Mandibular osteotomy-induced hypoxia enhances osteoclast activation and acid secretion by increasing glycolysis

The rapid bone remodeling after osteotomy has been reported for a long time. However, the underlying mechanism promoting the active bone reconstruction was still to be elucidated. Since not only the bone, blood vessels, and supportive tissues, but also the local microenvironment were destroyed, if the changes on the cell metabolism was contributed to the accelerated bone remodeling came into sight. In present study, we found that the mandibular osteotomy in rabbit activated osteoclasts, as well as the expression of hypoxia-inducible factor 1α (HIF-1α) in alveolar bone. Hypoxia or HIF-1α could enhanced osteoclastogenesis, bone absorption, and lactic acid concentration in receptor activator of nuclear factor κΒ ligand-induced RAW264.7 cells. Coincided with the upregulated HIF-1α expression, HIF-driven glycolytic enzymes, such as lactate dehydrogenase A (LDHA), glucokinase (GCK), pyruvate kinase M2 (PKM2), and phosphofructokinase1 (PFK1), were found massively increased in both hypoxic RAW264.7 cells and the alveolar HIF-1α-positive osteoclasts after mandibular osteotomy. Knockdown of HIF-1α suppressed not only the hypoxia-mediated glycolysis, but also the hypoxia-induced acid secretion and bone resorption in RAW264.7 cells. Application of inhibitor on glycolysis gave rise to the similar results as HIF-1α knockdown. Our findings suggested that hypoxia-driven glycolysis in osteoclasts was an adaptive mechanism to permit alveolar bone remodeling after mandibular osteotomy.     

IGF1 regulates PKM2 function through Akt phosphorylation

Pyruvate kinase M2 (PKM2) acts at the crossroad of growth and metabolism pathways in cells. PKM2 regulation by growth factors can redirect glycolytic intermediates into key biosynthetic pathway. Here we show that IGF1 can regulate glycolysis rate, stimulate PKM2 Ser/Thr phosphorylation and decrease cellular pyruvate kinase activity. Upon IGF1 treatment we found an increase of the dimeric form of PKM2 and the enrichment of PKM2 in the nucleus. This effect was associated to a reduction of pyruvate kinase enzymatic activity and was reversed using metformin, which decreases Akt phosphorylation. IGF1 induced an increased nuclear localization of PKM2 and STAT3, which correlated with an increased HIF1α, HK2, and GLUT1 expression and glucose entrapment. Metformin inhibited HK2, GLUT1, HIF-1α expression and glucose consumption. These findings suggest a role of IGFIR/Akt axis in regulating glycolysis by Ser/Thr PKM2 phosphorylation in cancer cells.     

Insulin Promotes Glucose Consumption via Regulation of miR-99a/mTOR/PKM2 Pathway

Insulin is known to regulate multiple cellular functions and is used for the treatment of diabetes. MicroRNAs have been demonstrated to be involved in many human diseases, including Type 2 diabetes. In this study, we showed that insulin decreased miR-99a expression levels, but induced glucose consumption and lactate production, and increased the expression of mTOR, HIF-1α and PKM2 in HepG2 and HL7702 cells. Forced expression of miR-99a or rapamycin treatment blocked insulin-induced PKM2 and HIF-1α expression, and glucose consumption and lactate production. Meanwhile, knockdown of HIF-1α inhibited PKM2 expression and insulin-induced glucose consumption. Taken together, these findings will reveal the role and mechanism ofinsulin in regulating glycolytic activities via miR-99a/mTOR.     

缺氧诱导因子-1和缺氧诱导因子-2：结构、功能及调节

缺氧诱导因子-1（HIF-1）和缺氧诱导因子-2（HIF-2）是细胞应对缺氧时关键的转录因子,在生物体生理及病理过程中有重要的作用。HIF由一个α亚基和一个β亚基组成二聚体。在蛋白水平上,HIF的稳定性及转录活性受到多种机制的调控,除为人所熟知的O2/PHDs/pVHL降解途径及FIH-1羟基化作用外,分别针对HIF-1α和HIF-2α的特异性调控机制也相继被报道。从HIF-1α和HIF-2α的蛋白结构、稳定性调控、转录激活功能以及两者在细胞代谢、肿瘤发生中的作用等方面对两者的相似性和差异性进行综述。     

ω-Alkynyl arachidonic acid promotes anti-inflammatory macrophage M2 polarization against acute myocardial infarction via regulating the cross-talk between PKM2, HIF-1α and iNOS

Macrophage polarization determines the timing for the switch from the inflammation phase to the inflammation resolution phase after acute myocardial infarction. The aim of the present study was to investigate whether ω-alkynyl arachidonic acid could mitigate the inflammatory lipid mediators in the regulation of macrophage phenotypes and functions with a special regard to myocardial infarction. We initially discovered that ω-alkynyl arachidonic acid selectively suppressed the up-regulation of inducible nitric oxide synthase (iNOS) over cyclooxygenase-2 (COX-2) in LPS-stimulated macrophages. ω-Alkynyl arachidonic acid also reduced the expression of macrophage M1 biomarkers (e.g., TNF-α, CXCL10, iNOS and IL-6) but increased the expression of macrophage M2 biomarkers (e.g., IL-10 and arginase-1) in LPS-stimulated macrophages. Moreover, ω-alkynyl arachidonic acid markedly enhanced the phagocytotic activity of macrophages against fluorescently-labeled beads or apoptotic H9c2 cardiac cells. We further investigated the in vivo cardioprotective activities of ω-alkynyl arachidonic acid in a mouse model of myocardial infarction. ω-Alkynyl arachidonic acid indeed reduced infarct size, cardiac damage and the leakage of myocardial enzymes CK-MB. Mechanistic studies revealed that ω-alkynyl arachidonic acid suppressed the overexpression and nuclear translocation of glycolytic enzyme PKM2 in LPS-stimulated macrophages. Furthermore, co-immunoprecipitation assay suggested that ω-alkynyl arachidonic acid disrupted the interaction between PKM2 and HIF-1α. Consequently, ω-alkynyl arachidonic acid diminished HIF-1α binding to the HRE sequence in iNOS promoter in response to LPS stimulation. Collectively, ω-alkynyl arachidonic acid may promote the anti-inflammatory M2 polarization of macrophages in acute myocardial infarction via regulating the cross-talk between PKM2, HIF-1α and iNOS.     

Lactate promotes glutamine uptake and metabolism in oxidative cancer cells

Oxygenated cancer cells have a high metabolic plasticity as they can use glucose, glutamine and lactate as main substrates to support their bioenergetic and biosynthetic activities. Metabolic optimization requires integration. While glycolysis and glutaminolysis can cooperate to support cellular proliferation, oxidative lactate metabolism opposes glycolysis in oxidative cancer cells engaged in a symbiotic relation with their hypoxic/glycolytic neighbors. However, little is known concerning the relationship between oxidative lactate metabolism and glutamine metabolism. Using SiHa and HeLa human cancer cells, this study reports that intracellular lactate signaling promotes glutamine uptake and metabolism in oxidative cancer cells. It depends on the uptake of extracellular lactate by monocarboxylate transporter 1 (MCT1). Lactate first stabilizes hypoxia-inducible factor-2α (HIF-2α), and HIF-2α then transactivates c-Myc in a pathway that mimics a response to hypoxia. Consequently, lactate-induced c-Myc activation triggers the expression of glutamine transporter ASCT2 and of glutaminase 1 (GLS1), resulting in improved glutamine uptake and catabolism. Elucidation of this metabolic dependence could be of therapeutic interest. First, inhibitors of lactate uptake targeting MCT1 are currently entering clinical trials. They have the potential to indirectly repress glutaminolysis. Second, in oxidative cancer cells, resistance to glutaminolysis inhibition could arise from compensation by oxidative lactate metabolism and increased lactate signaling.     

LncRNA FAM83A-AS1 facilitates tumor proliferation and the migration via the HIF-1α/ glycolysis axis in lung adenocarcinoma

Background: Lung adenocarcinoma (LUAD), the major subtype of lung cancer, is among the leading cause of cancer-related death worldwide. Energy-related metabolic reprogramming metabolism is a hallmark of cancer shared by numerous cancer types, including LUAD. Nevertheless, the functional pathways and molecular mechanism by which FAM83A-AS1 acts in metabolic reprogramming in lung adenocarcinoma have not been fully elucidated.Methods: We used transwell, wound-healing scratch assay, and metabolic assays to explore the effect of FAM83A-AS1 in LUAD cell lines. Western blotting, Co-IP assays, and ubiquitination assays were used to detect the effects of FAM83A-AS1 on HIF-1α expression, degradation, and its binding to VHL. Moreover, an in vivo subcutaneous tumor formation assay was used to detect the effect of FAM83A-AS1 on LUAD.Results: Herein, we identified FAM83A-AS1 as a metabolism-related lncRNA, which was highly correlated with glycolysis, hypoxia, and OXPHOS pathways in LUAD patients using bioinformatics analysis. In addition, we uncovered that FAM83A-AS1 could promote the migration and invasion of LUAD cells, as well as influence the stemness of LUAD cells in vivo and vitro. Moreover, FAM83A-AS1 was shown to promote glycolysis in LUAD cell lines in vitro and in vivo, and was found to influence the expression of genes related to glucose metabolism. Besides, we revealed that FAM83A-AS1 could affect glycolysis by regulating HIF-1α degradation. Finally, we found that FAM83A-AS1 knockdown could inhibit tumor growth and suppress the expression of HIF-1α and glycolysis-related genes in vivo.Conclusion: Our study demonstrates that FAM83A-AS1 contributes to LUAD proliferation and stemness via the HIF-1α/glycolysis axis, making it a potential biomarker and therapeutic target in LUAD patients.