bims-amsmem 2023-02-05 papers

bims-amsmem

Biomed News

on AMPK signaling mechanism in energy metabolism

Issue of 2023–02–05
ten papers selected by
Dipsikha Biswas, Københavns Universitet

AMPK-dependent phosphorylation of the GATOR2 component WDR24 suppresses glucose-mediated mTORC1 activation.
AMPK inhibition induces MCL1 mRNA destabilization via the p38 MAPK/miR-22/HuR axis in chronic myeloid leukemia cells.
Toll-Like Receptor 4 (TLR4) and AMPK Relevance in Cardiovascular Disease.
AMPK knocks at the gate of GATOR.
Metformin induces pyroptosis in leptin receptor-defective hepatocytes via overactivation of the AMPK axis.
Oroxylin-A alleviates hepatic lipid accumulation and apoptosis under hyperlipidemic conditions via AMPK/FGF21 signaling.
Protopanaxadiol ameliorates NAFLD by regulating hepatocyte lipid metabolism through AMPK/SIRT1 signaling pathway.
Fructose metabolism in tumor endothelial cells promotes angiogenesis by activating AMPK signaling and mitochondrial respiration.
Exposure to dipentyl phthalate in utero disrupts the adrenal cortex function of adult male rats by inhibiting SIRT1/PGC-1α and inducing AMPK phosphorylation.
Loss of Lactate/Proton Monocarboxylate Transporter 4 Induces Ferroptosis via the AMPK/ACC Pathway and Inhibition of Autophagy on Human Bladder Cancer 5637 Cell Line.

Nat Metab. 2023 Feb 02.

AMPK-dependent phosphorylation of the GATOR2 component WDR24 suppresses glucose-mediated mTORC1 activation.

Xiaoming Dai, Cong Jiang, Qiwei Jiang, Lan Fang, Haihong Yu, Jinhe Guo, Peiqiang Yan, Fangtao Chi, Tao Zhang, Hiroyuki Inuzuka, John M Asara, Ping Wang, Jianping Guo, Wenyi Wei.

The mechanistic target of rapamycin complex 1 (mTORC1) controls cell growth in response to amino acid and glucose levels. However, how mTORC1 senses glucose availability to regulate various downstream signalling pathways remains largely elusive. Here we report that AMP-activated protein kinase (AMPK)-mediated phosphorylation of WDR24, a core component of the GATOR2 complex, has a role in the glucose-sensing capability of mTORC1. Mechanistically, glucose deprivation activates AMPK, which directly phosphorylates WDR24 on S155, subsequently disrupting the integrity of the GATOR2 complex to suppress mTORC1 activation. Phosphomimetic Wdr24S155D knock-in mice exhibit early embryonic lethality and reduced mTORC1 activity. On the other hand, compared to wild-type littermates, phospho-deficient Wdr24S155A knock-in mice are more resistant to fasting and display elevated mTORC1 activity. Our findings reveal that AMPK-mediated phosphorylation of WDR24 modulates glucose-induced mTORC1 activation, thereby providing a rationale for targeting AMPK-WDR24 signalling to fine-tune mTORC1 activation as a potential therapeutic means to combat human diseases with aberrant activation of mTORC1 signalling including cancer.

DOI: https://doi.org/10.1038/s42255-022-00732-4
Biochem Pharmacol. 2023 Jan 28. pii: S0006-2952(23)00033-3. [Epub ahead of print] 115442

AMPK inhibition induces MCL1 mRNA destabilization via the p38 MAPK/miR-22/HuR axis in chronic myeloid leukemia cells.

Yuan-Chin Lee, Jing-Ting Chiou, Long-Sen Chang.

  The oncogenic and tumor-suppressive roles of AMPK in chronic myeloid leukemia (CML) are controvertible. This study aimed to investigate the cytotoxic effects of the AMPK inhibitor Compound C in the CML cell lines K562, KU812, and MEG-01. Compared to K562 cells, KU812 and MEG-01 cells were more sensitive to Compound C-mediated cytotoxicity. Moreover, Compound C induced SIRT3 upregulation in K562 cells but not in KU812 or MEG-01 cells. SIRT3 silencing increased the sensitivity of K562 cells to Compound C. Additionally; Compound C-induced autophagy attenuated its induced apoptosis in KU812 and MEG-01 cells. Compound C-induced ROS-mediated AMPKα inactivation resulted in the downregulation of apoptotic regulator MCL1 in KU812 and MEG-01 cells. Mechanistically, AMPK inhibition activated p38 MAPK-mediated miR-22 expression, which in turn inhibited HuR expression, thereby reducing MCL1 mRNA stability. Overexpression of constitutively active AMPKα1 and abolishment of the activation of p38 MAPK inhibited Compound C-induced cell death and MCL1 downregulation. Furthermore, Compound C synergistically enhanced the cytotoxicity of BCR-ABL inhibitors and the BCL2 inhibitor ABT-199. Collectively, this study indicates that Compound C induces MCL1 downregulation through the AMPK/p38 MAPK/miR-22/HuR pathway, thereby inducing apoptosis of KU812 and MEG-01 cells. Furthermore, our findings suggest that AMPK inhibition is a promising strategy for improving CML therapy.

Keywords:  AMPK; Chronic myeloid leukemia; HuR; MCL1; SIRT3; p38 MAPK

DOI:  https://doi.org/10.1016/j.bcp.2023.115442
Adv Pharm Bull. 2023 Jan;13(1): 36-47

Toll-Like Receptor 4 (TLR4) and AMPK Relevance in Cardiovascular Disease.

Haleh Vaez, Hamid Soraya, Alireza Garjani, Tooba Gholikhani.

  Toll-like receptors (TLRs) are essential receptors of the innate immune system, playing a significant role in cardiovascular diseases. TLR4, with the highest expression among TLRs in the heart, has been investigated extensively for its critical role in different myocardial inflammatory conditions. Studies suggest that inhibition of TLR4 signaling pathways reduces inflammatory responses and even prevents additional injuries to the already damaged myocardium. Recent research results have led to a hypothesis that there may be a relation between TLR4 expression and 5' adenosine monophosphate-activated protein kinase (AMPK) signaling in various inflammatory conditions, including cardiovascular diseases. AMPK, as a cellular energy sensor, has been reported to show anti-inflammatory effects in various models of inflammatory diseases. AMPK, in addition to its physiological acts in the heart, plays an essential role in myocardial ischemia and hypoxia by activating various energy production pathways. Herein we will discuss the role of TLR4 and AMPK in cardiovascular diseases and a possible relation between TLRs and AMPK as a novel therapeutic target. In our opinion, AMPK-related TLR modulators will find application in treating different immune-mediated inflammatory disorders, especially inflammatory cardiac diseases, and present an option that will be widely used in clinical practice in the future.

Keywords:  AMPK; Cardiovascular disease; Inflammation; TLRs

DOI:  https://doi.org/10.34172/apb.2023.004
Nat Metab. 2023 Feb 02.

AMPK knocks at the gate of GATOR.

Nerea Deleyto-Seldas, Alejo Efeyan.

DOI: https://doi.org/10.1038/s42255-022-00729-z
Cell Death Dis. 2023 Feb 03. 14(2): 82

Metformin induces pyroptosis in leptin receptor-defective hepatocytes via overactivation of the AMPK axis.

Bingli Liu, Jingyuan Xu, Linyao Lu, Lili Gao, Shengjuan Zhu, Yi Sui, Ting Cao, Tao Yang.

Metformin is the biguanide of hepatic insulin sensitizer for patients with non-alcohol fatty liver disease (NAFLD). Findings regarding its efficacy in restoring blood lipids and liver histology have been contradictory. In this study, we explore metformin's preventive effects on NAFLD in leptin-insensitive individuals. We used liver tissue, serum exosomes and isolated hepatocytes from high-fat diet (HFD)-induced Zucker diabetic fatty (ZDF) rats and leptin receptor (Lepr) knockout rats to investigate the correlation between hepatic Lepr defective and liver damage caused by metformin. Through immunostaining, RT-PCR and glucose uptake monitoring, we showed that metformin treatment activates adenosine monophosphate (AMP)-activated protein kinase (AMPK) and its downstream cytochrome C oxidase (CCO). This leads to overactivation of glucose catabolism-related genes, excessive energy repertoire consumption, and subsequent hepatocyte pyroptosis. Single-cell RNA sequencing further confirmed the hyper-activation of glucose catabolism after metformin treatment. Altogether, we showed that functional Lepr is necessary for metformin treatment to be effective, and that long-term metformin treatment might promote NAFLD progression in leptin-insensitive individuals. This provides important insight into the clinical application of metformin.

DOI: https://doi.org/10.1038/s41419-023-05623-4
Biochem Biophys Res Commun. 2023 Jan 30. pii: S0006-291X(23)00143-2. [Epub ahead of print]648 59-65

Oroxylin-A alleviates hepatic lipid accumulation and apoptosis under hyperlipidemic conditions via AMPK/FGF21 signaling.

Wonjun Cho, Sung Woo Choi, Heeseung Oh, A M Abd El-Aty, Ahmet Hacimuftuoglu, Ji Hoon Jeong, Jin-Ho Song, Yong Kyoo Shin, Tae Woo Jung.

  Oroxylin-A (OA) is an O-methylated flavone that has been demonstrated to have anti-inflammatory properties in various disease models. However, the roles of OA in hepatic lipid metabolism and the specific molecular mechanisms by which it exerts these effects are not yet fully understood. In the current study, we aimed to investigate the effects of OA on hepatic lipid deposition and apoptosis, which play a pivotal role in the development of nonalcoholic fatty liver disease (NAFLD) in obesity in vitro models. We found that treatment with OA attenuated lipid accumulation, the expression of lipogenesis-associated proteins and apoptosis in palmitate-treated primary mouse hepatocytes. OA treatment suppressed phosphorylated NFκB and IκB expression in as well as TNFα and MCP-1 release from hepatocytes treated with palmitate. Treatment of hepatocytes with OA augmented AMPK phosphorylation and FGF21 expression. siRNA of AMPK or FGF21 abolished the effects of OA on inflammation as well as lipid accumulation and apoptosis in hepatocytes under palmitate treatment conditions. In conclusion, OA improves inflammation through the AMPK/FGF21 pathway, thereby attenuating lipid accumulation and apoptosis in hepatocytes. This study may help identify new targets for developing treatments for NAFLD.

Keywords:  Hepatocyte; Lipogenesis; NAFLD; Obesity; Oroxylin-A

DOI:  https://doi.org/10.1016/j.bbrc.2023.01.090
Biomed Pharmacother. 2023 Jan 30. pii: S0753-3322(23)00107-5. [Epub ahead of print]160 114319

Protopanaxadiol ameliorates NAFLD by regulating hepatocyte lipid metabolism through AMPK/SIRT1 signaling pathway.

Yiping Li, Yang Liu, Zhiwei Chen, Kaiyue Tang, Lili Yang, Yuwei Jiang, Jue Wang, Ping Huang, Jianyi Wang, Peiyong Zheng, Haiyan Song.

  Non-alcoholic fatty liver disease (NAFLD) has become one of the main chronic liver diseases worldwide. Protopanaxadiol (PPD), an active compound derived from Gynostemma pentaphyllum, has been found able to improve free fatty acid-induced lipid accumulation in hepatocytes. However, the efficacy of PPD on NAFLD and the underlying mechanism remains unknown. In this study, the mice were fed with a high-fat diet for 22 weeks to induce the NAFLD model, and then were treated with PPD by gavage for 8 weeks. Moreover, AML12 and HepG2 cells induced by free fatty acids for 24 h, were treated with different doses of PPD and/or AMPK or SIRT1 inhibitor to explore the pharmacological mechanism of PPD. The results showed that mice with PPD treatment had significantly reduced liver weight and serum aminotransferase levels, less severe hepatosteatosis, and inflammatory cell infiltration in liver tissues when compared with the model mice. PPD also reversed the down-regulated activation of AMPK and SIRT1 expression as well as the change of lipid metabolism-related molecules in the mice liver tissues. Consistently, the in vitro experiments showed the effect of PPD in ameliorating lipid accumulation in hepatocytes. The inhibitor of AMPK or SIRT1 suppressed the AMPK and SIRT1 signaling and markedly diminished the anti-steatosis effect of PPD. In conclusion, our results prove the ameliorating impact of PPD on NAFLD and also reveal the involvement of regulation of AMPK/SIRT1 signaling pathway-mediated lipid metabolism in the underlying mechanism, suggesting PPD as a potential natural compound for the treatment of NAFLD.

Keywords:  AMPK; Lipid metabolism; Non-alcoholic fatty liver disease; Protopanaxadiol; SIRT1

DOI:  https://doi.org/10.1016/j.biopha.2023.114319
Cancer Res. 2023 Jan 30. pii: CAN-22-1844. [Epub ahead of print]

Fructose metabolism in tumor endothelial cells promotes angiogenesis by activating AMPK signaling and mitochondrial respiration.

Jian-Hong Fang, Jie-Ying Chen, Jia-Lin Zheng, Hui-Xian Zeng, Jun-Guang Chen, Chen-Hui Wu, Jia-Li Cai, Zhi-Yong Wang, Shi-Mei Zhuang.

Angiogenesis is vital for tumor growth and metastasis. Emerging evidence suggests that metabolic reprogramming in endothelial cells (ECs) may affect angiogenesis. Here, we showed that multiple regulators in the fructose metabolism pathway, especially fructose transporter SLC2A5 and fructose-metabolizing enzyme ketohexokinase (KHK), were upregulated in tumor endothelial cells from hepatocellular carcinoma (HCC). In mouse models with hepatoma xenografts or with Myc/sgp53-induced liver cancer, dietary fructose enhanced tumor angiogenesis, tumor growth, and metastasis, which could be attenuated by treatment with an inhibitor of SLC2A5. Furthermore, vessel growth was substantially increased in fructose-containing matrigel compared to PBS-matrigel. Inhibiting fructose metabolism in EC cells in vivo using EC-targeted nanoparticles loaded with siRNA against KHK significantly abolished fructose-induced tumor angiogenesis. Fructose treatment promoted the proliferation, migration and tube formation of ECs and stimulated mitochondrial respiration and ATP production. Elevated fructose metabolism activated AMPK to fuel mitochondrial respiration, resulting in enhanced EC migration. Fructose metabolism was increased under hypoxic conditions as a result of HIF1α-mediated upregulation of multiple genes in the fructose metabolism pathway. These findings highlight the significance of fructose metabolism in ECs for promoting tumor angiogenesis. Restricting fructose intake or targeting fructose metabolism is a potential strategy to reduce angiogenesis and suppress tumor growth.

DOI: https://doi.org/10.1158/0008-5472.CAN-22-1844
Environ Toxicol. 2023 Jan 30.

Exposure to dipentyl phthalate in utero disrupts the adrenal cortex function of adult male rats by inhibiting SIRT1/PGC-1α and inducing AMPK phosphorylation.

Haiqiong Chen, Miaoqing Liu, Qiyao Li, Pingjiang Zhou, Jie Huang, Qiqi Zhu, Zhongrong Li, Ren-Shan Ge.

  Di-n-pentyl phthalate (DPeP) is an endocrine-disrupting phthalate plasticizer. The objective of this study was to investigate the effect of DPeP on adrenocortical function in adult male rats following in utero exposure. DPeP (0, 10, 50, 100, and 500 mg/kg/day) was administered by gavage to pregnant Sprague-Dawley rats from gestational day 14 to 21. The morphology and function of the adrenal cortex in 56-day-old male offspring were studied. DPeP at 100 and 500 mg/kg/day significantly reduced serum aldosterone levels and at 500 mg/kg/day markedly reduced corticosterone and adrenocorticotropic hormone levels. DPeP at 10-500 mg/kg markedly reduced the thickness of zona glomerulosa without affecting the thickness of zona fasciculata. DPeP significantly downregulated the expression of Agtr1a, Mc2r, Scarb1, Cyp11a1, Hsd3b1, Cyp21, Cyp11b1, Cyp11b2, Nr5a1, Nr4a2, and Bcl2 genes as well as their proteins. DPeP at 500 mg/kg/day significantly increased phosphorylated AMPK, while DPeP at 100 mg/kg/day and higher doses reduced phosphorylated AKT1 and total SIRT1 level. DPeP at 100 and 500 μM markedly induced reactive oxygen species and apoptosis in H295R cells after 24 h of culture. In conclusion, in utero exposure to DPeP disrupts adrenocortical function of the adult male offspring by (1) increasing AMPK phosphorylation and decreasing AKT1 phosphorylation and SIRT1 levels, (2) reducing adrenocorticotropic hormone levels, and (3) possibly inducing oxidative stress and apoptosis.

Keywords:  adrenal functions; adult rat; aldosterone; dipentyl phthalate; in utero exposure

DOI:  https://doi.org/10.1002/tox.23743
J Oncol. 2023 ;2023 2830306

Loss of Lactate/Proton Monocarboxylate Transporter 4 Induces Ferroptosis via the AMPK/ACC Pathway and Inhibition of Autophagy on Human Bladder Cancer 5637 Cell Line.

Siqi Dong, Lei Zheng, Tao Jiang.

Background: Ferroptosis and autophagy have an important role in the occurrence and development of cancer, and lactate in cells and microenvironment is one of the influencing factors of ferroptosis and autophagy. The lactate/proton monocarboxylate transporter 4 (MCT4), which is expressed in the cell membrane, regulates the transport of intracellular lactic acid and lactate. The knockout of MCT4 can affect intracellular and extracellular lactic acid levels, thereby affecting the growth, proliferation, and metastasis of tumor cells via regulation of the oxidative stress in cells. However, whether MCT4 affects ferroptosis and autophagy in bladder cancer cells remains unclear.
Methods: Colony formation assay and bladder cancer xenograft animal model were used to assess the effect of MCT4 on the growth in 5637 cells. Reactive oxygen species (ROS) assay, lipid ROS assay, lipid peroxidation assay (MDA), and transmission electron microscopy were performed to assess the level of lipid peroxidation in 5637 cells. RNA-sequence, RT-PCR, and Western Blot were used to analyze the mechanism of MCT4 of ferroptosis and autophagy. AdPlus-mCherry-GFP-LC3B reporter system was used to detect the effect of MCT4 on autophagy in 5637 cells, and the effect of knockdown of MCT4 on apoptosis was analyzed by flow cytometry.
Results: The mRNA level of MCT4 was significantly upregulated in patients with bladder cancer, which was associated with a poor prognosis. In vivo and in vitro studies demonstrated that knockdown of MCT4 could inhibit the proliferation of bladder cancer cells. Furthermore, knockdown of MCT4 led to the significant increase of ROS and MDA levels in 5637 cells and ferroptosis in 5637 cells induced by ferroptosis inducers including RSL3 (APExBIO) and erastin (APExBIO) via inhibition of AMPK-related proteins. Moreover, knockdown of MCT4 inhibited autophagy in 5637 cells, while siMCT4 promoted inhibition of autophagy by CQ (an autophagy inhibitor), which increased the level of apoptosis.
Conclusion: This study confirmed that knockdown of MCT4 could affect oxidative stress and induce ferroptosis and inhibition of autophagy, thus suggesting that MCT4 may be a potential target for the treatment of bladder cancer.

DOI: https://doi.org/10.1155/2023/2830306