Relation of LDL size to the insulin resistance syndrome and coronary heart disease in American Indians. The Strong Heart Study

Association between atherogenic index of plasma control level and incident cardiovascular disease in middle-aged and elderly Chinese individuals with abnormal glucose metabolism

BACKGROUND

The atherogenic index of plasma (AIP) and cardiovascular disease (CVD) in participants with abnormal glucose metabolism have been linked in previous studies. However, it was unclear whether AIP control level affects the further CVD incidence among with diabetes and pre-diabetes. Therefore, our study aimed to investigate the association between AIP control level with risk of CVD in individuals with abnormal glucose metabolism.

METHODS

Participants with abnormal glucose metabolism were included from the China Health and Retirement Longitudinal Study. CVD was defined as self-reporting heart disease and/or stroke. Using k-means clustering analysis, AIP control level, which was the log-transformed ratio of triglyceride to high-density lipoprotein cholesterol in molar concentration, was divided into five classes. The association between AIP control level and incident CVD among individuals with abnormal glucose metabolism was investigated multivariable logistic regression analysis and application of restricted cubic spline analysis.

RESULTS

398 (14.97%) of 2,659 participants eventually progressed to CVD within 3 years. After adjusting for various confounding factors, comparing to class 1 with the best control of the AIP, the OR for class 2 with good control was 1.31 (95% CI, 0.90-1.90), the OR for class 3 with moderate control was 1.38 (95% CI, 0.99-1.93), the OR for class 4 with worse control was 1.46 (95% CI, 1.01-2.10), and the OR for class 5 with consistently high levels was 1.56 (95% CI, 1.03-2.37). In restricted cubic spline regression, the relationship between cumulative AIP index and CVD is linear. Further subgroup analysis demonstrated that the similar results were observed in the individuals with agricultural Hukou, history of smoking, diastolic blood pressure ≥ 80mmHg, and normal body mass index. In addition, there was no interaction between the AIP control level and the subgroup variables.

CONCLUSIONS

In middle-aged and elderly participants with abnormal glucose metabolism, constant higher AIP with worst control may have a higher incidence of CVD. Monitoring long-term AIP change will contribute to early identification of high risk of CVD among individuals with abnormal glucose metabolism.

Immunization with the Gly1127-Cys1140 amino acid sequence of the LRP1 receptor reduces atherosclerosis in rabbits. Molecular, immunohistochemical and nuclear imaging studies

Background: The LRP1 (CR9) domain and, in particular, the sequence Gly¹¹²⁷-Cys¹¹⁴⁰ (P3) plays a critical role in the binding and internalization of aggregated LDL (agLDL). We aimed to evaluate whether immunization with P3 reduces high-fat diet (HFD)-induced atherosclerosis. Methods: Female New Zealand White (NZW) rabbits were immunized with a primary injection and four reminder doses (R1-R4) of IrP (irrelevant peptide) or P3 conjugated to the carrier. IrP and P3-immunized rabbits were randomly divided into a normal diet group and a HFD-fed group. Anti-P3 antibody levels were determined by ELISA. Lipoprotein profile, circulating and tissue lipids, and vascular pro-inflammatory mediators were determined using standardized methods while atherosclerosis was determined by confocal microscopy studies and non-invasive imaging (PET/CT and Doppler ultrasonography). Studies treating human macrophages (hMΦ) and coronary vascular smooth muscle cells (hcVSMC) with rabbit serums were performed to ascertain the potential impact of anti-P3 Abs on the functionality of these crucial cells. Results: P3 immunization specifically induced the production of anti-P3 antibodies (Abs) and did not alter the lipoprotein profile. HFD strongly induced cholesteryl ester (CE) accumulation in the aorta of both the control and IrP groups, and their serum dose-dependently raised the intracellular CE of hMΦ and hcVSMC, promoting TNFR1 and phospho-NF-kB (p65) overexpression. These HFD pro-inflammatory effects were dramatically decreased in the aorta of P3-immunized rabbits and in hMΦ and hcVSMC exposed to the P3 rabbit serums. Microscopy studies revealed that P3 immunization reduced the percentage of lipids, macrophages, and SMCs in the arterial intima, as well as the atherosclerotic extent and lesion area in the aorta. PET/CT and Doppler ultrasonography studies showed that the average standardized uptake value (SUV_mean) of the aorta and the arterial resistance index (ARI) of the carotids were more upregulated by HFD in the control and IrP groups than the P3 group. Conclusions: P3 immunization counteracts HFD-induced fatty streak formation in rabbits. The specific blockade of the LRP1 (CR9) domain with Anti-P3 Abs dramatically reduces HFD-induced intracellular CE loading and harmful coupling to pro-inflammatory signaling in the vasculature.

Genetic associations with lipoprotein subfraction measures differ by ethnicity in the multi-ethnic study of atherosclerosis (MESA)

A recent genome-wide association study associated 62 single nucleotide polymorphisms (SNPs) from 43 genomic loci, with fasting lipoprotein subfractions in European–Americans (EAs) at genome-wide levels of significance across three independent samples. Whether these associations are consistent across ethnicities with a non-European ancestry is unknown. We analyzed 15 lipoprotein subfraction measures, on 1677 African–Americans (AAs), 1450 Hispanic–Americans (HAs), and 775 Chinese–Americans (CHN) participating in the multi-ethnic study of atherosclerosis (MESA). Genome-wide data were obtained using the Affymetrix 6.0 and Illumina HumanOmni chips. Linear regression models between genetic variables and lipoprotein subfractions were adjusted for age, gender, body mass index, smoking, study center, and genetic ancestry (based on principal components), and additionally adjusted for Mexican/Non-Mexican status in HAs. A false discovery rate correction was applied separately within the results for each ethnicity to correct for multiple testing. Power calculations revealed that we did not have the power for SNP-based measures of association, so we analyzed phenotype-specific genetic risk scores (GRSs), constructed as in the original genome-wide analysis. We successfully replicated all 15 GRS–lipoprotein associations in 2527 EAs. Among the 15 significant GRS–lipoprotein associations in EAs, 11 were significant in AAs, 13 in HAs, and 1 in CHNs. Further analyses revealed that ethnicity differences could not be explained by differences in linkage disequilibrium, lipid lowering drugs, diabetes, or gender. Our study emphasizes the importance of ethnicity (here indexing genetic ancestry) in genetic risk for CVD and highlights the need to identify ethnicity-specific genetic variants associated with CVD risk.

Pioglitazone reduces atherogenic dense low density lipoprotein (LDL) particles in patients with type 2 diabetes mellitus

Aim The new oral antidiabetic agent pioglitazone improves insulin sensitivity and glycaemic control, lowers triglycerides and increases high density lipoprotein (HDL) cholesterol in type 2 diabetes. The effect of pioglitazone on low density lipoprotein (LDL) subfractions is investigated, herein.

Methods The effect of pioglitazone monotherapy (45 mg o.d. for six months) on LDL subfractions was observed in 30 patients with poorly controlled type 2 diabetes (HbA1C ≥ 7.5% and < 11.5% and triglycerides ≥ 150 mg/dL). The distribution of LDL subfractions was determined by equilibrium density gradient ultracentrifugation before and during treatment.

Results HbA1C (9.5% before and 7.4% on treatment, p<0.001), triglycerides (-135 mg/dL [-32.2%], p=0.002) and apo B in LDL-6 (the most dense LDL subfraction) decreased significantly. The mean diameter of LDL particles increased (19.5 nm before and 19.8 nm on treatment, p=0.005), while the mean LDL density decreased significantly (from 1.0394 kg/L to 1.0381 kg/L on treatment; p=0.033). HDL increased from 36.3 mg/dL to 44.2 mg/dL (+ 21.6%, p<0.001). Total cholesterol and LDL-cholesterol did not change significantly.

Conclusions The results confirm that pioglitazone improves glycaemic control in patients with type 2 diabetes. In addition, pioglitazone reduced the proportion of atherogenic dense LDL. The effects of pioglitazone on lipoprotein metabolism may translate into a reduced risk for atherosclerotic complications in type 2 diabetes.

Genetics of non-conventional lipoprotein fractions

Lipoprotein subclass measures associate with cardiometabolic disease risk. Currently the information that lipoproteins convey on disease risk over that of traditional demographic and lipid measures is minimal, and so their use is clinics is limited. However, lipoprotein subclass perturbations represent some of the earliest manifestations of metabolic dysfunction, and their etiology is partially distinct from lipids, so information on the genetic etiology of lipoproteins offers promise for improved risk prediction, and unique mechanistic insights into IR and atherosclerosis. Here, I review the genetic variants validated as associating with lipoprotein measures to date, and show that the majority of identified variants have functionality that is best understood as related to lipid measures. Until we focus on the genes as they relate to lipoprotein subclass production, we are limiting our understanding of biological mechanisms underlying cardiometabolic disease.

Associations of small dense low-density lipoprotein and adiponectin with complications of type 2 diabetes

BACKGROUND

Small dense low-density lipoprotein (sd-LDL) has been demonstrated to be associated with cardiovascular diseases (CVD). The proposed atherogenic properties of hypoadiponectinemia might be mediated through increased sd-LDL. In this study, the associations of sd-LDL with cardiovascular and other complications of diabetes, and also with plasma levels of adiponectin, were investigated in diabetic patients.

METHODS

173 patients, with documented type 2 diabetes mellitus, were enrolled in this cross-sectional study. Laboratory, anthropometric, and clinical characteristics were all determined. The presence of CVD, hypertention, and microalbuminuria were also evaluated. Homeostasis model assessment of insulin resistance was calculated.

RESULTS

Sd-LDL concentrations were significantly lower in patients with CVD than those without CVD (p = 0.020); and also lower in hypertensive patients relative to non-hypertensive ones (p = 0.008). Serum levels of adiponectin were significantly lower in patients with CVD (p < 0.001), and hypertension (p = 0.002), compared with those without each of these complications. Sd-LDL and adiponectin concentrations were positively correlated (r = 0.36, p < 0.001). Sd-LDL was also significantly associated with HbA1c (r = 0.24, p = 0.002).

CONCLUSION

Our data suggest that decreased levels of adiponectin might be associated with developing complications of diabetes. This study did not provide any supportive results for the association of increased sd-LDL concentrations with CVD; neither for its association with other complications of diabetes.

Genetic risk scores associated with baseline lipoprotein subfraction concentrations do not associate with their responses to fenofibrate

Lipoprotein subclass concentrations are modifiable markers of cardiovascular disease risk. Fenofibrate is known to show beneficial effects on lipoprotein subclasses, but little is known about the role of genetics in mediating the responses of lipoprotein subclasses to fenofibrate. A recent genomewide association study (GWAS) associated several single nucleotide polymorphisms (SNPs) with lipoprotein measures, and validated these associations in two independent populations. We used this information to construct genetic risk scores (GRSs) for fasting lipoprotein measures at baseline (pre-fenofibrate), and aimed to examine whether these GRSs also associated with the responses of lipoproteins to fenofibrate. Fourteen lipoprotein subclass measures were assayed in 817 men and women before and after a three week fenofibrate trial. We set significance at a Bonferroni corrected alpha <0.05 (p < 0.004). Twelve subclass measures changed with fenofibrate administration (each p = 0.003 to <0.0001). Mixed linear models which controlled for age, sex, body mass index (BMI), smoking status, pedigree and study-center, revealed that GRSs were associated with eight baseline lipoprotein measures (p < 0.004), however no GRS was associated with fenofibrate response. These results suggest that the mechanisms for changes in lipoprotein subclass concentrations with fenofibrate treatment are not mediated by the genetic risk for fasting levels.

Methylation at CPT1A locus is associated with lipoprotein subfraction profiles

Lipoprotein subfractions help discriminate cardiometabolic disease risk. Genetic loci validated as associating with lipoprotein measures do not account for a large proportion of the individual variation in lipoprotein measures. We hypothesized that DNA methylation levels across the genome contribute to interindividual variation in lipoprotein measures. Using data from participants of the Genetics of Lipid Lowering Drugs and Diet Network (n = 663 for discovery and n = 331 for replication stages, respectively), we conducted the first systematic screen of the genome to determine associations between methylation status at ∼470,000 cytosine-guanine dinucleotide (CpG) sites in CD4(+) T cells and 14 lipoprotein subfraction measures. We modeled associations between methylation at each CpG site and each lipoprotein measure separately using linear mixed models, adjusted for age, sex, study site, cell purity, and family structure. We identified two CpGs, both in the carnitine palmitoyltransferase-1A (CPT1A) gene, which reached significant levels of association with VLDL and LDL subfraction parameters in both discovery and replication phases (P < 1.1 × 10(-7) in the discovery phase, P < .004 in the replication phase, and P < 1.1 × 10(-12) in the full sample). CPT1A is regulated by PPARα, a ligand for drugs used to reduce CVD. Our associations between methylation in CPT1A and lipoprotein measures highlight the epigenetic role of this gene in metabolic dysfunction.

Genetic variants associated with VLDL, LDL and HDL particle size differ with race/ethnicity

Specific constellations of lipoprotein particle features, reflected as differences in mean lipoprotein particle diameters, are associated with risk of insulin resistance (IR) and cardiovascular disease (CVD). The associations of lipid profiles with disease risk differ by race/ethnicity, the reason for this is not clear. We aimed to examine whether there were additional genetic differences between racial/ethnic groups on lipoprotein profile. Genotypes were assessed using the Affymetrix 6.0 array in 817 related Caucasian participants of the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN). Association analysis was conducted on fasting mean particle diameters using linear models, adjusted for age, sex and study center as fixed effects, and pedigree as a random effect. Replication of associations reaching P < 1.97 × 10(-05) (the level at which we achieved at least 80% power to replicate SNP-phenotype associations) was conducted in the Caucasian population of the Multi-Ethnic Study of Atherosclerosis (MESA; N = 2,430). Variants which replicated across both Caucasian populations were subsequently tested for association in the African-American (N = 1,594), Chinese (N = 758), and Hispanic (N = 1,422) populations of MESA. Variants in the APOB gene region were significantly associated with mean VLDL diameter in GOLDN, and in the Caucasian and Hispanic populations of MESA, while variation in the hepatic lipase (LIPC) gene was associated with mean HDL diameter in both Caucasians populations only. Our findings suggest that the genetic underpinnings of mean lipoprotein diameter differ by race/ethnicity. As lipoprotein diameters are modifiable, this may lead new strategies to modify lipoprotein profiles during the reduction of IR that are sensitive to race/ethnicity.

Genome-wide association study indicates variants associated with insulin signaling and inflammation mediate lipoprotein responses to fenofibrate

OBJECTIVE

A shift towards overall larger very low-density lipoprotein (VLDL), and smaller low-density lipoprotein and high-density lipoprotein (HDL) diameters occurs in insulin resistance (IR), which reflects shifts in the distribution of the subfraction concentrations. Fenofibrate, indicated for hypertriglyceridemia, simultaneously reduces IR and shifts in lipoprotein diameter. Individual responses to fenofibrate vary, and we conducted a genome-wide association study to identify genetic differences that could contribute to such differences.

METHODS

Association analysis was conducted between single nucleotide polymorphisms (SNPs) on the Affymetrix 6.0 array and fasting particle diameter responses to a 12-week fenofibrate trial, in 817 related Caucasian participants of the Genetics of Lipid Lowering Drugs and Diet Network. Linear models were conducted, which adjusted for age, sex and study center as fixed effects, and pedigree as a random effect. The top three SNPs associated with each fraction were examined subsequently for associations with changes in subfraction concentrations.

RESULTS

SNPs in AHCYL2 and CD36 genes reached, or closely approached, genome-wide levels of significance with VLDL and HDL diameter responses to fenofibrate, respectively (P=4×10(-9) and 8×10(-8)). SNPs in AHCYL2 were associated with a decrease in the concentration of the large VLDL subfraction only (P=0.002). SNPs associated with HDL diameter change were not associated with a single subfraction concentration change (P>0.05) indicating small shifts across all subfractions.

CONCLUSION

We report novel associations between lipoprotein diameter responses to fenofibrate and the AHCYL2 and CD36 genes. Previous associations of these genes with IR emphasize the role of IR in mediating lipoprotein response to fenofibrate.

LDL particle heterogeneity, and its association with other established cardiovascular risk factors in a young Indian industrial population

OBJECTIVE

Low density lipoprotein (LDL) particles are heterogeneous in terms of size, density, chemical composition and electric charge with certain particle of LDL being more atherogenic than the others. The present study aimed to look at the LDL particle heterogeneity, particle size and association with other cardiovascular disease (CVD) risk factors in young Indian industrial population.

METHODOLOGY

600 employees of an industry of Delhi, aged 20-39 years were selected for the study. Data on demographics, individual characteristics associated with major risk factors of CVD, past medical history, clinical and anthropometric profile was collected. Fasting glucose, lipid profile, apolipoprotein (A1, B, and E), lipoprotein (a), high sensitive C-reactive protein (hsCRP) and insulin were estimated. LDL particle size was determined in ethylenediamminetetraacetate (EDTA) plasma by 3% polyacrylamide gel electrophoresis.

RESULT

We found a prevalence of small dense LDL phenotype (LDL size ≤ 26.3) in 27.4% of males and 24.0% of females. The mean waist circumference, blood pressure, triglycerides (TAG), cholesterol, hsCRP, apolipoprotein (A1, B and E) and insulin were higher in males whereas mean high density lipoprotein was higher in females. Females also had a significantly higher mean LDL particle diameter as compared to males.

CONCLUSION

TAG, physical activity and lipoprotein (a) correlated with small dense LDL in this young Indian population.

The triglyceride/high-density lipoprotein cholesterol ratio, the small dense low-density lipoprotein phenotype, and ischemic heart disease risk

This study investigated the relevance of using the plasma triglyceride to high-density lipoprotein cholesterol ratio (Log TG/HDL-C) for the prediction of the small dense lowdensity lipoprotein (LDL) phenotype and the risk of ischemic heart disease (IHD). Analyses were based on data from the Quebec Cardiovascular Study in a cohort of 2072 men free of IHD at baseline, among whom 262 had a first IHD event (coronary death, non fatal myocardial infarction and unstable angina) during a 13-year follow-up period. LDL particle size phenotype was characterized using 2-16% polyacrylamide gradient gel electrophoresis (PAGGE) of whole plasma. There were significant associations between the Log TG/HDL-C ratio and features of LDL size phenotype such as the proportion of LDL with a diameter <255A (r = 0.43, p < 0.001) and LDL peak particle size (r = -20.55, p < 0.001). However, the Log TG/HDL-C ratio brought no additional value (p â yen 0.1) in predicting the small dense LDL phenotype (area under the receiver operating curve (AUROC = 71.9%) compared to TG alone (AUROC = 71.2%) or to a combination of Log TG and HDL-C (AUROC = 72.4%) after multivariate adjustment for non lipid risk factors. Finally, elevations in the Log TG/HDL-C ratio did not improve the discrimination of incident IHD cases from non IHD cases compared to the use of plasma TG levels alone (p = 0.5) or a combination of the individual TG and HDL-C values (p = 0.5). The Log TG/HDL-C ratio does not improve our ability to identify individuals with the small dense LDL phenotype compared to plasma TG levels alone. The Log TG/HDLC is also not superior to plasma TG levels alone in predicting IHD risk in men of the QuA(c)bec Cardiovascular Study.

Differences in risk factors for coronary heart disease among diabetic and nondiabetic individuals from a population with high rates of diabetes: the Strong Heart Study

CONTEXT

Coronary heart disease (CHD) is the leading cause of death in the United States.

OBJECTIVE

This study compares differences in risk factors for CHD in diabetic vs. nondiabetic Strong Heart Study participants.

DESIGN

This was an observational study.

SETTING

The study was conducted at three centers in Arizona, Oklahoma, and North and South Dakota.

PARTICIPANTS

Data were obtained from 3563 of 4549 American Indians free of cardiovascular disease at baseline.

INTERVENTION(S)

CHD events were ascertained during follow-up.

MAIN OUTCOME MEASURE

CHD events were classified using standardized criteria.

RESULTS

In diabetic and nondiabetic participants, 545 and 216 CHD events, respectively, were ascertained during follow-up (21,194 and 22,990 person-years); age- and sex-adjusted incidence rates of CHD were higher for the diabetic group (27.5 vs. 12.1 per 1,000 person-years). Risk factors for incident CHD common to both groups included older age, male sex, prehypertension or hypertension, and elevated low-density lipoprotein cholesterol. Risk factors specific to the diabetic group were lower high-density lipoprotein cholesterol, current smoking, macroalbuminuria, lower estimated glomerular filtration rate, use of diabetes medication, and longer duration of diabetes. Higher body mass index was a risk factor only for the nondiabetic group. The association of male sex and CHD was greater in those without diabetes than in those with diabetes.

CONCLUSIONS

In addition to higher incidence rates of CHD events in persons with diabetes compared with those without, the two groups differed in CHD risk factors. These differences must be recognized in estimating CHD risk and managing risk factors.

Distribuição de obesidade geral e abdominal em adultos de uma cidade no Sul do Brasil

O objetivo foi determinar a prevalência e a evolução da obesidade geral e abdominal em adultos com 20 anos ou mais em Pelotas, Rio Grande do Sul, Brasil. Estudo transversal de base populacional realizado em 2010. A obesidade geral foi definida pelo índice de massa corporal (IMC) > 30kg/m² e a obesidade abdominal definida como > 88cm para mulheres e > 102cm para homens. Foram entrevistados 2.448 indivíduos. A prevalência de obesidade foi de 21,7% nos homens e 29,2% nas mulheres, já a obesidade abdominal foi de 19,5% e 37,5%, respectivamente. Na análise multivariada, menor escolaridade esteve associada ao aumento da obesidade geral e abdominal em mulheres. Renda familiar apresentou relação inversa com obesidade abdominal em homens. Comparativamente, mostraram aumento das prevalências de obesidade de 1,2 vez para as mulheres e 1,5 vez para os homens, com estudos em 1994 e 2000. Porém, para obesidade abdominal houve pequena redução entre as mulheres e se manteve semelhante para os homens. A prevalência de obesidade geral aumentou nos últimos 10 anos, enquanto que a obesidade abdominal mostrou estabilidade.

A clustering analysis of lipoprotein diameters in the metabolic syndrome

Background

The presence of smaller low-density lipoproteins (LDL) has been associated with atherosclerosis risk, and the insulin resistance (IR) underlying the metabolic syndrome (MetS). In addition, some research has supported the association of very low-, low- and high-density lipoprotein (VLDL HDL) particle diameters with components of the metabolic syndrome (MetS), although this has been the focus of less research. We aimed to explore the relationship of VLDL, LDL and HDL diameters to MetS and its features, and by clustering individuals by their diameters of VLDL, LDL and HDL particles, to capture information across all three fractions of lipoprotein into a unified phenotype.

Methods

We used nuclear magnetic resonance spectroscopy measurements on fasting plasma samples from a general population sample of 1,036 adults (mean ± SD, 48.8 ± 16.2 y of age). Using latent class analysis, the sample was grouped by the diameter of their fasting lipoproteins, and mixed effects models tested whether the distribution of MetS components varied across the groups.

Results

Eight discrete groups were identified. Two groups (N = 251) were enriched with individuals meeting criteria for the MetS, and were characterized by the smallest LDL/HDL diameters. One of those two groups, one was additionally distinguished by large VLDL, and had significantly higher blood pressure, fasting glucose, triglycerides, and waist circumference (WC; P < .001). However, large VLDL, in the absence of small LDL and HDL particles, did not associate with MetS features. These associations held after additionally controlling for VLDL, LDL and HDL particle concentrations.

Conclusions

While small LDL diameters remain associated with IR and the MetS, the occurrence of these in conjunction with a shift to overall larger VLDL diameter may identify those with the highest fasting glucose, TG and WC within the MetS. If replicated, the association of this phenotype with more severe IR-features indicated that it may contribute to identifying of those most at risk for incident type II diabetes and cardiometabolic disease.

Association of hypertension with small, dense low-density lipoprotein in patients without metabolic syndrome

A higher proportion of small, dense low-density lipoprotein (sdLDL) is known to be associated with a high prevalence of cardiovascular disease in association with metabolic syndrome (MS). Hypertension (HTN) is one of the known risk factors for MS. However, whether HTN is associated with sdLDL in patients without MS is not yet clear. The lipid profiles, including low-density-lipoprotein (LDL) subfractions, of 383 consecutive subjects were evaluated. The patients without MS consisted of 198 hypertensive patients (non-MS/HTN group) and 108 normotensive subjects (non-MS/non-HTN group). The peak and mean particle diameter of LDL were measured by gradient gel electrophoresis. Plasma total cholesterol, LDL cholesterol, high-density lipoprotein (HDL) cholesterol, triglyceride (TG), HDL cholesterol/Apo A1, LDL-C/ApoB and Apo(A1, B, CII and E) levels did not differ between the non-MS/non-HTN and non-MS/HTN groups. When analyzing LDL subfraction, the absolute amount of patterns A and B was not different between the non-MS/non-HTN and non-MS/HTN groups. Compared with the non-MS/non-HTN groups, the proportion of sdLDL was higher in the non-MS/HTN group (37.7% versus 39.9%, P=0.046), but not significant after adjustment of waist circumference, serum TG, age and statin usage. The proportion of sdLDL to total LDL was higher in hypertensive subjects, even those without MS, than in normotensive subjects. However, this difference of LDL subfraction in hypertensive patients is associated with higher waist circumference, higher serum TG, older age and more statin usage. This result suggests that HTN may contribute to atherosclerosis and endothelial dysfunction with associated risk factors that influence LDL size.

Antidyslipidemic activity of hot-water extracts from leaves of Cinnamomum osmophloeum Kaneh

The antidyslipidemic activity of hot-water extracts of Cinnamomum osmophloeum leaves (COE) were evaluated on hamsters fed a high-fat diet. Oral administration of COE to hyperlipidemic hamsters reduced the total cholesterol (TC), triglyceride (TG) and low-density lipoprotein (LDL-C) levels. Compared with hyperlipidemic hamsters, the plasma TC and TG levels of hamsters fed with COE at a dosage of 100 mg/kg body weight for 5 and 10 weeks were significantly reduced to 12.63% and 34.25%, and 33.88% and 36.88%, respectively. Plasma LDL-C was also reduced to 27.77% after 10 weeks feeding with the same regimen. Standard diagnostic tests indicated that the extracts did not cause damage to hamster liver or kidneys. Based on these results, it is concluded that COE possesses antidyslipidemic activity. The composition of COE was characterized. Two main compounds, kaempferol 3-O-β-D-apiofuranosyl-(1 → 2)-α-L-arabinofuranosyl-7-O-α-L-rhamnopyranoside (1) and kaempferitrin (2) were identified in the hot-water extracts. Their contents were 7.56% and 9.95%, respectively.

Hypolipidemic activity of Semecarpus anacardium in Streptozotocin induced diabetic rats

Alterations in lipid metabolism and lipoprotein disturbances have played an important role in increasing the risk of cardiovascular mortality and morbidity in diabetes. A drug that has hypoglycemic activity can be used for the treatment of hyperlipidemia also. The present study was carried out to evaluate the hypolipidemic activity of Semecarpus anacardium. Male Wister rats weighing 250-270 g were injected with Streptozotocin at a dose of 50 mg/kg body weight and administered with S. anacardium (300 mg/kg body weight) and Metformin (500 mg/kg body weight) for 21 days. Control and drug control groups were also included in the study. After the experimental duration, serum was collected, liver and kidney were excised and used for the analysis of lipid and lipid metabolizing enzymes. The results of the study revealed that S. anacardium administration was able to decrease the levels of LDL, cholesterol, VLDL, TG, phospholipid and free fatty acid and increase the HDL levels and favorably modulate the lipid metabolizing enzymes in the liver and kidney. These results show that S. anacardium exerts hypolipidemic activity in diabetic rats.

Postprandial lipoproteins and cardiovascular disease risk in diabetes mellitus

Diabetes mellitus is associated with increased risk for atherosclerotic cardiovascular disease (CVD). Recent prospective studies in healthy individuals suggest that the postprandial triglyceride (TG) level is a better independent predictor for assessing future CVD events than fasting TG levels. In contrast, results have been more controversial among diabetic patients, as some studies report a positive association between postprandial TG and CVD. This raises the issue of to what extent postprandial TG levels may be of predictive value in the diabetic population. One possibility impacting on the predictive power of postprandial TG in identifying CVD risk may be the presence of other risk factors, including alterations in lipid and lipoprotein metabolism, which could make it more difficult to identify the impact of postprandial lipemia on cardiovascular risk. The findings provide a challenge to develop a better approach to assess the impact of postprandial lipemia on CVD risk under diabetic conditions.

Identifying obese women most at risk from cardiovascular disease

In Western countries, more women than men die every year of cardiovascular disease (CVD) and women spend more life years with cardiovascular disease than men. Fortunately, premature cardiovascular disease in women is preventable. Evidence-based guidelines for the prevention of cardiovascular disease in women recommend an initial risk assessment. However, recommended risk-assessment tools such as the Systematic Coronary Risk Evaluation (SCORE) system may not be sufficient to detect risk in women with obesity. A further barrier to prevention in women is the fact that physicians may underestimate the effects of risk factors that are particularly dangerous or prevalent in women. These include type 2 diabetes, hypertension, smoking, abdominal obesity, poor exercise capacity and the metabolic syndrome. Several of these factors, as well as some novel biomarkers, may increase the risk of cardiovascular disease relatively more in women than in men. To assess risk in obese women, a multifactorial assessment that encompasses assessment of body-fat distribution should be undertaken. Weight loss and lifestyle changes that have been shown to improve risk-factor profiles are crucial interventions and should be considered, even if standard risk calculators do not indicate an elevated cardiovascular risk.

PAI-1 activity, but not fibrinogen or von Willebrand factor, is inversely related to LDL particle size in type 2 diabetes

BACKGROUND

Levels of fibrinogen, von Willebrand factor (vWF) and plasminogen activator inhibitor-1 (PAI-1) have been associated with small low-density lipoprotein (LDL) particles. However, it is not clear whether these associations are independent of visceral adiposity or other components of the metabolic syndrome such as triglycerides or insulin resistance.

METHODS

Visceral adipose tissue (VAT; CT-scan), fibrinogen, von Willebrand factor antigen (vWF:Ag), PAI-1 activity and different metabolic parameters such as total cholesterol (chol), HDL-chol, triglycerides, insulin resistance (homeostasis model assessment; HOMA-IR) were determined in 41 women and 78 men with type 2 diabetes. LDL particle size was assessed by polyacrylamide gradient gel electrophoresis.

RESULTS

PAI-1 activity was inversely related to LDL particle size after adjustment for age and body mass index (BMI) (r=-0.28; p=0.006) or age and VAT (r=-0.26; p=0.01), but not after adjustment for age and HOMA-IR (r=-0.15; p=0.148) or age and triglycerides (r=-0.04; p=0.679). In multiple regression analysis, LDL particle size did not independently determine PAI-1 activity levels. Fibrinogen and vWF:Ag did not seem to be related to LDL size.

CONCLUSIONS

PAI-1 activity levels, in contrast to fibrinogen and vWF:Ag, seem to be related to the small LDL phenotype in patients with type 2 diabetes. However, this relationship was not independent of insulin resistance or triglycerides.

Postprandial lipemia: an under-recognized atherogenic factor in patients with diabetes mellitus

Atherosclerotic disease is the leading cause of both morbidity and mortality in patients with type 2 diabetes. In these patients, postprandial dyslipidemia include not only quantitative but also qualitative abnormalities of lipoproteins which are potentially atherogenic and seems to be a significant risk factor for cardiovascular disease since there is evidence that it results in endothelial dysfunction and enhanced oxidative stress. The most common pattern of postprandial dyslipidemia in diabetes consists of high concentrations of triglycerides, higher VLDLs production by the liver and a decrease in their clearance, a predominance of small dense LDL particles, and reduced levels of HDL. The cause of this postprandial dyslipidemia in diabetes is complex and involves a variety of factors including hyperinsulinemia, insulin resistance, hyperglycemia and disturbed fatty acid metabolism. Numerous clinical studies have shown that postprandial dyslipidemia is associated with endothelial dysfunction in type 2 diabetes and with alterations in other surrogate markers in the cascade of atherosclerosis. Current published guidelines indicate that in diabetics the primary lipid target is LDL<100 mg/dL (70 mg/dL in very high-risk patients) and the most appropriate class of drugs are statins although the issue of postprandial dyslipidemia has not been specifically addressed so far. Moreover, several other classes of medications (fibrates, niacin and antidiabetic drugs) as well as non-pharmacological interventions (i.e. diet, smoking cessation and exercise) can be used to treat lipid and lipoprotein abnormalities associated with insulin resistance and type 2 diabetes. These type of interventions may be more appropriate to ameliorate postprandial dyslipidemia. However, this remains to be confirmed on clinical grounds.

Management of dyslipidemia in the metabolic syndrome: recommendations of the Spanish HDL-Forum

In order to characterize the metabolic syndrome it becomes necessary to establish a number of diagnostic criteria. Because of its impact on cardiovascular morbidity/mortality, considerable attention has been focussed on the dyslipidemia accompanying the metabolic syndrome. The aim of this review is to highlight the fundamental aspects of the pathophysiology, diagnosis, and the treatment of the metabolic syndrome dyslipidemia with recommendations to clinicians. The clinical expression of the metabolic syndrome dyslipidemia is characterized by hypertriglyceridemia and low levels of high-density lipoprotein-cholesterol (HDL-C). In addition, metabolic syndrome dyslipidemia is associated with high levels of apolipoprotein (apo) B-100-rich particles of a particularly atherogenic phenotype (small dense low-density lipoprotein-cholesterol [LDL-C]. High levels of triglyceride-rich particles (very low-density lipoprotein) are also evident both at baseline and in overload situations (postprandial hyperlipidemia). Overall, the 'quantitative' dyslipidemia characterized by hypertriglyceridemia and low levels of HDL-C and the 'qualitative' dyslipidemia characterized by high levels of apo B-100- and triglyceride-rich particles, together with insulin resistance, constitute an atherogenic triad in patients with the metabolic syndrome. The therapeutic management of the metabolic syndrome, regardless of the control of the bodyweight, BP, hyperglycemia or overt diabetes mellitus, aims at maintaining optimum plasma lipid levels. Therapeutic goals are similar to those for high-risk situations because of the coexistence of multiple risk factors. The primary goal in treatment should be achieving an LDL-C level of <100 mg/dL (or <70 mg/dL in cases with established ischemic heart disease or risk equivalents). A further goal is increasing the HDL-C level to >or=40 mg/dL in men or 50 mg/dL in women. A non-HDL-C goal of 130 mg/dL should also be aimed at in cases of hypertriglyceridemia. Lifestyle interventions, such as maintaining an adequate diet, and a physical activity program, constitute an essential part of management. Nevertheless, when pharmacologic therapy becomes necessary, fibrates and HMG-CoA reductase inhibitors (statins) are the most effective drugs in controlling the metabolic syndrome hyperlipidemia, and are thus the drugs of first choice. Fibrates are effective in lowering triglycerides and increasing HDL-C levels, the two most frequent abnormalities associated with the metabolic syndrome, and statins are effective in lowering LDL-C levels, even though hypercholesterolemia occurs less frequently. In addition, the combination of fibrates and statins is highly effective in controlling abnormalities of the lipid profile in patients with the metabolic syndrome.

Electronegative LDLs from familial hypercholesterolemic patients are physicochemically heterogeneous but uniformly proapoptotic

A highly electronegative fraction of human plasma LDLs, designated L5, has distinctive biological activity that includes induction of apoptosis in bovine aortic endothelial cells (BAECs). This study was performed to identify a relationship between LDL density, electronegativity, and biological activity, namely, the induction of apoptosis in BAECs. Plasma LDLs from normolipidemic subjects and homozygotic familial hypercholesterolemia subjects were separated into five subfractions, with increasing electronegativity from L1 to L5, and into seven subfractions according to increasing density, D1 to D7. L1 to L5 were also separated according to density, and D1 to D7 were separated according to charge. The density profiles of L1 to L5 were similar (maximum density = 1.030 +/- 0.002 g/ml). Induction of apoptosis by all seven density subfractions was confined to the highly electronegative fraction, L5, and within each density subfraction the magnitude of apoptosis correlated with the L5 content. Electronegative LDL is heterogeneous with respect to density and composition, and induction of apoptosis is more strongly associated with LDL electronegativity than with LDL size or density.

Metabolism of phytol to phytanic acid in the mouse, and the role of PPARα in its regulation

Phytol, a branched-chain fatty alcohol, is the naturally occurring precursor of phytanic and pristanic acid, branched-chain fatty acids that are both ligands for the nuclear hormone receptor peroxisome proliferator-activated receptor alpha (PPARalpha). To investigate the metabolism of phytol and the role of PPARalpha in its regulation, wild-type and PPARalpha knockout (PPARalpha-/-) mice were fed a phytol-enriched diet or, for comparison, a diet enriched with Wy-14,643, a synthetic PPARalpha agonist. After the phytol-enriched diet, phytol could only be detected in small intestine, the site of uptake, and liver. Upon longer duration of the diet, the level of the (E)-isomer of phytol increased significantly in the liver of PPARalpha-/- mice compared with wild-type mice. Activity measurements of the enzymes involved in phytol metabolism showed that treatment with a PPARalpha agonist resulted in a PPARalpha-dependent induction of at least two steps of the phytol degradation pathway in liver. Furthermore, the enzymes involved showed a higher activity toward the (E)-isomer than the (Z)-isomer of their respective substrates, indicating a stereospecificity toward the metabolism of (E)-phytol. In conclusion, the results described here show that the conversion of phytol to phytanic acid is regulated via PPARalpha and is specific for the breakdown of (E)-phytol.

Effects of Pioglitazone Hydrochloride on Japanese Patients with Type 2 Diabetes Mellitus

AIM

The effects of pioglitazone hydrochloride monotherapy on abnormal lipid control were evaluated in Japanese patients with type 2 diabetes mellitus, comparing with glibenclamide monotherapy.

METHODS

Patients were randomly assigned to receive, once daily, pioglitazone hydrochloride, at 15 mg or 30 mg (n=46), or glibenclamide, at 1.25 mg or 2.5 mg (n=46). The 24-week study included patients with type 2 diabetes having high levels of triglyceride (TG).

RESULTS

Pioglitazone hydrochloride produced beneficial effects on dyslipidemia in patients with type 2 diabetes, compared with the baseline and the glibenclamide group, as demonstrated by increases in high-density lipoprotein cholesterol (HDL-C) levels and low-density lipoprotein cholesterol (LDL) particle size, a fall in TG levels, and an increased ratio of visceral to subcutaneous fat volumes (V/S). Pioglitazone hydrochloride reduced fasting serum insulin levels, with low fasting plasma glucose (FPG) and glycohemoglobin levels, compared to the baseline, suggesting an improvement of insulin resistance.

CONCLUSION

As expected, glibenclamide reduced FPG levels through increased insulin secretion. Pioglitazone hydrochloride and glibenclamide were well tolerated. Pioglitazone hydrochloride improved dyslipidemia related to insulin resistance, whereas glibenclamide enhanced insulin secretion, with only a minor effect on lipid control, in Japanese patients with type 2 diabetes.

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.

Coronary heart disease risk equivalence in diabetes depends on concomitant risk factors

OBJECTIVE

Diabetes has been defined as a coronary heart disease (CHD) risk equivalent, and more aggressive treatment goals have been proposed for diabetic patients.

RESEARCH DESIGN AND METHODS

We studied the influence of single and multiple risk factors on the 10-year cumulative incidence of fatal and nonfatal CHD and cardiovascular disease (CVD) in diabetic and nondiabetic men and women, with and without baseline CHD or CVD, in a population (n = 4,549) with a high prevalence of diabetes.

RESULTS

In both sexes, diabetes increased the risk for CHD (hazard ratio 1.99 and 2.93 for men and women, respectively). Diabetic men and women had a 10-year cumulative incidence of CHD of 25.9 and 19.1%, respectively, compared with 57.4 and 58.4% for nondiabetic men and women with previous CHD. The pattern was similar when only fatal events were considered. Diabetic individuals with one or two risk factors had a 10-year cumulative incidence of CHD that was only 1.4 times higher than that of nondiabetic individuals (14%). However, the 10-year incidence of CHD in diabetic subjects with multiple risk factors was >40%, and the incidence of fatal CHD was higher in these subjects than in nondiabetic subjects with previous CHD. Data for CVD showed similar patterns, as did separate analyses by sex.

CONCLUSIONS

Our results and comparisons with other available data show wide variation in the rate of CHD in diabetes, depending on the population and existing risk factors. Most individuals had a 10-year cumulative incidence >20%, but only those with multiple risk factors had a 10-year cumulative incidence that was equivalent to that of patients with CHD. Until more data are available, it may be prudent to consider targets based on the entire risk factor profile rather than just the presence of diabetes.

REVIEW: Efficacy and mechanisms of action of statins in the treatment of diabetic dyslipidemia

CONTEXT

The Adult Treatment Panel III recommends 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, or statins, as first-line lipid-altering therapy for all adult patients with diabetes mellitus. This is based on the well-characterized efficacy and safety profiles of this class of agents as well as several clinical trials demonstrating that statin treatment reduces the risk of cardiovascular events.

EVIDENCE ACQUISITION

This review provides an overview of the effectiveness and mechanisms of action of statins in patients with diabetes mellitus using small efficacy trials and large clinical outcomes trials as well as studies of the effects of statins on apolipoprotein B (apoB) metabolism.

EVIDENCE SYNTHESIS

The major findings presented are a review of mechanistic studies of selected subjects with diabetes mellitus and dyslipidemia and a compilation of results from large-scale clinical trials of patients with diabetes.

CONCLUSIONS

Statins are highly efficacious as low-density lipoprotein cholesterol-lowering agents and have more modest effects on very low-density lipoprotein triglyceride and high-density lipoprotein cholesterol levels. The effects of statins on plasma lipids and lipoproteins result from their ability to both increase the efficiency with which very low-density lipoprotein and low-density lipoprotein are cleared from the circulation and reduce the production of apoB-containing lipoproteins by the liver. Additional investigations are needed to clarify the mechanisms by which statins reduce apoB secretion from the liver.

Low-density lipoprotein size and cardiovascular risk assessment

A predominance of small, dense low-density lipoproteins (LDL) has been accepted as an emerging cardiovascular risk factor by the National Cholesterol Education Program Adult Treatment Panel III. LDL size seems to be an important predictor of cardiovascular events and progression of coronary heart disease and evidences suggests that both quality (particularly small, dense LDL) and quantity may increase cardiovascular risk. However, other authors have suggested that LDL size measurement does not add information beyond that obtained by measuring LDL concentration, triglyceride levels and HDL concentrations. Therefore, it remains debatable whether to measure LDL particle size in cardiovascular risk assessment and, if so, in which categories of patient. Therapeutic modulation of LDL particle size or number appears beneficial in reducing the risk of cardiovascular events, but no clear causal relationship has been shown, because of confounding factors, including lipid and non-lipid variables. Studies are needed to investigate the clinical significance of LDL size measurements in patients with coronary and non-coronary forms of atherosclerosis; in particular, to test whether LDL size is associated with even higher vascular risk, and whether LDL size modification may contribute to secondary prevention in such patients.

Association between LDL particle size and postprandial increase of remnant-like particles in Japanese type 2 diabetic patients

Small, dense LDL, as well as chylomicron- and VLDL-remnant lipoproteins, are known to be important risk factors for coronary heart disease in patients with type 2 diabetes mellitus. The aim of this study was to clarify the relationship between LDL particle size and postprandial remnant lipoprotein levels in Japanese type 2 diabetic patients. Forty-six patients with type 2 diabetes mellitus were divided into tertiles according to LDL particle size. The peak LDL particle diameter was <26.30 nm in tertile 1, 26.30-26.85 nm in tertile 2, and >26.85 nm in tertile 3. After a test meal, tertile 1 had a significantly greater increment of triglycerides (TG), remnant-like particle (RLP)-TG, and RLP-cholesterol (RLP-C) than tertiles 2 and 3. There was a negative correlation between LDL particle size and the postprandial increases of TG, RLP-TG, and RLP-C. These results indicate that smaller sized LDL particles may be a marker of fasting state for an exaggerated postprandial increase of remnant lipoproteins as well as an increase of TG-rich lipoproteins.

Fibrates in the metabolic syndrome and in diabetes

There is increasing evidence that fibrates can reduce coronary artery disease. This finding seems to be particularly the case inpatients with the metabolic syndrome or with diabetes. Their beneficial effects can be explained partly by their effects on lipoproteins,but these effects may also result from some of their nonlipid pleotropic effects. Clinical trials are still needed to determine the potential role played by such pleotropic actions.

Genetics of LDL particle heterogeneity

Substantial evidence exists suggesting that small, dense LDL particles are associated with an increased risk of coronary heart disease. This disease-related risk factor is recognized to be under both genetic and environmental influences. Several studies have been conducted to elucidate the genetic architecture underlying this trait, and a review of this literature seems timely. The methods and strategies used to determine its genetic component and to identify the genes have greatly changed throughout the years owing to the progress made in genetic epidemiology and the influence of the Human Genome Project. Heritability studies, complex segregation analyses, candidate gene linkage and association studies, genome-wide linkage scans, and animal models are all part of the arsenal to determine the susceptibility genes. The compilation of these studies clearly revealed the complex genetic nature of LDL particles. This work is an attempt to summarize the growing evidence of genetic control on LDL particle heterogeneity with the aim of providing a concise overview in one read.

Sex and age differences in lipoprotein subclasses measured by nuclear magnetic resonance spectroscopy: the Framingham Study

BACKGROUND

The sex differential in coronary heart disease (CHD) risk, which is not explained by male/female differences in lipid and lipoprotein concentrations, narrows with age. We examined whether this differential CHD risk might, in part, be attributable to the sizes of lipoprotein particles or concentrations of lipoprotein subclasses.

METHODS

We analyzed frozen plasma samples from 1574 men and 1692 women from exam cycle 4 (1988-1990) of the Framingham Offspring Study. Nuclear magnetic resonance (NMR) spectroscopy was used to determine the subclass concentrations and mean sizes of VLDL, LDL, and HDL particles. Concentrations of lipids and apolipoproteins were measured by standard chemical methods.

RESULTS

In addition to the expected sex differences in concentrations of triglycerides, LDL-cholesterol, and HDL-cholesterol, women also had a lower-risk subclass profile consisting of larger LDL (0.4 nm) and HDL (0.5 nm) particles. The sex difference was most pronounced for HDL, with women having a twofold higher (8 vs 4 micromol/L) concentration of large HDL particles than men. Furthermore, similar to the narrowing of the sex difference in CHD risk with age, the observed male/female difference in HDL particle size also decreased with age. Although lipoprotein particle sizes were highly correlated with lipid and lipoprotein concentrations, the sex differences in the mean sizes of lipoprotein particles persisted (P <0.001) even after adjustment for lipid and lipoprotein concentrations.

CONCLUSIONS

Women have a less atherogenic subclass profile than men, even after accounting for differences in lipid concentrations.

Preventing macrovascular disease in patients with type 2 diabetes mellitus

Type 2 diabetes mellitus (DM) is associated with an increased risk for both micro-and macrovascular complications, and cardiovascular diseases (CVD) are the most common causes of death in these patients, accounting for almost 70% of the deaths. Given the high prevalence of the condition and the expected global increase in the prevalence of type 2 DM, a case is made for prevention of these serious complications in order to reduce the individual morbidity and the economic burden on society. In this review we present the knowledge of how macrovascular disease in patients with type 2 DM may be prevented, and suggest possible strategies for doing so.A thorough search of the published literature was conducted and we first present relevant epidemiological studies demonstrating the impact of important risk factors for CVD in DM, such as dyslipidemia, hyperglycemia, hypertension, smoking, familial premature coronary heart disease and some non-classical risk factors such as hyperinsulinemia, insulin resistance, endothelial dysfunction and inflammation. Secondly, we review the results from published randomized controlled clinical trials and meta-analysis of these, evaluate the findings and suggest strategies for preventing CVD in patients with type 2 DM using non-pharmacological and pharmacological approaches. Present knowledge indicates that most patients with type 2 DM either have manifest CVD or have a high risk for future cardiovascular events, men with DM have a 2- to 4-fold; and women with DM a 3- to 5-fold increased risk for cardiovascular death compared with non-diabetic individuals. Care of patients with type 2 DM should include yearly risk assessment by the use of published risk equations or risk charts. On the background of this assessment, an individual risk reducing strategy should be tailored to each patient's need, including the treatment of hyperglycemia, hypertension and dyslipidemia together with the use of aspirin (acetylsalicylic acid) and ACE inhibitors. Such measures can reduce the risk of cardiovascular events in patients with type 2 DM.

Associations of low density lipoprotein particle composition with atherogenicity

PURPOSE OF REVIEW

A growing body of data suggests that in addition to LDL-cholesterol concentrations, compositional properties of LDL, including size and fatty acid composition, are important in determining the relative degree of atherogenicity. This review examines current research in this field to evaluate which properties of LDL may most directly influence the risk of coronary heart disease.

RECENT FINDINGS

The presence of small dense LDL has been correlated with an increased risk of coronary heart disease, but this has not been shown to be fully independent of related factors such as elevated plasma triacylglycerol concentrations. An increased susceptibility of small dense LDL to in-vitro oxidation has also been demonstrated, but its importance to coronary heart disease risk has not been established. Other studies have found that the presence of enlarged LDL, modified (oleate enriched) fatty acyl composition of LDL, and higher numbers of LDL particles in plasma also are endpoints associated with an increased risk of coronary heart disease.

SUMMARY

LDL size may indicate a metabolic condition associated with increased CHD risk as opposed to the direct promotion of atherosclerosis by specific particle types of LDL. In most claims of detrimental effects of small dense LDL, neither LDL particle concentrations nor the fatty acid composition of the particles were established, both factors being important in contributing to the atherogenic potential of LDL. The predisposition to premature coronary heart disease cannot currently be objectively assigned to any one type of LDL particle.

Lipid Analyses for the Management of Vascular Diseases

Despite a long history of studies on lipid abnormalities, numerous problems in laboratory technologies and techniques remain unresolved. One of the most commonly tested molecules is low-density lipoprotein (LDL) cholesterol, and a homogenous assay technique for measurement of this molecule has recently been introduced. Although the method represents remarkable technological breakthroughs with great potential for improving lipoprotein analysis, some discrepancies exist among assay protocols. Even for direct measurement of high-density lipoprotein (HDL) cholesterol, which has widely been accepted, there are still large discrepancies among data obtained by different protocols. Oxidatively modified LDL is an independent factor that is considered to directly contribute to the pathogenesis of early atherosclerosis. Lipid peroxidation products, surface charge, and spectrophotometric patterns are all applicable to the evaluation of in vitro oxidation. Only enzyme-linked immunosorbent assays using monoclonal antibodies have a potential for clinical use, but such methods are not yet standardized. There is also increasing evidence for the presence of anti-oxidized LDL autoantibodies in human sera, but the diagnostic utility remains controversial. In addition, small dense LDL has recently attracted much attention as an independent risk factor. Although this is a potential target of oxidization, a robust and simple analytical method does not yet exist. This review presents the current state of laboratory technologies for testing lipid abnormalities.

Low-density lipoprotein subclass and its correlating factors in diabetics

OBJECTIVES

Small dense LDL, low density lipoprotein (LDL) particles with small size and high density, is regarded as a significant risk factor for cardiovascular diseases. Diabetes mellitus is one of the conditions accompanied by increased small dense LDL. We analyzed LDL subclass in type 2 diabetics and normal controls with LipoPrint LDL System to investigate the LDL heterogeneity in diabetics and factors affecting it.

DESIGN AND METHODS

We selected 40 normal controls and 40 type 2 diabetics with fasting blood glucose level over 7.0 mmol/L and HbA1c level over 7%. LDL subclass was determined with LipoPrint LDL System. LipoPrint LDL System fractionates LDL into seven parts (LDL1-7) by size and LDL3 to LDL7 are defined as small-sized LDL. In addition we estimated 'the percent of small-sized LDL over whole LDL' and defined it as 'small-sized LDL proportion'.

RESULTS

Mean small-sized LDL proportion was significantly higher in diabetics (23.4%) than in controls (11.8%) (p<0.001) and small-sized LDL proportion showed positive correlation with blood levels of glucose, HbA1c, total cholesterol, triglyceride, and oxidized LDL and negative correlation with HDL cholesterol level in univariate analysis (p<0.001). Of these parameters, triglyceride, HbA1c, oxidized LDL were statistically significant variables contributing to the small-sized LDL proportion in stepwise multiple regression analysis.

CONCLUSIONS

We analyzed small-sized LDL proportion in type 2 diabetics and found that it was significantly increased in diabetics than control subjects and it was independently correlated with triglyceride, HbA1c, oxidized LDL in descending order, which are reflecting lipid metabolism, glycation, and oxidative stress, respectively.

Pioglitazone reduces atherogenic dense LDL particles in nondiabetic patients with arterial hypertension: a double-blind, placebo-controlled study

OBJECTIVE

The oral antidiabetic agent pioglitazone improves insulin sensitivity and glycemic control and appears to lower atherogenic dense LDL in type 2 diabetes. Insulin resistance may occur frequently in nondiabetic patients with hypertension. This study is the first to report the effect of pioglitazone on LDL subfractions in normolipidemic, nondiabetic patients with arterial hypertension.

RESEARCH DESIGN AND METHODS

We performed a monocentric, double-blind, randomized, parallel-group comparison of 45 mg pioglitazone (n = 26) and a placebo (n = 28), each given once daily for 16 weeks. Fifty-four moderately hypertensive patients (LDL cholesterol, 2.8 +/- 0.8 mmol/l; HDL cholesterol, 1.1 +/- 0.3 mmol/l; triglycerides, 1.4 mmol/l (median; range 0.5-7.1) were studied at baseline and on treatment.

RESULTS

At baseline, dense LDLs were elevated (apolipoprotein [apo]B in LDL-5 plus LDL-6 >250 mg/l) in 63% of all patients. Sixteen weeks of treatment with pioglitazone did not significantly change triglycerides, total, LDL, and HDL cholesterol. However, pioglitazone reduced dense LDLs by 22% (P = 0.024). The mean diameter of LDL particles increased from 19.83 +/- 0.30 to 20.13 +/- 0.33 nm (P < 0.001 vs. placebo), whereas the mean LDL density decreased from 1.0384 +/- 0.0024 to 1.0371 +/- 0.0024 kg/l (P = 0.005 vs. placebo). The effect of pioglitazone on LDL size and density was independent of fasting triglycerides and HDL cholesterol at baseline and of changes in fasting triglycerides and HDL cholesterol.

CONCLUSIONS

The prevalence of atherogenic dense LDL in nondiabetic, hypertensive patients is similar to patients with type 2 diabetes. Pioglitazone significantly reduces dense LDL independent from fasting triglycerides and HDL cholesterol. The antiatherogenic potential of pioglitazone may thus be greater than that expected from its effects on triglycerides, LDL, and HDL cholesterol alone.

LDL-cholesterol, HDL-cholesterol or triglycerides--which is the culprit?

Dyslipidaemia in patients with type 2 diabetes commonly consists of elevated triglyceride levels; normal or slightly elevated low-density lipoprotein (LDL)-cholesterol levels with a preponderance of small, dense LDL particles; and low high-density lipoprotein (HDL)-cholesterol levels with a preponderance of small, dense HDL. These abnormalities are closely connected, with prolonged residence of high levels of triglyceride-rich particles in the circulation favoring abnormalities in LDL and HDL. Each of these factors has been associated with endothelial dysfunction; each contributes directly or indirectly to atheroma formation, with small, dense LDL and triglyceride-rich remnants increasing deposition of cholesteryl ester in vessel walls. This process is facilitated by reduced reverse cholesterol transport in association with low levels of HDL-cholesterol and abnormal HDL. Lipid-lowering therapy focused on LDL-cholesterol reduction is highly successful in preventing coronary disease in diabetic patients. Additional strategies for treating the cluster of risk factors in dyslipidaemia are necessary to further reduce atherosclerotic disease in this population.

Diabetic dyslipidaemia: from basic research to clinical practice

The recognition that the increase of plasma triglyceride rich lipoproteins (TRLs) is associated with multiple alterations of other lipoproteins species that are potentially atherogenic has expanded the picture of diabetic dyslipidaemia. The discovery of heterogeneity within major lipoprotein classes VLDL, LDL and HDL opened new avenues to reveal the specific pertubations of diabetic dyslipidaemia. The increase of large VLDL 1 particles in Type 2 diabetes initiates a sequence of events that generates atherogenic remnants, small dense LDL and small dense HDL particles. Together these components comprise the atherogenic lipid triad. Notably the malignant nature of diabetic dyslipidaemia is not completely shown by the lipid measures used in clinical practice. The key question is what are the mechanisms behind the increase of VLDL 1 particles in diabetic dyslipidaemia? Despite the advances of recent years, our understanding of VLDL assembly and secretion is still surprisingly incomplete. To date it is still unclear how the liver is able to regulate the amount of triglycerides incorporated into VLDL particles to produce either VLDL 1 or VLDL 2 particles. The current evidence suggests that the machinery driving VLDL assembly in the liver includes (i) low insulin signalling via PI-3 kinase pathway that enhances lipid accumulation into "nascent " VLDL particles (ii) up-regulation of SREBP-1C that stimulates de novo lipogenesis and (iii) excess availability of "polar molecules" in hepatocytes that stabilizes apo B 100. Recent data suggest that all these steps could be fundamentally altered in Type 2 diabetes explaining the overproduction of VLDL apo B as well as the ability of insulin to suppress VLDL 1 apo B production in Type 2 diabetes. Recent discoveries have established the transcription factors including PPARs, SREBP-1 and LXRs as the key regulators of lipid assembly in the liver. These observations suggest these factors as a new target to tailor more efficient drugs to treat diabetic dyslipidaemia.

Intake of trans fatty acids and low-density lipoprotein size in a Costa Rican population

Intervention studies show that dietary composition altered low-density lipoprotein (LDL) particle size, but population studies are scarce, and the potential effects of trans fatty acids (FA) on LDL size are unknown. Trans FA intake has been associated with a more atherogenic lipid profile and increased coronary heart disease (CHD). We examined the association between dietary intake, including trans FA and LDL size, in 414 randomly selected subjects living in Puriscal, Costa Rica. Dietary intake was assessed by a validated food frequency questionnaire (FFQ). Women had larger LDL size (A) compared with men (263 v 261), and large LDL particles were correlated with increased intake (% energy) of protein (P =.005), animal fat (P =.041), trans FA (P <.0001), and decreased intake of carbohydrate (P =.052) in sex-, age-, and total energy intake-adjusted models. The correlation between trans FA intake and large LDL was significant in multivariate models that included dietary and nondietary factors; a 1% difference in trans FA was associated with a 2.44 A increase in LDL size (P =.004). In sum, it is possible that the effects of dietary factors, such as intake of trans FA on CHD are mediated through their effects on LDL size.

Effects of atorvastatin on electrophoretic characteristics of LDL particles among subjects with heterozygous familial hypercholesterolemia

The effects of the HMG CoA reductase inhibitor atorvastatin on electrophoretic characteristics of LDL particles were evaluated in 46 patients (28 males and 18 females) with heterozygous familial hypercholesterolemia (FH) aged 20-61 carrying either a negative or a defective LDL receptor gene mutation. Following a 6 week drug-free baseline period, FH heterozygotes were treated with atorvastatin (median dose: 20 mg/day, range 10-80 mg/day)) for 6 months to maintain their plasma LDL-cholesterol concentrations between 4.0 and 5.0 mmol/l. Atorvastatin treatment significantly reduced plasma total cholesterol, LDL-cholesterol and triglyceride levels and increased plasma HDL-cholesterol. Furthermore, atorvastatin treatment significantly increased LDL peak particle diameter (LDL-PPD) by 0.5% (from 255.0+/-6.2 to 256.4+/-5.5 A, P=0.004) and reduced the absolute concentration of cholesterol among small (<255 A) and large (>260 A) LDL particles by 35% (P<0.001). Changes in LDL-PPD and plasma triglyceride levels were inversely correlated (R=-0.34; P=0.02). Stepwise multiple linear regression analyses showed that 41.6% of the variation in the LDL-PPD response to atorvastatin was attributable to the initial LDL-PPD (14.4%, P=0.003), the apo E polymorphism (12.4%, P=0.02), the nature of the LDL receptor gene mutation (9.6%, P=0.01) and change in triglyceride levels (5.2%, P=0.04). Moreover, the reduction in the cholesterol content of LDL <255 A was directly correlated with the daily dosage of atorvastatin (P=0.05). Results of the present study showed that atorvastatin alters significantly LDL heterogeneity in patients at high risk of coronary heart disease (CHD) such as FH heterozygotes. These results also suggest that genetic and metabolic factors may be important determinants of atorvastatin-induced changes of LDL particle size and distribution among FH heterozygotes.

Low-density-lipoprotein peak particle size in a Mediterranean population

BACKGROUND

The predominance of small, dense low-density lipoprotein (LDL) particles ('LDL phenotype B') has been associated with a three-fold increased risk of myocardial infarction, but the feasibility of the identification of small, dense LDL as independent predictors of coronary artery disease risk in population studies remains questioned. Design We evaluated the LDL peak particle size and its relation with other established risk factors for coronary heart disease in a group of 156 randomized subjects living on the Mediterranean island of Ustica (71 males and 85 women, range of age 20-69 years), representing approximately 30% of the total population.

RESULTS

The prevalence of LDL phenotype B subjects was low (approximately 15% in both men and women) and there was a clear trend for both genders in reducing the LDL peak particle size with age. Moreover, LDL phenotype B subjects had higher BMI values, prevalence of diabetes and plasma triglyceride (TG) levels and lower plasma HDL-C concentrations in comparison with LDL phenotype A individuals; in a multivariate analysis, plasma TG levels were the only variable independently associated with LDL peak particle size.

CONCLUSIONS

In this population, which appears to be somewhat protected by premature coronary artery disease, a low prevalence of the LDL pattern B was found in both men and women, and plasma TG could have a key role in regulating the LDL peak particle size. The follow up, still ongoing, will provide useful information on the predictive role of LDL peak particle size on cardiovascular risk, at least in a low-risk population.