Purified dietary n − 3 polyunsaturated fatty acids alter diacylglycerol mass and molecular species composition in concanavalin A-stimulated murine splenocytes

Abstract

A low-dose, short-term dietary supplementation with highly purified ( n − 3) fatty acid ethyl esters was studied in mice to determine the effect on splenic cell membrane diacylglycerol mass and composition. Mice were fed diets containing either 3% safflower oil (SAP) ethyl esters, 2% SAP plus 1% eicosapentaenoic acid ethyl ester (EPA), or 2% SAP plus 1% docosahexaenoic acid ethyl ester (DHA). Following a 10-day feeding period, pathogen-free mice were sacrificed and splenic cells isolated and stimulated with concanavalin A (Con A) at 10 μg/ml. After 0 min (basal), 5 min, and 180 min, 1,2-diacyl, 1- O-alkyl-2-acyl, and 1- O-alkenyl-2-acyl- sn-glycerol subclasses were isolated and quantitated by HPLC. Diacylglycerol (DAG) was found to be the major diradylglycerol (DG) component in murine splenocytes. DHA-fed mice had significantly ( P < 0.05) higher levels of DAG at all stimulation time points relative to EPA and SAP animals. Significant effects ( P < 0.05) of diet, time, and a diet × time interaction ( P < 0.05) were noted for various DAG molecular species. In general, a significantly higher ( n − 3) polyunsaturated fatty acid (PUFA) content in the EPA and DHA groups, and a significantly higher ( n − 6) PUFA content in the SAF group was noted. 18:0–22: 5( n − 3), 18:1–22:5( n − 3) and 16:1–20:5( n − 3) species were present only in EPA and DHA-DAG, confirming the incorporation of ( n − 3) fatty acids into splenocyte DAG. The data indicate that the molecular species composition of murine splenocyte DAG is significantly modulated by low-dose, short-term EPA and DHA feeding. In addition, substitution of SAP with DHA results in an increase in DAG mass. These alterations could potentially influence signal transduction pathways regulating lymphocyte function.