Defects in the low density lipoprotein receptor gene affect lipoprotein (a) levels: multiplicative interaction of two gene loci associated with premature atherosclerosis

Lipoprotein(a) in Familial Hypercholesterolemia

Background

Low density lipoprotein (LDL) and Lipoprotein (Lp)(a) are proatherogenic apolipoprotein (apo) B-containing members of the non-high-density lipoprotein (non-HDL) family of particles. Elevated plasma levels of LDL cholesterol (C), non-HDL-C, and apo B are defining features of heterozygous familial hypercholesterolemia (HeFH), but reports of elevated plasma Lp(a) concentration are inconsistent.

Methods

We performed retrospective chart reviews of 256 genetically characterized patients with hypercholesterolemia and 272 control subjects from the Lipid Genetics Clinic at University Hospital in London, Ontario. We evaluated pairwise correlations between plasma levels of Lp(a) and those of LDL-C, non-HDL-C and apo B.

Results

Mean Lp(a) levels were not different between individuals with hypercholesterolemia and control subjects. No correlations were found between Lp(a) and LDL-C or non-HDL-C levels in controls or patients with hypercholesterolemia; all r values < 0.079 and all P values > 0.193. Borderline weak correlations between Lp(a) and apo B were identified in patients r = 0.103; P = 0.112) and controls (r = 0.175; P = 0.005). Results were similar across genotypic subgroups.

Conclusions

Lp(a) levels are independent of LDL-C and non-HDL-C; in particular Lp(a) levels are not increased in patients with hypercholesterolemia and molecularly proven HeFH. Apo B was only weakly associated with Lp(a). Elevated Lp(a) does not cause FH in our clinic patients. Genetic variants causing HeFH that raise LDL-C do not affect Lp(a), confirming that these lipoproteins are metabolically distinct. Lp(a) cannot be predicted from LDL-C and must be determined separately to evaluate its amplifying effect on atherosclerotic risk in patients with hypercholesterolemia.

Lipoprotein(a) Genotype Influences the Clinical Diagnosis of Familial Hypercholesterolemia

Background Evidence suggests that LPA risk genotypes are a possible contributor to the clinical diagnosis of familial hypercholesterolemia (FH). This study aimed at determining the prevalence of LPA risk variants in adult individuals with FH enrolled in the Italian LIPIGEN (Lipid Transport Disorders Italian Genetic Network) study, with (FH/M+) or without (FH/M-) a causative genetic variant. Methods and Results An lp(a) [lipoprotein(a)] genetic score was calculated by summing the number risk-increasing alleles inherited at rs3798220 and rs10455872 variants. Overall, in the 4.6% of 1695 patients with clinically diagnosed FH, the phenotype was not explained by a monogenic or polygenic cause but by genotype associated with high lp(a) levels. Among 765 subjects with FH/M- and 930 subjects with FH/M+, 133 (17.4%) and 95 (10.2%) were characterized by 1 copy of either rs10455872 or rs3798220 or 2 copies of either rs10455872 or rs3798220 (lp(a) score ≥1). Subjects with FH/M- also had lower mean levels of pretreatment low-density lipoprotein cholesterol than individuals with FH/M+ (t test for difference in means between FH/M- and FH/M+ groups <0.0001); however, subjects with FH/M- and lp(a) score ≥1 had higher mean (SD) pretreatment low-density lipoprotein cholesterol levels (223.47 [50.40] mg/dL) compared with subjects with FH/M- and lp(a) score=0 (219.38 [54.54] mg/dL for), although not statistically significant. The adjustment of low-density lipoprotein cholesterol levels based on lp(a) concentration reduced from 68% to 42% the proportion of subjects with low-density lipoprotein cholesterol level ≥190 mg/dL (or from 68% to 50%, considering a more conservative formula). Conclusions Our study supports the importance of measuring lp(a) to perform the diagnosis of FH appropriately and to exclude that the observed phenotype is driven by elevated levels of lp(a) before performing the genetic test for FH.

Lipoprotein(a) levels in children with suspected familial hypercholesterolaemia: a cross-sectional study

AIMS

Familial hypercholesterolaemia (FH) predisposes children to the early initiation of atherosclerosis and is preferably diagnosed by DNA analysis. Yet, in many children with a clinical presentation of FH, no mutation is found. Adult data show that high levels of lipoprotein(a) [Lp(a)] may underlie a clinical presentation of FH, as the cholesterol content of Lp(a) is included in conventional LDL cholesterol measurements. As this is limited to adult data, Lp(a) levels in children with and without (clinical) FH were evaluated.

METHODS AND RESULTS

Children were eligible if they visited the paediatric lipid clinic (1989-2020) and if Lp(a) measurement and DNA analysis were performed. In total, 2721 children (mean age: 10.3 years) were included and divided into four groups: 1931 children with definite FH (mutation detected), 290 unaffected siblings/normolipidaemic controls (mutation excluded), 108 children with probable FH (clinical presentation, mutation not detected), and 392 children with probable non-FH (no clinical presentation, mutation not excluded). In children with probable FH, 32% were found to have high Lp(a) [geometric mean (95% confidence interval) of 15.9 (12.3-20.6) mg/dL] compared with 10 and 10% [geometric means (95% confidence interval) of 11.5 (10.9-12.1) mg/dL and 9.8 (8.4-11.3) mg/dL] in children with definite FH (P = 0.017) and unaffected siblings (P = 0.002), respectively.

CONCLUSION

Lp(a) was significantly higher and more frequently elevated in children with probable FH compared with children with definite FH and unaffected siblings, suggesting that high Lp(a) may underlie the clinical presentation of FH when no FH-causing mutation is found. Performing both DNA analysis and measuring Lp(a) in all children suspected of FH is recommended to assess possible LDL cholesterol overestimation related to increased Lp(a).

Familial Hypercholesterolemia and Lipoprotein(a): A Gordian Knot in Cardiovascular Prevention

Familial hypercholesterolemia (FH) is the most frequent genetic disorder resulting in increased low-density lipoprotein cholesterol (LDL-C) levels from childhood, leading to premature atherosclerotic cardiovascular disease (ASCVD) if left untreated. FH diagnosis is based on clinical criteria and/or genetic testing and its prevalence is estimated as being up to 1:300,000−400,000 for the homozygous and ~1:200−300 for the heterozygous form. Apart from its late diagnosis, FH is also undertreated, despite the available lipid-lowering therapies. In addition, elevated lipoprotein(a) (Lp(a)) (>50 mg/dL; 120 nmol/L), mostly genetically determined, has been identified as an important cardiovascular risk factor with prevalence rate of ~20% in the general population. Novel Lp(a)-lowering therapies have been recently developed and their cardiovascular efficacy is currently investigated. Although a considerable proportion of FH patients is also diagnosed with high Lp(a) levels, there is a debate whether these two entities are associated. Nevertheless, Lp(a), particularly among patients with FH, has been established as a significant cardiovascular risk factor. In this narrative review, we present up-to-date evidence on the pathophysiology, diagnosis, and treatment of both FH and elevated Lp(a) with a special focus on their association and joint effect on ASCVD risk.

Use of Lipoprotein(a) in clinical practice: A biomarker whose time has come. A scientific statement from the National Lipid Association

Lipoprotein(a) [Lp(a)] is a well-recognized, independent risk factor for atherosclerotic cardiovascular disease, with elevated levels estimated to be prevalent in 20% of the population. Observational and genetic evidence strongly support a causal relationship between high plasma concentrations of Lp(a) and increased risk of atherosclerotic cardiovascular disease-related events, such as myocardial infarction and stroke, and valvular aortic stenosis. In this scientific statement, we review an array of evidence-based considerations for testing of Lp(a) in clinical practice and the utilization of Lp(a) levels to inform treatment strategies in primary and secondary prevention.

Lipoprotein (a) in familial hypercholesterolaemia

PURPOSE OF REVIEW

The role of lipoprotein (a) in atherogenesis has been the subject of argument for many years. Evidence that it is raised in familial hypercholesterolaemia has been disputed not least because a mechanism related to low density lipoprotein (LDL) receptor mediated catabolism has been lacking. Whether lipoprotein (a) increases the already raised atherosclerotic cardiovascular disease (ASCVD) risk in familial hypercholesterolaemia is also more dubious than is often stated. We review the evidence in an attempt to provide greater clarity.

RECENT FINDINGS

Lipoprotein (a) levels are raised as a consequence of inheriting familial hypercholesterolaemia. The mechanism for this is likely to involve increased hepatic production, probably mediated by PCSK9 augmented by apolipoprotein E. The extent to which raised lipoprotein (a) contributes to the increased ASCVD risk in familial hypercholesterolaemia remains controversial.Unlike, for example, statins which are effective across the whole spectrum of LDL concentrations, drugs in development to specifically lower lipoprotein (a) are likely to be most effective in people with the highest levels of lipoprotein (a). People with familial hypercholesterolaemia may therefore be in the vanguard of those in whom theses agents should be exhibited.

SUMMARY

Inheritance of familial hypercholesterolaemia undoubtedly increases the likelihood that lipoprotein (a) will be raised. However, in familial hypercholesterolaemia when ASCVD incidence is already greatly increased due to high LDL cholesterol, whether lipoprotein (a) contributes further to this risk cogently needs to be tested with drugs designed to specifically lower lipoprotein (a).

Familial Hypercholesterolemia and Lipoprotein(a): Two Partners in Crime?

PURPOSE OF REVIEW

Familial hypercholesterolemia is a high cardiovascular risk disorder. We will review the role of lipoprotein(a) in cardiovascular risk and in aortic valve stenosis in familial hypercholesterolemia, as well as its association with their phenotype, and strategies to identify this high-risk population.

RECENT FINDINGS

Patients with familial hypercholesterolemia have higher lipoprotein(a) levels mainly due to an increased frequency of LPA variants, and the cardiovascular risk is increased twofolds when both conditions coexist. Also, an increased risk for aortic valve stenosis and valve replacement has been observed with high lipoprotein(a) levels. Assessment of lipoprotein(a) during the cascade screening for familial hypercholesterolemia is a good opportunity to identify this high-risk population. High cardiovascular risk in familial hypercholesterolemia is increased even more when lipoprotein(a) is also elevated. Measurement of lipoprotein(a) in these patients is crucial to identify those subjects who need to intensify LDL-cholesterol reduction pending availability of lipoprotein(a)-specific treatments.

Improving Familial Hypercholesterolemia Diagnosis Using an EMR-based Hybrid Diagnostic Model

CONTEXT

Familial hypercholesterolemia (FH) confers a greatly increased risk for premature cardiovascular disease, but remains very underdiagnosed and undertreated in primary care populations.

OBJECTIVE

We assessed whether using a hybrid model consisting of 2 existing FH diagnostic criteria coupled with electronic medical record (EMR) data would accurately identify patients with FH in a Midwest US metropolitan healthcare system.

METHODS

We conducted a retrospective, records-based, cross-sectional study using datasets from unique EMRs of living patients. Using Structured Query Language to identify components of 2 currently approved FH diagnostic criteria, we created a hybrid model to identify individuals with FH.

RESULTS

Of 264 264 records analyzed, between 794 and 1571 patients were identified as having FH based on the hybrid diagnostic model, with a prevalence of 1:300 to 1:160. These patients had a higher prevalence of premature coronary artery disease (CAD) (38-58%) than the general population (1.8%) and higher than those having a high CAD risk but no FH (10%). Although most patients were receiving lipid-lowering therapies (LLTs), only 50% were receiving guideline-recommended high-intensity LLT.

CONCLUSION

Using the hybrid model, we identified FH with a higher clinical and genetic detection rate than using standard diagnostic criteria individually. Statin and other LLT use were suboptimal and below guideline recommendations. Because FH underdiagnosis and undertreatment are due partially to the challenges of implementing existing diagnostic criteria in a primary care setting, this hybrid model potentially can improve FH diagnosis and subsequent early access to appropriate treatment.

Lipids and Lipoproteins in Health and Disease: Focus on Targeting Atherosclerosis

Despite advances in pharmacotherapy, intervention devices and techniques, residual cardiovascular risks still cause a large burden on public health. Whilst most guidelines encourage achieving target levels of specific lipids and lipoproteins to reduce these risks, increasing evidence has shown that molecular modification of these lipoproteins also has a critical impact on their atherogenicity. Modification of low-density lipoprotein (LDL) by oxidation, glycation, peroxidation, apolipoprotein C-III adhesion, and the small dense subtype largely augment its atherogenicity. Post-translational modification by oxidation, carbamylation, glycation, and imbalance of molecular components can reduce the capacity of high-density lipoprotein (HDL) for reverse cholesterol transport. Elevated levels of triglycerides (TGs), apolipoprotein C-III and lipoprotein(a), and a decreased level of apolipoprotein A-I are closely associated with atherosclerotic cardiovascular disease. Pharmacotherapies aimed at reducing TGs, lipoprotein(a), and apolipoprotein C-III, and enhancing apolipoprotein A-1 are undergoing trials, and promising preliminary results have been reported. In this review, we aim to update the evidence on modifications of major lipid and lipoprotein components, including LDL, HDL, TG, apolipoprotein, and lipoprotein(a). We also discuss examples of translating findings from basic research to potential therapeutic targets for drug development.

Lipoprotein(a)

Lipoprotein(a) [Lp(a)] is an atherogenic lipoprotein with a strong genetic regulation. Up to 90% of the concentrations are explained by a single gene, the LPA gene. The concentrations show a several-hundred-fold interindividual variability ranging from less than 0.1 mg/dL to more than 300 mg/dL. Lp(a) plasma concentrations above 30 mg/dL and even more above 50 mg/dL are associated with an increased risk for cardiovascular disease including myocardial infarction, stroke, aortic valve stenosis, heart failure, peripheral arterial disease, and all-cause mortality. Since concentrations above 50 mg/dL are observed in roughly 20% of the Caucasian population and in an even higher frequency in African-American and Asian-Indian ethnicities, it can be assumed that Lp(a) is one of the most important genetically determined risk factors for cardiovascular disease.Carriers of genetic variants that are associated with high Lp(a) concentrations have a markedly increased risk for cardiovascular events. Studies that used these genetic variants as a genetic instrument to support a causal role for Lp(a) as a cardiovascular risk factor are called Mendelian randomization studies. The principle of this type of studies has been introduced and tested for the first time ever with Lp(a) and its genetic determinants.There are currently no approved pharmacologic therapies that specifically target Lp(a) concentrations. However, some therapies that target primarily LDL cholesterol have also an influence on Lp(a) concentrations. These are mainly PCSK9 inhibitors that lower LDL cholesterol by 60% and Lp(a) by 25-30%. Furthermore, lipoprotein apheresis lowers both, Lp(a) and LDL cholesterol, by about 60-70%. Some sophisticated study designs and statistical analyses provided support that lowering Lp(a) by these therapies also lowers cardiovascular events on top of the effect caused by lowering LDL cholesterol, although this was not the main target of the therapy. Currently, new therapies targeting RNA such as antisense oligonucleotides (ASO) or small interfering RNA (siRNA) against apolipoprotein(a), the main protein of the Lp(a) particle, are under examination and lower Lp(a) concentrations up to 90%. Since these therapies specifically lower Lp(a) concentrations without influencing other lipoproteins, they will serve the last piece of the puzzle whether a decrease of Lp(a) results also in a decrease of cardiovascular events.

Lipoprotein (a): Recent Updates on a Unique Lipoprotein

PURPOSE OF REVIEW

Genetic, epidemiological, and translational data indicate that Lipoprotein (a) [Lp(a)] is likely in the causal pathway for atherosclerotic cardiovascular diseases as well as calcification of the aortic valves.

RECENT FINDINGS

Lp(a) is structurally similar to low-density lipoprotein, but in addition to apolipoprotein B-100, it has a glycoprotein apolipoprotein(a) [apo(a)], which is attached to the apolipoprotein B-100. Several distinctive properties of Lp(a) can be attributed to the presence of apo(a). This review discusses the current state of literature on pathophysiological and clinical aspects of Lp(a). After five decades of research, the understanding of Lp(a) structure, biochemistry, and pathophysiology of its cardiovascular manifestations still remains less than fully understood. Universally, Lp(a) elevation may be the most predominant monogenetic lipid disorder with approximate prevalence of Lp(a)>50 mg/dL among estimated >1.4 billion people. This makes a compelling rationale for diagnosing and managing Lp(a)-mediated risk. In addition to discussing various cardiovascular phenotypes of Lp(a) and associated morbidity, we also outline current and emerging therapies aimed at identifying a definitive treatment for elevated Lp(a) levels.

Long term follow-up of genetically confirmed patients with familial hypercholesterolemia treated with first and second-generation statins and then with PCSK9 monoclonal antibodies

BACKGROUND AND AIMS

In Italy, the clinical and genetic characteristics of familial hypercholesterolemia (FH) have been extensively assessed in various lipid clinics, although no studies on long-term cardiovascular outcomes in heterozygous patients (He-FH) have been conducted. This study evaluated the incidence of atherosclerotic cardiovascular disease (ASCVD) in He-FH before and after a long-term period of lipid-lowering treatments to ascertain the interference of other risk factors.

METHODS

A total of 294 genetically characterised He-FH subjects from 1989 to 2019 were retrospectively analysed. General characteristics, lipid profiles, ASCVD prevalence, and ultrasound carotid atherosclerosis assessment were evaluated. Primary end points were ASCVD outcomes and the percentage of patients reaching recommended LDL-C targets.

RESULTS

During follow-up, despite a significant improvement in plasma lipid profiles, the ESC/EAS 2016 and 2019 recommended LDL cholesterol (LDL-C) goals were attained in only a few patients treated with anti-PCSK9 monoclonal antibodies added to the maximum tolerated oral therapy with statins plus ezetimibe. Forty-seven subjects had an ASCVD event before starting lipid-lowering therapy (LLT). During follow-up (median 13 years) on LLT, 28 patients had a first ASCVD event and 16 had recurrent ASCVD. In basal conditions and during follow-up, higher LDL-C levels were associated with increased ASCVD risk (p < 0.001). Prevention of recurrent ASCVD events was recorded with a long-term reduction of LDL-C below 100 mg/dl with statins plus ezetimibe.

CONCLUSIONS

PCSK9 inhibition is the only therapeutic option to achieve LDL-C goals as recommended for He-FH and can prevent ASCVD events as reported in large clinical trials. Long-term treatment with statins and ezetimibe seems to be effective at preventing ASCVD recurrence when LDL-C is maintained below 130 and 100 mg/dL for primary and secondary prevention, respectively.

Lipoprotein(a) concentration, genetic variants, apo(a) isoform size, and cellular cholesterol efflux in patients with elevated Lp(a) and coronary heart disease submitted or not to lipoprotein apheresis: An Italian case-control multicenter study on Lp(a)

BACKGROUND

Coronary artery disease (CAD) risk is greater with higher plasma lipoprotein(a)[Lp(a)] concentrations or smaller apoisoform size and putatively with increased cellular cholesterol loading capacity (CLC). The relationship between Lp(a) and CLC is not known. Information on Lp(a) polymorphisms in Italian patients is lacking.

OBJECTIVE

The objective of this study was to determine relationships between Lp(a) and CLC, the impact of lipoprotein apheresis (LA), and describe the genetic profile of Lp(a).

METHODS

We conducted a multicenter, observational study in Italian patients with hyperLp(a) and premature CAD with (n = 18)/without (n = 16) LA in which blood samples were analyzed for Lp(a) parameter and CLC. Genetic profiling of LPA was conducted in patient receiving LA.

RESULTS

Mean macrophage CLC of the pre-LA serum was significantly higher than that of normolipidemic controls (19.7 ± 0.9 μg/mg vs 16.01 ± 0.98 μg/mg of protein, respectively). After LA, serum macrophage CLC was markedly lower relative to preapheresis (16.1 ± 0.8 μg/mg protein; P = .003) and comparable with CLC of the normolipidemic serum. LA did not significantly affect average apo(a) isoform size distribution. No anthropometric or lipid parameters studied were related to serum CLC, but there was a relationship between CLC and the Lp(a) plasma concentration (P = .035). DNA analysis revealed a range of common genetic variants. Two rare, new variants were identified: LPA exon 21, c.3269C>G, p.Pro1090Arg, and rs41259144 p.Arg990Gln, c.2969G>A CONCLUSIONS: LA reduces serum Lp(a) and also reduces macrophage CLC. Novel genetic variants of the LPA gene were identified, and geographic variations were noted. The complexity of these polymorphisms means that genetic assessment is not a predictor of CAD risk in hyperLp(a).

Advanced fibrosis of non-alcoholic steatohepatitis affects the significance of lipoprotein(a) as a cardiovascular risk factor

BACKGROUND AND AIMS

Lipoprotein(a) [Lp(a)] is an important independent cardiovascular risk factor. However, Lp(a) levels are lower in patients with chronic liver disease than in healthy subjects. Furthermore, Lp(a) levels decrease as residual liver function declines. Although non-alcoholic fatty liver disease (NAFLD), especially advanced non-alcoholic steatohepatitis (NASH), increases the risk of cardiovascular diseases, the relationship between serum Lp(a) level and NASH is unknown. Thus, we examined the relationship between serum Lp(a) levels and biopsy-proved NAFLD and clarified the significance of Lp(a) measurements for cardiovascular disease screening in patients with NAFLD.

METHODS

A total of 176 patients with NAFLD were enrolled. Comprehensive blood chemistry tests and histological examinations of liver samples were conducted. The relationship between serum Lp(a) levels and NAFLD was analyzed.

RESULTS

Serum Lp(a) levels in advanced fibrosis (stage 3-4) were lower than those in non-advanced fibrosis (stage 0-2) (p < 0.05). After adjustment for age, sex, body mass index, alanine aminotransferase (ALT), creatinine (Cre), HbA_1c level, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and the use of lipid-lowering agents, the significant inverse association between advanced fibrosis and serum Lp(a) levels remained (p < 0.01). Although the Lp(a) level was inversely associated with an NAFLD Activity Score (NAS) of 5-8, there was no significant association between Lp(a) levels and NAS adjusted for age, sex, body mass index, ALT, Cre, HbA_1c level, HDL-C, LDL-C, TG, and the use of lipid-lowering agents.

CONCLUSIONS

Advanced NASH is associated with low serum Lp(a) levels; therefore, Lp(a) levels may not be useful in evaluating cardiovascular risk.

Familial hypercholesterolemia and elevated lipoprotein(a): double heritable risk and new therapeutic opportunities

There is compelling evidence that the elevated plasma lipoprotein(a) [Lp(a)] levels increase the risk of atherosclerotic cardiovascular disease (ASCVD) in the general population. Like low-density lipoprotein (LDL) particles, Lp(a) particles contain cholesterol and promote atherosclerosis. In addition, Lp(a) particles contain strongly proinflammatory oxidized phospholipids and a unique apoprotein, apo(a), which promotes the growth of an arterial thrombus. At least one in 250 individuals worldwide suffer from the heterozygous form of familial hypercholesterolemia (HeFH), a condition in which LDL-cholesterol (LDL-C) is significantly elevated since birth. FH-causing mutations in the LDL receptor gene demonstrate a clear gene-dosage effect on Lp(a) plasma concentrations and elevated Lp(a) levels are present in 30-50% of patients with HeFH. The cumulative burden of two genetically determined pro-atherogenic lipoproteins, LDL and Lp(a), is a potent driver of ASCVD in HeFH patients. Statins are the cornerstone of treatment of HeFH, but they do not lower the plasma concentrations of Lp(a). Emerging therapies effectively lower Lp(a) by as much as 90% using RNA-based approaches that target the transcriptional product of the LPA gene. We are now approaching the dawn of an era, in which permanent and significant lowering of the high cholesterol burden of HeFH patients can be achieved. If outcome trials of novel Lp(a)-lowering therapies prove to be safe and cost-effective, they will provide additional risk reduction needed to effectively treat HeFH and potentially lower the CVD risk in these high-risk patients even more than currently achieved with LDL-C lowering alone.

Serum lipoprotein (a) is associated with increased risk of stroke in Chinese adults: A prospective study

BACKGROUND AND AIMS

Epidemiological evidence on the association between elevated lipoprotein (a) (Lp (a)) with risk of stroke remains inconsistent. We aimed to investigate the association between serum Lp (a) level and the risk of stroke among middle-aged and elderly Chinese.

METHODS

A community-based prospective cohort study of 8500 participants aged 40 years or older was conducted in Jiading district, Shanghai, China, in 2010. The incident strokes were documented at follow-up visit during 2014-2015.

RESULTS

During a mean follow-up of 5.1 years, 444 incident cases of stroke occurred. The incidences of stroke were 4.44%, 5.14% and 6.14% from the lowest to the highest serum Lp (a) tertile, respectively. A significant association between serum Lp (a) tertile and the risk of incident stroke was observed (p for trend<0.05). Compared with individuals in the lowest tertile of serum Lp (a), the multivariable adjusted hazards ratio (HR) and 95% confidence interval (CI) for incident stroke in Lp (a) tertile 3 were 1.34 (1.06-1.70).

CONCLUSIONS

Serum Lp (a) concentration was associated with increased risk of incident stroke in Chinese adults.

Lipoprotein(a) in patients with hepatocellular carcinoma and portal vein thrombosis

BACKGROUND

The mechanism for hypercoagulability in malignancy is not entirely understood. Although several studies report contrasting finding about the link between elevated plasma levels of the lipoprotein(a) [Lp(a)] and the possible recurrence of venous thromboembolism, we perform a study to evaluate the impact of the Lp(a) in the development of portal vein thromboembolism (PVT) in patients with HCC.

METHODS

We compared 44 PVT patients with 50 healthy subjects and 50 HCC patients.

RESULTS

The comparison between PVT patients and HCC showed in the former the mean value of serum lipoprotein levels was higher than 37.3 mg/dl (p = 0.000). The comparison between PVT versus healthy controls showed that in the former, mean value of serum lipoprotein levels was higher than 75 mg/dl (p = 0.000). The predictive value test of serum lipoprotein(a) on PVT was 0.72 and on HCC was 0.83. The odds ratio of lipoprotein(a) was 9.21 on PVT and 6.33 on HCC.

CONCLUSION

Patients with PVT and HCC showed a statistical significant serum lipoprotein(a) level higher than the subjects with HCC and no PVT or the healthy subject. So we assume a role of lipoprotein(a) as predictor of venous thromboembolism in neoplastic patients.

Structure, function, and genetics of lipoprotein (a)

Lipoprotein (a) [Lp(a)] has attracted the interest of researchers and physicians due to its intriguing properties, including an intragenic multiallelic copy number variation in the LPA gene and the strong association with coronary heart disease (CHD). This review summarizes present knowledge of the structure, function, and genetics of Lp(a) with emphasis on the molecular and population genetics of the Lp(a)/LPA trait, as well as aspects of genetic epidemiology. It highlights the role of genetics in establishing Lp(a) as a risk factor for CHD, but also discusses uncertainties, controversies, and lack of knowledge on several aspects of the genetic Lp(a) trait, not least its function.

Lipoprotein (a): gene genie

PURPOSE OF REVIEW

Despite being both the longest known and the most prevalent genetic risk marker for atherosclerotic cardiovascular disease (CVD), little progress has been made in agreeing a role for lipoprotein (a) [Lp(a)] in clinical practice and developing therapies with specific Lp(a)-lowering activity. We review barriers to progress, and discuss areas of controversy which are important to future research.

RECENT FINDINGS

Epidemiological and genetic studies have supported a causal role for Lp(a) in accelerated atherosclerosis, independent of other risk factors. Progress continues to be made in the understanding of Lp(a) metabolism, and Lp(a) levels, rather than apolipoprotein (a) isoform size, have been shown to be more closely related to CVD risk. Selective Lp(a) apheresis has offered some evidence that Lp(a)-lowering can improve cardiovascular end-points.

SUMMARY

We have acquired a great deal of knowledge about Lp(a), but this has not yet led to reductions in CVD. This is at least partially due to disagreement over Lp(a) measurement methodologies, its physiological role and the importance of the elevations seen in renal diseases, diabetes mellitus and familial hypercholesterolaemia. Renewed focus is required to bring assays into clinical practice to accompany new classes of therapeutic agents with Lp(a)-lowering effects.

Lipoprotein(a): resurrected by genetics

Plasma lipoprotein(a) [Lp(a)] is a quantitative genetic trait with a very broad and skewed distribution, which is largely controlled by genetic variants at the LPA locus on chromosome 6q27. Based on genetic evidence provided by studies conducted over the last two decades, Lp(a) is currently considered to be the strongest genetic risk factor for coronary heart disease (CHD). The copy number variation of kringle IV in the LPA gene has been strongly associated with both Lp(a) levels in plasma and risk of CHD, thereby fulfilling the main criterion for causality in a Mendelian randomization approach. Alleles with a low kringle IV copy number that together have a population frequency of 25-35% are associated with a doubling of the relative risk for outcomes, which is exceptional in the field of complex genetic phenotypes. The recently identified binding of oxidized phospholipids to Lp(a) is considered as one of the possible mechanisms that may explain the pathogenicity of Lp(a). Drugs that have been shown to lower Lp(a) have pleiotropic effects on other CHD risk factors, and an improvement of cardiovascular endpoints is up to now lacking. However, it has been established in a proof of principle study that lowering of very high Lp(a) by apheresis in high-risk patients with already maximally reduced low-density lipoprotein cholesterol levels can dramatically reduce major coronary events.

Therapeutic potential of mipomersen in the management of familial hypercholesterolaemia

High levels of low-density lipoprotein cholesterol (LDL-C) and lipoprotein(a) [Lp(a)] are associated with early morbidity and mortality caused by cardiovascular disease (CVD). There are hints that a reduction of LDL-C levels beyond currently advocated targets, and the use of drugs that also have Lp(a)-lowering potential, could provide further clinical benefit. Today, LDL apheresis is the only available treatment option to achieve further lowering of apolipoprotein-B (apo-B)-containing lipoproteins, especially Lp(a). Mipomersen is currently being studied in patients with mild to severe hypercholesterolaemia as add-on therapy to other lipid-lowering therapy, as monotherapy in patients who are intolerant of HMG-CoA reductase inhibitors (statins) and who are at high risk for CVD. Patients affected by homozygous or heterozygous familial hypercholesterolaemia (FH), which are inherited autosomal co-dominant disorders characterized by a marked elevation of serum LDL-C concentration, remain a clinical challenge, especially when their CVD risk is aggravated by additionally elevated Lp(a) levels. Mipomersen is a 20-mer oligonucleotide [2'-O-(2-methoxy) ethyl-modified oligonucleotide], a second-generation antisense oligonucleotide (AOS), complementary to the coding region for human-specific apo-B-100 messenger RNA (mRNA). Mipomersen inhibits apo-B-100 synthesis and is consequently a new treatment strategy to lower apo-B-containing lipoproteins like LDL-C and Lp(a) in patients at high risk for CVD not on target or intolerant to statins. This article focuses on mipomersen and gives an overview of the current status of mipomersen as a promising treatment option. Recent studies have shown a decrease in LDL-C levels of 22-42.2% and in Lp(a) of 19.6-31.1% from baseline, depending on study design. Dose-dependent reductions of very low-density lipoprotein cholesterol (VLDL-C) and triglyceride levels have also been observed. Although the short-term efficacy and safety of mipomersen have been proven, side effects like injection-site reactions (up to 90-100%), increased liver enzymes, cephalgias, nasopharyngitis, myalgia, nausea and fatigue must be mentioned and critically discussed. Furthermore, we need more data on the long-term side effects, especially regarding the long-term potential for hepatic steatosis. Data on cardiovascular outcomes with mipomersen are also not yet available.

Transgenic rabbit models for studying human cardiovascular diseases

Cardiovascular diseases involve the heart or blood vessels and remain a leading cause of morbidity and mortality in developed countries. A variety of animal models have been used to study cardiovascular diseases and have contributed to our understanding of their pathophysiology and treatment. However, mutations or abnormal expression of specific genes play important roles in the pathophysiology of some heart diseases, for which a closely similar animal model often is not naturally available. With the advent of techniques for specific genomic modification, several transgenic and knockout mouse models have been developed for cardiovascular conditions that result from spontaneous mutations. However, mouse and human heart show marked electrophysiologic differences. In addition, cardiac studies in mouse models are extremely difficult because of their small heart size and fast heart rate. Therefore, larger genetically engineered animal models are needed to overcome the limitations of the mouse models. This review summarizes the transgenic rabbit models that have been developed to study cardiovascular diseases.

Lipoprotein (a) and other Lipid Profile in Patients with Thrombotic Stroke: Is it a Reliable Marker?

BACKGROUND

Cerebrovascular disease (CVD) and coronary heart disease (CHD) cause 40%-50% of deaths in developed countries with CVD causing 10%-12% of deaths. Though increased Lipoprotein (a) is a risk factor in developing CHD, its role is poorly defined in etiopathogenesis of CVD.

AIMS

To find the association of lipoprotein (a) and lipid profile in thrombotic stroke patients after acute phase.

SETTINGS AND DESIGN

The study was conducted at Kasturba Medical College, Manipal. Twenty one cases of thrombotic stroke and 18 cases of age and sex matched controls were taken for the study. Informed consent was taken from both case and control.

MATERIALS AND METHODS

Overnight fasting sample was collected from both case and control. Serum was separated and parameters such as total cholesterol, triglycerides, high density lipoproteins-C, low density lipoprotein-C, lipoprotein (a), fasting blood sugars were estimated.

STATISTICAL ANALYSIS

Data were analyzed by SPSS software, Student's t-test, standard deviation (SD), and standard error of mean (SEM), P-value <0.05 is considered to be significant.

RESULTS

In this study, we found no statistical significant differences in serum lipid and lipoprotein (a) profile between controls and thrombotic stroke patients.

CONCLUSIONS

Highest frequency (38%) of stroke was found in the age group of 7080 years. There were other associated risk factors such as diabetes in five cases (24%), hypertension in nine cases (43%), and family history of stroke in four cases. However, further studies are required to evaluate the importance of serum Lp(a) estimation in the assessment as a risk factor for thrombotic stroke.

The interaction between coagulation factor 2 receptor and interleukin 6 haplotypes increases the risk of myocardial infarction in men

The aim of the study was to investigate if the interaction between the coagulation factor 2 receptor (F2R) and the interleukin 6 (IL6) haplotypes modulates the risk of myocardial infarction (MI) in the Stockholm Heart Epidemiology Program (SHEEP). Seven SNPs at the F2R locus and three SNPs at the IL6 locus were genotyped. Haplotypes and haplotype pairs (IL6*F2R) were generated. A logistic regression analysis was performed to analyze the association of the haplotypes and haplotype pairs with the MI risk. Presence of an interaction between the two haplotypes in each haplotype pair was calculated using two different methods: the statistical, on a multiplicative scale, which includes the cross product of the two factors into the logistic regression model; the biological, on an additive scale, which evaluates the relative risk associated with the joint presence of both factors. The ratio between the observed and the predicted effect of the joint exposure, the synergy index (S), indicates the presence of a synergy (S>1) or of an antagonism (S<1). None of the haplotypes within the two loci was associated with the risk of MI. Out of 22 different haplotype pairs, the haplotype pair 17 GGG*ADGTCCT was associated with an increased risk of MI with an OR (95%CI) of 1.58 (1.05-2.41) (p = 0.02) in the crude and an OR of 1.72 (1.11-2.67) (p = 0.01) in the adjusted analysis. We observed the presence of an interaction on a multiplicative scale with an OR (95%CI) of 2.24 (1.27-3.95) (p = 0.005) and a slight interactive effect between the two haplotypes on an additive scale with an OR (95%CI) of 1.56 (1.02-2.37) (p = 0.03) and S of 1.66 (0.89-31). In conclusion, our results support the hypothesis that the interaction between these two functionally related genes may influence the risk of MI and suggest new mechanisms involved in the genetic susceptibility to MI.

Hyperlipoproteinaemia(a) is a common cause of autosomal dominant hypercholesterolaemia

Autosomal dominant hypercholesterolaemia (ADH) are a heterogeneous group of monogenic lipid disorders. The plasma level of lipoprotein(a) (Lp(a)) is a heritable trait associated with increased coronary heart disease (CHD) risk.

OBJECTIVE

To evaluate the frequency of elevated Lp(a) as a cause of ADH and the characteristics of subjects with high Lp(a) (hyperLp(a)).

MATERIAL AND METHODS

200 healthy subjects and 933 unrelated Spanish subjects with a clinical diagnosis of ADH who were screened for low-density lipoprotein receptor (LDLR) and apolipoprotein B (APOB) gene mutations. Standard cardiovascular risk factors and blood lipid levels, including Lp(a), were evaluated. HyperLp(a) was defined as Lp(a) levels >or=95th centile of control values.

RESULTS

Lp(a) was higher in 263 subjects without LDLR or APOB mutations (nonLDLR/nonAPOB group) than in 670 subjects with mutations (FH group): 40.0 mg/dl (interquartile range (IR) 15.0-89.0) versus 31.0 mg/dl (IR 11.0-73.7) respectively, p = 0.002. HyperLp(a) was present in 23% of ADH subjects (odds ratio (OR) 5.6 (95% CI, 2.9 to 10.7) versus controls) and 29% of nonLDLR/nonAPOB subjects (OR 7.7; 3.9 to 15.4). After adjusting for Lp(a), LDL cholesterol levels were <95th centile in 28 (10.6%) nonLDLR/nonAPOB subjects and in 9 (1.3%) FH subjects. Lp(a) levels were nonsignificantly higher in ADH subjects with early-onset CHD than in those without (43.5 mg/dl, (IR, 12.0-82.0) versus 31.7 mg/dl (11.8-76.5), respectively).

CONCLUSIONS

HyperLp(a) is responsible for ADH in approximately 6% of nonLDLR/nonAPOB subjects. HyperLp(a) would not appear to be a risk factor for early-onset CHD in ADH, independently of whether genetic defects have or have not been demonstrated.

Lipoprotein(a) and LDL Particle Size Are Related to the Severity of Coronary Artery Disease

BACKGROUND

The pathophysiological role and metabolic pathway of Lp(a) have not been clearly defined. An association between Lp(a) and oxidative low-density lipoprotein (LDL) were recently reported. And small dense LDL (sd-LDL) were associated with circulating malondialdehyde-modified LDL. We investigated the relationships between serum Lp(a) level and LDL particle size in coronary artery disease (CAD) patients. Further, we investigated the relationships of sd-LDL and Lp(a) with the extent and severity of CAD.

METHODS

A total of 490 patients (mean: 60.5 +/- 11.5 years old) who underwent coronary angiography to evaluate chest pain were investigated. Patients were classified into two groups, a CAD group (n = 256), who had significant stenosis observed by coronary angiogram, and a control group (n = 234), who had normal, or minimal coronary arteries. CAD severity was measured by Gensini scores. The distribution of the LDL subfraction was analyzed using a Quantimetrix Lipoprint LDL System.

RESULTS

The serum Lp(a) concentration was correlated with the fraction of sd-LDL (r = 0.193, p < 0.001) and mean LDL size (r = 0.160, p = 0.003). The Lp(a) level and mean LDL particle size were significantly correlated with a high Gensini score. LDL particle size in the CAD group was smaller than in the control group (26.74 +/- 0.64 vs. 26.43 +/- 0.93 nm, p < 0.001). The Gensini score was significantly higher in small LDL with high Lp(a) level groups.

CONCLUSION

The positive correlation of the level of Lp(a) and sd-LDL fraction were demonstrated. The mechanism of this association is not clearly defined; we can suggest that it may stem from the individual atherogenic condition that linked to increased oxidative stress. Both increased Lp(a) and sd-LDL fraction were correlated with the severity of CAD.

Lipoprotein [a] is cleared from the plasma primarily by the liver in a process mediated by apolipoprotein [a]

The cellular and molecular mechanisms responsible for lipoprotein [a] (Lp[a]) catabolism are unknown. We examined the plasma clearance of Lp[a] and LDL in mice using lipoproteins isolated from human plasma coupled to radiolabeled tyramine cellobiose. Lipoproteins were injected into wild-type, LDL receptor-deficient (Ldlr-/-), and apolipoprotein E-deficient (Apoe-/-) mice. The fractional catabolic rate of LDL was greatly slowed in Ldlr-/- mice and greatly accelerated in Apoe-/- mice compared with wild-type mice. In contrast, the plasma clearance of Lp[a] in Ldlr-/- mice was similar to that in wild-type mice and was only slightly accelerated in Apoe-/- mice. Hepatic uptake of Lp[a] in wild-type mice was 34.6% of the injected dose over a 24 h period. The kidney accounted for only a small fraction of tissue uptake (1.3%). To test whether apolipoprotein [a] (apo[a]) mediates the clearance of Lp[a] from plasma, we coinjected excess apo[a] with labeled Lp[a]. Apo[a] acted as a potent inhibitor of Lp[a] plasma clearance. Asialofetuin, a ligand of the asialoglycoprotein receptor, did not inhibit Lp[a] clearance. In summary, the liver is the major organ accounting for the clearance of Lp[a] in mice, with the LDL receptor and apolipoprotein E having no major roles. Our studies indicate that apo[a] is the primary ligand that mediates Lp[a] uptake and plasma clearance.

Apolipoprotein(a) isoforms in infarcted men under 60 years old

OBJECTIVE

The aim of this study was to compare the Lp(a) concentration and the frequency distribution of the apo(a) isoforms of a myocardial infarcted male group under 60 years old and a group of healthy subjects (controls).

METHODS

A total of 111 infarcted men and 99 men free from disease were enrolled in this study. Lp(a) concentrations were measured by a commercial available rate nephelometry method, and apolipoprotein(a) isoform analysis was performed by sodium dodecyl sulfate (SDS) polyacrilamide gel electrophoresis (PAGE) and immunoblotting.

RESULTS

Infarcted patients had higher Lp(a) concentrations (0.33 +/- 0.36 g/l) than noninfarcted subjects did (0.19 +/- 0.22 g/l), and these differences were significant (P = 0.001). Infarcted patients have also shown a greater proportion of elevated (> or = 0.30 g/l) Lp(a) concentrations 37.8% than controls 20.2% (P < 0.01). The distributions of apo(a) phenotypes for patients with myocardial infarction and controls were remarkably different (P < 0.001), and the proportions of smaller isoforms were significantly different by chi-square analysis (P < 0.01).

CONCLUSIONS

Infarcted patients under 60 years old display higher Lp(a) concentrations and a significantly higher proportion of low molecular weight apolipoprotein(a) isoforms than controls.

The transgenic rabbit as model for human diseases and as a source of biologically active recombinant proteins

Until recently, transgenic rabbits were produced exclusively by pronuclear microinjection which results in additive random insertional transgenesis; however, progress in somatic cell cloning based on nuclear transfer will soon make it possible to produce rabbits with modifications to specific genes by the combination of homologous recombination and subsequent prescreening of nuclear donor cells. Transgenic rabbits have been found to be excellent animal models for inherited and acquired human diseases including hypertrophic cardiomyopathy, perturbed lipoprotein metabolism and atherosclerosis. Transgenic rabbits have also proved to be suitable bioreactors for the production of recombinant protein both on an experimental and a commercial scale. This review summarizes recent research based on the transgenic rabbit model.

Lipoprotein(a): biology and clinical importance

Lipoprotein(a) [Lp(a)] is a unique lipoprotein that has emerged as an independent risk factor for developing vascular disease. Plasma Lp(a) levels above the common cut-off level of 300 mg/L place individuals at risk of developing heart disease particularly if combined with other lipid and thrombogenic risk factors. Studies in humans have shown Lp(a) levels to be hugely variable and under strict genetic control, largely by the apolipoprotein(a) [apo(a)] gene. In general, Lp(a) levels have proven difficult to manipulate, although some factors have been identified that can influence levels. Research has shown that Lp(a) has a high affinity for the arterial wall and displays many athero-thrombogenic properties. While a definite function for Lp(a) has not been identified, the last two decades of research have provided much information on the biology and clinical importance of Lp(a).

Lack of genetic linkage evidence for a trans-acting factor having a large effect on plasma lipoprotein[a] levels in African Americans

The distribution of plasma lipoprotein[a] (Lp[a]) concentrations, a risk factor for cardiovascular disease, varies greatly among racial groups, with African Americans having values that are shifted toward higher levels than those of whites. The underlying cause of this heterogeneity is unknown, but a role for "trans-acting" factors has been hypothesized. This study used genetic linkage analysis to localize genetic factors influencing Lp[a] levels in African Americans that were absent in other populations; linkage results were analyzed separately in non-Hispanic whites, Hispanic whites, and African Americans. As expected, all three samples showed highly significant linkage at the approximate location of the lysophosphatidic acid locus. The white populations also independently had regions of significant linkage on chromosome 19 (LOD 3.80) and suggestive linkage on chromosomes 12 (LOD 1.60), 14 (LOD 2.56), and 19 (LOD 2.52). No linkage evidence was found to support the hypothesis of another single gene with large effects specifically segregating in African Americans that may account for their elevated Lp[a] levels.

Prevalence and significance of cardiovascular risk factors in a large cohort of patients with familial hypercholesterolaemia

OBJECTIVE

Patients with familial hypercholesterolaemia (FH) vary widely in terms of onset of cardiovascular disease (CVD).

DESIGN

The association between cardiovascular risk factors and prevalent CVD was examined in a cross-sectional study in order to elucidate their contribution to atherogenesis.

SETTING AND SUBJECTS

Patients were recruited from 37 Dutch Lipid Clinics. The diagnosis of FH was based on a uniform diagnostic protocol, confirmed by DNA analysis in 62% of the cases. All patients were investigated free from any lipid-lowering drug for at least 6 weeks.

MAIN OUTCOME MEASURES

Differences in lipids, lipoproteins and other risk factors for CVD were analysed in FH patients with and without CVD.

RESULTS

A total of 526 patients were assessed and more than 37% had a history of CVD with a mean age of onset of 46.8 years. Mean LDL cholesterol (LDL-C) levels were severely elevated (8.38 +/- 2.13 mmol L-1). In univariate analysis, age, presence of hypertension or diabetes, body mass index, triglycerides (TG) and low HDL cholesterol (HDL-C) were all significantly associated with CVD. Also in multivariate analysis, all these risk factors, except TG and diabetes, were significantly linked to CVD.

CONCLUSION

A high CVD risk in this large well-documented characterized sample of FH patients is not only conferred by elevated LDL-C but also by low HDL-C.

Role of various tissues in apo(a) fragmentation and excretion of fragments by the kidney

BACKGROUND

Lipoprotein(a) [Lp(a)] is an atherothrombotic plasma lipoprotein with unknown function. Little is known about the catabolism of this lipoprotein, in particular the steps related to apolipoprotein(a) [apo(a)] fragmentation and excretion by the kidney.

MATERIAL AND METHODS

High plasma levels (up to 9 mg dL(-1)) of the N-terminal fragment of apo(a) were expressed in mice by adenovirus mediated gene transfer. Plasma of such N-apo(a) mice was injected into acceptor mice and the fragmentation and urinary secretion of N-apo(a) were followed by immunochemical techniques.

RESULTS

Mice transduced with N-Ad expressed apo(a)-fragments with 3-11 kringle-IV (KIV) repeats. Injection of N-apo(a)-plasma from donor mice into acceptor mice resulted in fragmentation of N-apo(a)s with 3-11 KIVs yielding smaller peptides down to 2 KIVs. Secretion of N-apo(a)-fragments with 2 to maximally 6 KIVs into urine occurred as early as 2 min after injection. Immunohistochemical studies of kidney suggested filtration as a mechanism of apo(a)-fragment excretion. When N-apo(a) was incubated in vitro with various tissues from perfused mice, skeletal muscle and kidney followed by liver and spleen contributed to fragmentation. Tissues from unperfused organs, or the addition of normal mouse plasma, caused marked reduction in N-apo(a) fragmentation. EDTA, and not aprotinin or leupeptin, prevented apo(a) cleavage.

CONCLUSION

Here we provide evidence that apo(a) is cleaved by metalloproteinases located on skeletal muscle, kidney and other organs. Small apo(a)-fragments up to a size of 6 KIVs are excreted into urine, yet a major portion of apo(a) fragments is removed from circulation extrarenally.

Large rearrangements of the LDL receptor gene and lipid profile in a FH Spanish population

BACKGROUND

Familial hypercholesterolemia (FH) is an autosomal dominant disease caused by mutations in the low-density lipoprotein receptor (LDLR) gene. To date, there has not been a systematic survey of the frequency of gross mutations in the LDLR gene in the Spanish population. The objective of our study was to investigate large rearrangements in the Spanish FH population and the relation between the kind of large rearrangement and the phenotype in carrier families.

MATERIALS AND METHODS

The LDLR gene was screened to detect major rearrangements in a sample of 89 probands. Southern blot, long polymerase chain reaction (PCR), reverse transcription (RT) -PCR and DNA sequencing were used to detect and characterize the mutations.

RESULTS

Five large rearrangements were found in six probands. Two mutations were due to duplications of internal regions of the gene, whereas the rest were caused by partial deletions, which eliminated the promoter region in two cases. The internal rearrangements, two duplications and one deletion, were apparently caused by recombination between ALU sequences and the study of their mRNA indicated that the reading frame was maintained. The analysis of the lipid profile between patients with similar characteristics (age, sex, body mass index, etc.) but carrying mutations that either eliminated the promoter region or produced internal rearrangements showed significant differences (total cholesterol: 366.6 +/- 81.8 vs. 304.6 +/- 25.1 P = 0.023, and LDL cholesterol: 317.7 +/- 65.1 vs. 249.2 +/- 27.4 P = 0.003).

CONCLUSIONS

The frequency of large mutations in a Spanish FH sample was close to 7% and at least four of the mutations found had not been described in other populations. Mutations that eliminate the promoter region originate more severe hypercholesterolemia than defective mutations, which suggests that the absence of the promoter region and transcription of the LDLR gene is worse compensated than the synthesis of a defective LDL receptor.

The effect of fasting in Ramadan on the values and interrelations between biochemical, coagulation and hematological factors

BACKGROUND

The possible consequences of the long intermittent fasting schedule during Ramadan (one month of food and water intake limited to night hours, a practice that is followed by the majority of the Muslims worldwide) on certain biochemical constituents or coagulation variables have not been extensively documented.

PATIENTS AND METHODS

During the month of Ramadan and two months after, we monitored the concentration of different plasma lipoproteins, lipoprotein (a) [Lp(a)], apoproteins A(1) and B, fibrinogen, factor VII activity and some selected hematological factors in 50 healthy subjects who were employees of institutes related to the Isfahan University of Medical Sciences and aged between 30 and 45 years. The effect of fasting in Ramadan on the relationship between biochemical and coagulation variables was also investigated.

RESULTS

The values of apoprotein B, Lp(a) and low-density lipoprotein cholesterol (LDL-C)/high-density lipoprotein cholesterol (HDL-C) ratio were significantly decreased during Ramadan (P<0.05), while total cholesterol (Tot-C), triglycerides (TG), LDL-C, HDL-C and fasting blood glucose did not change during that month. Among coagulation and hematological factors, fibrinogen level and factor VII activity were significantly decreased during the month (P<0.05). Results also indicated a significant positive association between fibrinogen level and Lp(a), factor VII activity and Tot-C, LDL-C, TG and Apo B during Ramadan.

CONCLUSION

Our findings contribute to a better understanding of previous reports, as the metabolic and coagulation changes that are considered as atherosclerosis risk factors are counterbalanced during Ramadan.

Evaluation of a new apolipoprotein(a) isoform-independent assay for serum Lipoprotein(a)

The risk factor, Lipoprotein(a), [(Lp(a)], has been measured in numerous clinical studies by a variety of immunochemical assay methods. It is becoming apparent that for many of these assays antibody specificity towards the apolipoprotein(a) [apo(a)] repetitive component [the kringle 4-type 2 repeats] and apo(a) size heterogeneity can significantly affect the accuracy of serum Lp(a) measurements. To address this issue, we investigated whether our current in house Lp(a) [Mercodia] assay showed such bias compared to a recently available assay [Apo-Tek], claiming to possess superior capability for isoform-independent measurement of Lp(a). Levels of Lipoprotein(a) by both Apo-Tek and Mercodia assays correlated inversely with apo(a) isoform sizes. No significant differences were observed between assays in ranges of Lp(a) concentration within each isoform group. The Mercodia assay exhibited similar isoform-independent behaviour to that of Apo-Tek for the quantitation of serum Lipoprotein(a). Essentially identical results were obtained by the two methods, suggesting that Mercodia assay's capture monoclonal antibody also (as is the case for Apo-Tek) does not recognize the kringle 4-type 2 repetitive domain of apo(a). Correlation of Lp(a) concentrations in patient specimens between Apo-Tek and Mercodia assays showed good agreement, although an overall higher degree of imprecision and non-linearity was noted for the Apo-Tek procedure. A change-over to the Apo-Tek assay would therefore not improve on our current assessment of risk contribution from Lp(a) for atherosclerotic vascular disease in individuals with measurable levels of circulating Lipoprotein(a).