Fig. 3: Metformin increases GLUT1 expression and its membrane localization in small intestine and colon cell lines by downregulating TXNIP.

a Top GO pathway enrichment scores for GLUT1. b Enrichment scores for TXNIP-related pathways. c A volcano plot showing the results of RNA sequencing analysis comparing the transcriptomes of mouse ileum samples from the control group and metformin-treated group. The left side of volcano plot is p-value <0.05 and fold change ≤2; the right side of volcano plot is p-value <0.05 and fold change ≥2. d qRT-PCR analysis of TXNIP mRNA expression in IEC6 and Caco-2 cells treated with biguanides. e, f IEC6 and Caco-2 cell lines were incubated in the absence or presence of biguanides for 16 h, after 8-h starvation in serum-free medium, and later collected for immunoblotting of TXNIP. e Total proteins showing that TXNIP decreases in IEC6 and Caco-2 cell lines after biguanide treatment. Expression levels were normalized to β-actin. f Membrane protein analysis showing that TXNIP decreases in the plasma membranes of IEC6 and Caco-2 cells after treatment with two representative biguanides, while GLUT1 levels increase. Expression levels were normalized to ATP1A1. g Immunoblots of plasma membrane lysates of organoids. ATP1A1 served as a loading control of membrane protein. All data are presented as the mean ± s.e.m. Data in d were analyzed using two-tailed Student’s t-tests; ***P < 0.001.