Activity measures in rhesus monkeys on long-term calorie restriction

Abstract

Calorie restriction (CR), undernutrition without malnutrition, extends the mean and maximal lifespan of several ecologically diverse species. Rodents on CR demonstrate increased activity measured as spontaneous locomotion, wheel running, open field behavior or movement. Activity measures were recorded from 19 male rhesus monkeys (Macaca mulatta) as either controls (C) which were fed a nutritious diet to approximate ad libitum levels, or as experimentals (E) which were fed 30% less than age- and weight-matched controls. Within each diet group, some monkeys (n = 10) began CR at 2.3 years of age (range 2.2-2.4 yrs, J Group) while another group (n = 9) began CR at approximately 4.6 years of age (range 4-5.25, A group). Beginning about 6 years after initiation of the study, behavioral activity was measured via ultrasonic motion detectors and recorded on videotape. Diurnal and circadian activity was clearly discernible. Peaks in activity were associated with mealtime and colony husbandry. Compared to Group A, Group J monkeys exhibited higher overall activity as measured by sensors, and also significantly more circling. Compared to AC monkeys, group AE monkeys demonstrated higher rates of gross motor behavior, pacing, stereotypies and grooming. The increases in motor activity observed in one group of monkeys were consistent with results obtained from rodent studies of CR and aging. CR did not significantly inhibit or negatively influence the display of behavior of rhesus monkeys in the laboratory environment. We report here, for the first time, increases in activity due to CR in a model other than the rodent.