Triglyceride accumulation in cultured human fibroblasts

Cultures of human diploid fibroblasts were shown to accumulate elevated levels of intracellular triglyceride when grown in medium supplemented with sera from patients with endogenous hypertriglyceridemia (Type IV hyperlipoproteinemia). Time course studies indicated cell triglyceride levels reached maxium in 6 to 12 hours. Isotopic studies indicated that the source of the accumulated cell triglyceride was serum triglyceride, and that most of the triglyceride was taken up without hydrolysis. Triglyceride was not significantly removed by trypsinization or extensive washing. The accumulated triglyceride was also demonostrated to be metabolized, as indicated by conversion to phospholipids and free fatty acids. Increasing concentrations of hypertriglyceridemic serum in the medium resulted in increasing cell triglyceride levels. However, increasing amounts of normal serum did not result in comparable cell triglyceride accumulation. Intracellular triglyceride accumulation seemed to correlate with levels of hypertriglyceridemic serum triglyceride, whether this serum was present at equivalent concentrations or normalized to triglyceride levels equivalent to normal serum. It is concluded that elevated serum triglyceride levels can result in intracellular triglyceride accumulation even in the absence of lipolytic activity.