scholarly journals Bispecific GRPR-Antagonistic Anti-PSMA/GRPR Heterodimer for PET and SPECT Diagnostic Imaging of Prostate Cancer

Cancers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1371 ◽  
Author(s):  
Bogdan Mitran ◽  
Zohreh Varasteh ◽  
Ayman Abouzayed ◽  
Sara S. Rinne ◽  
Emmi Puuvuori ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Diagnostic Imaging ◽  
Solid Phase ◽  
Solid Phase Peptide Synthesis ◽  
Binding Specificity ◽  
Tumor Uptake ◽  
Biodistribution Data ◽  
Positron Emission ◽  
Ic50 Values

Simultaneous targeting of the prostate-specific membrane antigen (PSMA) and gastrin-releasing peptide receptor (GRPR) could improve the diagnostic accuracy in prostate cancer (PCa). The aim of this study was to develop a PSMA/GRPR-targeting bispecific heterodimer for SPECT and positron emission tomography (PET) diagnostic imaging of PCa. The heterodimer NOTA-DUPA-RM26 was produced by manual solid-phase peptide synthesis. NOTA-DUPA-RM26 was labeled with 111In and 68Ga, with yields >98%, and demonstrated a high stability and binding specificity to PSMA and GRPR. IC50 values for natIn-NOTA-DUPA-RM26 were 4 ± 1 nM towards GRPR and 824 ± 230 nM towards PSMA. An in vivo binding specificity 1 h pi of 111In-NOTA-DUPA-RM26 in PC3-PIP-xenografted mice demonstrated partially blockable tumor uptake when co-injected with an excess of PSMA- or GRPR-targeting agents. Simultaneous co-injection of both agents induced pronounced blocking. The biodistribution of 111In-NOTA-DUPA-RM26 and 68Ga-NOTA-DUPA-RM26 revealed fast activity clearance from the blood and normal organs via the kidneys. Tumor uptake exceeded normal organ uptake for both analogs 1 h pi. 68Ga-NOTA-DUPA-RM26 had a significantly lower tumor uptake (8 ± 2%ID/g) compared to 111In-NOTA-DUPA-RM26 (12 ± 2%ID/g) 1 h pi. Tumor-to-organ ratios increased 3 h pi, but decreased 24 h pi, for 111In-NOTA-DUPA-RM26. MicroPET/CT and microSPECT/CT scans confirmed biodistribution data, suggesting that 68Ga-NOTA-DUPA-RM26 and 111In-NOTA-DUPA-RM26 are suitable candidates for the imaging of GRPR and PSMA expression in PCa shortly after administration.

scholarly journals Design of PSMA ligands with modifications at the inhibitor part: an approach to reduce the salivary gland uptake of radiolabeled PSMA inhibitors?

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Veronika Barbara Felber ◽  
Manuel Amando Valentin ◽  
Hans-Jürgen Wester
Keyword(s):  
Salivary Gland ◽  
Solid Phase ◽  
Solid Phase Peptide Synthesis ◽  
In Vivo Studies ◽  
Tumor Xenograft ◽  
Tumor Uptake ◽  
Lncap Cells ◽  
High Affinity

Abstract Aim To investigate whether modifications of prostate-specific membrane antigen (PSMA)-targeted radiolabeled urea-based inhibitors could reduce salivary gland uptake and thus improve tumor-to-salivary gland ratios, several analogs of a high affinity PSMA ligand were synthesized and evaluated in in vitro and in vivo studies. Methods Binding motifs were synthesized ‘on-resin’ or, when not practicable, in solution. Peptide chain elongations were performed according to optimized standard protocols via solid-phase peptide synthesis. In vitro experiments were performed using PSMA+ LNCaP cells. In vivo studies as well as μSPECT/CT scans were conducted with male LNCaP tumor xenograft-bearing CB17-SCID mice. Results PSMA ligands with A) modifications within the central Zn2+-binding unit, B) proinhibitor motifs and C) substituents & bioisosteres of the P1′-γ-carboxylic acid were synthesized and evaluated. Modifications within the central Zn2+-binding unit of PSMA-10 (Glu-urea-Glu) provided three compounds. Thereof, only natLu-carbamate I (natLu-3) exhibited high affinity (IC50 = 7.1 ± 0.7 nM), but low tumor uptake (5.31 ± 0.94% ID/g, 1 h p.i. and 1.20 ± 0.55% ID/g, 24 h p.i.). All proinhibitor motif-based ligands (three in total) exhibited low binding affinities (> 1 μM), no notable internalization and very low tumor uptake (< 0.50% ID/g). In addition, four compounds with P1′-ɣ-carboxylate substituents were developed and evaluated. Thereof, only tetrazole derivative natLu-11 revealed high affinity (IC50 = 16.4 ± 3.8 nM), but also this inhibitor showed low tumor uptake (3.40 ± 0.63% ID/g, 1 h p.i. and 0.68 ± 0.16% ID/g, 24 h p.i.). Salivary gland uptake in mice remained at an equally low level for all compounds (between 0.02 ± 0.00% ID/g and 0.09 ± 0.03% ID/g), wherefore apparent tumor-to-submandibular gland and tumor-to-parotid gland ratios for the modified peptides were distinctly lower (factor 8–45) than for [177Lu]Lu-PSMA-10 at 24 h p.i. Conclusions The investigated compounds could not compete with the in vivo characteristics of the EuE-based PSMA inhibitor [177Lu]Lu-PSMA-10. Although two derivatives (3 and 11) were found to exhibit high affinities towards LNCaP cells, tumor uptake at 24 h p.i. was considerably low, while uptake in salivary glands remained unaffected. Optimization of the established animal model should be envisaged to enable a clear identification of PSMA-targeting radioligands with improved tumor-to-salivary gland ratios in future studies.

scholarly journals Synthesis and Preclinical Evaluation of Radio-Iodinated GRPR/PSMA Bispecific Heterodimers for the Theranostics Application in Prostate Cancer

Pharmaceutics ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 358 ◽  
Author(s):  
Ayman Abouzayed ◽  
Cheng-Bin Yim ◽  
Bogdan Mitran ◽  
Sara S. Rinne ◽  
Vladimir Tolmachev ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Computed Tomography ◽  
Solid Phase ◽  
Single Photon ◽  
Solid Phase Peptide Synthesis ◽  
Photon Emission ◽  
Emission Computed Tomography ◽  
Radiochemical Yields

Gastrin-releasing peptide receptor (GRPR) and prostate-specific membrane antigen (PSMA) are overexpressed in most prostate cancers. GRPR expression is higher in early stages while PSMA expression increases with progression. The possibility of targeting both markers with a single theranostics radiotracer could improve patient management. Three GRPR/PSMA-targeting bispecific heterodimers (urea derivative PSMA-617 and bombesin-based antagonist RM26 linked via X-triazolyl-Tyr-PEG2, X = PEG2 (BO530), (CH2)8 (BO535), none (BO536)) were synthesized by solid-phase peptide synthesis. Peptides were radio-iodinated and evaluated in vitro for binding specificity, cellular retention, and affinity. In vivo specificity for all heterodimers was studied in PC-3 (GRPR-positive) and LNCaP (PSMA-positive) xenografts. [125I]I-BO530 was evaluated in PC-3pip (GRPR/PSMA-positive) xenografts. Micro single-photon emission computed tomography/computed tomography (microSPECT/CT) scans were acquired. The heterodimers were radiolabeled with high radiochemical yields, bound specifically to both targets, and demonstrated high degree of activity retention in PC-3pip cells. Only [125I]I-BO530 demonstrated in vivo specificity to both targets. A biodistribution study of [125I]I-BO530 in PC-3pip xenografted mice showed high tumor activity uptake (30%–35%ID/g at 3 h post injection (pi)). Activity uptake in tumors was stable and exceeded all other organs 24 h pi. Activity uptake decreased only two-fold 72 h pi. The GRPR/PSMA-targeting heterodimer [125I]I-BO530 is a promising agent for theranostics application in prostate cancer.

scholarly journals Zr-89 Immuno-PET Targeting Ectopic ATP Synthase Enables In-Vivo Imaging of Tumor Angiogenesis

2019 ◽  
Vol 20 (16) ◽  
pp. 3928
Author(s):  
Bok-Nam Park ◽  
Ga-Hee Kim ◽  
Seung-A Ko ◽  
Ga-Hee Shin ◽  
Su-Jin Lee ◽  
...  
Keyword(s):  
Cancer Cells ◽  
Cellular Uptake ◽  
Tumor Angiogenesis ◽  
Breast Cancer Cells ◽  
Xenograft Model ◽  
Tumor Uptake ◽  
Positron Emission ◽  
Pc3 Cells

In this study, we synthesized a Zr-89-labeled anti-adenosine triphosphate synthase monoclonal antibody (ATPS mAb) for applications in immuno-positron emission tomography (PET) and evaluated its feasibility for angiogenesis imaging. The cellular uptake of Zr-89 ATPS mAb was measured after treatment of cancer cell lines in vitro, and its biodistribution was evaluated at 4, 24 and 48 h in vivo in mice bearing xenografts. PET images were acquired at 4, 24, 48, and 96 h after Zr-89 ATPS mAb administration. Tumor angiogenesis was analyzed using anti-CD31 immunofluorescence staining. The cellular uptake of Zr-89 ATPS mAb increased over time in MDA-MB-231 breast cancer cells but did not increase in PC3 prostate cancer cells. The tumor uptake of Zr-89 ATPS mAb at 24 h was 9.4 ± 0.9% ID/g for MDA-Mb-231 cells and was 3.8 ± 0.6% ID/g for PC3 cells (p = 0.004). Zr-89 ATPS mAb uptake in MDA-MB-231 xenografts was inhibited by the administration of cold ATPS mAb (4.4 ± 0.5% ID/g, p = 0.011). Zr-89 ATPS mAb uptake could be visualized by PET for up to 96 h in MDA-MB-231 tumors. In contrast, there was no distinct tumor uptake detected by PET in the PC3 xenograft model. CD31-positive tumor vessels were abundant in MDA-MB-231 tumors, whereas they were scarcely detected in PC3 tumors. In conclusion, ATPS mAb was successfully labeled with Zr-89, which could be used for immuno-PET imaging targeting tumor angiogenesis.

scholarly journals Tumor Uptake of Triazine Dendrimers Decorated with Four, Sixteen, and Sixty-Four PSMA-Targeted Ligands: Passive versus Active Tumor Targeting

Biomolecules ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 421 ◽  
Author(s):  
Jongdoo Lim ◽  
Bing Guan ◽  
Kien Nham ◽  
Guiyang Hao ◽  
Xiankai Sun ◽  
...  
Keyword(s):  
Specific Binding ◽  
Quantitative Imaging ◽  
Molecular Size ◽  
Tumor Uptake ◽  
Competitive Binding Assay ◽  
The Core ◽  
Positron Emission ◽  
Pentanedioic Acid

Various glutamate urea ligands have displayed high affinities to prostate specific membrane antigen (PSMA), which is highly overexpressed in prostate and other cancer sites. The multivalent versions of small PSMA-targeted molecules are known to be even more efficiently bound to the receptor. Here, we employ a well-known urea-based ligand, 2-[3-(1,3-dicarboxypropyl)-ureido] pentanedioic acid (DUPA) and triazine dendrimers in order to study the effect of molecular size on multivalent targeting in prostate cancer. The synthetic route starts with the preparation of a dichlorotriazine bearing DUPA in 67% overall yield over five steps. This dichlorotriazine reacts with G1, G3, and G5 triazine dendrimers bearing a 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) group for 64Cu-labeling at the core to afford poly(monochlorotriazine) intermediates. Addition of 4-aminomethylpiperidine (4-AMP) and the following deprotection produce the target compounds, G1-(DUPA)4, G3-(DUPA)16, and G5-(DUPA)64. These targets include 4/16/64 DUPA groups on the surface and a DOTA group at the core, respectively. In vitro cell assay using PC3-PIP (PSMA positive) and PC3-FLU (PSMA negative) cells reveals that G1-(DUPA)4 has the highest PC3-PIP to PC3-FLU uptake ratio (10-fold) through the PSMA-mediated specific uptake. While G5-(DUPA)64 displayed approximately 12 times higher binding affinity (IC50 23.6 nM) to PC3-PIP cells than G1-(DUPA)4 (IC50 282.3 nM) as evaluated in a competitive binding assay, the G5 dendrimer also showed high non-specific binding to PC3-FLU cells. In vivo uptake of the 64Cu-labeled dendrimers was also evaluated in severe combined inmmunodeficient (SCID) mice bearing PC3-PIP and PC3-FLU xenografts on each shoulder, respectively. Interestingly, quantitative imaging analysis of positron emission tomograph (PET) displayed the lowest tumor uptake in PC3-PIP cells for the midsize dendrimer G3-(DUPA)16 (19.4 kDa) (0.66 ± 0.15%ID/g at 1 h. p.i., 0.64 ± 0.11%ID/g at 4 h. p.i., and 0.67 ± 0.08%ID/g at 24 h. p.i.). Through the specific binding of G1-(DUPA)4 to PSMA, the smallest dendrimer (5.1 kDa) demonstrated the highest PC3-PIP to muscle and PC3-PIP to PC3-FLU uptake ratios (17.7 ± 5.5 and 6.7 ± 3.0 at 4 h p.i., respectively). In addition, the enhanced permeability and retention (EPR) effect appeared to be an overwhelming factor for tumor uptake of the largest dendrimer G5-(DUPA)64 as the uptake was at a similar level irrelevant to the PSMA expression.

Synthesis of a new 18F labeled porphyrin for potential application in positron emission tomography. In vivo imaging and cellular uptake

RSC Advances ◽  
2015 ◽  
Vol 5 (120) ◽  
pp. 99540-99546 ◽  
Author(s):  
Ana V. C. Simões ◽  
Sara M. A. Pinto ◽  
Mário J. F. Calvete ◽  
Célia M. F. Gomes ◽  
Nuno C. Ferreira ◽  
...  
Keyword(s):  
In Vivo Imaging ◽  
Bladder Tumor ◽  
Radiochemical Purity ◽  
Cell Uptake ◽  
Emission Tomography ◽  
Human Bladder ◽  
Biodistribution Studies ◽  
Biodistribution Data ◽  
Positron Emission

Synthesis, labeling and initial biodistribution studies of a new [18F] radiolabeled meso-tetraphenylporphyrin (radiochemical purity >95%). Includes human bladder tumor cell uptake and biodistribution data.

scholarly journals Strain-Promoted Azide-Alkyne Cycloaddition-Based PSMA-Targeting Ligands For Multimodal Intraoperative Tumor Detection of Prostate Cancer

2021 ◽  
Author(s):  
Yvonne H.W. Derks ◽  
Mark Rijpkema ◽  
Helene I.V. Amatdjais-Groenen ◽  
Cato Loeff ◽  
Kim E. de Roode ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Fluorescence Imaging ◽  
Tumor Targeting ◽  
Solid Phase ◽  
Biodistribution Studies ◽  
Specific Tumor ◽  
Multiple Imaging ◽  
Specific Accumulation ◽  
Modular Platform

Abstract Purpose: Strain-promoted azide-alkyne cycloaddition (SPAAC) is a straightforward and multipurpose conjugation strategy. Use of SPAAC to link different functional elements to prostate specific membrane antigen (PSMA) ligands would facilitate the development of a modular platform for PSMA-targeted imaging and therapy of prostate cancer (PCa). As a first proof-of-concept for the SPAAC chemistry platform we synthesized and characterized four dual-labeled PSMA ligands for intraoperative radiodetection and fluorescence imaging of PCa. Methods: Ligands were synthesized using solid phase chemistry and contained a chelator for 111In or 99mTc labeling. The fluorophore IRDye800CW was conjugated using SPAAC chemistry or conventional N-hydroxysuccinimide (NHS)-ester coupling. LogD values were measured and PSMA-specificity of these ligands was determined in LS174T-PSMA cells. Tumor targeting was evaluated in BALB/c nude mice with subcutaneous LS174T-PSMA and LS174T wildtype tumors using µSPECT/CT imaging, fluorescence imaging, and biodistribution studies. Results: SPAAC chemistry increased lipophilicity of the ligands (range LogD: -2.4 to -4.4). In vivo, SPAAC chemistry ligands showed high and specific accumulation in s.c. LS174T-PSMA tumors up to 24 hours after injection, enabling clear visualization using µSPECT/CT and fluorescence imaging. Overall, no significant differences between the SPAAC chemistry ligands and their NHS-based counterparts were found (2 h p.i., p > 0.05), while 111In-labeled ligands outperformed the 99mTc ligands. Conclusion: Here we demonstrate that our newly developed SPAAC-based PSMA ligands show high PSMA-specific tumor targeting. Use of click-chemistry in PSMA ligand development opens up the opportunity for fast, efficient and versatile conjugations of multiple imaging moieties and/or drugs.

scholarly journals [18F]Fluoroethyltriazolyl Monocyclam Derivatives as Imaging Probes for the Chemokine Receptor CXCR4

Molecules ◽  
2019 ◽  
Vol 24 (8) ◽  
pp. 1612 ◽  
Author(s):  
Alejandro Amor-Coarasa ◽  
James M. Kelly ◽  
Pradeep K. Singh ◽  
Shashikanth Ponnala ◽  
Anastasia Nikolopoulou ◽  
...  
Keyword(s):  
Chemokine Receptor ◽  
Cxcr4 Expression ◽  
Tumor Uptake ◽  
Multiple Tumor ◽  
Chemokine Receptor Cxcr4 ◽  
Positron Emission ◽  
Imaging Probes ◽  
High Tumor Uptake ◽  
Tumor Types

Determining chemokine receptor CXCR4 expression is significant in multiple diseases due to its role in promoting inflammation, cell migration and tumorigenesis. [68Ga]Pentixafor is a promising ligand for imaging CXCR4 expression in multiple tumor types, but its utility is limited by the physical properties of 68Ga. We screened a library of >200 fluorine-containing structural derivatives of AMD-3465 to identify promising candidates for in vivo imaging of CXCR4 expression by positron emission tomography (PET). Compounds containing fluoroethyltriazoles consistently achieved higher docking scores. Six of these higher scoring compounds were radiolabeled by click chemistry and evaluated in PC3-CXCR4 cells and BALB/c mice bearing bilateral PC3-WT and PC3-CXCR4 xenograft tumors. The apparent CXCR4 affinity of the ligands was relatively low, but tumor uptake was CXCR4-specific. The tumor uptake of [18F]RPS-534 (7.2 ± 0.3 %ID/g) and [18F]RPS-547 (3.1 ± 0.5 %ID/g) at 1 h p.i. was highest, leading to high tumor-to-blood, tumor-to-muscle, and tumor-to-lung ratios. Total cell-associated activity better predicted in vivo tumor uptake than did the docking score or apparent CXCR4 affinity. By this metric, and on the basis of their high yielding radiosynthesis, high tumor uptake, and good contrast to background, [18F]RPS-547, and especially [18F]RPS-534, are promising 18F-labeled candidates for imaging CXCR4 expression.

A Facile Synthesis and Physical Properties of Nano-Sized Dendritic α,ε-Poly(L-lysine)s for the Delivery of Nucleic Acids

2006 ◽  
Vol 6 (11) ◽  
pp. 3532-3538
Author(s):  
Khee Dong Eom ◽  
Jin Sook Kim ◽  
Sun Mi Park ◽  
Myong Soo Kim ◽  
Rina Yu ◽  
...  
Keyword(s):  
Complex Formation ◽  
Nucleic Acids ◽  
Solid Phase ◽  
Polyacrylamide Gel Electrophoresis ◽  
Solid Phase Peptide Synthesis ◽  
Synthesis Method ◽  
Spherical Shape ◽  
Electrophoretic Mobilities ◽  
Lysine Residues

A series of nano-sized dendritic α,ε-poly(L-lysine)s (DPL) were synthesized by the solid-phase peptide synthesis method, using a core ε-peptide structure consisting of eight lysine residues. Surface amines of dendritic α,ε-poly(L-lysine) were characterized by comparing the retention times of a reverse phase HPLC with the electrophoretic mobilities of capillary zone electrophoresis (CZE) and non-denatured polyacrylamide gel electrophoresis (PAGE). The elution times of α,ε-poly(L-lysine) in HPLC were well correlated with the electrophoretic mobilities of CZE and PAGE. The separation was dependent on size, shape of molecule and the number of surface amine. The α,ε-poly(L-lysine) formed a complex with nucleic acids at various charge ratios and the degree of complex formation was size- and structure-dependent. Atomic force microscopy of the complex visualized the size and morphology of α,ε-poly(L-lysine)/DNA complex as a nano-sized spherical shape. The small size in complex formation provides a promise for in vivo therapeutic application of dendritic α,ε-poly(L-lysine)s or their derivatives in the delivery of gene or oligonucleotide.

scholarly journals Antibacterial Activity and Specificity of the Six Human α-Defensins

2005 ◽  
Vol 49 (1) ◽  
pp. 269-275 ◽  
Author(s):  
Bryan Ericksen ◽  
Zhibin Wu ◽  
Wuyuan Lu ◽  
Robert I. Lehrer
Keyword(s):  
Solid Phase ◽  
Solid Phase Peptide Synthesis ◽  
Antimicrobial Properties ◽  
Antimicrobial Activities ◽  
Gram Negative Bacteria ◽  
Host Defense Peptides ◽  
Gram Negative ◽  
Relative Potencies ◽  
Lethal Doses

ABSTRACT We developed a kinetic, 96-well turbidimetric procedure that is capable of testing the antimicrobial properties of six human α-defensins concurrently on a single microplate. The defensins were prepared by solid-phase peptide synthesis and tested against gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) and gram-negative bacteria (Enterobacter aerogenes and Escherichia coli). Analysis of the growth curves provided virtual lethal doses (vLDs) equivalent to conventional 50% lethal doses (LD50s), LD90s, LD99s, and LD99.9s obtained from colony counts. On the basis of their respective vLD90s and vLD99s, the relative potencies of human myeloid α-defensins against S. aureus were HNP2 > HNP1 > HNP3 > HNP4. In contrast, their relative potencies against E. coli and E. aerogenes were HNP4 > HNP2 > HNP1 = HNP3. HD5 was as effective as HNP2 against S. aureus and as effective as HNP4 against the gram-negative bacteria in our panel. HD6 showed little or no activity against any of the bacteria in our panel, including B. cereus, which was highly susceptible to the other five α-defensins. The assay described provides a quantitative, precise, and economical way to study the antimicrobial activities of host-defense peptides. Its use has clarified the relative potencies of human α-defensins and raised intriguing questions about the in vivo function(s) of HD6.

scholarly journals Evidence that the major degradation product of glucose-dependent insulinotropic polypeptide, GIP(3-42), is a GIP receptor antagonist in vivo

2002 ◽  
Vol 175 (2) ◽  
pp. 525-533 ◽  
Author(s):  
VA Gault ◽  
JC Parker ◽  
P Harriott ◽  
PR Flatt ◽  
FP O'Harte
Keyword(s):  
Insulin Secretion ◽  
Receptor Antagonist ◽  
Solid Phase ◽  
Solid Phase Peptide Synthesis ◽  
Chinese Hamster ◽  
Lung Fibroblasts ◽  
Incretin Hormone ◽  
Ionisation Mass Spectrometry ◽  
Gip Receptor

The incretin hormone glucose-dependent insulinotropic polypeptide (GIP) is rapidly degraded in the circulation by dipeptidyl peptidase IV forming the N-terminally truncated peptide GIP(3-42). The present study examined the biological activity of this abundant circulating fragment peptide to establish its possible role in GIP action. Human GIP and GIP(3-42) were synthesised by Fmoc solid-phase peptide synthesis, purified by HPLC and characterised by electrospray ionisation-mass spectrometry. In GIP receptor-transfected Chinese hamster lung fibroblasts, GIP(3-42) dose dependently inhibited GIP-stimulated (10(-7) M) cAMP production (up to 75.4+/-5.4%; P<0.001). In BRIN-BD11 cells, GIP(3-42) was significantly less potent at stimulating insulin secretion (1.9- to 3.2-fold; P<0.001), compared with native GIP and significantly inhibited GIP-stimulated (10(-7) M) insulin secretion with maximal inhibition (48.8+/-6.2%; P<0.001) observed at 10(-7) M. In (ob/ob) mice, administration of GIP(3-42) significantly inhibited GIP-stimulated insulin release (2.1-fold decrease; P<0.001) and exaggerated the glycaemic excursion (1.4-fold; P<0.001) induced by a conjoint glucose load. These data indicate that the N-terminally truncated GIP(3-42) fragment acts as a GIP receptor antagonist, moderating the insulin secreting and metabolic actions of GIP in vivo.

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