Nonalcoholic steatohepatitis versus steatosis: adipose tissue insulin resistance and dysfunctional response to fat ingestion predict liver injury and altered glucose and lipoprotein metabolism

Insulin Resistance/Sensitivity Measures as Screening Indicators of Metabolic-Associated Fatty Liver Disease and Liver Fibrosis

BACKGROUND

Measures of insulin resistance (IR)/sensitivity (IS) are emerging tools to identify metabolic-associated fatty liver disease (MAFLD). However, the comprehensive assessment of the performance of various indicators is limited. Moreover, the utility of measures of IR/IS in detecting liver fibrosis remains unclear.

AIMS

To evaluate the predictive ability of seventeen IR/IS and two beta cell function indices to identify MAFLD and liver fibrosis.

METHODS

A cross-sectional study was conducted on individuals aged 25-75 years. Transient elastography was used to estimate liver stiffness and controlled attenuation parameter. The following measures were computed: homeostatic model assessment (HOMA/HOMA2) for IR, IS, and beta cell function; QUICKI; Bennett index; glucose/insulin; FIRI; McAuley index; Reynaud index; SPISE index; TyG; TyG-BMI; TyG-WC; TyG-WHtR; TG/HDL; and METS-IR. Subgroup analyses were performed according to age, gender, diabetes status, and body weight.

RESULTS

A total of 644 individuals were included in our analysis. MAFLD and significant liver fibrosis were detected in 320 (49.7%) and 80 (12.4%) of the participants, respectively. All measures of IR/IS identified MAFLD and liver fibrosis. However, TyG-WC, TyG-BMI, and TyG-WHtR were the top three indicators that identified MAFLD. Measures that include insulin level in their mathematical calculation, namely, Raynaud index, HOMA-IR, HOMA 2-IR, FIRI, and QUICKI had the best performance in identifying liver fibrosis in the entire population, as well as among the study subgroups.

CONCLUSIONS

TyG-WC, TyG-BMI, and TyG-WHtR were the best predictors of MAFLD. Insulin-based measures had better performances in the detection of advanced fibrosis. This was independent of age, gender, obesity, or diabetes status.

Critical Evaluation of Indices Used to Assess β-Cell Function

The assessment of β-cell function, defined as the relationship between insulin secretion rate (ISR) and plasma glucose, is not standardized and often involves any of a number of β-cell function indices. We compared β-cell function by using popular indices obtained during basal conditions and after glucose ingestion, including the HOMA-B index, the basal ISR (or plasma insulin)-to-plasma glucose concentration ratio, the insulinogenic and ISRogenic indices, the ISR (or plasma insulin)-to-plasma glucose concentration areas (or incremental areas) under the curve ratio, and the disposition index, which integrates a specific β-cell function index value with an estimate of insulin sensitivity, between lean people with normal fasting glucose (NFG) and normal glucose tolerance (NGT) (n = 50) and four groups of people with obesity (n = 188) with 1) NFG-NGT, 2) NFG and impaired glucose tolerance (IGT), 3) impaired fasting glucose (IFG) and IGT, and 4) type 2 diabetes. We also plotted the ISR-plasma glucose relationship before and after glucose ingestion and used a statistical mixed-effects model to evaluate group differences in this relationship (i.e., β-cell function). Index-based group differences in β-cell function produced contradicting results and did not reflect the group differences of the actual observed ISR-glucose relationship or, in the case of the disposition index, group differences in glycemic status. The discrepancy in results is likely due to incorrect mathematical assumptions that are involved in computing indices, which can be overcome by evaluating the relationship between ISR and plasma glucose with an appropriate statistical model. Data obtained with common β-cell function indices should be interpreted cautiously.

ARTICLE HIGHLIGHTS

Thrombospondin-1 promotes liver fibrosis by enhancing TGF-β action in hepatic stellate cells

Insulin resistance in adipose tissue is thought to be a key contributor to the pathogenesis of various metabolic disorders including metabolic dysfunction-associated steatotic liver disease/metabolic dysfunction-associated steatohepatitis (MASLD/MASH), but the mechanism underlying this contribution to MASLD/MASH has remained unknown. We previously showed that dysregulation of the PDK1-FoxO1 signaling axis in adipocytes plays a role in the development of MASLD/MASH by analysis of adipocyte-specific PDK1 knockout (A-PDK1KO) and adipocyte-specific PDK1/FoxO1 double-knockout (A-PDK1/FoxO1DKO) mice. We here focused on the role of the extracellular matrix protein thrombospondin-1 (TSP-1) as a secreted factor whose expression in adipose tissue is increased in A-PDK1KO mice and normalized in A-PDK1/FoxO1DKO mice. Genetic ablation of TSP-1 markedly ameliorated liver fibrosis in A-PDK1KO mice fed a high-fat diet. With regard to the potential mechanism of this effect, TSP-1 augmented the expression of fibrosis-related genes induced by TGF-β in LX-2 human hepatic stellate cells. We also showed that TSP-1 expression and secretion were negatively regulated by insulin signaling via the PDK1-FoxO1 axis in cultured adipocytes. Our results thus indicate that TSP-1 plays a key role in the pathogenesis of liver fibrosis in MASH. Regulation of TSP-1 expression by PDK1-FoxO1 axis in adipocytes may provide a basis for targeted therapy of hepatic fibrosis in individuals with MASH.

Glucokinase regulatory protein: a balancing act between glucose and lipid metabolism in NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a common liver disease worldwide, affected by both genetics and environment. Type 2 diabetes (T2D) stands as an independent environmental risk factor that precipitates the onset of hepatic steatosis and accelerates its progression to severe stages of liver damage. Furthermore, the coexistence of T2D and NAFLD magnifies the risk of cardiovascular disease synergistically. However, the association between genetic susceptibility and metabolic risk factors in NAFLD remains incompletely understood. The glucokinase regulator gene (GCKR), responsible for encoding the glucokinase regulatory protein (GKRP), acts as a regulator and protector of the glucose-metabolizing enzyme glucokinase (GK) in the liver. Two common variants (rs1260326 and rs780094) within the GCKR gene have been associated with a lower risk for T2D but a higher risk for NAFLD. Recent studies underscore that T2D presence significantly amplifies the effect of the GCKR gene, thereby increasing the risk of NASH and fibrosis in NAFLD patients. In this review, we focus on the critical roles of GKRP in T2D and NAFLD, drawing upon insights from genetic and biological studies. Notably, prior attempts at drug development targeting GK with glucokinase activators (GKAs) have shown potential risks of augmented plasma triglycerides or NAFLD. Conversely, overexpression of GKRP in diabetic rats improved glucose tolerance without causing NAFLD, suggesting the crucial regulatory role of GKRP in maintaining hepatic glucose and lipid metabolism balance. Collectively, this review sheds new light on the complex interaction between genes and environment in NAFLD, focusing on the GCKR gene. By integrating evidence from genetics, biology, and drug development, we reassess the therapeutic potential of targeting GK or GKRP for metabolic disease treatment. Emerging evidence suggests that selectively activating GK or enhancing GK-GKRP binding may represent a holistic strategy for restoring glucose and lipid metabolic balance.

Lipidomics in pathogenesis, progression and treatment of nonalcoholic steatohepatitis (NASH): Recent advances

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease affecting up to 30% of the general adult population. NAFLD encompasses a histological spectrum ranging from pure steatosis to non-alcoholic steatohepatitis (NASH). NASH can progress to cirrhosis and is becoming the most common indication for liver transplantation, as a result of increasing disease prevalence and of the absence of approved treatments. Lipidomic readouts of liver blood and urine samples from experimental models and from NASH patients disclosed an abnormal lipid composition and metabolism. Collectively, these changes impair organelle function and promote cell damage, necro-inflammation and fibrosis, a condition termed lipotoxicity. We will discuss the lipid species and metabolic pathways leading to NASH development and progression to cirrhosis, as well as and those species that can contribute to inflammation resolution and fibrosis regression. We will also focus on emerging lipid-based therapeutic opportunities, including specialized proresolving lipid molecules and macrovesicles contributing to cell-to-cell communication and NASH pathophysiology.

Insulin resistance in adipose tissue and metabolic diseases

Adipose tissue regulates systemic energy metabolism through adipokine production as well as energy storage and energy supply to other organs in response to changes in energy status. Adipose tissue dysfunction is therefore thought to be a key contributor to the pathogenesis of a variety of metabolic disorders including nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Given that insulin plays a central role in the regulation of many aspects of adipocyte function, insulin resistance in adipose tissue is implicated in the pathogenesis of metabolic disorders as a cause of adipose tissue dysfunction. The concept of metabolic dysfunction-associated fatty liver disease (MAFLD) has recently been proposed for liver disease associated with metabolic disorders in both obese and nonobese individuals, with insulin resistance in adipose tissue likely being an important factor in its pathogenesis. This review outlines the relation between insulin resistance in adipose tissue and metabolic disorders, with a focus on the physiological relevance and mechanism of action of 3'-phosphoinositide-dependent kinase 1 (PDK1), a key kinase in insulin signaling, and its downstream transcription factor FoxO1 in adipocytes.

The association between visceral adipocyte hypertrophy and NAFLD in subjects with different degrees of adiposity

OBJECTIVE

To investigate the association between visceral adipocyte hypertrophy and the onset and development of non-alcoholic fatty liver disease (NAFLD) in subjects with different degrees of adiposity.

METHODS

Omental adipose tissue and liver biopsies were collected from obese subjects. NAFLD was defined according to the NASH Clinical Research Network scoring system. Adipocyte size was measured using pathological section analysis. Adipose tissue insulin resistance (Adipo-IR) was calculated as fasting insulin (pmol/L) × fasting free fatty acid concentration (mmol/L).

RESULTS

In total, 275 obese patients were enrolled, including 158 females and 58 males with NAFLD. In females, adipocyte size was significantly larger in NAFLD participants as compared to the controls (99.37 ± 14.18 vs. 84.14 ± 12.65 [Formula: see text]m, p < 0.001). Moreover, adipocyte size was larger in females with non-alcoholic steatohepatitis (NASH) as compared to those with non-alcoholic fatty liver (NAFL) (101.45 ± 12.77 vs. 95.79 ± 15.80 [Formula: see text]m, p = 0.015). Mediation analysis showed that adipocyte size impacted the NAFLD activity score through Adipo-IR (b = 0.007 [95% bootstrap CI 0.002, 0.013]). Furthermore, the females were divided into: Q1 (BMI < 32.5 kg/m²), Q2 (BMI 32.5-35.5 kg/m²), Q3 (BMI 35.5-38.8 kg/m²) and Q4 (BMI ≥ 38.8 kg/m²) according to BMI quartiles. Omental adipocyte size was larger in NAFLD subjects in Q1-Q3, but not in Q4. No similar results were observed in males.

CONCLUSION

For the first time, we reported that visceral adipocyte hypertrophy was associated with the onset and progression of NAFLD in mild to moderate adiposity but not in severe obesity, which may be mediated by adipose tissue insulin resistance.

ANALYSIS THE METABOLIC STATUS OF PATIENTS WITH CORONARY ARTERY DISEASE AND NONALCOHOLIC FATTY LIVER DISEASE DEPENDING ON BODY MASS INDEX

OBJECTIVE

The aim: To analyze the metabolic status of patients with coronary artery disease and nonalcoholic fatty liver disease depending on body mass index.

PATIENTS AND METHODS

Materials and methods: The cohort of patients included 107 people with coronary artery disease (CAD), nonalcoholic fatty liver disease (NAFLD) and over¬weight (n=56) or obesity (n=51). In all patients glucose, insulin, HbA1c, HOMA-IR, hsCRP, transaminases, creatinine, urea, uric acid, lipid profile, anthropometric parameters and ultrasound elastography were measured.

RESULTS

Results: During the analysis of serum lipid spectrum in patients with obesity: lower levels of HDL and higher TG concentration compared with patients who had overweight. The insulin level was almost twice as high as in patients with overweight and the HOMA-IR index was 3.49 (2.13;5.78), where as in patients with overweight it was 1.85 (1.28;3,01), p<0.01. In patients with coronary artery disease and overweight, the of hsCRP was 1.92 (1.18;2.98) mg/l and was significantly different from the hsCRP level in obese patients, which was 3.15 (2.64;3.66) mg/l, p=0,004.

CONCLUSION

Conclusions: In patients with coronary artery disease, non-alcoholic fatty liver disease and obesity, the metabolic profile was characterized by a more unfa¬vorable lipid spectrum: lower levels of HDL and higher triglicerid concentration. Carbohydrate metabolism in obese patients included disorders such us impared glucose tolerance, hyperinsulinemia and insulin resistance. There was also a correlation between body mass index with insulin and glycated hemoglobin. Higher concentration hsCRP in obese compared with patients with overweight was observed. This confirms the role of obesity in the patogenesis of coronary artery disease, non-alcoholic fatty liver disease and systemic inflammation.

NAFLD and HBV interplay - related mechanisms underlying liver disease progression

Non-alcoholic fatty liver disease (NAFLD) and Hepatitis B virus infection (HBV) constitute common chronic liver diseases with worldwide distribution. NAFLD burden is expected to grow in the coming decade, especially in western countries, considering the increased incidence of diabetes and obesity. Despite the organized HBV vaccinations and use of anti-viral therapies globally, HBV infection remains endemic and challenging public health issue. As both NAFLD and HBV have been associated with the development of progressive fibrosis, cirrhosis and hepatocellular carcinoma (HCC), the co-occurrence of both diseases has gained great research and clinical interest. The causative relationship between NAFLD and HBV infection has not been elucidated so far. Dysregulated fatty acid metabolism and lipotoxicity in NAFLD disease seems to initiate activation of signaling pathways that enhance pro-inflammatory responses and disrupt hepatocyte cell homeostasis, promoting progression of NAFLD disease to NASH, fibrosis and HCC and can affect HBV replication and immune encountering of HBV virus, which may further have impact on liver disease progression. Chronic HBV infection is suggested to have an influence on metabolic changes, which could lead to NAFLD development and the HBV-induced inflammatory responses and molecular pathways may constitute an aggravating factor in hepatic steatosis development. The observed altered immune homeostasis in both HBV infection and NAFLD could be associated with progression to HCC development. Elucidation of the possible mechanisms beyond HBV chronic infection and NAFLD diseases, which could lead to advanced liver disease or increase the risk for severe complications, in the case of HBV-NAFLD co-existence is of high clinical significance in the context of designing effective therapeutic targets.

The role of sphingolipids in meibomian gland dysfunction and ocular surface inflammation

Inflammation occurs in response to tissue injury and invasion of microorganisms and is carried out by the innate and adaptive immune systems, which are regulated by numerous chemokines, cytokines, and lipid mediators. There are four major families of bioactive lipid mediators that play an integral role in inflammation - eicosanoids, sphingolipids (SPL), specialized pro-resolving mediators (SPM), and endocannabinoids. SPL have been historically recognized as important structural components of cellular membranes; their roles as bioactive lipids and inflammatory mediators are recent additions. Major SPL metabolites, including sphingomyelin, ceramide, ceramide 1-phosphate (C1P), sphingosine, sphingosine 1-phosphate (S1P), and their respective enzymes have been studied extensively, primarily in cell-culture and animal models, for their roles in cellular signaling and regulating inflammation and apoptosis. Less focus has been given to the involvement of SPL in eye diseases. As such, the aim of this review was to examine relationships between the SPL family and ocular surface diseases, focusing on their role in disease pathophysiology and discussing the potential of therapeutics that disrupt SPL pathways.

Crosstalk between kidney and liver in non-alcoholic fatty liver disease: mechanisms and therapeutic approaches

Liver and kidney are vital organs that maintain homeostasis and injury to either of them triggers pathogenic pathways affecting the other. For example, non-alcoholic fatty liver disease (NAFLD) promotes the progression of chronic kidney disease (CKD), vice versa acute kidney injury (AKI) endorses the induction and progression of liver dysfunction. Progress in clinical and basic research suggest a role of excessive fructose intake, insulin resistance, inflammatory cytokines production, activation of the renin-angiotensin system, redox imbalance, and their impact on epigenetic regulation of gene expression in this context. Recent developments in experimental and clinical research have identified several biochemical and molecular pathways for AKI-liver interaction, including altered liver enzymes profile, metabolic acidosis, oxidative stress, activation of inflammatory and regulated cell death pathways. This review focuses on the current preclinical and clinical findings on kidney-liver crosstalk in NAFLD-CKD and AKI-liver dysfunction settings and highlights potential molecular mechanisms and therapeutic targets.

Celecoxib-mediated attenuation of non-alcoholic steatohepatitis is potentially relevant to redistributing the expression of adiponectin receptors in rats

Pharmacological inhibition of cyclooxygenase-2 (COX-2) activity ameliorated the severity of non-alcoholic steatohepatitis (NASH) rats. It is not completely understood that the role of COX-2 inhibitor celecoxib on adiponectin receptors (Adipo-R1/R2) expression in different tissues in NASH rats. Sprague-Dawley male NASH rats induced by a high-fat diet (HFD) were administrated with or without celecoxib for 8 weeks. Biochemical parameters of liver function, glucose, and lipid metabolism, and the levels of adiponectin, tumor necrosis factor-alpha (TNF-α), prostaglandin E₂ (PGE₂) in the serum or liver were collected according to the standard protocols. The mRNA and protein levels of Adipo-R1, Adipo-R2, and COX-2 in the liver, muscle, and visceral fat were performed by quantitative real-time polymerase chain reaction (q-PCR) and Western blot analysis, respectively. The results showed that celecoxib ameliorated the various clinical indicators and pathological characteristics in the NASH rats, including body weight, liver function, liver index, and redox activities in serum and hepatic samples. The serum concentrations of adiponectin and TNF-α and PGE₂ were negatively correlated. As expected, these ameliorative effects of celecoxib were associated with the gene and protein levels up-regulation of Adipo-R1, Adipo-R2 in the liver and visceral fat tissues, and seeming to be compensatory down-regulation expression in muscle tissues (P <0.05). Additionally, COX-2 protein expression was negatively correlated with serum adiponectin levels, protein expression of adiponectin receptors from the liver and visceral fat, conversely, positively correlated with those from the muscle. Our current study demonstrate that celecoxib might effectively alleviate NASH rats in a unique manner closely relevant to redistributing the expression of adiponectin receptors in the liver, visceral fat, and muscle. However, the precise molecular mechanism needs further study.

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NASH is a watershed in the progression of NAFLD.

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Finding a therapy for NASH is in urgent need.

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Pharmacological inhibition of COX-2 activity ameliorated the severity of NASH.

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Low-dose celecoxib, a COX-2 inhibitor, can improve NASH by redistributing the expression of adiponectin receptors.

Coagulation and Endothelial Dysfunction Associated with NAFLD: Current Status and Therapeutic Implications

Non-alcoholic fatty liver disease (NAFLD) is closely related to insulin resistance, type 2 diabetes mellitus and obesity. It is considered a multisystem disease and there is a strong association with cardiovascular disease and arterial hypertension, which interfere with changes in the coagulation system. Coagulation disorders are common in patients with hepatic impairment and are dependent on the degree of liver damage. Through a review of the literature, we consider and discuss possible disorders in the coagulation cascade and fibrinolysis, endothelial dysfunction and platelet abnormalities in patients with NAFLD.

Adipose tissue insulin resistance and lipidome alterations as the characterizing factors of non-alcoholic steatohepatitis

BACKGROUND

The prevalence of non-alcoholic fatty liver disease (NAFLD) is now 25% in the general population but increases to more than 55% in subjects with obesity and/or type 2 diabetes. Simple steatosis (NAFL) can develop into more severe forms, that is non-alcoholic steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma leading to death.

METHODS

In this narrative review, we have discussed the current knowledge in the pathophysiology of fatty liver disease, including both metabolic and non-metabolic factors, insulin resistance, mitochondrial function, as well as the markers of liver damage, giving attention to the alterations in lipid metabolism and production of lipotoxic lipids.

RESULTS

Insulin resistance, particularly in the adipose tissue, is the main driver of NAFLD due to the excess release of fatty acids. Lipidome analyses have shown that several lipids, including DAGs and ceramides, and especially if they contain saturated lipids, act as bioactive compounds, toxic to the cells. Lipids can also affect mitochondrial function. Not only lipids, but also amino acid metabolism is impaired in NAFL/NASH, and some amino acids, as branched-chain and aromatic amino acids, glutamate, serine and glycine, have been linked to impaired metabolism, insulin resistance and severity of NAFLD and serine is a precursor of ceramides.

CONCLUSIONS

The measurement of lipotoxic species and adipose tissue dysfunction can help to identify individuals at risk of progression to NASH.

The Visceral Adiposity Index in Non-Alcoholic Fatty Liver Disease and Liver Fibrosis-Systematic Review and Meta-Analysis

(1) Background: In order to avoid a liver biopsy in non-alcoholic fatty liver disease (NAFLD), several noninvasive biomarkers have been studied lately. Therefore, we aimed to evaluate the visceral adiposity index (VAI) in NAFLD and liver fibrosis, in addition to its accuracy in predicting NAFLD and NASH. (2) Methods: We searched PubMed, Embase, Scopus, and Cochrane Library, identifying observational studies assessing the VAI in NAFLD and liver fibrosis. QUADAS-2 was used to evaluate the quality of included studies. The principal summary outcomes were mean difference (MD) and area under the curve (AUC). (3) Results: A total of 24 studies were included in our review. VAI levels were significantly increased in NAFLD (biopsy-proven and ultrasound-diagnosed), simple steatosis vs. controls, and severe steatosis vs. simple steatosis. However, no significant MD was found according to sex, liver fibrosis severity, simple vs. moderate and moderate vs. severe steatosis, pediatric NAFLD, and NASH patients. The VAI predicted NAFLD (AUC 0.767) and NASH (AUC 0.732). (4) Conclusions: The VAI has a predictive value in diagnosing NAFLD and NASH, with significantly increased values in adult NAFLD patients, simple steatosis compared to controls, and severe steatosis compared to simple steatosis.

Nonalcoholic Fatty Liver Disease and Chronic Kidney Disease: A Review of Links and Risks

Nonalcoholic fatty liver disease and chronic kidney disease are both chronic conditions with rapidly increasing prevalence and incidence worldwide that have led to a significant burden on health-care systems. The association between these two disease entities is partly attributed to shared cardiometabolic comorbidities including diabetes, hypertension, obesity, and metabolic syndrome. However, independent of these overlapping risks, there are increased rates and more severe CKD in NAFLD patients. Conversely, more progressive NAFLD is seen with advanced stages of kidney injury. In addition to overlapping risk factors, shared pathogenic mechanisms suggest these two disease entities may resemble different manifestations of a single underlying disease process.

Pancreatic β-Cell Dysfunction Is Associated with Nonalcoholic Fatty Liver Disease

Background: Nonalcoholic fatty liver disease (NAFLD) is associated with decreased insulin sensitivity. However, the association between NAFLD and pancreatic β-cell function is still ambiguous. Here, we assessed whether pancreatic β-cell function is associated with NAFLD. Method: The data of NHANES III from 1988 to 1994 were used. NAFLD was diagnosed when subjects had ultrasonographically hepatic steatosis without other liver diseases. Disposition index (DI) was employed to assess pancreatic β-cell function. A total of 6168 participants were included in this study. Results: NAFLD participants had much higher HOMA2-%B (weighted mean, 124.1; standard error, 1.8) than the non-NAFLD participants (weighted mean, 100.7; standard error, 0.9). However, when evaluating the β-cell function in the context of insulin resistance by using DI index, DI levels were much lower in NAFLD subjects (weighted mean, 79.5; standard error, 1.0) compared to non-NAFLD (weighted mean, 95.0; standard error, 0.8). Multivariate logistic regression analyses showed that DI was inversely associated with NAFLD prevalence. The adjusted OR (95% CI) for quartile 1 versus quartile 4 was 1.81 (1.31–2.50) (p < 0.001 for trend). Moreover, DI was also inversely associated with the presence of moderate to severe hepatic steatosis. The multivariable-adjusted ORs across quartiles of DI were 2.47, 1.44, 0.96 and 1.00 for the presence of moderate to severe hepatic steatosis (p < 0.001 for trend). Conclusions: Pancreatic β-cell function might be a new predictor for the presence of NAFLD, and insufficient compensatory β-cell function is associated with NAFLD.

Serum Resistin Levels in Adult Patients with Nonalcoholic Fatty Liver Disease: A Systematic Review and Meta-analysis

BACKGROUND AND AIMS

Previous studies reported that serum resistin levels were remarkably changed in patients with nonalcoholic fatty liver disease (NAFLD) but the conclusions were inconsistent. The aim of this study was to investigate accurate serum resistin levels in adult patients with NAFLD.

METHODS

A complete literature research was conducted in the PubMed, Embase, and Cochrane Library databases, and all the available studies up to 7 May 2020 were reviewed. The pooled standardized mean difference (SMD) values were calculated to investigate the serum resistin levels in patients with NAFLD and healthy controls.

RESULTS

A total of 28 studies were included to investigate the serum resistin levels in patients with NAFLD. Patients with NAFLD had higher serum resistin levels than controls (SMD=0.522, 95% confidence interval [CI]: 0.004-1.040, I ²=95.9%). Patients with nonalcoholic steatohepatitis (NASH) had lower serum resistin levels than the healthy controls (SMD=-0.44, 95% CI: -0.83-0.55, I ²=74.5%). In addition, no significant difference of serum resistin levels was observed between patients with NAFL and healthy controls (SMD=-0.34, 95% CI: -0.91-0.23, I ²=79.6%) and between patients with NAFL and NASH (SMD=0.15, 95% CI: -0.06-0.36, I ²=0.00%). Furthermore, subgroup and sensitivity analyses suggested that heterogeneity did not affect the results of meta-analysis.

CONCLUSIONS

This meta-analysis investigated the serum resistin levels in adult patients with NAFLD comprehensively. Patients with NAFLD had higher serum resistin levels and patients with NASH had lower serum resistin levels than healthy controls. Serum resistin could serve as a potential biomarker to predict the development risk of NAFLD.

Emerging therapeutic approaches for the treatment of NAFLD and type 2 diabetes mellitus

Non-alcoholic fatty liver disease (NAFLD) has emerged as the most prevalent liver disease in the world, yet there are still no approved pharmacological therapies to prevent or treat this condition. NAFLD encompasses a spectrum of severity, ranging from simple steatosis to non-alcoholic steatohepatitis (NASH). Although NASH is linked to an increased risk of hepatocellular carcinoma and cirrhosis and has now become the leading cause of liver failure-related transplantation, the majority of patients with NASH will ultimately die as a result of complications of type 2 diabetes mellitus (T2DM) and cardiometabolic diseases. Importantly, NAFLD is closely linked to obesity and tightly interrelated with insulin resistance and T2DM. Thus, targeting these interconnected conditions and taking a holistic attitude to the treatment of metabolic disease could prove to be a very beneficial approach. This Review will explore the latest relevant literature and discuss the ongoing therapeutic options for NAFLD focused on targeting intermediary metabolism, insulin resistance and T2DM to remedy the global health burden of these diseases.

Oleanolic Acid Improves Obesity-Related Inflammation and Insulin Resistance by Regulating Macrophages Activation

The chronic low-grade inflammation of adipose tissues, primarily mediated by adipose tissue macrophages (ATMs), is the key pathogenic link between obesity and metabolic disorders. Oleanolic acid (OA) is a natural triterpenoid possessing anti-diabetic and anti-inflammation effects, but the machinery is poorly understood. This study investigated the detailed mechanisms of OA on adipose tissue inflammation in obese mice. C57BL/6J mice were fed with high-fat diet (HFD) for 12 weeks, then daily intragastric administrated with vehicle, 25 and 50 mg/kg OA for 4 weeks. Comparing with vehicle, OA administration in obese mice greatly improved insulin resistance, and reduced adipose tissue hypertrophy, ATM infiltration as well as the M1/M2 ratio. The pro-inflammatory markers were significantly down-regulated by OA in both adipose tissue of obese mice and RAW264.7 macrophages treated with interferon gamma/lipopolysaccharide (IFN-γ/LPS). Furthermore, it was found that OA suppressed activation of mitogen-activated protein kinase (MAPK) signaling and NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasome through decreasing voltage dependent anion channels (VDAC) expression and reactive oxygen species (ROS) production. This is the first report that oleanolic acid exerts its benefits by affecting mitochondrial function and macrophage activation.

Porphyran-derived oligosaccharides alleviate NAFLD and related cecal microbiota dysbiosis in mice

Porphyran and its derivatives possess a variety of biological activities, such as ameliorations of oxidative stress, inflammation, hyperlipemia, and immune deficiencies. In this study, we evaluated the potential efficacy of porphyran-derived oligosaccharides from Porphyra yezoensis (PYOs) in alleviating nonalcoholic fatty liver disease (NAFLD) and preliminarily clarified the underlying mechanism. NAFLD was induced by a high-fat diet for six months in C57BL/6J mice, followed by treatment with PYOs (100 or 300 mg/kg/d) for another six weeks. We found that PYOs reduced hepatic oxidative stress in mice with NAFLD, which plays a critical role in the occurrence and development of NAFLD. In addition, PYOs could markedly decrease lipid accumulation in liver by activating the IRS-1/AKT/GSK-3β signaling pathway and the AMPK signaling pathway in mice with NAFLD. PYOs also apparently relieved the hepatic fibrosis induced by oxidative stress via downregulation of TGF-β and its related proteins, so that liver injury was markedly alleviated. Furthermore, PYOs treatment relieved cecal microbiota dysbiosis (such as increasing the relative abundance of Akkermansia, while decreasing the Helicobacter abundance), which could alleviate oxidative stress, inflammation, and lipid metabolism, and protect the liver to a certain degree. In summary, PYOs treatment remarkably improved NAFLD via a specific molecular mechanism and reshaped the cecal microbiota.

Green Tea and Epigallocatechin Gallate (EGCG) for the Management of Nonalcoholic Fatty Liver Diseases (NAFLD): Insights into the Role of Oxidative Stress and Antioxidant Mechanism

Nonalcoholic fatty liver diseases (NAFLD) represent a set of liver disorders progressing from steatosis to steatohepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma, which induce huge burden to human health. Many pathophysiological factors are considered to influence NAFLD in a parallel pattern, involving insulin resistance, oxidative stress, lipotoxicity, mitochondrial dysfunction, endoplasmic reticulum stress, inflammatory cascades, fibrogenic reaction, etc. However, the underlying mechanisms, including those that induce NAFLD development, have not been fully understood. Specifically, oxidative stress, mainly mediated by excessive accumulation of reactive oxygen species, has participated in the multiple NAFLD-related signaling by serving as an accelerator. Ameliorating oxidative stress and maintaining redox homeostasis may be a promising approach for the management of NAFLD. Green tea is one of the most important dietary resources of natural antioxidants, above which epigallocatechin gallate (EGCG) notably contributes to its antioxidative action. Accumulative evidence from randomized clinical trials, systematic reviews, and meta-analysis has revealed the beneficial functions of green tea and EGCG in preventing and managing NAFLD, with acceptable safety in the patients. Abundant animal and cellular studies have demonstrated that green tea and EGCG may protect against NAFLD initiation and development by alleviating oxidative stress and the related metabolism dysfunction, inflammation, fibrosis, and tumorigenesis. The targeted signaling pathways may include, but are not limited to, NRF2, AMPK, SIRT1, NF-κB, TLR4/MYD88, TGF-β/SMAD, and PI3K/Akt/FoxO1, etc. In this review, we thoroughly discuss the oxidative stress-related mechanisms involved in NAFLD development, as well as summarize the protective effects and underlying mechanisms of green tea and EGCG against NAFLD.

Ligand-based pharmacophore modeling, virtual screening and biological evaluation to identify novel TGR5 agonists

Takeda G-protein-coupled receptor 5 (TGR5) is emerging as an important and promising target for the development of anti-diabetic drugs. To understand the structural characteristics of TGR5 agonists, the common feature pharmacophore models were generated and molecular docking was performed. The ligand-based virtual screening combined with pharmacophore mapping and molecular docking was performed to identify novel nonsteroidal TGR5 agonists. Finally, 20 compounds were screened for in vitro TGR5 agonistic activity assay, and results showed most compounds exhibiting TGR5 agonistic activity at 40 μM. Among these compounds, V12 and V14 displayed obvious TGR5 agonist activity, with the EC50 values of 19.5 μM and 7.7 μM, respectively. Compounds V12 and V14 could be considered potential TGR5 agonist candidates and also may be used as initial hits for developing novel TGR5 agonists.

Punicalagin Prevents Hepatic Steatosis through Improving Lipid Homeostasis and Inflammation in Liver and Adipose Tissue and Modulating Gut Microbiota in Western Diet-Fed Mice

SCOPE

Punicalagin (PU)-rich pomegranate peel extract has been shown before to exert protective effects against high fat-induced hepatic damage. The aim of this study is to explore whether and how PU antagonizes hepatic steatosis in Western diet-fed (WD) mice.

METHODS AND RESULTS

Mice are fed either chow diet, WD (containing 42% fat, 15% protein, and 43% carbohydrates), or WD supplemented with PU (50 mg kg-1 body weight/day) for 13 weeks. Weight gain, hepatic fat content, and inflammation in the liver and adipose tissues are measured. Compared to the WD group, PU-treated mice have lower fat content, decreased levels of alanine transaminase, and inflammation in liver. PU also changed the transcriptional expression of important genes in fatty acid oxidation pathway and alleviated glucose intolerance. Furthermore, PU improved adiponectin signaling and lipid metabolism in visceral adipose tissue. Moreover, PU improved gut microbiota dysbiosis induced by WD and enhanced gut barrier function.

CONCLUSIONS

The findings suggest that PU improves hepatic steatosis induced by WD, in part through regulating lipid homeostasis and inflammation in liver and adipose tissue and restoring microbiota shift and impaired gut barrier function. Thus, PU can be potentially developed as a potential prevention strategy in combating nonalcoholic fatty liver disease.

Long-term profile of serological biomarkers, hepatic inflammation, and fibrosis in a mouse model of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) can be typically classified into two subgroups: non-alcoholic fatty liver and non-alcoholic steatohepatitis. Mouse models of NAFLD are useful tools for understanding the pathogenesis and progression of NAFLD and for developing drugs for its treatment. Here, we investigated the time-dependent changes in serum lipids and biochemical markers of hepatic function, hepatic inflammation, and fibrosis in mice fed a normal diet (ND) or a NAFLD diet (choline deficient, L-amino acid-defined, high-fat diet; CDAHFD) for 12 weeks. CDAHFD-fed mice showed significantly reduced serum levels of total cholesterol, triglyceride, and high-density lipoprotein cholesterol throughout the treatment period compared with ND-fed mice. The changes in aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and total bilirubin showed an inverse U-shaped curve in the CDAHFD-fed mice. The serum alkaline phosphatase levels decreased in both ND- and CDAHFD-fed mice in a time-dependent manner. Furthermore, CDAHFD-fed mice showed a significant increase in the number of inflammatory foci and hepatic fibrosis at 6-12 weeks, although inflammatory foci and hepatic fibrogenesis were observable at relatively early stages as well (1-4 weeks). In conclusion, the long-term profile of serological biomarkers, hepatic inflammation, and fibrosis in CDAHFD-fed mice identified in this study may provide a better understanding of NAFLD pathogenesis.

Decrease in fasting insulin secretory function correlates with significant liver fibrosis in Japanese non-alcoholic fatty liver disease patients

Background and Aim

Non‐alcoholic fatty liver disease (NAFLD) is typically associated with metabolic syndrome and diabetes, and insulin resistance is involved in its pathogenesis. However, the relationship between insulin secretion and NAFLD is unclear. We aimed to characterize the relationship between fasting insulin secretory function (ISF), evaluated using the homeostatic model assessment‐beta cell function (HOMA‐β) and the severity of fibrosis during NAFLD.

Methods

A‐β was calculated in 188 patients with biopsy‐confirmed NAFLD, and the correlations between Log HOMA‐β and clinical parameters, including hepatic fibrosis, were calculated.

Results

Log HOMA‐β was significantly lower in NAFLD patients with significant fibrosis (stages 2–4) than in those in the early stages (stages 0–1) (median [interquartile range]) (2.1 [1.9–2.4] vs 2.0 [1.8–2.2], P = 0.04). The prevalence of significant fibrosis decreased with increasing Log HOMA‐β: it was 59.2% in participants with low ISF (Log HOMA‐β < 1.85), 43.6% in those with intermediate ISF (1.85 ≤ Log HOMA‐β < 2.25), and 68.0% in those with high ISF (Log HOMA‐β ≥ 2.25). Patients with lower Log HOMA‐β had lower current body mass index (BMI), BMI at 20 years of age, and peak lifetime BMI than patients with intermediate or high Log HOMA‐β.

Conclusions

Fasting ISF decreased alongside the development of liver fibrosis in NAFLD, suggesting that an impaired β cell function has a characteristic finding of significant liver fibrosis in relatively nonobese Japanese patients.

Adipose Tissue-Liver Cross Talk in the Control of Whole-Body Metabolism: Implications in Nonalcoholic Fatty Liver Disease

Adipose tissue and the liver play significant roles in the regulation of whole-body energy homeostasis, but they have not evolved to cope with the continuous, chronic, nutrient surplus seen in obesity. In this review, we detail how prolonged metabolic stress leads to adipose tissue dysfunction, inflammation, and adipokine release that results in increased lipid flux to the liver. Overall, the upshot of hepatic fat accumulation alongside an insulin-resistant state is that hepatic lipid enzymatic pathways are modulated and overwhelmed, resulting in the selective buildup of toxic lipid species, which worsens the pro-inflammatory and pro-fibrotic shift observed in nonalcoholic steatohepatitis.

Nonalcoholic Fatty Liver Disease in Adults: Current Concepts in Etiology, Outcomes, and Management

Nonalcoholic fatty liver disease (NAFLD) is a spectrum of disease, extending from simple steatosis to inflammation and fibrosis with a significant risk for the development of cirrhosis. It is highly prevalent and is associated with significant adverse outcomes both through liver-specific morbidity and mortality but, perhaps more important, through adverse cardiovascular and metabolic outcomes. It is closely associated with type 2 diabetes and obesity, and both of these conditions drive progressive disease toward the more advanced stages. The mechanisms that govern hepatic lipid accumulation and the predisposition to inflammation and fibrosis are still not fully understood but reflect a complex interplay between metabolic target tissues including adipose and skeletal muscle, and immune and inflammatory cells. The ability to make an accurate assessment of disease stage (that relates to clinical outcome) can also be challenging. While liver biopsy is still regarded as the gold-standard investigative tool, there is an extensive literature on the search for novel noninvasive biomarkers and imaging modalities that aim to accurately reflect the stage of underlying disease. Finally, although no therapies are currently licensed for the treatment of NAFLD, there are interventions that appear to have proven efficacy in randomized controlled trials as well as an extensive emerging therapeutic landscape of new agents that target many of the fundamental pathophysiological processes that drive NAFLD. It is highly likely that over the next few years, new treatments with a specific license for the treatment of NAFLD will become available.

New Perspectives on Genetic Prediction for Pediatric Metabolic Associated Fatty Liver Disease

Non-alcoholic or recently re-defined metabolic associated fatty liver disease (MAFLD), a spectrum of progressive hepatic disease, has become a public health issue in obese children and adolescents. MAFLD is a complex metabolic disease strongly associated with obesity and insulin resistance. It is not known why not every obese subject will develop MAFLD. Different ethnic/racial groups display differences in MAFLD prevalence, indicating genetic factor plays a role. In the past two decades, sequence variations in genetic loci, including PNPLA3, TM6SF2, GCKR, MBOAT7, HSD17B13, etc. have been shown to confer susceptibility to MAFLD in children and adults. This review article provides an updated viewpoint of genetic predictors related to pediatric MAFLD. We discuss whether these susceptible genes can be clinically used for risk stratification and personalized care. Understanding human genetics and molecular mechanisms can give important information not only for prediction of risk but also on how to design drugs. In view of current epidemic of MAFLD worldwide, it is necessary to identify which children with MAFLD progress rapidly and need earlier intervention. In the future, a comprehensive analysis of individualized genetic and environmental factors may help assess the risk of children with MAFLD and personalize their treatment.

In New-Onset Diabetes Mellitus, Metformin Reduces Fat Accumulation in the Liver, But Not in the Pancreas or Pericardium

Background: Nonalcoholic fatty pancreas and liver disease (NAFPD and NAFLD) and pericardial adipose tissue (PAT) are often associated with type 2 diabetes mellitus (T2DM). Our aim was to evaluate the incidence rate of NAFLD and NAFPD, PAT size, and the effect of metformin treatment on NAFLD, NAFPD, and PAT in new-onset T2DM (NODM). Methods: Seventeen patients with NODM and 10 subjects used as a control group were involved in the study. Computed tomography (CT) and laboratory tests were performed before the beginning of metformin therapy and 4 months afterward. PAT and the amount of fat in the pancreas and liver were determined by X-ray attenuation during unenhanced CT examination and compared with the values for the control subjects. Results: Metabolic parameters improved significantly after metformin therapy. NAFLD was diagnosed in 64.7% of the patients with NODM and in 10% of the control subjects. The radiation absorption of the liver was significantly lower in the patients with NODM compared with the control group and significantly higher after metformin therapy compared with the baseline values. Only six patients (35.3%) had NAFLD after metformin therapy. NAFPD was diagnosed in 82.3% of the patients with NODM and in 20% of the control subjects. The radiation absorption of the pancreas was significantly lower in the patients with NODM compared with the control group but did not change significantly after treatment. PAT size was significantly larger in the patients with NODM and did not change significantly after metformin treatment. Conclusions: NAFLD, NAFPD, and increased PAT were detected in the majority of patients with NODM. Metformin therapy decreased the amount of fat in the liver in parallel with an improvement in the metabolic parameters and may, thus, be beneficial for preventing the late consequences of NAFLD.

Angiotensin II Type 1 Receptor rs5186 Gene Variant Predicts Incident NAFLD and Associated Hypertension: Role of Dietary Fat-Induced Pro-Inflammatory Cell Activation

OBJECTIVES

Hypertension has been linked to the presence and severity of nonalcoholic fatty liver disease (NAFLD) through unclear mechanisms. The gain-of-function rs5186 A1166C variant in angtiotensin receptor type 1 (AGTR1) gene has been linked to hypertension, cardiovascular disease and metabolic syndrome. We assessed the impact of AGTR1 A1166C variant on NAFLD incidence and severity and on glucose and lipid metabolism and explored the underlying mechanisms.

METHODS

We followed up 314 healthy nonobese, nondiabetic, nonhypertensive, insulin-sensitive participants in a population-based study, characterized for AGTR1 rs5186 A1166C variant, adipokine profile, inflammatory and endothelial dysfunction markers. An independent cohort of 78 biopsy-proven nondiabetic NAFLD patients and controls underwent an oral glucose tolerance test with Minimal Model analysis of glucose homeostasis, and an oral fat tolerance test with measurement of plasma lipoproteins, adipokines, MCP-1, calprotectin, and nuclear factor-κB activation in circulating mononuclear cells.

RESULTS

AGTR1 A1166C polymorphism predicted 9.8-year incident NAFLD (odds ratio: 1.67, 95% CI: 1.26-2.21) and hypertension (odds ratio: 1.49, 95% CI: 1.12-2.63) and 9-year increase in cardiovascular disease risk and endothelial dysfunction markers. In the cross-sectional cohort, AGTR1 C allele carriers had higher insulin resistance. Despite comparable fasting lipid profiles, AGTR1 C allele carriers showed postprandial triglyceride-rich and cholesterol-rich VLDL lipoprotein accumulation, higher resistin, MCP-1 and calprotectin responses and nuclear factor-κB activation in mononuclear cells, and a blunted postprandial adiponectin response to fat, which predicted liver histology, hepatocyte apoptosis activation, insulin resistance, and endothelial dysfunction.

DISCUSSION

AGTR1 A1166C variant affects liver disease, insulin resistance, and endothelial dysfunction in NAFLD, at least in part by modulating adipokine, chemokine, and pro-inflammatory cell activation in response to fat ingestion.

Intestinal TGR5 agonism improves hepatic steatosis and insulin sensitivity in Western diet-fed mice

Takeda G protein-coupled receptor 5 (TGR5) agonists induce systemic release of glucagon-like peptides (GLPs) from intestinal L cells, a potentially therapeutic action against metabolic diseases such as nonalcoholic steatohepatitis (NASH), nonalcoholic fatty liver disease (NAFLD), and Type 2 diabetes. Historically, TGR5 agonist use has been hindered by side effects, including inhibition of gallbladder emptying. Here, we characterize RDX8940, a novel, orally administered TGR5 agonist designed to have minimal systemic effects and investigate its activity in mice fed a Western diet, a model of NAFLD and mild insulin resistance. Agonist activity, binding selectivity, toxicity, solubility, and permeability of RDX8940 were characterized in standard in vitro models. RDX8940 pharmacokinetics and effects on GLP secretion, insulin sensitivity, and liver steatosis were assessed in C57BL/6 mice fed normal or Western diet chow and given single or repeated doses of RDX8940 or vehicle, with or without dipeptidyl peptidase-4 (DPP4) inhibitors. Gallbladder effects were assessed in CD-1 mice fed normal chow and given RDX8940 or a systemic TGR5 agonist or vehicle. Our results showed that RDX8940 is minimally systemic, potent, and selective, and induces incretin (GLP-1, GLP-2, and peptide YY) secretion. RDX8940-induced increases in plasma active GLP-1 (aGLP-1) levels were enhanced by repeated dosing and by coadministration of DPP4 inhibitors. RDX8940 increased hepatic exposure to aGLP-1 without requiring coadministration of a DPP4 inhibitor. In mice fed a Western diet, RDX8940 improved liver steatosis and insulin sensitivity. Unlike systemic TGR5 agonists, RDX8940 did not inhibit gallbladder emptying. These results indicate that RDX8940 may have therapeutic potential in patients with NAFLD/NASH. NEW & NOTEWORTHY Takeda G protein-coupled receptor 5 (TGR5) agonists have potential as a treatment for nonalcoholic steatohepatitis and nonalcoholic fatty liver disease (NAFLD) but have until now been associated with undesirable side effects associated with systemic TGR5 agonism, including blockade of gallbladder emptying. We demonstrate that RDX8940, a potent, selective, minimally systemic oral TGR5 agonist, improves liver steatosis and insulin sensitivity in a mouse model of NAFLD and does not inhibit gallbladder emptying in mice.

Mesenteric adipose tissue B lymphocytes promote local and hepatic inflammation in non-alcoholic fatty liver disease mice

Mesenteric adipose tissue (MAT) inflammation is associated with non‐alcoholic fatty liver disease (NAFLD), and immune cells play pivotal roles in the inflammation of adipose tissue. Here, we investigated the roles of MAT B lymphocytes in NAFLD. Mice fed with high‐fat diet (HFD) and normal diet (ND) were killed in time gradients (4, 8 and 12 weeks). Compared with ND‐fed mice, intra‐hepatic CD45⁺CD19⁺ B lymphocytes increased after 4 weeks (P < 0.01) of HFD feeding, and lasted until the 12th week, infiltrated earlier than CD45⁺CD3⁺ T lymphocytes and CD45⁺F4/80⁺ macrophages. The mRNA expression of tumour necrosis factor (TNF)‐α, interleukin (IL)‐6 and monocyte chemotactic protein (MCP)‐1 decreased in MAT of B^null HFD‐fed mice compared to that in wild‐type HFD‐fed mice, along with lesser macrophages. Mesenteric adipose tissue B cells from HFD‐fed mice promoted macrophage differentiation to type‐Ι macrophages and expression of pro‐inflammatory cytokines in vitro. Macrophages pre‐treated with MAT B cells from HFD‐fed mice showed elevated mRNA expression of IL‐6 and TNF‐α and declined IL‐10 levels in adipocytes compared to ND MAT B cell pre‐treated macrophages. Besides, internal near‐infrared scanning and external transwell assay showed that HFD MAT B cells migrated to the liver more than ND MAT B cells. High‐fat diet MAT B cells induced higher MCP‐1 and lower IL‐10 expression in primary hepatocytes compared to ND MAT B cells in co‐culture experiment. These data indicate that B lymphocytes infiltrate early in MAT during the development of NAFLD, which may not only promote MAT inflammation by regulating macrophages but also migrate to the liver and induce hepatocytes inflammation.

A Pathophysiologic Approach Combining Genetics and Insulin Resistance to Predict the Severity of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a complex disease dictated by both genetic and environmental factors. While insulin resistance (IR) is a key pathogenic driver, two common genetic variants in patatin‐like phospholipase domain containing 3 (PNPLA3) and transmembrane 6 superfamily member 2 (TM6SF2) also impart significant risk for disease progression. Traditional approaches to NAFLD risk stratification rely on biomarkers of fibrosis, an end result of disease progression. We hypothesized that by combining genetics and a novel measurement for IR we could predict disease progression by the NAFLD activity score (NAS) and histologic presence of significant fibrosis. A total of 177 patients with biopsy‐proven NAFLD were enrolled in this cross‐sectional study. PNPLA3 I148M and TM6SF2 E167K genotypes were determined by TaqMan assays. The enhanced lipoprotein IR index (eLP‐IR) was calculated from serum biomarkers using nuclear magnetic resonance (NMR) spectroscopy. Multivariate regression models were used to study the relationships between genetics, IR, and histologic features of NAFLD. In the multivariate analysis, the eLP‐IR was strongly associated with histologic features of NAFLD activity and hepatic fibrosis (P < 0.001 to 0.02) after adjustment for potential confounders. PNPLA3 148M and TM6SF2 E167K genotypes were significantly associated with steatosis (P = 0.003 and P = 0.02, respectively). A combination of the eLP‐IR and genetic score was able to predict the presence of NAS ≥3 with an area under the receiver operating characteristic curve (AUROC) of 0.74. Adding age to this model predicted stages 3‐4 liver fibrosis with an AUROC of 0.82. Conclusion: This proof‐of‐concept study supports the hypothesis that genetics and IR are major determinants of NAFLD severity and demonstrates the feasibility of a new risk stratification paradigm using exclusively pathogenic factors.

Mesenteric adipose tissue contributes to intestinal barrier integrity and protects against nonalcoholic fatty liver disease in mice

Visceral adipose tissue (VAT) is related to nonalcoholic fatty liver disease (NAFLD). However, the role of mesenteric adipose tissue (MAT), part of the VAT, in NAFLD is unclear. In the present study, we monitored the liver and four depots of the VAT in high-fat diet (HFD)-feeding mice at multiple time points (4, 8, and 12 wk). The MAT had become inflamed by the eighth week of HFD feeding, earlier than other depots of VAT. Furthermore, MAT removal after 8 wk of HFD resulted in more severe steatosis and more foci of inflammation infiltration, as well as higher NAFLD activity scores. Consistent with these findings, the mRNA expression of proinflammatory cytokines and lipid anabolism genes was increased in the livers of inflamed MAT-removal mice. MAT removal also injured the intestinal barrier and promoted intestinal inflammation. The bacterial load translocated to the liver and circulating levels of lipopolysaccharide were also evaluated in inflamed MAT-removal mice. In a coculture experiment involving adipocytes and intestinal epithelial cells, mRNA expression of zonula occludens-1 (ZO-1), and occludin in CT-26 cells was upregulated and permeability of monolayer Caco-2 cells was elevated under stimulation from adipocytes or inflamed adipocytes. Taken together, these results demonstrated that MAT removal damaged the intestinal barrier and aggravated NAFLD and that MAT inflammation may be a compensatory response to protect the liver by maintaining the intestinal barrier. NEW & NOTEWORTHY The mesenteric adipose tissue (MAT) lies between the gut and liver and plays a critical role in hepatic metabolic diseases. In the present study, we found that the MAT was prone to inflammation in high-fat diet-fed mice. Removal of the inflamed MAT resulted in more hepatic inflammation, lipid accumulation, and decreased glucose tolerance. Furthermore, we showed that the MAT contributed to intestinal barrier integrity, thus clarifying why MAT removal aggravated nonalcoholic fatty liver disease.

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

Non-alcoholic fatty liver disease (NAFLD) is now the most common cause of chronic liver diseases worldwide. It encompasses a spectrum of disorders ranging from isolated hepatic steatosis to nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and hepatocellular carcinoma. One of the key challenges in NAFLD is identifying which patients will progress. Epidemiological and genetic studies indicate a strong pattern of heritability that may explain some of the variability in NAFLD phenotype and risk of progression. To date, at least three common genetic variants in the PNPLA3, TM6SF2, and GCKR genes have been robustly linked to NAFLD in the population. The function of these genes revealed novel pathways implicated in both the development and progression of NAFLD. In addition, candidate genes previously implicated in NAFLD pathogenesis have also been identified as determinants or modulators of NAFLD phenotype including genes involved in hepatocellular lipid handling, insulin resistance, inflammation, and fibrogenesis. This article will review the current understanding of the genetics underpinning the development of hepatic steatosis and the progression of NASH. These newly acquired insights may transform our strategy to risk-stratify patients with NAFLD and to identify new potential therapeutic targets.

Bioactive Lipid Species and Metabolic Pathways in Progression and Resolution of Nonalcoholic Steatohepatitis

The prevalence of nonalcoholic steatohepatitis (NASH) is increasing worldwide, yet there are no effective treatments. A decade has passed since the initial lipidomics analyses of liver tissues from patients with nonalcoholic fatty liver disease. We have learned that liver cells from patients with NASH have an abnormal lipid composition and that the accumulation of lipids leads to organelle dysfunction, cell injury and death, and chronic inflammation, called lipotoxicity. We review the lipid species and metabolic pathways that contribute to the pathogenesis of NASH and potential therapeutic targets, including enzymes involved in fatty acid and triglyceride synthesis, bioactive sphingolipids and polyunsaturated-derived eicosanoids, and specialized pro-resolving lipid mediators. We discuss the concept that NASH is a disease that can resolve and the roles of lipid molecules in the resolution of inflammation and regression of fibrosis.

The therapeutic effects of bee venom on some metabolic and antioxidant parameters associated with HFD-induced non-alcoholic fatty liver in rats

The present study was designed to investigate the therapeutic effects of bee venom (BV) on high-fat diet (HFD)-induced non-alcoholic fatty liver (NAFL) in rats at different levels. Histological manifestations, hepatic lipid content, liver function tests, glucose homeostasis, lipid abnormalities, adipocytokines, lipid peroxidation, disturbed glutathione and antioxidant enzymes systems and dysregulation of Nrf2 transcription factor were assessed. In the present study, the NAFL rats were subcutaneously treated with BV with different doses (0.01, 0.05, 0.1 mg/kg). The results indicated that BV treatment completely normalized the lipid profile values of NAFL rats. Fasting blood sugar, insulin level and homeostatic model assessment of insulin resistance significantly decreased. BV treated rats showed a significantly lower level of all liver enzymes and bilirubin. Moreover, BV treatment significantly increased the levels of active nuclear erythroid factor 2 like 2, glutathione (GSH) (total and reduced), GSH/glutathione disulphide ratio and activities of glutathione reductase, glutathione-S-transferase and glutathione peroxidase (total and Se-dependent). The level of tumor necrosis factor-α was reduced. Treatment showed correction of adiponectin level, and significant downregulation of hepatic triglycerides and cholesterol. At the histological level, BV improved the architecture of liver cells showing normal sinusoids. It may be concluded that BV may represent an interesting therapeutic alternative for the treatment of NAFL disease.

The antipsychotics sulpiride induces fatty liver in rats via phosphorylation of insulin receptor substrate-1 at Serine 307-mediated adipose tissue insulin resistance

Cumulative evidence has suggested that many antipsychotics cause metabolic abnormalities. Adipose tissue insulin resistance (Adipo-IR) contributes to the development and progress of metabolic abnormalities including fatty liver by inducing excessive free fatty acid release from adipose tissue. Sulpiride is an old antipsychotic still frequently used in many developing countries. However, its adverse metabolic effects remain poorly understood. Here, chronic administration of sulpiride (80 mg/kg, subcutaneously, once daily for 6 weeks) elevated fasting insulin concentration and the index of the homeostasis model assessment of insulin resistance in rats. More importantly, sulpiride increased hepatic triglyceride accumulation and Oil Red O-stained area, indicating the induction of fatty liver by sulpiride. Sulpiride also increased plasma non-esterified fatty acid concentrations at the baseline and during an oral glucose tolerance test, the Adipo-IR index, and adipocyte size. Adipose gene expression profile revealed that sulpiride decreased mRNA and protein expression of insulin receptor substrate (IRS)-1, but not IRS-2. Furthermore, sulpiride increased phosphorylation of both Ser³⁰⁷ in IRS-1 and Ser⁴⁷³ in Akt at baseline. Co-treatment with bromocriptine (a dopamine D₂ receptor agonist) attenuated sulpiride-induced hyperprolactinemia, but it was without effect on insulin resistance and fatty liver. Therefore, the present results suggest that sulpiride induces fatty liver in rats via phosphorylation of IRS-1 at Ser³⁰⁷-mediated adipose tissue insulin resistance, in which dopamine D₂ receptor is possibly not involved. Our findings may provide new insights into the mechanisms underlying the steatotic effect of the old antipsychotic.

A critical review of endpoints for non-cirrhotic NASH therapeutic trials

Non-alcoholic steatohepatitis is a disease without a single, specific, diagnostic marker, hence multiple indicators are required to measure therapeutic efficacy. Moreover, drug candidates for non-alcoholic steatohepatitis target many distinct mechanisms that are believed to promote hepatic injury. Therefore, a wide range of endpoints must be reached, sequentially, as required by the drug development process. Some of these endpoints validate the mechanism of action, others are used to anticipate histological efficacy. Histological endpoints are still considered the best predictors of clinical outcome, but they can only be reliably tested in larger, late phase trials. Herein, we will review the rationale and clinical data supporting the use of specific endpoints at different stages of therapeutic trials. We will also discuss the validity and limitations of current phase IIb histological endpoints, particularly a one stage reduction in fibrosis, for their ability to predict progression to cirrhosis, which is the ultimate outcome measure in therapeutic trials.

Characteristics of hepatic insulin-sensitive nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) plays a crucial role in type 2 diabetes and hepatocellular carcinoma. The major underlying pathogenesis is hepatic insulin resistance. The aim of the present study was to characterize patients with NAFLD with paradoxically normal hepatic insulin sensitivity relative to patients with NAFLD with hepatic insulin resistance. We recruited 26 patients with NAFLD and divided them into three groups ranked by the level of hepatic insulin sensitivity (HIS; high‐HIS, mid‐HIS, low‐HIS), as assessed by the hyperinsulinemic‐euglycemic clamp studies using stable isotope. Hepatic insulin sensitivity of the high‐HIS group was identical to that of the non‐NAFLD lean control (clamped percent suppression of endogenous glucose production, 91.1% ± 5.2% versus 91.0% ± 8.5%, respectively) and was significantly higher than that of the low‐HIS group (66.6% ± 7.5%; P < 0.01). Adiposity (subcutaneous, visceral, intrahepatic, and muscular lipid content), hepatic histopathology, and expression levels of various genes by using liver biopsies, muscle, and adipose tissue insulin sensitivity, plasma metabolites by metabolomics analysis, putative biomarkers, and lifestyles were assessed and compared between the high‐HIS and low‐HIS groups. Among these, adipose tissue insulin sensitivity assessed by clamped percent suppression of free fatty acid, serum high molecular weight adiponectin, and plasma tricarboxylic acid cycle metabolites, such as citric acid and cis‐aconitic acid, were significantly higher in the high‐HIS group compared to the low‐HIS group. In contrast, there were no differences in adiposity, including intrahepatic lipid content assessed by proton magnetic resonance spectroscopy (28.3% ± 16.1% versus 20.4% ± 9.9%, respectively), hepatic histopathology, other putative biomarkers, and lifestyles. Conclusion: High levels of adipose tissue insulin sensitivity, serum high molecular weight adiponectin, and plasma tricarboxylic acid cycle metabolites are unique characteristics that define patients with hepatic insulin‐sensitive NAFLD regardless of intrahepatic lipid content. (Hepatology Communications 2017;1:634–647)

Probiotic Therapy in Patients with Nonalcoholic Steatohepatitis in Zagazig University Hospitals

Aim:

Nonalcoholic fatty liver disease (NAFLD) is probably the most common liver disorder in the world. A subgroup of NAFLD patients is characterized by injury to the hepatocytes and inflammation in addition to excessive fat (steatohepatitis), the latter condition is nominated nonalcoholic steatohepatitis (NASH). This work aimed to evaluate the role of probiotics on the outcome of NASH in patients admitted to the Tropical Medicine Department, Faculty of Medicine, Zagazig University (inpatients and outpatients).

Materials and methods:

This study was performed on 30 patients (17 males and 13 females), with body mass index from 30 to 35 and average age of 44 years with bright fatty liver in ultrasonography and raised alanine transaminase (ALT) and aspartate transaminase (AST) and positive liver biopsy findings. The patients were divided into group I (case group) that included 15 patients who received probiotics and group II of 15 patients as control group who did not receive probiotics; the study was conducted between November 2014 and April 2016. Clinical assessment, laboratory evaluation, pelvic-abdominal ultrasound, and liver biopsy of all cases were carried out.

Results:

In this study, there was significant decrease in liver enzymes (ALT and AST) and no statistically significant other laboratory findings. Also there was relief for dyspepsia in some patients.

Conclusion:

Probiotics treatment is effective, safe, well-tolerated, inexpensive, appropriate for long-term use, and optimally, works at multiple levels to downregulate inflammatory mediators, and therefore, probiotics could be an option in the treatment of NASH.

How to cite this article: Monem SMA. Probiotic Therapy in Patients with Nonalcoholic Steatohepatitis in Zagazig University Hospitals. Euroasian J Hepato-Gastroenterol 2017;7(1):101-106.

Analysis of factors influencing glucose tolerance in Japanese patients with non-alcoholic fatty liver disease

BACKGROUND

While the association of the prevalence of non-alcoholic fatty liver disease (NAFLD) with impaired glucose metabolism has been reported, the factors influencing glucose tolerance in NAFLD remain to be clarified.

METHODS

Glucose tolerance of 131 Japanese patients diagnosed as NAFLD by histological findings of liver biopsy specimen was examined using 75 g-OGTT. According to Matteoni's classification, patients were divided to 4 groups [M1 ~ 4, M1, 2: non-alcoholic fatty liver (NAFL); and M3, 4: non-alcoholic steatohepatitis (NASH)]. Based on the OGTT data, insulinogenic index (IGI) and QUICKI were calculated as indices of insulin secretion and insulin sensitivity, respectively. Plasma glucose 120 min after glucose loading (G₁₂₀) was used as the index for glucose intolerance.

RESULTS

Stepwise multiple regression analysis using G₁₂₀ as a dependent variable and log_e-IGI, QUICKI, sex, BMI, age, NAFL/NASH as independent variables revealed that log_e-IGI (β = -0.595) and QUICKI (β = -0.323) are significant factors predicting glucose intolerance (R² = 0.403), indicating an important role of insulin secretion in glucose tolerance. These findings accord with glucose intolerance as high as 89.7% in patients with impaired insulin secretion defined by ≤43.2 pmol/mmol (40 μU/mg) IGI. Stepwise multiple regression analysis using QUICKI as a dependent variable and NAFL/NAFLD, sex, BMI, and age as independent variables revealed that BMI (β = -0.469) and NAFL/NAFLD (β = -0.204) are significant factors predicting insulin sensitivity (R² = 0.248).

CONCLUSION

Impairment of insulin secretion is the most important factor to predict glucose intolerance in NAFLD; severity of histological findings is associated with insulin sensitivity independent of adiposity in NAFLD.

The Serum Oxidative/Anti-oxidative Stress Balance Becomes Dysregulated in Patients with Non-alcoholic Steatohepatitis Associated with Hepatocellular Carcinoma

Objective Oxidative stress is associated with the progression of chronic liver disease. Non-alcoholic fatty liver disease (NAFLD) is also an oxidative stress-related disease. However, the oxidative/anti-oxidative balance has not been fully characterized in NAFLD. The objective of the present study was to investigate the balance between oxidative stress and the anti-oxidative activity in NAFLD, including non-alcoholic steatohepatitis (NASH)-related hepatocellular carcinoma (HCC). Patients We recruited 69 patients with histologically proven NAFLD without HCC (NAFLD; n=58), and with NASH-related HCC (NASH-HCC; n=11). The 58 NAFLD patients included patients with non-alcoholic fatty liver (NAFL; n=14) and NASH (n=44). Methods The serum levels of reactive oxygen metabolites (ROM) and anti-oxidative markers (OXY) were determined and then used to calculate the oxidative index. The correlations among such factors as ROM, OXY, oxidative index, and clinical characteristics were investigated. Results In NAFLD, ROM positively correlated with the body mass index (BMI), hemoglobin A1c (HbA1c), C-reactive protein (CRP), and the histological grade or inflammatory scores, while only high HbA1c and CRP levels were significant factors that correlated with a higher ROM according to a multivariate analysis. OXY positively correlated with the platelet counts, albumin, and creatinine levels, while negatively correlating with age. However, it improved after treatment intervention. The oxidative index positively correlated with BMI, CRP, and HbA1c. The NASH-HCC patients exhibited a lower OXY than the NASH patients, probably due to the effects of aging. Conclusion Oxidative stress correlated with the levels of NASH activity markers, while the anti-oxidative function was preserved in younger patients as well as in patients with a well-preserved liver function. The NASH-HCC patients tended to be older and exhibited a diminished anti-oxidative function.

Exenatide improves both hepatic and adipose tissue insulin resistance: A dynamic positron emission tomography study

Glucagon-like peptide 1 (GLP-1) receptor agonists (GLP-1-RAs) act on multiple tissues, in addition to the pancreas. Recent studies suggest that GLP-1-RAs act on liver and adipose tissue to reduce insulin resistance (IR). Thus, we evaluated the acute effects of exenatide (EX) on hepatic (Hep-IR) and adipose (Adipo-IR) insulin resistance and glucose uptake. Fifteen male subjects (age = 56 ± 8 years; body mass index = 29 ± 1 kg/m2 ; A1c = 5.7 ± 0.1%) were studied on two occasions, with a double-blind subcutaneous injection of EX (5 μg) or placebo (PLC) 30 minutes before a 75-g oral glucose tolerance test (OGTT). During OGTT, we measured hepatic (HGU) and adipose tissue (ATGU) glucose uptake with [18 F]2-fluoro-2-deoxy-D-glucose/positron emission tomography, lipolysis (RaGly) with [U-2 H5 ]-glycerol, oral glucose absorption (RaO) with [U-13 C6 ]-glucose, and hepatic glucose production (EGP) with [6,6-2 H2 ]-glucose. Adipo-IR and Hep-IR were calculated as (FFA0-120min ) × (Ins0-120min ) and (EGP0-120min ) × (Ins0-120min ), respectively. EX reduced RaO, resulting in reduced plasma glucose and insulin concentration from 0 to 120 minutes postglucose ingestion. EX decreased Hep-IR (197 ± 28 to 130 ± 37; P = 0.02) and increased HGU of orally administered glucose (23 ± 4 to 232 ± 89 [μmol/min/L]/[μmol/min/kg]; P = 0.003) despite lower insulin (23 ± 5 vs. 41 ± 5 mU/L; P < 0.02). EX enhanced insulin suppression of RaGly by decreasing Adipo-IR (23 ± 4 to 13 ± 3; P = 0.009). No significant effect of insulin was observed on ATGU (EX = 1.16 ± 0.15 vs. PLC = 1.36 ± 0.13 [μmol/min/L]/[μmol/min/kg]).

CONCLUSION

Acute EX administration (1) improves Hep-IR, decreases EGP, and enhances HGU and (2) reduces Adipo-IR, improves the antilipolytic effect of insulin, and reduces plasma free fatty acid levels during OGTT. (Hepatology 2016;64:2028-2037).

Fasting Plasma Insulin Concentrations Are Associated With Changes in Hepatic Fatty Acid Synthesis and Partitioning Prior to Changes in Liver Fat Content in Healthy Adults

Resistance to the action of insulin affects fatty acid delivery to the liver, fatty acid synthesis and oxidation within the liver, and triglyceride export from the liver. To understand the metabolic consequences of hepatic fatty acid synthesis, partitioning, oxidation, and net liver fat content in the fasted and postprandial states, we used stable-isotope tracer methodologies to study healthy men and women with varying degrees of insulin resistance before and after consumption of a mixed meal. Subjects were classified as being normoinsulinemic (NI) (fasting plasma insulin <11.2 mU/L, n = 18) or hyperinsulinemic (HI) (fasting plasma insulin >11.2 mU/L, n = 19). Liver fat content was similar between HI and NI individuals, despite HI subjects having marginally more visceral fat. However, de novo lipogenesis was higher and fatty acid oxidation was lower in HI individuals compared with NI subjects. These data suggest that metabolic pathways promoting fat accumulation are enhanced in HI but, paradoxically, without any significant effect on liver fat content when observed in healthy people. This is likely to be explained by increased triglyceride secretion as observed by hypertriglyceridemia.