Inhibition Of The Mechanistic Target Of Rapamycin (mTOR) – Rapamycin And Beyond

Research Summary

A review of the molecular biology of mTOR and of rapamycin as an anti-ageing compound: how it extends lifespan in model organisms, the mechanisms proposed for that effect, and whether its side effects can be separated from its benefits.

Who Or What Was Studied?

A review of published research rather than a new experiment. It draws on studies in yeast, worms, flies and mice – including the NIA Interventions Testing Program mouse lifespan studies – plus cell and tissue work on mTORC1 and mTORC2 signalling, and on human use of rapamycin and its analogues as immunosuppressants and cancer drugs.

What Did The Research Show?

• Rapamycin acutely inhibits mTORC1, but chronic dosing also disrupts mTORC2 in vivo in tissues including liver, white adipose tissue and skeletal muscle.
• Inhibition of the mTOR pathway extends lifespan in yeast, worms, flies and mice; across the mouse studies rapamycin consistently benefits females more than males.
• Proposed mechanisms for the lifespan effect include cancer suppression, reduced protein translation, better protein quality (autophagy and proteasome activity) and effects on stem cells, although the review notes that chronic rapamycin does not measurably reduce translation in mice.
• Many of the harmful effects – impaired glucose tolerance, insulin resistance, new-onset diabetes and immune changes – are attributed to mTORC2 inhibition, while the benefits are largely attributed to mTORC1 inhibition.
• Because rapamycin washes out of tissues within a few weeks, intermittent dosing and mTORC1-selective compounds are proposed as ways to keep the benefits while limiting the side effects.

Limitations And Interpretation

• It is a review, not a trial: it reports no new human outcomes and does not establish that rapamycin slows human ageing.
• Most of the lifespan evidence comes from mice and other model organisms; the human data cited come mainly from transplant and cancer patients, not healthy people.
• The idea that mTORC1-selective inhibition would separate the benefits from the side effects remains a hypothesis, and the review notes that the mechanism of lifespan extension is still unclear.