It was found that Trx1 protein levels were decreased in patients during amnestic mild cognitive impairment and in several regions of AD-affected brains [40,41,42]; however, in another study, there was no significant difference in the Trx levels between the brains of control and AD patients, although the TrxR1 activity was enhanced in the AD patients [37]. Here, TXNRD1 is linked to Alzheimer disease.