Redefining the role of AMPK in autophagy and the energy stress response

The ER protein CANX (calnexin)-mediated autophagy protects against alzheimer disease

Although the relationship between macroautophagy/autophagy and Alzheimer disease (AD) is widely studied, the underlying mechanisms are poorly understood, especially the regulatory role of the initiation signaling of autophagy on AD. Here, we find that the ER transmembrane protein CANX (calnexin) is a novel interaction partner of the autophagy-inducing kinase ULK1 and is required for ULK1 recruitment to the ER under basal or starved conditions. Loss of CANX results in the inactivity of ULK1 kinase and inhibits autophagy flux. In the brains of people with AD and APP-PSEN1 mice, the interaction of CANX and ULK1 declines. In mice, the lack of CANX in hippocampal neurons causes the accumulation of autophagy receptors and neuron damage, which affects the cognitive function of C57BL/6 mice. Conversely, overexpression of CANX in hippocampal neurons enhances autophagy flux and partially contributes to improving cognitive function of APP-PSEN1 mice, but not the CANX variant lacking the interaction domain with ULK1. These findings reveal a novel role of CANX in autophagy activity and cognitive function by cooperating with ULK1.Abbreviation: AD: Alzheimer disease; APEX: ascorbate peroxidase; APP: amyloid beta precursor protein; APP-PSEN1 mice: amyloid beta precursor protein-presenilin 1 transgenic mice; ATG: autophagy related; Aβ: amyloid-β; BiFC: bimolecular fluorescence complementation; CANX: calnexin; EBSS: Earle's balanced salt solution; EM: electron microscopy; IP: immunopurification; KO: knockout; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MWM: Morris water maze; PLA: proximity ligation assay; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; SQSTM1/p62, sequestosome 1.

Energy Metabolism and Brain Aging: Strategies to Delay Neuronal Degeneration

Aging is characterized by a gradual decline in physiological functions, with brain aging being a major risk factor for numerous neurodegenerative diseases. Given the brain's high energy demands, maintaining an adequate ATP supply is crucial for its proper function. However, with advancing age, mitochondria dysfunction and a deteriorating energy metabolism lead to reduced overall energy production and impaired mitochondrial quality control (MQC). As a result, promoting healthy aging has become a key focus in contemporary research. This review examines the relationship between energy metabolism and brain aging, highlighting the connection between MQC and energy metabolism, and proposes strategies to delay brain aging by targeting energy metabolism.

Polysaccharides from Dicliptera chinensis (L.) Juss. Attenuates drug-induced liver injury by phosphorylating AMPK and thus facilitating the entry of FOXO3 into the cell nucleus

BACKGROUND

Isoniazid and rifampicin, frontline tuberculosis drugs, frequently induce drug-induced liver injury (DILI), marked by hepatitis and hepatocyte necrosis. Polysaccharides from Dicliptera chinensis (L.) Juss. (DCP) exhibit anti-inflammatory, antioxidant, and hepatoprotective properties, but their effects on DILI remain unexplored OBJECTIVE: This study investigated DCP therapeutic potential against DILI and elucidated its molecular mechanisms METHODS: In vivo (using C57BL/6 mice) and in vitro (using HepG2 cells) DILI models were established and treated with DCP. Transcriptomics, qRT-PCR, and Western blotting were employed to analyze pathway regulation RESULTS: DCP significantly attenuated hepatocyte apoptosis, inflammation, and oxidative stress in DILI mice. Transcriptomic analysis linked DCP'S effects to the modulation of AMPK-FOXO3, p53, and NF-κB pathways, alongside regulation of antioxidant and cell cycle genes. In HepG2 cells, DCP similarly protected against DILI by enhancing AMPK phosphorylation, which facilitated the FOXO3 nuclear translocation. Both models demonstrated DCP'S suppression of p53 and NF-κB activation, restoration of antioxidant defenses, and correction of cell cycle dysregulation CONCLUSION: DCP mitigates DILI by reducing apoptosis, oxidative stress, and inflammation through activation of the AMPK-FOXO3 pathway, inhibition of p53/NF-κB signaling, and stabilization of the cell cycle. These findings highlight DCP'S potential as a therapeutic agent for DILI prevention and treatment.

The NR3C2-SIRT1 signaling axis promotes autophagy and inhibits epithelial mesenchymal transition in colorectal cancer

Colorectal cancer (CRC) is one of the most aggressive and lethal cancers with a complex pathogenesis, there is an urgent need to find new drug therapeutic targets. This study highlights the important role of the NR3C2-SIRT1 signaling axis in the metastasis mechanism of CRC. Our findings revealed that the expression of NR3C2 in CRC tissues was lower than that in adjacent non-cancerous tissues, and was negatively correlated with N stage by bioanalysis, IHC, western blot and qRT-PCR. NR3C2 overexpression / knockdown can significantly inhibit / promote the migration and invasion of CRC cells, at the same time inhibit / promote EMT. Mechanically, the regulatory molecule SIRT1 was identified by RNA-seq, bioinformatics analysis, western blot and ChIP. SIRT1 was also involved in the metastasis process of CRC, and NR3C2 was found to regulate the expression of LC3B and SQSTM1/p62 in a SIRT1-dependent manner. Therefore, NR3C2 forms a signaling axis with SIRT1, which can directly promote autophagy and inhibit EMT process in vivo and in vitro. Collectively, our findings suggest that NR3C2 - SIRT1 signal axis promote autophagy and inhibit EMT, ultimately inhibits lung metastasis of CRC.

Protocatechualdehyde induced tumor suppressive autophagy through AMPK/ULK1 signaling pathway in gastric cancer

Background

Gastric cancer (GC) is one of the primary causes of cancer-related fatalities, which requires novel treatment including traditional Chinese medicine (TCM) to prolong survival. Protocatechualdehyde (PCA), a monomer from Chinese herbs, exhibits an anti-cancer effect by inhibiting proliferation and migration, or inducing apoptosis in various types of tumors. However, the anti-cancer effect and underlying mechanism of PCA in gastric cancer are still unclear.

Methods

The cell proliferation ability was detected by the cell counting kit-8 (CCK-8) and colony formation. The occurrence of autophagy was observed by TEM (Tansmission electron microscopy) and immunofluorescence. The expression of proteins involved in AMPK/mTOC1 signaling pathway was detected by western blotting. Apoptosis and cell cycle analysis were determined through flow cytometry. A xenograft mouse model was employed to validate the anticancer effect of PCA in vivo.

Results

PCA was first identified as a specific inhibitor to gastric cancer cells that significantly inhibited the proliferation of human gastric cancer cells MKN45 and AGS in a dose- and time-dependent manner, but not that of human gastric epithelial cells. Furthermore, PCA induced tumor suppressive autophagy in both gastric cancer cells, and blockage of the autophagy by silencing ATG5 can partially reverse the proliferation inhibition of PCA. Mechanistically, PCA induced-autophagy was largely dependent on the activation of the AMPK/ULK1 signaling pathway, and blockage of the pathway through AMPK specific inhibitor Compound C (Com C) or siRNAs targeting ULK1 prevented the occurrence of autophagy and partially reversed the proliferation inhibition induced by PCA. In addition, PCA significantly suppressed the growth of gastric cancer in the gastric cancer xenograft mouse model by activating key proteins related to the AMPK/ULK1 signaling pathway of autophagy.

Conclusion

These findings demonstrated that PCA inhibited gastric cancer by inducing tumor suppressive autophagy through the AMPK/ULK1 signaling pathway. PCA may serve as a novel candidate for the treatment of gastric cancer.

Promising antifungal properties of the orally active autophagy inhibitor SBP-7455 against fluconazole-resistant Candida clinical isolates

Candida species, the single most common cause of fungal infections, are major opportunistic pathogens. Novel antifungal agents are needed to address the threat of Candida infections resistant to first-line antifungal agents and those that are multi-drug resistant, both being increasingly reported. Here, we explore the antifungal properties of the novel autophagy inhibitor SBP-7455, whose anticancer effects have been recently described. Using broth microdilution, SBP-7455 inhibited the fluconazole-resistant standard C. albicans strain with minimum inhibitory concentration (MIC) values of 43.91 and 21.95 µM in the presence and absence of d-glucose, respectively. SBP-7455 inhibited the growth of six fluconazole-resistant Candida clinical isolates (MIC range 5.48-87.82 µM). Using the checkerboard assay, the fluconazole-resistant standard strain (MIC > 250 µg/ml) was rendered sensitive (MIC = 3.9 µg/ml) to fluconazole when combined with SBP-7455, but combining SBP-7455 with chloroquine was antagonistic. Compared with control, SBP-7455 treated cell membranes showed disrupted integrity and bulging on SEM images. Treatment with SBP-7455 significantly (P < 0.01) increased reduced glutathione levels with no significant change in nitric oxide levels, possibly adapting to oxidative stress induced by autophagy inhibition. Taken together, our results report for the first time the promising antifungal effects of the dual autophagy inhibitor SBP-7455 against fluconazole-resistant Candida, worthy of further investigation.

Covalent inhibitors possessing autophagy-modulating capabilities: charting novel avenues in drug design and discovery

Autophagy is a crucial cellular process in degrading damaged organelles and maintaining cellular homeostasis. By forming irreversible bonds with specific proteins, covalent inhibitors present a distinct advantage in regulating autophagy and its related pathways. These inhibitors can provide sustained modulation of autophagy at lower doses, improving therapeutic efficacy while minimizing adverse effects. We discuss their mechanisms, including how they affect autophagy-related enzymes and pathways, and their potential applications in the treatment of cancers and other autophagy-related disorders. Studying autophagy-related pathway targets will provide new insights for the development of covalent inhibitors and enhance therapeutic strategies for complex conditions.

Twenty years of research on exercise-induced fatigue: A bibliometric analysis of hotspots, bursts, and research trends

Data from the Web of Science Core Collection (2004-2023) on "exercise-induced fatigue" were analyzed using bibliometric tools to explore research trends across countries, institutions, authors, journals, and keywords. The analysis was limited to "Article" and "Review" literature types. Among 4531 publications, the United States contributed the most articles (1005), followed by England (559) and China (516). The most influential institution was Universidade de São Paulo, while the most productive was Institut National de la Santé et de la Recherche Médicale with 103 papers. The European Journal of Applied Physiology ranked as the top journal with 233 articles. Millet Guillaume Y. emerged as the most prolific author, and Amann Markus was the most cited. Recent keyword trends showed a surge in terms like "physical activity" and "aerobic exercise," while "fatigue" and "exercise" remained dominant. Notable findings were observed in oncology, engineering, and multidisciplinary studies, indicating potential research trends. Oxidative stress was identified as the most commonly mentioned mechanism in exercise-induced fatigue studies. This bibliometric analysis highlights current research trends and gaps, suggesting that future studies should focus on understanding the mechanisms of exercise-induced fatigue, developing objective measurement criteria, and exploring strategies for its alleviation.

The Role of Autophagy in Excitotoxicity, Synaptic Mitochondrial Stress and Neurodegeneration

Brain and nervous system functions depend upon maintaining the integrity of synaptic structures over the lifetime. Autophagy, a key homeostatic quality control system, plays a central role not only in neuronal development and survival/cell death, but also in regulating synaptic activity and plasticity. Glutamate is the major excitatory neurotransmitter that activates downstream targets, with a key role in learning and memory. However, an excess of glutamatergic stimulation is pathological in stroke, epilepsy and neurodegeneration, triggering excitotoxic cell death or a sublethal process of excitatory mitochondrial calcium toxicity (EMT) that triggers dendritic retraction. Markers of autophagy and mitophagy are often elevated following excitatory neuronal injuries, with the potential to influence cell death or neurodegenerative outcomes of these injuries. Interestingly, leucine-rich repeat kinase 2 (LRRK2) and PTEN-induced kinase 1 (PINK1), two kinases linked to autophagy, mitophagy and Parkinson disease, play important roles in regulating mitochondrial calcium handling, synaptic density and function, and maturation of dendritic spines. Mutations in LRRK2, PINK1, or proteins linked to Alzheimer's disease perturb mitochondrial calcium handling to sensitize neurons to excitatory injury. While autophagy and mitophagy can play both protective and harmful roles, studies in various excitotoxicity and stroke models often implicate autophagy in a pathogenic role. Understanding the role of autophagic degradation in regulating synaptic loss and cell death following excitatory neuronal injuries has important therapeutic implications for both acute and chronic neurological disorders.

Crosstalk between degradation and bioenergetics: how autophagy and endolysosomal processes regulate energy production

Cells undergo metabolic reprogramming to adapt to changes in nutrient availability, cellular activity, and transitions in cell states. The balance between glycolysis and mitochondrial respiration is crucial for energy production, and metabolic reprogramming stipulates a shift in such balance to optimize both bioenergetic efficiency and anabolic requirements. Failure in switching bioenergetic dependence can lead to maladaptation and pathogenesis. While cellular degradation is known to recycle precursor molecules for anabolism, its potential role in regulating energy production remains less explored. The bioenergetic switch between glycolysis and mitochondrial respiration involves transcription factors and organelle homeostasis, which are both regulated by the cellular degradation pathways. A growing body of studies has demonstrated that both stem cells and differentiated cells exhibit bioenergetic switch upon perturbations of autophagic activity or endolysosomal processes. Here, we highlighted the current understanding of the interplay between degradation processes, specifically autophagy and endolysosomes, transcription factors, endolysosomal signaling, and mitochondrial homeostasis in shaping cellular bioenergetics. This review aims to summarize the relationship between degradation processes and bioenergetics, providing a foundation for future research to unveil deeper mechanistic insights into bioenergetic regulation.

Autophagy repression by antigen and cytokines shapes mitochondrial, migration and effector machinery in CD8 T cells

Autophagy shapes CD8 T cell fate; yet the timing, triggers and targets of this process are poorly defined. Herein, we show that naive CD8 T cells have high autophagic flux, and we identify an autophagy checkpoint whereby antigen receptor engagement and inflammatory cytokines acutely repress autophagy by regulating amino acid transporter expression and intracellular amino acid delivery. Activated T cells with high levels of amino acid transporters have low autophagic flux in amino-acid-replete conditions but rapidly reinduce autophagy when amino acids are restricted. A census of proteins degraded and fueled by autophagy shows how autophagy shapes CD8 T cell proteomes. In cytotoxic T cells, dominant autophagy substrates include cytolytic effector molecules, and amino acid and glucose transporters. In naive T cells, mitophagy dominates and selective mitochondrial pruning supports the expression of molecules that coordinate T cell migration and survival. Autophagy thus differentially prunes naive and effector T cell proteomes and is dynamically repressed by antigen receptors and inflammatory cytokines to shape T cell differentiation.

Fasting enhances the efficacy of Sorafenib in breast cancer via mitophagy mediated ROS-driven p53 pathway

The multi-kinase inhibitor sorafenib has shown potential to inhibit tumor cell growth and intra-tumoral angiogenesis by targeting several kinases, including VEGFR2 and RAF. Abnormal activation of the Ras/Raf/MAPK/ERK kinase cascade and the VEGF pathway is a common feature in breast cancer. However, the efficacy of sorafenib in breast cancer treatment remains limited. Recently, fasting has emerged as a promising non-pharmacological approach to modulate cancer metabolism and enhance the effectiveness of cancer therapies. In this study, we found that fasting significantly enhances the anti-cancer effects of sorafenib monotherapy and its combination with immunotherapy in breast cancer models without causing obvious side effects. This combined treatment effectively inhibits tumor cell proliferation and intra-tumoral angiogenesis. The fasting-induced reduction in peripheral blood glucose levels strongly correlated with enhanced sensitivity to sorafenib. Mechanistically, the combined treatment induced mitophagy, characterized by mitochondrial dysfunction and activation of the PINK1-Parkin pathway. Consequently, increased mitochondrial ROS levels promoted p53 expression, amplifying cell cycle arrest and apoptosis in breast cancer cells. Furthermore, fasting reduced lactate levels within the tumor, and the consequent glucose limitation synergized with sorafenib to activate AMPK, which in turn elevated PD-L1 expression in tumor cells, potentially enhancing their sensitivity to immunotherapy. In summary, our findings demonstrate that fasting and sorafenib, as a rational combination therapy, induce mitophagy, thereby enhancing sorafenib's efficacy in treating breast cancer through the ROS-driven p53 pathway. This study underscores the potential of fasting in breast cancer therapy and provides a foundation for optimizing the clinical application of sorafenib.

ImmunoMet Oncogenesis: A New Concept to Understand the Molecular Drivers of Cancer

The appearance of cancer progresses through a multistep process that includes genetic, epigenetic, mutational, inflammatory and metabolic disturbances to signaling pathways within an organ. The combined influence of these changes will dictate the growth properties of the cells; the direction of further malignancy depends on the severity of these "disturbances". The molecular mechanisms driving abnormal inflammation and metabolism are beginning to be identified and, in some cases, are quite prominent in pre-condition states of cancer and are significant drivers of the malignant phenotype. As such, utilizing signaling pathways linked to inflammation and metabolism as biomarkers of cancer is an emerging method and includes pathways beyond those well characterized to drive metabolism or inflammation. In this review, we will discuss several emerging elements influencing proliferation, inflammation and metabolism that may play a part as drivers of the cancer phenotype. These include AMPK and leptin (linked to metabolism), NOD2/RIPK2, TAK1 (linked to inflammation), lactate and pyruvate transporters (monocarboxylate transporter [MCT], linked to mitochondrial biogenesis and metabolism) and RASSF1A (linked to proliferation, cell death, cell cycle control, inflammation and epigenetics). We speculate that the aforementioned elements are important drivers of carcinogenesis that should be collectively referenced as being involved in "ImmunoMET Oncogenesis", a new tripartite description of the role of elements in driving cancer. This term would suggest that for a better understanding of cancer, we need to understand how proliferation, inflammation and metabolic pathways are impacted and how they influence classical drivers of malignant transformation in order to drive ImmunoMET oncogenesis and the malignant state.

The dual function of autophagy in doxorubicin-induced cardiotoxicity: Mechanism and natural products

Doxorubicin (DOX) is an anthracycline antitumor drug discovered in 1969, which can care for leukemia, breast cancer, lymphoma, and sarcoma. However, cardiotoxicity induced by DOX seriously limits its clinical value. The etiopathogenesis and therapeutic strategies are not unified. Autophagy is a critical mechanism in the progression of DOX-induced cardiotoxicity (DIC), autophagy intervention is a potential therapeutic strategy for DIC. Natural product has been considered as a complementary and alternative approach to treat cardiovascular disease. In this review, we summarize the pathology of autophagy in DIC and the natural products for DIC therapy.

The interplay between probiotics and host autophagy: mechanisms of action and emerging insights

Autophagy, a lysosome-dependent protein degradation mechanism, is a highly conserved catabolic process seen in all eukaryotes. This cell protection system, which is present in all tissues and functions at a basic level, can be up- or downregulated in response to various stresses. A disruption in the natural route of the autophagy process is frequently followed by an interruption in the inherent operation of the body's cells and organs. Probiotics are live bacteria that protect the host through various mechanisms. One of the processes through which probiotics exert their beneficial effects on various cells and tissues is autophagy. Autophagy can assist in maintaining host homeostasis by stimulating the immune system and affecting numerous physiological and pathological responses. In this review, we particularly focus on autophagy impairments occurring in several human illnesses and investigate how probiotics affect the autophagy process under various circumstances.Abbreviation: AD: Alzheimer disease; AKT: AKT serine/threonine kinase; AMPK: 5'AMP-activated protein kinase; ATG: autophagy related; CCl4: carbon tetrachloride; CFS: cell-free supernatant; CMA: chaperone-mediated autophagy; CRC: colorectal cancer; EPS: L. plantarum H31 exopolysaccharide; HD: Huntington disease; HFD: high-fat diet; HPV: human papillomavirus; IFNG/IFN-γ: interferon gamma; IL6: interleukin 6; LGG: L. rhamnosus GG; LPS: lipopolysaccharide; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; NAFLD: non-alcoholic fatty liver disease; NASH: non-alcoholic steatohepatitis; PD: Parkinson disease; Pg3G: pelargonidin-3-O-glucoside; PI3K: phosphoinositide 3-kinase; PolyQ: polyglutamine; ROS: reactive oxygen species; SCFAs: short-chain fatty acids; SLAB51: a novel formulation of lactic acid bacteria and bifidobacteria; Slp: surface layer protein (of acidophilus NCFM); SNCA: synuclein alpha; ULK1: unc-51 like autophagy-activating kinase 1; YB: B. longum subsp. infantis YB0411; YFP: yeast fermentate prebiotic.

A comparative genomic study across 396 liver biopsies provides deep insight into FGF21 mode of action as a therapeutic agent in metabolic dysfunction-associated steatotic liver disease

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a systemic disease with insulin resistance at its core. It affects one-third of the world population. Fibroblast growth factor (FGF21)-based therapies are effective in lowering hepatic fat content and fibrosis resolution; yet, its molecular functions remain uncertain. To gain insight into FGF21 mode of action (MoA), we investigated the transcriptomes of MASLD liver biopsies in relation to FGF21 expression.

METHODS

We compared N = 66 healthy controls with 396 MASLD patients and considered clinical characteristics relative to NAS disease activity scores (steatosis, lobular inflammation and ballooning), fibrosis grades and sex. We performed comparative genomics to identify FGF21-responsive DEGs, utilised information from FGF21-transgenic and FGF21-knockout mice and evaluated DEGs following FGF21 treatment of MASLD animal models. Eventually, we explored 188 validated FGF21 targets, and for ≥10 patients showing the same changes, we constructed MASLD-associated networks to determine the effects of FGF21 in reverting metabolic dysfunction.

RESULTS

We identified patients with increased 30% (N = 117), decreased 40% (N = 159) or unchanged 30% (N = 120) FGF21 expression, and the differences are caused by changes in FGF21 transcriptional control with ATF4 functioning as a key regulator. Based on comparative genomics, we discovered molecular circuitries of FGF21 in MASLD, notably FGF21-dependent induction of autophagy and oxidative phosphorylation/mitochondrial respiration. Conversely, FGF21 repressed hepatic glycogen-storage, its glucose release and gluconeogenesis, and therefore reduced glucose flux in conditions of insulin resistance. Furthermore, FGF21 repressed lipid transporters, and acetyl-CoA carboxylase-β to attenuate hepatic lipid overload and lipogenesis. Strikingly, FGF21 dampened immune response by repressing complement factors, MARCO, CD163, MRC1/CD206, CD4, CD45 and pro-inflammatory cytokine receptors. It also reverted procoagulant imbalance in MASLD, stimulated extracellular matrix degradation, repressed TGFβ- and integrin-signalling and lessened liver sinusoidal endothelial cell defenestration in support of fibrosis resolution.

CONCLUSIONS

We gained deep insight into FGF21-MoA in MASLD. However, heterogeneity in FGF21 expression calls for molecular stratifications as to identify patients which likely benefit from FGF21-based therapies.

KEY POINTS

Performed comprehensive genomics across liver biopsies of 396 MASLD patients and identified patients with increased, decreased and unchanged FGF21 expression. Used genomic data from FGF21 transgenic, knock-out and animal MASLD models treated with synthetic FGF21 analogues to identify FGF21-mode-of-action and metabolic networks in human MASLD. Given the significant heterogeneity in FGF21 expression, not all patients will benefit from FGF21-based therapies.

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.

Histone demethylases in autophagy and inflammation

Autophagy dysfunction is associated with changes in autophagy-related genes. Various factors are connected to autophagy, and the mechanism regulating autophagy is highly complicated. Epigenetic changes, such as aberrant expression of histone demethylase, are actively associated not only with oncogenesis but also with inflammatory responses. Among post-translational modifications, histone lysine methylation holds significant importance. There are over 30 members of histone lysine demethylases (KDMs), which act as epigenetic regulators in physiological processes and diseases. Importantly, KDMs are abnormally expressed in the regulation of cellular autophagy and inflammation, representing a crucial mechanism affecting inflammation-related diseases. This article reviewed the function of KDMs proteins in autophagy and inflammation. Specifically, It focused on the specific regulatory mechanisms underlying the activation or inhibition of autophagy, as well as their abnormal expression in inflammatory responses. By analyzing each KDM in epigenetic modification, this review provides a reliable theoretical basis for clinical decision marking regarding autophagy abnormalities and inflammatory diseases.

Crosstalk between ferroptosis and autophagy: broaden horizons of cancer therapy

Ferroptosis and autophagy are two main forms of regulated cell death (RCD). Ferroptosis is a newly identified RCD driven by iron accumulation and lipid peroxidation. Autophagy is a self-degradation system through membrane rearrangement. Autophagy regulates the metabolic balance between synthesis, degradation and reutilization of cellular substances to maintain intracellular homeostasis. Numerous studies have demonstrated that both ferroptosis and autophagy play important roles in cancer pathogenesis and cancer therapy. We also found that there are intricate connections between ferroptosis and autophagy. In this article, we tried to clarify how different kinds of autophagy participate in the process of ferroptosis and sort out the common regulatory pathways between ferroptosis and autophagy in cancer. By exploring the complex crosstalk between ferroptosis and autophagy, we hope to broaden horizons of cancer therapy.

New Insights into AMPK, as a Potential Therapeutic Target in Metabolic Dysfunction-Associated Steatotic Liver Disease and Hepatic Fibrosis

AMP-activated protein kinase (AMPK) activators have garnered significant attention for their potential to prevent the progression of metabolic dysfunction-associated steatotic liver disease (MASLD) into liver fibrosis and to fundamentally improve liver function. The broad spectrum of pathways regulated by AMPK activators makes them promising alternatives to conventional liver replacement therapies and the limited pharmacological treatments currently available. In this study, we aim to illustrate the newly detailed multiple mechanisms of MASLD progression based on the multiple-hit hypothesis. This model posits that impaired lipid metabolism, combined with insulin resistance and metabolic imbalance, initiates inflammatory cascades, gut dysbiosis, and the accumulation of toxic metabolites, ultimately promoting fibrosis and accelerating MASLD progression to irreversible hepatocellular carcinoma (HCC). AMPK plays a multifaceted protective role against these pathological conditions by regulating several key downstream signaling pathways. It regulates biological effectors critical to metabolic and inflammatory responses, such as SIRT1, Nrf2, mTOR, and TGF-β, through complex and interrelated mechanisms. Due to these intricate connections, AMPK's role is pivotal in managing metabolic and inflammatory disorders. In this review, we demonstrate the specific roles of AMPK and its related pathways. Several agents directly activate AMPK by binding as agonists, while some others indirectly activate AMPK by modulating upstream molecules, including adiponectin, LKB1, and the AMP: ATP ratio. As AMPK activators can target each stage of MASLD progression, the development of AMPK activators offers immense potential to expand therapeutic strategies for liver diseases such as MASH, MASLD, and liver fibrosis.

Autophagy in cancer development, immune evasion, and drug resistance

Macroautophagy/autophagy is a highly conserved evolutionary mechanism involving lysosomes for the degradation of cytoplasmic components including organelles. The constitutive, basal level of autophagy is fundamental for preserving cellular homeostasis; however, alterations in autophagy can cause disease pathogenesis, including cancer. The role of autophagy in cancer is particularly complicated, since this process acts both as a tumor suppressor in precancerous stages but facilitates tumor progression during carcinogenesis and later stages of cancer progression. This shift between anti-tumor and pro-tumor roles may be influenced by genetic and environmental factors modulating key pathways such as those involving autophagy-related proteins, the PI3K-AKT-MTOR axis, and AMPK, which often show dysregulation in tumors. Autophagy regulates various cellular functions, including metabolism of glucose, glutamine, and lipids, cell proliferation, metastasis, and several types of cell death (apoptosis, ferroptosis, necroptosis and immunogenic cell death). These multifaceted roles demonstrate the potential of autophagy to affect DNA damage repair, cell death pathways, proliferation and survival, which are critical in determining cancer cells' response to chemotherapy. Therefore, targeting autophagy pathways presents a promising strategy to combat chemoresistance, as one of the major reasons for the failure in cancer patient treatment. Furthermore, autophagy modulates immune evasion and the function of immune cells such as T cells and dendritic cells, influencing the tumor microenvironment and cancer's biological behavior. However, the therapeutic targeting of autophagy is complex due to its dual role in promoting survival and inducing cell death in cancer cells, highlighting the need for strategies that consider both the beneficial and detrimental effects of autophagy modulation in cancer therapy. Hence, both inducers and inhibitors of autophagy have been introduced for the treatment of cancer. This review emphasizes the intricate interplay between autophagy, tumor biology, and immune responses, offering insights into potential therapeutic approaches that deploy autophagy in the cancer suppression.

Oscillatory autophagy induction is enabled by an updated AMPK-ULK1 regulatory wiring

Autophagy-dependent survival relies on a crucial oscillatory response during cellular stress. Although oscillatory behaviour is typically associated with processes like the cell cycle or circadian rhythm, emerging experimental and theoretical evidence suggests that such periodic dynamics may explain conflicting experimental results in autophagy research. In this study, we demonstrate that oscillatory behaviour in the regulation of the non-selective, stress-induced macroautophagy arises from a series of interlinked negative and positive feedback loops within the mTORC1-AMPK-ULK1 regulatory triangle. While many of these interactions have been known for decades, recent discoveries have revealed how mTORC1, AMPK, and ULK1 are truly interconnected. Although these new findings initially appeared contradictory to established models, additional experiments and our systems biology analysis clarify the updated regulatory structure. Through computational modelling of the autophagy oscillatory response, we show how this regulatory network governs autophagy induction. Our results not only reconcile previous conflicting experimental observations but also offer insights for refining autophagy regulation and advancing understanding of its mechanisms of action.

Nucleo-cytosolic acetyl-CoA drives tumor immune evasion by regulating PD-L1 in melanoma

Acetyl coenzyme A (acetyl-CoA), a versatile central metabolite, plays a critical role in various metabolic processes and protein acetylation. While its impact on tumor cell properties is well established, the connection between acetyl-CoA metabolism and immune evasion in tumors remains unclear. Here, we uncover a mechanism by which nucleo-cytosolic acetyl-CoA contributes to immune evasion through regulation of programmed death ligand 1 (PD-L1). Specifically, bioinformatics analysis reveals a negative correlation between acetyl-CoA metabolism and anti-tumor immunity across multiple cancers. Inhibition of the acetyl-CoA-producing enzyme ATP-citrate lyase (ACLY) leads to a re-invigoration of cytotoxic T cells and enhances the efficacy of immunotherapy. Mechanistically, nucleo-cytosolic acetyl-CoA promotes PD-L1 transcription via P300-dependent histone H3K27 acetylation at the promoter region of CD274. The ACLY-H3K27ac-PD-L1 axis is verified in clinical specimens and predicts poor immunotherapy response. Our findings suggest that targeting acetyl-CoA metabolism may act as a promising strategy to overcome immune evasion and improve the outcomes of cancer immunotherapy.

Bee Pollen as a Source of Biopharmaceuticals for Neurodegeneration and Cancer Research: A Scoping Review and Translational Prospects

Bee Pollen (BP) has many advantageous properties relying on its multitargeting potential, a new tendency in managing many challenging illnesses. In cancer and neurodegeneration, the multiple effects of BP could be of unequaled importance and need further investigation. Although still limited, available data interestingly spotlights some floral sources with promising activities in line with this investigation. Adopting scoping review methodology, we have identified many crucial bioactivities that are widely recognized to individual BP compounds but remain completely untapped in this valuable bee cocktail. A wide range of these compounds have been recently found to be endowed with great potential in modulating pivotal processes in neurodegeneration and cancer pathophysiology. In addition, some ubiquitous BP compounds have only been recently isolated, while the number of studied BPs remains extremely limited compared to the endless pool of plant species worldwide. We have also elucidated that clinical profits from these promising perspectives are still impeded by challenging hurdles such as limited bioavailability of the studied phytocompounds, diversity and lack of phytochemical standardization of BP, and the difficulty of selective targeting in some pathophysiological mechanisms. We finally present interesting insights to guide future research and pave the way for urgently needed and simplified clinical investigations.

Amino Acid Metabolism and Autophagy in Atherosclerotic Cardiovascular Disease

Cardiovascular disease is the most common cause of mortality globally, accounting for approximately one out of three deaths. The main underlying pathology is atherosclerosis, a dyslipidemia-driven, chronic inflammatory disease. The interplay between immune cells and non-immune cells is of great importance in the complex process of atherogenesis. During atheroprogression, intracellular metabolic pathways, such as amino acid metabolism, are master switches of immune cell function. Autophagy, an important stress survival mechanism involved in maintaining (immune) cell homeostasis, is crucial during the development of atherosclerosis and is strongly regulated by the availability of amino acids. In this review, we focus on the interplay between amino acids, especially L-leucine, L-arginine, and L-glutamine, and autophagy during atherosclerosis development and progression, highlighting potential therapeutic perspectives.

Polysaccharides targeting autophagy to alleviate metabolic syndrome

Metabolic syndrome is a prevalent non-communicable disease characterized by central obesity, insulin resistance, hypertension, hyperglycemia, and hyperlipidemia. Epidemiological statistics indicate that one-third of the world's population is affected by metabolic syndrome. Unfortunately, owing to complicated pathogenesis and limited pharmacological options, the growing prevalence of metabolic syndrome threatens human health worldwide. Autophagy is an intracellular degradation mechanism that involves the degradation of unfolded or aggregated proteins and damaged cellular organelles, thereby maintaining metabolic homeostasis. Increasing evidence indicates that dysfunctional autophagy is closely associated with the development of metabolic syndrome, making it an attractive therapeutic target. Furthermore, a growing number of plant-derived polysaccharides have been shown to regulate autophagy, thereby alleviating metabolic syndrome, such as Astragalus polysaccharides, Laminaria japonica polysaccharides, Ganoderma lucidum polysaccharides and Lycium barbarum polysaccharides. In this review, we summarize recent advances in the discovery of autophagy modulators of plant polysaccharides for the treatment of metabolic syndrome, with the aim of providing precursor compounds for the development of new therapeutic agents. Additionally, we look forward to seeing more diseases being treated with plant polysaccharides by regulating autophagy, as well as the discovery of more intricate mechanisms that govern autophagy.

Programmed cell death: molecular mechanisms, biological functions, diseases, and therapeutic targets

Programmed cell death represents a precisely regulated and active cellular demise, governed by a complex network of specific genes and proteins. The identification of multiple forms of programmed cell death has significantly advanced the understanding of its intricate mechanisms, as demonstrated in recent studies. A thorough grasp of these processes is essential across various biological disciplines and in the study of diseases. Nonetheless, despite notable progress, the exploration of the relationship between programmed cell death and disease, as well as its clinical application, are still in a nascent stage. Therefore, further exploration of programmed cell death and the development of corresponding therapeutic methods and strategies holds substantial potential. Our review provides a detailed examination of the primary mechanisms behind apoptosis, autophagy, necroptosis, pyroptosis, and ferroptosis. Following this, the discussion delves into biological functions and diseases associated dysregulated programmed cell death. Finally, we highlight existing and potential therapeutic targets and strategies focused on cancers and neurodegenerative diseases. This review aims to summarize the latest insights on programmed cell death from mechanisms to diseases and provides a more reliable approach for clinical transformation.

The metabolic sensor AMPK: Twelve enzymes in one

BACKGROUND

AMP-activated protein kinase (AMPK) is an evolutionarily conserved regulator of energy metabolism. AMPK is sensitive to acute perturbations to cellular energy status and leverages fundamental bioenergetic pathways to maintain cellular homeostasis. AMPK is a heterotrimer comprised of αβγ-subunits that in humans are encoded by seven individual genes (isoforms α1, α2, β1, β2, γ1, γ2 and γ3), permitting formation of at least 12 different complexes with personalised biochemical fingerprints and tissue expression patterns. While the canonical activation mechanisms of AMPK are well-defined, delineation of subtle, as well as substantial, differences in the regulation of heterogenous AMPK complexes remain poorly defined.

SCOPE OF REVIEW

Here, taking advantage of multidisciplinary findings, we dissect the many aspects of isoform-specific AMPK function and links to health and disease. These include, but are not limited to, allosteric activation by adenine nucleotides and small molecules, co-translational myristoylation and post-translational modifications (particularly phosphorylation), governance of subcellular localisation, and control of transcriptional networks. Finally, we delve into current debate over whether AMPK can form novel protein complexes (e.g., dimers lacking the α-subunit), altogether highlighting opportunities for future and impactful research.

MAJOR CONCLUSIONS

Baseline activity of α1-AMPK is higher than its α2 counterpart and is more sensitive to synergistic allosteric activation by metabolites and small molecules. α2 complexes however, show a greater response to energy stress (i.e., AMP production) and appear to be better substrates for LKB1 and mTORC1 upstream. These differences may explain to some extent why in certain cancers α1 is a tumour promoter and α2 a suppressor. β1-AMPK activity is toggled by a 'myristoyl-switch' mechanism that likely precedes a series of signalling events culminating in phosphorylation by ULK1 and sensitisation to small molecules or endogenous ligands like fatty acids. β2-AMPK, not entirely beholden to this myristoyl-switch, has a greater propensity to infiltrate the nucleus, which we suspect contributes to its oncogenicity in some cancers. Last, the unique N-terminal extensions of the γ2 and γ3 isoforms are major regulatory domains of AMPK. mTORC1 may directly phosphorylate this region in γ2, although whether this is inhibitory, especially in disease states, is unclear. Conversely, γ3 complexes might be preferentially regulated by mTORC1 in response to physical exercise.

AMPK: Balancing mitochondrial quality and quantity through opposite regulation of mitophagy pathways

In this issue of Molecular Cell, Longo et al.1 reveal that AMPK, a regulatory kinase activated by metabolic stress, inhibits NIX/BNIP3-dependent mitophagy to preserve mitochondrial quantity and activates PINK1/Parkin-dependent mitophagy to ensure mitochondrial quality.

New developments in AMPK and mTORC1 cross-talk

Metabolic homeostasis and the ability to link energy supply to demand are essential requirements for all living cells to grow and proliferate. Key to metabolic homeostasis in all eukaryotes are AMPK and mTORC1, two kinases that sense nutrient levels and function as counteracting regulators of catabolism (AMPK) and anabolism (mTORC1) to control cell survival, growth and proliferation. Discoveries beginning in the early 2000s revealed that AMPK and mTORC1 communicate, or cross-talk, through direct and indirect phosphorylation events to regulate the activities of each other and their shared protein substrate ULK1, the master initiator of autophagy, thereby allowing cellular metabolism to rapidly adapt to energy and nutritional state. More recent reports describe divergent mechanisms of AMPK/mTORC1 cross-talk and the elaborate means by which AMPK and mTORC1 are activated at the lysosome. Here, we provide a comprehensive overview of current understanding in this exciting area and comment on new evidence showing mTORC1 feedback extends to the level of the AMPK isoform, which is particularly pertinent for some cancers where specific AMPK isoforms are implicated in disease pathogenesis.

Prolonged glutamine starvation reactivates mTOR to inhibit autophagy and initiate autophagic lysosome reformation to maintain cell viability

Autophagy, a cellular recycling mechanism, utilizes lysosomes for cellular degradation. Prolonged autophagy reduces the pool of functional lysosomes in the cell. However, lysosomal homeostasis is maintained through the regeneration of functional lysosomes during the terminal stage of autophagy, i.e. Autophagic lysosome reformation (ALR). Through confocal microscopy during glutamine starvation, we unravel the regeneration of tubules from autolysosomes by undertaking significant membrane remodeling, which majorly depends on mTOR reactivation, RAB7 dissociation, phosphatidyl inositol 3 phosphate (PI3P) dependent-dynamin 2 and clathrin recruitment. In glutamine-starved cells, we found mTOR is the central modulator in regulating ALR initiation, and its pharmacological inhibition with rapamycin leads to a decrease in lysosomal tubulation. Moreover, RAB7 and Clathrin are essential for tubule elongation and it showed that siRNA targeting RAB7 and Clathrin restricts tubule initiation under glutamine starvation. In this setting, we examined the physiological relevance of ALR during prolonged glutamine deprivation and found that genetic and pharmacological inhibition of critical proteins involved in ALR promotes cell death in oral cancer cells, establishing ALR is essential for maintaining cell survival during stress.

Integrated multiomics analysis identified comprehensive crosstalk between diverse programmed cell death patterns and novel molecular subtypes in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a highly aggressive malignancy with increasing global prevalence and is one of the leading causes of cancer-related mortality in the human population. Developing robust clinical prediction models and prognostic stratification strategies is crucial for developing individualized treatment plans. A range of novel forms of programmed cell death (PCD) plays a role in the pathological progression and advancement of HCC, and in-depth study of PCD is expected to further improve the prognosis of HCC patients. Sixteen patterns (apoptosis, autophagy, anoikis, lysosome-dependent cell death, immunogenic cell death, necroptosis, ferroptosis, netosis, pyroptosis, disulfidptosis, entotic cell death, cuproptosis, parthanatos, netotic cell death, alkaliptosis, and oxeiptosis) related to PCD were collected from the literatures and used for subsequent analysis. Supervised (Elastic net, Random Forest, XgBoost, and Boruta) and unsupervised (Nonnegative Matrix Factorization, NMF) clustering algorithms were applied to develop and validate a novel classifier for the individualized management of HCC patients at the transcriptomic, proteomic and single-cell levels. Multiple machine learning algorithms developed a programmed cell death index (PCDI) comprising five robust signatures (FTL, G6PD, SLC2A1, HTRA2, and DLAT) in four independent HCC cohorts, and a higher PCDI was predictive of higher pathological grades and worse prognoses. Furthermore, a higher PCDI was found to be correlated with the presence of a repressive tumor immune microenvironment (TME), as determined through an integrated examination of bulk and single-cell transcriptome data. In addition, patients with TP53 mutation had higher PCDI in comparison with TP53 WT patients. Three HCC subtypes were identified through unsupervised clustering (NMF), exhibiting distinct prognoses and significant biological processes, among the three subtypes, PCDcluster 3 was of particular interest as it contained a large proportion of patients with high risk and low metabolic activity. Construction and evaluation of the Nomogram model was drawn based on the multivariate logistic regression analysis, and highlighted the robustness of the Nomogram model in other independent HCC cohorts. Finally, to explore the prognostic value, we also validated the frequent upregulation of DLAT in a real-world cohort of human HCC specimens by qPCR, western blot, and immunohistochemical staining (IHC). Together, our work herein comprehensively emphasized PCD-related patterns and key regulators, such as DLAT, contributed to the evolution and prognosis of tumor foci in HCC patients, and strengthened our understanding of PCD characteristics and promoted more effective risk stratification strategies.

Mitochondrial Bioenergetics Deficiency in cisd-1 Mutants is Linked to AMPK-Mediated Lipid Metabolism

BACKGROUND

CISD-1 is a mitochondrial iron-sulfate [2Fe-2S] protein known to be associated with various human diseases, including cancer and diabetes. Previously, we demonstrated that CISD-1 deficiency in worms lowers glucose and ATP levels. In this study, we further explored how worms compensate for lower ATP levels by analyzing changes in cytoplasmic and mitochondrial iron content, AMPK activities, and total lipid profiles.

MATERIALS AND METHODS

Expression levels of CISD-1 and CISD-1::GFP fusion proteins in wild-type worms (N2), cisd-1-deletion mutants (tm4993 and syb923) and GFP insertion transgenic worms (PHX953 and SJL40) were examined by western blot. Fluorescence microscopy analyzed CISD-1::GFP pattern in PHX953 embryos and adults, and lipid droplet sizes in N2, cisd-1, aak-2 and aak-2;cisd-1 worms. Total and mitochondrial iron content, electron transport complex profiles, and AMPK activity were investigated in tm4993 and syb923 mutants. mRNA levels of mitochondrial β-oxidation genes, acs-2, cpt-5, and ech-1, were quantified by RT-qPCR in various genetic worm strains. Lipidomic analyses were performed in N2 and cisd-1(tm4993) worms.

RESULTS

Defects in cisd-1 lead to an imbalance in iron transport and cause proton leak, resulting in lower ATP production by interrupting the mitochondrial electron transport chain. We identified a signaling pathway that links ATP deficiency-induced AMPK (AMP activated protein kinase) activation to the expression of genes that facilitate lipolysis via β-oxidation.

CONCLUSION

Our data provide a functional coordination between CISD-1 and AMPK constitutes a mitochondrial bioenergetics quality control mechanism that provides compensatory energy resources.

An updated outlook on autophagy mechanism and how it supports acute myeloid leukemia maintenance

The gradual acquisition of genetic and epigenetic disturbances bestows malignant traits upon hematopoietic stem cells, subverting them into a founder and reservoir cell for de novo acute myeloid leukemia (AML) known as leukemic stem cells (LSC). Beyond its molecular heterogeneity, AML is also characterized by rewiring biological processes to support its onset and maintenance. LSC were observed to inherently and actively trigger mitochondrial turnover through selective autophagic removal such that impairing the process led to cell differentiation at the expense of its stemness. This review provides a current take on autophagy regulation mechanisms according to the current molecular characterization of the process; describes autophagy as a drug resistance mechanism, and a pivotal mechanism whereby LSC harmonize their strong reliance on mitochondrial respiration to obtain energy, and their necessity for lower internal oxidative stress to avoid exhaustion. Therefore, targeting autophagy presents a promising strategy to promote long-term remissions in AML.

Regulatory Mechanisms Governing the Autophagy-Initiating VPS34 Complex and Its inhibitors

VPS34 is a crucial protein in cells, essential for handling cellular stress through its involvement in autophagy and endocytosis. This protein functions as a Class III phosphatidylinositol 3-kinase, producing phosphatidylinositol 3-phosphate, which is necessary for autophagy and vesicle trafficking. Additionally, VPS34 forms two mutually exclusive complexes, each playing a vital role in autophagy and endocytic sorting. These complexes share common subunits, including VPS15, VPS34, and Beclin 1, with complex I having ATG14 as a specific subunit. Due to its association with various human diseases, regulation of the VPS34 complex I has garnered significant interest, emerging as a potential therapeutic target for drug discovery. Summaries of the structure, function of VPS34 complexes, and developed VPS34 inhibitors have been provided, along with discussions on the regulation mechanism of VPS34, particularly in relation to the initiation complex I of autophagy. This offers valuable insights for treating autophagy-related diseases.

No energy, no autophagy-Mechanisms and therapeutic implications of autophagic response energy requirements

Autophagy is a lysosome-mediated self-degradation process of central importance for cellular quality control. It also provides macromolecule building blocks and substrates for energy metabolism during nutrient or energy deficiency, which are the main stimuli for autophagy induction. However, like most biological processes, autophagy itself requires ATP, and there is an energy threshold for its initiation and execution. We here present the first comprehensive review of this often-overlooked aspect of autophagy research. The studies in which ATP deficiency suppressed autophagy in vitro and in vivo were classified according to the energy pathway involved (oxidative phosphorylation or glycolysis). A mechanistic insight was provided by pinpointing the critical ATP-consuming autophagic events, including transcription/translation/interaction of autophagy-related molecules, autophagosome formation/elongation, autophagosome fusion with the lysosome, and lysosome acidification. The significance of energy-dependent fine-tuning of autophagic response for preserving the cell homeostasis, and potential implications for the therapy of cancer, autoimmunity, metabolic disorders, and neurodegeneration are discussed.

AMPK, a hub for the microenvironmental regulation of bone homeostasis and diseases

AMP-activated protein kinase (AMPK), a crucial regulatory kinase, monitors energy levels, conserving ATP and boosting synthesis in low-nutrition, low-energy states. Its sensitivity links microenvironmental changes to cellular responses. As the primary support structure and endocrine organ, the maintenance, and repair of bones are closely associated with the microenvironment. While a series of studies have explored the effects of specific microenvironments on bone, there is lack of angles to comprehensively evaluate the interactions between microenvironment and bone cells, especially for bone marrow mesenchymal stem cells (BMMSCs) which mediate the differentiation of osteogenic lineage. It is noteworthy that accumulating evidence has indicated that AMPK may serve as a hub between BMMSCs and microenvironment factors, thus providing a new perspective for us to understand the biology and pathophysiology of stem cells and bone. In this review, we emphasize AMPK's pivotal role in bone microenvironment modulation via ATP, inflammation, reactive oxygen species (ROS), calcium, and glucose, particularly in BMMSCs. We further explore the use of AMPK-activating drugs in the context of osteoarthritis and osteoporosis. Moreover, building upon the foundation of AMPK, we elucidate a viewpoint that facilitates a comprehensive understanding of the dynamic relationship between the microenvironment and bone homeostasis, offering valuable insights for prospective investigations into stem cell biology and the treatment of bone diseases.

Dihydromyricetin Improves High Glucose-Induced Dopaminergic Neuronal Damage by Activating AMPK-Autophagy Signaling Pathway

INTRODUCTION

In recent years, a growing number of clinical and biological studies have shown that patients with type 2 diabetes mellitus (T2DM) are at increased risk of developing Parkinson's disease (PD). Prolonged exposure to hyperglycemia results in abnormal glucose metabolism, which in turn causes pathological changes similar to PD, leading to selective loss of dopaminergic neurons in the compact part of the substantia nigra. Dihydromyricetin (DHM) is a naturally occurring flavonoid with various biological activities including antioxidant and hepatoprotective properties. In this study, the effect of DHM on high glucose-induced dopaminergic neuronal damage was investigated.

METHODS

The potential modulatory effects of DHM on high glucose-induced dopaminergic neuronal damage and its mechanism were studied.

RESULTS

DHM ameliorated high glucose-induced dopaminergic neuronal damage and autophagy injury. Inhibition of autophagy by 3-methyladenine abrogated the beneficial effects of DHM on high glucose-induced dopaminergic neuronal damage. In addition, DHM increased levels of p-AMP-activated protein kinase (AMPK) and phosphorylated UNC51-like kinase 1. The AMPK inhibitor compound C eliminated DHM-induced autophagy and subsequently inhibited the ameliorative effects of DHM on high glucose-induced dopaminergic neuronal damage.

DISCUSSION

DHM ameliorates high glucose-induced dopaminergic neuronal damage by activating the AMPK-autophagy pathway.

Enhancing Cellular Homeostasis: Targeted Botanical Compounds Boost Cellular Health Functions in Normal and Premature Aging Fibroblasts

The human skin, the body's largest organ, undergoes continuous renewal but is significantly impacted by aging, which impairs its function and leads to visible changes. This study aimed to identify botanical compounds that mimic the anti-aging effects of baricitinib, a known JAK1/2 inhibitor. Through in silico screening of a botanical compound library, 14 potential candidates were identified, and 7 were further analyzed for their effects on cellular aging. The compounds were tested on both normal aged fibroblasts and premature aging fibroblasts derived from patients with Hutchinson-Gilford Progeria Syndrome (HGPS). Results showed that these botanical compounds effectively inhibited the JAK/STAT pathway, reduced the levels of phosphorylated STAT1 and STAT3, and ameliorated phenotypic changes associated with cellular aging. Treatments improved cell proliferation, reduced senescence markers, and enhanced autophagy without inducing cytotoxicity. Compounds, such as Resveratrol, Bisdemethoxycurcumin, Pinosylvin, Methyl P-Hydroxycinnamate, cis-Pterostilbene, and (+)-Gallocatechin, demonstrated significant improvements in both control and HGPS fibroblasts. These findings suggest that these botanical compounds have the potential to mitigate age-related cellular alterations, offering promising strategies for anti-aging therapies, particularly for skin health. Further in vivo studies are warranted to validate these results and explore their therapeutic applications.

c-Jun N-terminal Kinase Supports Autophagy in Testicular Ischemia but Triggers Apoptosis in Ischemia-Reperfusion Injury

Oxidative stress triggered by testicular torsion and detorsion in young males could negatively impact future fertility. Using a rat animal model for testicular IRI (tIRI), we aim to study the induction of autophagy (ATG) during testicular ischemia and tIRI and the role of oxidative-stress-induced c-Jun N-terminal Kinase (JNK) as a cytoprotective mechanism. Sixty male Sprague-Dawley rats were divided into five groups: sham, ischemia only, ischemia+SP600125 (a JNK inhibitor), tIRI only, and tIRI+SP600125. The tIRI rats underwent an ischemic injury for 1 h followed by 4 h of reperfusion, while ischemic rats were subjected to 1 h of ischemia only without reperfusion. Testicular-ischemia-induced Beclin 1 and LC3B expression was associated with decreased p62/SQSTM1 expression, increased ATP and alkaline phosphatase (AP) activity, and slightly impaired spermatogenesis. SP600125 treatment improved p62 expression and reduced the levels of Beclin 1 and LC3B but did not affect ATP or AP levels. The tIRI-induced apoptosis lowered the expression of the three ATG proteins and AP activity, activated caspase 3, and caused spermatogenic arrest. SP600125-inhibited JNK during tIRI restored sham levels to all investigated parameters. This study emphasizes the regulatory role of JNK in balancing autophagy and apoptosis during testicular oxidative injuries.

Poricoic acid a ameliorates high glucose-induced podocyte injury by regulating the AMPKα/FUNDC1 pathway

BACKGROUND

Poricoic acid A (PAA), a major triterpenoid component of Poria cocos with anti-tumor, anti-fibrotic, anti-inflammatory, and immune-regulating activities, has been shown to induce podocyte autophagy in diabetic kidney disease (DKD) by downregulating FUN14 domain containing 1 (FUNDC1). This study aimed to identify the role of adenosine monophosphate-activated protein kinase alpha (AMPKα) in PAA-mediated phosphorylation of FUNDC1 in podocyte injury occurring in the pathogenesis of DKD.

METHODS AND RESULTS

A cellular model of renal podocyte injury was established by culturing MPC5 cells under high-glucose (HG) conditions. MPC5 cells were subjected to transfection with small interfering RNA (siRNA) targeting AMPKα or siRNA targeting FUNDC1, an AMPKα activator, or PAA. PAA treatment induced the phosphorylation of AMPKα in HG-cultured podocytes. AMPKα activation was implicated in the inhibitory effect of PAA on FUNDC phosphorylation in HG-cultured podocytes. Treatment targeting the AMPKα activator also significantly augmented proliferation, migration, mitochondrial membrane potential, and autophagy levels, while reducing apoptosis levels, inhibiting oxidative stress, and suppressing the release of proinflammatory factors in HG-cultured MPC5 cells. In contrast, insufficient expression of AMPKα reversed the effects of PAA on the proliferation, migration, and apoptosis of podocytes and further exacerbated the reduction of phosphorylated FUNDC1 expression in podocytes under HG conditions.

CONCLUSIONS

AMPKα is involved in the regulation of FUNDC1 phosphorylation by PAA in HG-induced podocyte injury. Furthermore, the AMPKα/FUNDC1 pathway plays a crucial regulatory role in HG-induced podocyte injury. These findings support AMPKα, FUNDC1, and the AMPKα/FUNDC1 pathway as targets for PAA intervention.

Quercetin ameliorates oxidative stress-induced apoptosis of granulosa cells in dairy cow follicular cysts by activating autophagy via the SIRT1/ROS/AMPK signaling pathway

BACKGROUND

Follicular cysts contribute significantly to reproductive loss in high-yield dairy cows. This results from the death of follicular granulosa cells (GCs) caused by oxidative stress. Quercetin is known to have significant antioxidant and anti-apoptotic effects. However, the effect of quercetin on follicular cysts has yet been elucidated. Therefore, this study aimed to explore the anti-oxidant and anti-apoptosis effects and potential molecular mechanisms of quercetin in H2O2-induced primary cow GCs and 3-nitropropionic acid (3-NPA)-induced mouse model of oxidative stress and thus treat ovarian cysts in dairy cows.

RESULTS

In this study, compared with estrus cows, cows with follicular cysts showed heightened levels of oxidative stress and increased follicular cell apoptosis, while autophagy levels were reduced. A model of oxidative stress was induced in vitro by H2O2 and showed significant increases in apoptosis together with reduced autophagy. These effects were significantly ameliorated by quercetin. Effects similar to those of quercetin were observed after treatment of cells with the reactive oxygen species (ROS) inhibitor N-acetylcysteine (NAC). Further investigations using chloroquine (autophagy inhibitor), rapamycin (autophagy activator), selisistat (SIRT1 inhibitor), and compound C (AMPK inhibitor) showed that chloroquine counteracted the effects of quercetin on oxidative stress-induced apoptosis, while rapamycin had the same effect as quercetin. In addition, the SIRT1/AMPK pathway inhibitors antagonized quercetin-mediated mitigation of the effects of oxidative stress on increased apoptosis and reduced autophagy. Consistent with the results in vitro, in mouse ovarian oxidative stress model induced by 3-NPA, quercetin activated autophagy through the SIRT1/AMPK signaling pathway, while alleviating oxidative stress damage and inhibiting apoptosis in mouse ovaries.

CONCLUSIONS

These findings indicate that quercetin can inhibit apoptosis in GCs and restore ovarian function by activating autophagy through the SIRT1/ROS/AMPK signaling pathway, suggesting a new direction for the treatment of ovarian follicular cysts in high-yield dairy cows.

Unexpected roles for AMPK in the suppression of autophagy and the reactivation of MTORC1 signaling during prolonged amino acid deprivation

AMPK promotes catabolic and suppresses anabolic cell metabolism to promote cell survival during energetic stress, in part by inhibiting MTORC1, an anabolic kinase requiring sufficient levels of amino acids. We found that cells lacking AMPK displayed increased apoptotic cell death during nutrient stress caused by prolonged amino acid deprivation. We presumed that impaired macroautophagy/autophagy explained this phenotype, as a prevailing view posits that AMPK initiates autophagy (often a pro-survival response) through phosphorylation of ULK1. Unexpectedly, however, autophagy remained unimpaired in cells lacking AMPK, as monitored by several autophagic readouts in several cell lines. More surprisingly, the absence of AMPK increased ULK1 signaling and MAP1LC3B/LC3B lipidation during amino acid deprivation while AMPK-mediated phosphorylation of ULK1 S555 (a site proposed to initiate autophagy) decreased upon amino acid withdrawal or pharmacological MTORC1 inhibition. In addition, activation of AMPK with compound 991, glucose deprivation, or AICAR blunted autophagy induced by amino acid withdrawal. These results demonstrate that AMPK activation and glucose deprivation suppress autophagy. As AMPK controlled autophagy in an unexpected direction, we examined how AMPK controls MTORC1 signaling. Paradoxically, we observed impaired reactivation of MTORC1 in cells lacking AMPK upon prolonged amino acid deprivation. Together these results oppose established views that AMPK promotes autophagy and inhibits MTORC1 universally. Moreover, they reveal unexpected roles for AMPK in the suppression of autophagy and the support of MTORC1 signaling in the context of prolonged amino acid deprivation. These findings prompt a reevaluation of how AMPK and its control of autophagy and MTORC1 affect health and disease.

Ferroptosis and iron metabolism in diabetes: Pathogenesis, associated complications, and therapeutic implications

Diabetes mellitus is a complex chronic disease, considered as one of the most common metabolic disorders worldwide, posing a major threat to global public health. Ferroptosis emerges as a novel mechanism of programmed cell death, distinct from apoptosis, necrosis, and autophagy, driven by iron-dependent lipid peroxidation accumulation and GPx4 downregulation. A mounting body of evidence highlights the interconnection between iron metabolism, ferroptosis, and diabetes pathogenesis, encompassing complications like diabetic nephropathy, cardiomyopathy, and neuropathy. Moreover, ferroptosis inhibitors hold promise as potential pharmacological targets for mitigating diabetes-related complications. A better understanding of the role of ferroptosis in diabetes may lead to an improvement in global diabetes management. In this review, we delve into the intricate relationship between ferroptosis and diabetes development, exploring associated complications and current pharmacological treatments.

Autophagy: Are Amino Acid Signals Dependent on the mTORC1 Pathway or Independent?

Autophagy is a kind of "self-eating" phenomenon that is ubiquitous in eukaryotic cells. It mainly manifests in the damaged proteins or organelles in the cell being wrapped and transported by the autophagosome to the lysosome for degradation. Many factors cause autophagy in cells, and the mechanism of nutrient-deficiency-induced autophagy has been a research focus. It has been reported that amino-acid-deficiency-induced cellular autophagy is mainly mediated through the mammalian rapamycin target protein complex 1 (mTORC1) signaling pathway. In addition, some researchers also found that non-mTORC1 signaling pathways also regulate autophagy, and the mechanism of autophagy occurrence induced by the deficiency of different amino acids is not precisely the same. Therefore, this review aims to summarize the process of various amino acids regulating cell autophagy and provide a narrative review on the molecular mechanism of amino acids regulating autophagy.

AMPK regulates phagophore-to-autophagosome maturation

Autophagy is an important metabolic pathway that can non-selectively recycle cellular material or lead to targeted degradation of protein aggregates or damaged organelles. Autophagosome formation starts with autophagy factors accumulating on lipid vesicles containing ATG9. These phagophores attach to donor membranes, expand via ATG2-mediated lipid transfer, capture cargo, and mature into autophagosomes, ultimately fusing with lysosomes for their degradation. Autophagy can be activated by nutrient stress, for example, by a reduction in the cellular levels of amino acids. In contrast, how autophagy is regulated by low cellular ATP levels via the AMP-activated protein kinase (AMPK), an important therapeutic target, is less clear. Using live-cell imaging and an automated image analysis pipeline, we systematically dissect how nutrient starvation regulates autophagosome biogenesis. We demonstrate that glucose starvation downregulates autophagosome maturation by AMPK-mediated inhibition of phagophore tethering to donor membrane. Our results clarify AMPKs regulatory role in autophagy and highlight its potential as a therapeutic target to reduce autophagy.

Physiological functions of ULK1/2

UNC-51-like kinases 1 and 2 (ULK1/2) are serine/threonine kinases that are best known for their evolutionarily conserved role in the autophagy pathway. Upon sensing the nutrient status of a cell, ULK1/2 integrate signals from upstream cellular energy sensors such as mTOR and AMPK and relay them to the downstream components of the autophagy machinery. ULK1/2 also play indispensable roles in the selective autophagy pathway, removing damaged mitochondria, invading pathogens, and toxic protein aggregates. Additional functions of ULK1/2 have emerged beyond autophagy, including roles in protein trafficking, RNP granule dynamics, and signaling events impacting innate immunity, axon guidance, cellular homeostasis, and cell fate. Therefore, it is no surprise that alterations in ULK1/2 expression and activity have been linked with pathophysiological processes, including cancer, neurological disorders, and cardiovascular diseases. Growing evidence suggests that ULK1/2 function as biological rheostats, tuning cellular functions to intra and extra-cellular cues. Given their broad physiological relevance, ULK1/2 are candidate targets for small molecule activators or inhibitors that may pave the way for the development of therapeutics for the treatment of diseases in humans.

Autophagy alterations in obesity, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease: the evidence from human studies

Autophagy is an evolutionarily conserved process that plays a pivotal role in the maintenance of cellular homeostasis and its impairment has been implicated in the pathogenesis of various metabolic diseases including obesity, type 2 diabetes (T2D), and metabolic dysfunction-associated steatotic liver disease (MASLD). This review synthesizes the current evidence from human studies on autophagy alterations under these metabolic conditions. In obesity, most data point to autophagy upregulation during the initiation phase of autophagosome formation, potentially in response to proinflammatory conditions in the adipose tissue. Autophagosome formation appears to be enhanced under hyperglycemic or insulin-resistant conditions in patients with T2D, possibly acting as a compensatory mechanism to eliminate damaged organelles and proteins. Other studies have proposed that prolonged hyperglycemia and disrupted insulin signaling hinder autophagic flux, resulting in the accumulation of dysfunctional cellular components that can contribute to β-cell dysfunction. Evidence from patients with MASLD supports autophagy inhibition in disease progression. Nevertheless, given the available data, it is difficult to ascertain whether autophagy is enhanced or suppressed in these conditions because the levels of autophagy markers depend on the overall metabolism of specific organs, tissues, experimental conditions, or disease duration. Owing to these constraints, determining whether the observed shifts in autophagic activity precede or result from metabolic diseases remains challenging. Additionally, autophagy-modulating strategies are shortly discussed. To conclude, more studies investigating autophagy impairment are required to gain a more comprehensive understanding of its role in the pathogenesis of obesity, T2D, and MASLD and to unveil novel therapeutic strategies for these conditions.