Efectos del tratamiento antioxidante en la activación del eje hipotálamo-hipófiso-adrenal inducida por el consumo de dietas ricas en sacarosa / Effects of antioxidant treatment on the activation of the hipotalamo-hipofiso-adrenal axis induced by the consumption of sucrose rich diets

Introducción: dados los efectos pleiotrópicos de los glucocorticoides (GCs) sobre el metabolismo, los niveles excesivos y sostenidos de GCs circulantes tienen efectos deletéreos e incrementan la morbilidad y mortalidad cardiovascular. Objetivos: estudiar el efecto de la terapia antioxidante (con ácido lipoico o melatonina) sobre la hiperactivación del eje hipotálamo-hipófiso-adrenal (HHA) en animales alimentados con dieta rica en sacarosa (DRS). Materiales y métodos: se evaluó la actividad del eje HHA y se determinaron parámetros hormonales, de estrés oxidativo y de inflamación en la adenohipófisis de animales tratados con DRS durante tres semanas. Resultados: los animales del grupo DRS mostraron mayores niveles circulantes de hormona adrenocorticotropa (ACTH, por sus siglas en inglés) y corticosterona. En paralelo se detectó un aumento en la expresión del polipéptido precursor (proopiomelanocortina, POMC) y de ACTH en la adenohipófisis, donde también se observó un aumento de lipoperóxidos y proteínas nitradas en tirosina (daño oxidativo), un mayor número de macrófagos tisulares y un incremento en la producción de IL-1beta. El tratamiento antioxidante previno los cambios en estos parámetros. En particular la melatonina también normalizó la actividad del eje HHA y la expresión hipofisaria de POMC. Conclusiones: la sobrecarga metabólica inducida por la administración de DRS genera daño oxidativo e inflamación en la adenohipófisis. La activación de los macrófagos tisulares producida en consecuencia podría impactar sobre los corticotropos hipofisarios e inducir su hiperfunción. La melatonina podría utilizarse como herramienta terapéutica para normalizar la actividad del eje HHA en modelos de obesidad por dieta.

Introduction: given the pleiotropic effects of glucocorticoids (GCs) on metabolism, excessive and sustained levels of circulating GCs, have deleterious effects and increase cardiovascular morbidity and mortality. Objectives: to study the effect of antioxidant therapy on hyperactivation of the hypothalamic-pituitary-adrenal (HPA) axis in animals fed a sucrose-rich diet (SRD). Materials and methods: the activity of the HPA axis was evaluated and hormonal, oxidative stress and inflammation parameters were determined in the adenohypophysis of animals treated with SRD for trhee weeks. Results: animals from the SRD group showed higher circulating levels of adrenocorticotropic hormone (ACTH) and corticosterone. In parallel, an increase in the expression of the polypeptide precursors, POMC and ACTH were detected in the adenohypophysis. We also observed an increase in lipoperoxides and proteins nitrated in tyrosine (oxidative damage), a greater number of tissue macrophages and an increase in the production of IL-1beta. Antioxidant treatment prevented all these changes. In particular, melatonin also normalized the activity of the HPA axis and pituitary expression of POMC. Conclusions: the metabolic overload induced by the administration of SRD generates oxidative damage and inflammation in the adenohypophysis. Activation of tissue macrophages could affect, in turn, pituitary corticotrophs inducing their activation. Melatonin could be used as a therapeutic tool to normalize the activity of the HPA axis in diet obesity models.

Melatonin prevents early pituitary dysfunction induced by sucrose-rich diets.

While physiological levels of glucocorticoids are required to ensure proper functions of the body, consistently high levels may engender several deleterious consequences. We have previously shown an increase in the activity of the hypothalamic-pituitary-adrenal (HPA) axis in rats fed sucrose-rich diets (SRD). The main goal of this study was to analyze the processes involved in the modulation of the pituitary production of ACTH by SRD, and to test melatonin as a possible therapeutic agent for the prevention of the HPA axis dysfunction. Male Wistar rats were fed standard chow and either SRD (30% sucrose in the drinking water) or plain water for three weeks. Melatonin was administered as subcutaneous pellets. Results showed that SRD treatment induced an increase in systemic ACTH and corticosterone levels and a decrease in melatonin levels. In the pituitary gland, we also detected an increase in the expression levels of proopiomelanocortin (POMC) that was accompanied by increased levels of: lipoperoxides, nitro-tyrosine modified proteins, catalase, heme oxygenase-1, interleukin-1ß mRNA, and by an increase in the tissue number of inflammatory cells (F4/80 and Iba-1 positive cells). Melatonin treatment prevented all these systemic and pituitary changes as well as the increase in POMC expression induced by incubation of AtT-20 corticotrophs with conditioned media obtained from stimulated macrophages. In conclusion, stimulation of POMC/ACTH production in rats fed a SRD could involve the generation of oxidative stress and inflammation in the pituitary gland. Melatonin treatment prevented these effects and normalized the activity of the HPA axis.