Efeito da suplementação oral de zinco no ângulo de fase e na análise vetorial de bioimpedância em pacientes com distrofia muscular de Duchenne

Abstract

Zinc is one of the most abundant micronutrients in the human body, playing an important role in the stabilization of structural membranes, cellular integrity and functionality. The literature indicates that oral zinc supplementation offered to healthy children is positively associated with an increase in the phase angle (PA) value and improvement in bioelectrical impedance vector analysis (BIVA). However, there is a lack of studies involving zinc supplementation and its effects on cellular integrity and functionality in people with neurodegenerative diseases, such as Duchenne muscular dystrophy (DMD). Therefore, the objective of this thesis was to analyze the effect of zinc supplementation in boys with DMD. To achieve this objective, two studies were conducted. The first (study 1) described the reference values of PA and determined the BIVA tolerance ellipses of 108 healthy Brazilian children aged 6 to 9 years, while the second (study 2) evaluated the effect of zinc supplementation on the parameters of serum zinc, PA and BIVA in 33 boys with DMD. As results, in study 1, we found that before supplementation the mean serum zinc concentration was 74 μg/dL (12.0) and 29% of the participants had concentrations below the reference value. The basal values of the PA, resistance (R) and reactance (Xc) parameters were 2.59° (0.84°), 924.36 (212.31) Ω and 39.64 (8.41) Ω, respectively. After supplementation, an increase in R and a decrease in PA and lean mass proportional to age were observed, in addition to a negative correlation (r = −0.614; p < 0.001) between age and PA. The mean cell mass assessed by BIVA in G1 was greater than that of G3 (p = 0.012). However, no significant differences were found between the groups in serum zinc levels or in bioelectrical impedance parameters after supplementation. From the development of study 2, it was possible to suggest reference values of PA for healthy children according to sex, 5.79° and 5.40° for boys and girls, respectively. Likewise, new BIVA tolerance ellipses were proposed that can be used as a reference for children of the same age, but in different clinical conditions. Finally, considering the depth and detail of the approach to zinc functions and the pathophysiology of DMD, this thesis may serve as a basis for the development and implementation of strategies to prevent and correct zinc deficiency in the DMD population.