Effect of nanobubble water on medium chain carboxylic acids production in anaerobic digestion of cow manure.

Nanobubble water promotes the degradation of difficult-to-degrade organic matter, improves the activity of electron transfer systems during anaerobic digestion, and optimizes the composition of anaerobic microbial communities. Therefore, this study proposes the use of nanobubble water to improve the yield of medium chain carboxylic acids produced from cow manure by chain elongation. The experiment was divided into two stages: the first stage involved the acidification of cow manure to produce volatile acidic fatty acids as electron acceptors, and the second phase involved the addition of lactic acid as an electron donor for the chain elongation. Three experimental groups were established, and air, H2, and N2 nanobubble water were added in the second stage. Equal amounts of deionized water were added in the control group. The results showed that nanobubble water supplemented with air significantly increased the caproic acid concentration to 15.10 g/L, which was 55.03 % greater than that of the control group. The relative abundances of Bacillus and Caproiciproducens, which are involved in chain elongation, and Syntrophomonas, which is involved in electron transfer, increased. The unique ability of air nanobubble water supplemented to break down the cellulose matrix resulted in further decomposition of the recalcitrant material in cow manure. This effect subsequently increased the number of microorganisms associated with lignocellulose degradation, increasing carbohydrate metabolism and ATP-binding cassette transporter protein activity and enhancing fatty acid cycling pathways during chain elongation. Ultimately, this approach enabled the efficient production of medium chain carboxylic acids.

Comparative study on the structure characterization and activity of RS5 made from Canna edulis native starch and high-amylose corn starch.

In this study, the high amylose corn starch and Canna edulis native starch were compounded with lauric acid and fermented by human fecal inoculation in vitro. Changes in beneficial metabolite profile and microbiota composition were evaluated. The structural properties showed that both NS-12C and HAMS-12C formed V-shaped crystals under the same preparation method, but NS-12C had a higher composite index and resistance content than HAMS-12C. At the end of fermentation, the starch-lauric acid complexes prepared from the two types of starch significantly promoted the formation of short-chain fatty acids and the contents of acetic acid, butyric acid and valeric acid produced by NS-12C were higher than those of HAMS-12C(p>0.05). HAMS-12C and NS-12C both increased the relative abundance of Blautia. Notably, NS-12C also increased the relative abundance of beneficial bacteria Bifidobacterium and Meganomas, while HAMS-12C did not. These results suggested that this effect may be related to starch type and provide a basis for designing and producing functional foods to improve intestinal health in Canna edulis native starch.

Physicochemical and functional properties of short-chain fatty acid starch modified with different acyl groups and levels of modification.

Rice and quinoa starches are modified with short-chain fatty acids (SCFA) with different SCFA acyl chain lengths and levels of modification. This work is aimed to investigate the impact of modifying rice and quinoa starches with short-chain fatty acids (SCFAs) on various physicochemical properties, including particle size, protein and amylose content, thermal behavior, pasting characteristics, and in vitro digestibility. Both native and SCFA-starches showed comparable particle sizes, with rice starches ranging from 1.58 to 2.22 µm and quinoa starches from 5.18 to 5.72 µm. SCFA modification led to lower protein content in both rice (0.218-0.255 %) and quinoa starches (0.537-0.619 %) compared to their native counterparts. Esterification led to the reduction of gelatinization and pasting temperatures as well as the hardness of the paste of SCFA-starches were reduced while paste clarity increased. The highest level of modification in SCFA-starch was associated with the highest amount of resistant starch fraction. Principal component analysis revealed that modification levels exerted a greater influence on starch properties than the types of SCFA used (acetyl, propionyl, and butyryl). These findings is importance in considering the degree of substitution or level of modification when tailoring starch properties through SCFA modification, with implications for various applications in food applications.

Structural characterization of a novel polysaccharide from Tremella fuciformis and its interaction with gut microbiota.

BACKGROUND: Because of their diverse biological activities, polysaccharides derived from Tremella fuciformis have received growing attention. This study aimed to investigate the structural characterization of a purified polysaccharide (designated as PTP-3a) derived from T. fuciformis and explore its interaction with gut microbiota in vitro. RESULTS: The findings revealed that PTP-3a had a molecular weight of 1.22 × 103 kDa and consisted of fucose, glucose, xylose, mannose and glucuronic acid in a molar ratio of 0.271:0.016:0.275:0.400:0.038. The primary linkage types identified in PTP-3a were 1,3-linked-manp, 1,4-linked-xylp and 1,2,3-linked-fucp, with corresponding ratios of 0.215:0.161:0.15. In addition, PTP-3a demonstrated notable thermal stability and exhibited a triple-helical structure. Moreover, following in vitro fermentation for 48 h, PTP-3a was efficiently utilized, resulting in a reduction in carbohydrate levels, the production of short-chain fatty acids (SCFAs) and pH adjustment. Furthermore, during in vitro fecal microbial fermentation, PTP-3a decreased the relative abundance of Firmicutes while increasing the proportions of Bacteroidetes and Proteobacteria, resulting in a significantly reduced Firmicutes/Bacteroidetes ratio. Additionally, PTP-3a stimulated the growth of beneficial bacteria such as Parabacteroides merdae, Gordonibacter pamelaeae, Bifidobacterium pseudolongum and Parabacteroides distasonis. Importantly, a strong correlation was observed between the production of SCFAs and specific microorganisms. CONCLUSION: These findings suggested that PTP-3a has potential as a prebiotic for modulating the gut microbiota. © 2024 Society of Chemical Industry.

Structural changes of rice starch-anthocyanins complexes (V-type) and its impact on gut microbiotas and potential metabolic pathways during in vitro fermentation.

This study explored the differences in the in vitro fermentation properties of rice starch (RS) and rice starch-anthocyanins complexes (RS-A). Structural characterization suggested that RS and RS-A complexes showed a V-type crystalline structure. The degree of order (DO) and degree of double helix (DD) values of RS and RS-A complexes were enhanced after fermentation. Moreover, the RS-A complexes could improve the relative abundance of Bacteroidetes, Ruminococcaceae, and up-regulate gut microbiota diversity to maintain gut homeostasis. Relative abundance of potential metabolic pathways, such as energy metabolism, digestion system, and carbohydrate degradation overexpressed in the presence of RS-A complexes. The results demonstrated that the RS-A complexes had slower fermentation rates contributing to the transport of the formed short-chain fatty acid (SCFA) to the end of the colon and that the crystallinity might be a factor influencing the utilization of the starch matrix by the gut microbiota for SCFA formation.

Selective separation of nutrients and volatile fatty acids from food wastes using electrodialysis and membrane contactor for resource valorization.

Transport and selectivity parameters describe the quantity and purity of nutrients and volatile fatty acids (VFAs) separated from fermentation media. However, the complexity of fermentation media and low nutrient concentrations hinder the optimal conditions of such parameters. Exploring technologies to overcome such limitations is crucial for selectively separating VFAs from nutrients in fermented media. The objectives of this study were to investigate the: (1) flux, (2) recovery, (3) concentration factor, and (4) specific energy consumption of nutrients (NH4+, K+, NO3-, and PO43-) and VFAs (acetic, propionic, and butyric acid) via electrodialysis (ED), and (5) selectively separate the VFAs from the nutrients in the ED concentrate using a hydrophobic membrane contactor (HMC). Synthetic feed and real industrial fermented food wastes were used for ED and HMC experiments. The ED consumed 0.395 kWh/kg, recovering 64-95% of the nutrients and VFAs, corresponding to 4.1-9.4 and 0.6-22.1 g/L nutrients and VFAs, respectively. The HMC selectively separated over 94% of VFAs after ED, with <2% nutrients contamination in the final VFA stream. The results suggest that applying HMC after ED can concentrate and selectively separate VFAs from nutrients in fermented food wastes, which can be valorized for bio-based fertilizers and chemical platforms.

In vitro digestion and colonic fermentation characteristics of media-milled purple sweet potato particle-stabilized Pickering emulsions.

BACKGROUND: Pickering emulsions stabilized by multicomponent particles have attracted increasing attention. Research on characterizing the digestion and health benefit effects of these emulsions in the human gastrointestinal tract are quite limited. This work aims to reveal the digestive characteristics of media-milled purple sweet potato particle-stabilized Pickering emulsions (PSPP-Es) during in vitro digestion and colonic fermentation. RESULTS: The media-milling process improved the in vitro digestibility and fermentability of PSPP-Es by reaching afree fatty acids release rate of 43.11 ± 4.61% after gastrointestinal digestion and total phenolic content release of 101.00 ± 1.44 µg gallic acid equivalents/mL after fermentation. In addition, PSPP-Es exhibited good antioxidative activity (2,2-diphenyl-1-picrylhydrazyl and ferric reducing antioxidant power assays), α-glucosidase inhibitory activity (half-maximal inhibitory concentration: 6.70%, v/v), and prebiotic effects, reaching a total short-chain fatty acids production of 9.90 ± 0.12 mol L-1, boosting the growth of Akkermansia, Bifidobacterium, and Blautia and inhibiting the growth of Escherichia-Shigella. CONCLUSIONS: These findings indicate that the media-milling process enhances the potential health benefits of purple sweet potato particle-stabilized Pickering emulsions, which is beneficial for their application as a bioactive component delivery system in food and pharmaceutical products. © 2024 Society of Chemical Industry.

Alterations of the gut microbiota and fecal short-chain fatty acids in women undergoing assisted reproduction.

CONTEXT: The community structure of gut microbiota changes during pregnancy, which also affects the synthesis of short-chain fatty acids (SCFAs). However, the distribution of gut microbiota composition and metabolite SCFA levels are poorly understood in women undergoing assisted reproductive technology (ART). AIMS: To evaluate the changes in gut microbiota composition and metabolic SCFAs in women who received assisted reproduction treatment. METHODS: Sixty-three pregnant women with spontaneous pregnancy (SP) and nine with ART pregnancy were recruited to provide fecal samples. Gut microbiota abundance and SCFA levels were determined by 16S ribosomal RNA (rRNA) gene amplicon sequencing and gas chromatography-mass spectrometry (GC-MS). KEY RESULTS: The ART group showed decreased alpha diversity (the species richness or evenness in a sample). The principal coordinates analysis (a method of analysing beta diversity) showed significant difference in gut microbiota between the ART group versus the SP group (unweighted UniFrac distance, R 2 =0.04, P =0.003). Proteobacteria , Blautia and Escherichia-Shigella were enriched in the ART group, whereas the relative abundance of beneficial intestinal bacteria Faecalibacterium was lower than in the SP group. Different modes of conception were associated with several SCFAs (valeric acid (r =-0.280; P =0.017); isocaproic acid (r =-0.330; P =0.005); caproic acid (r =-0.336; P =0.004)). Significantly different SCFAs between the two groups were synchronously associated with the differential gut microbiota. CONCLUSIONS: The diversity and abundance of gut microbiota and the levels of SCFAs in women undergoing ART decreased. IMPLICATIONS: The application of ART shaped the microbial composition and metabolism, which may provide critical information for understanding the biological changes that occur in women with assisted reproduction.

High-Efficiency Recovery of Acetic Acid from Water Using Electroactive Gas-Stripping Membranes.

Recovery of carbon-based resources from waste is a critical need for achieving carbon neutrality and reducing fossil carbon extraction. We demonstrate a new approach for extracting volatile fatty acids (VFAs) using a multifunctional direct heated and pH swing membrane contactor. The membrane is a multilayer laminate composed of a carbon fiber (CF) bound to a hydrophobic membrane and sealed with a layer of polydimethylsiloxane (PDMS); this CF is used as a resistive heater to provide a thermal driving force for PDMS that, while a highly hydrophobic material, is known for its ability to rapidly pass gases, including water vapor. The transport mechanism for gas transport involves the diffusion of molecules through the free volume of the polymer matrix. CF coated with polyaniline (PANI) is used as an anode to induce an acidic pH swing at the interface between the membrane and water, which can protonate the VFA molecule. The innovative multilayer membrane used in this study has successfully demonstrated a highly efficient recovery of VFAs by simultaneously combining pH swing and joule heating. This novel technique has revealed a new concept in the field of VFA recovery, offering promising prospects for further advancements in this area. The energy consumption was 3.37 kWh/kg for acetic acid (AA), and an excellent separation factor of AA/water of 51.55 ± 2.11 was obtained with high AA fluxes of 51.00 ± 0.82 g.m-2hr-1. The interfacial electrochemical reactions enable the extraction of VFAs without the need for bulk temperature and pH modification.

In Vitro Gastrointestinal Digestion and Microbial Hydrolysis of Hydroxytyrosol-SCFA and Tyrosol-SCFA Acyl Esters: Controlled-Release of SCFAs and Polyphenols.

Phenolipids such as hydroxytyrosol-SCFA acyl esters (HTy-SEs) and tyrosol-SCFA acyl esters (TYr-SEs) with various alkyl chains lengths (C1-C4) and different isomers (branched-chain and straight-chain) were successfully synthesized. All esters were hydrolyzed by pancreatic lipase to produce polyphenols (HTy and TYr) and SCFAs (iso-butyric acid, acetic acid, propionic acid, and n-butyric acid). Moreover, HTy-SEs (and TYr-SEs) could also be hydrolyzed to free HTy (and TYr) and SCFAs by gut microbiota and Lactobacillus from mice feces. Especially, the hydrolysis rates showed positive correlation with the carbon skeleton length, and the hydrolysis degree (DH) of ester with a branched-chain fatty acid was weaker than that of ester with a straight-chain fatty acid. Besides, the DH values of TYr -SEs were significantly higher than those of HTy-SEs. Therefore, through regulating the structures of polyphenols, carbon skeleton lengths, and isomers, controlled-release of polyphenols and SCFAs from phenolipids will be easily achieved.

Regulation of short-chain fatty acids in the immune system.

A growing body of research suggests that short-chain fatty acids (SCFAs), metabolites produced by intestinal symbiotic bacteria that ferment dietary fibers (DFs), play a crucial role in the health status of symbiotes. SCFAs act on a variety of cell types to regulate important biological processes, including host metabolism, intestinal function, and immune function. SCFAs also affect the function and fate of immune cells. This finding provides a new concept in immune metabolism and a better understanding of the regulatory role of SCFAs in the immune system, which impacts the prevention and treatment of disease. The mechanism by which SCFAs induce or regulate the immune response is becoming increasingly clear. This review summarizes the different mechanisms through which SCFAs act in cells. According to the latest research, the regulatory role of SCFAs in the innate immune system, including in NLRP3 inflammasomes, receptors of TLR family members, neutrophils, macrophages, natural killer cells, eosinophils, basophils and innate lymphocyte subsets, is emphasized. The regulatory role of SCFAs in the adaptive immune system, including in T-cell subsets, B cells, and plasma cells, is also highlighted. In addition, we discuss the role that SCFAs play in regulating allergic airway inflammation, colitis, and osteoporosis by influencing the immune system. These findings provide evidence for determining treatment options based on metabolic regulation.

Fecal levels of SCFA and BCFA during capecitabine in patients with metastatic or unresectable colorectal cancer.

BACKGROUND: Gut bacteria-derived short-chain fatty acids (SCFA) and branched-chain fatty acids (BCFA) are considered to have beneficial metabolic, anti-inflammatory as well as anti-carcinogenic effects. Previous preclinical studies indicated bidirectional interactions between gut bacteria and the chemotherapeutic capecitabine or its metabolite 5-FU. This study investigated the effect of three cycles of capecitabine on fecal SCFA and BCFA levels and their associations with tumor response, nutritional status, physical performance, chemotherapy-induced toxicity, systemic inflammation and bacterial abundances in patients with colorectal cancer (CRC). METHODS: Forty-four patients with metastatic or unresectable CRC, scheduled for treatment with capecitabine (± bevacizumab), were prospectively enrolled. Patients collected a fecal sample and completed a questionnaire before (T1), during (T2) and after (T3) three cycles of capecitabine. Tumor response (CT/MRI scans), nutritional status (MUST score), physical performance (Karnofsky Performance Score) and chemotherapy-induced toxicity (CTCAE) were recorded. Additional data on clinical characteristics, treatment regimen, medical history and blood inflammatory parameters were collected. Fecal SCFA and BCFA concentrations were determined by gas chromatography-mass spectrometry (GC-MS). Gut microbiota composition was assessed using 16S rRNA amplicon sequencing. RESULTS: Fecal levels of the SCFA valerate and caproate decreased significantly during three cycles of capecitabine. Furthermore, baseline levels of the BCFA iso-butyrate were associated with tumor response. Nutritional status, physical performance and chemotherapy-induced toxicity were not significantly associated with SCFA or BCFA. Baseline SCFA correlated positively with blood neutrophil counts. At all time points, we identified associations between SCFA and BCFA and the relative abundance of bacterial taxa on family level. CONCLUSIONS: The present study provided first indications for a potential role of SCFA and BCFA during capecitabine treatment as well as implications for further research. TRIAL REGISTRATION: The current study was registered in the Dutch Trial Register (NTR6957) on 17/01/2018 and can be consulted via the International Clinical Trial Registry Platform (ICTRP).

Revealing an unrecognized role of free ammonia in sulfur transformation during sludge anaerobic treatment.

Free ammonia (FA), the unionized form of ammonium, is presented in anaerobic fermentation of waste activated sludge (WAS) at high levels. However, its potential role in sulfur transformation, especially H2S production, during WAS anaerobic fermentation process was unrecognized previously. This work aims to unveil how FA affects anaerobic sulfur transformation in WAS anaerobic fermentation. It was found that FA significantly inhibited H2S production. With an increase of FA from 0.04 to 159 mg/L, H2S production reduced by 69.9%. FA firstly attacked tyrosine-like proteins and aromatic-like proteins in sludge EPSs, with CO groups being responded first, which decreased the percentage of α-helix/(ß-sheet + random coil) and destroyed hydrogen bonding networks. Cell membrane potential and physiological status analysis showed that FA destroyed membrane integrity and increased the ratio of apoptotic and necrotic cells. These destroyed sludge EPSs structure and caused cell lysis, thus strongly inhibited the activities of hydrolytic microorganisms and sulfate reducing bacteria. Microbial analysis showed that FA reduced the abundance of functional microbes (e.g., Desulfobulbus and Desulfovibrio) and genes (e.g., MPST, CysP, and CysN) involved in organic sulfur hydrolysis and inorganic sulfate reduction. These findings unveil an actually existed but previously overlooked contributor to H2S inhibition in WAS anaerobic fermentation.

Production of prebiotic xylooligosaccharides from industrial-derived xylan residue by organic acid treatment.

In order to produce xylooligosaccharides (XOS) with excellent prebiotics properties from industrial-derived xylan residue (IDXR), maleic acid (MA) and citric acid (CA) were used as catalysts under different treatment conditions. Under the identified optimum conditions (0.1 M of MA and 0.5 M of CA at 150 °C for 40 min), CA showed a better ability than MA to maximumly produce XOS. The yields of XOS from MA and CA treatments were 48.9% and 52.3%, which were comprised of X2-X6 proportions of 69.47% and 66.70%, respectively. Anaerobic fermentation results demonstrated that both XOS-CA and XOS-MA exhibited pronounced prebiotic activity for proliferating Bifidobacterium adolescentis (B. adolescentis) and Lactobacillus acidophilus (L. acidophilus). XOS-CA possessed the better ability for B. adolescentis to produce the short-chain fatty acid (SCFA), while XOS-MA outperformed XOS-CA for L. acidophilus to produce SCFA. These results imply organic acid treatments can be applied to produce XOS with excellent prebiotic properties from IDXR.

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.

GC-MS analysis of short chain fatty acids and branched chain amino acids in urine and faeces samples from newborns and lactating mothers.

BACKGROUND: Short chain fatty acids (SCFAs) and branched chain amino acids (BCAAs) are frequently determined in faeces, and widely used as biomarkers of gut-microbiota activity. However, collection of faeces samples from neonates is not straightforward, and to date levels of these metabolites in newborn's faeces and urine samples have not been described. METHODS: A targeted gas chromatography - mass spectrometry (GC-MS) method for the determination of SCFAs and BCAAs in both faeces and urine samples has been validated. The analysis of 210 urine and 137 faeces samples collected from preterm (PI), term infants (TI) and their mothers was used to report faecal and urinary SCFA and BCAA levels in adult and neonatal populations. RESULTS: A significant correlation among five SCFAs and BCAAs in faeces and urine samples was observed. Reference ranges of SCFAs and BCAAs in mothers, PI and TI were reported showing infant's lower concentrations in faeces and higher concentrations in urine. CONCLUSION: This method presents a non-invasive approach for the simultaneous assessment of SCFAs and BCAAs in faecal and urine samples and the results will serve as a knowledge base for future experiments that will focus on the study of the impact of nutrition on the microbiome of lactating mothers and their infants.

Bio-oil production for biodiesel industry by Yarrowia lipolytica from volatile fatty acids in two-stage batch culture.

Microbial lipids-derived biodiesel is garnering much attention owing to its potential to substitute diesel fuel. In this study, lipid accumulation by Yarrowia lipolytica from volatile fatty acids (VFAs) was studied in a lab-scale stirred tank bioreactor. In batch cultures, Y. lipolytica NCYC 2904 was able to grow in 18 g·L-1 of VFAs (acetate, propionate, and butyrate), and the addition of a co-substrate (glucose) led to a fivefold improvement in lipid concentration. Furthermore, the two-stage batch culture (growth phase in glucose (1st stage) followed by a lipogenic phase in VFAs (2nd stage)) was the best strategy to obtain the highest lipid content in the cells (37%, w/w), with aeration conditions that kept dissolved oxygen concentration between 40% and 50% of saturation during the lipogenic phase. The estimated fuel properties of biodiesel produced from Y. lipolytica NCYC 2904 lipids are comparable with those of the biodiesel produced from vegetable oils and are in accordance with the international standards (EN 14214 and ASTM D6751). The cultivation strategies herein devised enable a sustainable, eco-friendly, and economical production of microbial lipids, based on feedstocks such as VFAs that can be derived from the acidogenic fermentation of organic wastes. KEY POINTS: • Addition of glucose to VFAs enhances lipids in Y. lipolytica in batch cultures • Two-stage batch culture - growth in glucose followed by VFAs pulse - rises lipids • Dissolved oxygen of 40-50% of saturation is crucial at the lipogenic phase.

Treatment of gouty arthritis is associated with restoring the gut microbiota and promoting the production of short-chain fatty acids.

INTRODUCTION: Although factors initiating the inflammatory response to monosodium urate crystals have been identified, the role of the gut microbiota and their metabolites on gout remains unknown. This study aimed to investigate the changes in both gut microbiota and short-chain fatty acids (SCFAs) according to inflammatory states of gout in the same patients. METHODS: This study enrolled 20 patients with gout in the acute state who had active joints and were followed up until the recovery state with no active joints. Blood and fecal samples were simultaneously collected within 3 days for each disease state. The stool microbiome was analyzed using 16S rRNA sequencing, and serum SCFAs were measured by gas chromatography-mass spectrometry. Differences in the gut microbiome and serum SCFAs were compared between the acute and recovery states. RESULTS: Beta diversity of the microbiome was significantly different between the acute and recovery states in terms of weighted UniFrac distance. In the recovery state, Prevotellaceae (p = 0.006) and the genus Prevotella (p = 0.009) were significantly enriched, whereas Enterobacteriaceae (p = 0.019) and its derivative genus Shigella (p = 0.023) were significantly decreased compared to the acute state. Similarly, the levels of acetate were dramatically increased in the recovery state compared to the acute state (p < 0.010). The levels of propionate and butyrate tended to increase but without statistical significance. CONCLUSION: Substantial alterations of bacterial composition with the promotion of SCFA formation (especially acetate) were found after treatment in patients with gouty arthritis.

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.

Detection and Structural Characterization of SFAHFA Homologous Series in Mouse Colon Contents by LTQ-Orbitrap-MS and Their Implication in Influenza Virus Infection.

Fatty acid esters of hydroxy fatty acids (FAHFAs) are a new class of endogenous lipids with promising physiological functions in mammals. We previously introduced a new type of lipids to this family called short-chain fatty acid esters of hydroxy fatty acids (SFAHFAs), branching specific to the C2 carbon of a long-chain fatty acid (≥C20). In this study, we discovered a homologous series of SFAHFAs comprising C16-C26 hydroxy fatty acids esterified with short-chain fatty acids (C2-C5) in mouse colon contents. The detected SFAHFAs were characterized by high-resolution mass spectrometry with MSn analysis. The double-bond position of monounsaturated SFAHFAs was determined by the epoxidation reaction of samples with m-chloroperoxybenzoic acid and their MSn analysis. Further, the measurement of SFAHFA concentration in the colon contents of mice infected with influenza A/Puerto Rico/8/34 (H1N1; PR8) virus revealed a significant increase in their levels compared to native control. A strong correlation was observed between hydroxy fatty acid and SFAHFAs. Detection, characterization, and profiling of these new SFAHFA levels in relation with pandemic H1N1; PR8 influenza virus will contribute to the in-depth study of their function and metabolism.