J.A. Schouten

Changes in membrane lipid composition of human erythrocytes after dietary supplementation of (n − 3) polyunsaturated fatty acids. Maintenance of membrane fluidity

The effect of dietary (n-3) polyunsaturated fatty acids on erythrocyte membrane lipid composition, fluidity, and flexibility was studied in seven healthy subjects. An eight weeks daily supplementation of 3 g of the (n-3) fatty acids eicosapentaenoic and docosahexaenoic acid resulted in an increased unsaturation of erythrocyte phosphatidylcholine (PC) and phosphatidylethanolamine (PE). This change was accompanied by a slight decrease in PC and PE content (P less than 0.05) and an increase in sphingomyelin content (P less than 0.01). The erythrocyte membrane fluidity, measured with electron spin resonance of intact erythrocytes and with fluorescence polarization of erythrocyte ghosts did not change. No change was seen in the viscosity of erythrocyte suspensions of haematocrit = 0.80, measured at various shear rates. The supplementation caused a 42% decrease in plasma triacylglycerol levels. We suggest that the change in the erythrocyte membrane fatty acid composition induced by the dietary supplementation of (n-3) fatty acids might be counteracted by a change in the phospholipid class distribution, resulting in overall maintenance of membrane fluidity.

Effect of dietary cod-liver oil on the lipid composition of human erythrocyte membranes

The effect of dietary cod-liver oil on factors which characterize membrane lipid fluidity was studied. To six volunteers a daily supplement of 15 ml of cod-liver oil, providing 3 g of omega 3 fatty acids, was given for 2 weeks. Changes induced by the supplement in the fatty acid patterns of the individual erythrocyte phospholipid classes did not occur at the same rate or in the same degree. A rapid incorporation of omega 3 fatty acids in plasma lipids and in erythrocyte phosphatidyl choline, at the expense of linoleic acid, was seen, resulting in increased total unsaturation. A slower and quantitatively smaller incorporation of omega 3 fatty acids in erythrocyte phosphatidyl ethanolamine and phosphatidyl serine was seen. No change in the fatty acid pattern of sphingomyelin was seen. Withdrawal of the supplement for 2 weeks did partly reverse the cod-liver oil induced changes in erythrocyte phosphatidyl choline, while the changes in erythrocyte phosphatidyl ethanolamine and phosphatidyl serine lasted. Neither a change in distribution of erythrocyte phospholipid classes, nor in the erythrocyte cholesterol/phospholipid ratio was found. The observed changes in lipid composition are indicative of an increased lipid fluidity.

myo-Inositol and sorbitol in erythrocytes from diabetic patients before and after sorbinil treatment

SummaryErythrocytes from diabetic patients before and after treatment with the aldose reductase inhibitor, sorbinil, were analyzed by a capillary gas chromatographic method for sorbitol and myo-inositol. The mean erythrocyte sorbitol level in the diabetic patients was significantly higher than in the control subjects (13.1±0.9 and 5.2±0.3 nmol/ml erythrocytes, respectively, mean±SEM, p< 0.001). The mean erythrocyte myo-inositol level in diabetic patients was not different from that in control subjects (43.2±2.9 and 40.5±1.9nmol/ ml erythrocytes, respectively). Sorbinil treatment reduced the elevated sorbitol levels in the diabetic patients to normal or slightly below normal, but did not affect the erythrocyte myo-inositol concentration. It is concluded that the erythrocyte is not a suitable model to monitor a possible effect of sorbinil on myo-inositol concentration in less accessible tissues.

The Effect of Dietary Linoleic Acid and Pectin on Lipoprotein and Apolipoprotein A1 Concentrations in Rhesus Monkeys

Medium term effects (3 months) on serum lipoprotein levels of a diet with a high P/S ratio (2.2) and a low P/S ratio (0.3) were investigated in 13 normolipoproteinemic rhesus monkeys. Both diets were studied with and without added gel-forming fibre, as pectin. Addition of pectin did not have major influences on serum lipid levels. Changing from a low to a high P/S diet resulted in a significant decrease of total cholesterol (23%) and LDL cholesterol (18%) levels, but also HDL cholesterol (23%) and apolipoprotein A1 (Apo A1; 13%) concentrations fell significantly. However, after 12 weeks on the high P/S diet, HDL cholesterol concentrations rose by 24%, not significantly different from the levels during the low P/S diet. We conclude that the medium-term effects of a high P/S diet are a decrease in LDL cholesterol with only a transient effect on HDL cholesterol.

Benefits of intensive treatment of insulin-dependent diabetes patients: The importance of patient education

In a study among 34 insulin-dependent diabetes patients the effects of a more intensive treatment by three regular specialists were examined. Compared with a matched control group (n = 34), the results showed that the intensively treated group had a better metabolic control and that they judged the relationship with their specialist more favourably. No differences were found regarding the satisfaction about the patient education, the knowledge about diabetes, the state anxiety, the general and health locus of control orientation nor the attitude towards diabetes. Also the correlations between these patient education variables and the regulation and the evaluation of the relationship with the doctor did not differ for both groups. The conclusion is stressed that patient education needs to be a part of the development of a more intensive treatment of diabetes patients.