Current status, problems, and perspectives of non-alcoholic fatty liver disease research

Non-alcoholic fatty liver disease(NAFLD) is a major chronic liver disease that can lead to liver cirrhosis, liver cancer, and ultimately death. NAFLD is pathologically classified as non-alcoholic fatty liver(NAFL) or non-alcoholic steatohepatitis(NASH) based on the existence of ballooned hepatocytes,although the states have been known to transform into each other. Moreover,since the detection of ballooned hepatocytes may be difficult with limited biopsied specimens, its clinical significance needs reconsideration. Repeated liver biopsy to assess histological NAFLD activity for therapeutic response is also impractical, creating the need for body fluid biomarkers and less invasive imaging modalities. Recent longitudinal observational studies have emphasized the importance of advanced fibrosis as a determinant of NAFLD outcome. Thus,identifying predictors of fibrosis progression and developing better screening methods will enable clinicians to isolate high-risk NAFLD patients requiring early intensive intervention. Despite the considerable heterogeneity of NAFLD with regard to underlying disease, patient age, and fibrosis stage, several clinical trials are underway to develop a first-in-class drug. In this review, we summarize the present status and future direction of NAFLD/NASH research towards solving unmet medical needs.

Mild drinking habit is a risk factor for hepatocarcinogenesis in non-alcoholic fatty liver disease with advanced fibrosis

AIM The impact of mild drinking habit(less than 20 g/d of ethanol) on the clinical course of non-alcoholic fatty liver disease(NAFLD) has not been determined. We examined the influence of a mild drinking habit on liver carcinogenesis from NAFLD. METHODS A total of 301 patients who had been diagnosed as having NAFLD by liver biopsy between 2003 and 2016 [median age: 56 years, 45% male, 56% with nonalcoholic steatohepatitis, 26% with advanced fibrosis(F3-4)] were divided into the mild drinking group withe thanol consumption of less than 20 g/d(mild drinking group, n = 93) and the non-drinking group(n = 208). Clinicopathological features at the time of liver biopsy and factors related to hepatocellular carcinoma(HCC) occurrence were compared between the groups.RESULTS We observed significant differences in male prevalence(P = 0.01), platelet count(P = 0.04), and gammaglutamyl transpeptidase(P = 0.02) between the test groups. Over 6 years of observation, the HCC appearance rate was significantly higher in the mild drinking group(6.5% vs 1.4%, P = 0.02). Multivariate survival analysis using Cox's regression model revealed that hepatic advanced fibrosis(F3-4)(P < 0.01, risk ratio: 11.60), diabetes mellitus(P < 0.01, risk ratio: 89.50), and serum triglyceride(P = 0.04, risk ratio: 0.98) were factors significantly related to HCC in all NAFLD patients, while the effect of a drinking habit was marginal(P = 0.07, risk ratio: 4.43). In patients with advanced fibrosis(F3-4), however, a drinking habit(P = 0.04, risk ratio: 4.83), alpha-fetoprotein(P = 0.01, risk ratio: 1.23), and diabetes mellitus(P = 0.03, risk ratio: 12.00) were identified as significant contributors to HCC occurrence. CONCLUSION A mild drinking habit appears to be a risk factor for hepatocarcinogenesis in NAFLD patients, especially those with advanced fibrosis.

Serum autotaxin levels are correlated with hepatic fibrosis and ballooning in patients with non-alcoholic fatty liver disease

AIM To examine the relationship between serum autotaxin(ATX) concentrations and clinicopathological findings in non-alcoholic fatty liver disease(NAFLD) patients.METHODS One hundred eighty-six NAFLD patients who had undergone liver biopsy between 2008 and 2017 were retrospectively enrolled.Serum samples were collected at the time of biopsy and ATX was measured by enzyme immunoassays.Sera obtained from 160 healthy,nonobese individuals were used as controls.Histological findings were graded according to an NAFLD scoring system and correlations with serum ATX were calculated by Spearman's test.Diagnostic accuracy was evaluated using the area under the receiver operating characteristic curve(AUC).Cut-off values were identified by the Youden index,and the nearest clinically applicable value to the cutoff was considered the optimal threshold for clinical convenience.RESULTS Serum ATX levels were significantly higher in NAFLD patients than in controls(0.86 mg/L vs 0.76 mg/L,P < 0.001) and correlated significantly with ballooning score and fibrosis stage(r = 0.36,P < 0.001 and r = 0.45,P < 0.001,respectively).Such tendencies were stronger in female patients.There were no remarkable relationships between ATX and serum alanine aminotransferase,lipid profiles,or steatosis scores.The AUC values of ATX for predicting the presence of fibrosis(≥ F1),significant fibrosis(≥ F2),severe fibrosis(≥ F3),and cirrhosis(F4),were all more than 0.70 in respective analyses.CONCLUSION Serum ATX levels may at least partially reflect histological severity in NAFLD.

Association between endotoxemia and histological features of nonalcoholic fatty liver disease

AIM To assess whether surrogate biomarkers of endotoxemia were correlated with the histological features ofnonalcoholic fatty liver disease(NAFLD).METHODS One hundred twenty-six NAFLD patients who had undergone percutaneous liver biopsy were enrolled. Serum lipopolysaccharide(LPS)-binding protein(LBP) and anti-endotoxin core immunoglobulin G(Endo Cab Ig G) antibody concentrations at the time of liver biopsy were measured using the enzyme-linked immunosorbent assays to examine for relationships between biomarker levels and histological scores. RESULTS Serum LBP concentration was significantly increased in nonalcoholic steatohepatitis(NASH) patients as compared with nonalcoholic fatty liver(NAFL) subjects and was correlated with steatosis(r = 0.38, P < 0.0001) and ballooning scores(r = 0.23, P = 0.01), but not with the severity of lobular inflammation or fibrosis. Multivariate linear regression analysis revealed that LBP was associated with steatosis score and circulating C-reactive protein, aspartate aminotransferase, and fibrinogen levels. Serum Endo Cab Ig G concentration was comparable between NASH and NAFL patients. No meaningful correlations were detected between Endo Cab Ig G and histological findings. CONCLUSION LBP/Endo Cab Ig G were not correlated with lobular inflammation or fibrosis. More accurate LPS biomarkers are required to stringently assess the contribution of endotoxemia to conventional NASH.

Mutations of pre-core and basal core promoter before and after hepatitis B e antigen seroconversion

AIM: To investigate the role of pre-core and basal core promoter(BCP) mutations before and after hepatitis Be antigen(HBe Ag) seroconversion.METHODS: The proportion of pre-core(G1896A) and basal core promoter(A1762T and G1764A) mutant viruses and serum levels of hepatitis B virus(HBV) DNA, hepatitis B surface antigen(HBs Ag), and HB core-related antigen were analyzed in chronic hepatitis B patients before and after HBe Ag seroconversion(n = 25), in those who were persistently HBe Ag positive(n = 18), and in those who were persistently anti-HBe positive(n = 43). All patients were infected with HBV genotype C and were followed for a median of 9 years.RESULTS: Although the pre-core mutant became predominant(24% to 65%, P = 0.022) in the HBe Ag seroconversion group during follow-up, the proportion of the basal core promoter mutation did not change. Median HBV viral markers were significantly higher in patients without the mutations in an HBe Ag positive status(HBV DNA: P = 0.003; HBs Ag: P < 0.001; HB core-related antigen: P = 0.001). In contrast, HBV DNA(P = 0.012) and HBs Ag(P = 0.041) levels were significantly higher in patients with the pre-core mutation in an anti-HBe positive status.CONCLUSION: There is an opposite association of the pre-core mutation with viral load before and after HBe Ag seroconversion in patients with HBV infection.