Tomie Muraoka

Esophageal function worsens with long duration of diabetes

BackgroundThe aim of this study was to assess the relationship between the duration of diabetes and esophageal dysfunction.MethodsWe examined 66 patients with type 2 diabetes. Duration of diabetes was determined by asking patients and from their medical records. The patients were divided into three groups according to the duration of their diabetes: group A, 1–4 years, n = 26; group B, 5–9 years, n = 20; and group C, 10+ years, n = 20. Ambulatory esophageal 24-h pH and motility were monitored, and gastroesophageal reflux and esophageal motility disorders were estimated in detail.ResultsWhen the duration of diabetes was long, the percentage of time with pH < 4 tended to increase. The amplitude of esophageal peristaltic waves and the frequency of effective peristalsis were reduced when the duration of diabetes was long. A significant correlation was observed between the duration of diabetes and the frequency of effective peristalsis. The number of esophageal peristaltic waves per minute and the percentage of multipeaked peristaltic waves increased significantly in group B, and decreased when the duration of diabetes became longer.ConclusionsGastroesophageal reflux and esophageal motility disorders worsened with long duration of diabetes. These esophageal dysfunctions should be considered in patients with long-standing diabetes.

Exendin-4 regulates glucokinase expression by CaMKK/ CaMKIV pathway in pancreatic β-cell line

Aim: Glucokinase (GK) in pancreatic β cells is thought to be involved in insulin secretion and glucose homeostasis. This study investigates whether the long‐acting agonist of the glucagon‐like peptide 1, namely exendin‐4, mediates stimulatory effects on GK gene expression through the Ca2+/calmodulin (CaM)‐dependent protein kinase (CaMK) cascade.

The Transcriptional Factor Prolactin Regulatory Element-Binding Protein Mediates the Gene Transcription of Adrenal Scavenger Receptor Class B Type I via 3′,5′-Cyclic Adenosine 5′-Monophosphate

Prolactin regulatory element-binding (PREB) protein is a transcription factor that regulates prolactin promoter activity in the rat anterior pituitary. The PREB protein is not only expressed in the anterior pituitary but also in the adrenal gland. However, the role of PREB in the adrenal gland is not clearly understood. Scavenger receptor class B type I (SR-BI) is a receptor for high-density lipoprotein that mediates the cellular uptake of high-density lipoprotein-cholesteryl ester and is a major route for cholesterol delivery to the steroidogenic pathway in the adrenal gland. In the present study, we have examined the role of PREB in regulating SR-BI. SR-BI expression was found to be regulated by cAMP, which stimulated the expression of PREB in a dose-dependent manner. Conversely, overexpression of PREB using a PREB-expressing adenovirus increased the expression of the SR-BI protein in the adrenocortical cell line Y-1. In addition, PREB induced the expression of the luciferase reporter protein that was under the control of the SR-BI promoter. EMSA showed that PREB mediates its transcriptional effect by binding to the PREB-responsive cis-element of the SR-BI promoter. Finally, we used small interfering RNA to inhibit PREB expression in the Y-1 cells and demonstrated that the knockdown of PREB expression attenuated the effects of cAMP on SR-BI expression. In summary, our data showed that in the adrenal gland, PREB regulates the transcription of the SR-BI gene via cAMP.

Exendin-4 regulates GLUT2 expression via the CaMKK/CaMKIV pathway in a pancreatic β-cell line

The GLUT2 glucose transporter plays an important role in glucose-induced insulin secretion in pancreatic β-cells by catalyzing the uptake of glucose into the cell. In this study, we investigated whether exendin-4, a long-acting agonist of glucagon-like peptide-1, mediates stimulatory effects on GLUT2 gene expression through the Ca²+/calmodulin (CaM)-dependent protein kinase IV (CaMKIV) cascade. GLUT2 expression was examined by real-time polymerase chain reaction, Western blot analysis, and a reporter gene assay in rat insulin-secreting INS-1 cells incubated with exendin-4. An increased expression level of GLUT2 protein was noted in response to increasing concentrations of exendin-4, with maximal induction at 10 nmol/L. Real-time polymerase chain reaction analysis similarly revealed a significant increase in the amount of GLUT2 messenger RNA by 10 nmol/L exendin-4. Exendin-4 also stimulated GLUT2 promoter activity in response to increasing exendin-4 concentrations, but failed to do so in the presence of STO-609, a CaMKK inhibitor. We also investigated the effect of the constitutively active form of CaMKK (CaMKKc) on GLUT2 promoter activity. The result is consistent with the observations that CaMKKc/CaMKIV enhanced or up-regulated GLUT2 promoter activity in INS-1 cells. Furthermore, exendin-4 induction of GLUT2 protein expression was significantly suppressed in the cells knocking down the CaMKIV. In summary, activation of the CaMKK/CaMKIV cascade might be required for exendin-4-induced GLUT2 gene transcription, indicating that exendin-4 plays an important role in insulin secretion in pancreatic β-cells.

Isolated follicle-stimulating hormone (FSH) deficiency without mutation of the FSHβ gene and successful treatment with human menopausal gonadotropin

OBJECTIVE To describe the case of isolated follicle-stimulating hormone (FSH) deficiency without mutation of the FSHbeta gene. DESIGN Case report. SETTING Division of Endocrinology and Metabolism, Department of Internal Medicine, Faculty of Medicine, Kagawa University, Kagawa, Japan. PATIENT(S) A 22-year-old man referred for infertility, azoospermia, and isolated FSH deficiency. INTERVENTION(S) The patients FSHbeta gene was sequenced. Pituitary function at baseline and after repeated GnRH administration was evaluated. Testicular biopsy was performed. The patient was treated with human menopausal gonadotropin (hMG). MAIN OUTCOME MEASURE(S) Pathologic examination revealed hypospermatogenesis with isolated FSH deficiency without mutation of the FSHbeta gene. RESULT(S) The FSH levels remained below the normal range despite repeated GnRH stimulation. Hypospermatogenesis was confirmed by testicular biopsy. After 6 months of hMG treatment, spermatogenesis was successfully induced. CONCLUSION(S) We report the case of an infertile male with isolated FSH deficiency without any evidence of mutation in the FSHbeta gene.

PREB regulates transcription of pancreatic glucokinase in response to glucose and cAMP

Prolactin regulatory element binding (PREB) is a transcription factor that regulates prolactin promoter activity in rat anterior pituitary. The PREB protein is not only expressed in the anterior pituitary but also in the pancreas. We have recently reported that in pancreatic β‐cells, PREB regulates the transcription of the insulin gene in response to glucose stimulation. In the current study, we have examined the role of PREB in regulating glucokinase (GK) in pancreatic β‐cells. To analyse the effects of PREB on GK gene transcription, we employed a reporter gene assay. In the cells expressing or with knocked down PREB, GK expression was determined. GK expression was regulated by glucose and cAMP, and both glucose and cAMP stimulated the expression of PREB in a dose‐dependent manner. Conversely, overexpression of PREB using a PREB‐expressing adenovirus increased the expression of the GK protein. GK enzymatic activity was also significantly increased in the cells that stably expressed PREB. In addition, PREB induced GK promoter activity. Chromatin immunoprecipitation (ChIP) analyses showed that PREB mediated its transcriptional effect by binding to the PREB‐responsive cis‐element of the GK promoter. Finally, we used siRNA to inhibit PREB expression in cells and demonstrated that the knockdown of PREB attenuated the effects of glucose and cAMP on GK expression. Our data show that in pancreatic β‐cells, PREB regulates the transcription of the GK gene in response to glucose and cAMP.

The prolactin regulatory element-binding regulates of the 11β-hydroxylase gene

Prolactin regulatory element-binding (PREB) protein is a transcription factor not only in pituitary but also adrenal gland. Steroid 11beta-hydroxylase (CYP11B1), a member of the cytochrome p-450 superfamily, is responsible for the last step of glucocorticoid biosynthesis in the adrenal cortices of many kinds of animals. In the present study, we have examined the role of PREB in regulating CYP11B1. CYP11B1 expression was found to be regulated by cAMP, which stimulated the expression of PREB. In addition, PREB induced the expression of the luciferase reporter protein that was under the control of the CYP11B1 promoter. Electrophoretic mobility shift analysis (EMSA) showed that PREB mediates its transcriptional effect by binding to the PREB-responsive cis-element (PRCE) of the CYP11B1 promoter. The knockdown of PREB expression attenuated the effects of cAMP on CYP11B1 expression. In summary, our data showed that in the adrenal gland, PREB regulates the transcription of the CYP11B1 gene via cAMP.

The transcriptional factor PREB mediates MCP-1 transcription induced by cytokines in human vascular endothelial cells

OBJECTIVE The prolactin regulatory element binding (PREB) protein is a transcriptional factor that regulates prolactin promoter activity in rat anterior pituitary. It is expressed not only in the anterior pituitary but also in the cardiovascular system, including in human umbilical vascular endothelial cells (HUVECs). Monocyte chemoattractant protein-1 (MCP-1) is a major chemotactic factor for monocytes and a key factor initiating the inflammatory process of atherogenesis. MCP-1 is expressed in HUVECs in response to several different stimuli, including interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha. METHODS AND RESULTS MCP-1 expression was regulated by IL-1beta and TNF-alpha and cytokine-induced PREB expression. Conversely, over-expression of PREB using a PREB-expressing adenovirus increased MCP-1 expression in HUVECs. In addition, PREB induced the expression of the luciferase reporter protein under the MCP-1 promoter control. EMSA showed that the transcriptional effect of PREB was mediated by its binding to the PREB-responsive cis-element of the MCP-1 promoter. Finally, we used siRNA to inhibit PREB expression in HUVECs and demonstrated that knockdown of PREB expression attenuated the effects of IL-1beta and TNF-alpha on MCP-1 expression. CONCLUSIONS In summary, our findings show that PREB can function as a transcriptional regulator of the MCP-1 promoter in response to cytokines.

Misdiagnosis of Two Cases of Primary Aldosteronism Owing to Failure of Computed Tomography to Detect Adrenal Microadenoma

Recent studies have suggested that primary aldosteronism (PA) is a common form of hypertension. However, some cases of PA are overlooked because microadenoma is difficult to detect by imaging. The author report 2 cases in which aldosterone-producing microadenoma was diagnosed by selective adrenal venous sampling (AVS) and furosemide plus upright test. These adenomas were resected by laparoscopic adrenalectomy. Both cases presented with hypertension and hypokalemia. Experimental data, including those obtained from furosemide plus upright test, suggested PA. In both cases, computed tomography imaging revealed a normal adrenal gland without any tumor. However, selective AVS indicated unilateral hypersecretion of aldosterone. Laparoscopic adrenalectomy was performed, and clinical symptoms of the patients improved. The histopathologic findings revealed aldosterone-producing microadenomas with diameters of 6 and 3 mm, respectively, in cases 1 and 2. In conclusion, AVS should be performed to confirm the diagnosis of PA when computed tomography imaging does not provide definite results.

Prolactin regulatory element–binding protein involved in cAMP-mediated suppression of adiponectin gene

Adiponectin (ApN) has several protective effects against diabetes and atherosclerosis. However, the detailed mechanisms of the regulation of the ApN gene have not yet been clarified. Prolactin regulatory element–binding (PREB) protein has been identified as a factor that regulates insulin gene expression in the pancreas. PREB is located not only in the pancreas but also in adipose tissue; however, its role in adipose tissue is not known. To analyse the effects of PREB on ApN gene transcription, we employed a reporter gene assay and electrophoretic mobility shift assay (EMSA). In the cells expressing or knocking down the PREB, ApN expression was determined. PREB was located mainly in the nuclei of adipose tissue and its cell line, 3T3‐L1 cells. The nuclear extract contained ApN promoter‐binding activity that was super‐shifted by PREB antiserum in EMSA studies. In the 3T3‐L1 cells, the co‐expression of PREB and the ApN promoter inhibited the activity of the latter. The addition of cAMP to the cells increased PREB expression in a dose‐dependent manner. A deletional analysis of the ApN promoter showed that the PREB‐responsive cis‐element in the ApN promoter mediated the transcriptional effect of PREB, whereas a mutant of this motif in the ApN promoter abrogated the effect of PREB, as well as that of cAMP. Furthermore, cells expressing or knocking down PREB exhibited decreased and increased ApN expression, respectively. These results demonstrate that PREB may contribute to the regulation of ApN gene transcription, in response to cAMP activation in adipocytes.