A novel dipeptidyl peptidase-4 inhibitor, alogliptin (SYR-322), is effective in diabetic rats with sulfonylurea-induced secondary failure.

AIMS: Loss of efficacy over time or secondary failure occurs somewhat often and remains a major concern of sulfonylurea (SU) therapy. In this study, we investigated the benefits of alogliptin, an oral, potent and highly selective dipeptidyl peptidase-4 (DPP-4) inhibitor, in a rat model exhibiting SU secondary failure. MAIN METHODS: Neonatally streptozotocin-induced diabetic rats (N-STZ-1.5 rats), a non-obese model of type 2 diabetes, were used in these studies. The effects of alogliptin on DPP-4 activity and glucagon-like peptide 1 (GLP-1) concentration were determined by measuring their levels in plasma. In addition, the effects of alogliptin on an oral glucose tolerance test were investigated by using an SU secondary failure model. KEY FINDINGS: Alogliptin dose dependently suppressed plasma DPP-4 activity leading to an increase in the plasma active form of GLP-1 and improved glucose excursion in N-STZ-1.5 rats. Repeated administration of glibenclamide resulted in unresponsiveness or loss of glucose tolerance typical of secondary failure. In these rats, alogliptin exhibited significant improvement of glucose excursion with significant increase in insulin secretion. By contrast, glibenclamide and nateglinide had no effect on the glucose tolerance of these rats. SIGNIFICANCE: The above findings suggest that alogliptin was effective at improving glucose tolerance and therefore overcoming SU induced secondary failure in N-STZ-1.5 rats.

Overexpression of GPR40 in pancreatic beta-cells augments glucose-stimulated insulin secretion and improves glucose tolerance in normal and diabetic mice.

OBJECTIVE: GPR40 is a G protein-coupled receptor regulating free fatty acid-induced insulin secretion. We generated transgenic mice overexpressing the hGPR40 gene under control of the mouse insulin II promoter and used them to examine the role of GPR40 in the regulation of insulin secretion and glucose homeostasis. RESEARCH DESIGN AND METHODS: Normal (C57BL/6J) and diabetic (KK) mice overexpressing the hGPR40 gene under control of the insulin II promoter were generated, and their glucose metabolism and islet function were analyzed. RESULTS: In comparison with nontransgenic littermates, hGPR40 transgenic mice exhibited improved oral glucose tolerance with an increase in insulin secretion. Although islet morphologic analysis showed no obvious differences between hGPR40 transgenic and nontransgenic mice, isolated islets from hGPR40 transgenic mice had enhanced insulin secretion in response to high glucose (16 mmol/l) compared with those from nontransgenic mice, and they both had similar low glucose (3 mmol/l)-stimulated insulin secretion. In addition, hGPR40 transgenic islets significantly increased insulin secretion against a naturally occurring agonist palmitate in the presence of 11 mmol/l glucose. hGPR40 transgenic mice were also found to be resistant to high-fat diet-induced glucose intolerance, and hGPR40 transgenic mice harboring KK background showed augmented insulin secretion and improved oral glucose tolerance compared with nontransgenic littermates. CONCLUSIONS: Our results suggest that GPR40 may have a role in regulating glucose-stimulated insulin secretion and plasma glucose levels in vivo and that pharmacological activation of GPR40 may provide a novel insulin secretagogue beneficial for the treatment of type 2 diabetes.

The dipeptidyl peptidase-4 inhibitor alogliptin in combination with pioglitazone improves glycemic control, lipid profiles, and increases pancreatic insulin content in ob/ob mice.

The combination of two agents with different but complementary mechanisms of action is a logical approach for treating patients with type 2 diabetes. Thus, we evaluated chronic combination therapy with alogliptin, a highly selective dipeptidyl peptidase-4 inhibitor that enhances the action of incretins, and pioglitazone, a thiazolidinedione that improves peripheral and hepatic insulin sensitivity. Studies were designed to investigate the chronic metabolic and pancreatic effects of alogliptin (0.03%) plus pioglitazone (0.003%) combination treatment in obese ob/ob mice. After 4-5 weeks of treatment, alogliptin significantly increased plasma active glucagon-like peptide-1 levels up to 4.1-fold and decreased plasma glucagon up to 25%, whereas pioglitazone significantly increased plasma adiponectin up to 1.3-fold. Combination treatment exhibited a complementary effect, increasing plasma insulin levels by 3.2-fold (alogliptin alone, 1.6-fold; pioglitazone alone, 1.5-fold) and decreasing glycosylated hemoglobin by 2.3% (alogliptin alone, 1.0%; pioglitazone alone, 1.5%), and non-fasting and fasting plasma glucose by 37% and 62% (alogliptin alone, 17% and 24%; pioglitazone alone, 30% and 45%), respectively. Combination treatment also decreased plasma triglycerides by 67% and non-esterified fatty acids by 25% (alogliptin alone, 24% and 11%; pioglitazone alone, 54% and 8%). Moreover, combination treatment increased pancreatic insulin content by 2.2-fold (alogliptin alone, 1.3-fold; pioglitazone alone, 1.6-fold), with no significant changes in body weight. These results indicate that combination treatment with alogliptin and pioglitazone improved glycemic control, lipid profiles and increased pancreatic insulin content in ob/ob mice by preventing incretin inactivation and improving insulin resistance. These results provide a strong argument for using alogliptin in combination with pioglitazone.

Chronic administration of alogliptin, a novel, potent, and highly selective dipeptidyl peptidase-4 inhibitor, improves glycemic control and beta-cell function in obese diabetic ob/ob mice.

Dipeptidyl peptidase-4 (DPP-4) inhibitors improve glycemic control in patients with type 2 diabetes by increasing plasma active glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide levels. However, the effects of chronic DPP-4 inhibition on in vivo beta-cell function are poorly characterized. We thus evaluated the chronic effects of the DPP-4 inhibitor alogliptin benzoate (formerly SYR-322) on metabolic control and beta-cell function in obese diabetic ob/ob mice. Alogliptin (0.002%, 0.01%, or 0.03%) was administered in the diet to ob/ob mice for 2 days to determine effects on plasma DPP-4 activity and active GLP-1 levels and for 4 weeks to determine chronic effects on metabolic control and beta-cell function. After 2 days, alogliptin dose-dependently inhibited DPP-4 activity by 28-82% and increased active GLP-1 by 3.2-6.4-fold. After 4 weeks, alogliptin dose-dependently decreased glycosylated hemoglobin by 0.4-0.9%, plasma glucose by 7-28% and plasma triglycerides by 24-51%, increased plasma insulin by 1.5-2.0-fold, and decreased plasma glucagon by 23-26%, with neutral effects on body weight and food consumption. In addition, after drug washout, alogliptin (0.03% dose) increased early-phase insulin secretion by 2.4-fold and improved oral meal tolerance (25% decrease in glucose area under the concentration-time curve), despite the lack of measurable plasma DPP-4 inhibition. Importantly, alogliptin also increased pancreatic insulin content up to 2.5-fold, and induced intense insulin staining of islets, suggestive of improved beta-cell function. In conclusion, chronic treatment with alogliptin improved glycemic control, decreased triglycerides, and improved beta-cell function in ob/ob mice, and may exhibit similar effects in patients with type 2 diabetes.

A novel oxyiminoalkanoic acid derivative, TAK-559, activates human peroxisome proliferator-activated receptor subtypes.

A novel oxyiminoalkanoic acid derivative, TAK-559, (E)-4-[4-[(5-methyl-2-phenyl-1, 3-oxazol-4-yl)methoxy]benzyloxyimino]-4-phenylbutyric acid, was synthesized as a candidate of a new type of insulin-sensitizing agent. We report here activation of human peroxisome proliferator-activated receptor (hPPAR) subtypes by TAK-559. In a transient transactivation assay, TAK-559 was a potent hPPARgamma1 and hPPARalpha agonist with EC50 values of 31 and 67 nM, respectively. Furthermore, TAK-559 was a partial agonist for hPPARgamma1 with about 68% of maximal activation obtained with rosiglitazone (5-(4-(2-(methyl(2-pyridinyl)amino)ethoxy) benzyl)-1,3-thiazolidine-2,4-dione), a thiazolidinedione derivative, which is known as a PPARgamma agonist. PPARdelta was significantly activated at a high concentration (10 microM) of TAK-559. Competition-binding assays using radiolabeled ligand indicated that the transactivation of all hPPAR subtypes by TAK-559 was due to direct binding of TAK-559 to each subtype. We also demonstrated that TAK-559 acts to recruit the coactivator SRC-1 to each of hPPARgamma1 and hPPARalpha, and to dissociate the corepressor NCoR from each of hPPARgamma1 and hPPARalpha. Taken together, we conclude that TAK-559 is a dual agonist for hPPARgamma1 and hPPARalpha with nearly equal EC50 values, a partial agonist for hPPARgamma1, and has a rather slight agonist activity for hPPARdelta.

Studies on non-thiazolidinedione antidiabetic agents. 3. Preparation and biological activity of the metabolites of TAK-559.

Preparation and biological activity of the metabolites of the potent antihyperglycemic and antihyperlipidemic agent, (E)-4-(4-[(5-methyl-2-phenyl-1,3-oxazol-4-yl)methoxy]benzyloxyimino)-4-phenylbutyric acid (TAK-559) (1), were investigated. Metabolites M-I (2), M-II (3), M-III (4) and M-IV (5) were synthesized and their biological activities were evaluated by in vitro and in vivo experiments. Compounds 2-4 activate human peroxisome proliferator-activated receptor gamma one (hPPARgamma1) and hPPARalpha, but their activities are weaker than those of TAK-559 (1). Compound 5 only activates hPPARgamma1 weakly. TAK-559 (1) showed potent in vivo plasma glucose and triglyceride lowering activities in Wistar fatty rats after intraperitoneal administration, while its metabolites (2-5) showed comparatively weak activities.

Changes in glycated haemoglobin levels in diabetic rats measured with an automatic affinity HPLC.

1. The level of glycated haemoglobin (GHb) in diabetic rats was measured using a newly developed automatic high-performance liquid chromatography (HPLC) with a boronate affinity column that requires only 2.5 min per sample for analysis. 2. Levels of GHb were 2.7% in normal 7-week-old Sprague-Dawley rats. These levels increased gradually following the abrupt induction of hyperglycaemia by intravenous injection of streptozotocin (STZ), reaching a maximal level of 10.1% after 6 weeks. 3. Glycosylated haemoglobin (HbA1) levels measured by cation-exchange chromatography were also increased by STZ treatment, although HbA1 values were lower than GHb measured by affinity column HPLC. 4. In Wistar fatty rats, GHb levels declined gradually over 5 weeks following the administration of pioglitazone (0.75 or 2.25 mg/kg per day) as a food admixture, which reduced plasma glucose (PG) levels to normal levels within 1 week. Glycated haemoglobin levels after 5 weeks treatment with pioglitazone correlated better with the area under the curve for PG over the entire 5 week treatment period than with the PG level at the end of treatment. 5. In addition, GHb determined by affinity column HPLC correlated well with HbA1 measured by cation-exchange chromatography, although the GHb value was higher than the HbA1 value. 6. Glycated haemoglobin levels in db/db and KKAy mice were higher than those in control normoglycaemic animals and were also higher than HbA1 values measured by the cation-exchange method, although the two values did show good correlation. 7. These results indicate that the newly developed affinity column HPLC system is useful for evaluating total GHb levels in rats as an index of antidiabetic treatment.

[Hypertension and insulin resistance in obese type 2 diabetic Wistar fatty rat].

The most common features of insulin resistance syndrome are obesity, insulin resistance/hyperinsulinemia, dyslipidemia, impaired glucose intolerance, and hypertension. A causal link between hypertension and insulin resistance has not been clearly established, but several lines of evidence suggest that insulin resistance and the resultant hyperinsulinemia are causally related to hypertension. The Wistar fatty rat develops hyperglycemia, hyperlipidemia, and hyperinsulinemia as features of insulin resistance followed by slight hypertension. Several studies indicate that insulin resistance is one of the pivotal factors for hypertension in Wistar fatty rats. Further studies on Wistar fatty rat are expected to elucidate the mechanism of hypertension induced by insulin resistance and suggest on approach to treat hypertension in obese or type 2 diabetes.

Anti-obesity effects of a mixture of thiamin, arginine, caffeine, and citric acid in non-insulin dependent diabetic KK mice.

Anti-obesity effects of a mixture of thiamin, arginine, caffeine, and citric acid (TACC) were investigated in non-insulin dependent diabetic KK mice. Feeding of either arginine or caffeine significantly suppressed an increase in hepatic lipid contents in fasted-refed KK mice. In addition, each component admixed with a low-calorie diet effectively reduced adipose tissue weight in KK mice previously fed a high-calorie diet. The decrease in adipose tissue weight was greater with a mixture of arginine and caffeine, and much greater with TACC than with arginine or caffeine alone. Moreover, plasma insulin concentration was significantly lower in mice fed TACC than in control mice. The anti-obesity effects of TACC were also shown when it was supplemented with a tea beverage. Adipose tissue weight, hepatic triglyceride contents, and plasma insulin concentration were significantly lower in mice given TACC-supplemented tea than in control mice. These results suggest that TACC is effective in reducing adipose tissue mass as well as improving disorders in lipid metabolism.

Effects of combined pioglitazone and metformin on diabetes and obesity in Wistar fatty rats.

1. The effects of combined treatment with pioglitazone.HCl and metformin on diabetes and obesity were investigated in Wistar fatty rats, which are hyperglycaemic and hypertriglyceridaemic and have higher plasma levels of total ketone bodies than lean rats. 2. Plasma glucose was significantly decreased when pioglitazone.HCl or metformin was administered alone and combined treatment accentuated this decrease. The administration of pioglitazone.HCl, but not metformin, also decreased plasma levels of triglyceride and total ketone bodies. 3. The glycogen content of skeletal muscle was not increased by pioglitazone.HCl or metformin alone, but was increased by combined treatment (P=0.003, ANOVA). 4. Pioglitazone.HCl produced increased food intake and bodyweight in hyperphagic Wistar fatty rats; however, concurrent administration of metformin significantly ameliorated these pioglitazone.HCl-induced increases. 5. These results indicate that combined treatment with pioglitazone.HCl and metformin induces a marked hypoglycaemic effect accompanied by a reduction in plasma levels of total ketone bodies and prevention of excessive bodyweight gain in Wistar fatty rats. These favourable effects suggest that the combination would be beneficial in treating patients with type 2 diabetes.

Novel 5-substituted 2,4-thiazolidinedione and 2,4-oxazolidinedione derivatives as insulin sensitizers with antidiabetic activities.

Two novel classes of 2,4-thiazolidinediones and 2,4-oxazolidinediones with an omega-(azolylalkoxyphenyl)alkyl substituent at the 5-position were prepared and their antidiabetic effects were evaluated in two genetically obese and diabetic animal models, KKA(y) mice and Wistar fatty rats. A large number of the 2,4-thia(oxa)zolidinediones showed potent glucose- and lipid-lowering activities. The antidiabetic activities of the 2,4-oxazolidinediones were superior to those of the 2,4-thiazolidinediones. Among the compounds, both enantiomers of 5-[3-[4-[2-(2-furyl)-5-methyl-4-oxazolylmethoxy]-3-methoxyphenyl]propyl]-2,4-oxazolidinedione (64), one of the most interesting compounds in terms of activity, were synthesized by using an asymmetric O-acetylation of the corresponding alpha-hydroxyvalerate (26) with immobilized lipase, followed by cyclization of the oxazolidinedione ring. (R)-(+)-64 showed more potent glucose-lowering activity (effective dose (ED)25 = 0.561 mg/kg/d) than (S)-(-)-64 (ED25 > 1.5 mg/kg/d) or pioglitazone (ED25 = 6 mg/kg/d) in KKA(y) mice. It also exhibited a 10-fold more potent antidiabetic activity (ED25 = 0.05 mg/kg/d) than pioglitazone (ED25 = 0.5 mg/kg/d) in Wistar fatty rats. The antidiabetic effects of this compound are considered to be due to its potent agonistic activity for peroxisome proliferator-activated receptor gamma (EC(50) = 8.87 nM).

Novel 5-substituted-1H-tetrazole derivatives as potent glucose and lipid lowering agents.

A series of 5-(4-alkoxyphenylalkyl)-1H-tetrazole derivatives, containing an oxazole-based group at the alkoxy moiety, was prepared and their antidiabetic effects were evaluated in two genetically obese and diabetic animal models, KKAy mice and Wistar fatty rats. Syntheses were performed by cyclization of the corresponding nitrites reacting with azide compounds. A large number of the 5-(4-alkoxyphenylalkyl)-1H-tetrazoles showed potent glucose and lipid lowering activities in KKAy mice. In particular, 5-[3-[6-(5-methyl-2-phenyl-4-oxazolyl-methoxy)-3-pyridyl]propyl]-1H-tetrazole had potent glucose lowering activity (ED25=0.0839 mg x kg(-1) x d(-1)), being 72 times more active than pioglitazone hydrochloride (ED25=6.0 mg x kg(-1) x d(-1)). This compound also showed strong glucose lowering (ED25=0.0873 mg x kg(-1) x d(-1)) and lipid lowering effects (ED25=0.0277 mg x kg(-1) x d(-1)) in Wistar fatty rats. The antidiabetic effects of this compound are considered to be due to its potent agonistic activity for peroxisome proliferator-activated receptor gamma (PPARgamma) (EC50 = 6.75 nM).