GW9508 inhibits insulin secretion by activating ATP-sensitive potassium channels in rat pancreatic β-cells

Incretins play an important role in FFA4/GPR120 regulation of glucose metabolism by GW-9508

AIMS

To assess the role of GPR120 in glucose metabolism and incretin regulation from enteroendocrine L- and K-cells with determination of the cellular localisation of GPR120 in intestinal tissue and clonal Glucagon-Like Peptide-1 (GLP-1)/Gastric Inhibitory Polypeptide (GIP) cell lines.

MAIN METHODS

Anti-hyperglycaemic, insulinotropic and incretin secreting properties of the GPR120 agonist, GW-9508 were explored in combination with oral and intraperitoneal glucose tolerance tests (GTT) in lean, diabetic and incretin receptor knockout mice. Cellular localisation of GPR120 was assessed by double immunofluorescence.

KEY FINDINGS

Compared to intraperitoneal injection, oral administration of GW-9508 (0.1 μmol/kg body weight) together with glucose reduced the glycaemic excursion by 22-31 % (p < 0.05-p < 0.01) and enhanced glucose-induced insulin release by 30 % (p < 0.01) in normal mice. In high fat fed diabetic mice, orally administered GW-9508 lowered plasma glucose by 17-27 % (p < 0.05-p < 0.01) and augmented insulin release by 22-39 % (p < 0.05-p < 0.001). GW-9508 had no effect on the responses of GLP-1 receptor knockout mice and GIP receptor knockout mice. Consistent with this, oral GW-9508 increased circulating total GLP-1 release by 39-44 % (p < 0.01) and total GIP by 37-47 % (p < 0.01-p < 0.001) after 15 and 30 min in lean NIH Swiss mice. Immunocytochemistry demonstrated GPR120 expression on mouse enteroendocrine L- and K-cells, GLUTag cells and pGIP/Neo STC-1 cells.

SIGNIFICANCE

GPR120 is expressed on intestinal L- and K-cells and stimulates GLP-1/GIP secretory pathways involved in mediating enhanced insulin secretion and improved glucose tolerance, following oral GW-9508. These novel data strongly support the development of potent and selective GPR120 agonists as an effective therapeutic approach for diabetes.

Free fatty acid receptors in the endocrine regulation of glucose metabolism: Insight from gastrointestinal-pancreatic-adipose interactions

Glucose metabolism is primarily controlled by pancreatic hormones, with the coordinated assistance of the hormones from gastrointestine and adipose tissue. Studies have unfolded a sophisticated hormonal gastrointestinal-pancreatic-adipose interaction network, which essentially maintains glucose homeostasis in response to the changes in substrates and nutrients. Free fatty acids (FFAs) are the important substrates that are involved in glucose metabolism. FFAs are able to activate the G-protein coupled membrane receptors including GPR40, GPR120, GPR41 and GPR43, which are specifically expressed in pancreatic islet cells, enteroendocrine cells as well as adipocytes. The activation of FFA receptors regulates the secretion of hormones from pancreas, gastrointestine and adipose tissue to influence glucose metabolism. This review presents the effects of the FFA receptors on glucose metabolism via the hormonal gastrointestinal-pancreatic-adipose interactions and the underlying intracellular mechanisms. Furthermore, the development of therapeutic drugs targeting FFA receptors for the treatment of abnormal glucose metabolism such as type 2 diabetes mellitus is summarized.

Free Fatty Acid Receptor 1 Signaling Contributes to Migration, MMP-9 Activity, and Expression of IL-8 Induced by Linoleic Acid in HaCaT Cells

Keratinocytes and neutrophils are the main cellular components in wound healing during re-epithelization and inflammation. Free fatty acids such as linoleic acid (LA) present beneficial properties for wound healing by modulating the inflammatory response. LA is a natural ligand of free fatty acids receptor 1 (FFA1), a G protein-coupled receptor (GPCR), able to modulate inflammatory process; however, the role of FFA1 in keratinocytes and wound healing remains poorly understood. In this study, we investigated the role of FFA1 signaling in migration, matrix metalloproteinase-9 (MMP-9) activity, and IL-8 expression induced by LA in keratinocytes. We confirmed that HaCaT cells, a human keratinocyte cell line, expresses the FFA1 receptor and GW1100, a selective antagonist of FFA1, decreased LA-induced migration of HaCaT cells. Also, GW9508, a synthetic agonist of FFA1, increased migration of these cells. Furthermore, ERK1/2 and p38 MAPK inhibitors abolished the LA-induced increase in cell migration. Besides, HaCaT cells stimulated with LA or GW9508 increased the activity of MMP-9 and the expression of IL-8. GW1100 partially inhibited both responses. We further evaluated the effects of HaCaT cells conditioned media stimulated with LA or GW9508 on neutrophil chemotaxis. Conditioned media induced neutrophil chemotaxis. Furthermore, IL-8 secreted by HaCaT cells stimulated with LA or GW9508, contributed to neutrophil chemotaxis. In conclusion, LA increased migration, MMP-9 activity, and expression of IL-8 from HaCaT cells via FFA1. Hence, these results showed that the effects induced by LA in keratinocytes can be mediated through FFA1, thus explaining a possible mechanism by which this fatty acid could accelerate wound healing.

FFAR1 activation attenuates histamine-induced myosin light chain phosphorylation and cortical tension development in human airway smooth muscle cells

BACKGROUND

Activation of free fatty acid receptors (FFAR1 and FFAR4) which are G protein-coupled receptors (GPCRs) with established (patho)physiological roles in a variety of obesity-related disorders, induce human airway smooth muscle (HASM) cell proliferation and shortening. We reported amplified agonist-induced cell shortening in HASM cells obtained from obese lung donors. We hypothesized that FFAR1 modulate excitation-contraction (EC) coupling in HASM cells and play a role in obesity-associated airway hyperresponsiveness.

METHODS

In HASM cells pre-treated (30 min) with FFAR1 agonists TAK875 and GW9508, we measured histamine-induced Ca²⁺ mobilization, myosin light chain (MLC) phosphorylation, and cortical tension development with magnetic twisting cytometry (MTC). Phosphorylation of MLC phosphatase and Akt also were determined in the presence of the FFAR1 agonists or vehicle. In addition, the effects of TAK875 on MLC phosphorylation were measured in HASM cells desensitized to β₂AR agonists by overnight salmeterol treatment. The inhibitory effect of TAK875 on MLC phosphorylation was compared between HASM cells from age and sex-matched non-obese and obese human lung donors. The mean measurements were compared using One-Way ANOVA with Dunnett's test for multiple group comparisons or Student's t-test two-group comparison. For cortical tension measurements by magnetic twisted cytometry, mixed effect model using SAS V.9.2 was applied. Means were considered significant when p ≤ 0.05.

RESULTS

Unexpectedly, we found that TAK875, a synthetic FFAR1 agonist, attenuated histamine-induced MLC phosphorylation and cortical tension development in HASM cells. These physiological outcomes were unassociated with changes in histamine-evoked Ca²⁺ flux, protein kinase B (AKT) activation, or MLC phosphatase inhibition. Of note, TAK875-mediated inhibition of MLC phosphorylation was maintained in β₂AR-desensitized HASM cells and across obese and non-obese donor-derived HASM cells.

CONCLUSIONS

Taken together, our findings identified the FFAR1 agonist TAK875 as a novel bronchoprotective agent that warrants further investigation to treat difficult-to-control asthma and/or airway hyperreactivity in obesity.

Pharmacokinetics and metabolism of GW9508 in rat by liquid chromatography/electrospray ionization tandem mass spectrometry

In this study, a simple, fast and sensitive LC/MS/MS method was developed and validated for the determination of GW9508 in rat plasma. The sample was precipitated with acetonitrile and subsequently separated on ZORBAX Eclipse XDB C₁₈ column (50 mm × 2.1 mm, 5 μm). Mobile phase was composed of 0.1% formic acid in water and acetonitrile with gradient elution, at a flow rate of 0.4 mL/min. The analyte and internal standard were quantitatively monitored with precursor-to-product transitions of m/z 348.2→183.1 and m/z 397.2→260.2, respectively. The linearity of the assay was evident in the range of 1-1000 ng/mL with correlation coefficient more than 0.998. The validation parameters were all within the acceptable limits. The validated method has been successfully applied to the pharmacokinetics study of GW9508 in rat plasma, and our results demonstrated that GW9508 showed low clearance, moderate half-life and ideal bioavailability (54.88%). Furthermore, metabolites stemmed from rat plasma, rat hepatocytes and human hepatocytes were analyzed by an LC-Q-Exactive-Orbitrap-MS assay, resulting in the identification of seven metabolites based on the accurate mass and fragment ions. Acylglucuronide conjugate (M6) was found as the most abundant metabolite in all tested matrices. The metabolic pathways were proposed as hydroxylation and glucuronidation. This study provided an overview of disposition of GW9508, which is highly instructive for better understanding the effectiveness and toxicity of this drug.

Optical control of GPR40 signalling in pancreatic β-cells

Fatty acids activate GPR40 and K+ channels to modulate β-cell function. Herein, we describe the design and synthesis of FAAzo-10, a light-controllable GPR40 agonist based on Gw-9508. FAAzo-10 is a potent GPR40 agonist in the trans-configuration and can be inactivated on isomerization to cis with UV-A light. Irradiation with blue light reverses this effect, allowing FAAzo-10 activity to be cycled ON and OFF with a high degree of spatiotemporal precision. In dissociated primary mouse β-cells, FAAzo-10 also inactivates voltage-activated and ATP-sensitive K+ channels, and allows us to control glucose-stimulated Ca2+ oscillations in whole islets with light. As such, FAAzo-10 is a useful tool to study the complex effects, with high specificity, which FA-derivatives such as Gw-9508 exert at multiple targets in mouse β-cells.

Evaluation of the insulin-releasing and glucose-lowering effects of GPR120 activation in pancreatic β-cells

AIMS

To assess the potency and selectivity of various GPR120 agonists and to determine the cellular localization of GPR120 in clonal β-cells and pancreatic islets.

METHODS

Insulin secretion and alterations in intracellular Ca(2+) and cAMP response to glucose and GPR120 agonists, including endogenous agonists α-linolenic acid (ALA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and a synthetic analogue (GW-9508), were examined using clonal pancreatic BRIN-BD11 cells, mouse pancreatic islets and in vivo studies using NIH Swiss mice. Cytotoxicity was assessed by lactate dehydrogenase release. Cellular localization of GPR120 was explored by double-staining immunohistochemistry.

RESULTS

The most potent and selective GPR120 agonist tested was ALA (half maximum effective concentration 1.2 × 10(-8) mol/l) with a maximum stimulation of insulin secretion of 53% at 10(-4) mol/l (p < 0.001) in BRIN-BD11 cells. Stimulation of insulin secretion was also observed with GW-9508 (6.4 × 10(-8) mol/l; 47%), EPA (7.9 × 10(-8) mol/l; 36%) and DHA (1.0 × 10(-7) mol/l; 50%). Results were corroborated by islet studies, with no evidence of cytotoxic effects. Dose-dependent insulin secretion by GPR120 agonists was glucose-sensitive and accompanied by significant elevations of intracellular Ca(2+) and cAMP. Immunocytochemistry showed GPR120 expression on BRIN-BD11 cells and was confined to islet β-cells with no distribution on α-cells. Administration of GPR120 agonists (0.1 µmol/kg body weight) in glucose tolerance studies significantly reduced plasma glucose and augmented insulin release in mice.

CONCLUSIONS

These results indicate that GPR120 is expressed on pancreatic β-cells and that agonists at this receptor are potent insulin secretagogues with therapeutic potential for type 2 diabetes.

Activation of free fatty acid receptor 1 improves hepatic steatosis through a p38-dependent pathway

Hepatic steatosis is highly correlated with insulin resistance and diabetes. Although, it has been demonstrated that activation of free fatty acid receptor 1 (FFAR1) by agonists showed benefits for the improvement of diabetes, the effects of FFAR1 agonists on hepatic steatosis were unknown. In this study, a high fat diet (HFD)-induced hepatic steatosis animal model was utilized to evaluate the effects of an FFAR1 agonist, GW9508, on hepatic lipid accumulation, and HepG2 hepatoma cells were also used to clarify the possible mechanisms. Administration of GW9508 significantly decreased the hepatic lipid accumulation with decreased expressions of lipogenesis-related proteins in HFD mice. Knockdown of hepatic Ffar1 by lentiviral vectors containing short hairpin RNA targeted to Ffar1 diminished the effect of GW9508 in HFD mice. In addition, GW9508 decreased oleic acid-induced lipid accumulation in HepG2 cells by decreases in the expression of lipogenesis-related proteins. Moreover, GW9508 downregulated the expression of sterol regulatory element-binding protein 1 (SREBP1) through a p38-dependent pathway, whereas knockdown of Ffar1 in HepG2 cells diminished the effect of GW9508 on the decrease in SREBP1. Considering all these results together, GW9508 exerts a therapeutic effect to improve hepatic steatosis through a p38-dependent pathway. Thus, investigation of chemicals that act on FFAR1 might be a new strategy for the treatment of hepatic steatosis.

Synergistic antinociceptive effect and gastric safety of the combination of docosahexaenoic acid and indomethacin in rats

The use of analgesics is limited by the presence of significant adverse side effects. Thus, combinations of non-steroidal anti-inflammatory drugs (NSAIDs) with other antinociceptive agents are frequently used to decrease these adverse reactions. The aims of this work were to evaluate the antinociceptive interaction of the systemic administration of the combination of DHA and indomethacin through an isobolographic analysis of the theoretical and experimental antinociceptive effect and to demonstrate the gastric safety of the mixture compared with indomethacin alone. Female Wistar rats were orally administered indomethacin (1-10 mg/kg), DHA (100-300 mg/kg), or the DHA-indomethacin mixture at a fixed-ratio combination (1:1, 1:3, 3:1), and the antinociceptive effects of these treatments were evaluated through the formalin (1%) test. An isobolographic analysis was performed to characterize the antinociceptive interaction between DHA and indomethacin. The degree of gastric injury in all of the rats was determined 1 h after the formalin test. The theoretical ED₃₀ values (Zadd) for the 1:1, 1:3, and 3:1 combinations were 73.48 ± 8.96, 37.75 ± 4.50, and 109.2 ± 13.43 mg/kg, p.o., respectively, and the experimental ED30 values (Zexp) were 43.63 ± 5.18, 13.13 ± 1.61, and 54.20 ± 6.53, respectively. The isobolographic analysis showed that the three fixed-ratio combinations studied exhibited a synergistic interaction. Furthermore, the gastric damage induced by indomethacin was abolished when this drug was combined with DHA. These data suggest that the systemic administration of the DHA-indomethacin combination induces a synergistic and gastric safety effect.