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 glycaemic 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 programmes within industry and academia aimed at improving the safety and effectiveness of these potential treatments

Management and pest management considerations on droughty soils: four year results

Four year survival of pines on droughty (Typic Quartzips~mments) soils was best for longleaf pine and Terr-Sorb -treated loblolly pine. Pest considerations include town ants and Nantucket pine tip moths on loblolly pine. Untreated loblolly pine had reduced leader and total height growth anH increased tip moth infestations, compared to Terra-Sorb and clay-slurry treated loblolly pine. Soil texture averaged less than eight percent silt and clay combined in the treatment areas

Differential transactivation of sphingosine-1-phosphate receptors modulates NGF-induced neurite extension

The process of neurite extension after activation of the TrkA tyrosine kinase receptor by nerve growth factor (NGF) involves complex signaling pathways. Stimulation of sphingosine kinase 1 (SphK1), the enzyme that phosphorylates sphingosine to form sphingosine-1-phosphate (S1P), is part of the functional TrkA signaling repertoire. In this paper, we report that in PC12 cells and dorsal root ganglion neurons, NGF translocates SphK1 to the plasma membrane and differentially activates the S1P receptors S1P1 and S1P2 in a SphK1-dependent manner, as determined with specific inhibitors and small interfering RNA targeted to SphK1. NGF-induced neurite extension was suppressed by down-regulation of S1P1 expression with antisense RNA. Conversely, when overexpressed in PC12 cells, transactivation of S1P1 by NGF markedly enhanced neurite extension and stimulation of the small GTPase Rac, important for the cytoskeletal changes required for neurite extension. Concomitantly, differentiation down-regulated expression of S1P2 whose activation would stimulate Rho and inhibit neurite extension. Thus, differential transactivation of S1P receptors by NGF regulates antagonistic signaling pathways that modulate neurite extension

Multiple AMPK activators inhibit L-Carnitine uptake in C2C12 skeletal muscle myotubes

Mutations in the gene that encodes the principal L-Carnitine transporter, OCTN2, can lead to a reduced intracellular L-Carnitine pool and the disease Primary Carnitine Deficiency. L-Carnitine supplementation is used therapeutically to increase intracellular L-Carnitine. As AMPK and insulin regulate fat metabolism and substrate uptake we hypothesised that AMPK activating compounds and insulin would increase L-Carnitine uptake in C2C12myotubes. The cells express all three OCTN transporters at the mRNA level and immunohistochemistry confirmed expression at the protein level. Contrary to our hypothesis, despite significant activation of PKB and 2DG uptake, insulin did not increase L-Carnitine uptake at 100nM. However, L-Carnitine uptake was modestly increased at a dose of 150nM insulin. A range of AMPK activators that increase intracellular calcium content [caffeine (10mM, 5mM, 1mM, 0.5mM), A23187 (10μM)], inhibit mitochondrial function [Sodium Azide (75μM), Rotenone (1μM), Berberine (100μM), DNP (500μM)] or directly activate AMPK [AICAR (250μM)] were assessed for their ability to regulate L-Carnitine uptake. All compounds tested significantly inhibited L-Carnitine uptake. Inhibition by caffeine was not dantrolene (10μM) sensitive. Saturation curve analysis suggested that caffeine did not competitively inhibit L-Carnitine transport. However, the AMPK inhibitor Compound C (10μM) partially rescued the effect of caffeine suggesting that AMPK may play a role in the inhibitory effects of caffeine. However, caffeine likely inhibits L-Carnitine uptake by alternative mechanisms independently of calcium release. PKA activation or direct interference with transporter function may play a role

Probe-dependent negative allosteric modulators of the long-chain free fatty acid receptor FFA4

High-affinity and selective antagonists that are able to block the actions of both endogenous and synthetic agonists of G protein–coupled receptors are integral to analysis of receptor function and to support suggestions of therapeutic potential. Although there is great interest in the potential of free fatty acid receptor 4 (FFA4) as a novel therapeutic target for the treatment of type II diabetes, the broad distribution pattern of this receptor suggests it may play a range of roles beyond glucose homeostasis in different cells and tissues. To date, a single molecule, 4-methyl-N-9H-xanthen-9-yl-benzenesulfonamide (AH-7614), has been described as an FFA4 antagonist; however, its mechanism of antagonism remains unknown. We synthesized AH-7614 and a chemical derivative and demonstrated these to be negative allosteric modulators (NAMs) of FFA4. Although these NAMs did inhibit FFA4 signaling induced by a range of endogenous and synthetic agonists, clear agonist probe dependence in the nature of allosteric modulation was apparent. Although AH-7614 did not antagonize the second long-chain free fatty acid receptor, free fatty acid receptor 1, the simple chemical structure of AH-7614 containing features found in many anticancer drugs suggests that a novel close chemical analog of AH-7614 devoid of FFA4 activity, 4-methyl-N-(9H-xanthen-9-yl)benzamide (TUG-1387), will also provide a useful control compound for future studies assessing FFA4 function. Using TUG-1387 alongside AH-7614, we show that endogenous activation of FFA4 expressed by murine C3H10T1/2 mesenchymal stem cells is required for induced differentiation of these cells toward a more mature, adipocyte-like phenotype

Dimethyl fumarate in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial

Dimethyl fumarate (DMF) inhibits inflammasome-mediated inflammation and has been proposed as a treatment for patients hospitalised with COVID-19. This randomised, controlled, open-label platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]), is assessing multiple treatments in patients hospitalised for COVID-19 (NCT04381936, ISRCTN50189673). In this assessment of DMF performed at 27 UK hospitals, adults were randomly allocated (1:1) to either usual standard of care alone or usual standard of care plus DMF. The primary outcome was clinical status on day 5 measured on a seven-point ordinal scale. Secondary outcomes were time to sustained improvement in clinical status, time to discharge, day 5 peripheral blood oxygenation, day 5 C-reactive protein, and improvement in day 10 clinical status. Between 2 March 2021 and 18 November 2021, 713 patients were enroled in the DMF evaluation, of whom 356 were randomly allocated to receive usual care plus DMF, and 357 to usual care alone. 95% of patients received corticosteroids as part of routine care. There was no evidence of a beneficial effect of DMF on clinical status at day 5 (common odds ratio of unfavourable outcome 1.12; 95% CI 0.86-1.47; p = 0.40). There was no significant effect of DMF on any secondary outcome

Subtype-specific kinetics of inhibitory adenosine receptor internalization are determined by sensitivity to phosphorylation by G protein-coupled receptor kinases.

Despite coupling to the same class of inhibitory G proteins and binding the same physiological ligand, the human A(1) and rat A(3) adenosine receptors (ARs) desensitize at different rates in response to sustained agonist exposure. This is due to the ability of the A(3)AR, but not the A(1)AR, to serve as a substrate for rapid phosphorylation and desensitization by members of the G protein-coupled receptor kinase (GRK) family. The aim of this study was to investigate whether these differences were also manifested in their abilities to undergo agonist-dependent receptor internalization. For the first time, we report that A(3)ARs internalize profoundly in response to short-term exposure to agonist but not activators of second messenger-regulated kinases. The A(3)AR-selective antagonist MRS1523 blocked both A(3)AR phosphorylation and internalization. Moreover, in contrast to the A(1)AR, which internalized quite slowly (t(1/2) = 90 min), A(3)ARs internalized rapidly (t(1/2) = 10 min) over a time frame that followed the onset of receptor phosphorylation. A nonphosphorylated A(3)AR mutant failed to internalize over a 60-min time course, suggesting that receptor phosphorylation was essential for rapid A(3)AR internalization to occur. In addition, fusion onto the A(1)AR of the A(3)AR C-terminal domain containing the sites for phosphorylation by GRKs conferred rapid agonist-induced internalization kinetics (t(1/2) = 10 min) on the resulting chimeric AR. In conclusion, these data suggest that GRK-stimulated phosphorylation of threonine residues within the C-terminal domain of the A(3)AR is obligatory to observe rapid agonist-mediated internalization of the receptor

The role of sphingosine-1-phosphate in smooth muscle contraction

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid metabolite that is known to mediate diverse cellular responses including cell growth, survival, and migration. Most of these effects have been attributed to its binding to a specific subfamily of G protein-coupled receptors (GPCR), namely S1P(1-5). Recent studies have suggested that S1P also plays a prominent role in the contraction of various types of smooth muscle. This review provides a brief overview of its role in this process and also highlights how S1P-dependent signaling serves as an important regulator of smooth muscle contraction

Regulation of fibroblast functions by lysophospholipid mediators: potential roles in wound healing

The bioactive lysophospholipids, primarily lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P), are recent additions to the list of potent mediators of tissue repair and wound healing. In this review, we highlight the diverse actions of LPA and S1P on many types of cells involved in the wound healing process, with special emphasis on their regulation of fibroblasts. The effects of LPA and S1P are principally mediated via specific cell surface receptors. Important signaling pathways downstream of these receptors and the importance of TGFbeta and S1P cross-talk for wound healing are also discussed. Moreover, specific agonists and antagonists of the lysophospholipid receptors may be useful for the treatment of wounds and abnormal wound healing