|| Checking for direct PDF access through Ovid
Creatine kinase (CK)-catalysed ATP–phosphocreatine (PCr) exchange is considered to play a key role in energy homeostasis of the brain. This study assessed the metabolic and anatomical consequences of partial or complete depletion of this system in transgenic mice without cytosolic B-CK (B-CK−/−), mitochondrial ubiquitous CK (UbCKmit−/−), or both isoenzymes (CK −/−), using non-invasive quantitative magnetic resonance (MR) imaging and spectroscopy. MR imaging revealed an increase in ventricle size in a subset of B-CK−/− mice, but not in animals with UbCKmit or compound CK mutations. Mice lacking single CK isoenzymes had normal levels of high-energy metabolites and tissue pH. In the brains of CK double knockouts pH and ATP and Pi levels were also normal, even though PCr had become completely undetectable. Moreover, a 20–30% decrease was observed in the level of total creatine and a similar increase in the level of neuronal N-acetyl-aspartate compounds. Although CKs themselves are not evenly distributed throughout the CNS, these alterations were uniform and concordant across different brain regions. Changes in myo-inositol and glutamate peaks did appear to be mutation type and brain area specific. Our results challenge current models for the biological significance of the PCr–CK energy system and suggest a multifaceted role for creatine in the brain.