High-density lipoproteins: from function to therapy

Association of remnant cholesterol with renal function and its progression in patients with type 2 diabetes related chronic kidney disease

Background

The association of Remnant cholesterol (RC) with renal function and its progression in patients with Type 2 diabetes (T2DM) related chronic kidney disease (CKD) remains unclear.

Methods

8,678 patients with T2DM-related CKD were included in cross-sectional analysis, and 6,165 patients were enrolled in longitudinal analysis and followed up for a median of 36.0 months. The outcomes were renal composite endpoint event and rapid progression of renal function.

Results

24.54% developed a renal composite endpoint event, and 27.64% rapid progression of renal function. RC levels above 0.56 mmol/L independently increased the risk of both renal composite endpoint (HR, 1.17; 95% CIs, 1.03-1.33) and rapid progression of renal function (OR, 1.17; 95% CIs, 1.01- 1.37). TG levels above 1.65 mmol/L only increased the risk of renal composite endpoint (HR, 1.16; 95% CIs, 1.02 -1.32). TC levels above 5.21 mmol/L increased the risk of renal composite endpoint (HR, 1.14; 95% CIs, 1.01-1.29) only in patients with proteinuria≥0.5g/d. Conversely, HDL-C levels below 1.20 mmol/L or above 1.84 mmol/L increased the risk of rapid progression of renal function (OR, 0.88; 95% CIs, 0.70 -0.99) in patients with proteinuria<0.5g/d (all P<0.05).

Conclusion

In patients with T2DM-related CKD, RC was an independent risk factor for progression of renal function, and maintaining it below 0.56 mmol/L could reduce the risk of renal function progression.

Association between the triglyceride to high-density lipoprotein cholesterol ratio and mortality in Chinese maintenance haemodialysis patients: a retrospective cohort study

OBJECTIVE

To investigate the relationship between the triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio and all-cause and cardiovascular (CV) mortality in Chinese haemodialysis (HD) patients.

DESIGN

Retrospective cohort study.

SETTING

Patients from June 2015 to September 2016 and followed through September 2021 were categorised into quartiles according to the follow-up averaged TG/HDL-C ratio. The association between TG/HDL-C and mortality was examined by univariate and multivariate time-varying Cox regression analyses. The C-index was used to assess the predictive accuracy of the Cox regression models.

PARTICIPANTS

A total of 534 maintenance HD patients were enrolled.

PRIMARY AND SECONDARY OUTCOME MEASURES

The outcomes were all-cause death and CV mortality.

RESULTS

During the median follow-up of 61 months, 207 patients died, with 94 (45.4%) classified as CV death. After adjusting for confounders, multivariate time-varying Cox regression analysis showed that the quartile 4 group (TG/HDL-C ≥2.64) was associated with decreased all-cause mortality (adjusted HR 0.51, 95% CI 0.33-0.77, p=0.001) and CV mortality (adjusted HR 0.31; 95% CI 0.16 to 0.62; p=0.001) in maintenance HD patients. Model 1 of all-cause mortality achieved a C-index of 0.72 (95% CI 0.68 to 0.75), and model 2 achieved a C-index of 0.77 (95% CI 0.73 to 0.82). The C-index for model 1 in CV mortality was 0.74 (95% CI 0.70 to 0.77), and the C-index for model 2 was 0.80 (95% CI 0.75 to 0.84).

CONCLUSIONS

High TG/HDL-C was associated with decreased all-cause and CV mortality in HD patients.

The Sizes and Composition of HDL-Cholesterol Are Significantly Associated with Inflammation in Rheumatoid Arthritis Patients

Rheumatoid arthritis (RA), a chronic inflammatory disease, carries a significant burden of atherosclerotic cardiovascular diseases (ASCVD). With their heterogeneous composition, high-density lipoprotein (HDL) particles have varied athero-protective properties, and some may even increase ASCVD risk. In this prospective and cross-sectional study, we aimed to examine the relationship between HDL sizes/metabolites and inflammation in RA. Using ¹H-NMR-based lipid/metabolomics, differential HDL-related metabolites were identified between RA patients and healthy control (HC) subjects and between RA patients with and without anti-citrullinated peptide antibodies (ACPA). The correlation between the discriminative HDL-related metabolites and C-reactive protein (CRP) was evaluated in RA patients. RA patients demonstrated higher particle number, lipids, cholesterol, cholesterol ester, free cholesterol, and phospholipids in large/very large-sized HDLs. ACPA-positive patients had higher L-HDL-C and L-HDL-CE but lower small-/medium-sized HDL-TG levels than ACPA-negative patients. An inverse correlation was found between CRP levels and small-sized HDLs. Janus kinase inhibitor treatment was associated with increased serum small-sized HDL-related metabolites and decreased CRP levels. We are the first to reveal the significant associations between RA inflammation and HDL sizes/metabolites. A potential link between ACPA positivity and changes in serum levels of HDL-related metabolites was also observed in RA patients.

Embracing nanomaterials' interactions with the innate immune system

Immunotherapy has firmly established itself as a compelling avenue for treating disease. Although many clinically approved immunotherapeutics engage the adaptive immune system, therapeutically targeting the innate immune system remains much less explored. Nanomedicine offers a compelling opportunity for innate immune system engagement, as many nanomaterials inherently interact with myeloid cells (e.g., monocytes, macrophages, neutrophils, and dendritic cells) or can be functionalized to target their cell-surface receptors. Here, we provide a perspective on exploiting nanomaterials for innate immune system regulation. We focus on specific nanomaterial design parameters, including size, form, rigidity, charge, and surface decoration. Furthermore, we examine the potential of high-throughput screening and machine learning, while also providing recommendations for advancing the field. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

The Potential Role of Electronegative High-Density Lipoprotein H5 Subfraction in RA-Related Atherosclerosis

Although the heterogeneity of high-density lipoprotein-cholesterol (HDL-c) composition is associated with atherosclerotic cardiovascular risk, the link between electronegative subfractions of HDL-c and atherosclerosis in rheumatoid arthritis (RA) remains unknown. We examined the association of the percentage of the most electronegative subfraction of HDL-c (H5%) and RA-related atherosclerosis. Using anion-exchange purification/fast-protein liquid chromatography, we demonstrated significantly higher H5% in patients (median, 7.2%) than HC (2.8%, p < 0.005). Multivariable regression analysis revealed H5% as a significant predictor for subclinical atherosclerosis. We subsequently explored atherogenic role of H5 using cell-based assay. The results showed significantly higher levels of IL-1β and IL-8 mRNA in H5-treated (mean ± SD, 4.45 ± 1.22 folds, 6.02 ± 1.43-folds, respectively) than H1-treated monocytes (0.89 ± 0.18-folds, 1.03 ± 0.26-folds, respectively, both p < 0.001). In macrophages, H5 upregulated the mRNA and protein expression of IL-1β and IL-8 in a dose-dependent manner, and their expression levels were significantly higher than H1-treated macrophages (all p < 0.001). H5 induced more foam cell formation compared with H1-treated macrophages (p < 0.005). In addition, H5 has significantly lower cholesterol efflux capacity than H1 (p < 0.005). The results of nanoLC-MS/MS approach reveal that the best discriminator between high-H5% and normal-H5% is Apo(a), the main constituent of Lp(a). Moreover, Lp(a) level is a significant predictor for high-H5%. These observations suggest that H5 is involved in RA-related atherosclerosis.

Different associations between HDL cholesterol and cardiovascular diseases in people with diabetes mellitus and people without diabetes mellitus: a prospective community-based study

BACKGROUND

Experimental studies have found that the functionality of HDL cholesterol may be lost in the presence of diabetes mellitus (DM).

OBJECTIVES

We aimed to elucidate whether DM modified the association between HDL-cholesterol concentrations and cardiovascular disease (CVD) outcomes.

METHODS

Included were 91,354 Chinese adults (8244 participants with DM and 83,110 participants without DM) free of CVD or cancer at baseline (2006) and without use of lipid-lowering drugs at baseline and during follow-up. The primary endpoint of interest was a composite of CVDs (myocardial infarction, ischemic stroke, and hemorrhagic stroke). Cumulative average HDL-cholesterol concentrations were calculated from all available HDL-cholesterol measures at baseline (2006) and during the follow-up period (2008, 2010, 2012, and 2014).

RESULTS

During a mean of 10.4 y of follow-up, there were 5076 CVD events identified. There was a significant interaction between DM and HDL-cholesterol concentrations on CVD risk (Pinteraction = 0.003). The association between HDL-cholesterol concentrations and CVD followed a U-shaped curve in individuals without DM (Pnonlinearity < 0.001). The adjusted HR of CVD was 1.26 (95% CI: 1.07, 1.48) for HDL-cholesterol concentrations < 1.04 mmol/L and 1.76 (95% CI: 1.53, 2.03) for HDL-cholesterol concentrations > 2.07 mmol/L, relative to the lowest-risk group (HDL-cholesterol concentrations of 1.30-1.42 mmol/L). In participants with DM, higher HDL-cholesterol concentrations were associated with a higher risk of CVD, in a dose-response manner (Pnonlinearity = 0.44; Ptrend < 0.001). The adjusted HR of CVD was 1.62 (95% CI: 1.19, 2.20) for HDL-cholesterol concentrations >2.07 mmol/L, relative to HDL-cholesterol concentrations of 1.30-1.42 mmol/L.

CONCLUSIONS

High HDL-cholesterol concentrations were paradoxically associated with high risk of composite CVD outcomes in individuals with or without DM. However, low HDL-cholesterol concentrations failed to predict future CVD risk in individuals with DM.

A modular approach toward producing nanotherapeutics targeting the innate immune system

Immunotherapies controlling the adaptive immune system are firmly established, but regulating the innate immune system remains much less explored. The intrinsic interactions between nanoparticles and phagocytic myeloid cells make these materials especially suited for engaging the innate immune system. However, developing nanotherapeutics is an elaborate process. Here, we demonstrate a modular approach that facilitates efficiently incorporating a broad variety of drugs in a nanobiologic platform. Using a microfluidic formulation strategy, we produced apolipoprotein A1-based nanobiologics with favorable innate immune system-engaging properties as evaluated by in vivo screening. Subsequently, rapamycin and three small-molecule inhibitors were derivatized with lipophilic promoieties, ensuring their seamless incorporation and efficient retention in nanobiologics. A short regimen of intravenously administered rapamycin-loaded nanobiologics (mTORi-NBs) significantly prolonged allograft survival in a heart transplantation mouse model. Last, we studied mTORi-NB biodistribution in nonhuman primates by PET/MR imaging and evaluated its safety, paving the way for clinical translation.

Lyso-diacylglyceryltrimethylhomoserine (lyso-DGTS) isolated from Nannochloropsis microalgae improves high-density lipoprotein (HDL) functions

Many population studies have shown that blood concentrations of high-density lipoprotein (HDL) cholesterol are inversely correlated with risk of cardiovascular disease (CVD). However, in recent studies, increasing blood HDL cholesterol concentrations failed to reduce CVD events. On the other hand, studies suggest that improving HDL quality can be a more efficient tool for assessing atherosclerotic risk than simply measuring blood HDL cholesterol concentration. Thus, improving HDL activity using natural substances might be a useful therapeutic approach to reducing CVD risk. We previously isolated a novel active compound from Nannochloropsis microalgae termed lyso-diacylglyceryltrimethylhomoserine (lyso-DGTS), which increased activity of paraoxonase 1, the main antioxidant enzyme associated with HDL. Here we examined the effect of lyso-DGTS on HDL quality and function. Tryptophan-fluorescence-quenching assay showed that lyso-DGTS interacts spontaneously with the entire HDL lipoprotein and with apolipoprotein A1 (ApoA1), the major structural and functional HDL protein, with high affinity (K_a = 2.17 × 10⁴  M^-1 at 37°C). Lyso-DGTS added to HDL and to ApoA1 increased cholesterol efflux from macrophage cells, the main antiatherogenic function of HDL, dose-dependently, and significantly increased HDL's ability to induce nitric oxide production from endothelial cells. In-vivo supplementation of lyso-DGTS to the circulation of mice fed a high-fat diet via osmotic mini-pumps implanted subcutaneously enhanced HDL anti-inflammatory effect significantly as compared to controls. Our findings suggest that lyso-DGTS may have a beneficial effect in decreasing atherosclerosis risk by interacting with HDL particles and improving their quality and antiatherogenic functions.

Regulation of lipid rafts, angiogenesis and inflammation by AIBP

PURPOSE OF REVIEW

Recent studies demonstrate an important role of the secreted apolipoprotein A-I binding protein (AIBP) in regulation of cholesterol efflux and lipid rafts. The article discusses these findings in the context of angiogenesis and inflammation.

RECENT FINDINGS

Lipid rafts are cholesterol-rich and sphingomyelin-rich membrane domains in which many receptor complexes assemble upon activation. AIBP mediates selective cholesterol efflux, in part via binding to toll-like receptor-4 (TLR4) in activated macrophages and microglia, and thus reverses lipid raft increases in activated cells. Recent articles report AIBP regulation of vascular endothelial growth factor receptor-2, Notch1 and TLR4 function. In zebrafish and mouse animal models, AIBP deficiency results in accelerated angiogenesis, increased inflammation and exacerbated atherosclerosis. Spinal delivery of recombinant AIBP reduces neuraxial inflammation and reverses persistent pain state in a mouse model of chemotherapy-induced polyneuropathy. Inhalation of recombinant AIBP reduces lipopolysaccharide-induced acute lung injury in mice. These findings are discussed in the perspective of AIBP's proposed other function, as an NAD(P)H hydrate epimerase, evolving into a regulator of cholesterol trafficking and lipid rafts.

SUMMARY

Novel findings of AIBP regulatory circuitry affecting lipid rafts and related cellular processes may provide new therapeutic avenues for angiogenic and inflammatory diseases.

AIBP augments cholesterol efflux from alveolar macrophages to surfactant and reduces acute lung inflammation

Acute respiratory distress syndrome (ARDS) is characterized by an excessive pulmonary inflammatory response. Removal of excess cholesterol from the plasma membrane of inflammatory cells helps reduce their activation. The secreted apolipoprotein A-I binding protein (AIBP) has been shown to augment cholesterol efflux from endothelial cells to the plasma lipoprotein HDL. Here, we find that AIBP was expressed in inflammatory cells in the human lung and was secreted into the bronchoalveolar space in mice subjected to inhalation of LPS. AIBP bound surfactant protein B and increased cholesterol efflux from alveolar macrophages to calfactant, a therapeutic surfactant formulation. In vitro, AIBP in the presence of surfactant reduced LPS-induced p65, ERK1/2 and p38 phosphorylation, and IL-6 secretion by alveolar macrophages. In vivo, inhalation of AIBP significantly reduced LPS-induced airspace neutrophilia, alveolar capillary leak, and secretion of IL-6. These results suggest that, similar to HDL in plasma, surfactant serves as a cholesterol acceptor in the lung. Furthermore, lung injury increases pulmonary AIBP expression, which likely serves to promote cholesterol efflux to surfactant and reduce inflammation.

Lyso-DGTS lipid isolated from microalgae enhances PON1 activities in vitro and in vivo, increases PON1 penetration into macrophages and decreases cellular lipid accumulation

High-density lipoprotein (HDL) plays an important role in preventing atherosclerosis. The antioxidant effect of HDL is mostly associated with paraoxonase 1 (PON1) activity. Increasing PON1 activity using nutrients might improve HDL function and quality and thus, decrease atherosclerotic risk. We previously isolated and identified a novel active compound, lyso-DGTS (C20:5,0) from Nannochloropsis sp. ethanol extract. In the present study, its effect on PON1 activities was examined and the mechanism by which the compound affects PON1 activity was explored. Lyso-DGTS elevated recombinant PON1 (rePON1) lactonase and esterase activities in a dose- and time-responsive manner, and further stabilized and preserved rePON1 lactonase activity. Incubation of lyso-DGTS with human serum for 4 h at 37 °C also increased PON1 lactonase activity in a dose-responsive manner. Using tryptophan-fluorescence-quenching assay, lyso-DGTS was found to interact with rePON1 spontaneously with negative free energy (ΔG = -22.87 kJ mol^-1 at 25 °C). Thermodynamic parameters and molecular modeling calculations showed that the main interaction of lyso-DGTS with the enzyme is through a hydrogen bond with supporting van der Waals interactions. Furthermore, lyso-DGTS significantly increased rePON1 influx into macrophages and prevented lipid accumulation in macrophages stimulated with oxidized low-density lipid dose-dependently. In vivo supplementation of lyso-DGTS to the circulation of mice fed a high-fat diet via osmotic mini-pumps implanted subcutaneously significantly increased serum PON1 lactonase activity and decreased serum glucose concentrations to the level of mice fed a normal diet. Our findings suggest a beneficial effect of lyso-DGTS on increasing PON1 activity and thus, improving HDL quality and atherosclerotic risk factors. © 2018 BioFactors, 44(3):299-310, 2018.

Modified risk associations of lipoproteins and apolipoproteins by chronic low-grade inflammation

INTRODUCTION

Lipoproteins and the apolipoproteins (apo) that they carry are major determinants of cardiovascular diseases (CVD) as well as metabolic, renal and inflammatory chronic disorders either directly or through mediation of risk factors. The notion that elevated low-density lipoprotein cholesterol (LDL-C) and apoB levels are related to the acquisition of CVD and, high-density lipoprotein cholesterol (HDL-C) and apoA-I indicate protection against CVD has been challenged in the past decade. Advanced age, adiposity, ethnicity or impaired glucose intolerance rendered autoimmune activation in an environment of pro-inflammatory state/oxidative stress and may disrupt the linear risk association between lipoproteins. Areas covered: This review summarizes the modified risk associations of lipoproteins and apolipoprotein by an environment of chronic systemic low-grade inflammation with special emphasis on the non-linear relationship of lipoprotein(a) [Lp(a)], a biomarker of renewed interest in cardiometabolic risk. Expert commentary: It seems that autoimmune activation in an environment of pro-inflammatory state/oxidative stress not only disrupts the linear risk association between lipoproteins, but also may cause interference in immunoassays. Hence, methodological improvement in immunoassays and much further research focusing on population segments susceptible to a pro-inflammatory state is necessary for further advances in knowledge.

Effect of low and high HDL-C levels on the prognosis of lupus nephritis patients: a prospective cohort study

Background

Few data has been available on the effect of serum HDL-C levels on the prognosis of lupus nephritis (LN) patients. The present study therefore aimed to explore the effect of serum HDL-C levels on LN patients.

Methods

We included 775 patients with follow-up information registered in an LN database between 1 January 2006 and 31 December 2011. The patients were divided into groups with low, intermediate and high HDL-C, according to NCEP ATPIII criteria. Cox regression analyses were used to explore the effects of HDL-C levels on end-stage renal disease (ESRD), all-cause mortality and cardiovascular disease (CVD) mortality.

Results

During a median follow-up of 56 months (3–206 months), 71 (9.2%) had ESRD. 84 (10.8%) deaths occurred, 17 (20.2%) of which were due to CVD. There was no statistically significant association of HDL-C category or continuous HDL-C levels with ESRD in the total cohort, but in subgroup analyses by eGFR, with each 0.1 mmol/L increase in HDL-C level, adjusted HRs for ESRD were 0.92 (95% CI: 0.83–1.04, P = 0.173) for eGFR ≥60 ml/min/1.73m² and 1.11 (95% CI: 1.01–1.23, P = 0.036) for eGFR <60 ml/min/1.73m². The effect of the interaction between eGFR category and serum HDL-C level on ESRD was statistically significant (β = −1.738, P = 0.005). Low HDL-C was associated with all-cause mortality (HR = 2.16, 95% CI: 1.06–4.40, P = 0.033) with intermediate HDL-C as reference category after adjusting for several variables.

Conclusions

Our results demonstrate that high HDL-C levels were associated with increased risk of ESRD in LN patients with advanced renal dysfunction. While low HDL-C levels were associated with increased risk of all-cause mortality in LN patients.

Trial registration

ClinicalTrials.gov Identifier: NCT03001973, 22 December 2016 retrospectively registered.

Electronic supplementary material

The online version of this article (10.1186/s12944-017-0622-3) contains supplementary material, which is available to authorized users.

Automation of PRM-dependent D3-Leu tracer enrichment in HDL to study the metabolism of apoA-I, LCAT and other apolipoproteins

We developed an automated quantification workflow for PRM-enabled detection of D3-Leu labeled apoA-I in high-density lipoprotein (HDL) isolated from humans. Subjects received a bolus injection of D3-Leu and blood was drawn at eight time points over three days. HDL was isolated and separated into six size fractions for subsequent proteolysis and PRM analysis for the detection of D3-Leu signal from ∼0.03 to 0.6% enrichment. We implemented an intensity-based quantification approach that takes advantage of high-resolution/accurate mass PRM scans to identify the D3-Leu 2HM3 ion from non-specific peaks. Our workflow includes five modules for extracting the targeted PRM peak intensities (XPIs): Peak centroiding, noise removal, fragment ion matching using Δm/z windows, nine intensity quantification options, and validation and visualization outputs. We optimized the XPI workflow using in vitro synthesized and clinical samples of D0/D3-Leu labeled apoA-I. Three subjects' apoA-I enrichment curves in six HDL size fractions, and LCAT, apoA-II and apoE from two size fractions were generated within a few hours. Our PRM strategy and automated quantification workflow will expedite the turnaround of HDL apoA-I metabolism data in clinical studies that aim to understand and treat the mechanisms behind dyslipidemia.

Unbiased and targeted mass spectrometry for the HDL proteome

PURPOSE OF REVIEW

Mass spectrometry is an ever evolving technology that is equipped with a variety of tools for protein research. Some lipoprotein studies, especially those pertaining to HDL biology, have been exploiting the versatility of mass spectrometry to understand HDL function through its proteome. Despite the role of mass spectrometry in advancing research as a whole, however, the technology remains obscure to those without hands on experience, but still wishing to understand it. In this review, we walk the reader through the coevolution of common mass spectrometry workflows and HDL research, starting from the basic unbiased mass spectrometry methods used to profile the HDL proteome to the most recent targeted methods that have enabled an unprecedented view of HDL metabolism.

RECENT FINDINGS

Unbiased global proteomics have demonstrated that the HDL proteome is organized into subgroups across the HDL size fractions providing further evidence that HDL functional heterogeneity is in part governed by its varying protein constituents. Parallel reaction monitoring, a novel targeted mass spectrometry method, was used to monitor the metabolism of HDL apolipoproteins in humans and revealed that apolipoproteins contained within the same HDL size fraction exhibit diverse metabolic properties.

SUMMARY

Mass spectrometry provides a variety of tools and strategies to facilitate understanding, through its proteins, the complex biology of HDL.

Multiple apolipoprotein kinetics measured in human HDL by high-resolution/accurate mass parallel reaction monitoring

Endogenous labeling with stable isotopes is used to study the metabolism of proteins in vivo. However, traditional detection methods such as GC/MS cannot measure tracer enrichment in multiple proteins simultaneously, and multiple reaction monitoring MS cannot measure precisely the low tracer enrichment in slowly turning-over proteins as in HDL. We exploited the versatility of the high-resolution/accurate mass (HR/AM) quadrupole Orbitrap for proteomic analysis of five HDL sizes. We identified 58 proteins in HDL that were shared among three humans and that were organized into five subproteomes according to HDL size. For seven of these proteins, apoA-I, apoA-II, apoA-IV, apoC-III, apoD, apoE, and apoM, we performed parallel reaction monitoring (PRM) to measure trideuterated leucine tracer enrichment between 0.03 to 1.0% in vivo, as required to study their metabolism. The results were suitable for multicompartmental modeling in all except apoD. These apolipoproteins in each HDL size mainly originated directly from the source compartment, presumably the liver and intestine. Flux of apolipoproteins from smaller to larger HDL or the reverse contributed only slightly to apolipoprotein metabolism. These novel findings on HDL apolipoprotein metabolism demonstrate the analytical breadth and scope of the HR/AM-PRM technology to perform metabolic research.

Effect of short-term, high-dose methylprednisolone on oxidative stress in children with acute immune thrombocytopenia

Background

Immune thrombocytopenia (ITP) is the most common cause of acquired childhood thrombocytopenia and is characterized by increased immune-mediated destruction of circulating thrombocytes. Oxidative damage may be involved in ITP pathogenesis; paraoxonase (PON) and arylesterase (ARE) enzymes are closely associated with the cellular antioxidant system. We investigated the effect of short-term high-dose methylprednisolone (HDMP) treatment on the total oxidant status (TOS), total antioxidant capacity (TAC), oxidative stress index (OSI), and PON and ARE enzymatic activity in children with acute ITP.

Methods

Thirty children with acute ITP constituted the study group and 30 healthy children constituted the control group. Children with acute ITP were treated with HDMP: 30 mg/kg for 3 days, then 20 mg/kg for 4 days. The TOS, TAC, OSI, PON, and ARE levels were determined before and after 7 days of HDMP treatment.

Results

The TAC level (P<0.001), and PON (P<0.001) and ARE (P=0.001) activities were lower and the TOS (P=0.003) and OSI (P<0.001) levels were higher in children with acute ITP than those in healthy children in the control group. We also observed statistically significant increases in the TAC (P<0.01), PON (P<0.001) and ARE levels (P=0.001) and decreases in the TOS (P<0.05) and OSI levels (P<0.05) with 7 days of HDMP treatment compared to their values before treatment.

Conclusion

Our study demonstrated increased oxidative stress (OSI and TOC) and decreased antioxidant capacity (TAC), PON, and ARE in ITP patients and that steroid treatment could be effective in reducing the oxidative stress.

Mass spectrometry meets the challenge of understanding the complexity of the lipoproteome: recent findings regarding proteins involved in dyslipidemia and cardiovascular disease

Despite the fact that link between dyslipidemia and atherosclerosis was made over 100 years ago, atherosclerosis remains a major cause of morbidity and mortality worldwide. Major efforts focus towards understanding lipid metabolism, particularly by studying its particle compartments in circulation: the lipoproteins. In recent years, mass spectrometry has played an integral role in the deep sequencing of the lipoproteome and in metabolism studies conducted in vivo. This review highlights the path of lipoprotein research towards state-of-the-art mass spectrometry with special emphasis on the method of selected reaction monitoring and its impact on apolipoprotein metabolism studies. Also presented is what is expected for the lipoprotein field with the recent advent of high resolution/accurate mass parallel reaction monitoring mass spectrometry. The benefits of high resolution/accurate mass measurements are demonstrated by example instrument workflows and by detailing a novel method to quantify very low levels of circulating proprotein convertase subtilisin-kexin type 9 in rabbit. It is anticipated that future clinical studies or clinical trials aimed to treat dyslipidemia by manipulating key regulatory proteins will benefit from the new and exciting opportunities afforded by the latest technologies in mass spectrometry.

New CETP inhibitor K-312 reduces PCSK9 expression: a potential effect on LDL cholesterol metabolism

Despite significant reduction of cardiovascular events by statin treatment, substantial residual risk persists, driving emerging needs for the development of new therapies. We identified a novel cholesteryl ester transfer protein (CETP) inhibitor, K-312, that raises HDL and lowers LDL cholesterol levels in animals. K-312 also suppresses hepatocyte expression of proprotein convertase subtilisin/kexin 9 (PCSK9), a molecule that increases LDL cholesterol. We explored the underlying mechanism for the reduction of PCSK9 expression by K-312. K-312 inhibited in vitro human plasma CETP activity (IC50; 0.06 μM). Administration of K-312 to cholesterol-fed New Zealand White rabbits for 18 wk raised HDL cholesterol, decreased LDL cholesterol, and attenuated aortic atherosclerosis. Our search for additional beneficial characteristics of this compound revealed that K-312 decreases PCSK9 expression in human primary hepatocytes and in the human hepatoma cell line HepG2. siRNA silencing of CETP in HepG2 did not compromise the suppression of PCSK9 by K-312, suggesting a mechanism independent of CETP. In HepG2 cells, K-312 treatment decreased the active forms of sterol regulatory element-binding proteins (SREBP-1 and -2) that regulate promoter activity of PCSK9. Chromatin immunoprecipitation assays demonstrated that K-312 decreased the occupancy of SREBP-1 and SREBP-2 on the sterol regulatory element of the PCSK9 promoter. PCSK9 protein levels decreased by K-312 treatment in the circulating blood of cholesterol-fed rabbits, as determined by two independent mass spectrometry approaches, including the recently developed, highly sensitive parallel reaction monitoring method. New CETP inhibitor K-312 decreases LDL cholesterol and PCSK9 levels, serving as a new therapy for dyslipidemia and cardiovascular disease.

Therapeutic ultrasound: Increased HDL-Cholesterol following infusions of acoustic microspheres and apolipoprotein A-I plasmids

BACKGROUND

Low levels of HDL-C are an independent cardiovascular risk factor associated with increased premature cardiovascular death. However, HDL-C therapies historically have been limited by issues relating to immunogenicity, hepatotoxicity and scalability, and have been ineffective in clinical trials.

OBJECTIVE

We examined the feasibility of using injectable acoustic microspheres to locally deliver human ApoA-I DNA plasmids in a pre-clinical model and quantify increased production of HDL-C in vivo.

METHODS

Our novel site-specific gene delivery system was examined in naïve rat model and comprised the following steps: (1) intravenous co-administration of a solution containing acoustically active microspheres (Optison™, GE Healthcare, Princeton, New Jersey) and human ApoA-I plasmids; (2) ultrasound verification of the presence of the microspheres within the liver vasculature; (3) External application of locally-directed acoustic energy, (4) induction of microsphere disruption and in situ sonoporation; (4) ApoA-I plasmid hepatic uptake; (5) transcription and expression of human ApoA-I protein; and (6) elevation of serum HDL-C.

RESULTS

Co-administration of ApoA-I plasmids and acoustic microspheres, activated by external ultrasound energy, resulted in transcription and production of human ApoA-I protein and elevated serum HDL-C in rats (up to 61%; p-value < 0.05).

CONCLUSIONS

HDL-C was increased in rats following ultrasound directed delivery of human ApoA-I plasmids by microsphere sonoporation. The present method provides a novel approach to promote ApoA-I synthesis and nascent HDL-C elevation, potentially permitting the use of a minimally-invasive ultrasound-based, gene delivery system for treating individuals with low HDL-C.

HDL cholesterol, apolipoproteins, and cardiovascular risk in hemodialysis patients

High concentrations of HDL cholesterol are considered to indicate efficient reverse cholesterol transport and to protect from atherosclerosis. However, HDL has been suggested to be dysfunctional in ESRD. Hence, our main objective was to investigate the effect of HDL cholesterol on outcomes in maintenance hemodialysis patients with diabetes. Moreover, we investigated the associations between the major protein components of HDL (apoA1, apoA2, and apoC3) and end points. We performed an exploratory, post hoc analysis with 1255 participants (677 men and 578 women) of the German Diabetes Dialysis study. The mean age was 66.3 years and the mean body mass index was 28.0 kg/m(2). The primary end point was a composite of cardiac death, myocardial infarction, and stroke. The secondary end point included all-cause mortality. The mean duration of follow-up was 3.9 years. A total of 31.3% of the study participants reached the primary end point and 49.1% died from any cause. HDL cholesterol and apoA1 and apoC3 quartiles were not related to end points. However, there was a trend toward an inverse association between apoA2 and all-cause mortality. The hazard ratio for death from any cause in the fourth quartile compared with the first quartile of apoA2 was 0.63 (95% confidence interval, 0.40 to 0.89). The lack of an association between HDL cholesterol and cardiovascular risk may support the concept of dysfunctional HDL in hemodialysis. The possible beneficial effect of apoA2 on survival requires confirmation in future studies.

Clinical Strategies for Managing Dyslipidemias

Dyslipidemia is defined as elevated fasting blood levels of total cholesterol (TC), and its primary lipoprotein carrier—low-density lipoprotein (LDL), triglycerides (TG), or reduced high-density lipoprotein (HDL), alone, or in combination (mixed dyslipidemia). Dyslipidemia is well known to be associated with cardiovascular disease (CVD) risk. All patients with dyslipidemia should initiate therapeutic lifestyle changes to target lifestyle-related factors such as physical inactivity, dietary habits, and obesity. The combination of a proper dietary plan and regular aerobic exercise has been reported to lower TC, LDL-C, and TG by 7% to 18%, while increasing HDL-C by 2% to 18%. Numerous pharmacological therapies are available and aggressive therapy using a HMG-CoA reductase (3-hydroxy-3-methyl-glutaryl coenzyme A reductase) inhibitor (statins) should be initiated if lifestyle therapy is not enough to achieve optimal lipid levels with a primary target of lowering LDL-C levels. Aggressive treatment of dyslipidemia with maximal dosage of statin drugs have been reported to reduce LDL-C by 30% to 60%. If mixed dyslipidemia is present, a combination therapy with statin, niacin, cholestyramine, or fibrates should be initiated to reduce the risk of CVD events. These strategies have been shown to reduce CVD risk and optimize LDL-C levels in primary and secondary prevention of CVD.

Elevated high-density lipoprotein cholesterol and cardiovascular mortality in maintenance hemodialysis patients

BACKGROUND

High-density lipoprotein (HDL) confers protection against atherosclerosis by several different mechanisms. Although in the general population, increasing levels of HDL are associated with reduced cardiovascular (CV) mortality, this association is not well known in patients with chronic disease states such as end-stage renal disease. We hypothesize that the association of serum HDL concentration and its ratio to total cholesterol with all-cause and CV mortality in hemodialysis patients is different from the general population.

METHODS

A 3-year (July 2004 to June 2007) cohort of 33 109 chronic hemodialysis patients was studied in the USA in the dialysis clinics where lipid profile was measured in at least 50% of all outpatients of the clinic during a given calendar quarter. Cox proportional hazard models were adjusted for demographics and case-mix variables and cubic splines were plotted.

RESULTS

Higher HDL concentrations up to 50 mg/dL were associated with better overall survival, while HDL at 60 mg/dL and above was associated with a rise in all-cause and CV mortality. All-cause and CV mortality hazard ratio was 1.28 (1.20-1.38) and 1.08 (1.01-1.16) for HDL <30 mg/dL and 1.05 (1.00-1.10) and 1.08 (1.00-1.16) for HDL ≥ 60 mg/dL, respectively (reference: HDL: 30-<60 mg/dL).

CONCLUSIONS

In contrast to the general population, low total cholesterol to HDL ratio was associated with higher mortality in hemodialysis patients. A U-shaped association between HDL cholesterol level and all-cause and CV mortality exists in hemodialysis patients with HDL between 50 and <60 mg/dL exhibiting the best survival. The underlying mechanisms responsible for these seemingly paradoxical associations await further investigation.

High-density lipoprotein cholesterol, size, particle number, and residual vascular risk after potent statin therapy

BACKGROUND

Chemically measured high-density lipoprotein cholesterol (HDL-C) may not be the best clinical measure of HDL. Little is known about alternative HDL measures such as HDL size or particle number (HDL-P) as determinants of residual risk after potent statin therapy.

METHODS AND RESULTS

In Justification for the Use of statins in Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER), HDL size and HDL-P were measured by nuclear magnetic resonance spectroscopy, and HDL-C and apolipoprotein A-I (apoA-I) were chemically assayed in 10 886 participants without cardiovascular disease (CVD) before and after random allocation to rosuvastatin 20 mg/d or placebo. Levels were examined with first CVD (n=234). HDL-P correlated better with apoA-I (Spearman r=0.69, P<0.0001) than with HDL-C (r=0.55, P<0.0001). Rosuvastatin lowered low-density lipoprotein cholesterol (49%) and raised HDL-C (6.1%), apoA-I (2.1%), HDL-P (3.8%), and HDL size (1.2%); all P<0.0001. Among placebo-allocated individuals, on-treatment HDL-C, apoA-I, and HDL-P had similar inverse associations with CVD (risk factor-adjusted hazard ratio and 95% confidence interval per 1 standard deviation: 0.79 [0.63-0.98], 0.75 [0.62-0.92], and 0.81 [0.67-0.97], respectively). Among rosuvastatin-allocated individuals, on-treatment HDL-P had a statistically significant and somewhat stronger association with CVD (0.73, 0.57-0.93, P=0.01) than HDL-C (0.82, 0.63-1.08, P=0.16) or apoA-I (0.86, 0.67-1.10, P=0.22). Among rosuvastatin-allocated individuals, on-treatment HDL-P remained significant (0.72, 0.53-0.97, P=0.03) after additionally adjusting for HDL-C. In risk factor-adjusted models, HDL size showed no significant association with CVD.

CONCLUSIONS

In the setting of potent statin therapy, HDL particle number may be a better marker of residual risk than chemically measured HDL-C or apoA-I. This has potential implications for evaluating novel therapies targeting HDL.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00239681.

High levels of asymmetric dimethylarginine are strongly associated with low HDL in patients with acute myocardial infarction

Objectives

Low levels of high-density lipoprotein (HDL) cholesterol are associated with an increased risk of acute myocardial infarction possibly through impaired endothelial atheroprotection and decreased nitric oxide (NO) bioavailability. Asymmetric dimethylarginine (ADMA) mediates endothelial function by inhibiting nitric oxide synthase activity. In patients with acute myocardial infarction, we investigated the relationship between serum levels of HDL and ADMA.

Approach and Results

Blood samples from 612 consecutive patients hospitalized for acute MI <24 hours after symptom onset were taken on admission. Serum levels of ADMA, its stereoisomer, symmetric dimethylarginine (SDMA) and L-arginine were determined using high-performance liquid chromatography. Patients with low HDL (<40 mg/dL for men and <50 mg/dL for women) were compared with patients with higher HDL. Most patients (59%) had low HDL levels. Median ADMA levels were markedly higher in the low HDL group (0.69 vs. 0.50 µmole/L, p<0.001). In contrast, SDMA and L-arginine levels were similar for the two groups (p = 0.120 and p = 0.064). Notably, ADMA, but not SDMA or L-arginine, was inversely correlated with HDL (r = −0.311, p<0.001). In stratified analysis, this relationship was only found for low HDL levels (r = −0.265, p<0.001), but not when HDL levels were higher (r = −0.077, p = 0.225). By multivariate logistic regression analysis, ADMA level was strongly associated with low HDL levels (OR(95%CI):6.06(3.48–10.53), p<0.001), beyond traditional confounding factors.

Conclusions

Our large population-based study showed for the first time a strong inverse relationship between HDL and ADMA in myocardial infarction patients, suggesting a functional interaction between HDL and endothelium, beyond metabolic conditions associated with low HDL levels.