Hepatocyte Nuclear Factor 4-α (HNF4α) controls the insulin resistance-induced pancreatic ß-cell mass expansion.

BACKGROUND: Regardless of the etiology, any type of DM presents a reduction of insulin-secreting cell mass, so it is important to investigate pathways that induce the increase of this cell mass. AIM: Based on the fact that (1) HNF4α is crucial for ß-cell proliferation, (2) DEX-induced IR promotes ß-cell mass expansion, and (3) the stimulation of ß-cell mass expansion may be an important target for DM therapies, we aimed to investigate whether DEX-induced proliferation of ß pancreatic cells is dependent on HNF4α. METHODS: We used WildType (WT) and Knockout (KO) mice for HNF4-α, treated or not with 100 mg/Kg/day of DEX, for 5 consecutive days. One day after the last injection of DEX the IR was confirmed by ipITT and the mice were euthanized for pancreas removal. RESULTS: In comparison to WT, KO mice presented increased glucose tolerance, lower fasting glucose and increased glucose-stimulates insulin secretion (GSIS). DEX induced IR in both KO and WT mice. In addition, DEX-induced ß-cell mass expansion and an increase in the Ki67 immunostaining were observed only in WT mice, evidencing that IR-induced ß-cell mass expansion is dependent on HNF4α. Also, we observed that DEX-treatment, in an HNF4α-dependent way, promoted an increase in PDX1, PAX4 and NGN3 gene expression. CONCLUSIONS: Our results strongly suggest that DEX-induced IR promotes ß-cell mass expansion through processes of proliferation and neogenesis that depend on the HNF4α activity, pointing to HNF4α as a possible therapeutic target in DM treatment.

Excess of glucocorticoids during late gestation impairs the recovery of offspring's ß-cell function after a postnatal injury.

Since prenatal glucocorticoids (GC) excess increases the risk of metabolic dysfunctions in the offspring and its effect on ß-cell recovery capacity remains unknown we investigated these aspects in offspring from mice treated with dexamethasone (DEX) in the late pregnancy. Half of the pups were treated with streptozotocin (STZ) on the sixth postnatal day (PN). Functional and molecular analyses were performed in male offspring on PN25 and PN225. Prenatal DEX treatment resulted in low birth weight. At PN25, both the STZ-treated offspring developed hyperglycemia and had lower ß-cell mass, in parallel with higher α-cell mass and glucose intolerance, with no impact of prenatal DEX on such parameters. At PN225, the ß-cell mass was partially recovered in the STZ-treated mice, but they remained glucose-intolerant, irrespective of being insulin sensitive. Prenatal exposition to DEX predisposed adult offspring to sustained hyperglycemia and perturbed islet function (lower insulin and higher glucagon response to glucose) in parallel with exacerbated glucose intolerance. ß-cell-specific knockdown of the Hnf4α in mice from the DS group resulted in exacerbated glucose intolerance. We conclude that high GC exposure during the prenatal period exacerbates the metabolic dysfunctions in adult life of mice exposed to STZ early in life, resulting in a lesser ability to recover the islets' function over time. This study alerts to the importance of proper management of exogenous GCs during pregnancy and a healthy postnatal lifestyle since the combination of adverse factors during the prenatal and postnatal period accentuates the predisposition to metabolic disorders in adult life.

Beneficial effects of physical exercise for ß-cell maintenance in a type 1 diabetes mellitus animal model.

NEW FINDINGS: What is the central question of this study? Type 1 diabetes mellitus (T1D) leads to hyperglycaemia owing to pancreatic ß-cell destruction by the immune system. Physical exercise has been shown to have potentially beneficial protective roles against cytokine-induced pancreatic ß-cell death, but its benefits are yet to be proved and should be understood better, especially in the islet environment. What is the main finding and its importance? Physical exercise protects against ß-cell loss in a well-described animal model for T1D, induced by multiple low doses of streptozotocin. This seems to be related to reduced cytokine-induced ß-cell death and increased islet cell proliferation. Contributions of islet neogenesis and/or transdifferentiation of pancreatic non-ß-cells into ß-cells cannot be excluded. ABSTRACT: Physical exercise has beneficial effects on pancreatic ß-cell function and survival in a pro-inflammatory environment. Although these effects have been linked to decreased islet inflammation and modulation of pro-apoptotic pathways, little is known about the islet microenvironment. Our aim was to evaluate the effects of physical exercise in islet histomorphology in a mouse model of type 1 diabetes mellitus induced by multiple low doses of streptozotocin. As expected, induction of type 1 diabetes mellitus led to ß-cell loss and, consequently, decreased islet area. Interestingly, although the decrease in islet area was not prevented by physical exercise, this was not the case for the decrease in ß-cell mass. This was probably related to induction of ß-cell regeneration, because we observed increased proliferation and regeneration markers, such as Ki67 and Pcna, in islets of trained mice. These were found in the central and peripheral regions of the islets. An increase in the percentage of α- and δ-cells in these conditions, combined with an increase in proliferation and Pax4 labelling in peripheral regions, suggest that ß-cell regeneration might also occur by transdifferentiation. This agrees with the presence of cells double stained for insulin and glucagon only in islets of diabetic trained mice. In addition, this group had more extra-islet insulin-positive cells and islets associated with ducts than diabetic mice. Physical exercise also decreased nuclear factor-κB activation in islet cells of diabetic trained compared with diabetic untrained mice, indicating a decrease in pro-inflammatory cytokine-induced ß-cell death. Taken together, these findings indicate that preservation of ß-cell mass induced by physical exercise involves an increase in ß-cell replication and decrease in ß-cell death, together with islet neogenesis and islet cell transdifferentiation.

Paternal Exercise Improves the Metabolic Health of Offspring via Epigenetic Modulation of the Germline.

BACKGROUND/AIMS: Epigenetic regulation is considered the main molecular mechanism underlying the developmental origin of health and disease's (DOHAD) hypothesis. Previous studies that have investigated the role of paternal exercise on the metabolic health of the offspring did not control for the amount and intensity of the training or possible effects of adaptation to exercise and produced conflicting results regarding the benefits of parental exercise to the next generation. We employed a precisely regulated exercise regimen to study the transgenerational inheritance of improved metabolic health. METHODS: We subjected male mice to a well-controlled exercise -training program to investigate the effects of paternal exercise on glucose tolerance and insulin sensitivity in their adult progeny. To investigate the molecular mechanisms of epigenetic inheritance, we determined chromatin markers in the skeletal muscle of the offspring and the paternal sperm. RESULTS: Offspring of trained male mice exhibited improved glucose homeostasis and insulin sensitivity. Paternal exercise modulated the DNA methylation profile of PI3Kca and the imprinted H19/Igf2 locus at specific differentially methylated regions (DMRs) in the skeletal muscle of the offspring, which affected their gene expression. Remarkably, a similar DNA methylation profile at the PI3Kca, H19, and Igf2 genes was present in the progenitor sperm indicating that exercise-induced epigenetic changes that occurred during germ cell development contributed to transgenerational transmission. CONCLUSION: Paternal exercise might be considered as a strategy that could promote metabolic health in the offspring as the benefits can be inherited transgenerationally.

Central and peripheral effects of physical exercise without weight reduction in obese and lean mice.

To investigate the central (hypothalamic) and peripheral effects of exercise without body weight change in diet-induced obesity (DIO). Twelve-week-old male C57Bl/6 mice received a control (C) or a high-fat diet (H). Half of them had free access to running wheels for 5 days/week for 10 weeks (CE) and HE, respectively). Hypothalamic expression of genes related to energy homeostasis, and leptin (Stat3 and p-Stat3) and insulin (Akt and p-Akt) signaling were evaluated. Glucose and leptin tolerance, peripheral insulin sensitivity, and plasma insulin, leptin and adiponectin were determined. Perigonadal and retroperitoneal fat depots were increased by diet but reduced by exercise despite lack of effect of exercise on body weight. Blood glucose during intraperitoneal glucose tolerance test (ipGTT) was higher and glucose decay during intraperitoneal insulin tolerance test (ipITT) was lower in H and HE compared with C and CE. Exercise increased liver p-Akt expression and reduced fast glycemia. High-fat diet increased plasma insulin and leptin. Exercise had no effect on insulin but decreased leptin and increased adiponectin. Leptin inhibited food intake in all groups. Hypothalamic total and p-Stat3 and Akt were similar amongst the groups despite higher plasma levels of leptin and insulin in H and HE mice. High-fat diet modulated gene expression favoring a positive energy balance. Exercise only marginally changed the gene expression. Exercise induced positive changes (decreased fast glycemia and fat depots; increased liver insulin signaling and adiponectin concentration) without weight loss. Thus, despite reducing body weight could bring additional benefits, the effects of exercise must not be overlooked when weight reduction is not achieved.

Bile acid TUDCA improves insulin clearance by increasing the expression of insulin-degrading enzyme in the liver of obese mice.

Disruption of insulin secretion and clearance both contribute to obesity-induced hyperinsulinemia, though reduced insulin clearance seems to be the main factor. The liver is the major site for insulin degradation, a process mainly coordinated by the insulin-degrading enzyme (IDE). The beneficial effects of taurine conjugated bile acid (TUDCA) on insulin secretion as well as insulin sensitivity have been recently described. However, the possible role of TUDCA in insulin clearance had not yet been explored. Here, we demonstrated that 15 days treatment with TUDCA reestablished plasma insulin to physiological concentrations in high fat diet (HFD) mice, a phenomenon associated with increased insulin clearance and liver IDE expression. TUDCA also increased IDE expression in human hepatic cell line HepG2. This effect was not observed in the presence of an inhibitor of the hepatic membrane bile acid receptor, S1PR2, nor when its downstream proteins were inhibited, including IR, PI3K and Akt. These results indicate that treatment with TUDCA may be helpful to counteract obesity-induced hyperinsulinemia through increasing insulin clearance, likely through enhanced liver IDE expression in a mechanism dependent on S1PR2-Insulin pathway activation.

Spontaneous physical activity and mediators of energy homeostasis in the hypothalamus of mice from 4 to 10 months of age.

NEW FINDINGS: What is the central question of this study? Is the initial decline of spontaneous physical activity (SPA) in mice related to impaired insulin and leptin signalling or brain-derived neurotrophic factor expression in the hypothalamus? What is the main finding and its importance? We showed that SPA started to decline at an early stage, concomitantly with an impairment of hypothalamic leptin signalling. Consequently, energy expenditure decreased and glucose tolerance worsened. Our results demonstrate the need to counteract the initial decline in SPA to avoid metabolic impairments and indicate the possible involvement of central leptin in the reduction in SPA with age. The biological control of physical activity is poorly understood. Age decreases insulin, leptin and brain-derived neurotrophic factor (BDNF) signalling in the hypothalamus, and all have been shown to modulate spontaneous physical activity (SPA). We investigated the age at which SPA starts to decline and whether this is associated with the emergence of hypothalamic insulin and leptin resistance and reduced BDNF expression. Spontaneous physical activity (and other parameters of locomotion) and energy expenditure were determined monthly in mice from the 4th to the 10th month of age. Metabolic and hypothalamic analyses were performed in 4-, 6- and 10-month-old mice. Spontaneous physical activity, distance travelled and speed of locomotion started to decrease in 6-month-old mice. The reduction in SPA became more evident from 8 months of age. Energy expenditure decreased from the 8th month. Hypothalamic BDNF protein expression and insulin signalling did not change throughout the time span studied. Leptin signalling decreased at 6 and 10 months compared with 4 months. Also, compared with 4 months, 6- and 10-month-old mice were glucose intolerant. In conclusion, SPA begins to decline in parallel with reduced hypothalamic leptin signalling. Metabolic impairment also manifests as SPA decreases, highlighting the need to understand the regulation of SPA in order to combat its decline.

Hyperinsulinemia caused by dexamethasone treatment is associated with reduced insulin clearance and lower hepatic activity of insulin-degrading enzyme.

OBJECTIVES: Glucocorticoid treatment induces insulin resistance (IR), which is counteracted by a compensatory hyperinsulinemia, due to increased pancreatic ß-cell function. There is evidence for also reduced hepatic insulin clearance, but whether this correlates with altered activity of insulin-degrading enzyme (IDE) in the liver, is not fully understood. Here, we investigated whether hyperinsulinemia, in glucocorticoid-treated rodents, is associated with any alteration in the insulin clearance and activity of the IDE in the liver. MATERIALS/METHODS: Adult male Swiss mice and Wistar rats were treated with the synthetic glucocorticoid dexamethasone intraperitoneally [1mg/kg body weight (b.w.)] for 5 consecutive days. RESULTS: Glucocorticoid treatment induced IR and hyperinsulinemia in both species, but was more impactful in rats that also displayed glucose intolerance and hyperglycemia. Insulin clearance was reduced in glucocorticoid-treated rats and mice, as judged by the reduction of insulin decay rate and increased insulin area-under-the-curve (47% and 87%, respectively). These results were associated with reduced activity (35%) of hepatic IDE in rats and a tendency to reduction (p=0.068) in mice, without alteration in hepatic IDE mRNA content, in both species. CONCLUSION: In conclusion, the reduced insulin clearance in glucocorticoid-treated rodents was due to the reduction of hepatic IDE activity, at least in rats, which may contributes to the compensatory hyperinsulinemia. These findings corroborate the idea that short-term and/or partial inhibition of IDE activity in the liver could be beneficial for the glycemic control.

ARHGAP21 prevents abnormal insulin release through actin rearrangement in pancreatic islets from neonatal mice.

AIMS: ARHGAP21 is a Rho GTPase-activating protein (RhoGAP) that associates with many proteins and modulates several cellular functions, including actin cytoskeleton rearrangement in different tissues. However, it is unknown whether ARHGAP21 is expressed in pancreatic beta cells and its function in these cells. Herein, we assess the participation of ARHGAP21 in insulin secretion. MAIN METHODS: Neonatal mice were treated with anti-sense oligonucleotide against ARHG AP21 (AS) for 2 days, resulting in a reduction of the protein's expression of about 60% in the islets. F-actin depolimerization, insulin secretion,mRNA level of genes involved in insulin secretion, maturation and proliferation were evaluated in islets from both control and AS-treated mice. KEY FINDINGS: ARHGAP21 co-localized with actin inMIN6 beta cells and with insulin in neonatal pancreatic islets. F-actin was reduced in AS-islets, as judged by lower phalloidin intensity. Insulin secretion was increased in islets from AS-treated mice, however no differences were observed in the GSIS (glucose-stimulated insulin secretion). In these islets, the pERK1/2 was increased, as well as the gene expressions of VAMP2 and SNAP25, proteins that are present in the secretory machinery. Maturation and cell proliferation were not affected in islets from AS-treated mice. SIGNIFICANCE: In conclusion, our data show, for the first time, that ARHGAP21 is expressed and participates in the secretory process of pancreatic beta cells. Its effect is probably via pERK1/2, which modulates the rearrangement of the cytoskeleton. ARHGAP21 also controls the expression of genes that encodes proteins of the secretory machinery.

Metabolic memory of ß-cells controls insulin secretion and is mediated by CaMKII.

Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) functions both in regulation of insulin secretion and neurotransmitter release through common downstream mediators. Therefore, we hypothesized that pancreatic ß-cells acquire and store the information contained in calcium pulses as a form of "metabolic memory", just as neurons store cognitive information. To test this hypothesis, we developed a novel paradigm of pulsed exposure of ß-cells to intervals of high glucose, followed by a 24-h consolidation period to eliminate any acute metabolic effects. Strikingly, ß-cells exposed to this high-glucose pulse paradigm exhibited significantly stronger insulin secretion. This metabolic memory was entirely dependent on CaMKII. Metabolic memory was reflected on the protein level by increased expression of proteins involved in glucose sensing and Ca(2+)-dependent vesicle secretion, and by elevated levels of the key ß-cell transcription factor MAFA. In summary, like neurons, human and mouse ß-cells are able to acquire and retrieve information.

Ocorrência de bullying nas aulas de educação física em uma escola do Distrito Federal / Bullying occurrence in physical education classes of a federal district school

O bullying representa o uso da superioridade física, intelectual ou financeira para humilhar outra pessoa. O objetivo deste trabalho foi investigar a existência e sob que forma o bullying ocorre nas aulas de educação física em uma escola do Distrito Federal. Para isso, participaram do estudo 140 alunos da 7ª e 8ª séries de uma escola da cidade do Guará – DF. Os participantes responderam a um questionário arespeito da ocorrência de maustratosnas aulas de educação física. Aproximadamente 28,0% dos alunos já se sentiram maltratados por colegas. Neste sentido, as aulas de educação física podem ser utilizadas promover atividades que visem à integraçãodos alunos, evitando ressaltar as qualidades e defeitos que possam resultar em agressões a outros, sejam elas verbais ou físicas

Bullying refers to the use of physical, intellectual or economic superiority to humliate another person. This study aimed to investigate the existence and how bullying occurs in physical education classes in a Federal District School. For this, 140 students of the 7th and 8th grades of a school in the city of Guará – DF participated in the study. The students answered a questionnaire about the occurrence of abuse in physical education classes. Approximately 28.0% of the students have felt abused by a colleague. In this scenario, physical education classes can be used to promote activities that aim to integrate students, avoiding highlighting abilities and inabilities which can result in physical or verbal aggressions