The long-range goal of this research program is to understand the physiology of ATP metabolism or energy production and utilization in the mature and the developing brain. A second goal is to understand the role of adaptations in ATP metabolism in maintaining brain cell viability in states of energy deficit (hypoxia) and high energy demand (seizures). The primary hypothesis for this proposal is that the activity of creatine kinase (CK), which catalyzes the phosphoryl transfer between PC and ATP, also is central in closely coupling ATP synthesis to the large and rapid changes in energy demand characteristic of the mature brain. A second hypothesis is that activity of the CK isoforms, specifically the mitochondrial CK, is critical for maintaining cellular energy under conditions of decreased energy availability. Thus, adaptations to a decrease in CK catalyzed reaction rates are expected to maintain close regulation of ATP during seizures but not hypoxia. The present proposal combines in vivo 31P-nuclear magnetic resonance spectroscopy with in vitro measures of enzymes and metabolites involved in ATP metabolism. Three conditions, in which brain CK activity is 20-30 percent of the activity in normal adult cortex, are used; immaturity, feeding an analogue of creatine, and cerebral white matter. The studies comparing gray and white matter use volume localized NMR spectroscopic techniques. In the other in vivo NMR studies, non-localized spectra with high signal-to-noise will be acquired frequently to provide close comparisons of cellular energy, pH, EEG, and EKG. The expectation is that the conditions in which the CK-catalyzed reaction rate is low will be associated with larger energy losses during hypoxia than seen in the mature brain where phosphocreatine (PC) losses are 30-50 percent and ATP is stable. In contrast, the physiology of ATP metabolism in the presence of rapid or slow CK catalyzed reaction rates is expected to maintain stable brain ATP and a small loss in PC during seizures. The results of these NMR studies will provide an understanding of the in vivo regulation of brain ATP while the in vitro studies will provide an initial understanding of the molecular and cellular bases for these metabolic properties. This understanding will allow more rational use of non-invasive clinical metabolic brain monitoring.The results also will provide a clearer understanding of the pathogenesis of brain cellular injury during the critical clinical conditions of hypoxia and seizures.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
1R01NS026371-01A4
Application #
3412170
Study Section
Neurology A Study Section (NEUA)
Project Start
1993-05-01
Project End
1996-04-30
Budget Start
1993-05-01
Budget End
1994-04-30
Support Year
1
Fiscal Year
1993
Total Cost
Indirect Cost
Name
Children's Hospital Boston
Department
Type
DUNS #
076593722
City
Boston
State
MA
Country
United States
Zip Code
02115
Kekelidze, T; Khait, I; Togliatti, A et al. (2001) Altered brain phosphocreatine and ATP regulation when mitochondrial creatine kinase is absent. J Neurosci Res 66:866-72
Kekelidze, T; Khait, I; Togliatti, A et al. (2000) Brain creatine kinase and creatine transporter proteins in normal and creatine-treated rabbit pups. Dev Neurosci 22:437-43
Holtzman, D; Khait, I; Mulkern, R et al. (1999) In vivo development of brain phosphocreatine in normal and creatine-treated rabbit pups. J Neurochem 73:2477-84
Kekelidze, T; Khait, I; Togliatti, A et al. (1999) Maturational changes in rabbit brain phosphocreatine and creatine kinase. Ann N Y Acad Sci 893:309-13
Holtzman, D; Brown, M; O'Gorman, E et al. (1998) Brain ATP metabolism in hypoxia resistant mice fed guanidinopropionic acid. Dev Neurosci 20:469-77
Holtzman, D; Togliatti, A; Khait, I et al. (1998) Creatine increases survival and suppresses seizures in the hypoxic immature rat. Pediatr Res 44:410-4
Holtzman, D; Mulkern, R; Meyers, R et al. (1998) In vivo phosphocreatine and ATP in piglet cerebral gray and white matter during seizures. Brain Res 783:19-27
Mulkern, R V; Chao, H; Bowers, J L et al. (1997) Multiecho approaches to spectroscopic imaging of the brain. Ann N Y Acad Sci 820:97-122
Holtzman, D; Meyers, R; Khait, I et al. (1997) Brain creatine kinase reaction rates and reactant concentrations during seizures in developing rats. Epilepsy Res 27:7-11
Chao, H; Bowers, J L; Holtzman, D et al. (1997) Multi-echo 31P spectroscopic imaging of ATP: a scan time reduction strategy. J Magn Reson Imaging 7:425-33

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