Non-alcoholic fatty liver disease: a narrative review of genetics

Steatotic Liver Disease: Pathophysiology and Emerging Pharmacotherapies

Steatotic liver disease (SLD) displays a dynamic and complex disease phenotype. Consequently, the metabolic dysfunction-associated steatotic liver disease (MASLD)/metabolic dysfunction-associated steatohepatitis (MASH) therapeutic pipeline is expanding rapidly and in multiple directions. In parallel, noninvasive tools for diagnosing and monitoring responses to therapeutic interventions are being studied, and clinically feasible findings are being explored as primary outcomes in interventional trials. The realization that distinct subgroups exist under the umbrella of SLD should guide more precise and personalized treatment recommendations and facilitate advancements in pharmacotherapeutics. This review summarizes recent updates of pathophysiology-based nomenclature and outlines both effective pharmacotherapeutics and those in the pipeline for MASLD/MASH, detailing their mode of action and the current status of phase 2 and 3 clinical trials. Of the extensive arsenal of pharmacotherapeutics in the MASLD/MASH pipeline, several have been rejected, whereas other, mainly monotherapy options, have shown only marginal benefits and are now being tested as part of combination therapies, yet others are still in development as monotherapies. Although the Food and Drug Administration (FDA) has recently approved resmetirom, additional therapeutic approaches in development will ideally target MASH and fibrosis while improving cardiometabolic risk factors. Due to the urgent need for the development of novel therapeutic strategies and the potential availability of safety and tolerability data, repurposing existing and approved drugs is an appealing option. Finally, it is essential to highlight that SLD and, by extension, MASLD should be recognized and approached as a systemic disease affecting multiple organs, with the vigorous implementation of interdisciplinary and coordinated action plans. SIGNIFICANCE STATEMENT: Steatotic liver disease (SLD), including metabolic dysfunction-associated steatotic liver disease and metabolic dysfunction-associated steatohepatitis, is the most prevalent chronic liver condition, affecting more than one-fourth of the global population. This review aims to provide the most recent information regarding SLD pathophysiology, diagnosis, and management according to the latest advancements in the guidelines and clinical trials. Collectively, it is hoped that the information provided furthers the understanding of the current state of SLD with direct clinical implications and stimulates research initiatives.

Impact of PNPLA3 and TM6SF2 polymorphisms on the prognosis of patients with MASLD and type 2 diabetes mellitus

BACKGROUND/AIMS

Longitudinal studies assessing the impact of genetic polymorphisms on outcomes in patients with Type 2 Diabetes Mellitus (T2DM) and Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) are scarce. This study aimed to evaluate the effect of PNPLA3 and TM6SF2 risk alleles on hepatic and extrahepatic outcomes in T2DM-MASLD individuals.

METHODS

Patients' polymorphisms were analysed as follows: PNPLA3 CC, CG and GG; TM6SF2 CC and CT + TT; combined comparing no mutant allele, one allele G or T or ≥2 alleles G or T. Hierarchical models were built to assess associations between polymorphisms and outcomes, independently of confounding factors. Multivariate logistic regression was used for cirrhosis and its complications and extrahepatic cancer, and Cox regression for cardiovascular events (CVEs) and all-cause mortality.

RESULTS

In total, 407 T2DM-MASLD patients (62.1 ± 10.5 years, 67.6% women) were followed for 11 (6-13) years. Having at least one G or T allele independently increased the risk of cirrhosis in the separate analysis of PNPLA3 and TM6SF2. Combined polymorphism analysis demonstrated an even higher risk of cirrhosis if two or more risk alleles were present (OR 18.48; 95% CI 6.15-55.58; p < .001). Regarding cirrhosis complications, the risk was higher in PNPLA3 GG and TM6SF2 CT + TT, also with an even higher risk when two or more risk alleles were present in the combined evaluation (OR 27.20; 95% CI 5.26-140.62; p < .001). There were no associations with CVEs or mortality outcomes.

CONCLUSION

In T2DM, PNPLA3 and TM6SF2 polymorphisms, individually and additively, impact MASLD severity, with an increased risk of cirrhosis and its complications.

Synergistic Differential DNA Demethylation Activity of Danshensu (Salvia miltiorrhiza) Associated with Different Probiotics in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a major hepatic disorder occurring in non-alcohol-drinking individuals. Salvianic acid A or Danshensu (DSS, 3-(3, 4-dihydroxyphenyl)-(2R)-lactic acid), derived from the root of Danshen (Salvia miltiorrhiza), has demonstrated heart and liver protective properties. In this work, we investigated the antioxidant activity and hepatoprotective activity of Danshensu alone and in combination with different agents, such as probiotic bacteria (Lactobacillus casei and Lactobacillus acidophilus), against several assays. The inhibition mechanism of the methylation gene biomarkers, such as DNMT-1, MS, STAT-3, and TET-1, against DSS was evaluated by molecular docking and RT-PCR techniques. The physicochemical and pharmacokinetic ADMET properties of DSS were determined by SwissADME and pkCSM. The results indicated that all lipid blood test profiles, including cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C), were reduced after the oral administration of Danshensu combined with probiotics (L. casei and L. acidophilus) that demonstrated good, efficient free radical scavenging activity, measured using anti-oxidant assays. ADMET and drug-likeness properties certify that the DSS could be utilized as a feasible drug since DSS showed satisfactory physicochemical and pharmacokinetic ADMET properties.

Advances in Noninvasive Biomarkers for Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) currently represents one of the most common liver diseases worldwide. Early diagnosis and disease staging is crucial, since it is mainly asymptomatic, but can progress to nonalcoholic steatohepatitis (NASH) or cirrhosis or even lead to the development of hepatocellular carcinoma. Over time, efforts have been put into developing noninvasive diagnostic and staging methods in order to replace the use of a liver biopsy. The noninvasive methods used include imaging techniques that measure liver stiffness and biological markers, with a focus on serum biomarkers. Due to the impressive complexity of the NAFLD's pathophysiology, biomarkers are able to assay different processes involved, such as apoptosis, fibrogenesis, and inflammation, or even address the genetic background and "omics" technologies. This article reviews not only the currently validated noninvasive methods to investigate NAFLD but also the promising results regarding recently discovered biomarkers, including biomarker panels and the combination of the currently validated evaluation methods and serum markers.

Genetic and metabolic aspects of non-alcoholic fatty liver disease (NAFLD) pathogenicity

Background

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease showing a rising prevalence globally. Genetic predisposition plays a key role in the development and progression of the disease pathogenicity.

Main body

This paper summarizes genetic associations based on their influence on several metabolic aspects such as lipid metabolism, glucose metabolism, hepatic iron accumulation and cholesterol metabolism toward the NAFLD pathogenicity. Furthermore, we present variations in some epigenetic characters and the microRNA profile with regard to NAFLD.

Conclusion

As reported in many studies, the PNPLA3 rs738409 variant seems to be significantly associated with NAFLD susceptibility. Other gene variants like TM6SF2 rs58542926, MBOAT7 rs641738 and GCKR variants also appear to be more prevalent among NAFLD patients. We believe these genetic variants may provide insights into new trends in developing noninvasive biomarkers and identify their suitability in clinical practice in the future.

Graphical abstract

Nanodrug delivery systems for metabolic chronic liver diseases: advances and perspectives

Nanomedicines are revolutionizing healthcare as recently demonstrated by the Pfizer/BioNTech and Moderna COVID-2019 vaccines, with billions of doses administered worldwide in a safe manner. Nonalcoholic fatty liver disease is the most common noncommunicable chronic liver disease, posing a major growing challenge to global public health. However, due to unmet diagnostic and therapeutic needs, there is great interest in the development of novel translational approaches. Nanoparticle-based approaches offer novel opportunities for efficient and specific drug delivery to liver cells, as a step toward precision medicines. In this review, the authors highlight recent advances in nanomedicines for the generation of novel diagnostic and therapeutic tools for nonalcoholic fatty liver disease and related liver diseases.

Plasma Metabolomic and Lipidomic Profiling of Metabolic Dysfunction-Associated Fatty Liver Disease in Humans Using an Untargeted Multiplatform Approach

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a complex disorder that is implicated in dysregulations in multiple biological pathways, orchestrated by interactions between genetic predisposition, metabolic syndromes and environmental factors. The limited knowledge of its pathogenesis is one of the bottlenecks in the development of prognostic and therapeutic options for MAFLD. Moreover, the extent to which metabolic pathways are altered due to ongoing hepatic steatosis, inflammation and fibrosis and subsequent liver damage remains unclear. To uncover potential MAFLD pathogenesis in humans, we employed an untargeted nuclear magnetic resonance (NMR) spectroscopy- and high-resolution mass spectrometry (HRMS)-based multiplatform approach combined with a computational multiblock omics framework to characterize the plasma metabolomes and lipidomes of obese patients without (n = 19) or with liver biopsy confirmed MAFLD (n = 63). Metabolite features associated with MAFLD were identified using a metabolome-wide association study pipeline that tested for the relationships between feature responses and MAFLD. A metabolic pathway enrichment analysis revealed 16 pathways associated with MAFLD and highlighted pathway changes, including amino acid metabolism, bile acid metabolism, carnitine shuttle, fatty acid metabolism, glycerophospholipid metabolism, arachidonic acid metabolism and steroid metabolism. These results suggested that there were alterations in energy metabolism, specifically amino acid and lipid metabolism, and pointed to the pathways being implicated in alerted liver function, mitochondrial dysfunctions and immune system disorders, which have previously been linked to MAFLD in human and animal studies. Together, this study revealed specific metabolic alterations associated with MAFLD and supported the idea that MAFLD is fundamentally a metabolism-related disorder, thereby providing new perspectives for diagnostic and therapeutic strategies.

Race and Ethnicity in Non-Alcoholic Fatty Liver Disease (NAFLD): A Narrative Review

Non-alcoholic fatty liver disease (NAFLD) is a significant public health concern worldwide with a complex etiology attributed to behavioural, environmental, and genetic causes. The worldwide prevalence of NAFLD is estimated to be 32.4% and constantly rising. Global data, however, indicate considerable heterogeneity among studies for both NAFLD prevalence and incidence. Identifying variables that affect the estimated epidemiological measures is essential to all stakeholders, including patients, researchers, healthcare providers, and policymakers. Besides helping with the research on disease etiology, it helps to identify individuals at risk of the disease, which in turn will outline the focus of the preventive measures and help to fittingly tailor individualized treatments, targeted prevention, screening, or treatment programs. Several studies suggest differences in the prevalence and severity of NAFLD by race or ethnicity, which may be linked to differences in lifestyle, diet, metabolic comorbidity profile, and genetic background, among others. Race/ethnicity research is essential as it can provide valuable information regarding biological and genetic differences among people with similar cultural, dietary, and geographical backgrounds. In this review, we examined the existing literature on race/ethnicity differences in susceptibility to NAFLD and discussed the contributing variables to such differences, including diet and physical activity, the comorbidity profile, and genetic susceptibility. We also reviewed the limitations of race/ethnicity studies in NAFLD.

Nonalcoholic fatty liver disease (NAFLD) from pathogenesis to treatment concepts in humans

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) comprises hepatic alterations with increased lipid accumulation (steatosis) without or with inflammation (nonalcoholic steatohepatitis, NASH) and/or fibrosis in the absence of other causes of liver disease. NAFLD is developing as a burgeoning health challenge, mainly due to the worldwide obesity and diabetes epidemics.

SCOPE OF REVIEW

This review summarizes the knowledge on the pathogenesis underlying NAFLD by focusing on studies in humans and on hypercaloric nutrition, including effects of saturated fat and fructose, as well as adipose tissue dysfunction, leading to hepatic lipotoxicity, abnormal mitochondrial function, and oxidative stress, and highlights intestinal dysbiosis. These mechanisms are discussed in the context of current treatments targeting metabolic pathways and the results of related clinical trials.

MAJOR CONCLUSIONS

Recent studies have provided evidence that certain conditions, for example, the severe insulin-resistant diabetes (SIRD) subgroup (cluster) and the presence of an increasing number of gene variants, seem to predispose for excessive risk of NAFLD and its accelerated progression. Recent clinical trials have been frequently unsuccessful in halting or preventing NAFLD progression, perhaps partly due to including unselected cohorts in later stages of NAFLD. On the basis of this literature review, this study proposed screening in individuals with the highest genetic or acquired risk of disease progression, for example, the SIRD subgroup, and developing treatment concepts targeting the earliest pathophysiolgical alterations, namely, adipocyte dysfunction and insulin resistance.

Human biomimetic liver microphysiology systems in drug development and precision medicine

Microphysiology systems (MPS), also called organs-on-chips and tissue chips, are miniaturized functional units of organs constructed with multiple cell types under a variety of physical and biochemical environmental cues that complement animal models as part of a new paradigm of drug discovery and development. Biomimetic human liver MPS have evolved from simpler 2D cell models, spheroids and organoids to address the increasing need to understand patient-specific mechanisms of complex and rare diseases, the response to therapeutic treatments, and the absorption, distribution, metabolism, excretion and toxicity of potential therapeutics. The parallel development and application of transdisciplinary technologies, including microfluidic devices, bioprinting, engineered matrix materials, defined physiological and pathophysiological media, patient-derived primary cells, and pluripotent stem cells as well as synthetic biology to engineer cell genes and functions, have created the potential to produce patient-specific, biomimetic MPS for detailed mechanistic studies. It is projected that success in the development and maturation of patient-derived MPS with known genotypes and fully matured adult phenotypes will lead to advanced applications in precision medicine. In this Review, we examine human biomimetic liver MPS that are designed to recapitulate the liver acinus structure and functions to enhance our knowledge of the mechanisms of disease progression and of the absorption, distribution, metabolism, excretion and toxicity of therapeutic candidates and drugs as well as to evaluate their mechanisms of action and their application in precision medicine and preclinical trials.

HbA1c may contribute to the development of non-alcoholic fatty liver disease even at normal-range levels

Previous clinical studies highlighted nonalcoholic fatty liver disease (NAFLD) as a hepatic facet of metabolic syndrome, which progresses toward Type 2 diabetes along with an elevation of HbA1c in the blood. Longitudinal observations were performed in a cohort of 2811 participants with no liver disease at inception. The rate of the conversion into NAFLD was 15.7% (440/2811), with a steady increase in prevalence observed in sub-cohorts with increasing HbA1c levels. Moreover, regression analysis indicated that HbA1c levels serve as the risk factors for NAFLD after multiple adjustments (odds ratio: 1.58, P-value < 0.004). When HbA1c-related molecular networks were investigated using natural language programming algorithms, multiple genetic/small molecular (SM) pathways were highlighted as connectors between the HbA1c levels and the development of NAFLD, including ones for nitric oxide, hypoxia and receptor for advanced glycation end products (RAGE). Our results suggest that increased levels of HbA1c may contribute to the progression of NAFLD either directly, by stimulating RAGE or indirectly, through the promotion of hypoxia and suppression of the release of NO. Further studies are needed to test the impact of HbA1c on the development of the chronic liver disease.

Development of a novel machine learning model to predict presence of nonalcoholic steatohepatitis

Objective

To develop a computer model to predict patients with nonalcoholic steatohepatitis (NASH) using machine learning (ML).

Materials and Methods

This retrospective study utilized two databases: a) the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) nonalcoholic fatty liver disease (NAFLD) adult database (2004-2009), and b) the Optum^® de-identified Electronic Health Record dataset (2007-2018), a real-world dataset representative of common electronic health records in the United States. We developed an ML model to predict NASH, using confirmed NASH and non-NASH based on liver histology results in the NIDDK dataset to train the model.

Results

Models were trained and tested on NIDDK NAFLD data (704 patients) and the best-performing models evaluated on Optum data (~3,000,000 patients). An eXtreme Gradient Boosting model (XGBoost) consisting of 14 features exhibited high performance as measured by area under the curve (0.82), sensitivity (81%), and precision (81%) in predicting NASH. Slightly reduced performance was observed with an abbreviated feature set of 5 variables (0.79, 80%, 80%, respectively). The full model demonstrated good performance (AUC 0.76) to predict NASH in Optum data.

Discussion

The proposed model, named NASHmap, is the first ML model developed with confirmed NASH and non-NASH cases as determined through liver biopsy and validated on a large, real-world patient dataset. Both the 14 and 5-feature versions exhibit high performance.

Conclusion

The NASHmap model is a convenient and high performing tool that could be used to identify patients likely to have NASH in clinical settings, allowing better patient management and optimal allocation of clinical resources.

Assessment of Lifestyle Factors Helps to Identify Liver Fibrosis Due to Non-Alcoholic Fatty Liver Disease in Obesity

Only some individuals with obesity develop liver fibrosis due to non-alcoholic fatty liver disease (NAFLD-fibrosis). We determined whether detailed assessment of lifestyle factors in addition to physical, biochemical and genetic factors helps in identification of these patients. A total of 100 patients with obesity (mean BMI 40.0 ± 0.6 kg/m²) referred for bariatric surgery at the Helsinki University Hospital underwent a liver biopsy to evaluate liver histology. Physical activity was determined by accelerometer recordings and by the Modifiable Activity Questionnaire, diet by the FINRISK Food Frequency Questionnaire, and other lifestyle factors, such as sleep patterns and smoking, by face-to-face interviews. Physical and biochemical parameters and genetic risk score (GRS based on variants in PNPLA3, TM6SF2, MBOAT7 and HSD17B13) were measured. Of all participants 49% had NAFLD-fibrosis. Independent predictors of NAFLD-fibrosis were low moderate-to-vigorous physical activity, high red meat intake, low carbohydrate intake, smoking, HbA_1c, triglycerides and GRS. A model including these factors (areas under the receiver operating characteristics curve (AUROC) 0.90 (95% CI 0.84–0.96)) identified NAFLD-fibrosis significantly more accurately than a model including all but lifestyle factors (AUROC 0.82 (95% CI 0.73–0.91)) or models including lifestyle, physical and biochemical, or genetic factors alone. Assessment of lifestyle parameters in addition to physical, biochemical and genetic factors helps to identify obese patients with NAFLD-fibrosis.

Effects of TM6SF2 E167K on hepatic lipid and very low-density lipoprotein metabolism in humans

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic lipid accumulation. The transmembrane 6 superfamily member 2 (TM6SF2) E167K genetic variant associates with NAFLD and with reduced plasma triglyceride levels in humans. However, the molecular mechanisms underlying these associations remain unclear. We hypothesized that TM6SF2 E167K affects hepatic very low-density lipoprotein (VLDL) secretion and studied the kinetics of apolipoprotein B100 (apoB100) and triglyceride metabolism in VLDL in homozygous subjects. In 10 homozygote TM6SF2 E167K carriers and 10 matched controls, we employed stable-isotope tracer and compartmental modeling techniques to determine apoB100 and triglyceride kinetics in the 2 major VLDL subfractions: large triglyceride-rich VLDL₁ and smaller, less triglyceride-rich VLDL₂. VLDL₁-apoB100 production was markedly reduced in homozygote TM6SF2 E167K carriers compared with controls. Likewise, VLDL₁-triglyceride production was 35% lower in the TM6SF2 E167K carriers. In contrast, the direct production rates for VLDL₂-apoB100 and triglyceride were not different between carriers and controls. In conclusion, the TM6SF2 E167K genetic variant was linked to a specific reduction in hepatic secretion of large triglyceride-rich VLDL₁. The impaired secretion of VLDL₁ explains the reduced plasma triglyceride concentration and provides a basis for understanding the lower risk of cardiovascular disease associated with the TM6SF2 E167K genetic variant.

Noncoding RNAs in Nonalcoholic Fatty Liver Disease: Potential Diagnosis and Prognosis Biomarkers

Nonalcoholic fatty liver disease (NAFLD) is currently the most common chronic liver disease worldwide in part due to the concomitant obesity pandemic and insulin resistance (IR). It is increasingly becoming evident that NAFLD is a disease affecting numerous extrahepatic vital organs and regulatory pathways. The molecular mechanisms underlying the nonalcoholic steatosis formation are poorly understood, and little information is available on the pathways that are responsible for the progressive hepatocellular damage that follows lipid accumulation. Recently, much research has focused on the identification of the epigenetic modifications that contribute to NAFLD pathogenesis. Noncoding RNAs (ncRNAs) are one of such epigenetic factors that could be implicated in the NAFLD development and progression. In this review, we summarize the current knowledge of the genetic and epigenetic factors potentially underlying the disease. Particular emphasis will be put on the contribution of microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs) to the pathophysiology of NAFLD as well as their potential use as therapeutic targets or as markers for the prediction and the progression of the disease.

Predicting and elucidating the etiology of fatty liver disease: A machine learning modeling and validation study in the IMI DIRECT cohorts

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is highly prevalent and causes serious health complications in individuals with and without type 2 diabetes (T2D). Early diagnosis of NAFLD is important, as this can help prevent irreversible damage to the liver and, ultimately, hepatocellular carcinomas. We sought to expand etiological understanding and develop a diagnostic tool for NAFLD using machine learning.

METHODS AND FINDINGS

We utilized the baseline data from IMI DIRECT, a multicenter prospective cohort study of 3,029 European-ancestry adults recently diagnosed with T2D (n = 795) or at high risk of developing the disease (n = 2,234). Multi-omics (genetic, transcriptomic, proteomic, and metabolomic) and clinical (liver enzymes and other serological biomarkers, anthropometry, measures of beta-cell function, insulin sensitivity, and lifestyle) data comprised the key input variables. The models were trained on MRI-image-derived liver fat content (<5% or ≥5%) available for 1,514 participants. We applied LASSO (least absolute shrinkage and selection operator) to select features from the different layers of omics data and random forest analysis to develop the models. The prediction models included clinical and omics variables separately or in combination. A model including all omics and clinical variables yielded a cross-validated receiver operating characteristic area under the curve (ROCAUC) of 0.84 (95% CI 0.82, 0.86; p < 0.001), which compared with a ROCAUC of 0.82 (95% CI 0.81, 0.83; p < 0.001) for a model including 9 clinically accessible variables. The IMI DIRECT prediction models outperformed existing noninvasive NAFLD prediction tools. One limitation is that these analyses were performed in adults of European ancestry residing in northern Europe, and it is unknown how well these findings will translate to people of other ancestries and exposed to environmental risk factors that differ from those of the present cohort. Another key limitation of this study is that the prediction was done on a binary outcome of liver fat quantity (<5% or ≥5%) rather than a continuous one.

CONCLUSIONS

In this study, we developed several models with different combinations of clinical and omics data and identified biological features that appear to be associated with liver fat accumulation. In general, the clinical variables showed better prediction ability than the complex omics variables. However, the combination of omics and clinical variables yielded the highest accuracy. We have incorporated the developed clinical models into a web interface (see: https://www.predictliverfat.org/) and made it available to the community.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03814915.

Noninvasive Evaluation of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent liver diseases and can progress to advanced fibrosis and end-stage liver disease. Thus, intensive research has been performed to develop noninvasive methods for the diagnosis of nonalcoholic steatohepatitis (NASH) and fibrosis. Currently, no single noninvasive tool covers all of the stages of pathologies and conditions of NAFLD, and the cost and feasibility of known techniques are also important issues. Blood biomarkers for NAFLD may be useful to select subjects who need ultrasonography (US) screening for NAFLD, and noninvasive tools for assessing fibrosis may be helpful to exclude the probability of significant fibrosis and to predict advanced fibrosis, thus guiding the decision of whether to perform liver biopsy in patients with NAFLD. Among various methods, magnetic resonance-based methods have been shown to perform better than other methods in assessing steatosis as well as in detecting hepatic fibrosis. Many genetic markers are associated with the development and progression of NAFLD. Further well-designed studies are needed to determine which biomarker panels, imaging studies, genetic marker panels, or combinations thereof perform well for diagnosing NAFLD, differentiating NASH and fibrosis, and following-up NAFLD, respectively.

Non-Alcoholic Fatty Liver Disease in Patients with Type 2 Diabetes Mellitus: A Position Statement of the Fatty Liver Research Group of the Korean Diabetes Association

This clinical practice position statement, a product of the Fatty Liver Research Group of the Korean Diabetes Association, proposes recommendations for the diagnosis, progression and/or severity assessment, management, and follow-up of non-alcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes mellitus (T2DM). Patients with both T2DM and NAFLD have an increased risk of non-alcoholic steatohepatitis (NASH) and fibrosis and a higher risk of cardiovascular diseases and diabetic complications compared to those without NAFLD. With regards to the evaluation of patients with T2DM and NAFLD, ultrasonography-based stepwise approaches using noninvasive biomarker models such as fibrosis-4 or the NAFLD fibrosis score as well as imaging studies such as vibration-controlled transient elastography with controlled attenuation parameter or magnetic resonance imaging-proton density fat fraction are recommended. After the diagnosis of NAFLD, the stage of fibrosis needs to be assessed appropriately. For management, weight reduction achieved by lifestyle modification has proven beneficial and is recommended in combination with antidiabetic agent(s). Evidence that some antidiabetic agents improve NAFLD/NASH with fibrosis in patients with T2DM is emerging. However, there are currently no definite pharmacologic treatments for NAFLD in patients with T2DM. For specific cases, bariatric surgery may be an option if indicated.

Differential Associations of Circulating MicroRNAs With Pathogenic Factors in NAFLD

Nonalcoholic fatty liver disease (NAFLD) is a heterogeneous disease driven by genetic and environmental factors. MicroRNAs (miRNAs) serve as pleiotropic post-transcriptional regulators of cellular pathways. Although several miRNAs have been associated with NAFLD and fibrosis, there are limited studies in humans examining their differential association with pathogenic factors or histological features of NAFLD. We examined the differential relationships of five of the best-described circulating microRNAs (miR-34a, miR-122, miR-191, miR-192, and miR-200a) with histological features and pathogenic factors of NAFLD. A cross-sectional study was conducted to examine the relationship between relative levels of circulating microRNAs standardized by z-scores and histological features of NAFLD, common NAFLD genetic polymorphisms, and insulin resistance measured by the enhanced lipoprotein insulin resistance index in 132 subjects with biopsy-proven NAFLD. We found that miR-34a, miR-122, miR-192, miR-200a, but not miR-191, strongly correlate with fibrosis in NAFLD by increases of 0.20 to 0.40 SD (P < 0.005) with each stage of fibrosis. In multivariate analysis, miR-34a, miR-122, and miR-192 levels are independently associated with hepatic steatosis and fibrosis, but not lobular inflammation or ballooning degeneration, whereas miR-200a is only associated with fibrosis. Among the four miRNAs, miR-34a, miR-122, and miR-192 are associated with pathogenic factors of NAFLD, including insulin resistance measured by eLP-IR, patatin-like phospholipase domain containing 3 I148M, and transmembrane 6 superfamily 2 (TM6SF2) E167K polymorphisms. In contrast, miR-200a is only associated with the TM6SF2 E167K variant. Finally, miR-34a has the strongest predictive value for various stages of fibrosis, with C-statistic approximates-combined predictive score for miRNAs. Conclusion: miR-34a, miR-122, miR-192, and miR-200a demonstrate strong associations with NAFLD severity by histology, but differential associations with pathogenic factors.

Association of GCKR Gene Polymorphisms with the Risk of Nonalcoholic Fatty Liver Disease and Coronary Artery Disease in a Chinese Northern Han Population

Background and Aims: Accumulated studies have evaluated the effects of glucokinase regulatory protein (GCKR) gene polymorphisms on the risk of nonalcoholic fatty liver disease (NAFLD) and coronary artery disease (CAD), but the association of GCKR polymorphisms with the risk of NAFLD and CAD in the Chinese Han population have remained unclear. The aim of this study was to investigate the association between GCKR gene polymorphisms (rs780094 and rs1260326) and the risk of NAFLD and CAD in NAFLD patients in a Chinese Northern Han population. Methods: GCKR rs780094 and rs1260326 gene polymorphisms were genotyped by polymerase chain reaction sequencing for B-type ultrasonography-proven NAFLD patients with (n = 82) or without (n = 142) CAD, and in healthy controls (n = 152). Serum lipid profiles' levels were determined using biochemical methods. Statistical analyses were conducted using SPSS 22.0 statistical software. Results: As the results showed, significant differences in the serum lipid profiles existed between each group. No significant differences were observed in the distributions of genotypes and alleles of GCKR rs780094 and rs1260326 in each group. The GCKR rs780094 T and rs1260326 T allele carriers possessed decreased body mass index value, and serum fasting plasma glucose and TG levels in the overall subjects, respectively. In addition, the GCKR rs780094 T allele carriers possessed decreased serum fasting plasma glucose level in the controls and NAFLD + CAD patients. Conclusions: GCKR rs780094 and rs1260326 polymorphisms were found to be not associated with the risk of NAFLD nor of CAD in NAFLD patients in this Chinese Northern Han population. GCKR rs780094 T and rs1260326 T alleles could affect the body mass index value and serum fasting plasma glucose and triglyceride levels.

Variations in hepatic lipid species of age-matched male mice fed a methionine-choline-deficient diet and housed in different animal facilities

Background

Non-alcoholic steatohepatitis (NASH) is a common disease and feeding mice a methionine-choline-deficient (MCD) diet is a frequently used model to study its pathophysiology. Genetic and environmental factors influence NASH development and liver lipid content, which was studied herein using C57BL/6 J mice bred in two different animal facilities.

Methods

Age-matched male C57BL/6 J mice bred in two different animal facilities (later on referred to as WT1 and WT2) at the University Hospital of Regensburg were fed identical MCD or control chows for 2 weeks. Hepatic gene and protein expression and lipid composition were determined.

Results

NASH was associated with increased hepatic triglycerides, which were actually higher in WT1 than WT2 liver in both dietary groups. Cholesterol contributes to hepatic injury but was only elevated in WT2 NASH liver. Ceramides account for insulin resistance and cell death, and ceramide species d18:1/16:0 and d18:1/18:0 were higher in the NASH liver of both groups. Saturated sphingomyelins only declined in WT1 NASH liver. Lysophosphatidylcholine concentrations were quite normal in NASH and only one of the 12 altered phosphatidylcholine species declined in NASH liver of both groups. Very few phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol species were comparably regulated in NASH liver of both animal groups. Seven of these lipid species declined and two increased in NASH. Notably, hepatic mRNA expression of proinflammatory (F4/80, CD68, IL-6, TNF and chemerin) and profibrotic genes (TGF beta and alpha SMA) was comparable in WT1 and WT2 mice.

Conclusions

Mice housed and bred in different animal facilities had comparable disease severity of NASH whereas liver lipids varied among the groups. Thus, there was no specific lipid signature for NASH in the MCD model.

Electronic supplementary material

The online version of this article (10.1186/s12944-019-1114-4) contains supplementary material, which is available to authorized users.

Magnitude of Nonalcoholic Fatty Liver Disease: Western Perspective

The incidence of nonalcoholic fatty liver disease (NAFLD) is continuing to rise worldwide, and it is estimated that this disquieting trend will continue for another 10-15 years before prevalence begins to decrease. NAFLD is the hepatic manifestation of metabolic syndrome. As obesity, diabetes, and other lifestyle-related diseases continue to rise, the spectrum of NAFLD, e.g., nonalcoholic steatohepatitis, liver fibrosis, liver cirrhosis, liver-related morbidity, and mortality, will increase in parallel. Its widespread prevalence and associated economic burden have drawn significant attention, and a multitude of pharmaceutical companies are participating in active research trying to find a "cure". Unfortunately, as of now, no targeted treatment exists to treat this condition, and therefore, emphasis has been on its prevention. The current review focuses on the epidemiology, clinical characteristics, risk factors, and clinical outcomes of NAFLD in Western countries. It is important to understand the magnitude of NAFLD and its risk factors in Western countries where the prevalence of NAFLD has now reached epidemic proportions to identify the best strategy to prevent and possibly control this epidemic.

TRIB1 rs17321515 and rs2954029 gene polymorphisms increase the risk of non-alcoholic fatty liver disease in Chinese Han population

BACKGROUND

Dysregulation of the lipid homeostasis is an independent risk factor for non-alcoholic fatty liver disease (NAFLD). Some studies had demonstrated that TRIB1 gene polymorphisms affect the plasma lipids metabolism, but no related data was available for TRIB1 gene polymorphisms in the lipids metabolism in Chinses Han population. The present study was conducted to investigate the association between TRIB1 gene polymorphisms (rs17321515 and rs2954029) and the risk of NAFLD in Chinese Han population and their effects on serum lipid profiles.

PATIENTS AND METHODS

TRIB1 rs17321515 and rs2954029 gene polymorphisms were genotyped using the polymerase chain reaction (PCR) in B-type ultrasonography-proven NAFLD patients (n = 146) and healthy controls (n = 175). Serum lipid profiles were determined using biochemical methods. Statistical analyses were performed using SPSS 22.0 statistical software.

RESULTS

The allele distributions of TRIB1 rs17321515 A and rs2954029 A were significant different between the NAFLD patients and healthy controls (P = 0.026, P = 0.045, respectively). The genotype distribution of TRIB1 rs17321515 was significant different between NAFLD patients and healthy controls (P = 0.038). The TRIB1 rs17321515 GA + AA genotype and TRIB1 rs2954029 TA + AA genotype markedly increase the NAFLD risk (OR = 1.885; 95%CI: 1.157-3.070; OR = 1.627; 95%CI: 1.011-2.619, respectively), after adjusted for age, gender, and body mass index, the NAFLD risk still significant (OR = 2.240; 95%CI: 1.196-4.197; OR = 2.050; 95%CI: 1.110-3.786, respectively). In addition, TRIB1 rs17321515 A and rs2954029 A carriers possess the higher lipid profiles in the included subjects.

CONCLUSIONS

TRIB1 rs17321515 and rs2954029 were significant associated with the risk of NAFLD in Chinese Han population. The rs17321515 A and rs2954029 A allele increases the serum lipid profiles in Chinese Han population.

Omega-3 fatty acids and nonalcoholic fatty liver disease in adults and children: where do we stand?

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic fatty liver disease worldwide. The incidence of NAFLD parallels the prevalence of obesity. Moreover, NAFLD can progress to nonalcoholic steatohepatitis (NASH), cirrhosis and primary hepatocellular cancer (HCC). As such, NAFLD has become a major public health concern. We discuss recent clinical trials and meta-analyses evaluating the efficacy of C20-22 ω3 polyunsaturated fatty acids (PUFA) to attenuate preexisting NAFLD in adults and children.

RECENT FINDINGS

Humans with NAFLD and NASH; and preclinical mouse models of NASH, have a high abundance of hepatic saturated (SFA) and monounsaturated (MUFA) fat, but a low abundance of hepatic C20-22 ω3 PUFA. This change in hepatic fat type and abundance is associated with hepatic lipotoxicity, inflammation, oxidative stress and fibrosis. Recent meta-analyses and clinical trials evaluated the capacity of C20-22 ω3 PUFA dietary supplementation to improve health outcomes in adults and children with preexisting NAFLD. Diets supplemented with docosahexaenoic acid (DHA, 22 : 6,ω3) alone or with eicosapentaenoic acid (EPA, 20 : 5,ω3) are tolerated and effective at lowering liver fat in NAFLD patients. However, outcomes are mixed with respect to C20-22 ω3 PUFA attenuation of more severe NAFLD markers, such as hepatic injury, inflammation and fibrosis.

SUMMARY

These studies suggest that dietary supplementation with C20-22 ω3 PUFA should be considered as a viable and effective option to lower liver fat in obese adults and children with NAFLD.