Oral Glucose Load and Human Cutaneous Microcirculation: An Insight into Flowmotion Assessed by Wavelet Transform

Abstract

Microcirculation in vivo has been assessed using non-invasive technologies such as laser Doppler flowmetry (LDF). In contrast to chronic hyperglycemia, known to induce microvascular dysfunction, the effects of short-term elevations in blood glucose on microcirculation are controversial. We aimed to assess the impact of an oral glucose load (OGL) on the cutaneous microcirculation of healthy subjects, quantified by LDF and coupled with wavelet transform (WT) as an interpretation tool. On two separate occasions, sixteen subjects drank either a glucose solution (75 g in 250 mL water) or water (equal volume). LDF signals were obtained in two anatomical sites (forearm and finger pulp) before and after each load (pre-load and post-load, respectively), in resting conditions and during post-occlusive reactive hyperemia (PORH). The WT allowed decomposition of the LDF signals into their spectral components (cardiac, respiratory, myogenic, sympathetic, endothelial NO-dependent). The OGL blunted the PORH response in the forearm, which was not observed with the water load. Significant differences were found for the cardiac and sympathetic components in the glucose and water groups between the pre-load and post-load periods. These results suggest that an OGL induces a short-term subtle microvascular impairment, probably involving a modulation of the sympathetic nervous system.

Wavelet analysis of laser Doppler microcirculatory signals: Current applications and limitations

“…In the equation above, the parameter s represents scale, i.e., it stretches and compresses the wavelet (s = 1 frequency , s ∈ R\{0}), and the parameter τ ∈ R represents the time-translation parameter. As a result, a wavelet can be observed as an adjustable window function that resolves low-frequency signal components using expanded wavelets (large values of scales, low time, and good frequency resolution) and higher frequencies using narrow wavelets (small values of scales, good time, and low-frequency resolution) (Silva et al, 2021).…”

“…oscillations related to endothelial influence are occasionally observed within two frequency bands: the endothelial nitric oxide (NO)dependent (0.0095-0.021 Hz) and the endothelial NO-independent one (0.005-0.0095 Hz) (Silva et al, 2021).…”

“…The approaches to calculating relative measures differ between authors. Some of these approaches include, but are not limited to, dividing the absolute oscillation amplitude in the frequency range of interest by the mean amplitude of the entire spectrum (relative amplitude) (Landsverk et al, 2007), dividing the mean amplitude of a particular frequency interval by that of the same frequency band of the baseline SkBF (normalized amplitude) (Jan et al, 2013), dividing the area under the curve of each component by the area under the curve of the entire spectrum (activity) (Rodrigues et al, 2020;Silva et al, 2021), or dividing the mean power of a particular frequency interval by the mean power of the entire spectrum (relative power) (Bagno and Martini, 2015).…”

“…Furthermore, vasomotion, the spontaneous, autonomous oscillation in a tone of blood vessel walls, independent of the heart, innervation, respiration, and endothelium (Lenasi, 2011) should also be considered when discussing microcirculatory control mechanisms. Currently, it is believed that vasomotion is associated with the intrinsic myogenic activity of the vascular smooth muscle cells (vSMC) (Silva et al, 2021); however, the exact mechanisms underlying this phenomenon require elucidation (Aalkjaer et al, 2011).…”

Evaluation of the Clinical Effectiveness of Sulfide Balneotherapy in Patients With Arterial Hypertension and Prediabetes With a Focus on the State of Hemodynamics and Microcirculation

“…Эндотелиальный (NO-зависимый) частотный диапазон, связан с продукцией оксида азота (NO) [13,14]. Диагностическое значение эндотелиальных колебаний заключается в оценке эндотелиальной функции по изменению нормированных амплитуд колебаний в диапазоне -0,007 и 0,01 Гц (NO-зависимый диапазон) [15].…”