ABSTRACT
Resumen En los últimos años, como resultado de una mayor oferta de «comida rápida¼ (CR), se ha inducido un incremento en la cantidad y el contenido calórico de los alimentos consumidos. El objetivo de este trabajo fue realizar una revisión de las investigaciones relativas al efecto de los ácidos grasos (AG) sobre el ciclo hambre-saciedad. En la CR predominan los AG saturados de cadena larga, los cuales tienden a incrementar el apetito. No obstante, las N-aciletanolaminas que se sintetizan minutos después de la ingesta de alimento pueden modular los niveles de apetito o de saciedad. Esto gracias a la capacidad de inducir la secreción de diferentes hormonas involucradas en la activación de las señales orexigénicas o anorexigénicas. Por el contrario, los AG insaturados pueden secretar hormonas anorexigénicas que inducen saciedad; tal es el caso de los omegas 3 y 9, por lo que sería recomendable incrementar su proporción en el proceso de elaboración de la CR. Por tanto, se concluye que el tipo de efecto que los AG tengan en el ciclo hambre-saciedad depende, por un lado, de la longitud de su cadena y, por otro, del número de insaturaciones que contengan.
Abstract In recent years, as a result of a greater offer of 'fast food' (FF), an increase has been induced in the quantity and caloric content of the foods consumed. The aim of this work was to carry out a review of the investigations related to the effect of fatty acids (FA) on the hunger-satiety cycle. Long-chain saturated FA predominate in FF, which tend to increase appetite. However, the N-acylethanolamines that are synthesized minutes after food intake can modulate appetite or satiety levels. This is due to the ability to induce different hormones secretion involved in orexigenic or anorexigenic signals activation. In contrast, unsaturated FA can secrete anorexigenic hormones that induce satiety, such as omegas 3 and 9, so it would be advisable to increase their proportion in the FF production process. Therefore, it is concluded that the type of effect that FA have on hunger-satiety cycle depends, on the one hand, on the length of their chain and, on the other hand, on the number of unsaturations contained in them.
ABSTRACT
Estradiol participates in the control of energy homeostasis, as demonstrated by an increase in food intake and in body weight gain after ovariectomy in rats. In the present study, female Wistar rats (200-230 g, N = 5-15 per group), with free access to chow, were individually housed in metabolic cages. We investigated food intake, body weight, plasma leptin levels, measured by specific radioimmunoassay, and the hypothalamic mRNA expression of orexigenic and anorexigenic neuropeptides, determined by real-time PCR, in ovariectomized rats with (OVX+E) and without (OVX) estradiol cypionate treatment (10 µg/kg body weight, sc, for 8 days). Hormonal and mRNA expression were determined at pre-feeding and 4 h after food intake. OVX+E rats showed lower food intake, less body weight gain and lower plasma leptin levels. In the OVX+E group, we also observed a reduction of neuropeptide Y (NPY), agouti-related protein (AgRP) and cocaine- and amphetamine-regulated transcript (CART) mRNA expression in the arcuate nucleus and a decrease in orexin A in the lateral hypothalamic area (LHA). There was an increase in leptin receptor (LepRb), melanocortin-4 receptor (MC4-R), CART, and mainly corticotropin-releasing hormone (CRH) mRNA in the paraventricular nucleus and LepRb and CART mRNA in the LHA. These data show that hypophagia induced by estradiol treatment is associated with reduced hypothalamic expression of orexigenic peptides such as NPY, AgRP and orexin A, and increased expression of the anorexigenic mediators MC4-R, LepRb and CRH. In conclusion, estradiol decreases food intake, and this effect seems to be mediated by peripheral factors such as leptin and the differential mRNA expression of neuropeptides in the hypothalamus.