The acute glucose lowering effect of specific GPR120 activation in mice is mainly driven by glucagon-like peptide 1

<div><p>The mechanism behind the glucose lowering effect occurring after specific activation of GPR120 is not completely understood. In this study, a potent and selective GPR120 agonist was developed and its pharmacological properties were compared with the previously described GPR120 agonist Metabolex-36. Effects of both compounds on signaling pathways and GLP-1 secretion were investigated <i>in vitro</i>. The acute glucose lowering effect was studied in lean wild-type and GPR120 <i>null</i> mice following oral or intravenous glucose tolerance tests. <i>In vitro</i>, in GPR120 overexpressing cells, both agonists signaled through Gα_q, Gα_s and the β-arrestin pathway. However, in mouse islets the signaling pathway was different since the agonists reduced cAMP production. The GPR120 agonists stimulated GLP-1 secretion both <i>in vitro</i> in STC-1 cells and <i>in vivo</i> following oral administration. <i>In vivo</i> GPR120 activation induced significant glucose lowering and increased insulin secretion after intravenous glucose administration in lean mice, while the agonists had no effect in GPR120 <i>null</i> mice. Exendin 9–39, a GLP-1 receptor antagonist, abolished the GPR120 induced effects on glucose and insulin following an intravenous glucose challenge. In conclusion, GLP-1 secretion is an important mechanism behind the acute glucose lowering effect following specific GPR120 activation.</p></div

<i>In vitro</i> pharmacology of AZ13581837 and Metabolex-36.

<p><i>In vitro</i> pharmacology of AZ13581837 and Metabolex-36.</p

Exendin 9–39 blocked the Metabolex-36 induced potentiation of insulin secretion in lean mice.

<p>Insulin levels following intravenous glucose challenge (<b>A</b>) and corresponding blood glucose (<b>C</b>), after administration of Metabolex-36, exendin 9–39 or a co-administration of both, with corresponding calculations of AIR (<b>B</b>) and glucose elimination (<b>D</b>). The IVGTT data are from two independent experiments with 6–7 mice per group. Data are presented as mean ± SEM.**p<0.01 and *p<0.05 versus vehicle control.</p

AZ13581837 and Metabolex-36 reduced cAMP production in mouse islets and induced GLP-1 secretion from STC-1 cells.

<p>Effect of 10 μM AZ13581837, 10 μM Metabolex-36, 50 nM Exendin-4 or vehicle control on cAMP production in dispersed islets from wild type (<b>A</b>) and GP120 <i>null</i> mice (<b>B</b>). Data represent mean ± SEM from three independent experiments where islet were isolated from two or four mice of each genotype. cAMP was measured in at least triplicates for both wild type and GPR120 <i>null</i> islet in each experiment. STC-1 cells were stimulated with Metabolex-36, AZ13581837 or vehicle control (0.1% DMSO) for 2 hours and secreted active GLP-1 was measured by ELISA (<b>C</b>). Three independent GLP-1 secretion experiments were run where n = 3 of each control and compound treatment. *p<0.05, **p<0.01, ***p<0.001 and ****p<0.0001 versus vehicle control (two sample, two sided t-test).</p

Exendin 9–39 blocked the AZ13581837 induced potentiation of insulin secretion in lean mice.

<p>Insulin levels following intravenous glucose challenge (<b>A</b>) and corresponding blood glucose (<b>C</b>), after administration of AZ13581837, exendin 9–39 or a co-administration of both, with corresponding calculations of AIR (<b>B</b>) and glucose elimination (<b>D</b>). The IVGTT data are from two independent experiments with n = 10 mice per group. Data are presented as mean ± SEM.***p<0.001 and *p<0.05 versus vehicle control.</p

Structure of AZ13581837 and Metabolex-36 and specificity of the compounds for human and mouse GPR120 and human or mouse GPR40.

<p><b>A)</b> Chemical structure of AZ13581837 and <b>B)</b> Metabolex-36.<b>C)</b> Effect of AZ13581837 (squares) and Metabolex-36 (circles) on DMR response in CHO-hGPR120 (filled symbols) and CHO (open symbols). <b>D)</b> Activity in CHO-GPR40 cells for AZ13581837 (filled squares), Metabolex-36 (filled circles) and GW9508 (filled triangles). Activity in CHO-hGPR120 cells is shown as reference for AZ13581837 (open squares), Metabolex-36 (open circles) and GW9508 (open triangles). <b>E)</b> Cross species selectivity evaluated in CHO-mGPR120 cells using a DMR assay. Activity of AZ13581837 (squares) and Metabolex-36 (circles) on mouse GPR120 (filled symbols) compared to human GPR120 (open symbols). <b>F)</b> Cross species selectivity for GPR40 evaluated using a calcium mobilization assay. Effect of AZ13581837 (filled squares) and Metabolex-36 (filled circles) on mouse GPR40 with GW9508 (filled triangles) as reference. Activity in CHO-hGPR120 cells is shown as comparison for AZ13581837 (open squares) and Metabolex-36 (open circles). Data are shown as mean ± SEM run in duplicates or more and representative for two or more independent experiments.</p

Metabolex-36 and AZ13581837 increased insulin secretion in IVGTT in lean mice.

<p>Insulin (<b>A</b>) and blood glucose (<b>C</b>) levels following an intravenous glucose challenge after oral administration of Metabolex-36 and AZ13581837 in lean female mice and corresponding AIR (<b>B</b>) and glucose elimination (<b>D</b>). Data represent six (Metabolex-36, n = 33, vehicle n = 34) and two (AZ13581837, n = 14) independent experiments and data are presented as mean ± SEM. Plasma levels of total GLP-1 (<b>E</b>) at time point was determined in separate experiments with n = 10 mice per group. ***p<0.001 and **p<0.01versus vehicle control.</p

Effect of Metabolex-36 and AZ13581837 on oral glucose tolerance in mice.

<p>Effect of Metabolex-36 (<b>A</b>) and AZ13581837 (<b>C</b>) on glucose response after an oral glucose challenge (2g/kg) in male mice and the corresponding unbound circulating concentrations of Metabolex-36 (<b>B</b>) and AZ13581837 (<b>D</b>) during the experiment. AZ13581837 and Metabolex-36 were given in different doses as indicated in the figures with n = 10 mice group and compared to vehicle treated mice (n = 12 mice per group). The EC₅₀ value for each GPR120 agonist assessed on mouse GPR120 using a DMR assay is indicated in figures. Blood glucose levels following oral glucose administration in GPR120 <i>null</i> mice (<b>E</b>) and wild type mice (<b>F</b>) were determined for vehicle (open squares) and Metabolex-36 (filled squares).</p