Comparison of age-related inflammation and oxidative stress in two lemur species

Oxidative damage and inflammation are mechanisms proposed to contribute to physiological senescence. Variation in oxidative damage and inflammation may reflect differential allocation of resources to reproduction and survival, contributing to differences in species-typical longevity and resulting from distinct, evolved life-history strategies. To investigate the link between molecular processes and physiological senescence, we compared urinary biomarkers of oxidative stress (8-isoprostane and 8-OHdG) and inflammation (neopterin) in a cross-sectional sample of two species that differ in life-history schedules: the relatively fast-paced ring-tailed lemur (Lemur catta; n = 41; ages = 1-32 years) and slow-paced Coquerel's sifaka (Propithecus coquereli; n = 49; ages = 1-27 years). Consistent with a faster life-history pace, ring-tailed lemurs showed significantly higher average levels of DNA damage than did sifakas (8-OHdG: ring-tailed lemur mean: 18.6 ± 10.3 ng/mg Cr, sifaka mean 8.0 ± 9.0 ng/mg Cr, p = 0.001). Species differences in lipid damage and inflammatory biomarkers were not significant (8-isoprostane: ring-tailed lemur mean: 0.5 ± 0.3 ng/mg Cr, sifaka mean: 0.3 ± 0.2 ng/mg Cr, p = 0.11), although sifakas tended to show greater inflammation (neopterin: ring-tailed lemur mean: 0.01 ± 0.02 ng/mg Cr, sifaka mean: 0.02 ± 0.02 ng/mg Cr; p = 0.14), which may reflect health challenges faced by this species in captivity. Contrary to our predictions, neither species showed age-related change in either marker of oxidative stress. Thus, although lemurs appear not to experience an increase in the rate of oxidative damage incurred with age, we cannot exclude the possibility that accumulated damage contributes to aging. Neither lemur species exhibited age-related change in inflammation; if anything, contrary to our prediction, ring-tailed lemurs showed marginal declines in inflammation with age. This finding, consistent with a few recent studies of other non-human primates, suggests that lemurs avoid the phenomenon of "inflammaging" widely observed in humans.