Serum protein complex profiling reveals heterogeneity of Balanced constitutional population in traditional Chinese medicine through blue native polyacrylamide gel electrophoresis

Background: Pulse-taking is widely used for diagnosis and treatment in traditional Chinese medicine (TCM), and protein complexes in serum perform various biological functions. The Balanced constitution is one of the major constitutions in TCM, people with Balanced constitution can also share some common characteristics with unbalanced constitution types. Methods: Blue native polyacrylamide gel electrophoresis (BN-PAGE) was applied to the serum of 25 people with balanced constitutions. The patterns of the protein complexes could be recognized according to the number, molecular weight, and intensity of the gel bands. All of the individual bands from these patterns were cut and in-gel-digested with trypsin, followed by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) analysis for protein identification and biological function analysis. Results: The protein complex patterns were roughly categorized as type A and B with high stability and reproducibility, and there were 15 and 16 gel bands in type A and type B, respectively. Among the 25 serum samples, 14 belonged to type A, and 11 belonged to type B. High-abundance proteins significantly decreased from 99% to 44% after BN-PAGE separation. The unique proteins in type A were mainly related to lipid metabolism, while the unique proteins in type B were involved in biological processes related to immune response and inflammatory regulation. The Qi-deficiency constitution converted score of type A was higher than that of type B, while the Damp-heat constitution converted score of type A was lower than that of type B. Conclusions: Our study provided an objective reference for diagnosis and prognosis, which might lay a foundation for establishing the characteristic protein complex spectra of all of the TCM constitutions.