Fig 1.
Metformin prevents induction of inflammatory bowel disease (IBD).
Metformin (1 mg/mouse) was administered daily to mice with IBD for 16 days. (A) Weight of mice with IBD. (B and C) disease activity index (DAI) score and colon length. (D) Histopathlogical analysis showed tissue degradation in mice with IBD, and metformin-treated IBD mice. All tissue sections were counterstained with hematoxylin (100× magnification). The scale bar indicates 50 μm. (E) mRNA levels of tumor necrosis factor alpha (TNF-α) and transforming growth factor beta (TGF-β) in the colon tissues of IBD mice and metformin-treated IBD mice were determined by qPCR. Data are presented as the mean ± SD from three independent experiments (*P < 0.05, **P < 0.03, ***P < 0.001).
Fig 2.
Metformin treatment suppresses inflammation and p-signal transducer and activator of transcription 3 (STAT3) expression, but enhances the expression of AMP-activated protein kinase (AMPK) in a mouse model of inflammatory bowel disease (IBD).
(A) Immunohistochemical detection of interleukin (IL)-1β, IL-6, IL-8, TNF-α, and vascular endothelial growth factor (VEGF) in the colon tissues of IBD mice and metformin-treated IBD mice. All tissue sections were counterstained with hematoxylin (400× magnification). The scale bar indicates 50 μm. (B) Expression of p-STAT3, p-mTOR, and p-AMPK proteins were determined by western blotting. Data are presented as the mean ± SD from three independent experiments (*P < 0.05, **P < 0.03).
Fig 3.
Metformin controls mRNA expression levels of inflammatory cytokines and the differentiation of Th17 and Treg cells through the regulation of signal transducer and activator of transcription 3 (STAT3) and STAT5 phosphorylation in lymph nodes.
(A) mRNA levels of proinflammatory cytokines [tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-8, IL-17, and interferon (IFN)-γ] decreased in the lymph nodes of metformin-treated inflammatory bowel disease (IBD) mice. (B) Lymph node tissue sections from IBD and metformin-treated IBD mice were subjected to immunostaining to determine the presence of CD4+IL-17+ or CD4+CD25+Foxp3+ cells. Data are presented as the mean ± SD from three independent experiments (*P < 0.05, **P < 0.03).
Fig 4.
Metformin controls the mRNA expression levels of inflammatory cytokines and the differentiation of Th17 and Treg cells through the regulation of signal transducer and activator of transcription 3 (STAT3) and STAT5 phosphorylation in the spleen.
(A) mRNA levels of proinflammatory cytokines [tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-8, IL-17, and interferon (IFN)-γ] decreased in the spleens of metformin-treated inflammatory bowel disease (IBD) mice. (B) Spleen tissue sections of IBD and metformin-treated IBD mice were subjected to immunostaining to determine the presence of CD4+IL-17+ or CD4+CD25+Foxp3+ cells. Data are presented as the mean ± SD from three independent experiments (*P < 0.05, **P < 0.03).
Fig 5.
Metformin treatment reduces the mRNA levels of proinflammatory cytokines in human HT-29 cells.
(A) Tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-8 mRNA expression levels decreased in human HT-29 cells stimulated with LPS and then treated with metformin. (B) The production of vascular endothelial growth factor (VEGF) decreased in human HT-29 cells stimulated with lipopolysaccharide (LPS) and then treated with metformin. (C) Cell viability was not altered by various concentrations of metformin. Data are presented as the mean ± SD from three independent experiments (*P < 0.05, **P < 0.03, ***P < 0.001).