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An Age-Related Decline in Melatonin Secretion Is Not Altered by Food Restriction

^a Department of Immunology, Concord Hospital, University of Sydney, New South Wales, 2139, Australia
^b Centre for Education and Research on Aging (CERA), Concord Hospital, University of Sydney, New South Wales, 2139, Australia

Mary F. MacGibbon, MacKillop Campus, Australian Catholic University, P.O. Box 968, North Sydney, NSW, Australia, 2059 E-mail: m.macgibbon{at}mackillop.acu.edu.au.

Decision Editor: John A. Faulkner, PhD

Melatonin has been found to exhibit youth-maintaining and disease-preventing properties. The current study examined whether the age-retarding regimen of chronic food restriction (FR) slowed the decline in melatonin secretion reported to occur with age. Total nocturnal melatonin secretion was assessed by radioimmunoassay of the primary metabolite, 6-sulphatoxymelatonin (6-S-OH-MLT), in urine. Measurements were made through adulthood (70 to 765 days) on male Wistar rats maintained on the FR regimen (60% of the normal intake) with the control animals fed ad libitum (AL). The data of animals exhibiting gross pathology were excluded. Analyses of covariance found the FR regimen had no effect on either the levels or pattern of decline observed in 6-S-OH-MLT excretion through adulthood. However, the FR body-weight–indexed metabolite measures were approximately double those of the AL ( p = .06). The possibility that this result may reflect unusually high melatonin peaks in the FR tissues is discussed.