Exendin-4 regulates the expression of the ATP-binding cassette transporter A1 via transcriptional factor PREB in the pancreatic ß cell line.

BACKGROUND: PRL regulatory element-binding (PREB) protein is a transcription factor that regulates insulin promoter activity in the rat anterior pituitary. The PREB protein is expressed not only in the anterior pituitary but also in pancreatic ß cells. Previously, we have reported that PREB plays an important role in glucose-mediated insulin gene expression in pancreatic ß cells. The ATP-binding cassette transporter A1 (ABCA1) in pancreatic ß cells influences insulin secretion and glucose homeostasis. Exendin-4 (Ex-4), a longacting agonist of the glucagon-like peptide 1, stimulates ABCA1 expression in pancreatic ß cells. AIMS: In this study, we examined the role played by PREB in Ex-4-induced ABCA1 expression in pancreatic ß cells. MATERIAL/SUBJECTS AND METHODS: PREB mRNA and protein expression were evaluated in pancreatic ß cell line (INS-1 cells) treated with Ex-4 (10 nM). RESULTS: Ex-4 stimulated PREB protein and mRNA expression in INS-1 cells. PREB stimulated the activity of the luciferase reporter protein that was under the control of the ABCA1 promoter. Chromatin immunoprecipitation assay showed that PREB mediates its transcriptional activity by directly binding to the ABCA1 promoter region. Finally, we used small interfering RNA to inhibit PREB expression in the cells and demonstrated that the knockdown of PREB expression attenuated the effects of Ex-4 on ABCA1 expression. CONCLUSION: PREB mediates Ex-4-stimulated transcription of the ABCA1 gene in pancreatic ß cells.

Raloxifene inhibits menin-dependent estrogen receptor activation in breast cancer cells.

BACKGROUND: Menin is a tumor suppressor encoded by Men1 that is mutated in the human-inherited tumor syndrome--multiple endocrine neoplasia type 1. Menin binds to estrogen receptors (ER) to enhance estrogen activity in breast cancer cells. AIM: Our clinical study showed that the outcome in the case of menin-positive tumors was worse than in the case of menin-negative tumors. We examined the role of raloxifene on the cell growth in a menin-positive breast cancer cell line. MATERIAL AND METHODS: To examine the mechanism of raloxifene on menin-dependent activation of ER, we employed the mammalian two-hybrid system. We have established a breast cancer cell line that stably expresses menin. Using these cells, we have examined the effect of raloxifene and tamoxifen on cell growth of menin-transfected cells. RESULTS: The expression of activation function (AF)-2 enhanced menin-mediated luciferase expression in the mammalian two-hybrid assay. Raloxifene attenuated the effect of menin on estrogen response element-luciferase activation, indicating that raloxifene inhibited the binding of menin to AF-2. Raloxifene significantly inhibited the growth of menin-transfected cells in a dose-dependent manner. Tamoxifen also inhibited menin-transfected MCF-7 cells; however, this inhibition was much less than that of raloxifene. CONCLUSION: Raloxifene inhibits the binding of menin to the AF-2 domain of ERα, suggesting that raloxifene is one of the therapeutic options for menin-positive breast cancer.

What factors are involved in the knowledge necessary for the self-management of diabetic patients?

The aim of this study is to obtain data for improving a training program for patients with diabetes mellitus. One hundred eighty-seven patients with non-insulin dependent diabetes mellitus were tested with 20 questions about their knowledge for self-management of diabetes mellitus. Then to draw out factors in their personal backgrounds relating to their correct answers, multiple regression analyses were conducted. As a result, four factors showed significant differences in the following order: Educational careers > ages > duration of disease > socioeconomic strata. The results of the present study have shown for the first time, that these four factors closely concern patients to acquire the necessary knowledge for their self-management of the disease. In addition, this study has raised some fundamental problems regarding the training program for patients: how education should be given to patients.

The effects of radical scavengers and leukocyte-depleted blood on reperfusion injury of extirpated rabbit lung.

Oxygen radicals produced by polymorphonuclear leukocytes were considered primarily responsible for reperfusion injury in lung transplantation. Using the extirpated rabbit lungs as a transplant model, we measured lung water volume, the oxygen radicals of lung tissue using a direct method (electron spin resonance) and an indirect method (measurement of peroxide lipids). The effects of free radical scavengers, human superoxide dismutase (h-SOD) and catalase (CAT), and leukocyte-depleted blood on reperfusion injury were evaluated in three experimental groups. Group I (n = 8, control): Lung reperfusion was performed with blood from other rabbits. Group II (n = 7): Immediately before reperfusion, h-SOD (1,500 u/ml) and CAT (3,000 u/ml) were added to the blood. Group III (n = 7): Reperfusion was performed with the leukocyte-depleted blood. Severe pulmonary edema and an elevation of malondialdehyde (MDA) occurred in Group I. In Group II, addition of radical scavengers to the reperfusion blood produced only mild pulmonary edema, but an elevation of MDA occurred as in Group I. In Group III, pulmonary edema and MDA elevation were almost completely suppressed.

Changes in levels of arachidonic acid metabolites in blood and bronchoalveolar lavage fluid after warm ischemia-reperfusion of lung.

The purpose of this study was to evaluate the role of arachidonic acid metabolites in the reimplantation response after lung transplantation in mongrel dogs. The left lung was used and two groups were studied. Group I underwent hilar stripping, while Group II underwent hilar stripping plus warm ischemia for 60 min., achieved by clamping the left pulmonary artery and veins. We measured the lung wet to dry weight ratio (W/D ratio), total pulmonary vascular resistance (TPVR), and blood and bronchoalveolar lavage fluid (BALF) levels of leukotriene B4 and C4 (LTB4,C4) and thromboxane B2 (TXB2). These parameters were measured periodically for 7 days after reperfusion. In group II, the W/D ratio and TPVR were significantly increased in comparison with Group I. The blood LTC4 level was elevated immediately after reperfusion, and BALF level of LTC4 also rose subsequently. These levels changed concomitantly with the W/D ratio. The above results suggest that arachidonic acid metabolism plays an important role in the reimplantation response, especially in pulmonary edema.

Decreased creatinine clearance which may be observed during prostaglandin E1 therapy: is it reversible with discontinuation of therapy?

A study was carried out in four patients with nephrotic diabetic nephropathy in order to determine if decreased creatinine clearance observed during prostaglandin E1 therapy was reversible on discontinuation of therapy. The patients received 40 micrograms prostaglandin E1 intravenously twice daily for 4 weeks and creatinine clearance and daily excretion of urinary protein were measured immediately before, during and 2 weeks after therapy. Total serum protein and serum albumin were also determined. There was a significant decrease in creatinine clearance during therapy and after therapy clearance increased but not significantly. It is concluded that decreased creatinine clearance during prostaglandin E1 therapy has a partial reversibility on discontinuation of the treatment.

Clinofibrate therapy raises high-density lipoprotein levels and lowers atherogenic index in diabetes mellitus patients.

The effects of clinofibrate on serum lipoprotein concentrations, lecithin cholesterol acyl transferase activity and atherogenic index were studied in 10 diabetes mellitus patients. The patients comprised five with well-controlled non-insulin-dependent diabetes, and five with poorly controlled insulin-dependent diabetes; six non-insulin-dependent diabetics acted as placebo controls. No adverse side-effects were reported and there were no significant changes in total cholesterol, triglyceride or high-density lipoprotein 3-cholesterol concentrations following 600 mg/kg clinofibrate treatment for 4 weeks in either insulin-dependent or non-insulin-dependent diabetics. High-density lipoprotein-cholesterol concentrations and lecithin cholesterol acyl transferase activity were significantly (P less than 0.05) increased by clinofibrate treatment in insulin-dependent and non-insulin-dependent diabetics and high-density lipoprotein 2-cholesterol concentrations were significantly (P less than 0.05) increased by clinofibrate in insulin-dependent diabetics. The atherogenic index was significantly (P less than 0.01) reduced in non-insulin-dependent diabetics. It is suggested that the enhanced plasma lecithin cholesterol acyl transferase activity following clinofibrate therapy is the result of increased high-density lipoprotein-cholesterol and high-density lipoprotein 2-cholesterol concentrations and may play a central role in the efficacy of clinofibrate.

Serum C3 and C4 levels and complement-dependent antibody-mediated cytotoxic activity of islet cell surface antibody in type 1 (insulin-dependent) diabetic children.

The role of complement in the pathogenesis of diabetes was studied in 31 Type 1 (insulin-dependent) diabetic children by assaying serum islet cell surface antibody, C3, C4 and serum complement-dependent antibody-mediated cytotoxicity. Nine of 21 islet cell surface antibody-positive children were within 5 months of disease onset and showed significantly lower serum C3 and C4 levels than either 1 year later or the remainder of the islet cell surface antibody-positive children at 6-12 months after disease onset. The overall trend of all islet cell surface antibody-positive diabetic children within 1 year of disease onset was toward increased serum C3 and C4 levels as the disease progressed. Serum C4 concentration and complement-dependent antibody-mediated cytotoxicity which showed an initial negative correlation were uncorrelated 1 year later. Four children who were initially strongly islet cell surface antibody-positive but negative 1 year later also exhibited significantly higher (p less than 0.05) mean serum C4 levels after 1 year. There was a significant decrease in complement-dependent antibody-mediated cytotoxicity when sera from the diabetic children were treated with either ethylene glycol tetra-acetic acid or ethylene diamine tetra-acetic acid. These data strongly suggest that complement-dependent antibody-mediated cytotoxicity induced by the classical complement pathway involving an islet cell surface antibody may play an important role in the pathogenesis of Type 1 diabetes.

Effect of clonidine on insulin secretion: a case report.

We have recently seen a case of non-insulin-dependent diabetes mellitus with hypertension in which chronic treatment with oral clonidine gave rise to elevation of blood glucose and decreased insulin secretion. When the response of insulin secretion to glucose administration during clonidine therapy was compared with that after 12 days of wash-out for clonidine in this patient (who was then receiving phentolamine mesylate), there was a marked suppression of insulin secretion to stimulation by intravenous glucose during oral clonidine therapy. This result indicates that the decreased insulin secretion associated with oral clonidine therapy is very unlikely to be due to any direct action of clonidine on beta cells of the pancreatic islets and may be due to suppression of catecholamine release via central alpha-adrenergic receptor stimulation.

Purification of insulin-binding antibody by affinity chromatography using monocomponent insulin as ligand.

Insulin-binding antibody (IBA) was purified by affinity chromatography using porcine monocomponent (MC) insulin as the ligand. The purity of the antibody was compared with that of the antibody extracted using porcine crystalline (Cr) insulin. Comparing the antibody solutions obtained with MC insulin (MC-lig-sol) or Cr insulin (Cr-lig-sol), the content of IBA in Cr-lig-sol was higher than in MC-lig-sol, but the content of proinsulin-binding antibody (PBA) in MC-lig-sol was very small and statistically lower than that in Cr-lig-sol (P less than 0.01). Adding native MC insulin to a competitive radioimmunoassay suppressed the IBA titer obtained with MC insulin more than that obtained with Cr insulin. By adding native proinsulin in a similar assay system, the PBA titer obtained with Cr insulin was suppressed more than that extracted with MC insulin. Scatchard analysis of the 2 solutions showed that the affinity constants of high affinity antibodies were almost identical, but that of low affinity antibody in MC-lig-sol was larger than in Cr-lig-sol. The binding capacity of low affinity antibody in Cr-lig-sol was 15 times as much as that in MC-lig-sol. Using MC insulin, instead of Cr insulin, as the ligand in affinity chromatography increased the purity of recovered IBA. chromatography increased the purity of recovered IBA.

Influence of an antianxiety drug on hyperemesis diabeticorum.

The patient was a 37-year-old female teacher with hyperemesis diabeticorum and juvenile Type-I diabetes. At the age of 29 years, nausea and vomiting developed and secured at nearly weekly intervals. She was started on clotiazepam (15 mg/day). The vomiting was cured and psychological improvement was evident; her anxiety about diabetes was markedly reduced. An X-ray examination after the administration of clotiazepam showed that she was entirely free from marked hypoperistalsis and the severe retention of gastric contents which had been present before this treatment. The present case is a clear example of stress closely related to the pathogenesis of hyperemesis diabeticorum.