Abstract
BackgroundOxidative stress, caused by an imbalance between reactive oxygen species and antioxidants, is thought to be an important intrinsic mechanism for aging. Ecologists have tested this hypothesis in birds, although the evidence supporting the link between oxidative stress and lifespan has so far been ambiguous. Two previous studies based on a wide range of different free-living bird species provided contradictory findings: antioxidants were negatively associated with survival rate in one study, but positively associated with longevity in another.MethodsIn this study, we identified possible shortcomings in previous research, and then used the comparative methods to test whether long-lived birds experience less oxidative stress reflected by four blood redox state markers (total antioxidant status, uric acid, total glutathione, malondialdehyde) based on data for 78 free-living species.ResultsRelatively long-lived bird species had high levels of antioxidants (total antioxidant status, total glutathione) and low levels of reactive oxygen species (malondialdehyde). These associations were independent of statistical control for any effects of body mass, sampling effort and similarity among taxa due to common phylogenetic descent.ConclusionsThe direction of these associations is consistent with the oxidative stress theory of aging.
Highlights
Oxidative stress, caused by an imbalance between reactive oxygen species and antioxidants, is thought to be an important intrinsic mechanism for aging
The markers were chosen for the following reasons (Costantini 2008, 2011; Vágási et al 2016): (1) total antioxidant status, uric acid and total glutathione are nonenzymatic antioxidants deployed to combat free radical insults and might play a role in ageing; (2) glutathione is the most important intracellular, endogenous, nonenzymatic antioxidant with multifaceted physiological effects including integral to the ageing process; (3) malondialdehyde, which results from lipid peroxidation of polyunsaturated fatty acids, is a widely used marker for oxidative stress, can react with deoxyadenosine and deoxyguanosine in DNA and was linked to ageing
Based on data for 78 free-living bird species, we found that lifespan was positively correlated with the concentration of antioxidants (TAS, tGSH), and negatively correlated with the concentration of reactive oxygen species (ROS) (MDA), which means that long-lived birds generally suffer low levels of oxidative stress
Summary
Oxidative stress, caused by an imbalance between reactive oxygen species and antioxidants, is thought to be an important intrinsic mechanism for aging Ecologists have tested this hypothesis in birds, the evidence supporting the link between oxidative stress and lifespan has so far been ambiguous. The intuitive logic is that differential rates of aging among species may be due to differences in oxidative stress (Sohal and Weindruch 1996; Finkel and Holbrook 2000; Barja 2004) Ecologists have tested this hypothesis in birds during the last 20 years, there is so far no consistent conclusion.
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