Low Protein Diet Reduces Alzheimer's Risk in Mice

Mice with symptoms of Alzheimer’s disease showed fewer signs of the disease when given a protein-restricted diet supplemented with amino acids every other week for four months, according to a new study.

Mice at advanced stages of the disease were put on the new diet, according to researchers, who report the mice showed improved cognitive abilities when their memory was tested using mazes.

In addition, fewer of their neurons contained abnormal levels of a damaged protein, called “tau.” This damaged protein accumulates in the brains of Alzheimer’s patients, according to the researchers.

Protein is the major dietary regulator of a growth hormone known as IGF-1, which has been associated with aging and diseases in mice and several diseases in older adults, according to the researchers.

Upcoming studies by Valter Longo, a professor at the University of Southern California and the study’s corresponding author, will attempt to determine whether humans respond the same way, while simultaneously examining the effects of dietary restrictions on cancer, diabetes and cardiac disease.

“We had previously shown that humans deficient in Growth Hormone receptor and IGF-I displayed reduced incidence of cancer and diabetes,” he said. “Although the new study is in mice, it raises the possibility that low protein intake and low IGF-I may also protect from age-dependent neurodegeneration.”

Longo’s research team found that a protein-restricted diet reduced levels of IGF-1 circulating through the body by 30 to 70 percent, and caused an eight-fold increase in a protein that blocks IGF-1′s effects by binding to it.

IGF-1 helps the body grow during youth but is associated with several diseases later in life in both mice and humans. Exploring dietary solutions to those diseases as opposed to developing new drugs to manipulate IGF-1 directly allows the research team to make strides that could help sufferers today or in the next few years, Longo said.

“We always try to do things for people who have the problem now,” he said. “Developing a drug can take 15 years of trials and a billion dollars.

“Although only clinical trials can determine whether the protein-restricted diet is effective and safe in humans with cognitive impairment, a doctor could read this study today and, if his or her patient did not have any other viable options, could consider introducing the protein restriction cycles in the treatment — understanding that effective interventions in mice may not translate into effective human therapies.”

Because many elderly people may already be frail, have lost weight or may not be healthy enough to eat a protein-restricted diet every other week, Longo advises that any dieting be monitored by a doctor or registered dietician to make sure that patients do not become amino acid deficient, lose additional weight or develop other side effects.
The results of the study were published online by Aging Cell.

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