Connexin36 contributes to INS-1E cells survival through modulation of cytokine-induced oxidative stress, ER stress and AMPK activity.

Cell-to-cell communication mediated by gap junctions made of Connexin36 (Cx36) contributes to pancreatic ß-cell function. We have recently demonstrated that Cx36 also supports ß-cell survival by a still unclear mechanism. Using specific Cx36 siRNAs or adenoviral vectors, we now show that Cx36 downregulation promotes apoptosis in INS-1E cells exposed to the pro-inflammatory cytokines (IL-1ß, TNF-α and IFN-γ) involved at the onset of type 1 diabetes, whereas Cx36 overexpression protects against this effect. Cx36 overexpression also protects INS-1E cells against endoplasmic reticulum (ER) stress-mediated apoptosis, and alleviates the cytokine-induced production of reactive oxygen species, the depletion of the ER Ca(2+) stores, the CHOP overexpression and the degradation of the anti-apoptotic protein Bcl-2 and Mcl-1. We further show that cytokines activate the AMP-dependent protein kinase (AMPK) in a NO-dependent and ER-stress-dependent manner and that AMPK inhibits Cx36 expression. Altogether, the data suggest that Cx36 is involved in Ca(2+) homeostasis within the ER and that Cx36 expression is downregulated following ER stress and subsequent AMPK activation. As a result, cytokine-induced Cx36 downregulation elicits a positive feedback loop that amplifies ER stress and AMPK activation, leading to further Cx36 downregulation. The data reveal that Cx36 plays a central role in the oxidative stress and ER stress induced by cytokines and the subsequent regulation of AMPK activity, which in turn controls Cx36 expression and mitochondria-dependent apoptosis of insulin-producing cells.

A novel ABCC8 mutation illustrates the variability of the diabetes phenotypes associated with a single mutation.

AIM: ATP-sensitive potassium channels are important regulators of insulin secretion. They consist of four sulphonylurea receptor (encoded by ABCC8) and four inwardly rectifying protein (encoded by KCNJ11) subunits. Activating ABCC8 mutations lead to decreased insulin secretion and to diabetes. Wide phenotype variability is associated with single ABCC8 mutations, ranging from transient or permanent neonatal diabetes (ND) with or without developmental delay (DEND syndrome) to very mild phenotypes. This report describes the case of a Caucasian infant diagnosed with ND at the age of 2 months due to a novel ABCC8 missense mutation. METHODS: ABCC8 was analyzed by sequence analysis. The mutation was present in the patient and her family and was found to be associated with phenotypes ranging from ND to asymptomatic impaired fasting glucose (IFG). RESULTS: A novel His863Tyr ABCC8 mutation was identified in a 2-month-old girl diagnosed with ND. After an initial insulin treatment, treatment with glibenclamide was initiated and the treatment with insulin discontinued. The same mutation was found in her father, who had been fortuitously diagnosed with diabetes and had an HbA(1c) level of 9% (74.8 mmol/mol). The patient's brother and mother both had normal fasting glucose, and were not found to be carriers of the mutation. However, the same mutation was found in her grandmother, who had been asymptomatic and discovered IFG (6.9 mmol/L) with an HbA(1c) of 6.8% (50.8 mmol/mol). CONCLUSION: This case describes a novel ABCC8 mutation and offers a further illustration of the highly variable phenotypes associated with an identical mutation present across three generations.

Modeling intrauterine growth retardation in rodents: Impact on pancreas development and glucose homeostasis.

Fetal adverse environment, such as insufficient maternal nutrition, placental insufficiency and stress, alters organ development and leads to poor fetal growth, also called intrauterine growth retardation (IUGR). IUGR is associated with an increased risk of perinatal mortality and morbidity as well as late-onset metabolic diseases, such as obesity, diabetes and hypertension in adulthood. In the rodent model, IUGR can be induced by fetal caloric restriction, fetal protein restriction, by exposure to high levels of glucocorticoids or by restricted placental blood supply. Such experimental IUGR models show a decreased beta cell mass and lower pancreatic insulin content. Recent research has provided an insight into the mechanisms responsible for the loss of beta cells. Here we review models that give further details about the molecular determinants of fetal and postnatal pancreatic islet development that are required to understand the consequences of fetal insults.

Islet-cell-to-cell communication as basis for normal insulin secretion.

The emergence of pancreatic islets has necessitated the development of a signalling system for the intra- and inter-islet coordination of beta cells. With evolution, this system has evolved into a complex regulatory network of partially cross-talking pathways, whereby individual cells sense the state of activity of their neighbours and, accordingly, regulate their own level of functioning. A consistent feature of this network in vertebrates is the expression of connexin (Cx)-36-made cell-to-cell channels, which cluster at gap junction domains of the cell membrane, and which adjacent beta cells use to share cytoplasmic ions and small metabolites within individual islets. This chapter reviews what is known about Cx36, and the mechanism whereby this beta-cell connexin significantly regulates insulin secretion. It further outlines other less established functions of the protein and evaluates its potential relevance for the development of novel therapeutic approaches to diabetes.

[Normalization of the vascular picture with sympathetic block in severe arterial ischemia from ergotism]. / Normalisierung des Gefässbildes durch Sympathikusblockade bei schwerer arterieller Durchblutungsstörung durch Ergotismus.

This case report presents a 44-year-old woman with severe arterial ischemia leading to claudicatio and acute pain in rest caused by an ergotism. In the history was an abuse of suppositories containing caffeine and ergotamine induced by chronic headache. The initial angiography showed occlusions of the femoral arteries. After excluding other vascular diseases, intraarterial infusions of prostaglandin E were administered. Additionally, physiotherapeutic treatment followed. An progrediency of the symptoms made a epidural catheter for sympathicolysis and treatment of the acute pain necessary. As the results of this intervention were encouraging, a sympathetic blockade with injection of 96% ethanol at the level of L 2/3 and 3/4 was performed. After treatment, the clinical symptoms and the blood flow measured by Doppler ultrasonography normalised. A final angiography demonstrated a now normal arterial status. Ergotism, indication and methods of sympathetic blockades are discussed.

[A check list for monitoring facilities within the scope of federal legislation for the prevention of blood contact infections]. / Checkliste für die Uberwachung von Einrichtungen im Geltungsbereich der Landesverordnungen zur Verhütung von Blutkontaktinfektionen.

Federal German Land legislation on the prevention of blood contact infections (legislation on hygiene) now also enforced in the Rhineland-palatinate (Rheinland-Pfalz) deals with relevant hygienic prerequisities for instalations and equipment that can be involved in spreading diseases which can be transmitted by blood. This legislation, however, does not apply to medical and dental practices and consulting rooms as far as the Rhineland-Palatinate is concerned. A check list is presented which can be used for controlling the relevant equipment and installations.