HDL Protein Research Articles

Apoprotein A-I mimetic peptides and their potential anti-atherogenic mechanisms of action

Peptides that resemble in physicochemical properties the helices of apoprotein A-I, the major protein of atheroprotective HDL, show promise for the treatment of atherosclerosis-related vascular disease. The properties and promise of these so-called mimetic peptides will be explored in this review. Both HDL and mimetic peptides are able to scavenge and sequester oxidized lipids and hence protect endothelial cells and arteries from the pro-inflammatory action of oxidized LDL. Active mimetic peptides have an amphipathic alpha-helical secondary structure, whose hydrophobic face is particularly important for its bioactivity. The most frequently employed peptide is 4F. The comparative bioactivity of variants of 4F, particularly tandem helical peptides, has been explored. The recent observation of the very high affinity of bioactive peptides for oxidized fatty acids and phospholipids provides a likely mechanism for the action of these peptides in inhibiting early atherosclerosis formation. It is not clear that these peptides alone are effective in reversing established atherosclerosis, although they may achieve this outcome in synergy with statin therapy. Recent observations of mimetic peptides have pointed to promising therapies for patients with cardiovascular disease. The peptides appear to be well tolerated and effective in promoting the anti-inflammatory properties of HDL.

The HDL proteome: a marker–and perhaps mediator–of coronary artery disease

One important cardioprotective function of HDL is to remove cholesterol from lipid-laden macrophages in the artery wall. HDL also exerts anti-inflammatory effects that might inhibit atherogenesis. However, HDL has been proposed to be dysfunctional in humans with established coronary artery disease (CAD), though the underlying mechanisms are unclear. Therefore, we used mass spectrometry to investigate the roles of HDL proteins in inflammation and cardiovascular disease. Shotgun proteomic analysis identified multiple complement regulatory proteins, protease inhibitors, and acute-phase response proteins in HDL, strongly implicating the lipoprotein in inflammation and the innate immune system. Moreover, mass spectrometry and biochemical analyses demonstrated that HDL3 from subjects with clinically significant CAD was selectively enriched in apolipoprotein E, suggesting that it carries a distinctive protein cargo in humans with atherosclerosis. HDL from CAD subjects also contained markedly elevated levels of chlorotyrosine and nitrotyrosine, two characteristic products of myeloperoxidase, indicating that oxidative damage might generate dysfunctional HDL. Aggressive lipid therapy with a statin and niacin remodeled the HDL proteome to resemble that of apparently healthy subjects. Collectively, our observations indicate that quantifying the HDL proteome by mass spectrometry should help identify novel anti-inflammatory and cardioprotective actions of HDL and provide insights into lipid therapy.

HDL, lipid peroxidation, and atherosclerosis

Genetic, clinical, and pharmacological studies implicate elevated levels of LDL in the pathogenesis of atherosclerotic vascular disease, the leading cause of death in industrialized societies (1). Paradoxically, native LDL fails to exert potentially atherogenic effects in vitro, suggesting that it must be modified to promote vascular disease. Indeed, many lines of evidence support the LDL oxidation hypothesis, which suggests that oxidative damage to LDL is one important mechanism for rendering lipoproteins atherogenic (as reviewed in Refs. 2, 3).

The role of reverse cholesterol transport in animals and humans and relationship to atherosclerosis

Reverse cholesterol transport (RCT) is a term used to describe the efflux of excess cellular cholesterol from peripheral tissues and its return to the liver for excretion in the bile and ultimately the feces. It is believed to be a critical mechanism by which HDL exert a protective effect on the development of atherosclerosis. In this paradigm, cholesterol is effluxed from arterial macrophages to extracellular HDL-based acceptors through the action of transporters such as ABCA1 and ABCG1. After efflux to HDL, cholesterol may be esterified in the plasma by the enzyme lecithin:cholesterol acyltransferase and is ultimately transported from HDL to the liver, either directly via the scavenger receptor BI or after transfer to apolipoprotein B-containing lipoproteins by the cholesteryl ester transfer protein. Methods for assessing the integrated rate of macrophage RCT in animals have provided insights into the molecular regulation of the process and suggest that the dynamic rate of macrophage RCT is more strongly associated with atherosclerosis than the steady-state plasma concentration of HDL cholesterol. Promotion of macrophage RCT is a potential therapeutic approach to preventing or regressing atherosclerotic vascular disease, but robust measures of RCT in humans will be needed in order to confidently advance RCT-promoting therapies in clinical development.

Phospholipids mediated conversion of HDLs generates specific apoA-II pre-β mobility particles

Apolipoproteins (apo)A-I and A-II are major proteins of human HDL. The cycling of apoA-I between lipid-poor and lipid-rich forms of HDL plays a key role in the transport of cholesterol by these particles. ApoA-II resides only in part of HDL particles, and little is known about its role in HDL metabolism. Our study investigates the redistribution of apoA-II after HDL remodelling induced by exogenous phospholipids (PL). During incubation with egg yolk lecithin (EYL) liposomes, human HDL became PL-enriched and free cholesterol (FC)-depleted, and lost small amounts of apoA-I and apoA-II. The loss of FC and apolipoproteins correlated with the rise of PL content in HDL. Agarose gel electrophoresis demonstrated the appearance of new pre-beta mobility fractions containing apoA-I and apoA-II in liposomes and HDL mixtures. Two-dimensional nondenaturing 2-27% PAGE has shown that the pre-beta mobility fraction that appeared at initial liposome-PL/HDL-PL ratio 5:1 consisted of two distinct heterogeneous subpopulations of particles containing either apoA-I or apoA-II. Our study provides evidence that during HDL conversion mediated by PL apoA-II dissociated from HDL particles yielding apoA-II-specific pre-beta mobility particles. This observation supports the hypothesis that apoA-II in plasma, like apoA-I, may cycle between lipid-poor and lipid-rich forms of HDL.

The Effect of Five Servings a Week of Pulses for Eight Weeks on Risk Factors for the Metabolic Syndrome in Overweight Human Subject

The objective of this study was to compare the effect of consuming for 8 weeks a diet rich in pulses (beans, lentils, chickpeas and yellow peas) with a conventional energy restriction diet on risk factors for the metabolic syndrome. Overweight/obese adults (n = 44) with BMI of 27‐40 kg/m2 were randomized to a treatment of 5 cups/week of pulses or to a diet restriction of 500 kcal/day. Blood glucose and insulin were measured over 120 min after a 75g glucose load. Both diets resulted in reduction (p<0.05) of body weight, waist circumference, systolic blood pressure, HbA1c and glucose area under the curve (AUC). Only the energy‐restricted diet reduced diastolic blood pressure. The effect of diet on insulin AUC was influenced by sex. Insulin decreased in both males and females on the energy‐restricted diet, while it was decreased in females and increased in males following the pulse diet (p<0.05). There was no statistically significant change in TC, TG, LDL, HDL or C‐reactive protein. In conclusion, the incorporation of 5 cups/week of pulses into the diet, with no other dietary guidance, had the same beneficial effect on risk factors for the metabolic syndrome as dietary counseling to reduce energy intake. Supported by Pulse Canada.

Proteomic Analysis of Defined HDL Subpopulations Reveals Particle-Specific Protein Clusters

Recent proteomic studies have identified multiple proteins that coisolate with human HDL. We hypothesized that distinct clusters of protein components may distinguish between physicochemically-defined subpopulations of HDL particles, and that such clusters may exert specific biological function(s). We investigated the distribution of proteins across 5 physicochemically-defined particle subpopulations of normolipidemic human HDL (HDL2b, 2a, 3a, 3b, 3c) fractionated by isopycnic density gradient ultracentrifugation. Liquid chromatography/electrospray mass spectrometry identified a total of 28 distinct HDL-associated proteins. Using an abundance pattern analysis of peptide counts across the HDL subfractions, these proteins could be grouped into 5 distinct classes. A more in-depth correlational network analysis suggested the existence of distinct protein clusters, particularly in the dense HDL3 particles. Levels of specific HDL proteins, primarily apoL-I, PON1, and PON3, correlated with the potent capacity of HDL3 to protect LDL from oxidation. These findings suggest that HDL is composed of distinct particles containing unique (apolipo)protein complements. Such subspeciation forms a potential basis for understanding the numerous observed functions of HDL. Further work using additional separation techniques will be required to define these species in more detail.

A sensitive and specific ELISA detects methionine sulfoxide-containing apolipoprotein A-I in HDL

Oxidized HDL has been proposed to play a key role in atherogenesis. A wide range of reactive intermediates oxidizes methionine residues to methionine sulfoxide (MetO) in apolipoprotein A-I (apoA-I), the major HDL protein. These reactive species include those produced by myeloperoxidase, an enzyme implicated in atherogenesis. The aim of the present study was to develop a sensitive and specific ELISA for detecting MetO residues in HDL. We therefore immunized mice with HPLC-purified human apoA-I containing MetO(86) and MetO(112) (termed apoA-I(+32)) to generate a monoclonal antibody termed MOA-I. An ELISA using MOA-I detected lipid-free apoA-I(+32), apoA-I modified by 2e-oxidants (hydrogen peroxide, hypochlorous acid, peroxynitrite), and HDL oxidized by 1e- or 2e-oxidants and present in buffer or human plasma. Detection was concentration dependent, reproducible, and exhibited a linear response over a physiologically plausible range of concentrations of oxidized HDL. In contrast, MOA-I failed to recognize native apoA-I, native apoA-II, apoA-I modified by hydroxyl radical or metal ions, or LDL and methionine-containing proteins other than apoA-I modified by 2e-oxidants. Because the ELISA we have developed specifically detects apoA-I containing MetO in HDL and plasma, it should provide a useful tool for investigating the relationship between oxidized HDL and coronary artery disease.

Effects of acceptor composition and mechanism of ABCG1-mediated cellular free cholesterol efflux

Among the known mechanisms of reverse cholesterol transport (RCT), ATP binding cassette transporter G1 (ABCG1)-mediated free cholesterol (FC) transport is the most recent and least studied. Here, we have characterized the efficiencies of different acceptors using baby hamster kidney (BHK) cells transfected with human ABCG1 cDNA, which is inducible upon treatment with mifepristone. When normalized on particle number and particle surface area, the acceptor efficiency for FC efflux was as follows: small unilamellar vesicles (SUV)>LDL>reconstituted HDL>HDL2 = HDL3. Based on phospholipid content, the order was reversed. ABCG1 also mediated phospholipid efflux to human serum and HDL3. ABCG1-mediated FC efflux correlated significantly with a number of HDL subfractions and components in serum collected from 25 normolipidemic individuals: apolipoprotein A-II (apoA-II) (r2 = 0.7), apolipoprotein A-I (apoA-I) (r2 = 0.5), HDL-C (r2 = 0.4), HDL-PL (r2 = 0.4), α-2 HDL (r2 = 0.4), and preβ HDL (r2 = 0.2). ABCG1 did not enhance influx of FC or cholesteryl oleyl ether (COE) when cells were incubated with radiolabeled HDL3. ABCG1 expression did not increase the association of HDL3 with cells. Compared with control cells, ABCG1 expression significantly increased the FC pool available for efflux and the rate constant for efflux. In conclusion, composition and particle size determine the acceptor efficiency for ABCG1-mediated efflux. ABCG1 increases cell membrane FC pools and changes its rate of desorption into the aqueous phase without enhancing the association with the acceptor.

Abstract 1690: Pre-Beta HDL and Lecithin:Cholesterol Acyltransferase Levels Are Strong Positive Diagnostic Risk Markers for Ischemic Heart Disease in Subjects with Both High and Low HDL-C Levels in the Copenhagen City Heart Study

Objective: We hypothesize that patients with high HDL-C levels and Ischemic Heart Disease (IHD) may have dysfunctional HDL or unrecognized non-conventional risk factors. Methods: Subjects with IHD and either high HDL-C (n = 53; women:≥ 73.5mg/dL; men: ≥ 61.9mg/dL) or low HDL-C (n = 42; women: ≤ 38.7mg/dL; men: ≤ 34.1mg/dL) were compared with subjects without IHD and matched HDL-C levels (n = 110). All subjects had normal LDL-C (< 160mg/dL) and triglyceride levels (< 150mg/dL) and none were treated with lipid-lowering medications. Pre-beta HDL and Phospholipid Transfer Protein (PLTP) levels were measured using commercial kits and Lecithin:Cholesterol Acyltransferase (LCAT) activity, using a proteoliposome cholesterol esterification assay. Results: Pre-beta HDL levels were 2–3 fold higher in subjects with IHD in the high (p < 0.0001) and low HDL-C (p = 0.001) groups. Interestingly, low LCAT activity was found in the same subjects with IHD and high (p = 0.002) or low (p = 0.03) HDL-C. Furthermore, higher PLTP levels were observed in the group with high HDL-C and IHD when compared to individuals without disease (p < 0.0001). Receiver operating characteristic curve for pre-beta HDL in the high HDL-C groups yielded an area under curve of 0.71 for predicting IHD, which increased to 0.92 when LCAT values were included. Similar results were obtained for the low HDL-C groups. A strong inverse correlation between LCAT activity and pre-beta HDL-C ( r 2 = 0.30, p < 0.0001), which was especially strong in the low HDL-C group ( r 2 = 0.56, p < 0.0001) was observed. Individuals with high HDL-C and IHD had approximately 15% more apoA-I (p = 0.001) and apoA-II (p = 0.002) and nearly 10% more phospholipid (p = 0.007) than subjects with similar HDL-C and no IHD. Likewise, the group with low HDL-C had 30% more apoE (p = 0.035) and approximately 10% more phospholipid (p = 0.047) than the group with similar HDL-C levels and no IHD. Conclusions: IHD was associated with high pre-beta HDL and low LCAT levels. Measuring both gave correct classification in 92% of cases with IHD, thus making pre-beta HDL and LCAT activity a powerful diagnostic tool for IHD, particularly in commonly found patients wtih isolated low HDL-C levels with low to intermediate risk of IHD based on conventional risk factors.

Bone-marrow derived progenitor cells are associated with psychosocial determinants of health after controlling for classical biological and behavioral cardiovascular risk factors

Background Circulating progenitor cells have been implicated with maintaining vascular integrity. Low counts are found in adults with high cardiovascular risk and are associated with impaired endothelial function. It remains unknown whether psychosocial risk factors are independently related to counts of circulating progenitor cells. Methods We investigated a random sample of 468 adult industrial employees (mean age 41.2 years, 89% men) of Caucasian origin. Cardiovascular risk factors (blood pressure, LDL, HDL and C-reactive protein), health behavior (smoking, alcohol and physical exercise), psychological variables (effort-reward imbalance social support, negative affectivity) and interaction terms served as predictors of circulating progenitor cells (CD34+ CD31dim) as enumerated by flow-cytometry. Findings Psychosocial variables were independently associated with progenitor cell counts. The association with risk factors increased with age (explained variance in 18–36 year olds R 2 = 0.17, p = 0.55; age 36.1–46 R 2 = 0.32, p = 0.001; age > 46 R 2 = 0.27, p < 0.001). Data revealed a shift from a larger association between behavioral and psychosocial variables and cell counts to a stronger association between biological variables and cell counts in older individuals. A significant interaction was observed between smoking and effort-reward imbalance in middle-aged subjects, those with both risk factors present had lower cell counts. In older employees, the interaction between biological risk factors and smoking was related to lower cell counts. Interpretation In working middle-aged and older men, psychosocial risk factors were related to circulating counts of progenitor cells. Smoking interacted negatively with psychosocial risk factors (middle-aged men) or with biological risk factors (older employees).

Methionine oxidation impairs reverse cholesterol transport by apolipoprotein A-I

HDL protects against vascular disease by accepting free cholesterol from macrophage foam cells in the artery wall. This pathway is critically dependent on lecithin:cholesterol acyltransferase (LCAT), which rapidly converts cholesterol to cholesteryl ester. The physiological activator of LCAT is apolipoprotein A-I (apoA-I), the major HDL protein. However, cholesterol removal is compromised if apoA-I is exposed to reactive intermediates. In humans with established cardiovascular disease, myeloperoxidase (MPO) oxidizes HDL, and oxidation by MPO impairs apoA-I's ability to activate LCAT in vitro. Because a single methionine residue in apoA-I, Met-148, resides near the center of the protein's LCAT activation domain, we determined whether its oxidation by MPO could account for the loss of LCAT activity. Mass spectrometric analysis demonstrated that oxidation of Met-148 to methionine sulfoxide associated quantitatively with loss of LCAT activity in both discoidal HDL and HDL(3), the enzyme's physiological substrates. Reversing oxidation with methionine sulfoxide reductase restored HDL's ability to activate LCAT. Discoidal HDL prepared with apoA-I containing a Met-148-->Leu mutation was significantly resistant to inactivation by MPO. Based on structural data in the literature, we propose that oxidation of Met-148 disrupts apoA-I's central loop, which overlaps the LCAT activation domain. These observations implicate oxidation of a single Met in apoA-I in impaired LCAT activation, a critical early step in reverse cholesterol transport.

Effect of lipid-bound apoA-I cysteine mutants on lipopolysaccharide-induced endotoxemia in mice

HDL has been shown to be able to neutralize the toxicity of lipopolysaccharide (LPS). Our previous study (J. Lipid Res. 2005. 46: 1303-1311) characterized the properties of secondary structure and in vitro functions of different cysteine mutants of apolipoprotein A-I. Here, we reconstituted recombinant HDLs (named rHDLwt, rHDL52, rHDL74, rHDL107, rHDL129, rHDL173, rHDL195, and rHDL228) by mixing wild type or those mutants with dipalmitoyl phosphatidylcholine and examined their in vivo effects on LPS-induced endotoxemia in mice. Our results showed that 24 h after injection, mice receiving rHDL74 or rHDL52 had a significant decrease of plasma tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta), compared with control mice receiving either saline or rHDLwt (P < 0.05). Administration of rHDL74 to mice injected with LPS also led to a decrease of plasma IL-6, protection of lung against acute injury, and attenuation of endotoxin-induced clinical symptoms in mice, compared with controls injected with LPS only. However, injection of rHDL228 significantly increased plasma concentration of TNF-alpha and exacerbated LPS-induced lung injury. In summary, compared with rHDLwt, rHDL74 and rHDL52 exhibit higher anti-inflammation capabilities, whereas rHDL228 shows hyper-proinflammation by exacerbating LPS-induced endotoxemia in mice.

When HDL Gets Fat …

See related article, pages 159–166 Because low levels of plasma high density lipoprotein cholesterol (HDL-C) are a major independent risk factor for atherosclerotic cardiovascular disease,1 the mechanisms leading to low HDL-C are of substantial biological and clinical importance. Low HDL-C is most commonly seen in persons who have other components of the “metabolic syndrome,” particularly increased waist circumference, elevated triglycerides (TG), and elevated fasting glucose, which along with low HDL-C are indicators of insulin resistance.2 Kinetic studies in humans have indicated that the turnover of the major HDL protein apolipoprotein A-I (apoA-I) is increased in patients with the characteristics of metabolic syndrome and insulin resistance.3,4 The mechanisms of hypercatabolism of HDL in this setting have been the subject of substantial investigation. The insulin resistant state is associated with elevated plasma levels of TG-rich lipoproteins (TRL),5 derived from the liver and the intestine, as well as with elevated levels of the cholesteryl ester transfer protein (CETP),6,7 which transfers TG from TRL to HDL in exchange for cholesteryl esters. Accelerated CETP-mediated lipid exchange siphons cholesterol out of and transfers TG into HDL, resulting in a cholesterol-depleted and TG-enriched HDL. Enrichment of HDL with TG makes it a much better substrate for hepatic lipase (HL), which is also clearly elevated in insulin resistant states. …

Acute and subchronic toxicological assessment of Byrsocarpus coccineus Schum. and Thonn. (Connaraceae) leaf aqueous extract

Summary: This study was conducted to determine the safety profile of Byrsocarpus coccineus (Connaraceae) by carrying out the acute and subchronic toxicological assessment of its aqueous leaf extract. In the acute toxicity test, mice were administered orally with the extract up to 10 g/kg and intraperitoneally at doses of 50 – 800 mg/kg. Animals were then observed for behavioural changes, signs of toxicity, and mortality within 24 h. Surviving mice were monitored for 7 days for signs of delayed toxicity. In the subchronic toxicity test, rats were daily treated with the extract at doses of 40, 200, and 1000 mg/kg orally, for 30 days and 60 days. Control animals received distilled water and all animals were weighed at 7 days interval. At the end of the test periods, haematological, biochemical, and urinary parameters were determined in blood, serum, and urine samples respectively and vital organs macroscopically examined and weighed. In the acute toxicity test, the extract was practically non-toxic showing no mortality and visible signs of delayed toxicity. The LD 50 , given intraperitoneally, was estimated to be 158.4 mg/kg. Administered for 30 days, the extract did not produce any significant ( P < 0.05) effect on haematological and biochemical parameters and vital organs. In the 60 day study, the extract elicited significant ( P < 0.05) increases in platelet and WBC count and reductions in levels of liver enzymes (AST, ALT, and ALP), total cholesterol, HDL, triglycerides, and total protein. The weight of the kidneys, spleen, epididymis, and testes were not significantly affected but significant changes were observed in the weight of the liver (↑), heart (↓), and lungs (↑). Generally, B. coccineus did not significantly affect body weight and urinary parameters. Results obtained in this study suggest that the aqueous leaf extract of B. coccineus is safe when administered orally with potential beneficial effects as immunostimulant, hepatoprotective, and hypocholestrolemic agent, when administered over a long period of time. Industrial relevance: The use of herbal remedies by all stratums of people is on the increase worldwide. The aqueous leaf extract of B. coccineus administered orally has shown great promise as a phytotherapeutic agent based on results of previous pharmacological investigations. In view of the importance of toxicological evaluation in drug and standardized herbal remedy development, this study was conducted to evaluate the extract for its acute and subchronic effects. The safety of the extract administered orally was established and other potential benefits in the treatment of human diseases were identified.

Serum resistin is positively correlated with the accumulation of metabolic syndrome factors in type 2 diabetes

Resistin, secreted from adipocytes, causes insulin resistance in rodents. We reported that the G/G genotype of a resistin gene promoter single nucleotide polymorphism (SNP) at -420 increases type 2 diabetes (T2DM) susceptibility by enhancing promoter activity. We also showed that serum resistin was positively correlated with G at SNP-420, the duration of T2DM, and HbA1c in T2DM. The aim of this study was to determine the relation between serum resistin and factors related to the metabolic syndrome (MetS) in T2DM. We analysed 238 Japanese T2DM subjects (124 males and 114 females, age 60.2 +/- 11.3 years, body mass index (BMI) 24.1 +/- 3.9) whose overnight fasting sera were available. Serum resistin was measured using ELISA. Serum resistin was higher in subjects with either obesity (P = 0.041), low HDL (P = 0.004), high triglycerides (TG) (P = 0.019), hypertension (HT) (P = 0.001) or atherosclerosis (P = 0.012). Simple regression analysis revealed that serum resistin was correlated with lower HDL, TG and high-sensitivity C-reactive protein (hsCRP). Multiple regression analysis (or logistic regression analysis for HT), adjusted for age, gender, BMI and the duration of T2DM, revealed that serum resistin was correlated with lower HDL (P = 0.008), TG (P = 0.041), HT (P = 0.031) and hsCRP (P = 0.004). Serum resistin was positively correlated with the number of MetS factors, independent of age, gender and the duration of T2DM (P < 0.001). Adjustment by either thiazolidinedione (TZD) treatment or hsCRP had no effects on these findings. Serum resistin was positively correlated with the accumulation of MetS factors in T2DM.

Niacin inhibits surface expression of ATP synthase β chain in HepG2 cells: implications for raising HDL

Niacin is an effective agent for raising HDL, but its cellular target sites are largely unknown. We examined effects of niacin on the surface expression of ATP synthase beta chain, a newly described HDL/apolipoprotein A-I (apoA-I) receptor for HDL endocytosis, in HepG2 cells. A significant amount of immunodetectable beta chain was observed on the surface of HepG2 cells, which was competitively displaced by apoA-I. Niacin treatment reduced the surface expression of beta chain in HepG2 cells by approximately 27%, and decreased (125)I-labeled HDL uptake up to approximately 35%. However, nicotinamide, a niacin metabolite that does not have clinical lipid effects, exhibited weaker inhibition on the beta chain cell surface expression, and failed to show inhibitory action on (125)I-labeled HDL uptake. Furthermore, anti-beta chain antibody significantly reduced (125)I-labeled HDL uptake and abolished the inhibitory effect of niacin. Niacin did not change beta chain mRNA expression. These data suggest that niacin inhibits cell surface expression of the ATP synthase beta chain, leading to reduced hepatic removal of HDL protein, thus implicating a potential cellular target for niacin action to raise HDL.

Ultrasound carotid intima-media thickness (CIMT) evaluation as a marker in vascular damage progression in hemodialysis and role of adequate calcium-phosphorus product control by sevelamer

It has been suggested that sPO4 should be maintained 5.5mg/dl and Ca x P>55mg/dl, in these pts (G 1; n=12) calcium salts were replaced with sevelamer, while the other pts kept on taking calcium salts (G 2; n=11). In all pts at baseline and after 5 and 10 months (F-U) were determined sCa, sPO4, PTH (n.v. 9–63 pg/ml), cholesterol, HDL, LDL and C-reactive protein. Baseline and after 10 months all pts underwent B-mode ultrasonography of the carotid (C) artery for the evaluation of intima-media thickness (IMT; mm) and echocardiogram for determination of the left ventricular mass index (LVMi:r/m2). Our results show as sevelamer provides an effective control of sPO4 and Ca xP product and decreases progression of cardiovascular disease, that can not be prevent by an adequate control of Ca x P with calcium salts. That suggests that besides inadequate control of sPO4 even oral calcium ingested may play a role in the progression of cardiovascular disease.

A Pivotal Role of the Human Kidney in Catabolism of HDL Protein Components Apolipoprotein A‐I and A‐IV but not of A‐II

Renal handling of major HDL components was studied by analyzing urine from patients with Fanconi syndrome, a rare renal proximal tubular reabsorption failure, including dysfunction of the kidney HDL receptor, cubilin. A high urinary excretion of apolipoprotein A-I and A-IV corresponding to a major part of the metabolism of these proteins was measured. In contrast, no urinary excretion of apolipoprotein A-II which is more hydrophobic and tighter bound to HDL was found. Control urines displayed absence of the three apolipoproteins. Urinary excretion of phospholipids, triglycerides, cholesterol and cholesterol esters in patients was as low as in controls. In conclusion, these data indicate that the human kidney is a major site for filtered nascent apolipoprotein A-I and A-IV but not for HDL particles.

Location of PRODAN in lipid layer of HDL particle: a Raman study

FT Raman spectroscopy has been applied to determine the location of PRODAN within HDL and to investigate its influence on the structure of the particle. The complex spectra of HDL and HDL labeled with PRODAN were divided into three regions according to the wave numbers, and adherent spectra were compared separately. Additionally, recorded spectra of protein and lipid fractions of HDL were used as a support for the assignment of particular vibrations in intact particles. In high frequency region, the shift in vibrational frequencies of CH3 groups but almost negligible shift of CH2 groups suggests that PRODAN is situated at the water/lipid interface in the vicinity of the protein. The statement is supported by the observed influence of PRODAN on particular lipid vibrations of phospholipids head-groups. In the fingerprint region, the influence of PRODAN is observed as the slight change in beta-strand secondary structure of apolipoprotein and strongly reduced vibrations of the acyl chain in lipids. That additionally confirms that PRODAN mainly interacts with the lipid domain of the particle. In the low frequency region, the lack of change in Tyr Fermi resonance doublet and only slight differences in the pattern of CS and SS stretching vibrations in labeled HDL confirms that PRODAN has no influence on structure of apolipoprotein embedded in lipid domain. The main conclusions drawn from the vibrational spectra of HDL with and without PRODAN clearly confirm that PRODAN induces negligible changes in HDL structure and hence is reliable fluorescent label for the structural analysis.