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Fecal microbiome, volatile organic compounds differ between obese NAFLD patients, controls

Obese patients with nonalcoholic fatty liver disease have increased fecal ester volatile organic compounds and significant differences in fecal microbiome compared with healthy controls, according to recent results.

In an observational case-control study, researchers evaluated the fecal microbiota in stool samples collected from 30 obese patients with nonalcoholic fatty liver disease (NAFLD) and 30 healthy controls. Fecal volatile organic compounds (VOC) were measured in both groups via gas chromatography-mass spectrometry. All participants were collected from the Foothills Medical Centre in Calgary, Alberta, between January and August 2009.

“The pathophysiology of NAFLD is incompletely understood,” researcher Maitreyi Raman, MD, MSc, clinical associate professor in the gastroenterology and hepatology division at the University of Calgary, told Healio.com. “Previous researchers have wondered about the production of endogenous alcohol in NAFLD patients. With the explosion of interest in the gut microbiome, there is plausibility that gut microbes that populate obese patients differ from those in lean healthy subjects, and that these microbes may contribute toward alcohol and VOC production. Potentially, therapeutically manipulating the gut microbiome may result in NAFLD improvement.”

Researchers detected 220 distinct VOC across both cohorts (controls, median, 64; NAFLD patients, median 72; P<.01 for difference). Most core and common VOC were similar between groups, including ethanol, acetone, heptanone and butanoic and pentanoic acid. Twelve VOC across several chemical classes were significantly more prominent among controls, while 18 VOC, primarily ester compounds, were more prevalent among patients.

Bacteroides and genera in the Firmicutes phylum were most prevalent in the fecal microbiota of each group. Analysis at the genus level indicated significant increases among patients with NAFLD of Robinsoniella, Roseburia and Dorea in the Lachnospiraceae family, and a significant decrease in Oscillibacter of the Ruminococcaceae family, compared with controls. Statistically significant increases of specific Firmicutes genera and Proteobacteria families also were noted among NAFLD patients.

“Obese patients with NAFLD have a significantly altered VOC profile compared with healthy lean control subjects,” Raman said. “Additionally, we identified small but significant differences in the fecal microbiota composition between obese patients with NAFLD compared with healthy lean controls.”