Bone mass 800% in­crease sug­gests osteoporosis break­through

Iran Daily - - Health -

Aground­break­ing set of stud­ies has found that blocking cer­tain re­cep­tors in the brain leads to the growth of re­mark­ably strong bones. Could a new osteoporosis treat­ment be on the hori­zon? Pri­mar­ily a dis­ease of old age, osteoporosis can cause bones to be­come grad­u­ally weaker.

Over time, bones be­come so por­ous that mi­nor im­pacts — even just a cough or a sneeze — might cause frac­tures, med­i­cal­new­sto­ wrote.

Ac­cord­ing to the Cen­ters for Dis­ease Con­trol and Preven­tion (CDC), osteoporosis af­fects al­most one in four women aged 65 and over in the US.

As it stands, there is no cure; treat­ment fo­cuses on re­duc­ing the risk of frac­tures but can­not slow the con­di­tion’s pro­gres­sion.

In a healthy per­son, the body breaks down old or dam­aged bone and re­places it with new bone.

How­ever, as we age, this cy­cle be­comes off-kil­ter, and the body breaks down more bone than can be re­made. This leads to pro­gres­sively weaker bones and, even­tu­ally, osteoporosis.

Es­tro­gen has a wide range of func­tions in the hu­man body, par­tic­u­larly re­gard­ing re­pro­duc­tion. The hor­mone also works in the brain, but sci­en­tists cur­rently know lit­tle about its func­tions there.

Re­cently, sci­en­tists from the Uni­ver­sity of Cal­i­for­nia, San Fran­cisco and the Uni­ver­sity of Cal­i­for­nia, Los An­ge­les ran a se­ries of stud­ies to learn more about es­tro­gen in the brain.

Along the way, they made a serendip­i­tous dis­cov­ery that could change the face of osteoporosis re­search.

Led by se­nior study au­thor Holly In­gra­ham, PH.D., the re­searchers were pri­mar­ily in­ter­ested in how es­tro­gen’s ac­tiv­ity in the brain alters me­tab­o­lism dur­ing dif­fer­ent stages of life.

In par­tic­u­lar, they were look­ing at the func­tion of es­tro­gensen­si­tive neu­rons in the hy­po­thal­a­mus. This is a part of the brain that links the ner­vous sys­tem to the en­docrine (hor­mone) sys­tem.

The hy­po­thal­a­mus plays an im­por­tant role in reg­u­lat­ing meta­bolic pro­cesses, such as by help­ing con­trol body tem­per­a­ture, hunger, sleep, fa­tigue, and cir­ca­dian rhythms.

The sci­en­tists blocked the ef­fects of es­tro­gen in the hy­po­thal­a­mus of an­i­mals. When they did this, the an­i­mals gained weight and be­came less ac­tive.

Ini­tially, the sci­en­tists as­sumed that the ad­di­tional weight would be ac­counted for by ex­tra fat or mus­cle tis­sue.

How­ever, upon fur­ther in­spec­tion, they found that the ex­tra weight was due to in­creased bone mass. Some of the an­i­mals had in­creased their to­tal bone mass by 800 per­cent.

When the in­ves­ti­ga­tors tested the dense mouse bones, they found that they were also par­tic­u­larly strong. In fact, ac­cord­ing to In­gra­ham:

“Our col­lab­o­ra­tors who study bone for a liv­ing said they’d never seen bone this strong.”

They have now pub­lished their find­ings in the jour­nal Na­ture Com­mu­ni­ca­tions. As In­gra­ham goes on to say, “Our cur­rent un­der­stand­ing of how the body con­trols bone growth can’t ex­plain this.”

“[This] sug­gests,” she added, “we may have un­cov­ered a com­pletely new path­way that could be used to im­prove bone strength in older women and oth­ers with frag­ile bones.”

In fol­low-up stud­ies, the re­searchers fo­cused on a par­tic­u­lar re­gion of the hy­po­thal­a­mus that seemed to be hav­ing this in­cred­i­ble ef­fect on bone: The ar­cu­ate nu­cleus.

Since re­moval of es­tro­gen re­cep­tors in this re­gion causes bone growth, they be­lieve that nor­mally, these cells siphon en­ergy and re­sources away from bone growth to be used else­where in the body.

This find­ing is ex­cit­ing and sur­pris­ing and only ap­peared in fe­male mice.

She con­tin­ues, “I’ve al­ways been in­ter­ested in how sex hor­mones make male and fe­male brains dif­fer­ent, and this is a re­ally won­der­ful ex­am­ple of how dra­matic those dif­fer­ences can be.”

The re­searchers ex­tended their ex­per­i­ments to un­der­stand how bone den­sity changed dur­ing the life­span of a mouse. They no­ticed that bone den­sity in these mice was main­tained through­out old age.

Test­ing this mech­a­nism fur­ther, the sci­en­tists deleted the ar­cu­ate es­tro­gen re­cep­tors in a mouse model of osteoporosis. In mice that had lost 70 per­cent of their bone mass, bone den­sity re­bounded by 50 per­cent in just a few weeks.

In the blood, es­tro­gen pro­motes bone growth; in the hy­po­thal­a­mus, how­ever, it ap­pears to have the op­po­site ef­fect.

In­gra­ham hy­poth­e­sizes that “after pu­berty, the es­tro­gen sys­tem in the fe­male brain ac­tively shifts re­sources away from bone growth and to­wards things like re­pro­duc­tion, which could con­trib­ute to women’s higher risk of weak­ened bones as we age.”

Since the re­sults are sur­pris­ing and novel, plenty more work will be needed; how­ever, they have al­ready opened some ex­cit­ing new av­enues for osteoporosis re­searchers.

“I’m in the clouds about this re­sult,” In­gra­ham said. “If our next ex­per­i­ments show that the brain re­leases a novel cir­cu­lat­ing fac­tor that trig­gers en­hanced bone growth, we might have a real chance of de­vel­op­ing a drug that coun­ter­acts osteoporosis.”

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