Compound 991 directly activated AMPK and extended lifespan in yeast, worms, and flies

Compound 991 directly activated AMPK and extended lifespan in yeast, worms, and flies

On September 29, a team from the UK, Germany, and France reported in Aging Cell that compound 991 directly activates AMPK, a cellular sensor of energy deficit, and extends lifespan in yeast, roundworms, and flies. In organisms lacking the AMPK gene, the compound did not extend lifespan and sometimes caused harm. In mice, three weeks of 991 shifted liver function toward a protein profile resembling that of long-lived animals, though lifespan itself was not measured.

AMPK is conserved from yeast to humans: when a cell runs low on fuel, AMPK switches on an energy-saving program that slows growth, increases fat oxidation, and repairs mitochondria. This program had previously extended lifespan in mutants with constitutively active AMPK and under caloric restriction. Metformin, the leading pharmacological candidate, activates AMPK indirectly, affecting many other cellular processes along the way.

Metformin also had a subtler problem. In 2013, in the journal Cell, one of the present co-authors, Filipe Cabreiro, showed that in roundworms metformin extends lifespan primarily through the metabolism of gut bacteria rather than through direct action on the worm's own AMPK. That finding left an open question: is AMPK activation itself sufficient, or is it a side effect of changes in bacteria? Thirteen years later, Cabreiro himself closes that question with an activator that works without bacterial intermediaries.

That activator is compound 991, whose precise binding pocket on human AMPK was identified as early as 2013. Co-senior author David Carling has studied AMPK for over thirty years and participated in cloning the enzyme in the 1990s. The authors showed that the same binding pocket is conserved in flies, worms, and yeast, and that 991 activates their AMPK at doses thousands of times lower than metformin.

In animals, 991 reduced fat stores without suppressing appetite and extended lifespan in flies, yeast, and worms. In worms, this held across two bacterial strains, meaning the effect was independent of the bacterial partner, unlike metformin. The dose-response followed a bell-shaped curve: excess shortened lifespan in both flies and yeast.

"This is a switch that needs to be tuned correctly, not jammed in the on position. I would not want anyone to rush out for a supplement because of this news," says co-author Charalampos Rallis.

The decisive test came from organisms with the AMPK gene knocked out: in yeast lacking it, 991 shortened lifespan; in worms, the life-extending effect disappeared entirely on both bacterial strains. This is direct genetic proof of causality: without AMPK, there is no effect, so the compound acts specifically through this target.

In mammals, the result is preliminary: three weeks of 991 delivered in nanoparticles (the free compound is toxic to rodents) shifted liver proteins in mice toward a longevity profile, with increased ATP synthesis and mitochondrial number and decreased activity of mTOR, another regulator of cell growth. The authors call this the first proof of principle; mouse lifespan is the next step. A related direct AMPK activator, PXL-770, has already reduced liver fat in humans with good tolerability.

"Our study is the first proof that directly targeting AMPK with a drug can extend lifespan in living organisms," says laboratory head Helena Cochemé.

Before this work, the link between AMPK and aging rested on correlations from mutations and from metformin with its off-target effects. Now it is confirmed causality across three branches of the evolutionary tree: yeast, worms, and flies. A mechanism to test in mammals already exists: besides PXL-770, ATX-304, which raised resting energy expenditure by 8%, has also been tested.