The amino acid, asparagine, found in foods such as meat, eggs, and dairy products as well as some plant foods, has long been considered non-essential because it is produced naturally by the body.
However new evidence from Canadian researchers, published in the journal Neuron, has found that this nutrient is essential for normal brain development. Its benefits are specific to the brain and do not appear to be necessary for other organs.
“The cells of the body can do without it because they use asparagine provided through diet. Asparagine, however, is not well transported to the brain via the blood-brain barrier,” said senior co-author of the study Dr. Jacques Michaud, who found that brain cells depend on the local synthesis of asparagine to function properly.
Spurred on by Tragedy
The discovery of the essential nature of asparagine arose out of tragedy. In April 2009, a Quebec family lost one of their sons to a rare genetic disease causing congenital microcephaly, intellectual disability, cerebral atrophy, and refractory seizures. The event was even more tragic because this child was the third infant in this family to die from the same disease.
This tragedy led Dr. Michaud and his team to study the genetic abnormality responsible for this developmental disorder.
The team identified the gene affected by the mutation code for asparagine synthetase, the enzyme responsible for synthesizing the amino acid asparagine. Their work was the first to associate a specific genetic variant with a deficiency of this enzyme.
“In healthy subjects, it seems that the level of asparagine synthetase in the brain is sufficient to supply neurons,” Michaud said. “In individuals with the disability, the enzyme is not produced in sufficient quantity, and the resulting asparagine depletion affects the proliferation and survival of cells during brain development.”