Nathalie Pamir

• Doctor of Philosophy, Master of Science
• Professor (Associate) at Oregon Health & Science University

High plasma apolipoprotein B (apoB)-containing lipoproteins are both a biomarker and a causal mediator of many metabolic diseases. Inhibition of APOB mRNA decreases plasma lipid levels but at a risk of lipid accumulation in tissues. To understand the global consequences of reduced apoB synthesis, we generated a human hepatoma (Huh-7) cell culture m...

Background: It is unknown how cardiovascular health (CVH) relates to severe Covid-19 illness in adults without clinical cardiovascular disease (CVD). We hypothesized that more optimal Life’s Essential 8 (LE8)-quantified CVH is associated with lower risk of severe Covid-19 among US adults without clinical CVD. Methods: C4R is ascertaining Covid-19 e...

We recently demonstrated that plasma lipoproteins play a major role in regulating the function of the hemostatic system by either inhibiting or promoting the self-association of von Willebrand factor (VWF) into large fibers and bundles that are hyperadhesive for platelets. Such fibers can form on the surface of activated endothelium such as during...

Von Willebrand factor (VWF) mediates primary hemostasis and thrombosis in response to hydrodynamic forces. We previously showed that high shear promoted self-association of VWF into hyperadhesive strands, which can be attenuated by high density lipoprotein (HDL) and apolipoprotein(apo) A-I. Here, we show that low density lipoprotein (LDL) binds VWF...

Aggressive lipid lowering in mice with established atherosclerosis induces plaque regression and is characterized by reduced monocyte recruitment and increased expression of the motility receptor C-C chemokine receptor 7 (CCR7) to promote macrophage egress from plaques to nearby lymph nodes. Notably, genetic deletion of receptors critical for the r...

Proprotein convertase subtilisin/kexin type 9 (PCSK9) increases plasma LDL levels due to the degradation of the LDL receptor (LDLR). Anti PCSK9 antibody treatment leads to up to 70% reduction in plasma LDL levels. However, for poorly understood reasons, the treatment has no effect in some patients. Glycosylation is one of several PCSK9 post-transla...

Background Plasma lipids are risk factors for coronary heart disease (CHD) in part because of race-specific associations of lipids with CHD. Objectives The purpose of this study was to understand why CHD risk equations underperform in Black adults. Methods Between 2003 and 2007, the REGARDS (REasons for Geographic and Racial Differences in Stroke...

Low-density lipoprotein (LDL) contributes to atherogenesis and cardiovascular disease through interactions with peripheral blood cells, especially platelets. However, mechanisms by which LDL affects platelet activation and atherothrombosis, and how to best therapeutically target and safely prevent such responses remains unclear. Here, we investigat...

High levels of circulating Lipoprotein (a) [Lp(a)] are an independent risk factor for CVD. One of the major limitations to investigating Lp(a) biology is the need for large volumes of plasma (4–10 mL) for its isolation. We developed an isolation technique requiring only 0.4 mL of plasma yielding an enriched Lp(a) fraction suitable for compositional...

Lipoprotein (a) [Lp(a)] is an independent risk factor for cardiovascular disease (CVD) and resembles an LDL-like lipoprotein with the addition of apolipoprotein(a) (LPA). The LPA gene results from a duplication of the plasminogen gene ( PLG ) and the proteins share 88% amino acid sequence homology in their protease domains. We recently identified L...

Background Understanding health care experiences during the COVID-19 pandemic may provide insights into patient needs and inform policy. The objective of this study was to describe health care experiences by race and social determinants of health. Methods We conducted a telephone survey (July 6, 2020-September 4, 2021) among 9492 Black and White p...

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Objective Antibody blockade of the do not eat me signal CD47 enhances efferocytosis and reduces lesion size and necrotic core formation in murine atherosclerosis. TNF (Tumor necrosis factor)-α expression directly enhances CD47 expression, and elevated TNF-α is observed in the absence of the proefferocytosis receptor LRP1 (low-density lipoprotein re...

Background Monoclonal antibodies against proprotein convertase subtilisin/kexin type 9 (PCSK9i) lower LDL-C by up to 60% and increase plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) levels by 10-fold. Objectives The authors studied the reasons behind the robust increase in plasma PCSK9 levels by testing the hypothesis that mechanisms...

Objective Black adults are less likely than White adults to present with adverse lipid profiles and more likely to present with low-grade inflammation. The impact of race on the association between atherogenic lipid profiles, inflammation, and coronary heart disease (CHD) is unknown. Methods We evaluated the association between high levels (>50th...

Plasminogen activator inhibitor 1 (PAI-1) is a functional biomarker of the metabolic syndrome. Previous studies have demonstrated that PAI-1 is a mechanistic contributor to several elements of the syndrome, including obesity, hypertension and insulin resistance. Here we show that PAI-1 is also a critical regulator of hepatic lipid metabolism. RNA s...

Proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates cholesterol metabolism by inducing the degradation of hepatic low-density lipoprotein receptor (LDLR). Plasma PCSK9 has two main molecular forms: a 62-kDa mature form (PCSK9_62) and a 55-kDa, furin-cleaved form (PCSK9_55). PCSK9_55 is considered less active than PCSK9_62 in degrading L...

Rationale: Prospective cohort studies question the value of HDL-C for stroke risk prediction. Objective: Investigate the relationship between long-term functional recovery and HDL proteome and function. Methods and Results: Changes in HDL protein composition and function (cholesterol efflux capacity, or CEC) in patients after acute ischemic stroke...

Introduction: Whether plasma lipid levels are associated with stroke risk remains controversial, with even less data for American blacks versus whites. Hypothesis: We hypothesized that abnormal lipid levels are not associated with stroke incidence in either blacks or whites. Methods: The REasons for Geographic And Racial Differences in Stroke (REGA...

Introduction: Abnormal plasma lipid levels associate with coronary heart disease (CHD) risk. Race interaction for these associations are not established. Hypothesis: We hypothesized that the association of HDL, LDL, and triglyceride with CHD is stronger in whites versus blacks. Methods: The REasons for Geographic and Racial Differences in Stroke (R...

Recent developments in in situ microscopy have enabled unparalleled resolution of the architecture of the bone marrow (BM) niche for murine hematopoietic stem and progenitor cells (HSPCs). However, the extent to which these observations can be extrapolated to human BM remains unknown. In humans, adipose tissue occupies a significant portion of the...

Objective: Atherosclerosis is a leading cause of death in developed countries. MicroRNAs act as fine-tuners of gene expression and have been shown to have important roles in the pathophysiology and progression of atherosclerosis. We, and others, previously demonstrated that microRNA-144 (miR-144) functions to post-transcriptionally regulate ABCA1...

Elevated serum lipoprotein(a) [Lp(a)] levels are associated with increased cardiovascular disease risk. We recently identified plasminogen (PLG) as a driver of ABCA1-mediated cholesterol efflux and demonstrated that its action is inhibited by purified human Lp(a). The effects of Lp(a) in human serum on ABCA1-mediated cholesterol efflux and on the i...

Regional fat distribution plays an important role in the development of an unfavorable metabolic and cardiovascular risk profile. The epicardial adipose tissue (EAT) size correlates with coronary and non-coronary artery disease even after adjusting for weight (or body mass index) and traditional cardiovascular risk factors. However, the mechanisms...

Rationale Elevated serum lipoprotein(a) [Lp(a)] levels are associated with increased cardiovascular disease risk. ABCA1-mediated cholesterol efflux from macrophages is believed to be an anti-atherogenic process. We recently identified plasminogen as a driver of ABCA1-mediated cholesterol efflux and showed that its action is inhibited by purified hu...

HDLs are nanoparticles with more than 80 associated proteins, phospholipids, cholesterol, and cholesteryl esters. The potential inverse relation of HDL to coronary artery disease (CAD) and the effects of HDL on myriad other inflammatory conditions warrant a better understanding of the genetic basis of the HDL proteome. We conducted a comprehensive...

In a GM-CSF driven myeloid cell deficient mouse model (Csf2−/−) that has preserved insulin sensitivity despite increased adiposity, we used unbiased three-dimensional integration of proteome profiles, metabolic profiles, and gene regulatory networks to understand adipose tissue proteome-wide changes and their metabolic implications. Multi-dimension...

Background: APOL1 renal risk variants are strongly associated with chronic kidney disease in Black adults, but reported associations with cardiovascular disease (CVD) have been conflicting. Methods: We examined associations of APOL1 with incident coronary heart disease (n=323), ischemic stroke (n=331), and the composite CVD outcome (n=500) in 10...

HDL protein composition and corresponding function may impact cardiovascular disease risk. Identifying genetic variation that influences the HDL proteome may reveal modifiable HDL functions that impact this risk. We studied genetic determinants of the HDL proteome in a cohort of rhesus macaques enriched for extreme HDL cholesterol levels (HDL-c). W...

Background: Prospective cohort studies and meta-analyses examining the relationship between HDL-cholesterol (C) and stroke risk are discordant and question the value of HDL-C as a marker for stroke risk prediction. Changes in HDL-C protein composition and function after acute ischemic stroke, and their relationship to stroke recovery have not been...

Background: Plasminogen, is a potent acceptor of cholesterol by the ABCA1 transporter in peripheral cells, and this function is inhibited by lipoprotein (a) [Lp(a)]. Patients with high Lp(a) have increased cardiovascular disease risk, but the mechanism for this effect is not known. The interplay of plasminogen and Lp(a) in contributing to the total...

Rationale: Removal of cholesterol from atherosclerotic lesions remains an unmet therapeutic need. The ATP Binding Cassette Transporter A1 (ABCA1) plays a key role in the efflux of cholesterol from macrophages, therefore strategies that increase macrophage ABCA1 levels are likely to be atheroprotective. Objective: To determine the potential of miR-1...

Using genetic and biochemical approaches, we investigated proteins that regulate macrophage cholesterol efflux capacity (CEC) and ABCA1-specific CEC (ABCA1 CEC), 2 functional assays that predict cardiovascular disease (CVD). Macrophage CEC and the concentration of HDL particles were markedly reduced in mice deficient in apolipoprotein A-I (APOA1) o...

Background: Prospective cohort studies and meta-analyses examining the relationship between HDL-cholesterol (C) and stroke are discordant and question the value of HDL-C as a marker for stroke risk prediction. Other properties of HDL-C such as cholesterol efflux capacity (CEC) and proteome, are less studied. Methods: We investigated the changes in...

The lack of high-throughput methods to analyze the adipose tissue protein composition limits our understanding of the protein networks responsible for age and diet related metabolic response. We have developed an approach using multiple-dimension liquid chromatography tandem mass spectrometry and extended multiplexing (24 biological samples) with T...

Classic clinical and epidemiological studies have long ago established the presence of an inverse relationship between high-density lipoprotein cholesterol (HDLC) levels and cardiovascular disease (CVD) risk, and thus, it was assumed that measures that increase HDLC levels would afford protection against atherosclerosis-based CVD.1,2 However, trial...

Recent data indicate that HDL function has effects independent of HDL cholesterol (HDL-C) levels that better predict cardiovascular risk. We aimed to characterize sterol efflux across a wide range of HDL-C, and to identify genetic determinants for both traits in a non-human primate model. To do this, we took advantage of rhesus macaque families tha...

Background: The cholesterol efflux capacity (CEC) of serum HDL, measured using cultured macrophages predicts incident and prevalent CVD risk in humans. The ABCA1 pathway is a key regulator of macrophage cholesterol homeostasis in vivo. Methods: We used genetic and biochemical approaches in mice to identify important mediators of CEC. Results: On hi...

Atherosclerosis is a disease of both lipids and inflammatory immune cells. More specifically, elevated plasma levels of low-density lipoproteins (LDL) leads to migration of circulating monocytes into the artery wall. Lipid loaded monocyte cells subsequently proliferate in the arterial walls becoming macrophage foam cells; a hallmark of atherosclero...

Recent data indicate that HDL function has effects independent of HDL cholesterol (HDL-C) levels that better predict cardiovascular risk. We aimed to characterize sterol efflux across a wide range of HDL-C, and to identify genetic determinants for both traits in a non-human primate model. To do this, we took advantage of rhesus macaque families tha...

Cholesterol efflux capacity associates strongly and negatively with the incidence and prevalence of human cardiovascular disease. We investigated the relationships of HDL's size and protein cargo with its cholesterol efflux capacity, using APOB-depleted serum and HDLs isolated from five inbred mouse strains with different susceptibilities to athero...

Background: Human HDL’s efflux capacity-the ability to promote cholesterol efflux from macrophages-associates strongly and negatively with risk of future cardiac events. However, the molecular factors that regulate efflux capacity remain poorly understood. Methods and Results: We investigated the relationships between HDL’s size, protein cargo, and...

The physiological roles of macrophages and dendritic cells (DCs) in lean white adipose tissue homeostasis have received little attention. Because DCs are generated from bone marrow progenitors in the presence of granulocyte macrophage-colony stimulating factor (GM-CSF), we used GM-CSF-deficient (Csf2(-/-)) mice fed a low-fat diet to test the hypoth...

Unlabelled: High-density lipoprotein (HDL), a lipid nanoparticle containing many different low abundance proteins, is an attractive target for clinical proteomics because its compositional heterogeneity is linked to its cardioprotective effects. Selected reaction monitoring (SRM) is currently the method of choice for targeted quantification of pro...

Background: It is critical to develop new metrics to determine whether HDL is cardioprotective in humans. One promising approach is HDL particle concentration (HDL-P), the size and concentration of HDL in plasma. However, the 2 methods currently used to determine HDL-P yield concentrations that differ >5-fold. We therefore developed and validated...

Macrophage metalloelastase, a matrix metallopeptidase (MMP12) predominantly expressed by mature tissue macrophages, is implicated in pathological processes. However, physiological functions for MMP12 have not been described. Because mRNA levels for the enzyme increase markedly in adipose tissue of obese mice, we investigated the role of MMP12 in ad...

Monocytes differentiate into heterogeneous populations of tissue macrophages and dendritic cells (DCs) that regulate inflammation and immunity. Identifying specific populations of myeloid cells in vivo is problematic, however, because only a limited number of proteins have been used to assign cellular phenotype. Using mass spectrometry and bone mar...

Plasma membrane proteins detected by LC-ESI-MS/MS in myeloid cells. Bone marrow precursor cells were differentiated into bone marrow-derived macrophages (BmM), classically-activated macrophages (M1), alternatively-activated macrophages (M2), and bone marrow-derived dendritic cells (BmDC). Plasma membrane proteins for each cell type (N = 6) were iso...

The plasma membrane proteome classifies myeloid cells. Panels A–B: Hierarchical cluster analysis. Spectral counts for each protein (192 total) in each cell type were normalized to the mean expression level across all four cell types and analyzed by hierarchical clustering with Pearson correlation as the distance metric and average linkage clusterin...

Immunocytochemical detection of plasma membrane protein markers. Expression levels of newly identified markers of M1 cells, M2 cells, BmMs and BmDCs was assessed by mass spectrometry (Panel A) and immunocytochemistry (Panel B). For MS/MS, proteins were quantified by spectral counting and expressed relative to the cell type with the highest expressi...

Identification of plasma membrane proteins that distinguish amongst polarized macrophages. Protein markers specific for each macrophage population tested (or signatures) were identified based on both the t-test (p-value) and G-test (G-statistic). Protein markers for a given cell type were defined as those that were consistently up-regulated (G>1.5...

Plasma membrane proteomics of bone marrow-derived dendritic cells (BmDC). Overlaps between plasma membrane protein expression in BmDCs and the macrophage signatures identified (see Fig. 1 and Table S2), as well as the BmDC signature were identified based on the t-test and G-test. Protein markers of BmDCs (BmDC signature) were defined as those that...

Plasma membrane proteins differentially expressed in Csf2−/− mice. eMPCs isolated from wild-type (wt) and Csf2−/− mice were analyzed by mass spectrometry. Differentially expressed proteins were identified by the t-test (p<0.05) and G-test (G>1.5 or <−1.5). Red = up-regulated and green = down-regulated in eMPCs isolated from Csf2−/− relative to wt m...

PCR primers used in this study. (XLSX)

Flow cytometric analysis of myeloid cells. Panel A: Bone marrow-derived macrophages (BmM) and dendritic cells (BmDCs) were obtained by culturing bone marrow cells with M-CSF and GM-CSF respectively. Flow cytometric analysis of CD11c, F4/80, and MHC-II expression in BmDCs and BmMs. Results are directly comparable to Figure 2B–C in the main manuscrip...

Plasma membrane proteomics of thioglycolate-elicited myeloid peritoneal cells (eMPCs). Overlaps between plasma membrane protein expression in eMPCs and BmMs, M1, M2, and BmDCs (highlighted in blue) were identified based on the t-test and G-test. For example, overlaps between eMPCs and the BmDC signature were defined as those proteins for which expr...

Lymphotoxin-α (LTα) is secreted by lymphocytes and acts through tumor necrosis factor-α receptors and the LTβ receptor. Our goals were to determine whether LT has a role in obesity and investigate whether LT contributes to the link between obesity and adipose tissue lymphocyte accumulation. LT deficient (LT(-/-)) and wild-type (WT) mice were fed st...

The prevalence of obesity has reached epidemic proportions and is associated with several co-morbid conditions including diabetes, dyslipidemia, cancer, atherosclerosis and gallstones. Obesity is associated with low systemic inflammation and an accumulation of adipose tissue macrophages (ATMs) that are thought to modulate insulin resistance. ATMs m...

TNF-alpha signals through two receptors, TNFR1 and TNFR2. Our goals were: 1) determine the role of TNFRs in obesity and metabolic disease and 2) investigate whether TNFRs contribute to the link between obesity and adipose tissue macrophage infiltration and polarization. R1(-/-)R2(-/-) (RKO) and wild-type (WT) mice were fed standard chow or a high-f...

Apolipoprotein A5 (APOA5) is expressed primarily in the liver and modulates plasma triglyceride levels in mice and humans. Mice overexpressing APOA5 exhibit reduced plasma triglyceride levels. Because there is a tight association between plasma triglyceride concentration and traits of the metabolic syndrome, we used transgenic mice overexpressing h...

The incretins glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are gut hormones that act via the enteroinsular axis to potentiate insulin secretion from the pancreas in a glucose-dependent manner. Both GLP-1 receptor and GIP receptor knockout mice (GLP-1R(-/-) and GIPR(-/-), respectively) have been generated to...

Recent studies into the physiology of the incretins glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) have added stimulation of beta-cell growth, differentiation, and cell survival to well-documented, potent insulinotropic effects. Unfortunately, the therapeutic potential of these hormones is limited by their ra...

Although type 2 diabetic patients exhibit resistance to GIP when the peptide is administered in doses that result in circulating levels approximating those found physiologically, it is likely that DP IV-resistant forms of the peptide administered in pharmacological doses will prove to be effective in improving glucose tolerance. Additionally, in vi...

Glucose-dependent insulinotropic polypeptide (GIP) is secreted postprandially and acts in concert with glucose to stimulate insulin secretion from the pancreas. Here, we describe a novel pathway for the regulation of GIP receptor (GIPR) expression within clonal beta-cell lines, pancreatic islets, and in vivo. High (25 mM) glucose was able to signif...

Glucose-dependent insulinotropic polypeptide (GIP) is a peptide hormone that is released postprandially from the small intestine and acts in concert with glucagon-like peptide (GLP)-1 to potentiate glucose-induced insulin secretion from the pancreatic beta-cell. In type 2 diabetes, there is a decreased responsiveness of the pancreas to GIP; however...

The incretins are a class of hormones released from the small bowel that act on the endocrine pancreas to potentiate insulin secretion in a glucose-dependent manner. Due to the requirement for an elevated glucose concentration for activity, the incretins, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1, have potential...