DIETARY RESTRICTION SLOWS AGE PIGMENT ACCUMULATION IN THE RETINAL-PIGMENT EPITHELIUM

Purpose. The accumulation of age pigment, or lipofuscin, in postmitoti c cells appears to be a universal feature of the aging process in anim als. In mammals, the lipofuscin content of the retinal pigment epithel ium (RPE) increases progressively during senescence. Dietary restricti on has been shown to slow the rate at which many biologic parameters c hange during aging. Experiments were conducted to determine if dietary restriction alters the rate of age pigment accumulation in the RPE. M ethods. Male Wistar rats were placed on one of three dietary regimens starting at weaning. One group was fed a nutritionally complete diet a d libitum. Another group was fed the same diet but was only allowed to consume 60% as much food daily as the ad libitum group ate. The final group was fed ad libitum a nutritionally complete diet that had a low er caloric density per gram than the diets fed to the other animals pr imarily because of the replacement of carbohydrate with oat fiber. Ult rastructural morphometric analysis was used to determine the RPE age p igment content in the first group at 6 months of age, and in all of th e groups at 18 months of age. Results. Dietary restriction, achieved e ither by reducing total food intake or by reducing the caloric content of the diet, resulted in significant decreases in RPE lipofuscin accu mulation. Conclusions. Dietary restriction provides a relatively simpl e means by which RPE age pigment content can be modulated. This should prove useful in assessing the role of RPE lipofuscin accumulation in age-related retinal disorders. That the oat fiber diet fed ad libitum was almost as effective as restriction of total food intake in slowing RPE age pigment accumulation indicates that the effect of restricted caloric intake is not mediated by almost constant hunger.