Low levels of an enzyme that degrades insulin could increase the risk for Alzheimer’s disease, according to a new study in mice by doctors at UT Southwestern Medical Center at Dallas. The study, available online and in a future issue of “Proceedings of the National Academy of Sciences,” is among the first to show a relationship between the enzyme insulysin and Alzheimer’s disease. The discovery also points to a new mechanism linking diseases like diabetes and Alzheimer’s’ an association that has not been understood, said Dr. Bonnie Miller, assistant professor of internal medicine and a lead author of the study. ‘What’s exciting is that this suggests a new mechanism that may contribute to Alzheimer’s disease’the competition of multiple substrates, such as insulin and amyloid-beta, for a limiting amount of the insulysin enzyme,’ said Miller. The researchers studied mice that were missing insulysin gene activity. They found that the insulysin enzyme ‘ in addition to degrading insulin’also degrades amyloid- beta peptides. Most importantly, even a partial decrease in insulysin activity was found to raise amyloid-beta peptide levels in the brain. High levels of the peptides increase the risk of Alzheimer’s disease, which affects more than 4 million Americans. ‘It identifies another pathway that’s important in regulating levels of amyloid- beta peptide,’ said Dr. Dwain Thiele, chief of hepatology at UT Southwestern and one of the study’s senior authors. ‘The next step is to use this animal model to see if there is a risk for developing Alzheimer’s disease.’ The study is the latest in ongoing research on the effects of the enzyme in T cells and more recently in the liver and brain. The research began in 1994, when the other senior author, Dr. Louis Hersh, was on the UT Southwestern faculty. He is now at the University of Kentucky. Investigators from the Mayo Clinic in Jacksonville, Fla., also served as lead authors of the study. The National Institutes of Health, the Alzheimer’s Association and two Mayo Clinic grants supported the study. Expert: Memory does not decline with age Feeling forgetful’ Don’t automatically blame your ‘aging brain.’ A Baylor College of Medicine expert said that memory loss has relatively little to do with growing old. ‘There is the assumption that memory fails when we get older when in fact, memory stays stable into old age,’ said Dr. Anita Woods, a geriatrician at Baylor’s Huffington Center on Aging at Baylor. Woods added that there are some normal changes in memory function expected as people age. The delayed recollection of names, for example, is not due to a deteriorating brain, but to a slowed down central nervous system and decreased cognitive energy. Older brains have an incredible potential for regeneration and growth, she said. Just as the body needs to be conditioned to stay healthy, it is important to exercise your brain with mental activities to keep neurons firing at an old age. ‘Meaningful mental activities, whether it’s doing a crossword puzzle or debating with loved ones or friends, keeps the mind active,’ she said. ‘Also, a high level of social engagement is correlated with good memory performance in old age.’ When older individuals forget something they often panic, assuming their mind is failing them, she said. This self-perpetuating thinking increases anxiety, which inadvertently blocks memory. Woods advised seniors to relax when they have trouble remembering something.