Gut microbiome: debugging the obesity and cancer link

Overview

Carrie R. Daniel-MacDougall, PhD, MPHDepartment of Epidemiology Division of Cancer Prevention and Population Sciences

Biological mechanisms linking adiposity and cancer risk

Adapted from Ho et al. Cancer Res 2012

Cancer

Secretion of leptinHepatic insulin sensitivity and lipid synthesisModulate intestinal environment and appetite signaling

Energy balance regulation

Diet, energy balance, and gut microbiomeDiet

The composition of bacteria living within the gut can be linked to functional metabolic pathways in the host

Figure of healthy gut (fecal) microbiome: NIH-HMP Consortium, Nature 2012

SCFA (Propionate, acetate, butyrate) act as signaling molecules on G-protein coupled receptors expressed in colon and adipocytes

Secretion of leptin; hepatic insulin sensitivity and lipid synthesis; modulate intestinal environment and appetite signaling

Prebiotic fibers (e.g., legumes) resist digestion until they reach the colon; undergo bacterial fermentation

Microbial energy harvest from the diet; fat storage by host; energy loss in fecesMicrobial

production of SCFA

Endocrine

Regulation of EB

Obesity or weight-loss

Diet may directly and indirectly modulate association between energy balance (EB) and cancer

Satiety

Insulin signaling

Diet, gut microbiome, obesity, and cancer

Gut microbiome

Obesity

Cancer

Energy balance

Inflammation

Insulin Resistance

Relevant exposures (e.g., diet, medications)

Nadim Ajami, PhD, Baylor College of Medicine– Alkek Center for Metagenomics and Microbiome Research

(Director: Joe Petrosino, PhD), Department of Molecular Virology and Microbiology

– Cross-talk between Akkermansia muciniphila and intestinal epithelium controls diet-induced obesity (Everard 2013)

Manasi Shah, MS, MD Anderson & UT-SPH– Decreased dietary fiber intake and structural alteration of gut

microbiota in patients with advanced colorectal adenoma (Chen 2013)

Nadim J. Ajami, Ph.D.Alkek Center for Metagenomics and Microbiome Research

Department of Molecular Virology and MicrobiologyBaylor College of Medicine

Houston, TX

Key concepts

Akkermansia muciniphila• Gram-negative anaerobe• Degrades mucin• Resides in the mucus layer of the intestinal epithelium• Abundant in nutrient-rich environments• Represents 3-5% of the microbial community in healthy subjects• Abundance inversely correlates with body weight, severity of appendicitis,

and T1D

Obesity and Type 2 Diabetes• Altered gut microbiota• Inflammation• Gut barrier disruption

• Increased gut permeability -> endotoxemia & metabolic inflammation

ObjectiveTo define the physiological role of Akkermansia muciniphila in obesity.

HypothesisA. Muciniphila controls gut barrier function

Experimental designAdministration of live or heat-killed A. muciniphila to mice fed a high-fat diet.

• Gut barrier• Glucose homeostasis• Adipose tissue metabolism

Findings

Akkermansia muciniphila treatment reverses high-fat diet-induced metabolic disorders, including fat-mass gain, metabolic endotoxemia, adipose tissue

inflammation, and insulin resistance.

Abundance of A. muciniphila is decreased in obese and diabetic mice

Prebiotic: Oligofructose 0.3gr/mouse/day

Prebiotic treatment restores A. muciniphila to basal levels and reverses metabolic endotoxemia

High fat (HF) diet increases macrophage infiltration and fat mass

Treatment with A. muciniphila does not induce changes in the gut microbiota

MITChipV1/V6 16S rRNA gene

A. Muciniphila counteracts metabolic endotoxemia, diet induced obesity, adipose tissue macrophage infiltration, improves glucose

homeostasis, and adipose tissue metabolism

A. Muciniphila colonization restores gut barrier function and increases intestinal endocannabinoids in diet-induced obese mice

Intestinal acylglycerols previously demonstrated to reduce metabolic endotoxemia and systemic inflammation gut barrier function

46% thinner mucus layer in HF-fed mice

A. Muciniphila treatment counteracts this decrease

Heat-killed A. muciniphila does not counteract metabolic endotoxemia, diet induced obesity, oral glucose intolerance, gut

barrier dysfunction or poor adipose tissue metabolism

EndotoxemiaFat massPlasma GlucoseMarkers of adipocyte differentiation

Viable A. muciniphila is required

Conclusions and future directions

• A. muciniphila:– Restores the mucus layer of the intestine– Restores gut barrier function and thereby contributes to

normalize metabolic endotoxemia and adipose tissue metabolism

– Improves glucose tolerance and decreases endogenous hepatic glucose production

Development of a treatment that uses A. muciniphila for the prevention or treatment of obesity and its associated metabolic disorders?

Thank you for your attention

Nadim J. Ajami, Ph.D.Alkek Center for Metagenomics and Microbiome Research

nadim.ajami@bcm.edu

Gut microbiome: debugging the obesity and cancer link

Manasi Shah, MSDepartment of Epidemiology

Division of Cancer Prevention and Population Sciences

The Gut Microbiome

Gut Microbiome

Surrogate marker of diet and

environmental history?

Emerging technology

Multiple sequencing

procedures being developed (WGS)

Modifiable!

Structural and functional

constitution related to diet,

obesity and inflammation

Background

Diet may influence colon cancer risk via the microbiota and its metabolites

Dietary habits may influence early events in the colon carcinogenic process Fiber Short Chain Fatty Acids (SCFA) in colon lower risk of CRC

Colon cancer risk influenced by the balance between microbial production of health-promoting metabolites, such as butyrate; and potentially carcinogenic metabolites, such as secondary bile acids

Gut Microbiome and Colon Cancer- The Balancing Act

Fig: Jobin, Inflamm Bowel Dis 2011

Gut Microbiome and Colorectal Neoplasia

Four high resolution maps of colonic dysbiosis have been independently reported:

CRC tissue as compared to adjacent non-malignant mucosa: Potential pathogenic bacteria in CRC tissue Coriobacteridae, Roseburia, Fusobacterium and Faecalibacterium (Marchesi, PLoS 2011)

Fusobacterium sequences were enriched in carcinomas while the Bacteroidetes and Firmicutes phyla were depleted (Kostic, Genome Res 2012)

Overabundance of Fusobacterium sequences in tumor vs matched control tissue ( Castellarin, Genome Res 2012)

Significantly lower level of Lachnospiraceace, Ruminococcaceae and Lactobacillaceae in cancerous tissues compared to normal intestinal lumen. Relative abundance of Bacteroidaceae, Streptococcacea, Fusobacteriaceae was also higher in the cancerous tissue (Chen, PLoS One 2012)

Cross Sectional Study Flow:

Subjects and Methods Consecutive patients who had undergone colonoscopy in 5 medical

centers in China, ≥ 50 yrs of age NO previous history of colorectal adenoma or carcinoma or IBD, normal

bowel movement Pathological confirmation of advanced colorectal adenoma (A-CRA) Patients with no obvious abnormalities allotted in the healthy control

(HC) group Data on demographics, colonoscopy results, lifestyle factors and dietary

intake were collected via interview-administered questionnaires Fresh stool samples were collected from all the participants. Fecal SCFA content analyzed by gas chromatography Analysis of 16s rRNA sequences done by 454 pyrosequencing of fecal

samples

Results

Multivariate logistic analysis identified four statistically significant factors associated with advanced colorectal adenoma (A-CRA)

Significantly lower yields of fecal SCFAs were found in the A-CRA group (n = 47) than in the HC group (n = 47).

Separation between the microbiota genus in the HC (n = 47) and A-CRA (n = 47) groups was significant

PC analysis plots based on the unweighted UniFrac. p = 0.001, t test of permutation

Differences in butyrate and butyrate-producing bacteria:

Summary and Discussion

Main Findings: Structural imbalance in the fecal gut microbiota and difference in SCFA

concentrations was defined in the A-CRA, as compared to HC Butyrate and other SCFA’s associated with reduced risk of CRC: 3

genera of butyrate-producing bacteria (Clostridium, Roseburia, and Eubacterium) were lower in the A-CRA group than in the HC group

Significant higher levels of opportunistic pathogens: Enterococcus and Streptococcus in A-CRA

Implications: Microbial community may play an important role in pathogenesis of

the progression from A-CRA to CRC via dietary SCFA products Persistent deficiency in substrate dietary fiber may result in a

deficiency in butyrate-producing bacteria fermentation of SCFAs increased risk of A-CRA

Limitations

Cross-sectional design: no cause-effect

Prospective human studies are required to determine whether an altered gut microbiome increases risk of colorectal cancer/adenoma or is an artifact of pre-existing disease

454 pyrosequencing identifies bacteria at genus, but not species level. Higher depth genomic techniques may be required to fully differentiate the colonizing groups and their subsequent functions

Fecal SCFA concentrations correlate with both formation and uptake throughout the gut, but do not necessarily reflect SCFA production

‘Food’ for Thought: Future Directions Transmissible and modifiable interactions between diet and microbiota

influence host biology and cancer development in mice: Intact uncultured and culturable bacterial component of Obese co-twin’s

fecal microbiota caused significantly greater increases in body mass and adiposity than those of lean communities (Ridaura, Science 2013)

Diet- or gene-induced obesity alters gut microbiota, thereby increasing the levels of metabolites that secrete inflammatory and tumor-promoting factors in the liver facilitating development of liver cancer (Yoshimoto, Nature 2013)

Potential for translation to humans…

Gut Microbiome

Obesity

Colorectal Cancer

Inflammation

Diet

Thank You!

In Conclusion

Gene Induced Obesity

Diet-Induced Obesity

Microbiome Induced Obesity

Mutation or polymorphism

High fat/high calorie diet

Disrupted microbial community

Microbe-dependent

effects

Increased Energy Harvest

Altered Metabolic Signaling

Altered Inflammation

Increased Adipose Tissue

Figure adapted from Blaser et al, Cell Press (2013)

- Microbe involvement in SCFA Metabolism & GPCR recognition- High Fiber diet- reduces insulin stimulation, increases gastric transit

time