Dapagliflozin administration to a mouse model of type 2 diabetes induces DNA methylation and gene expression changes in pancreatic islets.

Decreased pancreatic ß-cell volume is a serious problem in patients with type 2 diabetes mellitus, and there is a need to establish appropriate treatments. Increasingly, sodium/glucose cotransporter 2 (SGLT2) inhibitors, which have a protective effect on pancreatic ß-cells, are being prescribed to treat diabetes; however, the underlying mechanism is not well understood. We previously administered SGLT2 inhibitor dapagliflozin to a mouse model of type 2 diabetes and found significant changes in gene expression in the early-treated group, which led us to hypothesize that epigenetic regulation was a possible mechanism of these changes. Therefore, we performed comprehensive DNA methylation analysis by methylated DNA immunoprecipitation using isolated pancreatic islets after dapagliflozin administration to diabetic model mice. As a result, we identified 31 genes with changes in expression due to DNA methylation changes. Upon immunostaining, cystic fibrosis transmembrane conductance regulator and cadherin 24 were found to be upregulated in islets in the dapagliflozin-treated group. These molecules may contribute to the maintenance of islet morphology and insulin secretory capacity, suggesting that SGLT2 inhibitors' protective effect on pancreatic ß-cells is accompanied by DNA methylation changes, and that the effect is long-term and not temporary. In future diabetes care, SGLT2 inhibitors may be expected to have positive therapeutic effects, including pancreatic ß-cell protection.

A High Fibrosis-4 Index is Associated with a Reduction in the Estimated Glomerular Filtration Rate in Non-obese Japanese Patients with Type 2 Diabetes Mellitus.

Liver fibrosis is associated with non-alcoholic fatty liver disease (NAFLD), and one of the most important risk factors for NAFLD is type 2 diabetes (T2DM). The Fibrosis-4 (FIB-4) index, a noninvasive liver fibrosis score, has been found to be useful for estimating liver fibrosis. Because individuals with non-obese NAFLD were recently reported to be metabolically unhealthy and have a higher risk of T2DM than individuals with obese NAFLD, we hypothesized that the clinical factors related to a high FIB-4 index would differ between non-obese and obese Japanese T2DM patients. Accordingly, we examined the relationship between clinical factors and the FIB-4 index in non-obese and obese Japanese patients with T2DM. We divided 265 patients into two groups by BMI level - a non-obese group (n = 149) and an obese group (n = 116) - and examined the correlation between the FIB-4 index and clinical parameters. Single regression analysis revealed that a high FIB-4 index was correlated with a reduction in the estimated glomerular filtration rate and hypertension in the non-obese group. Importantly, multiple regression analysis showed that only a reduction in the estimated glomerular filtration rate was significantly associated with a high FIB-4 index in the non-obese group. These results demonstrated that non-obese T2DM patients with a high FIB-4 index might be at risk of kidney dysfunction. Our findings may enable the more appropriate treatment of T2DM patients based on BMI level.

Association of short-term changes in HbA1c with body composition and the importance of muscle maintenance in patients with Type 2 diabetes.

AIMS: This study aimed to investigate the relationship between changes in glucose metabolism and body composition in patients with diabetes. METHODS: We included 380 patients with type 2 diabetes, who underwent bioelectrical impedance analysis, in this longitudinal study. Changes in HbA1c (ΔHbA1c) levels and body composition indices were compared between baseline and 6 months. A multivariate analysis was performed to examine the relationship between ΔHbA1c and changes in body composition. RESULTS: HbA1c levels were significantly decreased at 6 months (P < 0.01), but there was no significant change in BMI. A linear multiple regression analysis showed that ΔHbA1c was negatively correlated with changes in muscle mass (ß = -0.18; P = 0.047) and bone mineral content (ß = -0.28; P < 0.001), but there was no significant association between ΔHbA1c levels and a change in body fat percentage. CONCLUSIONS: This study shows a limited association between short-term changes in glucose metabolism and changes in body composition in patients with type 2 diabetes. Therefore, interventions aimed at reducing adiposity may not affect glucose metabolism in the short term, while interventions focused on maintaining or enhancing muscle mass and bone mineral content may play an important role in diabetes management.

Dietary Intervention for Control of Clinical Symptom in Patients with Systemic Metal Allergy: A Single Center Randomized Controlled Clinical Study.

Patients with eczema with a systemic metal allergy, such as nickel (Ni), cobalt (Co), chromium (Cr), and tin (Sn), should pay attention to symptomatic exacerbation by excessive metal intake in food. However, dietary intervention for systemic metal allergy can be difficult. In this study, we evaluated the effect of dietary intervention by a registered dietitian on clinical symptoms in patients with a systemic metal allergy. Forty-four patients with cutaneous symptoms who were diagnosed with a metal allergy were randomly assigned to the dietary intervention group (DI group, n = 29) by a registered dietitian or the control group (C group, n = 15). The DI group was individually instructed by a registered dietitian how to implement a metal-restricted diet and then evaluated 1 month later. Dermatologists treated skin lesions of patients in both groups. Skin symptoms assessed by the Severity Scoring of Atopic Dermatitis (SCORAD) index, blood tests, and urinary metal excretion were evaluated. The DI group showed decreased Ni, Co, Cr, and Sn intake (all P ≤ 0.05), and an improved total SCORAD score, eczema area, erythema, edema/papulation, oozing/crust, excoriation, lichenization and dryness after 1 month of intervention compared with before the intervention (all P ≤ 0.05). However, the C group showed decreased Ni and Sn intake and an improved oozing/crust score (all P < 0.05). It showed the effective reduction of dietary metal intake controls dermatitis due to a metal allergy. In conclusion, dietary intervention by a registered dietitian is effective in improving skin symptoms with a reduction in metal intake.

Hepatic FASN deficiency differentially affects nonalcoholic fatty liver disease and diabetes in mouse obesity models.

Nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes are interacting comorbidities of obesity, and increased hepatic de novo lipogenesis (DNL), driven by hyperinsulinemia and carbohydrate overload, contributes to their pathogenesis. Fatty acid synthase (FASN), a key enzyme of hepatic DNL, is upregulated in association with insulin resistance. However, the therapeutic potential of targeting FASN in hepatocytes for obesity-associated metabolic diseases is unknown. Here, we show that hepatic FASN deficiency differentially affects NAFLD and diabetes depending on the etiology of obesity. Hepatocyte-specific ablation of FASN ameliorated NAFLD and diabetes in melanocortin 4 receptor-deficient mice but not in mice with diet-induced obesity. In leptin-deficient mice, FASN ablation alleviated hepatic steatosis and improved glucose tolerance but exacerbated fed hyperglycemia and liver dysfunction. The beneficial effects of hepatic FASN deficiency on NAFLD and glucose metabolism were associated with suppression of DNL and attenuation of gluconeogenesis and fatty acid oxidation, respectively. The exacerbation of fed hyperglycemia by FASN ablation in leptin-deficient mice appeared attributable to impairment of hepatic glucose uptake triggered by glycogen accumulation and citrate-mediated inhibition of glycolysis. Further investigation of the therapeutic potential of hepatic FASN inhibition for NAFLD and diabetes in humans should thus consider the etiology of obesity.

Chlorogenic Acid and Caffeine in Coffee Restore Insulin Signaling in Pancreatic Beta Cells.

The incidence of type 2 diabetes is reported to be lower in frequent coffee drinkers than in non-coffee drinkers. To elucidate the mechanism by which coffee prevents the onset of type 2 diabetes, we analyzed how caffeine and chlorogenic acid, which are components of coffee, alter insulin signaling in MIN6 cells, a mouse pancreatic Β cell line. The results showed that caffeine improved insulin signaling under endoplasmic reticulum stress, and chlorogenic acid protected pancreatic Β cells by enhancing the expression of insulin receptor substrate 2 via cAMP response element-binding protein and promoting insulin signaling downstream of insulin receptor substrate 2. In addition, chlorogenic acid was a potent antioxidant for the protection of pancreatic Β cells. Furthermore, in vivo and in vitro analyses revealed that the pancreatic Β cell-protective effect of chlorogenic acid was mediated by the alleviation of endoplasmic reticulum stress. The results suggest that these components of coffee have the potential to reduce the pathogenesis of type 2 diabetes and improve pancreatic Β cell insufficiency.

l-Asparaginase regulates mTORC1 activity via a TSC2-dependent pathway in pancreatic beta cells.

Eif2ak4, a susceptibility gene for type 2 diabetes, encodes GCN2, a molecule activated by amino acid deficiency. Mutations or deletions in GCN2 in pancreatic ß-cells increase mTORC1 activity by decreasing Sestrin2 expression in a TSC2-independent manner. In this study, we searched for molecules downstream of GCN2 that suppress mTORC1 activity in a TSC2-dependent manner. To do so, we used a pull-down assay to identify molecules that competitively inhibit the binding of the T1462 phosphorylation site of TSC2 to 14-3-3. l-asparaginase was identified. Although l-asparaginase is frequently used as an anticancer drug for acute lymphoblastic leukemia, little is known about endogenous l-asparaginase. l-Asparaginase, which is expressed downstream of GCN2, was found to bind 14-3-3 and thereby to inhibit its binding to the T1462 phosphorylation site of TSC2 and contribute to TSC2 activation and mTORC1 inactivation upon TSC2 dephosphorylation. Further investigation of the regulation of mTORC1 activity in pancreatic ß-cells by l-asparaginase should help to elucidate the mechanism of diabetes and insulin secretion failure during anticancer drug use.

Roles of mTOR in the Regulation of Pancreatic ß-Cell Mass and Insulin Secretion.

Pancreatic ß-cells are the only type of cells that can control glycemic levels via insulin secretion. Thus, to explore the mechanisms underlying pancreatic ß-cell failure, many reports have clarified the roles of important molecules, such as the mechanistic target of rapamycin (mTOR), which is a central regulator of metabolic and nutrient cues. Studies have uncovered the roles of mTOR in the function of ß-cells and the progression of diabetes, and they suggest that mTOR has both positive and negative effects on pancreatic ß-cells in the development of diabetes.

Regulation of Pancreatic ß-Cell Mass by Gene-Environment Interaction.

The main pathogenic mechanism of diabetes consists of an increase in insulin resistance and a decrease in insulin secretion from pancreatic ß-cells. The number of diabetic patients has been increasing dramatically worldwide, especially in Asian people whose capacity for insulin secretion is inherently lower than that of other ethnic populations. Causally, changes of environmental factors in addition to intrinsic genetic factors have been considered to have an influence on the increased prevalence of diabetes. Particular focus has been placed on "gene-environment interactions" in the development of a reduced pancreatic ß-cell mass, as well as type 1 and type 2 diabetes mellitus. Changes in the intrauterine environment, such as intrauterine growth restriction, contribute to alterations of gene expression in pancreatic ß-cells, ultimately resulting in the development of pancreatic ß-cell failure and diabetes. As a molecular mechanism underlying the effect of the intrauterine environment, epigenetic modifications have been widely investigated. The association of diabetes susceptibility genes or dietary habits with gene-environment interactions has been reported. In this review, we provide an overview of the role of gene-environment interactions in pancreatic ß-cell failure as revealed by previous reports and data from experiments.

Effect of a Combined Exercise and Cognitive Activity Intervention on Cognitive Function in Community-dwelling Older Adults: A Pilot Randomized Controlled Trial.

OBJECTIVE: The purpose of this study is to investigate the effect of an intervention combining exercise and cognitive activity on cognitive function in healthy older adults. METHODS: This pilot randomized controlled trial recruited 33 eligible, healthy communitydwelling older adults (mean age, 77.1 years old; women, 51.5%), who were divided into intervention and waitlist control groups. The intervention group was engaged weekly in a group activity comprising exercise and discussions of homework, which included reading aloud, simple arithmetic, and simple activities, like spotting differences, for cognitive stimulation. They were also required to complete cognitive activity homework twice a week. The waitlist control group received no intervention. The main outcomes were cognitive function assessed using the Mini-Mental State Examination, delayed recall score on the Logical Memory IIA of the Wechsler Memory Scale Revised, Trail Making Test, and digit symbol substitution test. RESULTS: According to the results, Mini-Mental State Examination scores were maintained in the intervention group but declined in the control group [Mean change in outcomes in control group (95% confidence interval): -1.68 (-2.89 to -0.48)]. Additional mean change in outcomes in intervention group were found [1.68 (0.02 to 3.35)]. CONCLUSIONS: Interventions combining exercise and cognitive activity can be helpful for preserving cognitive function in healthy older adults.

Oral administration of D-serine prevents the onset and progression of colitis in mice.

BACKGROUND: L-amino acids are the predominant forms of organic molecules on the planet, but recent studies have revealed that various foods contain D-amino acids, the enantiomers of L-amino acids. Though diet plays important roles in both the development and progression of inflammatory bowel disease (IBD), to our best knowledge, there has been no report on any potential interactions between D-amino acids and IBD. In this report, we aim to assess the effects of D-serine in a murine model of IBD. MATERIALS AND METHODS: To induce chronic colitis, naïve CD4 T cells (CD4+ CD62+ CD44low) from wild-type mice were adoptively transferred into Rag2-/- mice, after or before the mice were orally administered with D-serine. In vitro proliferation assays were performed to assess naïve CD4 T cell activation under the Th-skewing conditions in the presence of D-serine. RESULTS: Mice treated with D-serine prior to the induction of colitis exhibited a reduction in T-cell infiltration into the lamina propria and colonic inflammation that were not seen in mice fed with water alone or L-serine. Moreover, D-serine suppressed the progression of chronic colitis when administered after the disease induction. Under in vitro conditions, D-serine suppressed the proliferation of activated CD4 T cells and limited their ability to differentiate to Th1 and Th17 cells. CONCLUSION: Our results suggest that D-serine not only can prevent, but also has efficacious effects as a treatment for IBD.

Glutamate is an essential mediator in glutamine-amplified insulin secretion.

AIMS/INTRODUCTION: Glutamine is the most abundant amino acid in the circulation. In this study, we investigated cell signaling in the amplification of insulin secretion by glutamine. MATERIALS AND METHODS: Clonal pancreatic ß-cells MIN6-K8, wild-type B6 mouse islets, glutamate dehydrogenase (GDH) knockout clonal ß-cells (Glud1KOßCL), and glutamate-oxaloacetate transaminase 1 (GOT1) knockout clonal ß-cells (Got1KOßCL) were studied. Insulin secretion from these cells and islets was examined under various conditions, and intracellular glutamine metabolism was assessed by metabolic flux analysis. Intracellular Ca2+ concentration ([Ca2+ ]i ) was also measured. RESULTS: Glutamine dose-dependently amplified insulin secretion in the presence of high glucose in both MIN6-K8 cells and Glud1KOßCL. Inhibition of glutaminases, the enzymes that convert glutamine to glutamate, dramatically reduced the glutamine-amplifying effect on insulin secretion. A substantial amount of glutamate was produced from glutamine through direct conversion by glutaminases. Glutamine also increased [Ca2+ ]i at high glucose, which was abolished by inhibition of glutaminases. Glutamic acid dimethylester (dm-Glu), a membrane permeable glutamate precursor that is converted to glutamate in cells, increased [Ca2+ ]i as well as induced insulin secretion at high glucose. These effects of glutamine and dm-Glu were dependent on calcium influx. Glutamine also induced insulin secretion in clonal ß-cells MIN6-m14, which otherwise exhibit no insulin secretory response to glucose. CONCLUSIONS: Glutamate converted from glutamine is an essential mediator that enhances calcium signaling in the glutamine-amplifying effect on insulin secretion. Our data also suggest that glutamine exerts a permissive effect on glucose-induced insulin secretion.

Histone deacetylase 6 regulates insulin signaling in pancreatic ß cells.

The reduction of pancreatic ß cell mass is one of the key factors for the onset of type 2 diabetes. Many reports have indicated that insulin signaling is important for type 2 diabetes, but the mechanism by which insulin signaling is altered in pancreatic ß cells remains unclear. This study was designed to examine the role of histone deacetylases (HDACs) in the regulation of insulin signaling in pancreatic ß cells. We found that insulin signaling was downregulated by inhibition of HDAC6. HDAC6 expression was specifically observed in pancreatic ß cells and was decreased in the pancreatic islets of a type 2 diabetes mouse model. When a mouse pancreatic ß cell line (MIN6 cells) was treated with palmitic acid to mimic the effect of a high-fat diet on pancreatic ß cells, HDAC6 was imported into the nucleus. These results suggest that HDAC6 plays an important role in the regulation of insulin signaling in pancreatic ß cells. Therefore, clarifying the regulation of insulin signaling by HDAC6 may be a valuable approach for the treatment of type 2 diabetes.

GCN2 regulates pancreatic ß cell mass by sensing intracellular amino acid levels.

EIF2AK4, which encodes the amino acid deficiency-sensing protein GCN2, has been implicated as a susceptibility gene for type 2 diabetes in the Japanese population. However, the mechanism by which GCN2 affects glucose homeostasis is unclear. Here, we show that insulin secretion is reduced in individuals harboring the risk allele of EIF2AK4 and that maintenance of GCN2-deficient mice on a high-fat diet results in a loss of pancreatic ß cell mass. Our data suggest that GCN2 senses amino acid deficiency in ß cells and limits signaling by mechanistic target of rapamycin complex 1 to prevent ß cell failure during the consumption of a high-fat diet.

En face slab optical coherence tomography imaging successfully monitors progressive degenerative changes in the innermost layer of the diabetic retina.

OBJECTIVE: To evaluate the usefulness of en face slab optical coherence tomography (OCT) imaging for monitoring diabetic retinal neurodegeneration with supporting animal experimental data. RESEARCH DESIGN AND METHODS: We retrospectively examined 72 diabetic eyes over 3 years using Cirrus-HD OCT. Two-dimensional en face slab OCT images of the innermost retina were reconstructed and graded according to the ratio of dark area to total area, and relative red, green, and blue color area ratios were calculated and used as indexes for each en face slab OCT image. Values from en face OCT images were used for statistical analyses. To obtain insight into the pathogenesis of diabetic retinal neurodegeneration, we used the InsPr-Cre;Pdk1flox/flox diabetic mouse model. RESULTS: Both OCT grade and relative red color area ratio significantly increased with the advancing stage of diabetic retinopathy (p=0.018 and 0.006, respectively). After a mean follow-up period of 4.6 years, the trend was unchanged in the analyses of 42 untreated eyes (p<0.001 and 0.001, respectively). Visual acuity showed a weak but significant negative correlation with the red color ratio on en face slab OCT images, but central retinal thickness did not exhibit a clinically meaningful correlation with values obtained from en face slab OCT images. Immunohistochemical analyses of InsPr-Cre;Pdk1flox/flox diabetic mice demonstrated the loss of ganglion axon bundles and thinning of laminin without apparent retinal vascular change at the age of 20 weeks. CONCLUSIONS: En face slab OCT imaging would be a novel useful modality for the assessment of diabetic retinal neurodegeneration as it could detect subtle optical changes occurring in the innermost retina in diabetic eyes. Our animal experimental data suggest that dark areas observed on en face slab OCT images might be the impairment of the extracellular matrix as well as neurons.

Association between mean platelet volume in the pathogenesis of type 2 diabetes mellitus and diabetic macrovascular complications in Japanese patients.

AIMS/INTRODUCTION: Mean platelet volume (MPV) is a widely used biological marker of platelet function and activity. Increased MPV is associated with accelerated thrombopoiesis and an elevated risk of cardiovascular disease. However, it is not known whether higher MPV is related to the pathogenesis of type 2 diabetes and diabetic macrovascular complications in Japanese patients. Therefore, we analyzed MPV and its correlation with atherosclerosis in Japanese patients with type 2 diabetes and those who had prediabetes. MATERIALS AND METHODS: We divided the patients into three groups: normoglycemic patients (n = 56), prediabetes patients (n = 44) and type 2 diabetes patients group, (n = 115). We measured platelet parameters and evaluated arterial stiffness in the three groups. RESULTS: Significantly higher MPV was found in the type 2 diabetes mellitus and prediabetes patients compared with normoglycemic patients. MPV was significantly correlated with fasting blood glucose and glycated hemoglobin levels. Multiple linear regression analysis showed that MPV was positively correlated with HbA1c, even after adjustment for confounding factors. In the evaluation of arterial stiffness by measuring the cardio-ankle vascular index and maximum intima-media thickness, MPV showed a positive correlation with these parameters. CONCLUSIONS: These findings suggest that MPV was significantly increased in the early stage of type 2 diabetes. We showed positive correlations between MPV and HbA1c levels, and between MPV and arterial stiffness in Japanese patients with type 2 diabetes.

Early administration of dapagliflozin preserves pancreatic ß-cell mass through a legacy effect in a mouse model of type 2 diabetes.

AIMS/INTRODUCTION: The preservation of pancreatic ß-cell mass is an essential factor in the onset and development of type 2 diabetes mellitus. Recently, sodium-glucose cotransporter 2 inhibitors have been launched as antihyperglycemic agents, and their organ-protective effects are attracting attention. They are also reported to have favorable effects on the preservation of pancreatic ß-cell mass, but the appropriate timing for the administration of sodium-glucose cotransporter 2 inhibitors is obscure. MATERIALS AND METHODS: In the present study, we administered a sodium-glucose cotransporter 2 inhibitor, dapagliflozin, to an animal model of type 2 diabetes mellitus, db/db mice, and investigated the adequate timing and duration for its administration. We also carried out microarray analysis using pancreatic islets from db/db mice. RESULTS: We found that dapagliflozin preserved pancreatic ß-cell mass depending on the duration of administration and markedly improved blood glucose levels. If the duration was the same, the earlier administration of dapagliflozin was more effective in preserving pancreatic ß-cell mass, increasing serum insulin levels and improving blood glucose levels. From microarray analysis, we discovered that the expression of Agr2, Tff2 and Gkn3 was significantly upregulated after the early administration of dapagliflozin. This upregulated gene expression might provide a legacy effect for the preservation of pancreatic ß-cell mass. CONCLUSIONS: We expect that the early administration of dapagliflozin would provide a long-lasting effect in preserving pancreatic ß-cell mass.

Docosahexaenoic Acid Reduces Palmitic Acid-Induced Endoplasmic Reticulum Stress in Pancreatic Β Cells.

Endoplasmic reticulum (ER) stress leads to peripheral insulin resistance and the progression of pancreatic beta cell failure in type 2 diabetes. Although ER stress plays an important role in the pathogenesis of diabetes, it is indispensable for cellular activity. Therefore, when assessing the pathological significance of ER stress, it is important to monitor and quantify ER stress levels. Here, we have established a novel system to monitor ER stress levels quickly and sensitively, and using this method, we have clarified the effect of differences in glucose concentration and various fatty acids on the ER of pancreatic ß cells. First, we developed a cell system that secretes Gaussia luciferase in culture medium depending on the activation of the GRP78 promoter. This system could sensitively monitor ER stress levels that could not be detected with real-time RT-PCR and immunoblotting. This system revealed that hyperglycemia does not induce unfolded protein response (UPR) in a short period of time in MIN6 cells, a mouse pancreatic ß cell line. Physiological concentrations of palmitic acid, a saturated fatty acid, induced ER stress quickly, while physiological concentrations of oleic acid, an unsaturated fatty acid, did not. Docosahexaenoic acid, an n-3 unsaturated fatty acid, inhibited palmitic acid-induced ER stress. In this study, we have established a system that can sensitively detect ER stress levels of living cells in a short period of time. This system can be used to monitor the state of the ER in living cells and lead to the investigation of the significance of physiological or pathological ER stress levels.

PHD3 regulates glucose metabolism by suppressing stress-induced signalling and optimising gluconeogenesis and insulin signalling in hepatocytes.

Glucagon-mediated gene transcription in the liver is critical for maintaining glucose homeostasis. Promoting the induction of gluconeogenic genes and blocking that of insulin receptor substrate (Irs)2 in hepatocytes contributes to the pathogenesis of type 2 diabetes. However, the molecular mechanism by which glucagon signalling regulates hepatocyte metabolism is not fully understood. We previously showed that a fasting-inducible signalling module consisting of general control non-repressed protein 5, co-regulator cAMP response element-binding protein binding protein/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2, and protein kinase A is required for glucagon-induced transcription of gluconeogenic genes. The present study aimed to identify the downstream effectors of this module in hepatocytes by examining glucagon-induced potential target genes. One of these genes was prolyl hydroxylase domain (PHD)3, which suppressed stress signalling through inhibition of the IκB kinase-nuclear factor-κB pathway in a proline hydroxylase-independent manner to maintain insulin signalling. PHD3 was also required for peroxisome proliferator-activated receptor γ coactivator 1α-induced gluconeogenesis, which was dependent on proline hydroxylase activity, suggesting that PHD3 regulates metabolism in response to glucagon as well as insulin. These findings demonstrate that glucagon-inducible PHD3 regulates glucose metabolism by suppressing stress signalling and optimising gluconeogenesis and insulin signalling in hepatocytes.

Casein kinase 2 phosphorylates and stabilizes C/EBPß in pancreatic ß cells.

During the development of type 2 diabetes, endoplasmic reticulum (ER) stress leads to pancreatic ß cell failure. CCAAT/enhancer-binding protein (C/EBP) ß is highly induced by ER stress and AMP-activated protein kinase (AMPK) suppression in pancreatic ß cells, and its accumulation reduces pancreatic ß cell mass. We investigated the phosphorylation state of C/EBPß under these conditions. Casein kinase 2 (CK2) was found to co-localize with C/EBPß in MIN6 cells. It phosphorylated S222 of C/EBPß, a previously unidentified phosphorylation site. We found that C/EBPß is phosphorylated by CK2 under AMPK suppression and ER stress, which are important from the viewpoint of the worsening pathological condition of type 2 diabetes, such as decreased insulin secretion and apoptosis of pancreatic ß cells.