Using stable isotope dilution LC–MS/MS, we quantified the content of protein-bound HCit levels in circulating blood from subjects (n = 117) with normal renal function and without evidence of CVD, diabetes, or other comorbidities (Table S1), and compared it with protein-bound HCit within the apoA-I recovered from human atherosclerotic aortic lesions (n = 10) (Table S2). Here, APOA1 is linked to diabetes mellitus.