Effects of high-fiber diets enriched with carbohydrate, protein, or unsaturated fat on circulating short chain fatty acids: results from the OmniHeart randomized trial

Microbiota and Resveratrol: How Are They Linked to Osteoporosis?

Osteoporosis (OP), which is characterized by a decrease in bone density and increased susceptibility to fractures, is closely linked to the gut microbiota (GM). It is increasingly realized that the GM plays a key role in the maintenance of the functioning of multiple organs, including bone, by producing bioactive metabolites such as short-chain fatty acids (SCFA). Consequently, imbalances in the GM, referred to as dysbiosis, have been identified with a significant reduction in beneficial metabolites, such as decreased SCFA associated with increased chronic inflammatory processes, including the activation of NF-κB at the epigenetic level, which is recognized as the main cause of many chronic diseases, including OP. Furthermore, regular or long-term medications such as antibiotics and many non-antibiotics such as proton pump inhibitors, chemotherapy, and NSAIDs, have been found to contribute to the development of dysbiosis, highlighting an urgent need for new treatment approaches. A promising preventive and adjuvant approach is to combat dysbiosis with natural polyphenols such as resveratrol, which have prebiotic functions and ensure an optimal microenvironment for beneficial GM. Resveratrol offers a range of benefits, including anti-inflammatory, anti-oxidant, analgesic, and prebiotic effects. In particular, the GM has been shown to convert resveratrol, into highly metabolically active molecules with even more potent beneficial properties, supporting a synergistic polyphenol-GM axis. This review addresses the question of how the GM can enhance the effects of resveratrol and how resveratrol, as an epigenetic modulator, can promote the growth and diversity of beneficial GM, thus providing important insights for the prevention and co-treatment of OP.

Nexus Between Sarcopenia and Microbiome Research: A Bibliometric Exploration

Despite over 30 years of microbiome and skeletal muscle research, no quantitative analysis of sarcopenia and the microbiome literature had been conducted. Our bibliometric study examined research status, hotspots, and future trends. We utilized bibliometric techniques to search the Science Citation Index Extended Database on February 27, 2023, using the Bibliometrix package in R to create a map displaying scientific production and subject categories. Collaborative network maps between countries/regions were visualized using Scimago Graphica, while VOSviewer explored collaboration modes among individuals and institutions. We analyzed the top 25 emerging keywords, top co-occurring keyword networks, and co-occurring keyword clusters using CiteSpace. A total of 997 articles were retrieved for sarcopenia and microbiome, of which 633 papers were analyzed. Both the number of publications and total citation frequency had been continuously increasing. The United States had the highest total citation frequency, while China had the highest number of publications. Research on the impact of the microbiome on sarcopenia was in its nascent stage and spans multiple disciplines, including nutrition, microbiology, geriatrics, immunology, endocrinology and metabolism, molecular biology, and sports medicine. The University of Copenhagen contributed the most to the number of publications (n=16), with Tibbett M (n=7) and Hulver MW (n=7) among the top authors. The most published journal was "Nutrients" (n=24). Analysis of keywords and clusters revealed new research hotspots in microbes and sarcopenia, such as malnutrition, dietary fiber, signaling pathways, frailty, and intestinal permeability. Research on the impact of the microbiome on sarcopenia is in its infancy and spans multiple disciplines. Malnutrition, dietary fiber, signaling pathways, frailty, and intestinal microbes are currently research hotspots. Furthermore, the visual atlas analysis of research on microbes and sarcopenia helps to track the knowledge structure in research fields related to sarcopenia and microbes, providing direction for future research.

Short-term dietary fiber interventions produce consistent gut microbiome responses across studies

The composition of the human gut microbiome varies tremendously among individuals, making the effects of dietary or treatment interventions difficult to detect and characterize. The consumption of fiber is important for gut health, yet the specific effects of increased fiber intake on the gut microbiome vary across studies. The variation in study outcomes might be due to inter-individual (or inter-population) variation or to the details of the interventions including the types of fiber, length of study, size of cohort, and molecular approaches. Thus, to identify generally (on average) consistent fiber-induced responses in the gut microbiome of healthy individuals, we re-analyzed 16S rRNA sequencing data from 21 dietary fiber interventions from 12 human studies, which included 2,564 fecal samples from 538 subjects across all interventions. Short-term increases in dietary fiber consumption resulted in highly consistent gut bacterial community responses across studies. Increased fiber consumption explained an average of 1.5% of compositional variation (vs 82% of variation attributed to the individual), reduced alpha-diversity, and resulted in phylogenetically conserved responses in relative abundances among bacterial taxa. Additionally, we identified bacterial clades, at approximately the genus level, that were highly consistent in their response (on average, increasing or decreasing in their relative abundance) to dietary fiber interventions across the studies.

IMPORTANCE

Our study is an example of the power of synthesizing and reanalyzing 16S rRNA microbiome data from many intervention studies. Despite high inter-individual variation of the composition of the human gut microbiome, dietary fiber interventions cause a consistent response both in the degree of change and the particular taxa that respond to increased fiber.

Characterization of Urinary N-Acetyltaurine as a Biomarker of Hyperacetatemia in Mice

Acetate is an important metabolite in metabolic fluxes. Its presence in biological entities originates from both exogenous inputs and endogenous metabolism. Because the change in blood acetate level has been associated with both beneficial and adverse health outcomes, blood acetate analysis has been used to monitor the systemic status of acetate turnover. The present study examined the use of urinary N-acetyltaurine (NAT) as a marker to reflect the hyperacetatemic status of mice from exogenous inputs and endogenous metabolism, including triacetin dosing, ethanol dosing, and streptozotocin-induced diabetes. The results showed that triacetin dosing increased serum acetate and urinary NAT but not other N-acetylated amino acids in urine. The co-occurrences of increased serum acetate and elevated urinary NAT were also observed in both ethanol dosing and streptozotocin-induced diabetes. Furthermore, the renal cortex was determined as an active site for NAT synthesis. Overall, urinary NAT behaved as an effective marker of hyperacetatemia in three experimental mouse models, warranting further investigation into its application in humans.

Short-chain fatty acids inhibit bacterial plasmid transfer through conjugation in vitro and in ex vivo chicken tissue explants

The animal gut acts as a potent reservoir for spreading and maintaining conjugative plasmids that confer antimicrobial resistance (AMR), fitness, and virulence attributes. Interventions that inhibit the continued emergence and expansion of AMR and virulent strains in agricultural and clinical environments are greatly desired. This study aims to determine the presence and efficacy of short-chain fatty acids (SCFA) inhibitory effects on the conjugal transfer of AMR plasmids. In vitro broth conjugations were conducted between donor Escherichia coli strains carrying AMP plasmids and the plasmid-less Escherichia coli HS-4 recipient strain. Conjugations were supplemented with ddH2O or SCFAs at 1, 0.1, 0.01, or 0.001 molar final concentration. The addition of SCFAs completely inhibited plasmid transfer at 1 and 0.1 molar and significantly (p < 0.05) reduced transfer at 0.01 molar, regardless of SCFA tested. In explant models for the chicken ceca, either ddH2O or a final concentration of 0.025 M SCFAs were supplemented to the explants infected with donor and recipient E. coli. In every SCFA tested, significant decreases in transconjugant populations compared to ddH2O-treated control samples were observed with minimal effects on donor and recipient populations. Finally, significant reductions in transconjugants for plasmids of each incompatibility type (IncP1ε, IncFIβ, and IncI1) tested were detected. This study demonstrates for the first time the broad inhibition ability of SCFAs on bacterial plasmid transfer and eliminates AMR with minimal effect on bacteria. Implementing interventions that increase the concentrations of SCFAs in the gut may be a viable method to reduce the risk, incidence, and rate of AMR emergence in agricultural and human environments.

Regulation of glycose and lipid metabolism and application based on the colloidal nutrition science properties of konjac glucomannan: A comprehensive review

The physicochemical properties of dietary fiber in the gastrointestinal tract, such as hydration properties, adsorption properties, rheological properties, have an important influence on the physiological process of host digestion and absorption, leading to the differences in satiety and glucose and lipid metabolisms. Based on the diversified physicochemical properties of konjac glucomannan (KGM), it is meaningful to review the relationship of structural characteristics, physicochemical properties and glycose and lipid metabolism. Firstly, this paper bypassed the category of intestinal microbes, and explained the potential of dietary fiber in regulating glucose and lipid metabolism during nutrient digestion and absorption from the perspective of colloidal nutrition. Secondly, the modification methods of KGM to regulate its physicochemical properties were discussed and the relationship between KGM's molecular structure types and glycose and lipid metabolism were summarized. Finally, based on the characteristics of KGM, the application of KGM in the main material and ingredients of fat reduction food was reviewed. We hope this work could provide theoretical basis for the study of dietary fiber colloid nutrition science.

Impact of dietary carbohydrate, fat or protein restriction on the human gut microbiome: a systematic review

Restriction of dietary carbohydrates, fat and/or protein is often used to reduce body weight and/or treat (metabolic) diseases. Since diet is a key modulator of the human gut microbiome, which plays an important role in health and disease, this review aims to provide an overview of current knowledge of the effects of macronutrient-restricted diets on gut microbial composition and metabolites. A structured search strategy was performed in several databases. After screening for inclusion and exclusion criteria, thirty-six articles could be included. Data are included in the results only when supported by at least three independent studies to enhance the reliability of our conclusions. Low-carbohydrate (<30 energy%) diets tended to induce a decrease in the relative abundance of several health-promoting bacteria, including Bifidobacterium, as well as a reduction in short-chain fatty acid (SCFA) levels in faeces. In contrast, low-fat diets (<30 energy%) increased alpha diversity, faecal SCFA levels and abundance of some beneficial bacteria, including Faecalibacterium prausnitzii. There were insufficient data to draw conclusions concerning the effects of low-protein (<10 energy%) diets on gut microbiota. Although the data of included studies unveil possible benefits of low-fat and potential drawbacks of low-carbohydrate diets for human gut microbiota, the diversity in study designs made it difficult to draw firm conclusions. Using a more uniform methodology in design, sample processing and sharing raw sequence data could foster our understanding of the effects of macronutrient restriction on gut microbiota composition and metabolic dynamics relevant to health. This systematic review was registered at https://www.crd.york.ac.uk/prospero as CRD42020156929.

Butyrate as a promising therapeutic target in cancer: From pathogenesis to clinic (Review)

Cancer is one of the leading causes of mortality worldwide. The etiology of cancer has not been fully elucidated yet, and further enhancements are necessary to optimize therapeutic efficacy. Butyrate, a short‑chain fatty acid, is generated through gut microbial fermentation of dietary fiber. Studies have unveiled the relevance of butyrate in malignant neoplasms, and a comprehensive understanding of its role in cancer is imperative for realizing its full potential in oncological treatment. Its full antineoplastic effects via the activation of G protein‑coupled receptors and the inhibition of histone deacetylases have been also confirmed. However, the underlying mechanistic details remain unclear. The present study aimed to review the involvement of butyrate in carcinogenesis and its molecular mechanisms, with a particular emphasis on its association with the efficacy of tumor immunotherapy, as well as discussing relevant clinical studies on butyrate as a therapeutic target for neoplastic diseases to provide new insights into cancer treatment.

Associations of Lifestyle Patterns with Glucose and Lipid Metabolism in Finnish Adults at Increased Risk of Type 2 Diabetes

SCOPE

Various lifestyle and sociodemographic factors have been associated with risk factors for type 2 diabetes (T2D). However, their combined associations with T2D risk factors have been studied much less.

MATERIALS AND RESULTS

This study investigates cross-sectional associations of lifestyle patterns with T2D risk factors among 2925 adults at increased risk participating in the Stop Diabetes study. Lifestyle patterns are determined using principal component analysis (PCA) with several lifestyle and sociodemographic factors. The associations of lifestyle patterns with measures of glucose and lipid metabolism and serum metabolites analyzed by nuclear magnetic resonance (NMR) spectroscopy are studied using linear regression analysis. "Healthy eating" pattern is associated with better glucose and insulin metabolism, more favorable lipoprotein and fatty acid profiles and lower serum concentrations of metabolites related to inflammation, insulin resistance, and T2D. "High socioeconomic status and low physical activity" pattern is associated with increased serum concentrations of branched-chain amino acids, as are "Meat and poultry" and "Sleeping hours" patterns. "Snacks" pattern is associated with lower serum concentrations of ketone bodies.

CONCLUSIONS

Our results show, in large scale primary care setting, that healthy eating is associated with better glucose and lipid metabolism and reveal novel associations of lifestyle patterns with metabolites related to glucose metabolism.

Effect of Short-Chain Fatty Acids on Inflammatory and Metabolic Function in an Obese Skeletal Muscle Cell Culture Model

The fermentation of non-digestible carbohydrates produces short-chain fatty acids (SCFAs), which have been shown to impact both skeletal muscle metabolic and inflammatory function; however, their effects within the obese skeletal muscle microenvironment are unknown. In this study, we developed a skeletal muscle in vitro model to mimic the critical features of the obese skeletal muscle microenvironment using L6 myotubes co-treated with 10 ng/mL lipopolysaccharide (LPS) and 500 µM palmitic acid (PA) for 24 h ± individual SCFAs, namely acetate, propionate and butyrate at 0.5 mM and 2.5 mM. At the lower SCFA concentration (0.5 mM), all three SCFA reduced the secreted protein level of RANTES, and only butyrate reduced IL-6 protein secretion and the intracellular protein levels of activated (i.e., ratio of phosphorylated-total) NFκB p65 and STAT3 (p < 0.05). Conversely, at the higher SCFA concentration (2.5 mM), individual SCFAs exerted different effects on inflammatory mediator secretion. Specifically, butyrate reduced IL-6, MCP-1 and RANTES secretion, propionate reduced IL-6 and RANTES, and acetate only reduced RANTES secretion (p < 0.05). All three SCFAs reduced intracellular protein levels of activated NFκB p65 and STAT3 (p < 0.05). Importantly, only the 2.5 mM SCFA concentration resulted in all three SCFAs increasing insulin-stimulated glucose uptake compared to control L6 myotube cultures (p < 0.05). Therefore, SCFAs exert differential effects on inflammatory mediator secretion in a cell culture model, recapitulating the obese skeletal muscle microenvironment; however, all three SCFAs exerted a beneficial metabolic effect only at a higher concentration via increasing insulin-stimulated glucose uptake, collectively exerting differing degrees of a beneficial effect on obesity-associated skeletal muscle dysfunction.

Dietary (poly)phenols as modulators of the biophysical properties in endothelial cell membranes: its impact on nitric oxide bioavailability in hypertension

Hypertension is a major contributor to premature death, owing to the associated increased risk of damage to the heart, brain and kidneys. Although hypertension is manageable by medication and lifestyle changes, the risk increases with age. In an increasingly aged society, the incidence of hypertension is escalating, and is expected to increase the prevalence of (cerebro)vascular events and their associated mortality. Adherence to plant-based diets improves blood pressure and vascular markers in individuals with hypertension. Food flavonoids have an inhibitory effect towards angiotensin-converting enzyme (ACE1) and although this effect is greatly diminished upon metabolization, their microbial metabolites have been found to improve endothelial nitric oxide synthase (eNOS) activity. Considering the transmembrane location of ACE1 and eNOS, the ability of (poly)phenols to interact with membrane lipids modulate the cell membrane's biophysical properties and impact on nitric oxide (· NO) synthesis and bioavailability, remain poorly studied. Herein, we provide an overview of the current knowledge on the lipid remodeling of endothelial membranes with age, its impact on the cell membrane's biophysical properties and · NO permeability across the endothelial barrier. We also discuss the potential of (poly)phenols and other plant-based compounds as key players in hypertension management, and address the caveats and challenges in adopted methodologies.

Modulating a prebiotic food source influences inflammation and immune-regulating gut microbes and metabolites: insights from the BE GONE trial

BACKGROUND

Accessible prebiotic foods hold strong potential to jointly target gut health and metabolic health in high-risk patients. The BE GONE trial targeted the gut microbiota of obese surveillance patients with a history of colorectal neoplasia through a straightforward bean intervention.

METHODS

This low-risk, non-invasive dietary intervention trial was conducted at MD Anderson Cancer Center (Houston, TX, USA). Following a 4-week equilibration, patients were randomized to continue their usual diet without beans (control) or to add a daily cup of study beans to their usual diet (intervention) with immediate crossover at 8-weeks. Stool and fasting blood were collected every 4 weeks to assess the primary outcome of intra and inter-individual changes in the gut microbiome and in circulating markers and metabolites within 8 weeks. This study was registered on ClinicalTrials.gov as NCT02843425, recruitment is complete and long-term follow-up continues.

FINDINGS

Of the 55 patients randomized by intervention sequence, 87% completed the 16-week trial, demonstrating an increase on-intervention in diversity [n = 48; linear mixed effect and 95% CI for inverse Simpson index: 0.16 (0.02, 0.30); p = 0.02] and shifts in multiple bacteria indicative of prebiotic efficacy, including increased Faecalibacterium, Eubacterium and Bifidobacterium (all p < 0.05). The circulating metabolome showed parallel shifts in nutrient and microbiome-derived metabolites, including increased pipecolic acid and decreased indole (all p < 0.002) that regressed upon returning to the usual diet. No significant changes were observed in circulating lipoproteins within 8 weeks; however, proteomic biomarkers of intestinal and systemic inflammatory response, fibroblast-growth factor-19 increased, and interleukin-10 receptor-α decreased (p = 0.01).

INTERPRETATION

These findings underscore the prebiotic and potential therapeutic role of beans to enhance the gut microbiome and to regulate host markers associated with metabolic obesity and colorectal cancer, while further emphasizing the need for consistent and sustainable dietary adjustments in high-risk patients.

FUNDING

This study was funded by the American Cancer Society.

Maternal Supplementation of Vitamin E or Its Combination with Hydroxytyrosol Increases the Gut Health and Short Chain Fatty Acids of Piglets at Weaning

An adequate intestinal environment before weaning may contribute to diarrhea predisposition and piglet development. This study evaluates how the dietary supplementation of vitamin E (VE) (100 mg/kg), hydroxytyrosol (HXT) (1.5 mg/kg) or the combined administration (VE + HXT) given to Iberian sows from gestation affects the piglet's faecal characteristics, short chain fatty acids (SCFAs), fatty acid profile or intestinal morphology as indicators of gut health; and quantify the contribution of the oxidative status and colostrum/milk composition to the piglet's SCFAs content and intestinal health. Dietary VE increased isobutyric acid (iC4), butyric acid (C4), isovaleric acid (iC5), and ∑SCFAs, whereas HXT increased iC4 and tended to decrease ∑SCFAs of faeces. Piglets from HXT-supplemented sows also tended to have higher faecal C20:4n-6/C20:2 ratio C22:6 proportion and showed lower occludin gene expression in the duodenum. The combination of both antioxidants had a positive effect on iC4 and iC5 levels. Correlation analyses and regression equations indicate that faecal SCFAs were related to oxidative status (mainly plasma VE) and colostrum and milk composition (mainly C20:2, C20:3, C20:4 n-6). This study would confirm the superiority of VE over HXT supplementation to improve intestinal homeostasis, gut health, and, consequently piglet growth.

Short-term dietary fiber interventions produce consistent gut microbiome responses across studies

Background

The composition of the human gut microbiome varies tremendously among individuals, making the effects of dietary or treatment interventions difficult to detect and characterize. The consumption of fiber is important for gut health, yet the specific effects of increased fiber intake on the gut microbiome vary across studies. The variation in study outcomes might be due to inter-individual (or inter-population) variation or to the details of the interventions including the types of fiber, length of study, size of cohort, and molecular approaches. Thus, to identify consistent fiber-induced responses in the gut microbiome of healthy individuals, we re-analyzed 16S rRNA sequencing data from 21 dietary fiber interventions from 12 human studies, which included 2564 fecal samples from 538 subjects across all interventions.

Results

Short-term increases in dietary fiber consumption resulted in highly consistent gut microbiome responses across studies. Increased fiber consumption explained an average of 1.5% of compositional variation (versus 82% of variation attributed to the individual), reduced alpha diversity, and resulted in phylogenetically conserved responses in relative abundances among bacterial taxa. Additionally, we identified bacterial clades, at approximately the genus level, that were highly consistent in their response (increasing or decreasing in their relative abundance) to dietary fiber interventions across the studies.

Conclusions

Our study is an example of the power of synthesizing and reanalyzing microbiome data from many intervention studies. Despite high inter-individual variation of the composition of the human gut microbiome, dietary fiber interventions cause a consistent response both in the degree of change as well as the particular taxa that respond to increased fiber.

Urinary microbiota and serum metabolite analysis in patients with diabetic kidney disease

Background

Diabetic kidney disease (DKD) is a common and potentially fatal consequence of diabetes. Chronic renal failure or end-stage renal disease may result over time. Numerous studies have demonstrated the function of the microbiota in health and disease. The use of advanced urine culture techniques revealed the presence of resident microbiota in the urinary tract, undermining the idea of urine sterility. Studies have demonstrated that the urine microbiota is related with urological illnesses; nevertheless, the fundamental mechanisms by which the urinary microbiota influences the incidence and progression of DKD remain unclear. The purpose of this research was to describe key characteristics of the patients with DKD urinary microbiota in order to facilitate the development of diagnostic and therapeutic for DKD.

Methods

We evaluated the structure and composition of the microbiota extracted from urine samples taken from DKD patients (n = 19) and matched healthy controls (n = 15) using 16S rRNA gene sequencing. Meanwhile, serum metabolite profiles were compared using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Associations between clinical characteristics, urine microbiota, and serum metabolites were also examined. Finally, the interaction between urine microbiota and serum metabolites was clarified based on differential metabolite abundance analysis.

Results

The findings indicated that the DKD had a distinct urinary microbiota from the healthy controls (HC). Taxonomic investigations indicated that the DKD microbiome had less alpha diversity than a control group. Proteobacteria and Acidobacteria phyla increased in the DKD, while Firmicutes and Bacteroidetes decreased significantly (P < 0.05). Acidobacteria was the most prevalent microbiota in the DKD, as determined by the Linear discriminant analysis Effect Size (LEfSe) plot. Changes in the urinary microbiota of DKD also had an effect on the makeup of metabolites. Short-chain fatty acids (SCFAs) and protein-bound uremic toxins (PBUTs) were shown to be specific. Then we discovered that arginine and proline metabolism was the primary mechanism involved in the regulation of diabetic kidney disease.

Conclusions

This study placed the urinary microbiota and serum metabolite of DKD patients into a functional framework and identified the most abundant microbiota in DKD (Proteobacteria and Acidobacteria). Arginine metabolites may have a major effect on DKD patients, which correlated with the progression of DKD.

The effects of probiotics supplementation on glycaemic control among adults with type 2 diabetes mellitus: a systematic review and meta-analysis of randomised clinical trials

OBJECTIVE

This systematic review and meta-analysis study aimed to evaluate the effectiveness of probiotics supplementation on glycaemic control in patients with type 2 diabetes mellitus (T2DM) based on the data from the randomised clinical trials (RCTs).

METHODS

PubMed, Web of Sciences, Embase, and Cochrane Library were searched from the inception to October 2022, and RCTs about probiotics and T2DM were collected. The standardised mean difference (SMD) with 95% confidence interval (CI) was used to estimate the effects of probiotics supplementation on glycaemic control related parameters, e.g. fasting blood glucose (FBG), insulin, haemoglobin A1c (HbA1c), and homeostasis model of assessment of insulin resistance (HOMA-IR).

RESULTS

Thirty RCTs including 1,827 T2MD patients were identified. Compared with the placebo group, the probiotics supplementation group had a significant decrease in the parameters of glycaemic control, including FBG (SMD = - 0.331, 95% CI  - 0.424 to - 0.238, Peffect < 0.001), insulin (SMD = - 0.185, 95% CI  - 0.313 to - 0.056, Peffect = 0.005), HbA1c (SMD = - 0.421, 95% CI  - 0.584 to - 0.258, Peffect < 0.001), and HOMA-IR (SMD = - 0.224, 95% CI  - 0.342 to - 0.105, Peffect < 0.001). Further subgroup analyses showed that the effect was larger in the subgroups of Caucasians, high baseline body mass index (BMI ≥ 30.0 kg/m2), Bifidobacterium and food-type probiotics (Psubgroup < 0.050).

CONCLUSION

This study supported that probiotics supplementation had favourable effects on glycaemic control in T2DM patients. It may be a promising adjuvant therapy for patients with T2DM.

The Bridge Between Ischemic Stroke and Gut Microbes: Short-Chain Fatty Acids

Short-chain fatty acids (SCFAs) are monocarboxylates produced by the gut microbiota (GM) and result from the interaction between diet and GM. An increasing number of studies about the microbiota-gut-brain axis (MGBA) indicated that SCFAs may be a crucial mediator in the MGBA, but their roles have not been fully clarified. In addition, there are few studies directly exploring the role of SCFAs as a potential regulator of microbial targeted interventions in ischemic stroke, especially for clinical studies. This review summarizes the recent studies concerning the relationship between ischemic stroke and GM and outlines the role of SCFAs as a bridge between them. The potential mechanisms by which SCFAs affect ischemic stroke are described. Finally, the beneficial effects of SFCAs-mediated therapeutic measures such as diet, dietary supplements (e.g., probiotics and prebiotics), fecal microbiota transplantation, and drugs on ischemic brain injury are also discussed.

Dietary fiber and SCFAs in the regulation of mucosal immunity

Gut bacterial metabolites such as short-chain fatty acids (SCFAs) have important effects on immune cells and the gut. SCFAs derive from the fermentation of dietary fiber by gut commensal bacteria. Insufficient fiber intake thus compromises SCFA production and, as a consequence, the host's physiology (particularly immune functions). We propose that many Western diseases, including those associated with impaired mucosal responses such as food allergy and asthma, may be affected by insufficient fiber intake and reduced SCFA levels in the gut and blood. Insufficient fiber intake is 1 alternative, or contributor, on top of the "hygiene hypothesis" to the rise of Western lifestyle diseases, and the 2 ideas need to be reconciled. The mechanisms by which SCFAs influence immunity and gut homeostasis are varied; they include stimulation of G protein-coupled receptors (GPCRs), such as GPR43 or GPR41; inhibition of histone deacetylases (and hence, gene transcription changes); and induction of intracellular metabolic changes. SCFAs modulate at many different levels to alter mucosal homeostasis, including changes to gut epithelial integrity, increases in regulatory T-cell numbers and function, and decreased expression of numerous inflammatory cytokines. There is scope for preventing and/or treating diseases by using diets that alter SCFA levels.

Dietary Macronutrients and Circulating Nonesterified Fatty Acids: A Secondary Analysis of the OMNI Heart Crossover Trial

BACKGROUND

Nonesterified fatty acids (NEFAs) play key roles in the pathophysiology of diabetes and cardiovascular disease.

OBJECTIVES

We sought to determine whether macronutrient content differences affect NEFA concentrations in a randomized crossover trial.

METHODS

Total NEFAs were measured from postintervention specimens of participants in the OMNI Heart trial (Optimal Macronutrient Intake Trial to Prevent Heart Disease). OMNI Heart compared 3 healthful diets to evaluate their effect on systolic blood pressure and serum LDL cholesterol: carbohydrate-rich diet (58% carbohydrate); protein-rich diet (25% protein), about half from plant sources; and a diet rich in unsaturated fatty acids (21% unsaturated fat), predominantly monounsaturated. The trial included 164 participants who consumed the 3 diets, each for 6 wk. Data were analyzed from the 156 participants with unthawed serum available from the week 6 visit for all diet periods. We used ANCOVA and generalized estimating equations (GEEs) to compare serum NEFA concentrations across the 3 diet periods.

RESULTS

The mean ± SD age of study participants was 52.9 ± 10.6 y and mean BMI was 30.3 ± 6.1 kg/m2. Fifty-five percent of participants were women and 55% were African American. Comparisons of adjusted mean serum NEFA concentrations after each diet intervention identified no statistically significant differences (58% carbohydrate: 0.144 ± 0.083 mEq/L; 25% protein: 0.143 ± 0.076 mEq/L; 21% unsaturated fat: 0.143 ± 0.084 mEq/L; ANCOVA, P = 0.99). Likewise, we observed no significant serum NEFA concentration difference by diet in adjusted GEE models. In adjusted models, serum NEFA concentrations were positively associated, as anticipated, with female sex and higher BMI.

CONCLUSIONS

In this randomized crossover trial, we observed nearly identical serum NEFA concentrations after each of 3 healthful diets, regardless of macronutrient content.

Chardonnay Marc as a New Model for Upcycled Co-products in the Food Industry: Concentration of Diverse Natural Products Chemistry for Consumer Health and Sensory Benefits

Research continues to provide compelling insights into potential health benefits associated with diets rich in plant-based natural products (PBNPs). Coupled with evidence from dietary intervention trials, dietary recommendations increasingly include higher intakes of PBNPs. In addition to health benefits, PBNPs can drive flavor and sensory perceptions in foods and beverages. Chardonnay marc (pomace) is a byproduct of winemaking obtained after fruit pressing that has not undergone fermentation. Recent research has revealed that PBNP diversity within Chardonnay marc has potential relevance to human health and desirable sensory attributes in food and beverage products. This review explores the potential of Chardonnay marc as a valuable new PBNP ingredient in the food system by combining health, sensory, and environmental sustainability benefits that serves as a model for development of future ingredients within a sustainable circular bioeconomy. This includes a discussion on the potential role of computational methods, including artificial intelligence (AI), in accelerating research and development required to discover and commercialize this new source of PBNPs.

Characterization of diet-dependent temporal changes in circulating short-chain fatty acid concentrations: A randomized crossover dietary trial

BACKGROUND

Production of SCFAs from food is a complex and dynamic saccharolytic fermentation process mediated by both human and gut microbial factors. Knowledge of SCFA production and of the relation between SCFA profiles and dietary patterns is lacking.

OBJECTIVES

Temporal changes in SCFA concentrations in response to 2 contrasting diets were investigated using a novel GC-MS method.

METHODS

Samples were obtained from a randomized, controlled, crossover trial designed to characterize the metabolic response to 4 diets. Participants (n = 19) undertook these diets during an inpatient stay (of 72 h). Serum samples were collected 2 h after breakfast (AB), after lunch (AL), and after dinner (AD) on day 3, and a fasting sample (FA) was obtained on day 4. The 24-h urine samples were collected on day 3. In this substudy, samples from the 2 extreme diets representing a diet with high adherence to WHO healthy eating recommendations and a typical Western diet were analyzed using a bespoke GC-MS method developed to detect and quantify 10 SCFAs and precursors in serum and urine samples.

RESULTS

Considerable interindividual variation in serum SCFA concentrations was observed across all time points, and temporal fluctuations were observed for both diets. Although the sample collection timing exerted a greater magnitude of effect on circulating SCFA concentrations, the unhealthy diet was associated with a lower concentration of acetic acid (FA: coefficient: -17.0; SE: 5.8; P-trend = 0.00615), 2-methylbutyric acid (AL: coefficient: -0.1; SE: 0.028; P-trend = 4.13 × 10-4 and AD: coefficient: -0.1; SE: 0.028; P-trend = 2.28 × 10-3), and 2-hydroxybutyric acid (FA: coefficient: -15.8; SE: 5.11; P-trend: 4.09 × 10-3). In contrast, lactic acid was significantly higher in the unhealthy diet (AL: coefficient: 750.2; SE: 315.2; P-trend = 0.024 and AD: coefficient: 1219.3; SE: 322.6; P-trend: 8.28 × 10-4).

CONCLUSIONS

The GC-MS method allowed robust mapping of diurnal patterns in SCFA concentrations, which were affected by diet, and highlighted the importance of standardizing the timing of SCFA measurements in dietary studies. This trial was registered on the NIHR UK clinical trial gateway and with ISRCTN as ISRCTN43087333.

Differential Effects of Short-Chain Fatty Acids on L6 Myotube Inflammatory Mediator Production in Response to Lipopolysaccharide- or Palmitic Acid-Stimulation

Short-chain fatty acids (SCFA) produced from dietary non-digestible carbohydrate fermentation have metabolic effects in skeletal muscle; however, their effect on inflammatory mediator production is unknown. In this study, L6 myotubes were cultured with individual SCFA (acetate, propionate, and butyrate) at 0.5 mM and 2.5 mM ± 10 ng/mL lipopolysaccharide (LPS) or ± 500 µM palmitic acid (PA) for 24 h. In response to LPS, only butyrate had an effect at the lower concentration (0.5 mM), whereas at the higher concentration (2.5 mM) both propionate and butyrate reduced MCP-1, MIP-1α, and RANTES secretion (p < 0.05), and only butyrate reduced IL-6 secretion and intracellular protein levels of phospho-STAT3 (p < 0.05). In response to PA, 0.5 mM butyrate reduced protein expression of phospho-NFκB p65 and the secretion of IL-6, MIP-1α, and MCP-1, whereas all three SCFA reduced RANTES secretion (p < 0.05). At the 2.5 mM SCFA concentration combined with PA stimulation, all three SCFA reduced intracellular protein expression of phospho-NFκB p65 and phospho-STAT3 and secreted protein levels of MCP-1, IL-6, and RANTES, whereas only butyrate reduced secretion of MIP-1α (p < 0.05). Thus, SCFA exhibit differential effects on inflammatory mediator expression in response to LPS and PA stimulation, which has implications for their individual impacts on inflammation-mediated skeletal muscle dysfunction.

Sex Differences in Cardiovascular Impact of Early Metabolic Impairment: Interplay between Dysbiosis and Adipose Inflammation

The evolving view of gut microbiota has shifted toward describing the colonic flora as a dynamic organ in continuous interaction with systemic physiologic processes. Alterations of the normal gut bacterial profile, known as dysbiosis, has been linked to a wide array of pathologies. Of particular interest is the cardiovascular-metabolic disease continuum originating from positive energy intake and high-fat diets. Accumulating evidence suggests a role for sex hormones in modulating the gut microbiome community. Such a role provides an additional layer of modulation of the early inflammatory changes culminating in negative metabolic and cardiovascular outcomes. In this review, we will shed the light on the role of sex hormones in cardiovascular dysfunction mediated by high-fat diet-induced dysbiosis, together with the possible involvement of insulin resistance and adipose tissue inflammation. Insights into novel therapeutic interventions will be discussed as well. SIGNIFICANCE STATEMENT: Increasing evidence implicates a role for dysbiosis in the cardiovascular complications of metabolic dysfunction. This minireview summarizes the available data on the sex-based differences in gut microbiota alterations associated with dietary patterns leading to metabolic impairment. A role for a differential impact of adipose tissue inflammation across sexes in mediating the cardiovascular detrimental phenotype following diet-induced dysbiosis is proposed. Better understanding of this pathway will help introduce early approaches to mitigate cardiovascular deterioration in metabolic disease.

Increases in Circulating and Fecal Butyrate are Associated With Reduced Blood Pressure and Hypertension: Results From the SPIRIT Trial

Background Short chain fatty acids (SCFAs) are microbially derived end products of dietary fiber fermentation. The SCFA butyrate reduces blood pressure (BP) in mouse models. The association of SCFAs, including butyrate, with BP in humans is unclear, due in part to predominantly cross-sectional analyses and different biospecimens (blood versus fecal) for SCFA measurement. Longitudinal studies including both circulating and fecal SCFAs are lacking. Methods and Results We leveraged existing data from the SPIRIT (Survivorship Promotion In Reducing IGF-1 Trial), which randomized 121 adult cancer survivors with overweight/obesity to a behavioral weight-loss intervention, metformin, or self-directed weight-loss. Of participants with baseline serum and fecal SCFAs measured (n=111), a subset had serum (n=93) and fecal (n=89) SCFA measurements 12 months later. We used Poisson regression with robust error variance to estimate baseline associations of SCFAs with hypertension, and we assessed the percent change in SCFAs from baseline with corresponding 12-month changes in BP using multiple linear regression. Baseline fecal butyrate was inversely associated with prevalent hypertension (standardized PR [95%CI]: 0.71 [0.54, 0.92]). A 10% increase in fecal butyrate from baseline was associated with decreased systolic BP (β [95%CI]: -0.56 [-1.01, -0.10] mm Hg), and a 10% increase in serum butyrate was associated with decreased systolic (β [95%CI]: -1.39 [-2.15, -0.63] mm Hg) and diastolic (β [95%CI]: -0.55 [-1.03, -0.08] mm Hg) BPs. Butyrate associations with systolic BP were linear and not modified by sex, race, or intervention arm. Conclusions Increased serum or fecal butyrate is associated with lowered BP. Butyrate may be a target for SCFA-centered BP-lowering interventions. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT02431676.

Diet-gut microbiota interactions on cardiovascular disease

Cardiovascular diseases (CVD) are a group of disorders of the heart and blood vessels and remain the leading cause of morbidity and mortality worldwide. Over the past decades, accumulating studies indicated that the gut microbiota, an indispensable "invisible organ", plays a vital role in human metabolism and disease states including CVD. Among many endogenous and exogenous factors that can impact gut microbial communities, the dietary nutrients emerge as an essential component of host-microbiota relationships that can be involved in CVD susceptibility. In this review, we summarize the major concepts of dietary modulation of the gut microbiota and the chief principles of the involvement of this microbiota in CVD development. We also discuss the mechanisms of diet-microbiota crosstalk that regulate CVD progression, including endotoxemia, inflammation, gut barrier dysfunction and lipid metabolism dysfunction. In addition, we describe how metabolites produced by the microbiota, including trimethylamine-N-oxide (TMAO), secondary bile acids (BAs), short chain fatty acids (SCFAs) as well as aromatic amino acids (AAAs) derived metabolites play a role in CVD pathogenesis. Finally, we present the potential dietary interventions which interacted with gut microbiota as novel preventive and therapeutic strategies for CVD management.

Gut microbiota and diabetic kidney diseases: Pathogenesis and therapeutic perspectives

Diabetic kidney disease (DKD) is one of the major chronic complications of diabetes mellitus (DM), as well as a main cause of end-stage renal disease. Over the last few years, substantial research studies have revealed a contributory role of gut microbiota in the process of DM and DKD. Metabolites of gut microbiota like lipopolysaccharide, short-chain fatty acids, and trimethylamine N-oxide are key mediators of microbial–host crosstalk. However, the underlying mechanisms of how gut microbiota influences the onset and progression of DKD are relatively unknown. Besides, strategies to remodel the composition of gut microbiota or to reduce the metabolites of microbiota have been found recently, representing a new potential remedial target for DKD. In this mini-review, we will address the possible contribution of the gut microbiota in the pathogenesis of DKD and its role as a therapeutic target.

Intestinal Microbial Diversity of Free-Range and Captive Yak in Qinghai Province

Background: The gut microbiome is a large and complex organic assemblage with subtle and close relationships with the host. This symbiotic mechanism is important for the health and adaptability of the host to the environment. Compared with other ruminants, there are few studies on yak intestinal microbes. The study of the gut microbiota of the yak will help us better understand the correlation between the microbiota and the environmental adaptability of the host. In this study, we adapted 16S rDNA sequencing technology to investigate the diversity and composition of the intestinal microbial community in free-range yaks and captive yaks living on the Qinghai–Tibet Plateau (QTP). Results: Sequencing results showed that the intestinal microbial community diversity was significantly different between free-range yaks and captive yaks. Firmicutes and Bacteroidetes were the dominant bacteria in both free-range and captive yaks. However, there were differences between the microbes of the two analyzed feeding styles in different classification levels. Compared with the captive type, free-range yaks had a higher abundance of Ruminococcaceae, Eubacteriaceae, Desulfovibrionaceae, Elusimicrobium, and Oscillibacter, while the abundance of Succinivibrionaceae, Clostridiales, Lachnospiraceae, Prevotellaceae, Roseburia, and Barnesiella was relatively low. The feeding method may be the key factor for the formation of intestinal flora differences in yaks, while altitude did not significantly affect Qinghai yak. Conclusions: In this study, we used 16S rDNA sequencing technology to investigate the composition of intestinal flora in free-range and captive yaks living on the QTP. The exploration of dietary factors can provide a theoretical basis for scientifically and rationally breeding yaks and provides a new direction for the development of prebiotics and microecological agents.

Effects of Corn and Broken Rice Extrusion on the Feed Intake, Nutrient Digestibility, and Gut Microbiota of Weaned Piglets

Simple Summary

Extruded cereals are largely used in newly weaned piglet diets to increase nutrient digestibility and palatability. Our findings showed that corn and broken rice extrusion diets generated negative effects on average daily feed intake (−63.5 g/day, p = 0.054) and average daily gain (−60.6 g/d, p = 0.015) in weaned piglets. Decreased feed intake was associated with increased plasma levels of the gut-derived hormones, glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), which may have been attributed to increased microbiota pathogen abundance, including Sarcina, Clostridium_sensu_strictio_1, and Terrisporobacter, and decreased short-chain fatty acid-producing microbiota, such as Lactobaillaceae and Bifidobateriaceae. Our results showed that extruded cereals should be used cautiously when formulating diets for newly weaned piglets.

Abstract

In this study, we investigated the effects of corn and rice extrusion diets on feed intake, nutrient digestibility, and gut microbiota in weaned piglets. Animals were divided into four dietary groups and fed a controlled diet containing (1) 62.17% corn (CORN), 15% soybean, 10% extruded full-fat soybean, and 6% fishmeal (2) half the corn replaced by extruded corn (ECORN), (3) broken rice (RICE), and (4) extruded broken rice (ERICE) for 28 days. Rice supplementation increased dry matter total tract digestibility and gross energy. Extruded cereals generated a lower average daily feed intake (ADFI) at 15–28 and 1–28 days, decreased average daily growth (ADG) at 15–28 and 1–28 days, and a lowered body weight (BW) on day 28, regardless of cereal type. Dietary extruded cereals increased the appetite-regulating hormones glucagon-like peptide-1 (GLP-1) and peptide YY (PYY). Piglets fed extruded cereals displayed low short-chain fatty acid (SCFA) levels in plasma and low Lactobaillaceae and Bifidobateriaceae levels in feces, whereas a higher abundance of the potential pathogens Sarcina, Clostridium_sensu_strictio_1 and Terrisporobacter was observed. Piglets fed extruded cereals displayed significantly lower gas and SCFA levels during in vitro fermentation. Combined, 50% corn substituted with extruded corn or broken rice decreased piglet growth performance, possibly by altering their microbiota.

Effects of Moderate Alcohol Consumption in Non-Alcoholic Fatty Liver Disease

Alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD) have emerged as leading causes of chronic liver diseases worldwide. ALD and NAFLD share several pathophysiological patterns as well as histological features, while clinically, they are distinguished by the amount of alcohol consumed daily. However, NAFLD coexists with moderate alcohol consumption in a growing proportion of the population. Here, we investigated the effects of moderate alcohol consumption on liver injury, lipid metabolism, and gut microbiota in 30 NAFLD-patients. We anonymously assessed drinking habits, applying the AUDIT- and CAGE-questionnaires and compared subgroups of abstainers vs. low to harmful alcohol consumers (AUDIT) and Cage 0-1 vs. Cage 2-4. Patients who did not drink any alcohol had lower levels of γGT, ALT, triglycerides, and total cholesterol. While the abundance of Bacteroidaceae, Bifidobacteriaceae, Streptococcaceae, and Ruminococcaceae was higher in the low to harmful alcohol drinking cohort, the abundance of Rikenellaceae was higher in the abstainers. Our study suggests that even moderate alcohol consumption has an impact on the liver and lipid metabolism, as well as on the composition of gut microbiota.

The Role of Gut Microbiota and Metabolites in Obesity-Associated Chronic Gastrointestinal Disorders

The gut microbiota is a complex community of microorganisms that has become a new focus of attention due to its association with numerous human diseases. Research over the last few decades has shown that the gut microbiota plays a considerable role in regulating intestinal homeostasis, and disruption to the microbial community has been linked to chronic disease conditions such as inflammatory bowel disease (IBD), colorectal cancer (CRC), and obesity. Obesity has become a global pandemic, and its prevalence is increasing worldwide mostly in Western countries due to a sedentary lifestyle and consumption of high-fat/high-sugar diets. Obesity-mediated gut microbiota alterations have been associated with the development of IBD and IBD-induced CRC. This review highlights how obesity-associated dysbiosis can lead to the pathogenesis of IBD and CRC with a special focus on mechanisms of altered absorption of short-chain fatty acids (SCFAs)

Increased circulating butyrate and ursodeoxycholate during probiotic intervention in humans with type 2 diabetes

Background

An increasing body of evidence implicates the resident gut microbiota as playing a critical role in type 2 diabetes (T2D) pathogenesis. We previously reported significant improvement in postprandial glucose control in human participants with T2D following 12-week administration of a 5-strain novel probiotic formulation (‘WBF-011’) in a double-blind, randomized, placebo controlled setting (NCT03893422). While the clinical endpoints were encouraging, additional exploratory measurements were needed in order to link the motivating mechanistic hypothesis - increased short-chain fatty acids - with markers of disease.

Results

Here we report targeted and untargeted metabolomic measurements on fasting plasma (n = 104) collected at baseline and end of intervention. Butyrate and ursodeoxycholate increased among participants randomized to WBF-011, along with compelling trends between butyrate and glycated haemoglobin (HbA1c). In vitro monoculture experiments demonstrated that the formulation’s C. butyricum strain efficiently synthesizes ursodeoxycholate from the primary bile acid chenodeoxycholate during butyrogenic growth. Untargeted metabolomics also revealed coordinated decreases in intermediates of fatty acid oxidation and bilirubin, potential secondary signatures for metabolic improvement. Finally, improvement in HbA1c was limited almost entirely to participants not using sulfonylurea drugs. We show that these drugs can inhibit growth of formulation strains in vitro.

Conclusion

To our knowledge, this is the first description of an increase in circulating butyrate or ursodeoxycholate following a probiotic intervention in humans with T2D, adding support for the possibility of a targeted microbiome-based approach to assist in the management of T2D. The efficient synthesis of UDCA by C. butyricum is also likely of interest to investigators of its use as a probiotic in other disease settings. The potential for inhibitory interaction between sulfonylurea drugs and gut microbiota should be considered carefully in the design of future studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02415-8.

Association of the gut microbiota and fecal short-chain fatty acids with skeletal muscle mass and strength in children

We aimed to investigate whether the gut microbiota and fecal short-chain fatty acids (SCFAs) are associated with skeletal muscle mass and strength in healthy Chinese children aged 6-9 years. In this study, 412 children were enrolled. 16S rRNA gene sequencing was used to characterize the gut microbiota compositions. Fecal SCFAs were quantified using high-performance liquid chromatography. Dual X-ray absorptiometry was used to measure the total body lean soft tissue mass (TSM), total body fat mass (TBF), appendicular skeletal muscle mass (ASM), and appendicular fat mass (AFM). TSM/height² (TSMI), ASM/height² (ASMI), TSM/weight (TSMR), ASM/weight (ASMR), and the ratio of TSM/TBF and ASM/AFM were calculated. Handgrip strength (HGS) was measured using the Jamar® Plus+ Hand Dynamometer. A multiple regression analysis after adjustment for covariates and multiple test correction showed some operational taxonomic units in partial least squares models identified by Multivariate methods with Unbiased Variable selection analysis such as genera of Faecalibacterium, Lachnospira, Lachnospiraceae_ND3007_group, and Lachnospiraceae_UCG-004 were positively correlated with at least one measure of TSM, TSMI, ASM, ASMI, and ASMI Z-score (β: 0.103-0.143, p_FDR : .008-.032) but negatively correlated with at least one measure of TSMR, TSM/TBF, ASMR, ASM/AFM, and ASMR Z-score (β: -0.185 to 0.124, p_FDR  = .008-.045). Children with higher fecal butyric acid, acetic acid, and total SCFA levels exhibited higher TSM, ASM, TSMI, ASMI, and ASMI Z-score and lower TSM/TBF, ASM/AFM, TSMR, ASMR, and ASMR Z-score. However, after additional adjustment for TBF or body mass index, only the associations for Faecalitalea and Pyramidobacter still existed. Mediation analysis suggested that total body fat significantly mediated 66.3%-95.3% of the estimated association of microbiota and SCFAs with TSM, ASM, and ASMI Z-score. Our results suggest that the associations of gut microbiota and SCFAs with skeletal muscle quality in children may largely depend upon on total body fat content.

Development and Validation of a LC-MS/MS Technique for the Analysis of Short Chain Fatty Acids in Tissues and Biological Fluids without Derivatisation Using Isotope Labelled Internal Standards

The gut microbiota is critical to the maintenance of physiological homeostasis and as such is implicated in a range of diseases such as colon cancer, ulcerative colitis, diabetes, cardiovascular diseases, and neurodegenerative diseases. Short chain fatty acids (SCFAs) are key metabolites produced by the gut microbiota from the fermentation of dietary fibre. Here we present a novel, sensitive, and direct LC-MS/MS technique using isotopically labelled internal standards without derivatisation for the analysis of SCFAs in different biological matrices. The technique has significant advantages over the current widely used techniques based on sample derivatization and GC-MS analysis, including fast and simple sample preparation and short LC runtime (10 min). The technique is specific and sensitive for the quantification of acetate, butyrate, isobutyrate, isovalerate, lactate, propionate and valerate. The limits of detection were all 0.001 mM except for acetate which was 0.003 mM. The calibration curves for all the analytes were linear with correlation coefficients r² > 0.998. The intra- and inter-day precisions in three levels of known concentrations were <12% and <20%, respectively. The quantification accuracy ranged from 92% to 120%. The technique reported here offers a valuable analytical tool for use in studies of SCFA production in the gut and their distribution to host tissues.

Efficiency of Resistant Starch and Dextrins as Prebiotics: A Review of the Existing Evidence and Clinical Trials

In well-developed countries, people have started to pay additional attention to preserving healthy dietary habits, as it has become common knowledge that neglecting them may easily lead to severe health impairments, namely obesity, malnutrition, several cardiovascular diseases, type-2 diabetes, cancers, hypertensions, and inflammations. Various types of functional foods were developed that are enriched with vitamins, probiotics, prebiotics, and dietary fibers in order to develop a healthy balanced diet and to improve the general health of consumers. Numerous kinds of fiber are easily found in nature, but they often have a noticeable undesired impact on the sensory features of foods or on the digestive system. This led to development of modified dietary fibers, which have little to no impact on taste of foods they are added to. At the same time, they possess all the benefits similar to those of prebiotics, such as regulating gastrointestinal microbiota composition, increasing satiety, and improving the metabolic parameters of a human. In the following review, the evidence supporting prebiotic properties of modified starches, particularly resistant starches and their derivatives, resistant dextrins, was assessed and deliberated, which allowed drawing an interesting conclusion on the subject.

Post-weight loss changes in fasting appetite- and energy balance-related hormone concentrations and the effect of the macronutrient content of a weight maintenance diet: a randomised controlled trial

PURPOSE

We investigated the effects of the macronutrient composition of diets with differing satiety values on fasting appetite-related hormone concentrations after weight loss and examined whether the hormone secretion adapted to changes in body fat mass (FM) and fat-free mass (FFM) during the weight maintenance period (WM).

METHODS

Eighty-two men and women with obesity underwent a 7-week very-low-energy diet (VLED) and were then randomised to a higher-satiety food (HSF) group or a lower-satiety food (LSF) group during 24-weeks of the WM. The groups consumed isoenergetic foods with different satiety ratings and macronutrient compositions.

RESULTS

During the WM, the HSF group consumed more protein and dietary fibre and less fat than the LSF group, but the groups showed similar changes in body weight and fasting appetite-related hormones. In the whole study sample, VLED induced 12 kg (p < 0.001) weight loss. At the end of the WM, weight regain was 1.3 kg (p = 0.004), ghrelin concentration increased, whereas leptin, insulin, and glucose concentrations decreased compared to pre-VLED levels (p < 0.001 for all). Peptide YY did not differ from pre-VLED levels. Changes in ghrelin levels were inversely associated with changes in FFM during weeks 0-12 of the WM (p = 0.002), while changes in leptin and insulin levels were positively associated with changes in FM during weeks 0-12 (p = 0.015 and p = 0.038, respectively) and weeks 12-24 (p < 0.001 and p = 0.022) of the WM.

CONCLUSIONS

The macronutrient composition of an isoenergetic WM diet did not affect fasting appetite-related hormone concentrations. Leptin and insulin adjusted to the reduced FM, whereas ghrelin reflected FFM during the first months of the WM.

TRIAL REGISTRATION

isrctn.com, ID 67529475.

Metformin Affects Gut Microbiome Composition and Function and Circulating Short-Chain Fatty Acids: A Randomized Trial

OBJECTIVE

To determine the longer-term effects of metformin treatment and behavioral weight loss on gut microbiota and short-chain fatty acids (SCFAs).

RESEARCH DESIGN AND METHODS

We conducted a 3-parallel-arm, randomized trial. We enrolled overweight/obese adults who had been treated for solid tumors but had no ongoing cancer treatment and randomized them (n = 121) to either 1) metformin (up to 2,000 mg), 2) coach-directed behavioral weight loss, or 3) self-directed care (control) for 12 months. We collected stool and serum at baseline (n = 114), 6 months (n = 109), and 12 months (n = 105). From stool, we extracted microbial DNA and conducted amplicon and metagenomic sequencing. We measured SCFAs and other biochemical parameters from fasting serum.

RESULTS

Of the 121 participants, 79% were female and 46% were Black, and the mean age was 60 years. Only metformin treatment significantly altered microbiota composition. Compared with control, metformin treatment increased amplicon sequence variants for Escherichia (confirmed as Escherichia coli by metagenomic sequencing) and Ruminococcus torques and decreased Intestinibacter bartlettii at both 6 and 12 months and decreased the genus Roseburia, including R. faecis and R. intestinalis, at 12 months. Effects were similar in comparison of the metformin group with the behavioral weight loss group. Metformin versus control also increased butyrate, acetate, and valerate at 6 months (but not at 12 months). Behavioral weight loss versus control did not significantly alter microbiota composition but did increase acetate at 6 months (but not at 12 months). Increases in acetate were associated with decreases in fasting insulin. Additional whole-genome metagenomic sequencing of a subset of the metformin group showed that metformin altered 62 metagenomic functional pathways, including an acetate-producing pathway and three pathways in glucose metabolism.

CONCLUSIONS

Metformin, but not behavioral weight loss, impacted gut microbiota composition at 6 months and 12 months. Both metformin and behavioral weight loss altered circulating SCFAs at 6 months, including increasing acetate, which correlated with lower fasting insulin. Future research is needed to elucidate whether the gut microboime mediates or modifies metformin's health effects.

Potential Contribution of Short Chain Fatty Acids to Hepatic Apolipoprotein A-I Production

Apolipoprotein A-I (ApoA-I) is the major protein of high density lipoprotein (HDL) particles and has a crucial role in reverse cholesterol transport (RCT). It has been postulated that elevating production of de novo ApoA-I might translate into the formation of new functional HDL particles that could lower cardiovascular disease (CVD) risk via RCT. During inflammation, serum ApoA-I concentrations are reduced, which contributes to the development of dysfunctional HDL particles as Serum Amyloid A (SAA) overtakes the position of ApoA-I within the HDL particles. Therefore, instead of elevating serum HDL cholesterol concentrations, rescuing lower serum ApoA-I concentrations could be beneficial in both normal and inflamed conditions. Several nutritional compounds, amongst others short chain fatty acids (SCFAs), have shown their capacity to modulate hepatic lipoprotein metabolism. In this review we provide an overview of HDL and more specific ApoA-I metabolism, SCFAs physiology and the current knowledge regarding the influence of SCFAs on ApoA-I expression and synthesis in human liver cells. We conclude that the current evidence regarding the effect of SCFAs on ApoA-I transcription and secretion is promising, however there is a need to investigate which dietary fibres could lead to increased SCFAs formation and consequent elevated ApoA-I concentrations.

Probiotics Contribute to Glycemic Control in Patients with Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

This systematic review aimed to evaluate the effectiveness and safety of probiotics for glycemic control in adults with impaired glucose control, including prediabetes and type 2 diabetes mellitus (T2DM). We searched PubMed, Embase, and Cochrane databases, and trial registries up to February 2019. We included randomized controlled trials (RCTs) of participants with prediabetes or T2DM. Eligible trials compared probiotics versus either placebo, no intervention, or comparison probiotics, or compared synbiotics versus prebiotics. Primary outcomes were mean change in fasting blood glucose (FBG) and glycated hemoglobin (HbA1c) from baseline to short term (<12 wk) and long term (≥12 wk). We performed meta-analyses using the random-effects model. We included 28 RCTs (1947 participants). Overall, probiotics reduced FBG more than the placebo/no intervention group with a mean difference (MD) of -12.99 mg/dL (95% CI: -23.55, -2.42; P value: 0.016) over the short term; and -2.99 mg/dL (95% CI: -5.84, -0.13; P value: 0.040) over the long term. There was also some evidence for reduced HbA1c in the probiotics group at both short term (MD: -0.17; 95% CI: -0.37, 0.02; P value: 0.084) and long term (MD: -0.14; 95% CI: -0.34, 0.06; P value: 0.172), however, these did not reach statistical significance possibly because only a few trials reported HbA1c as an outcome. Subgroup analyses showed a greater reduction in HbA1c in participants not receiving insulin therapy than those receiving insulin therapy. Furthermore, the effect of probiotics on the reduction of FBG was more pronounced in participants with FBG >130 mg/dL and those not receiving insulin therapy than their counterparts. Probiotics were also effective in lowering serum cholesterol over the short and long term. In conclusion, we found that probiotics may have a glucose-lowering effect in T2DM participants. The effect appeared to be stronger in participants with poorly controlled diabetes and those not on insulin therapy. Systematic review registration: CRD42019121682.

Circulating bile acids as a link between the gut microbiota and cardiovascular health: impact of prebiotics, probiotics and polyphenol-rich foods

Beneficial effects of probiotic, prebiotic and polyphenol-rich interventions on fasting lipid profiles have been reported, with changes in the gut microbiota composition believed to play an important role in lipid regulation. Primary bile acids, which are involved in the digestion of fats and cholesterol metabolism, can be converted by the gut microbiota to secondary bile acids, some species of which are less well reabsorbed and consequently may be excreted in the stool. This can lead to increased hepatic bile acid neo-synthesis, resulting in a net loss of circulating low-density lipoprotein. Bile acids may therefore provide a link between the gut microbiota and cardiovascular health. This narrative review presents an overview of bile acid metabolism and the role of probiotics, prebiotics and polyphenol-rich foods in modulating circulating cardiovascular disease (CVD) risk markers and bile acids. Although findings from human studies are inconsistent, there is growing evidence for associations between these dietary components and improved lipid CVD risk markers, attributed to modulation of the gut microbiota and bile acid metabolism. These include increased bile acid neo-synthesis, due to bile sequestering action, bile salt metabolising activity and effects of short-chain fatty acids generated through bacterial fermentation of fibres. Animal studies have demonstrated effects on the FXR/FGF-15 axis and hepatic genes involved in bile acid synthesis (CYP7A1) and cholesterol synthesis (SREBP and HMGR). Further human studies are needed to determine the relationship between diet and bile acid metabolism and whether circulating bile acids can be utilised as a potential CVD risk biomarker.

Effects of cereal fibers on short-chain fatty acids in healthy subjects and patients: a meta-analysis of randomized clinical trials

Short-chain fatty acids (SCFAs) are involved in the regulation of a wide array of diseases. However, the effect of cereal dietary fibers on SCFA production remains unclear. We reviewed relevant clinical studies between 1950 and 2021 and aimed to evaluate the effect of cereal fiber consumption on SCFA production in healthy subjects and patients. PubMed, Web of Science, and the Cochrane Library databases were used for systematically searching published relevant trials with adults and a minimum intervention duration of 2 weeks. The effect size was estimated using standardized mean difference (SMD) and 95% confidence interval (CI). Of the 555 identified studies, 14 intervention groups involving 205 participants aged between 20 and 69 years are eligible. The results of meta-analysis revealed that cereal fiber supplementation significantly increased acetate [SMD: 0.86, 95% CI (0.46, 1.25), p < 0.0001], propionate [SMD: 0.48, 95% CI: (0.15, 0.81), p = 0.004], butyrate [SMD: 0.61, 95% CI: (0.20, 1.01), p = 0.003], and total SCFA [SMD, 0.96, 95% CI: (0.54, 1.39), p < 0.00001] concentrations. Subgroup analysis suggested that a long intervention duration (>4 weeks) significantly promoted acetate and propionate production, whereas a short intervention duration (≤4 weeks) significantly facilitated butyrate production. Cereal fiber supplementation had a more significant impact on overweight and obese subjects with body mass index (BMI) >29 kg m-2 than on individuals with BMI ≤29 kg m-2. Furthermore, we found that cereal fibers and wheat/rye arabinoxylan oligosaccharides, rather than wheat bran fibers, barley fibers, and barley β-glucan, could significantly elevate the SCFA concentration. Overall, our meta-analysis demonstrated that cereal fiber supplementation is helpful in increasing the SCFA concentration, which provided strong proof for the beneficial role of cereal fibers.

The associations of the gut microbiome composition and short-chain fatty acid concentrations with body fat distribution in children

BACKGROUND & AIMS

Previous studies linking the gut microbiome with childhood obesity largely used the body mass index to measure obesity and reached inconsistent findings. Little evidence has linked the gut microbiome to regional body fat deposition. We investigated whether the abundance of specific taxa in the gut microbiota and the concentrations of short-chain fatty acids (SCFAs) were associated with the content and regional deposition of body fat in children.

METHODS

This cross-sectional study involved 236 children aged 6-9 years. The fat mass contents/percentages in the total body and the android, gynoid, and limb regions were determined by dual-energy X-ray absorptiometry, and the android-to-gynoid fat mass ratio and fat-to-lean mass ratios were calculated. Fecal samples were subjected to16S rRNA amplicon sequencing, and the fecal SCFA concentrations were quantified via high-performance liquid chromatography.

RESULTS

A weighted gene co-expression network analysis identified seven modules of co-expressed operational taxonomic units (OTUs). A total of 57 OTUs from 4 key modules were selected for further analysis. After adjustment of covariates and controlling for the false discovery rate (FDR), a multiple linear regression analysis revealed significant correlations of the abundances of some OTUs with obesity and body fat measures. For instance, the OTUs classified to the species Ruminococcus gnavus and Flavonifractor plautii showed significant negative correlations with the total and regional body fat (β: -0.250 to -0.180, P_FDR: 0.041-0.049), whereas OTUs belonging to the genera Blautia and Romboutsia exhibited positive correlations with body fat measures (β: 0.184-0.222, P_FDR: 0.041-0.049). The fecal concentrations of acetic, propionic, and butyric acids and total SCFAs were significantly positively correlated with various parameters of body fat distribution (β: 0.160-0.275, P_FDR: <0.001-0.042).

CONCLUSION

The gut microbiome and SCFAs are significantly associated with obesity and body fat distribution in pediatric population.

Effects of microbiome changes on endocrine ghrelin signaling - A systematic review

The 28-amino acid peptide hormone ghrelin plays a unique role in the gut-brain axis: It is mainly produced peripherally in gastric X/A-like cells but stimulates food intake centrally via hypothalamic nuclei; thus, providing orexigenic communication between the gut and central food intake-regulatory centers. Another component of the gut-brain axis that gained increasing interest in recent years due to its ability to influence central signaling via metabolites is the gut microbiome. Interestingly, there is increasing evidence that changes in the microbiome are related to alterations in ghrelin expression, secretion, activation and signaling. Since ghrelin is supposedly implicated in the pathogenesis of obesity, changes in the microbiome were hypothesized to improve obesity via modulation of ghrelin abundance and receptor interaction. To shed more light on the association between the microbiome and ghrelin a systematic search of Medline, EMBASE and Web of science using the search term combination "microbiome AND ghrelin" was performed. As a result of the search, 42 publications were included into this systematic review, of which 30 publications reported preclinical and 12 manuscripts presented clinical data. In addition to a critical analysis of the present data, gaps in knowledge were highlighted in order to foster further research.

Gut microbiota-derived short-chain fatty acids and hypertension: Mechanism and treatment

Hypertension (HTN) is an growing emerging health issue around across the world. In recent years, increasing attention has been paid to the role of dysbacteriosis in HTN and its underlying mechanism. Short-chain fatty acids (SCFAs), which are novel metabolites of intestinal flora, exert substantial regulatory effects on HTN, providing an exciting avenue for novel therapies for this disease. They function primarily by activating transmembrane G protein-coupled receptors and inhibiting histone acetylation. In this review, we discuss the mechanisms underlying the complex interaction between SCFAs and gut microbiota composition to lower blood pressure by regulating the brain-gut and kidney-gut axes, and the role of high-salt diet, immune system, oxidative stress, and inflammatory mechanism in the development of HTN. Furthermore, we also discuss the various treatment strategies for HTN, including diet, antibiotics, probiotics, fecal microflora transplantation, and traditional Chinese medicine. In conclusion, manipulation of SCFAs opens new avenues to improve treatment of HTN.

Circulating Short-Chain Fatty Acids Are Positively Associated with Adiposity Measures in Chinese Adults

Epidemiological studies suggest a positive association between obesity and fecal short-chain fatty acids (SCFAs) produced by microbial fermentation of dietary carbohydrates, while animal models suggest increased energy harvest through colonic SCFA production in obesity. However, there is a lack of human population-based studies with dietary intake data, plasma SCFAs, gut microbial, and anthropometric data. In 490 Chinese adults aged 30–68 years, we examined the associations between key plasma SCFAs (butyrate/isobutyrate, isovalerate, and valerate measured by non-targeted plasma metabolomics) with body mass index (BMI) using multivariable-adjusted linear regression. We then assessed whether overweight (BMI ≥ 24 kg/m²) modified the association between dietary-precursors of SCFAs (insoluble fiber, total carbohydrates, and high-fiber foods) with plasma SCFAs. In a sub-sample (n = 209) with gut metagenome data, we examined the association between gut microbial SCFA-producers with BMI. We found positive associations between butyrate/isobutyrate and BMI (p-value < 0.05). The associations between insoluble fiber and butyrate/isobutyrate differed by overweight (p-value < 0.10). There was no statistical evidence for an association between microbial SCFA-producers and BMI. In sum, plasma SCFAs were positively associated with BMI and that the colonic fermentation of fiber may differ for adults with versus without overweight.

Engineered butyrate-producing bacteria prevents high fat diet-induced obesity in mice

Background

Obesity is a major problem worldwide and severely affects public safety. As a metabolite of gut microbiota, endogenous butyric acid participates in energy and material metabolism. Considering the serious side effects and weight regain associated with existing weight loss interventions, novel strategies are urgently needed for prevention and treatment of obesity.

Results

In the present study, we engineered Bacillus subtilis SCK6 to exhibited enhanced butyric acid production. Compared to the original Bacillus subtilis SCK6 strain, the genetically modified BsS-RS06550 strain had higher butyric acid production. The mice were randomly divided into four groups: a normal diet (C) group, a high-fat diet (HFD) group, an HFD + Bacillus subtilis SCK6 (HS) group and an HFD + BsS-RS06550 (HE) group. The results showed BsS-RS06550 decreased the body weight, body weight gain, and food intake of HFD mice. BsS-RS06550 had beneficial effects on blood glucose, insulin resistance and hepatic biochemistry. After the 14-week of experiment, fecal samples were collected for nontargeted liquid chromatography-mass spectrometry analysis to identify and quantify significant changes in metabolites. Sixteen potentially significant metabolites were screened, and BsS-RS06550 was shown to potentially regulate disorders in glutathione, methionine, tyrosine, phenylalanine, and purine metabolism and secondary bile acid biosynthesis.

Conclusions

In this study, we successfully engineered Bacillus subtilis SCK6 to have enhanced butyric acid production. The results of this work revealed that the genetically modified live bacterium BsS-RS06550 showed potential anti-obesity effects, which may have been related to regulating the levels of metabolites associated with obesity. These results indicate that the use of BsS-RS06550 may be a promising strategy to attenuate obesity.