A hormone made by the thymus appears to be a central brake on the chronic, low-grade inflammation that builds up with age. Researchers at the Keck School of Medicine of USC report in Nature Communications that thymulin, produced by the small organ tucked behind the breastbone, keeps inflammation in check - and that levels fall as animals age while inflammation climbs. When the team raised thymulin levels in older mice, cancer survival improved and immunotherapy worked better.
The target here is "inflammaging," the slow simmer of immune activity that increases over the years and has been tied to several of the leading causes of illness and death, including cancer, heart disease, metabolic conditions and neurodegenerative disease. Researchers have long been able to measure inflammaging without being able to explain what drives it, which has made it difficult to do anything about it.
That is what makes the thymus finding notable. "This is the first evidence of a substance that is naturally produced in the thymus, declines with age, and has the power to reverse age-related inflammation," said Fumito Ito, MD, PhD, professor of surgery and immunology and immune therapeutics at the Keck School of Medicine and the study's lead author. Identifying a specific molecule that rises and falls with age gives scientists something concrete to test, rather than treating inflammaging as an unavoidable feature of getting older.
The work, funded by the National Institutes of Health, was done in mice, and the disease outcomes measured were cancer-related. Whether restoring thymulin affects the inflammation implicated in brain disease, or does anything comparable in people, remains an open question for future research.