Nonobese Fatty Liver Disease

A Retrospective Study of Hospitalizations in the USA: Proportion of Hospitalizations With Non-Alcoholic Fatty Liver Disease in Non-Obese Population

Background Non-alcoholic fatty liver disease (NAFLD), one of the leading causes of end-stage liver disease, is known to be associated with obesity. However, only a few studies in the United States (US) have described non-obese NAFLD, most of which were on the outpatient population. Aim We aimed to investigate the proportion of hospitalizations in the US with a diagnosis code that included NAFLD in the non-obese population. Methods We analyzed adult discharges from the Nationwide Inpatient Sample with a diagnosis of NAFLD from January 2010 to December 2014. We created two groups: obese (overweight or obese) and non-obese (normal or underweight) groups. Basic demographic and clinical characteristics were compared using the chi-square test and Student's t-test. Results A total of 194,787 hospitalizations with NAFLD were identified over the five-year period. It was observed that the prevalence of non-obese NAFLD hospitalizations increased yearly. Non-obese NAFLD hospitalizations had a higher mean age (57.5 vs 51.5 years, p < 0.0001) and a higher proportion of males (43.3% vs 36.1%, p < 0.0001) than obese NAFLD hospitalizations. With univariate analysis, non-obese NAFLD hospitalizations had lower odds of hypertension (OR 0.74, p < 0.0001), diabetes mellitus (OR 0.65, p < 0.0001). Non-obese hospitalizations had higher odds of cirrhosis (OR 1.30, p < 0.001) and decompensated cirrhosis (OR 1.30, p < 0.001) after adjusting for age, sex, race, diabetes mellitus, and dyslipidemia. Hospitalizations with non-obese NAFLD had higher odds of death (OR 1.49, p < 0.001) after adjusting for age, gender, race, co-morbidities, cirrhosis, and liver decompensation. Conclusion There is a continued rise in the proportion of non-obese NAFLD among hospitalizations in the US. Non-obese NAFLD hospitalizations were less likely to have hypertension and diabetes, but more likely to have decompensated liver disease. Further studies are needed to better characterize these patients to enable early detection, treatment, and reduction in complications of liver disease.

Fatty liver index as a predictive marker for the development of diabetes: A retrospective cohort study using Japanese health check-up data

Background & aims

Fatty liver is associated with incident diabetes, and the fatty liver index (FLI) is a surrogate marker for non-alcoholic fatty liver disease (NAFLD). We aimed to determine whether or not FLI was associated with incident diabetes in relation to obesity and prediabetic levels in the general Japanese population.

Methods

This was a retrospective study using the Japanese health check-up database of one health insurance from FY2015 to FY2018. This study included 28,991 individuals with prediabetes. First, we stratified all participants into two groups: “high-risk,” comprising patients with HbA1c >6.0%, and “standard,” comprising the rest. Subsequently, we divided them into four groups according to FLI (<30 or not) and obesity (BMI <25 kg/m² or not). Subsequently, the incidence rate of diabetes was compared among the groups after 3 years of follow-up using multiple logistic regression models after adjusting for potential confounders.

Results

After 3 years of follow-up, 1,547 new cases of diabetes were found, and the cumulative incidence was 2.96% for the standard group and 26.1% for the high-risk group. In non-obese individuals, odds ratios (95% confidence interval) for FLI ≥30 versus FLI <30 were: 1.44 (1.09–1.92) for the standard group and 1.42 (0.99–2.03) for the high-risk group. In the high-risk group, obesity (BMI ≥25 kg/m²) but FLI <30 was not a risk factor for developing diabetes.

Conclusion

Although high FLI is generally considered to be a risk factor for developing diabetes, obesity might have been a confounding factor. However, the present study showed that high FLI is a risk factor for the development of diabetes, even in non-obese individuals. Our results include suggestion to develop a screening tool to effectively identify people at high risk of developing diabetes from the population (especially non-obese prediabetes) who are apparently at low health risk and are unlikely to be targeted for health guidance.

The Risk of Type 2 Diabetes and Coronary Artery Disease in Non-obese Patients With Non-alcoholic Fatty Liver Disease: A Cohort Study

Background: Non-alcoholic fatty liver disease (NAFLD) is not uncommon in non-obese subjects, referred to as non-obese NAFLD. It is not fully determined whether non-obese NAFLD is associated with increased risks of type 2 diabetes (T2D) and coronary artery disease (CAD) in Chinese. This study aimed to examine the association between NAFLD and risks of T2D and CAD in a non-obese Chinese population. Methods: The present cohort study included two stages. In the first cross-sectional study, 16,093 non-obese subjects with a body max index (BMI) < 25.0 kg/m² were enrolled from The Second Xiangya Hospital, China, from 2011 to 2014. Hepatic steatosis was evaluated by ultrasonography examination. Logistic regression analyses were used to examine the association of non-obese NAFLD with T2D and CAD at baseline. In the subsequent 5-year follow-up study, 12,649 subjects free of T2D and CAD at baseline were included, and the incidence of T2D and CAD were observed. Cox proportional hazard regression analyses were performed to determine the risk of incident T2D and CAD with NAFLD. Results: At baseline, the prevalence of NAFLD, T2D and CAD were 10.7% (1,717/16,093), 3.3% (529/16,093) and 0.7% (113/16,093), respectively. The univariate logistic regression analyses showed NAFLD associated with both T2D and CAD. Moreover, in a multivariate logistic regression model, NAFLD remained independently associated with T2D (OR: 2.7, 95% CI: 2.2-3.3, p < 0.001). However, no significant association was found between NAFLD and CAD by the multivariate logistic regression analyses (OR: 1.1, 95% CI: 0.6-1.8, p = 0.854). During a 5-year follow-up period, 177 (1.4%) patients developed T2D, and 134 (1.1%) developed CAD, respectively. In univariate Cox regression models, NAFLD associated with both T2D and CAD. Moreover, the multivariate Cox regression analysis revealed that NAFLD independently associated with an increased risk of T2D (HR: 2.3, 95% CI: 1.7-3.2, p < 0.001). However, the association between NAFLD and incident CAD was lost in the multivariate Cox regression analysis (HR = 1.5, 95% CI: 1.0-2.4, p = 0.059). Conclusions: NAFLD was an independent risk factor for T2D in non-obese subjects. However, no significant association was observed between non-obese NAFLD and incident CAD after adjusting other traditional cardiovascular risk factors, suggesting these factors might mediate the increased incidence of CAD in non-obese NAFLD patients.

Ectopic pancreatic fat as a risk factor for hypertension in children and adolescents with nonalcoholic fatty liver disease

Although nonalcoholic fatty liver disease (NAFLD) is known to be a risk factor for cardiovascular diseases, few studies have reported an association between ectopic fat deposition and metabolic complications, including hypertension, in children with NAFLD. The present study evaluated the risk factors for hypertension in children with NAFLD from the aspect of ectopic fat. This cross-sectional retrospective study investigated 65 children with NAFLD (49 boys, mean age 13.0 ± 3.2 years, mean body mass index z-score [BMI-z] 2.5 ± 1.2), who underwent liver biopsy and magnetic resonance imaging-based fat fraction measurement for ectopic hepatic and pancreatic fats, as well as anthropometry, blood pressure, laboratory tests, and body composition analysis. A logistic regression model was used to identify the risk factors for hypertension. Through a simple logistic regression analysis, age (OR 1.392), BMI-z (OR 3.971), waist circumference-to-height ratio (OR 1.136), fat-free mass index (OR 1.444), γ-glutamyl transferase (OR 1.021), quantitative insulin sensitivity check index (OR 0.743), dyslipidemia (OR 5.357), and pancreatic fat fraction (PFF) (OR 1.205) were associated with hypertension. The optimal cut-off of PFF to divide children with NAFLD into two groups with and without hypertension was 4.39% (area under the curve 0.754, p = .001, sensitivity 82.4%, specificity 73.9%). Multiple logistic regression analysis in the fully adjusted model revealed both BMI-z (OR 4.912, 95% CI, 1.463-16.497) and PFF (OR 1.279, 95% CI, 1.007-1.624) were independent risk factors for hypertension. In conclusions, in addition to BMI-z, ectopic pancreatic fat is an important risk factor for hypertension in children with NAFLD.

Dietary Interventions in Patients With Non-alcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis

Background: With no approved pharmacotherapy to date, the present therapeutic cornerstone for non-alcoholic fatty liver diseases (NAFLD) is a lifestyle intervention. Guidelines endorse weight loss through dietary modifications, physical exercise, or both. However, no consensus exists on the optimal dietary treatment. Objectives: The aim of our systematic review and meta-analysis was to summarize and assess the evidence for applied types of dietary interventions on the liver and metabolic outcomes in patients with NAFLD, aside from any effects of exercise intervention. Methods: This systematic review was conducted according to the Preferred Reporting Items of Systematic Reviews and Meta-analysis (PRISMA) statement guidelines. The search was conducted in PubMed, Scopus, and Cochrane databases in February 2020. Included were only dietary interventions without exercise. This study was registered at PROSPERO: CRD42020203573. Results: Eight randomized controlled trials, seven with endpoint reduction of hepatic steatosis, one with an assessment of endpoint fibrosis, were included in this systematic review, five of which were included in the meta-analysis. Mediterranean dietary interventions without energy restriction (n = 3) showed significant reduction of intrahepatic lipid content (IHL) (SDM: -0.57, 95% CI: -1.04, -0.10), but there was no significant change in alanine transaminase (ALT) (SDM: 0.59, 95% CI: -0.5, -1.68). Hypocaloric dietary interventions with foods high in unsaturated fatty acids (n = 2) led to a significant decrease in ALT (SDM: -1.09, 95% CI: -1.49, -0.69) and aspartate aminotransferase (AST) (SDM: -0.75, 95% CI: -1.27, 0.23); yet effects on steatosis could not be aggregated due to different assessment techniques. Mediterranean diet did not lead to significant changes in concentrations of gamma-glutamyl transpeptidase (γGT), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), fasting glucose or insulin, or homeostatic assessment for insulin resistance. Conclusions: In patients with NAFLD, Mediterranean and hypocaloric dietary interventions favoring unsaturated fatty acids result in improvements in IHL and transaminases. Since many dietary intervention studies are combined with exercise interventions and there is a paucity of ample-sized studies examining dietary interventions on the more advanced and clinically relevant stages of NAFLD, that is active and fibrotic NASH, with multiparametric imaging and liver histology as outcome measures, the optimal dietary invention in NAFLD remains to be defined.

Mitochondria Matter: Systemic Aspects of Nonalcoholic Fatty Liver Disease (NAFLD) and Diagnostic Assessment of Liver Function by Stable Isotope Dynamic Breath Tests

The liver plays a key role in systemic metabolic processes, which include detoxification, synthesis, storage, and export of carbohydrates, lipids, and proteins. The raising trends of obesity and metabolic disorders worldwide is often associated with the nonalcoholic fatty liver disease (NAFLD), which has become the most frequent type of chronic liver disorder with risk of progression to cirrhosis and hepatocellular carcinoma. Liver mitochondria play a key role in degrading the pathways of carbohydrates, proteins, lipids, and xenobiotics, and to provide energy for the body cells. The morphological and functional integrity of mitochondria guarantee the proper functioning of β-oxidation of free fatty acids and of the tricarboxylic acid cycle. Evaluation of the liver in clinical medicine needs to be accurate in NAFLD patients and includes history, physical exam, imaging, and laboratory assays. Evaluation of mitochondrial function in chronic liver disease and NAFLD is now possible by novel diagnostic tools. "Dynamic" liver function tests include the breath test (BT) based on the use of substrates marked with the non-radioactive, naturally occurring stable isotope 13C. Hepatocellular metabolization of the substrate will generate 13CO2, which is excreted in breath and measured by mass spectrometry or infrared spectroscopy. Breath levels of 13CO2 are biomarkers of specific metabolic processes occurring in the hepatocyte cytosol, microsomes, and mitochondria. 13C-BTs explore distinct chronic liver diseases including simple liver steatosis, non-alcoholic steatohepatitis, liver fibrosis, cirrhosis, hepatocellular carcinoma, drug, and alcohol effects. In NAFLD, 13C-BT use substrates such as α-ketoisocaproic acid, methionine, and octanoic acid to assess mitochondrial oxidation capacity which can be impaired at an early stage of disease. 13C-BTs represent an indirect, cost-effective, and easy method to evaluate dynamic liver function. Further applications are expected in clinical medicine. In this review, we discuss the involvement of liver mitochondria in the progression of NAFLD, together with the role of 13C-BT in assessing mitochondrial function and its potential use in the prevention and management of NAFLD.

Cardiovascular Risk Is Elevated in Lean Subjects with Nonalcoholic Fatty Liver Disease

Background/Aims

Nonalcoholic fatty liver disease (NAFLD) and obesity are independently associated with an increased risk for atherosclerotic cardiovascular disease (ASCVD), the leading cause of mortality in patients with NAFLD. Many NAFLD patients are lean, but their ASCVD risk compared to obese subjects with NAFLD is unclear.

Methods

Data from the 2008 to 2011 Korea National Health and Nutrition Examination Surveys database were analyzed (n=4,786). NAFLD was defined as a comprehensive NAFLD score ≥40 or a liver fat score ≥–0.640. ASCVD risk was evaluated using the American College of Cardiology/American Heart Association guidelines.

Results

The frequency of subjects without NAFLD, with obese NAFLD, and with lean NAFLD was 62.4% (n=2,987), 26.6% (n=1,274), and 11.0% (n=525), respectively. Subjects with lean NAFLD had a significantly higher ASCVD score and prevalence of a high ASCVD risk (mean 15.6±14.0, 51.6%) than those with obese NAFLD and without NAFLD (mean 11.2±11.4, 39.8%; mean 7.9±10.9, 25.5%; all p<0.001). Subjects with lean NAFLD and significant liver fibrosis showed a significantly higher odds ratio for a high risk for ASCVD than those with obese NAFLD with or without significant liver fibrosis (odds ratio, 2.60 vs 1.93; p=0.023).

Conclusions

Subjects with lean NAFLD had a significantly higher ASCVD score and prevalence of high risk for ASCVD than those with obese NAFLD. Similarly, lean subjects with significant liver fibrosis had a higher probability of ASCVD than obese subjects in the subpopulation with NAFLD.

PPARGC1A rs8192678 G>A polymorphism affects the severity of hepatic histological features and nonalcoholic steatohepatitis in patients with nonalcoholic fatty liver disease

BACKGROUND

The association between PPARGC1A rs8192678 and nonalcoholic fatty liver disease (NAFLD) requires further confirmation. In addition, it is still unknown whether PPARGC1A rs8192678 is associated with hepatic histological features in NAFLD in the Chinese population.

AIM

To investigate the interaction between PPARGC1A rs8192678 and nonalcoholic steatohepatitis (NASH), and whether this polymorphism is associated with hepatic histological features.

METHODS

Fifty-nine patients with liver biopsy-proven NAFLD and 93 healthy controls were recruited to a cohort representing the Chinese Han population. The SAF (steatosis, activity, and fibrosis) scoring system was used for hepatic histopathological evaluation. The polymorphisms of PPARGC1A rs8192678 and patatin-like phospholipase domain-containing protein 3 (PNPLA3) rs738409 were genotyped. The intrahepatic mRNA expression of PPARGC1A was evaluated by real-time polymerase chain reaction.

RESULTS

Thirty-seven patients with NAFLD had NASH, of which 12 were nonobese. The PPARGC1A rs8192678 risk A allele (carrying GA and AA genotypes) had the lowest P value in the dominant model; the odds ratio (OR) for NAFLD was 2.321 [95% confidence interval (CI): 1.121-4.806]. After adjusting for age, sex, and the PNPLA3 rs738409 risk G allele, the PPARGC1A rs8192678 A allele was a risk factor for NAFLD (OR 2.202, 95%CI: 1.030-4.705, P = 0.042). The genetic analysis showed that patients with NAFLD, moderate-to-severe steatosis (S2-3), and Activity 2-4 (A ≥ 2) were more likely to carry A in PPARGC1A rs8192678 (OR 5.000, 95%CI: 1.343-18.620, P = 0.012; and OR 4.071, 95%CI: 1.076-15.402, P = 0.031). The multivariate logistic regression analysis showed that PPARGC1A rs8192678 risk A allele was also independently associated with S2-3, A ≥ 2, and NASH (OR 6.190, 95%CI: 1.508-25.410, P = 0.011; OR 4.506, 95%CI 1.070-18.978, P = 0.040; and OR 6.337, 95%CI: 1.135-35.392, P = 0.035, respectively) after adjusting for age, sex, body mass index, and PNPLA3 rs738409 risk G allele. The results also showed that this polymorphism was associated with nonobese NASH (OR 22.000, 95%CI: 1.540-314.292, P = 0.021). The intrahepatic expression of PPARGC1A mRNA was significantly lower in the group of patients who carried the risk A allele (P = 0.014).

CONCLUSION

The PPARGC1A rs8192678 risk A allele is associated with NAFLD, and with S2-3, A ≥ 2 and NASH in NAFLD patients, independent of PNPLA3 rs738409, and may be associated with nonobese NASH.

Mice lacking endogenous TRPV1 express reduced levels of thermogenic proteins and are susceptible to diet-induced obesity and metabolic dysfunction

Transient receptor potential vanilloid subfamily 1 (TRPV1) is a non-selective cation channel protein expressed in neuronal and non-neuronal cells. Although TRPV1 is implicated in thermogenesis and diet-induced obesity (DIO), its precise role remains controversial. TRPV1-/- mice are protected from DIO, while TRPV1 activation enhances thermogenesis to prevent obesity. To reconcile this, we fed wild-type and TRPV1-/- mice for 32 weeks with normal chow or a high-fat diet and analyzed the weight gain, metabolic activities, and thermogenic protein expression in white and brown fats. TRPV1-/- mice became obese, exhibited reduced locomotor activity, reduced energy expenditure, enhanced hepatic steatosis, and decreased thermogenic protein expression in adipose tissues. Our data reveal that lack of TRPV1 does not prevent obesity, but rather enhances metabolic dysfunction.

Nonalcoholic fatty liver disease or metabolic dysfunction-associated fatty liver disease diagnoses and cardiovascular diseases: From epidemiology to drug approaches

BACKGROUND

A consensus of experts has proposed to replace the term nonalcoholic fatty liver disease (NAFLD), whose global prevalence is 25%, with metabolic dysfunction-associated fatty liver disease (MAFLD), to describe more appropriately the liver disease related to metabolic derangements. MAFLD is closely intertwined with type 2 diabetes, obesity, dyslipidaemia, all linked to a rise in the risk of cardiovascular disease (CVDs). Since controversy still stands on whether or not NAFLD/MAFLD raises the odds of CVD, the present review aims to evaluate the impact of NAFLD/MAFLD aetiologies on CV health and the potential correction by dietary and drug approaches.

RESULTS

Epidemiological studies indicate that NAFLD raises risk of fatal or non-fatal CVD events. NAFLD patients have a higher prevalence of arterial plaques and stiffness, coronary calcification, and endothelial dysfunction. Although genetic and environmental factors strongly contribute to NAFLD pathogenesis, a Mendelian randomization analysis indicated that the PNPLA3 genetic variant leading to NAFLD may not be causally associated with CVD risk. Among other genetic variants related to NAFLD, TM6SF2 appears to be protective, whereas MBOAT7 may favour venous thromboembolism.

CONCLUSIONS

NAFLD is correlated to a higher CVD risk which may be ameliorated by dietary interventions. This is not surprising, since new criteria defining MAFLD include other metabolic risk abnormalities fuelling development of serious adverse extrahepatic outcomes, for example CVD. The present lack of a targeted pharmacological approach makes the identification of patients with liver disease at higher CVD risk (eg diabetes, hypertension, obesity or high levels of C-reactive protein) of major clinical interest.

Application of a Novel Prediction Model for Predicting 2-Year Risk of Non-Alcoholic Fatty Liver Disease in the Non-Obese Population with Normal Blood Lipid Levels: A Large Prospective Cohort Study from China

Purpose

The purpose of this study was to develop and validate a nomogram to better assess the 2-year risk of non-alcoholic fatty liver disease (NAFLD) in non-obese population with normal blood lipid levels.

Patients and Methods

This study was a secondary analysis of a prospective study. We included 3659 non-obese adults with normal blood lipid levels without NAFLD at baseline. A total of 2744 participants were included in the development cohort and 915 participants were included in the validation cohort. The least absolute contraction selection operator (LASSO) regression model was used to identify the best risk factors. Multivariate Cox regression analysis was used to construct the prediction model. The performance of the prediction model was assessed using Harrell’s consistency index (C-index), area under the receiver operating characteristic (AUROC) curve and calibration curve. Decision curve analysis was applied to evaluate the clinical usefulness of the prediction model.

Results

After LASSO regression analysis and multivariate Cox regression analysis on the development cohort, BMI, TG, DBIL, ALT and GGT were found to be risk predictors and were integrated into the nomogram. The C-index of development cohort and validation cohort was 0.819 (95% CI, 0.798 to 0.840) and 0.815 (95% CI, 0.781 to 0.849), respectively. The AUROC of 2-year NAFLD risk in the development cohort and validation cohort was 0.831 (95% CI, 0.811 to 0.851) and 0.797 (95% CI, 0.765 to 0.829), respectively. From calibration curves, the nomogram showed a good agreement between predicted and actual probabilities. The decision curve analysis indicated that application of the nomogram is more effective than the intervention-for-all-patients scheme.

Conclusion

We developed and validated a nomogram for predicting 2-year risk of NAFLD in the non-obese population with normal blood lipid levels.

Plasma and stool metabolomics to identify microbiota derived-biomarkers of metabolic dysfunction-associated fatty liver disease: effect of PNPLA3 genotype

INTRODUCTION

Non-invasive biomarkers are needed for metabolic dysfunction-associated fatty liver disease (MAFLD), especially for patients at risk of disease progression in high-prevalence areas. The microbiota and its metabolites represent a niche for MAFLD biomarker discovery. However, studies are not reproducible as the microbiota is variable.

OBJECTIVES

We aimed to identify microbiota-derived metabolomic biomarkers that may contribute to the higher MAFLD prevalence and different disease severity in Latin America, where data is scarce.

METHODS

We compared the plasma and stool metabolomes, gene patatin-like phospholipase domain-containing 3 (PNPLA3) rs738409 single nucleotide polymorphism (SNP), diet, demographic and clinical data of 33 patients (12 simple steatosis and 21 steatohepatitis) and 19 healthy volunteers (HV). The potential predictive utility of the identified biomarkers for MAFLD diagnosis and progression was evaluated by logistic regression modelling and ROC curves.

RESULTS

Twenty-four (22 in plasma and 2 in stool) out of 424 metabolites differed among groups. Plasma triglyceride (TG) levels were higher among MAFLD patients, whereas plasma phosphatidylcholine (PC) and lysoPC levels were lower among HV. The PNPLA3 risk genotype was related to higher plasma levels of eicosenoic acid or fatty acid 20:1 (FA(20:1)). Body mass index and plasma levels of PCaaC24:0, FA(20:1) and TG (16:1_34:1) showed the best AUROC for MAFLD diagnosis, whereas steatosis and steatohepatitis could be discriminated with plasma levels of PCaaC24:0 and PCaeC40:1.

CONCLUSION

This study identified for the first time MAFLD potential non-invasive biomarkers in a Latin American population. The association of PNPLA3 genotype with FA(20:1) suggests a novel metabolic pathway influencing MAFLD pathogenesis.

Lean NAFLD: an underrecognized and challenging disorder in medicine

Classically, Non-Alcoholic Fatty Liver Disease (NAFLD) has been thought to be driven by excessive weight gain and obesity. The overall greater awareness of this disorder has led to its recognition in patients with normal body mass index (BMI). Ongoing research has helped to better understand potential causes of Lean NAFLD, the risks for more advanced disease, and potential therapies. Here we review the recent literature on prevalence, risk factors, severity of disease, and potential therapeutic interventions.

A review of non-alcoholic fatty liver disease in non-obese and lean individuals

Non-alcoholic fatty liver disease (NAFLD) is one of the most common causes of hepatic disorders. It represents a wide range of chronic liver diseases in patients with no history of significant alcohol consumption, starting with simple steatosis and progressing towards non-alcoholic steatohepatitis, cirrhosis, and ultimately hepatocellular carcinoma. NAFLD is usually associated with type 2 diabetes mellitus, dyslipidemia, metabolic syndrome, and obesity. This disease has mostly been studied in obese individuals; however, it has been widely reported and studied among the lean/non-obese population in recent years. The pathogenesis of NAFLD in non-obese patients is associated with various genetic predispositions, particularly a patatin-like phospholipase domain-containing protein 3 G allele polymorphism, which results in the accumulation of triglyceride in the liver and resistance to insulin. Additionally, dietary factors such as high fructose consumption seem to play a substantial role in the pathology of non-obese NAFLD. Although there is not enough evidence on the treatment of NAFLD in non-obese patients, the standard approach is to advise altering one's lifestyle in order to diminish visceral adiposity. Dietary modification, weight loss, and increased physical activity are highly recommended. We aimed to review and summarize the existing information on the prevalence, pathogenesis, genetic predispositions, diagnosis, and treatment of NAFLD in non-obese patients according to the latest literature.

The Role of Lipid Profile as an Independent Predictor of Non-alcoholic Steatosis and Steatohepatitis in Morbidly Obese Patients

Background and Aims: Obesity is one of the major health problems worldwide. Morbid obesity (body mass index >40 kg/m² or over 35 with a comorbidity) is associated, apart from other diseases, with an increased risk of non-alcoholic fatty liver disease (NAFLD). Moreover, dyslipidemia is an important comorbidity that is frequently found in NAFLD patients. The aim of this study was to analyze whether serum lipids in morbidly obese patients are associated with the spectrum of NAFLD.

Methods: Total serum cholesterol, LDL cholesterol, HDL cholesterol, non-HDL cholesterol, VLDL, and triglycerides were analyzed in 90 morbidly obese patients. The association of lipid profile parameters with histopathological, elastographic, and sonographic indices of NAFLD, non-alcoholic steatohepatitis (NASH), and liver fibrosis were explored.

Results: The mean levels of serum total cholesterol, LDL-C, and non-HDL cholesterol in patients with positive histology for liver steatosis and NASH were significantly higher than those in patients with negative histology. None of the indices showed a strong association with NAFLD, NASH, or liver fibrosis after adjustment for potential confounders.

Conclusion: A slight predictive value of lipid profile is not sufficiently enough to use solely as a non-invasive test in predicting NASH or liver fibrosis.

Early cardiac electrical and structural changes in patients with non-obese non-alcoholic fatty liver disease

Background    Obese non-alcoholic fatty liver disease (NAFLD) was found to increase the risk of developing atrial fibrillation (AF) regardless of the metabolic syndrome subgroups that may accompany it. In this study, the effect of NAFLD on the structural and electrical functions of the heart was investigated using tissue Doppler echocardiography (TDE) in non-obese NAFLD patients without any known risk factors for AF.Material and methods    The study included 43 female patients (31.3±3.8 years), who had stage 2-3 hepatosteatosis detected by liver ultrasonography and diagnosed as non-obese NAFLD (patient group), and 31 healthy women (control group, 32.5±3.6 years). In addition to standard echocardiographic parameters, inter- and intra-atrial electromechanical delay (EMD) were evaluated by TDE.Results    Interatrial EMD (PA lateral - PA tricuspid) and intraatrial EMD (PA septum - PA tricuspid) were significantly longer in patient group (16.1±3.4 vs. 12.5±2.3 ms, p&lt;0.001, and 8.4±1.6 vs. 6.6±1.6 ms, p&lt;0.001, respectively). At the subclinical level. atrial size, left ventricular diastolic function, and left ventricular wall thickness measurements were greater in the patient group.Conclusion    Inter-atrial and intra-atrial EMD were detected in young women with non-obese NAFLD. In addition, at the subclinical level, structural and functional impairment was detected However, large-volume prospective studies are required to cobfirm these findings regarding the development of AF in non-obese NAFLD patients.

Mechanisms and disease consequences of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the leading chronic liver disease worldwide. Its more advanced subtype, nonalcoholic steatohepatitis (NASH), connotes progressive liver injury that can lead to cirrhosis and hepatocellular carcinoma. Here we provide an in-depth discussion of the underlying pathogenetic mechanisms that lead to progressive liver injury, including the metabolic origins of NAFLD, the effect of NAFLD on hepatic glucose and lipid metabolism, bile acid toxicity, macrophage dysfunction, and hepatic stellate cell activation, and consider the role of genetic, epigenetic, and environmental factors that promote fibrosis progression and risk of hepatocellular carcinoma in NASH.

Abnormal Liver Blood Tests: Hepatologist Approach

BACKGROUND

Available data suggest that the prevalence of chronic liver disease (CLD) and primary liver cancer is rising in Europe and represents a major public health problem. Predictions are showing that these trends will continue to rise in the upcoming years.

SUMMARY

Alcohol-related liver disease, nonalcohol fatty liver disease, and viral hepatitis B and hepatitis C are the leading causes of liver cirrhosis and primary liver cancer in Europe. Drug-induced liver injury represents a major cause of acute hepatitis, while liver transplantation is the second most common solid organ transplantation in the world. Patients with CLD have increasing rates of hospitalization, longer hospital stays, and more adverse outcomes compared to the other chronic conditions. Direct targeting of risk factors can prevent complications of advanced liver disease and improve outcome. Patients with CLD should be referred to a hepatologist for assessment of the stage of liver disease, for specific treatment and screening for hepatocellular carcinoma. Moreover, patients with unknown etiology of abnormal liver blood tests should be referred to a hepatologist for assessment of liver disease, as well as for prevention and treatment of complications of cirrhosis and/or portal hypertension. Key Messages: CLD is amenable to prevention and treatment, while disease management strategies need to improve in order to reduce the burden of liver disease and deaths due to end-stage liver diseases.

Non-alcoholic fatty liver and chronic kidney disease: Retrospect, introspect, and prospect

With the growing prevalence of obesity and diabetes in the United States and across the world, a rise in the overall incidence and prevalence of non-alcoholic fatty liver disease (NAFLD) is expected. The risk factors for NAFLD are also associated with the development of chronic kidney disease (CKD). We review the epidemiology, risk factors, genetics, implications of gut dysbiosis, and specific pathogenic mechanisms linking NAFLD to CKD. Mechanisms such as ectopic lipid accumulation, cellular signaling abnormalities, and the interplay between fructose consumption and uric acid accumulation have led to the emergence of potential therapeutic implications for this patient population. Transplant evaluation in the setting of both NAFLD and CKD is also reviewed. Potential strategies for surveillance and management include the monitoring of comorbidities, the use of non-invasive fibrosis scoring systems, and the measurement of laboratory markers. Lastly, we discuss the management of patients with NAFLD and CKD, from preventative measures to experimental interventions.

Abnormal Liver Blood Tests: Primary Care Approach

BACKGROUND

According to recent epidemiological data, annual deaths due to liver disease have increased dramatically, while predictions show that trends will continue to rise in the upcoming years.

SUMMARY

Abnormal liver blood tests are one of the most common challenges encountered in the primary care setting. The prevalence of mildly elevated transaminase levels is around 10-20% in the general population. The most common causes for the rising burden of liver disease are nonalcoholic fatty liver disease (NAFLD), alcohol-related liver disease (ARLD), and viral hepatitis. With improvements in the management of viral hepatitis over the last decades, the causes for the rising burden of liver disease are shifting toward ARLD and NAFLD. It is well-known that liver disease usually progresses silently for years or decades until the complications of cirrhosis occur. The majority of patients will not require referral to a specialist but will need further assessment in primary care. They should be evaluated for the etiology of liver disease irrespective of the duration of abnormal liver blood tests or unmarked clinical presentation. The evaluation should include a history of alcohol use, a history of medicines or herbal supplements, testing for viral hepatitis, and assessment for NAFLD, especially in obese patients and patients with type 2 diabetes. Abdominal ultrasound should be performed. Key Messages: The general practitioner may contribute significantly by identifying and screening patients at risk for chronic liver disease, as well as prioritize individuals with symptoms or signs of advanced liver disease to the specialist clinic.

Impact of Body Weight Gain on the Incidence of Nonalcoholic Fatty Liver Disease in Nonobese Japanese Individuals

INTRODUCTION

We aimed to investigate the effect of recent short-term weight gain on the incidence of nonalcoholic fatty liver disease (NAFLD) in nonobese (body mass index < 25 kg/m) participants.

METHODS

This retrospective cohort study included nonobese individuals who participated in an annual health checkup between 2008 and 2018 in Tokyo, Japan. We estimated the multivariable adjusted hazard ratio for the development of NAFLD diagnosed via ultrasound after a 3-kg unit gain in weight measured at a 2-year landmark time point postbaseline. Multivariable adjustments included weight change from the age of 20 and other relevant confounding factors. Sensitivity analyses using additional landmark time points at 1, 3, 4, and 5 years postbaseline and time-dependent Cox proportional hazards regressions were performed.

RESULTS

Among the 27,064 nonobese participants (142,699 person years of follow-up), 2,895 were diagnosed with NAFLD. Approximately 90% of the patients with NAFLD maintained their nonobese status before disease diagnosis. The adjusted hazard ratio for the development of NAFLD (for a 3-kg unit of weight gain) at the 2-year landmark time point postbaseline was 1.60 (95% confidence interval, 1.46-1.76) in nonobese men and 1.66 (95% confidence interval, 1.51-1.83) in nonobese women. This association was maintained in the sensitivity analyses.

DISCUSSION

Recent short-term weight gain is an independent risk factor for NAFLD development in nonobese men and women. Clinicians should be mindful of the association between weight gain and NAFLD onset, even in the nonobese population.

Hepatic Senescence Accompanies the Development of NAFLD in Non-Aged Mice Independently of Obesity

Senescence is considered to be a cardinal player in several chronic inflammatory and metabolic pathologies. The two dominant mechanisms of senescence include replicative senescence, predominantly depending on age-induced telomere shortening, and stress-induced senescence, triggered by external or intracellular harmful stimuli. Recent data indicate that hepatocyte senescence is involved in the development of nonalcoholic fatty liver disease (NAFLD). However, previous studies have mainly focused on age-related senescence during NAFLD, in the presence or absence of obesity, while information about whether the phenomenon is characterized by replicative or stress-induced senescence, especially in non-aged organisms, is scarce. Herein, we subjected young mice to two different diet-induced NAFLD models which differed in the presence of obesity. In both models, liver fat accumulation and increased hepatic mRNA expression of steatosis-related genes were accompanied by hepatic senescence, indicated by the increased expression of senescence-associated genes and the presence of a robust hybrid histo-/immunochemical senescence-specific staining in the liver. Surprisingly, telomere length and global DNA methylation did not differ between the steatotic and the control livers, while malondialdehyde, a marker of oxidative stress, was upregulated in the mouse NAFLD livers. These findings suggest that senescence accompanies NAFLD emergence, even in non-aged organisms, and highlight the role of stress-induced senescence during steatosis development independently of obesity.

LDL/HDL cholesterol ratio is associated with new-onset NAFLD in Chinese non-obese people with normal lipids: a 5-year longitudinal cohort study

Background

Low-density lipoprotein to high density lipoprotein (LDL/HDL) cholesterol ratio has been reported to predict the risk of many metabolic diseases. However, the association between the LDL/HDL cholesterol ratio and nonalcoholic fatty liver disease (NAFLD) has not been established.

Methods

A longitudinal cohort design was adopted in this study; 9767 non-obese subjects without NAFLD were included and analyzed. The subjects were grouped according to the quintile of LDL/HDL cholesterol ratio. The cumulative incidence of NAFLD and the independent effect of the LDL/HDL cholesterol ratio on NAFLD during 5 years of follow-up were calculated using the Kaplan-Meier method and Cox proportional-hazards regression model.

Results

During the 5-year follow-up period, 841 subjects were diagnosed with new-onset NAFLD, and the 1-, 2-, 3-, 4-, and 5-year cumulative incidence rates of NAFLD were 1.16, 4.65, 8.33, 12.43, and 25.14%, respectively. In the multivariable-adjusted Cox proportional-hazards regression model, the LDL/HDL cholesterol ratio was significantly associated with the risk for NAFLD (HR: 1.66, 95% CI: 1.38–1.99, P trend< 0.001), especially among young people (HR: 3.96, 95% CI: 1.50–10.46, P interaction< 0.05). Additionally, receiver operating characteristic curve analysis showed that the LDL/HDL cholesterol ratio was better than HDL cholesterol and LDL cholesterol in predicting new-onset NAFLD.

Conclusions

LDL/HDL cholesterol ratio is an independent predictor of NAFLD in Chinese non-obese people with normal lipids, and its predictive value is higher than that of other lipoproteins. In clinical practice, the LDL/HDL cholesterol ratio can be used to identify people at high risk of NAFLD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-021-01457-1.

A significant association of non-obese non-alcoholic fatty liver disease with osteosarcopenic obesity in females 50 years and older

BACKGROUND & AIMS

Osteosarcopenic obesity (OSO) encompassing obesity, sarcopenia and osteopenia, is due to redistribution or infiltration of fat into muscle and bone. This cross-sectional study evaluated the association between OSO and non-alcoholic fatty liver disease (NAFLD).

METHODS

Obesity, sarcopenia and osteopenia was defined using the percentage of body fat mass, reduced muscle mass, and the percentage of young adult mean < 80%, measured by dual-energy x-ray absorptiometry, respectively. Non-obese and obese NAFLD was diagnosed by ultrasound and body mass index cut-off point (25 kg/m²). A total of 619 subjects ≥ 50 years who completed health checkups were divided into obesity group including OSO and sarcopenic obesity (SO) alone phenotype, and non-obesity group that did not belong to any phenotype, including standard (St).

RESULTS

Overall osteopenia and OSO were detected in only 10% and 1% in males, compared with 45% and 9% in females, respectively. Multivariate analysis for females demonstrated a significant association of OSO with non-obese NAFLD (odds ratio = 3.737, 95% confidence interval = 1.365-10.233, P = 0.010), while the association between SO alone and non-obese NAFLD was equivocal. The OSO phenotype had a significantly higher proportion of slower walking speed and weaker grip strength, compared to the St phenotype. The proportion of OSO increased with age in contrast to constant prevalence of non-obese NAFLD.

CONCLUSION

Non-obese NAFLD had a significant association with OSO in females, independent of plausible confounders. These results suggest that non-obese NAFLD might be an independent risk factor for OSO.

A human liver chimeric mouse model for non-alcoholic fatty liver disease

Background & Aims

The accumulation of neutral lipids within hepatocytes underlies non-alcoholic fatty liver disease (NAFLD), which affects a quarter of the world's population and is associated with hepatitis, cirrhosis, and hepatocellular carcinoma. Despite insights gained from both human and animal studies, our understanding of NAFLD pathogenesis remains limited. To better study the molecular changes driving the condition we aimed to generate a humanised NAFLD mouse model.

Methods

We generated TIRF (transgene-free Il2rg ^-/-/Rag2 ^-/-/Fah ^-/-) mice, populated their livers with human hepatocytes, and fed them a Western-type diet for 12 weeks.

Results

Within the same chimeric liver, human hepatocytes developed pronounced steatosis whereas murine hepatocytes remained normal. Unbiased metabolomics and lipidomics revealed signatures of clinical NAFLD. Transcriptomic analyses showed that molecular responses diverged sharply between murine and human hepatocytes, demonstrating stark species differences in liver function. Regulatory network analysis indicated close agreement between our model and clinical NAFLD with respect to transcriptional control of cholesterol biosynthesis.

Conclusions

These NAFLD xenograft mice reveal an unexpected degree of evolutionary divergence in food metabolism and offer a physiologically relevant, experimentally tractable model for studying the pathogenic changes invoked by steatosis.

Lay summary

Fatty liver disease is an emerging health problem, and as there are no good experimental animal models, our understanding of the condition is poor. We here describe a novel humanised mouse system and compare it with clinical data. The results reveal that the human cells in the mouse liver develop fatty liver disease upon a Western-style fatty diet, whereas the mouse cells appear normal. The molecular signature (expression profiles) of the human cells are distinct from the mouse cells and metabolic analysis of the humanised livers mimic the ones observed in humans with fatty liver. This novel humanised mouse system can be used to study human fatty liver disease.

Recent Epidemiology of Nonalcoholic Fatty Liver Disease

The ongoing obesity epidemic and the increasing recognition of metabolic syndrome have contributed to the growing prevalence of nonalcoholic fatty liver disease (NAFLD), the most common form of liver disease worldwide. It is imperative to understand the incidence and prevalence of NAFLD as it is associated with a profound economic burden of hospitalizations, including the shifting trends in liver transplantation. The long-term cumulative healthcare cost of NAFLD patients has been shown to be 80% higher than that of non-NAFLD patients. We explore diagnostic challenges in identifying those with NAFLD who have a higher predilection to progress to end-stage liver disease. We aim to assess all-cause and cause-specific mortality as it relates to NAFLD.

Visceral fat area to appendicular muscle mass ratio as a predictor for nonalcoholic fatty liver disease independent of obesity

OBJECTIVE

Obesity and sarcopenia are known to be closely related to nonalcoholic fatty liver disease (NAFLD). We attempted to explore the combined influence of fat and muscle tissue on NAFLD by using visceral fat area to appendicular muscle mass ratio (VAR) as a novel parameter.

MATERIAL AND METHODS

In this cross-sectional study, a total of 3255 adults (1399 men and 1856 women) coming for a health examination were enrolled. NAFLD was diagnosed using ultrasound and VAR was measured by bioelectrical impedance analyzer.

RESULTS

The prevalence of NAFLD was 46.5% in men and 26.6% in women. VAR differed significantly between subjects with and without NAFLD (4.27 vs. 3.26 in men, 7.89 vs. 5.01 in women, respectively, p < .001). Logistic regression analysis determined VAR as a risk factor for NAFLD, and the multivariable-adjusted odds ratios in the highest VAR quartile was 9.57 (95%CI: 5.98-15.30) for men and 12.37 (95%CI: 6.37-24.05) for women. From the receiver operating characteristic analysis, the area under the curve was 0.767 and 0.834, with the suitable cut-off VAR value of 3.469 and 6.357 for men and women, respectively. To control the influence of obesity, all subjects were stratified according to their BMI. For each BMI group, individuals with VAR above the cut-off value had significant higher prevalence and risk of NAFLD, with odds ratios ranging from 1.76 to 4.75.

CONCLUSIONS

Increased VAR is strongly associated with higher risk of NAFLD in both sexes independent of obesity and can serve as a screening reference for NAFLD.

Diversity in NAFLD: A Review of Manifestations of Nonalcoholic Fatty Liver Disease in Different Ethnicities Globally

Globally, the rise in prevalence of obesity and metabolic syndrome as a whole has been linked to increased access to processed foods, such as refined sugars and saturated fats. Consequently, nonalcoholic fatty liver disease (NAFLD) is on the rise in both developed and developing nations. However, much is still unknown on the NAFLD phenotype with regards to the effect of ethnic diversity. Despite similarities in dietary habits, it appears that certain ethnicities are more protected against NAFLD than others. However, manifestations of the same genetic polymorphisms in different groups of people increase those individuals' predisposition to NAFLD. Diets from different regions have been associated with a lower prevalence of NAFLD and have even been linked to regression of hepatic steatosis. Socioeconomic variations amongst different regions of the world also contribute to NAFLD prevalence and associated complications. Thus, a thorough understanding of ethnic variability in NAFLD is essential to tailoring treatment recommendations to patients of different backgrounds.

From heterogeneous healthcare data to disease-specific biomarker networks: A hierarchical Bayesian network approach

In this work, we introduce an entirely data-driven and automated approach to reveal disease-associated biomarker and risk factor networks from heterogeneous and high-dimensional healthcare data. Our workflow is based on Bayesian networks, which are a popular tool for analyzing the interplay of biomarkers. Usually, data require extensive manual preprocessing and dimension reduction to allow for effective learning of Bayesian networks. For heterogeneous data, this preprocessing is hard to automatize and typically requires domain-specific prior knowledge. We here combine Bayesian network learning with hierarchical variable clustering in order to detect groups of similar features and learn interactions between them entirely automated. We present an optimization algorithm for the adaptive refinement of such group Bayesian networks to account for a specific target variable, like a disease. The combination of Bayesian networks, clustering, and refinement yields low-dimensional but disease-specific interaction networks. These networks provide easily interpretable, yet accurate models of biomarker interdependencies. We test our method extensively on simulated data, as well as on data from the Study of Health in Pomerania (SHIP-TREND), and demonstrate its effectiveness using non-alcoholic fatty liver disease and hypertension as examples. We show that the group network models outperform available biomarker scores, while at the same time, they provide an easily interpretable interaction network.

High-dimensional and heterogeneous healthcare data, such as electronic health records or epidemiological study data, contain much information on yet unknown risk factors that are associated with disease development. The identification of these risk factors may help to improve prevention, diagnosis, and therapy. Bayesian networks are powerful statistical models that can decipher these complex relationships. However, high dimensionality and heterogeneity of data, together with missing values and high feature correlation, make it difficult to automatically learn a good model from data. To facilitate the use of network models, we present a novel, fully automated workflow that combines network learning with hierarchical clustering. The algorithm reveals groups of strongly related features and models the interactions among those groups. It results in simpler network models that are easier to analyze. We introduce a method of adaptive refinement of such models to ensure that disease-relevant parts of the network are modeled in great detail. Our approach makes it easy to learn compact, accurate, and easily interpretable biomarker interaction networks. We test our method extensively on simulated data as well as data from the Study of Health in Pomerania (SHIP-Trend) by learning models of hypertension and non-alcoholic fatty liver disease.

Nonalcoholic fatty liver disease and the risk of atrial fibrillation stratified by body mass index: a nationwide population-based study

We evaluated the association between nonalcoholic fatty liver disease (NAFLD) and incident atrial fibrillation (AF) and analyzed the impact of NAFLD on AF risk in relation to body mass index (BMI). A total of 8,048,055 subjects without significant liver disease who were available fatty liver index (FLI) values were included. Subjects were categorized into 3 groups based on FLI: < 30, 30 to < 60, and ≥ 60. During a median 8-year of follow-up, 534,442 subjects were newly diagnosed as AF (8.27 per 1000 person-years). Higher FLI was associated with an increased risk of AF (hazard ratio [HR] 1.053, 95% confidence interval [CI] 1.046–1.060 in 30 ≤ FLI < 60, and HR 1.115, 95% CI 1.106–1.125 in FLI ≥ 60). In underweight subjects (BMI < 18.5 kg/m²), higher FLI raised the risk of AF (by 1.6-fold in 30 ≤ FLI < 60 and by twofold in FLI ≥ 60). In normal- and overweight subjects, higher FLI was associated with an increased risk of AF, but the HRs were attenuated. In obese subjects, higher FLI was not associated with higher risk of AF. NAFLD as assessed by FLI was independently associated with an increased risk of AF in nonobese subjects with BMI < 25 kg/m². The impact of NAFLD on AF risk was accentuated in lean subjects with underweight.

Non-Alcoholic Fatty Liver in Patients with Chylomicronemia

Non-alcoholic fatty liver disease (NAFLD) is frequent in patients with features of the metabolic syndrome (MetS), obesity, or type 2 diabetes. Lipoprotein lipase (LPL) is the main driver of triglyceride (TG) hydrolysis in chylomicrons and very-low density lipoproteins (VLDL). In some patients with MetS, dysfunction of this pathway can lead to plasma TG values > 10 mmol/L (multifactorial chylomicronemia or MCS). Chylomicronemia also characterizes LPL deficiency (LPLD), a rare autosomal recessive disease called familial chylomicronemia syndrome (FCS), which is associated with an increased risk of recurrent pancreatitis. This study aims to investigate the expression of NAFLD, as assessed by transient elastography, in MCS and FCS subjects. Data were obtained from 38 subjects with chylomicronemia; 19 genetically confirmed FCS and 19 sex- and age-matched MCS. All participants underwent liver ultrasonography and stiffness measurement after a 4-h fast using transient elastography (FibroScan®, Echosens, Waltham, MA, USA). NAFLD (controlled attenuation parameter (CAP) > 280 dB/m) was observed in 42.1% of FCS and 73.7% of MCS subjects (p = 0.05). FCS subjects had lower body mass index (BMI) than MCS. Only 25% of FCS subjects with NAFLD had a BMI ≥ 30 compared to 64.3% in MCS (p = 0.004). In FCS, NAFLD occurred even in the presence of very low (≤18 kg/m2) BMI. In both FCS and MCS, CAP was negatively associated with acute pancreatitis risk. In this study, NAFLD was commonly observed in both FCS and MCS subjects and occurred independently of the BMI and fasting glucose values in FCS; NAFLD was associated with a lower occurrence of acute pancreatitis episodes.

Nonalcoholic Fatty Liver Disease: A Global Perspective

The prevalence of nonalcoholic fatty liver disease (NAFLD) has been increasing over the years and is now as high in Asia as in the Western world, so much so that it should no longer be considered a Western disease. In fact, China is expected to have the largest increase in the number of NAFLD cases in the coming years. The increase in prevalence of NAFLD in Asia lags behind that of the Western world; thus, there will be a lag in more severe liver disease in Asia despite a similar prevalence of the disease. NAFLD is more prevalent among patients with diabetes mellitus, which is also an important risk factor for more severe liver disease. Patients with diabetes mellitus thus represent an important target for screening for NAFLD and more severe liver disease. Although the PNPLA3 gene polymorphism is the most studied in NAFLD, it is increasingly clear that the cumulative effect of multiple genes likely predisposes to NAFLD and more severe liver disease in the different ethnic groups, and polygenic risk scores are emerging. Lean NAFLD has been largely reported in Asia but is increasingly recognized worldwide. Multiple risk factors have been identified for the disease that manifests in metabolically unhealthy normal weight individuals; however, it responds to lifestyle intervention, similar to the disease in obese individuals. Lastly, the newer term "metabolic dysfunction-associated fatty liver disease" provides a more accurate reflection of the disease, giving more focus to clinicians and researchers in tackling this increasingly common and challenging disease.

The protective effect of shrimp cooked in different methods on high-cholesterol- induced fatty liver in rats

This study examined the impact of different cooking methods on fatty acid (FAs) composition of shrimp meat and the ability of these foods to protect against high cholesterol (HC) diet-induced non-alcoholic fatty liver disease (NAFLD) in rats. Shrimp were cooked for 10 min boiled, grilled, or fried in sunflower oil. Rats (n = 6/group) were fed a normal diet (ND)or high-cholesterol diet (HC) each containing boiled, grilled or fried shrimp powder (15% w/w) (NDBS, NDFS, NDGS for ND or HCBS, HCFS, HCDGS for HC diet). Frying alone significantly reduced total levels of saturated FAs (SFA) and increased total mono- and polyunsaturated FAs (MSFA, and PUFAs, respectively) in shrimp meat. It also increased levels of n-6 PUFAs and linoleic acid (LA) and decreased levels of n-3 PUFAs including eicosapentaenoic FAs (EPA) and docosahexaenoic fatty acid (DHA). When fed to HC rats, only diets containing the grilled and boiled shrimp powders significantly prevented the weight loss, lowered fasting and glucose levels, improved glucose and insulin tolerance, and prevented the increase in serum liver markers, ALT and AST. They also reduced hepatic fat accumulation, reduced serum levels and hepatic levels of cholesterol and triglycerides (TGs), reduced hepatic levels of MDA, tumor necrosis factor-alpha (TNF-α), and IL-6, and increased those of glutathione (GSH) and superoxide dismutase (SOD). No alterations in all these parameters were observed in HC-fed rats which fed fried shrimp. In conclusion, boiling and grilling but not frying are the best method to cook shrimp to preserve their fatty acid content and its nutritional value in ameliorating NAFLD.

Dysregulation of intercellular signaling by MOF deletion leads to liver injury

Epigenetic mechanisms that alter heritable gene expression and chromatin structure play an essential role in many biological processes, including liver function. Human MOF (males absent on the first) is a histone acetyltransferase that is globally downregulated in human steatohepatitis. However, the function of MOF in the liver remains unclear. Here, we report that MOF plays an essential role in adult liver. Genetic deletion of Mof by Mx1-Cre in the liver leads to acute liver injury, with increase of lipid deposition and fibrosis akin to human steatohepatitis. Surprisingly, hepatocyte-specific Mof deletion had no overt liver abnormality. Using the in vitro coculturing experiment, we show that Mof deletion-induced liver injury requires coordinated changes and reciprocal signaling between hepatocytes and Kupffer cells, which enables feedforward regulation to augment inflammation and apoptotic responses. At the molecular level, Mof deletion induced characteristic changes in metabolic gene programs, which bore noticeable similarity to the molecular signature of human steatohepatitis. Simultaneous deletion of Mof in both hepatocytes and macrophages results in enhanced expression of inflammatory genes and NO signaling in vitro. These changes, in turn, lead to apoptosis of hepatocytes and lipotoxicity. Our work highlights the importance of histone acetyltransferase MOF in maintaining metabolic liver homeostasis and sheds light on the epigenetic dysregulation in liver pathogenesis.

A Model to Predict Significant Macrosteatosis in Hepatic Grafts

BACKGROUND AND AIMS

Assessing the risk of significant macrosteatosis in donors is crucial before considering hepatic graft procurement. We aimed to build a model to predict significant macrosteatosis based on noninvasive methods.

METHODS

From January 2012 to December 2018, liver attenuation indices and liver-to-spleen (L/S) ratio were measured in 639 brain-dead donors by local radiologists. Quantity and quality of steatosis were evaluated by an expert pathologist, blinded for attenuation indices measurement.

RESULTS

Macrosteatosis ≥ 30% was found in 33 donors (5.2%). Body weight, body mass index (BMI), abdominal perimeters, history of alcohol abuse, L/S ratio, and liver parenchyma attenuation were associated with macrosteatosis ≥ 30%. The L/S ratio, BMI, and a history of alcohol abuse remained independent predictors in multivariate analysis and were used to build a predictive model (C-index: 0.77). The optimal cutoff to predict macrosteatosis ≥ 60% was 0.85.

CONCLUSION

Our model, including L/S ratio, BMI, and history of alcohol, might be helpful to refine indication for liver biopsy before donation after brain death. External validation is required.

Untargeted metabolomics characteristics of nonobese nonalcoholic fatty liver disease induced by high-temperature-processed feed in Sprague-Dawley rats

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) has become one of the most common chronic liver diseases in the world. In our early clinical data and questionnaire analysis of NAFLD, it was found that the body mass index of some patients did not meet the diagnostic criteria for overweight or obesity. The consumption of high-temperature-processed foods such as fried food, hot pot and barbecue is closely related to the occurrence of nonobese NAFLD. Reducing the intake of this kind of food can reduce disease severity and improve prognosis.

AIM

To explore the untargeted metabolomics characteristics of nonobese nonalcoholic fatty liver disease in Sprague-Dawley rats induced by high-temperature-processed feed.

METHODS

Fifty-four male Sprague-Dawley rats were divided into three groups: The control group received a standard diet; the nonfried soybeans (NDFS) group received 60% NDFS and 40% basic feed and the dry-fried soybeans (DFS) group received 60% DFS and 40% basic feed. Six rats were sacrificed at week 4, 8, and 12 in each group. The food intake, body weight, Lee’s index, liver index, serological index and hepatic histopathology were assessed. Untargeted metabolomics characteristics were used to analyze the changes in liver metabolites of rats at week 12. Correlations between metabolites and pathology scores between the DFS and control groups and between the DFS and NDFS groups were analyzed. We selected some of the metabolites, both within the pathway and outside of the pathway, to explain preliminarily the difference in liver pathology in the three groups of rats.

RESULTS

There were no statistically significant differences in the food intake, body weight, Lee's index or serological index between the DFS group and the control group (P > 0.05). At week 8 and week 12, the steatosis scores in the DFS group were significantly higher than those in the other two groups (P < 0.05). At week 12, the liver index of the DFS group was the lowest (NDFS group vs DFS group, P < 0.05). The fibrosis score in the DFS group was significantly higher than those in the other two groups (P < 0.05). The correlation analysis of the liver pathology score and differential metabolites in the DFS and NDFS groups showed that there were 10 strongly correlated substances: Five positively correlated substances and five negatively correlated substances. The positively correlated substances included taurochenodeoxycholate-3-sulfate, acetylcarnitine, 20a,22b-dihydroxycholesterol, 13E-tetranor-16-carboxy-LTE4 and taurocholic acid. The negatively correlated substances included choline, cholesterane-3,7,12,25-tetrol-3-glucuronide, nicotinamide adenine dinucleotide phosphate, lysoPC [16:1 (9Z)] and glycerol 3-phosphate. The correlation analysis of the liver pathology score and differential metabolites in the DFS and control groups showed that there were 13 strongly correlated substances: Four positively correlated substances and 9 negatively correlated substances. The positively correlated substances included 4-hydroxy-6-eicosanone, 3-phosphoglyceric acid, 13-hydroxy-9-methoxy-10-oxo-11-octadecenoic acid and taurochenodeoxycholate-3-sulfate. The negatively correlated substances included lysoPC [16:1(9Z)], S-(9-hydroxy-PGA1)-glutathione, lysoPC [20:5 (5Z, 8Z, 11Z, 14Z, 17Z)], SM (d18:1/14:0), nicotinamide adenine dinucleotide phosphate, 5,10-methylene-THF, folinic acid, N-lactoyl-glycine and 6-hydroxy-5-methoxyindole glucuronide.

CONCLUSION

We successfully induced liver damage in rats by using a specially prepared high-temperature-processed feed and explored the untargeted metabolomics characteristics.

Global epidemiology of lean non-alcoholic fatty liver disease: A systematic review and meta-analysis

BACKGROUND AND AIM

Lean non-alcoholic fatty liver disease (NAFLD) is a potentially metabolically unhealthy state that refers to NAFLD occurring in non-overweight/nonobese subjects. Yet its global epidemiology and metabolic characteristics are not extensively elucidated.

METHODS

PubMed, EMBASE, Web of Science and Cochrane databases were searched for eligible studies until January 2020. Random-effects/fixed-effects models were used to estimate the global prevalence of lean NAFLD and to compare clinical characteristics among lean non-NAFLD, lean NAFLD, and overweight/obese NAFLD subjects. "Lean" NAFLD was defined by ethnic-specific body mass index measurements in the normal range. Meta-regression and subgroup analyses were performed to determine potential sources of heterogeneity.

RESULTS

A total of 33 observational studies were included with 205 307 individuals from 14 countries. The global prevalence of lean NAFLD was 4.1% (95% confidence interval [CI]: 3.4-4.8%). In lean subjects, the prevalence of NAFLD was 9.7% (95% CI: 7.7-11.8%). The prevalence of lean NAFLD with diabetes, hypertension, metabolic syndrome, dyslipidemia, or central obesity was 0.6% (95% CI: 0.4-0.9%), 1.8% (95% CI: 1.2-2.5%), 1.4% (95% CI: 1.0-1.9%), 2.8% (95% CI: 1.9-3.7%), and 2.0% (95% CI: 1.6-2.4%), respectively. The prevalence of lean NAFLD showed an upward trend between 1988 and 2017. Asian individuals had the highest prevalence of lean NAFLD (4.8%, 95% CI: 4.0-5.6%). Middle-aged people (45-59 years old) had the highest prevalence of lean NAFLD (4.4%, 95% CI: 3.2-5.5%). The prevalence of metabolic complications in lean non-NAFLD, lean NAFLD, and overweight/obese NAFLD groups increased sequentially.

CONCLUSIONS

Lean NAFLD occurs with metabolic complications and is not an uncommon condition. The highest prevalence of lean NAFLD occurs in middle-aged individuals of Asian countries.

Nonalcoholic fatty liver disease in lean subjects: Prognosis, outcomes and management

Nonalcoholic fatty liver disease (NAFLD) accounts for most cases of chronic liver disease worldwide, with an estimated global prevalence of approximately 25% and ranges from simple steatosis to nonalcoholic steatohepatitis and cirrhosis. NAFLD is strongly connected to metabolic syndrome, and for many years, fatty liver was considered to be an exclusive feature of obese patients. However, recent studies have highlighted the presence of NAFLD in non-obese subjects, with or without increased visceral fat or even in lean subjects without increased waist circumference. “Lean NAFLD” is a relatively new concept and there is significant scientific interest in understanding the differences in pathophysiology, prognosis and management compared with NAFLD in overweight/obese patients. In the present editorial, we discuss the clinical and metabolic profiles and outcomes of lean NAFLD compared with both obese NAFLD and lean healthy individuals from Asian and Western countries. Moreover, we shed light to the challenging topic of management of NAFLD in lean subjects since there are no specific guidelines for this population. Finally, we discuss open questions and issues to be addressed in the future in order to categorize NAFLD patients into lean and non-lean cohorts.

Estimation of visceral fat is useful for the diagnosis of significant fibrosis in patients with non-alcoholic fatty liver disease

BACKGROUND

Obesity is a risk factor for non-alcoholic fatty liver disease (NAFLD), although obese patients with NAFLD do not always develop significant fibrosis. The distribution of body fat could predict the risk of NAFLD progression. 

AIM

To investigate the role of bioelectrical impedance-estimated visceral fat (VF) in assessing NAFLD severity.

METHODS

In this cross-sectional study, patients with biopsy-proven NAFLD were prospectively included. All patients underwent anthropometric evaluation, blood tests and bioelectrical impedance analysis.

RESULTS

Between 2017 and 2020, 119 patients were included [66.4% male, 56 years (SD 10.7), 62.2% obese, 61.3% with metabolic syndrome]. Sixty of them (50.4%) showed significant fibrosis (≥ F2) in liver biopsy. Age, VF and metabolic syndrome were associated with significant fibrosis (61 years vs 52 years, 16.4 vs 13.1, 73.3% vs 49.2%, respectively; P < 0.001 for all). In the multivariate analysis, VF and age were independently associated with significant fibrosis (VF, OR: 1.11, 95%CI: 1.02-1.22, P = 0.02; age, OR: 1.08, 95%CI: 1.03-1.12, P < 0.01). A model including these variables showed and area under the receiver operating characteristic curve (AUROC) of 0.75, which was not inferior to transient elastography or NAFLD fibrosis score AUROCs. We developed a nomogram including age and VF for assessing significant fibrosis in routine practice.

CONCLUSION

VF is a surrogate marker of liver fibrosis in patients with NAFLD. Bioelectrical impedance analysis is an inexpensive and simple method that can be combined with age to guide patient referral when other resources may be unavailable.

A Nomogram Model Based on Noninvasive Bioindicators to Predict 3-Year Risk of Nonalcoholic Fatty Liver in Nonobese Mainland Chinese: A Prospective Cohort Study

The purpose of this study is to establish and validate an accurate and personalized nonalcoholic fatty liver disease (NAFLD) prediction model based on the nonobese population in China. This study is a secondary analysis of a prospective study. We included 6,155 nonobese adults without NAFLD at baseline, with a median follow-up of 2.3 years. Univariate and multivariate Cox regression analyses were used to determine independent predictors. The least absolute shrinkage and selection operator (LASSO) regression analysis was used to optimize the selection of variables. Based on the results of multivariate analysis, a prediction model was established. Harrell's consistency index (C-index) and area under the curve (AUC) were used to determine the discrimination of the proposed model. The goodness of fit of the calibration model was tested, and the clinical application value of the model was evaluated by decision curve analysis (DCA). The participants were randomly divided into a training cohort (n = 4,605) and a validation cohort (n = 1,550). Finally, seven of the variables (HDL-c, BMI, GGT, ALT, TB, DBIL, and TG) were included in the prediction model. In the training cohort, the C-index and AUC value of this prediction model were 0.832 (95% confidence interval (CI), 0.820-0.844) and 0.861 (95% CI, 0.849-0.873), respectively. In the validation cohort, the C-index and AUC values of this prediction model were 0.829 (95% CI, 0.806-0.852) and 0.859 (95% CI, 0.841-0.877), respectively. The calibration plots demonstrated good agreement between the estimated probability and the actual observation. DCA demonstrated a clinically effective predictive model. Our nomogram can be used as a simple, reasonable, economical, and widely used tool to predict the 3-year risk of NAFLD in nonobese populations in China, which is helpful for timely intervention and reducing the incidence of NAFLD.

Circulating lipidomic alterations in obese and non-obese subjects with non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) affects obese and non-obese individuals. However, mechanisms underlying non-obese non-alcoholic steatohepatitis (NASH) remain unclear.

AIMS

To attempt to identify metabolic perturbations associated with non-obese and obese NAFLD using a lipidomics approach.

METHODS

A cross-sectional analysis of 361 subjects with biopsy-proven NAFLD (157 NAFL and 138 NASH) and healthy controls (n = 66) was performed. Individuals were categorised as obese or non-obese based on the Asian cut-off for body mass index. Circulating lipidomic profiling of sera was performed based on the histological severity of NAFLD. Circulating lipidomic alterations were validated with an independent validation set (154 NAFLD subjects [93 NAFL and 61 NASH] and 21 healthy controls).

RESULTS

Saturated sphingomyelin (SM) species were significantly associated with visceral adiposity in non-obese NAFLD (SM d38:0; P < 0.001) but not in obese NAFLD. Additionally, SM levels were significantly associated with systemic and adipose tissue insulin resistance (SM d38:0; P = 0.002 and <0.001, respectively). Five potential lipid metabolites for non-obese subjects and seven potential lipids for obese subjects were selected to predict NAFLD and NASH. These lipid combinations showed good diagnostic performance for non-obese (area under the curve [AUC] for NAFLD/NASH = 0.916/0.813) and obese (AUC for NAFLD/NASH = 0.967/0.812) subjects. Moreover, distinctly altered patterns of diacylglycerol (DAG), triacylglycerol (TAG) and SM levels were confirmed in the validation set depending on the histological severity of NAFLD.

CONCLUSION

Non-obese and obese NAFLD subjects exhibit unique circulating lipidomic signatures, including DAGs, TAGs and SMs. These lipid combinations may be useful biomarkers for non-obese and obese NAFLD patients.

Performance of Simple Fibrosis Scores in Nonobese Patients With Nonalcoholic Fatty Liver Disease

Because only a minority of patients with nonalcoholic fatty liver disease (NAFLD) have advanced fibrosis and would eventually develop liver-related complications, current guidelines recommend initial assessment with noninvasive tests of fibrosis.^1-3 Most previous studies focused on overweight and obese patients. Despite a strong association between obesity and NAFLD, 3%-30% of people with relatively normal body mass index (BMI) may still have NAFLD.^4,5 Hence, this study aims to evaluate the performance of the common noninvasive tests in non-obese (BMI <25 kg/m²) and obese (BMI ≥25 kg/m²) NAFLD patients.

Association between triglyceride glucose-body mass index and non-alcoholic fatty liver disease in the non-obese Chinese population with normal blood lipid levels: a secondary analysis based on a prospective cohort study

Background

Both triglyceride glucose-body mass index (TyG-BMI) and non-alcoholic fatty liver disease (NAFLD) are linked to insulin resistance (IR). Prospective studies linking TyG-BMI to NAFLD have been limited by short follow-up. This study investigated the longitudinal association between TyG-BMI and NAFLD occurrence in the non-obese Chinese individuals.

Methods

This study determined TyG-BMI at baseline and the incidence of NAFLD at follow-up and performed a post hoc analysis of a prospective cohort study that involved assessing the risk of NAFLD in non-obese Chinese residents from January 2010 to December 2014. The incidence of NAFLD during the 5-year follow-up was identified as the endpoint. Cox proportional hazards regression analysis was used to evaluate hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the incidence of NAFLD. Receiver operating characteristic (ROC) curve analysis was conducted to estimate the predictive power of TyG-BMI and its components for NAFLD. Subgroup analysis was performed to better understand other factors that may affect the association between TyG-BMI and NAFLD to identify potential special populations.

Results

During the follow-up period, 841 (8.61%) of 9767 non-obese subjects who met the screening criteria were diagnosed with NAFLD. After confounding factors were fully adjusted for, the HR of NAFLD was 3.09 (95% CI 2.63–3.63) per standard deviation (SD) increase in TyG-BMI. Furthermore, TyG-BMI had a strong predictive value (area under ROC = 0.85; 95% CI 0.84–0.86) for the incidence of NAFLD, with a specificity of 0.73 and sensitivity of 0.82. Additionally, in the male population, each SD increase in TyG-BMI was linked to an increased risk of NAFLD (HR = 2.85, 95% CI 2.30–3.53), but the risk was higher in the female population (HR = 3.58, 95% CI 2.80–4.60). Gender and TyG-BMI interacted significantly with NAFLD incidence (P < 0.0001).

Conclusion

In the normolipidaemic and non-obese subset of the Chinese population, an increase in TyG-BMI is related to an increased incidence of NAFLD. TyG-BMI may have clinical significance in identifying groups at high risk of NAFLD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-020-01409-1.

Distinct signatures of gut microbiome and metabolites associated with significant fibrosis in non-obese NAFLD

Nonalcoholic fatty liver disease (NAFLD) is associated with obesity but also found in non-obese individuals. Gut microbiome profiles of 171 Asians with biopsy-proven NAFLD and 31 non-NAFLD controls are analyzed using 16S rRNA sequencing; an independent Western cohort is used for external validation. Subjects are classified into three subgroups according to histological spectra of NAFLD or fibrosis severity. Significant alterations in microbiome diversity are observed according to fibrosis severity in non-obese, but not obese, subjects. Ruminococcaceae and Veillonellaceae are the main microbiota associated with fibrosis severity in non-obese subjects. Furthermore, stool bile acids and propionate are elevated, especially in non-obese subjects with significant fibrosis. Fibrosis-related Ruminococcaceae and Veillonellaceae species undergo metagenome sequencing, and four representative species are administered in three mouse NAFLD models to evaluate their effects on liver damage. This study provides the evidence for the role of the microbiome in the liver fibrosis pathogenesis, especially in non-obese subjects.

Nonalcoholic fatty liver disease (NAFLD) is associated with obesity but also found in individuals without obesity. Here, gut microbiome analysis using a biopsy-proven NAFLD cohort reveal distinct signatures of microbiome-metabolites associated with significant fibrosis in patients with NAFLD without obesity.

The metabolic basis of nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a major cause of chronic liver disease and is associated with significant morbidity and mortality worldwide, with a high incidence in Western countries and non-Western countries that have adopted a Western diet. NAFLD is commonly associated with components of the metabolic syndrome, type 2 diabetes mellitus and cardiovascular disease, suggesting a common mechanistic basis. An inability to metabolically handle free fatty acid overload-metabolic inflexibility-constitutes a core node for NAFLD pathogenesis, with resulting lipotoxicity, mitochondrial dysfunction and cellular stress leading to inflammation, apoptosis and fibrogenesis. These responses can lead to the histological phenotype of nonalcoholic steatohepatitis (NASH) with varying degrees of fibrosis, which can progress to cirrhosis. This perspective review describes the key cellular and molecular mechanisms of NAFLD and NASH, namely an excessive burden of carbohydrates and fatty acids that contribute to lipotoxicity resulting in hepatocellular injury and fibrogenesis. Understanding the extrahepatic dysmetabolic contributors to NASH is crucial for the development of safe, effective and durable treatment approaches for this increasingly common disease.

Characteristic Features of Nonalcoholic Fatty Liver Disease in Japan with a Focus on the Roles of Age, Sex and Body Mass Index

This review provides an update on the characteristics of nonalcoholic fatty liver disease (NAFLD), with a focus on the effects of age, sex, and body mass index. Age is a risk factor for NAFLD progression; however, extremely old patients have unique features, namely, the associations between metabolic comorbidities and NAFLD are weaker and NAFLD is not a risk factor for mortality. The prevalence of NAFLD is higher in men than in premenopausal women, whereas the reverse is true after menopause. Thus, before menopause, estrogen may have protective effects against NAFLD. Our hospital data showed that over 25% of male patients with NAFLD and almost 40% of female patients with NAFLD, especially elderly patients, were nonobese. Although histological steatosis and activity were associated with body mass index, the prevalence of nonalcoholic steatohepatitis was not. The prevalence of advanced fibrosis showed a significant sex difference. Advanced fibrosis was significantly more frequent among severely obese men but the prevalence was lower among severely obese women. This difference could be because a substantial proportion of severely obese women were premenopausal; thus, estrogen may have much stronger effects on the development of fibrosis than on obesity. Further studies are required to develop tailored management strategies.

Does adipose tissue inflammation drive the development of non-alcoholic fatty liver disease in obesity?

Obesity, an increasingly common problem in modern societies, is associated with acquired metabolic disturbances. In this perspective, the development of insulin resistance is now recognized to be initiated by inflammation of the adipose tissue, but the events that lead to this inflammation are still vague. Furthermore, visceral adipose tissue plays a significant role in obesity pathophysiology and in its clinical effects, such as non-alcoholic fatty liver disease (NAFLD). Among the possible mechanisms linking NAFLD and obesity, we focused on Visfatin/NAMPT, mostly produced by macrophages infiltrated in adipose tissue and a biomarker of the inflammatory cascade affecting hepatic inflammation in NAFLD. We also addressed the signalling pathway triggered by the binding of VEGF-B to its receptor, which mediates lipid fluxes throughout the body, being a promising target to prevent ectopic lipid accumulation. We reviewed the available literature on the topic and we suggest a crosstalk between adipose tissue inflammation and NAFLD in order to provide new insights about the putative mechanisms involved in the development of NAFLD in the obesity context. A better understanding of the pathophysiological processes underlying NAFLD will allow the development of new therapeutic approaches.

Clinical and anthropometric characteristics of non-obese non-alcoholic fatty liver disease subjects in Japan

AIM

The underlying mechanism of non-obese non-alcoholic fatty liver disease (NAFLD) has not been fully elucidated. We classified patients with NAFLD by sex and body mass index and compared their clinical features to clarify the background pathophysiology of non-obese NAFLD.

METHODS

A total of 404 patients with NAFLD were divided according to their body mass index (<25 [non-obese], 25 to <30 [obese], and ≥30 [severe obese]), and were further compared with 253 patients without obesity and NAFLD (non-NAFLD).

RESULTS

The proportion of the individuals with non-obese NAFLD was 25.7% in men and 27.6% in women. The male and female non-obese NAFLD groups had lower skeletal muscle mass and muscle strength than the obese NAFLD groups. The visceral fat area, although low, was ≥100 cm² in 59.3% of men and 43.8% of women. An increase in liver fat accumulation, hepatic fibrosis, homeostasis model assessment of insulin resistance, and leptin levels was modest in the non-obese NAFLD group compared with a marked increase in the obese NAFLD groups. The muscle mass of the non-obese NAFLD group was similar to that of the non-NAFLD group, but muscle steatosis was particularly common among women. Multivariate analysis revealed that the factors contributing to increased liver fat accumulation in the non-obese NAFLD group were visceral fat area, HbA1c, myostatin, and leptin.

CONCLUSIONS

In patients with non-obese NAFLD, a sex difference was observed in the clinical features. In addition to increased visceral fat, decreased muscle mass and muscle strength, muscle atrophy (presarcopenia), and impaired glucose tolerance were considered to be important pathophysiological factors.