Fig 1.
Long-term exposure to high-fat diet increases body-weight (A), percentage of adipose body mass (B) and a relative decrease in percentage of lean body mass (C) in diet-induced obese (DIO) mice compared to lean controls fed on a low-fat diet. *** p<0.001; independent sample t-test; data represent mean ± standard error of the mean (SEM).
Fig 2.
Diet-induced obese mice present with visceral hypersensitivity.
In DIO mice visceral pain responses are increased (A) and similarly, the pain threshold is decreased (B) compared to lean animals. * p<0.05; ** p<0.01; *** p<0.001; independent sample t-test or repeated measures 1-way analysis of variance followed by Bonferroni’s post-hoc test; baseline response to CRD was not different between individual groups/conditions; data represent mean ± standard error of the mean (SEM).
Fig 3.
Increased TLR4 expression and microglia activation in the prefrontal cortex, hippocampus and the lumbar region of the spinal cord in DIO mice.
Western blot analysis for TLR4 and Cd11b (microglial marker) in the prefrontal cortex, hippocampus and the lumbar region of the spinal cord. TLR4 is significantly increased in the prefrontal cortex in DIO mice (A), hippocampus (B) and spinal cord (C). Moreover, microglia expression (Cd11b) is significantly increased in DIO in the prefrontal cortex (D) and hippocampus (E), but not in the lumbar region of the spinal cord (F) when compared with lean mice. * p<0.05; ** p<0.01; *** p<0.001; independent sample t-test; data represent mean ± standard error of the mean (SEM) expressed as percentage of the control group.
Fig 4.
Increased cytokine levels following LPS spleen stimulation in DIO mice.
Cytokine levels of IL6 and TNFα in spleen cell culture supernatant following stimulation with lipopolysaccharide (LPS; 1 μg/ml, 37°C, 24 h) were measured in mice fed on a low- or high-fat diet over 16 weeks. Exposure to HFD (DIO mice) increased significantly spleen levels of IL6 (A) and TNFα (B) after the stimulation with LPS, compared to mice fed on a LFD (lean mice). * p<0.05; ** p<0.01 vs. lean mice; 2-way analysis of variance followed by Bonferroni’s post-hoc test; data represent mean ± standard error of the mean (SEM).
Fig 5.
TAK-242 reverses the visceral hypersensitivity phenotype in DIO mice.
Administration of the selective TLR4 antagonist TAK-242 (i.v. 10mg/kg) significantly reduces visceral pain responses in DIO (A) but not in lean mice (B). Moreover, the antagonist normalizes the decreased pain threshold in DIO mice (C) without affecting the pain threshold in lean mice (D). * p<0.05; ** p<0.01; independent sample t-test or repeated measures 2-way analysis of variance followed by Bonferroni’s post-hoc test; baseline response to CRD was not different between individual groups/conditions; data represent mean ± standard error of the mean (SEM).