HDL-associated Apolipoprotein Research Articles

Vitamin D status affects proteomic profile of HDL-associated proteins and inflammatory mediators in dyslipidemia

Vitamin D deficiency and dyslipidemia have substantial implications for human health globally. Vitamin D is essential for bone metabolism and immune modulation, and its insufficiency is linked to various chronic inflammatory conditions. Dyslipidemia, characterized by low levels of high-density lipoprotein (HDL) and elevated levels of low-density lipoprotein (LDL) and triglycerides, is also prevalent. Previous research has shown a connection between vitamin D deficiency and low HDL, but the precise mechanism by which vitamin D influences HDL production and its anti-inflammatory properties remains unclear. This study aimed to investigate the proteomic profiles of individuals with and without vitamin D deficiency and dyslipidemia, specifically focusing on the effects of vitamin D on HDL production, its anti-inflammatory potential, and the molecular pathways associated with vitamin D deficiency and dyslipidemia, particularly inflammation and cancer pathways. By analyzing the proteomic profiles of 274 participants from the Qatar Biobank database, we identified 1301 proteins. Our findings indicated a decrease in HDL-associated apolipoproteins (ApoM and ApoD) in individuals with both dyslipidemia and vitamin D deficiency. Conversely, participants with these conditions exhibited increased expression of acute-phase proteins (SAA1 and SOD1), which are associated with inflammation. Pathway enrichment analysis revealed heightened inflammatory activity in individuals with vitamin D deficiency and dyslipidemia, with notable enrichments in pathways such as MAPK, JAK-STAT, Ras signaling, cytokine-cytokine receptor interaction, AGE-RAGE, ErbB signaling, and cancer pathways. Overall, cases of vitamin D deficiency showed enrichment in inflammation pathways, while individuals with both vitamin D deficiency and dyslipidemia demonstrated enhanced activation of cancer and inflammation pathways.

Stability Characterization of the Novel Anti-Cancer HM-10/10 HDL-Mimetic Peptide.

Epithelial adenocarcinoma of the ovary and colon are associated with the highest rates of cancer-related deaths in women in the U.S. The literature supports the role of HDL-associated apolipoproteins in the treatment of cancer and other pro-inflammatory diseases. Previously, we developed a novel 20-amino acid mimetic peptide, HM-10/10, which potently inhibits tumor development and growth in colon and ovarian cancer. Here, we report the properties of HM-10/10 relative to its stability in vitro. The results demonstrated that HM-10/10 had the highest half-life in human plasma compared to plasma from other species tested. HM-10/10 demonstrated stability in human plasma and simulated gastric environment, increasing its promise as an oral pharmaceutical. However, under conditions modeling the small intestine, HM-10/10 demonstrated significant degradation, likely due to the peptidases encountered therein. Furthermore, HM-10/10 demonstrated no evidence of time-dependent drug-drug interactions, although it demonstrated CYP450 induction slightly above cutoff. As proteolytic degradation is a common limitation of peptide-based therapeutics, we are pursuing strategies to improve the stability properties of HM-10/10 by extending its bioavailability while retaining its low toxicity profile. HM-10/10 holds promise as a new agent to address the international women's health crisis of epithelial carcinomas of the ovary and colon.

Abstract 679: HDL Apolipoproteomic Score, Cardiometabolic Risk, And Exercise Training

Background: Previous studies have derived and validated an HDL apolipoproteomic score (pCAD) that predicts coronary artery disease risk. However, the relationship between pCAD and the cardiometabolic profile in healthy adults, as well as the effects of regular exercise on pCAD are unknown. Methods: A total of 642 inactive but healthy adults (56% female, 36% Black, 35±13 yrs) completed 20 weeks of endurance exercise training. HDL-bound proteins were measured in APOA1-tagged serum using targeted LC-MS/MS (Quest Diagnostics). The pCAD index was calculated as a weighted sum of five HDL-associated apolipoproteins (APO A1, C1, C2, C3, C4) with scores from 0 to 100 (higher score=higher risk). Age-, sex-, and race-specific baseline pCAD quartiles were created. Results: The mean (SD) pCAD score at baseline was 29 (32). At baseline, increasing pCAD quartile was associated with a poorer cardiometabolic profile, including higher total and visceral fat, blood pressure, inflammation, and fasting glucose and lower insulin sensitivity and lipoprotein lipase activity ( Table ). In the total sample, pCAD significantly decreased with exercise training by 4.7 (25) pts or ~16%. Across pCAD quartiles, mean decreases in pCAD were 4.6 in quartile 3 and 21.3 in quartile 4, compared to mean increases of 3.6 in quartile 1 and 3.5 in quartile 2 (p<0.05 for all within group changes). The exercise-induced decrease in pCAD was largely driven by increases in HDL-associated APOA1 and APOC1 levels and inversely correlated with changes in HDL-C (r= -0.17, p<0.0001) and HDL size (r= -0.14, p=0.0006). Otherwise, changes in pCAD were not correlated with changes in other cardiometabolic traits. Conclusions: A higher pCAD index was associated with a poor cardiometabolic profile at baseline and improved with regular exercise in healthy adults with the worst profiles. These findings highlight the potential role of HDL apolipoproteins as a theranostic target for lifestyle interventions in these individuals.

Novel Anti-Ovarian Epithelial Adenocarcinoma Agent: HM-10/10 HDL-Mimetic Peptide—Pharmacokinetic and Pharmacodynamic Characterization [ID: 1377510

INTRODUCTION: Epithelial adenocarcinoma of the ovary (EOC) is the second most common cancer affecting the female reproductive system and is associated with the fifth highest rate of cancer-related deaths in women. With many women presenting in late stages, the estimated chance of survival for 2, 5, and 10 years were 65%, 44%, and 36%, respectively. In recent literature, the role of HDL-associated apolipoproteins has been shown to be effective in the treatment of proinflammatory diseases, including cancer. Previously we developed a novel 20-amino acid mimetic peptide, HM-10/10, which was able to inhibit tumor development and growth in EOC models in vitro and in vivo. These findings prompted our decision to further our research by performing characterization to advance HM-10/10 as our apolipoprotein mimetic peptide candidate of choice for use as a novel therapeutic agent against EOC. The aim of this study was to report the pharmacokinetic (PK) and pharmacodynamic (PD) properties of HM-10/10 relative to its stability in vitro. METHODS: To evaluate PK/PD, multiple procedures were performed in vitro. RESULTS: The results demonstrated PK/PD good stability in plasma and the gastric environment. However, under conditions modeling the small intestine, HM-10/10 demonstrated significant degradation, likely because of the diverse array of peptidases encountered therein. CONCLUSION: These data highlight the PK/PD of HM-10/10 and demonstrate its potential as an effective therapeutic for treating EOC. The preferred route of delivery of HM-10/10 is oral, and toward that end, HM-10/10 demonstrated remarkable stability over a broad physiologic pH range; however, its stability was significantly degraded by conditions simulating the small intestine.

Preeclampsia Affects Lipid Metabolism and HDL Function in Mothers and Their Offspring.

Preeclampsia (PE) is linked to an overall increased cardiovascular risk for both the mother and child. Functional impairment of high-density lipoproteins (HDL) may contribute to the excess cardiovascular risk associated with PE. In this study, we investigated the effects of PE on maternal and neonatal lipid metabolism, and the parameters of HDL composition and function. The study cohort included 32 normotensive pregnant women, 18 women diagnosed with early-onset PE, and 14 women with late-onset PE. In mothers, early- and late-onset PE was associated with atherogenic dyslipidemia, characterized by high plasma triglycerides and low HDL-cholesterol levels. We observed a shift from large HDL to smaller HDL subclasses in early-onset PE, which was associated with an increased plasma antioxidant capacity in mothers. PE was further associated with markedly increased levels of HDL-associated apolipoprotein (apo) C-II in mothers, and linked to the triglyceride content of HDL. In neonates of early-onset PE, total cholesterol levels were increased, whereas HDL cholesterol efflux capacity was markedly reduced in neonates from late-onset PE. In conclusion, early- and late-onset PE profoundly affect maternal lipid metabolism, potentially contributing to disease manifestation and increased cardiovascular risk later in life. PE is also associated with changes in neonatal HDL composition and function, demonstrating that complications of pregnancy affect neonatal lipoprotein metabolism.

The association of fasting plasma thiol fractions with body fat compartments, biomarker profile, and adipose tissue gene expression

People with high plasma total cysteine (tCys) have higher fat mass and higher concentrations of the atherogenic apolipoprotein B (apoB). The disulfide form, cystine, enhanced human adipogenesis and correlated with total fat mass in a Middle-Eastern cohort. In 35 European adults with overweight (88.6% women) and with dual-X-ray absorptiometry measurements of regional fat, we investigated how cystine compared to other free disulfides in their association with total regional adiposity, plasma lipid and glucose biomarkers, and adipose tissue lipid enzyme mRNA (n = 19). Most total plasma homocysteine (tHcy) (78%) was protein-bound; 63% of total glutathione (tGSH) was reduced. tCys was 49% protein-bound, 30% mixed-disulfide, 15% cystine, and 6% reduced. Controlling for age and lean mass, cystine and total free cysteine were the fractions most strongly associated with android and total fat: 1% higher cystine predicted 1.97% higher android fat mass (95% CI 0.64, 3.31) and 1.25% (0.65, 2.98) higher total fat mass (both p = 0.005). A positive association between tCys and apoB (β: 0.64%; 95% CI 0.17, 1.12%, p = 0.009) was apparently driven by free cysteine and cystine; cystine was also inversely associated with the HDL-associated apolipoprotein A1 (β: −0.57%; 95% CI −0.96, −0.17%, p = 0.007). No independent positive associations with adiposity were noted for tGSH or tHcy fractions. Plasma cystine correlated with CPT1a mRNA (Spearman’s r = 0.68, p = 0.001). In conclusion, plasma cystine—but not homocysteine or glutathione disulfides—is associated with android adiposity and an atherogenic plasma apolipoprotein profile. The role of cystine in human adiposity and cardiometabolic risk deserves investigation. ClinicalTrials.gov identifiers: NCT02647970 and NCT03629392.

Association of apolipoprotein M and sphingosine-1-phosphate with brown adipose tissue after cold exposure in humans

The HDL-associated apolipoprotein M (apoM) and its ligand sphingosine-1-phosphate (S1P) may control energy metabolism. ApoM deficiency in mice is associated with increased vascular permeability, brown adipose tissue (BAT) mass and activity, and protection against obesity. In the current study, we explored the connection between plasma apoM/S1P levels and parameters of BAT as measured via 18F-FDG PET/CT after cold exposure in humans. Fixed (n = 15) vs personalized (n = 20) short-term cooling protocols decreased and increased apoM (− 8.4%, P = 0.032 vs 15.7%, P < 0.0005) and S1P (− 41.0%, P < 0.0005 vs 19.1%, P < 0.005) plasma levels, respectively. Long-term cooling (n = 44) did not affect plasma apoM or S1P levels. Plasma apoM and S1P did not correlate significantly to BAT volume and activity in the individual studies. However, short-term studies combined, showed that increased changes in plasma apoM correlated with BAT metabolic activity (β: 0.44, 95% CI [0.06–0.81], P = 0.024) after adjusting for study design but not BAT volume (β: 0.39, 95% CI [− 0.01–0.78], P = 0.054). In conclusion, plasma apoM and S1P levels are altered in response to cold exposure and may be linked to changes in BAT metabolic activity but not BAT volume in humans. This contrasts partly with observations in animals and highlights the need for further studies to understand the biological role of apoM/S1P complex in human adipose tissue and lipid metabolism.

OR02-1 Differences in HDL Particle Composition in Patients with Nonalcoholic Fatty Liver Disease (NAFLD) and Advanced Liver Fibrosis May Explain Higher Cardiovascular Risk

Abstract The severity of liver fibrosis in patients with NAFLD is a strong predictor of cardiovascular mortality, independently of other well-known cardiovascular risk factors. However, the exact mechanisms leading to cardiovascular disease in patients with advanced liver fibrosis remain incompletely understood. As many of the apolipoproteins are synthesized in the liver, we hypothesized that lipoprotein composition may explain the association between liver disease and cardiovascular disease. Patients (n=185) underwent a liver proton magnetic resonance spectroscopy (1H-MRS) to measure intrahepatic triglyceride accumulation and a percutaneous liver biopsy if they had NAFLD. Advanced lipid testing and lipoprotein subfractions were measured by ion mobility. ApoA-I containing particles (i.e., HDL) were isolated and a novel targeted proteomic approach utilizing multiple reaction monitoring (MRM) by liquid chromatography and tandem mass spectrometry (LC-MS/MS) was undertaken to measure HDL-bound proteins that are associated with lipid metabolism. Forty-five patients did not have NAFLD by 1H-MRS and were used as controls for comparisons. One-hundred and forty patients had a liver biopsy, and 26 were diagnosed with advanced fibrosis. Patients with vs. without advanced fibrosis had similar clinical characteristics (Age: 54±9 vs. 52±11 years; sex: 77% vs. 76% males; BMI: 34.2±4.3 vs. 34.5±4.6 kg/m2). Patients with advanced fibrosis had lower HDL-C (34±8 vs. 38±9 mg/dl, p=0.024) and higher A1c (7.3±1.3% vs. 6.5±1.0%, p&amp;lt;0.001). No differences were observed in LDL or VLDL particle number or size between the groups. Patients with advanced fibrosis showed a mild reduction in HDL particle number, mainly driven by a reduction of small HDL particles (17269±3705 vs. 19057±4052 nmol/L, p=0.042). Despite this small difference in HDL particle number, a significant difference was observed in the proteomic signature of these particles. A panel of twenty-eight HDL-bound proteins were targeted and quantified by MRM LC-MS/MS. After adjustment for multiple comparisons based on a false discovery rate set at 10% (method of Benjamini-Krieger-Yekutieli), five proteins were found to be decreased in patients with advanced fibrosis (ApoC-I, ApoC-IV, ApoM, LCAT, and SAA4; all p&amp;lt;0.017). No differences were observed in these proteins in patients with vs. without NAFLD or steatohepatitis (NASH). The pCAD index [range from 0-100] is a well-validated model based on measurement of 5 HDL-associated apolipoproteins (Apolipoproteins A-I, C-I, C-II, C-III, and C-IV) that is associated with presence of coronary artery disease and cardiovascular mortality. We observed a stepwise increase in pCAD index with every stage of fibrosis among patients with NAFLD (F0: 84±3; F1: 88±3; F2: 90±6; F3-4: 97±1, p=0.037). Conclusion Patients with NAFLD with advanced fibrosis showed significant differences in the apolipoproteomic composition of HDL particles, and this translated into increased cardiovascular risk based on pCAD index. Different lipoprotein composition and function may explain the link between liver disease and increased cardiovascular mortality in these patients. Presentation: Saturday, June 11, 2022 11:30 a.m. - 11:45 a.m.

Association between plasma apolipoprotein M and cardiac autonomic neuropathy in type 1 diabetes

AimDiabetes may lead to severe complications e.g. cardiac autonomic neuropathy (CAN) characterized by an increased risk of cardiovascular mortality. CAN is diagnosed by a decreased heart rate viability (HRV). Sphingosine-1-Phosphate (S1P) carried by the HDL-associated apolipoprotein M (apoM) is linked to a reduction in the heart rate, and treatment with an S1P-agonist increases HRV. The present study aimed to investigate if plasma apoM was associated with an increased risk of CAN. MethodsThe study includes 278 individuals with Type 1 Diabetes recruited from Steno Diabetes Center in Copenhagen from 2010 to 2012. ResultsA change of 0.1 µM plasma apoM was associated with the diagnosis of CAN (Odds ratio: 1.11 (1.02; 1.21), p = 0.013). ApoM plasma levels were also positively associated with CAN when adjusted for age and gender (Odds ratio: 1.11 (1.02; 1.21), p = 0.013) as well as lipids, beta-blockers, blood pressure, and alcohol (Odds ratio: 1.14 (1.04; 1.26), p = 0.005) and Hbga1c and time with diabetes (Odds ratio: 1.13 (1.02; 1.25), p = 0.01). Plasma apoM was also associated with a significantly lower SDNN as well as high frequency power in all adjusted models. ConclusionIncreased plasma apoM was associated with an increased risk of CAN as well as a significant reduction in HRV indices. This could represent changes in parasympathetic activity, but, further studies are needed to also explore additional molecular alterations behind such observations.

Anorexia Nervosa Is Associated with a Shift to Pro-Atherogenic Low-Density Lipoprotein Subclasses.

Anorexia nervosa (AN) is a severe eating disorder affecting primarily female adolescents and younger adults. The energy deprivation associated with AN has been shown to alter lipoprotein metabolism, which may affect cardiovascular risk. However, the mechanisms leading to alterations in the composition, structure, and function of lipoproteins in AN patients are not well-understood yet. Here, we investigated the lipid abnormalities associated with AN, particularly changes in the distribution, composition, metabolism, and function of lipoprotein subclasses. In this exploratory study, we analyzed serum samples of 18 women diagnosed with AN (BMI < 17.5 kg/m2) and 24 normal-weight women (BMI from 18.5–24.9 kg/m2). Using the Quantimetrix Lipoprint® system, we determined low-density lipoprotein (LDL) subclass distribution, including quantitative measurements of very low-density lipoprotein (VLDL), intermediate density lipoprotein (IDL) and high-density lipoprotein (HDL) subclass distribution. We quantified the most abundant apolipoproteins of HDL and assessed lecithin-cholesterol acyltransferase (LCAT) and cholesteryl-ester transfer protein (CETP) activities. In addition, anti-oxidative capacity of apoB-depleted serum and functional metrics of HDL, including cholesterol efflux capacity and paraoxonase activity were assessed. The atherogenic lipoprotein subclasses VLDL and small LDL particles were increased in AN. Levels of VLDL correlated significantly with CETP activity (rs = 0.432, p = 0.005). AN was accompanied by changes in the content of HDL-associated apolipoproteins involved in triglyceride catabolism, such as apolipoprotein C-II (+24%) and apoA-II (−27%), whereas HDL-associated cholesterol, phospholipids, and triglycerides were not altered. Moreover, AN did not affect HDL subclass distribution, cholesterol efflux capacity, and paraoxonase activity. We observed a shift to more atherogenic lipoprotein subclasses in AN patients, whereas HDL functionality and subclass distribution were not altered. This finding underpins potential detrimental effects of AN on lipid metabolism and the cardiovascular system by increasing atherosclerotic risk factors.

Circulating HDL and Non-HDL Associated Apolipoproteins and Breast Cancer Severity.

Plasma lipids are carried within lipoproteins with various apolipoprotein content. This study evaluates the interest of measuring the apolipoproteins of circulating lipoproteins in breast cancer. Patients with early-stage breast cancer (n = 140) were included. Tumors differed by the expression of estrogen and progesterone receptor (HR− and HR+ for negative and positive expression) and the proliferation marker Ki-67 (≤20% or ≥30%). Apolipoprotein concentrations were determined in plasma, HDL and non-HDL fractions, and results are given in mg/dL, median (25th–75th). Patients did not differ in their plasma and lipoprotein lipid concentrations. HDL apoC-I and non-HDL apoC-II were reduced (1.34 (1.02–1.80) vs. 1.61 (1.32–2.04), p = 0.04; 0.31 (0.18–0.65) vs. 0.63 (0.39–1.02), p = 0.01; respectively), in RH-/high Ki-67 patients in comparison to RH-/low Ki-67 patients, while plasma apoD and HDL apoD were higher (3.24 (2.99–4.16) vs. 3.07 (2.39–3.51), p = 0.04; 2.74 (2.36–3.35) vs. 2.45 (2.01–2.99), p = 0.04; respectively). When RH+/high Ki-67 patients were compared with RH+/low Ki-67 patients, HDL apoC-I and HDL apoC-III were higher (1.56 (1.20–1.95) vs. 1.35 (1.10–1.62), p = 0.02; 2.80 (2.42–3.64) vs. 2.38 (1.69–2.96), p = 0.02; respectively). The distribution of exchangeable apolipoproteins, such as apoC-I, apoC-II, apoC-III, apoD, between lipoproteins is linked to the severity of breast cancer.

HDL-Associated Lipoproteins: Potential Prognostic Biomarkers for Gram-Negative Sepsis.

PurposeTo determine the levels of serum HDL-associated apolipoproteins (apoM and apoC) and HDL-binding receptor (scavenger receptor BI, SR-BI) in patients with gram-negative bacteria sepsis (G-sepsis) and to evaluate the value of lipoproteins in the diagnosis, severity and prognosis of G-sepsis.Patients and MethodsA total of 128 patients with sepsis, 40 patients with system inflammatory reaction syndrome (SIRS) and 40 healthy subjects were enrolled in the Second People’s Hospital of Hunan Province from September 2019 to September 2020. The levels and the correlation of lipoproteins were detected and dynamically monitored by enzyme-linked adsorption method, ROC curve for the diagnostic, severity and prognostic value of lipoproteins in G-sepsis.ResultsThe levels of serum HDL-associated lipoproteins in patients with G-sepsis were significantly decreased (P < 0.05), and the ROC curve showed that HDL-C, SR-BI, apoM and apoC had cut-off values of 0.915 mmol/L, 122.100 pg/mL, 102.400 ug/mL and 17.55 mg/mL, respectively, for the diagnosis of G-sepsis, with the sensitivity was 85.56%, 97.78%, 93.33% and 73.03%, and the specificity was 95.0%, 82.50%, 61.54% and 82.50%, respectively. There was a correlation between HDL-associated apolipoproteins. Changes in serum HDL-associated lipoproteins were more obvious in shock group than classic inflammation indicators, such as PCT, IL-6 and CRP. They showed a trend change on day 3, with the levels of SR-BI and apoC changing 2–3 times, and the sensitivity of HDL-C, SR-BI, apoM and apoC for the diagnosis of G-septic shock were 32.43%, 72.97%, 65.75%, and 43.24%, and specificity of 94.34%, 81.13%, 83.07%, and 86.79%, respectively. The AUC, sensitivity and specificity of apoM combined with SR-BI were improved.ConclusionHDL-associated lipoproteins were correlated with bacterial-infected types, and serum levels of HDL-associated lipoproteins can be used as potential biomarkers for early diagnosis and progress of G-sepsis. ApoM combined with SR-BI could improve the sensitivity and specificity of prognosis assessment.

ASsociation of the apolipoprotein M and sphingosine-1-phosphate complex with brown adipose tissue after cold exposure in humans

Background and Aims: The HDL-associated apolipoprotein M (apoM) and its ligand sphingosine-1-phosphate (S1P) may control energy metabolism, as supported by apoM-deficient mice showing a favorable metabolic phenotype with increased triglyceride turnover and protection against obesity-induced insulin resistance. In addition, apoM deficiency is associated with increased vascular permeability and brown adipose tissue (BAT) mass and activity, and these effects are partly mediated by the S1P receptor 1.

Current Understanding of the Immunomodulatory Activities of High-Density Lipoproteins

Lipoproteins interact with immune cells, macrophages and endothelial cells - key players of the innate and adaptive immune system. High-density lipoprotein (HDL) particles seem to have evolved as part of the innate immune system since certain HDL subspecies contain combinations of apolipoproteins with immune regulatory functions. HDL is enriched in anti-inflammatory lipids, such as sphingosine-1-phosphate and certain saturated lysophospholipids. HDL reduces inflammation and protects against infection by modulating immune cell function, vasodilation and endothelial barrier function. HDL suppresses immune cell activation at least in part by modulating the cholesterol content in cholesterol/sphingolipid-rich membrane domains (lipid rafts), which play a critical role in the compartmentalization of signaling pathways. Acute infections, inflammation or autoimmune diseases lower HDL cholesterol levels and significantly alter HDL metabolism, composition and function. Such alterations could have a major impact on disease progression and may affect the risk for infections and cardiovascular disease. This review article aims to provide a comprehensive overview of the immune cell modulatory activities of HDL. We focus on newly discovered activities of HDL-associated apolipoproteins, enzymes, lipids, and HDL mimetic peptides.

High-Density Lipoprotein (HDL) in Allergy and Skin Diseases: Focus on Immunomodulating Functions.

From an evolutionary perspective, lipoproteins are not only lipid transporters, but they also have important functions in many aspects of immunity. High-density lipoprotein (HDL) particles are the most abundant lipoproteins and the most heterogeneous in terms of their composition, structure, and biological functions. Despite strong evidence that HDL potently influences the activity of several immune cells, the role of HDL in allergies and skin diseases is poorly understood. Alterations in HDL-cholesterol levels have been observed in allergic asthma, allergic rhinitis, atopic dermatitis (eczema), psoriasis, urticaria, and angioedema. HDL-associated apolipoprotein (apo) A-I, apoA-IV, and apoC-III, and lyso-phosphatidylcholines potently suppress immune cell effector responses. Interestingly, recent studies provided evidence that allergies and skin diseases significantly affect HDL composition, metabolism, and function, which, in turn, could have a significant impact on disease progression, but may also affect the risk of cardiovascular disease and infections. Interestingly, not only a loss in function, but also, sometimes, a gain in function of certain HDL properties is observed. The objective of this review article is to summarize the newly identified changes in the metabolism, composition, and function of HDL in allergies and skin diseases. We aim to highlight the possible pathophysiological consequences with a focus on HDL-mediated immunomodulatory activities.

Serum amyloid A is not incorporated into HDL during HDL biogenesis

Liver-derived serum amyloid A (SAA) is present in plasma where it is mainly associated with HDL and from which it is cleared more rapidly than are the other major HDL-associated apolipoproteins. Although evidence suggests that lipid-free and HDL-associated forms of SAA have different activities, the pathways by which SAA associates and disassociates with HDL are poorly understood. In this study, we investigated SAA lipidation by hepatocytes and how this lipidation relates to the formation of nascent HDL particles. We also examined hepatocyte-mediated clearance of lipid-free and HDL-associated SAA. We prepared hepatocytes from mice injected with lipopolysaccharide or an SAA-expressing adenoviral vector. Alternatively, we incubated primary hepatocytes from SAA-deficient mice with purified SAA. We analyzed conditioned media to determine the lipidation status of endogenously produced and exogenously added SAA. Examining the migration of lipidated species, we found that SAA is lipidated and forms nascent particles that are distinct from apoA-I-containing particles and that apoA-I lipidation is unaltered when SAA is overexpressed or added to the cells, indicating that SAA is not incorporated into apoA-I-containing HDL during HDL biogenesis. Like apoA-I formation, generation of SAA-containing particles was dependent on ABCA1, but not on scavenger receptor class B type I. Hepatocytes degraded significantly more SAA than apoA-I. Taken together, our results indicate that SAA's lipidation and metabolism by the liver is independent of apoA-I and that SAA is not incorporated into HDL during HDL biogenesis.

Apolipoprotein M And High-Density Lipoprotein Subfraction Levels In Newly Diagnosed, Untreated Familial Hypercholesterolemia

Background and Aims: Familial hypercholesterolemia (FH) is an autosomal dominant disorder with extremely high plasma total- (TC) and LDL-cholesterol (LDL-C) levels and increased risk of premature cardiovascular disease. Although the HDL-cholesterol (HDL-C) level is usually in the high-normal range, the structure and function of the HDL particle is impaired. The HDL-associated apolipoprotein M (ApoM) has several anti-atherogenic properties and was found to be decreased in FH. However, its level was not studied in untreated FH patients.

Association of an HDL Apolipoproteomic Score With Coronary Atherosclerosis and Cardiovascular Death

BackgroundConcentrations of circulating apolipoproteins are strongly linked to risk for coronary artery disease (CAD). The relative importance of the additional knowledge of apolipoprotein concentrations within specific lipoprotein species for CAD risk prediction is limited. ObjectivesThis study sought to evaluate the performance of a high-density lipoprotein (HDL) apolipoproteomic score, based on targeted mass spectrometry of HDL-associated apolipoproteins, for the detection of angiographic CAD and outcomes. MethodsHDL-associated apolipoprotein (apo) A-1, apoC-1, apoC-2, apoC-3, and apoC-4 were measured in 943 participants without prevalent myocardial infarction (MI) referred for coronary angiography in the CASABLANCA (Catheter Sampled Blood Archive in Cardiovascular Diseases) study. A composite HDL apolipoproteomic score (pCAD) was associated with likelihood of obstructive CAD (≥70% lesion in ≥1 vessel) and with incident cardiovascular outcomes over 4-year follow-up. ResultsThere were 587 (62.2%) patients with coronary stenosis. The pCAD score was associated with the presence of obstructive CAD (odds ratio: 1.39; 95% confidence interval [CI]: 1.14 to 1.69; p < 0.001), independently of conventional cardiovascular risk factors including circulating plasma apoA-1 and apoB. The C-index for pCAD was 0.63 (95% CI: 0.59 to 0.67) for the presence of obstructive CAD. Although pCAD was not associated with cardiovascular mortality among all individuals (hazard ratio: 1.24; 95% CI: 0.93 to 1.66; p = 0.15), there was evidence of association for individuals with obstructive CAD (hazard ratio: 1.48; 95% CI: 1.07 to 2.05; p = 0.019). ConclusionsAn HDL apolipoproteomic score is associated with the presence of CAD, independent of circulating apoA-1 and apoB concentrations and other conventional cardiovascular risk factors. Among individuals with CAD, this score may be independently associated cardiovascular death. (The CASABLANCA Study: Catheter Sampled Blood Archive in Cardiovascular Diseases [CASABLANCA]; NCT00842868)

Abstract 392: Nanoparticle-based Biosensors for Measuring Apolipoprotein A-I and HDL Function

Background: High-density lipoproteins (HDL) are dynamic circulating nanoparticles that carry cholesterol and have numerous functions. Rapid measurement of HDL, the HDL-associated protein apolipoprotein A-I (apoAI), or HDL function(s) is not currently possible. Such technology may provide new opportunities for HDL monitoring. We utilized nanoparticles to develop a method of sequestering apoAI from solution, including human serum, and for measuring the activity of the HDL-maturing and apoAI-dependent enzyme, lecithin:cholesterol acyl transferase (LCAT). Methods: Gold nanoparticles were surface-functionalized with phospholipids. The synthesized particles were incubated with various amounts of apoAI or with purchased, LDL-depleted, human serum samples where the apoAI amount was measured using an ELISA. After incubation, the particles were easily isolated and apoAI sequestration by the nanoparticles was measured using ELISA. As apoAI is a cofactor that activates LCAT, nanoparticles were incubated with various amounts of apoA1, LCAT, and free cholesterol or with the LDL-depleted human serum samples (diluted) for 1 hour at 37°C to enable binding of apoAI, cholesterol, and LCAT activity. The nanoparticles were easily isolated and the particle-associated cholesteryl ester was measured using an Amplex Red Cholesterol Assay kit. Results: The nanoparticles sequester apoAI according to the concentration of apoAI in solution (R = 0.668, p = 0.035, N = 10). Also, data reveal that the LCAT binds the nanoparticle-apoAI structures and catalyzes the conversion of cholesterol to cholesteryl ester. The amount of cholesteryl ester bound to the nanoparticles is directly dependent on the amount of apoAI (R = 0.729, p = 0.016, N=10). Conclusion: These results demonstrate that specific, functionalized nanoparticles can be added to serum to sequester apoAI in dose-response. Also, the formed conjugate structures activate LCAT whereby the amount of cholesteryl ester formed on the nanoparticle directly correlates with apoAI. Overall, this technology provides a framework and new approach for developing next generation HDL- and HDL-function specific biosensors.

ATP-binding cassette transporter G1 and apolipoprotein M are ‘Novel players’ in cholesterol transport at the blood-brain barrier

Aim: Impaired cholesterol/lipoprotein metabolism is linked to neurodegenerative diseases. Cerebral cholesterol homeostasis is maintained by the highly efficient blood-brain barrier (BBB) and flux of the oxysterols 24(S)- and 27-hydroxycholesterol, potent liver-X-receptor (LXR) activators. HDL/apolipoproteins support cerebral lipid transfer and loss of ATP-binding cassette transporters (ABC)G1 and G4 results in toxic accumulation of oxysterols in the brain. The HDL-associated apolipoprotein (apo)M is positively correlated with pre-ß HDL formation in plasma; its presence and function in the brain was thus far unknown. Using an in vitro model of the BBB we examined expression, regulation and functions of ABCG1, ABCG4, and apoM in primary cerebrovascular endothelial cells.