Supplementation of
coconut oil to the diet for 1-2 weeks produced a significant
hypercholesterolemia in 14-day-old chicks. Changes in plasma
fatty acid composition correlated positively with those of diets. In this study, we have shown a different response of low- and
high-density lipoprotein (
LDL and HDL) fractions to dietary saturated fat (
coconut oil) rich in lauric and
myristic acids. Although all the components of these particles seemed to increase, the percentages of increases found in total (TC), free (FC) and esterified
cholesterol (EC) were higher in
LDL than in HDL. TC/
phospholipid (PL) ratio, considered as an inverse index of membrane fluidity, also increased with the dietary regimen in
LDL, while no significant differences were found in HDL. These results suggest that supplementation of
coconut oil to the diet decreased the fluidity of
LDL. The EC/
triglycerides (TG) ratio was also significantly increased in
LDL, corroborating the main atherogenic function of this
lipoprotein fraction in response to lauric and
myristic acids. We have also estimated the lipidic order parameter, S, from the steady-state fluorescence anisotropy of
1,6-diphenyl-1,3,5-hexatriene (DPH)-labelled low- and
high-density lipoproteins. In
LDL, temperature dependence of S shows two different behaviour zones at about 20 degrees C. In HDL, the plot of S values versus T is linear. DPH anisotropy and S increased in both
LDL and HDL from treated chicks. This increase becomes more evident as temperature rises and also with dietary treatment.