Journal
FASEB JOURNAL
Volume 28, Issue 3, Pages 1499-1510Publisher
FEDERATION AMER SOC EXP BIOL
DOI: 10.1096/fj.13-239806
Keywords
aging; food intake; spontaneous physical activity; mitochondria
Categories
Funding
- U.S. National Institutes of Health/National Institute on Aging [R01-AG09531]
- Mayo Foundation
- Dole-Murdock Professorship
- American Federation for Aging Research
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Hyperthyroidism causes increased energy intake and expenditure, although anorexia and higher weight loss have been reported in elderly individuals with hyperthyroidism. To determine the effect of age on energy homeostasis in response to experimental hyperthyroidism, we administered 200 g tri-iodothyronine (T3) in 7- and 27-mo-old rats for 14 d. T3 increased energy expenditure (EE) in both the young and the old rats, although the old rats lost more weight (147 g) than the young rats (58 g) because of the discordant effect of T3 on food intake, with a 40% increase in the young rats, but a 40% decrease in the old ones. The increased food intake in the young rats corresponded with a T3-mediated increase in the appetite-regulating proteins agouti-related peptide, neuropeptide Y, and uncoupling protein 2 in the hypothalamus, but no increase occurred in the old rats. Evidence of mitochondrial biogenesis in response to T3 was similar in the soleus muscle and heart of the young and old animals, but less consistent in old plantaris muscle and liver. Despite the comparable increase in EE, T3's effect on mitochondrial function was modulated by age in a tissue-specific manner. We conclude that older rats lack compensatory mechanisms to increase caloric intake in response to a T3-induced increase in EE, demonstrating a detrimental effect of age on energy homeostasis.Walrand, S., Short, K. R., Heemstra, L. A., Novak, C. M., Levine, J. A., Coenen-Schimke, J. M., Nair, K. S. Altered regulation of energy homeostasis in older rats in response to thyroid hormone administration.
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