RBP4 and Alzheimer disease: This has been for instance demonstratedfor amyloid-β (Aβ), Tau, or sTREM2 in Alzheimer’sdisease (AD)8−10 and retinol-binding protein 4 (RBP4) in diabetes.11 The measure of protein dynamics is commonlyperformed by mass spectrometry (MS), and it relies on the introductionof an isotopic tracer that labels newly synthesized proteins througha mass shift.12−16 The ratio of labeled versus unlabeled protein MS signals is namedthe relative isotope abundance (RIA).