Fatty Acids Propionate Research Articles

Direct anabolic metabolism of three-carbon propionate to a six-carbon metabolite occurs in vivo across tissues and species

Anabolic metabolism of carbon in mammals is mediated via the one- and two-carbon carriers S-adenosyl methionine and acetyl-coenzyme A. In contrast, anabolic metabolism of three-carbon units via propionate has not been shown to extensively occur. Mammals are primarily thought to oxidize the three-carbon short chain fatty acid propionate by shunting propionyl-CoA to succinyl-CoA for entry into the TCA cycle. Here, we found that this may not be absolute as, in mammals, one nonoxidative fate of propionyl-CoA is to condense to two three-carbon units into a six-carbon trans-2-methyl-2-pentenoyl-CoA (2M2PE-CoA). We confirmed this reaction pathway using purified protein extracts provided limited substrates and verified the product via LC-MS using a synthetic standard. In whole-body in vivo stable isotope tracing following infusion of 13C-labeled valine at steady state, 2M2PE-CoA was found to form via propionyl-CoA in multiple murine tissues, including heart, kidney, and to a lesser degree, in brown adipose tissue, liver, and tibialis anterior muscle. Using ex vivo isotope tracing, we found that 2M2PE-CoA also formed in human myocardial tissue incubated with propionate to a limited extent. While the complete enzymology of this pathway remains to be elucidated, these results confirm the in vivo existence of at least one anabolic three- to six-carbon reaction conserved in humans and mice that utilizes propionate.

The Short-Chain Fatty Acids Propionate and Butyrate Augment Adherent-Invasive Escherichia coli Virulence but Repress Inflammation in a Human Intestinal Enteroid Model of Infection.

ABSTRACTShort-chain fatty acids (SCFAs), which consist of six or fewer carbons, are fermentation products of the bacterial community that inhabits the intestine. Due to an immunosuppressive effect on intestinal tissue, they have been touted as a therapeutic for inflammatory conditions of the bowel. Here, we study the impact of acetate, propionate, and butyrate, the three most abundant SCFAs in the intestine, on gene expression in the intestinal pathobiont adherent-invasive Escherichia coli. We pair this with adherence, invasion, and inflammation in Caco-2 and human intestinal enteroid (HIE)-derived monolayer models of the intestinal epithelium. We report that propionate and butyrate upregulate transcription of adherent-invasive Escherichia coli (AIEC) flagellar synthesis genes and decrease expression of capsule assembly and transport genes. These changes are predicted to augment AIEC invasiveness. In fact, SCFA supplementation increases AIEC adherence to and invasion of the Caco-2 monolayer but has no effect on these parameters in the HIE model. We attribute this to the anti-inflammatory effect of propionate and butyrate on HIEs but not on Caco-2 cells. We conclude that the potential of SCFAs to increase the virulence of intestinal pathogens should be considered in their use as anti-inflammatory agents.IMPORTANCE The human terminal ileum and colon are colonized by a community of microbes known as the microbiota. Short-chain fatty acids (SCFAs) excreted by bacterial members of the microbiota define the intestinal environment. These constitute an important line of communication within the microbiota and between the microbiota and the host epithelium. In inflammatory conditions of the bowel, SCFAs are often low and there is a preponderance of a conditionally virulent bacterium termed adherent-invasive Escherichia coli (AIEC). A connection between SCFA abundance and AIEC has been suggested. Here, we study AIEC in monoculture and in coculture with human intestinal enteroid-derived monolayers and show that the SCFAs propionate and butyrate increase expression of AIEC virulence genes while concurrently bolstering the intestinal epithelial barrier and reducing intestinal inflammation. While these SCFAs have been promoted as a therapy for inflammatory bowel conditions, our findings demonstrate that their effect on bacterial virulence must be considered.

Propionic Acid Rescues High-Fat Diet Enhanced Immunopathology in Autoimmunity via Effects on Th17 Responses.

High-fat diets (HFD) are linked to obesity and associated comorbidities and induce pathogenic T helper (Th) 17 cells while decreasing regulatory T cells (Treg). This pro-inflammatory environment also aggravates immunopathology in experimental autoimmune encephalomyelitis (EAE) as a prototype model of T cell mediated autoimmunity. The strong association of HFD to obesity as well as the increasing risk of autoimmunity in the Western world stresses the importance to identify compounds that counteract this metabolically induced pro-inflammatory state in humans. One prominent candidate is the short-chain fatty acid propionate (PA) that was recently identified as potent therapy in the autoimmune disease multiple sclerosis by enhancing Treg cell frequencies and functionality. Mice were fed a HFD rich lauric acid (LA) and treated either with water or PA during MOG35-55-EAE. We analyzed Treg and Th17 cell frequencies in different tissues, antigen-specific cell proliferation and cytokine secretion, investigated Treg cell functionality by suppression assays and IL-10 signaling blockade and employed Western blotting to investigate the involvement of p38-MAPK signaling. Finally, we performed an explorative study in obese and non-obese MS patients, investigating fecal PA concentrations as well as peripheral Th17 and Treg frequencies before and after 90 days of daily PA intake. As compared to controls, mice on a HFD displayed a more severe course of EAE with enhanced demyelination and immune cell infiltration in the spinal cord. PA treatment prevented this disease enhancing effect of HFD by inhibiting Th17 mediated inflammatory processes in the gut and the spleen. Blocking experiments and signaling studies revealed p38-MAPK and IL-10 signaling as important targets linking the beneficial effects of PA treatment and reduced inflammation due to enhanced Treg frequency and functionality. An explorative study in a small group of MS patients revealed reduced PA concentrations in fecal samples of obese MS patients compared to the non-obese group, coinciding with increased Th17 but decreased Treg cells in obese patients. Importantly, PA intake could restore the Treg-Th17 homeostasis. Our data thus identify Th17 responses as an important target for the beneficial effects of PA in HFD and obesity in addition to the recently identified potential of PA as a Treg inducing therapy in T cell mediated autoimmunity.

A review of the antimicrobial and immune-modulatory properties of the gut microbiota-derived short chain fatty acid propionate – What is new?

As antimicrobial resistance poses a globally rising health problem, the identification of alternative antimicrobial agents is urgently required. The short chain fatty acid propionate which is physiologically produced by the gut microbiota constitutes a promising molecule given that it has been widely used as a cosmetics and food preservative due to its antimicrobial effects. This literature survey aims to determine the most recent state of knowledge about the antimicrobial and immune-modulatory properties of propionate. Both in vitro and in vivo studies published between 2011 and 2020 confirmed the ability of propionate to inhibit the growth of several cellular pathogens, including Gram-positive and Gram-negative multi-drug resistant bacteria and fungi. In addition, heterogenous immune-modulatory and in particular, anti-inflammatory effects of propionate could be assessed involving a diverse signaling network that needs further comprehension. In conclusion, our literature survey provides evidence that propionate displays a plethora of health-beneficial including antimicrobial and immune-modulatory effects. Future research is required to further unravel the underlying molecular mechanisms and to set the basis for in vivo infection and clinical studies to broaden the path of propionate as a promising adjunct antibiotics-independent option in the combat of infections caused by multi-drug resistant bacteria.

SER-287, AN INVESTIGATIONAL MICROBIOME THERAPEUTIC FOR PATIENTS WITH ACTIVE MILD-TO-MODERATE ULCERATIVE COLITIS, PRODUCES REMISSION ASSOCIATED METABOLITES, REDUCES INTESTINAL EPITHELIAL IL-8 SECRETION AND PROTECTS EPITHELIAL BARRIER FUNCTION IN VITRO

Abstract Background In a Phase 1b study of mild-to-moderate ulcerative colitis (UC) (Henn et al. Gastro 2020), oral daily dosing of SER-287, a purified consortium of Firmicutes spores administered after vancomycin pre-conditioning, led to significantly higher rates of clinical remission compared to placebo (40% versus 0%, respectively; p=0.024). Engraftment, defined as SER-287 spore germination and growth of metabolically-active bacteria, was associated with remission and shifts in disease relevant microbe-associated metabolites. To better understand the mechanism underlying these favorable clinical observations, we evaluated metabolite production by SER-287 and their impact on specific inflammatory pathways and barrier epithelial integrity in vitro. Methods Three SER-287 lots and a negative control pro-inflammatory consortium including three strains isolated from UC subjects (Escherichia coli, Bifidobacterium dentium, and Streptococcus parasanguinis) were grown in vitro in a complex medium designed to mimic the nutrient composition found in the human colon. Culture supernatants were assessed for the presence of anti-inflammatory and remission associated metabolites by GC-MS or LC-MS. Anti- and pro-inflammatory activities were determined by measuring IL-8 secretion, an inflammatory cytokine whose expression is elevated in UC patients, by HT29 epithelial cells after incubation with bacterial supernatants in the presence or absence of TNF-α. Epithelial integrity was assayed by measuring FITC-dextran leakage in a trans-well culture of differentiated primary human colonic epithelial cells challenged with IFN-γ in the presence or absence of culture supernatants. Results When cultured in vitro, all SER-287 lots tested produced the anti-inflammatory short-chain fatty acids butyrate and propionate and other metabolites associated with remission in the Phase 1b trial, including tryptophan metabolites, bile acids and medium-chain fatty acids. SER-287 culture supernatants significantly reduced IL-8 secretion in TNF-α stimulated HT29 cells while the pro-inflammatory consortium increased IL-8 secretion compared to TNF-α alone (Figure 1A). SER-287 lots induced minimal IL-8 secretion in the absence of TNF-α while the pro-inflammatory consortium strongly induced IL-8 (Figure 1B). SER-287 supernatants significantly decreased IFN-γ-mediated barrier disruption, while the pro-inflammatory consortium was not protective (Figure 2). Conclusions Production of remission-associated metabolites, reduction of epithelial inflammation, and protection from epithelial barrier damage are shown to be pharmacological properties of SER-287 which may underlie the mechanism of action of this microbiome therapeutic for mild-to-moderate UC.

The short-chain fatty acid propionate improved ventricular electrical remodeling in a rat model with myocardial infarction.

The short-chain fatty acid (SCFA) propionate (C3), a microorganism metabolite produced by gut microbial fermentation, has parasympathetic-activation effects. The cardiac autonomic rebalancing strategy is considered as an important therapeutic approach to myocardial infarction (MI)-produced ventricular arrhythmias (VAs). Thus, our research was designed to clarify the potential functions of the SCFA propionate in VAs and cardiac electrophysiology in MI rats. A hundred adult Sprague-Dawley rats were allocated to four groups: the sham group (200 mM sodium chloride), the sham + C3 group (200 mM propionate), the MI group (200 mM sodium chloride) and the MI + C3 group (200 mM propionate). In comparison with the sham group, propionate significantly increased the parasympathetic components heart rate variability (HRV) and acetylcholine levels, prolonged cardiac repolarization, induced STAT3 phosphorylation and up-regulated the c-fos expression in nodose ganglia and solitary nucleus. Propionate intake reduced the susceptibility to VAs. MI induced by coronary ligation caused a significant increase in the sympathetic components HRV, abnormal repolarization, global repolarization dispersion, norepinephrine and inflammatory cytokines, reduction and redistribution of Connexin 43 in the infarcted border zone, and activation of NFκB, which were attenuated in the MI + C3 group. Oral propionate supplementation, as a nutritional intervention, protected the heart against MI-induced VAs and cardiac electrophysiology instability partly by parasympathetic activation based on the gut-brain axis.

Effect of various salt concentrations on the ruminal parameters of goats

The objective of this study was to evaluate the effects of various concentrations of sodium chloride (NaCl), magnesium chloride (MgCl2), and calcium chloride (CaCl2) on the growth and in vitro fermentation of cellulolytic, glycolytic, and amylolytic microorganisms from the rumen of a goat. Six concentrations of each salt were tested separately, namely 0 mg/dL, 100 mg/dL, 200 mg/dL, 400 mg/dL, 800 mg/dL, and 1600 mg/dL in the culture medium. The experiments were conducted in a completely randomized design, in a 6 x 3 factorial arrangement of salt concentration and substrate (starch, cellulose, and glucose) with three replications of each treatment combination. Concentrations of microbial protein, ammonia (NH3-N), and volatile fatty acids (acetate, propionate, and butyrate) were measured. A quadratic effect of CaCl2 concentration on the production of microbial protein was observed in the cellulose medium. The effect of MgCl2 on NH3-N production in the cellulose medium decreased linearly. Propionate concentration decreased linearly with increasing levels of NaCl and MgCl2 in the media containing starch. There was a decreasing linear effect of MgCl2 on the concentration of butyrate in the media containing glucose. In conclusion, concentrations of NaCl and CaCl2 up to 1,600 mg/dL did not affect the microbial activity of starch, cellulose, and glucose-fermenting organisms. However, the microbial activity of starch-fermenting microbes was inhibited at salt concentrations above 800 mg/dL. Thus, brackish water could be used by goats in semiarid regions, but its use should be managed carefully so that it does not have a negative impact on rumen microbial populations.Keywords: cellulose, glucose, saline water, starch, ruminants

Metabolism of short-chain fatty acid propionate induces surface expression of NKG2D ligands on cancer cells.

SCFAs are primarily produced in the colon by bacterial fermentation of nondigestible carbohydrates. Besides providing energy, SCFAs can suppress development of colon cancer. The mechanism, however, remains elusive. Here, we demonstrate that the SCFA propionate upregulates surface expression of the immune stimulatory NKG2D ligands, MICA/B by imposing metabolic changes in dividing cells. Propionate-mediated MICA/B expression did not rely on GPR41/GPR43 receptors but depended on functional mitochondria. By siRNA-directed knockdown, we could further link phosphoenolpyruvate carboxykinase (PEPCK), the rate-limiting enzyme in gluconeogenesis to propionate regulation of MICA/B expression. Moreover, knockdown of Rictor and specific mTOR inhibitors implicated mTORC2 activity with metabolic changes that control MICA/B expression. SCFAs are precursors to short-chain acyl-CoAs that are used for histone acylation thereby linking the metabolic state to chromatin structure and gene expression. Propionate increased the overall acetylation and propionylation and inhibition of lysine acetyltransferases (KATs) that are responsible for adding acyl-CoAs to histones reduced propionate-mediated MICA/B expression, suggesting that propionate-induced acylation increases MICA/B expression. Notably, propionate upregulated MICA/B surface expression on colon cancer cells in an acylation-dependent manner; however, the impact of mitochondrial metabolism on MICA/B expression was different in colon cancer cells compared with Jurkat cells, suggesting that continuous exposure to propionate in the colon may provide an enhanced capacity to metabolize propionate. Together, our findings support that propionate causes metabolic changes resulting in NKG2D ligand surface expression, which holds potential as an immune activating anticancer therapy.

Co-Administration of Propionate or Protocatechuic Acid Does Not Affect DHA-Specific Transcriptional Effects on Lipid Metabolism in Cultured Hepatic Cells.

Long-chain n-3 polyunsaturated fatty acids (n-3 LC-PUFAs) are collectively recognized triglyceride-lowering agents, and their preventive action is likely mediated by changes in gene expression. However, as most studies employ fish oil, which contains a mixture of n-3 LC-PUFAs, the docosahexaenoic acid (DHA)-specific transcriptional effects on lipid metabolism are still unclear. The aim of the present study was to further elucidate the DHA-induced transcriptional effects on lipid metabolism in the liver, and to investigate the effects of co-administration with other bioactive compounds having effects on lipid metabolism. To this purpose, HepG2 cells were treated for 6 or 24 h with DHA, the short-chain fatty acid propionate (PRO), and protocatechuic acid (PCA), the main human metabolite of cyanidin-glucosides. Following supplementation, we mapped the global transcriptional changes. PRO and PCA alone had a very slight effect on the transcriptome; on the contrary, supplementation of DHA highly repressed the steroid and fatty acid biosynthesis pathways, this transcriptional modulation being not affected by co-supplementation. Our results confirm that DHA effect on lipid metabolism are mediated at least in part by modulation of the expression of specific genes. PRO and PCA could contribute to counteracting dyslipidemia through other mechanisms.

The microbe-derived short-chain fatty acids butyrate and propionate are associated with protection from chronic GVHD

AbstractStudies of the relationship between the gastrointestinal microbiota and outcomes in allogeneic hematopoietic stem cell transplantation (allo-HCT) have thus far largely focused on early complications, predominantly infection and acute graft-versus-host disease (GVHD). We examined the potential relationship of the microbiome with chronic GVHD (cGVHD) by analyzing stool and plasma samples collected late after allo-HCT using a case-control study design. We found lower circulating concentrations of the microbe-derived short-chain fatty acids (SCFAs) propionate and butyrate in day 100 plasma samples from patients who developed cGVHD, compared with those who remained free of this complication, in the initial case-control cohort of transplant patients and in a further cross-sectional cohort from an independent transplant center. An additional cross-sectional patient cohort from a third transplant center was analyzed; however, serum (rather than plasma) was available, and the differences in SCFAs observed in the plasma samples were not recapitulated. In sum, our findings from the primary case-control cohort and 1 of 2 cross-sectional cohorts explored suggest that the gastrointestinal microbiome may exert immunomodulatory effects in allo-HCT patients at least in part due to control of systemic concentrations of microbe-derived SCFAs.

Propionate supplementation promotes the expansion of peripheral regulatory T-Cells in patients with end-stage renal disease

Patients with end-stage renal disease (ESRD) suffer from a progressively increasing low-grade systemic inflammation, which is associated with higher morbidity and mortality. Regulatory T cells (Tregs) play an important role in regulation of the inflammatory process. Previously, it has been demonstrated that short-chain fatty acids reduce inflammation in the central nervous system in a murine model of multiple sclerosis through an increase in tissue infiltrating Tregs. Here, we evaluated the effect of the short-chain fatty acid propionate on the chronic inflammatory state and T-cell composition in ESRD patients. Analyzing ESRD patients and healthy blood donors before, during, and 60 days after the propionate supplementation by multiparametric flow cytometry we observed a gradual and significant expansion in the frequencies of CD25highCD127− Tregs in both groups. Phenotypic characterization suggests that polarization of naïve T cells towards Tregs is responsible for the observed expansion. In line with this, we observed a significant reduction of inflammatory marker CRP under propionate supplementation. Of interest, the observed anti-inflammatory surroundings did not affect the protective pathogen-specific immunity as demonstrated by the stable frequencies of effector/memory T cells specific for tetanus/diphtheria recall antigens. Collectively, our data suggest that dietary supplements with propionate have a beneficial effect on the elevated systemic inflammation of ESRD patients. The effect can be achieved through an expansion of circulating Tregs without affecting the protective pathogen-reactive immunity.

Association between the faecal short-chain fatty acid propionate and infant sleep.

The gut microbiota harvests energy from indigestible plant polysaccharides, forming short-chain fatty acids (SCFAs) that are absorbed from the bowel. SCFAs provide energy-presumably after easily digested food components have been absorbed from the small intestine. Infant night waking is believed by many parents to be due to hunger. Our objective was to determine whether faecal SCFAs are associated with longer uninterrupted sleep in infants. Infants (n = 57) provided faecal samples for determining SCFAs (7 months of age), and questionnaire data for determining infant sleep (7 and 8 months). Linear regression determined associations between SCFAs-faecal acetate, propionate and butyrate-and sleep. For each 1% higher propionate at 7 months of age, the longest night sleep was 6 (95% CI: 1, 10) minutes longer at both 7 and 8 months. A higher proportion of total faecal SCFA as propionate was associated with longer uninterrupted infant sleep.

Using Precisely Defined in vivo Microbiotas to Understand Microbial Regulation of IgE.

Early life exposure to microbes plays an important role in immune system development. Germ-free mice, or mice colonized with a low-diversity microbiota, exhibit high serum IgE levels. An increase in microbial richness, providing it occurs in a critical developmental window early in life, leads to inhibition of this hygiene-induced IgE. However, whether this inhibition is dependent solely on certain microbial species, or is an additive effect of microbial richness, remains to be determined. Here we report that mice colonized with a combination of bacterial species with specific characteristics is required to inhibit IgE levels. These defined characteristics include the presence in early life, acetate production and immunogenicity reflected by induction of IgA. Suppression of IgE did not correlate with production of the short chain fatty acids propionate and butyrate, or induction of peripherally induced Tregs in mucosal tissues. Thus, inhibition of IgE induction can be mediated by specific microbes and their associated metabolic pathways and immunogenic properties.

Residue of propolis extract in bovine diets with increasing levels of protein on rumen fermentation

Abstract: The objective of this work was to evaluate the effect of the residue from the extraction of propolis, added to bovine diets with increasing levels of protein, on ruminal fermentation in vitro. For this, the in vitro gas production technique was used. Incubation was carried out with inocula from three fistulated cows, in three periods. In each period, a cow received a daily dose of 100 g propolis residue. Four diets were evaluated: corn silage (control); and 25, 50, and 75% concentrate based on soybean meal. The following were determined: kinetics of rumen fermentation; dry matter degradation; production of gases, volatile fatty acids (acetate, propionate, and butyrate), methane, and ammonia nitrogen; and pH. The inclusion of 14.4, 15.1, and 9.5% propolis residue, respectively, to 25, 50, and 75% concentrate increased the production of gases from the degradation of fibrous carbohydrates, when compared with the control. The propolis residue reduces methane production and the acetate:propionate ratio at all tested concentrate inclusion levels.

Nutritional potential, in vitro ruminal fermentation kinetics and methanogenesis of stover from newer cultivars of sorghum (Sorghum bicolor) in buffalo

Context In developing countries of south Asia and Africa, cereal crop residues provide important fodder resources for ruminants. Genetic improvement through plant breeding for high-quality crop residues as well as for grain yield is gaining in demand among mixed crop–livestock farmers. Aims The present study investigated the potential nutritional quality, in vitro ruminal fermentation kinetics, gas production, enzyme activities and methane production of stover of newly developed brown midrib cultivars of sorghum (Sorghum bicolor (L.) Moench) compared with other cultivars in buffalo (Bubalus bubalis). Methods Stover from seven sorghum cultivars – brown midrib sorghum (SPV-2017, SPV-2018), normal grain sorghum (CSV-27), forage sorghum (SSG-59-3, CSV-32F) and sweet sorghum (CSH 22SS, CSV 24SS) – was analysed for chemical composition. Stover samples (200 ± 5 mg dry matter) from each cultivar were incubated with buffered rumen fluid (30 mL) in 100-mL calibrated glass syringes at 39°C for 72 h following a standard in vitro gas-production protocol for gas production and fermentation kinetics. Key results Stover chemical composition varied significantly (P < 0.05) among cultivars, with highest organic matter in forage sorghum SSG-59-3 and lowest in sweet sorghum CSV-24SS. Acid detergent lignin was lowest in stover of the brown midrib cultivars (1.27% in SPV-2018 and 1.67% in SPV-2017) and highest in forage sorghum SSG-59-3 (9.42%). The brown midrib cultivars showed highest (P < 0.001) total gas production, truly degradable dry matter, organic matter digestibility and metabolisable energy content. The brown midrib cultivars and forage sorghum CSV-32F had highest (P < 0.05) production of volatile fatty acids (acetate, propionate and butyrate) and activity of ruminal enzymes (carboxymethyl cellulase and xylanase) during fermentation. Conclusions This study demonstrates that stover from brown midrib sorghum cultivars (SPV-2017 and SPV-2018) and forage sorghum CSV-32F could be preferred over stover of other cultivars for animal feed owing to their potential for enhanced utilisation. Implications This study provides information on nutritional quality of stover from newly developed sorghum cultivars for large-scale utilisation as animal feed in smallholder production systems of developing countries.

Mixed Spices at Culinary Doses Have Prebiotic Effects in Healthy Adults: A Pilot Study

Spices were used as food preservatives prior to the advent of refrigeration, suggesting the possibility of effects on microbiota. Previous studies have shown prebiotic activities in animals and in vitro, but there has not been a demonstration of prebiotic or postbiotic effects at culinary doses in humans. In this randomized placebo-controlled study, we determined in twenty-nine healthy adults the effects on the gut microbiota of the consumption daily of capsules containing 5 g of mixed spices at culinary doses by comparison to a matched control group consuming a maltodextrin placebo capsule. The 16S ribosomal RNA sequencing data were used for microbial characterization. Spice consumption resulted in a significant reduction in Firmicutes abundance (p < 0.033) and a trend of enrichment in Bacteroidetes (p < 0.097) compared to placebo group. Twenty-six operational taxonomic units (OTUs) were different between the spice and placebo groups after intervention. Furthermore, there was a significant negative correlation between fecal short-chain fatty acid propionate concentration and Firmicutes abundance in spice intervention group (p < 0.04). The production of individual fecal short-chain fatty acid was not significantly changed by spice consumption in this study. Mixed spices consumption significantly modified gut microbiota, suggesting a prebiotic effect of spice consumption at culinary doses.

738-P: Meta’omic Analysis of Elite Athletes Identifies a Performance-Enhancing Microbe that Functions via Lactate Metabolism

The human gut microbiome encodes a vast metabolic repertoire with direct impacts on many aspects of host physiology, yet it is unknown whether it has any bearing on physical performance or exercise. To begin to address this question, we performed a longitudinal metagenomic analysis on runners in the 2015 Boston Marathon to identify microbiome features associated with intense physical activity. The strongest microbiome feature enriched post-marathon was an increase in the abundance of the bacterial genus Veillonella. We isolated Veillonella atypica directly from the marathon runners, and found that upon inoculation in laboratory mice in an AB/BA crossover study testing treadmill runtime to exhaustion, runtime was increased 13% in a V. atypica-dependent manner. V. atypica has a preference for lactate as its primary carbon source, and we find using shotgun metagenomic analysis in a cohort of elite athletes that every differentially expressed gene family in the pathway metabolizing lactate to the short-chain fatty acid propionate is at higher relative abundance post-exercise. Using 13C3-labeled lactate in mice we demonstrate that serum lactate crosses the epithelial barrier into the lumen of the gut. We also show that intrarectal instillation of propionate is sufficient to reproduce the increased treadmill runtime performance observed with V. atypica gavage. Taken together, these studies reveal that V. atypica improves runtime via its metabolic conversion of exercise-induced lactate into propionate, thereby identifying a natural, microbiome-encoded enzymatic process that enhances athletic performance. Disclosure A. Kostic: Stock/Shareholder; Self; DeepBiome Therapeutics, Inc., FitBiomics, Inc. Funding American Diabetes Association/Pathway to Stop Diabetes (1-17-INI-13)

Cecal Infusion of Sodium Propionate Promotes Intestinal Development and Jejunal Barrier Function in Growing Pigs.

Simple SummaryMicrobial-derived short-chain fatty acids can exert influence on intestinal development and intestinal barrier function. Usually, it is well known that short-chain fatty acid butyrate provides energy for the colonic cell turnover and maintains the integrity of the colonic epithelium. However, the effect of short-chain fatty acid propionate on intestinal development and jejunal barrier function is given less attention. In this study, we found that cecal infusion of propionate promoted development of the jejunum and colon, and selectively enhanced jejunal tight junction protein expression. These results suggest that propionate by microbial fermentation in the hindgut has an important role in intestinal development and gut health.Short-chain fatty acids (SCFAs) produced by microbial fermentation facilitate the differentiation and proliferation of intestinal epithelium. However, the role of individual SCFAs, such as propionate, on intestinal development is still unclear. In the present study, sixteen barrows fitted with a cecal fistula were randomly divided into two groups for cecal infusion of either saline (control group) or sodium propionate (propionate group). After 28 days, the length and the relative weight of intestinal segments were calculated, the intestinal morphology was assessed, and the expression of tight junction protein was measured using qPCR and Western blotting. Compared to the saline group, the length of the colon was significantly increased in the propionate group (p < 0.05). The jejunal villi length and villi/crypt ratio in the propionate group were significantly higher than in the saline group (p < 0.05). Furthermore, propionate infusion significantly upregulated the mRNA levels of Claudin-4 and the expression of Claudin-1, Claudin-4, and Occludin protein in the jejunal mucosa (p < 0.05). Collectively, these findings revealed that the short-chain fatty acid propionate in the hindgut contributed to intestinal development, and selectively enhanced jejunal tight junction protein expression.

Food preservative has metabolic side effects

The short-chain fatty acid propionate is used as a food preservative in cheeses and baked goods because it inhibits mold growth. It is also produced by microbes in the human gut. Now researchers report that it also has metabolic effects on animals and people. Amir Tirosh of Sheba Medical Center in Israel, Gökhan S. Hotamisligil of Harvard T.H. Chan School of Public Health, and their coworkers found that propionate induces increased glucose production and levels of the hormones norepinephrine, glucagon, and fatty acid–binding protein 4 (FABP4) in mice (Sci. Transl. Med. 2019, DOI: 10.1126/scitranslmed.aav0120). Mice lacking FABP4 or the liver glucagon receptor weren’t affected by the preservative. Some of the effects seen in animals were not observed in cell culture, suggesting they may be mediated by the sympathetic nervous system. Secretion of glucagon from pancreatic α cells and FABP4 from adipose cells didn’t change in response to propionate. Chronic exposure

The short-chain fatty acid propionate increases glucagon and FABP4 production, impairing insulin action in mice and humans.

The short-chain fatty acid propionate is a potent inhibitor of molds that is widely used as a food preservative and endogenously produced by gut microbiota. Although generally recognized as safe by the U.S. Food and Drug Administration, the metabolic effects of propionate consumption in humans are unclear. Here, we report that propionate stimulates glycogenolysis and hyperglycemia in mice by increasing plasma concentrations of glucagon and fatty acid-binding protein 4 (FABP4). Fabp4-deficient mice and mice lacking liver glucagon receptor were protected from the effects of propionate. Although propionate did not directly promote glucagon or FABP4 secretion in ex vivo rodent pancreatic islets and adipose tissue models, respectively, it activated the sympathetic nervous system in mice, leading to secretion of these hormones in vivo. This effect could be blocked by the pharmacological inhibition of norepinephrine, which prevented propionate-induced hyperglycemia in mice. In a randomized, double-blind, placebo-controlled study in humans, consumption of a propionate-containing mixed meal resulted in a postprandial increase in plasma glucagon, FABP4, and norepinephrine, leading to insulin resistance and compensatory hyperinsulinemia. Chronic exposure of mice to a propionate dose equivalent to that used for food preservation resulted in gradual weight gain. In humans, plasma propionate decreased with weight loss in the Dietary Intervention Randomized Controlled Trial (DIRECT) and served as an independent predictor of improved insulin sensitivity. Thus, propionate may activate a catecholamine-mediated increase in insulin counter-regulatory signals, leading to insulin resistance and hyperinsulinemia, which, over time, may promote adiposity and metabolic abnormalities. Further evaluation of the metabolic consequences of propionate consumption is warranted.