By Michelle Fay Cortez March 3 (Bloomberg) — Beta amyloid that builds up in the brains of patients with Alzheimer’s disease may go along with beneficial antimicrobial activity, researchers said. The findings from investigators at Massachusetts General Hospital raise the possibility that some cases of Alzheimer’s may stem from chronic, undetected brain infections. The results also cast doubt on the pharmaceutical industry’s efforts to find drugs to wipe out beta amyloid from the brain, one of the main methods now in development to fight the most common form of dementia in the elderly, the researchers said. Beta amyloid, or abeta, remains harmful in high concentrations, they said. “Most people think abeta is junk,” a toxic byproduct of other activity in the brain, said Rudolph Tanzi , director of genetics and aging at Massachusetts General’s Institute for Neurodegenerative Disease . “This says tread carefully. It may play a normal, essential role in the brain and be part of the way the brain protects itself.” Laboratory tests showed beta amyloid inhibited the growth of eight organisms, including the yeast Candida albicans , which can cause thrush, and bacteria such as Listeria, Staphylococcus and Streptococcus, according to a report in the journal PLoS One . Tissue taken from the brains of patients with Alzheimer’s disease suppressed Candida, while samples from people without it didn’t, the researchers said. They theorize that beta amyloid is an antimicrobial peptide, a natural part of the innate immune system found in plants, animals and the human brain. Antimicrobial peptides are the first line of defense against pathogens in the immune system, which may go awry in Alzheimer’s patients, they said. ‘Big Question’ “The big question is what is most often triggering the innate immune system in the elderly that are the most at risk for Alzheimer’s disease,” Tanzi said in a telephone interview. “Perhaps as we age, there may be unnoticed low-grade infections that are triggering the innate immune system to produce beta amyloid.” Johnson & Johnson , based in New Brunswick, New Jersey, Merck & Co., based in Whitehouse Station, New Jersey, Ireland’s Elan Corp. , New York-based Pfizer Inc. and Eli Lilly & Co. of Indianapolis are working on Alzheimer’s disease drugs that target beta amyloid. Alzheimer’s is a progressive disease that starts with mild forgetfulness and eventually robs patients of memories and independence. It afflicts 30 million people worldwide, a number that may exceed 100 million by 2050, according to Alzheimer’s Disease International, an advocacy group based in London. Short-Term Benefit Robert Moir , from Massachusetts General’s genetics and aging research unit and a senior author of the paper with Tanzi, compared beta amyloid to a fever. While both are bad for the patient, they are worse for bugs causing an infection, he said. A little bit is good for the patient, a lot of it may be helpful for a short period, while a lot of it for long periods is dangerous, he said in a telephone interview. “We really need to be thinking about what causes the amyloid beta to go up in the first place,” he said. “If it is a response to an infection, then by treating the infection you can treat the disease.” While the concept is surprising, it fits with existing knowledge, said Samuel Gandy , associate director of Mount Sinai School of Medicine’s Alzheimer’s Disease Research Center in New York. It gives researchers a new angle to approach Alzheimer’s and should be easy to test in animal models, he said. Additional research is under way, Tanzi and Moir said. “In the field, the concept that amyloid beta isn’t just pathological is heretical,” Moir said. “It’s my hope that this study will start people thinking about this much more than they have, rather than just being obsessively focused on reducing amyloid beta.” To contact the reporter on this story: Michelle Fay Cortez in London at mcortez@bloomberg.net
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Alzheimer’s Theory on Brain Material May Shift by Benefit Found in Study
