Figure 5. Genetic Deletion of FMO3 Protects Mice From Diet-Induced Obesity.

(A) Top panel: CRISPR-Cas9 strategy for generating Fmo3^−/− mice. The sequence of exon 2 of the murine Fmo3 coding sequence is shown. The target sequence (underlined) used for construction of the guide RNA is shown with arrows indicating predicted cleavage sites by Cas9. Bottom panel: immunoblotting analysis of FMO3 protein levels in the livers of wild-type (WT) and Fmo3^−/− (KO) mice.

(B) Decreased adiposity in Fmo3^−/− mice. Fmo3^+/+ (n=9), Fmo3^+/− (n=6), and Fmo3^−/− (n=11) mice were fed a 1.3% choline chloride (w/w) diet for 12 weeks before tissue collection. Plasma TMAO and TMA levels (top left), food intake (top right), body weight (bottom left) and 4 fat pads/body weight (%; bottom right) are shown. The four fat pads included in the 4 fat pads/body weight measurement were gonadal, mesentery, perirenal, and subcutaneous. *: p≤0.05 between Fmo3^+/+ and Fmo3^−/− groups. &: p≤0.05 between Fmo3^+/− and Fmo3^−/− genotype groups.

Panels (C–H) Ldlr^−/−; Fmo3^−/− mice are more resistant to obesity than Ldlr^−/− littermates when fed a Western diet for 12 weeks.

(C) Liver FMO activity

(D) Plasma TMAO levels

(E) Body weight changes over 12 weeks

(F) Fat mass/body weight (%)

(G) 4 fat pads weight/body weight (%); the 4 fat pads measured were gonadal, mesentery, perirenal, and subcutaneous

(H) Gene expression analysis of subcutaneous fat pads of Ldlr^−/− (n=17) and Ldlr^−/−; Fmo3^−/− (n=9) mice. Cell death-inducing DFFA-like effector A (Cidea), Cytochrome C oxidase subunit 8b (Cox8b), Elongation of very long chain fatty acids protein 3 (Elovl3), Uncoupling protein 1 (Ucp1), Diglyceride acyltransferase 1 (Dgat1), Leptin (Lep), Stearoyl CoA desaturase-1 (Scd1), Transducin-like enhancer of split 3 (Tle3)*, p≤0.05, **, p≤0.01, and ***, p≤0.0001 between the two genotype groups.