Free Fatty Acids Profiles Are Related to Gut Microbiota Signatures and Short-Chain Fatty Acids

Comparative Analysis of Gut Bacterial Diversity in Wild and Domestic Yaks on the Qinghai-Tibetan Plateau

The gut microbiota is a diverse and complex population, and it has a key role in the host's health and adaptability to the environment. The present study investigated the fecal bacterial community of wild grazing (WG) and domestic grazing (DG) yaks on natural grazing pastures, analyzing the gut microbiota using 16S rRNA sequencing to assess bacterial diversity. A total of 48 yak fecal samples were selected from two different grazing habitats. The DG group had more crude proteins and non-fiber carbohydrates. The WG group had more OM, insoluble dietary fiber such as NDF, ADF, ether extract, and TC. There were 165 and 142 unique operational taxonomic units (OTUs) in the WG and DG groups, respectively. Shannon index analysis revealed a higher bacterial diversity in the WG group than in the DG group. At the phylum level, Firmicutes were the dominant bacterial taxa in both groups. The relative abundance of Firmicutes in the WG group was higher than in the DG group. At the family level, the WG group had a significantly higher abundance of Ruminococcaceae (p < 0.001) and Rikenellaceae (p < 0.001) than the DG group. The abundances of Alloprevotella and Succinivibrio were more pronounced in the DG group than in the WG group at the genus level. This study presents a novel understanding of the bacterial communities of ruminants and their potential applications for livestock production.

Microbial dysbiosis in systemic lupus erythematosus: a scientometric study

Introduction

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease. Mounting evidence suggests microbiota dysbiosis augment autoimmune response. This study aims to provide a systematic overview of this research field in SLE through a bibliometric analysis.

Methods

We conducted a comprehensive search and retrieval of literature related to microbial researches in SLE from the Web of Science Core Collection (WOSCC) database. The retrieved articles were subjected to bibliometric analysis using VOSviewer and Bibliometricx to explore annual publication output, collaborative patterns, research hotspots, current research status, and emerging trends.

Results

In this study, we conducted a comprehensive analysis of 218 research articles and 118 review articles. The quantity of publications rises annually, notably surging in 2015 and 2018. The United States and China emerged as the leading contributors in microbial research of SLE. Mashhad University of Medical Sciences had the highest publication outputs among the institutions. Frontiers in Immunology published the most papers. Luo XM and Margolles A were the most prolific and highly cited contributors among individual authors. Microbial research in SLE primarily focused on changes in microbial composition, particularly gut microbiota, as well as the mechanisms and practical applications in SLE. Recent trends emphasize "metabolites," "metabolomics," "fatty acids," "T cells," "lactobacillus," and "dietary supplementation," indicating a growing emphasis on microbial metabolism and interventions in SLE.

Conclusion

This study provides a thorough analysis of the research landscape concerning microbiota in SLE. The microbial research in SLE mainly focused on three aspects: microbial dysbiosis, mechanism studies and translational studies (microbiota-based therapeutics). It identifies current research trends and focal points, offering valuable guidance for scholars in the field.

Ferroptosis: a potential bridge linking gut microbiota and chronic kidney disease

Ferroptosis is a novel form of lipid peroxidation-driven, iron-dependent programmed cell death. Various metabolic pathways, including those involved in lipid and iron metabolism, contribute to ferroptosis regulation. The gut microbiota not only supplies nutrients and energy to the host, but also plays a crucial role in immune modulation and metabolic balance. In this review, we explore the metabolic pathways associated with ferroptosis and the impact of the gut microbiota on host metabolism. We subsequently summarize recent studies on the influence and regulation of ferroptosis by the gut microbiota and discuss potential mechanisms through which the gut microbiota affects ferroptosis. Additionally, we conduct a bibliometric analysis of the relationship between the gut microbiota and ferroptosis in the context of chronic kidney disease. This analysis can provide new insights into the current research status and future of ferroptosis and the gut microbiota.

A mediation analysis of the role of total free fatty acids on pertinence of gut microbiota composition and cognitive function in late life depression

BACKGROUND

Extensive evidence demonstrates correlations among gut microbiota, lipid metabolism and cognitive function. However, there is still a lack of researches in the field of late-life depression (LLD). This research targeted at investigating the relationship among gut microbiota, lipid metabolism indexes, such as total free fatty acids (FFAs), and cognitive functions in LLD.

METHODS

Twenty-nine LLD patients from the Cognitive Outcome Cohort Study of Depression in Elderly were included. Cognitive functions were estimated through the Chinese version of Montreal Cognitive Assessment (MoCA). Blood samples were collected to evaluate serum lipid metabolism parameters. Fecal samples were evaluated for gut microbiota determination via 16S rRNA sequencing. Spearman correlation, linear regression and mediation analysis were utilized to explore relationship among gut microbiota, lipid metabolism and cognitive function in LLD patients.

RESULTS

Spearman correlation analysis revealed significant correlations among Akkermansia abundance, total Free Fatty Acids (FFAs) and MoCA scores (P < 0.05). Multiple regression indicated Akkermansia and total FFAs significantly predicted MoCA scores (P < 0.05). Mediation analysis demonstrated that the correlation between decreased Akkermansia relative abundance and cognitive decline in LLD patients was partially mediated by total FFAs (Bootstrap 95%CI: 0.023-0.557), accounting for 43.0% of the relative effect.

CONCLUSION

These findings suggested a significant relationship between cognitive functions in LLD and Akkermansia, as well as total FFAs. Total FFAs partially mediated the relationship between Akkermansia and cognitive functions. These results contributed to understanding the gut microbial-host lipid metabolism axis in the cognitive function of LLD.

High-throughput screening of the effects of 90 xenobiotics on the simplified human gut microbiota model (SIHUMIx): a metaproteomic and metabolomic study

The human gut microbiota is a complex microbial community with critical functions for the host, including the transformation of various chemicals. While effects on microorganisms has been evaluated using single-species models, their functional effects within more complex microbial communities remain unclear. In this study, we investigated the response of a simplified human gut microbiota model (SIHUMIx) cultivated in an in vitro bioreactor system in combination with 96 deep-well plates after exposure to 90 different xenobiotics, comprising 54 plant protection products and 36 food additives and dyes, at environmentally relevant concentrations. We employed metaproteomics and metabolomics to evaluate changes in bacterial abundances, the production of Short Chain Fatty Acids (SCFAs), and the regulation of metabolic pathways. Our findings unveiled significant changes induced by 23 out of 54 plant protection products and 28 out of 36 food additives across all three categories assessed. Notable highlights include azoxystrobin, fluroxypyr, and ethoxyquin causing a substantial reduction (log2FC < -0.5) in the concentrations of the primary SCFAs: acetate, butyrate, and propionate. Several food additives had significant effects on the relative abundances of bacterial species; for example, acid orange 7 and saccharin led to a 75% decrease in Clostridium butyricum, with saccharin causing an additional 2.5-fold increase in E. coli compared to the control. Furthermore, both groups exhibited up- and down-regulation of various pathways, including those related to the metabolism of amino acids such as histidine, valine, leucine, and isoleucine, as well as bacterial secretion systems and energy pathways like starch, sucrose, butanoate, and pyruvate metabolism. This research introduces an efficient in vitro technique that enables high-throughput screening of the structure and function of a simplified and well-defined human gut microbiota model against 90 chemicals using metaproteomics and metabolomics. We believe this approach will be instrumental in characterizing chemical-microbiota interactions especially important for regulatory chemical risk assessments.

The effect of metformin combined with liraglutide on gut microbiota of Chinese patients with type 2 diabetes

BACKGROUND

Metformin (MET) is a first-line therapy for type-2 diabetes mellitus (T2DM). Liraglutide (LRG) is a glucagon-like peptide-1 receptor agonist used as a second-line therapy in combination with MET.

METHODS

We performed a longitudinal analysis comparing the gut microbiota of overweight and/or pre-diabetic participants (NCP group) with that of each following their progression to T2DM diagnosis (UNT group) using 16S ribosomal RNA gene sequencing of fecal bacteria samples. We also examined the effects of MET (MET group) and MET plus LRG (MET+LRG group) on the gut microbiota of these participants following 60 days of anti-diabetic drug therapy in two parallel treatment arms.

RESULTS

In the UNT group, the relative abundances of Paraprevotella (P = 0.002) and Megamonas (P = 0.029) were greater, and that of Lachnospira (P = 0.003) was lower, compared with the NCP group. In the MET group, the relative abundance of Bacteroides (P = 0.039) was greater, and those of Paraprevotella (P = 0.018), Blautia (P = 0.001), and Faecalibacterium (P = 0.005) were lower, compared with the UNT group. In the MET+LRG group, the relative abundances of Blautia (P = 0.005) and Dialister (P = 0.045) were significantly lower than in the UNT group. The relative abundance of Megasphaera in the MET group was significantly greater than in the MET+LRG group (P = 0.041).

CONCLUSIONS

Treatment with MET and MET+LRG results in significant alterations in gut microbiota, compared with the profiles of patients at the time of T2DM diagnosis. These alterations differed significantly between the MET and MET+LRG groups, which suggests that LRG exerted an additive effect on the composition of gut microbiota.

Single-Cell Hemoprotein Diet Changes Adipose Tissue Distributions and Re-Shapes Gut Microbiota in High-Fat Diet-Induced Obese Mice

We have previously observed that feeding with single-cell hemoprotein (heme-SCP) in dogs (1 g/day for 6 days) and broiler chickens (1 ppm for 32 days) increased the proportion of lactic acid bacteria in the gut while reducing their body weights by approximately 1~2%. To define the roles of heme-SCP in modulating body weight and gut microbiota, obese C57BL/6N mice were administered varied heme-SCP concentrations (0, 0.05, and 0.5% heme-SCP in high fat diet) for 28 days. The heme-SCP diet seemed to restrain weight gain till day 14, but the mice gained weight again later, showing no significant differences in weight. However, the heme-SCP-fed mice had stiffer and oilier bodies compared with those of the control mice, which had flabby bodies and dull coats. When mice were dissected at day 10, the obese mice fed with heme-SCP exhibited a reduction in subcutaneous fat with an increase in muscle mass. The effect of heme-SCP on the obesity-associated dyslipidemia tended to be corroborated by the blood parameters (triglyceride, total cholesterol, and C-reactive protein) at day 10, though the correlation was not clear at day 28. Notably, the heme-SCP diet altered gut microbiota, leading to the proliferation of known anti-obesity biomarkers such as Akkermansia, Alistipes, Oscillibacter, Ruminococcus, Roseburia, and Faecalibacterium. This study suggests the potential of heme-SCP as an anti-obesity supplement, which modulates serum biochemistry and gut microbiota in high-fat diet-induced obese mice.

The relationship between gut microbiota, short-chain fatty acids, and glucolipid metabolism in pregnant women with large for gestational age infants

AIM

To elucidate the association between gut microbiota, short-chain fatty acids (SCFAs), and glucolipid metabolism in women with large for gestational age (LGA) infants.

METHODS AND RESULTS

A single-center, observational prospective cohort study was performed at a tertiary hospital in Wenzhou, China. Normal pregnant women were divided into LGA group and appropriate for gestational age (AGA) group according to the neonatal birth weight. Fecal samples were collected from each subject before delivery for the analysis of gut microbiota composition (GMC) and SCFAs. Blood samples were obtained at 24-28 weeks of gestation age to measure fasting blood glucose and fasting insulin levels, as well as just before delivery to assess serum triglycerides, total cholesterol, high-density lipoprotein (HDL), and low-density lipoprotein. The GMC exhibited differences at various taxonomic levels. Within the Firmicutes phylum, genus Lactobacillus, genus Clostridium, species Lactobacillus agil, and species Lactobacillus salivarius were enriched in the LGA group. Microbispora at genus level, Microbispora rosea at species level belonging to the Actinobacteria phylum, Neisseriales at order level, Bartonellaceae at family level, Paracoccus aminovorans, and Methylobacterium at genus level from the Proteobacteria phylum were more abundant in the LGA group. In contrast, within the Bacteroidetes phylum, Prevotella at genus level and Parabacteroides distasonis at species level were enriched in the AGA group. Although there were few differences observed in SCFA levels and most glucolipid metabolism indicators between the two groups, the serum HDL level was significantly lower in the LGA group compared to the AGA group. No significant relevance among GMC, SCFAs, and glucolipid metabolism indicators was found in the LGA group or in the AGA group.

CONCLUSIONS

Multiple different taxa, especially phylum Firmicutes, genus Prevotella, and genus Clostridium, might play an important role in excessive fetal growth, and LGA might be associated with the lower serum HDL level.

Exploring Plasma-Level Gut Microbiota Mediators and Pro-Inflammatory Markers in Pregnant Women with Short Cervix and Gestational Diabetes Mellitus

The composition of the gut microbiota (GM) undergoes significant changes during pregnancy, influenced by metabolic status, energy homeostasis, fat storage, and hormonal and immunological modifications. Moreover, dysbiosis during pregnancy has been associated with preterm birth, which is influenced by factors such as cervical shortening, infection, inflammation, and oxidative stress. However, dysbiosis also affects the levels of lipopolysaccharide-binding protein (LBP), short-chain fatty acids (SCFAs), and free fatty acids (FFA) in other tissues and the bloodstream. In this study, we investigated the plasmatic levels of some pro-inflammatory cytokines, such as matrix metalloproteinases-8 (MMP-8), interleukin-8 (IL-8), heat shock protein 70 (Hsp70), and microbial markers in pregnant women with a short cervix (≤25 mm) compared to those with normal cervical length (>25 mm). We examined the differences in the concentration of these markers between the two groups, also assessing the impact of gestational diabetes mellitus. Understanding the relationship between GM dysbiosis, inflammatory mediators, and cervical changes during pregnancy may contribute to the identification of potential biomarkers and therapeutic targets for the prevention and management of adverse pregnancy outcomes, including preterm birth.

The function of human milk oligosaccharides and their substitute oligosaccharides as probiotics in gut inflammation

Gut inflammation seriously affects the healthy life of patients, and has a trend of increasing incidence rate. However, the current methods for treating gut inflammation are limited to surgery and drugs, which can cause irreversible damage to patients, especially infants. As natural oligosaccharides in human breast milk, human milk oligosaccharides (HMOs) function as probiotics in treating and preventing gut inflammation: improving the abundance of the gut microbiota, increasing the gut barrier function, and reducing the gut inflammatory reaction. Meanwhile, due to the complexity and high cost of their synthesis, people are searching for functional oligosaccharides that can replace HMOs as a food additive in infants milk powder and adjuvant therapy for chronic inflammation. The purpose of this review is to summarize the therapeutic and preventive effects of HMOs and their substitute functional oligosaccharides as probiotics in gut inflammation, and to summarize the prospect of their application in infant breast milk replacement in the future.

Short-Chain Fatty-Acid-Producing Bacteria: Key Components of the Human Gut Microbiota

Short-chain fatty acids (SCFAs) play a key role in health and disease, as they regulate gut homeostasis and their deficiency is involved in the pathogenesis of several disorders, including inflammatory bowel diseases, colorectal cancer, and cardiometabolic disorders. SCFAs are metabolites of specific bacterial taxa of the human gut microbiota, and their production is influenced by specific foods or food supplements, mainly prebiotics, by the direct fostering of these taxa. This Review provides an overview of SCFAs' roles and functions, and of SCFA-producing bacteria, from their microbiological characteristics and taxonomy to the biochemical process that lead to the release of SCFAs. Moreover, we will describe the potential therapeutic approaches to boost the levels of SCFAs in the human gut and treat different related diseases.

Combing fecal microbial community data to identify consistent obesity-specific microbial signatures and shared metabolic pathways

Obesity is associated with altered gut microbiome composition but data across different populations remain inconsistent. We meta-analyzed publicly available 16S-rRNA sequence datasets from 18 different studies and identified differentially abundant taxa and functional pathways of the obese gut microbiome. Most differentially abundant genera (Odoribacter, Oscillospira, Akkermansia, Alistipes, and Bacteroides) were depleted in obesity, indicating a deficiency of commensal microbes in the obese gut microbiome. From microbiome functional pathways, elevated lipid biosynthesis and depleted carbohydrate and protein degradation suggested metabolic adaptation to high-fat, low-carbohydrate, and low-protein diets in obese individuals. Machine learning models trained on the 18 studies were modest in predicting obesity with a median AUC of 0.608 using 10-fold cross-validation. The median AUC increased to 0.771 when models were trained in eight studies designed for investigating obesity-microbiome association. By meta-analyzing obesity-associated microbiota signatures, we identified obesity-associated depleted taxa that may be exploited to mitigate obesity and related metabolic diseases.

Preclinical safety evaluation of Lipase OF from Candida cylindracea

Triacylglycerol lipases are enzymes commonly used to process foods and beverages such as oils, wines, and cheeses through catalyzation of long-chain triglyceride hydrolysis. Lipase OF derived from Candida cylindracea (strain MS-5-OF) is only intended for use as a processing aid in food production applications; however, it may be present at trace levels in some products. As such, the safety of Lipase OF was evaluated in this study that included a bacterial reverse mutation assay, an in vitro chromosome aberration test, and a 90-day subchronic toxicity study in rats. In the in vitro bacterial reverse mutation and chromosome aberration assays, Lipase OF was not observed to be mutagenic at concentrations up to 5000 μg/plate and 50 μg/ml, respectively, in the presence or absence of metabolic activation. Results from the 90-day subchronic toxicity study indicated only minimal adverse effects (i.e., increased platelet count and prothrombin time) in male rats from the high-dose group following administration of Lipase OF via the diet at levels of 0, 1.0, 2.5, and 5.0 w/w%. The no-observed-adverse-effect level (NOAEL) for Lipase OF was therefore considered 2.5 w/w% (1597.6 mg/kg body weight/day [1027.3 mg TOS/kg body weight/day]) in males and 5.0 w/w% (3700.4 mg/kg body weight/day [2379.4 mg TOS/kg body weight/day]) in females under the test conditions. Thus, the evidence presented within this study supports the safe use of Lipase OF as a processing aid in various food production applications for human consumption.

Essential Fatty Acid Deficiency Associates with Growth Faltering and Environmental Enteric Dysfunction in Children

Environmental enteric dysfunction (EED) is characterized by intestinal inflammation, malabsorption and growth-faltering in children with heightened exposure to gut pathogens. The aim of this study was to characterize serum non-esterified fatty acids (NEFA), in association with childhood undernutrition and EED, as potential biomarkers to predict growth outcomes. The study comprised a cohort of undernourished rural Pakistani infants (n = 365) and age-matched controls followed prospectively up to 24 months of age. Serum NEFA were quantified at ages 3–6 and 9 months and correlated with growth outcomes, serum bile acids and EED histopathological biomarkers. Serum NEFA correlated with linear growth-faltering and systemic and gut biomarkers of EED. Undernourished children exhibited essential fatty acid deficiency (EFAD), with low levels of linoleic acid and total n-6 polyunsaturated fatty acids, compensated by increased levels of oleic acid and increased elongase and desaturase activities. EFAD correlated with reduced anthropometric Z scores at 3–6 and 9 months of age. Serum NEFA also correlated with elevated BA and liver dysfunction. Essential fatty acid depletion and altered NEFA metabolism were highly prevalent and associated with acute and chronic growth-faltering in EED. The finding suggests that targeting early interventions to correct EFAD and promote FA absorption in children with EED may facilitate childhood growth in high-risk settings.

The Short-chain Fatty Acid Propionic Acid Activates the Rcs Stress Response System Partially through Inhibition of d-Alanine Racemase

The Enterobacterial Rcs stress response system reacts to envelope stresses through a complex two-component phosphorelay system to regulate a variety of environmental response genes, such as capsular polysaccharide and flagella biosynthesis genes. However, beyond Escherichia coli, the stresses that activate Rcs are not well-understood. In this study, we used a Rcs system-dependent luminescent transcriptional reporter to screen a library of over 240 antimicrobial compounds for those that activated the Rcs system in Serratia marcescens, a Yersiniaceae family bacterium. Using an isogenic rcsB mutant to establish specificity, both new and expected activators were identified, including the short-chain fatty acid propionic acid, which is found at millimolar levels in the human gut. Propionic acid did not reduce the bacterial intracellular pH, as was hypothesized for its antibacterial mechanism. Instead, data suggest that the Rcs-activation by propionic acid is due, in part, to an inactivation of alanine racemase. This enzyme is responsible for the biosynthesis of d-alanine, which is an amino-acid that is required for the generation of bacterial cell walls. Consistent with what was observed in S. marcescens, in E. coli, alanine racemase mutants demonstrated elevated expression of the Rcs-reporter in a d-alanine-dependent and RcsB-dependent manner. These results suggest that host gut short-chain fatty acids can influence bacterial behavior via the activation of the Rcs stress response system. IMPORTANCE The Rcs bacterial stress response system responds to envelope stresses by globally altering gene expression to profoundly impact host-pathogen interactions, virulence, and antibiotic tolerance. In this study, a luminescent Rcs-reporter plasmid was used to screen a library of compounds for activators of Rcs. Among the strongest inducers was the short-chain fatty acid propionic acid, which is found at high concentrations in the human gut. This study suggests that gut short-chain fatty acids can affect both bacterial virulence and antibiotic tolerance via the induction of the Rcs system.

The Role of the Gut Microbiota in the Relationship Between Diet and Human Health

The interplay between diet, the gut microbiome, and host health is complex. Diets associated with health have many similarities: high fiber, unsaturated fatty acids, and polyphenols while being low in saturated fats, sodium, and refined carbohydrates. Over the past several decades, dietary patterns have changed significantly in Westernized nations with the increased consumption of calorically dense ultraprocessed foods low in fiber and high in saturated fats, salt, and refined carbohydrates, leading to numerous negative health consequences including obesity, metabolic syndrome, and cardiovascular disease. The gut microbiota is an environmental factor that interacts with diet and may also have an impact on health outcomes, many of which involve metabolites produced by the microbiota from dietary components that can impact the host. This review focuses on our current understanding of the complex relationship between diet, the gut microbiota, and host health, with examples of how diet can support health, increase an individual's risk for disease, and be used as a therapy for specific diseases.

Improved Plasma Lipids, Anti-Inflammatory Activity, and Microbiome Shifts in Overweight Participants: Two Clinical Studies on Oral Supplementation with Algal Sulfated Polysaccharide

Seaweed polysaccharides in the diet may influence both inflammation and the gut microbiome. Here we describe two clinical studies with an Ulva sp. 84-derived sulfated polysaccharide—“xylorhamnoglucuronan” (SXRG84)—on metabolic markers, inflammation, and gut flora composition. The first study was a double-blind, randomized placebo-controlled trial with placebo, and either 2 g/day or 4 g/day of SXRG84 daily for six weeks in 64 overweight or obese participants (median age 55 years, median body mass index (BMI) 29 kg/m2). The second study was a randomized double-blind placebo-controlled crossover trial with 64 participants (median BMI 29 kg/m2, average age 52) on placebo for six weeks and then 2 g/day of SXRG84 treatment for six weeks, or vice versa. In Study 1, the 2 g/day dose exhibited a significant reduction in non-HDL (high-density lipoprotein) cholesterol (−10% or −0.37 mmol/L, p = 0.02) and in the atherogenic index (−50%, p = 0.05), and two-hour insulin (−12% or −4.83 mU/L) showed trends for reduction in overweight participants. CRP (C-reactive protein) was significantly reduced (−27% or −0.78 mg/L, p = 0.03) with the 4 g/day dose in overweight participants. Significant gut flora shifts included increases in Bifidobacteria, Akkermansia, Pseudobutyrivibrio, and Clostridium and a decrease in Bilophila. In Study 2, no significant differences in lipid measures were observed, but inflammatory cytokines were improved. At twelve weeks after the SXRG84 treatment, plasma cytokine concentrations were significantly lower than at six weeks post placebo for IFN-γ (3.4 vs. 7.3 pg/mL), IL-1β (16.2 vs. 23.2 pg/mL), TNF-α (9.3 vs. 12.6 pg/mL), and IL-10 (1.6 vs. 2.1 pg/mL) (p < 0.05). Gut microbiota abundance and composition did not significantly differ between groups (p > 0.05). Together, the studies illustrate improvements in plasma lipids and an anti-inflammatory effect of dietary SXRG84 that is participant specific.

Effects of Zymosan on Short-Chain Fatty Acid and Gas Production in in vitro Fermentation Models of the Human Intestinal Microbiota

In this study, the effects of zymosan (HG, hydrolyzed glucan) on the structure and metabolism of fecal microbiota in Chinese healthy people was investigated by an in vitro simulated intestinal microecology fermentation model. We found that HG significantly regulated fecal microbiota composition, including the increase of Bifidobacterium, Faecalibacterium, Prevotella and the decrease of Escherichia-Shigella. Moreover, HG significantly increased the total production of short chain fatty acids (SCFAs) and gases, in which the production of Acetic acid, Propionic acid, CO₂, and H₂ significantly increased while the production of Isovaleric acid and NH₃ significantly decreased. Additionally, the supplement of HG showed certain differences in the regulation of microbiota from four groups. HG significantly increased the relative abundance of Bifidobacterium and significantly decreased the relative abundance of Escherichia-Shigella excluding the older men group. Meanwhile, and the relative abundance of Lactobacillus was significantly increased in young populations. And the relative abundance of Bacteroides was significantly decreased only in the young women. Furthermore, HG significantly increased H₂ concentration only in older men. These findings suggest that HG, as a new generation of prebiotics, could regulate the structure of fecal microbiota and its metabolites in a better direction, but when HG participates in precision nutrition formula, it may be necessary to consider the differences in the utilization of different populations.

Gut Microbiota-Derived Metabolites and Cardiovascular Disease Risk: A Systematic Review of Prospective Cohort Studies

Gut microbiota-derived metabolites have recently attracted considerable attention due to their role in host-microbial crosstalk and their link with cardiovascular health. The MEDLINE-PubMed and Elsevier’s Scopus databases were searched up to June 2022 for studies evaluating the association of baseline circulating levels of trimethylamine N-oxide (TMAO), secondary bile acids, short-chain fatty acids (SCFAs), branched-chain amino acids (BCAAs), tryptophan and indole derivatives, with risk of cardiovascular disease (CVD). A total of twenty-one studies were included in the systematic review after evaluating 1210 non-duplicate records. There were nineteen of the twenty-one studies that were cohort studies and two studies had a nested case–control design. All of the included studies were of high quality according to the “Newcastle–Ottawa Scale”. TMAO was positively associated with adverse cardiovascular events and CVD/all-cause mortality in some, but not all of the included studies. Bile acids were associated with atrial fibrillation and CVD/all-cause mortality, but not with CVD. Positive associations were found between BCAAs and CVD, and between indole derivatives and major adverse cardiovascular events, while a negative association was reported between tryptophan and all-cause mortality. No studies examining the relationship between SCFAs and CVD risk were identified. Evidence from prospective studies included in the systematic review supports a role of microbial metabolites in CVD.

Shift and homogenization of gut microbiome during invasion in marine fishes

Biological invasion is one of the main components of global changes in aquatic ecosystems. Unraveling how establishment in novel environments affects key biological features of animals is a key step towards understanding invasion. Gut microbiome of herbivorous animals is important for host health but has been scarcely assessed in invasive species. Here, we characterized the gut microbiome of two invasive marine herbivorous fishes (Siganus rivulatus and Siganus luridus) in their native (Red Sea) and invaded (Mediterranean Sea) ranges. The taxonomic and phylogenetic diversity of the microbiome increased as the fishes move away from the native range and its structure became increasingly different from the native microbiome. These shifts resulted in homogenization of the microbiome in the invaded range, within and between the two species. The shift in microbial diversity was associated with changes in its functions related with the metabolism of short-chain fatty acids. Altogether, our results suggest that the environmental conditions encountered by Siganidae during their expansion in Mediterranean ecosystems strongly modifies the composition of their gut microbiome along with its putative functions. Further studies should pursue to identify the precise determinants of these modifications (e.g. changes in host diet or behavior, genetic differentiation) and whether they participate in the ecological success of these species.

Metabolites of Gut Microbiota and Possible Implication in Development of Diabetes Mellitus

Diabetes mellitus is characterized by having a disorder of glucose metabolism. The types of diabetes mellitus include type 1 diabetes mellitus, type 2 diabetes mellitus, gestational diabetes mellitus, and other specific types of diabetes mellitus. Many risk factors contribute to diabetes mellitus mainly including genetics, environment, obesity, and diet. In the recent years, gut microbiota has been shown to be linked to the development of diabetes. It has been reported that the gut microbiota composition of diabetic patients is different from that of healthy people. Although the mechanism behind the abnormality remains to be explored, most hypotheses focus on the inflammation response and leaky gut in relation to the changes in production of endotoxins and metabolites derived from the intestinal flora. Consequently, the above-mentioned abnormalities trigger a series of metabolic changes, gradually leading to development of hyperglycemia, insulin resistance, and diabetes. This review is (i) to summarize the differences in gut microbiota between diabetic patients and healthy people, (ii) to discuss the underlying mechanism(s) by which how lipopolysaccharide, diet, and metabolites of the gut microbiota affect diabetes, and (iii) to provide a new insight in the prevention and treatment of diabetes.

Chronic systemic low-grade inflammation and modern lifestyle: the dark role of gut microbiota on related diseases with a focus on pandemic COVID-19

Inflammation is a physiological, beneficial and auto-limiting response of the host to alarming stimuli. Conversely, a chronic systemic low-grade inflammation (CSLGI), known as a long-time persisting condition, causes organs and host tissues' damage, representing a major risk for chronic diseases. Currently, a worldwide a high incidence of inflammatory chronic diseases is observed, often linked to the lifestyle-related changes occurred in the last decade's society. The mains lifestyle-related factors are a proinflammatory diet, psychological stress, tobacco smoking, alcohol abuse, physical inactivity, and finally indoor living and working with its related consequences such as indoor pollution, artificial light exposure and low vitamin D production. Recent scientific evidences found that gut microbiota (GM) has a main role in shaping the host's health, particularly as CSLGI mediator. As a matter of facts, based on the last discoveries regarding the remarkable GM activity, in this manuscript we focused on the elements of actual lifestyle that influence the composition and function of intestinal microbial community, in order to elicit the CSLGI and its correlated pathologies. In this scenario, we provide a broad review of the interplay between modern lifestyle, GM and CSLGI with a special focus on the COVID symptoms and emerging long-COVID syndrome.

A Review of Metabolomic Profiling in Rheumatoid Arthritis: Bringing New Insights in Disease Pathogenesis, Treatment and Comorbidities

Metabolomic analysis provides a wealth of information that can be predictive of distinctive phenotypes of pathogenic processes and has been applied to better understand disease development. Rheumatoid arthritis (RA) is an autoimmune disease with the establishment of chronic synovial inflammation that affects joints and peripheral tissues such as skeletal muscle and bone. There is a lack of useful disease biomarkers to track disease activity, drug response and follow-up in RA. In this review, we describe potential metabolic biomarkers that might be helpful in the study of RA pathogenesis, drug response and risk of comorbidities. TMAO (choline and trimethylamine oxide) and TCA (tricarboxylic acid) cycle products have been suggested to modulate metabolic profiles during the early stages of RA and are present systemically, which is a relevant characteristic for biomarkers. Moreover, the analysis of lipids such as cholesterol, FFAs and PUFAs may provide important information before disease onset to predict disease activity and treatment response. Regarding therapeutics, TNF inhibitors may increase the levels of tryptophan, valine, lysine, creatinine and alanine, whereas JAK/STAT inhibitors may modulate exclusively fatty acids. These observations indicate that different disease modifying antirheumatic drugs have specific metabolic profiles and can reveal differences between responders and non-responders. In terms of comorbidities, physical impairment represented by higher fatigue scores and muscle wasting has been associated with an increase in urea cycle, FFAs, tocopherols and BCAAs. In conclusion, synovial fluid, blood and urine samples from RA patients seem to provide critical information about the metabolic profile related to drug response, disease activity and comorbidities.

Exogenous lipase administration alters gut microbiota composition and ameliorates Alzheimer's disease-like pathology in APP/PS1 mice

Alzheimer's disease (AD) represents the most common form of dementia in the elderly with no available disease modifying treatments. Altered gut microbial composition has been widely acknowledged as a common feature of AD, which potentially contributes to progression or onset of AD. To assess the hypothesis that Candida rugosa lipase (CRL), which has been shown to enhance gut microbiome and metabolite composition, can rebalance the gut microbiome composition and reduce AD pathology, the treatment effects in APPswe/PS1de9 (APP/PS1) mice were investigated. The analysis revealed an increased abundance of Acetatifactor and Clostridiales vadin BB60 genera in the gut; increased lipid hydrolysis in the gut lumen, normalization of peripheral unsaturated fatty acids, and reduction of neuroinflammation and memory deficits post treatment. Finally, we demonstrated that the evoked benefits on memory could be transferred via fecal matter transplant (FMT) into antibiotic-induced microbiome-depleted (AIMD) wildtype mice, ameliorating their memory deficits. The findings herein contributed to improve our understanding of the role of the gut microbiome in AD's complex networks and suggested that targeted modification of the gut could contribute to amelioration of AD neuropathology.

Association Between Gut Microbiota and Osteoarthritis: A Review of Evidence for Potential Mechanisms and Therapeutics

Osteoarthritis (OA) is a multifactorial joint disease characterized by degeneration of articular cartilage, which leads to joints pain, disability and reduced quality of life in patients with OA. Interpreting the potential mechanisms underlying OA pathogenesis is crucial to the development of new disease modifying treatments. Although multiple factors contribute to the initiation and progression of OA, gut microbiota has gradually been regarded as an important pathogenic factor in the development of OA. Gut microbiota can be regarded as a multifunctional “organ”, closely related to a series of immune, metabolic and neurological functions. This review summarized research evidences supporting the correlation between gut microbiota and OA, and interpreted the potential mechanisms underlying the correlation from four aspects: immune system, metabolism, gut-brain axis and gut microbiota modulation. Future research should focus on whether there are specific gut microbiota composition or even specific pathogens and the corresponding signaling pathways that contribute to the initiation and progression of OA, and validate the potential of targeting gut microbiota for the treatment of patients with OA.

Symposium review: Adipose tissue endocrinology in the periparturient period of dairy cows

The involvement of adipose tissue (AT) in metabolism is not limited to energy storage but turned out to be much more complex. We now know that in addition to lipid metabolism, AT is important in glucose homeostasis and AA metabolism and also has a role in inflammatory processes. With the discovery of leptin in 1994, the concept of AT being able to secrete messenger molecules collectively termed as adipokines, and acting in an endo-, para-, and autocrine manner emerged. Moreover, based on its asset of receptors, many stimuli from other tissues reaching AT via the bloodstream can also elicit distinct responses and thus integrate AT as a control element in the regulatory circuits of the whole body's functions. The protein secretome of human differentiated adipocytes was described to comprise more than 400 different proteins. However, in dairy cows, the characterization of the physiological time course of adipokines in AT during the transition from pregnancy to lactation is largely limited to the mRNA level; for the protein level, the analytical methods are limited and available assays often lack sound validation. In addition to proteinaceous adipokines, small compounds such as steroids can also be secreted from AT. Due to the lipophilic nature of steroids, they are stored in AT, but during the past years, AT became also known as being able to metabolize and even to generate steroid hormones de novo. In high-yielding dairy cows, AT is substantially mobilized due to increased energy requirements related to lactation. As to whether the steroidogenic system in AT is affected and may change during the common loss of body fat is largely unknown. Moreover, most research about AT in transition dairy cows is based on subcutaneous AT, whereas other depots have scarcely been investigated. This contribution aims to review the changes in adipokine mRNA and-where available-protein expression with time relative to calving in high-yielding dairy cows at different conditions, including parity, body condition, diet, specific feed supplements, and health disorders. In addition, the review provides insights into steroidogenic pathways in dairy cows AT, and addresses differences between fat depots where possible.

Role of the Gut Microbiome in Beta Cell and Adipose Tissue Crosstalk: A Review

In the last decades, obesity has reached epidemic proportions worldwide. Obesity is a chronic disease associated with a wide range of comorbidities, including insulin resistance and type 2 diabetes mellitus (T2D), which results in significant burden of disease and major consequences on health care systems. Of note, intricate interactions, including different signaling pathways, are necessary for the establishment and progression of these two closely related conditions. Altered cell-to-cell communication among the different players implicated in this equation leads to the perpetuation of a vicious circle associated with an increased risk for the development of obesity-related complications, such as T2D, which in turn contributes to the development of cardiovascular disease. In this regard, the dialogue between the adipocyte and pancreatic beta cells has been extensively studied, although some connections are yet to be fully elucidated. In this review, we explore the potential pathological mechanisms linking adipocyte dysfunction and pancreatic beta cell impairment/insulin resistance. In addition, we evaluate the role of emerging actors, such as the gut microbiome, in this complex crosstalk.

Dietary lipids from body to brain

Dietary habits have drastically changed over the last decades in Western societies. The Western diet, rich in saturated fatty acids (SFA), trans fatty acids (TFA), omega-6 polyunsaturated fatty acids (n-6 PUFA) and cholesterol, is accepted as an important factor in the development of metabolic disorders, such as obesity and diabetes type 2. Alongside these diseases, nutrition is associated with the prevalence of brain disorders. Although clinical and epidemiological studies revealed that metabolic diseases and brain disorders might be related, the underlying pathology is multifactorial, making it hard to determine causal links. Neuroinflammation can be a result of unhealthy diets that may cause alterations in peripheral metabolism. Especially, dietary fatty acids are of interest, as they act as signalling molecules responsible for inflammatory processes. Diets rich in n-6 PUFA, SFA and TFA increase neuroinflammation, whereas diets rich in monounsaturated fatty acids (MUFA), omega-3 (n-3) PUFA and sphingolipids (SL) can diminish neuroinflammation. Moreover, these pro- and anti-inflammatory diets might indirectly influence neuroinflammation via the adipose tissue, microbiome, intestine and vasculature. Here, we review the impact of nutrition on brain health. In particular, we will discuss the role of dietary lipids in signalling pathways directly applicable to inflammation and neuronal function.

A metabolome and microbiome wide association study of healthy eating index points to the mechanisms linking dietary pattern and metabolic status

BACKGROUND

Healthy eating index (HEI), a measure of diet quality, associates with metabolic health outcomes; however, the molecular basis is unclear. We conducted a multi-omic study to examine whether HEI associates with the circulatory and gut metabolome and investigated the gut microbiome-HEI interaction on circulating and gut metabolites.

METHODS

Through a cross-sectional study, we evaluated diet quality in healthy individuals [the ABO Glycoproteomics in Platelets and Endothelial Cells (ABO) Study, n = 73], metabolites (measured at Metabolon Inc.) in plasma (n = 800) and gut (n = 767) and the gut microbiome at enterotype and microbial taxa (n = 296) levels. Pathway analysis was conducted using Metaboanalyst 4.0. We performed multi-variable linear regression to explore both the HEI-metabolites and HEI-microbiome associations and how metabolites were affected by the HEI-microbiome interaction. In the Fish oils and Adipose Inflammation Reduction (FAIR) Study (n = 25), analyses on HEI and plasma metabolites were replicated. Estimates of findings from both studies were pooled in random-effects meta-analysis.

RESULTS

The HEI-2015 was associated with 74 plasma and 73 gut metabolites (mostly lipids) and with 47 metabolites in the meta-analysis of the ABO and FAIR Studies. Compared to Enterotype-1 participants, those with Enterotype-2 had higher diet quality (p = 0.01). We also identified 9 microbial genera associated with HEI, and 35 plasma and 40 gut metabolites linked to the HEI-gut microbiome interaction. Pathways involved in the metabolism of polar lipids, amino acids and caffeine strongly associated with diet quality. However, the HEI-microbiome interaction not only influenced the pathways involved in the metabolism of branch-chain amino acids, it also affected upstream pathways including nucleotide metabolism and amino acids biosynthesis.

CONCLUSIONS

Our multi-omic analysis demonstrated that changes in metabolism, measured by either circulatory/gut metabolites or metabolic pathways, are influenced by not only diet quality but also gut microbiome alterations shaped by the quality of diet consumed. Future work is needed to explore the causality in the interplay between HEI and gut-microbiome composition in metabolism.

Gut microbiota of patients with type 2 diabetes and gastrointestinal intolerance to metformin differs in composition and functionality from tolerant patients

OBJECTIVE

Metformin modifies the gut microbiome in type 2 diabetes and gastrointestinal tolerance to metformin could be mediated by the gut microbiome.

METHODS

We enrolled 35 patients with type 2 diabetes not receiving treatment with metformin due to suspected gastrointestinal intolerance. Metformin was reintroduced at 425 mg, increasing 425 mg every two weeks until reaching 1700 mg per day. According to the occurrence of metformin-related gastrointestinal symptoms, patients were classified into three groups: early intolerance, non-tolerant, and tolerant. Gut microbiota was profiled with 16 S rRNA. This sequencing aimed to determine the differences in the baseline gut microbiota in all groups and prospectively in the tolerant and non-tolerant groups.

RESULTS

The classification resulted in 15 early intolerant, 10 tolerant, and 10 non-tolerant subjects. Early tolerance was characterized by a higher abundance of Subdoligranulum; while Veillonella and Serratia were higher in the non-tolerant group. The tolerant group showed enrichment of Megamonas, Megamonas rupellensis, and Phascolarctobacterium spp; Ruminococcus gnavus was lower in the longitudinal analysis. At the end point Prevotellaceae, Prevotella stercorea, Megamonas funiformis, Bacteroides xylanisolvens, and Blautia producta had a higher relative abundance in the tolerant group compared to the non-tolerant group. Subdoligranulum, Ruminococcus torques_1, Phascolarctobacterium faecium, and Eubacterium were higher in the non-tolerant group. The PICRUSt analysis showed a lower activity of the amino acid biosynthesis pathways and a higher sugar degradation pathway in the intolerant groups.

CONCLUSIONS

Gut microbiota of subjects with gastrointestinal intolerance depicted taxonomic and functional differences compared to tolerant patients, and this changed differently after metformin administration.

Clustering of Stearic Acids in Model Phospholipid Membranes Revealed by Double Electron-Electron Resonance

Free fatty acids play various important roles in biological membranes. Double electron-electron resonance spectroscopy (DEER, also known as PELDOR) of spin-labeled biomolecules is capable of studying magnetic dipole-dipole (d-d) interactions between spin labels at the nanoscale range of distances. Here, DEER is applied to study intermolecular d-d interactions between doxyl-spin-labeled stearic acids (DSA) in gel-phase phospholipid bilayers composed either of an equimolecular mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phosphocholine or of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. DEER data obtained for different DSA concentrations showed that DSA molecules at their concentration in the bilayer χ larger than 0.5 mol % are assembled into lateral lipid-mediated clusters, with a characteristic intermolecular distance of 2 nm. Some evidences were obtained indicating that clusters may consist of "subclusters", alternatively appearing in two opposite leaflets. Conventional electron paramagnetic resonance (EPR) spectra for the gel-phase bilayers showed that for χ larger than 2 mol % the molecules in the clusters stick together, forming oligomers. Room-temperature EPR spectra for the liquid-crystalline phase were found to change noticeably for χ larger than 0.5 mol %, which may indicate the clustering in a liquid-crystalline phase similar to that observed by DEER in the gel phase.

Serratia symbiotica Enhances Fatty Acid Metabolism of Pea Aphid to Promote Host Development

Bacterial symbionts associated with insects are often involved in host development and ecological adaptation. Serratia symbiotica, a common facultative endosymbiont harbored in pea aphids, improves host fitness and heat tolerance, but studies concerning the nutritional metabolism and impact on the aphid host associated with carrying Serratia are limited. In the current study, we showed that Serratia-infected aphids had a shorter nymphal developmental time and higher body weight than Serratia-free aphids when fed on detached leaves. Genes connecting to fatty acid biosynthesis and elongation were up-regulated in Serratia-infected aphids. Specifically, elevated expression of fatty acid synthase 1 (FASN1) and diacylglycerol-o-acyltransferase 2 (DGAT2) could result in accumulation of myristic acid, palmitic acid, linoleic acid, and arachidic acid in fat bodies. Impairing fatty acid synthesis in Serratia-infected pea aphids either by a pharmacological inhibitor or through silencing FASN1 and DGAT2 expression prolonged the nymphal growth period and decreased the aphid body weight. Conversely, supplementation of myristic acid (C14:0) to these aphids restored their normal development and weight gain. Our results indicated that Serratia promoted development and growth of its aphid host through enhancing fatty acid biosynthesis. Our discovery has shed more light on nutritional effects underlying the symbiosis between aphids and facultative endosymbionts.

Implications of SCFAs on the Parameters of the Lipid and Hepatic Profile in Pregnant Women

Short-chain fatty acids (SCFAs) are the product of the anaerobic intestinal bacterial fermentation of dietary fiber and resistant starch. An abnormal intestinal microbiota may cause a reduction in the production of SCFAs, which stimulate the development of intestinal epithelial cells, nourish enterocytes, influence their maturation and proper differentiation, reduce the pH, and are an additional source of energy for the host. There have been reports of the special role of SCFAs in the regulation of glucose and lipid metabolism during pregnancy.

AIM

The aim of the study was to analyze the correlation of SCFAs with lipid and hepatic metabolism during pregnancy in relation to the body weight of pregnant women.

MATERIAL AND METHODS

This study was conducted in pregnant women divided into two groups: Obese (OW-overweight and obese women; n = 48) and lean (CG-control group; n = 48) individuals. The biochemical plasma parameters of lipid metabolism (TG, CH, LDL, HDL), inflammation (CRP), and liver function (ALT, AST, GGT) were determined in all of the subjects. SCFA analysis was performed in the stool samples to measure acetic acid (C 2:0), propionic acid (C 3:0), isobutyric acid (C 4:0 i), butyric acid (C 4:0 n), isovaleric acid (C 5:0 i) valeric acid (C 5:0 n), isocaproic acid (C 6:0 i), caproic acid (C 6:0 n), and heptanoic acid (C 7:0).

RESULTS

Statistically significant differences in the concentrations of C 3:0 and C 6:0 n were found between women in the OW group compared to the CG group. The other SCFAs tested did not differ significantly depending on BMI. The C 2:0, C 3:0, and C 4:0 n ratios showed differences in both OW and CG groups. In the OW group, no relationship was observed between the concentrations of the SCFAs tested and CRP, ALT, AST. A surprising positive relationship between C 5:0 n and all fractions of the tested lipids and branched C 5:0 with CHL, HDL, and LDL was demonstrated. In the OW group, HDL showed a positive correlation with C 3:0. However, lower GGT concentrations were accompanied by higher C 4:0 and C 5:0 values, and this tendency was statistically significant.

CONCLUSIONS

The results of our research show that some SCFAs are associated with hepatic lipid metabolism and CRP concentrations, which may vary with gestational weight. Obesity in pregnancy reduces the amount of SCFAs in the stool, and a decrease in the level of butyrate reduces liver function.

Effect of a TSPO ligand on retinal pigment epithelial cholesterol homeostasis in high-fat fed mice, implication for age-related macular degeneration

Age-related Macular Degeneration (AMD) is a major cause of sight impairment in the elderly with complex aetiology involving genetics and environment and with limited therapeutic options which have limited efficacy. We have previously shown in a mouse-model of the condition, induced by feeding a high fat diet, that adverse effects of the diet can be reversed by co-administration of the TSPO activator, etifoxine. We extend those observations showing improvements in retinal pigment epithelial (RPE) cells with decreased lipids and enhanced expression of cholesterol metabolism and transport enzymes. Further, etifoxine decreased levels of reactive oxygen species (ROS) in RPE and inflammatory cytokines in RPE and serum. With respect to gut microbiome, we found that organisms abundant in the high fat condition (e.g. in the genus Anaerotruncus and Oscillospira) and implicated in AMD, were much less abundant after etifoxine treatment. The changes in gut flora were associated with the predicted production of metabolites of benefit to the retina including tryptophan and other amino acids and taurine, an essential component of the retina necessary to counteract ROS. These novel observations strengthen earlier conclusions that the mechanisms behind improvements in etifoxine-induced retinal physiology involve an interaction between effects on the host and the gut microbiome.

Human Gut Microbiome and Liver Diseases: From Correlation to Causation

The important role of human gut microbiota in liver diseases has long been recognized as dysbiosis and the translocation of certain microbes from the gut to liver. With the development of high-throughput DNA sequencing, the complexity and integrity of the gut microbiome in the whole spectrum of liver diseases is emerging. Specific patterns of gut microbiota have been identified in liver diseases with different causes, including alcoholic, non-alcoholic, and virus induced liver diseases, or even at different stages, ranging from steatohepatitis, fibrosis, cirrhosis, to hepatocellular carcinoma. At the same time, the mechanism of how microbiota contributes to liver diseases goes beyond the traditional function of the gut-liver axis which could lead to liver injury and inflammation. With the application of proteomics, metabolomics, and modern molecular technologies, more microbial metabolites and the complicated interaction of microbiota with host immunity come into our understanding in the liver pathogenesis. Germ-free animal models serve as a workhorse to test the function of microbiota and their derivatives in liver disease models. Here, we review the current evidence on the relationship between gut microbiota and liver diseases, and the mechanisms underlying this phenotype. In addition to original liver diseases, gut microbiota might also affect liver injury in systemic disorders involving multiple organs, as in the case of COVID-19 at a severe state. A better understanding of the gut microbial contribution to liver diseases might help us better benefit from this guest-host relationship and pave the way for novel therapies.

Invited review: Effect of antihypertensive fermented milks on gut microbiota

Hypertension is a risk factor for the development of other cardiovascular diseases and remains one of the leading causes of death worldwide. Although genetic and environmental factors are associated with the development of hypertension, it has been recently recognized that gut microbiota (GM) may also have an effect on human health. In this sense, gut dysbiosis (a marked decrease in richness and diversity of GM) has been linked to different metabolic diseases, such as hypertension. Therefore, different studies have been pursued to reduce gut dysbiosis and diminish hypertension. Different strategies to maintain a balanced GM, particularly through diet and the use of probiotics, are being evaluated. Most recently, the effect of antihypertensive fermented milks on GM has been addressed. New evidence suggests that antihypertensive fermented milks may modulate GM. Thus, the aim of this review is to present available information related to the effect of antihypertensive fermented milks on gut microbiota.

Understanding the Holobiont: Crosstalk Between Gut Microbiota and Mitochondria During Long Exercise in Horse

Endurance exercise has a dramatic impact on the functionality of mitochondria and on the composition of the intestinal microbiome, but the mechanisms regulating the crosstalk between these two components are still largely unknown. Here, we sampled 20 elite horses before and after an endurance race and used blood transcriptome, blood metabolome and fecal microbiome to describe the gut-mitochondria crosstalk. A subset of mitochondria-related differentially expressed genes involved in pathways such as energy metabolism, oxidative stress and inflammation was discovered and then shown to be associated with butyrate-producing bacteria of the Lachnospiraceae family, especially Eubacterium. The mechanisms involved were not fully understood, but through the action of their metabolites likely acted on PPARγ, the FRX-CREB axis and their downstream targets to delay the onset of hypoglycemia, inflammation and extend running time. Our results also suggested that circulating free fatty acids may act not merely as fuel but drive mitochondrial inflammatory responses triggered by the translocation of gut bacterial polysaccharides following endurance. Targeting the gut-mitochondria axis therefore appears to be a potential strategy to enhance athletic performance.

Metabolic regulation of tissue-resident memory CD8+ T cells

Intracellular metabolic adaptations help define the function and homeostasis of memory CD8⁺ T cells. These cells, which promote protection against infections or cancer, undergo consecutive metabolic shifts, ultimately relying on mitochondrial-related pathways. Past CD8⁺ T cell metabolism studies focused on circulating memory cells, which are exclusive to secondary lymphoid organs or recirculate between lymphoid and non-lymphoid organs. Yet, now there is unequivocal evidence that memory CD8⁺ T cells reside in many non-lymphoid organs and mediate protective immunity in barrier tissues. The metabolic adaptations occurring in forming and established tissue-resident memory CD8⁺ T cells are currently subject of intense research. In this review, we discuss the latest breakthroughs on the transcriptional and protein control of tissue-resident memory CD8⁺ T cell metabolism.

Anti-listerial activity of microalgal fatty acid methyl esters and their possible applications as chicken marinade

Fatty acid methyl esters (FAMEs) from marine microalgae have been reported to possess antimicrobial activities against several Gram positive and Gram negative bacteria, but a majority of them needs to be explored. The objective of this study was to investigate the antibacterial activity, mechanism of FAMEs from selected marine microalgae against Listeria monocytogenes, and to elucidate its efficacy in food model. The minimum inhibitory concentration of FAMEs was calculated to be 155 μg/mL for Chromulina sp. and 162 μg/mL for Nannochloropsis sp. against L. monocytogenes. Time-killing kinetics showed that FAMEs efficiently inhibited the growth of L. monocytogenes in a time and concentration dependent manner. The mechanism of action of FAMEs was studied by analysing its effects at a MIC on the cellular metabolism, membrane permeability, and membrane integrity of L. monocytogenes. Transmission Electron Microscopy (TEM) results showed that cells exposed to FAMEs showed damaged cell membrane structure with leakage of the internal contents in the cells of L. monocytogenes. Fluorescence microscopy images showed that L. monocytogenes cells treated with FAMEs showed high dead cell population corresponding with propidium iodide positive cells. Furthermore, FAMEs significantly down regulated quorum sensing and biofilm related genes (DegU, FlaE, and FlaD). In vivo therapeutic potential of FAMEs revealed improved Caenorhabditis elegans survival and reduced intestinal colonization during L. monocytogenes infection. Growth of listeria was abolished in chicken meat during the cold storage of 9 days when the samples were pre-treated with FAMEs. These results suggest anti-L. monocytogenes activity of FAMEs and elucidated its use in food control of chicken meat at refrigerated conditions.

Comparison of Different Dietary Indices as Predictors of Inflammation, Oxidative Stress and Intestinal Microbiota in Middle-Aged and Elderly Subjects

During the last decades the gut microbiota has been identified as a key mediator in the diet-health interaction. However, our understanding on the impact of general diet upon microbiota is still limited. Dietary indices represent an essential approach for addressing the link between diet and health from a holistic point of view. Our aim was to test the predictive potential of seven dietary ratings on biomarkers of inflammation, oxidative stress and on the composition and metabolic activity of the intestinal microbiota. A cross-sectional descriptive study was conducted on a sample of 73 subjects aged >50 years with non-declared pathologies. Dietary inflammatory index (DII), Empirical Dietary Inflammatory Index (EDII), Healthy Eating Index (HEI), Alternative Healthy Eating Index (AHEI), Mediterranean adapted Diet Quality Index-International (DQI-I), Modified Mediterranean Diet Score (MMDS) and relative Mediterranean Diet Score (rMED) were calculated based on a Food Frequency Questionnaire. Major phylogenetic types of the intestinal microbiota were determined by real time polymerase chain reaction (qPCR) and fecal short chain fatty acids (SCFAs) by gas chromatography. While DII, HEI, DQI-I and MMDS were identified as predictors of Faecalibacterium prausnitzii levels, AHEI and MMDS were negatively associated with Lactobacillus group. HEI, AHEI and MMDS were positively associated with fecal SCFAs. In addition, DII and EDII explained lipoperoxidation level and Mediterranean scores the serum IL-8 concentrations. The lower detection of IL-8 in individuals with higher scores on Mediterranean indices may be partially explained by the increased levels of the anti-inflammatory bacterium F. prausnitzii in such individuals.

Ketogenic Diet: A Dietary Modification as an Anxiolytic Approach?

Anxiety disorders comprise persistent, disabling conditions that are distributed across the globe, and are associated with the high medical and socioeconomic burden of the disease. Within the array of biopsychosocial treatment modalities—including monoaminergic antidepressants, benzodiazepines, and CBT—there is an unmet need for the effective treatment of anxiety disorders resulting in full remission and recovery. Nutritional intervention may be hypothesized as a promising treatment strategy; in particular, it facilitates relapse prevention. Low-carbohydrate high-fat diets (LCHF) may provide a rewarding outcome for some anxiety disorders; more research is needed before this regimen can be recommended to patients on a daily basis, but the evidence mentioned in this paper should encourage researchers and clinicians to consider LCHF as a piece of advice somewhere between psychotherapy and pharmacology, or as an add-on to those two.

Profiling of Serum Oxylipins During the Earliest Stages of Rheumatoid Arthritis

OBJECTIVE

Eicosanoids modulate inflammation via complex networks involving different pathways and downstream mediators, including oxylipins. Although altered eicosanoids are linked to rheumatoid arthritis (RA), suggesting that metabolization is enhanced, the role of oxylipins in disease stratification remains unexplored. This study was undertaken to characterize oxylipin networks during the earliest stages of RA and evaluate their associations with clinical features and treatment outcomes.

METHODS

In total, 60 patients with early RA (according to the American College of Rheumatology/European League Against Rheumatism 2010 criteria), 11 individuals with clinically suspect arthralgia (CSA), and 28 healthy control subjects were recruited. Serum samples were collected at the time of onset. In the early RA group, 50 patients who had not been exposed to disease-modifying antirheumatic drug (DMARD) or glucocorticoid treatment at the time of recruitment were prospectively followed up at 6 and 12 months after having received conventional synthetic DMARDs. A total of 75 oxylipins, mostly derived from arachidonic, eicosapentanoic, and linoleic acids, were identified in the serum by liquid chromatography tandem mass spectrometry.

RESULTS

Univariate analyses demonstrated differences in expression patterns of 14 oxylipins across the RA, CSA, and healthy control groups, with each exhibiting a different trajectory. Network analyses revealed a strong grouping pattern of oxylipins in RA patients, whereas in individuals with CSA, a fuzzy network of oxylipins with higher degree and closeness was found. Partial least-squares discriminant analyses yielded variable important projection scores of >1 for 22 oxylipins, which allowed the identification of 2 clusters. Cluster usage differed among the groups (P = 0.003), and showed associations with disease severity and low rates of remission at 6 and 12 months in RA patients who were initially treatment-naive. Pathway enrichment analyses revealed different precursors and pathways between the groups, highlighting the relevance of the arachidonic acid pathway in individuals with CSA and the lipooxygenase pathway in patients with early RA. In applying distinct oxylipin signatures, subsets of seropositive and seronegative RA could be identified.

CONCLUSION

Oxylipin networks differ across stages during the earliest phases of RA. These distinct oxylipin networks could potentially elucidate pathways with clinical relevance for disease progression, clinical heterogeneity, and treatment response.

The Potential Role of Gut Microbiota in the Prevention and Treatment of Lipid Metabolism Disorders

Due to changes in lifestyle, diet structure, and aging worldwide, the incidence of metabolic syndromes such as hyperlipidemia, hypertension, diabetes, and obesity is increasing. Metabolic syndrome is considered to be closely related to cardiovascular disease and severely affects human health. In recent years, researchers have revealed that the gut microbiota, through its own or interacting metabolites, has a positive role in regulating metabolic syndrome. Therefore, the gut microbiota has been a new "organ" for the treatment of metabolic syndrome. The role has not been clarified, and more research is necessary to prove the specific role of specific strains. Probiotics are also believed to regulate metabolic syndromes by regulating the gut microbiota and are expected to become a new preparation for treating metabolic syndromes. This review focuses on the regulation of lipid metabolism disorders by the gut microbiota through the effects of bile acids (BA), short-chain fatty acids (SCFAs), bile salt hydrolase (BSH), and genes such as ABCG5 and ABCG8, FXR, NPC1L, and LDL-R.

Stachyose modulates gut microbiota and alleviates dextran sulfate sodium-induced acute colitis in mice

BACKGROUND/AIM

Ulcerative colitis (UC) has been implicated to imbalanced enteric flora and reduced microbial diversity. Stachyose is a kind of natural prebiotic which favorably modulate the composition of the gut microbiota. The present study aims to investigate the effects of stachyose on inflammatory levels and gut microbiota of acute colitis mice.

MATERIALS AND METHODS

In this study, the mice were randomly divided into four groups: (1) control group; (2) stachyose group; (3) dextran sulfate sodium (DSS) group; (4) stachyose + DSS group. Hemotoxylin and Eosin (H and E) staining was performed for the distal colon to examine the inflammation and tissue damage. The inflammatory cytokines including IL-6, IL-10, IL-17a, and TNF-α in serum were determined by ELISA assay. The differences in the gut microbiota were analyzed by 16S rDNA gene sequencing.

RESULTS

Histological assay showed that the stachyose treatment significantly reduced the lesions of the colon in DSS-induced colitis. And the upregulated inflammatory cytokines induced by DSS were significantly inhibited by stachyose treatment. Additionally, the sequencing analysis showed that the stachyose changed the gut microbiota composition with a higher level of Akkermansia, as well as selectively increasing some probiotics, including Lactobacillus.

CONCLUSIONS

Our results suggested that stachyose increased beneficial microbiota and bacterial diversity to alleviate acute colitis in mice, which might be a new promising option to UC patients.

Gut microbiome of a porcine model of metabolic syndrome and HF-pEF

Metabolic syndrome (MetS) is a composite of cardiometabolic risk factors, including obesity, dyslipidemia, hypertension, and insulin resistance, with a range of secondary sequelae such as nonalcoholic fatty liver disease and diastolic heart failure. This syndrome has been identified as one of the greatest global health challenges of the 21st century. Herein, we examine whether a porcine model of diet- and mineralocorticoid-induced MetS closely mimics the cardiovascular, metabolic, gut microbiota, and functional metataxonomic phenotype observed in human studies. Landrace pigs with deoxycorticosterone acetate-induced hypertension fed a diet high in fat, salt, and sugar over 12 wk were assessed for hyperlipidemia, hyperinsulinemia, and immunohistologic, echocardiographic, and hemodynamic parameters, as well as assessed for microbiome phenotype and function through 16S rRNA metataxonomic and metabolomic analysis, respectively. All MetS animals developed obesity, hyperlipidemia, insulin resistance, hypertension, fatty liver, structural cardiovascular changes including left ventricular hypertrophy and left atrial enlargement, and increased circulating saturated fatty acid levels, all in keeping with the human phenotype. A reduction in α-diversity and specific microbiota changes at phylum, family, and genus levels were also observed in this model. Specifically, this porcine model of MetS displayed increased abundances of proinflammatory bacteria coupled with increased circulating tumor necrosis factor-α and increased secondary bile acid-producing bacteria, which substantially impacted fibroblast growth factor-19 expression. Finally, a significant decrease in enteroprotective bacteria and a reduction in short-chain fatty acid-producing bacteria were also noted. Together, these data suggest that diet and mineralocorticoid-mediated development of biochemical and cardiovascular stigmata of metabolic syndrome in pigs leads to temporal gut microbiome changes that mimic key gut microbial population signatures in human cardiometabolic disease.NEW & NOTEWORTHY This study extends a prior porcine model of cardiometabolic syndrome to include systemic inflammation, fatty liver, and insulin sensitivity. Gut microbiome changes during evolution of porcine cardiometabolic disease recapitulate those in human subjects with alterations in gut taxa associated with proinflammatory bacteria, bile acid, and fatty acid pathways. This clinical scale model may facilitate design of future interventional trials to test causal relationships between gut dysbiosis and cardiometabolic syndrome at a systemic and organ level.

Effects of probiotics and prebiotics on intestinal microbiota in mice with acute colitis based on 16S rRNA gene sequencing

Background

Imbalance of intestinal microbiota was closely related to colitis. Under these circumstances, regulation of enteric flora may be beneficial to the repair of inflammation. We aimed to investigate the effects of probiotics (Bifidobacterium and Lactobacillus), prebiotics and their combination on inflammation, and microflora in mice of acute colitis.

Methods

C57BL/6J mice were divided into six groups randomly (blank control group, model control group, probiotics group, synbiotics group, lactitol group and probiotics + lactitol group). Each group was given 2.5% dextran sulfate sodium drinking water for 5 days other than the blank control group. Except for the model control group, the other four groups were intervened with probiotics, synbiotics (probiotics and inulin), lactitol, and probiotics + lactitol. Mice were sacrificed after 1 week of gavage, and pathologic scores were calculated. The feces of different periods and intestinal mucosa samples were collected to analyze the differences of intestinal microbiota by 16S rRNA sequencing. Differences of two groups or multiple groups were statistically examined through unpaired Student t test and analysis of variance (ANOVA), respectively. ANOVA, Tukey, Anosim, and metastats analysis were used to compare differences of microbiota among different groups.

Results

After gavage for 1 week, the pathologic scores of groups with the intervention were significantly lower than those in the model control group, and the difference was statistically significant (P < 0.05). The model control group was higher in the genus of Bacteroides (relative abundance: 0.3679 vs. 0.0099, P = 0.0016) and lower in Lactobacillus (relative abundance: 0.0020 vs. 0.0122, P = 0.0188), Roseburia (relative abundance: 0.0004 vs. 0.0109, P = 0.0157), compared with the blank control group. However, the same phenomenon was not found in groups gavaged with probiotics and lactitol. Compared with model control group, mice with intervention were increased with Bifidobacterium (relative abundance: 0.0172 vs. 0.0039, P = 0.0139), Lachnospiraceae_NK4A136_group (relative abundance: 0.1139 vs. 0.0320, P = 0.0344), Lachnospiraceae_UCG-006 (relative abundance: 0.0432 vs. 0.0054, P = 0.0454), and decreased with Alistipes (relative abundance: 0.0036 vs. 0.0105, P = 0.0207) in varying degrees. The mucosal flora was more abundant than the fecal flora, and genus of Mucispirillum (relative abundance: 0.0207 vs. 0.0001, P = 0.0034) was more common in the mucosa. Lactitol group showed higher level of Akkermansia than model control group (relative abundance: 0.0138 vs. 0.0055, P = 0.0415), probiotics group (relative abundance: 0.0138 vs. 0.0022, P = 0.0041), and synbiotics group (relative abundance: 0.0138 vs. 0.0011, P = 0.0034), while probiotics + lactitol group had more abundant Akkermansia than synbiotics group (relative abundance: 0.0215 vs. 0.0013, P = 0.0315).

Conclusions

Probiotics and prebiotics reduce the degree of inflammation in acute colitis mice obviously. Mice with acute colitis show reduced beneficial genera and increased harmful genera. Supplementation of probiotics and prebiotics display the advantage of increasing the proportion of helpful bacteria and regulating the balance of intestinal microbiota. Lactitol might promote the proliferation of Akkermansia.

Short Chain Fatty Acids Commonly Produced by Gut Microbiota Influence Salmonella enterica Motility, Biofilm Formation, and Gene Expression

Short chain fatty acids (SCFAs) are commonly produced by healthy gut microbiota and they have a protective role against enteric pathogens. SCFAs also have direct antimicrobial activity against bacterial pathogens by diffusion across the bacterial membrane and reduction of intracellular pH. Due to this antimicrobial activity, SCFAs have promising applications in human health and food safety. In this study, the minimum inhibitory concentrations (MICs) of four SCFAs (acetic acid, butyric acid, propionic acid, and valeric acid) in Salmonella strains isolated from poultry were determined. The effect of subinhibitory concentrations of SCFAs in Salmonella biofilm formation, motility, and gene expression was also evaluated. Butyric acid, propionic acid, and valeric acid showed a MIC of 3750 µg/mL in all strains tested, while the MIC of acetic acid was between 1875 and 3750 µg/mL. Subinhibitory concentrations of SCFAs significantly (p < 0.05) reduced the motility of all Salmonella strains, especially in the presence of acetic acid. Biofilm formation was also significantly (p < 0.05) lower in the presence of SCFAs in some of the Salmonella strains. Salmonella strain. Salmonella Typhimurium T7 showed significant (p < 0.05) upregulation of important virulence genes, such as invA and hilA, especially in the presence of butyric acid. Therefore, SCFAs are promising substances for the inhibition of the growth of foodborne pathogens. However, it is important to avoid the use of subinhibitory concentrations that could increase the virulence of foodborne pathogen Salmonella.

Wheat Bran for Colon Cancer Prevention: The Synergy between Phytochemical Alkylresorcinol C21 and Intestinal Microbial Metabolite Butyrate

There is convincing evidence that consuming whole grains (WGs) may decrease the risk of colorectal cancer (CRC). Wheat bran (WB) is a rich source of dietary fiber and phytochemicals with health-promoting properties. However, the active components especially the interaction between different components in WG wheat have not been fully explored. Here, we investigated whether one of the major WB phytochemicals, alkylresorcinol (AR) C21, and the major active intestinal microbial metabolite of fiber, butyrate, could synergistically suppress human colon cancer cells. Our results demonstrated for the first time that the combination of C21 and butyrate synergistically inhibited the growth of human colon cancer cells and induced apoptosis. Further mechanistic studies demonstrated that the cotreatment of C21 and butyrate induced significant up-regulations in cleaved Poly(ADP-ribose) polymerase (PARP), cleaved caspase 3, p53 upregulated modulator of apoptosis (PUMA), cytochrome C, lipid-conjugated membrane-bound form of microtubule-associated protein 1A/1B-light chain 3 (LC3-II), and C/EBP homologous protein (CHOP) expressions, indicating the synergistic anticancer effects of C21 and butyrate were associated with induction of apoptosis, autophagy, and ER stress pathways. Notably, the C21 concentrations in the large intestinal tract of mice treated with human relevant doses of C21, were from 0.86 to 1.78 μmol/g, suggesting the C21 doses used in vitro may be achievable after daily WG wheat intake. These results provide novel insights into the dietary prevention of CRC regarding the potential interaction of bioactive WG wheat phytochemicals and the microbial metabolites of fiber.