Two fluorescent wavelengths, 440(ex)/520(em) nm and 370(ex)/440(em) nm, reflect advanced glycation and oxidation end products in human skin without diabetes.
BACKGROUND
Advanced glycation end products (AGEs) and oxidation products (OPs) play an important role in diabetes complications, aging, and damage from sun exposure. Measurement of skin autofluorescence (SAF) has been promoted as a noninvasive technique to measure skin AGEs, but the actual products quantified are uncertain. We have compared specific SAF measurements with analytically determined AGEs and oxidative biomarkers in skin collagen and determined if these measurements can be correlated with chronological aging and actinic exposure.


METHODS
SAF at four excitation (ex)/emission (em) intensities was measured on the upper inner arm ("sun protected") and dorsal forearm ("sun exposed") in 40 subjects without diabetes 20-60 years old. Skin collagen from the same sites was analyzed by liquid chromatography-tandem mass spectrometry for three AGEs-pentosidine, carboxymethyllysine (CML), and carboxyethyllysine (CEL)-and the OP methionine sulfoxide (MetSO).


RESULTS
There was poor correlation of AGE-associated fluorescence spectra with AGEs and OP in collagen, with only pentosidine correlating with fluorescence at 370(ex)/440(em) nm. A little-studied SAF (440(ex)/520(em) nm), possibly reflecting elastin cross-links, correlated with all AGEs and OPs. Levels of CML, pentosidine, and MetSO, but not SAF, were significantly higher in sun-exposed skin. These AGEs and OPs, as well as SAF at 370(ex)/440(em) nm and 440(ex)/520(em) nm, increased with chronological aging.


CONCLUSIONS
SAF measurements at 370(ex)/440(em) nm and 335(ex)/385(em) nm, except for pentosidine, which correlated with fluorescence at 370(ex)/440(em), correlate poorly with glycated and oxidatively modified protein in human skin and do not reflect actinic modification. A new fluorescence measurement (440(ex)/520(em) nm) appears to reflect AGEs and OPs in skin.
Dartmouth Medical School, Hanover, New Hampshire 03755, USA. paul.j.Beisswenger@dartmouth.edu
Paul J
PJ
Beisswenger
Scott
S
Howell
Todd
T
Mackenzie
Hugo
H
Corstjens
Neelam
N
Muizzuddin
Mary S
MS
Matsui
D000328:Adult; D001120:Arginine / Q000031:analogs & derivatives / Q000378:metabolism; D003094:Collagen / Q000378:metabolism* / Q000528:radiation effects; D005260:Female; D017127:Glycation End Products, Advanced / Q000378:metabolism*; D006801:Humans; D008239:Lysine / Q000031:analogs & derivatives* / Q000378:metabolism; D008297:Male; D008715:Methionine / Q000031:analogs & derivatives / Q000378:metabolism; D008875:Middle Aged; D018384:Oxidative Stress / Q000528:radiation effects; D012867:Skin / Q000378:metabolism* / Q000528:radiation effects; D015595:Skin Aging / Q000528:radiation effects; D013050:Spectrometry, Fluorescence / Q000379:methods*
D017127:Glycation End Products, Advanced; C048496:N(6)-carboxymethyllysine; D003094:Collagen; D001120:Arginine; D008715:Methionine; C062187:pentosidine; D008239:Lysine; C013111:methionine sulfoxide