a, Choline supplementation promotes macrophage foam cell formation in gut flora dependent fashion. C57BL/6J.Apoe−/− mice at time of weaning (4 weeks) were provided drinking water with versus without broad spectrum antibiotics (Abx), and placed on chemically defined diets similar in composition to normal chow (control diet, 0.08 ± 0.01% total choline, wt/wt) or normal chow with high choline (choline diet, 1.00% ± 0.01% total choline, wt/wt). Resident peritoneal macrophages were recovered at 20 weeks of age. Typical images of oil-red-O/hematoxylin stained macrophages in each diet group are shown. b, Foam cell quantification from peritoneal macrophages recovered from mice in studies described in panel a. c, Macrophage cellular cholesterol content. d, Representative oil-red-O/hematoxylin stained aortic root sections from female C57BL/6J.Apoe−/− mice fed control and high choline diets in the presence versus absence of Abx. e,f, Aortic lesion area in 20 week old C57BL/6J.Apoe−/− mice off versus on Abx and fed with control versus choline diet. g, Aortic macrophage quantification with anti-F4/80 antibody staining. h, Quantitation of scavenger receptor CD36 in aorta within the indicated groups. Error bars represent s.e.m. from the indicated numbers of mice.