Researchers at Tufts University hypothesized that whole walnut extract inhibits lipopolysaccharide (LPS)-induced microglial activation by regulating calmodulin expression through calcium ions. They tested their hypothesis by treating a rat microglial cell line with different concentrations of whole walnut extracts.
The researchers found that treatment with whole walnut extract resulted in a slow increase in intracellular calcium in a dose- and time-dependent manner. This increase became amplified when cells were depolarized with potassium chloride.
In addition, whole walnut extract treatment also increased calmodulin protein levels in cells, regardless of the concentration levels. This increase was inhibited when the researchers pretreated cells with thapsigargin, a tumor promoter in mammalian cells.
Moreover, treatment with whole walnut extract one hour before LPS induction effectively prevented the rise of inducible nitric oxide synthase expression, increase of ionized calcium ion-binding adaptor-1, and downregulation of calmodulin. Overall, these findings suggest that walnuts contain bioactive compounds that help regulate inflammatory responses in the brain.
From these findings, the researchers suggest that walnuts may be used to reduce chronic inflammation and prevent brain degeneration.
An earlier study has revealed that walnuts provide protection against Alzheimer's disease, the most common neurodegenerative disease. Published in the Journal of Alzheimer's Disease, the animal study discovered that adhering to a walnut-enriched diet can lead to significant improvements in learning skills, memory, and motor development. Additionally, it can reduce anxiety.
For the study, the researchers looked at the effects of dietary walnut supplementation on mice. To do this, they fed mice with a diet consisting of six or nine percent walnuts. These are equivalent to an ounce and 1.5 ounces per day, respectively, of walnuts in humans. The results revealed that that feeding mice with a walnut-enriched diet improved the animals' cognitive function, motor development, and behavior.
The researchers suggested that the ability of walnuts to help reduce the risk, delay the onset, or hamper the progression of Alzheimer's disease may be attributed to the high antioxidant content of walnuts. Walnuts contain 3.7 millimoles per ounce (mmol/oz). Antioxidants fight oxidative stress and inflammation -- both of which are prominent characteristics of Alzheimer's disease. (Related: Walnuts rank as top nut, providing highest level of quality antioxidants.)
In addition, walnuts are the only type of nuts that contain high amounts of alpha-linolenic acid (ALA), which is an omega-3 fatty acid that has been shown to provide heart- and brain-health benefits. The researchers also suggested that this fatty acid may have contributed to the improvement of behavioral symptoms seen in the study.
"These findings are very promising and help lay the groundwork for future human studies on walnuts and Alzheimer's disease - a disease for which there is no known cure," said Abha Chauhan, leader of the study and head of the Developmental Neuroscience Laboratory at the New York State Institute for Basic Research in Developmental Disabilities (IBR).
Chauhan previously led a cell culture study that focused on the protective effects of walnut extract against the oxidative damage caused by amyloid beta protein. This protein is the primary component of amyloid plaques that form in the brains of people with Alzheimer's disease.
Read more news stories and studies on the health benefits of walnut consumption by going to FoodIsMedicine.com.