OBJECTIVE: Despite the number of potential biomarker proteins for diabetes, very few of them have proven useful as clinically beneficial indicators, because of the technical difficulties associated with their identification among highly abundant serum proteins. We attempted to identify a protein with distinguishable expression in human diabetes. METHODS: We applied a highly efficient strategy for the purification of endogenous low abundance proteins from diabetic and non-diabetic serum samples. Extracted sera were fractionated by SDS-PAGE and protein bands were isolated and analyzed by mass spectrometry using an ion-trap mass spectrometer. The identities of the proteins were confirmed by western blotting and the serum levels evaluated. RESULTS: A significantly upregulated protein in diabetic patients was identified as monomeric α2-macroglobulin. Its tetramer, another dominant circulating molecular form, was only marginally increased in diabetes. CONCLUSION: Serum monomeric α2-macroglobulin is highly expressed in many diabetic subjects. It is identical to the human 'cardiac isoform of α2-macroglobulin' described in the literature, a well-known acute phase serum biomarker protein mechanistically involved in cardiac and atherosclerotic diseases.
OBJECTIVE: Despite the number of potential biomarker proteins for diabetes, very few of them have proven useful as clinically beneficial indicators, because of the technical difficulties associated with their identification among highly abundant serum proteins. We attempted to identify a protein with distinguishable expression in humandiabetes. METHODS: We applied a highly efficient strategy for the purification of endogenous low abundance proteins from diabetic and non-diabetic serum samples. Extracted sera were fractionated by SDS-PAGE and protein bands were isolated and analyzed by mass spectrometry using an ion-trap mass spectrometer. The identities of the proteins were confirmed by western blotting and the serum levels evaluated. RESULTS: A significantly upregulated protein in diabeticpatients was identified as monomeric α2-macroglobulin. Its tetramer, another dominant circulating molecular form, was only marginally increased in diabetes. CONCLUSION: Serum monomeric α2-macroglobulin is highly expressed in many diabetic subjects. It is identical to the human 'cardiac isoform of α2-macroglobulin' described in the literature, a well-known acute phase serum biomarker protein mechanistically involved in cardiac and atherosclerotic diseases.