Non-invasive evaluation of advanced glycation end products in hair as early markers of diabetes and aging

Continuous metabolic monitoring is essential for assessing lifestyle-related disease risks. Hair, an easily accessible tissue, allows for long-term metabolic evaluation, with glycated proteins linked to diabetic complications found in hair. We established a mass spectrometry system to detect advanced glycation end products (AGEs) in hair samples from humans and rats, assessing their variations with aging and disease. Hair samples were hydrolyzed and processed using a cation-exchange column for mass spectrometric analysis. Regardless of temperature variations, the levels of AGEs [N^ε-(carboxymethyl)lysine (CML), and methylglyoxal-derived hydroimidazolone-1 (MG-H1)] in human hair remained stable for one week. Age and CML levels, or AGEs z-scores combined with CML and CEL levels in human hair samples, were positively correlated. In streptozotocin-induced insulin-deficient diabetic model (DM) rats, hair CEL and MG-H1 levels were higher than in non-diabetic rats. Receiver operating characteristic curve analysis showed an area under the curve of 1 for hair CEL and MG-H1 levels. Serum and hair CML levels were positively correlated. Hair AGE levels vary more between DM and non-DM rats than serum AGE levels. They remain stable under heat treatment and correlate with age, indicating that hair analysis is an effective non-invasive method for assessing metabolic fluctuations.