Of mice and men: Is there a future for metformin in the treatment of hepatic steatosis?

Inhibition of PLA2G4A attenuated valproic acid- induced lysosomal membrane permeabilization and restored impaired autophagic flux: Implications for hepatotoxicity

Valproic acid (VPA) has broad efficacy against several seizures but causes liver injury limiting its prolonged clinical use. Some studies have demonstrated that VPA-induced hepatotoxicity is characterized by microvesicular hepatic steatosis. However, novel detailed mechanisms to explain VPA-induced hepatic steatosis and experimentally rigorously validated protective agents are still lacking. In this study, 8-week-old C57BL/6J mice were gavaged with VPA (500 mg/kg/d) for 4 weeks to establish an in vivo model of VPA-induced chronic liver injury. Quantitative proteomic and non-targeted lipidomic analyses were performed to explore the underlying mechanisms of VPA-induced hepatotoxicity. As a result, VPA-induced hepatotoxicity is associated with impaired autophagic flux, which is attributed to lysosomal dysfunction. Further studies revealed that VPA-induced lysosomal membrane permeabilization (LMP), allows soluble lysosomal enzymes to leak into the cytosol, which subsequently led to impaired lysosomal acidification. A lower abundance of glycerophospholipids and an increased abundance of lysophospholipids in liver tissues of mice in the VPA group strongly indicated that VPA-induced LMP may be mediated by the activation of phospholipase PLA2G4A. Metformin (Met) acted as a potential protective agent attenuating VPA-induced liver dysfunction and excessive lipid accumulation. Molecular docking and cellular thermal shift assays demonstrated that Met inhibited the activity of PLA2G4A by directly binding to it, thereby ameliorating VPA-induced LMP and autophagic flux impairment. In conclusion, this study highlights the therapeutic potential of targeting PLA2G4A-mediated lysosomal dysfunction in VPA-induced hepatotoxicity.

Metformin Inefficiency to Lower Lipids in Vitamin B12 Deficient HepG2 Cells Is Alleviated via Adiponectin-AMPK Axis

Background: Prolonged metformin treatment decreases vitamin B12 (B12) levels, whereas low B12 is associated with dyslipidaemia. Some studies have reported that metformin has no effect on intrahepatic triglyceride (TG) levels. Although AMP-activated protein kinase (AMPK) activation via adiponectin lowers hepatic TG content, its role in B12 deficiency and metformin has not been explored. We investigated whether low B12 impairs the beneficial effect of metformin on hepatic lipid metabolism via the AMPK-adiponectin axis. Methods: HepG2 was cultured using custom-made B12-deficient Eagle's Minimal Essential Medium (EMEM) in different B12-medium concentrations, followed by a 24-h metformin/adiponectin treatment. Gene and protein expressions and total intracellular TG were measured, and radiochemical analysis of TG synthesis and seahorse mitochondria stress assay were undertaken. Results: With low B12, total intracellular TG and synthesized radiolabelled TG were increased. Regulators of lipogenesis, cholesterol and genes regulating fatty acids (FAs; TG; and cholesterol biosynthesis were increased. FA oxidation (FAO) and mitochondrial function were decreased, with decreased pAMPKα and pACC levels. Following metformin treatment in hepatocytes with low B12, the gene and protein expression of the above targets were not alleviated. However, in the presence of adiponectin, intrahepatic lipid levels with low B12 decreased via upregulated pAMPKα and pACC levels. Again, combined adiponectin and metformin treatment ameliorated the low B12 effect and resulted in increased pAMPKα and pACC, with a subsequent reduction in lipogenesis, increased FAO and mitochondrion function. Conclusions: Adiponectin co-administration with metformin induced a higher intrahepatic lipid-lowering effect. Overall, we emphasize the potential therapeutic implications for hepatic AMPK activation via adiponectin for a clinical condition associated with B12 deficiency and metformin treatment.

Characterization of hepatic fatty acids using magnetic resonance spectroscopy for the assessment of treatment response to metformin in an eNOS-/- mouse model of metabolic nonalcoholic fatty liver disease/nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease worldwide. Liver biopsy remains the gold standard for diagnosis and staging of disease. There is a clinical need for noninvasive diagnostic tools for risk stratification, follow-up, and monitoring treatment response that are currently lacking, as well as preclinical models that recapitulate the etiology of the human condition. We have characterized the progression of NAFLD in eNOS^-/- mice fed a high fat diet (HFD) using noninvasive Dixon-based magnetic resonance imaging and single voxel STEAM spectroscopy-based protocols to measure liver fat fraction at 3 T. After 8 weeks of diet intervention, eNOS^-/- mice exhibited significant accumulation of intra-abdominal and liver fat compared with control mice. Liver fat fraction measured by ¹ H-MRS in vivo showed a good correlation with the NAFLD activity score measured by histology. Treatment of HFD-fed NOS3^-/- mice with metformin showed significantly reduced liver fat fraction and altered hepatic lipidomic profile compared with untreated mice. Our results show the potential of in vivo liver MRI and ¹ H-MRS to noninvasively diagnose and stage the progression of NAFLD and to monitor treatment response in an eNOS^-/- murine model that represents the classic NAFLD phenotype associated with metabolic syndrome.

Combining Dietary Intervention with Metformin Treatment Enhances Non-Alcoholic Steatohepatitis Remission in Mice Fed a High-Fat High-Sucrose Diet

Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are serious health concerns for which lifestyle interventions are the only effective first-line treatment. Dietary interventions are effective in body weight reduction, but not in improving insulin sensitivity and hepatic lipid mobilization. Conversely, metformin increases insulin sensitivity and promotes the inhibition of de novo hepatic lipogenesis. In this study, we evaluated the metformin effectiveness in NASH prevention and treatment, when combined with dietary intervention in male mice fed a high-fat high-sucrose diet (HFHSD). Eighty 5-week-old C57BL/6J male mice were fed a chow or HFHSD diet and sacrificed at 20 or 40 weeks. The HFHSD-fed mice developed NASH after 20 weeks. Lipoprotein and lipidomic analyses showed that the changes associated with diet were not prevented by metformin administration. HFHSD-fed mice subject to dietary intervention combined with metformin showed a 19.6% body weight reduction compared to 9.8% in those mice subjected to dietary intervention alone. Lower hepatic steatosis scores were induced. We conclude that metformin should not be considered a preventive option for NAFLD, but it is effective in the treatment of this disorder when combined with dietary intervention.

Reversal of High-Fat Diet-Induced Non-Alcoholic Fatty Liver Disease by Metformin Combined with PGG, an Inducer of Glycine N-Methyltransferase

Nonalcoholic fatty liver disease (NAFLD) is a major cause of liver-related morbidities and mortality, and no effective drug treatment currently exists. We aimed to develop a novel treatment strategy to induce the expression of glycine N-methyltransferase (GNMT), which is an important enzyme regulating S-adenosylmethionine metabolism whose expression is downregulated in patients with NAFLD. Because 1,2,3,4,6-pentagalloyl glucose (PGG) is a GNMT inducer, and metformin was shown to upregulate liver mitochondrial GNMT protein expression, the effect of PGG and metformin was evaluated. Biochemical analysis, histopathological examination, immunohistochemical staining, reverse transcription-quantitative PCR (RT-qPCR), Western blotting (WB), proteomic analysis and Seahorse XF Cell Mito Stress Test were performed. The high-fat diet (HFD)-induced NAFLD mice were treated with PGG and metformin. Combination of PGG and metformin nearly completely reversed weight gain, elevation of serum aminotransferases, and hepatic steatosis and steatohepatitis. In addition, the downregulated GNMT expression in liver tissues of HFD-induced NAFLD mice was restored. The GNMT expression was further confirmed by RT-qPCR and WB analysis using both in vitro and in vivo systems. In addition, PGG treatment was shown to increase oxygen consumption rate (OCR) maximum capacity in a dose-dependent manner, and was capable of rescuing the suppression of mitochondrial OCR induced by metformin. Proteomic analysis identified increased expression of glutathione S-transferase mu 4 (GSTM4), heat shock protein 72 (HSP72), pyruvate carboxylase (PYC) and 40S ribosomal protein S28 (RS28) in the metformin plus PGG treatment group. Our findings show that GNMT expression plays an important role in the pathogenesis of NAFLD, and combination of an inducer of GNMT and metformin can be of therapeutic potential for patients with NAFLD.

Nonalcoholic Fatty Liver Disease: Review of Management for Primary Care Providers

Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease in the United States and worldwide. The progressive form of NAFLD, nonalcoholic steatohepatitis (NASH), is a leading indication for liver transplant. Comorbidities associated with NAFLD development and NASH include type 2 diabetes, obesity, metabolic syndrome, and dyslipidemia. Extrahepatic morbidity and mortality are considerable as NAFLD is associated with an increased risk of cardiovascular disease and chronic kidney disease. Once NAFLD is diagnosed, the presence of liver fibrosis is the central determinant of hepatic prognosis. Severe liver fibrosis requires aggressive clinical management. No pharmacologic agents have regulatory approval in the United States for the treatment of NAFLD or NASH. Management is centered on efforts to reduce underlying obesity (lifestyle, medications, surgical or endoscopic interventions) and metabolic derangements (prediabetes, type 2 diabetes, hypertension, hyperlipidemia, and others). Current pharmacologic therapy for NAFLD is limited mainly to the use of vitamin E and pioglitazone, although other agents are being investigated in clinical trials. Cardiovascular and metabolic risk factors must also be assessed and managed. Here, NAFLD evaluation, diagnosis, and management are considered in the primary care setting and endocrinology clinics.

Deciphering metformin action in obese mice: A critical re-evaluation of established protocols

BACKGROUND AND PURPOSE

Despite extensive efforts and a plethora of suggested targets and pathways, the mechanism via which metformin lowers blood glucose remains obscure. Obstacles that hamper progress in understanding metformin action include unexplained discrepancies between preclinical models and patients.

PROCEDURES

We treated obese male C57BL/6J mice fed high fat diet with metformin provided in the form of a single dose, daily intraperitoneal injections, admixture to drinking water, or continuous infusion via intraperitoneal minipumps.

RESULTS

The results suggest several superimposed components, via which metformin acts on blood glucose. These include (i) marked glucose lowering shortly after dosing, which fades rapidly with the decrease in metformin concentrations in plasma and liver, but could, at least to a major extent, rely on the mechanism also accounting for metformin's therapeutic action in humans; (ii) indirect action via reduced weight gain, which might be responsible for glucose lowering observed in many previous rodent studies; and (iii) deterioration of glucose homeostasis by prolonged treatment that can be unmasked by avoidance of dosing shortly before measuring blood glucose in combination with exclusion of weight-related actions via restricted feeding of the control mice.

CONCLUSIONS

Our work raises the question whether elucidation of metformin's anti-diabetic mechanism(s) in rodent experiments may in the past have been hampered by failure to mimic clinical circumstances, as caused by insufficient consideration of pharmacokinetics and multiplicity of involved actions.

Metformin maintains intrahepatic triglyceride content through increased hepatic de novo lipogenesis

OBJECTIVE

Metformin is a first-line pharmacotherapy in the treatment of type 2 diabetes, a condition closely associated with non-alcoholic fatty liver disease (NAFLD). Although metformin promotes weight loss and improves insulin sensitivity, its effect on intrahepatic triglyceride (IHTG) remains unclear. We investigated the effect of metformin on IHTG, hepatic de novo lipogenesis (DNL), and fatty acid (FA) oxidation in vivo in humans.

DESIGN AND METHODS

Metabolic investigations, using stable-isotope tracers, were performed in ten insulin-resistant, overweight/obese human participants with NAFLD who were treatment naïve before and after 12 weeks of metformin treatment. The effect of metformin on markers of s.c. adipose tissue FA metabolism and function, along with the plasma metabolome, was investigated.

RESULTS

Twelve weeks of treatment with metformin resulted in a significant reduction in body weight and improved insulin sensitivity, but IHTG content and FA oxidation remained unchanged. Metformin treatment was associated with a significant decrease in VLDL-triglyceride (TG) concentrations and a significant increase in the relative contribution of DNL-derived FAs to VLDL-TG. There were subtle and relatively few changes in s.c. adipose tissue FA metabolism and the plasma metabolome with metformin treatment.

CONCLUSIONS

We demonstrate the mechanisms of action of metformin whereby it improves insulin sensitivity and promotes weight loss, without improvement in IHTG; these observations are partly explained through increased hepatic DNL and a lack of change in FA oxidation.

Correlation between long-term use of metformin and incidence of NAFLD among patients with type 2 diabetes mellitus: A real-world cohort study

BACKGROUND AND AIMS

Studies have demonstrated that the short-term use of metformin benefits liver function among patients with type 2 diabetes mellitus (T2DM). However, few studies have reported on the effects of long-term metformin treatment on liver function or liver histology. This study investigated the correlation between metformin use and the incidence of nonalcoholic fatty liver disease (NAFLD) among patients with T2DM.

METHODS

This population-based study investigated the risk of NAFLD among patients with T2DM who received metformin treatment between 2001-2018. Metformin users and metformin nonusers were enrolled and matched to compare the risk of NAFLD.

RESULTS

After 3 years, the patients who received <300 cDDD of metformin and those with metformin use intensity of <10 and 10-25 DDD/month had odds ratios (ORs) of 1.11 (95% confidence interval [CI] = 1.06-1.16), 1.08 (95% CI = 1.02-1.13), and 1.18 (95% CI = 1.11-1.26) for NAFLD, respectively. Moreover, metformin users who scored high on the Diabetes Complications and Severity Index (DCSI) were at high risk of NAFLD. Patients with comorbid hyperlipidemia, hyperuricemia, obesity, and hepatitis C were also at high risk of NAFLD.

CONCLUSION

Patients with T2DM who received metformin of <300 cDDD or used metformin at an intensity of <10 and 10-25 DDD/month were at a high risk of developing NAFLD. The results of this study also indicated that patients with T2DM receiving metformin and with high scores on the DCSI were at a high risk of developing NAFLD.

The Beneficial Additive Effect of Silymarin in Metformin Therapy of Liver Steatosis in a Pre-Diabetic Model

The combination of plant-derived compounds with anti-diabetic agents to manage hepatic steatosis closely associated with diabetes mellitus may be a new therapeutic approach. Silymarin, a complex of bioactive substances extracted from Silybum marianum, evinces an antioxidative, anti-inflammatory, and hepatoprotective activity. In this study, we investigated whether metformin (300 mg/kg/day for four weeks) supplemented with micronized silymarin (600 mg/kg/day) would be effective in mitigating fatty liver disturbances in a pre-diabetic model with dyslipidemia. Compared with metformin monotherapy, the metformin-silymarin combination reduced the content of neutral lipids (TAGs) and lipotoxic intermediates (DAGs). Hepatic gene expression of enzymes and transcription factors involved in lipogenesis (Scd-1, Srebp1, Pparγ, and Nr1h) and fatty acid oxidation (Pparα) were positively affected, with hepatic lipid accumulation reducing as a result. Combination therapy also positively influenced arachidonic acid metabolism, including its metabolites (14,15-EET and 20-HETE), mitigating inflammation and oxidative stress. Changes in the gene expression of cytochrome P450 enzymes, particularly Cyp4A, can improve hepatic lipid metabolism and moderate inflammation. All these effects play a significant role in ameliorating insulin resistance, a principal background of liver steatosis closely linked to T2DM. The additive effect of silymarin in metformin therapy can mitigate fatty liver development in the pre-diabetic state and before the onset of diabetes.

Metformin ameliorates maternal high-fat diet-induced maternal dysbiosis and fetal liver apoptosis

BACKGROUND

The deleterious effect of maternal high-fat diet (HFD) on the fetal rat liver may cause later development of non-alcoholic fatty liver disease (NAFLD). The aim of this study was to evaluate the effect of maternal HFD-induced maternal hepatic steatosis and dysbiosis on the fetal liver and intestines, and the effect of prenatal metformin in a rat model.

METHODS

Sprague-Dawley rats were assigned to three groups (N = 6 in each group). Before mating, the rats were randomly assigned to HFD or normal-chow diet (NCD) group for 7 weeks. After mating, the HFD group rats were continued with high-fat diet during pregnancy and some of the HFD group rats were co-treated with metformin (HFMf) via drinking water during pregnancy. All maternal rats and their fetuses were sacrificed on gestational day 21. The liver and intestinal tissues of both maternal and fetal rats were analyzed. In addition, microbial deoxyribonucleic acid extracted from the maternal fecal samples was analyzed.

RESULTS

HFD resulted in maternal weight gain during pregnancy, intrahepatic lipid accumulation, and change in the serum short-chain fatty acid profile, intestinal tight junctions, and dysbiosis in maternal rats. The effect of HFD on maternal rats was alleviated by prenatal metformin, which also ameliorated inflammation and apoptosis in the fetal liver and intestines.

CONCLUSIONS

This study demonstrated the beneficial effects of prenatal metformin on maternal liver steatosis, focusing on the gut-liver axis. In addition, the present study indicates that prenatal metformin could ameliorate maternal HFD-induced inflammation and apoptosis in the fetal liver and intestines. This beneficial effect of in-utero exposure of metformin on fetal liver and intestines has not been reported. This study supports the use of prenatal metformin for pregnant obese women.

Emerging and Established Therapeutic Approaches for Nonalcoholic Fatty Liver Disease

PURPOSE

Nonalcoholic fatty liver disease (NAFLD), more recently referred to as metabolic-associated fatty liver disease, refers to a disease spectrum ranging from hepatic steatosis to nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis, associated with hepatic complications (including liver fibrosis, cirrhosis, and hepatocellular carcinoma) and extrahepatic complications (particularly cardiometabolic complications, including type 2 diabetes and cardiovascular disease). Treatment options include lifestyle interventions (dietary modification and physical activity programs) and pharmacologic interventions. Treatment aims should be broad, with a hepatic focus (to improve/reverse hepatic inflammation, fibrosis, and steatohepatitis), ideally with additional extrahepatic effects affecting metabolic co-morbidities (eg, insulin resistance, glucose dysregulation, dyslipidemia), causing weight loss and affording cardiovascular protection. NASH and fibrosis represent the main histopathological features that warrant treatment to prevent disease progression. Despite a paucity of established treatments, the array of potential molecular targets, pathways, and potential treatments is continually evolving. The goal of this article was to provide a narrative review summarizing the emerging and more established therapeutic options considering the complex pathophysiology of NAFLD and the important long-term sequelae of this condition.

METHODS

The literature was reviewed by using PubMed, conference abstracts, and press releases from early-phase clinical studies to provide an overview of the evidence.

FINDINGS

As understanding of the pathophysiology of NASH/NAFLD evolves, drugs with different mechanisms of action, targeting different molecular targets and aberrant pathways that mediate hepatic steatosis, inflammation, and fibrosis, have been developed and are being tested in clinical trials. Pharmacologic therapies fall into 4 main categories according to the molecular targets/pathways they disrupt: (1) meta-bolic targets, targeting insulin resistance, hepatic de novo lipogenesis, or substrate utilization; (2) inflam-matory pathways, inhibiting inflammatory cell recruitment/signaling, reduce oxidative/endoplasmic reticulum stress or are antiapoptotic; (3) the liver-gut axis, which modulates bile acid enterohepatic circulation/signaling or alters gut microbiota; and (4) antifibrotic targets, targeting hepatic stellate cells, decrease collagen deposition or increase fibrinolysis.

IMPLICATIONS

Lifestyle modification must remain the cornerstone of treatment. Pharmacologic treatment is reserved for NASH or fibrosis, the presence of which requires histopathological confirmation. The disease complexity provides a strong rationale for combination therapies targeting multiple pathways simultaneously.

Validation of an adipose-liver human-on-a-chip model of NAFLD for preclinical therapeutic efficacy evaluation

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease and strongly correlates with the growing incidence of obesity and type II diabetes. We have developed a human-on-a-chip model composed of human hepatocytes and adipose tissue chambers capable of modeling the metabolic factors that contribute to liver disease development and progression, and evaluation of the therapeutic metformin. This model uses a serum-free, recirculating medium tailored to represent different human metabolic conditions over a 14-day period. The system validated the indirect influence of adipocyte physiology on hepatocytes that modeled important aspects of NAFLD progression, including insulin resistant biomarkers, differential adipokine signaling in different media and increased TNF-α-induced steatosis observed only in the two-tissue model. This model provides a simple but unique platform to evaluate aspects of an individual factor's contribution to NAFLD development and mechanisms as well as evaluate preclinical drug efficacy and reassess human dosing regimens.

Therapeutic effect of oxyberberine on obese non-alcoholic fatty liver disease rats

BACKGROUND

Berberine (BBR) has been widely used to treat non-alcoholic fatty liver disease (NAFLD). The metabolites of BBR were believed to contribute significantly to its pharmacological effects. Oxyberberine (OBB), a gut microbiota-mediated oxidative metabolite of BBR, has been firstly identified in our recent work.

PURPOSE

Here, we aimed to comparatively investigate the anti-NAFLD properties of OBB and BBR.

METHODS

The anti-NAFLD effect was evaluated in high-fat diet-induced obese NAFLD rats with biochemical/ELISA tests and histological staining. The related gene and protein expressions were detected by qRT-PCR and Western blotting respectively. Molecular docking and dynamic simulation were also performed to provide further insight.

RESULTS

Results indicated OBB remarkably and dose-dependently attenuated the clinical manifestations of NAFLD, which (100 mg/kg) achieved similar therapeutic effect to metformin (300 mg/kg) and was superior to BBR of the same dose. OBB significantly inhibited aberrant phosphorylation of IRS-1 and up-regulated the downstream protein expression and phosphorylation (PI3K, p-Akt/Akt and p-GSK-3β/GSK-3β) to improve hepatic insulin signal transduction. Meanwhile, OBB treatment remarkably alleviated inflammation via down-regulating the mRNA expression of MCP-1, Cd68, Nos2, Cd11c, while enhancing Arg1 mRNA expression in white adipose tissue. Moreover, OBB exhibited closer affinity with AMPK in silicon and superior hyperphosphorylation of AMPK in vivo, leading to increased ACC mRNA expression in liver and UCP-1 protein expression in adipose tissue.

CONCLUSION

Taken together, compared with BBR, OBB was more capable of maintaining lipid homeostasis between liver and WAT via attenuating hepatic insulin pathway and adipocyte inflammation, which was associated with its property of superior AMPK activator.

Rationale and design of a randomised controlled trial testing the effect of personalised diet in individuals with pre-diabetes or type 2 diabetes mellitus treated with metformin

INTRODUCTION

Metformin and diets aimed at promoting healthy body weight are the first line in treating type 2 diabetes mellitus (T2DM). Clinical practice, backed by clinical trials, suggests that many individuals do not reach glycaemic targets using this approach alone. The primary aim of the Personalised Medicine in Pre-diabetes-Towards Preventing Diabetes in Individuals at Risk (PREDICT) Study is to test the efficacy of personalised diet as adjuvant to metformin in improving glycaemic control in individuals with dysglycaemia.

METHODS AND ANALYSIS

PREDICT is a two-arm, parallel group, single-masked randomised controlled trial in adults with pre-diabetes or early-stage T2DM (with glycated haemoglobin (HbA1c) up to 8.0% (64 mmol/mol)), not treated with glucose-lowering medication. PREDICT is conducted at the Clinical Research Facility at the Garvan Institute of Medical Research (Sydney). Enrolment of participants commenced in December 2018 and expected to complete in December 2021. Participants are commenced on metformin (Extended Release, titrated to a target dose of 1500 mg/day) and randomised with equal allocation to either (1) the Personalised Nutrition Project algorithm-based diet or (2) low-fat high-dietary fibre diet, designed to provide caloric restriction (75%) in individuals with body mass index >25 kg/m². Treatment duration is 6 months and participants visit the Clinical Research Facility five times over approximately 7 months. The primary outcome measure is HbA1c. The secondary outcomes are (1) time of interstitial glucose <7.8 mmol/L and (2) glycaemic variability (continuous glucose monitoring), (3) body weight, (4) fat mass and (5) abdominal visceral fat volume (dual-energy X-ray absorptiometry), serum (6) low-density lipoprotein cholesterol (7) high-density lipoprotein cholesterol and (8) triglycerides concentrations, (9) blood pressure, and (10) liver fat (Fibroscan).

ETHICS AND DISSEMINATION

The study has been approved by the St Vincent's Hospital Human Research Ethics Committee (File 17/080, Sydney, Australia) and the Weizmann Institutional Review Board (File 528-3, Rehovot, Israel). The findings will be published in peer-reviewed open access medical journals.

TRIAL REGISTRATION NUMBER

NCT03558867; Pre-results.

Metabolic alterations in spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (SBMA) is a rare, X-linked neuromuscular disease characterised by lower motor neurons degeneration, slowly progressive myopathy and multisystem involvement. SBMA is caused by trinucleotide repeat expansion in the first exon of the androgen receptor (AR) gene on chromosome X that encodes a polyglutamine (polyQ) tract in the AR protein. Disease onset occurs between 30-60 years of age with easy fatigability, muscle cramps, and weakness in the limbs. In addition to neuromuscular involvement, in SBMA phenotype, many non-neural manifestations are present. Recently, some studies have reported a high prevalence of metabolic and liver disorders in patients with SBMA. Particularly, fatty liver and insulin resistance (IR) have been found in many SBMA patients. The alteration of AR function and the androgen insensitivity can be involved in both fatty liver and IR. In turn, IR and liver alterations can influence neuromuscular damage through different mechanisms. These data lead to consider SBMA as a metabolic as well as a neuromuscular disease. The mechanism of metabolic alterations, their link with the neuromuscular damage, the effects on the course of disease and their treatment will have to be yet fully clarified.

L-Carnitine counteracts in vitro fructose-induced hepatic steatosis through targeting oxidative stress markers

PURPOSE

Nonalcoholic fatty liver disease (NAFLD) is defined by excessive lipid accumulation in the liver and involves an ample spectrum of liver diseases, ranging from simple uncomplicated steatosis to cirrhosis and hepatocellular carcinoma. Accumulating evidence demonstrates that high fructose intake enhances NAFLD development and progression promoting inhibition of mitochondrial β-oxidation of long-chain fatty acids and oxidative damages. L-Carnitine (LC), involved in β-oxidation, has been used to reduce obesity caused by high-fat diet, which is beneficial to ameliorating fatty liver diseases. Moreover, in the recent years, various studies have established LC anti-oxidative proprieties. The objective of this study was to elucidate primarily the underlying anti-oxidative mechanisms of LC in an in vitro model of fructose-induced liver steatosis.

METHODS

Human hepatoma HepG2 cells were maintained in medium supplemented with LC (5 mM LC) with or without 5 mM fructose (F) for 48 h and 72 h. In control cells, LC or F was not added to medium. Fat deposition, anti-oxidative, and mitochondrial homeostasis were investigated.

RESULTS

LC supplementation decreased the intracellular lipid deposition enhancing AMPK activation. However, compound C (AMPK inhibitor-10 μM), significantly abolished LC benefits in F condition. Moreover, LC, increasing PGC1 α expression, ameliorates mitochondrial damage-F induced. Above all, LC reduced ROS production and simultaneously increased protein content of antioxidant factors, SOD2 and Nrf2.

CONCLUSION

Our data seemed to show that LC attenuate fructose-mediated lipid accumulation through AMPK activation. Moreover, LC counteracts mitochondrial damages and reactive oxygen species production restoring antioxidant cellular machine. These findings provide new insights into LC role as an AMPK activator and anti-oxidative molecule in NAFLD.

Combined treatments with metformin and phosphodiesterase inhibitors alleviate nonalcoholic fatty liver disease in high-fat diet fed rats: a comparative study

Nonalcoholic fatty liver disease (NAFLD) is an excessive accumulation of fats in the liver resulting in hepatic inflammation and fibrous tissue formation along with insulin resistance. This study was designed to investigate the possible protective effects of metformin alone and in combination with different phosphodiesterase inhibitors (PDEIs). Rats were fed a high-fat diet (HFD) for 16 weeks to induce NAFLD. Starting from week 12, rats received metformin alone or in combination with pentoxifylline, cilostazol, or sildenafil. HFD administration resulted in hepatic steatosis and inflammation in rats. In addition, liver index, body composition index, activities of liver enzymes, and serum lipids deviated from normal. Further, significant elevations were recorded compared to control in terms of serum glucose, insulin, and HOMA-IR (homeostasis model assessment index for insulin resistance), oxidative stress parameters, hepatic TNF-α and NF-κB gene expression, and iNOS protein expression. Rats treated with metformin showed a significant improvement in the aforementioned parameters. However, the addition of pentoxifylline to metformin treatment synergized its action and produced a fortified effect against HFD-induced NAFLD better than other PDEIs. Data from this study indicated that combined treatment of metformin and pentoxifylline had the most remarkable ameliorated effects against HFD-induced NAFLD; further clinical investigations are needed to approve PDEIs for NAFLD treatment.

Nonalcoholic Fatty Liver Disease in Adults: Current Concepts in Etiology, Outcomes, and Management

Nonalcoholic fatty liver disease (NAFLD) is a spectrum of disease, extending from simple steatosis to inflammation and fibrosis with a significant risk for the development of cirrhosis. It is highly prevalent and is associated with significant adverse outcomes both through liver-specific morbidity and mortality but, perhaps more important, through adverse cardiovascular and metabolic outcomes. It is closely associated with type 2 diabetes and obesity, and both of these conditions drive progressive disease toward the more advanced stages. The mechanisms that govern hepatic lipid accumulation and the predisposition to inflammation and fibrosis are still not fully understood but reflect a complex interplay between metabolic target tissues including adipose and skeletal muscle, and immune and inflammatory cells. The ability to make an accurate assessment of disease stage (that relates to clinical outcome) can also be challenging. While liver biopsy is still regarded as the gold-standard investigative tool, there is an extensive literature on the search for novel noninvasive biomarkers and imaging modalities that aim to accurately reflect the stage of underlying disease. Finally, although no therapies are currently licensed for the treatment of NAFLD, there are interventions that appear to have proven efficacy in randomized controlled trials as well as an extensive emerging therapeutic landscape of new agents that target many of the fundamental pathophysiological processes that drive NAFLD. It is highly likely that over the next few years, new treatments with a specific license for the treatment of NAFLD will become available.

The regulation of hepatic fatty acid synthesis and partitioning: the effect of nutritional state

Nonalcoholic fatty liver disease (NAFLD) is an increasing global public health burden. NAFLD is strongly associated with type 2 diabetes mellitus, obesity and cardiovascular disease and begins with intrahepatic triacylglycerol accumulation. Under healthy conditions, the liver regulates lipid metabolism to meet systemic energy needs in the fed and fasted states. The processes of fatty acid uptake, fatty acid synthesis and the intracellular partitioning of fatty acids into storage, oxidation and secretion pathways are tightly regulated. When one or more of these processes becomes dysregulated, excess lipid accumulation can occur. Although genetic and environmental factors have been implicated in the development of NAFLD, it remains unclear why an imbalance in these pathways begins. The regulation of fatty acid partitioning occurs at several points, including during triacylglycerol synthesis, lipid droplet formation and lipolysis. These processes are influenced by enzyme function, intake of dietary fats and sugars and whole-body metabolism, and are further affected by the presence of obesity or insulin resistance. Insight into how the liver controls fatty acid metabolism in health and how these processes might be affected in disease would offer the potential for new therapeutic treatments for NAFLD to be developed.

Sesamin, a Naturally Occurring Lignan, Inhibits Ligand-Induced Lipogenesis through Interaction with Liver X Receptor Alpha (LXRα) and Pregnane X Receptor (PXR)

Liver X receptor (LXR) is a nuclear receptor that regulates various biological processes, including de novo lipogenesis, cholesterol metabolism, and inflammation. Selective inhibition of LXR may aid the treatment of nonalcoholic fatty liver disease (NAFLD). Sesamin is a naturally occurring lignan in many dietary plants and has a wide range of beneficial effects on metabolism. The mechanism underlying sesamin action especially on the regulation of LXR remains elusive. Reporter assays, mRNA and protein expression, and in silico modeling were used to identify sesamin as an antagonist of LXRα. Sesamin was applied to the hepatic HepaRG and intestinal LS174T cells and showed that it markedly ameliorated lipid accumulation in the HepaRG cells, by reducing LXRα transactivation, inhibiting the expression of downstream target genes. This effect was associated with the stimulation of AMP-activated protein kinase (AMPK) signaling pathway, followed by decreased T0901317-LXRα-induced expression of SREBP-1c and its downstream target genes. Mechanistically, sesamin reduced the recruitment of SRC-1 but enhanced that of SMILE to the SREBP-1c promoter region under T0901317 treatment. It regulated the transcriptional control exerted by LXRα by influencing its interaction with coregulators and thus decreased mRNA and protein levels of genes downstream of LXRα and reduced lipid accumulation in hepatic cells. Additionally, sesamin reduced valproate- and rifampin-induced LXRα and pregnane X receptor (PXR) transactivation. This was associated with reduced expression of target genes and decreased lipid accumulation. Thus, sesamin is an antagonist of LXRα and PXR and suggests that it may alleviate drug-induced lipogenesis via the suppression of LXRα and PXR signaling.

Metformin attenuates the onset of non-alcoholic fatty liver disease and affects intestinal microbiota and barrier in small intestine

The antidiabetic drug metformin has been proposed to affect non-alcoholic fatty liver disease (NAFLD) through its effects on intestinal microbiota and barrier function. However, so far most studies focused on long-term effects and more progressed disease stages. The aim of this study was to assess in two experimental settings, if the onset of NAFLD is associated with changes of intestinal microbiota and barrier function and to determine effects of metformin herein. C57Bl/6J mice were fed a liquid control diet (C) or fat-, fructose- and cholesterol-rich diet (FFC) for four days or six weeks ±300 mg/kg BW/day metformin (Met). Markers of liver health, intestinal barrier function and microbiota composition were assessed. Metformin treatment markedly attenuated FFC-induced NAFLD in both experiments with markers of inflammation and lipidperoxidation in livers of FFC + Met-fed mice being almost at the level of controls. Metformin treatment attenuated the loss of tight junction proteins in small intestine and the increase of bacterial endotoxin levels in portal plasma. Changes of intestinal microbiota found in FFC-fed mice were also significantly blunted in FFC + Met-fed mice. Taken together, protective effects of metformin on the onset of NAFLD are associated with changes of intestinal microbiota composition and lower translocation of bacterial endotoxins.