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Obesity is a complex metabolic disease caused, in part, by the interaction between an individual's genetics, metabolism, and environment. Emerging evidence supports the role of gut microbiota in mediating the interaction between the host and environment by extracting energy from food otherwise indigestible by the host and producing metabolites and cytokines that affect host metabolism. Furthermore, gut microbial imbalance or dysbiosis has been shown in metabolic diseases including obesity, and recent studies are beginning to unravel the mechanisms involved. The gut microbiota affects host metabolism and obesity through several pathways involving gut barrier integrity, production of metabolites affecting satiety and insulin resistance, epigenetic factors, and metabolism of bile acids and subsequent changes in metabolic signaling. While the field of gut microbiome and its role in obesity is early in its stage of development, it holds a promising future in providing us with novel therapeutic targets that may restore the gut microbiome to a healthy state and help in the prevention and treatment of obesity. [ABSTRACT FROM AUTHOR]

Meta-analysis is a practical and powerful analytic tool that enables a unified statistical inference across the results from multiple studies. Notably, researchers often report the results on multiple related markers in each study (eg, various α-diversity indices in microbiome studies). However, univariate meta-analyses are limited to combining the results on a single common marker at a time, whereas existing multivariate meta-analyses are limited to the situations where marker-by-marker correlations are given in each study. Thus, here we introduce two meta-analysis methods, multi-marker meta-analysis (mMeta) and adaptive multi-marker meta-analysis (aMeta), to combine multiple studies throughout multiple related markers with no priori results on marker-by-marker correlations. mMeta is a statistical estimator for a pooled estimate and its SE across all the studies and markers, whereas aMeta is a statistical test based on the test statistic of the minimum P-value among marker-specific meta-analyses. mMeta conducts both effect estimation and hypothesis testing based on a weighted average of marker-specific pooled estimates while estimating marker-by-marker correlations non-parametrically via permutations, yet its power is only moderate. In contrast, aMeta closely approaches the highest power among marker-specific meta-analyses, yet it is limited to hypothesis testing. While their applications can be broader, we illustrate the use of mMeta and aMeta to combine microbiome studies throughout multiple α-diversity indices. We evaluate mMeta and aMeta in silico and apply them to real microbiome studies on the disparity in α-diversity by the status of human immunodeficiency virus (HIV) infection. The R package for mMeta and aMeta is freely available at https://github.com/hk1785/mMeta. [ABSTRACT FROM AUTHOR]

ABSTRACT BACKGROUND Given ever-reducing budgets of community and school substance use prevention programs, there is a call for identifying the first substance in the sequence leading to polydrug use. METHODS Examining data from a nationally representative sample of 2835 United States 12th graders, we sought to determine (1) the first substance adolescents use; (2) order in which adolescents progress through alcohol, tobacco, and marijuana use; and (3) impact of age of initial substance use on lifetime and frequency of illicit substance use. RESULTS Alcohol is the most commonly used substance, and the majority of polysubstance using respondents consumed alcohol prior to tobacco or marijuana initiation. Respondents initiating alcohol use in sixth grade reported significantly greater lifetime illicit substance use (M = 1.9, standard deviation [ SD] = 1.7, p < .001) and more frequent illicit substance use (M = 6.0, SD = 6.5, p < .001) than those initiating alcohol use in ninth grade or later. Overall, effect sizes for these differences were large (eta squared = 0.30 and 0.28, respectively). CONCLUSIONS Findings underscore the importance of screening for substance use, even among youth enrolled in elementary/middle school. In addition, school prevention programs should begin in elementary school (third grade) and target alcohol use. [ABSTRACT FROM AUTHOR]

Enterotoxigenic Bacteroides fragilis (ETBF) is a commensal bacterium of great importance to human health due to its ability to induce colitis and cause colon tumor formation in mice through the production of B. fragilis toxin (BFT). The formation of tumors is dependent on a pro‐inflammatory signaling cascade, which begins with the disruption of epithelial barrier integrity through cleavage of E‐cadherin. Here, we show that BFT increases levels of glucosylceramide, a vital intestinal sphingolipid, both in mice and in colon organoids (colonoids) generated from the distal colons of mice. When colonoids are treated with BFT in the presence of an inhibitor of glucosylceramide synthase (GCS), the enzyme responsible for generating glucosylceramide, colonoids become highly permeable, lose structural integrity, and eventually burst, releasing their contents into the extracellular matrix. By increasing glucosylceramide levels in colonoids via an inhibitor of glucocerebrosidase (GBA, the enzyme that degrades glucosylceramide), colonoid permeability was reduced, and bursting was significantly decreased. In the presence of BFT, pharmacological inhibition of GCS caused levels of tight junction protein 1 (TJP1) to decrease. However, when GBA was inhibited, TJP1 levels remained stable, suggesting that BFT‐induced production of glucosylceramide helps to stabilize tight junctions. Taken together, our data demonstrate a glucosylceramide‐dependent mechanism by which the colon epithelium responds to BFT. [ABSTRACT FROM AUTHOR]

Summary To establish a recombinant system for high-level expression of biologically active Bacteroides fragilis toxin (BFT), we studied the expression of bft in non-toxigenic B. fragilis (NTBF) strains. The bft gene and the B. fragilis pathogenicity island (BfPAI) were cloned into NTBF strains with two distinct genetic patterns: (i) pattern II, strains lacking the BfPAI and its flanking region; and (ii) pattern III, strains lacking the BfPAI but containing its flanking region. Analysis of BFT activity of these recombinant strains on HT29/C1 cells showed that both the BfPAI and its flanking regions are important to optimal BFT activity. Reverse transcription polymerase chain reaction (RT-PCR) analysis indicated that the BfPAI and its flanking regions modulate bft expression. Further experiments demonstrated that the ≈ 700 bp region upstream of bft is the BfPAI region critical for optimal bft expression. We conclude that both the region flanking the BfPAI and ≈ 700 bp region upstream of bft are crucial to maximal BFT production by ETBF strains. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the epidemiology of Giardia lamblia infection, investigate factors which might be associated with clinical manifestations and recurrence, and examine the role of copathogens in disease course.Methods: Prospective 4-year cohort study of children born in an urban slum in north-eastern Brazil.Results: Of 157 children followed for > or = 3 months, 43 (27.4%) were infected with Giardia. The organism was identified in 8.8% of all stool specimens, and although found with similar frequency in non-diarrhoeal (7.4%) and diarrhoeal stools (9.7%), was more common in children with persistent (20.6%) than acute diarrhoea (7.6%, P=0.002). Recurrent or relapsing infections were common (46%). Children with symptomatic infections had significantly lower weight-for-age and height-for-age than asymptomatic children. Copathogens were not associated with disease course. CONCLUSION With its protean clinical manifestations, Giardia may be associated with substantial morbidity amongst children in Brazil. [ABSTRACT FROM AUTHOR]