Gut-flora metabolites is not associated with synchronous carotid artery plaque and non-alcoholic fatty liver disease in asymptomatic adults: A STROBE-compliant article

Blood Endotoxin Levels as Biomarker of Nonalcoholic Fatty Liver Disease: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

Growing evidence supports a role of gut-derived metabolites in nonalcoholic fatty liver disease (NAFLD), but the relation of endotoxin levels with gut permeability and NAFLD stage remains unclear. This systematic review with meta-analysis aims to provide further insights.

METHODS

PubMed, Embase, and Cochrane Library were searched for studies published until January 2022 assessing blood endotoxins in patients with NAFLD. Meta-analyses and univariate/multivariate meta-regression, as well as correlation analyses, were performed for endotoxin values and potential relationships to disease stage, age, sex, parameters of systemic inflammation, and metabolic syndrome, as well as liver function and histology.

RESULTS

Forty-three studies were included, of which 34 were used for meta-analyses. Blood endotoxin levels were higher in patients with simple steatosis vs liver-healthy controls (standardized mean difference, 0.86; 95% confidence interval, 0.62-1.11) as well as in patients with nonalcoholic steatohepatitis vs patients with nonalcoholic fatty liver/non-nonalcoholic steatohepatitis (standardized mean difference, 0.81; 95% confidence interval, 0.27-1.35; P = .0078). Consistently, higher endotoxin levels were observed in patients with more advanced histopathological gradings of liver steatosis and fibrosis. An increase of blood endotoxin levels was partially attributed to a body mass index rise in patients with NAFLD compared with controls. Nevertheless, significant increases of blood endotoxin levels in NAFLD retained after compensation for differences in body mass index, metabolic condition, or liver enzymes. Increases in blood endotoxin levels were associated with increases in C-reactive protein concentrations, and in most cases, paralleled a rise in markers for intestinal permeability.

CONCLUSION

Our results support blood endotoxin levels as relevant diagnostic biomarker for NAFLD, both for disease detection as well as staging during disease progression, and might serve as surrogate marker of enhanced intestinal permeability in NAFLD. Registration number in Prospero: CRD42022311166.

Insight into increased risk of portal vein thrombosis in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is one of the leading chronic liver diseases with increased morbidity and mortality rates for extrahepatic diseases (including cardiovascular disease, portal vein thrombosis, etc.). There is an increased risk of thrombosis in both the portal and systemic circulation in patients with NAFLD, independent of traditional liver cirrhosis. However, increased portal pressure, the most critical factor, is frequently observed in NAFLD patients, predisposing them to portal vein thrombosis (PVT). It has been reported that there is an 8.5% incidence of PVT among patients with non-cirrhotic NAFLD in a prospective cohort study. Based on the prothrombotic status of NAFLD itself, patients combined with cirrhosis may accelerate the development of PVT and lead to a poor prognosis. Moreover, PVT has been shown to complicate the procedure and adversely affect the outcome during liver transplantation surgery. NAFLD is in a prothrombotic state, and its underlying mechanisms have not been fully understood so far. Particularly noteworthy is that gastroenterologists currently overlook the higher risk of PVT in NAFLD. We investigate the pathogenesis of NAFLD complicated with PVT from the perspective of primary, secondary, and tertiary hemostasis, and also summarize relevant studies in humans. Some treatment options that may affect NAFLD and its PVT are also explored to improve patient-oriented outcomes.

Trimethylamine N-Oxide Levels in Non-Alcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis

Non-alcoholic fatty liver disease (NAFLD) represents an entity with an increasing prevalence which is characterized by significant hepatic and extrahepatic complications. Its pathophysiology is multifactorial, with gut dysbiosis being considered a major determinant. In this systematic review and meta-analysis, we tried to evaluate the association between the major gut microbial metabolite trimethylamine N-oxide (TMAO) and NAFLD. We performed a literature search for studies that determined circulating TMAO in patients with and without NAFLD. The database search identified 136 studies, and upon application of the exclusion criteria, 7 studies with 7583 individuals (NAFLD 2923, control 4660) were ultimately included in the meta-analysis. Compared to the control group, NAFLD patients had significantly higher circulating TMAO (SMD: 0.66, 95% CI -0.12 to 1.21, p = 0.02, I²: 94%). The results remained unaffected after the exclusion of one influential study. The subgroup analysis revealed significantly higher TMAO in individuals with histologically proven NAFLD and in studies measuring TMAO with high-performance liquid chromatography. No differences were observed according to the study design or study region. However, funnel plot asymmetry was observed, indicating publication bias. In conclusion, patients with NAFLD had increased levels of TMAO, a hazardous gut microbial metabolite, suggesting its important role in the gut-liver interaction.