scholarly journals Bioenergetic Analysis of Single Pancreatic β-Cells Indicates an Impaired Metabolic Signature in Type 2 Diabetic Subjects

Endocrinology ◽  
2015 ◽  
Vol 156 (10) ◽  
pp. 3496-3503 ◽  
Author(s):  
Akos A. Gerencser
Keyword(s):  
Insulin Secretion ◽  
Membrane Potential ◽  
Energy Metabolism ◽  
Tricarboxylic Acid Cycle ◽  
Atp Synthesis ◽  
Tricarboxylic Acid ◽  
Β Cells ◽  
Acid Cycle ◽  
Type 2 Diabetic

Impaired activation of mitochondrial energy metabolism by glucose has been demonstrated in type 2 diabetic β-cells. The cause of this dysfunction is unknown. The aim of this study was to identify segments of energy metabolism with normal or with altered function in human type 2 diabetes mellitus. The mitochondrial membrane potential (ΔψM), and its response to glucose, is the main driver of mitochondrial ATP synthesis and is hence a central mediator of glucose-induced insulin secretion, but its quantitative determination in β-cells from human donors has not been attempted, due to limitations in assay technology. Here, novel fluorescence microscopic assays are exploited to quantify ΔψM and its response to glucose and other secretagogues in β-cells of dispersed pancreatic islet cells from 4 normal and 3 type 2 diabetic organ donors. Mitochondrial volume densities and the magnitude of ΔψM in low glucose were not consistently altered in diabetic β-cells. However, ΔψM was consistently less responsive to elevation of glucose concentration, whereas the decreased response was not observed with metabolizable secretagogue mixtures that feed directly into the tricarboxylic acid cycle. Single-cell analysis of the heterogeneous responses to metabolizable secretagogues indicated no dysfunction in relaying ΔψM hyperpolarization to plasma membrane potential depolarization in diabetic β-cells. ΔψM of diabetic β-cells was distinctly responsive to acute inhibition of ATP synthesis during glucose stimulation. It is concluded that the mechanistic deficit in glucose-induced insulin secretion and mitochondrial hyperpolarization of diabetic human β-cells is located upstream of the tricarboxylic acid cycle and manifests in dampening the control of ΔψM by glucose metabolism.

Pyruvate dehydrogenase kinase 1 controls mitochondrial metabolism and insulin secretion in INS-1 832/13 clonal β-cells

2010 ◽  
Vol 429 (1) ◽  
pp. 205-213 ◽  
Author(s):  
Ulrika Krus ◽  
Olga Kotova ◽  
Peter Spégel ◽  
Elna Hallgard ◽  
Vladimir V. Sharoyko ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Insulin Secretion ◽  
Metabolic Flux ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Pyruvate Dehydrogenase Kinase ◽  
Β Cells ◽  
Acid Cycle ◽  
Metabolic Coupling ◽  
Pyruvate Dehydrogenase Kinase 1

Tight coupling between cytosolic and mitochondrial metabolism is key for GSIS (glucose-stimulated insulin secretion). In the present study we examined the regulatory contribution of PDH (pyruvate dehydrogenase) kinase 1, a negative regulator of PDH, to metabolic coupling in 832/13 clonal β-cells. Knockdown of PDH kinase 1 with siRNA (small interfering RNA) reduced its mRNA (>80%) and protein level (>40%) after 72 h. PDH activity, glucose-stimulated cellular oxygen consumption and pyruvate-stimulated mitochondrial oxygen consumption increased 1.7- (P<0.05), 1.6- (P<0.05) and 1.6-fold (P<0.05) respectively. Gas chromatography/MS revealed an altered metabolite profile upon silencing of PDH kinase 1, determined by increased levels of the tricarboxylic acid cycle intermediates malate, fumarate and α-ketoglutarate. These metabolic alterations were associated with exaggerated GSIS (5-fold compared with 3.1-fold in control cells; P<0.01). Insulin secretion, provoked by leucine and dimethylsuccinate, which feed into the tricarboxylic acid cycle bypassing PDH, was unaffected. The oxygen consumption and metabolic data strongly suggest that knockdown of PDH kinase 1 in β-cells permits increased metabolic flux of glucose-derived carbons into the tricarboxylic acid cycle via PDH. Enhanced insulin secretion is probably caused by increased generation of tricarboxylic acid cycle-derived reducing equivalents for mitochondrial electron transport to generate ATP and/or stimulatory metabolic intermediates. On the basis of these findings, we suggest that PDH kinase 1 is an important regulator of PDH in clonal β-cells and that PDH kinase 1 and PDH are important for efficient metabolic coupling. Maintaining low PDH kinase 1 expression/activity, keeping PDH in a dephosphorylated and active state, may be important for β-cells to achieve the metabolic flux rates necessary for maximal GSIS.

scholarly journals Tricarboxylic acid cycle and proton gradient in Pandoravirus massiliensis: Is it still a virus?

2020 ◽  
Author(s):  
Sarah Aherfi ◽  
Djamal Brahim Belhaouari ◽  
Lucile Pinault ◽  
Jean-Pierre Baudoin ◽  
Philippe Decloquement ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Isocitrate Dehydrogenase ◽  
Energy Production ◽  
Citrate Synthase ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Proton Gradient ◽  
Giant Virus ◽  
Acid Cycle ◽  
Key Enzyme

ABSTRACTSince the discovery of Acanthamoeba polyphaga Mimivirus, the first giant virus of amoeba, the historical hallmarks defining a virus have been challenged. Giant virion sizes can reach up to 2.3 µm, making them visible by optical microscopy. They have large genomes of up to 2.5 Mb that encode proteins involved in the translation apparatus. Herein, we investigated possible energy production in Pandoravirus massiliensis, the largest of our giant virus collection. MitoTracker and TMRM mitochondrial membrane markers allowed for the detection of a membrane potential in virions that could be abolished by the use of the depolarizing agent CCCP. An attempt to identify enzymes involved in energy metabolism revealed that 8 predicted proteins of P. massiliensis exhibited low sequence identities with defined proteins involved in the universal tricarboxylic acid cycle (acetyl Co-A synthase; citrate synthase; aconitase; isocitrate dehydrogenase; α-ketoglutarate decarboxylase; succinate dehydrogenase; fumarase). All 8 viral predicted ORFs were transcribed together during viral replication, mainly at the end of the replication cycle. Two of these proteins were detected in mature viral particles by proteomics. The product of the ORF132, a predicted protein of P. massiliensis, cloned and expressed in Escherichia coli, provided a functional isocitrate dehydrogenase, a key enzyme of the tricarboxylic acid cycle, which converts isocitrate to α-ketoglutarate. We observed that membrane potential was enhanced by low concentrations of Acetyl-CoA, a regulator of the tricarboxylic acid cycle. Our findings show for the first time that energy production can occur in viruses, namely, pandoraviruses, and the involved enzymes are related to tricarboxylic acid cycle enzymes. The presence of a proton gradient in P. massiliensis coupled with the observation of genes of the tricarboxylic acid cycle make this virus a form a life for which it is legitimate to question ‘what is a virus?’.

scholarly journals Role of Energy Metabolism in the Progression of Neuroblastoma

2021 ◽  
Vol 22 (21) ◽  
pp. 11421
Author(s):  
Monika Sakowicz-Burkiewicz ◽  
Tadeusz Pawełczyk ◽  
Marlena Zyśk
Keyword(s):  
Energy Metabolism ◽  
Extracellular Vesicles ◽  
Tricarboxylic Acid Cycle ◽  
Significant Risk ◽  
Metabolic Enzymes ◽  
Genetic Alterations ◽  
Tricarboxylic Acid ◽  
Primary Role ◽  
Acid Cycle ◽  
Risk Of Death

Neuroblastoma is a common childhood cancer possessing a significant risk of death. This solid tumor manifests variable clinical behaviors ranging from spontaneous regression to widespread metastatic disease. The lack of promising treatments calls for new research approaches which can enhance the understanding of the molecular background of neuroblastoma. The high proliferation of malignant neuroblastoma cells requires efficient energy metabolism. Thus, we focus our attention on energy pathways and their role in neuroblastoma tumorigenesis. Recent studies suggest that neuroblastoma-driven extracellular vesicles stimulate tumorigenesis inside the recipient cells. Furthermore, proteomic studies have demonstrated extracellular vesicles (EVs) to cargo metabolic enzymes needed to build up a fully operative energy metabolism network. The majority of EV-derived enzymes comes from glycolysis, while other metabolic enzymes have a fatty acid β-oxidation and tricarboxylic acid cycle origin. The previously mentioned glycolysis has been shown to play a primary role in neuroblastoma energy metabolism. Therefore, another way to modify the energy metabolism in neuroblastoma is linked with genetic alterations resulting in the decreased activity of some tricarboxylic acid cycle enzymes and enhanced glycolysis. This metabolic shift enables malignant cells to cope with increasing metabolic stress, nutrition breakdown and an upregulated proliferation ratio.

scholarly journals Metabolomic analyses reveal profound differences in glycolytic and tricarboxylic acid cycle metabolism in glucose-responsive and -unresponsive clonal β-cell lines

2011 ◽  
Vol 435 (1) ◽  
pp. 277-284 ◽  
Author(s):  
Peter Spégel ◽  
Siri Malmgren ◽  
Vladimir V. Sharoyko ◽  
Philip Newsholme ◽  
Thomas Koeck ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Cell Lines ◽  
Target Genes ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Gas Chromatography Mass Spectrometry ◽  
Glycolytic Metabolism ◽  
Β Cell ◽  
Acid Cycle ◽  
Stimulus Secretion Coupling

Insulin secretion from pancreatic β-cells is controlled by complex metabolic and energetic changes provoked by exposure to metabolic fuels. Perturbations in these processes lead to impaired insulin secretion, the ultimate cause of T2D (Type 2 diabetes). To increase our understanding of stimulus–secretion coupling and metabolic processes potentially involved in the pathogenesis of T2D, a comprehensive investigation of the metabolic response in the glucose-responsive INS-1 832/13 and glucose-unresponsive INS-1 832/2 β-cell lines was performed. For this metabolomics analysis, we used GC/MS (gas chromatography/mass spectrometry) combined with multivariate statistics. We found that perturbed secretion in the 832/2 line was characterized by disturbed coupling of glycolytic and TCA (tricarboxylic acid)-cycle metabolism. The importance of this metabolic coupling was reinforced by our observation that insulin secretion partially could be reinstated by stimulation of the cells with mitochondrial fuels which bypass glycolytic metabolism. Furthermore, metabolic and functional profiling of additional β-cell lines (INS-1, INS-1 832/1) confirmed the important role of coupled glycolytic and TCA-cycle metabolism in stimulus–secretion coupling. Dependence of the unresponsive clones on glycolytic metabolism was paralleled by increased stabilization of HIF-1α (hypoxia-inducible factor 1α). The relevance of a similar perturbation for human T2D was suggested by increased expression of HIF-1α target genes in islets from T2D patients.

Effect of Ca2+ on cardiac mitochondrial energy production is modulated by Na+ and H+ dynamics

2007 ◽  
Vol 292 (6) ◽  
pp. C2004-C2020 ◽  
Author(s):  
My-Hanh T. Nguyen ◽  
S. J. Dudycha ◽  
M. Saleet Jafri
Keyword(s):  
Energy Metabolism ◽  
Energy Production ◽  
Hydrogen Exchange ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Calcium Dynamics ◽  
Mitochondrial Energy Metabolism ◽  
Acid Cycle ◽  
Atp Production ◽  
Sodium Hydrogen

The energy production of mitochondria in heart increases during exercise. Several works have suggested that calcium acts at multiple control points to activate net ATP production in what is termed “parallel activation”. To study this, a computational model of mitochondrial energy metabolism in the heart has been developed that integrates the Dudycha-Jafri model for the tricarboxylic acid cycle with the Magnus-Keizer model for mitochondrial energy metabolism and calcium dynamics. The model improves upon the previous formulation by including an updated formulation for calcium dynamics, and new descriptions of sodium, hydrogen, phosphate, and ATP balance. To this end, it incorporates new formulations for the calcium uniporter, sodium-calcium exchange, sodium-hydrogen exchange, the F1F0-ATPase, and potassium-hydrogen exchange. The model simulates a wide range of experimental data, including steady-state and simulated pacing protocols. The model suggests that calcium is a potent activator of net ATP production and that as pacing increases energy production due to calcium goes up almost linearly. Furthermore, it suggests that during an extramitochondrial calcium transient, calcium entry and extrusion cause a transient depolarization that serve to increase NADH production by the tricarboxylic acid cycle and NADH consumption by the respiration driven proton pumps. The model suggests that activation of the F1F0-ATPase by calcium is essential to increase ATP production. In mitochondria very close to the release sites, the depolarization is more severe causing a temporary loss of ATP production. However, due to the short duration of the depolarization the net ATP production is also increased.

scholarly journals Integrative Analysis of Multiomics Data Identified Acetylation as Key Variable of Excessive Energy Metabolism in Hyperthyroidism-induced Osteoporosis Rats

2021 ◽  
Author(s):  
Jiaxin Bei ◽  
Shaoping Zhu ◽  
Minqun Du ◽  
Zheng Tang ◽  
Cailing Chen ◽  
...  
Keyword(s):  
Energy Metabolism ◽  
Bone Loss ◽  
Previous Experiment ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Creb Binding Protein ◽  
Acid Cycle ◽  
Metabolism Enzymes ◽  
Close Relationship

Abstract Background The results from the previous experiment have demonstrated that there were occurrence of bone loss and excess metabolism in Hyperthyroidism-induced rats. Thus, there was speculation that there may be an underlying relationship between metabolism and bone loss. In addition, there were past studies showing acetylation influencing metabolism in tissues and diseases. The hypothesis from this case study stated that excessive metabolism was induced upon acetylated vital metabolism enzymes. Results In the case study, a HYP-induced osteoporosis rats model was used and the glucose metabolite was tested through the acetylation of proteins by the mass spectrometer. The results showed that pivotal enzymes of Glycolysis-Tricarboxylic acid cycle-Oxidative phosphorylation were acetyled along with upregulated metabolites. All the acetyly-lysine sites of related enzymes were listed in this article.Our results showed that bone loss in HYP rats accompanied by upregulation of CREB-binding protein (Crebbp, CBP). Furthermore, our result indicated that CBP has a close relationship with enhancement of LDHa that promote glucose metabolism. Conclusions Acetylation is the key variable of energy metabolism in hyperthyroid osteoporosis rats, therein, we showed a representation relationship between CBP and LDHa.

Energy metabolism in the developing larval stages of Ancylostoma tubaeforme and Haemonchus contortus: glycolytic and tncarboxylic acid cycle enzymes

Parasitology ◽  
1985 ◽  
Vol 90 (1) ◽  
pp. 169-177 ◽  
Author(s):  
C. O. E. Onwuliri
Keyword(s):  
Energy Metabolism ◽  
Pyruvate Kinase ◽  
Metabolic Pathway ◽  
Haemonchus Contortus ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Aconitate Hydratase ◽  
Acid Cycle ◽  
Infective Larvae

The activities of glycolytic and related enzymes and the tricarboxylic acid cycle enzymes were measured in freshly isolated 1st- (Li), 2nd- (L2) and 3rd-stage (L3) larvae of both Ancylostoma tubaeforme and Haemonchus contortus. All enzymes of the glycolytic pathway were present in all developmental stages of both strongylid nematodes although higher levels of activities were obtained in the pre-infective 1st- and 2nd-stage larvae than in the infective 3rd stage. However, the pre-infective larvae contained lower levels of pyruvate kinase (PK) than the infective larvae. Consequently, the pyruvate kinase to phosphoenolpyruvate carboxykinase (PEPCK) ratios were 0·23 and 0·26 for the L1s and L2s for A. tubaeforme and 0·36 and 0·21 for those of H. contortus respectively. High levels of activity of glucose-6-phosphate dehydrogenase obtained in the bacteriophagous pre-infective larvae were consistent with high rates of morphogenesis and substrate synthesis characteristic of the pre-infective stages. All the tricarboxylic acid cycle enzymes were present in the infective larvae of both nematodes while in the pre-infective Li and L2 stages, the enzymes at the beginning of the cycle, namely aconitate hydratase and NAD-linked isocitrate dehydrogenase, were not detected. A scheme was proposed for the energy metabolism of these developing larvae. In this scheme, the pre-infective larvae were shown to operate an anaerobic metabolic pathway involving the carboxylation of phosphoenolpyruvate (PEP) by phosphoenolpyru vate carboxykinase (PEPCK) to form oxaloacetate (OAA), whereas in the infective larvae the metabolic pathway favouring the direct dephosphorylation of PEP, as in vertebrate tissues, was followed.

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