bims-amsmem 2022-08-14 papers

bims-amsmem

Biomed News

on AMPK signaling mechanism in energy metabolism

Issue of 2022–08–14
eightteen papers selected by
Dipsikha Biswas, Københavns Universitet

Molecular mechanism underlying impaired hepatic autophagy in glycogen storage disease type Ib.
The role of AMPK-Sirt1-autophagy pathway in the intestinal protection process by propofol against regional ischemia/reperfusion injury in rats.
Chronic AMPK Activation Reduces the Expression and Alters Distribution of Synaptic Proteins in Neuronal SH-SY5Y Cells.
2-deoxyglucose transiently inhibits yeast AMPK signaling and triggers glucose transporter endocytosis, potentiating the drug toxicity.
Hernandezine, a natural herbal alkaloid, ameliorates type 2 diabetes by activating AMPK in two mouse models.
Harmol promotes α-synuclein degradation and improves motor impairment in Parkinson's models via regulating autophagy-lysosome pathway.
Aerobic exercise ameliorates myocardial ischemia/reperfusion injury and thrombosis of diabetic rats via activation of AMPK/Sirt1/PGC-1α pathway.
Salvia-Nelumbinis naturalis improves lipid metabolism of NAFLD by regulating the SIRT1/AMPK signaling pathway.
Zinc Deficiency Induces Autophagy in HT-22 Mouse Hippocampal Neuronal Cell Line.
AXL Promotes Metformin-Induced Apoptosis Through Mediation of Autophagy by Activating ROS-AMPK-ULK1 Signaling in Human Esophageal Adenocarcinoma.
Resolvin D3 improves the impairment of insulin signaling in skeletal muscle and nonalcoholic fatty liver disease through AMPK/autophagy-associated attenuation of ER stress.
Aberrant HSF1 signaling activation underlies metformin amelioration of myocardial infarction in mice.
PTEN inhibits AMPK to control collective migration.
Silencing TUFM Inhibits Development of Monocrotaline-Induced Pulmonary Hypertension by Regulating Mitochondrial Autophagy via AMPK/mTOR Signal Pathway.
AMPKα2/HNF4A/BORIS/GLUT4 pathway promotes hepatocellular carcinoma cell invasion and metastasis in low glucose microenviroment.
Trehalose improves palmitic acid-induced apoptosis of osteoblasts by regulating SIRT3-medicated autophagy via the AMPK/mTOR/ULK1 pathway.
SESN2 prevents the slow-to-fast myofiber shift in denervated atrophy via AMPK/PGC-1α pathway.
The Mitochondrial NAD Kinase Functions as a Major Metabolic Regulator Upon Increased Energy Demand.

Hum Mol Genet. 2022 Aug 12. pii: ddac197. [Epub ahead of print]

Molecular mechanism underlying impaired hepatic autophagy in glycogen storage disease type Ib.

Sudeep Gautam, Lisa Zhang, Cheol Lee, Irina Arnaoutova, Hung Dar Chen, Roberta Resaz, Alessandra Eva, Brian C Mansfield, Janice Y Chou.

Type Ib glycogen storage disease (GSD-Ib) is caused by a deficiency in the G6P transporter (G6PT) that translocates G6P from the cytoplasm into the endoplasmic reticulum lumen, where the intraluminal G6P is hydrolyzed to glucose by glucose-6-phosphatase-α (G6Pase-α). Clinically, GSD-Ib patients manifest a metabolic phenotype of impaired blood glucose homeostasis and a long-term risk of hepatocellular adenoma/carcinoma (HCA/HCC). Studies have shown that autophagy deficiency contributes to hepatocarcinogenesis. In this study, we show that G6PT deficiency leads to impaired hepatic autophagy evident from attenuated expression of many components of the autophagy network, decreased autophagosome formation, and reduced autophagy flux. The G6PT-deficient liver displayed impaired SIRT1 and AMP-activated protein kinase (AMPK) signaling, along with reduced expression of SIRT1, forkhead boxO3a (FoxO3a), liver kinase B-1 (LKB1), and the active p-AMPK. Importantly, we show that overexpression of either SIRT1 or LKB1 in G6PT-deficient liver restored autophagy and SIRT1/FoxO3a and LKB1/AMPK signaling. The hepatosteatosis in G6PT-deficient liver decreased SIRT1 expression. LKB1 overexpression reduced hepatic triglycerides levels, providing a potential link between LKB1/AMPK signaling upregulation and the increase in SIRT1 expression. In conclusion, downregulation of SIRT1/FoxO3a and LKB1/AMPK signaling underlies impaired hepatic autophagy which may contribute to HCA/HCC development in GSD-Ib. Understanding this mechanism may guide future therapies.

DOI: https://doi.org/10.1093/hmg/ddac197
Int Immunopharmacol. 2022 Aug 04. pii: S1567-5769(22)00598-7. [Epub ahead of print]111 109114

The role of AMPK-Sirt1-autophagy pathway in the intestinal protection process by propofol against regional ischemia/reperfusion injury in rats.

Xiao Liu, Bo Yang, Ya-Fang Tan, Jian-Guo Feng, Jing Jia, Cheng-Jie Yang, Ye Chen, Mao-Hua Wang, Jun Zhou.

  Intestinal ischemia/reperfusion (II/R) is a clinical event associated with high morbidity and mortality. AMP-activated protein kinase (AMPK), a central cellular energy sensor, is associated with oxidative stress and inflammation. However, whether the AMPK is involved in the II/R-induced intestinal injury and the underlying mechanism is yet to be elucidated. Propofol has a protective effect on organs; yet, its specific mechanism of action remains unclear. This study explored the role of the AMPK-Sirt1-autophagy pathway in intestinal injury, and whether propofol could reduce intestinal injury and investigated the mechanisms in a rat model of II/R injury as well as a cell model (IEC-6 cells) of hypoxia/reoxygenation (H/R). Propofol, AMPK agonist (AICAR) and AMPK inhibitor (Compound C) were then administered, respectively. The histopathological changes, cell viability and apoptosis were detected. Furthermore, the levels of proinflammatory factors, the activities of oxidative stress, diamine oxidase, and signaling pathway were also analyzed. The results demonstrated that the AMPK-Sirt1-autophagy pathway of intestine was activated after II/R or H/R. Propofol could further activate the pathway, which reduced intestinal injury, inhibited apoptosis, reversed inflammation and oxidative stress, and improved the 24-hour survival rate in II/R rats in vivo, and attenuated H/R-induced IEC-6 cell injury, oxidative stress, and apoptosis in vitro, as fine as changes in AICAR treatment. Compound C abrogated the protective effect of propofol on II/R and H/R-induced injury. These results suggested a crucial effect of AMPK on the mechanism of intestinal injury and might provide a new insight into the mechanism of propofol reducing II/R injury.

Keywords:  AMPK; Autophagy; Intestinal injury; Propofol; Sirt1

DOI:  https://doi.org/10.1016/j.intimp.2022.109114
Cells. 2022 Jul 31. pii: 2354. [Epub ahead of print]11(15):

Chronic AMPK Activation Reduces the Expression and Alters Distribution of Synaptic Proteins in Neuronal SH-SY5Y Cells.

Alex J T Yang, Ahmad Mohammad, Evangelia Tsiani, Aleksandar Necakov, Rebecca E K MacPherson.

  Neuronal growth and synaptic function are dependent on precise protein production and turnover at the synapse. AMPK-activated protein kinase (AMPK) represents a metabolic node involved in energy sensing and in regulating synaptic protein homeostasis. However, there is ambiguity surrounding the role of AMPK in regulating neuronal growth and health. This study examined the effect of chronic AMPK activation on markers of synaptic function and growth. Retinoic-acid-differentiated SH-SY5Y human neuroblastoma cells were treated with A-769662 (100 nM) or Compound C (30 nM) for 1, 3, or 5 days before AMPK, mTORC1, and markers for synapse function were examined. Cell morphology, neuronal marker content, and location were quantified after 5 days of treatment. AMPK phosphorylation was maintained throughout all 5 days of treatment with A-769662 and resulted in chronic mTORC1 inhibition. Lower total, soma, and neuritic neuronal marker contents were observed following 5 d of AMPK activation. Neurite protein abundance and distribution was lower following 5 days of A-769662 treatment. Our data suggest that chronic AMPK activation impacts synaptic protein content and reduces neurite protein abundance and distribution. These results highlight a distinct role that metabolism plays on markers of synapse health and function.

Keywords:  AMPK; Homer-1; mTORC1; neuronal health; post-synaptic density

DOI:  https://doi.org/10.3390/cells11152354
PLoS Genet. 2022 Aug 11. 18(8): e1010169

2-deoxyglucose transiently inhibits yeast AMPK signaling and triggers glucose transporter endocytosis, potentiating the drug toxicity.

Clotilde Laussel, Véronique Albanèse, Francisco Javier García-Rodríguez, Alberto Ballin, Quentin Defenouillère, Sébastien Léon.

2-deoxyglucose is a glucose analog that impacts many aspects of cellular physiology. After its uptake and its phosphorylation into 2-deoxyglucose-6-phosphate (2DG6P), it interferes with several metabolic pathways including glycolysis and protein N-glycosylation. Despite this systemic effect, resistance can arise through strategies that are only partially understood. In yeast, 2DG resistance is often associated with mutations causing increased activity of the yeast 5'-AMP activated protein kinase (AMPK), Snf1. Here we focus on the contribution of a Snf1 substrate in 2DG resistance, namely the alpha-arrestin Rod1 involved in nutrient transporter endocytosis. We report that 2DG triggers the endocytosis of many plasma membrane proteins, mostly in a Rod1-dependent manner. Rod1 participates in 2DG-induced endocytosis because 2DG, following its phosphorylation by hexokinase Hxk2, triggers changes in Rod1 post-translational modifications and promotes its function in endocytosis. Mechanistically, this is explained by a transient, 2DG-induced inactivation of Snf1/AMPK by protein phosphatase 1 (PP1). We show that 2DG-induced endocytosis is detrimental to cells, and the lack of Rod1 counteracts this process by stabilizing glucose transporters at the plasma membrane. This facilitates glucose uptake, which may help override the metabolic blockade caused by 2DG, and 2DG export-thus terminating the process of 2DG detoxification. Altogether, these results shed a new light on the regulation of AMPK signaling in yeast and highlight a remarkable strategy to bypass 2DG toxicity involving glucose transporter regulation.

DOI: https://doi.org/10.1371/journal.pgen.1010169
Phytomedicine. 2022 Jul 28. pii: S0944-7113(22)00445-7. [Epub ahead of print]105 154366

Hernandezine, a natural herbal alkaloid, ameliorates type 2 diabetes by activating AMPK in two mouse models.

Jing Bai, Shuai Zhang, Jinjing Cao, Hongbin Sun, Zhiguo Mang, Wei L Shen, Hao Li.

   BACKGROUND: AMP-activated protein kinase (AMPK) is an effective target for treating diabetes. However, successful drug development is delayed due to issues including toxicity. Plant-derived natural product AMPK activators have emerged as a new way to treat diabetes due to its potential low safety risks. Here, we studied the effect of hernandezine (HER), a natural product derived from Thalictrum, in activating AMPK and treating T2D in mouse models.
METHOD: We tested HER in various cells and tissues, including primary hepatocytes, skeletal myotubes cell lines, as well as major metabolic tissues from diabetic (db/db) and diet-induced obesity (DIO) model mice. The effect of HER on glucose uptake via AMPK in vitro and in vivo was confirmed utilizing cell transfection and adenovirus interference analysis. Tissue staining assessed the effect of HER on adipogenesis. Real-time quantitative polymerase chain reaction (real-time PCR) was applied to verify the effect of HER on transcription factors. Western blot analysis was used to determine the activation of phosphorylated AMPK and ACC pathways.
RESULTS: Biochemically, we found that HER prevented pAMPK from dephosphorylation to prolong its activity, disproving previous direct activation model and providing a new model to explain HER-mediated AMPK activation. HER could be orally delivered to animals and has a 3-fold long half-life in vivo as compared to metformin. Importantly, long-term oral HER treatment potently reduced body weight and blood glucose in both type 2 diabetes mullitus (T2DM) mouse models by increasing glucose disposal and reducing lipogenesis, and appeared not to induce cardiac hypertrophy.
CONCLUSION: Natural product HER indirectly activates AMPK by suppressing its dephosphorylation. Oral HER effectively alleviated hyperglycemia and reduced body weight in T2D mouse models, appeared to have a low risk of causing cardiac hypertrophy, and might be a potential therapeutic option for T2DM.

Keywords:  AMPK; Diabetes mellitus; Glucose disposal; Hernandezine; Lipogenesis

DOI:  https://doi.org/10.1016/j.phymed.2022.154366
NPJ Parkinsons Dis. 2022 Aug 06. 8(1): 100

Harmol promotes α-synuclein degradation and improves motor impairment in Parkinson's models via regulating autophagy-lysosome pathway.

Jie Xu, Yun-Lin Ao, Chunhui Huang, Xiubao Song, Guiliang Zhang, Wei Cui, Yuqiang Wang, Xiao-Qi Zhang, Zaijun Zhang.

The abnormal accumulation of α-synuclein (α-syn) is a crucial factor for the onset and pathogenesis of Parkinson's disease (PD), and the autophagy-lysosome pathway (ALP) contributes to α-syn turnover. AMP-activated protein kinase (AMPK) and the mammalian target of rapamycin (mTOR) regulate autophagy by initiating the macroautophagy cascade and promoting lysosomal biogenesis via increased transcription factor EB (TFEB) activity. Hence, activation of AMPK-mTOR-TFEB axis-mediated autophagy might promote α-syn clearance in PD. Harmol is a β-carboline alkaloid that has been extensively studied in a variety of diseases but rarely in PD models. In this study, we aimed to evaluate the effect and underlying mechanism of harmol in PD models in vitro and in vivo. We show that harmol reduces α-syn via ALP in a dose- and time-dependent manner in cell model that overexpressed human A53T mutant α-syn. We also demonstrate that harmol promotes the translocation of TFEB into the nucleus and accompanies the restoration of autophagic flux and lysosomal biogenesis. Importantly, harmol improves motor impairment and down-regulates α-syn levels in the substantia nigra and prefrontal cortex in the α-syn transgenic mice model. Further studies revealed that harmol might activate ALP through AMPK-mTOR-TFEB to promote α-syn clearance. These in vitro and in vivo improvements demonstrate that harmol activates the AMPK-mTOR-TFEB mediated ALP pathway, resulting in reduced α-syn, and suggesting the potential benefit of harmol in the treatment of PD.

DOI: https://doi.org/10.1038/s41531-022-00361-4
Gen Physiol Biophys. 2022 Jul;41(4): 319-328

Aerobic exercise ameliorates myocardial ischemia/reperfusion injury and thrombosis of diabetic rats via activation of AMPK/Sirt1/PGC-1α pathway.

Guandong Wang.

This current work is aimed to make investigations for the action mechanism of aerobic exercise in rats with type 2 diabetes mellitus (T2DM) after myocardial ischemia/reperfusion injury (MI/RI). The high-fat diet was used to induce T2DM in male Wistar rats. After treatments, the rats in the exercise groups were underwent swimming training for 8 weeks. Two days later, all the rats were subjected to perform MI/RI experiments via left anterior descending artery ligation and reperfusion. The blood samples and myocardial tissues were collected for biochemistry analysis and histology assessment. The results demonstrated that aerobic exercise reduced the levels of serum glucose, total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and thrombosis in T2DM rats. In addition, aerobic exercise further decreased the levels of myocardial injury markers and also repressed inflammation responses. Furthermore, the AMP-activated protein kinase (AMPK)/silent information regulator factor 2-related enzyme 1 (Sirt1)/peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) pathway could be activated by aerobic exercise. In a word, aerobic exercise may attenuate myocardial ischemia/reperfusion injury and repress thrombosis via activation of the AMPK/Sirt1/PGC-1α pathway in DM rats.

DOI: https://doi.org/10.4149/gpb_2022010
BMC Complement Med Ther. 2022 Aug 09. 22(1): 213

Salvia-Nelumbinis naturalis improves lipid metabolism of NAFLD by regulating the SIRT1/AMPK signaling pathway.

Yang Liu, Yiping Li, Jue Wang, Lili Yang, Xiao Yu, Ping Huang, Haiyan Song, Peiyong Zheng.

   BACKGROUND: Salvia-Nelumbinis naturalis (SNN), the extract of Chinese herbal medicine, has shown effects on NAFLD. This study aims to explore the underlying mechanism of SNN for regulating the lipid metabolism disorder in NAFLD based on the SIRT1/AMPK signaling pathway.
METHODS: Male C57BL/6J mice fed with a high-fat diet (HFD) were used to establish the NAFLD model. Dynamic changes of mice including body weight, liver weight, serological biochemical indexes, liver histopathological changes, and protein level of AMPK and SIRT1 were monitored. After18 weeks, SNN treatment was administrated to the NAFLD mice for another 4 weeks. Besides the aforementioned indices, TC and TG of liver tissues were also measured. Western blot and quantitative RT-PCR were used to detect the expression and/or activation of SIRT1 and AMPK, as well as the molecules associated with lipid synthesis and β-oxidation. Furthermore, AML12 cells with lipid accumulation induced by fatty acids were treated with LZG and EX527 (SIRT1 inhibitor) or Compound C (AMPK inhibitor ) to confirm the potential pharmacological mechanism.
RESULTS: Dynamic observation found the mice induced by HFD with gradually increased body and liver weight, elevated serum cholesterol, hepatic lipid accumulation, and liver injury. After 16 weeks, these indicators have shown obvious changes. Additionally, the hepatic level of SIRT1 and AMPK activation was identified gradually decreased with NAFLD progress. The mice with SNN administration had lower body weight, liver weight, and serum level of LDL-c and ALT than those of the NAFLD model. Hepatosteatosis and hepatic TG content in the liver tissues of the SNN group were significantly reduced. When compared with control mice, the NAFLD mice had significantly decreased hepatic expression of SIRT1, p-AMPK, p-ACC, ACOX1, and increased total Acetylated-lysine, SUV39H2, and SREBP-1c. The administration of SNN reversed the expression of these molecules. In vitro experiments showed the effect of SNN in ameliorating hepatosteatosis and regulating the expression of lipid metabolism-related genes in AML12 cells, which were diminished by EX527 or Compound C co-incubation.
CONCLUSIONS: Taken together, the SIRT1/AMPK signaling pathway, involved in hepatic lipid synthesis and degradation, plays a pivotal role in the pathogenesis of NAFLD development. The regulation of SIRT1/AMPK signaling greatly contributes to the underlying therapeutic mechanism of SNN for NAFLD.

Keywords:  AMPK; Lipid metabolism; Nonalcoholic fatty liver disease; SIRT1; Salvia-Nelumbinis naturalis

DOI:  https://doi.org/10.1186/s12906-022-03697-9
Int J Mol Sci. 2022 Aug 08. pii: 8811. [Epub ahead of print]23(15):

Zinc Deficiency Induces Autophagy in HT-22 Mouse Hippocampal Neuronal Cell Line.

Si-Yeon Kim, Jung-Ho Lee, Soon-Ae Kim.

  Zinc is a trace metal vital for various functions in nerve cells, although the effect of zinc deficiency on neuronal autophagy remains unclear. This study aimed to elucidate whether zinc deficiency induced by treatment with N, N, N', N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN), a zinc chelator, affects and alters autophagy activity. In cell viability assays, TPEN showed cytotoxicity in HT-22 cells. TPEN treatment also increased LC3-II levels and the ratio of LC3-II to LC3-I. Western blot analysis showed that phospho-AMP-activated protein kinase levels and the ratio of phospho-AMP-activated protein kinase to total AMP-activated protein kinase increased. Protein levels of the mammalian target of rapamycin and sirtuin 1 decreased following TPEN treatment. When TPEN-treated HT-22 cells were cotreated with autophagy inhibitors, 3-methyladenine (1 mM), or bafilomycin A1 (3 nM), the TPEN-induced decrease in cell viability was exacerbated. Cotreatment with chloroquine (10 μM) partially restored cell viability. The study showed that zinc deficiency induces autophagy and may be cytoprotective in neurons. We expect our results to add a new perspective to our understanding of the neuronal pathology related to zinc deficiency.

Keywords:  AMPK; SIRT1; autophagy; mTOR; zinc; zinc deficiency

DOI:  https://doi.org/10.3390/ijms23158811
Front Oncol. 2022 ;12 903874

AXL Promotes Metformin-Induced Apoptosis Through Mediation of Autophagy by Activating ROS-AMPK-ULK1 Signaling in Human Esophageal Adenocarcinoma.

Jun Hong, Selma Maacha, Nataliya Pidkovka, Andreia Bates, Safia N Salaria, Mary K Washington, Abbes Belkhiri.

  AXL receptor tyrosine kinase promotes an invasive phenotype and chemotherapy resistance in esophageal adenocarcinoma (EAC). AXL has been implicated in the regulation of autophagy, but the underlying molecular mechanism remains poorly understood. Herein, we investigate the mechanistic role of AXL in autophagy as well as metformin-induced effects on the growth and survival of EAC. We demonstrate that AXL mediates autophagic flux through activation of AMPK-ULK1 signaling in a reactive oxygen species (ROS)-dependent mechanism by glucose starvation. AXL positively regulates basal cellular ROS levels without significantly affecting mitochondrial ROS production in EAC cells. Pharmacological inhibition of cellular ROS using Trolox abrogates glucose starvation-induced AMPK signaling and autophagy. We demonstrate that AXL expression is required for metformin-induced apoptosis in EAC cells in vitro. The apoptosis induction by metformin is markedly attenuated by inhibition of autophagy through genetic silencing of Beclin1 or ATG7 autophagy mediators, thereby confirming the requirement of intact autophagy for enhancing metformin-induced apoptosis in EAC cells. Our data indicate that metformin-induced autophagy displays a pro-apoptotic function in EAC cells. We show that the metformin-induced suppression of tumor growth in vivo is highly dependent on AXL expression in a tumor xenograft mouse model of EAC. We demonstrate that AXL promotes metformin-induced apoptosis through activation of autophagy in EAC. AXL may be a valuable biomarker to identify tumors that are sensitive to metformin. Therefore, AXL expression could inform the selection of patients for future clinical trials to evaluate the therapeutic efficacy of metformin in EAC.

Keywords:  AMPK; ATG7; Barrett’s esophagus; Beclin1; autophagic flux; glucose starvation; proliferation; reactive oxygen species

DOI:  https://doi.org/10.3389/fonc.2022.903874
Biochem Pharmacol. 2022 Aug 07. pii: S0006-2952(22)00297-0. [Epub ahead of print] 115203

Resolvin D3 improves the impairment of insulin signaling in skeletal muscle and nonalcoholic fatty liver disease through AMPK/autophagy-associated attenuation of ER stress.

Heeseung Oh, Wonjun Cho, A M Abd El-Aty, Cemil Bayram, Ji Hoon Jeong, Tae Woo Jung.

  Resolvin D3 (RD3), an endogenous lipid mediator derived from omega-3 fatty acids, has been documented to attenuate inflammation in various disease models. Although it has been reported that omega-3 fatty acids attenuate metabolic disorders, the roles of RD3 in insulin signaling in skeletal muscle and hepatic lipid metabolism remain unclear. In the current study, we examined the role of RD3 in skeletal muscle insulin resistance and hepatic steatosis using in vitro and in vivo obesity models. In mouse primary hepatocytes, RD3 treatment reduced lipid accumulation and the production of lipogenic proteins (processed SREBP1 and SCD1) while improving insulin signaling in C2C12 myocytes. Furthermore, RD3 treatment ameliorated palmitate-induced ER stress markers (phospho-eIF2α and CHOP) in mouse primary hepatocytes and C2C12 myocytes. Treatment with RD3 increased phospho-AMPK expression and autophagy markers (LC3 conversion, p62 degradation, and autophagosome formation). AMPK siRNA or 3-MA reduced the effects of RD3 on C2C12 myocytes and mouse primary hepatocytes treated with palmitate. Finally, we confirmed the therapeutic effects of RD3 on skeletal muscle insulin resistance and hepatic lipid metabolism in high-fat diet (HFD)-fed mice. In vivo transfection-mediated suppression of AMPK restored all these changes in animal models. The results of the present study suggest that RD3 alleviates insulin resistance in skeletal muscle and hepatic steatosis via AMPK/autophagy signaling and provides an effective and safe therapeutic approach for treating metabolic disorders, including insulin resistance, type 2 diabetes, and NAFLD.

Keywords:  AMPK; Autophagy; ER stress; Insulin resistance; NAFLD; Resolvin D3

DOI:  https://doi.org/10.1016/j.bcp.2022.115203
Mol Ther Nucleic Acids. 2022 Sep 13. 29 312-328

Aberrant HSF1 signaling activation underlies metformin amelioration of myocardial infarction in mice.

Mingyuan Wang, Jiang Zou, Jinjin Wang, Meidong Liu, Ke Liu, Nian Wang, Kangkai Wang.

  Myocardial infarction (MI) is a cardiovascular disease with high morbidity and mortality. Clinically, rehabilitation after massive MI often has a poor prognosis. Therefore, it is necessary to explore the therapeutic methods of myocardial protection after MI. As a first-line treatment for type 2 diabetes, metformin has been found to have a certain protective effect on myocardial tissue. However, its pharmacological mechanism remains unclear. In this study, we investigated key factors that reduced MI with metformin. Through in vivo, in vitro, and in silico analyses, we identified HSF1 as a key target for metformin. HSF1 could up-regulate the transcriptional level of AMPKα2 through transcriptional activation and stimulate the activity of the downstream AMPK/mTOR signaling pathway. Metformin stimulated cardiomyocytes to form stress granules (SGs), and knockdown of HSF1 reversed this process. Furthermore, HSF1 exhibited better in vitro affinity for metformin than AMPK, suggesting that HSF1 may be a more sensitive target for metformin.

Keywords:  AMPK; HSF1; metformin; myocardial infarction (MI); stress granules

DOI:  https://doi.org/10.1016/j.omtn.2022.07.009
Nat Commun. 2022 Aug 11. 13(1): 4528

PTEN inhibits AMPK to control collective migration.

Florent Peglion, Lavinia Capuana, Isabelle Perfettini, Laurent Boucontet, Ben Braithwaite, Emma Colucci-Guyon, Emie Quissac, Karin Forsberg-Nilsson, Flora Llense, Sandrine Etienne-Manneville.

Pten is one of the most frequently mutated tumour suppressor gene in cancer. PTEN is generally altered in invasive cancers such as glioblastomas, but its function in collective cell migration and invasion is not fully characterised. Herein, we report that the loss of PTEN increases cell speed during collective migration of non-tumourous cells both in vitro and in vivo. We further show that loss of PTEN promotes LKB1-dependent phosphorylation and activation of the major metabolic regulator AMPK. In turn AMPK increases VASP phosphorylation, reduces VASP localisation at cell-cell junctions and decreases the interjunctional transverse actin arcs at the leading front, provoking a weakening of cell-cell contacts and increasing migration speed. Targeting AMPK activity not only slows down PTEN-depleted cells, it also limits PTEN-null glioblastoma cell invasion, opening new opportunities to treat glioblastoma lethal invasiveness.

DOI: https://doi.org/10.1038/s41467-022-31842-y
Oxid Med Cell Longev. 2022 ;2022 4931611

Silencing TUFM Inhibits Development of Monocrotaline-Induced Pulmonary Hypertension by Regulating Mitochondrial Autophagy via AMPK/mTOR Signal Pathway.

Ruyuan Wei, Xin Lv, Changcun Fang, Chuanzhen Liu, Zengshan Ma, Kai Liu.

Pulmonary arterial hypertension (PAH) is an extremely malignant cardiovascular disease which mainly involves the uncontrollable proliferation of the pulmonary arterial smooth muscular cells (PASMCs). Recent studies have confirmed that mitochondria play an important role in the pathogenesis of pulmonary hypertension through sensing cell hypoxia, energy metabolism conversion, and apoptosis. As a mitochondrial membrane protein, TUFM has been regarded to be related to mitochondrial autophagy (mitophagy), apoptosis, and oxidative stress. Considering these factors are closely associated with the pathogenesis of PAH, we hypothesize that TUFM might play a role in the development of PAH. Our preliminary examination has showed TUFM mainly expressed in the PASMCs, and the subsequent test indicated an increased TUFM expression in the SMCs of pulmonary arteriole in monocrotaline- (MCT-) induced PAH rat model compared with the normal rat. The TUFM knockdown (Sh-TUFM) or overexpressed (OE-TUFM) rats were used to establish PAH by treating with MCT. A notable lower pulmonary arterial systolic pressure together with slightly morphological changes of pulmonary arteriole was observed in the Sh-TUFM group compared with the single MCT-induced PAH group. Increased levels of P62 and Bax and reduced LC3II/I, BECN1, and Bcl2 were detected in the Sh-TUFM group, while the expressions of these proteins in the OE-TUFM group were contrast to the results of the Sh-TUFM group. To elucidate the possible mechanism underlying biological effect of TUFM in PAH, PASMCs were treated with silence or overexpression of TUFM and then exposed to hypoxia condition. An obviously high levels of P62 and Bax along with a decreased LC3 II/I, BECN1, ULK1, Atg12, Atg13, and Bcl2 levels were noticed in cells with silence of TUFM. Moreover, the phosphorylated AMPK and mTOR which was well known in mitophagy modulating vary by the alternation of TUFM. These observations suggested that TUFM silence inhibits the development of MCT-induced PAH via AMPK/mTOR pathway.

DOI: https://doi.org/10.1155/2022/4931611
Biochem Pharmacol. 2022 Aug 06. pii: S0006-2952(22)00292-1. [Epub ahead of print]203 115198

AMPKα2/HNF4A/BORIS/GLUT4 pathway promotes hepatocellular carcinoma cell invasion and metastasis in low glucose microenviroment.

Yuan Huang, Longjun Xian, Zhongjian Liu, Ling Wei, Lu Qin, Yimei Xiong, Lei Hu, Siqi Zhou, Qiang Fu, Bo Li, Yang Qin.

  Increasing evidence has revealed that the invasion and metastasis of HCC are intimately related to the low-glucose microenvironment, but the intrinsic regulatory mechanism remains unclear. It has been well documented that AMPK regulates the transcriptional expression of GLUT4 and its catalytic subunit AMPKα2 can negatively regulate the downstream target molecule HNF4A. Meanwhile, BORIS (Brother of the Regulator of Imprinted Sites) is able to modulate the Warburg effect by regulating the splicing of pyruvate kinase M2 (PKM2), a critical enzyme in glycolysis. Through bioinformatic analysis and a series of overexpression, knockdown, and complementation experiments, we demonstrated that HNF4A can directly act on BORIS and negatively regulate its expression, thereby inhibiting hepatoma cell motility and tumor metastasis, whereas BORIS can directly act on GLUT4 and positively regulate its expression to enhance hepatoma cell motility and tumor metastasis. We also found that HNF4A agonist (Benfluorex) and GLUT4 inhibitor (antiviral drug Ritonavir) can suppress HCC cell proliferation and glucose uptake. Taken together, these results all suggest that activation of the AMPKα2/HNF4A/BORIS/GLUT4 signaling pathway in a low-glucose microenvironment can significantly promote the invasion and metastasis of HCC cells, while HNF4A and GLUT4 may have important potential applications as prognostic or drug target molecules.

Keywords:  BORIS; Benfluorex and Ritonavir; GLUT4; HCC; Invasion; Low glucose microenviroment

DOI:  https://doi.org/10.1016/j.bcp.2022.115198
FASEB J. 2022 Sep;36(9): e22491

Trehalose improves palmitic acid-induced apoptosis of osteoblasts by regulating SIRT3-medicated autophagy via the AMPK/mTOR/ULK1 pathway.

Lili Cao, Siming Zhou, Xueshan Qiu, Shui Qiu.

  Accumulation of lipid substances decreased the activity of osteoblasts. Trehalose is a typical stress metabolite to form a protective membrane on cell surface which has been demonstrated to regulate lipid metabolism. This activity of Trehalose indicates the potential effect of osteoporosis treatment. Our study aimed to determine the therapeutic effect of Trehalose in high fat-induced osteoporosis. We used palmitic acid (PA) to mimic the state of high fat and observed the apoptosis ratio of osteoblasts increased. After adding Trehalose, the apoptosis ratio decreased obviously. Autophagy is a regulatory means involved in the process of apoptosis. We detected the autophagy protein and found that the expression of Beclin-1, Atg5, and LC3 II increased, and p62 decreased after Trehalose treatment. When adding an autophagy inhibitor (3-MA), the expression of Beclin-1, Atg5, and LC3 II decreased, and p62 increased. These results indicated autophagy was an important factor involved in the preventive effect of Trehalose in PA-induced apoptosis. SIRT3 is a mitochondrial gene that can inhibit apoptosis, which has been reported to promote autophagy. We used SIRT3-siRNA to silence the expression of SIRT3 and found the effect of Trehalose was counteracted. The apoptosis ratio increased and the expression of Beclin-1, Atg5, and LC3 II decreased, p62 increased. Additionally, we also fed the mice with a high-fat diet (HFD) and intragastrical Trehalose. The results showed that Trehalose could inhibit the bone mass loss with HFD. Our study revealed the effect and mechanism of Trehalose in the treatment of osteoporosis.

Keywords:  SIRT3; Trehalose; autophagy; lipotoxicity; palmitic acid

DOI:  https://doi.org/10.1096/fj.202200608RR
Cell Mol Biol Lett. 2022 Aug 09. 27(1): 66

SESN2 prevents the slow-to-fast myofiber shift in denervated atrophy via AMPK/PGC-1α pathway.

Xiaofan Yang, Pingping Xue, Zhenyu Liu, Wenqing Li, Chuyan Li, Zhenbing Chen.

   BACKGROUND: Sestrin2 (SESN2), a stress-inducible protein, has been reported to protect against denervated muscle atrophy through unfolded protein response and mitophagy, while its role in myofiber type transition remains unknown.
METHODS: A mouse sciatic nerve transection model was created to evaluate denervated muscle atrophy. Myofiber type transition was confirmed by western blot, fluorescence staining, ATP quantification, and metabolic enzyme activity analysis. Adeno-associated virus (AAV) was adopted to achieve SESN2 knockdown and overexpression in gastrocnemius. AMPK/PGC-1α signal was detected by western blot and activated with 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR). C2C12 myotubes with rotenone treatment were adopted for in vitro experiments.
RESULTS: SESN2 was found to be upregulated in denervated skeletal muscles and rotenone-treated C2C12 cells. Knockdown of SESN2 aggravated muscle atrophy and accelerated myofiber type transition from slow-twitch to fast-twitch. Moreover, AMPK/PGC-1α signaling was proven to be activated by SESN2 after denervation, which further induced the expression of hypoxia-inducible factor HIF2α. Exogenous activation of AMPK/PGC-1α signaling could counteract the addition of slow-to-fast myofiber shift caused by SESN2 knockdown and lead to the retainment of muscle mass after denervation.
CONCLUSION: Collectively, the present study indicates that SESN2 prevents myofiber type transition from slow-twitch to fast-twitch and preserves muscle mass in denervated atrophy via AMPK/PGC-1α signaling. These findings contribute to a better understanding of the pathogenesis of muscle atrophy and provide novel insights into the role of SESN2 in myofiber type transition.

Keywords:  AMPK/PGC-1α; Denervation; Myofiber type transition; SESN2; Skeletal muscle atrophy

DOI:  https://doi.org/10.1186/s11658-022-00367-z
Mol Metab. 2022 Aug 06. pii: S2212-8778(22)00131-4. [Epub ahead of print] 101562

The Mitochondrial NAD Kinase Functions as a Major Metabolic Regulator Upon Increased Energy Demand.

Hyunbae Kim, Zhiyao Fu, Zhao Yang, Zhenfeng Song, El Hussain Shamsa, Thangal Yumnamcha, Shengyi Sun, Wanqing Liu, Ahmed S Ibrahim, Nathan R Qi, Ren Zhang, Kezhong Zhang.

The mitochondrial nicotinamide adenine dinucleotide (NAD) kinase (MNADK) mediates de novo mitochondrial NADP biosynthesis by catalyzing the phosphorylation of NAD to yield NADP. In this study, we investigated the function and mechanistic basis by which MNADK regulates metabolic homeostasis. Generalized gene-set analysis by aggregating human patient genomic databases indicated that human MNADK common gene variants or decreased expression of the gene are significantly associated with the occurrence of type-2 diabetes, non-alcoholic fatty liver disease (NAFLD), or hepatocellular carcinoma (HCC). Ablation of the MNADK gene in mice led to decreased fat oxidation, coincident with increased respiratory exchange ratio (RER) and decreased energy expenditure upon energy demand triggered by endurance exercise or fasting. On an atherogenic high-fat diet (HFD), MNADK-null mice exhibited hepatic insulin resistance and glucose intolerance, indicating a type-2 diabetes-like phenotype in the absence of MNADK. Further investigation revealed that MNADK deficiency led to a decrease in mitochondrial NADP(H) but an increase in cellular reactive oxygen species (ROS) in mouse livers. Consistently, protein levels of the major metabolic regulators or enzymes were decreased, while their acetylation modifications were increased in the livers of MNADK-null mice. Further, feeding mice with a HFD caused S-nitrosylation (SNO) modification, a posttranslational modification that represses protein activities, on MNADK protein in the liver. Reconstitution of an SNO-resistant MNADK variant, MNADK-S193, into MNADK-null mice mitigated hepatic steatosis induced by HFD. In summary, our studies define that MNADK, the only known mammalian mitochondrial NAD kinase, plays important roles in preserving energy homeostasis to mitigate the risk of metabolic disorders.

DOI: https://doi.org/10.1016/j.molmet.2022.101562