Hypothalamic-pituitary-adrenal responses to weight loss in mice following diet restriction, activity or separation stress: effects of tyrosine.
We have studied three different types of weight-loss stress caused by Diet restriction, Activity or Separation, for their effects on the hypothalamic-pituitary axis in young female mice and their responses to tyrosine 100 mg/kg/day. Plasma was assayed for ACTH and glucocorticoid determinations, and brain catecholamine concentrations were measured by HPLC/ECD. A similar weight loss of 24-28% was observed in the models despite significant differences in food intake. Diet restriction to 60% and Separation models produced a significant increase in hypothalamic noradrenaline (p < 0.01), while there was a significant decrease (p < 0.05) in the Diet restriction to 40% that was restored after tyrosine. After Activity, noradrenaline levels did not change. ACTH concentrations decreased following Diet restriction (p < 0.05) but were unaffected by Separation or Activity. The peripheral glucocorticoid response increased significantly after Activity and Diet restriction (p < 0.001), but decreased significantly after Separation (p < 0.001). Tyrosine increased glucocorticoid concentrations in the Activity and Separation models (p < 0.05), but not after Diet restriction. Despite similar weight loss in the three models there were no predictable associations between hypothalamic noradrenaline metabolism and plasma ACTH or glucocorticoid concentrations. Tyrosine might alleviate some of the different pathophysiological problems associated with the stress of weight loss.
Avraham
Yosefa
Y
Department of Human Nutrition and Metabolism, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
Hao
Shuzhen
S
Mendelson
Susan
S
Berry
Elliot M
EM
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D001010:Anxiety, Separation / Q000503:physiopathology*; D001835:Body Weight / Q000187:drug effects; D001921:Brain / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism; D004038:Diet, Reducing; D004195:Disease Models, Animal; D005260:Female; D005938:Glucocorticoids / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000503:physiopathology*; D051379:Mice; D008815:Mice, Inbred Strains; D009043:Motor Activity / Q000502:physiology*; D009638:Norepinephrine / Q000378:metabolism; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000503:physiopathology*; D013217:Starvation; D013315:Stress, Psychological / Q000523:psychology; D014443:Tyrosine / Q000494:pharmacology*; D015431:Weight Loss / Q000187:drug effects / Q000502:physiology*
D002395:Catecholamines; D005938:Glucocorticoids; D014443:Tyrosine; D000324:Adrenocorticotropic Hormone; D009638:Norepinephrine