Effects of environment on life span and pathobiological phenotypes in senescence-accelerated mice

Abstract

Experimental studies to observe the effects of environmental factors such as rearing conditions, nutritional status and extrinsic stress on life span, senescence scores and pathobiological phenotypes have been conducted using the senescence-accelerated mouse (SAM) consisting of senescence-prone (SAMP) and senescence-resistant (SAMR) strains. Both SAMP and SAMR mice showed reduced senescence scores and lived about 1.5 times longer when reared under specific pathogen-free (SPF) conditions compared to conventional conditions. There was still a significant difference between SAMP and SAMR in both life span and senescence scores under SPF conditions, suggesting that the characteristic of “accelerated senescence” was well preserved in SAMP mice even under SPF conditions. The incidence and severity of amyloidosis, contracted kidney and pneumonia were reduced significantly under SPF conditions, however the degenerative joint disease (SAMP3), osteoporosis (SAMP6) and deficits in learning and memory (SAMP8, SAMP10) were not affected by rearing conditions. Nutritional status such as caloric intake and diet composition in protein and fatty acids also had a significant influence on the aging process in the SAM model. Furthermore, the SAMP mice were more susceptible to several kinds of stress such as low temperature, tobacco smoke, paraquat, forced exercise, water immersion and restraint and influenza A virus infection than SAMR mice.