In vivo metabolic imaging of Traumatic Brain Injury.

Complex alterations in cerebral energetic metabolism arise after traumatic brain injury (TBI). To date, methods allowing for metabolic evaluation are highly invasive, limiting our understanding of metabolic impairments associated with TBI pathogenesis. We investigated whether 13C MRSI of hyperpolarized (HP) [1-13C] pyruvate, a non-invasive metabolic imaging method, could detect metabolic changes in controlled cortical injury (CCI) mice (n = 57). Our results show that HP [1-13C] lactate-to-pyruvate ratios were increased in the injured cortex at acute (12/24 hours) and sub-acute (7 days) time points after injury, in line with decreased pyruvate dehydrogenase (PDH) activity, suggesting impairment of the oxidative phosphorylation pathway. We then used the colony-stimulating factor-1 receptor inhibitor PLX5622 to deplete brain resident microglia prior to and after CCI, in order to confirm that modulations of HP [1-13C] lactate-to-pyruvate ratios were linked to microglial activation. Despite CCI, the HP [1-13C] lactate-to-pyruvate ratio at the injury cortex of microglia-depleted animals at 7 days post-injury remained unchanged compared to contralateral hemisphere, and PDH activity was not affected. Altogether, our results demonstrate that HP [1-13C] pyruvate has great potential for in vivo non-invasive detection of cerebral metabolism post-TBI, providing a new tool to monitor the effect of therapies targeting microglia/macrophages activation after TBI

Hyperpolarized 13 C magnetic resonance spectroscopy detects toxin-induced neuroinflammation in mice.

Lipopolysaccharide (LPS) is a commonly used agent for induction of neuroinflammation in preclinical studies. Upon injection, LPS causes activation of microglia and astrocytes, whose metabolism alters to favor glycolysis. Assessing in vivo neuroinflammation and its modulation following therapy remains challenging, and new noninvasive methods allowing for longitudinal monitoring would be highly valuable. Hyperpolarized (HP) 13 C magnetic resonance spectroscopy (MRS) is a promising technique for assessing in vivo metabolism. In addition to applications in oncology, the most commonly used probe of [1-13 C] pyruvate has shown potential in assessing neuroinflammation-linked metabolism in mouse models of multiple sclerosis and traumatic brain injury. Here, we aimed to investigate LPS-induced neuroinflammatory changes using HP [1-13 C] pyruvate and HP 13 C urea. 2D chemical shift imaging following simultaneous intravenous injection of HP [1-13 C] pyruvate and HP 13 C urea was performed at baseline (day 0) and at days 3 and 7 post-intracranial injection of LPS (n = 6) or saline (n = 5). Immunofluorescence (IF) analyses were performed for Iba1 (resting and activated microglia/macrophages), GFAP (resting and reactive astrocytes) and CD68 (activated microglia/macrophages). A significant increase in HP [1-13 C] lactate production was observed at days 3 and 7 following injection, in the injected (ipsilateral) side of the LPS-treated mouse brain, but not in either the contralateral side or saline-injected animals. HP 13 C lactate/pyruvate ratio, without and with normalization to urea, was also significantly increased in the ipsilateral LPS-injected brain at 7 days compared with baseline. IF analyses showed a significant increase in CD68 and GFAP staining at 3 days, followed by increased numbers of Iba1 and GFAP positive cells at 7 days post-LPS injection. In conclusion, we can detect LPS-induced changes in the mouse brain using HP 13 C MRS, in alignment with increased numbers of microglia/macrophages and astrocytes. This study demonstrates that HP 13 C spectroscopy has substantial potential for providing noninvasive information on neuroinflammation

Imaging Renal Urea Handling in Rats at Millimeter Resolution using Hyperpolarized Magnetic Resonance Relaxometry

\textit{In vivo} spin spin relaxation time ($T_2$) heterogeneity of hyperpolarized \textsuperscript{13}C urea in the rat kidney was investigated. Selective quenching of the vascular hyperpolarized \textsuperscript{13}C signal with a macromolecular relaxation agent revealed that a long-$T_2$ component of the \textsuperscript{13}C urea signal originated from the renal extravascular space, thus allowing the vascular and renal filtrate contrast agent pools of the \textsuperscript{13}C urea to be distinguished via multi-exponential analysis. The $T_2$ response to induced diuresis and antidiuresis was performed with two imaging agents: hyperpolarized \textsuperscript{13}C urea and a control agent hyperpolarized bis-1,1-(hydroxymethyl)-1-\textsuperscript{13}C-cyclopropane-$^2\textrm{H}_8$. Large $T_2$ increases in the inner-medullar and papilla were observed with the former agent and not the latter during antidiuresis suggesting that $T_2$ relaxometry may be used to monitor the inner-medullary urea transporter (UT)-A1 and UT-A3 mediated urea concentrating process. Two high resolution imaging techniques - multiple echo time averaging and ultra-long echo time sub-2 mm$^3$ resolution 3D imaging - were developed to exploit the particularly long relaxation times observed

Gene Expression Profile Identifies Tyrosine Kinase c-Met as a Targetable Mediator of Antiangiogenic Therapy Resistance

PURPOSE: To identify mediators of glioblastoma anti-angiogenic therapy resistance and target these mediators in xenografts. EXPERIMENTAL DESIGN: We performed microarray analysis comparing bevacizumab-resistant glioblastomas (BRGs) to pre-treatment tumors from the same patients. We established novel xenograft models of anti-angiogenic therapy resistance to target candidate resistance mediator(s). RESULTS: BRG microarray analysis revealed upregulation versus pre-treatment of receptor tyrosine kinase c-Met, which underwent further investigation because of its prior biologic plausibility as a bevacizumab resistance mediator. BRGs exhibited increased hypoxia versus pre-treatment in a manner correlating with their c-Met upregulation, increased c-Met phosphorylation, and increased phosphorylation of c-Met-activated focal adhesion kinase (FAK) and STAT3. We developed two novel xenograft models of anti-angiogenic therapy resistance. In the first model, serial bevacizumab treatment of an initially responsive xenograft generated a xenograft with acquired bevacizumab resistance, which exhibited upregulated c-Met expression versus pre-treatment. In the second model, a BRG-derived xenograft maintained refractoriness to the MRI tumor vasculature alterations and survival-promoting effects of bevacizumab. Growth of this BRG-derived xenograft was inhibited by a c-Met inhibitor. Transducing these xenograft cells with c-Met shRNA inhibited their invasion and survival in hypoxia, disrupted their mesenchymal morphology, and converted them from bevacizumab-resistant to bevacizumab-responsive. Engineering bevacizumab-responsive cells to express constitutively active c-Met caused these cells to form bevacizumab-resistant xenografts. CONCLUSION: These findings support the role of c-Met in survival in hypoxia and invasion, features associated with anti-angiogenic therapy resistance; and growth and therapeutic resistance of xenografts resistant to anti-angiogenic therapy. Therapeutically targeting c-Met could prevent or overcome anti-angiogenic therapy resistance

Predictors of hospital discharge and mortality in patients with diabetes and COVID-19: updated results from the nationwide CORONADO study

AIMS/HYPOTHESIS: This is an update of the results from the previous report of the CORONADO (Coronavirus SARS-CoV-2 and Diabetes Outcomes) study, which aims to describe the outcomes and prognostic factors in patients with diabetes hospitalised for coronavirus disease-2019 (COVID-19). METHODS: The CORONADO initiative is a French nationwide multicentre study of patients with diabetes hospitalised for COVID-19 with a 28-day follow-up. The patients were screened after hospital admission from 10 March to 10 April 2020. We mainly focused on hospital discharge and death within 28 days. RESULTS: We included 2796 participants: 63.7% men, mean age 69.7 ± 13.2 years, median BMI (25th-75th percentile) 28.4 (25.0-32.4) kg/m(2). Microvascular and macrovascular diabetic complications were found in 44.2% and 38.6% of participants, respectively. Within 28 days, 1404 (50.2%; 95% CI 48.3%, 52.1%) were discharged from hospital with a median duration of hospital stay of 9 (5-14) days, while 577 participants died (20.6%; 95% CI 19.2%, 22.2%). In multivariable models, younger age, routine metformin therapy and longer symptom duration on admission were positively associated with discharge. History of microvascular complications, anticoagulant routine therapy, dyspnoea on admission, and higher aspartate aminotransferase, white cell count and C-reactive protein levels were associated with a reduced chance of discharge. Factors associated with death within 28 days mirrored those associated with discharge, and also included routine treatment by insulin and statin as deleterious factors. CONCLUSIONS/INTERPRETATION: In patients with diabetes hospitalised for COVID-19, we established prognostic factors for hospital discharge and death that could help clinicians in this pandemic period. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT04324736

Mesure du métabolisme énergétique cérébral par RMN du 31P in vivo : Validation méthodologique multimodale et application à l'étude de la neurodégénérescence

The measurement of cerebral metabolic flows, in particular of those taking part in the energy metabolism, is of major interest as much fundamental point of view, for the comprehension of the biochemical reactions and of their coupling, that from a clinical point of view, for the update biomarqueurs of evolution of neurodégénératives pathologies and the determination of the defective mechanisms under unclaimed. Thus, during last decades, of the atraumatic and noninvasive techniques of neuroimagery allowing the measurement of cerebral metabolic flows, among which the tomography by emission of positrons (Mtoe) and the spectroscopy by nuclear magnetic resonance (SRM), experienced a considerable development. More particularly, the SRM of the 31P shows the characteristic and favours to allow the direct measurement of the cerebral flow of synthesis of ATP, and this without injection of marked precursor. However, this approach appears a methodological challenge still to date and complementary studies of validation remain necessary in order to show the relevance of the SRM of the 31P for the measurement of the cerebral energy synthesis. In this context, a study of multimode neuroimagery, based on the use of new techniques of neuroimagery, was undertaken in order to allow, in the same time, to obtain an integrated vision of the cerebral energy metabolism and to validate the method of transfer of saturation by SRM of the 31P like a method of robust and quantitative measurement of the synthesis of cerebral ATP. More precisely, the regional consumption of CMRglc glucose, the speed of the cycle of Krebs (VTCA) and the speed of synthesis of ATP (VATP) were measured in the brain of healthy primate respectively by FART 18F-FDG, SRM of the 13C and transfer of saturation by SRM of the 31P. These three complementary measurements, carried out in a definite cerebral zone in the same animals in identical physiological conditions, led to the following results: CMRglc= 0.27 ± 0.07 μmol/g/min, VTCA = 0.63 ± 0.12 μmol/g/min and VATP = 7.8 ± 2.3 μmol/g/min. The coherence of these three flows with the values reported in the literature, but especially their coherence one compared to the other, made it possible to validate the method of transfer of saturation by SMR of the 31P for the direct measurement of the synthesis of cerebral ATP. This stage of validation having been led, the interest of the technique of transfer of saturation has, in the second time, summer evaluated in private clinic on a population of patients reached of the disease of Huntington (MH). An exploratory attitude was adopted, in which the concentrations in metabolites phosphoryls, the cerebral pH and the speed of synthesis of ATP were evaluated. This study initially made it possible to highlight a maintenance of metabolic homeostasis among patients Huntington (HD), in particular in ATP, pi and PCr, and this in spite of an important cerebral atrophy. A reduction the speed of synthesis of cerebral ATP was also observed among these patients. However, within sight of the low sensitivity of the method of transfer of saturation by SRM of the 31P, the significativity of this reduction could not be established. Lastly, a significant increase in the cerebral pH was measured among patients HD relative with controls. This cerebral alkalisation, for the first time measured in the MH, presented moreover one correlation with the driving clinical scores evaluated among patients HD, showing the potential interest of the measurement of cerebral pH for the follow-up of pathology. Within sight of this result, a study aiming at evaluating the precocity of the variations of pH associated with laMH was carried out on a rodent model during a chronic intoxication with the acid 3-nitropropionic (3NP), neurotoxine mitochondriale. This study made it possible to highlight a significant increase in the cerebral pH preceding the appearance of lesions striatales, showing the potentiality of the cerebral pH as early biomarquor of the MH. At the biochemical level, it was shown that variations of pH and percentages of inhibition of succinate déshydrogénase (SDH), specific target of the 3NP, presented the same temporal evolution during the protocol of intoxication. Assumptions on the biochemical mechanisms under unclaimed were then proposed in order to try to explain the variations of cerebral pH measured in this study.La mesure de flux métaboliques cérébraux, en particulier de ceux participant au métabolisme énergétique, présente un intérêt majeur autant d'un point de vue fondamental, pour la compréhension des réactions biochimiques et de leur couplage, que d'un point de vue clinique, pour la mise à jour de biomarqueurs d'évolution des pathologies neurodégénératives et la détermination des mécanismes déficients sous jacents. Ainsi, au cours des dernières décennies, des techniques de neuroimagerie atraumatiques et non invasives permettant la mesure de flux métaboliques cérébraux, parmi lesquelles la tomographie par émission de positrons (TEP) et la spectroscopie par résonance magnétique nucléaire (SRM), ont connu un développement considérable. Plus particulièrement, la SRM du 31P présente la caractéristique et l'avantage de permettre la mesure directe du flux cérébral de synthèse d'ATP, et ce sans injection de précurseur marqué. Cependant, cette approche apparaît encore à ce jour un défi méthodologique et des études de validation complémentaires restent nécessaires afin de démontrer la pertinence de la SRM du 31P pour la mesure de la synthèse énergétique cérébrale. Dans ce contexte, une étude de neuroimagerie multimodale, basée sur l'utilisation de nouvelles techniques de neuroimagerie, a été menée afin de permettre, dans un même temps, d'obtenir une vision intégrée du métabolisme énergétique cérébral et de valider la méthode de transfert de saturation par SRM du 31P comme une méthode de mesure robuste et quantitative de la synthèse d'ATP cérébrale. Plus précisement, la consommation régionale de glucose CMRglc, la vitesse du cycle de Krebs (VTCA) et la vitesse de synthèse d'ATP (VATP) ont été mesurées dans le cerveau de primate sain respectivement par PET 18F-FDG, SRM du 13C et transfert de saturation par SRM du 31P. Ces trois mesures complémentaires, réalisées dans une zone cérébrale définie chez les mêmes animaux en conditions physiologiques identiques, ont conduit aux résultats suivants : CMRglc= 0.27 ± 0.07 μmol/g/min, VTCA = 0.63 ± 0.12 μmol/g/min et VATP = 7.8 ± 2.3 μmol/g/min. La cohérence de ces trois flux avec les valeurs rapportées dans la littérature, mais surtout leur cohérence l'un par rapport à l'autre, a permis de valider la méthode de transfert de saturation par SMR du 31P pour la mesure directe de la synthèse d'ATP cérébrale. Cette étape de validation ayant été conduite, l'intérêt de la technique de transfert de saturation a, dans un deuxième temps, été évalué en clinique sur une population de patients atteints de la maladie de Huntington (MH). Une attitude exploratoire a été adoptée, dans laquelle les concentrations en métabolites phosphorylés, le pH cérébral et la vitesse de synthèse d'ATP ont été évalués. Cette étude a permis en premier lieu de mettre en évidence un maintien de l'homéostasie métabolique chez les patients Huntington (HD), en particulier en ATP, Pi et PCr, et ce malgré une atrophie cérébrale importante. Une diminution de la vitesse de synthèse d'ATP cérébrale a également été observée chez ces patients. Cependant, au vu de la faible sensibilité de la méthode de transfert de saturation par SRM du 31P, la significativité de cette diminution n'a pu être établie. Enfin, une augmentation significative du pH cérébral a été mesurée chez les patients HD relativement aux contrôles. Cette alcalinisation cérébrale, pour la première fois mesurée dans la MH, présentait de plus une corrélation avec les scores cliniques moteurs évalués chez les patients HD, démontrant l'intérêt potentiel de la mesure de pH cérébral pour le suivi de la pathologie. Au vu de ce résultat, une étude visant à évaluer la précocité des variations de pH associées à laMH a été réalisée sur un modèle rongeur au cours d'une intoxication chronique à l'acide 3-nitropropionique (3NP), neurotoxine mitochondriale. Cette étude a permis de mettre en évidence une augmentation significative du pH cérébral précédant l'apparition de lésions striatales, démontrant la potentialité du pH cérébral comme biomarqueur précoce de la MH. Au niveau biochimique, il a été montré que variations de pH et pourcentages d'inhibition de la succinate déshydrogénase (SDH), cible spécifique du 3NP, présentaient la même évolution temporelle au cours du protocole d'intoxication. Des hypothèses sur les mécanismes biochimiques sous jacents ont alors été proposées afin de tenter d'expliquer les variations de pH cérébral mesurées dans cette étude

Mesure du métabolisme énérgétique cérébral par RMN du 31P in vivo (validation méthodologique multimodale et application à l'étude de la neurodégénérescence)

Au cours des dernières décennies, des techniques de neuroimagerie atraumatiques et non invasives visant à évaluer les flux métaboliques cérébraux ont été développées. Parmi elles, la spectroscopie par résonance magnétique (SRM) du 31P présente l'avantage de permettre la mesure directe du flux cérébral de synthèse d'ATP, mais apparaît encore à ce jour un défi méthodologique. Dans une première étude de neuroimagerie multimodale, la consommation régionale de glucose CMRglc, la vitesse du cycle de Krebs (Vtca) et la vitesse de synthèse d'ATP (Vatp) ont été mesurées dans le cerveau de primate sain respectivement par TEP (tomographie par émission de positrons) 18F-FDG, SRM du 13C et transfert de saturation par SRM du 31P. La cohérence de ces trois flux a permis de valider la méthode de transfert de saturation par SRM du 31P pour la mesure directe de Vatp cérébrale. L'intérêt de la SRM du 31P a ensuite été évalué sur des patients atteints de la maladie de Huntington (MH). Un maintien de l homéostasie métabolique, une diminution non significative de Vatp, et une augmentation significative du pH ont été mis en évidence dans le cerveau de ces patients. L'alcalinisation cérébrale, pour la première fois mesurée dans la MH, présentait de plus une corrélation avec les scores cliniques moteurs. Au vu de ce résultat, une étude visant à évaluer la précocité des variations de pH associées à la MH a été réalisée sur un modèle rongeur au cours d'une intoxication chronique à l'acide 3-nitropropionique (3NP). Une augmentation significative du pH précédant l'apparition de lésions striatales a été mise en évidence, démontrant la potentialité du pH comme biomarqueur précoce de la MH.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF