Glucagon-like peptide-1 receptor is present on human hepatocytes and has a direct role in decreasing hepatic steatosis in vitro by modulating elements of the insulin signaling pathway

GLP-1 Receptor Agonists in Non-Alcoholic Fatty Liver Disease: Current Evidence and Future Perspectives

To date, non-alcoholic fatty liver disease (NAFLD) is the most frequent liver disease, affecting up to 70% of patients with diabetes. Currently, there are no specific drugs available for its treatment. Beyond their anti-hyperglycemic effect and the surprising role of cardio- and nephroprotection, GLP-1 receptor agonists (GLP-1 RAs) have shown a significant impact on body weight and clinical, biochemical and histological markers of fatty liver and fibrosis in patients with NAFLD. Therefore, GLP-1 RAs could be a weapon for the treatment of both diabetes mellitus and NAFLD. The aim of this review is to summarize the evidence currently available on the role of GLP-1 RAs in the treatment of NAFLD and to hypothesize potential future scenarios.

Clinical Impact of Glucagon-Like Peptide-1 Receptor Analogs on the Complications of Obesity

BACKGROUND

Obesity is a chronic disease associated with increased morbidity and mortality due to its complications. The aims of obesity treatment are primarily to accomplish weight loss, and prevention or treatment of its complications. Lifestyle changes along with behavioral therapy constitute the first-line treatment of obesity followed by pharmacotherapy. Glucagon-like peptide receptor analogs (GLP-1 RAs) are among the approved pharmacotherapy options. Their central effect on suppressing appetite results in considerable weight loss. However, their effect on the complications of obesity has not been very well recognized. This review aims to analyze the effects of GLP-1 RAs on the complications of obesity, as diabetes mellitus, hypertension, nonalcoholic steatohepatitis (NASH), cardiovascular diseases, polycystic ovary syndrome, infertility, obstructive sleep apnea (OSA), osteoarthritis, cancer and central nervous system problems.

SUMMARY

Data from preclinical studies and clinical trials have been thoroughly evaluated. Effects regarding the complications as far as the scope of this review have covered can be summarized as blood glucose lowering, blood pressure lowering, resolution of NASH, improving major cardiovascular events, improving fertility and sex hormone levels, and improvement in OSA symptoms and in cognitive scores. Although the mechanisms are not fully elucidated, it is clear that the effects are not solely due to weight loss, but some pleiotropic effects like decreased inflammation, oxidative stress, and fibrosis also play a role in some of the complications.

KEY MESSAGES

Treating obesity is not only enabling weight loss but ameliorating complications related to obesity. Thus, any antiobesity medication has to have some favorable effects on the complications. As far as the GLP-RA's analogs are concerned, there seems to be an improvement in many of the complications regardless of the weight loss effect of these medications.

GLP-1 analogues in the treatment of obesity and non-alcoholic fatty liver disease

Type two diabetes has become a civilization disease in the recent years, and the accompanying obesity, metabolic syndrome and non-alcoholic fatty liver are often the inseparable components of the clinical presentation in patients with diabetes of this type. The treatment of each of these elements is important for optimal metabolic control of the patients, as well as directly affecting their life expectancy. However, The ideal solution would be to take as few drugs as possible, preferably drugs that have a beneficial effect on several coexisting diseases at the same time. In the recent years, there have been more and more reports about the pleiotropic effect of drugs affecting the incretin axis - GLP-1 analogues. The presented paper provides an overview of the latest knowledge on the effect of GLP-1 receptor agonists on weight reduction and reduction of changes in the course of non-alcoholic fatty liver disease.

Diagnostic and therapeutic strategies for non-alcoholic fatty liver disease

The global incidence rate of non-alcoholic fatty liver disease (NAFLD) is approximately 25%. With the global increase in obesity and its associated metabolic syndromes, NAFLD has become an important cause of chronic liver disease in many countries. Despite recent advances in pathogenesis, diagnosis, and therapeutics, there are still challenges in its treatment. In this review, we briefly describe diagnostic methods, therapeutic targets, and drugs related to NAFLD. In particular, we focus on evaluating carbohydrate and lipid metabolism, lipotoxicity, cell death, inflammation, and fibrosis as potential therapeutic targets for NAFLD. We also summarized the clinical research progress in terms of drug development and combination therapy, thereby providing references for NAFLD drug development.

Mroue K, Mall R, Ullah E, S. Al-Akl N, Arredouani A. Investigation of the Effect of Exendin-4 on Oleic Acid-Induced Steatosis in HepG2 Cells Using Fourier Transform Infrared Spectroscopy

Non-alcoholic fatty liver disease (NAFLD) is a common liver lesion that is untreatable with medications. Glucagon-like peptide-1 receptor (GLP-1R) agonists have recently emerged as a potential NAFLD pharmacotherapy. However, the molecular mechanisms underlying these drugs’ beneficial effects are not fully understood. Using Fourier transform infrared (FTIR) spectroscopy, we sought to investigate the biochemical changes in a steatosis cell model treated or not with the GLP-1R agonist Exendin-4 (Ex-4). HepG2 cells were made steatotic with 400 µM of oleic acid and then treated with 200 nM Ex-4 in order to reduce lipid accumulation. We quantified steatosis using the Oil Red O staining method. We investigated the biochemical alterations induced by steatosis and Ex-4 treatment using Fourier transform infrared (FTIR) spectroscopy and chemometric analyses. Analysis of the Oil Red O staining showed that Ex-4 significantly reduces steatosis. This reduction was confirmed by FTIR analysis, as the phospholipid band (C=O) at 1740 cm⁻¹ in Ex-4 treated cells is significantly decreased compared to steatotic cells. The principal component analysis score plots for both the lipid and protein regions showed that the untreated and Ex-4-treated samples, while still separated, are clustered close to each other, far from the steatotic cells. The biochemical and structural changes induced by OA-induced lipotoxicity are at least partially reversed upon Ex-4 treatment. FTIR and chemometric analyses revealed that Ex-4 significantly reduces OA-induced lipid accumulation, and Ex-4 also restored the lipid and protein biochemical alterations caused by lipotoxicity-induced oxidative stress. In combination with chemometric analyses, FTIR spectroscopy may offer new approaches for investigating the mechanisms underpinning NAFLD.

How Far beyond Diabetes Can the Benefits of Glucagon-like Peptide-1 Receptor Agonists Go? A Review of the Evidence on Their Effects on Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is characterized by poor survival rate and quality of life, while available treatments remain generally limited. Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) originally emerged as drugs for the management of diabetes, but have also been shown to alleviate cardiorenal risk. Furthermore, they have demonstrated a wide range of extraglycemic effects that led to their evaluation as potential therapies for a variety of diseases beyond diabetes, such as obesity, neurogenerative disorders and nonalcoholic fatty liver disease. Given the presence of the GLP-1 receptor in hepatocytes, animal data suggest that GLP-1 RAs could regulate molecular pathways that are deeply involved in the genesis and progression of HCC, including inflammatory responses, tumor cell proliferation and oxidative stress, through direct and indirect effects on liver cells. However, future studies must assess several aspects of the benefit-to-risk ratio of the use of GLP-1 RAs in patients with HCC, including co-administration with approved systemic therapies, the incidence of gastrointestinal side effects in a high-risk population, and weight loss management in individuals with poor nutritional status and high rates of cancer cachexia. In this narrative review, we discuss the potential role of GLP-1 analogs in the treatment of HCC, focusing on the molecular mechanisms that could justify a possible benefit, but also referring to the potential clinical implications and areas for future research.

Liraglutide Exerts Protective Effects by Downregulation of PPARγ, ACSL1 and SREBP-1c in Huh7 Cell Culture Models of Non-Alcoholic Steatosis and Drug-Induced Steatosis

(1) Background: With the aging of the population and polypharmacy encountered in the elderly, drug-induced steatosis (DIS) has become frequent cause of non-alcoholic steatosis (NAS). Indeed, NAS and DIS may co-exist, making the ability to distinguish between the entities ever more important. The aim of our study was to study cell culture models of NAS and DIS and determine the effects of liraglutide (LIRA) in those models. (2) Methods: Huh7 cells were treated with oleic acid (OA), or amiodarone (AMD) to establish models of NAS and DIS, respectively. Cells were treated with LIRA and cell viability was assessed by MTT, lipid accumulation by Oil-Red-O staining and triglyceride assay, and intracellular signals involved in hepatosteatosis were quantitated by RT-PCR. (3) Results: After exposure to various OA and AMD concentrations, those that achieved 80% of cells viabilities were used in further experiments to establish NAS and DIS models using 0.5 mM OA and 20 µM AMD, respectively. In both models, LIRA increased cell viability (p < 0.01). Lipid accumulation was increased in both models, with microsteatotic pattern in DIS, and macrosteatotic pattern in NAS which corresponds to greater triglyceride accumulation in latter. LIRA ameliorated these changes (p < 0.001), and downregulated expression of lipogenic ACSL1, PPARγ, and SREBP-1c pathways in the liver (p < 0.01) (4) Conclusions: LIRA ameliorates hepatocyte steatosis in Huh7 cell culture models of NAS and DIS.

Targeting bile acid signaling for the treatment of liver diseases: From bench to bed

Liver diseases and related complications have become one of the leading causes of morbidity and mortality worldwide, yet effective medicine or approved treatment approach is still limited. Thus, novel therapy is urgently required to prevent or at least slow down the growing burden of liver transplantation or even death caused by malignant liver diseases. As the irreplaceable modulator of hepatic and intestinal signaling cascades, bile acids (BAs) play complex physiological as well as pathological roles in regulating energy and immune homeostasis in various liver diseases, including but not limited to metabolic diseases and cholangiopathies, making them highly attractive therapeutic targets. In the current review, recent progress in the research of enterohepatic circulation of BAs and potential therapeutic targets of BAs signaling, especially the development of currently available treatments, including agonizts of FXR and TGR5, analogs of FGF19, inhibitors of ASBT, and the regulation of gut microbiome through fecal microbiota transplantation were extensively summarized. Their protective effects, molecular mechanisms, and outcomes of clinical trials were highlighted. The structural features of these candidates and perspectives for their future development were further discussed. In conclusion, we believe that pharmacological therapies targeting BAs signaling represent promising and efficient strategies for the treatment of complex and multifactorial liver disorders.

Nonalcoholic Steatohepatitis Drug Development Pipeline: An Update

Nonalcoholic steatohepatitis (NASH) is a burgeoning global health crisis that mirrors the obesity pandemic. This global health crisis has stimulated active research to develop novel NASH pharmacotherapies targeting dysregulated inflammatory, cellular stress, and fibrogenetic processes that include (1) metabolic pathways to improve insulin sensitivity, de novo lipogenesis, and mitochondrial utilization of fatty acids; (2) cellular injury or inflammatory targets that reduce inflammatory cell recruitment and signaling; (3) liver-gut axis targets that influence bile acid enterohepatic circulation and signaling; and (4) antifibrotic targets. In this review, we summarize several of the therapeutic agents that have been studied in phase 2 and 3 randomized trials. In addition to reviewing novel therapeutic drugs targeting nuclear receptor pathways, liver chemokine receptors, liver lipid metabolism, lipotoxicity or cell death, and glucagon-like peptide-1 receptors, we also discuss the rationale behind the use of combination therapy and the lessons learned from unsuccessful or negative clinical trials.

Semaglutide might be a key for breaking the vicious cycle of metabolically associated fatty liver disease spectrum?

Metabolically associated fatty liver disease (MAFLD) is a liver manifestation of metabolic syndrome potentially related to unfavorable hepatic and extrahepatic outcomes and progression to cirrhosis. Up to date, there are no approved pharmacotherapies for the treatment of MAFLD, so management focused on lifestyle interventions to encourage weight loss, and treatment of coexisting conditions is the only available option. Unfortunately, the aforementioned is often not potent enough to offer reversal or slow down hepatic inflammation and fibrosis. Glucagon-like peptide-1 receptor agonists have a favorable effect on glycemic management and weight loss of patients with type 2 diabetes mellitus and recently published data suggest their potential in MAFLD treatment. In addition, some of the agents have proven cardiovascular and renal benefits in dedicated cardiovascular outcome trials, making them an interesting therapeutic option. In this opinion review, we discuss the role of semaglutide in MAFLD.

GLP-1 Receptor Agonists in Neurodegeneration: Neurovascular Unit in the Spotlight

Defects in brain energy metabolism and proteopathic stress are implicated in age-related degenerative neuronopathies, exemplified by Alzheimer’s disease (AD) and Parkinson’s disease (PD). As the currently available drug regimens largely aim to mitigate cognitive decline and/or motor symptoms, there is a dire need for mechanism-based therapies that can be used to improve neuronal function and potentially slow down the underlying disease processes. In this context, a new class of pharmacological agents that achieve improved glycaemic control via the glucagon-like peptide 1 (GLP-1) receptor has attracted significant attention as putative neuroprotective agents. The experimental evidence supporting their potential therapeutic value, mainly derived from cellular and animal models of AD and PD, has been discussed in several research reports and review opinions recently. In this review article, we discuss the pathological relevance of derangements in the neurovascular unit and the significance of neuron–glia metabolic coupling in AD and PD. With this context, we also discuss some unresolved questions with regard to the potential benefits of GLP-1 agonists on the neurovascular unit (NVU), and provide examples of novel experimental paradigms that could be useful in improving our understanding regarding the neuroprotective mode of action associated with these agents.

A Novel Bacterium, Butyricimonas virosa, Preventing HFD-Induced Diabetes and Metabolic Disorders in Mice via GLP-1 Receptor

Knowledge of the impact of the gut microbiota on human health has increased, and modulation of the bacterial community is now considered a therapeutic target for various diseases. Certain novel bacterial species have probiotic properties associated with improvement in obesity and related metabolic disorders. The relative abundance of Butyricimonas spp. is correlated with metabolic parameters; however, the physiological role of Butyricimonas in metabolic improvement is unclear. In this study, live and heat-killed Butyricimonas virosa were administered to mice with high-fat diet (HFD)-induced obesity. Both live and heat-killed B. virosa ameliorated HFD-impaired body weight, serum glucose level, insulin resistance, and liver steatosis. Moreover, activation of the glucagon-like peptide-1 receptor (GLP-1R) and peroxisome proliferator-activated receptor α (PPARα) was observed in the liver, and the expression levels of insulin receptor substrate (IRS)-1, IRS-2, Toll-like receptor 5 (TLR5), and zonula occludens-1 (ZO-1) were upregulated in the ileum. Finally, we demonstrated that the effect of B. virosa treatment on glucose regulation may be linked to the upregulation of GLP-1R in the liver and is not a result of colonization of the gut by B. virosa or B. virosa-produced butyrate. Our results provide a rationale for the development of Butyricimonas spp.-based therapeutics and prophylactics for hyperglycemia.

A GLP-1/GLP-2 receptor dual agonist to treat NASH: Targeting the gut-liver axis and microbiome

BACKGROUND AND AIMS

Currently there is no Food and Drug Administration-approved drug to treat NAFLD and NASH, the rates of which are increasing worldwide. Although NAFLD/NASH are highly complex and heterogeneous conditions, most pharmacotherapy pipelines focus on a single mechanistic target. Considering the importance of the gut-liver axis in their pathogenesis, we investigated the therapeutic effect of a long-acting dual agonist of glucagon-like peptide (GLP)-1 and GLP-2 receptors in mice with NAFLD/NASH.

APPROACH AND RESULTS

C57BL/6J mice were fed a choline-deficient high-fat diet/high fructose and sucrose solution. After 16 weeks, mice were randomly allocated to receive vehicle, GLP1-Fc, GLP2-Fc, or GLP1/2-Fc fusion (GLP1/2-Fc) subcutaneously every 2 days for 4 weeks. Body weight was monitored, insulin/glucose tolerance tests were performed, feces were collected, and microbiome profiles were analyzed. Immobilized cell systems were used to evaluate direct peptide effect. Immunohistochemistry, quantitative PCR, immunoblot analysis, tunnel assay, and biochemical assays were performed to assess drug effects on inflammation, hepatic fibrosis, cell death, and intestinal structures. The mice had well-developed NASH phenotypes. GLP1/2-Fc reduced body weight, glucose levels, hepatic triglyceride levels, and cellular apoptosis. It improved liver fibrosis, insulin sensitivity, and intestinal tight junctions, and increased microvillus height, crypt depth, and goblet cells of intestine compared with a vehicle group. Similar effects of GLP1/2-Fc were found in in vitro cell systems. GLP1/2-Fc also changed microbiome profiles. We applied fecal microbiota transplantation (FMT) gain further insight into the mechanism of GLP1/2-Fc-mediated protection. We confirmed that FMT exerted an additive effect on GLP1-Fc group, including the body weight change, liver weight, hepatic fat accumulation, inflammation, and hepatic fibrosis.

CONCLUSIONS

A long-acting dual agonist of GLP-1 and GLP-2 receptors is a promising therapeutic strategy to treat NAFLD/NASH.

The anti-inflammatory feature of glucagon-like peptide-1 and its based diabetes drugs—Therapeutic potential exploration in lung injury

Since 2005, GLP-1 receptor (GLP-1R) agonists (GLP-1RAs) have been developed as therapeutic agents for type 2 diabetes (T2D). GLP-1R is not only expressed in pancreatic islets but also other organs, especially the lung. However, controversy on extra-pancreatic GLP-1R expression still needs to be further resolved, utilizing different tools including the use of more reliable GLP-1R antibodies in immune-staining and co-immune-staining. Extra-pancreatic expression of GLP-1R has triggered extensive investigations on extra-pancreatic functions of GLP-1RAs, aiming to repurpose them into therapeutic agents for other disorders. Extensive studies have demonstrated promising anti-inflammatory features of GLP-1RAs. Whether those features are directly mediated by GLP-1R expressed in immune cells also remains controversial. Following a brief review on GLP-1 as an incretin hormone and the development of GLP-1RAs as therapeutic agents for T2D, we have summarized our current understanding of the anti-inflammatory features of GLP-1RAs and commented on the controversy on extra-pancreatic GLP-1R expression. The main part of this review is a literature discussion on GLP-1RA utilization in animal models with chronic airway diseases and acute lung injuries, including studies on the combined use of mesenchymal stem cell (MSC) based therapy. This is followed by a brief summary.

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.

Renin–Angiotensin System in Liver Metabolism: Gender Differences and Role of Incretins

The impaired hepatic lipids and carbohydrates metabolism result in various metabolic disorders, including obesity, diabetes, insulin resistance, hyperlipidemia and metabolic syndrome. The renin–angiotensin system (RAS) has been identified in the liver and it is now recognized as an important modulator of body metabolic processes. This review is intended to provide an update of the impact of the renin–angiotensin system on lipid and carbohydrate metabolism, regarding gender difference and prenatal undernutrition, specifically focused on the role of the liver. The discovery of angiotensin-converting enzyme 2 (ACE2) has renewed interest in the potential therapeutic role of RAS modulation. RAS is over activated in non-alcoholic fatty liver disease (NAFLD) and hepatocellular carcinoma. Glucagon-like peptide-1 (GLP-1) has been shown to modulate RAS. The GLP-I analogue liraglutide antagonizes hepatocellular steatosis and exhibits liver protection. Liraglutide has a negative effect on the ACE/AngII/AT1R axis and a positive impact on the ACE2/Ang(1-7)/Mas axis. Activation of the ACE2/Ang(1-7)/Mas counter-regulatory axis is able to prevent liver injuries. Angiotensin(1-7) and ACE2 shows more favorable effects on lipid homeostasis in males but there is a need to do more investigation in female models. Prenatal undernutrition exerts long-term effects in the liver of offspring and is associated with a number of metabolic and endocrine alterations. These findings provide a novel therapeutic regimen to prevent and treat many chronic diseases by accelerating the effect of the ACE2/Ang1-7/Mas axis and inhibiting the ACE/AngII/AT1R axis.

GLP-1 mimetics as a potential therapy for nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH), as a severe form of nonalcoholic fatty liver disease (NAFLD), is characterized by liver steatosis, inflammation, hepatocellular injury and different degrees of fibrosis. The pathogenesis of NASH is complex and multifactorial, obesity and type 2 diabetes mellitus (T2DM) have been implicated as major risk factors. Glucagon-like peptide-1 receptor (GLP-1R) is one of the most successful drug targets of T2DM and obesity, and its peptidic ligands have been proposed as potential therapeutic agents for NASH. In this article we provide an overview of the pathophysiology and management of NASH, with a special focus on the pharmacological effects and possible mechanisms of GLP-1 mimetics in treating NAFLD/NASH, including dual and triple agonists at GLP-1R, glucose-dependent insulinotropic polypeptide receptor or glucagon receptor.

Comparative Transcriptome Analysis Reveals That Exendin-4 Improves Steatosis in HepG2 Cells by Modulating Signaling Pathways Related to Lipid Metabolism

No therapy exists for non-alcoholic fatty liver disease (NAFLD). However, glucagon-like peptide receptor agonists (GLP-1RAs) showed a beneficial effect on NAFLD, although the underpinning mechanisms remain unclear due to their pleiotropic effects. We examined the implicated signaling pathways using comparative transcriptomics in a cell model of steatosis to overcome pleiotropy. We treated steatotic HepG2 cells with the GLP-1RA Exendin-4 (Ex-4). We compared the transcriptome profiles of untreated steatotic, and Ex-4-treated steatotic cells, and used Ingenuity Pathway Analysis (IPA) to identify the signaling pathways and associated genes involved in the protective effect of Ex-4. Ex-4 treatment significantly reduces steatosis. RNA-seq analysis revealed 209 differentially expressed genes (DEGs) between steatotic and untreated cells, with farnesoid X receptor/retinoid X receptor (FXR/RXR) (p = 8.9 × 10−7) activation being the top regulated canonical pathway identified by IPA. Furthermore, 1644 DEGs were identified between steatotic cells and Ex-4-treated cells, with liver X receptor/retinoid X receptor (LXR/RXR) (p = 2.02 × 10−7) and FXR/RXR (p = 3.28 × 10−7) activation being the two top canonical pathways. The top molecular and cellular functions between untreated and steatotic cells were lipid metabolism, molecular transport, and small molecular biochemistry, while organismal injury and abnormalities, endocrine system disorders, and gastrointestinal disease were the top three molecular and cellular functions between Ex-4-treated and steatotic cells. Genes overlapping steatotic cells and Ex-4-treated cells were associated with several lipid metabolism processes. Unique transcriptomic differences exist between steatotic cells and Ex-4-treated steatotic cells, providing an important resource for understanding the mechanisms that underpin the protective effect of GLP-1RAs on NAFLD and for the identification of novel therapeutic targets for NAFLD.

Review article: role of glucagon-like peptide-1 receptor agonists in non-alcoholic steatohepatitis, obesity and diabetes-what hepatologists need to know

BACKGROUND

Non-alcoholic steatohepatitis (NASH) is characterised by hepatic lipid accumulation, cell injury, inflammation and fibrosis. Insulin resistance, a hallmark of type 2 diabetes (T2D) and obesity, is a key pathogenic driver of NASH. Other than difficult-to-maintain lifestyle changes, there are no approved treatments for NASH. Due to their effects on multiple pathophysiological processes, glucagon-like peptide-1 receptor agonists (GLP-1RAs) have been tested in disorders related to insulin resistance and metabolic defects.

AIMS

To summarise studies of GLP-1RAs relevant to the treatment of NASH.

METHODS

PubMed searches were performed and results were compiled.

RESULTS

Large trials with GLP-1RAs in T2D demonstrate highly effective glucose lowering, with body weight loss, and in some cases, reduced cardiovascular events and improved liver transaminases. The GLP-1RAs, liraglutide and semaglutide, were associated with clinically relevant, sustained body weight reduction in individuals with overweight or obesity and without T2D. In a phase II trial in NASH, liraglutide reduced metabolic dysfunction, insulin resistance and lipotoxicity in key organs associated with NASH pathogenesis. Furthermore, liraglutide and semaglutide led to histological resolution of NASH in ~40% to 60% of patients, although a statistically significant effect on fibrosis has not been confirmed. Regarding safety, GLP-1RAs are associated with gastrointestinal and gallbladder-related adverse events, with the latter perhaps related to weight loss. Meta-analyses do not indicate increased risk of acute pancreatitis, pancreatic cancer or other malignancies with GLP-1RAs.

CONCLUSIONS

These studies support the use of GLP-1RAs for the improvement of underlying metabolic dysfunction observed in NASH and suggest further long-term phase III trials are warranted.

Hepatic steatosis changes after early gastric cancer surgery

Background: Nonalcoholic fatty liver disease dramatically improves after bariatric surgery, primarily due to improvements in hepatic insulin sensitivity. Since the procedure for gastric cancer surgery is very similar to that for bariatric surgery, we investigated changes in fatty liver following gastrectomy for gastric cancer according to the type of surgery.Methods: We evaluated hepatic steatosis in 212 early gastric cancer patients using Hounsfield units (HUs) on non-contrast computed tomography preoperatively and 6, 12, and 24 months after surgery. We compared the preoperative and postoperative liver-to-spleen HU ratio according to the type of surgery: Billroth I, Billroth II, and total gastrectomy with Roux-en-Y reconstruction. Results: The initial results (liver/spleen HUs and the liver-to-spleen HU ratio) did not significantly differ according to surgical group. After surgery, only patients who underwent total gastrectomy with Roux-en-Y exhibited significant changes in the liver-to-spleen HU ratio at 6 months. In 26 patients who had higher initial HU levels of the spleen than the liver, the liver-to-spleen HU ratio significantly increased from 0.836 to 1.115 at 6 months, 1.109 at 12 months, and 1.102 at 24 months (P<0.01). Conclusion: Significant changes in hepatic steatosis were found in even normal patients (with higher liver than spleen HU values) who underwent total gastrectomy with Roux-en-Y. Patients who initially had fatty liver also showed a significant increase in the liver-to-spleen HU ratio. These results suggest that total gastrectomy with Roux-en-Y reconstruction can have a positive effect on the improvement of hepatic steatosis.

SGLT2 Inhibitors as the Most Promising Influencers on the Outcome of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD), the most frequent liver disease in the Western world, is a common hepatic manifestation of metabolic syndrome (MetS). A specific cure has not yet been identified, and its treatment is currently based on risk factor therapy. Given that the initial accumulation of triglycerides in the liver parenchyma, in the presence of inflammatory processes, mitochondrial dysfunction, lipotoxicity, glucotoxicity, and oxidative stress, can evolve into non-alcoholic steatohepatitis (NASH). The main goal is to identify the factors contributing to this evolution because, once established, untreated NASH can progress through fibrosis to cirrhosis and, ultimately, be complicated by hepatocellular carcinoma (HCC). Several drugs have been tested in clinical trials for use as specific therapy for NAFLD; most of them are molecules used to cure type 2 diabetes mellitus (T2DM), which is one of the main risk factors for NAFLD. Among the most studied is pioglitazone, either alone or in combination with vitamin E, glucagon-like peptide-1 (GLP-1) receptor agonists, dipeptidyl peptidase-4 (DPP-4) inhibitors. Actually, the most promising category seems to be sodium-glucose cotransporter (SGLT2) inhibitors. Their action is carried out by inhibiting glucose reabsorption in the proximal renal tubule, leading to its increased excretion in urine and decreased levels in plasma. Experimental studies in animal models have suggested that SGLT2 inhibitors may have beneficial modulatory effects on NAFLD/NASH, and several trials in patients have proven their beneficial effects on liver enzymes, BMI, blood lipids, blood glucose, and insulin resistance in NAFLD patients, thus creating strong expectations for their possible use in preventing the evolution of liver damage in these patients. We will review the main pathogenetic mechanisms, diagnostic modalities, and recent therapies of NAFLD, with particular attention to the use of SGLT2 inhibitors.

Role of diabetologists in the management of nonalcoholic fatty liver disease: Primary prevention and screening/management of fibrosis and cirrhosis

BACKGROUND AND AIMS

Nonalcoholic fatty liver disease (NAFLD) is a common condition, especially among individuals with type 2 diabetes (T2D). Presence of T2D increases the risk of progression of simple steatosis to more severe liver conditions, such as nonalcoholic steatohepatitis (NASH) and fibrosis (NASH-fibrosis). Since majority of patients with T2D are managed by diabetologists (including physicians and endocrinologists), their roles in the management of coexisting NAFLD are not well defined, partly due to lack of unambiguous guidelines.

METHODS

A literature search was performed with Medline (PubMed), Scopus and Google Scholar electronic databases till January 2022, using relevant keywords (nonalcoholic fatty liver disease and diabetologist; screening of NASH; management of NASH) to extract relevant studies describing prevention and screening of NAFLD/NASH, especially in people with T2D.

RESULTS

Diabetologists have two main roles for the management of patients with T2D and coexisting NAFLD. The most important role is to prevent the development of NASH-fibrosis in patients with simple steatosis (primary prevention). This can be achieved by reinforcing the importance of lifestyle measures, and by early use of glucose-lowering agents with beneficial effects on the liver. The second important role of diabetologists is to screen all patients with T2D for liver fibrosis and compensated cirrhosis, and provide appropriate referral for timely management of complications (secondary prevention).

CONCLUSION

Diabetologists can play a central role in mitigating the epidemic of NAFLD in individuals with T2D. However, diabetologists need to be aware about their roles in NASH-fibrosis prevention and screening. Furthermore, longitudinal studies should explore the role of newer glucose-lowering drugs in the primary prevention of NASH-fibrosis in individuals with coexisting T2D and simple steatosis.

Therapeutic developments in metabolic dysfunction-associated fatty liver disease

Metabolic dysfunction-associated fatty liver disease (MAFLD) has become one of the most prevalent chronic liver diseases worldwide, bringing risk of multiorgan disfunctions including cardiovascular events, complications of cirrhosis, and even malignance. In terms of health burden management, screening patients with high risk of MAFLD and providing individual comprehensive treatment is critical. Although there are numerous agents entering clinical trials for MAFLD treatment every year, there is still no effective approved drug. The nomenclature of MAFLD highlighted the concomitant metabolic disorders and obesity. MAFLD patients with type 2 diabetes had higher risk of developing liver cirrhosis and cancer, and would benefit from anti-hyperglycemic agents; overweight and obese patients may benefit more from weight loss therapies; for patients with metabolic syndrome, individual comprehensive management is needed to reduce the risk of adverse outcomes. In this review, we introduced the current status and advances of the treatment of MAFLD based on weight loss, improving insulin resistance, and management of cardiometabolic disorders, in order to provide individualized therapy approaches for patients with MAFLD.

Efficacy of Off-Label Therapy for Non-alcoholic Fatty Liver Disease in Improving Non-invasive and Invasive Biomarkers: A Systematic Review and Network Meta-Analysis of Randomized Controlled Trials

Objective

To evaluate the effects of vitamin E, pioglitazone, sodium-glucose cotransporter-2 (SGLT2) inhibitors, and glucagon-like peptide-1 (GLP-1) receptor agonists in patients with non-alcoholic fatty liver disease (NAFLD).

Design

A network meta-analysis.

Data Sources

PubMed, Embase, Cochrane Library, and Web of Science databases from their inception until September 1, 2021.

Eligibility Criteria for Selecting Studies

Randomized controlled trials (RCTs) comparing the effects of four different drugs in patients with NAFLD were included. All superiority, non-inferiority, phase II and III, non-blinded, single-blinded, and double-blinded trials were included. Interventions of interest included vitamin E (α-tocopherol and δ-tocotrienol), pioglitazone, three kinds of GLP-1 receptor agonists (liraglutide, semaglutide, and dulaglutide), four SGLT2 inhibitors (dapagliflozin, empagliflozin, ipragliflozin, and tofogliflozin), and comparisons of these different drugs, and placebos.

Main Outcome Measures

The outcome measures included changes in non-invasive tests [alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), controlled attenuation parameter (CAP), enhanced liver fibrosis (ELF) score, liver fat content (LFC), and keratin-18 (K-18)] and invasive tests [fibrosis score and resolution of non-alcoholic steatohepatitis (NASH)].

Results

Twenty-seven trials including 3,416 patients were eligible for inclusion in the study. Results refer to vitamin E, pioglitazone, GLP-1 receptor agonists, and SGLT2 inhibitors. First, placebos were used as a reference. δ-Tocotrienol was superior to placebo in decreasing the GGT level. Semaglutide, ipragliflozin, and pioglitazone induced a significantly higher decrease in the ALT level than a placebo. Semaglutide, pioglitazone, and dapagliflozin were superior to placebo in decreasing the AST level. Tofogliflozin and pioglitazone induced a significantly higher decrease in the K-18 level than a placebo. Liraglutide was superior to placebo in decreasing CAP. Liraglutide, pioglitazone, and vitamin E induced a significantly higher increase in resolution of NASH than a placebo. As for pairwise comparisons, semaglutide and pioglitazone were superior to liraglutide in decreasing the ALT level. Semaglutide induced a significantly higher decrease in the ALT level than dulaglutide. Semaglutide was obviously superior to empagliflozin, liraglutide, dulaglutide, and tofogliflozin in decreasing the AST level. Pioglitazone induced a significantly higher decrease in the GGT level than ipragliflozin. δ-Tocotrienol was superior to liraglutide in decreasing the GGT level. Tofogliflozin and pioglitazone induced a significantly higher decrease in the K-18 level than dulaglutide. Pioglitazone was superior to vitamin E in increasing the resolution of NASH. Furthermore, liraglutide treatment had the highest SUCRA ranking in decreasing CAP and ELF scores and increasing the resolution of NASH. Pioglitazone treatment had the highest SUCRA ranking in decreasing LFC and fibrosis scores. Tofogliflozin treatment had the highest SUCRA ranking in decreasing K-18, while dapagliflozin treatment had the highest SUCRA ranking in decreasing the GGT level. Semaglutide treatment had the highest SUCRA ranking in decreasing the levels of ALT and AST.

Conclusion

The network meta-analysis provided evidence for the efficacy of vitamin E, pioglitazone, SGLT2 inhibitors, and GLP-1 receptor agonists in treating patients with NAFLD. To find the best guide-level drugs, it is necessary to include more RCTs with these off-label drugs, so that patients and clinicians can make optimal decisions together.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero, identifier: CRD42021283129.

Exendin-4 alleviates steatosis in an in vitro cell model by lowering FABP1 and FOXA1 expression via the Wnt/-catenin signaling pathway

Non-alcoholic fatty liver disease (NAFLD) is the leading chronic liver disease worldwide. Agonists of the glucagon-like peptide-1 receptor (GLP-1R), currently approved to treat type 2 diabetes, hold promise to improve steatosis and even steatohepatitis. However, due to their pleiotropic effects, the mechanisms underlying their protective effect on NAFLD remain elusive. We aimed to investigate these mechanisms using an in vitro model of steatosis treated with the GLP-1R agonist Exendin-4 (Ex-4). We established steatotic HepG2 cells by incubating the cells with 400 µM oleic acid (OA) overnight. Further treatment with 200 nM Ex-4 for 3 h significantly reduced the OA-induced lipid accumulation (p < 0.05). Concomitantly, Ex-4 substantially reduced the expression levels of Fatty Acid-Binding Protein 1 (FABP1) and its primary activator, Forkhead box protein A1 (FOXA1). Interestingly, the silencing of β-catenin with siRNA abolished the effect of Ex-4 on these genes, suggesting dependency on the Wnt/β-catenin pathway. Additionally, after β-catenin silencing, OA treatment significantly increased the expression of nuclear transcription factors SREBP-1 and TCF4, whereas Ex-4 significantly decreased this upregulation. Our findings suggest that direct activation of GLP-1R by Ex-4 reduces OA-induced steatosis in HepG2 cells by reducing fatty acid uptake and transport via FABP1 downregulation.

State-of-the-Art Overview of the Pharmacological Treatment of Non-Alcoholic Steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide, and non-alcoholic steatohepatitis (NASH), a subtype of NAFLD, can progress to cirrhosis, hepatocellular carcinoma, and death. Nevertheless, the current treatment for NAFLD/NASH is limited to lifestyle modifications, and no drugs are currently officially approved as treatments for NASH. Many global pharmaceutical companies are pursuing the development of medications for the treatment of NASH, and results from phase 2 and 3 clinical trials have been published in recent years. Here, we review data from these recent clinical trials and reports on the efficacy of newly developed antidiabetic drugs in NASH treatment.

Novel Antidiabetic Strategies and Diabetologists' Views in Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease worldwide with high prevalence, especially in individuals with obesity and type 2 diabetes. Among individuals with type 2 diabetes, the severe insulin resistant subgroup has the greatest risk of NAFLD, likely due to dysfunctional adipose tissue mass but also genetic factors, and may progress earlier to inflammatory and profibrotic nonalcoholic steatohepatitis (NASH). NASH has been associated with increased liver-related as well as cardiovascular morbidity and mortality. International diabetes associations recommend certain screening and treatment strategies for NASH in type 2 diabetes, which, however, bear several limitations such as lack of accurate noninvasive diagnostic tools and targeted treatments. Currently, antihyperglycemic drug concepts based on glucagon-like peptide-1 receptor agonists and sodium glucose cotransporter 2 inhibitors offer metabolic as well as cardiorenal benefits and provide treatment options for both hyperglycemia and NASH in type 2 diabetes.

Myricetin Increases Circulating Adropin Level after Activation of Glucagon-like Peptide 1 (GLP-1) Receptor in Type-1 Diabetic Rats

Myricetin is a common plant-derived flavonoid, considered an agonist of glucagon-like peptide 1 (GLP-1) receptor. It improves glycemic control and helps reduce body weight in diabetic subjects. The potential mechanisms of action of myricetin in this context might be enhancing the secretion of β-endorphin (BER) to activate peripheral μ-opioid receptors. Moreover, adropin is a nutritionally regulated peptide hormone, which regulates energy metabolism, and plays a role in ameliorating diabetes. Because their mechanisms of insulin sensitivity are closely related, we hypothesized that myricetin may interact with adropin and plasma BER. The present study investigated the glucose-lowering effect of acute and chronic treatments of myricetin in type-1 diabetic rats. Plasma BER and adropin levels were determined by enzyme-linked immunosorbent assay (ELISA). The secretion of BER was measured in rats who received adrenalectomy. The changes in adropin gene (Enho) or mRNA level of GLP-1 receptor were measured using qPCR analysis. The results showed that myricetin dose-dependently increased plasma BER and adropin levels like the reduction of hyperglycemia after bolus injection as acute treatment. In addition, these effects of myricetin were inhibited by the antagonist of GLP-1 receptor. Moreover, in HepG2 cell line, myricetin induced GLP-1 receptor activation, which modulated the expression of adropin. In diabetic rats, the plasma adropin increased by myricetin is mainly through endogenous β-endorphin after activation of GLP-1 receptor via bolus injection as acute treatment. Additionally, chronic treatment with myricetin increased adropin secretion in diabetic rats. In conclusion, our results provide a new finding that activation of opioid μ-receptor in the liver may enhance circulating adropin in animals.

Sitagliptin Is More Effective Than Gliclazide in Preventing &nbsp;Pro-Fibrotic and Pro-Inflammatory Changes in a Rodent Model of Diet-Induced Non-Alcoholic Fatty Liver Disease

A diet-induced non-alcoholic fatty liver disease (NAFLD) model causing obesity in rodents was used to examine whether sitagliptin and gliclazide therapies have similar protective effects on pathological liver change. Methods: Male mice were fed a high-fat diet (HFD) or standard chow (Chow) ad libitum for 25 weeks and randomly allocated to oral sitagliptin or gliclazide treatment for the final 10 weeks. Fasting blood glucose and circulating insulin were measured. Inflammatory and fibrotic liver markers were assessed by qPCR. The second messenger ERK and autophagy markers were examined by Western immunoblot. F4/80, collagens and CCN2 were assessed by immunohistochemistry (IHC). Results: At termination, HFD mice were obese, hyperinsulinemic and insulin-resistant but non-diabetic. The DPP4 inhibitor sitagliptin prevented intrahepatic induction of pro-fibrotic markers collagen-IV, collagen-VI, CCN2 and TGF-β1 and pro-inflammatory markers TNF-α and IL-1β more effectively than sulfonylurea gliclazide. By IHC, liver collagen-VI and CCN2 induction by HFD were inhibited only by sitagliptin. Sitagliptin had a greater ability than gliclazide to normalise ERK-protein liver dysregulation. Conclusion: These data indicate that sitagliptin, compared with gliclazide, exhibits greater inhibition of pro-fibrotic and pro-inflammatory changes in an HFD-induced NAFLD model. Sitagliptin therapy, even in the absence of diabetes, may have specific benefits in diet-induced NAFLD.

Glucagon-Like Peptide-1 Receptor Agonists and Dual Glucose-Dependent Insulinotropic Polypeptide/Glucagon-Like Peptide-1 Receptor Agonists in the Treatment of Obesity/Metabolic Syndrome, Prediabetes/Diabetes and Non-Alcoholic Fatty Liver Disease-Current Evidence

The obesity pandemic is accompanied by increased risk of developing metabolic syndrome (MetS) and related conditions: non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH), type 2 diabetes mellitus (T2DM) and cardiovascular (CV) disease (CVD). Lifestyle, as well as an imbalance of energy intake/expenditure, genetic predisposition, and epigenetics could lead to a dysmetabolic milieu, which is the cornerstone for the development of cardiometabolic complications. Glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) and dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 RAs promote positive effects on most components of the "cardiometabolic continuum" and consequently help reduce the need for polypharmacy. In this review, we highlight the main pathophysiological mechanisms and risk factors (RFs), that could be controlled by GLP-1 and dual GIP/GLP-1 RAs independently or through synergism or differences in their mode of action. We also address the evidence on the use of GLP-1 and dual GIP/GLP-1 RAs in the treatment of obesity, MetS and its related conditions (prediabetes, T2DM and NAFLD/NASH). In conclusion, GLP-1 RAs have already been established for the treatment of T2DM, obesity and cardioprotection in T2DM patients, while dual GIP/GLP-1 RAs appear to have the potential to possibly surpass them for the same indications. However, their use in the prevention of T2DM and the treatment of complex cardiometabolic metabolic diseases, such as NAFLD/NASH or other metabolic disorders, would benefit from more evidence and a thorough clinical patient-centered approach. There is a need to identify those patients in whom the metabolic component predominates, and whether the benefits outweigh any potential harm.

Effects of sitagliptin on intrahepatic lipid content in patients with non-alcoholic fatty liver disease

PURPOSE

Dipeptidyl peptidase-4 inhibitors (DPP-4I), key regulators of the actions of incretin hormones, exert anti-hyperglycemic effects in type 2 diabetes mellitus (T2DM) patients. A major unanswered question concerns the potential ability of DPP-4I to improve intrahepatic lipid (IHL) content in nonalcoholic fatty liver disease (NAFLD) patients. The aim of this study was to evaluate the effects of sitagliptin on IHL in NAFLD patients.

METHODS

A prospective, 24-week, single-center, open-label, comparative study enrolled 68 Chinese NAFLD patients with T2DM. Subjects were randomly divided into 4 groups: control group who did not take medicine (14 patients); sitagliptin group who received sitagliptin treatment (100mg per day) (17 patients); metformin group who received metformin (500mg three times per day) (17 patients); and sitagliptin plus metformin group who received sitagliptin (100mg per day) and metformin (500 mg three times per day) (20 patients). IHL, physical examination (waist circumstances, WC; body mass index, BMI), glucose-lipid metabolism (fasting plasma glucose, FPG; hemoglobin A1c, Hb1A1c; triglycerides; cholesterol; alanine aminotransferase, ALT; aspartate aminotransferase, AST) were measured at baseline and at 24 weeks.

RESULTS

1) WC and BMI were decreased significantly in all groups except control group (all P<0.05). 2) There was no statistically significant difference in IHL among the sitagliptin, metformin, and sitagliptin plus metformin groups before and after treatment(all P>0.05). Only the metformin group showed a statistically significant difference in IHL before and after treatment(P<0.05). 3) Sitagliptin treatment led to a significant decrease in FBG and HbA1c when compared with the control group (all P<0.01). Additionally, HhA1c was significant decreased in the sitagliptin group when compared with the metformin group (P< 0.05). 4) HbA1c and FBG were decreased by 0.8% and 0.7 mmol/l respectively and the percentage of patients with HbA1c less than 7% was 65% with sitagliptin treatment.

CONCLUSION

Sitagliptin improves abnormalities in glucose metabolism, but not reduces the IHL in T2DM with NAFLD, indicating that sitagliptin might be a therapeutic option for treatment of NAFLD indirectly while not directly on IHL. Clinical Trial Registration: https://clinicaltrials.gov/, identifier CTR# NCT05480007.

Recovery of Bacteroides thetaiotaomicron ameliorates hepatic steatosis in experimental alcohol-related liver disease

Alcohol-related liver disease (ALD) is a major cause of liver disease and represents a global burden, as treatment options are scarce. Whereas 90% of ethanol abusers develop alcoholic fatty liver disease (AFLD), only a minority evolves to steatohepatitis and cirrhosis. Alcohol increases lipogenesis and suppresses lipid-oxidation implying steatosis, although the key role of intestinal barrier integrity and microbiota in ALD has recently emerged. Bacteroides thetaiotaomicron (Bt) is a prominent member of human and murine intestinal microbiota, and plays important functions in metabolism, gut immunity, and mucosal barrier. We aimed to investigate the role of Bt in the genesis of ethanol-induced liver steatosis. Bt DNA was measured in feces of wild-type mice receiving a Lieber-DeCarli diet supplemented with an increase in alcohol concentration. In a second step, ethanol-fed mice were orally treated with living Bt, followed by analysis of intestinal homeostasis and histological and biochemical alterations in the liver. Alcohol feeding reduced Bt abundance, which was preserved by Bt oral supplementation. Bt-treated mice displayed lower hepatic steatosis and triglyceride content. Bt restored mucosal barrier and reduced LPS translocation by enhancing mucus thickness and production of Mucin2. Furthermore, Bt up-regulated Glucagon-like peptide-1 (GLP-1) expression and restored ethanol-induced Fibroblast growth factor 15 (FGF15) down-regulation. Lipid metabolism was consequently affected as Bt administration reduced fatty acid synthesis (FA) and improved FA oxidation and lipid exportation. Moreover, treatment with Bt preserved the mitochondrial fitness and redox state in alcohol-fed mice. In conclusion, recovery of ethanol-induced Bt depletion by oral supplementation was associated with restored intestinal homeostasis and ameliorated experimental ALD. Bt could serve as a novel probiotic to treat ALD in the future.

Potential Effect of DPP-4 Inhibitors Towards Hepatic Diseases and Associated Glucose Intolerance

Dipeptidyl-peptidase-4 (DPP-4) is an enzyme having various properties and physiological roles in lipid accumulation, resistance to anticancer agents, and immune stimulation. DPP-4 includes membrane-bound peptidases and is a kind of enzyme that cleaves alanine or proline-containing peptides such as incretins, chemokines, and appetite-suppressing hormones (neuropeptide) at their N-terminal dipeptides. DPP-4 plays a role in the final breakdown of peptides produced by other endo and exo-peptidases from nutritious proteins and their absorption in these tissues. DPP-4 enzyme activity has different modes of action on glucose metabolism, hunger regulation, gastrointestinal motility, immune system function, inflammation, and pain regulation. According to the literature survey, as DPP-4 levels increase in individuals with liver conditions, up-regulation of hepatic DPP-4 expression is likely to be the cause of glucose intolerance or insulin resistance. This review majorly focuses on the cleavage of alanine or proline-containing peptides such as incretins by the DPP-4 and its resulting conditions like glucose intolerance and cause of DPP-4 level elevation due to some liver conditions. Thus, we have discussed the various effects of DPP-4 on the liver diseases like hepatitis C, non-alcoholic fatty liver, hepatic regeneration and stem cell, hepatocellular carcinoma, and the impact of elevated DPP-4 levels in association with liver diseases as a cause of glucose intolerance and their treatment drug of choices. In addition, the effect of DPP-4 inhibitors on obesity and their negative aspects are also discussed in brief.

The role of nursing care in the type 2 diabetes treatment associated with chronic liver diseases

OBJECTIVE

Diabetes is the fifth leading cause of death in the People's Republic of China. The aim of the article is to compare the effects of nursing care on the laboratory findings and ultrasound results of diabetic patients with chronic liver diseases (CLD) who were treated with antiglycemic drugs.

METHODS

Diabetic were patients treated with metformin hydrochloride in combination with gliclazide, pioglitazone hydrochloride, sitagliptin, exenatide or liraglutide. Non-alcoholic fatty liver disease (NAFLD) was evaluated by abdominal ultrasound, and fibrosis stages were evaluated at baseline and 8 months. All the patients were equally divided into two groups depending on the therapeutic approach.

RESULTS

The first group of patients additionally received nursing care, and the second group adhered to the prescribed therapy on their own. In total 90 patients, or 55.6%, had NAFLD at baseline, and its course was dependent upon changes in the weight (P = 0.009) and waist circumference (P = 0.012). The proportions of patients who demonstrated an ultrasonographic improvement in the control group were: 24 (56.8%) with gliclazide, 15 (41.3%) with pioglitazone hydrochloride, 28 (66.1%) with sitagliptin, 16 (79%) with exenatide and 15 (66.7%) with liraglutide (P = 0.2). For the group that received nursing care an ultrasonographic improvement was in: 29 (68.16%) with gliclazide, 18 (49.56%) with pioglitazone hydrochloride, 33 (79.32%) with sitagliptin, 19 (94.8%) with exenatide and 21 80.04% with liraglutide (P = 0.2).

CONCLUSIONS

Outcomes from the type 2 diabetes treatment paralleling of CLD were presented. Treatment of type 2 diabetes with pioglitazone hydrochloride, gliclazide, sitagliptin, liraglutide and exenatide was proven effective.

Pathophysiological Mechanisms in Non-Alcoholic Fatty Liver Disease: From Drivers to Targets

Non-alcoholic fatty liver disease (NAFLD) is characterized by the excessive and detrimental accumulation of liver fat as a result of high-caloric intake and/or cellular and molecular abnormalities. The prevalence of this pathological event is increasing worldwide, and is intimately associated with obesity and type 2 diabetes mellitus, among other comorbidities. To date, only therapeutic strategies based on lifestyle changes have exhibited a beneficial impact on patients with NAFLD, but unfortunately this approach is often difficult to implement, and shows poor long-term adherence. For this reason, great efforts are being made to elucidate and integrate the underlying pathological molecular mechanism, and to identify novel and promising druggable targets for therapy. In this regard, a large number of clinical trials testing different potential compounds have been performed, albeit with no conclusive results yet. Importantly, many other clinical trials are currently underway with results expected in the near future. Here, we summarize the key aspects of NAFLD pathogenesis and therapeutic targets in this frequent disorder, highlighting the most recent advances in the field and future research directions.

Beneficial effects of glucagon-like peptide 1 receptor agonists on glucose control, cardiovascular risk profile, and non-alcoholic fatty liver disease. An expert opinion of the Italian diabetes society

Patients with type 2 diabetes mellitus (T2DM) show an increased risk of cardiovascular diseases (CVD) and mortality. Many factors are implicated in the pathogenesis of CVD in patients with T2DM. Among the factors involved, chronic hyperglycemia and the cluster of CVD risk factors, such as dyslipidemia, hypertension, and obesity, play a major role. For many years, the control of hyperglycemia has been complicated by the fact that the use of many available drugs was associated with an increased risk of hypoglycemia. Paradoxically, hypoglycemia per se represents a risk factor for CVD. Recently, new drugs for the control of hyperglycemia have become available: many of them can determine a good control of hyperglycemia with minor risks of hypoglycemia. Among these new classes of drugs, glucagon-like peptide-1 receptor agonists (GLP-1RAs) offer many advantages. In addition to a strong anti-hyperglycemic action, they possess the ability to act on body weight and other relevant risk factors for CVD. Consistently, some of the GLP-1RAs have demonstrated, in RCT designed to assess their safety, to reduce the risk of major adverse cardiovascular events. Furthermore, GLP-1RAs possess properties useful to treat additional conditions, as the capability of improving liver damage in patients with NAFLD or NASH, highly prevalent conditions in people with T2DM. In this document, written by experts of the Italian diabetes society (SID), we will focus our attention on the therapy with GLP-1RAs in patients with T2DM, particularly on the effects on hyperglycemia, cardiovascular disease risk factors, NAFLD/NASH and CVD prevention.

Narrative review of current and emerging pharmacological therapies for nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is the most common cause of chronic liver disease today, and it has now emerged as the leading etiology of end-stage liver disease requiring liver transplantation. It is a progressive form of non-alcoholic fatty liver disease which can not only progress to cirrhosis of liver and hepatocellular carcinoma (HCC), but is associated with increased cardiovascular risks too. Despite all the advances in the understanding of the risk factors and the pathogenetic pathways involved in the pathogenesis and progression of NASH, an effective therapy for NASH has not been developed yet. Although lifestyle modifications including dietary modifications and physical activity remain the mainstay of therapy, there is an unmet need to develop a drug or a combination of drugs which can not only reduce the fatty infiltration of the liver, but also arrest the development and progression of fibrosis and advancement to cirrhosis of liver and HCC. The pharmacologic therapies which are being developed target the various components believed to be involved in the pathogenesis of nonalcoholic fatty liver disease (NAFLD)/NASH which includes insulin resistance, lipid metabolism oxidative stress, lipid peroxidation, inflammatory and cell death pathways, and fibrosis. In this review, we summarize the current state of knowledge on pharmacotherapy of NASH, and also highlight the recent developments in the field, for optimizing the management and treatment of NASH.

Non-Alcoholic Fatty Liver Disease and Its Association With Diabetes Mellitus

There is a bidirectional relationship between non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM). The liver has a vital role in the pathophysiology of both diseases as it leads to the development of insulin resistance (IR), which in turn results in NAFLD and T2DM. It has been shown that T2DM increases the risk of NAFLD progression. Furthermore, the presence of NAFLD raises the probability of T2DM complications, which explains the increased rates of NAFLD screening in patients with T2DM. In addition, there are common management options for the two diseases. Lifestyle changes can play a role in the initial management of both diseases. Medications that are used to treat T2DM are also used in the management of NAFLD, such as metformin, thiazolidinediones (TZD), glucagon-like peptide-1 (GLP-1) analogues, and dipeptidyl peptidase-4 (DPP4) inhibitors. Bariatric surgery is often used as a last resort and has shown promising results. Lifestyle interventions with diet and exercise are important postoperatively to maintain the weight loss. There are many novel treatments that are being investigated for the treatment of NAFLD, targeting multiple pathophysiologic pathways. This review aims to shed some light on the intricate relationship between NAFLD and T2DM and how IR links both diseases. We also try to raise awareness among clinicians about this relationship and how the presence of one disease should raise a high index of suspicion for the existence of the other.

Metabolic drivers of non-alcoholic fatty liver disease

BACKGROUND

The incidence of non-alcoholic fatty liver disease (NAFLD) is rapidly increasing worldwide parallel to the global obesity epidemic. NAFLD encompasses a range of liver pathologies and most often originates from metabolically driven accumulation of fat in the liver, or non-alcoholic fatty liver (NAFL). In a subset of NAFL patients, the disease can progress to non-alcoholic steatohepatitis (NASH), which is a more severe form of liver disease characterized by hepatocyte injury, inflammation, and fibrosis. Significant progress has been made over the past decade in our understanding of NASH pathogenesis, but gaps remain in our mechanistic knowledge of the precise metabolic triggers for disease worsening.

SCOPE OF REVIEW

The transition from NAFL to NASH likely involves a complex constellation of multiple factors intrinsic and extrinsic to the liver. This review focuses on early metabolic events in the establishment of NAFL and initial stages of NASH. We discuss the association of NAFL with obesity as well as the role of adipose tissue in disease progression and highlight early metabolic drivers implicated in the pathological transition from hepatic fat accumulation to steatohepatitis.

MAJOR CONCLUSIONS

The close association of NAFL with features of metabolic syndrome highlight plausible mechanistic roles for adipose tissue health and the release of lipotoxic lipids, hepatic de novo lipogenesis (DNL), and disruption of the intestinal barrier in not only the initial establishment of hepatic steatosis, but also in mediating disease progression. Human genetic variants linked to NASH risk to date are heavily biased toward genes involved in the regulation of lipid metabolism, providing compelling support for the hypothesis that NASH is fundamentally a metabolic disease.

Spatial expression of glucagon-like peptide 1 receptor and caveolin-1 in hepatocytes with macrovesicular steatosis in non-alcoholic steatohepatitis

Objective

Non-alcoholic steatohepatitis (NASH) can progress to fibrosis, cirrhosis and end-stage liver disease. Glucagon-like peptide 1 receptor (GLP-1R) mediates β cell function. Its receptor agonists, currently used to treat type 2 diabetes mellitus, might be effective against NASH. GLP-1R, a G protein-coupled receptor family member, preferentially localises to caveolae. Therefore, we ascertained the cellular localisation of GLP-1R and caveolin (CAV)-1 in NASH liver.

Methods

Liver biopsies were obtained from three patients with NASH and were compared with those of four normal patients. Immunohistochemistry (IHC) and immunoelectron microscopy (IEM) were used to compare GLP-1R and CAV-1 expression in the livers of patients with metastatic liver cancer and normal patients.

Results

IHC showed that GLP-1R localised to basolateral membranes of hepatocytes with macrovesicular steatosis and was expressed in monocytes infiltrating hepatic sinusoids. CAV-1 was minimally associated with low-electron density lipid droplets (LDs) in hepatocytes. IEM showed small clusters of GLP-1R molecules on the peripheral rims of LDs and on cytoplasmic leaflets of endoplasmic reticulum membranes and vesicles, whereas CAV-1 molecules were found in LD caveolae.

Conclusions

GLP-1R is present in the lipid microdomains of hepatocytes with macrovesicular steatosis. These results may help inform future studies about the liver-specific mechanisms of GLP-1 modulation in NASH therapy.

Abnormal Metabolism in the Progression of Nonalcoholic Fatty Liver Disease to Hepatocellular Carcinoma: Mechanistic Insights to Chemoprevention

Nonalcoholic fatty liver disease (NAFLD) is on the rise and becoming a major contributor to the development of hepatocellular carcinoma (HCC). Reasons for this include the rise in obesity and metabolic syndrome in contrast to the marked advances in prevention and treatment strategies of viral HCC. These shifts are expected to rapidly propel this trend even further in the coming decades, with NAFLD on course to become the leading etiology of end-stage liver disease and HCC. No Food and Drug Administration (FDA)-approved medications are currently available for the treatment of NAFLD, and advances are desperately needed. Numerous medications with varying mechanisms of action targeting liver steatosis and fibrosis are being investigated including peroxisome proliferator-activated receptor (PPAR) agonists and farnesoid X receptor (FXR) agonists. Additionally, drugs targeting components of metabolic syndrome, such as antihyperglycemics, have been found to affect NAFLD progression and are now being considered in the treatment of these patients. As NAFLD drug discovery continues, special attention should be given to their relationship to HCC. Several mechanisms in the pathogenesis of NAFLD have been implicated in hepatocarcinogenesis, and therapies aimed at NAFLD may additionally harbor independent antitumorigenic potential. This approach may provide novel prevention and treatment strategies.

Targeting the GPR119/incretin axis: a promising new therapy for metabolic-associated fatty liver disease

In the past decade, G protein-coupled receptors have emerged as drug targets, and their physiological and pathological effects have been extensively studied. Among these receptors, GPR119 is expressed in multiple organs, including the liver. It can be activated by a variety of endogenous and exogenous ligands. After GPR119 is activated, the cell secretes a variety of incretins, including glucagon-like peptide-1 and glucagon-like peptide-2, which may attenuate the metabolic dysfunction associated with fatty liver disease, including improving glucose and lipid metabolism, inhibiting inflammation, reducing appetite, and regulating the intestinal microbial system. GPR119 has been a potential therapeutic target for diabetes mellitus type 2 for many years, but its role in metabolic dysfunction associated fatty liver disease deserves further attention. In this review, we discuss relevant research and current progress in the physiology and pharmacology of the GPR119/incretin axis and speculate on the potential therapeutic role of this axis in metabolic dysfunction associated with fatty liver disease, which provides guidance for transforming experimental research into clinical applications.

Crosstalk between beta-adrenergic and insulin signaling mediates mechanistic target of rapamycin hyperactivation in liver of high-fat diet-fed male mice

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease. While increased nutrient intake and sympathetic activity have been associated with the disease, the pathogenesis of NAFLD remains incompletely understood. We investigated the impact of the interaction of high dietary fat and sugar intake with increased beta-adrenergic receptor (β-AR) signaling on the activity of nutrient-sensing pathways and fuel storage in the liver. C57BL/6J mice were fed a standard rodent diet (STD), a high-fat diet (HFD), a high-fat/high-sugar Western diet (WD), a high-sugar diet with mixed carbohydrates (HCD), or a high-sucrose diet (HSD). After 6 week on diets, mice were treated with isoproterenol (ISO) and the activity of liver mTOR complex 1 (mTORC1)-related signaling analyzed by immunoblotting and correlated with tissue triglyceride and glycogen contents. ISO-stimulated AKT- and ERK-mediated activation of mTORC1 in STD-fed mice. Consumption of all four high-calorie diets exacerbated downstream activation of ribosomal protein S6 kinase beta-1 (S6K1) in response to ISO. S6K1 activity was greater with the fat-enriched HFD and WD and correlated with the presence of metabolic syndrome and a stronger activation of AKT and ERK1/2 pathways. Fat-enriched diets also increased triglyceride accumulation and inhibited glycogen mobilization under β-AR stimulation. In conclusion, crosstalk between β-AR and insulin signaling may contribute to HFD-induced hepatic steatosis through ERK1/2- and AKT-mediated hyperactivation of the mTORC1/S6K1 axis. The findings provide further rationale for the development of therapies aimed at targeting augmented β-AR signaling in the pathogenesis of NAFLD.

The efficacy of glucagon-like peptide 1 receptor agonists in patients with non-alcoholic fatty liver disease: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

non-alcoholic fatty liver disease (NAFLD) is considered as the hepatic manifestation of metabolic syndrome and is highly prevalent all over the world. New drugs are urgently needed for the treatment of NAFLD. The aim of this meta-analysis was to assess the efficacy of glucagon-like peptide 1 receptor agonists (GLP-1RAs) in patients with NAFLD.

METHOD

English language publications in the PubMed, Cochrane Library, Embase and Web of Science databases were searched from inception to October 2019. All randomized controlled trials (RCTs) of GLP-1RAs treatment for NAFLD were considered. Standardized mean difference (SMD) with 95 % confidence intervals (CIs) were pooled using the fixed-effects or random-effects model.

RESULTS

six RCTs, involving 406 patients, were included in the analysis. A significant improvement was found in liver fat fraction (LFF) (SMD = -0.33, 95 % CI, -0.64 to -0.03, p = 0.034), body mass index (BMI) (SMD: -0.89, 95 % CI: -1.60 to -0.19, p = 0.012) and adiponectin (SMD: 0.66, 95 % CI: 0.37 to 0.95, p = 0.000) with GLP-1RAs treatment. There were no significant differences in serum alanine aminotransferase (ALT) (SMD: -0.52, 95 % CI: -1.04 to 0.01, p = 0.054) and aspartate transaminase (AST) (SMD: -0.20, 95 % CI: -0.54 to 0.15, p = 0.134) reduction between the GLP-1RAs and control groups. In the subgroup analysis, exenatide was associated with an improvement in serum ALT (SMD = -1.25, 95 % CI: -1.68 to -0.82, p = 0.000) and AST (SMD = -0.62, 95 % CI: -1.16 to -0.08, p = 0.024). Liraglutide was associated with a reduction in BMI (SMD = -0.44, 95 % CI: -0.77 to -0.11, p = 0.010) and an increase in adiponectin (SMD = -0.33, 95 % CI, -0.64 to -0.03, p = 0.034).

CONCLUSION

our study suggested that GLP-1RAs may improve LFF, BMI and adiponectin in patients with NAFLD. Furthermore, the potential efficacy to treat NAFLD was also shown. More high-quality RCTs are needed to validate our findings.

Peganum harmala enhanced GLP-1 and restored insulin signaling to alleviate AlCl3-induced Alzheimer-like pathology model

Peganum harmala (P. harmala) is a folk medicinal herb used in the Sinai Peninsula (Egypt) as a remedy for central disorders. The main constituents, harmine and harmaline, have displayed therapeutic efficacy against Alzheimer's disease (AD); however, the P. harmala potential on sensitizing central insulin to combat AD remains to be clarified. An AD-like rat model was induced by aluminum chloride (AlCl3; 50 mg/kg/day for six consecutive weeks; i.p), whereas a methanolic standardized P. harmala seed extract (187.5 mg/kg; p.o) was given to AD rats starting 2 weeks post AlCl3 exposure. Two additional groups of rats were administered either the vehicle to serve as the normal control or the vehicle + P. harmala seed extract to serve as the P. harmala control group. P. harmala enhanced cognition appraised by Y-maze and Morris water maze tests and improved histopathological structures altered by AlCl3. Additionally, it heightened the hippocampal contents of glucagon-like peptide (GLP)-1 and insulin, but abated insulin receptor substrate-1 phosphorylation at serine 307 (pS307-IRS-1). Besides, P. harmala increased phosphorylated Akt at serine 473 (pS473-Akt) and glucose transporter type (GLUT)4. The extract also curtailed the hippocampal content of beta amyloid (Aβ)42, glycogen synthase (GSK)-3β and phosphorylated tau. It also enhanced Nrf2, while reduced lipid peroxides and replenished glutathione. In conclusion, combating insulin resistance by P. harmala is a novel machinery in attenuating the insidious progression of AD by enhancing both insulin and GLP-1 trajectories in the hippocampus favoring GLUT4 production.

Comprehensive analysis of LncRNAs expression profiles in an in vitro model of steatosis treated with Exendin-4

Background and aims

The hallmark of non-alcoholic fatty liver disease (NAFLD) is the excessive hepatic lipid accumulation. Currently, no pharmacotherapy exists for NAFLD. However, the glucagon-like peptide-1 receptor agonists have recently emerged as potential therapeutics. Here, we sought to identify the long non-coding RNAs (LncRNAs) associated with the steatosis improvement induced by the GLP-1R agonist Exendin-4 (Ex-4) in vitro.

Methods

Steatosis was induced in HepG2 cells with oleic acid. The transcriptomic profiling was performed using total RNA extracted from untreated, steatotic, and Ex-4-treated steatotic cells. We validated a subset of differentially expressed LncRNAs with qRT-PCR and identified the most significantly enriched cellular functions associated with the relevant LncRNAs.

Results

We confirm that Ex-4 improves steatosis in HepG2 cells. We found 379 and 180 differentially expressed LncRNAs between untreated and steatotic cells and between steatotic and Ex-4-treated steatotic cells, respectively. Interestingly, 22 upregulated LncRNAs in steatotic cells became downregulated with Ex-4 exposure, while 50 downregulated LncRNAs in steatotic cells became upregulated in the presence of Ex-4. Although some LncRNAs, such as MALAT1, H19, and NEAT1, were previously associated with NAFLD, the association of others with steatosis and the positive effect of Ex-4 is being reported for the first time. Functional enrichment analysis identified many critical pathways, including fatty acid and pyruvate metabolism, and insulin, PPAR, Wnt, TGF-β, mTOR, VEGF, NOD-like, and Toll-like receptors signaling pathways.

Conclusion

Our results suggest that LncRNAs may play essential roles in the mechanisms underlying steatosis improvement in response to GLP-1R agonists and warrant further functional studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02885-4.