AMPK Activation Research Articles

A Natural Autophagy Activator Castanea crenata Flower Alleviates Skeletal Muscle Ageing.

Sarcopenia, characterized by a gradual decline in skeletal muscle mass and function with age, significantly impacts both quality of life and mortality. Autophagy plays a crucial role in maintaining muscle health. There is growing interest in leveraging autophagy to mitigate muscle ageing effects. The impact of natural autophagy activators on skeletal muscle ageing remains elusive. This study aims to identify natural autophagy activators and assess their effects on skeletal muscle ageing. To discover novel autophagy activators, we screened 493 natural products and identified Castanea crenata flower extract (CCFE) as a promising candidate. We investigated the effect of CCFE on cellular senescence in C2C12 cells induced by etoposide. In animal experiments, aged mice (18 months old) were fed a diet supplemented with 0.1% and 0.2% CCFE for 3 months. We assessed exercise capacity, mitochondrial function and autophagic flux to determine the impact of CCFE on skeletal muscle ageing. The components present in CCFE were analysed using LC-MS/MS, and their functional properties were examined. CCFE enhanced autophagic flux (LC3II 80% increase, p < 0.05) and reduced senescence-associated β-galactosidase activity (32.78% decrease, p < 0.001). In aged mice, a 3-month supplementation with CCFE improved muscle weight (18% increase, p < 0.05) and function (treadmill performance increased by 60%, p < 0.5; grip strength increased by 25%, p < 0.05). It alleviated mitochondrial dysfunction (basal oxygen consumption rate increased by 59%, p < 0.05) and restored autophagy. CCFE enhanced autophagy by activating AMPK (80% increase, p < 0.01) and inhibiting Atg5 protein acetylation (65% decrease, p < 0.001), with contributions from ellagic acid and polyamines. CCFE supplementation restored polyamine levels (serum spermidine increased from 0.98 ± 0.08 to 2.22 ± 0.05 μg/mL, p < 0.001) and increased urolithin levels (serum urolithin A increased from 0 to 18.79 ± 0.062 ng/mL, p < 0.001), metabolites produced by the gut microbiome from ellagic acid in aged mice. CCFE effectively suppressed skeletal muscle ageing by preventing mitochondrial dysfunction and restoring autophagic flux in aged mice. It achieved this by modulating AMPK and EP300 acetyltransferase activity, with contributions from its constituents, ellagic acid and polyamines. These findings highlight the potential of CCFE as a therapeutic agent for extending healthspan and mitigating sarcopenia, providing a basis for future clinical trials.

MTOR Ser1261 is an AMPK-dependent phosphosite in mouse and human skeletal muscle not required for mTORC2 activity.

The kinases AMPK, and mTOR as part of either mTORC1 or mTORC2, are major orchestrators of cellular growth and metabolism. Phosphorylation of mTOR Ser1261 is reportedly stimulated by both insulin and AMPK activation and a regulator of both mTORC1 and mTORC2 activity. Intrigued by the possibilities that Ser1261 might be a convergence point between insulin and AMPK signaling in skeletal muscle, we investigated the regulation and function of this site using a combination of human exercise, transgenic mouse, and cell culture models. Ser1261 phosphorylation on mTOR did not respond to insulin in any of our tested models, but instead responded acutely to contractile activity in human and mouse muscle in an AMPK activity-dependent manner. Contraction-stimulated mTOR Ser1261 phosphorylation in mice was decreased by Raptor muscle knockout (mKO) and increased by Raptor muscle overexpression, yet was not affected by Rictor mKO, suggesting most of Ser1261 phosphorylation occurs within mTORC1 in skeletal muscle. In accordance, HEK293 cells mTOR Ser1261Ala mutation strongly impaired phosphorylation of mTORC1 substrates but not mTORC2 substrates. However, neither mTORC1 nor mTORC2-dependent phosphorylations were affected in muscle-specific kinase-dead AMPK mice with no detectable mTOR Ser1261 phosphorylation in skeletal muscle. Thus, mTOR Ser1261 is an exercise but not insulin-responsive AMPK-dependent phosphosite in human and murine skeletal muscle, playing an unclear role in mTORC1 regulation but clearly not required for mTORC2 activity.

Autophagic flux-lipid droplet biogenesis cascade sustains mitochondrial fitness in colorectal cancer cells adapted to acidosis

Cancer development is associated with adaptation to various stressful conditions, such as extracellular acidosis. The adverse tumor microenvironment also selects for increased malignancy. Mitochondria are integral in stress sensing to allow for tumor cells to adapt to stressful conditions. Here, we show that colorectal cancer cells adapted to acidic microenvironment (CRC-AA) are more reliant on oxidative phosphorylation than their parental cells, and the acetyl-CoA in CRC-AA cells are generated from fatty acids and glutamine, but not from glucose. Consistently, CRC-AA cells exhibit increased mitochondrial mass and fitness that depends on an upregulated autophagic flux-lipid droplet axis. Lipid droplets (LDs) function as a buffering system to store the fatty acids derived from autophagy and to protect mitochondria from lipotoxicity in CRC-AA cells. Blockade of LD biogenesis causes mitochondrial dysfunction that can be rescued by inhibiting carnitine palmitoyltransferase 1 α (CPT1α). High level of mitochondrial superoxide is essential for the AMPK activation, resistance to apoptosis, high autophagic flux and mitochondrial function in CRC-AA cells. Thus, our results demonstrate that the cascade of autophagic flux and LD formation plays an essential role in sustaining mitochondrial fitness to promote cancer cell survival under chronic acidosis. Our findings provide insight into the pro-survival metabolic plasticity in cancer cells under microenvironmental or therapeutic stress and imply that this pro-survival cascade may potentially be targeted in cancer therapy.

Prussian Blue Nanozyme Featuring Enhanced Superoxide Dismutase-like Activity for Myocardial Ischemia Reperfusion Injury Treatment.

The blood flow, when restored clinically following a myocardial infarction (MI), disrupts the physiological and metabolic equilibrium of the ischemic myocardial area, resulting in secondary damage termed myocardial ischemia-reperfusion injury (MIRI). Reactive oxygen species (ROS) generation and inflammatory reactions stand as primary culprits behind MIRI. Current strategies focusing on ROS-scavenging and anti-inflammatory actions have limited remission of MIRI. Prussian blue nanozyme (PBNz) exhibits multiple enzyme-like activities including catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), which are beneficial for ROS clearance and fighting inflammation. Herein, a formulation of PBNz coated with polydextrose-sorbitol carboxymethyl ether (PBNz@PSC) was developed to enhance its efficacy, biocompatibility, and safety for the treatment of MIRI. PBNz@PSC not only showed enhanced SOD-like activity due to its polysaccharide attributes but also could passively target the damaged myocardium through the enhanced permeability and retention (EPR) effect. Both in vitro and in vivo studies have validated their excellent biocompatibility, safety, ROS-scavenging ability, and capacity to drive macrophage polarization from M1 toward M2, thereby diminishing the levels of IL-1β, IL-6, and TNF-α to combat inflammation. Consequently, PBNz@PSC can reverse ischemia reperfusion-induced myocardial injury, reduce coronary microvascular obstruction (MVO), and improve myocardial remodeling and cardiac function. Moreover, PBNz@PSC showed more pronounced therapeutic effects for MIRI than a clinical drug, sulfotanshinone IIA sodium. Notably, our findings revealed the possible mechanism of PBNz@PSC in treating MIRI, which mediated AMPK activation. In conclusion, this study presents a pioneering strategy for addressing MIRI, promising improved ischemia-reperfusion outcomes.

ADVANTAGES AND DISADVANTAGES OF USING METFORMIN IN AGING RELATED DISEASES

This review aimed to explore the anti-aging effects of metformin, which lowers glucose, slows down cell aging through regulating intracellular signaling molecules and activating AMPK, and protects against aging-related diseases. The activation of AMPK by Metformin allows it to control inflammatory conditions, improve oxidative status, regulate differentiation pathways of various cells, and ultimately provide positive therapeutic effects on these cells. Metformin plays a role in several cardiovascular diseases, neurological disorders, cancer, and fragile X syndrome by improving several parameters in some of these disease conditions. Metformin provides benefits in aging-related diseases, but further studies with various methods and samples are needed to assess the effectiveness and consider the side effects of metformin in diabetic and non-diabetic patients, as well as involving genetic factors associated with metformin.

Syringaldehyde Alleviates Cardiac Hypertrophy Induced by Hyperglycemia in H9c2 Cells Through GLP-1 Receptor Signals.

Background: Cardiac hypertrophy is a significant complication of diabetes, often triggered by hyperglycemia. Glucagon-like peptide-1 (GLP-1) receptor agonists alleviate cardiac hypertrophy, but their efficacy diminishes under GLP-1 resistance. Syringaldehyde (SA), a natural phenolic compound, may activate GLP-1 receptors and mitigate hypertrophy. This study explores SA's therapeutic potential in hyperglycemia-induced cardiac hypertrophy in H9c2 cardiomyocytes. Methods: H9c2 cells were exposed to high glucose to induce hypertrophy. Cells were treated with varying SA concentrations, and hypertrophic biomarkers were analyzed using ELISA, qPCR, and Western blot. Results: SA reduced cell size and hypertrophic biomarkers in a dose-dependent manner while increasing GLP-1 receptor expression and cAMP levels. These effects were attenuated in GLP-1-resistant cells, highlighting the role of GLP-1 receptor activation. AMPK activation was essential, as its inhibition abolished SA's effects. SA also decreased O-linked N-acetylglucosamine transferase (OGT) expression via AMPK activation, contributing to reduced hypertrophy. Conclusions: SA alleviates hyperglycemia-induced cardiac hypertrophy in H9c2 cells by activating the GLP-1 receptor and AMPK signaling pathway.

KAT6A acetylation drives metabolic adaptation to mediate cellular growth and mitochondrial metabolism through AMPK interaction.

Diets influence metabolism and disease susceptibility, with lysine acetyltransferases (KATs) serving as key regulators through acetyl-CoA. We have previously demonstrated that a ketogenic diet alleviates cardiac pathology, though the underlying mechanisms remain largely unknown. Here we show that KAT6A acetylation is crucial for mitochondrial function and cell growth. Proteomic analysis revealed that KAT6A is acetylated at lysine (K)816 in the hearts of mice fed a ketogenic diet under hypertension, which enhances its interaction with AMPK regulatory subunits. RNA-sequencing analysis demonstrated that the KAT6A acetylation-mimetic mutant stimulates AMPK signaling in cardiomyocytes. Moreover, the acetylation-mimetic mutant mitigated phenylephrine-induced mitochondrial dysfunction and cardiomyocyte hypertrophy via AMPK activation. However, KAT6A-K816R acetylation-resistant knock-in mice unexpectedly exhibited smaller hearts with enhanced AMPK activity, conferring protection against neurohumoral stress-induced cardiac hypertrophy and remodeling. These findings indicate that KAT6A regulates metabolism and cellular growth by interacting with and modulating AMPK activity through K816-acetylation in a cell type-specific manner.

The role of CNBP in brain atrophy and its targeting in myotonic dystrophy type 2.

Myotonic Dystrophy type 2 (DM2) is a multisystem disease affecting many tissues, including skeletal muscle, heart, and brain. DM2 is caused by unstable expansion of CCTG repeats in an intron 1 of a gene coding for cellular nuclear binding protein (CNBP). The expanded CCTG repeats cause DM2 pathology due to the accumulation of RNA CCUG repeats, which affect RNA processing in patients' cells. We have previously shown that mutant CCUG repeats reduce CNBP protein in DM2 patients. Reducing Cnbp in Cnbp KO mouse model causes late skeletal muscle atrophy. In this study, we examined if the reduction of Cnbp affects the Central Nervous System (CNS). MRI and DTI analyses showed that total brain volume and grey matter are reduced in Cnbp KO mice, while mean, radial and axonal brain diffusivity is increased. The morphological changes in the brains of Cnbp KO mice are accompanied by reduced stereotypic behavior, anxiety and neuromotor defects. These findings suggest that the reduction of CNBP contributes to CNS pathology in DM2. Since CNBP stability is regulated by pAMPK-dependent phosphorylation, we examined protein levels of pAMPK in DM2 cells and found that the active pAMPK is reduced in DM2. Interaction of CNBP with pAMPK and stability of CNBP protein are also decreased in DM2. Our data show that a small molecule AMPK activator A769662 corrects CNBP stability and normalizes CNBP targets in DM2 fibroblasts. Thus, activators of AMPK could potentially be developed as therapeutics to correct CNBP and reduce muscle and brain atrophies in DM2.

Growth differentiation factor 15 is a glucose-downregulated gene acting as the cross talk between stroma and cancer cells of the human bladder.

Hyperglycemia and hyperglycosuria, two primary characteristics of diabetes mellitus, may increase the risk of cancer initiation, particularly for bladder cancer. The effectiveness of metformin, a common antidiabetic agent, is determined by its ability to induce growth differentiation factor 15 (GDF15). However, the mechanism of the GDF15 in relation to glucose, which influences the tumor microenvironment in the human bladder, is not fully understood. This study explores the potential roles of GDF15 in response to glucose in the human bladder. High glucose treatment (30 mM) enhanced phosphorylation of AKT at S473 and AMP-activated protein kinase α1/2 (AMPKα1/2) at S485 to block the counteracting effect of metformin on the AMPK activity in bladder cancer and stroma [human bladder stromal fibroblast (HBdSF) and human bladder smooth muscle cell (HBdSMC)] cells compared with normal glucose treatment (5 mM). Metformin modulated the expressions of GDF15, NDRG1, Maspin, and epithelial-to-mesenchymal transition (EMT) markers to attenuate cell proliferation and invasion of bladder cancer cells. Caffeic acid phenethyl ester (CAPE), like metformin, behaves as an inducer of AMPK activity to stimulate GDF15 expression. Knockdown of GDF15 blocked the downregulation of CAPE on the contraction of HBdSMCs. Both CAPE-induced GDF15 expression and the supernatant from bladder cancer cells with overexpressing GDF15 impeded the HBdSF and HBdSMC migration, suggesting that CAPE-upregulated GDF15 blocked the cell migration. These findings reveal that high glucose treatment inhibits the counteracting effects of either metformin or CAPE on the AMPK activity and GDF15 is downregulated by glucose and induced by metformin and CAPE in both stroma and cancer cells. Furthermore, GDF15 is an antitumor gene facilitating communication between stroma and cancer cells in the human bladder.NEW & NOTEWORTHY This study investigates the counteraction of either CAPE or metformin with the AMPK activity increasing GDF15 expression in human bladder cells. The findings are the first study to indicate the secretion of GDF15 from cancer and stroma cells via autocrine or paracrine mechanisms. Our study suggests that GDF15, an antitumor gene in the human bladder induced by AMPK inducers, acts as a communication link between stroma and cancer cells in the human bladder.

Muscle Cell Palmitate-Induced Insulin Resistance, JNK, IKK/NF-κB and STAT3 Activation are Attenuated by Carnosic and Rosmarinic Acid.

The worldwide epidemic of obesity has drastically worsened with the increase in more sedentary lifestyles and increased consumption of fatty foods. Increased blood free fatty acids (FFAs), often observed in obesity, leads to impaired insulin action, and promotes the development of insulin resistance and Type 2 diabetes mellitus (T2DM). JNK, IKK-NF-κB, and STAT3 are known to be involved in skeletal muscle insulin resistance. We reported previously that carnosic acid (CA) and rosmarinic acid (RA), attenuated the palmitate-induced skeletal muscle insulin resistance, an effect that was associated with increased AMPK activation and reduced mTOR-p70S6K signaling. In the present study, we examined the effects of CA and RA on JNK, IKK-NF-κB, and STAT3. Exposure of cells to palmitate increased the phosphorylation/activation of JNK, IKKα/β, IκBα, NF-κBp65, and STAT3. Importantly, CA and RA attenuated the deleterious effects of palmitate. Our data indicate that CA and RA have the potential to counteract the palmitate-induced skeletal muscle cell insulin resistance by modulating JNK, IKK-NF-κB, and STAT3 signaling.

Revealing the Mechanism of Protein Degradation in Postmortem Meat: The Role of Phosphorylation and Ubiquitination.

The aim of this study was to investigate the possible effects of phosphorylation and ubiquitination on the degradation of myofibrillar proteins in mutton with different tenderness. The longissimus thoracis lumborum muscles were chosen and divided into tender and tough groups (n = 9), and then stored at 4 °C for 1 h, 12 h, 1 d, 3 d, and 5 d postmortem. Shear force, pH, myofibril fragmentation index, AMPK activity, E3 ubiquitin ligase abundance, protein phosphorylation, and the ubiquitination levels of muscle samples were measured. The results demonstrated that the meat of samples in the tender group had a higher degradation of desmin and a lower phosphorylation level of desmin at 1 d compared with the tough group. The ubiquitination level of desmin, AMPK activity, and E3 ubiquitin ligase abundance in the tender group were noticeably higher than those in the tough group at 12 h. There was a negative correlation between the shear force and desmin degradation. The desmin degradation was negatively correlated with desmin phosphorylation and ubiquitination levels. The phosphorylation level of desmin was positively correlated with its ubiquitination. In summary, this study suggests that AMPK and E3 ubiquitin ligase concurrently play significant roles in regulating meat tenderness by regulating phosphorylation and ubiquitination in meat postmortem.

TGFβ1 Restores Energy Homeostasis of Human Trophoblast Cells Under Hyperglycemia In Vitro by Inducing PPARγ Expression, AMPK Activation, and HIF1α Degradation.

Elevated glucose levels at the fetal-maternal interface are associated with placental trophoblast dysfunction and increased incidence of pregnancy complications. Trophoblast cells predominantly utilize glucose as an energy source, metabolizing it through glycolysis in the cytoplasm and oxidative respiration in the mitochondria to produce ATP. The TGFβ1/SMAD2 signaling pathway and the transcription factors PPARγ, HIF1α, and AMPK are key regulators of cell metabolism and are known to play critical roles in extravillous trophoblast cell differentiation and function. While HIF1α promotes glycolysis over mitochondrial respiration, PPARγ and AMPK encourage the opposite. However, the interplay between TGFβ1 and these energy-sensing regulators in trophoblast cell glucose metabolism remains unclear. This study aimed to investigate whether and how TGFβ1 regulates energy metabolism in trophoblast cells exposed to normal and high glucose conditions. The trophoblast JEG-3 cells were incubated in normal (5 mM) and high (25 mM) glucose conditions for 24 h in the absence and the presence of TGFβ1. The protein expression levels of phosphor (p)-SMAD2, GLUT1/3, HIF1α, PPARγ, p-AMPK, and specific OXPHOS protein subunits were determined by western blotting, and ATP and lactate production by bioluminescent assay kits. JEG-3 cells exposed to 25 mM glucose decreased ATP production but did not affect lactate production. These changes led to a reduction in the expression levels of GLUT1/3, mitochondrial respiratory chain proteins, and PPARγ, coinciding with an increase in HIF1α expression. Conversely, TGFβ1 treatment at 25 mM glucose reduced HIF1α expression while enhancing the expression levels of GLUT1/3, PPARγ, p-AMPK, and mitochondrial respiratory chain proteins, thereby rejuvenating ATP production. Our findings reveal that high glucose conditions disrupt cellular glucose metabolism in trophoblast cells by perturbing mitochondrial oxidative respiration and decreasing ATP production. Treatment with TGFβ1 appears to counteract this trend, probably by enhancing both glycolytic and mitochondrial metabolism, suggesting a potential regulatory role of TGFβ1 in placental trophoblast cell glucose metabolism.

Mammalian Mitochondrial Inorganic Polyphosphate (polyP) and Cell Signaling: Crosstalk Between PolyP and the Activity of AMPK.

Inorganic polyphosphate (polyP) is an evolutionary ancient polymer composed by orthophosphate units linked by phosphoanhydride bonds. In mammalian cells, polyP shows a high localization in mammalian mitochondria, and its regulatory role in various aspects of bioenergetics has already been demonstrated, via molecular mechanism(s) yet to be fully elucidated. In recent years, a role for polyP in signal transduction, from brain physiology to bloodstream, has also emerged. The intriguing possibility is that the effects of polyP on signal transduction could be mechanistically linked to those exerted on bioenergetics. Here, using a combination of cellular and animal models, we demonstrate for the first time the intimate crosstalk between the levels of polyP and the activation status of the AMPK signaling pathway, via a mechanism involving free phosphate homeostasis. AMPK is a key player in mammalian cell signaling, and a crucial regulator of cellular and mitochondrial homeostasis. Our results show that the depletion of mitochondrial polyP in mammalian cells downregulates the activity of AMPK. Moreover, increased levels of polyP activate AMPK. Accordingly, the genetic downregulation of AMPKα1 impairs polyP levels in both SH-SY5Y cells and in the brains of female mice. Our findings shed new light on the regulation of AMPK and position polyP as a potent regulator of mammalian cell physiology beyond mere bioenergetics, paving the road for using its metabolism as an innovative pharmacological target in pathologies characterized by dysregulated bioenergetics.

Protective effects of phosphocreatine against Doxorubicin-Induced cardiotoxicity through mitochondrial function enhancement and apoptosis suppression via AMPK/PGC-1α signaling pathway.

Doxorubicin (DOX), a potent chemotherapy drug, is limited by its cardiotoxic effects, which can lead to heart damage. This study explores the cardioprotective potential of Phosphocreatine (PCr) in vitro and in vivo models, focusing on its impact on the AMPK and PGC-1α pathways, apoptosis reduction, and mitochondrial function preservation. Advanced methodologies, including high-resolution respirometry (HRR), were employed to assess mitochondrial bioenergetics, AMPK activity, and apoptotic rates in cardiomyocytes. Electrocardiography (ECG) and echocardiography (echo) were used to monitor cardiac function in vivo. Results showed that PCr significantly activated the AMPK and PGC-1α pathways, reduced apoptosis, and stabilized mitochondrial function in cardiomyocytes exposed to DOX. There was an upregulation of AMPK and PGC-1α target genes, stabilization of mitochondrial membranes, and improvements in cellular energy production and antioxidant defenses. PCr also markedly reduced apoptotic markers, enhancing cardiomyocyte viability. ECG and echocardiography revealed that PCr preserved cardiac function, indicated by improved heart rate variability, reduced QT interval prolongation, and enhanced ejection fraction. These findings highlight PCr's potential in mitigating DOX-induced cardiotoxicity by enhancing mitochondrial function and reducing apoptosis. The study underscores the promise of PCr as an agent to reduce chemotherapy-related cardiac injuries, paving the way for further research to improve patient outcomes in cancer treatment.

Involvement of metformin and aging in salivary expression of ACE2 and TMPRSS2.

SARS-CoV-2-related proteins, ACE2 and TMPRSS2, are determinants of SARS-CoV-2 infection. Although these proteins are expressed in oral-related tissues, their expression patterns and modulatory mechanisms in the salivary glands remain unknown. We herein showed that full-length ACE2, which has both a fully functional enzyme catalytic site and high-affinity SARS-CoV-2 spike S1-binding sites, was more highly expressed in salivary glands than in oral mucosal epithelial cells and the lungs. Regarding TMPRSS2, zymogen and the cleaved form were both expressed in the salivary glands, whereas only zymogen was expressed in murine lacrimal glands and the lungs. Metformin, an AMPK activator, increased stimulated saliva secretion and full-length ACE2 expression and decreased cleaved TMPRSS2 expression in the salivary glands, and exerted the same effects on soluble ACE2 (sACE2) and sTMPRSS2 in saliva. Moreover, metformin decreased the expression of beta-galactosidase, a senescence marker, and ADAM17, a sheddase of ACE2 to sACE2, in the salivary glands. In aged mice, the expression of ACE2 was decreased in the salivary glands, whereas that of sACE2 was increased in saliva, presumably by the up-regulated expression of ADAM17. The expression of TMPRSS2 in the salivary glands and sTMPRSS2 in saliva were both increased. Collectively, these results suggest that the protein expression patterns of ACE2 and TMPRSS2 in the salivary glands differ from those in other oral-related cells and tissues, and also that metformin and aging affect the salivary expression of ACE2 and TMPRSS2, which have the potential as targets for preventing the transmission of SARS-CoV-2.

Dose-dependent effects of hydroquinone on liver injury and lipid dysregulation based on SCD1/AMPK signaling pathway in C57BL/6 mice.

Hydroquinone (HQ) is extensively utilized in various industrial applications and as a dermatological agent; however, its metabolic processes and toxicological effects, particularly in the liver, remain insufficiently understood. This study aimed to investigate the impact of different doses of HQ on liver injury and lipid metabolism in C57BL/6 mice, with a specific focus on the SCD1/AMPK signaling pathway. We administered HQ at doses of 0, 12.5, 25.0, and 50.0 mg/kg over a period of 13 weeks, followed by biochemical analyses, RNA sequencing, and Western blotting to elucidate the underlying mechanisms. Our findings indicated that lower doses of HQ (12.5 and 25.0 mg/kg) led to lipid accumulation in the liver, accompanied by increased liver TG and serum TC. In contrast, the highest dose (50.0 mg/kg) resulted in elevated liver enzyme levels, indicative of liver damage, while lipid levels decreased. Notably, the mRNA or protein levels of SCD1 were upregulated in response to the lower doses of HQ (12.5 and 25.0 mg/kg), whereas AMPK activation and enhanced autophagy were observed in the 50.0 mg/kg HQ-treated group, reflecting an energy stress response. These findings suggest that lipid dysregulation may serve as an early indicator of HQ-induced liver injury, and that the SCD1/AMPK pathway may play a protective role against chemically induced hepatotoxicity. This study offers new insights into the toxicological effects of HQ on the liver and underscores the necessity for further exploration of the protective mechanisms of SCD1 and AMPK in mitigating HQ-induced hepatotoxicity.

Abscisic acid improves non-alcoholic fatty liver disease in mice through the AMPK/NRF2/KEAP1 signaling axis.

Non-alcoholic fatty liver disease (NAFLD) has emerged as a global health concern, placing a substantial financial strain on public health systems. Currently, no specific pharmacological treatments are recommended in existing guidelines. Abscisic acid (ABA), a natural plant hormone, is recognized for its promising potential in the healthcare field due to its diverse biological activities. Therefore, this study is aimed at exploring the protective mechanism of ABA against NAFLD. In vitro, experiments were conducted using palmitic acid (PA) to establish a fatty liver cell model, whereas in vivo, an NAFLD model was established using a continuous high-fat diet (HFD). It was found that ABA, as a natural activator of NRF2 and AMPK, reduced lipid accumulation in hepatocytes and exerted anti-inflammatory and antioxidant effects by enhancing the nuclear expression of NRF2, thereby alleviating NAFLD in mice. Furthermore, AMPK was activated by ABA through the promotion of its phosphorylation, which subsequently enhanced the p62-dependent autophagic degradation of KEAP1, leading to the release and nuclear translocation of NRF2. In conclusion, it is indicated that ABA reduces lipid accumulation, inflammation, and oxidative stress in hepatocytes via the NRF2 and AMPK pathways, potentially serving as a promising candidate for alleviating NAFLD.

Activation of autophagy with PF-06409577 alleviates heatstroke-induced organ injury.

Heat waves are a significant environmental issue threatening global human health. Extreme temperatures can lead to various heat-related illnesses, with heatstroke being among the most severe. Currently, there are no effective treatments to mitigate the multi-organ damage caused by heatstroke. We found that heat stress activated autophagy. Knockdown of the autophagy-related gene 7 (ATG7) or knockout of the autophagy initiation regulatory genes UNC-51-like autophagy activating kinase 1/2 (ULK1/ULK2) increased cell death. PF-06409577, an allosteric activator of AMP-activated protein kinase β (AMPKβ), reduced heat stress-induced cell death by promoting autophagy. Inhibition of ATG7 or ULK1 weakened PF-06409577's protective effect on cells. Treatment of heatstroke mouse models with PF-06409577 suppressed high temperature-induced damage to multiple organs, including the liver, kidneys, lungs, and small intestine. PF-06409577 protected liver and kidney functions, lowered the expression of kidney injury markers neutrophil gelatinase associated lipocalin (Ngal), secreted phosphoprotein 1 (Spp1), and clusterin (Clu), and reduced levels of the inflammatory factor IL-6. Additionally, it decreased heat stress-induced macrophage infiltration and IL-6 production in the liver. The results indicate that activation of autophagy serves a protective function during heat stress, and the AMPK activator PF-06409577 exhibits potential in mitigating heatstroke-induced multi-organ damage through its ability to promote autophagy.

Poststroke hyperglycemia dysregulates cap-dependent translation in neural cells.

Post stroke hyperglycemia has been shown to deter functional recovery. Earlier findings have indicated the cap-dependent translation regulator 4E-BP1 is detrimentally upregulated in hyperglycemic conditions. The present study aims to test the hypothesis that hyperglycemic ischemic reperfusion injury (I/R) affects normal protein translation poststroke. Rat primary cortical neurons (PCNs) were exposed to oxygen glucose deprivation (OGD) followed by increasing glucose concentration (0, 5, 10, 25mM) at reoxygenation. In vivo, adult rats were subjected to two hours transient distal middle cerebral artery occlusion (t-dMCAO) and hyperglycemic reperfusion. In PCN cultures, high glucose levels impaired normal neurite growth at 24h I/R where it drastically depressed S6 ribosomal protein phosphorylation at serine 235/236 residues in 40S ribosomal subunit. This concurred with substantial hypoxia inducible factor-1α (HIF-1α) destabilization and sustained vascular endothelial growth factor (VEGF). Our immunoblotting findings indicated HIF-1α stabilization and AMPK activation rely on glucose availability. Incremental glucose concentrations above the physiological levels, induced a shift towards 4E-BP1, eIF-4E hypo-phosphorylated forms leading to reduced eIF-4E availability and efficacy, as the key to recruit the 40S ribosomal subunit to the 5' end of mRNA. In vivo, immunostaining of t-dMCAO rat brains showed remarkable decrease in phosphorylated 4E-BP1 and particularly s6 ribosomal protein in the marginal cortical tissue of hyperglycemic compared to normoglycemic animals. These findings suggest a remarkable association between hyperglycemic I/R injury with dysregulated cap-dependent translation poststroke. Further loss/gain of function experiment may elucidate the potential therapeutic targets in regulation of HIF-1α/translation in hyperglycemic I/R injury.

Bioenergetic adaptations of small intestinal epithelial cells reduce cell differentiation enhancing intestinal permeability in obese mice.

Obesity and overweight are associated with low-grade inflammation induced by adipose tissue expansion and perpetuated by altered intestinal homeostasis, including increased epithelial permeability. Intestinal epithelium functions are supported by intestinal epithelial cells (IEC) mitochondria function. Here, we report that diet-induced obesity (DIO) in mice induces lipid metabolism adaptations favoring lipid storage in IEC together with reduced number, altered dynamics and diminished oxidative phosphorylation activity of IEC mitochondria. Using the jejunal epithelial cell line IPEC-J2, we showed that IEC lipid metabolism and oxidative stress machinery adaptations preceded mitochondrial bioenergetic ones. Moreover, we unraveled the intricate link between IEC energetic status and proliferation / differentiation balance since enhancing mitochondrial function with the AMPK activator AICAR in jejunal organoids reduced proliferation and initiated IEC differentiation and conversely. We confirmed that the reduced IEC mitochondrial function observed in DIO mice was associated with increased proliferation and reduced differentiation, promoting expression of the permissive Cldn2 in the jejunal epithelium of DIO mice. Our study provides new insights into metabolic adaptations of IEC in obesity by revealing that excess lipid intake diminishes mitochondrial number in IEC, reducing IEC differentiation that contribute to increased epithelial permeability.