Villaseñor A

Idioma: Español
Referencias bibliográficas: 35
Paginas: 135-139
Archivo PDF: 64.84 Kb.

RESUMEN

La leptina, un péptido de 167 aminoácidos es sintetizado y secretado por el adipocito, el cual provee una señal retroalimentadora del tejido adiposo a sus receptores en el hipotálamo. Los adipocitos viscerales parecen producir menos leptina que su contraparte subcutánea. Este péptido es transportado en la sangre y atraviesa la barrera hematoencefálica inhibiendo el neuropéptido Y, una sustancia con gran efecto estimulante sobre el apetito, también inhibe a otros neuropéptidos orexígenos. Niveles altos de leptina son indicativos de un exceso de masa adiposa. Concomitantemente, el neuropéptido Y, produce un aumento en la actividad del eje hipotálamo-hipófisis-suprarrenal resultando en hipercortisolemia y además inhibición de la termogénesis. (El neuropéptido Y, también inhibe la actividad termogénica del tejido adiposo pardo de la rata). Estos efectos limitan aumento extra del peso. Modelos animales en los que la leptina (ratón ob/ob) o su receptor hipotalámico (ratón db/db y fa/fa) se encuentran ausentes, están asociados con obesidad y resistencia a la insulina. En la mayor parte de los humanos obesos la leptina se encuentra elevada, lo que sugiere más bien una resistencia a la leptina, que una deficiencia hormonal. Los niveles plasmáticos de leptina corresponden con la hiperinsulinemia independientemente del índice de masa corporal.

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