Butyric Acid

BackgroundThe fermentation of dietary fiber to various organic acids is a beneficial function provided by the microbiota in the human large intestine. In particular, butyric acid contributes to host health by facilitating maintenance of epithelial integrity, regulating inflammation, and influencing gene expression in colonocytes. We sought to increase the concentration of butyrate in 20 healthy young adults through dietary supplementation with resistant starch (unmodified potato starch-resistant starch (RS) type 2).MethodsFecal samples were collected from individuals to characterize butyrate concentration via liquid chromatography and composition of the microbiota via surveys of 16S rRNA-encoding gene sequences from the Illumina MiSeq platform. Random Forest and LEfSe analyses were used to associate responses in butyrate production to features of the microbiota.ResultsRS supplementation increased fecal butyrate concentrations in this cohort from 8 to 12 mmol/kg wet feces, but responses varied widely between individuals. Individuals could be categorized into three groups based upon butyrate concentrations before and during RS: enhanced, high, and low (n = 11, 3, and 6, respectively). Fecal butyrate increased by 67 % in the enhanced group (from 9 to 15 mmol/kg), while it remained ≥11 mmol/kg in the high group and ≤8 mmol/kg in the low group. Microbiota analyses revealed that the relative abundance of RS-degrading organisms-Bifidobacterium adolescentis or Ruminococcus bromii-increased from ~2 to 9 % in the enhanced and high groups, but remained at ~1.5 % in the low group. The lack of increase in RS-degrading bacteria in the low group may explain why there was no increase in fecal butyrate in response to RS. The microbiota of individuals in the high group were characterized by an elevated abundance of the butyrogenic microbe Eubacterium rectale (~6 % in high vs. 3 % in enhanced and low groups) throughout the study.ConclusionsWe document the heterogeneous responses in butyrate concentrations upon RS supplementation and identify characteristic of the microbiota that appear to underlie this variation. This study complements and extends other studies that call for personalized approaches to manage beneficial functions provided by gut microbiomes.

Alterations in gut microbiome composition have an emerging role in health and disease including brain function and behavior. Short chain fatty acids (SCFA) like propionic (PPA), and butyric acid (BA), which are present in diet and are fermentation products of many gastrointestinal bacteria, are showing increasing importance in host health, but also may be environmental contributors in neurodevelopmental disorders including autism spectrum disorders (ASD). Further to this we have shown SCFA administration to rodents over a variety of routes (intracerebroventricular, subcutaneous, intraperitoneal) or developmental time periods can elicit behavioral, electrophysiological, neuropathological and biochemical effects consistent with findings in ASD patients. SCFA are capable of altering host gene expression, partly due to their histone deacetylase inhibitor activity. We have previously shown BA can regulate tyrosine hydroxylase (TH) mRNA levels in a PC12 cell model. Since monoamine concentration is known to be elevated in the brain and blood of ASD patients and in many ASD animal models, we hypothesized that SCFA may directly influence brain monoaminergic pathways. When PC12 cells were transiently transfected with plasmids having a luciferase reporter gene under the control of the TH promoter, PPA was found to induce reporter gene activity over a wide concentration range. CREB transcription factor(s) was necessary for the transcriptional activation of TH gene by PPA. At lower concentrations PPA also caused accumulation of TH mRNA and protein, indicative of increased cell capacity to produce catecholamines. PPA and BA induced broad alterations in gene expression including neurotransmitter systems, neuronal cell adhesion molecules, inflammation, oxidative stress, lipid metabolism and mitochondrial function, all of which have been implicated in ASD. In conclusion, our data are consistent with a molecular mechanism through which gut related environmental signals such as increased levels of SCFA's can epigenetically modulate cell function further supporting their role as environmental contributors to ASD.

BackgroundButyrate has shown anti-inflammatory and regenerative properties, providing symptomatic relief when orally supplemented in patients suffering from various colonic diseases. We investigated the effect of a colonic-delivery formulation of butyrate on the fecal microbiota of patients with inflammatory bowel diseases (IBDs).MethodsIn this double-blind, placebo-controlled, pilot study, 49 IBD patients (n = 19 Crohn's disease, CD and n = 30 ulcerative colitis, UC) were randomized to oral administration of microencapsulated-sodium-butyrate (BLM) or placebo for 2 months, in addition to conventional therapy. Eighteen healthy volunteers (HVs) were recruited to provide a healthy microbiota model of the local people. Fecal microbiota from stool samples was assessed by 16S sequencing. Clinical disease activity and quality of life (QoL) were evaluated before and after treatment.Key resultsAt baseline, HVs showed a different microbiota composition compared with IBD patients. Sodium-butyrate altered the gut microbiota of IBD patients by increasing bacteria able to produce SCFA in UC patients (Lachnospiraceae spp.) and the butyrogenic colonic bacteria in CD patients (Butyricicoccus). In UC patients, QoL was positively affected by treatment.Conclusions and inferencesSodium-butyrate supplementation increases the growth of bacteria able to produce SCFA with potentially anti-inflammatory action. The clinical impact of this finding requires further investigation.

BackgroundDepression is closely associated with stress-induced hippocampal damage and dysfunction. Emerging evidence demonstrates that the gut microbiota and its metabolites, acting as probiotics or prebiotics, can modulate brain structure and function via the gut-brain axis, thereby offering therapeutic potential for ameliorating related neurological and psychiatric disorders. This study delves into the contribution of the gut microbiota and its metabolites to stress-induced ferroptosis of hippocampal neurons and the associated molecular pathways.MethodsThis study used time-course stress paradigms combined with ferroptosis inhibitors to identify hippocampal neuronal ferroptosis. Fecal microbiota transplantation were conducted to analyze the role of gut microbiota in this process. Subsequently, 16 S rDNA sequencing and metabolomics techniques were applied to identify key gut microbiota and metabolites. Metabolites intervention were performed to examine their causal relationship with neuronal ferroptosis. Finally, we used histochemical and molecular assays to assess both intestinal and blood-brain barrier integrity as well as inflammation in peripheral blood and hippocampal tissue, along with GPR41/RhoA/Rock1 pathway changes, to preliminarily investigate the molecular mechanisms underlying stress-induced hippocampal neuronal ferroptosis.ResultsWe demonstrated that stress triggered hippocampal neuronal ferroptosis and subsequent depressive-like behaviors in mice. Fecal microbiota transplantation successfully replicated the ferroptosis phenotype. Butyric acid and valeric acid were identified as key metabolites significantly reduced in the serum of acutely and chronically stressed mice, respectively. Intervention with these metabolites markedly alleviated ferroptosis. Furthermore, valerate intervention increased hippocampal GPR41 expression and significantly suppressed the pro-inflammatory RhoA/Rock1 pathway in chronically stressed mice, thereby reducing neuroinflammation and ameliorating neuronal ferroptosis. However, butyrate intervention showed no significant effect on the GPR41/RhoA/Rock1 pathway.ConclusionStress induces ferroptosis in hippocampal neurons, where reduced abundance of short-chain fatty acid-producing bacteria plays a key role. Key metabolites butyric acid and valeric acid alleviate neuroinflammation to improve ferroptosis via the gut-brain axis in acute and chronic stress, respectively. Specifically, valeric acid exerts neuroprotective effect through the GPR41/RhoA/Rock1 pathway, whereas butyric acid-mediated protection likely operates through alternative mechanisms.