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Diabetes & Vascular Disease Research

10(6) 489 –497

© The Author(s) 2013

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DOI: 10.1177/1479164113494881

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Introduction

The World Health Organization estimates that more than

439 million adults (aged 20–79 years) in the world will

have diabetes in 2030 and twice as many people will have

impaired glucose tolerance (IGT).1 The main reasons for

disability and mortality caused by diabetes are microvascu-

lar and macrovascular complications leading to cardiovas-

cular disease.2,3 At present, the diagnosis of diabetes

complications is made only at the clinical stage, and treat-

ment in most cases is directed towards reducing the pro-

gression of angiopathy.

The magnitude of endothelial dysfunction in diabetics is

often related to the severity and duration of the illness, as

well as to glycaemic and glycosylated haemoglobin A1c

levels.4 It is well recognized that vascular endothelial cells

play a major role in vascular tone regulation (vasodilationand vasoconstriction), in haemostasis (synthesis and inhibi-

tion of fibrinolysis and thrombocyte aggregation factors)

and in the development of remodelling processes and local

inflammation.5 The very location of the endothelium at the

blood flow boundary makes it highly sensitive to various

factors, including hyperglycaemia, which increase the risk

of vascular diseases.6,4

In the past years, methods for the exploration of cutane-

ous microcirculation have aroused considerable interest of

researchers. The skin is the most accessible site for non-

invasive assessing of microcirculation and for performing

measurements.7 Being a dynamic structure, the human skin

can be used as a microcirculation model for investigating

the generalized microvascular function. Investigations haverevealed a correlation of vascular reactivity in different

vascular beds over the body (e.g. coronary arteries, brachial

artery and skin microcirculation) of healthy people and

patients, at least for endothelial functions.8

Both the neural and local humoral factors affect the skin

blood flow. The endothelium plays an important role in the

regulation of vascular tone, and the endothelial function is

the ability to release substances, which cause local arteri-

olar vasodilation by inducing relaxation of the underlying

smooth muscle cells.9

There are no methods capable of providing accurate

quantitative estimation of the skin blood flow. Today, laserDoppler flowmetry (LDF) is widely used in clinical

research monitoring of the microvascular blood flow.10 To

Assessment of endothelial dysfunction inpatients with impaired glucose toleranceduring a cold pressor test

Elena Smirnova1, Sergey Podtaev2, Irina Mizeva2

and Evgenia Loran1

Abstract

The objective of this study is to explore changes in microvascular tone during a contralateral cold pressor test and tocompare the results obtained in healthy subjects and in patients with impaired glucose tolerance (IGT) and type 2 diabetes.Low-amplitude fluctuations of skin temperature in the appropriate frequency ranges were used as a characteristic for themechanism for vascular tone regulation. In total, 13 adults with type 2 diabetes aged 40–67 years and 18 adults with IGT

aged 31–60 years participated in this pilot study. The control group included 12 healthy men and women aged 39–60years. The response to the cold pressor test in patients with type 2 diabetes and with IGT differs essentially from thatof healthy subjects in the endothelial frequency range. Endothelial dysfunction occurs in the preclinical stage of diabetesand manifests, in particular, as a disturbance of the endothelial part of vascular tone regulation.

Keywords

Impaired glucose tolerance, type 2 diabetes, endothelial dysfunction, skin temperature fluctuations

1Perm State Medical Academy, Perm, Russian Federation2Institute of Continuous Media Mechanics, Ural Branch of Russian

Academy of Science, Perm, Russian Federation

Corresponding author:

Irina Mizeva, Institute of Continuous Media Mechanics, Ural Branch

of Russian Academy of Science, ak.Koroleva 1, 614013 Perm, Russian

Federation.

Email: [email protected]

DVR10610.1177/1479164113494881Diabetes& VascularDisease ResearchSmirnova et al.

Original Article



490 Diabetes & Vascular Disease Research 10(6)

avoid movement artefacts having a strong effect on the

LDF signal, a person must lie completely still, and the

probe must be in close contact with the skin.

Information about cutaneous microcirculation can also

be obtained by recording the low-amplitude skin tempera-

ture oscillations.11 In this case, the results of measurements

weakly depend on the mechanical transposition of temperature sensors, and the level of artefacts is quite low dur-

ing long-term measurements or functional tests. In our

work, the fluctuations of skin temperature in the appropri-

ate frequency intervals were used as a characteristic of the

vascular tone regulation mechanism. Low-amplitude skin

temperature fluctuations are caused by periodic changes in

the blood flow due to oscillations in vasomotor smooth

muscle tone.12,13 A cross-spectral analysis of the variations

in blood pressure waveforms and temperature shows a

high degree of correlation between the spontaneous fluc-

tuations of skin temperature and the vasomotor activity of

small arteries and arterioles in subcutaneous tissues.14

Weak phase coherence between temperature and blood

flow was observed for unperturbed skin, and due to heat-

ing, it increased in all frequency intervals.15 A wavelet

spectral analysis of fluctuations in the vasomotor tone of

the microcirculatory system registered by LDF and preci-

sion thermometry16 gives information about the local,

hormonal and neurogenic factors of microcirculatory

regulation.

It has been found that myogenic fluctuations are regis-

tered in the frequency range of 0.05–0.14 Hz, neurogenic

activity is observed in the range of 0.02–0.05 Hz and the

endothelial function of blood vessels is determined in the

range of 0.0095–0.02 Hz.17,10 The oscillations with fre-quency around 0.1 Hz correspond to the appearance of

vasomotion – rhythmic oscillations in the vascular tone.18

Vasomotions are caused by spontaneous rhythmic contrac-

tions of the vascular smooth muscles. These contractions

are always preceded by changes in the membrane potential

and intracellular free calcium concentration.19,20 The fre-

quencies around 0.03 Hz correspond to the neurogenic

activity.21 Kastrup et al.22 found out that the oscillations

around 0.03 Hz disappeared after local and ganglionic

nerve blockade in a chronically sympathectomized tissue in

a human. The studies examining the effects of local anaes-

thesia by Landsverk et al.23

supported the validity of therelation between the sympathetic activity and the spectral

peak in the interval of 0.02–0.05 Hz. The frequencies

around 0.01 Hz are associated with the NO-related endothe-

lial activity. Based on the results of tests on simultaneous

iontophoretic application of acetylcholine (ACh, an

endothelium-dependent vasodilator) and sodium nitroprus-

side (SNP, endothelium-independent vasodilator), Kvernmo

et al.24 and Kvandal et al.25 infer that the oscillations around

0.01 Hz evidently originate from the endothelial activity.

By means of the spectral analysis, the LDF signal can be

decomposed into components with different frequencies.

The most widely used spectral methods are the fast Fourier

transform, autoregressive modelling and wavelet analysis.

A wavelet transform is a kind of ‘local’ Fourier transform,

which allows us to isolate a given structure in the physical

space and in the Fourier space. The localization property of

wavelets makes the wavelet analysis capable of analysing

the non-stationary systems and detecting the dynamical parameters.26 In this article, we used the Morlet wavelet

because it provides good time resolution at high frequen-

cies and the best frequency resolution for low-frequency

components.

A common approach for testing the endothelial function

is to perform functional tests inducing local or systemic

changes in the skin blood flow. The stimuli used are phar-

macological and physical ones. The most important factors

for local heating and cooling tests are flow-mediated

vasodilatation or blood vessel vasoconstriction and varia-

tions of temperature.27 The cold pressor test, as a natural

constrictive test,28,29 allows us to estimate the adequacy of

the endothelial, myogenic and neurogenic mechanisms of

vascular tone regulation by studying low-frequency fluctu-

ations of skin temperature. The objective of this study is to

explore changes in the vascular tone over the endothelial,

neurogenic and myogenic frequency ranges during a con-

tralateral cold pressor test by performing a wavelet analysis

of the skin temperature fluctuations and to compare the

results obtained for healthy subjects and patients with IGT

and type 2 diabetes.

Subjects and methods

Subjects

The control group (first group) consisted of 12 healthy men

and women aged 39–60 years. Patients with cardiovascular

diseases (myocardial infarction, angina pectoris, cerebro-

vascular diseases, peripheral arterial disease or cardiac

insufficiency) and microvascular disorders (proteinuria and

retinopathy in stages 2 and 3) were excluded from the

investigation. The patients were examined at the Perm

Endocrinology and Diabetes Clinic. Clinical and laboratory

features are detailed in Table 1. The IGT group (second

group) included 18 patients aged 31–60 years with IGT,

who had a 2-h plasma glucose concentration of 7.8–11.0mmol/L measured by an oral glucose tolerance test. The

third group comprised 13 patients with type 2 diabetes aged

40–67 years (average diabetes duration of 10.6 ± 1.3 years)

who used glucose-lowering medication: 8 used a combina-

tion of metformin and gliclazide, 2 received insulin therapy

and 3 are treated with a combination of insulin and met-

formin. All patients in the third group have distal diabetic

polyneuropathy.

The study protocol was approved by the local ethics

committee of the Perm State Medical Academy. All subjects

gave written informed consent.



Smirnova et al. 491

Measurement procedure

The tests were carried out at room temperature of 22.5°С ±

0.5°С. Measurements were made after a fast and 4-h absti-

nence from smoking. The patients did not take any medica-

tion affecting vascular tone (nitrates or calcium antagonists).

During the contralateral cold test, the participants lay in the

supine position. The skin temperature was measured on

the palm surface of the distal phalanx of the index finger of

the right hand. The output signals of the temperature sensor

(HRTS-5760; Honeywell International, Inc., USA) were

transmitted after amplification to the 18-bit bipolar analogue-to-digital converter (AD7793; Analog Devices, USA) scaled

to ±5 V with sampling frequency of 200 Hz. For the tempera-

ture range of 20°C–40°C, with consideration for signal-to-

noise amplifier ratio, the actual resolution of temperature

was 0.005°C. During the measurements, all necessary pre-

cautions were taken to reduce the effect of external heat

flows on the thermistor recording the skin temperature. The

thermistor was placed in a specially designed plastic case (20

× 30 × 10 mm3) filled with a material with low thermal con-

ductivity ( λ < 0.02 W/(m K)) for its protection against ambi-

ent temperature variations. The case also allowed the sensors

to be fixed on the skin surface with a medical plaster, which

prevents sensor displacements during measurements.

Cooling of the contralateral limb (left hand) minimized the

motion artefacts of the sensor placed on the measured limb

(right hand) and reduced the direct effect of cooling on the

sensor during the registration procedure.

Temperature registration began after the establishment

of a stationary thermal regime approximately 10 min after

the beginning of the test. A distinct response to the cold test

was recorded only if there was a sufficient degree of

vasodilatation, which corresponds to a minimum initial

skin temperature of 30°С. During the cold test, the left hand

was immersed in a pan with an ice-water mixture (at 0°С)

for 3 min. Skin temperature measurements were carried out

continuously for 10 min before the test, for 3 min during the

test and for 10 min upon completion of the test (Figure 1,

upper panel).

Software and statistical analysis

A frequency–temporal analysis of temperature fluctua-

tions was made using gapped wavelet analysis.30,31 It has

several advantages over traditional time–frequency tech-niques based on Fourier analysis (e.g. short-term Fourier

transform), including a tailored time and frequency reso-

lution and a reduction in the spectral cross-terms.26

We applied the inverse wavelet transform in order to

reconstruct the signals reflecting the myogenic, neuro-

genic and endothelial activities (Appendix 1). Each of the

three signals is quasi-periodic signal consisting of a sum

of harmonics in the appropriate frequency range. For this

task, wavelet transforms are made with respect to a

Morlet mother wavelet. When choosing parameters for

the Morlet wavelet, care must be taken to ensure the bal-

ance between the time and frequency resolution. In this

work, we restricted ourselves to a relatively short dura-

tion of cold test (180 s) and a maximum scale of pulsation

(70 s – the mean period of oscillation, caused by endothe-

lial activity). Morlet wavelet (10) with κ = 1 provides a

rather good time resolution for this case, but insufficient

frequency resolution, which as a result leads to overlap-

ping of the frequency ranges. To diminish this effect, the

boundaries of the frequency ranges were corrected (in

comparison with Shiogai et al.10) in the following way:

myogenic frequency range = 0.14–0.07 Hz, neurogenic =

0.031–0.026 Hz and endothelial = 0.0139–0.0095 Hz.

Table 1. Baseline patient characteristics.

1 – Control(n = 12)

2 – IGT(n = 18)

3 – Diabetes(n = 13)

p1-2

p1-3

p2-3

Age 47 ± 11 52 ± 8 53 ± 7 0.44 0.81 0.48

Sex: male (%) 35.7 27.7 15.4

Body mass index (kg/m

2

) 28 ± 4 33 ± 5 33 ± 5 0.01 0.54 0.006Systolic blood pressure (mmHg) 128 ± 9 127 ± 12 132 ± 6 0.42 0.06 0.43

Diastolic blood pressure (mmHg) 73 ± 8 75 ± 8 81 ± 7 0.3 0.04 0.09

HbA1c (%) 5.1 ± 0.4 6.3 ± 0.5 9.1 ± 1.7 0.00003 0.0008 0.00007

Fasting glucose (mmol/L) 4.9 ± 0.3 5.9 ± 0.8 7.4 ± 2.9 0.001 0.03 0.35

Postprandial glucose (mmol/L) 6.2 ± 0.4 8.8 ± 1.5 9.1 ± 2.7 0.0006 0.04 0.59

C-peptide (nmol/L) 1.2 0 0.9 ± 0.5

Total cholesterol (mmol/L) 4.0 ± 0.3 5.5 ± 0.9 5.7 ± 1.1 0.0003 0.0001 0.78

LDL cholesterol (mmol/L) 3.2 ± 0.3 3.4 ± 0.6 3.5 ± 0.3 0.28 0.56 0.89

HDL cholesterol (mmol/L) 1.6 ± 0.1 1.2 ± 0.2 1.3 ± 0.3 0.009 0.02 0.86

Triglycerides (mmol/L) 1.2 ± 0.1 1.8 ± 0.8 2.1 ± 1.3 0.008 0.01 0.56

HbA1c: haemoglobin A1c; LDL: low-density lipoprotein; HDL: high-density lipoprotein.The results are presented as mean ± standard deviation. The Mann–Whitney U-test is used to calculate p.




After mathematical processing of the signal, we obtained

fluctuations in three frequency ranges corresponding to

myogenic, neurogenic and endothelial mechanisms of vas-

cular tone regulation. The contribution of different mecha-

nisms of vascular tone regulation was estimated in terms of

the mean-square amplitudes of the skin temperature oscilla-

tions δ T in the corresponding frequency range.

The mean-square amplitudes of the fluctuations were

calculated over four time intervals (Figure 1(a)). The base

level interval of 300–500 s (t 0) was selected with reference

to the time needed to establish a stationary thermal regime

in the system before the cold test. During this time, the patient was in a quiescent state, and the mean-square ampli-

tudes of fluctuations obtained during this time were used as

a reference level for calculating relative changes in the

amplitudes during and after the test. The response to the

cold test was registered during the interval t 1 (650–730 s).

After termination of the cold test, two intervals were used

to estimate the dynamics of the recovery recreation pro-

cess: interval t 2 was the first 3 min after the cold test (830–

960 s) and interval t 3 was 6 min after exposure to cold

(960–1100 s). Details of the experimental scheme are pre-

sented in the upper panel of Figure 1.

The response of each mechanism of vascular tone regu-

lation was estimated in terms of relative changes in the

mean-square amplitudes of temperature fluctuations in

comparison with the mean-square amplitudes under basal

conditions (time interval t 0) κ i i

T T T = −( ) /δ δ δ 0 0 , where

δ T i are the mean-square amplitudes for the corresponding

time intervals (i = 1, 2, 3). The parameter κ i

E N M , , is defined

for each frequency range ( E – endothelial, N – neurogenic

and M – myogenic). For example, κ 1

0 5 E

= − . means that

the mean-square amplitude of the oscillations in the

endothelial frequency range decreases by 50% during cool-

ing (time interval t 1 ) with respect to the basal mean-square

amplitude; κ 3

0 1 M = . indicates that during the relaxation

phase (time interval t 3 ), the mean-square amplitude of pul-sation increases by 10% compared to the basal level of the

pulsation amplitude.

The original algorithms of the wavelet analysis were

realized in C++. The data are represented as M ± SD, where

M is the average mean value and SD is the standard

deviation.

A comparison between groups was made using a non-

parametric statistic (the Mann–Whitney U -test).The

Wilcoxon test was used for comparison of paired data,

p values < 0.05 were considered statistically significant.

Statistical analysis was performed using Mathematica 7.0

and statistical software STATISTICA 6.0.

Results

The typical skin temperature as a function of time for a

healthy person during the indirect cold test is given in Figure 1,

upper panel. Figure 1(b) to (d) shows the results of wavelet

filtration of the temperature fluctuations δ T depicted in

Figure 1(a) for the frequency ranges corresponding to the

endothelial (Figure 1(b)), neurogenic (Figure 1(c)) and

myogenic (Figure 1(d)) mechanisms of vascular tone regu-

lation in healthy people.

Figure 1. Typical skin temperature behaviour for a healthyperson during the contralateral cold test. Upper panel:

experimental design scheme. Lower panel: temperature of theleft hand and time intervals. Panel (a): temperature record forthe contralateral extremity. Panels (b, c and d): wavelet filtrationof temperature in different frequency ranges – (b) endothelialrange, (c) neurogenic range and (d) myogenic range.



Smirnova et al. 493

Under stationary conditions (interval t 0

), the temperature

is liable to fluctuations. During the cold test (interval t 1

),

the temperature of the contralateral limb decreases, and

simultaneously, the amplitudes of the fluctuations in the

frequency ranges decrease (Figure 1(b) to (d)). After termi-

nation of the cold tests (intervals t 2

and t 3) throughout the

recovery period of approximately 3 min, the temperature

rises and the intensity of fluctuations increases.During the cold test for all groups, no significant changes

of the mean temperature in the time intervals were recorded

(Table 2). It is evident that the mean temperature dynamics

in both healthy and non-healthy patients undergoing cold

test is practically the same, and therefore, the absolute mag-

nitudes are of low informative value. Unlike the analysis of

the average values of temperature, the frequency analysis

of the skin temperature fluctuations allows us to gain dif-

ferential information on the vascular response to the cold

test. In the control group, during the cold test, the amplitude

of the skin temperature fluctuations in the endothelial, the

neurogenic and myogenic ranges decreased and then recov-

ered to the initial values within 3 min (Table 3, Figure 1).

The response to the cold test studied in patients with

type 2 diabetes (group 3) differed from that of healthy peo-

ple. After a decrease, the amplitudes of the skin tempera-

ture fluctuations did not recover except for the neurogenic

range (Figure 2). In the endothelial and myogenic ranges,

the increase of the amplitudes after the test was unreliable.

Furthermore, during the next 10 min, the amplitudes of the

fluctuations did not increase. In the neurogenic range, after

the completion of the test, the amplitudes of fluctuations

increased and reached their initial values.

The results for IGT patients (group 2) were similar to the

results for group 3 (Table 3). After cessation of cold expo-sure, we obtained reliable difference between the ampli-

tudes of the fluctuations during the cold test and the

amplitudes observed within the first 3 min in the neuro-

genic range, and then, the temperature fluctuations reached

their initial values. In the endothelial and myogenic ranges,

the amplitudes of the fluctuations decreased, and their sub-

sequent increase was of unreliable character compared to

the amplitudes of the fluctuations during the cold test.

Hence, the absence of a statistically significant difference

in the amplitudes of the skin temperature fluctuations in the

endothelial and myogenic ranges during and after the cold

pressor test suggests that the impairments of the vasodila-

tion mechanisms in patients with type 2 diabetes and IGT

patients are of a similar character.

The wavelet spectrum analysis of the temperature

records obtained in control group revealed the shift of myo-

genic frequency. The myogenic oscillation frequency was

0.097 ± 0.007 Hz during rest (time interval t 0) and 0.090 ±0.009 Hz in the cold test ( р < 0.05). During the recovery

period (t 2), the myogenic frequency increased and became

equal to 0.094 ± 0.008 Hz (differences in the pairs t 0 – t 2 and

t 2 – t 1 are not significant), and in the time interval t 3, this

value was equal to 0.090 ± 0.010 Hz (differences are also

not significant). These results are in qualitative agreement

with the observations discussed in Sheppard et al.15

However, some data sets do not contain distinct maxima in

the energy spectra of temperature oscillations, which are

required to define adequately the frequency shift; therefore,

we investigated nine temperature records of control sub-

jects, four records of the IGT group and six records of the

diabetes group. The data showed that the myogenic fre-

quency shift obtained for these groups was not significant.

These are only preliminary results, which may be used as a

basis for a more comprehensive investigation.

Discussion

One of the most significant functions of the endothelium is

to provide adequate cardiovascular tone, which is affected

by different internal and external factors. In this study, the

cold test plays the role of a physiological pressor agent. A

massive stimulation of thermoreceptors during exposure to

cold leads to activation of the sympathetic tone and a mod-

erate increase of catecholamines in the blood plasma, but

does not increase the frequency of the heartbeat. These pro-

cesses may cause vasoconstriction (in arteries, arterioles

and arteriovenous anastomoses) and possibly raise the arte-

rial blood pressure.27,32

Our investigation showed that vasoconstriction during

the cold test in patients without obvious vascular and meta-

bolic disorders is accompanied by a decrease in the ampli-

tudes of the skin temperature fluctuations. After completion

of cold exposure, the amplitudes regain their initial values

in the myogenic, neurogenic and endothelial frequency

ranges. This reaction can be considered to be an adequate

response to the cold pressor test. The group of patients withtype 2 diabetes was characterized by impaired reactions in

the endothelial and myogenic frequency ranges. In the

neurogenic frequency range, the amplitudes of oscilla-

tions decrease but to a lesser extent compared to the con-

trol group. We consider these changes to be due to an

impairment of the vasodilator mechanisms in patients with

endothelial dysfunction. Differences in body mass index

(BMI), blood pressure and lipids could contribute to vascu-

lar reactions, but we did not observe a correlation of these

parameters and the endothelial reaction to the cold pressor

test because of rather small and heterogeneous groups for

Table 2. Mean values of the right index finger skintemperature (°C) in the different time intervals for the threeinvestigated groups during the contralateral cold test.

t 0

t 1

t 2 t

3

Control 35.9 ± 2.7 35.7 ± 1.9 35.4 ± 1.7 35.7 ± 1.8

IGT 35.8 ± 1.6 35.6 ± 1.3 36.0 ± 1.5 36.2 ± 1.7

Diabetes 34.8 ± 2.2 34.9 ± 2.2 35.0 ± 2.2 35.2 ± 2.1

IGT: impaired glucose tolerance.



Smirnova et al. 495

the statistically meaningful correlation analysis. Changes in

lipid levels and arterial pressure were typical for diabetes,

IGT and could certainly influence the endothelial dysfunc-

tion. However, most authors support the idea that hypergly-

caemia (postprandial and fasting) is the major factor

responsible for vascular dysfunction.33–35

Long-lasting hyperglycaemia stimulating a polyol path-way of the glucose exchange essentially reduces the amount

of glutathione and nicotinamide adenine dinucleotide phos-

phate (NADPH) in endothelial cells. Moreover, hypergly-

caemia intensifies the activity of diacylglycerol and protein

kinase С, which inhibit NO synthase and reduce NO pro-

duction. Chronic hyperglycaemia facilitates the creation of

glycohaemoglobin and other products of final glycosyla-

tion, which lower NO activity, and is another additional

factor in the impairment of the endothelial function.36

When the endothelium is exposed to hyperglycaemia, an

array of negative intracellular events facilitates its dysfunc-

tion. In diabetic patients, the exposure of coronary circula-

tion to increasing amounts of ACh results in a paradoxical

constriction instead of vasodilation. Contraction instead of

vasodilation induced by ACh is mediated via the M3 sub-

type of muscarinic receptors in coronary arteries when

endothelial integrity is lost. This response suggests that

endothelial cells exposed to hyperglycaemia are involved

in the apoptotic process, leading to intimal denudation.37

However, diabetes mellitus is characterized by the

development of complications such as autonomic neuropa-

thy, which manifests as an impairment of vascular tone

regulation by the parasympathetic and sympathetic nervous

systems. Presumably, the high concentration of glucose in

the blood plasma blocks the adrenoceptors in blood vessels,which reduces their ability to contract in response to the

actions of catecholamines and other vasoconstrictors.2

Indirect evidence for the impairment of thermoregulatory

control of skin blood flow in patients with type 2 diabetes

has been presented in a number of articles, which includes

disorders of the sympathetic control of diaphoresis and

arterial blood pressure.28

Therefore impaired vasodilatation in patients with type

2 diabetes can be considered both as a reduction in the con-

tent of vasoactive substances (NO and prostacyclin) and the

prevalent activity of the sympathetic nervous system dys-

function, which is associated with autonomic neuropathy inthe skin.38

IGT patients have diabetes-like changes in the ampli-

tudes of skin temperature fluctuations in the endothelial

frequency range while the physiological reaction in the

neurogenic range remains invariant. These data suggest

that the endothelial dysfunction has already developed in

the preclinical diabetes stage, and the progression of glu-

cose metabolism disorders aggravates the pathological pro-

cess, which causes impairment of the endothelial and

myogenic effects of vasodilation.

Possible causes of weakening the myogenic frequency

pulsations during cooling are investigated in Sheppard

et al.15 There seems to be several reasons for the immedi-

ate decrease in the frequency of the myogenic oscillations

in the skin blood flow due to cooling. First, the reduced

perfusion slows down the metabolic activity in the smooth

muscle fibres and thus causes a decrease in the rate of

their spontaneous oscillations; second, the reduced fre-

quency of oscillation is a homeostatic response to cooling,which tends to increase the effective vascular resistance

and reduces blood flow. Another possible reason of this

effect is that despite the fact that cyclic myogenic varia-

tions of blood flow are related to spontaneous changes in

the tone of arterioles, they might be modulated by sympa-

thetic nerve activity.19 Therefore, the central nervous sys-

tem can exert a certain action on the vasomotion frequency

under in vivo conditions. This may possibly be of patho-

physiological significance since the vascular dysfunction

in diabetes is correlated with the development of diabetic

neuropathy, and vasomotion disappears simultaneously

with the appearance of neuropathy.39 The differences in

myogenic frequency changes obtained for the control

group, IGT and diabetes subjects can serve as additional

diagnostic criteria, but they require a more detailed

investigation.

Study limitations

Special emphasis should be placed on the limitations inevi-

tably occurring in our investigations. First, the sample size

was relatively small. Second, the study was mainly done on

female population; no gender differences were taken into

account during the cold pressor test. However, as it is

shown in Shiogai et al.,10 the blood flow dynamics and car-diovascular reactions such as endothelium-dependent vaso-

dilation are related to gender differences.

Conclusion

We have developed a new technique for assessing endothe-

lial dysfunction, which is based on the analysis of skin tem-

perature fluctuations. The method has high sensitivity in

detecting abnormal endothelial function, and thus, it should

be developed further and verified in practical applications.

Cold exposure in subjects without vascular pathology leadsto a reduction of skin temperature fluctuation amplitudes in

the endothelial, neurogenic and myogenic frequency ranges,

which afterwards return to their initial values. In patients

with type 2 diabetes and IGT patients, after termination of

cold exposure, the amplitudes of skin temperature fluctua-

tions in the endothelial and myogenic frequency ranges do

not recover during testing. This can be thought of as an

impairment of vasodilatation and a symptom of endothelial

dysfunction.

The impaired response to the cold pressor test in the

endothelial frequency range for skin temperature fluctua-

tions is the evidence of progressive endothelial dysfunction




and can be considered as the earliest manifestation of vas-

cular disorders.

Declaration of conflicting interests

The authors have no conflicts of interest to declare.

Funding

This work was supported by the Russian Foundation of Basic

Research (RFBR-Ural 13-04-96022).

References

1. Shaw JE, Sicree RA and Zimmet PZ. Global estimates of the

prevalence of diabetes for 2010 and 2030. Diabetes Res Clin

Pract 2010; 87: 4–14.

2. Stratton IM, Adler AI, Neil HA, et al. Association of gly-

caemia with macrovascular and microvascular complications

of type 2 diabetes (UKPDS 35): prospective observational

study. BMJ 2000; 321: 405–412.

3. Selvin E, Marinopoulos S, Berkenblit G, et al. Meta-analysis:glycosylated hemoglobin and cardiovascular disease in dia-

betes mellitus. Ann Intern Med 2004; 141: 421–431.

4. De Vriese AC, Verbeuren TJ, Van D, et al. Endothelial dys-

function in diabetes. Br J Pharmacol 2000; 130: 963–974.

5. Lusher TF and Barton M. Biology of the endothelium. Clin

Cardiol 1997; 20: 3–10.

6. Kolluru GP, Bir SC and Kevil CG. Endothelial dysfunction

and diabetes: effects on angiogenesis, vascular remodeling,

and wound healing. Int J Vasc Med 2012; 2012 (Article ID

918267): 30 pp. DOI: 10.1155/2012/918267.

7. Lenasi H. Assessment of human skin microcirculation and

its endothelial function using laser Doppler flowmetry. In:

Erondu OF (ed.) Medical imaging . Rijeka: InTech, 2011,

pp. 271–296. 8. Holowatz LA, Thompson-Torgerson CS and Kenney WL.

The human cutaneous circulation as a model of generalized

microvascular function. J Appl Physiol 2008; 105: 370–372.

9. Crakowski JL, Minson CT, Salvat-Melis M, et al.

Methodological issues in the assessment of skin microvas-

cular endothelial function in humans. Trends Pharmacol Sci

2006; 27: 503–508.

10. Shiogai Y, Stefanovska A and McClintock PVE. Nonlinear

dynamics of cardiovascular ageing. Phys Rep 2010; 488:

51–110.

11. Bandrivsky A, Bernjak A, McClintock P, et al. Wavelet

phase coherence analysis: application to skin temperature

and blood flow. Cardiovasc Eng 2004; 4: 89–93.12. Burton AC and Taylor RM. A study of the adjustment of

peripheral vascular tone to the requirements of the regulation

of body temperature. Am J Physiol 1940; 129: 566–577.

13. Mabuchi K, Chinzei T, Nasu Y, et al. Frequency analysis of

skin temperature and its application for clinical diagnosis.

Biomed Thermol 1989; 9: 30–33.

14. Shusterman V, Anderson KP and Barnea O. Spontaneous

skin temperature oscillations in normal human subjects. Am

J Physiol 1997; 273: 1173–1181.

15. Sheppard LW, Vuksanović V, McClintock PVE, et al.

Oscillatory dynamics of vasoconstriction and vasodilation

identified by time-localized phase coherence. Phys Med Biol

2011; 56: 3583–3601.

16. Podtaev S, Morozov M and Frick P. Wavelet-based cor-

relations of skin temperature and blood flow oscillations.

Cardiovasc Eng 2008; 8: 185–189.

17. Kvernmo HD, Stefanovska A, Bracic M, et al. Spectral

analysis of the laser Doppler perfusion signal in human skin

before and after exercise. Microvasc Res 1998; 56: 173–182.

18. Golenhofen K. Slow rhythms in smooth muscle. In:

Bühlbring E, Brading AF, Jones AW, et al. (eds) Smoothmuscle. London: Edward Arnold Ltd, 1970, pp. 316–342.

19. Nilsson H and Aalkjaer C. Vasomotion: mechanisms and

physiological importance. Mol Interv 2003; 3: 79–89.

20. Bollinger A, Hoffmann U and Franzeck UK. Evaluation of

flux motion in man by the laser Doppler technique. Blood

Vessels 1991; 28(Suppl. 1): 21–26.

21. Soderstrom T, Stefanovska A, Veber M, et al. Involvement

of sympathetic nerve activity in skin blood flow oscillations

in humans. Am J Physiol Heart Circ Physiol 2003; 284:

H1638–H1646.

22. Kastrup J, Bühlow J and Lassen NA. Vasomotion in human-

skin before and after local heating recorded with laser

Doppler flowmetry. A method for induction of vasomotion. Int J Microcirc Clin Exp 1989; 8: 205–215.

23. Landsverk SA, Kvandal P, Bernjak A, et al. The effects of

general anesthesia on human skin microcirculation evaluated

by wavelet transform. Anesth Analg 2007; 105: 1012–1019.

24. Kvernmo HD, Stefanovska A, Kirkebøen KA, et al.

Oscillations in the human cutaneous blood perfusion signal

modified by endothelium dependent and endothelium-inde-

pendent vasodilators. Microvasc Res 1999; 57: 298–309.

25. Kvandal P, Stefanovska A, Veber M, et al. Regulation of human

cutaneous circulation evaluated by laser Doppler flowmetry,

iontophoresis, and spectral analysis: importance of nitric oxide

and prostaglandines. Microvasc Res 2003; 65: 160–171.

26. Holshneider M. Wavelets: an analysis tool . Oxford: Clarendon

Press, 1995.27. Charkoudian N. Skin blood flow in adult human thermoregu-

lation: how it works, when it does not, and why. Mayo Clin

Proc 2003; 78: 603–612.

28. Kellogg DL. In vivo mechanisms of cutaneous vasodilation

and vasoconstriction in humans during thermoregulatory

challenges. J Appl Physiol 2006; 100: 1709–1718.

29. Isii Y, Matsukawa K, Tsuchimochi H, et al. Ice-water hand

immersion causes a reflex decrease in skin temperature in the

contralateral hand. J Physiol Sci 2007; 57: 241–248.

30. Frick P, Grossmann A and Tchamichian P. Wavelet analysis

of signals with gaps. J Math Phys 1998; 39: 4091–4107.

31. Frick P, Baliunas S, Galyagin D, et al. Wavelet analysis of

stellar chromospheric activity variations. Astrophys J 1997;483: 426–434.

32. Daanen HAM. Finger cold-induced vasodilation: a review.

Eur J Appl Physiol 2003; 89: 411–426.

33. Kawano H, Motoyama T, Hirashima O, et al. Hyperglycemia

rapidly suppresses flow-mediated endothelium-dependent

vasodilation of brachial artery. J Am Coll Cardiol 1999; 34:

146–154.

34. Hink U, Li H, Mollnau H, et al. Mechanisms underlying endothe-

lial dysfunction in diabetes mellitus. Circ Res 2001; 88: 14–22.

35. Schmoelzer I and Wascher TC. Effect of repaglinide on

endothelial dysfunction during a glucose tolerance test

in subjects with impaired glucose tolerance. Cardiovasc

Diabetol 2006; 5: 9.



Smirnova et al. 497

36. Caballero AE, Arora S, Saouaf R, et al. Microvascular and

macrovascular reactivity is reduced in subjects at risk for

type 2 diabetes. Diabetes 1999; 48: 1856–1862.

37. Avogaro A, Albiero M, Menegazzo L, et al. Endothelial

dysfunction in diabetes. The role of reparatory mechanisms.

Diabetes Care 2011; 34(Suppl. 2): S285–S290.

38. Rutkove SB, Veves A, Mitsa T, et al. Impaired distal ther-

moregulation in diabetes and diabetic polyneuropathy.

Diabetes Care 2009; 32: 671–676.

39. Stansberry KB, Shapiro SA, Hill MA, et al. Impaired

peripheral vasomotion in diabetes. Diabetes Care 1996; 19:

715–731.

Appendix 1

Signal decomposition

Using the continuous wavelet transform, the function

of one variable (time) f t ( ) can be represented as a

two-dimensional (2D) (time and scale) space. Thus, we

have

W a ba

f t t b

adt ,

*( ) = ( ) −

−∞

+∞

∫ 1

ψ

(1)

where ψ is the analysing wavelet, t is the time, * is the

complex conjugation, b is the time shift (wavelet position)

and a is the oscillation scale, which corresponds to the

inverse of the frequency (ν)

ν =

1

a (2)

In our work, each signal recorded and time averaged dur-

ing the measurement procedure had approximately 1000–

1200 time samples (typical time series length was about

1000–1200 s). Due to this fact, the boundary effectsappear to be of crucial importance16 because they essen-

tially affect the analysis of wavelet characteristics. These

boundary effects are caused by the violation of the admis-

sibility condition

ψ t dt ( ) =−∞

+∞

∫ 0

(3)

that is, when part of the wavelet falls outside the in-

terval under study or when it overlaps the gap in the

signal.

In this article, we propose to apply the gapped wavelettechnique30,31 as an effective tool for eliminating the

artefacts caused by the boundary effects. The mathemat-

ical properties of the gapped wavelet technique were

studied in detail by Frick et al.30 The gapped wavelets

have a twofold effect: they suppress noise caused by the

gaps and boundaries and also improve the accuracy of

frequency determinations for short or strongly gapped

signals. The gapped wavelet technique can restore the

admissibility condition by repairing the wavelet itself.

Following Frick et al.,31 we separated the analysing

wavelet into two parts: the oscillatory part ϕ ( )t and the

envelope ξ t ( )

When the wavelet is disturbed by a boundary or by a gap,

the admissibility condition is restored by including a con-

stant shift, G, in the oscillatory part of the wavelet

ψ ϕ ξ t b

a

t b

a

G a b t b

a

−

=

−

+ ( )

−

,

(5)

where

ψ t b

adt

−

=

−∞

+∞

∫ 0 (6)

The parameter G can be determined for each scale, a, and

position, b, from

G a b t b

adt

t b

adt ,( ) =

−

−

−∞

+∞

−∞

+∞ −

∫ ∫ ψ ξ

1

(7)

Moreover, the inverse of equation (1) can be written as

f t a C

W a b t b

adadb( ) = ( )

−

−∞

+∞+∞

∫ ∫ 1

2

0ψ

ψ , (8)

where C ψ is given by

C t e dt d i t

ψ

ω

π ω ψ ω = ( )

− −

−∞

+∞

−∞

+∞

∫ ∫ 1

2

1

2

(9)

Equation (9) allows the function f to be recovered from its

wavelet transform W (a, b). By changing the integration

limits for a in equation (9), we can obtain any spectral com-

ponents of f , which can then be studied independently.

In our work, we use the Morlet wavelet

ψ π κ

t it t

( ) = ( ) −

exp exp2

2

2 (10)

which offers a reasonable trade-off between localization in

time and scale domains.

(4)

ψ ϕ ξ

ϕ π

ξ

t t t

t it

t t

( ) = ( ) ( )

( ) = ( )

( ) = −

exp

exp

2

2

2

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