Introduction Les régimes alimentaires riches en gras saturés contribuent à la défaillance de la cellule β dans le diabète de type 2 (DT2). Le palmitate induit le stress du réticulum endoplasmique ...(RE) et le dysfonctionnement/apoptose des cellules β. Afin d'identifier les médiateurs moléculaires de la lipotoxicité, nous avons effectué un séquençage-ARN d'îlots humains et une analyse protéomique de cellules INS-1E après un traitement au palmitate. Matériels et Méthodes Six préparations d'îlots humains ont été exposées au palmitate (0,5 mM) durant 48 h et l'ARN a été séquencé. Les cellules INS-1E ont été exposées au palmitate durant 4, 16 ou 24 h et le protéome a été profilé par iTRAQ ( n = 2). Les analyses des réseaux de régulations ont fait usage des bases de données IPA, DAVID et TRANSFAC. L'expression des gènes a été réduite par siRNA dans les cellules β clonales et primaires. La mort cellulaire a été examinée par coloration nucléaire. Résultats Des analyses comparatives du transcriptome et du protéome des cellules β traitées au palmitate ont identifié 93 gènes/protéines régulés positivement et 133 régulés négativement communs aux 2 analyses. La classification en catégories fonctionnelles montre une modification des gènes/protéines régulant le métabolisme d'acides gras, le stress du RE, l'apoptose et de plusieurs transporteurs d'acides aminés. Nos études fonctionnelles ont confirmé l'augmentation d'expression des transporteurs d'acides aminés Lat1 et Cat1 (>25 %, n = 4-5). La diminution de leur expression par siRNA, par contre, ne modifie pas le stress du RE lipotoxique. Un réseau de régulations inféré dévoile Arnt, FoxO1, APP, JunD et Bach1 comme des régulateurs clés de la lipotoxicité. Les rôles de FoxO1, Arnt et App dans la sécrétion d'insuline, le stress du RE et l'apoptose ont déjà été démontrés, accréditant l'hypothèse d'un possible rôle biologique dans le contexte de la lipotoxicité. Conclusions Cette étude est la première du genre à fournir un profilage transcriptomique et protéomique de cellules β exposées au palmitate. Nos données dévoilent de nouveaux médiateurs de lipotoxicité et des réseaux de régulation complexes potentiellement impliqués dans la défaillance de la cellule β dans le DT2.
Introduction Nous avons précédemment identifié une mutation non-sens dans TRMT10A, une putative méthyltransférase d'ARNt, comme responsable d'un nouveau syndrome du diabète juvénile et microcéphalie. ...Plusieurs nouvelles mutations perte-de-fonction en TRMT10A ont récemment été identifiées chez des patients avec un syndrome similaire. Des polymorphismes dans CDKAL1, une methylthio-transferase d'ARNt, ont été associés au diabète de type 2, suggérant que des altérations dans la modification des ARNt provoquent la défaillance des cellules bêta. Notre objectif était d'étudier le rôle de TRMT10A et les mécanismes pathogènes de la déficience de cette protéine. Matériels et Méthodes La méthylation d'ARNt a été examinée par HPLC-MS/MS dans des lymphoblastes de patients déficients en TRMT10A, et les substrats de TRMT10A identifiés par des essais d'extension d'amorce. L'expression de TRMT10A a été réduite par siRNA dans des cellules productrices d'insuline INS-1E (rat) et EndoC-βH1 (humain), seule ou combinée avec siRNA contre les proteins pro-apoptotiques Bim ou Bad. Les cellules ont été exposées au palmitate (0,5 mM) ou à la thapsigargine (1 μM) et la mort cellulaire étudiée par coloration nucléaire et blots pour caspases. Résultats L'HPLC-MS/MS a montré une diminution de la méthylation des guanosines dans l'ARNt de lymphoblastes de patients. Les essais d'extension d'amorces ont montré que TRMT10A méthyle tRNAGln et tRNA-Meth sur la guanosine en position 9. Le silençage de TRMT10A dans les cellules bêta de rat et humaines induit l'activation de la voie intrinsèque de l'apoptose, évaluée par clivage de caspase-9, et induit l'expression de Bim et Bad (≥ 50 % d'induction, p < 0,05, n = 4-6). Uniquement le silençage de Bim protège les cellules déficientes en TRMT10A de l'apoptose en condition basale et après traitement avec le palmitate ou la thapsigargine ( p < 0,05, n = 4-5). Conclusions Nous avons confirmé la fonction de TRMT10A comme une méthyltransférase d'ARNt, et identifiés tRNAGln et tRNAMeth comme ses substrats. Un déficit en méthylation pourrait affecter la charge et la stabilité des ARNt. La déficience en TRMT10A conduit à l'activation de la voie intrinsèque de l'apoptose dans les cellules bêta. Nous avons identifié la protéine pro-apoptotique Bim comme médiateur clé de ce processus.
Wegner's Theory of Ironic Processes has been applied to study the effects of cognitive strategies to control pain. Research suggests that suppression contributes to a more distressing pain ...experience. Recently, the acceptance-based approach has been proposed as an alternative to cognitive control. This study assessed the tolerance time, the distress and the perceived pain intensity in three groups (suppression, acceptance and spontaneous coping groups) when the participants were exposed to a cold pressor procedure. Two hundred and nineteen undergraduates volunteered to participate. The suppression group showed the shortest tolerance time and the acceptance group showed the longest tolerance time. The acceptance group showed pain and distress immersion ratings that were significantly lower than in the other two groups, between which the differences were not significant. In the first recovery period, the suppression group showed pain and distress ratings that were higher than in the other two groups. In the second recovery period, although the acceptance group showed pain and distress ratings that were significantly lower than in the other two groups, the suppression and the spontaneous coping groups did not differ. The presence of a ‘rebound’ of physical discomfort and the effects of suppression on behavioural avoidance are discussed. These results support the acceptance approach in the management of pain.
Pancreatic β-cell dysfunction is central to the pathogenesis of type 2 diabetes, and the loss of functional β-cell mass in type 2 diabetes is at least in part secondary to increased β-cell apoptosis. ...Accumulating evidence suggests that endoplasmic reticulum (ER) stress is present in β-cells in type 2 diabetes. Free fatty acids (FFAs) cause ER stress and are putative mediators of β-cell dysfunction and death. In this review, we discuss the molecular mechanisms underlying ER stress induced by saturated and unsaturated FFAs. Oleate and palmitate trigger ER stress through ER Ca²⁺ depletion and build-up of unfolded proteins in the secretory pathway. Saturated and unsaturated FFAs elicit a differential signal transduction in the three branches of the ER stress response, resulting in different survival/apoptosis outcomes. The protection of β-cells against FFAs through the interference with ER stress signalling has opened novel therapeutic perspectives for type 2 diabetes. Chemical chaperones, salubrinal and glucagon-like peptide-1 (GLP-1) analogues have been used to protect β-cells from lipotoxic ER stress. Importantly, the pro- and antiapoptotic effects of these compounds are cell and context dependent.
Background: There is little information about the effect of infliximab on the clinical course of liver disease in Crohn’s disease patients with concomitant hepatitis B virus (HBV) infection. ...Theoretically, immunosuppression induced by infliximab will facilitate viral replication which could be followed by a flare or exacerbation of disease when therapy is discontinued. There are no specific recommendations on surveillance and treatment of HBV before infliximab infusion. Two cases of severe hepatic failure related to infliximab infusions have been described in patients with rheumatic diseases. Patients and methods: Hepatitis markers (C and B) and liver function tests were prospectively determined to 80 Crohn’s disease patients requiring infliximab infusion in three hospitals in Spain. Results: Three Crohn’s disease patients with chronic HBV infection were identified. Two of the three patients with chronic HBV infection suffered severe reactivation of chronic hepatitis B after withdrawal of infliximab therapy and one died. A third patient, who was treated with lamivudine at the time of infliximab therapy, had no clinical or biochemical worsening of liver disease during or after therapy. From the remaining 80 patients, six received the hepatitis B vaccine. Three patients had antibodies to both hepatitis B surface antigen (anti-HBs) and hepatitis B core protein (anti-HBc) with normal aminotransferase levels, and one patient had positive anti-hepatitis C virus (HCV) antibodies, negative HCV RNA, and normal aminotransferase levels. Except for the patients with chronic HBV infection, no significant changes in hepatic function were detected. Conclusions: Patients with Crohn’s disease who are candidates for infliximab therapy should be tested for hepatitis B serological markers before treatment and considered for prophylaxis of reactivation using antiviral therapy if positive.
Longevity of human islet α- and β-cells Cnop, M.; Igoillo-Esteve, M.; Hughes, S. J. ...
Diabetes, obesity & metabolism,
October 2011, Letnik:
13, Številka:
s1
Journal Article
Odprti dostop
Pancreatic islet cell regeneration is considered to be important in the onset and progression of diabetes and as a potential cell therapy. Current hypotheses, largely based on rodent studies, ...indicate continuous turnover and plasticity of α‐ and β‐cells in adults; cell populations in rodents respond to increased secretory demand in obesity (30‐fold β‐cell increase) and pregnancy. Turnover and plasticity of islet cells decrease in mice within >1 year. In man, morphometric observations on postmortem pancreas have indicated that the cellular expansion is much smaller than the increased insulin secretion that accompanies obesity. Longevity of β‐cells in humans >20–30 years has been shown by 14C measurements and bromo‐deoxyuridine (BrdU) incorporation and there is an age‐related decline in the expression of proteins associated with cell division and regeneration including cyclin D3 and PDX‐1. Quantitative estimation and mathematical modelling of the longevity marker, cellular lipofuscin body content, in islets of subjects aged 1–84 years indicated an age‐related increase and that 97% of the human β‐cell population was established by the age of 20. New data show that human α‐cell lipofuscin content is less than that seen in β‐cells, but the age‐related accumulation is similar; lipofuscin‐positive (aged) cells form ≥95% of the population after 20 years. Increased turnover of cellular organelles such as mitochondria and endoplasmic reticulum could contribute to lipofuscin accumulation with age in long‐lived cells. Induction of regeneration of human islet cells will require understanding of the mechanisms associated with age‐related senescence.
Two major mechanisms of intracellular protein degradation, autophagy and the ubiquitin-proteasome pathway, operate in mammalian cells. PTEN, which is frequently mutated in glioblastomas, is a tumor ...suppressor gene that encodes a dual specificity phosphatase that antagonizes the phosphatidylinositol 3-kinase class I/AKT/mTOR pathway, which is a key regulator of autophagy. Here, we investigated in U87MG human glioma cells the role of PTEN in the regulation of autophagy and the ubiquitin-proteasome pathway, because both are functionally linked and are relevant in cancer progression. Since U87MG glioma cells lack a functional PTEN, we used stable clones that express, under the control of a tetracycline-inducible system (Tet-on), wild-type PTEN and two of its mutants, G129E-PTEN and C124S-PTEN, which, respectively, lack the lipid phosphatase activity only and both the lipid and the protein phosphatase activities of this protein. Expression of PTEN in U87MG glioma cells decreased proteasome activity and also reduced protein ubiquitination. On the contrary, expression of PTEN increased the autophagic flux and the lysosomal mass. Interestingly, and although PTEN negatively regulates the phosphatidylinositol 3-kinase class I/AKT/mTOR signaling pathway by its lipid phosphatase activity, both effects in U87MG cells were independent of this activity. These results suggest a new mTOR-independent signaling pathway by which PTEN can regulate in opposite directions the main mechanisms of intracellular protein degradation.
Food waste produced in homes represents the largest fraction of food waste generated along the food chain. Therefore, adequate prevention measures based on the quantitative and qualitative dimensions ...of the problem need to be put in place to reduce waste. The objective of the review was to identify areas of interest in relation to the food waste in households, considering the family unit as a whole as well as individual family members. Quantifying the problem is an important aspect in order to know its scope and dimension, but prevention also involves knowing the causes in a home. This is a complex issue, which, on a family level, is related to socioeconomic status, educational level, composition and number of members of the household as well as culinary and buying food habits. Individual variables such as age, sex, values, awareness, lifestyle and time spent on food preparation were included to characterize consumers. The focus of the problem is also important because most consumers consider food waste from a social perspective, without being aware of the serious environmental and economic problems. Habits and customs of consumers are considered the leading cause of food waste in homes and knowledge of this issue raises consumer awareness as a preventive tool.
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