Effects of delipidated serum and lipoprotein-deficient serum on sterol biosynthesis and efflux in cultured skin fibroblasts - a comparison of the behaviour of cells from a control with those from a heterozygote and homozygote for familial hypercholesterolaemia

A lipid-free and insulin-supplemented medium supports De Novo fatty acid synthesis gene activation in melanoma cells

While investigating the role played by de novo lipid (DNL) biosynthesis in cancer cells, we sought a medium condition that would support cell proliferation without providing any serum lipids. Here we report that a defined serum free cell culture medium condition containing insulin, transferrin and selenium (ITS) supports controlled study of transcriptional regulation of de novo fatty acid (DNFA) production and de novo cholesterol synthesis (DNCS) in melanoma cell lines. This lipid-free ITS medium is able to support continuous proliferation of several melanoma cell lines that utilize DNL to support their lipid requirements. We show that the ITS medium stimulates gene transcription in support of both DNFA and DNCS, specifically mediated by SREBP1/2 in melanoma cells. We further found that the ITS medium promoted SREBP1 nuclear localization and occupancy on DNFA gene promoters. Our data show clear utility of this serum and lipid-free medium for melanoma cancer cell culture and lipid-related areas of investigation.

Familial hypercholesterolaemia: effect of low density lipoproteins on esterification of cholesterol in lymphocytes from homozygous and heterozygous subjects

The effect of low density lipoproteins on esterification of cholesterol was studied in lymphocytes from patients with familial hypercholesterolaemia; results were compared with those obtained using cells from normal individuals. Freshly isolated lymphocytes were maintained in lipoprotein-deficient medium for 48 h and the rate of formation of [3H] cholesteryl oleate from [3H] oleate was then determined in the presence or absence of low density lipoproteins. In the absence of low density lipoproteins, incorporation of [3H] oleate was higher in heterozygote and homozygote cells than in normal lymphocytes. Incorporation in the presence of low density lipoproteins was increased relative to that measured in their absence for all of the subjects studied; heterozygotes and homozygotes showed marked changes in some cases but not in others.

Cholesterol efflux from cultured skin fibroblasts in 12 patients clinically heterozygous for familial hypercholesterolemia

The [3H]cholesterol efflux from cultured skin fibroblasts was investigated in 12 patients, clinically heterozygous for familial hypercholesterolemia (FH). The [3H]cholesterol efflux from fibroblasts was studied in the presence of high-density lipoproteins, isolated either from control sera or from the patient's own serum. The [3H]cholesterol efflux from fibroblasts of 3 patients was increased; it was decreased for 4 patients and similar to that of control cells for 5 patients. This study indicates that in some patients with heterozygous FH, abnormalities of [3H]cholesterol efflux from fibroblasts can be detected. The heterogeneity of the results is consistent with the heterogeneity of the low-density lipoprotein receptor activity and with the variability of the clinical picture found in this disease.

Induction of corticosteroid biosynthetic pathway by ACTH and high-density lipoprotein in newborn rat adrenocortical cells cultured in serum-free medium

In order to investigate the role of rat high-density lipoprotein (HDL) on adrenal cholesterol accumulation and steroidogenic pathways (corticosteroid, i.e., 21-hydroxysteroid biosynthesis and reductive metabolism of progesterone), newborn rat adrenal cells cultured in serum-free medium were used. Incubation of [4-14C]cholesterol-HDL in serum-free medium compared to those in medium with lipoprotein-deficient serum, in serum-free medium with ACTH compared to those without ACTH, both showed an increase of labelled cholesterol in cells and of labelled 21-hydroxysteroids excreted in medium. Substitution of serum-supplemented medium by serum-free and cholesterol-free medium led to a deep decrease of ACTH-induced steroid biosynthesis with a predominance of 20 alpha-reduced steroids; addition of HDL restored the corticosteroid biosynthesis and decreased the reductive metabolism. Addition of increased concentrations of HDL (7-150 micrograms cholesterol/ml) enhanced, in a saturable fashion, the total cholesterol uptake and the corticosteroid biosynthesis. The total cholesterol accumulation in cells exceeded by 4-fold the steroid production at saturation. The ratio between the two steroidogenic pathways increased up to 40 at saturation in favor of corticosteroids. These results suggest that HDL is at least partly internalized and that probably its constituents contribute greatly to the control of the two different steroidogenic pathways.

Familial hypercholesterolaemia: esterification of cholesterol in lymphocytes from homozygous and heterozygous subjects

A comparative study of the rates of cholesterol esterification in lymphocytes from healthy subjects and patients with familial hypercholesterolaemia (25 heterozygotes and 10 homozygotes) was carried out. Freshly isolated lymphocytes were incubated at 37 degrees C in medium containing lipoprotein-deficient serum and [3H]oleate-albumin was extracted, isolated by thin layer chromatography and quantitated. Incorporation of [3H]oleate into cholesteryloleate was significantly higher in lymphocytes from both heterozygotes and homozygotes than in cells from normal subjects; there was no significant difference between the values for heterozygotes and homozygotes. For all three groups cholesteryloleate formation was dependent on the concentration of lipoprotein-deficient serum in the medium.