LONGEVITY IN THE RHESUS MONKEY: MULTIPLE AGING PROCESSES, MORBIDITY AND MORTALITY
Noni L. Bodkin.*
Obesity and Diabetes Research Center, School of Medicine, Department of Physiology, University of Maryland, Baltimore, MD 21201 USA.
Separation of the physiological changes of aging from the development of adult age-associated disease has been an ongoing challenge to gerontologists. Clearly, although some predictors have been identified, the rate of physiological aging and the propensity to develop age-associated disease is highly individualized. Metabolic diseases of aging include insulin resistance, type 2 diabetes, hypertension, cardiovascular disease, and dyslipidemia. Obesity is highly associated with all of these disorders. We have completed analysis of data related to the diseases of aging, morbidity and mortality in over 90 rhesus monkeys, maintained under ad libitum feeding and individually housed under identical environmental conditions. Measurements included body weight, body fat, fasting hormones and substrates, glucose tolerance, and lipidemia. Results showed the age of onset for specific diseases in the ad libitum fed laboratory primate was predictable (~ age 10-12 years) in regard to increased body weight (>12 kg) and development of obesity (>22% body fat) but more variable in regard to development of hyperinsulinemia (~ age 10-15 years), and in regard to glucose intolerance and type 2 diabetes (~ age 10-25 years). In regard to morbidity and mortality, the primary cause of death was cardiac-related at the average age of 22 years, although there was no higher risk in this group comparing type 2 diabetic monkeys to non-diabetic monkeys. The age at which significant pathology in major organ systems (respiratory, gastrointestinal and cardiac) occurred and the age at 50% mortality was identified to be approximately 25 years old, providing a clear definition of an "aged" rhesus monkey. In this group of laboratory-housed rhesus monkeys, there were 6 "centenarians", defined as primates > 30 years of age, the oldest of whom was a female rhesus monkey with type 2 diabetes mellitus who died just prior to 40 years of age. We conclude that in the captive rhesus monkey, as in humans, cardiovascular disease was a major contributing factor to mortality, causing death on average at 22 years old. Significant pathology is present at the age of 25 years old, also about the age at which 50% mortality occurs, and after which the "aged" rhesus monkey is likely to reflect the characteristic senescent changes of the human population. Finally, it appears that significant longevity (> 30 years) of the rhesus monkey in captivity is rare, but achievable, as evidenced by "centenarian" nonhuman primates living up to 40 years of age.
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