Microbial Production Of Short-chain Fatty Acids Research Articles

Ameliorative effect of peach gum on metabolic syndrome components and microbial short-chain fatty acids production in streptozotocin-induced rats

Peach gum (PG) contains a large number of polysaccharides and has hypolipidemic and anti-diabetic properties. Peach gum, specifically, may increase short-chain fatty acids (SCFAs), which modulate lipid, glucose, and insulin sensitivity and thus improve metabolic syndrome components (MetS). However, the mechanism remains unclear. This study aimed to reveal the effects of a whole PG intervention in ameliorating MetS conditions. Peach gum powder (PGP) was given in three dosages, comprised of PGP-L (210.64 mg), PGP-M (421.27 mg), and PGP-H (842.55 mg). Initially, PG was ground into powder (PGP). A total of five groups of Wistar rats were constituted. The healthy group was fed on a regular feeding (Comfeed AD II). MetS group was given a high-fat diet, a streptozotocin, and Nicotinamide injection. This study showed PGP significantly (p<0.001) ameliorate the condition of HDL-C (187.70%), triglycerides (TG) (-33.40%), fasting blood glucose (FBG) (-69.80%), insulin sensitivity (60.38%), also caecal SCFAs (p<0.05). It showed significant results of propionate and butyrate levels in the PHP-H group compared to the MetS group (p<0.05). The results indicated that PG has a significant hypolipidemic effect, particularly in improving HDL-C levels, as well as antidiabetic effects in MetS-induced rats, which are supported by an increase in SCFAs. The improvement in MetS components (HDL, TG, FBG) has improved in all PGP groups.

Intestinal permeability and gut microbiota interactions of pharmacologically active compounds in valerian and St. John’s wort

Phytomedicines such as valerian and St. John’s wort are widely used for the treatment of sleeping disorders, anxiety and mild depression. They are perceived as safe alternatives to synthetic drugs, but limited information is available on the intestinal absorption and interaction with human intestinal microbiota of pharmacologically relevant constituents valerenic acid in valerian, and hyperforin and hypericin in St. John’s wort. The intestinal permeability of these compounds and the antidepressant and anxiolytic drugs citalopram and diazepam was investigated in the Caco-2 cell model with bidirectional transport experiments. In addition, interaction of compounds and herbal extracts with intestinal microbiota was evaluated in artificial human gut microbiota. Microbiota-mediated metabolisation of compounds was assessed, and bacterial viability and short-chain fatty acids (SCFA) production were measured in the presence of compounds or herbal extracts. Valerenic acid and hyperforin were highly permeable in Caco-2 cell monolayers. Hypericin showed low-to-moderate permeability. An active transport process was potentially involved in the transfer of valerenic acid. Hyperforin and hypericin were mainly transported through passive transcellular diffusion. All compounds were not metabolized over 24 h in the artificial gut microbiota. Microbial SCFA production and bacterial viability was not substantially impaired nor promoted by exposure to the compounds or herbal extracts.

Gut microbiome signatures reflect different subtypes of irritable bowel syndrome

ABSTRACT Irritable bowel syndrome (IBS) is a heterogeneous condition with multifactorial pathogenesis. We studied deeply phenotyped individuals with microbiota sequencing enrolled in the American Gut Project. The IBS subjects were matched by age, gender, body mass index, geography, and dietary patterns with non-IBS controls. A total of 942 subjects with IBS-Diarrhea (IBS-D), IBS-Constipation (IBS-C), unclassified IBS (IBS-U), and 942 non-IBS controls were included. We compared taxonomic and functional composition of gut microbiota based on 16S sequencing data and linked them with clinical characteristics and dietary factors. Subjects with IBS-D or IBS-U but not IBS-C showed significantly reduced bacterial diversity (Shannon; p < .01). Distinct bacterial signatures were associated with different IBS subtypes, and the related functional changes were related to IBS pathogenesis, such as the increased hydrogen sulfide production pathway in IBS-D and the increased palmitoleate biosynthesis pathway in IBS-C. IBS subjects with depression showed lower abundance of Bifidobacterium, Sutterella, Butyricimonas and higher abundance of Proteus than those without depression. The relative abundance of microbial short-chain fatty acid production pathways was significantly lower in IBS patients with depression than those without depression in all three subtypes. Female, younger age in IBS-D, and older age in IBS-C were associated with more severe microbiota dysbiosis, and distinct dietary factors had significant effects on the gut microbiota in different IBS subtypes. Our analysis identified the compositional uniqueness of gut microbiota in different IBS subtypes. Distinct associations of the gut microbiota with depression in IBS provide insights into shared pathways in disease pathogenesis. These findings highlight the importance of personalized gut microbiome modulation approaches in different subtypes for optimal therapeutic effects.

Microbiota-dependent and -independent effects of dietary fibre on human health.

Dietary fibre, such as indigestible oligosaccharides and polysaccharides, occurs in many foods and has gained considerable importance related to its beneficial effects on host health and specific diseases. Dietary fibre is neither digested nor absorbed in the small intestine and modulates the composition of the gut microbiota. New evidence indicates that dietary fibre also interacts directly with the epithelium and immune cells throughout the gastrointestinal tract by microbiota-independent effects. This review focuses on how dietary fibre improves human health and the reported health benefits that are connected to molecular pathways, in (a) a microbiota-independent manner, via interaction with specific surface receptors on epithelial and immune cells regulating intestinal barrier and immune function, and (b) a microbiota-dependent manner via maintaining intestinal homeostasis by promoting beneficial microbes, including Bifidobacteria and Lactobacilli, limiting the growth, adhesion, and cytotoxicity of pathogenic microbes, as well as stimulating fibre-derived microbial short-chain fatty acid production. LINKED ARTICLES: This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc.

Proteomic analysis of the response of Escherichia coli to short-chain fatty acids

Given their simple and easy-to-manipulate chemical structures, short-chain fatty acids (SCFAs) are valuable feedstocks for many industrial applications. While the microbial production of SCFAs by engineered Escherichia coli has been demonstrated recently, productivity and yields are limited by their antimicrobial properties. In this work, we performed a comparative proteomic analysis of E. coli under octanoic acid stress (15mM) and identified the underlying mechanisms of SCFA toxicity. Out of a total of 33 spots differentially expressed at a p-value≤0.05, nine differentially expressed proteins involved in transport and structural roles (OmpF, HPr, and FliC), oxidative stress (SodA, SodB, and TrxA), protein synthesis (PPiB and RpsA) and metabolic functions (HPr, PflB) were selected for further investigation. Our studies suggest that membrane damage and oxidative stress are the main routes of inhibition by SCFAs in E. coli. The outer membrane porin OmpF had the greatest impact on SCFA tolerance. Intracellular pH analysis on ompF mutants grown under octanoic acid stress indicated that this porin facilitates transport of SCFAs into the cell. The same response was observed under hexanoic acid stress, further supporting the role of OmpF in response to the presence of SCFAs. Furthermore, analysis of membrane protein expression revealed that other outer membrane porins are also involved in the response of E. coli to SCFAs. Biological significanceThis work covers the first known proteomic analysis to assess the inhibitory effect of SCFAs in E. coli. SCFAs are molecules of great interest in the industry, but their microbial production is limited by their antimicrobial properties. This work allowed identification of differentially expressed proteins in response to SCFA stress and demonstrated the relevance of short- and medium-chain FA transport across the cell membrane via outer membrane porins, providing valuable insights on the toxicity mechanism of SCFAs in E. coli. These results could also benefit future engineering efforts by guiding the design and construction of industrial strains that produce SCFAs with increased tolerance and productivity.

Effect of gum arabic on glucose levels and microbial short-chain fatty acid production in white rice porridge model and mixed grain porridge model.

White rice porridge and mixed grain porridge, which are often consumed in many countries, were used as two models to evaluate the effects of gum arabic on glucose levels and microbial short-chain fatty acids (SCFA). Gum arabic was incorporated into the two porridges individually. Apparent viscosity of the two porridges was significantly increased, and their glucose productions during gastrointestinal digestion were notably lowered (p < 0.05). Diffused glucose amount was significantly decreased after gum arabic addition (p < 0.05). Furthermore, blood glucose rise after oral administration of porridges in mice was considerably lowered after fortified with gum arabic (p < 0.05). Microbial SCFA production during in vitro fermentation of porridges was significantly increased after gum arabic addition, which may also have beneficial effects on reducing postprandial glycemic response. Therefore, gum arabic may be a helpful ingredient, which could be added in porridges to have benefits for the reduction of postprandial glycemic response.

Microbial Short-Chain Fatty Acid Production and Extracellular Enzymes Activities during in Vitro Fermentation of Polysaccharides from the Seeds of Plantago asiatica L. Treated with Microwave Irradiation

Effects of microwave irradiation on microbial short-chain fatty acid production and the activites of extracellular enzymes during in vitro fermentation of the polysaccharide from Plantago asiatica L. were investigated in this study. It was found that the apparent viscosity, average molecular weight, and particle size of the polysaccharide decreased after microwave irradiation. Reducing sugar amount increased with molecular weight decrease, suggesting the degradation may derive from glycosidic bond rupture. The polysaccharide surface topography was changed from large flakelike structure to smaller chips. FT-IR showed that microwave irradiation did not alter the primary functional groups in the polysaccharide. However, short-chain fatty acid productions of the polysaccharide during in vitro fermentation significantly increased after microwave irradiation. Activities of microbial extracellular enzymes xylanase, arabinofuranosidase, xylosidase, and glucuronidase in fermentation cultures supplemented with microwave irradiation treated polysaccharide were also generally higher than those of untreated polysaccharide. This showed that microwave irradiation could be a promising degradation method for the production of value-added polysaccharides.

Mechanisms of acid injury in porcine gastroesophageal mucosa

Abstract Objective To identify the cause and mechanisms of injury in gastroesophageal ulcer disease in market weight swine. Design Comparison of mechanisms of injury caused by HCI with those caused by short chain fatty acids (SCFA) in gastric mucosa. Animals Pigs weighing 30 to 40 kg. Procedure Gastric tissues were studied in Ussing chambers; short-circuit current (Isc) and electrical resistance (R) were recorded in response to treatment, and tissues were examined histologically. Results 60 mM mucosal acetate abruptly (≤ 75 minutes) and irreversibly abolished Isc at pH ≤ 4.5, whereas R decreased more slowly. These data were associated with cell swelling and vesicle formation in mid-zonal layers, followed by sloughing of the outer barrier, erosion into deeper zones, and finally, ulceration. Mucosal HCI at pH &gt; 1.5 was ineffective; however, at pH 1.5, HCI induced an abrupt decrease in R, followed by a slow decrease in Isc, an effect opposite to that caused by SCFA. Serosal addition of HCI rapidly abolished Isc suggesting a barrier to free H+ diffusion from the mucosal solution. Conclusions Undissociated SCFA rapidly penetrate the outer barrier and acidify underlying viable tissue. Cellular acidification inhibits Na pumping and osmoregulation, resulting in cell swelling and necrosis. In contrast, HCI induces an increase in outer barrier permeability before accessing the transporting cells, a much longer process (≥ 5 hours) requiring a lower pH. These studies suggest that microbial production of SCFA may be important in the pathogenesis of porcine gastric ulcers. (Am J Vet Res 1996;57:564-573)