Efficient and specific analysis of red blood cell glycerophospholipid fatty acid composition.

Red blood cell (RBC) n-3 fatty acid status is related to various
health outcomes. Accepted biological markers for the fatty acid
status determination are RBC phospholipids, phosphatidylcholine,
and phosphatidyletholamine. The analysis of these lipid fractions
is demanding and time consuming and total phospholipid n-3 fatty
acid levels might be affected by changes of sphingomyelin contents
in the RBC membrane during n-3 supplementation. We developed a
method for the specific analysis of RBC glycerophospholipids. The
application of the new method in a DHA supplementation trial and
the comparison to established markers will determine the relevance
of RBC GPL as a valid fatty acid status marker in humans. Methyl
esters of glycerophospholipid fatty acids are selectively generated
by a two step procedure involving methanolic protein precipitation
and base-catalysed methyl ester synthesis. RBC GPL solubilisation
is facilitated by ultrasound treatment. Fatty acid status in RBC
glycerophospholipids and other established markers were evaluated
in thirteen subjects participating in a 30 days supplementation
trial (510 mg DHA/d). The intra-assay CV for GPL fatty acids ranged
from 1.0 to 10.5% and the inter-assay CV from 1.3 to 10.9%.
Docosahexaenoic acid supplementation significantly increased the
docosahexaenoic acid contents in all analysed lipid fractions. High
correlations were observed for most of the mono- and
polyunsaturated fatty acids, and for the omega-3 index (r = 0.924)
between RBC phospholipids and glycerophospholipids. The analysis of
RBC glycerophospholipid fatty acids yields faster, easier and less
costly results equivalent to the conventional analysis of RBC total
phospholipids.