Determination of Region-Specific Roles of the M3 Muscarinic Acetylcholine Receptor in Gastrointestinal Motility.

BACKGROUND: The specific role of the M3 muscarinic acetylcholine receptor in gastrointestinal motility under physiological conditions is unclear, due to a lack of subtype-selective compounds. AIMS: The objective of this study was to determine the region-specific role of the M3 receptor in gastrointestinal motility. METHODS: We developed a novel positive allosteric modulator (PAM) for the M3 receptor, PAM-369. The effects of PAM-369 on the carbachol-induced contractile response of porcine esophageal smooth muscle and mouse colonic smooth muscle (ex vivo) and on the transit in mouse small intestine and rat colon (in vivo) were examined. RESULTS: PAM-369 selectively potentiated the M3 receptor under the stimulation of its orthosteric ligands without agonistic or antagonistic activity. Half-maximal effective concentrations of PAM activity for human, mouse, and rat M3 receptors were 0.253, 0.345, and 0.127 µM, respectively. PAM-369 enhanced carbachol-induced contraction in porcine esophageal smooth muscle and mouse colonic smooth muscle without causing any contractile responses by itself. The oral administration of 30 mg/kg PAM-369 increased the small intestinal transit in both normal motility and loperamide-induced intestinal dysmotility mice but had no effects on the colonic transit, although the M3 receptor mRNA expression is higher in the colon than in the small intestine. CONCLUSIONS: This study provided the first direct evidence that the M3 receptor has different region-specific roles in the motility function between the small intestine and colon in physiological and pathophysiological contexts. Selective PAMs designed for targeted subtypes of muscarinic receptors are useful for elucidating the subtype-specific function.

Free fatty acid receptor 1 agonist, MR1704, lowers blood glucose levels in rats unresponsive to the sulfonylurea, glibenclamide.

Preclinical Research & Development MR1704 is a selective G protein-coupled receptor 40/free fatty acid receptor 1 agonist, which exhibited favorable pharmacokinetic profiles and glucose-lowering effects in animal models. We studied the effects of MR1704 in a sulfonylurea-desensitized Sprague-Dawley rat model and evaluated the risk of pancreatic ß-cell exhaustion compared to that of glibenclamide in Zucker fatty rats. Rats fed ad libitum a diet containing 0.03% glibenclamide exhibited lower non-fasting blood glucose levels compared to those in rats fed a control diet during the first 6 days. However, the response to glibenclamide disappeared on day 9. In a rat oral glucose tolerance test (OGTT), MR1704 reduced the plasma glucose excursion, whereas glibenclamide did not show this effect. In Zucker fatty rats, oral administration of MR1704 reduced glucose excursion during the OGTT, and the effects of MR1704 were maintained after 2-week treatment. In contrast, the glucose-lowering effects of glibenclamide were diminished, and glucose tolerance was aggravated after 2-week treatment. These results indicated that MR1704 provided more sustainable effects compared to those of the sulfonylurea, glibenclamide suggesting that MR1704 may be an attractive therapeutic option for diabetic patients who are unresponsive to sulfonylurea treatment.

Nrf2 induces fibroblast growth factor 21 in diabetic mice.

Transcription factor Nrf2 (nuclear factor E2-related factor 2) is a master regulator of cellular defense system against oxidative and electrophilic stresses and is negatively regulated by an adaptor protein Keap1 (Kelch-like ECH-associated protein 1). Nrf2 also plays a pivotal role in metabolic homeostasis, such as lipid metabolism and energy expenditure as well as redox homeostasis. FGF21 (fibroblast growth factor 21) is known as a key mediator of glucose and lipid metabolism. Here, we found that Nrf2 is involved in FGF21 regulation in diabetic model mice. Nrf2 induction by genetic knockdown of Keap1 increased plasma FGF21 level and hepatic Fgf21 expression in diabetic db/db mice and high-calorie-diet-induced obesity model mice. Administration of CDDO-Im (oleanolic triterpenoid 1-[2-cyano-3,12-dioxooleane-1, 9(11)-dien-28-oyl] imidazole), a potent Nrf2 inducer, up-regulated plasma FGF21 level and hepatic Fgf21 expression in db/db mice, whereas CDDO-Im did not induce FGF21 in db/db mice with Nrf2 knockout background. Furthermore, in Keap1-knockdown db/db mice, Nrf2 enhanced expression of glucose- and lipid-metabolism-related genes in adipose tissues, which improved plasma lipid profiles. These results show that Nrf2 positively regulates FGF21 expression in diabetic mice. We propose that FGF21 is a potential efficacy biomarker that mediates metabolic regulation by the Keap1-Nrf2 system.

Transcription factor NF-E2-related factor 1 impairs glucose metabolism in mice.

Nrf1 (NF-E2-related factor 1) is a basic region leucine zipper-type transcription factor belonging to the CNC (cap-'n'-collar) family. Major pathophysiological contribution of Nrf1 remains unclear. As single nucleotide polymorphism rs3764400 in 5'-flanking region of NRF1 gene appears to associate with obesity, in this study, we focused on the Nrf1 function on metabolism. We found that the risk C allele of rs3764400 increased NRF1 gene transcriptional activity compared with the T allele in hepatoma cell lines. Therefore, we newly established Nrf1 transgenic (Nrf1-Tg) mouse lines and examined roles that Nrf1 plays on the obesity and metabolism. Unexpectedly, Nrf1 over-expression repressed bodyweight gain in both lean and diet-induced obesity mice. Of note, Nrf1-Tg mice showed rise in blood glucose levels; Nrf1 strongly reduced glucose infusion rate in euglycemic-hyperinsulinemic clamp test and increased blood glucose levels in insulin tolerance test, indicating that Nrf1 induces insulin resistance in mice. Nrf1 repressed insulin-regulated glycolysis-related gene expression and gave rise to loss of glucose-6-phosphate and fructose-6-phosphate contents in liver. Consistently, Nrf1 heterozygote improved impaired glucose regulations in diet-induced obesity model. These results showed that Nrf1 contributes to metabolic regulation, which gain-of-function develops diabetes mellitus in mice.

Acute Kidney Injury Caused by Evans Syndrome with Systemic Lupus Erythematosus and Systemic Sclerosis.

A 65-year-old woman with systemic sclerosis and systemic lupus erythematosus developed acute kidney injury (AKI), Coombs-positive autoimmune hemolytic anemia and autoimmune thrombocytopenia; therefore, she was diagnosed with Evans syndrome (ES). Intravascular hemolysis was suggested as the cause of AKI based on the presence of acute tubular injury and trace hemosiderin deposits on the renal biopsy. The renal function, hemolytic anemia and thrombocytopenia were restored by an increased dose of glucocorticoids, hemodialysis, and plasma exchange. Although ES with severe hemolytic anemia is very rare, it is important to detect possible renal dysfunction when encountering patients with severe hemolysis.

Zinc finger-zinc finger interaction between the transcription factors, GATA-1 and Sp1.

In contrast to the extensive understanding of the zinc finger-DNA interactions, less is known about zinc finger-zinc finger interactions. GATA-1 and Sp1 are transcription factors with zinc finger domains for DNA binding. The interaction between the GATA-1 and Sp1 zinc finger domains is important for synergistic transcriptional effects in erythroid genes. Despite the biological importance of the GATA-1 and Sp1 interaction, the molecular mechanism of the interaction remains unclear. We constructed a series of deletion mutants of the zinc finger domains of GATA-1 and Sp1 to identify the regions within the GATA-1 and Sp1 zinc finger domains that interact. The zinc finger-zinc finger interaction modes were also estimated from calorimetric measurements. This revealed that the interaction between the Sp1 and GATA-1 zinc finger domains was primarily electrostatic, and that the linker region of the Sp1 zinc fingers is important for the association with the GATA-1 zinc finger domains. We propose a new molecular mechanism for zinc finger-zinc finger interactions that should contribute to our understanding of the bio-functional role of the interaction between GATA-1 and Sp1.

Pharmacological characterization of a novel potent, selective, and orally active orexin 2 receptor antagonist, SDM-878.

AIMS: Recently, we identified a novel orexin 2 (OX2 ) receptor antagonist, SDM-878 (2-(3-(2-(1H-pyrazol-1-yl)nicotinoyl)-3,8-diazabicyclo[3.2.1]octan-8-yl)-3-methoxyisonicotinonitrile). The purpose of the present study is to characterize the in vitro and in vivo pharmacological effects of SDM-878. METHODS: The in vitro potency and selectivity of SDM-878 were examined in CHO cells that exhibit stable expression of human orexin 1 (OX1 ), human orexin 2 (OX2 ), rat OX1 , and rat OX2 receptors. Then, the plasma half-life, oral bioavailability, and brain penetration of SDM-878 were examined in rats. The in vivo effect of SDM-878 in rats was tested using electroencephalography (EEG). The target engagement of SDM-878 in the rat brain was examined using the antagonistic effect against hyperlocomotion caused by the intracerebroventricular administration of the OX2 receptor agonist, ADL-OXB ([Ala11 , d-Leu15 ]-orexin B). RESULTS: SDM-878 showed potent inhibitory activities for human and rat OX2 receptors with IC values of 10.6 and 8.8 nM, respectively, and approximately 1000-fold selectivity against the OX1 receptor. In rat studies, SDM-878 exhibited a relatively short half-life in plasma, oral bioavailability, and good brain penetration. These data indicate that SDM-878 is a potent, selective, orally active, and brain-penetrable OX2 receptor antagonist. In behavioral studies using rats, SDM-878 (100 mg/kg) antagonized hyperlocomotion caused by intracerebroventricular administration of ADL-OXB. SDM-878 exhibited a potent sleep-promoting effect at the same dose (100 mg/kg) in a rat EEG study. CONCLUSION: Our results suggest that SDM-878 is likely to be a good pharmacological tool for investigating the role of the OX2 receptor and may have therapeutic potential for the treatment of insomnia.

The novel Nrf2 inducer TFM-735 ameliorates experimental autoimmune encephalomyelitis in mice.

The transcription factor NF-E2-related factor 2 (Nrf2) is a key regulator of cellular defense mechanisms against oxidative stress. Multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system, is characterized by progressive demyelination and neurodegeneration induced by inflammation and oxidative stress. The induction of Nrf2 signaling has been shown to inhibit disease development and progression in the experimental autoimmune encephalomyelitis (EAE) model of MS in mice. In the present study, we performed a high-throughput screening assay using a chimeric construct of the N-terminal portion of Nrf2 fused to LacZ. Using this approach, we identified the novel Nrf2 inducer TFM-735. Using human primary cell profiling systems, we found that TFM-735 inhibited T cell proliferation and exerted immuno-modulatory effects by inhibiting the production of IL-6 and IL-17. TFM-735 also inhibited IL-17 secretion from human peripheral blood mononuclear cells stimulated with anti-CD3 and anti-CD28. In EAE mice treated with TFM-735, the expression of the Nrf2 target gene Nqo1 increased in the brain and spleen, disease severity was ameliorated, and plasma IL-17 levels decreased. Furthermore, TFM-735 inhibited luciferase activity in Wim-6 transgenic EAE mice expressing the human interleukin 6-luciferase (hIL6-BAC-Luc) reporter. Therefore, these findings indicate that TFM-735 is a potent Nrf2 inducer that inhibits inflammatory cytokine production and disease progression in mice with EAE and that TFM-735 is a promising therapeutic agent for MS.

A novel free fatty acid receptor 1 (GPR40/FFAR1) agonist, MR1704, enhances glucose-dependent insulin secretion and improves glucose homeostasis in rats.

Activation of G protein-coupled receptor 40/Free fatty acid receptor 1 (GPR40/FFAR1), which is highly expressed in pancreatic ß cells, is considered an important pharmacologic target for the treatment of type 2 diabetes mellitus. The aim of this study was to determine the effect of MR1704, a novel GPR40/FFAR1 agonist, on glucose homeostasis in rats. MR1704 is a highly potent and selective, orally bioavailable agonist with similar in vitro potencies among humans, mice, and rats. Treatment of rat islets with MR1704 increased glucose-dependent insulin secretion. Augmentation of glucose-dependent insulin secretion was abolished by adding a GPR40/FFAR1 antagonist. In mouse, insulinoma MIN6 cells, palmitic acid induced the activity of caspase 3/7 after a 72-h exposure, while pharmacologically active concentrations of MR1704 did not. In an oral glucose tolerance test in normal Sprague-Dawley rats, orally administered MR1704 (1-10 mg·kg-1 ) reduced plasma glucose excursion and enhanced insulin secretion, but MR1704 did not induce hypoglycemia, even at 300 mg·kg-1 , in fasted Sprague-Dawley rats. In addition, orally administered MR1704 reduced plasma glucose excursion and enhanced insulin secretion in diabetic Goto-Kakizaki rats. Oral administration of MR1704 once daily to Goto-Kakizaki rats reduced their blood glucose levels during a 5-week treatment period without reducing pancreatic insulin content; as a result, hemoglobin A1C levels significantly decreased. These results suggest that MR1704 improves glucose homeostasis through glucose-dependent insulin secretion with a low risk of hypoglycemia and pancreatic toxicity. MR1704 shows promise as a new, glucose-lowering drug to treat type 2 diabetes mellitus.

Intestine-targeted DGAT1 inhibition improves obesity and insulin resistance without skin aberrations in mice.

OBJECTIVE: Diacylglycerol O-acyltransferase 1 (DGAT1) catalyzes the final committed step in triglyceride biosynthesis. DGAT1 null mice are known to be resistant to diet-induced obesity, and more insulin sensitive relative to the wild-type; however, the mice exhibit abnormalities in the skin. This work determined whether the intestine-targeted DGAT1 inhibitor could improve obesity and insulin resistance without skin aberrations in mice. DESIGN AND METHODS: We synthesized 2 DGAT1 inhibitors: Compound A, described in the patent application from the Japan Tobacco, and Compound B (A-922500), reported by Abbott Laboratories. Both compounds were evaluated for inhibitory activities against DGAT1 enzymes and effects on the skin in mice in vivo. Compound B was further investigated for effects on obesity and insulin resistance in diet-induced-obese (DIO) mice. RESULTS: The 2 compounds comparably inhibited the DGAT1 enzyme activity and the cellular triglyceride synthesis in vitro, while they showed different distribution patterns in mice in vivo. Compound A, which distributed systemically, caused skin aberrations, while Compound B, which preferentially distributed to the intestine, improved obesity and insulin resistance without skin aberrations in DIO mice. CONCLUSIONS: Our results suggest that the intestine is the key tissue in which DGAT1 plays a role in promoting obesity and insulin resistance.