Treating nonalcoholic steatohepatitis with antidiabetic drugs: Will GLP-1 agonists end the struggle?

Advanced microbiome therapeutics as a novel modality for oral delivery of peptides to manage metabolic diseases

The rising prevalence of metabolic diseases calls for innovative treatments. Peptide-based drugs have transformed the management of conditions such as obesity and type 2 diabetes. Yet, challenges persist in oral delivery of these peptides. This review explores the potential of 'advanced microbiome therapeutics' (AMTs), which involve engineered microbes for delivery of peptides in situ, thereby enhancing their bioavailability. Preclinical work on AMTs has shown promise in treating animal models of metabolic diseases, including obesity, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease. Outstanding challenges toward realizing the potential of AMTs involve improving peptide expression, ensuring predictable colonization control, enhancing stability, and managing safety and biocontainment concerns. Still, AMTs have potential for revolutionizing the treatment of metabolic diseases, potentially offering dynamic and personalized novel therapeutic approaches.

Semaglutide improves metabolic dysfunction-associated steatohepatitis: A 10-year retrospective study

Background and Aims

Semaglutide has been studied in patients with metabolic dysfunction-associated steatohepatitis (MASH) due to potential benefit from weight loss on liver inflammation. However, preclinical studies suggest that MASH improvement may be independent of weight loss. We aim to assess the impact of semaglutide on MASH in relation to weight loss.

Methods

This retrospective study included 420 patients with diabetes on semaglutide for at least 12 months between 2011 and 2022. Exclusion criteria were liver disease other than MASH, decompensated cirrhosis, malignancy, and bariatric surgery. Primary endpoints were clinically significant improvements in AST or ALT (mean difference > 6.3 U/L and > 10.6 U/L respectively). Statistical analysis included Student's t-test/ANOVA, Wilcoxon signed-rank test/Friedman test as appropriate, and binary logistic regression.

Results

Median duration of semaglutide was 22.5 months and 80% of patients received 1 mg/week. BMI improved by a mean (SD) of 1.9 points (2.8), weight by 13.3 lbs. (19.1), AST by 4.1 U/L (11.5), and ALT by 5.3 U/L (14.2). In 28% and 22% of patients respectively, AST and ALT had a clinically significant improvement. MASH scores (NFS, FIB4, APRI) improved after semaglutide (p < 0.001). No statistically significant differences in AST or ALT improvement were found when patients were stratified by BMI prior to semaglutide or when stratified by percentage of weight loss. On logistic regression, the duration of semaglutide and pretreatment APRI score increased the odds of clinically significant improvements of AST and ALT.

Conclusion

Semaglutide treatment was associated with improvement in transaminases and MASH scores. Higher odds of positive semaglutide effects were observed with longer treatment duration and were independent of weight loss.

Metabolic improvement and liver regeneration by inhibiting CXXC5 function for non-alcoholic steatohepatitis treatment

Non-alcoholic steatohepatitis (NASH) is a chronic liver disease that results from multiple metabolic disorders. Considering the complexity of the pathogenesis, the identification of a factor mediating the multiple pathogenic phenotypes of NASH will be important for treatment. In this study, we found that CXXC5, a negative feedback regulator of the Wnt/β-catenin pathway, was overexpressed with suppression of Wnt/β-catenin signaling and its target genes involved in hepatic metabolism in obese-NASH patients. Cxxc5−/− mice were found to be resistant to NASH pathogenesis with metabolic improvements. KY19334, a small molecule that activates the Wnt/β-catenin pathway via interference of the CXXC5-Dvl interaction, reversed the overall pathogenic features of NASH as Cxxc5−/− mice. The improvement in NASH by KY19334 is attributed to its regenerative effects through restorative activation of the suppressed Wnt/β-catenin signaling. Overall, the pronounced metabolic improvements with the stimulation of liver regeneration by interfering with the CXXC5-Dvl interaction provide a therapeutic approach for NASH.

Therapeutic Potential of Semaglutide, a Newer GLP-1 Receptor Agonist, in Abating Obesity, Non-Alcoholic Steatohepatitis and Neurodegenerative diseases: A Narrative Review

INTRODUCTION

Semaglutide, a peptidic GLP-1 receptor agonist, has been clinically approved for treatment of type 2 diabetes mellitus and is available in subcutaneous and oral dosage form. Diabetes, insulin resistance, and obesity are responsible for the pathological manifestations of non-alcoholic steatohepatitis (NASH). Similarly, insulin resistance in brain is also responsible for neurodegeneration and impaired cognitive functions.

BACKGROUND

Observations from phase-3 clinical trials like SUSTAIN and PIONEER indicated anti-obesity potential of semaglutide, which was established in STEP trials. Various pre-clinical and phase-2 studies have indicated the therapeutic potential of semaglutide in non-alcoholic steatohepatitis and neurodegenerative disorders like Parkinson's and Alzheimer's disease.

DISCUSSION

Significant weight reduction ability of semaglutide has been demonstrated in various phase-3 clinical trials, for which recently semaglutide became the first long-acting GLP-1 receptor agonist to be approved by the United States Food and Drug Administration for management of obesity. Various pre-clinical and clinical studies have revealed the hepatoprotective effect of semaglutide in NASH and neuroprotective effect in Parkinson's and Alzheimer's disease.

CONCLUSION

Many GLP-1 receptor agonists have shown hepatoprotective and neuroprotective activity in animal and human trials. As semaglutide is an already clinically approved drug, successful human trials would hasten its inclusion into therapeutic treatment of NASH and neurodegenerative diseases. Semaglutide improves insulin resistance, insulin signalling pathway, and reduce body weight which are responsible for prevention or progression of NASH and neurodegenerative diseases.

Nonalcoholic Steatohepatitis (NASH) and Atherosclerosis: Explaining Their Pathophysiology, Association and the Role of Incretin-Based Drugs

Nonalcoholic steatohepatitis (NASH) is the most severe manifestation of nonalcoholic fatty liver disease (NAFLD), a common complication of type 2 diabetes, and may lead to cirrhosis and hepatocellular carcinoma. Oxidative stress and liver cell damage are the major triggers of the severe hepatic inflammation that characterizes NASH, which is highly correlated with atherosclerosis and coronary artery disease. Regarding drug therapy, research on the role of GLP-1 analogues and DPP4 inhibitors, novel classes of antidiabetic drugs, is growing. In this review, we outline the association between NASH and atherosclerosis, the underlying molecular mechanisms, and the effects of incretin-based drugs, especially GLP-1 RAs, for the therapeutic management of these conditions.

Liraglutide in patients with non-alcoholic fatty liver disease: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

A few randomized controlled trials (RCTs) have assessed the use of liraglutide as a treatment option in patients with non-alcoholic fatty liver disease (NAFLD). We aimed at critically appraising and summarizing these RCTs, providing precise effect estimates regarding the safety and efficacy of liraglutide in NAFLD.

METHODS

We searched major databases and grey literature from their inception to May 2019, for RCTs comparing liraglutide with placebo or active comparator in patients with NAFLD. We defined as primary efficacy outcomes the observed changes in hepatic fat content (HFC) and alanine aminotransferase levels (ALT). Metabolic outcomes of interest and major safety endpoints were also assessed.

RESULTS

We included five trials with 371 randomised participants in total. Liraglutide produced a non-significant decrease in HFC and ALT levels, compared to control. It induced a significant reduction in body mass index, primarily driven by reduction in patients with type 2 diabetes, while it did not affect significantly glycated hemoglobin levels and Homeostatic Model Assessment of Insulin Resistance. We also showed that liraglutide significantly decreased serum triglyceride levels, also driven by the observed reduction in patients with type 2 diabetes, however it did not significantly affect the rest lipid parameters. Liraglutide was associated with increased incidence of gastrointestinal adverse events, while, no other safety issues were identified.

CONCLUSION

Our results do not substantiate the use of liraglutide in patients with NAFLD yet, despite its promising role.

Glucagon-Like Peptide-1 Receptor Agonists for Non-Alcoholic Fatty Liver Disease in Type 2 Diabetes: A Meta-Analysis

OBJECTIVE

Non-alcoholic fatty liver disease is highly prevalent in patients with type 2 diabetes mellitus. Studies on glucagon-like peptide-1 receptor agonists for the treatment of non-alcoholic fatty liver disease have reported promising results. Despite this, there has been limited evidence of its efficacy in non-alcoholic fatty liver disease patients with type 2 diabetes mellitus. This meta-analysis examined existing evidence on the efficacy of glucagon-like peptide-1 receptor agonists on the management of non-alcoholic fatty liver disease in patients with type 2 diabetes mellitus.

METHODS

Medline, Embase and Cochrane Central Register of Controlled Trials (CENTRAL) were searched for articles discussing the efficacy of glucagon-like peptide-1 receptor agonists on non-alcoholic fatty liver disease in patients with type 2 diabetes mellitus. Values of standardized mean differences (SMD) and risk ratio (RR) were determined for continuous outcomes and dichotomous outcomes respectively.

RESULTS

8 studies involving 1,454 patients from 5 randomized controlled trials and 3 cohort studies were included in the analysis. Our analysis found significant improvements in hepatic fat content, liver biochemistry, body composition, glucose parameters, lipid parameters, insulin sensitivity and inflammatory markers following glucagon-like peptide-1 receptor agonist treatment. Glucagon-like peptide-1 receptor agonists significantly decreased hepatic fat content compared to metformin and insulin-based therapies. Glucagon-like peptide-1 receptor agonists also improved fibrosis markers, but this did not reach statistical significance.

CONCLUSION

With a high prevalence of obesity and non-alcoholic fatty liver disease among patients with type 2 diabetes mellitus, glucagon-like peptide-1 receptor agonist treatment shows promise in improving both diabetes and non-alcoholic fatty liver disease phenotype.

The role of bacterial metabolites derived from aromatic amino acids in non-alcoholic fatty liver disease

The review deals with the role of aromatic amino acids and their microbial metabolites in the development and progression of non-alcoholic fatty liver disease (NAFLD). Pathological changes typical for NAFLD, as well as abnormal composition and/or functional activity of gut microbiota, results in abnormal aromatic amino acid metabolism. The authors discuss the potential of these amino acids and their bacterial metabolites to produce both negative and positive impact on the main steps of NAFLD pathophysiology, such as lipogenesis and inflammation, as well as on the liver functions through regulation of the intestinal barrier and microbiota-gut-liver axis signaling. The review gives detailed description of the mechanism of biological activity of tryptophan and its derivatives (indole, tryptamine, indole-lactic, indole-propyonic, indole-acetic acids, and indole-3-aldehyde) through the activation of aryl hydrocarbon receptor (AhR), preventing the development of liver steatosis. Bacteria-produced phenyl-alanine metabolites could promote liver steatosis (phenyl acetic and phenyl lactic acids) or, on the contrary, could reduce liver inflammation and increase insulin sensitivity (phenyl propionic acid). Tyramine, para-cumarate, 4-hydroxyphenylacetic acids, being by-products of bacterial catabolism of tyrosine, can prevent NAFLD, whereas para-cresol and phenol accelerate the progression of NAFLD by damaging the barrier properties of intestinal epithelium. Abnormalities in bacterial catabolism of tyrosine, leading to its excess, stimulate fatty acid synthesis and promote lipid infiltration of the liver. The authors emphasize a close interplay between bacterial metabolism of aromatic amino acids by gut microbiota and the functioning of the human body. They hypothesize that microbial metabolites of aromatic amino acids may represent not only therapeutic targets or non-invasive biomarkers, but also serve as bioactive agents for NAFLD treatment and prevention.

PNPLA3 I148M is involved in the variability in anti-NAFLD response to exenatide

PURPOSE

GLP-1 receptor agonists, such as exenatide, have been proven to attenuate nonalcoholic fatty liver disease (NAFLD) in vivo and in vitro. However, the efficiency of exenatide had interindividual differences. PNPLA3 is a major susceptibility gene for NAFLD and its I148M polymorphism increases the risk of all disorders of the NAFLD spectrum. Whether this variant contributes to variability in exenatide response is still unclear.

METHODS

PNPLA3 148I knockin HepG2 cells were constructed using the Cas9/sgRNA system. Oil Red O staining combined with TG quantification was used to evaluate lipid accumulation. Western blotting and qRT-qPCR were conducted, respectively, to measure the protein and mRNA expression of lipid metabolic and endoplasmic reticulum (ER) stress-related inflammatory markers. PNPLA3 I148M was genotyped in type 2 diabetics using Sanger sequencing. The exenatide-induced changes in liver fat content and other clinical parameters were compared between PNPLA3 I148M genotypes.

RESULTS

Lipid deposition increased in both PNPLA3 148I/I and 148M/M HepG2 cells treated with palmitoleic acid, while cells with 148M/M had a higher TG content than those with 148I/I. Exendin-4 treatment was showed to be more significant in 148I/I cells than in 148M/M cells in terms of reducing the intrahepatic fat content, inhibiting SREBP-1c and ER stress-related inflammation, and activating AMPK-ACC lipid oxidation pathway. In patients with type 2 diabetes, 24-week treatment with exenatide improved liver fat content in patients carrying PNPLA3 148I/I better than in patients with 148M/M.

CONCLUSIONS

PNPLA3 I148M might modify the anti-NAFLD response to exenatide.

β-catenin mediates the effect of GLP-1 receptor agonist on ameliorating hepatic steatosis induced by high fructose diet

The hypoglycemic drug GLP-1 receptor agonist can ameliorate hepatic steatosis but the mechanism is not clear. Intake of high fructose leads to non-alcoholic fatty liver disease by stimulating lipid synthesis, and β-catenin is the key molecule for realizing GLP-1 function in extrahepatic tissues; with the discovery of GLP-1 receptor in liver, we speculate that β-catenin might mediate GLP-1 receptor agonist on ameliorating hepatic steatosis induced by high fructose. Wistar rats were fed with high fructose diet for 8 weeks and then treated with GLP-1 receptor agonist exenatide for 4 weeks; the changes of lipid synthesis pathway factors, the expression and nuclear translocation of β-catenin, and the hepatic steatosis of the rats were observed. After the intervention of exenatide, the hepatic steatosis induced by high fructose was improved, the nuclear translocation and expression of β-catenin were facilitated, and the mRNA and protein expression of the upstream regulator SREBP-1 and the downstream key enzymes ACC, FAS and SCD-1 of de novo lipogenesis were down-regulated. GLP-1 receptor agonist may ameliorate hepatic steatosis induced by high fructose by β-catenin regulating de novo lipogenesis pathway. GLP-1 receptor agonist may be a potential new drug for the treatment of non-alcoholic fatty liver disease, and the β-catenin may be an important target for the drug therapy.

Current and emerging pharmacotherapeutic interventions for the treatment of liver fibrosis

INTRODUCTION

Chronic liver disease is due to various causes of persistent liver damage and will eventually lead to the development of liver fibrosis. If no treatment is initiated, this condition may progress to cirrhosis and hepatocellular carcinoma. Current treatments comprise the elimination of the cause of injury, such as by lifestyle changes, alcohol abstinence, and antiviral agents. However, such etiology-driven therapy is often insufficient in patients with late-stage fibrosis/cirrhosis, therefore maintaining the need for efficient antifibrotic pharmacotherapeutic interventions.

AREAS COVERED

The authors discuss the recent advances in the development of antifibrotic drugs, which target various pathways of the fibrogenesis process, including cell death, inflammation, gut-liver axis, and myofibroblast activation. Due to the significant burden of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), various agents which specifically target metabolic pathways and their related receptors/ligands have been developed. For some of them, e.g., obeticholic acid, advanced stage clinical trials indicate antifibrotic efficacy in NAFLD and NASH.

EXPERT OPINION

Significant advances have been made in the development of novel antifibrotic pharmacotherapeutics. The authors expect that the development of combinatorial therapies, which combine compounds that target various pathways of fibrosis progression, will have a major impact as future etiology-independent therapies.

Post-transplant diabetes mellitus and preexisting liver disease - a bidirectional relationship affecting treatment and management

Liver cirrhosis and diabetes mellitus (DM) are both common conditions with significant socioeconomic burden and impact on morbidity and mortality. A bidirectional relationship exists between DM and liver cirrhosis regarding both etiology and disease-related complications. Type 2 DM (T2DM) is a well-recognized risk factor for chronic liver disease and vice-versa, DM may develop as a complication of cirrhosis, irrespective of its etiology. Liver transplantation (LT) represents an important treatment option for patients with end-stage liver disease due to non-alcoholic fatty liver disease (NAFLD), which represents a hepatic manifestation of metabolic syndrome and a common complication of T2DM. The metabolic risk factors including immunosuppressive drugs, can contribute to persistent or de novo development of DM and NAFLD after LT. T2DM, obesity, cardiovascular morbidities and renal impairment, frequently associated with metabolic syndrome and NAFLD, may have negative impact on short and long-term outcomes following LT. The treatment of DM in the context of chronic liver disease and post-transplant is challenging, but new emerging therapies such as glucagon-like peptide-1 receptor agonists (GLP-1RAs) and sodium–glucose cotransporter 2 inhibitors (SGLT2i) targeting multiple mechanisms in the shared pathophysiology of disorders such as oxidative stress and chronic inflammation are a promising tool in future patient management.

Molecular mechanisms of hepatic insulin resistance in nonalcoholic fatty liver disease and potential treatment strategies

The prevalence of nonalcoholic fatty liver disease (NAFLD) in the general population is estimated at 25 %, and there is currently no effective treatment of NAFLD. Although insulin resistance (IR) is not the only factor causing the pathogenesis of NAFLD, hepatic IR has a cause-effective relationship with NAFLD. Improving hepatic IR is a potential therapeutic strategy to treat NAFLD. This review highlights the molecular mechanisms of hepatic IR in the development of NAFLD. Available data on potential drugs including glucagon-like peptide 1 receptor (GLP-1) agonists, peroxisome proliferator-activated receptor (PPAR-γ/α/δ) agonists, farnesoid X receptor (FXR) agonists, etc. are carefully discussed.

Role of ATP-binding cassette transporter A1 in suppressing lipid accumulation by glucagon-like peptide-1 agonist in hepatocytes

Objective

Adenosine triphosphate (ATP)-binding cassette transporter A1 (ABCA1) influences hepatic cholesterol transportation. Accumulation of hepatic cholesterol leads to fatty liver disease, which is improved by glucagon-like peptide 1 (GLP-1) in diabetes. Therefore, we analyzed the molecular mechanism in the regulation of hepatic ABCA1 by GLP-1 analogue exendin-4.

Methods

Hepatic ABCA1 expression and transcription were checked by western blotting, real-time polymerase chain reaction (PCR), and luciferase assay in HepG2 cells. Chromatin immunoprecipitation (ChIP) and site-directed mutagenesis were employed to determine transcriptional regulation of the ABCA1 gene. Prolactin regulatory element-binding (PREB)-transgenic mice were generated to access the effect of exendin-4 on improving lipid accumulation caused by a high-fat diet (HFD).

Results

Exendin-4 stimulated hepatic ABCA1 expression and transcription via the Ca²⁺/calmodulin (CaM)-dependent protein kinase kinase/CaM-dependent protein kinase IV (CaMKK/CaMKIV) pathway, whereas GLP-1 receptor antagonist exendin9-39 cancelled this effect. Therefore, exendin-4 decreased hepatic lipid content. ChIP showed that PREB could directly bind to the ABCA1 promoter, which was enhanced by exendin-4. Moreover, PREB stimulated ABCA1 promoter activity, and mutation of PREB-binding site in ABCA1 promoter cancelled exendin-4-enhanced ABCA1 promoter activity. Silencing of PREB attenuated the effect of exendin-4 and induced hepatic cholesterol accumulation. Blockade of CaMKK by STO-609 or siRNA cancelled the upregulation of ABCA1 and PREB induced by exendin-4. In vivo, exendin-4 or overexpression of PREB increased hepatic ABCA1 expression and decreased hepatic lipid accumulation and high plasma cholesterol caused by a HFD.

Conclusions

Our data shows that exendin-4 stimulates hepatic ABCA1 expression and decreases lipid accumulation by the CaMKK/CaMKIV/PREB pathway, suggesting that ABCA1 and PREB might be the therapeutic targets in fatty liver disease.

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The GLP-1R agonist exendin-4 suppressed lipid accumulation by upregulating ABCA1 expression in hepatocytes.

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Exendin-4 regulated the expression and transcription of hepatic ABCA1 via the CaMKK/CaMKIV/PREB pathway.

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Overexpression of PREB or exendin-4 protected mouse liver from fatty liver by upregulation of ABCA1.

Effects of newer antidiabetic drugs on nonalcoholic fatty liver and steatohepatitis: Think out of the box!

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in Western societies and a major cause of hepatic disease worldwide. Its more severe type, namely nonalcoholic steatohepatitis (NASH), may result in the development of cirrhosis and hepatocellular carcinoma. NAFLD, and especially NASH, are also associated with increased cardiovascular morbidity and mortality. Type 2 diabetes mellitus (T2DM) predisposes to NAFLD development and progression via insulin resistance and hyperglycemia. It has also been reported that the majority of T2DM patients have NAFLD/NASH, thus potentially further increasing their cardiometabolic risk. Current guidelines recommend to screen for NAFLD in all T2DM patients and vice-versa. Lifestyle remains the first-line therapeutic option for NAFLD/NASH. Among antidiabetic drugs, pioglitazone was shown to improve histological features of NASH. More recently, there is an increasing interest regarding the effects of newer anti-diabetic drugs, such as dipeptidyl peptidase 4 inhibitors (DPP-4i), sodium glucose cotransporter 2 inhibitors (SGLT2i), and glucagon-like peptide-1 receptor agonists (GLP-1 RAs) on NAFLD/NASH. The present narrative review considers the up-to-date data on the impact of DPP-4i, SGLT2i, and GLP-1 RAs on biochemical and/or histological markers of NAFLD/NASH. The potential clinical implications of these findings in daily practice are also discussed. Taking into consideration the global increasing prevalence of NAFLD/NASH, therapeutic options that can prevent or treat this disease will exert considerable benefits on human health.