Relationship between skin blood flow regulation mechanisms and vascular endothelial growth factor in patients with metabolic syndrome.

The focus of this paper is the determination of endothelial dysfunction in patients with metabolic syndrome (MetS) and the establishment of a relationship between the traditional biomarkers of endothelial dysfunction and the vascular tone regulation indices obtained from indirect cold tests in MetS patients. Our investigation was conducted on 30 patients aged 45.5±9 years. The control group comprised 14 healthy subjects aged 48.2±2.4 years. The mechanism of vascular tone regulation was investigated using the wavelet analysis of skin temperature oscillations (WAST). The degrees of microvascular vasoconstriction and vasodilatation were determined during contralateral cold tests in the endothelial (0.02-0.0095 Hz), neurogenic (0.05-0.02 Hz) and myogenic (0.05-0.14 Hz) frequency ranges. In MetS patients, vasoconstriction indices were higher and vasodilatation indices were lower than in the subjects of the control group, which is indicative of disorders in the mechanisms of microvascular tone regulation. These indices correlate with the metabolic parameters and VEGF (vascular endothelial growth factor) levels. The correlation of vasoconstriction and vasodilatation indices with the main factors of the metabolic syndrome testifies that the biological and functional aspects of the endothelial dysfunction are closely related.

Comparative study between microvascular tone regulation and rheological properties of blood in patients with type 2 diabetes mellitus.

The aim of the study is to investigate the changes of the skin blood flow responses to cold stress in patients with diabetes mellitus type 2 through wavelet analysis of the peripheral skin temperature oscillations and to estimate their relationship with the blood viscosity values. The amplitudes of the skin temperature pulsations (ASTP) were monitored by "Microtest" device ("FM-Diagnostics", Russia); the whole blood viscosity and the shear stresses were measured by Contraves LS30 viscometer (Switzerland) at a steady flow in 9 healthy subjects and in 30 patients with type 2 diabetes mellitus. Power law and Herschel-Bulkley (HB) equations were applied to describe the blood rheology. Both models include consistency (k) and flow index (m), and the HB also gives the yield stress (τ0). The Spearman rank correlations between these parameters and the ASTP in the frequency ranges, corresponding to the myogenic, neurogenic and endothelial mechanisms of the microcirculation tone regulation were calculated. The ASTP values decreased when the blood viscosity increased. The correlation analysis revealed good ASTP-m (r > 0.5) and ASTP-k (r < -0.5) relationships in the endothelial range, while the ASTP-τ0 correlation was weaker (r≈-0.4). These correlations became lower for the ASTP during the cold stress. The results prompt manifestation of endothelial dysfunction in patients with type 2 diabetes.

Frequency and temperature dependence of skin bioimpedance during a contralateral cold test.

A study of the α- and ß-dispersion of skin bioimpedance dependence on temperature and micro-hemodynamics is presented. The vascular tone changes during the cold test are verified by the wavelet-analysis of skin temperature signals obtained simultaneously with impedance measurements. Thirty three normal healthy subjects of 28  ±  7 years old were entered into the study. The tetra-polar electrode system was used to record the resistance and reactance; measurements were carried out at 67 frequencies, in a frequency range from 2 Hz to 50 kHz. It has been found that the impedance decreases with vasodilation and increases with vasoconstriction. The high values of correlation among thermal oscillation amplitudes and Nyquist diagram parameters prove the impedance dependence on blood flow in three frequency bands corresponding to the myogenic, neurogenic and endothelial vascular tone regulation mechanisms. Using an equivalent RC circuit, we obtained the changes in the Nyquist diagram matching the experimental data. The proposed descriptive α-dispersion model can be used to study mechanisms responsible for intercellular interaction.