Dietary linoleate increases fluidity and influences chemical composition of plasma low density lipoprotein in adult men.

Dietary linoleate was effective to increase LDL fluidity in adult men but did not significantly influence VLDL or HDL fluidities. Lipoproteins were isolated ultracentrifugally from plasma of sixteen healthy, free living male volunteers consuming controlled diets formulated from typical U.S.A. foods to have 35 energy % fat with 10 g (diet L) or 30 g (diet H) linoleate per day, 30-50 g saturated fatty acids/day and the balance mainly monounsaturated fatty acids. Calculated cholesterol intakes were 500 mg/day at each calorie level. Changes in LDL fluidity were detected as differences in diphenylhexatriene (DPH) fluorescence polarization upon crossover between the two controlled diets. Thermotropic measurement of DPH fluorescence anisotropy and compositional analyses indicated that LDL and HDL fluidities were dependent upon phospholipid and triacylglycerol concentrations, respectively, and were modulated by the presence of cholesteryl esters. Fatty acid analyses of the major lipid classes of the isolated lipoproteins indicated that changes, upon diet crossover, in DPH fluorescence anisotropy, were a linear function of the incremental change in LDL phospholipid linoleate. The fluorescent probe described an environment corresponding to the fatty acyl moieties of the phospholipids on the LDL periphery, which composition is apparently under dietary control. It is suggested that the diet induced fluidity changes may affect the conformation of the apoprotein moiety on the LDL surface and thus the potential for LDL interaction with cellular LDL receptors.