1.
Factors influencing the infant gut microbiome at age 3-6 months: Findings from the ethnically diverse Vitamin D Antenatal Asthma Reduction Trial (VDAART).
Sordillo, JE, Zhou, Y, McGeachie, MJ, Ziniti, J, Lange, N, Laranjo, N, Savage, JR, Carey, V, O'Connor, G, Sandel, M, et al
The Journal of allergy and clinical immunology. 2017;(2):482-491.e14
-
-
Free full text
-
Abstract
BACKGROUND The gut microbiome in infancy influences immune system maturation, and may have an important impact on allergic disease risk. OBJECTIVE We sought to determine how prenatal and early life factors impact the gut microbiome in a relatively large, ethnically diverse study population of infants at age 3 to 6 months, who were enrolled in Vitamin D Antenatal Asthma Reduction Trial, a clinical trial of vitamin D supplementation in pregnancy to prevent asthma and allergies in offspring. METHODS We performed 16S rRNA gene sequencing on 333 infants' stool samples. Microbial diversity was computed using the Shannon index. Factor analysis applied to the top 25 most abundant taxa revealed 4 underlying bacterial coabundance groups; the first dominated by Firmicutes (Lachnospiraceae/Clostridiales), the second by Proteobacteria (Klebsiella/Enterobacter), the third by Bacteriodetes, and the fourth by Veillonella. Scores for coabundance groups were used as outcomes in regression models, with prenatal/birth and demographic characteristics as independent predictors. Multivariate analysis, using all microbial community members, was also conducted. RESULTS White race/ethnicity was associated with lower diversity but higher Bacteroidetes coabundance scores. C-section birth was associated with higher diversity, but decreased Bacteroidetes coabundance scores. Firmicutes scores were higher for infants born by C-section. Breast-fed infants had lower proportions of Clostridiales. Cord blood vitamin D was linked to increased Lachnobacterium, but decreased Lactococcus. CONCLUSIONS The findings presented here suggest that race, mode of delivery, breast-feeding, and cord blood vitamin D levels are associated with infant gut microbiome composition, with possible long-term implications for immune system modulation and asthma/allergic disease incidence.
2.
Effects of surgical and dietary weight loss therapy for obesity on gut microbiota composition and nutrient absorption.
Damms-Machado, A, Mitra, S, Schollenberger, AE, Kramer, KM, Meile, T, Königsrainer, A, Huson, DH, Bischoff, SC
BioMed research international. 2015;:806248
Abstract
Evidence suggests a correlation between the gut microbiota composition and weight loss caused by caloric restriction. Laparoscopic sleeve gastrectomy (LSG), a surgical intervention for obesity, is classified as predominantly restrictive procedure. In this study we investigated functional weight loss mechanisms with regard to gut microbial changes and energy harvest induced by LSG and a very low calorie diet in ten obese subjects (n = 5 per group) demonstrating identical weight loss during a follow-up period of six months. For gut microbiome analysis next generation sequencing was performed and faeces were analyzed for targeted metabolomics. The energy-reabsorbing potential of the gut microbiota decreased following LSG, indicated by the Bacteroidetes/Firmicutes ratio, but increased during diet. Changes in butyrate-producing bacterial species were responsible for the Firmicutes changes in both groups. No alteration of faecal butyrate was observed, but the microbial capacity for butyrate fermentation decreased following LSG and increased following dietetic intervention. LSG resulted in enhanced faecal excretion of nonesterified fatty acids and bile acids. LSG, but not dietetic restriction, improved the obesity-associated gut microbiota composition towards a lean microbiome phenotype. Moreover, LSG increased malabsorption due to loss in energy-rich faecal substrates and impairment of bile acid circulation. This trial is registered with ClinicalTrials.gov NCT01344525.
3.
Physiological role for nitrate-reducing oral bacteria in blood pressure control.
Kapil, V, Haydar, SM, Pearl, V, Lundberg, JO, Weitzberg, E, Ahluwalia, A
Free radical biology & medicine. 2013;:93-100
Abstract
Circulating nitrate (NO(3)(-)), derived from dietary sources or endogenous nitric oxide production, is extracted from blood by the salivary glands, accumulates in saliva, and is then reduced to nitrite (NO(2)(-)) by the oral microflora. This process has historically been viewed as harmful, because nitrite can promote formation of potentially carcinogenic N-nitrosamines. More recent research, however, suggests that nitrite can also serve as a precursor for systemic generation of vasodilatory nitric oxide, and exogenous administration of nitrate reduces blood pressure in humans. However, whether oral nitrate-reducing bacteria participate in "setting" blood pressure is unknown. We investigated whether suppression of the oral microflora affects systemic nitrite levels and hence blood pressure in healthy individuals. We measured blood pressure (clinic, home, and 24-h ambulatory) in 19 healthy volunteers during an initial 7-day control period followed by a 7-day treatment period with a chlorhexidine-based antiseptic mouthwash. Oral nitrate-reducing capacity and nitrite levels were measured after each study period. Antiseptic mouthwash treatment reduced oral nitrite production by 90% (p < 0.001) and plasma nitrite levels by 25% (p = 0.001) compared to the control period. Systolic and diastolic blood pressure increased by 2-3 .5mmHg, increases correlated to a decrease in circulating nitrite concentrations (r(2) = 0.56, p = 0.002). The blood pressure effect appeared within 1 day of disruption of the oral microflora and was sustained during the 7-day mouthwash intervention. These results suggest that the recycling of endogenous nitrate by oral bacteria plays an important role in determination of plasma nitrite levels and thereby in the physiological control of blood pressure.