Impaired intermediate-density lipoprotein triglyceride hydrolysis in familial lecithin:cholesterol acyltransferase (LCAT) deficiency.

A new lecithin:cholesterol acyltransferase (LCAT)-deficient family was found in Japan. In the proband, both LCAT activity and LCAT mass were deficient. The patient's parents, child, and sister, diagnosed as heterozygotes, had half-normal LCAT activity and LCAT mass. In the patient, an increase of intermediate-density lipoprotein (IDL, 1.006 less than d less than 1.019) fraction was observed. In postheparin plasma, both lipoprotein lipase and hepatic triglyceride lipase activities were low. Hydrolysis of [14C] triolein by human hepatic triglyceride lipase in patient IDL was decreased compared to that in IDL from normal postprandial serum. Preincubation of these IDL with normal plasma in the absence of 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) increased the rate of hydrolysis, in the presence of DTNB, this increment was not observed. These results suggest that one cause of IDL increase in the LCAT-deficient patient might be the difficulty of hydrolysis of these lipoprotein particles by hepatic triglyceride lipase.