Variants in KCNQ1 are associated with susceptibility to type 2 diabetes mellitus.

We carried out a multistage genome-wide association study of type 2 diabetes mellitus in Japanese individuals, with a total of 1,612 cases and 1,424 controls and 100,000 SNPs. The most significant association was obtained with SNPs in KCNQ1, and dense mapping within the gene revealed that rs2237892 in intron 15 showed the lowest Pvalue (6.7 x 10(-13), odds ratio (OR) = 1.49). The association of KCNQ1 with type 2 diabetes was replicated in populations of Korean, Chinese and European ancestry as well as in two independent Japanese populations, and meta-analysis with a total of 19,930 individuals (9,569 cases and 10,361 controls) yielded a P value of 1.7 x 10(-42) (OR = 1.40; 95% CI = 1.34-1.47) for rs2237892. Among control subjects, the risk allele of this polymorphism was associated with impairment of insulin secretion according to the homeostasis model assessment of beta-cell function or the corrected insulin response. Our data thus implicate KCNQ1 as a diabetes susceptibility gene in groups of different ancestries.

ATF4-mediated induction of 4E-BP1 contributes to pancreatic beta cell survival under endoplasmic reticulum stress.

Endoplasmic reticulum (ER) stress-mediated apoptosis may play a crucial role in loss of pancreatic beta cell mass, contributing to the development of diabetes. Here we show that induction of 4E-BP1, the suppressor of the mRNA 5' cap-binding protein eukaryotic initiation factor 4E (eIF4E), is involved in beta cell survival under ER stress. 4E-BP1 expression was increased in islets under ER stress in several mouse models of diabetes. The Eif4ebp1 gene encoding 4E-BP1 was revealed to be a direct target of the transcription factor ATF4. Deletion of the Eif4ebp1 gene increased susceptibility to ER stress-mediated apoptosis in MIN6 beta cells and mouse islets, which was accompanied by deregulated translational control. Furthermore, Eif4ebp1 deletion accelerated beta cell loss and exacerbated hyperglycemia in mouse models of diabetes. Thus, 4E-BP1 induction contributes to the maintenance of beta cell homeostasis during ER stress and is a potential therapeutic target for diabetes.

Blockade of the nuclear factor-κB pathway in the endothelium prevents insulin resistance and prolongs life spans.

BACKGROUND: Nuclear factor-κB (NF-κB) signaling plays critical roles in physiological and pathological processes such as responses to inflammation and oxidative stress. METHODS AND RESULTS: To examine the role of endothelial NF-κB signaling in vivo, we generated transgenic mice expressing dominant-negative IκB under the Tie2 promoter/enhancer (E-DNIκB mice). These mice exhibited functional inhibition of NF-κB signaling specifically in endothelial cells. Although E-DNIκB mice displayed no overt phenotypic changes when young and lean, they were protected from the development of insulin resistance associated with obesity, whether diet- or genetics-induced. Obesity-induced macrophage infiltration into adipose tissue and plasma oxidative stress markers were decreased and blood flow and mitochondrial content in muscle and active-phase locomotor activity were increased in E-DNIκB mice. In addition to inhibition of obesity-related metabolic deteriorations, blockade of endothelial NF-κB signaling prevented age-related insulin resistance and vascular senescence and, notably, prolonged life span. These antiaging phenotypes were also associated with decreased oxidative stress markers, increased muscle blood flow, enhanced active-phase locomotor activity, and aortic upregulation of mitochondrial sirtuin-related proteins. CONCLUSIONS: The endothelium plays important roles in obesity- and age-related disorders through intracellular NF-κB signaling, thereby ultimately affecting life span. Endothelial NF-κB signaling is a potential target for treating the metabolic syndrome and for antiaging strategies.

Bach1 deficiency protects pancreatic ß-cells from oxidative stress injury.

BTB and CNC homology 1 (Bach1) is a transcriptional repressor of antioxidative enzymes, such as heme oxygenase-1 (HO-1). Oxidative stress is reportedly involved in insulin secretion impairment and obesity-associated insulin resistance. However, the role of Bach1 in the development of diabetes is unclear. HO-1 expression in the liver, white adipose tissue, and pancreatic islets was markedly upregulated in Bach1-deficient mice. Unexpectedly, glucose and insulin tolerance tests showed no differences in obese wild-type (WT) and obese Bach1-deficient mice after high-fat diet loading for 6 wk, suggesting minimal roles of Bach1 in the development of insulin resistance. In contrast, Bach1 deficiency significantly suppressed alloxan-induced pancreatic insulin content reduction and the resultant glucose elevation. Furthermore, TUNEL-positive cells in pancreatic islets of Bach1-deficient mice were markedly decreased, by 60%, compared with those in WT mice. HO-1 expression in islets was significantly upregulated in alloxan-injected Bach1-deficient mice, whereas expression of other antioxidative enzymes, e.g., catalase, superoxide dismutase, and glutathione peroxidase, was not changed by either alloxan administration or Bach1 deficiency. Our results suggest that Bach1 deficiency protects pancreatic ß-cells from oxidative stress-induced apoptosis and that the enhancement of HO-1 expression plays an important role in this protection.

Chronic mild stress alters circadian expressions of molecular clock genes in the liver.

Chronic stress is well known to affect metabolic regulation. However, molecular mechanisms interconnecting stress response systems and metabolic regulations have yet to be elucidated. Various physiological processes, including glucose/lipid metabolism, are regulated by the circadian clock, and core clock gene dysregulation reportedly leads to metabolic disorders. Glucocorticoids, acting as end-effectors of the hypothalamus-pituitary-adrenal (HPA) axis, entrain the circadian rhythms of peripheral organs, including the liver, by phase-shifting core clock gene expressions. Therefore, we examined whether chronic stress affects circadian expressions of core clock genes and metabolism-related genes in the liver using the chronic mild stress (CMS) procedure. In BALB/c mice, CMS elevated and phase-shifted serum corticosterone levels, indicating overactivation of the HPA axis. The rhythmic expressions of core clock genes, e.g., Clock, Npas2, Bmal1, Per1, and Cry1, were altered in the liver while being completely preserved in the hypothalamic suprachiasmatic nuculeus (SCN), suggesting that the SCN is not involved in alterations in hepatic core clock gene expressions. In addition, circadian patterns of glucose and lipid metabolism-related genes, e.g., peroxisome proliferator activated receptor (Ppar) α, Pparγ-1, Pparγ-coactivator-1α, and phosphoenolepyruvate carboxykinase, were also disturbed by CMS. In contrast, in C57BL/6 mice, the same CMS procedure altered neither serum corticosterone levels nor rhythmic expressions of hepatic core clock genes and metabolism-related genes. Thus, chronic stress can interfere with the circadian expressions of both core clock genes and metabolism-related genes in the liver possibly involving HPA axis overactivation. This mechanism might contribute to metabolic disorders in stressful modern societies.

Wolfram syndrome 1 gene (WFS1) product localizes to secretory granules and determines granule acidification in pancreatic beta-cells.

Wolfram syndrome is an autosomal recessive disorder characterized by juvenile-onset insulin-dependent diabetes mellitus and optic atrophy. The gene responsible for the syndrome (WFS1) encodes an endoplasmic reticulum (ER) resident transmembrane protein. The Wfs1-null mouse exhibits progressive insulin deficiency causing diabetes. Previous work suggested that the function of the WFS1 protein is connected to unfolded protein response and to intracellular Ca(2+) homeostasis. However, its precise molecular function in pancreatic ß-cells remains elusive. In our present study, immunofluorescent and electron-microscopic analyses revealed that WFS1 localizes not only to ER but also to secretory granules in pancreatic ß-cells. Intragranular acidification was assessed by measuring intracellular fluorescence intensity raised by the acidotrophic agent, 3-[2,4-dinitroanilino]-3'-amino-N-methyldipropyramine. Compared with wild-type ß-cells, there was a 32% reduction in the intensity in WFS1-deficient ß-cells, indicating the impairment of granular acidification. This phenotype may, at least partly, account for the evidence that Wfs1-null islets have impaired proinsulin processing, resulting in an increased circulating proinsulin level. Morphometric analysis using electron microscopy evidenced that the density of secretory granules attached to the plasma membrane was significantly reduced in Wfs1-null ß-cells relative to that in wild-type ß-cells. This may be relevant to the recent finding that granular acidification is required for the priming of secretory granules preceding exocytosis and may partly explain the fact that glucose-induced insulin secretion is profoundly impaired in young prediabetic Wfs1-null mice. These results thus provide new insights into the molecular mechanisms of ß-cell dysfunction in patients with Wolfram syndrome.

Baseline and 1-year interim follow-up assessment of Japanese patients initiating insulin therapy who were enrolled in the cardiovascular risk evaluation in people with type 2 diabetes on insulin therapy study: an international, multicenter, observational study.

BACKGROUND: The Cardiovascular Risk Evaluation in people with type 2 Diabetes on Insulin Therapy (CREDIT) study is an international, multicenter, observational study designed to assess metabolic parameters and cardiovascular risk of patients with type 2 diabetes mellitus (T2DM) on insulin therapy. The present report summarizes results at baseline and 1-year follow-up for the cohort of Japanese patients. METHODS: Male and female patients (n = 511), aged >40 years, with T2DM for >1 year, treated with insulin therapy for ≥1 month and <6 months were eligible for participation in the study. Glycemic and lipid parameters, duration of diabetes, diabetic complications, oral antidiabetic medications, and all hypoglycemic episodes were recorded. Effectiveness was assessed based on changes in clinical parameters and attainment of target HbA1c levels. Safety was evaluated based on episodes of hypoglycemia and weight gain. RESULTS: At baseline, the mean ± SD duration of diabetes was 11.8 ± 8.8 years. Microvascular and macrovascular diabetic complications were present in 83.4% and 25.1% of patients, respectively. At the 1-year follow-up, significant improvements were observed in mean HbA1c (10.3 ± 2.0% vs. 7.5 ± 1.3%, P < .001), fasting plasma glucose (217.3 ± 80.8 mg/dL vs. 139.0 ± 48.7 mg/dL, P < .001), and postprandial plasma glucose levels (296.1 ± 96.0 mg/dL vs. 178.2 ± 68.6 mg/dL, P < .001) compared with baseline. Mean total cholesterol (P < .001), low-density lipoprotein cholesterol (P < .001), triglycerides (P < .01), and diastolic blood pressure (P < .01) also significantly decreased. Good glycemic control (HbA1c < 7.0%) was achieved in 40% of patients at the 1-year follow-up. Glycemic control tended to be better in patients with lower baseline HbA1c levels (P < .01). Patients with a shorter duration of diabetes were more likely to achieve glycemic control and discontinue insulin for diabetes control at the 1-year follow-up (P < .05 for trend). Symptomatic hypoglycemic episodes occurred in 21.8% of patients over 6 to 12 months. CONCLUSIONS: Our results suggest that insulin treatment is an effective and safe therapeutic option in Japanese patients with T2DM, and earlier insulin initiation might be associated with better glycemic control.

Hepatic peroxisome proliferator-activated receptor-γ-fat-specific protein 27 pathway contributes to obesity-related hypertension via afferent vagal signals.

AIMS: Obesity is commonly associated with hypertension. Increased sympathetic tonus in obese subjects contributes to the underlying mechanism. However, the precise mechanisms whereby obesity induces this sympathetic activation remain unclear. Hepatic peroxisome proliferator-activated receptor (PPAR)-γ2 expression, which is reportedly upregulated during obesity development, affects sympathetic activation via hepatic vagal afferents. Herein, we report involvement of this neuronal relay in obesity-related hypertension. METHODS AND RESULTS: Peroxisome proliferator-activated receptor-γ and a direct PPARγ target, fat-specific protein 27 (Fsp27), were adenovirally overexpressed or knocked down in the liver, in combination with surgical dissection or pharmacological deafferentation of the hepatic vagus. Adenoviral PPARγ2 expression in the liver raised blood pressure (BP) in wild-type but not in ß1/ß2/ß3 adrenergic receptor-deficient mice. In addition, knockdown of endogenous PPARγ in the liver lowered BP in murine obesity models. Either surgical dissection or pharmacological deafferentation of the hepatic vagus markedly blunted BP elevation in mice with diet-induced and genetically-induced obesity. In contrast, BP was not elevated in other models of hepatic steatosis, DGAT1 and DGAT2 overexpressions, in which PPARγ is not upregulated in the liver. Thus, hepatic PPARγ upregulation associated with obesity is involved in BP elevation during obesity development. Furthermore, hepatic expression of Fsp27 raised BP and the effect was blocked by hepatic vagotomy. Hepatic Fsp27 is actually upregulated in murine obesity models and its knockdown reversed BP elevation. CONCLUSION: The hepatic PPARγ-Fsp27 pathway plays important roles in the development of obesity-related hypertension via afferent vagal signals from the liver.

Peptidyl-prolyl cis/trans isomerase NIMA-interacting 1 associates with insulin receptor substrate-1 and enhances insulin actions and adipogenesis.

Peptidyl-prolyl cis/trans isomerase NIMA-interacting 1 (Pin1) is a unique enzyme that associates with the pSer/Thr-Pro motif and catalyzes cis-trans isomerization. We identified Pin1 in the immunoprecipitates of overexpressed IRS-1 with myc and FLAG tags in mouse livers and confirmed the association between IRS-1 and Pin1 by not only overexpression experiments but also endogenously in the mouse liver. The analysis using deletion- and point-mutated Pin1 and IRS-1 constructs revealed the WW domain located in the N terminus of Pin1 and Ser-434 in the SAIN (Shc and IRS-1 NPXY binding) domain of IRS-1 to be involved in their association. Subsequently, we investigated the role of Pin1 in IRS-1 mediation of insulin signaling. The overexpression of Pin1 in HepG2 cells markedly enhanced insulin-induced IRS-1 phosphorylation and its downstream events: phosphatidylinositol 3-kinase binding with IRS-1 and Akt phosphorylation. In contrast, the treatment of HepG2 cells with Pin1 siRNA or the Pin1 inhibitor Juglone suppressed these events. In good agreement with these in vitro data, Pin1 knock-out mice exhibited impaired insulin signaling with glucose intolerance, whereas adenoviral gene transfer of Pin1 into the ob/ob mouse liver mostly normalized insulin signaling and restored glucose tolerance. In addition, it was also demonstrated that Pin1 plays a critical role in adipose differentiation, making Pin1 knock-out mice resistant to diet-induced obesity. Importantly, Pin1 expression was shown to be up-regulated in accordance with nutrient conditions such as food intake or a high-fat diet. Taken together, these observations indicate that Pin1 binds to IRS-1 and thereby markedly enhances insulin action, essential for adipogenesis.

Involvement of endoplasmic stress protein C/EBP homologous protein in arteriosclerosis acceleration with augmented biological stress responses.

BACKGROUND: The processes of arteriosclerosis, including atherosclerosis and vascular remodeling, are affected by interactions among numerous biological pathways such as responses to inflammation, oxidative stress, and endoplasmic reticulum stress. C/EBP homologous protein (CHOP), which is well known to induce cellular apoptosis in response to severe endoplasmic reticulum stress, is reportedly upregulated in plaque lesions. METHODS AND RESULTS: We examined the effects of CHOP deficiency on 2 types of arteriosclerosis: cuff injury-induced neointimal formation and hypercholesterolemia-induced atherosclerosis. Cuff injury-induced neointimal formation was markedly inhibited in CHOP(-/-) mice with suppressed aortic expression of inflammatory factors and smooth muscle cell proliferation-related proteins. A CHOP deficiency also inhibited aortic plaque formation in hypercholesterolemic apolipoprotein E(-/-) mice with suppressed aortic expression of inflammatory factors and oxidative stress markers. Bone marrow transplantation experiments revealed that recipient CHOP deficiency significantly suppressed both cuff injury-induced neointimal formation and hypercholesterolemia-induced atherosclerotic plaque formation to a greater extent than donor CHOP deficiency, suggesting the importance of CHOP in vascular cells for arteriosclerosis progression. Furthermore, in our in vitro experiments, in not only macrophages but also endothelial and smooth muscle cell lines, endoplasmic reticulum stress inducers upregulated inflammation-, adhesion-, or smooth muscle cell proliferation-related proteins, whereas decreased CHOP expression remarkably suppressed endoplasmic reticulum stress-induced upregulation of these proteins. CONCLUSIONS: In addition to the well-known signaling for apoptosis induction, CHOP may play important roles in augmenting potentially pathological biological stress responses. This noncanonical role of CHOP, especially that expressed in vascular cells, may contribute to the progression of vascular remodeling and atherosclerosis.

Signals from intra-abdominal fat modulate insulin and leptin sensitivity through different mechanisms: neuronal involvement in food-intake regulation.

Intra-abdominal fat accumulation is involved in development of the metabolic syndrome, which is associated with insulin and leptin resistance. We show here that ectopic expression of very low levels of uncoupling protein 1 (UCP1) in epididymal fat (Epi) reverses both insulin and leptin resistance. UCP1 expression in Epi improved glucose tolerance and decreased food intake in both diet-induced and genetically obese mouse models. In contrast, UCP1 expression in Epi of leptin-receptor mutant mice did not alter food intake, though it significantly decreased blood glucose and insulin levels. Thus, hypophagia induction requires a leptin signal, while the improved insulin sensitivity appears to be leptin independent. In wild-type mice, local-nerve dissection in the epididymis or pharmacological afferent blockade blunted the decrease in food intake, suggesting that afferent-nerve signals from intra-abdominal fat tissue regulate food intake by modulating hypothalamic leptin sensitivity. These novel signals are potential therapeutic targets for the metabolic syndrome.

4F2hc stabilizes GLUT1 protein and increases glucose transport activity.

Glucose transporter 1 (GLUT1) is widely distributed throughout various tissues and contributes to insulin-independent basal glucose uptake. Using a split-ubiquitin membrane yeast two-hybrid system, we newly identified 4F2 heavy chain (4F2hc) as a membrane protein interacting with GLUT1. Though 4F2hc reportedly forms heterodimeric complexes between amino acid transporters, such as LAT1 and LAT2, and regulates amino acid uptake, we investigated the effects of 4F2hc on GLUT1 expression and the associated glucose uptake. First, FLAG-tagged 4F2hc and hemagglutinin-tagged GLUT1 were overexpressed in human embryonic kidney 293 cells and their association was confirmed by coimmunoprecipitation. The green fluorescent protein-tagged 4F2hc and DsRed-tagged GLUT1 showed significant, but incomplete, colocalization at the plasma membrane. In addition, an endogenous association between GLUT1 and 4F2hc was demonstrated using mouse brain tissue and HeLa cells. Interestingly, overexpression of 4F2hc increased the amount of GLUT1 protein in HeLa and HepG2 cells with increased glucose uptake. In contrast, small interfering RNA (siRNA)-mediated 4F2hc gene suppression markedly reduced GLUT1 protein in both cell types, with reduced glucose uptake. While GLUT1 mRNA levels were not affected by overexpression or gene silencing of 4F2hc, GLUT1 degradation after the addition of cycloheximide was significantly suppressed by 4F2hc overexpression and increased by 4F2hc siRNA treatment. Taken together, these observations indicate that 4F2hc is likely to be involved in GLUT1 stabilization and to contribute to the regulation of not only amino acid but also glucose metabolism.

Pin1 associates with and induces translocation of CRTC2 to the cytosol, thereby suppressing cAMP-responsive element transcriptional activity.

Pin1 is a unique regulator, which catalyzes the conversion of a specific phospho-Ser/Thr-Pro-containing motif in target proteins. Herein, we identified CRTC2 as a Pin1-binding protein by overexpressing Pin1 with Myc and FLAG tags in mouse livers and subsequent purification of the complex containing Pin1. The association between Pin1 and CRTC2 was observed not only in overexpression experiments but also endogenously in the mouse liver. Interestingly, Ser(136) in the nuclear localization signal of CRTC2 was shown to be involved in the association with Pin1. Pin1 overexpression in HepG2 cells attenuated forskolin-induced nuclear localization of CRTC2 and cAMP-responsive element (CRE) transcriptional activity, whereas gene knockdown of Pin1 by siRNA enhanced both. Pin1 also associated with CRTC1, leading to their cytosol localization, essentially similar to the action of CRTC2. Furthermore, it was shown that CRTC2 associated with Pin1 did not bind to CREB. Taken together, these observations indicate the association of Pin1 with CRTC2 to decrease the nuclear CBP·CRTC·CREB complex. Indeed, adenoviral gene transfer of Pin1 into diabetic mice improved hyperglycemia in conjunction with normalizing phosphoenolpyruvate carboxykinase mRNA expression levels, which is regulated by CRE transcriptional activity. In conclusion, Pin1 regulates CRE transcriptional activity, by associating with CRTC1 or CRTC2.

Cognitive decline in a patient with anti-glutamic acid decarboxylase autoimmunity; case report.

BACKGROUND: Glutamic acid decarboxylase (GAD) is the rate-limiting enzyme for producing γ-aminobutyric acid, and it has been suggested that antibodies against GAD play a role in neurological conditions and type 1 diabetes. However, it is not known whether dementia appears as the sole neurological manifestation associated with anti-GAD antibodies in the central nervous system. CASE PRESENTATION: We describe the clinical, neuropsychological, and neuroradiological findings of a 73-year-old female with cognitive dysfunction and type 1A diabetes. Observation and neuropsychological studies revealed linguistic problems, short-term memory disturbance, and frontal dysfunction. MRI showed no significant lesion except for confluent small T2-hyperintensity areas localized in the left basal ganglia. ¹8F-fluorodeoxy glucose-positron emission tomography (FDG-PET) and ¹²³I-N-isopropyl-p-iodoamphetamine-single photon emission computed tomography (IMP-SPECT) studies showed bifrontal hypometabolism and hypoperfusion. Immunomodulating therapy with intravenous high-dose immunoglobulin resulted in no remission of the cognitive symptoms. CONCLUSIONS: Cognitive dysfunction may develop as an isolated neurological manifestation in association with type 1A diabetes and anti-GAD autoimmunity. A systematic study with extensive neuropsychological assessment is indicated in patients with type 1 diabetes and anti-GAD autoimmunity.

Characterization of a novel murine preadipocyte line, AP-18, isolated from subcutaneous tissue: analysis of adipocyte-related gene expressions.

Adipocyte lines are a useful tool for adipocyte research. Recently, a new preadipocyte line designated AP-18 was established from subcutaneous tissue of the C3H/He mouse. In this study, we further characterized AP-18 cells. Adipocyte differentiation was assessed by accumulation of fat droplets stained by Oil Red O. The expression of the preadipocyte- or adipocyte-specific genes and adipocytokine genes was analysed qualitatively by RT-PCR and quantitatively by real-time PCR in comparison with the LM cell, a murine fibroblast line, and the 3T3-L1 cell, respectively. AP-18 cells were fibroblastoid in maintenance culture. After the confluence, fat droplets were accumulated in 50-60% of the cells cultured in the medium alone and in 70-90% of the cells cultured with insulin within 2 to 3 weeks. The fat accumulation was not promoted by the addition of dexamethazone, IBMX (3-isobutyl-1-methylxanthine) or troglitazone in combination with insulin, which were obligatory for differentiation of the 3T3-L1 cell, a murine preadipocyte line. Throughout the differentiation, AP-18 cells expressed Pref-1, LPL, C/EBP beta, C/EBP delta, RXR alpha, C/EBP alpha, PPAR gamma, RXR gamma, aP2, GLUT4, SCD1, UCP2, UCP3, TNFalpha, resistin, leptin, adiponectin and PAI-1 genes, but not the UCP1 gene, indicating that the cell is derived from WAT (white adipose tissue). The time course of these gene expressions was similar to that of 3T3-L1 cells, although the expressions were slower and lower in AP-18 cells. These data indicate that AP-18 cells are preadipocytes originated from WAT and differentiate into adipocytes under more physiological conditions than 3T3-L1 cells. AP-18 may be useful in adipocyte research.

The JNK pathway modulates expression and phosphorylation of 4E-BP1 in MIN6 pancreatic beta-cells under oxidative stress conditions.

Stress-mediated apoptosis may play a crucial role in loss of pancreatic beta-cell mass, contributing to the development of diabetes. We have recently identified that translational control involving the translational suppressor eIF4E binding protein-1 (4E-BP1) which is important for beta-cell survival under endoplasmic reticulum (ER) stress. The Eif4ebp1 gene, encoding 4E-BP1, is a direct target of a transcription factor activating transcription factor-4 (ATF4), a master regulator of gene expression in stress responses. In the current study, we investigated 4E-BP1 expression in mouse insulinoma line 6 (MIN6) cells treated with arsenite, an inducer of oxidative stress which is another contributor of beta-cell loss. We found that arsenite-induced 4E-BP1 expression level was lower than that induced by thapsigargin, an ER stress inducer, although ATF4 was similarly induced by these agents. The ratio of the dephosphorylated form of 4E-BP1, which has the highest activity, to phosphorylated forms was, however, greater in MIN6 cells treated with arsenite as compared to that in thapsigargin-treated cells. Arsenite-induced 4E-BP1 mRNA and protein expressions were augmented by simultaneous treatment with a c-Jun N-terminal kinase (JNK) specific inhibitor, SP600125. The agent also suppressed the level of the dephosphrylated form of 4E-BP1 in arsenite-treated MIN6 cells. Thus, JNK activated by oxidative stress is involved in the modulation of 4E-BP1 expression and phosphorylation in MIN6 cells, which may contribute to fine tuning of translational control under stress conditions.

Circulating oxidized LDL: a biomarker and a pathogenic factor.

PURPOSE OF REVIEW: Oxidized LDL (oxLDL) contributes to many atherogenic steps in the vascular wall, but the significance of oxLDL in circulating blood remains unclear. Recent progress in procedures for measuring both human and murine oxLDL has provided growing evidence of the importance of circulating oxLDL. RECENT FINDINGS: Circulating oxLDL is elevated in patients with advanced atherosclerosis, such as coronary heart disease and ischemic stroke, and also reflects early atherosclerotic changes and metabolic disorders including diabetes and obesity. In-vitro exposure to oxLDL increased mononuclear cell nuclear factor-kappaB activity, suggesting a pathogenic role of circulating oxLDL in exacerbation of oxidative stress. In addition, adenoviral administration of secreted scavenger receptor-A1, which functions as a decoy, suppresses foam cell formation in LDL receptor-deficient mice via a blockade of modified LDL incorporation into macrophages. Furthermore, when lectin-like oxLDL receptor-1 was ectopically expressed in the liver, circulating oxLDL was reduced, resulting in complete prevention of atherosclerotic progression in apolipoprotein E-deficient mice. Thus, circulating oxLDL impacts atherogenic formation. SUMMARY: The roles of circulating oxLDL in atherosclerotic pathogenesis are now attracting considerable attention. OxLDL removal from circulating blood is a promising therapeutic strategy against atherosclerosis.

Impact of plasma oxidized low-density lipoprotein removal on atherosclerosis.

BACKGROUND: Several clinical studies of statin therapy have demonstrated that lowering low-density lipoprotein (LDL) cholesterol prevents atherosclerotic progression and decreases cardiovascular mortality. In addition, oxidized LDL (oxLDL) is suggested to play roles in the formation and progression of atherosclerosis. However, whether lowering oxLDL alone, rather than total LDL, affects atherogenesis remains unclear. METHODS AND RESULTS: To clarify the atherogenic impact of oxLDL, lectin-like oxLDL receptor 1 (LOX-1), an oxLDL receptor, was expressed ectopically in the liver with adenovirus administration in apolipoprotein E-deficient mice at 46 weeks of age. Hepatic LOX-1 expression enhanced hepatic oxLDL uptake, indicating functional expression of LOX-1 in the liver. Although plasma total cholesterol, triglyceride, and LDL cholesterol levels were unaffected, plasma oxLDL was markedly and transiently decreased in LOX-1 mice. In controls, atherosclerotic lesions, detected by Oil Red O staining, were markedly increased (by 38%) during the 4-week period after adenoviral administration. In contrast, atherosclerotic progression was almost completely inhibited by hepatic LOX-1 expression. In addition, plasma monocyte chemotactic protein-1 and lipid peroxide levels were decreased, whereas adiponectin was increased, suggesting decreased systemic oxidative stress. Thus, LOX1 expressed in the livers of apolipoprotein E-deficient mice transiently removes oxLDL from circulating blood and possibly decreases systemic oxidative stress, resulting in complete prevention of atherosclerotic progression despite the persistence of severe LDL hypercholesterolemia and hypertriglyceridemia. CONCLUSIONS: OxLDL has a major atherogenic impact, and oxLDL removal is a promising therapeutic strategy against atherosclerosis.

Inter-organ metabolic communication involved in energy homeostasis: potential therapeutic targets for obesity and metabolic syndrome.

The global rate of obesity is rising alarmingly, exerting a major adverse impact on human health by increasing the prevalences of disorders, such as diabetes, hypertension and heart disease. To maintain systemic energy homeostasis, metabolic information must be communicated among organs/tissues. Obesity-related disorders can be thought of as resulting from dysregulation of this vital inter-tissue communication. Remarkable advances in obesity research during this decade have shown humoral factors manufactured and secreted by adipose tissue (adipocytokines) to be of great importance. In addition to these humoral factors, such as nutrients (glucose, fatty acids and amino acids) and hormones (insulin, adipocytokines and so on), the functional significance of the autonomic nervous system has recently attracted research attention. Autonomic nerves are essential components of the endogenous system for maintaining energy homeostasis, making them potential therapeutic targets for obesity-related disorders. This review focuses on the therapeutic possibilities of targeting inter-organ communication systems.

Construction of a prediction model for type 2 diabetes mellitus in the Japanese population based on 11 genes with strong evidence of the association.

Prediction of the disease status is one of the most important objectives of genetic studies. To select the genes with strong evidence of the association with type 2 diabetes mellitus, we validated the associations of the seven candidate loci extracted in our earlier study by genotyping the samples in two independent sample panels. However, except for KCNQ1, the association of none of the remaining seven loci was replicated. We then selected 11 genes, KCNQ1, TCF7L2, CDKAL1, CDKN2A/B, IGF2BP2, SLC30A8, HHEX, GCKR, HNF1B, KCNJ11 and PPARG, whose associations with diabetes have already been reported and replicated either in the literature or in this study in the Japanese population. As no evidence of the gene-gene interaction for any pair of the 11 loci was shown, we constructed a prediction model for the disease using the logistic regression analysis by incorporating the number of the risk alleles for the 11 genes, as well as age, sex and body mass index as independent variables. Cumulative risk assessment showed that the addition of one risk allele resulted in an average increase in the odds for the disease of 1.29 (95% CI=1.25-1.33, P=5.4 x 10(-53)). The area under the receiver operating characteristic curve, an estimate of the power of the prediction model, was 0.72, thereby indicating that our prediction model for type 2 diabetes may not be so useful but has some value. Incorporation of data from additional risk loci is most likely to increase the predictive power.