Submitted on March 16, 2006
Accepted on July 26, 2006
Influences of calorie restriction and age on energy expenditure in the rhesus monkeys
Aarthi Raman1, Jon J. Ramsey2, Joseph W Kemnitz3, Scott T Baum3, Wendy Newton3, Ricki J Colman3, Richard Weindruch4, Mark T Beasley5, and Dale Alan Schoeller6*
1 Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin, United States
2 VM Molecular Biosciences, University of California, Davis, California, United States
3 Wisconsin Primate Research Center, University of Wisconsin, Madison, Wisconsin, United States
4 VA Hospital(GRECC-11G), University of Wisconsin-Madison, Madison, Wisconsin, United States
5 Biostatistics, University Alabama-Birmingham, Birmingham, Alabama, United States
6 Nutritional Science, University of Wisconsin, Madison, Wisconsin, United States
* To whom correspondence should be addressed. E-mail: dschoell{at}nutrisci.wisc.edu.
Caloric restriction (CR) is known to retard the aging process and a marker of aging is decreased energy expenditure (EE). To assess longitudinal effects of CR on EE in rhesus monkeys (Macaca mulata), data from 41 males and 26 females subjected to 9 or 15 years of CR were studied. EE and body composition of monkeys 11-28 years of age were measured using indirect calorimetry and dual x-ray absorptiometry. Total 24hEE was divided into day (day EE), night (night EE) and day minus night [(D-N) EE]. Male CR monkeys showed a lower 24hEE (mean ± sd =568±96 kcal/d; p<0.0001) than controls (C) (630 ± 129 kcal/d). CR males had a lower night EE (diff. = 36 kcal p<0.0001) compared to C males, but after adjusting for FFM and FM, night EE was not different between CR and C males (p=0.72). The 24hEE decreased with age (13 kcal decrease/yr; p<0.0001), but there was no difference between CR and C. Adjusted for FFM and FM, (D-N) EE decreased with age (9 kcal/year; p<0.0001) with no interaction with age (p=0.72). The females were compared with age-matched males selected from the male cohort. Females (F) had a lower 24hrEE (496 ± 84 kcal/d) than M (636 ± 139 kcal/d) (p<0.0001). Adjusting for FFM and FM, night EE was lower in the F compared to M (diff. = 18 kcal; p=0.077). Night EE did not differ between CR and C younger monkeys after adjusting for FFM and FM. In conclusion, CR did not alter the age-related decrease in EE with CR.
