Figure 2.

Plasma lipid profiles and aortic cholesterol levels of germ-free (white bars) and control (black bars) apo E^−/− mice. Apo E^−/− mice were reared germ free or in the presence of ambient pathogens. At 22 or 32 wk of age, animals were killed, blood was collected for analysis of plasma cholesterol and triglyceride, and aortas were harvested and extracted for determination of cholesterol content. (A and B) Comparisons of plasma cholesterol and triglyceride levels in control and germ free yield nearly identical values in male (A) and female (B) apo E^−/− mice at both 22 and 32 wk. None of the small differences reached statistical significance, with the exception of decreased triglyceride levels for the male germ-free animals at 22 wk (*P < 0.005) and increased triglyceride levels for the female germ-free animals at 32 wk (**P = 0.03). (C and D) Comparisons of aortic free cholesterol and cholesteryl ester levels in male (C) and female (D) apo E^−/− mice at 22 and 32 wk show a trend toward lower levels in the germ-free animals at both time points, although statistical significance was achieved only for the cholesteryl ester in germ-free males at 22 wk (*P < 0.005) and for the germ-free cholesterol in germ-free females at 22 wk (^† P = 0.05). However, data shown are expressed on a per aorta basis, and after correction for the decreased body weight of the germ-free mice, none of the differences attained statistical significance. For each time point and sex, group size was ≥10 animals, with the exception of the 32-wk male germ-free mice, which were reduced to 3 by mortality caused by aggressive behavior.