Evolutionary conservation of regulated longevity assurance mechanisms

Background: To what extent are the determinants of aging in animal species universal? Insulin/ insulin-like growth factor ( IGF)-1 signaling ( IIS) is an evolutionarily conserved ( public) regulator of longevity; yet it remains unclear whether the genes and biochemical processes through which IIS acts on aging are public or private ( that is, lineage specific). To address this, we have applied a novel, multi-level cross-species comparative analysis to compare gene expression changes accompanying increased longevity in mutant nematodes, fruitflies and mice with reduced IIS. Results: Surprisingly, there is little evolutionary conservation at the level of individual, orthologous genes or paralogous genes under IIS regulation. However, a number of gene categories are significantly enriched for genes whose expression changes in long-lived animals of all three species. Down-regulated categories include protein biosynthesis-associated genes. Up-regulated categories include sugar catabolism, energy generation, glutathione-S-transferases ( GSTs) and several other categories linked to cellular detoxification ( that is, phase 1 and phase 2 metabolism of xenobiotic and endobiotic toxins). Protein biosynthesis and GST activity have recently been linked to aging and longevity assurance, respectively. Conclusion: These processes represent candidate, regulated mechanisms of longevity-control that are conserved across animal species. The longevity assurance mechanisms via which IIS acts appear to be lineage-specific at the gene level ( private), but conserved at the process level ( or semi-public). In the case of GSTs, and cellular detoxification generally, this suggests that the mechanisms of aging against which longevity assurance mechanisms act are, to some extent, lineage specific.