Apolipoprotein(a), an enigmatic anti-angiogenic glycoprotein in human plasma: A curse or cure?

Angiogenesis is a finely co-ordinated, multi-step developmental process of the new vascular structure. Even though angiogenesis is regularly occurring in physiological events such as embryogenesis, in adults, it is restricted to specific tissue sites where rapid cell-turnover and membrane synthesis occurs. Both excessive and insufficient angiogenesis lead to vascular disorders such as cancer, ocular diseases, diabetic retinopathy, atherosclerosis, intra-uterine growth restriction, ischemic heart disease, stroke etc. Occurrence of altered lipid profile and vascular lipid deposition along with vascular disorders is a hallmark of impaired angiogenesis. Among lipoproteins, lipoprotein(a) needs special attention due to the presence of a multi-kringle protein subunit, apolipoprotein(a) [apo(a)], which is structurally homologous to many naturally occurring anti-angiogenic proteins such as plasminogen and angiostatin. Researchers have constructed different recombinant forms of apo(a) (rhLK68, rhLK8, RHACK2, KV-11, and AU-6) and successfully exploited its potential to inhibit unwanted angiogenesis during tumor metastasis and retinal neovascularization. Similar to naturally occurring anti-angiogenic proteins, apo(a) can directly interfere with angiogenic signaling pathways. Besides this, apo(a) can also exert its anti-angiogenic effect indirectly by inducing endothelial cell apoptosis, by inhibiting endothelial progenitor cell functions or by upregulating nuclear factors in endothelial cells via apo(a)-bound oxPLs. However, the impact of the anti-angiogenic potential of native apo(a) during physiological angiogenesis in embryos and wounded tissues is not yet explored. In this context, we review the studies so far done to demonstrate the anti-angiogenic activity of apo(a) and the recent developments in using apo(a) as a therapeutic agent to treat impaired angiogenesis during vascular disorders, with emphasis on the gaps in the literature.

Apolipoproteins A and B and PCSK9: Nontraditional Cardiovascular Risk Factors in Chronic Kidney Disease and in End-Stage Renal Disease.

PURPOSE: Nontraditional cardiovascular risk factors as apolipoprotein A (ApoA), apolipoprotein B (ApoB), and the proprotein convertase subtilisin/kexin type 9 (PCSK9) increase the prevalence of cardiovascular mortality in chronic kidney disease (CKD) or in end-stage renal disease (ESRD) through quantitative alterations. This review is aimed at establishing the biomarker (ApoA, ApoB, and PCSK9) level variations in uremic patients, to identify the studies showing the association between these biomarkers and the development of cardiovascular events and to depict the therapeutic options to reduce cardiovascular risk in CKD and ESRD patients. METHODS: We searched the electronic database of PubMed, Scopus, EBSCO, and Cochrane CENTRAL for studies evaluating apolipoproteins and PCSK9 in CKD and ESRD. Randomized controlled trials, observational studies (including case-control, prospective or retrospective cohort), and reviews/meta-analysis were included if reference was made to those keys and cardiovascular outcomes in CKD/ESRD. RESULTS: 18 studies met inclusion criteria. Serum ApoA-I has been significantly associated with the development of new cardiovascular event and with cardiovascular mortality in ESRD patients. ApoA-IV level was independently associated with maximum carotid intima-media thickness (cIMT) and was a predictor for sudden cardiac death. The ApoB/ApoA-I ratio represents a strong predictor for coronary artery calcifications, cardiovascular mortality, and myocardial infarction in CKD/ESRD. Plasma levels of PCSK9 were not associated with cardiovascular events in CKD patients. CONCLUSIONS: Although the "dyslipidemic status" in CKD/ESRD is not clearly depicted, due to different research findings, ApoA-I, ApoA-IV, and ApoB/ApoA-I ratio could be predictors of cardiovascular risk. Serum PCSK9 levels were not associated with the cardiovascular events in patients with CKD/ESRD. Probably in the future, the treatment of dyslipidemia in CKD/ESRD will be aimed at discovering new effective therapies on the action of these biomarkers.

Apolipoprotein A-IV constrains HPA and behavioral stress responsivity in a strain-dependent manner.

There is a critical gap in our knowledge of the mechanisms that govern interactions between daily life experiences (e.g., stress) and metabolic diseases, despite evidence that stress can have profound effects on cardiometabolic health. Apolipoprotein A-IV (apoA-IV) is a protein found in chylomicrons (lipoprotein particles that transport lipids throughout the body) where it participates in lipid handling and the regulation of peripheral metabolism. Moreover, apoA-IV is expressed in brain regions that regulate energy balance including the arcuate nucleus. Given that both peripheral and central metabolic processes are important modulators of hypothalamic-pituitary-adrenocortical (HPA) axis activity, the present work tests the hypothesis that apoA-IV activity affects stress responses. As emerging data suggests that apoA-IV actions can vary with background strain, we also explore the strain-dependence of apoA-IV stress regulation. These studies assess HPA axis, metabolic (hyperglycemia), and anxiety-related behavioral responses to psychogenic stress in control (wildtype) and apoA-IV-deficient (KO) mice on either the C57Bl/6J (C57) or 129×1/SvJ (129) background strain. The results indicate that apoA-IV KO increases post-stress corticosterone and anxiety-related behavior specifically in the 129 strain, and increases stress-induced hyperglycemia exclusively in the C57 strain. These data support the hypothesis that apoA-IV is a novel factor that limits stress reactivity in a manner that depends on genetic background. An improved understanding of the complex relationship among lipid homeostasis, stress sensitivity, and genetics is needed to optimize the development of personalized treatments for stress- and metabolism-related diseases.

Apolipoprotein A5: Extracellular and Intracellular Roles in Triglyceride Metabolism.

This review addresses two major functions of apolipoprotein (apo) A5 including (1) its role in maintaining normal plasma levels of circulating triglyceride (TG) and (2) its role as a component of hepatic lipid droplets. ApoA5 is synthesized solely in the liver and circulating concentrations are extremely low. In the plasma, ApoA5 associates with TG-rich lipoproteins and enhances TG hydrolysis and remnant lipoprotein clearance. ApoA5 loss-of-function single nucleotide polymorphisms are associated with reduced lipolysis, poor remnant clearance and concomitantly, hypertriglyceridemia. Although there have been substantial breakthroughs in understanding pathophysiology associated with secreted ApoA5, there is a paucity of knowledge on the functionality of intracellular ApoA5. However, recent studies indicate that overexpression of intracellular ApoA5 is positively associated with accumulation of TG-rich lipid droplets in hepatocytes. It is thought that ApoA5 may have a causal role in non-alcoholic fatty liver disease (NAFLD) and thus, may serve as a target for developing therapeutics for NAFLD.

Different Functional and Structural Characteristics between ApoA-I and ApoA-4 in Lipid-Free and Reconstituted HDL State: ApoA-4 Showed Less Anti-Atherogenic Activity.

Apolipoprotein A-I and A-IV are protein constituents of high-density lipoproteins although their functional difference in lipoprotein metabolism is still unclear. To compare anti-atherogenic properties between apoA-I and apoA-4, we characterized both proteins in lipid-free and lipid-bound state. In lipid-free state, apoA4 showed two distinct bands, around 78 and 67 Å on native gel electrophoresis, while apoA-I showed scattered band pattern less than 71 Å. In reconstituted HDL (rHDL) state, apoA-4 showed three major bands around 101 Å and 113 Å, while apoA-I-rHDL showed almost single band around 98 Å size. Lipid-free apoA-I showed 2.9-fold higher phospholipid binding ability than apoA-4. In lipid-free state, BS3-crosslinking revealed that apoA-4 showed less multimerization tendency upto dimer, while apoA-I showed pentamerization. In rHDL state (95:1), apoA-4 was existed as dimer as like as apoA-I. With higher phospholipid content (255:1), five apoA-I and three apoA-4 were required to the bigger rHDL formation. Regardless of particle size, apoA-I-rHDL showed superior LCAT activation ability than apoA-4-rHDL. Uptake of acetylated LDL was inhibited by apoA-I in both lipid-free and lipid-bound state, while apoA-4 inhibited it only lipid-free state. ApoA-4 showed less anti-atherogenic activity with more sensitivity to glycation. In conclusion, apoA-4 showed inferior physiological functions in lipid-bound state, compared with those of apoA-I, to induce more pro-atherosclerotic properties.

Amphipathic α-helices in apolipoproteins are crucial to the formation of infectious hepatitis C virus particles.

Apolipoprotein B (ApoB) and ApoE have been shown to participate in the particle formation and the tissue tropism of hepatitis C virus (HCV), but their precise roles remain uncertain. Here we show that amphipathic α-helices in the apolipoproteins participate in the HCV particle formation by using zinc finger nucleases-mediated apolipoprotein B (ApoB) and/or ApoE gene knockout Huh7 cells. Although Huh7 cells deficient in either ApoB or ApoE gene exhibited slight reduction of particles formation, knockout of both ApoB and ApoE genes in Huh7 (DKO) cells severely impaired the formation of infectious HCV particles, suggesting that ApoB and ApoE have redundant roles in the formation of infectious HCV particles. cDNA microarray analyses revealed that ApoB and ApoE are dominantly expressed in Huh7 cells, in contrast to the high level expression of all of the exchangeable apolipoproteins, including ApoA1, ApoA2, ApoC1, ApoC2 and ApoC3 in human liver tissues. The exogenous expression of not only ApoE, but also other exchangeable apolipoproteins rescued the infectious particle formation of HCV in DKO cells. In addition, expression of these apolipoproteins facilitated the formation of infectious particles of genotype 1b and 3a chimeric viruses. Furthermore, expression of amphipathic α-helices in the exchangeable apolipoproteins facilitated the particle formation in DKO cells through an interaction with viral particles. These results suggest that amphipathic α-helices in the exchangeable apolipoproteins play crucial roles in the infectious particle formation of HCV and provide clues to the understanding of life cycle of HCV and the development of novel anti-HCV therapeutics targeting for viral assembly.

Inhibition of plasminogen activation by apo(a): role of carboxyl-terminal lysines and identification of inhibitory domains in apo(a).

Apo(a), the distinguishing protein component of lipoprotein(a) [Lp(a)], exhibits sequence similarity to plasminogen and can inhibit binding of plasminogen to cell surfaces. Plasmin generated on the surface of vascular cells plays a role in cell migration and proliferation, two of the fibroproliferative inflammatory events that underlie atherosclerosis. The ability of apo(a) to inhibit pericellular plasminogen activation on vascular cells was therefore evaluated. Two isoforms of apo(a), 12K and 17K, were found to significantly decrease tissue-type plasminogen activator-mediated plasminogen activation on human umbilical vein endothelial cells (HUVECs) and THP-1 monocytes and macrophages. Lp(a) purified from human plasma decreased plasminogen activation on THP-1 monocytes and HUVECs but not on THP-1 macrophages. Removal of kringle V or the strong lysine binding site in kringle IV10 completely abolished the inhibitory effect of apo(a). Treatment with carboxypeptidase B to assess the roles of carboxyl-terminal lysines in cellular receptors leads in most cases to decreases in plasminogen activation as well as plasminogen and apo(a) binding; however, inhibition of plasminogen activation by apo(a) was unaffected. Our findings directly demonstrate that apo(a) inhibits pericellular plasminogen activation in all three cell types, although binding of apo(a) to cell-surface receptors containing carboxyl-terminal lysines does not appear to play a major role in the inhibition mechanism.

Apolipoprotein A-IV improves glucose homeostasis by enhancing insulin secretion.

Apolipoprotein A-IV (apoA-IV) is secreted by the small intestine in response to fat absorption. Here we demonstrate a potential role for apoA-IV in regulating glucose homeostasis. ApoA-IV-treated isolated pancreatic islets had enhanced insulin secretion under conditions of high glucose but not of low glucose, suggesting a direct effect of apoA-IV to enhance glucose-stimulated insulin release. This enhancement involves cAMP at a level distal to Ca(2+) influx into the ß cells. Knockout of apoA-IV results in compromised insulin secretion and impaired glucose tolerance compared with WT mice. Challenging apoA-IV(-/-) mice with a high-fat diet led to fasting hyperglycemia and more severe glucose intolerance associated with defective insulin secretion than occurred in WT mice. Administration of exogenous apoA-IV to apoA-IV(-/-) mice improved glucose tolerance by enhancing insulin secretion in mice fed either chow or a high-fat diet. Finally, we demonstrate that exogenous apoA-IV injection decreases blood glucose levels and stimulates a transient increase in insulin secretion in KKAy diabetic mice. These results suggest that apoA-IV may provide a therapeutic target for the regulation of glucose-stimulated insulin secretion and treatment of diabetes.

Assessment of leisure-time physical activity for the prediction of inflammatory status and cardiometabolic profile.

OBJECTIVES: Associations of leisure-time physical activity (LTPA), commuting and total physical activity with inflammatory markers, insulin resistance and metabolic profile in individuals at high cardiometabolic risk were investigated. DESIGN: This was a cross-sectional study. METHODS: A total of 193 prediabetic adults were compared according to physical activity levels measured by the international physical activity questionnaire; p for trend and logistic regression was employed. RESULTS: The most active subset showed lower BMI and abdominal circumference, reaching significance only for LTPA (p for trend=0.02). Lipid profile improved with increased physical activity levels. Interleukin-6 decreased with increased total physical activity and LTPA (p for trend=0.02 and 0.03, respectively), while adiponectin increased in more active subsets for LTPA (p for trend=0.03). Elevation in adjusted OR for hypercholesterolemia was significant for lower LTPA durations (p for trend=0.04). High apolipoprotein B/apolipoprotein A ratio was inversely associated with LTPA, commuting and total physical activity. Increase in adjusted OR for insulin resistance was found from the highest to the lowest category of LTPA (p for trend=0.04) but significance disappeared after adjustments for BMI and energy intake. No association of increased C-reactive protein with physical activity domains was observed. CONCLUSIONS: In general, the associations of LTPA, but not commuting or total physical activity, with markers of cardiometabolic risk reinforces the importance of initiatives to increase this domain in programs for the prevention of lifestyle-related diseases.

Functional importance of apolipoprotein A5 185G in the activation of lipoprotein lipase.

BACKGROUND: Apolipoprotein A5 (APOA5) over-expression enhances lipolysis of triglyceride (TG) through stimulation of lipoprotein lipase (LPL) activity; however, an APOA5 G185C variant was found associated with hypertriglyceridemia. The aim of this study was, therefore, to explore the importance of APOA5 185GG in the activation of LPL. METHODS: A fragment containing mature human APOA5 cDNA was obtained by RT-PCR and subcloned into pET-15b vector. Site-directed mutagenesis was performed to generate 19 variants. Recombinant human APOA5 wild type and variants were produced in Escherichia coli, and then activation of LPL was measured. RESULTS: Activity of APOA5 variants on LPL-mediated 1,2-dimyristoyl-sn-glycero-3-phosphocholine hydrolysis was reduced by 17 to 74% in comparison to wild type APOA5 (P<0.0001). All variants also showed reduced activation (P<0.0001) of LPL-mediated hydrolysis of very low-density lipoprotein (VLDL); activation abilities of APOA5 variants ranged from 31 to 81% of wild-type APOA5. CONCLUSIONS: APOA5 residue 185G is very important in LPL-mediated VLDL hydrolysis, and any mutation at this residue will decrease LPL activation and concomitant TG modulation.

Apolipoprotein A-V; a potent triglyceride reducer.

Since its discovery, apolipoprotein A-V has been considered to be a potent factor affecting plasma triglycerides (TG) in humans and mice. Several single nucleotide polymorphisms in the APOA5 gene are associated with increased TG levels in humans, and some nonsense mutations affecting protein structure predispose for familial hypertriglyceridemia and late onset chylomicronemia. It is not clear, how apoA-V decreases plasma TG. There are three major hypotheses: apolipoprotein A-V could work through (1) an intracellular mechanism affecting VLDL production in the liver, (2) stimulation of proteoglycan-bound lipoprotein lipase at the endothelium of capillaries in peripheral organs, or (3) enhancing the clearance of TG-rich lipoproteins via lipoprotein receptors in the liver. There is good evidence for a role of apoA-V in extracellular TG metabolism and increasing support for an additional function of ApoA-V as a receptor ligand. The intracellular role of apoA-V for lipoprotein assembly and secretion is still speculative. This review discusses these possible mechanisms.

The role of apolipoprotein A5 in non-alcoholic fatty liver disease.

BACKGROUND: Apolipoprotein A5 (apoA5) is a recently described liver-specific protein that has been shown to influence triglyceride (TG) metabolism. ApoA5 transgenic mice display dramatically reduced TG levels, while in contrast apoA5 deficiency in humans was reported to result in marked hypertriglyceridemia. ApoA5 exerts its extracellular effects by increasing lipolysis of TG-rich lipoproteins, while in vitro data suggest additional intrahepatic effects. METHODS: In this study the authors set out to investigate a possible role of apoA5 in non-alcoholic fatty liver disease (NAFLD). We thus determined hepatic apoA5 expression in 15 obese subjects with histologically proven NAFLD undergoing bariatric surgery. In addition, the authors established a hepatic cell culture model of apoA5 knockdown by transfecting human hepatoma cells (HepG2) with apoA5 small interfering (si) RNA, and determined intracellular TG content and expression levels of key enzymes and transcription factors of intrahepatic lipid metabolism in these cells. RESULTS: Pronounced weight loss and associated histologically verified improvement of hepatic steatosis were accompanied by significant reductions of hepatic apoA5 mRNA expression levels. Significant apoA5 knockdown in HepG2 cells resulted in a marked decrease of intracellular TG content. When HepG2 cells were co-transfected with apoA5 and peroxisome proliferator-activated receptor gamma (PPARγ), reductions in hepatic TG accumulation were significantly less pronounced when compared to apoA5 siRNA transfected HepG2 cells. CONCLUSIONS: In obese subjects, hepatic apoA5 mRNA expression decreases after weight loss and improvements in hepatic steatosis. The authors' in vitro data demonstrate that apoA5 influences intrahepatic TG metabolism and that these intracellular effects of apoA5 are accompanied by changes in PPARγ mRNA expression. In summary, the data suggest that as well as several other factors, apoA5 might be involved in the pathogenesis of hepatic steatosis.

[Impact of apolipoprotein A5 on cardiovascular risk. Genetic and environmental modulation]. / Impacto de la apolipoproteína A5 en el riesgo cardiovascular. Modulaciones genéticas y ambientales.

Triglyceride concentrations are an independent risk factor for coronary heart disease. Apolipoprotein A5 gene (APOAS) has an important role determining triglyceride metabolism and it is a potential cardiovascular risk. However the mechanisms for these actions are not well-known. Despite the different allelic frequency of its major polymorphisms in different populations, multiple studies have shown consistent associations between these variants and fasting triglycerides. Variations in the APOA5 gene have also been associated with postprandial triglycerides, as well as with different sizes of lipoproteins and other markers. Moreover, some of the APOA5 gene variants have been associated with ischemic heart disease, stroke, and carotid intima media thickness, although the references on this issue are scanty and contradictory. This may be due to the presence of gene-environment interactions that have been poorly studied until now. Among the few studies that have examined the influence of environmental factors on possible genetic variations, the most important are those that contemplate possible gene-diet interactions. However, the evidence is still scarce and more research is required in the field of nutrigenomics. To understand the impact of this gene on cardiovascular disease, we review the genetic functionality and variability of APOA5, its associations with intermediate and final phenotypes and gene-environment interactions detected.

Impacto de la apolipoproteína A5 en el riesgo cardiovascular: Modulaciones genéticas y ambientales / Impact of apolipoprotein A5 on cardiovascular risk: Genetic and environmental modulation

Triglyceride concentrations are an independent risk factor for coronary heart disease. Apolipoprotein A5 gene (APOA5) has an important role determining triglyceride metabolism and it is a potential cardiovascular risk. However the mechanisms for these actions are not well-known. Despite the different allelic frequency of its major polymorphisms in different populations, multiple studies have shown consistent associations between these variants and fasting triglycerides. Variations in the APOA5 gene have also been associated with postprandial triglycerides, as well as with different sizes of lipoproteins and other markers. Moreover, some of the APOA5 gene variants have been associated with ischemic heart disease, stroke, and carotid intima media thickness, although the references on this issue are scanty and contradictory. This may be due to the presence of gene-environment interactions that have been poorly studied until now. Among the few studies that have examined the infuence of environmental factors on possible genetic variations, the most important are those that contemplate possible gene-diet interactions. However, the evidence is still scarce and more research is required in the feld of nutrigenomics. To understand the impact of this gene on cardiovascular disease, we review the genetic functionality and variability of APOA5, its associations with intermediate and fnal phenotypes and gene-environment interactions detected.

Estradiol increases the anorectic effect of central apolipoprotein A-IV.

Estrogens have potent suppressive effects on food intake and body weight in many species, including humans. Compelling evidence suggests estrogen's anorectic action is through an indirect mechanism by enhancing the strength of other physiological signals that reduce meal size such as apolipoprotein A-IV (apo A-IV), a satiation factor from the gut and brain. We determined whether estradiol, the primary form of estrogen, modulates the anorectic effect of apo A-IV. Intrafourth ventricular administration of low doses of apo A-IV reduced food intake to a greater extent in ovariectomized (OVX) rats cyclically treated with estradiol than in vehicle-treated OVX controls, implying that cyclic estradiol replacement increases the satiating potency of apo A-IV. OVX significantly increased food intake and body weight but decreased apo A-IV gene expression in the nucleus tractus solitarius (NTS). All of these alterations were reversed by cyclic regimen of estradiol treatment. The finding of colocalization of apo A-IV with estrogen receptor-alpha in the NTS suggests that estradiol might act locally in the NTS to up-regulate apo A-IV gene expression. Finally, OVX apo A-IV knockout mice had a smaller feeding response to estradiol because they ate significantly more food and gained more body weight than OVX wild-type controls during the period of cyclic estradiol replacement. These data indicate that an increased signaling of endogenous apo A-IV may partially mediate estradiol-induced inhibitory effect on feeding.

The APOA5-1131 T>C variant enhances the association between RBP4 and hypertriglyceridemia in diabetes.

BACKGROUND AND AIM: Type 2 diabetic patients have an increased prevalence of hypertriglyceridemia. RBP4 has been associated with insulin resistance and hypertriglyceridemia in obesity, the metabolic syndrome and type 2 diabetes. APOA5 is proposed to be a genetic modulator of triglycerides. The aim of this study was to evaluate the relationship between RBP4 plasma levels and lipid disturbances and to determine the impact of the APOA5-1131 T>C variant on this relationship in type 2 diabetic patients. METHODS AND RESULTS: A total of 165 type 2 diabetic patients were included in the study. RBP4 plasma levels and the APOA5-1131 T>C variant were determined and the complete lipid profile was assessed by sequential ultracentrifugation. RBP4 was positively correlated with triglyceride levels in plasma and with all the components of triglyceride-rich lipoproteins. Despite the fact that a statistically significant relationship between the APOA5 genetic variant and RBP4 plasma levels was not found, the hypertriglyceridemic effect of high RBP4 levels was enhanced by the presence of the APOA5-1131 T>C genetic variant. Correlation coefficients were 2-fold higher for TC carriers compared to TT carriers with regard to RBP4 plasma levels and all the components of triglyceride-rich lipoproteins. Those type 2 diabetic patients with high RBP4 plasma concentrations and who were TC carriers showed an increased incidence of hypertriglyceridemia (OR=7.46, P=0.010). CONCLUSION: RBP4 is associated with hypertriglyceridemia in type 2 diabetic patients. The RBP4 effect is conditioned by the presence of the APOA5-1131 T>C genetic variant.

A physiological function for apolipoprotein(a): a natural regulator of the inflammatory response.

Structural similarities between apolipoprotein(a) (apo(a)), the unique apoprotein of lipoprotein(a), and plasminogen, the zymogen of plasmin, can interfere with functions of plasmin (ogen) in vitro. The purpose of this study was to evaluate the role of apo(a) in inflammation in vivo using apo(a) transgenic mice and to determine if effects are plasminogen-dependent using backgrounds that are either plasminogen-replete or plasminogen-deficient. After administration of peritoneal inflammatory stimuli, thioglycollate, bioimplants or lipopolysaccharide, the number of responding peritoneal neutrophils and macrophages were quantified. Apo(a), in either wild-type or plasminogen deficient backgrounds, inhibited neutrophil recruitment but had no effect on plasminogen-dependent macrophage recruitment. Macrophage-inflammatory protein-2, a neutrophil chemokine, was reduced in apo(a) mice, and injection of this chemokine prior to thioglycollate restored neutrophil recruitment in apo(a) transgenic mice. In the lipopolysaccharide model, mice with apo(a), unlike mice without apo(a), did not increase neutrophil recruitment in response to the stimulus. In the bioimplant model, neutrophil recruitment and neutrophil cytokines were reduced in apo(a)tg mice but only in a plasminogen-deficient background. These results indicate for the first time that apo(a), independent of plasminogen interaction, inhibits neutrophil recruitment in vivo in diverse peritoneal inflammatory models. Hence, apo(a) may function as a cell specific suppressor of the inflammatory response.

Intestinal hormones and regulation of satiety: the case for CCK, GLP-1, PYY, and Apo A-IV.

Satiety, the physiologic processes that combine to bring about the cessation of a meal, is controlled in part by intestinal peptide secretion. The effects of cholecystokinin, glucagon-like peptide I, peptide YY, and apolipoprotein A-IV are described.

Secreted human apolipoprotein(a) kringle IV-10 and kringle V inhibit angiogenesis and xenografted tumor growth.

Abstract Angiogenesis plays an important role in normal physiology of blood vessel growth, but can contribute to the pathogenesis of diseases, such as cancer. A new anti-angiogenic recombinant kringle protein, composed of the fused domains of human apolipoprotein(a) carboxyl-terminal kringle IV-10 and kringle V, was expressed in Pichia pastoris and human colorectal carcinoma (HCT 116) cells to investigate its influence on angiogenesis and tumor growth. The mature recombinant protein exhibited the characteristic features of kringle-containing proteins (glycosylation and disulfide bond formation) and, when added to cultures of human umbilical vein endothelial cell, resulted in a 31% decrease in proliferation relative to untreated controls (p<0.05). The neo-angiogenesis was diminished by 63% in chick embryos treated with 10 mug recombinant protein compared with 7% for phosphate buffer solution-treated embryos (p<0.01). Transfection of a kringle IV-10-kringle V fusion protein construct into HCT 116 cells decreased tumorigenesis and inhibited tumor growth in vivo without affecting tumor cell proliferation. HCT 116 cells that expressed recombinant protein displayed a much lower relative growth ratio of 8% (p<0.01) against the control tumor cells. From these results, we conclude that human apolipoprotein(a) carboxyl-terminal kringle IV-10-kringle V fusion protein is an effective inhibitor of angiogenesis and angiogenesis-dependent tumor growth.