Biomedical subjects

B A Kottke

Publications and source records attributed to B A Kottke.

At least 73 records · Page 4Linked to original sources

PubMed1987

Role of macrophages in lipid metabolism.

One of the cells involved in lipid metabolism and thought to have adrenergic receptors is the macrophage. Low-density lipoprotein (LDL), once modified, can bind to modified LDL receptors on the macrophage. After binding to these receptors, LDL is internalized by a mechanism that is not controlled by feedback inhibition. This unregulated uptake results in massive cholesterol ester accumulation in atherosclerotic plaques. Macrophages secrete apolipoprotein E, a process that appears to be regulated by the cholesterol content of the macrophage, as well as by lipoprotein lipase. Macrophages are also thought to have receptors for high-density lipoprotein (HDL) on their surface, receptors that may play a key role in reverse cholesterol transport of cholesterol esters from the cells. Studies are being conducted to determine the effects of alpha 1-adrenergic activation on lipoprotein metabolism in these cells.

Animals↗

PubMed1986

Metabolism of apolipoprotein E-containing human plasma lipoproteins by rat and human cells in culture.

Cultured preadipocytes from rat epididymal fat pads were able to bind, internalize, and degrade human plasma very-low-density lipoproteins (VLDL) more efficiently than low-density lipoproteins (LDL). VLDL, but not LDL, activated acyl-CoA: cholesterol acyltransferase (ACAT) and increased cholesterol accumulation in these cells. However, trypsin-treated VLDL (T-VLDL) lost the capacity to bind, activate ACAT, and increase cholesterol accumulation. After the treatment of VLDL with trypsin, SDS/polyacrylamide-gel electrophoresis and immunoblotting showed that apolipoprotein E (apo E) was completely degraded, whereas apolipoprotein CII (apo C-II) was preserved. ApoE complexed with dimyristoyl phosphatidylcholine (DMPC) was able to complete with VLDL for binding to the cells. Although T-VLDL did not bind to the preadipocytes, these cells accumulate triacylglycerols from T-VLDL, presumably after lipolysis, as efficiently as from native VLDL. Rat smooth muscle cells and skin fibroblasts also bind and metabolize human VLDL better than LDL. However, human skin fibroblasts and omental preadipocytes metabolized LDL better than VLDL. These studies indicate that rat tissues can recognize and metabolize apoE-containing human plasma VLDL although they cannot recognize human LDL.

Adipose Tissue↗

PubMed1986

A rapid apolipoprotein E radioimmunoassay using solid-phase staphylococcus protein. Use of pooled plasma as a secondary standard.

A rapid apolipoprotein E (apo E) radioimmunoassay, which requires a total of 24 hour incubation as compared to the usual 3-5 days, has been developed in our laboratory. Solid phase staphylococcus protein A was used to separate bound and unbound labeled antigen. Use of a pooled plasma (quality control sample) as a secondary standard to reduce interassay variation was also described.

Adult↗

PubMed1986

Lipid markers for atherosclerosis.

Atherogenesis results from the simultaneous occurrence of 2 important processes: platelet-endothelial interaction, with its consequences mediated by the platelet-derived growth factor, and lipid accumulation. Lipid accumulation results from the balance or imbalance of cellular uptake of lipoproteins versus the removal of cholesterol esters. Uptake results from activity of the low-density lipoprotein (LDL) receptor of smooth muscle cells and fibroblasts, modified LDL receptor and remnant receptors of macrophages. Cholesterol-ester removal is regulated by apolipoprotein A-l. Low levels of apolipoprotein A-l are found in most patients with clinically significant coronary artery disease, suggesting that defects in cellular cholesterol ester removal may play an important role in atherogenesis.

Apolipoprotein A-I↗

PubMed1986

Metabolism of glycosylated very-low-density lipoproteins in human skin fibroblasts.

Very-low-density lipoproteins (VLDL) were glycosylated using glucose and sodium cyanoborohydride. The binding and rate of degradation of glycosylated VLDL in human skin fibroblasts were reduced significantly compared to native VLDL. These glycosylated VLDL were not able to activate acyl-CoA:cholesterol acyltransferase or inhibit cholesterol synthesis in fibroblasts. Glycosylated VLDL showed higher mobility on agarose electrophoresis, and apolipoprotein E in these lipoproteins showed higher molecular weight on SDS-polyacrylamide gel electrophoresis. The physiological significance of glycosylation of VLDL in hyperglycemic subjects is speculated.

Borohydrides↗

PubMed1986

Univariate and bivariate analyses of cholesterol and triglyceride levels in pedigrees.

A multivariate normal model for pedigree analysis is applied to fasting total serum cholesterol and total serum triglyceride measurements on 771 individuals in 95 pedigrees from Rochester, MN. Univariate and bivariate analyses are carried out to determine to what extent the aggregation and coaggregation in families of these two traits may be attributed to shared genetic and environmental factors. Pedigrees were ascertained through a sample of schoolchildren enriched for those with serum cholesterol levels in the highest and lowest deciles of their age- and sex-specific distributions. Ascertainment is corrected for by conditioning the likelihood on the trait values of the probands. Univariate results confirm the findings of previous studies indicating that familial aggregation of serum cholesterol and triglyceride levels is due both to shared genes and to shared environmental factors. Results of the bivariate analyses suggest that the coaggregation of cholesterol and triglyceride levels in these families is strongly influenced by both shared genes (pleiotropy) and shared environmental factors. These findings are consistent with our understanding of lipid metabolism and of specific environmental factors known to influence both traits.

Adolescent↗

PubMed1986

Quantification and immunolocalization of apolipoprotein E in experimental atherosclerosis.

We developed a radioimmunoassay for rabbit apolipoprotein E (apo E) for studying their plasma apo E levels and its accumulation in the aorta of rabbits fed a cholesterol diet. Delipidation of plasma did not increase the apo E immunoreactivity and this immunoreactivity was indistinguishable from that in an apo E-phospholipid complex. The antigenic determinants of apo E in lipoprotein particles were therefore fully reacted with our goat anti-apo E antibodies. In our assay system, the non-ionic detergent Tween-20 was found to be necessary to significantly reduce the non-specific binding of 125I-labeled apo E to polystyrene tubes, and yet not interfere with the assay. In rabbits (n = 6) fed a high cholesterol (1%) diet, plasma apo E increased at least 10-fold above baseline levels and reached maximal levels within 17-20 days after the onset of cho-diet feeding. These levels were sharply reduced only 10 days after resuming a normal diet. Plasma total cholesterol levels went through a similar pattern. Thus, the plasma cholesterol concentration can simply be used to monitor the increase of apo E in cholesterol-fed rabbits. All the cholesterol-fed rabbits developed atherosclerotic fatty streak lesions and apo E located mostly in the thoracic region and was significantly correlated with the accumulation of lipids in the areas of lesion. In addition, the apo E deposition was limited to the aortic areas where lipids were present. On the other hand, apo A-I was not detectable in any lesion area. Our data suggest that apo E or apo E-containing lipoproteins, may be involved in the development of atherosclerosis in cholesterol-fed rabbits.

Animals↗

PubMed1986

Apolipoproteins and coronary artery disease.

In this study, we compared the relative utility of plasma levels of cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol, and apolipoproteins in identifying men with angiographically significant coronary artery disease in a combined sample of consecutive male patients undergoing coronary angiography (N = 304) and healthy, normal male control subjects (N = 135). The plasma apolipoprotein levels were measured by using specific radioimmunoassays. We found that plasma levels of apolipoprotein A-I, followed by those of apolipoproteins A-II and B, were better discriminators than plasma cholesterol, triglycerides, or HDL cholesterol levels for identifying those with coronary artery disease. In confirmation of previous findings, the presence of coronary artery disease resulted in lower levels of apolipoproteins A-I and A-II and HDL cholesterol and higher levels of apolipoprotein B, cholesterol, and triglycerides. Linear and quadratic discriminant function analysis demonstrated that by using the age of the patients and apolipoprotein A-I, A-II, and B levels, one could correctly classify patients either as being normal or as having angiographically significant coronary artery disease in more than 75% of the cases. Thus, plasma apolipoprotein levels (especially A-I and A-II) may be considerably better markers for coronary artery disease than traditional lipid determinations.

Adult↗

PubMed1986

Plasma lipids and apolipoprotein A-I and A-II levels in alcoholic patients.

This prospective study compared total plasma lipids, high-density lipoprotein cholesterol (HDL-C), and apolipoproteins A-I (apo A-I) and A-II (apo A-II) in 72 alcoholic patients and in 285 nonalcoholic controls. The HDL-C in the alcoholic group was not significantly different from that in the nonalcoholic controls. Alcoholic men had significantly higher levels of cholesterol and triglycerides and lower levels of apo A-I when compared with nonalcoholic controls. Alcoholic women had significantly higher levels of cholesterol and apo A-II when compared with nonalcoholic controls. Serial measurements in 25 alcoholic patients showed a significant decline in HDL-C, apo A-I, and apo A-II levels during the 4-wk hospital stay. HDL-C demonstrated its expected inverse relationship with plasma triglyceride level and its direct relationship with apo A-I, apo A-II, and the hepatic enzyme aspartate aminotransferase.

Adult↗

PubMed1986

Sterol excretion and cholesterol absorption in diabetics and nondiabetics with and without hyperlipidemia.

Fecal neutral and acidic sterols and cholesterol absorption were measured in 12 normal control subjects, 40 diabetic subjects with and without hyperlipidemia, and 27 subjects with hyperlipidemia but without diabetes mellitus. All subjects were on a low-cholesterol diet (less than 300 mg cholesterol/day). Fecal excretion of neutral and acidic sterols was increased in patients with hypertriglyceridemia and was more marked in diabetic patients with hypertriglyceridemia. Cholesterol absorption was decreased in diabetic patients with hypertriglyceridemia. Otherwise, there were no significant differences in sterol excretion or cholesterol absorption in diabetic and nondiabetic subjects compared with control groups with similar lipid levels. The best predictors of fecal neutral- and acidic-sterol excretion and of estimated cholesterol synthesis were very low [corrected]-density lipoprotein triglycerides and high-density lipoprotein cholesterol. Correction of hyperlipidemia may be beneficial in decreasing cholesterol synthesis and, thereby, in decreasing the risk of atherogenesis.

Adult↗

PubMed1986

The genetic determination of plasma apolipoprotein A-I levels measured by radioimmunoassay: a study of high-risk pedigrees.

Apolipoprotein A-I (apo A-I) is the major protein component of the high-density lipoprotein (HDL) found in all primates. Using radioimmunoassay, we measured plasma apo A-I levels in 97 individuals from 23 pedigrees ascertained through cases of hypertension or early coronary artery disease (CAD). Using complex segregation analysis, we found that a genetic model with both a single locus with a major effect and polygenic loci gave the best explanation for the distribution of apo A-I levels in these pedigrees. There was no evidence for a major locus effect on HDL cholesterol in these pedigrees. This is the first study to show evidence of a major effect of a single genetic locus on the quantitative variation of plasma apo A-I in a sample of pedigrees enriched for individuals at risk for CAD.

Apolipoprotein A-I↗

PubMed1986

Use of a quality-control plasma sample to decrease interassay variation in radioimmunoassays of apolipoprotein A-I.

The apolipoprotein A-I (apo A-I) radioimmunoassay established in our laboratory involves use of purified apo A-I as the primary standard for quantifying apo A-I in plasma and a pooled plasma (quality-control sample) as a secondary standard to decrease interassay variation. The measured values for apo A-I increased over time as the labeled antigen degraded. We observed these results in two separate studies: (a) apo A-I in plasma from 16 subjects was measured 12 times during four months, and (b) apo A-I in a single pooled plasma was measured 48 times during 10 months. We show that use of a quality-control plasma sample as a secondary standard decreased interassay variation, which was, in part, ascribable to degradation of the labeled antigen.

Adult↗

PubMed1985

Structure and function of human low density lipoproteins. Studies using proteolytic cleavage by plasma kallikrein.

Kallikrein digestion of human low density lipoproteins (LDL) has recently been shown to result in the degradation of apolipoprotein B (apo-B) into four major fragments, two of them being B-26 and B-74, which have been reported to be present in the LDL of some individuals. We studied the binding of kallikrein-treated LDL to human fibroblasts; digestion did not affect binding. Digested LDL was not taken up by macrophages, showing that it behaved like normal LDL. The activation of acyl-CoA cholesterol acyltransferase by LDL in fibroblasts was also not altered by kallikrein digestion. When delipidated LDL was treated with kallikrein, apo-B was digested into very small fragments, indicating that kallikrein can cleave apo-B at sites other than those which result in the formation of B-26 and B-74. The partial delipidation of LDL with heptane also resulted in more extensive digestion of apo-B, although binding to cells was unaffected. These studies suggest that the cholesterol core maintains the proper orientation of apo-B in the LDL particle and that kallikrein may be used as a tool to elucidate the association of apo-B and lipids in the LDL particle.

Apolipoproteins B↗

PubMed1985

Human breast milk stimulates prostaglandin synthesis in cultured human skin fibroblasts.

Effect of human breast milk or its fractions on prostaglandin synthesis was investigated in cultured human skin fibroblasts. Prostaglandins released into the media were measured by radioimmunoassay. Incorporation of breast milk (2% level) into 10% fetal calf serum media (for 48 hours) stimulated the synthesis of 6-keto-PGF1 alpha (stable product of prostacyclin) by 800%. This stimulating effect of milk persisted after cold acetone extraction to remove phospholipids and potentiated further after dialysis. Stimulation by one of the commercial formulas (Similac) was less than 50% of the milk effect. Milk also stimulated PGE2 synthesis, although to a much lesser degree. These studies show for the first time that a) human breast milk contains potent factor(s) capable of influencing prostaglandin synthesis and suggest that b) these factors might have a role in the development of lipid synthetic pathways during early life.

6-Ketoprostaglandin F1 alpha↗

PubMed1985

Human breast milk stimulates low density lipoprotein (LDL) binding to human skin fibroblasts in culture.

Human breast milk incorporated at 1% concentration into the culture medium significantly (p less than 0.05) increased the binding of 125I-LDL to receptors of human skin fibroblasts in culture. Homogenized cows milk and infant formula (Similac) also possessed this stimulating property. The stimulating activity of milk persisted after dialysis and extraction with cold acetone. These preliminary studies suggest that milk might contain potent factor(s) influencing cholesterol metabolic process in early life.

Cells, Cultured↗

PubMed1985

Postprandial distribution of apolipoproteins C-II and C-III in normal subjects and patients with mild hypertriglyceridemia: comparison of meals containing corn oil and medium-chain triglyceride oil.

Five healthy male subjects and five patients with mild hypertriglyceridemia were studied following the administration of 800-kcal liquid meals containing 40% of energy from fat, 40% from carbohydrate, and 20% from protein. On the first day of the study, the fat source was corn oil (long-chain triglyceride), whereas medium-chain triglyceride (MCT) oil was used the second day. Meals were infused into the duodenum using a peristaltic pump. Plasma samples, obtained at hourly intervals for 8 hours, were analyzed for glucose, cholesterol, triglyceride, and apolipoproteins C-II and C-III. The distribution of apoC-II and apoC-III between ultracentrifugally-separated triglyceride-rich lipoproteins (TRL) and high-density lipoproteins (HDL) was also evaluated. The patient group had significantly elevated fasting levels of triglyceride, apoC-II and apoC-III, as well as much greater lipemic response to the meal containing corn oil. In both groups, TRL apoC-II and apoC-III levels were positively correlated with the triglyceride level as it increased following the corn oil meal. These correlations were also observed in the normal subjects when the MCT oil meal was administered, even though changes in plasma triglycerides were minimal. In normal subjects, whole plasma levels of apoC-II and apoC-III decreased significantly following the meal containing corn oil, whereas no net changes occurred following the MCT oil meal. In hypertriglyceridemic subjects, small decreases in plasma apoC-II and apoC-III levels occurred after both meals, although the changes in apoC-II were not statistically significant. The tendency for decreased plasma apoC levels following alimentary lipemia confirms previous reports, and provides further data to support the concept that some apoC is cleared from plasma in association with TRL remnants. The finding that mildly hypertriglyceridemic subjects responded similarly to both conventional fat and MCT may indicate that their rates of remnant clearance were similar following the two meals.

Adult↗

PubMed1985

Interaction of normolipidemic very low density lipoproteins with receptors in human skin fibroblasts.

Very low density lipoproteins (VLDL) from normolipidemic subjects were able to bind to the cultured human skin fibroblasts almost as efficiently as low density lipoproteins (LDL). The rate of esterification of cholesterol in the fibroblasts was enhanced by VLDL to the same extent as by LDL. Trypsin treatment of VLDL abolished the binding capacity completely. When trypsin-treated VLDL was partially delipidated with heptane, part of the binding capacity to the fibroblasts was restored. SDS polyacrylamide gel electrophoresis showed that apolipoprotein E (apo E) in VLDL was digested completely by trypsin. Although normal VLDL are recognized by the cells through apolipoprotein E, the major apoprotein of VLDL, that is apolipoprotein B (apo B), is not functional unless the core triglycerides are removed. In contrast to the previous reports which indicate that only hypertriglyceridemic VLDL and not normal VLDL interact with fibroblast receptors, our results clearly show that VLDL from normolipidemic subjects can also bind to these receptors.

Cholesterol↗

PubMed1985

Monoclonal antibodies can precipitate low-density lipoprotein. II. Radioimmunoassays with single and combined monoclonal antibodies for determining apolipoprotein B in serum of patients with coronary artery disease.

We have established four lines of monoclonal antibodies against human low-density lipoproteins (LDL) that, mixed in equal proportions, can precipitate LDL in gel and so can be used for apolipoprotein (apo) B determination in plasma. One monoclonal antibody (clone A), with a relatively low binding affinity to LDL (ka = 0.6 X 10(9) L/mol) and recognizing only two species of apo B, significantly underestimated the concentration of apo B in 74 patients with and 27 without coronary artery disease (CAD). High-affinity monoclonal antibody C (Ka = 3.8 X 10(9) L/mol), which recognized all four apo B species, gave the same value for apo B as determined with the mixture of monoclonal antibodies. The latter results (by radioimmunoassay, y) correlated well with those by radial immunodiffusion (chi): y = 0.994 chi + 0.003 (r = 0.987). The CAD patients showed an increased concentration of apo B as compared to the angiographically documented CAD-negative patients. Except for the values determined by clone B (p = 0.07), the increase was statistically significant (p = 0.002-0.018) for values determined by use of the other clones or their mixture.

Antibodies, Monoclonal↗