Metformin-treated Cells Research Articles

An antifibrotic compound that ameliorates hyperglycaemia and fat accumulation in cell and HFD mouse models.

Appropriate management of blood glucose levels and the prevention of complications are important in the treatment of diabetes. We have previously reported on a compound named HPH-15 that is not only antifibrotic but also AMP-activated protein kinase (AMPK)-activating. In this study, we evaluated whether HPH-15 is useful as a therapeutic medication for diabetes. We examined the effects of HPH-15 on AMPK activation, glucose uptake, fat accumulation and lactic acid production in L6-GLUT4, HepG2 and 3T3-L1 cells, as a model of muscle, liver and fat tissue, respectively. Additionally, we investigated the glucose-lowering, fat-accumulation-suppressing, antifibrotic and AMPK-activating effect of HPH-15 in mice fed a high-fat diet (HFD). HPH-15 at a concentration of 10 µmol/l increased AMPK activation, glucose uptake and membrane translocation of GLUT4 in each cell model to the same extent as metformin at 2 mmol/l. The production of lactic acid (which causes lactic acidosis) in HPH-15-treated cells was equal to or less than that observed in metformin-treated cells. In HFD-fed mice, HPH-15 lowered blood glucose from 11.1±0.3 mmol/l to 8.2±0.4 mmol/l (10 mg/kg) and 7.9±0.4 mmol/l (100 mg/kg) and improved insulin resistance. The HPH-15 (10 mg/kg) group showed the same level of AMPK activation as the metformin (300 mg/kg) group in all organs. The HPH-15-treated HFD-fed mice also showed suppression of fat accumulation and fibrosis in the liver and fat tissue; these effects were more significant than those obtained with metformin. Mice treated with high doses of HPH-15 also exhibited a 44% reduction in subcutaneous fat. HPH-15 activated AMPK at lower concentrations than metformin in vitro and in vivo and improved blood glucose levels and insulin resistance in vivo. In addition, HPH-15 was more effective than metformin at ameliorating fatty liver and adipocyte hypertrophy in HFD-fed mice. HPH-15 could be effective in preventing fatty liver, a common complication in diabetic individuals. Additionally, in contrast to metformin, high doses of HPH-15 reduced subcutaneous fat in HFD-fed mice. Presumably, HPH-15 has a stronger inhibitory effect on fat accumulation and fibrosis than metformin, accounting for the reduction of subcutaneous fat. Therefore, HPH-15 is potentially a glucose-lowering medication that can lower blood glucose, inhibit fat accumulation and ameliorate liver fibrosis.

Metformin modulates corticosteroids hormones in adrenals cells promoting Mycobacterium tuberculosis elimination in human macrophages

Research suggests that both tuberculosis (TB) and type 2 diabetes mellitus (T2DM) have an immuno-endocrine imbalance characterized by dysregulated proinflammatory molecules and hormone levels (high cortisol/DHEA ratio), impeding an effective immune response against Mycobacterium tuberculosis (Mtb) driven by cytokines, antimicrobial peptides (AMPs), and androgens like DHEA. Insulin, sulfonylurea derivatives, and metformin are commonly used glucose-lowering drugs in patients suffering from TB and T2DM. For this comorbidity, metformin is an attractive target to restore the immunoendocrine mechanisms dysregulated against Mtb. This study aimed to assess whether metformin influences cortisol and DHEA synthesis in adrenal cells and if these hormones influence the expression of proinflammatory cytokines and AMPs in Mtb-infected macrophages. Our results suggest that metformin may enhance DHEA synthesis while maintaining cortisol homeostasis. In addition, supernatants from metformin-treated adrenal cells decreased mycobacterial loads in macrophages, which related to rising proinflammatory cytokines and AMP expression (HBD-2 and 3). Intriguingly, we find that HBD-3 and LL-37 can modulate steroid synthesis in adrenal cells with diminished levels of cortisol and DHEA, highlighting the importance of crosstalk communication between adrenal hormones and these effectors of innate immunity. We suggest that metformin's effects can promote innate immunity against Mtb straight or through modulation of corticosteroid hormones.

Exosomes biogenesis was increased in metformin-treated human ovary cancer cells; possibly to mediate resistance

BackgroundExosomes derived from tumor cells contribute to the pathogenesis of cancers. Metformin, the most usually used drug for type 2 diabetes, has been frequently investigated for anticancer effects. Here, we examined whether metformin affects exosomes signaling in human ovary cancer cells in vitro.MethodsHuman ovary cancer cells, including A2780 and Skov3 cells, were treated with metformin for either 24–48 h. Cell viability and caspase-3 activity were determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) and colorimetric assays respectively. Oil-Red-O staining and in vitro, scratch assays were used to examine cellular toxicity and wound healing rate. After treatment with metformin, exosomes were isolated from cells and quantified by acetylcholinesterase (AChE) assay, Dynamic Light Scattering (DLS), and their markers. Genes related to exosomes signaling were analyzed by real-time PCR or western blotting.ResultsOur results showed that metformin decreased the viability of both cells dose/time-dependently (P < 0.05). Metformin increased the activity of caspase-3 (P < 0.05) as well as the number of Oil-Red-O positive cells in both cell lines. In vitro scratch assay showed that the cell migration rate of metformin-treated cells was decreased (P < 0.05), whereas AChE activity of exosomes from metformin-treated cells was increased (P < 0.05). Concurrent with an increase in CD63 protein levels, expression of Alix, CD63, CD81, Lamp-2, and Rab27b up-regulated in treated cells (P < 0.05).ConclusionResults indicated that metformin had a cytotoxic effect on ovary cancer cells and enhanced exosome biogenesis and secretion.

Microarray analysis of tRNA-derived small RNA (tsRNA) in LPS-challenged macrophages treated with metformin

Metformin, a widely used anti-diabetic drug, has demonstrated its efficacy in addressing various inflammatory conditions. tRNA-derived small RNA (tsRNA), a novel type of small non-coding RNA, exhibits diverse regulatory functions and holds promise as both a diagnostic biomarker and a therapeutic target for various diseases. The purpose of this study is to investigate whether the abundance of tsRNAs changed in LPS versus LPS + metformin-treated cells, utilizing microarray technology. Firstly, we established an in vitro lipopolysaccharide (LPS)-induced inflammation model using RAW264.7 macrophages and assessed the protective effects of metformin against inflammatory damage. Subsequently, we extracted total RNA from both LPS-treated and metformin + LPS-treated cell samples for microarray analysis to identify differentially abundant tsRNAs (DA-tsRNAs). Furthermore, we conducted bioinformatics analysis to predict target genes for validated DA-tsRNAs and explore the biological functions and signaling pathways associated with DA-tsRNAs. Notably, metformin was found to inhibit the inflammatory response in RAW264.7 macrophages. The microarray results revealed a total of 247 DA-tsRNAs, with 58 upregulated and 189 downregulated tsRNAs in the Met + LPS group compared to the LPS group. The tsRNA-mRNA network was visualized, shedding light on potential interactions. The results of bioinformatics analysis suggested that these potential targets of specific tsRNAs were mainly related to inflammation and immunity. Our study provides compelling evidence that metformin exerts anti-inflammatory effects and modulates the abundance of tsRNAs in LPS-treated RAW264.7 macrophages. These findings establish a valuable foundation for using tsRNAs as potential biomarkers for metformin in the treatment of inflammatory conditions.

Metformin promotes anti-tumor immunity in STK11 mutant NSCLC through AXIN1-dependent upregulation of multiple nucleotide metabolites.

Metformin has pleiotropic effects beyond glucose reduction, including tumor inhibition and immune regulation. It enhanced the anti-tumor effects of programmed cell death protein 1 (PD-1) inhibitors in serine/threonine kinase 11 (STK11) mutant non-small cell lung cancer (NSCLC) through an axis inhibition protein 1 (AXIN1)-dependent manner. However, the alterations of tumor metabolism and metabolites upon metformin administration remain unclear. We performed untargeted metabolomics using liquid chromatography (LC)-mass spectrometry (MS)/MS system and conducted cell experiments to verify the results of bioinformatics analysis. According to the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database, most metabolites were annotated into metabolism, including nucleotide metabolism. Next, the differentially expressed metabolites in H460 (refers to H460 cells), H460_met (refers to metformin-treated H460 cells), and H460_KO_met (refers to metformin-treated Axin1 -/- H460 cells) were distributed into six clusters based on expression patterns. The clusters with a reversed expression pattern upon metformin treatment were selected for further analysis. We screened out metabolic pathways through KEGG pathway enrichment analysis and found that multiple nucleotide metabolites enriched in this pathway were upregulated. Furthermore, these metabolites enhanced the cytotoxicity of activated T cells on H460 cells in vitro and can activate the stimulator of the interferon genes (STING) pathway independently of AXIN1. Relying on AXIN1, metformin upregulated multiple nucleotide metabolites which promoted STING signaling and the killing of activated T cells in STK11 mutant NSCLC, indicating a potential immunotherapeutic strategy for STK11 mutant NSCLC.

Metformin inhibits cell proliferation and ACTH secretion in AtT20 cells via regulating the MAPK pathway

We investigated the impact of metformin on ACTH secretion and tumorigenesis in pituitary corticotroph tumors. The mouse pituitary tumor AtT20 cell line was treated with varying concentrations of metformin. Cell viability was assessed using the CCK-8 assay, ACTH secretion was measured using an ELISA kit, changes in the cell cycle were analyzed using flow cytometry, and the expression of related proteins was evaluated using western blotting. RNA sequencing was performed on metformin-treated cells. Additionally, an in vivo BALB/c nude xenograft tumor model was established in nude mice, and immunohistochemical staining was conducted for further verification. Following metformin treatment, cell proliferation was inhibited, ACTH secretion decreased, and G1/S phase arrest occurred. Analysis of differentially expressed genes revealed cancer-related pathways, including the MAPK pathway. Western blotting confirmed a decrease in phosphorylated ERK1/2 and phosphorylated JNK. Combining metformin with the ERK1/2 inhibitor Ulixertinib resulted in a stronger inhibitory effect on cell proliferation and POMC (Precursors of ACTH) expression. In vivo studies confirmed that metformin inhibited tumor growth and reduced ACTH secretion. In conclusion, metformin inhibits tumor progression and ACTH secretion, potentially through suppression of the MAPK pathway in AtT20 cell lines. These findings suggest metformin as a potential drug for the treatment of Cushing's disease.

Metformin-Induced Ferroptosis Is a Therapeutic Vulnerability in IDH2-Mutant AML Linked to Metabolic Rewiring Towards Fatty Acid Oxidation

Metabolic rewiring is an essential feature of leukemic cells to sustain tumorigenesis and is largely influenced by mutational status. We previously demonstrated this phenomenon in FLT3-ITD acute myeloid leukemia (AML) upon combined inhibition of complex II activity and lactate import (Erdem et al., 2022). Mutations in isocitrate dehydrogenase ( IDH1/2mut) occur in about 20% of AML cases, and despite the emergence of targeted therapies, patients often relapse. The molecular and epigenetic outcomes of 2-R-hydroxyglutarate accumulation and competitive inhibition of histone demethylases have been extensively studied in IDH1/2mut AMLs, but the metabolic consequences are still largely unexplored. Here, we applied multi-omics studies on cell line models and primary AML samples combined with functional studies to unravel the metabolic rewiring of IDH1/2mut AMLs. Transcriptional characterization of isogenic TF1 wt and IDH2R140Q cell lines (10978 genes) revealed increased expression of CD36, a major fatty acid (FA) transporter, and gene set enrichment analysis (GSEA) associated IDH2R140Q cells with terms related to FA processes and activity of mitochondrial complex I. Quantitative metabolome analysis of TF1 wt and IDH2R140Q (180 metabolites) revealed lower levels of acylcarnitines of variable carbon lengths, suggesting increased FA oxidation, and upregulation of glycerophospholipid and glycerolipid metabolism in IDH2R140Q cells. Next, we validated our findings by performing a metabolomic profiling (172 metabolites) on primary AML samples (n=26, including 4 IDH1mut and 2 IDH2mut), for which label-free quantitative proteome data (11272 proteins) was also generated. Proteome analysis confirmed increased CD36 expression and enrichment for FA and mitochondrial processes in IDH1/2mut patients. In line, metabolome data also revealed increased oxidation of branched-chain FAs in this sample group. Altogether, these findings suggested a profound disturbance in lipid metabolism and supported the notion that IDH1/2 mutant cells rely on mitochondrial respiration, whereby FAs seem to be the preferred carbon source. Next, we performed an in vitro drug screen targeting the main metabolic pathways, which revealed increased sensitivity of IDH2R140Q cells to the FDA-approved complex I inhibitor metformin. Extracellular flux analysis indicated no significant difference in the oxygen consumption rate (OCR) between TF1 wt and IDH2R140Q upon metformin treatment, while the viability of mutant cells was significantly diminished. Contrarily, the basal extracellular acidification rate (ECAR) was increased in TF1 wt cells upon complex I inhibition, suggesting that these cells rewire their metabolism towards glycolysis more efficiently than mutant cells. Furthermore, we knocked down CD36 expression to investigate whether disrupting lipid metabolism in IDH2R140Q cells would constitute a metabolic vulnerability. Notably, CD36 knockdown resulted in increased resistance to metformin in IDH2R140Q cells. These data suggested that enhanced lipid uptake mediated by CD36 in IDH2R140Q cells not only boosts OCR but may also disrupt lipid homeostasis, causing cells to become more susceptible to lipid peroxidation. Since the role of metformin-induced ferroptosis in AML is still unclear, we performed an RNA-seq analysis on TF1 wt and IDH2R140Q cells treated with metformin (5 mM) for 72 hours (10326 genes). Single-sample GSEA associated the transcriptome of metformin-treated cells with ferroptosis signatures in both cell lines but to a significantly higher extent in IDH2R140Q. We functionally validated this finding by using the BODIPY C11 probe, a lipid peroxidation sensor. After 24h of metformin treatment, both TF1 wt and IDH2R140Q displayed increased lipid ROS. Lipid peroxidation levels were further enhanced by combining metformin with palmitate, a saturated FA, supporting the notion that elevated lipid availability and uptake may increase cell death via ferroptosis. Altogether, we identified a new metabolic vulnerability in IDH1/2mut AMLs associated with a profound disturbance in lipid metabolism. Moreover, we show that treatment with metformin not only inhibits complex I but also induces cell death via ferroptosis in IDH2mut cells providing an alternative treatment option in combination with available IDH2mut targeted therapies for this subgroup of patients.

Metformin impairs trophoblast metabolism and differentiation in a dose-dependent manner.

Metformin is a widely prescribed medication whose mechanism of action is not completely defined and whose role in gestational diabetes management remains controversial. In addition to increasing the risk of fetal growth abnormalities and preeclampsia, gestational diabetes is associated with abnormalities in placental development including impairments in trophoblast differentiation. Given that metformin impacts cellular differentiation events in other systems, we assessed metformin's impact on trophoblast metabolism and differentiation. Using established cell culture models of trophoblast differentiation, oxygen consumption rates and relative metabolite abundance were determined following 200µM (therapeutic range) and 2000µM (supra-therapeutic range) metformin treatment using Seahorse and mass-spectrometry approaches. While no differences in oxygen consumption rates or relative metabolite abundance were detected between vehicle and 200µM metformin-treated cells, 2000µM metformin impaired oxidative metabolism and increased the abundance of lactate and TCA cycle intermediates, α-ketoglutarate, succinate, and malate. Examining differentiation, treatment with 2000μM, but not 200µM metformin, impaired HCG production and expression of multiple trophoblast differentiation markers. Overall, this work suggests that supra-therapeutic concentrations of metformin impair trophoblast metabolism and differentiation whereas metformin concentrations in the therapeutic range do not strongly impact these processes.

Investigating the effects of Ceylon cinnamon water extract on HepG2 cells for Type 2 diabetes therapy.

Cinnamon and its extracts have been used as herbal remedies for many ailments, including for reducing insulin resistance and diabetes complications. Type 2 diabetes mellitus (T2DM) is a rapidly growing health concern around the world. Although many drugs are available for T2DM treatment, side effects and costs can be considerable, and there is increasing interest in natural products for managing chronic health conditions. Cinnamon may decrease the expression of genes associated with T2DM risk. The purpose of this study was to evaluate the effects of cinnamon water extract (CWE) compared with metformin on T2DM-related gene expression. HepG2 human hepatoma cells, widely used in drug metabolism and hepatotoxicity studies, were treated with different concentrations of metformin or CWE for 24 or 48 h. Cell viability was assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and glucose uptake was compared in untreated and CWE- or metformin-treated cells under high-glucose conditions. Finally, total RNA was extracted and analyzed by RNA sequencing (RNA-seq), and bioinformatics analyses were performed to compare the transcriptional effects of CWE and metformin. We found cell viability was better in cells treated with CWE than in metformin-treated cells, demonstrating that CWE was not toxic at tested doses. CWE significantly increased glucose uptake in HepG2 cells, to the same degree as metformin (1.4-fold). RNA-seq data revealed CWE and metformin both induced significantly increased (1.3- to 1.4-fold) glucose uptake gene expression compared with untreated controls. Transcriptional differences between CWE and metformin were not significant. The effects of 0.125 mg mL-1 CWE on gene expression were comparable to 1.5 mg mL-1 (9.5 mM) metformin. In addition, gene expression at 0.125 mg mL-1 CWE was comparable to 1.5 mg mL-1 (9.5 mM) metformin. Our results reveal that CWE's effects on cell viability, glucose uptake, and gene expression in HepG2 cells are comparable to those of metformin, suggesting CWE may be an effective dietary supplement for mitigating T2DM-related metabolic dysfunction.

Low-Dose Metformin Treatment Reduces In Vitro Growth of the LL/2 Non-small Cell Lung Cancer Cell Line.

Lung cancer maintains a relatively small survival rate (~19%) over a 5-year period and up to 80-85% of all lung cancer diagnoses are Non-Small Cell Lung Cancer (NSCLC). To determine whether metformin reduces non-small cell lung cancer (NSCLC) LL/2 cell growth, cells were grown in vitro and treated with metformin for 48 h. qPCR was used to assess genes related to cell cycle regulation and pro-apoptotic markers, namely Cyclin D, CDK4, p27, p21, and HES1. Treatment with 10 mM metformin significantly reduced HES1 expression (p = 0.011). Furthermore, 10 mM metformin treatment significantly decreased REDD1 (p = 0.0082) and increased p-mTOR Ser2448 (p = 0.003) protein expression. Control cells showed significant reductions in phosphorylated p53 protein expression (p = 0.0367), whereas metformin treated cells exhibited reduced total p53 protein expression (p = 0.0078). There were no significant reductions in AMPK, PKB/AKT, or STAT3. In addition, NSCLC cells were treated for 48 h. with 10 mM metformin, 4 µM gamma-secretase inhibitor (GSI), or the combination of metformin (10 mM) and GSI (4 µM) to determine the contribution of respective signaling pathways. Metformin treatment significantly reduced total nucleus expression of the proliferation maker Ki-67 with an above 65% reduction in Ki-67 expression between control and metformin-treated cells (p = 0.0021). GSI (4 µM) treatment significantly reduced Ki-67 expression by ~20% over 48 h (p = 0.0028). Combination treatment (10 mM metformin and 4 µM GSI) significantly reduced Ki-67 expression by more than 50% over 48 h (p = 0.0245). As such, direct administration of metformin (10 mM for 48 h) proved to be an effective pharmaceutical agent in reducing the proliferation of cultured non-small cell cancer cells. These intriguing in vitro results, therefore, support the further study of metformin in appropriate in vivo models as an anti-oncogenic agent and/or an adjunctive therapy.

Metformin Treatment Abrogates the Competitive Advantage of Dnmt3a R878H HSPCs By Enhancing DNA Methylation Activity

Clonal hematopoiesis of indeterminate potential (CHIP) refers to the clonal expansion of hematopoietic stem and progenitor cells (HSPCs) carrying leukemogenic mutations in individuals without evidence of a blood disorder. CHIP carriers are at an increased risk of blood cancers and cardiovascular diseases. Targeting the clonal expansion of mutant HSPCs has the potential to mitigate CHIP-related illnesses. The most commonly mutated gene in CHIP is DNMT3A, which encodes an enzyme that catalyzes the methyl transfer from S-adenosylmethionine (SAM) to cytosines in DNA. The heterozygous DNMT3A hotspot mutation at R882 exerts a dominant negative effect on the wild-type (WT) allele, resulting in decreased DNA methylation activity. Prior studies have shown that murine HSPCs carrying mutant Dnmt3a R878H (equivalent to R882 in humans) have an advantage over WT cells in competition assays. Here, we aimed to first identify differences in the functional properties between Dnmt3a-mutated and WT HSPCs. Given the crosstalk between mitochondrial metabolism and DNA methylation, we investigated potential differences in mitochondrial activity and found that the level of mitochondrial respiration was higher in Dnmt3aR878H/+ HSPCs than in WT cells. To determine if this translated to differential dependencies, we silenced the expression of critical subunits in the each of five electron transport chain (ETC) complexes. Knockdown of NDUFV1 in Complex I was the most effective in reducing the competitive advantage of Dnmt3aR878H/+ cells in vitro. To explore translational relevance of this finding, we tested the impact of metformin, a pharmacologic inhibitor of Complex I, on Dnmt3a-mutated HSPCs. Treatment with metformin at clinically relevant concentrations suppressed the competitive advantage of mutant cells in vitro. Importantly, this effect was rescued by expression of NDI1, a metformin-resistant yeast analog of Complex I. To extend these findings, we conducted a competitive repopulation assay between CD45.2+ Dnmt3aR878H/+ and CD45.1+ Dnmt3a+/+ HSPCs. Metformin treatment abrogated the in vivo competitive advantage of mutant cells over an 8-month period based on peripheral blood chimerism. To decipher the mechanism of action, we performed transcriptome and metabolome profiling of mutant HSPCs treated with or without metformin for 1 month. GSEA analysis of the transcriptome data revealed a downregulation of genes associated with stemness in metformin-treated cells. Intriguingly, we found that metformin increased the expression of genes involved in one-carbon metabolism, which generates SAM. Consistent with these findings, metabolomics analysis showed that the levels of several key metabolites in one-carbon metabolism, including SAM, were higher in metformin-treated cells compared with controls. Genetic and pharmacologic inhibition of serine hydroxymethyltransferase 2 (SHMT2), a key enzyme in one-carbon metabolism, as well as the addition of exogeneous S-adenosylhomocysteine (SAH), an inhibitor of SAM-dependent methyltransferases, effectively rescued the effect of metformin on mutant cells in vitro. Based on the above findings, we hypothesized that metformin treatment might enhance the residual DNA methylation activity found in Dnmt3aR878H/+ mutated cells by increasing SAM concentration. In support of this hypothesis, we found that exogeneous SAM reproduced the effect of metformin, and HSPCs with homozygous Dnmt3aR878H mutations were insensitive to metformin. Furthermore, we performed DNA methylome profiling of untreated and metformin-treated mutant and WT HSPCs using RRBS. This analysis revealed that the hypomethylated regions (HMRs) in untreated Dnmt3aR878H/+ HSPCs relative to WT controls were enriched for regions of repressed chromatin with H3K27 methylation. Importantly, metformin treatment increased the level of DNA methylation at these regions in mutated HSPCs. In summary, our findings demonstrate that Dnmt3aR878H/+ HSPCs depend on ETC activity and particularly complex I activity to maintain their competitive advantage over WT cells. We propose a model in which inhibition of complex I activity with metformin increases one-carbon metabolism and SAM level, thereby restoring DNA methylation at HMRs and the differentiation of mutant HSPCs. Our findings have important implications for the development of preventive interventions against DNMT3A-mutated CHIP.

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

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.

Exploring the Mechanism of Adjuvant Treatment of Glioblastoma Using Temozolomide and Metformin.

Glioblastoma is the most frequent and lethal primary central nervous system tumor in adults, accounting for around 15% of intracranial neoplasms and 40–50% of all primary malignant brain tumors, with an annual incidence of 3–6 cases per 100,000 population. Despite maximum treatment, patients only have a median survival time of 15 months. Metformin is a biguanide drug utilized as the first-line medication in treating type 2 diabetes. Recently, researchers have noticed that metformin can contribute to antineoplastic activity. The objective of this study is to investigate the mechanism of metformin as a potential adjuvant treatment drug in glioblastoma. Glioblastoma cell lines U87MG, LNZ308, and LN229 were treated with metformin, and several cellular functions and metabolic states were evaluated. First, the proliferation capability was investigated using the MTS assay and BrdU assay, while cell apoptosis was evaluated using the annexin V assay. Next, a wound-healing assay and mesenchymal biomarkers (N-cadherin, vimentin, and Twist) were used to detect the cell migration ability and epithelial–mesenchymal transition (EMT) status of tumor cells. Gene set enrichment analysis (GSEA) was applied to the transcriptome of the metformin-treated glioblastoma cell line. Then, DCFH-DA and MitoSOX Red dyes were used to quantify reactive oxygen species (ROS) in the cytosol and mitochondria. JC-1 dye and Western blotting analysis were used to evaluate mitochondrial membrane potential and biogenesis. In addition, the combinatory effect of temozolomide (TMZ) with metformin treatment was assessed by combination index analysis. Metformin could decrease cell viability, proliferation, and migration, increase cell apoptosis, and disrupt EMT in all three glioblastoma cell lines. The GSEA study highlighted increased ROS and hypoxia in the metformin-treated glioblastoma cells. Metformin increased ROS production, impaired mitochondrial membrane potential, and reduced mitochondrial biogenesis. The combined treatment of metformin and TMZ had U87 as synergistic, LNZ308 as antagonistic, and LN229 as additive. Metformin alone or combined with TMZ could suppress mitochondrial transcription factor A, Twist, and O6-methylguanine-DNA methyltransferase (MGMT) proteins in TMZ-resistant LN229 cells. In conclusion, our study showed that metformin decreased metabolic activity, proliferation, migration, mitochondrial biogenesis, and mitochondrial membrane potential and increased apoptosis and ROS in some glioblastoma cells. The sensitivity of the TMZ-resistant glioblastoma cell line to metformin might be mediated via the suppression of mitochondrial biogenesis, EMT, and MGMT expression. Our work provides new insights into the choice of adjuvant agents in TMZ-resistant GBM therapy.

Investigation of mechanisms underlying the inhibitory effects of metformin against proliferation and growth of neuroblastoma SH-SY5Y cells

Besides being anti-diabetic drug, metformin also has anti-proliferation and growth in several tumors; however, details of possible mechanism have not been elucidated. Here, we investigated the effects of metformin in neuroblastoma which has been termed as extra-cranial solid tumor that is due to a differentiation block with more stemness. The results showed that 5 mM metformin inhibited cell cycle progression at G0/G1 phase. Metformin also induced morphological differentiation of neuroblastoma into neuron-like phenotypes by which upregulation of MAP2, β-tubulin III and tyrosine hydroxylase expressions with no significant difference to retinoic acid (RA)-treated cells. We also tested proliferative, growth and self-renewal ability after neuroblastoma being differentiated by metformin for 24 h. The proliferative rate, sizes and numbers of colonies and spheroids were significantly reduced in differentiated neuroblastoma compared to undifferentiated neuroblastoma. A significant increase of ROS and ADP/ATP ratio with decreased mitochondrial membrane potential (MMP) were observed in metformin-treated cells, indicating mitochondrial biogenesis and metabolic change during metformin-mediated differentiation. The further studies exhibited that p-Erk1/2 and Cdk5 levels were reduced in metformin treatment whereas using PD98095 and roscovitine, selectively inhibited Erk1/2 and Cdk5, respectively, significantly increased neurite length and MAP2 expression. In addition, cell proliferation was decreased by cell cycle arrested at G0/G1 phase. Taken together, this study suggests the inhibitory effects of metformin against proliferation and growth of neuroblastoma due to induced morphological differentiation may be through Erk1/2 and Cdk5 pathways. Therefore, metformin might be eventually considered as a differentiation agent for neuroblastoma treatment in term of differentiation therapy.

New non‐canonical function of catalytically dead hexokinase 1 in ovarian cancer

Hexokinases (HKs) have been found amplified in primary cancer cells, with the amplification of HK1 reported commonly in ovarian cancer cells. The function of HKs extends beyond glucose phosphorylation, and HKs serve as regulatory proteins in tumorigenesis. We addressed the non‐canonical roles of HK1 in ovarian cancer cells by examining the effects of the deletions of HK1 and HK2 in TOV‐112D ovarian adenocarcinoma cells. We reverted these effects by re‐introducing wild‐type HK1 and HK2, and we compared the HK1 revertant with the knock‐in of catalytically‐dead HK1 p.D656A. We subjected these cells to a battery of metabolic and proliferation assays and targeted GCxGC‐MS metabolomics. When expressed in vitro, the p.D656A mutant did not manifest a measurable KM and exhibited Vmax lower by almost two orders of magnitude when compared to the wild‐type enzyme. Knock‐in of HK1 p.D656A into HK1 KO cells reverted the HK1 KO‐induced effects in a broad range of assays, including the alamarBlue cell viability assay under low glucose conditions, the NADPH/NADP and NAD/NADH ratios, and glutathione levels in metformin‐treated cells. In the presence of 0.4 mM glucose, the phenotype of HK1 p.D656A knock‐in cells resembled the phenotype of cells with deleted HK2 but not those with deleted HK1 with regards to the levels of TCA intermediates, aspartate and cysteine, and glutamate. Moreover, HK1 deletion increased the levels of branched amino acids, which was completely eliminated by the expression of catalytically‐dead HK1. The HK1 deletion (but not HK2 deletion) suppressed the growth of xenotransplanted ovarian cancer cells, and nearly abolished the tumor growth when the mice were fed the glucose‐free diet. In summary, we provided the evidence that HK1 is involved in the so far unknown glycolysis‐independent moonlighting function and influences metabolism even in the glucose‐free conditions.

Metformin alleviates ionizing radiation-induced senescence by restoring BARD1-mediated DNA repair in human aortic endothelial cells.

Metformin is one of the most effective therapies for treating type 2 diabetes and has been shown to also attenuate aging and age-related disorders. In this study, we explored the relationship between metformin and DNA damage repair in ionizing radiation (IR)-induced damage of human aortic endothelial cells (HAECs). Metformin treatment suppressed IR-induced senescence phenotypes, such as increased senescent-associated β-galactosidase (SA β-gal) activity and decreased tube formation and proliferation. Moreover, metformin increased BRCA1-associated RING domain protein 1 (BARD1) and RAD51 expression in both aging and IR-exposed cells. Metformin-treated cells exhibited higher levels of the BRCA1-BARD1-RAD51 complex during irradiation, even in the presence of compound C, an AMP-activated protein kinase inhibitor. BARD1 knockdown confirmed its critical role in metformin-mediated inhibition of endothelial senescence. Metformin increased blood vessel sprouting and decreased SA β-gal activity in mouse aortas. Collectively, our findings provide new insights into how metformin can prevent endothelial cell senescence by promoting BARD1-related DNA damage repair, suggesting that metformin may be an effective anti-aging agent and a promising therapeutic for protecting against radiation-induced cardiotoxicity.

Microarray analysis of breast cancer gene expression profiling in response to 2-deoxyglucose, metformin, and glucose starvation

BackgroundBreast cancer (BC) is the most frequently diagnosed cancer in women. Altering glucose metabolism and its effects on cancer progression and treatment resistance is an emerging interest in BC research. For instance, combining chemotherapy with glucose-lowering drugs (2-deoxyglucose (2-DG), metformin (MET)) or glucose starvation (GS) has shown better outcomes than with chemotherapy alone. However, the genes and molecular mechanisms that govern the action of these glucose deprivation conditions have not been fully elucidated. Here, we investigated the differentially expressed genes in MCF-7 and MDA-MB-231 BC cell lines upon treatment with glucose-lowering drugs (2-DG, MET) and GS using microarray analysis to study the difference in biological functions between the glucose challenges and their effect on the vulnerability of BC cells.MethodsMDA-MB-231 and MCF-7 cells were treated with 20 mM MET or 4 mM 2-DG for 48 h. GS was performed by gradually decreasing the glucose concentration in the culture medium to 0 g/L, in which the cells remained with fetal bovine serum for one week. Expression profiling was carried out using Affymetrix Human Clariom S microarrays. Differentially expressed genes were obtained from the Transcriptome Analysis Console and enriched using DAVID and R packages.ResultsOur results showed that MDA-MB-231 cells were more responsive to glucose deprivation than MCF-7 cells. Endoplasmic reticulum stress response and cell cycle inhibition were detected after all three glucose deprivations in MDA-MB-231 cells and only under the metformin and GS conditions in MCF-7 cells. Induction of apoptosis and inhibition of DNA replication were observed with all three treatments in MDA-MB-231 cells and metformin-treated MCF-7 cells. Upregulation of cellular response to reactive oxygen species and inhibition of DNA repair mechanisms resulted after metformin and GS administration in MDA-MB-231 cell lines and metformin-treated MCF-7 cells. Autophagy was induced after 2-DG treatment in MDA-MB-231 cells and after metformin in MCF-7 cells. Finally, inhibition of DNA methylation were observed only with GS in MDA-MB-231 cells.ConclusionThe procedure used to process cancer cells and analyze their expression data distinguishes our study from others. GS had the greatest effect on breast cancer cells compared to 2-DG and MET. Combining MET and GS could restrain both cell lines, making them more vulnerable to conventional chemotherapy.

Plantamajoside promotes metformin-induced apoptosis, autophagy and proliferation arrest of liver cancer cells via suppressing Akt/GSK3β signaling.

Metformin, a well-known antidiabetic drug, exhibits anticancer effect in a variety of cancers, including liver cancer. Plantamajoside (PMS), a phenylethanoid glycoside compound isolated from Plantago asiatica, is proved to possess anticancer effects, too. In our study, we hypothesized that PMS might promote metformin mediated anticancer effects on liver cancer. The half maximal inhibitory concentration (IC50) of metformin was evaluated by cell viability assay. The influence of PMS on proliferation, migration, invasion and apoptosis of metformin-treated cells was evaluated by BrdU incorporation assay, flow cytometry, western blot, wound scratch healing assay, transwell cell migration assay and immunofluorescence. A fasting/feeding mouse model was built to evaluate the influence of PMS on metformin sensitivity in vivo. PMS (2.5, 10 or 40μg/mL) treatment reduced the IC50 of metformin under different glucose concentrations. PMS (10μg/mL) promoted metformin (5mm) induced apoptosis and autophagy, and inhibition on proliferation, migration and invasion of HepG2 and HuH-7 cells. In the fasting/feeding mouse model, PMS (50mg/kg) promoted metformin (200mg/kg) induced proliferation arrest and apoptosis in vivo. Meanwhile, PMS reduced the level of pAkt(ser473) and GSK3β(ser9) in HepG2 and HuH-7 cells. Restoration of Akt/GSK3β signaling by a constitutively activated myr-Akt1 abrogated the effects of PMS on metformin-treated liver cancer cells. Our results demonstrated that PMS promoted the anticancer effects of metformin on liver cancer in vitro and in vivo.

Metformin promotes autophagy activity and constrains HSV-1 replication in neuroblastoma cells

Problem consideredMetformin is an antihyperglycemic drug with effective clinical functions in type 2 diabetes patients. Recent evidence indicates that metformin can change natural cellular signaling to induce autophagy. Furthermore, infection could rise autophagy activity, but herpes simplex virus 1 (HSV-1) constructs, particularly virulence factors, constrain autophagy promotion, we used HSV-1 because of its ability to escape from autophagy by inhibiting beclin-1 formation, reversing PKR signaling and also induce mTOR activity. This study aimed to compare the extent of autophagic activity in metformin-treated cells infected with HSV-1 and determine the effect of metformin on HSV-1 replication. MethodsNeuroblastoma cells were cultured and then divided into the two separate groups of infected with HSV-1 and expose with metformin. Autophagy was evaluated via microtubule-associated protein 1 light chain 3 (LC3-II) monitoring by affix staining antibodies to this protein using flow cytometry. To evaluate viral load, HSV-1 was inoculated for 4 h post metformin treatment, and to evaluate viral load in the post-infection pathway, cells were inoculated with HSV-1. Then, after a 2-hour viral attachment time, metformin was administered to the cells. Viral nucleic acid was purified 48 h post-infection, and virus titer was calculated by real-time polymerase chain reaction (PCR). ResultsOur real-time PCR results indicated that HSV-1 viral load in pre-infection pathway reduced from 1.3 × 106 in positive control to 8 × 105 in cells exposed to metformin. Additionally, the TCID50/ml at 12 and 24 h after infection was 10 times lower than in HSV-1 positive control. However, after 48 h, HSV-1 titer in the metformin-treated group was equal with non-treated cells. For the post-infection pathway, real-time PCR results exhibited that HSV-1 titer was 2.3 × 106 in virus control cells compared to 1.8 × 106 in treated cells. That is, TCID50/ml in the medium of metformin-treated cells was 10 times lower in comparison with non-treated cells after 72 h. ConclusionThe study of the effect of metformin on neuroblastoma cells indicates high autophagic flux and lesser HSV-1 propagation in treated cells.

Identification of Hub Genes Associated with Diabetes Mellitus and Tuberculosis Using Bioinformatic Analysis.

PurposeTo investigate the potential pathophysiological association between tuberculosis (TB) and diabetes mellitus (DM) using bioinformatic analyses.Patients and MethodsGene expression datasets for healthy controls (HCs), TB patients, DM patients, TB+DM patients (GSE114192), and metformin-treated cells (GSE102677) were obtained from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were identified from pairwise dataset comparisons TB vs HCs and DM vs HCs. DEGs were verified by comparing them to DEGs for TB+DM vs HCs. Enrichment analysis of DEGs common to all three dataset comparisons was conducted using DAVID. The protein–protein interaction (PPI) network was established via STRING and visualised in Cytoscape. Hub genes were identified using the Cytoscape plug-in cytoHubba and then were verified using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. Targeted miRNA prediction analysis identified metformin treatment-induced gene expression changes in peripheral blood mononuclear cells.ResultsA total of 422 DEGs were common to all three dataset comparisons. Functional enrichment analysis revealed these DEGs were enriched for functional terms of type I interferon signaling pathway, innate immune response, inflammatory response, and infectious diseases. Ten hub genes identified using PPI network analysis were screened for interactions with metformin target gene INS using cytoHubba based on maximal clique centrality (MCC) score. Subsequently, five hub genes were predicted to functionally interact with INS, including STAT1, IFIT3, RSAD2, IFI44L, and XAF1, as verified by RT-qPCR. Meanwhile, seven miRNAs (miR-3680-3p, miR-3059-5p, miR-629-3p, miR-29b-2-5p, miR-514b-5p, miR-4755-5p, miR-4691-3p) were associated with regulation of hub genes. Notably, six hub genes (STAT1, IFIT3, RSAD2, ISG15, IFI44, IFI6) were down-regulated in cells exposed to both metformin and Mycobacterium tuberculosis antigens.ConclusionNetwork hub genes hold promise as disease status biomarkers and as metformin treatment targets for alleviating TB and DM. This study describes a strategy for exploring pathogenic mechanisms of diseases such as TB and DM.