Clinical Verification of Peptide Biomarkers for Human Aging by Standard-Free, Label-Free LC-MS/MS Quanification of Aldehyde-modified Peptides

Aging in human physically refers to a multidimensional process that all the changes were accumulated in a person over time. These aging changes are responsible for the progressive increases in the chance of disease and death associated with them. So far, there are several theories have been developed to understand the aging process, such as cross-linking, which is led by Maillard Reactions. Maillard Reaction is a complex series of reactions between reducing sugar/aldehydes and amino groups on proteins. Under physiological conditions, aldehydes are products of various exogenous and endogenous amines catalyzed by semicarbazide-sensitive amine oxidase (SSAO), a family of heterogeneous enzyme. It was reported that SSAO shows a significant higher catalytic activity, producing more aldehydes in age-related diseases. However, SSAO is not a perfect candidate to be monitored for evaluating aging, because it is widely distributed in tissues, which are not readily accessible sample-sources for clinical applications. In this work, the investigators have found 6 biomarker candidates by developing a standard-free, label-free MS-based proteomics method based on standard protein (human serum albumin, the highest abundance protein in human plasma) model in vitro. Then, the investigators wanted to verify these biomarker candidates by clinical plasma samples to see if there is significant quantitative difference among people with different ages.