MR spectroscopic neurometabolite profile in aged rodents: a study in Sprague‐Dawley and Wistar rats, and C57bl/6J mice

Abstract Background Cognitive decline and Alzheimer’s disease (AD) are closely related to aging in human population and the need for translational biomarkers is of crucial importance. Several approaches have been proposed to study Alzheimer’s disease in rodent models, including transgenic mice and rats to model either amyloid‐ or tau‐pathologies. We have shown age‐related 1H‐MRS phenotype in female Fisher rats (22‐24 months, Bolognin et al. 2014 Neurobiol Aging:2134‐46) with reduced N‐acetyl aspartate (NAA), GABA and glutamate, and increased myo‐inositol together with other AD‐like biomarkers (increased CSF levels of AbPP and Tau, defect in Morris Water Maze, Khatoon et al 2015 J Alzheimer’s Disease: 557‐564). The aim of this study was to explore if similar 1H‐MRS phenotype is present in other strains of aged rats and mice to allow easier access to cohorts of aged rodents and enable utilization of different strains to model pathology. Method Eighteen male Sprague‐Dawley rats (n=10/8, 4/24 months), 24 male Wistar rats (n=12/12, 3.25 /21.75 months) and 23 male C57Bl/6J mice (n=12/11, 4.75/23 months) were used. Hippocampal MRS was performed at 11.7T magnet using PRESS sequence and metabolites analyzed using LCModel. Result Although the evaluation was done at slightly different ages, all three models shared a similar phenotype in hippocampal metabolites, i.e. decreased GABA and glutamate, and increased glutamine and myo‐inositol. NAA was significantly reduced in aged Wistar rats and C57Bl/6J mice whereas the SD rats showed only non‐significant trend of decrease. Conclusion Based on the current data, the MRS phenotype is remarkably repeatable in aged rats (SD, Wistar) and in aged C57Bl/6J mice. Furthermore, the pattern of increased myo‐inositol with decreased levels of glutamate and NAA is descriptive of human AD. Aged rodents can therefore model biochemical changes potentially related to natural aging/AD.