Be kind to your brain, go work out

The Tribune (SLO) - - Classifieds - BY GRETCHEN REYNOLDS

A hor­mone that is re­leased dur­ing ex­er­cise may im­prove brain health and lessen the dam­age and me­mory loss that oc­cur dur­ing de­men­tia, a new study finds. The study, pub­lished this month in Na­ture Medicine, in­volved mice, but its find­ings could help to ex­plain how, at a molec­u­lar level, ex­er­cise pro­tects our brains and pos­si­bly pre­serves me­mory and think­ing skills, even in peo­ple whose pasts are fad­ing.

Con­sid­er­able sci­en­tific ev­i­dence al­ready demon­strates that ex­er­cise re­mod­els brains and af­fects think­ing. Re­searchers have shown in rats and mice that run­ning ramps up the cre­ation of new brain cells in the hip­pocam­pus, a part of the brain de­voted to me­mory for­ma­tion and stor­age. Ex­er­cise also can im­prove the health and func­tion of the synapses be­tween neu­rons there, let­ting brain cells com­mu­ni­cate bet­ter.

In peo­ple, epi­demi­o­log­i­cal re­search in­di­cates that be­ing phys­i­cally ac­tive re­duces the risk for Alzheimer’s dis­ease and other de­men­tias and may slow dis­ease pro­gres­sion.

But many ques­tions re­main on just how ex­er­cise al­ters the in­ner work­ings of the brain and whether the ef­fects are a re­sult of changes else­where in the body that also hap­pen to be good for the brain or whether the changes ac­tu­ally oc­cur within the brain it­self. Those is­sues at­tracted the at­ten­tion of an in­ter­na­tional con­sor­tium of sci­en­tists – some neu­ro­sci­en­tists, oth­ers cell bi­ol­o­gists – all fo­cused on pre­vent­ing, treat­ing and un­der­stand­ing Alzheimer’s dis­ease.

Those con­cerns had brought a hor­mone called irisin into their sphere of in­ter­est. Irisin, first iden­ti­fied in 2012 and named for Iris, the gods’ mes­sen­ger in Greek mythol­ogy, is pro­duced by mus­cles dur­ing ex­er­cise. The hor­mone jump-starts mul­ti­ple bio­chem­i­cal re­ac­tions through­out the body, most of them re­lated to en­ergy me­tab­o­lism.

Be­cause Alzheimer’s dis­ease is be­lieved to in­volve, in part, changes in how brain cells use en­ergy, the sci­en­tists rea­soned that ex­er­cise might be help­ing to pro­tect brains by in­creas­ing lev­els of irisin there.

But if so, they re­al­ized, irisin would have to ex­ist in hu­man brains. To see if it did, they gath­ered tis­sues from brain banks and, us­ing so­phis­ti­cated test­ing, found irisin there. Gene ex­pres­sion pat­terns in those tis­sues also sug­gested that much of this irisin had been cre­ated in the brain it­self. Lev­els of the hor­mone were es­pe­cially high in the brains of peo­ple free of de­men­tia when they died, but were barely de­tectable in the brains of peo­ple who had died with Alzheimer’s.

The sci­en­tists in­volved in the study hope soon to test a phar­ma­ceu­ti­cal form of irisin as a treat­ment for de­men­tia in an­i­mals and even­tu­ally peo­ple.

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