Abstract
Clinical and biochemical features of type V hyperlipoproteinemia (HLP) were examined in our five cases of familial type V HLP. The VLDL (including chylomicron) cholesterol and triglyceride levels were significantly increased and the IDL, LDL and HDL cholesterol levels significantly reduced in type V HLP. There was no difference in the increase of serum FFA levels after intravenous injection of heparin between type V HLP and normal or other types of HLP. Reduction of serum triglyceride levels after intravenous injection of heparin was significantly smaller in type V HLP than in normal or other types of HLP. Fasting serum triglyceride levels showed significant correlations to the decrease of serum triglyceride after intravenous injection of heparin. The regression equation in normal or other types of HLP was Y (fasting serum triglyceride in mg/dl)=1.28X (decrease of serum triglyceride after heparin injection in mg/dl)+20.2 (r=0.966, p<0.01), while the regression equation in type V HLP was Y=4.56X+71.2 (r=0.964, p<0.01).
In 4 out of 5 cases of type V HLP, lipoprotein lipase (LPL) activity was definitely low, while hepatic triglyceride lipase (HTGL) activity was normal or slightly low. In one case (Y. M.) of type V HLP the LPL activity against 14C-triolein emulsion was normal, and the LPL activity against rat or human chylomicron was low. Thus, the LPL able to hydrolyze the emulsion but unable to hydrolyze rat or human chylomicrons is an “abnormal” LPL according to Schreibman et al..
From these data and the results of other reports, seven possible biochemical abnormalities in the pathogenesis of type V HLP are discussed.
