Evidences suggest a rising trend in the incidence of obesity and its related conditions, including non-alcoholic fatty liver disease (NAFLD), in all age groups worldwide. These conditions concomitantly pose subsequent huge economic burden on healthcare systems, which makes their prevention and treatment mandatory. Although standard dietary and lifestyle changes and pathogenically-oriented therapies including antioxidants, oral hypoglycemic agents, and lipid-lowering agents are most common applied strategies, but they often fail due to poor compliance and/or lack of efficiency, there is imperative need for introduction of novel approaches directed toward other pathomechanisms. 

Thus, the authors of the present study suggested evidence signifying that, by increasing energy extraction in some dysbiosis conditions or small intestinal bacterial overgrowth, specific gut microbiota and/or a low bacterial richness may play a role in obesity, metabolic syndrome, and fatty liver. The gut-liver axis in situations with damaged intestinal barrier may increase the natural interactions between intestinal bacterial products and hepatic receptors, thus supporting the following cascade of events; oxidative stress, insulin-resistance, hepatic inflammation, and fibrosis. 

The study also highlighted the approach of probiotics as a promising and innovative add-on therapeutic tool for NAFLD in the context of multi-target therapy. The researchers reviewed the possible modulation of gut microbiota by probiotics, with evidence of NAFLD animal model studies and in several pilot pediatric and adult human studies. 

The author retrieved ten such studies including seven randomized controlled trials. The included two pilot non-randomized studies showed that Lactobacilli plus a prebiotic and vitamin mixture were well tolerated, and ameliorated conventional liver function tests and reduced the levels of markers of lipid peroxidation and/or TNF-α. Additionally, a 2-month supplementation with probiotic combination decreased the levels of liver enzymes in 10 biopsied adults affected by NASH and both ALT and gamma glutamyltransferase improved significantly post one month washout. The treatment also induced a decrease in oxidative stress markers [malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). 

Another study conducted in pediatric data showed that probiotic treatment including Lactobacillus bulgaricus and Streptococcus thermophilus in adults with histologically proven NAFLD confirmed a significant decrease in liver enzymes. Treatment with Bifidobacterium longum along with prebiotic fructooligosaccharide induced a significant improvement in serum inflammatory, metabolic, and liver enzyme parameters.

Another study compared the effects of metformin and probiotics in 32 adult NAFLD patients showed a more remarkable reduction in aminotransferase, cholesterol, triglyceride levels, and BMI levels in the metformin and probiotic group in contrast to metformin placebo group. Therefore, these clinical studies substantiates the therapeutic role of probiotics in NAFLD treatment. The probiotics act on different targets and can modify the gut microbiota composition, decrease intestinal permeability and the translocation of bacterial products in portal circulation and modulate the liver inflammation pathways and collagen deposition.

Source: Paolella G, Mandato C, Pierri L, Poeta M, Di Stasi M, Vajro P. Gut-liver axis and probiotics: their role in non-alcoholic fatty liver disease. World J Gastroenterol. 2014;20(42):15518-15531.