Farnesoid X Receptor Deficiency Improves Glucose Homeostasis in Mouse Models of Obesity

FXR deficiency improves glucose homeostasis in ob/ob mice. A: Fasting blood glucose was measured weekly in FXR^+/+ob/ob (white bars or circles) and FXR^−/−ob/ob mice (black bars or circles) (n = 9 to 10/group). Significance of the overall effect of the genotype (P < 0.0001) was calculated by two-way ANOVA. B: Plasma insulin was determined in 12-week-old mice (n = 9 to 10/group). Blood glucose excursion (C) and integrated AUC (D) after administration of an intraperitoneal glucose bolus (1 g/kg glucose) were measured in 12-week-old mice (n = 9 to 10/group). Significance of the overall effect of genotype (P < 0.0001) and time (P < 0.0001) was calculated by two-way ANOVA. E: MCR was determined by stable isotope dilution in 14-week-old mice (n = 5 to 6/group). Blood glucose excursion (F) and iAUC (G) after administration of an intraperitoneal insulin bolus (2 IU insulin/kg) were measured in 13-week-old mice (n = 9 to 10/group). Significance of the overall effect of genotype (P < 0.0001) and time (P < 0.0001) was calculated by two-way ANOVA. H: Pancreata of 20-week-old mice (n = 9 to 10/group) were sectioned and submitted to Papanicolaou staining. Arrows indicate islets of Langerhans (scale bar = 1 mm). I: Mean surface of the islets of Langerhans was quantified. Values are means ± SEM. Differences between genotypes over time were analyzed by two-way ANOVA and Bonferroni post hoc test; differences between genotypes were calculated by Mann-Whitney test (*P = 0.05, **P < 0.01, ***P < 0.001). (A high-quality digital representation of this figure is available in the online issue.)

FXR deficiency improves adipose tissue, but not hepatic insulin sensitivity in ob/ob mice. A: Female FXR^+/+ob/ob (13-week-old; white bars) and FXR^−/−ob/ob mice (black bars) (n = 4/group) were injected with either saline or insulin. Phosphorylation of Akt at Serine473 and total Akt protein expression was determined by Western blot and the signal quantified. B: Gene expression was measured by QPCR. C: Triglyceride content was determined enzymatically in livers of 20-week-old mice (n = 9 to 10/group). Values are means ± SEM. Differences between genotypes were calculated by Mann-Whitney test (*P < 0.05, **P < 0.01, ***P < 0.001). WAT, white adipose tissue; pAkt, Serine473-phosphorylated Akt; TG, triglyceride.

FXR deficiency in ob/ob mice results in the accumulation of plasma triglycerides. A and B: Lipid parameters were measured in plasma of 12-week-old FXR^+/+ob/ob (white bars or circles) and FXR^−/−ob/ob mice (black bars or circles) (n = 9 to 10/group). C: Lipoprotein profiles were determined in plasma pools of 13-week-old mice. D: VLDL production was assessed in 13-week-old female mice (n = 8–10/group) by measuring plasma triglyceride concentrations subsequent to Tyloxapol injection. E: Gene expression was measured by QPCR in livers of 20-week-old mice (n = 9 to 10/group). Values are means ± SEM. Differences between genotypes were calculated by Mann-Whitney test (***P < 0.001). FFA, free fatty acid; OD, optical density; TG, triglyceride.

FXR deficiency protects from diet-induced obesity and insulin resistance. FXR^+/+ (white bars or circles) and FXR^−/− mice (black bars or circles) (n = 7–11/group) were fed a HFD for 20 weeks. A: Body weight was monitored weekly (n = 7–11/group). Significance of the overall effect of genotype (P < 0.0001) and age (P < 0.0001) as well as their interaction (P < 0.0001) was calculated by two-way ANOVA. Plasma leptin (B), plasma triglyceride (TG) (C), blood glucose (D), and plasma insulin (E) were determined at the end of the feeding period (n = 4–9/group). Blood glucose excursion (F) and integrated AUC (G) after administration of an intraperitoneal glucose bolus (1 g/kg glucose) were measured at the end of the feeding period (n = 6–9/group). Significance of the overall effect of genotype (P < 0.0001) and time (P < 0.0001) was calculated by two-way ANOVA. Values are means ± SEM. Differences between genotypes over time were analyzed by two-way ANOVA and Bonferroni post hoc test; differences between genotypes were calculated by Mann-Whitney test (*P < 0.05, **P < 0.01, ***P < 0.001).

Liver-specific FXR deficiency does not protect from diet-induced obesity and insulin resistance. LFXR^−/− mice and LFXR^+/+ littermates (n = 7–12/group) were fed a HFD or a control diet (CD) for 10 weeks (LFXR^+/+, white bars and symbols; LFXR^−/−, black bars and symbols). A: Body weight was monitored weekly. Significance of the effect of diet (P < 0.0001) and age (P < 0.0001) as well as their interaction (P < 0.0001) was calculated by two-way ANOVA. Plasma leptin (B) and plasma triglyceride (TG) (C) were determined at the end of the feeding period. D: Fasting blood glucose was measured weekly. Significance of the overall effect of diet (P < 0.0001) and age (P < 0.0001) as well as their interaction (P = 0.0217) was calculated by two-way ANOVA. E: Plasma insulin was measured after 6 weeks of feeding. Blood glucose excursion (F) and integrated AUC (G) after administration of an intraperitoneal glucose bolus (1 g/kg glucose) were measured after 5 weeks of feeding (n = 6/group). Values are means ± SEM. Differences between diet groups over time were analyzed by two-way ANOVA and Bonferroni post hoc test; differences between genotypes or diet groups were calculated by Mann-Whitney test. *Compares genotypes of the same diet group; $compares diet groups for LFXR^+/+; §compares diet groups for LFXR^−/− ($ or §P < 0.05; **, $$, or §§P < 0.01; $$$ or §§§P < 0.001).

Modulation of BA metabolism does not affect glucose homeostasis in FXR^−/−ob/ob mice. FXR^+/+ob/ob and FXR^−/−ob/ob mice (10 weeks old) were administered 2% colesevelam mixed in the diet or plain diet for 3 weeks (n = 13/group) (FXR^+/+ob/ob control, white bars or circles; FXR^+/+ob/ob treated, horizontally hatched bars or white squares; FXR^−/−ob/ob control, black bars or circles; FXR^−/−ob/ob treated, diagonally hatched bars or black squares). A: TGR5 target gene expression was measured by QPCR in BAT of 20-week-old mice (n = 9 to 10/group). B: Plasma BA were measured after 9 days of treatment. C: Body weight was monitored weekly during the treatment period. Significance of the overall effect of treatment (P < 0.0001) and age (P = 0.0002) was calculated by two-way ANOVA. D: Fasting blood glucose was determined weekly during the treatment period. Blood glucose excursion (E) and integrated AUC (F) after administration of an intraperitoneal glucose bolus (1 g/kg glucose) were measured at the end of the treatment period. G: Plasma insulin was measured at the end of the treatment period. Values are means ± SEM. Differences between treatment groups over time were analyzed by two-way ANOVA and Bonferroni post hoc test; differences between genotypes or treatment groups were calculated by Mann-Whitney test. *Compares genotypes of the same treatment group; $compares treatment groups of the same genotype (* or $P < 0.05, ** or $$P < 0.01, ***P < 0.001).