EXERCÍCIO DE CORRIDA DE ALTA INTENSIDADE ALTERA A EXPRESSÃO DE THY-1 E ECTONUCLEOTIDASE NA SUPERFÍCIE DE LINFÓCITOS

O exercício agudo é um desafio a homeostase e após exercício físico intenso ocorre transiente linfopenia e imunossupressão. As moléculas de adesaão celular são expressas na superfície dos leucócitos e das células endoteliais, tendo um papel fundamental nas interações entre linfócito e endotélio. O objetivo do presente estudo foi analisar a expressão de CD73, CD90 e CD105 em leucócitos após corrida de alta intensidade. Dez homens jovens foram inscritos em uma corrida de 4 km e o sangue foi coletado 60 minutos antes, 5 minutos, 1, 3, 6 e 24 hs após a o exercício, para avaliação hematológica e determinação de marcadores de superfície celulares por citometria de fluxo. Foi utilizado o teste ANOVA de uma via com o teste de Dunnet's como post hoc para a análise estatística. Os dados foram considerados diferentes estatisticamente quando p0,05. Os leucócitos aumentaram 30% e os granulócitos 40 -- 70% após 6h de exercício físico. Linfopenia foi observada 1 h após o exercício, como esperado. Monócitos, eosinófilos e basófilos, e outros parâmetros hematológicos não se alteraram. Linfócitos T, linfócitos T helper e células citotóxicas aumentaram em resposta ao exercício. Linfócitos B e as células exterminadoras naturais (natural killers) aumentaram imediatamente após o exercício. A células CD73+ aumentaram somente imediatamente após o exercício e as células CD90+ diminuíram 24h após o exercício. Podemos concluir que a corrida de alta intensidade induziu a resposta clássica do sistema imuno-endócrino e é capaz de alterar o número de células CD73+ e CD90+

Loss of mTORC1 signalling impairs β-cell homeostasis and insulin processing

Deregulation of mTOR complex 1 (mTORC1) signalling increases the risk for metabolic diseases, including type 2 diabetes. Here we show that β-cell-specific loss of mTORC1 causes diabetes and β-cell failure due to defects in proliferation, autophagy, apoptosis and insulin secretion by using mice with conditional (βraKO) and inducible (MIP-βraKO(f/f)) raptor deletion. Through genetic reconstitution of mTORC1 downstream targets, we identify mTORC1/S6K pathway as the mechanism by which mTORC1 regulates β-cell apoptosis, size and autophagy, whereas mTORC1/4E-BP2-eIF4E pathway regulates β-cell proliferation. Restoration of both pathways partially recovers β-cell mass and hyperglycaemia. This study also demonstrates a central role of mTORC1 in controlling insulin processing by regulating cap-dependent translation of carboxypeptidase E in a 4EBP2/eIF4E-dependent manner. Rapamycin treatment decreases CPE expression and insulin secretion in mice and human islets. We suggest an important role of mTORC1 in β-cells and identify downstream pathways driving β-cell mass, function and insulin processing

The microRNA 199a Family Is Regulated by Glucose Levels in Pancreatic Beta Cells

The mechanistic target of rapamycin complex 1 (mTORC1) integrates nutrient availability and hormone/growth factors signaling to regulate cell metabolism; being essential to beta-cell mass and function. The microRNA 199a-3p negatively regulates translation of mTORC1 mRNA and impacts beta-cell function. We investigated how miR-199a expression is regulated in beta-cells by examining expression responses of miR-199a precursors genes (primiR-199-a1, a2 and b) and its mature forms (miR-199a-3p and -5p) and promoter transcriptional activity assays in mouse islets and mouse insulinoma (MIN6) cells treated with different stimuli. We found that islets from male and female mice equally express the mature miR-199a-3p and -5p. However, the primiR expression is different: while primiR-199a1 expression is 2-fold greater than primiR-199a2, primir-199b is barely detected in mouse islets. The same primiR expression profile was found in MIN6 cells except that only the mature miR-199a-3p is expressed. A 2-fold increase in primiR-199a1 and -a2 mRNA levels was observed by 24 h culture of mouse islets in high glucose compared to 5.5 mM. Similar responses to high and low glucose were observed in MIN6 cells as early as 6 h. Interestingly, 30 mM of KCl treatment was sufficient to prevent the low glucose-induced decline in primiR-199-a2 expression but not in 199-a1 in MIN6 cells, indicating that calcium influx was involved. Transcriptional activity studies in MIN6 also reveal that low glucose or 2-DG glucose-induced starvation decreases the primir-199a2 promoter activity and this decrease was rescued by KCl and Tolbutamide (Potassium channel blocker), confirming that calcium influx is playing a role. Indeed, blocking calcium channels with 20 uM Nifedipine reduced primiR-199-a2 promoter activity in MIN6 cells under 25 mM glucose. In conclusion, we uncover that glucose regulates microRNA 199a family expression in beta cells and that glucose metabolism and calcium influx are involved. Disclosure J. Werneck de Castro: None. M. Blandino-Rosano: None. E. Bernal-Mizrachi: None

Exercise-Stimulated ROS Sensitive Signaling Pathways in Skeletal Muscle

International audiencePhysical exercise represents a major challenge to whole-body homeostasis, provoking acute and adaptative responses at the cellular and systemic levels. Different sources of reactive oxygen species (ROS) have been described in skeletal muscle (e.g., NADPH oxidases, xanthine oxidase, and mitochondria) and are closely related to the physiological changes induced by physical exercise through the modulation of several signaling pathways. Many signaling pathways that are regulated by exercise-induced ROS generation, such as adenosine monophosphate-activated protein kinase (AMPK), mitogen activated protein kinase (MAPK), nuclear respiratory factor2 (NRF2), and PGC-1α are involved in skeletal muscle responses to physical exercise, such as increased glucose uptake, mitochondriogenesis, and hypertrophy, among others. Most of these adaptations are blunted by antioxidants, revealing the crucial role played by ROS during and after physical exercise. When ROS generation is either insufficient or exacerbated, ROS-mediated signaling is disrupted, as well as physical exercise adaptations. Thus, an understanding the limit between “ROS that can promote beneficial effects” and “ROS that can promote harmful effects” is a challenging question in exercise biology. The identification of new mediators that cause reductive stress and thereby disrupt exercise-stimulated ROS signaling is a trending on this topic and are covered in this current review

The Transcription Factor YY1 is Essential for Normal DNA Repair and Cell Cycle in Human and Mouse β-cells

Identifying the mechanisms behind the β-cell adaptation-to-failure is important to develop strategies to manage type 2 diabetes (T2D). Using db/db mice at early stages of the disease process, we took advantage of unbiased RNAseq to identify genes/pathways regulated by insulin resistance in β-cells. We demonstrate herein that islets from 4-week-old non-obese and non-diabetic leptin-receptor deficient db/db mice exhibited downregulation of several genes involved in cell-cycle regulation and DNA repair. We identified the transcription factor Yin Yang 1 (YY1) as a common gene between both pathways. The expression of YY1 and its targeted genes was decreased in the db/db islets. We confirmed the reduction in YY1 expression in β-cells from diabetic db/db mice, mice fed high fat diet (HFD) and individuals with T2D. ChIP-seq profiling in EndocBH1 cells, a human pancreatic β-cell line, indicated that YY1 binding regions regulate cell-cycle control, DNA damage recognition and repair. We then generated mouse models with constitutive and inducible YY1 deficiency in β-cells. YY1 deficient mice developed diabetes early in life due to β-cell loss. β-cells from these mice exhibited higher DNA damage, cell cycle arrest and cell death as well as decreased maturation markers. Tamoxifen-induced YY1 deficiency in mature β-cells impaired β-cell function and induced DNA damage. In summary, we identified YY1 as a critical factor for β-cell DNA repair and cell-cycle progression

Redox Signaling in Widespread Health Benefits of Exercise

International audienc

Physical exercise improves mitochondrial function in ovariectomized rats

Estrogen deficiency causes metabolic disorders in humans and rodents, including in part due to changes in energy expenditure. We have shown previously that skeletal muscle mitochondrial function is compromised in ovariectomized (Ovx) rats. Since physical exercise is a powerful strategy to improve skeletal muscle mitochondrial content and function, we hypothesize that exercise training would counteract the deficiency-induced skeletal muscle mitochondrial dysfunction in Ovx rats. We report that exercised Ovx rats, at 60-65% of maximal exercise capacity for 8 weeks, exhibited less fat accumulation and body weight gain compared with sedentary controls. Treadmill exercise training decreased muscle lactate production, indicating a shift to mitochondrial oxidative metabolism. Furthermore, reduced soleus muscle mitochondrial oxygen consumption confirmed that estrogen deficiency is detrimental to mitochondrial function. However, exercise restored mitochondrial oxygen consumption in Ovx rats, achieving similar levels as in exercised control rats. Exercise-induced skeletal muscle peroxisome proliferator-activated receptor-gamma coactivator-1 alpha expression was similar in both groups. Therefore, the mechanisms by which exercise improves mitochondrial oxygen consumption appears to be different in Ovx-exercised and sham-exercised rats. While there was an increase in mitochondrial content in sham-exercised rats, demonstrated by a greater citrate synthase activity, no induction was observed in Ovx-exercised rats. Normalizing mitochondrial respiratory capacity by citrate synthase activity indicates a better oxidative phosphorylation efficiency in the Ovx-exercised group. In conclusion, physical exercise sustains mitochondrial function in ovarian hormone-deficient rats through a non-conventional mitochondrial content-independent manner