Lathosterol level in plasma is elevated in type III hyperlipoproteinemia, but not in non-type III subjects with apolipoprotein E2/2 phenotype, nor in type IIa or IIb hyperlipoproteinemia.

We measured the serum lathosterol level, a reflection of the rate of whole body cholesterol synthesis, in 15 patients with manifest type III hyperlipoproteinemia (HLP), in 20 subjects with apolipoprotein (apo) E2/2 phenotype, but without type III HLP, in 21 patients with type IIA and 10 patients with type IIB HLP. A group of 100 subjects with apo E3/3 phenotype served as reference. Using ANCOVA, lathosterol was adjusted for serum cholesterol and triglyceride concentrations, since these parameters were found to independently correlate with lathosterol. The adjusted means (+/- SEM), in mumol/L, in these groups were 12.9 +/- 1.1, 8.2 +/- 1.1, 4.8 +/- 0.9, 9.8 +/- 1.4, and 7.8 +/- 0.4, respectively. Type III HLP patients had significantly higher lathosterol levels than all other groups except type IIB HLP. In addition, lathosterol was significantly lower in type IIA patients than in all other groups. The serum levels of plant sterols, used as a reflection of cholesterol absorption, did not differ among the various groups after adjustment for serum cholesterol. These findings suggest that an overproduction of cholesterol is one factor discriminating E2/2 homozygotes with type III HLP from those without the disease.