bims-camemi 2018-10-14 papers

bims-camemi

Biomed News

on Mitochondrial metabolism in cancer

Issue of 2018–10–14
ten papers selected by
Christian Frezza, , University of Cambridge, MRC Cancer Unit

Recent advances in using mass spectrometry for mitochondrial metabolomics and lipidomics - A review.
Basal fatty acid oxidation increases after recurrent low glucose in human primary astrocytes.
VDAC electronics: 5. Mechanism and computational model of hexokinase-dependent generation of the outer membrane potential in brain mitochondria.
A Potent and Selective ULK1 Inhibitor Suppresses Autophagy and Sensitizes Cancer Cells to Nutrient Stress.
Fragmentation of kidney epithelial cell primary cilia occurs by cisplatin and these cilia fragments are excreted into the urine.
Mitochondrial therapeutic interventions in Alzheimer's disease.
"Regulation of mitochondrial electron transport chain assembly".
OSCP subunit of mitochondrial ATP synthase: Role in regulation of enzyme function and of its transition to a pore.
Metabolomics studies on db/db diabetic mice in skeletal muscle reveal effective clearance of overloaded intermediates by exercise.
Decreased PGC-1α Post-Cardiopulmonary Bypass Leads To Impaired Oxidative Stress In Diabetic Patients.

Anal Chim Acta. 2018 Dec 11. pii: S0003-2670(17)31375-2. [Epub ahead of print]1037 3-12

Recent advances in using mass spectrometry for mitochondrial metabolomics and lipidomics - A review.

Xinyu Liu, Guowang Xu.

  Metabolomics and lipidomics generally targets a huge number of intermediate and end products of cellular metabolism in body fluids, tissues, and cells etc. At present, mass spectrometry (MS) based metabolic or lipid profiling of routine biological specimens including the whole cells, tissues, plasma, serum and urine etc., can cover hundreds of metabolites or lipid species in one analysis, which has qualified deep elucidation of global metabolic and lipid networks. Mitochondria are important intracellular organelles and many critical biochemical reactions occur here, they provide building block for new cells, control redox balance, participate in apoptosis and behave as a signalling platform. Evidence suggests high prevalence of mitochondrial dysfunction occurs in a variety of cancers and other diseases, thus there is an urgent demand for investigating and clarifying mitochondrial metabolic and lipid alterations induced by diseases. Nevertheless, mitochondria contribute a small fraction to cellular contents, profiling of whole cell is probably unsuitable for monitoring alterations in mitochondria. Therefore, metabolomics and lipidomics analyses specially for mitochondria are necessary to understand disturbed metabolic and lipid pathways induced by environment and diseases. However, methods for comprehensively profiling metabolites and lipids in mitochondria have been limited at present. This review summarizes the current states and progress of MS-based mitochondrial metabolomics and lipidomics study. Details of mitochondrial isolation procedure, analytical methods and their applications are described. The challenges and opportunities are also given.

Keywords:  Lipidomics; Mass spectrometry; Metabolic profiling; Metabolomics; Mitochondria

DOI:  https://doi.org/10.1016/j.aca.2017.11.080
Diabetologia. 2018 Oct 06.

Basal fatty acid oxidation increases after recurrent low glucose in human primary astrocytes.

Paul G Weightman Potter, Julia M Vlachaki Walker, Josephine L Robb, John K Chilton, Ritchie Williamson, Andrew D Randall, Kate L J Ellacott, Craig Beall.

   AIMS/HYPOTHESIS: Hypoglycaemia is a major barrier to good glucose control in type 1 diabetes. Frequent hypoglycaemic episodes impair awareness of subsequent hypoglycaemic bouts. Neural changes underpinning awareness of hypoglycaemia are poorly defined and molecular mechanisms by which glial cells contribute to hypoglycaemia sensing and glucose counterregulation require further investigation. The aim of the current study was to examine whether, and by what mechanism, human primary astrocyte (HPA) function was altered by acute and recurrent low glucose (RLG).
METHODS: To test whether glia, specifically astrocytes, could detect changes in glucose, we utilised HPA and U373 astrocytoma cells and exposed them to RLG in vitro. This allowed measurement, with high specificity and sensitivity, of RLG-associated changes in cellular metabolism. We examined changes in protein phosphorylation/expression using western blotting. Metabolic function was assessed using a Seahorse extracellular flux analyser. Immunofluorescent imaging was used to examine cell morphology and enzymatic assays were used to measure lactate release, glycogen content, intracellular ATP and nucleotide ratios.
RESULTS: AMP-activated protein kinase (AMPK) was activated over a pathophysiologically relevant glucose concentration range. RLG produced an increased dependency on fatty acid oxidation for basal mitochondrial metabolism and exhibited hallmarks of mitochondrial stress, including increased proton leak and reduced coupling efficiency. Relative to glucose availability, lactate release increased during low glucose but this was not modified by RLG. Basal glucose uptake was not modified by RLG and glycogen levels were similar in control and RLG-treated cells. Mitochondrial adaptations to RLG were partially recovered by maintaining euglycaemic levels of glucose following RLG exposure.
CONCLUSIONS/INTERPRETATION: Taken together, these data indicate that HPA mitochondria are altered following RLG, with a metabolic switch towards increased fatty acid oxidation, suggesting glial adaptations to RLG involve altered mitochondrial metabolism that could contribute to defective glucose counterregulation to hypoglycaemia in diabetes.

Keywords:  AMP-activated protein kinase; Adenosine triphosphate; Astrocyte; Diabetes; Fatty acid oxidation; Glia; Hypoglycaemia; Lactate; Low glucose; Mitochondrial metabolism

DOI:  https://doi.org/10.1007/s00125-018-4744-6
Biochim Biophys Acta Biomembr. 2018 Oct 04. pii: S0005-2736(18)30297-9. [Epub ahead of print]1860(12): 2599-2607

VDAC electronics: 5. Mechanism and computational model of hexokinase-dependent generation of the outer membrane potential in brain mitochondria.

Victor V Lemeshko.

  Glycolysis plays a key role in brain energy metabolism. The initial and rate-limiting step of brain glycolysis is catalyzed mainly by hexokinase I (HKI), the majority of which is bound to the mitochondrial outer membrane (MOM), mostly through the mitochondrial inter-membrane contact sites formed by the voltage-dependent anion channel (VDAC, outer membrane) and the adenine nucleotide translocator (ANT, inner membrane). Earlier, we proposed a mechanism for the generation of the mitochondrial outer membrane potential (OMP) as a result of partial application of the inner membrane potential (IMP) to MOM through the electrogenic ANT-VDAC-HK inter-membrane contact sites. According to this previous mechanism, the Gibbs free energy of the hexokinase reaction might modulate the generated OMP (Lemeshko, Biophys. J., 2002). In the present work, a new computational model was developed to perform thermodynamic estimations of the proposed mechanism of IMP-HKI-mediated generation of OMP. The calculated OMP was high enough to electrically regulate MOM permeability for negatively charged metabolites through free, unbound VDACs in MOM. On the other hand, the positive-inside polarity of OMP generated by the IMP-HKI-mediated mechanism is expected to protect mitochondria against elevated concentrations of cytosolic Ca2+. This computational analysis suggests that metabolically-dependent generation of OMP in the brain mitochondria, controlled by many factors that modulate VDAC1-HKI interaction, VDAC's voltage-gating properties and permeability, might represent one of the physiological mechanisms of regulation of the brain energy metabolism and of neuronal death resistance, and might also be involved in various neurodegenerative disorders, such as Alzheimer's disease.

Keywords:  Brain mitochondria; Hexokinase; Membrane potential; Mitochondrial outer membrane; VDAC

DOI:  https://doi.org/10.1016/j.bbamem.2018.10.004
iScience. 2018 Sep 19. pii: S2589-0042(18)30147-0. [Epub ahead of print]8 74-84

A Potent and Selective ULK1 Inhibitor Suppresses Autophagy and Sensitizes Cancer Cells to Nutrient Stress.

Katie R Martin, Stephanie L Celano, Abigail R Solitro, Hakan Gunaydin, Mark Scott, Ronan C O'Hagan, Stuart D Shumway, Peter Fuller, Jeffrey P MacKeigan.

  In response to stress, cancer cells generate nutrients and energy through a cellular recycling process called autophagy, which can promote survival and tumor progression. Accordingly, autophagy inhibition has emerged as a potential cancer treatment strategy. Inhibitors targeting ULK1, an essential and early autophagy regulator, have provided proof of concept for targeting this kinase to inhibit autophagy; however, these are limited individually in their potency, selectivity, or cellular activity. In this study, we report two small molecule ULK1 inhibitors, ULK-100 and ULK-101, and establish superior potency and selectivity over a noteworthy published inhibitor. Moreover, we show that ULK-101 suppresses autophagy induction and autophagic flux in response to different stimuli. Finally, we use ULK-101 to demonstrate that ULK1 inhibition sensitizes KRAS mutant lung cancer cells to nutrient stress. ULK-101 represents a powerful molecular tool to study the role of autophagy in cancer cells and to evaluate the therapeutic potential of autophagy inhibition.

Keywords:  Cancer; Functional Aspects of Cell Biology; Therapeutics

DOI:  https://doi.org/10.1016/j.isci.2018.09.012
Redox Biol. 2018 Sep 25. pii: S2213-2317(18)30715-8. [Epub ahead of print]20 38-45

Fragmentation of kidney epithelial cell primary cilia occurs by cisplatin and these cilia fragments are excreted into the urine.

Min Jung Kong, Sang Hong Bak, Ki-Hwan Han, Jee In Kim, Jeen-Woo Park, Kwon Moo Park.

  The primary cilium, which protrudes from the cell surface, is associated with the pathogenesis of various diseases, including acute kidney injury (AKI). Primary cilium length dynamically changes during the progression of diseases. However, its relevance in disease and the underlying mechanism are largely unknown. In this study, we investigated the role of primary cilia in AKI induced by cisplatin, an effective anticancer drug, and the underlying mechanisms. In addition, we evaluated the usefulness of length alteration and deciliation of primary cilia into the urine for the diagnosis of AKI. Cisplatin induced shortening, elongation, and normalization of the primary cilia in kidney epithelial cells over time. During shortening, primary cilia fragments and ciliary proteins were excreted into the urine. During deciliation, cell proliferation and the expression of cyclin-dependent kinase inhibitor and proliferating cell nuclear antigen were not significantly changed. Shortening and deciliation of primary cilia were observed before significant increases in plasma creatinine and blood urea nitrogen concentration occurred. Pretreatment with Mito-Tempo, a mitochondria-targeted antioxidant, prevented cisplatin-induced primary cilium shortening and inhibited the increases in superoxide formation, lipid peroxidation, blood urea nitrogen, and tissue damage. In contrast, isocitrate dehydrogenase 2 (Idh2) gene deletion, which results in defect of the NADPH-associated mitochondrial antioxidant system, exacerbated cisplatin-induced changes in mice. Taken together, our findings demonstrate that cisplatin induces deciliation into the urine and antioxidant treatment prevents this deciliation, renal dysfunction, and tissue damage after cisplatin injection. These results suggest that cisplatin-induced AKI is associated with primary cilia and urine primary cilia proteins might be a non-invasive biomarker of kidney injury.

Keywords:  Acetylated a-tubulin; Acute kidney injury; Cisplatin; Deciliation; IDH2; Primary cilia; ROS

DOI:  https://doi.org/10.1016/j.redox.2018.09.017
J Neurol Sci. 2018 Sep 28. pii: S0022-510X(18)30395-2. [Epub ahead of print]395 62-70

Mitochondrial therapeutic interventions in Alzheimer's disease.

Vo Van Giau, Seong Soo A An, John P Hulme.

  Alzheimer's Disease (AD) is one of the most common age-related neurodegenerative diseases in the developed world. Treatment of AD is particularly challenging as the drug must overcome the blood brain barrier (BBB) before it can reach its target. Mitochondria are recognized as one of the most important targets for neurological drugs as the organelle is known to play a critical role in diverse cellular processes such as energy production and apoptosis regulation. Mitochondrial targeting was originally developed to study mitochondrial dysfunction and the organelles interaction with other sub-cellular organelles. The purpose of this review is to provide an overview of mitochondrial dysfunction and its role in late onset AD pathology. We then highlight recent antioxidant and enzymatic treatments used to alleviate mitochondrial dysfunction. Finally, we describe current applications of targeted mitochondrial delivery in the treatment of AD.

Keywords:  Alzheimer's disease; Central nervous system; Drug delivery; Mitochondria

DOI:  https://doi.org/10.1016/j.jns.2018.09.033
J Mol Biol. 2018 Oct 04. pii: S0022-2836(18)31156-2. [Epub ahead of print]

"Regulation of mitochondrial electron transport chain assembly".

Sara Cogliati, Isotta Lorenzi, Giovanni Rigoni, Federico Caicci, Maria Eugenia Soriano.

  Mitochondrial function depends on the correct synthesis, transport, and assembly of proteins and cofactors of the electron transport chain (ETC). The initial idea that the respiratory chain protein complexes (RCCs) were independent structures in the inner mitochondrial membrane evolved after the identification of higher quaternary structures called Supercomplexes (SCs), which formation is dynamically regulated in order to accommodate cellular metabolic demands. Due to the dual genetic origin of the mitochondrial proteome, ETC and SCs formation must be tightly regulated to coordinate the expression and assembly of components encoded by both genomes. This regulation occurs at different levels from gene transcription to protein, complex or SCs assembly, and might involve the participation of factors that contribute to the formation and stability of the RCCs and SCs. Here we review the cellular pathways and assembly factors that regulate RCCs and SCs formation.

Keywords:  OXPHOS; assembly factors; mitochondrial translation; respiratory chain complexes; supercomplexes

DOI:  https://doi.org/10.1016/j.jmb.2018.09.016
Br J Pharmacol. 2018 Oct 06.

OSCP subunit of mitochondrial ATP synthase: Role in regulation of enzyme function and of its transition to a pore.

Valentina Giorgio, Federico Fogolari, Giovanna Lippe, Paolo Bernardi.

  The permeability transition pore (PTP) is a latent, high-conductance channel of the inner mitochondrial membrane. When activated, it plays a key role in cell death and therefore in several diseases. The pursuit of the PTP has taken an unexpected turn after the discovery that cyclophilin D (the target of the PTP inhibitory effect of cyclosporin A) binds FO F1 (F)-ATP synthase resulting in inhibition of its catalytic activity by about 30% [Giorgio et al. (2009) J. Biol. Chem. 284, 33982-33988]. This observation was followed by the demonstration that binding occurs at the oligomycin sensitivity conferral protein (OSCP) and that F-ATP synthase can form Ca2+ -activated, high conductance channels with features matching those of the PTP, suggesting that the latter originates from a conformational change of F-ATP synthase [Giorgio et al. (2013) Proc Natl Acad Sci USA 110, 5887-5892]. This review is specifically dedicated to F-ATP synthase OSCP subunit, whose unique features make it a potential pharmacological target both for modulation of F-ATP synthase and its transition to a pore.

Keywords:  F-ATP synthase; OSCP subunit; channels; permeability transition

DOI:  https://doi.org/10.1111/bph.14513
Anal Chim Acta. 2018 Dec 11. pii: S0003-2670(17)31379-X. [Epub ahead of print]1037 130-139

Metabolomics studies on db/db diabetic mice in skeletal muscle reveal effective clearance of overloaded intermediates by exercise.

Li Xiang, Hongsong Zhang, Juntong Wei, Xiao Yu Tian, Hemi Luan, Shangfu Li, Hongzhi Zhao, Guodong Cao, Arthur C K Chung, Chunxue Yang, Yu Huang, Zongwei Cai.

  Type 2 diabetes mellitus (T2DM) is characterized by hyperinsulinemia, hyperglycemia and insulin resistance, which correlated with high mortality worldwide. Exercise is one of the effective lifestyle interventions in maintaining blood glucose level in the normal range and lowering risk factors. Metabolomics approaches are powerful tools in systematic study of overall metabolic changes in response to disease or interventions. In this study, mass spectrometry-based metabolomics studies were performed to investigate the regulatory effect of moderate intensity of exercise on db/db diabetic mice in skeletal muscle. Both liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) have been carried out to monitor a wide range of regulated metabolites. Ninety-five metabolites were identified which contributing to the discrimination of db/m  + control and db/db diabetic mice. The regulatory effects of exercise on these metabolites were mainly focusing on attenuating the levels of long-chain fatty acids (C14 to C18) and medium-to long-chain acylcarnitines (C12 to C18), indicated that exercise might play a positive role in inhibiting the accumulation of excessive lipids, which is positively related to insulin resistance. In addition, uric acid, which is a risk factor for inflammation, cardiovascular complications, and fatty liver in diabetic patients, together with its intermediates (such as inosinic acid, hypoxanthine, etc.) in purine metabolism pathway, were also substantially down regulated after exercise, indicating exercise might also be protective against hyperuricemia related risks in T2DM. These findings reveal that moderate intensity of exercise might play a positive role in improving the efficiency of lipid metabolism in skeletal muscle and meanwhile enhancing uric acid clearance to prevent lipid accumulation, which might contribute to improved body fitness and body muscle composition.

Keywords:  Db/db; Diabetes; Exercise; Mass spectrometry; Metabolomics; Skeletal muscle

DOI:  https://doi.org/10.1016/j.aca.2017.11.082
Ann Thorac Surg. 2018 Oct 03. pii: S0003-4975(18)31351-1. [Epub ahead of print]

Decreased PGC-1α Post-Cardiopulmonary Bypass Leads To Impaired Oxidative Stress In Diabetic Patients.

Eitezaz Mahmood, Jelliffe Jeganathan, Ruby Feng, Maria Saraf, Kamal Khabbaz, Faraz Mahmood, Senthilnathan Venkatachalam, David Liu, Louis Chu, Samir M Parikh, Robina Matyal.

BACKGROUND: The mechanism of mitochondrial dysfunction following cardiopulmonary bypass (CPB) in diabetics lacks understanding. We hypothesized that impaired beta-oxidation of fatty acids leads to worsened stress response in this patient population after cardiac surgery.
METHODS: After IRB approval, right atrial tissue samples were collected from 35 diabetic and 33 non-diabetics pre- and post-CPB. Patients with HbA1c ≥ 6.0 and a clinical diagnosis of diabetes mellitus were considered to be diabetic. Immunoblotting and microarray analysis were performed to assess protein and gene expression changes. Blots were quantified with ImageJ and analyzed using one-way ANOVA with multiple t-test comparisons after normalization. P-values < 0.05 were considered significant. Immunohistochemistry was performed for cellular lipid deposition assessment.
RESULTS: Diabetics had significantly lower levels of PGC-1α pre- and post-CPB (p < 0.01 for both) compared to non-diabetics. Several upstream regulators of PGC-1α (SIRT1 and CREB) were significantly higher in non-diabetics pre-CPB (p = 0.01 and 0.0018, respectively). Antioxidant markers (NOX4 and GPX4), angiogenic factors (TGF-β, NT3, and Ang1), and the anti-apoptotic factor Bcl-xL were significantly lower in diabetics post-CPB (p < 0.05). The expression of genes supporting mitochondrial energy production (CREB5 and SLC25A40) and angiogenic genes (p < 0.05) was significantly down-regulated in diabetics post-CPB. Immunohistochemistry results showed significantly increased lipid deposition in diabetic myocardial tissue.
CONCLUSIONS: Decreased PGC-1α in diabetics may lead to impaired mitochondrial function and attenuated anti-apoptotic and angiogenic responses post-CPB. PGC-1α and upstream regulators could serve as a target for improving beta-oxidation in diabetics.

DOI: https://doi.org/10.1016/j.athoracsur.2018.08.009