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The physiological and metabolic functions of PIMT/TGS1, a third-generation transcriptional apparatus protein, in glucose homeostasis sustenance are unclear. Here, we observed that the expression of PIMT was upregulated in the livers of short-term fasted and obese mice. Lentiviruses expressing Tgs1-specific shRNA or cDNA were injected into wild-type mice. Gene expression, hepatic glucose output, glucose tolerance, and insulin sensitivity were evaluated in mice and primary hepatocytes. Genetic modulation of PIMT exerted a direct positive impact on the gluconeogenic gene expression program and hepatic glucose output. Molecular studies utilizing cultured cells, in vivo models, genetic manipulation, and PKA pharmacological inhibition establish that PKA regulates PIMT at post-transcriptional/translational and post-translational levels. PKA enhanced 3'UTR-mediated translation of TGS1 mRNA and phosphorylated PIMT at Ser656, increasing Ep300-mediated gluconeogenic transcriptional activity. The PKA-PIMT-Ep300 signaling module and associated PIMT regulation may serve as a key driver of gluconeogenesis, positioning PIMT as a critical hepatic glucose sensor.
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BACKGROUND: Deregulated translation initiation is implicated extensively in cancer initiation and progression. It is actively pursued as a viable target that circumvents the dependency on oncogenic signaling, a significant factor in current strategies. Eukaryotic translation initiation factor (eIF) 4A plays an essential role in translation initiation by unwinding the secondary structure of messenger RNA (mRNA) upstream of the start codon, enabling active ribosomal recruitment on the downstream genes. Several natural product molecules with similar scaffolds, such as Rocaglamide A (RocA), targeting eIF4A have been reported in the last decade. However, their clinical utilization is still elusive due to several pharmacological limitations. In this study we identified new eIF4A1 inhibitors and their possible mechanisms. METHODS: In this report, we conducted a pharmacophore-based virtual screen of RocA complexed with eIF4A and a polypurine RNA strand for novel eIF4A inhibitors from commercially available compounds in the MolPort Database. We performed target-based screening and optimization of active pharmacophores. We assessed the effects of novel compounds on biochemical and cell-based assays for efficacy and mechanistic evaluation. RESULTS: We validated three new potent eIF4A inhibitors, RBF197, RBF 203, and RBF 208, which decreased diffuse large B-cell lymphoma (DLBCL) cell viability. Biochemical and cellular studies, molecular docking, and functional assays revealed that thosenovel compounds clamp eIF4A into mRNA in an ATP-independent manner. Moreover, we found that RBF197 and RBF208 significantly depressed eIF4A-dependent oncogene expression as well as the colony formation capacity of DLBCL. Interestingly, exposure of these compounds to non-malignant cells had only minimal impact on their growth and viability. CONCLUSIONS: Identified compounds suggest a new strategy for designing novel eIF4A inhibitors.
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Linfoma , Neoplasias , Factor 4A Eucariótico de Iniciación/química , Factor 4A Eucariótico de Iniciación/genética , Factor 4A Eucariótico de Iniciación/metabolismo , Humanos , Linfoma/tratamiento farmacológico , Simulación del Acoplamiento Molecular , ARN Mensajero/metabolismoRESUMEN
The clinical outcomes of patients with acute myeloid leukemia (AML) treated with available therapy remain unsatisfactory. We recently reported that the BCL-2 inhibitor venetoclax synergizes with pegcrisantaspase (Ven-PegC) and exhibits remarkable in vivo efficacy in a preclinical model of AML with complex karyotype. The Ven-PegC combination blocks synthesis of proteins in AML cells by inhibiting cap-dependent translation of mRNA. To further explore the impact of Ven-PegC on protein translation, we used polysome profiling and high-throughput RNA sequencing to characterize Ven-PegC-dependent changes to the translatome. Here we report that the translation of five mRNAs, including two microRNAs, one rRNA, and two mitochondrial genes, was altered after exposure to all three treatments (Ven, PegC, and Ven-PegC). We focused our translatome validation studies on six additional genes related to translational efficiency that were modified by Ven-PegC. Notably, Ven-PegC treatment increased the RNA translation and protein levels of Tribbles homologue 3 (TRIB3), eukaryotic translation initiation factor 3 subunit C (eIF3C), doublesex and mab-3-related transcription factor 1 (DMRT1), and salt-inducible kinase 1 (SIK1). We validated the observed changes in gene/protein expression in vitro and confirmed our cell line-based studies in the bone marrow of an AML patient-derived xenograft model after Ven-PegC treatment. These results support examining alterations in the translatome post chemotherapy to offer insight into the drug's mechanism of action and to inform future therapeutic decisions.
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Protocolos de Quimioterapia Combinada Antineoplásica , Leucemia Mieloide Aguda , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Compuestos Bicíclicos Heterocíclicos con Puentes/uso terapéutico , Humanos , Leucemia Mieloide Aguda/tratamiento farmacológico , Leucemia Mieloide Aguda/genética , Sulfonamidas/farmacología , Sulfonamidas/uso terapéuticoRESUMEN
Patients with high-risk diffuse large B-cell lymphoma (DLBCL) have poor outcomes following first-line cyclophosphamide, doxorubicin, vincristine, prednisone, and rituximab (R-CHOP); thus, treatment of this fatal disease remains an area of unmet medical need and requires identification of novel therapeutic approaches. Dysregulation of protein translation initiation has emerged as a common downstream node in several malignancies, including lymphoma. Ubiquitination, a prominent post-translational modification associated with substrate degradation, has recently been shown to be a key modulator of nascent peptide synthesis by limiting several translational initiation factors. While a few deubiquitinases have been identified, the E3-ligase responsible for the critical ubiquitination of these translational initiation factors is still unknown. In this study, using complementary cellular models along with clinical readouts, we establish that PARK2 ubiquitinates eIF4B and consequently regulates overall protein translational activity. The formation of this interaction depends on upstream signaling, which is negatively regulated at the protein level of PARK2. Through biochemical, mutational, and genetic studies, we identified PARK2 as a mTORC1 substrate. mTORC1 phosphorylates PARK2 at Ser127, which blocks its cellular ubiquitination activity, thereby hindering its tumor suppressor effect on eIF4B's stability. This resultant increase of eIF4B protein level helps drive enhanced overall protein translation. These data support a novel paradigm in which PARK2-generated eIF4B ubiquitination serves as an anti-oncogenic intracellular inhibitor of protein translation, attenuated by mTORC1 signaling. Implications: Our data implicates the FASN/mTOR-PARK2-eIF4B axis as a critical driver of enhanced oncogene expression contributing to lymphomagenesis.
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Patients with high-risk diffuse large B-cell lymphoma (DLBCL) have poor outcomes following first-line cyclophosphamide, doxorubicin, vincristine, prednisone, and rituximab (R-CHOP); thus, treatment of this fatal disease remains an area of unmet medical need and requires identification of novel therapeutic approaches. Dysregulation of protein translation initiation has emerged as a common downstream node in several malignancies, including lymphoma. Ubiquitination, a prominent post-translational modification associated with substrate degradation, has recently been shown to be a key modulator of nascent peptide synthesis by limiting several translational initiation factors. While a few deubiquitinases have been identified, the E3-ligase responsible for the critical ubiquitination of these translational initiation factors is still unknown. In this study, using complementary cellular models along with clinical readouts, we establish that PARK2 ubiquitinates eIF4B and consequently regulates overall protein translational activity. The formation of this interaction depends on upstream signaling, which is negatively regulated at the protein level of PARK2. Through biochemical, mutational, and genetic studies, we identified PARK2 as a mTORC1 substrate. mTORC1 phosphorylates PARK2 at Ser127, which blocks its cellular ubiquitination activity, thereby hindering its tumor suppressor effect on eIF4B's stability. This resultant increase of eIF4B protein level helps drive enhanced overall protein translation. These data support a novel paradigm in which PARK2-generated eIF4B ubiquitination serves as an anti-oncogenic intracellular inhibitor of protein translation, attenuated by mTORC1 signaling. Implications: Our data implicates the FASN/mTOR-PARK2-eIF4B axis as a critical driver of enhanced oncogene expression contributing to lymphomagenesis.
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BACKGROUND: The clinical outcomes of patients with Acute Myeloid Leukemia (AML) remain unsatisfactory. Therefore the development of more efficacious and better-tolerated therapy for AML is critical. We have previously reported anti-leukemic activity of synthetic halohydroxyl dimeric naphthoquinones (BiQ) and aziridinyl BiQ. OBJECTIVE: This study aimed to improve the potency and bioavailability of BiQ compounds and investigate antileukemic activity of the lead compound in vitro and a human AML xenograft mouse model. METHODS: We designed, synthesized, and performed structure-activity relationships of several rationally designed BiQ analogues with amino alcohol functional groups on the naphthoquinone core rings. The compounds were screened for anti-leukemic activity and the mechanism as well as in vivo tolerability and efficacy of our lead compound was investigated. RESULTS: We report that a dimeric naphthoquinone (designated BaltBiQ) demonstrated potent nanomolar anti-leukemic activity in AML cell lines. BaltBiQ treatment resulted in the generation of reactive oxygen species, induction of DNA damage, and inhibition of indoleamine dioxygenase 1. Although BaltBiQ was tolerated well in vivo, it did not significantly improve survival as a single agent, but in combination with the specific Bcl-2 inhibitor, Venetoclax, tumor growth was significantly inhibited compared to untreated mice. CONCLUSION: We synthesized a novel amino alcohol dimeric naphthoquinone, investigated its main mechanisms of action, reported its in vitro anti-AML cytotoxic activity, and showed its in vivo promising activity combined with a clinically available Bcl-2 inhibitor in a patient-derived xenograft model of AML.
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Amino Alcoholes/farmacología , Antineoplásicos/farmacología , Leucemia Mieloide Aguda/tratamiento farmacológico , Naftoquinonas/farmacología , Amino Alcoholes/química , Animales , Antineoplásicos/química , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Leucemia Mieloide Aguda/patología , Ratones , Microsomas Hepáticos/química , Microsomas Hepáticos/metabolismo , Estructura Molecular , Naftoquinonas/química , Relación Estructura-ActividadRESUMEN
Complex karyotype acute myeloid leukemia (CK-AML) has a dismal outcome with current treatments, underscoring the need for new therapies. Here, we report synergistic anti-leukemic activity of the BCL-2 inhibitor venetoclax (Ven) and the asparaginase formulation Pegylated Crisantaspase (PegC) in CK-AML in vitro and in vivo. Ven-PegC combination inhibited growth of multiple AML cell lines and patient-derived primary CK-AML cells in vitro. In vivo, Ven-PegC showed potent reduction of leukemia burden and improved survival, compared with each agent alone, in a primary patient-derived CK-AML xenograft. Superiority of Ven-PegC, compared to single drugs, and, importantly, the clinically utilized Ven-azacitidine combination, was also demonstrated in vivo in CK-AML. We hypothesized that PegC-mediated plasma glutamine depletion inhibits 4EBP1 phosphorylation, decreases the expression of proteins such as MCL-1, whose translation is cap dependent, synergizing with the BCL-2 inhibitor Ven. Ven-PegC treatment decreased cellular MCL-1 protein levels in vitro by enhancing eIF4E-4EBP1 interaction on the cap-binding complex via glutamine depletion. In vivo, Ven-PegC treatment completely depleted plasma glutamine and asparagine and inhibited mRNA translation and cellular protein synthesis. Since this novel mechanistically-rationalized regimen combines two drugs already in use in acute leukemia treatment, we plan a clinical trial of the Ven-PegC combination in relapsed/refractory CK-AML.
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Antineoplásicos/farmacología , Protocolos de Quimioterapia Combinada Antineoplásica/farmacología , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Leucemia Mieloide Aguda/tratamiento farmacológico , Sulfonamidas/farmacología , Animales , Línea Celular Tumoral , Femenino , Células HL-60 , Humanos , Células K562 , Leucemia Mieloide Aguda/metabolismo , Masculino , Ratones , Ratones Endogámicos NOD , Proteína 1 de la Secuencia de Leucemia de Células Mieloides/metabolismo , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Células U937RESUMEN
Cancer cells revamp the regulatory processes that control translation to induce tumor-specific translational programs that can adapt to a hostile microenvironment as well as withstand anticancer therapeutics. Translational initiation has been established as a common downstream effector of numerous deregulated signaling pathways that together culminate in prooncogenic expression. Other mechanisms, including ribosomal stalling and stress granule assembly, also appear to be rewired in the malignant phenotype. Therefore, better understanding of the underlying perturbations driving oncogenic translation in the transformed state will provide innovative therapeutic opportunities. This review highlights deubiquitinating enzymes that are activated/dysregulated in hematologic malignancies, thereby altering the translational output and contributing to tumorigenesis.
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Carcinogénesis , Enzimas Desubicuitinizantes/metabolismo , Neoplasias Hematológicas/enzimología , Biosíntesis de Proteínas , Proteínas Proto-Oncogénicas/metabolismo , Neoplasias Hematológicas/genética , Neoplasias Hematológicas/metabolismo , Humanos , Modelos Biológicos , Proteínas Proto-Oncogénicas/genética , Microambiente TumoralRESUMEN
Statins are first-line therapy drugs for cholesterol lowering. While they are highly effective at lowering cholesterol, they have propensity to induce hyperglycemia in patients. Only limited studies have been reported which studied the impact of statins on (a) whether they can worsen glucose tolerance in a high sucrose fed animal model and (b) if so, what could be the molecular mechanism. We designed studies using high sucrose fed animals to explore the above questions. The high sucrose fed animals were treated with atorvastatin and simvastatin, the two most prescribed statins. We examined the effects of statins on hyperglycemia, glucose tolerance, fatty acid accumulation and insulin signaling. We found that chronic treatment with atorvastatin made the animals hyperglycemic and glucose intolerant in comparison with diet alone. Treatment with both statins lead to fatty acid accumulation and inhibition of insulin signaling in the muscle tissue at multiple points in the pathway.
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Conducta Alimentaria , Intolerancia a la Glucosa/inducido químicamente , Inhibidores de Hidroximetilglutaril-CoA Reductasas/efectos adversos , Hiperglucemia/inducido químicamente , Animales , Atorvastatina/efectos adversos , Dieta , Modelos Animales de Enfermedad , Ácidos Grasos/metabolismo , Regulación de la Expresión Génica/efectos de los fármacos , Intolerancia a la Glucosa/genética , Hiperglucemia/genética , Insulina/metabolismo , Músculos/metabolismo , Ratas , Transducción de Señal/efectos de los fármacos , Simvastatina/efectos adversos , SacarosaRESUMEN
Nutritional abundance associated with chronic inflammation and dyslipidemia impairs the functioning of endoplasmic reticulum (ER) thereby hampering cellular responses to insulin. PHLPP1 was identified as a phosphatase which inactivates Akt, the master regulator of insulin mediated glucose homeostasis. Given the suggestive role of PHLPP1 phosphatase in terminating insulin signalling pathways, deeper insights into its functional role in inducing insulin resistance are warranted. Here, we show that PHLPP1 expression is enhanced in skeletal muscle of insulin resistant rodents which also displayed ER stress, an important mediator of insulin resistance. Using cultured cells and PHLPP1 knockdown mice, we demonstrate that PHLPP1 facilitates the development of ER stress. Importantly, shRNA mediated ablation of PHLPP1 significantly improved glucose clearance from systemic circulation with enhanced expression of glucose transporter 4 (GLUT-4) in skeletal muscle. Mechanistically, we show that endogenous PHLPP1 but not PP2Cα interacts with and directly dephosphorylates AMPK Thr172 in myoblasts without influencing its upstream kinase, LKB1. While the association between endogenous PHLPP1 and AMPK was enhanced in ER stressed cultured cells and soleus muscle of high fat diet fed mice, the basal interaction between PP2Ac and AMPK was minimally altered. Further, we show that PHLPP1α is phosphorylated by ERK1/2 at Ser932 under ER stress which is required for its ability to interact with and dephosphorylate AMPK and thereby induce ER stress. Taken together, our data position PHLPP1 as a key regulator of ER stress.
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Proteínas Quinasas Activadas por AMP/metabolismo , Estrés del Retículo Endoplásmico , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Músculo Esquelético/metabolismo , Proteínas Nucleares/metabolismo , Fosfoproteínas Fosfatasas/metabolismo , Proteínas Quinasas Activadas por AMP/genética , Animales , Transportador de Glucosa de Tipo 4/genética , Transportador de Glucosa de Tipo 4/metabolismo , Células HEK293 , Humanos , Ratones , Proteína Quinasa 1 Activada por Mitógenos/genética , Proteína Quinasa 3 Activada por Mitógenos/genética , Proteínas Nucleares/genética , Fosfoproteínas Fosfatasas/genética , Proteína Fosfatasa 2/genética , Proteína Fosfatasa 2/metabolismo , Proteína Fosfatasa 2C/genética , Proteína Fosfatasa 2C/metabolismo , Ratas , Ratas WistarRESUMEN
Altered lipid metabolism and aberrant protein translation are strongly associated with cancerous outgrowth; however, the inter-regulation of these key processes is still underexplored in diffuse large B-cell lymphoma (DLBCL). Although fatty acid synthase (FASN) activity is reported to positively correlate with PI3K-Akt-mTOR pathway that can modulate protein synthesis, the precise impact of FASN inhibition on this process is still unknown. Herein, we demonstrate that attenuating FASN expression or its activity significantly reduces eIF4B (eukaryotic initiation factor 4B) levels and consequently overall protein translation. Through biochemical studies, we identified eIF4B as a bonafide substrate of USP11, which stabilizes and enhances eIF4B activity. Employing both pharmacological and genetic approaches, we establish that FASN-induced PI3K-S6Kinase signaling phosphorylates USP11 enhancing its interaction with eIF4B and thereby promoting oncogenic translation.
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Factores Eucarióticos de Iniciación/genética , Acido Graso Sintasa Tipo I/genética , Regulación Neoplásica de la Expresión Génica , Biosíntesis de Proteínas , Proteínas Quinasas S6 Ribosómicas/genética , Tioléster Hidrolasas/genética , Animales , Linfocitos B/metabolismo , Linfocitos B/patología , Carcinogénesis/genética , Carcinogénesis/metabolismo , Carcinogénesis/patología , Línea Celular Tumoral , Factores Eucarióticos de Iniciación/metabolismo , Acido Graso Sintasa Tipo I/metabolismo , Femenino , Humanos , Metabolismo de los Lípidos/genética , Linfoma de Células B Grandes Difuso/genética , Linfoma de Células B Grandes Difuso/metabolismo , Linfoma de Células B Grandes Difuso/patología , Ratones , Ratones Desnudos , Trasplante de Neoplasias , Fosfatidilinositol 3-Quinasas/genética , Fosfatidilinositol 3-Quinasas/metabolismo , Fosforilación , Unión Proteica , Proteínas Proto-Oncogénicas c-akt/genética , Proteínas Proto-Oncogénicas c-akt/metabolismo , Proteínas Quinasas S6 Ribosómicas/metabolismo , Transducción de Señal , Serina-Treonina Quinasas TOR/genética , Serina-Treonina Quinasas TOR/metabolismo , Tioléster Hidrolasas/metabolismoRESUMEN
Electroporation is the most widely employed method of gene transfer into macrophages which are hard to transfect. RAW 264.7 is a widely used cell line for studying macrophage responses. Electroporation of RAW 264.7 cells with commercial reagents although very efficient is expensive necessitating the development of cost effective alternatives. In this study, we have formulated an economical electroporation buffer for electroporation of RAW 264.7 cells compatible with commercial nucleofector apparatus. We observed that supplementation of membrane fusogenic agents such as Ficoll, PEG and membrane resealing agent, poloxamer P188, enhanced the transfection efficiency of macrophages to a level comparable to the commercially available solutions thereby providing us a cost effective solution for genetic manipulation of macrophages especially in large numbers.
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Medios de Cultivo Condicionados/economía , Ingeniería de Proteínas/economía , Células RAW 264.7/fisiología , Proteínas Recombinantes/economía , Transfección/economía , Transfección/métodos , Animales , Técnicas de Cultivo Celular por Lotes/economía , Técnicas de Cultivo Celular por Lotes/métodos , Tampones (Química) , Análisis Costo-Beneficio/economía , Análisis Costo-Beneficio/métodos , Medios de Cultivo Condicionados/metabolismo , India , Ratones , Ingeniería de Proteínas/métodos , Células RAW 264.7/citología , Proteínas Recombinantes/biosíntesisRESUMEN
The mechanisms underlying inflammation induced insulin resistance are poorly understood. Here, we report that the expression of PIMT, a transcriptional co-activator binding protein, was up-regulated in the soleus muscle of high sucrose diet (HSD) induced insulin resistant rats and TNF-α exposed cultured myoblasts. Moreover, TNF-α induced phosphorylation of PIMT at the ERK1/2 target site Ser(298). Wild type (WT) PIMT or phospho-mimic Ser298Asp mutant but not phospho-deficient Ser298Ala PIMT mutant abrogated insulin stimulated glucose uptake by L6 myotubes and neonatal rat skeletal myoblasts. Whereas, PIMT knock down relieved TNF-α inhibited insulin signaling. Mechanistic analysis revealed that PIMT differentially regulated the expression of GLUT4, MEF2A, PGC-1α and HDAC5 in cultured cells and skeletal muscle of Wistar rats. Further characterization showed that PIMT was recruited to GLUT4, MEF2A and HDAC5 promoters and overexpression of PIMT abolished the activity of WT but not MEF2A binding defective mutant GLUT4 promoter. Collectively, we conclude that PIMT mediates TNF-α induced insulin resistance at the skeletal muscle via the transcriptional modulation of GLUT4, MEF2A, PGC-1α and HDAC5 genes.
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Transportador de Glucosa de Tipo 4/metabolismo , Proteína D-Aspartato-L-Isoaspartato Metiltransferasa/metabolismo , Transcripción Genética/efectos de los fármacos , Factor de Necrosis Tumoral alfa/farmacología , Animales , Glucemia/análisis , Células Cultivadas , Regulación hacia Abajo/efectos de los fármacos , Transportador de Glucosa de Tipo 4/genética , Células HEK293 , Histona Desacetilasas/genética , Histona Desacetilasas/metabolismo , Humanos , Resistencia a la Insulina , Factores de Transcripción MEF2/genética , Factores de Transcripción MEF2/metabolismo , Masculino , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Mioblastos Esqueléticos/citología , Mioblastos Esqueléticos/metabolismo , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma , Fosforilación/efectos de los fármacos , Proteína D-Aspartato-L-Isoaspartato Metiltransferasa/genética , Ratas , Ratas Wistar , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Factor de Necrosis Tumoral alfa/sangreRESUMEN
Uncontrolled inflammation leads to several diseases such as insulin resistance, T2D and several types of cancers. The functional role of microRNAs in inflammation induced insulin resistance is poorly studied. MicroRNAs are post-transcriptional regulatory molecules which mediate diverse biological processes. We here show that miR-16 expression levels are down-regulated in different inflammatory conditions such as LPS/IFNγ or palmitate treated macrophages, palmitate exposed myoblasts and insulin responsive tissues of high sucrose diet induced insulin resistant rats. Importantly, forced expression of miR-16 in macrophages impaired the production of TNF-α, IL-6 and IFN-ß leading to enhanced insulin stimulated glucose uptake in co-cultured skeletal myoblasts. Further, ectopic expression of miR-16 enhanced insulin stimulated glucose uptake in skeletal myoblasts via the up-regulation of GLUT4 and MEF2A, two key players involved in insulin stimulated glucose uptake. Collectively, our data highlight the important role of miR-16 in ameliorating inflammation induced insulin resistance.
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Regulación hacia Abajo , Resistencia a la Insulina , Activación de Macrófagos , Macrófagos/metabolismo , MicroARNs/metabolismo , Mioblastos/metabolismo , Animales , Comunicación Celular/efectos de los fármacos , Línea Celular , Polaridad Celular/efectos de los fármacos , Técnicas de Cocultivo , Sacarosa en la Dieta/efectos adversos , Regulación hacia Abajo/efectos de los fármacos , Endotoxinas/toxicidad , Ácidos Grasos no Esterificados/efectos adversos , Interferón gamma/genética , Interferón gamma/metabolismo , Interferón gamma/farmacología , Activación de Macrófagos/efectos de los fármacos , Macrófagos/efectos de los fármacos , Macrófagos/inmunología , Ratones , MicroARNs/antagonistas & inhibidores , Músculo Esquelético/metabolismo , Mioblastos/efectos de los fármacos , Mioblastos/inmunología , Células RAW 264.7 , Ratas , Ratas Wistar , Proteínas Recombinantes/metabolismo , Proteínas Recombinantes/farmacologíaRESUMEN
Statins are a class of oral drugs that are widely used for treatment of hypercholesterolemia. Recent clinical data suggest that chronic use of these drugs increases the frequency of new onset diabetes. Studies to define the risks of statin-induced diabetes and its underlying mechanisms are clearly necessary. We explored the possible mechanism of statin induced insulin resistance using a well-established cell based model and simvastatin as a prototype statin. Our data show that simvastatin induces insulin resistance in a cholesterol biosynthesis inhibition independent fashion but does so by a fatty acid mediated effect on insulin signaling pathway. These data may help design strategies for prevention of statin induced insulin resistance and diabetes in patients with hypercholesterolemia.
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Colesterol/metabolismo , Ácidos Grasos/metabolismo , Inhibidores de Hidroximetilglutaril-CoA Reductasas/farmacología , Resistencia a la Insulina , Simvastatina/farmacología , Glucosa/metabolismo , Hipercolesterolemia/metabolismo , Insulina/metabolismo , Ácido Mevalónico/farmacología , PPAR gamma/metabolismo , Transducción de Señal/efectos de los fármacosRESUMEN
PRIP-Interacting protein with methyl transferase domain (PIMT) serves as a molecular bridge between CREB-binding protein (CBP)/ E1A binding protein p300 (Ep300) -anchored histone acetyl transferase and the Mediator complex sub-unit1 (Med1) and modulates nuclear receptor transcription. Here, we report that ERK2 phosphorylates PIMT at Ser(298) and enhances its ability to activate PEPCK promoter. We observed that PIMT is recruited to PEPCK promoter and adenoviral-mediated over-expression of PIMT in rat primary hepatocytes up-regulated expression of gluconeogenic genes including PEPCK. Reporter experiments with phosphomimetic PIMT mutant (PIMT(S298D)) suggested that conformational change may play an important role in PIMT-dependent PEPCK promoter activity. Overexpression of PIMT and Med1 together augmented hepatic glucose output in an additive manner. Importantly, expression of gluconeogenic genes and hepatic glucose output were suppressed in isolated liver specific PIMT knockout mouse hepatocytes. Furthermore, consistent with reporter experiments, PIMT(S298D) but not PIMT(S298A) augmented hepatic glucose output via up-regulating the expression of gluconeogenic genes. Pharmacological blockade of MAPK/ERK pathway using U0126, abolished PIMT/Med1-dependent gluconeogenic program leading to reduced hepatic glucose output. Further, systemic administration of T4 hormone to rats activated ERK1/2 resulting in enhanced PIMT ser(298) phosphorylation. Phosphorylation of PIMT led to its increased binding to the PEPCK promoter, increased PEPCK expression and induction of gluconeogenesis in liver. Thus, ERK2-mediated phosphorylation of PIMT at Ser(298) is essential in hepatic gluconeogenesis, demonstrating an important role of PIMT in the pathogenesis of hyperglycemia.