[Development of a highly sensitive separation method for the analysis of metabolites in human nails and applications in the diagnosis of chronic disease].

We have recently developed target-specific derivatization methods for determining the metabolites in human nails. The nails can be used to obtain physiologic information and may serve as noninvasive biosamples for the diagnosis of chronic disease. Certain endogenous biogenic D,L-amino acids, polyamines, and advanced glycation end-products (AGEs) have been detected in human nails. By identifying biological trace components in human samples, we tested the possibility of using these new methods to diagnose chronic disease, i.e., diabetes and lung cancer. When comparing the index from diabetic patients to that from healthy volunteers, there was no significant difference in the content of L-amino acids, methylglyoxal, and glyoxal in the nails. However, a statistically significant correlation was observed between the D/L-amino acid concentration ratios (Ala, Val, Ile, Leu; p<0.01), and 3-deoxyglucosone concentrations (p<0.001). Additionally, in the lung cancer patient group, as compared with healthy volunteers, the concentrations of spermine showed a statistically significant (p<0.05) correlation. This review describes our current target-specific derivatization UPLC-ESI-MS methods for the determination of metabolites and related compounds, e.g., D,L-amino acids, polyamines, and AGEs, in human nails. Advanced applications of human nails as new, noninvasively obtained biosamples for the diagnosis of chronic disease are also described.