WASHINGTON, Jan. 11 (Xinhua) -- A hormone that extends lifespan in mice by 40 percent is produced by specialized cells in the thymus gland and protects against the loss of immune function that comes with age, a U.S. study said Monday.
Published online in the U.S. journal Proceedings of the National Academy of Sciences, the study's findings have future implications for improving immune function in the elderly, for obesity, and for illnesses such as cancer and type-2 diabetes.
When functioning normally, the thymus produces new T cells for the immune system, but with age, the thymus becomes fatty and loses its ability to produce new T cells. This loss of new T cells in the body is one cause of increased risk of infections and certain cancers in the elderly.
Led by Vishwa Deep Dixit, professor of comparative medicine and immunobiology at Yale School of Medicine, the researchers studied transgenic mice with elevated or reduced levels of a life-extending hormone called FGF21.
They found that increasing the levels of FGF21 in old mice protected the thymus from age-related fatty degeneration and increased the ability of the thymus to produce new T cells, while FGF21 deficiency accelerated the degeneration of the thymus in old mice.
We found that FGF21 levels in thymic epithelial cells is several fold higher than in the liver -- therefore FGF21 acts within the thymus to promote T cell production, said Dixit.
Elevating the levels of FGF21 in the elderly or in cancer patients who undergo bone marrow transplantation may be an additional strategy to increase T cell production, and thus bolster immune function, Dixit said.
Further studies will focus on understanding how FGF21 protects the thymus from aging, and whether elevating FGF21 pharmacologically can extend the human healthspan and lower the incidence of disease caused by age-related loss of immune function, he added.