Metformin showed little benefit for flu immunity in aged mice
Six weeks of metformin before flu infection, continued for 10 days afterward, did not improve lung immune memory in aged male mice.
Our read
Interventions- Studied:
- Experiments in young and aged male mice, against aged control-treated mice
- What changed:
- Lung memory T cell populations did not improve in metformin-treated aged mice compared with aged controls
- The catch:
- Metformin was stopped before secondary infection; protection with continued treatment was not measured
- In the record:
- One of 2,351 papers on metformin on record: 749 with results in people, 413 in animals. Its result on weight loss agrees with 1 of 3 other findings on record; 2 point the other way.
Editor of record: Boris Djordjevic · AgingResearch.News
Young (3–4 months) and aged (18–19 months) male C57BL/6JN mice received standard food or food containing 0.1% metformin in an animal experiment. The metformin diet began six weeks before an initial flu infection and ended 10 days afterward. The mice received a different flu strain 30 days after the first infection.
Metformin did not improve lung populations of memory T cells, immune cells that remember previous infections, in aged mice. It altered some immune responses, more in young mice than aged mice. During the second infection, aged metformin-fed mice lost more weight on day six but regained more weight on days 10–14 than aged controls. These weight differences were small. They also had temporarily higher amounts of virus in their lungs on day seven. Lung virus levels fell below detection in all groups by day 10.
Why it matters
Age-related declines in immune memory can leave older bodies less prepared for later infections. The authors concluded that metformin’s usefulness for improving this aspect of aging immunity remains unclear.
Caveats
The experiment tested a single dosing schedule in male mice of one strain, not treatment during the second infection. One aged mouse in each diet group was excluded after severe weight loss during the first infection.
Metformin is part of Bryan Johnson's Blueprint and David Sinclair's daily regimen in Lifespan
The paper
University of Connecticut
Frontiers in Aging, Jun 17, 2026, Open access
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