Correlations between fatty acid composition of the erythrocyte membrane and blood rheology data.

The fatty acid composition of erythrocyte membrane phospholipids (phosphatidyl choline, PC, and phosphatidyl ethanolamine, PE) and erythrocyte filterability was studied in seven subjects with type II diabetics before and after change of therapy from oral hypoglycaemic agents to insulin. For comparison the same variables were also studied in 10 healthy controls. In the diabetic group the greatest changes in fatty acid composition were found before treatment in the PE fraction, corresponding to the inner part of the red cell membrane. We found increased values for 16:0 (p < 0.001), 18:1 (p < 0.01) and 20:4 (omega-6) (p < 0.05) and decreased values for 16:1 (p < 0.01) and 18:3 (omega-6) (p < 0.001), compared to values for the healthy controls. The proportion of fatty acids in the inner leaflet of the membrane did not correlate to the red cell filtrability in diabetics or healthy subjects. In the PC fraction, which corresponds to the outer leaflet of the erythrocyte membrane, we found higher values for 16:0 (NS), 18:1 (p < 0.05), 20:4 (omega-6) (NS) and 22:5 (omega-3) (p < 0.01), and lower values for 16:1 (p < 0.05) in diabetics, compared to healthy controls. In the PC fraction an increased proportion of 16:0 was inversely correlated with red cell transit time (RCTT) (p < 0.05), and increased proportions of 16:1 and 18:0 were correlated with a high RCTT (p < 0.05). Insulin treatment did not significantly change red cell deformability or the fatty acid composition of the red cell membrane. Our results also indicate that palmitic acid (16:0) may be favourable in the PC fraction and stearic acid (18:0) unfavourable with respect to the rheological properties of erythrocytes.