Measurement of regional rates of protein synthesis in human brain in vivo with L-[1-¹¹C]-leucine PET

Sir,

We read with interest the paper recently published in Brain by Smeets et al. on measurement of rates of protein synthesis in brain in human subjects. We were surprised by the authors’ claims that ‘Because of obvious limitations with regard to brain tissue sampling no study has ever measured brain protein synthesis rates in vivo in humans’ (Abstract) and that ‘This is the first study to measure high brain tissue protein synthesis rates in vivo in humans’ (Discussion).

These claims overlook several studies in which regional rates of cerebral protein synthesis have been measured in vivo in human subjects with the quantitative L-[1-¹¹C]-leucine PET method developed and validated by our group (Schmidt et al., 2005; Smith et al., 2005). We have measured cerebral protein synthesis rates in healthy young males awake (Bishu et al., 2008) and under propofol anaesthesia (Bishu et al., 2009). Our measurements show that rates are highest in areas of cortex, lower in hippocampus and lowest in white matter regions. We have also studied subjects with a developmental disorder, fragile X syndrome, and reported changes in rates of protein synthesis in cortex in this population (Qin et al., 2013).

It is important for your readers to know that regional cerebral protein synthesis rates can be measured in vivo without surgical sampling of brain tissue.

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