RESUMEN
1. The MIN6 cell line derived from in vivo immortalized insulin-secreting pancreatic beta cells was used to study the insulin-releasing capacity and the cellular mode of action of S-22068, a newly synthesized imidazoline compound known for its antidiabetic effect in vivo. 2. S-22068, was able to release insulin from MIN6 cells in a dose-dependent manner with a half-maximal stimulation at 100 micronM. Its efficacy (8 fold over the basal value), which did not differ whatever the glucose concentration (stimulatory or not), was intermediate between that of sulphonylurea and that of efaroxan. 3. Similarly to sulphonylureas and classical imidazolines, S-22068 blocked K(ATP) channels and, in turn, opened nifedipine-sensitive voltage-dependent Ca2+ channels, triggering Ca2+ entry. 4. Similarly to other imidazolines, S-22068 induced a closure of cloned K(ATP) channels injected to Xenopus oocytes by interacting with the pore-forming Kir6.2 moiety. 5. S-22068 did not interact with the sulphonylurea binding site nor with the non-I1 and non-I2 imidazoline site evidenced in the beta cells that is recognized by the imidazoline compounds efaroxan, phentolamine and RX821002. 6. We conclude that S-22068 is a novel imidazoline compound which stimulates insulin release via interaction with an original site present on the Kir6.2 moiety of the beta cell K(ATP) channels.
Asunto(s)
Hipoglucemiantes/farmacología , Imidazoles/farmacología , Insulina/metabolismo , Islotes Pancreáticos/metabolismo , Piperazinas/farmacología , Canales de Potasio de Rectificación Interna , Antagonistas Adrenérgicos alfa/metabolismo , Animales , Calcio/metabolismo , Canales de Calcio/efectos de los fármacos , Canales de Calcio/metabolismo , Línea Celular , Humanos , Idazoxan/análogos & derivados , Idazoxan/metabolismo , Islotes Pancreáticos/efectos de los fármacos , Potenciales de la Membrana/fisiología , Oocitos/efectos de los fármacos , Oocitos/metabolismo , Bloqueadores de los Canales de Potasio , Canales de Potasio/efectos de los fármacos , Ensayo de Unión Radioligante , Receptor de Insulina/efectos de los fármacos , Radioisótopos de Rubidio , Xenopus laevisRESUMEN
We have investigated the possible mechanisms underlying the antihyperglycaemic effect of the imidazoline derivative S-22068. In vitro, in the presence of 5 mmol/l glucose, S-22068 (100 micromol/l) induced a significant and sustained increase in insulin secretion from isolated, perifused, rat islets and a marked sensitization to a subsequent glucose challenge (10 mmol/l). S-22068 (100 micromol/l was able to antagonize the stimulatory effect of diazoxide on 86Rb efflux from preloaded islets incubated in the presence of 20 mmol/l glucose. Experiments were also performed to investigate whether S-22068 can alter glucose turnover and peripheral insulin sensitivity in vivo in mildly diabetic rats and obese, insulin resistant, Zucker rats. Neither glucose production nor individual tissue glucose utilization was modified by S-22068 in either group of rats. Similar results were obtained whether the studies were performed under basal conditions or during euglycaemic/hyperinsulinemic clamps. The results suggest that S-22068 exerts part of its antihyperglycaemic effect by promoting insulin secretion without alteration of peripheral insulin sensitivity.
Asunto(s)
Glucosa/metabolismo , Hipoglucemiantes/farmacología , Imidazoles/farmacología , Insulina/metabolismo , Piperazinas/farmacología , Animales , Antihipertensivos/farmacología , Diabetes Mellitus Experimental/metabolismo , Diazóxido/farmacología , Glucosa/farmacología , Técnica de Clampeo de la Glucosa , Técnicas In Vitro , Secreción de Insulina , Islotes Pancreáticos/efectos de los fármacos , Islotes Pancreáticos/metabolismo , Hígado/efectos de los fármacos , Hígado/metabolismo , Masculino , Ratas , Ratas Wistar , Ratas Zucker , Radioisótopos de Rubidio/farmacocinéticaRESUMEN
Piperazine derivatives have been identified as new antidiabetic compounds. Structure-activity relationship studies in a series of 1-benzyl-4-alkyl-2-(4',5'-dihydro-1'H-imidazol-2'-yl)piperazines resulted in the identification of 1-methyl-4-(2', 4'-dichlorobenzyl)-2-(4',5'-dihydro-1'H-imidazol-2'-yl)piperazine, PMS 812 (S-21663), as a highly potent antidiabetic agent on a rat model of diabetes, mediated by an important increase of insulin secretion independently of alpha2 adrenoceptor blockage. These studies were extended to find additional compounds in these series with improved properties. In such a way, substitution of both piperazine N atoms was first optimized by using various alkyl, branched or not, and benzyl groups. Second, some modifications of the imidazoline ring and its replacement by isosteric heterocycles were carried out, proceeding from PMS 812, to evaluate their influence on the antidiabetic activity. The importance of the distance between the imidazoline ring and the piperazine skeleton was studied third. Finally, the influence of the N-benzyl moiety was also analyzed compared to a direct N-phenyl substitution. The pharmacological evaluation was performed in vivo using glucose tolerance tests on a rat model of type II diabetes. The most active compounds were 1,4-diisopropyl-2-(4', 5'-dihydro-1'H-imidazol-2'-yl)piperazine (41a), PMS 847 (S-22068), and 1,4-diisobutyl-2-(4',5'-dihydro-1'H-imidazol-2'-yl)piperazine (41b), PMS 889 (S-22575), which strongly improved glucose tolerance without any side event or hypoglycemic effect. More particularly, PMS 847 proved to be as potent after po (100 micromol/kg) as after ip administration and appears as a good candidate for clinical investigations.
Asunto(s)
Glucemia/metabolismo , Diabetes Mellitus Tipo 2/tratamiento farmacológico , Hipoglucemiantes/síntesis química , Imidazoles/síntesis química , Piperazinas/síntesis química , Animales , Bovinos , Corteza Cerebral/metabolismo , Diabetes Mellitus Tipo 2/sangre , Diabetes Mellitus Tipo 2/fisiopatología , Diseño de Fármacos , Evaluación Preclínica de Medicamentos , Prueba de Tolerancia a la Glucosa , Homeostasis , Hipoglucemiantes/administración & dosificación , Hipoglucemiantes/química , Hipoglucemiantes/farmacología , Imidazoles/administración & dosificación , Imidazoles/química , Imidazoles/farmacología , Receptores de Imidazolina , Técnicas In Vitro , Inyecciones Intraperitoneales , Insulina/metabolismo , Secreción de Insulina , Corteza Renal/metabolismo , Masculino , Piperazinas/administración & dosificación , Piperazinas/química , Piperazinas/farmacología , Conejos , Ensayo de Unión Radioligante , Ratas , Ratas Wistar , Receptores Adrenérgicos alfa 2/metabolismo , Receptores de Droga/metabolismo , Relación Estructura-ActividadRESUMEN
Recent data suggest that some imidazoline derivatives can lower plasma glucose in experimental animal models of diabetes. We studied the activity of an imidazoline S-22068, in rat model of non-insulin-dependent diabetes mellitus (NIDDM) produced with a low dose of streptozotocin (35 mg kg(-1), i.v.) in the adult. The respective increase over basal value in glucose (deltaG) and insulin (deltaI), and the rate of glucose disappearance (K), were measured during a 30 min intravenous glucose tolerance test. After an intraperitoneal injection of S-22068 (24 mg kg(-1)), deltaG (mM min(-1)) was decreased (91.67+/-5.83 vs 120.5+/-3.65; P<0.001), whereas K was increased (1.74+/-0.09 vs 1.18+/-0.05; P<0.001). Although insulinaemia was increased at time-point 0 of the test, deltaI was unchanged. During oral glucose tolerance tests (OGTT), S-22068 (24 mg kg(-1), p.o.) improved glucose tolerance, and its efficiency was potentiated after chronic treatment (15 days). Basal glycaemia was unaffected by the treatment. Under the same conditions, a higher dose of S-22068 (40 mg kg(-1)) further improved glucose tolerance without causing hypoglycaemia. Binding experiments revealed that S-22068 displays no affinity for either adrenoceptors or the two imidazoline receptors I1 or I2. These results demonstrate that S-22068 improves glucose tolerance without causing hypoglycaemia. Thus S-22068 represents a new potential option in the treatment of NIDDM.
Asunto(s)
Diabetes Mellitus Experimental/tratamiento farmacológico , Hipoglucemiantes/uso terapéutico , Imidazoles/uso terapéutico , Piperazinas , Animales , Glucemia/metabolismo , Relación Dosis-Respuesta a Droga , Prueba de Tolerancia a la Glucosa , Hemodinámica/efectos de los fármacos , Hipoglucemiantes/efectos adversos , Imidazoles/efectos adversos , Insulina/sangre , Insulina/metabolismo , Ensayo de Unión Radioligante , Ratas , Ratas WistarRESUMEN
The physiopathology of non-insulin-dependent diabetes mellitus is associated with a dysfunction in the regulation of insulin secretion. The alpha 2-adrenoceptors have been reported to be involved in this alteration, although alpha 2-antagonists containing an imidazoline ring may stimulate insulin secretion independently of alpha 2-adrenoceptor blockage. Recently, a new "imidazoline-binding site" involved in the control of K(+)-ATP channels in the B cell has been proposed. In the course of searching for new antidiabetic agents, 1-alkyl-2-(4',5'-dihydro-1'H-imidazol-2'-yl)-4-benzylpiperazines, 1-benzyl-2-(4',5'-dihydro-1'H-imidazol-2'-yl)-4-alkylpiperazines, and 1-benzyl-2-(4',5'-dihydro-1'H-imidazol-2'-yl)-4-benzylpiperazines have been designed and evaluated as potential adrenoceptor antagonists. Pharmacological evaluation was performed in vivo using glucose tolerance tests performed on a rat model of type II diabetes obtained by injection of a low dose (35 mg/kg) of streptozotocin (STZ). For some compounds, binding experiments were performed on alpha 2 adrenoceptors and I1 and I2 imidazoline-binding sites. The biological and physicochemical data have been combined with molecular modeling studies to establish structure-activity relationships. The most active compound was 1-(2',4'-dichlorobenzyl)-2-(4',5'-dihydro-1'H-imidazol-2'-yl)- 4-methylpiperazine (7f); intraperitoneal administration (100 mumol/kg) of 7f strongly improved glucose tolerance in STZ diabetic rats. This effect seemed at least partly mediated by a significant increase of insulin secretion. Other compounds of the same family (7b, 16f, 23b) have also shown potent activity. We found no correlation between in vivo antihyperglycemic properties and in vitro affinities for alpha 2-adrenoceptors or I1, and I2 binding sites. These compounds can be considered as antihyperglycemic agents potentially useful for treatment of type II diabetes and are currently under complementary investigation.
Asunto(s)
Glucemia/metabolismo , Diabetes Mellitus Tipo 2/sangre , Diabetes Mellitus Tipo 2/tratamiento farmacológico , Imidazoles/síntesis química , Imidazoles/farmacología , Piperazinas/síntesis química , Piperazinas/farmacología , Animales , Glucemia/efectos de los fármacos , Bovinos , Modelos Animales de Enfermedad , Diseño de Fármacos , Prueba de Tolerancia a la Glucosa , Homeostasis/efectos de los fármacos , Masculino , Modelos Moleculares , Ratas , Ratas Wistar , Receptores Adrenérgicos alfa 2/efectos de los fármacos , Receptores Adrenérgicos alfa 2/metabolismoRESUMEN
1. The MIN6 cell line derived from in vivo immortalized insulin-secreting pancreatic beta cells was used to study the insulin-releasing capacity and the cellular mode of action of S-21663, a newly synthesized imadizoline compound known for its antidiabetic effect in vivo and its ability to release insulin from perfused pancreas. 2. S-21663, at concentrations ranging from 10(-5) M to 10(-3) M was able to release insulin from MIN6 cells; its activity peaked at 10(-4) M, a drop in the stimulant factor being noted between 10(-4) and 10(-3) M. Its efficacy, which did not differ whatever the glucose concentration (stimulant or not), was higher than that of the other secretagogues tested, glucose, sulphonylureas or the peptide tGLP-1. 3. In contrast to tGLP-1, S-21663 did not change the cyclic AMP content, whereas it increased Ca2+ influx via verapamil- and nifedipine-sensitive voltage-dependent calcium channels, the insulin release being a direct consequence of this Ca2+ entry. The S-21663-induced Ca2+ influx appears to be essentially the consequence of closure of K+ channels which differ from the ATP-dependent K+ (K-ATP) channels as determined by measurement of 86Rb efflux and use of a K-ATP channel opener. 4. Comparison of the effects of S-21663 to that of efaroxan, another imidazoline compound shown to act on insulin release in a glucose-dependent way via binding sites distinct from the imidazoline I1 and I2 sites, suggested that S-21663 acts through a novel site which displays a remarkably stable expression along the cell culture. 5. It is concluded that S-21663 is a very efficient, glucose-independent insulin secretagogue acting through a novel imidazoline site, linked to K+ channels, distinct from the I1, I2 and 'efaroxan' binding sites. In vitro and in vivo features of S-21663 indicate that this compound, or new drugs derived from it, might be the basis for a new pharmacological approach to the mangement of type II (non insulin-dependent) diabetes.
Asunto(s)
Imidazoles/farmacología , Insulina/metabolismo , Islotes Pancreáticos/efectos de los fármacos , Sitios de Unión , Línea Celular Transformada , Imidazoles/metabolismo , Islotes Pancreáticos/metabolismoRESUMEN
We have studied the activity of S-21663 (PMS 812), a new imidazoline derivative, in a rat model of Type II diabetes obtained by i.v. injection of a low dose (35 mg/kg) of streptozotocin, using glucose tolerance tests. Glucose tolerance and insulin secretion were measured as the delta G and the delta l, i.e., the respective increase in glycemia and insulinemia over 30 min after the glucose load. The rate of glucose disappearance was calculated as the K coefficient and the insulin response to glucose as the delta l/delta G. After i.p. injection of S-21663, delta G (millimoles per liter per minute) was decreased (71.7 +/- 10.1 vs. 112.6 +/- 15.1; P < .05), whereas K was increased (3.3 +/- 0.3 vs. 1.5 +/- 0.1; P < .05). Insulin secretion was also largely improved (delta l/delta G: 90.9 +/- 22.2 vs. 18.3 +/- 2.6; P < .05). Oral administration of the product was almost as efficient as i.p. injection. Chronic treatment (15 days) increased the efficiency. Insulin secretion measured in vitro at both 2.8 and 16.6 mM glucose was quadrupled by S-21663 (100 microM). S-21663 binds neither to alpha-2 adrenoceptors nor to known imidazoline binding sites. S-21663 can be considered as a potential hypoglycemic agent in Type II diabetes.
Asunto(s)
Diabetes Mellitus Experimental/tratamiento farmacológico , Imidazoles/farmacología , Insulina/sangre , Animales , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Prueba de Tolerancia a la Glucosa , Masculino , Ratas , Ratas WistarRESUMEN
Tissue transglutaminase (tTG) activity was used to test the potent regulatory role of vasoactive intestinal peptide (VIP) on Retinoic Acid-induced effect in human neuroblastoma cell line. The comparison between both differentiation and cell death related to tissue transglutaminase was discussed in this model. VIP alone was a potent differentiating agent in SK-N-SH cells but in the presence of retinoic acid (RA), this peptide rather potentiates RA-induced tTG activity which is now considered as an apoptosis marker in neuroblastoma cell line. This paper demonstrated an additional neuromodulator role for VIP.