Production Of Short-chain Fatty Acids Research Articles

Mini-Review: the gut microbiota-muscle axis and its role in aging research

BACKGROUND: Aging is a multifactorial process, one of whose key consequences is the decline in muscle strength and mass, which directly impacts the functional capacity of older adults. One possible mechanism involved in this process is the role of gut microbiota in muscle atrophy. AIM: To explore the role of the gut microbiota-muscle axis during aging, investigating its relationship with functional outcomes and the potential for intervention. METHOD: A mini-review of the literature was conducted using the PubMed, Scopus, and Embase databases with the keywords “microbiota”, “microbiome”, “gut-muscle axis”, “aging” and “muscle”. RESULTS: Aging affects the gut microbiota, notably its bacterial composition (with increases in Proteobacteria, Clostridium, and Enterococcus), along with an increased release of lipopolysaccharides and a reduction in short-chain fatty acid production. These changes are linked to signaling pathways involved in muscle atrophy. Despite evidence showing how the gut microbiota-muscle axis influences muscle mass loss during aging, the direct relationship with functional capacity remains limited. However, physical training and diet are non-pharmacological interventions that can modify the gut microbiota. CONCLUSION: The mechanisms underlying the gut microbiota-muscle axis present opportunities for further investigation into aging health and motor performance, particularly concerning nutrition and physical training.

Oxidized yeast glucan alleviates lead-induced toxicity in mice by improving intestinal health to inhibit Pb absorption and reducing kidney oxidative stress.

This study investigated the protective effects and Pb-excretion mechanisms of yeast glucans (YG) with varying oxidation degrees in Pb-exposed mice. Results demonstrated that all three glucans effectively reduced blood lead levels, alleviated inflammation, and mitigated liver damage in Pb-exposed mice, with highly oxidized yeast glucan (OYG2) exhibiting the greatest efficacy. Furthermore, the glucans attenuated Pb-induced oxidative stress and pathological changes in the kidney by elevating glutathione and superoxide dismutase levels, thereby restoring renal excretory function (blood urea nitrogen and creatinine). This restoration contributed to maintaining electrolyte homeostasis (Na+, Cl-, K+) and significantly enhanced lead excretion efficiency via urine. Additionally, the glucans modulated intestinal microbiota balance, promoted short-chain fatty acid production, and repaired Pb-induced intestinal barrier damage by upregulating tight junction proteins (ZO-1, Occludin, Claudin-1). In conclusion, yeast glucans, particularly OYG2, effectively inhibited Pb absorption and facilitated its excretion through feces, highlighting their potential as a therapeutic strategy for lead toxicity.

Characteristics of the Stool, Blood and Skin Microbiome in Rosacea Patients

Several research groups have confirmed that in the pathogenesis of the chronic inflammatory skin disorder rosacea, the composition of the skin and fecal microbiome of affected patients differs from that of healthy individuals. We studied the stool, blood and skin microbiomes of rosacea and control patients using 16S rRNA sequencing. Our goals were to determine 1. whether the microbiome characteristics of rosacea patients differ from that of healthy individuals, 2. whether the change experienced on the skin can be confirmed by alterations in the stool microbiome through the mediation of the blood and 3. whether the metabolic activity of the changed skin, blood or fecal microbiome can play a role in the pathogenesis of rosacea. The rosacea skin microbiome differed significantly from the healthy skin microbiome in both alpha and beta diversity, as well as in the abundance of the genera. Only a few genera abundances differed significantly in stool and blood samples. The most significant representatives of the rosacea skin microbiome, Staphylococcus, Cutibacterium, Corynebacterium and Neisseria, cannot be derived from the feces or blood. The metabolic pathways associated with healthy fecal microbiome contributed to the production of anti-inflammatory short-chain fatty acids. While the increased production of adenosylcobalamin, L-isoleucine and thiazole by the microbiome of healthy skin appeared to have a protective effect, the excessive heme and H2S production experienced in rosacea skin likely contribute to the deterioration of the pathology.

Brazilin-Rich Extract from Caesalpinia sappan L. Attenuated the Motor Deficits and Neurodegeneration in MPTP/p-Induced Parkinson's Disease Mice by Regulating Gut Microbiota and Inhibiting Inflammatory Responses.

Parkinson's disease (PD) is a complicated neurological disease with an unclear pathogenesis. However, dysregulation of gut microbiota and inflammation response play crucial roles in the progression of PD. Caesalpinia sappan L., a traditional medicinal plant containing brazilin as its primary active compound, is known for its anti-inflammatory and neuroprotective properties. However, the impact of C. sappan L. extract (SE) on PD through the regulation of the microbiota-gut-brain axis remains unclear. This study investigated the effects and mechanisms of a 91.23% brazilin-enriched SE on MPTP/p-induced PD mice. Results showed that SE significantly ameliorated motor deficits and protected dopaminergic neurons in PD mice. Additionally, SE reduced oxidative stress and inflammation in the brain. SE also restored gut microbiota by increasing Firmicutes and decreasing Bacteroidetes, alongside enhancing the production of short-chain fatty acids (SCFAs) like butyric acid. Furthermore, SE mitigated intestinal barrier damage by enhancing the expression of ZO-1 and occludin, thereby decreasing lipopolysaccharide leakage and inflammatory factor release. Molecular simulations suggested that butyric acid may maintain intestinal integrity by stabilizing ZO-I and occludin conformations. In conclusion, SE exhibited a protective effect on motor deficits and neurodegeneration in PD by regulating gut microbiota and SCFAs, repairing the intestinal barrier, and mitigating inflammatory responses.

Exploring the Prebiotic Potential of Fermented Astragalus Polysaccharides on Gut Microbiota Regulation In Vitro.

Astragalus polysaccharides (APS) are known for their prebiotic properties, and fermentation by probiotics is a promising strategy to enhance the prebiotic activity of polysaccharides. In this study, Lactobacillus rhamnosus was used to ferment APS, and response surface methodology was applied to optimize the fermentation parameters. The optimal conditions were determined as follows: 10.28% APS addition, 5.83% inoculum, 35.6h of fermentation time, and a temperature of 34.6°C. Additionally, the effects of Fermented Astragalus polysaccharides (FAPS) on human gut microbiota were investigated through in vitro anaerobic incubation. Fecal samples were obtained from 6 healthy volunteers, which were then individually incubated with FAPS. Results demonstrated that FAPS significantly regulated microbial composition and diversity, increasing the abundance of beneficial gut bacteria such as Lactobacillus, E. faecalis, and Brautobacterium, while inhibiting harmful species such as Shigella, Romboutsia, and Clostridium_sensu_stricto_1. Furthermore, FAPS enhanced the production of short-chain fatty acids (SCFAs), which are increasingly recognized to play a role in intestinal homeostasis. These findings suggested that FAPS offers several advantages in terms of increasing beneficial metabolites and regulating gut microbial composition. This study provides valuable insights for expanding the use of plant-derived polysaccharides in the food industry and for developing functional dietary supplements.

Escherichia coli Nissle Improves Short-Chain Fatty Acid Absorption and Barrier Function in a Mouse Model for Chronic Inflammatory Diarrhea.

Defects in SLC26A3, the major colonic Cl-/HCO3- exchanger, result in chloride-rich diarrhea, a reduction in short-chain fatty acid (SCFA)-producing bacteria, and a high incidence of inflammatory bowel disease in humans and in mice. Slc26a3-/- mice are, therefore, an interesting animal model for spontaneous but mild colonic inflammation and for testing strategies to reverse or prevent the inflammation. This study investigates the effect of Escherichia coli Nissle (EcN) application on the microbiome, SCFA production, barrier integrity, and mucosal inflammation in slc26a3-/- mice. In vivo fluid absorption and bicarbonate secretion were assessed in the gut of slc26a3+/+ and slc26a3-/- mice before and during luminal perfusion with 100mM sodium acetate. Age-matched slc26a3+/+ and slc26a3-/- mice were intragastrically gavaged twice daily with 2 × 108 CFU/100 µL of EcN for 21 days. Body weight and stool water content were assessed daily, and stool and tissues were collected for further analysis. Addition of sodium acetate to the lumen of the proximal colon significantly increased fluid absorption and luminal alkalinization in the slc26a3-/- mice. Gavage with EcN resulted in a significant increase in SCFA levels and the expression of SCFA transporters in the slc26a3-/- cecum, the predominant habitat of EcN in mice. This was accompanied by an increase in mucus-producing goblet cells and a decrease in the expression of inflammatory markers as well as host defense antimicrobial peptides. EcN did not improve the overall diversity of the luminal microbiome but resulted in a significant increase in SCFA producers Lachnospiraceae and Ruminococcaceae in the slc26a3-/- feces. These findings suggest that EcN is able to proliferate in the inflamed cecum, resulting in increased microbial SCFA production, decreased inflammation, and improved gut barrier properties. In sufficient dosage, probiotics may thus be an effective anti-inflammatory strategy in the diseased gut.

Changes in Human Colonic Microbiota Promoted by Synbiotic Açai Juice Composed of Gluco-Oligosaccharides, Dextran, and Bifidobacterium breve NRRL B-41408.

The present study evaluates the effects of açai juice containing gluco-oligosaccharides and dextran, fermented by Bifidobacterium breve NRRL B-41408 (synbiotic juice), on the human fecal microbiota. The juice is subjected to simulated digestion and fecal fermentation after production and 42 days of refrigerated storage. High throughput 16S rRNA sequencing and HPLC are used to identify the bacterial cells and metabolites. The results show that the viability of B. breve is stable during the refrigerated storage, indicating that the metabolism is maintained even under low temperatures and pH. Furthermore, gluco-oligosaccharides and dextran prove to be resistant to gastrointestinal conditions and are quickly consumed during fecal fermentation. The synbiotic açai juice enhances the microbial diversity and stimulates the production of short-chain fatty acids (SCFA), including acetate, propionate, and isobutyrate. Elevated propionate levels are directly associated with an increased abundance of Bacteroides thetaiotaomicron, Bacteroides uniformis, Bacteroides xylanisolvens, Bacteroides dorei, Bacteroides stercoris, and Bacteroides massiliensis after 48 h of fermentation. This highlights the potential of synbiotic açai juice as a functional beverage, supported by the significant increase in microbial diversity reflected in the Shannon and Simpson's diversity indexes (Shannon = 116.6%, 117.2%, 125.15%, and 116.02%; Simpson's = 151.86%, 177.22%, 152.5%, and 163.73%).

Metabolic modelling uncovers the complex interplay between fungal probiotics, poultry microbiomes, and diet

BackgroundThe search for alternatives to antibiotic growth promoters in poultry production has increased interest in probiotics. However, the complexity of the interactions between probiotics, gut microbiome, and the host hinders the development of effective probiotic interventions. This study explores metabolic modelling to examine the possibility of designing informed probiotic interventions within poultry production.ResultsGenomic metabolic models of fungi were generated and simulated in the context of poultry gut microbial communities. The modelling approach correlated with short-chain fatty acid production, particularly in the caecum. Introducing fungi to poultry microbiomes resulted in strain-specific and diet-dependent effects on the gut microbiome. The impact of fungal probiotics on microbiome diversity and pathogen inhibition varied depending on the specific strain, resident microbiome composition, and host diet. This context-dependency highlights the need for tailored probiotic interventions that consider the unique characteristics of each poultry production environment.ConclusionsThis study demonstrates the potential of metabolic modelling to elucidate the complex interactions between probiotics, the gut microbiome, and diet in poultry. While the effects of specific fungal strains were found to be context-dependent, the approach itself provides a valuable tool for designing targeted probiotic interventions. By considering the specific characteristics of the host microbiome and dietary factors, this methodology could guide the deployment of effective probiotics in poultry production. However, the current work relies on computational predictions, and further in vivo validation studies are needed to confirm the efficacy of the identified probiotic candidates. Nonetheless, this study represents a significant step in using metabolic models to inform probiotic interventions in the poultry industry.8kJrTXnG6ubMgktD71ewfiVideo

Nopalea cochenillifera Regulates the Immune Response and Gut Microbiota in Mice.

Cactus contains dietary fiber and minerals and is expected to have preventive effects against diabetes, arteriosclerosis, and other diseases. Additionally, cactus intake induces the production of short-chain fatty acids derived from the gut microbiota, which might influence immune functions. In this study, we examined the effects of a cactus (Nopalea cochenillifera: NC)-supplemented diet on lipopolysaccharide (LPS)-induced immune responses and intestinal barrier function. Male C3H/HeN mice were randomly divided into three groups-no fiber (NF), cellulose-containing fiber (Cellu), and cactus-added (NC) diets-for 6 weeks. The TNF-α and IL-10 responses to LPS, antibody titers, and intestinal barrier function, as well as the fecal microbiota, were analyzed. The plasma TNF-α but not the IL-10 concentrations were significantly higher in the NC group than in the NF and Cellu groups. Furthermore, the plasma IgG antibody titers were significantly higher in the NC group than in the other groups. The NC group showed higher mucin content and IgA antibody titers in their feces compared with the Cellu group. The succinate and lactate contents, which induce a reduction in TNF-α secretion by macrophages, in the cecum of the NC group were significantly lower than those in the Cellu and NF groups. In contrast, the butyrate content was significantly higher in the cecum of the NC group compared to that of the Cellu group, with a significantly higher relative abundance of butyrate-producing bacteria. Taken together, we found that cactus intake regulates innate and adaptive immune function via the gut microbiota in mice. Therefore, cactus supplementation might serve as a strategy to develop novel functional foods with dietary fiber.

In Vitro Evaluation of Probiotic Activities and Anti-Obesity Effects of Enterococcus faecalis EF-1 in Mice Fed a High-Fat Diet.

This research sought to assess the anti-obesity potential of Enterococcus faecalis EF-1. An extensive and robust in vitro methodology confirmed EF-1's significant potential in combating obesity, probably due to its excellent gastrointestinal tract adaptability, cholesterol-lowering property, bile salt hydrolase activity, α-glucosidase inhibition, and fatty acid absorption ability. Moreover, EF-1 exhibited antimicrobial activity against several pathogenic strains, lacked hemolytic activity, and was sensitive to all antibiotics tested. To further investigate EF-1's anti-obesity properties in vivo, a high-fat diet (HFD) was used to induce obesity in C57BL/6J mice. Treatment with EF-1 (2 × 109 CFU/day) mitigated HFD-induced body weight gain, reduced adipose tissue weight, and preserved liver function. EF-1 also ameliorated obesity-associated microbiota imbalances, such as decreasing the Firmicutes/Bacteroidetes ratio and boosting the levels of bacteria (Faecalibacterium, Mucispirillum, Desulfovibrio, Bacteroides, and Lachnospiraceae_NK4A136_group), which are responsible for the generation of short-chain fatty acids (SCFAs). Concurrently, the levels of total SCFAs were elevated. Thus, following comprehensive safety and efficacy assessments in vitro and in vivo, our results demonstrate that E. faecalis EF-1 inhibits HFD-induced obesity through the regulation of gut microbiota and enhancing SCFA production. This strain appears to be a highly promising candidate for anti-obesity therapeutics or functional foods.

Beneficial modulation of the gut microbiome by leachates of Penicillium purpurogenum in the presence of clays: A model for the preparation and efficacy of historical Lemnian Earth.

The experiments presented here are based on the reconfiguration of an ancient medicine, Lemnian Earth (LE) (terra sigillata, stamped earth, sphragis), an acclaimed therapeutic clay with a 2500-year history of use. Based on our hypothesis that LE was not a natural material but an artificially modified one involving a clay-fungus interaction, we present results from experiments involving the co-culture of a common fungus, Penicillium purpurogenum (Pp), with two separate clay slurries, smectite and kaolin, which are the principal constituents of LE. Our results show: (a) the leachate of the Pp+smectite co-culture is antibacterial in vitro, inhibiting the growth of both Gram-positive and Gram-negative bacteria; (b) in vivo, supplementation of regular mouse diet with leachates of Pp+smectite increases intestinal microbial diversity; (c) Pp+kaolin does not produce similar results; (d) untargeted metabolomics and analysis of bacterial functional pathways indicates that the Pp+smectite-induced microbiome amplifies production of short-chain fatty acids (SCFAs) and amino acid biosynthesis, known to modulate intestinal and systemic inflammation. Our results suggest that the combination of increased microbial diversity and SCFA production indicates beneficial effects on the host microbiome, thus lending support to the argument that the therapeutic properties of LE may have been based on the potential for modulating the gut microbiome. Our experiments involving reconfigured LE open the door to future research into small molecule-based sources for promoting gut health.

Galacto-oligosaccharides alone and combined with lactoferrin impact the Kenyan infant gut microbiota and epithelial barrier integrity during iron supplementation in vitro

Aim: Iron supplementation to African weaning infants was associated with increased enteropathogen levels. While cohort studies demonstrated that specific prebiotics inhibit enteropathogens during iron supplementation, their mechanisms remain elusive. Here, we investigated the in vitro impact of galacto-oligosaccharides (GOS) and iron-sequestering bovine lactoferrin (bLF) alone and combined on the gut microbiota of Kenyan infants during low-dose iron supplementation. Methods: Different doses of iron, GOS, and bLF were first screened during batch fermentations (n = 3), and the effect of these factors was studied on microbiota community structure and activity in the new Kenyan infant continuous intestinal PolyFermS model. The impact of different fermentation treatments on barrier integrity, enterotoxigenic Escherichia coli (ETEC) infection, and inflammatory response was assessed using a transwell co-culture of epithelial and immune cells. Results: A dose-dependent increase in short-chain fatty acid (SCFA) production, Bifidobacterium and Lactobacillus /Leuconostoc /Pediococcus (LLP) growth was detected with GOS alone and combined with bLF during iron supplementation in batches. This was confirmed in the continuous PolyFermS model, which also showed a treatment-induced inhibition of opportunistic pathogens C. difficile and C. perfringens . In all tests, supplementation of iron alone and combined with bLF did not have a significant effect on microbiota composition and activity. We observed a strengthening of the epithelial barrier and a decrease in cell death and pro-inflammatory response during ETEC infection with microbiota fermentation supernatants from iron + GOS, iron + bLF, and iron + GOS + bLF treatments compared to iron alone. Conclusion: Overall, beneficial effects on infant gut microbiota were shown using advanced in vitro models for GOS alone and combined with bLF during low-dose iron supplementation.

Screening study of hydroxytyrosol metabolites from in vitro fecal fermentation and their interaction with intestinal barrier repair receptor AhR.

Olive oil polyphenol hydroxytyrosol (HT) significantly repairs intestinal barrier function, but its absorption in the stomach and small intestine is limited. The metabolites of unabsorbed HT that reach the colon are crucial, yet their effects on colonic microbiota and intestinal barrier repair remain unclear. This study utilized in vitro simulated digestion and colonic fecal fermentation to investigate HT's digestion and fermentation. Results indicated that 79.25% of HT potentially reached the colon intact. Further 16S rDNA, targeted, and untargeted metabolomics analyses showed that HT can be decomposed by colonic microbiota, producing aromatic hydrocarbon metabolites and regulating gut microbiota structure. It promotes the growth of gut microbiota, such as Bacteroides, Faecalibacterium, Klebsiella, and Lachnospira, which degrade HT. Additionally, HT's intervention conversely affected the production of tryptophan-derived metabolites and short-chain fatty acids (SCFAs). Subsequently, computer-simulated molecular docking technology was used to simulate the binding affinity between HT metabolites and derived metabolites and the intestinal barrier repair-related receptor aryl hydrocarbon receptor (AhR). Indole-3-acetic acid, indole-3-acetaldehyde, skatole, kynurenine, and homovanillic acid could tightly bind to the amino acid residues of the AhR receptor, with binding energies all ˂-6.0kcal/mol, suggesting that these metabolites may enhance the intestinal barrier function through the AhR signaling pathway.

Radiation-Resistant Bacteria Deinococcus radiodurans-Derived Extracellular Vesicles as Potential Radioprotectors.

The increasing use of radiation presents a risk of radiation exposure, making the development of radioprotectors necessary. In the previous study, it is investigated that Deinococcus radiodurans (R1-EVs) exert the antioxidative properties. However, the radioprotective activity of R1-EVs remains unclear. In the present study, the protective effects of R1-EVs against total body irradiation (TBI)-induced acute radiation syndrome (ARS) are investigated. To assess R1-EVs' radioprotective efficacy, ARS is induced in mice with 8 Gy of TBI, and protection against hematopoietic (H)- and gastrointestinal (GI)-ARS is evaluated. The survival rate of irradiated mice group decreases substantially after irradiation. In contrast, pretreatment with R1-EVs increases the survival rates of the mice. The administration of R1-EVs provides effective protection against radiation-induced death of bone marrow cells and splenocytes by scavenging reactive oxygen species (ROS). Additionally, R1-EVs protect both intestinal stem and epithelial cells from radiation-induced apoptosis. R1-EVs stimulate the production of short-chain fatty acids in the gastrointestinal tract, suppress proinflammatory cytokines, and increase regulatory T cells in pretreated mice versus the irradiation-only group. Proteomic analysis shows that the R1-EV proteome is significantly enriched with proteins involved in oxidative stress response. These findings highlight R1-EVs as potent radioprotectors with applications against radiation damage and ROS-mediated diseases.

Lactobacillus acidophilus 6074 Fermented Jujube Juice Ameliorated DSS-induced Colitis via Repairing Intestinal Barrier, Modulating Inflammatory Factors, and Gut Microbiota.

Lactobacillus acidophilus L. acidophilus Lactobacillus, Bifidobacterium, and Akkermansia, This study aimed to explore the ameliorative effects and underlying mechanisms of oral administration Lactobacillus acidophilus 6074 fermented jujube juice (LAFJ) on dextran sulfate sodium (DSS)-induced colitis in mice. In this study, jujube juice was used as a substrate and fermented by L. acidophilus 6074 to investigate its effects on gut microbiota, intestinal barrier function, oxidative stress, inflammatory factors, and short-chain fatty acids (SCFAs) in mice with colitis and to reveal its potential mechanism for alleviating colitis. The results demonstrated that fermentation caused significant changes in the nutrients and nonnutrients of jujube juice, mainly in organic acids (malic acid, lactic acid, citric acid, and succinic acid) and free amino acids (Thr, Met, Ser, Ile, and Lys). High-dose LAFJ (20 mL/kg/day) significantly reduced the disease activity index (DAI), improved histopathological morphology, and increased colon length in colitis mice. LAFJ alleviated colon damage and preserved the integrity of the colonic mucosal barrier by promoting the expression of colonic tight junction proteins occludin, claudin-1, and zonula occluden-1 (ZO-1). Furthermore, LAFJ inhibited the production of proinflammatory factors and attenuated oxidative stress. Gut microbiota of mice revealed that LAFJ increased beneficial bacteria such as Lactobacillus, Bifidobacterium, and Akkermansia, promoted the production of SCFAs, and inhibited the growth of harmful microorganisms. Overall, LAFJ could reshape and restore gut microbiota imbalance caused by intestinal inflammation and alleviate the development of colitis, which may become a novel dietary intervention.

Gut Dysbiosis and Probiotic Therapy in Chronic Kidney Disease: A Comprehensive Review.

Chronic kidney disease (CKD) is a multifactorial disease affecting more than 13.4% of the world's population and is a growing public health problem. It is silent in its early stages and leads to irreversible kidney damage as the disease progresses. A key factor in this progression is the bidirectional relationship between CKD and gut dysbiosis, which creates an imbalance that promotes the accumulation of uremic toxins (UTs), contributing to renal fibrosis, endothelial dysfunction, and decreased glomerular filtration rate. In addition, CKD itself exacerbates gut dysbiosis by altering the composition of the gut microbiota (GM) and promoting the growth of pathogenic microorganisms. Therefore, it is crucial to explore new therapeutic strategies, and the use of probiotics and synbiotics has shown promise in modulating the GM. Numerous preclinical studies have shown that the use of probiotics in CKD has a beneficial effect on the kidney by reducing UTs, apoptosis, inflammation, and oxidative stress. Probiotic treatment has also been associated with restoration of intestinal integrity, modulation of microbial composition and diversity, and increased production of short-chain fatty acids (SCFAs). These positive results have also been observed in patients at different stages of CKD, where the use of probiotics and/or synbiotics was able to improve creatinine levels and uremic parameters and alleviate abdominal discomfort, in addition to modulating GM and reducing serum endotoxin levels. Although recent studies have explored the benefits of probiotics in the treatment of CKD, further research is needed to determine their long-term efficacy and clinical relevance. This review focuses on the factors driving gut dysbiosis in CKD, its role in disease progression, and the potential of probiotics as a therapeutic strategy.

Impact of smoking on gut microbiota and short-chain fatty acids in human and mice: Implications for COPD.

We aimed to elucidate the dynamic changes in short-chain fatty acids (SCFA) produced by the gut microbiota following smoking exposure and their role in chronic obstructive pulmonary disease (COPD) pathogenesis. SCFA concentrations were measured in human plasma, comparing non-smokers (n=6) and smokers (n=12). Using a mouse COPD model induced by cigarette smoke exposure or elastase-induced emphysema, we modulated SCFA levels through dietary interventions and antibiotics to evaluate their effects on inflammation and alveolar destruction. Human smokers showed lower plasma SCFA concentrations than non-smokers, with plasma propionic acid positively correlating with forced expiratory volume in 1s/forced vital capacity. Three-month smoking-exposed mice demonstrated altered gut microbiota and significantly reduced fecal SCFA concentrations compared to air-exposed controls. In these mice, a high-fiber diet increased fecal SCFAs and mitigated inflammation and alveolar destruction, while antibiotics decreased fecal SCFAs and exacerbated disease features. However, in the elastase-induced model, fecal SCFA concentration remained unchanged, and high-fiber diet or antibiotic interventions had no significant effect. These findings suggest that smoking exposure alters gut microbiota and SCFA production through its systemic effects. The anti-inflammatory properties of SCFAs may play a role in COPD pathogenesis, highlighting their potential as therapeutic targets.

Modulation of Gut Microbiota by the Complex of Caffeic Acid and Corn Starch.

To understand the impact of different types of polyphenol-starch complexes on digestibility and gut microbiota, caffeic acid (CA) and corn starch (CS) complexes were prepared by coheating and high-pressure homogenization. The resistant starch content in CS coheated with CA (HCS-CA) and HCS-CA after high-pressure homogenization (HCS-CA-HPH) was 47.75 and 56.65%, respectively. Fourier transform infrared spectroscopy and X-ray diffraction analysis revealed hydrogen bonding in coheated samples and enhanced V-complex formation with high-pressure homogenization. The in vitro-digested complexes were of the B + V type, with higher relative crystallinity and short-range ordering of HCS-CA-HPH. Fermentation of the digested complex with human feces increased the yield of acetate, butyrate, and total short-chain fatty acids (SCFAs), which was more pronounced for HCS-CA-HPH. HCS-CA increased torques-Ruminococcaceae abundance, while HCS-CA-HPH boosted Prevotella, Roseburia, Lachnospiraceae, and Lachnospiraceae-NK4A136. Overall, CA and CS complexes enhanced beneficial bacteria and increased SCFA production.

Bacteroides thetaiotaomicron enhances oxidative stress tolerance through rhamnose-dependent mechanisms.

This study probes into the unique metabolic responses of Bacteroides thetaiotaomicron (B. thetaiotaomicron), a key player in the gut microbiota, when it metabolizes rhamnose rather than typical carbohydrates. Known for its predominant role in the Bacteroidetes phylum, B. thetaiotaomicron efficiently breaks down poly- and mono-saccharides into beneficial short-chain fatty acids (SCFAs), crucial for both host health and microbial ecology balance. Our research focused on how this bacterium's SCFA production differ when utilizing various monosaccharides, with an emphasis on the oxidative stress responses triggered by rhamnose consumption. Notably, rhamnose use results in unique metabolic byproducts, including substantial quantities of 1,2-propanediol, which differs significantly from those produced during glucose metabolism. Our research reveals that rhamnose consumption is associated with a reduction in reactive oxygen species (ROS), signifying improved resistance to oxidative stress compared to other sugars. This effect is attributed to specific gene expressions within the rhamnose metabolic pathway. Notably, overexpression of the rhamnose metabolism regulator RhaR in B. thetaiotaomicron enhances its survival in oxygen-rich conditions by reducing hydrogen peroxide production. This reduction is linked to decreased expression of pyruvate:ferredoxin oxidoreductase (PFOR). In contrast, experiments with a rhaR-deficient strain demonstrated that the absence of RhaR causes B. thetaiotaomicron cells growing on rhamnose to produce ROS at rates comparable to cells grown on glucose, therefore, losing their advantage in oxidative resistance. Concurrently, the expression of PFOR is no longer suppressed. These results indicate that when B. thetaiotaomicron is cultured in a rhamnose-based medium, RhaR can restrain the expression of PFOR. Although PFOR is not a primary contributor to intracellular ROS production, its sufficient inhibition does reduce ROS levels to certain extent, consequently improving the bacterium's resistance to oxidative stress. It highlights the metabolic flexibility and robustness of microbes in handling diverse metabolic challenges and oxidative stress in gut niches through the consumption of alternative carbohydrates.

Combination of Inulin and Resistant Dextrin Has Superior Prebiotic Effects and Reduces Gas Production During In Vitro Fermentation of Fecal Samples from Older People.

Older people are more susceptible to deterioration of the gut microbiota. Prebiotics help improve the gut microbiota. Inulin, a major prebiotic, stimulates the growth of Bifidobacterium; however, it produces a large amount of gas, which leads to abdominal symptoms. In this study, in vitro fecal fermentation was performed using fecal samples from seven older people (mean subject age, 73.4 years; five men and two women) to examine whether combining inulin with another prebiotic material, resistant dextrin, could lead to decreased gas production and show prebiotic effects. The Bifidobacterium counts and short-chain fatty acid production did not differ significantly between the inulin 0.5% group and the inulin 0.25% plus resistant dextrin 0.25% combination group. However, the inulin 0.25% plus resistant dextrin 0.25% combination group had lower gas production than the inulin 0.5% group (p < 0.10). Furthermore, compared with the inulin 0.5% group, the 0.25% combination group showed significantly greater gut microbiota diversity and tended toward a lower pH in the fermentation medium at the end of fermentation (p = 0.09). These effects are believed to be due to the combination of inulin, which is highly selective for Bifidobacterium and rapidly utilized by the gut microbiota, and resistant dextrin, which is slowly utilized by various bacterial genera. These findings suggest that the inulin plus resistant dextrin combination has superior prebiotic effects in older people and causes less gas production than inulin alone.