Low-Density Lipoprotein Subfractions and the Prevalence of Silent Lacunar Infarction in Subjects with Essential Hypertension

Prevalence and associated factors of silent brain infarcts in a Mediterranean cohort of hypertensives

Silent brain infarcts (SBIs) are detected by neuroimaging in approximately 20% of elderly patients in population-based studies. Limited evidence is available for hypertensives at low cardiovascular risk countries. Investigating Silent Strokes in Hypertensives: a Magnetic Resonance Imaging Study (ISSYS) is aimed to assess the prevalence and risk factors of SBIs in a hypertensive Mediterranean population. This is a cohort study in randomly selected hypertensives, aged 50 to 70 years old, and free of clinical stroke and dementia. On baseline, all participants underwent a brain magnetic resonance imaging to assess prevalence and location of silent infarcts, and data on vascular risk factors, comorbidities, and the presence of subclinical cardiorenal damage (left ventricular hypertrophy and microalbuminuria) were collected. Multivariate analyses were performed to determine SBIs associated factors. A total of 976 patients (49.4% men, mean age 64 years) were enrolled, and 163 SBIs were detected in 99 participants (prevalence 10.1%; 95% CI, 8.4%-12.2%), most of them (64.4%) located in the basal ganglia and subcortical white matter. After adjustment, besides age and sex, microalbuminuria and increasing total cardiovascular risk (assessed by the Framingham-calibrated for Spanish population risk function) were independently associated with SBIs. Male sex increased the odds of having SBIs in 2.5 as compared with females. Our results highlight the importance of considering both global risk assessment and sex differences in hypertension and may be useful to design future preventive interventions of stroke and dementia.

Decreased Serum Bilirubin Is Associated With Silent Cerebral Infarction

Objective—

The presence of silent cerebral infarction (SCI) increases the risk of transient ischemia attack, symptomatic stroke, cardiovascular disease, and dementia. Total bilirubin (TB) levels were demonstrated to be decreased in carotid intima–media thickness, cardiovascular disease, stroke, and peripheral arterial disease. However, little information is available concerning the correlation between TB and SCI.

Approach and Results—

A cross-sectional study was conducted to evaluate the association between TB and SCI in 2865 subjects (1831 men and 1034 women) undergoing medical checkup. The participants with SCI had lower TB levels than those without SCI. The subjects with a low TB had a higher prevalence of SCI. Moreover, partial correlation showed that TB levels were tightly correlated with brachial-ankle pulse wave velocity after adjusting for confounding covariates ( r =−0.149; P <0.001). Multivariate logistic regression analysis revealed that higher TB was associated with a lower risk of SCI (odds ratio, 0.925; 95% confidence interval, 0.897–0.954; P <0.001).

Conclusions—

TB is a novel biochemical indicator for SCI regardless of classical cardiovascular risk factors. Early measurement of TB may be useful to assess the risk of SCI.

Silent Brain Infarction – A Review of Recent Observations

Silent brain infarction is a cerebral ischaemic event evident on brain imaging without any clinical symptom. Silent brain infarction is often detected in apparently healthy, elderly people and in different selected patient groups as well. Lately, several studies were carried out in order to identify the clinical conditions leading to silent brain infarction. A large number of clinical and paraclinical parameters were found to increase silent brain infarction prevalence, and the continuously growing list of risk factors revealed that the majority of them are similar to those related to stroke. Accordingly, some consider silent brain infarction the preclinical stage of clinically overt stroke. This point of view emphasizes the early recognition and management of silent brain infarction-related risk factors, and a great need for comparative studies, which could elicit the most sensitive indicators of the increased silent brain infarction risk, especially the ones that could be cost-effectively screened in the large populations as well.

Negatively charged low-density lipoprotein is associated with atherogenic risk in hypertensive patients

Negatively charged low-density lipoprotein (LDL), generated via multiple processes such as oxidation, acetylation, or glycosylation, plays a key role in the initiation and progression of atherosclerosis and related diseases. Anion-exchange high-performance liquid chromatography (AE-HPLC) can subfractionate LDL into LDL-1, LDL-2, and LDL-3 based on LDL particle charge, but the clinical significance of LDL subfractions has not yet been elucidated. The aim of this study was to determine the clinical significance of these fractions with particular regard to atherogenic risk in hypertensive patients. Ninety-eight patients with essential hypertension (age 67.0 ± 10.7 years; 54 males) were enrolled in the present study. The relationships between LDL subfractions and atherogenic risk factors, including lipid profiles, blood pressure and plasma 8-isoprostane as a marker of oxidative stress, were examined. LDL-1 levels were significantly and negatively correlated with body mass index (r = -0.384, p < 0.001), systolic blood pressure (r = -0.457, p < 0.001), non-high-density lipoprotein cholesterol levels (r = -0.457, p < 0.001) and 8-isoprostane levels (r = -0.415, p < 0.001). LDL-3, which is the most negatively charged fraction of total LDL, was significantly and positively correlated with these parameters (r = 0.267, 0.481, 0.357, and 0.337, respectively). LDL-1 levels were significantly lower (p < 0.001), and LDL-2 and LDL-3 levels were significantly higher (each p < 0.001) in patients with poorly controlled hypertension than in patients with well-controlled hypertension. In addition, an increase in the total number of traditional risk factors at time of study participation, but not previous diagnosis, was associated with a decrease in LDL-1 levels and increases in LDL-2 and LDL-3 levels. These data suggest that LDL subfractions are associated with multiple atherogenic risk factors and that treatment to modify these risk factors could result in changes in LDL subfraction levels. In conclusion, LDL subfractions isolated by AE-HPLC may represent a marker of atherogenic risk in patients with hypertension.

An improved anion-exchange high-performance liquid chromatography method for measuring oxidized form of LDLs in human plasma

Background

Circulating oxidized low-density lipoproteins (LDLs) (ox-LDLs) could be a sensitive marker to predict future cardiovascular events. However, a method to evaluate oxidized forms of LDLs systemically in human plasma is not yet established. In this study, we developed a novel and convenient high-performance liquid chromatography (HPLC) method for measuring ox-LDL levels in humans.

Methods

Human plasma lipoproteins were separated by a modified HPLC method using a diethylaminoethyl-type anion-exchange gel column with stepwise elution. Ox-LDLs were detected by postcolumn reaction with a regent containing cholesterol esterase and cholesterol oxidase. Particle size of each LDL fraction separated by HPLC was determined in 61 healthy subjects.

Results

Our HPLC method separated LDLs into three fractions, which were designated as LDL-1, LDL-2 and LDL-3, on the basis of their negative charges, with LDL-3 the most strongly retained fraction migrating fastest in the anodic direction, a property that reflects the net negative charge of the molecule. Western blot analysis revealed that apolipoprotein B100 in LDL-3 fraction was the most fragmented and oxidatively modified. When LDLs were oxidized in vitro by Cu2+ or 2,2-azo-bis (2-aminopropane)-2HCl or modified by various aldehydes, all of the LDL fractions migrated at the position of LDL-3. Further, among three fractions, particle size was smallest in LDL-3 fraction.

Conclusion

Here, we developed a convenient HPLC method and identified LDL-3 as oxidized LDL fractions, although ox-LDLs were present in LDL-2 fraction, albeit lesser concentrations than in LDL-3 subfraction. Measuring ox-LDL levels in human plasma by this method may be useful to evaluate atherosclerotic disorders.

Association between cholesterols, homocysteine and silent brain infarcts

BACKGROUND

The aim of this study was to assess the relationship between total plasma homocysteine, cholesterol levels, vitamin B(12), folate, thyroid hormones, urea, ferritin, uric acid, C-reactive protein, cardiovascular risk factors and silent brain infarct (SBI) in patients without any neurological disorder. Whether the factors of interest were associated with SBI is investigated.

METHODS

One hundred and forty-two subjects with a mean age of 52.1 +/- 13.1 years (21-87 years) without any history of stroke, transient ischaemic attack and neurological abnormality were enrolled in this cross-sectional study. The subjects underwent brain magnetic resonance imaging and blood chemistry determinations. Student's t-test was used to compare differences in means of laboratory results between the groups with and without SBI. The chi(2)-test was used for categorized variables. Multiple logistic regression analysis was used to determine the independent predictors of SBI.

RESULTS

The group comprised 56 men and 86 women. SBI were found in 40 patients (28%). The low-density lipoprotein levels were significantly higher in the infarct group (P = 0.019), homocysteine concentrations were significantly higher in the men-infarct group (P = 0,029) and total cholesterol levels were significantly higher in the women-infarct group than the women non-infarct group (P = 0.006).

CONCLUSION

Serum low-density lipoprotein, total cholesterol and homocysteine levels were associated with SBI.

Silent brain infarcts: a systematic review

As the availability and quality of imaging techniques improve, doctors are identifying more patients with no history of transient ischaemic attack or stroke in whom imaging shows brain infarcts. Until recently, little was known about the relevance of these lesions. In this systematic review, we give an overview of the frequency, causes, and consequences of MRI-defined silent brain infarcts, which are detected in 20% of healthy elderly people and up to 50% of patients in selected series. Most infarcts are lacunes, of which hypertensive small-vessel disease is thought to be the main cause. Although silent infarcts, by definition, lack clinically overt stroke-like symptoms, they are associated with subtle deficits in physical and cognitive function that commonly go unnoticed. Moreover, the presence of silent infarcts more than doubles the risk of subsequent stroke and dementia. Future studies will have to show whether screening and treating high-risk patients can effectively reduce the risk of further infarcts, stroke, and dementia.

Elevated circulating oxidized LDL levels in Japanese subjects with the metabolic syndrome

In the present study, we examined the relationship between circulating oxidized low-density lipoprotein (LDL) and the metabolic syndrome in Japanese patients. Subjects who had no histories of coronary or peripheral artery disease and were taking no medications (n=119; age 57+/-10 years; male/female, 90:29) underwent a complete history and physical examination, determination of blood chemistries and oxidized LDL levels. In stepwise regression analysis, triglycerides (p=0.0001) and HDL-cholesterol (p=0.0493, inversely) were independently correlated to oxidized LDL levels. Furthermore, a significant association (p<0.0001) was found between circulating oxidized LDL levels and the accumulation of the number of the components of the metabolic syndrome. Oxidized LDL levels were one of the independent determinants of intima-media thickness of the common carotid artery, a surrogate marker of atherosclerosis. The present study reveals that circulating oxidized LDL levels are strongly associated with the metabolic syndrome. Our results suggest that elevation of oxidized LDL may be a possible molecular link between accelerated atherosclerosis and the metabolic syndrome in Japanese subjects.