The contribution of the reticular Pentose Phosphate Pathway in glucose metabolism, cell proliferation and in the regulation of the redox state

The use of Positron Emission Tomography (PET)/ Computed tomography (CT) with 18F-2-deoxy-glucose (FDG) represents a clinical standard for the diagnosis and monitoring of cancer evolution and in the evaluation of many neurodegenerative syndromes. This method relies on the concept that FDG competes with glucose for trans-membrane transport (GLUTs) and hexokinase (HK)-catalyzed phosphorylation (1). However, FDG-6-phosphate (FDG6P) is a false substrate for downstream enzymes channeling glucose-6P (G6P) to glycolysis, pentose phosphate pathway (PPP) or glycogen synthesis (2-3) and thus accumulates within the cytosol as a function of glucose consumption. Despite the universal acceptance of this kinetic model, the link between glucose consumption and FDG uptake might be relatively looser than conventionally assumed. Indeed, glucose consumption is invariably high also in those cancers (prostate, urothelial and neuroendocrine cancers or glioblastoma) characterized by a very low FDG uptake (4-6). Finally, the theoretical nondegradability of 2DG6P/FDG6P has been recently challenged by two main observations: on the one hand, stoichiometry indicates that a significant fraction of intracellular 2DG is not processed by HKs (7); on the other hand, magnetic resonance spectroscopy documents significant degradation of FDG6 (8-10). To date, the relationship between FDG uptake and glucose consumption is almost universally accepted. Nevertheless, several observations indicate that the link between glucose consumption and FDG accumulation may be relatively looser than conventionally assumed. In agreement with this concept, recent studies recently documented cancer uptake of FDG is closely and selectively dependent on a specific metabolism triggered within the endoplasmic reticulum (ER) by the enzyme hexose-6- phosphate dehydrogenase (H6PD) whose silencing profoundly diminished FDG uptake despite an increase in glycolytic flux (11). This autosomic counterpart of the cytosolic glucose-6-phosphate-dehydrogenase (G6PD) can dehydrogenate many hexoses, including 2-deoxy-glucose (2DG), to trigger pentose-phosphate pathway (PPP) and thus to fuel the high NADPH within the ER lumen (12-14). My project aimed to study the role of H6PD in FDG uptake or, more in general, to evaluate the contribution of the ER-PPP in global cell glucose metabolism, proliferation, and regulation of the redox state. Obtained results indicate that FDG uptake is indeed strictly dependent upon the activation of ER metabolic machinery and only loosely related to glycolytic flux. More importantly, they also suggest an unexpected relevance of ER glucose metabolism in feeding the high NADPH equivalents required by cells with high proliferating activity or exposed to an intense redox stress

Effect of starvation on brain glucose metabolism and 18F-2-fluoro-2-deoxyglucose uptake: an experimental in-vivo and ex-vivo study

Background: The close connection between neuronal activity and glucose consumption accounts for the clinical value of 18F-fluoro-2-deoxyglucose (FDG) imaging in neurodegenerative disorders. Nevertheless, brain metabolic response to starvation (STS) might hamper the diagnostic accuracy of FDG PET/CT when the cognitive impairment results in a severe food deprivation. Methods: Thirty six-week-old BALB/c female mice were divided into two groups: \u201ccontrol\u201d group (n = 15) were kept under standard conditions and exposed to fasting for 6 h before the study; the remaining \u201cSTS\u201d mice were submitted to 48 h STS (absence of food and free access to water) before imaging. In each group, nine mice were submitted to dynamic micro-PET imaging to estimate brain and skeletal muscle glucose consumption (C- and SM-MRGlu*) by Patlak approach, while six mice were sacrificed for ex vivo determination of the lumped constant, defined as the ratio between CMRGlu* and glucose consumption measured by glucose removal from the incubation medium (n = 3) or biochemical analyses (n = 3), respectively. Results: CMRGlu* was lower in starved than in control mice (46.1 \ub1 23.3 vs 119.5 \ub1 40.2 nmol 7 min 121 7 g 121 , respectively, p < 0.001). Ex vivo evaluation documented a remarkable stability of lumped constant as documented by the stability of GLUT expression, G6Pase activity, and kinetic features of hexokinase-catalyzed phosphorylation. However, brain SUV in STS mice was even (though not significantly) higher with respect to control mice. Conversely, a marked decrease in both SM-MRGlu* and SM-SUV was documented in STS mice with respect to controls. Conclusions: STS markedly decreases brain glucose consumption without altering measured FDG SUV in mouse experimental models. This apparent paradox does not reflect any change in lumped constant. Rather, it might be explained by the metabolic response of the whole body: the decrease in FDG sequestration by the skeletal muscle is as profound as to prolong tracer persistence in the bloodstream and thus its availability for brain uptak

Ecosistemi per la ricerca Atti Convegno ACNP/NILDE Trieste, 22-23 maggio 2014

Il secondo convegno congiunto ACNP / NILDE: ecosistemi per la ricerca è stato ospitato dal 22 al 23 maggio 2014 dall’Università di Trieste. Sotto gli auspici della stessa Università di Trieste e degli altri enti di ricerca del Friuli Venezia Giulia1 sono stati affrontati in un’ottica internazionale i temi del rapporto tra cataloghi collettivi e servizi interbibliotecari, e il più generale ambito dei servizi bibliografici per la ricerca scientifica. ACNP e NILDE possono essere considerati un vero e proprio ecosistema. Le biblioteche e i bibliotecari collaborano tra di loro in maniera reciproca e secondo modalità interconnesse, offrendo agli utenti servizi sempre più evoluti e dinamici. Questo ecosistema, essendo aperto, mette i propri servizi a disposizione della ricerca scientifica in senso generale. Il convegno di Trieste ha offerto l’occasione di investigare e proporre soluzioni innovative, interconnessioni e relazioni nuove e più proficue. Il convegno ha presentato alcune rilevanti esperienze internazionali in tema di servizi interbibliotecari e cataloghi collettivi e la prosecuzione di attività che erano state proposte come spunti di ispirazione nel convegno precedente2 inoltre si sono condotte delle riflessioni sulle nuove esigenze dell’utenza. Una ultima parte è dedicata alla illustrazione degli sviluppi tecnici e le prospettive future di ACNP e di NILDE. Hanno partecipato all’evento oltre 200 colleghi italiani e stranieri ed i relatori dei 18 contributi provenivano da Italia, Germania, Austria, Grecia, Slovenia e Stati Uniti. Il carattere di confronto e di condivisione delle esperienze tipico della realtà partecipativa di ACNP e NILDE, è emerso anche in questa occasione nella tavola rotonda - di cui viene riportato un resoconto dettagliato - che ha affrontato il tema della valutazione della ricerca dal punto di vista delle biblioteche. Inoltre, la molto partecipata sessione poster ha ospitato 13 lavori- anch’essi riportati nel volume - incentrati oltre che su ACNP e NILDE anche sul tema ricerca e sistema biblioteca, dando ottimi spunti di partecipazione, dialogo e confronto sulle diverse realtà in cui operiamo

Defects in mitochondrial energetic function compels Fanconi Anaemia cells to glycolytic metabolism

Energetic metabolism plays an essential role in the differentiation of haematopoietic stem cells (HSC). In Fanconi Anaemia (FA), DNA damage is accumulated during HSC differentiation, an event that is likely associated with bone marrow failure (BMF). One of the sources of the DNA damage is altered mitochondrial metabolism and an associated increment of oxidative stress. Recently, altered mitochondrial morphology and a deficit in the energetic activity in FA cells have been reported. Considering that mitochondria are the principal site of aerobic ATP production, we investigated FA metabolism in order to understand what pathways are able to compensate for this energy deficiency. In this work, we report that the impairment in mitochondrial oxidative phosphorylation (OXPHOS) in FA cells is countered by an increase in glycolytic flux. By contrast, glutaminolysis appears lower with respect to controls. Therefore, it is possible to conclude that in FA cells glycolysis represents the main pathway for producing energy, balancing the NADH/NAD+ratio by the conversion of pyruvate to lactate. Finally, we show that a forced switch from glycolytic to OXPHOS metabolism increases FA cell oxidative stress. This could be the cause of the impoverishment in bone marrow HSC during exit from the homeostatic quiescent state. This is the first work that systematically explores FA energy metabolism, highlighting its flaws, and discusses the possible relationships between these defects and BMF

Defects in mitochondrial energetic function compels Fanconi Anaemia cells to glycolytic metabolism

Energetic metabolism plays an essential role in the differentiation of haematopoietic stem cells (HSC). In Fanconi Anaemia (FA), DNA damage is accumulated during HSC differentiation, an event that is likely associated with bone marrow failure (BMF). One of the sources of the DNA damage is altered mitochondrial metabolism and an associated increment of oxidative stress. Recently, altered mitochondrial morphology and a deficit in the energetic activity in FA cells have been reported. Considering that mitochondria are the principal site of aerobic ATP production, we investigated FA metabolism in order to understand what pathways are able to compensate for this energy deficiency. In this work, we report that the impairment in mitochondrial oxidative phosphorylation (OXPHOS) in FA cells is countered by an increase in glycolytic flux. By contrast, glutaminolysis appears lower with respect to controls. Therefore, it is possible to conclude that in FA cells glycolysis represents the main pathway for producing energy, balancing the NADH/NAD+ratio by the conversion of pyruvate to lactate. Finally, we show that a forced switch from glycolytic to OXPHOS metabolism increases FA cell oxidative stress. This could be the cause of the impoverishment in bone marrow HSC during exit from the homeostatic quiescent state. This is the first work that systematically explores FA energy metabolism, highlighting its flaws, and discusses the possible relationships between these defects and BMF

Genotoxic and physiological effects of nCeO2 on a freshwater bivalve (Corbicula fluminea)

International audienc

Abscisic Acid and Its Receptors LANCL1 and LANCL2 Control Cardiomyocyte Mitochondrial Function, Expression of Contractile, Cytoskeletal and Ion Channel Proteins and Cell Proliferation via ERRα

The cross-kingdom stress hormone abscisic acid (ABA) and its mammalian receptors LANCL1 and LANCL2 regulate the response of cardiomyocytes to hypoxia by activating NO generation. The overexpression of LANCL1/2 increases transcription, phosphorylation and the activity of eNOS and improves cell vitality after hypoxia/reoxygenation via the AMPK/PGC-1α axis. Here, we investigated whether the ABA/LANCL system also affects the mitochondrial oxidative metabolism and structural proteins. Mitochondrial function, cell cycle and the expression of cytoskeletal, contractile and ion channel proteins were studied in H9c2 rat cardiomyoblasts overexpressing or silenced by LANCL1 and LANCL2, with or without ABA. Overexpression of LANCL1/2 significantly increased, while silencing conversely reduced the mitochondrial number, OXPHOS complex I, proton gradient, glucose and palmitate-dependent respiration, transcription of uncoupling proteins, expression of proteins involved in cytoskeletal, contractile and electrical functions. These effects, and LANCL1/2-dependent NO generation, are mediated by transcription factor ERRα, upstream of the AMPK/PGC1-α axis and transcriptionally controlled by the LANCL1/2–ABA system. The ABA-LANCL1/2 hormone-receptor system controls fundamental aspects of cardiomyocyte physiology via an ERRα/AMPK/PGC-1α signaling axis and ABA-mediated targeting of this axis could improve cardiac function and resilience to hypoxic and dysmetabolic conditions

Brief Communication: Capturing scales of spatial heterogeneity of Antarctic sea ice algae communities

Identifying spatial heterogeneity of sea ice algae communities is critical to predicting ecosystem response under future climate scenarios. Using an autonomous robotic sampling platform beneath sea ice in McMurdo Sound, Antarctica, we measured irradiance in spectral bands expected to describe the spatial heterogeneity. Derived estimates of ice algae biomass identified patchiness at length scales varying from 50-70 m under first-year sea ice. These results demonstrate that a step-change in how these communities can be assessed and monitored. The developed methodologies could be subsequently refined to further categorize different ice algae communities and their associated productivity in both Arctic and Antarctic waters