Lifespan‐extending interventions enhance lipid‐supported mitochondrial respiration in Caenorhabditis elegans

Abstract

Dietary restriction and reduced reproduction have been linked to long lifespans in the vast majority of species tested. Although decreased mitochondrial mass and/or function are hallmarks of aging, little is known about the mechanisms by which these organelles contribute to physiological aging or to the effects of lifespan-extending interventions, particularly with respect to oxidative phosphorylation and energy production. Here, we employed the nematode Caenorhabditis elegans to examine the effects of inhibition of germline proliferation and dietary restriction, both of which extend the lifespan of C. elegans, on mitochondrial respiratory activity in whole animals and isolated organelles. We found that oxygen consumption rates and mitochondrial mass were reduced in wild-type (WT) C. elegans subjected to bacterial deprivation (BD) compared with animals fed ad libitum (AL). In contrast, BD decreased the rate of oxygen uptake but not mitochondrial mass in germline-less glp-1(e2144ts) mutants. Interestingly, mitochondria isolated from animals subjected to BD and/or inhibition of germline proliferation showed no differences in complex I-mediated respiratory activity compared to control mitochondria, whereas both interventions enhanced the efficiency with which mitochondria utilized lipids as respiratory substrates. Notably, the combination of BD and inhibition of germline proliferation further increased mitochondrial lipid oxidation compared to either intervention alone. We also detected a striking correlation between lifespan extension in response to BD and/or inhibition of germline proliferation and the capacity of C. elegans to generate ATP from lipids. Our results thus suggest that the ability to oxidize lipids may be determinant in enhanced longevity.

Preservation of Mitochondrial Membrane Potential is Necessary for Lifespan Extension from Dietary Restriction

“…The ability of DR to preserve Δψ m during early aging does not appear to involve the activity of UCPs, but instead requires both mitochondrial ANT and IF1 activity. We also find that fatty acid metabolism is required for preservation of Δψ m by DR, consistent with a recent report in worms that fatty acid metabolism promotes longevity [21], as well as numerous studies in mammals showing that DR increases fatty acid oxidation [36, 47-49]. While it remains difficult to quantify or control Δψ m in vivo in mammals, this work should serve to orient future experiments to define mechanisms underlying these observations in worms and other systems.…”

“…Therefore we tested the hypothesis that fatty acid oxidation is what fuels preservation of Δψ m by DR by directly inhibiting fat oxidation with the drug perhexiline [20]. Prior work has shown that perhexiline prevents lifespan extension from DR [21], and we found that perhexiline prevented preservation of Δψ m in response to DR and, instead, significantly reduced it (Figure 1D). Perhexiline also significantly reduced Δψ m compared to fed control animals, suggesting fatty acid oxidation supports baseline in vivo Δψ m .…”

“…There is emerging evidence that fat metabolism and mitochondrial function play a fundamental role in DR longevity in both C. elegans [21] and mammals [36]. BD upregulates fatty acid oxidation by mitochondria, a process that is required for DR-mediated longevity [21]. Therefore we tested the hypothesis that fatty acid oxidation is what fuels preservation of Δψ m by DR by directly inhibiting fat oxidation with the drug perhexiline [20].…”

“…Animals stained with TMRE were exposed to FCCP in 500 μL M9 at a final concentration of 10 μM for four hours. Perhexiline was used at 30 μM final concentration for 24 hours according to previous protocols [20, 21]. MitoTracker Green FM was dissolved in DMSO and worms were exposed at a final concentration of 10 μM in 500 μL M9 buffer for 24 hours.…”

“…There is emerging evidence that fat metabolism and mitochondrial function play a fundamental role in DR longevity in both C. elegans [21] and mammals [36]. BD upregulates fatty acid oxidation by mitochondria, a process that is required for DR-mediated longevity [21].…”