Project

Discipline

Hepatic Encephalopathy; in vivo Magnetic Resonance Spectroscopy / Imaging; creatine; brain energy metabolism; osmoregulation; brain metabolism; brain edema; Chronic liver disease

Lead
L’encéphalopathie hépatique est une complication neurologique grave due à l’insuffisance hépatique chronique, affectant à la fois les adultes et les enfants. L’atrésie des voies biliaires est la cause la plus fréquente de l’insuffisance hépatique chronique chez les enfants et est également l'indication la plus fréquente de transplantation hépatique pédiatrique. L'augmentation de la concentration cérébrale de l'ammoniaque est considérée à être la cause majeure de l’encéphalopathie hépatique mais sa relation avec les lésions neurologiques est mal comprise. Le rôle des acides biliaires est aussi mal connu.Le projet apporte sa contribution a ce domaine de recherche
Lay summary
Chez les adultes ayant une l’insuffisance hépatique chronique il est bien accepte que l’hyperammonémie va générer une augmentation de la glutamine cérébrale et une perturbation osmotique secondaire qui va entrainer un œdème cérébrale diffus.  Bien que dans l'âge adulte l’encéphalopathie hépatique est en grande partie réversible lors du retour de l'ammoniac sérique à des valeurs normales, l’hyperammonémie est associée à des dommages irréversibles au système nerveux central chez l'enfant. Des déficits résiduels similaires n'ont pas été décrits chez les patients adultes après l’insuffisance hépatique chronique. La compréhension des mécanismes moléculaires qui sont à la base de ces déficits neurocognitifs est importante pour finalement être en mesure de proposer des stratégies de neuroprotection pour ces enfants dans le but d'améliorer leurs résultats à long terme. En se basant sur nos résultats préliminaires, nous émettons l'hypothèse que des différences dans l'osmoregulation, les neurotransmetteurs, antioxydants et les métabolites énergétiques sont à la base des différences neurologiques observés dans le cerveau mature et en développement durant une l’insuffisance hépatique chronique. Cette susceptibilité différentielle peut être liée à la déficience secondaire en Cr et à la toxicité combinée de l’ammoniac avec les acides biliaires. Le projet est divisé en plusieurs phases. Dans une première phase nous allons étudier les différences entre le cerveau en développement et celui mature pendant l’insuffisance hépatique chronique en réalisant des mesures in vitro et in vivo et en utilisant l’imagerie et la spectroscopie de résonance magnétique. Dans une deuxième partie nous allons évaluer le rôle neuroprotecteur de la créatine dans l’insuffisance hépatique chronique. La dernière partie de notre projet implique l'étude métabolique du cerveau chez les patient pédiatriques atteints d'une insuffisance hépatique chronique.

Direct link to Lay Summary

Last update: 05.04.2017

MR Spectra from rat hippocampus with LCModel quantification and the corresponding basis set

Author	Simicic, Dunja; Cudalbu, Cristina
Publication date	23.06.2021
Persistent Identifier (PID)	https://doi.org/10.5281/zenodo.3904443
Repository	Spectra_hippocampus(rat)_TE02.rar
Abstract

This folder contains the LCModel quantifications of spectra acquired in hippocampus from 7 rats. The spectra were quntified using six different DKNTMN (spline stiffness) values (0.1, 0.25, 0.4, 0.5, 1, 5). In the folder Control_files_Basis_set you can find all the control files used in this quantification along with the corresponding basis set (metabolites/simulated using NMRScopeB from jMRUI and in vivo parameters + full MM spectrum).

Active participation

Communication	Title	Media	Place	Year

Number	Title	Start	Funding scheme

1.1BackgroundChronic hepatic encephalopathy (HE) is a well-accepted complication of cholestatic, chronic liver disease (CLD) in adults. It is less well understood in children, although many children with cholestatic CLD display an array of neurocognitive deficits. Increase in ammonium (NH4+) delivery to the brain in CLD is thought to be the main culprit. The role of bile acids in these deficits is unknown. It is commonly accepted in adults with CLD that increased central nervous system NH4+ generates a rise in the osmolyte glutamine and a secondary osmotic imbalance, recently shown to be associated with low grade brain edema. These changes might impact brain energy metabolism, but seem to be largely corrected when blood NH4+ declines. However, based on current understanding of infants with urea cycle defects (UCD)-characterized by acute and extreme hyperammonemia (HA), it appears that the developing (infant) brain under HA faces irreversible impairment of brain cell migration and differentiation and ultimately significant brain cell death. Additionally, there is emerging evidence that chronic cholestasis early in life may be associated with long-term neurocognitive and neuromotor deficits. No similar long-term deficits have been described in adult patients. How the infant or child’s brain responds to the metabolic changes of CLD, and how these mechanisms differ from those in adult patients are both unknown. Further, prophylactic or therapeutic measures are needed to prevent or treat the effects of CLD in children. Our previous in vitro measurements showed that NH4+ in developing brain cells leads to cell death, inhibition of axonal growth and generates a secondary creatine (Cr) deficiency, while Cr supplementation shows neuroprotective effects. Our preliminary data also show in vitro that several bile acids occurring in CLD may be toxic to neurons and astrocytes. Using in vivo 1H, 31P,13C MR spectroscopy (MRS) and Diffusion Tensor Imaging (DTI) in a rat model of CLD we have recently shown that rat pups display a distinct brain metabolism from adults. First, we observed a greater glutamine increase, together with the predicted myo-inositol decrease, yet more pronounced brain edema than predicted. Next, pups displayed a stronger decrease in neurotransmitters, and antioxidants and evidence of altered energy metabolism (lactate). Importantly for the proposal, there was a significant decrease in measured Cr, while Cr treatment increased brain N-acetylaspartate levels in rat pups. Cr has multiple essential functions in the central nervous system: it participates in energy metabolism, osmoregulation, and neurotransmission. Therefore, Cr emerges as a likely candidate underlying the differential susceptibility to CLD between adults and pups.1.2Working hypothesisWe hypothesize that differences in osmoregulation, neurotransmitter, antioxidant and energy metabolism underlie the differential susceptibility to CLD-induced neurological changes observed in the mature and developing brain, and that this differential susceptibility may be related to secondary Cr deficiency, and the combined toxicities of bile acids and NH4+.1.3AimsI: Differences between mature and developing brain during CLD: from 3D organotypic brain cell cultures to an in vivo rat modelII: Neuroprotective role of Cr in the adult and developing rat brain with CLD-induced HE.III: Abnormalities in brain Gln, Ins, Cr, Glu and cognitive performance in children with CLD1.4Experimental design and/or methods-We will assess the effects of bile acids with/without NH4+ on 3D brain cell cultures using biochemical and histological methods.-We will analyze the longitudinal progression of 16 brain metabolites non-invasively, in vivo, with a focus on osmoregulation, energy, neurotransmitter, antioxidant metabolites, using 1H MRS in rats and children with CLD. -We will simultaneously measure brain edema and changes in white matter maturation in vivo by DTI in rats with CLD. -We will investigate neuroglial energy metabolism in vivo using 13C MRS and 31P MRS in rats with CLD.-We will analyze the effects of HE using biochemical and histological methods in the brain of the same rats evaluated by 1H, 13C, 31P MRS as well as DTI.-The neuroprotective effects of Cr supplementation will be assessed in vitro against the toxic effects of bile acids with- or without NH4+ exposure, as well as in vivo in pups and adult CLD rats by looking at the effect of Cr supplementation using the approaches described above.1.5Expected values of the proposed projectThe proposed experiments aim to decipher the molecular underpinnings behind the differential vulnerability of the developing vs the mature brain to the insults of CLD using a 3D brain cell culture model to analyze the impact of HA and bile acids. This will be correlated with in vivo studies to analyze the temporal differences between pup and adult rats with CLD by examining in detail the longitudinal variations in osmoregulation, neurotransmission, antioxidants, energy metabolites, white matter maturation and edema. Using this multimodal approach, we will specifically monitor differences in Cr metabolism and analyze the response to Cr supplementation in the diet of CLD animals, thereby testing for the first time the hypothesis that fluctuations in Cr may underlie the age-dependent differential susceptibility to HE, and the potential neuroprotective effect of Cr supplementation. In parallel, we will pave the way to future interventional studies in children, in whom we will analyze the link between neurometabolism and neurocognitive performance in a preliminary study.