Plasma lipid transfer activities in hyper-high-density lipoprotein cholesterolemic and healthy control subjects

The relationships between plasma lipid transfer protein (LTP) activity and various lipid or lipoprotein concentrations were studied in 14 hyper-high-density lipoprotein (hyper-HDL) cholesterolemic subjects and 152 healthy controls. We measured plasma LTP activity by our sensitive assay method, using radiolabeled proteoliposomes as the lipid donor, low-density lipoprotein (LDL) as the acceptor, and a very small amount of untreated plasma (typically 1 to 2 microliters) as the sample. Control subjects had the mean of LTP activity at 206 +/- 45 nmol/mL/h. The difference of LTP activity between men and women was not statistically significant. In the control subjects, the activity of plasma LTP had a significantly positive correlation with the concentrations of total cholesterol (r = .639, P less than .01) and LDL cholesterol (r = .634, P less than .01), but not with those of HDL cholesterol and total triglyceride, nor with percent ideal body weight. One of 14 patients with hyper-HDL cholesterolemia had no detectable LTP activity, and three others had very low LTP activity. From these data, LTP activity may be one of the important factors to influence plasma LDL concentration, and the lack of LTP activity may be related to a subclass of hyper-HDL cholesterolemias.