Glucagon like peptide-1 receptor agonists for the management of obesity and non-alcoholic fatty liver disease: a novel therapeutic option

Interplay of gut microbiota, glucagon-like peptide receptor agonists, and nutrition: New frontiers in metabolic dysfunction-associated steatotic liver disease therapy

The gut-liver axis plays a crucial role in the development and progression of metabolic dysfunction-associated steatotic liver disease (MASLD). Key metabolites, including lipopolysaccharides, short-chain fatty acids (SCFAs), bile acids, and beneficial gut bacteria such as Bifidobacterium and Lactobacillus, are pivotal in this process. Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) show promise in managing MASLD by promoting weight loss, enhancing insulin secretion, and improving liver health. They restore gut-liver axis functionality, and their effects are amplified through dietary modifications and gut microbiome-targeted therapies. Emerging research highlights the interplay between GLP-1 RAs and gut microbiota, indicating that the gut microbiome significantly influences therapeutic outcomes. Metabolites produced by gut bacteria, can stimulate glucagon-like peptide-1 (GLP-1) secretion, further improving metabolic health. Integrating dietary interventions with GLP-1 RA treatment may enhance liver health by modulating the gut microbiota-SCFAs-GLP-1 pathway. Future research is needed to understand personalized effects, with prebiotics and probiotics offering treatment avenues for MASLD.

Cardiovascular and mortality outcomes with GLP-1 receptor agonists vs other glucose-lowering drugs in individuals with NAFLD and type 2 diabetes: a large population-based matched cohort study

AIMS/HYPOTHESIS

We aimed to determine whether the use of glucagon-like peptide-1 receptor agonists (GLP-1RA) in individuals with non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus decreases the risk of new-onset adverse cardiovascular events (CVEs) and mortality rate compared with other glucose-lowering drugs in a real setting at a population level.

METHODS

We conducted a population-based propensity-matched retrospective cohort study using TriNetX. The cohort comprised patients over 20 years old who were newly treated with glucose-lowering drugs between 1 January 2013 and 31 December 2021, and followed until 30 September 2022. New users of GLP-1RAs were matched based on age, demographics, comorbidities and medication use by using 1:1 propensity matching with other glucose-lowering drugs. The primary outcome was the new onset of adverse CVEs, including heart failure, composite incidence of major adverse cardiovascular events (MACE; defined as unstable angina, myocardial infarction, or coronary artery procedures or surgeries) and composite cerebrovascular events (defined as the first occurrence of stroke, transient ischaemic attack, cerebral infarction, carotid intervention or surgery), and the secondary outcome was all-cause mortality. Cox proportional hazards models were used to estimate HRs.

RESULTS

The study involved 2,835,398 patients with both NAFLD and type 2 diabetes. When compared with the sodium-glucose cotransporter 2 (SGLT2) inhibitors group, the GLP-1RAs group showed no evidence of a difference in terms of new-onset heart failure (HR 0.97; 95% CI 0.93, 1.01), MACE (HR 0.95; 95% CI 0.90, 1.01) and cerebrovascular events (HR 0.99; 95% CI 0.94, 1.03). Furthermore, the two groups had no evidence of a difference in mortality rate (HR 1.06; 95% CI 0.97, 1.15). Similar results were observed across sensitivity analyses. Compared with other second- or third-line glucose-lowering medications, the GLP-1RAs demonstrated a lower rate of adverse CVEs, including heart failure (HR 0.88; 95% CI 0.85, 0.92), MACE (HR 0.89; 95% CI 0.85, 0.94), cerebrovascular events (HR 0.93; 95% CI 0.89, 0.96) and all-cause mortality rate (HR 0.70; 95% CI 0.66, 0.75).

CONCLUSIONS/INTERPRETATION

In individuals with NAFLD and type 2 diabetes, GLP-1RAs are associated with lower incidences of adverse CVEs and all-cause mortality compared with metformin or other second- and third-line glucose-lowering medications. However, there was no significant difference in adverse CVEs or all-cause mortality when compared with those taking SGLT2 inhibitors.

Understanding the Burden of Nonalcoholic Fatty Liver Disease: Time for Action

The prevalence of nonalcoholic fatty liver disease (NAFLD) in the United States is 38%, having increased by 50% within the past 3 decades. The estimated NAFLD prevalence among people with type 2 diabetes is 55-70%. The presence of type 2 diabetes is associated with a higher likelihood of progression of NAFLD to fibrosis development, liver transplant, and death. Cardiovascular disease is the main cause of mortality among people with NAFLD, and the risk of death is significantly higher in people with both NAFLD and type 2 diabetes. NAFLD carries high patient and economic burdens but low awareness among both the general public and health care providers. This article reviews the epidemiology of NAFLD and discusses the need for appropriate risk stratification, referral for specialty care, management of cardiometabolic risk factors, and treatment of the disease. The authors present a call to action to raise awareness of NAFLD and address its increasing burden in a systematic and efficient manner.

Anti-inflammatory role of glucagon-like peptide 1 receptor agonists and its clinical implications

Glucagon-like peptide 1 receptor agonists (GLP-1RAs) have emerged as promising therapeutic agents with potent anti-inflammatory properties and diverse clinical implications. This in-depth review article explores the mechanisms behind the anti-inflammatory actions of GLP-1RAs and assesses their prospective applicability in a wide range of disease scenarios. The current review establishes the significance of comprehending the anti-inflammatory role of GLP-1RAs and identifies pertinent research gaps. A concise overview of inflammation and its clinical consequences underscores the critical need for effective anti-inflammatory interventions. Subsequently, the article elucidates the intricate mechanisms through which GLP-1RAs modulate immune cell signaling and regulate the nuclear factor-kappa B (NF-κB) pathway. Detailed discussions encompass their impact on inflammatory responses, cytokine production, and attenuation of oxidative stress. The exposition is substantiated by a collection of pertinent examples and an extensive array of references from both preclinical and clinical investigations. The historical trajectory of GLP-1RA drugs, including exenatide, lixisenatide, liraglutide, and semaglutide, is traced to delineate their development as therapeutic agents. Moreover, the review emphasizes the therapeutic potential of GLP-1RAs in specific disease contexts like type 2 diabetes, a neurodegenerative disorder, and inflammatory bowel disease (IBD), shedding light on their anti-inflammatory effects through rigorous examination of preclinical and clinical studies. The article also provides an outlook on future perspectives for GLP-1RAs, encompassing the domains of diabetes, neurodegenerative diseases, and IBD. In conclusion, GLP-1RAs exhibit substantial anti-inflammatory effects, rendering them promising therapeutic agents with broad clinical implications. They are very useful in a wide variety of diseases because they regulate immunological responses, block NF-κB activation, and decrease production of pro-inflammatory cytokines. Ongoing research endeavors aim to optimize their therapeutic use, delineate patient-specific treatment paradigms, and explore novel therapeutic applications. GLP-1RAs represent a significant breakthrough in anti-inflammatory therapy, offering novel treatment options, and improved patient outcomes.

The effects of GLP-1 receptor agonists on visceral fat and liver ectopic fat in an adult population with or without diabetes and nonalcoholic fatty liver disease: A systematic review and meta-analysis

AIM

To uncover the effect of GLP-1 receptor agonists (GLP-1 RAs) on the visceral- and hepatic fat content of adults.

METHODS

PubMed, EMBASE, Cochrane Library, and Web of Science were searched from inception until November 2022. Randomized controlled trials (RCTs) of GLP-1Ras was extracted, including reports of effects on visceral adipose tissue and hepatic fat content in individuals with type 2 diabetes, non-type 2 diabetes, NAFLD (non-alcoholic fatty liver disease), and non-NAFLD. Meta-analyses used random-effects models.

RESULTS

1736 individuals in the 30 qualified RCTs were included, comprising 1363 people with type 2 diabetes and 318 with NFLD. GLP-1 RAs reduced visceral adipose tissue (standard mean difference [SMD] = -0.59, 95% CI [-0.83, -0.36], P<0.00001) and hepatic fat content (weighted mean difference [WMD] = -3.09, 95% CI [-4.16, -2.02], P<0.00001) compared to other control treatment. Subgroup analysis showed that GLP-1Ras dramatically decreased visceral fat in patients with type 2 diabetes (SMD = -0.49, 95% CI [-0.69, -0.29] P<0.00001), NAFLD (SMD = -0.99, 95% CI [-1.64, -0.34] P = 0.003), non-type 2 diabetes (SMD = -1.38, 95% CI [-2.44, -0.32] P = 0.01), and non-NAFLD (SMD = -0.53, 95% CI [-0.78, -0.28] P<0.0001). GLP-1Ras reduced the liver fat level of type 2 diabetes (WMD = -3.15, 95% CI [-4.14, -2.15] P<0.00001), NAFLD (WMD = -3.83, 95% CI [-6.30, -1.37] P = 0.002), and type 2 diabetes with NAFLD (WMD = -4.27, 95% CI [-6.80, -1.74] P = 0.0009), while showed no impact on the hepatic fat content in non-Type 2 diabetes (WMD = -12.48, 95% CI [-45.19, 20.24] P = 0.45).

CONCLUSIONS

LP-1 RAs significantly reduce visceral- and liver fat content in adults.

Diabetes medications and risk of HCC

Type 2 diabetes mellitus is a recognized risk factor for HCC in patients with liver disease, independent from the etiology of their liver disease. Hence, prevention and treatment of type 2 diabetes mellitus and its underlying cause, insulin resistance, should be considered a treatment target for patients with liver disease. The drug armamentarium for diabetes is wide and consists of agents with insulin-sensitizing activity, agents that stimulate insulin secretion, insulin itself, and agents that reduce gastrointestinal and urinary glucose absorption. From an endocrinology perspective, the main goal of treatment is the achievement of euglycemia; however, in patients at risk of, or with known underlying liver disease, the choice of diabetic medication as it relates to potential hepatic carcinogenesis remains complex and should be carefully considered. In the last decade, increasing evidence has suggested that metformin may reduce the risk of HCC, whereas evidence for other classes of diabetic medications, particularly some of the newer agents including the sodium glucose cotransporter-2 inhibitors and glucagon-like peptide-1 receptor agonists, is fewer and often inconsistent. In this review, we aim to summarize the current evidence on the potential effects of the most widely used diabetic agents on liver cancer tumorigenesis.

The effects of the voglibose on non-alcoholic fatty liver disease in mice model

The α-glucosidase inhibitor (α-GI) delays the intestinal absorption of glucose, which reduces postprandial hepatic glucose intake. This mechanism is considered to be effective in treating non-alcoholic fatty liver disease (NAFLD). Here, we investigated the effect of voglibose, an α-glucosidase inhibitor, on high-fat, high-fructose (HFHFr) diet-induced NAFLD models. Seven-week-old male C57BL/6J mice were randomly placed in a chow diet group or an HFHFr diet group. After 10 weeks, mice in the HFHFr group were randomly assigned to one of three groups: HFHFr diet with vehicle, HFHFr with voglibose, or HFHFr with pioglitazone. Each diet and treatment was continued for 10 weeks. The HFHFr diet induced severe NAFLD in terms of steatosis, hepatitis, and fibrosis. Administration of voglibose improved all aspects of NAFLD, comparable to those of pioglitazone, a positive control. In voglibose-treated mice, gene expressions of hepatic lipogenesis markers were significantly downregulated. In the in vitro experiment, reducing the influx of glucose into hepatocytes significantly reduced steatosis and de novo lipogenesis even in the presence of sufficient fructose and fat, demonstrating that the mechanism of voglibose could be effective in treating HFHFr diet-induced NAFLD. These results indicate that voglibose improves HFHFr diet-induced NAFLD by suppressing hepatic de novo lipogenesis.

A randomized triple-blind controlled clinical trial evaluation of sitagliptin in the treatment of patients with non-alcoholic fatty liver diseases without diabetes

The current study aimed to evaluate the efficacy of sitagliptin vs. placebo in treating non-alcoholic fatty liver disease (NAFLD). In a triple-blind randomized clinical trial, we assigned 120 eligible subjects with NAFLD to receive daily dosing of 50 mg sitagliptin (n = 60) or the placebo (n = 60) for 56 weeks and lifestyle modification in both groups. Laboratory and anthropometric outcomes were measured, and liver stiffness was assessed using a fibroscan. The primary outcome measures were changes from baseline in fibrosis scores and liver transferases. Out of 120 patients randomized into sitagliptin and placebo groups, 76 patients completed the trial, of whom 44 were in the sitagliptin and 32 in the placebo groups. Patients receiving sitagliptin showed a significant decrease in the fibrosis scores (P = 0.001). The reductions in the alanine aminotransferase (AST) (P = 0.036) and aspartate AST (P < 0.001) levels were also statistically significant. The effect of sitagliptin in reducing fibrosis scores was significantly greater in normal-weight and overweight individuals than in obese individuals (p = 0.036, and p = 0.018, respectively), whereas the effects of sitagliptin on AST levels were greater among overweight/obese patients (p = 0.028, and p = 0.016, respectively). Sitagliptin reduced fibrosis scores and liver enzymes in NAFLD patients after 56 weeks of therapy. The changes in fibrosis scores were more prominent in patients with normal weight and overweight than obese patients, whereas the effects on AST levels were greater among overweight/obese patients. Other randomized trials with larger sample sizes and longer treatment durations may be required before precise results can be reached.

CLINICAL TRIAL REGISTRATION

[https://www.irct.ir/trial/46140], identifier [IRCT20140430017505N2].

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.

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.

The Emerging Role of Glucagon-like Peptide-1 Receptor Agonists for the Management of NAFLD

CONTEXT

The burden of cirrhosis from nonalcoholic fatty liver disease (NAFLD) is reaching epidemic proportions in the United States. This calls for greater awareness among endocrinologists, who often see but may miss the diagnosis in adults with obesity or type 2 diabetes mellitus (T2D) who are at the highest risk. At the same time, recent studies suggest that glucagon-like peptide-1 receptor agonists (GLP-1RAs) are beneficial vs nonalcoholic steatohepatitis (NASH) in this population. This minireview aims to assist endocrinologists to recognize the condition and recent work on the role of GLP-1RAs in NAFLD/NASH.

EVIDENCE ACQUISITION

Evidence from observational studies, randomized controlled trials, and meta-analyses.

EVIDENCE SYNTHESIS

Endocrinologists should lead multidisciplinary teams to implement recent consensus statements on NAFLD that call for screening and treatment of clinically significant fibrosis to prevent cirrhosis, especially in the high-risk groups (ie, people with obesity, prediabetes, or T2D). With no US Food and Drug Administration (FDA)-approved agents, weight loss is central to successful management, with pharmacological treatment options limited today to vitamin E (in people without T2D) and diabetes medications that reverse steatohepatitis, such as pioglitazone or GLP-1RA. Recently, the benefit of GLP-1RAs in NAFLD, suggested from earlier trials, has been confirmed in adults with biopsy-proven NASH. In 2021, the FDA also approved semaglutide for obesity management.

CONCLUSION

A paradigm change is developing between the endocrinologist's greater awareness about their critical role to curve the epidemic of NAFLD and new clinical care pathways that include a broader use of GLP-1RAs in the management of these complex patients.

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.

Metabolic Messengers: glucagon-like peptide 1

Glucagon like peptide-1 (GLP-1), a peptide hormone from the intestinal tract, plays a central role in the coordination of postprandial glucose homeostasis through actions on insulin secretion, food intake and gut motility. GLP-1 forms the basis for a variety of current drugs for the treatment of type 2 diabetes and obesity, as well as new agents currently being developed. Here, we provide a concise overview of the core physiology of GLP-1 secretion and action, and the role of the peptide in human health, disease and therapeutics.

Advanced Liver Fibrosis Is Common in Patients With Type 2 Diabetes Followed in the Outpatient Setting: The Need for Systematic Screening

OBJECTIVE

Assess the prevalence of nonalcoholic fatty liver disease (NAFLD) and of liver fibrosis associated with nonalcoholic steatohepatitis in unselected patients with type 2 diabetes mellitus (T2DM).

RESEARCH DESIGN AND METHODS

A total of 561 patients with T2DM (age: 60 ± 11 years; BMI: 33.4 ± 6.2 kg/m²; and HbA_1c: 7.5 ± 1.8%) attending primary care or endocrinology outpatient clinics and unaware of having NAFLD were recruited. At the visit, volunteers were invited to be screened by elastography for steatosis and fibrosis by controlled attenuation parameter (≥274 dB/m) and liver stiffness measurement (LSM; ≥7.0 kPa), respectively. Secondary causes of liver disease were ruled out. Diagnostic panels for prediction of advanced fibrosis, such as AST-to-platelet ratio index (APRI) and Fibrosis-4 (FIB-4) index, were also measured. A liver biopsy was performed if results were suggestive of fibrosis.

RESULTS

The prevalence of steatosis was 70% and of fibrosis 21% (LSM ≥7.0 kPa). Moderate fibrosis (F2: LSM ≥8.2 kPa) was present in 6% and severe fibrosis or cirrhosis (F3-4: LSM ≥9.7 kPa) in 9%, similar to that estimated by FIB-4 and APRI panels. Noninvasive testing was consistent with liver biopsy results. Elevated AST or ALT ≥40 units/L was present in a minority of patients with steatosis (8% and 13%, respectively) or with liver fibrosis (18% and 28%, respectively). This suggests that AST/ALT alone are insufficient as initial screening. However, performance may be enhanced by imaging (e.g., transient elastography) and plasma diagnostic panels (e.g., FIB-4 and APRI).

CONCLUSIONS

Moderate-to-advanced fibrosis (F2 or higher), an established risk factor for cirrhosis and overall mortality, affects at least one out of six (15%) patients with T2DM. These results support the American Diabetes Association guidelines to screen for clinically significant fibrosis in patients with T2DM with steatosis or elevated ALT.

Glucagon-Like Peptide-1 Receptor Agonists for Treatment of Nonalcoholic Fatty Liver Disease and Nonalcoholic Steatohepatitis: An Updated Meta-Analysis of Randomized Controlled Trials

To assess the efficacy of glucagon-like peptide-1 receptor agonists (GLP-1 RAs) for treatment of nonalcoholic fatty liver disease (NAFLD) or steatohepatitis (NASH), we performed a systematic review and meta-analysis of randomized controlled trials (RCTs). Three large electronic databases were systematically searched (up to 15 December 2020) to identify placebo-controlled or active-controlled RCTs using different GLP-1 RAs. We included eleven placebo-controlled or active-controlled phase-2 RCTs (involving a total of 936 middle-aged individuals) that used liraglutide (n = 6 RCTs), exenatide (n = 3 RCTs), dulaglutide (n = 1 RCT) or semaglutide (n = 1 RCT) to specifically treat NAFLD or NASH, detected by liver biopsy (n = 2 RCTs) or imaging techniques (n = 9 RCTs). Compared to placebo or reference therapy, treatment with GLP-1 RAs for a median of 26 weeks was associated with significant reductions in the absolute percentage of liver fat content on magnetic resonance-based techniques (pooled weighted mean difference: −3.92%, 95% confidence intervals (CI) −6.27% to −1.56%) and serum liver enzyme levels, as well as with greater histological resolution of NASH without worsening of liver fibrosis (pooled random-effects odds ratio 4.06, 95% CI 2.52–6.55; for liraglutide and semaglutide only). In conclusion, treatment with GLP-1 RAs (mostly liraglutide and semaglutide) is a promising treatment option for NAFLD or NASH that warrants further investigation.

Glucagon-Like Peptide-1 Receptor Agonists for Treatment of Nonalcoholic Fatty Liver Disease and Nonalcoholic Steatohepatitis: An Updated Meta-Analysis of Randomized Controlled Trials

To assess the efficacy of glucagon-like peptide-1 receptor agonists (GLP-1 RAs) for treatment of nonalcoholic fatty liver disease (NAFLD) or steatohepatitis (NASH), we performed a systematic review and meta-analysis of randomized controlled trials (RCTs). Three large electronic databases were systematically searched (up to 15 December 2020) to identify placebo-controlled or active-controlled RCTs using different GLP-1 RAs. We included eleven placebo-controlled or active-controlled phase-2 RCTs (involving a total of 936 middle-aged individuals) that used liraglutide (n = 6 RCTs), exenatide (n = 3 RCTs), dulaglutide (n = 1 RCT) or semaglutide (n = 1 RCT) to specifically treat NAFLD or NASH, detected by liver biopsy (n = 2 RCTs) or imaging techniques (n = 9 RCTs). Compared to placebo or reference therapy, treatment with GLP-1 RAs for a median of 26 weeks was associated with significant reductions in the absolute percentage of liver fat content on magnetic resonance-based techniques (pooled weighted mean difference: -3.92%, 95% confidence intervals (CI) -6.27% to -1.56%) and serum liver enzyme levels, as well as with greater histological resolution of NASH without worsening of liver fibrosis (pooled random-effects odds ratio 4.06, 95% CI 2.52-6.55; for liraglutide and semaglutide only). In conclusion, treatment with GLP-1 RAs (mostly liraglutide and semaglutide) is a promising treatment option for NAFLD or NASH that warrants further investigation.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Exenatide Attenuates Non-Alcoholic Steatohepatitis by Inhibiting the Pyroptosis Signaling Pathway

BACKGROUND/AIMS

Exenatide is a glucagon-like polypeptide-1 analog, whose main clinical use is to treat type 2 diabetes. However, the mechanism of exenatide in mitigating non-alcoholic steatohepatitis (NASH) remains unclear. This study aimed to investigate the in vitro and in vivo effect of exenatide on NASH.

METHODS

Leptin receptor-deficient C57BL/KsJ- db/db male mice were fed with methionine-choline-deficient (MCD) diet for 4 weeks to induce NASH, while oleic acid/LPS-treated HepG2 cells were used as an in vitro cell model. Exenatide (20 µg/kg/day, subcutaneous) and specific exenatide inhibitors (20 µg/kg/day, intraperitoneal) were used to determine the effects of exenatide on NASH.

RESULTS

Exenatide treatment inhibited the pyroptosis signaling pathway to attenuate NASH.

CONCLUSION

To the best of our knowledge, this report provides the first evidence showing that exenatide attenuated NASH by inhibiting the pyroptosis signaling pathway. Exenatide thus has important pathophysiological functions in NASH and may represent a useful new therapeutic target.

Current treatment paradigms and emerging therapies for NAFLD/NASH

Non-alcoholic fatty liver disease (NAFLD) is one the fastest emerging manifestations of the metabolic syndrome worldwide. Non-alcoholic steatohepatitis (NASH), the progressive form of NAFLD, may culminate into cirrhosis and hepatocellular cancer (HCC) and is presently a leading cause of liver transplant. Although a steady progress is seen in understanding of the disease epidemiology, pathogenesis and identifying therapeutic targets, the slowest advancement is seen in the therapeutic field. Currently, there is no FDA approved therapy for this disease and appropriate therapeutic targets are urgently warranted. In this review we discuss the role of lifestyle intervention, pharmacological agents, surgical approaches, and gut microbiome, with regard to therapy for NASH. In particular, we focus the role of insulin sensitizers, thyroid hormone mimetics, antioxidants, cholesterol lowering drugs, incretins and cytokines as therapeutic targets for NASH. We highlight these targets aiming to optimize the future for NASH therapy.

The metabolic basis of nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a major cause of chronic liver disease and is associated with significant morbidity and mortality worldwide, with a high incidence in Western countries and non-Western countries that have adopted a Western diet. NAFLD is commonly associated with components of the metabolic syndrome, type 2 diabetes mellitus and cardiovascular disease, suggesting a common mechanistic basis. An inability to metabolically handle free fatty acid overload-metabolic inflexibility-constitutes a core node for NAFLD pathogenesis, with resulting lipotoxicity, mitochondrial dysfunction and cellular stress leading to inflammation, apoptosis and fibrogenesis. These responses can lead to the histological phenotype of nonalcoholic steatohepatitis (NASH) with varying degrees of fibrosis, which can progress to cirrhosis. This perspective review describes the key cellular and molecular mechanisms of NAFLD and NASH, namely an excessive burden of carbohydrates and fatty acids that contribute to lipotoxicity resulting in hepatocellular injury and fibrogenesis. Understanding the extrahepatic dysmetabolic contributors to NASH is crucial for the development of safe, effective and durable treatment approaches for this increasingly common disease.

Glucagon Like Peptide-1 Receptor Agonists Alters Pancreatic and Hepatic Histology and Regulation of Endoplasmic Reticulum Stress in High-fat Diet Mouse Model

BACKGROUND

Obesity is a major health problem worldwide, and non-alcoholic fatty pancreas disease (NAFPD) and non-alcoholic fatty liver disease (NAFLD) are obesity-associated complications. Liraglutide, a glucagon-like peptide-1 (GLP-1) agonist, has been approved for treatment of obesity. We aimed to evaluate the therapeutic effects of liraglutide on the complications through its regulation of endoplasmic reticulum (ER) stress.

METHODS

A high-fat diet mouse model was established in C57BL/6J mice. Two groups of mice were fed a high-fat diet with 60% fat for 16 weeks and control mice were fed standard chow. A four-week 0.6 mg/kg/day liraglutide treatment was started in one high-fat diet group after 12 weeks of the high-fat diet. After sacrificing the mice, pancreatic and hepatic tissues were prepared for western blot and immunohistochemistry for ER stress proteins, including activating transcription factor 4 (ATF4), caspase 12, C/EBP homologous protein (CHOP) eukaryotic initiation factor 2 α (eIF2α), glucose regulated protein (GRP) 78 and protein kinase RNA-like endoplasmic reticulum kinase (PERK).

RESULTS

Liraglutide significantly decreased body weight gained by mice consuming a high-fat diet (27.6 g vs. 34.5 g, P<0.001), and levels of all ER proteins increased significantly in both the pancreas and liver (all P<0.05). Expression of most ER stress proteins in pancreatic tissue correlated with disease scores of NAFLD (all P<0.05). However, no significant differences were found in pancreatic ATF 4 expression between mice without NAFLD, and those with early non-alcoholic steatohepatitis (NASH) and fibrotic NASH (P=0.122).

CONCLUSION

Liraglutide reduces the severity of NAFPD and NAFLD may through regulating the ER stress pathway and downstream apoptosis signaling.

Morphological evaluation of the effects of exercise on high-fat-diet-induced liver damage in rats

BACKGROUND/AIMS

This study was aimed to investigate the protective effects of swimming exercise on nonalcoholic fatty liver disease (NAFLD) associated with high fat diet-induced obesity, using microscopical and biochemical parameters.

MATERIALS AND METHODS

Sprague Dawley male rats were fed either standard chow (STD group; 6% fat) or high-fat diet (HFD group; 45% fat) for 18 weeks. Animals were divided into four groups, STD, STD + EXC, HFD, HFD + EXC. Exercise groups were submitted to swimming training 5 days of week and 1h of per day, during the last 6 weeks of the experiment. At the end of the experiment, liver samples were evaluated for morphologically and ultrastructurally. Moreover, malondialdehyde (MDA) and glutathione (GSH) levels were evaluated in liver samples.

RESULTS

Normal morphology of liver parancyma with hepatocytes and sinusoids was observed in the STD and STD+EXC groups. Steatosis, lipid accumulation, ballooned hepatocytes, decrease of glycogen deposits and fibrosis in periportal area were observed in HFD group. Liver MDA level was increased and GSH level was decreased in HFD group. Exercise treatment ameliorated these morphological and oxidative changes in HFD induced liver damage.

CONCLUSION

Based on morphological and biochemical analysis, we could conclude that swimming training ameliorated obesity-induced liver damage by regulating lipid accumulation and oxidative damage.

A glycosylated Fc-fused glucagon-like peptide-1 receptor agonist exhibits equivalent glucose lowering to but fewer gastrointestinal side effects than dulaglutide

AIM

To evaluate the pharmacokinetic and pharmacodynamic properties of a novel glycosylated Fc-fused glucagon-like peptide-1(GLP-1-gFc) receptor agonist with distinctive receptor binding affinity, designed to improve in vivo stability and safety relative to the commercial GLP-1 analogue dulaglutide, and assess its safety profile and pharmacokinetics in healthy humans.

MATERIALS AND METHODS

We constructed GLP-1-gFc and determined its binding affinity and potency using in vitro instrumental and cell-based analyses followed by in vivo comparison of the glucose-lowering and gastrointestinal side effects between GLP-1-gFc and dulaglutide. A phase 1 clinical trial was conducted to confirm the efficacy and safety profile of GLP-1-gFc.

RESULTS

GLP-1-gFc showed 10-fold less binding affinity and 4-fold less potency than dulaglutide in in vitro. A potency-adjusted dose delayed HbA1c increase comparable with that of dulaglutide (Change for 6 weeks: 2.4 mg/kg GLP-1-gFc, 4.34 ± 0.40 vs. 0.6 mg/kg dulaglutide, 4.26 ± 0.22; n.s.). However, the equivalent efficacy dose and higher dose did not induce malaise-related responses (blueberry bar consumption, g/mouse: 2.4 mg/kg GLP-1-gFc, 0.15% ± 0.03% vs. 0.6 mg/kg dulaglutide, 0.04% ± 0.01%; P < .01) or QT interval changes (mean at 14-20 hours, mSc: 0.28 mg/kg GLP-1-gFc, 0.0-8.0 vs. 0.07 mg/kg dulaglutide, 8.0-27.7; n.s.), observed as safety variables in rats and monkeys, compared with those of dulaglutide. Glucose reductions in an oral glucose tolerance test were significant at day 3 postdose without severe gastrointestinal adverse events and pulse rate changes in healthy subjects.

CONCLUSIONS

These results suggest that GLP-1-gFc could be used as a novel GLP-1 receptor agonist with better safety than dulaglutide to maximize therapeutic benefits in subjects with type 2 diabetes.

Effect of glucagon-like peptide-1 receptor agonists on adipokine level of nonalcoholic fatty liver disease in rats fed high-fat diet

Background

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of liver disease worldwide, and no effective treatment exists until now. Glucagon-like peptide-1 receptor agonists are becoming the preferred therapeutic option for the management of obesity and are becoming the preferred treatment options for the management of both NAFLD and type 2 diabetes mellitus, but the molecular mechanisms are still unclear.

Methods

Forty-five healthy male Wistar rats were divided into three groups: normal control, high-fat diet (HFD) group, HFD + liraglutide (100 mg/kg body weight) group. Biochemical parameters and adipokine levels were examined in the serum of rats. In order to judge the degree of steatosis of NAFLD, the magnetic resonance imaging and histopathology of the liver were also studied.

Results and conclusion

Liraglutide caused a significant decrease in the serum fasting glucose and improved the insulin resistance, dyslipidemia, and liver enzymes. It reduced the adipokine level, and alleviated the histopathology of liver of rats in the steatosis, ballooning, and lobular inflammation when compared to the HFD group. Thus, liraglutide demonstrated amelioration of NAFLD by decreasing the adipokine levels in this animal model and seems to be a promising molecule for the management of NAFLD.

Liraglutide ameliorates obesity-related nonalcoholic fatty liver disease by regulating Sestrin2-mediated Nrf2/HO-1 pathway

Liraglutide, a glucagon-like peptide 1 (GLP-1) analogue, could reverse NAFLD-induced liver damage by improving metabolic profiles, but the exact molecular mechanism has not been elucidated. Sestrin2 is a novel antioxidant protein, essential for regulating metabolic homeostasis. However, whether sestrin2-mediated redox balance participated in the protective effects of liraglutide against NAFLD is still elusive. The aim of the study was to determine whether liraglutide could ameliorate NAFLD by increasing Sestrin2-mediated signaling in obese mice. Following a normal diet or high fat diet (HFD) for 8 weeks, male C57BL/6 mice were treated with or without liraglutide for 4 weeks. Function and histopathology of liver were conducted to evaluate liver injury. Sestrin2-related AMPK and Nrf2/HO-1 pathway were examined. Antioxidative and inflammatory genes and were determined. HFD mice displayed significantly increased body weight, fat mass, lipids levels and impaired glucose homeostasis with reduced glucose tolerance and insulin sensitivity. Metabolic profiles, hepatic injury, and hepatic lipid accumulation from HFD mice were improved by liraglutide treatment. Liraglutide enhanced Sestrin2, phosphorylated AMPK, Nrf2, and HO-1 protein levels. Additionally, Liraglutide treatment increased mRNA levels of Sestrin2, Nrf2, HO-1 and down-stream genes catalase, GCLM and NQO1, but reduced malondialdehyde and TNF-α levels. Our findings indicated that liraglutide ameliorated obesity-related NAFLD through upregulating Sestrin2-mediated Nrf2/HO-1 pathway.

Recent advances in understanding the role of glucagon-like peptide 1

The discovery that glucagon-like peptide 1 (GLP-1) mediates a significant proportion of the incretin effect during the postprandial period and the subsequent observation that GLP-1 bioactivity is retained in type 2 diabetes (T2D) led to new therapeutic strategies being developed for T2D treatment based on GLP-1 action. Although owing to its short half-life exogenous GLP-1 has no use therapeutically, GLP-1 mimetics, which have a much longer half-life than native GLP-1, have proven to be effective for T2D treatment since they prolong the incretin effect in patients. These GLP-1 mimetics are a desirable therapeutic option for T2D since they do not provoke hypoglycaemia or weight gain and have simple modes of administration and monitoring. Additionally, over more recent years, GLP-1 action has been found to mediate systemic physiological beneficial effects and this has high clinical relevance due to the post-diagnosis complications of T2D. Indeed, recent studies have found that certain GLP-1 analogue therapies improve the cardiovascular outcomes for people with diabetes. Furthermore, GLP-1-based therapies may enable new therapeutic strategies for diseases that can also arise independently of the clinical manifestation of T2D, such as dementia and Parkinson's disease. GLP-1 functions by binding to its receptor (GLP-1R), which expresses mainly in pancreatic islet beta cells. A better understanding of the mechanisms and signalling pathways by which acute and chronic GLP-1R activation alleviates disease phenotypes and induces desirable physiological responses during healthy conditions will likely lead to the development of new therapeutic GLP-1 mimetic-based therapies, which improve prognosis to a greater extent than current therapies for an array of diseases.

Retinoprotection by BGP-15, a Hydroximic Acid Derivative, in a Type II Diabetic Rat Model Compared to Glibenclamide, Metformin, and Pioglitazone

High blood glucose and the consequential ischemia-reperfusion (I/R) injury damage vessels of the retina, deteriorating its function, which can be clearly visualized by electroretinography (ERG). The aim of the present study was to evaluate the possible retinoprotective effects of systemic BGP-15, an emerging drug candidate, in an insulin resistant animal model, the Goto-Kakizaki rat, and compare these results with well-known anti-diabetics such as glibenclamide, metformin, and pioglitazone, which even led to some novel conclusions about these well-known agents. Experiments were carried out on diseased animal model (Goto-Kakizaki rats). The used methods include weight measurement, glucose-related measurements—like fasting blood sugar analysis, oral glucose tolerance test, hyperinsulinemic euglycemic glucose clamp (HEGC), and calculations of different indices from HEGC results—electroretinography and Western Blot. Beside its apparent insulin sensitization, BGP-15 was also able to counteract the retina-damaging effect of Type II diabetes comparable to the aforementioned anti-diabetics. The mechanism of retinoprotective action may include sirtuin 1 (SIRT1) and matrix metalloproteinase 9 (MMP9) enzymes, as BGP-15 was able to elevate SIRT1 and decrease MMP9 expression in the eye. Based on our results, this emerging hydroximic acid derivative might be a future target of pharmacological developments as a potential drug against the harmful consequences of diabetes, such as diabetic retinopathy.

The Race to Bash NASH: Emerging Targets and Drug Development in a Complex Liver Disease

Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease (NAFLD) characterized by liver steatosis, inflammation, and hepatocellular damage. NASH is a serious condition that can progress to cirrhosis, liver failure, and hepatocellular carcinoma. The association of NASH with obesity, type 2 diabetes mellitus, and dyslipidemia has led to an emerging picture of NASH as the liver manifestation of metabolic syndrome. Although diet and exercise can dramatically improve NASH outcomes, significant lifestyle changes can be challenging to sustain. Pharmaceutical therapies could be an important addition to care, but currently none are approved for NASH. Here, we review the most promising targets for NASH treatment, along with the most advanced therapeutics in development. These include targets involved in metabolism (e.g., sugar, lipid, and cholesterol metabolism), inflammation, and fibrosis. Ultimately, combination therapies addressing multiple aspects of NASH pathogenesis are expected to provide benefit for patients.

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

Objective

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

Methods

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

Results

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

Conclusions

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

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

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

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

Effects of Exenatide and Humalog Mix25 on Fat Distribution, Insulin Sensitivity, and β-Cell Function in Normal BMI Patients with Type 2 Diabetes and Visceral Adiposity

In China, most normal BMI (body mass index of ≥18.5 to <25 kg/m²) adults with type 2 diabetes (T2DM) exhibit visceral adiposity. This study compared the effects of exenatide and humalog Mix25 on normal BMI patients with T2DM and visceral adiposity. A total of 95 patients were randomized to receive either exenatide or humalog Mix25 treatment for 24 weeks. Subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) were quantified by magnetic resonance imaging (MRI) and liver fat content (LFC) by liver proton magnetic resonance spectroscopy (¹H MRS). Each patient's weight, waist circumference, BMI, blood glucose, insulin sensitivity, pancreatic β-cell function, and fibroblast growth factor 21 (FGF-21) levels were measured. Data from 81 patients who completed the study (40 and 41 in the exenatide and humalog Mix25 groups, respectively) were analysed. The change in 2 h plasma blood glucose was greater in the exenatide group (P = 0.039). HOMA-IR and MBCI improved significantly after exenatide therapy (P < 0.01, P = 0.045). VAT and LFC decreased in both groups (P < 0.01 for all) but to a greater extent in the exenatide group, while SAT only decreased with exenatide therapy (P < 0.01). FGF-21 levels declined more in the exenatide group (P < 0.01), but were positively correlated with VAT in the entire cohort before (r = 0.244, P = 0.043) and after (r = 0.290, P = 0.016) the intervention. The effects of exenatide on glycaemic metabolism, insulin resistance, pancreatic β-cell function, and fat deposition support its administration to normal BMI patients with T2DM and visceral adiposity.

Non-alcoholic Fatty Liver Disease and Diabetes Mellitus

Nonalcoholic fatty liver disease (NAFLD) has emerged as the leading liver disease globally. NAFLD patients can have a progressive phenotype, non-alcoholic steatohepatitis (NASH) that could lead to cirrhosis, liver failure and cancer. There is a close bi-directional relationship between NAFLD and type 2 diabetes mellitus (T2DM); NAFLD increases the risk for T2DM and its complications whereas T2DM increases the severity of NAFLD and its complications. The large global impact of NAFLD and T2DM on healthcare systems requires a paradigm shift from specialty care to early identification and risk stratification of NAFLD in primary care and diabetes clinics. Approach to diagnosis, risk stratification and management of NAFLD is discussed. In addition to optimizing the control of coexisting cardiometabolic comorbidities, early referral of NAFLD patients at high risk of having NASH or significant fibrosis to hepatology specialist care may improve management and allow access for clinical trials. Lifestyle modifications, vitamin E, pioglitazone and metformin are currently available options that may benefit patients with T2DM and NAFLD. The burst of clinical trials investigating newer therapeutic agents for NAFLD and NASH offer hope for new, effective and safe therapies in the near future.

Human Umbilical Cord-Derived Mesenchymal Stem Cell Therapy Ameliorates Nonalcoholic Fatty Liver Disease in Obese Type 2 Diabetic Mice

Nonalcoholic fatty liver disease (NAFLD) is increasingly common among patients with type 2 diabetes mellitus (T2DM). The two conditions can act synergistically to produce adverse outcomes. However, the therapeutic options for patients with NAFLD and T2DM are currently limited. Human umbilical cord-derived mesenchymal stem cells (UC-MSCs) have shown therapeutic potential for diabetes and hepatic disorders such as liver cirrhosis and fulminant hepatic failure. The present study is aimed at investigating the effect of human UC-MSCs on a mouse model of NAFLD and T2DM, characterized by obesity-induced hyperglycaemia, dyslipidaemia, hepatic steatosis, and liver dysfunction. Thirty-week-old male C57BL/6 db/db mice were infused with human UC-MSCs or phosphate-buffered saline (PBS) via the tail vein once a week for six weeks. Age-matched male C57BL/6 wild-type db/+ mice were used as controls. Body weight and random blood glucose were measured every week. One week after the sixth infusion, intraperitoneal glucose tolerance tests and insulin tolerance tests were performed and the blood and liver were harvested for biochemical and histopathological examinations. Quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR), immunofluorescence staining, and western blot were performed to monitor the expression of the lipid metabolism- and regulatory pathway-related genes. UC-MSC infusions significantly ameliorated hyperglycaemia, attenuated the elevation of hepatic transaminases, and decreased lipid contents, including triglyceride, total cholesterol, and low-density lipoprotein cholesterol. Moreover, histological lesions in the liver diminished markedly, as evidenced by reduced lipid accumulation and attenuated hepatic steatosis. Mechanistically, UC-MSCs were found to regulate lipid metabolism by increasing the expression of fatty acid oxidation-related genes and inhibiting the expression of lipogenesis-related genes, which were associated with the upregulation of the HNF4α-CES2 pathway. Our results demonstrate that human UC-MSCs can ameliorate NAFLD and reverse metabolic syndrome in db/db mice. Thus, UC-MSCs may serve as a novel therapeutic agent for T2DM patients with NAFLD.

Antidiabetic Drugs and Statins in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) has become the most prevalent liver disease worldwide. Despite its high prevalence and rising incidence, there are currently no specific targeted pharmacotherapies approved by the Food and Drug Administration (FDA) for nonalcoholic steatohepatitis (NASH). Current therapies for patients with NAFLD include lifestyle modification. Vitamin E and pioglitazone are recommended for those confirmed to have NASH. However, there are concerns about the long-term safety of both pioglitazone and vitamin E in higher doses. Metformin is essential for managing the abnormal metabolic parameters in patients with NAFLD. Glucagon-like peptide-1 analogue, sodium-dependent glucose cotransporter inhibitors, and peroxisome proliferator-activated receptor agonists have shown benefits in improving metabolic parameters and reducing hepatic lipid accumulation and inflammation. However, the role of these antidiabetic agents in specifically reversing NASH needs to be established. Indeed, statins have been underprescribed in patients with NASH owing to fear of hepatotoxicity despite coronary artery disease being a common cause of death in patients with NAFLD. Statins reduce the risk of cardiovascular morbidity and mortality in patients with NASH and dyslipidemia. However, their use specifically for treatment of NASH needs further evaluation. Optimizing the control of risk factors remains the main strategy for treatment until targeted pharmacotherapies for NASH are available.

Consensus Recommendations on GLP-1 RA Use in the Management of Type 2 Diabetes Mellitus: South Asian Task Force

The advent of incretin mimetics such as glucagon-like peptide-1 receptor agonists (GLP-1 RAs) has enriched the armamentarium for diabetes management owing to their glycaemic as well as extra-glycaemic benefits. The approval status and availability of this class of drugs vary widely across the globe. Being a relatively newer class of drug with numerous benefits, several national and international guidelines are working towards addressing clinical questions pertaining to the optimal use of GLP-1 RAs for the management of diabetes. Although the newer class of drugs are associated with significant benefits such as patient-centric approach, these drugs demand the providers to be vigilant and knowledgeable about the medication. The South Asian population is at higher risk of type 2 diabetes mellitus (T2DM) because of their genetic predisposition and lifestyle changes. Hence, prevention and management of T2DM and its associated complications in this population are of paramount importance. The current report aims to present an overview of current knowledge on GLP-1 RAs based on pragmatic review of the available clinical evidence. In addition, this report is a consensus of expert endocrinologists representing South Asian countries including India, Pakistan, Bangladesh, Nepal, Sri Lanka, Afghanistan and the Maldives on essential recommendations related to the use of GLP-1 RAs in a real-world scenario.

Effect of semaglutide on liver enzymes and markers of inflammation in subjects with type 2 diabetes and/or obesity

BACKGROUND

Obesity and type 2 diabetes are drivers of non-alcoholic fatty liver disease (NAFLD). Glucagon-like peptide-1 analogues effectively treat obesity and type 2 diabetes and may offer potential for NAFLD treatment.

AIM

To evaluate the effect of the glucagon-like peptide-1 analogue, semaglutide, on alanine aminotransferase (ALT) and high-sensitivity C-reactive protein (hsCRP) in subjects at risk of NAFLD.

METHODS

Data from a 104-week cardiovascular outcomes trial in type 2 diabetes (semaglutide 0.5 or 1.0 mg/week) and a 52-week weight management trial (semaglutide 0.05-0.4 mg/day) were analysed. Treatment ratios vs placebo were estimated for ALT (both trials) and hsCRP (weight management trial only) using a mixed model for repeated measurements, with or without adjustment for change in body weight.

RESULTS

Elevated baseline ALT (men >30 IU/L; women >19 IU/L) was present in 52% (499/957) of weight management trial subjects. In this group with elevated ALT, end-of-treatment ALT reductions were 6%-21% (P<0.05 for doses≥0.2 mg/day) and hsCRP reductions 25%-43% vs placebo (P < 0.05 for 0.2 and 0.4 mg/day). Normalisation of elevated baseline ALT occurred in 25%-46% of weight management trial subjects, vs 18% on placebo. Elevated baseline ALT was present in 41% (1325/3268) of cardiovascular outcomes trial subjects. In this group with elevated ALT, no significant ALT reduction was noted at end-of-treatment for 0.5 mg/week, while a 9% reduction vs placebo was seen for 1.0 mg/week (P = 0.0024). Treatment ratios for changes in ALT and hsCRP were not statistically significant after adjustment for weight change.

CONCLUSIONS

Semaglutide significantly reduced ALT and hsCRP in clinical trials in subjects with obesity and/or type 2 diabetes.

Impact of exenatide on mitochondrial lipid metabolism in mice with nonalcoholic steatohepatitis

Exenatide (Exe) is a glucagon-like peptide (GLP)-1 receptor agonist that enhances insulin secretion and is associated with induction of satiety with weight loss. As mitochondrial dysfunction and lipotoxicity are central features of nonalcoholic steatohepatitis (NASH), we tested whether Exe improved mitochondrial function in this setting. We studied C57BL/6J mice fed for 24 weeks either a control- or high-fructose, high-trans-fat (TFD)-diet (i.e., a NASH model previously validated by our laboratory). For the final 8 weeks, mice were treated with Exe (30 µg/kg/day) or vehicle. Mitochondrial metabolism was assessed by infusion of [13C3]propionate, [3,4-13C2]glucose and NMR-based 13C-isotopomer analysis. Exenatide significantly decreased fasting plasma glucose, free fatty acids and triglycerides, as well as adipose tissue insulin resistance. Moreover, Exe reduced 23% hepatic glucose production, 15% tri-carboxylic acid (TCA) cycle flux, 20% anaplerosis and 17% pyruvate cycling resulting in a significant 31% decrease in intrahepatic triglyceride content (P = 0.02). Exenatide improved the lipidomic profile and decreased hepatic lipid byproducts associated with insulin resistance and lipotoxicity, such as diacylglycerols (TFD: 111 ± 13 vs Exe: 64 ± 13 µmol/g protein, P = 0.03) and ceramides (TFD: 1.6 ± 0.1 vs Exe: 1.3 ± 0.1 µmol/g protein, P = 0.03). Exenatide lowered expression of hepatic lipogenic genes (Srebp1C, Cd36) and genes involved in inflammation and fibrosis (Tnfa, Timp1). In conclusion, in a diet-induced mouse model of NASH, Exe ameliorates mitochondrial TCA cycle flux and significantly decreases insulin resistance, steatosis and hepatocyte lipotoxicity. This may have significant clinical implications to the potential mechanism of action of GLP-1 receptor agonists in patients with NASH. Future studies should elucidate the relative contribution of direct vs indirect mechanisms at play.

Metabolic Targets in Nonalcoholic Fatty Liver Disease

The prevalence and diagnosis of nonalcoholic fatty liver disease (NAFLD) is on the rise worldwide and currently has no FDA-approved pharmacotherapy. The increase in disease burden of NAFLD and a more severe form of this progressive liver disease, nonalcoholic steatohepatitis (NASH), largely mirrors the increase in obesity and type 2 diabetes (T2D) and reflects the hepatic manifestation of an altered metabolic state. Indeed, metabolic syndrome, defined as a constellation of obesity, insulin resistance, hyperglycemia, dyslipidemia and hypertension, is the major risk factor predisposing the NAFLD and NASH. There are multiple potential pharmacologic strategies to rebalance aspects of disordered metabolism in NAFLD. These include therapies aimed at reducing hepatic steatosis by directly modulating lipid metabolism within the liver, inhibiting fructose metabolism, altering delivery of free fatty acids from the adipose to the liver by targeting insulin resistance and/or adipose metabolism, modulating glycemia, and altering pleiotropic metabolic pathways simultaneously. Emerging data from human genetics also supports a role for metabolic drivers in NAFLD and risk for progression to NASH. In this review, we highlight the prominent metabolic drivers of NAFLD pathogenesis and discuss the major metabolic targets of NASH pharmacotherapy.

Non-alcoholic fatty liver disease: causes, diagnosis, cardiometabolic consequences, and treatment strategies

The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing worldwide. In some patients with NAFLD, isolated steatosis can progress to advanced stages with non-alcoholic steatohepatitis (NASH) and fibrosis, increasing the risk of cirrhosis and hepatocellular carcinoma. Furthermore, NAFLD is believed to be involved in the pathogenesis of common disorders such as type 2 diabetes and cardiovascular disease. In this Review, we highlight novel concepts related to diagnosis, risk prediction, and treatment of NAFLD. First, because NAFLD is a heterogeneous disease, the advanced stages of which seem to be strongly affected by comorbidities such as insulin resistance and type 2 diabetes, early use of reliable, non-invasive diagnostic tools is needed, particularly in patients with insulin resistance or diabetes, to allow the identification of patients at different disease stages. Second, although the strongest genetic risk alleles for NAFLD (ie, the 148Met allele in PNPLA3 and the 167Lys allele in TM6SF2) are associated with increased liver fat content and progression to NASH and cirrhosis, these alleles are also unexpectedly associated with an apparent protection from cardiovascular disease. If consistent across diverse populations, this discordance in NAFLD-related risk prediction between hepatic and extrahepatic disease might need to be accounted for in the management of NAFLD. Third, drug treatments assessed in NAFLD seem to differ with respect to cardiometabolic and antifibrotic efficacy, suggesting the need to better identify and tailor the most appropriate treatment approach, or to use a combination of approaches. These emerging concepts could contribute to the development of a multidisciplinary approach for endocrinologists and hepatologists working together in the management of NAFLD.

Postglucose Hyperinsulinemia in Black Women Is Not What We Thought

Chung et al. present data showing altered insulin secretion and metabolism in black women across the lifespan. This work is critical to move our field toward personalized patient-centered care.

Sodium butyrate reduces high-fat diet-induced non-alcoholic steatohepatitis through upregulation of hepatic GLP-1R expression

Glucagon-like peptide-1 (GLP-1) has a broad spectrum of biological activity by regulating metabolic processes via both the direct activation of the class B family of G protein-coupled receptors and indirect nonreceptor-mediated pathways. GLP-1 receptor (GLP-1R) agonists have significant therapeutic effects on non-alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) in animal models. However, clinical studies indicated that GLP-1 treatment had little effect on hepatic steatosis in some NAFLD patients, suggesting that GLP-1 resistance may occur in these patients. It is well-known that the gut metabolite sodium butyrate (NaB) could promote GLP-1 secretion from intestinal L cells. However, it is unclear whether NaB improves hepatic GLP-1 responsiveness in NAFLD. In the current study, we showed that the serum GLP-1 levels of NAFLD patients were similar to those of normal controls, but hepatic GLP-1R expression was significantly downregulated in NAFLD patients. Similarly, in the NAFLD mouse model, mice fed with a high-fat diet showed reduced hepatic GLP-1R expression, which was reversed by NaB treatment and accompanied by markedly alleviated liver steatosis. In addition, NaB treatment also upregulated the hepatic p-AMPK/p-ACC and insulin receptor/insulin receptor substrate-1 expression levels. Furthermore, NaB-enhanced GLP-1R expression in HepG2 cells by inhibiting histone deacetylase-2 independent of GPR43/GPR109a. These results indicate that NaB is able to prevent the progression of NAFL to NASH via promoting hepatic GLP-1R expression. NaB is a GLP-1 sensitizer and represents a potential therapeutic adjuvant to prevent NAFL progression to NASH.

Advances in Pediatric Fatty Liver Disease: Pathogenesis, Diagnosis, and Treatment

Pediatric nonalcoholic fatty liver disease is an increasingly prevalent disease, but its pathophysiology is not fully elucidated, diagnosis is difficult and invasive, and therapeutic options are limited. This article addresses the recent advancements made in understanding the pathophysiology of nonalcoholic fatty liver disease, the development of less invasive diagnostic modalities, and emerging therapeutic options, including ongoing clinical trials in children.

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

Nonalcoholic fatty liver disease (NAFLD) is highly associated with insulin resistance (IR), type 2 diabetes mellitus and metabolic syndrome, being characterized as the hepatic component of metabolic syndrome. Despite its high prevalence, no pharmacological treatment has been established, as of yet. A growing body of evidence, however, shows that reducing IR can result in improvement of the biochemical and histological features of nonalcoholic steatohepatitis (NASH)-the aggressive form of NAFLD that can lead to cirrhosis and hepatocellular carcinoma. Unfortunately, the several trials that have assessed the effect of various antidiabetic agents to date have failed to establish an effective and safe treatment regimen for patients with NAFLD. Glucagon-like peptide-1 (commonly known as GLP-1) agonists are a novel class of antidiabetic drugs that improve insulin sensitivity and promote weight loss. They also appear to have a direct effect on the lipid metabolism of hepatocytes, reducing hepatic steatosis. Several trials have demonstrated that GLP-1 agonists can reduce aminotransferase levels and improve liver histology in patients with NAFLD, suggesting that these agents could serve as an alternative treatment option for these patients. This manuscript discusses the role and potential mechanisms of GLP-1 agonists in the treatment of NASH.

Clinical pharmacology of glucagon-like peptide-1 receptor agonists

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are an important asset in the armamentarium for the treatment of type 2 diabetes mellitus (type 2 DM). Incretin failure is a critical etiopathogenetic feature of type 2 DM, which, if reversed, results in improved glycaemic control. GLP-1 RAs are injectable peptides that resemble the structure and function of endogenous incretin GLP-1, but as they are not deactivated by the dipeptidyl peptidase-4 (DPP-4), their half-life is prolonged compared with native GLP-1. Based on their ability to activate GLP-1 receptor, GLP-1 RAs are classified as short-acting (exenatide twice-daily and lixisenatide once-daily), and long-acting (liraglutide once-daily and the once-weekly formulations of exenatide extended-release, dulaglutide, and albiglutide). Semaglutide, another long-acting, once-weekly GLP-1 RA, was recently approved by the FDA and EMA. Although all of these agents potently reduce haemoglobin A1C (HbA1c), there are unique features and fundamental differences among them related to fasting and postprandial hyperglycaemia reduction, weight loss potency, cardiovascular protection efficacy, and adverse events profile. It is imperative that current evidence be integrated and applied in the context of an individualised patient-centred approach. This should include not only glucose management but also targeting as many as possible of the pathophysiologic mechanisms responsible for type 2 DM development and progression.

How does glucagon-like peptide 1 stimulate human β-cell proliferation? A lesson from islet graft experiments

The incidence of type 2 diabetes increases with age. The age‐dependent decline in functional β‐cell mass contributes to the increased risk of onset of diabetes, reflecting the central role of pancreatic β‐cells in glucose homeostasis. Indeed, the replication rate of human and rodent β‐cells is known to decline sharply with age, and such a characteristic of β‐cells might explain the increased onset of type 2 diabetes in the older population. The molecular mechanism involved in the age‐dependent decline of β‐cell proliferation has been extensively studied, mainly using rodents and in vitro culture systems, but its molecular basis is still largely unknown. A mechanism by which glucagon‐like peptide‐1 receptor activation induces human β‐cell proliferation only within a restricted time window was recently suggested in a study in which human islets were grafted into immunodeficient mice. The authors found that the mitogenic effects of exendin‐4 require calcineurin/nuclear factor of activated T‐cells signaling, and that only in juvenile islets, exendin‐4 induced the expression of nuclear factor of activated T‐cells signaling components, as well as downstream target genes that facilitate β‐cell proliferation. These findings provide a mechanistic explanation as to why glucagon‐like peptide 1 exerts mitogenic effects only in juvenile human β‐cells.

Dissecting the Physiology and Pathophysiology of Glucagon-Like Peptide-1

An aging world population exposed to a sedentary life style is currently plagued by chronic metabolic diseases, such as type-2 diabetes, that are spreading worldwide at an unprecedented rate. One of the most promising pharmacological approaches for the management of type 2 diabetes takes advantage of the peptide hormone glucagon-like peptide-1 (GLP-1) under the form of protease resistant mimetics, and DPP-IV inhibitors. Despite the improved quality of life, long-term treatments with these new classes of drugs are riddled with serious and life-threatening side-effects, with no overall cure of the disease. New evidence is shedding more light over the complex physiology of GLP-1 in health and metabolic diseases. Herein, we discuss the most recent advancements in the biology of gut receptors known to induce the secretion of GLP-1, to bridge the multiple gaps into our understanding of its physiology and pathology.