Lipoprotein abnormalities in patients with extra-coronary arteriosclerosis

The genetic basis of peripheral arterial disease: current knowledge, challenges, and future directions

Several risk factors for atherosclerotic peripheral arterial disease (PAD), such as dyslipidemia, diabetes mellitus, and hypertension, are heritable. However, predisposition to PAD may be influenced by genetic variants acting independently of these risk factors. Identification of such genetic variants will provide insights into underlying pathophysiologic mechanisms and facilitate the development of novel diagnostic and therapeutic approaches. In contrast to coronary heart disease, relatively few genetic variants that influence susceptibility to PAD have been discovered. This may be, in part, because of greater clinical and genetic heterogeneity in PAD. In this review, we (1) provide an update on the current state of knowledge about the genetic basis of PAD, including results of family studies and candidate gene, linkage as well as genome-wide association studies; (2) highlight the challenges in investigating the genetic basis of PAD and possible strategies to overcome these challenges; and (3) discuss the potential of genome sequencing, RNA sequencing, differential gene expression, epigenetic profiling, and systems biology in increasing our understanding of the molecular genetics of PAD.

High-density lipoprotein subclasses and their relationship to cardiovascular disease

OBJECTIVE

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

METHODS

Literature review of 80 published investigations.

RESULTS

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

CONCLUSIONS

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

Peripheral Arterial Disease

Risk factors for atherosclerosis should be identified and reduced in all patients who have peripheral arterial disease. Cessation of smoking, strict control of diabetes and hypertension, and aggressive reduction in low-density lipoprotein cholesterol level result in a slowdown of disease progression and a reduction in cardiovascular events. Unless contraindicated, all patients with peripheral arterial disease should receive antiplatelet therapy. New pharmacologic therapies are emerging, but supervised exercise rehabilitation is the most effective medical therapy to restore pain-free walking for patients with intermittent claudication. Patients with symptoms that limit their lifestyles may benefit from elective invasive revascularization. Symptoms consistent with limb-threatening ischemia (such as rest pain) or a foot ulcer that does not heal (especially in a patient with diabetes) requires immediate attention and possibly revascularization.

Clinical significance of plasma HDL subfractions (HDL2, HDL3) in patients with peripheral arterial disease (PAD) in the Greek population

OBJECTIVE

In this study the major high density lipoprotein (HDL) subfractions (HDL2, HDL3) were examined, in angiographically selected patients with peripheral arterial disease (PAD).

RESULTS

Patients with PAD have significantly high triglyceride levels. HDL2 and HDL3 levels were found significantly reduced in patients with PAD. Also, the ratio HDL2-C/HDL3-C was significantly reduced in patients with PAD.

CONCLUSIONS

The aim of the present study is to provide additional support to the hypothesis that the determination of HDL subfractions could be useful to elucidate possible mechanism(s) for a better assessment of the risk profile for PAD.

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

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

Secondary prevention of coronary heart disease in patients with extracoronary atherosclerosis: a need for accuracy of low density lipoprotein determination

According to the new guidelines of the National Cholesterol Education Program (NCEP) for secondary prevention in adults with evidence of coronary heart disease or other clinical atherosclerotic disease, lipoprotein analysis is required and classification is based on low density lipoprotein (LDL) cholesterol. The aim of the present study was to analyze the reliability of calculated LDL cholesterol by the Friedewald formula compared with measured LDL cholesterol after separation by ultracentrifugation in 202 male patients with extracoronary atherosclerosis (100 patients with ischemic cerebrovascular disease and 102 patients with peripheral vascular disease) and in 117 health control subjects. Calculated LDL cholesterol coincided with measured LDL cholesterol, with less than 10% error, in 118 patients (58.4%) with extracoronary atherosclerosis and in 87 controls (74.4%). Calculated LDL cholesterol was overestimated, with an error of 10% or more compared with measured LDL cholesterol, in 34.6% of patients and 22.2% of controls, and underestimated in 6.9% and 3.4% respectively. Despite a good correlation between calculated and measured LDL cholesterol, the intraclass correlation coefficients demonstrate a poor concordance between calculated and measured LDL cholesterol, both in patients and controls. The authors underline the need for caution in assessing the reliability of calculated LDL cholesterol.

Carotid plaque, aging, and risk factors. A study of 457 subjects

BACKGROUND AND PURPOSE

The aim of this study was to assess the prevalence of extracranial carotid artery atherosclerosis and its relation to principal cardiovascular risk factors at different ages in a sample of the general population.

METHODS

B-mode ultrasonography was used to investigate the carotid district in 457 subjects (231 men and 226 women; mean age, 55.4 +/- 18.7 years; range, 18 to 97 years) in the metropolitan area. The ultrasonographic findings were then related to risk factors.

RESULTS

Carotid plaques were found in 178 subjects (38.9%). The prevalence of atherosclerosis, number of plaques, and severity of stenosis were observed to increase with age. Age (P < .0001), cigarette smoking (P < .0001), male sex (P < .001), total cholesterol (P < .05), and, inversely, the ratio of high-density lipoprotein cholesterol to total cholesterol (P < .05) were found to be independently associated with carotid atherosclerosis. Stratified analysis by sex and age showed effect modifications by age on cigarette smoking, total cholesterol, and the ratio of high-density lipoprotein cholesterol to total cholesterol. After multivariate analysis including interaction terms, cigarette smoking and cholesterol levels were not longer found to be associated with carotid atherosclerosis in elderly subjects. Age (P < .01), total cholesterol (P < .05), and diabetes (P < .05) were positively related to the severity of vascular narrowing.

CONCLUSIONS

There is a high prevalence of asymptomatic carotid atherosclerosis in the general population, particularly among the very old. The association between risk factors and carotid atherosclerosis is less pronounced in the elderly than in younger subjects.

Ankle-arm index as a marker of atherosclerosis in the Cardiovascular Health Study. Cardiovascular Heart Study (CHS) Collaborative Research Group

BACKGROUND

Peripheral arterial disease measured noninvasively by the ankle-arm index (AAI) is common in older adults, largely asymptomatic, and associated with clinically manifest cardiovascular disease (CVD). The criteria for an abnormal AAI have varied in previous studies. To determine whether there is an inverse dose-response relation between the AAI and clinical CVD, subclinical disease, and risk factors, we examined the relation of the AAI to cardiovascular risk factors, other noninvasive measures of subclinical atherosclerosis using carotid ultrasound, echocardiography and electrocardiography, and clinical CVD.

METHODS AND RESULTS

The AAI was measured in 5084 participants > or = 65 years old at the baseline examination of the Cardiovascular Health Study. All subjects had detailed assessment of prevalent CVD, measures of cardiovascular risk factors, and noninvasive measures of disease. Participants were stratified by baseline clinical CVD status and AAI (< 0.8, > or = 0.8 to < 0.9, > or = 0.9 to < 1.0, > or = 1.0 to < 1.5). Analyses tested for a dose-response relation of the AAI with clinical CVD, risk factors, and subclinical disease. The cumulative frequency of a low AAI was 7.4% of participants < 0.8, 12.4% < 0.9, and 23.6% < 1.0. participants with an AAI < 0.8 were more than twice as likely as those with an AAI of 1.0 to 1.5 to have a history of myocardial infarction, angina, congestive heart failure, stroke, or transient ischemic attack (all P < .01). In participants free of clinical CVD at baseline, the AAI was inversely related to history of hypertension, history of diabetes, and smoking, as well as systolic blood pressure, serum creatinine, fasting glucose, fasting insulin, measures of pulmonary function, and fibrinogen level (all P < .01). Risk factor associations with the AAI were similar in men and women free of CVD except for serum total and low-density lipoprotein cholesterol, which were inversely associated with AAI level only in women. Risk factors associated with an AAI of < 1.0 in multivariate analysis included smoking (odds ratio [OR], 2.55), history of diabetes (OR, 3.84), increasing age (OR, 1.54), and nonwhite race (OR, 2.36). In the 3372 participants free of clinical CVD, other noninvasive measures of subclinical CVD, including carotid stenosis by duplex scanning, segmental wall motion abnormalities by echocardiogram, and major ECG abnormalities were inversely related to the AAI (all P < .01).

CONCLUSIONS

There was an inverse dose-response relation of the AAI with CVD risk factors and subclinical and clinical CVD among older adults. The lower the AAI, the greater the increase in CVD risk; however, even those with modest, asymptomatic reductions in the AAI (0.8 to 1.0) appear to be at increased risk of CVD.

Prevalence of apolipoprotein E phenotypes in ischemic cerebrovascular disease. A case-control study

BACKGROUND AND PURPOSE

Apolipoprotein E polymorphism may influence the early development of coronary artery disease. We investigated the putative role of apolipoprotein E phenotypes in cerebral infarction.

METHODS

The apolipoprotein E phenotypes of 69 patients (mean +/- SD age, 72 +/- 11 years) who had suffered completed stroke or a transient ischemic attack and 68 sex- and age-matched control subjects free of cerebrovascular disease were determined by isoelectric focusing. The relative frequency of the apolipoprotein E phenotypes in the general population was estimated in 498 healthy blood donors (mean age, 37 years).

RESULTS

The prevalences of hypertension, diabetes mellitus, obesity, and intermittent claudication were significantly higher in patients than in control subjects. Serum lipid and apolipoprotein B concentrations and the composition of very low density lipoproteins were not significantly different between patients and control subjects. Apolipoprotein A-I and E levels were significantly lower in patients. Cholesterol levels were higher in male patients than in male control subjects (5.10 +/- 1.46 versus 4.41 +/- 0.80 mmol/L; p = 0.036), and the ratio of apolipoprotein A-I to B was lower (0.77 +/- 0.29 versus 1.03 +/- 0.37; p < 0.001). The E3/E3 phenotype was more frequent in control subjects (85%) than in patients (72.5%; p < 0.05) and healthy blood donors (64%; p < 0.02). The E3/E2 phenotype was more frequent in patients (10.1%) than in control subjects (1.4%; p < 0.05). A stepwise logistic regression showed that the presence of stroke was significantly related to high blood pressure (p < 0.0001), low apo E levels (p < 0.008), obesity (p < 0.041), the apo E phenotype (p < 0.05), and diabetes mellitus (p < 0.05).

CONCLUSIONS

The E3/E3 phenotype may protect against early vascular morbidity, and the epsilon 2 gene may be a risk factor for cerebrovascular morbidity, possibly related to diabetes, hypertension, and/or obesity.

Effects of lovastatin on high-density lipoprotein subfractions in hypercholesterolemic patients with peripheral vascular disease

The effects of lovastatin treatment on high-density lipoprotein subfractions (HDL2 and HLD3) were investigated in 34 patients with severe peripheral vascular disease and type IIa or type IIb hyperlipoproteinemia by use of a density gradient ultracentrifugation method. Lovastatin therapy caused greater percentage changes in HDL2 than in HDL3. In HDL2 the increases of cholesterol, total lipid, apolipoprotein AI (apoAI) and apolipoprotein AII (apoAII) concentrations were 23% (p < 0.05), 28% (p < 0.01), 24% (p < 0.01) and 11% (p < 0.01), respectively, in subjects with the type IIa phenotype. In patients with the type IIb phenotype the corresponding increases were 42% (p < 0.01), 44% (p < 0.01), 38% (p < 0.01) and 21% (p < 0.05), respectively. The apoAI/apoAII weight ratio in HDL2 rose by 11% and by 13% in type IIa and type IIb patients, respectively. The present results suggest that during lovastatin treatment the slight increase in serum HDL-cholesterol concentration was due, not to cholesterol enrichment by high-density lipoproteins, but more probably to an increase of the number of HDL particles. The observed changes were more pronounced in type IIb than in type IIa patients.

Lipoprotein [Lp(a)] and peripheral vascular disease

Lipoprotein(a) [Lp(a)], which combines structural elements of the lipid and fibrinolytic systems, is a major independent risk factor for the development of coronary heart disease. Eighty-four consecutive patients with peripheral vascular disease (of whom 42 had concomitant ischaemic heart disease) and 43 healthy controls were enrolled in a case-control study. We found that the mean Lp(a) concentration in male patients with peripheral vascular disease (PVD) was almost threefold higher than that of controls, while in female patients the Lp(a) concentration was more than twice that of controls. This marked difference was borne out in patients with and without concomitant ischaemic heart disease (IHD). A multivariate logistic regression analysis indicated that Lp(a) is independently associated with PVD when adjusted for age and sex (odds ratio per 100 mg l-1 increase in Lp(a) = 1.35; P < 0.01). A similar association is observed for patients with concomitant IHD (odds ratio per 100 mg l-1 increase in Lp(a) = 1.65; P < 0.01).

Lipids and other risk factors selected by discriminant analysis in symptomatic patients with supra-aortic and peripheral atherosclerosis

BACKGROUND

Different patterns of risk factors might be related to the involvement of specific vascular districts by atherosclerosis. In this sense, many investigations have addressed coronary artery disease, whereas extracoronary atherosclerosis has received less extensive attention.

METHODS AND RESULTS

Vascular risk factors, with particular attention to lipid parameters (total cholesterol [TC]; triglycerides; high density lipoprotein cholesterol [HDL-C], HDL2 and HDL3 cholesterol [HDL2-C, HDL3-C]), were evaluated by means of univariate and multivariate (discriminant) analysis in a group of 169 patients (128 men and 41 women; mean ages, 58 +/- 7 and 62 +/- 7 years, respectively) with clinically and angiographically demonstrated atherosclerosis of the supra-aortic trunk and/or lower limbs. Patients with coronary artery disease were excluded from this study. The control group consisted of 140 age- and sex-matched individuals. By univariate analysis, smoking was more closely associated with peripheral atherosclerosis, whereas blood pressure was higher in patients with supra-aortic disease. Unrecognized diabetes mellitus was a frequent finding in patients with peripheral disease. The percentage of hyperlipidemias was fourfold higher in patients than in control subjects, with differences consisting of higher triglycerides and lower HDL-C, HDL2-C, and HDL3-C concentrations. By discriminant analysis, high correct classification (CC) rates were achieved in the various patient subgroups on the basis of variables selected from the statistical function. In male patients with peripheral disease, the variables HDL-C, smoking, diastolic blood pressure, uric acid, and glucose, in that order, yielded a CC in 90.4% of the cases; in female patients, smoking, TC/HDL-C, and body mass index gave a CC rate of 95.9%. In men with cerebral disease, the selected variables TC/HDL-C, diastolic blood pressure, and TC yielded a CC of 90.7%; in women, uric acid, TC/HDL-C, and fibrinogen levels produced a CC rate of 89.2%.

CONCLUSIONS

Risk profiles in atherosclerosis of the supra-aortic trunks and lower limbs seem to differ in relation to gender and circulatory district involved. The importance of lipid parameters, in particular HDL-C, HDL2-C, and TC/HDL-C, as extracoronary risk factors is further confirmed.

Lower extremity arterial disease and the aging process: a review

Atherosclerotic disease is a major health problem in the elderly population in the U.S. To date, most research has focused on the coronary and cerebral manifestations of the disease. Lower extremity arterial disease (LEAD) has received less attention. However, the use of simple objective non-invasive diagnostic techniques in recent population-based studies has allowed identification of asymptomatic LEAD and shown that the prevalence of disease is several fold higher than previously estimated. The prevalence increases sharply with age, from 3% in those under 60 years to over 20% at 75+ years. Detection of LEAD in the elderly provides a rapid, easy assessment of the level of atherosclerosis in the body and identifies those at high risk for mortality and morbidity. LEAD is associated with a relative risk of 4 to 5 for all cause mortality. In about 25% of those with LEAD, the disease progresses over time, leading to loss of mobility, gangrene or amputation. This review summarizes current knowledge regarding the etiology and natural history of LEAD from an epidemiologic viewpoint, delineating areas in which additional research is needed.

Relation of lipid peroxides to macrovascular disease in type 2 diabetes

Lipid peroxides are thought to be formed by free radicals and may play an important role in the development of atheromatous vascular disease. We have investigated the relationship between lipids, lipoproteins, coagulation factors, and lipid peroxides (measured as thiobarbituric acid reacting species (TBARS) in Type 2 diabetic patients with macrovascular disease. Eighteen diabetic and 20 non-diabetic subjects with clinical evidence of ischaemic heart disease and/or peripheral vascular disease were investigated, together with 28 healthy subjects without evidence of vascular disease. TBARS concentrations in non-diabetic (mean 5.0 (95% Cl 4.5-5.7) mumol l-1) and diabetic groups (5.6 (5.1-6.0) mumol l-1) with macrovascular disease were not significantly different although values were higher in both groups of patients with vascular disease by comparison with control subjects (2.7 (2.4-3.1) mumol l-1, p less than 0.001). Significant univariate correlations between TBARS concentrations and measures of blood glucose control (fructosamine, blood glucose and HbA1) were found for all 66 subjects (r = 0.35-0.42, p less than 0.01-p less than 0.001), although no independent association between these parameters and TBARS was demonstrated in multiple regression analysis.(ABSTRACT TRUNCATED AT 250 WORDS)