Blood clearance kinetics and organ delivery of medium-chain triglyceride and fish oil-containing lipid emulsions: Comparing different animal species.

BACKGROUND & AIMS: Medium-chain triglycerides (TG) (MCT) and fish oil (FO) TG are incorporated as the core TG component into intravenous (IV) lipid emulsions for infusion in parenteral nutrition. Bolus injections of IV emulsions, on the other hand, have emerged as a novel therapeutic approach to treat various acute disorders. However, intravascular metabolism and organ delivery of acute IV injection of emulsions containing both MCT and FO are not fully defined, nor have they been characterized across common experimental animal models. We characterized and compared blood clearance kinetics and organ distribution of bolus injections of MCT/FO emulsions among different animal species. We also examined whether sex differences or feeding status can affect catabolic properties of MCT/FO lipid emulsions. DESIGN: Blood clearance rates of lipid emulsions with specific TG composition were compared in rats IV injected with [3H]cholesteryl hexadecyl ether labeled pure n-6 long-chain (LCT) and n-3 FO TG lipid emulsions, or emulsions containing MCT and FO at different ratios (wt/wt), which include 8:2 (80% MCT: 20% FO), 5:4:1 (50% MCT: 40% LCT: 10% FO) and SMOF (30% LCT: 30% MCT: 25% olive oil: 10% FO). Dose-response effects (0.016 mg-1.6 mg TG/g body weight) of the MCT/FO 8:2 emulsions on blood clearance properties and organ delivery were determined in both mice and rats. Blood clearance kinetics and organ uptake of MCT/FO 8:2 emulsions were compared between male and female rats and between fed and fasted rats. Changes in plasma lipid profiles after acute injections of MCT/FO 8:2 lipid emulsion at different doses (0.043, 0.133, and 0.4 mg TG/g body weight) were characterized in non-human primates (Cynomolgus monkeys). RESULTS: MCT/FO 8:2 emulsion was cleared faster in rats when compared with other emulsions with different TG contents. Mice had faster blood clearance and higher fractional catabolic rates (FCR) when compared with the rats injected with MCT/FO 8:2 emulsions regardless of the injected doses. Mice and rats had similar plasma TG and free fatty acid (FFA) levels after low- or high-dose injections of the MCT/FO emulsion. Tissue distribution of the MCT/FO 8:2 lipid emulsion are comparable between mice and rats, where liver had the highest uptake per recovered dose among all organs (>60%). Feeding status and sex differences did not alter the blood clearance rate of the MCT/FO 8:2 emulsion in rats. In a nonhuman primate model, dose-response increases in plasma TG and FFA were observed after IV injection of MCT/FO 8:2 emulsions within the 1st 10 min. CONCLUSION: A lipid emulsion containing both MCT and FO TG is cleared rapidly in blood and readily available for organ uptake in rodent and primate animal models. Characterization of the blood clearance properties of the MCT/FO 8:2 emulsion administered in various animal models may provide further insight into the safety and efficacy profiles for future therapeutic use of bolus injections of MCT/FO emulsions in humans.

Lipoprotein Lipase Deficiency Impairs Bone Marrow Myelopoiesis and Reduces Circulating Monocyte Levels.

OBJECTIVE: Tissue macrophages induce and perpetuate proinflammatory responses, thereby promoting metabolic and cardiovascular disease. Lipoprotein lipase (LpL), the rate-limiting enzyme in blood triglyceride catabolism, is expressed by macrophages in atherosclerotic plaques. We questioned whether LpL, which is also expressed in the bone marrow (BM), affects circulating white blood cells and BM proliferation and modulates macrophage retention within the artery. APPROACH AND RESULTS: We characterized blood and tissue leukocytes and inflammatory molecules in transgenic LpL knockout mice rescued from lethal hypertriglyceridemia within 18 hours of life by muscle-specific LpL expression (MCKL0 mice). LpL-deficient mice had ≈40% reduction in blood white blood cell, neutrophils, and total and inflammatory monocytes (Ly6C/Ghi). LpL deficiency also significantly decreased expression of BM macrophage-associated markers (F4/80 and TNF-α [tumor necrosis factor α]), master transcription factors (PU.1 and C/EBPα), and colony-stimulating factors (CSFs) and their receptors, which are required for monocyte and monocyte precursor proliferation and differentiation. As a result, differentiation of macrophages from BM-derived monocyte progenitors and monocytes was decreased in MCKL0 mice. Furthermore, although LpL deficiency was associated with reduced BM uptake and accumulation of triglyceride-rich particles and macrophage CSF-macrophage CSF receptor binding, triglyceride lipolysis products (eg, linoleic acid) stimulated expression of macrophage CSF and macrophage CSF receptor in BM-derived macrophage precursor cells. Arterial macrophage numbers decreased after heparin-mediated LpL cell dissociation and by genetic knockout of arterial LpL. Reconstitution of LpL-expressing BM replenished aortic macrophage density. CONCLUSIONS: LpL regulates peripheral leukocyte levels and affects BM monocyte progenitor differentiation and aortic macrophage accumulation.

Acute administration of n-3 rich triglyceride emulsions provides cardioprotection in murine models after ischemia-reperfusion.

Dietary n-3 fatty acids (FAs) may reduce cardiovascular disease risk. We questioned whether acute administration of n-3 rich triglyceride (TG) emulsions could preserve cardiac function and decrease injury after ischemia/reperfusion (I/R) insult. We used two different experimental models: in vivo, C57BL/6 mice were exposed to acute occlusion of the left anterior descending coronary artery (LAD), and ex-vivo, C57BL/6 murine hearts were perfused using Langendorff technique (LT). In the LAD model, mice treated with n-3 TG emulsion (1.5 g/kg body weight), immediately after ischemia and 1 h later during reperfusion, significantly reduced infarct size and maintained cardiac function (p<0.05). In the LT model, administration of n-3 TG emulsion (300 mg TG/100 ml) during reperfusion significantly improved functional recovery (p<0.05). In both models, lactate dehydrogenase (LDH) levels, as a marker of injury, were significantly reduced by n-3 TG emulsion. To investigate the mechanisms by which n-3 FAs protects hearts from I/R injury, we investigated changes in key pathways linked to cardioprotection. In the ex-vivo model, we showed that n-3 FAs increased phosphorylation of AKT and GSK3ß proteins (p<0.05). Acute n-3 TG emulsion treatment also increased Bcl-2 protein level and reduced an autophagy marker, Beclin-1 (p<0.05). Additionally, cardioprotection by n-3 TG emulsion was linked to changes in PPARγ protein expression (p<0.05). Rosiglitazone and p-AKT inhibitor counteracted the positive effect of n-3 TG; GSK3ß inhibitor plus n-3 TG significantly inhibited LDH release. We conclude that acute n-3 TG injection during reperfusion provides cardioprotection. This may prove to be a novel acute adjunctive reperfusion therapy after treating patients with myocardial infarction.

Incremental replacement of saturated fats by n-3 fatty acids in high-fat, high-cholesterol diets reduces elevated plasma lipid levels and arterial lipoprotein lipase, macrophages and atherosclerosis in LDLR-/- mice.

OBJECTIVE: Effects of progressive substitution of dietary n-3 fatty acids (FA) for saturated FA (SAT) on modulating risk factors for atherosclerosis have not been fully defined. Our previous reports demonstrate that SAT increased, but n-3 FA decreased, arterial lipoprotein lipase (LpL) levels and arterial LDL-cholesterol deposition early in atherogenesis. We now questioned whether incremental increases in dietary n-3 FA can counteract SAT-induced pro-atherogenic effects in atherosclerosis-prone LDL-receptor knockout (LDLR-/-) mice and have identified contributing mechanisms. METHODS AND RESULTS: Mice were fed chow or high-fat diets enriched in SAT, n-3, or a combination of both SAT and n-3 in ratios of 3:1 (S:n-3 3:1) or 1:1 (S:n-3 1:1). Each diet resulted in the expected changes in fatty acid composition in blood and aorta for each feeding group. SAT-fed mice became hyperlipidemic. By contrast, n-3 inclusion decreased plasma lipid levels, especially cholesterol. Arterial LpL and macrophage levels were increased over 2-fold in SAT-fed mice but these were decreased with incremental replacement with n-3 FA. n-3 FA partial inclusion markedly decreased expression of pro-inflammatory markers (CD68, IL-6, and VCAM-1) in aorta. SAT diets accelerated advanced atherosclerotic lesion development, whereas all n-3 FA-containing diets markedly slowed atherosclerotic progression. CONCLUSION: Mechanisms whereby dietary n-3 FA may improve adverse cardiovascular effects of high-SAT, high-fat diets include improving plasma lipid profiles, increasing amounts of n-3 FA in plasma and the arterial wall. Even low levels of replacement of SAT by n-3 FA effectively reduce arterial lipid deposition by decreasing aortic LpL, macrophages and pro-inflammatory markers.

Adipose-specific lipoprotein lipase deficiency more profoundly affects brown than white fat biology.

Adipose fat storage is thought to require uptake of circulating triglyceride (TG)-derived fatty acids via lipoprotein lipase (LpL). To determine how LpL affects the biology of adipose tissue, we created adipose-specific LpL knock-out (ATLO) mice, and we compared them with whole body LpL knock-out mice rescued with muscle LpL expression (MCK/L0) and wild type (WT) mice. ATLO LpL mRNA and activity were reduced, respectively, 75 and 70% in gonadal adipose tissue (GAT), 90 and 80% in subcutaneous tissue, and 84 and 85% in brown adipose tissue (BAT). ATLO mice had increased plasma TG levels associated with reduced chylomicron TG uptake into BAT and lung. ATLO BAT, but not GAT, had altered TG composition. GAT from MCK/L0 was smaller and contained less polyunsaturated fatty acids in TG, although GAT from ATLO was normal unless LpL was overexpressed in muscle. High fat diet feeding led to less adipose in MCK/L0 mice but TG acyl composition in subcutaneous tissue and BAT reverted to that of WT. Therefore, adipocyte LpL in BAT modulates plasma lipoprotein clearance, and the greater metabolic activity of this depot makes its lipid composition more dependent on LpL-mediated uptake. Loss of adipose LpL reduces fat accumulation only if accompanied by greater LpL activity in muscle. These data support the role of LpL as the "gatekeeper" for tissue lipid distribution.

Fatty acids regulate endothelial lipase and inflammatory markers in macrophages and in mouse aorta: a role for PPARγ.

OBJECTIVE: Macrophage endothelial lipase (EL) is associated with increased atherosclerosis and inflammation. Because of their anti-inflammatory properties we hypothesized that n-3 fatty acids, in contrast to saturated fatty acids, would lower macrophages and arterial EL and inflammatory markers. METHODS AND RESULTS: Murine J774 and peritoneal macrophages were incubated with eicosapentaenoic acid or palmitic acid in the presence or absence of lipopolysaccaride (LPS). LPS increased EL mRNA and protein. Palmitic acid alone or with LPS dose-dependently increased EL mRNA and protein. In contrast, eicosapentaenoic acid dose-dependently abrogated effects of LPS or palmitic acid on increasing EL expression. EL expression closely linked to peroxisome proliferator activated receptor (PPAR)γ expression. Eicosapentaenoic acid blocked rosiglitazone (a PPARγ agonist)-mediated EL activation and GW9662 (a PPARγ antagonist)-blocked palmitic acid-mediated EL stimulation. Eicosapentaenoic acid alone or with LPS blunted LPS-mediated stimulation of macrophage proinflammatory interleukin-6, interleukin-12p40, and toll-like receptor-4 mRNA and increased anti-inflammatory interleukin-10 and mannose receptor mRNA. In vivo studies in low density lipoprotein receptor knockout mice showed that high saturated fat rich diets, but not n-3 diets, increased arterial EL, PPARγ, and proinflammatory cytokine mRNA. CONCLUSIONS: n-3 fatty acids, in contrast to saturated fatty acids, decrease EL in parallel with modulating pro- and anti-inflammatory markers, and these effects on EL link to PPARγ.

Rapid cellular enrichment of eicosapentaenoate after a single intravenous injection of a novel medium-chain triacylglycerol:fish-oil emulsion in humans.

BACKGROUND: Dietary deficiency in n-3 (omega-3) polyunsaturated fatty acids (PUFAs) prevails in Western populations and potentially results in adverse health outcomes. To circumvent the slow n-3 PUFA incorporation in phospholipids of key cells after oral supplementation, a new preparation for intravenous bolus injection was developed with 20 g triacylglycerols/100 mL of a mixture of 80% medium-chain triacylglycerols (MCTs) and 20% fish oil (FO) (wt:wt), and 0.4 g alpha-tocopherol/100 mL of the same mixture. OBJECTIVE: Our objective was to document the enrichment of n-3 PUFAs in leukocyte and platelet phospholipids after a bolus intravenous injection of MCT:FO in men. DESIGN: Twelve healthy male subjects received injections over a 5-min period of 50 mL of either MCT:FO or a control MCT:long-chain triacylglycerol (MCT:LCT) emulsion containing 20 g triacylglycerols/100 mL with equal amounts (wt:wt) of MCT and soybean triacylglycerols (LCT) and containing 0.02 g alpha-tocopherol/100 mL; after an 8-wk interval, the subjects received injections of the other preparation. RESULTS: Clinical and biological variables that assessed tolerance and safety remained unchanged. Plasma elimination was faster for MCT:FO than for MCT:LCT (half-life: 24.5 +/- 3.5 min compared with 32.9 +/- 3.0 min; P < 0.025). This was associated with a greater increase in the plasma nonesterified fatty acid concentration. The content of n-3 PUFAs, specifically eicosapentaenoic acid (20:5n-3), increased in leukocyte and platelet phospholipids within 60 min and > or =24 h after MCT:FO injection. CONCLUSION: Bolus intravenous injection of a novel MCT:FO emulsion allows rapid enrichment of cells with n-3 PUFAs.

Adiposity is associated with endothelial activation in healthy 2-3 year-old children.

Adiposity is associated with C-reactive protein level in healthy 2-3 year-old children and with other markers of endothelial activation in adults, but data are lacking in very young children. Data from 491 healthy Hispanic children were analyzed. Mean age was 2.7 years (SD 0.5, range 2-3 years); mean body mass index (BMI) was 17.2 kg/m2 (SD 1.9) among boys and 17.1 kg/m2 (SD 2.1) among girls. E-selectin level was associated with BMI (R = 0.11; p < 0.02), ponderal index (p < 0.02), waist circumference (p = 0.02), fasting insulin (p < 0.02), and insulin resistance (p < or = 0.05); these associations remained significant after adjustment for age, sex and fasting glucose. sVCAM was also associated with BMI (R = 0.12; p < 0.05). These observations indicate that adiposity is associated with inflammation and endothelial activation in very early childhood.

Inclusion of 10% fish oil in mixed medium-chain triacylglycerol-long-chain triacylglycerol emulsions increases plasma triacylglycerol clearance and induces rapid eicosapentaenoic acid (20:5n-3) incorporation into blood cell phospholipids.

BACKGROUND: Lipolysis of a fish oil (FO) emulsion is much slower than that of a soybean [long-chain triacylglycerol (LCT)] emulsion; in contrast, emulsions containing medium-chain triacylglycerol (MCT) are efficiently hydrolyzed by lipoprotein lipase. OBJECTIVES: We questioned whether incorporating 10% FO in a mixed MCT-LCT emulsion would affect plasma triacylglycerol clearance and provide efficient delivery of n-3 polyunsaturated fatty acids to cells and tissues. DESIGN: This prospective crossover study was conducted in 8 normolipidemic subjects with the use of the hypertriglyceridemic clamp model and compared plasma triacylglycerol clearance of a lipid emulsion (5:4:1) made of 50% MCT, 40% LCT, and 10% FO (wt:wt:wt) to a control (5:5) preparation with 50% MCT and 50% LCT. Subjects were daily infused for 5 h, over 4 consecutive days. Fatty acyl pattern was daily measured in plasma phospholipids as well as in leukocyte and platelet phospholipids. RESULTS: Inclusion of 10% FO in mixed emulsion particles enhanced plasma clearance of infused triacylglycerols (18%; P < 0.0001). The faster elimination of the 5:4:1 emulsion appears related to an enhanced uptake of remnant particles rather than to faster intravascular lipolysis. Each infusion of 5:4:1 raised the eicosapentaenoic acid (C20:5n-3) concentration in blood cell phospholipids to reach a 7-fold enrichment in platelets and a >2-fold enrichment in leukocytes after 4 infusions. In contrast, the docosahexaenoic acid (C22:6n-3) concentration remained unchanged in blood cell phospholipids. CONCLUSIONS: Infusion of a mixed emulsion with MCTs, soy LCTs, and FO is associated with efficient plasma triacylglycerol clearance and results in rapid incorporation of C20:5n-3 but not C22:6n-3 in leukocyte and platelet phospholipids.

Triglycerides in fish oil affect the blood clearance of lipid emulsions containing long- and medium-chain triglycerides in mice.

Lipid emulsions containing long-chain triglycerides (LCT) and medium chain triglycerides (MCT) are widely used in parenteral nutrition. Recently, fish oil (FO) triglyceride (TG)-derived emulsions are considered therapeutic because of their many beneficial biological modulatory actions. We investigated in mice whether adding 10% FO to an intravenous lipid emulsion with MCT and LCT (MCT:LCT:FO -50:40:10% by wt) would affect particle blood clearance and tissue targeting in comparison to LCT (100% by wt) and MCT:LCT (50:50% by wt) emulsions. The 3 emulsions were labeled with [3H] cholesteryl oleoyl ether and administered by bolus injection (400 microg TG/mouse) to C57BL/6J mice. Contributions of LDL receptor (LDL-R) and LDL-R-related protein to emulsion catabolism were assessed using LDL-R-deficient mice and preinjection of lactoferrin, and the effects of lipoprotein lipase (LPL) were determined by preinjection of heparin and Triton WR 1339. Although fractional catabolic rates did not differ among the 3 emulsions, blood removal at each time point after injection was greater for MCT:LCT:FO particles due to their higher initial margination volume. Compared with MCT:LCT and LCT emulsions, patterns of tissue uptake of the MCT:LCT:FO emulsions were different, e.g. MCT:LCT:FO emulsion particle uptake was lower in heart, adipose tissue, and muscle, and higher in lung, and the removal of MCT:LCT:FO emulsion particles was less dependent on LPL, LDL-R, and lactoferrin-sensitive pathways. These data suggest that the addition of a low percentage of FO to MCT:LCT emulsions substantially changes their particle clearance and tissue uptake mechanisms.

n-3 fatty acids and gene expression.

Accumulating evidence in both humans and animal models clearly indicates that a group of very-long-chain polyunsaturated fatty acids, the n-3 fatty acids (or omega-3), have distinct and important bioactive properties compared with other groups of fatty acids. n-3 Fatty acids are known to reduce many risk factors associated with several diseases, such as cardiovascular diseases, diabetes, and cancer. The mechanisms whereby n-3 fatty acids affect gene expression are complex and involve multiple processes. As examples, n-3 fatty acids regulate 2 groups of transcription factors, such as sterol-regulatory-element binding proteins and peroxisome proliferator-activated receptors, that are critical for modulating the expression of genes controlling both systemic and tissue-specific lipid homeostasis. Modulation of specific genes by n-3 fatty acids and cross-talk between these genes are responsible for many effects of n-3 fatty acids.

In vivo and in vitro properties of an intravenous lipid emulsion containing only medium chain and fish oil triglycerides.

BACKGROUND & AIMS: The triglyceride (TG) fatty acyl composition in lipid emulsions influences their metabolism. Little is known about the effects of long chain omega-3 polyunsaturated fatty acids (PUFA) on lipid emulsion metabolism. We investigated possible differences between omega-3 containing emulsions in their metabolism and tissue-targeting in vivo in a mouse model, and in vitro using lipolysis and cell culture experiments. METHODS: Soy oil (LCT), MCT/LCT/omega-3 (5:4:1, wt/wt/wt), and MCT/omega-3 (8:2, wt/wt) emulsions were radiolabeled with nondegradable 1alpha,2alpha (n)-[3H] cholesteryl oleoyl ether to trace core particle metabolism in C57BL/6J mice following a bolus injection. Blood samples obtained over 25 min and extracted organs were used to measure the tissue distribution of lipid emulsion particles. Lipoprotein lipase (LpL)-mediated hydrolysis experiments and cell uptake studies in cultured J774 murine macrophages were also performed. RESULTS: Blood clearance of 8:2 was 13.4% and 29.8% faster compared to 5:4:1 and LCT, respectively. LCT had greatest liver uptake. LpL-mediated hydrolysis was greatest in 8:2 and lowest in LCT. Overall, cell TG accumulation in the presence of apolipoprotein E was least with 8:2. CONCLUSIONS: Our data shows that 8:2 had the most efficient blood clearance but less hepatic uptake in vivo. In vitro, 8:2 had both highest hydrolysis by LpL and intracellular TG utilization in the presence of apoE. Thus, an 8:2 lipid emulsion undergoes efficient blood clearance and may direct omega-3 PUFA more towards extrahepatic tissues.

Omega-3 fatty acids: molecular approaches to optimal biological outcomes.

PURPOSE OF REVIEW: This review discusses recent advances in delineating basic mechanisms underlying the beneficial effects of omega-3 fatty acids on health and on disease. RECENT FINDINGS: While a substantial number of studies have delineated many differences between the biological effects of saturated versus polyunsaturated fatty acids, less is known about the long-chain omega-3 fatty acids commonly present in certain fish oils. In this review, we focus on recent studies relating to basic mechanisms whereby omega-3 fatty acids modulate cellular pathways to exert beneficial effects on promoting health and decreasing risks of certain diseases. We will use, as examples, conditions of the cardiovascular, neurological, and immunological systems as well as diabetes and cancer, and then discuss basic regulatory pathways. SUMMARY: Omega-3 fatty acids are major regulators of multiple molecular pathways, altering many areas of cellular and organ function, metabolism and gene expression. Generally, these regulatory events lead to "positive" endpoints relating to health and disease.

Sterol and fatty acid regulatory pathways in a Giardia lamblia-derived promoter: evidence for SREBP as an ancient transcription factor.

The sterol regulatory element binding-proteins (SREBPs) are transcription factors that regulate the genes of lipid metabolism. Cholesterol and unsaturated fatty acids regulate SREBPs. Giardia lamblia (GL) is an intestinal parasite and one of the earliest derived members within the eukaryotic lineage. GLs exist as trophozoites and cysts. Growth in cholesterol depletion induces transcription of cyst-wall protein (CWP) genes that are upregulated during encystation. The hypothesis was investigated that SREBP-like pathways have a role in cwp gene transcription. Chinese hamster ovary cells were transfected with a cwp-2 promoter reporter construct. Incubation with cholesterol or oleate reduced cwp-2 mediated gene transcription to about half of the control. Incubation in sterol-depleted media, or in the presence of either an inhibitor of intracellular cholesterol movement or inhibitor of cholesterol synthesis, increased gene expression up to 3-fold. Overexpression of SREBPs increased reporter gene activity 2.5-fold. In the absence of functional SREBPs, cwp-2 was not regulated by cholesterol. Footprint analysis of cwp-2 reveals three novel binding sites for mammalian SREBPs with no homologies in other species or humans. The data show that SREBP binds to and can modulate transcription of a regulatory element from an ancient eukaryote and suggest the existence of an SREBP homolog in GL.

Selective uptake from LDL is stimulated by unsaturated fatty acids and modulated by cholesterol content in the plasma membrane: role of plasma membrane composition in regulating non-SR-BI-mediated selective lipid transfer.

We previously reported that unsaturated fatty acids stimulated low-density lipoprotein (LDL) particle uptake in J774 macrophages by increasing LDL receptor activity. Since free fatty acids (FFA) also change plasma membrane properties, a putative cholesteryl ester (CE) acceptor for selective uptake (SU), we questioned the ability of FFA to modulate SU from LDL. Using [(3)H]cholesteryl ether/(125)I-LDL to trace CE core and whole particle uptake, we found that oleic acid and eicosapentaenoic acid, but not saturated stearic acid, increased SU by 30% over control levels. An ACAT inhibitor, Dup128, abolished FFA effects on SU, indicating that increased SU by FFA was secondary to changes in cell-free cholesterol (FC). Consistent with these observations, ACAT inhibition increased cell FC and reduced LDL SU by half. The important role of plasma membrane composition was further demonstrated in that beta-cyclodextrin- (beta-CD-) mediated FC removal from the plasma membrane increased SU from LDL and was further stimulated by U18666A, a compound that inhibits FC transport between lysosomes and the plasma membrane. In contrast, cholesterol-saturated beta-CD markedly reduced LDL SU. In contrast to LDL SU, oleic acid, ACAT inhibition, U18666A, or beta-CD had no effects on HDL SU. Moreover, HDL SU was inhibited by antimouse SR-BI antibody by more than 50% but had little effect on LDL SU. In C57BL/6 mice fed a high fat diet, plasma FFA levels increased, and SU accounted for an almost 4-fold increased proportion of total cholesterol delivery to the arterial wall. Taken together, these data suggest that LDL SU is mediated by pathways independent of SR-BI and is influenced by plasma membrane FC content. Moreover, in conditions where elevated plasma FFA occur, SU from LDL can be an important mechanism for cholesterol delivery in vivo.