Evaluation of Nonenzymatic Posttranslational Modification–Derived Products as Biomarkers of Molecular Aging of Proteins

BACKGROUND During their biological life, proteins are exposed in a cumulative fashion to irreversible nonenzymatic, late posttranslational modifications that are responsible for their molecular aging. It is now well established that these damaged proteins constitute a molecular substratum for many dysfunctions described in metabolic and age-related diseases, such as diabetes mellitus, renal insufficiency, atherosclerosis, or neurodegenerative diseases. Accordingly, the specific end products derived from these reactions are considered potentially useful biomarkers for these diseases. CONTENT The aim of this review is to give an overview of nonenzymatic posttranslational modifications of proteins and their influence in vivo, take inventory of the analytical methods available for the measurement of posttranslational modification–derived products, and assess the potential contribution of new technologies for their clinical use as biological markers of protein molecular aging. SUMMARY Despite their clinical relevance, biomarkers of posttranslational modifications of proteins have been studied only in the context of experimental clinical research, owing to the analytical complexity of their measurement. The recent implementation in clinical chemistry laboratories of mass spectrometry–based methods that provide higher specificity and sensitivity has facilitated the measurement of these compounds. These markers are not used currently by clinicians in routine practice, however, and many challenges, such as standardization, have to be confronted before these markers can be used as efficient tools in the detection and monitoring of long-term complications of metabolic and age-related diseases.