Fatty acids and the selective death of old cells

The cells that go wrong with age are not the cells that die. Damaged cells are normally cleared by programmed cell death, but some of them enter a quieter state called senescence: they stop dividing, yet they do not leave, and over the years they accumulate in tissues, secrete inflammatory signals, and accelerate everything from cardiovascular disease to metabolic decline. The dream of ageing research for two decades has been a way to clear these cells selectively, without killing the healthy cells around them. A paper recently published in Cell, from an international team led by the University of Eastern Finland, reports that the switch may lie in a single fatty acid.

The starting observation was metabolic. When the team compared senescent cells with healthy ones, they found that the metabolism of polyunsaturated fats was altered, and that one fatty acid in particular, dihomo-gamma-linolenic acid, or DGLA, was depleted in the senescent cells. DGLA is an intermediate in the body’s handling of long-chain fats, normally converted onward by an enzyme called Delta-5 desaturase. The depletion mattered because of what DGLA does next: it is one of the fats that make cell membranes susceptible to ferroptosis, a form of regulated cell death driven by iron and by the peroxidation of membrane lipids.

The intervention followed directly. When the team supplemented cells with DGLA, or inhibited the enzyme that consumes it, the senescent cells died by ferroptosis. The healthy cells, for reasons the paper describes as metabolic rather than mechanical, were largely unaffected. The selectivity is the point of the result: senescent cells, already depleted of DGLA, are pushed over the ferroptosis threshold by the supplement, while healthy cells with normal DGLA handling are not.

The effect translated to whole animals. Aged mice given oral DGLA showed fewer senescent cells in their tissues, less inflammation in fat and liver, and signs of improved liver and kidney function. The team also looked at humans, using data from a Finnish cohort: a genetic variant known to raise DGLA levels in the body was associated with lower senescence markers in fat tissue. The human evidence is observational, not a trial, but it points in the same direction as the mouse experiment.

The authors are careful about what the work does and does not establish. It is not a treatment yet; it is a route to one. The route is attractive because the proposed drug target, Delta-5 desaturase, is an enzyme that already exists and can in principle be inhibited, and because ferroptosis as a clearance mechanism is being explored for other conditions. The caveats are the usual ones: mouse ageing is not human ageing, oral DGLA is a blunt intervention, and a genetic association in a Finnish cohort is not a clinical response. What the paper offers is a plausible, mechanistically clear handle on a problem that has resisted the field for years, and a reason to put DGLA on the short list of things to try.