title: Increased methionine sulfoxide content of apoA-I in type 1 diabetes.
abstract: Cardiovascular disease is a major cause of morbidity and premature mortality in diabetes. HDL plays an important role in limiting vascular damage by removing cholesterol and cholesteryl ester hydroperoxides from oxidized low density lipoprotein and foam cells. Methionine (Met) residues in apolipoprotein A-I (apoA-I), the major apolipoprotein of HDL, reduce peroxides in HDL lipids, forming methionine sulfoxide [Met(O)]. We examined the extent and sites of Met(O) formation in apoA-I of HDL isolated from plasma of healthy control and type 1 diabetic subjects to assess apoA-I exposure to lipid peroxides and the status of oxidative stress in the vascular compartment in diabetes. Three tryptic peptides of apoA-I contain Met residues: Q(84)-M(86)-K(88), W(108)-M(112)-R(116), and L(144)-M(148)-R(149). These peptides and their Met(O) analogs were identified and quantified by mass spectrometry. Relative to controls, Met(O) formation was significantly increased at all three locations (Met(86), Met(112), and Met(148)) in diabetic patients. The increase in Met(O) in the diabetic group did not correlate with other biomarkers of oxidative stress, such as N(epsilon)-malondialdehyde-lysine or N(epsilon)-(carboxymethyl)lysine, in plasma or lipoproteins. The higher Met(O) content in apoA-I from diabetic patients is consistent with increased levels of lipid peroxidation products in plasma in diabetes. Using the methods developed here, future studies can address the relationship between Met(O) in apoA-I and the risk, development, or progression of the vascular complications of diabetes.
authors.affiliation: Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, USA.
authors.forename: Jonathan W C
authors.initials: JW
authors.lastname: Brock
authors.forename: Alicia J
authors.initials: AJ
authors.lastname: Jenkins
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Lyons
authors.forename: Richard L
authors.initials: RL
authors.lastname: Klein
authors.forename: Eunsil
authors.initials: E
authors.lastname: Yim
authors.forename: Maria
authors.initials: M
authors.lastname: Lopes-Virella
authors.forename: Rickey E
authors.initials: RE
authors.lastname: Carter
authors.forename: Suzanne R
authors.initials: SR
authors.lastname: Thorpe
authors.forename: John W
authors.initials: JW
authors.lastname: Baynes
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D016632:Apolipoprotein A-I / Q000097:blood* / Q000737:chemistry; D002318:Cardiovascular Diseases / Q000097:blood; D008076:Cholesterol, HDL / Q000097:blood / Q000737:chemistry / Q000302:isolation & purification; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D006801:Humans; D013058:Mass Spectrometry; D008715:Methionine / Q000031:analogs & derivatives* / Q000097:blood / Q000737:chemistry; D010084:Oxidation-Reduction; D012307:Risk Factors; D012680:Sensitivity and Specificity
chemical_list: D016632:Apolipoprotein A-I; D008076:Cholesterol, HDL; D008715:Methionine; C013111:methionine sulfoxide