To investigate the relationships between aging and selenium status, vitamins A and E, and plasma and erythrocyte fatty acids, we studied 105 healthy subjects (53 women, 52 men) living in Nove, a village near Vicenza (Veneto Region, northern Italy). The subjects were distributed equally for age and sex into four groups: group 1, 20-39 y; group 2, 40-59 y; group 3, 60-75 y; and group 4, > 75 y. A careful selection of subjects to exclude those with chronic or acute diseases was obtained with the collaboration of the three general practitioners operating in Nove. Aging was associated with a progressive decrease in selenium status and in the ratio of plasma and erythrocyte polyunsaturated to saturated fatty acids (P:S). Stepwise multiple linear analysis revealed age, vitamin A, and n-6 polyunsaturated fatty acids (PUFAs) as useful predictors of a substantial proportion of the selenium variability (R = 0.618, R2 = 0.382; P < 0.001) and age and erythrocyte oleic acid as predictors of erythrocyte glutathione peroxidase variability (R = 0.413, R2 = 0.17; P < 0.001).

1. In this study we sought to test the possibility that an olive-oil-rich diet might influence the membrane lipid composition and cation transport mechanisms in erythrocytes. 2. To this end, 11 normotensive normolipidaemic healthy volunteers were given a standard relatively low fat diet (28% of total energy) for 3 weeks, followed by a high fat (38% of total energy), olive-oil (100 g/day)-enriched diet for the 3 subsequent weeks, in a metabolic ward. The two diets contained the same amount of cholesterol (400 mg), and the polyunsaturated fatty acid/saturated fatty acid ratio was similar and comparatively low (0.35 on the standard vs 0.36 on the olive oil diet). 3. At the end of the study the lipid composition of the erythrocyte membranes showed the following changes: the oleic acid content increased by 15.7% and the amount of saturated fatty acid decreased by 3.2%. The polyunsaturated fatty acid content tended to decrease, while the polyunsaturated fatty acid/saturated fatty acid ratio did not change significantly. The cholesterol/phospholipid molar ratio increased significantly by 7.8%, still remaining within the reference range. 4. At the same time, the mean values of the maximum rates of the cation fluxes mediated by the Na+ -K+ pump, and by Na+ -K+ co-transport rose significantly, while the maximal rate of Na+ -L+ countertransport showed a non-significant trend towards lower values. 5. Urinary excretion of Na+ and K+, body weight and blood pressure did not change significantly.

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Since we have observed that monounsaturated fatty acids (MUFA) enriched diet modifies red cell membrane lipids and cation transport systems in normotensive subjects, we similarly evaluated a group of hypertensive patients undergoing an analogous dietary modification. In a group of 18 moderately hypertensive women, the diet was supplemented for two months with olive oil (about 45 g/day), which replaced an equal amount of seasoning fats. Before and after this period, red cell fatty acid composition was evaluated by gas-chromatography in order to verify diet compliance: a significant increase in oleic acid was observed, while the content of saturated and polyunsaturated fatty acids remained unchanged. After olive oil, maximal rates of Na-K pump (5580 +/- 329 vs 6995 +/- 390, p less than 0.001) and Na-K cotransport (Na-COT 544 +/- 52 vs 877 +/- 46, p less than 0.001: K-COT 790 +/- 76 vs 1176 +/- 66, p less than 0.001), cell Na content (9.58 +/- 0.4 vs 10.61 +/- 0.6, p less than 0.03) and passive permeability for Na (936 +/- 74 vs 1836 +/- 102, p less than 0.001) rose significantly. Although the reduction in maximal rate of the Li-Na CT after olive oil was not significant, it was the only cation transport parameter being correlated with the variations of membrane lipids, namely negatively with UFA (r = -0.528, p less than 0.05) and positively with SFA (r = 0.482, p less than 0.005). The change in maximal rate of Li-Na CT was also correlated with the variation of systolic and diastolic BP (r = 0.50, p less than 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

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