The effects of different levels of dietary restriction on neoplastic pathology in the male Sprague-Dawley rat.
OBJECTIVE
The primary purpose of this study was to evaluate the effects of varied levels of dietary restriction (DR) on neoplastic pathologies in rodents at 58 and 110 weeks of age.


METHODS
Male Sprague-Dawley (SD) rats were divided into four nutritional groups; an ad libitum (AL) control group, and three dietary restricted (DR) groups that were fed the NIH-31 diet reduced in amount by 10, 25, and 40%.


RESULTS
At 110 weeks of age, compared to AL rats, the incidence of benign tumors was significantly lower in all DR groups while primary tumors were significantly lower in the 10 and 40% DR groups; no malignant tumors were detected in the 10% DR group. Most defined mortalities were caused by neoplastic lesions. All levels of DR reduced the percentage of tumor-bearing animals, the incidence of skin tumors (combined), and the total number of tumors. Pituitary, skin, and pancreatic tumors were the most prolific lesions; pituitary and skin tumors were the most fatal. Compared to AL rats, the time to onset of skin and pancreatic tumors was longer in all of the DR groups.


CONCLUSIONS
In many cases, the incidences of neoplastic lesions were similar among the DR groups, clearly indicating that the DR effect is not linear and that even a very low level of DR (10%) can have a significant effect on many important neoplastic lesions and tumor burden. The main effect of DR was to decrease the incidence of some neoplastic lesions and to increase the time to onset and/or decrease the progression of tumors, thereby increasing the 110-week survival rate of DR rats.
Duffy
Peter H
PH
Division of Genetic and Reproductive Toxicology, National Center for Toxicological Research, FDA, Jefferson, AR 72079, USA. pduffy@nctr.fda.gov
Lewis
Sherry M
SM
Mayhugh
Martha A
MA
Trotter
Ronald W
RW
Latendresse
John R
JR
Thorn
Brett T
BT
Feuers
Ritchie J
RJ
D000375:Aging / Q000502:physiology; D000818:Animals; D004032:Diet; D005508:Food Deprivation / Q000502:physiology*; D008297:Male; D009369:Neoplasms / Q000178:diet therapy* / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016019:Survival Analysis