Absence of somatostatin SST(2) receptor internalization in vivo after intravenous SOM230 application in the AR42J animal tumor model

Among clinically relevant somatostatin functions, agonist-induced somatostatin receptor subtype 2 (sst(2)) internalization is a potent mechanism for tumor targeting with sst(2) affine radioligands such as octreotide. Since, as opposed to octreotide, the second generation multi-somatostatin analog SOM230 (pasireotide) exhibits strong functional selectivity, it appeared of interest to evaluate its ability to affect sst(2) internalization in vivo. Rats bearing AR42J tumors endogenously expressing somatostatin sst(2) receptors were injected intravenously with SOM230 or with the [Tyr(3), Thr(8)]-octreotide (TATE) analog; they were euthanized at various time points; tumors and pancreas were analyzed by immunohistochemistry for the cellular localization of somatostatin sst(2) receptors. SOM230-induced sst(2) internalization was also evaluated in vitro by immunofluorescence microscopy in AR42J cells. At difference to the efficient in vivo sst(2) internalization triggered by intravenous [Tyr(3), Thr(8)]-octreotide, intravenous SOM230 did not elicit sst(2) internalization: immunohistochemically stained sst(2) in AR42J tumor cells and pancreatic cells were detectable at the cell surface at 2.5min, 10min, 1h, 6h, or 24h after SOM230 injection while sst(2) were found intracellularly after [Tyr(3), Thr(8)]-octreotide injection. The inability of stimulating sst(2) internalization by SOM230 was confirmed in vitro in AR42J cells by immunofluorescence microscopy. Furthermore, SOM230 was unable to antagonize agonist-induced sst(2) internalization, neither in vivo, nor in vitro. Therefore, SOM230 does not induce sst(2) internalization in vivo or in vitro in AR42J cells and pancreas, at difference to octreotide derivatives with comparable sst(2) binding affinities. These characteristics may point towards different tumor targeting but also to different desensitization properties of clinically applied SOM230.

Synthesis and in vitro characterization of radioiodinatable benzodiazepines selective for type 1 and type 2 cholecystokinin receptors

Radiolabeled antagonists of specific peptide receptors identify a higher number of receptor binding sites than agonists and may thus be preferable for in vivo tumor targeting. In this study, two novel radioiodinated 1,4-benzodiazepines, (S)-1-(3-iodophenyl)-3-(1-methyl-2-oxo-5-phenyl-2,3-dihydro-1H-benzo[e][1,4]diazepin-3-yl)urea (9) and (R)-1-(3-iodophenyl)-3-(1-methyl-2-oxo-5-phenyl-2,3-dihydro-1H-benzo[e][1,4]diazepin-3-yl)urea (7), were developed. They were characterized in vitro as high affinity selective antagonists at cholecystokinin types 1 and 2 (CCK(1) and CCK(2)) receptors using receptor binding, calcium mobilization, and internalization studies. Their binding to human tumor tissues was assessed with in vitro receptor autoradiography and compared with an established peptidic CCK agonist radioligand. The (125)I-labeled CCK(1) receptor-selective compound 9 often revealed a substantially higher amount of CCK(1) receptor binding sites in tumors than the agonist (125)I-CCK. Conversely, the radioiodinated CCK(2) receptor-selective compound 7 showed generally weaker tumor binding than (125)I-CCK. In conclusion, compound 9 is an excellent radioiodinated nonpeptidic antagonist ligand for direct and selective labeling of CCK(1) receptors in vitro. Moreover, it represents a suitable candidate to test antagonist binding to CCK(1) receptor-expressing tumors in vivo.

Fructose overconsumption causes dyslipidemia and ectopic lipid deposition in healthy subjects with and without a family history of type 2 diabetes

BACKGROUND: Both nutritional and genetic factors are involved in the pathogenesis of nonalcoholic fatty liver disease and insulin resistance. OBJECTIVE: The aim was to assess the effects of fructose, a potent stimulator of hepatic de novo lipogenesis, on intrahepatocellular lipids (IHCLs) and insulin sensitivity in healthy offspring of patients with type 2 diabetes (OffT2D)--a subgroup of individuals prone to metabolic disorders. DESIGN: Sixteen male OffT2D and 8 control subjects were studied in a crossover design after either a 7-d isocaloric diet or a hypercaloric high-fructose diet (3.5 g x kg FFM(-1) x d(-1), +35% energy intake). Hepatic and whole-body insulin sensitivity were assessed with a 2-step hyperinsulinemic euglycemic clamp (0.3 and 1.0 mU x kg(-1) x min(-1)), together with 6,6-[2H2]glucose. IHCLs and intramyocellular lipids (IMCLs) were measured by 1H-magnetic resonance spectroscopy. RESULTS: The OffT2D group had significantly (P < 0.05) higher IHCLs (+94%), total triacylglycerols (+35%), and lower whole-body insulin sensitivity (-27%) than did the control group. The high-fructose diet significantly increased IHCLs (control: +76%; OffT2D: +79%), IMCLs (control: +47%; OffT2D: +24%), VLDL-triacylglycerols (control: +51%; OffT2D: +110%), and fasting hepatic glucose output (control: +4%; OffT2D: +5%). Furthermore, the effects of fructose on VLDL-triacylglycerols were higher in the OffT2D group (group x diet interaction: P < 0.05). CONCLUSIONS: A 7-d high-fructose diet increased ectopic lipid deposition in liver and muscle and fasting VLDL-triacylglycerols and decreased hepatic insulin sensitivity. Fructose-induced alterations in VLDL-triacylglycerols appeared to be of greater magnitude in the OffT2D group, which suggests that these individuals may be more prone to developing dyslipidemia when challenged by high fructose intakes. This trial was registered at clinicaltrials.gov as NCT00523562.

1,2-Bis(2-benzimidazolyl)-1,2-ethanediol, a chiral, tridentate, facially coordinating ligand

The ligand 1,2-bis(1H-benzimidazol-2-yl)-1,2-ethanediol, 1, and its methylated derivative 2 are readily synthesized from tartaric acid, and act as chiral, facially coordinating tridentate ligands, forming complexes of composition ML2 with octahedral transition metals. The copper(II) complexes show distorted 4 + 2 coordination with benzimidazoles occupying the equatorial sites and alcohol functions weakly binding in the axial sites. Nickel(II) complexes in three different states of protonation show regular octahedral geometry with the alcohols mutually cis. Deprotonation of the coordinated alcohol produces little structural change but the monodeprotonated complex forms a hydrogen bonded dimer. Magnetic measurements show the hydrogen bonded bridge to offer a pathway for weak antiferromagnetic coupling. UV-Visible spectroscopy shows the ligand to have a field intermediate between water and pyridine. The diastereoselectivity of complexation depends on the geometry: nickel(II) shows a weak preference for the homochiral complex, whereas copper(II) forms almost exclusively homochiral complexes.