Glycative Stress Research
Online edition : ISSN 2188-3610
Print edition : ISSN 2188-3602
Received : November 18, 2023
Accepted : April 11, 2024
Published online : June 30, 2024
doi:10.24659/gsr.11.2_62

Original article

Glycation and biologic clock: DNA methylation age
Jana Janovska 1), Claude Dalle 2)
1) European Prevention Center, Düsseldorf, Germany2) World Society Interdisciplinary Anti-Aging Medicine, Paris, France

Abstract

Background and Purpose: Advanced glycation endproducts (AGEs) produced by glycative stress are implicated in therisk of various age-related diseases. We hypothesized that DNA methylation is involved as a mechanism linking the two. This
study analyzed the relationship between DNA methylation in skin samples and physical information, especially in terms ofglycation stress.
Methods: Male and female Caucasian patients aged 40 - 75 years at Riga Stradins University were included (296 patients),
consisting of two groups: 149 patients in the metabolic syndrome (MS) group and 147 in the non-MS group. Methylationage (MethylAge) was calculated by measuring hydroxymethylated DNA by LC-MS and matching with cohort data from theReunis Institute. Glycative stress indices were measured by skin AGE fluorescence (SAF) with an AGE Reader (DiagnOptics,
The Netherland). In addition, physical measurements and blood sex chemistry tests were performed.
Results: Items that showed significant correlations with MethylAge were chronological age (r = 0.594), waist circumference(r = 0.261), triglyceride (r = 0.317), and skin aging index (SAI, r = 0.318, p < 0.05 for each). The correlation between
methylation age ( y) and SAF (x) was particularly high (y = 131.9x ² - 490.1x + 491. 5, R² = 0.989, p < 0.001). The items
that showed significant differences in MethylAge depending on the presence or absence of disease/lesions were MS, SAI,
Sebhoroic keratosis and Lentigo type of hyperpigmentation (p < 0.05 for each). The glycation stress index SAF showed asignificant correlation with the presence or absence of MS, oxidative stress index (glutathione, superoxide dismutase), andglycolipid metabolism index (fasting plasma glucose, total cholesterol, high-density lipoprotein-cholesterol).
Conclusion: Assessment of MethylAge may be an important indicator for physiological aging affected by glycative andoxidative stress. The mechanism by which these stress affects methylation age requires further investigation.

KEY WORDS: DNA hydroximethylation, biological clock, advanced glycation end products (AGEs), metabolic syndrome,		oxidative stress, aging, premature skin aging.

Introduction
Approximately 20 -25% of the World’s adult population
aged 40 -75 years have metabolic syndrome (MS) and they
are twice as likely to die from and three times as likely tohave a heart attack or a stroke in comparison to those without
MS. According to the International Diabetes Federation
definition1), a person can be characterized as having MS if hehas central obesity (waist circumference for women ≥ 80 cm,
man ≥ 94 cm) and additionally two of any of the following
factors: raised triglyceride (TG), reduced high-density
lipoprotein-cholesterol (HDL-C), raised blood pressure, raised
fasting plasma glucose (FPG). The cluster of cardiovasculardisease (CVD) risk factors that defy MS is now considered
to be the driving force for the uprising CVD epidemic 2). MS
maintains a chronic inflammatory reaction throughout the

body due to the presence of oxidative stress. Application ofearly treatment strategies may result in control of symptoms
and complications of MS. However, severe sequelae such as
myocardial infarction, cerebral stroke and disability remainvery high 3).
MS, due to the oxidative stress, supports a chronic
inflammatory reaction in the skin and in the other partsof the body 4). Oxidative stress is a condition of oxidant /antioxidant imbalance, in which the net amount of reactive
oxygen species (ROS) exceeds the antioxidant capacity of the
body. Excessive ROS can react with cellular macromoleculesand cause lipid peroxidation, protein oxidation and oxidative
DNA damage 5).
The skin is a major component of the antioxidant
defence system, primarily through its xenobiotic/ drug
biotransformation system, ROS-scavenging system and an

Corresponding to: Jana Janovska, MD
European Prevention Center Düsseldorf
Luise -Rainer-Straße 6 -10, 40235 Düsseldorf, Germany
TEL: + 49-211-83862850 e -mail: j.a.janovska@gmail.com
Co-authors: Dalle C, contacts@drclaudedalle.com

Glycative Stress Research 2024; 11 (2): 62- 70(c) Society for Glycative Stress Research_ 62 _Glycative Stress Research

excretory system mediated via sweat and sebaceous glands.
In the circumstances of chronic excessive energy uptake andinhibition of sebum secretion, excessive lipids are primarily
stored as adipose tissue, whereas excessive cholesterol canaccumulate in the arterial wall. Inhibition of sebum secretion
increases the levels of circulating lipids and cholesterol, andsubsequently the risk of dyslipidaemia and MS 6).
Nowadays we know good about ageing theories, which
we define as intrinsic and extrinsic. Intrinsic ageing theories
are genetically programmed events causing cellular damage
that accelerates aging of the body. Extrinsic are associatedless or more with environment, i.e., ultraviolet ( UV) damage.
Ageing itself is inevitable process accompanied by progressive
decline in physical functions and increased risk of disease,i.e., CVD, cancer. In fact, CVD, one of the most common
disease of aging, accounted for 30 % of all death worldwide
per year 7).
The process of ageing in multiple changes at both
molecular and cellular level, including cellular senescenceand telomere attrition, and epigenetic alteration 8). Telomere
length, which experiences progressive shortening during
replication of somatic cells is remarkable characteristic ofaging and linked with age-related health status 9).
Thus, various factors are intricately involved in vivo, andjust by analysing the relationship between DNA methylationand MS, oxidative stress, glycative stress (accumulation ofAGEs), and inflammation are involved. We have reported theassociation of AGE accumulation with skin manifestations,
i.e., epidermoid melanoma, seborrheic keratosis, facial
cutaneous telangiectasia, as well as with increased skin aging
index (SAI). We hypothesized that DNA methylation is
involved as the mechanism linking the two. In this study,
we analysed the association between glycative stress andbiological age, indices in terms of DNA methylation.

Methods
Current prospective study was done and both genderCaucasian patients were analysed age group 30 - 60 years
in Riga Stradins University. Altogether 296 patients wereanalysed. Analysed group included 2 specific categories MS
and non-MS (based on IDF criterion). Waist circumference
and body mass index (BMI) were conducted, as well as
lifestyle factors and skin ageing signs using SAI 10).
Generally, MS (n = 149) and Non-MS (n = 147) patientswere clinically and biochemically diagnosed with MS basedon the IDF (2006) criteria 1) :Essential major criteria:
・ Central obesity with a waist circumference of 80 cm (women)
and 94 cm (men).
・ Additional 2 minor criteria out of the following:・ Raised TG > 1.7 mmol/ L;
・ Reduced HDL - C < 1. 3 mmol/L (women) and < 1.0 mmol/L(men);
・ Raised blood pressure ≥ 130 mmHg (systolic) or/and ≥ 85
mmHg (diastolic);・ Raised FPG ≥ 5.6 mmol/L;
During the study several parameters were evaluated in all
patients:

Clinical examination:
・ Measurement of the arterial blood pressure by Korotkov’s
method.
・ Measurement of the waist circumference using centimeter.
・ Biochemical analyses were performed in E. Gulbis
laboratory; levels of total cholesterol (TC), fasting plasma
glucose (FPG), high - density lipoprotein-cholesterol( HDL-C), low- density lipoprotein-cholesterol (LDL- C )and C- reactive protein (CRP).

Oxidative stress parameters (selenium, superoxide
dismutase; SOD, malondialdehyde; MDA, glutathione; GPx)
were determined in the RSU Biochemistry Laboratory. The
principle for determination of MDA is to determine MDA
alone (in hydrochloric acid) or MDA in combination withhydroxynonenal (HNE) in the presence of methanesulphonicacid. Two molecules, 4-HNE and MDA, react with N-methyl-2-phenylindole at 45°C to form a stable chromophore with
an absorption peak at 586 nm 11, 12). GPx peroxidase isdetected automatically by spectrophotometry according to
the manufacturer’s instructions for the RX Daytona analyser( Randox laboratories, Ltd., Crumlin, UK). GPx peroxidase
catalyses oxidation of GPx (GSH) in the presence of cumenehydroperoxide. Oxidised GPx (GSSG) is further converted toa reduced form, GSH, by GPx reductase (GR) and NADPH,
while NADPH is oxidised to NADP +. GPx peroxidase
activity corresponds to a decrease in absorbance at 340 nm
caused by NADP oxidation. One unit corresponds to theamount of enzyme produced by the oxidation of 1.0 μM
NADPH to NADP + per minute at 340 nm at 37 °C.
For glycation index, the intensity of skin fluorescence
was measured by the AGE Reader TM (DiagnOptics B.V.,
Groningen, The Netherlands). The AGE Reader TM is a noninvasive device that measures tissue accumulation of AGEs
in human skin on the forearm, and the results are expressed
as values of skin autofluorescence (SAF).
The patient's clinical examination, blood pressure andwaist circumference were measured. Clinical examination of
the skin was performed using dermatoscopy (Dermlite DL;
Derma Medical Systems, Vienna, Austria). The detectedskin manifestations (seborrheic keratosis, actinic keratosis,
acanthosis nigricans, and facial telangiectasia) were divided
into several subtypes (mild, expressive, and extreme
expressive).
Biological age was determined by measuring DNA
hydroxymethylation status by LC-MS 13, 14) and correlationof the result to a reference cohort to calculate the biologicalage in Reunis laboratories. DNA hydroxymethylation wasmeasured for all patients. Hydroxymethylation measurement
was done using a gold standard technique (liquid
chromatography + mass spectrometry), the biological age
equivalent was calculated. AGE Reader was used to measure
AGE accumulation in skin by fluorescence techniques, SAF.

Ethical Standards

This study was conducted using existing materials
that were not linked to personal information. Our study was
designed in conformation to the Helsinki Declaration. The
study protocol was approved by the Committee of Ethics,
Riga Stradins University. No conflict of interest.

_ 63 _Glycation and Biological Clock: DNA Methylation Age

Statistics

Statistical methods were used, t-test for independent
samples, Spearman’s correlation, Mann Whitney test. Data
was documented and analysed with Microsoft Excel 2010
software.

Results

MS and MethylAge

Of a total of 296 subjects (age; 47.0 ± 11.2, BMI; 26.3
± 4.8), 149 (50.4%) were MS (age; 51.4 ± 9.8, BMI; 29.0
± 4.2) and 147 (49.6%) non-MS (age; 42.4 ± 10.8, BMI;
23.6 ± 3.6). The analysis was same as the previous report 15);comparing the MS and non-MS groups, the MS group
had higher BMI (p < 0.001), LDL-C (p < 0.001), TG (p <0.001), MDA (p = 0.003) were significantly higher ( Table 1).
MethylAge was significantly higher in MS (median; 33.5) vs.
non-MS (median; 61.7, p < 0.05, Fig. 1 ).

MethylAge and results

Correlation analysis was performed between MethylAge
and measurement results ( Fig. 2 ). The items that showedsignificant correlation with MethylAge were actual age (r =0.594, p < 0.05, Fig. 2-a), waist circumference (r = 0.261, p <0.05, Fig. 2-b), TG ( r = 0.317, p < 0.05, Fig. 2-c), SAI (r =0.318, p < 0.05, Fig. 2-d ).

MethylAge and skin lesions

The skin lesions were classified as seborrheic keratosis(n = 109), actinic keratosis (n = 25), acanthosis nigricans (n =16), aging wrinkles (n = 126), gravity wrinkles (n = 34), andfacial telangiectasia (n = 242).
Skin lesions that correlated with MethylAge and presenceof disease were seborrheic keratosis (r = 0.346, p < 0.05)
and lentigo pigmentation (r = 0.415, p < 0.05, Fig. 3 ). There

were no differences in other diseases between lesion andnon-lesion areas.

SAF, oxidative stress and skin aging

For SAF, an indicator of glycative stress, it has beenfound to be higher in MS (p = 0.024); Spearman and rankcorrelation analysis between SAF and measures also showedthat FPG (r = 0.345, p = 0.036), TC (r = 0.328, p = 0.023),
HDL- C (r = − 0.399, p = 0.019), and CRP (r = 0.372, p =0.028) 15).
As for the relationship with skin lesions, SAF was
significantly lower in individuals with black seborrheic
keratosis (r = − 0.034, p = 0.588), but there were no differences
between lesion and non-lesion areas in other diseases (Fig. 4 ).
There was also a significant positive correlation between
AGEs and SAI, indicating that the more AGE accumulationin the skin, the worse the skin condition (p < 0.02).
SAF was positively correlated ( p < 0.05) with theoxidative stress GPx ( Fig. 5-a), SOD ( Fig. 5-b), andvitamin D supplementation; the regression equation for the
relationship between SAF (y) and SOD (x) was y = 0.001164x+ 0.219931 ( R2 = 0.753, p < 0.001). When SOD is nearits minimum value of 1,145, the predicted value of SAF is
1.6; when SOD is near its maximum value of 2,24 0, thepredicted value of AGEs is 2.8.

MethylAge and SAF

The correlation between age of methylation and SAF
was analyzed using the Single Factor ANOVA test (trendline).
A significant correlation was found between age at methylationand SAF, and the equation y = 131.9x 2 − 490.1x + 491. 5 (R 2
= 0.989, p < 0.001), a quadratic regression equation, can beused to predict MethylAge (prognostic indicator) (Fig. 6 ). The
predicted MethylAge was 36.676 years when SAF was lessthan 1.8 and 51.676 years when SAF was 2.2; the MethylAge
increased with the SAF value, and the mean relative errorof these predictions was 11%.

Table 1. Profiles of the subjects.
unitMS(n = 149)

Non-MS(n = 147)

p valueAge

year

51.4 ± 9.8

42.4 ± 10.8

< 0.001

MethylAge

year

55.0 ± 19.7

40.9 ± 20.7

0.001

BMI

kg/m2

29.0 ± 4.2

23.6 ± 3.6< 0.001

Waist circumferencecm

99.4 ± 10.6

81.8 ± 10.3

< 0.001

LDL-C

mmol/L

3.6 ± 1.0

3.0 ± 0.7

< 0.001

HDL-C

mmol/L

1.6 ± 0.4

1.7 ± 0.4

0.001

TG

mmol/L1.9 ± 1.4

1.0 ± 0.5

< 0.001

CRP

mg/L

2.8 ± 3.6

1.8 ± 2.7

0.059

MDA

mM

3.0 ± 0.8

2.6 ± 0.6

0.003

Results are expressed as mean ± SD. MS, metabolic syndrome; MethylAge, DNA methylation age; BMI, body mass index; LDL-C,
low-density-lipoprotein cholesterol; HDL-C, high-density lipoprotein cholesterol; TG, triglyceride, CRP, C-reactive protein; MDA,
malondialdehyde; SD, standard deviation.

_ 64 _Glycative Stress Research

100

MethylAge

80

60

Indicator;
MethylAge

40

Non-MS(n = 149)

MS(n = 147)

3.0
28.5
33.5
56.6
90.4

16.4
38.6
61.7
70.0
85.6

Minimum
The 1st quartile
MedianThe 3rd quartile
Maximum

20

0
(- )

( +)

Metabolic syndrome

Fig. 1. MS and MethylAge.

Horizontal line indicates median, Bar shows minimum and maximum, box shows from the 1st to the 3rd quartile. MS, metabolic
syndrome; MethylAge, DNA methylation age.

a)b)
(year)
100

80

MethylAge

MethylAge

80
60
40

60
40
20

20
0

(year)
100

0

20

40

60

0

80

0

80

Chronological age (year)

c)

d)

140

(year)
80

MethylAge

80

MethylAge

120

Waist circumference (cm)

(year)
100

60
40

60
40
20

20
0

100

0

1

2

3

4

5

0

6

TG (mmol/L)

0

2

4

6

8

10

12

SA I

Fig. 2. Correlation analysis with MethylAge.
a) Chronological age, b) Waist circumference, c) TG, d) SAI. a: r = 0.594, p < 0.05, b: r = 0.261, p < 0.05, c: r = 0.317,
p < 0.05, d: r = 0.318, p < 0.05, n = 149. MethylAge, DNA methylation age; TG, triglyceride; SAI, skin aging index.

_ 65 _Glycation and Biological Clock: DNA Methylation Age( year)100

MethylAge

80

60

40

20

0
(−)
92

(+)
5

(−)
35

(+)
62

(−)
79

(+)
18

(−)
96

(+)
1

(−)
63

(+)
33

(−)
62

(+)
34

(+)
96

an
c ta
se
s

is

les

l es

t os

s

is

an

to s

ric

ra
ke

ni g

ink

ink

wr

gie

it y

wr

ra
ke

ei c

sis

rrh

ic

in g

av

le
Te

Gr

Ag

tin

bo

tho

go

an

nt i

Ac

Se

Le

Ac

Fig. 3. MethylAge in lesion and non-lesion areas.

Horizontal line indicates median, bar shows minimum and maximum, and box shows from the 1st to the 3rd quartile.
(+) lesion aareas, (−) non-lesion areas. Digit show number of cases. All skin problems or different skin problems do nothave all MethylAge data, that is why in graph we have different number of cases. MethylAge, DNA methylation age.

4.0

*

*

3.5

*

*

(+)
122

(−)
75

SAF

3.0

*

*

*
*

*
*

*

2.5

2.0

1.5

1.0
(−)
122

(+)
5

(−)
16

(+)
63

(−)
121

(+)
17

(−)
74

(+)
63

(−)
62

(+)
27

(−)
4

(+)
133

s

les

is

se

ink

c ta

wr

gie

it y

an

av
l es

t os

s

is

an

to s

ric

ra
ke

ni g

i nk

ra
ke

wr

ic

in g

tin

le
Te

Gr

Ag

Ac

ei c

sis

rrh

go

tho

bo

nt i

an

Se

Le

Ac

Fig. 4. SAF in lesion and non-lesion areas.

Horizontal line indicates median, Bar shows minimum and maximum, box shows from the 1st to the 3rd quartile.
Digit show number of cases. * p < 0.05 by t test. SAF, skin auto fluorescence.

_ 66 _Glycative Stress Research

b)
4.0

4.0

3.0

3.0

SAF

SAF

a)

2.0
1.0
0
4,000

2.0
1.0

5,000

6,000

7,000

8,000

9,000

0
1,100

10,0001,30001,500

GPx (nmol/g tissue)

1,700

1,900

2,000

2,100

SOD (U/g Hb)

Fig. 5. SAF and oxidative stress index: GPx, SOD.
a) GP x, b) SOD. Regression line a: n = 16, b: y = 0.001164x + 0.219931, R2 = 0.753, p < 0.001, n = 16.
SAF, skin auto fluorescence; GPx, gulutathion; SOD, superoxide dysmutase.

100

MethylAge

80

60

40

20

0

20

30

40

50

60

70

SAF

Fig. 6. SAF and MethylAge.

Regression line; y = 131.9x ² − 490.1x + 491.5, R² = 0.989, p < 0.001, n = 150. SAF, skin auto fluorescence;
MethylAge, DNA methylation age.

Discussion
In this study we measured the MethylAge and analyzed
its relationship to physical information and differences byskin lesion. The items that showed significant correlation withMethylAge were chronological age, waist circumference, TG,
SAI, and SAF. Skin lesions included seborrheic keratosis,
actinic keratosis, epidermoid melanoma, aging wrinkles,
gravity wrinkles, and facial telangiectasia, of which
seborrheic keratosis and lentigo pigmentosa were the items
that showed differences in methylation age between lesion
and non-lesion areas.
DNA hydroxymethylation, which is the criterion for
MethylAge, has been elucidated to occur as an epigenomicchange and can be physiological or non-physiological. The
process of non-physiological changes involves oxidation andcarbonylation reactions at the molecular level, which are
involved in lesion formation and aging of MethylAge. Theseissues are discussed below, citing the literature.

How epigenetic is linked to aging?

Epigenetics has been defined as heritable changes ingene function that take place without a change in the DNA
sequence. The study of epigenetics and its involvement
in metabolic diseases is still a young research field, but it
is now attracting a lot of attention and growing at a fast
pace. Methodological improvements, with crucial progresseach year, have contributed to the current interest andadvancements in the field. The epigenome includes DNA
methylation, histone modifications, and non-coding RNAs,
which can regulate cell differentiation, cell-specific gene
expression, parental imprinting, X chromosome inactivation,
as well as genomic stability and structure. DNA methylation
takes place on a cytosine, mainly in CG context or the socalled CpG sites, and to a less extent in non-CG context 16).
The degree of active or inactive states of our genes isdynamic and can be impacted by environment; UV exposure,radiation, chemicals, medications, and DNA methylation.

_ 67 _Glycation and Biological Clock: DNA Methylation Age

Age dependent changes in DNA methylation include
global hypomethylation Region specific hypermethylation 17).
This finding has impelled researchers to develop age predictors
based on the correlation between methylation changes andchronological age.
DNA methylation, epigenetic modification, refers to thetransfer of methyl (CH 3) group from S-adenosyl methionine(SAM) to the fifth position of cytosine nucleotides, forming
5-methylcytosine (5mC). Important that abnormal methylation
plays an important role in the pathogenesis of autoimmune
disease, metabolic syndromes, and neurological disorders 18).
Factors impacting epigenetic age we can divide into
extrinsic and intrinsic. Insulin and its resistance, CRP, BMI
and waist-to-hip ratio, systolic blood pressure all thesefactors mat impact epigenetic age.
Important factor for accelerated ageing is obesity.
Telomere length is inversely correlated with lifespan, andtelomere dysfunction accelerates the aging process. Obesity
is associated with chronic latent inflammation and oxidative
stress, that may accelerate shortening of telomeres. Humanstudies indicate that telomere shortening is directly correlated
to adiposity, and telomere length is inversely associated with
BMI 19).

Epigenetics and obesity
The prevalence of obesity is increasing at a rate thatcannot be explained by genetic factors; rather environmental
factors are the likely driver. Because of aging populations
and an increasing prevalence of obesity, the number ofpatients with type 2 diabetes mellitus ( T2DM) is increasingat alarming rates worldwide, and the current prevalence of
422 million people is expected to rise to 592 million in 2035.
Of note, 5 million people die from diabetes every year, mostoften because of cardiovascular events 20). Considering therate of the obesity epidemic, it is an appealing thought thatour genes are programmed to store fat or to store as much as
possible of all the excess energy the body is exposed to 21).
Prospective studies comparing the DNA methylome fromvarious tissues before and after weight loss have shown small
but widespread changes across the genome and suggested
that baseline DNA methylation can be used as a biomarker
for the outcome, i.e., the weight loss response 22). Obesity
and related phenotypes induce epigenetic dysregulation,
seen as increased variability in DNA methylation. Obesity is
considered a heterogeneous disease, which could influence
the outcome, together with different genetic background,gender, and tissue specificity. The latter is an important
limitation, as many studies are performed on blood cells,
which most likely do not contribute to obesity.

DNA glycation

In recent years, the role of AGEs in promoting andexacerbating metabolic and skin abnormalities has received
increasing attention. AGEs are produced when reducing sugars
are non-enzymatically bound to proteins and lipids. This
process is facilitating by is facilitated by the hyperglycemicand hyperlipidemic environment characteristic of many
metabolic disorders, including diabetes, obesity, MS, and theircomplications 15). AGEs play crucial role in the pathogenesisof CVD, kidney, Alzheimer’s, neurological, T2DM and joints

diseases and aging process. Depletion of cellular antioxidant
GSH led to increase binding of glucose derivatives to DNA.
DNA can be cross-linked with different substances, some of
the nucleotide AGEs are N2-carboxymethyl oxyguanosine,
5-glycolyldeoxycytidine 23).
AGEs yield characteristics type of nucleotide adducts
which are indicator of many abnormal conditions, i. e.,oxidative stress, arthritis. AGEs cause damage to DNA
which is associated with important factors for mutagenesis,
carcinogenesis and diabetes mellitus 24). Reaction with sugars
and free amino group on DNA is the first step in the evolutionof these molecules through a complex series of very slow
reactions in the body known as Amadori reactions, Schiffbase reactions, and Maillard reactions, which may all lead toAGEs. Some AGEs are very useful compounds, but others
are very reactive as they are responsible in many age-related
chronic diseases what was mention above 25). It effects thenucleic acid by modifying, mutation and breaking the strandof DNA which are the process on glycation. Glycation of DNA
gives rise to characteristic nucleotide adduct, some of whichhave been found to increase in oxidative stress. Potent glycating
agents in physiological system are a-oxoaldehydeglyoxal,
methylglyoxal (MGO) and 3- deoxyglucosone (3DG) 26).
These adducts are also formed by glycation of DNA withglucose and ascorbic acid; since, glucose and other saccharide
derivatives fragment to form glyoxal (GO) and MGO in theearly stages of glycation reaction-the Namiki pathway ofglycation 27). Glycated DNA is a toxic compound called as
glycotoxin may contribute to the toxicity of several anti-tumor
agents and over expression of enzymatic anti-glycation defensewith multi drug resistance in major classes of tumors 28).

AGEs, oxidative stress and carbonyl stress

AGE formation takes place under normal physiologic
conditions but is accelerated in hyperglycemia. AGEs may
also form from non-glucose sources including lipid and aminoacid oxidation 29).
Increased level of ROS cause oxidative stress; in analogy,
increased concentration of sugars (glucose, deoxyglucose,fructose, ribose and triose phosphates) and active dicarbonylcompounds (GO, MGO) can cause “carbonyl stress” resulting
in the increased rate of formation of AGEs 30).
Accumulation of glycation products is associated withvarious diseases including, first of all, diabetes and diabetic
nephropathy, microangiopathy and atherosclerosis. Regarding
atherosclerosis, AGEs play a significant role in the formationand progression of atherosclerosis lesions AGE-cross linkformation results in arterial stiffening with the loss of elasticityof large vessels 30). Increased AGE accumulation in the diabetic
vascular tissues has been associated with the changes infunctions of endothelial cells, macrophages and smoothmuscles cells 31).

Significance of the present results

In the present study, MethylAge was associated withwaist circumference, hypertriglyceridemia, the presenceof MS, and also with SAF, suggesting that glycative stress
may play a major role. Carbohydrate-derived aldehydes,i.e., GO, MGO, have been shown to be formed 32, 33 ). TG,
once oxidized, also produces fatty acid-derived aldehydes,_ 68 _Glycative Stress Researchi.e., MDA, HNE, acrolein. The high reactivity of thesealdehydes suggests that they may induce non-physiologicalcarbonylative modifications at the epigenomic modificationsites of histone proteins or DNA. In the future, it is necessary
to take into account non-physiological epigenomic changes
in order to promote health and prevent pathological aging.

Conclusions
Assessment of MethylAge using skin samples may
be an important indicator of the degree of physiologicalaging of the body undergoing epigenomic changes due toglycative stress and oxidative stress. The mechanism bywhich glycative stress affects MethylAge requires further
investigation.

Funding
None in particular.

Conflict of interest declaration
There are no specific applicable matters.

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