GLP-1 analogue prevents NAFLD in ApoE KO mice with diet and Acrp30 knockdown by inhibiting c-JNK

Gut-Liver-Pancreas Axis Crosstalk in Health and Disease: From the Role of Microbial Metabolites to Innovative Microbiota Manipulating Strategies

The functions of the gut are closely related to those of many other organs in the human body. Indeed, the gut microbiota (GM) metabolize several nutrients and compounds that, once released in the bloodstream, can reach distant organs, thus influencing the metabolic and inflammatory tone of the host. The main microbiota-derived metabolites responsible for the modulation of endocrine responses are short-chain fatty acids (SCFAs), bile acids and glucagon-like peptide 1 (GLP-1). These molecules can (i) regulate the pancreatic hormones (insulin and glucagon), (ii) increase glycogen synthesis in the liver, and (iii) boost energy expenditure, especially in skeletal muscles and brown adipose tissue. In other words, they are critical in maintaining glucose and lipid homeostasis. In GM dysbiosis, the imbalance of microbiota-related products can affect the proper endocrine and metabolic functions, including those related to the gut-liver-pancreas axis (GLPA). In addition, the dysbiosis can contribute to the onset of some diseases such as non-alcoholic steatohepatitis (NASH)/non-alcoholic fatty liver disease (NAFLD), hepatocellular carcinoma (HCC), and type 2 diabetes (T2D). In this review, we explored the roles of the gut microbiota-derived metabolites and their involvement in onset and progression of these diseases. In addition, we detailed the main microbiota-modulating strategies that could improve the diseases' development by restoring the healthy balance of the GLPA.

Therapeutic potentials of glucose-dependent insulinotropic polypeptide (GIP) in T2DM: Past, present, and future

Type 2 diabetes mellitus (T2DM) is a worldwide health problem that has raised major concerns to the public health community. This chronic condition typically results from the cell's inability to respond to normal insulin levels. Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are the primary incretin hormones secreted from the intestinal tract. While clinical research has extensively explored the therapeutic potential of GLP-1R in addressing various T2DM-related abnormalities, the possibility of GIPR playing an important role in T2DM treatment is still under investigation. Evidence suggests that GIP is involved in the pathophysiology of T2DM. This chapter focuses on examining the role of GIP as a therapeutic molecule in combating T2DM, comparing the past, present, and future scenarios. Our goal is to delve into how GIP may impact pancreatic β-cell function, adipose tissue uptake, and lipid metabolism. Furthermore, we will elucidate the mechanistic functions of GIP and its receptors in relation to other clinical conditions like cardiovascular diseases, non-alcoholic fatty liver diseases, neurodegenerative diseases, and renal disorders. Additionally, this chapter will shed light on the latest advancements in pharmacological management for T2DM, highlighting potential structural modifications of GIP and the repurposing of drugs, while also addressing the challenges involved in bringing GIP-based treatments into clinical practice.

New advances of adiponectin in regulating obesity and related metabolic syndromes

Obesity and related metabolic syndromes have been recognized as important disease risks, in which the role of adipokines cannot be ignored. Adiponectin (ADP) is one of the key adipokines with various beneficial effects, including improving glucose and lipid metabolism, enhancing insulin sensitivity, reducing oxidative stress and inflammation, promoting ceramides degradation, and stimulating adipose tissue vascularity. Based on those, it can serve as a positive regulator in many metabolic syndromes, such as type 2 diabetes (T2D), cardiovascular diseases, non-alcoholic fatty liver disease (NAFLD), sarcopenia, neurodegenerative diseases, and certain cancers. Therefore, a promising therapeutic approach for treating various metabolic diseases may involve elevating ADP levels or activating ADP receptors. The modulation of ADP genes, multimerization, and secretion covers the main processes of ADP generation, providing a comprehensive orientation for the development of more appropriate therapeutic strategies. In order to have a deeper understanding of ADP, this paper will provide an all-encompassing review of ADP.

Glucagon-like Peptide 1, Glucose-Dependent Insulinotropic Polypeptide, and Glucagon Receptor Agonists in Metabolic Dysfunction-Associated Steatotic Liver Disease: Novel Medication in New Liver Disease Nomenclature

Glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are incretins that regulate postprandial glucose regulation, stimulating insulin secretion from pancreatic β-cells in response to food ingestion. Modified GLP-1 receptor agonists (GLP-1RAs) are being administered for the treatment of obesity and type 2 diabetes mellitus (T2DM). Strongly related to those disorders, metabolic dysfunction-associated steatotic liver disease (MASLD), especially its aggressive form, defined as metabolic dysfunction-associated steatohepatitis (MASH), is a major healthcare burden associated with high morbidity and extrahepatic complications. GLP-1RAs have been explored in MASH patients with evident improvement in liver dysfunction enzymes, glycemic control, and weight loss. Importantly, the combination of GLP-1RAs with GIP and/or glucagon RAs may be even more effective via synergistic mechanisms in amelioration of metabolic, biochemical, and histological parameters of MASLD but also has a beneficial impact on MASLD-related complications. In this current review, we aim to provide an overview of incretins' physiology, action, and signaling. Furthermore, we provide insight into the key pathophysiological mechanisms through which they impact MASLD aspects, as well as we analyze clinical data from human interventional studies. Finally, we discuss the current challenges and future perspectives pertinent to this growing area of research and clinical medicine.

The intestine as an endocrine organ and the role of gut hormones in metabolic regulation

Gut hormones orchestrate pivotal physiological processes in multiple metabolically active tissues, including the pancreas, liver, adipose tissue, gut and central nervous system, making them attractive therapeutic targets in the treatment of obesity and type 2 diabetes mellitus. Most gut hormones are derived from enteroendocrine cells, but bioactive peptides that are derived from other intestinal epithelial cell types have also been implicated in metabolic regulation and can be considered gut hormones. A deeper understanding of the complex inter-organ crosstalk mediated by the intestinal endocrine system is a prerequisite for designing more effective drugs that are based on or target gut hormones and their receptors, and extending their therapeutic potential beyond obesity and diabetes mellitus. In this Review, we present an overview of gut hormones that are involved in the regulation of metabolism and discuss their action in the gastrointestinal system and beyond.

Increased let-7d-5p in non-alcoholic fatty liver promotes insulin resistance and is a potential blood biomarker for diagnosis

BACKGROUND AND AIMS

The molecular mechanisms driving non-alcoholic fatty liver disease (NAFLD) are poorly understood; however, microRNAs might play a key role in these processes. We hypothesize that let-7d-5p could contribute to the pathophysiology of NAFLD and serve as a potential diagnostic biomarker.

METHODS

We evaluated let-7d-5p levels and its targets in liver biopsies from a cross-sectional study including patients with NAFLD and healthy donors, and from a mouse model of NAFLD. Moreover, the induction of let-7d-5p expression by fatty acids was evaluated in vitro. Further, we overexpressed let-7d-5p in vitro to corroborate the results observed in vivo. Circulating let-7d-5p and its potential as a NAFLD biomarker was determined in isolated extracellular vesicles from human plasma by RT-qPCR.

RESULTS

Our results demonstrate that hepatic let-7d-5p was significantly up-regulated in patients with steatosis, and this increase correlated with obesity and a decreased expression of AKT serine/threonine kinase (AKT), insulin-like growth factor 1 (IGF1), IGF-I receptor (IGF1R) and insulin receptor (INSR). These alterations were corroborated in a NAFLD mouse model. In vitro, fatty acids increased let-7d-5p expression, and its overexpression decreased AKT, IGF-IR and IR protein expression. Furthermore, let-7d-5p hindered AKT phosphorylation in vitro after insulin stimulation. Finally, circulating let-7d-5p significantly decreased in steatosis patients and receiver operating characteristic (ROC) analyses confirmed its utility as a diagnostic biomarker.

CONCLUSIONS

Our results highlight the emerging role of let-7d-5p as a potential therapeutic target for NAFLD since its overexpression impairs hepatic insulin signalling, and also, as a novel non-invasive biomarker for NAFLD diagnosis.

Therapeutic Mechanisms and Clinical Effects of Glucagon-like Peptide 1 Receptor Agonists in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) can lead to liver fibrosis and cirrhosis. Recently, glucagon-like peptide 1 receptor agonists (GLP-1RAs), a class of drugs used to treat type 2 diabetes and obesity, have shown therapeutic effects against NAFLD. In addition to reducing blood glucose levels and body weight, GLP-1RAs are effective in improving the clinical, biochemical, and histological markers of hepatic steatosis, inflammation, and fibrosis in patients with NAFLD. Additionally, GLP-1RAs have a good safety profile with minor side effects, such as nausea and vomiting. Overall, GLP-1RAs show promise as a potential treatment for NAFLD, and further studies are required to determine their long-term safety and efficacy.

Nootkatone, a Sesquiterpene Ketone From Alpiniae oxyphyllae Fructus, Ameliorates Metabolic-Associated Fatty Liver by Regulating AMPK and MAPK Signaling

Metabolic-associated fatty liver disease (MAFLD) is becoming more common due to lifestyle changes. A long-term high-fat and high-glucose diet induces glycolipid metabolism disorders in the liver, which results in the development of MAFLD. To date, there is no specific clinically useful therapeutics for this disease. Natural products or synthetic compounds were screened and investigated to find effective agents for treating MAFLD. In this study, nootkatone (Nok), a natural sesquiterpene ketone isolated from Alpiniae oxyphyllae fructus, was explored for its potential to treat MAFLD, and underlying mechanisms were studied. Our results show that Nok dramatically ameliorated the disordered lipid and glucose metabolism in MAFLD mice, decreased fat accumulation in hepatic tissue, and improved liver injury. Inflammation, metabolic disorder, and oxidative stress were ameliorated in liver tissue based on RNA-seq transcriptome comparison between a Nok-treated group and an MAFLD model group. Furthermore, Nok significantly activated AMPK activity and inhibited MAPK activity, especially the p38 and JNK signaling pathways, in vivo based on western blot analysis. The pharmaceutical effects and potential signaling pathways impacted by Nok were also investigated in L02 cells. Nok significantly promoted the consumption of glucose and decreased the deposition of triglycerides in vitro. The p-AMPKα level was notably upregulated by Nok, indicating dramatic AMPK activation. In addition, Nok decreased the levels of p-ERK1/2, p-p38, and p-JNK. Nok also inhibited the activation of MAPK signaling and, thus, alleviated MAFLD development. Our results suggest that Nok may be useful in treating MAFLD. Nok may ameliorate MAFLD by regulating glycolipid metabolism disorders by activating AMPK and inhibiting MAPK activity. Collectively, this study suggests that Nok is an effective compound for the treatment of MAFLD.

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.

The Impact of Incretin-Based Medications on Lipid Metabolism

Pathophysiological pathways that are induced by chronic hyperglycemia negatively impact lipid metabolism. Thus, diabetes is commonly accompanied by varying degrees of dyslipidemia which is itself a major risk factor for further macro- and microvascular diabetes complications such as atherosclerosis and nephropathy. Therefore, normalizing lipid metabolism is an attractive goal for therapy in patients with diabetes. Incretin-based medications are a novel group of antidiabetic agents with potent hypoglycemic effects. While the impact of incretins on glucose metabolism is clear, recent evidence indicates their positive modulatory roles on various aspects of lipid metabolism. Therefore, incretins may offer additional beneficial effects beyond that of glucose normalization. In the current review, how these antidiabetic medications can regulate lipid homeostasis and the possible cellular pathways involved are discussed, incorporating related clinical evidence about incretin effects on lipid homeostasis.

Effectiveness of drug interventions in nonalcoholic fatty liver disease: A network meta-analysis

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a major chronic liver disorder worldwide, and there is no established treatment for this disease. We conducted a network meta-analysis (NMA) to compare existing treatments, which include four classes of antidiabetic drugs, and examined the optimum treatments for NAFLD.

AIM

To compare the effectiveness of different treatments for NAFLD.

METHODS

An NMA was conducted using Stata 14.0 (Corporation LLC, College Station, United States) and R (X64 3.6.3 version) in this study. Eligible randomized controlled trials (RCTs) were searched in the PubMed, Cochrane Library, Embase, Medline and Web of Science databases from database inception to April 2021. Two researchers independently screened the available studies in strict accordance with inclusion and exclusion criteria. The Cochrane Risk of Bias tool was used to evaluate the risk of bias of the included studies. The variables with and without dimensional differences were calculated as the standardized mean difference and weighted mean difference, respectively. An inconsistency model and “node-splitting” technique were used to test for inconsistency. Funnel plots were used to evaluate publication bias.

RESULTS

Twenty-two eligible RCTs involving 1377 participants were eventually included in our analysis. Data were pooled using a random-effects model. Our NMA results revealed that glucagon-like peptide-1 receptor agonists (GLP-1RAs) were the most effective treatment, yielding improvements in hepatic fat content (HFC), alanine aminotransferase (ALT), aspartate aminotransferase (AST), serum γ-glutamyl transferase (GGT) and body weight [surface under the cumulative ranking curve (SUCRA) = 99.6%, 92.6%, 82.8%, 92.3% and 99.6%, respectively], while thiazolidinediones (TZDs) were the best intervention for reducing the NAFLD activity score (NAS; SUCRA = 98.9%). In addition, moderate performance was observed for the sodium glucose cotransporter-2 inhibitors groups (SUCRA = 25.1%, 66.2%, 63.5%, 58.2% and 71.9% for HFC, ALT, AST, GGT and body weight, respectively). However, metformin performed poorly according to most indicators (SUCRA = 54.5%, 0.3%, 19.5%, 33.7%, 57.7% and 44.3% for HFC, NAS, ALT, AST, GGT and body weight, respectively).

CONCLUSION

GLP-1RAs may be the optimum choice for most patients with NAFLD. However, TZDs are considered the most effective therapies in NAFLD patients with histological disease activity.

Elafibranor and liraglutide improve differentially liver health and metabolism in a mouse model of non-alcoholic steatohepatitis

BACKGROUND & AIMS

This study aimed to assess and compare the effects of the GLP-1 analog liraglutide and the PPARα/δ agonist elafibranor on liver histology and their impact on hepatic lipidome, metabolome, Kupffer and hepatic stellate cell activation in a model of advanced non-alcoholic fatty liver disease (NAFLD).

METHODS

Male C57BL/6JRj mice with biopsy-confirmed hepatosteatosis and fibrosis induced by 36-week Amylin liver NASH (AMLN) diet (high-fat, fructose and cholesterol) were randomized to receive for 12 weeks: (a) liraglutide (0.4 mg/kg/day s.c.), (b) elafibranor (30 mg/kg/day p.o.) and (c) vehicle. Metabolic status, liver pathology, markers of inflammation, Kupffer and stellate cell activation, and metabolomics/lipidomics were assessed at study completion.

RESULTS

Elafibranor and liraglutide improved weight, insulin sensitivity, glucose homeostasis and NAFLD activity score (pre-to-post biopsy). Elafibranor had a profound effect on hepatic lipidome, demonstrated by reductions in glycerides, increases in phospholipids, and by beneficial regulation of mediators of fatty acid oxidation, inflammation and oxidative stress. Liraglutide had a major impact on inflammatory and fibrogenic markers of Kupffer and hepatic stellate cell activation (Galectin-3, Collagen type I alpha 1, alpha-smooth muscle actin). Liraglutide exerted beneficial effects on bile acid and carbohydrate metabolism, demonstrated by restorations of the concentrations of bile acids, glycogen metabolism by-products and pentoses, thus facilitating glycogen utilization turnover and nucleic acid formation.

CONCLUSIONS

Liraglutide and elafibranor robustly but through different pathways improve overall metabolic health and liver status in NAFLD. These data indicate important differences in the respective mechanisms of action and support the notion for their evaluation as combination therapies in the future.

The GLP-1R agonist liraglutide limits hepatic lipotoxicity and inflammatory response in mice fed a methionine-choline deficient diet

Nonalcoholic fatty liver disease (NAFLD) is the most common hepatic disorder related to type 2 diabetes (T2D). The disease can evolve toward nonalcoholic steatohepatitis (NASH), a state of hepatic inflammation and fibrosis. There is presently no drug that effectively improves and/or prevents NAFLD/NASH/fibrosis. GLP-1 receptor agonists (GLP-1Ra) are effective in treating T2D. As with the endogenous gut incretins, GLP-1Ra potentiate glucose-induced insulin secretion. In addition, GLP-1Ra limit food intake and weight gain, additional beneficial properties in the context of obesity/insulin-resistance. Nevertheless, these pleiotropic effects of GLP-1Ra complicate the elucidation of their direct action on the liver. In the present study, we used the classical methionine-choline deficient (MCD) dietary model to investigate the potential direct hepatic actions of the GLP-1Ra liraglutide. A 4-week infusion of liraglutide (570 µg/kg/day) did not impact body weight, fat accretion or glycemic control in MCD-diet fed mice, confirming the suitability of this model for avoiding confounding factors. Liraglutide treatment did not prevent lipid deposition in the liver of MCD-fed mice but limited the accumulation of C16 and C24-ceramide/sphingomyelin species. In addition, liraglutide treatment alleviated hepatic inflammation (in particular accumulation of M1 pro-inflammatory macrophages) and initiation of fibrosis. Liraglutide also influenced the composition of gut microbiota induced by the MCD-diet. This included recovery of a normal Bacteroides proportion and, among the Erysipelotrichaceae family, a shift between Allobaculum and Turicibacter genera. In conclusion, liraglutide prevents accumulation of C16 and C24-ceramides/sphingomyelins species, inflammation and initiation of fibrosis in MCD-diet-fed mice liver, suggesting beneficial hepatic actions independent of weight loss and global hepatic steatosis.

Interaction Mechanisms Between Major Depressive Disorder and Non-alcoholic Fatty Liver Disease

Major depressive disorder (MDD), which is highly associated with non-alcoholic fatty liver disease (NAFLD), has complex pathogenic mechanisms. However, a limited number of studies have evaluated the mutual pathomechanisms involved in MDD and NAFLD development. Chronic stress-mediated elevations in glucocorticoid (GC) levels play an important role in the development of MDD-related NAFLD. Elevated GC levels can induce the release of inflammatory factors and changes in gut permeability. Elevated levels of inflammatory factors activate the hypothalamic-pituitary-adrenal (HPA) axis, which further increases the release of GC. At the same time, changes in gut permeability promote the release of inflammatory factors, which results in a vicious circle among the three, causing disease outbreaks. Even though the specific role of the thyroid hormone (TH) in this pathogenesis has not been fully established, it is highly correlated with MDD and NAFLD. Therefore, changing lifestyles and reducing psychological stress levels are necessary measures for preventing MDD-related NAFLD. Among them, GC inhibitors and receptor antagonists may be key in the alleviation of early and mid-term disease progression. However, combination medications may be important in late-stage diseases, but they are associated with various side effects. Traditional Chinese medicines have been shown to be potential therapeutic alternatives for such complex diseases.

GLP-1 Receptor Agonists: Beyond Their Pancreatic Effects

Glucagon like peptide-1 (GLP-1) is an incretin secretory molecule. GLP-1 receptor agonists (GLP-1RAs) are widely used in the treatment of type 2 diabetes (T2DM) due to their attributes such as body weight loss, protection of islet β cells, promotion of islet β cell proliferation and minimal side effects. Studies have found that GLP-1R is widely distributed on pancreatic and other tissues and has multiple biological effects, such as reducing neuroinflammation, promoting nerve growth, improving heart function, suppressing appetite, delaying gastric emptying, regulating blood lipid metabolism and reducing fat deposition. Moreover, GLP-1RAs have neuroprotective, anti-infectious, cardiovascular protective, and metabolic regulatory effects, exhibiting good application prospects. Growing attention has been paid to the relationship between GLP-1RAs and tumorigenesis, development and prognosis in patient with T2DM. Here, we reviewed the therapeutic effects and possible mechanisms of action of GLP-1RAs in the nervous, cardiovascular, and endocrine systems and their correlation with metabolism, tumours and other diseases.

Liraglutide or insulin glargine treatments improves hepatic fat in obese patients with type 2 diabetes and nonalcoholic fatty liver disease in twenty-six weeks: A randomized placebo-controlled trial

BACKGROUND

Type 2 diabetes mellitus is closely related to nonalcoholic fatty liver disease(NAFLD). More and more attention has been paid to the efficacy of liraglutide in the treatment of NAFLD, but the clinical evidence is still insufficient.

OBJECTIVE

The purpose of this study was to use proton magnetic resonance spectroscopy (H-MRS) assessment of metformin alone poor blood glucose control of obese patients type 2 diabetes with NAFLD, added with insulin glargine, liraglutide or placebo effect in improving the fatty liver.

METHODS

This is a 26-week, single-center, prospective, randomized placebo-controlled study. From September 2016 to July 2018, 128 patients with type 2 diabetes and NAFLD were enrolled in the China joint logistics team 900 hospital. The primary endpoints were the changes in intrahepatic content of lipid (IHCL), abdominal adiposity [subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT)], from baseline to week 26 (end of treatment) and the changes in liraglutide group or insulin glargine group versus change in placebo group. Secondary endpoints included the changes in liver function (AST and ALT), glycemia (HbA1c and FPG), body weight, and BMI.

RESULTS

A total of 96 patients with type 2 diabetes and NAFLD under inadequate glycemic control by metformin were randomized (1:1:1) to receive add-on insulin glargine, liraglutide, or placebo. After 26 weeks of treatment, compared to the placebo group, in the liraglutide and insulin glargine groups, IHCL significantly decreased from baseline to week 26 (liraglutide 26.4% ± 3.2% to 20.6% ± 3.9%, P < 0.05; insulin glargine 25.0% ± 4.3% to 22.6% ± 5.8%, P > 0.05). SAT and VAT decreased significantly in the liraglutide group and in the insulin glargine group (P < 0.05). ΔSAT and ΔVAT were greater with liraglutide than insulin glargine, they were significantly different between the two groups (ΔSAT, -36 vs. - 24.5, P < 0.05; and ΔVAT, -47 vs. - 16.6, P > 0.05). In the liraglutide group, AST, ALT, and HOMA-IR decreased significantly from baseline. There was no significant difference in glucose-lowering among the three groups. During the treatment, the safety of the three groups performed well.

CONCLUSION

Compared with placebo, treatment with liraglutide plus an adequate dose of metformin (2000 g/ day) for 26 weeks is more effective in reducing IHCL, SAT and VAT in patients with type 2 diabetes and NAFLD. And it has additional advantages in weight loss, waist circumference reduction and liver function improvement.

Efficacy of Glucagon-Like Peptide-1 Analogs in Nonalcoholic Fatty Liver Disease: A Systematic Review

Background

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. It is believed to be the hepatic manifestation of the metabolic syndrome. Many treatment approaches have been suggested so far, and several types of studies have been done to find treatment for NAFLD, the most promising of which are those with lifestyle interventions.

Objective

The aim of this systematic review was to evaluate the efficacy and safety of glucagon-like peptide-1 (GLP-1) analogs on the management of NAFLD.

Methods

The PubMed, MEDLINE, and Cochrane Central Library were searched to identify randomized controlled trials, single arm trials, and cohorts that compared GLP-1 analogs with a control treatment or baseline values with respect to efficacy and safety in patients living with NAFLD. The key outcomes were a change in serum transaminase, resolution of disease status measured by imaging or histological techniques, improvement in insulin resistance, and reduction in body weight.

Results

Initial searching retrieved 201 peer-reviewed articles and abstracts. Ten studies met all inclusion criteria. The review included a total of 590 participants with NAFLD. Following administration of GLP-1 analogs, a decrease in serum transaminases, improvement in liver histology and insulin resistance, and a reduction in body weight were observed. Compared with baseline, body weight, alanine aminotransferase, aspartate aminotransferase, and gamma glutamyltransferase were decreased by 5.5%, 59.5%, 52.8%, and 44.8%, respectively, due to GLP-1. Likewise, a reduction of proinflammatory cytokines and fibrosis markers and an enhancement of protective adipokines were observed in some of the studies.

Conclusion

The decrease in a key biochemical marker of liver injury following treatment with GLP-1 analogs, as well as improvements in imaging and histology, suggests that these agents may be effective alternatives for managing NAFLD.

Registration

CRD42018087262.

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.

Betaine prevented high-fat diet-induced NAFLD by regulating the FGF10/AMPK signaling pathway in ApoE-/- mice

PURPOSE

Nonalcoholic fatty liver disease (NAFLD) is currently the leading cause of chronic liver disease in developing countries. The pathogenesis is complex, and there is currently no effective treatment. Betaine is an essential intermediate in choline catabolism and an important component of the methionine cycle. Betaine deficiency is associated with NAFLD severity, and its mechanism needs to be further elaborated.

METHODS

In this study, an NAFLD mouse model was established by feeding ApoE^-/- mice a high-fat diet. The effects of betaine on NAFLD were investigated, including its mechanism.

RESULTS

In this study, after treatment with betaine, blood lipid levels and liver damage were significantly decreased in the NAFLD mouse model. The fat infiltration of the liver tissues of high-fat diet (HFD)-fed mice after betaine administration was significantly improved. Betaine treatment significantly upregulated AMP-activated protein kinase (AMPK), fibroblast growth factor 10 (FGF10), and adipose triglyceride lipase (ATGL) protein levels both in vivo and in vitro and suppressed lipid metabolism-related genes. Furthermore, the overexpression of FGF10 increased the protein level of AMPK and decreased lipid accumulation in HepG2 cells.

CONCLUSION

Taken together, the data strongly suggest that betaine significantly prevents high-fat diet-induced NAFLD through the FGF10/AMPK signaling pathway in ApoE^-/- mice.

Gut-Pancreas-Liver Axis as a Target for Treatment of NAFLD/NASH

Non-alcoholic fatty liver disease (NAFLD) represents the most common form of chronic liver disease worldwide. Due to its association with obesity and diabetes and the fall in hepatitis C virus morbidity, cirrhosis in NAFLD is becoming the most frequent indication to liver transplantation, but the pathogenetic mechanisms are still not completely understood. The so-called gut-liver axis has gained enormous interest when data showed that its alteration can lead to NAFLD development and might favor the occurrence of non-alcoholic steatohepatitis (NASH). Moreover, several therapeutic approaches targeting the gut-pancreas-liver axis, e.g., incretins, showed promising results in NASH treatment. In this review, we describe the role of incretin hormones in NAFLD/NASH pathogenesis and treatment and how metagenomic/metabolomic alterations in the gut microbiota can lead to NASH in the presence of gut barrier modifications favoring the passage of bacteria or bacterial products in the portal circulation, i.e., bacterial translocation.

Liraglutide in combination with human umbilical cord mesenchymal stem cell could improve liver lesions by modulating TLR4/NF-kB inflammatory pathway and oxidative stress in T2DM/NAFLD rats

Studies have shown that liraglutide, or human umbilical cord mesenchymal stem cell (hUC-MSCs) can improve non-alcoholic fatty liver disease (NAFLD). However there have been no studies on the combination of the two used to treat NAFLD. This study aimed to explore the therapeutic effects of combination of liraglutide and hUC-MSCs on liver injury in rats with type 2 diabetes mellitus (T2DM) and NAFLD, and further investigate their mechanisms. Sprague Dawley rats fed by a high fat and high sucrose diet were randomly divided into 5 groups, including NC group, T2DM/NAFLD group, liraglutide group (treated with liraglutide, 200 μg/kg, twice daily for 8 weeks), hUC-MSCs group (treated with hUC-MSCs at the first and fifth weeks), liraglutid＋hUC-MSCs group (treated with liraglutide and hUC-MSCs). Liver tissue was procured for histological examination, real-time qRT-PCR and Western blot analysis. After treatment, liraglutide and hUC-MSCs reduced serum ALT and AST levels, alleviate liver inflammation and improved liver histopathology. The expressions of inflammatory cytokines, TLR4 and NF-κB in serum and liver were significantly inhibited, particularly in the combination treatment group. Eight weeks after liraglutide or hUC-MSCs administration, FBG, HbA1c, HOMA-IR, ALT, AST, Liver wet eight and hepatic TLR4, NF-κB, IL-6, TNF-α, 8-OHdG mRNA and proteins were significantly decreased, and the levels of SOD expression were significantly increased in three treatment groups compared with T2DM/NAFLD group. This study suggests that liraglutide in combination with hUC-MSCs could significantly improve glycolipid metabolism, insulin resistance and liver injury in T2DM/NAFLD rats. Its mechanism may be related to the down-regulation of the TLR4/NF-κB inflammatory pathway and improvement in oxidative stress.

Liraglutide Attenuates Non-Alcoholic Fatty Liver Disease in Mice by Regulating the Local Renin-Angiotensin System

The renin-angiotensin system (RAS) is involved in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) and represents a potential therapeutic target for NAFLD. Glucagon-like peptide-1 (GLP-1) signaling has been shown to regulate the RAS within various local tissues. In this study, we aimed to investigate the functional relationship between GLP-1 and the local RAS in the liver during NAFLD. Wild-type and ACE2 knockout mice were used to establish a high-fat-induced NAFLD model. After the mice were treated with liraglutide (a GLP-1 analogue) for 4 weeks, the key RAS component genes were up-regulated in the liver of NAFLD mice. Liraglutide treatment regulated the RAS balance, preventing a reduction in fatty acid oxidation gene expression and increasing gluconeogenesis and the expression of inflammation-related genes caused by NAFLD, which were impaired in ACE2 knockout mice. Liraglutide-treated HepG2 cells exhibited activation of the ACE2/Ang1-7/Mas axis, increased fatty acid oxidation gene expression, and decreased inflammation, which could be reversed by A779 and AngII. These results indicate that the local RAS in the liver becomes overactivated in response to NAFLD. Moreover, ACE2 knockout increases the severity of liver steatosis. Liraglutide has a negative and antagonistic effect on the ACE/AngII/AT1R axis, a positive impact on the ACE2/Ang1-7/Mas axis, and is mediated through the PI3K/AKT pathway. This may represent a potential new mechanism by which liraglutide improves NAFLD.

Mesencephalic astrocyte-derived neurotrophic factor ameliorates steatosis in HepG2 cells by regulating hepatic lipid metabolism

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a global metabolism-associated liver disease. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a newly discovered secreted protein that is involved in metabolic homeostasis. However, much remains to be discovered about its function in hepatic lipid metabolism; thus, we assessed whether MANF could regulate hepatic metabolism.

AIM

To establish in vivo and in vitro NAFLD models to explore the role of MANF in hepatic lipid metabolism.

METHODS

HepG2 cells treated with free fatty acids (FFAs) and ob/ob mice were used as NAFLD models. Liver tissues collected from wild type and ob/ob mice were used to detect MANF expression. Cells were treated with FFAs for different durations. Moreover, we used lentiviral constructs to establish overexpression and knockdown cell models in order to interfere with MANF expression levels and observe whether MANF influences hepatic steatosis. Western blot analysis and quantitative real-time PCR were used to detect protein and gene expression, and oil red O staining was used to visualize intracellular lipid droplets.

RESULTS

Hepatic MANF protein and mRNA expression in wild type mice were 10-fold and 2-fold higher, respectively, than those in ob/ob mice. The MANF protein was temporarily increased by 1.3-fold after stimulation with FFAs for 24 h and gradually decreased to 0.66-fold that of the control at the 72 h time point in HepG2 cells. MANF deficiency upregulated the expression of genes involved in fatty acid synthesis, cholesterol synthesis, and fatty acid uptake and aggravated HepG2 cell steatosis, while MANF overexpression inhibited fatty acid synthesis and uptake and cholesterol synthesis, and rescued HepG2 cells from FFAs-induced steatosis. Furthermore, a significant decrease in triglyceride levels was observed in the MANF overexpression group compared with the control group (0.4288 ± 0.0081 mmol/g vs 0.3746 ± 0.0121 mmol/g, P < 0.05) upon FFAs treatment. There was also a 17% decrease in intracellular total cholesterol levels between the MANF overexpression group and the control group (0.1301 ± 0.0059 mmol/g vs 0.1088 ± 0.0009 mmol/g, P < 0.05) upon FFAs treatment. Moreover, MANF suppressed lipid deposition in HepG2 cells.

CONCLUSION

Our findings indicate that MANF improves the phenotype of liver cell steatosis and may be a potential therapeutic target in hepatic steatosis processes.

Effects of liraglutide on metabolic syndrome in WBN/Kob diabetic fatty rats supplemented with a high-fat diet

BACKGROUND

Liraglutide, a GLP-1 receptor agonist, has recently been used to treat metabolic syndrome (MS) because of its anti-diabetic and anti-obesity effects. We have previously shown that Wistar Bonn Kobori diabetic and fatty (WBN/Kob-Lepr fa , WBKDF) rats fed a high-fat diet (HFD) developed MS including marked obesity, hyperglycemia, and dyslipidemia. To obtain further information on WBKDF-HFD rats as a severe MS model, we performed a pharmacological investigation into the anti-MS effects of liraglutide in this model.

METHODS

Seven-week-old male WBKDF-HFD rats were allocated to three groups (N = 8 in each group): a vehicle group, a low-dose liraglutide group, and a high-dose liraglutide group. They received subcutaneous injections of either saline or liraglutide at doses of 75 or 300 μg/kg body weight once daily for 4 weeks.

RESULTS

Results showed that liraglutide treatment reduced body weight gain and food intake in a dose-dependent manner. The marked hyperglycemia and the glucose tolerance were also significantly ameliorated in the liraglutide-treated groups. Moreover, liraglutide also reduced the plasma triglyceride concentration and liver fat accumulation.

CONCLUSIONS

The present study demonstrated that liraglutide could significantly alleviate MS in WBKDF-HFD rats, and the reaction to liraglutide is similar to human patients with MS. WBKDF-HFD rats are therefore considered to be a useful model for research on severe human MS.

Targeting DUSP16/TAK1 signaling alleviates hepatic dyslipidemia and inflammation in high fat diet (HFD)-challenged mice through suppressing JNK MAPK

Nonalcoholic fatty liver disease (NAFLD) is featured by hepatic steatosis, insulin resistance, lipid deposition and inflammation. However, the pathogenic mechanism of NAFLD is still poorly understood. Dual-specificity phosphatase 16 (DUSP16), a c-Jun N-terminal kinase-specific phosphatase, has been reported to negatively modulate the mitogen-activated protein kinases (MAPKs) signaling, and it has never been investigated in NAFLD progression. In the study, we identified that DUSP16 could directly interact with TAK1 in human hepatocytes. DUSP16 knockdown in the isolated primary hepatocytes stimulated by palmitate (PA) showed accelerated lipid deposition and inflammatory response, along with the exacerbated activation of c-Jun NH2-terminal kinase (JNK), Transforming growth factor β (TGF-β)-activated kinase (TAK1) and nuclear factor-κB (NF-κB) signaling pathways; however, the opposite results were detected in PA-treated hepatocytes with DUSP16 over-expression. The in vivo experiments confirmed that DUSP16 knockout significantly aggravated the metabolic disorder and insulin resistance in high fat diet (HFD)-challenged mice. In addition, HFD-provoked hepatic lipid accumulation and inflammation were further promoted in mice with DUSP16 knockout through the same molecular mechanism as detected in vitro. Herein, these findings demonstrated that DUSP16 could directly interact with TAK1 and negatively regulate JNK signaling to alleviate metabolic stress-induced hepatic steatosis, and thus could be considered as a promising new molecular target for NAFLD treatment.

NAFLD as a continuum: from obesity to metabolic syndrome and diabetes

BACKGROUND

The prevalence of non-alcoholic fatty liver disease (NAFLD) has been increasing rapidly. It is nowadays recognized as the most frequent liver disease, affecting a quarter of global population and regularly coexisting with metabolic disorders such as type 2 diabetes, hypertension, obesity, and cardiovascular disease. In a more simplistic view, NAFLD could be defined as an increase in liver fat content, in the absence of secondary cause of steatosis. In fact, the clinical onset of the disease is a much more complex process, closely related to insulin resistance, limited expandability and dysfunctionality of adipose tissue. A fatty liver is a main driver for a new recognized liver-pancreatic α-cell axis and increased glucagon, contributing to diabetes pathophysiology.

MAIN TEXT

This review will focus on the clinical and pathophysiological connections between NAFLD, insulin resistance and type 2 diabetes. We reviewed non-invasive methods and several scoring systems for estimative of steatosis and fibrosis, proposing a multistep process for NAFLD evaluation. We will also discuss treatment options with a more comprehensive view, focusing on the current available therapies for obesity and/or type 2 diabetes that impact each stage of NAFLD.

CONCLUSION

The proper understanding of NAFLD spectrum-as a continuum from obesity to metabolic syndrome and diabetes-may contribute to the early identification and for establishment of targeted treatment.

Activation of pCREB/Nrf-2 signaling mediates re-positioning of liraglutide as hepato-protective for methotrexate -induced liver injury (MILI)

Methotrexate (MTX) is commonly used to treat several types of cancer and autoimmune diseases. However, there is increasing concern over its organs toxicities particularly liver toxicity. Liraglutide, a glucagon like peptide-1 agonist, possesses antioxidant and anti-inflammatory features. This study aimed to explore the potential protective effect of liraglutide pre-treatment in ameliorating MTX-induced hepatotoxicity and to further investigate the underlying mechanisms. Rats received 1.2 mg/kg liraglutide intraperitoneal twice daily for 7 days before MTX. Results revealed that liraglutide significantly decreased activities of liver enzymes and oxidative stress in hepatocytes. Furthermore, NF-kB expression and related inflammatory markers (TNF-α, COX-2 and IL-6) were reduced in the pre-treatment group of liraglutide. These data validate the advantageous effects of liraglutide in MTX hepatotoxic animals. In addition, liraglutide increased the expression of the antioxidant transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf-2), along with the transcription of downstream phosphorylated cAMP response element-binding protein (pCREB) which increases the activity of Nrf-2. Additionally, caspase-3 expression/activity and BAX/Bcl-2 ratio were decreased following liraglutide pre-treatment. In conclusion, it was confirmed that liraglutide enhanced the antioxidant activity of liver cells by activating the Nrf-2 and pCREB signaling, thereby, reducing liver cell inflammation and apoptosis induced by MTX.

Multiple target tissue effects of GLP-1 analogues on non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH)

Accumulating experimental and clinical evidences over the last decade indicate that GLP-1 analogues have a series of central nervous system and peripheral target tissues actions which are able to significantly influence the liver metabolism. GLP-1 analogues pleiotropic effects proved to be efficacious in T2DM subjects not only reducing liver steatosis and ameliorating NAFLD and NASH, but also in lowering plasma glucose and liver inflammation, improving cardiac function and protecting from kidney dysfunction. While the experimental and clinical data are robust, the precise mechanisms of action potentially involved in these protective multi-target effects need further investigation. Here we present a systematic review of the most recent literature data on the multi-target effects of GLP-1 analogues on the liver, on adipose and muscular tissue and on the nervous system, all capable of influencing significant aspects of the fatty liver disease physiopathology. From this analysis, we can conclude that the multi-target beneficial action of the GLP-1 analogues could explain the positive effects observed in animal and human models on progression of NAFLD to NASH.

GLP-1 receptor agonists in NAFLD

Non-alcoholic fatty liver disease (NAFLD) is very common in patients with type 2 diabetes (T2D), with approximately two-thirds having a diagnosis of the disease. Currently, the only validated treatment for NAFLD is weight loss. A number of studies of animal models and human trials have evaluated the effects of glucagon-like peptide-1 receptor agonists (GLP-1RAs) on liver fat content and suggest that the treatment could represent a new alternative for NAFLD management. In this review, our focus is on the main studies regarding the effects of GLP-1RAs on NAFLD. Also, the mechanisms that might explain their beneficial effects on liver diseases are analyzed.

Bariatric Surgery and Non-Alcoholic Fatty Liver Disease: a Systematic Review of Liver Biochemistry and Histology

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is becoming a leading cause of global liver disease that is associated with the rising prevalence of obesity worldwide. There is now increasing clinical and mechanistic evidence reporting on the metabolic and weight loss effects of bariatric surgery on improving NAFLD in obese patients.

OBJECTIVES

The aim of this paper was to quantify the effects of bariatric surgery on NAFLD by appraising the modulation between pre- and post-operative liver enzyme levels (as markers of liver injury) and liver histology.

METHODS

A systematic review of studies reporting pre-operative and post-operative liver enzymes or liver histology was done in obese patients with NAFLD undergoing bariatric surgery. Data were meta-analysed using random-effects modelling. Subgroup analysis, quality scoring and risk of bias were assessed.

RESULTS

Bariatric surgery is associated with a significant reduction in the weighted incidence of a number of histological features of NAFLD including steatosis (50.2 and 95 %CI of 35.5-65.0), fibrosis (11.9 and 95 %CI of 7.4-16.3 %), hepatocyte ballooning (67.7 and 95 %CI 56.9-78.5) and lobular inflammation (50.7 and 95 %CI 26.6-74.8 %). Surgery is also associated with a reduction in liver enzyme levels, with statistically significant reductions in ALT (11.36 u/l, 95 %CI 8.36-14.39), AST (3.91 u/l, 95 %CI 2.23-5.59), ALP (10.55 u/l, 95 %CI 4.40-16.70) and gamma-GT (18.39 u/l, 95 %CI 12.62-24.16). Heterogeneity in results was high.

CONCLUSIONS

Bariatric surgery is associated with a significant improvement in both histological and biochemical markers of NAFLD. Future studies must focus on higher levels of evidence to better identify the benefits of bariatric surgery on liver disease in order to enhance future treatment strategies in the management of NAFLD.

NAMPT knockdown attenuates atherosclerosis and promotes reverse cholesterol transport in ApoE KO mice with high-fat-induced insulin resistance

NAMPT has been suggested association with atherosclerosis and insulin resistance. However, the impact of NAMPT on atherosclerosis remained unknown. Therefore, the objective of this study was to use a NAMPT loss-of-function approach to investigate the effect of NAMPT on atherosclerosis in hypercholesterolemic mice. We demonstrated that a specific NAMPT knockdown increased plasma HDL-C levels, reduced the plaque area of the total aorta en face and the cross-sectional aortic sinus, decreased macrophage number and apoptosis, and promoted RCT in HFD-fed ApoE KO mice. These changes were accompanied by increased PPARα, LXRα, ABCA1 and ABCG1 expressions in the liver. NAMPT knockdown also facilitated cholesterol efflux in RAW264.7 cells. We further investigated the effect of NAMPT knockdown on the PPARα-LXRα pathway of cholesterol metabolism with MK886 (a selective inhibitor of PPARα) in RAW264.7 macrophages. MK886 abolished the ability of NAMPT knockdown to decrease intracellular cholesterol levels to enhance the rate of (3)H-cholesterol efflux and to increase ABCA1/G1 and LXRα expressions in RAW264.7 macrophages. Our observations demonstrate that NAMPT knockdown exerted antiatherogenic effects by promoting cholesterol efflux and macrophage RCT through the PPARα- LXRα- ABCA1/G1pathway in vitro and in vivo.

The Glucagon-Like Peptide-1 Analogue Liraglutide Inhibits Oxidative Stress and Inflammatory Response in the Liver of Rats with Diet-Induced Non-alcoholic Fatty Liver Disease

Liraglutide, a glucagon-like peptide-1 (GLP-1) analogue, has been demonstrated to reduce hepatic steatosis. However, the mechanism of the lipid-lowering effect of liraglutide in the liver remains unclear. The aim of the present study was to investigate the beneficial effect of liraglutide on diet-induced non-alcoholic fatty liver disease (NAFLD) and the underlying mechanism in rats. NAFLD was induced in Sprague-Dawley rats by feeding a high fat and high cholesterol (HFHC) diet. Liraglutide (0.6 mg/kg body weight/d) was injected intraperitoneally to the rats subjected to HFHC diet four weeks before sacrificing the animals. Body and liver weight, fasting blood glucose (FBG), fasting insulin, serum aminotransferase (ALT) and lipid accumulation in the liver were determined. Markers of oxidative stress, such as malondialdehyde (MDA), free fatty acid (FFAs), superoxide dismutase (SOD), and pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) were detected by colorimetric detection or enzyme-linked immunosorbent assay (ELISA). Serum and hepatic adiponectin were measured by ELISA. The expression of c-Jun N-terminal kinase-1 (JNK-1) and phosphorylated JNK-1 were examined by Western blotting. Liraglutide improved insulin resistance, decreased hepatic steatosis and reversed liver dysfunction. The hepatic levels of MDA, FFAs, and TNF-α were significantly decreased versus controls. Meanwhile, administration of liraglutide significantly increased SOD and adiponectin levels in the liver and inhibited the expression of JNK-1 and phosphorylated JNK-1 versus control rats. Liraglutide exerted anti-oxidative and anti-inflammatory effects in the liver and consequently reversed hepatic steatosis and insulin resistance. Such effects might be mediated by the elevation of adiponectin levels and the inactivation of JNK-1.

Glucagon-like peptide-1 preserves non-alcoholic fatty liver disease through inhibition of the endoplasmic reticulum stress-associated pathway

AIM

Glucagon-like peptide-1 (GLP-1) has been increasingly recognized for treating diabetes mellitus, and for its potential to effectively treat non-alcoholic fatty liver disease (NAFLD). However, the mechanisms of GLP-1 induction in NAFLD are not completely known. We investigated whether GLP-1 can protect against NAFLD by alleviating endoplasmic reticulum (ER) stress.

METHODS

Male Sprague-Dawley rats were fed a high-fat diet and treated with a long-acting GLP-1 receptor agonist, liraglutide. Biochemical, morphological, genetic and protein expression of ER stress were investigated. In vitro, HepG2 cells were exposed to 0.4 mM palmitate fatty acid and treated with different concentrations of GLP-1, and ER protein 46 (ERp46) and ER stress pathways were analyzed. Cellular response to ER stress and apoptosis were determined upon transfection with either ERp46 siRNA or a negative control siRNA.

RESULTS

In vivo, the treatment of GLP-1 attenuated the hepatic accumulation of lipids, reduced inflammation and improved metabolic parameters. GLP-1 treatment significantly upregulated the expression of ERp46 and downregulated the ER stress marker. Activation of ER pathways was restrained by GLP-1. Similar observations were made in vitro. Furthermore, inhibition of ERp46 expression by siRNA-mediated silencing increased the ER stress response and enhanced cell apoptosis rates. In addition, GLP-1 could not reduce the levels of ER stress and apoptosis in cells transfected with ERp46 siRNA compared with in negative control transfected cells after palmitate treatment.

CONCLUSION

GLP-1 protected against NAFLD by inactivating the ER stress-associated apoptosis pathway. In addition, the effect was possibly related to the signaling pathway of ERp46.

Circulating adiponectin levels in type 2 diabetes mellitus patients with or without non-alcoholic fatty liver disease: Results of a small, open-label, randomized controlled intervention trial in a subgroup receiving short-term exenatide

AIM

Diabetes mellitus type 2 (DMT2) and non-alcoholic fatty liver disease (NAFLD) are both characterized by decreased circulating adiponectin. Recently, glucagon-like peptide-1 receptor agonists have been shown to induce adiponectin's expression. However, their interaction on clinical grounds needs to be further elucidated.

METHODS

DMT2 patients with abnormal aminotransferases were screened for NAFLD and subjected to liver biopsy (group A, n=17). A subgroup of patients (n=110), after assessed for eligibility criteria, was blindly randomized to receive either 6-month exenatide supplementation on glargine insulin (group B) or intense, self-regulated, insulin therapy alone (group C).

RESULTS

Baseline patient characteristics: 49(38.6%) males, aged 63.1 ± 7.5 years-old, BMI 32.9 ± 4.9 kg/m(2), HbA1c 8.1 ± 1.2% (65 ± 14 mmol/mol), median ALT 23 U/L (range 5-126), AST 20 U/L (7-72). Group A had biopsy-proven NAFLD with a median Activity Score of 5 and fibrosis stage 3. Presence of NAFLD was accompanied by a significant decline in adiponectin (p<0.001), which was negatively correlated with the degree of ALT in all groups (Spearman's correlation, rs=-0.644, p<0.001). In the subgroup intervention trial, adiponectin was significantly raised in both groups B and C (t-Student for paired samples, p=0.001) by Δ=+24.2% (interquartile range 14.8-53.2%). This elevation was not associated with the type of intervention but with weight loss, glycemic control and reduction of C-reactive protein (one-way ANCOVA).

CONCLUSION

Supplementation of exenatide to glargine insulin compared to standard insulin was: (i) effective in inducing weight loss, (ii) non-inferior in lowering HbA1c and (iii) non-inferior in increasing circulating adiponectin. Higher adiponectin was associated with lower ALT, suggesting a hepato-protective role for this cytokine.

Glucagon-like peptide 1 decreases lipotoxicity in non-alcoholic steatohepatitis

BACKGROUND & AIMS

Insulin resistance and lipotoxicity are pathognomonic in non-alcoholic steatohepatitis (NASH). Glucagon-like peptide-1 (GLP-1) analogues are licensed for type 2 diabetes, but no prospective experimental data exists in NASH. This study determined the effect of a long-acting GLP-1 analogue, liraglutide, on organ-specific insulin sensitivity, hepatic lipid handling and adipose dysfunction in biopsy-proven NASH.

METHODS

Fourteen patients were randomised to 1.8mg liraglutide or placebo for 12-weeks of the mechanistic component of a double-blind, randomised, placebo-controlled trial (ClinicalTrials.gov-NCT01237119). Patients underwent paired hyperinsulinaemic euglycaemic clamps, stable isotope tracers, adipose microdialysis and serum adipocytokine/metabolic profiling. In vitro isotope experiments on lipid flux were performed on primary human hepatocytes.

RESULTS

Liraglutide reduced BMI (-1.9 vs. +0.04kg/m(2); p<0.001), HbA1c (-0.3 vs. +0.3%; p<0.01), cholesterol-LDL (-0.7 vs. +0.05mmol/L; p<0.01), ALT (-54 vs. -4.0IU/L; p<0.01) and serum leptin, adiponectin, and CCL-2 (all p<0.05). Liraglutide increased hepatic insulin sensitivity (-9.36 vs. -2.54% suppression of hepatic endogenous glucose production with low-dose insulin; p<0.05). Liraglutide increased adipose tissue insulin sensitivity enhancing the ability of insulin to suppress lipolysis both globally (-24.9 vs. +54.8pmol/L insulin required to ½ maximally suppress serum non-esterified fatty acids; p<0.05), and specifically within subcutaneous adipose tissue (p<0.05). In addition, liraglutide decreased hepatic de novo lipogenesis in vivo (-1.26 vs. +1.30%; p<0.05); a finding endorsed by the effect of GLP-1 receptor agonist on primary human hepatocytes (24.6% decrease in lipogenesis vs. untreated controls; p<0.01).

CONCLUSIONS

Liraglutide reduces metabolic dysfunction, insulin resistance and lipotoxicity in the key metabolic organs in the pathogenesis of NASH. Liraglutide may offer the potential for a disease-modifying intervention in NASH.

Exendin-4 attenuates brain death-induced liver damage in the rat

The majority of liver grafts destined for transplantation originate from brain dead donors. However, significantly better posttransplantation outcomes are achieved when organs from living donors are used, suggesting that brain death (BD) causes irreversible damage to the liver tissue. Recently, glucagon-like peptide-1 (GLP1) analogues were shown to possess interesting hepatic protection effects in different liver disease models. We hypothesized that donor treatment with the GLP1 analogue exendin-4 (Ex-4) could alleviate BD-induced liver damage. A rat model of BD was employed in order to estimate BD-induced liver damage and Ex-4's potential protective effects. Liver damage was assessed by biochemical determination of circulating hepatic markers. Apoptosis in the hepatic tissue was assessed by immunoblot and immunohistochemistry using an antibody that only recognizes the active form of caspase-3. Gene expression changes in inflammation and stress response genes were monitored by quantitative real-time polymerase chain reaction. Here, we show that Ex-4 administration to the brain dead liver donors significantly reduces levels of circulating aspartate aminotransferase and lactate dehydrogenase. This was accompanied by a remarkable reduction in hepatocyte apoptosis. In this model, BD caused up-regulation of tumor necrosis factor and stress-related genes, confirming previous findings in clinical and animal studies. In conclusion, treatment of brain dead rats with Ex-4 reduced BD-induced liver damage. Further investigation is needed to determine the molecular basis of the observed liver protection. After testing in a randomized clinical trial, the inclusion of GLP1 analogues in organ donor management might help to improve organ quality, maximize organ donation, and possibly increase liver transplantation success rates.

Liraglutide reduces fatty degeneration in hepatic cells via the AMPK/SREBP1 pathway

Recent studies have suggested that liraglutide could have a potential function in improving non-alcoholic fatty liver disease (NAFLD); however, the underlying molecular mechanism remains unclear. The aim of the present study was to investigate the role of the AMP-activated protein kinase (AMPK)/sterol regulatory element binding protein 1 (SREBP1) pathway in mediating the effect of liraglutide in reducing fatty degeneration in an in vitro NAFLD model. To resemble the NAFLD condition in vitro, L-02 cells were treated with 0.5 mM free fatty acids (FFAs) for 24 h. Liraglutide could affect the expression of AMPKα1, phosphorylated AMPKα1 and SREBP1 in a dose-dependent manner in FFA-exposed L-02 cells, as demonstrated by western blot analysis. The intracellular lipid accumulation was significantly decreased, as shown by oil red O staining. A significant decrease in the content of triglyceride and total cholesterol was observed when the FFA-exposed L-02 cells were incubated with liraglutide. In addition, the increased expression of liver-type fatty acid-binding protein in FFA-exposed L-02 cells was suppressed by liraglutide. These effects were reversed by compound C, an AMPK inhibitor. In conclusion, this study has demonstrated that liraglutide can reduce fatty degeneration induced by FFAs in hepatocytes, and this effect may be partially mediated by the AMPK/SREBP1 pathway.

Bariatric surgery and nonalcoholic fatty liver disease

The rising prevalence of nonalcoholic fatty liver disease (NAFLD) is associated with the increasing global pandemic of obesity. These conditions cluster with type II diabetes mellitus and the metabolic syndrome to result in obesity-associated liver disease. The benefits of bariatric procedures on diabetes and the metabolic syndrome have been recognized for some time, and there is now mounting evidence to suggest that bariatric procedures improve liver histology and contribute to the beneficial resolution of NAFLD in obese patients. These beneficial effects derive from a number of weight-dependent and weight-independent mechanisms including surgical BRAVE actions (bile flow changes, restriction of stomach size, anatomical gastrointestinal rearrangement, vagal manipulation, enteric hormonal modulation) and subsequent effects such as reduced lipid intake, adipocytokine secretion, modulation of gut flora, improvements in insulin resistance and reduced inflammation. Here, we review the clinical investigations on bariatric procedures for NAFLD, in addition to the mounting mechanistic data supporting these findings. Elucidating the mechanisms by which bariatric procedures may resolve NAFLD can help enhance surgical approaches for metabolic hepatic dysfunction and also contribute toward developing the next generation of therapies aimed at reducing the burden of obesity-associated liver disease.

Review on the effect of glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors for the treatment of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a common liver disease and it represents the hepatic manifestation of metabolic syndrome, which includes type 2 diabetes mellitus (T2DM), dyslipidemia, central obesity and hypertension. Glucagon-like peptide-1 (GLP-1) analogues and dipeptidyl peptidase-4 (DPP-4) inhibitors were widely used to treat T2DM. These agents improve glycemic control, promote weight loss and improve lipid metabolism. Recent studies have demonstrated that the GLP-1 receptor (GLP-1R) is present and functional in human and rat hepatocytes. In this review, we present data from animal researches and human clinical studies that showed GLP-1 analogues and DPP-4 inhibitors can decrease hepatic triglyceride (TG) content and improve hepatic steatosis, although some effects could be a result of improvements in metabolic parameters. Multiple hepatocyte signal transduction pathways and mRNA from key enzymes in fatty acid metabolism appear to be activated by GLP-1 and its analogues. Thus, the data support the need for more rigorous prospective clinical trials to further investigate the potential of incretin therapies to treat patients with NAFLD.

GLP-1 receptor agonists: effects on the progression of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases, and its incidence has been increasing recently. In addition to hepatic complications, NAFLD is also recognized as an independent risk factor for cardiovascular disease. Unfortunately, the current therapies for NAFLD display variable efficacy; a novel and effective drug is urgently needed. Glucagon-like peptide-1 (GLP-1), a receptor agonist is a new drug approved for treating type 2 diabetes. Recently, these types of agents have shown a novel therapeutic effect on NAFLD. However, the mechanisms of GLP-1 receptor agonists on the treatment of NAFLD have not yet been explained precisely. Recent studies have demonstrated that GLP-1 reverses the progression of NAFLD not only indirectly through an incretin effect that improves key parameters involved in NAFLD, but also a direct effect on lipid metabolism of hepatocytes and inflammation in liver. In this review, we provided an overview of the role and mechanisms of GLP-1 in the therapy of NAFLD.

Total aralosides of aralia elata (Miq) seem (TASAES) ameliorate nonalcoholic steatohepatitis by modulating IRE1α-mediated JNK and NF-κB pathways in ApoE-/- mice

ETHNOPHARMACOLOGICAL RELEVANCE

Total saponins of Aralia elata (Miq) Seem (TASAES) from the Chinese traditional herb Long ya Aralia chinensis L. is popularly used as a folk medicine to treat rheumatism, neurasthenia, diabetes, hepatitis and antivirus in Asian countries. However, there was poor study of TASAES on Non-alcoholic steatohepatitis (NASH), which is characterized by inflammatory responses and hepatocellular apoptosis exacerbating liver injury. This study aimed to clarify whether or not the anti-inflammatory and anti-apoptotic activities and protective mechanisms of the total aralosides of Aralia elata (Miq) Seem (TASAES) ameliorate NASH in a high-fat diet (HFD)-induced ApoE-/- mouse model.

MATERIAL AND METHODS

C57/BL6N and ApoE-/- mice were fed with HFD containing 0.3% cholesterol and 20% fat to induce NASH and then treated with TASAES (75,150mg/kg/day, i.g.) for 12 weeks. Liver tissue was procured for histological examination, real-time RT-PCR and Western blot analysis.

RESULTS

ASAES treatment groups exhibited lower serum alanine and aspartate aminotransferases than the NASH group. TASAES could also reduce hepatic steatosis, as revealed by histological changes. In addition, TASAES treatment groups showed lower protein and mRNA expression levels of pro-inflammatory cytokines, such as IL-6, MCP-1, and TNF-α than NASH group. Reduced TUNEL-positive cells were also found in TASAES treatment groups. Western blot and immunohistochemical results indicated that TASAES regulated apoptosis and inflammation-related protein expression. Furthermore, TASAES treatment significantly reduced the phosphorylation of IRE1α, JNK and IκB and the downstream activation of NF-κB p65 was also reduced.

CONCLUSION

These findings suggested that the ameliorative effects of TASASE in HFD-induced NASH were associated with the regulation of IRE1α-mediated JNK and NF-κB signal pathways, thereby protecting the liver against NASH.

Rapid and body weight-independent improvement of endothelial and high-density lipoprotein function after Roux-en-Y gastric bypass: role of glucagon-like peptide-1

BACKGROUND

Roux-en-Y gastric bypass (RYGB) reduces body weight and cardiovascular mortality in morbidly obese patients. Glucagon-like peptide-1 (GLP-1) seems to mediate the metabolic benefits of RYGB partly in a weight loss-independent manner. The present study investigated in rats and patients whether obesity-induced endothelial and high-density lipoprotein (HDL) dysfunction is rapidly improved after RYGB via a GLP-1-dependent mechanism.

METHODS AND RESULTS

Eight days after RYGB in diet-induced obese rats, higher plasma levels of bile acids and GLP-1 were associated with improved endothelium-dependent relaxation compared with sham-operated controls fed ad libitum and sham-operated rats that were weight matched to those undergoing RYGB. Compared with the sham-operated rats, RYGB improved nitric oxide (NO) bioavailability resulting from higher endothelial Akt/NO synthase activation, reduced c-Jun amino terminal kinase phosphorylation, and decreased oxidative stress. The protective effects of RYGB were prevented by the GLP-1 receptor antagonist exendin9-39 (10 μg·kg(-1)·h(-1)). Furthermore, in patients and rats, RYGB rapidly reversed HDL dysfunction and restored the endothelium-protective properties of the lipoprotein, including endothelial NO synthase activation, NO production, and anti-inflammatory, antiapoptotic, and antioxidant effects. Finally, RYGB restored HDL-mediated cholesterol efflux capacity. To demonstrate the role of increased GLP-1 signaling, sham-operated control rats were treated for 8 days with the GLP-1 analog liraglutide (0.2 mg/kg twice daily), which restored NO bioavailability and improved endothelium-dependent relaxations and HDL endothelium-protective properties, mimicking the effects of RYGB.

CONCLUSIONS

RYGB rapidly reverses obesity-induced endothelial dysfunction and restores the endothelium-protective properties of HDL via a GLP-1-mediated mechanism. The present translational findings in rats and patients unmask novel, weight-independent mechanisms of cardiovascular protection in morbid obesity.

Effects of glucagon-like peptide-1 receptor agonists on non-alcoholic fatty liver disease and inflammation

Glucagon-like peptide1 (GLP-1) is secreted from Langerhans cells in response to oral nutrient intake. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are a new class of incretin-based anti-diabetic drugs. They function to stimulate insulin secretion while suppressing glucagon secretion. GLP-1-based therapies are now well established in the management of type 2 diabetes mellitus (T2DM), and recent literature has suggested potential applications of these drugs in the treatment of obesity and for protection against cardiovascular and neurological diseases. As we know, along with change in lifestyles, the prevalence of non-alcoholic fatty liver disease (NAFLD) in China is rising more than that of viral hepatitis and alcoholic fatty liver disease, and NAFLD has become the most common chronic liver disease in recent years. Recent studies further suggest that GLP-1RAs can reduce transaminase levels to improve NAFLD by improving blood lipid levels, cutting down the fat content to promote fat redistribution, directly decreasing fatty degeneration of the liver, reducing the degree of liver fibrosis and improving inflammation. This review shows the NAFLD-associated effects of GLP-1RAs in animal models and in patients with T2DM or obesity who are participants in clinical trials.

Liraglutide reduces lipid accumulation in steatotic L‑02 cells by enhancing autophagy

Simple hepatic steatosis is the early stage of non-alcoholic fatty liver disease and is recognized as a benign process. Previous studies show that glucagon-like peptide-1 has great potential in improving hepatic steatosis. Recent data have revealed that inhibiting autophagy exacerbates lipid accumulation in hepatocytes. Therefore, the present study aimed to determine the effects of liraglutide (LG) on simple hepatic steatosis and the possible role of autophagy. Firstly, steatotic L-02 cells were induced by incubating L-02 cells with 1 mmol/l free fatty acid (FFA) mixture (oleic acid and palmitic acid at a molar ratio of 2:1) for 24 h. Intracellular lipid accumulation, cell viability, oxidative stress and apoptosis were evaluated. Secondly, steatotic L-02 cells were treated with 10 or 100 nmol/l LG, 100 nmol/l LG plus 3-methyladenine (3-MA), or rapamycin for 24 h, and then lipid accumulation was measured. Next, the degree of lipid accumulation and the intensity of autophagy were assessed. Oil red O staining and triglyceride quantification demonstrated notable steatosis in L-02 cells following exposure to 1 mmol/l FFA mixture for 24 h. There was no significant cytotoxicity, oxidative stress or apoptosis in steatotic L-02 cells. Treatment with 100 nmol/l LG reduced lipid accumulation in steatotic L-02 cells and increased the mRNA levels of microtubule-associated protein 1 light chain 3B. Additionally, it enhanced the autophagic flux in steatotic L-02 cells, as measured by western blot analysis and shown by electron microscopy. Additionally, 3-MA weakened the ability of LG to improve hepatic steatosis and enhance autophagy. Our data indicate that LG reduces the lipid accumulation in steatotic L-02 cells, and the activation of autophagy plays a significant role in this process.

Silencing of FGF-21 expression promotes hepatic gluconeogenesis and glycogenolysis by regulation of the STAT3-SOCS3 signal

Insulin resistance is a metabolic disorder associated with type 2 diabetes. Recent reports have shown that fibroblast growth factor-21 (FGF-21) plays an important role in the progression of insulin resistance. However, the biochemical and molecular mechanisms by which changes in FGF-21 activation result in changes in the rates of hepatic gluconeogenesis and glycogenolysis remain to be elucidated. In this study, we developed adenovirus-mediated shRNA against FGF-21 to inhibit FGF-21 expression in ApoE knockout mice. Using this mouse model, we determined the effects of FGF-21 knockdown in vivo on hepatic glucose production, gluconeogenesis and glycogenolysis, and their relationship with the signal transducer and activator of transcription 3 (STAT3)/suppressor of cytokine signaling 3 (SOCS3) signal pathways. We show that liver-specific knockdown of FGF-21 in high-fat diet-fed ApoE knockout mice resulted in a 39% increase in glycogenolysis and a 75% increase in gluconeogenesis, accompanied by increased hepatic expression of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase. Furthermore, FGF-21 knockdown decreased phosphorylation of STAT3 and SOCS3 expression in high-fat diet-fed mice. Our data suggest that hepatic FGF-21 knockdown increases gluconeogenesis and glycogenolysis by activation of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase via the STAT3/SOCS3 pathway, ultimately leading to exacerbation of hepatic insulin resistance.

Risk of cardiovascular, cardiac and arrhythmic complications in patients with non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) has emerged as a public health problem of epidemic proportions worldwide. Accumulating clinical and epidemiological evidence indicates that NAFLD is not only associated with liver-related morbidity and mortality but also with an increased risk of coronary heart disease (CHD), abnormalities of cardiac function and structure (e.g., left ventricular dysfunction and hypertrophy, and heart failure), valvular heart disease (e.g., aortic valve sclerosis) and arrhythmias (e.g., atrial fibrillation). Experimental evidence suggests that NAFLD itself, especially in its more severe forms, exacerbates systemic/hepatic insulin resistance, causes atherogenic dyslipidemia, and releases a variety of pro-inflammatory, pro-coagulant and pro-fibrogenic mediators that may play important roles in the pathophysiology of cardiac and arrhythmic complications. Collectively, these findings suggest that patients with NAFLD may benefit from more intensive surveillance and early treatment interventions to decrease the risk for CHD and other cardiac/arrhythmic complications. The purpose of this clinical review is to summarize the rapidly expanding body of evidence that supports a strong association between NAFLD and cardiovascular, cardiac and arrhythmic complications, to briefly examine the putative biological mechanisms underlying this association, and to discuss some of the current treatment options that may influence both NAFLD and its related cardiac and arrhythmic complications.