Effect of the cannabinoid receptor-1 antagonist rimonabant on inflammation in mice with diet-induced obesity

Abstract

We studied whether cannabinoid receptor (CB1) blockade with rimonabant has an anti-inflammatory effect in obese mice, and whether this effect depends on weight loss and/or diet consumption. High-fat diet (HFD)-induced obese mice were treated orally with rimonabant (HFD-R) or vehicle (HFD-V) for 4 weeks. Paired-feeding was conducted in two additional groups of obese mice to achieve either the same body weight (HFD-BW) or the same HFD intake (HFD DI) as HFD-R. All these groups of mice were maintained on HFD throughout, with mice on normal diet (ND) throughout as lean controls. Rimonabant treatment of obese mice induced marked diet-intake reduction and weight loss during the first week, which was followed by maintenance of low body weight but not diet-intake reduction. Lower HFD intake was required to reach the same degree of weight loss in HFD-BW. HFD-DI had similar weight loss initially, but then started to gain weight, reaching a higher body weight than HFD-R. Despite the same degree of weight loss, HFD-R had less fat mass and lower adipogenic gene expression than HFD-BW. Compared to HFD-V or HFD-DI, HFD-R had reduced inflammation in adipose tissue (AT) and/or liver indicated primarily by lower monocyte chemoattractant protein-1 (MCP-1) levels. However, MCP-1 levels were not significantly different between HFD-R and HFD-BW. In vitro incubation of rimonabant with AT explants did not change MCP-1 levels. Thus, rimonabant induced weight loss in obese mice by diet-intake-dependent and -independent fashions. Rimonabant decreased inflammation in obese mice, possibly through a primary effect on weight reduction.

Figure 1. Effect of rimonabant on diet intake and physical characteristics

Mice with diet-induced obesity were treated with rimonabant in 0.1% Tween 80 (10 mg/kg/day; HFD-R) or 0.1% Tween 80 vehicle alone (HFD-V) by daily oral gavage for 4 weeks and received HFD ad libitum; pair-feeding was conducted in 2 separate groups of obese mice to achieve either the same body weight (HFD-BW) by adjusting HFD intake or the same HFD consumption (HFD-DI) as HFD-R; lean mice (ND-V), HFD-BW, and HFD-DI mice were also administered 0.1% Tween 80 alone by daily oral gavage during this period; n=12–19 mice/group. (a) Daily diet intake during the whole period of treatment and average daily diet intake for the period of stable body weight (days 10–28 after starting treatment) of HFD-V, HFD-R, and HFD-BW mice; diet intake by HFD-DI mice was the same as HFD-R mice. Daily body weight of each group of mice is shown during the whole period of treatment. (b) Body weight, weights of perigonadal fat pads and livers, and total fat mass expressed as percentage of total body mass at the end of treatment.

Figure 1. Effect of rimonabant on diet intake and physical characteristics

Mice with diet-induced obesity were treated with rimonabant in 0.1% Tween 80 (10 mg/kg/day; HFD-R) or 0.1% Tween 80 vehicle alone (HFD-V) by daily oral gavage for 4 weeks and received HFD ad libitum; pair-feeding was conducted in 2 separate groups of obese mice to achieve either the same body weight (HFD-BW) by adjusting HFD intake or the same HFD consumption (HFD-DI) as HFD-R; lean mice (ND-V), HFD-BW, and HFD-DI mice were also administered 0.1% Tween 80 alone by daily oral gavage during this period; n=12–19 mice/group. (a) Daily diet intake during the whole period of treatment and average daily diet intake for the period of stable body weight (days 10–28 after starting treatment) of HFD-V, HFD-R, and HFD-BW mice; diet intake by HFD-DI mice was the same as HFD-R mice. Daily body weight of each group of mice is shown during the whole period of treatment. (b) Body weight, weights of perigonadal fat pads and livers, and total fat mass expressed as percentage of total body mass at the end of treatment.

Figure 2. Effect of rimonabant on AT expression of adipogenic genes

mRNA levels of selected adipogenic genes in mouse AT after rimonabant treatment or other interventions were examined by RT-QPCR; n=3 samples/group; each sample was pooled from 3 mice.

Figure 3. Effect of rimonabant on AT inflammation

(a) mRNA levels of chemokines or (b) T cell (CD3, TCRα) and macrophage/DC markers (F4/80) in AT examined by RPA at 4 weeks after rimonabant treatment or other interventions; n=7–14 mice/group. (c) T cells and CD11c⁺/CD11b⁺ cells examined by flow cytometry in stromal/vascular cells (S/Vs) of mouse AT; n=9–11 samples/group. (d) Adiponectin mRNA quantitated in mouse AT by RT-QPCR; n=9–17 mice/group.

Figure 3. Effect of rimonabant on AT inflammation

(a) mRNA levels of chemokines or (b) T cell (CD3, TCRα) and macrophage/DC markers (F4/80) in AT examined by RPA at 4 weeks after rimonabant treatment or other interventions; n=7–14 mice/group. (c) T cells and CD11c⁺/CD11b⁺ cells examined by flow cytometry in stromal/vascular cells (S/Vs) of mouse AT; n=9–11 samples/group. (d) Adiponectin mRNA quantitated in mouse AT by RT-QPCR; n=9–17 mice/group.

Figure 3. Effect of rimonabant on AT inflammation

(a) mRNA levels of chemokines or (b) T cell (CD3, TCRα) and macrophage/DC markers (F4/80) in AT examined by RPA at 4 weeks after rimonabant treatment or other interventions; n=7–14 mice/group. (c) T cells and CD11c⁺/CD11b⁺ cells examined by flow cytometry in stromal/vascular cells (S/Vs) of mouse AT; n=9–11 samples/group. (d) Adiponectin mRNA quantitated in mouse AT by RT-QPCR; n=9–17 mice/group.

Figure 3. Effect of rimonabant on AT inflammation

(a) mRNA levels of chemokines or (b) T cell (CD3, TCRα) and macrophage/DC markers (F4/80) in AT examined by RPA at 4 weeks after rimonabant treatment or other interventions; n=7–14 mice/group. (c) T cells and CD11c⁺/CD11b⁺ cells examined by flow cytometry in stromal/vascular cells (S/Vs) of mouse AT; n=9–11 samples/group. (d) Adiponectin mRNA quantitated in mouse AT by RT-QPCR; n=9–17 mice/group.

Figure 4. Effect of rimonabant on liver inflammation

(a) mRNA levels of chemokines in mouse liver assayed by RPA; n=7–15 mice/group. (b) Relationship of liver weight with MCP-1 mRNA in the liver from mice without rimonabant treatment (n=45) and relationship of liver weight with hepatic TG content (n=66). (c) mRNA levels of T cell (CD3, TCRα) and macrophage/DC (F4/80, CD11c) markers in mouse liver examined by RPA or RT-QPCR; n=7–15 mice/group.

Figure 4. Effect of rimonabant on liver inflammation

(a) mRNA levels of chemokines in mouse liver assayed by RPA; n=7–15 mice/group. (b) Relationship of liver weight with MCP-1 mRNA in the liver from mice without rimonabant treatment (n=45) and relationship of liver weight with hepatic TG content (n=66). (c) mRNA levels of T cell (CD3, TCRα) and macrophage/DC (F4/80, CD11c) markers in mouse liver examined by RPA or RT-QPCR; n=7–15 mice/group.

Figure 4. Effect of rimonabant on liver inflammation

(a) mRNA levels of chemokines in mouse liver assayed by RPA; n=7–15 mice/group. (b) Relationship of liver weight with MCP-1 mRNA in the liver from mice without rimonabant treatment (n=45) and relationship of liver weight with hepatic TG content (n=66). (c) mRNA levels of T cell (CD3, TCRα) and macrophage/DC (F4/80, CD11c) markers in mouse liver examined by RPA or RT-QPCR; n=7–15 mice/group.

Figure 5. Effect of rimonabant on plasma MCP-1 levels

MCP-1 protein levels examined in mouse plasma by ELISA; n=9–19 mice/group.