Low-density lipoprotein particle size, central obesity, cardiovascular fitness, and insulin resistance syndrome markers in obese youths

Use of Apolipoprotein B in the Era of Precision Medicine: Time for a Paradigm Change?

Atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of death worldwide and the risk of a major cardiovascular event is highest among those with established disease. Ongoing management of these patients relies on the accurate assessment of their response to any prescribed therapy, and their residual risk, in order to optimize treatment. Recent international guidelines and position statements concur that the plasma concentration of apolipoprotein B (apoB) is the most accurate measure of lipoprotein associated ASCVD risk. This is especially true for the growing number of individuals with diabetes, obesity, or the metabolic syndrome, and those on statin therapy. Most guidelines, however, continue to promote LDL-C as the primary risk marker due to uncertainty as to whether the greater accuracy of apoB is sufficient to warrant a paradigm shift. Recommendations regarding apoB measurement vary, and the information provided on how to interpret apoB results is sometimes insufficient, particularly for non-lipid specialists. Misinformation regarding the reliability of the assays is also frequently repeated despite its equivalent or better standardization than many other diagnostic assays. Thus, demand for apoB testing is relatively low, which means there is little incentive to increase its availability or reduce its cost. In this review, we examine the results of recent clinical outcomes studies and meta-analyses on the relative values of apoB, LDL-C, and non-HDL-C as markers of ASCVD risk. Although there is seemingly minimal difference among these markers when only population-based metrics are considered, it is evident from our analysis that, from a personalized or precision medicine standpoint, many individuals would benefit, at a negligible total cost, if apoB measurement were better integrated into the diagnosis and treatment of ASCVD.

Association between triglyceride-glucose index and low-density lipoprotein particle size in korean obese adults

BACKGROUND

Small dense low-density lipoprotein cholesterol (sdLDL-C) is the lipoprotein marker among the various lipoproteins that is most strongly related to atherosclerosis. Insulin resistance (IR) can alter lipid metabolism, and sdLDL-C is characteristic of diabetic dyslipidemia. Therefore, this study sought to inspect the relationship between the triglyceride-glucose (TyG) index and mean low-density lipoprotein (LDL) particle size.

METHODS

In this study, a total of 128 adults participated. The correlation coefficients between various lipoproteins and the TyG index were compared using Steiger's Z test and the Spearman correlation. The independent link between the TyG index and mean LDL particle size was demonstrated by multiple linear regression analysis. To identify the TyG index cutoff value for the predominance of sdLDL particles, receiver operating characteristic curves were plotted.

RESULTS

Mean LDL particle size correlated more strongly with the TyG index than did very low-density lipoprotein, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol. Regression analysis demonstrated that mean LDL particle size had a strong association with the TyG index (β coefficient = -0.038, P-value < 0.001). The TyG index optimal cutoff value for sdLDL particle predominance and the corresponding area under the curve (standard error: 0.028, 95% confidence interval: 0.842-0.952) were 8.72 and 0.897, respectively, which were close to the cutoff value of diabetes risk in Koreans.

CONCLUSIONS

Mean LDL particle size is more strongly correlated with the TyG index than do other lipid parameters. After correcting for confounding variables, mean LDL particle size is independently linked with the TyG index. The study indicates that the TyG index is strongly related to atherogenic sdLDL particles predominance.

Helpful or harmful? The impact of the ketogenic diet on eating disorder outcomes in type 1 diabetes mellitus

INTRODUCTION

Eating disorders (EDs) are common complications in people with type 1 diabetes (PwT1D), given the rigid focus on food and insulin dose adjustment. Dietary recommendations for T1D match those for the general population, yet many fail to achieve target HbA1c. Evidence suggests that lower carbohydrate meals and thus reduced insulin requirements may decrease inconsistencies in insulin absorption, maintain euglycemia and weight. Dietary restriction is a recognized risk factor for ED development, and Ketogenic Diets (KD) involve restriction of common family-based foods, thus impacting social normality and microbiome diversity. We reviewed the current literature on PwT1D following a KD to understand effects on ED risks.

AREAS COVERED

Published data from MEDLINE, Embase, and PsycINFO were used. Search terms included: type 1 diabetes mellitus; or insulin dependent diabetes or T1D AND EDs or anorexia or bulimia or disordered eating AND low-carbohydrate diet or carbohydrate restricted diet or low carb diet or ketogenic diet.

EXPERT OPINION

Research into the effects of KDs on ED outcomes in PwT1D are limited, given the concerns over risks of diabetic ketoacidosis, hypoglycemia, and dyslipidemia. Longer term studies on the participants' experience and motivations of adhering or admonishing the diet are needed.

The Relationship Between Lipoproteins and Insulin Sensitivity in Youth With Obesity and Abnormal Glucose Tolerance

CONTEXT

Youth with obesity and abnormal glucose tolerance have an increased risk for atherosclerosis but the relative contributions of insulin resistance and hyperglycemia to dyslipidemia and the development of subclinical atherosclerosis are unknown.

OBJECTIVE

This work aims to determine the association between insulin resistance, dyslipidemia, and carotid intimal thickness (cIMT) in adolescents with normal and abnormal glucose tolerance.

METHODS

An observational cohort study in 155 youth: 44 obese insulin sensitive (OIS; fasting insulin ≤ 20 µM/mL, body mass index [BMI] ≥ 95th percentile), 35 obese insulin resistant (OIR; fasting insulin > 20 µM/mL, BMI ≥ 95th percentile), 34 obese abnormal glucose tolerant (AGT; BMI ≥ 95th percentile), and 42 Lean (BMI 5th-85th percentile). Lipids, lipoprotein particle size and concentration (-P), insulin sensitivity (SI an intravenous glucose test), and CMIT were compared using linear models adjusted for age, race/ethnicity, biological sex, and Tanner stage. Lipid/lipoprotein profile and CMIT were reevaluated in a subset after 2 years.

RESULTS

Compared to OIS and Lean, OIR and AGT had elevated triglycerides and low high-density lipoprotein cholesterol (HDL-C) but similar total cholesterol and low-density lipoprotein cholesterol (LDL-C). Among OIS, OIR, AGT, lower SI was associated with atherogenic lipids (higher triglycerides, LDL-C, non-HDL-C, and lower HDL-C) and lipoproteins (higher total LDL-P and small HDL-P, and lower large HDL-P). There was a steeper decline in the association of SI with HDL-C and large HDL-P in AGT compared with OIR and OIS. cIMT was comparable across groups and inversely correlated with SI, with no change after 2 years.

CONCLUSION

Among youth with obesity, insulin resistance was associated with an atherogenic lipoprotein/lipid profile and cIMT, regardless of glucose tolerance status. Insulin resistance in AGT youth was associated with a shift to smaller HDL-P compared to normoglycemic youth with obesity. Alterations in HDL-P metabolism may be early adverse manifestations of hyperglycemia in youth with obesity.

Cardiometabolic Associations between Physical Activity, Adiposity, and Lipoprotein Subclasses in Prepubertal Norwegian Children

Lipoprotein subclasses possess crucial cardiometabolic information. Due to strong multicollinearity among variables, little is known about the strength of influence of physical activity (PA) and adiposity upon this cardiometabolic pattern. Using a novel approach to adjust for covariates, we aimed at determining the "net" patterns and strength for PA and adiposity to the lipoprotein profile. Principal component and multivariate pattern analysis were used for the analysis of 841 prepubertal children characterized by 26 lipoprotein features determined by proton nuclear magnetic resonance spectroscopy, a high-resolution PA descriptor derived from accelerometry, and three adiposity measures: body mass index, waist circumference to height, and skinfold thickness. Our approach focuses on revealing and validating the underlying predictive association patterns in the metabolic, anthropologic, and PA data to acknowledge the inherent multicollinear nature of such data. PA associates to a favorable cardiometabolic pattern of increased high-density lipoproteins (HDL), very large and large HDL particles, and large size of HDL particles, and decreasedtriglyceride, chylomicrons, very low-density lipoproteins (VLDL), and their subclasses, and to low size of VLDL particles. Although weakened in strength, this pattern resists adjustment for adiposity. Adiposity is inversely associated to this pattern and exhibits unfavorable associations to low-density lipoprotein (LDL) features, including atherogenic small and very small LDL particles. The observed associations are still strong after adjustment for PA. Thus, lipoproteins explain 26.0% in adiposity after adjustment for PA compared to 2.3% in PA after adjustment for adiposity.

Identification of Metabolic Phenotypes in Young Adults with Obesity by 1H NMR Metabolomics of Blood Serum

(1) Since the obesity prevalence rate has been consistently increasing, it is necessary to find an effective way to prevent and treat it. Although progress is being made to reduce obesity in the young adult population, a better understanding of obesity-related metabolomics and related biochemical mechanisms is urgently needed for developing appropriate screening strategies. Therefore, the aim of this study is to identify the serum metabolic profile associated with young adult obesity and its metabolic phenotypes. (2) Methods: The serum metabolic profile of 30 obese and 30 normal-weight young adults was obtained using proton nuclear magnetic resonance spectroscopy (¹H NMR). ¹H NMR spectra were integrated into 24 integration regions, which reflect relative metabolites, and were used as statistical variables. (3) Results: The obese group showed increased levels of lipids, glucose, glutamate, N-acetyl glycoprotein, alanine, lactate, 3 hydroxybutyrate and branch chain amino acid (BCAA), and decreased levels of choline as compared with the normal-weight group. Non-hyperlipidemia obese adults showed lower levels of lipids and lactate, glutamate, acetoacetate, N-acetyl glycoprotein, isoleucine, and higher levels of choline and glutamine, as compared with hyperlipidemic obese adults. (4) Conclusions: This study reveals valuable findings in the field of metabolomics and young adult obesity. We propose several serum biomarkers that distinguish between normal weight and obese adults, i.e., glutamine (higher in the normal group, p < 0.05), and lactate, BCAAs, acetoacetate and 3-hydroxybutyrate (higher in the obese group, p < 0.05). In addition, visceral fat and serum TG, glutamate, acetoacetate, N-acetyl glycoprotein, unsaturated lipid, isoleucine, and VLDL/LDL are higher (p < 0.05) in the obese with hyperlipidemia. Therefore, they can be used as biomarkers to identify these two types of obesity.

Subclass distribution of low-density lipoprotein triglyceride and the clustering of metabolic syndrome components in Japanese children

BACKGROUND

Recent studies demonstrated that low-density lipoprotein-tryglyceride (LDL-TG) may represent another marker of cardiovascular risks. We therefore measured LDL-TG including the low-density lipoprotein (LDL) subclass distribution and investigated the association between LDL-TG subclass profile and the clustering of metabolic syndrome (MetS) components and insulin resistance in Japanese children.

METHODS

The study included 237 schoolchildren (boys 115, girls 122). Four subclasses of low-density lipoprotein-tryglyceride (large, medium, small, and very small) was quantified using high-performance liquid chromatography. Total LDL-TG and TG levels in LDL subclasses were evaluated among four MetS component groups; non-abdominal obesity, abdominal obesity, pre-MetS, and MetS.

RESULTS

Total LDL-TG (P = 0.0003, P = 0.0175) and triglyceride levels in LDL subclasses were significantly different among four MetS component groups (large: P = 0.0002, P = 0.0084; medium: P = 0.0009, P = 0.0491; small: P =0.0025, P = 0.0509; very small: P = 0.0808, P = 0.0228; boys and girls, respectively). Total LDL-TG (r = 0.411, P < 0.0001, r = 0.378. P < 0.0001) and triglyceride levels in LDL subclasses correlated positively with the homeostasis model of assessment ratio (large: r = 0.396, P < 0.0001, r = 0.346, P < 0.0001; medium: r = 0.274, P = 0.0030, r = 0.228, P = 0.0115; small: r = 0.342, P = 0.0002, r = 0.292, P = 0.0011; very small: r = 0.385, P < 0.0001, r = 0.426, P < 0.0001, boys and girls, respectively).

CONCLUSIONS

Subclass distribution of LDL-TG was significantly associated with the clustering of MetS components in both sexes, and insulin resistance is a significant determinant of LDL-TG in all LDL subclasses. Lipoprotein-tryglyceride subclass analysis, rather than LDL-C, may provide a precise evaluation for cardiovascular disease risks in children with MetS.

Effects of macronutrient intake in obesity: a meta-analysis of low-carbohydrate and low-fat diets on markers of the metabolic syndrome

The metabolic syndrome (MetS) comprises cardiometabolic risk factors frequently found in individuals with obesity. Guidelines to prevent or reverse MetS suggest limiting fat intake, however, lowering carbohydrate intake has gained attention too. The aim for this review was to determine to what extent either weight loss, reduction in caloric intake, or changes in macronutrient intake contribute to improvement in markers of MetS in persons with obesity without cardiometabolic disease. A meta-analysis was performed across a spectrum of studies applying low-carbohydrate (LC) and low-fat (LF) diets. PubMed searches yielded 17 articles describing 12 separate intervention studies assessing changes in MetS markers of persons with obesity assigned to LC (<40% energy from carbohydrates) or LF (<30% energy from fat) diets. Both diets could lead to weight loss and improve markers of MetS. Meta-regression revealed that weight loss most efficaciously reduced fasting glucose levels independent of macronutrient intake at the end of the study. Actual carbohydrate intake and actual fat intake at the end of the study, but not the percent changes in intake of these macronutrients, improved diastolic blood pressure and circulating triglyceride levels, without an effect of weight loss. The homeostatic model assessment of insulin resistance improved with both diets, whereas high-density lipoprotein cholesterol only improved in the LC diet, both irrespective of aforementioned factors. Remarkably, changes in caloric intake did not play a primary role in altering MetS markers. Taken together, these data suggest that, beyond the general effects of the LC and LF diet categories to improve MetS markers, there are also specific roles for weight loss, LC and HF intake, but not reduced caloric intake, that improve markers of MetS irrespective of diet categorization. On the basis of the results from this meta-analysis, guidelines to prevent MetS may need to be re-evaluated.

A Randomized Study of the Effect of Replacing Sugar-Sweetened Soda by Reduced Fat Milk on Cardiometabolic Health in Male Adolescent Soda Drinkers

Soda consumption in adolescents has been linked to poorer metabolic outcomes. We tested whether replacing soda with reduced fat milk would improve features of atherogenic dyslipidemia and other cardiometabolic risk factors. Thirty overweight and obese adolescent boys who were habitual consumers of sugar-sweetened beverages were randomly assigned to consume 24 oz/day of sugar-sweetened soda or an energy equivalent of reduced fat (2%) milk for 3 weeks with crossover to the alternate beverage after a ≥ 2 weeks washout. Plasma lipids and lipoproteins and other laboratory measures were assessed after each beverage period. Lipid and lipoprotein measurements, C-reactive protein, and serum transaminases did not differ significantly between the soda and milk phases of the study. Systolic blood pressure z-score and uric acid concentration were significantly lower after consuming milk compared to soda. Milk consumption also significantly decreased plasma glucosyl ceramide (d18:1/C16:0) and lactosylceramides (d18:1/C16:0 and d18:1/C18:0). While no effects of replacing soda with milk on lipid and lipoprotein measurements were observed in these normolipidemic weight-stable adolescent boys, decreases in systolic blood pressure, uric acid, and glycosphingolipids suggest that an overall favorable effect on cardiometabolic risk can be achieved following a short-term dietary intervention.

Effects of FABP2 Ala54Thr gene polymorphism on obesity and metabolic syndrome in middle-aged Korean women with abdominal obesity

OBJECTIVES

Asians (including Chinese, Japanese and Koreans), who generally have a relatively smaller body size and a lower mean body mass index (BMI), have a relatively higher risk of developing android-type obesity than westerners. Substitution of alanine for threonine (Ala54Thr) on the FABP2 gene (rs 1799883) is related to insulin resistance and obesity. However, few studies have examined this substitution in Koreans, and the number of Korean subjects in those studies is limited. For this reason, we investigated the differences between the FABP2 Ala54Thr polymorphism and obesity, hemodynamic variables, blood lipid profile results, and insulin resistance among middle-aged Korean women with abdominal obesity.

METHODS

We studied 243 middle-aged community-dwelling Korean women with abdominal obesity from Gyeonggi Province, Republic of Korea, who had no history of taking chronic medications. We examined each subject (n = 243) for the presence of FABP2 Ala54Thr polymorphism using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Subjects were also examined for obesity hemodynamic variables (n = 243), lipid profiles (n = 142), and insulin resistance (n = 142).

RESULTS

Of the 243 subjects, 117 had AA ("normal") homozygotic genotype, 100 had AT heterozygotic genotype, and 26 had TT homozygotic genotype for the FABP2 Ala54Thr polymorphism. The AT heterozygotic individuals had a significantly higher mean waist-to-hip ratio, abdominal fat area, and visceral fat area than individuals with other genotypes. TT homozygotic individuals had higher mean triglyceride and fasting glucose levels than individuals with other genotypes.

CONCLUSIONS

The results of this study show that the FABP2 Ala54Thr polymorphism was associated with central obesity and obesity-related metabolic syndrome among middle-aged Korean women.

Peroxidación lipídica en adolescentes púberes

Objetivo Evaluar la peroxidación lipídica en adolescentes púberes con exceso de peso y la presencia o no de resistencia a la insulina.Métodos El estudio fue descriptivo, correlacional y transversal en 80 adolescentes entre 12 y 15 años. Se determinó el perfil lipídico, LDL oxidada, 8-Isoprostano y se estimaron los índices de oxidación de LDL. Se determinó el IMC y se midió la circunferencia de cintura.Resultados Los adolescentes con exceso de peso y resistencia a la insulina mostraron la LDL oxidada, 8-isoprostano y el índice LDL oxidada/c-HDL superior a los de quienes tenían exceso de peso sin resistencia a la insulina y que el grupo control (p<0,05).Conclusión Los adolescentes con exceso de peso y resistencia a la insulina mostraron mayores concentraciones de marcadores de peroxidación lipídica que el resto de los adolescentes evaluados, lo que implicaría un posible papel del estrés oxidativo en el desarrollo de la resistencia a la insulina. Estos resultados ponen de manifiesto la importancia de promover una buena alimentación y estilos de vida saludables para evitar que estos adolescentes se conviertan en adultos obesos con comorbilidades asociadas a la obesidad, lo cual afectarían su calidad y tiempo de vida.

Cardiovascular and Metabolic Complications - Diagnosis and Management in Obese Children

The world at present is facing a burden of rising prevalence of obesity in children and adolescents. The developing countries are particularly facing the dual burden on under-nutrition and obesity. This is associated with appearance and clustering of cardiometabolic abnormalities at an early age with development of chronic complications early and possible decrease in life span of these children and adolescents. In adults this clustering has been termed as 'metabolic syndrome' with definitions that can be used universally. However, in children and adolescents there is no consensus on a uniform definition of metabolic syndrome that can be applicable across the age groups and various ethnicities. Further, as childhood is a period of growth and development, changes in body composition and insulin sensitivity that occur with puberty may influence the thresholds of components used to define metabolic syndrome. Children of South Asian ethnicity appear to be more predisposed to develop abnormalities of metabolic syndrome, possible due to their adverse body fat patterning and genetic influences. The definition of pediatric metabolic syndrome proposed by International Diabetes Federation is useful across different ethnicities. Presence of at least one component of metabolic syndrome should lead to detailed screening for other components and complications. A multimodality approach including therapeutic lifestyle changes targeted at the individual, family and community is essential for management. Pharmacotherapy for individual components may be required if initial management strategies fail to achieve the goals.

Atherogenic dyslipidemia and cardiovascular risk factors in obese children

Childhood obesity when associated with serum lipoprotein changes triggers atherosclerosis. Evidences suggest that the atherosclerotic process begins in childhood and that the extent of early atherosclerosis of the aorta and coronary arteries can be associated with lipoprotein levels and obesity. Furthermore, many studies in childhood demonstrate an important relationship between parameters of insulin sensitivity, body fat distribution, and the development of lipid abnormalities. This review focuses on the most recent findings on the relationship between obesity, dyslipidemia, and cardiovascular risk in children.

The metabolic inter-relationships between changes in waist circumference, triglycerides, insulin sensitivity and small, dense low-density lipoprotein particles with acute weight loss in clinically obese children and adolescents

OBJECTIVE

Small, dense low-density lipoprotein (LDL) particles are highly atherogenic and strongly associated with obesity-related dyslipidemia. The metabolic inter-relationships between weight loss induced changes in waist circumference, triglycerides, insulin sensitivity and small-dense LDL particles in clinically obese children and adolescents have not been studied.

METHODS

Seventy-five clinically obese boys and girls (standardized body mass index 3.07 ± 0.59, aged 8-18 years) were recruited. Anthropometric, body composition and cardiometabolic risk factors were measured pre- and post-weight loss.

RESULTS

There were highly significant reductions in anthropometric, body composition and cardiometabolic risk factors. Triglyceride change was positively correlated with LDL peak particle density and percentage LDL pattern B changes (relative abundance of small, dense LDL particles). Multiple regression analyses showed that changes in triglyceride concentration accounted for between 24 and 18% of the variance in LDL peak particle density and percentage LDL pattern B change, respectively. Changes in waist circumference and insulin sensitivity did not predict these changes in LDL characteristics.

CONCLUSION

Acute and highly significant weight loss significantly decreased LDL peak particle density and percentage LDL pattern B. The change in triglycerides was a strong predictor of LDL peak particle density and percentage LDL pattern B change.

Plant sterols-enriched diet decreases small, dense LDL-cholesterol levels in children with hypercholesterolemia: a prospective study

Background

Small dense low density lipoprotein-cholesterol (sdLDL-C) molecules are more atherogenic compared with large buoyant ones. Phytosterols-enriched diets are effective in decreasing total cholesterol (TC) and low density lipoprotein-cholesterol (LDL-C) concentrations in hyperlipidemic children without significant adverse effects. Limited data on the impact of such a diet on sdLDL-C levels is available in adults while there are no reports concerning children. The purpose of this study is to prospectively evaluate the effect of the daily consumption of 2 g of plant sterols on sdLDL-C levels in children with hypercholesterolemia.

Methods

Fifty-nine children, 25 with LDL-C ≥ 3.4 mmol/l (130 mg/dl) and 34 with LDL-C < 3.4 mmol/l, aged 4.5-15.9 years, were included in the study. A yogurt-drink enriched with 2 g of plant sterols was added to the daily diet of hypercholesterolemic children and 6–12 months later lipid profiles were reassessed. Direct quantitative methods were used to measure LDL-C and sdLDL-C levels.

Results

The consumption of plant sterols reduced sdLDL-C significantly (p < 0.001), but levels remained higher compared with controls (p < 0.001). TC, LDL-C, non high density lipoprotein-cholesterol (NonHDL-C) and apolipoprotein B (ApoB) levels also decreased significantly (p < 0.05). The median reduction of sdLDL-C and LDL-C was 16.6% and 13%, respectively. These variables decreased >10% in sixteen children (64%), independently from baseline levels, sex, age and body mass index (BMI). High density lipoprotein-cholesterol (HDL-C), lipoprotein a [Lp(a)], and triglycerides (TGs) levels remained unaffected.

Conclusions

Plant sterols decrease sdLDL-C significantly and may be beneficial for children with hypercholesterolemia.

Does a diet high or low in fat influence the oxidation potential of VLDL, LDL and HDL subfractions?

BACKGROUND AND AIMS

High-fat diets have become increasingly popular for weight-loss, but their effect on the oxidation potential of lipoprotein subfractions has not been studied. Therefore, this study compared the effects of high-fat vs. low-fat weight reduction diets on this parameter.

METHODS AND RESULTS

Very-low, low- and high-density lipoprotein (VLDL, LDL & HDL) subfractions were isolated by rapid ultracentrifugation from 24-overweight/obese subjects randomised to a high- or low-fat diet. The lipoprotein subfractions were assessed for oxidation potential by measuring conjugated diene (CD) production and time at half maximum. We found a significant between-group difference in oxidation potential. Specifically, a high-fat diet led to increased CD production in VLDL(A-D) and HDL(2&3), and a prolongation of time at half maximum. Within-group differences found that CDs increased in VLDL(A&D), LDL(I-III) and HDL(2&3) in the high-fat group and fell in VLDL(A-C) and HDL(2&3) and increased in LDL(I&II), in the low-fat group. Furthermore, following both diets all lipoprotein subfractions, except LDL(II) in the low-fat group, were protected against oxidation.

CONCLUSION

These results demonstrate that at first glance, a high-fat diet may be indicative of having heart-protective properties. However, this may be erroneous, as although the time for oxidation to occur was prolonged, once this occurred these lipoproteins had the potential to produce significantly more oxidised substrate. Conversely, a low-fat diet may be considered anti-atherogenic, as these subfractions were protected against oxidation and mainly contained fewer oxidised substrate. Thus, increased fat intake may, by increasing the oxidation product within lipoprotein subfractions, increase cardiovascular disease.

Surrogate lipid markers for small dense low-density lipoprotein particles in overweight youth

OBJECTIVES

To determine if the ratio of triglycerides to high-density lipoprotein cholesterol (TG/HDL) and non-HDL cholesterol concentration could identify youth with small dense low-density lipoprotein (LDL).

STUDY DESIGN

One hundred forty-one (75 black and 66 white) overweight adolescents (9 to <18 years) had a fasting measurement of plasma lipids and LDL particle concentrations and size. Receiver operating characteristic curves were used to indicate the ability of different TG/HDL ratios and non-HDL cholesterol concentrations to identify overweight youth with atherogenic LDL concentration and size.

RESULTS

Youth with a TG/HDL ratio of ≥3 vs <3 had higher concentrations of small dense LDL (1279.5 ± 60.1 vs 841.8 ± 24.2 nmol/L, P < .001) and smaller LDL particle size (20.3 ± 0.1 vs 21.2 ± 0.1 nm, P < .001). In receiver operating characteristic analyses a TG/HDL cut-point of 3 best predicted LDL concentration in white youth, and 2.5 in black youth. Non-HDL cholesterol cut-point of 120 mg/dL and 145 mg/dL predicted LDL particle concentration in white and in black youth, respectively. TG/HDL ratio with body mass index or waist circumference explained 71% and 79% of the variance, respectively, in total small LDL.

CONCLUSIONS

TG/HDL ratio and non-HDL cholesterol can identify overweight youth with atherogenic LDL particles. These easily obtained clinical lipid markers, in combination with body mass index and waist circumference, could be cost effective, in observational or interventional studies, for screening and follow-up of youth at heightened risk for atherogenic LDL.

Prediabetic obese adolescents have a more atherogenic lipoprotein profile compared with normoglycemic obese peers

OBJECTIVE

To compare lipoprotein profiles of prediabetic to normoglycemic obese adolescents.

STUDY DESIGN

Cross-sectional study of 95 obese, pubertal adolescents (12-17 years), who underwent oral glucose tolerance test, lipid panel, and lipoprotein subclass particle analysis (nuclear magnetic resonance spectroscopy). Univariate and linear regression analyses compared prediabetic and normoglycemic groups.

RESULTS

Of 95 obese adolescents enrolled in the study, 22.1% (n = 21) had prediabetes. They were similar to normoglycemic adolescents (n = 74) in age, race, body mass index, standard lipids, total low-density lipoprotein particles (LDL-P), and total high-density lipoprotein particles (HDL-P). However, prediabetics had higher concentrations of small LDL-P (714.0 ± 288.0 vs 537.7 ± 266.5 nmol/L, P = .01) and smaller LDL-P size (20.73 ± 0.41 vs 21.18 ± 0.65 nm, P = .003), than normoglycemic youth. Prediabetics had higher small HDL-P (18.5 ± 3.8 vs 16.6 ± 3.9 umol/L, P = .046), lower large HDL-P (4.49 ± 2.0 vs 6.32 ± 2.6 umol/L, P = .004), and smaller HDL-P size (8.73 ± 0.31 vs 9.01 ± 0.39 nm, P = .003). After adjusting for demographics, Tanner stage, and body mass index using multiple linear regression, all differences remained significant except for small HDL-P. After additional adjustment for Homeostasis Model Assessment-Insulin Resistance Index, only LDL-P size difference remained significant.

CONCLUSION

Obese prediabetic adolescents have a significantly more atherogenic lipoprotein profile compared with obese normoglycemic peers. Prediabetic adolescents may benefit from more aggressive interventions to decrease future cardiovascular risk.

Smaller Mean LDL Particle Size and Higher Proportion of Small Dense LDL in Korean Type 2 Diabetic Patients

BACKGROUND

Small dense low density lipoprotein (sdLDL) has recently emerged as an important risk factor of coronary heart disease.

METHODS

The mean LDL particle size was measured in 203 patients with type 2 diabetes mellitus (T2DM) and 212 matched subjects without diabetes using polyacrylamide tube gel electrophoresis. Major vascular complications were defined as stroke, angiographically-documented coronary artery disease or a myocardial infarction. Peripheral vascular stenosis, carotid artery stenosis (≥50% in diameter) or carotid artery plaque were considered minor vascular complications. Overall vascular complications included both major and minor vascular complications.

RESULTS

Diabetic patients had significantly smaller mean-LDL particle size (26.32 nm vs. 26.49 nm) and a higher percentage of sdLDL to total LDL compared to those of subjects without diabetes (21.39% vs. 6.34%). The independent predictors of sdLDL in this study were serum triglyceride level and body mass index (odds ratio [OR], 1.020 with P<0.001 and OR 1.152 with P<0.027, respectively). However, no significant correlations were found between sdLDL and major vascular complications (P=0.342), minor vascular complications (P=0.573) or overall vascular complications (P=0.262) in diabetic subjects.

CONCLUSION

Diabetic patients had a smaller mean-LDL particle size and higher proportion of sdLDL compared to those of subjects without diabetes. Obese diabetic patients with hypertriglyceridemia have an increased risk for atherogenic small dense LDL. However, we could not verify an association between LDL particle size and vascular complications in this study.

Atherogenic dyslipidemia and cardiovascular risk in children with nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease is now regarded as the most common form of chronic liver disease in adults and children. The close association between nonalcoholic fatty liver disease (NAFLD) and the metabolic syndrome has been extensively described. Moreover, a growing body of evidence suggest that NAFLD by itself confers a substantial cardiovascular risk independent of the other components of the metabolic syndrome. Given the significant potential for morbidity and mortality in these patients, and the large proportion of both pediatric and adult population affected, it is important that we clearly define the overall risk, identify early predictors for cardiovascular disease progression, and establish management strategies. In this article, we will focus on current data linking NAFLD and the severity of liver damage present in children with cardiovascular risk.

Waist circumference, atherogenic lipoproteins, and vascular smooth muscle biomarkers in children

OBJECTIVE

Large waist circumference (WC) is associated with cardiovascular disease and type 2 diabetes. The present study determined differences in lipoprotein particle size and subclass concentration and markers of vascular smooth muscle function in children using WC percentile cutoffs.

RESEARCH DESIGN AND METHODS

Participants were 182 children (87 black, 92 female) aged 8-<18 yr. Each participant had a measurement of WC and a fasting blood draw for the measurement of lipoprotein particle concentration and size and circulating biomarkers of endothelial function. Participants were divided into age-, sex-, and ethnicity-specific WC percentiles of below 75th, 75th to 90th, and at least 90th percentiles, and differences in lipoproteins and vascular smooth muscle markers were compared among groups.

RESULTS

Children in the 90th percentile or higher for WC had significantly smaller low-density lipoprotein and high-density lipoprotein size than children with WC below this percentile. For lipoprotein concentration, small low-density lipoprotein and large very low density lipoprotein and chylomicrons were lower, and large high density lipoprotein concentrations were higher in children whose WC was below the 75th percentile compared with those with WC in the 90th percentile or higher. Concentrations of the vascular smooth muscle biomarkers, intercellular adhesion molecule-1, and E-selectin were significantly higher in children with WC in the 90th percentile or higher than in children below the 75th percentile.

CONCLUSION

Youths with WC in the 90th percentile or higher have an atherogenic lipoprotein profile with increased concentrations of biomarkers of vascular smooth muscle dysfunction. Given that atherosclerosis begins in childhood, such evidence suggests that these children should be targeted for interventions to reduce adiposity at an early age.

In vivo insulin sensitivity and lipoprotein particle size and concentration in black and white children

OBJECTIVE

To examine sex-specific black/white differences in lipoprotein profile and the role of visceral adiposity and to assess the relationship between insulin sensitivity and lipoprotein profiles in each group.

RESEARCH DESIGN AND METHODS

Fasting lipoprotein particle size and concentration and visceral adipose tissue (VAT) were determined in 226 children (117 black, 101 male) aged 8 to <18 years. The relationship between lipoproteins and insulin sensitivity was evaluated in a subset of 194 children (100 black, 88 male) who underwent a hyperinsulinemic-euglycemic clamp.

RESULTS

Black male children had smaller VLDL and black female children had larger HDL size than their white counterparts. Overall, blacks had larger LDL size with no sex-specific race differences. After adjusting for VAT and sex, only VLDL size and concentrations remained significantly favorable in blacks. Analysis of lipoprotein particle size and concentration across insulin sensitivity quartiles revealed that in both racial groups, the most insulin-resistant children had higher concentrations of small dense LDL, small HDL, and large VLDL and smaller LDL and HDL sizes than their more insulin-sensitive counterparts.

CONCLUSIONS

The previously reported favorable lipoprotein profiles in black versus white children is partly due to race differences in VAT. In both groups, however, the most insulin-resistant youths have a high-risk atherogenic profile of small dense LDL, small HDL, and large VLDL, akin to the atherogenic lipoprotein pattern in adults with coronary artery disease.

Characterization of metabolic interrelationships and in silico phenotyping of lipoprotein particles using self-organizing maps

Plasma lipid concentrations cannot properly account for the complex interactions prevailing in lipoprotein (patho)physiology. Sequential ultracentrifugation (UCF) is the gold standard for physical lipoprotein isolations allowing for subsequent analyses of the molecular composition of the particles. Due to labor and cost issues, however, the UCF-based isolations are usually done only for VLDL, LDL, and HDL fractions; sometimes with the addition of intermediate density lipoprotein (IDL) particles and the fractionation of HDL into HDL(2) and HDL(3) (as done here; n = 302). We demonstrate via these data, with the lipoprotein lipid concentration and composition information combined, that the self-organizing map (SOM) analysis reveals a novel data-driven in silico phenotyping of lipoprotein metabolism beyond the experimentally available classifications. The SOM-based findings are biologically consistent with several well-known metabolic characteristics and also explain some apparent contradictions. The novelty is the inherent emergence of complex lipoprotein associations; e.g., the metabolic subgrouping of the associations between plasma LDL cholesterol concentrations and the structural subtypes of LDL particles. Importantly, lipoprotein concentrations cannot pinpoint lipoprotein phenotypes. It would generally be beneficial to computationally enhance the UCF-based lipoprotein data as illustrated here. Particularly, the compositional variations within the lipoprotein particles appear to be a fundamental issue with metabolic and clinical corollaries.

Tracking and determinants of LDL particle size in healthy children from 7 to 11 years of age: the STRIP Study

Serum low-density lipoprotein (LDL) particle composition varies according to lifestyle and age. To analyze its long-term tracking, we studied LDL particle size consecutively in 100 children at the ages of 7, 9 and 11 years using a high-resolution 3% polyacrylamide gel tube, electrophoresis method, searching also for long-term determinants of the particle size. The mean LDL particle sizes at 7 and 9 years, and at 7 and 11 years correlated directly (r=0.72 and 0.39, respectively). The probability that children would remain in the same LDL particle size tertile between 7 and 11 years of age was 48% (p=0.008). Longitudinally, total, high-density lipoprotein (HDL) and LDL cholesterol concentrations and body mass index (BMI) associated directly with mean LDL particle size, and triglyceride concentration and triglyceride/HDL cholesterol ratio correlated inversely. A shift from pre-puberty to puberty was associated with an increase in LDL particle size. Sex, serum insulin concentration, or energy nutrient intakes did not associate with LDL particle size. In conclusion, although mean LDL particle size tracks in 7- to 11-year-old healthy children, changes in serum triglycerides, HDL, LDL, and total cholesterol concentration, BMI, and pubertal status all modify LDL particle size.

Metabolic syndrome and dyslipidemia in youth

Obesity is a well-known risk factor for metabolic syndrome. Although the cause or causes of metabolic syndrome are debated, insulin resistance, dyslipidemia, and hypertension are increasingly recognized in children and adolescents, especially those who are overweight or obese. Although adoption of a healthy lifestyle early in life offers the best long-term solution, many children and adolescents are currently at risk for future cardiovascular disease. Although long-term outcome data are lacking, the dyslipidemic triad commonly seen in youth with metabolic syndrome (elevated triglycerides, low high-density lipoprotein, and small dense low-density lipoprotein) is likely to significantly contribute to future vascular disease. Surrogate markers (carotid intima-media thickness and flow-mediated vasodilatation) for the precursors of cardiovascular disease are increased in obese youth, consistent with early vascular damage. In this work, we review the features of metabolic syndrome in children and adolescents, including age- and gender-specific norms for lipid values. Diagnostic criteria and modifications of screening guidelines unique to youth are discussed. Although recommendations for lifestyle modification are suggested for all, many youth at high risk of future cardiovascular risk may need more aggressive medical interventions to improve insulin sensitivity, achieve a less atherogenic lipid profile, and lower blood pressure.

Low-density lipoprotein sub-fraction profiles in obese children before and after attending a residential weight loss intervention

AIM

Small dense LDL particles are associated with an increased risk of coronary heart disease and are prevalent in obesity related dyslipidaemia. This study evaluated the effect of weight loss in nine children (BMI 33.4 +/- 8.4 kg.m(-2) and age 15.1 +/- 2.9 years) on LDL peak particle size, and cholesterol concentrations within particular LDL sub-fractions.

METHODS

Each child undertook fun based physical activity, dietary restriction and modification and lifestyle education classes in a residential summer weight loss intervention. Blood was drawn before and after intervention and LDL heterogeneity measured by ultracentrifugation.

RESULTS

The mean change in body weight were -6.8 +/- 4.9 kg, BMI units -2.5 +/- 1.4 kg.m(-2), and waist circumference -6.3 +/- 6.3 cm (all p < 0.01). Absolute LDL-c concentration reduced from 106.2 mg/dL to 88.3 mg/dL (p < 0.01). The cholesterol contained within the small dense LDL sub-fraction (LDL-c III) reduced from 54.1 mg/dL to 40.4 mg/dL (p < 0.01). Peak particle density decreased from 1.041g/mL to 1.035g/mL (p < 0.01). At pre intervention 50.9% of absolute cholesterol was within LDL-c III particles, changing to 46.2%.

CONCLUSION

Mean weight loss of -6.8 +/- 4.9 kg lowers absolute LDL-c and the cholesterol specifically within LDL-c III particles. LDL peak particle size increased and a degree of LDL particle remodelling occurred. These favourable adaptations, accrued in a matter of 4 weeks, maybe associated with a reduction in CHD risk.

Intrahepatic fat accumulation and alterations in lipoprotein composition in obese adolescents: a perfect proatherogenic state

OBJECTIVE

Among other metabolic consequences, a dyslipidemic profile often accompanies childhood obesity. In adults, type 2 diabetes and hepatic steatosis have been shown to alter lipoprotein subclass distribution and size; however, these alterations have not yet been shown in children or adolescents. Therefore, our objective was to determine the effect of hepatic steatosis on lipoprotein concentration and size in obese adolescents.

RESEARCH DESIGN AND METHODS

Using fast magnetic resonance imaging, we measured intrahepatic fat content in 49 obese adolescents with normal glucose tolerance. The presence or absence of hepatic steatosis was determined by a threshold value for hepatic fat fraction (HFF) of 5.5%; therefore, the cohort was divided into two groups (HFF > or <5.5%). Fasting lipoprotein subclasses were determined using nuclear magnetic resonance spectroscopy.

RESULTS

Overall, the high-HFF group had 88% higher concentrations of large VLDL compared with the low-HFF group (P < 0.001). Likewise, the high-HFF group had significantly higher concentrations of small dense LDL (P < 0.007); however, the low-HFF group had significantly higher concentrations of large HDL (P < 0.001). Stepwise multiple regression analysis revealed that high HFF was the strongest single correlate, accounting for 32.6% of the variance in large VLDL concentrations (P < 0.002).

CONCLUSIONS

The presence of fatty liver was associated with a pronounced dyslipidemic profile characterized by large VLDL, small dense LDL, and decreased large HDL concentrations. This proatherogenic phenotype was strongly related to the intrahepatic lipid content.

Factors influencing the formation of small dense low-density lipoprotein particles in dependence on the presence of the metabolic syndrome and on the degree of glucose intolerance

BACKGROUND

Small dense low-density lipoprotein (LDL) particles are known to be especially atherogenic. Several mechanisms are involved in this atherogenicity.

AIMS

We wanted to look for the presence of small dense LDL particles depending on gender, metabolic syndrome (MS) and different degrees of glucose intolerance. Moreover, we looked for anthropometric factors and factors of lipid and carbohydrate metabolism that are associated with changes in the LDL size.

RESULTS

We studied 752 persons (330 males, 422 females; age 40 +/- 17 years). LDL particle size was estimated with polyacrylamide gel electrophoresis. Males had smaller LDL particles than females. Probands with the MS had smaller LDL particles than those without this syndrome. With rising plasma triglyceride (TG) levels more small dense LDL particles were seen. The highest proportion of these small dense LDL particles was observed in the subgroup of type 2 diabetic patients. In the whole material, the mean LDL diameter was correlated negatively with plasma TG and very low-density lipoprotein components (TG, cholesterol and proteins) and positively with high-density lipoprotein cholesterol. In a linear stepwise regression analysis different significant factors influencing the LDL size were found in the whole population, in normoglycaemic probands, in persons with impaired glucose tolerance, in type 2 diabetic patients and in type 2 diabetic patients injecting insulin.

CONCLUSIONS

Our data point to different mechanisms of the formation of small dense LDL particles in dependence on the degree of glucose intolerance. Moreover, the target values for plasma TG should be set lower.

Fructose intake is a predictor of LDL particle size in overweight schoolchildren

BACKGROUND

High amounts of dietary fructose may contribute to dyslipidemia in adults, but there are few data in children. Childhood adiposity is associated with smaller LDL particle size, but the dietary predictors of LDL size in overweight children have not been studied.

OBJECTIVES

We aimed to determine whether LDL particle size is associated with dietary factors and specifically with fructose intake in normal-weight and overweight children.

DESIGN

In a cross-sectional study of normal-weight and overweight 6-14 y-old Swiss children (n = 74), dietary intakes were assessed by using two 24-h-recalls and a 1-d dietary record. Body mass index (BMI) and waist-hip ratio (WHR) were measured, and plasma lipid profile and LDL particle size were determined.

RESULTS

Compared with the normal-weight group, overweight children had significantly higher plasma triacylglycerol concentrations, lower HDL-cholesterol concentrations, and smaller LDL particle size (P < 0.05). LDL particle size was inversely correlated to BMI SD scores and WHR (P = 0.007). Although there were no significant differences in total fructose intake, the overweight children consumed a significantly (P < 0.05) higher percentage of fructose from sweets and sweetened drinks than did the normal-weight children. After control for adiposity, the only dietary factor that was a significant predictor of LDL particle size was total fructose intake (P = 0.024).

CONCLUSIONS

In school-age children, greater total and central adiposity are associated with smaller LDL particle size and lower HDL cholesterol. Overweight children consume more fructose from sweets and sweetened drinks than do normal-weight children, and higher fructose intake predicts smaller LDL particle size.

Anthropometric Determinants of a Clustering of Lipid-Related Metabolic Risk Factors in Overweight and Non-Overweight Adolescents – Influence of Cardiorespiratory Fitness

BACKGROUND/AIMS

To explore in adolescents the associations between simple anthropometric variables with a continuously distributed summary score for lipid-related metabolic risk in both overweight and non-overweight adolescents, and to test whether these associations are modified by the level of cardiorespiratory fitness.

METHODS

Cardiorespiratory fitness, BMI, skinfold thicknesses, body circumferences, and a continuously distributed clustering of lipid- related metabolic risk (calculated from LDL and HDL cholesterol, triglycerides, and glucose) were measured in 524 adolescents (265 males, 259 females, 15.3 +/- 1.4 years) from the cross-sectional multicentric AVENA study. Participants were classified as overweight (including obesity) or non-overweight.

RESULTS

Most anthropometric parameters were univariately related to the continuous lipid-related metabolic risk. However, after multicollinear analysis and generalized linear modelling, suprailiac skinfold thickness in males (p < 0.001, explained variance 12.2%) and waist-to-height ratio in females (p < 0.001, explained variance 10.0%) were the best determinants of the continuous metabolic risk score, after adjustment for age, sexual maturation, and economic status. These associations were slightly weakened in overweight males (p = 0.034) and females (p = 0.087), and did not interact with cardiorespiratory fitness.

CONCLUSION

Our data emphasize the usefulness of suprailiac skinfold thickness in males and waist-to-height ratio in females as simple anthropometric measurements associated to an overall lipid-related metabolic risk, mainly in non-overweight adolescents and regardless their cardiorespiratory status.

Clinical importance and therapeutic modulation of small dense low-density lipoprotein particles

The National Cholesterol Education Programme Adult Treatment Panel III accepted the predominance of small dense low-density lipoprotein (sdLDL) as an emerging cardiovascular disease (CVD) risk factor. Most studies suggest that measuring low-density lipoprotein (LDL) particle size, sdLDL cholesterol content and LDL particle number provides additional assessment of CVD risk. Therapeutic modulation of small LDL size, number and distribution may decrease CVD risk; however, no definitive causal relationship is established, probably due to the close association between sdLDL and triglycerides and other risk factors (e.g., high-density lipoprotein, insulin resistance and diabetes). This review addresses the formation and measurement of sdLDL, as well as the relationship between sdLDL particles and CVD. The effect of hypolipidaemic (statins, fibrates and ezetimibe) and hypoglycaemic (glitazones) agents on LDL size and distribution is also discussed.

LDL particle size, fat distribution and insulin resistance in obese children

BACKGROUND

The importance of small dense low-density lipoprotein (sdLDL) cholesterol in coronary heart disease has been demonstrated in many studies. Body fat accumulation, especially abdominal adiposity, is one of the important factors modifying the expression of sdLDL in adults.

OBJECTIVE

To determine the prevalence of sdLDL in obese children, and to investigate its relationship with anthropometric and metabolic variables.

SUBJECTS

A total of 30 obese children (22 males, 8 females) aged 12.6+/-0.6 years (mean+/-s.e.), who presented to our outpatient clinic with obesity.

METHODS

LDL peak particle diameter was determined using gel electrophoresis. LDL subclasses were classified into sdLDL (pattern B; diameter<25.5 nm) and non-sdLDL (pattern A; diameter>or=25.5 nm). Anthropometric and metabolic variables were also determined to identify factors modifying LDL particle size.

RESULTS

sdLDL was detected in 11 children (40.0%). In children with sdLDL, waist/height ratio was significantly higher (P=0.0466), and they had significantly higher triglyceride (TG) (P=0.0035) and lower high-density lipoprotein cholesterol (HDLC) levels (P=0.036). Peak LDL diameter as a continuous variable was significantly correlated with HDLC and TG levels. In multiple regression analysis, body mass index and waist/height ratio were significant determinants of the peak LDL diameter variability.

CONCLUSIONS

We found a high prevalence of sdLDL in obese children, and a relationship of peak LDL diameter with abdominal fat accumulation, HDLC and TG levels. The presence of sdLDL might be an important risk factor for the metabolic syndrome.

The metabolic syndrome: prevalence, CHD risk, and treatment

An increased risk of coronary heart disease (CHD) morbidity and mortality is associated with the metabolic syndrome, a condition characterized by the concomitant presence of several abnormalities, including abdominal obesity, dyslipidemia, hypertension, insulin resistance (with or without glucose intolerance or diabetes), microalbuminuria, prothrombotic, and proinflammatory states. Estimates of the prevalence of the metabolic syndrome indicate that this condition is now common and likely to increase dramatically over the coming decades, in parallel with greater rates of obesity and Type 2 diabetes. Risk factors for the metabolic syndrome are already present in obese children and adolescents. Thus, identifying and treating all affected individuals promptly and optimally are critical to ensure that this potentially challenging healthcare burden is minimized. Here, we review the prevalence of the metabolic syndrome, dyslipidemias, and CHD risk. Although changes in lifestyle are fundamental to reducing many of the CHD risk factors associated with the metabolic syndrome, pharmacologic interventions also play an important role. Retrospective subanalyses of the effects of statins on coronary event rates and lipid levels in patients with the metabolic syndrome included in clinical trials indicate that these agents are beneficial in correcting the extensive lipid abnormalities that are frequently present in these individuals. However, the optimal management of metabolic syndrome dyslipidemia will depend on the outcomes of future prospective clinical trials. This review examines the underlying causes and prevalence of the metabolic syndrome and its impact on CHD morbidity and mortality and discusses the role of statins in optimizing its management.

Visceral Adiposity and Apolipoprotein C-III in Apolipoprotein B-Containing Lipoproteins Are Independent Predictors in Determining Atherogenic Lipid Profiles

BACKGROUND/AIMS

Little is known about how visceral adiposity and apolipoprotein CIII in apoB-containing lipoproteins influence atherogenic lipids profiles. The purpose of this study was to determine the relationships of visceral adiposity and apoC-III in apoB-containing lipoproteins (LpB:C-III) with lipoprotein lipids in circulating plasma.

METHODS

A subgroup of 46 men (n = 20, aged 29.1-33.4 years) and women (n = 26, aged 29.1-33.8 years) were recruited from an ongoing population study at our institution. Anthropometric variables including weight, height, and waist circumference were measured using standard procedures, and body mass index was calculated (kg/m(2)). Visceral adipose tissue (VAT) was measured with magnetic resonance imaging. Plasma apolipoproteins, lipids, glucose, and insulin were measured after an overnight fasting.

RESULTS

The men had a significantly higher waist circumference, glucose, and TC/HDL-C ratio, while the women had a significantly higher HDL-C and apoA-I. In particular, this is the first study to report that VAT and LpB:C-III were independent predictors in determining plasma triglyceride concentrations.

CONCLUSION

The relations of plasma triglyceride concentration with VAT and LpB:C-III suggest that information on VAT and apoC-III in apoB-containing lipoproteins may provide additional information on the atherogenic lipid profiles.

Common set of genes regulates low-density lipoprotein size and obesity-related factors in Alaskan Eskimos: Results from the GOCADAN Study

Increasing incidence of cardiovascular disease in traditionally low-risk Alaskan Eskimos is a cause for concern. The purpose of this study was to examine the genetic and environmental correlations of low-density lipoprotein (LDL) subfractions with obesity-related factors in Alaskan Eskimos, using data from the first 954 participants of the Genetics of Coronary Artery Disease in Alaska Natives Study. Estimates of genetic and environmental influence were calculated using a maximum likelihood variance component method implemented in SOLAR. Mean values of weight, body mass index (BMI), and waist were 73.4 +/- 0.5 kg, 27.6 +/- 0.2 kg/m2, and 88.0 +/- 0.4 cm, respectively. LDL, and its small (LDL1), medium (LDL2), and large (LDL3) subfractions, had mean values of 115.8 +/- 1.2 mg/dl, 8.3 +/- 0.4 mg/dl, 19.6 +/- 0.8 mg/dl, and 71.5 +/- 1.5 mg/dl, respectively. Bivariate analysis displayed significant genetic correlations between LDL subfractions and obesity-related factors: LDL1 with BMI (rhoG = 0.67, P < 0.05), waist (rhoG = 0.80, P < 0.001), and subscapular and tricep skinfolds (rhoG = 0.93, P < 0.005, and rhoG = 0.78, P < 0.05, respectively); LDL2 with BMI (rhoG = 0.52, P < 0.05), waist (rhoG = 0.46, P < 0.05), and tricep skinfold (rhoG = 0.60, P < 0.05); and mean LDL size with BMI (rhoG = -0.36), waist (rhoG = -0.42,), and subscapular and tricep skinfolds (rhoG = -0.44 and -0.43, respectively) (P < 0.005). These results show that a common set of genes is influencing LDL size and obesity-related factors in Alaskan Eskimos.

Threshold values of visceral fat and waist girth in Japanese obese children

BACKGROUND

In order to define the diagnostic criteria for visceral adipose tissue (VAT) accumulation and abdominal obesity in Japanese youths, a cross-sectional, multicenter study was conducted.

METHODS

Subjects were 194 boys and 96 girls ranging in age from 6 to 15 years. Obese youths were classified according to the occurrence of abnormal values in serum triglyceride, alanine aminotransferase or insulin level. A threshold value of each criterion was calculated, using the analysis of receiver operating characteristic (ROC) curve. The areas of total abdominal adipose tissue (AT), VAT and subcutaneous adipose tissue (SAT) were estimated by single slice computed tomography at the level of umbilicus.

RESULTS

VAT area was greater in boys than it was in girls. The critical values for VAT area and waist circumference in all subjects were 54.8 cm2 and 83.5 cm, respectively. The values for the area under the ROC curves were VAT area > total AT area > waist circumference > SAT area > percentage overweight > percentage body fat. The sensitivity and specificity for VAT area were 90.5 and 79.5%, respectively. Those for waist circumference were high enough (> 70%) for clinical use. In the linear regression analysis assigning VAT area as an independent variable and waist circumference as a dependent variable, the expected value for the waist circumference was 82 cm.

CONCLUSION

In Japanese obese youths ranging in age from 6 to 15 years, the diagnostic criteria for the waist circumference was 82 cm, and that for VAT area was 55 cm2.

Relations of body fatness and cardiovascular fitness to lipid profile in black and white adolescents

High body fatness is associated with unfavorable cardiovascular disease risk profiles in juveniles. However, the degree to which the deleterious effects attributed to fatness may actually be due to the low cardiovascular fitness (CVF) that is usually confounded with fatness is not known. This study determined in 14- to 18-y-old (n = 398) youths the degree to which percentage body fat (%BF) and CVF explained variability in lipids and lipoproteins. Blood samples were taken after a 12-h fast. %BF was measured with dual-energy x-ray absorptiometry. CVF was determined with a multistage treadmill test. The degree to which %BF and CVF explained variance in outcome variables was determined by regression analyses, controlling for demographic variables before entering %BF or CVF and their interactions with race and sex. Because %BF and CVF were highly correlated (r = -0.69, p < 0.001), they were first entered separately in the regression models before being considered together. Both higher %BF and lower CVF were associated with unfavorable concentrations of total cholesterol to HDLC ratio and triglycerides. However, the effects of %BF and CVF were not additive; once %BF was in the regression model, CVF did not explain additional variance. For Lp(a), only %BF explained a significant portion of the variance. For triglycerides, there was a %BF by race interaction, such that the deleterious effects of high %BF were greater in whites than in blacks. These results suggest that interventions to improve lipid profile in youths should be designed primarily to minimize fatness.

Distribution of LDL particle size in a population-based sample of children and adolescents and relationship with other cardiovascular risk factors

BACKGROUND

Smaller, denser LDL particles are associated with an increased risk for cardiovascular diseases (CVD). In youths, data on the distribution of LDL particle size and on its association with other CVD risk factors are limited.

METHODS

We determined LDL peak particle size by nondenaturing 2%-16% gradient gel electrophoresis in a representative sample of 2249 youths 9, 13, and 16 years of age who participated in a school-based survey conducted in 1999 in the province of Quebec, Canada. Standardized clinical measurements and fasting plasma lipid, glucose, and insulin concentrations were available.

RESULTS

The LDL peak particle size distribution was gaussian. The 5th, 50th (median), and 95th percentiles by age and sex were 255.5-258.6, 262.1-263.2, and 268.1-269.5 A, respectively. The prevalence of the small, dense LDL phenotype (LDL peak particle size <or=255 A) was 10% in participants with insulin resistance syndrome (IRS), in contrast to 1% in those without IRS. In a multiple regression analysis, the association of LDL size with other CVD risk factors [apolipoprotein B, HDL-cholesterol (HDL-C), triglyceride (TG), and insulin concentrations, and body mass index] was strongest with TG and HDL-C concentrations: a 1 SD increase in log(e)-transformed TG concentration was associated with a 1.2 A reduction in LDL size, and a 1 SD increase in HDL-C was associated with a 1.1 A increase in LDL size.

CONCLUSIONS

Although the small, dense LDL phenotype is less prevalent in youths than adults, its prevalence is clearly increased in childhood IRS. Metabolic correlates of LDL size are similar in youths and adults.

A randomized study comparing the effects of a low-carbohydrate diet and a conventional diet on lipoprotein subfractions and C-reactive protein levels in patients with severe obesity

PURPOSE

To compare the effects of a low-carbohydrate diet and a conventional (fat- and calorie-restricted) diet on lipoprotein subfractions and inflammation in severely obese subjects.

METHODS

We compared changes in lipoprotein subfractions and C-reactive protein levels in 78 severely obese subjects, including 86% with either diabetes or metabolic syndrome, who were randomly assigned to either a low-carbohydrate or conventional diet for 6 months.

RESULTS

Subjects on a low-carbohydrate diet experienced a greater decrease in large very low-density lipoprotein (VLDL) levels (difference = -0.26 mg/dL, P = 0.03) but more frequently developed detectable chylomicrons (44% vs. 22%, P = 0.04). Both diet groups experienced similar decreases in the number of low-density lipoprotein (LDL) particles (difference = -30 nmol/L, P = 0.74) and increases in large high-density lipoprotein (HDL) concentrations (difference = 0.70 mg/dL, P = 0.63). Overall, C-reactive protein levels decreased modestly in both diet groups. However, patients with a high-risk baseline level (>3 mg/dL, n = 48) experienced a greater decrease in C-reactive protein levels on a low-carbohydrate diet (adjusted difference = -2.0 mg/dL, P = 0.005), independent of weight loss.

CONCLUSION

In this 6-month study involving severely obese subjects, we found an overall favorable effect of a low-carbohydrate diet on lipoprotein subfractions, and on inflammation in high-risk subjects. Both diets had similar effects on LDL and HDL subfractions.

Apolipoprotein C-III SstI genotypes modulate exercise-induced hypotriglyceridemia

PURPOSE

To investigate whether the efficacy of exercise as an antitriglyceridemic treatment was dependent on the apolipoprotein (apo) C-III SstI gene polymorphism.

METHODS

A subgroup of 100 Korean men, who were prescreened by genotypes (S1S1 = 40, S1S2 = 40, S2S2 = 20), participated in a 6-d moderate-exercise intervention using either a motor-driven treadmill or a cycle ergometer. Height and weight for body mass index and waist circumference were measured. Fasting total cholesterol, triglycerides (TG), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, glucose, and insulin were measured. Univariate analysis of variance and ANCOVA followed by Bonferroni post hoc tests were used to compare the preintervention values and the pre- to postexercise change (delta) scores in the measured variables across the genotypes, respectively. Multivariate linear regressions were carried out with age, smoking, waist circumference, body mass index, and genotype as independent variables and lipids, glucose, and insulin as dependent variables.

RESULTS

Subjects with the S2S2 genotype had a significantly higher preintervention TG concentration than subjects with the S1S1 genotype (P = 0.022). Waist circumference and genotype were the only significant predictors for the preintervention TG (P < 0.001). With respect to the delta scores, the subjects with the S2S2 genotype had a greater reduction in TG than the subjects with the S1S1 genotype, adjusted for the preintervention difference (P = 0.047).

CONCLUSION

This study suggests that the apo C-III SstI gene polymorphism might be useful for determining who is most susceptible to intervention by exercise in lowering fasting TG concentration.

Insulin resistance: from predisposing factor to therapeutic target in type 2 diabetes

BACKGROUND

Insulin resistance contributes to the pathogenesis of type 2 diabetes and is closely linked with cardiovascular risk factors and premature cardiovascular disease.

OBJECTIVE

The purpose of this paper was to review the importance of insulin resistance as a core defect in type 2 diabetes, a potential contributor to accelerated atherosclerosis, and a potential target for insulin-sensitizing agents.

METHODS

Articles considered for inclusion in this review were identified through a search of MEDLINE/PubMed for reports published from 1966 to April 2003. Search terms used were insulin resistance, diabetes, insulin sensitivity, obesity, cardiovascular disease, metformin, thiazolidinediones, pioglitazone, rosiglitazone, and troglitazone.

RESULTS

An overview of the epidemiology, natural history, and pathophysiology of type 2 diabetes is provided, with a focus on insulin resistance and a related discussion of the impact of current therapies used to treat insulin-resistant patients. In particular, information on insulin-sensitizing agents-metformin and the currently available thiazolidinediones (TZDs), pioglitazone and rosiglitazone-is presented. Although metformin has been shown to indirectly reduce insulin resistance, TZDs are the only available agents that have been shown to directly lower insulin resistance.

CONCLUSIONS

Recent evidence indicates that metformin, pioglitazone, and rosiglitazone may improve the dyslipidemic profile, reduce vascular inflammation, and improve endothelial dysfunction, all of which may be particularly important to physicians seeking treatment options to prevent or reduce cardiovascular complications in patients with type 2 diabetes.