Effects of calorie restriction in growing male rats on the 24 h variations of pituitary, adrenal hormones and leptin

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Puerto de la Cruz, Tenerife (2003) J Physiol 548P, O28

Oral Communications: Effects of calorie restriction in growing male rats on the 24 h variations of pituitary, adrenal hormones and leptin

F. Chacón, V. Jiménez, M. Perello, P Alvarez, A. Marcos, E. Spinedi and A.I. Esquifino

Departamentos de Bioquímica y *Biología Celular, Facultad de Medicina, UCM, †Instituto de Nutrición y Bromatología (CSIC), Edificio del Instituto del Frío Madrid, Spain and Unidad de Neuroendocrinología Instituto Multidisciplinar de Biología Celular, La Plata, Argentina

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The effect on the endocrine system of controlled diets with calorie restriction is a matter of controversy. The aim of the present work was to determine the possible effect of calorie restriction on the secretory patterns of plasma adrenocorticotropin (ACTH), corticosterone (B) and leptin as well as the content of B in the adrenal gland.

Growing male Wistar rats were submitted to a 66 % calorie restriction from days 35 to 65 of life. To avoid cannibalism, calorie-restricted animals were isolated. Age-matched intact and isolated rats were used as controls. On day 65 of life, animals were humanely killed by decapitation at six time intervals around the clock beginning at 09.00 h. Specific RIA systems were used to measure plasma levels of ACTH, B and leptin as well as B content in the adrenal gland.

Plasma ACTH levels in intact control rats peaked at 17.00-21.00 h. In isolated controls plasma ACTH levels peaked at 17.00 h. The mean 24 h values of the hormone remained similar in both groups. However, in calorie restricted rats the mean values of the hormone were reduced. The pattern of ACTH showed lower amplitude in calorie-restricted rats, although the pattern was similar to that described in intact controls. Plasma B levels showed a plateau between 17.00 and 05.00 h. The mean levels of the hormone were increased and the pattern disappeared in both isolated control and calorie-restricted rats, as compared to intact controls. These changes were associated with a marked decrease in adrenal B content in both isolated groups and was higher in intact controls. Plasma levels of leptin peaked at 05.00 h in intact controls. In isolated controls a phase advance in leptin peak to 21.00-01.00 h. was observed. In calorie-restricted rats this pattern disappeared as compared to either isolated or intact controls. Mean values of leptin were markedly increased in isolated controls and in calorie restricted rats it was markedly decreased as compared to intact controls.

All these data suggest that calorie restriction disrupts the regulatory mechanism that modulates carbohydrate and lipid metabolisms.

Where applicable, experiments conform with Society ethical requirements.

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