Metabolomics studies hold promise for discovery of pathways linked to disease processes. Cardiovascular disease (CVD) represents the leading cause of death and morbidity worldwide. A metabolomics approach was used to generate unbiased small molecule metabolic profiles in plasma that predict risk for CVD. Three metabolites of the dietary lipid phosphatidylcholine, namely choline, trimethylamine N-oxide (TMAO), and betaine, were identified and then shown to predict risk for CVD in an independent large clinical cohort. Dietary supplementation of mice with choline, TMAO or betaine promoted up-regulation of multiple macrophage scavenger receptors linked to atherosclerosis, and supplementation with choline or TMAO promoted atherosclerosis. Studies using germ-free mice confirmed a critical role for dietary choline and gut flora in TMAO production, augmented macrophage cholesterol accumulation and foam cell formation. Suppression of intestinal microflora in atherosclerosis-prone mice inhibited dietary choline-enhanced atherosclerosis. Genetic variations controlling expression of flavin monooxygenases (FMOs), an enzymatic source of TMAO, segregated with atherosclerosis in hyperlipidemic mice. Discovery of a relationship between gut flora-dependent metabolism of dietary phosphatidylcholine and CVD pathogenesis provides opportunities for development of both novel diagnostic tests and therapeutic approaches for atherosclerotic heart disease.

Intestinal microbiota metabolism of choline/phosphatidylcholine produces trimethylamine (TMA), which is further metabolized to a proatherogenic species, trimethylamine-N-oxide (TMAO). Herein we demonstrate that intestinal microbiota metabolism of dietary L-carnitine, a trimethylamine abundant in red meat, also produces TMAO and accelerates atherosclerosis. Omnivorous subjects are shown to produce significantly more TMAO than vegans/vegetarians following ingestion of L-carnitine through a microbiota-dependent mechanism. Specific bacterial taxa in human feces are shown to associate with both plasma TMAO and dietary status. Plasma L-carnitine levels in subjects undergoing cardiac evaluation (n = 2,595) predict increased risks for both prevalent cardiovascular disease (CVD) and incident major adverse cardiac events (MI, stroke or death), but only among subjects with concurrently high TMAO levels. Chronic dietary L-carnitine supplementation in mice significantly altered cecal microbial composition, markedly enhanced synthesis of TMA/TMAO, and increased atherosclerosis, but not following suppression of intestinal microbiota. Dietary supplementation of TMAO, or either carnitine or choline in mice with intact intestinal microbiota, significantly reduced reverse cholesterol transport in vivo. Intestinal microbiota may thus participate in the well-established link between increased red meat consumption and CVD risk.

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Apolipoprotein E is associated with age-related risk for Alzheimer's disease and plays critical roles in Aβ homeostasis. We report that ApoE plays a previously unappreciated role in facilitating the proteolytic clearance of soluble Aβ from the brain. The endolytic degradation of Aβ peptides within microglia by neprilysin and related enzymes is dramatically enhanced by ApoE. Similarly, Aβ degradation extracellularly by insulin degrading enzyme is facilitated by ApoE. The capacity of ApoE to promote Aβ degradation is dependent upon the ApoE isoform and its lipidation status. The enhanced expression of lipidated ApoE, through the activation of liver X receptors, stimulates Aβ degradation. Indeed, aged Tg2576 mice treated with the LXR agonist GW3965 exhibited a dramatic reduction in brain Aβ load. GW3965 treatment also reversed contextual memory deficits. These data demonstrate a novel mechanism through which ApoE facilitates the clearance of Aβ from the brain and suggest that LXR agonists may represent a novel therapy for AD. Alzheimer's disease (AD) is characterized by the accumulation and deposition of Aβ peptides within the brain, leading to the perturbation of synaptic function and neuronal loss that typifies the disease (Tanzi and Bertram, 2005). Genetic analysis of familial forms of AD has established the centrality of APP processing and Aβ production to disease pathogenesis. Aβ peptides are normally produced by neurons in the brain and cleared through efflux into the peripheral Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

IntroductionIn vitro and in vivo studies support the hypothesis that macrophages are key early mediators of atherogenesis (1-3) and their impaired recruitment and activation protects against lesion development (4-6). A significant amount of research also supports the hypothesis that subendothelial modified LDLs provide the initiating ligands for the macrophage (7,8), and these are recognized by scavenger receptors (9-13).Oxidized LDL is a ligand for the class A scavenger receptors type I and II (SRA-I/II), MARCO, the class B scavenger receptor, CD36, and the class D receptor, CD68. This modified lipoprotein has been considered the most important atherogenic LDL (14-16). In vitro studies have provided evidence that SRA-I/II and CD36 are the major oxidized LDL receptors mediating lipid accumulation and foam cell formation, whereas MARCO and CD68 play a more minor role (17-21). Absence of SRA-I/II in atherogenic murine models has had a variable impact on atherosclerosis (22-24). Thus, an essential contribution of scavenger receptors to the pathogenesis of atherosclerosis in vivo remains unresolved.CD36 has been shown to be highly regulated in monocytes/macrophages during differentiation (25,26) and to be present in lipid-laden macrophages in atherosclerotic lesions (27,28). This scavenger receptor is upregulated by IL-4 (25), macrophage colony stimulating factor (26), modified LDL (17, 18), cellular cholesterol content (29), and peroxisome proliferator-activated receptor-γ (PPAR-γ) ligands (30, 31). Unlike SRA I/II, CD36 is more broadly expressed (32-35) and has been shown to play a strategic role in lipoprotein and lipid metabolism (36, 37). The phenotype of CD36-null mice generated in our laboratory included increased plasma levels of cholesterol, triacylglycerol, and fatty acids and supported a major role for CD36 in fatty acid uptake and lipid metabolism in vivo (36). In transgenic mice, overexpression of CD36 in muscle enhanced fatty acid oxidation during stimulation/contraction and also had significant influence on plasma lipoprotein and fatty acid levels (37). Absence of CD36 was implicated recently in insulin resistance in the spontaneous hypertensive rat by using genetic analysis (37, 38). These studies point to an essential role for CD36 not only in uptake of lipid but in determination of cellular lipid stores.To determine if CD36 is a major macrophage scavenger receptor responsible for early lipid accumulation and foam cell formation, which can predispose animals to the development of fatty streaks and ultimately more advanced atherosclerotic lesions, we generated CD36-apo E double-null mice and evaluated aortic lesions on normal chow and Western diets. Macrophage scavenger receptors have been implicated as key players in the pathogenesis of atherosclerosis. To assess the role of the class B scavenger receptor CD36 in atherogenesis, we crossed a CD36-null strain with the atherogenic apo E-null strain and quantified lesion development. There was a 76.5% decrease in aortic tree lesion area (Western diet) a...

Ice formation and accretion may hinder the operation of many systems critical to national infrastructure, including airplanes, power lines, windmills, ships, and telecommunications equipment. Yet despite the pervasiveness of the icing problem, the fundamentals of ice adhesion have received relatively little attention in the scientific literature and it is not widely understood which attributes must be tuned to systematically design "icephobic" surfaces that are resistant to icing. Here we probe the relationships between advancing/receding water contact angles and the strength of ice adhesion to bare steel and twenty-one different test coatings (∼200-300 nm thick) applied to the nominally smooth steel discs. Contact angles are measured using a commercially available goniometer, whereas the average strengths of ice adhesion are evaluated with a custom-built laboratory-scale adhesion apparatus. The coatings investigated comprise commercially available polymers and fluorinated polyhedral oligomeric silsesquioxane (fluorodecyl POSS), a low-surface-energy additive known to enhance liquid repellency. Ice adhesion strength correlates strongly with the practical work of adhesion required to remove a liquid water drop from each test surface (i.e., with the quantity [1 + cos θ(rec)]), and the average strength of ice adhesion was reduced by as much as a factor of 4.2 when bare steel discs were coated with fluorodecyl POSS-containing materials. We argue that any further appreciable reduction in ice adhesion strength will require textured surfaces, as no known materials exhibit receding water contact angles on smooth/flat surfaces that are significantly above those reported here (i.e., the values of [1 + cos θ(rec)] reported here have essentially reached a minimum for known materials).

The apolipoprotein E (APOE) E4 allele is associated with Alzheimer's disease, cardiovascular disease, and decreased longevity. To probe the mechanism of these associations, cell lines were created which secrete each apoE isoform. ApoE conditioned media, purified apoE, and commercially obtained apoE protected B12 cells from hydrogen peroxide cytotoxicity with E2 > E3 > E4. Physiological levels of apoE protected cells from beta-amyloid peptides, while higher doses of apoE led to increased cytotoxicity. E2 > E3 > E4 possessed antioxidant activity, and apoE bound certain metal ions. The decreased antioxidant activity of E4 could contribute to its association with Alzheimer's disease, cardiovascular disease and decreased longevity.