Studies on the characterization of human serum lipoproteins separated by ultracentrifugation in a density gradient. I. Serum lipoproteins in normal, hyperthyroid and hypercholesterolemic subjects

Calculation of serum "total lipid" concentrations for the adjustment of persistent organohalogen toxicant measurements in human samples

Persistent organohalogen toxicants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin or polychlorinated biphenyls measured in human serum are often expressed on a lipid weight basis, most commonly by dividing the toxicants' concentration by the weight of total lipids in the sample. Therefore, the manner in which this lipid adjustment is calculated may influence the final reported result. Gravimetric total lipid assays have been used, but they are time-consuming and sometimes may be ill-defined. Consequently, alternative methods using enzymatic assays have been developed based on summing the individual lipid species measured. Recent reports, however, have suggested that significantly different total lipid results may be obtained when using alternative formulae in a summation approach. In this report, we summarize the results obtained from lipid measurements of nearly 900 samples made as part of a study of a group of older American men (mean age 62 years), and we compare our total lipid estimates obtained by using both our standard and "short" formula (the latter based on total cholesterol and triglycerides only) with results obtained using the recently proposed alternative formulae. Our findings indicate that both our long and short formulae provide similar estimates of serum total lipid concentrations, and that differences observed in lipid estimates when using the newer alternative summation methods may reflect differences in how the term "total lipid" is defined, especially with regard to the need to include the contribution of the weight of the cholesterol ester fatty acids in the calculation.

Crosstalk of sterol-dependent and non-sterol-dependent signaling in human monocytes after in vitro addition of LDL

The aim of the present study was to investigate low density lipoprotein (LDL)-induced, non-sterol-dependent signaling and its possible role in cholesterol balance. LDL in 10 microg ml(-1) concentration could induce inositol trisphosphate (IP3) and Ca2+ signal generation through a pertussis toxin (PT) sensitive G protein in human monocytes. The increase in [Ca2+]i was derived from the intracellular pools. LDL also induced activation and translocation of protein kinase C (PKC) into the cell membrane, by processes, which were significantly inhibited in the first 20 min by preincubation with PT and PKC-inhibitor H-7. The PKC-activating phorbol-12-myristate-13-acetate (PMA), differently from LDL, enhanced the LDL-receptor (LDL-R)-mediated binding and degradation of [125I]LDL, but inhibited endogenous cholesterol synthesis, and both effects were inhibited by H-7. The LDL-induced inhibition of binding and degradation of [125I]LDL was not affected by H-7, whereas decreased cholesterol synthesis was counteracted by H-7. These results suggest the existence of a non-sterol-dependent signal pathway of LDL-Rs, by which endogenous cholesterol synthesis, that is, the [14C]acetate incorporation, is regulated through PKC activation.

Disturbed LDL and scavenger receptor functions in monocytes from chronic haemodialysed patients

BACKGROUND

The most frequent complication in patients with end-stage renal failure on chronic haemodialysis (HD) treatment is atherosclerosis, i.e. the different forms of heart and vascular diseases. The complete disorder of serum lipid and lipoprotein patterns is well demonstrated, whereas our knowledge about the low-density lipoprotein (LDL) and scavenger receptor expression and function are poorly understood.

METHODS

In our current work, LDL and scavenger receptor expression and functions were simultaneously studied in monocytes obtained from 15 healthy male control subjects and from 11 chronic HD male patients applied with (125)I-labelled LDL, isolated from healthy volunteers. To study the scavenger LDL receptors, labelled acetylated LDL (acLDL) was used.

RESULTS

LDL binding to the monocytes of the HD-group was found to be decreased in comparison to that of the controls. As a result, the 50 microg LDL protein-induced inhibition of endogenous cholesterol synthesis was also diminished. In contrast, acLDL binding was greatly increased, though it could trigger only a low apoE synthesis. Consequently the number of cholesterol inclusions in monocytes was increased.

CONCLUSIONS

The disturbed expression and function of LDL and scavenger receptors both may play significant roles in pathogenesis of cardiovascular complications in chronic HD patients. Based on our present results, it can be assumed that dysfunction of scavenger receptors is at the centre of cardiovascular complications of HD patients with renal failure.

Specific and scavenger low-density lipoprotein receptors involved in the disturbed lipid metabolism of patients with non-insulin-dependent diabetes mellitus are independent of obesity

Comparative studies were performed on monocyte-derived macrophages (MDMs), prepared by a 72-hour incubation of blood monocytes obtained from patients with non-insulin-dependent diabetes mellitus (NIDDM) and age-matched obese and non-obese controls. The MDMs, after a 72-hour culturing, expressed both specific and scavenger low-density lipoprotein (LDL) receptors on their surfaces. To study the binding capacity of both receptor types, [125I]LDL and [125I] acetylated LDL (acLDL) were applied to cells and the labeled ligands were then monitored to estimate the rate of intracellular degradations. The LDL-induced inhibition of endogenous cholesterol synthesis and the acLDL-triggered apolipoprotein (apo) E secretion were also studied, as the biological marker of receptor activation. The results indicate that the binding capacities of both specific and scavenger LDL receptors were not reduced in MDMs of diabetic patients. However, the intracellular degradation after LDL incorporation was decreased. The LDL-induced inhibition of cholesterol synthesis and the acLDL-transmitted apo E secretion were also found to be decreased in the MDMs of patients with NIDDM as compared with the obese and non-obese control groups. The NIDDM-induced impaired signal transduction of both specific and scavenger LDL receptors suggests an unclarified functional alteration of both receptor structures.

ESTIMATION OF THE LOW-DENSITY (BETA) LIPOPROTEINS OF SERUM IN HEALTH AND DISEASE USING LARGE MOLECULAR WEIGHT DEXTRAN SULPHATE

Studies have been made of the factors affecting the specificity of the interaction between high molecular weight dextran sulphate and low-density lipoproteins, both in pure solution and in serum. The results have been used in the development of a simple assay method for the serum concentration of low-density lipoproteins in small volumes of serum. The results obtained by this assay procedure have been found to correlate acceptably with parallel estimations of low-density lipoproteins by an ultracentrifugal technique and by paper electrophoresis. The technique has been applied to a survey of serum levels of these proteins in a normal population. The results have been compared with data in the literature. Satisfactory agreement was found between mean levels, matched for age and sex, between the dextran sulphate method and those methods based ultimately on chemical estimation of one or more components of the isolated lipoproteins. A systematic difference was observed when the dextran sulphate method was compared with estimates based on analytical ultracentrifugation or turbidimetry using amylopectin sulphate.Some indication of the range of application of the dextran sulphate method in clinical chemistry is provided.

Soy products and the human diet

This review focuses upon the nutritional significance of soy products in the human diet. The impact of the consumption of soy foods on a range of diet and health issues are discussed, including protein quality and growth promoting effects of soy protein, allergies in children, hypocholesterolemic effects of soy protein and soy fiber, effects of soy products upon glucose tolerance, and the bioavailability of zinc and iron from soy foods. Recent research reports involving humans and relevant animal studies are reviewed.

The effect of hypothyroidism and thyroxine replacement on hepatic and intestinal HMG-CoA reductase and ACAT activities and biliary lipids in the rat

Hepatic and intestinal cholesterol metabolism were investigated in the hypothyroid and thyroxine-treated hypothyroid rat. Plasma cholesterol levels were significantly increased in hypothyroid animals. After thyroxine administration, plasma cholesterol levels were reduced to levels observed in euthyroid controls. Hypothyroidism caused a significant decrease in biliary cholesterol output, which was reversed with thyroxine treatment. In contrast, biliary bile acid output was unchanged by the thyroid status. Cholesterol synthesis, as estimated by HMG-CoA reductase activity, was decreased in the liver of hypothyroid animals. Thyroxine administration, however, significantly increased reductase activity returning it to control levels. Hypothyroidism did not affect HMG-CoA reductase activity in the intestine, but thyroxine administration markedly stimulated the activity of this enzyme in this organ. Cholesterol esterification, as estimated by ACAT activity, was decreased in the liver of hypothyroid rats, while intestinal ACAT activity was greatly increased. Thyroxine treatment reversed these effects of hypothyroidism on ACAT activity in both organs. An increase in microsomal cholesterol content in the intestine of hypothyroid rats was associated with the observed increase in intestinal ACAT activity. The percent of cholesterol that was absorbed in the intestine was not changed by the thyroid status of the animal. The data suggest that the changes observed in cholesterol metabolism in hypothyroid rats or hypothyroid rats treated with thyroxine for 1 week cannot account for the increase in plasma cholesterol levels observed in the hypothyroid rat. This implies that other factors that were not studied, such as changes in lipoprotein catabolism, are likely to contribute to the hypercholesterolemia of hypothyroidism.

Age-dependent variations of intralysosomal enzyme release from human PMN leukocytes under various stimuli

The intralysosomal beta glucuronidase and elastase release from polymorphonuclear leukocytes (PMNL) of young and aged male subjects were determined after 60-min incubation with 10 micrograms/ml Cytochalasin B (CB), 10(-6) M of Ca ionophore A 23187 and various concentrations of human low density lipoprotein (LDL). The beta glucoronidase secretion was triggered by both A 23187 and LDL; however, no significant differences were found between the enzyme release from PMNLs of young and aged subjects. In contrast, a marked elastase release was triggered in the young group only by LDL, whereas in the aged group, all of the applied drugs induced a significant elastase release. LDL caused the most dramatic enzyme release from PMNLs of aged males. It was concluded that the release of PMNL-elastase after LDL incorporation as well as by CB and Ca ionophore stimulation may be an age-related process.

Dietary protein effects on cholesterol and lipoprotein concentrations: a review

Different dietary proteins exert different effects on plasma cholesterol concentrations. Animal studies have shown that animal proteins, most notably casein, increase plasma total cholesterol concentrations compared with vegetable proteins, such as soy. Soy protein has been shown to be hypocholesterolemic in rats, swine, primates, and rabbits. Epidemiologic studies have disclosed that vegetarians have lower mean plasma cholesterol concentrations than populations consuming diets of mixed proteins, but it is unclear whether this effect results specifically from the animal or vegetable nature of the protein. In human clinical experiments, substituting soy protein for mixed protein reduces plasma total cholesterol concentration in hypercholesterolemic subjects, but it causes only a small, nonsignificant change in persons with normal plasma cholesterol concentrations. The mechanism responsible for the effects of different proteins on plasma cholesterol concentrations has not been established. One hypothesis suggests that animal proteins, which have a greater content of phosphorylated amino acids than vegetable proteins, interfere with bile acid reabsorption. Another hypothesis suggests that the amino acid content of the protein affects cholesterol absorption, tissue storage, synthesis, and excretion. The dietary protein may also alter cholesterol metabolism by affecting plasma hormone concentrations, either postprandially or over weeks to months. Among the hormones thought to be affected by dietary protein source are insulin, glucagon, and thyroid hormones. Gastrointestinal hormones, such as gastrointestinal inhibitory polypeptide, may also be affected by dietary protein.

Free and complexed anti-lipoprotein antibodies in vascular diseases

The cell-mediated immune response against low density lipoproteins (LDL) was demonstrated by the migration inhibition test in patients with various vascular diseases. Anti-high density lipoprotein2 (HDL2) cellular immune response was found only in a few patients. LDL and HDL2 binding factors were detected in about 50% of coronary patients. No significant difference in their occurrence was found between the normolipidemic and hyperlipidemic patients nor between patients with hyperlipidemia type II/b and type IV. On the assumption that lipoproteins may act as auto-antigens by forming immune complexes, the presence of anti-LDL and anti-HDL2 activity was investigated in circulating immune complexes obtained by polyethylene glycol (PEG) precipitation from the sera of coronary patients and controls. Using an ELISA technique, PEG-precipitable anti-LDL activity was detected in 23, 11 and 18% of cases with myocardial infarction, angina pectoris and healthy old subjects, respectively. In the immune complexes obtained from the sera of the healthy young donors no anti-LDL activity was found. Anti-HDL2 activity in the immune complexes was demonstrated only in a few cases from among the patients and elderly persons we investigated.

Quantitation of lipid profiles from isolated serum lipoproteins using small volumes of human serum

Methodology is described that isolates the individual serum lipoproteins, VLDL, LDL and HDL and quantitates the free cholesterol, esterified cholesterol, triglycerides and phospholipid classes in each fraction using 2-3 mL of serum. The determination of the methyl esters of fatty acids from the various lipid classes is described. The lipoproteins are isolated by non-linear density ultracentrifugation using 1 mL of serum per swinging bucket. The lipids are obtained by solvent extraction. The cholesterol, cholesterol esters and triglycerides are separated by TLC using a petroleum ether:diethyl ether system and the phospholipids are separated using a chloroform:methanol system. All lipid classes are quantitatively determined and recovery data are presented. Analysis of the fatty acid profiles of the lipid classes using GLC is described. The methodology can be adapted to partial determination if in-depth studies are not required.

The effect of pregnancy and two different contraceptive pills on serum lipids and lipoproteins in a woman with a type III hyperlipoproteinaemia pattern

We report a woman who had a moderate elevation of serum triglycerides with a type III pattern of hyperlipoproteinaemia when taking a normal diet. She developed eruptive xanthomata with a grossly raised serum triglyceride concentration and chylomicronaemia when pregnant and also when taking a combined oral contraceptive pill containing 50 microgram of oestrogen. The xanthomata cleared and the triglyceride level fell when the combined oral contraceptive pill was changed to one with a lower oestrogen content, clofibrate was prescribed and the diet was restricted in carbohydrate and fat. Persistent chylomicronaemia is a serious complication of pregnancy because of the risk of pancreatitis and the potential risk of fetal malnutrition. Treatment with diet and clofibrate is indicated. High oestrogen-containing contraceptive pills appear to be contraindicated in patients with type III or other hypertriglyceridaemic states.

Diagnosing familial hypercholesterolaemia in childhood by measuring serum cholesterol

The serum cholesterol concentrations of 134 children aged 1-16 years who had at least one first-degree relative with presumed familial hypercholesterolaemia showed a bimodal distribution, and, using the maximum likelihood technique, two overlapping curves could be fitted. The mean value of the affected children (heterozygotes) was 8-9 mmol/l and that of the unaffected 4-9 mmol/l. The two curves intersected at 6-77 mmol/l, and at this point 5% of the unaffected children had values over 6-77 mmol/l and 3-5% of the heterozygotes had values under 6-77 mmol/l. If this cholesterol concentration is used as a cut-off point 4-25% of cases would be misdiagnosed.

Clearance of chylomicron triacylglycerol and cholesteryl ester from the plasma of streptozotocin-induced diabetic and hypercholesterolemic hypothyroid rats

Labeled chylomicrons in thoracic duct lymph were collected after test meals containing 14C cholesterol and 2-3H glyceryl trioleate and were given by intravenous injection to groups of control rats, rats made diabetic by treatment with streptozotocin, and rats made hypothyroid and hypercholesterolemic by a diet containing cholesterol, peanut oil, cholic acid, and thiouracil. In the diabetic rats clearances from the plasma of chylomicron triacylglycerol and cholesteryl ester were impaired. A large variability in triacylglycerol clearance in diabetic rats was ascribed to variability in plasma triacylglycerol concentrations. Adipose tissue lipoprotein lipase activity was not impaired in the female diabetic rats used in this study. In the hypothyroid hypercholesterolemic rats chylomicron cholesteryl ester clearance from the plasma was impaired but chylomicron triacylglycerol was cleared efficiently, and adipose tissue lipoprotein lipase activity was similar to or greater than activity in controls. Ten minutes after intravenous injection most plasma radioactivity was recovered in lipoproteins of density less than 1.006 g/ml in all groups of rats, but relatively more was recovered at this density in both treatment groups. We suggest that chylomicron remnants accumulate in the plasma and contribute to the development of hyperlipemia in both treatment groups, but that the remnants formed in the diabetic rat are less depleted of triacylglycerol than the remnants formed in the hypothyroid hypercholesterolemic rat. It is suggested that factors other than measured lipoprotein lipase activities of adipose tissues may be important in determining the initial extent of hydrolysis of chylomicron triacyglycerol. We propose that the hypercholesterolemic hypothyroid rat is a useful model for the experimental production of the remnants of triacylglycerol-rich primary lipoproteins.

Fatty acid composition of adipose tissue in patients with coronary heart disease

In order to study the relationship between the fatty acid composition of adipose tissue and coronary heart disease (CHD), 34 consecutive male patients with acute myocardial infarction and 33 hospitalized men free of CHD were compared. Patients with diabetes mellitus, endocrine disorders, liver and kidney diseases, recent changes in body weight and deviations from the "normal", customary diet were exlcuded. A statistically significant difference between the two groups was observed only in stearic acid, its proportion being lower in CHD patients (3.25% vs. 4.13%). Using multivariate discriminant analysis, age discriminated best between the groups, followed by stearic acid. The signs observed were positive for the former and negative for the latter. All other acids, relative body weight, and skinfold measurements did not significantly contribute to the discrimination. Age did not correlate with the proportion of stearic acid. Blood lipids from samples taken within 24 h of admission did not significantly differ between the groups. Three months later they had risen considerably in the infarct patients. The metabolic basis of the relationship between CHD and stearic acid is not clear at present. Additional studies are necessary to substantiate the importance of this acid as an indicator of CHD.

Screening for familial hyper-beta-lipoproteinaemia in children in hospital

1510 plasma cholesterol estimations were made in 1391 children admitted to hospital as part of a biochemical profile. Babies under 1 year and children known to have familial hyperlipoproteinaemia were excluded. The mean concentration was 4-28 mmol/l +/- 1-04 (1 SD) (165-3 mg/100 ml +/- 38-6), and levels exceeded 5-93 mmol/l (229 mg/100 ml) in 68 children. Repeat estimations on 55 of these children showed 34 still to have values greater than 5-93 mmol/l and family studies were performed in 19 of these. In 8 children hypercholesterolaemia was secondary and no familial lipoprotein disorder was present. Familial hyper-beta-lipoproteinaemia (FH) was diagnosed in 3 children and in 2 of the families there was a history of early ischaemic heart disease. In 2 children the diagnosis was in doubt. In the remaining 6 children FH and secondary hyperlipoproteinaemia were excluded so the hypercholesterolaemia was presumably environmentally induced, possibly in association with polygenic inheritance. In the present state of knowledge screening of the childhood population for FH by means of plasma cholesterol determinations cannot be recommended. Studies of lipoproteins should, however, be made in children from families known to have FH or early coronary heart disease.

Composition of low-density lipoprotein in children with hyperlipoproteinaemia

Low-density lipoprotein composition, studied in 7 pre-pubertal children with secondary hyperlipoproteinaemia, did not differ significantly from that found in 12 normal children. This contrasts with the findings in 12 children with the heterozygous form of familial hypercholesterolaemia in whom the low-density lipoprotein was significantly deficient in triglyceride (p smaller than 0.001) and protein (p smaller than 0.025), and had an increased proportion of cholesterol esters compared with normal (p greater than 0.01). Treatment which lowered serum cholesterol and low-density lipoprotein concentration in these children did not materially alter the abnormalities of composition of the low-density lipoprotein. The data support the hypothesis that an abnormality of composition of low-density lipoprotein is an integral feature of familial hypercholesterolaemia and does not simply result from an increased concentration of low-density lipoprotein of whatever cause.

Familial hypo-beta-lipoproteinaemia

A 2-year-old boy investigated because of small stature, had low serum levels of cholesterol (74 mg/100 ml) and β-lipoprotein cholesterol (20 mg/100 ml). Faecal fat, jejunal biopsy, red cell morphology, and plasma growth hormone and thyroxine were normal, and it was concluded that the small stature was hereditary. A family study showed a similar lipoprotein abnormality in the patient's mother; her serum cholesterol was 83 mg/100 ml and β-lipoprotein cholesterol 34 mg/100 ml. Analysis of the β-lipoprotein fraction in both child and mother showed it to have an abnormal lipid composition; the cholesterol/phospholipid ratio was 1·0 and 0·8, respectively (normal 1·7), and within the phospholipid components the proportion of sphingomyelin was markedly reduced (11% and 5%, normal 30%). These findings differ from previous reports that the composition of β-lipoprotein is normal. Familial hypo-β-lipoproteinaemia has been shown to be inherited as an autosomal dominant, and our findings are in agreement. Although a few individuals with this condition have been reported to have some of the features associated with a-β-lipoproteinaemia, neither our patient nor his mother had any gastrointestinal, haematological, or neurological abnormalities.

Use of cholestyramine in treatment of children with familial hypercholesterolaemia

19 children with heterozygous familial hypercholesterolaemia have been treated with cholestyramine administered twice daily in a total dosage of 8 to 24 g/day (0·3 to 1·1 g/kg body weight per day). Serum cholesterol concentration was reduced by a mean of 36% (range 27 to 47%). The therapeutic effect was similar whether or not dietary fat was restricted, and the reduction in serum cholesterol has been maintained for periods of up to 20 months. Side effects of cholestyramine have been confined to the gastrointestinal tract. Absorption of fat was impaired in some patients, but has not been associated with diarrhoea. Serum folate levels have decreased in all patients, and 6 out of 12 tested have had subnormal red blood cell folate. There has been no evidence of malabsorption of other vitamins or of minerals. Growth rate has been normal in all children.

Studies on the mode of uptake of blood triglycerides by the mammary gland of the lactating goat. The uptake and incorporation into milk fat and mammary lymph of labelled glycerol, fatty acids and triglycerides

1. The mode of uptake of the precursors of milk fat by the mammary gland of the lactating goat has been examined by infusing radioactive fatty acids, glucerol or doubly labelled triglycerides into the mammary artery or jugular vein of animals surgically prepared to permit samples of arterial and venous blood to be withdrawn without disturbance to the animal. 2. Acetate was taken up by the mammary gland and incorporated into milk fat. The decrease in the specific radioactivity of blood acetate across the gland was evidence of acetate production, but there was no significant release of labelled lipid from the mammary gland. 3. When labelled long-chain fatty acids or glycerol were infused into the lactating goat, there was extensive transfer of radioactivity into milk in spite of the absence of net uptake of substrate by the mammary gland. The decrease in the specific radioactivity of each substrate across the mammary gland, however, showed that both fatty acids and glycerol were simultaneously taken up and released by mammary tissue. 4. The infusion of chylomicra and triglyceride emulsions labelled with (3)H and (14)C revealed that both glycerol and fatty acids were released during triglyceride uptake by mammary tissue. Changes in the (3)H/(14)C ratio during the transfer of triglyceride from blood into milk showed that at least 80% of the triglyceride was hydrolysed during uptake, but the potential re-utilization of both products of hydrolysis for triglyceride synthesis in mammary tissue implied that only a minimum value could be obtained from the change in the ratio. 5. The time-course of the transfer of (3)H and (14)C into milk and lymph were closely similar after the infusion of [2-(3)H]glycerol tri[1-(14)C]oleate or of a mixture of [2-(3)H]glycerol and [1-(14)C]oleate. 6. The results were consistent with the hypothesis that plasma triglycerides are extensively or completely hydrolysed during mammary uptake.

Progeria. Case report with long-term studies of serum lipids

A girl with the typical features of progeria died at the age of 10 years from cardiac failure following repeated myocardial infarctions. Serial studies of the serum lipids were made from the age of 2 years 3 months. Variable hyperlipidaemia, increased β- and pre-β-lipoproteins, and impaired clearing of absorbed dietary fat were shown. A polyunsaturated fat diet, which was started at the age of 2 years 5 months and continued throughout the rest of her life, controlled the hyperlipidaemia and the clearing of fat became normal. Pre-β-lipoprotein could still, however, be seen occasionally. The dietary regimen did not delay the development of atherosclerosis, the pathogenesis of which, in progeria, may be due to factors other than hyperlipidaemia.

Effects of short-term high-carbohydrate feeding on serum triglyceride of children with familial hypercholesterolaemia

In 5 children with familial hypercholesterolaemia, serum triglyceride levels, which were initially normal, rose after three days on a high-carbohydrate diet; a similar response occurred in one child with normal serum lipoproteins. These observations suggest that a rise in serum triglyceride on high-carbohydrate feeding is a normal finding in children and therefore should not be used as a test for the diagnosis of the pathological state of `carbohydrate-induced hypertriglyceridaemia'. The findings in familial hypercholesterolaemia indicate that diets used in the treatment of this condition should not contain an unduly high proportion of carbohydrate. Detailed investigations showed that most of the increase in triglyceride occurred in the very low density lipoproteins, but small increases were also found in the other lipoproteins. The lipid composition of all the lipoproteins changed, the proportion of triglyceride being increased. In all children the fatty acid composition of serum triglyceride (g./100 g. total fatty acids) showed an increase in palmitoleic acid and a decrease in linoleic acid. A raised percentage of palmitoleic acid appears to be the most consistent indicator of accelerated lipogenesis during high-carbohydrate feeding. Changes in triglyceride fatty acid composition were similar in all the lipoproteins. On high-carbohydrate feeding the absolute concentration of all triglyceride fatty acids, including linoleic acid, increase.

Wolman's disease. A rare lipidosis with adrenal calcification

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Disorders of the serum lipoproteins. I. Lipoprotein deficiency states

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THE LIPOTROPIC ACTION OF COLD: 2. THE INFLUENCE OF COLD AND CHOLINE DEFICIENCY ON SERUM LIPIDS OF RATS AT DIFFERENT INTAKES OF DIETARY METHIONINE

The effect of exposure of rats to cold for a 10-day period on the concentration of serum lipids in control and choline-deficient animals was studied at four dietary intakes of methionine. Changes in total lipids, total and free cholesterol, phospholipid, and triglyceride levels were measured.In control (choline-fed) animals, phospholipid, cholesterol, and the ratio of free:ester cholesterol levels were not altered by cold exposure, but a marked decrease (25–30%, P < 0.01) in the levels of total serum lipids occurred. This was a result of a 45–70% decrease in triglyceride levels. The concentration of the triglyceride-rich low-density lipoproteins (Sf 10–400) in the serum fell in the cold-exposed animals as indicated by lowered triglyceride:cholesterol ratios.Although cold exposure prevented fatty livers in choline-deficient rats at high methionine intakes, it did not prevent the characteristic decrease in serum lipids found in choline deficiency at any of the methionine intakes studied. Decreases in total lipids (20–40%), triglyceride (10–50%), cholesterol (15–40%), and phospholipids (15–40%) were found. It was concluded that the ability of cold exposure to overcome choline deficiency is limited, apparently, to the fatty liver syndrome and has no effect on the decreased serum lipid levels.

A-BETA-LIPOPROTEINAEMIA

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