Molecular modeling studies also revealed insignificant

Molecular modeling studies also revealed insignificant differences in ligand-receptor interaction energies between R and S enantiomers of LPCs or their 2-OMe-analogues, suggesting that enantiomers of a particular structure should exert similar GPR119-mediated biological effect. Indeed, when studied for 2-OMe-LPC 14:0 (1.1a), we have shown that R and S enantiomers enhance GSIS in βTC-3 cells to almost identical extent (Fig. 9A) suggesting that the overall impact on secretory activity does not depend on chirality. However, significant differences were observed in the case of [Ca]i mobilization (Fig. 9B,C). The fact that the 1.1a racemate and its R/S enantiomers led to similar GSIS results suggests that both R/S structures possess similar chronic biological properties. However, the observed differences in [Ca]i flux enhancement signifies differences in acute effects. Hence the effect of 1.1a (R) on the [Ca]i mobilization seems when in 1:1 mixture with 1.1a (S) unaffected as the racemate of 1.1a, it seems likely that the R structures possess higher affinity towards the GPR119 target compared to their S counterparts. This hypothesis is consistent with the modeling results (Fig. 10), where the native and modified LPC 14:0 R enantiomers strongly anchor at several points of ECL-2 and/or ECL-3 of GPR119, whereas S enantiomers anchor mainly inside the receptor. Since extracellular loops reside in the outside environment of the cell they are accessible easier to the external agents than the middle (S)-Crizotinib of the helices, we assume that this is the main reason for differences in acute biological tests. The S enantiomer remains active in chronic tests, which indicates that R/S structures of 2-OMe-LPCs do not act antagonistically and can be applied in racemic solutions, which is cost-effective compared to synthesis of enantiomerically pure compounds. In conclusion, our findings present new insight into biological activity of novel 2-OMe-LPC analogues as well as their native counterparts in the scope of modulation of pancreatic β cell function. Continuation of the research on more advanced models is recommended to confirm ligand-like features of the tested compounds and understand their potential role in stimulation of pancreatic hormones secretion.
Author contributions A. Drzazga, A. Sowińska, A. Krzemińska, and E. Gendaszewska-Darmach performed research; A. Drzazga., P. Paneth, M. Koziołkiewicz, E. Gendaszewska-Darmach designed research; A. Okruszek designed 2-OMe-LPC synthesis; A. Drzazga prepared illustrations; A. Drzazga and E. Gendaszewska-Darmach wrote the manuscript.
Conflict of interest
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Introduction GPR119 is a class A G protein-coupled receptor (GPCR) that signals predominantly through cAMP via the stimulatory G-protein (Gαs) (Lauffer et al., 2009, Syed et al., 2012). GPR119 demonstrates a highly localized pattern of expression within the gastrointestinal tract and pancreas (Lan et al., 2009, Lauffer et al., 2009, Soga et al., 2005) consistent with a role in metabolic function. Endogenous agonists for GPR119 are lipids such as oleoylethanolamine and 2-oleoyl glycerol, further supporting this role (Cornall et al., 2013, Hansen et al., 2011, Syed et al., 2012). Indeed, stimulation of GPR119 is strongly linked with glucose homoeostasis with a direct effect on insulin release from pancreatic β-cells, as well as an indirect effect on insulin signalling via glucagon-like peptide 1 (GLP-1) release from enteroendocrine cells (Chu et al., 2008, Chu et al., 2007, Soga et al., 2005). For these reasons, the development of GPR119 agonists has attracted considerable interest as potential pharmacotherapies for type-2 diabetes and obesity (Cornall et al., 2013, Kang, 2013, Ohishi and Yoshida, 2012). A number of chemically diverse synthetic GPR119 agonists have been developed and characterized (Brocklehurst et al., 2011, Scott et al., 2012, Semple et al., 2008, Semple et al., 2011), with four having advanced to clinical trials (Ohishi and Yoshida, 2012).