The flavonoid Sudachitin regulates glucose metabolism via PDE inhibition.

Sudachitin, a member of the flavonoid family, reportedly improves glucose metabolism after long-term administration, but details of the underlying mechanisms are unknown. We found that Sudachitin approximately doubles insulin secretion under high glucose concentrations in mouse pancreatic islets and MIN6 cells. When Sudachitin was orally administered to mice, early-phase insulin secretion was increased and a 30 % reduction in blood glucose levels was demonstrated 30 min after glucose loading. Insulin tolerance tests also showed Sudachitin to increase systemic insulin sensitivity. Additionally, we observed that Sudachitin raised intracellular cAMP levels in pancreatic islets. Phosphodiesterase (PDE) activity assays revealed Sudachitin to inhibit PDE activity and computer simulations predicted a high binding affinity between PDEs and Sudachitin. These findings suggest that Sudachitin enhances both insulin secretion and insulin sensitivity via an increase in intracellular cAMP resulting from PDE inhibition. These insights may facilitate understanding the mechanisms underlying the regulation of glucose metabolism by Sudachitin and other isoflavones.

E4BP4 in macrophages induces an anti-inflammatory phenotype that ameliorates the severity of colitis.

Macrophages are versatile cells of the innate immune system that work by altering their pro- or anti-inflammatory features. Their dysregulation leads to inflammatory disorders such as inflammatory bowel disease. We show that macrophage-specific upregulation of the clock output gene and transcription factor E4BP4 reduces the severity of colitis in mice. RNA-sequencing and single-cell analyses of macrophages revealed that increased expression of E4BP4 leads to an overall increase in expression of anti-inflammatory genes including Il4ra with a concomitant reduction in pro-inflammatory gene expression. In contrast, knockout of E4BP4 in macrophages leads to increased proinflammatory gene expression and decreased expression of anti-inflammatory genes. ChIP-seq and ATAC-seq analyses further identified Il4ra as a target of E4BP4, which drives anti-inflammatory polarization in macrophages. Together, these results reveal a critical role for E4BP4 in regulating macrophage inflammatory phenotypes and resolving inflammatory bowel diseases.

Effects of pemafibrate on left ventricular diastolic function in patients with type 2 diabetes mellitus: a pilot study.

Aims/introduction: Diabetic cardiomyopathy (DCM) is characterized predominantly by diastolic dysfunction. The multiple mechanisms underlying DCM include altered energy substrate utilization. Recent studies indicate that PPARα plays an important role in the pathogenesis of lipotoxic cardiomyopathy. Pemafibrate is known to be a selective PPARα modulator (SPPARMα). We thus investigated the effects of pemafibrate on cardiac diastolic function in patients with type 2 diabetes. Materials and methods: Seventeen patients with type 2 diabetes (T2D) and hypertriglyceridemia were screened and treated with pemafibrate at a dose of 0.2 mg/day for 8-16 weeks. Fourteen patients were eligible for analysis. Echocardiography was used for assessment of diastolic function. Early diastolic filling velocity (E), late atrial filling velocity (A) and the E/A ratio were included in this study. Peak early diastolic annular velocities (e') were also assessed using color tissue Doppler images. The primary endpoints were changes in the ratio of E to A (E/A), e', and the ratio of E to e' (E/e') from baseline. Results: Pemafibrate significantly increased average e' (7.24 ± 0.58 vs 7.94 ± 0.67, p = 0.019) and a significant reduction in E/e' (9.01 ± 0.94 vs 8.20 ± 0.91, p = 0.041). The increase in e' was significantly related to increases in fasting blood glucose (r = 0.607, p = 0.021) and non-esterified fatty acid (r = 0.592, p = 0.026). Conclusion: Pemafibrate improved diastolic function in patients with T2D and hypertriglyceridemia, suggesting that PPARα activation by pemafibrate prevents the development of DCM at an early stage.

Gsk-3-Mediated Proteasomal Degradation of ATF4 Is a Proapoptotic Mechanism in Mouse Pancreatic ß-Cells.

Endoplasmic reticulum (ER) stress is a key pathogenic factor in type 1 and 2 diabetes. Glycogen synthase kinase 3 (Gsk-3) contributes to ß-cell loss in mice. However, the mechanism by which Gsk-3 leads ß-cell death remains unclear. ER stress was pharmacologically induced in mouse primary islets and insulinoma cells. We used insulinoma cells derived from Akita mice as a model of genetic ER stress. Gsk-3 activity was blocked by treating with Gsk-3 inhibitors or by introducing catalytically inactive Gsk-3ß. Gsk-3 inhibition prevented proteasomal degradation of activating transcriptional factor 4 (ATF4) and alleviated apoptosis. We found that ATF4-S214 was phosphorylated by Gsk-3, and that this was required for a binding of ATF4 with ßTrCP, which mediates polyubiquitination. The anti-apoptotic effect of Gsk-3 inhibition was attenuated by introducing DN-ATF4 or by knockdown of ATF4. Mechanistically, Gsk-3 inhibition modulated transcription targets of ATF4 and in turn facilitated dephosphorylation of eIF2α, altering the protein translational dynamism under ER stress. These observations were reproduced in the Akita mouse-derived cells. Thus, these results reveal the role of Gsk-3 in the regulation of the integrated stress response, and provide a rationale for inhibiting this enzyme to prevent ß-cell death under ER stress conditions.

Metabolic state switches between morning and evening in association with circadian clock in people without diabetes.

AIMS/INTRODUCTION: Understanding morning-evening variation in metabolic state is critical for managing metabolic disorders. We aimed to characterize this variation from the viewpoints of insulin secretion and insulin sensitivity, including their relevance to the circadian rhythm. MATERIALS AND METHODS: A total of 14 and 10 people without diabetes were enrolled, and underwent a 75-g oral glucose tolerance test (OGTT) and hyperinsulinemic-euglycemic clamp study, respectively. Participants completed the OGTT or hyperinsulinemic-euglycemic clamp at 08.00 hours and 20.00 hours in random order. Before each study, hair follicles were collected. In mice, phosphorylation levels of protein kinase B were examined in the liver and muscle by western blotting. RESULTS: Glucose tolerance was better at 08 .00 hours, which was explained by the higher 1-h insulin secretion on OGTT and increased skeletal muscle insulin sensitivity on hyperinsulinemic-euglycemic clamp. Hepatic insulin sensitivity, estimated by the hepatic insulin resistance index on OGTT, was better at 20.00 hours. The 1-h insulin secretion and hepatic insulin resistance index correlated significantly with Per2 messenger ribonucleic acid expression. The change (evening value - morning value) in the glucose infusion rate correlated significantly with the change in non-esterified fatty acid, but not with clock gene expressions. The change in non-esterified fatty acid correlated significantly with E4bp4 messenger ribonucleic acid expression and the change in cortisol. In mice, phosphorylation of protein kinase B was decreased in the liver and increased in muscle in the beginning of the active period as, expected from the human study. CONCLUSIONS: Glucose metabolism in each tissue differed between the morning and evening, partly reflecting lipid metabolism, clock genes and cortisol levels. Deeper knowledge of these associations might be useful for ameliorating metabolic disorders.

Ultrasound analysis of gray-scale median value of carotid plaques is a useful reference index for cerebro-cardiovascular events in patients with type 2 diabetes.

AIMS/INTRODUCTION: Measurements of plaque echogenicity, the gray-scale median (GSM), were shown to correlate inversely with risk factors for cerebro-cardiovascular disease (CVD). The eicosapentaenoic acid (EPA)/arachidonic acid (AA) ratio is a potential predictor of CVD risk. In the present study, we assessed the usefulness of carotid plaque GSM values and EPA/AA ratios in atherosclerotic diabetics. MATERIALS AND METHODS: A total of 84 type 2 diabetics with carotid artery plaques were enrolled. On admission, platelet aggregation and lipid profiles, including EPA and AA, were examined. Using ultrasound, mean intima media thickness and plaque score were measured in carotid arteries. Plaque echogenicity was evaluated using computer-assisted quantification of GSM. The patients were then further observed for approximately 3 years. RESULTS: Gray-scale median was found to be a good marker of CVD events. On multivariate logistic regression analysis, GSM <32 and plaque score ≥5 were significantly associated with past history and onset of CVD during the follow-up period, the odds ratios being 7.730 (P = 0.014) and 4.601 (P = 0.046), respectively. EPA/AA showed a significant correlation with GSM (P = 0.012) and high-density lipoprotein cholesterol (P = 0.039), and an inverse correlation with platelet aggregation (P = 0.046) and triglyceride (P = 0.020). Although most patients with CVD had both low GSM and low EPA/AA values, an association of EPA/AA with CVD events could not be statistically confirmed. CONCLUSIONS: The present results suggest the GSM value to be useful as a reference index for CVD events in high-risk atherosclerotic diabetics. Associations of the EPA/AA ratio with known CVD risk factors warrant a larger and more extensive study to show the usefulness of this parameter.

Clock-controlled output gene Dbp is a regulator of Arnt/Hif-1ß gene expression in pancreatic islet ß-cells.

Aryl hydrocarbon receptor nuclear translocator (ARNT)/hypoxia inducible factor-1ß (HIF-1ß) has emerged as a potential determinant of pancreatic ß-cell dysfunction and type 2 diabetes in humans. An 82% reduction in Arnt expression was observed in islets from type 2 diabetic donors as compared to non-diabetic donors. However, few regulators of Arnt expression have been identified. Meanwhile, disruption of the clock components CLOCK and BMAL1 is known to result in hypoinsulinemia and diabetes, but the molecular details remain unclear. In this study, we identified a novel molecular connection between Arnt and two clock-controlled output genes, albumin D-element binding protein (Dbp) and E4 binding protein 4 (E4bp4). By conducting gene expression studies using the islets of Wfs1(-/-) A(y)/a mice that develop severe diabetes due to ß-cell apoptosis, we demonstrated clock-related gene expressions to be altered in the diabetic mice. Dbp mRNA decreased by 50%, E4bp4 mRNA increased by 50%, and Arnt mRNA decreased by 30% at Zeitgever Time (ZT) 12. Mouse pancreatic islets exhibited oscillations of clock gene expressions. E4BP4, a D-box negative regulator, oscillated anti-phase to DBP, a D-box positive regulator. We also found low-amplitude circadian expression of Arnt mRNA, which peaked at ZT4. Over-expression of DBP raised both mRNA and protein levels of ARNT in HEK293 and MIN6 cell lines. Arnt promoter-driven luciferase reporter assay in MIN6 cells revealed that DBP increased Arnt promoter activity by 2.5-fold and that E4BP4 competitively inhibited its activation. In addition, on ChIP assay, DBP and E4BP4 directly bound to D-box elements within the Arnt promoter in MIN6 cells. These results suggest that in mouse pancreatic islets mRNA expression of Arnt fluctuates significantly in a circadian manner and that the down-regulation of Dbp and up-regulation E4bp4 contribute to direct suppression of Arnt expression in diabetes.

Clinical impact of thymidine phosphorylase expression in gastric cancer.

Thymidine phosphorylase (dThdPase) is an enzyme that is involved in pyrimidine nucleoside metabolism and DNA synthesis and converts 5'-deoxy-5-fluorouridine (5'-DFUR) to 5-fluorouracil (5-FU). The aim of this study was to elucidate the relationship between dThdPase expression and biological malignancy, prognosis, and sensitivity to postoperative chemotherapy, using immunohistochemical staining. We studied 148 patients with gastric cancer who underwent surgery at Department of Surgery II in Oita Medical University between 1990 and 1999. Immunohistochemical expression of dThdPase was correlated to clinicopathological factors and postoperative survival. Tumor tissue was dThdPase-positive in 112 patients. The results suggested a relationship between the degree of histological differentiation and dThdPase expression (p=0.0697). Examination of dThdPase expression based on the site of the tumor revealed that the groups with upper or lower gastric cancer included a significantly greater number of dThdPase-positive patients (p=0.0011). Analysis of the patients as a whole showed no significant difference between the survival. In the chemotherapy group, the dThdPase-positive patients tended to have a more favorable prognosis than the dThdPase-negative patients (p=0.0578). The results suggest that postoperative adjuvant chemotherapy that makes use of FU metabolic pathways may improve prognosis in patients with dThdPase-positive gastric cancer.