Could FFAR1 assist insulin secretion in type 2 diabetes?

Polymorphic Variation in FFA Receptors: Functions and Consequences

Overfeeding of fat can cause various metabolic disorders including obesity and type 2 diabetes (T2D). Diet provided free fatty acids (FFAs) are not only essential nutrients, but they are also recognized as signaling molecules, which stimulate various important biological functions. Recently, several G protein-coupled receptors (GPCRs), including FFA1-4, have been identified as receptors of FFAs by various physiological and pharmacological studies. FFAs exert physiological functions through these FFA receptors (FFARs) depending on carbon chain length and degree of unsaturation. Functional analyses have revealed that several important metabolic processes, such as peptide hormone secretion, cell maturation and nerve activities, are regulated by FFARs and thereby FFARs contribute to the energy homeostasis through these physiological functions. Hence, FFARs are expected to be promising pharmacological targets for metabolic disorders since imbalances in energy homeostasis lead to metabolic disorders. In human, it is established that different responses of individuals to endogenous ligands and chemical drugs may be due to differences in the ability of such ligands to activate nucleotide polymorphic variants of receptors. However, the clear links between genetic variations that are involved in metabolic disorders and polymorphisms receptors have been relatively difficult to assess. In this review, I summarize current literature describing physiological functions of FFARs and genetic variations of those receptors to discuss the potential of FFARs as drug targets for metabolic disorders.

Efficacy and safety of fasiglifam (TAK-875), a G protein-coupled receptor 40 agonist, in Japanese patients with type 2 diabetes inadequately controlled by diet and exercise: a randomized, double-blind, placebo-controlled, phase III trial

AIM

To assess the efficacy and safety of fasiglifam 25 and 50 mg in Japanese patients with type 2 diabetes inadequately controlled by diet and exercise.

METHODS

This phase III, double-blind, placebo-controlled, multicentre study included 192 patients randomized to once-daily treatment with fasiglifam 25 mg (n = 63) or 50 mg (n = 62) or placebo (n = 67) for 24 weeks. The primary efficacy endpoint was the change from baseline in glycated haemoglobin (HbA1c) at week 24.

RESULTS

At week 24, both fasiglifam groups had significantly reduced HbA1c levels compared with the placebo group (p < 0.0001). The least squares mean change from baseline in HbA1c was 0.16% with placebo, -0.57% with fasiglifam 25 mg and -0.83% with fasiglifam 50 mg. The percentage of patients who achieved an HbA1c target of <6.9% at week 24 was also significantly higher (p < 0.05) for fasiglifam 25 mg (30.2%) and 50 mg (54.8%) compared with placebo (13.8%). Fasiglifam significantly reduced fasting plasma glucose levels at all assessment points, starting from week 2. The incidence and types of treatment-emergent adverse events in each fasiglifam group were similar to those in the placebo group, and hypoglycaemia was reported in 1 patient receiving fasiglifam 50 mg. There were no clinically meaningful changes in body weight in any treatment group.

CONCLUSIONS

Fasiglifam significantly improved glycaemic control and was well tolerated, with a low risk of hypoglycaemia in Japanese patients with type 2 diabetes inadequately controlled by diet and exercise; however, in a recent review of data from overall fasiglifam global clinical trials, concerns about liver safety arose and the clinical development of fasiglifam was terminated after this trial was completed.

G-protein-coupled receptors for free fatty acids: nutritional and therapeutic targets

It is becoming evident that nutrients and metabolic intermediates derived from such nutrients regulate cellular function by activating a number of cell-surface G-protein coupled receptors (GPCRs). Until now, members of the GPCR family have largely been considered as the molecular targets that communicate cellular signals initiated by hormones and neurotransmitters. Recently, based on tissue expression patterns of these receptors and the concept that they may elicit the production of a range of appetite- and hunger-regulating peptides, such nutrient sensing GPCRs are attracting considerable attention due to their potential to modulate satiety, improve glucose homeostasis and supress the production of various pro-inflammatory mediators. Despite the developing interests in these nutrients sensing GPCR both as sensors of nutritional status, and targets for limiting the development of metabolic diseases, major challenges remain to exploit their potential for therapeutic purposes. Mostly, this is due to limited characterisation and validation of these receptors because of paucity of selective and high-potency/affinity pharmacological agents to define the detailed function and regulation of these receptors. However, ongoing clinical trials of agonists of free fatty acid receptor 1 suggest that this receptor and other receptors for free fatty acids may provide a successful strategy for controlling hyperglycaemia and providing novel approaches to treat diabetes. Receptors responsive to free fatty acid have been of particular interest, and some aspects of these are considered herein.

Treatment of type 2 diabetes by free Fatty Acid receptor agonists

Dietary free fatty acids (FFAs), such as ω-3 fatty acids, regulate metabolic and anti-inflammatory processes, with many of these effects attributed to FFAs interacting with a family of G protein-coupled receptors. Selective synthetic ligands for free fatty acid receptors (FFA1-4) have consequently been developed as potential treatments for type 2 diabetes (T2D). In particular, clinical studies show that Fasiglifam, an agonist of the long-chain FFA receptor, FFA1, improved glycemic control and reduced HbA1c levels in T2D patients, with a reduced risk of hypoglycemia. However, this ligand was removed from clinical trials due to potential liver toxicity and determining if this is a target or a ligand-specific feature is now of major importance. Pre-clinical studies also show that FFA4 agonism increases insulin sensitivity, induces weight loss, and reduces inflammation and the metabolic and anti-inflammatory effects of short chain fatty acids (SCFAs) are linked with FFA2 and FFA3 activation. In this review, we therefore show that FFA receptor agonism is a potential clinical target for T2D treatment and discuss ongoing drug development programs within industry and academia aimed at improving the safety and effectiveness of these potential treatments.