Skin autofluorescence, a novel marker for glycemic and oxidative stress-derived advanced glycation endproducts: an overview of current clinical studies, evidence, and limitations.

BACKGROUND: Advanced glycation endproducts (AGEs) predict long-term complications in agerelated diseases. However, there are no clinically applicable markers for measuring AGEs in vivo.
METHODS: We have recently introduced the AGE-Reader (DiagnOptics B.V., Groningen, The Netherlands) to noninvasively measure AGE accumulation in the human skin of the forearm, making use of the characteristic autofluorescence (AF) pattern that AGEs encompass. Skin AF is calculated as a ratio of mean intensities detected from the skin between 420-600 nm and 300-420 nm. It correlates with collagen-linked fluorescence and specific skin AGE levels from skin biopsies in diabetes, renal failure, and control subjects. Skin AF levels are increased in patients with diabetes and renal failure and are associated with the presence of vascular complications. Additionally, skin AF is strongly related to the progression of coronary heart disease and mortality, independently of traditional risk factors. Since skin pigmentation might influence skin AF, we have investigated the relation of relative skin reflectance (R%) to skin AF in subjects with varying skin phototypes (SPT).
RESULTS: The data presented in this article suggest that only in subjects with an SPT of V and VI or R% <12%, no reliable measurement can be performed. Therefore, the current prototype of the AGE-Reader is suitable for subjects with SPT I-IV or R% >12%, and more research is needed for a broader application.
CONCLUSION: The AGE-Reader is useful as a noninvasive clinical tool for assessment of risk for long-term vascular complications in diabetes and in other conditions associated with AGE accumulation.