Pancreatic beta cell dysfunction is pivotal to the development of diabetes, and restoration of insulin action is of primary importance. Here, we present a review of the mechanism of insulin secretion by pancreatic beta cells and discuss the mutual interaction of signaling pathways in stimulus - secretion coupling to better understand the scientific basis of pharmacological treatment for insulin secretion deficiency. Glucose stimulates insulin secretion via membrane depolarization by closure of ATP-sensitive K⁺ channels (K_ATP channels) and opening of L-type voltage-dependent Ca²⁺ channels. The resultant elevation of cytosolic free Ca²⁺ triggers insulin exocytosis. This is termed the “K_ATP-dependent pathway” and is shared by sulfonylurea, which closes K_ATP channels. Glucose also stimulates insulin release independent of its action on K_ATP channels. This is referred to as the “K_ATP-independent pathway,” the molecular basis of which remains elusive. In the pancreatic beta cell, incretin hormones increase cAMP level, which enhances glucose-stimulated insulin release by protein kinase A-dependent and -independent mechanisms. Importantly, cAMP does not directly augment Ca²⁺-stimulated insulin release per se. The stimulatory level of ambient glucose is an absolute requirement for incretin to enhance insulin release. Therefore, incretin/cAMP enhances K_ATP-independent insulinotropic action of glucose. The robust glucose-lowering effect of DPP4 inhibitor add-on in diabetic patients with sulfonylurea secondary failure is intriguing. With the clinical availability of DPP4 inhibitor and GLP-1 mimetics, the importance of the interactions between cAMP signaling and K_ATP channel-independent actions of glucose is reappraised.

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Adrenocortical carcinoma (ACC) is a very rare malignant tumor with poor prognosis. To gain insight into the pathogenic significance of ACC, we studied clinicopathological features and gene expression profile in ACC. We analyzed five ACC cases (two men and three women) with the median age of 45-year-old who underwent adrenalectomy at our institute. Endocrine studies revealed that two cases had subclinical Cushing’s syndrome (SCS) and one with concomitant estrogen-secreting tumor, while the rest of three cases had non-functioning tumors. Analysis of urinary steroids profile by gas chromatography/mass spectrometry showed increased metabolites of corticosteroid precursors, such as 17-OH pregnenolone, 17-OH progesterone, dehydroepiandorosterone (DHEA), and 11-deoxycortisol in all five cases. The pathological diagnosis of ACC was based on Weiss’s criteria with its score ≥ 3. The mean size of the resected tumors was 87 mm and Ki67/MIB1 labeling index, a proliferative marker, was 3 - 27%. Immunohistochemical analysis revealed a disorganized expression of several steroidogenic enzymes, such as 3β-hydroxysteroid dehydrogenase, 17α-hydroxylase, and DHEA-sulfotransferase. Among several genes determined by RT-PCR, insulin-like growth factor (IGF)-II mRNA was consistently and abundantly expressed in all 5 tumor tissues. Postoperatively, two cases with SCS developed local recurrence and liver metastasis. The present study suggests that the disorganized expression of steroidogenic enzymes and the overexpression of IGF-II by the tumor are hallmarks of ACC, which could be used as biochemical and molecular markers for ACC.

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This study was to determine whether glycemic variability is related to hypoglycemic events in type 1 diabetic patients, and whether the hypoglycemic events during a short-term continuous glucose monitoring system (CGMS) period parallel those measured during a 4-week self-monitoring of blood glucose (SMBG) period. We also evaluated whether glycemic variability indexes from a short-term CGMS correlate with those from a 4-week SMBG. A total of 49 type 1 diabetic patients wore CGMS devices for 3 days. These patients also performed SMBG for 4 weeks. Several indexes from the CGMS data were compared with indexes from the SMBG data. Hypoglycemic events (glucose levels < 70 mg/dL) that occurred during the 3-day CGMS and 4-week SMBG periods were evaluated and compared. Hypoglycemic events were detected in 33 patients (67%) during the 3-day CGMS period. The patients with hypoglycemic events had a significantly higher glycemic variability index divided by mean glucose of CGMS, and a higher number of hypoglycemic events during the 4-week SMBG, compared to those with non-hypoglycemic events during the 3-day CGMS period. The percentage of hypoglycemic events using the 3-day CGMS was correlated with that from the 4-week SMBG (r = 0.49, P < 0.05) and low blood glucose index (r = 0.51, P < 0.05). The glycemic variability indexes from the 4-week SMBG correlated with the glycemic variability indexes from the 3-day CGMS. The short-term CGMS appears to be clinically useful for rapidly assessing the risk of hypoglycemic events and glycemic variability.

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Primary aldosteronism (PA), an autonomous aldosterone hypersecretion from adrenal adenoma and/or hyperplasia, and subclinical Cushing syndrome (SCS), a mild but autonomous cortisol hypersecretion from adrenal adenoma without signs or symptoms of Cuhing’s syndrome, are now well-recognized clinical entities of adrenal incidentaloma. However, the clinicopathological features of PA associated with SCS (PA/SCS) remain unknown. The present study was undertaken to study the prevalence of PA/SCS among PA patients diagnosed at our institute, and characterize their clinicopathlogical features. The prevalence of PA/SCS was 8 of 38 PA patients (21%) studied. These 8 PA/SCS patients were significantly older and had larger tumor, higher serum potassium levels, lower basal plasma levels of aldosterone, ACTH and DHEA-S as well as lower response of aldosterone after ACTH stimulation than those in 12 patients with aldosterone-producing adenoma without hypercortisolism. All 8 PA/SCS patients showed unilateral uptake by adrenal scintigraphy at the ipsilateral side, whereas the laterality of aldosterone hypersecretion as determined by adrenal venous sampling varied from ipsilateral (3), contralateral (2), and bilateral side (2). 6 PA/SCS patinets who underwent adrenalectomy required hydrocortisone replacement postoperatively. Histopathological analysis of the resected adrenal tumors from 5 PA/SCS patients revealed a single adenoma in 3, and double adenomas in 2, with varying degrees of positive immunoreactivities for steroidgenic enzymes (3β-HSD, P450_C17) by immunohistochemical study as well as CYP11B2 mRNA expression as measured by real-time RT-PCR. In conclusion, PA/SCS consists of a variety of adrenal pathologies so that therapeutic approach differs depending on the disease subtype.

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This report presents the case of a 47-year-old female patient with fulminant type 1 diabetes mellitus and myocarditis. Following a high fever, nausea, vomiting and diarrhea, diabetic ketoacidosis occurred and she was transferred to the hospital. The plasma glucose level was 63.6mmol/L and HbA1c was 7.0%. C-peptide was undetectable in her plasma. Blood gas analysis showed a pH of 6.99. Antibodies to glutamic acid decarboxylase nor insulinoma associated antigen-2 were not detected. She was diagnosed to have fulminant type 1 diabetes mellitus. Her electrocardiogram showed diffuse ST-segment elevations on the second day of admission, along with a positive troponin test. However coronary angiography revealed neither occlusion nor stenosis of the cardiac arteries. An endomyocardial biopsy revealed hypertrophic cardiomyocytes with a disarrangement of myofibers and the focal accumulation of mononuclear cells in the stroma, thus suggesting myocarditis or mild myocarditic change. Viruses are an important cause of myocarditis and the preceding flu-like symptoms indicate the association of viral infection with myocarditis in this case. The mechanisms by which fulminant type 1 diabetes mellitus occurs is still uncertain, but the presence of islet injury accompanied by myocardial inflammation in the current case suggested that a viral infection accounted for the onset of this type of diabetes.

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The anteroventral third ventricular region (AV3V) is a pivotal area for osmotic responses and integration of autonomic functions. The purpose of this study was to investigate whether the gamma-aminobutyric acid (GABA)-ergic activity in the AV3V may be involved in the regulation of arginine vasopressin (AVP) secretion and related phenomena under the conditions with or without hypovolemia. Experiments were performed in conscious rats. We found that AV3V infusion with the GABA_A receptor antagonist bicuculline in euvolemic rats caused prompt increases in plasma AVP, osmolality, glucose, arterial pressure and heart rate. The effects of the bicuculline infusion were abolished by prior infusion of a GABA_A receptor agonist, muscimol. When repeated twice with a 10-min interval, removal of systemic blood (10 mL/kg body weight) lowered arterial pressure and enhanced plasma AVP, osmolality, glucose and angiotensin II. Muscimol infusion in the AV3V, but not in the cerebral ventricle, inhibited the responses of plasma AVP and glucose, despite having no effect in a sham hemorrhagic state. The inhibition of the AVP response by the muscimol infusion was also verified in rats given a combined stimulus of bleeding plus an osmotic load. In contrast, AV3V infusion with the GABA_B receptor agonist baclofen tended to intensify the hemorrhagic responses of plasma AVP and glucose, despite its potency to prevent the hemorrhagic fall in arterial pressure. These results, taken together with our previous data, suggest that hypovolemic stimuli, like hyperosmotic stimuli, may promote AVP secretion by causing the inhibition of AV3V GABA_A-ergic activity responsible for potentiation of glutamatergic activity.

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Radioiodine (RI) such as ¹³¹I or ¹²⁴I, can generate luminescent emission and be detected with an optical imaging (OI) device. To evaluate the possibility of a novel Cerenkov luminescence imaging (CLI) for application in thyroid research, we performed feasibility studies of CLI by RI in the thyroid gland and human anaplastic thyroid carcinoma cells expressing sodium iodide symporter gene (ARO-NIS). For in vitro study, FRTL-5 and ARO-NIS were incubated with RI, and the luminometric and CLI intensity was measured with luminometer and OI device. Luminescence intensity was compared with the radioactivity measured with γ-counter. In vivo CLI of the thyroid gland was performed in mice after intravenous injection of RI with and without thyroid blocking. Mice were implanted with ARO-NIS subcutaneously, and CLI was performed with injection of ¹²⁴I. Small animal PET or γ-camera imaging was also performed. CLI intensities of thyroid gland and ARO-NIS were quantified, and compared with the radioactivities measured from nuclear images (NI). Luminometric assay and OI confirmed RI uptake in the cells in a dose-dependent manner, and luminescence intensity was well correlated with radioactivity of the cells. CLI clearly demonstrated RI uptake in thyroid gland and xenografted ARO-NIS cells in mice, which was further confirmed by NI. A strong positive correlation was observed between CLI intensity and radioactivity assessed by NI. We successfully demonstrated dual molecular imaging of CLI and NI using RI both in vitro and in vivo. CLI can provide a new OI strategy in preclinical thyroid studies.

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The aim of the present study was to establish new reference intervals for serum thyrotropin (TSH) levels in Japanese subjects without antithyroid antibodies. We reviewed the serum TSH level of all patients 20 years of age and over who attended the outpatient clinic of our hospital between January 1, 2003, and September 20, 2010. The thyroid gland of every patient was examined by ultrasonography, and subjects found to have a normal thyroid were chosen. The following subjects were excluded: subjects with past history of thyroid diseases; subjects whose serum was positive for antithyroid antibodies; pregnant women; patients taking medication that might affect their free thyroxine (fT₄) level or TSH levels. Ultimately, 1388 subjects were included in the reference population. The serum TSH levels shifted to higher ranges as the age of the groups increased. The calculated reference range was 0.39-4.29 mIU/L in the 20-29-year-old group, 0.34-3.90 mIU/L in the 30-39-year-old group, 0.56-5.02 mIU/L in the 40-49-year-old group, 0.51-5.30 mIU/L in the 50-59-year-old group, 0.60-4.85 mIU/L in the 60-69-year-old group, 0.62-6.15 mIU/L in the over 70-year-old group. The results of this study showed that the upper limit of the normal range of serum TSH levels increased with age in a Japanese population. Since the number of elderly reference subjects was relatively small, further study is needed. Setting the age- and race-specific reference limits for serum TSH levels is important in order to prevent significant misclassifications of patients with abnormal TSH levels.

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The prevalence of diabetes is increasing globally. In addition to established risk factors for diabetes, such as diet, inactivity, overweight and obesity, the involvement of persistent organic pollutants, including dioxins and polychlorinated biphenyls (PCBs), has also been suggested to be a possible, but controversial, cause of this epidemic. The present study investigated the association between blood PCB congener levels and the prevalence of diabetes among middle-aged, overweight and obese Japanese participants in the Saku Control Obesity Program. One hundred seventeen participants had their congener-specific PCB levels measured in addition to undergoing routine blood analyses at the time of a medical checkup. Prevalent diabetes was defined according to two methods: definite diabetes was defined as people with an HbA1c level ≥ 6.9% or who were taking medication for diabetes, and all diabetes was defined as people with an HbA1c level ≥ 6.5%, a fasting plasma glucose level ≥ 126 mg/dL, or a history of doctor-diagnosed diabetes. A multiple logistic regression analysis was performed to analyze the association between the PCB levels and the prevalence of diabetes, with adjustments for sex, age, body mass index and total lipids. As a result, PCB 146 and 180 were positively associated and PCB 163/164 and 170 were negatively associated with the prevalence of definite diabetes. The significance of the association of PCB 180 and 163/164 with the prevalence of diabetes persisted regardless of the definition of diabetes or adjustments for total lipids, suggesting the possibility that these parameters may modify the risk of diabetes.

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Syndrome of inappropriate secretion of thyrotropin (SITSH) is a clinical state of inappropriately elevated secretion of thyrotropin (TSH) in the presence of elevated free thyroid hormones. Peripheral nerve hyperexcitability (PNH) is a rare disorder characterized by muscle twitching at rest. No relation between them is known. A 49-year-old man was referred to our hospital because of elevated serum free thyroxine (2.6 ng/dL; normal range, 0.9-1.7) and normal TSH (2.7 mIU/L; normal range, 0.5-5.0). Genetic analysis revealed no mutations of the thyroid hormone receptor β gene. Magnetic resonance imaging visualized no pituitary adenoma. He complained of appetite loss, weight loss, myokymia, paraesthesia, hyperhydrosis and insomnia. Chest X ray and computed tomography (CT) scan showed a mediastinal tumor diagnosed as a thymoma by CT-guided biopsy. Electromyography disclosed fasciculations and myokymic discharges. Nerve conduction studies showed prolonged after-discharges following evoked compound muscle action potential. The patient was diagnosed with thymoma-associated PNH based on neurological manifestations and neurophysiological findings, and was treated with pulse therapy with methylprednisolone after thymectomy. Interestingly, the SITSH state became less prominent as his neurological manifestations improved. This is the first case of SITSH possibly caused by thymoma-associated PNH.

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Patients with 21-hydroxyase deficiency (21-OHD) usually do not present clinical symptoms other than female ambiguous genitalia and skin pigmentation at birth. However, we have found a case of neonatal transient tachypnea with spontaneous pneumomediastinum in a neonate with 21-OHD at birth. The purpose of this study was to investigate the occurrence of neonatal respiratory disorders in 21-OHD patients. From April 1989 to March 2009, 478,337 Japanese newborns were screened for congenital adrenal hyperplasia in Niigata prefecture. Among these newborns, 26 patients were diagnosed as having 21-OHD. We investigated the presence of neonatal respiratory disorders based on the retrospective medical records of 24 full-term patients with 21-OHD. Three of the 24 patients (12.5%) had neonatal acute respiratory disorders. Neonatal transient tachypnea developed in all patients with only oxygenation for two or three days after birth. Chest X-rays showed spontaneous pneumothorax or pneumomediastinum in two patients. In conclusion, 21-OHD patients may present with acute respiratory disorders, especially transient tachypnea with spontaneous pneumothorax, at birth. In cases of delivering mothers having other children with 21-OHD, newborns require attention regarding neonatal respiratory disorders if a prenatal diagnosis has not been performed.

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Insulin overdose results in prolonged hypoglycemia. We hypothesized that if a huge amount of insulin is subcutaneously injected, the duration of hypoglycemia depends on the dose of insulin rather than the type of insulin. We conducted a literature review of insulin overdose and 33 cases were included in this study. We assessed the correlation between recovery time from hypoglycemia and insulin dose. As a result, there was a significant correlation between recovery time from hypoglycemia and insulin dose (r = 0.88, p <0.0001) and this correlation was expressed as y = 0.045x; where y is time (h) and x is insulin dose (U), corresponding to that if 1000 U insulin is injected, hypoglycemia will persist for _~45 h. This equation may be useful to predict the duration of glucose supplementation for treatment of insulin overdose.

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