Hepatic insulin resistance in KKA(y) mice and its amelioration by pioglitazone do not involve alterations in phospholipase C activity

Oral administration of Bis(aspirinato)zinc(II) complex ameliorates hyperglycemia and metabolic syndrome-like disorders in spontaneously diabetic KK-A(y) mice: structure-activity relationship on zinc-salicylate complexes

In recent years, the number of patients suffering from diseases, such as cancer, apoplexy, osteoporosis, hypertension, and type 2 diabetes mellitus is increasing worldwide. Type 2 diabetes, a lifestyle-related disease, is recognized as a serious disease. Various types of pharmaceutics for diabetes have been used. Since the relationship between diabetes and biometals such as vanadium, copper, and zinc ions has been recognized for many years, we have been developing the anti-diabetic metal complexes as new candidates. We found that several zinc(II) (Zn) complexes exhibit glucose-lowering activity for treating type 2 diabetes. High doses of salicylates have been known to reverse hyperglycemia and hyperinsulinemia in type 2 diabetic patients. These findings strongly suggest that the combined use of Zn and salicylates achieves the synergism in treating type 2 diabetes. Because aspirin, acetyl salicylic acid, has a chelating ability, we used it as a ligand to Zn. Several Zn-salicylate complexes were prepared and their biological activities were examined in this study. The complexes with an electron-withdrawing group in the ligand exhibited higher in vitro insulinomimetic activity than those of Zn complexes with an electron-donating group in the ligand. When bis(aspirinato)Zn (Zn(asp)₂) complex was orally administered on KK-A(y) mice with hereditary type 2 diabetes, the diabetic state was improved. In addition, this complex exhibited normalizing effects on serum adiponectin level and high blood pressure in metabolic syndrome. In conclusion, Zn(asp)₂ complex is newly proposed as a potent anti-diabetic and anti-metabolic syndrome agent.

A [meso-tetrakis(4-sulfonatophenyl)porphyrinato]zinc(ii) complex as an oral therapeutic for the treatment of type 2 diabetic KKA(y) mice

We prepared and characterized [meso-tetrakis(4-sulfonatophenyl)porphyrinato]zinc(II) ([Zn(tpps)]), and investigated its in vitro insulin-mimetic activity and in vivo hypoglycemic effect in type 2 diabetic KKA(y) mice. The results were compared with those of previously proposed insulin-mimetic zinc(II) complexes and zinc sulfate (ZnSO(4)). The in vitro insulin-mimetic activity of [Zn(tpps)] was considerably better than that of bis(allixinato)zinc(II) ([Zn(alx)(2)]), bis(maltolato)zinc(II) ([Zn(mal)(2)]), bis(2-aminomethylpyridinato)zinc(II) ([Zn(2-ampy)(2)](2+)), and ZnSO(4). In particular, the order of in vitro insulin-mimetic activity of the complexes was determined to be: [Zn(tpps)]>[Zn(alx)(2)]>[Zn(mal)(2)]>[Zn(2-ampy)](2+)>ZnSO(4). [Zn(tpps)] normalized the hyperglycemia of KKA(y) mice within 21 days when administered orally at doses of 10-20 mg (0.15-0.31 mmol) Zn per kg body mass for 28 days. In addition, metabolic syndromes such as insulin resistance, the degree of renal disturbance, and the degree of liver disturbance were significantly improved in [Zn(tpps)]-treated KKA(y) mice relative to those administered with saline and ZnSO(4). The improvement in diabetes was validated by the results of oral glucose-tolerance tests and the decrease in the HbA(1c) level observed. In contrast, ZnSO(4) and the ligand H(2)tpps did not lower the elevated blood glucose level under the same experimental conditions. Based on these observations, [Zn(tpps)] is proposed to be the first orally active zinc(II)-porphyrin complex for the efficacious treatment of not only type 2 diabetes but also metabolic syndromes in animals.

A family of insulinomimetic zinc(II) complexes of amino ligands with Zn(Nn) (n=3 and 4) coordination modes

Several metal ions and their complexes have been known to mimic the action of insulin in in vitro and in vivo systems. We prepared a family of Zn(II) complexes derived from amino ligands with Zn(Nn) (n=3 and 4) coordination modes, the insulinomimetic activity being estimated by an inhibitory effect of free fatty acid release from isolated rat adipocytes treated with epinephrine. In comparison with the positive controls VOSO(4) and ZnSO(4), Zn(II)-amine complexes with stability constants (log beta) lower than 11.5 exhibited higher insulinomimetic activities. Among them, a bis(2-aminomethyl pyridinato)Zn(II) (Zn(2-ampy)(2)(2+)) complex with the highest insulinomimetic activity and a higher stability constant but lower than 11.5 was selected, and subjected to in vivo evaluation in KK-A(y) mice with a genetically type 2 diabetes mellitus. The high blood glucose level of the mice was lowered by daily intraperitoneal injections of Zn(2-ampy)(2)(2+) at a dose of 2 mg Zn/kg body weight for 14 days. Based on the results, Zn(2-ampy)(2)(2+) with Zn(N(4)) coordination mode was proposed to have both a high in vitro insulinomimetic activity and an in vivo blood glucose lowering effect.

Production of beta-defensin-2 by human colonic epithelial cells induced by Salmonella enteritidis flagella filament structural protein

We recently showed that FliC of Salmonella enteritidis increased human beta-defensin-2 (hBD-2) expression, and now describe the signaling responsible pathway. FliC increased the intracellular Ca(2+) concentration ([Ca(2+)](in)) in Caco-2 cells. The [Ca(2+)](in) increase induced by FliC was prevented by U73122 and heparin, but not by chelating extracellular Ca(2+) or pertussis toxin. The FliC-induced increase in hBD-2 promoter activity via nuclear factor kappaB (NF-kappaB) was also inhibited by chelation of intracellular Ca(2+) or by U73122. We conclude that FliC increased [Ca(2+)](in) via inositol 1,4,5-trisphosphate, which was followed by up-regulating hBD-2 mRNA expression via an NF-kappaB-dependent pathway.

Pioglitazone promotes insulin-induced activation of phosphoinositide 3-kinase in 3T3-L1 adipocytes by inhibiting a negative control mechanism

Activation of phosphoinositide 3-kinase (PI 3-kinase) is an early event in insulin signal transduction that is blocked completely in adipocytes from insulin-resistant KKAy mice. Treatment of KKAy mice with pioglitazone, an anti-diabetic thiazolidinedione, partially restores insulin-dependent changes in PI 3-kinase. The mechanism of this effect of pioglitazone was investigated using murine 3T3-L1 cells as an experimental model. Insulin and insulin-like growth factor I (IGF-I) each elicited rapid (within 2 min) and large (2-5-fold) increases in PI 3-kinase activity that could be immunoprecipitated using anti-phosphotyrosine (pY) antibodies. Maximal insulin-induced activity of PI 3-kinase in pY-immunoprecipitates was similar in 3T3-L1 adipocytes and mouse adipocytes, but the kinetics of activation differed. Insulin- and IGF-I-induced changes in PI 3-kinase were each half-maximal at 3-5 nM of hormone and were not additive. Increases in both insulin-induced and IGF-I-induced pY-immunoprecipitable PI 3-kinase activity were observed when 3T3-L1 fibroblasts became confluent and when they adopted the adipocyte phenotype. Pioglitazone (10 microM), administered either acutely or chronically to either 3T3-L1 adipocytes or 3T3-L1 fibroblasts, did not greatly alter the kinetics, magnitude or sensitivity of changes in PI 3-kinase elicited by either insulin or IGF-I. In contrast, the attenuation by isoproterenol of insulin-induced changes in PI 3-kinase was prevented in cells pretreated with pioglitazone. This effect of pioglitazone did not involve inhibition of isoproterenol-elicited accumulation of cyclic AMP. Pioglitazone also prevented attenuation of insulin induced changes in PI 3-kinase by cell penetrating analogs of cyclic AMP. Pioglitazone, therefore, has no direct effect on insulin-stimulated PI 3-kinase activity, but interferes with a cyclic AMP-dependent mechanism that normally antagonizes this action of insulin. These data support the proposition that the facilitation of insulin action by pioglitazone involves, at least in part, an inhibition of a negative control mechanism.

Pioglitazone promotes insulin-induced activation of phosphoinositide 3-kinase in 3T3-L1 adipocytes by inhibiting a negative control mechanism

Activation of phosphoinositide 3-kinase (PI 3-kinase) is an early event in insulin signal transduction that is blocked completely in adipocytes from insulin-resistant KKAy mice. Treatment of KKAy mice with pioglitazone, an anti-diabetic thiazolidinedione, partially restores insulin-dependent changes in PI 3-kinase. The mechanism of this effect of pioglitazone was investigated, using murine 3T3-L1 cells as an experimental model. Insulin and insulin-like growth factor I (IGF-I) each elicited rapid (within 2 min) and large (2- to 5-fold) increases in PI 3-kinase activity that could be immunoprecipitated using anti-phosphotyrosine (pY) antibodies. Maximal insulin-induced activity of PI 3-kinase in pY-immunoprecipitates was similar in 3T3-L1 adipocytes and mouse adipocytes, but the kinetics of activation differed. Insulin- and IGF-I-induced changes in PI 3-kinase were each half-maximal at 3-5 nM of hormone and were not additive. Increases in both insulin-induced and IGF-I-induced pY-immunoprecipitable PI 3-kinase activity were observed when 3T3-L1 fibroblasts became confluent and when they adopted the adipocyte phenotype. Pioglitazone (10 microM), administered either acutely or chronically to either 3T3-L1 adipocytes or 3T3-L1 fibroblasts, did not alter greatly the kinetics, magnitude or sensitivity of changes in PI 3-kinase elicited by either insulin or IGF-I. In contrast, the attenuation by isoproterenol of insulin-induced changes in PI 3-kinase was prevented in cells pretreated with pioglitazone. This effect of pioglitazone did not involve inhibition of isoproterenol-elicited accumulation of cyclic AMP. Pioglitazone also prevented attenuation of insulin induced changes in PI 3-kinase by cell penetrating analogs of cyclic AMP. Pioglitazone, therefore, has no direct effect on insulin-stimulated PI 3-kinase activity, but interferes with a cyclic AMP-dependent mechanism that normally antagonizes this action of insulin. These data support the proposition that the facilitation of insulin action by pioglitazone involves, at least in part, an inhibition of a negative control mechanism.