bims-amsmem 2022-11-06 papers

bims-amsmem

Biomed News

on AMPK signaling mechanism in energy metabolism

Issue of 2022‒11‒06
fourteen papers selected by
Dipsikha Biswas, Københavns Universitet

New insights into activation and function of the AMPK.
Paliperidone-Induced Acute Hyperglycemia Is Caused by Adrenaline Secretion via the Activation of Hypothalamic AMP-Activated Protein Kinase.
Absence of ULK1 decreases AMPK activity in the kidney, leading to chronic kidney disease progression.
HM-chromanone reverses the blockade of insulin signaling induced by high glucose levels in human HepG2 cells.
Allicin promotes autophagy and ferroptosis in esophageal squamous cell carcinoma by activating AMPK/mTOR signaling.
Therapeutic metformin concentrations positively regulate proliferation in endometrial epithelial cells (EECs) via mTOR activation and augmented mitochondrial strength.
Critical Reanalysis of the Mechanisms Underlying the Cardiorenal Benefits of SGLT2 Inhibitors and Reaffirmation of the Nutrient Deprivation Signaling/Autophagy Hypothesis.
Role of metformin in inflammation.
1,25-D3 attenuates cerebral ischemia injury by regulating mitochondrial metabolism via the AMPK/AKT/GSK3β pathway.
Pheophorbide A isolated from Gelidium amansii inhibits adipogenesis by regulating adipogenic transcription factors and AMPK in 3T3-L1 adipocytes.
Metformin confers longitudinal cardiac protection by preserving mitochondrial homeostasis following myocardial ischemia/reperfusion injury.
Metformin alleviates HFD-induced oxidative stress in hepatocyte via activating SIRT6/PGC-1α/ENDOG signaling.
Metformin increases natural killer cell functions in head and neck squamous cell carcinoma through CXCL1 inhibition.
Metformin ameliorates olanzapine-induced obesity and glucose intolerance by regulating hypothalamic inflammation and microglial activation in female mice.

Nat Rev Mol Cell Biol. 2022 Oct 31.

New insights into activation and function of the AMPK.

Gregory R Steinberg, D Grahame Hardie.

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

DOI: https://doi.org/10.1038/s41580-022-00547-x
Biol Pharm Bull. 2022 ;45(11): 1669-1677

Paliperidone-Induced Acute Hyperglycemia Is Caused by Adrenaline Secretion via the Activation of Hypothalamic AMP-Activated Protein Kinase.

Bingyang Xue, Yasuyoshi Ishiwata, Yohei Kawano, Hiromitsu Takahashi, Kenichi Negishi, Takao Aoyama, Masashi Nagata.

  Although paliperidone-related hyperglycemia has been extensively examined, the underlying mechanisms have not yet been elucidated. We investigated the effects of a single intravenous injection of paliperidone (0.2, 0.4, or 0.6 mg/kg) on serum concentrations of glucose and other endogenous metabolites in rats. We also examined the effects of a single intravenous injection of paliperidone (0.4 mg/kg) on AMP-activated protein kinase (AMPK) activity in the hypothalamus and liver. To clarify the relationship between AMPK activity and adrenaline secretion, the effects of berberine, which inhibits hypothalamic AMPK, on paliperidone-induced hyperglycemia were assessed. Significant increases were observed in serum glucose, adrenaline, and insulin concentrations following intravenous injections of paliperidone at doses of 0.4 and 0.6 mg/kg. A propranolol pretreatment attenuated paliperidone-induced increases in serum concentrations of glucose, but not adrenaline. Significant increases were also noted in phosphorylated AMPK concentrations in the hypothalamus following the administration of paliperidone at a dose of 0.4 mg/kg. A berberine pretreatment attenuated paliperidone-induced increases in blood concentrations of glucose, adrenaline, and insulin and phosphorylated AMPK concentrations in the hypothalamus. Collectively, the present results demonstrated that an acute treatment with paliperidone induced hyperglycemia, which was associated with the effects of hypothalamic AMPK activation on the secretion of adrenaline.

Keywords:  AMP activated protein kinase (AMPK); adrenaline; berberine; hyperglycemia; paliperidone

DOI:  https://doi.org/10.1248/bpb.b22-00497
Genes Cells. 2022 Nov 01.

Absence of ULK1 decreases AMPK activity in the kidney, leading to chronic kidney disease progression.

Tomoki Yanagi, Hiroaki Kikuchi, Koichiro Susa, Naohiro Takahashi, Hiroki Bamba, Takefumi Suzuki, Yuta Nakano, Tamami Fujiki, Yutaro Mori, Fumiaki Ando, Shintaro Mandai, Takayasu Mori, Koh Takeuchi, Shinya Honda, Satoru Torii, Shigeomi Shimizu, Tatemitsu Rai, Shinichi Uchida, Eisei Sohara.

  AMP-activated protein kinase (AMPK) inactivation in chronic kidney disease (CKD) leads to energy status deterioration in the kidney, constituting the vicious cycle of CKD exacerbation. Unc-51-like kinase 1 (ULK1) is considered a downstream molecule of AMPK; however, it was recently reported that the activity of AMPK could be regulated by ULK1 conversely. We demonstrated that AMPK and ULK1 activities were decreased in the kidneys of CKD mice. However, whether and how ULK1 is involved in the underlying mechanism of CKD exacerbation remains unknown. In this study, we investigated the ULK1 involvement in CKD, using ULK1 knockout mice. The CKD model of Ulk1-/- mice exhibited significantly exacerbated renal function and worsening renal fibrosis. In the kidneys of the CKD model of Ulk1-/- mice, reduced AMPK and its downstream β-oxidation could be observed, leading to an energy deficit of increased AMP/ATP ratio. In addition, AMPK signaling in the kidney was reduced in control Ulk1-/- mice with normal renal function compared to control wild-type mice, suggesting that ULK1 deficiency suppressed AMPK activity in the kidney. This study is the first to present ULK1 as a novel therapeutic target for CKD treatment, which regulates AMPK activity in the kidney. This article is protected by copyright. All rights reserved.

Keywords:  AMPK; Chronic kidney disease, CKD, Renal fibrosis; ULK1

DOI:  https://doi.org/10.1111/gtc.12989
Eur J Pharmacol. 2022 Nov 01. pii: S0014-2999(22)00619-7. [Epub ahead of print] 175358

HM-chromanone reverses the blockade of insulin signaling induced by high glucose levels in human HepG2 cells.

Jae Eun Park, Ji Sook Han.

  This study investigated whether (E)-5-hydroxy-7-methoxy-3-(2'-hydroxybenzyl)-4-chromanone (HM-chromanone) could counteract the high glucose level-induced blockade of insulin signaling in human HepG2 cells. Cells were pre-incubated with glucose (5.5 or 33 mM) and then incubated with a medium containing various concentrations of HM-chromanone. Assays for glucose uptake, glycogen synthesis, and glucose production were performed. Western blotting helped elucidate the underlying molecular mechanisms. High glucose concentration (33 mM) significantly increased p-IRS-1ser307 levels and decreased p-Akt levels. However, HM-chromanone significantly decreased p-IRS-1ser307 levels while increasing p-IRS-1tyr612 and Akt levels, which restored insulin signaling disturbed by high glucose concentration. HM-chromanone significantly increased p-AMPK levels, which were reduced by high glucose in HepG2 cells. Knockdown of AMPK using siRNA increased p-IRS-1ser307 and decreased p-Akt levels, even after treatment with HM-chromanone in high glucose concentration-treated cells. HM-chromanone stimulated glycogen synthesis by increasing p-GSK3βser9 and decreasing p-GSser641 levels in HepG2 cells under high glucose concentration; this effect was blocked by AMPK siRNA. HM-chromanone significantly decreased PEPCK, G6Pase, and hepatic glucose production, which were also blocked by AMPK siRNA. These results suggest that HM-chromanone could reverse insulin signaling blockade (induced by high glucose levels) through the activation of AMPK and stimulation of glucose uptake and glycogen synthesis in HepG2 cells.

Keywords:  AMPK; Glucose uptake; HepG2; IRS-1; Insulin signaling

DOI:  https://doi.org/10.1016/j.ejphar.2022.175358
Heliyon. 2022 Oct;8(10): e11005

Allicin promotes autophagy and ferroptosis in esophageal squamous cell carcinoma by activating AMPK/mTOR signaling.

Zhanfang Guo, Yanjiao Zhang.

  The antitumor effects of allicin have been demonstrated in various cancers. However, whether allicin improves esophageal squamous cell carcinoma (ESCC) has not yet been explored. The present study aimed to explore the function and underlying mechanism of action of allicin in ESCC treatment. Our data showed that allicin significantly suppressed ESCC cell proliferation in a dose- and time-dependent manner. A green fluorescent protein-light chain 3 (LC3) transfection assay showed that autophagosomes were elevated in ESCC cells treated with allicin compared with control ESCC cells and that 3-methyladenine (an autophagy inhibitor) reversed allicin-induced LC3 puncta. Furthermore, allicin significantly elevated the ratio of LC3II/LC3I but decreased p62 expression in ESCC cells. Allicin also increased adenosine monophosphate-activated protein kinase (AMPK) phosphorylation but decreased that of the mechanistic target of rapamycin kinase (mTOR), which then induced the elevation of autophagy-related 5 and autophagy-related 7 proteins in ESCC cells. Furthermore, allicin treatment increased the expression of nuclear receptor coactivator 4 (a selective cargo receptor) but suppressed the expression of ferritin heavy chain 1 (the major intracellular iron-storage protein) in ESCC cells and elevated malondialdehyde and Fe2+ production levels. In vivo assays showed that allicin significantly decreased tumor weight and volume. In summary, allicin may induce cell death in ESCC cells by activating AMPK/mTOR-mediated autophagy and ferroptosis. Therefore, allicin may have excellent potential for use in the treatment of ESCC.

Keywords:  AMPK/mTOR signaling; Autophagy; Esophageal squamous cell carcinoma; Ferroptosis

DOI:  https://doi.org/10.1016/j.heliyon.2022.e11005
Can J Physiol Pharmacol. 2022 Nov 02.

Therapeutic metformin concentrations positively regulate proliferation in endometrial epithelial cells (EECs) via mTOR activation and augmented mitochondrial strength.

M Imran, Geetanjali Sachdeva, Shyla Menon, Dhanjit Das, Sravanthi Davuluri, Kshitish Acharya, Uddhav Chaudhari.

Metformin, an antidiabetic drug, has recently been repositioned in the treatment of several nondiabetic disorders including reproductive disorders such as polycystic ovarian syndrome (PCOS), where it improves endometrial functions. In vitro studies employing supratherapeutic concentrations (5-20 mM) of metformin, have reported anti-proliferative effects on endometrial epithelial and stromal cells. However, animal and human studies have revealed that therapeutic serum concentrations of metformin range between 20-70 µM. In the present study, the effect of therapeutic concentrations of metformin was studied on endometrial epithelial cells (EECs). Therapeutic concentrations of metformin induced proliferation in Ishikawa and HEC-1A cells. The proliferation of EECs was found mTOR dependent. Interestingly, therapeutic metformin concentrations were not able to activate the classical AMPK signaling. On the contrary, supratherapeutic metformin concentration (10 mM) inhibited mTOR and activated AMPK signaling. Microarray analysis of metformin-treated HEC-1A cells revealed dose-dependent differential effects on biological pathways associated with translation, ribosomal RNA processing, mitochondrial translation and cell proliferation. Therapeutic concentrations of metformin upregulated mitochondrial number as demonstrated by increased MitotrackerTM Red staining and enhanced succinate dehydrogenase (SDHD) expression; however higher concentration (10 mM) abrogated the same. Our results suggest that therapeutic concentrations of metformin augment mitochondrial strength and induce mTOR dependent endometrial cell proliferation.

DOI: https://doi.org/10.1139/cjpp-2022-0307
Circulation. 2022 Nov;146(18): 1383-1405

Critical Reanalysis of the Mechanisms Underlying the Cardiorenal Benefits of SGLT2 Inhibitors and Reaffirmation of the Nutrient Deprivation Signaling/Autophagy Hypothesis.

Milton Packer.

  SGLT2 (sodium-glucose cotransporter 2) inhibitors produce a distinctive pattern of benefits on the evolution and progression of cardiomyopathy and nephropathy, which is characterized by a reduction in oxidative and endoplasmic reticulum stress, restoration of mitochondrial health and enhanced mitochondrial biogenesis, a decrease in proinflammatory and profibrotic pathways, and preservation of cellular and organ integrity and viability. A substantial body of evidence indicates that this characteristic pattern of responses can be explained by the action of SGLT2 inhibitors to promote cellular housekeeping by enhancing autophagic flux, an effect that may be related to the action of these drugs to produce simultaneous upregulation of nutrient deprivation signaling and downregulation of nutrient surplus signaling, as manifested by an increase in the expression and activity of AMPK (adenosine monophosphate-activated protein kinase), SIRT1 (sirtuin 1), SIRT3 (sirtuin 3), SIRT6 (sirtuin 6), and PGC1-α (peroxisome proliferator-activated receptor γ coactivator 1-α) and decreased activation of mTOR (mammalian target of rapamycin). The distinctive pattern of cardioprotective and renoprotective effects of SGLT2 inhibitors is abolished by specific inhibition or knockdown of autophagy, AMPK, and sirtuins. In the clinical setting, the pattern of differentially increased proteins identified in proteomics analyses of blood collected in randomized trials is consistent with these findings. Clinical studies have also shown that SGLT2 inhibitors promote gluconeogenesis, ketogenesis, and erythrocytosis and reduce uricemia, the hallmarks of nutrient deprivation signaling and the principal statistical mediators of the ability of SGLT2 inhibitors to reduce the risk of heart failure and serious renal events. The action of SGLT2 inhibitors to augment autophagic flux is seen in isolated cells and tissues that do not express SGLT2 and are not exposed to changes in environmental glucose or ketones and may be related to an ability of these drugs to bind directly to sirtuins or mTOR. Changes in renal or cardiovascular physiology or metabolism cannot explain the benefits of SGLT2 inhibitors either experimentally or clinically. The direct molecular effects of SGLT2 inhibitors in isolated cells are consistent with the concept that SGLT2 acts as a nutrient surplus sensor, and thus, its inhibition causes enhanced nutrient deprivation signaling and its attendant cytoprotective effects, which can be abolished by specific inhibition or knockdown of AMPK, sirtuins, and autophagic flux.

Keywords:  TOR serine-threonine kinases; autophagy; heart failure; sirtuins; sodium-glucose transporter 2 inhibitors

DOI:  https://doi.org/10.1161/CIRCULATIONAHA.122.061732
Mol Biol Rep. 2022 Nov 01.

Role of metformin in inflammation.

Yu Yue Feng, Zhengjie Wang, Hua Pang.

  BACKGROUND: Metformin has good anti-hyperglycemic effectiveness, but does not induce hypoglycemia，is very safe, and has become the preferred drug for the treatment of type 2 diabetes. Recently, the other effects of metformin, such as being anti-inflammatory and delaying aging, have also attracted increased attention.METHODS AND RESULTS: The relevant literatures on pubmed and other websites for reading, classification and sorting, and did not involve any animal experiments.
CONCLUSION: Metformin has anti-inflammatory effects through multiple routes, which provides potential therapeutic targets for certain inflammatory diseases, such as neuroinflammation and rheumatoid arthritis. In addition, inflammation is a key component of tumor occurrence and development ; thus, targeted inflammatory intervention is a significant benefit for both cancer prevention and treatment. Therefore, metformin may have further potential for inflammation-related disease prevention and treatmen. However, the inflammatory mechanism is complex; various molecules are connected and influence each other. For example, metformin significantly inhibits p65 nuclear translocation, but pretreatment with compound C, an AMPK inhibitor, abolishes this effect, and silencing of HMGB1 inhibits NF-κB activation . SIRT1 deacetylates FoxO, increasing its transcriptional activity . mTOR in dendritic cells regulates FoxO1 via AKT. The interactions among various molecules should be further explored to clarify their specific mechanisms and provide more direction for the treatment of inflammatory diseases, as well as cancer.

Keywords:  Anti-inflammation; Inflammatory cytokine; Mechanisms; Metformin

DOI:  https://doi.org/10.1007/s11033-022-07954-5
Front Aging Neurosci. 2022 ;14 1015453

1,25-D3 attenuates cerebral ischemia injury by regulating mitochondrial metabolism via the AMPK/AKT/GSK3β pathway.

Yutian Li, Xiangling Li, Shuangli Xu, Yingzhe Zhao, Meng Pang, Xiaojun Zhang, Xuejian Wang, Yanqiang Wang.

  The brain injury caused by cerebral ischemia-reperfusion is related to mitochondrial damage. Maintaining the normal function of mitochondria, promoting angiogenesis, protecting neuronal cells, and resisting oxidative stress are the keys to functional recovery after acute ischemic stroke. In this study, we established a middle cerebral artery occlusion (MCAO) model and investigated the effects of 1α,25-dihydroxyvitamin D3 (VitD or 1,25-D3) on mitochondrial function via the adenosine 5'-monophosphate-activated protein kinase (AMPK)/protein kinase B (AKT)/glycogen synthase kinase-3β (GSK-3β) signaling pathway in rats with cerebral ischemia-reperfusion injury. The neurological function and infarct size were measured in each group. Hematoxylin-eosin, neuronal nucleus, and Nissl staining procedures were conducted to observe the morphology and number of the cerebral cortical neurons. Western blotting was then used to analyze p-AMPK, vitamin D receptor (VDR), p-GSK-3β, p-AKT, P53, cytochrome C (CytC), TGF-β, and vascular endothelial growth factor (VEGF) in mitochondria. Immunofluorescence staining was used to observe the expression of CytC and caspase-3. Succinate dehydrogenase, ATPase, reactive oxygen species, and malondialdehyde were detected by kits. RT-qPCR was used to analyze TGF-β, VEGF, P53, and CytC mRNA. The results revealed that the cerebral infarct volume, neurological function score, apoptotic protein P53, CytC, caspase-3, reactive oxygen species, and malondialdehyde were significantly increased in MCAO rats. 1,25-D3 reduced the infarct size and neurological function score, activated VDR, upregulated TGF-β, p-AMPK, p-AKT, p-GSK-3β, VEGF, ATP, and succinate dehydrogenase, and downregulated P53, CytC, caspase-3, reactive oxygen species, and malondialdehyde. As an antagonist of VDRs, pyridoxal-5-phosphate could partially block the neuroprotective effect of 1,25-D3. In conclusion, 1,25-D3 activated AMPK/AKT/GSK-3β signaling and VDRs, inhibited P53, CytC, and caspase-3, increased TGF-β and VEGF, regulated mitochondrial metabolism, reduced neuronal apoptosis, promoted vascular growth, and exerted neuroprotective effects. These findings suggest that this signaling pathway may be an effective target for the treatment of ischemic stroke.

Keywords:  1; 25-D3; MCAO/R; P53; caspase-3; cerebral ischemia-reperfusion; cytochrome C; mitochondrial metabolism; vitamin D receptor

DOI:  https://doi.org/10.3389/fnagi.2022.1015453
Nutr Res. 2022 Oct 07. pii: S0271-5317(22)00093-8. [Epub ahead of print]107 187-194

Pheophorbide A isolated from Gelidium amansii inhibits adipogenesis by regulating adipogenic transcription factors and AMPK in 3T3-L1 adipocytes.

Mi Hwa Park, Hak-Ju Kim, Ji-Sook Han.

  Adipocyte lipid accumulation causes adipocyte hypertrophy and adipose tissue increment, leading to obesity. As part of our efforts to isolate antiobesity agents from natural products, we first isolated the active compound from the extract of Gelidium amansii through bioassay-guided fractionation. We then hypothesized that pheophorbide A isolated from G amansii inhibits adipogenesis by downregulating adipogenic transcription factors; therefore, the antiadipogenic effects of pheophorbide A were investigated in 3T3-L1 adipocytes. On differentiation of 3T3-L1 preadipocytes into adipocytes, they were treated with pheophorbide A (0-83 µM). Pheophorbide A inhibited triglyceride accumulation (half maximal inhibitory concentration = 114.2 µM) and stimulated glycerol release in a dose-dependent manner in 3T3-L1 adipocytes. In addition, pheophorbide A significantly decreased leptin concentrations in 3T3-L1 adipocytes. Pheophorbide A inhibited adipogenesis by suppressing the expression of adipogenic transcriptional factors including peroxisome proliferator-activated receptor γ, CCATT/enhancer binding protein α, sterol regulatory element binding protein 1c, and fatty acid synthase. It also induced the expression of phosphorylation of AMP-activated protein kinase. Therefore, these results suggest that pheophorbide A may be useful for preventing or treating obesity because of its inhibitory effect on adipogenesis.

Keywords:  3T3-L1 adipocytes; Adipogenesis; Gelidium amansii; Obesity; Pheophorbide A

DOI:  https://doi.org/10.1016/j.nutres.2022.10.001
Eur J Nucl Med Mol Imaging. 2022 Nov 02.

Metformin confers longitudinal cardiac protection by preserving mitochondrial homeostasis following myocardial ischemia/reperfusion injury.

Jing Tian, Yaqi Zheng, Tiantian Mou, Mingkai Yun, Yi Tian, Yao Lu, Yujie Bai, Yihan Zhou, Marcus Hacker, Xiaoli Zhang, Xiang Li.

  PURPOSE: Myocardial ischemia-reperfusion (I/R) injury is associated with systemic oxidative stress, cardiac mitochondrial homeostasis, and cardiomyocyte apoptosis. Metformin has been recognized to attenuate cardiomyocyte apoptosis. However, the longitudinal effects and pathomechanism of metformin on the regulation of myocardial mitohormesis following I/R treatment remain unclear. This study aimed to investigate the longitudinal effects and mechanism of metformin in regulating cardiac mitochondrial homeostasis by serial imaging with the 18-kDa translocator protein (TSPO)-targeted positron emission tomography (PET) tracer 18F-FDPA.METHODS: Myocardial I/R injury was established in Sprague-Dawley rats, which were treated with or without metformin (150 mg/kg per day). Serial gated 18F-FDG and 18F-FDPA PET imaging were performed at 1, 4, and 8 weeks after surgery, followed by analysis of ventricular remodelling and cardiac mitochondrial homeostasis. The correlation between Hsp60 and 18F-FDPA uptake was analyzed. After PET imaging, the activity of antioxidant enzymes, immunostaining, and western blot analysis were performed to analyze the spatio-temporal effects and pathomechanism of metformin for cardiac protection after myocardial I/R injury.
RESULTS: Oxidative stress and apoptosis increased 1 week after myocardial I/R injury (before significant progression of ventricular remodelling). TSPO expression was correlated with Hsp60 expression and was co-localized with inflammatory CD68+ macrophages in the infarct area, and TSPO uptake was associated with an upregulation of AMPK-p/AMPK and a downregulation of Bcl-2/Bax. However, these effects were reversed with metformin treatment. Eight weeks after myocardial I/R injury (representing the advanced stage of heart failure), 18F-FDPA uptake in myocardial cells in the distal non-infarct area increased without CD68+ expression, whereas the activity decreased with metformin treatment.
CONCLUSION: Taken together, these results show that a prolonged metformin treatment has pleiotropic protective effects against myocardial I/R injury associated with a regional and temporal dynamic balance between mitochondrial homeostasis and cardiac outcome, which were assessed by TSPO-targeted imaging during cardiac remodelling.

Keywords:  Metformin; Mitochondrial homeostasis; Myocardial I/R injury; Spatio-temporal effect; TSPO

DOI:  https://doi.org/10.1007/s00259-022-06008-z
Clin Sci (Lond). 2022 Oct 31. pii: CS20220242. [Epub ahead of print]

Metformin alleviates HFD-induced oxidative stress in hepatocyte via activating SIRT6/PGC-1α/ENDOG signaling.

Shuya Gao, Qingchen Yang, Zekun Liu, Weixian Kong, Jiawen Chen, Xie Li, Yue Peng, Mengmeng Bao, Xiaohong Bian, Yuexin Zhang, Qizhou Jiang, Zhe Li, Yubin Zhang, Fangrong Yan, Junmei Ye.

  Metformin is accepted as a first-line drug for the therapy of type 2 diabetes (T2D), while its mechanism is still controversial. In this study, by taking advantage of mouse model of high-fat-diet (HFD)-induced obesity and primary mouse hepatocytes (PMHCs) as well as human hepatocyte L02 cell line, we aimed to investigate the involvement of SIRTs during the application of metformin for the therapy of T2D. Our data evidenced that during HFD-induced obesity, there was elevation of nucleus protein acetylation. Analysis of liver tissue showed that among all SIRT members, SIRT6 expression was significantly downregulated during HFD feeding, which was sustained to regular level with metformin administration. Our result also showed that SIRT6 suppressed intracellular oxidative stress upon FAs stimulation in PMHCs and L02 cells. Mechanistically, SIRT6, but not SIRT1 promoted PGC-1α expression. We further prove that ENDOG is downstream of PGC-1α. In addition, we evidenced that ENDOG protects hepatocytes from lipid-induced oxidative stress, and downregulation of Endog blunted the protective role of metformin in defending against FAs-induced oxidative stress. Our study established a novel mechanism of metformin in counteracting lipid-induced hepatic injury via activating SIRT6/PGC-1α/ENDOG signaling, thus provides novel targets of metformin in the therapy of T2D.

Keywords:  endonuclease G; high fat-diet; liver; metformin; oxidative stress

DOI:  https://doi.org/10.1042/CS20220242
J Immunother Cancer. 2022 Nov;pii: e005632. [Epub ahead of print]10(11):

Metformin increases natural killer cell functions in head and neck squamous cell carcinoma through CXCL1 inhibition.

McKenzie Crist, Benyamin Yaniv, Sarah Palackdharry, Maria A Lehn, Mario Medvedovic, Timothy Stone, Shuchi Gulati, Vidhya Karivedu, Michael Borchers, Bethany Fuhrman, Audrey Crago, Joseph Curry, Ubaldo Martinez-Outschoorn, Vinita Takiar, Trisha M Wise-Draper.

  BACKGROUND: Metformin slows tumor growth and progression in vitro, and in combination with chemoradiotherapy, resulted in high overall survival in patients with head and neck cancer squamous cell carcinoma (HNSCC) in our phase 1 clinical trial (NCT02325401). Metformin is also postulated to activate an antitumor immune response. Here, we investigate immunologic effects of metformin on natural killer (NK) and natural killer T cells, including results from two phase I open-label studies in patients with HNSCC treated with metformin (NCT02325401, NCT02083692).METHODS: Peripheral blood was collected before and after metformin treatment or from newly diagnosed patients with HNSCC. Peripheral immune cell phenotypes were evaluated using flow cytometry, cytokine expression by ELISA and/or IsoLight, and NK cell-mediated cytotoxicity was determined with a flow-based NK cell cytotoxicity assay (NKCA). Patient tumor immune infiltration before and after metformin treatment was analyzed with immunofluorescence. NK cells were treated with either vehicle or metformin and analyzed by RNA sequencing (RNA-seq). NK cells were then treated with inhibitors of significant pathways determined by RNA-seq and analyzed by NKCA, ELISA, and western blot analyses.
RESULTS: Increased peripheral NK cell activated populations were observed in patients treated with metformin. NK cell tumor infiltration was enhanced in patients with HNSCC treated with metformin preoperatively. Metformin increased antitumorigenic cytokines ex vivo, including significant increases in perforin. Metformin increased HNSCC NK cell cytotoxicity and inhibited the CXCL1 pathway while stimulating the STAT1 pathway within HNSCC NK cells. Exogenous CXCL1 prevented metformin-enhanced NK cell-mediated cytotoxicity. Metformin-mediated NK cell cytotoxicity was found to be AMP-activated protein kinase independent, but dependent on both mechanistic target of rapamycin and pSTAT1.
CONCLUSIONS: Our data identifies a new role for metformin-mediated immune antitumorigenic function through NK cell-mediated cytotoxicity and downregulation of CXCL1 in HNSCC. These findings will inform future immunomodulating therapies in HNSCC.

Keywords:  cytotoxicity, immunologic; head and neck neoplasms; immunity, cellular; immunotherapy; killer cells, natural

DOI:  https://doi.org/10.1136/jitc-2022-005632
Front Pharmacol. 2022 ;13 906717

Metformin ameliorates olanzapine-induced obesity and glucose intolerance by regulating hypothalamic inflammation and microglial activation in female mice.

Sang Bum Suh, Nayoung Lee, Jaedeok Kim, Saeha Kim, Sooyeon Jang, Jong Kook Park, Keunwook Lee, Soo Young Choi, Hyung-Joo Kwon, Chan Hee Lee.

  Olanzapine (OLZ), a widely used second-generation antipsychotic drug, is known to cause metabolic side effects, including diabetes and obesity. Interestingly, OLZ-induced metabolic side effects have been demonstrated to be more profound in females in human studies and animal models. Metformin (MET) is often used as a medication for the metabolic side effects of OLZ. However, the mechanisms underlying OLZ-induced metabolic disturbances and their treatment remain unclear. Recent evidence has suggested that hypothalamic inflammation is a key component of the pathophysiology of metabolic disorders. On this background, we conducted this study with the following three objectives: 1) to investigate whether OLZ can independently induce hypothalamic microgliosis; 2) to examine whether there are sex-dependent differences in OLZ-induced hypothalamic microgliosis; and 3) to examine whether MET affects hypothalamic microgliosis. We found that administration of OLZ for 5 days induced systemic glucose intolerance and hypothalamic microgliosis and inflammation. Of note, both hypothalamic microglial activation and systemic glucose intolerance were far more evident in female mice than in male mice. The administration of MET attenuated hypothalamic microglial activation and prevented OLZ-induced systemic glucose intolerance and hypothalamic leptin resistance. Minocycline, a tetracycline derivative that prevents microgliosis, showed similar results when centrally injected. Our findings reveal that OLZ induces metabolic disorders by causing hypothalamic inflammation and that this inflammation is alleviated by MET administration.

Keywords:  hypothalamus; leptin resistance; metabolic disease; metformin; microglia; olanzapine; second-generation antipsychotic drug

DOI:  https://doi.org/10.3389/fphar.2022.906717