A single copy of klotho allele KL-VS is associated with longevity, better health, increased cognition, and bigger regional brain volume. However, its longitudinal effects on cognition and brain volumes, both global and regional, in late life are unclear. In this study we show that, relative to noncarriers, KL-VS heterozygotes had (1) shorter survival; (2) smaller white matter volumes; (3) slower cognitive decline; and (4) greater right frontal lobe volumes. The KL-VS heterozygote survival and white matter volume disadvantages were unexpected. A possible explanation for these results in the context of the literature is a potential interaction between the environment and/or age of the participants, leading to a heterozygote disadvantage. The longitudinal cognitive trajectories indicate that heterozygotes would have an advantage in very late life. Collectively these results suggest that the genotype-survival advantage of the KL-VS allele is age-dependent and possibly mediated through differential cognition and brain volume.

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Most eukaryotes respire oxygen, using it to generate biomass and energy. Yet, a few organisms lost the capacity to respire. Understanding how they manage biomass and energy production may illuminate the critical points at which respiration feeds into central carbon metabolism and explain possible routes to its optimization. Here we use two related fission yeasts, Schizosaccharomyces pombe and Schizosaccharomyces japonicus, as a comparative model system. We show that although S. japonicus does not respire oxygen, unlike S. pombe, it is capable of efficient NADH oxidation, amino acid synthesis and ATP generation. We probe possible optimization strategies using stable isotope tracing metabolomics, mass isotopologue distribution analysis, genetics, and physiological experiments. S. japonicus appears to have optimized cytosolic NADH oxidation via glycerol-3-phosphate synthesis. It runs a fully bifurcated TCA cycle, supporting higher amino acid production. Finally, it uses the pentose phosphate pathway both to support faster biomass generation and as a shunt to optimize glycolytic flux, thus producing more ATP than the respiro-fermenting S. pombe. By comparing two related organisms with vastly different metabolic strategies, our work highlights the versatility and plasticity of central carbon metabolism in eukaryotes, illuminating critical adaptations supporting the preferential use of glycolysis over oxidative phosphorylation.