Free Fatty Acid Receptor Research Articles

A high-throughput structural dynamics approach for identification of potential agonists of FFAR4 for type 2 diabetes mellitus therapy

Diabetes mellitus is a metabolic disorder that persists as a global threat to the world. A G-protein coupled receptor (GPCR), free fatty acid receptor 4 (FFAR4), has emerged as a potential target for type 2 diabetes mellitus (T2DM) and obesity-related disorders. The current study has investigated the FFAR4, deploying 3-dimensional structure modeling, molecular docking, machine learning, and high-throughput virtual screening methods to unravel the receptor’s crucial and non-crucial binding site residues. We screened four lakh compounds and shortlisted them based on binding energy, stereochemical considerations, non-bonded interactions, and pharmacokinetic profiling. Out of the screened compounds, four compounds were selected for ligand-bound simulations. The molecular dynamic simulations were carried out for 1µs for native FFAR4 and 500 ns each for complexes of FFAR4 with compound 1, compound 2, compound 3, and compound 4. Our findings showed that in addition to reported binding site residues ARG99, ARG183, and VAL98 in known agonists like TUG-891, the amino acids ARG22, ARG24, THR23, TRP305, and GLU43 were also critical binding site residues. These amino acids impart stability to the FFAR4 complexes and contribute to the stronger binding affinity of the compounds. The study also indicated that aromatic residues like PHE211 are crucial for recognizing the active site’s pi-pi and C-C double bonds. Since FFAR4 is a membrane protein, the simulation studies give an insight into the mechanisms of the crucial protein-lipid and lipid-water interactions. The analysis of the molecular dynamics trajectories showed all four compounds as potential hit molecules that can be developed further into potential agonists for T2DM therapy. Amongst the four compounds, compound 4 showed relatively better binding affinity, stronger non-bonded interactions, and a stable complex. Communicated by Ramaswamy H. Sarma

Dapagliflozin downregulates G protein-coupled receptor Kinase-2 and upregulates regulator of g protein signaling-4 in adrenals to exert sympatholysis in heart failure

Abstract Dapagliflozin is a sodium-glucose co-transporter (SGLT)-2 inhibitor with beneficial cardiovascular effects independent of its anti-diabetic actions. Among these is sympatholysis, i.e., norepinephrine (NE) lowering which is beneficial in chronic human heart failure (HF). Adrenal G protein-coupled receptor kinase (GRK)-2 upregulation is a major driver of circulating catecholamine (CA) elevation and sympathetic nervous system (SNS) hyperactivity in HF due to dysregulation of adrenal sympatho-inhibitory α2-adrenergic receptors (ARs) [1]. On the other hand, we recently reported that signaling by neuronal free fatty acid receptor (FFAR)-3, which stimulates NE release from sympathetic neurons, is blocked by Regulator of G protein Signaling (RGS)-4 [2,3]. We hypothesized herein that dapagliflozin may lower SNS hyperactivity in the adrenal gland by improving α2AR, and antagonizing FFAR3 signaling in adrenal chromaffin cells. We used the rat pheochromocytoma PC12 cell line expressing human α2A-AR, as well as freshly isolated adrenal glands from rats treated with dapagliflozin in vivo. Dapagliflozin treatment for 7 consecutive days (20 mg/kg/d in drinking water) led to a significant reduction in blood circulating NE levels (217+67 pg/ml, n=6), compared to control, vehicle-treated rats (363+77 pg/ml, n=6, p<.05), suggesting reduced SNS activity. This was accompanied by reduced GRK2 and tyrosine hydroxylase (TH) mRNA and protein levels in dapagliflozin-treated rat adrenals vs. vehicle-treated animal-derived glands. In contrast, RGS4 mRNA levels were increased in dapagliflozin-treated adrenals. Adrenal α2AR density was higher in dapagliflozin- vs. vehicle-treated rats (51.3+7.3 vs. 26.1+8.1 fmol/mg of protein, respectively; n=12 glands from 6 animals per group, p<.05). These results (i.e., GRK2 & TH downregulation with RGS4 upregulation) were completely recapitulated in PC12 cells in culture, treated with 5 microM dapagliflozin (or vehicle) for 24 hours. Importantly, α2AR-dependent G protein-mediated signaling towards inhibition of CA secretion was markedly enhanced, whereas FFAR3-dependent phospholipase C/calcium signaling was reduced, at 24 hrs post-dapagliflozin treatment of PC12 cells. GRK2 overexpression partially reversed dapagliflozin`s effect on cholinergic-induced CA secretion. In conclusion, dapagliflozin exerts a sympatholytic action in the adrenal medulla via a) downregulation of TH, which reduces CA biosynthesis, and GRK2, which reduces α2AR desensitization; and b) upregulation of RGS4 to block FFAR3-stimulated CA secretion (Figure).Figure

Effect of pregnancy on the expression of nutrient-sensors and satiety hormones in mice

Small intestinal satiation pathways involve nutrient-induced stimulation of chemoreceptors leading to release of satiety hormones from intestinal enteroendocrine cells (ECCs). Whether adaptations in these pathways contribute to increased maternal food intake during pregnancy is unknown.To determine the expression of intestinal nutrient-sensors and satiety hormone transcripts and proteins across pregnancy in mice.Female C57BL/6J mice (10–12 weeks old) were randomized to mating and then tissue collection at early- (6.5 d), mid- (12.5 d) or late-pregnancy (17.5 d), or to an unmated age matched control group. Relative transcript expression of intestinal fatty acid, peptide and amino acid and carbohydrate chemoreceptors, as well as gut hormones was determined across pregnancy. The density of G-protein coupled receptor 93 (GPR93), free fatty acid receptor (FFAR) 4, cholecystokinin (CCK) and glucagon-like peptide1 (GLP-1) immunopositive cells was then compared between non-pregnant and late-pregnant mice.Duodenal GPR93 expression was lower in late pregnant than non-pregnant mice (P < 0.05). Ileal FFAR1 expression was higher at mid- than at early- or late-pregnancy. Ileal FFAR2 expression was higher at mid-pregnancy than in early pregnancy. Although FFAR4 expression was consistently lower in late-pregnant than non-pregnant mice (P < 0.001), the density of FFAR4 immunopositive cells was higher in the jejunum of late-pregnant than non-pregnant mice.A subset of protein and fatty acid chemoreceptor transcripts undergo region-specific change during murine pregnancy, which could augment hormone release and contribute to increased food intake. Further investigations are needed to determine the functional relevance of these changes.

A Metabolomics Study of Feces Revealed That a Disturbance of Selenium-Centered Metabolic Bioprocess Was Involved in Kashin-Beck Disease, an Osteoarthropathy Endemic to China.

Background: Kashin-Beck disease (KBD) is a distinct osteoarthropathy in China with an unclear pathogenesis. This study aims to explore whether perturbations in the intestine metabolome could be linked to KBD individuals. Methods: An investigation was conducted in KBD endemic villages and fecal samples were collected. After applying inclusion and exclusion criteria, a total of 75 subjects were enrolled for this study, including 46 KBD (including 19 Grade I KBD and 27 Grade II KBD) and 29 controls. Untargeted metabolomics analysis was performed on the platform of UHPLC-MS. PLS-DA and OPLS-DA were conducted to compare the groups and identify the differential metabolites (DMs). Pathway analysis was conducted on MPaLA platform to explore the functional implication of the DMs. Results: Metabolomics analysis showed that compared with the control group, KBD individuals have a total of 584 differential metabolites with dysregulated levels such as adrenic acid (log2FC = -1.87, VIP = 4.84, p = 7.63 × 10-7), hydrogen phosphate (log2FC = -2.57, VIP = 1.27, p = 1.02 × 10-3), taurochenodeoxycholic acid (VIP = 1.16, log2FC = -3.24, p = 0.03), prostaglandin E3 (VIP = 1.17, log2FC = 2.67, p = 5.61 × 10-4), etc. Pathway analysis revealed several significantly perturbed pathways associated with KBD such as selenium micronutrient network (Q value = 3.11 × 10-3, Wikipathways), metabolism of lipids (Q value = 8.43 × 10-4, Reactome), free fatty acid receptors (Q value = 3.99 × 10-3, Reactome), and recycling of bile acids and salts (Q value = 2.98 × 10-3, Reactome). Subgroup comparisons found a total of 267 differential metabolites were shared by KBD vs. control, KBD II vs. control, and KBD I vs. control, while little difference was found between KBD II and KBD I (only one differential metabolite detected). Conclusions: KBD individuals showed distinct metabolic features characterized by perturbations in lipid metabolism and selenium-related bioprocesses. Our findings suggest that the loss of nutrients metabolism balance in intestine was involved in KBD pathogenesis. Linking the nutrients metabolism (especially selenium and lipid) to KBD cartilage damage should be a future direction of KBD study.

Free fatty acid receptor 2 (FFAR2) expression by intestinal epithelial cells (IEC) is not integral for regulating the microglia response to intestinal inflammation

Free fatty acid receptor 2 (FFAR2) expression by intestinal epithelial cells (IEC) is not integral for regulating the microglia response to intestinal inflammation

α-Synuclein expression in response to bacterial ligands and metabolites in gut enteroendocrine cells: an in vitro proof of concept study.

Caudo-rostral migration of pathological forms of α-synuclein from the gut to the brain is proposed as an early feature in Parkinson's disease pathogenesis, but the underlying mechanisms remain unknown. Intestinal epithelial enteroendocrine cells sense and respond to numerous luminal signals, including bacterial factors, and transmit this information to the brain via the enteric nervous system and vagus nerve. There is evidence that gut bacteria composition and their metabolites change in Parkinson's disease patients, and these alterations can trigger α-synuclein pathology in animal models of the disorder. Here, we investigated the effect of toll-like receptor and free fatty acid receptor agonists on the intracellular level of α-synuclein and its release using mouse secretin tumour cell line 1 enteroendocrine cells. Secretin tumour cell line 1 enteroendocrine cells were treated for 24 or 48 h with toll-like receptor agonists (toll-like receptor 4 selective lipopolysaccharide; toll-like receptor 2 selective Pam3CysSerLys4) and the free fatty acid receptor 2/3 agonists butyrate, propionate and acetate. The effect of selective receptor antagonists on the agonists' effects after 24 hours was also investigated. The level of α-synuclein protein was measured in cell lysates and cell culture media by western blot and enzyme-linked immunosorbent assay. The level of α-synuclein and tumour necrosis factor messenger RNA was measured by quantitative reverse transcription real-time polymerase chain reaction. Stimulation of secretin tumour cell line 1 enteroendocrine cells for 24 and 48 hours with toll-like receptor and free fatty acid receptor agonists significantly increased the amount of intracellular α-synuclein and the release of α-synuclein from the cells into the culture medium. Both effects were significantly reduced by antagonists selective for each receptor. Toll-like receptor and free fatty acid receptor agonists also significantly increased tumour necrosis factor transcription, and this was effectively inhibited by corresponding antagonists. Elevated intracellular α-synuclein increases the likelihood of aggregation and conversion to toxic forms. Factors derived from bacteria induce α-synuclein accumulation in secretin tumour cell line 1 enteroendocrine cells. Here, we provide support for a mechanism by which exposure of enteroendocrine cells to specific bacterial factors found in Parkinson's disease gut dysbiosis might facilitate accumulation of α-synuclein pathology in the gut.

FRI012 Exploring The Role Of FFA2 In Western Diet-induced Obesity And Metabolic Changes

Abstract Disclosure: C. Nnyamah: None. B. Wicksteed: None. B.T. Layden: None. The obesity pandemic is a major health concern driving Type 2 Diabetes (T2D) and cardiovascular disease (CVD). One novel pathogenetic factor of obesity is the gut microbiome (GM), that is the microbes that reside in the digestive tract. Changes in the GM have profound effects on obesity. These symbiotic microbes break down dietary fiber that are otherwise indigestible, releasing nutrients (in particular, short chain fatty acids, SCFAs). Free Fatty Acid Receptor 2 (FFA2) is a G-protein coupled receptor (GPCR) that senses SCFAs and has been shown to influence the function of various organs responsible for nutrient-sensing and energy balance. Among other roles, FFA2 has been suggested to modulate the secretion of the appetite-regulating proteins GLP-1 and PYY from intestinal enteroendocrine cells and secretion of insulin (the master fuel-supply hormone) from the pancreatic beta cells. However, its role in adipose tissue is less clear. While highly expressed in adipose tissue, research using global knockouts (KOs) of FFA2 in mouse models has observed conflicting phenotypic results. Here, we use novel adipose-specific FFA2 KO (AdFFA2-KO) mice to explore adipose-determined outcomes when mice are fed obesogenic challenge diets with or without fiber-induced production of SCFAs for receptor activation. After confirming that Adiponectin-Cre x FFA2 fl/fl mice have no congenital defects and are metabolically similar to FFA2 fl/fl control mice on a normal chow diet, mice were placed on either a high fat, high sugar Western Diet (WD) or on WD supplemented with 10% fructooligosaccharides – a fermentable dietary fiber. On WD, AdFFA2-KO mice had significantly decreased glucose tolerance compared to floxed controls with no other clearly observable effects on basic metabolic parameters. Interestingly, upon receptor activation with a fiber-supplemented diet, AdFFA2-KO mice were moderately protected from WD-induced weight gain. Our ongoing research aims to detangle the observed phenotypic differences and demystify the FFA2-adipose signaling cascade using a multifaceted approach including in vivo assessment of food intake and energy expenditure, ex vivo evaluation of lipolysis and fatty-acid uptake with FFA2 agonists and antagonists, as well as RTqPCR probing of adipose-derived cytokines (adipokines) with known roles in the weight gain-weight loss cycle. Presentation: Friday, June 16, 2023

FRI013 Free Fatty Acid Receptors 2 And 3 Mediate The Beneficial Effects Of Fiber

Abstract Disclosure: N.S. Pandya: None. M. Priyadarshini: None. B.T. Layden: None. The Gut Microbiome (GM) is a key player in whole body metabolism. Microbial dysregulation and dysbiosis have been linked to multiple pathologies including obesity and type 2 diabetes. Microbes influence host function by releasing various metabolites when interacting with ingested materials. Key metabolites include short chain fatty acids (SCFAs) produced through microbial fermentation of fiber. Fiber intake is known to increase GM diversity; this process has been suggested to protect against obesity and type 2 diabetes. While SCFAs have been implicated in this process, the overall mechanism is still unclear. Free fatty acid receptors 2 and 3 (FFA2 and FFA3) occupy a unique position through which the GM can exert an effect on host metabolism. These G-protein coupled receptors are known to sense SCFAs and can modulate the subsequent secretion of incretin and insulin hormones thus regulating host appetite and blood-glucose control. FFA2 and FFA3 are expressed in many tissues, including adipocytes, neurons, and most importantly, intestinal enteroendocrine L cells and pancreatic β cells. For this reason, complete understanding of their function is necessary, and elucidating their signaling mechanisms may have significant therapeutic value in the treatment of the obesity epidemic and diabetes. Here, we seek to understand the whole-body impact of the gut microbiota-SCFA-FFA2/3 axis in the metabolically protective role of fiber. We used here a novel whole-body FFA2/FFA3 double knockout (F2,3-dKO) mouse model to obtain a holistic understanding of SCFA sensing mechanisms when mice are fed obesogenic diets supplemented with or without fermentable fiber. Double knockout mice, alongside matched wild-type controls were challenged with either a high fat western diet (WD), or WD supplemented with 20% fructooligosaccharides (FOS), a fermentable fiber (WD + 20% FOS). Preliminary data showed a significant rise in body weight, fat mass, and insulin resistance in WD fed F2,3-dKO mice alongside matched wild-type controls. Wild-type mice, when challenged with WD supplemented with fiber, were protected from this effect with only a mild increase in body weight and insulin resistance. Interestingly, F2,3-dKO mice, fed WD + 20% FOS were insensitive to fiber induced metabolic benefits. This suggests that FFA2 and FFA3 are essential for fermentable fiber mediated metabolic benefits against WD induced obesity. Further studies are now aimed to understand the mechanism behind this protective effect. Presentation: Friday, June 16, 2023

Akkermansia muciniphila supplementation improves glucose tolerance in intestinal Ffar4 knockout mice during the daily light to dark transition.

Alterations in the intestinal environment are associated with various diseases, and FFAR4 is abundantly enriched in the intestine, where it has been shown to have the ability to regulate intestinal hormone secretion and intestinal microbiota; here, we confirmed previous reports. Meanwhile, we found that intestinal FFAR4 regulates glucagon-like peptide 1 secretion by decreasing Akkermansia muciniphila abundance and show that such change is associated with the level of glucose utilization at ZT12 in mice. Intestinal FFAR4 deficiency leads to severely impaired glucose tolerance at the ZT12 moment in mice, and Akkermansia muciniphila supplementation ameliorates the abnormal glucose utilization at the ZT12 moment caused by FFAR4 deficiency, which is very similar to the dawn phenomenon in diabetic patients. Collectively, our data suggest that intestinal Ffar4 deteriorates glucose tolerance at the daily light to dark transition by affecting Akkermansia muciniphila.

Gut microbiota of old mice worsens neurological outcome after brain ischemia via increased valeric acid and IL-17 in the blood

BackgroundAging is a significant risk factor for ischemic stroke and worsens its outcome. However, the mechanisms for this worsened neurological outcome with aging are not clearly defined.ResultsOld C57BL/6J male mice (18 to 20 months old) had a poorer neurological outcome and more severe inflammation after transient focal brain ischemia than 8-week-old C57BL/6J male mice (young mice). Young mice with transplantation of old mouse gut microbiota had a worse neurological outcome, poorer survival curve, and more severe inflammation than young mice receiving young mouse gut microbiota transplantation. Old mice and young mice transplanted with old mouse gut microbiota had an increased level of blood valeric acid. Valeric acid worsened neurological outcome and heightened inflammatory response including blood interleukin-17 levels after brain ischemia. The increase of interleukin-17 caused by valeric acid was inhibited by a free fatty acid receptor 2 antagonist. Neutralizing interleukin-17 in the blood by its antibody improved neurological outcome and attenuated inflammatory response in mice with brain ischemia and receiving valeric acid. Old mice transplanted with young mouse feces had less body weight loss and better survival curve after brain ischemia than old mice transplanted with old mouse feces or old mice without fecal transplantation.ConclusionsThese results suggest that the gut microbiota-valeric acid-interleukin-17 pathway contributes to the aging-related changes in the outcome after focal brain ischemia and response to stimulus. Valeric acid may activate free fatty acid receptor 2 to increase interleukin-17.

Free Fatty Acid Receptors (FFARs): Emerging Therapeutic Targets for the Management of Diabetes Mellitus.

Free fatty acids (FFAs) present in our dietary fats not only act as vital nutrients but also function as signalling molecules and modulate key biological functions through their active involvement in a multitude of energy metabolism pathways. However, it has been reported that excessive intake of dietary fat contributes to the development of different types of Diabetes mellitus. Free fatty acid receptors are the key regulators of most metabolic disorders. Among them, diabetes mellitus is a severe growing disorder and found in every corner of the world. For various metabolic disorders, particularly type 2 diabetes mellitus, these different free fatty acid receptors are being explored as drug targets. In the present review, various FFAs sensing G-protein coupled receptors (GPR) like GPR40 (FFAR1), GPR43 (FFAR2), GPR41 (FFAR3), GPR120 (FFAR4), and GPR84 are being explored as emerging novel therapeutic targets for antidiabetic drugs. Additionally, this review has covered pre-clinical discovery and development of different selective ligands targeted to these receptors starting from hit identification to lead optimization via chemical modification and the challenges and tactics selected by different medicinal chemists to improve potency, physicochemical properties, safety profiles, and pharmacokinetics of different FFAR agonists for making a potential drug candidate. Several molecules have been withdrawn in the clinical trials without reporting any reasons. We believe that this review will help the researchers to find a new direction in the discovery of new antidiabetic drugs.

Double knockout of FFAR4 and FGF21 aggravates metabolic disorders in mice

Several investigations have examined the involvement of free fatty acid receptor 4 (FFAR4) in metabolic disorders, but its action remains controversial. To investigate whether endogenous fibroblast growth factor 21 (FGF21)-mediated signaling controls the metabolic status in FFAR4-deficient mice, we generated FFAR4/FGF21 double knockout (DKO) mice. We also evaluated the role of FGF21 on glucose and lipid metabolism in FFAR4 KO mice fed a high-fat diet. Levels of FGF21 were significantly increased in FFAR4-deficient mice and double deletion of FGF21 and FFAR4 led to severe metabolic disorders. Additionally, FFAR4/FGF21 DKO mice displayed metabolic abnormalities that may be caused by decreased energy expenditure. Collectively, this study characterized the effects of endogenous FGF21, which acts as a master feedback regulator in the absence of FFAR4.

A novel PPARβ/FFA1 dual agonist Y8 promotes diabetic wound healing

BackgroundDiabetes ulcer is one of the leading causes of disability and death in diabetics. Y8 [(2-(2-fluoro-4-((4-methyl-2-(4-(trifluoromethyl)phenyl)thiazol-5-yl)methoxy) phenoxy)acetic acid)], a dual agonist of peroxisome proliferation activated receptorβ (PPARβ) and free fatty acid receptor 1 (FFA1/FFAR1/GPR40), a new compound molecule with the potential for diabetes ulcer treatment. ObjectiveTo research the effect of the dual target agonist Y8 and its mechanism of action in the treatment of diabetic ulcers. MethodsWe have established a wound model in diabetic mice. After treatment with Y8, wound healing was evaluated by tissue pathology, reactive oxygen species (ROS) levels, and gene expression testing. Under high sugar conditions, the mechanism of Y8 affecting fibroblasts' proliferation and keratinocytes' migration is further studied. ResultsWe found that Y8 accelerated wound healing and shortened healing time in diabetic mice. Granulation tissue generation and extracellular matrix (ECM) deposition were significantly increased in Y8-treated mice. Mechanistically, Y8 promotes keratinocyte proliferation by activating PPARβ and migration of keratinocytes by triggering FFA1 in vitro. In addition, Y8 also decreased ROS levels in fibroblasts in vitro and in vivo by activating PPARβ, reducing their release of superoxide anions. ConclusionOur results suggest that PPARβ/FFA1 dual agonist Y8 has the effect of promoting the healing of diabetic ulcer wounds in vivo and in vitro, and its therapeutic effect is better than that of single-target agonists.

Regulation of serotonin production by specific microbes from piglet gut

BackgroundSerotonin is an important signaling molecule that regulates secretory and sensory functions in the gut. Gut microbiota has been demonstrated to affect serotonin synthesis in rodent models. However, how gut microbes regulate intestinal serotonin production in piglets remains vague. To investigate the relationship between microbiota and serotonin specifically in the colon, microbial composition and serotonin concentration were analyzed in ileum-cannulated piglets subjected to antibiotic infusion from the ileum when comparing with saline infusion. Microbes that correlated positively with serotonin production were isolated from piglet colon and were further used to investigate the regulation mechanisms on serotonin production in IPEC-J2 and a putative enterochromaffin cell line RIN-14B cells.ResultsAntibiotic infusion increased quantities of Lactobacillus amylovorus (LA) that positively correlated with increased serotonin concentrations in the colon, while no effects observed for Limosilactobacillus reuteri (LR). To understand how microbes regulate serotonin, representative strains of LA, LR, and Streptococcus alactolyticus (SA, enriched in feces from prior observation) were selected for cell culture studies. Compared to the control group, LA, LR and SA supernatants significantly up-regulated tryptophan hydroxylase 1 (TPH1) expression and promoted serotonin production in IPEC-J2 cells, while in RIN-14B cells only LA exerted similar action. To investigate potential mechanisms mediated by microbe-derived molecules, microbial metabolites including lactate, acetate, glutamine, and γ-aminobutyric acid were selected for cell treatment based on computational and metabolite profiling in bacterial supernatant. Among these metabolites, acetate upregulated the expression of free fatty acid receptor 3 and TPH1 while downregulated indoleamine 2,3-dioxygenase 1. Similar effects were also recapitulated when treating the cells with AR420626, an agonist targeting free fatty acid receptor 3.ConclusionsOverall, these results suggest that Lactobacillus amylovorus showed a positive correlation with serotonin production in the pig gut and exhibited a remarkable ability to regulate serotonin production in cell cultures. These findings provide evidence that microbial metabolites mediate the dialogue between microbes and host, which reveals a potential approach using microbial manipulation to regulate intestinal serotonin biosynthesis.

Long-term regulation of fat sensing in rainbow trout (Oncorhynchus mykiss) fed a vegetable diet from the first feeding: focus on free fatty acid receptors and their signalling.

Taste plays a fundamental role in an animal’s ability to detect nutrients and transmits key dietary information to the brain, which is crucial for its growth and survival. Providing alternative terrestrial ingredients early in feeding influences the growth of rainbow trout (RT, Oncorhynchus mykiss). Thus, the present study aimed to assess the influence, via long-term feeding (from the first feeding to 8 months), of alternative plant ingredients (V diet for vegetable diet v. C diet for a control diet) in RT on the mechanism of fat sensing at the gustatory level. After the feeding trial, we studied the pathways of the fat-sensing mechanism in tongue tissue and the integrated response in the brain. To this end, we analysed the expression pattern of free fatty acid receptors (ffar) 1 and 2, markers of calcium-signalling pathways (phospholipase Cβ, Orai, Stim or Serca), the serotonin level (a key neurotransmitter in taste buds) and the expression pattern of appetite-regulating neuropeptides in the hypothalamus (central area of appetite regulation). The results revealed that the V diet modified the expression pattern of ffar1 and paralogs of ffar2 genes in tongue tissue, along with differential regulation of calcium-signalling pathways and a defect in serotonin level and brain turnover, without influencing neuropeptide expression. This study is the first to support that changes in feeding behaviour of RT fed a V diet could be due to the difference in nutrient sensing and a decrease in hedonic sensation. We revealed that RT have similar fat-detection mechanisms as mammals.

Free-fatty acid receptor-1 (FFA1/GPR40) promotes papillary RCC proliferation and tumor growth via Src/PI3K/AKT/NF-κB but suppresses migration by inhibition of EGFR, ERK1/2, STAT3 and EMT

BackgroundPapillary renal cell carcinoma (pRCC) is a highly metastatic genitourinary cancer and is generally irresponsive to common treatments used for the more prevalent clear-cell (ccRCC) subtype. The goal of this study was to examine the novel role of the free fatty-acid receptor-1 (FFA1/GPR40), a cell-surface expressed G protein-coupled receptor that is activated by medium-to-long chained dietary fats, in modulation of pRCC cell migration invasion, proliferation and tumor growth.MethodsWe assessed the expression of FFA1 in human pRCC and ccRCC tumor tissues compared to patient-matched non-cancerous controls, as well as in RCC cell lines. Using the selective FFA1 agonist AS2034178 and the selective FFA1 antagonist GW1100, we examined the role of FFA1 in modulating cell migration, invasion, proliferation and tumor growth and assessed the FFA1-associated intracellular signaling mechanisms via immunoblotting.ResultsWe reveal for the first time that FFA1 is upregulated in pRCC tissue compared to patient-matched non-cancerous adjacent tissue and that its expression increases with pRCC cancer pathology, while the inverse is seen in ccRCC tissue. We also show that FFA1 is expressed in the pRCC cell line ACHN, but not in ccRCC cell lines, suggesting a unique role in pRCC pathology. Our results demonstrate that FFA1 agonism promotes tumor growth and cell proliferation via c-Src/PI3K/AKT/NF-κB and COX-2 signaling. At the same time, agonism of FFA1 strongly inhibits migration and invasion, which are mechanistically mediated via inhibition of EGFR, ERK1/2 and regulators of epithelial–mesenchymal transition.ConclusionsOur data suggest that FFA1 plays oppositional growth and migratory roles in pRCC and identifies this receptor as a potential target for modulation of pathogenesis of this aggressive cancer.

1537-P: Regulation of Energy Balance by a Gut–Brain Axis Mediated by SCFAs and FFA2/3 in the Brain

Short-chain fatty acids (SCFAs) derived from gut microbiota fermentation have been shown to generate beneficial metabolic effects on energy and glucose homeostasis by binding with free fatty acid receptors 2 (FFA2) and 3 (FFA3). Accumulating evidence indicates that the gut microbiota/SCFAs interact with the central nervous system (CNS) to regulate central metabolic function. Interestingly, we found that a single bolus intracerebroventricular (ICV) injection of acetate (ACE), propionate (PRO), or butyrate (BUT) dose-dependently inhibited food intake in an FFA2/3-dependent manner. Notably, both in situ hybridization and RNAscope analysis showed that FFA3 but not FFA2 was expressed in the cerebellar granule neurons, which was inhibited by PRO or FFA3-selective agonists in a Gi/o-dependent mechanism. We also showed that high-fat diet (HFD)-induced hypothalamic inflammation is diminished by dietary fiber supplementation, which is associated with increased circulating SCFAs. Notably, these anti-inflammatory effects of dietary fiber supplementation were partially attenuated in FFA2/3 double-knockout mice, suggesting a beneficial effect of FFA2/3 on hypothalamic inflammation. Taking all these together, our results suggest a model that SCFAs act on the brain to regulate energy homeostasis and hypothalamic inflammation. Disclosure X.Yang: None. P.Xu: None. P.Luo: None. B.Feng: None. H.Ye: None. N.Antony: None. L.Carrillo-sáenz: None. V.C.Torres irizarry: None. B.T.Layden: Consultant; Bayer Inc. Y.He: None. Funding National Institutes of Health (R01DK123098, P30DK020595 to P.X.), (P20GM135002, R01DK129548 to Y.H.), (T32AA026577 to V.C.T.I.); American Heart Association (915789 to V.C.T.I.), (20POST35120600 to Y.H.); U.S. Department of Defense (W81XWH-20-1-0075 to P.X

Free fatty acid receptor 1 stimulates cAMP production and gut hormone secretion through Gq-mediated activation of adenylate cyclase 2

ObjectiveFree fatty acid receptor 1 (FFAR1) is highly expressed in enteroendocrine cells of the small intestine and pancreatic beta cells, where FFAR1 agonists function as GLP-1 and insulin secretagogues, respectively. Most efficacious are so-called second-generation synthetic agonists such as AM5262, which, in contrast to endogenous long-chain fatty acids are able to signal through both IP3/Ca2+ and cAMP pathways. Whereas IP3 signaling is to be expected for the mainly Gq-coupled FFAR1, the mechanism behind FFAR1-induced cAMP accumulation remains unclear, although originally proposed to be Gs mediated. Methods and resultsWhen stimulated with AM5262, we observe that FFAR1 can activate the majority of the Gα proteins, except - surprisingly - members of the Gs family. AM5262-induced FFAR1-mediated transcriptional activation through cAMP response element (CREB) was blocked by the specific Gq inhibitor, YM253890. Furthermore, in Gq-deficient cells no CREB signal was observed unless Gq or G11 was reintroduced by transfection. By qPCR we determined that adenylate cyclase 2 (Adcy2) was highly expressed and enriched relative to the nine other Adcys in pro-glucagon expressing enteroendocrine cells. Co-transfection with ADCY2 increased the FFAR1-induced cAMP response 4-5-fold in WT HEK293 cells, an effect fully inhibited by YM253890. Moreover, co-transfection with ADCY2 had no effect in Gq-deficient cells without reintroduction of either Gq or G11. Importantly, although both AM5262/FFAR1 and isoproterenol/β2 adrenergic receptor (β2AR) induced cAMP production was lost in Gs-deficient cells, only the β2AR response was rescued by Gs transfection, whereas co-transfection with ADCY2 was required to rescue the FFAR1 cAMP response. In situ hybridization demonstrated a high degree of co-expression of ADCY2 and FFAR1 in enteroendocrine cells throughout the intestine. Finally, in the enteroendocrine STC-1 and GLUTag cell lines AM5262-induced cAMP accumulation and GLP-1 secretion were both blocked by YM253890. ConclusionsOur results show that Gq signaling is responsible not only for the IP3/Ca2+ but also the cAMP response, which together are required for the highly efficacious hormone secretion induced by second-generation FFAR1 agonists - and that ADCY2 presumably mediates the Gq-driven cAMP response.

Bornyl-Containing Derivatives of Benzyloxyphenylpropanoic Acid as FFAR1 Agonists: In Vitro and In Vivo Studies.

Type 2 diabetes mellitus (T2DM) is one of the most common chronic diseases worldwide. Several classes of hypoglycemic drugs are used to treat it, but various side effects limit their clinical use. Consequently, the search for new anti-diabetic agents remains an urgent task for modern pharmacology. In this investigation, we examined the hypoglycemic effects of bornyl-containing benzyloxyphenylpropanoic acid derivatives (QS-528 and QS-619) in a diet-induced model of T2DM. Animals were given the tested compounds per os at a dose of 30 mg/kg for 4 weeks. At the end of the experiment, compound QS-619 demonstrated a hypoglycemic effect, while QS-528 showed hepatoprotection. In addition, we performed a number of in vitro and in vivo experiments to study the presumed mechanism of action of the tested agents. Compound QS-619 was determined to activate the free fatty acid receptor-1 (FFAR1) similarly to the reference agonist GW9508 and its structural analogue QS-528. Both agents also increased insulin and glucose-dependent insulinotropic polypeptide concentrations in CD-1 mice. Our results indicate that QS-619 and QS-528 are probably full FFAR1 agonists.

Placental gene expression reveals reduced angiogenesis in primiparous mares

Primiparous mares produce smaller and lighter foals than in subsequent pregnancies. In most studies, their placenta is also smaller, more efficient and presents structural alterations, but maternal age is a confounding factor. This study aimed to characterize the effects of maternal parity using the mare's first two pregnancies or by comparing young mares with different parities over the same gestation year. The same young mares (4–6-year-old over the study) foaled for the first time in 2018 (primiparous in 2018, P18, n=10) and for the second time in 2020 (multiparous in 2020, M20, n=10). In 2020, another group of young mares foaled for the first time (primiparous in 2020, P20, n=18). All mares were inseminated with the semen of the same stallion and were fed identically over the study. To assess the effect of primiparity, M20 were compared to P18 (effect on the same mare), or P20 (effect in the same year). Placentas were recovered at foaling, measured, weighed and sampled close to the umbilical cord. Stereology was performed using MercartorPro software on HES-stained paraffin-embedded samples and analyzed using a linear model for paired samples or not and permutations with R software. Paired-end RNA-sequencing was performed (Illumina, NextSeq500) on 6 randomly chosen snap-frozen placentas/group. Differential expression was analyzed (DESeq2) using a false discovery rate (FDR) <0.05 cutoff. Gene Set Enrichment Analysis was performed on differential expressed genes using PANTHER overrepresentation test with GOBP database. Placental weight and surface were reduced and the efficiency (foal weight/placental surface, in kg/m2) was increased in primiparous mares in both comparisons (p<0.05). Volume was not modified by parity between the consecutives gestations but reduced in P20 vs M20 (p<0.05). Only the volume of allantoic stroma was significantly reduced in P18 vs M20 (p<0.05), whereas hemotrophic trophoblast and microcotyledonary vessels’ volume tended to be reduced in P20 vs M20 placentas (p<0.1). In consecutive gestations, 118 genes were differentially expressed in placenta while in the same year, only 2 genes (IL4R and FFAR, interleukin-4 and free fatty acid receptors) were differentially expressed (FDR <0.05). Among the 118 genes differentially expressed between consecutive pregnancies, apelin signaling, angiogenesis and catalytic activity were overrepresented. All genes involved in these pathways were under-expressed in P18 mares. Both the apelin (normalized enrichment score, NES=-2.16, FDR <0.05) and its receptor (NES=-2.48, FDR <0.05) were less expressed in the placenta of P18 vs M20. This is also observed in intrauterine growth retardation in humans. Although placental morphology was lightly affected in both analyses, the inter-individual variability seemed to hide parity effects for transcriptomic analysis. Consecutive gestations, however, demonstrate that the smaller placental and foal size in primiparous mares seems to originate from reduced vascularization.