Mice with many of the pathologies of Alzheimer's Disease showed fewer signs of the disease when given a protein-restricted diet supplemented with specific amino acids every other week for four months.
Mice at advanced stages of the disease were put on the new diet. They showed improved cognitive abilities over their non-dieting peers when their memory was tested using mazes. In addition, fewer of their neurons contained abnormal levels of a damaged protein, called "tau," which accumulates in the brains of Alzheimer's patients.
Dietary 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.
Upcoming studies by USC Professor Valter Longo, the study's corresponding author, will attempt to determine whether humans respond similarly - 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. 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," said Longo, who directs the Longevity Institute of the USC Davis School of Gerontology and has a joint appointment the USC Dornsife College of Letters, Arts and Sciences.
Longo worked with Pinchas Cohen, dean of the USC Davis School, as well as USC graduate students Edoardo Parrella, Tom Maxim, Lu Zhang, Junxiang Wan and Min Wei; Francesca Maialetti of the Istituto Superiore di Sanit- in Rome; and Luigi Fontana of Washington University in St. Louis.
"Alzheimer's Disease and other forms of neurodegeneration are a major burden on society, and it is a rising priority for this nation to develop new approaches for preventing and treating these conditions, since the frequencies of these disorders will be rising as the population ages over the next several decades," said Cohen, who became dean of the School of Gerontology in summer 2012. "New strategies to address this, particularly non-invasive, non-pharmacological approaches such as tested in Dr. Longo's study are particularly exciting."
The results of their study were published online by Aging Cell last month.
The 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.