DHA, a type of omega-3 fatty acid naturally found in breast milk and fish oil, is an important nutrient for brain development and function. It is primarily obtained from diet, and preferentially transferred from mother to fetus across the placenta. However, for people who struggle to get sufficient DHA from normal dietary sources, supplementation is recommended. DHA is highly unsaturated and is vulnerable to oxidation and degradation under acid conditions.
Led by Wang Yi, assistant professor at PolyU’s Department of Applied Biology and Chemical Technology (ABCT), and Wong Man-sau, professor at ABCT, the research team innovated a nano-encapsulation technology to protect DHA from oxidation. The team used Zein, an edible corn protein, as the encapsulation material to mimic milk fat globule membrane. The nano-encapsulation forms a core-shell structure to protect DHA in fish oil throughout gastric digestion and facilitates DHA absorption in the brain, intestine and placenta.
“Our team innovated the nano-encapsulation technology, which is proven to be an effective technology to protect DHA from oxidation in vivo, thus enhancing the absorption and efficacy of DHA. Our findings also indicated that the technology can help overcome blood-brain barrier in DHA delivery. We therefore believe that the technology could be further applied to enhance the efficiency of drug delivery for the brain, such as those for patients with dementia or Alzheimer’s disease,” said Dr Wang Yi.
DHA in Maternal Tissues
To test the effectiveness of nano-encapsulation technology in enhancing DHA absorption, PolyU’s team conducted some experiments on maternal mice and their offspring.
In two groups of maternal mice (each of six) fed with normal fish oil (Normal FO) and nano-encapsulated fish oil (Nano FO), respectively, it was found that the DHA concentration in the duodenum and jejunum of the Nano FO group is significantly higher than the Normal FO group. The result implies that DHA, being protected by the encapsulation structure from oxidation and degradation under stomach’s acidic conditions, is successfully released in the upper two parts of the small intestine of the Nano FO group.
Also, DHA content in the brain of the Nano FO maternal mice were significantly higher. This indicates that DHA was delivered to the brain of the Nano FO group more effectively as the challenge of the blood-brain barrier was overcome, researchers said.
DHA in Offspring
The team also conducted tracer studies on offspring of maternal mice. The mice were divided into six groups, each with 10, and were fed with different diets including: 1) no DHA meal; 2) Zein; 3) normal low dose fish oil (Normal FO-low); 4) normal high dose fish oil (Normal FO-high); 5) Nano-encapsulated low dose fish oil (Nano FO-low); and 6) Nano-encapsulated high dose fish oil (Nano FO-high).
The findings showed that three groups, namely: Normal FO-high, Nano FO-low and Nano FO-high spent more time on novel objects rather than on familiar objects, implying that they were more curious about new things and demonstrated better memory and learning capabilities.
For the Nano FO-high group, they had a higher amount of Brain-Derived Neurotrophic Factor (BDNF) in the hippocampus. BDNF, a protein activated by DHA, plays an important role in supporting the survival of existing brain neurons and encouraging the growth and differentiation of new neurons and synapses. They also demonstrated a significant difference to other groups in terms of better spatial learning and memory abilities in the Y-maze experiment.
The research project was funded by the Health and Medical Research Fund (HMRF) of the Food and Health Bureau of the Hong Kong SAR Government and the Shenzhen Basic Research (Layout of Disciplines) Project Fund.