Yasufumi Nagata

An Allosteric Activator of Glucokinase Impairs the Interaction of Glucokinase and Glucokinase Regulatory Protein and Regulates Glucose Metabolism

Glucokinase (GK) plays a key role in the control of blood glucose homeostasis. We identified a small molecule GK activator, compound A, that increased the glucose affinity and maximal velocity (Vmax) of GK. Compound A augmented insulin secretion from isolated rat islets and enhanced glucose utilization in primary cultured rat hepatocytes. In rat oral glucose tolerance tests, orally administrated compound A lowered plasma glucose elevation with a concomitant increase in plasma insulin and hepatic glycogen. In liver, GK activity is acutely controlled by its association to the glucokinase regulatory protein (GKRP). In order to decipher the molecular aspects of how GK activator affects the shuttling of GK between nucleus and cytoplasm, the effect of compound A on GK-GKRP interaction was further investigated. Compound A increased the level of cytoplasmic GK in both isolated rat primary hepatocytes and the liver tissues from rats. Experiments in a cell-free system revealed that compound A interacted with glucose-bound free GK, thereby impairing the association of GK and GKRP. On the other hand, compound A did not bind to glucose-unbound GK or GKRP-associated GK. Furthermore, we found that glucose-dependent GK-GKRP interaction also required ATP. Given the combined prominent role of GK on insulin secretion and hepatic glucose metabolism where the GK-GKRP mechanism is involved, activation of GK has a new therapeutic potential in the treatment of type 2 diabetes.

Prognostic value of LA volumes assessed by transthoracic 3D echocardiography: comparison with 2D echocardiography.

OBJECTIVES The hypothesis of this study was that minimal left atrial volume index (LAVImin) by 3-dimensional echocardiography (3DE) is the best predictor of future cardiovascular events. BACKGROUND Although maximal left atrial volume index (LAVImax) by 2-dimensional echocardiography (2DE) is a robust index for predicting prognosis, the prognostic value of LAVImin and the superiority of measurements by 3DE over 2DE have not been determined in a large group of patients. METHODS In protocol 1, we assessed age and sex dependency of LAVIs using 2DE and 3DE in 124 normal subjects and determined their cutoff values (mean + 2 SD). In protocol 2, 2-dimensional (2D) and 3-dimensional (3D) LAVImax/LAVImin were measured in 556 patients with high prevalence of cardiovascular disease. After excluding patients with atrial fibrillation, mitral valve disease, and age <18 years, 439 subjects were followed to record major adverse cardiovascular events (MACE). Patients were divided into 2 groups by the cutoff criteria of LAVI in each method. RESULTS In protocol 1, there was no significant age and sex dependency for each 2D and 3D LAVI. In protocol 2, during a mean of 2.5 years of follow-up, MACE developed in 88 patients, including 32 cardiac deaths. Kaplan-Meier survival analyses showed that all 4 LAVI cutoff criteria had significant predictive power of MACE. After variables were adjusted for clinical variables and left ventricular ejection fraction, all 4 methods were still independently and significantly associated with MACE, but 3D-derived LAVImin had the highest risk ratio. 3D LAVImin also had an incremental prognostic value over 3D LAVImax. CONCLUSIONS LAVIs by both 2DE and 3DE are powerful predictors of future cardiac events. 3D LAVImin tended to have a stronger and additive prognostic value than 3D LAVImax.

Discovery of novel 3,6-disubstituted 2-pyridinecarboxamide derivatives as GK activators

A novel class of 3,6-disubstituted 2-pyridinecarboxamide derivatives was designed based on X-ray analysis of the 2-aminobenzamide lead class. Subsequent chemical modification led to the discovery of potent GK activators which eliminate potential toxicity concerns associated with an aniline group of the lead structure. Compound 7 demonstrated glucose lowering effect in a rat OGTT model.

Structure-activity relationships of 3,5-disubstituted benzamides as glucokinase activators with potent in vivo efficacy

The optimization of our lead GK activator 2a to 3-[(1S)-2-hydroxy-1-methylethoxy]-5-[4-(methylsulfonyl)phenoxy]-N-1,3-thiazol-2-ylbenzamide (6g), a potent GK activator with good oral availability, is described, including to uncouple the relationship between potency and hydrophobicity. Following oral administration, this compound exhibited robust glucose lowering in diabetic model rodents.

Identification of novel and potent 2-amino benzamide derivatives as allosteric glucokinase activators

The identification and structure-activity-relationships (SARs) of novel 2-amino benzamide glucokinase activators are described. Compounds in this series were developed to be potent GK activators, and their binding mode to the GK protein was determined by crystal structure analysis. In vivo pharmacokinetic and acute in vivo efficacy studies of compound 18 are also described.

The design and optimization of a series of 2-(pyridin-2-yl)-1H-benzimidazole compounds as allosteric glucokinase activators

The optimization of a series of benzimidazole glucokinase activators is described. We identified a novel and potent achiral benzimidazole derivative as an allosteric GK activator. This activator was designed and synthesized via removal of the chiral center of the lead compound, 6-(N-acylpyrrolidin-2-yl)benzimidazole. The activator exhibited good PK profiles in rats and dogs, and significant hypoglycemic efficacy at 1 mg/kg po dosing in a rat OGTT model. The binding site and binding mode of the benzimidazole class of GKA with GK protein was confirmed by X-ray crystallographic analysis.

Direct comparison of cardiac magnetic resonance feature tracking and 2D/3D echocardiography speckle tracking for evaluation of global left ventricular strain.

AIMS Cardiac magnetic resonance (CMR) feature tracking (FT) with steady-state free precession (SSFP) has advantages over traditional myocardial tagging to analyse left ventricular (LV) strain. However, direct comparisons of CMRFT and 2D/3D echocardiography speckle tracking (2/3DEST) for measurement of LV strain are limited. The aim of this study was to investigate the feasibility and reliability of CMRFT and 2D/3DEST for measurement of global LV strain. METHODS AND RESULTS We enrolled 106 patients who agreed to undergo both CMR and 2D/3DE on the same day. SSFP images at multiple short-axis and three apical views were acquired. 2DE images from three levels of short-axis, three apical views, and 3D full-volume datasets were also acquired. Strain data were expressed as absolute values. Feasibility was highest in CMRFT, followed by 2DEST and 3DEST. Analysis time was shortest in 3DEST, followed by CMRFT and 2DEST. There was good global longitudinal strain (GLS) correlation between CMRFT and 2D/3DEST (r = 0.83 and 0.87, respectively) with the limit of agreement (LOA) ranged from ±3.6 to ±4.9%. Excellent global circumferential strain (GCS) correlation between CMRFT and 2D/3DEST was observed (r = 0.90 and 0.88) with LOA of ±6.8-8.5%. Global radial strain showed fair correlations (r = 0.69 and 0.82, respectively) with LOA ranged from ±12.4 to ±16.3%. CMRFT GCS showed least observer variability with highest intra-class correlation. CONCLUSION Although not interchangeable, the high GLS and GCS correlation between CMRFT and 2D/3DEST makes CMRFT a useful modality for quantification of global LV strain in patients, especially those with suboptimal echo image quality.

Discovery of novel 2-(pyridine-2-yl)-1H-benzimidazole derivatives as potent glucokinase activators

The synthesis and structure-activity-relationships (SARs) of novel 2-(pyridine-2-yl)-1H-benzimidazole glucokinase activators are described. Systematic modification of benzimidazole lead 5a identified from a high-throughput screening led to the discovery of a potent and metabolically stable glucokinase activator 16p(R) with greater structural diversity from GKAs reported to date. The compound also demonstrated acute oral glucose lowering efficacy in rat OGTT model.

Discovery of potent and orally active 3-alkoxy-5-phenoxy-N-thiazolyl benzamides as novel allosteric glucokinase activators

Identification and synthesis of novel 3-alkoxy-5-phenoxy-N-thiazolyl benzamides as glucokinase activators are described. Removal of an aniline structure of the prototype lead (2a) and incorporation of an alkoxy or phenoxy substituent led to the identification of 3-Isopropoxy-5-[4-(methylsulfonyl)phenoxy]-N-(4-methyl-1,3-thiazol-2-yl)benzamide (27e) as a novel, potent, and orally bioavailable GK activator. Rat oral glucose tolerance test indicated that 27e exhibited a glucose-lowering effect after 10 mg/kg oral administration.

Pharmacokinetic and Pharmacodynamic Properties of the Glucokinase Activator MK-0941 in Rodent Models of Type 2 Diabetes and Healthy Dogs

Glucokinase activators (GKAs) are small-molecule agents that enhance glucose sensing by pancreatic β cells and glucose metabolism by hepatocytes. There is strong interest in these agents as potential therapies for type 2 diabetes. Here, we report key pharmacokinetic and pharmacodynamic findings from preclinical studies of the GKA 3-[[6-(ethylsulfonyl)-3-pyridinyl]oxy]-5-[(1S)-2-hydroxy-1-methylethoxy]-N-(1-methyl-1H-pyrazol-3-yl)benzamide (MK-0941). Incubated in vitro with recombinant human glucokinase, 1 μM MK-0941 lowered the S0.5 of this enzyme for glucose from 6.9 to 1.4 mM and increased the maximum velocity of glucose phosphorylation by 1.5-fold. In 2.5 and 10 mM glucose, the EC50 values for activation of GK by MK-0941 were 0.240 and 0.065 μM, respectively. Treatment of isolated rat islets of Langerhans and hepatocytes with 10 μM MK-0941 increased insulin secretion by 17-fold and glucose uptake up to 18-fold, respectively. MK-0941 exhibited strong glucose-lowering activity in C57BL/6J mice maintained on a high-fat diet (HFD), db/db mice, HFD plus low-dose streptozotocin-treated mice, and nondiabetic dogs. In both mice and dogs, oral doses of MK-0941 were rapidly absorbed and rapidly cleared from the blood; plasma levels reached maximum within 1 h and fell thereafter with a half-life of ∼2 h. During oral glucose tolerance testing in dogs, MK-0941 reduced total area-under-the-curve postchallenge (0–2 h) plasma glucose levels by up to 48% compared with vehicle-treated controls. When administered twice daily to mice for 16 days, and once daily to the dog for 4 days, MK-0941 remained efficacious on successive days. These findings support further investigation of MK-0941 as a potential therapeutic agent for treatment of type 2 diabetes.