Efectos de sustratos competitivos y de la insulina sobre la captación y el destino metabólico de la glucosa en corazón perfundido de ratas dislipémicas / Effects of competitive substrates ans insulin on glucose uptake and utilization in isolated perfused hearts of dyslipemic rats

Rats chronically fed (15 weeks) a sucrose-rich diet (SRD) developed hypertriglyceridemia (hyperTg), increased plasma free fatty acids (FFA), impaired glucose homeostasis and insulin insensitivity. An increase of Tg and glycogen (Gly) in heart muscle was also observed. HyperTg with altered glucose metabolism could have profound effects on myocardial glucose utilization. To test this hypothesis male Wistar rats were fed a semi-synthetic SRD (w/w: 62.5% sucrose, 8% corn-oil, 17% protein), and the control group (CD) received the same semi-synthetic diet, except that sucrose was replaced with starch for 90 days. At that time, the hearts from these animals were isolated and perfused for 30 min in the presence or absence of insulin (30 mU/ml). Levels of the exogenous substrates were similar to those found in the plasma of the animal in vivo in both dietary groups (glucose 8.5 mM, palmitate 0.8 mM in SRD and glucose 5-5 mM, palmitate 0.3 mM in CD). In the absence of insulin glucose uptake was reduced (40%) and lactate release was increased (50%) in SRD hearts. Glucose oxidation was depressed mainly due to both, an increase of PDH kinase and a decrease of 60% of PDHa (active form of PDHc). Insulin in the perfusion medium improved only glucose uptake. The results suggest that at least two different mechanisms might contribute to insulin resistance and to impaired glucose metabolism in the perfused hearts of dyslipemic SRD fed rats: 1) reduced basal and insulin-stimulated glucose uptake and its utilization and 2) increased availability and oxidation of lipids (low PDHa and PDH kinase activities), which in turn decreased glucose uptake and utilization. Thus, this experimental model may be useful to study how impaired glucose homeostasis, increased plasma FFA and hyperTg could contribute to heart tissue malfunction.

Efectos toxicológicos producidos por la ingesta crónica de aceites vegetales bromados / Toxicological effects induced by the chronic intake of brominated vegetable oils

Se estudiaron las alteraciones de parámetros lipídicos a nivel tisular y plasmático en un grupo de ratas macho de la cepa Wistar, alimentadas con una dieta normal de laboratorio suplementada con aceites vegetales-oliva, girasol-bromados (0.1 g/100 g de dieta), durante 15 semanas, comparando los resultados obtenidos con un grupo control. El primer grupo presentó niveles estadísticamente elevados de triglicéridos en corazón y soleus, y de colesterol total y esterificado en músculo cardíaco, acompañados por un descenso en los niveles plasmáticos de colesterol total y de la fracción de lipoproteínas de alta densidad (HDL-colesterol). Algunas de estas anormalidades fueron compartidas por ratas alimentadas con la dieta normal de laboratorio suplementada con 0.5 g de aceites vegetales bromados/100 g dieta. Los niveles hepáticos de triglicéridos, proteínas totales y glucógeno, así como la curva de crecimiento y la ingesta calórica de los animales que fueron alimentados con una dosis de aceites bromados de 0.1 g/100 g de dieta, fueron similares a los del grupo control. En síntesis, los efectos toxicológicos observados durante la ingesta crónica de dietas suplementadas con dosis relativamente bajas de aceites bromados, señalan la necesidad de emprender un estudio bioquímico más exhaustivo de los mismos. Ello es imperativo para establecer los niveles máximos con que estos agentes podrían ser utilizados sin riesgo de producir alteraciones biológicas considerables