Fig. 2

A combination of glucose, fructose, and palmitate ligands induces production and secretion of pro-inflammatory cytokines and chemokine in EECs via TAS1R3 activation. a qRT-PCR of relative mRNA expression of intestinal TAS1R3 in NCI-H716 cells after 12 h of treatment with individual or combined glucose, fructose, and palmitate to activate TAS1R3 (n = 3/group). Time course of (b) GLP1 mRNA expression, c active GLP-1 levels, d IL1B mRNA expression, e IL6 mRNA expression, f TNFɑ mRNA expression, and g MCP1 mRNA expression in NCI-H716 cells after stimulation with individual or combined glucose, fructose, and palmitate (n = 3/group). h–l NCI-H716 cells were transfected with TAS1R3 (10 nM) or scrambled control (10 nM) siRNA for 48 h and then stimulated with or without fructose (10 mM), glucose (10 mM), and palmitate (10 μM) for 12 h (n = 3/group). Evaluation of TAS1R3 siRNA h mRNA and i protein knockdown in EECs. Transfection with TAS1R3 siRNA inhibited TAS1R3 mRNA and protein expression in differentiated NCI-H716 cells. The collected supernatants were assayed for active j GLP-1, k IL-8, and l TNF-α levels. m–o NCI-H716 cells were pretreated with the TAS1R3 antagonist, lactisole (2.5 mM), for 30 min and then stimulated with fructose (10 mM), glucose (10 mM), and palmitate (10 μM) for 12 h (n = 3/group). The collected supernatants were assayed by active m GLP-1, n IL-8, and o TNF-α enzyme-linked immunosorbent assay. Data represent means ± standard errors of the mean of three to five independent experiments. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001 (one-way analysis of variance followed by Bonferroni post-hoc test). EEC, enteroendocrine cell; GLP-1, glucagon-like peptide 1; IL, interleukin; MCP-1, monocyte chemoattractant protein-1; qRT-PCR, quantitative reverse transcription PCR; TAS1R3, taste receptor type 1 member 3; TNFα, tumor necrosis factor-alpha; WD, western diet