Gut Microbiome Influences on Obesity and NAFLD

Joanna Yeh

Pediatric GI Conference

December 2012

Objectives

• Review the basics of gut microbiome and its relationship to health.

• Understand how influences of microbiome are being investigated with increasing number of diseases.

• Review current understanding of microbiome in relation to obesity.

• Discuss two recent papers regarding microbiome and NAFLD.

Definitions

• Microbiota: microbial community. • Microbiome: can refer to microbiota but can also

refer to collective genomes and gene products of microbes living within and on humans.

• Metagenome: collection of genomes within complex microbial communities and human DNA, some also include RNA and proteins and other metabolites.

• Biodiversity is a measure of the complexity of a community. Includes number of taxa (richness) and their range of abundance (evenness).

Johnson, Pediatrics, 2012 Weinstock, Nature, 2012

The human gut metagenome has at least 100 times as many genes as “us.”

There are 10 to 100 trillion microbes in our GI tract, most in the distal gut.

Two phyla (Bacteroidetes and Firmicutes) make up >90% in adults.

Gill, Science, 2006

In 2007, the NIH Human Microbiome Project was formed.

O’Hara, EMBO, 2006

Johnson, Pediatrics, 2012

Our Disease Burden is Changing.

• Rising rates of: – IBD – Allergic disease (eczema,

food allergy, asthma) – Celiac disease – EoE – “Autoimmune disease” – IBS – Obesity and NAFLD

De Vos, Nutrition Review, 2012

Early Influences on Microbiota

• Gestational age

• Mode of birth (vaginal vs. c-section)

• Maternal microbiome

• Exposure to environment (city vs. farm)

• Diet including breast milk vs. formula

• Hospitalization and use of antibiotics

KOALA Birth Cohort Study • C/S infants have lower

bifidobacteria and baceteroides and more C difficile.

• Bifido and bacteroides may be protective against obesity.

Reinhardt, JPGN, 2009

Breast milk vs. formula fed

• Human milk oligosaccharides stimulate growth of bifidobacterium and selectively alter microbial composition.

• Microbiomes of BF babies have higher bifidobacterium and lactobacillus.

• Formula fed babies have higher clostridium.

• Possible protection against allergies, neonatal diarrhea, NEC, obesity, DM2.

Johnson, Pediatrics, 2012

Thompson, Am J Human Bio, 2012

Celemente, Cell, 2012

Impact of Diet on Microbiota

Filippo, PNAS, 2010

Moschen, Gut and Liver, 2012

Gut microbiome may alter obesity.

• Mice and human microbiotas have Firmicutes and Bacteroidetes dominating.

• Transplantation of an “obese microbiota” to germ free mice results in increased adiposity compared to transplantation of a lean microbiota.

• Mice fed high calorie Western diet for 8 weeks increased levels of Firmicutes and decreased Bacteroidetes; this has been seen in humans as well.

Reinhardt, JPGN, 2009 Ferrer, Env Micro, 2012

Kallus, J Clin Gastro, 2012

Reinhardt, JPGN, 2009

Tehrani, Neurogastroenterol Motil, 2012

Peripheral metabolism

Enteroendocrine

Innate immune system

“Developmental Origins of Obesity”

Thompson, Am J Human Bio, 2012

Potential Therapeutics

• Microbial supplements – Probiotic or synbiotics (pro+pre)

Lactobacillus, bifidobacterium, streptococcus. Saccharomyces.

• Foods – Diet or prebiotics

• Antibiotics

• Fecal transplantation

• Prevention / Behavior Change

Hepatology, 2012 (ahead of print)

Methods

• 3 pediatric groups (n=63 total) – NASH defined by biopsy (Kleiner’s criteria: hepatic fat

infiltration, inflammation, and fibrosis)

– Obese (BMI>95% with normal LFTs)

– Normal (BMI<85%)

• Microbiome assessed using stool sample via 16S rRNA sequencing

• Blood sample taken for serum alcohol concentration

• Dietary assessments

Health status is a major impact factor for the phylogenetic composition of

fecal samples.

Is gut microbiota enriched in alcohol producing bacteria like E. coli supplying a constant source of reactive oxygen

species (alcohol metabolism) to the liver, thus causing liver inflammation?

Conclusions

• NASH microbiome is distinct from normal and obese microbiomes.

• Some statistically significant differences: – Bifidobacterium: NASH<obese <normal

– Prevotella: NASH>obese>>>normal

– Escherichia: NASH>>obese>normal

• Escherichia is abundant in NASH microbiome compared to obese.

• The fact that Escherichia are ethanol producers may provide a mechanism.

Questions

• Liver ultrasound indicated that some obese patients had fatty liver.

• Conflicting microbiomes compared to prior studies in mice and humans.

• What other mechanisms might contribute to NAFLD besides alcohol production? Absorption of nutrients/digestion? Immune mediated? Gut hormones?

• Does fatty liver lead to microbiome changes? (chicken/egg)

• Why would Escherichia be increased in NASH patients?

JPGN, 2011

Methods

• Double blind, placebo controlled pilot study.

• Recruit obese children, ALT>40 at least 3 months, US diagnosed fatty liver.

• Exclude: other causes of liver disease were ruled out, on antibiotics, past pharmacologic treatment for obesity.

• Randomized to placebo vs. Lactobacillus GG (12 billion CFU/day) x 8 weeks.

• Primary outcome: ALT improvement or normalization.

• Secondary outcome: changes in liver echogenicity, TNFalpha, H2BT, PG-PS ab.

Results

Conclusions

• Short course of probiotic treatment improved ALT value independent of weight changes.

• Differences in bacterial overgrowth as measured by breath test vs. PG-PS IgA are inconsistent. Mechanism is unclear.

• Lactobacillus rhamnosus strain GG could be a potential therapeutic tool for pediatric NAFLD.

Questions

• What about biopsy proven NAFLD? How about NASH patients? Patients with fibrosis?

• Larger RCT looking at microbiome?

• What about other end points? Histology? Ultrasound findings?

• Is SIBO in NAFLD patients the culprit?

Take home points

• Microbiome is increasingly being investigated for potential contribution to many diseases.

• Individual microbiomes are influenced by many factors starting from birth.

• Microbiome, through a variety of possible mechanisms, may influence obesity.

• Pro and prebiotics are being investigated as treatment options for NAFLD.

References • Clemente, et al, “The impact of the gut microbiota on human health: an integrative view,” Cell, 2012.

• De Filippo, et al, “Impact of diet in shaping gut microbiota revealed by a comparative study in children from Europe and rural Africa,” PNAS, 2010.

• Ferrer, et al, “Microbiota from the distal guts of lean and obese adolescents exhibit partial functional redundancy besides clear differences in community structure,” Env Microbiology, 2012.

• Gill, et al, “Metagenomic analysis of the human distal gut microbiome,” Science, 206.

• Harris, et al, “Is the gut microbiota a new factor contributing to obesity and its metabolic disorders?” J Obesity, 2012.

• Johnson, et al, “The human microbiome and its potential importance to pediatrics,” Pediatrics, 2012.

• Kallus, et al, “The intestinal microbiota and obesity,” J Clin Gastro, 2012.

• Moschen, et al, “Dietary factors: major regulartors of the gut’s microbiota,” Gut and Liver, 2012.

• O’Hara, et al, “The gut as a forgotten organ,” EMBO Reports, 2006.

• Reinhardt, et al, “Intestinal microbiota during infancy and its implications for obesity,” JPGN, 2009.

• Tehrani, “Obesity and its associated disease: a role for microbiota?” Neurogastroenterol Motil, 2012.

• Thompson, “Developmental origins of obesity,” Am J Human Bio, 2012.

• Vajro, et al, “Effects of lactobacillus rhamnosus strain GG in pediatric obesity-related liver disease,” JPGN, 2011.

• Weinstock, “Genomic approaches to studying the human microbiota,” Nature, 2012.

• Zhu, et al, “Characterization of the gut microbiome in non-alcoholic steatohepatitis (NASH) patients: a connection between endogenous alcohol and NASH,” Hepatology, 2012.