Monoamine oxidase A (MAO-A), a mitochondrial enzyme, catalyzes the degradation of monoamines. Studies show that increased expression of MAO-A promotes prostate cancer metastasis by activating the Shh-IL6-RANKL signaling network. In addition, MAO-A expression in adipose tissue macrophages is upregulated in aging, leading to the reduction of noradrenaline availability in adipose tissue. Decreased levels of noradrenaline contribute to the aging-related decline of catecholamine-induced lipolysis in adipocytes. Furthermore, sympathetic neuron–associated macrophages import and degrade norepinephrine via the transporter SLC6A2 and MAO-A, respectively, and thus contribute to obesity.
