Modulation of the gut microbiota represents a new management for non-alcoholic fatty liver disease

With the worldwide spread of diet westernization,
sedentary lifestyle, and obesity, non-alcoholic fatty liver
disease (NAFLD) has becoming frequent disorder. NAFLD
is the presence of hepatic fat infiltration more than 5% of
liver cells, in lack of alcohol abuse or steatogenic drugs.
NAFLD includes a spectrum of liver disorder, ranging
from steatosis and non-alcoholic steatohepatitis (NASH)
to fibrosis, cirrhosis and hepatocellular carcinoma (1).
Metabolic syndrome and systemic micro-inflammation
are the most relevant metabolic disorders related to this
spectrum of diseases (2). There is currently no approved
pharmacological treatment for NAFLD. The management
strategy of NAFLD involves lifestyle interventions,
including diet, exercise, and behavior modification (1).
The intestinal microbiota has been a topic of scientific
research for a recent decade. The gut microbiota composed
of organized community of microorganisms (3). The
literature to date suggests points to a critical impact of the
intestinal flora and intestinal barrier on the pathogenesis
of NAFLD and other metabolic disorders (4). Dysbiosis,
which is defined as changes in intestinal bacteria, and small
intestine bacterial overgrowth, which is related to dietary
habits, genetic predisposition, and physical inactivity
can influence energy homeostasis. Dysbiosis, impaired
intestinal barrier function, and adipose tissue related
inflammation act directly through increased translocation
of bacterial endotoxins or lipotoxins, or indirectly, through
the regulation of insulin sensitivity and resulting liver
steatosis (5). The interplay between gut microbiota and
NAFLD onset is summarized and illustrated in Figure 1.
Previous studies documented that severity of steatosis in
NAFLD patients correlated with small bowel bacterial
overgrowth and increased intestinal permeability (6).
The novel progresses in knowledge about the human gut
microbiota have changed our sight of disease and treatment.
Therapeutic manipulations with prebiotics, probiotics,
and synbiotic as microbiome-based interventions are
potential targets for NAFLD management via modulating
the enteric flora (Figure 2). Considering the ease of use
of these supplements, their safety and low cost, they
beneficial impact on hepatic steatosis and fibrosis (7,8); oral
probiotics are live microorganisms that have potentially
benefits for the host through its effects in the intestinal
tract if consumed in adequate amounts (9). Prebiotics are
fermentable fibers that facilitate the growth of probiotics
and thereby benefit health (10). Synbiotics which are
combination of prebiotics and probiotics have a potentially
stronger effect in modulating the gut microbiota than
either probiotics or prebiotics alone (11). A meta-analysis
has reported probiotic supplementation can improve liver
enzymes, serum cholesterol, and insulin sensitivity in
patients with NAFLD (12). Evidence of a meta-analysis
declare that probiotic and synbiotic supplementation may
improve lipid profile, glycemic variable, liver enzymes,
and inflammatory mediator by alternating the type and/or
function of the intestinal microbiota (11). In our previous
study, we found th