The blood-brain barrier protects the brain from harmful chemicals in the blood, but it also blocks drugs from reaching it.
However, researchers have suggested that omega-3 fatty acid supplements can cross this barrier in Alzheimer's patients, influencing markers for the disease and inflammation.
"Earlier population studies indicate that omega-3 can protect against Alzheimer's disease, which makes it interesting to study the effects of dietary supplements containing this group of fatty acids in patients who have already developed the disease," says the study's lead author Dr Yvonne Freund-Levi.Omega-3 and other essential polyunsaturated fatty acids accumulate in the central nervous system (CNS) during gestation. It has been assumed that these acids are continually replaced throughout life, but little is known about how this occurs and whether changes in diet can affect the transport of important fatty acids across the blood-brain barrier. The blood-brain barrier serves to protect the brain from harmful chemicals existing naturally in the blood, but also blocks the delivery of drug substances to the brain.
Several diseases can affect the fatty acid profile of the CNS; in patients with Alzheimer's disease, for example, previous research has observed lower than normal brain concentrations of docosahexaenoic acid (DHA), an omega-3 fatty acid.
In the present study, part of the larger OmegAD project, scientists examined whether omega-3 dietary supplements change the fatty acid profile of the CNS in patients with mild Alzheimer's disease. Thirty-three patients participated in the study, 18 of whom received a daily omega-3 supplement and 15 a placebo for six months. The results show that the first group had higher levels of both DHA and eicosapentaenoic acid (EPA, another omega-3 fatty acid) in their cerebrospinal fluid (which surrounds the CNS) and blood. No such change was seen in the placebo group.
Moreover, they also found that levels of DHA correlated directly with the degree of change in Alzheimer's disease and inflammatory markers in the cerebrospinal fluid. Researchers in the field have long been interested in this link between Alzheimer's disease and inflammation, but attempts to treat the disease using traditional anti-inflammatory drugs have failed to produce any improvements in memory function.
"In animals, DHA dietary supplements can lead to an increase in DHA concentrations in the CNS," says Professor Jan Palmblad, who initiated the study. "Here we show that the same applies to humans, which suggests that omega-3 fatty acids in dietary supplements cross the blood-brain barrier. However, much work remains to be done before we know how these fatty acids can be used in the treatment of Alzheimer's disease to halt memory loss."The study was financed with grants from the Capio Research Foundation, the Dementia Association, the Gamla Tjänarinnor Foundation, the Swedish Alzheimer's Society, Oddfellows Sweden, the Swedish Nutrition Foundation, the Gun and Bertil Stohne Foundation, the Swedish Society of Medicine, Lions Sweden, the Norwegian Omega-3 producer Pronova Biocare A/S, and Stockholm County Council through its ALF funding agreement with Karolinska Institutet.
Transfer of omega-3 fatty acids across the blood brain barrier after dietary supplementation with a docosahexaenoic acid (DHA)-rich omega-3 fatty acid preparation in patients with Alzheimer's disease: the OmegAD study
vonne Freund-Levi*, Inger Vedin*, Tommy Cederholm, Hans Basun, Gerd Faxén Irving, Maria Eriksdotter, Erik Hjorth, Marianne Schultzberg, Bengt Vessby, Lars-Olof Wahlund, Norman Salem Jr, and Jan Palmblad
Journal of Internal Medicine, accepted manuscript online 23 November 2013, doi: 10.1111/joim.12166 *These authors contributed equally.
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