Effects of caloric restriction or augmentation in adult rats: Longevity and lesion biomarkers of aging

Caloric restriction(CR) initiated in young rodents has been thoroughly docu mented to enhance longevity, but its efficacy when introduced at older ages has not been well investigated. Cohorts of 18- and 26-month-old male F344 x BN F1 hybrid rats were fed either: 1) NIH-31 meal (C); 2) vitamin and min eral fortified NIH-31 meal (R); or 3) vitamin and mineral fortified NIH-31 meal supplemented with corn oil and sweetened condensed milk (S). The C con trol rats were fed ad libitum, R rats were restricted to 32% of the caloric intake of the controls, and S rats were allowed to consume not more than 8 % more calories than C rats. After 6 weeks, the average weights were signif icantly different between all diet and age groups. Although calorie manipul ation altered body weight, no significant effect of the dietary interventio n on longevity was found. The average lesion burden, including tumor burden and prevalence of nearly all commonly occurring lesions, were comparable b etween the groups. Thus, the manipulation of weight at ages beyond middle a ge has a much less profound impact than similar interventions during growth and maturation in rats. (C) 1998, Editrice Kurtis.