Omega-3 Polyunsaturated Fatty Acids, Gut Microbiota, Microbial Metabolites, and Risk of Colorectal Adenomas

Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) are thought to protect against colorectal adenoma (CRA) development. We aimed to further understand the underlying mechanisms by examining the relationships between ω-3 PUFAs and the gut microbiota on CRAs. We assessed the mucosal microbiota via bacterial 16S rRNA sequencing among 217 CRA cases and 218 controls who completed PUFA intake questionnaires. The overall microbial composition was assessed by α-diversity measurements (diversity, richness, and evenness). Global metabolomics was conducted using a random subset of case−control pairs (n = 50). We compared microbiota and metabolite signatures between cases and controls according to fold change (FC). Odds ratios (OR) and confidence intervals (CI) were estimated from logistic regression for associations of ω-3 PUFAs and the microbiota with CRAs. We observed an inverse association between overall ω-3 PUFA intake and CRAs, especially for short-chain ω -3 PUFAs (OR = 0.45, 95% CI: 0.21, 0.97). Such inverse associations were modified by bacterial evenness (p-interaction = 0.03). Participants with higher levels (FC > 2) of bile acid-relevant metabolites were more likely to have CRAs than the controls, and the correlation between bile acids and bacterial diversity differed by case−control status. Our findings suggest that ω-3 PUFAs are inversely associated with CRA development, and the association may be modified by gut microbiota profiles.

Differences in the microbial profiles of early stage endometrial cancers between Black and White women

OBJECTIVE

Black women suffer a higher mortality from endometrial cancer (EC) than White women. Potential biological causes for this disparity include a higher prevalence of obesity and more lethal histologic/molecular subtypes. We hypothesize that another biological factor driving this racial disparity could be the EC microbiome.

METHODS

Banked tumor specimens of postmenopausal, Black and White women undergoing hysterectomy for early stage endometrioid EC were identified. The microbiota of the tumors were characterized by bacterial 16S rRNA sequencing. The microbial component of endometrioid ECs in The Cancer Genome Atlas (TCGA) database were assessed for comparison.

RESULTS

95 early stage ECs were evaluated: 23 Black (24%) and 72 White (76%). Microbial diversity was increased (p < 0.001), and Firmicutes, Cyanobacteria and OD1 phyla abundance was higher in tumors from Black versus White women (p < 0.001). Genus level abundance of Dietzia and Geobacillus were found to be lower in tumors of obese Black versus obese White women (p < 0.001). Analysis of early stage ECs in TCGA found that microbial diversity was higher in ECs from Black versus White women (p < 0.05). When comparing ECs from obese Black versus obese White women, 5 bacteria distributions were distinct, with higher abundance of Lactobacillus acidophilus in ECs from Black women being the most striking difference. Similarly in TCGA, Dietzia and Geobacillus were more common in ECs from White women compared to Black.

CONCLUSION

Increased microbial diversity and the distinct microbial profiles between ECs of obese Black versus obese White women suggests that intra-tumoral bacteria may contribute to EC disparities and pathogenesis.

Lack of association of the esophageal microbiome in adults with eosinophilic esophagitis compared with non-EoE controls

BACKGROUND AND AIMS

Changes in the esophageal microbiome have been reported in children with eosinophilic esophagitis (EoE), but few data exist for adults. We aimed to determine whether the esophageal microbiome differs in adults with and without EoE.

METHODS

In a prospective cohort study, adults undergoing outpatient endoscopy were enrolled as incident EoE cases or non-EoE controls. Clinical, endoscopic, and histologic data were collected. An esophageal biopsy was utilized for microbiome analysis. Bacterial DNA was extracted and the V3-V4 region of the 16S rRNA gene was amplified and sequenced. Analyses were performed comparing microbiome features for cases and controls, and within cases for disease features, with correction for multiple hypothesis testing.

RESULTS

A total of 24 incident EoE cases (mean age 40 years; 63% male; 100% white; 97 eos/hpf) and 25 controls (mean age 48, 36% male; 76% white; 1 eos/hpf) were analyzed. Principal coordinate analysis ordination failed to distinguish cases from controls. There were no microbiome differences within EoE cases based on clinical phenotype, presence of atopy, or endoscopic features. Use of proton pump inhibitors (PPIs), however, was significantly associated with 5 taxa including SR1 at the phylum level and Burkholderia at the genus level.

CONCLUSIONS

There were no significant differences in the esophageal microbiome between newly diagnosed EoE cases and non-EoE controls in adults, or within EoE cases based on clinical features. However, given the strong rationale for the esophageal microbiome in EoE pathogenesis, future studies should explicitly consider the presence of PPIs as a confounding feature.

Abstract PR07: Impact of race on the uterine microbiome in women with early stage endometrial cancer

Introduction: African American (AA) women suffer a higher mortality from endometrial cancer (EC) than non-Hispanic white (NHW) women. Potential biological causes for this disparity in AA women include a higher risk of more lethal histologic/molecular subtypes and greater rates of obesity. We hypothesize that another biological factor driving his racial disparity is the uterine microbiome. Thus, we evaluated the microbiota of human ECs and assessed for variations by race. Methods: Banked tumor specimens of post-menopausal patients undergoing hysterectomy for early stage endometrioid ECs were identified. Tumors were analyzed from AA and NHW women and stratified as obese (BMI≥30kg/m2) or non-obese (BMI&lt;30kg/m2). The microbiota of the human ECs were characterized by bacterial 16S rRNA high throughput sequencing, and data was analyzed using MicrobiomeAnalyst. The microbial component of endometrioid ECs in The Cancer Genome Atlas (TCGA) database was also assessed. Results: 95 EC specimens were evaluated. Of these, 23 were from AA (24%) and 72 from NHW (76%). When analyzed by race and obesity status, we observed significant differences in EC microbiota composition. Microbial diversity was increased (p&lt;0.001), and abundance of Firmicutes (p=0.014) and OD1 (p=0.006) were higher ECs in obese vs non-obese NHW women. When comparing ECs from obese AA vs obese NHW women, microbial diversity was increased (p&lt;0.001), and Firmicutes, Cyanobacteria and OD1 phyla abundance was higher in the tumors from AA vs NHW women (p&lt;0.001). Genus level abundance of Dietzia (p&lt;0.001) and Geobacillus (p&lt;0.001) were the top bacteria found to be lower in tumors of obese AA vs obese NHW women. Similarly, analysis of the endometrioid ECs in the TCGA database found that microbial diversity was higher in ECs from AA versus NHW women. When comparing early stage ECs from obese AA (N=11) versus obese NHW (N=115) women, 5 bacteria distinguished these two groups, with higher abundance of Lactobacillus acidophilus in AA tumors being the most striking difference. Confirming the 16S analysis, Dietzia and Geobacillus were also observed to be associated with NHW tumors, though at lower significance. Conclusion: Microbial diversity was higher in the ECs from AA versus NHW women as seen in both our institutional and TCGA dataset. Distinct microbiota profiles were found between ECs of obese AA versus obese NHW women. Better understanding of the inter-relationship of obesity and race on the EC microbiota may provide critical insight into the disparate clinical outcomes between AA and NHW women with EC.

Citation Format: Gabrielle M. Hawkins, Amber N. McCoy, Andrew Olshan, Russell Broaddus, Wendy R. Brewster, Jeffrey Roach, Temitope Keku, Victoria L. Bae-Jump. Impact of race on the uterine microbiome in women with early stage endometrial cancer [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr PR07.

Co-morbid risk factors and NSAID use among white and black Americans that predicts overall survival from diagnosed colon cancer

Black Americans (BA) have higher incidence and higher mortality rates for colorectal cancers (CRC) as compared to White Americans (WA). While there are several identified risk factors associated with the development of CRC and evidence that high levels of adequate screening can reduce differences in incidence for CRC between BA and WA, there remains little data regarding patient co-morbid contributions towards survival once an individual has CRC. Here we set out to identify patient risk factors that influenced overall survival in a cohort of 293 BA and 348 WA with colon cancer. Amid our cohort, we found that patients’ age, tobacco usage, and pre-diagnosed medical conditions such as hypertension and diabetes were associated with shorter overall survival (OS) from colon cancer. We identified pre-diagnosed hypertension and diabetes among BA were responsible for one-third of the colon cancer mortality disparity compared with WA. We also identified long-term regular use of non-steroidal anti-inflammatory drugs (NSAIDs), including aspirin, was associated with shorter OS from colon cancer among WA >65 years of age, but not younger WA patients or any aged BA patients. Our results raise the importance of not only treating the colon cancer itself, but also taking into consideration co-morbid medical conditions and NSAID usage to enhance patient OS. Further evaluation regarding adequate treatment of co-morbidities and timing of NSAID continuance after cancer therapy will need to be studied.

Fusobacterium nucleatum infection correlates with two types of microsatellite alterations in colorectal cancer and triggers DNA damage

Fusobacterium nucleatum (Fn) is frequently found in colorectal cancers (CRCs). High loads of Fn DNA are detected in CRC tissues with microsatellite instability-high (MSI-H), or with the CpG island hypermethylation phenotype (CIMP). Fn infection is also associated with the inflammatory tumor microenvironment of CRC. A subtype of CRC exhibits inflammation-associated microsatellite alterations (IAMA), which are characterized by microsatellite instability-low (MSI-L) and/or an elevated level of microsatellite alterations at selected tetra-nucleotide repeats (EMAST). Here we describe two independent CRC cohorts in which heavy or moderate loads of Fn DNA are associated with MSI-H and L/E CRC respectively. We also show evidence that Fn produces factors that induce γ-H2AX, a hallmark of DNA double strand breaks (DSBs), in the infected cells.

Abstract B29: Impact of obesity on the uterine microbiome in pre- and postmenopausal mice with endometrial cancer

Introduction: Endometrial cancer (EC) is the 4th most common cancer in US women. The relentless rise of EC frequency and mortality is due in part to the obesity epidemic (Annual Report to the Nation on the Status of Cancer, 2019). Obesity is associated with higher risk of both developing and dying from EC. The microbiome is known to play a complex role in the regulation of obesity and cancer, yet the inter-relationship of obesity, the uterine tumor microbiota, and EC pathogenesis is unknown, including the potential influence of menopausal status. Thus, we characterized the microbiota of the malignant uterus using pre- and postmenopausal, obese and lean genetically engineered mouse models of endometrioid EC.

Methods: The Lkb1fl/flp53fl/fl mouse is a genetically engineered, preclinical model of endometrioid EC. At 3 wks of age, Lkb1fl/flp53fl/fl mice were fed a low-fat diet (LFD, 10% calories from fat) versus a high-fat diet (HFD, 60% calories from fat) to mimic diet-induced obesity. At 6 wks of age, the right uterine horn was injected with AdenoCre virus to delete Lkb1 and p53 and induce EC. Concurrently, mice either underwent bilateral oophorectomy to induce the postmenopausal state or retained their ovaries to maintain a premenopausal status. EC tumors were collected from all mice 12 wks after tumor induction. The microbiota profiles were characterized by bacterial 16S rRNA high-throughput sequencing, and the data were analyzed using Qiime2 and MicrobiomeAnalyst.

Results: When analyzed by obesity and menopausal status, we observed significant differences in the EC microbiota composition of Lkb1fl/flp53fl/fl mice at the phylum and genus level. OD1 and TM7 phyla abundance was higher among obese post- versus premenopausal mice (p&lt;0.05). At the genus level, there was a significant increase in the abundance of Delftia (p&lt;0.01) in obese premenopausal mice whereas the abundance of Helicobacter (p=0.01), Oscillospira (p&lt;0.01), and Ruminococcus (p&lt;0.01) was increased in obese postmenopausal mice. In lean mice, the phylum-level abundance of Proteobacteria (p&lt;0.01) was increased in pre- versus postmenopausal mice. There was also a higher abundance of Delftia (p&lt;0.01) in lean pre- versus postmenopausal mice at the genus level. In postmenopausal mice, the relative abundance of Helicobacter (p=0.02) was increased in obese versus lean mice.

Conclusion: There were distinct differences in the bacterial composition of the ECs in Lkb1fl/flp53fl/fl mice according to obesity and menopausal status, suggesting that the microbiome may play a role in the pathogenesis of obesity-driven EC.

Citation Format: Gabrielle M. Hawkins, Amber N. McCoy, Wenchuan Sun, Temitope Keku, Chunxiao Zhou, Wendy R. Brewster, Victoria L. Bae-Jump. Impact of obesity on the uterine microbiome in pre- and postmenopausal mice with endometrial cancer [abstract]. In: Proceedings of the AACR Special Conference on the Microbiome, Viruses, and Cancer; 2020 Feb 21-24; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2020;80(8 Suppl):Abstract nr B29.

Colonic Diverticula Are Not Associated With Mucosal Inflammation or Chronic Gastrointestinal Symptoms

BACKGROUND & AIMS

Colonic diverticulosis has been reported to be associated with low-grade mucosal inflammation, possibly leading to chronic gastrointestinal symptoms. However, there is poor evidence for this association. We aimed to determine mucosal inflammation and whether diverticula are associated with chronic gastrointestinal symptoms. We explored whether inflammation was present among symptomatic participants with and without diverticula.

METHODS

We analyzed data from a prospective study of 619 patients undergoing a screening colonoscopy from 2013 through 2015 at the University of North Carolina Hospital in Chapel Hill, North Carolina. Among our participants, 255 (41%) had colonic diverticula. Colonic mucosal biopsy specimens were analyzed for levels of interleukin 6 (IL6), IL10, and tumor necrosis factor messenger RNAs by quantitative reverse-transcriptase polymerase chain reaction, and numbers of immune cells (CD4+, CD8+, CD57+, and mast cell tryptase) by immunohistochemistry. Gastrointestinal symptoms were assessed using Rome III criteria. Proportional odds models were used to estimate odds ratios (ORs) and 95% confidence interval (CIs).

RESULTS

After adjustment for potential confounders, there was no association between diverticulosis and tumor necrosis factor (OR, 0.85; 95% CI, 0.63-1.16), and no association with CD4+ cells (OR, 1.18; 95% CI, 0.87-1.60), CD8+ cells (OR, 0.97; 95% CI, 0.71-1.32), or CD57+ cells (OR, 0.80; 95% CI, 0.59-1.09). Compared with controls without diverticulosis, biopsy specimens from individuals with diverticulosis were less likely to express the inflammatory cytokine IL6 (OR, 0.59; 95% CI, 0.36-0.96). There was no association between diverticulosis and irritable bowel syndrome (OR, 0.53; 95% CI, 0.26-1.05) or chronic abdominal pain (OR, 0.68; 95% CI, 0.38-1.23). There was no evidence for inflammation in patients with symptoms when patients with vs without diverticulosis were compared.

CONCLUSIONS

We found no evidence that colonic diverticulosis is associated with mucosal inflammation or gastrointestinal symptoms. Among patients with symptoms and diverticula, we found no mucosal inflammation.

Abstract 239: Associations of polyunsaturated fat, bile acids, and gut microbiota on colorectal adenoma risk

Background: Intestinal microbiota, and their metabolites are increasingly recognized as important players in the genesis of colorectal adenomas and cancer. Epidemiological studies have also shown that polyunsaturated fat intake is associated with decreased risk of colorectal adenomas. This study examined the association between adherent gut microbiota and mucosal bile acids, and total polyunsaturated fat intake in relation to colorectal adenomas in a case-control study.

Methods: Participants were 217 adenoma cases and 218 adenoma-free controls who underwent screening colonoscopies and completed food frequency questionnaires. The mucosal adherent microbiota was characterized by bacterial 16S rRNA sequencing. Global metabolomics of colonic mucosal tissue was conducted by gas chromatography and mass spectrometry on a subset of samples. Genus level microbiota and bile acids were compared between cases and controls using t-test with correction for multiple comparison. Logistic regression and Pearson correlations were used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs), and correlation coefficients for the association among microbiota abundance, bile acids concentration, and total polyunsaturated fat intake.

Results: Adenoma subjects had a significantly higher bacterial abundance of Sphingomonas, Marinomonas and Ralstonia, but lower abundance of Adlercreutzia compared to controls. The concentration of eleven bile acids (Chenodeoxycholate, Cholate, Deoxycholate, Glycochenodeoxycholate, Glycocholenate sulfate, 7-ketodeoxycholate; 12-dehydrocholate, Taurochenodeoxycholate, Taurocholate, Taurodeoxycholate, Taurolithocholate 3-sulfate, and Tauroursodeoxycholate) were significantly elevated in cases compared to controls. Subjects with increased abundance of Sphingomonas and Ralstonia were significantly more likely to have adenomas (OR 2.17, 95% CI 1.31-3.57; OR 1.19, 95% CI 1.02-1.38) respectively. Subjects with increased abundance of Adlercreutzia were less likely to have adenomas (OR 0.44, 95% CI 0.21-0.93). The multivariable adjusted OR for those in the high relative to the low level of total polyunsaturated fat intake was 0.46 (95% CI 0.27-0.80). The correlations between bacterial diversity and eleven bile acids also significantly differed by case control status.

Conclusion: The interactions of the gut microbiota, bile acids and consumption of polyunsaturated fat are associated with colorectal adenoma risk.

Citation Format: Tengteng Wang, Nicole M. Brown, Amber N. McCoy, Robert S. Sandler, Temitope O. Keku. Associations of polyunsaturated fat, bile acids, and gut microbiota on colorectal adenoma risk [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 239. doi:10.1158/1538-7445.AM2017-239

Abstract 1259: Gut microbiota and mucosal inflammation and colorectal neoplasia

Colorectal cancer (CRC) is a leading cause of cancer death in the United States. Chronic inflammation has been linked to colorectal neoplasia. More recent studies also implicate imbalances in the gut microbiota (bacteria) CRC. We sought to understand the relationship between the gut microbiota, mucosal inflammation and colorectal adenomas, CRC precursors. We hypothesized that the gut microbiota promotes inflammation via activation of mucosal immune cells to elevate adenoma risk. We examined the relationship between adherent gut bacteria, mucosal immune cells, namely T cells (CD4+ and CD8+), macrophages (CD11b+) and natural killer cells (CD57+) and adenomas in a case control study.

Methods: Participants were consenting screening colonoscopy patients at UNC Hospitals without history or diagnosis of inflammatory bowel disease. Subjects were defined as cases (n=42) or controls (n=35) based on the presence or absence of adenomas. High throughput deep sequencing method was used to assess the microbiota in normal colonic mucosa of cases and controls. Immune cells were assessed by immunohistochemistry and automated image analysis using Aperio software. Differences in microbiota abundance or mucosal immune cell numbers between cases and controls were evaluated by t-tests. Diversity was measured by Shannon diversity. Correlation between bacteria and immune cells was performed using Spearman's correlation.

Results: Cases had higher WHR than controls (p=0.0001). No difference was observed for age, sex, BMI among cases and controls. The abundance of several bacteria taxa differed significantly between cases and controls. We observed a positive relationship between mucosal immune cell density and adenomas. In particular, CD 4+ density and CD4/CD8 ratio were higher in cases than controls (CD4; 1.44 case, 0.69 control p = 0.001; CD4/CD8 1.66 case, 0.56 control, p= 0.002). There were no statistically significant differences in CD 57+, CD11b or CD 8+ cell density between cases and controls. The correlation patterns between the gut microbiota and immune cells differed markedly for cases and controls. There was a positive correlation between Proteobacteria and CD4 or CD4/CD8+ cells among cases but not controls.

Conclusions: our results suggest that the gut bacteria and immune cells are interacting differently depending on adenoma status. These findings suggest activation of mucosal immune cells by bacteria may promote local inflammation and contribute to the etiology of colorectal cancer.

Citation Format: Temitope O. Keku, Romin Bonakdar, Felix Araujo Perez, Amber N. McCoy, Patrick Edmundson, Kevin Smith. Gut microbiota and mucosal inflammation and colorectal neoplasia. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1259. doi:10.1158/1538-7445.AM2014-1259

Altered tissue metabolites correlate with microbial dysbiosis in colorectal adenomas

Several studies have linked bacterial dysbiosis with elevated risk of colorectal adenomas and cancer. However, the functional implications of gut dysbiosis remain unclear. Gut bacteria contribute to nutrient metabolism and produce small molecules termed the “metabolome”, which may contribute to the development of neoplasia in the large bowel. We assessed the metabolome in normal rectal mucosal biopsies of 15 subjects with colorectal adenomas and 15 nonadenoma controls by liquid chromatography and gas chromatography time-of-flight mass spectrometry. Quantitative real-time PCR was used to measure abundances of specific bacterial taxa. We identified a total of 274 metabolites. Discriminant analysis suggested a separation of metabolomic profiles between adenoma cases and nonadenoma controls. Twenty-three metabolites contributed to the separation, notably an increase in adenoma cases of the inflammatory metabolite prostaglandin E2 and a decrease in antioxidant-related metabolites 5-oxoproline and diketogulonic acid. Pathway analysis suggested that differential metabolites were significantly related to cancer, inflammatory response, carbohydrate metabolism, and GI disease pathways. Abundances of six bacterial taxa assayed were increased in cases. The 23 differential metabolites demonstrated correlations with bacteria that were different between cases and controls. These findings suggest that metabolic products of bacteria may be responsible for the development of colorectal adenomas and CRC.

Optic Atrophy in End-Stage Giant Axonal Neuropathy: A Case Report

A 32-year-old woman with a history of biopsy-proven giant axonal neuropathy (GAN) and no past ocular history presented after failing a vision-screening test conducted by her primary doctor. Bilateral optic atrophy was observed on fundus examination with cup-to-disc ratio of 0.7. Kinetic visual fields showed moderate constriction in both eyes. Optical coherence tomography (OCT) of the retinal nerve fibre layer (RNFL) exhibited diffuse thinning, a pattern atypical of glaucomatous or nutritional optic atrophy and most likely secondary to the optic atrophy associated with GAN. Serial OCT to monitor RNFL thickness may offer a non-invasive means of monitoring progression in GAN for future therapeutic studies.

Fusobacterium spp. and colorectal cancer: cause or consequence?

Although increasing evidence suggests a relationship between bacterial dysbiosis and colorectal cancer (CRC), few studies have identified specific microbial etiologic factors. Recent studies have implicated overabundance of Fusobacterium in association with colorectal adenomas and cancer. Two articles published in Cell Host & Microbe provide insights into the Fusobacterium-CRC relationship.

Association of plasma endotoxin, inflammatory cytokines and risk of colorectal adenomas

Background

Recent studies suggest that bacterial endotoxins may be associated with various chronic diseases, including colorectal adenomas and cancer. Given the evidence linking inflammation and colorectal cancer, we sought to determine if plasma endotoxin concentrations are associated with indicators of systemic or local inflammation and colorectal adenomas.

Methods

This cross-sectional study consisted of participants who underwent screening colonoscopies and included adenoma cases (n=138) and non-adenoma controls (n=324). Plasma concentrations of endotoxin were measured with Limulus Amebocyte Lysate (LAL) assay. We quantified concentrations of inflammatory cytokines, interleukin-4 (IL-4), IL-6, IL-8, IL-10, IL-12, tumor necrosis factor-alpha (TNF-α), and interferon-γ (IFN-γ) in plasma by ELISA and mRNA expression levels in rectal mucosal biopsies by quantitative RT-PCR. Interleukin-17 was evaluated only in the rectal mucosa.

Results

Compared to subjects with low plasma endotoxin concentrations, those with higher concentrations were more likely to have adenomas (OR 1.4, 95% CI 1.0-2.1). Among subjects with adenomas, those with villous histology were more likely to have higher endotoxin concentrations (5.4 vs. 4.1EU/mL, p=0.05) and lower plasma IFN-γ (0 vs. 1.64 pg/mL, p=0.02) compared to those with only tubular adenomas. Cases showed a trend of having higher plasma TNF-α levels than controls (p=0.06), but none of the other plasma or rectal mucosal cytokine levels differed between cases and controls. Elevated mucosal IL-12 levels were associated with having multiple adenomas (p=0.04). Higher concentrations of plasma endotoxin predicted increased plasma IL-12 levels (OR 1.5, 95% CI 1.0-2.2) and rectal mucosal IL-12 (OR 1.9, 95% CI 1.0-3.7) and IL-17 gene expression (OR 2.2, 95% CI 1.0-4.6).

Conclusions

These findings suggest that interactions between elevated plasma endotoxin concentrations and inflammatory cytokines may be relevant to the development of colorectal adenomas.

Fusobacterium is associated with colorectal adenomas

The human gut microbiota is increasingly recognized as a player in colorectal cancer (CRC). While particular imbalances in the gut microbiota have been linked to colorectal adenomas and cancer, no specific bacterium has been identified as a risk factor. Recent studies have reported a high abundance of Fusobacterium in CRC subjects compared to normal subjects, but this observation has not been reported for adenomas, CRC precursors. We assessed the abundance of Fusobacterium species in the normal rectal mucosa of subjects with (n = 48) and without adenomas (n = 67). We also confirmed previous reports on Fusobacterium and CRC in 10 CRC tumor tissues and 9 matching normal tissues by pyrosequencing. We extracted DNA from rectal mucosal biopsies and measured bacterial levels by quantitative PCR of the 16S ribosomal RNA gene. Local cytokine gene expression was also determined in mucosal biopsies from adenoma cases and controls by quantitative PCR. The mean log abundance of Fusobacterium or cytokine gene expression between cases and controls was compared by t-test. Logistic regression was used to compare tertiles of Fusobacterium abundance. Adenoma subjects had a significantly higher abundance of Fusobacterium species compared to controls (p = 0.01). Compared to the lowest tertile, subjects with high abundance of Fusobacterium were significantly more likely to have adenomas (OR 3.66, 95% CI 1.37-9.74, p-trend 0.005). Cases but not controls had a significant positive correlation between local cytokine gene expression and Fusobacterium abundance. Among cases, the correlation for local TNF-α and Fusobacterium was r = 0.33, p = 0.06 while it was 0.44, p = 0.01 for Fusobacterium and IL-10. These results support a link between the abundance of Fusobacterium in colonic mucosa and adenomas and suggest a possible role for mucosal inflammation in this process.

Differences in microbial signatures between rectal mucosal biopsies and rectal swabs

There is growing evidence the microbiota of the large bowel may influence the risk of developing colorectal cancer as well as other diseases including type-1 diabetes, inflammatory bowel diseases and irritable bowel syndrome. Current sampling methods to obtain microbial specimens, such as feces and mucosal biopsies, are inconvenient and unappealing to patients. Obtaining samples through rectal swabs could prove to be a quicker and relatively easier method, but it is unclear if swabs are an adequate substitute. We compared bacterial diversity and composition from rectal swabs and rectal mucosal biopsies in order to examine the viability of rectal swabs as an alternative to biopsies. Paired rectal swabs and mucosal biopsy samples were collected in un-prepped participants (n = 11) and microbial diversity was characterized by Terminal Restriction Fragment Length polymorphism (T-RFLP) analysis and quantitative polymerase chain reaction (qPCR) of the 16S rRNA gene. Microbial community composition from swab samples was different from rectal mucosal biopsies (p = 0.001). Overall the bacterial diversity was higher in swab samples than in biopsies as assessed by diversity indexes such as: richness (p = 0.01), evenness (p = 0.06) and Shannon's diversity (p = 0.04). Analysis of specific bacterial groups by qPCR showed higher copy number of Lactobacillus (p < 0.0001) and Eubacteria (p = 0.0003) in swab samples compared with biopsies. Our findings suggest that rectal swabs and rectal mucosal samples provide different views of the microbiota in the large intestine.

Chronic overexpression of proinflammatory cytokines and histopathology in the brains of rats infected with Trypanosoma brucei

Overproduction of proinflammatory cytokines in the brains of transgenic animals causes brain pathology. To investigate the relationship between brain cytokines and pathology in the brains of animals with adult-onset, pathophysiologically induced brain cytokine expression, we studied rats infected with the parasite Trypanosoma brucei. Several weeks after infection, in situ hybridization histochemistry showed a pattern of chronic overexpression of the mRNAs for proinflammatory cytokines interleukin-1beta and tumor necrosis factor-alpha in the brains of the animals. Similar spatiotemporal inductions of mRNAs for inhibitory factor kappaBalpha and interleukin-1beta converting enzyme were found and quantified. The mRNAs for inducible nitric oxide synthase and interleukin-1 receptor antagonist were highly localized to the choroid plexus, which showed evidence of structural abnormalities associated with the parasites' presence there. The mRNAs for interleukin-6, interferon-gamma, and inducible cyclooxygenase showed restricted induction patterns. Another set of animals was processed for degeneration-induced silver staining, TdT-mediated dUTP-digoxigenin nick end-labeling (TUNEL) staining, glial fibrillary acidic protein (GFAP) immunohistochemistry, and several other histological markers. Apoptosis of scattered small cells and degeneration of certain nerve fibers was found in patterns spatially related to the cytokine mRNA patterns and to cerebrospinal fluid diffusion pathways. Furthermore, striking cytoarchitectonically defined clusters of degenerating non-neuronal cells, probably astrocytes, were found. The results reveal chronic overexpression of potentially cytotoxic cytokines in the brain and selective histopathology patterns in this natural disease model. J. Comp. Neurol. 414:114-130, 1999. Published 1999 Wiley-Liss, Inc.

An empirical explanation of brightness

In this second part of our study on the mechanism of perceived brightness, we explore the effects of manipulating three-dimensional geometry. The additional scenes portrayed here demonstrate that the same luminance profile can elicit different sensations of brightness as a function of how the objects in the scene are arranged in space. This further evidence confirms the implication of the scenes presented in the accompanying paper, namely that sensations of relative brightness-including standard demonstrations of simultaneous brightness contrast-cannot arise by computations of local contrast. The most plausible explanation of the full range of perceptual phenomena we have described is an empirical strategy that links the luminance profile in a visual stimulus with an association (the percept) that represents the profile's most probable real-world source.

The influence of depicted illumination on brightness

The striking illusions produced by simultaneous brightness contrast generally are attributed to the center-surround receptive field organization of lower order neurons in the primary visual pathway. Here we show that the apparent brightness of test objects can be either increased or decreased in a predictable manner depending on how light and shadow are portrayed in the scene. This evidence suggests that perceptions of brightness are generated empirically by experience with luminance relationships, an idea whose implications we pursue in the accompanying paper.

The distribution of oriented contours in the real world

In both humans and experimental animals, the ability to perceive contours that are vertically or horizontally oriented is superior to the perception of oblique angles. There is, however, no consensus about the developmental origins or functional basis of this phenomenon. Here, we report the analysis of a large library of digitized scenes using image processing with orientation-sensitive filters. Our results show a prevalence of vertical and horizontal orientations in indoor, outdoor, and even entirely natural settings. Because visual experience is known to influence the development of visual cortical circuitry, we suggest that this real world anisotropy is related to the enhanced ability of humans and other animals to process contours in the cardinal axes, perhaps by stimulating the development of a greater amount of visual circuitry devoted to processing vertical and horizontal contours.

Can illusory motion disrupt tracking real motion?

When rotating stripes or other periodic stimuli cross the retina at a critical rate, a reversal in the direction of motion of the stimuli is often seen. This illusion of motion perception was used to explore the roles of retinal and perceived motion in the generation of optokinetic nystagmus. Here we show that optokinetic nystagmus is disrupted during the perception of this illusion. Thus, when perceived and actual motion are in conflict, subjects fail to track the veridical movement. This observation suggests that the perception of motion can directly influence optokinetic nystagmus, even in the presence of a moving retinal image. A conflict in the neural representation of motion in different brain areas may explain these findings.