Pharmacological characterization of mono-, dual- and tri-peptidic agonists at GIP and GLP-1 receptors.
Glucose-dependent insulinotropic peptide (GIP) is an incretin hormone with physiological roles in adipose tissue, the central nervous system and bone metabolism. While selective ligands for GIP receptor (GIPR) have not been advanced for disease treatment, dual and triple agonists of GIPR, in conjunction with that of glucagon-like peptide-1 (GLP-1) and glucagon receptors, are currently in clinical trials, with an expectation of enhanced efficacy beyond that of GLP-1 receptor (GLP-1R) agonist monotherapy for diabetic patients. Consequently, it is important to understand the pharmacological behavior of such drugs. In this study, we have explored signaling pathway specificity and the potential for biased agonism of mono-, dual- and tri-agonists of GIPR using human embryonic kidney 293 (HEK293) cells recombinantly expressing human GIPR or GLP-1R. Compared to GIP(1-42), the GIPR mono-agonists Pro3GIP and Lys3GIP are biased towards ERK1/2 phosphorylation (pERK1/2) relative to cAMP accumulation at GIPR, whereas the triple agonist at GLP-1R/GCGR/GIPR is biased towards pERK1/2 relative to β-arrestin2 recruitment. Moreover, the dual GIPR/GLP-1R agonist, LY3298176, is biased towards pERK1/2 relative to cAMP accumulation at both GIPR and GLP-1R compared to their respective endogenous ligands. These data reveal novel pharmacological properties of potential therapeutic agents that may impact on diversity in clinical responses.
Yuliantie E
，Darbalaei S
，Dai A
，Zhao P
，Yang D
，Sexton PM
，Wang MW
，Wootten D
... -
《-》
Genetic and biased agonist-mediated reductions in β-arrestin recruitment prolong cAMP signaling at glucagon family receptors.
Receptors for the peptide hormones glucagon-like peptide-1 (GLP-1R), glucose-dependent insulinotropic polypeptide (GIPR), and glucagon (GCGR) are important regulators of insulin secretion and energy metabolism. GLP-1R agonists have been successfully deployed for the treatment of type 2 diabetes, but it has been suggested that their efficacy is limited by target receptor desensitization and downregulation due to recruitment of β-arrestins. Indeed, recently described GLP-1R agonists with reduced β-arrestin-2 recruitment have delivered promising results in preclinical and clinical studies. We therefore aimed to determine if the same phenomenon could apply to the closely related GIPR and GCGR. In HEK293 cells depleted of both β-arrestin isoforms the duration of G protein-dependent cAMP/PKA signaling was increased in response to the endogenous ligand for each receptor. Moreover, in wildtype cells, "biased" GLP-1, GCG, and GIP analogs with selective reductions in β-arrestin-2 recruitment led to reduced receptor endocytosis and increased insulin secretion over a prolonged stimulation period, although the latter effect was only seen at high agonist concentrations. Biased GCG analogs increased the duration of cAMP signaling, but this did not lead to increased glucose output from hepatocytes. Our study provides a rationale for the development of GLP-1R, GIPR, and GCGR agonists with reduced β-arrestin recruitment, but further work is needed to maximally exploit this strategy for therapeutic purposes.
Jones B
，McGlone ER
，Fang Z
，Pickford P
，Corrêa IR Jr
，Oishi A
，Jockers R
，Inoue A
，Kumar S
，Görlitz F
，Dunsby C
，French PMW
，Rutter GA
，Tan T
，Tomas A
，Bloom SR
... -
《-》
Human epicardial adipose tissue expresses glucose-dependent insulinotropic polypeptide, glucagon, and glucagon-like peptide-1 receptors as potential targets of pleiotropic therapies.
Human epicardial adipose tissue (EAT) plays a crucial role in the development and progression of coronary artery disease, atrial fibrillation, and heart failure. Microscopically, EAT is composed of adipocytes, nerve tissues, inflammatory, stromovascular, and immune cells. Epicardial adipose tissue is a white adipose tissue, albeit it also has brown fat-like or beige fat-like features. No muscle fascia divides EAT and myocardium; this allows a direct interaction and crosstalk between the epicardial fat and the myocardium. Thus, it might be a therapeutic target for pharmaceutical compounds acting on G-protein-coupled receptors, such as those for glucose-dependent insulinotropic polypeptide (GIP), glucagon (GCG), and glucagon-like peptide-1 (GLP-1), whose selective stimulation with innovative drugs has demonstrated beneficial cardiovascular effects. The precise mechanism of these novel drugs and their tissue and cellular target(s) need to be better understood. We evaluate whether human EAT expresses GIP, GCG, and GLP-1 receptors and whether their presence is related to EAT transcriptome. We also investigated protein expression and cell-type localization specifically for GIP receptor (GIPR) and glucagon receptor (GCGR).
Epicardial adipose tissue samples were collected from 33 patients affected by cardiovascular diseases undergoing open heart surgery (90.9% males, age 67.2 ± 10.5 years mean ± SD). Microarray and immunohistochemistry analyses were performed. Microarray analysis showed that GIPR and GCGR messenger ribonucleic acids (mRNAs) are expressed in EAT, beyond confirming the previously found GLP-1 [3776 ± 1377 arbitrary unit (A.U.), 17.77 ± 14.91 A.U., and 3.41 ± 2.27 A.U., respectively]. The immunohistochemical analysis consistently indicates that GIPR and GCGR are expressed in EAT, mainly in macrophages, isolated, and in crown-like structures. In contrast, only some mature adipocytes of different sizes showed cytoplasmic immunostaining, similar to endothelial cells and pericytes in the capillaries and pre-capillary vascular structures. Notably, EAT GIPR is statistically associated with the low expression of genes involved in free fatty acid (FFA) oxidation and transport and those promoting FFA biosynthesis and adipogenesis (P < 0.01). Epicardial adipose tissue GCGR, in turn, is related to genes involved in FFA transport, mitochondrial fatty acid oxidation, and white-to-brown adipocyte differentiation, in addition to genes involved in the reduction of fatty acid biosynthesis and adipogenesis (P < 0.01).
Having reported the expression of the GLP-1 receptor previously, here, we showed that GIPR and GCGR similarly present at mRNA and protein levels in human EAT, particularly in macrophages and partially adipocytes, suggesting these G-protein-coupled receptors as pharmacological targets on the ongoing innovative drugs, which seem cardiometabolically healthy well beyond their effects on glucose and body weight.
Malavazos AE
，Iacobellis G
，Dozio E
，Basilico S
，Di Vincenzo A
，Dubini C
，Menicanti L
，Vianello E
，Meregalli C
，Ruocco C
，Ragni M
，Secchi F
，Spagnolo P
，Castelvecchio S
，Morricone L
，Buscemi S
，Giordano A
，Goldberger JJ
，Carruba M
，Cinti S
，Corsi Romanelli MM
，Nisoli E
... -
《-》
ResearchGate
(全网免费下载)
钛学术
(全网免费下载)
