SAN DIEGO – Patients with hepatitis C virus (HCV) infections had distinct duodenal mucosal microbiomes and greater intestinal permeability, compared with healthy controls and patients with other chronic liver diseases, Dr. Ashok Raj reported.
The findings might one day lead to therapies that aim to restore or normalize the microbiomes of patients with HCV, Dr. Raj said in an interview at the annual Digestive Disease Week.
Amy Karon/Frontline Medical News
Dr. Ashok Raj
Chronic liver disease (CLD) has been linked to dysbiosis, or abnormal shifts of the microbiome. But most studies have focused on fecal specimens, and “recent evidence suggests that the mucosal microbiota differ from fecal microbiota,” said Dr. Raj, a gastroenterologist and hepatologist at Princess Alexandra Hospital in Brisbane, Australia, and a PhD candidate at the University of Queensland at Brisbane.
“The small-intestinal mucosal microbiota are of particular interest to us,” Dr. Raj explained. “Anatomically, all the blood from this region of the gut drains into the portal vein and flows directly to the liver. Because of small-intestinal permeability, either bacteria or their products could travel to the liver and contribute to disease. But very little is known about this microbiota in CLD.”
Therefore, Dr. Raj and his associates sequenced bacterial DNA from mucosal biopsies of the second part of the duodenum from 38 prospectively recruited endoscopy patients with CLD and 13 healthy controls. The researchers also evaluated dietary habits, intestinal permeability, hepatic stiffness based on transient elastography, and the presence of metabolic syndrome, as measured by the International Diabetes Federation/American Heart Association/National Heart, Lung, and Blood Institute 2009 Consensus criteria. The CLD group included 28 men and 10 women aged 36-82 years, including 16 patients with HCV, 10 patients with nonalcoholic fatty liver disease, 7 patients with fatty liver disease, 3 patients with autoimmune hepatitis, and 2 patients with hepatitis B virus infection. The controls were between 24 and 73 years old, and 70% were women.
Sequencing of bacteria DNA revealed significant differences between patients and controls, particularly among patients with HCV, Dr. Raj said. The HCV patients not only had significantly less microbial diversity (P less than .02), but the overall changes in their microbiota were significant enough for them to cluster separately from controls and from patients with other types of CLD (P less than .01 for both comparisons). Furthermore, HCV patients had significantly greater small-intestinal permeability (mean ± SD log lactulose to rhamnose ratio, 1.57 ± 0.27) than controls (1.21 ± 0.25; P less than .01) or patients with other CLDs (1.24 ± 0.39; P = .01).
“Additionally, for the HCV patients, dietary fat intake showed a moderately strong positive correlation with intestinal permeability,” Dr. Raj said (r = 0.58; P = .03). “These findings are in keeping with animal models, which have shown that dietary fat can change the microbiota and also increase intestinal permeability.” However, the multivariate analysis found no links between microbial characteristics and hepatic stiffness or metabolic syndrome – perhaps because most patients were “at the cirrhotic end of the spectrum, reflecting their indication for endoscopy,” or because “these relationships are subtler and require larger sample numbers,” he said.
“Patients with HCV may have a unique small-intestinal microbiome,” Dr. Raj concluded. “These patients had higher intestinal permeability, and it is possible that the microbiota have a part to play in that.” Exactly how microbiota and gut permeability contribute to disease remains unclear, but pathology in the small intestine could help explain some features of the HCV trajectory, such as extrahepatic manifestations or variations in disease progression, he added. “Future studies may lead to targeting the small-intestinal gut microbiome to modulate and even treat HCV.”
The study was funded by a postgraduate award from the government of Australia and by the Princess Alexandra Hospital Research Foundation. Dr. Raj had no disclosures.