Efeito de compostos presentes na dieta e de drogas de abuso na captação de glicose numa linha celular de trofoblastos humanos (células BeWo) : trabalho de investigação

Abstract

Resumo da tese:Os mecanismos que regulam o transporte placentar de glicose são ainda pouco conhecidos. Por isso o objectivo deste trabalho, foi caracterizar a captação de glicose da circulação materna e estudar a modulação desse processo por diversas substâncias (polifenóis, metilxantinas, etanol e o seu metabolito acetaldeído), presentes em bebidas alcoólicas e não-alcoólicas de consumo habitual (como o vinho, chá e café) e por drogas de abuso. Para tal, determinouse o efeito agudo (26 minutos) e crónico (48 horas) desses compostos na captação de desoxiglicose marcada radioactivamente com trício (3H-DG), numa linha celular de trofoblastos humanos (BeWo). Verificamos que a captação de 3H-DG (1 M) ocorre principalmente por um mecanismo facilitado (GLUT), e é modulada de modo diferente pelos compostos das bebidas e pelas drogas de abuso. Agudamente, o acetaldeído (30 e 100 mM), o resveratrol, o xanto-humol, a epigalocatequina-3-galato (100 M), e a quercetina e crisina (ambos a 10 e 100 M) reduziram o transporte apical de 3H-DG, enquanto que a rutina, a catequina (ambos a 10 e 100 M), a epicatequina (100 M) e o etanol (10 mM) aumentaram-no. A catequina e a epicatequina em conjunto (ambas a 100 M) reduziram a captação de 3H-DG, enquanto que a epicatequina e o xanto-humol (ambos a 100 M) contrabalançaram os efeitos que cada um tinha isoladamente. Todos estes compostos parecem interagir com o GLUT para exercerem os seus efeitos; contudo o acetaldeído parece exercer o seu efeito por outro mecanismo. A quercetina e o xanto-humol são inibidores não competitivos da captação de 3H-DG, ao passo que a epigalocatequina-3-galato e o acetaldeído reduziram ambos o valor de Km e Vmax. (...)

Thesis abstract:Very little is known concerning the mechanisms responsible for the regulation of the placental transfer of glucose. So, the aim of this work was to characterize the placental uptake of glucose from the maternal circulation, and to study the modulation of that process by several compounds (polyphenols, methylxanthines, ethanol and its metabolite acetaldehyde), present in alcoholic and nonalcoholic drinks (such as wine, tea and coffee) and by drugs of abuse. For this, the acute (26 min) and chronic (48 h) effect of these compounds upon the vi uptake of 3H-2-deoxy-D-glucose (3H-DG) by a human trophoblast cell line (BeWo) was determined. We verified that the uptake of 3H-DG occurs mainly by a facilitated mechanism (GLUT), that is differentially modulated by compounds present in drinks and by drugs of abuse. Acutely, acetaldehyde (30-100 mM), resveratrol, xanthohumol, epigallocatechin-3-gallate (100 μM), chrysin and quercetine (both at 10-100 μM), decreased 3H-DG uptake, whereas rutin, catechin (both at 10-100 μM), epicatechin (100 μM) and ethanol (10 mM) increased it. Together, catechin and epicatechin (both at 100 μM) decreased the uptake of 3H-DG, whereas epicatechin and xanthohumol (both at 100 μM) counterbalanced each one’s isolated effect. All these compounds seem to interact with GLUT in order to exert their effects, except acetaldehyde that seems to exert its effect by a different mechanism. Quercetin and xanthohumol are non-competitive inhibitors of 3H-DG uptake, whereas both epigallocatechin-3-gallate and acetaldehyde decreased both the Km and Vmax values. Chronically, rutin and miricetin increased the uptake of 3H-DG both isolated (both at 0,1-1 M) and in combination (both at 1 M), whereas theophylline (0,1-1 μM) and the drugs amphetamine, 3,4-methylenedioxymethamphetamine (0,1-2,5 M) and D9-tetrahydrocannabinol (1 nM decreased it. In order to exert their chronic effects, these compounds seem to interact with GLUT. (...)