Mitochondrial DNA from hepatocytes as a ligand for TLR9: Drivers of nonalcoholic steatohepatitis?

Nonalcoholic fatty liver disease(NAFLD) is the most common liver disease worldwide, affecting approximately one third of the Western world. It consists of a wide spectrum of liver disorders, ranging from fatty liver to nonalcoholic steatohepatitis(NASH), which consists of steatosis, ballooning injury and inflammation. Despite an alarming growth in the statistics surrounding NAFLD, there are as yet no effective therapies for its treatment. Innate immune signaling has been thought to play a significant role in initiating and augmenting hepatic inflammation, contributing to the transition from nonalcoholic fatty liver to NASH. An immune response is triggered by countless signals called damage-associated molecular patterns(DAMPs) elicited by lipid-laden and damaged hepatocytes, which are recognized by pattern recognition receptors(PRRs) on hepatic immune cells to initiate inflammatory signaling. In this editorial, in addition to summarizing innate immune signaling in NAFLD and discussing potential therapies that target innate immune pathways, we have described a recent study that demonstrated that mitochondrial DNA serves as a DAMP activating a hepatic PRR, TLR9, in mice and in the plasma of NASH patients. In addition to identifying a new ligand for TLR9 during NASH progression, the study shows that blocking TLR9 reverses NASH, paving the way for the development of future NASH therapy.

Characterization of patients with both alcoholic and nonalcoholic fatty liver disease in a large United States cohort

BACKGROUND Nonalcoholic fatty liver disease(NAFLD)is the hepatic manifestation of the metabolic syndrome(MetS)and is characterized by steatosis in the absence of significant alcohol consumption.However,MetS and significant alcohol intake coexist in certain individuals which may lead to the development of BAFLD.AIM To assess the clinical characteristics of patients with both alcoholic and NAFLD(BAFLD)in a large cohort in the United States.METHODS Adults from the National Health and Nutrition Examination Survey between 2003-2014 were included.NAFLD was diagnosed based on elevated alanine aminotransferase(ALT)and being overweight or obese in the absence of other liver diseases.BAFLD patients met the criteria for NAFLD but also had either MetS or type 2 diabetes and consumed excessive amounts of alcohol.Univariable and multivariable analysis were performed to assess differences between NAFLD and BAFLD and to compare severity based on a validated fibrosis score(FIB4 index).RESULTS The prevalence of NAFLD was at 25.9%(95%CI;25.1-26.8)and that of BAFLD was 0.84%(0.67,1.02)which corresponds to an estimated 1.24 million Americans affected by BAFLD.Compared to NAFLD,patients with BAFLD were more likely to be male,smokers,have higher ALT,aspartate aminotransferase,triglycerides,and lower platelets;P<0.01 for all.More importantly,after adjusting for MetS components,BAFLD patients were significantly more likely to have advanced fibrosis[adjusted OR(95%CI)based on FIB4 index>2.67 was 3.2(1.4,7.0),P=0.004].CONCLUSION A significant percentage of the American general population is afflicted by BAFLD and these patients tend to have more advanced liver fibrosis.