▁is ▁later ▁in ▁a ▁person ’ s ▁life , ▁it ▁has ▁been ▁suggested ▁that ▁age ▁plays ▁a ▁role ▁in ▁contrib uting , ▁along ▁with ▁the ▁reduced ▁ATP / AD P ▁ratio , ▁to ▁the ▁slow ▁d eter ior ation ▁of ▁the ▁function ▁of ▁B - cell s . ▁ ▁Met abol ic ▁characteristics ▁of ▁de af ness ▁in ▁M ID D ▁ ▁H ear ing ▁loss , ▁as ▁caused ▁by ▁the ▁ 3 2 4 3 ▁mit och ond rial ▁DNA ▁mut ation , ▁is ▁seen ▁in ▁the ▁form ▁of ▁progress ive ▁co ch lear ▁d ys function . ▁Although ▁the ▁mechanism ▁by ▁which ▁the ▁mut ation ▁in ▁the ▁t R N AL eu ( U UR ) ▁causes ▁this ▁d ys function ▁of ▁the ▁co ch lea ▁is ▁still ▁under ▁investigation , ▁it ▁has ▁been ▁hypoth es ized ▁that ▁it ▁involves ▁the ▁ion ▁p umps ▁required ▁for ▁sound ▁trans du ction . ▁As ▁the ▁mut ation ▁in ▁the ▁t R N AL eu ( U UR ) ▁leads ▁to ▁un bal anced ▁amounts ▁or ▁un stable ▁resp ir atory ▁chain ▁en zym es , ▁resp iration ▁and ▁ox id ative ▁ph osph ory lation ▁are ▁reduced , ▁leading ▁to ▁lower ▁levels ▁of ▁ATP . ▁ ▁Natur ally , ▁the ▁most ▁met abol ically ▁active ▁org ans ▁in ▁a ▁person ▁will ▁be ▁affected ▁by ▁this ▁ATP ▁def ic iency . ▁In cluded ▁in ▁these ▁met abol ically ▁active ▁org ans ▁is ▁the ▁co ch lear ▁st ria ▁v asc ular is . ▁The