Nonalcoholic fatty liver disease as a sentinel marker for the development of diabetes mellitus in non-obese subjects

Referral to hepatologists or a second-line examination requirement is common in patients with type 2 diabetes mellitus

BACKGROUND AND AIMS

To estimate the number of patients who required a referral to hepatologists following the 2016 EASL-EASD-EASO guideline and a second-line vibration controlled transient elastography (VCTE) examination following the 2021 EASL guideline according to obesity, glycated hemoglobin (HbA1c), blood pressure (BP), and low-density lipoprotein cholesterol (LDL-C) control status in patients with type 2 diabetes mellitus (T2DM).

METHODS AND RESULTS

A total of 2515 T2DM patients who were hospitalized were cross-sectionally assessed. When we applied the 2016 EASL-EASD-EASO guideline, 26.8 %-46.4 % (depending on the scores used for diagnosing fibrosis) of T2DM patients needed a referral to hepatologists. When we applied the 2021 EASL guideline, a VCTE examination was required in 10.9 %-35 % (depending on the scores used for diagnosing fibrosis) of T2DM patients. The referral rates and the VCTE requirement were even higher in patients who were obese and/or had poor HbA1c, BP, and/or LDL-C control.

CONCLUSIONS

Application of the screening guidelines would lead to a referral to hepatologists or a second-line VCTE examination requirement for a substantial number of T2DM patients, regardless of obesity and metabolic goal attainment status.

Global epidemiology of type 2 diabetes in patients with NAFLD or MAFLD: a systematic review and meta-analysis

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) and metabolic-associated fatty liver disease (MAFLD) shares common pathophysiological mechanisms with type 2 diabetes, making them significant risk factors for type 2 diabetes. The present study aimed to assess the epidemiological feature of type 2 diabetes in patients with NAFLD or MAFLD at global levels.

METHODS

Published studies were searched for terms that included type 2 diabetes, and NAFLD or MAFLD using PubMed, EMBASE, MEDLINE, and Web of Science databases from their inception to December 2022. The pooled global and regional prevalence and incidence density of type 2 diabetes in patients with NAFLD or MAFLD were evaluated using random-effects meta-analysis. Potential sources of heterogeneity were investigated using stratified meta-analysis and meta-regression.

RESULTS

A total of 395 studies (6,878,568 participants with NAFLD; 1,172,637 participants with MAFLD) from 40 countries or areas were included in the meta-analysis. The pooled prevalence of type 2 diabetes among NAFLD or MAFLD patients was 28.3% (95% confidence interval 25.2-31.6%) and 26.2% (23.9-28.6%) globally. The incidence density of type 2 diabetes in NAFLD or MAFLD patients was 24.6 per 1000-person year (20.7 to 29.2) and 26.9 per 1000-person year (7.3 to 44.4), respectively.

CONCLUSIONS

The present study describes the global prevalence and incidence of type 2 diabetes in patients with NAFLD or MAFLD. The study findings serve as a valuable resource to assess the global clinical and economic impact of type 2 diabetes in patients with NAFLD or MAFLD.

Longitudinal Outcomes Associated With Metabolic Dysfunction-Associated Steatotic Liver Disease: A Meta-analysis of 129 Studies

BACKGROUND & AIMS

The progression of metabolic dysfunction-associated steatotic liver disease (MASLD) has been found to manifest in a series of hepatic and extrahepatic complications. A comprehensive meta-analysis of the longitudinal outcomes associated with MASLD has yet to be conducted.

METHODS

To investigate the longitudinal outcomes associated with MASLD, Medline and Embase databases were searched to identify original studies that evaluated the longitudinal risks of incident clinical outcomes among MASLD patients compared with non-MASLD individuals. DerSimonian Laird random-effects meta-analysis was performed. Pooled effect estimates were calculated, and heterogeneity among studies was evaluated.

RESULTS

One hundred twenty-nine studies were included in the meta-analysis. Meta-analysis revealed a significant increase in the risk of cardiovascular outcomes (hazard ratio [HR], 1.43; 95% confidence interval [CI], 1.27-1.60; P < .01), various metabolic outcomes such as incident hypertension (HR, 1.75; 95% CI, 1.46-2.08; P < .01), diabetes (HR, 2.56; 95% CI, 2.10-3.13; P < .01), pre-diabetes (HR, 1.69; 95% CI, 1.22-2.35; P < .01), metabolic syndrome (HR, 2.57; 95% CI, 1.13-5.85; P = .02), chronic kidney disease (HR, 1.38; 95% CI, 1.27-1.50; P < .01), as well as all cancers (HR, 1.54; 95% CI, 1.35-1.76; P < .01) among MASLD patients compared with non-MASLD individuals. By subgroup analysis, MASLD patients with advanced liver disease (HR, 3.60; 95% CI, 2.10-6.18; P < .01) were also found to be associated with a significantly greater risk (P = .02) of incident diabetes than those with less severe MASLD (HR, 1.63; 95% CI, 1.0-2.45; P = .02) when compared with non-MASLD.

CONCLUSIONS

The present study emphasizes the association between MASLD and its clinical outcomes including cardiovascular, metabolic, oncologic, and other outcomes. The multisystemic nature of MASLD found in this analysis requires treatment targets to reduce systemic events and end organ complications.

Associations of advanced liver fibrosis with heart failure with preserved ejection fraction in type 2 diabetic patients according to obesity and metabolic goal achievement status

Background

Heart failure with preserved ejection fraction (HFpEF), a major cause of morbidity and mortality in patients with type 2 diabetes mellitus (T2DM), is frequently coexisted with obesity, poor glycemic, blood pressure (BP), and/or lipid control. We aimed to investigate the associations of nonalcoholic fatty liver disease (NAFLD) and its advanced fibrosis with HFpEF according to obesity, glycated hemoglobin A1c (HbA1c), BP, and low-density lipoprotein cholesterol (LDL-C) goal achievement status in T2DM patients.

Methods

A total of 2,418 T2DM patients who were hospitalized were cross-sectionally assessed. Liver fibrosis was evaluated by non-invasive biomarkers. Logistic regression analysis was used to evaluate the independent and combined associations of fibrosis status and diabetic care goal attainments with HFpEF risk.

Results

Simple steatosis was not associated with HFpEF risk compared with patients without steatosis, while advanced liver fibrosis was found to have significantly higher odds for HFpEF risk (odds ratio,1.59; 95% confidence interval, 1.22-2.08). Advanced fibrosis in NAFLD was significantly associated with an increased risk of HFpEF, regardless of obesity status, HbA1c, BP, and LDL-C goal achievement status. P values for the interactions between fibrosis status and HbA1c control status, fibrosis status and BP control status, fibrosis status and LDL-C control status, and fibrosis status and body mass index (BMI) status on HFpEF risk were 0.021, 0.13, 0.001, and 0.23, respectively.

Conclusion

In patients with T2DM, advanced hepatic fibrosis was significantly associated with HFpEF risk, irrespective of obesity status, HbA1c, BP, and LDL-C goal attainment status. Further, HbA1c and LDL-C goal attainment status modified this association.

Lean Nonalcoholic Fatty Liver Disease and Risk of Incident Type 2 Diabetes mellitus: A Literature Review and Meta-analysis

OBJECTIVE

There is limited data regarding the risk of incident type 2 diabetes mellitus(T2DM) among lean nonalcoholic fatty liver disease (NAFLD) individuals. We performed a meta-analysis of relevant studies. Research design and methods We collected data using PubMed, Scopus, Cochrane and Web of Science from the databases' inception until December 2022. We included cohort studies in which lean NAFLD was diagnosed through imaging methods or biopsy. Eligible studies were selected according to predefined keywords and clinical outcomes.

RESULTS

A total of 16 observational studies with 304,975 adult individuals (7.7% with lean NAFLD) and nearly 1300 cases of incident diabetes followed up over a median period of 5.05 years were included in the final analysis. Patients with lean NAFLD had a greater risk of incident diabetes than those without NAFLD (random-effects hazard ratio [HR] 2.72, 95% CI 1.56-4.74; I2 = 93.8%). Compared with the lean without NAFLD group, the adjusted HRs (95% CIs) of incident diabetes for participants in the overweight/obese without NAFLD and overweight/obese with NAFLD groups were 1.32 (0.99- 1.77) and 2.98(1.66-5.32). It appeared to be even greater among NAFLD patients with advanced high NAFLD fibrosis score (random-effects HR 3.48, 95% CI 1.92-6.31). Sensitivity analyses and publication bias did not alter these findings.

CONCLUSIONS

Lean NAFLD is significantly associated with at least twofold increased risk of incident diabetes in non-overweight subjects. This risk parallels the underlying severity of NAFLD. The presence of NAFLD in non-overweight individuals had a more significant impact on the development of diabetes than being overweight itself.

Therapeutic Potentials of Reducing Liver Fat in Non-Alcoholic Fatty Liver Disease: Close Association with Type 2 Diabetes

Nonalcoholic fatty liver disease (NAFLD), the most widespread chronic liver disease worldwide, confers a significant burden on health systems and leads to increased mortality and morbidity through several extrahepatic complications. NAFLD comprises a broad spectrum of liver-related disorders, including steatosis, cirrhosis, and hepatocellular carcinoma. It affects almost 30% of adults in the general population and up to 70% of people with type 2 diabetes (T2DM), sharing common pathogenetic pathways with the latter. In addition, NAFLD is closely related to obesity, which acts in synergy with other predisposing conditions, including alcohol consumption, provoking progressive and insidious liver damage. Among the most potent risk factors for accelerating the progression of NAFLD to fibrosis or cirrhosis, diabetes stands out. Despite the rapid rise in NAFLD rates, identifying the optimal treatment remains a challenge. Interestingly, NAFLD amelioration or remission appears to be associated with a lower risk of T2DM, indicating that liver-centric therapies could reduce the risk of developing T2DM and vice versa. Consequently, assessing NAFLD requires a multidisciplinary approach to identify and manage this multisystemic clinical entity early. With the continuously emerging new evidence, innovative therapeutic strategies are being developed for the treatment of NAFLD, prioritizing a combination of lifestyle changes and glucose-lowering medications. Based on recent evidence, this review scrutinizes all practical and sustainable interventions to achieve a resolution of NAFLD through a multimodal approach.

Assessing the longitudinal association between the GGT/HDL-C ratio and NAFLD: a cohort study in a non-obese Chinese population

BACKGROUND

A cross-sectional association between the combination indicator of high-density lipoprotein cholesterol (HDL-C) and gamma-glutamyl transferase (GGT) and fatty liver has been described in several recent studies, and this study aims to further evaluate the longitudinal relationship between the ratio of GGT to HDL-C (GGT/HDL-C ratio) and nonalcoholic fatty liver disease (NAFLD).

METHODS

This cohort study included 12,126 individuals without NAFLD at baseline, followed prospectively for 5 years, and the endpoint of interest was new-onset NAFLD. The relationship of the GGT/HDL-C ratio with new-onset NAFLD and the shape of the association was assessed by Cox regression models and restricted cubic spline (RCS) regression, respectively. Time-dependent receiver operator characteristics (ROC) curves were constructed to evaluate the predictive value of GGT, HDL-C, GGT/HDL-C ratio and BMI for the occurrence of NAFLD at different time points in the future.

RESULTS

The prevalence of NAFLD was 72.46/1000 person-years during the 5-year follow-up period. Results of multivariate Cox regression analysis showed a positive association of the GGT/HDL-C ratio with new-onset NAFLD after adequate adjustment of the related confounding factors, and the degree of correlation was slightly higher than that of GGT, and further subgroup analysis found that this association was more significant in the population with elevated systolic blood pressure (SBP). In addition, we also found a nonlinear relationship of the GGT/HDL-C ratio with the risk of new-onset NAFLD using the RCS regression, where the saturation threshold was about 31.79 U/mmol. Time-dependent ROC analysis results showed that the GGT/HDL-C ratio was increasingly valuable in predicting NAFLD over time, and was better than HDL-C in predicting NAFLD in the early stage (1-3 years), but was not superior to BMI and GGT.

CONCLUSIONS

In this large longitudinal cohort study based on a Chinese population, our results supported that the GGT/HDL-C ratio was positively and nonlinearly associated with the risk of new-onset NAFLD in a non-obese population. In the assessment of future NAFLD risk, the GGT/HDL-C ratio was slightly better than GGT alone; However, the GGT/HDL-C ratio did not appear to have a significant advantage over GGT and BMI alone in predicting NAFLD.

2019 Global NAFLD Prevalence: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

The increasing rates of obesity and type 2 diabetes mellitus may lead to increased prevalence of nonalcoholic fatty liver disease (NAFLD). We aimed to determine the current and recent trends on the global and regional prevalence of NAFLD.

METHODS

Systematic search from inception to March 26, 2020 was performed without language restrictions. Two authors independently performed screening and data extraction. We performed meta-regression to determine trends in NAFLD prevalence.

RESULTS

We identified 17,244 articles from literature search and included 245 eligible studies involving 5,399,254 individuals. The pooled global prevalence of NAFLD was 29.8% (95% confidence interval [CI], 28.6%-31.1%); of these, 82.5% of included articles used ultrasound to diagnose NAFLD, with prevalence of 30.6% (95% CI, 29.2%-32.0%). South America (3 studies, 5716 individuals) and North America (4 studies, 18,236 individuals) had the highest NAFLD prevalence at 35.7% (95% CI, 34.0%-37.5%) and 35.3% (95% CI, 25.4%-45.9%), respectively. From 1991 to 2019, trend analysis showed NAFLD increased from 21.9% to 37.3% (yearly increase of 0.7%, P < .0001), with South America showing the most rapid change of 2.7% per year, followed by Europe at 1.1%.

CONCLUSIONS

Despite regional variation, the global prevalence of NAFLD is increasing overall. Policy makers must work toward reversing the current trends by increasing awareness of NAFLD and promoting healthy lifestyle environments.

Urinary volatile Organic compounds in non-alcoholic fatty liver disease (NAFLD), type two diabetes mellitus (T2DM) and NAFLD-T2DM coexistence

INTRODUCTION

Accumulating evidence have shown a significant correlation between urinary volatile organic compounds (VOCs) profile and the manifestation of several physiological and pathological states, including liver diseases. Previous studies have investigated the urinary metabolic signature as a non-invasive tool for the early discrimination between non-alcoholic fatty liver (NAFL) and non-alcoholic steatohepatitis (NASH), which nowadays represents one of the most important challenges in this context, feasible only by carrying out liver biopsy.

OBJECTIVES

The aim of the study was to investigate the differences in the urinary VOCs profiles of non-alcoholic fatty liver disease (NAFLD) patients, diabetes mellitus (T2DM) subjects and NAFLD/T2DM patients.

METHODS

Headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was applied to profile the urinary VOCs. Urine samples were analysed both under acid and alkaline conditions, to obtain a range of urinary volatiles with different physicochemical properties.

RESULTS

Urinary VOCs profiles of 13 NAFLD patients, 13 T2DM subjects and 13 NAFLD/T2DM patients were investigated by multivariate and univariate data analysis techniques which allowed to identify 21 volatiles under alkaline conditions able to describe the NAFLD/T2DM group concerning the other two groups.

CONCLUSION

Our results suggest that VOCs signatures can improve the knowledge of the pathological condition where NAFLD coexists with T2DM and discovering new features that are not simply the sum of the two diseases. These preliminary findings may be considered as hypothesis-generating, to be clearly confirmed by larger prospective investigations.

Association between serum uric acid-to-creatinine ratio and non-alcoholic fatty liver disease: a cross-sectional study in Chinese non-obese people with a normal range of low-density lipoprotein cholesterol

Objective

Evidence regarding the relationship between serum uric acid-to-creatinine (SUA/Scr) ratio and non-alcoholic fatty liver disease (NAFLD) in Chinese non-obese people is still limited. Therefore, the present study was undertaken to analyze the association between the SUA/Scr ratio and NAFLD.

Methods

This study was a cross-sectional study that non-selectively and consecutively collected 182,320 non-obese individuals with a normal range of low-density lipoprotein cholesterol in a Chinese hospital from January 2010 to December 2014. A binary logistic regression model was used to evaluate the independent association between the SUA/Scr ratio and NAFLD. A generalized additive model (GAM) and smooth curve fitting (penalized spline method) was conducted to explore the exact shape of the curve between them. A series of sensitivity analyses were used to ensure the robustness of the results. Moreover, subgroup analyses were conducted. In addition, the diagnostic value of the SUA/Scr ratio for NAFLD was evaluated based on the area under the receiver-operating characteristic curve (AUROC). It was stated that the data had been uploaded to the DATADRYAD website.

Results

The average participants' age was 40.96 ± 14.05 years old, and 90,305 (49.5%) were male. The prevalence of NAFLD was 13.7%, and the mean SUA/Scr was 3.62 ± 0.92. After adjusting covariates, the results showed that SUA/Scr ratio was positively associated with NAFLD (OR = 1.424, 95%CI: 1.396, 1.454). There was also a non-linear relationship between SUA/Scr ratio and NAFLD in participants with normal kidney function, and the inflection point of the SUA/Scr ratio was 4.425. The effect sizes (OR) on the left and right sides of the inflection point were 1.551 (1.504, 1.599) and 1.234 (1.179, 1.291), respectively. And the sensitive analysis demonstrated the robustness of the results. Subgroup analysis showed a stronger association between SUA/Scr ratio and NAFLD in females and the population with age < 50 years, FPG ≤ 6.1 mmol/L, BMI < 24 kg/m², and HDL-c ≥ 1 mmol/L. In contrast, the weaker association was probed in males and the population with age ≥ 50 years, BMI ≥ 24 kg/m², FPG > 6.1 mmol/L, and HDL-c < 1 mmol/L. The SUA/Scr ratio had an AUC of 0.6624 (95% CI 0.6589, 0.6660) for diagnosing NAFLD. Based on the best cut-off value of 3.776, the negative predictive value of the SUA/Scr ratio for identifying NAFLD was 91.0%.

Conclusion

This study demonstrates an independent positive association between SUA/Scr ratio and NAFLD in Chinese non-obese people with a normal range of low-density lipoprotein cholesterol. There is also a non-linear relationship between the SUA/Scr ratio and NAFLD in participants with normal kidney function, and the SUA/Scr ratio is strongly related to NAFLD when SUA/Scr ratio is less than 4.425. The SUA/Scr ratio has a certain reference value for determining NAFLD. When the SUA/Scr ratio is lower than 3.776, identifying NAFLD patients with low risk is a great reference.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-022-02500-w.

Comparative Burden of Metabolic Dysfunction in Lean NAFLD vs Non-lean NAFLD - A Systematic Review and Meta-analysis

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is traditionally associated with obesity. However, there is a subtype of NAFLD, namely NAFLD in lean, that occurs without obesity. However, a recent call to redefine NAFLD to metabolic-associated fatty liver disease focuses on obesity and metabolic dysfunction. Criticism has arisen from the perceived over emphasis on systemic comorbidities, which may disadvantage the lean. The current analysis seeks to quantify the degree of metabolic dysfunction in NAFLD in lean and compare with NAFLD in overweight and obese and non-NAFLD.

METHODS

Medline and Embase databases were searched from inception to March 3, 2022. The inclusion criteria were articles with NAFLD in lean patients presenting with baseline metabolic parameters. Comparisons were conducted with subgroup analysis.

RESULTS

Eighty-five articles were included in the meta-analysis. NAFLD in lean accounted for 13.11% (95% confidence interval [CI], 10.26%-16.62%) of the global population and 14.55% (95% CI, 11.32%-18.51%) in Asia. The degree of metabolic dysfunction was weight dependent with significantly less metabolic dysfunction in NAFLD in lean subjects as compared with NAFLD in overweight counterparts. For NAFLD in lean, only 19.56% (95% CI, 15.28%-24.69%) of the subjects were diabetic, whereas 45.70% (95% CI, 35.01%-56.80%) of obese subjects with NAFLD had diabetes (P < .01). Fasting blood glucose and systolic and diastolic blood pressure values were significantly lower in subjects with NAFLD in lean than in overweight and obese.

CONCLUSION

The current analysis highlights the weight-dependent nature of metabolic dysfunction in NAFLD. Lean subjects with NAFLD were significantly less metabolically unhealthy than were obese and overweight persons with NAFLD. An overreliance on metabolic dysfunction in defining fatty liver will be a flaw in potentially excluding previously characterized NAFLD.

Quantitative analysis of the risk of type 2 diabetes and fatty liver in non-obese individuals by computed tomography

PURPOSE

To explore the risk of fatty liver and type 2 diabetes with quantitative parameters of abdominal computed tomography (CT) in a non-obese population.

METHODS

A retrospective analysis of abdominal CT and hospitalization records of inpatients admitted from May 2019 to May 2021 were divided into a non-obese control group (n = 143 cases) and a non-obese diabetes group (n = 105 cases). The measured abdominal CT parameters included body width, liver and spleen CT values, and the ratio of the liver CT value to the spleen CT value (L/S ratio). Logistic regression was used to analyze the risk factors for diabetes in non-obese individuals.

RESULTS

Three variables including body width (P < 0.001), liver CT value (P = 0.013), and L/S ratio (P = 0.002) were significantly correlated with the presence of diabetes in non-obese individuals.

CONCLUSION

Body width, liver CT value, and L/S ratio can be used to indicate the risk of type 2 diabetes in non-obese individuals.

Nonalcoholic fatty liver disease and risk of incident hypertension: a systematic review and meta-analysis

Several studies reported an association between nonalcoholic fatty liver disease (NAFLD) and the risk of incident hypertension. The objective of this systematic review and meta-analysis was to obtain a precise and reliable estimate of the nature and magnitude of this association. We systematically searched Ovid-MEDLINE up to March 2021 for observational studies in which NAFLD was diagnosed in adults using blood-based panels, imaging techniques or liver biopsy and with a follow-up ≥1 year. Measures of association from individual studies were meta-analyzed using random-effects models. Of the 1108 titles initially scrutinized, we included 11 cohort studies with data on 390 348 participants (52% male) and a mean follow-up of 5.7 years. In the overall analysis, NAFLD was associated with a moderately increased risk of incident hypertension (hazard ratio 1.66; 95% confidence interval (CI), 1.38-2.01; test for overall effect z = 5.266; P < 0.001). There was significant heterogeneity among the studies (P < 0.001). Sensitivity analyses showed that estimates were not affected by geographical location, duration of follow-up and adjustment for baseline blood pressure values. On the other hand, the magnitude of the association was lower in studies that adjusted for baseline adiposity compared with those that did not, explaining part of the observed heterogeneity. No significant publication bias was detected by funnel plot analysis and Egger's and Begg's tests. This large meta-analysis indicates that NAFLD is associated with a ~1.6-fold increased risk of developing hypertension. Further studies are needed to investigate the role of NAFLD severity in terms of inflammation and fibrosis on incident hypertension.

Dietary and Lifestyle Inflammation Scores Are Inversely Associated with Metabolic-Associated Fatty Liver Disease among Iranian Adults: A Nested Case-Control Study

BACKGROUND

Diet and lifestyle may affect risk for metabolic-associated fatty liver disease (MAFLD) by chronically elevating systemic inflammation.

OBJECTIVES

In this study we investigated the separate and joint associations of dietary and lifestyle inflammation scores (DIS and LIS, respectively) with MAFLD risk.

METHODS

For this nested case-control study we identified and recruited 968 patients with MAFLD (defined as having a fatty liver index ≥60 plus ≥1 of the following conditions: overweight or obese, type II diabetes mellitus, evidence of metabolic dysregulation) and 964 controls from among 35-70-y-old men and women in the baseline phase of the Sabzevar Persian Cohort Study. We collected demographic, lifestyle, anthropometric, biochemical, and dietary intake information (via a validated FFQ) from which we calculated a circulating inflammation biomarker-weighted, predominantly whole foods and beverages-based, 19-component DIS and a 3-component LIS. We estimated DIS- and LIS-MAFLD associations using multivariable unconditional logistic regression. We also calculated equal-weight DIS and LIS to capture all potential mechanisms (inflammation plus other mechanisms) for associations of diet and lifestyle with MAFLD risk.

RESULTS

Among those in the highest relative to the lowest DIS and LIS tertiles, the multivariable-adjusted ORs and their 95% CIs were OR: 1.84; 95% CI: 1.61, 2.07; Ptrend < 0.001, and OR: 1.96; 95% CI: 1.69, 2.21; Ptrend < 0.001, respectively. For those in the highest relative to the lowest joint DIS and LIS tertile, the values were OR: 2.56; 95% CI: 2.19, 2.93; Pinteraction < 0.001. The findings were similar by sex. The third tertile values for the equal-weight DIS- and LIS-MAFLD associations were OR: 1.87; 95% CI: 1.41, 2.34; and OR: 2.16; 95% CI: 1.85, 2.46, respectively.

CONCLUSIONS

Our results suggest that higher balances of pro- relative to anti-inflammatory dietary and lifestyle exposures, separately and especially jointly, may be associated with higher MAFLD risk among adults. Also, inflammation may be the primary mechanism through which diet affects MAFLD risk.

Serum Metabolomics in Patients with Coexisting NAFLD and T2DM Using Liquid Chromatography-Mass Spectrometry

OBJECTIVE

Nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM) frequently coexist and can act synergistically to drive adverse outcomes of one another. This study aimed to unravel the metabolomic changes in patients with NAFLD and T2DM, to identify potential noninvasive biomarkers, and to provide insights for understanding the link between NAFLD and T2DM.

METHODS

Three hundred participants aged 35 to 70 years who were diagnosed with NAFLD (n = 100), T2DM (n = 100), or a comorbidity of NAFLD and T2DM (n = 100) were included in this study. Anthropometrics and routine blood chemistry were assessed after overnight fast. The global serum metabolomic analysis was performed by ultra-performance liquid chromatography-Orbitrap mass spectrometry. Multivariate data analysis methods were utilized to identify the potential biomarkers.

RESULTS

A set of serum biomarkers that could effectively separate NAFLD from NAFLD + T2DM and T2DM from NAFLD + T2DM were identified. We found that patients with coexisting NAFLD and T2DM had significantly higher levels of total protein (TP), triglycerides (TG), glucose in urine, and gamma-hydroxybutyric acid than those with NAFLD and had significant increased levels of TP, albumin, alanine aminotransferase, aspartate aminotransferase, total cholesterol, cholinesterase, TG, low-density lipoprotein, and apolipoprotein A when compared to patients with T2DM.

CONCLUSION

The metabolomics results provide evidence that the comorbidity of NAFLD and T2DM considerably altered patients' metabolomics patterns compared to those of patients with only NAFLD or T2DM.

Association between the atherogenic index of plasma and new-onset non-alcoholic fatty liver disease in non-obese participants

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) in the non-obese population accounts for a large proportion of NAFLD. Atherogenic index of plasma (AIP, defined as the logarithm of the triglyceride/high-density lipoprotein cholesterol ratio.) can provide a stronger reflection of dyslipidemia and studies on the longitudinal association between AIP and NAFLD were limited in non-obese participants, especially in different BMI groups.

METHODS

We performed a post-hoc analysis of data obtained from the Dryad data repository (Dryad is a nonprofit open database of medicine.) and explored the predictive value of AIP on the risk of NAFLD among non-obese participants.

RESULTS

This study included 16173 participants with AIP, of which 2322(14.4%) non-obese participants developed into individuals with NAFLD with the 5-year follow-up examination. The difference between AIP quartiles in the cumulative estimation of new-onset NAFLD was significant, and with increased AIP, the cumulative new-onset NAFLD gradually increased. Participants in higher AIP quartiles had a significantly increased risk of NAFLD. In the fully adjusted model 3, hazard ratios of the new-onset NAFLD for subjects in Q2, Q3, and Q4 of AIP were 2.00 (1.59, 2.53), 2.61 (2.09, 3.72), and 4.49 (3.62, 5.57) respectively. Meanwhile, the trend test for the association between AIP quartiles and the new-onset NAFLD presented that AIP quartile was positively and strongly associated with the new-onset NAFLD (adjusted hazard ratio (95%CI) in Model 3: 1.59 (1.51, 1.67), P<0.001). We found that AIP was also positively and strongly associated with new-onset NAFLD in different sex groups and different age groups in female patients. Moreover, the predictive ability of AIP was no significant difference in different sex groups and different age groups in female patients. In the subgroup analysis, we found that in the low BMI population, the predictive effect of AIP for new-onset NAFLD was expanded by 2-3 times for each quality increase of AIP.

CONCLUSION

This study found that AIP was a strong independent risk factor for new-onset NAFLD among non-obese individuals especially in the low BMI participants, and screening for AIP in this population can be used to prevent future NAFLD.

Nonalcoholic fatty liver disease increases the risk of diabetes in young adults: A nationwide population-based study in Korea

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is associated with an increased risk of diabetes but has been rarely investigated in young adults. In this study, we investigated the relationship between NAFLD and incident diabetes risk in young adults using nationwide Korean population data.

METHODS

This population-based cohort study from the Korean National Health Insurance Service included adults aged 20 through 39 years who underwent a health examination from 2009 to 2012. NAFLD was defined as a fatty liver index (FLI) ≥60 in the absence of alcohol consumption of ≥30 g/day. Newly diagnosed diabetes during follow-up was identified using claims data. Cox regression was used to calculate the hazard ratio for incident diabetes after adjusting for classical confounders.

FINDINGS

Among the 5,254,786 participants, 9.3% had an FLI ≥60. During the median follow-up of 8.6 years, 91,885 cases of incident diabetes occurred. In multivariable analysis, the risk of incident diabetes was significantly higher in the NAFLD group than the control group (adjusted hazard ratio = 4.97, 95% confidence interval, 4.90-5.05). Stratified analyses showed higher associations in those who were ≥30 years, male, obese, smokers, alcohol consumers, and did not regularly exercise (all P < 0.001).

CONCLUSIONS

NAFLD is associated with a five-fold increased risk of incident diabetes in young adults. These results suggest an independent high risk for incident diabetes in young adults and underscore the importance of paying early attention to patients who develop NAFLD before middle age.

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.

Links between metabolic syndrome and metabolic dysfunction-associated fatty liver disease

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a chronic condition characterized by hepatic fat accumulation combined with underlying metabolic dysregulation. Having evolved from the previous term of nonalcoholic fatty liver disease (NAFLD), the term MAFLD more closely implicates the presence of overweight/obesity, type 2 diabetes, or metabolic dysregulation as essential pathogenic factors, leading to better identification of individuals with this metabolic liver disease. Low-grade inflammation, increased oxidative stress, mitochondrial dysfunction, and intestinal dysbiosis are also involved in its pathogenesis. MAFLD is not only associated with liver-related complications, but also with adverse cardiometabolic outcomes. Further studies are needed to assess whether the newly proposed definition of MAFLD is more accurate than the NAFLD in predicting the adverse liver-related and extrahepatic outcomes.

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.

Changes in body composition and low blood urea nitrogen level related to an increase in the prevalence of fatty liver over 20 years: A cross-sectional study

AIM

Qualitative body composition (BC) change, characterized by the combination of visceral fat gain and muscle loss, is drawing attention as a risk factor for fatty liver (FL). The present study aimed to describe trends in BC change and its association with FL in the Japanese population.

METHODS

Data from medical checkups carried out on 56 639 Japanese participants every 5 years from 1997 to 2017 were analyzed. Fat mass index (FMI) and fat-free mass index (FFMI) were calculated using body mass index and body fat percentage. Subjects were divided into two groups according to deviations from the correlation line of FMI and FFMI as the reference: FMI-predominant BC and FFM-dominant BC. Fatty liver was determined using abdominal ultrasonography.

RESULTS

The prevalence of FL significantly increased from 27.3% to 42.7% in men and from 18.0% to 25.5% in women. The prevalence of FMI predominance significantly increased from 33.6% to 43.9% in men and from 29.1% to 47.0% in women. Fat mass index predominance was independently associated with FL in men and women (odds ratio: 1.96 and 1.94, respectively). Serum blood urea nitrogen level was inversely associated with FL in men and women (0.958 and 0.961, respectively) and significantly decreased from 15.8 to 14.9 mg/dl in men and from 15.1 to 14.0 mg/dl in women.

CONCLUSIONS

Increasing FMI-predominant BC and decreasing serum blood urea nitrogen level could account for the increase in the prevalence of FL over 20 years. We believe that these factors stem from current lifestyle habits in Japan.

Serum Uric Acid Is a Mediator of the Association Between Obesity and Incident Nonalcoholic Fatty Liver Disease: A Prospective Cohort Study

OBJECTIVE

Obesity has been demonstrated to show a consistent link with the increased possibility of nonalcoholic fatty liver disease (NAFLD). Since both serum uric acid (SUA) and obesity are essential components of metabolic syndrome (MetS), it is uncertain whether the incidence of NAFLD results from serum uric acid, obesity, or other potential factors based on previous studies.

PATIENTS AND METHODS

This study enrolled 16,839 participants with no history of alcohol consumption and no fatty liver disease in 2010. All participants completed a survey which included health and lifestyle questionnaires, and underwent physical examination, ultrasonography, and laboratory examinations of blood samples. After the four-year follow up, 5,104 (30.31%) participants were diagnosed with NAFLD. The associations between SUA, BMI or obesity, and incident NAFLD were assessed by multivariate linear regression, logistic regression analysis, and mediation analysis, respectively.

RESULTS

By adjusting demographic and serum characteristics, linear correlation coefficients between obesity and SUA were 20.26 [95% confidence interval (CI)]: 15.74, 24.77), 13.31 (95% CI: 6.63, 19.99) and 22.21 (95% CI: 16.41, 28.02) in the total population, and in the female and male groups, respectively. The odds ratios were 2.49 (95% CI: 1.61, 3.87) in the total population, 5.71 (95% CI: 2.25, 14.45) in the female group and 1.99 (95% CI: 1.15, 3.45) in the male group for the correlation between obesity and incident NAFLD. The mediation analysis showed that SUA contributed to 10.03%, 0.58%, and 12.54% of obesity-related NAFLD development in the total population, females and males, respectively.

CONCLUSION

The findings showed mediation linkages of both obesity and SUA with the incident NAFLD. The role of SUA as a mediator constitutes clinical significance that should be recognized and considered.

Association Between Diabetes Mellitus and All-Cause and Cardiovascular Mortality Among Individuals With Ultrasound-Defined Non-Alcoholic Fatty Liver Disease

OBJECTIVE

The influence of diabetes on mortality among patients with non-alcoholic fatty liver disease (NAFLD) in the general population has not been extensively studied. This study aimed to determine the relationship between diabetes and all-cause and cardiovascular mortality in patients with hepatic ultrasound-confirmed NAFLD using data from the Third National Health and Nutrition Examination Survey (NHANES III), 1988-1994.

METHODS

Data from 4,037 adult individuals with NAFLD from the NHANES III and mortality outcomes linked to National Death Index records through December 31, 2015, were included. Cox proportional hazards models were used to calculate the hazard ratio (HR) and corresponding 95% CI for mortality from all causes and cardiovascular disease after adjusting for multiple variables.

RESULTS

Among 4,037 subjects with NAFLD (55.9% female), 483 had diabetes at baseline. During a median follow-up of 22.1 years, 1,517 (11.5%) died, including 332 (8.22%) from cardiovascular causes. Diabetes was associated with increased all-cause (HR 3.02 [95% CI 2.67-3.41]) and cardiovascular (HR 3.36 [95% CI 2.61-4.32]) mortality in an unadjusted multivariable Cox regression model. The association remained statistically significant after adjusting for a range of potential confounders (HR 2.20 [95% CI 1.90-2.55] for all-cause mortality and HR 2.47 [95% CI 1.81-3.37] for cardiovascular mortality). An additional stratified analysis did not reveal significantly altered results.

CONCLUSION

Diabetes was associated with all-cause and cardiovascular mortality in patients with NAFLD. This link could be further characterized in future studies assessing the degree of glycemic control and its relationship with mortality in patients with diabetes and NAFLD.

Association between the alanine aminotransferase/aspartate aminotransferase ratio and new-onset non-alcoholic fatty liver disease in a nonobese Chinese population: a population-based longitudinal study

BACKGROUND

The alanine aminotransferase (ALT)/aspartate aminotransferase (AST) ratio has been considered an alternative marker for hepatic steatosis. However, few studies have investigated the association of the ALT/AST ratio with non-alcoholic fatty liver disease (NAFLD) in nonobese people.

METHODS

A total of 12,127 nonobese participants who were free of NAFLD participated in this study. The participants were divided into quintiles of the ALT/AST ratio. Multiple Cox regression models were used to explore the association of the ALT/AST ratio with new-onset NAFLD.

RESULTS

During the five-year follow-up period, 2147 individuals (17.7%) developed new-onset NAFLD. After adjusting for all non-collinear covariates, the multiple Cox regression analysis results showed that a higher ALT/AST ratio was independently associated with new-onset NAFLD in nonobese Chinese (adjusted hazard ratios [aHRs]: 2.10, 95% confidence intervals: 1.88, 2.36). The aHRs for NAFLD across increasing quintiles of the ALT/AST ratio were 1, 1.63 (1.30, 2.04), 2.07 (1.65, 2.60), 2.84 (2.33, 3.48) and 3.49 (2.78, 4.39) (P for trend< 0.001). The positive association was more significant among people with high blood pressure, high blood lipids and hyperglycaemia, as well as in men. Additionally, the regression spline showed that the saturation effect of the ALT/AST ratio on NAFLD risk was at 0.93 in this study population, which was 1.22 in males and 0.89 in females.

CONCLUSIONS

In nonobese Chinese individuals without NAFLD at baseline, the increase in the ALT/AST ratio is closely associated with the risk of new-onset NAFLD.

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.

A hypocaloric high-protein diet supplemented with β-cryptoxanthin improves non-alcoholic fatty liver disease: a randomized controlled trial

Background

Despite promising animal data, there is no randomized controlled trial (RCT) on the effects of high protein (HP)-diet and/or β-cryptoxanthin in non-alcoholic fatty liver disease (NAFLD). Aims: Safety and efficacy assessment of a hypocaloric HP-diet supplemented with β-cryptoxanthin in NAFLD.

Methods

Ninety-two Iranian NAFLD outpatients were recruited for this 12-week, single-center, parallel-group, double-blind RCT and randomized into 4 arms (n = 23): HP-diet and β-cryptoxanthin (hypocaloric HP-diet + β-cryptoxanthin), HP-diet (hypocaloric HP-diet + placebo), β-cryptoxanthin (standard hypocaloric diet + β-cryptoxanthin), and control (standard hypocaloric diet + placebo). Serum levels of liver enzymes and grade of hepatic steatosis were assessed at baseline and study endpoint as outcome measures.

Results

In the intention-to-treat population (N = 92), HP-diet and β-cryptoxanthin group experienced greater 12-week reductions in serum levels of liver enzymes than control group (mean difference for alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and gamma-glutamyl transferase: − 27.2, − 7.2, − 39.2, and − 16.3 IU/L, respectively; all p < 0.010). Clinical remission rate (achieving grade 0 hepatic steatosis) in HP-diet and β-cryptoxanthin group (82.6%) was also higher than other groups (13.0%, 17.4%, and 0.0% in HP-diet, β-cryptoxanthin, and control groups, respectively; p < 0.001). Sixteen patients reported minor adverse events.

Conclusion

A hypocaloric HP-diet supplemented with β-cryptoxanthin safely and efficaciously improves NAFLD.

Trial registration number

This trial was registered at https://www.irct.ir as IRCT2017060210181N10.

Human and molecular genetics shed lights on fatty liver disease and diabetes conundrum

The causal role of abdominal overweight/obesity, insulin resistance and type 2 diabetes (T2D) on the risk of fatty liver disease (FLD) has robustly been proven. A consensus of experts has recently proposed the novel definition of 'metabolic dysfunction-associated fatty liver disease, MAFLD' instead of 'nonalcoholic fatty liver disease, NAFLD', emphasizing the central role of dysmetabolism in the disease pathogenesis. Conversely, a direct and independent contribution of FLD per se on risk of developing T2D is still a controversial topic. When dealing with FLD as a potential risk factor for T2D, it is straightforward to think of hepatic insulin resistance as the most relevant underlying mechanism. Emerging evidence supports genetic determinants of FLD (eg PNPLA3, TM6SF2, MBOAT7, GCKR, HSD17B13) as determinants of insulin resistance and T2D. However, recent studies highlighted that the key molecular mechanism of dysmetabolism is not fat accumulation per se but the degree of hepatic fibrosis (excess liver fat content-lipotoxicity), leading to reduced insulin clearance, insulin resistance and T2D. A consequence of these findings is that drugs that will ameliorate liver fat accumulation and fibrosis in principle may also exert a beneficial effect on insulin resistance and risk of T2D in individuals with FLD. Finally, initial findings show that these genetic factors might be directly implicated in modulating pancreatic beta-cell function, although future studies are needed to fully understand this relationship.

Liver Steatosis, Gut-Liver Axis, Microbiome and Environmental Factors. A Never-Ending Bidirectional Cross-Talk

The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing worldwide and parallels comorbidities such as obesity, metabolic syndrome, dyslipidemia, and diabetes. Recent studies describe the presence of NAFLD in non-obese individuals, with mechanisms partially independent from excessive caloric intake. Increasing evidences, in particular, point towards a close interaction between dietary and environmental factors (including food contaminants), gut, blood flow, and liver metabolism, with pathways involving intestinal permeability, the composition of gut microbiota, bacterial products, immunity, local, and systemic inflammation. These factors play a critical role in the maintenance of intestinal, liver, and metabolic homeostasis. An anomalous or imbalanced gut microbial composition may favor an increased intestinal permeability, predisposing to portal translocation of microorganisms, microbial products, and cell wall components. These components form microbial-associated molecular patterns (MAMPs) or pathogen-associated molecular patterns (PAMPs), with potentials to interact in the intestine lamina propria enriched in immune cells, and in the liver at the level of the immune cells, i.e., Kupffer cells and stellate cells. The resulting inflammatory environment ultimately leads to liver fibrosis with potentials to progression towards necrotic and fibrotic changes, cirrhosis. and hepatocellular carcinoma. By contrast, measures able to modulate the composition of gut microbiota and to preserve gut vascular barrier might prevent or reverse NAFLD.

Global prevalence, incidence, and outcomes of non-obese or lean non-alcoholic fatty liver disease: a systematic review and meta-analysis

BACKGROUND

Although non-alcoholic fatty liver disease (NAFLD) is commonly associated with obesity, it is increasingly being identified in non-obese individuals. We aimed to characterise the prevalence, incidence, and long-term outcomes of non-obese or lean NAFLD at a global level.

METHODS

For this systematic review and meta-analysis, we searched PubMed, Embase, Scopus, and the Cochrane Library from inception to May 1, 2019, for relevant original research articles without any language restrictions. The literature search and data extraction were done independently by two investigators. Primary outcomes were the prevalence of non-obese or lean people within the NAFLD group and the prevalence of non-obese or lean NAFLD in the general, non-obese, and lean populations; the incidence of NAFLD among non-obese and lean populations; and long-term outcomes of non-obese people with NAFLD. We also aimed to characterise the demographic, clinical, and histological characteristics of individuals with non-obese NAFLD.

FINDINGS

We identified 93 studies (n=10 576 383) from 24 countries or areas: 84 studies (n=10 530 308) were used for the prevalence analysis, five (n=9121) were used for the incidence analysis, and eight (n=36 954) were used for the outcomes analysis. Within the NAFLD population, 19·2% (95% CI 15·9-23·0) of people were lean and 40·8% (36·6-45·1) were non-obese. The prevalence of non-obese NAFLD in the general population varied from 25% or lower in some countries (eg, Malaysia and Pakistan) to higher than 50% in others (eg, Austria, Mexico, and Sweden). In the general population (comprising individuals with and without NAFLD), 12·1% (95% CI 9·3-15·6) of people had non-obese NAFLD and 5·1% (3·7-7·0) had lean NAFLD. The incidence of NAFLD in the non-obese population (without NAFLD at baseline) was 24·6 (95% CI 13·4-39·2) per 1000 person-years. Among people with non-obese or lean NALFD, 39·0% (95% CI 24·1-56·3) had non-alcoholic steatohepatitis, 29·2% (21·9-37·9) had significant fibrosis (stage ≥2), and 3·2% (1·5-5·7) had cirrhosis. Among the non-obese or lean NAFLD population, the incidence of all-cause mortality was 12·1 (95% CI 0·5-38·8) per 1000 person-years, that for liver-related mortality was 4·1 (1·9-7·1) per 1000 person-years, cardiovascular-related mortality was 4·0 (0·1-14·9) per 1000 person-years, new-onset diabetes was 12·6 (8·0-18·3) per 1000 person-years, new-onset cardiovascular disease was 18·7 (9·2-31·2) per 1000 person-years, and new-onset hypertension was 56·1 (38·5-77·0) per 1000 person-years. Most analyses were characterised by high heterogeneity.

INTERPRETATION

Overall, around 40% of the global NAFLD population was classified as non-obese and almost a fifth was lean. Both non-obese and lean groups had substantial long-term liver and non-liver comorbidities. These findings suggest that obesity should not be the sole criterion for NAFLD screening. Moreover, clinical trials of treatments for NAFLD should include participants across all body-mass index ranges.

FUNDING

None.

Epidemiology of nonalcoholic fatty liver disease in non-obese populations: Meta-analytic assessment of its prevalence, genetic, metabolic, and histological profiles

OBJECTIVE

As a subgroup of nonalcoholic fatty liver disease (NAFLD), patients with non-obese NAFLD may also have an increased risk of adverse hepatic and metabolic outcomes. We aimed to estimate the prevalence and incidence of non-obese NAFLD and to describe its clinical characteristics in this systematic review and meta-analysis.

METHODS

We performed a systematic search of 1235 citations published up to Mar 2020. Meta-analyses, stratified analyses and meta-regression were all performed.

RESULTS

Of the 46 studies included, 28 cross-sectional and longitudinal studies of 155 846 non-obese participants reported a pooled NAFLD prevalence of 14.5% (95% confidence interval [CI] 12.3%-17.1%). A multivariate meta-regression analysis showed the trend that the prevalence varied by their geographical location. Further stratified analyses showed that NAFLD was relatively prevalent among people aged ≥45 years (16.2%; 95% CI 10.8-23.4) and those in South America (25.7%; 95% CI 24.4-27.0). The PNPLA3 rs738409 gene polymorphism was more frequently observed in non-obese NAFLD than in both obese NAFLD and non-obese controls, while the metabolic profiles of non-obese NAFLD were less severe than those of the obese NAFLD group. Patients with non-obese NAFLD had 4.81-fold and 5.43-fold higher risk of diabetes mellitus and metabolic syndrome, respectively, than the non-obese controls.

CONCLUSIONS

Non-obese NAFLD is common, particularly in South America and among people aged ≥45 years. Metabolic diseases and PNPLA3 rs738409 gene polymorphism are more frequent in the non-obese NAFLD group than in non-obese controls.

The Prevalence of Lean/Nonobese Nonalcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis

BACKGROUND AND AIM

The prevalence of lean/nonobese nonalcoholic fatty liver disease (NAFLD) ranges widely in studies. Thus, here, we aimed to perform a meta-analysis on NAFLD prevalence in the lean or nonobese population to give clarity.

MATERIALS AND METHODS

PubMed, Embase, and the Cochrane Library databases were systematically searched to identify studies reporting NAFLD prevalence in the lean/nonobese population. Lean or nonobese was defined by body mass index cutoffs reported by authors in original studies. NAFLD prevalence based on community, population, or health checkups was combined with random-effect model after logit transformation. Subgroup analysis and meta-regression were further performed to investigate the heterogenicity.

RESULTS

A total of 45 studies were enrolled in the final analysis, with 55,936 lean/nonobese subjects included, among whom 7351 NAFLD patients were diagnosed. Overall, the pooled NAFLD prevalence of the lean or nonobese population was 10.2% (95% confidence interval: 7.6%-13.6%) and 15.7% (95% confidence interval: 12.5%-19.6%), respectively. Compared with western studies, the NAFLD prevalence in the lean or nonobese population was lower in eastern studies. In addition, the NAFLD prevalence in both the lean and nonobese population showed a general upward trend during recent years. The prevalence was similar in community-based and health checkup-based studies. Lean/nonobese NAFLD patients had significantly lower rates of hypertension, lower uric acid and fasting plasma glucose, and a higher level of high-density lipoprotein than nonlean/obese patients.

CONCLUSIONS

The prevalence of NAFLD in the lean/nonobese population is not rare in either the western or eastern regions of the world. This meta-analysis of prevalence assessment and clinical characteristics should enable higher confidence in more specific interventions and health care standards for these patients.

Association between Serum Uric Acid to HDL-Cholesterol Ratio and Nonalcoholic Fatty Liver Disease in Lean Chinese Adults

METHODS

A cross-sectional study was performed among 6285 lean Chinese adults (body mass index < 24 kg/m²) who took their annual health checkups. NAFLD was diagnosed based on hepatic ultrasound examination, with exclusion of other etiologies.

RESULTS

Of 6285 lean participants enrolled, 654 NAFLD cases were diagnosed. The overall NAFLD prevalence was 10.41%, and the prevalence was 15.45% and 7.16% in men and women, respectively. UHR was significantly higher in NAFLD patients than in controls (14.25 ± 5.33% versus 10.09 ± 4.23%, P < 0.001). UHR quintiles were positively associated with NAFLD prevalence, which was 1.91% in the first UHR quintile and increased to 3.58%, 7.81%, 14.17%, and 24.54% in the second, third, fourth, and fifth quintile groups, respectively (P < 0.001 for trend). Multivariate logistic regression analysis showed that UHR was independently associated with an increased risk of NAFLD (odds ratio: 1.105; 95% CI: 1.076-1.134; P < 0.001). Sensitivity analysis showed that UHR remained significantly associated with NAFLD in lean participants with normal range of serum uric acid and HDL-cholesterol levels.

CONCLUSIONS

UHR was significantly associated with NAFLD and may serve as a novel and reliable marker for NAFLD in lean adults.

Higher Serum Uric Acid Level Predicts Non-alcoholic Fatty Liver Disease: A 4-Year Prospective Cohort Study

Background: Non-alcoholic fatty liver disease (NAFLD) has become a serious disease affecting people's health in the world. This article studies the causal relationship between NAFLD and serum uric acid (SUA) levels. Methods: During the 4 years of follow-up in a fixed cohort that was established in 2014, 2,832 follow-up subjects without NAFLD were finally included in this study. The study population was divided into four groups according to baseline SUA levels. Cox hazard regression model and Kaplan-Meier survival curves analysis were used to predict risk factors of NAFLD. The receiver operating characteristic curve analyses were used to determine SUA cutoffs for predicting NAFLD. Results: The cumulative prevalence rates of NAFLD were 33.97% (962/2,832), 38.93% (758/1,947) in males and 23.05% (204/885) in females. The results showed that males had a higher incidence of NAFLD (χ² = 68.412, P = 0.000). The Cox regression analysis disclosed that the hazard ratios of NAFLD [95% confidence interval (CI)] were 1.431 (95% CI, 1.123~1.823), 1.610 (95% CI, 1.262-2.054), and 1.666 (95% CI, 1.287-2.157) across the second to the fourth quartile of SUA adjusted for other confounders. The SUA cutoffs, sensitivity, specificity, and area under the curve (AUC) (95% CI) were ≥288.5 μmol/L, 75.5, 46.5%, 0.637(0.616-0.658), respectively, for total; ≥319.5 μmol/L, 65.8%, 48.4%, 0.590 (0.564-0.615), respectively, for males; and ≥287.5 μmol/L, 51.0%, 75.6%, 0.662 (0.619-0.704), respectively, for females. Kaplan-Meier survival curves revealed that individuals with higher SUA level had an increased risk of NAFLD in comparison to lower SUA level (P = 0.000). Conclusion: Serum uric acid is positively correlated with NAFLD, and elevated SUA level can be used as an independent predictor for NAFLD.

Non-Alcoholic Fatty Liver Disease in Non-Obese Individuals: Prevalence, Pathogenesis and Treatment

Non-alcoholic fatty liver disease (NAFLD) parallels comorbidities such as metabolic syndrome, dyslipidaemia or diabetes. Although NAFLD is very prevalent in overweight-obese individuals (i.e. body mass index ≥25 kg/m2), recent studies point to the presence of NAFLD in non-obese individuals, for both the Asian (<25 kg/m2) and Caucasian (<30 kg/m2) populations. This paper discusses the pathogenic pathways and current treatment options of NAFLD in non-obese populations. In this respect, non-obese subjects also need to undergo the medical screening for NAFLD. Across the scientific community, we aim to promote the advancement of knowledge in this emerging field.

Overview of the Pathogenesis, Genetic, and Non-Invasive Clinical, Biochemical, and Scoring Methods in the Assessment of NAFLD

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease worldwide. It represents a range of disorders, including simple steatosis, nonalcoholic steatohepatitis (NASH), and liver cirrhosis, and its prevalence continues to rise. In some cases, hepatocellular carcinoma (HCC) may develop. The develop;ment of non-invasive diagnostic and screening tools is needed, in order to reduce the frequency of liver biopsies. The most promising methods are those able to exclude advanced fibrosis and quantify steatosis. In this study, new perspective markers for inflammation, oxidative stress, apoptosis, and fibrogenesis; emerging scoring models for detecting hepatic steatosis and fibrosis; and new genetic, epigenetic, and multiomic studies are discussed. As isolated biochemical parameters are not specific or sensitive enough to predict the presence of NASH and fibrosis, there is a tendency to use various markers and combine them into mathematical algorithms. Several predictive models and scoring systems have been developed. Current data suggests that panels of markers (NAFLD fibrosis score, Fib-4 score, BARD score, and others) are useful diagnostic modalities to minimize the number of liver biopsies. The review unveils pathophysiological aspects related to new trends in current non-invasive biochemical, genetic, and scoring methods, and provides insight into their diagnostic accuracies and suitability in clinical practice.

Ultrasound-Diagnosed Nonalcoholic Fatty Liver Disease Independently Predicts a Higher Risk of Developing Diabetes Mellitus in Nonoverweight Individuals

RATIONALE AND OBJECTIVES

This study was aimed to evaluate the independent value of ultrasound-diagnosed nonalcoholic fatty liver disease (us-NAFLD), as a surrogate imaging marker of the pathologic entity of NAFLD, in predicting incident diabetes mellitus (DM) in nonoverweight individuals.

MATERIALS AND METHODS

A total of 10,064 participants who had a body mass index <23 kg/m² were included in this retrospective cohort study. us-NAFLD was diagnosed using abdominal ultrasound. All participants were divided into subgroups according to the presence or absence of us-NAFLD and metabolic syndrome (MS).

RESULTS

Over a mean follow-up of 6.0 years, 125 participants (1.2%) developed DM. The incidence rates of DM were 1.0% in participants without us-NAFLD, 6.2% in participants with us-NAFLD, 1.1% in participants without MS, and 13.2% in participants with MS. The adjusted hazard ratios for incident DM were 2.52 (95% confidence interval:1.58-4.03) for us-NAFLD and 2.64 (95% confidence interval:1.54-4.54) for MS.

CONCLUSION

This study demonstrates that us-NAFLD has an independent value in predicting incident DM in non-overweight individuals.

Improvement of Nonalcoholic Fatty Liver Disease Reduces the Risk of Type 2 Diabetes Mellitus

BACKGROUND/AIMS

Little evidence is available about the effect of change in nonalcoholic fatty liver disease (NAFLD) status on risk of diabetes mellitus (DM) development. In this study, we tried to analyze the DM risk according to change in NAFLD status over time.

METHODS

Among a total of 10,141 individuals for whom routine healthcare assessment was performed, 2,726 subjects were selected according to the inclusion/exclusion criteria. NAFLD status change was determined by using serial abdominal ultrasonography and fatty liver index (FLI) during the follow-up period.

RESULTS

Subjects were categorized according to change in NAFLD status as follows: 670 subjects in the persistent NAFLD group, 155 subjects in the resolved NAFLD group, 498 subjects in the incident NAFLD group, and 1,403 subjects in the no NAFLD group. Multivariate Cox regression analysis revealed that incident NAFLD (hazard ratio [HR], 1.94; 95% confidence interval [CI], 1.08 to 3.50; p=0.026) and persistent NAFLD (HR, 3.59; 95% CI, 2.05 to 6.27; p<0.001) were independent risk factors for predicting DM development, whereas the risk with resolved NAFLD was not significantly different from that with no NAFLD. FLI could reproduce the results acquired by ultrasonography.

CONCLUSIONS

This study demonstrated that future DM risk could be influenced by changes in NAFLD status over time. Resolution of NAFLD could reduce the risk of future DM development, while the development of new NAFLD could increase the risk of DM development.

A round trip from nonalcoholic fatty liver disease to diabetes: molecular targets to the rescue?

Evidence suggests a close relationship between nonalcoholic fatty liver disease (NAFLD) and type two diabetes (T2D). On the grounds of prevalence of disease, both conditions account for a significant financial cost for health care systems and individuals. Aim of this review article is to explore the epidemiological basis and the putative molecular mechanisms underlying the association of NAFLD with T2D. Epidemiological studies have shown that NAFLD is associated to the development of incident T2D and either reversal or improvement of NAFLD will result into decreased risk of developing incident T2D. On the other side of the coin data have shown that T2D will worsen the course of NAFLD doubling the risk of disease progression (i.e. evolution from simple steatosis to advanced fibrosis, cirrhosis, hepatocellular carcinoma, liver transplant and death). Conversely, NAFLD will contribute to metabolic decompensation of T2D. The pathogenesis of T2D in NAFLD patients may be mediated by several hepatokines impairing metabolic control. Among these, Fetuin-B, which causes glucose intolerance and is increased in patients with T2D and NAFLD with fibrosis is one of the most promising. T2D may affect the progression of NAFLD by acting at different levels of the pathogenic cascade involving gut microbiota and expanded, inflamed, dysfunctional adipose tissue. In conclusion, T2D and NAFLD are mutually, closely and bi-directionally associated. An improved understanding of molecular pathogenesis underlying this bi-directional association may allow us to be able to prevent the development of T2D by halting the progression of NAFLD.

Nonalcoholic Fatty Liver Disease and Risk of Diabetes: A Prospective Study in China

OBJECTIVE

We aimed to investigate whether liver steatosis severity affects the risk of developing diabetes in a large cohort study.

METHODS

We prospectively examined the association in 41,650 Chinese adults with negative hepatitis-B surface antigen who were free of alcohol consumption, diabetes, and liver cirrhosis at baseline. Cox proportional models were used to estimate the risk of diabetes after a mean of 3.6 years of follow-up. Nonalcoholic fatty liver disease (NAFLD) was assessed with hepatic ultrasonography. Elevated alanine transaminase (ALT) was defined as ALT concentrations >19 and >30 U/L in females and males, respectively. Diabetes was defined as a fasting glucose ³7.0 mmol/L or treatment with hypoglycemic medication.

RESULTS

Liver steatosis severity was significantly associated with higher risks of developing diabetes (adjusted hazard ratio [HR] for severe vs. without NAFLD = 2.66, 95% confidence interval [CI]: 2.17-3.25, P-trend<.001) and impaired fasting glucose (fasting glucose between 5.6 and 6.9 mmol/L, adjusted HR = 1.36, 95% CI: 1.16-1.59, P-trend<.001), as well as a faster increase rate of fasting glucose concentrations ( P-trend<.001), during 3.6 years of follow-up. Elevated ALT was also associated with incident diabetes (HR = 1.12, 95% CI: 1.02-1.22), adjusting for NAFLD and other covariates.

CONCLUSION

We observed a dose-response relationship between liver steatosis severity and increased diabetes risk, and ALT may predict incident diabetes independently of NAFLD.

ABBREVIATIONS

ALT = alanine transaminase; BP = blood pressure; CI = confidence interval; HCV = hepatitis C virus; HR = hazard ratio; IFG = impaired fasting glucose; NAFLD = nonalcoholic fatty liver disease; ULN = upper limit of normal.