Impact of acute exercise on immediate and following early post-exercise FGF-21 concentration in adults: Systematic review and meta-analysis

FGF21 is a polypeptide hormone recognized for its roles in regulating glucose and lipid homeostasis and energy metabolism.

“Fibroblast growth factor 21 (FGF21) is a polypeptide hormone belonging to the fibroblast growth factor family, recognized for its multifaceted roles in regulating glucose and lipid homeostasis and energy metabolism [50].”

After acute exercise, circulating FGF21 levels rise rapidly, typically peaking around 1 h post-exercise and returning to baseline approximately 3 h later.

“After acute exercise, circulating FGF21 levels rise rapidly, typically peaking around 1 h post-exercise and returning to baseline approximately 3 h later [50].”

FGF21 is expressed in multiple organs including liver, white and brown adipose tissue, skeletal muscle, pancreas, heart, and brain, and can be induced under stress conditions such as exercise, cold exposure, and nutritional imbalance.

“It is expressed in multiple organs including liver, white and brown adipose tissue, skeletal muscle, pancreas, heart, and brain, and can be induced under stress conditions such as exercise, cold exposure, and nutritional imbalance.”

FGF21 functions as an endocrine factor with pleiotropic metabolic effects.

“Unlike classical FGFs, FGF21 functions as an endocrine factor with pleiotropic metabolic effects.”

While the liver is the primary source of circulating FGF21 under most conditions, skeletal muscle has been shown to secrete FGF21 during exercise, particularly under metabolic stress.

“While the liver is the primary source of circulating FGF21 under most conditions, skeletal muscle has been shown to secrete FGF21 during exercise, particularly under metabolic stress [50].”

Acute exercise transiently increases FGF21 in a duration- and intensity-dependent manner.

“In contrast, acute exercise transiently increases FGF21 in a duration- and intensity-dependent manner.”

Aerobic exercise predominantly triggers metabolic stress: increased AMP/ATP ratio activates AMPK, and calcium release activates CaMK; both phosphorylate PGC-1α, enhancing FGF21 and irisin expression, but without strong MSTN suppression.

“Aerobic exercise predominantly triggers metabolic stress: an increased AMP/ATP ratio activates AMPK, and calcium release from the sarcoplasmic reticulum activates calmodulin-dependent kinases (CaMK). Both AMPK and CaMK phosphorylate PGC-1α, enhancing FGF21 and irisin expression [20,50], but without the strong MSTN suppression seen with resistance training.”

Training status can affect both baseline and exercise-induced myokine levels; individuals with metabolic syndrome exhibit attenuated irisin responses, and failure to distinguish acute and chronic measurement time points may have contributed to contradictory findings.

“Training status can affect both baseline and exercise-induced myokine levels. For instance, individuals with metabolic syndrome have been found to exhibit attenuated irisin responses [19], and failure to distinguish between acute and chronic measurement time points may have contributed to some contradictory findings in the literature [18,42,50,80].”