Intermediate-density lipoprotein and cholesterol-rich very low density lipoprotein in angiographically determined coronary artery disease

Cholesterol rich apo B containing lipoproteins and smoking are independently associated with macrovascular disease in normotensive NIDDM patients

A cross-sectional study of macrovascular disease (MVD) and associated metabolic and other risk factors was conducted in 87 normotensive NIDDM patients. MVD was assessed by Rose questionnaire, 12 lead resting ECG, duplex scanning of carotid and peripheral vessels, and ankle:brachial systolic blood pressure ratio. Fasting serum total cholesterol, total triglycerides, LDL cholesterol, HDL cholesterol, apolipoproteins AI and B, lipoprotein (a), HbA1, plasma glucose, insulin, and C-peptide responses to a carbohydrate rich meal, body mass index (BMI), waist-hip ratio, urinary albumin excretion rate, blood pressure, smoking and family history were assessed as possible 'risk factors'. Apolipoprotein:lipid ratios were calculated to estimate lipoprotein composition. Thirty-six patients had demonstrable MVD. The presence of MVD was associated with higher total triglycerides (p < 0.05), BMI (p < 0.05), systolic blood pressure (p < 0.01), a lower apo B:non HDL cholesterol ratio (p < 0.001), and smoking (p < 0.005) but no other measures. Multiple regression analysis revealed smoking and a low apo B:non HDL cholesterol to be independently associated with MVD. The low apo B:non HDL cholesterol suggests a high cholesterol content of apo B containing lipoproteins. This lipoprotein abnormality is not a feature of NIDDM, but when present in these patients may be particularly atherogenic.

Cholesterol and cardiovascular disease: basic science

Cholesterol is a normal constituent of blood plasma and of cell membranes in every tissue of the body. It is transported in plasma as a component of lipoproteins. Increased concentrations of specific lipoprotein fractions, namely low density lipoproteins (LDL) and intermediate density lipoproteins (IDL), have been implicated both in vitro and in vivo as causes of atherosclerosis. The mechanism by which these lipoproteins initiate atherosclerosis is unknown, although there is growing evidence that it involves interactions between lipoproteins and cells within the artery wall, setting in train complex, reactions which lead ultimately to the fully developed lesions.

Long-term effects of three fat-modified diets in hypercholesterolemic subjects

Altogether 160 free living subjects (aged 30-60 years) most of whom had moderate hypercholesterolemia were randomised into the following diet groups to find out long-term effects of different fat-modified diets: (1) control diet 35/14:10:4 (energy percents from fat/saturated:monounsaturated:polyunsaturated fatty acids in actual diets); (2) AHA type diet 32/10:8:8; (3) monoene-enriched diet 34/11:11:5; (4) reduced-fat diet 30/12:8:3. LDL cholesterol fell equally with the AHA type diet (4.54 +/- 0.97 vs. 4.21 +/- 0.89 mmol/l (mean +/- S.D., 0 vs. 6 months), P = 0.001) and with the monoene-enriched diet (4.55 +/- 0.95 vs. 4.25 +/- 0.95 mmol/l, P = 0.004) during the 6-month study. Moderate amounts of polyenes or monoenes as part of natural diets did not decrease HDL cholesterol level in the long term. Serum lipid values remained unchanged with the reduced-fat diet. Analysis by apolipoprotein E phenotypes showed a decrease in LDL cholesterol only in subjects with phenotype 3/3 in the monoene-enriched group (-8.6 +/- 8.7 vs. +1.3 +/- 15.4, percent change in LDL cholesterol E 3/3 vs. E 4/3 + 4/4), but in the AHA type group LDL cholesterol decreased similarly in phenotypes E 3/3 and E 4/3 + 4/4 (-6.9 +/- 10.1 vs -6.9 +/- 16.5).

Cholesterol in remnant-like lipoproteins in human serum using monoclonal anti apo B-100 and anti apo A-I immunoaffinity mixed gels

We have developed a simple, rapid assay method for apo E-rich lipoproteins (d < 1.006 g/ml), using an immunoaffinity gel mixture of anti apo B-100 and apo A-I antibodies coupled to Sepharose 4B. The immunoaffinity mixed gels adsorb normal lipoproteins containing apo A-I quantitatively as well as most lipoproteins containing apo B-100. Unbound lipoproteins are quantified by assay of cholesterol. Characterization of the unbound lipoproteins of d < 1.006 g/ml (J Lipid Res 1992; 33: 369-380) has shown that they represent chylomicron and VLDL remnant-like particles (RLP). RLP-Cholesterol(C) levels in plasma have been determined in 363 male and female normolipidemic subjects (mean +/- S.D.: 72 +/- 16 mg/l) and have been found to be higher in patients with coronary heart disease and familial dysbetalipoproteinemia. Triglyceride-rich lipoproteins may well contain both atherogenic and non-atherogenic particles that can be separated by this simple immunoadsorption assay.

Ten-year cardiovascular mortality in relation to risk factors and abnormalities in lipoprotein composition in type 2 (non-insulin-dependent) diabetic and non-diabetic subjects

The purpose of the present study was to examine 10-year cardiovascular morbidity and mortality in patients with newly-diagnosed Type 2 (non-insulin-dependent) diabetes mellitus and non-diabetic control subjects and to evaluate the effects of general risk factors, plasma insulin, urinary albumin excretion, lipoprotein abnormalities characteristic of Type 2 diabetes and the degree of hyperglycaemia in diabetic patients on cardiovascular mortality. Furthermore, the extent to which the above-mentioned factors could contribute to the excessive cardiovascular mortality observed in diabetic patients was examined. In the years 1979-1981, altogether 133 (70 men, 63 women) newly-diagnosed patients with Type 2 diabetes and 144 (62 men, 82 women) non-diabetic control subjects aged 45-64 years were studied. Both groups were re-examined in the years 1985-1986 and 1991-1992. The impact of different factors on cardiovascular mortality was examined by univariate analyses after adjustment for age and sex and by multiple logistic regression analyses. The age-standardized total and cardiovascular mortality rates were substantially higher in diabetic men (17.8 and 15.0%, total and cardiovascular mortality, respectively p = 0.06 and NS) and women (18.5 and 16.6%, p < 0.01 for both) than in non-diabetic control men (5.2% both total and cardiovascular mortality) and women (4.2 and 2.2%). Cardiovascular mortality was not related to the treatment modality (diet, oral drugs, insulin) at 5 years from diagnosis. Use of diuretics, beta-blocking agents or their combination at baseline did not make a significant contribution to cardiovascular mortality either. In multiple logistic regression analysis on diabetic patients, age, LDL triglycerides, smoking, blood glucose and ischaemic ECG at baseline had independent associations with cardiovascular mortality. Interestingly, urinary albumin excretion rate measured at 5-year examination also predicted 10-year cardiovascular mortality after adjustment for the effects of major risk factors including lipoprotein abnormalities, but its predictive power reduced to a nonsignificant level when the effect of plasma glucose was taken into account. The relative risk of cardiovascular mortality associated with diabetes was 8.2 after allowing for age alone, but it declined to 3.7 when all contributing factors from the baseline examination (except blood glucose) were taken into account. In conclusion, the present results indicate that LDL triglycerides and/or other changes in lipoprotein composition characteristic of Type 2 diabetes and manifesting as elevated serum triglycerides are atherogenic and they strongly predict increased cardiovascular mortality.(ABSTRACT TRUNCATED AT 400 WORDS)

Independent associations between plasma lipoprotein subfraction levels and the course of coronary artery disease in the St. Thomas' Atherosclerosis Regression Study (STARS)

Associations between plasma lipoprotein subfractions and changes in coronary artery diseases (CAD) were examined in 74 men who completed the St. Thomas' Atherosclerosis Regression Study (STARS). Plasma lipoproteins were isolated by stepwise, preparative ultracentrifugation at repeated intervals during the 38-month trial. Paired coronary angiograms were quantitatively analyzed by a computerized method. In univariate linear regression analysis, changes in mean absolute width (delta MAWS) and minimum absolute with (delta MinAWS) of coronary segments were significantly correlated with in-trial concentrations of cholesterol in intermediate-density lipoprotein ([IDL] d = 1.006 to 1.019 kg/L), low-density lipoprotein ([LDL2] d = 1.019 to 1.040 kg/L; LDL3, d = 1.040 to 1.063 kg/L), and high-density lipoprotein ([HDL3] d = 1.125 to 1.210 kg/L) subfractions; no significant associations were found with other lipoproteins. IDL, LDL3, and HDL3 cholesterol were then selected for multiple linear regression analysis because these variables were not co-correlated and because they attained a significance of P less than or equal to .1 in univariate regression. In this analysis, only LDL3 cholesterol level was a significant negative predictor (P < .05) of both delta MAWS and delta MinAWS; a positive association between delta MinAWS and HDL3 cholesterol level just failed to reach conventional statistical significance (P = .066). Correlations between changes in coronary luminal dimensions and LDL3 cholesterol level were independent of age, smoking, weight, and blood pressure. Most patients showing regression of coronary atherosclerosis had an LDL3 cholesterol level of less than 1.8 mmol/L. The findings suggest that LDL3 is the plasma lipoprotein subfraction that exerts the single most powerful effect on the course of CAD in middle-aged men with hypercholesterolemia.

Differential effects of estrogen on low-density lipoprotein subclasses in healthy postmenopausal women

The use of estrogen by postmenopausal women decreases plasma low-density lipoprotein (LDL) cholesterol levels. To determine whether LDL subclass profiles influence this response, we studied 31 healthy postmenopausal women who were administered two doses (0.625 and 1.25 mg/d) of conjugated equine estrogen in a placebo-controlled double-blind crossover study. Lipid-stained gradient gels were used to categorize LDL subclass patterns. All women were classified as LDL subclass pattern A (predominant LDL peak > or = 260 A). Within the pattern A classification, there were 12 women during placebo treatment with LDL subclass I pattern (predominant LDL peak > 271 A) and 19 women with LDL subclass II pattern (predominant LDL peak < or = 271 and > or = 260 A). Postmenopausal women with LDL subclass I on placebo treatment had significantly lower LDL cholesterol levels compared with women having LDL subclass II (126 +/- 28 v 147 +/- 23 mg/dL, P < .03). Postmenopausal women with LDL subclass I also had significantly (P < .05) lower very-low-density lipoprotein (VLDL) cholesterol, VLDL triglyceride, and VLDL apo B levels and significantly higher (P < .05) high-density lipoprotein 2 (HDL2) cholesterol, HDL3 cholesterol, and HDL2 apo A-I levels. Estrogen replacement significantly (P < .05) decreased LDL cholesterol levels and increased VLDL and LDL triglyceride, HDL2 and HDL3 cholesterol and apo A-I, and HDL2 apo A-II levels to a similar extent in postmenopausal women with LDL I or II subclass patterns.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal aortic aneurysms in familial hypercholesterolemia--case reports

Familial hypercholesterolemia (FH) is a genetic disease characterized by high serum cholesterol levels and premature coronary atherosclerosis. Hypercholesterolemia is one of the factors promoting the arteriosclerotic process and is a major cause of aortic aneurysm. Few data are available, however, about abdominal aortic aneurysms (AAAs) in patients with FH. In this study, the clinical and angiographic characteristics of AAAs found in patients with FH were investigated. Thirty-one cases (23 men, 8 women, aged fifty +/- fourteen years) were examined by coronary angiography, thoracic and abdominal aortography, and clinical data. Abdominal aortography detected abdominal aneurysms in 8 cases (26%), all of whom were men, including 4 cases (50%) that were complicated by diabetes mellitus. The abdominal aneurysm patients manifested severe coronary atherosclerosis, severe abdominal aortic irregularity, and higher blood pressure than the nonaneurysm FH patients. These findings suggest that AAAs are an important and prevalent feature in FH, especially in men with diabetes mellitus and high blood pressure.

Replacement of dietary fat with palm oil: effect on human serum lipids, lipoproteins and apolipoproteins

Thirty-eight male volunteers participated in a double-blind cross-over trial evaluating the effect of replacing the usual sources of saturated fat in the Dutch diet (animal fats and hydrogenated oils) by palm oil, which is virtually free of cholesterol and trans-fatty acids, on serum lipids, lipoproteins and apolipoproteins. Maximum (about 70%) replacement had no significant effect on serum total cholesterol or most lipoprotein fractions, but resulted in an 11% increase in serum high-density-lipoprotein (HDL)2-cholesterol relative to the control (P2 = 0.01). The palm-oil diet also caused an 8% decrease in low-density-lipoprotein (LDL):HDL2 + HDL3-cholesterol ratio (P2 = 0.02) as well as a 9% decrease in triacylglycerols in the low-density-lipoprotein fractions (P2 = 0.01). Palm oil consumption resulted in a 4% increase in serum apolipoprotein AI (P2 = 0.008) and a 4% decrease in apolipoprotein B (P2 = 0.01) relative to the control diet; the B:AI apolipoprotein ratio was decreased by 8% (P2 < 0.0001). These results were not significantly affected by the different lipoprotein E phenotypes of the volunteers. Although the observed differences were relatively modest, the present study, nonetheless, indicates that dietary palm oil, when replacing a major part of the normal fat content in a Dutch diet, may slightly reduce the lipoprotein- and apolipoprotein-associated cardiovascular risk profiles.

Postprandial lipoprotein metabolism in obese patients with moderate hypertriglyceridaemia: effects of gemfibrozil

After an oral fat load of 1 g/kg body weight in 10 obese females with hyperlipoproteinaemia type IV, serum triglycerides concentrations were maximal at 4 h with a slight decline at 6 h, whereas serum cholesterol concentrations rose slightly at 4 h and 6 h. After 6 h, concentrations of triglycerides and cholesterol were significantly increased in chylomicrons and very low-density lipoprotein (VLDL), whereas cholesterol concentrations were decreased in high-density lipoprotein 2 (HDL2) plus HDL3. After oral treatment with 450 mg gemfibrozil twice daily for 28 days, triglyceride concentrations were reduced in serum, chylomicrons, VLDL and low-density lipoprotein, and total cholesterol concentrations were reduced in serum, chylomicrons and VLDL, and increased in HDL2 plus HDL3. At 6 h after a fat load following 28 days' gemfibrozil treatment, triglyceride and cholesterol concentrations were reduced in serum, chylomicrons and VLDL when compared with pretreatment results. It is concluded that gemfibrozil is effective in lowering triglycerides and cholesterol, particularly in triglyceride-rich particles, and raising the cholesterol content of HDL2 plus HDL3. After an oral fat load gemfibrozil inhibits the increase in serum cholesterol and partly prevents postprandial hypertriglyceridaemia.

IDL, VLDL, chylomicrons and atherosclerosis

In humans with the lipoprotein lipase deficiency disorder large amounts of chylomicrons and large very low-density lipoprotein (VLDL) accumulate in plasma. In spite of this, atherosclerosis does not seem to develop at an accelerated rate, suggesting that these lipoproteins do not promote atherogenesis. In humans with dysbetalipoproteinemia remnant lipoproteins (intermediate density lipoprotein (IDL) plus beta-VLDL) accumulate in plasma and these particles may therefore be the factor causing accelerated atherosclerosis in this disorder. Epidemiological studies in humans suggest that IDL or remnant lipoproteins are predictors of the severity or progression of atherosclerosis. Similar studies in the St. Thomas' Hospital rabbit strain, an animal model with genetically elevated plasma levels of VLDL, IDL and low-density lipoprotein (LDL), showed that IDL or remnant lipoproteins were better predictors of the extent of atherosclerosis than were LDL or VLDL. Studies of lipoprotein/arterial wall interactions have demonstrated that the larger the lipoprotein particle, the lower the influx into intima. Very large VLDL and chylomicrons do not seem to enter intima. Although high-density lipoprotein (HDL) enters intima faster than other lipoproteins, the small HDL particles seem to penetrate the entire arterial wall and leave via lymphatics and vasa vasorum in the outer media and adventitia. In contrast, LDL, and possibly also IDL and smaller VLDL, may only leave the intima via the lumen of the artery. In conclusion, a substantial body of evidence suggests that remnant lipoproteins (IDL and smaller VLDL) share with LDL the potential for promoting atherosclerosis, whereas very large VLDL and chylomicrons do not seem to have this effect.

Intermediate density lipoprotein levels are strong predictors of the extent of aortic atherosclerosis in the St. Thomas's Hospital rabbit strain

This study assessed nonfasting cholesterol and triglyceride in plasma and in lipoproteins as predictors of the extent of aortic atherosclerosis in 2 similar groups of rabbits from the St. Thomas's Hospital strain; the lipoprotein classes studied in the 2 groups were very low (VLDL), intermediate (IDL), low (LDL), and high density lipoprotein (HDL), and Sf greater than 60 lipoprotein, Sf 12-60 lipoprotein, LDL and HDL, respectively. These rabbits exhibit elevated plasma levels of VLDL, IDL, and LDL, with plasma cholesterol and triglyceride of up to 23 mmol/l and 7 mmol/l, respectively, and with up to 100% of the aortic intima bearing atherosclerosis-like lesions. In group 1 rabbits (n = 25), univariate linear regression showed that cholesterol in plasma, LDL, IDL and in VLDL each were positively associated with the extent of aortic atherosclerosis. In group 2 rabbits (n = 20), cholesterol in plasma, LDL and Sf 12-60, but not in Sf greater than 60 lipoprotein, was consistently positively associated with the extent of aortic atherosclerosis. Neither plasma triglyceride, triglyceride in lipoprotein fractions nor HDL cholesterol was associated consistently with the extent of atherosclerosis. Using step-up multiple linear regression among lipoprotein lipids, IDL and Sf 12-60 lipoprotein cholesterol were the most powerful independent predictors of the extent of aortic atherosclerosis in the 2 groups of rabbits. LDL cholesterol was the only other independent predictor. The results suggest that remnant lipoproteins, whether defined as IDL or Sf 12-60 lipoprotein, play an important causal role in atherosclerosis under conditions where plasma levels of these lipoproteins are elevated.

Postprandial plasma retinyl ester response is greater in older subjects compared with younger subjects. Evidence for delayed plasma clearance of intestinal lipoproteins

Postprandial vitamin A and intestinal lipoprotein metabolism was studied in 86 healthy men and women, aged 19-76 yr. Three independent experiments were carried out. In the first experiment, a supplement dose of vitamin A (3,000 retinol equivalents [RE]) was given without a meal to 59 subjects, aged 22-76 yr. In the second experiment, 20 RE/kg body wt was given with a fat-rich meal (1 g fat/kg body wt) to seven younger subjects (aged less than 50 yr) and seven older subjects (aged greater than or equal to 50 yr). In both experiments, postprandial plasma retinyl ester response increased significantly with advancing age (P less than 0.05). In the third experiment, retinyl ester-rich plasma was infused intravenously into nine young adult subjects (aged 18-30 yr) and nine elderly subjects (aged greater than or equal to 60 yr), and the rate of retinyl ester disappearance from plasma during the subsequent 3 h was determined. Mean (+/- SE) plasma retinyl ester residence time was 31 +/- 4 min in the young adult subjects vs. 57 +/- 8 min in the elderly subjects (P less than 0.05). These data are consistent with the concept that increased postprandial plasma retinyl ester concentrations in older subjects are due to delayed plasma clearance of retinyl esters in triglyceride-rich lipoproteins of intestinal origin.

Pravastatin therapy in primary moderate hypercholesterolaemia: changes in metabolism of apolipoprotein B-containing lipoproteins

This study examined the actions of pravastatin on the metabolism of apolipoprotein B (apo B) in very low-, intermediate-, and low-density lipoproteins (VLDL, IDL, and LDL) in 10 patients with primary moderate hypercholesterolaemia. 131I-VLDL apo B was used as a tracer, and appearance of label was followed into IDL apo B and LDL apo B. Compared to placebo, pravastatin therapy reduced levels of cholesterol in total plasma. LDL, VLDL, and IDL cholesterol by 25%, 29%, 31%, and 47%, respectively. Pravastatin treatment also significantly decreased concentrations of apo B in LDL, IDL, and VLDL. The drug significantly reduced the mean production rate for VLDL apo B by 40%, and decreased production rates for LDL apo B in eight of 10 patients. In contrast, fractional catabolic rates (FCRs) were not altered significantly in any of the three lipoprotein fractions on pravastatin therapy. Further, pravastatin produced no consistent changes in LDL particle size, composition, or LDL subclass pattern. Thus pravastatin seemingly reduced input rates for all apo B-containing lipoproteins. Consistent with previous studies, this response was most likely the result of enhanced removal of nascent lipoproteins by increased activity of LDL receptors, although decreased synthesis of apo B in the liver is a possible second action.

Increased frequencies of apolipoprotein epsilon 2 and epsilon 4 alleles in patients with ischemic heart disease

It has been demonstrated that the genetic polymorphism of apolipoprotein (apo) E is associated with atherosclerosis. Thus, in this study, we have examined the apo E allele frequencies in 109 patients with ischemic heart disease (IHD) and 576 Japanese people as controls, and we have compared these frequencies between patients with IHD and controls. The frequencies of the epsilon 2 and epsilon 4 alleles were significantly higher in patients with IHD than in the controls (epsilon 2: 8.2% vs 3.7%, epsilon 4: 17.0% vs 11.7%), whereas the frequency of the epsilon 3 allele was significantly lower in patients with IHD than in the controls (74.8% vs 84.6%). The epsilon 2-carrying patients with IHD were characterized by type III (43.8%) and IV (25.0%) hyperlipoproteinemia (HLP), whereas the epsilon 4-carrying patients with IHD were characterized by hypercholesterolemia (type IIb HLP: 42.8%, type IIa HLP: 28.6%). It is concluded that both epsilon 2 and epsilon 4 alleles are more associated with IHD than the epsilon 3 allele.

Influence of plasma triglycerides on lipoprotein patterns in normal subjects and in patients with coronary artery disease

This study examined the correlation of plasma triglyceride levels with concentrations of intermediate, low and high density lipoproteins (IDL, LDL, and HDL, respectively) and to particle sizes of LDL in 93 normal men and 106 men with coronary artery disease. Plasma triglyceride concentrations were in the normal range for all persons in both groups. Analysis of lipoproteins of density less than 1.063 g/ml was carried out by analytical ultracentrifugation. The analytical pattern gave the peak Sf for LDL as well as an indication of heterogeneity of particle sizes in the density range of LDL. In both normal subjects and patients with coronary artery disease, a positive correlation was found between peak Sf for LDL and concentrations of plasma triglycerides. Plasma triglyceride levels also were correlated positively with concentrations of Sf 20 to 60 lipoproteins and total IDL mass, and inversely with HDL cholesterol levels. Furthermore, the value for peak Sf for LDL correlated inversely with the IDL mass concentration and IDL/LDL mass ratio, and positively with the HDL cholesterol levels. The results indicate that the lipoprotein pattern, including lipoprotein concentrations and particle sizes, is sensitive to concentrations of plasma triglycerides even when the latter are within the normal range.

Relation between baseline lipid and lipoprotein values and the incidence of coronary heart disease in the Helsinki Heart Study

A 34% reduction in the incidence of definite coronary heart disease events was observed in dyslipidemic men treated with gemfibrozil in the Helsinki Heart Study, a controlled 5-year, double-blind primary prevention trial for coronary heart disease. Over the entire study period, gemfibrozil therapy induced mean decreases of 10% in serum total cholesterol levels, 11% in low-density lipoprotein (LDL) cholesterol, 35% in triglyceride levels, and a mean increase of 11% in high-density lipoprotein (HDL) cholesterol level, compared with placebo. The differences in percentage changes in LDL cholesterol between gemfibrozil- and placebo-treated men varied among Fredrickson hyperlipoproteinemia types; after 1 year of treatment the difference was greatest for type IIA hyperlipoproteinemia (14 percentage units) and smallest for IIB hyperlipoproteinemia (3 percentage units). The treatment-associated changes in HDL cholesterol and triglycerides did not differ materially between the 3 hyperlipoproteinemia types, when calculated in the same way. The gemfibrozil-associated reduction in incidence of definite coronary events varied among Fredrickson types and among tertiles of baseline HDL cholesterol and triglycerides. The greatest rate reductions were seen in subjects with type IIB hyperlipoproteinemia, low initial HDL level or high initial triglycerides. These results suggest that subjects with low HDL cholesterol and type IIB hyperlipoproteinemia (and possibly type IV hyperlipoproteinemia) would benefit from treatment with gemfibrozil.

Lipolytic surface remnants of triglyceride-rich lipoproteins are cytotoxic to macrophages but not in the presence of high density lipoprotein. A possible mechanism of atherogenesis?

Hypertriglyceridemic (HTG) serum, lipolyzed in vitro by purified bovine milk lipoprotein lipase, was found to be cytotoxic to cultured macrophages. Surviving macrophages contained numerous lipid inclusions similar to those found in foam cells. Individual lipoprotein fractions isolated from the lipolyzed HTG serum, including HDL, were also cytotoxic. Lipolysis of isolated lipoprotein fractions (either HTG or normal) allowed localization of cytotoxicity to postlipolysis remnant VLDL and chylomicron particles. The presence of a critical concentration of HDL in either the lipolysis mixture or the culture dishes inhibited the cytotoxicity. Below this critical concentration HDL itself became cytotoxic, producing lipid inclusions in surviving macrophages. The lipid fraction of the cytotoxic remnants contained the cytotoxic factor(s); neither FFA nor lysolecithin alone could account for this cytotoxicity. Postprandial lipemic sera from subjects with a brisk chylomicron response, when lipolyzed in vitro, were cytotoxic to cultured macrophages; neither fasted sera from these subjects, nor postprandial sera from normolipidemic subjects with a normal chylomicron response, were cytotoxic. Postheparin (in vivo lipolyzed) serum and its isolated lipoprotein fractions obtained 30 min after heparin injection in subjects with HTG were shown to be cytotoxic to macrophages; by 60 min most of the cytotoxicity had disappeared. The postprandial and postheparin observations support an in vivo significance for remnant-associated cytotoxicity. We hypothesize that cytotoxic remnants of lipolyzed VLDL and chylomicrons may be one of the major atherogenic lipoproteins. Further, we suggest that inhibition of the cytotoxicity of these remnants may be one important way that HDL prevents atherosclerosis.

Combined effect of exogenous insulin and sucrose on alterations in plasma lipoproteins induced by cholesterol feeding in the rat

We have recently reported increased cholesterol concentrations in high-density and very-low-density lipoproteins (HDL and VLDL) in sucrose-fed rats with exogenous hyperinsulinemia. In order to see if exogenous hyperinsulinemia has any effect on the alterations in plasma lipoproteins induced by cholesterol feeding, we fed a cholesterol-rich diet supplemented with lard, cholic acid and propylthiouracil to hyperinsulinemic, sucrose-supplemented rats and examined plasma lipoprotein profiles. Three control groups were investigated: one receiving chow only, the other receiving a cholesterol-rich diet, the third receiving exogenous insulin, sucrose, and no cholesterol-rich diet but chow. Hyperinsulinemia was induced by a constant s.c. infusion of porcine insulin (6 U/day) from an osmotic minipump. Insulin infusion plus sucrose produced an increase in HDL cholesterol concentrations similar to that seen in the previously reported injection model in the face of no change in total and low-density lipoprotein (LDL) cholesterol. Rats receiving a cholesterol-rich diet but no insulin developed marked hypercholesterolemia characterized by an elevation of cholesterol not only in LDL but also in intermediate-density lipoprotein (IDL) and VLDL. Infusing insulin into cholesterol-fed rats produced a further increase in IDL and VLDL cholesterol but was not accompanied by any further increase in LDL cholesterol. HDL cholesterol was decreased below normal.

Appearance of multidisperse low density lipoprotein and altered lipoprotein composition in non-insulin-dependent diabetes with type IIa hyperlipoproteinemia

The purpose of the present study is to elucidate the characteristics of lipoprotein disorders in diabetes mellitus. By analytical ultracentrifugation, non-insulin-dependent diabetic patients (NIDDM) with type IIa hyperlipoproteinemia (HLP) showed significantly higher incidence of multidisperse low density lipoprotein (LDL) than non-diabetics with type IIa HLP. Furthermore, LDL multidispersity in diabetic subjects seemed to be directly related to neither triglyceride (TG) levels in very low density lipoprotein (VLDL) nor the degree of glycemic control. Diabetics with multidisperse LDL had a lipoprotein profile that was different from the subjects with paucidisperse LDL as follows: (1) enrichment in the cholesterol content of VLDL, (2) TG-rich LDL with small flotation coefficient, (3) low cholesterol levels in high density lipoprotein2 along with enrichment in TG, and (4) high plasma concentrations of apoprotein B. Although the underlying mechanism behind the prevalence of multidisperse LDL in NIDDM with type IIa HLP remains unknown, it seems important that lipoprotein disorders in diabetics with multidisperse LDL were potentially atherogenic.

Apo E 2 phenotypes in type II diabetics with and without insulin therapy

In 106 type II diabetics with persisting hyperlipidemia (i.e. persistently increased triglycerides greater than 200 mg/dl during intensive diabetes therapy) the Apo E polymorphism was examined in relation to IDDM (n = 68) and NIDDM (n = 38). It was shown that Apo E2 phenotypes are more (22.6% vs. 14.5%, p less than 0.05) and Apo E3 phenotypes less frequent in type II diabetics than in non-diabetic controls (86.8% vs. 94.7%, p less than 0.001). Looking at the increase in Apo E2 phenotypes it could be proved that the phenotype composition was distinctly different between diabetics with and in those without insulin therapy. While in NIDDM the increase was consequent to a higher concentration of Apo E2 homozygotes (p less than 0.005) it was caused by Apo E2 heterozygotes in IDDM (p less than 0.025) accompanied by a simultaneous decrease in Apo E3 homozygotes (p less than 0.025). Regarding blood lipids there was an increase in total cholesterol due only to VLDL cholesterol in IDDM as well as in NIDDM. It is concluded that in spite of similar hyperlipidemias in type II diabetics the increase in Apo E2 phenotypes is different; it is induced by heterozygotes in IDDM and by homozygotes in NIDDM.

Effect of insulin therapy on lipoproteins in non-insulin dependent diabetes mellitus (NIDDM)

Thirty patients with NIDDM and severe hyperglycemia (fasting plasma glucose greater than 200 mg/dl) were initiated on insulin therapy. Lipoprotein concentrations were measured by the Vertical Autoprofile procedure before insulin therapy and 1, 3, 6 and 26 weeks after insulin initiation. Patients were divided into 4 phenotypes based on their pretreatment lipoprotein profile: HyperVLDL (elevated VLDL), HyperLDL (elevated LDL), HyperVLDL-LDL (elevated VLDL and LDL), and non-hyperlipidemic. There were no differences in the initial fasting plasma glucose, Hgb Alc, or fasting free insulin concentrations between the groups. Both the HyperVLDL and HyperLDL groups had significantly lower HDL-C concentrations that the non-hyperlipidemic group and the HyperVLDL-LDL group had significantly higher IDL-C than any of the other groups. Insulin therapy resulted in similar decreases in fasting plasma glucose and increases in fasting free insulin concentrations in all 4 groups. HDL-C increased in all 4 groups. The most marked improvements in HDL-C were seen in the non-hyperlipidemic (+37%) and HyperLDL (+42%) groups while the HyperVLDL group had only an 18% increase. VLDL-C fell in all groups but in the HyperVLDL group it fell dramatically to almost normal levels within the first week, whereas it took 6 weeks for the HyperVLDL-LDL group to reach its VLDL-C nadir and this was still significantly higher than normal. LDL-C improved modestly in only the HyperLDL patients after 6 weeks of insulin therapy. There were no statistically significant changes in either the IDL-C or Lp(a)-C in any of the groups during insulin therapy. The changes in HDL-C and IDL-C were negatively correlated with the fasting plasma glucose and Hgb Alc but not with the free insulin concentration. We conclude that: 1) Insulin therapy can cause dramatic improvements in HDL-C and VLDL-C while it has only a mild suppressive effect on LDL-C and no statistically significant effect on IDL-C or Lp(a)-C. The degree of improvement in the lipid profiles varied considerably between the different lipid phenotypes. 2) The hyperlipidemic phenotypes seen in these patients appear to be determined primarily by factors other than the degree of hyperglycemia and hypoinsulinemia.

Coronary angiographic characteristics in Japanese patients with heterozygous familial hypercholesterolemia

Coronary angiographic findings were analyzed in 51 consecutive patients (36 males and 15 females) with heterozygous familial hypercholesterolemia (FH) and 279 consecutive patients (216 males and 63 females) without FH (non-FH). The coronary stenosis index and over 75% stenosis vessel subset were almost three times as high in the FH group. The incidence of myocardial infarction was almost twice as high in the FH group. Levels of total cholesterol and its lipoprotein fractions, except HDL-cholesterol, were almost twice as high in the FH group. In the FH group aged under 50 years, the two parameters of coronary angiogram and the incidence of myocardial infarction were significantly higher in males than in females. However, in the group aged over 50 years, all three parameters were not significantly different between those in males and females. The level of HDL-cholesterol was significantly lower in males than in females. A significantly higher incidence (18%) of coronary ectasia was observed in the FH group compared with the incidence (2%) in non-FH. All patients with coronary ectasia were males, except one female with FH. On comparison of the males among the FH patients with those among the non-FH patients matched for total cholesterol, age and other risk factors, the FH patients were associated with a significantly higher degree of coronary atherosclerosis and lower level of HDL-cholesterol. Seven FH patients with a normal coronary angiogram were observed. However, any factors as regards age, total cholesterol, HDL-cholesterol and Achilles tendon thickness failed to distinguish between the FH patients with a normal coronary angiogram and those without.(ABSTRACT TRUNCATED AT 250 WORDS)

Chylomicrons and chylomicron remnants in coronary artery disease: a case-control study

Epidemiologic studies of coronary artery disease have largely overlooked the role of triglyceride-rich lipoproteins circulating in the post-prandial state. We have conducted a case-control study in males which examined fasting plasma lipoproteins and lipoproteins circulating 4 h after ingestion of a test meal containing fat and cholesterol. The cases were 82 subjects with coronary artery disease confirmed by angiography, while there were two control groups: one group of 38 'hospital controls' free of significant coronary disease by angiography, and a second group of 61 'workforce controls' free of coronary disease on historical grounds. Mean plasma and LDL cholesterol levels were significantly higher and HDL cholesterol levels were significantly lower in cases than in controls. The apo-B48/apo-B100 ratio in lipoproteins Sf greater than 60 obtained 4 h post-prandially, a relative measure of chylomicron and remnant presence, was significantly higher in cases than in controls. After pooling of all data, the prevalence of coronary artery disease was found to increase progressively with the concentration of plasma cholesterol and triglycerides, total cholesterol/HDL cholesterol ratio and the apo-B48/apo-B100 ratio in Sf greater than 60, the relative risk being highest for total cholesterol/HDL cholesterol ratio. After controlling for the confounding effects of age and other lipid factors via multiple logistic regression, apo-B48/apo-B100 ratio was still a significant predictor of coronary artery disease presence (z = 1.97, P less than 0.05) in a 'dose-response' fashion. The risk of coronary artery disease in the top quartile of apo-B48/apo-B100 distribution was 2.2-fold greater than that for the bottom quartile, after adjustment for the effects of other risk factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of CS-514 on serum lipoprotein lipid and apolipoprotein levels in patients with familial hypercholesterolemia

Effects of CS-514, a new competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, on serum lipoprotein lipid and apolipoprotein levels were studied in 13 heterozygous patients with familial hypercholesterolemia. Treatment with 10 mg of CS-514 twice daily reduced total serum cholesterol, low-density lipoprotein (LDL), and intermediate-density lipoprotein (IDL) cholesterol levels by 25%, 33%, and 33%, respectively, and increased high-density lipoprotein (HDL) cholesterol levels by 15%. Apolipoprotein B, E, and C-II levels decreased by 24%, 20%, and 19%, and apolipoproteins A-I and A-II levels increased by 10% and 7%, respectively. One patient showed abnormally high levels of SGOT, SGPT, and serum alkaline phosphatase, which returned to normal levels immediately after the cessation of CS-514. No other adverse effects were observed. Thus, CS-514 reduces atherogenic lipoproteins and apolipoprotein B, and increases HDL and apolipoprotein A-I and A-II, and appears to be a useful drug for heterozygous familial hypercholesterolemia.

Type 1 (insulin-dependent) versus type 2 (non-insulin-dependent) diabetes mellitus: characterization of serum lipoprotein alterations

Serum lipoprotein lipids and apolipoproteins A-I, B, and E were investigated in Type 1 (insulin-dependent) diabetics, Type 2 (non-insulin-dependent) diabetics, and two control groups, twenty subjects each. Lipoproteins were separated and analysed by common methods, apolipoproteins were measured by endpoint immunonephelometry. Compared with controls, Type 2 diabetics had increased serum apolipoprotein E levels (0.116 +/- 0.020 vs. 0.079 +/- 0.014 g 1-1, P less than 0.01) together with an increased content of cholesteryl ester-enriched very low-density lipoproteins. Furthermore, Type 2 diabetics had higher apolipoprotein B concentrations (1.06 +/- 0.21 vs. 0.85 +/- 0.21 g l-1 P less than 0.01), but lower high-density lipoprotein cholesterol concentrations than the controls. Conversely, Type 1 diabetics had elevated serum apolipoprotein A-I values vs. controls and Type 2 diabetics (1.70 +/- 0.33 vs. 1.49 +/- 0.22 and 1.43 +/- 0.21 g 1-1, P less than 0.01). It is concluded that Type 2 diabetics, like other groups at risk for atherosclerotic diseases, are characterized by an increased concentration of partly catabolized very low-density lipoproteins. Sufficiently insulinized Type 1 diabetics have, on the other hand, an increased number of high-density lipoprotein particles.

Increased cholesterol concentration in intermediate density lipoprotein fraction of normolipidemic non-insulin-dependent diabetics

There is increasing agreement about the atherogenicity of intermediate density lipoprotein (IDL). In order to determine whether normocholesterolemic diabetics are at a higher risk of atherosclerosis, cholesterol concentrations in three subclasses of triglyceride-rich lipoprotein fraction (Sf 12-400) were examined. Their plasma triglyceride and cholesterol levels were limited to below 150 and 250 mg/dl, respectively. They were divided into 3 groups according to their treatment: insulin injection (group I), sulphonylurea (group S) and diet alone (group D). Age-matched healthy normolipidemic non-obese subjects served as controls (group C). Triglyceride-rich lipoproteins were separated by ultracentrifugation: very low density lipoprotein (VLDL), Sf 60-400; intermediate density lipoprotein (IDL1), Sf 20-60; IDL2; Sf 12-20. Cholesterol concentrations in total plasma, VLDL, IDL2 and high density lipoprotein (HDL) were all identical in every group. A significant increase in cholesterol concentration was found in IDL1 of groups S and D. Low density lipoprotein-cholesterol of group I was also increased. These findings indicate an increased risk factor in normolipidemic diabetics.

Relationship of intermediate and low-density lipoprotein subspecies to risk of coronary artery disease

Recent studies have shown that heterogeneity of human plasma low-density lipoproteins (LDL) is, in part, the result of production of different LDL products from two subspecies of intermediate-density lipoproteins (IDL). Cholesterol-enriched forms of both IDL species are found in plasma of patients with atherogenic dyslipidemias (familial hypercholesterolemia and type 3 hyperlipoproteinemia) and have physical properties similar to the major species in plasma of cholesterol-fed monkeys. Patients with familial combined hyperlipidemia have been shown to have increased plasma levels of IDL and of a smaller, denser LDL subclass (LDL-IIIA) that appears to be a metabolic product of the smaller IDL subspecies. Results from the NHLBI Type II Coronary Intervention study have supported a link between the small IDL-LDL pathway and coronary disease, in that 2-year changes in levels of these species were associated with disease progression. Furthermore, therapeutic reductions in IDL levels were correlated with increases in high-density lipoprotein cholesterol. Thus variation in IDL levels might influence coronary disease risk by both a direct effect and indirectly by affecting LDL particle number and possibly high-density lipoprotein metabolism.

The anticoagulant, hepatic lipase-releasing and lipoprotein lipase-releasing activities of several natural and chemically modified heparins differ

Several 'natural' heparins have been found to have different potencies for releasing hepatic lipase and lipoprotein lipase. These differences can also be obtained by treating heparins with physical and chemical methods, which also affect the anticoagulant activity. These differences in potency in hepatic lipase-releasing activity are discussed in terms of the role of this lipase in lipoprotein and cholesterol metabolism.

Lipoprotein changes during continuous subcutaneous insulin infusion in insulin-dependent diabetic patients

We have studied the long-term effects (9 months) in plasma lipoprotein concentrations during continuous subcutaneous insulin infusion (CSII) (n = 11, six females, five males) and compared these changes to conventional insulin therapy (CIT) (n = 12, six females, six males). The two groups were allocated to CSII or CIT randomly, and were comparable as regards lipoprotein values at the start of the study. There were initially normal total plasma cholesterol values in both groups (CSII group: mean plasma cholesterol 3.77 +/- 0.57 mmol/l, CIT group: mean plasma cholesterol 4.37 +/- 0.55 mmol/l, means +/- SD). Further, there were normal total plasma triglyceride values at the start of the study (CSII group: mean plasma triglyceride 0.86 +/- 0.23 mmol/l, CIT group: mean plasma triglyceride 0.84 +/- 0.26 mmol/l, means +/- SD). There were no alterations seen in total plasma cholesterol and total plasma triglyceride in either groups during a 9 months observation period. In the same period no changes in LDL and HDL levels were registered. The very low density lipoprotein (VLDL) was separated into VLDL-1 and VLDL-2 by its binding to heparin-sepharose columns. It was found that CSII treatment for 9 months resulted in a decline in VLDL-2-triglyceride values (0.18 +/- 0.07 mmol/l before versus 0.10 +/- 0.07 mmol/l after, p less than 0.05, means +/- SD) which was not seen in the CIT group. Decline in VLDL-2-triglyceride might delay the development of late diabetic manifestations.

Treatment of homozygous patients with familial hypercholesterolemia by double-filtration plasmapheresis

Two homozygous patients with familial hypercholesterolemia were treated by double-filtration plasmapheresis. The plasma separated by the first filter was subsequently led to the second filter of ethylene vinylalcohol co-polymer hollow fibers, which trap very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL) and low density lipoprotein (LDL) preferentially to other plasma constituents. Serum, VLDL, IDL, LDL cholesterol levels decreased by 55, 68, 59 and 55%, respectively. HDL cholesterol levels decreased by 39%. Immunoglobulins and fibrinogen levels decreased significantly. Cutaneous and tendinous xanthomas became smaller. off

[Persisting hyperlipidemias as risk factors of diabetic macroangiopathy]

Severe forms of arterial occlusive diseases occurred more frequently in 11 insulin-treated diabetics with persisting hyperlipidemia than in 10 control subjects who were 11 years older. Triglycerides and cholesterol of total serum and of VLDL were 2-7 times higher (P less than 0.01); however, LDL-cholesterol was 2 times lower than in control subjects (P less than 0.025). HDL-cholesterol was not significantly different in either group. After insulin administration (81 U/die vs 37 U/die, P less than 0.00251), the increased lipids were only insignificantly reduced, while LDL-cholesterol and the ratio of LDL-/HDL-cholesterol was even increased (P less than 0.0025 and P less than 0.05). In contrast to control subjects, VLDL-cholesterol was positively correlated to the tolbutamide-induced insulin reserve (before insulin administration) and to the diurnal insulin dosage (after insulin administration) (P less than 0.01 and P less than 0.001). The results show that the atherosclerotic risk in diabetics with persisting hyperlipidemia is higher than in control subjects and that the risk is distinguished by increased VLDL-cholesterol in correlation with increased insulin concentrations. Since the atherosclerotic risk is even more accentuated by the fact that insulin administration increases LDL-cholesterol, insulin therapy must be observed carefully in these patients.

Physical training and plasma intermediate density lipoprotein cholesterol levels in men with hypertriglyceridemia

Plasma lipoprotein lipid levels including IDL cholesterol concentration, physical fitness parameters, and anthropometric data were measured in 10 men with primary hypertriglyceridemia during a 12 week program of moderate physical training. Reduced pulse rate at submaximal workload and increased work performed on the treadmill indicated that the men had increased their physical fitness during the training period. Body weight (-4.9%) and total skinfold thickness (-15.6%) fell during the training program. A characteristic fall (-23%) in plasma triglyceride levels was seen over the first 8 weeks training. Plasma IDL cholesterol concentration fell (-18%) after 2 weeks training but then rose after 8 weeks to levels which tended to be higher than baseline values. Our data suggest that regular physical exercise is more likely to raise levels of the "proatherogenic" IDL than to lower them in hypertriglyceridemic patients.

Reciprocal effects of apolipoprotein E alleles (epsilon 2 and epsilon 4) on plasma lipid levels in normolipidemic subjects

A significantly lower frequency of the epsilon 2 allele and a significantly higher frequency of the epsilon 3 allele were found in the normolipidemic Japanese population than those in the normolipidemic Caucasian populations. We have compared plasma lipid variables among the apolipoprotein (apo) E phenotype groups and estimated the average effects of the three common alleles (epsilon 2, epsilon 3 and epsilon 4) on plasma lipid levels in normolipidemic subjects. Plasma triglyceride (TG), very low density lipoprotein (VLDL)-TG, VLDL-cholesterol (C) and apo E levels were high in the apo E3/2 group, intermediate in the apo E3/3 group and low in the apo E4/3 group, whereas plasma total cholesterol (TC), low density lipoprotein (LDL)-C and high density lipoprotein (HDL)-C levels were low in the apo E3/2 group, intermediate in the apo E3/3 group and high in the apo E4/3 group. Furthermore, the epsilon 2 allele had an effect to increase the TG, VLDL-TG, VLDL-C and apo E levels and decrease the TC, LDL-C and HDL-C levels, whereas the epsilon 4 allele had an effect opposite to the epsilon 2 allele. These results indicate that the epsilon 2 and epsilon 4 alleles have the reciprocal effects on plasma lipid, lipoprotein and apo E levels.

Hypertriglyceridemia and carbohydrate intolerance: interrelations and therapeutic implications

Atherosclerosis, the most frequent complication of diabetes, could be the result of hyperlipidemia, among other factors. Mounting evidence suggests that reducing the concentration of triglyceride-rich lipoprotein, which influences the production of the possibly atherogenic intermediate density lipoprotein (IDL), might diminish the circulating level of potentially atherogenic lipoproteins. Hypertriglyceridemia, even in the absence of obesity, is associated with insulin resistance. To compensate, pancreatic B cells respond to glucose challenge by producing hyperinsulinemia. If the B cells cannot respond adequately, carbohydrate intolerance ensues. Insulin-treated diabetics may also become hyperinsulinemic because routine insulin injection may not reflect physiologic need and because the insulin is administered peripherally rather than portally. Hyperinsulinemia increases the production of circulating triglyceride. It appears to do this in rats by causing the production of more triglyceride-rich lipoprotein particles rather than by increasing the triglyceride content of each particle. Further, at least in rats, the insulin-induced increase in triglyceride production requires the presence of supplementary dietary fructose. Hyperinsulinemia also increases the activity of adipose tissue lipoprotein lipase and the degradation of very low density lipoprotein (VLDL). The concentration of VLDL depends on balance of production and degradation. Accelerated VLDL degradation leads to an increase in IDL production. Because there is mounting evidence that IDL may be atherogenic, this cycle could accelerate atherogenesis. As such, it is reasonable to postulate that reducing the concentration of triglyceride-rich lipoproteins would break this cycle and would diminish the circulating level of potentially atherogenic lipoproteins.

Analysis of risk factors in 532 survivors of first myocardial infarction hospitalized in Jerusalem

During the period January 1979-March 1983, we have conducted in Jerusalem a case control study of all patients under the age of 65 surviving their first diagnosed myocardial infarction, in order to evaluate the importance of the conventional risk factors and to detect additional factors through quantifying plasma apolipoprotein concentrations. As a control group, we have chosen a sample from a previously studied Jewish population (LRC study), representative of the adult Jerusalemite population, parents of children born during 1958-1961. To complete the younger age group missing in the LRC population, we added a population studied in the Kiryat Yovel district of Jerusalem. We report here the results obtained from interviews and analysis of 532 cases (448 males and 84 females), and 869 controls (457 males and 412 females). In order to overcome the effects of age and ethnic origin on the risk factors, we have divided our populations according to age and country of origin of their fathers. Age, sex, smoking, history of high blood pressure, diabetes, elevated plasma triglycerides and/or cholesterol, and decrease in plasma HDL cholesterol, emerged as the most powerful and significant risk factors in this study. Other putative risk factors such as socioeconomic status, dietary habits, physical activity and obesity index were not found to be significantly different between cases and controls. It is noteworthy that smoking was more important as a risk factor in the younger age groups, whereas hypertension and diabetes were more important in the older age groups, particularly in females. The differences in lipid levels were considerably more prominent in the young age groups in both sexes. Myocardial infarction was observed more frequently in patients of European or American extractions. Apolipoproteins A-I, A-II, E and B determined in this study were shown to be affected partly by age and country of origin. Apo E and apo B levels were significantly higher and Apo A-I significantly lower in patients with myocardial infarction when compared to controls.