Atherogenic hyperlipoproteinemia. The cellular and molecular biology of plasma lipoproteins altered by dietary fat and cholesterol

Severe Hypertriglyceridaemia and Chylomicronaemia Syndrome-Causes, Clinical Presentation, and Therapeutic Options

We have reviewed the genetic basis of chylomicronaemia, the difference between monogenic and polygenic hypertriglyceridaemia, its effects on pancreatic, cardiovascular, and microvascular complications, and current and potential future pharmacotherapies. Severe hypertriglyceridaemia (TG > 10 mmol/L or 1000 mg/dL) is rare with a prevalence of <1%. It has a complex genetic basis. In some individuals, the inheritance of a single rare variant with a large effect size leads to severe hypertriglyceridaemia and fasting chylomicronaemia of monogenic origin, termed as familial chylomicronaemia syndrome (FCS). Alternatively, the accumulation of multiple low-effect variants causes polygenic hypertriglyceridaemia, which increases the tendency to develop fasting chylomicronaemia in presence of acquired factors, termed as multifactorial chylomicronaemia syndrome (MCS). FCS is an autosomal recessive disease characterized by a pathogenic variant of the lipoprotein lipase (LPL) gene or one of its regulators. The risk of pancreatic complications and associated morbidity and mortality are higher in FCS than in MCS. FCS has a more favourable cardiometabolic profile and a low prevalence of atherosclerotic cardiovascular disease (ASCVD) compared to MCS. The cornerstone of the management of severe hypertriglyceridaemia is a very-low-fat diet. FCS does not respond to traditional lipid-lowering therapies. Several novel pharmacotherapeutic agents are in various phases of development. Data on the correlation between genotype and phenotype in FCS are scarce. Further research to investigate the impact of individual gene variants on the natural history of the disease, and its link with ASCVD, microvascular disease, and acute or recurrent pancreatitis, is warranted. Volanesorsen reduces triglyceride concentration and frequency of pancreatitis effectively in patients with FCS and MCS. Several other therapeutic agents are in development. Understanding the natural history of FCS and MCS is necessary to rationalise healthcare resources and decide when to deploy these high-cost low-volume therapeutic agents.

Whole grain intake favorably affects blood glucose and serum triacylglycerols in overweight and obese children: A randomized controlled crossover clinical trial

OBJECTIVES

The aim of this study was to determine the effects of whole grain consumption on the metabolic profiles of overweight or obese children.

METHODS

This was a randomized crossover clinical trial with 44 overweight or obese girls. After a 2-wk run-in period, girls were randomly assigned to either intervention or control groups. Participants in the intervention group were asked to obtain 50% of their grain servings from whole grain foods each day for 6 wk. Those in the control group were asked not to consume any of these foods. A 4-wk washout period was applied following which participants were crossed over to the alternate arm. Fasting blood samples were taken before and after each phase of study.

RESULTS

Mean (± SD) age and body mass index was 11.2 ± 1.49 y and 23.5 ± 2.5 kg/m², respectively. Mean whole grain intake in intervention and control groups throughout the study was 26.5 and 3.7 g/d, respectively (P = 0.01). Whole grain consumption resulted in lower concentrations of plasma glucose (changes from baseline in intervention group: -0.10 versus 0.21 mmol/L in control group, P = 0.01), serum triacylglycerols (changes from baseline in intervention group: -0.18 versus 0.08 mmol/L in control group, P = 0.01) and higher concentrations of serum high-density lipoprotein cholesterol (changes from baseline in intervention group: 0.16 versus -0.14 mmol/L in control group, P = 0.05) after 6 wk of intervention. No effects of whole grain intake on serum concentrations of total- and low-density lipoprotein cholesterol or on blood pressure were found.

CONCLUSION

This study provided evidence supporting the beneficial effects of whole grain foods on serum concentrations of glucose, triacylglycerols and high-density lipoprotein cholesterol in overweight children.

An Overview of Atherosclerosis: A Look to the Future*

This overview briefly summarizes the cellular pathobiology of experimental atherosclerosis and is then followed by a consideration of how 3 major risk factors interact with the hypothesized pathogenetic process. First, since hemodynamics and blood flow influence the localization of atherosclerotic plaques, possible mechanisms and directions of research are considered. Secondly, the recent hypothesis relating the oxidation of LDL to several of the early processes of atherogenesis is briefly discussed in view of the fact that hyperlipidemia is a major risk factor. The possibility that subsets of LDL and lipoproteins other than LDL might be involved is also discussed. Family history is the last of the 3 contributors to atherosclerosis reviewed and some prototypes of gene abnormalities are considered. Finally, the needs and prospects of future research are summarized.

Can Carob-Fruit-Extract-Enriched Meat Improve the Lipoprotein Profile, VLDL-Oxidation, and LDL Receptor Levels Induced by an Atherogenic Diet in STZ-NAD-Diabetic Rats?

Carob fruit extract (CFE) has shown remarkable in vitro antioxidant properties and reduces postprandial hyperglycemia and hyperlipidemia in healthy animals. Development of functional meat products that contain bioactive components are presented as a great nutritional strategy. Until now, the effect of the consumption of restructured meat enriched with CFE in a murine model of diabetes has not been investigated. The objective of this study was to evaluate the effect on glycemia, lipemia, lipoprotein profile, Ldlr, arylesterase (AE), and very low-density lipoproteins (VLDL) and liver oxidation in streptozotocin-nicotinamide (STZ-NAD) growing Wistar diabetic rats fed restructured meat in the frame of a high cholesterol/high saturated-fat diet. In the present study, three groups (D, ED and DE) were fed cholesterol-enriched (1.4% cholesterol and 0.2% cholic acid) and high saturated-fat diets (50% of total energy from fats and 20.4% from saturated fatty acids). Rats were subjected to a STZ-NAD administration at the 3rd week. Group D did not receive CFE, while ED and DE rat groups received CFE before and after the diabetic induction, respectively. After eight weeks, D rats showed hyperglycemia and hypercholesterolemia, an increased amount cholesterol-enriched VLDL (β-VLDL), IDL and LDL particles and triglyceride-enriched HDL. ED and DE partially blocked the hypercholesterolemic induction with respect to D group (p < 0.001) and improved glycemia, cholesterol levels, lipoprotein profile, Ldlr, plasma AE activity and liver oxidation (p < 0.001). Fecal fat, moisture and excretion were higher while dietary digestibility was lower in ED and DE vs. D counterparts (p < 0.0014). In conclusion, CFE-enriched meat shows, for the first time, hypoglycemic and hypolipidemic effects in STZ-NAD animals fed high cholesterol/high saturated-fat diets. Likewise, it manages to reverse possible diabetes lipoprotein alterations if CFE-enriched meat is consumed before pathology development or improves said modifications if Type 2 Diabetes Mellitus is already established.

Lipoprotein Profile in Aged Rats Fed Chia Oil- or Hydroxytyrosol-Enriched Pork in High Cholesterol/High Saturated Fat Diets

Restructuring pork (RP) by adding new functional ingredients, like Chia oil (one of the richest natural source of α-linolenic acid) or hydroxytyrosol (HxT) (potent antioxidant), both with hypolipidemic activities, is one of the strategies that may help to reduce the potential negative effects of high meat products consumption. The aim of this study was to evaluate the Chia oil- or HxT-enriched-RP effect on the lipoprotein profile of aged rats fed high-fat, high-energy, and cholesterol-enriched diets. RP samples were prepared by mixing lean pork and lard with or without Chia oil (152.2 g/kg fresh matter) or HxT (3.6 g/kg fresh matter). Diets were prepared by mixing a semisynthetic diet with freeze-dried RP. Groups of 1-year male Wistar rats were fed the following experimental diets for 8 weeks: C, control-RP diet; HC, cholesterol-enriched-RP diet; and Chia oil-RP (CHIA) and HxT, Chia oil- or hydroxytyrosol-RP, cholesterol-enriched diet. Plasma lipid, lipoprotein profile, SREBP-1c protein, and low-density lipoproteins (LDL) receptor gene (Ldlr) expressions were evaluated. Compared to C diet, the HC diet increased plasma cholesterol, triglycerides, free fatty acids, total lipids, and SREBP-1c expression, but reduced Ldlr expression and significantly modified the lipoprotein profile, giving rise to the presence of high levels of atherogenic cholesterol-enriched very low-density lipoproteins (VLDL) particles. Compared to the HC diet, the HxT diet did not produce significant changes in feed intake but it reduced the body weight. Chia oil and HxT partially arrested the negative effects of the high-fat, high-energy, and cholesterol-enriched meat-based diets on lipemia and lipoproteinemia, mostly by reducing the amount of cholesterol content in VLDL (60% and 74% less in CHIA and HxT vs. HC, respectively) and the VLDL total mass (59% and 63% less in CHIA and HxT vs. HC, respectively). Free fatty acids (FFA) significantly correlated with adipose tissue weight and VLDL total mass (both p < 0.05), and plasma triglycerides, phospholipids, total lipids, and SREBP-1c (all p < 0.001), suggesting the important role of FFA in lipoprotein metabolism. Results support the recommendation to include these ingredients in pork products addressed to reduce the presence of increased atherogenic particles in aged people at CVD risk consuming large amounts of pork.

Lipid nephrotoxicity: new concept for an old disease

The prevalence of obesity in the United States remains high, exceeding 30% in most states. As this trend continues unhindered, we will continue see a persistent rise in obesity-related metabolic effects—hypertension, dyslipidemia, diabetes mellitus, and atherosclerosis. These diseases are also the leading causes of chronic kidney diseases and end-stage renal disease. The lipid nephrotoxicity hypothesis, proposed over three decades ago, suggested that proteinuria, decreased albumin levels, and the resultant hyperlipidemia may cause a glomerulosclerosis similar to atherosclerosis. More recent studies have demonstrated the role of oxidized high-density lipoprotein (HDL) and low-density lipoprotein (LDL) particles in the progression of kidney disease. Elucidation of the role of lipid-lowering therapies and the concomitant improvement in tubulointerstitial and glomerular diseases is a further evidence of the role of lipids in renal injury. Synergistic effects of lipid-lowering drugs and blockers of the renin-angiotensin-aldosterone system (RAAS) in renal protection have also been documented. Dyslipidemia in renal disease is usually characterized by elevated LDL cholesterol, low HDL cholesterol, and high triglycerides. After an initial glomerular injury, likely to be inflammatory, a series of self-perpetuating events occur. Increased glomerular basement permeability leads to loss of lipoprotein lipase activators, which results in hyperlipidemia. Circulating LDL has a charge affinity for glycoaminoglycans in the glomerular basement membrane and further increases its permeability. Substantial amounts of filtered lipoprotein cause proliferation of mesangial cells. Proximal tubules reabsorb some of the filtered lipoprotein, and the remainder is altered during passage through the nephron. If intraluminal pH is close to the isoelectric point of the apoprotein, luminal apoprotein will precipitate, causing tubulointerstitial disease. This review shows the evidence for the role of lipids in development of chronic renal disease, the pathophysiology of lipid nephrotoxicity, and strategies available to clinicians to slow the progression of disease.

LCAT cholesterol esterification is associated with the increase of ApoE/ApoA-I ratio during atherosclerosis progression in rabbit

Apolipoprotein A-I and Apolipoprotein E promote different steps of reverse cholesterol transport, including lecithin-cholesterol acyltransferase stimulation. Our aim was to study the changes in the levels of Apolipoprotein A-I, Apolipoprotein E, and lecithin-cholesterol acyltransferase activity during atherosclerosis progression in rabbits. Quantitative echocardiographic parameters were analyzed in order to evaluate, for the first time, whether atherosclerosis progression in rabbit is associated to apolipoproteins changes and alteration of indices of cardiac function, such as systolic strain and strain rate of the left ventricle. Atherosclerosis was induced by feeding rabbits for 8 weeks with 2 % cholesterol diet. The HDL levels of cholesterol and cholesteryl esters were measured by HPLC. The lecithin-cholesterol acyltransferase activity was evaluated both ex vivo, as cholesteryl esters/cholesterol molar ratio, and in vitro. Apolipoproteins levels were analyzed by ELISA. The HDL levels of cholesterol and cholesteryl esters increased, during treatment, up to 3.7- and 2.5-fold, respectively, compared to control animals. The lecithin-cholesterol acyltransferase activity in vitro was halved after 4 weeks. During cholesterol treatment, Apolipoprotein A-I level significantly decreased, whereas Apolipoprotein E concentration markedly increased. The molar ratio Apolipoprotein E/Apolipoprotein A-I was negatively correlated with the enzyme activity, and positively correlated with both increases in the intima-media thickness of common carotid wall and cardiac dysfunction signs, such as systolic strain and strain rate of the left ventricle.

The effect of apoE genotype and sex on ApoE plasma concentration is determined by dietary fat in healthy subjects

The interindividual variation in ApoE plasma concentration is considerable, mainly determined by apoE genotype and sex. However, a large amount of variability remains unexplained by these factors. We have evaluated whether the quantity and quality of dietary fat interacts with the apoE genotype and sex modifying ApoE plasma levels in young healthy subjects. Eighty-four volunteers (sixty-six apoE3/3, eight apoE4/3 and ten apoE3/2) were subjected to three dietary periods, each lasting 4 weeks. The first was a SFA-enriched diet (38 % fat and 20 % SFA), which was followed by a carbohydrate (CHO)-rich diet (30 % fat, < 10 % SFA and 55 % carbohydrate) or a MUFA-rich diet (38 % fat and 22 % MUFA) following a randomised crossover design. apoE2 carriers have the highest ApoE levels, whereas apoE4 individuals show the lowest concentration after the SFA, CHO and MUFA diets. Women had significantly higher ApoE concentration than men only after the consumption of the SFA diet. The SFA diet increased the ApoE plasma concentration when compared with the CHO- and MUFA-rich diets in women, but not in men. In women, but not in men, the shift from the SFA- to CHO- or MUFA-rich diets significantly decreased the ApoE concentration in apoE3/2 and apoE3/3 subjects, whereas no differences were observed in women with the apoE4/3 genotype. Sex and apoE genotype determine ApoE plasma levels; however, this effect is dependent on dietary fat.

Oat: unique among the cereals

This review is intended to focus on the composition of oat and its therapeutic potential in the pharmacology that supports its use to cure various maladies. Oat (Avena sativa) is distinct among the cereals due to its multifunctional characteristics and nutritional profile. Recent advancement in food and nutrition has revealed the importance of its various components. It is a good source of dietary fiber especially beta-glucan, minerals and other nutrients. Oat and oat by products have been proven to be helpful in the treatment of diabetes and cardiovascular disorders. Oat bran in particular, is good source of B complex vitamins, protein, fat, minerals besides heart healthy soluble fiber beta-glucan. The beta-glucan has outstanding functional properties and is of immense importance in human nutrition. Different physiological effects of beta-glucan are related to its viscosity, attenuation of postprandial plasma glucose and insulin responses, high transport of bile acids towards lower parts of the intestinal tract and high excretion of bile acids thereby lowering of serum cholesterol levels. Moreover, it is helpful against coeliac disease. The incorporation of oat grains and oat bran in the food products improves not only the nutrition but also a therapy against various maladies.

Structure and evolution of human apolipoprotein genes: identification of regulatory elements of the human apolipoprotein E gene

The structures of the major human apolipoprotein genes have been determined. The genes for apoE, apoC-I, apoC-II, apoC-III, apoA-I, apoA-II and apoA-IV have similar structures, consisting of four exons and three introns, which suggests that they evolved from a common ancestral gene. The third and fourth exons of the ancestral gene appear to have evolved from the duplication of a 66-nucleotide repeat unit that encodes a 22-residue alpha-helical peptide element of amphipathic character. The apoA-I, apoC-III and apoA-IV genes are linked closely within a 20-kilobase (kb) span of chromosome 11. The apoE and apoC-I genes, together with an apoC-I' pseudogene, are linked closely within a 25-kb span of chromosome 19. To characterize potential functional relationships among the apolipoprotein genes, initial studies have been done to identify the molecular elements involved in the regulation of the human apoE gene. Fragments of the 5'-flanking portion of this gene were inserted into appropriate plasmid vectors, which contained the bacterial chloramphenicol acetyl transferase gene, and were examined for promoter activity and potential enhancer activity after transfection into cultured mammalian cells. Deletion mapping of the promoter region has identified multiple functional elements, including an enhancer, two G-C boxes (Sp 1 transcription factor binding sites) and an upstream control element. In addition, there is an enhancer located in the first intron. Interactions among these various control elements are likely to determine the ways in which the expression of the apoE gene is regulated.

Enlargement of high density lipoprotein in mice via liver X receptor activation requires apolipoprotein E and is abolished by cholesteryl ester transfer protein expression

The factors involved in the generation of larger high density lipoprotein (HDL) particles, HDL1 and HDLc, are still not well understood. Administration of a specific synthetic liver X receptor (LXR) agonist, T0901317, in mice resulted in an increase of not only HDL cholesterol but also HDL particle size (Cao, G., Beyer, T. P., Yang, X. P., Schmidt, R. J., Zhang, Y., Bensch, W. R., Kauffman, R. F., Gao, H., Ryan, T. P., Liang, Y., Eacho, P. I., and Jiang, X. C. (2002) J. Biol. Chem. 277, 39561-39565). We have investigated the roles that apoE and CETP may play in this process. We treated apoE-deficient, cholesterol ester transport protein (CETP) transgenic, and wild type mice with various doses of the LXR agonist and monitored their HDL levels. Fast protein liquid chromatography and apolipoprotein analysis revealed that in apoE knockout mouse plasma, there was neither induction of larger HDL formation nor increase of HDL cholesterol, suggesting that apoE is essential for the LXR agonist effects on HDL metabolism. In CETP transgenic mice, CETP expression completely abolished LXR agonist-mediated HDL enlargement and greatly attenuated HDL cholesterol levels. Analysis of HDL particles by electron microscope and nondenaturing gel electrophoresis revealed similar findings. In apoE-deficient mice, LXR agonist also produced a significant increase in very low density lipoprotein/low density lipoprotein cholesterol and apolipoprotein B content. Our studies provide direct evidence that apoE and CETP are intimately involved in the accumulation of the enlarged HDL (HDL1 or HDLc) particles in mice.

Short-term control of capsaicin on blood and oxidative stress of rats in vivo

Capsaicin (8-methyl-n-vanillyl-6-nonenamide), a pungent component found in red pepper can induce body heat and possibly enhance blood flow as well as increase energy expenditure, and prevent oxidative stress. Male Wistar rats were divided into vehicle, 1 mg/kg body weight capsaicin and 3 mg/kg body weight capsaicin groups. Samples were taken from the animals on day 1 of i.p. treatment with capsaicin and on 3 consecutive days of i.p. treatment with capsaicin. Our investigation demonstrated that blood flow measurements in rats was negatively correlated with LDL after treatment with capsaicin. Although capsaicin did not show a noticeable effect on the serum total cholesterol level, LDL decreased while HDL and triglyceride increased in rats treated with 3 mg/kg capsaicin for 3 days. The antioxidant effect of capsaicin was not shown when the rats were treated with 1 mg/kg body weight capsaicin. However, rats treated with 3 mg/kg body weight capsaicin for 3 days showed a reduction of oxidative stress measured as malondialdehyde in the liver, lung, kidney and muscle. Liver glycogen was found to decrease after 3 days treatment with 3 mg/kg body weight capsaicin. From this study, it is hypothesized that capsaicin can be a potent antioxidant and aid in lowering LDL even when consumed for a short period.

Hypercholesterolemia and Dyslipidemia: Issues for the Clinician

The current state of the art in the diagnosis and treatment of lipoprotein disorders has progressed beyond the standard "lipid profile," which includes total low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol, along with fasting triglycerides. Incorporating aspects of the atherogenic lipoprotein profile (ALP) (ALP and LDL subclass distribution), HDL subclass distribution, apolipoprotein E isoforms, lipoprotein (a), homocysteine, and high-sensitivity C-reactive protein provides the clinician with the tools to create a more detailed, accurate, and personalized diagnosis of disorders contributing to coronary artery disease in their patients. Sophisticated laboratory tests are available to clinicians through technology transfer programs as exemplified by the Lawrence Berkeley National Laboratory/Berkeley HeartLab, Berkeley, CA, collaboration and allow clinicians access to research quality laboratory tools. This has significant clinical relevance because the presence of these disorders guides treatment that is specific to the disorder(s). Appropriate treatment has been shown to have significantly greater clinical benefit in patient subgroups exhibiting the disorder the therapy is most likely to correct. A single drug or lifestyle therapy plan is no longer appropriate for all patients. The treatment must match the individual disorder(s).

Diabetes-induced accelerated atherosclerosis in swine

Patients with diabetes are at higher risk for atherosclerotic disease than nondiabetic individuals with other comparable risk factors. Studies examining mechanisms underlying diabetes-accelerated atherosclerosis have been limited by the lack of suitable humanoid animal models. In this study, diabetes was superimposed on a well-characterized swine model of atherosclerosis by injection of the beta-cell cytotoxin streptozotocin (STZ), resulting in a >80% reduction in beta-cells and an increase in plasma glucose to diabetic levels. Animals were maintained without exogenous insulin for up to 48 weeks. Plasma glucose and cholesterol levels and lesion extent and severity were quantified in swine with diabetes and hyperlipemia alone and in combination compared with controls. Diabetes had no effect on plasma cholesterol levels, but diabetic/hyperlipemic (D-HL) swine developed hypertriglyceridemia and showed a doubling in aortic sudanophilia over nondiabetic/hyperlipemic (N-HL) swine as early as 12 weeks (47.25 +/- 4.5 vs. 24.0 +/- 4.6%). At 20 weeks, coronary artery stenosis was significantly greater in D-HL than in N-HL animals (86 +/- 10 vs. 46 +/- 8%). Coronary lesions predominantly arose in the first 2-3 cm of the vessels and displayed humanoid morphology. Aortic lesions in D-HL swine had double the cholesterol content of those in N-HL swine, and incorporation of oleate into cholesteryl ester was significantly greater in grossly normal aortic areas of D-HL swine compared with N-HL and was attributed to similar elevated incorporation in monocytes. This large study demonstrates that a model of diabetes with humanoid characteristics, including hypertriglyceridemia and severe, accelerated atherosclerosis can be reproducibly induced and maintained in swine. This model should potentially be of great value in elucidating mechanisms underlying the accelerated atherosclerosis seen in human diabetic individuals.

Apolipoprotein A-I regulates lipid hydrolysis by hepatic lipase

Association of hepatic lipase (HL) with pure heparan sulfate proteoglycans (HSPG) has little effect on hydrolysis of high density lipoprotein (HDL) particles, but significantly inhibits (>80%) the hydrolysis of low (LDL) and very low density lipoproteins (VLDL). Lipolytic inhibition is associated with a differential ability of the lipoproteins to remove HL from the HSPG. LDL and VLDL are unable to displace HL, whereas HDL readily displaces HL from the HSPG. These data show that HSPG-bound HL is inactive. Purified apolipoprotein (apo) A-I is more efficient than HDL at liberating HL from HSPG, and HL displacement is associated with the direct binding of apoA-I to HSPG. However, displacement of HL by apoA-I does not enhance hydrolysis of VLDL particles. This appears due to the direct inhibition of HL by apoA-I. Both apoA-I and HDL are able to inhibit VLDL lipid hydrolysis by up to 60%. Inhibition of VLDL hydrolysis is associated with the binding of apoA-I to the surface of the VLDL particle and a concomitant decreased affinity for HL. These data show that apoA-I can regulate lipid hydrolysis by HL by liberating/activating the enzyme from cell surface proteoglycans and by directly modulating lipoprotein binding and hydrolysis.

Hypercholesterolemia and Dyslipidemia

Disorders of cholesterol and lipoprotein metabolism are at the heart of atherosclerosis and coronary artery disease (CAD). CAD, however, is a metabolic disorder that involves a complex interaction between genetic susceptibility and environmental conditions. Despite considerable success in the treatment of hypercholesterolemia, atherosclerosis remains the leading cause of death in most Western countries. Although cholesterol-lowering trials have revealed a 25% to 30% reduction in clinical events, most patients continue to have events even when treated successfully with cholesterol-lowering medications (Fig. 1). This less-than-optimal result is partly because atherosclerosis is a multifactorial disease. Although disorders of lipoprotein metabolism are found in more than 80% of patients with CAD, these disorders are very heterogeneous, and single-drug therapy aimed at one disorder should not be expected to improve the disease status in most patients. Metabolic treatment still requires identification and treatment of patients with high cholesterol levels, but the focus has shifted to identifying high-risk patients in groups previously thought to be low risk, or to identifying disorders coexistent with high cholesterol levels that are not corrected by standard cholesterol-lowering medications (Table 1). The ability to detect high-risk CAD traits, which are often inherited, and to predict response to treatment has substantially improved in the past few years. These improvements allow identification of metabolic subgroups of patients, which can alter risk prediction and response to specific treatments. Sophisticated laboratory methods permit physicians to apply this knowledge to patient care and to enter a new era of CAD risk factor detection and treatment. These advances allow for a more scientific approach than did the previously standard epidemiologic risk factors and routine blood lipid profiles. The current state-of-the-art method of diagnosing and treating lipoprotein disorders has progressed beyond the standard "lipid profile," which includes total, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol along with fasting triglyceride levels. Incorporating aspects of the atherogenic lipid profile (ALP), LDL subclass distribution, HDL subclass distribution, apo E isoforms, and lipoprotein (a) provides the interested clinician with the tools to create a more detailed and accurate diagnosis of lipoprotein disorders. Sophisticated laboratory tests are available to clinicians through technology transfer programs, as exemplified by the Lawrence Berkeley National Laboratory/Berkeley HeartLab collaboration, and allow clinicians access to research-quality laboratory tools. This has significant clinical relevance because the presence of these disorders guides treatment specific to the disorder(s). Appropriate treatment is more beneficial in subgroups exhibiting the disorder that the therapy is most likely to correct. A single drug or lifestyle therapy is no longer appropriate for all patients. The treatment must match the disorder.

Dyslipidemia and vascular dysfunction in diabetic pigs fed an atherogenic diet

Diabetic patients typically have not only hyperglycemia but also dyslipidemia. Study of the pathogenic components of the diabetic milieu and mechanisms of accelerated atherosclerosis is hindered by inadequate animal models. A potentially suitable animal model for human diabetic dyslipidemia is the pig, because it carries a large fraction of total cholesterol in low-density lipoprotein (LDL), similar to humans. In this study, male Sinclair miniature pigs were made diabetic by destroying the insulin-producing cells of the pancreas with alloxan and then were fed a high fat and high cholesterol diet for comparison with pigs fed a nondiabetic high fat and high cholesterol diet and control pigs. Diabetic pigs exhibited hyperglycemia, but plasma urea nitrogen, creatinine, and transaminase levels were in the normal range, indicating no adverse effects on kidney and liver function. The lipoprotein profile in diabetic pigs was similar to that found in human diabetic patients and was characterized by hypertriglyceridemia (2.8-fold increase versus control and high fat-fed pigs) and a profound shift of cholesterol distribution into the LDL fraction (81%) versus the distribution in high fat-fed (64%) and control (57%) pigs. LDL particles were lipid-enriched and more heterogeneous in diabetic pigs. Apolipoprotein B was distributed among a much broader spectrum of LDL particles, and apolipoprotein E was partially redistributed from high-density lipoprotein to apolipoprotein B-containing lipoproteins in diabetic pigs. There was little change in apolipoprotein A-I distribution. Diabetic pigs showed several early signs of excess vascular disease. In diabetic pigs, 75% of the coronary artery segments showed contractile oscillations in response to prostaglandin F(2alpha) compared with 25% in high fat-fed pigs and 10% in control pigs. Endothelium-dependent relaxation of brachial arteries was nearly abolished in diabetic pigs but unchanged in high fat-fed versus control pigs. Carotid artery Sudan IV staining for fatty streaks was significantly increased only in diabetic pigs. This porcine model should provide insights into the etiology of human diabetic dyslipidemia and facilitate study of peripheral vascular and coronary artery disease in diabetic patients.

Detection, quantification, and characterization of potentially atherogenic triglyceride-rich remnant lipoproteins

Triglyceride-rich lipoprotein (TRL) remnants are formed in the circulation when apolipoprotein (apo) B-48-containing chylomicrons of intestinal origin or apoB-100-containing VLDL of hepatic origin are converted by lipoprotein lipase, and to a lesser extent by hepatic lipase, into smaller and more dense particles. Compared with their nascent precursors, TRL remnants are depleted of triglyceride, phospholipid, and C apolipoproteins and are enriched in cholesteryl esters and apoE. They can thus be identified, separated, and/or quantified in plasma according to their density, charge, size, specific lipid components, apolipoprotein composition, and/or apolipoprotein immunospecificity. Each of these approaches has contributed to our current understanding of the compositional characteristics of TRL remnants and their potential to promote atherosclerosis. An ongoing search is nevertheless under way for more accurate and clinically applicable remnant lipoprotein assays that will be able to better define coronary artery disease risk in patients with hypertriglyceridemia.

Accelerated cholesteryl ester transfer in patients with essential hypertension and the effect of ramipril treatment

Although the transfer of cholesteryl ester (CE) from high-density lipoprotein (HDL) to the apolipoprotein B-containing lipoproteins (very-low-density lipoproteins + low-density lipoproteins) has been shown to be abnormally increased in a number of conditions associated with increased cardiovascular risk, it has not been studied in patients with essential hypertension (EH). To determine whether subjects with EH have increased CE transport, CE transfer (CET) was estimated isotopically and lipoprotein lipid and phospholipid composition determined in a group of 14 untreated normolipidemic (triglycerides 116+/-46, cholesterol 185+/-30, HDL 38+/-10 mg/dl) otherwise healthy ethnically diverse EH subjects. CET was significantly increased in EH subjects compared to a similar group of normotensive controls (EH: k = 0.27+/- 0.09 vs. control k = 0.11+/-0.02: P < 0.01). Lipoprotein concentration and composition were comparable in the two groups and closely resembled that of an age- and sex-matched reference group. The abnormal increase in CET persisted (k = 0.25+/-0.12) after 3 months of treatment with the angiotensin converting enzyme (ACE) inhibitor ramipril without a change in either plasma or lipoprotein lipids. Thus, CET is increased in normolipidemic subjects with EH and is not affected by the ACE inhibitor ramipril.

Hypertriglyceridemia, atherogenic dyslipidemia, and the metabolic syndrome

The importance of high serum cholesterol, especially a high level of low-density lipoprotein (LDL) cholesterol, as a risk factor for coronary artery disease is well established. Likewise, efficacy for decreasing risk for coronary artery disease by LDL-lowering therapy has recently been documented through clinical trials. However, many high-risk patients manifest elevated serum triglyceride levels, and the role of hypertriglyceridemia in causation of coronary artery disease remains to be elucidated. Nonetheless, there is growing evidence that hypertriglyceridemia is a marker for increased risk for coronary artery disease; in fact, it can serve as a marker for several atherogenic factors. These factors include increased concentrations of atherogenic triglyceride-rich lipoproteins; the atherogenic lipoprotein phenotype, or lipid triad; and the metabolic syndrome. The lipid triad consists of elevated serum triglycerides, small LDL particles, and low high-density lipoprotein (HDL) cholesterol. The metabolic syndrome includes the coexistence of the lipid triad, elevated blood pressure, insulin resistance (plus glucose intolerance), and a prothrombotic state. Many previous studies indicate that hypertriglyceridemia is strongly associated with all of these atherogenic factors. The clinical approach to treatment of patients with hypertriglyceridemia thus requires a broad-based strategy that includes reduction of atherogenic triglyceride-rich lipoproteins, reversal of the lipid triad, and favorable modification of the metabolic syndrome. The development of therapeutic regimens to effect these changes poses a challenge for future research on the problem of hypertriglyceridemia.

Heparan sulfate proteoglycans participate in hepatic lipaseand apolipoprotein E-mediated binding and uptake of plasma lipoproteins, including high density lipoproteins

High density lipoprotein (HDL) particles and HDL cholesteryl esters are taken up by both receptor-mediated and non-receptor-mediated pathways. Here we show that cell surface heparan sulfate proteoglycans (HSPG) participate in hepatic lipase (HL)- and apolipoprotein (apo) E-mediated binding and uptake of mouse and human HDL by cultured hepatocytes. The HL secreted by HL-transfected McA-RH7777 cells enhanced both HDL binding at 4 degrees C (approximately 2-4-fold) and HDL uptake at 37 degrees C (approximately 2-5-fold). The enhanced binding and uptake of HDL were partially inhibited by the 39-kDa protein, an inhibitor of low density lipoprotein receptor-related protein (LRP), but were almost totally blocked by heparinase, which removes the sulfated glycosaminoglycan chains from HSPG. Therefore, HL may mediate the uptake of HDL by two pathways: an HSPG-dependent LRP pathway and an HSPG-dependent but LRP-independent pathway. The HL-mediated binding and uptake of HDL were only minimally reduced when catalytically inactive HL or LRP binding-defective HL was substituted for wild-type HL, indicating that much of the HDL uptake required neither HL binding to the LRP nor lipolytic processing. To study the role of HL in facilitating the selective uptake of cholesteryl esters, we used HDL into which radiolabeled cholesteryl ether had been incorporated. HL increased the selective uptake of HDL cholesteryl ether; this enhanced uptake was reduced by more than 80% by heparinase but was unaffected by the 39-kDa protein. Like HL, apoE enhanced the binding and uptake of HDL (approximately 2-fold) but had little effect on the selective uptake of HDL cholesteryl ether. In the presence of HL, apoE did not further increase the uptake of HDL, and at a high concentration apoE impaired or decreased the HL-mediated uptake of HDL. Therefore, HL and apoE may utilize similar (but not identical) binding sites to mediate HDL uptake. Although the relative importance of cell surface HSPG in the overall metabolism of HDL in vivo remains to be determined, cultured hepatocytes clearly displayed an HSPG-dependent pathway that mediates the binding and uptake of HDL. This study also demonstrates the importance of HL in enhancing the binding and uptake of remnant and low density lipoproteins via an HSPG-dependent pathway.

Alterations in plasma lipids, lipoproteins and high density lipoprotein subfractions in peripheral arterial disease

The concentrations of the major lipoprotein classes and of high density lipoprotein (HDL) subfractions in 63 male patients with arteriosclerosis of the lower limbs (claudication) were determined and compared with values from 63 healthy controls. The patients with peripheral arterial disease (PAD) had reduced levels of total HDL-cholesterol and HDL2b of large particle size, increased levels of small HDL3c particles and a high ratio of total plasma-cholesterol to HDL-cholesterol (coronary risk factor). The PAD patients, however, had lower levels of low density lipoprotein (LDL)-cholesterol but higher concentrations of very low density lipoprotein (VLDL)-cholesterol and plasma triglyceride than healthy subjects. This study therefore suggests that in PAD, the protective effect of HDL may be more important than the atherogenic effect of LDL. It further suggests that while HDL-cholesterol HDL2b and the ratio of total plasma-cholesterol to HDL-cholesterol may provide valid indices for identifying individuals at risk of PAD, other factors, such as LDL and total cholesterol, may not provide such an appropriate risk indicator.

Opposite effects of bezafibrate and gemfibrozil in both normal and hypertriglyceridemic rats

Chow and sucrose-fed rats were used as animal models to study the dose-responses of bezafibrate and gemfibrozil in normolipidemic and hypertriglyceridemic states, respectively. Although both drugs lowered plasma triglycerides (TG) to about the same extent in chow-fed rats, gemfibrozil lowered liver TG as well as plasma total and LDL-cholesterol (LDL-C), but elevated HDL-cholesterol (HDL-C) and plasma apo E concentrations. Bezafibrate produced opposite effects, namely, decreased HDL-C, apo E and liver TG, and tended to increase LDL-C. TG lowering for both drugs in chow-fed rats was not due to changes in TG secretion (production) in normal rats but was associated with enhanced LPL activity. In hypertriglyceridemic rats both drugs modestly reduced TG secretion rates about 40% at a dose producing maximal TG lowering, but again, gemfibrozil elevated and bezafibrate lowered HDL-C and apo E. Unlike gemfibrozil, bezafibrate induced the appearance of LDL-C in hypertriglyceridemic rats which was not detected in control animals, and also tended to increase rather than decrease plasma apo B levels. Finally, changes in liver TG concentration (mg/g) in hypertriglyceridemic rats were opposite for these drugs, resulting in significant drug-related differences in liver TG content (mg/organ). From these data we postulate that, although similar with regard to TG lowering activity and mechanisms thereof, gemfibrozil and bezafibrate produce fundamentally different effects on LDL, HDL and apolipoprotein metabolism (apo B and apo E) in rats which may relate to potential differential effects on reverse cholesterol transport and atherogenesis.

Marine lipids normalize cholesteryl ester transfer in IDDM

Patients with insulin-dependent diabetes mellitus (IDDM) have a pathological increase in cholesteryl ester transfer (CET) that enriches the apolipoprotein B-containing lipoproteins with cholesteryl ester and increases their atherogenicity. Since we have shown earlier that omega-3 (n-3) fatty acids present in marine lipids normalize both CET and lipoprotein composition in non-diabetic patients with hypercholesterolaemia, we sought to determine whether the same beneficial effects could be achieved in nine normolipidaemic (triglycerides 1.10; cholesterol 4.94, high density lipoprotein 1.10 mmol/l) IDDM patients (fructosamine 424 +/- 156; normal 174-286 mumol/l) treated for 2 months with n-3 fatty acids (4.6 g/day). Before treatment, CET measured by both mass and isotopic assays was abnormally accelerated (p < 0.001). While marine lipids modestly decreased triglyceride levels (-14%; p < 0.05 ), CET fell dramatically in all subjects (mass assay: -97% at 1 h; isotopic assay: -58%; p < 0.001) to below control levels with no change in glycaemic control (fructosamine 408 +/- 103 mumol/l). The mass of cholesteryl ester transfer protein paradoxically increased significantly (pre-treatment: 2.04 +/- 0.86 vs post-treatment 2.48 +/- 0.97 micrograms/ml; p < 0.05). Since it is believed that accelerated CET promotes the formation of atherogenic cholesteryl ester-enriched apo B-containing lipoproteins, the capacity of marine lipids to reverse this functional abnormality without altering glycaemic control suggests that these agents may have an adjunctive role to play in the nutritional therapy of IDDM.

Sensitivity to platelet aggregation appears related to the lipoprotein profile and atherosclerosis risk in humans and across species

Platelet aggregation sensitivity was assessed in nine species of animals, including humans, with disparate susceptibility to atherosclerosis and a wide range in their LDL/HDL profiles. Platelet aggregation sensitivity between species varied almost 20-fold. The most sensitive platelets were found in humans and rabbits, followed by squirrel and rhesus monkeys with the most resistant platelets in cats, hamsters, rats, cebus monkeys, and gerbils. Species platelet aggregation sensitivity correlated well with relative susceptibility to atherosclerosis. The relationship between LDL/HDL ratio and platelet aggregation was significant, both across species (r = 0.76, without cebus) and within species (r = 0.50 for humans).

Plasma concentration of apolipoprotein E in intermediate-sized remnant-like lipoproteins in normolipidemic and hyperlipidemic subjects

Triglyceride-rich lipoprotein (TRL) remnants have been strongly implicated in the pathogenesis of atherosclerosis. To further investigate plasma remnant lipoprotein metabolism, we have determined the plasma concentration of apolipoprotein (apo) E (by polyclonal enzyme-linked immunoassay) in remnant-like lipoproteins, isolated by automated gel filtration chromatography as a fraction intermediate in size between VLDL and HDL. In normolipidemic subjects (n = 12), 1.2 +/- 0.11 mg/dL (33 +/- 2%, mean +/- SE) of total plasma apoE was associated with this fraction (termed ISL apoE). In hypercholesterolemic (type IIa, n = 12), hypertriglyceridemic (type IV, n = 12), and mixed hyperlipidemic (type IIb, n = 12) subjects, mean ISL apoE concentrations were 2.1 +/- 0.2, 2.5 +/- 0.2, and 3.8 +/- 0.4 mg/dL, respectively (P < .001 versus normal values) (45 +/- 2%, 32 +/- 2%, and 44 +/- 2% of total). ISL apoE was 8.7 +/- 1.4 mg/dL (42 +/- 3%) in type III dyslipidemic subjects (apoE2/2, n = 8). ISL apoE was positively correlated with plasma triglyceride (r = .41, P < .01), and at any given level of plasma triglyceride, subjects with an apoE2/2 or apoE3/2 phenotype tended to have a higher concentration of ISL apoE (P < .01) than apoE3/3 or E4/3 individuals. ISL apoE was also correlated (P < .001) with total plasma cholesterol (r = .66), TRL cholesterol (r = .49), TRL apoE (r = .47), LDL apoB (r = .42), and LDL+HDL triglyceride (r = .74). These results suggest that (1) a significant proportion of plasma apoE resides within an intermediate-sized remnant-like lipoprotein fraction in both normolipidemic and hyperlipidemic subjects; (2) plasma remnant lipoprotein accumulation is associated with an elevation in ISL apoE concentration; and (3) ISL apoE concentration is significantly correlated with various proatherogenic lipid parameters and may itself be a potentially important atherogenic index.

Uptake of apolipoprotein E-rich and apolipoprotein E-poor subfractions of high-density lipoprotein by liver membranes and HepG2 cells

Apolipoprotein (apo) E plays an important role in mediating high-density lipoprotein (HDL) cholesterol transport and uptake by the liver. Evidence for and against the existence of conventional liver receptors for HDL containing apoE have been reported, although the selective uptake of the cholesterol moiety of HDL has been demonstrated. The present study investigated the hepatic uptake of subfractions of HDL separated on the basis of their apoE content. Rabbit HDL and its apoE-rich and apoE-poor subfractions, separated by heparin-Sepharose affinity chromatography, were labelled in their apoprotein moieties with [14C]sucrose and in their cholesteryl ester moiety with 3H. No binding of either subfraction to rabbit liver membranes could be detected. With cultured HepG2 cells, however, there was a high uptake of 3H but a very low uptake of 14C from both HDL subfractions, demonstrating that selective uptake was operating. Addition of unlabelled apoE-poor HDL inhibited the uptake of both labels from the two subfractions to the same extent. These studies, which differed from previously reported investigations by employing native homologous HDL subfractions of known apolipoprotein composition, demonstrated that apoE is not directly involved in the selective uptake of HDL cholesterol by the liver. In the absence of specific binding sites on liver membranes, it is suggested that an alternative mechanism might exist for the clearance of HDL cholesterol from the plasma.

Failure of exogenous apoprotein E-3 to enhance cholesterol egress from J-774 murine macrophages in culture

HDL has been shown to enhance the removal of cholesterol from cultured fibroblasts, smooth muscle cells and macrophages, but fails to stimulate cholesterol removal from J-774 macrophages. Since J-774 macrophages do not synthesize or secrete apolipoprotein E, the effect of exogenous apolipoprotein E on HDL-mediated cellular cholesterol efflux was studied in this cell line. In cholesterol loaded J-774 macrophages total cellular cholesterol increased up to 6-7-fold, mainly cholesteryl esters. HDL3 removed up to 30% of total cellular cholesterol with a decrease in cholesteryl ester levels while free cholesterol levels remained unchanged. HDL3 was slightly superior to albumin in promoting cellular cholesterol removal. Exogenous apo E, over a wide range of apo E concentrations, did not enhance the ability of HDL3 to remove cellular cholesterol from cholesterol loaded J-774 cells. Exogenous apo E did not promote HDL-mediated cholesterol efflux from cells, thus suggesting a possible role for the intracellular route of newly synthesized apo E in these processes.

Alteration of plasma lipids in the rat by fractionation of modified milk fat (butterfat)

Our objective was to determine the nutritional effects of defined fat fractions of modified milk fat, or butterfat (anhydrous butter without the milk fat globule membrane) on lipid and lipoprotein cholesterol concentrations in plasma of rats fed diets containing 16% fat and two amounts of cholesterol. Five dietary fats were compared: 1) intact butterfat, 2) a liquid butterfat fraction enriched in oleic acid and unsaturated triacylglycerols with < 40 carbon atoms, 3) a solid butterfat fraction enriched in palmitic and stearic acids, 4) corn oil, and 5) palm oil. The extent of diet-induced hypercholesterolemia was the greatest with palm oil, followed by solid butterfat, corn oil, intact butterfat, and the lowest with liquid butterfat. Triacylglycerol concentrations in plasma were greater for rats fed palm oil than for those fed corn oil or liquid or intact butterfat. Among the high cholesterol dietary groups, ingestion of the liquid butterfat diet resulted in similar lipoprotein cholesterol and very low density lipoprotein concentrations relative to the corn oil diet, and ingestion of the solid butterfat diet resulted in similar lipoprotein cholesterol and very low density lipoprotein concentrations relative to the palm oil diet. These results suggest that changes in the triacylglycerol and fatty acid composition of butterfat by fractionation processes may improve its nutritional profile.

The effect of triacylglycerol fatty acid positional distribution on postprandial plasma metabolite and hormone responses in normal adult men

The present study has examined the possibility that the positional distribution of fatty acids on dietary triacyglycerol (TAG) influences the postprandial response to a liquid meal in adult subjects. Postprandial TAG, non-esterified fatty acids (NEFA), ketones, glucose, insulin and gastric inhibitory polypeptide (GIP) responses were monitored in sixteen normal adult male subjects over 6 h following consumption of test meals containing dietary TAG in which palmitic acid was predominantly on the sn-1 (Control) or sn-2 positions (Betapol). Plasma total TAG, chylomicron-rich TAG and chylomicron-poor TAG concentrations were identical in response to the two test meals. The peak increase (mean (SD)) in chylomicron TAG was 0.85 (0.46) mmol/l after the Control meal and 0.85 (0.42) mmol/l after the Betapol meal. Plasma glucose, insulin, GIP, NEFA and ketone concentrations were also very similar following the two meals. It is concluded that dietary TAG containing saturated fatty acids on the sn-2 position appear in plasma at a similar level and over a similar timescale to TAG in which saturated fatty acids are predominantly located on sn-1 or sn-3 positions. The results reported in the present study demonstrate that the positional distribution of fatty acids on dietary TAG is not an important determinant of postprandial lipaemia in adult male subjects, but do not exclude the possibility that different responses may occur when these dietary TAG are given long term.

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.

Alterations in the concentration of an apolipoprotein E-containing subfraction of plasma high density lipoprotein in coronary heart disease

The concentrations of high density lipoprotein (HDL) subfractions in 100 healthy male subjects were compared with 100 newly presenting patients with myocardial infarction (MI) within 12 h of the onset of chest pain. A subfraction of HDL enriched in apolipoprotein E (apo E), separated by heparin-Sepharose affinity chromatography, was present in lower concentrations (P < 0.001) in the plasma of the coronary patients than in the control subjects. This finding was confirmed by a lower content (P < 0.02) of apo E, measured by ELISA, in the total HDL fraction isolated from the coronary patients. Gradient gel electrophoresis of the total HDL demonstrated that the coronary patients had a significantly decreased concentration of the large HDL particles, HDL2b, of mean diameter 10.57 nm and a higher concentration of the smaller-sized HDL3, especially HDL3c, of mean diameter 7.62 nm. The coronary patients had a lower concentration of HDL cholesterol than the control subjects, attributable to the HDL2 fraction, with no difference in HDL2a between the two groups. There was no difference in the concentration of plasma cholesterol or triglyceride. The distribution of apo E phenotypes was similar in the two groups. HDL2b produced the highest discriminant power between the two groups, followed by apo E-rich HDL, HDL2 and HDL3c Plasma cholesterol correlated strongly with apo E-rich HDL for control subjects but not for MI survivors. This study demonstrates that the inverse relationship between HDL cholesterol and coronary risk shown in epidemiological studies is attributable to the large, apo E-containing HDL subspecies which under some circumstances are implicated in cholesterol removal by reverse cholesterol transport. This study also suggests that the concentration of the large, apo E-containing HDL may provide a sensitive predictor for subjects at risk of developing coronary heart disease.

Apolipoprotein E phenotypes and genotypes as determined by polymerase chain reaction using allele-specific oligonucleotide probes and the amplification refractory mutation system in children with insulin-dependent diabetes mellitus

The frequency of apolipoprotein E (apo E) phenotypes and genotypes due to allelic variation at amino acids 112 and 158 was analysed in 50 children with type I diabetes. Phenotypes were determined by isoelectric focusing and genotypes by the technique of polymerase chain reaction using allele-specific oligonucleotide probes (PCR/ASO) and the amplification refractory mutation system (ARMS). Discrepancies between phenotypes and genotypes as assigned by PCR/ASO were observed in 12 (24%) cases and by ARMS in eight (16%) cases. Results revealed the apo E3/3 genotype, as assigned by ARMS, to be the most frequent one (70%), followed by apo E3/4 in 16%, apo E2/2 in 2%, apo E2/3 in 8%, apo E2/4 in 2% and apo E4/4 in 2% of the cases. Apo E3/4 genotype and phenotype were more frequently present in the children with type I diabetes as compared with the diabetic adults previously reported on.

Severe atherosclerosis in transgenic mice expressing simian cholesteryl ester transfer protein

Cholesteryl ester transfer protein (CETP) is a plasma protein that mediates the exchange of neutral lipids among the lipoprotein. Because the principal core lipid of very-low-density lipoprotein (VLDL) is triglyceride and that of high-density lipoprotein (HDL) is cholesterol ester, CETP mediates a 'heteroexchange' of cholesterol ester for triglyceride between those lipoproteins. As a result, animals that express CETP tend to have higher VLDL and low-density lipoprotein (LDL) cholesterol levels, whereas those with no CETP activity tend to have high HDL cholesterol levels. Because VLDL and LDL are associated with the progression of atherosclerosis, and HDL are considered anti-atherogenic, CETP could be an 'atherogenic' protein, that is, given the other conditions required for atherosclerosis to develop, expression of CETP would accelerate the rate at which the arterial lesions progress. We report here that transgenic mice expressing CETP had much worse atherosclerosis than did non-expressing controls, and we suggest that the increase in lesion severity was due largely to CETP-induced alterations in the lipoprotein profile.