to establish the cardiometabolic health effects and mechanisms of action of fish nutrients-it takes a village

People use dietary supplements to offset nutritional deficiencies and manage metabolic dysfunction. While the beneficial effect of fish proteins on glucose homeostasis is well established, the ability of fish peptides to replicate the protein findings is less clear. With financial support from a programmatic Canadian Institutes of Health Research (CIHR) Team grant, we aimed to identify salmon peptide fractions (SPFs) with the potential to mitigate metabolic dysfunction. Additionally, the grant aims included assessing whether vitamin D, a nutrient commonly found in salmon, could potentiate the beneficial effects of salmon peptides. In parallel, technologies were developed to separate and filter the isolated peptides. We employed an integrative approach that combined nutritional interventions in animal models and human subjects to identify metabolic pathways regulated by salmon peptides and other fish nutrients. This combination of interdisciplinary expertise revealed that a SPF could be a therapeutic tool used in the prevention and management of cardiometabolic diseases. Herein, we present a perspective of our CIHR funded grant that utilized a translational approach to establish the cardiometabolic health effects and mechanisms of action of fish nutrients: from animal models to clinical trials.

Food-breastmilk combinations alter the colonic microbiome of weaning infants: an in silico study

The introduction of solid foods to infants, also known as weaning, is a critical point for the development of the complex microbial community inhabiting the human colon, impacting host physiology in infancy and later in life. This research investigated in silico the impact of food-breastmilk combinations on growth and metabolite production by colonic microbes of New Zealand weaning infants using the metagenome-scale metabolic model named Microbial Community. Eighty-nine foods were individually combined with breastmilk, and the 12 combinations with the strongest influence on the microbial production of short-chain fatty acids (SCFAs) and branched-chain fatty acids (BCFAs) were identified. Fiber-rich and polyphenol-rich foods, like pumpkin and blackcurrant, resulted in the greatest increase in predicted fluxes of total SCFAs and individual fluxes of propionate and acetate when combined, respectively, with breastmilk. Identified foods were further combined with other foods and breastmilk, resulting in 66 multiple food-breastmilk combinations. These combinations altered in silico the impact of individual foods on the microbial production of SCFAs and BCFAs, suggesting that the interaction between the dietary compounds composing a meal is the key factor influencing colonic microbes. Blackcurrant combined with other foods and breastmilk promoted the greatest increase in the production of acetate and total SCFAs, while pork combined with other foods and breastmilk decreased the production of total BCFAs.IMPORTANCELittle is known about the influence of complementary foods on the colonic microbiome of weaning infants. Traditional in vitro and in vivo microbiome methods are limited by their resource-consuming concerns. Modeling approaches represent a promising complementary tool to provide insights into the behavior of microbial communities. This study evaluated how foods combined with other foods and human milk affect the production of short-chain fatty acids and branched-chain fatty acids by colonic microbes of weaning infants using a rapid and inexpensive in silico approach. Foods and food combinations identified here are candidates for future experimental investigations, helping to fill a crucial knowledge gap in infant nutrition.

Macleaya cordata extract exhibits some potential as a surrogate antibiotic by improving gastrointestinal epithelial status and humoral response in goats

Macleaya cordata extract (MCE) is a potential replacement for antibiotics. In the current study, effects of MCE on the gastrointestinal health and humoral responses of host animals were explored. A total of 30 weanling goats with similar body weight of 9.15 ± 1.36 kg were randomly allocated into three groups (n = 10 per group): control group (CON group, fed with a basal diet), antibiotic group (Abx group, fed with the basal diet supplemented with 0.18 g/d vancomycin and 0.36 g/d neomycin), and MCE group (fed with the basal diet supplemented with 5 g/d MCE), for three weeks. Results showed that antibiotic addition decreased the height and area of rumen papillae, ruminal mucosa Toll-like receptor 8 (TLR8), interleukin-8 (IL-8) and interleukin-1β (IL-1β) gene relative expression levels and microbial diversity, altered the volatile fatty acid (VFA) profile in the rumen, and increased monocytes amount and CD4+ T cells percentage in the peripheral blood (P < 0.05) compared to CON group. MCE addition increased the average daily gain, ileal villus height, villus height/crypt depth, and immunoglobulin M (IgM) content in the peripheral blood (P < 0.05) compared to the CON. Additionally, MCE addition decreased the proportion of isobutyric acid in the chyme of the ileum (P = 0.005) compared to the CON group. These results suggest that antibiotic supplementation may suppress the epithelial state and microbial diversity and fermentation in goats, but stimulate cellular response to maintain the growth performance of goats. MCE administration improved the epithelial state and humoral response to promote the growth performance in goats.

Dietary supplementation with capsaicinoids alleviates obesity in mice fed a high-fat-high-fructose diet

Capsaicinoids are the pungent compounds in chili peppers. The present study investigated the effect of capsaicinoids on obesity in mice induced by a high-fat-high-fructose diet. Thirty-two male C57BL/6J mice were randomly divided into four groups (n = 8) and fed one of the following diets, namely, a low-fat diet (LFD), a high-fat-high-fructose diet (HFF), an HFF + 0.015% capsaicinoids (LCP), and an HFF + 0.045% capsaicinoids (HCP), for 12 weeks. Results showed that capsaicinoids significantly reversed HFF-induced obesity. Supplementation with capsaicinoids improved glucose tolerance, reduced plasma lipids, and attenuated inflammation. Capsaicinoids also reduced hepatic lipid accumulation by upregulating the expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). In addition, capsaicinoids enhanced the production of fecal short-chain fatty acids (SCFAs) and increased the fecal excretion of lipids. Gut microbiota analysis revealed that capsaicinoids decreased the Firmicutes/Bacteroidetes ratio and beneficially reconstructed the microbial community. However, the effects of capsaicinoids on intestinal villus length and lipid tolerance were negligible. In conclusion, capsaicinoids effectively attenuated HFF-induced obesity and metabolic syndrome by favorably modulating lipid metabolism, improving SCFA production, and reshaping gut microbial structure.

The potential role of gut microbiota-derived metabolites as regulators of metabolic syndrome-associated mitochondrial and endolysosomal dysfunction in Alzheimer's disease

Although the role of gut microbiota (GMB)-derived metabolites in mitochondrial and endolysosomal dysfunction in Alzheimer's disease (AD) under metabolic syndrome remains unclear, deciphering these host-metabolite interactions represents a major public health challenge. Dysfunction of mitochondria and endolysosomal networks (ELNs) plays a crucial role in metabolic syndrome and can exacerbate AD progression, highlighting the need to study their reciprocal regulation for a better understanding of how AD is linked to metabolic syndrome. Concurrently, metabolic disorders are associated with alterations in the composition of the GMB. Recent evidence suggests that changes in the composition of the GMB and its metabolites may be involved in AD pathology. This review highlights the mechanisms of metabolic syndrome-mediated AD development, focusing on the interconnected roles of mitochondrial dysfunction, ELN abnormalities, and changes in the GMB and its metabolites. We also discuss the pathophysiological role of GMB-derived metabolites, including amino acids, fatty acids, other metabolites, and extracellular vesicles, in mediating their effects on mitochondrial and ELN dysfunction. Finally, this review proposes therapeutic strategies for AD by directly modulating mitochondrial and ELN functions through targeting GMB metabolites under metabolic syndrome.

Diet and the Gut Microbiome as Determinants Modulating Metabolic Outcomes in Young Obese Adults

Obesity, along with metabolic disorders such as dyslipidemia and insulin resistance, increases the risk of cardiovascular disease, diabetes, various cancers, and other non-communicable diseases, thereby contributing to higher mortality rates. The intestinal microbiome plays a crucial role in maintaining homeostasis and influencing human metabolism. This study enrolled 82 young obese individuals, who were stratified into groups with or without metabolic disturbances. No significant differences in the alpha or beta diversity of the microbiota were observed among the groups. Insulin resistance was characterized by an increase in the number of Adlercreutzia and Dialister as well as a decrease in Collinsella, Coprococcus and Clostridiales. The dyslipidemia and dyslipidemia+insulin resistance groups had no significant differences in the gut microbiota. Dietary patterns also influenced microbial composition, with high protein intake increasing Leuconostoc and Akkermansia, and high fiber intake boosting Lactobacillus and Streptococcus. The genus Erwinia was associated with increases in visceral fat and serum glucose as well as a decrease in high-density lipoprotein cholesterol. Our findings highlight a significant association between gut microbiota composition and metabolic disturbances in young obese individuals, and they suggest that dietary modifications may promote a healthy microbiome and reduce the risk of developing metabolic disorders.

The role of branched-chain amino acids and their downstream metabolites in mediating insulin resistance

Elevated levels of circulating branched-chain amino acids (BCAAs) and their associated metabolites have been strongly linked to insulin resistance and type 2 diabetes. Despite extensive research, the precise mechanisms linking increased BCAA levels with these conditions remain elusive. In this review, we highlight the key organs involved in maintaining BCAA homeostasis and discuss how obesity and insulin resistance disrupt the intricate interplay among these organs, thus affecting BCAA balance. Additionally, we outline recent research shedding light on the impact of tissue-specific or systemic modulation of BCAA metabolism on circulating BCAA levels, their metabolites, and insulin sensitivity, while also identifying specific knowledge gaps and areas requiring further investigation. Finally, we summarize the effects of BCAA supplementation or restriction on obesity and insulin sensitivity.

Therapeutic effects of Lingguizhugan decoction in a rat model of high-fat diet-induced insulin resistance

BACKGROUND

Lingguizhugan (LGZG) decoction is a widely used classic Chinese medicine formula that was recently shown to improve high-fat diet (HFD)-induced insulin resistance (IR) in animal studies.

AIM

To assess the therapeutic effect of LGZG decoction on HFD-induced IR and explore the potential underlying mechanism.

METHODS

To establish an IR rat model, a 12-wk HFD was administered, followed by a 4-wk treatment with LGZG. The determination of IR status was achieved through the use of biochemical tests and oral glucose tolerance tests. Using a targeted meta-bolomics platform to analyze changes in serum metabolites, quantitative real-time PCR (qRT-PCR) was used to assess the gene expression of the ribosomal protein S6 kinase beta 1 (S6K1).

RESULTS

In IR rats, LGZG decreased body weight and indices of hepatic steatosis. It effectively controlled blood glucose and food intake while protecting islet cells. Metabolite analysis revealed significant differences between the HFD and HFD-LGZG groups. LGZG intervention reduced branched-chain amino acid levels. Levels of IR-related metabolites such as tryptophan, alanine, taurine, and asparagine decreased significantly. IR may be linked to amino acids due to the contemporaneous increase in S6K1 expression, as shown by qRT-PCR.

CONCLUSIONS

Our study strongly suggests that LGZG decoction reduces HFD-induced IR. LGZG may activate S6K1 via metabolic pathways. These findings lay the groundwork for the potential of LGZG as an IR treatment.

Gut microbiota promoting propionic acid production accompanies caloric restriction-induced intentional weight loss in cats

Rodent models and human clinical studies have shown gut microbiota-derived short-chain fatty acids (SCFAs) play roles in obesity and insulin resistance. These roles have been minimally explored in cats, where in the USA an estimated 60% of cats are overweight or obese. Overweight/obese research cats (n = 7) were transitioned from a maintenance diet to a reduced calorie diet fed ad libitum for 7 days, then calories were restricted to achieve 1-2% weight loss per week for an additional 77 days. Cats then received their original maintenance diet again for 14 days. Significant intentional weight loss was noted after calorie restriction (adjusted p < 0.0001). 16S rRNA gene amplicon sequencing and targeted SCFA metabolomics were performed on fecal samples. Fecal microbial community structure significantly differed between the four study phases (PERMANOVA p = 0.011). Fecal propionic acid was significantly higher during caloric restriction-induced weight loss (adjusted p < 0.05). Repeated measures correlation revealed the relative abundances of Prevotella 9 copri (correlation coefficient = 0.532, 95% CI (0.275, 0.717), p = 0.0002) significantly correlated with propionic acid composition. Like humans, obese cats experienced an altered microbial community structure and function, favoring propionic acid production, during caloric restriction-induced weight loss.

Butyrate and iso-butyrate: a new perspective on nutrition prevention of gestational diabetes mellitus

BACKGROUND

Dietary imbalance, such as a lower proportion of complex carbohydrates and a higher protein diet, may contribute to gestational diabetes mellitus (GDM) risks through their metabolisms. However, there is a lack of knowledge regarding the association between butyrate, iso-butyrate, and GDM, which are metabolisms of the two primary nutrients above. This study aimed to clarify the association of butyrate and iso-butyrate with GDM.

METHODS

A nested case-control study was conducted based on the Beijing Birth Cohort Study (BBCS) from 2017 to 2018. Totally, 99 singleton women were involved (GDM: n = 49, control: n = 50). All participants provided blood samples twice (in their first and second trimesters). Gas chromatography-mass spectrometry (GC-MS) was used for butyrate and iso-butyrate detection. Unconditional logistic regression and receiver operating characteristic (ROC) curve analysis were used for statistical analysis.

RESULTS

The results showed that butyrate in the first trimester was negatively correlated with GDM (odds ratio (OR): 0.00, 95% confidential interval (CI): 0.00-0.21, P = 0.008), and iso-butyrate in the second trimester was positively related to GDM (OR: 627.68, 95% CI: 40.51-9724.56, P < 0.001). The ratio (butyrate/iso-butyrate) was negatively associated with GDM, both in the first trimester (OR: 0.00, 95%CI: 0.00-0.05, P < 0.001) and in the second trimester (OR: 0.52, 95% CI: 0.34-0.80, P = 0.003). The area under the curve (AUC) using the ratio in the first trimester combined with clinical risk factors achieved 0.89 (95% CI: 0.83-0.95). Iso-butyrate in the second trimester combined with clinical risk factors achieved an AUC of 0.97 (95% CI: 0.92-1.00).

CONCLUSIONS

High iso-butyrate and low butyrate levels may be associated with an increased risk of GDM. As they are produced through dietary nutrient formation by gut microbiota, further studies on the association of dietary intake and butyrate or iso-butyrate concentration in plasma may help find a novel approach to nutritional intervention for GDM.

Antibiotics and probiotics-induced effects on the total fatty acid composition of feces in a rat model

Fatty acids (FAs) play important roles as membrane components and signal transduction molecules. Changes in short chain FA (SCFA) composition are associated with gut microbiota modifications. However, the effect of bacteria-driven changes on the detailed FA spectrum has not been explored yet. We investigated the effect of antibiotics (ABx) and/or probiotics, in four treatment groups on rat stool FA composition. Principal component analysis indicated that the chromatogram profiles of the treatment groups differ, which was also observed at different time points. Linear mixed effects models showed that in the parameters compared (sampling times, treatments. and their interactions), both the weight percentage and the concentration of FAs were affected by ABx and probiotic administration. This study found that the gut microbiome defines trans and branched saturated FAs, most saturated FAs, and unsaturated FAs with less carbon atoms. These results are among the first ones to demonstrate the restoring effects of a probiotic mixture on a substantial part of the altered total FA spectrum, and also revealed a previously unknown relationship between gut bacteria and a larger group of FAs. These findings suggest that intestinal bacteria produce not only SCFAs but also other FAs that may affect the host's physiological processes.

Electrospray alginate microgels co-encapsulating degraded Konjac glucomannan and quercetin modulate human gut microbiota in vitro

Alginate microgels co-encapsulating degraded Konjac glucomannan (KGM60) underwent in vitro fecal fermentation and their effects on human microbiota and metabolites were investigated. KGM60 delayed quercetin release and enhanced phenolic metabolites production. Microgels co-encapsulating KGM60 and quercetin increased linear short chain fatty acid but decreased branched chain fatty acid production. Microgels encapsulated with quercetin with or without KGM60 decreased Firmicutes while increased Bacteroidetes over 24 h of fermentation, at genus level promoted Bacteroides growth at 24 h and decreased the abundance of Negativibacillus, Ruminococcus_NK4A214, and Christensenellaceae R_7. Faecalibacterium and Collinsella levels were exclusively promoted by microgels encapsulating KGM60 with or without quercetin, highlighting prebiotic effect of KGM60. Only microgels co-encapsulating both KGM60 and quercetin enhanced Dialister while inhibited Lachnoclostridium, indicating synergism between KGM60 and quercetin. Our study indicates that co-encapsulating KGM60 and quercetin in alginate microgel is effective in modulating human gut microbiota and metabolites production potentially beneficial to gut health.

Rebaudioside D decreases adiposity and hepatic lipid accumulation in a mouse model of obesity

Overconsumption of added sugars has been pointed out as a major culprit in the increasing rates of obesity worldwide, contributing to the rising popularity of non-caloric sweeteners. In order to satisfy the growing demand, industrial efforts have been made to purify the sweet-tasting molecules found in the natural sweetener stevia, which are characterized by a sweet taste free of unpleasant aftertaste. Although the use of artificial sweeteners has raised many concerns regarding metabolic health, the impact of purified stevia components on the latter remains poorly studied. The objective of this project was to evaluate the impact of two purified sweet-tasting components of stevia, rebaudioside A and D (RebA and RebD), on the development of obesity, insulin resistance, hepatic health, bile acid profile, and gut microbiota in a mouse model of diet-induced obesity. Male C57BL/6 J mice were fed an obesogenic high-fat/high-sucrose (HFHS) diet and orally treated with 50 mg/kg of RebA, RebD or vehicle (water) for 12 weeks. An additional group of chow-fed mice treated with the vehicle was included as a healthy reference. At weeks 10 and 12, insulin and oral glucose tolerance tests were performed. Liver lipids content was analyzed. Whole-genome shotgun sequencing was performed to profile the gut microbiota. Bile acids were measured in the feces, plasma, and liver. Liver lipid content and gene expression were analyzed. As compared to the HFHS-vehicle treatment group, mice administered RebD showed a reduced weight gain, as evidenced by decreased visceral adipose tissue weight. Liver triglycerides and cholesterol from RebD-treated mice were lower and lipid peroxidation was decreased. Interestingly, administration of RebD was associated with a significant enrichment of Faecalibaculum rodentium in the gut microbiota and an increased secondary bile acid metabolism. Moreover, RebD decreased the level of lipopolysaccharide-binding protein (LBP). Neither RebA nor RebD treatments were found to impact glucose homeostasis. The daily consumption of two stevia components has no detrimental effects on metabolic health. In contrast, RebD treatment was found to reduce adiposity, alleviate hepatic steatosis and lipid peroxidation, and decrease LBP, a marker of metabolic endotoxemia in a mouse model of diet-induced obesity.

The Effects of Yeast Protein on Gut Microbiota in Mice When Compared with Soybean Protein and Whey Protein Isolates

Different protein sources can impact gut microbiota composition and abundance, and also participate in health regulation. In this study, mice were gavaged with yeast protein (YP), soybean protein isolate (SPI), and whey protein isolate (WPI) for 28 days. Body weights showed similar patterns across different protein administration groups. The ileum in YP-supplemented mice exhibited good morphology, and tight-junction (TJ) proteins were slightly upregulated. Immunoglobulin (Ig)A, IgM, and IgG levels in the ileum of different protein groups were significantly increased (p < 0.05). Interleukin (IL)-10 levels were significantly increased, whereas IL-6 levels were significantly reduced in the YP group when compared with the control (C) (p < 0.05). Glutathione peroxidase (GSH-Px) levels in the ileum were significantly increased in the YP group (p < 0.05). These results indicate that YP potentially improved intestinal immunity and inflammatory profiles. The relative abundances of Parabacteroides, Prevotella, and Pseudobutyrivibrio in the YP group were more enriched when compared with the C and SPI groups, and Parabacteroides was significantly upregulated when compared with the WPI group (p < 0.05). Overall, the results indicate that YP upregulates the beneficial bacteria and improves ileal immunity and anti-inflammatory capabilities.

l-valine supplementation disturbs vital molecular pathways and induces apoptosis in mouse testes

The branched-chain amino acids (BCAAs: leucine, isoleucine and valine) are essential for animal growth and metabolic health. However, the effect of valine on male reproduction and its underlying molecular mechanism remain largely unknown. Here, we showed that l-valine supplementation (0.30% or 0.45%, water drinking for 3 weeks) did not change body and testis weights, but significantly altered morphology of sertoli cells and germ cells within seminiferous tubule, and enlarged the space between seminiferous tubules within mouse testis. l-valine treatment (0.45%) increased significantly the Caspase3/9 mRNA levels and CASPASE9 protein levels, therefore induced apoptosis of mouse testis. Moreover, gene expression levels related to autophagy (Atg5 and Lamb3), DNA 5 mC methylation (Dnmt1, Dnmt3a, Tet2 and Tet3), RNA m6A methylation (Mettl14, Alkbh5 and Fto), and m6A methylation binding proteins (Ythdf1/2/3 and Igf2bp1/2) were significantly reduced. Protein abundances of ALKBH5, FTO and YTHDF3 were also significantly reduced, but not for ATG5 and TET2. Testis transcriptome sequencing detected 537 differentially expressed genes (DEGs, 26 up-regulated and 511 down-regulated), involved in multiple important signaling pathways. RT-qPCR validated 8 of 9 DEGs (Cd36, Scd1, Insl3, Anxa5, Lcn2, Hsd17b3, Cyp11a1, Cyp17a1 and Agt) to be decreased significantly, consistent with RNA-seq results. Taken together, l-valine treatment could disturb multiple signaling pathways (autophagy and RNA methylation etc.), and induce apoptosis to destroy the tissue structure of mouse testis.

Biotics and bacterial function: impact on gut and host health

The human gut microbiota, the vast community of microbes inhabiting the gastrointestinal tract, plays a pivotal role in maintaining health. Bacteria are the most abundant organism, and the composition of bacterial communities is strongly influenced by diet. Gut bacteria can degrade complex dietary carbohydrates to produce bioactive compounds such as short-chain fatty acids. Such products influence health, by acting on systemic metabolism, or by virtue of anti-inflammatory or anti-carcinogenic properties. The composition of gut bacteria can be altered through overgrowth of enteropathogens (e.g. Campylobacter, Salmonella spp.), leading to dysbiosis of the gut ecosystem, with some species thriving under the altered conditions whereas others decline. Various "biotics" strategies, including prebiotics, probiotics, synbiotics, and postbiotics, contribute to re-establishing balance within the gut microbial ecosystem conferring health benefits. Prebiotics enhance growth of beneficial members of the resident microbial community and can thus prevent pathogen growth by competitive exclusion. Specific probiotics can actively inhibit the growth of pathogens, either through the production of bacteriocins or simply by reducing the gastrointestinal pH making conditions less favorable for pathogen growth. This review discusses the importance of a balanced gut ecosystem, and strategies to maintain it that contribute to human health.

Dietary isoacids effects on growth, nitrogen, and energy digestibility, and fecal volatile fatty acids and microbial ecology in finishing pigs

Isoacids are branched ketoacids which when fed to ruminants have been shown to enhance the growth of fiber-digesting organisms. Ninety finishing gilts were individually fed dietary treatments consisting of diet type: corn-soybean meal (CSBM), a diet containing 40% distillers dried grains with solubles (DDGS), or a diet containing 40% sugar beet pulp (SBP); in combination with either no feed additive (CNT), the addition of 0.50% isobutyrate (IB), or the addition of a 0.88% mix of isobutyrate, isovalerate, and 2-methylbutyrate (MX). Gilts consumed an average of 2.171 kg/d over the 28-d trial. On d 26, fresh fecal samples were collected for determination of apparent total tract digestibility (ATTD) of gross energy (GE) and nitrogen (N), determination of fecal volatile fatty acids (VFA), and evaluation of microbial ecology. There was no interaction between diet type and isoacid addition, and no main effect of isoacid or diet type on alpha or Shannon microbial diversity measures (P > 0.05). There was no interaction between isoacid addition and diet type, and no main effect of isoacid addition on microbial beta diversity (P > 0.05), but differences were observed in microbial beta diversity due to diet type (P ≤ 0.05). There was no interaction between diet type and isoacid addition observed in fecal VFA concentrations (P > 0.05), with only minor differences in fecal VFA concentrations noted due to isoacid addition (P ≤ 0.05). The interaction between diet type and isoacid addition on ATTD of dietary GE and N (P ≤ 0.01) was large because the addition of IB did not affect the ATTD of GE or N in pigs fed the CSBM diet, but increased ATTD of GE and N in pigs fed diets containing DDGS and decreased the ATTD of GE and N in pigs fed diets containing SBP. In contrast, adding a blend of isoacids (i.e., MX) reduced the ATTD of GE and N, regardless of diet type. There was no interaction between diet type and isoacid addition, and no effect of isoacid addition was observed on pig performance (P > 0.05). Diet type did not affect average daily gain (P > 0.05), but pigs fed diets containing DDGS or SBP consumed less feed (P = 0.01) and exhibited greater GF ratios compared to pigs fed the low-fiber CSBM diet (P ≤ 0.05). In conclusion, there was little to no effect of isoacid addition on microbial ecology, fecal VFA concentrations, ATTD of GE or N, or pig performance, but the improvement in ATTD of GE and N in pigs fed diets containing DDGS when IB was added warrants further investigation.

Gut microbiota-mediated polyphenol metabolism is restrained by parasitic whipworm infection and associated with altered immune function in mice

Polyphenols are phytochemicals commonly found in plant-based diets which have demonstrated immunomodulatory and anti-inflammatory properties. However, the interplay between polyphenols and pathogens at mucosal barrier surfaces has not yet been elucidated in detail. Here, we show that proanthocyanidin (PAC) polyphenols interact with gut parasites to influence immune function and gut microbial-derived metabolites in mice. PAC intake inhibited mastocytosis during infection with the small intestinal roundworm Heligmosomoides polygyrus, and altered the host tissue transcriptome at the site of infection with the large intestinal whipworm Trichuris muris, with a notable enhancement of type-1 inflammatory and interferon-driven gene pathways. In the absence of infection, PAC intake promoted the expansion of Turicibacter within the gut microbiota, increased fecal short chain fatty acids, and enriched phenolic metabolites such as phenyl-γ-valerolactones in the cecum. However, these putatively beneficial effects were reduced in PAC-fed mice infected with T. muris, suggesting concomitant parasite infection can attenuate gut microbial-mediated PAC catabolism. Collectively, our results suggest an inter-relationship between a phytonutrient and infection, whereby PAC may augment parasite-induced inflammation (most prominently with the cecum dwelling T. muris), and infection may abrogate the beneficial effects of health-promoting phytochemicals.

Dietary Amino Acid Source Elicits Sex-Specific Metabolic Response to Diet-Induced NAFLD in Mice

SCOPE

Non-alcoholic fatty liver disease (NAFLD) is a sexually dimorphic disease influenced by dietary factors. Here, the metabolic and hepatic effects of dietary amino acid (AA) source is assessed in Western diet (WD)-induced NAFLD in male and female mice.

METHODS AND RESULTS

The AA source is either casein or a free AA mixture mimicking the composition of casein. As expected, males fed a casein-based WD display glucose intolerance, fasting hyperglycemia, and insulin-resistance and develop NAFLD associated with changes in hepatic gene expression and microbiota dysbiosis. In contrast, males fed the AA-based WD show no steatosis, a similar gene expression profile as males fed a control diet, and a distinct microbiota composition compared to males fed a casein-based WD. Females are protected against WD-induced liver damage, hepatic gene expression, and gut microbiota changes regardless of the AA source.

CONCLUSIONS

Free dietary AA intake prevents the unhealthy metabolic outcomes of a WD preferentially in male mice.

Aggravated hepatic fibrosis induced by phenylalanine and tyrosine was ameliorated by chitooligosaccharides supplementation

Hepatic fibrosis is a classic pathological manifestation of metabolic chronic hepatopathy. The pathological process might either gradually deteriorate into cirrhosis and ultimately liver cancer with inappropriate nutrition supply, or be slowed down by several multifunctional nutrients, alternatively. Herein, we found diet with excessive phenylalanine (Phe) and tyrosine (Tyr) exacerbated hepatic fibrosis symptoms of liver dysfunction and gut microflora dysbiosis in mice. Chitooligosaccharides (COS) could ameliorate hepatic fibrosis with the regulation of amino acid metabolism by downregulating the mTORC1 pathway, especially that of Phe and Tyr, and also with the alleviation of the dysbiosis of gut microbiota, simultaneously. Conclusively, this work presents new insight into the role of Phe and Tyr in the pathologic process of hepatic fibrosis, while revealing the effectiveness and molecular mechanism of COS in improving hepatic fibrosis from the perspective of metabolites.

Effects of Mealworm Fermentation Extract and Soy Protein Mix Ratio on Hepatic Glucose and Lipid Metabolism in Obese-Induced Mice

Previous studies found that mealworm fermentation extract (TMP) reduced alcoholic hepatic steatogenesis. This study examined how the ratio of TMP and soy protein (SP) mix affected glucose and lipid metabolism in obese mice given a high-fat diet (HFD). Mice were given HFD supplemented with 100% SP or the following three ratios of TMP and SP mix for 12 weeks: 20% (S4T1), 40% (S3T2), and 60% (S2T3) TMP. When compared to the SP group, the S2T3 group had considerably lower body weight gain and food consumption. When compared to the SP group, the S2T3 group had slightly lower blood insulin and leptin levels, as well as a lower homeostasis model assessment of insulin resistance score. The use of TMP instead of SP reduced the size of epididymal adipose tissue cells. An increase in the extent of substitution of SP with TMP inhibited the gene expression of hepatic fructolysis/gluconeogenesis (KHK, ALDOB, DLD, and FBP1), lipogenesis (FAS, SCD1, CD36, and DGAT2), and its transcriptional factors (PPARγ and ChREBP). Furthermore, the S2T3 group dramatically reduced the expression of hepatic genes implicated in endoplasmic reticulum stress (PDI) and antioxidant defense (SOD1). The 60% TMP mix, in particular, reduced the expression of hepatic glucose and lipid metabolismrelated genes in HFD-fed mice. The manufacturing of functional processed goods may be accomplished by combining SP and TMP in a 2:3 ratio.

Essential Amino Acid Metabolites as Chemical Mediators of Host-Microbe Interaction in the Gut

Amino acids are indispensable substrates for protein synthesis in all organisms and incorporated into diverse aspects of metabolic physiology and signaling. However, animals lack the ability to synthesize several of them and must acquire these essential amino acids from their diet or perhaps their associated microbial communities. The essential amino acids therefore occupy a unique position in the health of animals and their relationships with microbes. Here we review recent work connecting microbial production and metabolism of essential amino acids to host biology, and the reciprocal impacts of host metabolism of essential amino acids on their associated microbes. We focus on the roles of the branched-chain amino acids (valine, leucine, and isoleucine) and tryptophan on host-microbe communication in the intestine of humans and other vertebrates. We then conclude by highlighting research questions surrounding the less-understood aspects of microbial essential amino acid synthesis in animal hosts.

Gut microbiota promoting propionic acid production accompanies diet-induced intentional weight loss in cats

Rodent models and human clinical studies have shown gut microbiota-derived short-chain fatty acids (SCFAs) play roles in obesity and insulin resistance. These roles have been minimally explored in cats, where in the USA an estimated 60% of cats are overweight or obese. Overweight/obese research cats (n = 7) were transitioned from a maintenance diet to a reduced calorie diet fed ad libitum for seven days, then calories were restricted to achieve 1-2% weight loss per week for an additional 77 days. Cats then received their original maintenance diet again for 14 days. Significant intentional weight loss was noted after calorie restriction (adjusted p < 0.0001). 16S rRNA gene amplicon sequencing and targeted SCFA metabolomics were performed on fecal samples. Fecal microbial community structure significantly differed between the four study phases (PERMANOVA p = 0.011). Fecal propionic acid was significantly higher during diet-induced weight loss (adjusted p < 0.05). Spearman correlation revealed the relative abundances of Prevotella 9 copri (ρ = 0.6385, p = 0.0006) and Blautia caecimuris (ρ = 0.5269, p = 0.0068) were significantly correlated with propionic acid composition. Like humans, obese cats experienced an altered microbial community structure and function, favoring propionic acid production, during diet-induced weight loss.

The gut microbiome, short chain fatty acids, and related metabolites in cystic fibrosis patients with and without colonic adenomas

BACKGROUND

Adults with cystic fibrosis (CF) are at increased risk for colon cancer. CF patients have reductions in intestinal bacteria that produce short chain fatty acids (SCFAs), although it is unclear whether this corresponds with intestinal SCFA levels and the presence of colonic neoplasia. The aim of this study was to compare gut microbiome and SCFA composition in patients with and without CF, and to assess associations with colonic adenomas.

METHODS

Colonic aspirates were obtained from adults with and without CF undergoing colon cancer screening or surveillance colonoscopy. Microbiome characterization was performed by 16S rRNA V3-V4 sequencing. Targeted profiling of SCFAs and related metabolites was performed by LC-MS.

RESULTS

42 patients (21 CF, 21 control) were enrolled. CF patients had significantly reduced alpha diversity and decreased relative abundance of many SCFA-producing taxa. There were no significant differences in SCFA levels in CF patients, although there were reduced levels of branched chain fatty acids (BCFAs) and related metabolites. CF patients with adenomas, but not controls with adenomas, had significantly increased relative abundance of Bacteroides fragilis. CF microbiome composition was significantly associated with isovalerate concentration and the presence of adenomas.

CONCLUSIONS

CF patients have marked disturbances in the gut microbiome, and CF patients with adenomas had notably increased relative abundance of B. fragilis, a pathogen known to promote colon cancer. Reductions in BCFAs but not SCFAs were found in CF. Further studies are warranted to evaluate the role of B. fragilis as well the biological significance of reductions in BCFAs in CF.

Monomethyl branched-chain fatty acids: Health effects and biological mechanisms

Branched-chain fatty acids (BCFA) are a group of lipids that are widely present in various organisms; they take part in numerous biochemical processes and affect multiple signaling pathways. However, BCFA are not well explored in terms of their effects on human health. Recently, they have been gaining interest, especially in relation to various human diseases. This review describes the occurrence of BCFA, their dietary sources, their potential health effects, and the current state of knowledge concerning their mechanism(s) of action. Many studies have been conducted so far in cellular and animal models, which reveal potent anti-cancer, lipid lowering, anti-inflammatory and neuroprotective actions. Research in humans is scarce. Therefore, further studies on animals and humans should be performed to confirm and expand these findings, and improve our understanding of the potential relevance of BCFA to human health and disease.

Anti-Obesity Effects of Dietary Fibers Extracted from Flaxseed Cake in Diet-Induced Obese Mice

Although many efforts have been made to characterize the functional properties of flaxseed, knowledge concerning the properties of insoluble and soluble dietary fibers in flaxseed is still limited. Here, insoluble and soluble dietary fibers were extracted from flaxseed cake—a valuable resource that has not been fully exploited. Subsequently, their monosaccharide compositions, structural properties, and anti-obesity effects in male mice were characterized. The anti-obesity effects of flaxseed cake insoluble dietary fiber (FIDF), flaxseed cake soluble dietary fiber (FSDF), and FIDF combined with FSDF in diet-induced obese mice were investigated in our study. Supplementation with FSDF alone or FIDF and FSDF together lowered the fat accumulation, improved the serum lipid profile, increased the basal metabolism, and improved the gut microbiota of obese mice. Supplementation with FIDF and FSDF together significantly enriched the abundance of g_Akkermansia and g_Bifidobacterium, which are negatively associated with obesity. Supplementation with FIDF alone improved the liver lipid profile, raised the basal metabolism, and enhanced the short-chain fatty acid levels in the guts of the mice. In conclusion, our results collectively support the therapeutic potential of FIDF and FSDF in obesity treatment and indicate that FIDF and FSDF play different roles in the process of obesity treatment. Furthermore, our results provide critical information for flaxseed cake resource exploitation.

Trust the gut: outcomes of gut microbiota transplant in metabolic and cognitive disorders

Type 2 diabetes mellitus (T2DM) is a main public health concern, with increasing prevalence and growingly premature onset in children, in spite of emerging and successful therapeutic options. T2DM promotes brain aging, and younger age at onset is associated with a higher risk of subsequent dementia. Preventive strategies should address predisposing conditions, like obesity and metabolic syndrome, and be started from very early and even prenatal life. Gut microbiota is an emerging target in obesity, diabetes and neurocognitive diseases, which could be safely modulated since pregnancy and infancy. Many correlative studies have supported its involvement in disease pathophysiology. Faecal material transplantation (FMT) studies have been conducted in clinical and preclinical settings to deliver cause-effect proof and mechanistic insights. This review provides a comprehensive overview of studies in which FMT was used to cure or cause obesity, metabolic syndrome, T2DM, cognitive decline and Alzheimer's disease, including the evidence available in early life. Findings were analysed to dissect consolidated from controversial results, highlighting gaps and possible future directions.

Advantageous tactics with certain probiotics for the treatment of graft-versus-host-disease after hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) becomes a standard form of cellular therapy for patients with malignant diseases. HSCT is the first-choice of immunotherapy, although HSCT can be associated with many complications such as graft-versus-host disease (GVHD) which is a major cause of morbidity and mortality after allogeneic HSCT. It has been shown that certain gut microbiota could exert protective and/or regenerative immunomodulatory effects by the production of short-chain fatty acids (SCFAs) such as butyrate in the experimental models of GVHD after allogeneic HSCT. Loss of gut commensal bacteria which can produce SCFAs may worsen dysbiosis, increasing the risk of GVHD. Expression of G-protein coupled receptors such as GPR41 seems to be upre-gulated in the presence of commensal bacteria, which might be associated with the biology of regulatory T cells (Tregs). Treg cells are a suppressive subset of CD4 positive T lymphocytes implicated in the prevention of GVHD after allogeneic HSCT. Here, we discuss the current findings of the relationship between the modification of gut microbiota and the GVHD-related immunity, which suggested that tactics with certain probiotics for the beneficial symbiosis in gut-immune axis might lead to the elevation of safety in the allogeneic HSCT.

The gut microbiota in obesity and weight management: microbes as friends or foe?

Obesity is caused by a long-term difference between energy intake and expenditure - an imbalance that is seemingly easily restored by increasing exercise and reducing caloric consumption. However, as simple as this solution appears, for many people, losing excess weight is difficult to achieve and even more difficult to maintain. The reason for this difficulty is that energy intake and expenditure, and by extension body weight, are regulated through complex hormonal, neural and metabolic mechanisms that are under the influence of many environmental factors and internal responses. Adding to this complexity, the microorganisms (microbes) that comprise the gut microbiota exert direct effects on the digestion, absorption and metabolism of food. Furthermore, the gut microbiota exerts a miscellany of protective, structural and metabolic effects both on the intestinal milieu and peripheral tissues, thus affecting body weight by modulating metabolism, appetite, bile acid metabolism, and the hormonal and immune systems. In this Review, we outline historical and recent advances in understanding how the gut microbiota is involved in regulating body weight homeostasis. We also discuss the opportunities, limitations and challenges of using gut microbiota-related approaches as a means to achieve and maintain a healthy body weight.

Expression and clinical significance of short-chain fatty acids in pregnancy complications

Objective

To investigate the expression of short-chain fatty acids (SCFAs)-metabolites of intestinal flora-in gestational complications of gestational diabetes mellitus (GDM), preeclampsia (PE), and intrahepatic cholestasis of pregnancy (ICP), and its clinical significance.

Methods

Targeted metabonomics was used to detect SCFAs in the serum of 28 GDM pregnant women, 28 PE pregnant women, 29 ICP pregnant women, and 27 healthy pregnant women (NP); their expression changes were observed; the correlation between SCFAs and clinical characteristics was studied; and their potential as biomarkers for clinical diagnosis was evaluated.

Results

There were significant differences in the SCFA metabolic spectrum between the GDM, PE, ICP, and NP groups. Quantitative analysis showed that the content of isobutyric acid in the three pregnancy complications groups (the GDM, PE, and ICP groups) was significantly higher than that in the NP group (p < 0.05), and other SCFAs also showed significant differences in the three pregnancy complications groups compared with the NP group (p < 0.05). Receiver operating characteristic (ROC) curve analysis of the generalized linear model showed that multiple SCFAs were highly sensitive and specific as diagnostic markers in the pregnancy complications groups, where isobutyric acid was highly predictive in GDM (area under the ROC curve (AUC) = 0.764) and PE (AUC = 1), and caproic acid was highly predictive in ICP (AUC = 0.968), with potential clinical application.

Conclusion

The metabolic products of intestinal flora, SCFAs, during pregnancy are closely related to pregnancy complications (GDM, PE, and ICP), and SCFAs can be used as potential markers of pregnancy complications.

Bacteroides-derived isovaleric acid enhances mucosal immunity by facilitating intestinal IgA response in broilers

BACKGROUND

The interaction between nutrition and immunity plays a vital role in nutrient digestion, absorption, and metabolism during poultry production. Recent studies showed that the gut microbiota contributes to the development of intestinal mucosal immunity. However, the mechanisms by which gut microbes regulate this process remain unclear.

METHODS

We compared the intestinal mucosal immunity and gut microbiota of Arbor Acre broilers (AA (lower mucosal immunity) and Chinese native Wuliang Mountain Black-bone chickens (WLMB) (higher mucosal immunity) using 16S rDNA sequencing, transcriptomic analysis, and immunoglobulin A (IgA) antibody repertoire sequencing. We then combined 16S rDNA sequencing with transcriptomics to identify the key microbes and found that they were positively correlated with IgA production. Next, we transplanted candidate microbes into 1-day-old broiler to explore their role in intestinal mucosal immunity. Finally, we verified the function of candidate microbial metabolites in regulating the immune function of macrophages and the intestinal-epithelial cells (IECs) using in vitro experiments.

RESULTS

WLMB performs stronger mucosal immunity than AA, including higher IgA levels, more diverse IgA antibody repertoire, and higher bacterial affinity. Bacteroides was identified as the key microbes related to the intestinal IgA response. Bacteroides transplantation could increase IgA concentration in the duodenal contents by enhancing the expression of IgA, polymeric immunoglobin receptor (PIgR), B cell-activating factor of the TNF family (BAFF), and activation-induced cytidine deaminase (AID) in the duodenum. Additionally, Bacteroides-derived isovaleric acid promoted M2 macrophage polarization of macrophage via mTOR/PPAR-γ/STAT3 signaling pathways and regulated the immunologic function of IECs to produce cytokines, including interleukin (IL)-10, IL-4, BAFF, and transforming growth factor-beta (TGF-β), thus promoting IgA production in B cells by facilitating AID expression.

CONCLUSION

Our study revealed that Bacteroides modulate the intestinal IgA response and maintain gut health in broilers. Bacteroides may be a promising alternative as an immunomodulatory microbial agent for developing next-generation probiotics for broiler production.

Dietary protein and the intestinal microbiota: An understudied relationship

Diet has a profound impact on the microbial community in the gastrointestinal tract, the intestinal microbiota, to the benefit or detriment of human health. To understand the influence of diet on the intestinal microbiota, research has focused on individual macronutrients. Some macronutrients (e.g. fiber) have been studied in great detail and have been found to strongly influence the intestinal microbiota. The relationship between dietary protein, a vital macronutrient, and the intestinal microbiota has gone largely unexplored. Emerging evidence suggests that dietary protein strongly impacts intestinal microbiota composition and function and that protein-microbiota interactions can have critical impacts on host health. In this review, we focus on recent studies investigating the impact of dietary protein quantity and source on the intestinal microbiota and resulting host health consequences. We highlight major open questions critical to understanding health outcomes mediated by interactions between dietary protein and the microbiota.

Yeast mannoproteins are expected to be a novel potential functional food for attenuation of obesity and modulation of gut microbiota

The yeast mannoproteins (MPs), a major component of yeast cell walls with large exploration potentiality, have been attracting increasing attention due to their beneficial effects. However, the information about the anti-obesogenic activity of MPs is still limited. Thus, the effects of MPs on the high-fat diet (HFD)-induced obesity and dysbiosis of gut microbiota were investigated in this work. The results showed that MPs could significantly attenuate the HFD-induced higher body weight, fat accumulation, liver steatosis, and damage. Simultaneously, the inflammation in HFD-induced mice was also ameliorated by MPs. The pyrosequencing analysis showed that intervention by MPs could lead to an obvious change in the structure of gut microbiota. Furthermore, the prevention of obesity by MPs is highly linked to the promotion of Parabacteroides distasonis (increased from 0.39 ± 0.12% to 2.10 ± 0.20%) and inhibition of Lactobacillus (decreased from 19.99 ± 3.94% to 2.68 ± 0.77%). Moreover, the increased level of acetate (increased from 3.28 ± 0.22 mmol/g to 7.84 ± 0.96 mmol/g) and activation of G protein-coupled receptors (GPRs) by MPs may also contribute to the prevention of obesity. Thus, our preliminary findings revealed that MPs from yeast could be explored as potential prebiotics to modulate the gut microbiota and prevent HFD-induced obesity.

Fluoride induced leaky gut and bloom of Erysipelatoclostridium ramosum mediate the exacerbation of obesity in high-fat-diet fed mice

INTRODUCTION

Fluoride is widely presented in drinking water and foods. A strong relation between fluoride exposure and obesity has been reported. However, the potential mechanisms on fluoride-induced obesity remain unexplored. Objectives and methods The effects of fluoride on the obesity were investigated using mice model. Furthermore, the role of gut homeostasis in exacerbation of the obesity induced by fluoride was evaluated. Results The results showed that fluoride alone did not induce obesity in normal diet (ND) fed mice, whereas, it could trigger exacerbation of obesity in high-fat diet (HFD) fed mice. Fluoride impaired intestinal barrier and activated Toll-like receptor 4 (TLR4) signaling to induce obesity, which was further verified in TLR4^-/- mice. Furthermore, fluoride could deteriorate the gut microbiota in HFD mice. The fecal microbiota transplantation from fluoride-induced mice was sufficient to induce obesity, while the exacerbation of obesity by fluoride was blocked upon gut microbiota depletion. The fluoride-induced bloom of Erysipelatoclostridium ramosum was responsible for exacerbation of obesity. In addition, a potential strategy for prevention of fluoride-induced obesity was proposed by intervention with polysaccharides from Fuzhuan brick tea. Conclusion Overall, these results provide the first evidence of a comprehensive cross-talk mechanism between fluoride and obesity in HFD fed mice, which is mediated by gut microbiota and intestinal barrier. E. ramosum was identified as a crucial mediator of fluoride induced obesity, which could be explored as potential target for prevention and treatment of obesity with exciting translational value.

Central and peripheral regulations mediated by short-chain fatty acids on energy homeostasis

The human gut microbiota influences obesity, insulin resistance, and the subsequent development of type 2 diabetes (T2D). The gut microbiota digests and ferments nutrients resulting in the production of short-chain fatty acids (SCFAs), which generate various beneficial metabolic effects on energy and glucose homeostasis. However, their roles in the central nervous system (CNS)-mediated outputs on the metabolism have only been minimally studied. Here, we explore what is known and future directions that may be worth exploring in this emerging area. Specifically, we searched studies or data in English by using PubMed, Google Scholar, and the Human Metabolome Database. Studies were filtered by time from 1978 to March 2022. As a result, 195 studies, 53 reviews, 1 website, and 1 book were included. One hundred and sixty-five of 195 studies describe the production and metabolism of SCFAs or the effects of SCFAs on energy homeostasis, glucose balance, and mental diseases through the gut-brain axis or directly by a central pathway. Thirty of 195 studies show that inappropriate metabolism and excessive of SCFAs are metabolically detrimental. Most studies suggest that SCFAs exert beneficial metabolic effects by acting as the energy substrate in the TCA cycle, regulating the hormones related to satiety regulation and insulin secretion, and modulating immune cells and microglia. These functions have been linked with AMPK signaling, GPCRs-dependent pathways, and inhibition of histone deacetylases (HDACs). However, the studies focusing on the central effects of SCFAs are still limited. The mechanisms by which central SCFAs regulate appetite, energy expenditure, and blood glucose during different physiological conditions warrant further investigation.

The Metabolic Role and Therapeutic Potential of the Microbiome

We are host to an assembly of microorganisms that vary in structure and function along the length of the gut and from the lumen to the mucosa. This ecosystem is collectively known as the gut microbiota and significant efforts have been spent during the past 2 decades to catalog and functionally describe the normal gut microbiota and how it varies during a wide spectrum of disease states. The gut microbiota is altered in several cardiometabolic diseases and recent work has established microbial signatures that may advance disease. However, most research has focused on identifying associations between the gut microbiota and human diseases states and to investigate causality and potential mechanisms using cells and animals. Since the gut microbiota functions on the intersection between diet and host metabolism, and can contribute to inflammation, several microbially produced metabolites and molecules may modulate cardiometabolic diseases. Here we discuss how the gut bacterial composition is altered in, and can contribute to, cardiometabolic disease, as well as how the gut bacteria can be targeted to treat and prevent metabolic diseases.

Astragali Radix-Codonopsis Radix-Jujubae Fructus water extracts ameliorate exercise-induced fatigue in mice via modulating gut microbiota and its metabolites

BACKGROUD

Astragali Radix (AR) and Codonopsis Radix (CR) are widely used as the tonic herbal medicine with efficacy of tonifying qi in traditional Chinese medicine (TCM), which showed significant antifatigue activities. In this study, AR and CR were combined, with Jujubae Fructus (JF) further added to improve the taste, to afford the ACJ extracts in the ratio of 2:1:2.

RESULTS

The results showed that ACJ water extract exhibited antifatigue effect by the weight-loaded exhaustive swimming test in mice. The untargeted fecal metabolomic approach and 16S rRNA gene sequencing analysis showed that ACJ could improve exercise performance by regulating changes of gut metabolites and microbiota to alleviate fatigue. Four pathways were determined as the key pathways relating with its antifatigue effect, which included sphingolipid metabolism, glycerophospholipid metabolism, valine, leucine and isoleucine biosynthesis and d-arginine and d-ornithine metabolism. Correlation analysis showed the complex association among bacteria, metabolites and phenotypes.

CONCLUSION

In conclusion, this study revealed new perspectives to study the antifatigue mechanism of ACJ extracts from the gut microbiota, which provided the basis for further functional food development. © 2022 Society of Chemical Industry.

Dietary regulation in health and disease

Nutriments have been deemed to impact all physiopathologic processes. Recent evidences in molecular medicine and clinical trials have demonstrated that adequate nutrition treatments are the golden criterion for extending healthspan and delaying ageing in various species such as yeast, drosophila, rodent, primate and human. It emerges to develop the precision-nutrition therapeutics to slow age-related biological processes and treat diverse diseases. However, the nutritive advantages frequently diversify among individuals as well as organs and tissues, which brings challenges in this field. In this review, we summarize the different forms of dietary interventions extensively prescribed for healthspan improvement and disease treatment in pre-clinical or clinical. We discuss the nutrient-mediated mechanisms including metabolic regulators, nutritive metabolism pathways, epigenetic mechanisms and circadian clocks. Comparably, we describe diet-responsive effectors by which dietary interventions influence the endocrinic, immunological, microbial and neural states responsible for improving health and preventing multiple diseases in humans. Furthermore, we expatiate diverse patterns of dietotheroapies, including different fasting, calorie-restricted diet, ketogenic diet, high-fibre diet, plants-based diet, protein restriction diet or diet with specific reduction in amino acids or microelements, potentially affecting the health and morbid states. Altogether, we emphasize the profound nutritional therapy, and highlight the crosstalk among explored mechanisms and critical factors to develop individualized therapeutic approaches and predictors.

Mitochondrial Function and Microbial Metabolites as Central Regulators of Intestinal Immune Responses and Cancer

Energy and anabolic metabolism are essential for normal cellular homeostasis but also play an important role in regulating immune responses and cancer development as active immune and cancer cells show an altered metabolic profile. Mitochondria take a prominent position in these metabolic reactions. First, most key energetic reactions take place within or in conjunction with mitochondria. Second, mitochondria react to internal cues from within the cell but also to external cues originating from the microbiota, a vast diversity of associated microorganisms. The impact of the microbiota on host physiology has been largely investigated in the last decade revealing that the microbiota contributes to the extraction of calories from the diet, energy metabolism, maturation of the immune system and cellular differentiation. Thus, changes in the microbiota termed dysbiosis have been associated with disease development including metabolic diseases, inflammation and cancer. Targeting the microbiota to modulate interactions with the mitochondria and cellular metabolism to delay or inhibit disease development and pathogenesis appears an attractive therapeutic approach. Here, we summarize recent advances in developing the therapeutic potential of microbiota-mitochondria interactions for inflammation and cancer.