Using chromatographic and mass spectrometry tools to probe albumin and its cargos : in search of understanding type II diabetes

Abstract

We measured molecules carried as cargos on the abundant blood protein human serum albumin (1) in patients with newly diagnosed, untreated type II diabetes (T2D) compared to healthy controls (HC). The HSA cargos measured included lipids, minerals, peptides, and metabolites. Differences in these cargos associated with T2D were measured, using chromatography and mass spectrometry, seeking to identify biological markers that may enhance early diagnosis of T2D. An extrinsic fluorescent probe of binding sites on HSA, ANS, revealed that there were distinct differences in loading of hydrophobic cargo between HC and systemic lupus erythematosus, T2D, and Lyme disease plasma samples. A decrease in mineral levels on HSA was also measured in T2D plasma compared to healthy control plasma, using ICP-MS. Zinc ions showed the largest changes and were reduced three fold in T2D. The hydrophobic cargo of HSA revealed a decrease in HSA-associated fatty acids in T2D, measured by GCMS using negative chemical ionization. In this same GCMS study new classes of glycine-containing compounds bound to HSA were found to be increased by two fold in T2D in the hydrophobic extract of HSA. A metabolomic study using RP-uHPLC QTOF MS in both positive and negative ionization modes examined differences in the hydrophobic extract of whole plasma in T2D compared to healthy controls. Increased levels of branched chain amino acids were found in T2D compared to HC. Decreased levels of phosphatidylcholines, phosphatidylethanol amines, and vitamin D3 metabolites were found in T2D compared to HC. The results suggests that the HSA cargo in T2D, SLE, and other disease states, may provide new diagnostic markers and lead to deeper understanding of the mechanisms of disease in humans.