Effects of Aging on the Human Brain: A Proton and Phosphorus MR Spectroscopy Study at 3T

Abstract

Background and purpose: To investigate accumulative aging effects on neurometabolism in human brain and to collect a reference dataset.

Methods: Fifty-four healthy volunteers aged evenly between 22 and 73 years were studied using whole-brain ¹ H-MR spectroscopic imaging in combination with ³¹ P-MRS at 3T. Global metabolite concentrations of brain N-acetylaspartate (NAA), total choline (tCho), and total creatine (tCr), as well as phosphocreatine (PCr), adenosine-5'-triphosphate (ATP), phosphomonoesters (PME), phosphodiesters (PDE), and inorganic phosphate (Pi) were determined. Fractional volumes of brain gray matter (FVGM), white matter (FVWM), and total tissue (FVTB, GM+WM) were also estimated.

Results: With age, NAA, ATP, and PME, as well as FVTB and FVGM decreased and tCho and FVWM increased linearly. Positive correlations were found between FVGM and global concentrations of NAA, ATP, PME, and Pi.

Conclusion: Age-related accumulative metabolic changes in aging human brain correlated with reduced neuronal metabolic activity and density, reflected by decreased NAA, reduced mitochondrial activity by decreased ATP, and reduced membrane synthesis by decreased PME. These changes are associated with age-related decrease of neuronal volume. Global NAA and ATP might be used as surrogate biomarker for monitoring aging in human brain.

Keywords: Aging; MRS; N-acetylaspartate; adenosine triphosphate; global brain metabolites.