TAK-875, an orally available G protein-coupled receptor 40/free fatty acid receptor 1 agonist, enhances glucose-dependent insulin secretion and improves both postprandial and fasting hyperglycemia in type 2 diabetic rats

GPCRs involved in metabolic diseases: pharmacotherapeutic development updates

G protein-coupled receptors (GPCRs) are expressed in a variety of cell types and tissues, and activation of GPCRs is involved in enormous metabolic pathways, including nutrient synthesis, transportation, storage or insulin sensitivity, etc. This review intends to summarize the regulation of metabolic homeostasis and mechanisms by a series of GPCRs, such as GPR91, GPR55, GPR119, GPR109a, GPR142, GPR40, GPR41, GPR43 and GPR120. With deep understanding of GPCR's structure and signaling pathways, it is attempting to uncover the role of GPCRs in major metabolic diseases, including metabolic syndrome, diabetes, dyslipidemia and nonalcoholic steatohepatitis, for which the global prevalence has risen during last two decades. An extensive list of agonists and antagonists with their chemical structures in a nature of small molecular compounds for above-mentioned GPCRs is provided as pharmacologic candidates, and their preliminary data of preclinical studies are discussed. Moreover, their beneficial effects in correcting abnormalities of metabolic syndrome, diabetes and dyslipidemia are summarized when clinical trials have been undertaken. Thus, accumulating data suggest that these agonists or antagonists might become as new pharmacotherapeutic candidates for the treatment of metabolic diseases.

Oral administration of linoleic acid immediately before glucose load ameliorates postprandial hyperglycemia

Introduction: Fatty acids are a major nutrient in dietary fat, some of which are ligands of long-chain fatty acid receptors, including G-protein-coupled receptor (GPR) 40 and GPR120. Pretreatment with GPR40 agonists enhanced the secretion of insulin in response to elevating blood glucose levels after glucose load in a diabetes model, but pretreatment with GPR120 agonist did not ameliorate postprandial hyperglycemia. This study examined whether oral administration of linoleic acid (LA), a GPR40 and GPR120 agonist, immediately before glucose load would affect the elevation of postprandial blood glucose levels in rats. Methods: Male rats and rats with type 1 diabetes administered streptozocin were orally administered LA, trilinolein, α-linolenic acid (α-LA), oleic acid, TAK-875, or TUG-891 immediately before glucose load. Blood glucose levels were measured before, then 15, 30, 60 and 120 min after glucose load. CACO-2 cells were used to measure the uptake of [14C] α-MDG for 30 min with or without LA. Gastric content from rats administered LA was collected 15 and 30 min after glucose load, and blood samples were collected for measurement of glucagon-like peptide 1 (GLP-1) and cholecystokinin concentrations. Results: The elevation of postprandial blood glucose levels was slowed by LA but not by trilinolein in rats without promotion of insulin secretion, and this effect was also observed in rats with type 1 diabetes. The uptake of α-MDG, an SGLT-specific substrate, was, however, not inhibited by LA. Gastric emptying was slowed by LA 15 min after glucose load, and GLP-1, but not cholecystokinin, level was elevated by LA 15 min after glucose load. TUG-891, a GPR120 agonist, ameliorated postprandial hyperglycemia but TAK-875, a GPR40 agonist, did not. Pretreatment with AH7614, a GPR120 antagonist, partially canceled the improvement of postprandial hyperglycemia induced by LA. α-LA, which has high affinity with GPR120 as well as LA, slowed the elevation of postprandial blood glucose levels, but oleic acid, which has lower affinity with GPR120 than LA, did not. Conclusion: Oral administration of LA immediately after glucose load ameliorated postprandial hyperglycemia due to slowing of gastric emptying via promotion of GLP-1 secretion. The mechanisms may be associated with GPR120 pathway.

Anthocyanins: Potential Therapeutic Approaches towards Obesity and Diabetes Mellitus Type 2

Overweight and obesity are present in about three-quarters of the adult population in Mexico. The inflammatory mechanisms subjacent to visceral white adipose tissue are accountable for the initiation and development of cardiometabolic alterations, including type 2 diabetes. Lifestyle changes are pillars within its therapeutics and, thus, current dietary modifications should include not only hypocaloric prescriptions with balanced macronutrient intake, preferably by increasing the amount of whole grains, fruits, vegetables, nuts and legumes, but in concomitance, bioactive substances, such as anthocyanins, have been correlated with lower incidence of this disease.

Learn from failures and stay hopeful to GPR40, a GPCR target with robust efficacy, for therapy of metabolic disorders

GPR40 is a class A G-protein coupled receptor (GPCR) mainly expressed in pancreas, intestine, and brain. Its endogenous ligand is long-chain fatty acids, which activate GPR40 after meal ingestion to induce secretion of incretins in the gut, including GLP-1, GIP, and PYY, the latter control appetite and glucose metabolism. For its involvement in satiety regulation and metabolic homeostasis, partial and AgoPAM (Positive Allosteric Modulation agonist) GPR40 agonists had been developed for type 2 diabetes (T2D) by many pharmaceutical companies. The proof-of-concept of GPR40 for control of hyperglycemia was achieved by clinical trials of partial GPR40 agonist, TAK-875, demonstrating a robust decrease in HbA1c (-1.12%) after chronic treatment in T2D. The development of TAK-875, however, was terminated due to liver toxicity in 2.7% patients with more than 3-fold increase of ALT in phase II and III clinical trials. Different mechanisms had since been proposed to explain the drug-induced liver injury, including acyl glucuronidation, inhibition of mitochondrial respiration and hepatobiliary transporters, ROS generation, etc. In addition, activation of GPR40 by AgoPAM agonists in pancreas was also linked to β-cell damage in rats. Notwithstanding the multiple safety concerns on the development of small-molecule GPR40 agonists for T2D, some partial and AgoPAM GPR40 agonists are still under clinical development. Here we review the most recent progress of GPR40 agonists development and the possible mechanisms of the side effects in different organs, and discuss the possibility of developing novel strategies that retain the robust efficacy of GPR40 agonists for metabolic disorders while avoid toxicities caused by off-target and on-target mechanisms.

High-resolution accurate mass approach to characterization of SCO-267 metabolites using liquid chromatography hybrid quadrupole Orbitrap mass spectrometry

RATIONALE

SCO-267 is a potent full agonist of G-protein-coupled receptor 40. As a promising therapeutic agent for type 2 diabetes mellitus, it is necessary to elucidate its metabolite profiles during the stage of drug development for safety considerations.

METHODS

The in vitro metabolism was investigated by incubating SCO-267 (5 μM) with liver microsomes and hepatocytes (rat and human). For in vivo metabolism, SCO-267 (10 mg/kg) was orally administered to rats and plasma samples were collected. The metabolites were identified via measurements of accurate mass, elemental composition and product ions using liquid chromatography coupled to hybrid quadrupole Orbitrap high-resolution mass spectrometry (LC-Orbitrap-MS).

RESULTS

A total of 19 metabolites were structurally identified. M2 (hydroxyl-SCO-267), M15 (SCO-267-acyl-glucuronide), M16 (desmethyl-SCO-267) and M17 (desneopentyl-SCO-267) were verified with reference standards. M2, M11, M16 and M17 were the major metabolites originating from hydroxylation, O-demethylation and N-dealkylation, respectively. Phenotyping study with recombinant human P450 enzymes demonstrated that hydroxylation (M2 and M11) was mainly catalyzed by CYP2C8 and 3A4; demethylation (M16) was mainly catalyzed by CYP2D6, and less catalyzed by CYP2C8 and 3A4; and N-dealkylation (M17) was exclusively triggered by CYP3A4.

CONCLUSIONS

Hydroxylation, O-demethylation, N-dealkylation and acyl glucuronidation were the major metabolic pathways of SCO-267. This study is the first to discover the metabolic fates of SCO-267, which provides a basis for safety assessment of this drug candidate.

Free Fatty Acid Receptors (FFARs) in Adipose: Physiological Role and Therapeutic Outlook

Fatty acids (FFAs) are important biological molecules that serve as a major energy source and are key components of biological membranes. In addition, FFAs play important roles in metabolic regulation and contribute to the development and progression of metabolic disorders like diabetes. Recent studies have shown that FFAs can act as important ligands of G-protein-coupled receptors (GPCRs) on the surface of cells and impact key physiological processes. Free fatty acid-activated receptors include FFAR1 (GPR40), FFAR2 (GPR43), FFAR3 (GPR41), and FFAR4 (GPR120). FFAR2 and FFAR3 are activated by short-chain fatty acids like acetate, propionate, and butyrate, whereas FFAR1 and FFAR4 are activated by medium- and long-chain fatty acids like palmitate, oleate, linoleate, and others. FFARs have attracted considerable attention over the last few years and have become attractive pharmacological targets in the treatment of type 2 diabetes and metabolic syndrome. Several lines of evidence point to their importance in the regulation of whole-body metabolic homeostasis including adipose metabolism. Here, we summarize our current understanding of the physiological functions of FFAR isoforms in adipose biology and explore the prospect of FFAR-based therapies to treat patients with obesity and Type 2 diabetes.

Advanced Bioinformatics Tools in the Pharmacokinetic Profiles of Natural and Synthetic Compounds with Anti-Diabetic Activity

Diabetes represents a major health problem, involving a severe imbalance of blood sugar levels, which can disturb the nerves, eyes, kidneys, and other organs. Diabes management involves several synthetic drugs focused on improving insulin sensitivity, increasing insulin production, and decreasing blood glucose levels, but with unclear molecular mechanisms and severe side effects. Natural chemicals extracted from several plants such as Gymnema sylvestre, Momordica charantia or Ophiopogon planiscapus Niger have aroused great interest for their anti-diabetes activity, but also their hypolipidemic and anti-obesity activity. Here, we focused on the anti-diabetic activity of a few natural and synthetic compounds, in correlation with their pharmacokinetic/pharmacodynamic profiles, especially with their blood-brain barrier (BBB) permeability. We reviewed studies that used bioinformatics methods such as predicted BBB, molecular docking, molecular dynamics and quantitative structure-activity relationship (QSAR) to elucidate the proper action mechanisms of antidiabetic compounds. Currently, it is evident that BBB damage plays a significant role in diabetes disorders, but the molecular mechanisms are not clear. Here, we presented the efficacy of natural (gymnemic acids, quercetin, resveratrol) and synthetic (TAK-242, propofol, or APX3330) compounds in reducing diabetes symptoms and improving BBB dysfunctions. Bioinformatics tools can be helpful in the quest for chemical compounds with effective anti-diabetic activity that can enhance the druggability of molecular targets and provide a deeper understanding of diabetes mechanisms.

Recent Updates on Free Fatty Acid Receptor 1 (GPR-40) Agonists for the Treatment of Type 2 Diabetes Mellitus

BACKGROUND

The global incidence of type 2 diabetes mellitus (T2DM) has enthused the development of new antidiabetic targets with low toxicity and long-term stability. In this respect, free fatty acid receptor 1 (FFAR1), which is also recognized as a G protein-coupled receptor 40 (GPR40), is a novel target for the treatment of T2DM. FFAR1/GPR40 has a high level of expression in β-cells of the pancreas, and the requirement of glucose for stimulating insulin release results in immense stimulation to utilise this target in the medication of T2DM.

METHODS

The data used for this review is based on the search of several scienctific databases as well as various patent databases. The main search terms used were free fatty acid receptor 1, FFAR1, FFAR1 agonists, diabetes mellitus, G protein-coupled receptor 40 (GPR40), GPR40 agonists, GPR40 ligands, type 2 diabetes mellitus and T2DM.

RESULTS

The present review article gives a brief overview of FFAR1, its role in T2DM, recent developments in small molecule FFAR1 (GPR40) agonists reported till now, compounds of natural/plant origin, recent patents published in the last few years, mechanism of FFAR1 activation by the agonists, and clinical status of the FFAR1/GPR40 agonists.

CONCLUSION

The agonists of FFAR1/GRP40 showed considerable potential for the therapeutic control of T2DM. Most of the small molecule FFAR1/GPR40 agonists developed were aryl alkanoic acid derivatives (such as phenylpropionic acids, phenylacetic acids, phenoxyacetic acids, and benzofuran acetic acid derivatives) and thiazolidinediones. Some natural/plant-derived compounds, including fatty acids, sesquiterpenes, phenolic compounds, anthocyanins, isoquinoline, and indole alkaloids, were also reported as potent FFAR1 agonists. The clinical investigations of the FFAR1 agonists demonstrated their probable role in the improvement of glucose control. Though, there are some problems still to be resolved in this field as some FFAR1 agonists terminated in the late phase of clinical studies due to "hepatotoxicity." Currently, PBI-4050 is under clinical investigation by Prometic. Further investigation of pharmacophore scaffolds for FFAR1 full agonists as well as multitargeted modulators and corresponding clinical investigations will be anticipated, which can open up new directions in this area.

Structure-Activity Relationship Study and Biological Evaluation of 2-(Disubstituted phenyl)-indole-5-propanoic Acid Derivatives as GPR40 Full Agonists

G-protein-coupled receptor 40 (GPR40) is considered as an attractive drug target for treating type 2 diabetes, owing to its role in the free fatty acid-mediated increase in glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells. To identify a new chemotype of GPR40 agonist, a series of 2-aryl-substituted indole-5-propanoic acid derivatives were designed and synthesized. We identified two GPR40 agonist lead compounds-4k (3-[2-(4-fluoro-2-methylphenyl)-1H-indol-5-yl]propanoic acid) and 4o (3-[2-(2,5-dimethylphenyl)-1H-indol-5-yl]propanoic acid), having GSIS and glucagon-like peptide 1 secretory effects. Unlike previously reported GPR40 partial agonists that only activate the Gq pathway, 4k and 4o activated both the Gq and Gs signaling pathways and were characterized as GPR40 full agonists. In in vivo efficacy studies, 4o significantly improved glycemic control in both C57BL/6J and db/db mice and increased plasma-active GLP-1 in C57BL/6J mice. Thus, 4o represents a promising lead for further development as a novel GPR40 full agonist against type 2 diabetes.

Targeting lipid GPCRs to treat type 2 diabetes mellitus - progress and challenges

Therapeutic approaches to the treatment of type 2 diabetes mellitus that are designed to increase insulin secretion either directly target β-cells or indirectly target gastrointestinal enteroendocrine cells (EECs), which release hormones that modulate insulin secretion (for example, incretins). Given that β-cells and EECs both express a large array of G protein-coupled receptors (GPCRs) that modulate insulin secretion, considerable research and development efforts have been undertaken to design therapeutic drugs targeting these GPCRs. Among them are GPCRs specific for free fatty acid ligands (lipid GPCRs), including free fatty acid receptor 1 (FFA1, otherwise known as GPR40), FFA2 (GPR43), FFA3 (GPR41) and FFA4 (GPR120), as well as the lipid metabolite binding glucose-dependent insulinotropic receptor (GPR119). These lipid GPCRs have demonstrated important roles in the control of islet and gut hormone secretion. Advances in lipid GPCR pharmacology have led to the identification of a number of synthetic agonists that exert beneficial effects on glucose homeostasis in preclinical studies. Yet, translation of these promising results to the clinic has so far been disappointing. In this Review, we present the physiological roles, pharmacology and clinical studies of these lipid receptors and discuss the challenges associated with their clinical development for the treatment of type 2 diabetes mellitus.

Chronic Exposure to SCO-267, an Allosteric GPR40 Full Agonist, Is Effective in Improving Glycemic Control in Rats

Full agonist-mediated activation of free fatty acid receptor 1 (FFAR1/GPR40) alleviates diabetes in rodents. Considering that diabetes is a chronic disease, assessment of treatment durability of chronic exposure to a GPR40 full agonist is pivotal for treating patients with diabetes. However, the physiologic significance of chronic in vitro and in vivo exposure to GPR40 full agonists is largely unclear. Here, we evaluated the in vitro and in vivo effects of chronic treatment with SCO-267, a GPR40 full agonist, on signal transduction and glucose control. In vitro experiments showed that SCO-267 is an allosteric full agonist for GPR40, which activates the Gα _q, Gα _s, and Gα _12/13 pathways and β-arrestin recruitment. The calcium signal response was largely sustained in GPR40-overexpressing CHO cells even after prolonged incubation with SCO-267. To evaluate the in vivo relevance of chronic exposure to GPR40 full agonists, SCO-267 (1 and 10 mg/kg) was administered once daily to neonatally streptozotocin-induced diabetic rats for 15-33 days, and glucose control was evaluated. After 15 days of dosing followed by the drug washout period, SCO-267 improved glucose tolerance, most likely by increasing insulin sensitivity in rats. After 33 days, repeated exposure to SCO-267 was highly effective in improving glucose tolerance in rats. Furthermore, chronic exposure to SCO-267 increased pancreatic insulin content. These results demonstrated that even after chronic exposure, SCO-267 effectively activates GPR40 in cells and rats, suggesting the clinical application of SCO-267 in treating chronic diseases including diabetes. SIGNIFICANCE STATEMENT: GPR40 is a validated therapeutic target for diabetes. This study showed that even after chronic exposure, SCO-267, an allosteric GPR40 full agonist, effectively activates GPR40 in cells and rats; these results suggest a durable efficacy of SCO-267 in patients.

Untargeted Metabolomic Analysis Combined With Multivariate Statistics Reveal Distinct Metabolic Changes in GPR40 Agonist-Treated Animals Related to Bile Acid Metabolism

Metabolomics has been increasingly applied to biomarker discovery, as untargeted metabolic profiling represents a powerful exploratory tool for identifying causal links between biomarkers and disease phenotypes. In the present work, we used untargeted metabolomics to investigate plasma specimens of rats, dogs, and mice treated with small-molecule drugs designed for improved glycemic control of type 2 diabetes mellitus patients via activation of GPR40. The in vivo pharmacology of GPR40 is not yet fully understood. Compounds targeting this receptor have been found to induce drug-induced liver injury (DILI). Metabolomic analysis facilitating an integrated UPLC-TWIMS-HRMS platform was used to detect metabolic differences between treated and non-treated animals within two 4-week toxicity studies in rat and dog, and one 2-week toxicity study in mouse. Multivariate statistics of untargeted metabolomics data subsequently revealed the presence of several significantly upregulated endogenous compounds in the treated animals whose plasma level is known to be affected during DILI. A specific bile acid metabolite useful as endogenous probe for drug-drug interaction studies was identified (chenodeoxycholic acid-24 glucuronide), as well as a metabolic precursor indicative of acidic bile acid biosynthesis (7α-hydroxy-3-oxo-4-cholestenoic acid). These results correlate with typical liver toxicity parameters on the individual level.

Design and Identification of a GPR40 Full Agonist () Possessing a 2-Carbamoylphenyl Piperidine Moiety

GPR40/FFAR1 is a G-protein-coupled receptor expressed in pancreatic β-cells and enteroendocrine cells. GPR40 activation stimulates secretions of insulin and incretin, both of which are the pivotal regulators of glycemic control. Therefore, a GPR40 agonist is an attractive target for the treatment of type 2 diabetes mellitus. Using the reported biaryl derivative 1, we shifted the hydrophobic moiety to the terminal aryl ring and replaced the central aryl ring with piperidine, generating 2-(4,4-dimethylpentyl)phenyl piperidine 4a, which had improved potency for GPR40 and high lipophilicity. We replaced the hydrophobic moiety with N-alkyl-N-aryl benzamides to lower the lipophilicity and restrict the N-alkyl moieties to the presumed lipophilic pocket using the intramolecular π-π stacking of cis-preferential N-alkyl-N-aryl benzamide. Among these, orally available (3S)-3-cyclopropyl-3-(2-((1-(2-((2,2-dimethylpropyl)(6-methylpyridin-2-yl)carbamoyl)-5-methoxyphenyl)piperidin-4-yl)methoxy)pyridin-4-yl)propanoic acid (SCO-267) effectively stimulated insulin secretion and GLP-1 release and ameliorated glucose tolerance in diabetic rats via GPR40 full agonism.

HWL-088, a new potent free fatty acid receptor 1 (FFAR1) agonist, improves glucolipid metabolism and acts additively with metformin in ob/ob diabetic mice

BACKGROUND AND PURPOSE

The free fatty acid receptor 1 (FFAR1) plays an important role in glucose-stimulated insulin secretion making it an attractive anti-diabetic target. This study characterizes the pharmacological profile of HWL-088 (2-(2-fluoro-4-((2'-methyl-[1,1'- biphenyl]-3-yl)methoxy)phenoxy)acetic acid), a novel highly potent FFAR1 agonist in vitro and in vivo. Moreover, we investigated the long-term effects of HWL-088 alone and in combination with metformin in diabetic mice.

EXPERIMENTAL APPROACH

In vitro effects of HWL-088 on FFAR1 and PPARα/γ/δ were studied in cell-based assays. Glucose-dependent insulinotropic effects were evaluated in MIN6 cell line and in rats. Long-term effects on glucose and lipid metabolism were investigated in ob/ob mice.

KEY RESULTS

HWL-088 is a highly potent FFAR1 agonist (EC50 = 18.9 nM) with moderate PPARδ activity (EC50 = 570.9 nM) and promotes glucose-dependent insulin secretion in vitro and in vivo. Long-term administration of HWL-088 exhibited better glucose control and plasma lipid profiles than those of another FFAR1 agonist, TAK-875, and synergistic improvements were observed when combined with metformin. Moreover, HWL-088 and combination therapy improved β-cell function by up-regulation of pancreas duodenum homeobox-1, reduced fat accumulation in adipose tissue and alleviated fatty liver in ob/ob mice. The effect of HWL-088 involves a reduction in hepatic lipogenesis and oxidative stress, increased lipoprotein lipolysis, glucose uptake, mitochondrial function and fatty acid β-oxidation.

CONCLUSION AND IMPLICATIONS

These data indicate that long-term treatment with HWL-088, a highly potent FFAR1 agonist, improves glucose and lipid metabolism and may be useful for the treatment of diabetes mellitus by mono-therapy or combination with metformin.

Perfluoroalkyl Substances Stimulate Insulin Secretion by Islet β Cells via G Protein-Coupled Receptor 40

The potential causal relationship between exposure to environmental contaminants and diabetes is troubling. Exposure of perfluoroalkyl substances (PFASs) is found to be associated with hyperinsulinemia and the enhancement of insulin secretion by islet β cells in humans, but the underlying mechanism is still unclear. Here, by combining in vivo studies with both wild type and gene knockout mice and in vitro studies with mouse islet β cells (β-TC-6), we demonstrated clearly that 1 h exposure of perfluorooctanesulfonate (PFOS) stimulated insulin secretion and intracellular calcium level by activating G protein-coupled receptor 40 (GPR40), a vital free fatty acid regulated membrane receptor on islet β cells. We further showed that the observed effects of PFASs on the mouse model may also exist in humans by investigating the molecular binding interaction of PFASs with human GPR40. We thus provided evidence for a novel mechanism for how insulin-secretion is disrupted by PFASs in humans.

Free Fatty Acid Receptors as new potential therapeutic target in inflammatory bowel diseases

Family of Free Fatty Acid Receptors (FFARs), specific G protein-coupled receptors comprises of four members: FFAR1-4, where each responds to different chain length of fatty acids (FAs). Over the years, FFARs have become attractive pharmacological targets in the treatment of type 2 diabetes, metabolic syndrome, cardiovascular diseases and asthma; recent studies also point to their role in inflammation. It is now well-established that activation of FFAR1 and FFAR4 by long and medium chain FAs may lead to reduction of inflammatory state; FFAR2 and FFAR3 are activated by short chain FAs, but only FFAR2 was shown to alleviate inflammation, mostly by neutrophil inhibition. All FFARs have thus been proposed as targets in inflammatory bowel diseases (IBD). Here we discuss current knowledge and future directions in FFAR research related to IBD.

GPR40 activation initiates store-operated Ca2+ entry and potentiates insulin secretion via the IP3R1/STIM1/Orai1 pathway in pancreatic β-cells

The long-chain fatty acid receptor GPR40 plays an important role in potentiation of glucose-induced insulin secretion (GIIS) from pancreatic β-cells. Previous studies demonstrated that GPR40 activation enhances Ca²⁺ release from the endoplasmic reticulum (ER) by activating inositol 1,4,5-triphosphate (IP3) receptors. However, it remains unknown how ER Ca²⁺ release via the IP3 receptor is linked to GIIS potentiation. Recently, stromal interaction molecule (STIM) 1 was identified as a key regulator of store-operated Ca²⁺ entry (SOCE), but little is known about its contribution in GPR40 signaling. We show that GPR40-mediated potentiation of GIIS is abolished by knockdown of IP3 receptor 1 (IP3R1), STIM1 or Ca²⁺-channel Orai1 in insulin-secreting MIN6 cells. STIM1 and Orai1 knockdown significantly impaired SOCE and the increase of intracellular Ca²⁺ by the GPR40 agonist, fasiglifam. Furthermore, β-cell-specific STIM1 knockout mice showed impaired fasiglifam-mediated GIIS potentiation not only in isolated islets but also in vivo. These results indicate that the IP3R1/STIM1/Orai1 pathway plays an important role in GPR40-mediated SOCE initiation and GIIS potentiation in pancreatic β-cells.

GPR40 full agonism exerts feeding suppression and weight loss through afferent vagal nerve

GPR40/FFAR1 is a Gq protein-coupled receptor expressed in pancreatic β cells and enteroendocrine cells, and mediates insulin and incretin secretion to regulate feeding behavior. Several GPR40 full agonists have been reported to reduce food intake in rodents by regulating gut hormone secretion in addition to their potent glucose-lowering effects; however, detailed mechanisms of feeding suppression are still unknown. In the present study, we characterized T-3601386, a novel compound with potent full agonistic activity for GPR40, by using in vitro Ca²⁺ mobilization assay in Chinese hamster ovary (CHO) cells expressing FFAR1 and in vivo hormone secretion assay. We also evaluated feeding suppression and weight loss after the administration of T-3601386 and investigated the involvement of the vagal nerve in these effects. T-3601386, but not a partial agonist fasiglifam, increased intracellular Ca²⁺ levels in CHO cells with low FFAR1 expression, and single dosing of T-3601386 in diet-induced obese (DIO) rats elevated plasma incretin levels, suggesting full agonistic properties of T-3601386 against GPR40. Multiple doses of T-3601386, but not fasiglifam, in DIO rats showed dose-dependent weight loss accompanied by feeding suppression and durable glucagon-like peptide-1 elevation, all of which were completely abolished in Ffar1^-/- mice. Immunohistochemical analysis in the nuclei of the solitary tract demonstrated that T-3601386 increased the number of c-Fos positive cells, which also disappeared in Ffar1^-/- mice. Surgical vagotomy and drug-induced deafferentation counteracted the feeding suppression and weight loss induced by the administration of T-3601386. These results suggest that T-3601386 exerts incretin release and weight loss in a GPR40-dependent manner, and that afferent vagal nerves are important for the feeding suppression induced by GPR40 full agonism. Our novel findings raise the possibility that GPR40 full agonist can induce periphery-derived weight reduction, which may provide benefits such as less adverse effects in central nervous system compared to centrally-acting anti-obesity drugs.

Free Fatty Acid Receptors in Health and Disease

Fatty acids are metabolized and synthesized as energy substrates during biological responses. Long- and medium-chain fatty acids derived mainly from dietary triglycerides, and short-chain fatty acids (SCFAs) produced by gut microbial fermentation of the otherwise indigestible dietary fiber, constitute the major sources of free fatty acids (FFAs) in the metabolic network. Recently, increasing evidence indicates that FFAs serve not only as energy sources but also as natural ligands for a group of orphan G protein-coupled receptors (GPCRs) termed free fatty acid receptors (FFARs), essentially intertwining metabolism and immunity in multiple ways, such as via inflammation regulation and secretion of peptide hormones. To date, several FFARs that are activated by the FFAs of various chain lengths have been identified and characterized. In particular, FFAR1 (GPR40) and FFAR4 (GPR120) are activated by long-chain saturated and unsaturated fatty acids, while FFAR3 (GPR41) and FFAR2 (GPR43) are activated by SCFAs, mainly acetate, butyrate, and propionate. In this review, we discuss the recent reports on the key physiological functions of the FFAR-mediated signaling transduction pathways in the regulation of metabolism and immune responses. We also attempt to reveal future research opportunities for developing therapeutics for metabolic and immune disorders.

Activating Effects of Phenolics from Apache Red Zea mays L. on Free Fatty Acid Receptor 1 and Glucokinase Evaluated with a Dual Culture System with Epithelial, Pancreatic, and Liver Cells

The aim was to characterize a phenolic-rich water extract from the pericarp of an improved genotype of Apache red maize (RPE) and evaluate its ability to activate the type 2 diabetes markers free fatty acid receptor 1 (GPR40) and glucokinase (GK) in vitro. The extract contained mainly phenolic acids, anthocyanins, and other flavonoids. RPE inhibited α-amylase (IC₅₀ = 88.3 μg/mL), α-glucosidase (IC₅₀ = 169.3 μg/mL), and reduced glucose transport in a Caco-2 cell monolayer (up to 25%). Furthermore, RPE activated GPR40 (EC₅₀ = 77.7 μg/mL) in pancreatic INS-1E cells and GK (EC₅₀ = 43.4 μg/mL) in liver HepG2 cells, potentially through allosteric modulation. RPE activated GPR40-related insulin secretory pathway and activated the glucose metabolism regulator AMPK (up to 78%). Our results support the hypothesis that foods with a high concentration of anthocyanins and phenolic acids, such as in the selected variety of maize used, could ameliorate obesity and type 2 diabetes comorbidities.

Palmitic acid-induced lipotoxicity promotes a novel interplay between Akt-mTOR, IRS-1, and FFAR1 signaling in pancreatic β-cells

Background

Free fatty acid receptor 1 (FFAR1) is G-protein coupled receptor predominantly expressed in pancreatic β-cells that is activated by a variety of free fatty acids (FFAs). Once activated, it promotes glucose-stimulated insulin secretion (GSIS). However, increased levels of FFAs lead to lipotoxicity, inducing loss of β-cell function. FFAR1 plays a key role in the development of type 2 diabetes (T2D), and previous studies have indicated the importance of developing anti-diabetic therapies against FFAR1, although its role in the regulation of β-cell function remains unclear. The present study investigated the role of FFAR1 under lipotoxic conditions using palmitic acid (PA). The rat insulinoma 1 clone 832/13 (INS-1 832/13) cell line was used as a model as it physiologically resembles native pancreatic β-cells. Key players of the insulin signaling pathway, such as mTOR, Akt, IRS-1, and the insulin receptor (INSR1β), were selected as candidates to be analyzed under lipotoxic conditions.

Results

We revealed that PA-induced lipotoxicity affected GSIS in INS-1 cells and negatively modulated the activity of both IRS-1 and Akt. Reduced phosphorylation of both IRS-1 S636/639 and Akt S473 was observed, in addition to decreased expression of both INSR1β and FFAR1. Moreover, transient knockdown of FFAR1 led to a reduction in IRS-1 mRNA expression and an increase in INSR1β mRNA. Finally, PA affected localization of FFAR1 from the cytoplasm to the perinucleus.

Conclusions

In conclusion, our study suggests a novel regulatory involvement of FFAR1 in crosstalk with mTOR–Akt and IRS-1 signaling in β-cells under lipotoxic conditions.

Targeting GPCRs Activated by Fatty Acid-Derived Lipids in Type 2 Diabetes

G protein-coupled receptors (GPCRs) are the most intensively studied drug targets, because of their diversity, cell-specific expression, and druggable sites accessible at the cell surface. Preclinical and clinical studies suggest that targeting GPCRs activated by fatty acid-derived lipids may have potential to improve glucose homeostasis and reduce complications in patients with type 2 diabetes (T2D). Despite the discontinued development of fasiglifam (TAK-875), the first FFA1 agonist to reach late-stage clinical trials, lipid-sensing receptors remain a viable target, albeit with a need for further characterization of their binding mode, intracellular signaling, and toxicity. Herein, we analyze general discovery trends, various signaling pathways, as well as possible challenges following activation of GPCRs that have been validated clinically to control blood glucose levels.

Characterization of Fasiglifam-Related Liver Toxicity in Dogs

Fasiglifam, a potent and highly selective agonist of G protein-coupled receptor 40, was developed for the treatment of type 2 diabetes mellitus. However, phase III clinical programs were terminated owing to liver safety concerns. Fasiglifam-related liver toxicity was also observed in repeat-dose dog toxicology studies, characterized by granulomatous inflammation with crystal formation in the liver and/or bile ducts. These histopathological changes were not observed in rat toxicology studies. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of dog liver sections obtained from a repeat-dose toxicology study indicated that the crystalline material in the affected dog liver contained fasiglifam and fasiglifam glucuronide (fasiglifam-G). Nonclinical mechanistic studies indicated that after 14 days of repeated oral dosing with [¹⁴C]fasiglifam at 200 mg/kg per day to dogs, the concentrations of fasiglifam and fasiglifam-G in the bile exceeded the solubility limit of these compounds in the bile (approximately 3000 µg/ml). After single oral 2- and 200-mg/kg doses administered to rats and dogs, fasiglifam and fasiglifam-G concentrations in dog bile were 5- to 10-fold higher than those in rat bile for the same dose of fasiglifam, while the bile flow rate adjusted by body weight was 4- to 8-fold lower in dogs than in rats. High fasiglifam and fasiglifam-G concentrations in dog bile together with lower bile flow rate could cause crystal formation in dog bile, resulting in secondary granulomatous inflammation in the dog liver.

Fasiglifam (TAK-875), a G Protein-Coupled Receptor 40 (GPR40) Agonist, May Induce Hepatotoxicity through Reactive Oxygen Species Generation in a GPR40-Dependent Manner

Fasiglifam (TAK-875) a G-protein coupled receptor 40 (GPR40) agonist, significantly improves hyperglycemia without hypoglycemia and weight gain, the major side effects of conventional anti-diabetics. Unfortunately, during multi-center Phase 3 clinical trials, unexpected liver toxicity resulted in premature termination of its development. Here, we investigated whether TAK-875 directly inflicts toxicity on hepatocytes and explored its underlying mechanism of toxicity. TAK-875 decreased viability of 2D and 3D cultures of HepG2, a human hepatocarcinoma cell line, in concentration- (>50 μM) and time-dependent manners, both of which corresponded with ROS generation. An antioxidant, N-acetylcysteine, attenuated TAK-875-mediated hepatotoxicity, which confirmed the role of ROS generation. Of note, knockdown of GPR40 using siRNA abolished the hepatotoxicity of TAK-875 and attenuated ROS generation. In contrast, TAK-875 induced no cytotoxicity in fibroblasts up to 500 μM. Supporting the hepatotoxic potential of TAK-875, exposure to TAK-875 resulted in increased mortality of zebrafish larvae at 25 μM. Histopathological examination of zebrafish exposed to TAK-875 revealed severe hepatotoxicity as manifested by degenerated hypertrophic hepatocytes with cytoplasmic vacuolation and acentric nuclei, confirming that TAK-875 may induce direct hepatotoxicity and that ROS generation may be involved in a GPR40-dependent manner.

Liver Safety of Fasiglifam (TAK-875) in Patients with Type 2 Diabetes: Review of the Global Clinical Trial Experience

INTRODUCTION

Fasiglifam (TAK-875) is a G protein-coupled receptor 40 agonist that was being investigated for treatment of type 2 diabetes mellitus (T2DM). A development program was terminated late in phase III clinical trials due to liver safety concerns.

METHODS

The liver safety of fasiglifam was assessed from data based on six phase II and nine phase III double-blind studies and two open-label studies with emphasis on pooled data from 15 double-blind studies from both global and Japanese development programs. Taking into consideration different daily doses of fasiglifam administered in clinical studies, the primary comparisons were between all patients exposed to fasiglifam (any dose) versus placebo, and, where applicable, versus the two active comparators, sitagliptin or glimepiride. A Liver Safety Evaluation Committee consisting of hepatologists blinded to treatment assignments evaluated hepatic adverse events (AEs) and serious AEs (SAEs) for causal relationship to study drug.

RESULTS

The analysis included data from 9139 patients with T2DM in 15 double-blind controlled studies who received either fasiglifam (n = 5359, fasiglifam group), fasiglifam and sitagliptin (n = 123), or a comparator agent (n = 3657, non-exposed group consisting of placebo and other antidiabetic agents). Exposure to treatment for more than 1 year ranged from 249 patients in the placebo arm, to 370 patients in the glimepiride arm and 617 patients in the fasiglifam 50 mg arm. The primary focus of the analysis was on the hepatic safety of fasiglifam. The overall safety profile based on treatment-emergent AEs (TEAEs), SAEs, deaths, and withdrawal due to AEs was similar between fasiglifam and placebo (excluding liver test abnormalities). However, there was an increased incidence rate of serum alanine aminotransferase (ALT) elevations > 3 × upper limit of normal (ULN), 5 × ULN, and 10 × ULN in fasiglifam-treated patients compared with those treated with placebo or active comparators. ALT elevations > 3 × ULN for fasiglifam were 2.7% compared with 0.8 and 0.5% for the active comparators and placebo. There did not appear to be a clear dose response in incidence of ALT elevations between patients receiving 25 or 50 mg daily. The cumulative incidence of elevations in serum ALT > 3 × ULN was higher in the first 6 months of treatment with fasiglifam compared with both placebo and the active comparators, but the rate of new ALT elevations appeared to be similar across all treatment groups thereafter. No demographic or baseline patient characteristics were identified to predict elevations exceeding ALT > 3 × ULN in fasiglifam-treated patients. The pattern of liver injury with fasiglifam was hepatocellular, and there were no reports of liver-related deaths, liver failure or life-threatening liver injury. Most fasiglifam-associated ALT elevations were asymptomatic and resolved promptly upon discontinuing treatment, but in two patients the recovery was prolonged. Importantly, three important serious liver injury cases were identified among fasiglifam-treated patients; one case was adjudicated to be a clear Hy's Law case and the two remaining cases were considered to closely approximate Hy's Law cases.

CONCLUSIONS

Although the incidence of overall AEs, SAEs, and deaths was similar between fasiglifam and placebo, a liver signal was identified based primarily on the difference in liver chemistry values in the fasiglifam group compared with the placebo and active comparator groups. Three serious liver injuries were attributed to fasiglifam treatment. Clinical development of fasiglifam was halted due to these liver safety concerns.

FFAR4 Is Involved in Regulation of Neurotensin Release From Neuroendocrine Cells and Male C57BL/6 Mice

Neurotensin (NT), a 13 amino-acid peptide, is predominantly released from enteroendocrine cells of the small bowel in response to fat ingestion. Free fatty acid receptors (FFARs) FFAR1 and FFAR4 regulate secretion of gut hormones and insulin. Here, we show that docosahexaenoic acid, a long-chain fatty acid, has the most dramatic effect on NT release. FFAR1 agonists slightly stimulate and FFAR4 agonists dramatically stimulate and amplify NT secretion. Double knockdown of FFAR1 and FFAR4 decreases NT release, whereas overexpression of FFAR4, but not FFAR1, increases NT release. Administration of cpdA, an FFAR4 agonist, but not TAK-875, a selective FFAR1 agonist, increases plasma NT levels and further increases olive oil-stimulated plasma NT levels. Inhibition of MAPK kinase (MEK)/ERK1/2 decreased fatty acid-stimulated NT release but increased AMP-activated protein kinase (AMPK) phosphorylation. In contrast, inhibition of AMPK further increased NT secretion and ERK1/2 phosphorylation mediated by FFAR1 or FFAR4. Our results indicate that FFAR4 plays a more critical role than FFAR1 in mediation of fat-regulated NT release and in inhibitory crosstalk between MEK/ERK1/2 and AMPK in the control of NT release downstream of FFAR1 and FFAR4.

Anthocyanins from purple corn activate free fatty acid-receptor 1 and glucokinase enhancing in vitro insulin secretion and hepatic glucose uptake

The objective of this study was to evaluate the ability of anthocyanins (ANC) present in purple corn to enhance insulin secretion and hepatic glucose uptake in pancreatic cells and hepatocytes, through activation of the free fatty acid receptor-1 (FFAR1) and glucokinase (GK), respectively. Using a dual-layer cell culture with Caco-2 cells, INS-1E or HepG2 cells were treated with an anthocyanin-rich extract from the pericarp of purple corn (PCW), as well as pure ANC cyanidin-3-O-glucoside (C3G), peonidin-3-O-glucoside, pelargonidin-3-O-glucoside. Delphinidin-3-O-glucoside (D3G) was used for comparative purposes. Semipurified C3G (C3G-P) and condensed forms (CF-P) isolated from PCW were also used. At 100 μM, the pure ANC enhanced glucose-stimulated insulin secretion (GSIS) in INS-1E cells ranging from 18% to 40% (p<0.05) compared to untreated cells. PCW increased GSIS by 51%. D3G was the most effective anthocyanin activating FFAR1 (EC50: 196.6 μM). PCW had activating potential on FFAR1 (EC50: 77 μg/mL). PCW, as well as C3G and D3G increased the expression of FFAR1, PLC, and phosphorylation of PKD, related to the FFAR1-dependent insulin secretory pathway. The treatment with 100 μM of P3G and C3G increased (p<0.05) glucose uptake in HepG2 cells by 19% and 31%. PCW increased the glucose uptake in HepG2 cells by 48%. It was determined that CF-P was the most effective for activating GK (EC50: 39.9 μM) and the PCW extracts had an efficacy of EC50: 44 μg/mL. The ANC in purple corn also reduced AMPK phosphorylation and PEPCK expression in HepG2 cells, known to be related to reduction in gluconeogenesis. It is demonstrated for the first time that dietary ANC can enhance the activity of novel biomarkers FFAR1 and GK and potentially ameliorate type-2 diabetes comorbidities.

Cross-Talk Between Insulin Signaling and G Protein-Coupled Receptors

Diabetes is a major risk factor for the development of heart failure. One of the hallmarks of diabetes is insulin resistance associated with hyperinsulinemia. The literature shows that insulin and adrenergic signaling is intimately linked to each other; however, whether and how insulin may modulate cardiac adrenergic signaling and cardiac function remains unknown. Notably, recent studies have revealed that insulin receptor and β2 adrenergic receptor (β2AR) forms a membrane complex in animal hearts, bringing together the direct contact between 2 receptor signaling systems, and forming an integrated and dynamic network. Moreover, insulin can drive cardiac adrenergic desensitization via protein kinase A and G protein-receptor kinases phosphorylation of the β2AR, which compromises adrenergic regulation of cardiac contractile function. In this review, we will explore the current state of knowledge linking insulin and G protein-coupled receptor signaling, especially β-adrenergic receptor signaling in the heart, with emphasis on molecular insights regarding its role in diabetic cardiomyopathy.

Evaluation of the Pharmacokinetics and Safety of a Single Oral Dose of Fasiglifam in Subjects with Mild or Moderate Hepatic Impairment

BACKGROUND AND AIMS

Fasiglifam, a potent, selective novel agonist of G protein-coupled receptor 40, stimulates insulin secretion at elevated blood glucose levels in a glucose-dependent manner. This study evaluated the potential effect of hepatic impairment on the pharmacokinetics and safety of a single dose of fasiglifam and its metabolite M-I. Fasiglifam's clinical development was halted due to liver safety concerns.

METHODS

In this phase I, open-label study, subjects with mild or moderate hepatic impairment, along with matched controls (gender, weight, age, and smoking status), received a single, 25-mg oral dose of fasiglifam. Blood samples were collected through 336 h post-dose for pharmacokinetic evaluation.

RESULTS

Overall, 73% of subjects were male with a mean age of 54 years. Compared with normal hepatic function subjects (n = 14), mean systemic fasiglifam exposure (C_max and AUC_∞) was reduced in mild (n = 8) and moderate (n = 8) hepatic impairment subjects by approximately 20-40%. However, the observed percent unbound drug plasma concentration appeared comparable across all groups. Mean oral clearance was higher and terminal half-life lower in subjects with mild or moderate hepatic impairment compared with normal hepatic function subjects. Fasiglifam M-I systemic exposure increased by approximately twofold in subjects with mild or moderate hepatic impairment compared with those with normal hepatic function. Fasiglifam was well tolerated, and there were no reports of hypoglycemia.

CONCLUSION

Hepatic status did not significantly impact systemic exposure of fasiglifam in this study, in fact, a decrease was observed, suggesting no dose reduction would be required for patients with hepatic impairment.

Enhanced survival and insulin secretion of insulinoma cell aggregates by incorporating gelatin hydrogel microspheres

Introduction

The objective of this study is to evaluate the survival and glucose-induced insulin secretion of rat-derived insulinoma cells (INS-1) from their aggregates incorporating different size of gelatin hydrogel microspheres comparing with microspheres-free cell aggregates.

Methods

The gelatin hydrogel microspheres were prepared by the conventional w/o emulsion method. The INS-1 cells were cultured in a V-bottomed well, combining with or without the gelatin hydrogel microspheres to form their aggregates with or without microspheres.

Results

When the cell viability, the live cell number, the reductase activity, and the insulin secretion of cell aggregates were evaluated 7 or 14 days after incubation, the cell aggregates incorporating gelatin hydrogel microspheres showed higher cell viability, reductase activity and a larger number of live cells. The cell aggregates incorporating larger size and number of gelatin hydrogel microspheres secreted a larger amount of insulin, compared with those incorporating smaller size and number of microspheres or without microspheres.

Conclusion

It is conceivable that the incorporation of gelatin hydrogel microspheres in cell aggregates is promising to improve their survival and insulin secretion function.

•

INS-1 cell aggregates incorporating gelatin hydrogel microspheres are prepared.

•

Gelatin hydrogel microspheres incorporation improves cell viability and glucose-induced insulin secretion of cell aggregates.

•

The size and number of gelatin hydrogel microspheres affected the cell condition and function.

Insulin secretion of mixed insulinoma aggregates-gelatin hydrogel microspheres after subcutaneous transplantation

Introduction

The objective of this study is to evaluate the insulin secretion of mixed aggregates of insulinoma cells (INS-1) and gelatin hydrogel microspheres after their subcutaneous transplantation.

Methods

Gelatin hydrogel microspheres were prepared by the conventional w/o emulsion method. Cell aggregates mixed with or without the hydrogel microspheres were encapsulated into a pouched-device of polytetrafluoroethylene membrane. An agarose hydrogel or MedGel™ incorporating basic fibroblast growth factor (bFGF) was subcutaneously implanted to induce vascularization. After the vascularization induction, cell aggregates encapsulated in the pouched-device was transplanted.

Results

The vascularization had the potential to enable transplanted cell aggregates to enhance the level of insulin secretion compared with those of no vascularization induction. In addition, the insulin secretion of cell aggregates was significantly promoted by the mixing of gelatin hydrogel microspheres even in the pouched-device encapsulated state.

Conclusion

It is possible that the microspheres mixing gives cells in aggregates better survival condition, resulting in promoted insulin secretion.

•

INS-1 cell aggregates incorporating gelatin hydrogel microspheres are prepared.

•

The ratio and number of cells and gelatin hydrogel microspheres affected the formation of cell aggregates.

•

Gelatin hydrogel microspheres incorporation improves glucose-induced insulin secretion of cell aggregates in vitro.

•

Gelatin hydrogel microspheres incorporation has the tendency to improve glucose-induced insulin secretion of cell aggregates in vivo.

•

Vascularization has the potential to improve cell function.

SAR Studies of Indole-5-propanoic Acid Derivatives To Develop Novel GPR40 Agonists

G-protein coupled receptor 40 (GPR40) has been considered to be an attractive drug target for the treatment of type 2 diabetes because of its role in free fatty acids-mediated enhancement of glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells. A series of indole-5-propanoic acid compounds were synthesized, and their GPR40 agonistic activities were evaluated by nuclear factor of activated T-cells reporter assay and GSIS assay in the MIN-6 insulinoma cells. Three compounds, 8h (EC₅₀ = 58.6 nM), 8i (EC₅₀ = 37.8 nM), and 8o (EC₅₀ = 9.4 nM), were identified as potent GPR40 agonists with good GSIS effects.

Fasiglifam for glycaemic control in people with type 2 diabetes: A phase III, placebo-controlled study

AIM

To investigate the effect of fasiglifam on glycaemic control in people with type 2 diabetes mellitus (T2DM).

METHODS

In total, 421 people with T2DM and glycated haemoglobin (HbA1c) ≥7.0% and ≤10.5% who had received only diet and exercise treatment for ≥12 weeks prior to screening were randomized to receive fasiglifam 25 or 50 mg or placebo. The primary efficacy endpoint was change from baseline in HbA1c at week 24.

RESULTS

The mean participant age was 53.5 years, mean baseline body mass index 32.3 kg/m² , and mean baseline HbA1c level 8.05%. Least squares mean changes in HbA1c from baseline to week 24 were: -0.93% (fasiglifam 50 mg), -0.65% (fasiglifam 25 mg) and -0.17% (placebo). Treatment-emergent adverse events (TEAEs) occurred in 53.3%, 48.2% and 39.9% of participants receiving fasiglifam 25 mg, fasiglifam 50 mg, and placebo, respectively. Three participants in each group experienced a serious adverse event (AE). Nine participants had alanine aminotransferase (ALT) elevations >3× upper limit of normal: 5 (3.6%) in the fasiglifam 25-mg group, 4 (2.8%) in the fasiglifam 50-mg group, and none in the placebo group.

CONCLUSIONS

The data indicate that fasiglifam effectively reduced HbA1c from baseline for 24 weeks in participants with T2DM. The incidence of TEAEs was higher in the fasiglifam groups; however, the incidence of serious AEs was low overall and similar between groups. ALT elevations were observed only in the fasiglifam groups, which contributed to the decision to terminate the fasiglifam programme after completion of the present study.

Agonism of free fatty acid receptors 1 and 4 generates peptide YY-mediated inhibitory responses in mouse colon

BACKGROUND AND PURPOSE

Free fatty acid receptors FFA1 and FFA4 are located on enteroendocrine L cells with the highest gastrointestinal (GI) expression in descending colon. Their activation causes the release of glucagon-like peptide 1 and peptide YY (PYY) from L cells. Additionally, FFA1 agonism releases insulin from pancreatic β cells. As these receptors are modulators of nutrient-stimulated glucose regulation, the aim of this study was to compare the pharmacology of commercially available agonists (TUG424, TUG891, GW9508) with proven selective agonists (JTT, TAK-875, AZ423, Metabolex-36) in mice.

EXPERIMENTAL APPROACH

Mouse mucosa was mounted in Ussing chambers, voltage-clamped and the resultant short-circuit current (I_sc ) was recorded continuously. Pretreatments included antagonists of FFA1, Y₁  or Y₂ receptors. Glucose sensitivity was investigated by mannitol replacement apically, and colonic and upper GI transit was assessed in vitro and in vivo.

KEY RESULTS

FFA1 and FFA4 agonism required glucose and reduced I_sc in a PYY-Y₁ receptor-dependent manner. The novel compounds were more potent than GW9508. The FFA1 antagonists (GW1100 and ANT825) blocked FFA1 activity only and revealed FFA1 tonic activity. The FFA4 agonist, Metabolex-36, slowed colonic transit in vitro but increased small intestinal transit in vivo.

CONCLUSIONS AND IMPLICATIONS

The selective FFA1 and FFA4 agonists were more potent at reducing I_sc than GW9508, a dual FFA1 and FFA4 agonist. A paracrine epithelial mechanism involving PYY-stimulated Y₁ receptors mediated their responses, which were glucose sensitive, potentially limiting hypoglycaemia. ANT825 revealed tonic activity and the possibility of endogenous FFA1 ligands causing PYY release. Finally, FFA4 agonism induced regional differences in transit.

Free fatty acid receptor 1 agonist, MR1704, lowers blood glucose levels in rats unresponsive to the sulfonylurea, glibenclamide

Preclinical Research & Development MR1704 is a selective G protein-coupled receptor 40/free fatty acid receptor 1 agonist, which exhibited favorable pharmacokinetic profiles and glucose-lowering effects in animal models. We studied the effects of MR1704 in a sulfonylurea-desensitized Sprague-Dawley rat model and evaluated the risk of pancreatic β-cell exhaustion compared to that of glibenclamide in Zucker fatty rats. Rats fed ad libitum a diet containing 0.03% glibenclamide exhibited lower non-fasting blood glucose levels compared to those in rats fed a control diet during the first 6 days. However, the response to glibenclamide disappeared on day 9. In a rat oral glucose tolerance test (OGTT), MR1704 reduced the plasma glucose excursion, whereas glibenclamide did not show this effect. In Zucker fatty rats, oral administration of MR1704 reduced glucose excursion during the OGTT, and the effects of MR1704 were maintained after 2-week treatment. In contrast, the glucose-lowering effects of glibenclamide were diminished, and glucose tolerance was aggravated after 2-week treatment. These results indicated that MR1704 provided more sustainable effects compared to those of the sulfonylurea, glibenclamide suggesting that MR1704 may be an attractive therapeutic option for diabetic patients who are unresponsive to sulfonylurea treatment.

Gut Hormone Regulation and Secretion via FFA1 and FFA4

The digestion, absorption and utilisation of dietary triglycerides are controlled by gut hormones, released from enteroendocrine cells along the length of the gastrointestinal tract. Major players in the detection of ingested lipids are the free fatty acid receptors FFA1 and FFA4, which are highly expressed on enteroendocrine cells. These receptors are activated when free fatty acids (FFA) are absorbed across the intestinal epithelium, and provide a dynamic hormonal signal indicating that lipids are arriving in the bloodstream from the gut. This review addresses our current knowledge of how ingested triglycerides modulate gut hormone release via FFA1 and FFA4.

Combining the G-protein-coupled receptor 40 agonist fasiglifam with sitagliptin improves glycaemic control in patients with type 2 diabetes with or without metformin: A randomized, 12-week trial

AIMS

To evaluate the efficacy and safety of fasiglifam, an orally active G-protein-coupled receptor 40 agonist, in combination with the dipeptidyl peptidase-4 inhibitor sitagliptin, in patients with type 2 diabetes inadequately controlled with diet/exercise (± metformin).

MATERIALS AND METHODS

In this randomized, double-blind, phase II study, 368 patients received once-daily placebo, sitagliptin 100 mg, fasiglifam 25 or 50 mg, or the combination of sitagliptin 100 mg plus fasiglifam 25 or 50 mg. The primary endpoint was change from baseline glycated haemoglobin (HbA1c) at 12 weeks; a key secondary endpoint was change in fasting plasma glucose (FPG).

RESULTS

The fasiglifam 25 and 50 mg combination regimens produced significantly greater HbA1c reductions than sitagliptin (treatment differences of -0.45% and -0.61%; P < .01, respectively) or respective doses of fasiglifam monotherapy (-0.43% and -0.48%; P < .01) and significantly greater FPG reductions than sitagliptin (-1.1 mmol/L for both combination regimens; P < .01). Improved glycaemic control occurred by week 1 for FPG and week 4 for HbA1c in all groups. Hypoglycaemia rates were low (≤3.3%) and similar across treatments. Liver enzymes >3 × upper limit of normal occurred in four patients (fasiglifam 25 mg, n = 1; fasiglifam 50 mg, n = 2; 1 fasiglifam/sitagliptin 50/100 mg, n = 1).

CONCLUSIONS

Combination of fasiglifam and sitagliptin provided significant additional effects on glycaemic control, with hypoglycaemia rates similar to placebo with or without metformin. This study provides supportive clinical evidence for the complementary mechanism of actions of this GPR40 agonist and DPP-4 inhibitor.

A novel free fatty acid receptor 1 (GPR40/FFAR1) agonist, MR1704, enhances glucose-dependent insulin secretion and improves glucose homeostasis in rats

Activation of G protein‐coupled receptor 40/Free fatty acid receptor 1 (GPR40/FFAR1), which is highly expressed in pancreatic β cells, is considered an important pharmacologic target for the treatment of type 2 diabetes mellitus. The aim of this study was to determine the effect of MR1704, a novel GPR40/FFAR1 agonist, on glucose homeostasis in rats. MR1704 is a highly potent and selective, orally bioavailable agonist with similar in vitro potencies among humans, mice, and rats. Treatment of rat islets with MR1704 increased glucose‐dependent insulin secretion. Augmentation of glucose‐dependent insulin secretion was abolished by adding a GPR40/FFAR1 antagonist. In mouse, insulinoma MIN6 cells, palmitic acid induced the activity of caspase 3/7 after a 72‐h exposure, while pharmacologically active concentrations of MR1704 did not. In an oral glucose tolerance test in normal Sprague‐Dawley rats, orally administered MR1704 (1–10 mg·kg⁻¹) reduced plasma glucose excursion and enhanced insulin secretion, but MR1704 did not induce hypoglycemia, even at 300 mg·kg⁻¹, in fasted Sprague‐Dawley rats. In addition, orally administered MR1704 reduced plasma glucose excursion and enhanced insulin secretion in diabetic Goto‐Kakizaki rats. Oral administration of MR1704 once daily to Goto‐Kakizaki rats reduced their blood glucose levels during a 5‐week treatment period without reducing pancreatic insulin content; as a result, hemoglobin A1C levels significantly decreased. These results suggest that MR1704 improves glucose homeostasis through glucose‐dependent insulin secretion with a low risk of hypoglycemia and pancreatic toxicity. MR1704 shows promise as a new, glucose‐lowering drug to treat type 2 diabetes mellitus.

GPR40 reduces food intake and body weight through GLP-1

G protein-coupled receptor 40 (GPR40) partial agonists lower glucose through the potentiation of glucose-stimulated insulin secretion, which is believed to provide significant glucose lowering without the weight gain or hypoglycemic risk associated with exogenous insulin or glucose-independent insulin secretagogues. The class of small-molecule GPR40 modulators, known as AgoPAMs (agonist also capable of acting as positive allosteric modulators), differentiate from partial agonists, binding to a distinct site and functioning as full agonists to stimulate the secretion of both insulin and glucagon-like peptide-1 (GLP-1). Here we show that GPR40 AgoPAMs significantly increase active GLP-1 levels and reduce acute and chronic food intake and body weight in diet-induced obese (DIO) mice. These effects of AgoPAM treatment on food intake are novel and required both GPR40 and GLP-1 receptor signaling pathways, as demonstrated in GPR40 and GLP-1 receptor-null mice. Furthermore, weight loss associated with GPR40 AgoPAMs was accompanied by a significant reduction in gastric motility in these DIO mice. Chronic treatment with a GPR40 AgoPAM, in combination with a dipeptidyl peptidase IV inhibitor, synergistically decreased food intake and body weight in the mouse. The effect of GPR40 AgoPAMs on GLP-1 secretion was recapitulated in lean, healthy rhesus macaque demonstrating that the putative mechanism mediating weight loss translates to higher species. Together, our data indicate effects of AgoPAMs that go beyond glucose lowering previously observed with GPR40 partial agonist treatment with additional potential for weight loss.

GPR40 partial agonist MK-2305 lower fasting glucose in the Goto Kakizaki rat via suppression of endogenous glucose production

GPR40 (FFA1) is a fatty acid receptor whose activation results in potent glucose lowering and insulinotropic effects in vivo. Several reports illustrate that GPR40 agonists exert glucose lowering in diabetic humans. To assess the mechanisms by which GPR40 partial agonists improve glucose homeostasis, we evaluated the effects of MK-2305, a potent and selective partial GPR40 agonist, in diabetic Goto Kakizaki rats. MK-2305 decreased fasting glucose after acute and chronic treatment. MK-2305-mediated changes in glucose were coupled with increases in plasma insulin during hyperglycemia and glucose challenges but not during fasting, when glucose was normalized. To determine the mechanism(s) mediating these changes in glucose metabolism, we measured the absolute contribution of precursors to glucose production in the presence or absence of MK-2305. MK-2305 treatment resulted in decreased endogenous glucose production (EGP) driven primarily through changes in gluconeogenesis from substrates entering at the TCA cycle. The decrease in EGP was not likely due to a direct effect on the liver, as isolated perfused liver studies showed no effect of MK-2305 ex vivo and GPR40 is not expressed in the liver. Taken together, our results suggest MK-2305 treatment increases glucose stimulated insulin secretion (GSIS), resulting in changes to hepatic substrate handling that improve glucose homeostasis in the diabetic state. Importantly, these data extend our understanding of the underlying mechanisms by which GPR40 partial agonists reduce hyperglycemia.

Discovery of new dual PPARγ-GPR40 agonists with robust antidiabetic activity: Design, synthesis and in combo drug evaluation

The design of compounds 1 and 2 was based on the similar scaffold of pharmacophoric groups for PPARγ and GPR40 agonists. In order to find new compounds with improved biological activity, the current manuscript describes a new dual PPARγ-GPR40 agonist. We synthesized two compounds, which were prepared following a multistep synthetic route, and the relative mRNA expression levels of PPARγ, GLUT4, and GPR40 were quantified in cell culture, as well as insulin secretion and [Ca²⁺] intracellular levels. Compound 1 showed a 7-times increase in the mRNA expression of PPARγ, which in turn enhanced the expression levels of GLUT4 respect to control and pioglitazone. It also showed an increase of 2-fold in the [Ca²⁺]_i level allowing an increment on insulin release, being as active as the positive control (glibenclamide), causing also an increase of 2-fold in mRNA expression of GPR40. Furthermore, the compound 2 showed lower activity than the compound 1. The ester of 1 showed antidiabetic activity at a 50mg/kg single dose in streptozotocin-nicotinamide-induced diabetic mice model. In addition, we achieved a molecular docking study of compound 1 on PPARγ and GPR40 receptors, showing a great affinity for both targets. We observed important polar interactions between the carboxylic group and main residues into the binding pocket. Therefore, the compound 1 has a potential for the development of antidiabetic agents with newfangled dual action.