Lipoprotein lipase activator deficiency in very low density lipoproteins in rat nephrotic syndrome.

Marked urinary loss of lipoprotein lipase activator in experimental rat nephrotic syndrome may be partly responsible for its deficiency in plasma very low density lipoproteins.

Radioimmunoassay of human apolipoprotein CII. A study in normal and hypertriglyceridemic subjects.

A specific, precise, and sensitive double-antibody radioimmunoassay for the measurement of human apolipoprotein CII (apoCII) was developed. ApoCII was labeled with (125)I (chloramine-T) and monospecific antibody was raised in rabbits. No appreciable cross-reactivity with apolipoproteins CI, CIII, AI, AII, low density lipoproteins, and lipoprotein-free plasma was observed. Lipoproteins containing apoCII displaced the standard curve in parallel. ApoCII measurement was not affected by pretreatment of plasma with tetramethylurea, ethanol-diethyl ether, or heating. Mean (+/-SE) plasma-immunoreactive apoCII in 47 normotriglyceridemic subjects was 51.8+/-3.2 mug/ml, generally comparable with previous estimates of its concentration by other methods. ApoCII levels in 9 subjects with type IIB lipoprotein pattern, 14 with the type IV lipoprotein pattern, and 5 with type V lipoprotein pattern were respectively, 89.9+/-4.6, 85.4+/-6.9, 132.8+/-21.0 mug/ml, all higher than normals (P < 0.001). Plasma apoCII and triglyceride concentrations correlated in normo- and hypertriglyceridemics (r = 0.36 and 0.58, P < 0.05). Plasma triglycerides correlated inversely with the fraction of total apoCII in very low density lipoprotein (VLDL)-free plasma (r = -0.75, P < 0.01). There was no correlation between plasma apoCII and high density lipoprotein cholesterol. In normotriglyceridemics, VLDL apoCII levels correlated with in vitro lipoprotein lipase (LPL) activator activities (r = 0.89, P < 0.01). In hypertriglyceridemic subjects the mean concentrations of apoCII per milligrams VLDL protein, LPL activator activity per milligrams VLDL protein, and LPL activator activity per micrograms VLDL apoCII were all lower than in normotriglyceridemics, P < 0.05. As plasma triglycerides and apoCII increase, apoCII is redistributed from high density lipoprotein to VLDL. However, the amount of apoCII per milligram VLDL protein and its LPL activator potency per milligram VLDL protein are reduced. These factors may contribute to impaired VLDL catabolism.

Short term study of sucrose polyester a nonabsorbable fat-like material as a dietary agent for lowering plasma cholesterol.

The efficacy, safety, and acceptability of sucrose polyester (SPE), a fat-like material that is neither digested nor absorbed, were assessed in 13 normal and seven hypercholesterolemic subjects for its potential as a cholesterol-lowering agent. Addition or substitution of SPE for culinary fats in the diets of the normocholesterolemic individuals produced a mean reduction of total and low-density lipoprotein cholesterol of 14 and 17%, respectively (P less than 0.001), despite the daily ingestion of a diet containing 800 mg of cholesterol and of dietary fat with a P/S ratio of 0.4. Total and low-density lipoprotein cholesterol were not significantly reduced by similar 10-day feeding periods of SPE in seven subjects with familial hypercholesterolemia. High-density lipoprotein cholesterol and triglycerides were not changed in normal or hypercholesterolemic subject receiving SPE. Plasma vitamin A and E levels were reduced by 10 and 21% (p less than 0.02 and less than 0.001) in both normal and hypercholesterolemic subjects on SPE. These returned to the basal levels when SPE consumption was discontinued. SPE was recovered quantitatively (greater than 97%) in the stools, with the last measurable SPE being found day 3 to 5 after cessation of SPE intake. Despite recovery of 50 g or more of unhydrolyzed SPE in stools during SPE feeding, there was no clinical or chemical steatorrhea. On subtracting SPE's input to total stool fatty acids, it was found that "non-SPE" fatty acids in the stool had not increased during SPE feeding, SPE was easily incorporated into routine foodstuffs in addition to, or in substitution for, conventional dietary fats. On the basis of this short term evaluation in humans and other investigations with the rat and dog. SPE appears to have potential as a cholesterol-lowering agent.

High density lipoproteinuria in nephrotic syndrome.

Intravenous administration of the aminonucleoside of puromycin produces the nephrotic syndrome (proteinuria, hypercholesterolemia, hypoproteinemia and edema) in rats. This model is very similar to human nephrotic syndrome caused by various disease states. The current study was designed to assess the nature of urinary lipoproteins in the urine of nephrotic rats, including studies related to the urinary loss of the "activator" apolipoproteins for the lipoprotein lipase-triglyceride interaction. Sprague-Dawley rats were given a single intravenous injection (10 mg/100 g) of puromycin aminonucleoside. Plasma and urine were collected before and 7, 18, 29, 36, and 53 days after injection of puromycin. Urine was fractionated in the preparative ultracentrifuge into density (d) fractions less than 1.006 (very low-density lipoproteins), d = 1.006-1.063 (low-density lipoproteins), and d = 1.063-1.210 (high-density lipoproteins--HDL). The cholesterol, triglyceride, phospholipid, and protein content of these fractions was analyzed. Lipoprotein electrophoresis was performed in agarose agar. Urine from normal and nephrotic rats was added to an in vitro system containing lipoprotein lipase and triglyceride. The free fatty acids (FFA) liberated were then measured as an index of urinary activator property on this system. Measurable urinary lipoproteins were present only on days 7 and 18 after induction of the nephrotic syndrome. Coelectrophoresis of these urinary lipoproteins with rat plasma revealed a single band having alpha- (HDL) electrophoretic mobility. The total mean protein content of day-7 urinary lipoproteins (64.3%) was greater than the content of plasma HDL (52.9%). The protein content of urinary lipoproteins also increased with time. When day-7 and day-18 postinjection urine at nephrotic rats was added to the lipoprotein lipase system, the hydrolysis of triglyceride yielded a mean of 0.320 and 0.235 muEq FFA/ml/20 min, respectively. Control rat urine yielded 0.030 muEq FFA/ml/20 min and 0.000 muEq FFA/ml/20 min 7 and 18 days after injection of normal saline, respectively. It is inferred that in this experimental model (1) high-density lipoproteins are probably excreted in the glomerular filtrate, (2) alterations in the composition of the excreted lipoproteins may occur during their passage through the nephron. The possibility that only a selective portion of the HDL spectrum is excreted into the glomerular filtrate cannot be excluded. It is suggested that the urinary or renal loss of this functionally important lipoprotein may contribute to the pathophysiology of hyperlipoproteinemia in the nephrotic syndrome.

Composition of HDL-2 and HDL-3 in familial hyperalphalipoproteinemia.

The content and percent composition of cholesterol, triglyceride, phospholipids, and total proteins in HDL-2 and HDL-3 were quantitated in 5 women with familial hyperalphalipoproteinemia to determine if there are any distinctive characteristics of the high density lipoproteins in this heritable disorder. The 5 women with familial hyperalphalipoproteinemia (FHA) were compared to 4 normal women, with the groups being comparable in regards to age (40 +/- 3 and 37 +/- 5 years), total plasma cholesterol (202 +/- 9 and 188 +/- 16 mg/100 ml), triglyceride (75 +/- 12 and 95 +/- 19), and differing in levels of high density lipoprotein cholesterol (C-HDL, 84 +/- 6 and 61 +/- 3 mg/100 ml) respectively. Total cholesterol in the HDL-2 and HDL-3 fractions obtained by ultracentrifugation were 43.2 +/- 3.3 and 33.8 +/- 4.1 in FHA subjects, higher than total cholesterol in HDL-2 and HDL-3 in normals, 25.8 +/- 6.2 and 21.5 +/- 1.3 mg/100 ml, P less than 0.025. Total concentration of HDL-3 was higher in FHA than in normal subjects, respectively 222.4 +/- 22.6 and 149 +/- 7.2 mg/100 ml, P less than 0.025. Lipid-protein percent composition of HDL-2 and HDL-3 in FHA and normals was nearly identical, and polyacrylamide gel electrophoresis revealed no qualitative differences in band migration and appearance of the HDL-2 and HDL-3 fractions in normal and FHA subjects. In these women with FHA, there appears to be an increased concentration of normal HDL-2 and HDL-3.

ACTH content of pituitary glands of arteriosclerotic breeder vs. non-arteriosclerotic virgin rats.

Acid extracts were made of the pituitary glands of non-arteriosclerotic male and female virgin rats and arteriosclerotic, male and female breeder rats. The ACTH content of these pituitary glands was determined by measuring the amount of corticosterone produced by the adrenal glands of healthy but hypophysectomized rats when challenged by the various ACTH acid extracts. The pituitary glands of the arteriosclerotic animals were significantly heavier than non-arteriosclerotic rats and contained decreased amounts of ACTH commensurate with the severity of the pituitary donor's arteriosclerosis. Similarly, arteriosclerotic donors had heavier adrenal glands but contained considerably less corticosterone than non-arteriosclerotic virgin rats. Male breeder rats developed microscopic aortic lesions involving intimal mesenchymal cell and ground substance alterations whereas the female breeder lesions progressed from intimal ground substance and connective tissue changes to medial elastolytic degeneration and eventual medial cartilaginous and osseous metaplasia. Histopathologic examination of the pituitary and adrenal glands demonstrated hyperplasia of basophil and other cytologic elements of the pituitary gland including colloid-filled cysts and lipid depletion of the zona glomerulosa as well as hemorrhage and thrombosis of the adrenal cortex of the arteriosclerotic breeder rats. The hypothesis is made that repeated breeding leads to abnormal hypothalamic regulation of pituitary gland synthesis and release of ACTH, which, in turn, contributes to abnormal adrenal glandular function conditioning the aortic wall toward abnormal changes in mesenchymal cell activity and metabolism of connective tissue ground substance.

Adrenal glandular lipids and circulating corticosterone in severely diabetic rats.

Young, adult, female Sprague-Dawley rats were fasted for 18 h and then given a single s.c. injection of alloxan (10 mg/100 g body weight) which promptly induced a severe state of diabetes. The animals were killed at frequent time intervals during the 7-day study period in order to record the dynamic changes in their capacity for adrenal steroidogenesis and secretion as measured by fluorometric determination of their circulating corticosterone (Cmpd B) levels as well as by thin layer chromatographic identification of cortical lipid moieties used for steroidogenesis. In addition to severe polydypsia, polyuria and polyphagia, these animals manifested super-normal glucose, triglycerides, free fatty acids and cholesterol in their blood, severe hepatic steatosis, adrenal hyperplasia with lipid depletion from the mineralocorticoid producing z. glomerulosa, thymus gland involution and complete degranulation of their insulin producing islet beta cells. Despite an initial high output of Cmpd B and despite progressive cortical hyperplasia, the serum Cmpd B levels became reduced and many of the animals succumbed suddenly, due most likely to inadequate adrenocortical steroidogenesis. Adrenocortical lipids showed a progressive accumulation of free fatty acids, di- and triglycerides, suggesting that some lipid enzymatic defect could be responsible for the lack of conversion of these lipid entities essential for proper steroidogenesis.

Analysis of alpha-lipoprotein cholesterol in 50 microl of plasma.

A micromethod for quantitation of alpha-lipoprotein cholesterol was devised for gas-liquid chromatography to minimize plasma sample size and facilitate lipid studies using capillary blood from children or small animals. alpha-Lipoprotein cholesterol was measured by gas-liquid chromatography in 20 micro l of the centrifuged supernate obtained after addition of 5 micro l of mixed heparin-manganese chloride solution 1:1 (v/v) to 50 micro l of plasma. Comparison of venous alpha-lipoprotein cholesterol measured by gas-liquid chromatography with venous alpha-lipoprotein cholesterol measured by conventional heparin-manganese precipitation and ferric chloride (colorimetric) cholesterol determination gave a correlation coefficient of 0.98 for 80 plasma samples. Capillary alpha-lipoprotein cholesterol and venous alpha-lipoprotein cholesterol were closely correlated in 31 patients (r = 0.97).