Microvascular Reactivity in Prepubertal Children

Nailfold videocapillaroscopy is performed using the fourth finger of the left hand in a temperature-controlled environment (22ºC). The following microvascular parameters are determined at resting state: (a) functional capillary density (FCD), the number of capillaries/mm2 with red blood cell flux, evaluated with 250x magnification in a 3-mm area of the distal row of capillaries in three different areas (lateral, central and medial); (b) red blood cell velocity at rest (RBCV) and during post occlusive reactive hyperemia (PORH); c) the peak RBCV after 1-min arterial occlusion (RBCVmax); and (d) the time taken to reach RBCVmax (TRBCVmax). Firstly, a pressure cuff (1-cm wide) is placed around the proximal phalanx and connected to a mercury manometer.

Univariate intergroup comparisons are performed by ANOVA or Kruskal-Wallis tests according to whether the tested variables followed a normal or non-normal distribution, respectively. Post hoc Bonferroni and Dunn tests were then performed.

Biological systems, as many processes in nature, are inherently multivariate, therefore, a multivariate approach to determine which variables discriminate between the groups is taken and then the investigators applies Canonical Discriminant Function Analysis. This analysis determines how well it is possible to distinguish groups from a multivariate data set. The variation of a specific physiological parameter may influence other parameters and their synergistic action can generate results not easily detectable through a univariate analysis. The level of significance adopted was 0.05.

Laboratory testing includes fasting plasma glucose, insulin, total cholesterol and HDL-cholesterol, triglycerides, leptin, adiponectin, high sensitivity C-reactive protein, and interleukin-6 levels. Biochemical analysis is performed using the following methods: for FPG, the GOD-PAP enzymatic (oxidase); for cholesterol, the CHOP-POD enzymatic (esterase-oxidase); for triglycerides, the GPO/PAP enzymatic (oxidase); and for HDL-cholesterol, the colorimetric without precipitation. Insulin, leptin and adiponectin levels are measured using a solid phase radioimmunoassay. Interleukin-6 level is measured by the electrochemiluminescence method and Hs-CRP level is measured by the turbidimetric method.