Pilot study to asses the dependence of skin autofluorescence (SAF) on skin color
and skin tissue characteristics in humans with dark skin

Skin autofluorescence measurements are increasingly used to estimate
cardiovascular risk. Skin autofluorescence is assumed to give an
estimate of the accumulation of advanced gl.ycation endproducts (AGE) in
the dermis of the skin, and with that, in other tissues of the body
with slow turnover such as the vessel wall and the myocardium.
This accumulation of AGE deteriorates vessel function and structure.
Skin autofluorescence has been shown to be an independent predictor of
cardiovascular events. This has been supported by earlier studies of our
group and others using skin biopsies, and with skin autofluorescence
measurements, in clinical follow-up studies, which were performed in the
large majority in Caucasian and North-Asian healthy persons and in
people with diabetes, renal failure or pre-existing cardiovascular
disease.
For persons with the darker skin types such as persons from sub-Saharan
Africa and South Asia (Tamil Nadu) support is lacking for the relation
between measured skin autofluorescence and AGE accumulation.
In the present pilot proposal a set of skin measurements is performed, which
should make it clear whether further development of a skin colour-independent
assessment of AGEs is feasible

Assess feasibility of development of skin colour independent assessment of
skin AGE accumulation by measurement of skin autofluorescence
in persons with dark skin

The current pilot proposal concerns the following parts:
- experimental part with skin measurements and skin biopsies in persons
with dark skin colour
- assessment of feasibility to develop model based translation of measured skin
fluorescence into AGE
accumulation, independent of skin colour and skin type

The following measurements, and a two 3 mm punch skin biopsies will be
performed on the volar side of one of the forearms approximately 10 cm
below the elbow fold.
- In vivo skin autofluorescence and reflection measurements, with the
conventional research version (which includes a high-quality spectrometer) of
the AGE reader
- Measurement of skin colour and type using non-invasive Mexameter.
- In vivo skin diffuse optical spectroscopy for the assessment of optical
properties of the skin measurements will be made by a
non-invasive instrument of Quaspec.
- Standard biochemical assay of one of two conventional 3 mm skin
biopsies for the assessment of concentrations of the following advanced
glycation endproducts, pentosidine, CML and MGH-1 with use of UPLC and
tandem mass spectroscopy
- light microscopy of the other 3 mm skin biopsy. In transversal coupes
autofluorescence measurements will be performed with a
set of different excitation wavelengths, including 370 nm, similar to that of
the AGE reader.
Also, in contiguous slices of the skin biopsy, imaging will be performed using
AGE antibodies to assess the spatial distribution of
autofluorescence and of specific advanced glycation endproducts.

The participants will make one study visit to the UMCG.

The main burden is two conventional 3 mm punch skin biopsies from the inner
side of the lowerarm 10 cm below the elbow fold, after local
anesthesia. In case of persistent bleeding a suture will be placed. The risk
associated with this biopsy is local bleeding or infection,
this risk is low (both < 1%).

All other (preceding) measurements (with AGE readers, Mexameter, Quaspec) are
noninvasve, not painful, en without risk, the measurements will
take appr. 30 minutes overall.

The participants will have no direct benefit.

Group relatedness not applicable