Fecal short chain fatty acids in children living on farms and a link between valeric acid and protection from eczema

Children growing up on farms have low rates of allergy, but the mechanism for this protective effect has not been fully elucidated. Short chain fatty acids (SCFAs) produced by the gut microbiota may play a role in protection from allergy. We measured fecal SCFA levels in samples collected from 28 farming and 37 control children over the first 3\ua0years of life using gas chromatography. Data on diet and other host factors were recorded and allergy was diagnosed at 8\ua0years of age. Among all children, median propionic and butyric acid concentration increased over the first 3\ua0years, and longer SCFAs typically appeared by 1\ua0year of age. Farm children had higher levels of iso-butyric, iso-valeric and valeric acid at 3\ua0years of age than rural controls. In addition, children with elder siblings had higher levels of valeric acid at 3\ua0years of age, and dietary factors also affected SCFA pattern. High levels of valeric acid at 3\ua0years of age were associated with low rate of eczema at 8\ua0years of age. The fecal SCFA pattern in farm children suggests a more rapid maturation of the gut microbiota. Valeric acid or associated microbes may have protective potential against eczema

Are all faecal bacteria detected with equal efficiency? A study using next-generation sequencing and quantitative culture of infants\u27 faecal samples

Background: Many species of intestinal bacteria are present in moderate numbers in the faecal microbiota, which is dominated by obligate anaerobes. Little is known regarding the detection sensitivity of next-generation sequencing for these microbes in samples of complex microbiota. Methods: Twenty stool samples from six healthy infants, who were followed from 1 week to 1 year of age, were previously cultured quantitatively for total population counts, as well as for counts of relevant facultative bacteria and a limited selection of obligate anaerobes that are prevalent in the neonatal microbiota. The same samples were analysed by Next-generation sequencing (NGS, pyrosequencing) of the 16S rRNA gene (V1–V3 regions; average read length, 500 nucleotides; average number of reads per sample, 30,000). We used the bacterial culture data to determine the lowest bacterial populations that could be detected by NGS. Different DNA extraction kits (QIAamp DNA Stool Mini, ZR Faecal DNA MiniPrep, and PowerSoil DNA Isolation) were compared for efficacy in extracting DNA from Gram-negative and Gram-positive Type strains. Results: NGS yielded one read per 106 CFU/g faeces of the Gram-negative commensal gut bacteria Bacteroides and Enterobacteriaceae, but only one read per 108 CFU/g faeces of Gram-positive bifidobacteria. The Gram-positive facultative bacteria Enterococcus was often undetectable by DNA-based methods despite being present at >106 CFU/g faeces. The DNA extraction kits tested varied considerably in their ability to extract DNA from bacterial samples, and showed considerably lower efficacies in extracting DNA from Gram-positive than from Gram-negative bacteria. Conclusions: NGS has lower sensitivity for detecting Gram-positive bacteria than Gram-negative bacteria, due at least in part to inefficient extraction of DNA from Gram-positive bacteria. Therefore, enzymatic lysis may enhance the yield of DNA and increase the sensitivity of NGS methods for Gram-positive bacteria, and the inclusion of positive and negative controls during DNA extraction is indicated for validation purposes. The differential extraction of DNA from bacterial samples by different DNA extraction kits may limit comparability between studies on the gut microbiota. Finally, quantitative culture methods detect certain bacteria with greater sensitivity than NGS techniques, and thus culture- and DNA-based methods can be used in tandem to define the complex composition of the gut microbiota with greater accuracy

Low Concentration of Fecal Valeric Acid at 1 Year of Age Is Linked with Eczema and Food Allergy at 13 Years of Age : Findings from a Swedish Birth Cohort

Background: Short-chain fatty acids (SCFAs) are abundant bacterial metabolites in the gut, with immunomodulatory properties. Hence, they may influence allergy development. Previous studies have linked fecal SCFA pattern during infancy with allergy. However, the association of SCFAs to allergic outcomes in adolescence is not well established. Here, we examined how the fecal SCFA pattern at 1 year of age related to allergy at 13 years of age. Methods: Levels of 8 SCFAs in fecal samples collected at 1 year of age from 110 children were quantified using gas chromatography. The same individuals were evaluated at 13 years of age for allergic symptoms, allergy diagnosis and allergy medication by questionnaire, and for sensitization using skin prick test against egg, milk, fish, wheat and soy, cat, dog, horse, birch, and timothy grass. Results: The concentration of fecal valeric acid at 1 year of age was inversely associated with eczema at 13 years of age (OR 0.6, 95% CI: 0.4-1.0, p = 0.049) and showed a trend for inverse association with food allergy at 13 years of age (OR 0.6, 95% CI: 0.4-1.0, p = 0.057). In a sub-group analysis of children with eczema at 1 year of age, a higher concentration of fecal valeric acid was linked with reduced risk of their eczema remaining at 13 years of age (OR 0.2, 95% CI: 0.0-1.5), although this latter analysis did not reach statistical significance (p = 0.12). Conclusions: Our findings lend further support to the notion of early childhood as a critical period when allergy may be programmed via the gut microbiota. Higher levels of fecal valeric acid may be characteristic of a protective gut microbiota and/or actively contribute to protection from eczema and food allergy

Short-chain fatty acids (SCFA) in infants’ plasma and corresponding mother’s milk and plasma in relation to subsequent sensitisation and atopic diseaseResearch in context

Summary: Background: Short-chain fatty acids (SCFAs) in intestinal contents may influence immune function, while less is known about SCFAs in blood plasma. The aims were to investigate the relation between infants’ and maternal plasma SCFAs, as well as SCFAs in mother’s milk, and relate SCFA concentrations in infant plasma to subsequent sensitisation and atopic disease. Methods: Infant plasma (N = 148) and corresponding mother’s milk and plasma were collected four months postpartum. Nine SCFA (formic, acetic, propionic, isobutyric, butyric, succinic, valeric, isovaleric, and caproic acid) were analysed by UPLC-MS. At 12 months of age, atopic disease was diagnosed by a pediatric allergologist, and sensitisation was measured by skin prick test. All families participated in the Swedish birth cohort NICE (Nutritional impact on Immunological maturation during Childhood in relation to the Environment). Findings: Infants with sensitisation, atopic eczema, or food allergy had significantly lower concentrations of five, three, and two SCFAs, respectively, in plasma at four months. Logistic regressions models showed significant negative associations between formic, succinic, and caproic acid and sensitisation [ORadj (95% CI) per SD: 0.41 (0.19–0.91); 0.19 (0.05–0.75); 0.25 (0.09–0.66)], and between acetic acid and atopic eczema [0.42 (0.18–0.95)], after adjusting for maternal allergy. Infants’ and maternal plasma SCFA concentrations correlated strongly, while milk SCFA concentrations were unrelated to both. Butyric and caproic acid concentrations were enriched around 100-fold, and iso-butyric and valeric acid around 3-5-fold in mother’s milk, while other SCFAs were less prevalent in milk than in plasma. Interpretation: Butyric and caproic acid might be actively transported into breast milk to meet the needs of the infant, although mechanistic studies are needed to confirm this. The negative associations between certain SCFAs on sensitisation and atopic disease adds to prior evidence regarding their immunoregulatory potential. Funding: Swedish Research Council (Nr. 2013-3145 and 2019-0137 to A-S.S.), Swedish Research Council for Health, Working Life and Welfare FORTE, Nr 2018-00485 to A.W.), The Swedish Asthma and Allergy Association's Research Fund (2020-0020 to A.S.)

Safety of vitamin K antagonist treatment for splanchnic vein thrombosis: A multicenter cohort study

Background: The treatment of splanchnic vein thrombosis (SVT) is challenging, due to the increased risk of bleeding and potentially life-threatening complications. Current recommendations are based on evidence from the treatment of venous thrombosis in usual sites, but small observational studies in SVT population suggest that the bleeding risk may offset the benefit of anticoagulant treatment in this setting. The aim of this study was to evaluate the safety of vitamin K antagonists (VKAs) in SVT patients. Methods: We retrospectively included SVT patients treated with VKAs followed by 37 Italian anticoagulation clinics, until June 2013. The primary outcome was the incidence of major bleeding (MB), according to the ISTH definition, during VKA treatment. Vascular events, including both arterial and venous thrombosis, and mortality were also documented. Results: Three hundred and seventy-five patients were included (median age 53 years; 54.7% males). During a median VKA treatment duration of 1.98 years, 15 MB events occurred, corresponding to an incidence rate of 1.24 (95% confidence interval [CI], 0.75-2.06) per 100 patient-years. Gastrointestinal bleeding represented 40% of all MB events. At multivariate analysis, the presence of esophageal varices emerged as independent predictor of MB (hazard ratio 5.4; 95% CI, 1.4-21.1). The incidence rate of vascular events on treatment was 1.37 (95% CI, 0.84-2.23) per 100 patient-years and the mortality rate was 0.83 (95% CI, 0.44-1.54) per 100 patient-years. Conclusions: Selected SVT patients followed by anticoagulation clinics for the management of VKA treatment show a low rate of major bleeding and vascular events