Metabolic Differences in Cells from Long-lived Mice.

Abstract

Recent studies of aging have identified several ways to increase the mean and maximum lifespan of a variety of species. In spite of these successes, little is known about the specific mechanisms that control the aging process.

Snell dwarf mice, homozygous for the dw mutation at the Pit1 locus, live ~40% longer than control mice and have slowed development of many age-related pathologies. Previous work established that isolated dermal fibroblasts from long-lived Snell dwarf mice show increased resistance to many toxic stresses as compared to cells from normal littermates. Using a similar approach, we found that dwarf cells were also resistant to the short-term metabolic effects of glucose deprivation and rotenone exposure, measured using a reducible extracellular dye (WST-1). The inhibitory effects were non-lethal and reversible at the doses used, and cellular resistance to low glucose inhibition correlated with resistance to the toxicity of cadmium and hydrogen peroxide among a range of mouse cell lines. In fibroblasts derived from multiple species of rodents, resistance to the effects of rotenone and low glucose medium was correlated with higher species maximum lifespan, consistent with the idea that resistance may evolve with longevity.

Additional work explored the mechanism of resistance to rotenone and low glucose in cells from Snell dwarf mutant mice, focusing on the antioxidant response element (ARE) and its main transcription factor, Nrf2. These studies showed small (~30%) but significant increases in steady-state levels of Nrf2 protein in dwarf-derived cells, accompanied by larger (approximately two-fold) increases in transcription of many ARE-regulated genes. Increased ARE transduction is likely to have wide ranging effects, including increases in the antioxidant glutathione and activity of the plasma membrane redox system (PMRS), both of which were observed in dwarf cells.

Together, these results suggest that increases in Nrf2/ARE-dependent pathways might contribute to dwarf cellular resistance to the metabolic effects of rotenone and low glucose media, as well as to their resistance to several cytotoxic stresses. Further studies of this pathway may lead to insights as to how the ARE is regulated by dwarf cells, and how ARE activation and stress resistance affect the aging process.