Synbiotics can alter gut microbiota in patients with nonalcoholic fatty liver disease (NAFLD), but associated liver benefits remain unseen, according to a recent phase II study.
NAFLD patients who received a year-long regimen of fructo-oligosaccharides and Bifidobacterium animalis had no significant changes in liver fat content or fibrosis, compared with those who received placebo, reported lead author Eleonora Scorletti, MD, of the University of Pennsylvania, Philadelphia, and colleagues.
“There is recent growing interest in the role of gut microbiota in NAFLD pathogenesis, and there are several metaorganismal pathways linking altered gut microbiota ... and NAFLD,” the investigators wrote in Gastroenterology.According to the investigators, previous studies have shown that patients with NAFLD may have some characteristic alterations to their microbiota, such as increased Gram-negative bacteria or more abundant Ruminococcus species, the latter of which were associated with worse fibrosis.
“However, there is currently a lack of consistency in these findings due to the marked variance in the population studied, with differing ages, diets, and geographic locations,” the investigators wrote. “Nonetheless, despite these inconsistencies, there is the possibility that manipulation of the gut microbiota to a more favorable profile could provide a beneficial effect on liver disease in patients with NAFLD.”
To evaluate this possibility, the investigators enrolled 104 patients with NAFLD in the United Kingdom. Patients were randomly divided into a placebo (n = 49) and synbiotic group (n = 55), with the latter receiving 4 grams of fructo-oligosaccharides twice per day plus 10 billion colony-forming units of Bifidobacterium animalis subspecies lactis BB-12 on a daily basis. Treatments were given for 10-14 months.
Diagnostics were conducted across all participants at the beginning and end of the study. These included fecal microbiota analysis by 16s ribosomal DNA sequencing, liver fat measurement by proton magnetic resonance spectroscopy, biomarker-based liver fibrosis scoring, and liver stiffness assessment by vibration-controlled transient elastography.
At the end of the study, patients in the synbiotic group had increased abundance of Bifidobacterium and Faecalibacterium species and reduced proportions of Oscillibacter and Alistipes species, compared with baseline. These changes were not observed in the placebo group.
But changes in microbiota had no apparent impact on liver pathology. Although mean liver fat percentages dropped from 32.3% to 28.5% in the synbiotic group (approximately 4%), they also dropped in the placebo group, from 31.3% to 25.2% (approximately 6%), with differences between groups lacking statistical significance. Using multivariate analysis, the investigators linked these liver fat improvements, which occurred in 65% of participants, with weight loss.
“The fact that most patients had an improvement in ... liver fat, regardless of treatment allocation, is consistent with the so-called clinical trial effect, whereby participants benefit from participating in clinical trials,” the investigators wrote.
Similarly to liver fat content, no significant intergroup differences were found for liver fibrosis or stiffness, whereas, again, weight loss was linked with improvements in both disease parameters.
“Our randomized clinical trial suggests that changing the gut microbiota with this synbiotic may occur without clinically significant effects on the liver in NAFLD,” the investigators concluded.
Still, they noted that the failure of one synbiotic regimen does not discount the possibility of microbiota-based NAFLD interventions as a whole.
“Previous studies that have tested the effects of synbiotic treatment in NAFLD have also used a combination of multiple strains of probiotics as a component of the synbiotic treatment,” the investigators wrote. “Therefore, it might be possible that, because the intestine harbors trillions of bacteria, adding 1 single type of bacterium in a synbiotic may not be as effective as adding 3 or 6 different types of bacteria with the potential to influence many more bacterial species.”
The study was supported by the National Institute of Health Research, the Parnell Diabetes Trust, and Chr. Hansen Holding. One author reported funding from Chr. Hansen unrelated to this trial.
SOURCE: Scorletti E et al. Gastro. 2020 Jan 24. doi: 10.1053/j.gastro.2020.01.031.