Lipoprotein(a), atherosclerosis, and apolipoprotein(a) gene polymorphism

ALOX5, LPA, MMP9 and TPO gene polymorphisms increase atherothrombosis susceptibility in middle-aged Mexicans

Atherothrombosis is the cornerstone of cardiovascular diseases and the primary cause of death worldwide. Genetic contribution to disturbances in lipid metabolism, coagulation, inflammation and oxidative stress increase the susceptibility to its development and progression. Given its multifactorial nature, the multiloci studies have been proposed as potential predictors of susceptibility. A cross-sectional study was conducted to explore the contribution of nine genes involved in oxidative stress, inflammatory and thrombotic processes in 204 subjects with atherothrombosis matched by age and gender with a healthy group (n = 204). To evaluate the possibility of spurious associations owing to the Mexican population genetic heterogeneity as well as its ancestral origins, 300 unrelated mestizo individuals and 329 Native Americans were also included. ALOX5, LPA, MMP9 and TPO gene polymorphisms, as well as their multiallelic combinations, were twice to four times more frequent in those individuals with clinical manifestations of atherothrombosis than in the healthy group. Once adjusting for population stratification was done, these differences remained. Our results add further evidence on the contribution of ALOX5, LPA, MMP9 and TPO polymorphisms to atherothrombosis development in the middle-aged group, emphasizing the multiethnic studies in search of gene risk polymorphisms.

Lipoprotein (a) in patients with psoriasis: associations with lipid profiles and disease severity

BACKGROUND

Lipoprotein (a) [Lp(a)] is a genetically determined molecule whose role has been implied in cardiovascular pathology, and whose levels have been reported to be elevated in patients with psoriasis. Aim To assess the serum levels of Lp(a) in patients with psoriasis, and to investigate the associations of Lp(a) with other lipids and with psoriasis severity.

METHODS

Thirty-four patients with psoriasis and 26 healthy control subjects took part in the study. Serum levels of Lp(a) and total, high density lipoprotein (HDL), low density lipoprotein (LDL), and very low density lipoprotein (VLDL) cholesterol fractions were measured in all participants. The levels of triglycerides and total cholesterol were measured using enzymatic colorimetric tests; HDL and LDL cholesterol concentrations were determined by precipitation methods; the VLDL concentration was calculated according to the formula: VLDL cholesterol = triglycerides/5.

RESULTS

Patients with psoriasis showed significantly higher serum levels of Lp(a) relative to controls. Even when controlling for normolipidemic vs. hyperlipidemic status, abnormal levels of Lp(a) (> 30 mg/dL) were observed significantly more often in patients than in controls. In both patients and controls, Lp(a) levels correlated positively with total and HDL cholesterol levels. In patients, Lp(a) levels correlated positively with psoriasis severity.

CONCLUSIONS

Lp(a) may be a factor contributing to an increased cardiovascular risk in patients with psoriasis. A pathogenetic link may exist between this lipoprotein and psoriatic pathophysiology.

Variable number tandem repeat typing of bacteria

Analysis of bacterial genomes revealed a high percentage of DNA consisting of repeats, in which DNA motifs existed in multiple copies. Study of these DNA motifs has resulted in the development of variable number tandem repeat (VNTR) or multilocus variant-repeat analysis (MLVA) assays, which have shown to be valuable bacterial typing methods, especially in relation to disease outbreaks. The VNTR-based assay is based on direct PCR amplification of a specific locus, which is well defined. The range and polymorphism index of each locus can be calculated. This chapter describes the VNTR analysis of Neisseria meningitides-based on separation in low resolution media agarose, and VNTR analysis of Salmonella enterica subsp. enterica serovars Typhimurium-based on high resolution capillary electrophoresis.

The genetics of cerebrovascular atherosclerosis

Ischemic stroke attributable to atherosclerosis remains a major public health problem. Genetic factors are increasingly recognized as influencing risk for atherosclerosis directly and indirectly. Genetic makeup may influence the development of major vascular risk factors or alter susceptibility of the cerebral vasculature to these risk factors. More recently, newly identified risk factors for atherosclerosis, such as plasma homocysteine and infection, have also been reported to be influenced by important genetic determinants. This article reviews the current nature on genetics of cerebral and precerebral atherosclerosis and seeks to identify areas of promise for future clinical application.

Lipoprotein[a] and cancer: Anti-neoplastic effect besides its cardiovascular potency

While the death rate from cancer has substantially decreased over the past decade, the search for effective and tolerable therapies is a great challenge as yet. The evidence that malignant cells cannot grow to a clinically detectable tumor mass and spread in the absence of an adequate vascular support, has opened a new area of research towards the selective inhibition or even destruction of tumor vessels. Angiostatin and angiostatin-related proteins are a family of specific angiogenesis inhibitors produced by tumors from a family of naturally occurring proteins, which also includes plasminogen and lipoprotein[a]. The anti-angiogenic activity of these proteins resides in cryptic and highly-repetitive molecular domains hidden within the protein moiety, called kringles. Lipoprotein[a] is an intriguing molecule consisting of a low-density lipoprotein core in addition to the covalently bound apolipoprotein[a]. Apolipoprotein[a] is characterized by an inactive protease domain, a single copy of the plasminogen kringle V and multiple repeats of domains homologous to the plasminogen kringle IV. Reliable studies on animal models indicate that the proteolytic break-down products of apolipoprotein[a] would posses anti-angiogenic and anti-tumoral properties both in vitro and in vivo, a premise to develop novel therapeutic modalities which may efficiently suppress tumor growth and metastasis. This review is focused on the biochemical structure, metabolism and the anti-angiogenic activity of this unique and elusive kringle-containing lipoprotein.

Lipoprotein(a) as a cardiovascular risk factor

Evidence for the role of lipoprotein(a) (Lp[a]) in atherosclerosis and thrombosis has considerably increased over the past few years. Therefore, Lp(a) is currently classified as an emerging lipid risk factor for cardiovascular disease. High Lp(a) plasma levels carried in particles with small-sized apolipoprotein(a) isoforms are associated with preclinical vascular changes, cardiovascular disease and the mode of presentation of coronary artery disease (acute coronary syndromes). However, randomized clinical trials with an emphasis on agents that specifically lower plasma Lp(a) do not exist. At present, screening for increases in Lp(a) in the general population is not recommended. The measurement of Lp(a) may be of value in individuals with an increased risk of cardiovascular disease, particularly in patients with high low-density lipoprotein cholesterol plasma levels, since a high Lp(a) concentration in such subjects further increases the risk of coronary heart disease.

Use of variable-number tandem repeats to examine genetic diversity of Neisseria meningitidis

Repetitive DNA motifs with potential variable-number tandem repeats (VNTR) were identified in the genome of Neisseria meningitidis and used to develop a typing method. A total of 146 meningococcal isolates recovered from carriers and patients were studied. These included 82 of the 107 N. meningitidis isolates previously used in the development of multilocus sequence typing (MLST), 45 isolates recovered from different counties in Norway in connection with local outbreaks, and 19 serogroup W135 isolates of sequence type 11 (ST-11), which were recovered in several parts of the world. The latter group comprised isolates related to the Hajj outbreak of 2000 and isolates recovered from outbreaks in Burkina Faso in 2001 and 2002. All isolates had been characterized previously by MLST or multilocus enzyme electrophoresis (MLEE). VNTR analysis showed that meningococcal isolates with similar MLST or MLEE types recovered from epidemiologically linked cases in a defined geographical area often presented similar VNTR patterns while isolates of the same MLST or MLEE types without an obvious epidemiological link showed variable VNTR patterns. Thus, VNTR analysis may be used for fine typing of meningococcal isolates after MLST or MLEE typing. The method might be especially valuable for differentiating among ST-11 strains, as shown by the VNTR analyses of serogroup W135 ST-11 meningococcal isolates recovered since the mid-1990s.

Relation of apolipoprotein(a) size to alzheimer's disease and vascular dementia

Lipoprotein(a) [Lp(a)] level is a newly established vascular risk factor which has been suggested to play a role in dementia. However, the majority of Lp(a) cell-to-cell interactions are mediated by its specific apolipoprotein(a) [apo(a)] moiety. This suggests that the size polymorphism of apo(a) may be of importance in conveying the Lp(a)-related risk. Specifically, we postulated that variation in apo(a) isoform size may lead to increased risk of vascular dementia (VaD), Alzheimer's disease (AD), stroke, or all three of them. Under a case-control design we compared Lp(a) plasma levels and the distribution of apo(a) phenotypes in groups of subjects consisting of 50 VaD patients, 162 sporadic AD patients, 95 non-demented stroke patients (NDS), and 105 normal controls. The prevalence of small-sized apo(a) isoforms in the VaD group was significantly higher than that in the stroke and normal control groups, with an odds ratio of 5.29 (95% CI 2.24-12.49, p = 0.0001) for the development of VaD for individuals with at least one apo(a) isoform of low molecular weight (LMW). Furthermore, the possession of at least one small-sized apo(a) isoform significantly increased the risk of AD to 1.92 (95% CI 1.02-3.61, p = 0.0434). Our results demonstrate that possession of at least one LMW apo(a) isoform is significantly associated with dementia and specifically offer new evidence of a strong association between the lipoprotein system and post-stroke dementia.

Lipoprotein(a): an emerging cardiovascular risk factor

Lipoprotein(a) is a cholesterol-enriched lipoprotein, consisting of a covalent linkage joining the unique and highly polymorphic apolipoprotein(a) to apolipoprotein B100, the main protein moiety of low-density lipoproteins. Although the concentration of lipoprotein(a) in humans is mostly genetically determined, acquired disorders might influence synthesis and catabolism of the particle. Raised concentration of lipoprotein(a) has been acknowledged as a leading inherited risk factor for both premature and advanced atherosclerosis at different vascular sites. The strong structural homologies with plasminogen and low-density lipoproteins suggest that lipoprotein(a) might represent the ideal bridge between the fields of atherosclerosis and thrombosis in the pathogenesis of vascular occlusive disorders. Unfortunately, the exact mechanisms by which lipoprotein(a) promotes, accelerates, and complicates atherosclerosis are only partially understood. In some clinical settings, such as in patients at exceptionally low risk for cardiovascular disease, the potential regenerative and antineoplastic properties of lipoprotein(a) might paradoxically counterbalance its athero-thrombogenicity, as attested by the compatibility between raised plasma lipoprotein(a) levels and longevity.

Possible association between genetic variability at the apolipoprotein(a) locus and Alzheimer's disease in apolipoprotein E2 carriers

Apolipoprotein(a) (Apo(a)) is a glycoprotein that is linked by a disulfide bond to apolipoprotein B on low density lipoprotein particles to form lipoprotein(a) (Lp(a)). High plasma levels of Lp(a) are thought to contribute directly to the development of atherosclerosis. We tested a variant (T3888P) located in the Kringle-IV region of Apo(a) in a case-control series. Overall, there were no differences between case and controls. However, in the apoE2 positive subgroup, we noticed that the mutant allele is over-represented in the cases (P=0.005). We suggest that this polymorphism and others at the Apo(a) locus be further studied in relation to Alzheimer's disease.

Multiple liver-specific factors bind to a 64-bp element and activate apo(a) gene

The high plasma levels of lipoprotein(a) [Lp(a)] are associated with atherosclerosis. The apo(a) gene is responsible for the variance of Lp(a) concentration and its expression is liver-specific. By 5'-deletion analysis, we, in a luciferase gene reporter assay, have identified a 64-bp AT-rich region of upstream apo(a) gene (-703 to -640) that binds to multiple liver-specific factors. The 64 bp cis-element contained three dyad symmetry elements (DSEs) that are crucial for synergistic binding to the factors. We have demonstrated that both DSE-2 and -3 together are responsible for factor binding in vitro, and for gene activation in liver cells. Further, we have purified one of the UV cross-linked DNA-protein complexes to homogeneity by streptavidin magnetic bead chromatography. The identification of a further upstream negative regulatory region (-1432 to -704) led us to predict that as yet unidentified transcriptional repressor(s) might also repress apo(a) gene transcription.