Effect of Dietary Restriction on Estrous Cyclicity and Follicular Reserves in Aging C57BL/6J Mice 1

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Abstract
Restricting the food intake of female mice by alternating days of feeding and fasting delayed the age-related loss of estrous cycling potential and retarded the rate of follicular depletion, as determined after reinstatement of ad libitum (AL) feeding. During the period of food restriction (FR; 3.5-10.5 mo.), food intake and body wt were about 80% of AL values. Mice were cyclic and predominantly in a state of diestrus during FR, but aftr reinstatement of an AL diet at 10.5 mo. all FR mice resumed cycling regularly. Eighty percent of AL controls had become acyclic by this age; the cycles of the remaining mice were significantly longer than those of the reinstated FR mice. Follicular reserves of 12.5 mo. old FR mice were twice those of age-matched AL controls. Cycling performance of reinstated FR mice, measured by cycle length and the proportion of mice still cycling, was equivalent to that of AL mice when the latter were 2-5 mo. younger. Ovarian age, measured by the site of the follicular reserve, was similarly retarded in FR mice. Based on these data and previous evidence that follicular depletion plays a major role in the cessation of cyclicity in this strain, the delayed loss of estrous cyclicity in aging Fr mice apparently is mediated at least in part by the retarding effect of dietary restriction on the rate of follicular depletion.