APOA2 increases cholesterol efflux capacity to plasma HDL by displacing the C-terminus of resident APOA1.

The ability of high-density lipoprotein (HDL) to promote cellular cholesterol efflux is a more robust predictor of cardiovascular disease protection than HDL-cholesterol levels in plasma. Previously, we found that lipidated HDL containing both apolipoprotein A-I (APOA1) and A-II (APOA2) promotes cholesterol efflux via the ATP-binding cassette transporter (ABCA1). In the current study, we directly added purified, lipid-free APOA2 to human plasma and found a dose-dependent increase in whole plasma cholesterol efflux capacity.

A fast and sensitive size-exclusion chromatography method for plasma extracellular vesicle proteomic analysis.

Extracellular vesicles (EVs) carry diverse biomolecules derived from their parental cells, making their components excellent biomarker candidates. However, purifying EVs is a major hurdle in biomarker discovery since current methods require large amounts of samples, are time-consuming and typically have poor reproducibility. Here we describe a simple, fast, and sensitive EV fractionation method using size exclusion chromatography (SEC) on a fast protein liquid chromatography (FPLC) system.

Lipoprotein Particles in Cerebrospinal Fluid.

The brain is the most lipid-rich organ in the body, and the intricate interplay between lipid metabolism and pathologies associated with neurodegenerative disorders is being increasingly recognized. The brain is bathed in cerebrospinal fluid (CSF), which, like plasma, contains lipid-protein complexes called lipoproteins that are responsible for extracellular lipid transport. Multiple CSF lipoprotein populations exist, some of which are produced de novo in the central nervous system and others that appear to be generated from protein constituents that are produced in the periphery.

A novel assay to measure low-density lipoproteins binding to proteoglycans.

Background: The binding of low-density lipoprotein (LDL) to proteoglycans (PGs) in the extracellular matrix (ECM) of the arterial intima is a key initial step in the development of atherosclerosis. Although many techniques have been developed to assess this binding, most of the methods are labor-intensive and technically challenging to standardize across research laboratories. Thus, sensitive, and reproducible assay to detect LDL binding to PGs is needed to screen clinical populations for atherosclerosis risk.

A fast and sensitive size-exclusion chromatography method for plasma extracellular vesicle proteomic analysis.

Extracellular vesicles (EVs) carry diverse biomolecules derived from their parental cells, making their components excellent biomarker candidates. However, purifying EVs is a major hurdle in biomarker discovery since current methods require large amounts of samples, are time-consuming and typically have poor reproducibility. Here we describe a simple, fast, and sensitive EV fractionation method using size exclusion chromatography (SEC) on a fast protein liquid chromatography (FPLC) system.

Protection of β cells against pro-inflammatory cytokine stress by the GDF15-ERBB2 signaling.

Aim/hypothesis: Growth/differentiation factor 15 (GDF15) is a therapeutic target for a variety of metabolic diseases, including type 1 diabetes (T1D). However, the nausea caused by GDF15 is a challenging point for therapeutic development. In addition, it is unknown why the endogenous GDF15 fails to protect from T1D development.

Proteomic Determinants of Variation in Cholesterol Efflux: Observations from the Dallas Heart Study.

High-density lipoproteins (HDLs) are promising targets for predicting and treating atherosclerotic cardiovascular disease (ASCVD), as they mediate removal of excess cholesterol from lipid-laden macrophages that accumulate in the vasculature. This functional property of HDLs, termed cholesterol efflux capacity (CEC), is inversely associated with ASCVD. HDLs are compositionally diverse, associating with >250 different proteins, but their relative contribution to CEC remains poorly understood.

Human cerebrospinal fluid contains diverse lipoprotein subspecies enriched in proteins implicated in central nervous system health.

Lipoproteins in cerebrospinal fluid (CSF) of the central nervous system (CNS) resemble plasma high-density lipoproteins (HDLs), which are a compositionally and structurally diverse spectrum of nanoparticles with pleiotropic functionality. Whether CSF lipoproteins (CSF-Lps) exhibit similar heterogeneity is poorly understood because they are present at 100-fold lower concentrations than plasma HDL. To investigate the diversity of CSF-Lps, we developed a sensitive fluorescent technology to characterize lipoprotein subspecies in small volumes of human CSF.

Systematic review of type 1 diabetes biomarkers reveals regulation in circulating proteins related to complement, lipid metabolism, and immune response.

Aims: Type 1 diabetes (T1D) results from an autoimmune attack of the pancreatic β cells that progresses to dysglycemia and symptomatic hyperglycemia. Current biomarkers to track this evolution are limited, with development of islet autoantibodies marking the onset of autoimmunity and metabolic tests used to detect dysglycemia. Therefore, additional biomarkers are needed to better track disease initiation and progression.

Lipoprotein subfraction patterns throughout gestation in The Gambia: changes in subfraction composition and their relationships with infant birth weights.

Background: Lipoprotein subfraction concentrations have been shown to change as gestation progresses in resource-rich settings. The objective of the current study was to evaluate the impact of pregnancy on different-sized lipoprotein particle concentrations and compositions in a resource-poor setting.

Method: Samples were collected from pregnant women in rural Gambia at enrollment (8-20 weeks), 20 weeks, and 30 weeks of gestation.

GDF15: a potential therapeutic target for type 1 diabetes.

Introduction: Current treatment for type 1 diabetes (T1D) is centered around insulin supplementation to manage the effects of pancreatic β cell loss. GDF15 is a potential preventative therapy against T1D progression that could work to curb increasing disease incidence.

Areas Covered: This paper discusses the known actions of GDF15, a pleiotropic protein with metabolic, feeding, and immunomodulatory effects, connecting them to highlight the open opportunities for future research.

Pregnancy is accompanied by larger high density lipoprotein particles and compositionally distinct subspecies.

Pregnancy is accompanied by significant physiological changes, which can impact the health and development of the fetus and mother. Pregnancy-induced changes in plasma lipoproteins are well documented, with modest to no impact observed on the generic measure of high density lipoprotein (HDL) cholesterol. However, the impact of pregnancy on the concentration and composition of HDL subspecies has not been examined in depth.

Apolipoprotein A-I modulates HDL particle size in the absence of apolipoprotein A-II.

Human high-density lipoproteins (HDLs) are a complex mixture of structurally related nanoparticles that perform distinct physiological functions. We previously showed that human HDL containing apolipoprotein A-I (APOA1) but not apolipoprotein A-II (APOA2), designated LpA-I, is composed primarily of two discretely sized populations. Here, we isolated these particles directly from human plasma by antibody affinity chromatography, separated them by high-resolution size-exclusion chromatography and performed a deep molecular characterization of each species.

Modified sites and functional consequences of 4-oxo-2-nonenal adducts in HDL that are elevated in familial hypercholesterolemia.

The lipid aldehyde 4-oxo-2-nonenal (ONE) is a highly reactive protein crosslinker derived from peroxidation of n-6 polyunsaturated fatty acids and generated together with 4-hydroxynonenal (HNE). Lipid peroxidation product-mediated crosslinking of proteins in high-density lipoprotein (HDL) causes HDL dysfunction and contributes to atherogenesis. Although HNE is relatively well-studied, the role of ONE in atherosclerosis and in modifying HDL is unknown.

Distinct Proteomic Signatures in 16 HDL (High-Density Lipoprotein) Subspecies.

Objective- HDL (high-density lipoprotein) in plasma is a heterogeneous group of lipoproteins typically containing apo AI as the principal protein. Most HDLs contain additional proteins from a palate of nearly 100 HDL-associated polypeptides. We hypothesized that some of these proteins define distinct and stable apo AI HDL subspecies with unique proteomes that drive function and associations with disease.

A thumbwheel mechanism for APOA1 activation of LCAT activity in HDL.

APOA1 is the most abundant protein in HDL. It modulates interactions that affect HDL's cardioprotective functions, in part via its activation of the enzyme, LCAT. On nascent discoidal HDL, APOA1 comprises 10 α-helical repeats arranged in an anti-parallel stacked-ring structure that encapsulates a lipid bilayer.

Characterization of homodimer interfaces with cross-linking mass spectrometry and isotopically labeled proteins.

Cross-linking coupled with mass spectrometry (XL-MS) has emerged as a powerful strategy for the identification of protein-protein interactions, characterization of interaction regions, and obtainment of structural information on proteins and protein complexes. In XL-MS, proteins or complexes are covalently stabilized with cross-linkers and digested, followed by identification of the cross-linked peptides by tandem mass spectrometry (MS/MS). This provides spatial constraints that enable modeling of protein (complex) structures and regions of interaction.

Effects of Multiple Freeze/Thaw Cycles on Measurements of Potential Novel Biomarkers Associated With Adverse Pregnancy Outcomes.

World-wide, millions of women enter preterm labor or have small newborns. Effective biomarkers are needed to identify women at risk for these adverse outcomes. A time and cost effective way to examine any potentially new biomarkers in samples collected during prior studies or trials that had been assayed for other metabolites would be highly useful.

A consensus model of human apolipoprotein A-I in its monomeric and lipid-free state.

Apolipoprotein (apo)A-I is an organizing scaffold protein that is critical to high-density lipoprotein (HDL) structure and metabolism, probably mediating many of its cardioprotective properties. However, HDL biogenesis is poorly understood, as lipid-free apoA-I has been notoriously resistant to high-resolution structural study. Published models from low-resolution techniques share certain features but vary considerably in shape and secondary structure.

Studies in genetically modified mice implicate maternal HDL as a mediator of fetal growth.

Studies in humans have shown a direct association between maternal plasma cholesterol concentrations and infant birthweight. Similarly, previous studies in our laboratory have shown that chow-fed mice lacking apolipoprotein (apo) A-I, the major protein in HDL, have low HDL-cholesterol (HDL-C) concentrations and smaller fetuses in midgestation. In the current study, we measured fetal weights in mice with varying levels of apoA-I gene dose (knockout, wild-type, and transgenic) and examined metabolic pathways known to affect fetal growth.

Obesity is associated with an altered HDL subspecies profile among adolescents with metabolic disease.

We aimed to determine the risk factors associated with the depletion of large HDL particles and enrichment of small HDL particles observed in adolescents with T2D. Four groups of adolescents were recruited: ) lean insulin-sensitive (L-IS), normal BMI and no insulin resistance; ) lean insulin-resistant (L-IR), normal BMI but insulin resistance (fasting insulin levels ≥ 25 mU/ml and homeostatic model assessment of insulin resistance ≥ 6); ) obese insulin-sensitive (O-IS), BMI ≥ 95th percentile and no insulin resistance; and ) obese insulin-resistant (O-IR), BMI ≥ 95th percentile and insulin resistance. Plasma was separated by using gel-filtration chromatography to assess the HDL subspecies profile and compared with that of obese adolescents with T2D (O-T2D).

Apolipoprotein A-II alters the proteome of human lipoproteins and enhances cholesterol efflux from ABCA1.

HDLs are a family of heterogeneous particles that vary in size, composition, and function. The structure of most HDLs is maintained by two scaffold proteins, apoA-I and apoA-II, but up to 95 other "accessory" proteins have been found associated with the particles. Recent evidence suggests that these accessory proteins are distributed across various subspecies and drive specific biological functions.

High density lipoproteins selectively promote the survival of human regulatory T cells.

HDLs appear to affect regulatory T cell (Treg) homeostasis, as suggested by the increased Treg counts in HDL-treated mice and by the positive correlation between Treg frequency and HDL-cholesterol levels in statin-treated healthy adults. However, the underlying mechanisms remain unclear. Herein, we show that HDLs, not LDLs, significantly decreased the apoptosis of human Tregs in vitro, whereas they did not alter naïve or memory CD4 T cell survival.

The effects of apolipoprotein B depletion on HDL subspecies composition and function.

HDL cholesterol (HDL-C) efflux function may be a more robust biomarker of coronary artery disease risk than HDL-C. To study HDL function, apoB-containing lipoproteins are precipitated from serum. Whether apoB precipitation affects HDL subspecies composition and function has not been thoroughly investigated.