Role of Short Chain Fatty Acids and Apolipoproteins in the Regulation of Eosinophilia-Associated Diseases

Eosinophils are key components of our host defense and potent effectors in allergic and inflammatory diseases. Once recruited to the inflammatory site, eosinophils release their cytotoxic granule proteins as well as cytokines and lipid mediators, contributing to parasite clearance but also to exacerbation of inflammation and tissue damage. However, eosinophils have recently been shown to play an important homeostatic role in different tissues under steady state. Despite the tremendous progress in the treatment of eosinophilic disorders with the implementation of biologics, there is an unmet need for novel therapies that specifically target the cytotoxic effector functions of eosinophils without completely depleting this multifunctional immune cell type. Recent studies have uncovered several endogenous molecules that decrease eosinophil migration and activation. These include short chain fatty acids (SCFAs) such as butyrate, which are produced in large quantities in the gastrointestinal tract by commensal bacteria and enter the systemic circulation. In addition, high-density lipoprotein-associated anti-inflammatory apolipoproteins have recently been shown to attenuate eosinophil migration and activation. Here, we focus on the anti-pathogenic properties of SCFAs and apolipoproteins on eosinophil effector function and provide insights into the potential use of SCFAs and apolipoproteins (and their mimetics) as effective agents to combat eosinophilic inflammation.

Butyrate Prevents TGF-β1-Induced Alveolar Myofibroblast Differentiation and Modulates Energy Metabolism

Idiopathic pulmonary fibrosis (IPF) is a serious lung disease characterized by excessive collagen matrix deposition and extracellular remodeling. Signaling pathways mediated by fibrotic cytokine transforming growth factor β1 (TGF-β1) make important contributions to pulmonary fibrosis, but it remains unclear how TGF-β1 alters metabolism and modulates the activation and differentiation of pulmonary fibroblasts. We found that TGF-β1 lowers NADH and NADH/NAD levels, possibly due to changes in the TCA cycle, resulting in reductions in the ATP level and oxidative phosphorylation in pulmonary fibroblasts. In addition, we showed that butyrate (C4), a short chain fatty acid (SCFA), exhibits potent antifibrotic activity by inhibiting expression of fibrosis markers. Butyrate treatment inhibited mitochondrial elongation in TGF-β1-treated lung fibroblasts and increased the mitochondrial membrane potential (MMP). Consistent with the mitochondrial observations, butyrate significantly increased ADP, ATP, NADH, and NADH/NAD levels in TGF-β1-treated pulmonary fibroblasts. Collectively, our findings indicate that TGF-β1 induces changes in mitochondrial dynamics and energy metabolism during myofibroblast differentiation, and that these changes can be modulated by butyrate, which enhances mitochondrial function.

Effects of Anthocyanin on Intestinal Health: A Systematic Review

Intestinal health relies on the association between the mucosal immune system, intestinal barrier and gut microbiota. Bioactive components that affect the gut microbiota composition, epithelial physical barrier and intestinal morphology were previously studied. The current systematic review evaluated evidence of anthocyanin effects and the ability to improve gut microbiota composition, their metabolites and parameters of the physical barrier; this was conducted in order to answer the question: "Does food source or extract of anthocyanin promote changes on intestinal parameters?". The data analysis was conducted following the PRISMA guidelines with the search performed at PubMed, Cochrane and Scopus databases for experimental studies, and the risk of bias was assessed by the SYRCLE tool. Twenty-seven studies performed in animal models were included, and evaluated for limitations in heterogeneity, methodologies, absence of information regarding allocation process and investigators' blinding. The data were analyzed, and the anthocyanin supplementation demonstrated positive effects on intestinal health. The main results identified were an increase of Bacteroidetes and a decrease of Firmicutes, an increase of short chain fatty acids production, a decrease of intestinal pH and intestinal permeability, an increase of the number of goblet cells and tight junction proteins and villi improvement in length or height. Thus, the anthocyanin supplementation has a potential effect to improve the intestinal health. PROSPERO (CRD42020204835).

Polyphenols from Arctium lappa L ameliorate doxorubicin-induced heart failure and improve gut microbiota composition in mice

In this study, the ameliorative effect of purified polyphenols from Arctium lappa L (ALPP) on doxorubicin (DOX)-induce heart failure was investigated. Results indicated that ALPP pretreatment significantly reduced the activities of casein kinase and lactate dehydrogenase, lowered the levels of inflammatory indexes (TNF-α and NO), and alleviated antioxidant stress in DOX-induce mice, thus leading to a reduced heart failure syndrome. In addition, according to 16s high-throughput sequencing, the increased abundance of Lactobacillaceae, Muribaculaceae, and Ruminococcaceae and the decreased abundance of Proteobacteria, Enterobacteriaee, and Escherichia_Shigella were observed in ALPP treatment group. ALPP could significantly enhance the abundance of bacteria producing short chain fatty acids (SCFAs) and then promote the increase of SCFAs. Consequently, ALPP might be a therapeutic alternative in the treatment of DOX-induced heart failure. PRACTICAL APPLICATIONS: The effect of Arctium lappa L (ALPP) on doxorubicin (DOX)-induced heart failure was investigated. It provided experimental basis for further studies on the biological activity of polyphenols from ALPP. The results demonstrated that ALPP could significantly ameliorate DOX-induced heart failure and improve the gut microbiota composition. The obtained results could provide the potential application of ALPP as an alternative therapy for heart failure in the functional food industry.

The Gut Microbiome and Cardiovascular Disease

Cardiovascular disease (CVD) is currently the leading cause of death worldwide. Although many well-known conditions cause CVD, recent research has suggested that alterations to the gut microbiome may also promote CVD. The gastrointestinal tract houses trillions of bacteria, some of which in large numbers are considered to be part of a healthy gut microbiome profile. These "good" bacteria have the ability to process and digest complex carbohydrates into short-chain fatty acids (SFCA). These SCFA serve as signaling molecules, immune-modulating molecules, and sources of energy. However, with gut dysbiosis, there is an overgrowth of certain bacteria and these bacteria overly produce phosphatidylcholine, choline, and carnitine into the waste product trimethylamine-N-oxide (TMAO). Elevated TMAO levels are associated with an increased risk of atherosclerosis, myocardial infarction, thrombosis, and stroke. Therefore, introducing therapeutic interventions that alter a dysbiotic gut profile back to a healthy gut microbiome may be the key to reducing the incidence of cardiovascular disease in some conditions. The purpose of this review is to critically examine and consolidate the relevant information bearing on this concept. Our goal is to provide the informational framework for the possible use of microbiome modification as an optional therapeutic modality.

Colonic Dopaminergic Neurons Changed Reversely With Those in the Midbrain via Gut Microbiota-Mediated Autophagy in a Chronic Parkinson's Disease Mice Model

The role of gut-brain axis in the pathogenesis of Parkinson's disease (PD) have become a research hotspot, appropriate animal model to study gut-brain axis in PD is yet to be confirmed. Our study employed a classical PD mice model achieved by chronic MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) injection to study concurrent changes of dopaminergic neurons in the midbrain and the colon of mice. Our results showed such a PD model exhibited apparent locomotor deficits but not gastrointestinal dysfunction. Tyrosine hydroxylase expressions and dopamine content reduced greatly in the substantia nigra pars compacta (SNpc) or striatum, but increased in the colon of PD mice. Mechanism investigation indicated autophagy activity and apoptosis were stimulated in the SNpc, but inhibited in the colon of PD mice. Interplay of gut microbiota (GM) and autophagy in response to chronic MPTP injection led to GM dysbiosis and defective autophagy in mice colon. Meanwhile, fecal short chain fatty acids (SCFAs), acetate and propionate in particular, declined greatly in PD mice, which could be attributed to the decreased bacteria abundance of phylum Bacteroidetes, but increased abundance of phylum Firmicutes. GM dysbiosis derived fecal SCFAs might be one of the mediators of downregulated autophagy in the colon of PD mice. In conclusion, colonic dopaminergic neurons changed in the opposition direction with those in the midbrain via GM dysbiosis-mediated autophagy inhibition followed by suppressed apoptosis in response to chronic MPTP injection. Such a chronic PD mice model might not be an ideal model to study role of gut-brain axis in PD progression.

One Month of Classic Therapeutic Ketogenic Diet Decreases Short Chain Fatty Acids Production in Epileptic Patients

Ketogenic diet (KD), a high fat and very low carbohydrates diet, is used worldwide for the treatment of drug resistant epilepsy but, due to its composition, it might exert an impact on gut health. Even though data of KD effects on intestinal microbiota changes are recently emerging, its influence on the gut environment has been scarcely addressed so far. The aim of this study was to investigate whether 1 month of KD affects the gut environment in epileptic patients, by analyzing short chain fatty acids (SCFA) production and fecal water toxicity. A total of seven patients were enrolled. Stool samples were collected before (T0) and after 1 month of KD (4:1 ketogenic ratio) (T1). SCFA were determined by GC-FID and fecal water toxicity in Caco-2 cell culture by comet assay. Concentrations of SCFA significantly decreased after KD (p < 0.05): in particular, we found a 55% reduction of total SCFA level, a 64% reduction of acetate, 33% of propionate, and 20% of butyrate (p < 0.05). Cytotoxicity of fecal water extracted from stool samples was not significantly altered by diet, while genotoxicity was slightly decreased after KD (p < 0.05). Genotoxicity values were consistent with data previously obtained from a healthy Italian population. The present study suggests that 1 month of KD significantly reduce SCFA production. Since SCFA produced by gut microbiota exert many health promoting effects on either the gut environment or human metabolism, these results open a new branch of investigation into KD effects.

Enrichment of Food With Tannin Extracts Promotes Healthy Changes in the Human Gut Microbiota

Food and food bioactive components are major drivers of modulation of the human gut microbiota. Tannin extracts consist of a mix of bioactive compounds, which are already exploited in the food industry for their chemical and sensorial properties. The aim of our study was to explore the viability of associations between tannin wood extracts of different origin and food as gut microbiota modulators. 16S rRNA amplicon next-generation sequencing (NGS) was used to test the effects on the gut microbiota of tannin extracts from quebracho, chestnut, and tara associated with commercial food products with different composition in macronutrients. The different tannin-enriched and non-enriched foods were submitted to in vitro digestion and fermentation by the gut microbiota of healthy subjects. The profile of the short chain fatty acids (SCFAs) produced by the microbiota was also investigated. The presence of tannin extracts in food promoted an increase of the relative abundance of the genus Akkermansia, recognized as a marker of a healthy gut, and of various members of the Lachnospiraceae and Ruminococcaceae families, involved in SCFA production. The enrichment of foods with tannin extracts had a booster effect on the production of SCFAs, without altering the profile given by the foods alone. These preliminary results suggest a positive modulation of the gut microbiota with potential benefits for human health through the enrichment of foods with tannin extracts.

The Intestinal Fatty Acid-Enteroendocrine Interplay, Emerging Roles for Olfactory Signaling and Serotonin Conjugates

Intestinal enteroendocrine cells (EECs) respond to fatty acids from dietary and microbial origin by releasing neurotransmitters and hormones with various paracrine and endocrine functions. Much has become known about the underlying signaling mechanisms, including the involvement of G-protein coupled receptors (GPCRs), like free fatty acids receptors (FFARs). This review focusses on two more recently emerging research lines: the roles of odorant receptors (ORs), and those of fatty acid conjugates in gut. Odorant receptors belong to a large family of GPCRs with functional roles that only lately have shown to reach beyond the nasal-oral cavity. In the intestinal tract, ORs are expressed on serotonin (5-HT) and glucagon-like-peptide-1 (GLP-1) producing enterochromaffin and enteroendocrine L cells, respectively. There, they appear to function as chemosensors of microbiologically produced short-, and branched-chain fatty acids. Another mechanism of fatty acid signaling in the intestine occurs via their conjugates. Among them, conjugates of unsaturated long chain fatty acids and acetate with 5-HT, N-acyl serotonins have recently emerged as mediators with immune-modulatory effects. In this review, novel findings in mechanisms and molecular players involved in intestinal fatty acid biology are highlighted and their potential relevance for EEC-mediated signaling to the pancreas, immune system, and brain is discussed.

Bioanalysis of plasma acetate levels without derivatization by LC-MS/MS

Background: The acetate ion has important physiological functions and important therapeutic applications. A rapid LC-MS/MS method is described to measure acetate ions in human plasma without chemical derivatization. Materials & methods: A 200 μl sample was spiked with the internal standard 1,2-¹³C-acetate and proteins precipitated with trichloroacetic acid. The supernatant was recovered and separated under acidic conditions on a C18-column. The eluent was alkalinized by post-column infusion of methanolic ammonium hydroxide. Acetate ions were monitored on a low resolution mass spectrometer in negative ion mode. Results: Method was validated for accuracy and precision with a lower limit of quantitation of 9.7 μM and linear dynamic range up to 339.6 μM. Conclusion: The method is open for analytical improvement and adapts with metabolomic and pharmacometabolomic studies on chemicals of similar nature.

[Long-chain fatty acids and short-chain fatty acids in exhaled breath condensate of patients with chronic obstructive pulmonary disease]

In present study we performed gas-liquid chromatographic analysis of exhaled breath condensate to measure volatile fatty acids (C2 - acetic, C3 - propionic, C4 - butanoic, isoC4 - isobutyric, C5 - valerianic, C6 - caproic, C7 - heptanoic) and fatty acid with a long aliphatic chain (C14:0 - myristic, C15:0 - pentadecanoic, C16:0 - palmitic, C16:1 - palmitooleic, C17:0 - heptadecanoic, C17:1 - heptadecenoic, C18:0 - stearic, C18:1 - oleic, C18:2 - linolenic, C18:3ω3 - α-linolenic, C20:4ω6 - arachidonic) in patients suffering from moderate chronic obstructive pulmonary disease (2nd stage, GOLD). We revealed the increase of the total amount of short chain fatty acids (C2, C3, C4, C5) and polyunsaturated (C18:2, C20:4ω6) fatty acids, meanwhile the level of saturated fatty acids (C16:0, C17:0, C18:0) decreased.

Evolution of the Gut Microbiota and Its Fermentation Characteristics of Ningxiang Pigs at the Young Stage

Simple Summary

The current study described the evolution of the gut microbiota of an indigenous pig breeds, Ningxiang pigs (NXP), from one week before weaning to the end of nursery. The results showed that dietary factors mainly drove the evolution of the microbial community of NXP. Our results contributed to a better understanding of the evolutionary characteristics and influencing factors of the gut microbiota of indigenous pig breeds.

Abstract

The current study aimed to investigate the evolution of gut microbiota and its influencing factors for NXP in youth. The results showed that Shannon index increased from d 21 to d 28 whereas the ACE index increased from d 21 until d 60. Firmicutes, mainly Lactobacillus dominated on d 21. The Bacteroides and Spirochetes showed highest relative abundance on d 28. Fiber-degrading bacteria, mainly Prevotellaceae, Lachnospiraceae, Ruminococcaceae, Muribaculaceae, and Oscillospiraceae_UCG−002, dominated the microbial communities at d 28 and d 35. The microbial communities at d 60 and d 75 contained more Clostridium_sensu_stricto_1, Terrisporobacter and Oscillospiraceae_UCG−005 than other ages, which had significantly positive correlations with acetate and total SCFAs concentration. In conclusion, the evolution of gut microbiota was mainly adapted to the change of dietary factors during NXP growth. The response of fiber-degrading bacteria at different stages may help NXP better adapt to plant-derived feeds.

Non-Digestible Oligosaccharides and Short Chain Fatty Acids as Therapeutic Targets against Enterotoxin-Producing Bacteria and Their Toxins

Enterotoxin-producing bacteria (EPB) have developed multiple mechanisms to disrupt gut homeostasis, and provoke various pathologies. A major part of bacterial cytotoxicity is attributed to the secretion of virulence factors, including enterotoxins. Depending on their structure and mode of action, enterotoxins intrude the intestinal epithelium causing long-term consequences such as hemorrhagic colitis. Multiple non-digestible oligosaccharides (NDOs), and short chain fatty acids (SCFA), as their metabolites produced by the gut microbiota, interact with enteropathogens and their toxins, which may result in the inhibition of the bacterial pathogenicity. NDOs characterized by diverse structural characteristics, block the pathogenicity of EPB either directly, by inhibiting bacterial adherence and growth, or biofilm formation or indirectly, by promoting gut microbiota. Apart from these abilities, NDOs and SCFA can interact with enterotoxins and reduce their cytotoxicity. These anti-virulent effects mostly rely on their ability to mimic the structure of toxin receptors and thus inhibiting toxin adherence to host cells. This review focuses on the strategies of EPB and related enterotoxins to impair host cell immunity, discusses the anti-pathogenic properties of NDOs and SCFA on EPB functions and provides insight into the potential use of NDOs and SCFA as effective agents to fight against enterotoxins.

Can we modulate the breastfed infant gut microbiota through maternal diet?

Initial colonisation of the infant gut is robustly influenced by regular ingestion of human milk, a substance that contains microbes, microbial metabolites, immune proteins, and oligosaccharides. Numerous factors have been identified as potential determinants of the human milk and infant gut microbiota, including maternal diet; however, there is limited data on the influence of maternal diet during lactation on either of these. Here, we review the processes thought to contribute to human milk and infant gut bacterial colonisation and provide a basis for considering the role of maternal dietary patterns during lactation in shaping infant gut microbial composition and function. Although only one observational study has directly investigated the influence of maternal diet during lactation on the infant gut microbiome, data from animal studies suggests that modulation of the maternal gut microbiota, via diet or probiotics, may influence the mammary or milk microbiota. Additionally, evidence from human studies suggests that the maternal diet during pregnancy may affect the gut microbiota of the breastfed infant. Together, there is a plausible hypothesis that maternal diet during lactation may influence the infant gut microbiota. If substantiated in further studies, this may present a potential window of opportunity for modulating the infant gut microbiome in early life.

Influence of a Biotechnologically Produced Oyster Mushroom (Pleurotus sajor-caju) on the Gut Microbiota and Microbial Metabolites in Obese Zucker Rats

Mushrooms are a rich source of dietary fiber. This study aimed to characterize the modulation of colonic microbiota in Zucker rats after supplementing their diet with a biotechnologically produced oyster mushroom (Pleurotus sajor-caju). Microbiota composition and short chain fatty acids (SCFAs) in the colon and bile acids in the plasma of the rats were analyzed to assess the effects of P. sajor-caju supplementation on the microbiota in the colon and its interplay with the host in the event of hepatic steatosis. Microbiota profiles were distinctly modulated by P. sajor-caju supplementation between the obese control rats and the obese rats fed the 5% P. sajor-caju-supplemented diet. P. sajor-caju enhanced the growth of SCFAs-producing bacterial genera, including Faecalibaculum, Bifidobacterium, Roseburia, and Blautia, and decreased the relative abundance of the pathogenic genus Escherichia-Shigella. This was also accompanied by distinct changes in the concentrations of bile acids in the plasma and concentrations of SCFAs in the colon, supporting the initial potentiality of P. sajor-caju as a prebiotic in cases of hepatic steatosis and liver inflammation.

Virus Infections and Host Metabolism-Can We Manage the Interactions?

When viruses infect cells, they almost invariably cause metabolic changes in the infected cell as well as in several host cell types that react to the infection. Such metabolic changes provide potential targets for therapeutic approaches that could reduce the impact of infection. Several examples are discussed in this review, which include effects on energy metabolism, glutaminolysis and fatty acid metabolism. The response of the immune system also involves metabolic changes and manipulating these may change the outcome of infection. This could include changing the status of herpesviruses infections from productive to latency. The consequences of viral infections which include coronavirus disease 2019 (COVID-19), may also differ in patients with metabolic problems, such as diabetes mellitus (DM), obesity, and endocrine diseases. Nutrition status may also affect the pattern of events following viral infection and examples that impact on the pattern of human and experimental animal viral diseases and the mechanisms involved are discussed. Finally, we discuss the so far few published reports that have manipulated metabolic events in-vivo to change the outcome of virus infection. The topic is expected to expand in relevance as an approach used alone or in combination with other therapies to shape the nature of virus induced diseases.

Gut Hormones in Health and Obesity: The Upcoming Role of Short Chain Fatty Acids

We are currently facing an obesity pandemic, with worldwide obesity rates having tripled since 1975. Obesity is one of the main risk factors for the development of non-communicable diseases, which are now the leading cause of death worldwide. This calls for urgent action towards understanding the underlying mechanisms behind the development of obesity as well as developing more effective treatments and interventions. Appetite is carefully regulated in humans via the interaction between the central nervous system and peripheral hormones. This involves a delicate balance in external stimuli, circulating satiating and appetite stimulating hormones, and correct functioning of neuronal signals. Any changes in this equilibrium can lead to an imbalance in energy intake versus expenditure, which often leads to overeating, and potentially weight gain resulting in overweight or obesity. Several lines of research have shown imbalances in gut hormones are found in those who are overweight or obese, which may be contributing to their condition. Therefore, this review examines the evidence for targeting gut hormones in the treatment of obesity by discussing how their dysregulation influences food intake, the potential possibility of altering the circulating levels of these hormones for treating obesity, as well as the role of short chain fatty acids and protein as novel treatments.

The Neuroprotective Effect of Short Chain Fatty Acids Against Sepsis-Associated Encephalopathy in Mice

Short chain fatty acids (SCFAs) are known to be actively involved in multiple brain disorders, but their roles in sepsis-associated encephalopathy (SAE) remain unclear. Here, we investigated the neuroprotective effects of SCFAs on SAE in mice. Male C57BL/6 mice were intragastrically pretreated with SCFAs for seven successive days, and then subjected to SAE induced by cecal ligation and puncture. The behavioral impairment, neuronal degeneration, and levels of inflammatory cytokines were assessed. The expressions of tight junction (TJ) proteins, including occludin and zoula occludens-1 (ZO-1), cyclooxygenase-2 (COX-2), cluster of differentiation 11b (CD11b), and phosphorylation of JNK and NF-κB p65 in the brain, were measured by western blot and Immunofluorescence analysis. Our results showed that SCFAs significantly attenuated behavioral impairment and neuronal degeneration, and decreased the levels of IL-1β and IL-6 in the brain of SAE mice. Additionally, SCFAs upregulated the expressions of occludin and ZO-1 and downregulated the expressions of COX-2, CD11b, and phosphorylation of JNK and NF-κB p65 in the brain of SAE mice. These findings suggested that SCFAs could exert neuroprotective effects against SAE in mice.

Butyrate Protects Porcine Colon Epithelium from Hypoxia-Induced Damage on a Functional Level

The large intestinal epithelium is confronted with the necessity to adapt quickly to varying levels of oxygenation. In contrast to other tissues, it meets this requirement successfully and remains unharmed during (limited) hypoxic periods. The large intestine is also the site of bacterial fermentation producing short-chain fatty acids (SCFA). Amongst these SCFA, butyrate has been reported to ameliorate many pathological conditions. Thus, we hypothesized that butyrate protects the colonocytes from hypoxic damage. We used isolated porcine colon epithelium mounted in Ussing chambers, incubated it with or without butyrate and simulated hypoxia by changing the gassing regime to test this hypothesis. We found an increase in transepithelial conductance and a decrease in short-circuit current across the epithelia when simulating hypoxia for more than 30 min. Incubation with 50 mM butyrate significantly ameliorated these changes to the epithelial integrity. In order to characterize the protective mechanism, we compared the effects of butyrate to those of iso-butyrate and propionate. These two SCFAs exerted similar effects to butyrate. Therefore, we propose that the protective effect of butyrate on colon epithelium under hypoxia is not (only) based on its nutritive function, but rather on the intracellular signaling effects of SCFA.

A Mitochondrial Polymorphism Alters Immune Cell Metabolism and Protects Mice from Skin Inflammation

Several genetic variants in the mitochondrial genome (mtDNA), including ancient polymorphisms, are associated with chronic inflammatory conditions, but investigating the functional consequences of such mtDNA polymorphisms in humans is challenging due to the influence of many other polymorphisms in both mtDNA and the nuclear genome (nDNA). Here, using the conplastic mouse strain B6-mt^FVB, we show that in mice, a maternally inherited natural mutation (m.7778G > T) in the mitochondrially encoded gene ATP synthase 8 (mt-Atp8) of complex V impacts on the cellular metabolic profile and effector functions of CD4⁺ T cells and induces mild changes in oxidative phosphorylation (OXPHOS) complex activities. These changes culminated in significantly lower disease susceptibility in two models of inflammatory skin disease. Our findings provide experimental evidence that a natural variation in mtDNA influences chronic inflammatory conditions through alterations in cellular metabolism and the systemic metabolic profile without causing major dysfunction in the OXPHOS system.

Propionate and Alzheimer's Disease

Propionate, a short-chain fatty acid, serves important roles in the human body. However, our review of the current literature suggests that under certain conditions, excess levels of propionate may play a role in Alzheimer's disease (AD). The cause of the excessive levels of propionate may be related to the Bacteroidetes phylum, which are the primary producers of propionate in the human gut. Studies have shown that the relative abundance of the Bacteroidetes phylum is significantly increased in older adults. Other studies have shown that levels of the Bacteroidetes phylum are increased in persons with AD. Studies on the diet, medication use, and propionate metabolism offer additional potential causes. There are many different mechanisms by which excess levels of propionate may lead to AD, such as hyperammonemia. These mechanisms offer potential points for intervention.

Effects of Iron and Zinc Biofortified Foods on Gut Microbiota In Vivo (Gallus gallus): A Systematic Review

Dietary iron and zinc deficiencies are a global health concern. Bacteria that colonize the gastrointestinal tract depend on minerals to maintain their activities; thus, recent evidence suggests that biofortified foods can modulate the host’s beneficial bacterial taxa. The current review analyzed the research data that linked between iron and zinc biofortified foods and gut microbiota modulation. The data analysis was based on the PRISMA guidelines and the data search was performed at PubMed, Web of Science, Science Direct, and Scopus databases for experimental studies published from January 2010 until December 2020. The five selected studies were conducted in an experimental in vivo model (Gallus gallus). The identified and discussed research showed positive effects of biofortified foods on the composition and function of the gut microbiota. Further, an increase in short chain fatty acids producing bacterial populations as Lactobacillus and Ruminococcus, and a decrease in potentially pathogenic bacteria as Streptococcus, Escherichia, and Enterobacter was identified due to the consumption of biofortified foods. In conclusion, biofortified foods may contribute to improved gut health without increasing the colonization of pathogenic bacteria. The dietary inclusion of approximately 50% of iron/zinc biofortified foods has a significant beneficial effect on the gut microbiota. Additional studies in humans and animal models are warranted to further establish the suggested effects on the intestinal microbiome. PROSPERO (CRD42020184221).

Gut-Induced Inflammation during Development May Compromise the Blood-Brain Barrier and Predispose to Autism Spectrum Disorder

Recently, the gut microbiome has gained considerable interest as one of the major contributors to the pathogenesis of multi-system inflammatory disorders. Several studies have suggested that the gut microbiota plays a role in modulating complex signaling pathways, predominantly via the bidirectional gut-brain-axis (GBA). Subsequent in vivo studies have demonstrated the direct role of altered gut microbes and metabolites in the progression of neurodevelopmental diseases. This review will discuss the most recent advancements in our understanding of the gut microbiome’s clinical significance in regulating blood-brain barrier (BBB) integrity, immunological function, and neurobiological development. In particular, we address the potentially causal role of GBA dysregulation in the pathophysiology of autism spectrum disorder (ASD) through compromising the BBB and immunological abnormalities. A thorough understanding of the complex signaling interactions between gut microbes, metabolites, neural development, immune mediators, and neurobiological functionality will facilitate the development of targeted therapeutic modalities to better understand, prevent, and treat ASD.

The gut microbiome as a target for adjuvant therapy in obstructive sleep apnea

Introduction: Gut dysbiosis is assumed to play a role in obstructive sleep apnea (OSA)-associated morbidities. Pre- and probiotics, short chain fatty acids (SCFA) and fecal matter transplantation (FMT) may offer potential as novel therapeutic strategies that target this gut dysbiosis. As more mechanisms of OSA-induced dysbiosis are being elucidated, these novel approaches are being tested in preclinical and clinical development. Areas covered: We examined the evidence linking OSA to gut dysbiosis and discuss the effects of pre- and probiotics on associated cardiometabolic, neurobehavioral and gastrointestinal disorders. The therapeutic potential of SCFA and FMT are also discussed. We reviewed the National Center for Biotechnology Information database, including PubMed and PubMed Central between 2000 - 2020. Expert opinion: To date, there are no clinical trials and only limited evidence from animal studies describing the beneficial effects of pre- and probiotic supplementation on OSA-mediated dysbiosis. Thus, more work is necessary to assess whether prebiotics, probiotics and SCFA are promising future novel strategies for targeting OSA-mediated dysbiosis.

Gut microbiome changes induced by a diet rich in fruits and vegetables

Habitual dietary intake is a major determinant of the species composition and functional output of the trillions of microorganisms residing in the human gut. Diet influences which microbes will colonise, flourish or disappear throughout life. An increase in polyphenols, oligosaccharides and fibre, which are all components found in a fruit and vegetable-rich diet, have long been associated with decreased risk of chronic diseases. Many of the benefits induced by this type of diet result from the interaction of these dietary components with the gut microbiome, where they selectively enrich specific microbial species and increase microbial diversity. Understanding the interaction of habitual dietary patterns on the gut microbiome will lead to rational dietary manipulation to improve human health through prevention and treatment of disease.

Effects of β-glucan Rich Barley Flour on Glucose and Lipid Metabolism in the Ileum, Liver, and Adipose Tissues of High-Fat Diet Induced-Obesity Model Male Mice Analyzed by DNA Microarray

We evaluated whether intake of β-glucan-rich barley flour affects expression levels of genes related to glucose and lipid metabolism in the ileum, liver, and adipose tissues of mice fed a high-fat diet. C57BL/6J male mice were fed a high-fat diet supplemented with high β-glucan barley, for 92 days. We measured the expression levels of genes involved in glucose and lipid metabolism in the ileum, liver, and adipose tissues using DNA microarray and q-PCR. The concentration of short-chain fatty acids (SCFAs) in the cecum was analyzed by GC/MS. The metabolic syndrome indices were improved by barley flour intake. Microarray analysis showed that the expression of genes related to steroid synthesis was consistently decreased in the liver and adipose tissues. The expression of genes involved in glucose metabolism did not change in these organs. In liver, a negative correlation was showed between some SCFAs and the expression levels of mRNA related to lipid synthesis and degradation. Barley flour affects lipid metabolism at the gene expression levels in both liver and adipose tissues. We suggest that SCFAs are associated with changes in the expression levels of genes related to lipid metabolism in the liver and adipose tissues, which affect lipid accumulation.

Understanding the mechanisms of efficacy of fecal microbiota transplant in treating recurrent Clostridioides difficile infection and beyond: the contribution of gut microbial-derived metabolites

Fecal microbiota transplant (FMT) is a highly-effective therapy for recurrent Clostridioides difficile infection (rCDI), and shows promise for certain non-CDI indications. However, at present, its mechanisms of efficacy have remained poorly understood. Recent studies by our laboratory have noted the particular key importance of restoration of gut microbe-metabolite interactions in the ability of FMT to treat rCDI, including the impact of FMT upon short chain fatty acid (SCFAs) and bile acid metabolism. This includes a significant impact of these metabolites upon the life cycle of C. difficile directly, along with potential postulated additional benefits, including effects upon host immune response. In this Addendum, we first present an overview of these recent advancements in this field, and then describe additional novel data from our laboratory on the impact of FMT for rCDI upon several gut microbial-derived metabolites which had not previously been implicated as being of relevance.

Regulation of Enteroendocrine Cell Networks by the Major Human Gut Symbiont Bacteroides thetaiotaomicron

Gut microbes have critical roles in maintaining host physiology, but their effects on epithelial chemosensory enteroendocrine cells (EEC) remain unclear. We investigated the role that the ubiquitous commensal gut bacterium Bacteriodes thetaiotaomicron (Bt) and its major fermentation products, acetate, propionate, and succinate (APS) have in shaping EEC networks in the murine gastrointestinal tract (GIT). The distribution and numbers of EEC populations were assessed in tissues along the GIT by fluorescent immunohistochemistry in specific pathogen free (SPF), germfree (GF) mice, GF mice conventionalized by Bt or Lactobacillus reuteri (Lr), and GF mice administered APS. In parallel, we also assessed the suitability of using intestinal crypt-derived epithelial monolayer cultures for these studies. GF mice up-regulated their EEC network, in terms of a general EEC marker chromogranin A (ChrA) expression, numbers of serotonin-producing enterochromaffin cells, and both hormone-producing K- and L-cells, with a corresponding increase in serum glucagon-like peptide-1 (GLP-1) levels. Bt conventionalization restored EEC numbers to levels in SPF mice with regional specificity; the effects on ChrA and L-cells were mainly in the small intestine, the effects on K-cells and EC cells were most apparent in the colon. By contrast, Lr did not restore EEC networks in conventionalized GF mice. Analysis of secretory epithelial cell monolayer cultures from whole small intestine showed that intestinal monolayers are variable and with the possible exclusion of GIP expressing cells, did not accurately reflect the EEC cell makeup seen in vivo. Regarding the mechanism of action of Bt on EECs, colonization of GF mice with Bt led to the production and accumulation of acetate, propionate and succinate (APS) in the caecum and colon, which when administered at physiological concentrations to GF mice via their drinking water for 10 days mimicked to a large extent the effects of Bt in GF mice. After withdrawal of APS, the changes in some EEC were maintained and, in some cases, were greater than during APS treatment. This data provides evidence of microbiota influences on regulating EEC networks in different regions of the GIT, with a single microbe, Bt, recapitulating its role in a process that may be dependent upon its fermentation products.

Pinto beans modulate the gut microbiome, augment MHC II protein, and antimicrobial peptide gene expression in mice fed a normal or western-style diet

The onset of type 2 diabetes in obesity is associated with gut dysbiosis and a failure to confine commensal bacteria and toxins to the gut lumen while prebiotics may prevent these effects. This study evaluated the effects of pinto beans (PB) supplementation on cecal bacteria, short-chain fatty acids (SCFAs), distal ileal antigen presentation marker (major histocompatibility complex [MHC] II) and antimicrobial peptide genes during short-term high-fat, high sucrose (HFS) feeding. Six-week-old, male C57BL/6J mice were randomly assigned to four groups (n=12/group), and fed a control (C) or HFS diet with or without cooked PB (10%, wt/wt) for 30 days. Supplemental PB in both the C and HFS diets decreased the abundance of Tenericutes and the sulfate-reducing bacteria Bilophila. In contrast, PB raised the abundance of taxa within the SCFAs-producing family, Lachnospiraceae, compared to groups without PB. Consequently, fecal butyric acid was significantly higher in PB-supplemented groups compared to C and HFS groups. PB reversed the HFS-induced ablation of the distal ileal STAT3 phosphorylation, and up-regulated antimicrobial peptide genes (Reg3γ and Reg3β). Furthermore, the expression of MHC II protein was elevated in the PB supplemented groups compared to C and HFS. Tenericutes and Bilophilia negatively correlated with activated STAT3 and MHC II proteins. Finally, supplemental PB improved fasting blood glucose, glucose tolerance and suppressed TNFα and inducible nitric oxide synthase mRNA in the visceral adipose tissue. Put together, the beneficial impact of PB supplementation on the gut may be central to its potential to protect against diet-induced inflammation and impaired glucose tolerance.

Gut Biofactory-Neurocompetent Metabolites within the Gastrointestinal Tract. A Scoping Review

The gut microbiota have gained much scientific attention recently. Apart from unravelling the taxonomic data, we should understand how the altered microbiota structure corresponds to functions of this complex ecosystem. The metabolites of intestinal microorganisms, especially bacteria, exert pleiotropic effects on the human organism and contribute to the host systemic balance. These molecules play key roles in regulating immune and metabolic processes. A subset of them affect the gut brain axis signaling and balance the mental wellbeing. Neurotransmitters, short chain fatty acids, tryptophan catabolites, bile acids and phosphatidylcholine, choline, serotonin, and L-carnitine metabolites possess high neuroactive potential. A scoping literature search in PubMed/Embase was conducted up until 20 June 2020, using three major search terms "microbiota metabolites" AND "gut brain axis" AND "mental health". This review aimed to enhance our knowledge regarding the gut microbiota functional capacity, and support current and future attempts to create new compounds for future clinical interventions.

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

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

Exopolysaccharides From Lactobacillus paracasei Isolated From Kefir as Potential Bioactive Compounds for Microbiota Modulation

Microbiota coexists in true symbiosis with the host playing pivotal roles as a key element for well-being and health. Exopolysaccharides from lactic acid bacteria are an alternative as novel potential prebiotics that increase microbiota diversity. Considering this, the aim of the present work was to evaluate the capacity of the EPS produced by two L. paracasei strains isolated from kefir grains, to be metabolized in vitro by fecal microbiota producing short chain fatty acids. For this purpose, fecal samples from healthy children were inoculated in a basal medium with EPS and incubated in anaerobiosis at 37°C for 24, 48, and 72 h. DGGE profiles and the production of SCFA after fermentation were analyzed. Additionally, three selected samples were sequenced by mass sequencing analysis using Ion Torrent PGM. EPS produced by L. paracasei CIDCA 8339 (EPS₈₃₃₉) and CIDCA 83124 (EPS₈₃₁₂₄) are metabolized by fecal microbiota producing a significant increase in SCFA. EPS₈₃₃₉ fermentation led to an increment of propionate and butyrate, while fermentation of EPS₈₃₁₂₄ increased butyrate levels. Both EPS led to a profile of SCFA different from the ones obtained with inulin or glucose fermentation. DGGE profiles of 72 h fermentation demonstrated that both EPS showed a different band profile when compared to the controls; EPS profiles grouped in a cluster that have only 65% similarity with glucose or inulin profiles. Mass sequencing analysis demonstrated that the fermentation of EPS₈₃₃₉ leads to an increase in the proportion of the genera Victivallis, Acidaminococcus and Comamonas and a significant drop in the proportion of enterobacteria. In the same direction, the fermentation of EPS₈₃₁₂₄ also resulted in a marked reduction of Enterobacteriaceae with a significant increase in the genus Comamonas. It was observed that the changes in fecal microbiota and SCFA profile exerted by both polymers are different probably due to differences in their structural characteristics. It can be concluded that EPS synthesized by both L. paracasei strains, could be potentially used as bioactive compound that modify the microbiota increasing the production of propionic and butyric acid, two metabolites highly associated with beneficial effects both at the gastrointestinal and extra-intestinal level.

Daily Fermented Whey Consumption Alters the Fecal Short-Chain Fatty Acid Profile in Healthy Adults

Gut microbiota influences many aspects of host health including immune, metabolic, and gut health. We examined the effect of a fermented whey concentrate (FWC) drink rich in L-(+)-Lactic acid, consumed daily, in 18 healthy men (n = 5) and women (n = 13) in free-living conditions.

Objective: The aims of this 6-weeks pilot trial were to (i) identify changes in the gut microbiota composition and fecal short chain fatty acid (SCFA) profile, and (ii) to monitor changes in glucose homeostasis.

Results: Total fecal SCFA (mM) concentration remained constant throughout the intervention. Proportionally, there was a significant change in the composition of different SCFAs compared to baseline. Acetate levels were significantly reduced (−6.5%; p < 0.01), coupled to a significant increase in the relative amounts of propionate (+2.2%; p < 0.01) and butyrate (+4.2%; p < 0.01), respectively. No changes in the relative abundance of any specific bacteria were detected. No significant changes were observed in glucose homeostasis in response to an oral glucose tolerance test.

Conclusion: Daily consumption of a fermented whey product led to significant changes in fecal SCFA metabolite profile, indicating some potential prebiotic activity. These changes did not result in any detectable differences in microbiota composition. Post-hoc analysis indicated that baseline microbiota composition might be indicative of participants likely to see changes in SCFA levels. However, due to the lack of a control group these findings would need to be verified in a rigorously controlled trial. Future work is also required to identify the biological mechanisms underlying the observed changes in microbiota activity and to explore if these processes can be harnessed to favorably impact host health.

Clinical Trial Registration: www.clinicaltrials.gov, identifier NCT03615339; retrospectively registered on 03/08/2018.

Impact of the source of fermentable carbohydrate on SCFA production by human gut microbiota in vitro - a systematic scoping review and secondary analysis

Short chain fatty acids (SCFA) are produced by bacterial fermentation of non-digestible carbohydrates (NDC) and have many potential tissue and SCFA specific actions, from providing fuel for colonic cells to appetite regulation. Many studies have described the fermentation of different carbohydrates, often using in vitro batch culture. As evidence-based critical evaluation of substrates selectively promoting production of individual SCFA is lacking, we performed a systematic scoping literature review. Databases were searched to identify relevant papers published between 1900 and 12/06/2016. Search terms included In vitro batch fermentation and In vitro short chain fatty acid production. Articles were considered for essential criteria allowing equivalent comparison of SCFA between NDC. Seventy seven articles were included in the final analysis examining 29 different carbohydrates. After 24-hour fermentation, galacto-oligosaccharide ranked highest for butyrate and total SCFA production and second for acetate production. Rhamnose ranked highest for propionate production. The lowest SCFA production was observed for kiwi fiber, polydextrose, and cellulose. This review demonstrates that choosing a substrate to selectively enhance a specific SCFA is difficult, and the molar proportion of each SCFA produced by individual substrates may be misleading. Instead the rate and ratio of SCFA production should be evaluated in parallel.

The Role of Diet Related Short-Chain Fatty Acids in Colorectal Cancer Metabolism and Survival: Prevention and Therapeutic Implications

Colorectal Cancer (CRC) is a major cause of cancer-related death worldwide. CRC increased risk has been associated with alterations in the intestinal microbiota, with decreased production of Short Chain Fatty Acids (SCFAs). SCFAs produced in the human colon are the major products of bacterial fermentation of undigested dietary fiber and starch. While colonocytes use the three major SCFAs, namely acetate, propionate and butyrate, as energy sources, transformed CRC cells primarily undergo aerobic glycolysis. Compared to normal colonocytes, CRC cells exhibit increased sensitivity to SCFAs, thus indicating they play an important role in cell homeostasis. Manipulation of SCFA levels in the intestine, through changes in microbiota, has therefore emerged as a potential preventive/therapeutic strategy for CRC. Interest in understanding SCFAs mechanism of action in CRC cells has increased in the last years. Several SCFA transporters like SMCT-1, MCT-1 and aquaporins have been identified as the main transmembrane transporters in intestinal cells. Recently, it was shown that acetate promotes plasma membrane re-localization of MCT-1 and triggers changes in the glucose metabolism. SCFAs induce apoptotic cell death in CRC cells, and further mechanisms have been discovered, including the involvement of lysosomal membrane permeabilization, associated with mitochondria dysfunction and degradation. In this review, we will discuss the current knowledge on the transport of SCFAs by CRC cells and their effects on CRC metabolism and survival. The impact of increasing SCFA production by manipulation of colon microbiota on the prevention/therapy of CRC will also be addressed.

The Influence of Hypertensive Therapies on Circulating Factors: Clinical Implications for SCFAs, FGF21, TNFSF14 and TNF-α

Studying the role of circulatory factors in the pathogenesis of diseases has been key to the development of effective therapies. We sought to examine the effect of antihypertensive therapies on numerous circulatory factors including short chain fatty acids and growth factors in a human cohort. A subset of participants from an earlier study was characterized by their hypertensive and/or treatment status and separated into three groups: (i) normotensives; (ii) untreated hypertensive and (iii) treated hypertensive subjects. Circulating levels of short chain fatty acids, FGF21 and TNF superfamily members were measured as part of this study. Both F2-isoprostane and circulating lipid levels were reanalysed as part of this current study. We found that antihypertensive treatment increased butyrate levels and decreased acetate levels to levels similar to normotensives. We also found that antihypertensive treatments reduced levels of circulating FGF21, TNFSF14 and TNF-α. In conclusion, we identified several circulatory factors that are altered in hypertension.

Constant Light Exposure Alters Gut Microbiota and Promotes the Progression of Steatohepatitis in High Fat Diet Rats

Background

Non-alcoholic fatty liver disease (NAFLD) poses a significant health concern worldwide. With the progression of urbanization, light pollution may be a previously unrecognized risk factor for NAFLD/NASH development. However, the role of light pollution on NAFLD is insufficiently understood, and the underlying mechanism remains unclear. Interestingly, recent studies indicate the gut microbiota affects NAFLD/NASH development. Therefore, the present study explored effects of constant light exposure on NAFLD and its related microbiotic mechanisms.

Materials and Methods

Twenty-eight SD male rats were divided into four groups (n = 7 each): rats fed a normal chow diet, and exposed to standard light-dark cycle (ND-LD); rats fed a normal chow diet, and exposed to constant light (ND-LL); rats fed a high fat diet, and exposed to standard light-dark cycle (HFD-LD); and rats on a high fat diet, and exposed to constant light (HFD-LL). Body weight, hepatic pathophysiology, gut microbiota, and short/medium chain fatty acids in colon contents, serum lipopolysaccharide (LPS), and liver LPS-binding protein (LBP) mRNA expression were documented post intervention and compared among groups.

Result

In normal chow fed groups, rats exposed to constant light displayed glucose abnormalities and dyslipidemia. In HFD-fed rats, constant light exposure exacerbated glucose abnormalities, insulin resistance, inflammation, and liver steatohepatitis. Constant light exposure altered composition of gut microbiota in both normal chow and HFD fed rats. Compared with HFD-LD group, HFD-LL rats displayed less Butyricicoccus, Clostridium, and Turicibacter, butyrate levels in colon contents, decreased colon expression of occludin-1 and zonula occluden−1 (ZO-1), and increased serum LPS and liver LBP mRNA expression.

Conclusion

Constant light exposure impacts gut microbiota and its metabolic products, impairs gut barrier function and gut-liver axis, promotes NAFLD/NASH progression in HFD rats.

Dietary Lipids Influence Bioaccessibility of Polyphenols from Black Carrots and Affect Microbial Diversity under Simulated Gastrointestinal Digestion

The bioaccessibility and activity of polyphenols is dependent on their structure and entrapment in the food matrix. While dietary lipids are known to transit into the colon, the impact of different lipids on the microbiome, and their interactions with dietary polyphenols are largely unknown. Here, we investigated the effect of dietary lipids on the bioaccessibility of polyphenols from purple/black carrots and adaptation of the gut microbiome in a simulated in vitro digestion-fermentation. Coconut oil, sunflower oil, and beef tallow were selected to represent common dietary sources of medium-chain fatty acids (MCFAs), long-chain polyunsaturated fatty acids (PUFAs), and long-chain polysaturated fatty acids (SFAs), respectively. All lipids promoted the bioaccessibility of both anthocyanins and phenolic acids during intestinal digestion with coconut oil exhibiting the greatest protection of anthocyanins. Similar trends were shown in antioxidant assays (2,2-Diphenyl-1-pricrylhydrazyl (DPPH), ferric reducing ability (FRAP), and total phenolic content (TPC)) with higher phytochemical bioactivities observed with the addition of dietary lipids. Most bioactive polyphenols were decomposed during colonic fermentation. Black carrot modulated diversity and composition of a simulated gut microbiome. Dramatic shifts in gut microbiome were caused by coconut oil. Inclusion of sunflower oil improved the production of butyrate, potentially due to the presence of PUFAs. The results show that the impact of polyphenols in the digestive tract should be considered in the context of other components of the diet, particularly lipids.

The Facts about Food after Cancer Diagnosis: A Systematic Review of Prospective Cohort Studies

Nutritional guidelines suggest specific energy and protein requirements for patients with cancer. However, cancer patients, often malnourished, use self-made or web-based diets to ameliorate the prognosis of their disease. This review aimed to investigate the associations between post-diagnostic diet and prognostic outcomes in cancer patients. A systematic literature search was performed in Pubmed and Web of Science databases from inception to 30 October 2019, based on fixed inclusion and exclusion criteria. The risk of bias was assessed. A total of 29 prospective studies was identified. Breast (n = 11), colorectal (n = 9), prostate (n = 8) cancers are the most studied. Low- fat diet, healthy quality diet, regular consumption of fiber such as vegetables and high-quality protein intake are beneficial while Western diet (WD) and high consumption of saturated fats could be associated with a higher risk of mortality. Bladder (n = 1), gynecological (n = 1), lung, stomach, and pancreatic cancers still remain almost unexplored. This systematic review suggested that detrimental dietary patterns such as WD should be avoided but none of the food categories (meat, dairy products) should be eliminated in cancer patients' diet. Further large prospective studies are needed to assess the role of post-diagnostic diet in patients with cancer.

Effects of fibre-degrading enzymes in combination with different fibre sources on ileal and total tract nutrient digestibility and fermentation products in pigs

The study was conducted to determine effects of a complex of fibre-degrading enzymes (xylanase, cellulase and β-glucanase) on nutrient digestibility, fibre fermentation and concentrations of short chain fatty acids (SCFA) at different parts of digestive tract in pigs fed different fibre-rich ingredients. A total of 36 barrows fitted with T-cannulas in the distal ileum (initial body weight of 41.1 ± 2.7 kg) were randomly allotted to six dietary treatments with three different high-fibre diets including maize bran (MB), sugar beet pulp (SBP) and soybean hulls (SH) with or without supplementation of fibre-degrading enzymes. Enzyme supplementation improved (p < 0.05) apparent ileal digestibility (AID) of dietary gross energy (GE), crude protein, dry matter (DM), organic matter (OM), total dietary fibre (TDF), neutral detergent fibre (NDF) and apparent total tract digestibility (ATTD) of dietary GE, DM, OM, TDF, insoluble dietary fibre (IDF) when pigs were fed MB, SBP or SH diets. When compared to the SBP and SH diets, the AID of GE, DM, ash, OM and NDF in diet MB was higher (p < 0.05), but the hindgut disappearance and ATTD of nutrients, except for ether extract and crude ash, were lower (p < 0.05). Enzyme supplementation increased acetate and total SCFA concentrations in ileal digesta and faeces of pigs. In conclusion, enzyme addition improved IDF fermentation and SCFA concentration in the whole intestine of pigs, and there was a large variation of digestibility of fibre components among MB, SH and SBP owing to their different fibre composition. Therefore, fibre-degrading enzymes should be applied to fibrous diets to improve efficient production of swine, especially considering low fibre digestibility of fibre-rich ingredients.

Short-chain fatty acids as novel therapeutics for gestational diabetes

Gestational diabetes mellitus (GDM) affects up to 16% of pregnant women and is associated with significant long-term health detriments for the mother and her offspring. Two central features of GDM are low-grade inflammation and maternal peripheral insulin resistance, therefore therapeutics which target these may be most effective at preventing the development of GDM. Short-chain fatty acids (SCFAs), such as butyrate and propionate, are metabolites produced from the fermentation of dietary fibre by intestinal microbiota. SCFAs possess anti-inflammatory, anti-obesity and anti-diabetic properties. Therefore, this study aimed to investigate the effect of SCFAs on inflammation and insulin signalling defects in an in vitro model of GDM. Human placenta, visceral adipose tissue (VAT) and s.c. adipose tissue (SAT) were stimulated with either the pro-inflammatory cytokine TNF or bacterial product lipopolysaccharide (LPS). The SCFAs butyrate and propionate blocked TNF- and LPS-induced mRNA expression and secretion of pro-inflammatory cytokines and chemokines in placenta, VAT and SAT. Primary human cells isolated from skeletal muscle were stimulated with TNF to assess the effect of SCFAs on inflammation-induced defects in the insulin signalling pathway. Butyrate and propionate were found to reverse TNF-induced increases in IRS-1 serine phosphorylation and decreases in glucose uptake. Butyrate and propionate exerted these effects by preventing ERK activation. Taken together, these results suggest that the SCFAs may be able to improve insulin sensitivity and prevent inflammation induced by sterile or bacterial inflammation. Future in vivo studies are warranted to investigate the efficacy and safety of SCFAs in preventing insulin resistance and inflammation associated with GDM.

Potential Role of SLC5A8 Expression in the Etiology of Subacute Ruminal Acidosis

Rumen fluid of cows with subacute ruminal acidosis (SARA) has high concentrations of short chain fatty acids (SCFA). However, the mechanism of SCFA accumulation is unknown. The solute-linked carrier 5a8 (SLC5A8) plays a key role in the transportation and absorption of SCFA in the intestinal epithelium. The objective of the current study was to investigate (1) SLC5A8 gene and protein expression in various parts of the bovine gastrointestinal tract, (2) the effect of SCFA on SLC5A8 expression in rumen epithelial cells, and (3) SLC5A8 gene and protein expression in SARA and healthy cows. A total of 10 dairy cows, 84 ± 26 days in milk and in their second to fourth parity were allocated to control (n = 5) and SARA groups (n = 5). Three cows from the control group and three calves (1-day-old, female, 45–50 kg, healthy, fasting) were chosen to collect a total of 10 sections of digestive tract, from rumen to rectum, and then bovine ruminal epithelial cells were isolated from the three calves. Gene and protein expression of SLC5A8 was detected in all tested regions of the gastrointestinal tract in calves and adult cows by Western blot and quantitative real-time PCR and were both highest in the rumen. Gene and protein expression of SLC5A8 was more than 50% lower in the rumen epithelium of SARA vs. control cows and was partly restored after therapy of SARA cows. Compared with SCFA concentrations typical for control cows (60 mM acetate, 30 mM propionate, and 20 mM butyrate), gene and protein expression of SLC5A8 in rumen epithelium was lower at elevated SCFA concentrations typical for SARA cows (90 mM acetate, 40 mM propionate, and 30 mM butyrate), specifically for elevated concentrations of propionate or butyrate in contrast to elevated concentrations of acetate increased gene and protein expression of SLC5A8 in rumen epithelium. In conclusion, the elevated concentrations of propionate and butyrate inhibit ruminal absorption of SCFA via downregulation of SLC5A8 in SARA cows; the expression of SLC5A8 plays an important role in the etiology of SARA.

A Marine-Derived, Multi-mineral Supplement Influences Bacterial Fermentation and Short Chain Fatty Acid Profile In Vitro

Aquamin is a calcium-rich multi-mineral supplement derived from the red marine algae, Lithothamnion species. Calcium supplementation has been shown to exert a prebiotic-like effect on the gut microbiota and has been associated with distinct changes in lactate and short chain fatty acid (SCFA) production. Irritable bowel syndrome (IBS) subtype is associated with changes in SCFA levels compared with healthy controls. Using an ex vivo simulation model, and a fecal inoculum from a patient diagnosed with IBS, we evaluated the effects of Aquamin (at 6 and 30 mg/mL) on SCFAs and lactate production, pH and gas production, and human microbiota composition. Our results demonstrate that Aquamin increased SCFA production (acetate and propionate by 8% and 24%, respectively, at 30 mg/mL dose), significantly decreased lactate production (30 mg/mL), and increased colonic fluid pH without inducing changes in colonic gas production or gastrointestinal (GI) microbiota composition. These results indicate that Aquamin may play a role in optimizing GI microbial function in an ex vivo setting.

Effects of Vitamin B2 Supplementation in Broilers Microbiota and Metabolome

The study of the microbiome in broiler chickens holds great promise for the development of strategies for health maintenance and performance improvement. Nutritional strategies aimed at modulating the microbiota-host relationship can improve chickens' immunological status and metabolic fitness. Here, we present the results of a pilot trial aimed at analyzing the effects of a nutritional strategy involving vitamin B2 supplementation on the ileum, caeca and litter microbiota of Ross 308 broilers, as well as on the metabolic profile of the caecal content. Three groups of chickens were administered control diets and diets supplemented with two different dosages of vitamin B2. Ileum, caeca, and litter samples were obtained from subgroups of birds at three time points along the productive cycle. Sequencing of the 16S rRNA V3-V4 region and NMR metabolomics were used to explore microbiota composition and the concentration of metabolites of interest, including short-chain fatty acids. Vitamin B2 supplementation significantly modulated caeca microbiota, with the highest dosage being more effective in increasing the abundance of health-promoting bacterial groups, including Bifidobacterium, resulting in boosted production of butyrate, a well-known health-promoting metabolite, in the caeca environment.

Human Milk From Atopic Mothers Has Lower Levels of Short Chain Fatty Acids

Short chain fatty acids (SFCAs) are microbial metabolites produced in the gut upon fermentation of dietary fiber. These metabolites interact with the host immune system and can elicit epigenetic effects. There is evidence to suggest that SCFAs may play a role in the developmental programming of immune disorders and obesity, though evidence in humans remains sparse. Here we have quantified human milk (HM) SCFA levels in an international cohort of atopic and non-atopic mothers (n = 109). Our results demonstrate that human milk contains detectable levels of the SCFAs acetate, butyrate, and formate. Samples from atopic mothers had significantly lower concentrations of acetate and butyrate than those of non-atopic mothers. HM SCFA levels in atopic and non-atopic women also varied based on maternal country of residence (Australia, Japan, Norway, South Africa, USA). Reduced exposure to HM SCFA in early life may program atopy or overweight risk in breastfed infants.

Effects of banana powder (Musa acuminata Colla) on the composition of human fecal microbiota and metabolic output using in vitro fermentation

Bananas are rich in indigestible carbohydrates and are considered potential whole-fruit prebiotics. To investigate banana-induced changes in the composition of the human gut microbiota and the production of short chain fatty acids (SCFAs), ripe banana (Musa acuminata Colla, Degrees Brix: 22.6 ± 0.2° Bé), from Hainan, China, was powdered and fermented in vitro for 24 hr with the feces of six Chinese donors. The degradation of banana polysaccharides was observed in all six fecal samples. During in vitro fecal fermentation, banana polysaccharides were gradually degraded up to approximately 80%. The production of SCFAs was also measured. The addition of banana powder increased the concentrations of acetate, propionate, and butyrate, with the production of acetate being higher than that of propionate and butyrate. Changes in the human gut microbiota were assessed using high-throughput sequencing of the 16S ribosomal RNA (rRNA) gene. The results indicated that banana powder significantly altered bacterial diversity, increasing the relative abundance of Bacteroides, while maintaining the proportion of Bifidobacterium in the feces. At the same time, banana powder also increased the proportion of Lactobacillus; however, a significant difference was not observed. In summary, banana powder can be utilized by specific bacteria in human intestines, providing data support for the study of the effects of banana powder on the human intestinal health. PRACTICAL APPLICATION: In this study, in vitro batch fermentation was used to evaluate the effect of banana powder on the human intestinal microbial community, and the metabolized products of banana powder were determined. Our study showed that banana powder improved the human intestinal microbial flora and promoted the growth of Bifidobacterium and Bacteroides and could produce beneficial SCFAs (acetate, propionate, and butyrate). This study provided a theoretical basis for the use of banana powder as a potential prebiotic in production applications and our daily diet.

The relationship between gut microbiota and short chain fatty acids in the renal calcium oxalate stones disease

The relationship of gut microbiota and calcium oxalate stone has been limited investigated, especially with no study of gut microbiota and short chain fatty acids (SCFAs) in nephrolithiasis. We provided Sprague Dawley rats of renal calcium oxalate stones with antibiotics and examined the renal crystals deposition. We also performed a case-control study by analyzing 16S rRNA microbial profiling, shotgun metagenomics and SCFAs in 153 fecal samples from non-kidney stone (NS) controls, patients with occasional renal calcium oxalate stones (OS) and patients with recurrent stones (RS). Antibiotics reduced bacterial load in feces and could promote the formation of renal calcium crystals in model rats. In addition, both OS and RS patients exhibited higher fecal microbial diversity than NS controls. Several SCFAs-producing gut bacteria, as well as metabolic pathways associated with SCFAs production, were considerably lower in the gut microbiota among the kidney stone patients compared with the NS controls. Representation of genes involved in oxalate degradation showed no significance difference among groups. However, fecal acetic acid concentration was the highest in RS patients with high level of urinary oxalate, which was positively correlated with genes involvement in oxalate synthesis. Administration of SCFAs reduced renal crystals. These results shed new light on bacteria and SCFAs, which may promote the development of treatment strategy in nephrolithiasis.

Following the community development of SIHUMIx - a new intestinal in vitro model for bioreactor use

Diverse intestinal microbiota is frequently used in in vitro bioreactor models to study the effects of diet, chemical contaminations, or medication. However, the reproducible cultivation of fecal microbiota is challenging and the resultant communities behave highly dynamic. To approach the issue of reproducibility in in vitro models, we established an intestinal microbiota model community of reduced complexity, SIHUMIx, as a valuable model for in vitro use. The development of the SIHUMIx community was monitored over time with methods covering the cellular and the molecular level. We used microbial flow cytometry, intact protein profiling and terminal restriction fragment length polymorphism analysis to assess community structure. In parallel, we analyzed the functional level by targeted analysis of short-chain fatty acids and untargeted metabolomics. The stability properties constancy, resistance, and resilience were approached both on the structural and functional level of the community. We show that the SIHUMIx community is highly reproducible and constant since day 5 of cultivation. Furthermore, SIHUMIx has the ability to resist and recover from a pulsed perturbation, with changes in community structure recovered earlier than functional changes. Since community structure and function changed divergently, both levels need to be monitored at the same time to gain a full overview of the community development. All five methods are highly suitable to follow the community dynamics of SIHUMIx and indicated stability on day five. This makes SIHUMIx a suitable in vitro model to investigate the effects of e.g. medical, chemical, or dietary interventions.