Posttranslational modifications of apolipoprotein A-II proteoforms in type 2 diabetes.

ABSTRACT

BACKGROUND: Apolipoprotein A-II (apoA-II) is the second most abundant protein in high-density lipoprotein particles. However, it exists in plasma in multiple forms. The effect of diabetes on apoA-II proteoforms is not known. OBJECTIVE: Our objective was to characterize plasma apoA-II proteoforms in participants with and without type 2 diabetes. METHODS: Using a novel mass spectrometric immunoassay, the relative abundance of apoA-II proteoforms was examined in plasma of 30 participants with type 2 diabetes and 25 participants without diabetes. RESULTS: Six apoA-II proteoforms (monomer, truncated TQ monomer, truncated Q monomer, dimer, truncated Q dimer, and truncated 2Qs dimer) and their oxidized proteoforms were identified. The ratios of oxidized monomer and all oxidized proteoforms to the native apoA-II were significantly greater in the diabetic group (P = .004 and P = .005, respectively) compared with the nondiabetic group. CONCLUSION: The relative abundance of oxidized apoA-II is significantly increased in type 2 diabetes.