%0 PDF %T Regulation of Monocyte/Macrophage ATP-Binding Cassette Transporters and Cholesterol Efflux by Elevated Glucose and Free Fatty Acid Concentrations. %A Spartano, Nicole. %8 2017-04-14 %R http://localhost/files/8s45qn29g %X Abstract: Individuals with diseases of poor glycemic control, including pre-diabetes and type 2 diabetes mellitus, are at increased risk of developing atherosclerosis, the major form of cardiovascular disease (CVD). Atherosclerotic lesion formation is promoted by monocyte/macrophage recruitment into the arterial wall and subsequent cholesterol accumulation in macrophages. However, the relationship between elevated circulating glucose and free fatty acids (FFA) concentrations, frequently associated with poor glycemic control, and macrophage cholesterol accumulation is yet to be fully elucidated. We hypothesized that factors which regulate monocyte/macrophage cholesterol efflux, particularly ATP-binding cassette (ABC) transporter expression will be down-regulated in response to elevated glucose and FFA conditions in vitro and in vivo, mediated by liver-x-receptor (LXR)-α and sterol regulatory element binding protein (SREBP)-1c. The goal of this thesis was to determine the effect of elevated glucose and FFA concentrations on factors mediating macrophage cholesterol homeostasis using two different systems: human monocytes and cultured murine bone marrow-derived macrophage cells (BMDM). Human monocytes were isolated from individuals in the fasting state and after an oral glucose challenge to determine the relationship between elevated blood glucose concentration and changes in monocyte ABC-transporter (ABCA1 and ABCG1) mRNA expression. Additionally, murine BMDM were used as a model system to determine the effect of elevated glucose and FFA concentrations on factors governing macrophage intracellular cholesterol accumulation and cellular cholesterol efflux through ABC-transporters and scavenger receptor (SR)-B1. LXR-α and SREBP-1a, -1c and -2 were also targeted for their potential role as transcriptional mediators of transporters involved in macrophage cholesterol efflux, specifically with respect to glucose and FFA concentrations. In humans a glucose challenge increased leukocyte ABCA1 and ABCG1 mRNA expression but had no significant effect on monocyte ABCA1 or ABCG1 mRNA expression. We also determined that leukocyte ABC-transporter mRNA expression was significantly higher than PBMC or monocytes in vivo. However, in an in vitro macrophage model, BMDM, cholesterol efflux was suppressed after exposure to elevated glucose concentrations, a FFA mixture (linoleic acid [18:2], palmitic acid [16:0], and oleic acid [18:1]) as well as 18:2 alone, but not 16:0 alone. Elevated glucose concentrations did not have a significant effect on ABC-transporter mRNA or protein expression in oxidized low density lipoprotein (oxLDL)-stimulated BMDM. In contrast, ABC-transporter and SREBP-1c mRNA expression and ABCA1 protein expression was suppressed by 18:2. Neither LXR-α or SREBP-1 protein expression was affected by 18:2, indicating that changes in expression of these transcription factors are not mediating the effect. The results of this research will add to our understanding of the relationship between glucose and FFA concentrations, and monocyte/macrophage cholesterol homeostasis, in vivo and in vitro. These data will advance efforts to gain perspective on novel mechanisms by which diseases of poor glycemic control accelerate the development of CVD.; Thesis (Ph.D.)--Tufts University, 2013.; Submitted to the Dept. of Biochemical and Molecular Nutrition.; Advisor: Alice Lichtenstein.; Committee: Andrew Greenberg, Stefania Lamon-Fava, Nirupa Matthan, and Martin Obin.; Keywords: Nutrition, Biochemistry, and Molecular biology. %[ 2022-10-11 %9 Text %~ Tufts Digital Library %W Institution