Dual defect in metabolism of very-low-density lipoprotein triglycerides. Patients with type 5 hyperlipoproteinemia.

Transport of very-low-density lipoprotein (VLDL) triglycerides (TGs) were studied in eight patients with type 5 hyperlipoproteinemia (HLP). Results were compared to those from patients with type 4 HLP. Type 4 patients had either overproduction of VLDL TGs (nine patients) or defective clearance of VLDL TGs (eight patients). Patients with type 5 HLP were found to have increased production rates of VLDL TG, but also reduced fractional catabolic rates of VLDL TGs. Synthesis rates of VLDL TGs in type 5 were similar to those in type 4 patients with overproduction of VLDL TGs. The mean fractional catabolic rate in patients with type 5 HLP also were similar to those of type 4 patients with defective clearance. This study demonstrates that in most patients with type 5 HLP there is a dual defect in TG metabolism--overproduction of VLDL TGs and a clearance defect for TG-rich lipoproteins.