Late life metformin treatment limits cell survival and shortens lifespan by triggering an aging-associated failure of energy metabolism, bioRxiv, 2019-12-04

SummaryThe diabetes drug metformin is to be clinically tested in aged humans to achieve health span extension, but little is known about responses of old non-diabetic individuals to this drug. By in vitro and in vivo tests we found that metformin shortens life span and limits cell survival when provided in late life, contrary to its positive early life effects. Mechanistically, metformin exacerbates aging-associated mitochondrial dysfunction towards respiratory failure, aggravated by the inability of old cells to upregulate glycolysis in response to metformin, leading to ATP exhaustion. The beneficial dietary restriction effect of metformin on lipid reserves is abrogated in old animals, contributing to metabolic failure, while ectopic stabilization of cellular ATP levels alleviates late life metformin toxicity in vitro and in vivo. The toxicity is also suspended in nematodes carrying diabetes-like insulin receptor insufficiency and showing prolonged resilience to metabolic stress induced by metformin. In sum, we uncovered an alarming metabolic decay triggered by metformin in late life which may limit its benefits for non-diabetic elderly patients. Novel regulators of life extension by metformin are also presented.Highlights<jatslist list-type=bullet><jatslist-item>Late life metformin treatment limits cell survival and shortens lifespan.<jatslist-item><jatslist-item>Metformin exacerbates aging-associated mitochondrial dysfunction causing fatal ATP exhaustion.<jatslist-item><jatslist-item>Old cells fail to upregulate glycolysis as a compensatory response to metformin.<jatslist-item><jatslist-item>The dietary restriction (DR) mimetic response to metformin is abrogated in old animals.<jatslist-item><jatslist-item>PKA and not AMPK pathway instigates the early life DR response to metformin.<jatslist-item><jatslist-item>Stabilization of cellular ATP levels alleviates late life metformin toxicity in vitro and in vivo.<jatslist-item>

biorxiv physiology 200-500-users 2019

Generalizing RNA velocity to transient cell states through dynamical modeling, bioRxiv, 2019-10-29

AbstractThe introduction of RNA velocity in single cells has opened up new ways of studying cellular differentiation. The originally proposed framework obtains velocities as the deviation of the observed ratio of spliced and unspliced mRNA from an inferred steady state. Errors in velocity estimates arise if the central assumptions of a common splicing rate and the observation of the full splicing dynamics with steady-state mRNA levels are violated. With scVelo (<jatsext-link xmlnsxlink=httpwww.w3.org1999xlink ext-link-type=uri xlinkhref=httpsscvelo.org>httpsscvelo.org<jatsext-link>), we address these restrictions by solving the full transcriptional dynamics of splicing kinetics using a likelihood-based dynamical model. This generalizes RNA velocity to a wide variety of systems comprising transient cell states, which are common in development and in response to perturbations. We infer gene-specific rates of transcription, splicing and degradation, and recover the latent time of the underlying cellular processes. This latent time represents the cell’s internal clock and is based only on its transcriptional dynamics. Moreover, scVelo allows us to identify regimes of regulatory changes such as stages of cell fate commitment and, therein, systematically detects putative driver genes. We demonstrate that scVelo enables disentangling heterogeneous subpopulation kinetics with unprecedented resolution in hippocampal dentate gyrus neurogenesis and pancreatic endocrinogenesis. We anticipate that scVelo will greatly facilitate the study of lineage decisions, gene regulation, and pathway activity identification.

biorxiv bioinformatics 200-500-users 2019

 

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