Dietary restriction modifies fever response in aging rats.

Intermittent (every-other-day) feeding initiated at 19 months of age and continued for 12 weeks, led to a moderate decrease in body weight of aging rats, enhanced survival and modified diurnal changes in body temperature and fever response to bacterial endotoxin (E. coli lipopolysaccharide, LPS). Diet-restricted animals which survived LPS administration, displayed reduced febrile response, i.e. (i) a moderate hypothermia in an early phase, and (ii) a delayed onset of body temperature elevation, as compared with their ad libitum-fed controls. However, peak body temperature values were similar in both groups. The rats of both groups which did not develop hyperthermia in response to LPS, died within 24 h of LPS administration. In control, but not in diet-restricted rats, variations in body weight during the 12 weeks prior LPS administration may be predictable in regard to their survival after LPS treatment. It seems that the resistance to bacterial endotoxin in aging rats is associated with their ability to develop hyperthermia.