Glucotoxicity-induced suppression of Cox6a2 expression provokes ß-cell dysfunction via augmented ROS production.

Oxidative stress is a deteriorating factor for pancreatic ß-cells under chronic hyperglycemia in diabetes. However, the molecular mechanism underlying the increase in oxidative stress in ß-cells under diabetic conditions remains unclear. We demonstrated previously that the selective alleviation of glucotoxicity ameliorated the downregulation of several ß-cell factors, including Cox6a2. Cox6a2 encodes a subunit of the respiratory chain complex IV in mitochondria. In this study, we analyzed the role of Cox6a2 in pancreatic ß-cell function and its pathophysiological significance in diabetes mellitus. Cox6a2-knockdown experiments in MIN6-CB4 cells indicated an increased production of reactive oxygen species as detected by CellROX Deep Red reagent using flow cytometry. In systemic Cox6a2-knockout mice, impaired glucose tolerance was observed under a high-fat high-sucrose diet. However, insulin resistance was reduced when compared with control littermates. This indicates a relative insufficiency of ß-cell function. To examine the transcriptional regulation of Cox6a2, ATAC-seq with islet DNA was performed and an open-chromatin area within the Cox6a2 enhancer region was detected. Reporter gene analysis using this area revealed that MafA directly regulates Cox6a2 expression. These findings suggest that the decreased expression of Cox6a2 increases the levels of reactive oxygen species and that Mafa is associated with decreased Cox6a2 expression under glucotoxic conditions.

Production scheme for diagnostic-therapeutic radioisotopes by accelerator neutrons.

Interest has been growing in the development of medical radioisotopes used for noninvasive nuclear medicine imaging of disease and cancer therapy. Especially the development of an alternative production scheme of 99Mo, the mother radioisotope of 99mTc used for imaging, is required, because the current supply chain of the reactor product 99Mo is fragile worldwide. We have proposed a new production scheme of 99Mo as well as therapeutic radioisotopes, such as 64Cu and 67Cu, using accelerator neutrons provided by the natC(d,n) reaction. Based on this scheme we have obtained high-quality 99mTc, 64Cu, and 67Cu suitable for clinical use by developing both production and separation methods of the radioisotopes. We proposed a new facility to constantly and reliably produce a wide variety of high-quality, carrier-free radioisotopes, including 99Mo, with accelerator neutrons. We report on the development of the proposed scheme and future prospects of the facility toward the domestic production of medical radioisotopes.

A case of ectopic ACTH syndrome due to DDAVP-sensitive but V1b receptor-negative bronchial typical carcinoid with lymphatic metastasis and plasma ProGRP elevation.

Ectopic ACTH syndrome (EAS) is a potentially fatal endocrine disease that results from a variety of neuroendocrine tumors (NETs), such as small cell lung cancer (SCLC) and bronchial typical carcinoid. Typical carcinoid is usually slow growing, not associated with plasma progastrin releasing peptide (ProGRP) elevation. Here, we report a 47-year-old female smoker with progressive typical carcinoid and plasma ProGRP elevation. Several types of Cushingoid features were found on physical examination. In addition, laboratory examination showed elevated plasma ACTH and serum cortisol levels. These findings indicated ACTH-dependent Cushing's syndrome. Moreover, the serum cortisol level was not suppressed by overnight high-dose dexamethasone treatment, suggesting the presence of an extra-pituitary tumor. Contrast-enhanced brain MRI revealed no pituitary adenoma, which also supported the idea that EAS occurred in the present case. Strikingly, chest computed tomographic (CT) scan showed a single 18-mm peripheral nodule in the right middle lobe of the lung. Tumor marker analysis revealed an elevation in plasma ProGRP. These data suggested a possibility that SCLC secreted ACTH and caused EAS in this patient. Of note, the plasma ACTH level was increased (1.7 fold) in l-desamino-8-D-arginine vasopressin (DDAVP) test, also suggesting the specific clinical feature in this case. After additional imaging examinations, we performed surgical resection with the suspicion of limited SCLC. As a result, pathological examination revealed a vasopressin receptor Ib (V1b) receptor-negative bronchial typical carcinoid with ACTH production and mediastinal lymphatic metastasis. In summary, we present a case of EAS caused by progressive bronchial typical carcinoid with plasma ProGRP elevation. We propose a novel subtype of lung typical carcinoid.

Suppression Failure of Cortisol Secretion by Dexamethasone May Occur in Glucagon-like Peptide-1 Receptor Agonist-treated Patients with Diabetic Autonomic Neuropathy.

Two diabetic women (case 1, 75 years old; case 2, 49 years old) being treated with glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1 RAs) showed no suppression of cortisol secretion on a dexamethasone suppression test (DST). However, its secretion was suppressed after switching from GLP-1 RAs to insulin. We also checked the cortisol secretion by a DST in five consecutive inpatients (case 3-7) being treated with GLP-1 RAs. The coefficients of R-R interval variation at rest and during deep breathing were lower in the two false-positive cases (case 1 and 2) than in the five true-negative cases (case 3-6). GLP-1 RAs can be switched to insulin in order to eliminate the slow absorption effect of dexamethasone by GLP-1 RAs if a DST is planned in diabetic patients receiving GLP-1 RAs.