Hypertension, lipoprotein(a), and apolipoprotein A-I as risk factors for stroke in the Chinese

Cardiac markers: Role in the pathogenesis of arterial hypertension

Cardiac biomarkers may play unique roles in the prognostic evaluation of patients with hypertension, as many cardiac biomarker levels become abnormal long before the onset of obvious cardiovascular disease (CVD). There are numerous cardiac markers. However, this review article only reported the roles of creatinine kinase-MB, cardiac troponins, lipoprotein a, osteopontin, cardiac extracellular matrix, C-reactive protein, cardiac matrix metalloproteinases, cardiac natriuretic peptides, myoglobin, renin, and dynorphin in the pathogenesis of hypertension. This article explained recent major advances, as well as discoveries, significant gaps, and current debates and outlined possible directions for future research. Further studies are required to determine the association between myoglobin and other cardiac markers in hypertension. Moreover, therapeutic approaches are required to determine the early control of these cardiac markers, which ultimately reduce the prevalence of CVDs.

The Predicting Role of Neutrophil- Lymphocyte Ratio in Patients with Acute Ischemic and Hemorrhagic Stroke

BACKGROUND AND AIM

The neutrophil-to-lymphocyte ratio (NLR) is considered as an independent and easy-to-measure inflammatory predictor of mortality in patients with acute stroke. However, it is unclear whether the NLR is related to other problems caused by stroke. This study evaluated the possible roles of the NLR in estimating mortality rate and health problems in patients with acute ischemic (IS) and hemorrhagic (H) stroke.

METHODS

A total of 180 patients with acute IS and H stroke were enrolled. NLR was calculated from the admission blood work. Patients were divided into two groups according to the NLR values (<5 and >5). Demographic, clinical, and laboratory findings were collected for the subjects. The correlations of NLR with mortality, infection incidences, and other parameters were determined using statistical analyses.

RESULTS

The percentages of lymphocytes and WBCs were significantly higher in IS stroke patients than H group, unlike neutrophil number (P < 0. 0001-0.01). In contrast with the serum levels of hemoglobin, Na, Chol, HTN, LDL, ESR, MCV, and CRP, triglyceride was significantly decreased in H group (P < 0.0001). IS group had a significant reduction in NLR (P < 0.0001). Patients with NLR of < 5 had a significant reduction in infectious diseases, unlike H group (P < 0.01). The NLR had no associations with bedscore, GIB, DVT, mortality rate. However, it was positively correlated to the numbers of WBC and RBC, and values of CRP, ESR, and hypertension (P < 0.001-0.05), unlike MCV in H group (P < 0.05). The NLR was not associated hemoglobin, triglyceride, Chol, and LDL levels.

CONCLUSION

Unlike previous studies, this study suggests that the NLR, along with other clinical and laboratory parameters, may be used to determine stroke type and predict patient susceptibility to some infectious diseases such as pneumonia. However, more investigations are required to clarify the role of the NLR in different aspects of acute stroke.

Apolipoprotein A1, B levels, and their ratio and the risk of a first stroke: a meta-analysis and case-control study

The associations of levels of apolipoprotein A1 (ApoA1) and apolipoprotein B and ApoB/A1 ratio and risk of a first stroke have not been reliably documented. We performed a meta-analysis to summarize the relationships and confirmed them in a case-control study. We identified relevant publications in PubMed and Embase databases up to June 1, 2015. A Dersimonian-Laird random effects model was used to compute summary relative risks (RRs) and 95 % confidence intervals (CIs). A case-control study was conducted in a southern Chinese population. We included 8 cohort and 4 case-control studies (222,774 subjects; 10,032 first stroke events) in the meta-analysis. Reduced ApoA1 level and increased ApoB level and ApoB/A1 ratio was associated with a first stroke in cohort studies (RR 0.86 [95 % CI 0.79-0.94], 1.66 [1.62-1.69], and 1.66 [1.63-1.70], respectively) and reduced ApoA1 level and increased ApoB/A1 ratio in case-control studies (0.68 [0.47-0.99] and 1.76 [1.50-2.06], respectively). When stratified by stroke type in cohort studies, the RR for ischemic stroke was 0.83 (0.76-0.90), 1.36 (1.32-1.40), and 1.38 (1.35-1.42) for the 3 factors, respectively. In our case-control study (1013 cases; 1029 controls), the OR for a first ischemic stroke was 0.83 (0.74-0.92), 1.33 (1.18-1.48) and 2.10 (1.76-2.51), respectively, with increased ApoA1 level associated with hemorrhagic stroke (1.37 [1.06-1.78]). Meta-analysis suggests that reduced ApoA1 level and increased ApoB level and ApoB/A1 ratio are risk factors for a first ischemic but not hemorrhagic stroke. Elevated ApoA1 level may be a risk factor for a first hemorrhagic stroke.

Paradoxical Elevation of High Density Lipoprotein Cholesterol in Association with Lacunar-Type Cerebral Infarction

Background

The aim of this study was to evaluate the association between high-density lipoprotein cholesterol (HDLC) levels and the risk of lacunar infarction (LI) in a retrospective cohort study in China.

Material/Methods

We recruited 229 patients with obsolete brain infarctions single side (SOBI), 218 with obsolete brain infarctions bilateral sides (BOBI), 193 with both acute stroke and obsolete lacunar infarctions single side (AI&SOBI), 113 with both acute stroke and obsolete lacunar infarctions bilateral sides (AI&BOBI), and 203 without any infarctions (Control).

Results

1) The plasma levels of HDLC in group BOBI, AI&SOBI, and AI&BOBI were higher than in the control group, and lower in group SOBI than in the control group (p<0.01). 2) The plasma levels of HDLC in group AI&SOBI were significantly higher than in group SOBI (p<0.01). 3) The plasma levels of HLDL were similar between group AI&SOBI and AI&BOBI. 4) There were significant relationships between HDLC and acute lacunar stroke, even after adjusting for these factors such as age, sex, triglyceride, total cholesterol, low-density lipoprotein cholesterol, and history of diabetes (p=0.001). 4) Compared with the controls, the calculation of odds ratios indicated relative risk estimates of higher HDLC for acute lacunar stroke with obsolete lacunar infarction.

Conclusions

Elevated HDLC may be an independent predictor of recurrent stroke with obsolete lacunar infarctions single side in Chinese people, justifying clinical trials for secondary prevention of stroke by generally increasing HLDL level. According to the difference between single and bilateral side multiple silent lacunar infarcts, it is inferred that HDLC may increase the risk of atherothrombotic infarction but reduce the risk of cardioembolic infarction in the general Chinese population.

Reduced serum levels of triglyceride, very low density lipoprotein cholesterol and apolipoprotein B in Parkinson's disease patients

BACKGROUND

Previous studies have shown a lower incidence of stroke in Parkinson's disease (PD) patients. The role of the lipids and lipoproteins as risk factors for stroke is uncertain in the lower prevalence of stroke in PD patients.

OBJECTIVES

To explore the lipids and lipoproteins serum levels in PD patients.

METHODS

A retrospective study was performed on 110 PD patients (PD group), 130 controls with non-cerebrovascular neurological diseases (OD group), 140 acute intracerebral hemorrhage patients (ICH group) and 140 acute cerebral infarction patients (CI group). The records about serum levels of lipids and lipoproteins were analyzed.

RESULTS

There were significant differences for the serum level of triglyceride (F = 5.031, p=0.002), very low density lipoprotein cholesterol (F = 5.313, p=0.001), apolipoprotein B (F = 16.038, p<0.0001) in the four groups. PD group had a significantly lower serum level of triglyceride (TG) than the OD (p=0.032), ICH (p=0.00047) and CI (p=0.001) groups. Very low density lipoprotein cholesterol (VLDL-C) serum level was significantly lower in PD group than in OD (p=0.039), ICH (p=0.00021) and CI (p=0.001) groups. There was a significantly lower serum level of apolipoprotein B (apo B) in PD group than in OD (p=0.002), ICH (p<0.0001) and CI (p<0.0001) groups.

CONCLUSIONS

There are reduced serum levels of TG, VLDL-C and apo B in PD patients, which may be related to the decreased prevalence of stroke in PD patients.

Sex differences in risk factors, etiology, and short-term outcome of cerebral infarction in young patients

Investigations to date have demonstrated that the underlying etiology, causes and burden of stroke may be different for women and men. However, data regarding sex differences among young cerebral ischemic stroke patients remains scarce. We conducted this study in 669 young Chinese adults with acute ischemic stroke as determined by the modified Rankin Scale at discharge. Stepwise multiple logistic regression analysis confirmed that NIHSS score (OR 1.277; 95% CI 1.179-1.383, p=0.000), diabetes mellitus (OR 0.121; 95% CI 0.0209-0.718, p=0.020) and serum glucose levels on admission (OR 1.135; 95% CI 0.997-1.293, p=0.046) independently predict short-term outcomes at discharge in young female patients with acute stroke, but the significant variables related to male patients appeared to be Apo A1 (OR 0.165; 95% CI 0.035-0.776, p=0.023) and NIHSS score on admission (OR 1.458; 95% CI 1.325-1.605, p=0.000). In our series, our data suggest that there are several sex differences for risk of cerebral infarction in young patients, which have important implications for the diagnosis, management and prognosis of stroke in young adults.

Characteristics of acute cerebral hemorrhage with regard to lipid metabolism and glycometabolism among different age groups

OBJECTIVE

This study investigated the lipid metabolism and glycometabolism of patients with acute cerebral hemorrhage from 2006-2008 in order to find a possible association among lipid metabolism, glycometabolism and different age groups of adults in the Chinese Chongqing population.

METHODS

Data on levels of total cholesterol (TC), triglyceride (TG), high density lipoprotein (HDL-C), low density lipoprotein (LDL-C) and fasting serum glucose (GLU) were obtained from records of patients (548) from the Department of Neurology of the First Affiliated Hospital of Chongqing Medical University. Participants ranging in age from 21-94 years were divided into three groups; the first group was the young group in which all participants were 21-44 years old; the second group was the middle-age group in which all participants were 45-59 years old, and the last group was the elderly group in which all participants were 60-94 years old.

RESULTS

Levels of TC, TG, HDL-C, LDL-C and GLU were not significantly different among the three groups (P>0.05). Proportions of hypercholesterolemia high LDL-C, low HDL-C, impaired fasting glucose and diabetes mellitus were not different among the three groups (P>0.05). Only the proportion of hypertriglyceridemia patients was significantly different. The risk of being diagnosed with hypertriglyceridemia in the middle-age group was increased 2.371 times (95% CI: 1.542-3.645) and in the young group increased 2.281 times (95% CI: 1.211 -4.296).

CONCLUSION

Age and hypertriglyceridemia are risk factors associated with an increased incidence rate of acute cerebral hemorrhage in the Chongqing population in China.

Risk factors for ischaemic stroke

Stroke is a leading cause of morbidity and mortality in western populations, with up to 40% of survivors not expected to recover independence from severe disabilities. This equates to an immense financial burden on health systems worldwide. Hence further education is required to inform individuals of the risks to promote secondary prevention strategies in future generations. Stroke is a heterogeneous, multifactorial disease regulated by modifiable and nonmodifiable risk factors. Modifiable factors include a history of high blood pressure, diabetes mellitus and coronary heart disease. Nonmodifiable factors include age, sex and race. Other less-well documented risk factors include geographic location, socioeconomic status and alcoholism. Approximately 80% of stroke events could be reduced by making simple lifestyle modifications. Further studies are required to clarify the role and interplay of the risk factors outlined to give a more comprehensive understanding of stroke and to aid and drive the development of more effective stroke prevention programs, in high risk groups.

High-density lipoprotein-cholesterol and risk of stroke and carotid atherosclerosis: a systematic review

BACKGROUND AND PURPOSE

Epidemiological studies have found no relationship between total cholesterol and stroke risk, but little attention has been paid to high-density lipoprotein-cholesterol (HDL-C).

METHODS

We performed a systematic PubMed literature search for epidemiological studies that examined the association between HDL-C level and stroke or carotid intima-media thickness (IMT).

RESULTS

We identified 18 studies on the relationship between HDL-C and stroke risk and 37 on HDL-C and carotid IMT. Eight of ten prospective cohort studies (n=238,739) and three of eight case-control studies (n=3604 cases, 8220 controls) supported an association between elevated HDL-C level and decreased risk of stroke. Prospective cohort studies reporting on relative risk per unit increase in HDL-C showed an 11-15% decreased stroke risk per 10-mg/dl increase in HDL-C. Of 37 studies on carotid IMT, 31 reported cross-sectional, one longitudinal, and five both cross-sectional and longitudinal associations between HDL-C level and carotid IMT. Of 36 cross-sectional studies (n=51,288), 20 showed an inverse association between HDL-C level and carotid IMT. Of six longitudinal studies (n=20,065), three showed no association, one showed a weak association in a subgroup of white women and two showed a significant inverse relationship between HDL-C level and carotid IMT. Pooled estimates could not be calculated because of the variation in study designs and analysis.

CONCLUSIONS

The weight of evidence in the literature supports an inverse association between HDL-C level and stroke or carotid atherosclerosis, but more data are needed to firmly establish this protective effect.

Lp(a) lipoprotein and plasminogen activity in patients with different etiology of ischemic stroke

BACKGROUND AND PURPOSE

Lp(a) lipoprotein plays an important part in atherothrombogenesis and is considered an independent risk factor for coronary heart disease. However, its role in cerebrovascular disease remains unclear, in particular because of the heterogeneous nature of strokes. We investigated whether elevated Lp(a) is more frequent in ischemic stroke related to atherothrombosis than in other etiologies of stroke. Because of the close structural homology between Lp(a) and plasminogen, we also studied the role of plasminogen in different stroke subtypes and whether there is a dependency on Lp(a) plasma levels.

METHODS

Lp(a) levels and plasminogen activity were measured in 253 consecutive patients with acute ischemic stroke and in 63 controls (CS). Subtypes of stroke were established according to the TOAST criteria.

RESULTS

Median Lp(a) levels were found to be higher in the total cerebral infarction group and in patients with large artery atherosclerosis (LAA) when compared with CS (20.9 and 22.0 mg/dl, respectively, vs. 16.0 mg/dl; p < 0.05). In addition, elevated Lp(a) levels >30 mg/dl were more frequent among the LAA subgroup than among CS (39.4 vs. 11.1%; p < 0.001). Mean plasminogen activity was lower in the total cerebral infarction group (110.8 vs. 120.3%; p < 0.001) and in patients with cardioembolic stroke (109.8 vs. 120.3%; p < 0.05) when compared with CS. There was no correlation between Lp(a) levels and plasminogen activity.

CONCLUSIONS

Our results support the hypothesis that elevated Lp(a) is a risk factor for ischemic stroke and especially for strokes caused by LAA. Low plasminogen activity may play a role in the pathogenesis of cerebrovascular disease, especially for the development of cardioembolic stroke.

Apolipoproteins as Predictors of Ischaemic Stroke in Patients with a Previous Transient Ischaemic Attack

BACKGROUND

Weak associations between total and LDL cholesterol and ischaemic stroke compared with coronary heart disease (CHD) are at odds with the similar effectiveness of statin drugs in preventing ischaemic stroke and CHD, suggesting that other lipid sub-fractions that are affected by statins might be better predictors of ischaemic stroke. Apolipoprotein B levels are reduced by statins and are a stronger predictor of CHD than total and LDL cholesterol in patients both on and off statins. However, there are very few published data on apolipoproteins and stroke risk and no studies in patients with previous transient ischaemic attack (TIA).

METHODS

We performed a prospective cohort study of the associations of baseline total cholesterol, LDL, HDL, apolipoproteins A1 and B (apo A1; apo B) and risk of ischaemic stroke in 261 patients with previous TIA. Cox proportional hazards models were used to determine crude and multivariate-adjusted hazard ratios (HR) above versus below median values at 10-years follow-up.

RESULTS

The apo B/apo A1 ratio was the strongest independent predictor of ischaemic stroke (HR=2.94, 95% CI 1.43-5.88, p=0.003) followed by apo B (HR=2.26, 95% CI 1.16-4.38, p=0.02). The associations between total cholesterol, LDL, HDL, LDL/HDL ratio and apo A1 and ischaemic stroke risk did not reach statistical significance.

CONCLUSIONS

Apo B and the apo B/apo A1 ratio are predictive of ischaemic stroke in patients with previous TIA. Further studies are required to determine whether the prognostic value of apolipoprotein levels is maintained in patients on statins.

Long-Term Effects of Lipoprotein(a) on Carotid Atherosclerosis in Elderly Japanese

BACKGROUND

Serum level of lipoprotein(a) [Lp(a)] is hereditarily constant throughout life within an individual, but the relationship between Lp(a) and atherosclerosis in elderly people is still controversial.

METHODS

Serum Lp(a) levels were studied in 208 elderly Japanese participants aged 80 years with a variety of diseases, using carotid ultrasonography (US), brain computerized tomography (CT), electrocardiography (ECG), and ankle brachial pressure index (ABPI). Carotid plaque lesions were divided into 3 types based on the US echogenicity assessed by a computer-assisted system: L type (hypoechoic plaque), H type (hyperechoic plaque), and M type (heterogeneous plaque).

RESULTS

The frequency of the L type and occlusion was significantly higher in the high Lp(a) group (n = 38) than in the normal Lp(a) group (n = 170). The mean height of the plaque was also greater in the high Lp(a) group than in the normal Lp(a) group. There was no difference in CT findings between the two groups. Myocardial ischemia on ECG and low ABPI (<0.9) were both frequently, but not significantly, seen in the high Lp(a) group. Among factors influencing US findings, multiple regression analysis showed that high Lp(a) correlated markedly to L type and cigarette smoking correlated to M type.

CONCLUSIONS

These findings indicate that, in Japanese elderly patients aged 80, serum Lp(a) strongly correlates with hypoechoic carotid lesions, which correspond histologically to lipid-rich, unstable atherosclerosis. This suggested that Lp(a) could promote the formation of atherosclerosis throughout life, and play a role as an independent risk factor for circulatory disturbance of the organ later in life.

Relationship of lipoprotein(a) with intimal medial thickness of the carotid artery in Type 2 diabetic patients in south India

OBJECTIVE

The objective of this study was to investigate the association of lipoprotein(a) [Lp(a)] levels with intimal medial thickness (IMT) in Type 2 diabetic patients in south India.

STUDY DESIGN

We studied 587 consecutive Type 2 diabetic patients at the M.V. Diabetes Specialities Centre, Chennai. The mean age of the study group was 55 +/- 10 years and 71.2% were males. IMT of the right common carotid artery was determined using high-resolution B mode ultrasonography. Lp(a) levels were measured using ELISA. Since the frequency distribution of Lp(a) was skewed, Lp(a) values were log transformed and the geometric mean was used for statistical analysis. The tertiles of IMT were determined to analyse the association of Lp(a) and other factors with IMT.

RESULT

The mean Lp(a) level in the study patients was 18.9 +/- 3.1 mg/dl (geometric mean +/- sd) and the mean IMT of the study subjects was 0.93 +/- 0.19 mm (mean +/- sd). The prevalence of carotid atherosclerosis (defined as IMT > 1.1 mm) among subjects with elevated Lp(a) levels > 20 mg/dl was significantly higher compared with those with Lp(a) levels </= 20 mg/dl (26.9% vs. 16.3%, P = 0.003). Lp(a) levels increased with increase in tertiles of IMT (anova, P < 0.05). Pearson correlation analysis of carotid IMT with other cardiovascular risk factors revealed strong correlation of IMT with age (P < 0.0001), duration of diabetes (P < 0.0001), systolic blood pressure (P < 0.0001), diastolic blood pressure (P = 0.006), LDL-cholesterol (P = 0.023), HbA1c (P = 0.017) and Lp(a) (P < 0.0001). Multiple logistic regression analysis showed age (P = 0.010), LDL-cholesterol (P = 0.032) and Lp(a) (P = 0.021) to be associated with carotid atherosclerosis.

CONCLUSION

The results suggest that Lp(a) has a strong association with IMT of carotid arteries in Type 2 diabetic subjects in south India.

Is hypertension a leading cause of heart failure in Chinese?

1. There is considerable uncertainty regarding the importance of various risk factors in the development of heart failure. Most data are from Caucasian populations, where hypertension and coronary artery disease appear dominant. 2. Because it cannot be presumed that risk factor profiles will be identical for all races, we reviewed the literature on the aetiology of heart failure in Chinese. 3. There are, apparently, no long-term prospective studies defining the risk factors for heart failure in Chinese. Studies from Hong Kong in the 1990s point to an overlap of risk factors (especially hypertension, ischaemic heart disease and diabetes) and a high prevalence of diastolic heart failure (66%). Antihypertensive drug treatment appears likely to protect against the development of heart failure but end-points from formal trials are too small to be certain. 4. Available data, short of being definitive, point to hypertension being the most important identifiable risk factor in Chinese with heart failure. This may change with diabetes mellitus becoming more prevalent in the Chinese population.

Analytic strategies for stroke genetics

Strokes occur in first-degree relatives of stroke patients at rates approximating 40%; estimated population prevalences range from 3%-12%. The recent discovery of the Strk1 gene in Icelandic families, associated with a 7-fold increased stroke risk in carriers, strongly implicates a genetic contribution to stroke independent of other genetically based risk factors such as hypertension or diabetes. In this article we review the evidence for genetic contributions to stroke. We describe roles for genetic and molecular epidemiology in evaluating this complex disease. We delineate study design issues and analytic strategies to determine genetic association.

Relation of lipid and lipoprotein(a) to ischaemic stroke

The relationship of lipids and Lp(a) to ischemic stroke hasn't been established yet. Our aim was to determine lipid profile and vascular risk factors in stroke patients and compare them with control subjects. Seventy-nine consecutive patients with ischemic stroke were analyzed by total cholesterol, HDL-C, LDL-C, triglyceride, Lp(a) and doppler ultrasonography and vascular risk factors were recorded. Thirty control subjects of same ages were compared with the patient group. Lp(a) and lipids were correlated with stroke subtype and carotid atherosclerosis. There was no statistical significance between patients and control subjects related to total cholesterol, triglyceride, HDL-C, LDL-C and Lp(a) (P>0.05). Atherotrombotic and lacunar strokes didn't show any difference correlated with lipids and Lp(a). Hypertension and diabetes mellitus were important risk factors with (OR=4.50, 95% CI=1.25-16.22) and (OR=4.43, 95% CI=1.79-10.93) respectively. These results were statistically significant (P<0.05). Total cholesterol (308.67+/-85.82) and Lp(a) (32.10+/-17.30) values showed statistical significance (P<0.05) in patients with marked stenosis when compared with patients of normal doppler ultrasonography. Hypertension and diabetes mellitus were found as independent risk factors for ischemic stroke. Lipids and Lp(a) were not independent for atherotrombotic and lacunar stroke. Lp(a) concentration and carotid atherosclerosis in ultrasonography were associated significantly.

Detection of lipoprotein(a) in intraparenchymal cerebral vessels: correlation with vascular pathology and clinical history

Serum levels of lipoprotein(a), Lp(a), have been shown to be associated with increased risk of atherosclerosis (AS) and AS-related diseases such as myocardial and ischemic cerebral infarcts (ICI). Lp(a) has been detected in the vascular wall of the aorta and coronary vessels, and we documented the presence of apo(a) in cerebral vessels of the Circle of Willis, associated with AS changes. In this study we further investigated and characterized the biochemical nature of Lp(a) detected in both large and small cerebral parenchymal vessels. Autopsy specimens of cerebral vessels of 51 patients were examined by immunohistochemistry with monoclonal antibodies against apo(a), apoB, and plasminogen. Lp(a) was detected in cerebral capillaries and arterioles. All of the 8 patients with ICI expressed Lp(a) in parenchymal vessels, generally (6/8) in both capillaries and arterioles. Of 43 patients without ICI only 25 had Lp(a) detected. Among the patients without ICI, there was a slightly increased incidence of parenchymal Lp(a) in those patients who had severe hypoxic brain damage (12/20) compared to those patients without severe hypoxic damage (9/23). Thus, the presence of Lp(a) in small cerebral parenchymal vessels may reflect the role of Lp(a) in ICI.

Lipoprotein(a) serum levels and vascular diseases in an older Caucasian population cohort. Italian Longitudinal Study on Aging (ILSA)

OBJECTIVE

To investigate elevated lipoprotein(a) [Lp(a)] levels as a risk factor for stroke, myocardial infarction, angina, intermittent claudication, and combination of the above in a cohort of unselected older individuals.

DESIGN

Population cohort from one of the eight centers participating in the Italian Longitudinal Study on Aging (ILSA).

SETTING

General community.

PARTICIPANTS

A subsample of 446 subjects (M/F: 231/ 215, mean age: 74.5 +/- 5.7 years) of the original, randomly selected, population cohort of 704 individuals, 65 to 84 years of age, free-living or institutionalized in the Impruneta Municipality, area of Florence, Italy.

MEASUREMENTS

Conventional vascular risk factors and vascular diseases defined following a two-step procedure (screening phase and confirmation on positives) using standard and validated criteria. Lp(a) levels determined by an ELISA method.

RESULTS

No association was observed between elevated Lp(a) levels alone and any of the examined vascular diseases (stroke, myocardial infarction, angina, and intermittent claudication). In contrast, examining the interactions between elevated Lp(a) and conventional vascular risk factors, when elevated Lp(a) was combined with a history of smoking, a marked increase in the risk of vascular diseases combined (odds ratio [OR]: 4.12; 95% confidence interval [CI]: 1.27-13.40) was observed, much higher than that expected based on the additive effect of smoking and elevated Lp(a) alone.

CONCLUSIONS

With the cautions due to the cross-sectional design of the study and the limited statistical power, these results suggest a possible synergistic effect between elevated Lp(a) levels and other pro-atherogenic factors such as smoking on the risk of vascular diseases in older individuals.

The relationship between cholesterol and stroke: implications for antihyperlipidaemic therapy in older patients

Various studies on the relationship between serum cholesterol level and the risk of stroke have been published recently. Subsequent reviews have extrapolated information on stroke from the clinical trials originally aimed at lowering cholesterol for the primary and secondary prevention of myocardial infarction (MI) in middle-aged patients. We have reviewed the epidemiological knowledge on the relationship between serum cholesterol levels and stroke, and also focused on possible reduction of the risk of stroke with hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitor treatment. Possible benefits from such therapy are particularly relevant for the elderly population which is at particularly high risk for stroke. The effects of serum cholesterol levels on the risk for haemorrhagic and ischaemic stroke have been evaluated. Indirect epidemiological evidence indicates that serum levels of total cholesterol and its subfractions are determinants of stroke, but their associations are relatively weak. When exploring the possible association of serum cholesterol levels with the increased risk of stroke with aging, we concluded that, as in younger adults, elevated total cholesterol and decreased high density lipoprotein-cholesterol levels predispose to ischaemic stroke in the elderly. The mechanism through which serum cholesterol levels increase stroke risk is based on its actions on the artery walls. Indirect evidence suggests that the reduction in the stroke risk with HMG-CoA reductase inhibitors is larger than would be expected with reduction of elevated serum cholesterol level alone. Therefore, antioxidant and endothelium-stabilising properties of HMG-CoA reductase inhibitors may contribute in reducing the risk of stroke in recipients. Lowering high serum cholesterol with HMG-CoA reductase inhibitors has been beneficial in the primary and secondary prevention of MI. No trials have specifically tested the effect of cholesterol lowering with HMG-CoA reductase inhibitors on stroke occurrence. High serum cholesterol levels are a risk factor for ischaemic stroke, although the risk imparted is lower than that for MI. Although the relative risk of stroke associated with elevated serum cholesterol levels is only moderate, its population attributable risk is high given the increase in the elderly population worldwide. The effect of cholesterol reduction with HMG-CoA reductase inhibitors on prevention of ischaemic stroke should be evaluated in prospective, randomised, placebo-controlled trials in the elderly. The tolerability of lipid-lowering drugs in the elderly and the cost effectiveness of primary prevention of stroke using lipid-lowering drugs also needs to be assessed in the elderly.

Serum lipids in young patients with ischaemic stroke: a case-control study

OBJECTIVES

The relation between serum lipids and ischaemic stroke remains controversial. Studies of lipid related risk factors in cerebrovascular disease have varied greatly in their findings and also in their definition of the cerebrovascular end points. Serum lipids are thought to interact with the pathogenesis of stroke through an atherosclerosis mechanism. Stroke in young patients have been shown to be related to non-atherosclerotic causes most of the time. The aim was to determine the serum lipid profile and the vascular risk factors for ischaemic stroke in a series of patients under 45 with an ischaemic stroke and to compare them with a series of controls of the same age.

METHODS

Ninety four consecutive patients with ischaemic stroke were compared with 111 controls of the same age recruited from a regional electoral list. Vascular risk factors were recorded and serum lipid profile was determined in all of them.

RESULTS

Multivariate analyses showed that low HDL cholesterol, male sex, smoking, hypertension, and oral contraceptives were risk factors for intracerebral arterial occlusion.

CONCLUSION

Low HDL cholesterol was the only serum lipid index to be associated to an increased risk of stroke in this population. Low HDL cholesterol must be considered in the care management of young patients regardless of the detectable presence of atherosclerosis.

Lipoprotein (a) and the risk of ischemic stroke in young women

BACKGROUND AND PURPOSE

lipoprotein (a) (lp (a)) is a lipid-containing particle similar to LDL which has been found in atherosclerotic plaque. The role of lp (a) in ischemic stroke remains controversial, but some studies suggest lp (a) is particularly important as a risk factor for stroke in young adults. We investigated the role of lp (a) as a risk factor for stroke in young women enrolled in the Stroke Prevention in Young Women Study.

METHODS

subjects were participants in a population-based, case-control study of risk factors for ischemic stroke in young women. Cases were derived from surveillance of 59 regional hospitals in the central Maryland, Washington DC, Pennsylvania and Delaware area. Lp (a) was measured in 110 cases and 216 age-matched controls. Demographics, risk factors, and stroke subtype were determined by interview and review of medical records.

RESULTS

lp (a) values were higher in blacks than whites, but within racial groups, the distribution of lp (a) values was similar between cases and controls. After adjustment for age, race, hypertension, diabetes, cigarette smoking, coronary artery disease, total cholesterol and HDL cholesterol, the odds ratio for an association of lp (a) and stroke was 1.36 (95% CI 0.80-2.29). There was no dose-response relationship between lp (a) quintile and stroke risk. Among stroke subtypes, only lacunar stroke patients had significantly elevated lp (a) values compared to controls.

CONCLUSIONS

we found no association of lp (a) with stroke in a population of young women with ischemic stroke. Small numbers of patients limit conclusions regarding risk in ischemic stroke subtypes, but we could not confirm previous suggestions of an association of lp (a) with atherosclerotic stroke in young adults.

Vascular risk factors for atherosclerotic lesions of the middle cerebral artery detected by magnetic resonance angiography (MRA)

OBJECTIVES

To examine the relationship between atherosclerotic lesions of the middle cerebral artery (MCA) detected on MRA and vascular risk factors.

MATERIAL AND METHODS

We retrospectively assessed 279 patients (mean age, 69.0+/-11.3 years) who visited the Department of Neurology of Masuda Red Cross Hospital and underwent three-dimensional, time-of-flight MRA of the head between January 1996 and October 1998. Cases of cerebral embolism and internal carotid artery occlusion were excluded. Diagnoses were cerebral infarction (n = 152) and others (n = 127). We evaluated stenotic or occlusive lesions of the MCA (M1 portion), using MRA. Age, sex, history of hypertension, HbA1c, total cholesterol, fasting triglyceride, high density lipoprotein, lipoprotein(a), blood pressure, hematocrit, smoking and left ventricular hypertrophy (LVH) on ECG were included in the analysis.

RESULTS

36 patients (12.9%) had stenotic or occlusive lesions of the MCA on MRA. Univariate analysis showed that age, hypertension and HbA1c were significantly correlated with MCA lesions. Multiple logistic regression analysis showed that HbA C and hypertension were significant and independent predictors for MCA lesions.

CONCLUSION

Hypertension and high serum HbAlc levels may contribute to the development of atherosclerotic lesions of the MCA in Japanese people.

International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Standardization Project for the Measurement of Lipoprotein(a). Phase 2: selection and properties of a proposed secondary reference material for lipoprotein(a)

The International Federation of Clinical Chemistry and Laboratory Medicine Working Group for the Standardization of Lipoprotein(a) Assays has initiated a project to select a secondary reference material for lipoprotein(a) that can standardize the measurement of this lipoprotein. Most of the analytical problems with lipoprotein(a) assays are due to apolipoprotein(a) kringle 4 type 2 reactive antibodies and values being expressed in mg/l mass units rather than as nmol/l of apolipoprotein(a) particles. In Phase 2, four manufactured materials were compared for analytical performance, commutability properties and method harmonization in 27 lipoprotein(a) test systems. Results of precision and linearity testing were comparable for all materials whereas testing for the harmonization effect resulted in an among-assay coefficient of variation for corrected lipoprotein(a) values of between 11% and 22%. The material that gave maximum harmonization achieved a variation of < 8% for 18 immunonephelometric and immunoturbidimetric assay systems. It can be hypothesized that this residual variation in part takes into account the inaccuracy of lipoprotein(a) measurement due to apolipoprotein(a) size polymorphism. On the basis of acceptable analytical performance, maximal harmonization effect and documented stability, a lyophilized material has been selected as the common calibrator for lipoprotein(a) to be used in a value transfer procedure by diagnostic companies.

New evidence for the spasm-of-resistance-vessel concept of ischemic diseases

The spasm of resistance vessel (S-RV) concept of ischemic diseases avers that S-RV representing vascular autoregulatory dysfunction directly induces symptoms in ischemic diseases. The most important ischemic diseases, ischemic heart disease (IHD) and stroke, generally are not attributed to S-RV, and new evidence will be provided in this communication that S-RV induces IHD and stroke. Hypertension and the ischemic disorders of migraine and Raynaud's disease have been attributed to S-RV and to vascular dysregulation, and this information was used to help structure the study. It was found that these disorders are closely associated with IHD and stroke, and this is consistent with S-RV and vascular dysregulation as the mechanism for IHD and stroke. Also, it was found that multiple risk factors for IHD foster S-RV and are risk factors for hypertension, migraine, Raynaud's disease, and stroke, and this supports S-RV as the mechanism for IHD and stroke.

Differential distribution of apolipoprotein E in young and aged spontaneously hypertensive and stroke-prone rats

OBJECTIVES

To evaluate whether the differential distribution of apolipoprotein E among lipoprotein fractions and hepatic expression of the apolipoprotein E gene are causal factors in the regulation of lipid metabolism and physiological functions in young and aged spontaneously hypertensive and stroke-prone rats.

DESIGN AND METHODS

Biochemical analyses were performed on serum and hepatic specimens from young (2-month-old) and aged (8-month-old) spontaneously hypertensive rats, stroke-prone spontaneously hypertensive rats and normotensive Wistar-Kyoto rats. Levels of apolipoprotein E among various lipoprotein fractions were determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Liver concentrations of apolipoprotein E mRNA were analyzed by Northern blotting and relative levels of apolipoprotein E mRNA in different strains of rats were compared. Statistical analysis was performed by measuring correlations between hepatic apolipoprotein E mRNA levels and biological parameters.

RESULTS

Levels of apolipoprotein E in high-density and low-density lipoproteins were significantly lower in hypertensive rats than in age-matched normotensive Wistar- Kyoto rats. Although there was a significant increase in high-density lipoprotein apolipoprotein E contents in all aged animals, the elevation in aged hypertensive rats was much less than that in aged normotensive rats. Levels of apolipoprotein E in the very-low-density lipoprotein fraction were diminished in young stroke-prone rats but were remarkably high in aged rats. Steady-state levels of apolipoprotein E mRNA increased with age in all strains of rats, whereas aged hypertensive rats exhibited lower apolipoprotein E mRNA levels than aged normotensive rats.

CONCLUSIONS

The distribution of apolipoprotein E among various lipoprotein fractions was dramatically altered with age, and the alteration varied among different strains of rats. The differential distribution of apolipoprotein E in young and aged spontaneously hypertensive and stroke-prone rats suggests that apolipoprotein E could be a causal factor that disturbs the homeostasis of lipids and lipoproteins and perturbs physiological functions in hypertensive rats.

Apolipoprotein(a) size polymorphism in young adults with ischemic stroke

High serum lipoprotein(a) (Lp(a)) concentration which is largely determined by genetic factors, mainly the apolipoprotein(a) (apo(a)) polymorphism, is associated with ischemic cerebrovascular disease. The aim of this study was to investigate whether apo(a) size was associated with acute ischemic stroke in young adults for which causal factors often remain undetermined. Lipid parameters, Lp(a) concentration and apo(a) isoform size distribution were determined in 90 young patients (37.4+/-8.7 years) with acute cerebral ischemia, and compared to those of control subjects with similar age and sex ratio. Apo(a) size was expressed as its apparent number of kringle 4 (Kr 4) repeats. Serum Lp(a) concentrations were significantly higher in patients than in controls (median values: 0.18 vs. 0.07 g/l, P=0.009) and were as expected inversely related to the number of kringle 4 repeats in both controls (r2=-0.61, P < 0.001) and patients (r2=-0.56, P < 0.001). However there was no difference in the apo(a) isoform size distributions between the two groups (median isoform size: 27 vs. 27 Kr 4, P=0.25). Lp(a) levels were increased as well in patients with size apo(a) isoform < or = 22 Kr 4 as in those with isoforms > 25 Kr 4. Multivariate analysis showed that apo(a) phenotype did not appear as a risk factor for cerebrovascular infarction. Thus, our results indicate that serum Lp(a) was significantly increased in young people with ischemic stroke but fail to reveal a role of small-sized apo(a) isoforms in the occurrence of this event. They suggest that other factors, genetic or environmental in nature, than the apo(a) size contribute to increase the serum Lp(a) concentrations in these young patients.

Lipoprotein (a) induces angiogenesis on the chick embryo chorioallantoic membrane

BACKGROUND

Both lipoprotein (a) [Lp(a)] and angiogenesis have been shown to be associated with initiation and progression of atherosclerotic plaque. Lp(a) and two neutralizing anti-Lp(a) antibodies were investigated for their capacity to affect the vasoproliferative processes of the chick embryo chorioallantoic membrane (CAM), a useful model for such an investigation.

METHODS

Gelatin sponges loaded with Lp(a) alone or together with anti-Lp(a) antibodies, or with vehicle alone, phosphate-buffered saline (PBS), were implanted in vivo onto the CAM at incubation day 8. Four days later, sponges and the adjacent CAM tissues were assessed for the extent of angiogenesis in terms of microvessel counts.

RESULTS

Lp(a)-loaded sponges gave significantly higher counts than those loaded with the LP(a)-anti-Lp(a) antibodies complex, which overlapped those treated with PBS. The angiogenic response was similar to that obtained with basic fibroblast growth factor, a well known angiogenic molecule.

CONCLUSION

These data suggest that Lp(a) is capable of inducing angiogenesis in vivo, which might account for its ability to enhance and support atherosclerosis.

Genetics of stroke--a review

Evidence from twin and family shows that genetic factors contribute to the risk of stroke and that their role may be at least as important in stroke as in coronary heart disease. Additional support for the significance of genetic factors comes from other findings such as epidemiological data showing phenotypic heterogeneity of stroke, genetic influence on many of the risk factors for stroke, and racial and geographic differences in morbidity and mortality in stroke victims. Yet, apart from the reported associations of a small number of cases with Mendelian cerebrovascular diseases, only a few studies have directly investigated gene markers or molecular genetics of stroke. This review presents the existing evidence on the genetic background of stroke and discusses results from the genetic studies of stroke published to date.

Identification of apo(a) phenotypes in a Korean population using a standardized nomenclature system based on the number of kringle IV repeats

We determined serum lipoprotein(a) [Lp(a)] concentrations and apolipoprotein(a) [apo(a)] phenotypes in 193 healthy Koreans. We analysed the apo(a) phenotypes by a simplified sodium dodecyl sulphate-polyacrylamide gel electrophoresis method and classified apo(a) isoforms objectively using an apo(a) phenotype standard with a known number of kringle IV repeats. The frequency distribution of Lp(a) levels showed marked positive skew with a mean of 0.143 g/L and a median of 0.052 g/L. Of the 193 subjects tested, no bands were detected in three, and single- and double-band phenotypes were observed in 103 and 87, respectively. Among the Koreans, the most frequent phenotype was S5(39.4%), followed by S4S5(17.1%), S5S5(14.0%), S4(11.4%), S3S5(5.2%), and the remaining phenotypes (13.0%). The calculated apo(a) allele frequencies were LpF, 0.003; LpS1, 0.013; LpS2, 0.010; LpS3, 0.048; LpS4, 0.198; LpS5, 0.563 and Lp0, 0.165. We found that the serum Lp(a) concentration in Koreans was similar to that of Caucasians, but the apo(a) allele size distribution was shifted toward higher molecular weights.

Changes in atherogenic lipids and lipoproteins during natural and hyperstimulated cycles in healthy women

OBJECTIVE

To compare changes in the concentrations of Lp(a) lipoprotein and other atherogenic lipids and lipoproteins in natural and hyperstimulated ovarian cycles.

DESIGN

Open, prospective study.

SETTING

Academic department in a teaching hospital.

PATIENT(S)

Normal ovulatory women served as controls and the treatment group consisted of women undergoing ovarian hyperstimulation.

INTERVENTION(S)

The treatment group received hMG on a fixed regimen.

MAIN OUTCOME MEASURE(S)

Measurements of serum lipids and lipoproteins were made in both natural and hyperstimulated cycles.

RESULT(S)

There was a significant increase in the median concentration of Lp(a) lipoprotein from 10.1 to 10.7 mg/dL in the luteal compared with the proliferative phase of unstimulated cycles. In hyperstimulated cycles, there was a significant increase in the median concentration of Lp(a) lipoprotein from 9.7 mg/dL in the proliferative phase to 11.3 mg/dL in the luteal phase. Reductions in concentrations of total cholesterol and low-density lipoprotein cholesterol were found in the luteal phase of hyperstimulated cycles.

CONCLUSION

Concentrations of Lp(a) lipoprotein increase during the luteal phase of both natural and hyperstimulated ovarian cycles.

Relationship between lipoprotein (a) and both stroke and carotid atheroma

In vitro studies provide mechanisms by which elevated lipoprotein (a) [Lp(a)] concentrations may promote both thrombosis and atherogenesis. Case-control studies have reported raised Lp(a) concentrations in patients with stroke, but prospective studies have failed to confirm the association. A potential confounding factor is that Lp(a) may rise acutely after stroke. We determined Lp(a) concentrations in 164 patients studied at least 21 days after stroke or transient ischaemic attack, and in 91 controls. In the patient group we correlated Lp(a) concentrations with both the degree of carotid stenosis estimated on duplex ultrasonography, and with stroke subtype (large vessel disease, lacunar infarction, and cardioembolic and unknown pathogenesis). There was no difference between Lp(a) concentration in cases and controls [median (quartiles) 0.10 (0.04, 0.39) versus 0.12 (0.04, 0.30) g/L, P = 0.34]. There was no difference in the proportion of cases compared with controls with a markedly elevated Lp(a) of > 0.4 g/L (21.3 versus 16.5%, P = 0.34). There was non-significant trend towards higher median Lp(a) concentrations in women [median (quartiles) 0.16 (0.04, 0.32) g/L versus 0.12 (0.04, 0.28) g/L, P = 0.3]. In view of this trend we analysed the differences between cases and controls for each sex separately. Lp(a) concentrations in men were median (quartiles) 0.08 (0.04, 0.26) g/L in the 101 cases and 0.12 (0.04, 0.28) g/L in the 43 controls (P = 0.6). Lp(a) concentrations in women were median (quartiles) 0.25 (0.04, 0.44) g/L in the 63 cases, and 0.16 (0.04, 0.32) g/L in the 48 controls (P = 0.16). Within the patient group there was no difference between Lp(a) concentrations in the different stroke subgroups. There was no relationship between Lp(a) concentrations and mean percentage carotid stenosis (rs = 0.14, P = 0.07). Our results suggest that in an unselected population of men studied more than 3 weeks post event there is no relationship between lipoprotein(a) concentrations and either stroke/transient ischaemic attack, or carotid atheroma. The relationship in women requires further study.

Lipoprotein (a) and its relationship to risk factors and severity of atherosclerotic peripheral vascular disease

OBJECTIVES

To determine the significance of Lipoprotein (a) (Lp(a)) as a risk factor for atherosclerotic lower limb peripheral vascular disease (PVD), and its relationship to other demographic and biochemical variables and disease pattern and severity.

DESIGN

Prospective case-control study.

MATERIAL AND METHODS

Demographic and biochemical risk factors, lipoprotein fractions and Lp(a) were measured in 200 patients with PVD and 200 age- and sex-matched control subjects. Lp(a) levels were correlated with traditional risk factors and clinical and vascular laboratory disease parameters.

RESULTS

Patients with PVD have a higher incidence of smoking, hypertension, and diabetes mellitus; and had significantly higher levels of serum cholesterol, triglycerides, LDL, VLDL, apolipoprotein B, fasting glucose, fibrinogen, plasminogen, haematocrit, white cell and platelet counts; but lower levels of HDL and apolipoprotein A1. Fasting Lp (a) concentration is an independent risk factor for PVD and is significantly higher in the patients (median = 26.1 mg/dl [4.8-195], mean = 36.5 +/- 32.6 mg/dl) than in controls (median = 18.2 mg/dl [5.4-216], mean = 27.2 +/- 28.1 mg/dl; p < 0.0001). In patients with PVD, Lp(a) correlated positively with plasma LDL, cholesterol, fibrinogen, renal disease, and apolipoprotein B. Fasting levels of > 24 mg/dl incurred a two-fold increase in risk of PVD. Patients with a higher Lp(a) have a significantly higher incidence of resting pain and ulcerations, and regression analysis confirmed smoking and Lp(a) level to be associated with the SVS category of disease severity.

CONCLUSIONS

Lipoprotein (a) is a significant independent risk factor for PVD. Lp(a) levels correlated with LDL, cholesterol, fibrinogen, apolipoprotein B and disease severity. An elevated Lp(a) level may be associated with more severe forms of PVD.

Lipoprotein (a): its role in childhood thromboembolism

PURPOSE

Elevated lipoprotein (a) [LP (a)] concentrations are independent risk factors of coronary heart disease or stroke in young adults. To clarify its role in childhood thromboembolism, Lp (a) was measured in 72 children with thromboembolism.

METHODS

In addition to Lp (a), defects of the protein C anticoagulant system, antithrombin, and antiphospholipid antibodies were investigated in children with arterial (n = 36) or venous (n = 36) thrombosis.

RESULTS

Enhanced Lp (a) >50 mg/dL was diagnosed in 8 out of 36 children with arterial and 5 out of 36 patients with venous thrombosis. Of the 72 children, 25 showed the factor V Leiden mutation, 10 showed protein C deficiency, 2 showed antithrombin deficiency, and 4 showed primary antiphospholipid syndrome. Three children with increased Lp (a) were heterozygous for the factor V Leiden mutation, and 1 girl showed additional protein C deficiency.

CONCLUSIONS

Data of this study indicate that increased concentrations of Lp (a) play an important role in childhood thrombosis.

Arterial Damage, Triglycerides, Apolipoprotein, and Lp-(a) Values in PVD Patients

The aim of the study was to provide a detailed apolipoproteic profile in stage II peripheral vascular disease (PVD) patients and to ascertain whether lower ankle/ arm pressure index (API) values were associated with a worse profile.

Apolipoproteins of 83 stage II PVD patients (average age 64.7 ± 9.3 years) were selected and compared with those of a group of 44 normal control subjects, similar in terms of age, sex, and smoking and eating habits. Neither PVD patients nor controls had ever received lipid-lowering agents or defined dietary treatment. A diagnosis of PVD was confirmed by an API of <0.85. Arteriopathic patients were also split into two groups, depending on their API values, similar in terms of age, sex and smoking habits: API values of one group (n = 38) were ≥0.6, those of the other group (n = 45) were <0.6. The following biohumoral parameters were considered: fasting glycemia, total cholesterol, triglycerides (TGs); high-density lipoprotein cholesterol (HDL-C); low density lipoprotein cholesterol (LDL-C), very low density lipoprotein cholesterol (VLDL-C), total cholesterol (TC)/HDL-C (TC/ HDL-C), Apoproteins (Apos) AI, AII, B, CII, CIII, and E; and lipoprotein a [Lp(a)].

HDL-C and Apo AI were lower ( p < 0.01), while TC/ HDL-C ratios, Apo B, and Apo CII were higher ( p < 0.01) in PVD patients compared with controls. The comparison between the two PVD groups with different API values showed higher blood TG and VLDL-C values for the patients with lower API values (p < 0.05), indicating a relationship between hypertriglyceridemia and greater arterial damage. Key Words: Peripheral arterial occlusive disease-Triglyceride-Lipoprotein a.

Lipoprotein(a): structural implications for pathophysiology

The assembly between a low-density lipoprotein particle and apolipoprotein(a), a highly carbohydrate-rich protein, gives origin to a peculiar class of lipoproteins, only found in the hedgehog, primates, and humans, termed lipoprotein(a). Apolipoprotein(a), which shares a high degree of sequence homology with the fibrinolytic proenzyme plasminogen, is linked to the apolipoprotein B-100 component of low-density lipoprotein via a disulfide bond and confers distinct biochemical and metabolic properties to lipoprotein(a). Because of its peculiar structural features and the observed correlation between high lipoprotein(a) levels and the development of a variety of atherosclerotic disorders, this lipoprotein has become the focus of an intense research effort. Although accumulation of lipoprotein(a) in the vessel wall at sites of vascular injury has been clearly evidenced, the mechanism(s) by which lipoprotein(a) exerts its pathogenic effect in this milieu remain largely unknown. It has been hypothesized that the pathological effect of lipoprotein(a) is related either to its similarity to low-density lipoprotein (i.e., a pro-atherogenic effect) or to the apolipoprotein(a) similarity to plasminogen (i.e., a pro-thrombotic/anti-fibrinolytic effect). However, it is probable that both components contribute to the pathogenicity of lipoprotein(a). The fact that lipoprotein(a) levels are largely genetically determined, varying widely among individuals and racial groups, adds additional elements to the scientific interest that surrounds this lipoprotein. Both clinical and biochemical studies of lipoprotein(a) have been complicated by the high degree of structural heterogeneity of apolipoprotein(a), which is considered the most polymorphic protein in human plasma. Our aim in this paper is to provide an overview of the most salient structural features of lipoprotein(a) and their possible pathophysiological implications.

Association of lipoprotein cholesterol and triglycerides with the severity of coronary artery disease in men and women

The differences between the lipid profiles of male and female patients and the effect of plasma lipids on the extent of coronary artery disease were evaluated in 122 angiographically assessed coronary artery disease patients (95 males and 27 females) and 60 controls. Both male and female patients had lower HDL-cholesterol and higher total cholesterol, LDL-cholesterol, triglyceride, VLDL-cholesterol and VLDL-triglyceride concentrations than the controls. The VLDL lipid values did not differ significantly between the male patients with different extent of CAD, whereas the VLDL lipid values of female patients tended to increase with an increasing severity of CAD. High Lp(a) (> or = 35 mg/dl) values were more prevalent in patients with > 50% coronary stenosis compared to patients with < 50% stenosis and the controls (29%, 17% and 12%, respectively). The apolipoprotein E phenotypes and epsilon allele frequencies were similar in the patients and the controls. Low HDL-cholesterol and high LDL-cholesterol are CAD risk factors for both sexes. For women, elevated VLDL-triglycerides seem to be an additional risk factor for CAD.

Case-control study of serum lipoprotein(a) and apolipoproteins A-I and B in stroke in the young

OBJECTIVES

Abnormalities of lipoprotein(a) and apolipoproteins A-I and B are being recognised as independent risk factors in ischaemic heart disease and atherosclerosis. There are no studies from India where stroke in the young constitutes nearly 20-30% of all strokes.

SUBJECTS AND METHODS

Fasting serum lipids, lipoproteins, apolipoproteins A-I and B and lipoprotein(a) were measured in 50 patients aged less than 40 years presenting with completed stroke and 50 normal, age and sex-matched control subjects. Apolipoproteins A-I and B were measured by immunoturbidimetry and lipoprotein(a) by enzyme-linked immunosorbent assay.

RESULTS

The serum total cholesterol, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol, triglycerides and apolipoproteins A-I and B were not significantly different in the test group as compared to the controls. However, serum lipoprotein(a) was significantly higher in the young stroke patients.

CONCLUSION

These findings confirm the hypothesis that an elevated serum lipoprotein(a) level is an important risk factor in the development of cerebral ischaemia in patients aged less than 40 years. It may be worthwhile to study whether it is useful in identifying patients most at risk for stroke.

Lipoprotein(a) is an independent risk factor for multiple cerebral infarctions

In an attempt to ascertain whether Lp(a) is a risk factor for multiple cerebral infarctions (MCI), we have studied 83 patients with proven MCI and 39 subjects without MCI by computed tomography (CT). Seventy-one patients with non-insulin-dependent diabetes mellitus (NIDDM) were included: 52 with and 19 without MCI. Serum Lp(a) levels were significantly higher in patients with MCI than in subjects without MCI. There were no differences in serum Lp(a) levels between NIDDM and non-diabetic patients with MCI. The logistic regression analysis revealed that Lp(a) and hypertension were independent risk factors for the cerebral event. The current study demonstrated that Lp(a) and hypertension are significant risk factors for multiple cerebral infarctions.

Low serum cholesterol and the risk of cerebral haemorrhage

In addressing the potential for any hazards associated with lowering serum cholesterol, a recent meta-analysis by Law and colleagues (Br Med J 1994;308:373) concluded that that there was no evidence that a low or reduced serum cholesterol concentration increases mortality from any cause other than haemorrhagic stroke. In this review, the evidence for this unexpected association will be addressed, and possible mechanisms discussed. Overall implications of the phenomenon, particularly for the hypertensive patient, will be addressed in the context of the anticipated consequences of lipid-lowering therapy for all stroke, haemorrhagic and non-haemorrhagic, as well as ischaemic heart disease (IHD).

Intraindividual variations in lipoprotein (a) levels and factors related to these changes

Lp(a) levels are genetically determined and remain stable without major changes throughout lives. However, when an individual's Lp(a) levels are observed over a one-year period, they show spontaneous variation. The rate of intraindividual variation in Lp(a) was observed in 16 patients with hypertension, hyperlipidemia and/or glucose intolerance in a chronic stable state who regularly visited the hospital clinic once a month, at least 10 times during the year, and in whom a total of 42 blood and clinical chemistry tests including serum lipids, Lp(a) and apoproteins were performed. The rate of annual intraindividual variation of Lp(a) averaged out as 16.6%. The rate was 18.8% for isoform S4 (n = 10), 18.6% for S3 (n = 3), and although small in number of subjects, other isoforms showed minor variation rates. There was a significant negative correlation between the rate of variation (y%) and LP(a) level (xmg/dl) r = -0.605, p < 0.05, y = -0.461 x +29.8). Therefore, when Lp(a) was high, the rate of variation (SD%) was low. This was consistent with the finding that the rates of variation were low for isoforms S2, S3S4 and F, whose molecular weights were low, accompanied by high Lp(a) levels. On the other hand, when the relationship between Lp(a) level and the amount of variation (SD mg/dl) was examined, there was no correlation between the two, since the amounts of variation were almost constant at a level of 3.8 mg/dl, regardless of Lp(a) level. The annual variation of Lp(a) level was found to be related to three groups of factors based on comparison of the variations among WHO phenotypes of hyperlipidemias, univariate correlation analysis with the clinical parameters tested, and multivariate analysis: the first group of factors was related to structure and metabolism of very low-density lipoprotein such as triglycerides, phospholipids, apo C-II, C-III, E, A-II and uric acid; the second group was related to thrombosis centering on platelets; and the third group involved those in the acute phase reactions represented by 1 hr and 2 hr erythrocyte sedimentation rates.