['The choline metabolite, betaine, plays a role in lipid metabolism, and may predict the development of cardiovascular disease and type 2 diabetes mellitus (T2DM). Phospholipid transfer protein (PLTP) and lecithin:cholesterol acyltransferase (LCAT) require phosphatidylcholine as substrate, raising the possibility that there is an intricate relationship of these protein factors with choline metabolism. Here we determined the relationships of PLTP and LCAT activity with betaine in subjects with and without T2DM.', 'Plasma betaine (nuclear magnetic resonance spectroscopy), PLTP activity (liposome-vesicle HDL system), LCAT activity (exogenous substrate assay) and (apo)lipoproteins were measured in 65 type 2 diabetic (T2DM) and in 55 non-diabetic subjects.', 'PLTP and LCAT activity were elevated in T2DM (p\u2009<\u20090.05), whereas the difference in betaine was not significant. In age-, sex- and diabetes status-controlled correlation analysis, betaine was inversely correlated with triglycerides and positively with HDL cholesterol (p\u2009<\u20090.05 to 0.01). PLTP and LCAT activity were positively correlated with triglycerides and inversely with HDL cholesterol (p\u2009<\u20090.05 to 0.001). PLTP (r\u2009=\u2009-0.245, p\u2009=\u20090.006) and LCAT activity (r\u2009=\u2009-0.195, p\u2009=\u20090.035) were correlated inversely with betaine. The inverse association of PLTP activity with betaine remained significant after additional adjustment for body mass index and lipoprotein variables (β\u2009=\u2009-0.179, p\u2009=\u20090.034), whereas its association with LCAT activity lost significance (β\u2009=\u2009-0.056, p\u2009=\u20090.44).'] Is plasma phospholipid transfer protein activity inversely associated with betaine in diabetic and non-diabetic subjects?