Clinical and Metabolic Characterization of Lean Caucasian Subjects With Non-alcoholic Fatty Liver

Dietary inflammatory impact on NAFLD development in obese vs. lean individuals: an analysis based on NHANES 2003-2018

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD), often linked with obesity, can also affect individuals with normal weight, a condition known as "lean NAFLD", imposing comparable burdens and adverse effects. However, the impact of diet on lean NAFLD remains underexplored. The objective of this study is to investigate the correlation between the Dietary Inflammatory Index (DII) and NAFLD among Americans, stratified by waist-to-height ratio (WHtR) and body mass index (BMI).

METHODS

Five thousand one hundred fifty-two participants from the National Health and Nutrition Examination Survey (NHANES) 2003-2018 were comprised in the final analysis. NAFLD and advanced liver fibrosis were diagnosed by serological markers. Lean and abdominal lean individuals were identified using BMI and WHtR, separately. DII was determined by assigning scores to 28 distinct food parameters based on their inflammatory potential, obtained from the NAHNES website. Differences across DII quartiles were evaluated using the Kruskal-Wallis H Test, Chi-Square Test along with One-Way ANOVA. The correlation between DII and NAFLD was determined by multiple regression models and subgroup analyses.

RESULTS

Among the 5152 subjects, 2503 were diagnosed with NAFLD, including 86 cases of lean NAFLD and 8 cases of abdominal lean NAFLD. DII was positively linked with NAFLD (Odds Ratio (OR) = 1.81 [1.48-2.21], P < 0.001) and advanced liver fibrosis (OR = 1.46 [1.02-2.07], P = 0.037). Further analysis revealed that this association was primarily observed in obese or abdominal obese participants (In BMI ≥ 25.00 kg/m^2, OR = 1.56 [1.23-1.98], P < 0.001. In WHtR> 0.50, OR = 1.48 [1.23-1.79], P < 0.001.), rather than their lean counterparts. Subgroup analyses indicated that female individuals, without a diagnosis of hypertension or diabetes appeared to be more sensitive to the rise in DII.

CONCLUSIONS

Our data demonstrated a significant positive correlation between DII and NAFLD in the general population. However, the impact of a pro-inflammatory diet was less prominent in lean individuals compared to obese ones.

Relationship between phthalates exposures and metabolic dysfunction-associated fatty liver disease in United States adults

As a new definition for the evidence of hepatic steatosis and metabolic dysfunctions, the relationship between phthalates (PAEs) and metabolic dysfunction-associated fatty liver disease (MAFLD) remains virtually unexplored. This study included 3,137 adults from the National Health and Nutrition Examination Survey spanning 2007-2018. The diagnosis of MAFLD depended on the US Fatty Liver Index (US FLI) and evidence of metabolic dysregulation. Eleven metabolites of PAEs were included in the study. Poisson regression, restricted cubic spline (RCS), and weighted quantile sum (WQS) regression were used to assess the associations between phthalate metabolites and MAFLD. After adjusting for potential confounders, Poisson regression analysis showed that mono-2-ethyl-5-carboxypentyl phthalate (MECPP), mono-n-butyl phthalate, mono-(3-carboxypropyl) phthalate, mono-ethyl phthalate (MEP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono-(2-ethyl-5-oxohexyl) phthalate were generally significant positively associated with MAFLD (P<0.05). Furthermore, the WQS index constructed for the eleven phthalates was significantly related to MAFLD (OR:1.43; 95%CI: 1.20, 1.70), MEHHP (33.30%), MEP (20.84%), MECPP (15.43%), and mono-isobutyl phthalate (11.78%) contributing the most. This study suggests that exposure to phthalates, individually or in combination, may be associated with an increased risk of MAFLD.

Innate Immunity and MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) has emerged as the most common liver disease worldwide in recent years. MASLD commonly presents as simple hepatic steatosis, but ~25% of patients develop liver inflammation, progressive fibrosis, liver cirrhosis and related hepatocellular carcinoma. Liver inflammation and the degree of fibrosis are key determinants of the prognosis. The pathophysiology of liver inflammation is incompletely understood and involves diverse factors and specifically innate and adaptive immune responses. More specifically, diverse mediators of innate immunity such as proinflammatory cytokines, adipokines, inflammasomes and various cell types like mononuclear cells, macrophages and natural killer cells are involved in directing the inflammatory process in MASLD. The activation of innate immunity is driven by various factors including excess lipids and lipotoxicity, insulin resistance and molecular patterns derived from gut commensals. Targeting pathways of innate immunity might therefore appear as an attractive therapeutic strategy in the future management of MASLD and possibly its complications.

l-Ornithine-l-Aspartate (LOLA) Normalizes Metabolic Parameters in Models of Steatosis, Insulin Resistance and Metabolic Syndrome

l-Ornithine- l-aspartate (LOLA) reduces toxic ammonium (NH3) plasma levels in hepatic encephalopathy. NH3 detoxification/excretion is achieved by its incorporation into urea and glutamine via activation of carbamoyl phosphate synthetase 1 (CSP1) by l-ornithine and stimulation of arginase by l-aspartate. We aimed at identifying additional molecular targets of LOLA as a potential treatment option for non-alcoholic fatty liver disease (NAFLD). In primary hepatocytes from NAFLD patients, urea cycle enzymes CSP1 and ornithine transcarbamylase (OTC) increase, while the catabolism of branched-chain amino acids (BCAAs) decreases with disease severity. In contrast, LOLA increased the expression rates of the BCAA enzyme transcripts bcat2, bckdha, and bckdk. In untreated HepG2 hepatoblastoma cells and HepG2-based models of steatosis, insulin resistance, and metabolic syndrome (the latter for the first time established herein), LOLA reduced the release of NH3; beneficially modulated the expression of genes related to fatty acid import/transport (cd36, cpt1), synthesis (fasn, scd1, ACC1), and regulation (srbf1); reduced cellular ATP and acetyl-CoA; and favorably modulated the expression of master regulators/genes of energy balance/mitochondrial biogenesis (AMPK-α, pgc1α). Moreover, LOLA reconstituted the depolarized mitochondrial membrane potential, while retaining mitochondrial integrity and avoiding induction of superoxide production. Most effects were concentration-dependent at ≤40 mM LOLA. We demonstrate for l-ornithine-l-aspartate a broad range of reconstituting effects on metabolic carriers and targets of catabolism/energy metabolism impaired in NAFLD. These findings strongly advocate further investigations to establish LOLA as a safe, efficacious, and cost-effective basic medication for preventing and/or alleviating NAFLD.

Exploring the role of genetic variations in NAFLD: implications for disease pathogenesis and precision medicine approaches

Non-alcoholic fatty liver disease (NAFLD) is one of the leading causes of chronic liver diseases, affecting more than one-quarter of people worldwide. Hepatic steatosis can progress to more severe forms of NAFLD, including NASH and cirrhosis. It also may develop secondary diseases such as diabetes and cardiovascular disease. Genetic and environmental factors regulate NAFLD incidence and progression, making it a complex disease. The contribution of various environmental risk factors, such as type 2 diabetes, obesity, hyperlipidemia, diet, and sedentary lifestyle, to the exacerbation of liver injury is highly understood. Nevertheless, the underlying mechanisms of genetic variations in the NAFLD occurrence or its deterioration still need to be clarified. Hence, understanding the genetic susceptibility to NAFLD is essential for controlling the course of the disease. The current review discusses genetics' role in the pathological pathways of NAFLD, including lipid and glucose metabolism, insulin resistance, cellular stresses, and immune responses. Additionally, it explains the role of the genetic components in the induction and progression of NAFLD in lean individuals. Finally, it highlights the utility of genetic knowledge in precision medicine for the early diagnosis and treatment of NAFLD patients.

The association between platelet-related parameters and nonalcoholic fatty liver disease in a metabolically healthy nonobese population

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease characterized by subclinical inflammation and is related to obesity and metabolic syndrome (MS), but it is also frequently observed in nonobese populations. We aimed to evaluate the relationship between the white blood cell count-to-mean platelet volume ratio (WBC/MPV), platelet-to-lymphocyte count ratio (PLR) and lymphocyte-monocyte ratio (LMR) in association with NAFLD, considering the presence of obesity and MS. Additionally, we aimed to investigate whether these parameters exhibited similar correlations in metabolic dysfunction-associated steatotic liver disease (MASLD) as observed in NAFLD. This cross-sectional study included subjects who underwent a comprehensive health evaluation, including blood tests and abdominal ultrasonography. Subgroup analyses were conducted based on obesity and MS. Out of a total 5929 subjects (3271 males, mean age 49.7 ± 10.6 years), 2253 (38.0%) had NAFLD. WBC/MPV was significantly higher, and PLR was significantly lower in subjects with NAFLD. In the analysis restricted to the nonobese (BMI < 25 kg/m2) population without MS, both WBC/MPV and PLR were independently associated with NAFLD: WBC/MPV (adjusted OR 3.366; 95% CI 2.238-5.066) and PLR (adjusted OR 0.997; 95% CI 0.996-0.999). When assessing the risk of NAFLD based on the WBC/MPV and PLR quartiles, the adjusted OR and 95% CI for the lowest quartile compared to the highest were 2.055 (95% CI 1.626-2.602) for WBC/MPV and 0.660 (95% CI 0.523-0.832) for PLR in the nonobese, metabolically healthy group. The levels of WBC/MPV and PLR were independently associated with NAFLD. Furthermore, in MASLD, an association with WBC/MPV, PLR and LMR was identified, similar to the results observed in NAFLD, even after adjusting for confounding variables. In conclusion, the present study demonstrated a significant association between NAFLD and platelet-related parameters, especially in nonobese, metabolically healthy subjects.

The metabolic profiles and body composition of non-obese metabolic associated fatty liver disease

Background/purpose

Metabolic-associated fatty liver disease (MAFLD) is a major cause of chronic liver disease worldwide and is generally thought to be closely related to obesity and diabetes. However, it also affects non-obese individuals, particularly in Asian cultures.

Methods

Healthy physical examination subjects and MAFLD patients were included in the endocrinology department of Jiangsu Provincial Hospital of Traditional Chinese Medicine. MAFLD was defined as fatty liver in imaging without virus infection, drug, alcohol, or other known causes of chronic liver disease. Non-obese MAFLD was defined as MAFLD in non-obese subjects (BMI<25 kg/m2).

Results

The final analysis comprised 1047 participants in total. Of 946 MAFLD patients, 162 (17.12%) were diagnosed with non-obese MAFLD. Non-obese MAFLD patients were older, had lower alanine aminotransferase (ALT), triglyceride, and waist circumference, but had higher high density lipoprotein cholesterol (HDL-c) than obese MAFLD patients. Compared with non-obese healthy controls, non-obese MAFLD patients had higher BMI, ALT, gamma-glutamyl transferase (GGT), uric acid (UA), triglycerides (TG), and low density lipoprotein cholesterol (LDL-c). In terms of body composition, body fat mass (BFM), waist-hip ratio (WHR), percent body fat (PBF), visceral fat area (VFA), and fat mass index (FMI) were lower in non-obese healthy controls than non-obese MAFLD patients. A binary logistic regression analysis revealed that non-obese MAFLD was linked with lower GGT and higher HDL-c.

Conclusion

In this study cohort, non-obese MAFLD was present at a prevalence of 13.90%. In contrast to non-obese healthy controls, non-obese MAFLD patients exhibited different metabolic profiles, but they also had different body compositions.

Risk Stratification of Advanced Fibrosis in Patients With Human Immunodeficiency Virus and Hepatic Steatosis Using the Fibrosis-4, Nonalcoholic Fatty Liver Disease Fibrosis, and BARD Scores

Background

Nonalcoholic fatty liver disease (NAFLD) and subsequent progression to fibrosis is increasingly prevalent in people with HIV (PWH). We used noninvasive methods to stratify risk and identify associated factors of advanced fibrosis in PWH with NAFLD.

Methods

We conducted a retrospective study of PWH in our clinic from 2005 to 2022. We used liver imaging or biopsy reports to identify cases of hepatic steatosis after excluding specified etiologies. We used the Fibrosis-4 (FIB-4), NAFLD Fibrosis (NFS), and body mass index, aspartate transaminase/alanine transaminase ratio, and diabetes score scores to stratify fibrosis. We used logistic regression to identify factors associated with advanced fibrosis.

Results

Among 3959 PWH in care, 1201 had available imaging or liver biopsies. After exclusions, 114 of 783 PWH had evidence of hepatic steatosis (14.6%). Most were male (71.1%), with a median age of 47 years, and median body mass index of 30.1 kg/m2. Approximately 24% had lean NAFLD (ie, body mass index < 25 kg/m2). Based on the FIB-4 and NFS, 34 (29.8%) and 36 (31.6%) had advanced fibrosis, whereas 1 in 4 had low risk of fibrosis based on FIB-4, NFS, and BARD scores. In adjusted analysis using FIB-4, advanced fibrosis was associated with age > 45 years (adjusted odds ratio, 6.29; 95% confidence interval, 1.93-20.50) and hypoalbuminemia (adjusted odds ratio, 9.45; 95% confidence interval, 2.45-32.52) in addition to elevated transaminases and thrombocytopenia, whereas using the NFS did not identify associations with advanced fibrosis.

Conclusions

We found 14.6% of PWH had NAFLD, with 1 in 3 having advanced fibrosis. Our study provides practical insights into fibrosis risk stratification in HIV primary care settings.

Gender-Specific Bile Acid Profiles in Non-Alcoholic Fatty Liver Disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is increasing worldwide. A main cause is the obesogenic, so-called Western lifestyle. NAFLD follows a long, unperceived course, and ends potentially fatally. Early diagnosis of aggressive subtypes saves lives. So far, non-invasive means of detection are limited. A better understanding of the pathogenic interplay among insulin resistance, immune inflammation, microbiome, and genetic background is important. Metabolomics may give insight into these interlaced processes.

METHODS

In this study, we measured bile acids (BA) in the plasma of adult NAFLD and alcohol-associated liver disease (ALD) patients and healthy controls with targeted mass spectrometry. We focused on gender-related bile acid production pathology in NAFLD and ALD.

RESULTS

Compared to healthy controls, women with NAFLD had significantly higher concentrations of total BA, total primary BA, total cholic (CA), total chenodeoxycholic (CDCA), total glycine-conjugated, and total non-12-a-OH BA. Concerning subtypes, glycocholic (GCA) and glycochenodeoxycholic (GCDCA), BA were elevated in women with NAFLD. In contrast, men with NAFLD had no significantly altered total BA fractions. However, the subtypes GCA, glycodeoxycholic (GDCA), glycolithocholic (GLCA), lithocholic (LCA), taurolithocholic (TLCA), and tauroursodeoxycholic acid (TUDCA) were elevated, while CA was significantly decreased. In NAFLD, except ursodeoxycholic acid (UDC), all total BA correlated significantly positively in both sexes with the ELF score, while in ALD, only males showed significant correlations exceptive for total UDC BA. In NAFLD, total BA, total primary BA, total secondary BA, total free secondary BA, total CA, total CDCA, total taurine conjugated, total glycine conjugated, total 12-a-OH, and total non-12-a-OH were significantly higher in cases of a high enhanced liver fibrosis (ELF) score above 9.8. In ALD, total UDC was additionally elevated. Between NAFLD with and without NASH, we found no significant differences.

CONCLUSION

Our data show gender-specific bile acid profiles in NAFLD and markedly different BA patterns in ALD. Women with NAFLD had more severe cholestasis. Men may better compensate fat storage-driven bile acid dynamics, indicated by higher levels of taurine-conjugated BA, which associate with beneficial metabolic functions.

Association of Uric Acid to Creatinine Ratio with Metabolic Dysfunction-Associated Fatty Liver in Non-Obese Individuals Without Type 2 Diabetes Mellitus

Introduction

Metabolic dysfunction-associated fatty liver disease (MAFLD) is the most common chronic liver disease, which is usually associated with type 2 diabetes mellitus (T2DM) and obesity. However, the incidence of MALFD in non-obese individuals without T2DM is increasing, and the pathogenesis is unclear. Serum uric acid to creatinine ratio (sUA/Cr) can reflect overall metabolic status. This study aims to observe the association between sUA/Cr and MAFLD in non-obese individuals without T2DM.

Methods

A total of 21,996 individuals were included in this study. The subjects were divided into four subgroups: non-obese patients without T2DM, obese patients without T2DM, non-obese patients with T2DM, and obese patients with T2DM. Logistic regression analyzed the correlation between sUA/Cr and MAFLD subgroups. Receiver operating characteristics analyzed the predictive value of sUA/Cr for MAFLD subgroups. The stratified analyses by sex and age were performed.

Results

Non-obese MAFLD individuals without T2DM had higher sUA/Cr levels than their counterparts. sUA/Cr was significantly correlated positively with MAFLD in non-obese patients. Similar results were observed in both males and females and in populations at all age stages (all p<0.01). sUA/Cr was capable of discriminating MAFLD in non-obese individuals without T2DM (AUC: 0.667), especially for patients over 60 years old (AUC: 0.704).

Conclusion

The sUA/Cr ratio was correlated with MAFLD in non-obese patients without T2DM. The predictive value of sUA/Cr for MAFLD was observed. Hence, the sUA/Cr ratio might be given more concern for the risk of MAFLD in non-obese individuals without T2DM.

What Is New in Metabolic Dysfunction-Associated Steatotic Liver Disease in Lean Individuals: From Bench to Bedside

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects more than 30% of the world's adult population. While it is associated with obesity and metabolic syndrome, emerging evidence has shown that a substantial number of MASLD patients have a normal body mass index ("lean individuals with MASLD"). In this article, we provide an overview of the definition, epidemiology, pathogenesis, and clinical outcomes associated with lean individuals with MASLD and updates on current management.

Parental sex-dependent effects of either maternal or paternal eNOS deficiency on the offspring's phenotype without transmission of the parental eNOS deficiency to the offspring

Background: Preclinical animal studies and clinical studies indicate that both maternal as well as paternal genetic alterations/gene defects might affect the phenotype of the next-generation without transmissions of the affected gene. Currently, the question of whether the same genetic defect present in the mother or father leads to a similar phenotype in the offspring remains insufficiently elucidated. Methods: In this head-to-head study, we crossbred female and male mice with heterozygous endothelial eNOS knockout (eNOS+/-) with male and female wild-type (wt) mice, respectively. Subsequently, we compared the phenotype of the resulting wt offspring with that of wt offspring born to parents with no eNOS deficiency. Results: Wt female offspring of mothers with heterozygous eNOS showed elevated liver fat accumulation, while wt male offspring of fathers with heterozygous eNOS exhibited increased fasting insulin, heightened insulin levels after a glucose load, and elevated liver glycogen content. By quantitative mass-spectrometry it was shown that concentrations of six serum metabolites (lysoPhosphatidylcholine acyl C20:3, phosphatidylcholine diacyl C36:2, phosphatidylcholine diacyl C38:1, phosphatidylcholine acyl-alkyl C34:1, phosphatidylcholine acyl-alkyl C36:3, and phosphatidylcholine acyl-alkyl C42:5 (PC ae C42:5) as well as four liver carbon metabolites (fructose 6-phosphate, fructose 1,6-bisphosphate, glucose 6-phosphate and fumarate) were different between wt offspring with eNOS+/- mothers and wt offspring with eNOS+/- fathers. Importantly, fumarate was inversely correlated with the liver fat accumulation in female offspring with eNOS+/- mothers and increased liver glycogen in offspring of both sexes with eNOS+/- fathers. The qRT-PCR results revealed that the gene expression patterns were different between wt offspring with eNOS+/- mothers and those offspring with eNOS+/- fathers. Different gene expression patterns were correlated with different observed phenotypic changes in male/female offspring born to mothers or fathers with a heterozygous eNOS genotype. Conclusion: The identical parental genetic alteration (heterozygous eNOS deficiency), without being passed on to the offspring, results in distinct metabolic, liver phenotype, and gene expression pattern variations depending on whether the genetic alteration originated from the father or the mother.

Familial clustering of nonalcoholic fatty liver disease in first-degree relatives of adults with lean nonalcoholic fatty liver disease

BACKGROUND AND AIMS

The heritability of nonalcoholic fatty liver disease (NAFLD) in lean individuals is undetermined. This familial aggregation study aimed to evaluate familial linkage for NAFLD and the risk of NAFLD among first-degree relatives of probands with lean NAFLD.

METHODS

This study prospectively recruited cohorts of probands with lean NAFLD, probands with obese NAFLD, and lean probands with non-NAFLD and their respective first-degree relatives. A total of 257 participants were evaluated for liver steatosis, defined by the controlled attenuation parameter ≥288 dB/m2 , metabolic characteristics, and the PNPLA3, TM6SF2, and MBOAT7 polymorphisms.

RESULTS

The prevalence of NAFLD in first-degree relatives of lean NAFLD probands (39.9%) was similar to that in the obese NAFLD group (36.9%) and was significantly higher than in lean persons without NAFLD (19.1%). First-degree relatives of probands with NAFLD who were male, and had central obesity, hypertriglyceridaemia, insulin resistance, and the PNPLA3 rs738409C>G allele had a significantly higher prevalence of NAFLD. After multivariable adjustment for gender, metabolic characteristics, and the PNPLA3 rs738409C>G allele, first-degree relatives of probands with lean NAFLD (odds ratio [OR], 5.13; 95% CI, 1.77-14.86) and obese NAFLD (OR, 3.20; 95% CI, 1.14-8.99) exhibited an increased risk of NAFLD compared with those of lean controls without NAFLD.

CONCLUSIONS

Our well-phenotype cohorts revealed familial clustering of NAFLD and higher risks of NAFLD in first-degree relatives of probands with lean or obese NAFLD. The findings encourage clinicians caring for NAFLD patients to be more vigilant for NAFLD in their family members.

Adiponectin-leptin ratio for the early detection of lean non-alcoholic fatty liver disease independent of insulin resistance

BACKGROUND

Lean Non-alcoholic Fatty Liver Disease (NAFLD) shares a similar disease burden to those of their overweight counterparts and should be detected early. We hypothesized that the adiponectin-leptin ratio (AL ratio) could be a good marker for early detection of lean NAFLD independent of insulin resistance.

MATERIALS AND METHODS

A total of 575 adults without diabetes were enrolled in a community-based study. The subjects were stratified into the lean controls, lean NAFLD, simple overweight/obesity and overweight/obesity NAFLD groups according to body mass index (BMI) and ultrasonographic fatty liver indicators. Serum adiponectin and leptin levels were measured by enzyme-linked immunosorbent assay. Multivariate logistic regression analyses were performed to estimate the odds ratio of having NAFLD in relation to the tertiles of serum AL concentration after adjustment. Receiver operating characteristic (ROC) analyses were applied to evaluate the diagnostic performance of the AL ratio for NAFLD.

RESULTS

The mean age of the participants was 42.8 ± 11.5 years. Comparing with the lean controls, the odds of having lean NAFLD for the highest versus the lowest tertile of AL ratio was 0.28(95%CI: 0.12-0.69) after adjustment. Putting AL ratio, BMI, triglyceride, AST/ALT ratio to the diagnosis performance of NAFLD, the ROC was 0.85 (95% CI: 0.82-0.88), 0.83 (95% CI 0.78-0.87) and 0.86 (95% CI 081-0.91) for all NAFLD, NAFLD in women and NAFLD in men, respectively. (p < .001).

CONCLUSIONS

The study revealed that the AL ratio could be a good biomarker to early distinguish lean NAFLD patients from lean controls independent of insulin resistance. [AQ3]Key messagesThe prevalence of non-alcoholic fatty liver disease (NAFLD) increases globally and is related to liver diseases and metabolic dysfunctions. Lean subset of NAFLD shares a similar disease burden to those of their overweight counterparts and should be detected early.Adiponectin-leptin ratio were associated with the severity of steatosis and was a predictor of obese NAFLD better than each single adipokine. To date, there is no investigation that explores specifically for the relationship between lean NAFLD and AL ratio.Our study found that adiponectin-leptin ratio is a sole independent marker regardless of insulin resistance in lean NAFLD. Having lean NAFLD for the highest versus the lowest tertile of adiponectin-leptin ratio was 0.28(95%CI: 0.12-0.69) after adjustment of age, sex, current smoking, exercise habits, HOMA-IR and AST/ALT. ROC for the NAFLD performance is good for the early detection (0.85; 95% CI: 0.82-0.88). Further rigorous investigation is necessary and should be promptly performed.

Lean nonalcoholic fatty liver disease: Age-dependent differences in pathology, prognosis, and liver-related events

AIM

This study aimed to evaluate the age-specific characteristics, prognosis, and complications of patients with lean nonalcoholic fatty liver disease (NAFLD).

METHODS

Background factors (age, sex, diabetes, dyslipidemia, hypertension, and PNPLA3 gene polymorphism), blood test results, liver histology findings, muscle mass, and grip strength were investigated in 782 patients with NAFLD who underwent liver biopsy. Prognosis and complications were compared among 549 patients with nonlean or lean NAFLD who were followed up for 6.5 years. Additionally, background factors, blood test results, liver histology findings, prognosis, and complications were compared according to age (≥60 years vs. <60 years) in patients with lean NAFLD.

RESULTS

Lean NAFLD patients showed lower aspartate aminotransferase, alanine aminotransferase, homeostasis model assessment-insulin resistance, high-sensitivity C-reactive protein, ferritin, and leptin but higher adiponectin and hemoglobin A1c (HbA1c) levels than patients with nonlean NAFLD. Furthermore, lean NAFLD patients showed less liver fibrosis, inflammation, steatosis, and ballooning. Among lean NAFLD patients, those aged 60 years and older were more frequently female, showed higher rates of hypertension, diabetes, and dyslipidemia, had higher HbA1c and type IV collagen 7S levels, lower platelet count, higher liver fibrosis and inflammation grades, and lower muscle mass and grip strength. Lean NAFLD was associated with a worse prognosis in patients aged 60 years and over than in those younger than 60 years of age and with a higher incidence of liver-related disease, cerebrocardiovascular events, and nonliver cancer.

CONCLUSIONS

Age is an important consideration in patients with lean NAFLD. Compared with nonlean NAFLD, lean NAFLD was associated with a worse prognosis and higher risk of complications in patients aged 60 years and older.

Long working hours and increased risks of lean non-alcoholic fatty liver disease among Korean men and women

Despite the increasing prevalence of lean nonalcoholic fatty liver disease (NAFLD), its risk factors are not well established. We examined the association between long working hours and incident NAFLD in lean Korean workers with emphasis on sex-based effect modification. This cohort study involved 46,113 non-overweight (BMI < 23 kg/m²) and NAFLD-free Korean workers (mean age, 35.5 years). Working hours were categorized into 35-40 (reference), 41-52, and ≥ 53 h. The presence of fatty liver and its severity were determined using ultrasonography and NAFLD fibrosis score (NFS), respectively. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using parametric proportional hazards models. Incident cases of 5901 lean NAFLD developed over a median follow-up of 3.8 years. The incidence of lean NAFLD increased with increasing working hours with a stronger association in men than in women (P for interaction < 0.001). For men, multivariable-adjusted HRs (95% CIs) for lean NAFLD in time-dependent models comparing working hours of 41-52 and ≥ 53 h compared to the reference category were 1.17 (1.07-1.28) and 1.25 (1.12-1.39), respectively. The excess relative risk of developing lean NAFLD with intermediate/high NFS was observed in working hours of 41-52 and ≥ 53 h with a corresponding HR of 1.66 (1.13-2.43) and 1.54 (0.94-2.51), respectively. Conversely, no significant associations were found between working hours and incidence of lean NAFLD in women. In conclusion, long working hours were significantly associated with an increased incidence of lean NAFLD and its severe form in men but not in women.

Risk Stratification of Advanced Fibrosis in HIV Patients With Hepatic Steatosis Using the NAFLD Fibrosis and BARD Scores

Background

Nonalcoholic fatty liver disease (NAFLD) is increasingly prevalent in people with HIV (PWH), yet the risk factors for disease progression are poorly understood, due to inadequate surveillance. We employed non-invasive methods to estimate the prevalence and associated factors of advanced NAFLD in PWH.

Methods

We conducted a retrospective study of PWH enrolled in our clinic from 2005 to 2022. We employed imaging (ultrasound, computer tomography, magnetic resonance imaging, and transient elastography) or biopsy reports to identify cases of hepatic steatosis. We excluded patients with harmful alcohol use, hepatitis B or C infection, and other specified etiologies. We used the NAFLD Fibrosis Score (NFS), BARD Score, AST to Platelet Index (APRI), and Fibrosis-4 (FIB-4) Score to stratify fibrosis. We used logistic regression to identify predictors of advanced fibrosis.

Results

Among 3959 PWH in care, 1201 had available imaging or liver biopsies. After exclusions, 114 of the remaining 783 had evidence of hepatic steatosis (prevalence 14.6%). The majority were male (71.1%), with mean age 46.1 years, and mean body mass index (BMI) 31.4 ± 8.1 kg/m2. About 24% had lean NAFLD (BMI < 25 kg/m2). Based on the NFS, 27.2% had advanced fibrosis, which was corroborated by estimates from the other scores. In adjusted regression analysis, advanced fibrosis was associated with BMI > 35 kg/m2 (4.43, 1.27-15.48), thrombocytopenia (4.85, 1.27-18.62) and hypoalbuminemia (9.01, 2.39-33.91).

Conclusion

We found a NAFLD prevalence of 14.6%, with 27.2% of cases having advanced fibrosis. Our study provides practical insights into the surveillance of NAFLD in PWH.

Innovative Therapeutic Approaches in Non-Alcoholic Fatty Liver Disease: When Knowing Your Patient Is Key

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of disorders ranging from simple steatosis to non-alcoholic steatohepatitis (NASH). Hepatic steatosis may result from the dysfunction of multiple pathways and thus multiple molecular triggers involved in the disease have been described. The development of NASH entails the activation of inflammatory and fibrotic processes. Furthermore, NAFLD is also strongly associated with several extra-hepatic comorbidities, i.e., metabolic syndrome, type 2 diabetes mellitus, obesity, hypertension, cardiovascular disease and chronic kidney disease. Due to the heterogeneity of NAFLD presentations and the multifactorial etiology of the disease, clinical trials for NAFLD treatment are testing a wide range of interventions and drugs, with little success. Here, we propose a narrative review of the different phenotypic characteristics of NAFLD patients, whose disease may be triggered by different agents and driven along different pathophysiological pathways. Thus, correct phenotyping of NAFLD patients and personalized treatment is an innovative therapeutic approach that may lead to better therapeutic outcomes.

miR-27b targets MAIP1 to mediate lipid accumulation in cultured human and mouse hepatic cells

Non-alcoholic liver disease (NAFLD) is a condition caused by excessive fat accumulation in the liver and developed via multiple pathways. miR-27b has been suggested to play crucial roles in the development of NAFLD, assuming via targeting genes involved in lipid catabolism and anabolism. However, other pathways regulated by miR-27b are largely unknown. Here we show that lipid accumulation was induced in miR-27b-transfected human and mouse hepatic cells and that knockdowns of three miR-27b-target genes, β-1,4-galactosyltransferase 3 (B4GALT3), matrix AAA peptidase interacting protein 1 (MAIP1) and PH domain and leucine rich repeat protein phosphatase 2 (PHLPP2), induced lipid accumulation. We also show that B4GALT3 and MAIP1 were direct targets of miR-27b and overexpression of MAIP1 ameliorated miR-27b-induced lipid accumulation. In addition, we show that hepatic Maip1 expression declined in mice fed a high-fat diet, suggesting the involvement of decreased Maip1 expression in the condition of fatty liver. Overall, we identified MAIP1/miR-27b axis as a mediator of hepatic lipid accumulation, a potential therapeutic target for NAFLD.

Lean nonalcoholic fatty liver disease and sarcopenia

Nonalcoholic fatty liver disease (NAFLD) has become one of the most common chronic liver diseases in the world. The risk factor for NAFLD is often considered to be obesity, but it can also occur in people with lean type, which is defined as lean NAFLD. Lean NAFLD is commonly associated with sarcopenia, a progressive loss of muscle quantity and quality. The pathological features of lean NAFLD such as visceral obesity, insulin resistance, and metabolic inflammation are inducers of sarcopenia, whereas loss of muscle mass and function further exacerbates ectopic fat accumulation and lean NAFLD. Therefore, we discussed the association of sarcopenia and lean NAFLD, summarized the underlying pathological mechanisms, and proposed potential strategies to reduce the risks of lean NAFLD and sarcopenia in this review.

Higher mortality among lean patients with non-alcoholic fatty liver disease despite fewer metabolic comorbidities

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) can develop in individuals who are not overweight. Whether lean persons with NAFLD have lower mortality and lower incidence of cirrhosis, cardiovascular diseases (CVD), diabetes mellitus (DM) and cancer than overweight/obese persons with NAFLD remains inconclusive. We compared mortality and incidence of cirrhosis, CVD, DM and cancer between lean versus non-lean persons with NAFLD.

METHODS

This is a retrospective study of adults with NAFLD in a single centre from 2012 to 2021. Primary outcomes were mortality and new diagnosis of cirrhosis, CVD, DM and cancer. Outcomes were modelled using competing risk analysis and Cox proportional hazards regression analysis.

RESULTS

A total of 18,594 and 13,420 patients were identified for cross-sectional and longitudinal analysis respectively: approximately 11% lean, 25% overweight, 28% class 1 obesity and 35% class 2-3 obesity. The median age was 51.0 years, 54.6% were women. The median follow-up was 49.3 months. Lean patients had lower prevalence of metabolic diseases at baseline and lower incidence of cirrhosis and DM than non-lean patients and no difference in CVD, any cancer or obesity-related cancer during follow-up. However, lean patients had significantly higher mortality with incidence per 1000 person-years of 16.67, 10.11, 7.37 and 8.99, respectively, in lean, overweight, obesity class 1 and obesity class 2-3 groups respectively.

CONCLUSIONS

Lean patients with NAFLD had higher mortality despite lower incidence of cirrhosis and DM, and similar incidence of CVD and cancer and merit similar if not more attention as non-lean patients with NAFLD.

Mechanisms of non-alcoholic fatty liver disease development in normal-weight individuals

While non-alcoholic fatty liver disease (NAFLD) without inflammation or fibrosis is considered a relatively 'benign' disease, non-alcoholic steatohepatitis (NASH), by contrast, is characterized by marked inflammation in addition to lipid accumulation, and may include fibrosis, progression to cirrhosis and hepatocellular carcinoma. Obesity and type II diabetes are frequently associated with NAFLD/NASH; however, a significant number of lean individuals may develop these diseases. Little attention has been paid to the causes and mechanisms contributing to NAFLD development in normal-weight individuals. One of the main causes of NAFLD in normal-weight individuals is the accumulation of visceral and muscular fat and its interaction with the liver. Myosteatosis (triglyceride accumulation in the muscle) induces a loss of muscle by reducing blood flow and insulin diffusion, contributing to NAFLD. Normal-weight patients with NAFLD exhibit higher serum markers of liver damage and C-reactive protein levels, as well as more pronounced insulin resistance, compared to healthy controls. Notably, increased levels of C-reactive protein and insulin resistance are strongly correlated with the risk of developing NAFLD/NASH. Gut dysbiosis has also been associated with NAFLD/NASH progression in normal-weight individuals. More investigation is required to elucidate the mechanisms leading to NAFLD in normal-weight individuals.

Metabolic dysfunction and nonalcoholic fatty liver disease risk in individuals with a normal body mass index

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is strongly associated with obesity, but is also common in individuals with a normal body mass index (BMI), who also experience the hepatic inflammation, fibrosis, and decompensated cirrhosis associated with NAFLD progression. The clinical evaluation and treatment of NAFLD in this patient population are challenging for the gastroenterologist. A better understanding of the epidemiology, natural history, and outcomes of NAFLD in individuals with normal BMI is emerging. This review examines the relationship between metabolic dysfunction and clinical characteristics associated with NAFLD in normal-weight individuals.

RECENT FINDINGS

Despite a more favorable metabolic profile, normal-weight NAFLD patients exhibit metabolic dysfunction. Visceral adiposity may be a critical risk factor for NAFLD in normal-weight individuals, and waist circumference may be better than BMI for assessing metabolic risk in these patients. Although screening for NAFLD is not presently recommended, recent guidelines may assist clinicians in the diagnosis, staging, and management of NAFLD in individuals with a normal BMI.

SUMMARY

Individuals with a normal BMI likely develop NAFLD as a result of different etiologies. Subclinical metabolic dysfunction may be a key component of NAFLD in these patients, and efforts to better understand this relationship in this patient population are needed.

Special Population: Lean Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is strongly associated with obesity but around 10% to 20% of patients with NAFLD have normal body mass index, a condition referred to as lean or nonobese NAFLD. Although lean patients more often have milder liver disease, a proportion may nonetheless develop steatohepatitis and advanced liver fibrosis. Both genetic and environmental factors contribute to the development of NAFLD. Noninvasive tests have similarly good accuracy as initial assessments for lean NAFLD. Future studies should determine the most appropriate treatment in this special population.

Nonalcoholic Fatty Liver Disease in Lean/Nonobese and Obese Individuals: A Comprehensive Review on Prevalence, Pathogenesis, Clinical Outcomes, and Treatment

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide, with an estimated prevalence of 25% globally. NAFLD is closely associated with metabolic syndrome, which are both becoming increasingly more common with increasing rates of insulin resistance, dyslipidemia, and hypertension. Although NAFLD is strongly associated with obesity, lean or nonobese NAFLD is a relatively new phenotype and occurs in patients without increased waist circumference and with or without visceral fat. Currently, there is limited literature comparing and illustrating the differences between lean/nonobese and obese NAFLD patients with regard to risk factors, pathophysiology, and clinical outcomes. In this review, we aim to define and further delineate different phenotypes of NAFLD and present a comprehensive review on the prevalence, incidence, risk factors, genetic predisposition, and pathophysiology. Furthermore, we discuss and compare the clinical outcomes, such as insulin resistance, dyslipidemia, hypertension, coronary artery disease, mortality, and progression to nonalcoholic steatohepatitis, among lean/nonobese and obese NAFLD patients. Finally, we summarize the most up to date current management of NAFLD, including lifestyle interventions, pharmacologic therapies, and surgical options.

Correlation between nonalcoholic fatty liver disease and left ventricular diastolic dysfunction in non-obese adults: a cross-sectional study

BACKGROUND AND AIMS

Non-alcoholic fatty liver disease (NAFLD) is associated with a greater risk of developing cardiovascular disease and have adverse impacts on the cardiac structure and function. Little is known about the effect of non-obese NAFLD upon cardiac function. We aimed to compare the echocardiographic parameters of left ventricle (LV) between non-obese NAFLD group and control group, and explore the correlation of non-obese NAFLD with LV diastolic dysfunction.

METHODS AND RESULTS

In this cross-sectional study, 316 non-obese inpatients were enrolled, including 72 participants with NAFLD (non-obese NAFLD group) and 244 participants without NAFLD (control group). LV structural and functional indices of two groups were comparatively analyzed. LV diastolic disfunction was diagnosed and graded using the ratio of the peak velocity of the early filling (E) wave to the atrial contraction (A) wave and E value. Compared with control group, the non-obese NAFLD group had the lower E/A〔(0.80 ± 0.22) vs (0.88 ± 0.35), t = 2.528, p = 0.012〕and the smaller LV end-diastolic diameter〔(4.51 ± 0.42)cm vs (4.64 ± 0.43)cm, t = 2.182, p = 0.030〕. And the non-obese NAFLD group had a higher prevalence of E/A < 1 than control group (83.3% vs 68.9%, X² = 5.802, p = 0.016) while two groups had similar proportions of LV diastolic dysfunction (58.3% vs 53.7%, X² = 0.484, p = 0.487). Multivariate logistic regression analysis showed that non-obese NAFLD was associated with an increase in E/A < 1 (OR = 6.562, 95%CI 2.014, 21.373, p = 0.002).

CONCLUSIONS

Non-obese NAFLD was associated with decrease of E/A, while more research will be necessary to evaluate risk of non-obese NAFLD for LV diastolic dysfunction in future.

Comparison of MAFLD and NAFLD Characteristics in Children

Background & aims: An international panel proposed a diagnostic framework for metabolic-associated fatty liver disease (MAFLD) in children. The aim was to compare the clinical features of MAFLD and nonalcoholic fatty liver disease (NAFLD) in children. Methods: The characteristic differences between NAFLD and MAFLD in children were compared with the National Health and Nutrition Examination Survey (NHANES) 2017–2018 in the U.S. and the Comprehensive Prevention Project for Overweight and Obese Adolescents (CPOOA) study in China. Results: In NHANES 2017–2018, regardless of which criteria were implemented, participants with hepatic steatosis were more likely to have higher BMI z-scores, a higher prevalence of hypertension or higher metabolic indices and higher non-invasive liver fibrosis scores (all p < 0.05). The cases diagnosed by those two definitions had a similarity of over 75%. More obese children were diagnosed with MAFLD than NAFLD (p < 0.001). However, approximately 19% of children with NAFLD present with normal weight and fasting glucose levels and cannot be diagnosed with MAFLD. The CPOOA study excluded viral infected liver disease and certain kinds of congenital causes of liver steatosis patients, resulting in children with NAFLD being identical with MAFLD children. Conclusions: Most clinical features were similar between children with MAFLD and children with NAFLD, and more than 75% of children with NAFLD can also be diagnosed with MAFLD. However, approximately 19% of children with NAFLD cannot be categorized as MAFLD. Therefore, to gain greater benefits from renaming NAFLD to MAFLD in pediatrics, the prevalence of different causes of hepatic steatosis in children needs to be understood.

Clinical features of chronic hepatitis B patients with lean nonalcoholic fatty liver disease

BACKGROUND

The clinical features have been well described in obese chronic hepatitis B (CHB) patients with nonalcoholic fatty liver disease (NAFLD). However, little is known about the clinical features of lean CHB-NAFLD patients.

METHODS

The study retrospectively included treatment-naïve CHB patients who underwent ultrasound between 2015 and 2021. Liver fibrosis was assessed by aspartate aminotransferase (AST) to platelet ratio index (APRI), Fibrosis-4 score (FIB-4), NAFLD fibrosis score (NFS), and transient elastography.

RESULTS

Among 1226 CHB-NAFLD patients, 25.0% patients were lean. The age, gender, and platelet, alanine aminotransferase, AST, and albumin levels were comparable between lean CHB-NAFLD and nonlean patients. The levels of plasma glucose, triglycerides, total cholesterol, and uric acid, as well as proportions of concurrent hypertension and diabetes, were lower in lean patients. Lean patients presented higher hepatitis B surface antigen (HBsAg) levels (3.4 log₁₀ IU/ml vs. 3.2 log₁₀ IU/ml, p = 0.006), hepatitis B virus (HBV) DNA levels (4.1 log₁₀ IU/ml vs. 3.2 log₁₀ IU/ml, p < 0.001), and hepatitis B e antigen (HBeAg) positive proportions (40.4% vs. 30.2%, p = 0.002) than nonlean patients. The values of APRI, FIB-4, and liver stiffness were comparable between two groups. However, lean patients had lower NFS values (-3.0 vs. -2.6, p < 0.001) and lower proportions (12.6% vs. 21.1%, p = 0.003) of advanced fibrosis (NFS ≥ -1.5) than nonlean patients. Similar results were observed in HBeAg-positive and HBeAg-negative subgroups.

CONCLUSIONS

Nearly a quarter of CHB-NAFLD patients were lean. Lean patients had lower proportions of metabolic abnormalities and advanced liver fibrosis than nonlean patients. However, lean CHB-NAFLD patients had higher HBsAg levels, HBV DNA levels, and HBeAg-positive proportions. Registry and registration no. of the study/trial: Clinicaltrials.gov, Identifier: NCT03097952.

Prevalence, characteristics, and mortality outcomes of obese and nonobese MAFLD in the United States

BACKGROUND AND AIMS

Metabolic dysfunction-associated fatty liver disease (MAFLD) establishes new criteria for diagnosis of fatty liver disease independent of alcohol intake. We aimed to describe the prevalence and compare characteristics and mortality outcomes of persons with nonobese and obese MAFLD.

METHODS

Using data from 13,640 participants from the third National Health and Nutrition Examination Survey (NHANES III) 1988-1994, we identified participants with fatty liver on ultrasound who had MAFLD and analyzed them by the presence of obesity.

RESULTS

Overall prevalence of MAFLD was 19%; amongst those, 54% were obese and 46% were nonobese. Nonobese MAFLD was more common in participants older than 65 than in younger participants (56.8% vs. 43.2%, p < 0.0001). Nonobese MAFLD was more common in males (63.2% vs. 48.3%, p < 0.0001). Obese MAFLD was more common in females (51.7% vs. 48.3%, p < 0.0001). After adjusting for several demographic factors and alcohol use, older age [adjusted odds ratio (aOR) 1.02, 95% CI 1.00-1.02, p = 0.003] and being male (aOR: 1.65, 95% CI 1.25-2.17, p = 0.001) were independent risk factors for nonobese MAFLD. Nonobese MAFLD participants had a higher 20-year cumulative incidence for all-cause mortality compared to obese MAFLD participants (33.2% vs. 28.8%, p = 0.0137). However, nonobese MAFLD was not independently associated with mortality after adjusting for relevant confounders, while FIB-4 > 1.3 and cardiovascular disease were the strongest risk factors associated with increased mortality [adjusted hazard ratio (aHR)  > 2.7 for both, p < 0.0001 for both].

CONCLUSIONS

Nonobese MAFLD constitutes about half of the MAFLD in the United States, especially among males and the elderly. Notably, nonobese MAFLD carries higher mortality than obese MAFLD. Screening and diagnosis of MAFLD should be considered in nonobese populations.

Genetic variation in TBC1 domain family member 1 gene associates with the risk of lean NAFLD via high-density lipoprotein

Objective: Non-alcoholic fatty liver disease (NAFLD) affects almost a quarter of the world's population. Although NAFLD often co-exists with obesity, a substantial proportion of NAFLD patients are lean which is relatively unexplored. This study aimed to examine the association between genetic variation in candidate genes, e.g., TBC1D1 and the risk of lean NAFLD in the elderly Chinese Han population. Methods: This is an extension of the research on physical examination in the Zhanjiang community center including 5387 residents, Shanghai, China, in 2017. According to the classification in adult Asian populations, participants were categorized into four groups: lean NAFLD (BMI <23, n = 106), non-lean NAFLD (BMI ≥23, n = 644), lean non-NAFLD (BMI <23, n = 216) and non-lean non-NAFLD (BMI ≥23, n = 253).116 NAFLD-related candidate genes, which cover 179 single nucleotide polymorphisms (SNPs) were included in the KEGG enrichment analysis. Independent samples t-test was adopted for the group comparison. The associations between genetic variations with the specific phenotype in five genetic models were analyzed with the "SNPassoc" R package and rechecked with logistic regression analysis. Mediation models were conducted to explore whether the certain phenotype can mediate the association between SNPs and the risk of lean NAFLD. Results: Compared with lean non-NAFLD individuals, lean NAFLD patients had higher BMI, low-density lipoprotein and triglyceride, and lower HDL. The AMPK signaling pathway, which includes TBC1D1 and ADIPOQ genes, was the most significant (p < .001). The A allele frequency of rs2279028 in TBC1D1 (p = .006) and G allele frequency of rs17366568 in ADIPOQ (p = .038) were significantly lower in lean NAFLD. The association between rs2279028 and the risk of lean NAFLD was mediated by HDL (p = .014). No significant mediation effect was found between rs17366568 and the risk of lean NAFLD. Conclusion: This study, for the first time, indicated that rs2279028 of TBC1D1 may contribute to the progression of lean NAFLD through HDL. This finding provides more evidence for exploring the mechanism of lean NAFLD and suggests practical solutions for the treatment of lean NAFLD.

Precision Nutrition in NAFLD: Effects of a High-Fiber Intervention on the Serum Metabolome of NAFD Patients-A Pilot Study

Non-alcoholic fatty liver disease (NAFLD) is associated with dysfunction of the intestinal microbiota and its metabolites. We aimed to assess whether replacing bread with high-fiber buns beneficially changes the metabolome in NAFLD patients. This study involved 27 adult patients with NAFLD validated by FibroScan^® (CAP ≥ 234 dB/m). Patients were asked to replace their existing bread for two meals with high-fiber buns. In this way, the patients ate two rolls every day for 2 months. The following parameters were analysed (at the beginning and after 2 months): the anthropometric data (BIA), eating habits (24 h food recalls), gut barrier markers (lipopolysaccharide S and liposaccharide binding protein (LPS, LBP)), serum short-chain fatty acids (SCFAs) and branched chain fatty acids (BCFAs) by GC/MS chromatography, as well as serum metabolites (by ¹H NMR spectroscopy). After 2 months of high-fiber roll consumption, the reduction of liver steatosis was observed (change Fibroscan CAP values from 309-277 dB/m). In serum propionate, acetate, isovaleric, and 2-methylbutyric decrease was observed. Proline, choline and one unknown molecule had higher relative concentration in serum at endpoint. A fiber-targeted dietary approach may be helpful in the treatment of patients with NAFLD, by changing the serum microbiota metabolome.

Non-obese NAFLD had no better cardio-metabolic risk profile than obese NAFLD in type 2 diabetic patients

Background

Non-obese non-alcoholic fatty liver disease (NAFLD) has been reported to share clinical outcomes with its obese counterpart in the general population. However, conflicting results have been observed regarding the cardio-metabolic risk profile of non-obese NAFLD as compared to obese NAFLD. Moreover, in the context of type 2 diabetes mellitus (T2DM), this issue has been even less addressed. We hence aimed to examine the association of NAFLD with the cardio-metabolic risk profile in patients with T2DM according to their obesity status.

Methods

A total of 2,708 patients with T2DM who were hospitalized between June 2018 and May 2021 were cross-sectionally assessed.

Results

The prevalence of NAFLD was 49.3%. NAFLD was found in 34.1% of non-obese patients and 66.0% of obese patients. Non-obese NAFLD patients had more and worse metabolic disorders than obese patients without NAFLD in both men and women. Comparable cardio-metabolic risk profiles were noted between non-obese and obese NAFLD subjects. The associations of worse cardio-metabolic risk profiles with NAFLD were overall stronger in non-obese than in obese subjects among women with T2DM, while more pronounced in obese than in non-obese subjects among men with T2DM.

Conclusion

In patients with T2DM, non-obese NAFLD had no better cardio-metabolic risk profile than obese NAFLD. The associations of metabolic disorders with NAFLD were stronger in non-obese than in obese patients in women patients with T2DM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01648-9.

Non-alcoholic fatty liver disease (NAFLD) in lean individuals - Single centre large cohort clinicopathologic and immunophenotypic study

BACKGROUND

Non-alcoholic fatty liver disease is one of the most common causes of chronic liver diseases and occurs even in lean individuals having normal or low body mass index (BMI). Crucial issue is understanding the clinical, pathobiologic and metabolic characteristics in comparison to obese patients. Very few studies have compared clinicopathological characteristics between lean and obese. Published literature is generally in a small cohort of patients, rarely included over-weight as separate category, and most often had non-standardized use of BMI criteria with discordant conclusions. There is very sparse published literature on liver biopsy-confirmed cohort and that to from Asia; also, none had explored the role of mediators such as stellate cells, progenitor cells and macrophages.

AIMS

To evaluate the prevalence of NAFLD in lean patients in a large cohort of histology-confirmed NAFLD, and explore clinico-pathological spectrum of lean NAFLD in comparison to over-weight and obese. Also, to investigate role of hepatic stellate cells, macrophage polarization and their relation to hepatic progenitor cells, in particular the relation to fibrosis and to different BMI categories.

METHODS

Prospective analysis of eleven-year retrospective cross-sectional data of all consecutive patients of NAFLD diagnosed in the period between the year 2011 and 2021. All histologically confirmed cases of NAFLD fulfilling inclusion and exclusion criteria were stratified to three groups according to BMI based on Asian criteria. Demographic, lab, metabolic, and histological comparisons between lean and overweight-obese patients were performed. Histological grading and staging of NAFLD components were performed by NAS-CRN score. Immunohistochemical and image analysis-based assessment and quantification of stellate cells, progenitor cells, and macrophage polarization was performed. Appropriate statistical methods were applied, and study was approved by the Institutional ethics committee.

RESULTS

Lean patients with biopsy-proven diagnosis constituted 21 % (n = 267) of total NAFLD (n = 1273). Other groups were-over-weight patients (232;18.2 %), and the highest were obese patients (774; 60.8 %). 13.9 % of the lean patients with NAFLD were under-weight with BMI<18.5 kg/m2. Lean patients had significantly lower BMI and waist circumference along with lesser fasting glucose levels in comparison to the other groups. Rest of the metabolic parameters were nearly similar. Lean patients showed higher serum ALT levels, and histological characteristics such as ballooning of hepatocytes and steatosis were also more marked in comparison to other groups. Lobular inflammation and advanced fibrosis were significantly less common in lean patients with NASH related cirrhosis found in only 20.9 % of them. Immunophenotypic studies revealed the inter-relationship of HPCs, HSCs, and macrophages was influenced by the stage of fibrosis and not by the BMI.

CONCLUSIONS

Prevalence of NAFLD in lean individuals in a histological-confirmed patient cohort was 21 %. (n = 267/1273). Major strengths of this study are large cohort of lean individuals from a single center, inclusion of only histology-confirmed cases, Asia specific BMI criteria usage, comparative clinical, metabolic, immune-morphologic and image analysis-based characterization, inclusion of over-weight in addition to obese patients, and investigating cross-talk of principal patho-physiologic markers.

Extrahepatic morbidities and mortality of NAFLD: an umbrella review of meta-analyses

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) has reached pandemic proportions currently and may contribute to multiple extrahepatic outcomes.

AIM

To comprehensively summarise evidence of associations between NAFLD and risk of extrahepatic outcomes.

METHODS

We conducted an umbrella review. We searched PubMed, Web of Science and Cochrane database from inception to 27 November 2021.

RESULTS

We included 22 meta-analyses with 374 original studies in our analysis. Subjects with NAFLD had an increased risk of mortality, multiple cardiovascular complications, extrahepatic cancers, diabetes and chronic kidney disease (CKD) than those without NAFLD. Excess risks of several other extrahepatic outcomes including hypothyroidism, urolithiasis, gastro-oesophageal reflux disease, gallstones, depression and worse maternal and foetal outcomes were also observed in this population. However, associations were not significant for prostate cancer, female organ genital cancer, haematological cancer, diabetic retinopathy or osteoporotic fracture. The risks of CVD, diabetes and CKD were similar in obese and non-obese patients. Most associations were heterogeneous across regions; significantly, Europeans with NAFLD were more prone to all-cause mortality than North Americans. The certainty of evidence was graded from only very low to moderate as all included studies were observational.

CONCLUSIONS

Patients with NAFLD are at heightened risk of extrahepatic outcomes. However, the certainty of evidence is only from very low to moderate. Further studies at low risk of bias are required to support the evidence and elucidate any causal associations.

Nonalcoholic fatty liver disease in inflammatory arthritis: Relationship with cardiovascular risk

Liver disease is one of the most important causes of morbidity and mortality worldwide whose prevalence is dramatically increasing. The first sign of hepatic damage is inflammation which could be accompanied by the accumulation of fat called non-alcoholic fatty liver disease (NAFLD), causing damage in the hepatocytes. This stage can progress to fibrosis where the accumulation of fibrotic tissue replaces healthy tissue reducing liver function. The next stage is cirrhosis, a late phase of fibrosis where a high percentage of liver tissue has been replaced by fibrotic tissue and liver functionality is substantially impaired. There is a close interplay of cardiovascular disease (CVD) and hepatic alterations, where different mechanisms mediating this relation between the liver and systemic vasculature have been described. In chronic inflammatory diseases such as rheumatoid arthritis (RA) and psoriatic arthritis (PsA), in which the CVD risk is high, hepatic alterations seem to be more prevalent compared to the general population and other rheumatic disorders. The pathogenic mechanisms involved in the development of this comorbidity are still unraveled, although chronic inflammation, autoimmunity, treatments, and metabolic deregulation seem to have an important role. In this review, we will discuss the involvement of liver disease in the cardiovascular risk associated with inflammatory arthritis, the pathogenic mechanisms, and the recognized factors involved. Likewise, monitoring of the liver disease risk in routine clinical practice through both, classical and novel techniques and indexes will be exposed. Finally, we will examine the latest controversies that have been raised about the effects of the current therapies used to control the inflammation in RA and PsA, in the liver damage of those patients, such as methotrexate, leflunomide or biologics.

Indole supplementation ameliorates MCD-induced NASH in mice

Indole is a microbiota metabolite that functions to protect against obesity-associated non-alcoholic fatty liver disease. The present study examined the extent to which indole supplementation alleviates the severity of non-alcoholic steatohepatitis (NASH), which is the advanced form of non-alcoholic fatty liver disease. In C57BL/6J mice, feeding a methionine- and choline-deficient diet (MCD) resulted in significant weight loss, overt hepatic steatosis, and massive aggregations of macrophages in the liver compared with control diet-fed mice. Upon indole supplementation, the severity of MCD-induced hepatic steatosis and inflammation, as well as liver fibrosis, was significantly decreased compared with that of MCD-fed and control-treated mice. In vitro, indole treatment caused significant decreases in lipopolysaccharide-induced proinflammatory responses in hepatocytes incubated with either basal or MCD-mimicking media. However, indole treatment only significantly decreased lipopolysaccharide-induced proinflammatory responses in bone marrow-derived macrophages incubated with basal, but not MCD-mimicking media. These differential effects suggest that, relative to the responses of macrophages to indole, the responses of hepatocytes to indole appeared to make a greater contribution to indole alleviation of NASH, in particular liver inflammation. While indole supplementation decreased liver expression of desmin in MCD-fed mice, treatment of LX2 cells (a line of hepatic stellate cells) with indole also decreased the expression of various markers of hepatic stellate cell fibrogenic activation. Lastly, indole supplementation decreased intestinal inflammation in MCD-fed mice, suggesting that decreased intestinal inflammation also was involved in indole alleviation of NASH. Collectively, these results demonstrate that indole supplementation alleviates MCD-induced NASH, which is attributable to, in large part, indole suppression of hepatocyte proinflammatory responses and hepatic stellate cell fibrogenic activation, as well as intestinal proinflammatory responses.

Sex-specific Cutoff Values of Visceral Fat Area for Lean vs. Overweight/Obese Nonalcoholic Fatty Liver Disease in Asians

BACKGROUND AND AIMS

Visceral obesity is a risk factor for nonalcoholic fatty liver disease (NAFLD). We investigated sex-specific optimal cutoff values for visceral fat area (VFA) associated with lean and overweight/obese NAFLD in an Asian population.

METHODS

This retrospective study included 678 potential living liver donors (mean age, 30.8±9.4 years; 434 men and 244 women) who had undergone abdominal computed tomography (CT) imaging and liver biopsy between November 2016 and October 2017. VFA was measured using single-slice abdominal CT. NAFLD was evaluated by liver biopsy (≥5% hepatic steatosis). Receiver operating characteristic curve analysis was used to determine cutoff values for VFA associated with lean (body mass index [BMI] <23 kg/m²) and overweight/obese (BMI ≥23 kg/m²) NAFLD.

RESULTS

Area under the curve (AUC) values with 95% confidence intervals (CI) for VFA were 0.82 (95% CI, 0.75-0.88) for lean and 0.74 (95% CI, 0.69-0.79) for overweight/obese men with NAFLD. The AUC values were 0.67 (95% CI, 0.58-0.75) for lean and 0.71 (95% CI, 0.62-0.80) for overweight/obese women with NAFLD. The cutoff values for VFA associated with lean NAFLD were 50.2 cm² in men and 40.5 cm² in women. The optimal cutoff values for VFA associated with overweight/obese NAFLD were 100.6 cm² in men and 68.0 cm² in women.

CONCLUSIONS

Sex-specific cutoff values for VFA may be useful for identifying subjects at risk of lean and overweight/obese NAFLD.

Comparison of long‐term prognosis between non‐obese and obese patients with non‐alcoholic fatty liver disease

Background and Aim

Non‐alcoholic fatty liver disease (NAFLD) can progress in non‐obese patients as in obese patients. Reports on long‐term prognosis in non‐obese NAFLD patients are controversial. Therefore, we aimed to examine the long‐term prognosis of non‐obese patients with NAFLD.

Methods

This single‐center, retrospective cohort study enrolled biopsy‐proven non‐obese and obese NAFLD patients between January 2002 and December 2011 and followed them up until 31 March 2021, for death and clinical events (cardiovascular and liver‐related events and extrahepatic cancers).

Results

Of the 223 NAFLD patients, 58 (26.0%) were non‐obese. Compared with obese patients, they had a lower fibrosis stage (0.8 ± 0.80 vs 1.2 ± 0.91; P = 0.004), milder lobular inflammation (0.9 ± 0.7 vs 1.1 ± 0.7; P = 0.02), and significantly lower serum creatinine, total bilirubin, ferritin, and type IV collagen 7S and higher high‐density lipoprotein levels. After a median follow‐up of 8.9 years, no significant difference was noted in mortality between the two groups (2 [3.4%] non‐obese vs 5 [3.0%] obese; log‐rank test, P = 0.63). Twelve patients (20.7%) in the non‐obese group and 32 (19.4%) in the obese group had clinical events. Although the obese group had a higher incidence of clinical events during the first 10 years of follow‐up, the non‐obese group had a higher incidence after that (log‐rank test, P = 0.67). The non‐obese group had a high incidence of malignancy (9 [15.5%] non‐obese vs 14 [8.3%] obese; P = 0.13).

Conclusion

Non‐obese NAFLD does not necessarily have a good prognosis, and some cases have a poor prognosis such as extrahepatic cancers. Further validation is required in the future.

Association of fatty liver index with all-cause and disease-specific mortality: A nationwide cohort study

BACKGROUND

Population-based data regarding the prognostic implications of hepatic steatosis have been inconsistent. We examined the association between the fatty liver index (FLI) with all-cause and disease-specific mortality in the general population.

METHODS

We included subjects who underwent a health examination in 2009 using the Korean nationwide health screening database. Death and cause of death data were provided by Statistics Korea. The causes of death were classified using 10th Revision of the International Classification of Diseases codes.

RESULTS

Among the included 10,585,844 participants, there were 418,296 deaths during a median follow-up period of 8.3 years. When adjusting for possible confounding factors, the risk of all-cause mortality linearly increased with a higher FLI score (hazard ratio [HR], 95% confidence interval [CI]: FLI 30-59, 1.19, 1.18-1.20; FLI ≥ 60, 1.67, 1.65-1.69, P for trend <0.001). The risk of disease-specific mortality including cardiovascular disease (CVD), cancer, respiratory disease and liver disease, linearly increased as the FLI score became higher (HR, 95% CI: FLI 30-59, 1.18, 1.16-1.20, FLI ≥ 60: 1.61, 1.56-1.65 for CVD; FLI 30-59, 1.13, 1.11-1.14, FLI ≥ 60, 1.41, 1.38-1.44 for cancer; FLI 30-59, 1.26, 1.22-1.29, FLI ≥ 60, 1.96, 1.88-2.05 for respiratory disease, FLI 30-59, 2.29, 2.21-2.38, FLI ≥ 60, 5.57, 5.31-5.85 for liver disease). The risk of all-cause mortality increased as the FLI score became higher across all the body mass index groups, and the greatest risk was observed in those who were underweight (HR, 95% CI = 2.43, 2.09-2.82 in FLI ≥ 60).

CONCLUSION

FLI may serve as a prognostic indicator of death and a high FLI is associated with a poor prognosis particularly in the underweight group.

Reduced Equol Production and Gut Microbiota Features in Men With Lean Nonalcoholic Fatty Liver Disease

Patients with lean nonalcoholic fatty liver disease (NAFLD) may have different metabolic profiles than those with NAFLD. Estrogenic activity is associated with NAFLD pathogenesis. We evaluated the production ability of equol, which has estrogenic activity, in lean NAFLD and assessed their gut microbiota in relation to their equol-producing ability. Among 684 adult participants, 276 (40%) had NAFLD and 293 (43%) were equol producers. The rates of equol producers in the normal and NAFLD groups were 43% and 42%, respectively. Among the patients with NAFLD, 55 (20%) had lean NAFLD of which 18 (33%) were equol producers. The rate of equol production in men with lean NAFLD was 8%, which was the lowest, while the corresponding rate in the other participants was approximately 40%. The gut microbiota composition of equol producers and nonproducers showed many significant differences. The gut microbiota of men with lean NAFLD showed increased abundance of Caulobacter and decreased abundances of Slackia and Terrisporobacter. Thus, almost all men with lean NAFLD lacked equol-producing ability, and their gut microbiota showed a reduced abundance of Slackia, which is related to equol production. The pathology of lean NAFLD in men may be strongly associated with equol-producing ability and gut microbiota.

Non-alcoholic fatty liver disease in adults 2021: A clinical practice guideline of the Italian Association for the Study of the Liver (AISF), the Italian Society of Diabetology (SID) and the Italian Society of Obesity (SIO)

Nonalcoholic fatty liver disease (NAFLD) is a common and emerging liver disease in adults, paralleling the epidemic of obesity and diabetes and leading to worrisome events (hepatocellular carcinoma and end-stage liver disease). In the past years, mounting evidence added insights about epidemiology, natural history, diagnosis and lifestyle-based or drug treatment of NAFLD. In this rapidly evolving scenario, members of the Associazione Italiana per lo Studio del Fegato, the Società Italiana di Diabetologia and the Società Italiana dell'Obesità reviewed current knowledge on NAFLD. The quality of the published evidence is graded, and practical recommendations are made following the rules and the methodology suggested in Italy by the Centro Nazionale per l'Eccellenza delle cure and Istituto Superiore di Sanità. Whenever possible, recommendations are placed within the context the Italian Healthcare system, with reference to specific experience and local diagnostic and management resources.Level of evidence Level of evidence of recommendations for each PICO question were reported according to available evidence.

Lower Circulating Leptin Levels Are Related to Non-Alcoholic Fatty Liver Disease in Children With Obesity

Background

While for individuals with obesity an association between hyperleptinemia and an increased risk of non-alcoholic fatty liver disease (NAFLD) is assumed, a leptin deficiency is also related to the development of NAFLD early in life in ob/ob mice, in patients with leptin deficiency due to biallelic likely pathogenic variants in the leptin gene, and in patients with lipodystrophy.

Objectives

To investigate the association of circulating leptin levels in pre-pubertal children with obesity and steatosis hepatis.

Methods

The cross-sectional study consisted data of n=97 (nmale=76) pre-pubertal children (11.8 ± 1.5 years) with obesity (BMIz: 2.4 ± 0.4). Fasting concentrations of cardiometabolic parameters were measured: insulin, c-peptide, glucose, triglyceride, cholesterol, HDL, LDL, AST, ALT, GGT, leptin. Steatosis hepatis was diagnosed by an ultrasound examination (mild, moderate or severe). Patients were categorized into two groups: low z-score of circulating leptin levels (≤25th percentile) vs. normal z-score of circulating leptin levels.

Results

One-third of the children with obesity were diagnosed with steatosis hepatis (I°: 63.6%, II°/III°: 36.4%). Children with steatosis hepatis had significantly lower z-scores of circulating leptin levels compared to children with an unremarkable liver ultrasonography (-2.1 ± 0.8 vs. -0.7 ± 0.6). Z-scores of circulating leptin levels correlate negatively with degree of steatosis hepatis. Children with low z-scores of circulating leptin levels had significantly higher triglyceride, fasting insulin and c-peptide levels compared to children with normal z-scores of circulating leptin levels.

Conclusion

Prepubertal children with NAFLD and obesity and partial leptin deficiency might be defined as a clinical subgroup.

Association of Low Skeletal Muscle Mass with the Phenotype of Lean Non-Alcoholic Fatty Liver Disease

Low skeletal muscle mass (LSMM) has emerged as a potential risk factor for non-alcoholic fatty liver disease (NAFLD). However, its clinical implications in patients with lean NAFLD have not yet been elucidated. We investigated the role of LSMM in patients with lean NAFLD. Lean NAFLD was defined as a body mass index of ≤23 kg/m2. Using bioelectrical impedance analysis, the appendicular skeletal muscle mass (ASM) was adjusted by height squared. The LSMM was based on 1 SD below the sex-specific mean for young, healthy Asian adults. Of the 8905 ultrasound-confirmed NAFLD patients, 3670 (41.2%) were diagnosed with lean NAFLD. The lean NAFLD group was younger (45.0 vs. 49.0 years, p < 0.001), and had a lower waist circumference (74.0 vs. 85.0 cm, p < 0.001), lower prevalence of diabetes (3.1 vs. 7.4%, p < 0.001) and hypertension (4.2 vs. 15.2%, p < 0.001), and a higher proportion of LSMM (28.0 vs. 2.2%, p < 0.001) than the non-lean NAFLD group. Stepwise adjusted models suggested that LSMM was associated with lean individuals with NAFLD (odds ratio = 7.02, p < 0.001). LSMM may be a novel risk factor for lean NAFLD patients more than non-lean NAFLD patients, independent of classic metabolic factors.

Lifestyle Interventions for Non-Obese Patients Both with, and at Risk, of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease occurring in non-obese subjects (the so-called non-obese NAFLD) is a highly prevalent but neglected liver condition, which is closely associated with metabolic disorders and suboptimal lifestyles. Landmark studies have shown that lifestyle interventions are potentially beneficial in decreasing the risk of developing non-obese NAFLD and in ameliorating NAFLD in non-obese individuals with pre-existing NAFLD. Lifestyle interventions usually refer to changes in eating habits and physical activity, both of which have a powerful effect on non-obese NAFLD and on risk factors for non-obese NAFLD. However, to date, patients and health-care professionals have a poor awareness and understanding of non-obese NAFLD and the beneficial effects of lifestyle interventions in this patient population. The aim of this narrative review is to briefly discuss the evidence for the effects of lifestyle changes and what changes are needed amongst medical personnel and other stakeholders in order to raise awareness of non-obese NAFLD.

Metabolic determinants of NAFLD in adults with type 1 diabetes

AIM

To assess the main metabolic determinants of non-alcoholic fatty liver disease (NAFLD) in adult patients with type 1 diabetes (T1D).

METHODS

115 patients with T1D were divided into 4 groups according to NAFLD grade. NAFLD was diagnosed via transient elastography when CAP > 233 dB/m. Body composition was evaluated by Inbody720, Biospace. Serum lipids, liver enzymes, uric acid, creatinine, hsCRP and HbA1c were evaluated at fasting.

RESULTS

The overall prevalence of NAFLD was 47% (n = 54). In the subgroup with BMI > 25 kg/m² NAFLD prevalence was 66%; and positive family history of type 2 diabetes brought the risk up to 76%. 37% of the lean individuals also had NAFLD. HbA1c > 7% doubled the risk of NAFLD. Waist circumference > 82.5 cm was independently related to NAFLD, accounting for 24% of its variation in females. Accumulation of two and three metabolic syndrome (MetS) components, besides hyperglycemia, increased the risk of NAFLD by 14% (p < 0.0001) and 6% (p = 0.024), respectively. Lean NAFLD correlated with total insulin dose; NAFLD in overweight T1D patients correlated with triglycerides.

CONCLUSIONS

NAFLD is highly prevalent in adults with T1D and obesity or other metabolic derangements and might be independently related to poor long-term glycemic control and waist circumference in females.

Macrophage SCAP Contributes to Metaflammation and Lean NAFLD by Activating STING-NF-κB Signaling Pathway

BACKGROUND & AIMS

Sterol regulatory element binding protein cleavage-activating protein (SCAP) is a cholesterol sensor that confers a broad range of functional effects in metabolic diseases. Lean nonalcoholic fatty liver disease (NAFLD) is characterized by a decrease in subcutaneous fat and ectopic fat deposition in the liver. SCAP may mediate the development of lean NAFLD, but the mechanism of action remains unclear.

METHODS

C57BL/6J wild-type and macrophage SCAP-specific knockout mice (SCAP^ΔMϕ) were subjected to Paigen diet (PD) feeding induced lean NAFLD. Inflammation and lipid metabolism of adipose and liver were evaluated. The STING-NF-κB signaling pathway was examined in vivo and in vitro to explore the underlying mechanism of macrophage SCAP on metaflammation.

RESULTS

The data showed heterogeneity of lipid metabolic processes in liver and epididymal white adipose tissue due to inflammation mediated by macrophage infiltration. Meanwhile, we found that the macrophage SCAP was abnormally increased in the adipose and liver tissues of PD-fed mice. Intriguingly, the SCAP^ΔMϕ mice attenuated PD-induced metaflammation and ectopic lipid deposition by reducing hepatic stimulator of interferon gene (STING)-nuclear factor kappa B (NF-κB) pathway activation. In-depth molecular analysis revealed that SCAP specifically recruits the STING and tank-binding kinase 1 onto the Golgi to activate the NF-κB in macrophages, thereby promoting the release of inflammatory factors. This process ultimately led to an increased lipolysis in adipocytes and lipid uptake and synthesis in hepatocytes.

CONCLUSIONS

Our findings suggest that SCAP acts as a novel regulator of the macrophage inflammatory response and the pathogenesis of lean NAFLD by activating the STING-NF-κB signaling pathway. Inhibition of macrophage SCAP may represent a new therapeutic strategy for the treatment of lean NAFLD.

Clinical and Laboratory Characteristics of Normal Weight and Obese Individuals with Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) has had, over the past few decades, a progressively growing prevalence among the general population all over the world, in parallel with metabolic conditions such as type 2 diabetes mellitus (T2DM), dyslipidemia, and obesity. However, NAFLD is also detected in 10−13% of subjects with a body mass index (BMI) ≤ 25 kg/m² (lean-NAFLD), whose major risk factors remain unknown. In this study, we aimed to characterize the clinical features and associated risk factors of lean-NAFLD in comparison with obese-NAFLD patients. Consecutive patients diagnosed with NAFLD by vibration-controlled transient elastography and controlled attenuation parameter were prospectively enrolled. Biological and clinical data obtained from the participants were stratified according to their BMI in two groups: lean-NAFLD and obese-NAFLD. In total, 331 patients (56.8% males) were included in the final analysis. Most of the subjects were obese-NAFLD (n = 258, 77.9%) and had a higher prevalence of T2DM, dyslipidemia, and components of the metabolic syndrome, together with abnormal biological parameters. Regarding liver stiffness measurements, the proportion of subjects with at least significant fibrosis (≥F2) was approximately twofold higher among obese-NAFLD (43.81%) in comparison with lean-NAFLD patients (23.29%). Moreover, obese individuals had a higher risk for liver fibrosis (OR = 2.6, 95%, CI 1.5−4.42, p < 0.001) than lean individuals. Although associated metabolic conditions and at least significant liver fibrosis were present in approximately one-quarter of the patients, these were more frequent among obese-NAFLD patients. Therefore, individualized screening strategies for NAFLD should be established according to BMI.

NAFLD in normal weight individuals

Nonalcoholic fatty liver disease (NAFLD) can develop in lean individuals. Despite a better metabolic profile, the risk of disease progression to hepatic inflammation, fibrosis, and decompensated cirrhosis in the lean is similar to that in obesity-related NAFLD and lean individuals may experience more severe hepatic consequences and higher mortality relative to those with a higher body mass index (BMI). In the absence of early symptoms and abnormal laboratory findings, lean individuals are not likely to be screened for NAFLD or related comorbidities; however, given the progressive nature of the disease and the increased risk of morbidity and mortality, a clearer understanding of the natural history of NAFLD in lean individuals, as well as efforts to raise awareness of the potential health risks of NAFLD in lean individuals, are warranted. In this review, we summarize available data on NAFLD prevalence, clinical characteristics, outcomes, and mortality in lean individuals and discuss factors that may contribute to the development of NAFLD in this population, including links between dietary and genetic factors, menopausal status, and ethnicity. We also highlight the need for greater representation of lean individuals in NAFLD-related clinical trials, as well as more studies to better characterize lean NAFLD, develop improved screening algorithms, and determine specific treatment strategies based on underlying etiology.

Dose-Response Associations of Metabolic Score for Insulin Resistance Index with Nonalcoholic Fatty Liver Disease among a Nonobese Chinese Population: Retrospective Evidence from a Population-Based Cohort Study

Purpose

This study is aimed at investigating the association between the metabolic score for insulin resistance (METS-IR) index and nonalcoholic fatty liver disease (NAFLD) in the nonobese population and its predictive value.

Methods

10730 nonobese subjects were selected from longitudinal cohort research conducted from January 2010 to December 2014. Cox proportional hazards models were employed to assess the relationship between METS-IR and new-onset NAFLD. Generalized additive models were used to identify nonlinear relationships. In addition, we performed subgroup analyses and interaction tests. The time-dependent receiver operating curve (ROC) and area under the ROC (AUC) were utilized to measure the discriminatory ability of METS-IR for new-onset NAFLD. Beyond clinical risk factors, the incremental predictive value of METS-IR was appraised using integrated discrimination improvement (IDI), C-index, and net reclassification index (NRI).

Results

Over a median period of 804.50 days of follow-up, 1859 (17.33%) participants had a new onset of NAFLD. After adjusting for confounders, the HR for new-onset NAFLD in the Q4 group was 6.40 compared with the Q1 group. When METS-IR was considered a continuous variable, the risk of NAFLD increased by 34% for every 1 SD increase in METS-IR. The smoothing curve shows the dose-response relationship between METS-IR and the presence of new-onset NAFLD. Using a two-piecewise linear regression model, we derived a METS-IR inflection point of 36. HRs were 1.31 on the left side of the inflection point and 1.04 on the right side of the inflection point (log-likelihood ratio test, P < 0.001). Subgroup analyses and interaction tests revealed an interaction between gender and SBP in the association between METS-IR and new-onset NAFLD. In the subgroup analysis of gender and SBP, we observed a higher risk of new-onset NAFLD in men and in those with abnormal SBP levels. We evaluated the ability of METS-IR to identify new-onset NAFLD at different time points. The AUCs at 1, 2, 3, and 4 years were 0.784, 0.756, 0.758, and 0.752, respectively, which represent good discrimination of new-onset NAFLD. The addition of METS-IR greatly improved the reclassification and differentiation of clinical risk factors, with an NRI of 0.276 and an IDI of 0.068. In addition, the addition of METS-IR increased the C-index from 0.719 to 0.771.

Conclusion

In a nonobese Chinese population, elevated METS-IR was independently associated with an enhanced risk of NAFLD development and a dose-response relationship existed. In addition, METS-IR might be a reliable indicator for screening individuals at risk for early NAFLD, especially in nonobese populations.