Electrical determination of current injection and internal quantum efficiencies in AlGaN-based deep-ultraviolet light-emitting diodes.

We propose a method to determine the current injection efficiency (CIE) and internal quantum efficiency (IQE) of light-emitting diodes (LEDs) during current injection. The method is based on fourth-order polynomial fitting of a modified rate equation to electroluminescence data. Our method can extract the CIE at low injection current densities, unlike conventional methods that generally assume the CIE to be unity. We apply the method to AlGaN-based deep-ultraviolet LEDs. Results show that the CIE was only approximately 51% at low injection current densities and was almost independent of injection current density up to 100 A/cm2. The peak IQE was 77%.

Intra-islet insulin suppresses glucagon release via GABA-GABAA receptor system.

Excessive secretion of glucagon is a major contributor to the development of diabetic hyperglycemia. Secretion of glucagon is regulated by various nutrients, with glucose being a primary determinant of the rate of alpha cell glucagon secretion. The intra-islet action of insulin is essential to exert the effect of glucose on the alpha cells since, in the absence of insulin, glucose is not able to suppress glucagon release in vivo. However, the precise mechanism by which insulin suppresses glucagon secretion from alpha cells is unknown. In this study, we show that insulin induces activation of GABAA receptors in the alpha cells by receptor translocation via an Akt kinase-dependent pathway. This leads to membrane hyperpolarization in the alpha cells and, ultimately, suppression of glucagon secretion. We propose that defects in this pathway(s) contribute to diabetic hyperglycemia.

Transcription factor AP-2beta: a negative regulator of IRS-1 gene expression.

Down-regulation of insulin receptor substrate-1 (IRS-1) expression could modify the ability of IRS-1 to fulfill its functions. It has been proposed that the phosphorylation of IRS-1 on serine residues could promote its degradation. However, few studies have investigated the transcriptional regulation of IRS-1 in the pathogenesis of insulin resistance. Genotyping for genome-wide single nucleotide polymorphisms revealed that the transcription factor activating enhancer-binding protein-2beta (AP-2beta) is a novel candidate gene for conferring susceptibility to obesity and type 2 diabetes. AP-2beta is expressed in adipose tissue and its expression is increased during the maturation of adipocytes. Overexpression of AP-2beta leads to adipocyte hypertrophy, directly inhibits adiponectin expression, and enhanced the expression of inflammatory adipokines such as IL-6 and MCP-1. In this study, we found that overexpression of AP-2beta in 3T3-L1 adipocytes impaired the promoter activity of IRS-1, and subsequently decreased mRNA and protein expression. Electrophoretic mobility shift assays showed that AP-2beta bound specifically to the IRS-1 promoter region. Furthermore, site-directed mutagenesis of the AP-2 binding site located at -362 to -351, relative to the transcription start site, markedly decreased AP-2-induced suppression of IRS-1 promoter activity, whereas other putative AP-2 binding sites did not. Our results clearly showed that AP-2beta directly decreased IRS-1 expression by binding to its promoter. Based on these findings, we speculate that the AP-2beta transcriptional factor is a unique regulator of IRS-1 and a candidate gene for insulin resistance.

The Rab GTPase-activating protein AS160 as a common regulator of insulin- and Galphaq-mediated intracellular GLUT4 vesicle distribution.

Akt substrate of 160kDa (AS160) is a Rab GTPase activating protein (GAP) and was recently identified as a component of the insulin signaling pathway of glucose transporter type 4 (GLUT4) translocation. We and others, previously reported that the activation of Galphaq protein-coupled receptors (GalphaqPCRs) also stimulated GLUT4 translocation and glucose uptake in several cell lines. Here, we report that the activation of GalphaqPCRs also promoted phosphorylation of AS160 by the 5'-AMP activated protein kinase (AMPK). The suppression of AS160 phosphorylation by the siRNA mediated AMPKalpha1 subunit knockdown promoted GLUT4 vesicle retention in intracellular compartments. This suppression did not affect the ratio of non-induced cell surface GLUT4 to Galphaq-induced it. Rat 3Y1 cells lacking AS160 did not show insulin-induced GLUT4 translocation. The cells stably expressing GLUT4 revealed GLUT4 vesicles that were mainly localized in the perinuclear region and less frequently on the cell surface. After expression of exogenous AS160, GLUT4 on the cell surface decreased and GLUT4 vesicles were redistributed throughout the cytoplasm. Although PMA-induced or sodium fluoride-induced GLUT4 translocation was significantly increased in these cells, insulin did not affect GLUT4 translocation. These results suggest that AS160 is a common regulator of insulin- and GalphaqPCR activation-mediated GLUT4 distribution in the cells.

IgM-mediated Warm Autoimmune Hemolytic Anemia: An Autopsy Report.

A 79-year-old man with Sjögren's syndrome and systemic lupus erythematosus developed acute impaired consciousness and hemolytic anemia. The patient's red blood cells agglutinated spontaneously at 25-37°C. The treatment of red blood cells with 2-mercaptoethanol resulted in the loss of spontaneous agglutination. A diagnosis of IgM-mediated warm autoimmune hemolytic anemia was made. The patient received steroid pulse and plasma exchange therapies. Rituximab was also administered. However, the patient died from multiple organ failure at six days from the symptom onset. The clinical progress of the patient and autopsy findings suggested that complement activation might have been associated with the pathology.

AKT1 overexpression in endothelial cells leads to the development of cutaneous vascular malformations in vivo.

BACKGROUND: Vascular malformations are clinical disorders in which endothelial cells fail to remodel and/or undergo programmed cell death, leading to abnormal persistence of blood vessels. The abnormal persistence of vessels makes therapy difficult because these lesions are resistant to interventions that are effective against hemangiomas. Akt1 is a serine-threonine protein kinase, which is a key mediator of resistance to programmed cell death. Our objective was to determine whether sustained activation of Akt1 could lead to vascular malformation in mice. OBSERVATIONS: We examined the effect of constitutive activation of Akt1 in murine endothelial cells (MS1 cells). Overexpression of active AKT1 in MS1 cells led to the development of vascular malformations, characterized by wide endothelial lumens and minimal investment of smooth muscle surrounding the vessels. The histologic features of these vascular malformations is distinct from ras-transformed MS1 cells (angiosarcoma) and suggest that differing signal abnormalities give rise to human vascular malformations vs malignant vascular tumors. CONCLUSIONS: Inhibition of Akt signaling may be useful in the treatment of vascular malformations. Examination of problematic hemangiomas and vascular malformations for the presence of activated Akt or downstream targets of Akt, such as mammalian target of rapamycin (mTOR), may predict response to treatment with Akt inhibitors or rapamycin. This study provides a potential rationale for the systemic and topical use of these inhibitors for vascular malformations and hemangiomas.

Protein phosphatase 2A negatively regulates insulin's metabolic signaling pathway by inhibiting Akt (protein kinase B) activity in 3T3-L1 adipocytes.

Protein phosphatase 2A (PP2A) is a multimeric serine/threonine phosphatase which has multiple functions, including inhibition of the mitogen-activated protein (MAP) kinase pathway. Simian virus 40 small t antigen specifically inhibits PP2A function by binding to the PP2A regulatory subunit, interfering with the ability of PP2A to associate with its cellular substrates. We have reported that the expression of small t antigen inhibits PP2A association with Shc, leading to augmentation of insulin and epidermal growth factor-induced Shc phosphorylation with enhanced activation of the Ras/MAP kinase pathway. However, the potential involvement of PP2A in insulin's metabolic signaling pathway is presently unknown. To assess this, we overexpressed small t antigen in 3T3-L1 adipocytes by adenovirus-mediated gene transfer and found that the phosphorylation of Akt and its downstream target, glycogen synthase kinase 3beta, were enhanced both in the absence and in the presence of insulin. Furthermore, protein kinase C lambda (PKC lambda) activity was also augmented in small-t-antigen-expressing 3T3-L1 adipocytes. Consistent with this result, both basal and insulin-stimulated glucose uptake were enhanced in these cells. In support of this result, when inhibitory anti-PP2A antibody was microinjected into 3T3-L1 adipocytes, we found a twofold increase in GLUT4 translocation in the absence of insulin. The small-t-antigen-induced increase in Akt and PKC lambda activities was not inhibited by wortmannin, while the ability of small t antigen to enhance glucose transport was inhibited by dominant negative Akt (DN-Akt) expression and Akt small interfering RNA (siRNA) but not by DN-PKC lambda expression or PKC lambda siRNA. We conclude that PP2A is a negative regulator of insulin's metabolic signaling pathway by promoting dephosphorylation and inactivation of Akt and PKC lambda and that most of the effects of PP2A to inhibit glucose transport are mediated through Akt.

Akt/protein kinase B promotes organ growth in transgenic mice.

One of the least-understood areas in biology is the determination of the size of animals and their organs. In Drosophila, components of the insulin receptor phosphoinositide 3-kinase (PI3K) pathway determine body, organ, and cell size. Several biochemical studies have suggested that Akt/protein kinase B is one of the important downstream targets of PI3K. To examine the role of Akt in the regulation of organ size in mammals, we have generated and characterized transgenic mice expressing constitutively active Akt (caAkt) or kinase-deficient Akt (kdAkt) specifically in the heart. The heart weight of caAkt transgenic mice was increased 2.0-fold compared with that of nontransgenic mice. The increase in heart size was associated with a comparable increase in myocyte cell size in caAkt mice. The kdAkt mutant protein attenuated the constitutively active PI3K-induced overgrowth of the heart, and the caAkt mutant protein circumvented cardiac growth retardation induced by a kinase-deficient PI3K mutant protein. Rapamycin attenuated caAkt-induced overgrowth of the heart, suggesting that the mammalian target of rapamycin (mTOR) or effectors of mTOR mediated caAkt-induced heart growth. In conclusion, Akt is sufficient to induce a marked increase in heart size and is likely to be one of the effectors of the PI3K pathway in mediating heart growth.

Functional analysis of PIK3CA gene mutations in human colorectal cancer.

Mutations in the PIK3CA gene, which encodes the p110alpha catalytic subunit of phosphatidylinositol 3-kinase (PI3K), have been reported in human cancers, including colorectal cancer. Most of the mutations cluster at hotspots within the helical and kinase domains. Whereas H1047R, one of the hotspot mutants, is reported to have elevated lipid kinase activity, the functional consequences of other mutations have not been examined. In this study, we examined the effects of colon cancer-associated PIK3CA mutations on the lipid kinase activity in vitro, activation of the downstream targets Akt and p70S6K in vivo and NIH 3T3-transforming ability. Of eight mutations examined, all showed increased lipid kinase activity compared with wild-type p110alpha. All the mutants strongly activated Akt and p70S6K compared with wild-type p110alpha as determined by immunoblotting using phospho-specific antibodies. These mutants also induced morphologic changes, loss of contact inhibition, and anchorage-independent growth of NIH 3T3 cells. The hotspot mutations examined in this study, E542K, E545K, and H1047R, all had high enzymatic and transforming activities. These results show that almost all the colon cancer-associated PIK3CA mutations are functionally active so that they are likely to be involved in carcinogenesis.

Comparative Effects of Direct Renin Inhibitor and Angiotensin Receptor Blocker on Albuminuria in Hypertensive Patients with Type 2 Diabetes. A Randomized Controlled Trial.

BACKGROUND: In patients with diabetes, albuminuria is a risk marker of end-stage renal disease and cardiovascular events. An increased renin-angiotensin system activity has been reported to play an important role in the pathological processes in these conditions. We compared the effect of aliskiren, a direct renin inhibitor (DRI), with that of angiotensin receptor blockers (ARBs) on albuminuria and urinary excretion of angiotensinogen, a marker of intrarenal renin-angiotensin system activity. METHODS: We randomly assigned 237 type 2 diabetic patients with high-normal albuminuria (10 to <30 mg/g of albumin-to-creatinine ratio) or microalbuminuria (30 to <300 mg/g) to the DRI group or ARB group (any ARB) with a target blood pressure of <130/80 mmHg. The primary endpoint was a reduction in albuminuria. RESULTS: Twelve patients dropped out during the observation period, and a total of 225 patients were analyzed. During the study period, the systolic and diastolic blood pressures were not different between the groups. The changes in the urinary albumin-to-creatinine ratio from baseline to the end of the treatment period in the DRI and ARB groups were similar (-5.5% and -6.7%, respectively). In contrast, a significant reduction in the urinary excretion of angiotensinogen was observed in the ARB group but not in the DRI group. In the subgroup analysis, a significant reduction in the albuminuria was observed in the ARB group but not in the DRI group among high-normal albuminuria patients. CONCLUSION: DRI and ARB reduced albuminuria in hypertensive patients with type 2 diabetes. In addition, ARB, but not DRI, reduced albuminuria even in patients with normal albuminuria. DRI is not superior to ARB in the reduction of urinary excretion of albumin and angiotensinogen.

Platelet-derived growth factor stimulates glucose transport in skeletal muscles of transgenic mice specifically expressing platelet-derived growth factor receptor in the muscle, but it does not affect blood glucose levels.

Insulin stimulates the disposal of blood glucose into skeletal muscle and adipose tissues by the translocation of GLUT4 from intracellular pools to the plasma membrane, and consequently the concentration of blood glucose levels decreases rapidly in vivo. Phosphatidylinositol (PI) 3-kinase and Akt play a pivotal role in the stimulation of glucose transport by insulin, but detailed mechanisms are unknown. We and others reported that not only insulin but also platelet-derived growth factor (PDGF) and epidermal growth factor facilitate glucose uptake through GLUT4 translocation by activation of PI 3-kinase and Akt in cultured cells. However, opposite results were also reported. We generated transgenic mice that specifically express the PDGF receptor in skeletal muscle. In these mice, PDGF stimulated glucose transport into skeletal muscle in vitro and in vivo. Thus, PDGF apparently shares with insulin some of the signaling molecules needed for the stimulation of glucose transport. The degree of glucose uptake in vivo reached approximately 60% of that by insulin injection in skeletal muscle, but blood glucose levels were not decreased by PDGF in these mice. Therefore, PDGF-induced disposal of blood glucose into skeletal muscle is insufficient for rapid decrease of blood glucose levels.

Increased insulin sensitivity and hypoinsulinemia in APS knockout mice.

A tyrosine kinase adaptor protein containing pleckstrin homology and SH2 domains (APS) is rapidly and strongly tyrosine phosphorylated by insulin receptor kinase upon insulin stimulation. The function of APS in insulin signaling has heretofore remained unknown. APS-deficient (APS(-/-)) mice were used to investigate its function in vivo. The blood glucose-lowering effect of insulin, as assessed by the intraperitoneal insulin tolerance test, was increased in APS(-/-) mice. Plasma insulin levels during fasting and in the intraperitoneal glucose tolerance test were lower in APS(-/-) mice. APS(-/-) mice showed an increase in the whole-body glucose infusion rate as assessed by the hyperinsulinemic-euglycemic clamp test. These findings indicated that APS(-/-) mice exhibited increased sensitivity to insulin. However, overexpression of wild-type or dominant-negative APS in 3T3L1 adipocytes did not affect insulin receptor numbers, phosphorylations of insulin receptor, insulin receptor substrate-1, or Akt and mitogen-activated protein kinase. The glucose uptake and GLUT4 translocation were not affected by insulin stimulation in these cells. Nevertheless, the insulin-stimulated glucose transport in isolated adipocytes of APS(-/-) mice was increased over that of APS(+/+) mice. APS(-/-) mice also showed increased serum levels of leptin and adiponectin, which might explain the increased insulin sensitivity of adipocytes.

ZFH4 protein is expressed in many neurons of developing rat brain.

The zinc finger-homeodomain (ZFH) transcription factors contain a zinc finger motif and a homeodomain that might regulate neural and mesenchymal cell differentiation. We have cloned the ZFH4 gene that encodes a protein with structures closely related to ATBF1. In order to study the expression pattern of ZFH4 in the developing rat brain, we raised an antibody against a glutathione-S-transferase (GST) fusion protein of ZFH4. Western blotting with this antibody identified a gene product of 390 kDa in the normal rat brain. Levels of the protein were high in the brainstem at embryonic and neonatal periods and in the midbrain and diencephalon in neonatal rat brain. In addition, the corresponding mRNA of 12.5 kb was detected by Northern blotting. An immunolocalization study showed that postmitotic neurons in the brainstem were the major site of ZFH4 expression, and the levels of expression varied depending on age and anatomical sites. Expression was transient and weak in precursor cells at early neurogenesis. Although ZFH4 levels decreased after birth, ZFH4 continued to be expressed in the mature neurons including DOPA decarboxylase-positive neurons. High levels of expression were also detected in non-neuronal cells of the subcommissural organ, but the expression was almost undetectable throughout precursor cells to mature neurons in the cerebral cortex and hippocampus. The spatial and temporal expression patterns closely resembled those of ATBF1, and we detected neurons that expressed ZFH4, ATBF1, or both. We postulate that ZFH4 participates in the regulation of neural cell maturation or of region-specific differentiation of the brain.

Granulomatosis with polyangiitis presenting as an orbital inflammatory pseudotumor: a case report.

INTRODUCTION: Granulomatosis with polyangiitis is a systemic inflammatory disease that often presents with necrosis, granuloma formation and vasculitis of small- to medium-sized vessels. Affected patients usually present with disease of the upper respiratory tract, lungs and kidneys, but this disease has been reported to involve almost any organ. We report the case of a patient with ocular manifestations of granulomatosis with polyangiitis after the remission of renal and auditory manifestations. CASE PRESENTATION: An 81-year-old Japanese woman had a four-year history of biopsy-proven antineutrophil cytoplasmic antibody-related glomerulonephritis that had been treated with oral prednisolone and was in serological remission. She had also recovered from a one-year history of complete hearing loss immediately following the steroid treatment for glomerulonephritis. She gradually experienced right eye visual disturbance and exophthalmos over a two-month period. Radiographic and histopathological findings revealed an orbital inflammatory pseudotumor. The administration of prednisolone completely restored her right eye visual acuity and eye movement after two weeks. Considering this case retrospectively, our patient had an orbital inflammatory pseudotumor caused by granulomatosis with polyangiitis including a medical history of reversible hearing loss, although her glomerulonephritis had remitted with an undetectable level of specific antineutrophil cytoplasmic antibody. CONCLUSIONS: In this patient, hearing loss and visual loss occurred at different times during the course of treatment of granulomatosis with polyangiitis. Clinicians should consider a differential diagnosis of granulomatosis with polyangiitis in patients with treatable hearing and visual loss.

Carnitine deficiency presenting with a decreased mental state in a patient with amyotrophic lateral sclerosis receiving long-term tube feeding: a case report.

INTRODUCTION: L-carnitine is an important metabolic mediator involved in fatty acid transport. It is obtained from the diet, particularly from animal products, such as red meat. Previous reports have revealed that long-term tube feeding with a commercial product containing no or low levels of carnitine can lead to an altered mental state caused by hyperammonemia. CASE PRESENTATION: A 72-year-old Japanese man had a 12-year history of amyotrophic lateral sclerosis. He was bedridden and had required mechanical ventilation and enteral tube feeding for 10 years at home. His main enteral solution was a commercial product that contained low carnitine levels, and he sometimes received coffee and homemade products such as miso soup. Our patient's ability to communicate gradually deteriorated over a period of one year. His serum total carnitine level was abnormally low, at 26.7µmol/L (normal range, 45 to 91µmol/L), but his ammonium level was normal. His mental state improved dramatically after starting L-carnitine supplementation (600mg twice daily). CONCLUSION: This case highlights the importance of avoiding carnitine deficiency in patients with amyotrophic lateral sclerosis undergoing long-term tube feeding. These patients experience progressive muscle atrophy that might cause impaired carnitine storage and might manifest as communication difficulties. Carnitine deficiency can be misdiagnosed as a progression of systemic muscle atrophy. Clinicians should be aware of this disorder and should consider periodically measuring carnitine levels, regardless of the patient's serum ammonium levels.

Postprandial activation of protein kinase Cµ regulates the expression of adipocytokines via the transcription factor AP-2ß.

Abnormal secretion of adipocytokines promotes atherosclerosis, diabetes and insulin resistance, and is mainly induced by adipocyte hypertrophy. Recently, the circulating adipocytokine concentrations were reported to change in the postprandial period, as the levels of TNFα, IL-6 IL-8 and MCP-1 increased after a meal, whereas that of adiponectin decreased. These data suggest that prandial modulation of cytokines may be involved in the pathogenesis of atherosclerosis in type 2 diabetes. However, the regulatory mechanism of such change is still unclear. In the present study, we identified this mechanism with a special focus on the functions of protein kinase C (PKC) and of the transcription factor AP-2ß, both of which are associated with the pathophysiology of adipocytokine regulation. PKCµ was highly phosphorylated in the re-feeding condition compared to the fasting condition in mouse adipose tissue, while other PKC isoforms remained unchanged. Furthermore, overexpression of PKCµ in 3T3-L1 adipocytes, but not other PKC isoforms, positively regulated the mRNA expression and promoter activity of MCP-1 and IL-6, and negatively regulated those of adiponectin. AP-2ß had similar effects on the expression and promoter activity of these adipocytokines. Interestingly, overexpression of PKCµ enhanced the stimulatory and inhibitory effects of AP-2ß on the expression of these adipocytokines. Finally, PKCµ could not activate a mutant MCP-1 promoter lacking the AP-2ß binding domain. Our results suggest that postprandial activation of PKCµ plays a role in disordered postprandial adipocytokine expression through AP-2ß.

Association between serum soluble TNFα receptors and renal dysfunction in type 2 diabetic patients without proteinuria.

AIM: The aim of our study was to investigate whether serum levels of soluble tumor necrosis factor α receptor (sTNFR) 1 and 2 are markers for renal dysfunction in type 2 diabetic patients without overt proteinuria. METHODS: Japanese type 2 diabetic patients without overt proteinuria (n = 168) enrolled in the prospective observational follow-up study in 2001 were retrospectively analyzed. At baseline, the serum levels of sTNFR1 and sTNFR2 were measured by sandwich ELISA. The associations between these markers and change in estimated glomerular filtration rate (eGFR) after 5 years were evaluated. RESULTS: The levels of sTNFR1 and sTNFR2 closely correlated. At baseline, sTNFR1 and sTNFR2 associated inversely with eGFR. After 5 years, patients with high level of both sTNFR1 and sTNFR2 showed a greater decline in eGFR (-13.8 ± 15.5% versus -8.5 ± 11.8%, P = 0.027) and a 4-fold higher risk for a GFR decline of ≥ 25% than those with high level of only one receptor or low level of both receptors. These associations were enhanced in diabetic women. CONCLUSIONS: The higher levels of sTNFR1 and sTNFR2 were associated with a greater decline in eGFR in type 2 diabetic patients without proteinuria, especially in diabetic women.

Relation of the expression of transcriptional factor TFAP2B to that of adipokines in subcutaneous and omental adipose tissues.

To determine the potential role of the transcriptional factor-activating enhancer-binding protein-2beta (TFAP2B) in the regulation of expression of adipokines, adiponectin, leptin, and interleukin-6 (IL-6) in vivo, we quantified the mRNA expression levels of these adipokines and TFAP2B in visceral (omental) and abdominal subcutaneous adipose tissues of 66 individuals with variable degree of adiposity and studied their correlations with BMI and their plasma concentrations. We found that BMI correlated negatively with plasma adiponectin levels and positively with those of leptin. Adiponection mRNA expression in subcutaneous fat correlated negatively with BMI, whereas leptin mRNA levels in the omentum correlated with plasma leptin levels and BMI. In contrast, IL-6 mRNA levels in subcutaneous and omental fat did not correlate with BMI. IL-6 mRNA levels in the omental fat correlated with plasma IL-6 levels. Whereas TFAP2B mRNA expression did not correlate with BMI, it correlated negatively with adiponectin expression in the subcutaneous adipose tissue. Furthermore, TFAP2B mRNA expression correlated negatively with leptin and positively with IL-6 expression in both subcutaneous and omental adipose tissues. These relationships are consistent with our in vitro observations and indicate that TFAP2B seems to regulate the expression of various adipokines in vivo.