-
Current Opinion in Lipidology Feb 2017Chronic kidney disease (CKD) is a common disease with an estimated prevalence of 10-12%. There are pronounced differences between ethnicities with a 3-fold to 4-fold... (Review)
Review
PURPOSE OF REVIEW
Chronic kidney disease (CKD) is a common disease with an estimated prevalence of 10-12%. There are pronounced differences between ethnicities with a 3-fold to 4-fold higher lifetime risk for end-stage kidney disease in African Americans compared to European Americans. The purpose of this review was to discuss recent findings on two apolipoproteins (apolipoprotein L1 and A-IV) in the context of kidney disease and kidney function.
RECENT FINDINGS
The observation that certain apolipoprotein L1 risk genotypes that are only present in African Americans might explain a major fraction of the ethnic differences for nondiabetic CKD has set the stage for this otherwise under-researched apolipoprotein. These risk genotypes on the one hand protect African Americans against African sleeping sickness but cause on the other hand several types of nondiabetic CKD. We are currently beginning to understand the mechanisms how apolipoprotein L1 is involved in the modification of lysosomal and cytoplasmic membranes. The second protein, apolipoprotein A-IV (apoA-IV), turned out to be an early marker of kidney impairment not only in patients with primary CKD but also in individuals from the general population. Genetic studies provided strong support of a causal effect of kidney function on apoA-IV concentrations.
SUMMARY
These two apolipoproteins have very distinct properties. Apolipoprotein L1 is causally involved in the development of nondiabetic CKD in African Americans. In contrast, apoA-IV is an early marker for kidney impairment.
Topics: Apolipoprotein L1; Apolipoproteins A; Evolution, Molecular; Genetic Testing; Humans; Kidney; Renal Insufficiency, Chronic
PubMed: 27870653
DOI: 10.1097/MOL.0000000000000371 -
Cells Apr 2019Apolipoprotein A-IV (apoA-IV) is a lipid-binding protein, which is primarily synthesized in the small intestine, packaged into chylomicrons, and secreted into intestinal... (Review)
Review
Apolipoprotein A-IV (apoA-IV) is a lipid-binding protein, which is primarily synthesized in the small intestine, packaged into chylomicrons, and secreted into intestinal lymph during fat absorption. In the circulation, apoA-IV is present on chylomicron remnants, high-density lipoproteins, and also in lipid-free form. ApoA-IV is involved in a myriad of physiological processes such as lipid absorption and metabolism, anti-atherosclerosis, platelet aggregation and thrombosis, glucose homeostasis, and food intake. ApoA-IV deficiency is associated with atherosclerosis and diabetes, which renders it as a potential therapeutic target for treatment of these diseases. While much has been learned about the physiological functions of apoA-IV using rodent models, the action of apoA-IV at the cellular and molecular levels is less understood, let alone apoA-IV-interacting partners. In this review, we will summarize the findings on the molecular function of apoA-IV and apoA-IV-interacting proteins. The information will shed light on the discovery of apoA-IV receptors and the understanding of the molecular mechanism underlying its mode of action.
Topics: Animals; Apolipoproteins A; Atherosclerosis; Cholesterol; Diabetes Mellitus; Glucose; Homeostasis; Humans
PubMed: 30959835
DOI: 10.3390/cells8040319 -
Arteriosclerosis, Thrombosis, and... Oct 2023High levels of Lp(a) (lipoprotein(a)) are associated with multiple forms of cardiovascular disease. Lp(a) consists of an apoB-containing particle attached to the...
BACKGROUND
High levels of Lp(a) (lipoprotein(a)) are associated with multiple forms of cardiovascular disease. Lp(a) consists of an apoB-containing particle attached to the plasminogen homologue apo(a). The pathways for Lp(a) clearance are not well understood. We previously discovered that the plasminogen receptor PlgRKT (plasminogen receptor with a C-terminal lysine) promoted Lp(a) uptake in liver cells. Here, we aimed to further define the role of PlgRKT and to investigate the role of 2 other plasminogen receptors, annexin A2 and S100A10 (S100 calcium-binding protein A10) in the endocytosis of Lp(a).
METHODS
Human hepatocellular carcinoma (HepG2) cells and haploid human fibroblast-like (HAP1) cells were used for overexpression and knockout of plasminogen receptors. The uptake of Lp(a), LDL (low-density lipoprotein), apo(a), and endocytic cargos was visualized and quantified by confocal microscopy and Western blotting.
RESULTS
The uptake of both Lp(a) and apo(a), but not LDL, was significantly increased in HepG2 and HAP1 cells overexpressing PlgRKT, annexin A2, or S100A10. Conversely, Lp(a) and apo(a), but not LDL, uptake was significantly reduced in HAP1 cells in which PlgRKT and S100A10 were knocked out. Surface binding studies in HepG2 cells showed that overexpression of PlgRKT, but not annexin A2 or S100A10, increased Lp(a) and apo(a) plasma membrane binding. Annexin A2 and S100A10, on the other hand, appeared to regulate macropinocytosis with both proteins significantly increasing the uptake of the macropinocytosis marker dextran when overexpressed in HepG2 and HAP1 cells and knockout of S100A10 significantly reducing dextran uptake. Bringing these observations together, we tested the effect of a PI3K (phosphoinositide-3-kinase) inhibitor, known to inhibit macropinocytosis, on Lp(a) uptake. Results showed a concentration-dependent reduction confirming that Lp(a) uptake was indeed mediated by macropinocytosis.
CONCLUSIONS
These findings uncover a novel pathway for Lp(a) endocytosis involving multiple plasminogen receptors that enhance surface binding and stimulate macropinocytosis of Lp(a). Although the findings were produced in cell culture models that have limitations, they could have clinical relevance since drugs that inhibit macropinocytosis are in clinical use, that is, the PI3K inhibitors for cancer therapy and some antidepressant compounds.
Topics: Humans; Plasminogen; Lipoprotein(a); Annexin A2; Dextrans; Phosphatidylinositol 3-Kinases; Carrier Proteins; Apolipoproteins A
PubMed: 37589135
DOI: 10.1161/ATVBAHA.123.319344 -
Atherosclerosis May 2022Lipoprotein (a) (Lp(a)) is a strange lipoprotein species causatively independently and significantly associated with cardiovascular diseases and calcified aortic valve... (Review)
Review
Lipoprotein (a) (Lp(a)) is a strange lipoprotein species causatively independently and significantly associated with cardiovascular diseases and calcified aortic valve stenosis. Elevated plasma Lp(a) levels increase the rate of cardiovascular events at any achieved low-density lipoprotein (LDL) level. The major structural difference between Lp(a) and LDL is that Lp(a) has a second large protein, apolipoprotein (a) (apo(a)), bound to the apolipoprotein B100 moiety of an LDL sized particle by a single disulfide bond. Over the past decades, several investigators have tried to elucidate the molecular, cellular and metabolic pathways governing the production of Lp(a), the contribution of Lp(a) to lipid transport in the plasma, and the catabolic fate of Lp(a). The metabolism of this enigmatic lipoprotein nevertheless still remains poorly understood. The objectives of the present manuscript are to comprehensively review the knowns and unknowns of the complexities of Lp(a) metabolism with a focus on apo(a) biosynthesis in hepatocytes, Lp(a) assembly, and Lp(a) plasma clearance and catabolism. We also discuss the controversy surrounding the exact role of the LDL receptor in mediating Lp(a) cellular uptake by reviewing seminal in vitro and in vivo data, the metabolism of Lp(a) in familial hypercholesterolemia, as well as the divergent effects of statins and proprotein convertase subtilisin kexin type 9 inhibitors in modulating Lp(a) plasma concentrations. We also provide new insights into the physiology and pathophysiology of Lp(a) metabolism from human kinetic studies in the context of contemporary molecular and cell biological investigations.
Topics: Apolipoproteins A; Apoprotein(a); Humans; Hyperlipidemias; Hyperlipoproteinemia Type II; Kinetics; Lipoprotein(a); Proprotein Convertase 9
PubMed: 35606080
DOI: 10.1016/j.atherosclerosis.2022.04.002 -
Clinical Pharmacokinetics Apr 2023Cardiovascular diseases are the leading cause of death worldwide. Although there have been substantial advances over the last decades, recurrent adverse cardiovascular... (Review)
Review
Cardiovascular diseases are the leading cause of death worldwide. Although there have been substantial advances over the last decades, recurrent adverse cardiovascular events after myocardial infarction are still frequent, particularly during the first year of the index event. For decades, high-density lipoprotein (HDL) has been among the therapeutic targets for long-term prevention after an ischemic event. However, early trials focusing on increasing HDL circulating levels showed no improvement in clinical outcomes. Recently, the paradigm has shifted to increasing the functionality of HDL rather than its circulating plasma levels. For this purpose, apolipoprotein-AI-based infusion therapies have been developed, including reconstituted HDL, such as CSL112. During the last decade, CSL112 has been extensively studied in Phase 1 and 2 trials and has shown promising results. In particular, CSL112 has been studied in the Phase 2b AEGIS trial exhibiting good safety and tolerability profiles, which has led to the ongoing large-scale Phase 3 AEGIS-II trial. This systematic overview will provide a comprehensive summary of the CSL112 drug development program focusing on its pharmacodynamic, pharmacokinetic, and safety profiles.
Topics: Humans; Lipoproteins, HDL; Myocardial Infarction; Apolipoprotein A-I; Drug Development
PubMed: 36928983
DOI: 10.1007/s40262-023-01224-8 -
Journal of Healthcare Engineering 2022To analyze apolipoprotein-A for its predictive value for long-term death in individuals suffering from acute ST-segment elevation myocardial infarction following...
OBJECTIVE
To analyze apolipoprotein-A for its predictive value for long-term death in individuals suffering from acute ST-segment elevation myocardial infarction following percutaneous coronary intervention.
METHODS
We selected patients suffering from acute ST-segment elevation myocardial infarction who underwent emergency PCI at the Affiliated Hospital of Putian University from January 2017 to August 2019. The patients were divided into a high-Apo-A group and low-Apo-A group, and we observed all-cause deaths of patients in the 2 groups within 2 years.
RESULTS
The ROC curve analysis indicated the best critical value for predicting 2-year mortality as 0.8150 (area under the curve was 0.626, sensitivity 75.1%, and specificity 51.9%). There was no statistical difference among the two groups in gender, age, lesion vessel, and comorbidities. The two groups had statistically significant differences in apolipoprotein-B/A, high-density lipoprotein, apolipoprotein-A, and hypersensitivity C-reactive protein. Correlation analysis showed a significant negative correlation between apolipoprotein-A and hypersensitive C-reactive protein. The results of the 24-month analysis indicated the incidence of all-cause mortality as higher in the low-Apo-A group, and Kaplan-Meier survival analysis showed the same trend.
CONCLUSION
Apolipoprotein-A can predict the potential for long-term mortality among individuals having acute ST-segment elevation myocardial infarction.
Topics: Apolipoproteins; Apolipoproteins A; C-Reactive Protein; Humans; Percutaneous Coronary Intervention; ST Elevation Myocardial Infarction; Treatment Outcome
PubMed: 35075388
DOI: 10.1155/2022/5941117 -
Biochemistry Apr 2020High-density lipoprotein (HDL) is a naturally occurring composite of lipids and lipid-binding proteins. The cholate dialysis method, first reported by Jonas in 1969, is...
High-density lipoprotein (HDL) is a naturally occurring composite of lipids and lipid-binding proteins. The cholate dialysis method, first reported by Jonas in 1969, is the most widely used approach for reconstituting discoidal HDL (dHDL) in test tubes with phospholipids and the most dominant protein, apolipoprotein A-1 (apoA-I). Here, we show that a dHDL-relevant complex can also be prepared by gently mixing 1,2-dimyristoyl--glycero-3-phosphocholine (DMPC) and apoA-I or its mutants in ethanol/HO solutions containing urea at a concentration of a few molar and then incubating the mixture at the gel-liquid crystalline phase transition temperature in test tubes. Subsequent purification steps involve quick dialysis following size exclusion chromatography. The yields (73 ± 3% and 70 ± 1% protein and DMPC, respectively) of the resulting HDL-like nanoparticles, designated as uHDL, were comparable to the values of 68 ± 9% and 71 ± 12% obtained in the cholate dialysis method. Using apoA-I and two mutants, the key factor in this method was found to be urea at the folded and unfolded transition midpoint concentration. By using this urea-assisted method in the presence of a hydrophobic drug, all--retinoic acid (ATRA), one-step preparation of ATRA-loaded uHDL was also possible. The loading efficiency was comparable to that in the mixing of ATRA and uHDL or dHDL reconstituted by the cholate dialysis method. Atomic force microscopy analysis revealed that uHDL and ATRA-loaded uHDL were discoidal. Our urea-assisted method is an easy and efficient method for reconstituting dHDL and can be utilized to prepare various drug-dHDL complexes.
Topics: Apolipoprotein A-I; Humans; Hydrophobic and Hydrophilic Interactions; Lipoproteins, HDL; Tretinoin; Urea
PubMed: 32223124
DOI: 10.1021/acs.biochem.0c00075 -
Atherosclerosis Dec 2014Lipoprotein lipase (LPL) is a key enzyme in lipid metabolism and responsible for catalyzing lipolysis of triglycerides in lipoproteins. LPL is produced mainly in adipose... (Review)
Review
Lipoprotein lipase (LPL) is a key enzyme in lipid metabolism and responsible for catalyzing lipolysis of triglycerides in lipoproteins. LPL is produced mainly in adipose tissue, skeletal and heart muscle, as well as in macrophage and other tissues. After synthesized, it is secreted and translocated to the vascular lumen. LPL expression and activity are regulated by a variety of factors, such as transcription factors, interactive proteins and nutritional state through complicated mechanisms. LPL with different distributions may exert distinct functions and have diverse roles in human health and disease with close association with atherosclerosis. It may pose a pro-atherogenic or an anti-atherogenic effect depending on its locations. In this review, we will discuss its gene, protein, synthesis, transportation and biological functions, and then focus on its regulation and relationship with atherosclerosis and potential underlying mechanisms. The goal of this review is to provide basic information and novel insight for further studies and therapeutic targets.
Topics: Angiopoietin-Like Protein 4; Angiopoietins; Animals; Apolipoprotein A-V; Apolipoprotein C-I; Apolipoprotein C-II; Apolipoprotein C-III; Apolipoproteins A; Arteries; Atherosclerosis; Exons; Gene Expression Regulation; Humans; Inflammation; Lipid Metabolism; Lipids; Lipoprotein Lipase; Mice; Mice, Transgenic; Receptors, Lipoprotein
PubMed: 25463094
DOI: 10.1016/j.atherosclerosis.2014.10.016 -
Metabolism: Clinical and Experimental Apr 2016Lipoprotein(a) [Lp(a)] is mainly similar in composition to LDL, but differs in having apolipoprotein (apo) (a) covalently linked to apoB-100. Our purpose was to examine...
OBJECTIVES
Lipoprotein(a) [Lp(a)] is mainly similar in composition to LDL, but differs in having apolipoprotein (apo) (a) covalently linked to apoB-100. Our purpose was to examine the individual metabolism of apo(a) and apoB-100 within plasma Lp(a).
MATERIALS AND METHODS
The kinetics of apo(a) and apoB-100 in plasma Lp(a) were assessed in four men with dyslipidemia [Lp(a) concentration: 8.9-124.7nmol/L]. All subjects received a primed constant infusion of [5,5,5-(2)H3] L-leucine while in the constantly fed state. Lp(a) was immunoprecipitated directly from whole plasma; apo(a) and apoB-100 were separated by gel electrophoresis; and isotopic enrichment was determined by gas chromatography/mass spectrometry.
RESULTS
Multicompartmental modeling analysis indicated that the median fractional catabolic rates of apo(a) and apoB-100 within Lp(a) were significantly different at 0.104 and 0.263 pools/day, respectively (P=0.04). The median Lp(a) apo(a) production rate at 0.248nmol/kg·day(-1) was significantly lower than that of Lp(a) apoB-100 at 0.514nmol/kg·day(-1) (P=0.03).
CONCLUSION
Our data indicate that apo(a) has a plasma residence time (11days) that is more than twice as long as that of apoB-100 (4days) within Lp(a), supporting the concept that apo(a) and apoB-100 within plasma Lp(a) are not catabolized from the bloodstream as a unit in humans in the fed state.
Topics: Apolipoprotein B-100; Apolipoproteins A; Dyslipidemias; Humans; Hypertriglyceridemia; Kinetics; Leucine; Lipids; Lipoprotein(a); Male; Middle Aged
PubMed: 26975530
DOI: 10.1016/j.metabol.2015.10.031 -
Atherosclerosis May 2022Oxidized phospholipids (OxPL) are key mediators of the pro-atherosclerotic effects of oxidized lipoproteins. They are particularly important for the pathogenicity of... (Review)
Review
Oxidized phospholipids (OxPL) are key mediators of the pro-atherosclerotic effects of oxidized lipoproteins. They are particularly important for the pathogenicity of lipoprotein(a) (Lp(a)), which is the preferred lipoprotein carrier of phosphocholine-containing OxPL in plasma. Indeed, elevated levels of OxPL-apoB, a parameter that almost entirely reflects the OxPL on Lp(a), are a potent risk factor for atherothrombotic diseases as well as calcific aortic valve stenosis. A substantial fraction of the OxPL on Lp(a) are covalently bound to the KIV domain of apo(a), and the strong lysine binding site (LBS) in this kringle is required for OxPL addition. Using apo(a) species lacking OxPL modification - by mutating the LBS - has allowed direct assessment of the role of apo(a) OxPL in Lp(a)-mediated pathogenesis. The OxPL on apo(a) account for numerous harmful effects of Lp(a) on monocytes, macrophages, endothelial cells, smooth muscle cells, and valve interstitial cells documented both in vitro and in vivo. In addition, the mechanisms underlying these effects have begun to be unraveled by identifying the cellular receptors that respond to OxPL, the intracellular signaling pathways turned on by OxPL, and the changes in gene and protein expression evoked by OxPL. The emerging picture is that the OxPL on Lp(a) are central to its pathobiology. The OxPL modification may explain why Lp(a) is such a potent risk factor for cardiovascular disease despite being present at concentrations an order of magnitude lower than LDL, and they account for the ability of elevated Lp(a) to cause both atherothrombotic disease and calcific aortic valve stenosis.
Topics: Aortic Valve; Aortic Valve Stenosis; Apolipoproteins A; Apoprotein(a); Calcinosis; Endothelial Cells; Humans; Lipoprotein(a); Oxidation-Reduction; Phospholipids
PubMed: 35606081
DOI: 10.1016/j.atherosclerosis.2022.04.001