As mentioned early, BDNF has been shown to regulate neuronal development and plasticity and plays a role in learning and memory. Low levels of BDNF are found in patients with neurodegenerative diseases, including Alzheimer's disease and major depression. In addition, BDNF levels are low in obesity and independently so in patients with type 2 diabetes. Interestingly it has been shown that exercise increases BDNF levels not only in the brain and in plasma, but in skeletal muscle as well [109]. BDNF mRNA and protein expression was increased in muscle cells that were electrically stimulated, and BDNF increased phosphorylation of AMP-activated protein kinase (AMPK) and acetyl coenzyme A carboxylase-beta (ACCbeta) and enhanced fatty oxidation both in vitro and ex vivo. Thus, BDNF appears to play a role both in neurobiology and in central as well as peripheral metabolism. The finding of low BDNF levels both in neurodegenerative diseases and in type 2 diabetes may explain the clustering of these diseases. Therefore BDNF is likely to mediate some of the beneficial effects of exercise with regard to protection against dementia, obesity, and type 2 diabetes [109].
