Interleukin-6 enhances glucose-stimulated insulin secretion from pancreatic beta-cells: potential involvement of the PLC-IP3-dependent pathway

OBJECTIVE

Interleukin-6 (IL-6) has a significant impact on glucose metabolism. However, the effects of IL-6 on insulin secretion from pancreatic β-cells are controversial. Therefore, we analyzed IL-6 effects on pancreatic β-cell functions both in vivo and in vitro.

RESEARCH DESIGN AND METHODS

First, to examine the effects of IL-6 on in vivo insulin secretion, we expressed IL-6 in the livers of mice using the adenoviral gene transfer system. In addition, using both MIN-6 cells, a murine β-cell line, and pancreatic islets isolated from mice, we analyzed the in vitro effects of IL-6 pretreatment on insulin secretion. Furthermore, using pharmacological inhibitors and small interfering RNAs, we studied the intracellular signaling pathway through which IL-6 may affect insulin secretion from MIN-6 cells.

RESULTS

Hepatic IL-6 expression raised circulating IL-6 and improved glucose tolerance due to enhancement of glucose stimulated-insulin secretion (GSIS). In addition, in both isolated pancreatic islets and MIN-6 cells, 24-h pretreatment with IL-6 significantly enhanced GSIS. Furthermore, pretreatment of MIN-6 cells with phospholipase C (PLC) inhibitors with different mechanisms of action, U-73122 and neomycin, and knockdowns of the IL-6 receptor and PLC-β(1), but not with a protein kinase A inhibitor, H-89, inhibited IL-6-induced enhancement of GSIS. An inositol triphosphate (IP(3)) receptor antagonist, Xestospondin C, also abrogated the GSIS enhancement induced by IL-6.

CONCLUSIONS

The results obtained from both in vivo and in vitro experiments strongly suggest that IL-6 acts directly on pancreatic β-cells and enhances GSIS. The PLC-IP(3)-dependent pathway is likely to be involved in IL-6-mediated enhancements of GSIS.

Neural relay from the liver induces proliferation of pancreatic beta cells: a path to regenerative medicine using the self-renewal capabilities

Systemic homeostasis requires coordinated metabolic regulation among multiple tissues/organs via inter-organ communication. We have reported that neuronal signaling plays important roles in this inter-organ metabolic communication. First, we found that liver-selective extracellular signal-regulated kinase (ERK) activation induces insulin hypersecretion and pancreatic beta cell proliferation. Denervation experiments revealed that these inter- organ (liver-to-pancreas) effects are mediated by a neural relay consisting of splanchnic afferents (from the liver) and vagal efferents (to the pancreas). The central nervous system also participates in this inter-organ communication. This neural relay system originating in the liver is physiologically involved in the anti-diabetes mechanism whereby, during obesity development, insulin hypersecretion and pancreatic beta cell hyperplasia occur in response to insulin resistance. This indicates the pathophysiological importance of this system in diabetes prevention and hyperinsulinemia development. Furthermore, when applied to mouse models of insulin-deficient diabetes, both type 1 and type 2, hepatic activation of ERK signaling increased pancreatic beta cell mass and normalized blood glucose. Thus, this inter-organ system may serve as a valuable therapeutic target for diabetes by regenerating pancreatic beta cells. The concept that manipulation of an endogenous mechanism can regenerate a damaged tissue in vivo may open a new paradigm for regenerative trreatments for degenerative disorders.

Identification of a novel mechanism regulating β-cell mass: neuronal relay from the liver to pancreatic β-cells

Recent studies have demonstrated that β-cell replication plays a central role in maintaining adult β-cell mass. β-cell proliferative activity changes dynamically to meet systemic needs throughout life. One condition in which β-cell proliferation is enhanced is obesity-related insulin resistance. However, the mechanism underlying this compensatory β-cell response is not well understood. We have identified a neuronal relay, originating in the liver, which enhances both insulin secretion and pancreatic β-cell proliferation. Blockade of this neural relay in murine obesity models inhibited pancreatic islet expansion during obesity development, showing this inter-organ communication system to be physiologically involved in compensatory β-cell proliferation. While there is controversy about which mechanism, proliferation of pre-existing β-cells or production of new β cells from progenitor cells, plays the dominant role in maintaining or regulating β-cell mass, we herein provide an example that proliferation of pre-existing β-cells contributes to a β-cell increment in obesity-related insulin resistance. Furthermore, we have shown the potential for clinical application of this inter-organ system as a therapeutic target for insulin-deficient diabetes.

Safety and effectiveness of malignant pleural mesothelioma patients treated with pemetrexed: A postmarketing drug registered study under performance linked access system

e19084

Background: Approximately 1000 patients are newly diagnosed as malignant pleural mesothelioma (MPM) each year in Japan, however MPM patient profile and their outcome are not well understood. Pemetrexed is the only approved chemotherapeutic agent for MPM. Limited safety information was available at launch of pemetrexed in Japan where drug induced interstitial pneumonitis are reported at higher rate than the rest of the world. Therefore postmarketing drug registered study (PDRS) for pemetrexed was conducted in Japan to investigate patient characteristics, adverse events and survival of MPM patients based on a regulatory requirement for approval. Methods: From February 2007 to May 2008, all of histologically proven MPM patients to be treated with pemetrexed were required to register the PDRS in Japan. The observation period was six-months. Supply of pemetrexed was restricted to institutes with experienced medical oncologists based on pre-determined criteria. Results: During the 15-months enrollment period, 948 MPM patients were registered. Until August 3th 2008, data for 437 patients were collected. Among these, 389 were male, 48 female, median of age 65 (35–86). 72.3% patients had a known history of being exposed to asbestos. The treatment regimen mainly consists of 500 mg/m2 of pemetrexed and 75 mg/m2 of cisplatin every 21 days. Median treatment cycle was 3.0. Hematological NCI-CTC Grade ¾ adverse events in laboratory data were hemoglobin decrease 19.9 %, neutropenia 20.1%, thrombocytopenia 7.6%. Serious non-hematological adverse events were nausea 3%, vomiting 3.2%, fatigue 0.2%, constipation 0.2%, diarrhea 0.9%. Pneumotoxicity was found in 1.4%. 152 deaths (34.8%) were observed and six-month survival rate estimated by Kaplan-Meier method was 70.9%. Conclusions: This large size PDRS shows that safety profile of pemetrexed appeared similar to the previous clinical trial without additional safety signal. The study has minimum selection bias and provides useful information to health care professionals on safety and effectiveness of pemetrexed in real clinical setting in Japan.

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Peginterferon (PEG-IFN) plus ribavirin combination therapy, but neither interferon nor PGE-IFN alone, induced type 1 diabetes in a patient with chronic hepatitis C

Interferon (IFN) therapies, including IFN, peginterferon (PEG-IFN) and ribavirin (RBV) plus PEG-IFN combination, are widely used for patients with chronic hepatitis C. We encountered a patient with chronic hepatitis C in whom previous IFN or PEG-IFN alone had not induced type 1 diabetes (T1D), while the addition of RBV to PEG-IFN did induce T1D. The patient had HLA types conferring highly susceptibility to T1D. Thus, adding RBV to PEG-IFN may render chronic hepatitis C patients, with T1D-susceptible HLA types, more prone to developing T1D than IFN or PEG-IFN alone. To prevent T1D development, we recommend HLA typing prior to initiating RBV plus PEG-IFN administration.

Regulation of pancreatic beta cell mass by neuronal signals from the liver

Metabolic regulation in mammals requires communication between multiple organs and tissues. The rise in the incidence of obesity and associated metabolic disorders, including type 2 diabetes, has renewed interest in interorgan communication. We used mouse models to explore the mechanism whereby obesity enhances pancreatic beta cell mass, pathophysiological compensation for insulin resistance. We found that hepatic activation of extracellular regulated kinase (ERK) signaling induced pancreatic beta cell proliferation through a neuronal-mediated relay of metabolic signals. This metabolic relay from the liver to the pancreas is involved in obesity-induced islet expansion. In mouse models of insulin-deficient diabetes, liver-selective activation of ERK signaling increased beta cell mass and normalized serum glucose levels. Thus, interorgan metabolic relay systems may serve as valuable targets in regenerative treatments for diabetes.

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.

Bone marrow (BM) transplantation promotes beta-cell regeneration after acute injury through BM cell mobilization

There is controversy regarding the roles of bone marrow (BM)-derived cells in pancreatic beta-cell regeneration. To examine these roles in vivo, mice were treated with streptozotocin (STZ), followed by bone marrow transplantation (BMT; lethal irradiation and subsequent BM cell infusion) from green fluorescence protein transgenic mice. BMT improved STZ-induced hyperglycemia, nearly normalizing glucose levels, with partially restored pancreatic islet number and size, whereas simple BM cell infusion without preirradiation had no effects. In post-BMT mice, most islets were located near pancreatic ducts and substantial numbers of bromodeoxyuridine-positive cells were detected in islets and ducts. Importantly, green fluorescence protein-positive, i.e. BM-derived, cells were detected around islets and were CD45 positive but not insulin positive. Then to examine whether BM-derived cell mobilization contributes to this process, we used Nos3(-/-) mice as a model of impaired BM-derived cell mobilization. In streptozotocin-treated Nos3(-/-) mice, the effects of BMT on blood glucose, islet number, bromodeoxyuridine-positive cells in islets, and CD45-positive cells around islets were much smaller than those in streptozotocin-treated Nos3(+/+) controls. A series of BMT experiments using Nos3(+/+) and Nos3(-/-) mice showed hyperglycemia-improving effects of BMT to correlate inversely with the severity of myelosuppression and delay of peripheral white blood cell recovery. Thus, mobilization of BM-derived cells is critical for BMT-induced beta-cell regeneration after injury. The present results suggest that homing of donor BM-derived cells in BM and subsequent mobilization into the injured periphery are required for BMT-induced regeneration of recipient pancreatic beta-cells.

Involvement of apolipoprotein E in excess fat accumulation and insulin resistance

Although apolipoprotein E (apoE) is well known to play a major role in lipid metabolism, its role in glucose and energy homeostasis remains unclear. Herein, we established apoE-deficient genetically obese Ay (apoE(-/-);Ay/+) mice. ApoE deficiency in Ay mice prevented the development of obesity, with decreased fat accumulation in the liver and adipose tissues. ApoE(-/-);Ay/+ mice exhibited better glucose tolerance than apoE(+/+);Ay/+ mice. Insulin tolerance testing and hyperinsulinemic-euglycemic clamp study revealed marked improvement of insulin sensitivity, despite increased plasma free fatty acid levels. These metabolic phenotypes were reversed by adenoviral replenishment of apoE protein, indicating circulating apoE to be involved in increased adiposity and obesity-related metabolic disorders. Uptake of apoE-lacking VLDL into the liver and adipocytes was markedly inhibited, but adipocytes in apoE(-/-);Ay/+ mice exhibited normal differentiation, suggesting that apoE-dependent VLDL transport is involved in the development of obesity, i.e., surplus fat accumulation. Interestingly, apoE(-/-);Ay/+ mice exhibited decreased food intake and increased energy expenditure. Pair-feeding experiments indicate these phenomena to both contribute to the obesity-resistant phenotypes associated with apoE deficiency. Thus, apoE is involved in maintaining energy homeostasis. ApoE-dependent excess fat accumulation is a promising therapeutic target for the metabolic syndrome.

Neuronal pathway from the liver modulates energy expenditure and systemic insulin sensitivity

Coordinated control of energy metabolism and glucose homeostasis requires communication between organs and tissues. We identified a neuronal pathway that participates in the cross talk between the liver and adipose tissue. By studying a mouse model, we showed that adenovirus-mediated expression of peroxisome proliferator-activated receptor (PPAR)-g2 in the liver induces acute hepatic steatosis while markedly decreasing peripheral adiposity. These changes were accompanied by increased energy expenditure and improved systemic insulin sensitivity. Hepatic vagotomy and selective afferent blockage of the hepatic vagus revealed that the effects on peripheral tissues involve the afferent vagal nerve. Furthermore, an antidiabetic thiazolidinedione, a PPARg agonist, enhanced this pathway. This neuronal pathway from the liver may function to protect against metabolic perturbation induced by excessive energy storage.

Cold exposure suppresses serum adiponectin levels through sympathetic nerve activation in mice

OBJECTIVE

Several lines of evidence suggest important roles for adiponectin in glucose and lipid metabolism and atherosclerosis. However, the mechanisms regulating serum adiponectin levels and adiponectin production are still not completely understood. Our aim was to determine whether adiponectin synthesis is physiologically regulated by the sympathetic nervous system (SNS).

RESEARCH METHODS AND PROCEDURES

Mice were exposed to cold (4 degrees C) for 12 hours and for 24 hours with or without inhibition of noradrenaline synthesis or pan-beta adrenergic function, followed by measurement of serum adiponectin concentrations and levels of adiponectin and uncoupling protein (UCP) 1 expressions in various white adipose tissues (WATs).

RESULTS

Cold exposure significantly reduced serum adiponectin concentrations without changing body weights or WAT sizes in either subcutaneous or intra-abdominal fat tissues. The serum adiponectin reduction was associated with a decrease in adiponectin mRNA expression in subcutaneous, epididymal, and mesenteric fat tissues. In these adipose tissues, UCP1 expression was markedly enhanced, suggesting SNS activation in these tissues. Administration of alpha-methyl-p-tyrosine or a combination of SR59230A and propranolol reversed the cold-exposure-induced decreases in serum adiponectin concentrations and adiponectin mRNA expression in these tissues. In contrast, in retroperitoneal fat, the effects of cold exposure on adiponectin and UCP1 expressions were strikingly weak but were not reversed by SNS inhibitors.

DISCUSSION

SNS physiologically regulates serum adiponectin levels and adiponectin synthesis in WATs in vivo, although responsiveness to SNS stimulation differs markedly among WATs. Sympathetic activation might be involved in development of the metabolic syndrome by modulation of serum adiponectin concentrations.

Effusion and solid lymphomas have distinctive gene and protein expression profiles in an animal model of primary effusion lymphoma

Lymphoma usually forms solid tumours in patients, and high expression levels of adhesion molecules are observed in these tumours. However, Kaposi's sarcoma-associated herpesvirus (KSHV)-related primary effusion lymphoma (PEL) does not form solid tumours and adhesion molecule expression is suppressed in the cells. Inoculation of a KSHV-associated PEL cell line into the peritoneal cavity of severe combined immunodeficiency mice resulted in the formation of effusion and solid lymphomas in the peritoneal cavity. Proteomics using two-dimensional difference gel electrophoresis and DNA microarray analyses identified 14 proteins and 105 genes, respectively, whose expression differed significantly between effusion and solid lymphomas. Five genes were identified as having similar expression profiles to that of lymphocyte function-associated antigen 1, an important adhesion molecule in leukocytes. Among these, coronin 1A, an actin-binding protein, was identified as a molecule showing high expression in solid lymphoma by both DNA microarray and proteomics analyses. Western and northern blotting showed that coronin 1A was predominantly expressed in solid lymphomas. Moreover, KSHV-encoded lytic proteins, including viral interleukin-6, were highly expressed in effusion lymphoma compared with solid lymphoma. These data demonstrate that effusion and solid lymphomas possess distinctive gene and protein expression profiles in our mouse model, and suggest that differences in gene and protein expression between effusion and solid lymphomas may be associated with the formation of effusion lymphoma or invasive features of solid lymphoma. Furthermore, the results obtained using this combination of proteomics and DNA microarray analyses indicate that protein synthesis partly reflects, but does not correlate strictly with, mRNA production.

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.

Restoration of transforming growth factor-beta type II receptor reduces tumorigenicity in the human adrenocortical carcinoma SW-13 cell line

Transforming growth factor-beta (TGF-beta) is a potent growth suppressor. Acquisition of TGF-beta resistance has been reported in many tumors, and has been associated with reduced TGF-beta receptor expression. In this study, we examined TGF-beta 1, TGF-beta type I receptor (TbetaRI) and TGF-beta type II receptor (TbetaRII) expression in SW-13 adrenocortical carcinoma cells by Northern and Western blot analysis. SW-13 cells did not express TbetaRII mRNA or protein. We have investigated the role of TbetaRII in modulating tumorigenic potential using stably transfected SW-13 cells with TbetaRII expression plasmid. TbetaRII-positive SW-13 cell growth was inhibited by exogenous human TGF-beta1 (hTGF-beta1) in a dose-dependent manner. In contrast, SW-13 cells and control clones transfected with empty vector remained hTGF-beta1-insensitive. Xenograft examination in athymic nude mice demonstrated that TbetaRII-positive SW-13 cells reduced tumor-forming activity. Reconstructing the TbetaRII can lead to reversion of the malignant phenotype of TbetaRII-negative human adrenocortical carcinoma, which contains SW-13 cells. Reduced TbetaRII expression may play a critical role in determining the malignant phenotype of human adrenocortical carcinoma.

Dissipating excess energy stored in the liver is a potential treatment strategy for diabetes associated with obesity

For examining whether dissipating excess energy in the liver is a possible therapeutic approach to high-fat diet-induced metabolic disorders, uncoupling protein-1 (UCP1) was expressed in murine liver using adenoviral vectors in mice with high-fat diet-induced diabetes and obesity, and in standard diet-fed lean mice. Once diabetes with obesity developed, hepatic UCP1 expression increased energy expenditure, decreased body weight, and reduced fat in the liver and adipose tissues, resulting in markedly improved insulin resistance and, thus, diabetes and dyslipidemia. Decreased expressions of enzymes for lipid synthesis and glucose production and activation of AMP-activated kinase in the liver seem to contribute to these improvements. Hepatic UCP1 expression also reversed high-fat diet-induced hyperphagia and hypothalamic leptin resistance, as well as insulin resistance in muscle. In contrast, intriguingly, in standard diet-fed lean mice, hepatic UCP1 expression did not significantly affect energy expenditure or hepatic ATP contents. Furthermore, no alterations in blood glucose levels, body weight, or adiposity were observed. These findings suggest that ectopic UCP1 in the liver dissipates surplus energy without affecting required energy and exerts minimal metabolic effects in lean mice. Thus, enhanced UCP expression in the liver is a new potential therapeutic target for the metabolic syndrome.

Constitutively active PDX1 induced efficient insulin production in adult murine liver

To generate insulin-producing cells in the liver, recombinant adenovirus containing a constitutively active mutant of PDX1 (PDX1-VP16), designed to activate target genes without the need for protein partners, was prepared and administered intravenously to streptozotocin (STZ)-treated diabetic mice. The effects were compared with those of administering wild-type PDX1 (wt-PDX1) adenovirus. Administration of these adenoviruses at 2x10(8)pfu induced similar levels of PDX1 protein expression in the liver. While wt-PDX1 expression exerted small effects on blood glucose levels, treatment with PDX1-VP16 adenovirus efficiently induced insulin production in hepatocytes, resulting in reversal of STZ-induced hyperglycemia. The effects were sustained through day 40 when exogenous PDX1-VP16 protein expression was undetectable in the liver. Endogenous PDX1 protein came to be expressed in the liver, which is likely to be the mechanism underlying the sustained effects. On the other hand, albumin and transferrin expressions were observed in insulin-producing cells in the liver, suggesting preservation of hepatocytic functions. Thus, transient expression of an active mutant of PDX1 in the liver induced sustained PDX1 and insulin expressions without loss of hepatocytic function.

[A case of advanced gastric cancer showing complete response to chemotherapy of peroral carcinostatic only]

The patient was a 68-year-old woman. She was referred to our hospital because of advanced gastric cancer. Endoscopic examination showed that the tumor was located in the Subcardia, with its oral margin invading the esophagus. Histologic examination of biopsy specimen led to a diagnosis of moderately to poorly differentiated adenocarcinoma. Apparent lymph node swellings (No. 7, No. 11) on enhanced CT examination indicated the metastasis of the gastric cancer. Consulting with her family, we decided to treat the cancer with chemotherapy using the peroral carcinostatic "UFT", and started it on November 18, 1997. Follow-up endoscopic examination confirmed that the tumor was reduced in size immediately after starting chemotherapy, and then finally disappeared on December 10, 1999. Since then, there has been no recurrence of the tumor. This is a rare case of gastric cancer showing complete response to chemotherapy using a peroral carcinosatatic alone.

Pharmacokinetic behaviour of cisplatin in peritoneal fluid after intraperitoneal administration of cisplatin-loaded microspheres

The objective of this study was to establish a pharmacokinetic model for the estimation of unchanged cis-dichlorodiammine-platinum (II) (CDDP) concentration in peritoneal fluid after intraperitoneal administration of cisplatin-loaded microspheres (CDDP-MS) and to elucidate the accuracy of this model by comparisons between actual and simulated values after intraperitoneal administration of CDDP-MS. We developed a method enabling the precise and quick assessment of the drug concentration in the peritoneal cavity. The pharmacokinetic parameters obtained after intravenous bolus injection at a dose of 2 mg kg(-1) were total body clearance (1026 mL h(-1) kg(-1)), elimination rate constant (3.24 h(-1)) and distribution volume of systemic circulation (316.7 mL kg(-1)). After an intraperitoneal bolus injection at a dose of 5 mg kg(-1), the absorption rate constant from the peritoneal cavity (3.64 h(-1)) and the distribution volume of the peritoneal cavity (13.5 mL kg(-1)) were determined. The protein-binding rate constant in ascites was 0.58 h(-1). Using these pharmacokinetic parameters, we established a pharmacokinetic model consisting of two compartments. Administration of CDDP-MS at a dose of 10 mg kg(-1), which released CDDP over 7 days in-vitro, yielded sustained concentrations of unchanged CDDP (1-2 mg mL(-1)) in the peritoneal cavity that persisted for 7 days, and that were predictable by applying the in-vitro dissolution profile to the pharmacokinetic model. The findings obtained from this study are useful for understanding the basic pharmacokinetic characteristics of unchanged CDDP in the peritoneal cavity and may also be important in the development of optimized CDDP-MS formulations.