PDB rendering based on 1i71.
|Symbols||; AK38; APOA; LP|
|RNA expression pattern|
Lipoprotein(a) (also called Lp(a) or LPA) is a lipoprotein subclass. Genetic studies and numerous epidemiologic studies have identified Lp(a) as a risk factor for atherosclerotic diseases such as coronary heart disease and stroke.
Lipoprotein(a) [Lp(a)] consists of an LDL-like particle and the specific apolipoprotein(a) [apo(a)], which is covalently bound to the apoB of the LDL like particle. Lp(a) plasma concentrations are highly heritable and mainly controlled by the apolipoprotein(a) gene [LPA] located on chromosome 6q26-27. Apo(a) proteins vary in size due to a size polymorphism [KIV-2 VNTR], which is caused by a variable number of so-called kringle IV repeats in the LPA gene. This size variation at the gene level is expressed on the protein level as well, resulting in apo(a) proteins with 10 to > 50 kringle IV repeats (each of the variable kringle IV consists of 114 amino acids). These variable apo(a) sizes are known as "apo(a) isoforms". There is a general inverse correlation between the size of the apo(a) isoform and the Lp(a) plasma concentration One theory for the size/plasma level correlation involves difference rates of protein synthesis. There appears to be a relationship between the number of kringle repeats and the processing time of the precursor apo (a) protein. That is, the larger the isoform, the more apo(a) precursor protein accumulates intracellularly in the endoplasmic reticulum. Lipoprotein (a) is not fully synthesized until the precursor protein is released from the cell, so the slower rate of production for the larger isoforms limits the plasma concentration.
Apo(a) is expressed by liver cells (hepatocytes), and the assembly of apo(a) and LDL particles seems to take place at the outer hepatocyte surface. The half-life of Lp(a) in the circulation is about 3 to 4 days.
Catabolism and clearance
The mechanism and sites of Lp(a) catabolism are largely unknown. Uptake via the LDL receptor is not a major pathway of Lp(a) metabolism. The kidney has been identified as playing a role in Lp(a) clearance from plasma.
Lp(a) concentrations vary over one thousandfold between individuals, from < 0.2 to > 200 mg/dL. This range of concentrations is observed in all populations studied so far. The mean and median concentrations between different world populations show distinct particularities, the main being the two- to threefold higher Lp(a) plasma concentration of populations of African descent compared to Asian, Oceanic, or European populations. The general inverse correlation between apo(a) isoform size and Lp(a) plasma concentration is observed in all populations. However, mean Lp(a) associated with certain apo(a) isoforms varies between populations.
The physiological function of Lp(a)/apo(a) is still unknown. A function within the coagulation system seems plausible, given the aspect of the high homology between apo(a) and plasminogen. In fact, the LPA gene derives from a duplication of the plasminogen gene.
Other functions have been related to recruitment of inflammatory cells through interaction with Mac-1 integrin, angiogenesis, and wound healing.
However, individuals without Lp(a) or with very low Lp(a) levels seem to be healthy. Thus, plasma Lp(a) is not vital, at least under normal environmental conditions. Since apo(a)/Lp(a) derived rather recently in mammalian evolution - only old world monkeys and humans have been shown to harbour Lp(a) - its function might not be vital but just evolutionarily advantageous under certain environmental conditions, e.g. in case of exposure to certain infectious diseases.
Another possibility, suggested by Linus Pauling, is that Lp(a) is a primate adaptation to L-gulonolactone oxidase (GULO) deficiency, found only in certain lines of mammals. GULO is required for converting glucose to ascorbic acid (vitamin C), which is needed to repair arteries; following the loss of GULO, those primates that adopted diets less abundant in vitamin C may have used Lp(a) as an ascorbic-acid surrogate to repair arterial walls.
The structure of lipoprotein (a) is similar to plasminogen and tPA (tissue plasminogen activator) and it competes with plasminogen for its binding site, leading to reduced fibrinolysis. Also, because Lp(a) stimulates secretion of PAI-1, it leads to thrombogenesis. Lp(a) also carries cholesterol and thus contributes to atherosclerosis. In addition, Lp(a) transports the more atherogenic proinflammatory oxidized phospholipids, which attract inflammatory cells to vessel walls, and leads to smooth muscle cell proliferation.
Lipoprotein(a) and disease
High Lp(a) in blood is a risk factor for coronary heart disease (CHD), cerebrovascular disease (CVD), atherosclerosis, thrombosis, and stroke. The association between Lp(a) levels and stroke is not as strong as that between Lp(a) and cardiovascular disease. Lp-a concentrations may be affected by disease states, (for example kidney failure), but are only slightly affected by diet, exercise, and other environmental factors. Most commonly prescribed lipid-reducing drugs have little or no effect on Lp(a) concentration. Results using statin medications have been mixed in most trials, although a meta-analysis published in 2012 suggests that atorvastatin may be of benefit. Niacin (nicotinic acid) and aspirin are two relatively safe, easily available and inexpensive drugs known to significantly reduce the levels of Lp(a) in some individuals with high Lp(a); they should be used under the supervision of a qualified physician.
High Lp(a) predicts risk of early atherosclerosis independently of other cardiac risk factors, including LDL. In patients with advanced cardiovascular disease, Lp(a)indicates a coagulant risk of plaque thrombosis. Apo(a) contains domains that are very similar to plasminogen (PLG). Lp(a) accumulates in the vessel wall and inhibits binding of PLG to the cell surface, reducing plasmin generation, which increases clotting. This inhibition of PLG by Lp(a) also promotes proliferation of smooth muscle cells. These unique features of Lp(a) suggest Lp(a) causes generation of clots and atherosclerosis.
Vegetarians have higher levels of Lp-a than fish eaters in one homogeneous tribal population of Tanzania raising the possibility that pharmacologic amounts of fish oil supplements may be helpful to lower the levels of Lp-a.
Some studies have shown that regular consumption of moderate amounts of alcohol leads to significant decline in plasma levels of Lp-a while other studies have not.
Numerous studies confirming a strong correlation between elevated Lp(a) and heart disease have led to the consensus that Lp(a) is an important, independent predictor of cardiovascular disease. Animal studies have shown that Lp(a) may directly contribute to atherosclerotic damage by increasing plaque size, inflammation, instability, and smooth muscle cell growth. Genetic data also support the theory that Lp(a) causes cardiovascular disease.
The European Atherosclerosis Society currently recommends that patients with a moderate or high risk of cardiovascular disease have their lipoprotein (a) levels checked. Any patient with one of the following risk factors should be screened;
- premature cardiovascular disease
- familial hypercholesterolaemia
- family history of premature cardiovascular disease
- family history of elevated lipoprotein (a)
- recurrent cardiovascular disease despite statin treatment
- ≥3% 10-year risk of fatal cardiovascular disease according to the European guidelines
- ≥10% 10-year risk of fatal and/or non-fatal cardiovascular disease according to the US guidelines
If the level is elevated, treatment should be initiated with a goal of bringing the level below 50 mg/dL. In addition, the patient's other cardiovascular risk factors (including LDL levels) should be optimally managed. Apart from the total Lp(a) plasma concentration, the apo(a) isoform might be an important risk parameter as well.
Prior studies of the relationship between LP(a) and ethnicity have shown inconsistent results. Lipoprotein (a) levels seem to differ in different populations. For example, in some African populatation, Lp(a) levels are, on average higher, than other groups, so that using a risk threshold of 30 mg/dl would classify up to > 50% of the individuals as higher risk. Some part of this complexity may be related to the different genetic factors involved in determining Lp(a) levels. One recent study showed that in different ethnic groups, different genetic alterations were associated with increased Lp(a) levels.
More recent data suggest that prior studies were under-powered. The Atherosclerosis Risk in Communities (ARIC) followed 3467 African Americans and 9851 whites for 20 years. The researchers found that an elevated Lp(a) conferred the same risk in each group. However, African Americans had roughly three times the level of Lp(a), and Lp(a) also predicted an increased risk of stroke.
Approximate levels of risk are indicated by the results below, although at present there are a variety of different methods by which to measure Lp(a). A standardized international reference material has been developed and is accepted by the WHO Expert Committee on Biological Standardization and the International Federation of Clinical Chemistry and Laboratory Medicine. Although further standardization is still needed, development of a reference material is an importance step towards standardizing results.
Lipoprotein(a) - Lp(a)
- Desirable: < 14 mg/dL (< 35 nmol/l)
- Borderline risk: 14 - 30 mg/dL (35 - 75 nmol/l)
- High risk: 31 - 50 mg/dL (75 - 125 nmol/l)
- Very high risk: > 50 mg/dL (> 125 nmol/l)
LP(a) appears with different isoforms (per kringle repeats) of apolipoprotein - 40% of the variation in Lp(a) levels when measured in mg/dl can be attributed to different isoforms. Lighter Lp(a) are also associated with disease. Thus a test with simple quantitative results may not provide a complete assessment of risk.
At the current time, the recommended treatment for an elevated lipoprotein(a) is niacin, 1-3 grams daily, in general in an extended-release form. Niacin therapy can reduce lipoprotein(a) levels by 20-30%. Aspirin may be beneficial, as well. A recent meta-analysis suggests that atorvastatin may also lower Lp(a) levels. In severe cases, such as familial hypercholesterolemia, or treatment resistant hypercholesterolemia, lipid apheresis may result in dramatic reductions of lipoprotein(a). The goal of treatment is to reduce levels to below 50 mg/dL.
Other medications that are in various stages of development include thyromimetics, cholesterol-ester-transfer protein (CETP inhibitors), anti-sense oligonucleopeptides, and proprotein convertase subtilisin/kexin type 9 (PCSK-9) inhibitors. L-carnitine may also reduce lipoprotein a levels.
Gingko biloba may be beneficial, but has not been clinically verified. Coenzyme Q-10 and pine bark extract have been suggested as beneficial, but neither has been proven in clinical trials.
The effect of estrogen on lipoprotein(a) levels is controversial. Estrogen replacement therapy in post-menopausal women appears to be associated with lower lipoprotein(a) levels. However one large study suggested that there was a decreased association between lipoprotein(a) levels and risk. In other words, it is unclear what a high lipoprotein(a) level means in a woman on estrogen therapy. Estrogen as a prevention strategy for heart disease is current topic of much research and debate. Risks and benefits may need to be considered for each individual. At present, estrogen is not indicated for treatment of elevated lipoprotein(a). Tamoxifen and raloxifen have not been shown to reduce levels.
The American Association of Pediatrics now recommends that all children be screened for cholesterol between the ages of 9 and 11. lipoprotein(a) levels should be considered in particular in children with a family history of early heart disease or hypercholesterolemia. Unfortunately, there have not been enough studies to determine which therapies might be beneficial.
- Very-low-density lipoprotein
- Low-density lipoprotein
- Combined hyperlipidemia
- Nordestgaard BG, Chapman MJ, Ray K, Borén J, Andreotti F, Watts GF et al. (December 2010). "Lipoprotein(a) as a cardiovascular risk factor: current status". Eur. Heart J. 31 (23): 2844–53. doi:10.1093/eurheartj/ehq386. PMC 3295201. PMID 20965889.
- Kamstrup PR, Tybjærg-Hansen A, Nordestgaard BG (April 2011). "Lipoprotein(a) and risk of myocardial infarction--genetic epidemiologic evidence of causality". Scand. J. Clin. Lab. Invest. 71 (2): 87–93. doi:10.3109/00365513.2010.550311. PMID 21231777.
- Danesh J, Collins R, Peto R (2000). "Lipoprotein(a) and coronary heart disease. Meta-analysis of prospective studies". Circulation 102 (10): 1082–5. doi:10.1161/01.CIR.102.10.1082. PMID 10973834.
- Smolders B, Lemmens R, Thijs V (2007). "Lipoprotein (a) and stroke: a meta-analysis of observational studies". Stroke 38 (6): 1959–66. doi:10.1161/STROKEAHA.106.480657. PMID 17478739.
- Schreiner PJ, Morrisett JD, Sharrett AR, Patsch W, Tyroler HA, Wu K et al. (1993). "Lipoprotein[a] as a risk factor for preclinical atherosclerosis" (PDF). Arterioscler. Thromb. 13 (6): 826–33. doi:10.1161/01.ATV.13.6.826. PMID 8499402.
- Berg K (1963). "A NEW SERUM TYPE SYSTEM IN MAN--THE LP SYSTEM". Acta Pathol Microbiol Scand 59 (3): 369–82. doi:10.1111/j.1699-0463.1963.tb01808.x. PMID 14064818.
- McLean JW, Tomlinson JE, Kuang WJ, Eaton DL, Chen EY, Fless GM et al. (1987). "cDNA sequence of human apolipoprotein(a) is homologous to plasminogen". Nature 330 (6144): 132–7. doi:10.1038/330132a0. PMID 3670400.
- Utermann G, Menzel HJ, Kraft HG, Duba HC, Kemmler HG, Seitz C (August 1987). "Lp(a) glycoprotein phenotypes. Inheritance and relation to Lp(a)-lipoprotein concentrations in plasma". J. Clin. Invest. 80 (2): 458–65. doi:10.1172/JCI113093. PMC 442258. PMID 2956279.
- Sandholzer C, Hallman DM, Saha N, Sigurdsson G, Lackner C, Császár A et al. (1991). "Effects of the apolipoprotein(a) size polymorphism on the lipoprotein(a) concentration in 7 ethnic groups". Hum. Genet. 86 (6): 607–14. doi:10.1007/BF00201550. PMID 2026424.
- Lobentanz EM, Krasznai K, Gruber A, Brunner C, Müller HJ, Sattler J et al. (April 1998). "Intracellular metabolism of human apolipoprotein(a) in stably transfected Hep G2 cells". Biochemistry 37 (16): 5417–25. doi:10.1021/bi972761t. PMID 9548923.
- Brunner C, Lobentanz EM, Pethö-Schramm A, Ernst A, Kang C, Dieplinger H et al. (1996). "The number of identical kringle IV repeats in apolipoprotein(a) affects its processing and secretion by HepG2 cells". J. Biol. Chem. 271 (50): 32403–10. doi:10.1074/jbc.271.50.32403. PMID 8943305.
- Rader DJ, Cain W, Zech LA, Usher D, Brewer HB (February 1993). "Variation in lipoprotein(a) concentrations among individuals with the same apolipoprotein (a) isoform is determined by the rate of lipoprotein(a) production". J. Clin. Invest. 91 (2): 443–7. doi:10.1172/JCI116221. PMC 287951. PMID 8432853.
- Knight BL, Perombelon YF, Soutar AK, Wade DP, Seed M (1991). "Catabolism of lipoprotein(a) in familial hypercholesterolaemic subjects". Atherosclerosis 87 (2-3): 227–37. doi:10.1016/0021-9150(91)90025-X. PMID 1830206.
- Rader DJ, Mann WA, Cain W, Kraft HG, Usher D, Zech LA et al. (March 1995). "The low density lipoprotein receptor is not required for normal catabolism of Lp(a) in humans". J. Clin. Invest. 95 (3): 1403–8. doi:10.1172/JCI117794. PMC 441483. PMID 7883987.
- Albers JJ, Koschinsky ML, Marcovina SM (2007). "Evidence mounts for a role of the kidney in lipoprotein(a) catabolism". Kidney Int. 71 (10): 961–2. doi:10.1038/sj.ki.5002240. PMID 17495935.
- Pauling L, Rath M (1992). "A Unified Theory of Human Cardiovascular Disease" (PDF). Journal of Orthomolecular Medicine 7 (1).
- Sotiriou SN, Orlova VV, Al-Fakhri N, Ihanus E, Economopoulou M, Isermann B et al. (2006). "Lipoprotein(a) in atherosclerotic plaques recruits inflammatory cells through interaction with Mac-1 integrin". FASEB J. 20 (3): 559–61. doi:10.1096/fj.05-4857fje. PMID 16403785.
- Gouni-Berthold I, Berthold HK (November 2011). "Lipoprotein(a): current perspectives". Curr Vasc Pharmacol 9 (6): 682–92. doi:10.2174/157016111797484071. PMID 21529331.
- Tsimikas S, Witztum JL (August 2008). "The role of oxidized phospholipids in mediating lipoprotein(a) atherogenicity". Curr. Opin. Lipidol. 19 (4): 369–77. doi:10.1097/MOL.0b013e328308b622. PMID 18607184.
- Ichikawa T, Unoki H, Sun H, Shimoyamada H, Marcovina S, Shikama H et al. (January 2002). "Lipoprotein(a) promotes smooth muscle cell proliferation and dedifferentiation in atherosclerotic lesions of human apo(a) transgenic rabbits". Am. J. Pathol. 160 (1): 227–36. doi:10.1016/S0002-9440(10)64366-0. PMC 1867144. PMID 11786416.
- Christian Wilde (2003). Hidden Causes of Heart Attack and Stroke: Inflammation, Cardiology's New Frontier. Abigon Press. pp. 182–183. ISBN 0-9724959-0-8.
- Takagi H, Umemoto T (January 2012). "Atorvastatin decreases lipoprotein(a): a meta-analysis of randomized trials". Int. J. Cardiol. 154 (2): 183–6. doi:10.1016/j.ijcard.2011.09.060. PMID 21996415.
- Caplice NM, Panetta C, Peterson TE, Kleppe LS, Mueske CS, Kostner GM et al. (2001). "Lipoprotein (a) binds and inactivates tissue factor pathway inhibitor: a novel link between lipoproteins and thrombosis". Blood 98 (10): 2980–7. doi:10.1182/blood.V98.10.2980. PMID 11698280.
- Marcovina SM, Kennedy H, Bittolo Bon G, Cazzolato G, Galli C, Casiglia E et al. (May 1999). "Fish intake, independent of apo(a) size, accounts for lower plasma lipoprotein(a) levels in Bantu fishermen of Tanzania: The Lugalawa Study". Arterioscler. Thromb. Vasc. Biol. 19 (5): 1250–6. doi:10.1161/01.ATV.19.5.1250. PMID 10323776.
- Sharpe PC, Young IS, Evans AE (May 1998). "Effect of moderate alcohol consumption on lp(a) lipoprotein concentrations. Reduction is supported by other studies". BMJ 316 (7145): 1675. doi:10.1136/bmj.316.7145.1675. PMC 1113249. PMID 9603764.
- Kamstrup PR, Nordestgaard BG (October 2009). "Lipoprotein(a) should be taken much more seriously". Biomark Med 3 (5): 439–41. doi:10.2217/bmm.09.57. PMID 20477514.
- Klausen IC, Sjøl A, Hansen PS, Gerdes LU, Møller L, Lemming L et al. (July 1997). "Apolipoprotein(a) isoforms and coronary heart disease in men: a nested case-control study". Atherosclerosis 132 (1): 77–84. doi:10.1016/S0021-9150(97)00071-3. PMID 9247362.
- Paultre F, Pearson TA, Weil HF, Tuck CH, Myerson M, Rubin J et al. (2000). "High levels of Lp(a) with a small apo(a) isoform are associated with coronary artery disease in African American and white men". Arterioscler. Thromb. Vasc. Biol. 20 (12): 2619–24. doi:10.1161/01.ATV.20.12.2619. PMID 11116062.
- Helmhold M, Bigge J, Muche R, Mainoo J, Thiery J, Seidel D et al. (1991). "Contribution of the apo[a] phenotype to plasma Lp[a] concentrations shows considerable ethnic variation". J. Lipid Res. 32 (12): 1919–28. PMID 1840066.
- Cobbaert C, Mulder P, Lindemans J, Kesteloot H (1997). "Serum LP(a) levels in African aboriginal Pygmies and Bantus, compared with Caucasian and Asian population samples". J Clin Epidemiol 50 (9): 1045–53. doi:10.1016/S0895-4356(97)00129-7. PMID 9363039.
- Schmidt K, Kraft HG, Parson W, Utermann G (2006). "Genetics of the Lp(a)/apo(a) system in an autochthonous Black African population from the Gabon". Eur. J. Hum. Genet. 14 (2): 190–201. doi:10.1038/sj.ejhg.5201512. PMID 16267501.
- Dahlén GH, Ekstedt B (2001). "The importance of the relation between lipoprotein(a) and lipids for development of atherosclerosis and cardiovascular disease". J. Intern. Med. 250 (3): 265–7. doi:10.1046/j.1365-2796.2001.00889.x. PMID 11555135.
- Dumitrescu L, Glenn K, Brown-Gentry K, Shephard C, Wong M, Rieder MJ et al. (2011). Kloss-Brandstaetter A, ed. "Variation in LPA is associated with Lp(a) levels in three populations from the Third National Health and Nutrition Examination Survey". PLoS ONE 6 (1): e16604. doi:10.1371/journal.pone.0016604. PMC 3030597. PMID 21305047.
- Virani SS, Brautbar A, Davis BC, Nambi V, Hoogeveen RC, Sharrett AR et al. (January 2012). "Associations between lipoprotein(a) levels and cardiovascular outcomes in black and white subjects: the Atherosclerosis Risk in Communities (ARIC) Study". Circulation 125 (2): 241–9. doi:10.1161/CIRCULATIONAHA.111.045120. PMID 22128224.
- Marcovina SM, Albers JJ, Scanu AM, Kennedy H, Giaculli F, Berg K et al. (2000). "Use of a reference material proposed by the International Federation of Clinical Chemistry and Laboratory Medicine to evaluate analytical methods for the determination of plasma lipoprotein(a)". Clin. Chem. 46 (12): 1956–67. PMID 11106328.
- Dati F, Tate JR, Marcovina SM, Steinmetz A (2004). "First WHO/IFCC International Reference Reagent for Lipoprotein(a) for Immunoassay--Lp(a) SRM 2B". Clin. Chem. Lab. Med. 42 (6): 670–6. doi:10.1515/CCLM.2004.114. PMID 15259385.
- Ryan, George M; Julius Torelli (2005). Beyond cholesterol: 7 life-saving heart disease tests that your doctor may not give you. New York: St. Martin's Griffin. p. 91. ISBN 0-312-34863-0.
- Boerwinkle E, Menzel HJ, Kraft HG, Utermann G (April 1989). "Genetics of the quantitative Lp(a) lipoprotein trait. III. Contribution of Lp(a) glycoprotein phenotypes to normal lipid variation". Hum. Genet. 82 (1): 73–8. doi:10.1007/BF00288277. PMID 2523852.
- Parhofer KG (2011). "Lipoprotein(a): medical treatment options for an elusive molecule". Curr. Pharm. Des. 17 (9): 871–6. doi:10.2174/138161211795428777. PMID 21476974.
- Rodríguez M, Ringstad L, Schäfer P, Just S, Hofer HW, Malmsten M et al. (June 2007). "Reduction of atherosclerotic nanoplaque formation and size by Ginkgo biloba (EGb 761) in cardiovascular high-risk patients". Atherosclerosis 192 (2): 438–44. doi:10.1016/j.atherosclerosis.2007.02.021. PMID 17397850.
- Lee YJ, Cho WJ, Kim JK, Lee DC (April 2011). "Effects of coenzyme Q10 on arterial stiffness, metabolic parameters, and fatigue in obese subjects: a double-blind randomized controlled study". J Med Food 14 (4): 386–90. doi:10.1089/jmf.2010.1202. PMID 21370966.
- Drieling RL, Gardner CD, Ma J, Ahn DK, Stafford RS (September 2010). "No beneficial effects of pine bark extract on cardiovascular disease risk factors". Arch. Intern. Med. 170 (17): 1541–7. doi:10.1001/archinternmed.2010.310. PMID 20876405.
- Suk Danik J, Rifai N, Buring JE, Ridker PM (July 2008). "Lipoprotein(a), hormone replacement therapy, and risk of future cardiovascular events". J. Am. Coll. Cardiol. 52 (2): 124–31. doi:10.1016/j.jacc.2008.04.009. PMC 2958092. PMID 18598891.
- Harman SM, Vittinghoff E, Brinton EA, Budoff MJ, Cedars MI, Lobo RA et al. (March 2011). "Timing and duration of menopausal hormone treatment may affect cardiovascular outcomes". Am. J. Med. 124 (3): 199–205. doi:10.1016/j.amjmed.2010.09.021. PMC 3107840. PMID 21396500.
- "Expert panel on integrated guidelines for cardiovascular health and risk reduction in children and adolescents: summary report". Pediatrics. 128 Suppl 5: S213–56. December 2011. doi:10.1542/peds.2009-2107C. PMID 22084329.
- Bonen DK, Nassir F, Hausman AM, Davidson NO (August 1998). "Inhibition of N-linked glycosylation results in retention of intracellular apo[a] in hepatoma cells, although nonglycosylated and immature forms of apolipoprotein[a] are competent to associate with apolipoprotein B-100 in vitro". J. Lipid Res. 39 (8): 1629–40. PMID 9717723.
- Nassir F, Xie Y, Davidson NO (April 2003). "Apolipoprotein[a] secretion from hepatoma cells is regulated in a size-dependent manner by alterations in disulfide bond formation". J. Lipid Res. 44 (4): 816–27. doi:10.1194/jlr.M200451-JLR200. PMID 12562843.
- Salonen EM, Jauhiainen M, Zardi L, Vaheri A, Ehnholm C (December 1989). "Lipoprotein(a) binds to fibronectin and has serine proteinase activity capable of cleaving it". EMBO J. 8 (13): 4035–40. PMC 401578. PMID 2531657.
- Klose R, Fresser F, Kochl S, Parson W, Kapetanopoulos A, Fruchart-Najib J et al. (December 2000). "Mapping of a minimal apolipoprotein(a) interaction motif conserved in fibrin(ogen) beta - and gamma -chains". J. Biol. Chem. 275 (49): 38206–12. doi:10.1074/jbc.M003640200. PMID 10980194.
- Utermann G (1989). "The mysteries of lipoprotein(a)". Science 246 (4932): 904–10. doi:10.1126/science.2530631. PMID 2530631.
- Salonen EM, Jauhiainen M, Zardi L, Vaheri A, Ehnholm C (1989). "Lipoprotein(a) binds to fibronectin and has serine proteinase activity capable of cleaving it". EMBO J. 8 (13): 4035–40. PMC 401578. PMID 2531657.
- Frank SL, Klisak I, Sparkes RS, Mohandas T, Tomlinson JE, McLean JW et al. (1988). "The apolipoprotein(a) gene resides on human chromosome 6q26-27, in close proximity to the homologous gene for plasminogen". Hum. Genet. 79 (4): 352–6. doi:10.1007/BF00282175. PMID 3410459.
- McLean JW, Tomlinson JE, Kuang WJ, Eaton DL, Chen EY, Fless GM et al. (1987). "cDNA sequence of human apolipoprotein(a) is homologous to plasminogen". Nature 330 (6144): 132–7. doi:10.1038/330132a0. PMID 3670400.
- Scanu AM, Pfaffinger D, Lee JC, Hinman J (1994). "A single point mutation (Trp72-->Arg) in human apo(a) kringle 4-37 associated with a lysine binding defect in Lp(a)". Biochim. Biophys. Acta 1227 (1-2): 41–5. doi:10.1016/0925-4439(94)90104-X. PMID 7918682.
- Grainger DJ, Kemp PR, Liu AC, Lawn RM, Metcalfe JC (1994). "Activation of transforming growth factor-beta is inhibited in transgenic apolipoprotein(a) mice". Nature 370 (6489): 460–2. doi:10.1038/370460a0. PMID 8047165.
- Mikol V, LoGrasso PV, Boettcher BR (1996). "Crystal structures of apolipoprotein(a) kringle IV37 free and complexed with 6-aminohexanoic acid and with p-aminomethylbenzoic acid: existence of novel and expected binding modes". J. Mol. Biol. 256 (4): 751–61. doi:10.1006/jmbi.1996.0122. PMID 8642595.
- Edelstein C, Italia JA, Klezovitch O, Scanu AM (1996). "Functional and metabolic differences between elastase-generated fragments of human lipoprotein[a] and apolipoprotein[a]". J. Lipid Res. 37 (8): 1786–801. PMID 8864963.
- Edelstein C, Italia JA, Scanu AM (1997). "Polymorphonuclear cells isolated from human peripheral blood cleave lipoprotein(a) and apolipoprotein(a) at multiple interkringle sites via the enzyme elastase. Generation of mini-Lp(a) particles and apo(a) fragments". J. Biol. Chem. 272 (17): 11079–87. doi:10.1074/jbc.272.17.11079. PMID 9111002.
- Köchl S, Fresser F, Lobentanz E, Baier G, Utermann G (1997). "Novel interaction of apolipoprotein(a) with beta-2 glycoprotein I mediated by the kringle IV domain". Blood 90 (4): 1482–9. PMID 9269765.
- Bonen DK, Nassir F, Hausman AM, Davidson NO (1998). "Inhibition of N-linked glycosylation results in retention of intracellular apo[a] in hepatoma cells, although nonglycosylated and immature forms of apolipoprotein[a] are competent to associate with apolipoprotein B-100 in vitro". J. Lipid Res. 39 (8): 1629–40. PMID 9717723.
- Niemeier A, Willnow T, Dieplinger H, Jacobsen C, Meyer N, Hilpert J et al. (1999). "Identification of megalin/gp330 as a receptor for lipoprotein(a) in vitro". Arterioscler. Thromb. Vasc. Biol. 19 (3): 552–61. doi:10.1161/01.ATV.19.3.552. PMID 10073957.
- Edelstein C, Shapiro SD, Klezovitch O, Scanu AM (1999). "Macrophage metalloelastase, MMP-12, cleaves human apolipoprotein(a) in the linker region between kringles IV-4 and IV-5. Potential relevance to lipoprotein(a) biology". J. Biol. Chem. 274 (15): 10019–23. doi:10.1074/jbc.274.15.10019. PMID 10187779.
- Ogorelkova M, Gruber A, Utermann G (1999). "Molecular basis of congenital lp(a) deficiency: a frequent apo(a) 'null' mutation in caucasians". Hum. Mol. Genet. 8 (11): 2087–96. doi:10.1093/hmg/8.11.2087. PMID 10484779.
- Røsby O, Berg K (2000). "LPA gene: interaction between the apolipoprotein(a) size ('kringle IV' repeat) polymorphism and a pentanucleotide repeat polymorphism influences Lp(a) lipoprotein level". J. Intern. Med. 247 (1): 139–52. doi:10.1046/j.1365-2796.2000.00628.x. PMID 10672142.
- Klose R, Fresser F, Kochl S, Parson W, Kapetanopoulos A, Fruchart-Najib J et al. (2000). "Mapping of a minimal apolipoprotein(a) interaction motif conserved in fibrin(ogen) beta - and gamma -chains". J. Biol. Chem. 275 (49): 38206–12. doi:10.1074/jbc.M003640200. PMID 10980194.
- Ogorelkova M, Kraft HG, Ehnholm C, Utermann G (2001). "Single nucleotide polymorphisms in exons of the apo(a) kringles IV types 6 to 10 domain affect Lp(a) plasma concentrations and have different patterns in Africans and Caucasians". Hum. Mol. Genet. 10 (8): 815–24. doi:10.1093/hmg/10.8.815. PMID 11285247.
- Garner B, Merry AH, Royle L, Harvey DJ, Rudd PM, Thillet J (2001). "Structural elucidation of the N- and O-glycans of human apolipoprotein(a): role of o-glycans in conferring protease resistance". J. Biol. Chem. 276 (25): 22200–8. doi:10.1074/jbc.M102150200. PMID 11294842.
- Xue S, Madison EL, Miles LA (2001). "The Kringle V-protease domain is a fibrinogen binding region within Apo(a)". Thromb. Haemost. 86 (5): 1229–37. PMID 11816712.