High-density Lipoprotein Components Research Articles

Differences in HDL Remodeling during Healthy Pregnancy and Pregnancy with Cardiometabolic Complications.

This study investigated the longitudinal trajectory of changes in antioxidative and anti-inflammatory high-density lipoprotein (HDL) components during healthy pregnancy and pregnancy with cardiometabolic complications. We recruited and longitudinally followed 84 women with healthy pregnancies and 46 pregnant women who developed cardiometabolic pregnancy complications (gestational diabetes mellitus and hypertensive disorders of pregnancy). Their general lipid profiles, oxidative stress status, inflammatory status, and antioxidative and anti-inflammatory HDL components were analyzed. The results of our study confirmed the expected trajectory for the routine lipid parameters. Our study results indicate more intensive oxidative stress and a higher level of inflammation in the group with complications compared with the control group. Sphingosine-1-phosphate (S1P) was significantly lower in the first trimester in the group with complications compared with the control group (p < 0.05). We did not find significant differences in the apolipoprotein A1 (Apo A1) concentrations in the first trimester between the control group and the group with complications, but in the second and third trimesters, the group with complications had significantly higher concentrations (p < 0.001, p < 0.05, respectively). The S1P, paraoxonase 1 (PON1), and serum amyloid A (SAA) concentrations were significantly lower in the group with complications in the first trimester. During the second trimester, only the SAA concentrations were identified as significantly lower in the group with complications compared with the control group, while in the third trimester, the PON1, apolipoprotein M (Apo M), and SAA concentrations were all significantly lower in the group with complications. Through a multivariate binary logistic regression analysis, the S1P concentration in the first trimester was distinguished as an HDL-associated marker independently associated with cardiometabolic pregnancy complications. In conclusion, our study results showed that HDL remodeling differs between healthy pregnancies and pregnancies with maternal cardiometabolic complications, with changed HDL composition and functionality consequently impacting its biological functionality in the latter case.

Association of apolipoprotein A1 levels with lumbar bone mineral density and β-CTX in osteoporotic fracture individuals: a cross-sectional investigation.

The relationship between the levels of high-density lipoprotein (HDL) and bone mineral density (BMD) is controversial. Furthermore, the specific role of apolipoprotein A1 (APOA1), a primary HDL component, in regulating BMD remains unclear. This study aimed to elucidate the correlation between APOA1 levels and lumbar BMD in patients with osteoporotic fracture (OPF) for novel insights into potential therapeutic strategies against osteoporosis. This study included 587 OPF patients enrolled at the Kunshan Hospital, Affiliated with Jiangsu University between January 2017 and July 2022. The patient's serum APOA1 levels were determined, followed by the assessment of lumbar BMD and C-terminal telopeptide of type I collagen (β-CTX) as outcome variables. The association of APOA1 levels with lumbar BMD and β-CTX was assessed via Generalized Estimating Equations (GEE) and spline smoothing plot analyses. A generalized additive model (GAM) helped ascertain non-linear correlations. Moreover, a subgroup analysis was also conducted to validate the result's stability. It was observed that APOA1 levels were positively correlated with lumbar BMD (β = 0.07, 95% CI: 0.02 to 0.11, p = 0.0045), indicating that increased APOA1 levels were linked with enhanced lumbar BMD. Furthermore, APOA1 levels were negatively related to β-CTX (β = -0.19, 95% CI: -0.29 to -0.09, p = 0.0003), suggesting APOA1 might reduce osteolysis. In addition, these findings were robustly supported by subgroup and threshold effect analyses. This study indicated that increased APOA1 levels were correlated with enhanced lumbar BMD and decreased osteolysis in OPF patients. Therefore, APOA1 may inhibit osteoclast activity to prevent further deterioration in osteoporotic patients. However, further research I warranted to validate these conclusions and elucidate the underlying physiologies.

Prevalence of metabolic syndrome and its risk factors among newly diagnosed type 2 diabetes mellitus patients - A hospital-based cross-sectional study.

Metabolic syndrome (MetS) raises the chance of cerebrovascular accidents and cardiovascular illness in type 2 diabetes mellitus (T2DM) individuals. Early identification of MetS allows for suitable prophylactic and treatment strategies to reduce the risks. To estimate the prevalence of MetS and its risk factors in T2DM individuals. This cross-sectional study investigated MetS and its component's prevalence among newly diagnosed T2DM at the tertiary care hospital. The study was conducted from January 2022 to December 2022 and included 300 participants above 18 years, with most being men (55%, 165), and using the World Health Organization (WHO) STEPS questionnaire for assessing selected risk factors. Along with blood glucose, different components of MetS were assessed, that is serum triglyceride (TG) level, serum high-density lipoprotein (HDL) level, blood pressure (BP) and waist circumference (WC), as per the National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III) criteria. Data analysis includes mean and standard deviation (SD) for numerical variables with an unpaired t-test to compare means and percentage and proportions for categorical variables with the Chi-square test for the associations. Multivariate logistic regression was used for assessing the predictors of MetS. The prevalence of components of MetS, that is obesity, hypertension (HTN), TG and HDL components, was 64.0% (192), 45.7% (137), 46.0% (138) and 30% (90), respectively. Overall, MetS was 57% (170). Moderate activity of 150 min/week, sitting/reclining, WC, diastolic BP, TG and HDL had a significant association with MetS. MetS was highly associated with newly diagnosed T2DM with obesity being the most common component.

Anti-inflammatory mechanism of Apolipoprotein A-I.

Apolipoprotein A-I(ApoA-I) is a member of blood apolipoproteins, it is the main component of High density lipoprotein(HDL). ApoA-I undergoes a series of complex processes from its generation to its composition as spherical HDL. It not only has a cholesterol reversal transport function, but also has a function in modulating the inflammatory response. ApoA-I exerts its anti-inflammatory effects mainly by regulating the functions of immune cells, such as monocytes/macrophages, dendritic cells, neutrophils, and T lymphocytes. It also modulates the function of vascular endothelial cells and adipocytes. Additionally, ApoA-I directly exerts anti-inflammatory effects against pathogenic microorganisms or their products. Intensive research on ApoA-I will hopefully lead to better diagnosis and treatment of inflammatory diseases.

Secreted dengue virus NS1 from infection is predominantly dimeric and in complex with high-density lipoprotein

Severe dengue infections are characterized by endothelial dysfunction shown to be associated with the secreted nonstructural protein 1 (sNS1), making it an attractive vaccine antigen and biotherapeutic target. To uncover the biologically relevant structure of sNS1, we obtained infection-derived sNS1 (isNS1) from dengue virus (DENV)-infected Vero cells through immunoaffinity purification instead of recombinant sNS1 (rsNS1) overexpressed in insect or mammalian cell lines. We found that isNS1 appeared as an approximately 250 kDa complex of NS1 and ApoA1 and further determined the cryoEM structures of isNS1 and its complex with a monoclonal antibody/Fab. Indeed, we found that the major species of isNS1 is a complex of the NS1 dimer partially embedded in a high-density lipoprotein (HDL) particle. Crosslinking mass spectrometry studies confirmed that the isNS1 interacts with the major HDL component ApoA1 through interactions that map to the NS1 wing and hydrophobic domains. Furthermore, our studies demonstrated that the sNS1 in sera from DENV-infected mice and a human patient form a similar complex as isNS1. Our results report the molecular architecture of a biological form of sNS1, which may have implications for the molecular pathogenesis of dengue.

Secreted dengue virus NS1 from infection is predominantly dimeric and in complex with high-density lipoprotein.

Severe dengue infections are characterized by endothelial dysfunction shown to be associated with the secreted nonstructural protein 1 (sNS1), making it an attractive vaccine antigen and biotherapeutic target. To uncover the biologically relevant structure of sNS1, we obtained infection-derived sNS1 (isNS1) from dengue virus (DENV)-infected Vero cells through immunoaffinity purification instead of recombinant sNS1 (rsNS1) overexpressed in insect or mammalian cell lines. We found that isNS1 appeared as an approximately 250 kDa complex of NS1 and ApoA1 and further determined the cryoEM structures of isNS1 and its complex with a monoclonal antibody/Fab. Indeed, we found that the major species of isNS1 is a complex of the NS1 dimer partially embedded in a high-density lipoprotein (HDL) particle. Crosslinking mass spectrometry studies confirmed that the isNS1 interacts with the major HDL component ApoA1 through interactions that map to the NS1 wing and hydrophobic domains. Furthermore, our studies demonstrated that the sNS1 in sera from DENV-infected mice and a human patient form a similar complex as isNS1. Our results report the molecular architecture of a biological form of sNS1, which may have implications for the molecular pathogenesis of dengue.

ANGPTL3 is a novel HDL component that regulates HDL function

BackgroundAngiopoietin-like protein 3 (ANGPTL3) is secreted by hepatocytes and inhibits lipoprotein lipase and endothelial lipase activity. Previous studies reported the correlation between plasma ANGPTL3 levels and high-density lipoprotein (HDL). Recently ANGPTL3 was found to preferentially bind to HDL in healthy human circulation. Here, we examined whether ANGPTL3, as a component of HDL, modulates HDL function and affects HDL other components in human and mice with non-diabetes or type 2 diabetes mellitus.MethodsHDL was isolated from the plasma of female non-diabetic subjects and type-2 diabetic mellitus (T2DM) patients. Immunoprecipitation, western blot, and ELISA assays were used to examine ANGPTL3 levels in HDL. Db/m and db/db mice, AAV virus mediated ANGPTL3 overexpression and knockdown models and ANGPTL3 knockout mice were used. The cholesterol efflux capacity induced by HDL was analyzed in macrophages preloaded with fluorescent cholesterol. The anti-inflammation capacity of HDL was assessed using flow cytometry to measure VCAM-1 and ICAM-1 expression levels in TNF-α-stimulated endothelial cells pretreated with HDL.ResultsANGPTL3 was found to bind to HDL and be a component of HDL in both non-diabetic subjects and T2DM patients. Flag-ANGPTL3 was found in the HDL of transgenic mice overexpressing Flag-ANGPTL3. ANGPLT3 of HDL was positively associated with cholesterol efflux in female non-diabetic controls (r = 0.4102, p = 0.0117) but not in female T2DM patients (r = − 0.1725, p = 0.3224). Lower ANGPTL3 levels of HDL were found in diabetic (db/db) mice compared to control (db/m) mice and were associated with reduced cholesterol efflux and inhibition of VCAM-1 and ICAM-1 expression in endothelial cells (p < 0.05 for all). Following AAV-mediated ANGPTL3 cDNA transfer in db/db mice, ANGPTL3 levels were found to be increased in HDL, and corresponded to increased cholesterol efflux and decreased ICAM-1 expression. In contrast, knockdown of ANGPTL3 levels in HDL by AAV-mediated shRNA transfer led to a reduction in HDL function (p < 0.05 for both). Plasma total cholesterol, total triglycerides, HDL-c, protein components of HDL and the cholesterol efflux function of HDL were lower in ANGPTL3−/− mice than ANGPTL3+/+ mice, suggesting that ANGPTL3 in HDL may regulate HDL function by disrupting the balance of protein components in HDL.ConclusionANGPTL3 was identified as a component of HDL in humans and mice. ANGPTL3 of HDL regulated cholesterol efflux and the anti-inflammatory functions of HDL in T2DM mice. Both the protein components of HDL and cholesterol efflux capacity of HDL were decreased in ANGPTL3−/− mice. Our findings suggest that ANGPTL3 in HDL may regulate HDL function by disrupting the balance of protein components in HDL. Our study contributes to a more comprehensive understanding of the role of ANGPTL3 in lipid metabolism.

Lipoprotein dysfunction in patients with chronic kidney disease (CKD). Pathogenesis and treatment of CKD dyslipidemia (literature review)

Dyslipidemia develops in the initial stages of chronic kidney disease (CKD) and worsens as nephropathy progresses. The main manifestation of dyslipidemia is hypercholesterolemia, especially in nephrotic syndrome. However, with CKD of stages 4-5, it is replaced by hypertriglyceridemia in combination with an increase in blood levels of lipoproteins low and very low density. Such changes are closely related to the development of cardiovascular pathology with high mortality. The content of high-density lipoproteins (HDL) in the blood is gradually decreasing, as well as the reversible transport of cholesterol. Thus, their anti-atherogenic, antioxidant and anti-inflammatory functions are lost. The main components of HDL – apolipoproteins ApoA-I and ApoA-II, which provide functionality, are replaced by acute-phase proteins, and HDL lose their cardioprotective potential and acquire a proinflammatory and proatherogenic phenotype. According to modern concepts, HDL dysfunction, along with metabolic shifts, is largely due to epigenetic disorders affecting gene expression and partially eliminated by prescribing drugs containing microRNAs (mRNAs) or antisense nucleotides. Drugs with interfering RNAs created in recent years have been successfully used not only for the treatment of dyslipidemia in nephrological patients, but also in patients with neoplastic processes, inflammatory arthritis, degenerative diseases of the central nervous system, porphyria, hemophilia and many other diseases. The proposed review is devoted to the mechanisms of disorders of the structure and functions of HDL in patients with CKD and the correction of these disorders.

HDL inhibits pancreatic acinar cell NLRP3 inflammasome activation and protect against acinar cell pyroptosis in acute pancreatitis

Background and PurposeRecent clinical studies have shown that serum high-density lipoprotein (HDL) levels are correlated with acute pancreatitis (AP) severity. We aimed to investigate the role of HDL in pancreatic necrosis in AP. Experimental approachApoA-I is the main constitution and function component of HDL. The roles of healthy human-derived HDL and apoA-I mimic peptide D4F were demonstrated in AP models in vivo and in vitro. Constitutive Apoa1 genetic inhibition on AP severity, especially pancreatic necrosis was assessed in both caerulein and sodium taurocholate induced mouse AP models. In addition, constitutive (Casp1-/-) and acinar cell conditional (Pdx1CreNlrp3Δ/Δ and Pdx1CreGsdmdΔ/Δ) mice were used to explore the effects of HDL on acinar cell pyroptosis in AP. Key resultsApoa1 knockout dramatically aggravated pancreatic necrosis. Human-derived HDL protected against acinar cell death in vivo and in vitro. We found that mimic peptide D4F also protected against AP very well. Constitutive Casp1 or acinar cell-conditional Nlrp3 and Gsdmd genetic inhibition could counteract the protective effects of HDL, implying HDL may exert beneficial effects on AP through inhibiting acinar cell pyroptosis. Conclusion and implicationsThis work demonstrates the protective role of HDL and apoA-I in AP pathology, potentially driven by the inhibition of NLRP3 inflammasome signaling and acinar cell pyroptosis. Mimic peptides have promise as specific therapies for AP.

Critical assessment of the metabolic syndrome definitions in the adult general population of the United States - the Multi-Ethnic Study of Atherosclerosis (MESA).

Metabolic syndrome (MetS) consists of a cluster of cardiometabolic risk factors and is an important determining factor for cardiovascular diseases (CVDs). We intended to use latent class analysis to classify the study population into several clusters. The baseline information of 6,814 participants of the Multi-Ethnic Study of Atherosclerosis (MESA) aged 45-84 years in 2000-2002 was used. The latent class analysis was conducted to extract different patterns of components. SAS 9.2 and Stata 12 software were used for analysis. The components of MetS tend to accumulate, hence it would be feasible to categorize the population into three classes: [1] Non-Metabolic Syndrome Latent Class (NonMetS-LC), [2] Low Risk Latent Class (LowR-LC), and [3] Metabolic Syndrome Latent Class (MetS-LC). In women, adding high-density lipoprotein (HDL) component to the two-component combinations of NonMetS-LC will transfer the individual to MetS-LC, and it was found in 100% of combinations of MetS-LC. However, in men, blood pressure (BP) played such a similar role, which was found in 97.36% of combinations of MetS-LC. Results showed that clinical value of each MetS component is different by gender. The main component in men was elevated BP; while low HDL and elevated fasting blood sugar (FBS) were in next ranks. However, the main component in women was low HDL; while elevated BP and FBS were in next ranks. Special attention should be paid to BP and HDL components, because these can be useful for clinicians and health policy-makers in diagnosis and screening. In conclusion, this study showed that revisions might be needed for the MetS definitions.

Atherosclerosis Calcification: Focus on Lipoproteins.

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of lipids in the vessel wall, leading to the formation of an atheroma and eventually to the development of vascular calcification (VC). Lipoproteins play a central role in the development of atherosclerosis and VC. Both low- and very low-density lipoproteins (LDL and VLDL) and lipoprotein (a) (Lp(a)) stimulate, while high-density lipoproteins (HDL) reduce VC. Apolipoproteins, the protein component of lipoproteins, influence the development of VC in multiple ways. Apolipoprotein AI (apoAI), the main protein component of HDL, has anti-calcific properties, while apoB and apoCIII, the main protein components of LDL and VLDL, respectively, promote VC. The role of lipoproteins in VC is also related to their metabolism and modifications. Oxidized LDL (OxLDL) are more pro-calcific than native LDL. Oxidation also converts HDL from anti- to pro-calcific. Additionally, enzymes such as autotaxin (ATX) and proprotein convertase subtilisin/kexin type 9 (PCSK9), involved in lipoprotein metabolism, have a stimulatory role in VC. In summary, a better understanding of the mechanisms by which lipoproteins and apolipoproteins contribute to VC will be crucial in the development of effective preventive and therapeutic strategies for VC and its associated cardiovascular disease.

Abstract TP226: Impact Of Apolipoprotein A-i In The Attenuation Of Stroke And Stroke Symptoms

Apolipoprotein AI is the major protein component of high-density lipoprotein (HDL) particles in plasma. Inflammatory cytokines such as TNF and IL-1β repress the production of ApoA-I from hepatocytes and increase the expression of serum amyloid A (SAA), which becomes the major protein component of HDL in this context. Consequently, lipid-poor ApoA-I is rapidly catabolized in the liver and the kidney. These findings could be meaningful if ApoA-I, in addition to its proimmune features, had anti-inflammatory potential. In this way, removal of ApoA-I could intensify the inflammatory response, resulting in a more robust effect. Recent studies have suggested that serum apolipoprotein A1 maybe a predictor and prognostic biomarker in acute ischemic stroke in humans. To understand the impact of ApoA-I in stroke, we have begun to analyze the role of ApoA-I in mouse models of stroke. Mice with reduced or deficient in ApoA-I and subjected to ischemia and reperfusion injury or permanent ischemia, had increased inflammatory responses, larger infarct volumes, and poorer outcomes than wildtype mice. Mice transgenic for the human ApoA-I gene showed a level of protection not seen in the wildtype mice when given an ischemic injury. Administration of AAV human ApoA-I increased HDL levels in deficient mice and provided protection against ischemic injury. Additionally, drugs to enhance ApoA-I expression showed protection against strokes in the mouse models. These studies, along with subsequent investigations will provide a better understanding and potential therapeutic approaches in the field of stroke.

High-density lipoproteins: from quantitative measures to functional assessment and therapy (review of literature).

The antiatherogenic role of high-density lipoproteins (HDL) is associated primarily with their participation in the reverse transport of excess cholesterol from peripheral tissues to the liver. The efficiency of this mechanism depends on the ability of apolipoprotein A-I (apoA-I), the main protein component of HDL, to capture cholesterol from cells. It is known that the acceptor properties of this protein can change under the influence of various factors. This review discusses modern approaches aimed both at increasing the plasma level of HDL and preserving their native functional properties. As one of the key criteria of HDL functionality it is proposed to determine the ability of HDL to accept labeled cholesterol from macrophages. Studies have shown that injection of recombinant HDL or apoA-I mimetic peptides accelerates cholesterol efflux from peripheral tissues, improves vascular endothelial state, and leads to regression of atherosclerotic plaque. Thus, therapy with recombinant HDL/apoA-I may become an effective way to treat cardiovascular diseases caused by cholesterol accumulation in the vascular wall.

The Role of High-Density Lipoprotein in Cardiovascular Disease: Benefits, Functions, and Treatments

There is evidence that high-density lipoprotein (HDL) can prevent the development of cardiovascular disease, particularly atherosclerotic. The beneficial effects of HDL on the arterial wall are largely due to its rich function. For example, one of the essential components of HDL's atherosclerotic protective characteristics is reverse cholesterol transport (RCT). The low-density lipoprotein (LDL) oxidation risk may be decreased attributable to the anti-oxidation function of HDL, which would also decrease the possibility of atherosclerosis. In recent years, the anti-inflammatory function of HDL has been demonstrated to modulate and participate in several inflammatory phenomena of atherosclerotic plaque formation. Since various functional features of HDL have gradually shown to have positive effects on the treatment and prevention of atherosclerotic plaque development, a growing number of researchers are working to develop effective strategies to boost HDL. Fortunately, several treatment options have developed to increase HDL levels, including drugs and dietary patterns. This article will focus on the functional properties of HDL levels and several therapeutic approaches to raise HDL levels.

Effects of superoxide anion attack on the lipoprotein HDL

High-density lipoprotein (HDL) is an anti-atherosclerotic lipoprotein. Thanks to the activity of apolipoprotein ApoA1, the principal protein component of HDL, this last is responsible for converting cholesterol into ester form and transporting excessive cholesterol to the liver (“reverse cholesterol transport” RCT). When HDL undergoes oxidation, it becomes dysfunctional and proatherogenic. ApoA1 is a target of oxidation, and its alteration affects RCT and contributes to atherosclerosis development. Until now, the mechanism of HDL oxidation is not fully understood and only hydroxyl radicals seem to induce direct oxidation of protein and lipidic components of lipoproteins. Here we demonstrate that superoxide radical, widely produced in early atherosclerosis, directly oxidizes HDL, and as a consequence, ApoA1 undergoes structural alterations impairing its anti-atherosclerotic functions. Our results highlight in an in vitro system the potential mechanism by which O2·− triggers atherosclerotic pathogenesis in vivo. Our study gets the basis for therapeutic approaches focused on the management of superoxide generation in early atherosclerosis onset.

Apolipoprotein A-II, a Player in Multiple Processes and Diseases.

Apolipoprotein A-II (apoA-II) is the second most abundant apolipoprotein in high-density lipoprotein (HDL) particles, playing an important role in lipid metabolism. Human and murine apoA-II proteins have dissimilar properties, partially because human apoA-II is dimeric whereas the murine homolog is a monomer, suggesting that the role of apoA-II may be quite different in humans and mice. As a component of HDL, apoA-II influences lipid metabolism, being directly or indirectly involved in vascular diseases. Clinical and epidemiological studies resulted in conflicting findings regarding the proatherogenic or atheroprotective role of apoA-II. Human apoA-II deficiency has little influence on lipoprotein levels with no obvious clinical consequences, while murine apoA-II deficiency causes HDL deficit in mice. In humans, an increased plasma apoA-II concentration causes hypertriglyceridemia and lowers HDL levels. This dyslipidemia leads to glucose intolerance, and the ensuing high blood glucose enhances apoA-II transcription, generating a vicious circle that may cause type 2 diabetes (T2D). ApoA-II is also used as a biomarker in various diseases, such as pancreatic cancer. Herein, we provide a review of the most recent findings regarding the roles of apoA-II and its functions in various physiological processes and disease states, such as cardiovascular disease, cancer, amyloidosis, hepatitis, insulin resistance, obesity, and T2D.

ANGPTL3 Is Involved in the Post-prandial Response in Triglyceride-Rich Lipoproteins and HDL Components in Patients With Coronary Artery Disease.

It is well-established that there exists an inverse relationship between high-density lipoprotein (HDL) cholesterol and triglyceride (TG) levels in the plasma. However, information is lacking on the impact of post-prandial triglyceride-rich lipoproteins (TRLs) on the structure of HDL subclasses in patients with coronary artery disease (CAD). In this study, the data of 49 patients with CAD were analyzed to evaluate dynamic alterations in post-prandial lipid profiles using nuclear magnetic resonance-based methods. An enzyme-linked immunosorbent assay was used to quantify the serum angiopoietin-like protein 3 (ANGPTL3). After glucose supplementation, the expression of hepatic ANGPTL3 was evaluated both in vitro and in vivo. Compared to fasting levels, the post-prandial serum TG level of all participants was considerably increased. Although post-prandial total cholesterol in HDL (HDL-C) remained unchanged, free cholesterol in HDL particles (HDL-FC) was significantly reduced after a meal. Furthermore, the post-prandial decrease in the HDL-FC level corresponded to the increase in remnant cholesterol (RC), indicating the possible exchange of free cholesterol between HDL and TRLs after a meal. Moreover, CAD patients with exaggerated TG response to diet, defined as TG increase >30%, tend to have a greater post-prandial increase of RC and decrease of HDL-FC compared to those with TG increase ≤30%. Mechanistically, the fasting and post-prandial serum ANGPTL3 levels were significantly lower in those with TG increase ≤30% than those with TG increase >30%, suggesting that ANGPTL3, the key lipolysis regulator, may be responsible for the different post-prandial responses of TG, RC, and HDL-FC.

Abstract 119: Into The Wormhole: Understanding SR-B1’s Cholesterol Transport Functions Through Structural Studies

Scavenger receptor Class B type 1 (SR-B1) is a glycosylated integral membrane protein that serves as the primary receptor for high density lipoprotein (HDL) and plays a central role in the reverse cholesterol transport pathway (RCT). In RCT, HDL removes cholesterol within atherosclerotic plaques and delivers it to the liver for excretion. HDL-cholesterol is delivered into hepatocytes through interaction with SR-B1, highlighting the need to improve our understanding of SR-B1 structure-function relationships to effectively lower plasma cholesterol levels and cardiovascular disease risk. Currently, structural information about SR-B1 remains limited to a structure of short transmembrane-spanning peptide segment, homology models, and transient transfection studies in cultured cells. Towards our long-term goal of resolving a full-length structure of human SR-B1, we have expressed and purified full-length human SR-B1 from an Sf9 insect cell baculoviral infection system. To verify function, human full-length SR-B1 expressed in plated Sf9 cells displayed a significant increase in DiI-HDL binding and DiI-lipid uptake compared to empty vector controls. Using PFO-PAGE, we demonstrated that SR-B1 forms dimers and higher order oligomers in Sf9 cells. After functional verification, we successfully incorporated purified protein into detergent micelles. Thermal shift assays revealed purified SR-B1 remained stable over a 6-week period. Purified SR-B1 also maintained the ability to bind to apolipoprotein A-I (the main protein component of HDL) and holoparticle HDL with high affinity (K D = 42.77 ± 7.15 μg/mL) by microscale thermophoresis (MST). Additionally, SR-B1 was able to bind oxidized low density lipoprotein (oxLDL). Further, while glycosylation remains important for SR-B1 expression, we are the first to demonstrate by MST that SR-B1’s glycosylation status did not impact HDL binding affinity (K D of 42.77 ± 7.15 μg/mL for glycosylated vs. 41.25 ± 4.92 μg/mL for unglycosylated SR-B1). Availability of functional purified human SR-B1 is a critical step towards a high-resolution structure and these studies lay the foundation for understanding the dynamics of SR-B1-mediated cholesterol transport and novel ways to modulate cardiovascular disease risk.

Abstract 206: Into The Wormhole: Understanding SR-B1’s Cholesterol Transport Functions Through Structural Studies

Scavenger receptor Class B type 1 (SR-B1) is a glycosylated integral membrane protein that serves as the primary receptor for high density lipoprotein (HDL) and plays a central role in the reverse cholesterol transport pathway (RCT). In RCT, HDL removes cholesterol within atherosclerotic plaques and delivers it to the liver for excretion. HDL-cholesterol is delivered into hepatocytes through interaction with SR-B1, highlighting the need to improve our understanding of SR-B1 structure-function relationships to effectively lower plasma cholesterol levels and cardiovascular disease risk. Currently, structural information about SR-B1 remains limited to a structure of short transmembrane-spanning peptide segment, homology models, and transient transfection studies in cultured cells. Towards our long-term goal of resolving a full-length structure of human SR-B1, we have expressed and purified full-length human SR-B1 from an Sf9 insect cell baculoviral infection system. To verify function, human full-length SR-B1 expressed in plated Sf9 cells displayed a significant increase in DiI-HDL binding and DiI-lipid uptake compared to empty vector controls. Using PFO-PAGE, we demonstrated that SR-B1 forms dimers and higher order oligomers in Sf9 cells. After functional verification, we successfully incorporated purified protein into detergent micelles. Thermal shift assays revealed purified SR-B1 remained stable over a 6-week period. Purified SR-B1 also maintained the ability to bind to apolipoprotein A-I (the main protein component of HDL) and holoparticle HDL with high affinity (K D = 42.77 ± 7.15 μg/mL) by microscale thermophoresis (MST). Additionally, SR-B1 was able to bind oxidized low density lipoprotein (oxLDL). Further, while glycosylation remains important for SR-B1 expression, we are the first to demonstrate by MST that SR-B1’s glycosylation status did not impact HDL binding affinity (K D of 42.77 ± 7.15 μg/mL for glycosylated vs. 41.25 ± 4.92 μg/mL for unglycosylated SR-B1). Availability of functional purified human SR-B1 is a critical step towards a high-resolution structure and these studies lay the foundation for understanding the dynamics of SR-B1-mediated cholesterol transport and novel ways to modulate cardiovascular disease risk.

The lipid components of high-density lipoproteins (HDL) are essential for the binding and transportation of antimicrobial peptides in human serum

Antimicrobial peptides (AMPs) have been developed for the treatment of bacterial infections, but their applications are limited to topical infections since they are sequestered and inhibited in serum. Here we have discovered that the inhibition of AMPs by human serum was mediated through high-density lipoproteins (HDL) which are known to remove cholesterol from peripheral tissues. The susceptibility of AMPs to HDL varied depending on the degree of hydrophobicity of AMPs and their binding affinities to HDL. The phospholipids, such as phosphatidylcholine, of HDL were essential for AMP-binding. The dynamic binding interactions between AMPs and HDL were mediated through the hydrophobic interactions rather than by ionic strength. Interestingly, some AMPs, such as SMAP29, dissociated from the AMP-HDL complex and translocated to bacteria upon contact, while some AMPs, such as LL37, remained in complex with HDL. These results suggest that HDL binds AMPs and facilitates the translocation of them to the bacteria.