Reduced cellular cholesterol content in peroxisome-deficient fibroblasts is associated with impaired uptake of the patient's low density lipoprotein and with reduced cholesterol synthesis.

Abstract

Mammalian cells acquire cellular cholesterol by de novo synthesis as well as by uptake of low density lipoprotein (LDL). Peroxisomes contain enzymes involved in the synthesis of cholesterol, and peroxisome-deficient (PD) patients have been shown to have hypocholesterolemia and abnormal LDL. We therefore decided to study whether cholesterol synthesis and cellular uptake of LDL are impaired in cultured PD fibroblasts. The present study demonstrates a significantly lower cellular cholesterol mass in fibroblasts from three PD patients, as compared to control cells (41-59% of controls). The rate of cholesterol synthesis was also reduced in all three PD cell lines, being 16-20% of the control values. LDL binding and degradation by fibroblasts were 3- to 5-fold higher in the PD cells as compared to control cells. Similarly, enrichment of normal fibroblasts with tetracosanoic acid (C-24:0), a situation that could mimic the in vivo accumulation of very long chain fatty acid (VLCFA) in PD cells, caused LDL binding and degradation to be 4-fold higher than in non-treated cells. On the other hand, the uptake of LDL derived from PD patients by normal fibroblasts was markedly reduced (by up to 67%) in comparison to the cellular uptake of normal LDL. Similar results were obtained in PD cells. This study demonstrates a lower cellular cholesterol content and reduced cholesterol synthesis rate in PD cell lines. In addition, we demonstrate that regulation of the uptake of normal LDL by cellular LDL receptors is operative in PD cells, whereas LDL derived from PD patients is not recognized normally by the LDL receptor.(ABSTRACT TRUNCATED AT 250 WORDS)