Longitudinal analysis of the impact of oral contraceptive use on the gut microbiome.

Introduction. Evidence has linked exogenous and endogenous sex hormones with the human microbiome.Hypothesis/Gap statement. The longitudinal effects of oral contraceptives (OC) on the human gut microbiome have not previously been studied.Aim. We sought to examine the longitudinal impact of OC use on the taxonomic composition and metabolic functions of the gut microbiota and endogenous sex steroid hormones after initiation of OC use.Methodology. We recruited ten healthy women who provided blood and stool samples prior to OC use, 1 month and 6 months after starting OC. We measured serum levels of sex hormones, including estradiol, progesterone, sex hormone-binding globulin (SHBG), and total testosterone. Shotgun metagenomic sequencing was performed on DNA extracted from faecal samples. Species and metabolic pathway abundances were determined using MetaPhlAn2 and HUMAnN2. Multivariate association with linear models was used to identify microbial species and metabolic pathways associated with OC use and endogenous levels of sex hormones.Results. The percentage variance of the microbial community explained by individual factors ranged from 9.9 % for age to 2.7 % for time since initiation of OC use. We observed no changes in the diversity or composition of the gut microbiome following OC initiation. However, the relative abundance of the biosynthesis pathways of peptidoglycan, amino acids (lysine, threonine, methionine, and tryptophan), and the NAD salvage pathway increased after OC initiation. In addition, serum levels of estradiol and SHBG were positively associated with Eubacterium ramulus, a flavonoid-degrading bacterium. Similarly, microbes involving biosynthesis of l-lysine, l-threonine, and l-methionine were significantly associated with lower estradiol, SHBG, and higher levels of total testosterone.Conclusion. Our study provides the first piece of evidence supporting the association between exogenous and endogenous sex hormones and gut microbiome composition and function.

Fruit and vegetable consumption is associated with lower prevalence of asymptomatic diverticulosis: a cross-sectional colonoscopy-based study.

BACKGROUND: Previous studies of the relationship between dietary factors and risk of diverticulosis have yielded inconsistent results. We therefore sought to investigate the association between consumption of fruit and vegetables and prevalent diverticulosis. METHODS: Our study population included participants in the Gastrointestinal Disease and Endoscopy Registry (GIDER), a colonoscopy-based longitudinal cohort at the Massachusetts General Hospital, who provided comprehensive information on dietary intake and lifestyle factors using validated questionnaires prior to colonoscopy. Information on presence and location of diverticula was obtained from the endoscopist at the end of each procedure. We used Poisson regression modeling to calculate the prevalence ratios (PRs) and 95% confidence intervals (CIs). RESULTS: Among 549 participants with a mean age of 61 years enrolled in GIDER, we confirmed diverticulosis in 245 (44.6%). The prevalence of diverticulosis appeared to decrease with higher consumption of fruit and vegetables (Ptrend = 0.007 for fruit and 0.008 for vegetables, respectively). Compared to participants with less than five servings of vegetables per week, the multivariable-adjusted PRs of diverticulosis were 0.84 (95% CI, 0.60-1.17) with five to seven servings per week and 0.62 (95% CI, 0.44-0.89) with greater than one serving per day. Similarly, compared to participants with less than five servings per week of fruit, the multivariable-adjusted PR of diverticulosis was 0.60 (95% CI, 0.41-0.87) with greater than one serving per day. These associations were not modified by age, BMI, smoking, or red meat intake (All Pinteraction > 0.055). CONCLUSION: In a colonoscopy-based longitudinal cohort study, we show that higher consumption of fruit and vegetables is associated with lower risk of prevalent diverticulosis.

Microscopic Colitis Is Characterized by Intestinal Dysbiosis.

The critical role of the gut microbiome in microscopic colitis (MC) is evident by the observation that fecal diversion is associated with resolution of mucosal inflammation while restoration of fecal stream is associated with recurrence of disease.1 Characterization of the composition and function of the gut microbiome in MC therefore could provide insights into disease pathogenesis.

Cancer risk in microscopic colitis: a retrospective cohort study.

BACKGROUND: The long-term natural history of microscopic colitis (MC) (collagenous colitis (CC), lymphocytic colitis (LC)), traditionally considered relapsing but non-progressive diseases, is poorly defined. Whether persistent histologic inflammation in such diseases is associated with an increased risk of colorectal neoplasia (CRN) or extracolonic cancers has not been robustly established. METHODS: This retrospective cohort included diagnosed with MC at a referral center. Rates of CRN and extracolonic cancer were compared to patients undergoing screening colonoscopy (n = 306) and to the United States population using data from the Surveillance, Epidemiology, and End-Results (SEER) program. Standardized incidence ratios (SIR) and 95% confidence intervals were calculated and multivariable regression models used to identify the effect of MC diagnosis and severity on cancer risk. RESULTS: Our study included 221 patients with microscopic colitis (112 CC, 109 LC) among whom 77% were women. Compared to the colonoscopy control population, MC was associated with similar odds of tubular adenoma (Odds ratio (OR) 1.07, 95% CI 0.69-1.66) or villous adenoma (OR 1.26, 95% CI 0.17-9.42). Compared to patients with a single episode of MC, those with 2 or more episodes had similar risk of colon cancer (OR 0.83, 95% CI 0.20-3.39) or tubular adenoma (OR 1.49 95% CI 0.83-2.67). We also identified no statistical increase in the rates of cancer in the MC population compared to US-SEER data. CONCLUSION: Microscopic colitis was not associated with increased risk of CRN and extracolonic cancers when compared to controls undergoing colonoscopy or the US SEER population.

Visceral Adiposity, Genetic Susceptibility, and Risk of Complications Among Individuals with Crohn's Disease.

INTRODUCTION: Adipose tissue in mesenteric fat plays a key role in systemic and luminal inflammation. However, little is known about the role of visceral adipose tissue (VAT) and its interaction with genetic predisposition in Crohn's disease (CD) progression. METHODS: Our study population included patients with CD enrolled in Prospective Registry in Inflammatory Bowel Disease Study at Massachusetts General Hospital (PRISM). VAT volume was measured from computed tomography using Aquarius 3D. We used logistic regression models to estimate the multivariable-adjusted odds ratio and 95% CI. We tested for effect modification by genetic predisposition using the log likelihood ratio test. RESULTS: Among 482 patients with CD with available data on VAT, 174 developed penetrating disease, 132 developed stricturing disease, 147 developed perianal disease, and 252 required surgery. Compared with individuals in the lowest quartile of VAT volume, the multivariable-adjusted odds ratio of surgery among individuals in the highest quartile was 2.02 (95% CI, 1.09-3.76; Ptrend = 0.006). Similarly, the risk of penetrating disease seemed to increase with greater VAT volume (Ptrend = 0.022) but not stricturing or perianal disease (all Ptrend > 0.23). The associations between VAT volume and CD complications were not modified by genetic predisposition (all Pinteraction > 0.12). CONCLUSIONS: Visceral adiposity as measured by VAT volume may be associated with a significant increase in the risk of penetrating disease and surgery in CD. Our data suggest that visceral adiposity as measured by VAT may negatively impact long-term progression of CD regardless of genetic predisposition.

Tropomyosin and Profilin Cooperate to Promote Formin-Mediated Actin Nucleation and Drive Yeast Actin Cable Assembly.

Tropomyosins comprise a large family of actin-binding proteins with critical roles in diverse actin-based processes [1], but our understanding of how they mechanistically contribute to actin filament dynamics has been limited. We addressed this question in S. cerevisiae, where tropomyosins (Tpm1 and Tpm2), profilin (Pfy1), and formins (Bni1 and Bnr1) are required for the assembly of an array of actin cables that facilitate polarized vesicle delivery and daughter cell growth. Formins drive cable formation by promoting actin nucleation and by accelerating actin filament elongation together with profilin [2]. In contrast, how tropomyosins contribute mechanistically to cable formation has been unclear, but genetic studies demonstrate that Tpm1 plays a more important role than Tpm2 [3, 4]. Here, we found that loss of TPM1 in strains lacking BNR1, but not BNI1, leads to severe defects in cable formation, polarized secretion, and cell growth, suggesting that TPM1 function is required for proper Bni1-mediated cable assembly. Furthermore, in vitro total internal reflection fluorescence (TIRF) microscopy demonstrated that Tpm1 strongly enhances Bni1-mediated, but not Bnr1-mediated, actin nucleation without affecting filament elongation rate, whereas Tpm2 has no effects on Bni1 or Bnr1. Tpm1 stimulation of Bni1-mediated nucleation also requires profilin and its interactions with both G-actin and formins. Together, these results demonstrate that yeast Tpm1 works in concert with profilin to promote formin-dependent nucleation of actin cables, thus expanding our understanding of how specific tropomyosin isoforms influence actin dynamics.

Combinatorial genetic analysis of a network of actin disassembly-promoting factors.

The patterning of actin cytoskeleton structures in vivo is a product of spatially and temporally regulated polymer assembly balanced by polymer disassembly. While in recent years our understanding of actin assembly mechanisms has grown immensely, our knowledge of actin disassembly machinery and mechanisms has remained comparatively sparse. Saccharomyces cerevisiae is an ideal system to tackle this problem, both because of its amenabilities to genetic manipulation and live-cell imaging and because only a single gene encodes each of the core disassembly factors: cofilin (COF1), Srv2/CAP (SRV2), Aip1 (AIP1), GMF (GMF1/AIM7), coronin (CRN1), and twinfilin (TWF1). Among these six factors, only the functions of cofilin are essential and have been well defined. Here, we investigated the functions of the nonessential actin disassembly factors by performing genetic and live-cell imaging analyses on a combinatorial set of isogenic single, double, triple, and quadruple mutants in S. cerevisiae. Our results show that each disassembly factor makes an important contribution to cell viability, actin organization, and endocytosis. Further, our data reveal new relationships among these factors, providing insights into how they work together to orchestrate actin turnover. Finally, we observe specific combinations of mutations that are lethal, e.g., srv2Δ aip1Δ and srv2Δ crn1Δ twf1Δ, demonstrating that while cofilin is essential, it is not sufficient in vivo, and that combinations of the other disassembly factors perform vital functions.