Energy restriction does not alter bone mineral metabolism or reproductive cycling and hormones in female rhesus monkeys

Energy restriction (ER) extends the life span and slows aging and age-relat ed diseases in short-lived mammalian species. Although a wide variety of ph ysiological systems have been studied using this paradigm, little is known regarding the effects of ER on skeletal health and reproductive aging. Stud ies in rhesus monkeys have reported that ER delays sexual and skeletal matu ration in young male monkeys and reduces bone mass in adult males. No studi es have examined the chronic effects on bone health and reproductive aging in female rhesus monkeys. The present cross-sectional study examined the ef fects of chronic (6 y) ER on skeletal and reproductive indices in 40 premen opausal and perimenopausal (7-27 y old) female rhesus macaques (Macaca mula tta). Although ER monkeys weighed less and had lower fat mass, ER did not a lter bone mineral density, bone mineral content, osteocalcin, 25-hydroxyvit amin D, 1,25-hydroxyvitamin D or parathyroid hormone concentrations, menstr ual cycling or reproductive hormone concentrations. Body weight and lean ma ss were significantly related to bone mineral density and bone mineral cont ent at all skeletal sites (total body, lumbar spine, mid and distal radius; P less than or equal to 0.04). The number of total menstrual cycles over 2 y, as well as the percentage of normal-length cycles (24-31 d), was lower in older than in younger monkeys (P less than or equal to 0.05). Older monk eys also had lower estradiol (P = 0.02) and higher follicle-stimulating hor mone (P = 0.02) concentrations than did younger monkeys. We conclude that E R does not negatively affect these indices of skeletal or reproductive heal th and does not alter age-associated changes in the same variables.