The long-term objective of this research is to develop medical interventions to delay and/or slow aging, and thereby increase the number of years of healthy adult life (YHL). The interventions that have been validated in extending the adult healthspan of mammals to date (dietary, life style, pharmacologic, or genetic) have provided approximately a two-fold increase in YHL at best. Yet evolution, via unidentified genetic changes, has produced a 200-fold range of Maximum Lifespan (MLS) across mammalian species: from about one year for the shrew to over 200 years for the bowhead whale. Once we discover the genetic and biochemical pathways by which evolution has achieved such huge differences in YHL across species, then we may be able to design effective interventions to dramatically boost the human healthspan. Recently published studies suggest that mitochondrial sequence features (only some of which change protein structure) may be responsible for up to half of the variation in MLS across species, with remaining variation statistically attributable to differences in Resting Metabolic Rate (RMR) and/or body mass (which is highly correlated with RMR). No published studies have investigated whether mtDNA sequence features associated with MLS of species are also associated with variation in lifespan in normal human populations. Furthermore, the few mitochondrial sequence variants known to be associated with human longevity have not yet been tested for association with other biomarkers that vary with MLS of species (e.g. reactive oxygen species (ROS) production rates, cellular resistance to heat stress, and mtDNA mutation rates). With previous NIA funding under the P.I.'s K01 award (1997-2002), we screened a large genealogical database (the Utah Population Database) for mitochondrial lineages (matrilineages) in which exceptional human longevity was clustering, and collected whole blood DNA samples and lymphoblastoid cell lines from 55 such matrilineages. Analyses of the DNA sequences of all protein-coding genes from the mitochondrial genomes of 20 of these matrilineages, and from control mitochondrial genomes, revealed several amino acid changes significantly associated with longevity. We now propose to obtain the complete sequences of the mitochondrial genomes in these 55 longevity-selected matrilineages, and in 141 control matrilineages, and identify all sequence features associated with exceptional longevity. We will also test whether the longevity- selected matrilineages show favorable shifts in three biomarkers of MLS of species: towards lower ROS production rates, higher cellular resistance to heat stress, and lower mtDNA mutation rates. We will also collect comprehensive gene expression profiles, and additional measures of nuclear and mitochondrial genomic integrity, from the longevity-selected and control matrilineages. Bioinformatics tools applied to all available data may identify genetic and biochemical pathways regulating longevity across and within species, and identify possible targets for pharmaceutical and/or gene therapies aimed at delaying and/or slowing aging.
Patterns of exceptional longevity in large pedigrees suggest that longevity is, in part, mitochondrially inherited. This project will investigate the genetics, biochemistry, and possible influences on genomic integrity, of mitochondrially inherited exceptional longevity, in order to advance our understanding of the molecular mechanisms of aging, and identify targets for the future development of pharmaceuticals and gene therapies to increase the human healthspan.
