GLP-1 analogs reduce hepatocyte steatosis and improve survival by enhancing the unfolded protein response and promoting macroautophagy

Effects of GLP-1 receptor agonists on the degree of liver fibrosis and CRP in non-alcoholic fatty liver disease and non-alcoholic steatohepatitis: A systematic review and meta-analysis

BACKGROUND

Based on the rapidly growing global burden of non-alcoholic fatty liver disease (NAFLD) or steatohepatitis (NASH), in order to evaluate the efficacy of glucagon-like peptide-1 receptor agonists (GLP-1RAs) in the treatment of NAFLD or NASH this paper presents a systematic review and meta-analysis of randomized controlled trials(RCTs).

METHODS

In this systematic review and meta-analysis, We searched PubMed, Medline, Web of Science and The Cochrane Library databases. All randomized controlled trials involving GLP-1RAs and NAFLD or NASH were collected since the database was established. A meta-analysis of proportions was done with the generalised linear mixed model. Continuous variables were represented by Mean and Standard Deviation (SD), and binary variable were represented by Relative Risk (RR) and 95% Confidence Interval (CI) as effect indicators. The research results were presented by Revman 5.4. This study is registered with PROSPERO (CRD42023390735).

FINDING

We included 16 placebo-controlled or active drug-controlled randomized controlled trials (involving 2178 patients) that used liraglutide, exenatide, dulaglutide, or semaglutie in the treatment of NAFLD or NASH, as measured by liver biopsy or imaging techniques. This study found that the effect of GLP-1RAs on histologic resolution of NASH with no worsening of liver fibrosis (n=2 RCTs; WMD:4.08, 95%CI 2.54-6.56, p < 0.00001) has statistically significant. At the same time, GLP-1RAs affected CRP (n = 7 RCTs; WMD:-0.41, 95% CI-0.78 to -0.04, p =0.002) and other serological indicators were significantly improved.

CONCLUSION

This study evaluated the efficacy of GLP-1RAs in patients with NAFLD and NASH. These results suggest that GLP-1RAs may be a potential and viable therapeutic approach as a targeted agent to intervene in disease progression of NAFLD and NASH.

3D microscaffolds with triple-marker sensitive nanoprobes for studying fatty liver disease in vitro

Non-alcoholic fatty liver disease (NAFLD) is a heterogeneous condition that encompasses a wide range of liver diseases that progresses from simple hepatic steatosis to the life-threatening state of cirrhosis. However, due to the heterogeneity of this disease, comprehensive analysis of several physicochemical and biological factors that drive its progression is necessary. Therefore, an in vitro platform is required that would enable real-time monitoring of these changes to better understand the progression of these diseases. The earliest stage of NAFLD, i.e. hepatic steatosis, is characterised by triglyceride accumulation in the form of lipid vacuoles in the cytosol of hepatocytes. This fatty acid accumulation is usually accompanied by hepatic inflammation, leading to tissue acidification and dysregulated expression of certain proteases such as matrix metalloproteinases (MMPs). Taking cues from the biological parameters of the disease, we report here a 3D in vitro GelMA/alginate microscaffold platform encapsulating a triple-marker (pH, MMP-3 and MMP-9) sensitive fluorescent nanoprobe for monitoring, and hence, distinguishing the fatty liver disease (hepatic steatosis) from healthy livers on the basis of pH change and MMP expression. The nanoprobe consists of a carbon nanoparticle (CNP) core, which exhibits intrinsic pH-dependent fluorescence properties, decorated either with an MMP-3 (NpMMP3) or MMP-9 (NpMMP9) sensitive peptide substrate. These peptide substrates are flanked with a fluorophore-quencher pair that separates on enzymatic cleavage, resulting in fluorescence emission. The cocktail of these nanoprobes generated multiple fluorescence signals corresponding to slightly acidic pH (blue) and overexpression of MMP-3 (green) and MMP-9 (red) enzymes in a 3D in vitro fatty liver model, whereas no/negligible fluorescence signals were observed in a healthy liver model. Moreover, this platform enabled us to mimic fatty liver disease in a more realistic manner. Therefore, this 3D in vitro platform encapsulating triple-marker sensitive fluorescent nanoprobes would facilitate the monitoring of the changes in pH and MMP expression, thereby enabling us to distinguish a healthy liver from a diseased liver and to study liver disease stages on the basis of these markers.

Autophagy and metabolic aging: Current understanding and future applications

"Metabolic aging" refers to the gradual decline in cellular metabolic function across various tissues due to defective hormonal signaling, impaired nutrient sensing, mitochondrial dysfunction, replicative stress, and cellular senescence. While this process usually corresponds with chronological aging, the recent increase in metabolic diseases and cancers occurring at younger ages in humans suggests the premature onset of cellular fatigue and metabolic aging. Autophagy, a cellular housekeeping process facilitated by lysosomes, plays a crucial role in maintaining tissue rejuvenation and health. However, various environmental toxins, hormones, lifestyle changes, and nutrient imbalances can disrupt autophagy in humans. In this review, we explore the connection between autophagy and cellular metabolism, its regulation by extrinsic factors and its modulation to prevent the early onset of metabolic aging.

Glucagon-Like Peptide-1: New Regulator in Lipid Metabolism

Glucagon-like peptide-1 (GLP-1) is a 30-amino acid peptide hormone that is mainly expressed in the intestine and hypothalamus. In recent years, basic and clinical studies have shown that GLP-1 is closely related to lipid metabolism, and it can participate in lipid metabolism by inhibiting fat synthesis, promoting fat differentiation, enhancing cholesterol metabolism, and promoting adipose browning. GLP-1 plays a key role in the occurrence and development of metabolic diseases such as obesity, nonalcoholic fatty liver disease, and atherosclerosis by regulating lipid metabolism. It is expected to become a new target for the treatment of metabolic disorders. The effects of GLP-1 and dual agonists on lipid metabolism also provide a more complete treatment plan for metabolic diseases. This article reviews the recent research progress of GLP-1 in lipid metabolism.

Organoid-guided precision hepatology for metabolic liver disease

Metabolic dysfunction-associated steatotic liver disease affects millions of people worldwide. Progress towards a definitive cure has been incremental and treatment is currently limited to lifestyle modification. Hepatocyte-specific lipid accumulation is the main trigger of lipotoxic events, driving inflammation and fibrosis. The underlying pathology is extraordinarily heterogenous, and the manifestations of steatohepatitis are markedly influenced by metabolic communications across non-hepatic organs. Synthetic human tissue models have emerged as powerful platforms to better capture the mechanistic diversity in disease progression, while preserving person-specific genetic traits. In this review, we will outline current research efforts focused on integrating multiple synthetic tissue models of key metabolic organs, with an emphasis on organoid-based systems. By combining functional genomics and population-scale en masse profiling methodologies, human tissues derived from patients can provide insights into personalised genetic, transcriptional, biochemical, and metabolic states. These collective efforts will advance our understanding of steatohepatitis and guide the development of rational solutions for mechanism-directed diagnostic and therapeutic investigation.

Role of β-cell autophagy in β-cell physiology and the development of diabetes

Elucidating the molecular mechanism of autophagy was a landmark in understanding not only the physiology of cells and tissues, but also the pathogenesis of diverse diseases, including diabetes and metabolic disorders. Autophagy of pancreatic β-cells plays a pivotal role in the maintenance of the mass, structure and function of β-cells, whose dysregulation can lead to abnormal metabolic profiles or diabetes. Modulators of autophagy are being developed to improve metabolic profile and β-cell function through the removal of harmful materials and rejuvenation of organelles, such as mitochondria and endoplasmic reticulum. Among the known antidiabetic drugs, glucagon-like peptide-1 receptor agonists enhance the autophagic activity of β-cells, which might contribute to the profound effects of glucagon-like peptide-1 receptor agonists on systemic metabolism. In this review, the results from studies on the role of autophagy in β-cells and their implication in the development of diabetes are discussed. In addition to non-selective (macro)autophagy, the role and mechanisms of selective autophagy and other minor forms of autophagy that might occur in β-cells are discussed. As β-cell failure is the ultimate cause of diabetes and unresponsiveness to conventional therapy, modulation of β-cell autophagy might represent a future antidiabetic treatment approach, particularly in patients who are not well managed with current antidiabetic therapy.

Semaglutide Improves Liver Steatosis and De Novo Lipogenesis Markers in Obese and Type-2-Diabetic Mice with Metabolic-Dysfunction-Associated Steatotic Liver Disease

Metabolic-dysfunction-associated steatotic liver disease (MASLD) is a prevalent clinical condition associated with elevated morbidity and mortality rates. Patients with MASLD treated with semaglutide, a glucagon-like peptide-1 receptor agonist, demonstrate improvement in terms of liver damage. However, the mechanisms underlaying this beneficial effect are not yet fully elucidated. We investigated the efficacy of semaglutide in halting MASLD progression using a genetic mouse model of diabesity. Leptin-receptor-deficient mice with obesity and diabetes (BKS db/db) were either untreated or administered with semaglutide for 11 weeks. Changes in food and water intake, body weight and glycemia were monitored throughout the study. Body fat composition was assessed by dual-energy X-ray absorptiometry. Upon sacrifice, serum biochemical parameters, liver morphology, lipidomic profile and liver-lipid-related pathways were evaluated. The semaglutide-treated mice exhibited lower levels of glycemia, body weight, serum markers of liver dysfunction and total and percentage of fat mass compared to untreated db/db mice without a significant reduction in food intake. Histologically, semaglutide reduced hepatic steatosis, hepatocellular ballooning and intrahepatic triglycerides. Furthermore, the treatment ameliorated the hepatic expression of de novo lipogenesis markers and modified lipid composition by increasing the amount of polyunsaturated fatty acids. The administration of semaglutide to leptin-receptor-deficient, hyperphagic and diabetic mice resulted in the amelioration of MASLD, likely independently of daily caloric intake, suggesting a direct effect of semaglutide on the liver through modulation of the lipid profile.

The GLP-1 receptor agonist exenatide improves recovery from spinal cord injury by inducing macrophage polarization toward the M2 phenotype

Although a wide variety of mechanisms take part in the secondary injury phase of spinal cord injury (SCI), inflammation is the most important factor implicated in the sequelae after SCI. Being central to the inflammation reaction, macrophages and their polarization are a topic that has garnered wide interest in the studies of SCI secondary injury. The glucagon-like peptide 1 (GLP-1) receptor agonist exenatide has been shown to enhance the endoplasmic reticulum stress response and improve motor function recovery after spinal cord injury (SCI). Since exenatide has also been reported to induce the production of M2 cells in models of cerebral infarction and neurodegenerative diseases, this study was conducted to examine the effects of exenatide administration on the inflammation process that ensues after spinal cord injury. In a rat contusion model of spinal cord injury, the exenatide group received a subcutaneous injection of 10 μg exenatide immediately after injury while those in the control group received 1 mL of phosphate-buffered saline. Quantitative RT-PCR and immunohistochemical staining were used to evaluate the effects of exenatide administration on the macrophages infiltrating the injured spinal cord, especially with regard to macrophage M1 and M2 profiles. The changes in hind limb motor function were assessed based on Basso, Beattie, Bresnahan locomotor rating scale (BBB scale) scores. The improvement in BBB scale scores was significantly higher in the exenatide group from day 7 after injury and onwards. Quantitative RT-PCR revealed an increase in the expression of M2 markers and anti-inflammatory interleukins in the exenatide group that was accompanied by a decrease in the expression of M1 markers and inflammatory cytokines. Immunohistochemical staining showed no significant difference in M1 macrophage numbers between the two groups, but a significantly higher number of M2 macrophages was observed in the exenatide group on day 3 after injury. Our findings suggest that exenatide administration promoted the number of M2-phenotype macrophages after SCI, which may have led to the observed improvement in hind limb motor function in a rat model of SCI.

GLP-1/GLP-1RAs: New Options for the Drug Treatment of NAFLD

Non-alcoholic fatty liver disease (NAFLD) has recently emerged as a global public health concern. Currently, the cornerstone of NAFLD treatment is lifestyle modification and, if necessary, weight loss. However, compliance is a challenge, and this approach alone may not be sufficient to halt and treat the more serious disease development, so medication is urgently needed. Nevertheless, no medicines are approved to treat NAFLD. Glucagon-like peptide-1 (GLP-1) is an enteropeptide hormone that inhibits glucagon synthesis, promotes insulin secretion, and delays gastric emptying. GLP-1 has been found in recent studies to be beneficial for the management of NAFLD, and the marketed GLP-1 agonist drugs have different degrees of effectiveness for NAFLD while lowering blood glucose. In this article, we review GLP-1 and its physiological roles, the pathogenesis of NAFLD, the correlation between NAFLD and GLP-1 signaling, and potential strategies for GLP-1 treatment of NAFLD.

Sex difference in liver diseases: How preclinical models help to dissect the sex-related mechanisms sustaining NAFLD and hepatocellular carcinoma

Only a few preclinical findings are confirmed in the clinic, posing a critical issue for clinical development. Therefore, identifying the best preclinical models can help to dissect molecular and mechanistic insights into liver disease pathogenesis while being clinically relevant. In this context, the sex relevance of most preclinical models has been only partially considered. This is particularly significant in NAFLD and HCC, which have a higher prevalence in men when compared to pre-menopause women but not to those in post-menopausal status, suggesting a role for sex hormones in the pathogenesis of the diseases. This review gathers the sex-relevant findings and the available preclinical models focusing on both in vitro and in vivo studies and discusses the potential implications and perspectives of introducing the sex effect in the selection of the best preclinical model. This is a critical aspect that would help to tailor personalized therapies based on sex.

Comparative effectiveness of multiple different treatment regimens for nonalcoholic fatty liver disease with type 2 diabetes mellitus: a systematic review and Bayesian network meta-analysis of randomised controlled trials

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM) are closely related and mutually contribute to the disease's development. There are many treatment options available to patients. We provide a comprehensive overview of the evidence on the treatment effects of several potential interventions for NAFLD with T2DM.

METHODS

This systematic review and network meta-analysis included searches of PubMed, Embase, Cochrane Library, and Web of Science from inception to June 30, 2023, for randomised controlled trials of treatment of NAFLD with T2DM. We performed Bayesian network meta-analyses to summarise effect estimates of comparisons between interventions. We applied the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) frameworks to rate all comparative outcomes' certainty in effect estimates, categorise interventions, and present the findings. This study was registered with PROSPERO, CRD42022342373.

RESULTS

Four thousand three hundred and sixty-nine records were retrieved from the database and other methods, of which 24 records were eligible for studies enrolling 1589 participants. Eight clinical indicators and 14 interventions were finally in focus. Referring to the lower surface under the cumulative ranking curves (SUCRA) and the league matrix table, exenatide and liraglutide, which are also glucagon-like peptide-1 receptor agonists (GLP-1RAs), showed excellent potential to reduce liver fat content, control glycemia, reduce body weight, and improve liver function and insulin resistance. Exenatide was more effective in reducing glycated haemoglobin (HbA1c) (mean difference (MD) 0.32, 95%CI 0.12 to 0.52), lowering BMI (MD 0.81, 95%CI 0.18 to 1.45), and lowering alanine transaminase (ALT) (MD 10.96, 95%CI 5.27 to 16.66) compared to liraglutide. However, this evidence was assessed as low certainty. Omega-3 was the only intervention that did not have a tendency to lower HbA1c, with standard-treatment (STA-TRE) as reference (MD - 0.17, 95%CI - 0.42 to 0.07). Glimepiride is the only intervention that causes an increase in ALT levels, with standard-treatment (STA-TRE) as reference (MD - 11.72, 95%CI - 17.82 to - 5.57). Based on the available evidence, the treatment effects of pioglitazone, dapagliflozin, and liraglutide have a high degree of confidence.

CONCLUSIONS

The high confidence mandates the confident application of these findings as guides for clinical practice. Dapagliflozin and pioglitazone are used for glycaemic control in patients with NAFLD combined with T2DM, and liraglutide is used for weight loss therapy in patients with abdominal obesity. The available evidence does not demonstrate the credibility of the effectiveness of other interventions in reducing liver fat content, visceral fat area, ALT, and insulin resistance. Future studies should focus on the clinical application of GLP-1Ras and the long-term prognosis of patients.

Development of a novel human triculture model of non-alcoholic fatty liver disease and identification of berberine as ameliorating steatosis, oxidative stress and fibrosis

Objectives: Non-alcoholic fatty liver disease (NAFLD) and its progression to non-alcoholic steatohepatitis (NASH) and hepatocarcinoma is a serious and growing problem. However, the development of new therapies is severely hindered by a lack of high-throughput assays for drug testing. Methods: We have developed a simple transwell assay comprised of HepG2 hepatocytes, hepatic LX-2 stellate cells, and differentiated THP-1 cells. The cells were incubated with an activating mixture containing the NASH-associated risk factors, glucose, insulin, free fatty acids (FFAs), and lipopolysaccharide (LPS) for 72 h. We compared different combinations of culture conditions to obtain a model system that recapitulates the main features of NAFLD/NASH, i.e., increased steatosis, reactive oxygen species (ROS), secretion of pro-inflammatory cytokines/chemokines, and presence of fibrosis. To confirm the usefulness of the optimized model system, we screened for compounds that inhibit steatosis in the hepatocytes and evaluated the most effective compound in the triculture model system. Results: The activating mixture stimulated HepG2 cells in this triculture to accumulate more fat and produce higher levels of reactive oxygen species (ROS) than HepG2 cells in monocultures. As well, higher levels of inflammatory cytokines and chemokines (IL-8, IL-6, MIP-1α, etc.) were produced in this triculture compared to monocultures. In addition, in all LX-2 monocultures and cocultures, exposure to the activating mixture increased markers of fibrosis. A major strength of our triculture system is that it makes possible the simultaneous monitoring of 4 main features of NASH, i.e., steatosis, oxidative stress, inflammation and fibrosis. Screening potential modulators that may reduce steatosis in HepG2 cells revealed the protective effects of the isoalkaloid, berberine. Tested using this novel triculture assay, treatment with 5 µM berberine decreased steatosis and ROS in HepG2 hepatocytes, reduced inflammatory cytokine production and inhibited collagen production from LX-2 cells. Conclusion: This simple triculture model recapitulates the main features of NAFLD/NASH and should be useful for high-throughput preclinical drug discovery. In this model, berberine showed promising results in decreasing steatosis and ROS and protection against fibrosis.

Liraglutide ameliorates hepatic steatosis via retinoic acid receptor-related orphan receptor α-mediated autophagy pathway

Liraglutide, an analog of human glucagon-like peptide-1 (GLP-1), has been found to improve hepatic steatosis in clinical practice. However, the underlying mechanism remains to be fully defined. Increasing evidence suggests that retinoic acid receptor-related orphan receptor α (RORα) is involved in hepatic lipid accumulation. In the current study, we investigated whether the ameliorating impact of liraglutide on lipid-induced hepatic steatosis is dependent on RORα activity and examined the underlying mechanisms. Cre-loxP-mediated, liver-specific Rorα knockout (Rora LKO) mice, and littermate controls with a Roraloxp/loxp genotype were established. The effects of liraglutide on lipid accumulation were evaluated in mice challenged with a high-fat diet (HFD) for 12 weeks. Moreover, mouse AML12 hepatocytes expressing small interfering RNA (siRNA) of Rora were exposed to palmitic acid to explore the pharmacological mechanism of liraglutide. The results showed that liraglutide treatment significantly alleviated HFD-induced liver steatosis, marked by reduced liver weight and triglyceride accumulation, improved glucose tolerance and serum levels of lipid profiles and aminotransferase. Consistently, liraglutide also ameliorated lipid deposits in a steatotic hepatocyte model in vitro. In addition, liraglutide treatment reversed the HFD-induced downregulation of Rora expression and autophagic activity in mouse liver tissues. However, the beneficial effect of liraglutide on hepatic steatosis was not observed in Rora LKO mice. Mechanistically, the ablation of Rorα in hepatocytes diminished liraglutide-induced autophagosome formation and the fusion of autophagosomes and lysosomes, resulting in weakened autophagic flux activation. Thus, our findings suggest that RORα is essential for the beneficial impact of liraglutide on lipid deposition in hepatocytes and regulates autophagic activity in the underlying mechanism.

Customized liver organoids as an advanced in vitro modeling and drug discovery platform for non-alcoholic fatty liver diseases

Non-alcoholic fatty liver disease (NAFLD) and its progressive form non-alcoholic steatohepatitis (NASH) have presented a major and common health concern worldwide due to their increasing prevalence and progressive development of severe pathological conditions such as cirrhosis and liver cancer. Although a large number of drug candidates for the treatment of NASH have entered clinical trial testing, all have not been released to market due to their limited efficacy, and there remains no approved treatment for NASH available to this day. Recently, organoid technology that produces 3D multicellular aggregates with a liver tissue-like cytoarchitecture and improved functionality has been suggested as a novel platform for modeling the human-specific complex pathophysiology of NAFLD and NASH. In this review, we describe the cellular crosstalk between each cellular compartment in the liver during the pathogenesis of NAFLD and NASH. We also summarize the current state of liver organoid technology, describing the cellular diversity that could be recapitulated in liver organoids and proposing a future direction for liver organoid technology as an in vitro platform for disease modeling and drug discovery for NAFLD and NASH.

Mechanism of preventive effects of exendin-4 and des-fluoro-sitagliptin in a murine model of fructose-induced prediabetes

Protective effects of exendin-4 (glucagon-like peptide-1 -GLP-1- receptor agonist) and des-fluoro-sitagliptin (dipeptidyl peptidase-4 inhibitor) on fructose-induced hepatic disturbances were evaluated in prediabetic rats. Complementary, a possible direct effect of exendin-4 in human hepatoblastoma-derived cell line HepG2 incubated with fructose in presence/absence of exendin-9-39 (GLP-1 receptor antagonist) was investigated. In vivo, after 21 days of fructose rich diet, we determined: glycemia, insulinemia, and triglyceridemia; hepatic fructokinase, AMP-deaminase, and G-6-P dehydrogenase (G-6-P DH) activities; carbohydrate-responsive element-binding protein (ChREBP) expression; triglyceride content and lipogenic gene expression (glycerol-3-phosphate acyltransferase -GPAT-, fatty acid synthase -FAS-, sterol regulatory element-binding protein-1c -SREBP-1c); oxidative stress and inflammatory markers expression. In HepG2 cells we measured fructokinase activity and triglyceride content. Hypertriglyceridemia, hyperinsulinemia, enhanced liver fructokinase, AMP-deaminase, and G-6-P DH activities, increased ChREBP and lipogenic genes expression, enhanced triglyceride level, oxidative stress and inflammatory markers recorded in fructose fed animals, were prevented by co-administration of either exendin-4 or des-fluoro-sitagliptin. Exendin-4 prevented fructose-induced increase in fructokinase activity and triglyceride contain in HepG2 cells. These effects were blunted co-incubating with exendin-9-39. The results demonstrated for the first time that exendin-4/des-fluro-sitagliptin prevented fructose-induced endocrine-metabolic oxidative stress and inflammatory changes probably acting on the purine degradation pathway. Exendin 9-39 blunted in vitro protective exendin-4 effects, thereby suggesting a direct effect of this compound on hepatocytes through GLP-1 receptor. Direct effect on fructokinase and AMP-deaminase activities, with a key role in the pathogenesis of liver dysfunction induced by fructose, suggests purine degradation pathway constitute a potential therapeutic objective for GLP-1 receptor agonists.

Exendin-4 protects against high glucose-induced mitochondrial dysfunction and oxidative stress in SH-SY5Y neuroblastoma cells through GLP-1 receptor/Epac/Akt signaling

Mitochondrial dysfunction under diabetic condition leads to the development and progression of neurodegenerative complications. Recently, the beneficial effects of glucagon-like peptide-1 (GLP-1) receptor agonists on diabetic neuropathies have been widely recognized. However, molecular mechanisms underlying the neuroprotective effects of GLP-1 receptor agonists against high glucose (HG)-induced neuronal damages is not completely elucidated. Here, we investigated the underlying mechanisms of GLP-1 receptor agonist treatment against oxidative stress, mitochondrial dysfunction, and neuronal damages under HG-conditions mimicking a diabetic hyperglycemic state in SH-SY5Y neuroblastoma cells. We revealed that treatment with exendin-4, a GLP-1 receptor agonist, not only increased the expression of survival markers, phospho-Akt/Akt and Bcl-2, but also decreased the expression of pro-apoptotic marker, Bax, and reduced the levels of reactive oxygen species (ROS) defense markers (catalase, SOD-2, and HO-1) under HG conditions. The expressions of mitochondrial function associated genes, MCU and UCP3, and mitochondrial fission genes, DRP1 and FIS1, were decreased by exendin-4 compared to non-treated levels, while the protein expression levels of mitochondrial homeostasis regulators, Parkin and PINK1, were enhanced. In addition, blockade of Epac and Akt activities was able to antagonize these neuroprotective effects of exendin-4. Collectively, we demonstrated that stimulation of GLP-1 receptor propagates a neuroprotective cascade against the oxidative stresses and mitochondrial dysfunctions as well as augments survival through the Epac/Akt-dependent pathway. Therefore, the revealed mechanisms underlying GLP-1 receptor pathway by preserving mitochondrial homeostasis would be a therapeutic candidate to alleviate neuronal dysfunctions and delay the progression of diabetic neuropathies.

Inhibition of PERK Kinase, an Orchestrator of the Unfolded Protein Response (UPR), Significantly Reduces Apoptosis and Inflammation of Lung Epithelial Cells Triggered by SARS-CoV-2 ORF3a Protein

SARS-CoV-2 ORF3a accessory protein was found to be involved in virus release, immunomodulation and exhibited a pro-apoptotic character. In order to unravel a potential ORF3a-induced apoptotic and inflammatory death mechanism, lung epithelial cells (A549) were transfected with in vitro synthesized ORF3a mRNA. The protein's dynamic involvement as "stress factor" for the endoplasmic reticulum, causing the activation of PERK kinase and other UPR-involved proteins and therefore the upregulation of their signaling pathway executioners (ATF6, XBP-1s, PERK, phospho eIF2a, ATF4, CHOP, GADD34), has been clearly demonstrated. Furthermore, the overexpression of BAX and BH3-only pro-apoptotic protein PUMA, the upregulation of Bcl-2 family genes (BAX, BAK, BID, BAD), the reduced expression of Bcl-2 in mRNA and protein levels, and lastly, the cleavage of PARP-1 and caspase family members (caspase-3,-8 and -9) indicate that ORF3a displays its apoptotic character through the mitochondrial pathway of apoptosis. Moreover, the upregulation of NFκB, phosphorylation of p65 and IκΒα and the elevated expression of pro-inflammatory cytokines (IL-1b, IL-6, IL-8 and IL-18) in transfected cells with ORF3a mRNA indicate that this protein causes the inflammatory response through NFκB activation and therefore triggers lung injury. An intriguing finding of our study is that upon treatment of the ORF3a-transfected cells with GSK2606414, a selective PERK inhibitor, both complications (apoptosis and inflammatory response) were neutralized, and cell survival was favored, whereas treatment of transfected cells with z-VAD (a pan-caspase inhibitor) despite inhibiting cell death, could not ameliorate the inflammatory response of transfected A549 cells. Given the above, we point out that PERK kinase is a "master tactician" and its activation constitutes the main stimulus for the emergence of ORF3a apoptotic and inflammatory nature and therefore could serve as potential target for developing novel therapeutic approaches against COVID-19.

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.

Glp-1 Receptor Agonists Regulate the Progression of Diabetes Mellitus Complicated with Fatty Liver by Down-regulating the Expression of Genes Related to Lipid Metabolism

Non-alcoholic fatty liver disease is mostly associated with diabetes mellitus. Dulaglutide is approved in type 2 diabetes as a hypoglycemic agent. However, its effects on liver fat and pancreatic fat contents are not evaluated yet. The objectives of the study were to evaluate the effects of dulaglutide on liver fat content, pancreatic fat content, liver stiffness, and liver enzyme levels. Patients have taken 0.75 mg subcutaneous dulaglutide each week for 4 weeks, then 1.5 mg weekly for 20 weeks plus standard treatment (metformin plus sulfonylurea and/or insulin; DS group, n = 25), or patients have taken standard treatment (metformin plus sulfonylurea and/or insulin) alone (ST group, n = 46) for type 2 diabetes management. Both groups reported a decrease in liver fat content, pancreatic fat content, and liver stiffness after interventions (p < 0.001 for all). After interventions, the DS group reported a higher decrease in liver fat content, pancreatic fat content, and liver stiffness than that of the ST group (p < 0.001 for all). After interventions, the DS group reported a higher decrease in body mass index than that of the ST group (p < 0.05). There were significant improvements in liver function tests, kidney function tests, lipid profiles, and blood counts after interventions (p < 0.05 for all). Both groups reported a decrease in body mass index after interventions (p < 0.001 for both). The DS group significantly decrease body mass index after interventions (p < 0.05) than the ST group.

Sleeve gastrectomy decreased hepatic lipid accumulation by inducing autophagy via AMPK/mTOR pathway

This study was designed to investigate the roles of autophagy in the attenuation of hepatic lipid accumulation after sleeve gastrectomy (SG). Thirty-two rats were divided into normal control, obesity group, sham group, and SG group. Then serum glucagon-like polypeptide-1 (GLP-1) and lipid accumulation were determined, followed by measuring the activity of autophagy based on immunohistochemistry (IHC) and Western blot analysis. Our data showed significant decrease in the lipid accumulation after SG compared with sham group. GLP-1 and autophagy showed significant increase in rats underwent SG compared with the sham group (P < 0.05). In vitro experiments were conducted to analyze the roles of GLP-1 in autophagy. We knock-downed the expression of Beclin-1 in HepG2, and then analyzed the expression of autophagy-related protein (i.e. LC3BII and LC3BI) and lipid droplet accumulation. In HepG2 cells, GLP-1 analog reduced lipid accumulation by activating autophagy through modulating the AMPK/mTOR signaling pathway. All these concluded that SG decreased hepatic lipid accumulation by inducing autophagy through modulating AMPK/mTOR pathway.

A novel approach to repositioning memantine for metabolic syndrome-induced steatohepatitis: Modulation of hepatic autophagy, inflammation, and fibrosis

AIMS

This study investigated the possible hepatoprotective effects of memantine, compared to pioglitazone, in rat steatohepatitis, emphasizing its role in modulating hepatic autophagy.

MAIN METHODS

Metabolic syndrome (MetS) was provoked in adult male Wistar rats by a high fructose/fat/salt regimen for eight weeks. Then, rats were administered either memantine or pioglitazone daily for 10 weeks (both at 20 mg/kg, orally). An oral glucose tolerance test (OGTT) was done at the end of the study, and serum liver enzymes, lipids, and fasting blood glucose were measured. Also, hepatic contents of inflammatory, oxidative, and autophagy markers were quantified. Additionally, histopathological examinations of general hepatic structure and glycogen content were performed.

KEY FINDINGS

Compared to the MetS rats, memantine normalized fasting serum insulin, Homeostatic Model Assessment (HOMA-IR), serum lipids, and liver enzymes (ALT and AST). Memantine also markedly reduced hepatic inflammatory markers; NF-κB and TNF-α. In addition, hepatic NRF2 and GSH were augmented, while hepatic MDA was reduced by memantine. Interestingly, livers of the memantine group showed elevated Beclin1 and LC3 and reduced p62 contents compared to the MetS group indicating that memantine preserved hepatic autophagy. Histopathological examination revealed that memantine ameliorated hepatic steatosis and inflammation. Pioglitazone also mitigated most of the steatohepatitis-related changes, however, memantine was more effective in most of the studied parameters.

SIGNIFICANCE

The hepatoprotective effect of memantine against steatohepatitis is mediated, at least partly, through conserving hepatic autophagy along with anti-inflammatory, antioxidant, and anti-fibrotic effects.

In vitro to in vivo extrapolation and high-content imaging for simultaneous characterization of chemically induced liver steatosis and markers of hepatotoxicity

Chemically induced steatosis is characterized by lipid accumulation associated with mitochondrial dysfunction, oxidative stress and nucleus distortion. New approach methods integrating in vitro and in silico models are needed to identify chemicals that may induce these cellular events as potential risk factors for steatosis and associated hepatotoxicity. In this study we used high-content imaging for the simultaneous quantification of four cellular markers as sentinels for hepatotoxicity and steatosis in chemically exposed human liver cells in vitro. Furthermore, we evaluated the results with a computational model for the extrapolation of human oral equivalent doses (OED). First, we tested 16 reference chemicals with known capacities to induce cellular alterations in nuclear morphology, lipid accumulation, mitochondrial membrane potential and oxidative stress. Then, using physiologically based pharmacokinetic modeling and reverse dosimetry, OEDs were extrapolated from data of any stimulated individual sentinel response. The extrapolated OEDs were confirmed to be within biologically relevant exposure ranges for the reference chemicals. Next, we tested 14 chemicals found in food, selected from thousands of putative chemicals on the basis of structure-based prediction for nuclear receptor activation. Amongst these, orotic acid had an extrapolated OED overlapping with realistic exposure ranges. Thus, we were able to characterize known steatosis-inducing chemicals as well as data-scarce food-related chemicals, amongst which we confirmed orotic acid to induce hepatotoxicity. This strategy addresses needs of next generation risk assessment and can be used as a first chemical prioritization hazard screening step in a tiered approach to identify chemical risk factors for steatosis and hepatotoxicity-associated events.

Bone Marrow-Derived Mesenchymal Stem Cells and Pioglitazone or Exendin-4 Synergistically Improve Insulin Resistance via Multiple Modulatory Mechanisms in High-Fat Diet/Streptozotocin-Induced Diabetes in Rats

Background

Diabetes mellitus (DM) is a metabolic disease, characterized by hyperglycemia resulting from defects in insulin secretion and/or insulin action. The current study was designed to assess the therapeutic potential of bone marrow-derived mesenchymal stem cells (BM-MSCs) alone and in combination with pioglitazone (Pz) or exendin-4 (Ex) in high-fat diet/streptozotocin (HFD/STZ)-induced diabetes in rats.

Methods

The rats were subjected to the HFD for three weeks before being injected with a single low dosage of STZ (35 mg/kg bw). The animals were assigned to different treatment groups after type II diabetes mellitus (T2DM) induction was confirmed.

Results

Severe insulin resistance was verified in untreated HFD/STZ T2DM rats, along with the exaggeration of oxidative stress, inflammation, apoptosis, and autophagy suppression in the adipose tissues. Monotherapy of HFD/T2DM rats with BM-MSCs and Pz or Ex alleviated diabetic complications by increasing insulin sensitivity, decreasing apoptosis and inflammation as evidenced by a decrease in serum tumor necrosis factor-alpha, caspase-3, and nuclear factor-kappa B (NF-κB) genes expression and Janus kinase (JNK) protein expression, and enhancing autophagy as revealed by upregulation in beclin and LC3, as well as peroxisome proliferator-activated receptor-γ coactivator-1 alpha (PGC-1α) genes expression in the adipose tissues. An augmented ameliorative efficacy was recorded in combined treatments. The biochemical and molecular results were confirmed by histological investigation of pancreatic tissues.

Conclusions

Combining Pz or Ex with BM-MSCs is a synergistic therapeutic option that reduces insulin resistance and subsequent complications in T2DM via multiple molecular mechanisms.

Bioengineering liver microtissues for modeling non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) has become the world's most common chronic liver disease. However, due to the lack of reliable in vitro NAFLD models, drug development studies have faced many limitations, and there is no food and drug administration-approved medicine for NAFLD treatment. A functional biomimetic in vitro human liver model requires an optimized natural microenvironment using appropriate cellular composition, to provide constructive cell-cell interactions, and niche-specific bio-molecules to supply crucial cues as cell-matrix interplay. Such a suitable liver model could employ appropriate and desired biochemical, mechanical, and physical properties similar to native tissue. Moreover, bioengineered three-dimensional tissues, specially microtissues and organoids, and more recently using infusion-based cultivation systems such as microfluidics can mimic natural tissue conditions and facilitate the exchange of nutrients and soluble factors to improve physiological function in the in vitro generated constructs. This review highlights the key players involved in NAFLD initiation and progression and discussed the available cells and matrices for in vitro NAFLD modeling. The strategies for optimizing the liver microenvironment to generate a powerful and biomimetic in vitro NAFLD model were described as well. Finally, the current challenges and future perospective for promotion in this subject were discussed.

Novel Therapeutics in Nonalcoholic Fatty Liver Disease: A Focus on Adult Stem Cells

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disorder that is associated with abnormal accumulation of fat in the liver, which can lead to a wide variety of pathological liver defects and associated insulin resistance (IR), obesity, hypertension, dyslipidemia, diabetes, and cardiovascular disease. The molecular mechanisms that cause the initiation and progression of NAFLD are not fully understood. Increased lipolysis and de novo hepatic lipid synthesis lead to oxidative stress induced by reactive oxygen species and inflammation. Both these two entities could be interrelated and be an important mechanistic pathway, which can lead to tissue injury and hepatic cell death. Mechanisms for worsening of NAFLD include mitochondrial abnormalities, downregulation of glutathione (GSH), decreased activity of GSH-dependent antioxidants, accumulation of activated macrophages, hepatic inflammation, systemic inflammation, IR, and poorly controlled type 2 diabetes mellitus. Although no specific therapy has been approved for NAFLD, we review the latest medical therapeutics with emphasis on stem cell-based possibilities based on the presumed pathophysiology of NAFLD.

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

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

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.

SGLT-2 inhibitors and GLP-1 receptor agonists in metabolic dysfunction-associated fatty liver disease

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a chronic condition that affects nearly one billion people globally, characterized by triacylglycerol accumulation in the liver as a consequence of metabolic abnormalities (obesity and impaired glucose regulation). Low-grade inflammation, oxidative stress, mitochondrial dysfunction, and dysbiosis in gut microbiota are involved in the etiology of MAFLD, and both cardiovascular events and hepatic complications are the long-term consequences. In the absence of approved therapies for this condition, sodium-glucose cotransporter 2 inhibitors (SGLT-2 Is) and glucagon-like peptide 1 receptor agonists (GLP-1 RAs) have the specific advantage of lowering body weight and providing cardiovascular benefits. Here, we discuss potential roles for SGLT-2 Is and GLP-1 RAs in the prevention and treatment of intrahepatic triacylglycerol accumulation and associated inflammation and/or fibrosis.

The Interplay Between Nonalcoholic Fatty Liver Disease and Kidney Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide, involving approximately 25% of the general population and increasing in prevalence in patient populations afflicted with metabolic syndrome and type 2 diabetes. This article discusses the complex interplay between NAFLD and chronic kidney disease (CKD), as well as the underlying pathogenesis and mechanisms through which NAFLD and CKD are linked. Exploration of these sophisticated relationships and causative factors is essential to accurately assessing kidney function in patients with NAFLD, recommending pharmacologic treatment of disease, and identifying favorable avenues for future investigation.

Novel Insights into the Roles and Mechanisms of GLP-1 Receptor Agonists against Aging-Related Diseases

Aging and aging-related diseases have emerged as increasingly severe health and social problems. Therefore, it is imperative to discover novel and effective therapeutics to delay the aging process and to manage aging-related diseases. Glucagon-like peptide-1 receptor agonists (GLP-1 RAs), one of the classes of antihyperglycemic drugs, have been recommended to manage type 2 diabetes mellitus (T2DM). Moreover, GLP-1 RAs have been shown to protect against oxidative stress, cellular senescence and chronic inflammation, which are widely accepted as the major risk factors of aging. However, their significance in aging or aging-related diseases has not been elucidated. Herein, we explain the underlying mechanisms and protective roles of GLP-1 RAs in aging from a molecular, cellular and phenotypic perspective. We provide novel insights into the broad prospect of GLP-1 RAs in preventing and treating aging-related diseases. Additionally, we highlight the gaps for further studies in clinical applications of GLP-1 RAs in aging-related diseases. This review forms a basis for further studies on the relationship between aging-related diseases and GLP-1 RAs.

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

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Current Status of Autophagy Enhancers in Metabolic Disorders and Other Diseases

Autophagy is pivotal in the maintenance of organelle function and intracellular nutrient balance. Besides the role of autophagy in the homeostasis and physiology of the individual tissues and whole organism in vivo, dysregulated autophagy has been incriminated in the pathogenesis of a variety of diseases including metabolic diseases, neurodegenerative diseases, cardiovascular diseases, inflammatory or immunological disorders, cancer and aging. Search for autophagy modulators has been widely conducted to amend dysregulation of autophagy or pharmacologically modulate autophagy in those diseases. Current data support the view that autophagy modulation could be a new modality for treatment of metabolic syndrome associated with lipid overload, human-type diabetes characterized by deposition of islet amyloid or other diseases including neurodegenerative diseases, infection and cardiovascular diseases. While clinically available bona fide autophagy modulators have not been developed yet, it is expected that on-going investigation will lead to the development of authentic autophagy modulators that can be safely administered to patients in the near future and will open a new horizon for treatment of incurable or difficult diseases.

The dual roles of autophagy and the GPCRs-mediating autophagy signaling pathway after cerebral ischemic stroke

Ischemic stroke, caused by a lack of blood supply in brain tissues, is the third leading cause of human death and disability worldwide, and usually results in sensory and motor dysfunction, cognitive impairment, and in severe cases, even death. Autophagy is a highly conserved lysosome-dependent process in which eukaryotic cells removal misfolded proteins and damaged organelles in cytoplasm, which is critical for energy metabolism, organelle renewal, and maintenance of intracellular homeostasis. Increasing evidence suggests that autophagy plays important roles in pathophysiological mechanisms under ischemic conditions. However, there are still controversies about whether autophagy plays a neuroprotective or damaging role after ischemia. G-protein-coupled receptors (GPCRs), one of the largest protein receptor superfamilies in mammals, play crucial roles in various physiological and pathological processes. Statistics show that GPCRs are the targets of about one-fifth of drugs known in the world, predicting potential values as targets for drug research. Studies have demonstrated that nutritional deprivation can directly or indirectly activate GPCRs, mediating a series of downstream biological processes, including autophagy. It can be concluded that there are interactions between autophagy and GPCRs signaling pathway, which provides research evidence for regulating GPCRs-mediated autophagy. This review aims to systematically discuss the underlying mechanism and dual roles of autophagy in cerebral ischemia, and describe the GPCRs-mediated autophagy, hoping to probe promising therapeutic targets for ischemic stroke through in-depth exploration of the GPCRs-mediated autophagy signaling pathway.

Efficacy and safety of semaglutide for weight management: evidence from the STEP program

Obesity is a global health challenge. It is a multifactorial, complex, and progressive disease associated with various health complications and increased mortality. Lifestyle modifications are central to weight management but may be insufficient to maintain clinically meaningful weight loss. Pharmacotherapies are recommended as an adjunct to lifestyle interventions to induce and sustain clinically meaningful weight loss and reduce the risk of comorbidities in appropriate patients. Glucagon-like peptide-1 is an incretin metabolic hormone responsible for a range of physiological effects, including glucose and appetite regulation. Several glucagon-like peptide-1 receptor agonists (GLP-1RAs) have been approved for the treatment of type 2 diabetes since 2005 including exenatide (short- and extended-release), lixisenatide, liraglutide, dulaglutide, albiglutide, and semaglutide. Of these, semaglutide (subcutaneous) and liraglutide are currently US Food and Drug Administration (FDA)-approved for chronic weight management in patients with or without diabetes. The phase 3 Semaglutide Treatment Effect in People with obesity (STEP) program was designed to investigate the effect of semaglutide versus placebo on weight loss, safety, and tolerability in adults with overweight or obesity. Following the submission of the results of the STEP 1-4 trials, the FDA approved once-weekly subcutaneous semaglutide 2.4 mg for chronic weight management in people with overweight or obesity in April 2021. Data from the program demonstrated that semaglutide (2.4 mg once weekly) achieved significant and sustained weight loss, together with improvements in cardiometabolic risk factors compared with placebo, and was generally well tolerated, with a safety profile consistent with other GLP-1RAs. The most common adverse events reported in STEP 1-5 were gastrointestinal events, which were transient, mild-to-moderate in severity, and typically resolved without permanent treatment discontinuation. This article reviews the data from STEP 1-5 and highlights clinically relevant findings for primary care providers.

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

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

Non-alcoholic Fatty Liver Disease and Liver Fibrosis during Aging

Non-alcoholic fatty liver disease (NAFLD) and its progressive form non-alcoholic steatohepatitis (NASH) have emerged as the leading causes of chronic liver disease-related mortality. The prevalence of NAFLD/NASH is expected to increase given the epidemics of obesity and type 2 diabetes mellitus. Older patients are disproportionally affected by NASH and related complications such as progressive fibrosis, cirrhosis and hepatocellular carcinoma; however, they are often ineligible for liver transplantation due to their frailty and comorbidities, and effective medical treatments are still lacking. In this review we focused on pathways that are key to the aging process in the liver and perpetuate NAFLD/NASH, leading to fibrosis. In addition, we highlighted recent findings and cross-talks of normal and/or senescent liver cells, dysregulated nutrient sensing, proteostasis and mitochondrial dysfunction in the framework of changing metabolic milieu. Better understanding these pathways during preclinical and clinical studies will be essential to design novel and specific therapeutic strategies to treat NASH in the elderly.

Autophagy in metabolic disease and ageing

Autophagy is an evolutionarily conserved, lysosome-dependent catabolic process whereby cytoplasmic components, including damaged organelles, protein aggregates and lipid droplets, are degraded and their components recycled. Autophagy has an essential role in maintaining cellular homeostasis in response to intracellular stress; however, the efficiency of autophagy declines with age and overnutrition can interfere with the autophagic process. Therefore, conditions such as sarcopenic obesity, insulin resistance and type 2 diabetes mellitus (T2DM) that are characterized by metabolic derangement and intracellular stresses (including oxidative stress, inflammation and endoplasmic reticulum stress) also involve the accumulation of damaged cellular components. These conditions are prevalent in ageing populations. For example, sarcopenia is an age-related loss of skeletal muscle mass and strength that is involved in the pathogenesis of both insulin resistance and T2DM, particularly in elderly people. Impairment of autophagy results in further aggravation of diabetes-related metabolic derangements in insulin target tissues, including the liver, skeletal muscle and adipose tissue, as well as in pancreatic β-cells. This Review summarizes the role of autophagy in the pathogenesis of metabolic diseases associated with or occurring in the context of ageing, including insulin resistance, T2DM and sarcopenic obesity, and describes its potential as a therapeutic target.

Chaperone-mediated autophagy and disease: Implications for cancer and neurodegeneration

Chaperone-mediated autophagy (CMA) is a proteolytic process whereby selected intracellular proteins are degraded inside lysosomes. Owing to its selectivity, CMA participates in the modulation of specific regulatory proteins, thereby playing an important role in multiple cellular processes. Studies conducted over the last two decades have enabled the molecular characterization of this autophagic pathway and the design of specific experimental models, and have underscored the importance of CMA in a range of physiological processes beyond mere protein quality control. Those findings also indicate that decreases in CMA function with increasing age may contribute to the pathogenesis of age-associated diseases, including neurodegeneration and cancer. In the context of neurological diseases, CMA impairment is thought to contribute to the accumulation of misfolded/aggregated proteins, a process central to the pathogenesis of neurodegenerative diseases. CMA therefore constitutes a potential therapeutic target, as its induction accelerates the clearance of pathogenic proteins, promoting cell survival. More recent evidence has highlighted the important and complex role of CMA in cancer biology. While CMA induction may limit tumor development, experimental evidence also indicates that inhibition of this pathway can attenuate the growth of established tumors and improve the response to cancer therapeutics. Here, we describe and discuss the evidence supporting a role of impaired CMA function in neurodegeneration and cancer, as well as future research directions to evaluate the potential of this pathway as a target for the prevention and treatment of these diseases.

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.

Bioengineered Liver Models for Investigating Disease Pathogenesis and Regenerative Medicine

Owing to species-specific differences in liver pathways, in vitro human liver models are utilized for elucidating mechanisms underlying disease pathogenesis, drug development, and regenerative medicine. To mitigate limitations with de-differentiated cultures, bioengineers have developed advanced techniques/platforms, including micropatterned cocultures, spheroids/organoids, bioprinting, and microfluidic devices, for perfusing cell cultures and liver slices. Such techniques improve mature functions and culture lifetime of primary and stem-cell human liver cells. Furthermore, bioengineered liver models display several features of liver diseases including infections with pathogens (e.g., malaria, hepatitis C/B viruses, Zika, dengue, yellow fever), alcoholic/nonalcoholic fatty liver disease, and cancer. Here, we discuss features of bioengineered human liver models, their uses for modeling aforementioned diseases, and how such models are being augmented/adapted for fabricating implantable human liver tissues for clinical therapy. Ultimately, continued advances in bioengineered human liver models have the potential to aid the development of novel, safe, and efficacious therapies for liver disease.

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

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

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

BACKGROUND

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

METHOD

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

RESULTS

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

CONCLUSION

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

Endoplasmic Reticulum Stress and Autophagy in the Pathogenesis of Non-alcoholic Fatty Liver Disease (NAFLD): Current Evidence and Perspectives

PURPOSE OF REVIEW

Non-alcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease with rising prevalence worldwide. Herein, we provide a comprehensive overview of the current knowledge supporting the role of ER stress and autophagy processes in NAFLD pathogenesis and progression. We also highlight the interrelation between these two pathways and the impact of ER stress and autophagy modulators on NAFLD treatment.

RECENT FINDINGS

The pathophysiological mechanisms involved in NAFLD progression are currently under investigation. The endoplasmic reticulum (ER) stress and the concomitant unfolded protein response (UPR) seem to contribute to its pathogenesis mainly due to high ER content in the liver which exerts significant metabolic functions and can be dysregulated. Furthermore, disruption of autophagy processes has also been identified in NAFLD. The crucial role of these two pathways in NAFLD is underlined by the fact that they have recently emerged as promising targets of therapeutic interventions. There is a greater need for finding the natural/chemical compounds and drugs which can modulate the ER stress pathway and autophagy for the treatment of NAFLD. Clarifying the inter-relation between these two pathways and their interaction with inflammatory and apoptotic mechanisms will allow the development of additional therapeutic options which can better target and reprogram the underlying pathophysiological pathways, aiming to attenuate NAFLD progression.

A scalable and sensitive steatosis chip with long-term perfusion of in situ differentiated HepaRG organoids

Nonalcoholic fatty liver disease (NAFLD) is a significant liver disease without approved therapy, lacking human NAFLD models to aid drug development. Existing models are either under-performing or too complex to allow robust drug screening. Here we have developed a 100-well drug testing platform with improved HepaRG organoids formed with uniform size distribution, and differentiated in situ in a perfusion microfluidic device, SteatoChip, to recapitulate major NAFLD features. Compared with the pre-differentiated spheroids, the in situ differentiated HepaRG organoids with perfusion experience well-controlled chemical and mechanical microenvironment, and 3D cellular niche, to exhibit enhanced hepatic differentiation (albumin⁺ cells ratio: 66.2% in situ perfusion vs 46.1% pre-differentiation), enriched and uniform hepatocyte distribution in organoids, higher level of hepatocyte functions (5.2 folds in albumin secretion and 7.6 folds in urea synthesis), enhanced cell polarity and bile canaliculi structures. When induced with free fatty acid (FFA), cells exhibit significantly higher level of lipid accumulation (6.6 folds for in situ perfusion vs 4.4 folds for pre-differentiation), altered glucose regulation and reduced Akt phosphorylation in the organoids. SteatoChip detects reduction of steatosis when cells are incubated with three different anti-steatosis compounds, 78.5% by metformin hydrochloride, 71.3% by pioglitazone hydrochloride and 66.6% by obeticholic acid, versus the control FFA-free media (38% reduction). The precision microenvironment control in SteatoChip enables improved formation, differentiation, and function of HepaRG organoids to serve as a scalable and sensitive drug testing platform, to potentially accelerate the NAFLD drug development.

The role of bariatric surgery in the management of nonalcoholic steatohepatitis

PURPOSE OF REVIEW

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in the United States and increasing globally. The progressive form of NAFLD, nonalcoholic steatohepatitis (NASH), can lead to cirrhosis and complications of end-stage liver disease. No FDA-approved therapy for NAFLD/NASH exists. Treatment of NAFLD/NASH includes effective and sustained life-style modification and weight loss. This review reports on the recent findings of bariatric surgery in the management of NASH.

RECENT FINDINGS

NAFLD, at all stages, is common in those who meet indication for bariatric surgery. Bariatric surgery resolves NAFLD/NASH and reverses early stages of fibrosis. Although randomized controlled trials of bariatric surgery in NASH are infeasible, studies defining the metabolic changes induced by bariatric surgery, and their effect on NASH, provide insight for plausible pharmacologic targets for the nonsurgical treatment of NASH.

SUMMARY

Resolution of NASH and fibrosis regression can occur after bariatric surgery. Although the exact mechanism(s) underlying the improvement of NASH and hepatic fibrosis following bariatric surgery is not fully elucidated, emerging data on this topic is vitally important for lending insight into the pharmacotherapies for NASH for patients who are not otherwise suitable candidates for bariatric surgery.

Metabolic responses and benefits of glucagon-like peptide-1 (GLP-1) receptor ligands

Glucagon-like peptide-1 (GLP-1) is an incretin hormone that has undergone a revolutionary turnaround from discovery to clinically approved therapeutic. Rapid progress in drug design and formulation has led from initial development of short- and long-acting drugs suitable for daily or weekly parenteral administration, respectively, through to the most recent approval of an orally active GLP-1 agent. The current review outlines the biological action profile of GLP-1 including the various beneficial metabolic responses in pancreatic and extra-pancreatic tissues, including the gastrointestinal tract, liver, bone and kidney as well as the reproductive cardiovascular and CNS. We then briefly consider clinically approved GLP-1 receptor ligands and recent advances in this field. Given the sustained evolution in the area of GLP-1 drug development and excellent safety profile, as well as the plethora of metabolic benefits, clinical approval for use in diseases beyond diabetes and obesity is very much conceivable.

In vitro hepatic steatosis model based on gut-liver-on-a-chip

Hepatic steatosis, also known as fatty liver disease, occurs due to abnormal lipid accumulation in the liver. It has been known that gut absorption also plays an important role in the mechanism underlying hepatic steatosis. Conventional in vitro cell culture models have limitations in recapitulating the mechanisms of hepatic steatosis because it does not include the gut absorption process. Previously, we reported development of a microfluidic gut-liver chip that can recapitulate the gut absorption of fatty acids and subsequent lipid accumulation in liver cells. In this study, we performed a series of experiments to verify that our gut-liver chip reproduces various aspects of hepatic steatosis. The absorption of fatty acids was evaluated under various culture conditions. The anti-steatotic effect of turofexorate isopropyl (XL-335) and metformin was tested, and both drugs showed different action mechanisms. In addition, the oxidative stress induced by lipid absorption was evaluated. Our results demonstrate the potential of the gut-liver chip for use as a novel, physiologically realistic in vitro model to study fatty liver disease.

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.