Development and validation of a GC-FID method for the analysis of short chain fatty acids in rat and human faeces and in fermentation fluids

Fructooligosaccharides act on the gut-bone axis to improve bone independent of Tregs and alter osteocytes in young adult C57BL/6 female mice

Targeting the gut-bone axis with probiotics and prebiotics is considered as a promising strategy to reduce the risk of osteoporosis. Gut-derived short chain fatty acids (SCFA) mediate the effects of probiotics on bone via Tregs, but it is not known whether prebiotics act through a similar mechanism. We investigated how 2 different prebiotics, tart cherry (TC) and fructooligosaccharide (FOS), affect bone, and whether Tregs are required for this response. Eight-wk-old C57BL/6 female mice were fed with diets supplemented with 10% w/w TC, FOS, or a control diet (Con; AIN-93M) diet, and they received an isotype control or CD25 Ab to suppress Tregs. The FOS diet increased BMC, density, and trabecular bone volume in the vertebra (~40%) and proximal tibia (~30%) compared to the TC and control diets (Con), irrespective of CD25 treatment. Both prebiotics increased (P < .01) fecal SCFAs, but the response was greater with FOS. To determine how FOS affected bone cells, we examined genes involved in osteoblast and osteoclast differentiation and activity as well as genes expressed by osteocytes. The FOS increased the expression of regulators of osteoblast differentiation (bone morphogenetic protein 2 [Bmp2], Wnt family member 10b [Wnt10b] and Osterix [Osx]) and type 1 collagen). Osteoclasts regulators were unaltered. The FOS also increased the expression of genes associated with osteocytes, including (Phex), matrix extracellular phosphoglycoprotein (Mepe), and dentin matrix acidic phosphoprotein 1 (Dmp-1). However, Sost, the gene that encodes for sclerostin was also increased by FOS as the number and density of osteocytes increased. These findings demonstrate that FOS has a greater effect on the bone mass and structure in young adult female mice than TC and that its influence on osteoblasts and osteocytes is not dependent on Tregs.

Comparison of 3-nitrophenylhydrazine, O-benzyl hydroxylamine, and 2-picolylamine derivatizations for analysis of short-chain fatty acids through liquid chromatography coupled with tandem mass spectrometry

Short-chain fatty acids (SCFAs) are metabolites derived from gut microbiota and implicated in host homeostasis. Hence, the profiling SCFAs from biological samples plays an important role in revealing the interaction between gut microbiota and pathogens. Previous studies, liquid chromatography-tandem mass spectrometry (LC-MS/MS) combined with various derivatization strategies have been performed to obtain the SCFA profiles from biological samples. However, it is poor evidence to compare these derivatization regents and conditions. Thus, we present the evaluation of three major derivatization reagents, namely 3-nitrophenylhydrazine (3-NPH), O-benzylhydroxylamine (O-BHA), and 2-picolylamine (2-PA), for the analysis of eight SCFAs classified as C2-C5 isomers using LC-MS/MS. First, in a reversed-phase LC separation, 3-NPH showed good retention capacity. Although O-BHA derivatization showed higher sensitivity and good retention capacity than 2-PA, only 2-PA derivatization could successfully separate eight SCFAs. The matrix effects in human serum ranged 77.1-99.0% (RSD ≤ 3.4%, n = 6) for 3-NPH derivatives, 91.0-94.6% (RSD ≤ 5.4%, n = 6) for O-BHA derivatives, 81.6-99.5% (RSD ≤ 8.0%, n = 6) for 2-PA derivatives. These compared results showed each characteristic of 3-NPH, O-BHA, and 2-PA for SCFA derivatization based on LC-MS/MS approaches.

Effect of Stool Sampling on a Routine Clinical Method for the Quantification of Six Short Chain Fatty Acids in Stool Using Gas Chromatography-Mass Spectrometry

Short chain fatty acids (SCFAs) are primarily produced in the caecum and proximal colon via the bacterial fermentation of undigested carbohydrates that have avoided digestion in the small intestine. Increasing evidence supports the critical role that SCFAs play in health and homeostasis. Microbial SCFAs, namely butyric acid, serve as a principal energy source for colonocytes, and their production is essential for gut integrity. A direct link between SCFAs and some human pathological conditions, such as inflammatory bowel disease, irritable bowel syndrome, diarrhea, and cancer, has been proposed. The direct measurement of SCFAs in feces provides a non-invasive approach to demonstrating connections between SCFAs, microbiota, and metabolic diseases to estimate their potential applicability as meaningful biomarkers of intestinal health. This study aimed to adapt a robust analytical method (liquid-liquid extraction, followed by isobutyl chloroformate derivatization and GC-MS analysis), with comparable performances to methods from the literature, and to use this tool to tackle the question of pre-analytical conditions, namely stool processing. We focused on the methodology of managing stool samples before the analysis (fresh stool or dilution in either ethanol/methanol, lyophilized stool, or RNAlater®), as this is a significant issue to consider for standardizing results between clinical laboratories. The objective was to standardize methods for future applications as diagnostic tools. In this paper, we propose a validated GC-MS method for SCFA quantification in stool samples, including pre- and post-analytical comparison studies that could be easily used for clinical laboratory purposes. Our results show that using lyophilization as a stool-processing method would be the best method to achieve this goal.

Effect of a high-fat high-fructose diet on the composition of the intestinal microbiota and its association with metabolic and anthropometric parameters in a letrozole-induced mouse model of polycystic ovary syndrome

OBJECTIVE

It has been suggested that dysbiosis of the gut microbiota is associated with the pathogenesis of Polycystic Ovary Syndrome (PCOS), and that improper diet can aggravate these changes. This study thus aimed to investigate the effects of a high-fat/high-fructose (HF/HFr) diet on the gut microbial community and their metabolites in prepubertal female mice with letrozole (LET)-induced PCOS. We also tested the correlations between the relative abundance of microbial taxa and selected PCOS parameters.

RESEARCH METHODS & PROCEDURES

Thirty-two C57BL/6 mice were randomly divided into four groups (n = 8) and implanted with LET or a placebo, with simultaneous administration of a HF/HFr diet or standard diet (StD) for 5 wk. The blood and intestinal contents were collected after the sacrifice.

RESULTS

Placebo + HF/HFr and LET + HF/HFr had significantly higher microbial alpha diversity than either group fed StD. The LET-implanted mice fed StD had a significantly higher abundance of Prevotellaceae_UCG-001 than the placebo mice fed StD. Both groups fed the HF/HFr diet had significantly lower fecal levels of short-chain fatty acids than the placebo mice fed StD, while the LET + HF/HFr animals had significantly higher concentrations of lipopolysaccharides in blood serum than either the placebo or LET mice fed StD. Opposite correlations were observed between Turicibacter and Lactobacillus and the lipid profile, CONCLUSION: HF/HFr diet had a much stronger effect on the composition of the intestinal microbiota of prepubertal mice than LET itself.

A new isopropyl esterification method for quantitative profiling of short-chain fatty acids in human and cow milk by gas chromatograph-mass spectrometer

Short-chain fatty acids (SCFAs) content in milk may have been underestimated due to the neglect of the esterified SCFAs content and the lack of an accurate detection method, especially for C1:0, C2:0, and C3:0 SCFAs. In this study, an accurate gas chromatography-mass spectrometry profiling method was established for 10 SCFAs. A 2-step esterification, including alkaline saponification (60°C for 30 min) and acid-catalyzed esterification (80°C for 150 min) in water/isopropyl/hexane (1:2:1, volume ratio), was found to be the most suitable for the quantification of esterified and nonesterified SCFAs analysis. The validation results demonstrate satisfactory linearity, sensitivity, matrix effects, precision, and accuracy. The recoveries of nonesterified and esterified SCFAs ranged from 82.78% to 112.49%, respectively. Human milk is distinguished from cow milk by its higher C1:0 and C2:0 content and lower C4:0 and C6:0 content. This method successfully accomplished qualitative and quantitative estimation of all 10 SCFAs in milk, including both nonesterified and esterified SCFAs. Furthermore, whether our method is applicable for the determination of SCFAs in serum, rumen fluid, and feces remains to be explored.

Effect of Blueberry Supplementation on a Diet-Induced Rat Model of Prediabetes-Focus on Hepatic Lipid Deposition, Endoplasmic Stress Response and Autophagy

Blueberries, red fruits enriched in polyphenols and fibers, are envisaged as a promising nutraceutical intervention in a plethora of metabolic diseases. Prediabetes, an intermediate state between normal glucose tolerance and type 2 diabetes, fuels the development of complications, including hepatic steatosis. In previous work, we have demonstrated that blueberry juice (BJ) supplementation benefits glycemic control and lipid profile, which was accompanied by an amelioration of hepatic mitochondrial bioenergetics. The purpose of this study is to clarify the impact of long-term BJ nutraceutical intervention on cellular mechanisms that govern hepatic lipid homeostasis, namely autophagy and endoplasmic reticulum (ER) stress, in a rat model of prediabetes. Two groups of male Wistar rats, 8-weeks old, were fed a prediabetes-inducing high-fat diet (HFD) and one group was fed a control diet (CD). From the timepoint where the prediabetic phenotype was achieved (week 16) until the end of the study (week 24), one of the HFD-fed groups was daily orally supplemented with 25 g/kg body weight (BW) of BJ (HFD + BJ). BW, caloric intake, glucose tolerance and insulin sensitivity were monitored throughout the study. The serum and hepatic lipid contents were quantified. Liver and interscapular brown and epidydimal white adipose tissue depots (iBAT and eWAT) were collected for histological analysis and to assess thermogenesis, ER stress and autophagy markers. The gut microbiota composition and the short-chain fatty acids (SCFAs) content were determined in colon fecal samples. BJ supplementation positively impacted glycemic control but was unable to prevent obesity and adiposity. BJ-treated animals presented a reduction in fecal SCFAs, increased markers of arrested iBAT thermogenesis and energy expenditure, together with an aggravation of HFD-induced lipotoxicity and hepatic steatosis, which were accompanied by the inhibition of autophagy and ER stress responses in the liver. In conclusion, despite the improvement of glucose tolerance, BJ supplementation promoted a major impact on lipid management mechanisms at liver and AT levels in prediabetic animals, which might affect disease course.

In vitro study of potential prebiotic properties of monovarietal extra virgin olive oils

Olive oil, essential ingredient of the Mediterranean diet, is attracting a growing interest due to increasing evidence on its beneficial effects on human health. This study investigated whether extra virgin olive oil (EVOO) possess prebiotic properties. Twenty different monovarietal EVOO samples from 5 Marche region cultivars (Italy) were studied. The prebiotic activity of EVOOs was assessed monitoring the selective stimulation of gut bacterial species and the short chain fatty acids (SCFAs) production, using an in vitro fermentation system. All EVOOs selectively stimulated Lactobacillus spp., with a stronger activity than that observed in the inulin fermentation (positive control). Also, the bifidobacteria population increased; this bifidogenic stimulation was of EVOOs from Raggia cultivar. SCFAs appeared significantly higher after 24 h in all EVOO fermentations than in the control. Acetic and propionic acids production was particularly stimulated. Overall, most of the investigated EVOOs had a potential prebiotic activity, similar or stronger than inulin.

In Vitro Assessment of Postbiotic and Probiotic Commercial Dietary Supplements Recommended for Counteracting Intestinal Dysbiosis in Dogs

Many environmental aspects influence the preservation of a beneficial microbiome in dogs, and gut dysbiosis occurs when imbalances in the intestinal ecosystem cause functional changes in the microbial populations. The authors evaluated the effects of two specific commercial dietary supplements: a combination of a postbiotic and prebiotics (Microbiotal cane®) and a probiotic product (NBF 1®) recommended for counteracting intestinal dysbiosis in dogs, on the gut canine microbiota composition and its metabolic activities (production of short-chain fatty acids). The investigation was performed using an in vitro fermentation system inoculated with dog fecal samples. Microbiotal cane® promoted a more immediate increase in Lactobacillus spp. after the first 6 h of fermentation, whereas NBF 1® promoted the increase at the end of the process only. The two supplements supported an increase in the Bifidobacterium spp. counts only after 24 h. The in vitro abilities of Microbiotal cane® and NBF 1® to increase selectively beneficial bacterial groups producing acetic, propionic, and butyric acids suggest a possible positive effect on the canine gut microbiota, even if further in vivo studies are needed to confirm the beneficial effects on the intestinal health.

An Improved Validated Method for the Determination of Short-Chain Fatty Acids in Human Fecal Samples by Gas Chromatography with Flame Ionization Detection (GC-FID)

Short-chain fatty acids (SCFAs) are metabolites produced by the gut microbiota through the fermentation of non-digestible carbohydrates. Recent studies suggest that the gut microbiota composition, diet and metabolic status play an important role in the production of SCFAs. The primary objective of this study was to develop a simplified method for SCFA analysis in human fecal samples by gas chromatography with flame ionization detection (GC-FID). The secondary objective was to apply the method to fecal samples collected from a clinical trial. The developed GC-FID method showed excellent linearity (R2 > 0.99994), with a limit of detection (LOD) ranging from 0.02 to 0.23 µg/mL and a limit of quantification (LOQ) ranging from 0.08 to 0.78 µg/mL. Recovery for the method ranged between 54.24 ± 1.17% and 140.94 ± 2.10%. Intra- and inter-day repeatability ranged from 0.56 to 1.03 and from 0.10 to 4.76% RSD, respectively. Nine SCFAs were identified and quantified (acetic, propionic, iso-butyric, butyric, iso-valeric, valeric, 4-methyl valeric, hexanoic and heptanoic acids) in freeze-dried fecal samples. The clinical trial compared participants with prediabetes mellitus and insulin resistance (IR-group, n = 20) to metabolically healthy participants (reference group, R-group, n = 9) following a 4-week intervention of a daily red raspberry smoothie (RRB, 1 cup fresh-weight equivalent) with or without fructo-oligosaccharide (RRB + FOS, 1 cup RRB + 8 g FOS). The statistical analysis (Student's t-test, ANCOVA) was performed on PC-SAS 9.4 (SAS Institute). Acetic acid was higher in the R-group compared to the IR-group at baseline/week 0 (p = 0.14). No significant changes in fecal SCFA content were observed after 4 weeks of either RRB or RRB + FOS.

Analytical factors for eight short-chain fatty acid analyses in mouse feces through headspace solid-phase microextraction-triple quadrupole gas chromatography tandem mass spectrometry

This study developed a method for quantifying eight short-chain fatty acids (SCFAs) in mouse fecal samples using solid-phase microextraction (SPME) coupled with triple quadrupole gas chromatography tandem mass spectrometry. Furthermore, significant factors affecting SCFA analysis, including SPME fiber selection, pH, salting-out agent, and sample collection time, were investigated. Contrary to previous studies, we found that the CAR/PDMS fiber had the highest extraction efficiency for all SCFAs. The optimal extraction efficiency was observed at pH 2.0, particularly for low-molecular-weight SCFAs. NaH2PO4 showed a more effective extraction efficiency than NaCl, owing to its pH stability and less interference with the solvent matrix. Additionally, our results showed that the SCFA concentration increased over collection time. The composition ratio of the eight SCFAs was maintained for up to 24 h; thus, we concluded that samples should be collected within four hours to obtain reliable results. Our findings may improve laboratory methods for SCFA extraction and mouse fecal sample analysis.

Characteristics of the microstructure and the key components of white kidney bean sourdough bread induced by mixed-strain fermentation and its influence on gut microbiota

In this study, the effect of mixed-strain fermentation using Kluyveromyces marxianus with either Lactobacillus plantarum or Pediococcus pentosaceus on the physiochemical and nutritional properties of white kidney bean flour sourdough was investigated. The results indicated that mixed-strain fermentation reduced the anti-nutritional factors produced from the white kidney bean flour, especially in the sourdough fermented by L. plantarum and K. marxianus (WKS-LK) compared to that by P. pentosaceus and K. marxianus (WKS-JK). Meanwhile, the content of lactic acid and acetic acid and the proportion of peptides with molecular weights ranging from <500 to 5000 Da were increased in the sourdoughs (WKS-LK > WKS-JK). Compared to the control (WK), microstructural characteristics of the dough seemed to be improved in WKS-LK followed by WKS-JK in terms of their corresponding gluten network consistency. Moreover, mixed fermentation led to a reduced starch digestibility accompanied by a higher content of resistant starch and slowly digestible starch. In contrast, protein digestibility was enhanced in WKS-LK and WKS-JK sourdough breads. More importantly, the changes in gut microbiota composition, short-chain fatty acid (SCFA) production, systemic inflammation, glucose tolerance and liver tissue histopathology following 21-day consumption of the sourdough bread were also evaluated via an animal model. The intake of sourdough breads reduced the abundance of the pathogenic microbiota Escherichia shigella. In contrast, the corresponding abundance of Rikenellaceae, Akkermansiaceae, Erysipelotrichaceae, Prevotellaceae and Eubacterium coprostanoligenes was increased, followed by enhanced SCFA generation, with the highest in WKS-LK and then WKS-JK. Meanwhile, a reduced level of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α in the serum and improved glucose tolerance and liver tissue histopathology following the bread consumption were also achieved in the order of WKS-LK, then WKS-JK mice compared to WK.

Gut microbiota short-chain fatty acids and their impact on the host thyroid function and diseases

Thyroid disorders are clinically characterized by alterations of L-3,5,3',5'-tetraiodothyronine (T4), L-3,5,3'-triiodothyronine (T3), and/or thyroid-stimulating hormone (TSH) levels in the blood. The most frequent thyroid disorders are hypothyroidism, hyperthyroidism, and hypothyroxinemia. These conditions affect cell differentiation, function, and metabolism. It has been reported that 40% of the world's population suffers from some type of thyroid disorder and that several factors increase susceptibility to these diseases. Among them are iodine intake, environmental contamination, smoking, certain drugs, and genetic factors. Recently, the intestinal microbiota, composed of more than trillions of microbes, has emerged as a critical player in human health, and dysbiosis has been linked to thyroid diseases. The intestinal microbiota can affect host physiology by producing metabolites derived from dietary fiber, such as short-chain fatty acids (SCFAs). SCFAs have local actions in the intestine and can affect the central nervous system and immune system. Modulation of SCFAs-producing bacteria has also been connected to metabolic diseases, such as obesity and diabetes. In this review, we discuss how alterations in the production of SCFAs due to dysbiosis in patients could be related to thyroid disorders. The studies reviewed here may be of significant interest to endocrinology researchers and medical practitioners.

Cobalt-induced neuro-behavioural alterations are accompanied by profound Purkinje cell and gut-associated responses in rats

Metal ions including cobalt (Co) ions reportedly exhibit neurotoxic and antimicrobial properties. We hypothesized that oral exposure to Co may have implications for gut-dysbiosis with possible alterations of microbiota-gut-brain signaling in the host. In this preliminary study, we sought to examine whether exposure of male Wistar rats to cobalt chloride (CoCl2) at 0, 25, 50 and 100 mg/kg for two weeks affects select neurobehavioural indices, vagus nerve and brain morphology along with evaluation of associated changes in faecal bacterial flora, faecal fatty acids and the morphology of the intestines. CoCl2-exposed rats showed a dose-dependent reduction in hanging latency in the hanging wire (HW) test, reduced tendency to recognize novel objects in a Novel Object recognition (NOR) test, but increased interaction with open arms in the elevated plus maze (EPM) test, compared to controls. There were dose-dependent reductions in total heterotrophic count, coliforms, E. coli, Enterococcal and Lactobacilli counts in the faeces. Administration of CoCl2 at 100 mg/kg evoked the appearance of unsaturated fatty acids including palmitoleic, oleic and linoleic acids in the faeces as detected by gas chromatography-flame ion detection (GD-FID) analysis using fatty acid methyl esters (FAME) standards. Histopathological examination revealed chromatolysis of Purkinje cells in the cerebellum, although no significant lesions were present in the vagus nerve isolated from all the groups. In the intestines, there was moderate to severe infiltration of inflammatory cells into the duodenum, ileum, jejunum and colon while villi erosions were seen prominently in the ileum. These initial findings suggest that short-term exposure to Co can lead to gut-associated changes that may underlie neurotoxicity and alterations in behavior induced by Co.

Strategies to Assess the Impact of Sustainable Functional Food Ingredients on Gut Microbiota

Nowadays, it is evident that food ingredients have different roles and distinct health benefits to the consumer. Over the past years, the interest in functional foods, especially those targeting gut health, has grown significantly. The use of industrial byproducts as a source of new functional and sustainable ingredients as a response to such demands has raised interest. However, the properties of these ingredients can be affected once incorporated into different food matrices. Therefore, when searching for the least costly and most suitable, beneficial, and sustainable formulations, it is necessary to understand how such ingredients perform when supplemented in different food matrices and how they impact the host's health. As proposed in this manuscript, the ingredients' properties can be first evaluated using in vitro gastrointestinal tract (GIT) simulation models prior to validation through human clinical trials. In vitro models are powerful tools that mimic the physicochemical and physiological conditions of the GIT, enabling prediction of the potentials of functional ingredients per se and when incorporated into a food matrix. Understanding how newly developed ingredients from undervalued agro-industrial sources behave as supplements supports the development of new and more sustainable functional foods while scientifically backing up health-benefits claims.

Hydrolysis of pea protein differentially modulates its effect on iron bioaccessibility, sulfur availability, composition and activity of gut microbial communities in vitro

Both plant proteins and iron supplements can demonstrate high susceptibility to escape small intestinal digestion and absorption, hence are often present throughout colonic fermentation. Whilst colonic iron delivery may adversely affect the gut microbiota and epithelial integrity, nascent evidence suggests that pea proteins may possess beneficial prebiotic and antioxidant effects during gut fermentation. This study investigated the interaction between exogenously added iron and pea protein isolate (PPI) or pea protein hydrolysate (PPH) during in vitro gastrointestinal digestion and colonic fermentation. Results revealed that enzymatic hydrolysis mitigated the crude protein's inhibitory effects on iron solubility during small intestinal digestion. Colonic fermentation of iron-containing treatments led to an increase in iron bioaccessibility and was characterized by a loss of within-species diversity, a marked increase in members of Proteobacteria, and eradication of some species of Lactobacillaceae. Although these patterns were also observed with pea proteins, the extent of the effects differed. Only PPI displayed significantly higher levels of total short-chain fatty acids in the presence of iron, accompanied by greater abundance of Propionibacteriaceae relative to other treatments. Additionally, we provide evidence that the iron-induced changes in the gut microbiome may be associated with its effect on endogenous sulfur solubility. These findings highlight the potential trade-off between protein-induced enhancements in fortified iron bioaccessibility and effects on the gut microbiome, and the role of iron in facilitating colonic sulfur delivery.

Wheat Germ Supplementation Reduces Inflammation and Gut Epithelial Barrier Dysfunction in Female Interleukin-10 Knockout Mice Fed a Pro-Atherogenic Diet

BACKGROUND

Mice lacking IL-10 are prone to gut inflammation. Additionally, decreased production of short-chain fatty acids (SCFAs) plays a significant role in the high-fat (HF) diet-induced loss of gut epithelial integrity. We have previously shown that wheat germ (WG) supplementation increased ileal expression of IL-22, an important cytokine in maintaining gut epithelial homeostasis.

OBJECTIVES

This study investigated the effects of WG supplementation on gut inflammation and epithelial integrity in IL-10 knockout mice fed a pro-atherogenic diet.

METHODS

Eight-week-old female C57BL/6 wild type mice were fed a control diet (10% fat kcal), and age-matched knockout mice were randomly assigned to 1 of 3 diets (n = 10/group): control, high-fat high-cholesterol (HFHC) [(43.4% fat kcal (∼49% saturated fat, 1% cholesterol)], or HFHC + 10% WG (HFWG) for 12 wk. Fecal SCFAs and total indole, ileal, and serum proinflammatory cytokines, gene or protein expression of tight junctions, and immunomodulatory transcription factors were assessed. Data were analyzed by 1-way ANOVA, and P < 0.05 was considered statistically significant.

RESULTS

Fecal acetate, total SCFAs, and indole increased (P < 0.05) by at least 20% in HFWG compared with the other groups. WG increased (P < 0.0001, 2-fold) ileal Il22 (interleukin 22) to Il22ra2 (interleukin 22 receptor, alpha 2) mRNA ratio and prevented the HFHC diet-mediated increase in ileal protein expression of indoleamine 2,3 dioxygenase and pSTAT3 (phosphorylated signal transducer and activator of transcription 3). WG also prevented the HFHC diet-mediated reduction (P < 0.05) in ileal protein expression of the aryl hydrocarbon receptor and the tight junction protein, zonula occludens-1. Serum and ileal concentrations of the proinflammatory cytokine, IL-17, were lower (P < 0.05) by at least 30% in the HFWG group than in the HFHC group.

CONCLUSIONS

Our findings demonstrate that the anti-inflammatory potential of WG in IL-10 KO mice consuming an atherogenic diet is partly attributable to its effects on the IL-22 signaling and pSTAT3-mediated production of T helper 17 proinflammatory cytokines.

Development and Validation of a New GC-FID Method for the Determination of Short and Medium Chain Free Fatty Acids in Wine

A new analytical method for the determination of six volatile short and medium-chain fatty acids (acetic, propionic, isobutyric, isovaleric, hexanoic, and octanoic acids) through liquid-liquid extraction with diethyl ether, followed by GC-FID analysis, was developed and validated. The extraction conditions were optimized by evaluating the effect of the number of extractions (1 to 3) and the effect of the addition of salts (NaH₂PO₄, (NH₄)₂SO₄, NaCl, (NH₄)₂SO₄/NaH₂PO₄) to increase the concentration of the analytes in the ethyl ether phase. Results showed that a single extraction allows obtaining the highest sensitivity (due to the impossibility of evaporating the solvent to avoid losses of the analytes). The use of salting out agents, in particular, NaH₂PO₄, showed an important increase in the extraction extent, on average, 1.5 times higher as compared to the extraction performed without salt. The proposed method is rapid, requiring a total of 30 min for preparation and analysis, and it makes use of small amounts of sample (500 µL) and solvent (400 µL). The method was then applied to quantify the analytes in 5 white wines and 5 red wines, allowing to highlight some clear differences between red and white wines, with the red ones having a significantly higher amount of acetic acid (715.7 ± 142.3 mg/L in red wines and 351.5 ± 21.2 mg/L in white wines) and the white wines having a significantly higher amount of hexanoic and octanoic acid (6.1 ± 3.0 mg/L and 2.6 ± 0.8 mg/L, respectively, are the mean concentrations in white wines, and 4.7 ± 0.8 and 2.4 ± 0.4 mg/L, respectively, are the mean concentrations in red wines).

Potential Health Benefits of Yeast-Leavened Bread Containing LAB Pediococcus pentosaceus Fermented Pitaya (Hylocereus undatus): Both In Vitro and In Vivo Aspects

This study aimed to investigate the effect of the incorporation of 0–25% pitaya (Hylocereus undatus) fermented by Pediococcus pentosaceus on physicochemical and bioactive properties of yeast-leavened wheat-mung bean bread. The results revealed that β-glucosidase activity increased during dough proofing, which may contribute to changes in dietary fiber. Compared to wheat bread, experimental bread had an increased content of soluble dietary fiber (SDF), total phenolic, total flavonoid, and slowly digestible starch, especially in wheat-mung bean bread prepared with 15% pitaya fermentates (WMB-15F). The effect of bread consumption on systemic inflammation, glucose tolerance, and blood lipid profiles was also evaluated via a mice model. The results indicated that levels of pro-inflammatory cytokines declined and glucose tolerance improved, while LDL and HDL were positively modified compared to control. Furthermore, an increased abundance of Lactobacillus, Lachnospiraceae, and Bifidobacterium spp. was observed in WMB-15F mice. Acetic acid was the dominant short-chain fatty acids (SCFAs) in feces and serum in all groups. Total SCFAs in circulation were highest in WMB-15F mice compared to other groups. In summary, an increased abundance of beneficial gut microbiota and promoted SCFA production might be highly associated with increased SDF and the release of key phenolic compounds during dough proofing, which exerts health benefits aroused from the consumption of yeast-leavened bread.

Ephedra sinica polysaccharide alleviates airway inflammations of mouse asthma-like induced by PM2.5 and ovalbumin via the regulation of gut microbiota and short chain fatty acid

Objectives

Epidemiological investigations show that long-term exposure to PM2.5 is directly related to asthma-like and other respiratory diseases. This study aims to further explore the pharmacological effect of Ephedra sinica polysaccharide (ESP) on lung injury caused by atmospheric PM2.5.

Methods

To achieve the aim, we explored the therapeutic effect of ESP on an aggravated asthma-like mouse induced by PM2.5 combined with ovalbumin (OVA), and explored mechanisms underlying the connection between gut microbiota and lung function.

Key findings

Preliminary results showed that ESP alleviated the symptoms of aggravated allergic asthma-like in mice; reduced the number of eosinophils in BALF; reduced the levels of serum Ig-E, IL-6, TNF-α, and IL-1β. Further qRT-PCR detected that ESP inhibited the NF-κB pathway. The final analysis detected by 16S rRNA and short chain fatty acid (SCFA) confirmed that ESP increased relative proportions of Bacteroides, Lactobacillus, Prevotella, Butyricicoccus and Paraprevotella, but decreased that of Enterococcus and Ruminococcus; increased acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, and isohexanic acid in the meanwhile.

Conclusions

The study showed that ESP has a potential for future therapeutical applications in the prevention and treatment of asthma-like disease induced by PM2.5 and OVA via regulation of gut microbiota and SCFA.

The Correlation of Short-Chain Fatty Acids with Peripheral Arterial Disease in Diabetes Mellitus Patients

Diabetes mellitus (DM) is a significant risk factor for peripheral arterial disease (PAD). PAD affects 20% of DM patients over 40 and has increased by 29% in the last 50 years. The gut microbiota produces short-chain fatty acids (SCFAs) that affect atherosclerosis. SCFA inhibits inflammation, which contributes to atherosclerosis. This study tried to link feces SCFA levels to atherosclerosis in people with diabetes with peripheral arterial disease (PAD). The study included 53 people with diabetes and PAD: gas chromatography-mass spectrometry measured acetate, butyrate, and propionate levels in feces samples (GC-MS). There was a positive correlation between random blood glucose (RBG) levels, peak systolic velocity (PSV), volume flow (VF), plaque, relative and absolute acetate, relative valerate, butyrate, and propionate. This supports the idea that elevated SCFA levels in type 2 diabetic (T2D) patients reduce adipose tissue inflammation and cholesterol metabolism, contributing to atherosclerosis pathogenesis. We conclude that increased fecal SCFA excretion is linked to cardiovascular disease. To determine the causal effect correlation of the SCFA with clinical and laboratory parameters for PAD in DM patients, compare the SCFA in plasma and feces, and account for confounding variables, a specific method with larger sample sizes and more extended follow-up periods is required.

Effects of Fermented Milk Containing Bifidobacterium animalis Subsp. lactis MN-Gup (MN-Gup) and MN-Gup-Based Synbiotics on Obesity Induced by High Fat Diet in Rats

Given the probiotic effects previously found in Bifidobacterium animalis subsp. lactis MN-Gup (MN-Gup) and its great application potential in dairy products, this study aimed to investigate the effects of fermented milk containing MN-Gup or MN-Gup-based synbiotics on high fat diet (HFD)-induced obesity in rats. Galacto-oligosaccharides (GOS) and xylo-oligosaccharides (XOS) were selected as the tested prebiotics in MN-Gup-based synbiotics due to their promotion of MN-Gup growth in vitro. After nine weeks of HFD feeding, the obese rats were intervened with fermented milk containing MN-Gup (MN-Gup FM) or its synbiotics (MN-Gup + GOS FM, MN-Gup + XOS FM) for eight weeks. The results showed that the interventions could alleviate HFD-induced body weight gain, epididymal fat deposition, adipocyte hypertrophy, dyslipidemia and inflammation, but GOS and XOS did not exhibit significant synergies with MN-Gup on those alleviations. Furthermore, the interventions could regulate the HFD-affected gut microbiota and microbial metabolites, as shown by the increases in short chain fatty acids (SCFAs) and alterations in obesity-related bile acids (BAs), which may play important roles in the mechanism underlying the alleviation of obesity. This study revealed the probiotic effects of MN-Gup on alleviating obesity and provided the basis for MN-Gup applications in the future.

Oral administration of octacosanol modulates the gut bacteria and protects the intestinal barrier in ulcerative colitis mice

Octacosanol (Oct), a kind of long-chain fatty alcohol extracted from rice bran was applied to study its effects on alleviating ulcerative colitis (UC). Oct was orally administered at 10 mg/kg (Oct-L) and 30 mg/kg (Oct-H) to dextran sulfate sodium (DSS)-induced mice. Here, we reported that oral administration of 30 mg/kg Oct can significantly prevent the weight loss, colon shortening, and decrease the disease activity index (DAI) score. Oct-H supplementation modified the intestinal flora by lowering the Firmicutes/Bacteroidetes (F/B) ratio, increasing the abundance of Prevotellaceae, S24-7, Turicibacter, and meanwhile decreasing Enterococcus and Stenotrophomonas. Based on the PICRUSt2 analysis, Oct-H may exert effects by anti-inflammation and xenobiotics degradation. Furthermore, short-chain fatty acids (SCFAs) levels were raised and the integrity of the gut barrier was protected. In conclusion, Oct-H can relieve clinical symptoms, modulate the gut bacteria and protect the intestinal barrier in UC mice, suggesting the potential of Oct as a food supplementation in alleviating UC. PRACTICAL APPLICATIONS: Ulcerative colitis (UC) is a hard-to-cure disease, with increasing morbidity in recent years. Therefore, finding out a food supplement to alleviate UC is very meaningful. In this work, we showed that octacosanol significantly alleviated ulcerative colitis in mice. We revealed, for the first time, octacosanol's effects on protecting the integrity of the gut barrier, modulating the intestinal flora and its metabolism (SCFAs). Therefore, octacosanol was expected to prevent colitis in an all-round way. Our research might also lay the theoretical foundation for the further development of related functional foods.

Isotope-Coded Chemical Derivatization Method for Highly Accurately and Sensitively Quantifying Short-Chain Fatty Acids

Short-chain fatty acids (SCFAs) are major gut microbiota-derived metabolites, which can reshape the intestine and regulate gut immunity. The application of conventional GC methods has been hampered for quantifying low-concentrated SCFAs, such as in serum, saliva, and digesta of germ-free animals. Herein, we established a LC-MS method to quantify SCFAs after 5-(dimethylamino)-1-carbohydrazide-isoquinoline (DMAQ) derivatization. The DMAQ derivatization significantly enhanced the detection sensitivity and improved separation of SCFAs. 2-methylbutyric acid and 3-methylbutyric acid were separately quantitated. Moreover, the matrix effect was diminished using DMAQ-¹³C/¹⁵N-tagged SCFAs as internal standards. The established quantitation method was successfully applied in the analysis of plasma and cecum digesta collected from neonatal piglets, revealing that significant increases in biological SCFA contents in cecum digesta were closely related to the variation of gut microbial diversity. The established quantitation method is capable of sensitively and comprehensively quantifying SCFAs that may provide insights into underlying gut-microbiota functions.

Optimization and validation of direct gas chromatography-mass spectrometry method for simultaneous quantification of ten short-chain fatty acids in rat feces

Short-chain fatty acids (SCFAs) play key roles in maintaining health and treating disease. Quantification of important fecal SCFAs is necessary to facilitate the clarification of their biological roles. However, the existing quantifying methods mainly depend on complicated precolumn derivatization, and/or are unable to determine formic acid, a SCFA commonly associated with toxicity. In this study, a direct gas chromatography-mass spectrometry (GC-MS) method for simultaneous quantification of ten SCFAs including formic acid in rat feces was developed. The approach was optimized in terms of chromatographic and spectrometric conditions as well as sample preparation. DB-FFAP capillary column with temperature programming was used to get baseline separation and symmetrical peak shape of SCFAs without precolumn derivatization in a relatively short running time (8 min). Multiple reaction monitoring (MRM) scan mode was employed to enhance the sensitivity and selectivity of SCFAs. Acidification with 50% HCl and immediate extraction with diethyl ether were utilized to achieve sample preparation of ten SCFAs from feces. Furthermore, the developed method was validated with wide linear range, high sensitivity and precision, low matrix effect and acceptable accuracy. The established method was successfully applied to compare the contents of fecal SCFAs between normal and immunosuppressed animal models.

Fiber Nanoarchitectonics for Pre-Treatments in Facile Detection of Short-Chain Fatty Acids in Waste Water and Faecal Samples

Short-chain fatty acids (SCFAs) are among the active metabolites in biological process both in the intestinal tract and the bioconversion of organic wastes, which has resulted in various human diseases and environmental problems. In order to accurately detect SCFAs, we introduced a novel extraction sorbent. Electrospun polyacrylonitrile (PAN) nanofiber membrane was synthesized, then poly (3, 4-Ethylenedioxythiophene) (PEDOT) was deposited onto the surface of electrospun PAN nanofibers by in situ polymerization. The morphology of the composite PAN/PEDOT nanofiber was characterized by scanning electronic microscopy (SEM) and FTIR spectrum. PAN/PEDOT was used to isolate and concentrate the SCFAs in waste water and fecal samples before gas chromatography mass spectrometry (GC-MS) analysis. The analytical method was evaluated systematically, and low limits of detection (LODs) of 0.34–0.87 μg/L and good linearity (R² ≥ 0.9953) were obtained. The method was applied successfully for the determination of SCFAs in waste water and fecal samples, with good recovery (87.5–104.6%) and satisfactory reproducibility (relative standard deviation: 6.5–14.1%). The results indicated that the proposed method can be used as a potential approach for the determination of SCFAs with high sensitivity in waste water and biological samples.

Rapid Quantification of Gut Microbial Short-Chain Fatty Acids by pDART-MS

Short-chain fatty acids (SCFAs) are small molecules ubiquitous in nature. In mammalian guts, SCFAs are mostly produced by anaerobic intestinal microbiota through the fermentation of dietary fiber. Levels of microbe-derived SCFAs are closely relevant to human health status and indicative to gut microbiota dysbiosis. However, the quantification of SCFA using conventional chromatographic approaches is often time consuming, thus limiting high-throughput screening tests. Herein, we established a novel method to quantify SCFAs by coupling amidation derivatization of SCFAs with paper-loaded direct analysis in real time mass spectrometry (pDART-MS). Remarkably, SCFAs of a biological sample were quantitatively determined within a minute using the pDART-MS platform, which showed a limit of detection at the μM level. This platform was applied to quantify SCFAs in various biological samples, including feces from stressed rats, sera of patients with kidney disease, and fermentation products of metabolically engineered cyanobacteria. Significant differences in SCFA levels between different groups of biological practices were promptly revealed and evaluated. As there is a burgeoning demand for the analysis of SCFAs due to an increasing academic interest of gut microbiota and its metabolism, this newly developed platform will be of great potential in biological and clinical sciences as well as in industrial quality control.