Multi-species synbiotic supplementation increased fecal short chain fatty acids and anti-inflammatory cytokine interleukin-10 in adult men with dyslipidemia; A randomized, double-blind, clinical trial.

BACKGROUND: Mounting evidence revealed that an imbalance of Gut Microbiota (GM) leads to metabolic disorders. Synbiotics through regulation of GM composition can be an effective intervention in the management of metabolic diseases. This study aimed to investigate the effects of multi-species synbiotic supplementation on serum interleukin10 (IL-10) and fecal Short Chain Fatty Acids (SCFAs) in patients with dyslipidemia. METHODS: In this double-blind, randomized, placebo-controlled clinical trial, fifty-six adult men with dyslipidemia were randomly allocated to intervention and control groups and received either synbiotic or placebo powder twice a day for 12 weeks. Each synbiotic sachet contained 6 species of probiotic microorganisms with a total dose of 3 × 1010 Colony Forming Unit (CFU) and 5 gr inulin and Fructooligosaccharide (FOS) as prebiotics. Blood and stool samples were collected at the baseline and end of the study. Dietary intake, physical activity, anthropometric measurements, serum IL-10, and fecal SCFAs were assessed before and after the intervention. RESULT: There were no significant differences between the baseline characteristics of patients in the two groups. Serum IL-10 was increased in the synbiotic group (p < 0.0001). Moreover, synbiotic supplementation increased fecal concentration of acetate (p < 0.0001), butyrate (p = 0.043), propionate (p < 0.0001), and valerate (p < 0.026). A significant positive correlation was observed between the changes in fecal butyrate level and serum IL-10 concentration in the control group (r = 0.48, p = 0.01). CONCLUSIONS: A Twelve-week synbiotic supplementation increased fecal SCFAs and improved inflammation in adult men with dyslipidemia.

Circulating Short-Chain Fatty Acids and Non-Alcoholic Fatty Liver Disease Severity in Patients with Type 2 Diabetes Mellitus.

(1) Background: Non-alcoholic fatty liver disease (NAFLD) is a major global health concern. The increasing prevalence of NAFLD has been related to type 2 diabetes mellitus (T2D). However, the relationship between short-chain fatty acids (SCFAs) and NAFLD severity is ambiguous in T2D subjects. This study aimed to explore the association of SCFAs with the severity of NAFLD in T2D patients. (2) Methods: We employed echography to examine the severity of hepatic steatosis. The serum levels of nine SCFAs, namely, formate, acetate, propionate, butyrate, isobutyrate, methylbutyrate, valerate, isovalerate, and methylvalerate, were measured using gas chromatography mass spectrometry. (3) Results: A total of 259 T2D patients was enrolled in this cross-sectional study. Of these participants, 117 with moderate to severe NAFLD had lower levels of formate, isobutyrate, and methylbutyrate than the 142 without NAFLD or with mild NAFLD. Lower circulating levels of isobutyrate and methylbutyrate were associated with an increased severity of NAFLD. A relationship between NAFLD severity and circulating isobutyrate and methylbutyrate levels was found independently of a glycated hemoglobin (HbA1C) level of 7.0%. (4) Conclusion: Circulating levels of isobutyrate and methylbutyrate were significantly and negatively correlated with NAFLD severity in the enrolled T2D patients. SCFAs may be related to NAFLD severity in T2D patients.

Gut Microbiome-Targeted Modulations Regulate Metabolic Profiles and Alleviate Altitude-Related Cardiac Hypertrophy in Rats.

It is well known that humans physiologically or pathologically respond to high altitude, with these responses accompanied by alterations in the gut microbiome. To investigate whether gut microbiota modulation can alleviate high-altitude-related diseases, we administered probiotics, prebiotics, and synbiotics in rat model with altitude-related cardiac impairment after hypobaric hypoxia challenge and observed that all three treatments alleviated cardiac hypertrophy as measured by heart weight-to-body weight ratio and gene expression levels of biomarkers in heart tissue. The disruption of gut microbiota induced by hypobaric hypoxia was also ameliorated, especially for microbes of Ruminococcaceae and Lachnospiraceae families. Metabolome revealed that hypobaric hypoxia significantly altered the plasma short-chain fatty acids (SCFAs), bile acids (BAs), amino acids, neurotransmitters, and free fatty acids, but not the overall fecal SCFAs and BAs. The treatments were able to restore homeostasis of plasma amino acids and neurotransmitters to a certain degree, but not for the other measured metabolites. This study paves the way to further investigate the underlying mechanisms of gut microbiome in high-altitude related diseases and opens opportunity to target gut microbiome for therapeutic purpose. IMPORTANCE Evidence suggests that gut microbiome changes upon hypobaric hypoxia exposure; however, it remains elusive whether this microbiome change is a merely derivational reflection of host physiological alteration, or it synergizes to exacerbate high-altitude diseases. We intervened gut microbiome in the rat model of prolonged hypobaric hypoxia challenge and found that the intervention could alleviate the symptoms of pathological cardiac hypertrophy, gut microbial dysbiosis, and metabolic disruptions of certain metabolites in gut and plasma induced by hypobaric hypoxia. Our study suggests that gut microbiome may be a causative factor for high-altitude-related pathogenesis and a target for therapeutic intervention.

Optimised Method for Short-Chain Fatty Acid Profiling of Bovine Milk and Serum.

Short-chain fatty acids (SCFA, C2-C5) in milk and serum are derived from rumen bacterial fermentation and, thus, have the potential to be used as biomarkers for the health status of dairy cows. Currently, there is no comprehensive and validated method that can be used to analyse all SCFAs in both bovine serum and milk. This paper reports an optimised protocol, combining 3-nitrophenylhydrazine (3-NPH) derivatisation and liquid chromatography-mass spectrometry (LC-MS) analysis for quantification of SCFA and ß-hydroxybutyric acid (BHBA) in both bovine milk and bovine serum. This method is sensitive (limit of detection (LOD) ≤ 0.1 µmol/L of bovine milk and serum), accurate (recovery 84-115% for most analytes) and reproducible (relative standard deviation (RSD) for repeated analyses below 7% for most measurements) with a short sample preparation step. The application of this method to samples collected from a small cohort of animals allowed us to reveal a large variation in SCFA concentration between serum and milk and across different animals as well as the strong correlation of some SCFAs between milk and serum samples.

Increased circulating butyrate and ursodeoxycholate during probiotic intervention in humans with type 2 diabetes.

BACKGROUND: An increasing body of evidence implicates the resident gut microbiota as playing a critical role in type 2 diabetes (T2D) pathogenesis. We previously reported significant improvement in postprandial glucose control in human participants with T2D following 12-week administration of a 5-strain novel probiotic formulation ('WBF-011') in a double-blind, randomized, placebo controlled setting (NCT03893422). While the clinical endpoints were encouraging, additional exploratory measurements were needed in order to link the motivating mechanistic hypothesis - increased short-chain fatty acids - with markers of disease. RESULTS: Here we report targeted and untargeted metabolomic measurements on fasting plasma (n = 104) collected at baseline and end of intervention. Butyrate and ursodeoxycholate increased among participants randomized to WBF-011, along with compelling trends between butyrate and glycated haemoglobin (HbA1c). In vitro monoculture experiments demonstrated that the formulation's C. butyricum strain efficiently synthesizes ursodeoxycholate from the primary bile acid chenodeoxycholate during butyrogenic growth. Untargeted metabolomics also revealed coordinated decreases in intermediates of fatty acid oxidation and bilirubin, potential secondary signatures for metabolic improvement. Finally, improvement in HbA1c was limited almost entirely to participants not using sulfonylurea drugs. We show that these drugs can inhibit growth of formulation strains in vitro. CONCLUSION: To our knowledge, this is the first description of an increase in circulating butyrate or ursodeoxycholate following a probiotic intervention in humans with T2D, adding support for the possibility of a targeted microbiome-based approach to assist in the management of T2D. The efficient synthesis of UDCA by C. butyricum is also likely of interest to investigators of its use as a probiotic in other disease settings. The potential for inhibitory interaction between sulfonylurea drugs and gut microbiota should be considered carefully in the design of future studies.

Effect of incremental proportions of Desmanthus spp. in isonitrogenous forage diets on growth performance, rumen fermentation and plasma metabolites of pen-fed growing Brahman, Charbray and Droughtmaster crossbred beef steers.

Desmanthus (Desmanthus spp.), a tropically adapted pasture legume, is highly productive and has the potential to reduce methane emissions in beef cattle. However, liveweight gain response to desmanthus supplementation has been inconclusive in ruminants. This study aimed to evaluate weight gain, rumen fermentation and plasma metabolites of Australian tropical beef cattle in response to supplementation with incremental levels of desmanthus forage legume in isonitrogenous diets. Forty-eight Brahman, Charbray and Droughtmaster crossbred beef steers were pen-housed and fed a basal diet of Rhodes grass (Chloris gayana) hay supplemented with 0, 15, 30 or 45% freshly chopped desmanthus forage on dry matter basis, for 140 days. Varying levels of lucerne (Medicago sativa) hay were added in the 0, 15 and 30% diets to ensure that all diets were isonitrogenous with the 45% desmanthus diet. Data were analyzed using the Mixed Model procedures of SAS software. Results showed that the proportion of desmanthus in the diet had no significant effect on steer liveweight, rumen volatile fatty acids molar proportions and plasma metabolites (P ≥ 0.067). Total bilirubin ranged between 3.0 and 3.6 µmol/L for all the diet treatments (P = 0.67). All plasma metabolites measured were within the expected normal range reported for beef cattle. Rumen ammonia nitrogen content was above the 10 mg/dl threshold required to maintain effective rumen microbial activity and maximize voluntary feed intake in cattle fed low-quality tropical forages. The average daily weight gains averaged 0.5 to 0.6 kg/day (P = 0.13) and were within the range required to meet the target slaughter weight for prime beef markets within 2.5 years of age. These results indicate that desmanthus alone or mixed with other high-quality legume forages can be used to supplement grass-based diets to improve tropical beef cattle production in northern Australia with no adverse effect on cattle health.

Metabolite trajectories across the perinatal period and mental health: A preliminary study of tryptophan-related metabolites, bile acids and microbial composition.

Depression and anxiety during pregnancy and postpartum are common, but affected women differ in timing, trajectories, and extent of symptoms. The objective of this pilot, feasibility study is to analyze trajectories of serotonin and tryptophan-related metabolites, bile acid metabolites, and microbial composition, in relation to psychiatric history and current symptoms across the perinatal period. Serum and fecal samples were collected from 30 women at three times points in the perinatal period and assayed with LC-MS/MS and 16S sequencing respectively. We defined mean trajectories for each metabolite, clustered individuals by metabolite trajectories, tested associations between metabolites, and examined metabolite levels in relation to microbial composition. Findings of note include: (1) changes in kynurenine and the ratio of kynurenic acid to kynurenine from second trimester to third trimester were strongly associated with baseline primary and secondary bile acids. (2) Secondary bile acid UDCA and its conjugated forms were associated with lower bacterial diversity and levels of Lachnospiraceae, a taxa known to produce Short Chain Fatty Acids. (3) History of anxiety was associated with UDCA levels, but history of major depression was not associated with any of the bile acids. (4) There was a trend towards lower dietary fiber for those with history of anxiety or depression. Overall, our results reveal substantial temporal variation in tryptophan-related metabolites and in bile acid metabolites over the perinatal period, with marked inter-individual variability. Trajectories of TRP -related metabolites, primary and secondary bile acids, and the absence or presence of microbes that produce Short Chain Fatty Acids (SCFAs) considered in concert have the potential to differentiate individuals based on perinatal adaptations that may impact mental and overall health.

The Prebiotic Effects of Oats on Blood Lipids, Gut Microbiota, and Short-Chain Fatty Acids in Mildly Hypercholesterolemic Subjects Compared With Rice: A Randomized, Controlled Trial.

Phytochemicals derived from oats are reported to possess a beneficial effect on modulating dyslipidemia, specifically on lowering total and LDL cholesterol. However, deeper insights into its mechanism remain unclear. In this randomized controlled study, we assigned 210 mildly hypercholesterolemic subjects from three study centers across China (Beijing, Nanjing, and Shanghai) to consume 80 g of oats or rice daily for 45 days. Plasma lipid profiles, short chain fatty acids (SCFAs), and fecal microbiota were measured. The results showed that total cholesterol (TC) and non-high-density lipoprotein cholesterol (non-HDL-C) decreased significantly with both oats and rice intake after 30 and 45 days. The reduction in TC and non-HDL-C was greater in the participants consuming oats compared with rice at day 45 (p = 0.011 and 0.049, respectively). Oat consumption significantly increased the abundance of Akkermansia muciniphila and Roseburia, and the relative abundance of Dialister, Butyrivibrio, and Paraprevotella, and decreased unclassified f-Sutterellaceae. In the oat group, Bifidobacterium abundance was negatively correlated with LDL-C (p = 0.01, r = -0.31) and, TC and LDL-C were negatively correlated to Faecalibacterium prausnitzii (p = 0.02, r = -0.29; p = 0.03, r = -0.27, respectively). Enterobacteriaceae, Roseburia, and Faecalibacterium prausnitzii were positively correlated with plasma butyric acid and valeric acid concentrations and negatively correlated to isobutyric acid. HDL-C was negatively correlated with valeric acid (p = 0.02, r = -0.25) and total triglyceride (TG) was positively correlated to isovaleric acid (p = 0.03, r = 0.23). Taken together, oats consumption significantly reduced TC and LDL-C, and also mediated a prebiotic effect on gut microbiome. Akkermansia muciniphila, Roseburia, Bifidobacterium, and Faecalibacterium prausnitzii, and plasma SCFA correlated with oat-induced changes in plasma lipids, suggesting prebiotic activity of oats to modulate gut microbiome could contribute towards its cholesterol-lowering effect.

The gut microbiota and microbial metabolites are associated with tail biting in pigs.

Tail biting is an abnormal behaviour that causes stress, injury and pain. Given the critical role of the gut-microbiota in the development of behavioural problems in humans and animals, the aim of this study was to determine whether pigs that are biters, victims of tail biting or controls (nine matched sets of pigs) have a different microbiota composition, diversity and microbial metabolite profile. We collected faecal and blood samples from each individual for analysis. The gut microbiota composition was most different between the biter and the control pigs, with a higher relative abundance of Firmicutes in tail biter pigs than the controls. Furthermore, we detected differences in faecal and plasma short chain fatty acids (SCFA) profiles between the biter and victim pigs, suggesting physiological differences even though they are kept in the same pen. Thus, in addition to supporting an association between the gut microbiota and tail biting in pigs, this study also provides the first evidence of an association between tail biting and SCFA. Therefore, further research is needed to confirm these associations, to determine causality and to study how the SCFA profiles of an individual play a role in the development of tail biting behaviour.

Consumption of peanut products improves memory and stress response in healthy adults from the ARISTOTLE study: A 6-month randomized controlled trial.

BACKGROUND: Peanuts are rich in bioactive compounds that may have a positive impact on memory and stress response. OBJECTIVE: To evaluate the effect of regular consumption of peanut products on cognitive functions and stress response in healthy young adults. DESIGN: A three-arm parallel-group randomized controlled trial was conducted in 63 healthy young adults that consumed 25 g/day of skin roasted peanuts (SRP, n = 21), 32 g/d of peanut butter (PB, n = 23) or 32 g/d of a control butter made from peanut oil (free of phenolic compounds and fiber) (CB, n = 19) for six months. Polyphenol intake, cognitive functions, and anxiety and depression scores were evaluated using validated tests. Fecal short-chain fatty acids (SCFAs) and plasma and fecal fatty acids were assessed by chromatographic methods. Urinary cortisol was quantified by an enzymatic method. RESULTS: Comparing the two interventions with the control, a significant reduction in anxiety scores was observed in the SRP compared to the CB group. After the intervention, consumers of SRP and PB had an improved immediate memory (p = 0.046 and p = 0.011). Lower anxiety scores were associated with SRP and PB (p < 0.001 and p = 0.002, respectively) and lower depression scores with SRP, PB and CB (p = 0.007, p = 0.003 and p = 0.032, respectively). Memory functions and stress response were significantly correlated with polyphenol intake, fecal SCFAs, plasma and fecal very long chain saturated fatty acids (VLCSFAs). CONCLUSIONS: Regular peanut and peanut butter consumption may enhance memory function and stress response in a healthy young population. These effects seem to be associated with the intake of peanut polyphenols, increased levels of fecal SCFAs, and unexpectedly, VLCSFAs, which were also present in the control product.

The change of gut microbiota-derived short-chain fatty acids in diabetic kidney disease.

BACKGROUND: Previous studies found the dysbiosis of intestinal microbiota in diabetic kidney disease (DKD), especially the decreased SCFA-producing bacteria. We aimed to investigate the concentration of the stool and serum short-chain fatty acids (SCFAs), gut microbiota-derived metabolites, in individuals with DKD and reveal the correlations between SCFAs and renal function. METHODS: A total of 30 participants with DKD, 30 participants with type 2 diabetes mellitus (DM), and 30 normal controls (NC) in HwaMei Hospital were recruited from 1/1/2018 to 12/31/2019. Participants with DKD were divided into low estimated glomerular filtration rate (eGFR)(eGFR<60ml/min, n=14) and high eGFR (eGFR≥60ml/min, n=16) subgroups. Stool and serum were measured for SCFAs with gas chromatograph-mass spectrometry. RESULTS: The DKD group showed markedly lower levels of fecal acetate, propionate, and butyrate versus NC (p<0.001, p<0.001, p=0.018, respectively) [1027.32(784.21-1357.90)]vs[2064.59(1561.82-2637.44)]µg/g,[929.53(493.65-1344.26)]vs[1684.57(1110.54-2324.69)]µg/g,[851.39(409.57-1611.65)] vs[1440.74(1004.15-2594.73)]µg/g, respectively, and the lowest fecal total SCFAs concentration among the groups. DKD group also had a lower serum caproate concentration than that with diabetes (p=0.020)[0.57(0.47-0.61)]vs[0.65(0.53-0.79)]µmol/L. In the univariate regression analysis, fecal and serum acetate correlated with eGFR (OR=1.013, p=0.072; OR=1.017, p=0.032). The correlation between serum total SCFAs and eGFR showed statistical significance (OR=1.019, p=0.024) unadjusted and a borderline significance (OR=1.024, p=0.063) when adjusted for Hb and LDL. The decrease in serum acetate and total SCFAs were found of borderline significant difference in both subgroups (p=0.055, p=0.050). CONCLUSION: This study provides evidence that in individuals with DKD, serum and fecal SCFAs levels (fecal level in particular) were lowered, and there was a negative correlation between SCFAs and renal function.

Alteration of the gut microbiome in mycophenolate-induced enteropathy: impacts on the profile of short-chain fatty acids in a mouse model.

BACKGROUND: Mycophenolic acid (MPA) is the most widely used immunosuppressive drug in transplantation and for autoimmune diseases. Unfortunately, more than 30% of patients experience a typical gastrointestinal adverse effect also referred to as mycophenolate-induced enteropathy. Due to its antibacterial, antifungal, and antiviral properties, MPA exposure is associated with intestinal dysbiosis characterized by a decrease in density and diversity of the microbiome regarding the main bacterial phyla (Firmicutes and Bacteroidetes). These bacterial phyla are known for their metabolic role in maintaining the homeostasis of the digestive tract, particularly through the production of short-chain fatty acids (SCFA) that could contribute to the pathophysiology of mycophenolate-induced enteropathy. Our study aimed at deciphering short-chain fatty acids (SCFA) profile alterations associated with gastrointestinal toxicity of MPA at the digestive and systemic levels in a mouse model. METHODS: Ten-week old C57BL/6 (SOPF) mice were randomly assigned in 2 groups of 9 subjects: control, and mycophenolate mofetil (MMF, 900 mg/kg/day). All mice were daily treated by oral gavage for 7 days. Individual faecal pellets were collected at days 0, 4 and 8 as well as plasma at day 8 for SCFA profiling. Additionally, after the sacrifice on day 8, the caecum was weighted, and colon length was measured. The proximal colon was cut for histological analysis. RESULTS: MMF treatment induced around 10% weight loss at the end of the protocol associated with a significant decrease in caecum weight and a slight reduction in colon length. Histological analysis showed significant architectural changes in colon epithelium. Moreover, we observed an overall decrease in SCFA concentrations in faecal samples, especially regarding acetate (at day 8, control 1040.6 ± 278.161 µM versus MMF 384.7 ± 80.5 µM, p < 0.01) and propionate (at day 8, control 185.94 ± 51.96 µM versus MMF 44.07 ± 14.66 µM, p < 0.001), and in plasma samples for butyrate (at day 8, control 0.91 ± 0.1 µM versus MMF 0.46 ± 0.1 µM, p < 0.01). CONCLUSIONS: These results are consistent with functional impairment of the gut microbiome linked with digestive or systemic defects during MMF treatment.

A highly sensitive, simple, and fast gas chromatography-mass spectrometry method for the quantification of serum short-chain fatty acids and their potential features in central obesity.

Short-chain fatty acids (SCFAs) are the main gut microbe metabolites, which have no more than six carbons. SCFAs are an emerging biomarker in metabolic diseases, including central obesity. Commonly, SCFAs are measured in fecal samples, where they are highly abundant, but here they do not reflect direct interactions with related organs. Serum SCFAs are assumed to be more associated with metabolic disease than fecal SCFAs, albeit at very low concentrations. The aim of the present study is to develop a highly sensitive, simple, and fast method for measuring six SCFAs in the serum by gas chromatography-mass spectrometry (GCMS). The serum is mixed with meta-phosphoric acid and 2,2-dimethylbutyric acid, followed by homogenization and centrifugation. Supernatant is then injected into the fused silica capillary column. The method is linear from 0.12-500 µmol/L for all SCFAs with an accuracy of 90-117%. The total coefficient of variation for precision ranges from 3.8 to 14.1%. A preliminary study is performed with 32 centrally obese subjects and 17 lean subjects. The mean values of all SCFAs, including acetic, propionic, isobutyric, butyric, isovaleric, and valeric acid, in the centrally obese subjects are significantly higher compared with lean subjects. A significant correlation also exists between all SCFAs, with the waist circumference indicating that serum SCFAs have potential features with respect to metabolic diseases, especially central obesity. The validated GCMS method provides highly sensitive, fast, simple, and reliable SCFA quantitation in the serum and demonstrates the potential features of circulating SCFAs in central obesity.

Beneficial effects of inorganic nitrate in non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is considered the hepatic representation of the metabolic disorders. Inorganic nitrate/nitrite can be converted to nitric oxide, regulate glucose metabolism, lower lipid levels, and reduce inflammation, thus raising the hypothesis that inorganic nitrate/nitrite could be beneficial for improving NAFLD. This study assessed the therapeutic effects of chronic dietary nitrate on NAFLD in a mouse model. 60 ApoE-/- mice were fed a high-fat diet (HFD) for 12 weeks to allow for the development of atherosclerosis with associated NAFLD. The mice were then randomly assigned to different groups (20/group) for a further 12 weeks: (i) HFD + NaCl (1 mmol/kg/day), (ii) HFD + NaNO3 (1 mmol/kg/day), and (iii) HFD + NaNO3 (10 mmol/kg/day). A fourth group of ApoE-/- mice consumed a normal chow diet for the duration of the study. At the end of the treatment, caecum contents, serum, and liver were collected. Consumption of the HFD resulted in significantly greater lipid accumulation in the liver compared to mice on the normal chow diet. Mice whose HFD was supplemented with dietary nitrate for the second half of the study, showed an attenuation in hepatic lipid accumulation. This was also associated with an increase in hepatic AMPK activity compared to mice on the HFD. In addition, a significant difference in bile acid profile was detected between mice on the HFD and those receiving the high dose nitrate supplemented HFD. In conclusion, dietary nitrate attenuates the progression of liver steatosis in ApoE-/- mice fed a HFD.

Sensitive and quantitative determination of short-chain fatty acids in human serum using liquid chromatography mass spectrometry.

Short-chain fatty acids (SCFAs) are increasingly being monitored to elucidate the link between gut health and disease. These metabolites are routinely measured in faeces, but their determination in serum is more challenging due to their low concentrations. A method for the determination of eight SCFAs in serum is described here. High-resolution mass spectrometry and gas chromatography were used to identify the presence of isomeric interferences, which were then overcome through a combination of chromatographic separation and judicious choice of MS fragment ion. The SCFAs were derivatised to form 3-nitrophenylhydrazones before being separated on a reversed-phase column and then detected using liquid chromatography tandem mass spectrometry (LC-QQQ-MS). The LODs and LOQs of SCFAs using this method were in the range 1 to 7 ng mL-1 and 3 to 19 ng mL-1, respectively. The recovery of the SCFAs in serum ranged from 94 to 114% over the three concentration ranges tested.

Reproducibility, Temporal Variability, and Concordance of Serum and Fecal Bile Acids and Short Chain Fatty Acids in a Population-Based Study.

BACKGROUND: Bile acid (BA) and short chain fatty acid (SCFA) production is affected by diet and microbial metabolism. These metabolites may play important roles in human carcinogenesis. METHODS: We used a fully quantitative targeted LC-MS/MS system to measure serum and fecal BA and SCFA concentrations in 136 Costa Rican adults at study baseline and 6-months. We randomly selected 50 participants and measured their baseline samples in duplicate. Our objective was to evaluate: Technical reproducibility; 6-month temporal variability; and concordance between sample type collected from the same individual at approximately the same time. RESULTS: Technical reproducibility was excellent, with intraclass correlation coefficients (ICC) ≥0.83 for all BAs except serum tauroursodeoxycholic acid (ICC = 0.72) and fecal glycolithocholic acid (ICC = 0.66) and ICCs ≥0.81 for all SCFAs except serum 2-methylbutyric acid (ICC = 0.56) and serum isobutyric acid (ICC = 0.64). Temporal variability ICCs were generally low, but several BAs (i.e., deoxycholic, glycoursodeoxycholic, lithocholic, taurocholic, and tauroursodeoxycholic acid) and SCFAs (i.e., 2-methylbutyric, butyric, propionic, and valeric acid) had 6-month ICCs ≥0.44. The highest degree of concordance was observed for secondary and tertiary BAs. CONCLUSIONS: Serum and fecal BAs and SCFAs were reproducibly measured. However, 6-month ICCs were generally low, indicating that serial biospecimen collections would increase statistical power in etiologic studies. The low concordance for most serum and fecal metabolites suggests that consideration should be paid to treating these as proxies. IMPACT: Our findings will inform the design and interpretation of future human studies on associations of BAs, SCFAs, and potentially other microbial metabolites, with disease risk.

Wheat bran with reduced particle size increases serum SCFAs in obese subjects without improving health parameters compared with a maltodextrin placebo.

BACKGROUND: Wheat bran (WB) has been associated with improved gastrointestinal health and a reduced risk of metabolic disorders. Reducing the particle size of WB might increase its fermentability and facilitate cross-feeding between the gut bacteria and in this way produce health effects. OBJECTIVES: We investigated the impact of WB with reduced particle size (WB RPS) on colonic fermentation and host health in normal-weight (NW) and obese (OB) participants compared with placebo (PL). METHODS: During 1 mo, 36 NW and 14 OB participants daily consumed 20 g WB RPS or PL (maltodextrin). Before and after the intervention, fasting serum and fecal SCFAs, fecal metabolite profiles, and microbiota composition were measured as fermentation parameters. Fecal output, fecal dry weight (%), fat excretion, transit, stool consistency, intestinal permeability, and serum total cholesterol, triglyceride, and C-reactive protein concentrations were measured as health parameters. The impact of WB RPS on the fermentation of other carbohydrates was assessed by quantifying postprandial cumulative serum 13C-SCFA after a challenge with 13C-inulin. RESULTS: WB RPS increased fasting serum acetate (P < 0.05) and total SCFA (P < 0.05) concentrations in OB participants. Fasting serum propionate concentrations were lower in OB than in NW participants at baseline (NW: 1.57 ± 0.75 µmol/L; OB: 0.89 ± 0.52 µmol/L; P < 0.01), but not after WB RPS (NW: 1.75 ± 0.77 µmol/L; OB: 1.35 ± 0.63 µmol/L; P = not significant). WB RPS did not enhance colonic fermentation of 13C-inulin and did not affect microbiota composition. Health parameters were not affected by the WB RPS intervention, either in NW or in OB participants. CONCLUSIONS: WB RPS increased fasting serum SCFA concentrations in OB participants. These changes were not associated with beneficial effects on host health.

Short-chain fatty acids combined with intronic DNA methylation of HIF3A: Potential predictors for diabetic cardiomyopathy.

BACKGROUND: Hyperglycemia can induce the heart to enter an oxygen-restricted environment, which results in diabetic cardiomyopathy (DCM). Microbiota-derived short-chain fatty acids (SCFAs) affect O2 consumption and play crucial roles in modulating metabolic and cardiovascular health. The epigenetic regulation of the hypoxia-inducible factor 3A (HIF3A) gene is implicated in oxidative metabolism in the pathogenesis of diabetes. Identifying the associations between plasma SCFA levels and intronic DNA methylation of HIF3A may reveal useful predictors or provide insights into the disease processes of DCM. METHODS: In this cross-sectional study, we analyzed plasma SCFA levels, HIF3A expression, and CpG methylation of HIF3A intron 1 in peripheral blood from patients with type 2 diabetes presenting with (n = 92) and without (n = 105) cardiomyopathy. RESULTS: Plasma butyric acid levels and HIF3A mRNA expression in peripheral blood were decreased in DCM patients, whereas 3 CpGs in HIF3A intron 1 (CpG 6, CpG 7 and CpG 11) were highly methylated in DCM patients. Interestingly, butyric acid levels positively correlated with HIF3A levels, while a negative association was identified between butyric acid levels and the methylation rates of HIF3A intron 1 at CpG 6. Butyric acid levels also correlated with several clinical/echocardiographic factors in DCM patients. Additionally, the combination of plasma butyric acid levels and HIF3A intron 1 methylation at CpG 6 discriminated DCM patients from type2 diabetes mellitus (T2DM) patients. CONCLUSIONS: The novel associations between plasma butyric acid levels and HIF3A intron 1 methylation at CpG 6 may highlight an underlying mechanism by which the "microbial-myocardial" axis and host-microbe interactions may participate in the pathogenesis of DCM.

Effects of cereal fibers on short-chain fatty acids in healthy subjects and patients: a meta-analysis of randomized clinical trials.

Short-chain fatty acids (SCFAs) are involved in the regulation of a wide array of diseases. However, the effect of cereal dietary fibers on SCFA production remains unclear. We reviewed relevant clinical studies between 1950 and 2021 and aimed to evaluate the effect of cereal fiber consumption on SCFA production in healthy subjects and patients. PubMed, Web of Science, and the Cochrane Library databases were used for systematically searching published relevant trials with adults and a minimum intervention duration of 2 weeks. The effect size was estimated using standardized mean difference (SMD) and 95% confidence interval (CI). Of the 555 identified studies, 14 intervention groups involving 205 participants aged between 20 and 69 years are eligible. The results of meta-analysis revealed that cereal fiber supplementation significantly increased acetate [SMD: 0.86, 95% CI (0.46, 1.25), p < 0.0001], propionate [SMD: 0.48, 95% CI: (0.15, 0.81), p = 0.004], butyrate [SMD: 0.61, 95% CI: (0.20, 1.01), p = 0.003], and total SCFA [SMD, 0.96, 95% CI: (0.54, 1.39), p < 0.00001] concentrations. Subgroup analysis suggested that a long intervention duration (>4 weeks) significantly promoted acetate and propionate production, whereas a short intervention duration (≤4 weeks) significantly facilitated butyrate production. Cereal fiber supplementation had a more significant impact on overweight and obese subjects with body mass index (BMI) >29 kg m-2 than on individuals with BMI ≤29 kg m-2. Furthermore, we found that cereal fibers and wheat/rye arabinoxylan oligosaccharides, rather than wheat bran fibers, barley fibers, and barley ß-glucan, could significantly elevate the SCFA concentration. Overall, our meta-analysis demonstrated that cereal fiber supplementation is helpful in increasing the SCFA concentration, which provided strong proof for the beneficial role of cereal fibers.