Vitamin B6 deficiency hyperactivates the noradrenergic system, leading to social deficits and cognitive impairment.

We have reported that a subpopulation of patients with schizophrenia have lower levels of vitamin B6 (VB6) in peripheral blood than do healthy controls. In a previous study, we found that VB6 level was inversely proportional to the patient's positive and negative symptom scale (PANSS) score for measuring symptom severity, suggesting that the loss of VB6 might contribute to the development of schizophrenia symptoms. In the present study, to clarify the relationship between VB6 deficiency and schizophrenia, we generated VB6-deficient (VB6(-)) mice through feeding with a VB6-lacking diet as a mouse model for the subpopulation of schizophrenia patients with VB6 deficiency. After feeding for 4 weeks, plasma VB6 level in VB6(-) mice decreased to 3% of that in control mice. The VB6(-) mice showed social deficits and cognitive impairment. Furthermore, the VB6(-) mice showed a marked increase in 3-methoxy-4-hydroxyphenylglycol (MHPG) in the brain, suggesting enhanced noradrenaline (NA) metabolism in VB6(-) mice. We confirmed the increased NA release in the prefrontal cortex (PFC) and the striatum (STR) of VB6(-) mice through in vivo microdialysis. Moreover, inhibiting the excessive NA release by treatment with VB6 supplementation into the brain and α2A adrenoreceptor agonist guanfacine (GFC) suppressed the increased NA metabolism and ameliorated the behavioral deficits. These findings suggest that the behavioral deficits shown in VB6(-) mice are caused by enhancement of the noradrenergic (NAergic) system.

Discovery of novel spiro[chromane-2,4'-piperidine] derivatives as potent and orally bioavailable G-protein-coupled receptor 119 agonists.

Herein, we describe the discovery, synthesis, and evaluation of a novel series of spiro[chromane-2,4'-piperidine] derivatives as G-protein-coupled receptor 119 agonists. Their initial design exploited the conformational restriction in the linker-to-tail moiety, which was a key concept in this study, to give lead compound 11 (EC50 = 369 nM, Emax = 82%). An extensive structure-activity relationship study resulted in the identification of the optimized drug candidate (R)-29 (EC50 = 54 nM, Emax = 181%). The defining structural features of the series were a terminal benzyl-type bulky substituent and a methylene linker between the sulfonyl and phenyl groups, both of which were in the head moiety as well as the spiro-type scaffold in the linker-to-tail moiety. An in vivo oral glucose-tolerance test using C57BL/6N mice showed that (R)-29 reduced glucose excursion at a dose of 3 mg/kg in a dose-dependent manner.

Optimization of a novel series of potent and orally bioavailable GPR119 agonists.

We describe the discovery and optimization of a novel series of furo[3,2-d]pyrimidines as G protein-coupled receptor 119 agonists. Agonistic activity of 4 (EC50=129nM) was improved by replacing the intramolecular hydrogen bond between the fluorine atom and the aniline hydrogen in the head moiety with a covalent C-C bond to enhance conformational restriction, which consequently gave a lead compound 12 (EC50=53nM). Optimized compound 26, which was identified by the further optimization of 12, exhibited potent activity (EC50=42nM) with improved clearance in liver microsomes and induced a 33% reduction in blood glucose area under the curve at a dose of 10mg/kg in an oral glucose tolerance test in C57BL/6N mice.