Lipoprotein deficient serum

Lipoprotein-deficient serum (LPDS Biomedical Technologies). 

A. Medium supplemented with 12% fetal calf serum B. Medium supplemented with 5% lipoprotein-deficient serum ... 

Incorporation of radioactivity derived from [14C] Leucine, [3H] Thymidine and [3H]2-deoxy glucose into normal and familial hypercholesterolemic homozygous fibroblasts incubated in fetal calf serum and lipoprotein deficient serum containing medium... 

H] thymidine, 2-deoxy [1-3H] glucose antibiotics, and 1% fetal calf serum or 5% lipoprotein deficient serum was added to each dish and the cells incubated for 48 hrs. Subsequently, the medium was removed and the monolayers washed as described above, but at 4° C. The entire monolayer was solubilized in 1 N NaOH. Radioactivity and protein were subsequently measured in the alkali solubilized cell extracts. The data are expressed as c.p.m. per mg protein. 

In a typical experiment, normal and FH mutant cells were grown to confluence as described in the legend for Table VII. On the sixth day, medium was removed, the monolayers washed twice with PBS-2% BSA and five times with PBS. Ten ml of fresh medium containing 5% lipoprotein deficient serum, antibiotics and 5 y Ci of [3H]-D-galactose was added to each flask and cells incubated for another 48 hrs. Subsequently, the cells were harvested, GSLs isolated and their radioactivity measured as described in the legend for Table... 

Fig. 8. Ability of apolipoprotein E-dimyristoylphosphatidylcholine (DMPC) complexes of the three major isoforms to compete with human I-labeled LDL for binding to normal human fibroblasts. Cells incubated in medium containing 10% human lipoprotein-deficient serum received 1 ml of the same medium with 2 of 1-labeled...

Studies of cells in culture have provided considerable information about the control of this pathway [97]. In early studies, cultured skin fibroblasts were maintained for 24 h in a medium containing lipoprotein-deficient serum. These cells showed increased binding of LDL to cell surface receptors and increased HMG-CoA reductase activity. When LDL were added to the medium, binding, uptake, and degradation of the LDL followed. LDL CE were hydrolyzed, and decreased levels of both HMG-CoA reductase and the apo B/E receptor were seen. Furthermore, increased formation of cholesteryl oleate could be demonstrated. In subsequent studies, modified LDL with a net positive charge were used. These cationized LDL were internalized by a mechanism that did not depend on the apo B/E receptor, and that led to a substantial increase in cell cholesterol [103]. Under these conditions there was again increased synthesis of cholesteryl oleate. These findings support two principal conclusions (1) plasma lipoprotein CE is an important source of cholesterol for fibroblasts and similar cells and (2) the formation of intracellular... 

Fig. 1. Gel filtration chromatography of Apo A-IV and Apo A-I/DMPC/cholesteroI complexes prepared by the cholate dialysis procedure. Apo A-IV was isolated from lipoprotein-deficient serum and Apo A-I from HDL. Note that Apo A-IV completely associates with lipids and elutes at a volume slightly less than Apo A-I/lipid complexes...

The assay described above has a limited sensitivity (80-85%) to detect patients, especially patients with the so-called variant biochemical phenotype, and should be considered as an initial screening test [52, 55]. For increased sensitivity the cells should be cultured in medium with 10% lipoprotein-deficient medium (LPDS) for 2 days and subsequently with medium supplemented with 10% fresh human serum as described below for low-density lipoprotein (LDL)-stimulated cholesteryl ester formation. 

Fig. 5. Serum triglycerides following the ingestion of 30 ml corn oil in normal subjects and in two cases with beta-lipoprotein deficiency. In normal subjects the peak level occurs at 4 hours. In cases 1 and 2 fasting triglycerides were 3 and 6 mg/100 ml serum and no detectable increase occurred for 8 hours (Isselbacher et al. 1964). (With kind permission of Dr. Kurt J.

Changes in fatty acid compositions of total serum and lipoprotein particles, in growing rats given protein-deficient diets with either hydrogenated coconut or salmon oils as fat sources. Br J Nutr 1994 71(3) 375-387. 

Insulin, among other things, also stimulates production of lipoprotein lipase (LPL). With insulin deficiency in diabetes, there is insufficient LPL to release fatty acids from the triglycerides of VLDL and chylomicrons (see Fig. 6.4), another reason for accumulating serum triglycerides, apart from increased VLDL production by the liver. 

A. Familial lipoprotein lipase deficiency (Type I lipoprotein pattern on electrophoresis). Serum triglycerides become elevated with particular elevation of chylomicrons. Tliere are xanthomas, rather than atherosclerosis. Pancreatitis may result from the action of pancreatic lipase on these elevated chylomicrons, with resultant excess triglyceride breakdown in the pancreas, pancreatic injury, and release of more pancreatic lipase. (Note that the body contains different kinds of lipases. There is a pancreatic lipase, which is a digestive enzyme a lipoprotein lipase, which is an extracellular enzyme that breaks down plasma triglycerides, thereby enabling fatty acids to enter cells and an intracellular lipase that breaks down stored triglycerides). 

Liver health. As noted above, a biomarker of choline deficiency is elevated serum ALT levels, which is an indication of liver damage. One of the many functions of the liver is its role in fat metabolism. Without PC, the liver is unable to synthesize lipoproteins. Of particular importance in liver is the synthesis of very low-density lipoproteins (VLDL). With diminished VLDL production, the liver is not able to export lipid. This results in an accumulation of fat in the liver. Lipid accumulation in the liver leads to various stages of liver disease such as liver cell death, fibrosis, cirrhosis, and liver cancer (248-250). The role of choline in liver disease was underscored in the early 1990s when it was determined that patients on extended total parental nutrition (TPN) treatment developed fatty livers (251). At that time, TPN formulas did not include choline. Adding choline (in the form of lecithin) to TPN formulas reversed fatty buildup in these patients, and a... 

Figure 2. A negative correlation between lipoprotein lipase activity in epididymal fat tissue and triglyceride concentration in blood serum of conrtol male guinea pigs (0.5% i.-ascorbic acid in diet) and in guinea pigs with a marginal vitamin C deficiency (0.5 mg of i.-ascorbic acidjanimaljd). Equation of the...

The extreme hypoalbuminemia of the nephrotic syndrome can be attributed to the sustained urinary loss of albumin (S39), but it is doubtful whether albumin deficiency plays a causal role in the hyperlipemia and hypercholesterolemia found in this condition. Low-density lipoprotein (LDL) (90% lipids) is converted by lipoprotein lipase in vivo to high-density lipoprotein (HDL) (70% lipids), and the liberated fatty acid anions are bound and transported by plasma albumin. In normal nonlipemic serum the mean nonesterifled fatty acid/albumin molar ratio is 0.95 0.04, while in nephrotic sera—lipemic because of accumulation of LDL-triglycerides —the corresponding ratio is about 3 (C4). The plasma hyperlipemia which is observed in the nephrotic syndrome, and can be induced in rats by injections of antikidney serum, has been considered to result from albumin deficiency (R26). However this suggestion is not borne out by more recent studies (R25) and is contradicted by the failure of LDL to accumulate in the blood of analbuminic subjects (03). Plasma lipemia in the nephrotic syndrome apparently is due to loss or inhibition of lipoprotein lipase activity. 

D. Hepatic lipase. The abnormal buoyancies of the LDL and HDL fractions due to their increased TG content indicate that IDL is not being processed to LDL and HDL is not being remodeled. Both of these processes are accomplished by hepatic lipase. A deficiency in LCAT would lead to elevated serum cholesterol levels, almost all as free cholesterol. Deficiencies in lipoprotein lipase or apoC-II would lead to hypertriglyceridemia as increased chylomicrons and/or VLDL. An apoB-100 deficiency would lead to increased levels of LDL, but they would have the normal TG/cholesterol ratio. 

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