Clinical evaluation of plasma high-density lipoprotein subfractions (HDL2, HDL3) in non-insulin-dependent diabetics with coronary artery disease

High-density lipoprotein in diabetes: Structural and functional relevance

Low levels of high-density lipoprotein-cholesterol (HDL-C) is considered a major cardiovascular risk factor. However, recent studies have suggested a more U-shaped association between HDL-C and cardiovascular disease. It has been shown that the cardioprotective effect of HDL is related to the functions of HDL particles rather than their cholesterol content. HDL particles are highly heterogeneous and have multiple functions relevant to cardiometabolic conditions including cholesterol efflux capacity, anti-oxidative, anti-inflammatory, and vasoactive properties. There are quantitative and qualitative changes in HDL as well as functional abnormalities in both type 1 and type 2 diabetes. Non-enzymatic glycation, carbamylation, oxidative stress, and systemic inflammation can modify the HDL composition and therefore the functions, especially in situations of poor glycemic control. Studies of HDL proteomics and lipidomics have provided further insights into the structure-function relationship of HDL in diabetes. Interestingly, HDL also has a pleiotropic anti-diabetic effect, improving glycemic control through improvement in insulin sensitivity and β-cell function. Given the important role of HDL in cardiometabolic health, HDL-based therapeutics are being developed to enhance HDL functions rather than to increase HDL-C levels. Among these, recombinant HDL and small synthetic apolipoprotein A-I mimetic peptides may hold promise for preventing and treating diabetes and cardiovascular disease.

High-Density Lipoprotein Modifications: Causes and Functional Consequences in Type 2 Diabetes Mellitus

High-density lipoprotein (HDL) is a group of small, dense, and protein-rich lipoproteins that play a role in cholesterol metabolism and various cellular processes. Decreased levels of HDL and HDL dysfunction are commonly observed in individuals with type 2 diabetes mellitus (T2DM), which is also associated with an increased risk for cardiovascular disease (CVD). Due to hyperglycemia, oxidative stress, and inflammation that develop in T2DM, HDL undergoes several post-translational modifications such as glycation, oxidation, and carbamylation, as well as other alterations in its lipid and protein composition. It is increasingly recognized that the generation of HDL modifications in T2DM seems to be the main cause of HDL dysfunction and may in turn influence the development and progression of T2DM and its related cardiovascular complications. This review provides a general introduction to HDL structure and function and summarizes the main modifications of HDL that occur in T2DM. Furthermore, the potential impact of HDL modifications on the pathogenesis of T2DM and CVD, based on the altered interactions between modified HDL and various cell types that are involved in glucose homeostasis and atherosclerotic plaque generation, will be discussed. In addition, some perspectives for future research regarding the T2DM-related HDL modifications are addressed.

High-Density Lipoprotein Subfractions Remodeling: A Critical Process for the Treatment of Atherosclerotic Cardiovascular Diseases

Numerous studies have shown that a low level of high-density lipoprotein cholesterol (HDL-C) is an independent biomarker of cardiovascular disease. High-density lipoprotein (HDL) is considered to be a protective factor for atherosclerosis (AS). Therefore, raising HDL-C has been widely recognized as a promising strategy to treat atherosclerotic cardiovascular diseases (ASCVD). However, several studies have found that increasing HDL-C levels does not necessarily reduce the risk of ASCVD. HDL particles are highly heterogeneous in structure, composition, and biological function. Moreover, HDL particles from atherosclerotic patients exhibit impaired anti-atherogenic functions and these dysfunctional HDL particles might even promote ASCVD. This makes it uncertain that HDL-raising therapy will prevent and treat ASCVD. It is necessary to comprehensively analyze the structure and function of HDL subfractions. We review current advances related to HDL subfractions remodeling and highlight how current lipid-modifying drugs such as niacin, statins, fibrates, and cholesteryl ester transfer protein inhibitors regulate cholesterol concentration of HDL and specific HDL subfractions.

Dysfunctional High-Density Lipoproteins in Type 2 Diabetes Mellitus: Molecular Mechanisms and Therapeutic Implications

High density lipoproteins (HDLs) are commonly known for their anti-atherogenic properties that include functions such as the promotion of cholesterol efflux and reverse cholesterol transport, as well as antioxidant and anti-inflammatory activities. However, because of some chronic inflammatory diseases, such as type 2 diabetes mellitus (T2DM), significant changes occur in HDLs in terms of both structure and composition. These alterations lead to the loss of HDLs' physiological functions, to transformation into dysfunctional lipoproteins, and to increased risk of cardiovascular disease (CVD). In this review, we describe the main HDL structural/functional alterations observed in T2DM and the molecular mechanisms involved in these T2DM-derived modifications. Finally, the main available therapeutic interventions targeting HDL in diabetes are discussed.

The Difference Between High Density Lipoprotein Subfractions and Subspecies: an Evolving Model in Cardiovascular Disease and Diabetes

PURPOSE OF REVIEW

The term high density lipoproteins (HDL) refers to an eclectic collection of subparticles that play diverse roles in physiology. Here, we define the term "HDL subspecies" and review recent work on their molecular characterization and relation to disease, focusing on cardiovascular disease and diabetes.

RECENT FINDINGS

The HDL family contains over 200 proteins and nearly 200 lipids that partition into different particles in plasma. Simple subfractionation of HDL based on a particular physicochemical property has not risen to the challenge of revealing the roles of specific particles in disease. However, by targeting minor protein or lipid components, a handful of compositionally defined HDL subspecies have been described and characterized. By combining targeted particle isolation techniques with the power of large human studies, progress is being made in understanding HDL subspecies functions and implications for disease. However, much work remains before these advancements can be translated into disease mitigation strategies.

Arylesterase activity of paraoxonase 1 (PON1) on HDL3 and HDL2: Relationship with Q192R, C-108T, and L55M polymorphisms

Background

Controversy exists regarding the role of the subfractions of high-density lipoproteins (HDL₂ and HDL₃) in cardiovascular disease. The functionality of these particles, and their protective role, is due in part to the paraoxonase 1 (PON1) presence in them. The polymorphisms rs662 (Q192R, A/G), rs854560 (L55 M, T/A), and rs705379 (C-108T) of the PON1 gene have been related to enzyme activity and, with the anti-oxidative capacity of the HDL. The objective was to determine the arylesterase PON1 activity in HDL₃ and HDL₂ and its relationship with the polymorphisms mentioned, in a young population.

Methods

The polymorphisms were determined through mini-sequencing (SnaPshot). The HDL subpopulations were separated via ionic precipitation, cholesterol was measured with enzymatic methods, and PON1 activity was measured through spectrophotometry.

Results

The results show that the PON1 polymorphisms do not influence the cholesterol in the HDL. A variation between 40.02 and 43.9 mg/dL was in all the polymorphisms without significant differences. Additionally, PON1 activity in the HDL₃ subfractions was greater (62.83 ± 20 kU/L) than with HDL₂ (35.8 ± 20.8 kU/L) in the whole population and in all the polymorphisms (p < 0.001), and it was independent of the polymorphism and differential arylesterase activity in the Q192R polymorphism (QQ > QR > RR). Thus, 115.90 ± 30.7, 88.78 ± 21.3, 65.29 ± 10.2, respectively, for total HDL, with identical behavior for HDL₃ and HDL₂.

Conclusions

PON1 polymorphisms do not influence the HDL_-c, and the PON activity is greater in the HDL₃ than in the HDL₂, independent of the polymorphism, but it is necessary to delve into the functionality of these findings in different populations.

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PON1 polymorphisms do not influence the cholesterol in the HDL subfractions.

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PON1 arylesterase activity in the HDL₃ subfractions was greater than with HDL₂.

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In Q192R, L55 M and C-108T polymorphisms, PON1 activity is always higher in HDL3.

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This study shows that healthy young people in Colombia have very low HDL cholesterol.

A homogeneous assay to determine high-density lipoprotein subclass cholesterol in serum

Existing methods to measure high-density lipoprotein cholesterol (HDL-C) subclasses (HDL₂-C and HDL₃-C) are complex and require proficiency, and thus there is a need for a convenient, homogeneous assay to determine HDL-C subclasses in serum. Here, cholesterol reactivities in lipoprotein fractions [HDL₂, HDL₃, low-density lipoprotein (LDL), and very-low-density lipoprotein (VLDL)] toward polyethylene glycol (PEG)-modified enzymes were determined in the presence of varying concentrations of dextran sulfate and magnesium nitrate. Particle sizes formed in the lipoprotein fractions were measured by dynamic light scattering. We optimized the concentrations of dextran sulfate and magnesium nitrate before assay with PEG-modified enzymes to provide selectivity for HDL₃-C. On addition of dextran sulfate and magnesium nitrate, the sizes of particles of HDL₂, LDL, and VLDL increased, but the size of HDL₃ fraction particles remained constant, allowing only HDL₃-C to participate in coupled reactions with the PEG-modified enzymes. In serum from both healthy volunteers and patients with type 2 diabetes, a good correlation was observed between the proposed assay and ultracentrifugation in the determination of HDL-C subclasses. The assay proposed here enables convenient and accurate determination of HDL-C subclasses in serum on a general automatic analyzer and enables low-cost routine diagnosis without preprocessing.

Effects of Virgin Olive Oil and Phenol-Enriched Virgin Olive Oils on Lipoprotein Atherogenicity

The atherogenicity of low-density lipoprotein (LDL) and triglyceride-rich lipoproteins (TRLs) may be more significant than LDL cholesterol levels. Clinical trials which have led to increased high-density lipoprotein (HDL) cholesterol have not always seen reductions in cardiovascular disease (CVD). Furthermore, genetic variants predisposing individuals to high HDL cholesterol are not associated with a lower risk of suffering a coronary event, and therefore HDL functionality is considered to be the most relevant aspect. Virgin olive oil (VOO) is thought to play a protective role against CVD. This review describes the effects of VOO and phenol-enriched VOOs on lipoprotein atherogenicity and HDL atheroprotective properties. The studies have demonstrated a decrease in LDL atherogenicity and an increase in the HDL-mediated macrophage cholesterol efflux capacity, HDL antioxidant activity, and HDL anti-inflammatory characteristics after various VOO interventions. Moreover, the expression of cholesterol efflux-related genes was enhanced after exposure to phenol-enriched VOOs in both post-prandial and sustained trials. Improvements in HDL antioxidant properties were also observed after VOO and phenol-enriched VOO interventions. Furthermore, some studies have demonstrated improved characteristics of TRL atherogenicity under postprandial conditions after VOO intake. Large-scale, long-term randomized clinical trials, and Mendelian analyses which assess the lipoprotein state and properties, are required to confirm these results.

High-Density Lipoprotein Subspecies in Health and Human Disease: Focus on Type 2 Diabetes

Plasma cholesterol levels of high-density lipoproteins (HDL) have been associated with cardioprotection for decades. However, there is an evolving appreciation that this lipoprotein class is highly heterogeneous with regard to composition and functionality. With the advent of advanced lipid-testing techniques and methods that allow both the quantitation and recovery of individual particle populations, we are beginning to connect the functionality of HDL subspecies with chronic metabolic diseases. In this review, we examine type 2 diabetes (T2D) and explore our current understanding of how obesity, insulin resistance, and hyperglycemia affect, and may be affected by, HDL subspeciation. We discuss mechanistic aspects of how insulin resistance may alter lipoprotein profiles and how this may impact the ability of HDL to mitigate both atherosclerotic disease and diabetes itself. Finally, we call for more detailed studies examining the impact of T2D on specific HDL subspecies and their functions. If these particles can be isolated and their compositions and functions fully elucidated, it may become possible to manipulate the levels of these specific particles or target the protective functions to reduce the incidence of coronary heart disease.

Serum Apolipoprotein B and A1 Concentrations Predict Late-Onset Posttransplant Diabetes Mellitus in Prevalent Adult Kidney Transplant Recipients

BACKGROUND

Glucose metabolism links closely to cholesterol metabolism. Posttransplant diabetes mellitus (PTDM) adversely affects posttransplant outcomes, but its risk factors in relation to cholesterol metabolism have not been fully delineated. The apolipoprotein B/A1 (Apo B/A1) ratio, which is associated with insulin resistance, has not been evaluated in kidney transplant recipients as a risk factor for PTDM.

OBJECTIVE

The objective of this study was to determine whether serum apolipoprotein profiles predict late PTDM, defined as a new onset diabetes occurring greater than 3 months posttransplant.

DESIGN

Retrospective chart review of a prevalent population of kidney transplant recipients.

SETTING

Large transplant center in Ontario, Canada.

PATIENTS

We identified 1104 previously nondiabetic adults who received a kidney transplant between January 1, 1998, and December 1, 2015, and were followed at 1 transplant center.

MEASUREMENTS

Recipients provided testing for serum apolipoprotein B (Apo B) and apolipoprotein A1 (Apo A1) concentrations from 2010, either at 3 months posttransplant for new transplant recipients or the next clinic visit for prevalent recipients. Late PTDM defined using Canadian Diabetes Association criteria as occurring ≥3 months posttransplant was recorded until May 1, 2016.

METHODS

All analyses were conducted with R, version 3.4.0 (The R Foundation for Statistical Computing). Comparisons were made using Student t test, Fisher exact test or chi-square test, Kaplan-Meier methodology with the logrank test, or Cox proportional hazards analysis as appropriate. Covariates for the multivariate Cox proportional hazards models of PTDM as the outcome variable were selected based on significance of the univariate associations and biological plausibility.

RESULTS

There were 53 incident late PTDM cases, or 1.71 cases per 100 patient-years. Incident late PTDM differed between the highest and lowest quartiles for Apo B/A1 ratio, 2.47 per 100 patient-years vs 0.88 per 100 patient-years (P = .005 for difference). In multiple Cox regression analysis, first measured serum Apo B/A1 concentration better predicted subsequent PTDM than low-density lipoprotein cholesterol (LDL-C; hazard ratio [HR] = 7.80 per unit increase, P = .039 vs HR = 1.05 per unit increase, P = .774). Non-high-density lipoprotein cholesterol (HDL-C) concentrations also did not predict PTDM (P = .136). By contrast to Apo B, Apo A1 was protective against PTDM in statin users (HR = 0.17 per unit increase, P = .016).

LIMITATIONS

Posttransplant diabetes mellitus cases occurring before apolipoprotein testing was implemented were not included in the analysis.

CONCLUSIONS

Apolipoproteins B and A1 better predict late PTDM than conventional markers of cholesterol metabolism.

Optical Properties of Europium Tetracycline Complexes in the Presence of High-Density Lipoproteins (HDL) Subfractions

Standard lipoprotein measurements of triglycerides, total cholesterol, low-density lipoproteins (LDL), and high-density lipoproteins (HDL) fail to identify many lipoprotein abnormalities that contribute to cardiovascular heart diseases (CHD). Studies suggested that the presence of CHD is more strongly associated with the HDL subspecies than with total HDL cholesterol levels. The HDL particles can be collected in at least three subfractions, the HDL2b, HDL2a, and HDL3. More specifically, atherosclerosis is associated with low levels of HDL2. In this work, the optical spectroscopic properties of europium tetracycline (EuTc) complex in the presence of different HDL subspecies was studied. The results show that the europium spectroscopic properties in the EuTc complex are influenced by sizes and concentrations of subclasses. Eu³⁺ emission intensity and lifetime can discriminate the subfractions HDL3 and HDL2b.

Padina arborescens Ameliorates Hyperglycemia and Dyslipidemia in C57BL/KsJ-db/db Mice, a Model of Type 2 Diabetes Mellitus

Recently, there has been a growing interest in alternative therapies and in the therapeutic use of natural products for the treatment of diabetes. Therefore, in this study, we investigated the hypoglycemic and hypolipidemic effects of brown algae, Padina arborescens, in an animal model of type 2 diabetes. For 6 weeks, male C57BL/KsJ-db/db mice were administrated either control diet with no treatment or were treated with rosiglitazone (RG; 0.005%, w/w) or P. arborescens extract (PAE; 0.5%, w/w). At the end of the experimental period, the blood glucose levels, glycosylated hemoglobin levels, and plasma insulin levels were significantly lower in the RG and PAE groups compared with the control group. In addition, glucose tolerance was significantly improved in the RG and PAE groups. The homeostatic index of insulin resistance was lower in the RG and PAE groups than the diabetic control group. Also, the total cholesterol, LDL-cholesterol, triglyceride, and free fatty acid levels were lower in the PAE group than in the control group, whereas the HDL-C level was higher in the PAE group. Supplementation with PAE significantly lowered hepatic glucose-6-phosphatase and phosphoenolpyruvate carboxykinase activities, and increased glucokinase activity in the liver. Consequently, these results suggest that PAE may be beneficial in improving insulin resistance, hyperglycemia, and dyslipidemia in type 2 diabetics.

Validation of a novel homogeneous assay for of HDL3-C measurement

BACKGROUND

Low serum concentration of high density lipoprotein2 cholesterol (HDL2-C) is associated with increased risk of cardiovascular events. HDL2-C is calculated indirectly by subtracting high density lipoprotein3 cholesterol (HDL3-C) from total high density lipoprotein cholesterol (HDL-C). However, the special equipment and long assay times required for HDL3-C measurement have hindered the use of HDL2-C clinically. Here, we report the validation of a simple and rapid homogeneous assay for HDL3-C that is adaptable to clinical chemistry analyzers.

MATERIALS AND METHODS

Method comparison based on 2740 serum specimens spanning the physiological range of HDL3-C was analyzed in singlicate to evaluate and validate a new homogeneous assay from Denka Seiken against the conventional dextran sulfate precipitation method. This study was performed over five days. Serum pools were prepared for the analysis of precision over 5 days (5 measurements per day), linearity, and interference (hemoglobin, bilirubin, and triglycerides) evaluation.

RESULT

The homogeneous method had good within-run precision at concentrations of 24, 36, and 46 mg/dl, yielding standard deviations (SD) of 0.2 (0.9%) 0.4 (1.2%), and 0.5 (1.1%), respectively. Between-day precision, performed over 5 days using the same serum pools, yielded SD of 0.3 (1.4%), 1.0 (2.8%), and 0.9 (2.0%), respectively. The assay was linear from 1 to 100 mg/dl and correlated very well with the dextran sulfate precipitation method. There was no interference from hemoglobin up to 500 mg/dl, bilirubin up to 25 mg/dl, or triglycerides up to 1500 mg/dl.

CONCLUSION

This homogeneous HDL3-C assay quantitatively measures HDL3-C in serum samples and has excellent precision, and can be implemented on an automated chemistry analyzer, thereby facilitating rapid measurement (~10 min) of a large number of samples in a standard clinical laboratory without the need for additional expensive equipment, laboratory space, or specially-trained staff.

High-density lipoprotein subclasses and their relationship to cardiovascular disease

OBJECTIVE

To assess the clinical utility of measuring high-density lipoprotein (HDL) subfractions to assess coronary heart disease (CHD) risk.

METHODS

Literature review of 80 published investigations.

RESULTS

Measurements of HDL2b by gradient gel electrophoresis provided more consistent evidence of CHD risk than measurement of HDL2 cholesterol. Five of the seven studies that compared the extent or progression of atherosclerosis with gradient gel electrophoresis estimates of HDL subclasses (71%) assigned statistical significance to HDL2b. Ten of the 11 case-control comparisons (91%) reported lower HDL2b in cases. In contrast, of the 16 association studies relating HDL2 cholesterol and HDL3 cholesterol to extent of disease, five reported no significant relationships with either subfraction, two reported significant relationships with both HDL2 and HDL3 cholesterol, four reported significant relationships with HDL2 but not HDL3 cholesterol, and five reported relationships with HDL3 but not HDL2 cholesterol. Forty-five percent of the case-control comparisons reported that both HDL2 cholesterol and HDL3 cholesterol were significantly lower in cases than controls, 17% failed to find significance for either subfraction, and the remainder reported significantly lower values in cases for HDL2 cholesterol only (26%) or HDL3 cholesterol only (11%). On average, the case-control differences were similar for HDL2 (-0.12 ± 0.01 mmol/L) and HDL3 cholesterol (-0.10 ± 0.02 mmol/L), although relative to controls, the percent reduction was twice as great for HDL2 (-25.7 ± 2.9%) than HDL3 cholesterol (-12.1 ± 1.5%). Eight prospective studies were identified and four reported that both HDL2 and HDL3 predicted lower risk for CHD, one reported reductions in risk for HDL2 but not HDL3 cholesterol, and three reported reductions in risk for HDL3 but not HDL2 cholesterol. None of the prospective studies show that measurements of HDL cholesterol subfractions improve the identification of persons at risk.

CONCLUSIONS

HDL2 and HDL3 cholesterol do not distinguish cardioprotective differences between HDL subclasses. More extensive characterization of HDL particles by one or two dimensional gel electrophoresis, ion mobility, or ultracentrifugation may provide more specific information about CHD risk than the measurement of HDL cholesterol, HDL3 cholesterol, or HDL2 cholesterol.

High-density lipoprotein subspecies between patients with type 1 diabetes and type 2 diabetes without / with intensive insulin therapy

The reduced levels of high-density lipoprotein (HDL) 2-cholesterol (C) in diabetes and other metabolic disorders associated with a high risk of cardiovascular disease are well established. Few studies, however, have compared the HDL subspecies in type 1 diabetes (T1D) with those in type 2 diabetes (T2D) with or without insulin. We examined HDL subspecies in 27 T1D with insulin, 33 T2D with insulin or insulin plus oral-anti-diabetic drugs (OADs), 36 T2D with OADs or diet/exercise, and 25 non-diabetic controls. Insulin was injected four times daily in a basal-bolus manner for both T1D and T2D. Plasma levels of C, apolipoprotein (apo) AI, and AII were determined in HDL2 and HDL3 by the single precipitation method. HDL-C levels were significantly higher in T1D and lower in T2D, compared with the controls. Insulin-treated T2D had higher HDL-C than non-insulin-treated T2D. T1D had higher HDL2-C and HDL2-apo AI levels than T2D. Insulin-treated T2D had higher HDL2-C and HDL2-apo AI levels than non-insulin-treated T2D. All of these differences were more pronounced for men than for women. HDL3 levels were comparable among controls,T1D and T2D. HDL2-C levels were inversely associated with BMI, HbA1c, triglyceride, small dense LDL-C, and LDL-C. Multiple regression analysis revealed that HDL2-C was independently associated with triglyceride, LDL-C, and intensive insulin therapy but not with HbA1c. In conclusion, these results suggest that intensive insulin therapy is associated with alterations of HDL subspecies, irrespective of the type of diabetes.

Predictive value of different HDL particles for the protection against or risk of coronary heart disease

The inverse relationship between plasma HDL levels and the risk of developing coronary heart disease is well established. The underlying mechanisms of this relationship are poorly understood, largely because HDL consist of several functionally distinct subpopulations of particles that are continuously being interconverted from one to another. This review commences with an outline of what is known about the origins of individual HDL subpopulations, how their distribution is regulated, and describes strategies that are currently available for isolating them. We then summarise what is known about the functionality of specific HDL subpopulations, and how these findings might impact on cardiovascular risk. The final section highlights major gaps in existing knowledge of HDL functionality, and suggests how these deficiencies might be addressed. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).

Activation of lipoprotein lipase increases serum high density lipoprotein 2 cholesterol and enlarges high density lipoprotein 2 particles in rats

It is known that postheparin plasma lipoprotein lipase (LPL) activity correlates with serum high density lipoprotein cholesterol (HDL-C) levels in humans and animals. Furthermore, LPL has been reported to cause enlargement of HDL particle size in vitro. However, these effects have not yet been experimentally proven. The aim of this study was to determine whether LPL has a role in increase in HDL-C and enlargement of HDL particle by activating the LPL function with NO-1886, the LPL promoting agent. NO-1886 administration increased postheparin plasma LPL activity without influencing hepatic triglyceride lipase activity. NO-1886 increased serum HDL(2)-cholesterol (HDL(2)-C) concentration and enlarged HDL(2) particle size, but did not increase serum HDL(3)-cholesterol concentration or enlarge HDL(3) particle size. Also, serum HDL(2)-C concentrations were positively correlated with HDL(2) particle size (r=0.910). Our study demonstrates that the LPL activation induced with NO-1886 may cause production of HDL(2)-C by catabolism of triglyceride-rich lipoproteins and enlarges HDL(2) particle size in rats.

Modeling the time evolution of the nanoparticle-protein corona in a body fluid

Background

Nanoparticles in contact with biological fluids interact with proteins and other biomolecules, thus forming a dynamic corona whose composition varies over time due to continuous protein association and dissociation events. Eventually equilibrium is reached, at which point the continued exchange will not affect the composition of the corona.

Results

We developed a simple and effective dynamic model of the nanoparticle protein corona in a body fluid, namely human plasma. The model predicts the time evolution and equilibrium composition of the corona based on affinities, stoichiometries and rate constants. An application to the interaction of human serum albumin, high density lipoprotein (HDL) and fibrinogen with 70 nm N-iso-propylacrylamide/N-tert-butylacrylamide copolymer nanoparticles is presented, including novel experimental data for HDL.

Conclusions

The simple model presented here can easily be modified to mimic the interaction of the nanoparticle protein corona with a novel biological fluid or compartment once new data will be available, thus opening novel applications in nanotoxicity and nanomedicine.

High-density lipoprotein subfractions in normolipidemic individuals without clinical atherosclerosis lipoprotein subfractions in an adult population

This study evaluated the serum concentrations of lipids, lipoproteins, apolipoproteins, and high-density lipoprotein (HDL) subfractions in Brazilian adults. We analyzed the distribution of lipids in HDL2 and HDL3 in a normolipidemic population without evidence of established cardiovascular disease (CVD). A total of 93 males and 92 females, healthy and normolipidemic, volunteered to be submitted to a clinical examination, a blood collection, and to answer a questionnaire aimed at determining signs and symptoms of atherosclerotic disease. Their fasting plasma lipid, lipoproteins, apolipoproteins, and the cholesterol and triglyceride concentrations in HDL2 and HDL3, isolated by microultracentrifugation, were determined by enzymatic-colorimetric methods. The interpercentile intervals (2.5-97.5) for the population were established as being 5-18 mg/dL in men and 4-28 mg/dL in women for HDL2 cholesterol (HDL2chol) and 1-57 mg/dL in men and 2-61 mg/dL in women for HDL3 cholesterol (HDL3chol). HDL2 triglyceride levels (HDL2Tg) in men were 1-26 mg/dL and in women 2-28 mg/dL; moreover, the HDL3 triglyceride (HDL3Tg) intervals were established as 4-46 mg/dL for both sexes. The determination of reference ranges for lipids in HDL subfractions in populations without clinical atherosclerosis, is an useful tool for metabolic, diagnostic, and therapeutic approaches. We determined the intervals for HDL2chol, HDL3chol, HDL2Tg, and HDL3Tg. There were variations with sex and/or age for HDL2chol, HDL3chol, and HDL2Tg in the studied population.

Reverse cholesterol transport and cholesterol efflux in atherosclerosis

Reverse cholesterol transport (RCT) is a pathway by which accumulated cholesterol is transported from the vessel wall to the liver for excretion, thus preventing atherosclerosis. Major constituents of RCT include acceptors such as high-density lipoprotein (HDL) and apolipoprotein A-I (apoA-I), and enzymes such as lecithin:cholesterol acyltransferase (LCAT), phospholipid transfer protein (PLTP), hepatic lipase (HL) and cholesterol ester transfer protein (CETP). A critical part of RCT is cholesterol efflux, in which accumulated cholesterol is removed from macrophages in the subintima of the vessel wall by ATP-binding membrane cassette transporter A1 (ABCA1) or by other mechanisms, including passive diffusion, scavenger receptor B1 (SR-B1), caveolins and sterol 27-hydroxylase, and collected by HDL and apoA-I. Esterified cholesterol in the HDL is then delivered to the liver for excretion. In patients with mutated ABCA1 genes, RCT and cholesterol efflux are impaired and atherosclerosis is increased. In studies with transgenic mice, disruption of ABCA1 genes can induce atherosclerosis. Levels of HDL are inversely correlated with incidences of cardiovascular disease. Supplementation with HDL or apoA-I can reverse atherosclerosis by accelerating RCT and cholesterol efflux. On the other hand, pro-inflammatory factors such as interferon-gamma (IFN-gamma), endotoxin, tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1beta), can be atherogenic by impairing RCT and cholesterol efflux, according to in vitro studies. RCT and cholesterol efflux play a major role in anti-atherogenesis, and modification of these processes may provide new therapeutic approaches to cardiovascular disease. Further research on new modifying factors for RCT and cholesterol efflux is warranted.

Pathogenesis and management of diabetic dyslipidemia

Patients with diabetes mellitus have a 2- to 4-fold increased risk of atherosclerotic cardiovascular, peripheral vascular, and cerebrovascular disease, which are the leading causes of morbidity and mortality in this population. Several epidemiological studies have shown an association between diabetic dyslipidemia, which is characterized by hypertriglyceridemia, low levels of high density lipoprotein-cholesterol, postprandial lipemia and small, dense low density lipoprotein-cholesterol (LDL-C) particles, and the occurrence of cardiovascular disease. Other studies have established the beneficial effects of lipid lowering on the reduction of major coronary events in diabetic patients. The recent National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III) guidelines emphasize diabetes as a coronary heart disease risk equivalent. The NCEP ATP III states that elevated LDL-C is a major risk factor for coronary heart disease, and the primary goal of risk-reduction therapy is the reduction of LDL-C levels to 100 mg/dL. This article defines and describes diabetic dyslipidemia and its etiology and pathogenesis, as well as reviewing guidelines and recommendations for treatment of this disorder. Treatment of diabetic dyslipidemia includes 1) lifestyle modifications: physical activity and a diet low in saturated fats and cholesterol and high in complex carbohydrates and fiber; and 2) pharmacological treatment with (i) oral antihyperglycemic agents: metformin and thiazolidinediones; (ii) weight reduction drugs: orlistat and sibutramine and; (iii) lipid-lowering drugs: HMG-CoA reductase inhibitors, fibric acid derivatives, nicotinic acid, and bile acid sequestrants.

Common genetic and environmental effects on lipid phenotypes: the HERITAGE family study

OBJECTIVE

Despite the well known genetic component influencing plasma lipid-lipoprotein levels and the observed correlations among these traits, little is known about pleiotropic heritable determinants among them. Our aim is to investigate pair-wise polygenic and environmental correlations among lipid-lipoprotein levels at baseline and in response to regular exercise in Whites and Blacks.

METHODS

Common pair-wise genetic and environmental correlations among levels of total cholesterol (TC), LDL-C, ApoB, HDL-C (also HDL2-C and HDL3-C), triglycerides (TG, HDL-TG and LDL-TG) and ApoA-1 were investigated at baseline and again after a 20-week endurance exercise program using a variance-components-decomposition.

RESULTS

With a few exceptions, all lipid phenotypes were heritable at baseline and for training responses in Blacks and Whites. Strong to high genetic and environmental correlations (0.4 < rho(g) < 0.7) were observed for the majority of the baseline pair-wise traits. For training responses, many of the same patterns were noted, although fewer genetic correlations were significant as compared to the baseline results.

CONCLUSIONS

Results suggest that the observed phenotypic correlations among many of these traits may be due to in part to pleiotropic genes, in particular between LDL-C and ApoB and between TG and HDL-C. This shared genetic architecture should be considered in follow-up gene finding studies.

Glitazones and the management of insulin resistance: what they do and how might they be used

Thiazolidinediones (glitazones) are the only compounds currently available that specifically target tissue insulin resistance. The two currently available drugs in this class, pioglitazone and rosiglitazone,are approved by the Food and Drug Administration for the treatment of type 2 diabetes mellitus only. The therapeutic potential of the glitazones for other consequences of insulin resistance has stirred considerable interest, especially with regard to their potential beneficial impact on atherosclerotic cardiovascular disease and diabetes prevention. They also have been considered in the management of polycystic ovarian syndrome, nonalcoholic fatty liver disease, and other consequences of insulin resistance. The nonglycemic potential of glitazones is a clinical area in rapid evolution, wherein most data are on the impact of the glitazones onsurrogate markers that are associated with diseases, not on disease outcomes. This article provides insight and guidance to clinicians on the diverse nonglycemic potential of glitazones until conclusive outcome data become available.

Isolation of plasma small-dense low-density lipoprotein using a simple air-driven ultracentrifuge and quantification using immunassay of apolipoprotein B

Small-dense low-density lipoprotein (SD-LDL) is associated with coronary heart disease risk. Current methods for its quantification are expensive, complex and time-consuming. Plasma was adjusted to a density (D) of 1.044 g/ml in a volume of 0.18 ml and centrifuged in a Beckman Airfuge at 160 000×

The effect of a rapid weight loss on lipid profile and glycemic control in obese type 2 diabetic patients

OBJECTIVE

To test the effect of low calorie diet (LCD) on body weight, lipid profile, and glycemic control in obese type 2 diabetes mellitus (DM) patients.

DESIGN

Dietary intervention.

SETTING

Department of Human Nutrition, Copenhagen.

SUBJECTS

Outpatients: 11 type 2 DM patients (three males/eight females) (10 completed), four on oral hypoglycemic agents (OHA). Body mass index (BMI) 36.8 +/- 5.5 kg/m2 and age 62 +/- 5.7 y.

INTERVENTIONS

In all, 8 weeks full meal-replacement diet: eight sachets of a nutrition powder (Nutrilett, 850 kcal/day). Lipid profile assessed by NMR spectroscopy.

RESULTS

Mean body weight fell by 10.9 kg (approximately 11%, P<0.001). Fasting insulin, fasting blood glucose, hemoglobin A1c, fasting plasma triglycerides, total cholesterol, and low-density lipoprotein (LDL) cholesterol fell significantly. There were large positive changes (statistically insignificant) in LDL subclass distribution and a similar shift in high-density lipoprotein subclass distribution. Medication was discontinued in all four subjects taking OHA for 2 weeks prior to the intervention and throughout the whole 8-week intervention period.

CONCLUSION

LCD is effective in improving glycemic control and blood lipids through weight loss in overweight type 2 DM patients.

How to carry out a health-orientated marathon training programme for running and inline skating

BACKGROUND

More and more people want to do something for their health. Nevertheless, certain reluctance exists when it comes to committing oneself to higher sporting aims, as well as some uncertainty concerning proper training.

DESIGN AND METHODS

Two model projects have been developed, aimed at motivating larger parts of the population towards a health-orientated training programme. Both projects serve as a basis for further, similarly designed large-scale projects. In the running project a health-focused run training programme was set up aimed at preparing people, previously inexperienced in running, for a marathon. In the inline project an inline training programme was developed which comprised both the training of essential techniques as well as individualized endurance training, the aim being the participation in an inline marathon.

RESULTS

A total of more than 1000 people participated in both projects. The health check performed before the beginning of the project revealed some pathological findings, demonstrating the necessity of a medical examination before taking up regular training. Both projects led to an improvement in endurance performance. In addition, the blood-chemical metabolic parameters showed clear optimization, in particular the lipid profile. The inline technique training resulted in an improvement of the braking skills, which is accompanied by a reduction in the risk of injuries.

CONCLUSIONS

Both model projects have shown that large-scale sports programmes that focus primarily on the prevention of injuries and disease (under sport-medical guidance) with a performance incentive are accepted by the population, provided they offer a high fun factor.

Measurement of plasma small-dense LDL concentration by a simplified ultracentrifugation procedure and immunoassay of apolipoprotein B

BACKGROUND

Existing methods for detecting small-dense low-density lipoprotein (SD-LDL) are either semiquantitative (e.g., gradient gel electrophoresis) or require specialised laboratory methods (e.g., density-gradient ultracentrifugation, DGU).

METHODS

We report a method in which plasma was adjusted to a density (D) of 1.044 and 1.060 g/ml, respectively, in two tubes, both of which underwent ultracentrifugation (UC). A measure of SD-LDL apolipoprotein B (apo B) was obtained by subtraction of the apo B concentration in D>1.060 g/ml lipoproteins from that in D>1.044 g/ml lipoproteins to correct for apo B associated with lipoprotein (a) [Lp(a)]. This procedure was evaluated in paired plasma samples in healthy men (n=62) and in age-matched healthy women (n=74) and in age-matched primary dyslipidaemic men (n=72) and women (n=29) and compared with an established density-gradient ultracentrifugation (DGU) method.

RESULTS

The dyslipidaemic patients had either decreased high-density lipoprotein cholesterol (HDL-C) and/or increased triglycerides. In dyslipidaemic men, SD-LDL apo B level (23 [5-77] mg/dl) was significantly higher than in healthy men (P<0.001). In dyslipidaemic women, the SD-LDL apo B levels (11 [4-71] mg/dl) were significantly higher than in healthy women (7 [1-45] mg/dl; P<0.005). The concentration of SD-LDL apo B correlated inversely with HDL-C in both women (r=-0.280: P<0.005) and men (r=-0.464; P<0.0001) and positively with triglyceride concentration in both women (r=0.213; P<0.05) and men (r=0.592: P<0.0001). Correction for apo B in Lp(a) increased the analytical variation, which was 12% for apo B at D=1.044-1.060 g/ml and 9% for apo B measured at D>1.044 g/ml. Although the correlation between the new method and DGU results was high (r=0.830; P<0.0001, n=43), the concentration of apo B at D>1.044 g/ml correlated strongly with both corrected results (r=0.978; P<0.0001; n=237) and also with SD-LDL isolated using the DGU method (r=0.832; P<0.0001). Results at D>1.044 g/ml showed the expected correlations both with HDL-C (r=-0.465: P<0.0001) and triglycerides (r=0.526; P<0.0001).

CONCLUSIONS

The new method gave results consistent with earlier published findings using other techniques. Further simplification of the method using a single-density spin at D>1.044 g/ml appears feasible and may provide an easier quantitative method for clinical use.

Separation and selective detection of lipoprotein particles of patients with coronary artery disease by frit-inlet asymmetrical flow field-flow fractionation

An analytical method to improve the characterization of lipoprotein fractions is presented. Human plasma samples were treated with Sudan Black B to stain the lipid component in lipoproteins, then the stained lipoproteins were separated by frit inlet asymmetrical flow field-flow fractionation (FI-AFlFFF), according to the lipoprotein particle sizes, with the selective detection of eluting lipoprotein fractions, high-density lipoproteins (HDL), low-density lipoproteins (LDL) and very-low-density lipoproteins (VLDL), at 610 nm. The capability of this technique has been evaluated with plasma samples obtained from patients with coronary artery disease (CAD), and it showed that the retention profile of patients' lipoprotein samples was clearly distinct from those of healthy persons. The potential of this technique comes with the direct injection of a stained lipoprotein sample without a prior procedure such as ultracentrifugation for sample preparation, and the size calculation of lipoprotein particles from the experimental retention time by theory. Since sample relaxation was achieved hydrodynamically in an FI-AFlFFF channel, sample injection and separation processes were continuously made without stopping the separation flow. This study demonstrated the potential of the FI-AFlFFF technique to be utilized as a powerful tool for the determination of the LDL profiles of patients with CAD.

Atherosclerosis in type 2 diabetes mellitus and insulin resistance: mechanistic links and therapeutic targets

The ongoing heavy burden of cardiovascular disease associated with diabetes mellitus highlights the failure of current treatment strategies to address effectively the cardiovascular risk profile in such patients. Insulin resistance is not only an underlying feature in most cases of type 2 diabetes, but is also associated, through the Insulin Resistance Syndrome, with cardiovascular risk factors that promote atherothrombosis through diverse mechanisms. Growing evidence suggests that treatment with anti-diabetic agents that improve insulin sensitivity, such as the thiazolidinediones, improve multiple components of the Insulin Resistance Syndrome, have beneficial effects on various atherothrombotic mechanisms, and reduce atherosclerosis in animal models and perhaps humans as well. Given data implicating chronic inflammation as a central feature of atherosclerosis, the anti-inflammatory activity of the thiazolidinediones may contribute to their potential anti-atherosclerotic effects. An improved understanding of the mechanisms linking diabetes, atherosclerosis, and cardiovascular disease is needed in order to understand how these and other current and emerging therapies might reduce diabetes-associated cardiovascular disease.

Effects of rosiglitazone alone and in combination with atorvastatin on the metabolic abnormalities in type 2 diabetes mellitus

This study evaluated the effects of rosiglitazone therapy on lipids and the efficacy and safety of rosiglitazone in combination with atorvastatin in patients with type 2 diabetes mellitus. Three-hundred thirty-two patients entered an 8-week, open-label, run-in treatment phase with rosiglitazone 8 mg/day, and 243 were randomized to a 16-week, double-blinded period of continued rosiglitazone plus placebo, atorvastatin 10 mg/day, or atorvastatin 20 mg/day. With rosiglitazone alone, a modest increase in low-density lipoprotein (LDL) cholesterol (9%), a shift in LDL phenotype from dense to large buoyant subfractions (52% of patients), and an increase in total high-density lipoprotein (HDL) cholesterol levels (6%), predominantly in HDL(2) levels (13%), occurred from week 0 to week 8. When atorvastatin was added, there was a further increase in HDL(3) (5%) and expected significant reductions (p <0.0001) in LDL cholesterol (-39%), apolipoprotein B (-35%), and triglyceride levels (-27%). Glycemic control achieved with rosiglitazone alone was not adversely affected by add-on atorvastatin. The combination was well tolerated compared with placebo. To conclude, in addition to the beneficial effects of rosiglitazone on glycemic control, rosiglitazone and atorvastatin in combination achieved 2 goals: the reduction of LDL cholesterol to <100 mg/dl and the removal of small dense LDL in patients with type 2 diabetes mellitus.