ABSTRACT
Insulin secretagogues are used for treatment of type 2 diabetes. We attempted to discover novel small molecules to stimulate insulin secretion by using in silico similarity search using sulfonylureas as query, followed by measurement of insulin secretion. Among 38 compounds selected by in silico similarity search, we found three diphenylsemicarbazides and one quinolone that stimulate insulin secretion. We focused on compound 8 (C8), which had the strongest insulin-secreting effect. Based on the structure-activity relationship of C8-derivatives, we identified diphenylthiosemicarbazide (DSC) 108 as the most potent secretagogue. DSC108 increased the intracellular Ca2+ level in MIN6-K8 cells. Competitive inhibition experiment and electrophysiological analysis revealed sulfonylurea receptor 1 (SUR1) to be the target of DSC108 and that this diphenylthiosemicarbazide directly inhibits ATP-sensitive K+ (KATP) channels. Pharmacokinetic analysis showed that DSC108 has a short half-life in vivo. Oral administration of DSC108 significantly suppressed the rises in blood glucose levels after glucose load in wild-type mice and improved glucose tolerance in the Goto-Kakizaki (GK) rat, a model of type 2 diabetes with impaired insulin secretion. Our data indicate that DSC108 is a novel insulin secretagogue, and is a lead compound for development of a new anti-diabetic agent.
Subject(s)
Amino Acids, Cyclic/pharmacology , Hypoglycemic Agents/pharmacology , Insulin/metabolism , Membrane Potentials/drug effects , Semicarbazides/pharmacology , Thiosemicarbazones/pharmacology , Administration, Oral , Amino Acids, Cyclic/chemistry , Amino Acids, Cyclic/metabolism , Amino Acids, Cyclic/therapeutic use , Animals , Blood Glucose/analysis , Calcium/metabolism , Cell Line , Diabetes Mellitus, Experimental/drug therapy , Diabetes Mellitus, Experimental/pathology , Glucose Tolerance Test , Glyburide/pharmacology , Glyburide/therapeutic use , Half-Life , Hypoglycemic Agents/chemistry , Hypoglycemic Agents/metabolism , Hypoglycemic Agents/therapeutic use , Insulin Secretion , Islets of Langerhans/drug effects , Islets of Langerhans/metabolism , KATP Channels/antagonists & inhibitors , KATP Channels/metabolism , Male , Mice , Mice, Inbred C57BL , Protein Binding , Rats , Semicarbazides/blood , Semicarbazides/chemistry , Semicarbazides/metabolism , Structure-Activity Relationship , Sulfonylurea Compounds/chemistry , Sulfonylurea Compounds/metabolism , Sulfonylurea Compounds/pharmacology , Sulfonylurea Receptors/antagonists & inhibitors , Sulfonylurea Receptors/metabolism , Thiosemicarbazones/chemistry , Thiosemicarbazones/metabolism , Thiosemicarbazones/therapeutic useABSTRACT
Unnatural cyclic amino acids (UNAAs) are a new class of boron delivery agents that are in a pre-clinical stage of evaluation. In the present study, the biodistribution of racemic forms of the cis- and trans-isomers of the boronated UNAA 1-amino-3-boronocyclopentanecarboxylic acid (ABCPC) and 1-amino-3-boronocycloheptanecarboxylic acid (ABCHC) were evaluted in B16 melanoma bearing mice and this was compared to l-p-boronophenylalanine (BPA). Boron concentrations were determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES) at 2.5h following intraperitoneal (i.p.) injection of the test agents at a concentration equivalent to 24mg/B/kg. While all compounds attained comparable tumor boron concentrations, the tumor/blood (T/Bl) boron concentration ratios were far superior for both cis-ABCPC and cis-ABCHC compared to BPA (T/Bl=16.4, and 15.1 vs. 5.4). Secondary ion mass spectrometry (SIMS) imaging revealed that the cis-ABCPC delivered boron to the nuclei, as well as the cytoplasm of B16 cells. Next, a biodistribution study of cis-ABCPC and BPA was carried out in F98 glioma bearing rats following i.p. administration. Both compounds attained comparable tumor boron concentrations but the tumor/brain (T/Br) boron ratio was superior for cis-ABCPC compared to BPA (6 vs. 3.3). Since UNAAs are water soluble and cannot be metabolized by tumor cells, they could be potentially more effective boron delivery agents than BPA. Our data suggest that further studies are warranted to evaluate these compounds prior to the initiation of clinical studies.
Subject(s)
Amino Acids, Cyclic/pharmacokinetics , Amino Acids, Cyclic/therapeutic use , Boron Compounds/pharmacokinetics , Boron Compounds/therapeutic use , Boron Neutron Capture Therapy/methods , Glioma/metabolism , Melanoma/metabolism , Amino Acids, Cyclic/chemistry , Animals , Boron Compounds/chemistry , Cell Line, Tumor , Drug Carriers , Female , Glioma/radiotherapy , Melanoma/radiotherapy , Metabolic Clearance Rate , Mice , Mice, Inbred C57BL , Organ Specificity , Rats , Rats, Inbred F344 , Tissue Distribution , Treatment OutcomeABSTRACT
Transport of large neutral amino acids (LNAA) across the blood brain barrier (BBB) is facilitated by the L-type amino acid transporter, LAT1. Peripheral accumulation of one LNAA (e.g., phenylalanine (phe) in PKU) is predicted to increase uptake of the offending amino acid to the detriment of others, resulting in disruption of brain amino acid homeostasis. We hypothesized that selected non-physiological amino acids (NPAAs) such as DL-norleucine (NL), 2-aminonorbornane (NB; 2-aminobicyclo-(2,1,1)-heptane-2-carboxylic acid), 2-aminoisobutyrate (AIB), and N-methyl-aminoisobutyrate (MAIB), acting as competitive inhibitors of various brain amino acid transporters, could reduce brain phe in Pah (enu2) mice, a relevant murine model of PKU. Oral feeding of 5 % NL, 5 % AIB, 0.5 % NB and 3 % MAIB reduced brain phe by 56 % (p < 0.01), -1 % (p = NS), 27 % (p < 0.05) and 14 % (p < 0.01), respectively, compared to untreated subjects. Significant effects on other LNAAs (tyrosine, methionine, branched chain amino acids) were also observed, however, with MAIB displaying the mildest effects. Of interest, MAIB represents an inhibitor of the system A (alanine) transporter that primarily traffics small amino acids and not LNAAs. Our studies represent the first in vivo use of these NPAAs in Pah (enu2) mice, and provide proof-of-principle for their further preclinical development, with the long-term objective of identifying NPAA combinations and concentrations that selectively restrict brain phe transport while minimally impacting other LNAAs and downstream intermediates.
Subject(s)
Amino Acids/therapeutic use , Brain/metabolism , Phenylalanine/metabolism , Phenylketonurias/drug therapy , Amino Acids, Cyclic/therapeutic use , Aminoisobutyric Acids/therapeutic use , Animals , Brain/drug effects , Down-Regulation/drug effects , Drug Evaluation, Preclinical , Female , Male , Mice , Mice, Inbred C57BL , Mice, Transgenic , Models, Biological , Molecular Targeted Therapy , Norleucine/therapeutic use , Phenylketonurias/genetics , Phenylketonurias/metabolism , Phenylketonurias/pathology , Pilot ProjectsABSTRACT
BACKGROUND: Postoperative paraplegia remains a serious complication after repair of a thoracoabdominal aortic aneurysm. The release of the excitatory neurotransmitter glutamate might be responsible for ischemic neuronal damage. We investigated the effect of 1-Aminocyclopropanecarboxylic acid (ACPC) on the prevention of paraplegia in a rabbit model of spinal cord ischemia. METHODS: The infrarenal abdominal aorta was clamped in eighteen rabbits. Saline (group A), 20 mg/kg of ACPC (group B), or 10 mg/kg of ACPC (group C), was injected into the clamped aorta. The animals were neurologically evaluated by Tarlov's score. The spinal cord was obtained for histopathologic examination, including hematoxylin and eosin staining and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining method. RESULTS: Postoperative complete paraplegia with marked neuronal necrosis appeared in group A animals. Four of the six group C animals showed intact neurological function. Scattered TUNEL positive neurons were seen within areas containing necrotic cells in sections from paraplegic animals in group A. CONCLUSIONS: ACPC can prevent spinal cord injury in a rabbit model of spinal cord ischemia.