Endothelial dysfunction in men with small LDL particles

The Beneficial Effect of Lomitapide on the Cardiovascular System in LDLr-/- Mice with Obesity

OBJECTIVES

Homozygous familial hypercholesteremia (HoFH) is a rare, life-threatening metabolic disease, mainly caused by a mutation in the LDL receptor. If untreated, HoFH causes premature death from acute coronary syndrome. Lomitapide is approved by the FDA as a therapy to lower lipid levels in adult patients with HoFH. Nevertheless, the beneficial effect of lomitapide in HoFH models remains to be defined. In this study, we investigated the effect of lomitapide on cardiovascular function using LDL receptor-knockout mice (LDLr-/-).

METHODS

Six-week-old LDLr-/- mice were fed a standard diet (SD) or a high-fat diet (HFD) for 12 weeks. Lomitapide (1 mg/Kg/Day) was given by oral gavage for the last 2 weeks in the HFD group. Body weight and composition, lipid profile, blood glucose, and atherosclerotic plaques were measured. Vascular reactivity and markers for endothelial function were determined in conductance arteries (thoracic aorta) and resistance arteries (mesenteric resistance arteries (MRA)). Cytokine levels were measured by using the Mesoscale discovery V-Plex assays.

RESULTS

Body weight (47.5 ± 1.5 vs. 40.3 ± 1.8 g), % of fat mass (41.6 ± 1.9% vs. 31.8 ± 1.7%), blood glucose (215.5 ± 21.9 vs. 142.3 ± 7.7 mg/dL), and lipid levels (cholesterol: 600.9 ± 23.6 vs. 451.7 ± 33.4 mg/dL; LDL/VLDL: 250.6 ± 28.9 vs. 161.1 ± 12.24 mg/dL; TG: 299.5 ± 24.1 vs. 194.1 ± 28.1 mg/dL) were significantly decreased, and the % of lean mass (56.5 ± 1.8% vs. 65.2 ± 2.1%) was significantly increased in the HFD group after lomitapide treatment. The atherosclerotic plaque area also decreased in the thoracic aorta (7.9 ± 0.5% vs. 5.7 ± 0.1%). After treatment with lomitapide, the endothelium function of the thoracic aorta (47.7 ± 6.3% vs. 80.7 ± 3.1%) and mesenteric resistance artery (66.4 ± 4.3% vs. 79.5 ± 4.6%) was improved in the group of LDLr-/- mice on HFD. This was correlated with diminished vascular endoplasmic (ER) reticulum stress, oxidative stress, and inflammation.

CONCLUSIONS

Treatment with lomitapide improves cardiovascular function and lipid profile and reduces body weight and inflammatory markers in LDLr-/- mice on HFD.

The microsomal triglyceride transfer protein inhibitor lomitapide improves vascular function in mice with obesity

OBJECTIVE

In this study, the effect of lomitapide, a microsomal triglyceride transfer protein inhibitor, on the cardiovascular function in obesity was investigated.

METHODS

Eight-week-old C57BL/6 mice were fed with high-fat diet for 12 weeks in the presence and absence of lomitapide. Lomitapide was administered by gavage (1 mg/kg/d) during the last 2 weeks of high-fat feeding. Body weight, blood glucose, body composition, and lipid profile were determined. Vascular function and endothelial function markers were studied in the aorta and mesenteric resistance arteries.

RESULTS

Lomitapide treatment reduced body weight in mice with obesity. Blood glucose, percentage of fat mass, total cholesterol, and low-density lipoprotein levels were significantly reduced, and the percentage of lean mass was significantly increased after lomitapide treatment. The vascular response to sodium nitroprusside in the aorta and mesenteric arteries was similar among groups. However, the vascular response to acetylcholine was improved in the treated group. This was associated with decreased levels of vascular endoplasmic reticulum stress, inflammation, and oxidative stress.

CONCLUSIONS

Treatment with lomitapide attenuated the increase in body weight in mice with obesity and restored the lipid profile and vascular function. These effects were accompanied by a decrease in inflammation and oxidative stress.

Novel insights: Dynamic foam cells derived from the macrophage in atherosclerosis

Atherosclerosis can be regarded as a chronic disease derived from the interaction between disordered lipoproteins and an unsuitable immune response. The evolution of foam cells is not only a significant pathological change in the early stage of atherosclerosis but also a key stage in the occurrence and development of atherosclerosis. The formation of foam cells is mainly caused by the imbalance among lipids uptake, lipids treatment, and reverse cholesterol transport. Although a large number of studies have summarized the source of foam cells and the mechanism of foam cells formation, we propose a new idea about foam cells in atherosclerosis. Rather than an isolated microenvironment, the macrophage multiple lipid uptake pathways, lipid internalization, lysosome, mitochondria, endoplasmic reticulum, neutral cholesterol ester hydrolase (NCEH), acyl-coenzyme A-cholesterol acyltransferase (ACAT), and reverse cholesterol transport are mutually influential, and form a dynamic process under multi-factor regulation. The macrophage takes on different uptake lipid statuses depending on multiple uptake pathways and intracellular lipids, lipid metabolites versus pro-inflammatory factors. Except for NCEH and ACAT, the lipid internalization of macrophages also depends on multicellular organelles including the lysosome, mitochondria, and endoplasmic reticulum, which are associated with each other. A dynamic balance between esterification and hydrolysis of cholesterol for macrophages is essential for physiology and pathology. Therefore, we propose that the foam cell in the process of atherosclerosis may be dynamic under multi-factor regulation, and collate this study to provide a holistic and dynamic idea of the foam cell.

One-year daily consumption of buttermilk drink containing lutein-enriched egg-yolks does not affect endothelial function in fasting and postprandial state

Previous results have shown that one-year daily consumption of a lutein-enriched egg yolk containing dairy drink did not significantly affect fasting serum lipid and lipoprotein concentrations in adults with early signs of macular degeneration. The current study further substantiates these findings with parameters reflecting endothelial function. Additionally, we extend our observations from the fasting to the postprandial situation. Subjects participated in a 1-y randomized placebo-controlled dietary intervention trial. 52 subjects were included in the active (Egg) group and 49 in the control (Con) group. Changes in postprandial biochemistry (triacylglycerol (TAG), glucose and non-esterified fatty acids (NEFA)) following a mixed meal and flow-mediated dilation (FMD) analyses were evaluated at the start and after one year intervention. Postprandial glycemic and lipemic responses before the intervention as well as the differences in postprandial responses after one-year intervention were comparable between the Egg and the Con group. Fasting FMD was comparable between the groups before the intervention started and at the end of intervention. Additionally, the change in FMD following a mixed meal was comparable between the groups. To conclude, one-year consumption of a lutein-enriched egg yolk incorporated in a dairy drink has no effect on postprandial lipid and glucose metabolism or endothelial function.

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.

Twice weekly intake of farmed Atlantic salmon (Salmo salar) positively influences lipoprotein concentration and particle size in overweight men and women

The US Dietary Guidelines for Americans recommend twice weekly fish intake. Farmed Atlantic salmon is a good source of omega-3 (n-3) fatty acids which have positive lipid modifying effects; however, it is unknown whether these responses are dose-dependent. Our primary research objective was to determine the effect of dose-dependent intake of farmed Atlantic salmon on lipoprotein particle (P) size and concentration. We hypothesized that low-density lipoprotein (LDL)-P and high-density lipoprotein (HDL)-P size and concentration would increase with salmon intake in a dose-dependent manner. Overweight, adult participants (n = 19) were enrolled in a cross-over designed clinical trial evaluating intake of farmed Atlantic salmon. In random order, participants were assigned to 90, 180, or 270 g of salmon twice weekly for 4-week dietary treatments. Following a 4- to 8-week washout, participants crossed over to another dose of fish intake until all treatments were completed. Plasma lipid concentrations were determined and serum lipoprotein concentrations and particle size were determined by nuclear magnetic resonance. Intake of salmon reduced plasma and serum triglyceride (TG) concentrations and increased plasma HDL-C concentrations. The concentrations of large very low-density lipoprotein (VLDL)-P and chylomicron (CM)-P were reduced. Large LDL-P concentrations were increased in a dose-dependent manner. The mean size of VLDL-P was reduced and that of LDL was increased. Total TG was reduced as was the TG content of VLDL-P and CM-P. Twice weekly intake of farmed Atlantic salmon portions influences lipoprotein particle size and concentration in a manner associated with cardiovascular disease risk reduction.

Coronary endothelial dysfunction in non-obstructive coronary artery disease: Risk, pathogenesis, diagnosis and therapy

Up to half of patients with signs and symptoms of stable ischemic heart disease have non-obstructive coronary artery disease (NoCAD). Recent evidence demonstrates that two-thirds of patients with NoCAD have demonstrable coronary endothelial dysfunction represented by microvascular or diffuse epicardial spasm following acetylcholine challenge. Patients with coronary endothelial dysfunction are recognized to have significant health services use and morbidity as well as increased risk of developing flow-limiting coronary artery disease and myocardial events, including death. Currently, there are few centers that test for this etiology owing to lack of knowledge, limited evidence for treatment options and invasive diagnostic strategies. This article reviews the pathophysiology, epidemiology, diagnosis and treatment of coronary endothelial dysfunction as a subgroup of NoCAD.

Pathophysiology of diabetic dyslipidaemia: where are we?

Cardiovascular disease is a major cause of morbidity and mortality in patients with type 2 diabetes mellitus, with a two- to fourfold increase in cardiovascular disease risk compared with non-diabetic individuals. Abnormalities in lipid metabolism that are observed in the context of type 2 diabetes are among the major factors contributing to an increased cardiovascular risk. Diabetic dyslipidaemia includes not only quantitative lipoprotein abnormalities, but also qualitative and kinetic abnormalities that, together, result in a shift towards a more atherogenic lipid profile. The primary quantitative lipoprotein abnormalities are increased triacylglycerol (triglyceride) levels and decreased HDL-cholesterol levels. Qualitative lipoprotein abnormalities include an increase in large, very low-density lipoprotein subfraction 1 (VLDL1) and small, dense LDLs, as well as increased triacylglycerol content of LDL and HDL, glycation of apolipoproteins and increased susceptibility of LDL to oxidation. The main kinetic abnormalities are increased VLDL1 production, decreased VLDL catabolism and increased HDL catabolism. In addition, even though LDL-cholesterol levels are typically normal in patients with type 2 diabetes, LDL particles show reduced turnover, which is potentially atherogenic. Although the pathophysiology of diabetic dyslipidaemia is not fully understood, the insulin resistance and relative insulin deficiency observed in patients with type 2 diabetes are likely to contribute to these lipid changes, as insulin plays an important role in regulating lipid metabolism. In addition, some adipocytokines, such as adiponectin or retinol-binding protein 4, may also contribute to the development of dyslipidaemia in patients with type 2 diabetes.

The Association between Serum LDL Cholesterol and Genetic Variation in Chromosomal Locus 1p13.3 among Coronary Artery Disease Patients

Background. Several polymorphisms of a locus on chromosome 1p13.3 have a significant effect on low-density lipoprotein cholesterol (LDL-C), atherosclerosis, and acute coronary syndrome (ACS). Methods. We aimed to investigate the association between rs599839, rs646776, and rs4970834 of locus 1p13.3 and serum LDL-C and severity of coronary artery stenosis in ACS patients. Genotyping of the rs599839, rs646776, and rs4970834 polymorphisms was performed on Arab patients undergoing coronary angiography for ACS. Patients were divided into group A (ACS with insignificant stenosis (<50%)) and group B (with significant stenosis (≥50%)). Results. Patients carrying the minor G allele in rs599839 had significantly lower mean of LDL-C (2.58 versus 3.44 mM, P = 0.026) than homozygous A allele carriers (GG versus AA). Carriers of minor C allele in rs64776 had significantly higher mean of HDL-C (2.16 versus 1.36 mM, P = 0.004) than carriers of the T alleles (AA versus GG). The odd ratio and 95% confidence interval for dominant model for G allele carriers of rs599839 were 0.51 (0.30–0.92), P = 0.038, among patients with significant stenosis. Conclusions. Polymorphisms rs646776 and rs599839 of locus 1p13.3 were significantly associated with LDL-C and other lipid parameters. In addition, the G-allele carriers of variant rs599839 had a significant protective effect against the atherosclerosis.

Effects of fenofibrate on albuminuria in patients with hypertriglyceridemia and/or hyperuricemia: a multicenter, randomized, double-blind, placebo-controlled, crossover study

BACKGROUND

A slight increase in albuminuria (urinary albumin excretion [UAE] ≥30 mg/d) is associated with hypertension, type 2 diabetes mellitus, dyslipidemia (high triglyceride [TG] and low high-density lipoprotein cholesterol [HDL-C] concentrations), and hyperuricemia. Although antihypertensive and antidiabetic therapies have been reported to reduce UAE, an association between improvement in dyslipidemia and/or hyperuricemia and a reduction in UAE has not been reported.

OBJECTIVE

The aim of this study was to investigate the efficacy and tolerability of fenofibrate on albuminuria in patients with hypertriglyceridemia and/or hyperuricemia.

METHODS

Patients with hypertriglyceridemia and/or hyperuricemia were recruited from general clinics and lipid clinics in Japan; they received fenofibrate (300 mg once daily) in this randomized, double-blind, placebo-controlled, crossover study. Patients in group A received fenofibrate for 8 weeks followed by placebo for an additional 8 weeks, whereas those in group B received placebo for 8 weeks followed by fenofibrate for 8 additional weeks. UAE was measured at baseline and at the end of each 8-week period. Blood tests were performed at baseline and every 4 weeks until study end. Each physician who participated in the study was to record adverse events at each study visit.

RESULTS

A total of 43 patients entered this study (38 men, 5 women; mean [SE] age, 57.1 [1.4] years; mean [SE] body mass index, 24.3 [0.4] kg/m(2)). Twenty-one patients (18 men, 3 women) were randomly assigned to group A and 22 (20 men, 2 women) to group B. In group A, serum TG (P<0.001) and apolipoprotein (apo) C2, C3, and E (all P<0.01) concentrations decreased significantly with fenofibrate, and HDL-C and apo A1 and A2 increased significantly (all P<0.001). All of these parameters returned to near-baseline levels after placebo administration. In group B, serum TG, HDL-C, or apo A1, A2, B, C2, C3, and E concentrations did not change significantly with placebo, but TG (P<0.01), apo C3 (P<0.05), and apo E (P<0.05) were significantly decreased with fenofibrate. In addition, HDL-C (P<0.05), apo A1 (P<0.001), and apo A2 (P<0.01) were significantly increased with fenofibrate. Serum concentrations of TG (group A, P<0.001; group B, P<0.001); apo C2 (group A, P<0.01), C3 (group A, P<0.01; group B, P<0.05), and E (group A, P<0.01; group B, P<0.05); and uric acid (group A, P<0.001; group B, P<0.01) were significantly decreased with fenofibrate compared with placebo. HDL-C and apo A1 and A2 were significantly increased with fenofibrate compared with placebo (all P<0.001 in both groups). Fenofibrate treatment was associated with significant reductions in UAE (group A, P<0.05; group B, P<0.01). Spearman rank correlation analysis showed that changes in UAE were associated with changes in apo C2 (ρ = 0.43; P = 0.02) and apo C3 (ρ = 0.49; P = 0.01) concentrations. Multiple regression analysis revealed that a decrease in apo C3 concentration was independently and significantly associated with reductions in albuminuria (ρ = 0.48; P = 0.01). At the end of the study, neither drug-related nor clinical adverse events were evident in any of the patients, except for an increase in serum creatinine concentration above the upper limit of normal (1.40 mg/dL) in 3 patients (14.3%) in group A and 1 patient (4.5%) in group B.

CONCLUSIONS

In our study population of patients with hypertriglyceridemia and/or hyperuricemia, fenofibrate-induced ameliorations of impaired TG-rich lipoprotein metabolism were associated with reductions in albuminuria.

Lifestyle intervention improves lipoprotein particle size and distribution without weight loss in obese Latino adolescents

Childhood obesity is associated with a pro-atherogenic phenotype contributing to increased cardiovascular disease (CVD) risk. This single-arm pilot study examined the effects of a lifestyle intervention on lipoprotein particle size and cholesterol distribution in obese Latino adolescents. Fifteen obese Latino adolescents (15.0 ± 1.0 years) completed a 12-week nutrition education and exercise intervention. Low-density lipoprotein (LDL) particle size and distribution of cholesterol in lipoprotein subclasses were determined via polyacrylamide gel electrophoresis. The intervention resulted in increases in mean LDL particle size (269.3 ± 3.4 to 271.6 ± 2.9 Å, P = 0.0003) and cholesterol in large high-density lipoprotein (HDL) subfractions (22.4 ± 11.2 to 26.8 ± 10.6% area, P = 0.007) along with decreases of cholesterol in small LDL (1.6 ± 2.0 to 0.6 ± 1.2% area, P < 0.01) and HDL subfractions (23.2 ± 9.4 to 19.0 ± 6.7% area, P = 0.05). These improvements were observed independent of changes in weight (90.7 ± 26.2 to 89.9 ± 27.8 kg, P > 0.05) and suggest that lifestyle modification in obese youth may reduce cardiovascular risk by shifting lipoprotein particle size and cholesterol distribution to a less atherogenic phenotype.

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.

Anti-inflammatory effect of atorvastatin on vascular reactivity and insulin resistance in fructose fed rats

We investigated the possible protective effect of atorvastatin against vascular dysfunction associated with insulin resistance (IR) in fructose-fed model rats. The effect of atorvastatin (10 mg/kg/day for 8 weeks) on vascular reactivity, glucose, cholesterol, insulin, and the IR index in a well-established model of dietary hypertriglyceridemia, the fructose-fed rat, was investigated. Fructose feeding (10% fructose in drinking water for 8 weeks) induced hypercholesterolemia and hyperinsulinemia without any change in blood glucose levels. Fructose feeding also elevated serum tumor necrosis factor-alpha (TNF-α), the insulin resistance index, leukocyte infiltration, and endothelial cell pyknosis. Fructose feeding induced hyper-responsiveness to both phenylephrine (PE), KCl, and hyporesponsiveness to acetylcholine (Ach) but not to sodium nitroprusside-induced relaxation. Atorvastatin, given concurrently with fructose, reduced hypercholesterolemia, hyperinsulinemia, TNF-α level, and the IR index. It also reduced leukocyte infiltration and endothelial cell pyknosis and decreased hyper-responsiveness to both PE and KCl but did not affect hyporesponsiveness to Ach relaxation. In conclusion, atorvastatin protected against impairment in aortic vascular reactivity associated with insulin resistance, particularly increased contractility, but not reduced endothelium-dependent relaxation, by a mechanism involving a reduction in cholesterol and IR in addition to anti-inflammatory effects.

Administration of highly purified eicosapentaenoic acid to statin-treated diabetic patients further improves vascular function

We prospectively examined the additional effects of highly purified eicosapentaenoic acid (EPA) particularly on the vascular function of diabetic patients with hypercholesterolemia receiving statin therapy. We enrolled 28 patients with type 2 diabetes complicated by dyslipidemia who had been treated with statins for at least one year. The patients were randomly assigned to 2 groups: administration of statin alone (group S: n = 13) and addition of EPA to the current statin therapy (group SE: n = 15). The highly purified EPA was administered at a dose of 1,800 mg/day for 6 months. To evaluate vascular function, the duration of reactive hyperemia (DRH), which is the time required for forearm blood flow to return to the basal level after inducing reactive hyperemia, was measured using strain gauge plethysmography. There were no significant differences in the clinical background factors between the 2 groups. Low-density lipoprotein cholesterol (LDL-C), and non-high-density lipoprotein cholesterol levels significantly decreased after 6 months only in group SE. Compared with the baseline data, no significant change in DRH was observed after 6 months in group S. By contrast, DRH was significantly prolonged after 6 months in group SE, indicating that the addition of highly purified EPA improved vascular function. Our results showed that in patients with type 2 diabetes and receiving statin therapy whose LDL-C level was less than 100 mg/dL, the addition of highly purified EPA for 6 months significantly improved vascular function.

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.

Lipid disorders in type 1 diabetes

Patients with type 1 diabetes (T1D) also present with lipid disorders. Quantitative abnormalities of lipoproteins are observed in T1D patients with poor glycaemic control (increased plasma triglycerides and low-density lipoprotein [LDL] cholesterol) or nephropathy (increased triglycerides and LDL cholesterol, low level of high density lipoprotein [HDL] cholesterol). In cases of T1D with optimal glycaemic control, plasma triglycerides and LDL cholesterol are normal or slightly decreased, while HDL cholesterol is normal or slightly increased. Several qualitative abnormalities of lipoproteins, which are potentially atherogenic, are observed in patients with T1D, even in those with good metabolic control. These abnormalities include increased cholesterol-to-triglyceride ratios within very low-density lipoprotein (VLDLs), increased triglycerides in LDLs and HDLs, compositional changes in the peripheral layer of lipoproteins, glycation of apolipoproteins, increased oxidation of LDLs and an increase in small, dense LDL particles. These qualitative changes in lipoproteins are likely to impair their function. In vitro, VLDLs and LDLs from patients with T1D induced abnormal responses in the cellular cholesterol metabolism of human macrophages. HDLs from patients with T1D are thought to be less effective in promoting cholesterol efflux from cells, and have been shown to have reduced antioxidative and vasorelaxant properties. These qualitative abnormalities are not fully explained by hyperglycaemia and may be partly due to peripheral hyperinsulinaemia associated with subcutaneous insulin administration. However, the precise consequences of these qualitative lipid changes on the development of cardiovascular disease in T1D are, as yet, unknown.

The role of pioglitazone in modifying the atherogenic lipoprotein profile

Pioglitazone, a thiazolidinedione, has established efficacy in improving glycaemic control in patients with type 2 diabetes. Pioglitazone also improves components of the mixed dyslipidaemia profile common in these patients, as typified by raised levels of plasma triglycerides, low levels of HDL cholesterol (HDL-C) and a raised proportion of LDL cholesterol (LDL-C) occurring as the small dense subfraction. In head-to-head trials, pioglitazone has consistently shown superior benefits on LDL-C and HDL-C as well as triglycerides compared with rosiglitazone and sulphonylureas. Pioglitazone used as monotherapy or combination therapy reduces levels of small dense LDL3 particles while raising levels of larger and less atherogenic LDL fractions. In addition, pioglitazone reduces cholesterol load and particle numbers of LDL3. Importantly, the differential effects of pioglitazone on LDL subfractions are complimentary and additive to those of simvastatin. Pioglitazone increases total HDL-C levels by 10-20%, mainly because of an increase in the larger HDL2 subfraction. Pioglitazone also significantly reduces plasma triglyceride levels by 10-25%. In recent studies, pioglitazone significantly reduced carotid and coronary atherosclerosis compared with the sulphonylurea glimepiride. The antidyslipidaemic effects of pioglitazone--in particular, improvements in HDL-C and reduction of small dense LDL3--may have contributed to these effects.

Fluvastatin/fenofibrate vs. simvastatin/ezetimibe in patients with metabolic syndrome: different effects on LDL-profiles

BACKGROUND

Patients with metabolic syndrome (MS) and type 2 diabetes (T2DM) show increased risk for coronary artery disease. Lipoprotein metabolism is characterized by elevated triglycerides (TG), low high-density lipoprotein cholesterol (HDL-C) and predominance of atherogenic small, dense low-density lipoprotein (sdLDL), while low-density lipoprotein (LDL) cholesterol is only slightly elevated.

METHODS

Multicentre, randomized, open-label cross-over study investigating the effect of combination of fluvastatin/fenofibrate (80/200 mg) (F&F) on LDL-subfractions compared with combination of simvastatin/ezetimibe (20/10 mg) (S&E) in patients with MS/T2DM.

RESULTS

Seventy-five patients were randomized, 69 completed the study and LDL-subfractions of 56 patients were analysed. Thirty-eight out of 56 patients (68%) showed a profile dominated by sdLDL. In these, TG and total cholesterol (TC) were elevated compared with non-sdLDL patients. In all patients, reduction of TC and LDL cholesterol (LDL-C) by S&E was stronger than by F&F. The increase of HDL-C was stronger with S&E in the non-sdLDL group, whereas in the sdLDL group, there was no difference between treatments. In non-sdLDL patients, there was no effect on TG or LDL-radius. However, in the sdLDL group, F&F was more effective in reducing TG and increased LDL radius, whereas S&E reduced LDL radius even further.

CONCLUSIONS

S&E is more efficient in reducing TC and LDL-C. This is also true for HDL-C increase in non-sdLDL patients. However, in patients with sdLDL, F&F was more efficient in reducing TG and increasing LDL radius.

Coronary artery endothelial dysfunction is positively correlated with low density lipoprotein and inversely correlated with high density lipoprotein subclass particles measured by nuclear magnetic resonance spectroscopy

OBJECTIVE

The association between cholesterol and endothelial dysfunction remains controversial. We tested the hypothesis that lipoprotein subclasses are associated with coronary endothelial dysfunction.

METHODS AND RESULTS

Coronary endothelial function was assessed in 490 patients between November 1993 and February 2007. Fasting lipids and nuclear magnetic resonance (NMR) lipoprotein particle subclasses were measured. There were 325 females and 165 males with a mean age of 49.8+/-11.6 years. Coronary endothelial dysfunction (epicardial constriction>20% or increase in coronary blood flow<50% in response to intracoronary acetylcholine) was diagnosed in 273 patients, the majority of whom (64.5%) had microvascular dysfunction. Total cholesterol and LDL-C (low density lipoprotein cholesterol) were not associated with endothelial dysfunction. One-way analysis and multivariate methods adjusting for age, gender, diabetes, hypertension and lipid-lowering agent use were used to determine the correlation between lipoprotein subclasses and coronary endothelial dysfunction. Epicardial endothelial dysfunction was significantly correlated with total (p=0.03) and small LDLp (LDL particles) (p<0.01) and inversely correlated with total and large HDLp (high density lipoprotein particles) (p<0.01).

CONCLUSIONS

Epicardial, but not microvascular, coronary endothelial dysfunction was associated directly with LDL particles and inversely with HDL particles, suggesting location-dependent impact of lipoprotein particles on the coronary circulation.

Small dense LDL and VLDL predict common carotid artery IMT and elicit an inflammatory response in peripheral blood mononuclear and endothelial cells

OBJECTIVE

The presence of small dense LDL has been associated with increased cardiovascular risk and with the progression of coronary and carotid atherosclerosis in case-control and prospective studies. The aim of this study was to investigate the relation between different lipoprotein subfractions with intima-media thickness of the common carotid artery in a free-living, healthy population, and to evaluate whether in patients with comparable LDL-C, the different lipoprotein subclasses differently affected the expression of chemokines, cytokines and adhesion molecules in peripheral blood mononuclear and endothelial cells.

METHODS AND RESULTS

The lipoprotein cholesterol profile and the LDL buoyancy (LDL-RF) were evaluated in a cohort of 156 healthy subjects randomly selected from the PLIC (Progressione Lesione Intimale Carotidea) study. The LDL-RF was directly and significantly correlated to weight, body mass index, waist, hip, waist/hip ratio, triglycerides, fasting glycemia and intima media thickness (IMT) of the common carotid artery and inversely related to HDL-C. After multivariate statistical analysis, IMT was independently associated with age, LDL-RF and HDL-C and among the lipoprotein subclasses, only those corresponding to triglyceride-rich lipoproteins (TGRL) and small dense LDL (sdLDL) independently predicted IMT variance. Peripheral blood mononuclear cells (PBMC) isolated from patients with the predominance of sdLDL (pattern B) had an increased mRNA expression of pro-inflammatory molecules compared to PBMC from patients with the predominance of large LDL (pattern A); in endothelial cells TGRL from pattern B subjects and much less those from pattern A induced the expression of pro-inflammatory genes while sdLDL from either pattern A or B subjects were less effective and showed comparable effects.

CONCLUSION

LDL-relative flotation rate significantly correlates with several cardiometabolic parameters. Furthermore cholesterol levels lipoprotein subfractions within the TGRL and sdLDL density range are independent predictors of IMT variance and are associated with a pro-inflammatory activation of PBMC and endothelial cells.

Effects of increasing particle size of low-density lipoprotein on restenosis after coronary stent implantation

BACKGROUND

Small dense low-density lipoprotein (LDL) has emerged as an important risk factor in coronary atherosclerosis and vascular inflammation, which is related to neointimal hyperplasia. Therefore, the aim of the present study was to investigate whether changes in LDL particle size are related to in-stent restenosis (ISR).

METHODS AND RESULTS

The LDL subfraction and lipid profiles were measured in 274 patients (412 stents) at both baseline and follow-up coronary angiography (CAG). The incidence of ISR (80 lesions, 19.4%) was lower in the patients with increased LDL particle size than in those with no change or decrease (14.2% vs 25.8%, p=0.004). Logistic multivariate analysis revealed that stent length (>or=24 mm) (odds ratio (OR) =1.913, p=0.027), post minimal luminal diameter (>3 mm) (OR =0.528, p=0.028), acute coronary syndrome (OR =2.294, p=0.005), decrease in high-density lipoprotein-cholesterol (OR =1.028, p=0.047) and increase in LDL particle size (OR =0.528, p=0.031) were independent predictors for ISR.

CONCLUSIONS

In the present study, an increase in the LDL particle size between baseline and follow-up CAG was associated with reduced incidence of ISR. Therefore, modification of LDL particle size may have a beneficial effect on the risk of ISR.

Effects of insulin resistance on endothelial function: possible mechanisms and clinical implications

Insulin resistance (IR) is defined as a reduced responsiveness of peripheral tissues to the effects of the hormone, referring to abated ability of insulin in stimulating glucose uptake in peripheral tissues and in inhibiting hepatic glucose output. Insulin has both a vasodilatory effect, which is largely endothelium dependent through the release of nitric oxide, and a vasoconstrictory effect through the stimulation of the sympathetic nervous system and the release of endothelin-1. IR and endothelial dysfunction (ED) are not only linked by common pathogenetic mechanisms, involving deranged insulin signalling pathways, but also by other, indirect to the hormone's actions, mechanisms. Different treatment modalities have been proposed to affect positively both the metabolic effects of insulin and ED. Weight loss has been shown to improve sensitivity to insulin as a result of either altered diet or exercise. Exercise has favourable effects on endothelial function in normal states and in states of disease, in men and women, and throughout the age spectrum and, hence, in IR states. Metformin improves sensitivity to insulin and most likely affects positively ED. Studies have shown that inhibitors of the renin-angiotensin system alter IR favourably, while Angiotensin converting enzyme (ACE) inhibitors and Angiotensin receptor type II (ATII) inhibitors improve ED. Ongoing studies are expected to shed more light on the issue of whether treatment with the thiazolidinediones results in improvement of endothelial function, along with the accepted function of improving insulin sensitivity. Finally, improved endothelial function by such treatments is not in itself proof of reduced risk for atherosclerosis; this remains to be directly tested in clinical trials.

Relationships between exercise-induced reductions in thigh intermuscular adipose tissue, changes in lipoprotein particle size, and visceral adiposity

Small LDL and HDL particle size are characteristic of a proatherogenic lipoprotein profile. Aerobic exercise increases these particle sizes. Although visceral adipose tissue (VAT) has been strongly linked with dyslipidemia, the importance of intermuscular adipose tissue (IMAT) to dyslipidemia and exercise responses is less well understood. We measured exercise-associated changes in thigh IMAT and VAT and examined their relationships with changes in LDL and HDL particle size. Sedentary, dyslipidemic, overweight subjects (n = 73) completed 8-9 mo of aerobic training. Linear regression models were used to compare the power of IMAT change and VAT change to predict lipoprotein size changes. In men alone (n = 40), IMAT change correlated inversely with both HDL size change (r = -0.42, P = 0.007) and LDL size change (r = -0.52, P < 0.001). That is, reduction of IMAT was associated with a shift toward larger, less atherogenic lipoprotein particles. No significant correlations were observed in women. After adding VAT change to the model, IMAT change was the only significant predictor of either HDL size change (P = 0.034 for IMAT vs. 0.162 for VAT) or LDL size change (P = 0.004 for IMAT vs. 0.189 for VAT) in men. In conclusion, in overweight dyslipidemic men, exercise-associated change in thigh IMAT was inversely correlated with both HDL and LDL size change and was more predictive of these lipoprotein changes than was change in VAT. Reducing IMAT through aerobic exercise may be functionally related to some improvements in atherogenic dyslipidemia in men.

Inactivity, exercise training and detraining, and plasma lipoproteins. STRRIDE: a randomized, controlled study of exercise intensity and amount

Exercise has beneficial effects on lipoproteins. Little is known about how long the effects persist with detraining or whether the duration of benefit is effected by training intensity or amount. Sedentary, overweight subjects ( n = 240) were randomized to 6-mo control or one of three exercise groups: 1) high-amount/vigorous-intensity exercise; 2) low-amount/vigorous-intensity exercise; or 3) low-amount/moderate-intensity exercise. Training consisted of a gradual increase in amount of exercise followed by 6 mo of exercise at the prescribed level. Exercise included treadmill, elliptical trainer, and stationary bicycle. The number of minutes necessary to expend the prescribed kilocalories per week (14 kcal·kg body wt−1·wk−1for both low-amount groups; 23 kcal·kg body wt−1·wk−1for high-amount group) was calculated for each subject. Average adherence was 83–92% for the three groups; minutes per week were 207, 125, and 203 and sessions per week were 3.6, 2.9, and 3.5 for high-amount/vigorous-intensity, low-amount/vigorous intensity, and low-amount/moderate-intensity groups, respectively. Plasma was obtained at baseline, 24 h, 5 days, and 15 days after exercise cessation. Continued inactivity resulted in significant increases in low-density lipoprotein (LDL) particle number, small dense LDL, and LDL-cholesterol. A modest amount of exercise training prevented this deterioration. Moderate-intensity but not vigorous-intensity exercise resulted in a sustained reduction in very-low-density lipoprotein (VLDL)-triglycerides over 15 days of detraining ( P < 0.05). The high-amount group had significant improvements in high-density lipoprotein (HDL)-cholesterol, HDL particle size, and large HDL levels that were sustained for 15 days after exercise stopped. In conclusion, physical inactivity has profound negative effects on lipoprotein metabolism. Modest exercise prevented this. Moderate-intensity but not vigorous-intensity exercise resulted in sustained VLDL-triglyceride lowering. Thirty minutes per day of vigorous exercise, like jogging, has sustained beneficial effects on HDL metabolism.

Diabetes mellitus as a prothrombotic condition

Diabetes mellitus (DM) is characterized by fasting hyperglycaemia and a high risk of atherothrombotic disorders affecting the coronary, cerebral and peripheral arterial trees. The risk of myocardial infarction (MI) is 3-5 fold higher in Type 2 DM and a DM subject with no history of MI has the same risk as a non-DM subject with a past history of MI. In total around 70% of deaths are vascular with poorer outcomes to both acute events and cardiological interventions. It was proposed that clustering of vascular risk factors (hyperinsulinaemia, dysglycaemia, dyslipidaemia and hypertension) around insulin resistance (IR) accounted for the increase in risk with Type 2 DM. The importance of this became apparent with the recognition that risk clustering occurs in normoglycaemic and impaired glucose tolerance (IGT) subjects with IR, in total around 25% of the population in addition to long-standing Type 1 subjects with renal disease. Evidence indicates that thrombotic risk clustering also occurs in association with IR, suppression of fibrinolysis due to elevated concentrations of the fibrinolytic inhibitor, plasminogen activator inhibitor-1 (PAI-1) is invariable with IR and there is evidence that this is regulated by the effects of triglyceride on the PAI-1 gene promoter. Other studies indicated that prothrombotic risk (coagulation factors VII, XII and fibrinogen) also associates with the IR syndrome. The development of endothelial cell dysfunction with suppression of nitric oxide and prostacyclin synthesis, combined with platelet resistance to the anti-aggregatory effects of these hormones leads to loss of control over platelet activation. In addition, hyperglycaemia and glycation have marked effects on fibrin structure function, generating a clot which has a denser structure, resistant to fibrinolysis. The combination of increased circulating coagulation zymogens, inhibition of fibrinolysis, changes in fibrin structure/function and alterations in platelet reactivity creates a thrombotic risk clustering which underpins the development of cardiovascular disease.

Vascular defect beyond the endothelium in type II diabetic patients with overt nephropathy and moderate renal insufficiency

There is a paucity of data on the effects of overt nephropathy and moderate renal impairment on endothelial function in diabetic patients. A total of 26 type II diabetic (DM) patients with nephropathy (DMN+) (mean +/- s.d. age: 63.7 +/- 6.3 years), 32 diabetic patients without nephropathy (DMN-) (59.4 +/- 10.1 years), and 52 non-diabetic subjects (54.9 +/- 8.2 years) were recruited. High-resolution ultrasound scan was used to measure carotid intima media thickness (IMT) and flow-mediated dilation (FMD) of the brachial artery. Endothelium-independent dilation was determined by maximal vascular dilation after sublingual nitroglycerine (glyceryl trinitrate (GTN)-induced dilation). The mean carotid IMT increased progressively from non-DM to DMN- to DMN+ groups (0.74 +/- 0.23 vs 0.80 +/- 0.25 vs 1.03 +/- 0.38 mm; P=0.001 for trend) whereas FMD- (4.3 +/- 2.5 vs 3.9 +/- 1.7 vs 1.9 +/- 2.0%, P<0.001 for trend) and GTN-induced dilation (14.7 +/- 4.0 vs 14.5 +/- 3.9 vs 10.3 +/- 3.2%; P<0.001 for trend) declined in an opposite manner. On multivariate analysis, age (beta=0.257, P=0.009), glomerular filtration rate (beta=-0.364, P<0.001), and smoking (beta=0.25, P=0.013) were independently associated with carotid IMT (F=15.76, R(2)=0.340, P<0.001). After adjustment for baseline brachial arterial diameter, history of smoking (beta=-0.039, P<0.001), fasting plasma glucose (beta=-0.033, P=0.002), and total cholesterol (beta=-0.023, P=0.024) were independently associated with vessel diameter after FMD (F=2446.5, R(2)=0.992, P<0.001); whereas age (beta=-0.069, P=0.001) and urinary albumin excretion (beta=-0.048, P=0.018) were independently associated with vessel diameter after GTN (F=851.6, R(2)=0.967, P<0.001). Type II diabetic patients with overt nephropathy and moderate renal impairment had both structural and functional vascular abnormalities beyond the endothelium.

The effect of PPARgamma-agonism on LDL subclass profile in patients with type 2 diabetes and coronary artery disease

Patients with type 2 diabetes (T2DM) often present a preponderance of small, dense LDL particles (small-LDL), which are associated with a high risk of myocardial infarction. Some studies suggest that PPARgamma-agonists increase LDL cholesterol but have divergent effects on various LDL subclasses in T2DM patients. We studied the effect of rosiglitazone on the LDL subclass profile in T2DM patients with verified coronary artery disease (CAD). 58 patients with T2DM (HbA1c < 8.5%) and CAD were enrolled in a 16-week, randomized, double-blind and placebo-controlled trial with rosiglitazone 8 mg/day (n = 29) or placebo (n = 29). The LDL subclass profile was measured with gel electrophoresis. Rosiglitazone improved insulin sensitivity and glycemic control. Total cholesterol did not change after rosiglitazone treatment (p = 0.062, ANCOVA adjusted for gender and baseline values), whereas LDL (including IDL) cholesterol increased from 2.33 +/- 0.48 to 2.67 +/- 0.61 mmol/l (p = 0.002 vs. baseline, p = 0.0497 vs. placebo) and large buoyant LDL (large-LDL < 250A) increased from 1.31 +/- 0.36 to 1.46 +/- 0.42 mmol/l (p = 0.010 vs. baseline, p = 0.044 vs. placebo) in the rosiglitazone group. No significant changes occurred to the concentration of small-LDL (< 250A), the average LDL particle size, or HDL or triglyceride concentrations. Whole-body insulin sensitivity was associated with the average LDL particle size after intervention in the whole population (r = 0.40, p = 0.002) and in the rosiglitazone group (r = 0.43, p = 0.020). In conclusion, in T2DM patients with CAD, rosiglitazone treatment significantly increases the concentration of large (buoyant) LDL cholesterol, but not of small dense LDL cholesterol. The long term consequences of this divergent effect of rosiglitazone on LDL subfractions require further exploration.

Impaired vascular dilatation in women with a history of pre-eclampsia

OBJECTIVE

The mechanisms underlying increased cardiovascular risk among women with a history of pre-eclampsia remain unclear. Impaired endothelial function has been observed in both pre-eclampsia and atherosclerosis, and provides a plausible link between the two conditions. We studied endothelial function and arterial compliance in non-pregnant, previously pre-eclamptic women.

DESIGN

A study of 30 women with a history of pre-eclampsia and 21 women with a previous normotensive, uncomplicated pregnancy was carried out.

METHODS

Changes in brachial artery blood flow, induced by intra-arterial infusions of an endothelium-independent (sodium nitroprusside) and an endothelium-dependent (acetylcholine) vasodilator, were measured by venous occlusion plethysmography. Arterial stiffness was assessed by pulse-wave analysis.

RESULTS

Vasodilatation was impaired in women with previous pre-eclampsia; at low and high concentrations of endothelium-independent (P = 0.004 and P = 0.057, respectively) and endothelium-dependent (P = 0.045 and P = 0.02) vasodilators, respectively. There was no difference in arterial stiffness between the groups (P = 0.45). In multiple regression analyses both endothelium-independent and endothelium-dependent vasodilatations were independently associated with a history of pre-eclampsia and parity. There was no correlation with blood pressure, body mass index (BMI), smoking or age.

CONCLUSIONS

The finding of impaired vascular dilatation several years after a pre-eclamptic pregnancy could contribute to the higher risk of cardiovascular disease in these women.

Women and Ischemic Heart Disease

The current review highlights gender-specific issues in ischemic heart disease (IHD) presentation, evaluation, and outcomes with a special focus on the results derived from the National Institutes of Health-National Heart, Lung, and Blood Institute-sponsored Women's Ischemia Syndrome Evaluation (WISE) study. New evidence on gender-based differences in vascular wall, atherosclerotic plaque deposition, pathophysiology, and innovative cardiovascular imaging techniques are reviewed. Critical areas of further inquiry needed to advance new gender-specific IHD understanding are detailed.

New insight into the pathophysiology of lipid abnormalities in type 2 diabetes

Lipid abnormalities in patients with type 2 diabetes are likely to play an important role in the development of atherogenesis. These lipid disorders include not only quantitative but also qualitative abnormalities of lipoproteins which are potentially atherogenic. The main quantitative abnormalities are increased triglyceride levels, related to an augmented hepatic production of VLDL and a reduction of both VLDL and IDL catabolism, and decreased HDL-Cholesterol levels due to an accelerated HDL catabolism. The main qualitative abnormalities include large VLDL particles (VLDL1), relatively rich in triglycerides, small dense LDL particles, increase in triglyceride content of LDL and HDL, glycation of apolipoproteins and increased susceptibility of LDL to oxidation. Moreover, although plasma LDL-cholesterol level is usually normal in type 2 diabetic patients, LDL particles show significant kinetic abnormalities, such as reduced turn-over, which is potentially harmful. The pathophysiology of lipid abnormalities in type 2 diabetes is not yet totally explained. However, insulin resistance and the "relative" insulin deficiency, observed in patients with type 2 diabetes, are likely to play a crucial role since insulin has an important function in the regulation of lipid metabolism. In addition, it is not excluded that adipocytokines, such as adiponectin, could play a role in the pathophysiology of lipid abnormalities in type 2 diabetes.

Microvascular endothelial function in subjects with Type 2 diabetes and the effect of lipid-lowering therapy

AIMS

Abnormalities of microvascular and endothelial function are present in subjects with Type 2 diabetes. Although statin therapy improves cardiovascular risk in diabetes, dyslipidaemia in diabetes may be more responsive to combined statin and fibrate therapy. We examined the effect of cerivastatin and fenofibrate on microvascular function in subjects with Type 2 diabetes with no clinical evidence of cardiovascular disease and near normal lipid levels.

METHODS

Age-, sex-, lipid- and blood pressure-matched subjects with Type 2 diabetes were randomized in double-blind fashion to one of four treatment groups: group 1 placebo/placebo (n=12), group 2 fenofibrate/placebo (n=10), group 3 cerivastatin/placebo (n=20) and group 4 cerivastatin/fenofibrate (n=11). The subjects were recruited from the Lipid in Diabetes Study. Microvascular function was assessed by skin blood flow response to iontophoresis of acetylcholine and sodium nitroprusside and by skin maximum hyperaemia to local heating. Measurements were carried out at baseline and 3 months later.

RESULTS

Although all lipid parameters improved in groups 2-4 after 3 months' therapy, no difference was detected in skin blood flow to iontophoresis or maximum hyperaemia in any of the groups. Highly sensitive c-reactive protein (Hs-CRP) did not change with therapy.

CONCLUSIONS

In conclusion, we were unable to demonstrate any improvement in microvascular endothelial function in non-hyperlipidaemic Type 2 diabetic subjects treated with single or combination lipid-lowering therapy.

Review article: the metabolic syndrome--a chronic cardiovascular inflammatory condition

The atherosclerotic process is regulated by inflammatory mechanisms, which also appear to be involved in the modulation of insulin-resistance, a key player in the pathogenesis of the metabolic syndrome (MS). The interaction between components of the clinical phenotype of the MS with its biological phenotype (insulin resistance, dyslipidaemia, etc.) contributes to the development of a pro-inflammatory state characterized by an increased oxidative stress (i.e. oxidized lipoproteins) and a chronic, subclinical vascular inflammation, as also suggested by the increased C reactive protein (CRP) concentration found in patients with MS. The subclinical inflammatory state peculiar of the MS modulates the atherosclerotic process at different stages, resulting in: (i) endothelial dysfunction and increased expression of endothelial adhesion molecules; (ii) an enhanced recruitment of monocytes within the arterial wall, in the early stages of the atherosclerotic process; leading to (iii) the formation of an unstable atherosclerotic plaque, rich in inflammatory cells, which is the culprit lesion in the vast majority of both coronary and cerebrovascular events observed in with MS.

Oxidized LDL and small LDL particle size are independently predictive of a selective defect in microcirculatory endothelial function in type 2 diabetes

AIM

To explore the associations of LDL (low-density lipoprotein) particle size and oxidized LDL with endothelium-dependent function of the forearm microcirculation in diabetes.

METHODS

Endothelium-dependent function was examined in 43 middle-aged men and women with type 2 diabetes and 10 age-matched controls. All received aspirin to inhibit endothelial cyclo-oxygenase. Forearm blood flow (FBF) was measured using venous occlusion plethysmography with separate administration of acetylcholine (ACh) and bradykinin (BK) into the brachial artery. Endothelium-independent function was assessed using sodium nitroprusside (SNP). N(G)-monomethyl-L-arginine (L-NMMA) was co-infused with ACh (ACh + L-NMMA) and BK (BK + L-NMMA) to assess non-NO-mediated contributions to endothelium-dependent function.

RESULTS

Subjects with diabetes had impaired endothelium-dependent and endothelium-independent function compared with controls (p < 0.01 for ACh, BK and SNP). In multivariate regression analysis, LDL size (r = 0.41 and p = 0.007), oxidized LDL (r = -0.41 and p = 0.007) and duration of diabetes (r = -0.37 and p = 0.02) predicted FBF response to ACh independently of age, gender and systolic blood pressure. There were no associations between LDL size, oxidized LDL, duration of diabetes and FBF response to BK, SNP, ACh + L-NMMA or BK + L-NMMA.

CONCLUSION

In type 2 diabetes, small dense LDL particles, duration of diabetes and oxidized LDL may independently contribute to endothelial dysfunction of the microcirculation. These disturbances may occur via a selective defect, because ACh and BK activate endothelial NO synthase via different G-protein signal transduction pathways.

No relationship between low-density lipoproteins and endothelial function in hemodialysis patients

BACKGROUND

Relationships between low-density lipoprotein cholesterol and endothelial function in hemodialysis patients have yet to be investigated. Furthermore, current reporting of endothelial function data using flow-mediated dilatation has recognised limitations. The aims of the study were to determine the relationship between low-density lipoproteins and endothelial function in hemodialysis patients and to investigate the validity of determining the area under the curve for data collected during the flow-mediated dilatation technique.

METHODS

Brachial artery responses to reactive hyperemia (endothelial-dependent) and glyceryl trinitrate (endothelial-independent) were assessed in 19 hemodialysis patients using high-resolution ultrasound. Lipid profiles and other factors known to effect brachial artery reactivity were also measured prior to the flow-mediated dilatation technique.

RESULTS

There were no significant relationships between serum low-density lipoproteins and endothelial-dependent or -independent vasodilation using absolute change (mm), relative change (%), time to peak change (s) or area under the curve (mm x s). In hemodialysis patients with atherosclerosis, area under the curve analysis showed a significantly (p<0.05) decreased endothelial-dependent response (mean+/-S.D.: 19.2+/-17.4) compared to non-atherosclerotic patients (42.3+/-28.6). However, when analysing these data using absolute change, relative change or time to peak dilatation, there were no significant differences between the two groups.

CONCLUSIONS

In summary, there was no relationship between low-density lipoproteins and endothelial function in hemodialysis patients. In addition, area under the curve analysis of flow-mediated vasodilatation data may be a useful method of determining the temporal vascular response during the procedure.

Determinants of endothelial dysfunction and carotid intima???media thickness in combined hyperlipidemia

BACKGROUND

Early functional and morphological changes in the course of the atherosclerotic process are manifested as endothelial dysfunction and increased intima-media thickness (IMT) of the arterial wall. These are both associated with various atherosclerotic risk factors. We investigated whether the same factors are associated with functional and morphological changes of the arterial wall in men with combined hyperlipidemia.

METHODS

Flow-mediated dilatation (FMD) of the brachial artery and carotid IMT were measured in 72 male patients aged 46+/-5 years with combined hyperlipidemia. Serum lipoproteins, fibrinolytic and coagulation parameters, blood glucose, proinflammatory cytokines and C-reactive protein were also measured.

RESULTS

Tumor necrosis factor-alpha, interleukin 6 and apolipoprotein (apo) B were found to be independent predictors of FMD, explaining 87% of FMD variability in multivariate analysis. On the other hand, total tissue factor pathway inhibitor and apo B were independent predictors of increased carotid IMT, explaining 82% of the variation in carotid IMT.

CONCLUSIONS

Apo B, which is a marker for the presence of the atherogenic lipoproteins, is associated with both functional and morphological changes of the artery wall. In addition, in asymptomatic overweight middle-aged men with combined hyperlipidemia, functional changes are associated with proinflammatory cytokines, while morphological changes are associated with coagulation parameters.

Small low-density lipoprotein particles and endothelium-dependent vasodilation in postmenopausal women

Low concentrations of estrogen may decrease endothelial function in postmenopausal women. Elevated plasma triglycerides after menopause are frequently associated with a small, dense low-density lipoprotein (LDL) phenotype. Small LDL particles that are more susceptible to oxidation can also inhibit endothelium-dependent vasodilation. The purpose of the present study was to investigate whether hypertriglyceridemia-induced small LDL particles are associated with endothelial dysfunction in postmenopausal women. We studied 15 premenopausal and 41 postmenopausal women. Postmenopausal subjects were divided into those with LDL subclass pattern A (large particles) and those with pattern B (small particles). Plasma lipids, hormones, and diameter and oxidative susceptibility of LDL were measured. Vasodilatory responses of the brachial artery were evaluated by measuring flow-mediated vasodilation (FMD) and nitroglycerin-induced vasodilation (NID). FMD in both postmenopausal groups was significantly lower than in premenopausal women. FMD in subjects with pattern B was significantly smaller than in those with pattern A (4.9 +/- 1.9% versus 8.8 +/- 3.6%). NID did not differ significantly among the groups. Plasma triglyceride concentrations were higher, lag time for LDL oxidation was shortened, and LDL-derived thiobarbituric acid-reactive substance (TBARS) concentrations were significantly greater in subjects with pattern B than in premenopausal or pattern A subjects. LDL diameter correlated negatively with plasma triglycerides (r = -0.51) or LDL-derived TBARS (r = -0.44) and positively with LDL-lag time (r = 0.66). FMD correlated negatively with LDL-derived TBARS (r = -0.36) and positively with LDL diameter (r = 0.44) or LDL-lag time (r = 0.43). Vascular endothelial dysfunction may be associated with elevated triglyceride-induced small LDL particles that have enhanced oxidative susceptibility in postmenopausal women.

Differential effect of two nicotinic acid preparations on low-density lipoprotein subclass distribution in patients classified as low-density lipoprotein pattern A, B, or I

We tested the hypothesis that treatment with nicotinic acid results in a differential blood lipid response in subjects classified as having a low-density lipoprotein (LDL) pattern A or B. One hundred eighty hypercholesterolemic subjects were randomized to placebo (n = 61), immediate-release niacin (3,000 mg/day, n = 59), or extended-release niacin (1,500 mg/day, n = 60) for 14 weeks. Lipids and lipoprotein cholesterol were determined with enzymatic methods. LDL subclass distribution was determined with 2% to 16% polyacrylamide gradient gel electrophoresis. Extended- and immediate-release niacin had significant effects on the decrease of triglycerides, total cholesterol, LDL cholesterol, apoprotein B, lipoprotein(a), and apoprotein A-I and significantly increased high-density lipoprotein cholesterol. The 2 nicotinic acid compounds and doses significantly increased mean LDL peak particle diameter and percent distribution in large LDL I and IIa, with a significant decrease in small LDL IIIa, IIIb, and IVb. In patients with LDL pattern B compared with those with pattern A, extended-release niacin (1,500 mg/day) increased LDL peak particle diameter significantly more and decreased the percent distributions of small LDL IIIa, LDL IIIb, and LDL IVa significantly more. With 3,000 mg/day, immediate-release nicotinic acid in patients with LDL pattern B exhibited a significantly greater increase in LDL peak particle diameter and large LDL IIa and IIb and significantly greater decreases in small LDL IIIa, IIIb, and IVa compared with patients with pattern A. These differences in response between patients with LDL pattern A and those with pattern B were not reflected by changes in the standard lipid profile, including apoproteins A-I and B. Nicotinic acid has a significantly different effect on lipids and lipoprotein subclass distribution in subjects classified as having LDL subclass pattern A or B. Nicotinic acid has a significantly greater effect on the decrease of small LDL subclass distribution and increase in LDL peak particle diameter in pattern B versus pattern A.

Oolong tea increases plasma adiponectin levels and low-density lipoprotein particle size in patients with coronary artery disease

BACKGROUND

Oolong tea has been studied for its effect on cardiovascular disease and obesity. Plasma adiponectin levels are reduced in obesity, in patients with type 2 diabetes mellitus and in coronary artery disease (CAD).

OBJECTIVE

To investigate prospectively, whether intake of Oolong tea influences plasma adiponectin levels, low-density lipoprotein (LDL) particle size, total cholesterol, high-density lipoprotein (HDL) cholesterol, LDL cholesterol, serum triglyceride and plasma glucose levels in patients with CAD.

METHODS

Twenty two patients in our study consumed Oolong tea (1000 ml) or water for 1 month in our randomized cross-over study design.

RESULTS

There was a significant difference in plasma adiponectin levels before and after 1 month intake of Oolong tea (6.26 +/- 3.26 microg/ml versus 6.88 +/- 3.28 microg/ml, P < 0.05), and in plasma level LDL particle size (25.02+/-0.67 nm versus 25.31+/-0.60 nm, P < 0.01). The water-consuming control group showed no changes (6.28+/-3.28 microg/ml versus 6.23+/-3.21 microg/ml) in adiponectin levels or LDL particle sizes (25.03+/-0.70 nm versus 25.02+/-0.72 nm). We also observed a significant difference in hemoglobin A1c levels (7.23 +/- 4.45% versus 6.99 +/- 4.30%, P < 0.05) before and after intake of Oolong tea.

CONCLUSION

Oolong tea may have beneficial effects on the progression of atherosclerosis in patients with CAD.

Lipoprotein transport in the metabolic syndrome: pathophysiological and interventional studies employing stable isotopy and modelling methods

The accompanying review in this issue of Clinical Science [Chan, Barrett and Watts (2004) Clin. Sci. 107, 221–232] presented an overview of lipoprotein physiology and the methodologies for stable isotope kinetic studies. The present review focuses on our understanding of the dysregulation and therapeutic regulation of lipoprotein transport in the metabolic syndrome based on the application of stable isotope and modelling methods. Dysregulation of lipoprotein metabolism in metabolic syndrome may be due to a combination of overproduction of VLDL [very-LDL (low-density lipoprotein)]-apo (apolipoprotein) B-100, decreased catabolism of apoB-containing particles and increased catabolism of HDL (high-density lipoprotein)-apoA-I particles. These abnormalities may be consequent on a global metabolic effect of insulin resistance, partly mediated by depressed plasma adiponectin levels, that collectively increases the flux of fatty acids from adipose tissue to the liver, the accumulation of fat in the liver and skeletal muscle, the hepatic secretion of VLDL-triacylglycerols and the remodelling of both LDL (low-density lipoprotein) and HDL particles in the circulation. These lipoprotein defects are also related to perturbations in both lipolytic enzymes and lipid transfer proteins. Our knowledge of the pathophysiology of lipoprotein metabolism in the metabolic syndrome is well complemented by extensive cell biological data. Nutritional modifications may favourably alter lipoprotein transport in the metabolic syndrome by collectively decreasing the hepatic secretion of VLDL-apoB and the catabolism of HDL-apoA-I, as well as by potentially increasing the clearance of LDL-apoB. Several pharmacological treatments, such as statins, fibrates or fish oils, can also correct the dyslipidaemia by diverse kinetic mechanisms of action, including decreased secretion and increased catabolism of apoB, as well as increased secretion and decreased catabolism of apoA-I. The complementary mechanisms of action of lifestyle and drug therapies support the use of combination regimens in treating dyslipoproteinaemia in subjects with the metabolic syndrome.

Nonglycemic effects of insulin

Insulin affects multiple metabolic pathways in many tissues. Nonglycemic effects include inhibiting production of triglyceride-rich particles and platelet aggregation and increasing vasodilatation. In persons with normal insulin sensitivity, these actions are considered antiatherogenic. However, insulin's normal antiatherogenic actions are defective in persons who are insulin resistant, which results in hypertriglyceridemia, increased platelet aggregation, and endothelial dysfunction. Insulin therapy in patients with type 2 diabetes can lead to improved glycemic control, insulin sensitivity, lipid profile, and endothelial function and may impact the incidence and severity of cardiovascular disease.

Effects of rosiglitazone on endothelial function in men with coronary artery disease without diabetes mellitus

Recent data have shown that peroxisome proliferator-activated receptor-gamma agonists may exert protective effects on the vascular endothelium by amelioration of insulin resistance and through direct anti-inflammatory effects. In this study we assessed the effect of rosiglitazone on biochemical and biophysical indexes of endothelial function in male, nondiabetic patients with coronary artery disease. Consecutive male subjects (n = 71) with clinically stable, angiographically documented coronary artery disease and without diabetes mellitus were investigated. Patients were randomized in a double-blind manner to placebo or rosiglitazone for a total of 24 weeks. Flow-mediated dilation (FMD) of the brachial artery, C-reactive protein, von Willebrand factor, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 levels, and parameters of glucose and lipid metabolism were measured at baseline and after 12 and 24 weeks of treatment. Rosiglitazone treatment significantly reduced C-reactive protein (median 0.56 mg/L [interquartile range 0.33 to 1.02] to 0.33 mg/L [interquartile range 0.26 to 0.40], p <0.01), von Willebrand factor (139 +/- 47 to 132 +/- 44 IU/dl, p = 0.02), insulin resistance index (p = 0.05), and mean low-density lipoprotein (LDL) density (p <0.001) compared with placebo. However, no significant differences were seen between the rosiglitazone and placebo groups with regard to brachial artery FMD, intercellular adhesion molecule-1, or vascular cell adhesion molecule-1 levels. Rosiglitazone treatment significantly increased LDL (2.62 +/- 0.72 to 2.95 +/- 0.84 mmol/L, p = 0.03) and triglyceride (1.23 +/- 0.63 to 1.56 +/- 0.98 mmol/L, p = 0.04) levels. Thus, rosiglitazone reduced markers of inflammation and endothelial activation, but this did not translate into an improvement in FMD. Increased LDL and triglyceride levels may have played a role.

Fluvastatin improves endothelial dysfunction in overweight postmenopausal women through small dense low-density lipoprotein reduction

Small dense low-density lipoprotein (sdLDL), which are often associated with obesity, are considered as the most atherogenic and have been shown to impair endothelial function. It is not known whether reduction of sdLDL by pharmacological intervention can improve endothelial function. Thirty-four consecutive postmenopausal women with >/=5.70 mmol/L total cholesterol were placed into either an overweight (body mass index [BMI] >/= 25.0, n = 22) or a normal-weight (BMI < 25.0, n = 12) group, and forearm blood flow (FBF) was measured using strain-gauge plethysmography during reactive hyperemia before and after fluvastatin treatment. At baseline, the peak FBF during reactive hyperemia in the overweight group was less than that in the normal-weight group (mean +/- SD, 13.6 +/- 4.4 v 22.2 +/- 4.0 mL/min/100 mL, P <.01). The maximal FBF after nitroglycerin was similar in both groups. In the stepwise multiple regression analysis, only the concentration of sdLDL was the predictor for peak FBF (standard coefficient = -0.517, P =.0115). The nonsignificant parameters for the correlations in the model were age, BMI, systolic blood pressure, the homeostasis model assessment of insulin resistance (HOMA-IR), hemoglobin A(1c) (HbA(1c)), and LDL-cholesterol. Fluvastatin treatment was associated with the recovery of the peak FBF in the overweight group but it did not influence that of the normal-weight group. Changes in sdLDL fractions by fluvastatin correlated well with the peak FBF recovery. These results suggested that an increased sdLDL was linked to endothelial dysfunction in overweight postmenopausal women and fluvastatin treatment improved endothelial dysfunction by decreasing the atherogenic sdLDL fraction in this population.

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.

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.