FGF21 hormone prevents loss of immune function in old age, also being studied for insulin sensitivity benefits

The hormone FGF21 can protect against the loss of immune function that tends to occur with age, a new study finds.
The research, conducted at the Yale School of Medicine, also found that FGF21 is produced in the thymus gland. The findings have the potential to improve the immune function of elderly people.
FGF21 is also being studied for its potential benefits for people with type 2 diabetes. Several studies have found links between FGF21 and increased insulin sensitivity. This study, which sheds new light on the production and nature of FGF21, could therefore hold significance for diabetes research.
Normally, the thymus generates T cells, which bolster the immune system. But as we age, the thymus loses this function. With fewer T cells, one is at greater risk of infections and certain types of cancer.
In this study, the researchers studied a group of mice with heightened levels of FGF21. They found that higher levels of FGF21 increased or maintained T cell production in older mice and stopped the thymus from becoming fatty and dysfunctional. Lowering levels of FGF21 accelerated the breakdown of T cell function.
“We 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 Vishwa Deep Dixit, professor of comparative medicine and immunobiology at Yale School of Medicine.
“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.
“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.”
FGF21 is produced in the liver, Dixit noted. Levels of FGF21 increase when calorie intake is restricted, because it enables the body to burn fats when glucose levels run low. FGF21 could also benefit people with obesity and type 2 diabetes, because it improves insulin sensitivity and accelerates weight loss.
A recent study found that FGF21 is released in response to high refined carbohydrate levels, when it sends signals to the brain to indicate that sweet foods are no longer needed. According to the study, FGF21 is the first study discovered that regulates appetite for a particular macronutrient – in this case, sugar and other refined carbohydrates. The research could lead to positive developments for people who find it difficult not to consume too many sweet foods.
The findings are published in the Proceedings of the National Academy of Sciences.