Transport Mechanisms of Intracellular Metabolites in the Brain: New Insights by Diffusion-Weighted NMR Spectroscopy with Oscillating Gradients

Charlotte Marchadour¹, ², Vincent Lebon¹, ², Julien Valette¹, ²

Transport of molecules within cells is a key process that can be achieved either passively by random diffusion, or by active transport (e.g. cytoplasmic streaming). The relative contribution of passive and active transport mechanisms to the ADC of intracellular metabolites and intracellular water is still debated. We investigate metabolite motion in the rat brain using diffusion-weighted spectroscopy with oscillating gradients. The dependence of metabolite ADC on the diffusion frequency is observed for the first time, making random diffusion emerge as the dominant transport mechanism. Subsequent data modeling further rules out the plausibility of significant active transport.