Liver-Specific Activation of AMPK Prevents Steatosis on a High-Fructose Diet

Chronic treatment with glucagon-like peptide-1 and glucagon receptor co-agonist causes weight loss-independent improvements in hepatic steatosis in mice with diet-induced obesity

OBJECTIVES

Co-agonists at the glucagon-like peptide-1 and glucagon receptors (GLP1R/GCGR) show promise as treatments for metabolic dysfunction-associated steatotic liver disease (MASLD). Although most co-agonists to date have been heavily GLP1R-biased, glucagon directly acts on the liver to reduce fat content. The aims of this study were to investigate a GCGR-biased co-agonist as treatment for hepatic steatosis in mice.

METHODS

Mice with diet-induced obesity (DIO) were treated with Dicretin, a GLP1/GCGR co-agonist with high potency at the GCGR, Semaglutide (GLP1R monoagonist) or food restriction over 24 days, such that their weight loss was matched. Hepatic steatosis, glucose tolerance, hepatic transcriptomics, metabolomics and lipidomics at the end of the study were compared with Vehicle-treated mice.

RESULTS

Dicretin lead to superior reduction of hepatic lipid content when compared to Semaglutide or equivalent weight loss by calorie restriction. Markers of glucose tolerance and insulin resistance improved in all treatment groups. Hepatic transcriptomic and metabolomic profiling demonstrated many changes that were unique to Dicretin-treated mice. These include some known targets of glucagon signaling and others with as yet unclear physiological significance.

CONCLUSIONS

Our study supports the development of GCGR-biased GLP1/GCGR co-agonists for treatment of MASLD and related conditions.

Myeloid AMPK signaling restricts fibrosis but is not required for metformin improvements during CDAHFD-induced NASH in mice

Metabolic programming underpins inflammation and liver macrophage activation in the setting of chronic liver disease. Here, we sought to identify the role of an important metabolic regulator, AMP-activated protein kinase (AMPK), specifically within myeloid cells during the progression of non-alcoholic steatohepatitis (NASH) and whether treatment with metformin, a firstline therapy for diabetes and activator of AMPK could stem disease progression. Male and female Prkaa1fl/fl/Prkaa2fl/fl (Flox) control and Flox-LysM-Cre+ (MacKO) mice were fed a low-fat control or a choline-deficient, amino acid defined 45% Kcal high-fat diet (CDAHFD) for 8 weeks, where metformin was introduced in the drinking water (50 or 250 mg/kg/day) for the last 4 weeks. Hepatic steatosis and fibrosis were dramatically increased in response to CDAHFD-feeding compared to low-fat control. While myeloid AMPK signaling had no effect on markers of hepatic steatosis or circulating markers, fibrosis as measured by total liver collagen was significantly elevated in livers from MacKO mice, independent of sex. Although treatment with 50 mg/kg/day metformin had no effect on any parameter, intervention with 250 mg/kg/day metformin completely ameliorated hepatic steatosis and fibrosis in both male and female mice. While the protective effect of metformin was associated with lower final body weight, and decreased expression of lipogenic and Col1a1 transcripts, it was independent of myeloid AMPK signaling. These results suggest that endogenous AMPK signaling in myeloid cells, both liver-resident and infiltrating, acts to restrict fibrogenesis during CDAHFD-induced NASH progression but is not the mechanism by which metformin improves markers of NASH.

AMP-activated protein kinase activation suppresses leptin expression independently of adipogenesis in primary murine adipocytes

Adipogenesis, defined as the development of mature adipocytes from stem cell precursors, is vital for the expansion, turnover and health of adipose tissue. Loss of adipogenic potential in adipose stem cells, or impairment of adipogenesis is now recognised as an underlying cause of adipose tissue dysfunction and is associated with metabolic disease. In this study, we sought to determine the role of AMP-activated protein kinase (AMPK), an evolutionarily conserved master regulator of energy homeostasis, in adipogenesis. Primary murine adipose-derived stem cells were treated with a small molecule AMPK activator (BI-9774) during key phases of adipogenesis, to determine the effect of AMPK activation on adipocyte commitment, maturation and function. To determine the contribution of the repression of lipogenesis by AMPK in these processes, we compared the effect of pharmacological inhibition of acetyl-CoA carboxylase (ACC). We show that AMPK activation inhibits adipogenesis in a time- and concentration-dependent manner. Transient AMPK activation during adipogenic commitment leads to a significant, ACC-independent, repression of adipogenic transcription factor expression. Furthermore, we identify a striking, previously unexplored inhibition of leptin gene expression in response to both short-term and chronic AMPK activation irrespective of adipogenesis. These findings reveal that in addition to its effect on adipogenesis, AMPK activation switches off leptin gene expression in primary mouse adipocytes independently of adipogenesis. Our results identify leptin expression as a novel target of AMPK through mechanisms yet to be identified.

New Insights into the Role of KLF10 in Tissue Fibrosis

Fibrosis, characterized by excessive extracellular matrix accumulation, disrupts normal tissue architecture, causes organ dysfunction, and contributes to numerous chronic diseases. This review focuses on Krüppel-like factor 10 (KLF10), a transcription factor significantly induced by transforming growth factor-β (TGF-β), and its role in fibrosis pathogenesis and progression across various tissues. KLF10, initially identified as TGF-β-inducible early gene-1 (TIEG1), is involved in key biological processes including cell proliferation, differentiation, apoptosis, and immune responses. Our analysis investigated KLF10 gene and protein structures, interaction partners, and context-dependent functions in fibrotic diseases. This review highlights recent findings that underscore KLF10 interaction with pivotal signaling pathways, such as TGF-β, and the modulation of gene expression in fibrotic tissues. We examined the dual role of KLF10 in promoting and inhibiting fibrosis depending on tissue type and fibrotic context. This review also discusses the therapeutic potential of targeting KLF10 in fibrotic diseases, based on its regulatory role in key pathogenic mechanisms. By consolidating current research, this review aims to enhance the understanding of the multifaceted role of KLF10 in fibrosis and stimulate further research into its potential as a therapeutic target in combating fibrotic diseases.

Exercise training adaptations in liver glycogen and glycerolipids require hepatic AMP-activated protein kinase in mice

Regular exercise elicits adaptations in glucose and lipid metabolism that allow the body to meet energy demands of subsequent exercise bouts more effectively and mitigate metabolic diseases including fatty liver. Energy discharged during the acute exercise bouts that comprise exercise training may be a catalyst for liver adaptations. During acute exercise, liver glycogenolysis and gluconeogenesis are accelerated to supply glucose to working muscle. Lower liver energy state imposed by gluconeogenesis and related pathways activates AMP-activated protein kinase (AMPK), which conserves ATP partly by promoting lipid oxidation. This study tested the hypothesis that AMPK is necessary for liver glucose and lipid adaptations to training. Liver-specific AMPKα1α2 knockout (AMPKα1α2fl/fl+AlbCre) mice and littermate controls (AMPKα1α2fl/fl) completed sedentary and exercise training protocols. Liver nutrient fluxes were quantified at rest or during acute exercise following training. Liver metabolites and molecular regulators of metabolism were assessed. Training increased liver glycogen in AMPKα1α2fl/fl mice, but not in AMPKα1α2fl/fl+AlbCre mice. The inability to increase glycogen led to lower glycogenolysis, glucose production, and circulating glucose during acute exercise in trained AMPKα1α2fl/fl+AlbCre mice. Deletion of AMPKα1α2 attenuated training-induced declines in liver diacylglycerides. In particular, training lowered the concentration of unsaturated and elongated fatty acids comprising diacylglycerides in AMPKα1α2fl/fl mice, but not in AMPKα1α2fl/fl+AlbCre mice. Training increased liver triacylglycerides and the desaturation and elongation of fatty acids in triacylglycerides of AMPKα1α2fl/fl+AlbCre mice. These lipid responses were independent of differences in tricarboxylic acid cycle fluxes. In conclusion, AMPK is required for liver training adaptations that are critical to glucose and lipid metabolism.NEW & NOTEWORTHY This study shows that the energy sensor and transducer, AMP-activated protein kinase (AMPK), is necessary for an exercise training-induced: 1) increase in liver glycogen that is necessary for accelerated glycogenolysis during exercise, 2) decrease in liver glycerolipids independent of tricarboxylic acid (TCA) cycle flux, and 3) decline in the desaturation and elongation of fatty acids comprising liver diacylglycerides. The mechanisms defined in these studies have implications for use of regular exercise or AMPK-activators in patients with fatty liver.

A Mammalian Conserved Circular RNA CircLARP1B Regulates Hepatocellular Carcinoma Metastasis and Lipid Metabolism

Circular RNAs (circRNAs) have emerged as crucial regulators in physiology and human diseases. However, evolutionarily conserved circRNAs with potent functions in cancers are rarely reported. In this study, a mammalian conserved circRNA circLARP1B is identified to play critical roles in hepatocellular carcinoma (HCC). Patients with high circLARP1B levels have advanced prognostic stage and poor overall survival. CircLARP1B facilitates cellular metastatic properties and lipid accumulation through promoting fatty acid synthesis in HCC. CircLARP1B deficient mice exhibit reduced metastasis and less lipid accumulation in an induced HCC model. Multiple lines of evidence demonstrate that circLARP1B binds to heterogeneous nuclear ribonucleoprotein D (HNRNPD) in the cytoplasm, and thus affects the binding of HNRNPD to sensitive transcripts including liver kinase B1 (LKB1) mRNA. This regulation causes decreased LKB1 mRNA stability and lower LKB1 protein levels. Antisense oligodeoxynucleotide complementary to theHNRNPD binding sites in circLARP1B increases the HNRNPD binding to LKB1 mRNA. Through the HNRNPD-LKB1-AMPK pathway, circLARP1B promotes HCC metastasis and lipid accumulation. Results from AAV8-mediated hepatocyte-directed knockdown of circLARP1B or Lkb1 in mouse models also demonstrate critical roles of hepatocytic circLARP1B regulatory pathway in HCC metastasis and lipid accumulation, and indicate that circLARP1B may be potential target of HCC treatment.

A natural Nrf2 activator glucoraphanin improves hepatic steatosis in high-fat diet-induced obese male mice associated with AMPK activation

Genetic and pharmacological activation of the transcription factor nuclear factor, erythroid derived 2, like 2 (Nrf2) alleviates high-fat diet (HFD)-induced obesity in mice; however, synthetic Nrf2 activators are not clinically available due to safety concerns. Dietary glucoraphanin (GR), a naturally occurring compound found in cruciferous vegetables that activates Nrf2 and induces its target antioxidant genes. We previously demonstrated that GR increased thermogenesis and mitigated HFD-induced obesity in lean healthy mice. In this study, we investigated the therapeutic effects of GR on pre-existing obesity and associated metabolic disorders, such as hepatic steatosis, with or without low-fat dietary intervention. Eight-week-old male C57BL/6J mice were fed an HFD for 9 weeks to induce obesity. Subsequently, these obese mice were fed either the HFD or a normal chow diet, supplemented with or without GR, for an additional 11 weeks. GR supplementation did not decrease the body weight of HFD-fed mice; however, it significantly reduced plasma alanine aminotransferase and aspartate aminotransferase levels and hepatic triglyceride accumulation. These improvements in liver damage by GR were associated with decreased expression levels of fatty acid synthesis genes and proinflammatory chemokine genes, suppressed c-Jun N-terminal kinase activation, and reduced proinflammatory phenotypes of macrophages in the liver. Moreover, metabolome analysis identified increased hepatic levels of adenosine 5'-monophosphate (AMP) in HFD-GR mice compared with those in HFD mice, which agreed with increased phosphorylation levels of AMP-activated protein kinase. Our results show that GR may have a therapeutic potential for treating obesity-associated hepatic steatosis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13340-023-00658-6.

Cydonia oblonga Miller fruit extract exerts an anti-obesity effect in 3T3-L1 adipocytes by activating the AMPK signaling pathway

BACKGROUND/OBJECTIVES

The fruit of Cydonia oblonga Miller (COM) is used traditionally in Mediterranean region medicine to prevent or treat obesity, but its mechanism of action is still unclear. Beyond a demonstrated anti-obesity effect, the fruit was tested for the mechanism of adipogenesis in 3T3-L1 preadipocytes.

MATERIALS/METHODS

3T3-L1 preadipocytes were cultured for 8 days with COM fruit extract (COME) at different concentrations (0-600 µg/mL) with adipocyte differentiation medium. The cell viability was measured using an MTT assay; triglyceride (TG) was stained with Oil Red O. The expression levels of the adipogenesis-related genes and protein expression were analyzed by reverse transcription polymerase chain reaction and Western blotting, respectively.

RESULTS

COME inhibited intracellular TG accumulation during adipogenesis. A COME treatment in 3T3-L1 cells induced upregulation of the adenosine monophosphate-activated protein kinase (AMPK)α phosphorylation and downregulation of the adipogenic transcription factors, such as sterol regulatory element-binding protein 1c, peroxisome proliferator-activated receptor γ, and CCAAT/enhancer binding protein α. The COME treatment reduced the mRNA expression of fatty acyl synthetase, adenosine triphosphate-citrate lyase, adipocyte protein 2, and lipoprotein lipase. It increased the mRNA expression of hormone-sensitive lipase and carnitine palmitoyltransferase I in 3T3-L1 cells.

CONCLUSIONS

COME inhibits adipogenesis via the AMPK signaling pathways. COME may be used to prevent and treat obesity.

Effects of oleoylethanolamide supplementation on the expression of lipid metabolism-related genes and serum NRG4 levels in patients with non-alcoholic fatty liver disease: A randomized controlled trial

BACKGROUND

This study investigated the effects of oleoylethanolamide (OEA) supplementation on the expression levels of SIRT1, AMPK, PGC-1α, PPAR-γ, CEBP-α and CEBP-β genes and serum neuregulin 4 (NRG4) levels in patients with non-alcoholic fatty liver diseases (NAFLD).

METHODS

Sixty obese patients with NAFLD were equally allocated into either OEA or placebo group for 12 weeks. The mRNA expression levels of genes were determined using the reverse transcription polymerase chain reaction (RT-PCR) technique. Serum NRG4 level was also assessed using an enzyme-linked immunosorbent assay (ELISA) kit.

RESULTS

At the endpoint, mRNA expression levels of SIRT1(p = 0.001), PGC-1α (p = 0.011) and AMPK (p = 0.019) were significantly higher in the OEA group compared to placebo group. However, no significant differences were observed in the expression levels of PPAR-γ, CEBP-α and CEBP-β between the two groups. Serum NRG4 levels significantly increased in the OEA group compared with the placebo group after controlling for confounders (p = 0.027). In the OEA group, significant relationships were found between percent of changes in the expression levels of the SIRT1, AMPK and PGC-1α as well as serum NRG4 level with percent of changes in some anthropometric measures. Moreover, in the intervention group, percent of changes in high-density lipoprotein cholesterol was positively correlated with percent of changes in the expression levels of the SIRT1 and AMPK. While, percent of changes in triglyceride was inversely correlated with percent of changes in the expression levels of SIRT1.

CONCLUSION

OEA could beneficially affect expression levels of some lipid metabolism-related genes and serum NRG4 level. "REGISTERED UNDER IRANIAN REGISTRY OF CLINICAL TRIALS IDENTIFIER NO: IRCT20090609002017N32".

Gossypetin Prevents the Progression of Nonalcoholic Steatohepatitis by Regulating Oxidative Stress and AMP-Activated Protein Kinase

Nonalcoholic steatohepatitis (NASH) is a severe liver metabolic disorder, however, there are still no effective and safe drugs for its treatment. Previous clinical trials used various therapeutic approaches to target individual pathologic mechanisms, but these approaches were unsuccessful because of the complex pathologic causes of NASH. Combinatory therapy in which two or more drugs are administered simultaneously to patients with NASH, however, carries the risk of side effects associated with each individual drug. To solve this problem, we identified gossypetin as an effective dual-targeting agent that activates AMP-activated protein kinase (AMPK) and decreases oxidative stress. Administration of gossypetin decreased hepatic steatosis, lobular inflammation and liver fibrosis in the liver tissue of mice with choline-deficient high-fat diet and methionine-choline deficient diet (MCD) diet-induced NASH. Gossypetin functioned directly as an antioxidant agent, decreasing hydrogen peroxide and palmitate-induced oxidative stress in the AML12 cells and liver tissue of MCD diet-fed mice without regulating the antioxidant response factors. In addition, gossypetin acted as a novel AMPK activator by binding to the allosteric drug and metabolite site, which stabilizes the activated structure of AMPK. Our findings demonstrate that gossypetin has the potential to serve as a novel therapeutic agent for nonalcoholic fatty liver disease /NASH. SIGNIFICANCE STATEMENT: This study demonstrates that gossypetin has preventive effect to progression of nonalcoholic steatohepatitis (NASH) as a novel AMP-activated protein kinase (AMPK) activator and antioxidants. Our findings indicate that simultaneous activation of AMPK and oxidative stress using gossypetin has the potential to serve as a novel therapeutic approach for nonalcoholic fatty liver disease /NASH patients.

MicroRNA regulation of AMPK in nonalcoholic fatty liver disease

Obesity-associated nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and is the leading cause of liver failure and death. The function of AMP-activated protein kinase (AMPK), a master energy sensor, is aberrantly reduced in NAFLD, but the underlying mechanisms are not fully understood. Increasing evidence indicates that aberrantly expressed microRNAs (miRs) are associated with impaired AMPK function in obesity and NAFLD. In this review, we discuss the emerging evidence that miRs have a role in reducing AMPK activity in NAFLD and nonalcoholic steatohepatitis (NASH), a severe form of NAFLD. We also discuss the underlying mechanisms of the aberrant expression of miRs that can negatively impact AMPK, as well as the therapeutic potential of targeting the miR-AMPK pathway for NAFLD/NASH.

Sleeve gastrectomy causes weight-loss independent improvements in hepatic steatosis

BACKGROUND AND AIMS

Sleeve gastrectomy (VSG) leads to improvement in hepatic steatosis, associated with weight loss. The aims of this study were to investigate whether VSG leads to weight-loss independent improvements in liver steatosis in mice with diet-induced obesity (DIO); and to metabolically and transcriptomically profile hepatic changes in mice undergoing VSG.

METHODS

Mice with DIO were treated with VSG, sham surgery with subsequent food restriction to weight-match to the VSG group (Sham-WM), or sham surgery with return to unrestricted diet (Sham-Ad lib). Hepatic steatosis, glucose tolerance, insulin and glucagon resistance, and hepatic transcriptomics were investigated at the end of the study period and treatment groups were compared with mice undergoing sham surgery only (Sham-Ad lib).

RESULTS

VSG led to much greater improvement in liver steatosis than Sham-WM (liver triglyceride mg/mg 2.5 ± 0.1, 2.1 ± 0.2, 1.6 ± 0.1 for Sham-AL, Sham-WM and VSG respectively; p = 0.003). Homeostatic model assessment of insulin resistance was improved following VSG only (51.2 ± 8.8, 36.3 ± 5.3, 22.3 ± 6.1 for Sham-AL, Sham-WM and VSG respectively; p = 0.03). The glucagon-alanine index, a measure of glucagon resistance, fell with VSG but was significantly increased in Sham-WM (9.8 ± 1.7, 25.8 ± 4.6 and 5.2 ± 1.2 in Sham Ad-lib, Sham-WM and VSG respectively; p = 0.0003). Genes downstream of glucagon receptor signalling which govern fatty acid synthesis (Acaca, Acacb, Me1, Acly, Fasn and Elovl6) were downregulated following VSG but upregulated in Sham-WM.

CONCLUSIONS

Changes in glucagon sensitivity may contribute to weight-loss independent improvements in hepatic steatosis following VSG.

Genetic perturbation of AMP biosynthesis extends lifespan and restores metabolic health in a naturally short-lived vertebrate

During aging, the loss of metabolic homeostasis drives a myriad of pathologies. A central regulator of cellular energy, the AMP-activated protein kinase (AMPK), orchestrates organismal metabolism. However, direct genetic manipulations of the AMPK complex in mice have, so far, produced detrimental phenotypes. Here, as an alternative approach, we alter energy homeostasis by manipulating the upstream nucleotide pool. Using the turquoise killifish, we mutate APRT, a key enzyme in AMP biosynthesis, and extend the lifespan of heterozygous males. Next, we apply an integrated omics approach to show that metabolic functions are rejuvenated in old mutants, which also display a fasting-like metabolic profile and resistance to high-fat diet. At the cellular level, heterozygous cells exhibit enhanced nutrient sensitivity, reduced ATP levels, and AMPK activation. Finally, lifelong intermittent fasting abolishes the longevity benefits. Our findings suggest that perturbing AMP biosynthesis may modulate vertebrate lifespan and propose APRT as a promising target for promoting metabolic health.

Pyridylnidulin exerts anti-diabetic properties and improves non-alcoholic fatty liver disease in diet-induced obesity mice

Introduction: Non-alcoholic fatty liver disease (NAFLD) is one of the metabolic disorders related to the pathophysiology of type 2 diabetes mellitus (T2DM). Therapeutic strategies are focused on the improvement of energy balance and lifestyle modification. Additionally, the derivative of the bioactive fungal metabolite is of interest to provide health benefits, especially in obese and pre-diabetic conditions. In our screening of anti-diabetic compounds from fungal metabolites and semisynthetic derivatives, a depsidone derivative, namely pyridylnidulin (PN), showed potent glucose uptake-inducing activity. The present study aimed to investigate the liver lipid metabolism and anti-diabetic properties of PN in diet-induced obesity mice. Methods: Male C57BL/6 mice were induced obesity and pre-diabetic conditions by dietary intervention with a high-fat diet (HFD) for 6 weeks. These obese mice were orally administered with PN (40 or 120 mg/kg), metformin (150 mg/kg), or vehicle for 4 weeks. Glucose tolerance, plasma adipocytokines, hepatic gene and protein expressions were assessed after treatment. Results: Improved glucose tolerance and reduced fasting blood glucose levels were found in the PN and metformin-treated mice. Additionally, hepatic triglyceride levels were consistent with the histopathological steatosis score regarding hepatocellular hypertrophy in the PN and metformin groups. The levels of plasma adipocytokines such as tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) were reduced in the PN (120 mg/kg) and metformin-treated mice. In addition, hepatic gene expression involved in lipid metabolism, including lipogenic enzymes was significantly reduced in the PN (120 mg/kg) and metformin-treated mice. The increased protein expression levels of phosphorylated AMP-activated protein kinase (p-AMPK) was also found in PN and metformin-treated mice. Discussion: Considering the increased p-AMPK protein expression levels in PN and metformin-treated mice were revealed as the underlying mechanisms to improve metabolic parameters. These results suggested that PN provided the health benefit to slow the progression of NAFLD and T2DM in obese and pre-diabetic conditions.

Obesity, non-alcoholic fatty liver disease and hepatocellular carcinoma: current status and therapeutic targets

Obesity is a global epidemic and overwhelming evidence indicates that it is a risk factor for numerous cancers, including hepatocellular carcinoma (HCC), the third leading cause of cancer-related deaths worldwide. Obesity-associated hepatic tumorigenesis develops from nonalcoholic fatty liver disease (NAFLD), progressing to nonalcoholic steatohepatitis (NASH), cirrhosis and ultimately to HCC. The rising incidence of obesity is resulting in an increased prevalence of NAFLD and NASH, and subsequently HCC. Obesity represents an increasingly important underlying etiology of HCC, in particular as the other leading causes of HCC such as hepatitis infection, are declining due to effective treatments and vaccines. In this review, we provide a comprehensive overview of the molecular mechanisms and cellular signaling pathways involved in the pathogenesis of obesity-associated HCC. We summarize the preclinical experimental animal models available to study the features of NAFLD/NASH/HCC, and the non-invasive methods to diagnose NAFLD, NASH and early-stage HCC. Finally, since HCC is an aggressive tumor with a 5-year survival of less than 20%, we will also discuss novel therapeutic targets for obesity-associated HCC and ongoing clinical trials.

AMPK activation protects against prostate cancer by inducing a catabolic cellular state

Emerging evidence indicates that metabolic dysregulation drives prostate cancer (PCa) progression and metastasis. AMP-activated protein kinase (AMPK) is a master regulator of metabolism, although its role in PCa remains unclear. Here, we show that genetic and pharmacological activation of AMPK provides a protective effect on PCa progression in vivo. We show that AMPK activation induces PGC1α expression, leading to catabolic metabolic reprogramming of PCa cells. This catabolic state is characterized by increased mitochondrial gene expression, increased fatty acid oxidation, decreased lipogenic potential, decreased cell proliferation, and decreased cell invasiveness. Together, these changes inhibit PCa disease progression. Additionally, we identify a gene network involved in cell cycle regulation that is inhibited by AMPK activation. Strikingly, we show a correlation between this gene network and PGC1α gene expression in human PCa. Taken together, our findings support the use of AMPK activators for clinical treatment of PCa to improve patient outcome.

Acute Kidney Injury Induces Oxidative Stress and Hepatic Lipid Accumulation through AMPK Signaling Pathway

Acute kidney injury (AKI) often impairs the function of other organs leading to distant organ injury. The liver is the major organ that regulates metabolism and lipid homeostasis in the body. It has been reported that AKI causes liver injury with increased oxidative stress, inflammatory response and steatosis. In the present study, we investigated the mechanisms by which ischemia-reperfusion-induced AKI caused hepatic lipid accumulation. Kidney ischemia (45 min)-reperfusion (24 h) led to a significant increase in plasma creatinine and transaminase in Sprague Dawley rats, indicating kidney and liver injury. Histological and biochemical analyses revealed hepatic lipid accumulation with a significant elevation of triglyceride and cholesterol levels in the liver. This was accompanied by a decreased AMP-activated protein kinase (AMPK) phosphorylation, indicating the reduced activation of AMPK, which is an energy sensor that regulates lipid metabolism. The expression of AMPK-regulated genes that were responsible for fatty acid oxidation (CPTIα, ACOX) was significantly decreased, while the expression of lipogenesis genes (SREPB-1c, ACC1) was significantly elevated. The oxidative stress biomarker malondialdehyde was elevated in the plasma and liver. Incubation of HepG2 cells with an oxidative stress inducer hydrogen peroxide inhibited AMPK phosphorylation and caused cellular lipid accumulation. This was accompanied by decreased expression of genes responsible for fatty acid oxidation and increased expression of genes responsible for lipogenesis. These results suggest that AKI elicits hepatic lipid accumulation through decreased fatty acid metabolism and increased lipogenesis. Oxidative stress may contribute, in part, to the downregulation of the AMPK signaling pathway leading to hepatic lipid accumulation and injury.

New insights into activation and function of the AMPK

The classical role of AMP-activated protein kinase (AMPK) is as a cellular energy sensor activated by falling energy status, signalled by increases in AMP to ATP and ADP to ATP ratios. Once activated, AMPK acts to restore energy homeostasis by promoting ATP-producing catabolic pathways while inhibiting energy-consuming processes. In this Review, we provide an update on this canonical (AMP/ADP-dependent) activation mechanism, but focus mainly on recently described non-canonical pathways, including those by which AMPK senses the availability of glucose, glycogen or fatty acids and by which it senses damage to lysosomes and nuclear DNA. We also discuss new findings on the regulation of carbohydrate and lipid metabolism, mitochondrial and lysosomal homeostasis, and DNA repair. Finally, we discuss the role of AMPK in cancer, obesity, diabetes, nonalcoholic steatohepatitis (NASH) and other disorders where therapeutic targeting may exert beneficial effects.

Uncarboxylated Osteocalcin Decreases SCD1 by Activating AMPK to Alleviate Hepatocyte Lipid Accumulation

Uncarboxylated osteocalcin (GluOC), a small-molecule protein specifically synthesized and secreted by osteoblasts, is important in the regulation of energy metabolism. In our previous study, GluOC was shown to be effective in ameliorating dyslipidemia and hepatic steatosis in KKAy mice. However, the underlying mechanism of GluOC action on hepatocytes has not been well validated. In this study, oleic acid/palmitic acid (OA/PA)-induced HepG2 and NCTC 1469 cells were used as non-alcoholic fatty liver disease (NAFLD) cell models, and triacylglycerol (TG) levels were measured by oil red O staining, Nile Red staining, and ELISA. The fatty acid synthesis-related protein expression was detected by real-time quantitative polymerase chain reaction, Western blotting, and immunofluorescence. The results show that GluOC reduced triglyceride levels, and decreased the expression of sterol regulatory element-binding protein-1c (SREBP-1c) and stearyl-coenzyme A desaturase 1 (SCD1). si-SCD1 mimicked the lipid accumulation-reducing effect of GluOC, while overexpression of SCD1 attenuated the effect of GluOC. In addition, GluOC activated AMP-activated protein kinase (AMPK) phosphorylation to affect lipid metabolism in hepatocytes. Overall, the results of this study suggest that GluOC decreases SCD1 by activating AMPK to alleviate hepatocyte lipid accumulation, which provides a new target for improving NAFLD in further research.

Honokiol acts as an AMPK complex agonist therapeutic in non-alcoholic fatty liver disease and metabolic syndrome

BACKGROUND

Non-alcoholic fatty liver (NAFLD) and its related metabolic syndrome have become major threats to human health, but there is still a need for effective and safe drugs to treat these conditions. Here we aimed to identify potential drug candidates for NAFLD and the underlying molecular mechanisms.

METHODS

A drug repositioning strategy was used to screen an FDA-approved drug library with approximately 3000 compounds in an in vitro hepatocyte model of lipid accumulation, with honokiol identified as an effective anti-NAFLD candidate. We systematically examined the therapeutic effect of honokiol in NAFLD and metabolic syndrome in multiple in vitro and in vivo models. Transcriptomic examination and biotin-streptavidin binding assays were used to explore the underlying molecular mechanisms, confirmed by rescue experiments.

RESULTS

Honokiol significantly inhibited metabolic syndrome and NAFLD progression as evidenced by improved hepatic steatosis, liver fibrosis, adipose inflammation, and insulin resistance. Mechanistically, the beneficial effects of honokiol were largely through AMPK activation. Rather than acting on the classical upstream regulators of AMPK, honokiol directly bound to the AMPKγ1 subunit to robustly activate AMPK signaling. Mutation of honokiol-binding sites of AMPKγ1 largely abolished the protective capacity of honokiol against NAFLD.

CONCLUSION

These findings clearly demonstrate the beneficial effects of honokiol in multiple models and reveal a previously unappreciated signaling mechanism of honokiol in NAFLD and metabolic syndrome. This study also provides new insights into metabolic disease treatment by targeting AMPKγ1 subunit-mediated signaling activation.

SAPS3 subunit of protein phosphatase 6 is an AMPK inhibitor and controls metabolic homeostasis upon dietary challenge in male mice

Inhibition of AMPK is tightly associated with metabolic perturbations upon over nutrition, yet the molecular mechanisms underlying are not clear. Here, we demonstrate the serine/threonine-protein phosphatase 6 regulatory subunit 3, SAPS3, is a negative regulator of AMPK. SAPS3 is induced under high fat diet (HFD) and recruits the PP6 catalytic subunit to deactivate phosphorylated-AMPK, thereby inhibiting AMPK-controlled metabolic pathways. Either whole-body or liver-specific deletion of SAPS3 protects male mice against HFD-induced detrimental consequences and reverses HFD-induced metabolic and transcriptional alterations while loss of SAPS3 has no effects on mice under balanced diets. Furthermore, genetic inhibition of AMPK is sufficient to block the protective phenotype in SAPS3 knockout mice under HFD. Together, our results reveal that SAPS3 is a negative regulator of AMPK and suppression of SAPS3 functions as a guardian when metabolism is perturbed and represents a potential therapeutic strategy to treat metabolic syndromes.

The therapeutic potential of arctigenin against multiple human diseases: A mechanistic review

BACKGROUND

Arctigenin (ATG), a dibenzyl butyrolactone lignan compound, is one of the major bioactive components from the medicinal plant Arctium lappa. ATG possesses remarkable therapeutic potential against a wide range of human diseases, such as cancers, immune disorders and chronical diseases. The molecular mechanisms behind the biological effects of ATG have been intensively studied.

PURPOSE

This review aims to systematically summarize the updated knowledge of the proteins and signaling pathways behind the curative property of ATG, and further analyze the potential connections between them.

METHOD

SciFinder, Pubmed, Web of Science and Cochrane Library databases were queried for publications reporting the therapeutic properties of ATG. "Arctigenin", "disease", "cancer", "inflammation", "organ damage", "infection", "toxicity" and "pharmacokinetics" were used as the searching titles.

RESULT

625 publications were identified and 95 met the inclusion criteria and exclusion criteria. 42 studies described the molecular mechanisms implicated in ATG treatments. Several proteins including phosphodiesterase subtype 4D (PDE4D), estrogen receptor (ER) β, protein phosphatase 2A (PP2A), phosphoinositide 3-kinase (PI3K) and transmembrane protein 16A (TMEM16A) are targeted by ATG in different settings. The frequently described signaling pathways are TLR4/NF-κB, PI3K/AKT/mTOR, AMP-activated protein kinase (AMPK) and nuclear factor erythroid 2-related factor 2 (Nrf-2) signalings.

CONCLUSION

Inhibition of PI3K/AKT pathway and activation of AMPK signaling play the pivotal roles in the therapeutic effects of ATG. PI3K/AKT and AMPK signaling widely link to other signaling pathways, modulating various biological processes such as anti-inflammation, anti-oxidative stress, anti-fibrosis, anti-ER stress, anti-steatosis and pro-apoptosis, which constitute the curative mechanisms of ATG against multiple human diseases.

Inhibition on XBP1s-driven lipogenesis by Qushi Huayu Decoction contributes to amelioration of hepatic steatosis induced by fructose

ETHNOPHARMACOLOGICAL RELEVANCE

Qushi Huayu Decoction (QHD) is a traditional Chinese medicine formula consisting of five herbs, which has been used for non-alcoholic fatty liver disease (NAFLD) treatment in clinic for decades in China and validated in several NAFLD animal models. The hepatic de novo lipogenesis (DNL) is enhanced greatly to contribute to steatosis in NAFLD. The spliced form of X-box binding protein 1 (XBP1s) initiates DNL independently of sterol regulatory element-binding protein (SREBP) and carbohydrate-responsive element-binding protein (ChREBP).

AIM OF THE STUDY

To disclose the mechanism of inhibition on hepatic DNL by QHD and the responsible compounds.

METHODS

The effects of QHD on hepatic DNL were evaluated in mice induced by high-fructose diet (HFru). The effects of the serum-absorbed compounds of QHD on XBP1s were evaluated in HepG2 cells induced by tunicamycin. Hepatic histology, triglyceride (TG) and nonesterified fatty acids were observed. Hepatic apolipoprotein B100 and very low-density lipoprotein were measured to reflect lipid out-transport. The mRNA expression of XBP1s and its target genes were detected by real-time polymerase chain reaction. The protein expression of TG synthetases and DNL enzymes, and inositol requirement enzyme 1 alpha (IRE1α), phosphorylated IRE1α and XBP1s were detected in liver tissue and HepG2 cells by western-blot. The binding activity of SREBP1, protein expression of ChREBP and XBP1s were detected in the nuclear extracts of liver tissue.

RESULTS

Dynamical observing suggested feeding with HFru for 2 weeks was sufficient to induce hepatic lipogenesis and XBP1s. QHD ameliorated liver steatosis without enhancing out-transport of lipids, accompanied with more inhibitory effects on DNL enzymes than TG synthetases. QHD inhibits the nuclear XBP1s without affecting ChREBP and SREBP1. In QHD, chlorogenic acid, geniposide and polydatin inhibit lipogenesis initiated by XPB1s.

CONCLUSION

QHD probably decreases hepatic DNL by inhibiting XBP1s independent of SREBP1 and ChREBP. Chlorogenic acid, geniposide and polydatin are the potential responsible compounds.

AMPK inhibits liver gluconeogenesis: fact or fiction?

Is there a role for AMPK in the control of hepatic gluconeogenesis and could targeting AMPK in liver be a viable strategy for treating type 2 diabetes? These are frequently asked questions this review tries to answer. After describing properties of AMPK and different small-molecule AMPK activators, we briefly review the various mechanisms for controlling hepatic glucose production, mainly via gluconeogenesis. The different experimental and genetic models that have been used to draw conclusions about the role of AMPK in the control of liver gluconeogenesis are critically discussed. The effects of several anti-diabetic drugs, particularly metformin, on hepatic gluconeogenesis are also considered. We conclude that the main effect of AMPK activation pertinent to the control of hepatic gluconeogenesis is to antagonize glucagon signalling in the short-term and, in the long-term, to improve insulin sensitivity by reducing hepatic lipid content.

Blocking AMPK β1 myristoylation enhances AMPK activity and protects mice from high-fat diet-induced obesity and hepatic steatosis

AMP-activated protein kinase (AMPK) is a master regulator of cellular energy homeostasis and a therapeutic target for metabolic diseases. Co/post-translational N-myristoylation of glycine-2 (Gly2) of the AMPK β subunit has been suggested to regulate the distribution of the kinase between the cytosol and membranes through a "myristoyl switch" mechanism. However, the relevance of AMPK myristoylation for metabolic signaling in cells and in vivo is unclear. Here, we generated knockin mice with a Gly2-to-alanine point mutation of AMPKβ1 (β1-G2A). We demonstrate that non-myristoylated AMPKβ1 has reduced stability but is associated with increased kinase activity and phosphorylation of the Thr172 activation site in the AMPK α subunit. Using proximity ligation assays, we show that loss of β1 myristoylation impedes colocalization of the phosphatase PPM1A/B with AMPK in cells. Mice carrying the β1-G2A mutation have improved metabolic health with reduced adiposity, hepatic lipid accumulation, and insulin resistance under conditions of high-fat diet-induced obesity.

Camel milk protein hydrosylate alleviates hepatic steatosis and hypertension in high fructose-fed rats

CONTEXT

Camel milk is used in traditional medicine to treat diabetes mellitus hypertension and other metabolic disorders.

OBJECTIVE

This study evaluated the antisteatotic and antihypertensive effects of camel milk protein hydrolysate (CMH) in high fructose (HF)-fed rats and compared it with the effects afforded by the intact camel milk protein extract (ICM).

MATERIALS AND METHODS

Adult male Wistar rats were divided into 6 groups (n = 8 each) as 1) control, 2) ICM (1000 mg/kg), 3) CMH (1000 mg/kg), 4) HF (15% in drinking water), 5) HF (15%) + ICM (1000 mg/kg), and 6) HF (15%) + CMH (1000 mg/kg). All treatments were given orally for 21 weeks, daily.

RESULTS

Both ICM and CMH reduced fasting glucose and insulin levels, serum and hepatic levels of cholesterol and triglycerides, and serum levels of ALT and AST, angiotensin II, ACE, endothelin-1, and uric acid in HF-fed rats. In addition, both ICM and CMH reduced hepatic fat deposition in the hepatocytes and reduced hepatocyte damage. This was associated with an increase in the hepatic activity of AMPK, higher PPARα mRNA, reduced expression of fructokinase C, SREBP1, SREBP2, fatty acid synthase, and HMG-CoA-reductase. Both treatments lowered systolic and diastolic blood pressure. However, the effects of CMH on all these parameters were greater as compared to ICM.

DISCUSSION AND CONCLUSIONS

The findings of this study encourage the use of CMH in a large-scale population and clinical studies to treat metabolic steatosis and hypertension.

Stachydrine alleviates lipid-induced skeletal muscle insulin resistance via AMPK/HO-1-mediated suppression of inflammation and endoplasmic reticulum stress

OBJECTIVE

Insulin resistance develops due to skeletal muscle inflammation and endoplasmic reticulum (ER) stress. Stachydrine (STA), extracted from Leonurus heterophyllus, has been shown to suppress proliferation and induce apoptosis in breast cancer cells and exert anti-inflammatory properties in the brain, heart, and liver. However, the roles of STA in insulin signaling in skeletal muscle remain unclear. Herein, we examined the impacts of STA on insulin signaling in skeletal muscle under hyperlipidemic conditions and its related molecular mechanisms.

METHODS

Various protein expression levels were determined by Western blotting. Levels of mouse serum cytokines were measured by ELISA.

RESULTS

We found that STA-ameliorated inflammation and ER stress, leading to attenuation of insulin resistance in palmitate-treated C2C12 myocytes. STA dose-dependently enhanced AMPK phosphorylation and HO-1 expression. Administration of STA attenuated not only insulin resistance but also inflammation and ER stress in the skeletal muscle of high-fat diet (HFD)-fed mice. Additionally, STA-ameliorated glucose tolerance and insulin sensitivity, as well as serum TNFα and MCP-1, in mice fed a HFD. Small interfering (si) RNA-associated suppression of AMPK or HO-1 expression abolished the effects of STA in C2C12 myocytes.

CONCLUSIONS

These results suggest that STA activates AMPK/HO-1 signaling, resulting in reduced inflammation and ER stress, thereby improving skeletal muscle insulin resistance. Using STA as a natural ingredient, this research successfully treated insulin resistance and type 2 diabetes.

The aldolase inhibitor aldometanib mimics glucose starvation to activate lysosomal AMPK

The activity of 5'-adenosine monophosphate-activated protein kinase (AMPK) is inversely correlated with the cellular availability of glucose. When glucose levels are low, the glycolytic enzyme aldolase is not bound to fructose-1,6-bisphosphate (FBP) and, instead, signals to activate lysosomal AMPK. Here, we show that blocking FBP binding to aldolase with the small molecule aldometanib selectively activates the lysosomal pool of AMPK and has beneficial metabolic effects in rodents. We identify aldometanib in a screen for aldolase inhibitors and show that it prevents FBP from binding to v-ATPase-associated aldolase and activates lysosomal AMPK, thereby mimicking a cellular state of glucose starvation. In male mice, aldometanib elicits an insulin-independent glucose-lowering effect, without causing hypoglycaemia. Aldometanib also alleviates fatty liver and nonalcoholic steatohepatitis in obese male rodents. Moreover, aldometanib extends lifespan and healthspan in both Caenorhabditis elegans and mice. Taken together, aldometanib mimics and adopts the lysosomal AMPK activation pathway associated with glucose starvation to exert physiological roles, and might have potential as a therapeutic for metabolic disorders in humans.

FGF4 protects the liver from nonalcoholic fatty liver disease by activating the AMP-activated protein kinase-Caspase 6 signal axis

BACKGROUND AND AIMS

NAFLD represents an increasing health problem in association with obesity and diabetes with no effective pharmacotherapies. Growing evidence suggests that several FGFs play important roles in diverse aspects of liver pathophysiology. Here, we report a previously unappreciated role of FGF4 in the liver.

APPROACH AND RESULTS

Expression of hepatic FGF4 is inversely associated with NAFLD pathological grades in both human patients and mouse models. Loss of hepatic Fgf4 aggravates hepatic steatosis and liver damage resulted from an obesogenic high-fat diet. By contrast, pharmacological administration of recombinant FGF4 mitigates hepatic steatosis, inflammation, liver damage, and fibrogenic markers in mouse livers induced to develop NAFLD and NASH under dietary challenges. Such beneficial effects of FGF4 are mediated predominantly by activating hepatic FGF receptor (FGFR) 4, which activates a downstream Ca²⁺ -Ca²⁺ /calmodulin-dependent protein kinase kinase beta-dependent AMP-activated protein kinase (AMPK)-Caspase 6 signal axis, leading to enhanced fatty acid oxidation, reduced hepatocellular apoptosis, and mitigation of liver damage.

CONCLUSIONS

Our study identifies FGF4 as a stress-responsive regulator of liver pathophysiology that acts through an FGFR4-AMPK-Caspase 6 signal pathway, shedding light on strategies for treating NAFLD and associated liver pathologies.

A non-mitogenic FGF4 analog alleviates non-alcoholic steatohepatitis through an AMPK-dependent pathway

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) has emerged as a major liver disease increasingly in association with non-alcoholic steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma (HCC). However, there are currently no approved therapies for treating NAFLD and NASH. Fibroblast growth factor 4 (FGF4) has recently been shown as a promising drug candidate for several metabolic diseases.

METHODS

Mice fed a high-fat diet with high fructose/glucose drinking water (HF/HFG, Western-like diet) for 21 weeks were intraperitoneally injected with non-mitogenic recombinant FGF4^△NT (rFGF4^△NT, 1.0 mg/kg body weight) every other day for 8 weeks. Primary mouse hepatocytes cultured in medium containing high glucose/palmitic acid (HG/PA) or TNFα/cyclohexane (TNFα/CHX) were treated with 1.0 μg/ml rFGF4^△NT. Changes in parameters for histopathology, lipid metabolism, inflammation, hepatocellular apoptosis and fibrosis were determined. The Caspase6 activity and AMPK pathway were assessed.

RESULTS

Administration of rFGF4^△NT significantly attenuated the Western-like diet-induced hepatic steatosis, inflammation, liver injury and fibrosis in mice. rFGF4^△NT treatment reduced fatty acid-induced lipid accumulation and lipotoxicity-induced hepatocyte apoptosis, which were associated with inhibition of Caspase6 cleavage and activation. Inhibition of AMP-activated protein kinase (AMPK) by Compound C or deficiency of Ampk abrogated rFGF4^△NT-induced hepatoprotection in primary hepatocytes and in mice with NASH.

CONCLUSION

rFGF4^△NT exerts significant protective effects on NASH via an AMPK-dependent signaling pathway. Our study indicates that FGF4 analogs may have therapeutic potential for the Western-like diet induced NASH.

Obesity-induced miR-802 directly targets AMPK and promotes nonalcoholic steatohepatitis in mice

OBJECTIVE

Obesity-associated nonalcoholic fatty liver disease (NAFLD) is a leading cause of liver failure and death. However, the pathogenesis of NAFLD and its severe form, nonalcoholic steatohepatitis (NASH), is poorly understood. The energy sensor, AMP-activated protein kinase (AMPK), has decreased activity in obesity and NAFLD, but the mechanisms are unclear. Here, we examined whether obesity-induced miR-802 has a role in promoting NASH by targeting AMPK. We also investigated whether miR-802 and AMPK have roles in modulating beneficial therapeutic effects mediated by obeticholic acid (OCA), a promising clinical agent for NASH.

METHODS

Immunoblotting, luciferase assays, and RNA-protein interaction studies were performed to test whether miR-802 directly targets AMPK. The roles of miR-802 and AMPK in NASH were examined in mice fed a NASH-promoting diet.

RESULTS

Hepatic miR-802 and AMPK levels were inversely correlated in both NAFLD patients and obese mice. MicroRNA in silico analysis, together with biochemical studies in hepatic cells, suggested that miR-802 inhibits hepatic expression of AMPK by binding to the 3' untranslated regions of both human AMPKα1 and mouse Ampkβ1. In diet-induced NASH mice, OCA treatment reduced hepatic miR-802 levels and improved AMPK activity, ameliorating steatosis, inflammation, and apoptosis, but these OCA-mediated beneficial effects on NASH pathologies, particularly reducing apoptosis, were reversed by overexpression of miR-802 or downregulation of AMPK.

CONCLUSIONS

These results indicate that miR-802 inhibits AMPK by directly targeting Ampkβ1, promoting NAFLD/NASH in mice. The miR-802-AMPK axis that modulates OCA-mediated beneficial effects on NASH may represent a new therapeutic target.

Hepatocyte cholesterol content modulates glucagon receptor signalling

OBJECTIVE

To determine whether glucagon receptor (GCGR) actions are modulated by cellular cholesterol levels.

METHODS

We determined the effects of experimental cholesterol depletion and loading on glucagon-mediated cAMP production, ligand internalisation and glucose production in human hepatoma cells, mouse and human hepatocytes. GCGR interactions with lipid bilayers were explored using coarse-grained molecular dynamic simulations. Glucagon responsiveness was measured in mice fed a high cholesterol diet with or without simvastatin to modulate hepatocyte cholesterol content.

RESULTS

GCGR cAMP signalling was reduced by higher cholesterol levels across different cellular models. Ex vivo glucagon-induced glucose output from mouse hepatocytes was enhanced by simvastatin treatment. Mice fed a high cholesterol diet had increased hepatic cholesterol and a blunted hyperglycaemic response to glucagon, both of which were partially reversed by simvastatin. Simulations identified likely membrane-exposed cholesterol binding sites on the GCGR, including a site where cholesterol is a putative negative allosteric modulator.

CONCLUSIONS

Our results indicate that cellular cholesterol content influences glucagon sensitivity and indicate a potential molecular basis for this phenomenon. This could be relevant to the pathogenesis of non-alcoholic fatty liver disease, which is associated with both hepatic cholesterol accumulation and glucagon resistance.

IL11 stimulates ERK/P90RSK to inhibit LKB1/AMPK and activate mTOR initiating a mesenchymal program in stromal, epithelial, and cancer cells

IL11 initiates fibroblast activation but also causes epithelial cell dysfunction. The mechanisms underlying these processes are not known. We report that IL11-stimulated ERK/P90RSK activity causes the phosphorylation of LKB1 at S325 and S428, leading to its inactivation. This inhibits AMPK and activates mTOR across cell types. In stromal cells, IL11-stimulated ERK activity inhibits LKB1/AMPK which is associated with mTOR activation, ⍺SMA expression, and myofibroblast transformation. In hepatocytes and epithelial cells, IL11/ERK activity inhibits LKB1/AMPK leading to mTOR activation, SNAI1 expression, and cell dysfunction. Across cells, IL11-induced phenotypes were inhibited by metformin stimulated AMPK activation. In mice, genetic or pharmacologic manipulation of IL11 activity revealed a critical role of IL11/ERK signaling for LKB1/AMPK inhibition and mTOR activation in fatty liver disease. These data identify the IL11/mTOR axis as a signaling commonality in stromal, epithelial, and cancer cells and reveal a shared IL11-driven mesenchymal program across cell types.

Lower serum copper concentrations are associated with higher prevalence of nonalcoholic steatohepatitis: a matched case-control study

BACKGROUND AND AIM

Copper is an essential trace element involved in oxidative stress reactions and energy metabolism. While nonalcoholic fatty liver disease (NAFLD) is closely related to metabolic dysfunction, the role of copper in the development of simple steatosis (NAFL) and nonalcoholic steatohepatitis (NASH) is still unclear. We aimed to compare serum copper levels between patients with simple steatosis and those with NASH.

METHODS AND RESULTS

We studied 102 patients with biopsy-proven NASH (cases) and 102 NAFL controls, who were matched for age, sex, and residential city. Multivariable conditional logistic analysis was performed to explore associations between serum copper levels and the presence of NASH. Serum copper levels were significantly lower in patients with NASH than in those with matched NAFL controls (15.53 ± 2.41 μmol/l vs. 16.34 ± 3.23 μmol/l; P = 0.029). This intergroup difference in serum copper levels was more pronounced in men than in women. The per unit, per SD, and per doubling of serum copper levels were associated, respectively, with an approximately 20, 40, and 90% decrease in risk of having NASH, even after adjustment for potential confounding factors.

CONCLUSION

Lower serum copper concentrations are significantly associated with higher prevalence of NASH among biopsied-proven NAFLD patients, particularly in men.

Polydatin, A Glycoside of Resveratrol, Is Better Than Resveratrol in Alleviating Non-alcoholic Fatty Liver Disease in Mice Fed a High-Fructose Diet

Resveratrol (RES) is considered to be an activator of AMP-activated protein kinase (AMPK) with many reported health benefits. Polydatin (POD) is a natural precursor and glycosylated form of RES. The glycoside structure of POD alters the bioactivity. Overnutrition-stimulated reactive oxygen species (ROS) promote the AMPK suppression and metabolic dysregulation. The present work compared the effects of POD and RES in ameliorating energy homeostasis imbalance in mice fed a high-fructose diet and elucidated the underlying mechanisms of action. Our results showed that POD elevated the fecal levels of valeric acid and caproic acid via modification of gut microbiota, while RES did not significantly influence the levels of fecal short-chain fatty acids (SCFAs). Both POD and RES markedly decreased the oxidative stress and activated the AMPK signaling pathways in the liver. POD and RES exerted a similar effect in alleviating glucose dysmetabolism, but POD was more effective in ameliorating lipid dysmetabolism than RES. Furthermore, valeric acid and caproic acid alone can activate the AMPK and ameliorate hypercholesterolemia, and enhance the effects of POD on improving lipid metabolism in mice. Overall, for the first time, we demonstrated that POD administration elevated the fecal levels of valeric acid and caproic acid by modifying gut microbiota, thus promoting AMPK activation may be the underlying mechanism that POD is superior to RES in alleviating the lipid dysmetabolism. Our results suggest that POD may be an alternative for RES as an AMPK activator.

Opposing effects on regulated insulin secretion of acute vs chronic stimulation of AMP-activated protein kinase

AIMS/HYPOTHESIS

Although targeted in extrapancreatic tissues by several drugs used to treat type 2 diabetes, the role of AMP-activated protein kinase (AMPK) in the control of insulin secretion is still debatable. Previous studies have used pharmacological activators of limited selectivity and specificity, and none has examined in primary pancreatic beta cells the actions of the latest generation of highly potent and specific activators that act via the allosteric drug and metabolite (ADaM) site.

METHODS

AMPK was activated acutely in islets isolated from C57BL6/J mice, and in an EndoC-βH3 cell line, using three structurally distinct ADaM site activators (991, PF-06409577 and RA089), with varying selectivity for β1- vs β2-containing complexes. Mouse lines expressing a gain-of-function mutation in the γ1 AMPK subunit (D316a) were generated to examine the effects of chronic AMPK stimulation in the whole body, or selectively in the beta cell.

RESULTS

Acute (1.5 h) treatment of wild-type mouse islets with 991, PF-06409577 or RA089 robustly stimulated insulin secretion at high glucose concentrations (p<0.01, p<0.05 and p<0.001, respectively), despite a lowering of glucose-induced intracellular free Ca2+ dynamics in response to 991 (AUC, p<0.05) and to RA089 at the highest dose (25 μmol/l) at 5.59 min (p<0.05). Although abolished in the absence of AMPK, the effects of 991 were observed in the absence of the upstream kinase, liver kinase B1, further implicating 'amplifying' pathways. In marked contrast, chronic activation of AMPK, either globally or selectively in the beta cell, achieved using a gain-of-function mutant, impaired insulin release in vivo (p<0.05 at 15 min following i.p. injection of 3 mmol/l glucose) and in vitro (p<0.01 following incubation of islets with 17 mmol/l glucose), and lowered glucose tolerance (p<0.001).

CONCLUSIONS/INTERPRETATION

AMPK activation exerts complex, time-dependent effects on insulin secretion. These observations should inform the design and future clinical use of AMPK modulators.

Mitochondrial phosphatidylethanolamine synthesis affects mitochondrial energy metabolism and quiescence entry through attenuation of Snf1/AMPK signaling in yeast

The Ups2-Mdm35 complex mediates intramitochondrial phosphatidylserine (PS) transport to facilitate mitochondrial phosphatidylethanolamine (PE) synthesis. In the present study, we found that ups2∆ yeast showed increased mitochondrial ATP production and enhanced quiescence (G0) entry in the post-diauxic shift phase. Transcriptomic and biochemical analyses revealed that the depletion of Ups2 leads to overactivation of the yeast AMPK homolog Snf1. Inactivation of Snf1 by depletion of an Snf1-activating kinase, Sak1 canceled the changes in mitochondrial ATP production and quiescence entry observed in ups2∆ cells. Furthermore, among the factors regulated by Snf1, upregulation of pyruvate carboxylase, Pyc1 and downregulation of acetyl-CoA carboxylase, Acc1, respectively, were sufficient to increase mitochondrial ATP production and quiescence entry. These results suggested that a normal PE synthesis mediated by Ups2-Mdm35 complex attenuates Snf1/AMPK activity, and that Snf1-mediated regulation of carbon metabolisms has great impacts on mitochondrial energy metabolism and quiescence entry. We also found that depletion of Ups2 together with the cell-cycle regulators Whi5 and Whi7, functional orthologs of the Rb1 tumor suppressor, caused a synthetic growth defect in yeast. Similarly, knockdown of PRELID3b, the human homolog of Ups2, decreased the viability of Rb1-deficient breast cancer cells, suggesting that PRELID3b is a potential target for cancer therapy.

Liver PP2A-Cα Protects From Parenteral Nutrition-associated Hepatic Steatosis

BACKGROUND & AIMS

Parenteral nutrition (PN) is a lifesaving therapy for patients with intestinal failure. Hepatic steatosis is a potentially fatal complication of long-term PN, but the involved pathological mechanisms are incompletely unclarified. Herein, we identify the role of protein phosphatase 2A (PP2A) in the pathogenesis of parenteral nutrition-associated hepatic steatosis (PNAHS).

METHODS

Proteomic/phosphoproteomic analyses of liver samples from patients with PNAHS were applied to identify the mechanism of PNAHS. Total parenteral nutrition (TPN) mice model, in vivo, and in vitro experiments were used to assess the effect of PP2A-Cα on liver fatty acid metabolism.

RESULTS

Reduced expression of PP2A-Cα (catalytic subunit) enhanced activation of serine/threonine kinase Akt2 and decreased activation of adenosine monophosphate-activated protein kinase (AMPK) were associated with hepatic steatosis in patients with PNAHS. Mice given PN for 14 days developed hepatic steatosis, down-regulation of PP2A-Cα, activation of Akt2, and inhibition of AMPK. Hepatocyte-specific deletion of PP2A-Cα in mice given PN exacerbated Akt2 activation, AMPK inhibition, and hepatic steatosis through an effect on fatty acid degradation, whereas hepatocyte-specific PP2A-Cα overexpression significantly ameliorated hepatic steatosis accompanied with Akt2 suppression and AMPK activation. Additionally, pharmacological activation of Akt2 in mice overexpressing PP2A-Cα led to the aggravation of hepatic steatosis.

CONCLUSIONS

Our findings demonstrate that hepatic PP2A-Cα serves as a protective factor of PNAHS due to ameliorating hepatic steatosis and improving liver function. Our study provides a strong rationale that PP2A-Cα may be involved in the pathogenesis of PNAHS.

Hepatic IRF3 fuels dysglycemia in obesity through direct regulation of Ppp2r1b

Inflammation has profound but poorly understood effects on metabolism, especially in the context of obesity and nonalcoholic fatty liver disease (NAFLD). Here, we report that hepatic interferon regulatory factor 3 (IRF3) is a direct transcriptional regulator of glucose homeostasis through induction of Ppp2r1b, a component of serine/threonine phosphatase PP2A, and subsequent suppression of glucose production. Global ablation of IRF3 in mice on a high-fat diet protected against both steatosis and dysglycemia, whereas hepatocyte-specific loss of IRF3 affects only dysglycemia. Integration of the IRF3-dependent transcriptome and cistrome in mouse hepatocytes identifies Ppp2r1b as a direct IRF3 target responsible for mediating its metabolic actions on glucose homeostasis. IRF3-mediated induction of Ppp2r1b amplified PP2A activity, with subsequent dephosphorylation of AMPKα and AKT. Furthermore, suppression of hepatic Irf3 expression with antisense oligonucleotides reversed obesity-induced insulin resistance and restored glucose homeostasis in obese mice. Obese humans with NAFLD displayed enhanced activation of liver IRF3, with reversion after bariatric surgery. Hepatic PPP2R1B expression correlated with HgbA1C and was elevated in obese humans with impaired fasting glucose. We therefore identify the hepatic IRF3-PPP2R1B axis as a causal link between obesity-induced inflammation and dysglycemia and suggest an approach for limiting the metabolic dysfunction accompanying obesity-associated NAFLD.

AMPK and the Adaptation to Exercise

Noncommunicable diseases are chronic diseases that contribute to death worldwide, but these diseases can be prevented and mitigated with regular exercise. Exercise activates signaling molecules and the transcriptional network to promote physiological adaptations, such as fiber type transformation, angiogenesis, and mitochondrial biogenesis. AMP-activated protein kinase (AMPK) is a master regulator that senses the energy state, promotes metabolism for glucose and fatty acid utilization, and mediates beneficial cellular adaptations in many vital tissues and organs. This review focuses on the current, integrative understanding of the role of exercise-induced activation of AMPK in the regulation of system metabolism and promotion of health benefits.

Chitosan oligosaccharide regulates AMPK and STAT1 pathways synergistically to mediate PD-L1 expression for cancer chemoimmunotherapy

After regular chemotherapy, the expression of programmed cell death ligand 1 (PD-L1) in almost all kinds of cancers is significantly increased, leading to reduced efficacy of T cell mediated immune killing in tumors. To solve this, a lot of PD-L1 antibodies were produced and used, but their high cost and serious toxic side effects still limit its usage. Recently, small molecule compounds that could effectively regulate PD-L1 expression possess the edges to solve the problems of PD-L1 antibodies. Chitosan oligosaccharide (COS), a biomaterial derived from the N-deacetylation product of chitin, has a broad spectrum of biological activities in treating tumors. However, the mechanism of its anti-cancer effect is still not well understood. Here, for the first time, we clearly identified that COS could inhibit the upregulated PD-L1 expression induced by interferon γ (IFN-γ) in various tumors via the AMPK activation and STAT1 inhibition. Besides, COS itself significantly restricted the growth of CT26 tumors by enhancing the T cell infiltration in tumors. Furthermore, we observed that combining COS with Gemcitabine (GEM), one of the typical chemotherapeutic drugs, leaded to a more remarkable tumor remission. Therefore, it was demonstrated that COS could be used as a useful way to improve the efficacy of existing chemotherapies by effective PD-L1 downregulation.

Direct AMPK Activation Corrects NASH in Rodents Through Metabolic Effects and Direct Action on Inflammation and Fibrogenesis

No approved therapies are available for nonalcoholic steatohepatitis (NASH). Adenosine monophosphate-activated protein kinase (AMPK) is a central regulator of cell metabolism; its activation has been suggested as a therapeutic approach to NASH. Here we aimed to fully characterize the potential for direct AMPK activation in preclinical models and to determine mechanisms that could contribute to efficacy for this disease. A novel small-molecule direct AMPK activator, PXL770, was used. Enzyme activity was measured with recombinant complexes. De novo lipogenesis (DNL) was quantitated in vivo and in mouse and human primary hepatocytes. Metabolic efficacy was assessed in ob/ob and high-fat diet-fed mice. Liver histology, biochemical measures, and immune cell profiling were assessed in diet-induced NASH mice. Direct effects on inflammation and fibrogenesis were assessed using primary mouse and human hepatic stellate cells, mouse adipose tissue explants, and human immune cells. PXL770 directly activated AMPK in vitro and reduced DNL in primary hepatocytes. In rodent models with metabolic syndrome, PXL770 improved glycemia, dyslipidemia, and insulin resistance. In mice with NASH, PXL770 reduced hepatic steatosis, ballooning, inflammation, and fibrogenesis. PXL770 exhibited direct inhibitory effects on pro-inflammatory cytokine production and activation of primary hepatic stellate cells. Conclusion: In rodent models, direct activation of AMPK is sufficient to produce improvements in all core components of NASH and to ameliorate related hyperglycemia, dyslipidemia, and systemic inflammation. Novel properties of direct AMPK activation were also unveiled: improved insulin resistance and direct suppression of inflammation and fibrogenesis. Given effects also documented in human cells (reduced DNL, suppression of inflammation and stellate cell activation), these studies support the potential for direct AMPK activation to effectively treat patients with NASH.

The protease SENP2 controls hepatic gluconeogenesis by regulating the SUMOylation of the fuel sensor AMPKα

Uncontrolled gluconeogenesis results in elevated hepatic glucose production in type 2 diabetes. The SUMO-specific protease 2 (SENP2) is known to catalyze deSUMOylation of target proteins, with broad effects on cell growth, signal transduction, and developmental processes. However, the role of SENP2 in hepatic gluconeogenesis and the occurrence of type 2 diabetes remains unknown. Herein, we established SENP2 hepatic knockout mice and found that SENP2 deficiency could protect against high fat diet-induced hyperglycemia. Pyruvate or glucagon-induced elevation in blood glucose was attenuated by disruption of SENP2 expression, whereas overexpression of SENP2 in the liver facilitated high fat diet-induced hyperglycemia. Using an in vitro assay, we showed that SENP2 regulated hepatic glucose production. Mechanistically, the effects of SENP2 on gluconeogenesis were found to be mediated by the cellular fuel sensor kinase AMPKα, which is a negative regulator of gluconeogenesis. SENP2 interacted with and deSUMOylated AMPKα, thereby promoting its ubiquitination and reducing its protein stability. Inhibition of AMPKα kinase activity dramatically reversed impaired hepatic gluconeogenesis and reduced blood glucose levels in SENP2-deficient mice. Our study highlights the novel role of hepatic SENP2 in regulating gluconeogenesis and furthers our understanding of the pathogenesis of type 2 diabetes.

Specificities of lipotoxicity of free fatty acids and cytokine profile in patients with chronic diffuse liver diseases

Non-alcoholic fatty liver disease is an important cause of global liver disease characterized by diffuse hepatocytes with hepatocellular ballooning, intrahepatic inflammation and progressive fibrosis. A relevant task is the study of the relationship between content of free fatty acids and serum cytokine profile in patients with chronic diffuse liver diseases. A total of 74 people with chronic diffuse liver diseases were examined, including 32 patients with non-alcoholic fatty liver disease, 22 patients with alcoholic liver disease, 20 patients with toxic hepatitis. Chromatographic examination of free fatty acids (FFA) in blood serum was carried out using a Chromatek-Crystal 5000 gas chromatography system. Patients with chronic diffuse liver diseases had a significant increase in the level of unsaturated free fatty acids (USFA) in cases of toxic hepatitis (by 2.92 times, P > 0.05) and a decrease in the level of saturated free fatty acids (SFA) in cases of non-alcoholic fatty liver disease (by 1.52 times, P > 0.05) compared with the control group; the balance between omega-6 and omega-3 PUFA significantly changed due to increase in linoleic acid in patients with alcoholic liver disease and toxic hepatitis (by 1.91 and 2.11 times, respectively) and arachidonic acid in patients with toxic hepatitis (by 1.78 times). The level of interleukin (IL)-6, IL-10, tumor necrosis factor alpha (TNF-α) were determined. In patients suffering chronic diffuse liver diseases there were multidirectional changes in the composition of free fatty acids of blood serum: a significant increase in the level of USFA, levels ІL-6 in toxic hepatitis; a decrease in the level of SFA, levels ІL-6 and TNF-α during non-alcoholic fatty liver disease; increased TNF-α production, ІL-6 during alcoholic liver disease compared with the control group. Significant change occurred in the balance between omega-6 and omega-3 PUFA due to increase in linoleic acid in cases of alcoholic liver disease and toxic hepatitis and arachidonic acid in cases of toxic hepatitis. The revealed correlations support the hypothesis that inflammation and lipotoxicity of FFA of blood serum contribute to the development and progression of structural changes in the liver. However, the pathomechanism of lipid metabolism and cytokine regulation with different etiological factors have their own characteristics, which should be taken into account when treating patients of these groups. Prospects for further research: these parameters may be used for serologic biomarkers of liver disease and development and implementation of the ratio between FFA and cytokines for the differential diagnosis of chronic diffuse liver disease in medical practice.

Protective Effects and Mechanisms of Polyethylene Glycol Loxenatide Against Hyperglycemia and Liver Injury in db/db diabetic Mice

Background: Type 2 diabetes mellitus (T2DM) is a metabolic disorder with insulin resistance and impaired insulin secretion that can cause complications, including liver injury. Polyethylene glycol loxenatide (PEG-Loxe), a glucagon-like peptide-1 (GLP-1) analog, is widely used to treat T2DM. However, its specific glucose-lowering and hepatoprotective mechanisms of action have not been established yet.

METHODS: Using a high glucose-induced hepatocyte injury model and a type 2 diabetic db/db mouse model, we assessed PEG-Loxe’s impact on reducing blood glucose and improving liver injury in T2DM and revealed its mechanism.

RESULTS: PEG-Loxe treatment significantly reduced body weight and fasting glucose, increased glucose tolerance, improved serum and liver biochemical parameters (glycated hemoglobin, serum insulin, triglycerides, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, alanine aminotransferase, and aspartate aminotransferase), and attenuated hepatic steatosis and liver and pancreatic tissue damages in db/db mice. Additionally, PEG-Loxe considerably inhibited oxidative stress, decreased pro-inflammatory factor (TNF-α, IL-6, and MCP-1) levels, and increased anti-inflammatory factor IL-10 levels. PEG-Loxe possibly inhibits hepatic lipid synthesis, oxidative stress, and inflammatory response by upregulating Sirt1, p-AMPK, and p-ACC expressions in the Sirt1/AMPK/ACC pathway of lipid metabolism, thereby improving T2DM liver injury. PEG-Loxe most likely also promotes GLP-1R expression by inhibiting β-cell apoptosis, which in turn activates the insulin PI3K/AKT pathway to promote insulin synthesis and secretion, thereby exerting hypoglycemic effects. In vitro cellular experiments further confirmed that PEG-Loxe possibly exerts hypoglycemic effects by activating the insulin PI3K/AKT pathway.

Conclusion: PEG-Loxe improved liver injury in T2DM probably by activating Sirt1/AMPK/ACC lipid metabolism pathway, and exerted hypoglycemic effects through activation of insulin PI3K/AKT pathway.

Pharmacodynamic effects of direct AMP kinase activation in humans with insulin resistance and non-alcoholic fatty liver disease: A phase 1b study

AMPK is an energy sensor modulating metabolism, inflammation, and a target for metabolic disorders. Metabolic dysfunction results in lower AMPK activity. PXL770 is a direct AMPK activator, inhibiting de novo lipogenesis (DNL) and producing efficacy in preclinical models. We aimed to assess pharmacokinetics, safety, and pharmacodynamics of PXL770 in humans with metabolic syndrome-associated fatty liver disease. In a randomized, double-blind four-week trial, 12 overweight/obese patients with non-alcoholic fatty liver disease (NAFLD) and insulin resistance received PXL770 500 mg QD; 4 subjects received matching placebo. Endpoints included pharmacokinetics, hepatic fractional DNL, oral glucose tolerance testing, additional pharmacodynamic parameters, and safety. PK parameters show adequate plasma exposure in NAFLD patients for daily oral dosing. PXL770 decreases DNL—both peak and AUC are reduced versus baseline—and improves glycemic parameters and indices of insulin sensitivity versus baseline. Assessment of specific lipids reveals decrease in diacyglycerols/triacylglycerols. Safety/tolerability are similar to placebo. These results unveil initial human translation of AMPK activation and support this therapeutic strategy for metabolic disorders.

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AMPK is impaired in metabolic diseases—PXL770 is a direct AMPK activator

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In humans with NAFLD, PXL770 inhibits hepatic de novo lipogenesis (target engagement)

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PXL770 also improves glucose tolerance and insulin sensitivity

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PXL770 reduces plasma levels of di- and triglycerides

Integrated or Independent Actions of Metformin in Target Tissues Underlying Its Current Use and New Possible Applications in the Endocrine and Metabolic Disorder Area

Metformin is considered the first-choice drug for type 2 diabetes treatment. Actually, pleiotropic effects of metformin have been recognized, and there is evidence that this drug may have a favorable impact on health beyond its glucose-lowering activity. In summary, despite its long history, metformin is still an attractive research opportunity in the field of endocrine and metabolic diseases, age-related diseases, and cancer. To this end, its mode of action in distinct cell types is still in dispute. The aim of this work was to review the current knowledge and recent findings on the molecular mechanisms underlying the pharmacological effects of metformin in the field of metabolic and endocrine pathologies, including some endocrine tumors. Metformin is believed to act through multiple pathways that can be interconnected or work independently. Moreover, metformin effects on target tissues may be either direct or indirect, which means secondary to the actions on other tissues and consequent alterations at systemic level. Finally, as to the direct actions of metformin at cellular level, the intracellular milieu cooperates to cause differential responses to the drug between distinct cell types, despite the primary molecular targets may be the same within cells. Cellular bioenergetics can be regarded as the primary target of metformin action. Metformin can perturb the cytosolic and mitochondrial NAD/NADH ratio and the ATP/AMP ratio within cells, thus affecting enzymatic activities and metabolic and signaling pathways which depend on redox- and energy balance. In this context, the possible link between pyruvate metabolism and metformin actions is extensively discussed.

Comparative impact of dietary carbohydrates on the liver transcriptome in two strains of mice

Excessive long-term consumption of dietary carbohydrates, including glucose, sucrose, or fructose, has been shown to have significant impact on genome-wide gene expression, which likely results from changes in metabolic substrate flux. However, there has been no comprehensive study on the acute effects of individual sugars on the genome-wide gene expression that may reveal the genetic changes altering signaling pathways, subsequent metabolic processes, and ultimately physiological/pathological responses. Considering that gene expressions in response to acute carbohydrate ingestion might be different in nutrient sensitive and insensitive mammals, we conducted comparative studies of genome-wide gene expression by deep mRNA sequencing of the liver in nutrient sensitive C57BL/6J and nutrient insensitive BALB/cJ mice. Furthermore, to determine the temporal responses, we compared livers from mice in the fasted state and following ingestion of standard laboratory mouse chow supplemented with plain drinking water or water containing 20% glucose, sucrose, or fructose. Supplementation with these carbohydrates induced unique extents and temporal changes in gene expressions in a strain specific manner. Fructose and sucrose stimulated gene changes peaked at 3 h postprandial, whereas glucose effects peaked at 12 h and 6 h postprandial in C57BL/6J and BABL/cJ mice, respectively. Network analyses revealed that fructose changed genes were primarily involved in lipid metabolism and were more complex in C57BL/6J than in BALB/cJ mice. These data demonstrate that there are qualitative and antitative differences in the normal physiological responses of the liver between these two strains of mice and C57BL/6J is more sensitive to sugar intake than BALB/cJ.

Beneficial effects of inorganic nitrate in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is considered the hepatic representation of the metabolic disorders. Inorganic nitrate/nitrite can be converted to nitric oxide, regulate glucose metabolism, lower lipid levels, and reduce inflammation, thus raising the hypothesis that inorganic nitrate/nitrite could be beneficial for improving NAFLD. This study assessed the therapeutic effects of chronic dietary nitrate on NAFLD in a mouse model. 60 ApoE-/- mice were fed a high-fat diet (HFD) for 12 weeks to allow for the development of atherosclerosis with associated NAFLD. The mice were then randomly assigned to different groups (20/group) for a further 12 weeks: (i) HFD + NaCl (1 mmol/kg/day), (ii) HFD + NaNO3 (1 mmol/kg/day), and (iii) HFD + NaNO3 (10 mmol/kg/day). A fourth group of ApoE-/- mice consumed a normal chow diet for the duration of the study. At the end of the treatment, caecum contents, serum, and liver were collected. Consumption of the HFD resulted in significantly greater lipid accumulation in the liver compared to mice on the normal chow diet. Mice whose HFD was supplemented with dietary nitrate for the second half of the study, showed an attenuation in hepatic lipid accumulation. This was also associated with an increase in hepatic AMPK activity compared to mice on the HFD. In addition, a significant difference in bile acid profile was detected between mice on the HFD and those receiving the high dose nitrate supplemented HFD. In conclusion, dietary nitrate attenuates the progression of liver steatosis in ApoE-/- mice fed a HFD.