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National Institute on Aging
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Translational Gerontology Branch
Nonhuman Primate Unit
Julie A. Mattison, Ph.D.
Facility Head
NIA Primate Aging Study: Although the primary focus has been a long-term study of calorie restriction, the Laboratory of Experimental Gerontology (LEG) has collaborated with the Laboratory of Cardiovascular Science (LCS) to study additional projects of dietary interventions that more specifically affect cardiovascular aging.
Dietary calorie restriction (CR) has been shown to benefit health and longevity in a wide variety of species, although most have maximal lifespans of only a few years. In 1987, the National Institute on Aging Intramural Research Program began the first well controlled long-term study in a species with a considerably longer lifespan and a closer physiology to humans. Using rhesus monkeys (Macaca mulatta), an extensive array of physiological measures have been conducted in both male and females to evaluate the effects of CR. A smaller group of squirrel monkeys (Saimiri sciureus) have also been studied. Although it is not yet known if CR extends maximal lifespan in these long-lived primate species, our findings indicate that physiological responses are in general agreement with the extensive literature in rodents and that nonhuman primates on CR are likely to experience fewer incidences and less severe effects of age-related disease, in particular, cardiovascular disease and diabetes.
With an average lifespan of 25 years and a maximum of 40 years, studies of longevity in rhesus monkeys are challenging to conduct. Effective anti-aging interventions should result in decreasing the incidence and delaying the age of onset of characteristic age-related diseases and pathology. In additions, there must be maintenance of cellular, organ, physiologic, and behavioral function into old age. By using criteria in the three main categories of mortality, morbidity, and function, the NIA hopes to clearly establish that CR retarded the rate of aging in rhesus monkeys.
Study Background: The study began with a group of 30 male rhesus monkeys and was doubled to 60 in 1988. Sixty females were added in 1992. Monkeys ranged in age from 2 to 23 years at the initiation of the study and have been fed either a diet approximating ad libitum (CON) intake or a CR diet that targeted 30% less calories than age- and weight-matched controls since initiation. The large age range provided a unique opportunity to study CR initiated in juvenile, adolescent, young adult, and old animals. Subsequently, a similar study was undertaken at the University of Wisconsin (UW); however, all monkeys in the UW study were adults (8-14 years of age) at initiation.
A group of 30 male squirrel monkeys also entered the study in 1987 with a wide span of start ages. This New World species of NHP has a maximal life span of about 25 years and a body weight of only 0.5 to 1 kg. Data from this species has been more difficult to obtain and will not be detailed here.
Beginning in 1995, a smaller number of both male and female rhesus monkeys were incorporated into the diet paradigm for additional short-term studies of CR. Data were collected from this group of both young and old monkeys during the initiation of CR to evaluate the adaptive period of this nutritional stress. In 2001, this group was transferred to the Oregon National Primate Research Center in Beaverton where they continued in CR studies.
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Updated: Wednesday May 15, 2013