Exercise Hormone Helps Memory
Studies connect cardio exercise with improved memory and brain function–but how? We’re just starting to see the molecular clues. Exercised muscles releas a hormone called irisin, which influences the brain’s memory center. Original report is here.
Where does irisin come from? The exercising muscles express a particular gene (that is, make messenter RNA and protein specified by the gene). The gene is called FNDC5 or Fibronectin Type III Domain Containing 5. The gene is found in humans and mice–but not invertebrates, which lack the vertebrate central nervous system. It is expressed strongly during embryonic formation of the heart. A particular peptide (short part of a protein) is cut off the FNDC5 protein; this peptide is called irision. In adults, FNDC5 expression from myocytes (muscle cells) releases irisin, whose signal is associated with converting “white fat” cells to “brown fat” with expenditure of energy.
But now, exercise is also shown to cause irisin expression and release in the hippocampus. Is this unusual, for a very particular signal molecule to have different roles in different tissues? Actually, it is very common in eukaryotic organisms (plants and animals, including us humans). Most of our proteins are multitaskers. In particular, much of brain function depends upon multitasking proteins. That is why so many single-gene birth defects have multiple effects on the body, including cognitive problems.
The hippocampus is the brain’s memory center. In the hippocampus, FNDC5 expression induces expression of BDNF (brain-derived neurotrophic factor). BDNF protects the neurons that encode memories.
So the moral is, now that spring is here (ignore the dusting of snow this morning) let’s get out and start running.