Evasion of NKG2D-mediated cytotoxic immunity by sarbecoviruses

SARS-CoV-2 and other sarbecoviruses continue to threaten humanity, highlighting the need to characterize common mechanisms of viral immune evasion for pandemic preparedness. Cytotoxic lymphocytes are vital for antiviral immunity and express NKG2D, an activating receptor conserved among mammals that recognizes infection-induced stress ligands (e.g., MIC-A/B). We found that SARS-CoV-2 evades NKG2D recognition by surface downregulation of MIC-A/B via shedding, observed in human lung tissue and COVID-19 patient serum. Systematic testing of SARS-CoV-2 proteins revealed that ORF6, an accessory protein uniquely conserved among sarbecoviruses, was responsible for MIC-A/B downregulation via shedding. Further investigation demonstrated that natural killer (NK) cells efficiently killed SARS-CoV-2-infected cells and limited viral spread. However, inhibition of MIC-A/B shedding with a monoclonal antibody, 7C6, further enhanced NK-cell activity toward SARS-CoV-2-infected cells. Our findings unveil a strategy employed by SARS-CoV-2 to evade cytotoxic immunity, identify the culprit immunevasin shared among sarbecoviruses, and suggest a potential novel antiviral immunotherapy.

Body mass variability in age-matched outbred male Swiss mice is associated to differential control of food intake by ghrelin

Swiss mice belong to an outbred strain of mice largely used as a model for experimental obesity induced by high fat diet (HFD). We have previously demonstrated that a given cohort of age-matched Swiss mice is hallmarked by heterogeneous changes in body weight when exposed to HFD. The reasons underlying such variability, however, are not completely understood. Therefore we aimed to clarify the mechanisms underlying the variability in spontaneous weight gain in age-matched male swiss mice. To achieve that, individuals in a cohort of age-matched male Swiss mice were categorized as prone to body mass gain (PBMG) and resistant to body mass gain (RBMG). PBMG animals had higher caloric intake and body mass gain. RBMG and PBMG mice had a similar reduction in food intake when challenged with leptin but only RBMG exhibited a drop in ghrelin concentrations after refeeding. PBMG also showed increased midbrain levels of ghrelin receptor (Ghsr) and Dopamine receptor d2 (Drd2) mRNAs upon refeeding. Pharmacological blockade of GHSR with JMV3002 failed to reduce food intake in PMBG mice as it did in RBMG. On the other hand, the response to JMV3002 seen in PBMG was hallmarked by singular transcriptional response in the midbrain characterized by a simultaneous increase in both tyrosine hydroxylase (Th) and Proopiomelanocortin (Pomc) expressions. In conclusion, our data show that differences in the expression of genes related to the reward system in the midbrain as well as in ghrelin concentrations in serum correlate with spontaneous variability in body mass and food intake seen in age-matched male Swiss mice.

Combined training increases thermogenic fat activity in patients with overweight and type 2 diabetes

BACKGROUND

Exercise is an important strategy in the management of diabetes. Experimental studies have shown that exercise acts, at least in part, by inducing the production of myokines that improve metabolic control and activate brown/beige adipose tissue depots. Combined training (CT) is recommended by the major diabetes guidelines due to its metabolic and cardiovascular benefits, however, its impact on brown/beige adipose tissue activities has never been tested in humans with overweight and type 2 diabetes (T2D). Here, we evaluated the effects of 16-week combined training (CT) program on brown adipose tissue activity; browning and autophagy markers, and serum pro-thermogenic/inflammatory inducers in patients with overweight and T2D.

METHODS

Thirty-four patients with overweight and T2D were assigned to either a control group (CG) or a combined training group (CTG) in a randomized and controlled study. Functional/fitness parameters, anthropometry/body composition parameters, blood hormone/biochemical parameters, thermogenic/autophagic gene expression in subcutaneous adipose tissue were evaluated before and at the end of the intervention. In addition, cold-induced 18-Fluoroxyglucose Positron Emission Computed Tomography (18^F-FDG PET/CT) was performed in the training group before and after the end of the intervention.

RESULTS

CT increased cervical/supraclavicular brown adipose tissue (BAT) thermogenic activity (p = 0.03) as well as in perirenal adipose tissue (p = 0.02). In addition, CT increased the expression of genes related to thermogenic profile (TMEM26: + 95%, p = 0.04; and EPSTI1: + 26%, p = 0.03) and decreased autophagic genes (ULK1: -15%, p = 0.04; LC3: -5%, p = 0.02; and ATG4: -22%, p < 0.001) in subcutaneous adipose tissue. There were positive correlations between Δ% BAT activity with Δ% of post training energy expenditure cold exposure, HDL-c, IL4, adiponectin, irisin, meteorin-like, and TMEM26 and ZIC1 genes, besides negative correlations with LDL-c, total cholesterol and C-reactive protein.

CONCLUSION

This is the first evidence of the beneficial actions of CT on adipose tissue thermogenic activity in humans, and it adds important support for the recommendation of CT as a strategy in the management of diabetes.

Acute/Chronic Responses of Combined Training on Serum Pro-thermogenic/Anti-inflammatory Inducers and Its Relation With Fed and Fasting State in Overweight Type 2 Diabetic Individuals

Concentrations of pro-thermogenic/anti-inflammatory inductors are influenced by fed/fasting, sedentary/trained states, and metabolic pattern. However, there is a lack of information on the interactions of these conditions, especially in humans. Thus, the present study aimed to evaluate the chronic and acute training responses as well as the fed/fasted states of serum pro-thermogenic/anti-inflammatory inducers in overweight type 2 diabetics individuals. Fifteen individuals with type 2 diabetes [body mass index (BMI): 29.61 ± 3.60 kg/m2; age: 50.67 ± 3.97 years] participated in the study. In the pre- and post-experimental periods, baseline clinical parameters analyses were performed. Pro-thermogenic/anti-inflammatory inductors were evaluated pre/post-baseline and before, shortly after, and after 30′ and 60′ in the first and last sessions of a 16-week combined training (CT) period. These inducers were also compared for fasting and feeding before and after the training period. CT has improved baseline physical fitness, metabolic pattern, and it has also increased interleukin (IL)33 and FNDC5/irisin. In the first training session, there was a decrease in IL4, IL13, and IL33, besides an increase in FNDC5/irisin, and natriuretic peptides. In the last training session, there was an increase in natriuretic peptides and bone morphogenic protein 4 (BMP4). Differences in responses between the first and last training sessions were observed at certain post-session times for IL4, IL33, and natriuretic peptides, always with higher concentrations occurring in the last session. In evaluating the area under the curve (AUC) of the first and last training session, FNDC5/irisin, natriuretics peptides, and meteorin-like showed increased areas in the last training session. The pre-training fed state showed an increase in IL4 and IL33, while in fasting there was an increase in meteorin-like, natriuretic peptides, and FNDC5/irisin. In the post-training, IL4, IL13, and IL33 were increased in the fed state, while meteorin-like, natriuretic peptides, and FNDC5/irisin remained increased in the fast. Adaptation to physical training and a better metabolic pattern favor an improvement in the acute secretory pattern in part of pro-thermogenic and anti-inflammatory substances analyzed. The fed and fasting states also interfere differently in these substances, where fasting interferes with the increase of myokines, while the fed state induces an increase in interleukins.

Clinical Trial Registration: [http://www.ensaiosclinicos.gov.br/rg/RBR-62n5qn/], identifier [U1111-1202-1476].

Behavioral, neuroplasticity and metabolic effects of 7,8-dihydroxy-4-methylcoumarin associated with physical activity in mice

The search for strategies to develop resilience against metabolic and neuropsychiatric disorders has motivated the clinical and experimental assessment of early life interventions such as lifestyle-based and use of unconventional pharmacological compounds. In this study, we assessed the effects of voluntary physical activity and 7,8-Dihydroxy-4-methylcoumarin (DHMC), independently or in combination, over mice physiological and behavioral parameters, adult hippocampal and hypothalamic neurogenesis, and neurotrophic factors expression in the hypothalamus. C57Bl/6J mice were submitted to a 29-day treatment with DHMC and allowed free access to a running wheel. We found that DHMC treatment alone reduced fasting blood glucose levels. Moreover, physical activity showed an anxiolytic effect in the elevated plus maze task and DHMC produced additional anxiolytic behavior, evidenced by reduced activity during the light cycle in the physical activity group. Although we did not find any differences in hypothalamic or hippocampal adult neurogenesis, DHMC increased gene expression levels of VEGF, which was correlated to the reduced fasting glucose levels. In conclusion, our data emphasize the potential of physical activity in reducing development of neuropsychiatric conditions, such as anxiety, and highlights DHMC as an attractive compound to be investigated in future studies addressing neuropsychiatric disorders associated with metabolic conditions.

AVALIAÇÃO DA INTEGRIDADE DA BARREIRA ENDOTELIAL E SUA RELAÇÃO COM AS MANIFESTAÇÕES CLÍNICAS E LABORATORIAIS NA COVID-19

Objetivos

Os mecanismos fisiopatológicos que determinam a gravidade da Covid-19 estão associados a ativação da hemostasia e da imunidade inata, em um processo coletivamente referido como imunotrombose, e que envolve ativação plaquetária, geração de NETs (do inglês, Nucleo extracelular traps), expressão de fator tecidual, ativação do complemento e ativação endotelial. Um elemento importante da ativação endotelial é a quebra da barreira endotelial (BE), que ocorre para facilitar o acesso de leucócitos aos tecidos, onde contribuem para erradicação dos patógenos. No entanto, a avaliação da integridade da BE é desafiadora, exigindo o uso de modelos celulares. O objetivo desse estudo foi avaliar o efeito do soro de pacientes com Covid-19 sobre a integridade da BE em monocamadas de células endoteliais, e sua correlação com características clínicas da doença.

Materiais e métodos

A população do estudo consistiu em 30 pacientes com Covid-19 que apresentavam comprometimento pulmonar confirmado por tomografia de tórax, e necessidade de internação hospitalar por hipoxemia e 30 controles saudáveis pareados por sexo e idade. Os pacientes recrutados fizeram parte de um estudo clínico (REBEC: U1111-1250-1843), e as amostras utilizadas nesta avaliação foram obtidas no momento da internação, antes de qualquer intervenção. Monocamadas de células endoteliais de duas fontes (HUVECs: células de cordão umbilical; HULECs: células endoteliais pulmonares) foram estimuladas com soro de pacientes e indivíduos saudáveis (diluição 15% em meio de cultura) e a integridade da BE foi avaliada por um sensor de impedância celular (ECIS; Eletric Cell-substrate Impedance Sensing System) continuamente por 36 horas. Biomarcadores de gravidade e relacionados à ativação da hemostasia foram avaliados por kits comerciais. Dados clínicos foram obtidos a partir dos prontuários digitais.

Resultados

O soro de pacientes com Covid-19 induziu quebra de BE significativamente mais acentuada que o de indivíduos saudáveis em HUVECs nos tempos 15 min (p < 0,01); 30 min (p ≤ 0,001); 1h (p ≤ 0,0001); 2h (p ≤ 0,0001); 3h (p ≤ 0,0001); 4h (p ≤ 0,01) e 5h (p ≤ 0,05). Estes resultados foram confirmados no modelo de células endoteliais pulmonares (HULECs). A magnitude da quebra apresentou correlação significativa com desfechos clínicos relevantes como tempo de internação total (R_S até 0.57) e tempo de UTI (R_S = 0,47). Em relação a biomarcadores de interesse na Covid-19, a quebra da BE apresentou correlação significativa com neutrofilia, relação neutrófilo/linfócito, fator de Von Willebrand, fatores IX e XI, fibrinogênio, D-dímero e uPAR (Receptor de Uroquinase).

Discussão

Através de um método considerado padrão-ouro para avaliação in vitro da integridade da BE nós demonstramos que componentes presentes no soro de pacientes com Covid-19 são capazes de promover a quebra da BE, e que a magnitude deste processo está relacionada à gravidade desta doença. A correlação com outros marcadores inflamatórios corrobora a conexão entre os mecanismos envolvidos na imunotrombose em pacientes com Covid-19.

Conclusão

nossos resultados apontam a quebra da BE como um alvo terapêutico atrativo nestes pacientes.

AVALIAÇÃO DOS NÍVEIS CIRCULANTES DE MEDIADORES DA INTEGRIDADE DA BARREIRA ENDOTELIAL NA COVID-19 E SUA RELAÇÃO COM A ATIVAÇÃO DA HEMOSTASIA

Objetivos

a imunotrombose consiste no processo que envolve a ativação concomitante da imunidade inata, hemostasia e endotélio como parte da resposta a patógenos, e vem sendo colocada no centro da fisiopatologia da Covid-19. Um elemento menos explorado da imunotrombose é a ruptura da barreira endotelial (BE), que permite o acesso dos leucócitos aos tecidos inflamados. Entre os reguladores da integridade da BE destacam-se as vias que envolvem a angiopoietina (Ang) 1 e 2 e seu receptor Tie2, e a via do VEGF-A/VE-caderina (VEC). Além deste papel, foi recentemente demonstrado que a ativação da via Ang/Tie2 inibe a ativação endotelial e a expressão de fator tecidual, estabilizando o endotélio no estado quiescente. Neste estudo determinamos os níveis circulantes de mediadores da integridade da BE na Covid-19, e exploramos sua associação com a gravidade da doença, assim como com a ativação da hemostasia através de um painel abrangente de biomarcadores.

Materiais e métodos

as amostras foram obtidas de 30 pacientes internados por Covid-19 devido à hipoxemia e achados tomográficos típicos, e recrutados para um estudo clínico (REBEC: U1111-1250-1843). As amostras foram coletadas em até 24h do diagnóstico, antes de qualquer intervenção terapêutica. Os níveis de reguladores da BE foram medidos por métodos imunológicos (Elisa ou multiplex), e o de biomarcadores da hemostasia por kits comerciais específicos. Um grupo de 30 indivíduos saudáveis pareados por idade e sexo foram utilizados como controle. Dados clínicos e laboratoriais foram obtidos dos prontuários digitais.

Resultados

o tempo médio de internação foi de 12,9 ± 9,8 dias, e 12 pacientes (40%) necessitaram de UTI. O dímero D médio foi de 3.609 ± 14.440 ng/mL. Os níveis circulantes de todos reguladores da integridade da BE encontraram-se aumentados em pacientes, quando comparado com controles (Ang1: 463.2 ± 194.6 vs 237.4 ± 104.9 pg/mL, p < 0.0001; Ang2: 1.926 (1.275-3.134) vs 1.215 (9-1.444) pg/mL, p < 0.0001; Tie2: 10.753 ± 2.377 vs 8.603 ± 1.851 pg/mL, p < 0.0001 e VEGF-A: 94.7 (73.4-116.0) vs 45.9 (39.7-57.0), p < 0.0001. Além disso, os níveis de alguns destes reguladores se associaram significativamente a desfechos de relevância clínica, a saber: (i) extensão da lesão pulmonar na tomografia: Ang2 e VEGF-A; (ii) tempo de internação em UTI: VEGF-A. Interessantemente, observamos correlações consistentes e significativas entre os níveis de reguladores da BE a proteínas envolvidas na ativação da hemostasia (fibrinogênio, VWF: Ag, uPAR, PAI-1 e P-selectina).

Discussão

o interesse no estudo de reguladores da integridade da BE na Covid-19 já se justifica pelo fato de a doença envolver tanto o comprometimento da barreira alvéolo-capilar quanto a ativação da angiogênese, como demonstrado por outros autores. Nossos resultados reforçam a relevância destas vias através da associação observada com desfechos clínicos. Além disso, os resultados mostram pela primeira vez uma associação entre mediadores da integridade da BE e um painel amplo de biomarcadores da ativação da hemostasia, sugerindo um crosstalk entre estas vias na Covid-19, como demonstrado recentemente no contexto da sepse.

Conclusões

nossos resultados apontam que a via Ang/Tie2 deve ser considerada um alvo terapêutico atrativo na Covid-19, por representar um elemento central da imunotrombose nestes pacientes.

AVALIAÇÃO DOS NÍVEIS DE MARCADORES DA VIA HEME/HEMOPEXINA/HEME-OXIGENASE 1 E SUA ASSOCIAÇÃO COM PARÂMETROS CLÍNICOS E LABORATORIAIS NA COVID-19

Objetivos

Material e métodos

Resultados

Discussão

Conclusão

Elevated Glucose Levels Favor SARS-CoV-2 Infection and Monocyte Response through a HIF-1α/Glycolysis-Dependent Axis

COVID-19 can result in severe lung injury. It remained to be determined why diabetic individuals with uncontrolled glucose levels are more prone to develop the severe form of COVID-19. The molecular mechanism underlying SARS-CoV-2 infection and what determines the onset of the cytokine storm found in severe COVID-19 patients are unknown. Monocytes and macrophages are the most enriched immune cell types in the lungs of COVID-19 patients and appear to have a central role in the pathogenicity of the disease. These cells adapt their metabolism upon infection and become highly glycolytic, which facilitates SARS-CoV-2 replication. The infection triggers mitochondrial ROS production, which induces stabilization of hypoxia-inducible factor-1α (HIF-1α) and consequently promotes glycolysis. HIF-1α-induced changes in monocyte metabolism by SARS-CoV-2 infection directly inhibit T cell response and reduce epithelial cell survival. Targeting HIF-1ɑ may have great therapeutic potential for the development of novel drugs to treat COVID-19.

Combining Machine Learning and Metabolomics to Identify Weight Gain Biomarkers

Weight gain is a metabolic disorder that often culminates in the development of obesity and other comorbidities such as diabetes. Obesity is characterized by the development of a chronic, subclinical systemic inflammation, and is regarded as a remarkably important factor that contributes to the development of such comorbidities. Therefore, laboratory methods that allow the identification of subjects at higher risk for severe weight-associated morbidity are of utter importance, considering the health, and safety of populations. This contribution analyzed the plasma of 180 Brazilian individuals, equally divided into a eutrophic control group and case group, to assess the presence of biomarkers related to weight gain, aiming at characterizing the phenotype of this population. Samples were analyzed by mass spectrometry and most discriminant features were determined by a machine learning approach using Random Forest algorithm. Five biomarkers related to the pathogenesis and chronicity of inflammation in weight gain were identified. Two metabolites of arachidonic acid were upregulated in the case group, indicating the presence of inflammation, as well as two other molecules related to dysfunctions in the cycle of nitric oxide (NO) and increase in superoxide production. Finally, a fifth case group marker observed in this study may indicate the trigger for diabetes in overweight and obesity individuals. The use of mass spectrometry combined with machine learning analyses to prospect and characterize biomarkers associated with weight gain will pave the way for elucidating potential therapeutic and prognostic targets.

Swimming reduces fatty acids-associated hypothalamic damage in mice

The arcuate and the paraventricular and lateral hypothalamic nuclei, related to hunger and satiety control, are generally compromised by excess fatty acids. In this situation, fatty acids cause inflammation via TLR4 (toll like receptor 4) and the nuclei become less responsive to the hormones leptin and insulin, contributing to the development of obesity. In this work, these nuclei were analyzed in animals fed with high-fat diet and submitted to swimming without and with load for two months. For this, frontal sections of the hypothalamus were immunolabelled with GFAP (glial fibrillary acidic protein), synaptophysin, IL-6 (interleukin 6) and TLR4. Also, proteins extracted from the hypothalamus were analyzed using Western blotting (GFAP and synaptophysin), fluorometric analysis for caspases 3 and 7, and CBA (cytometric bead array) for Th1, Th2, and Th17 profiles. The high-fat diet significantly caused overweight and, in the hypothalamus, decreased synapses and increased astrocytic reactivity. The swimming with load, especially 80 % of the maximum load, reduced those consequences. The high-fat diet increased TLR4 in the arcuate nucleus and the swimming exercise with 80 % of the maximum load showed a tendency of reducing this expression. Swimming did not significantly influence the inflammatory or anti-inflammatory cytokines in the hypothalamus or in plasma. The high-fat diet in sedentary animals increased the expression of caspases 3 and 7 and swimming practice reduced this increment to levels compatible with animals fed on a normal diet. The set of results conclude that the impact of swimming on the damage caused in the hypothalamus by a high-fat diet is positive. The different aspects analyzed in here point to better cellular viability and conservation of the synapses in the hypothalamic nuclei of overweight animals that practiced swimming with a load.

Retraction Note to: L-glutamine supplementation induces insulin resistance in adipose tissue and improves insulin signalling in liver and muscle of rats with diet-induced obesity

In light of forensic evidence indicating duplication and/or manipulation of western blot images the Editor-in-Chief is retracting the article cited above.

Tumor necrosis factor-alpha levels in blood cord is directly correlated with the body weight of mothers

Background

Obesity has emerged as major public health problem leading to increased morbidity and mortality. Epidemiological studies indicate that in many regions of the world, children and teenagers are increasingly affected by obesity, which contributes for a pessimistic projection for the near future. Maternal obesity has been implicated in metabolic disorders of the offspring, but there are no biological markers that can be detected early on life that predict the development of obesity in the offspring.

Objective

To evaluate the expression of inflammatory markers in the umbilical cord blood of babies of mothers with obesity/overweight, and correlate these markers with the body weight at age 9 months.

Methods

Anthropometric data of mothers and babies were obtained during prenatal evaluation, at birth and 9 months after birth. Cord blood was collected during delivery of 54 babies from mothers with obesity/overweight and of 50 babies from lean mothers. Tumour necrosis factor‐alpha (TNF‐α), transforming growth factor 1 beta, monocyte chemoattractant protein‐1 and 2 (MCP‐1/MCP‐2) were determined in serum samples using enzyme‐linked immunosorbent assay methods. Correlations were evaluated using the Spearman correlation coefficient, and comparisons were evaluated using the non‐parametric Mann–Whitney U‐test.

Results

Cord blood TNF‐α was positively correlated with maternal body mass index. There was an inverse correlation between cord blood transforming growth factor 1 beta and baby body weight at birth. There was no biological marker that predicted body weight at age 9 months.

Conclusion

Although we have not found a biological marker to predict increased body weight at 9 months of age, the study shows that maternal obesity exposes the baby to higher TNF‐α level in the early stages of life, and this can affect metabolic and inflammatory parameters during adulthood.

Diets Containing α-Linolenic (ω3) or Oleic (ω9) Fatty Acids Rescues Obese Mice From Insulin Resistance

Subclinical systemic inflammation is a hallmark of obesity and insulin resistance. The results obtained from a number of experimental studies suggest that targeting different components of the inflammatory machinery may result in the improvement of the metabolic phenotype. Unsaturated fatty acids exert antiinflammatory activity through several distinct mechanisms. Here, we tested the capacity of ω3 and ω9 fatty acids, directly from their food matrix, to exert antiinflammatory activity through the G protein-coupled receptor (GPR)120 and GPR40 pathways. GPR120 was activated in liver, skeletal muscle, and adipose tissues, reverting inflammation and insulin resistance in obese mice. Part of this action was also mediated by GPR40 on muscle, as a novel mechanism described. Pair-feeding and immunoneutralization experiments reinforced the pivotal role of GPR120 as a mediator in the response to the nutrients. The improvement in insulin sensitivity in the high-fat substituted diets was associated with a marked reduction in tissue inflammation, decreased macrophage infiltration, and increased IL-10 levels. Furthermore, improved glucose homeostasis was accompanied by the reduced expression of hepatic gluconeogenic enzymes and reduced body mass. Thus, our data indicate that GPR120 and GPR40 play a critical role as mediators of the beneficial effects of dietary unsaturated fatty acids in the context of obesity-induced insulin resistance.

Hypothalamic AMPK activation blocks lipopolysaccharide inhibition of glucose production in mice liver

Endotoxic hypoglycaemia has an important role in the survival rates of septic patients. Previous studies have demonstrated that hypothalamic AMP-activated protein kinase (hyp-AMPK) activity is sufficient to modulate glucose homeostasis. However, the role of hyp-AMPK in hypoglycaemia associated with endotoxemia is unknown. The aims of this study were to examine hyp-AMPK dephosphorylation in lipopolysaccharide (LPS)-treated mice and to determine whether pharmacological hyp-AMPK activation could reduce the effects of endotoxemia on blood glucose levels. LPS-treated mice showed reduced food intake, diminished basal glycemia, increased serum TNF-α and IL-1β levels and increased hypothalamic p-TAK and TLR4/MyD88 association. These effects were accompanied by hyp-AMPK/ACC dephosphorylation. LPS-treated mice also showed diminished liver expression of PEPCK/G6Pase, reduction in p-FOXO1, p-AMPK, p-STAT3 and p-JNK level and glucose production. Pharmacological hyp-AMPK activation blocked the effects of LPS on the hyp-AMPK phosphorylation, liver PEPCK expression and glucose production. Furthermore, the effects of LPS were TLR4-dependent because hyp-AMPK phosphorylation, liver PEPCK expression and fasting glycemia were not affected in TLR4-mutant mice. These results suggest that hyp-AMPK activity may be an important pharmacological target to control glucose homeostasis during endotoxemia.

Serum levels and mesenteric fat tissue expression of adiponectin and leptin in patients with Crohn's disease

Crohn's disease (CD) is characterized by inflammation and an aetiology that is still unknown. Hypertrophy of mesenteric fat is a reflection of disease activity, as this fat covers the entire length of the affected area. Adipocytes synthesize leptin and adiponectin, adipocytokines responsible for pro- and anti-inflammatory effects. Therefore, we evaluated serum levels of adiponectin and leptin, as well as mesenteral expression of adiponectin in active CD and those in remission. Sixteen patients with ileocaecal CD followed at the Outpatient Clinic, Coloproctology Unit of University of Campinas Clinical Hospital, participated in the study. Analysis of serum adiponectin and leptin by enzyme-linked immunosorbent assay was performed in patients with active CD (ACD group), remission CD (RCD group) and in six healthy controls. Ten patients with active ileocaecal CD (FCD group) and eight patients with non-inflammatory disease selected for surgery were also studied. The specimens were snap-frozen and the expression of adiponectin was determined by immunoblot of protein extracts. Serum C-reactive protein levels were higher in the ACD group when compared to the others and no difference of body mass index was observed between the groups. Serum adiponectin was lower in the ACD group when compared to control, but no differences were seen when comparing the ACD and RCD groups. Mesenteric adiponectin expression was lower in the FCD group when compared to the FC group. Serum leptin was similar in all groups. The lower levels of serum and mesenteric adiponectin in active CD suggest a defective regulation of anti-inflammatory pathways in CD pathogenesis.

Opposing effects of Toll-like receptors 2 and 4 on synaptic stability in the spinal cord after peripheral nerve injury

Background

Glial cells are involved in the synaptic elimination process that follows neuronal lesions, and are also responsible for mediating the interaction between the nervous and immune systems. Neurons and glial cells express Toll-like receptors (TLRs), which may affect the plasticity of the central nervous system (CNS). Because TLRs might also have non-immune functions in spinal-cord injury (SCI), we aimed to investigate the influence of TLR2 and TLR4 on synaptic plasticity and glial reactivity after peripheral nerve axotomy.

Methods

The lumbar spinal cords of C3H/HePas wild-type (WT) mice, C3H/HeJ TLR4-mutant mice, C57BL/6J WT mice, and C57BL/6J TLR2 knockout (KO) mice were studied after unilateral sciatic nerve transection. The mice were killed via intracardiac perfusion, and the spinal cord was processed for immunohistochemistry, transmission electron microscopy (TEM), western blotting, cell culture, and reverse transcriptase PCR. Primary cultures of astrocytes from newborn mice were established to study the astrocyte response in the absence of TLR2 and the deficiency of TLR4 expression.

Results

The results showed that TLR4 and TLR2 expression in the CNS may have opposite effects on the stability of presynaptic terminals in the spinal cord. First, TLR4 contributed to synaptic preservation of terminals in apposition to lesioned motor neurons after peripheral injury, regardless of major histocompatibility complex class I (MHC I) expression. In addition, in the presence of TLR4, there was upregulation of glial cell-derived neurotrophic factor and downregulation of interleukin-6, but no morphological differences in glial reactivity were seen. By contrast, TLR2 expression led to greater synaptic loss, correlating with increased astrogliosis and upregulation of pro-inflammatory interleukins. Moreover, the absence of TLR2 resulted in the upregulation of neurotrophic factors and MHC I expression.

Conclusion

TLR4 and TLR2 in the CNS may have opposite effects on the stability of presynaptic terminals in the spinal cord and in astroglial reactions, indicating possible roles for these proteins in neuronal and glial responses to injury.

Hip circumference is associated with high density lipoprotein cholesterol response following statin therapy in hypertensive subjects

AIM

This report investigated the relationship between anthropometric measurements of body fat distribution and lipid response to statins in hypercholesterolemic hypertensive patients.

METHODS

We prospectively examined 129 subjects who used either simvastatin 20 mg/day (no.=83) or atorvastatin 10 mg/day (no.=46) for 3 months. Anthropometry included evaluation of body mass index, waist and hip circumferences, and waist-to-hip-ratio.

RESULTS

Significant decreases in LDL (p<0.001), total cholesterol (p<0.001), and triglycerides (p=0.04) levels were detected after 3 months of therapy in the whole sample. At baseline, only an inverse correlation between waist circumference and HDLcholesterol levels was detected (r=-0.18; p=0.04). Conversely, a direct relationship between hip circumference and HDLcholesterol response to statins was found in the whole sample (r=0.24; p=0.006), while no other anthropometric measurement displayed significant correlation with lipid changes. The association between HDL-cholesterol response and hip circumference was further confirmed by stepwise regression analysis adjusted for baseline HDL-cholesterol levels, metabolic syndrome, body mass index, and waist circumference.

CONCLUSIONS

Hip circumference, a surrogate marker of peripheral adiposity, is associated with HDL-cholesterol changes following statin therapy in hypertensive patients.

PGC1α gene Gly482Ser polymorphism predicts improved metabolic, inflammatory and vascular outcomes following bariatric surgery

AIMS/HYPOTHESIS

Bariatric surgery is currently employed as an effective approach to treat class III obesity and class II obesity with co-morbidities. Unfortunately, the general anthropometric and metabolic outcomes of the surgery are not homogeneous, and defining the eligibility criteria that allow for a more precise prediction of the outcomes of this invasive procedure will refine the selection of patients. Here we tested the hypothesis that the Gly482Ser polymorphism of the ppargc1a gene would predict different outcomes following bariatric surgery.

METHODS

Fifty-five patients (26 Gly/Gly and 29 Gly/Ser+Ser/Ser) selected for the Roux-en-Y gastric bypass according to the National Institutes of Health Consensus Statement criteria were followed up for 1 year, monitoring their anthropometric, metabolic and inflammatory parameters.

RESULTS

Patients with the Gly482Ser polymorphism had significantly improved reductions in the waist/hip ratio, fasting blood glucose, C-reactive protein, blood leukocyte count, serum interleukin-6 and intima-media thickness of the carotid artery, as compared with Gly/Gly patients.

CONCLUSIONS/INTERPRETATION

Thus, the Gly482Ser polymorphism may predict a more favorable metabolic and inflammatory outcome for obese patients submitted to bariatric surgery, leading to a reduced atherosclerotic risk.

Interferon (IFN) beta treatment induces major histocompatibility complex (MHC) class I expression in the spinal cord and enhances axonal growth and motor function recovery following sciatic nerve crush in mice

AIMS

Major histocompatibility complex (MHC) class I expression by neurones and glia constitutes an important pathway that regulates synaptic plasticity. The upregulation of MHC class I after treatment with interferon beta (IFN beta) accelerates the response to injury. Therefore the present work studied the regenerative outcome after peripheral nerve lesion and treatment with IFN beta, aiming at increasing MHC class I upregulation in the spinal cord.

METHODS

C57BL/6J mice were subjected to unilateral sciatic nerve crush and treatment with IFN beta. The lumbar spinal cords were processed for immunohistochemistry, in situ hybridization, Western blotting and RT-PCR, while the sciatic nerves were submitted for immunohistochemistry, morphometry and counting of regenerated axons. Motor function recovery was monitored using the walking track test.

RESULTS

Increased MHC class I expression in the motor nucleus of IFN beta-treated animals was detected. In the peripheral nerve, IFN beta-treated animals showed increased S100, GAP-43 and p75NTR labelling coupled with a significantly greater number of regenerated axons. No significant differences were found in neurofilament or laminin labelling. The morphological findings, indicating improvements in the regenerative process after IFN treatment were in line with the motor behaviour test applied to the animals during the recovery process.

CONCLUSIONS

The present data reinforce the role of MHC class I upregulation in the response to injury, and suggest that IFN treatment may be beneficial to motor recovery after axotomy.

Type III hypersensitivity to insulin leading to leukocytoclastic vasculitis

Here, we report the occurrence of leukocytoclastic vasculitis as an outcome of type III allergy to insulin in a patient with type II diabetes mellitus. The diagnosis was made on the basis of anatomo-pathological examination of a skin biopsy.

TNF-α transiently induces endoplasmic reticulum stress and an incomplete unfolded protein response in the hypothalamus

In diet-induced obesity, hypothalamic inflammation is triggered as an outcome of prolonged exposure to dietary fats. Toll-like receptor 4 (TLR4) activation plays a central role in this process, inducing endoplasmic reticulum stress and activating inflammatory cytokine gene transcription. Although saturated fatty acids can induce endoplasmic reticulum stress in the hypothalamus, it is unknown whether inflammatory cytokines alone can activate this mechanism. Here, rats were treated with TNF-α or lyposaccharide (LPS) and endoplasmic reticulum stress and unfolded protein response were evaluated by immunoblot and polymerase chain reaction (PCR). Activation of TLR4 by LPS was capable of inducing a complete endoplasmic reticulum stress and unfolded protein response through the PERK/eIF2α and IRE1α/XBP1 pathways. Conversely, TNF-α, injected either locally or systemically, was unable to induce a complete program of unfolded protein response, although the activation of endoplasmic reticulum stress was achieved to a certain degree. Thus, in the hypothalamus, the isolated action of TNF-α is insufficient to produce the activation of a complete program of unfolded protein response.

UPR-mediated TRIB3 expression correlates with reduced AKT phosphorylation and inability of interleukin 6 to overcome palmitate-induced apoptosis in RINm5F cells

Unfolded protein response (UPR)-mediated pancreatic beta-cell death has been described as a common mechanism by which palmitate (PA) and pro-inflammatory cytokines contribute to the development of diabetes. There are evidences that interleukin 6 (IL6) has a protective action against beta-cell death induced by pro-inflammatory cytokines; the effects of IL6 on PA-induced apoptosis have not been investigated yet. In the present study, we have demonstrated that PA selectively disrupts IL6-induced RAC-alpha serine/threonine-protein kinase (AKT) activation without interfering with signal transducer and activator of transcription 3 phosphorylation in RINm5F cells. The inability of IL6 to activate AKT in the presence of PA correlated with an inefficient protection against PA-induced apoptosis. In contrast to PA, IL6 efficiently reduced apoptosis induced by pro-inflammatory cytokines. In addition, we have demonstrated that IL6 is unable to overcome PA-stimulated UPR, as assessed by activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP) expression, X-box binding protein-1 gene mRNA splicing, and pancreatic eukaryotic initiation factor-2 alpha kinase phosphorylation, whereas no significant induction of UPR by pro-inflammatory cytokines was detected. This unconditional stimulation of UPR and apoptosis by PA was accompanied by the stimulation of CHOP and tribble3 (TRIB3) expression, irrespective of the presence of IL6. These findings suggest that IL6 is unable to protect pancreatic beta-cells from PA-induced apoptosis because it does not repress UPR activation. In this way, CHOP and ATF4 might mediate PA-induced TRIB3 expression and, by extension, the suppression of IL6 activation of pro-survival kinase AKT.

Activation of signal transducer and activator of transcription-1 (STAT-1) and differential expression of interferon-gamma and anti-inflammatory proteins in pelvic ileal pouches for ulcerative colitis and familial adenomatous polyposis

Pouchitis after total rectocolectomy is the most common complication of ulcerative colitis (UC). The immunological mechanisms involved in the genesis of pouchitis are unclear. Therefore, we evaluated the inflammatory activity in normal ileal pouch mucosa by determining signal transducers and activators of transcription (STAT-1) activation and cytokine expression in patients operated for UC and familial adenomatous polyposis (FAP). Eighteen asymptomatic patients, who underwent total rectocolectomy and J pouch, were evaluated: nine with UC and nine with FAP. The activation of STAT-1 and cytokine expression were determined by immunoblot of total protein extracts from pouch mucosal biopsies. The absence of pouchitis was assessed by clinical, histological and endoscopic parameters, according to the Pouchitis Disease Activity Index. The patients were not receiving any medication. Analysis of variance (anova) and Tukey-Kramer's test were applied. The local ethical committee approved the study and informed consent was signed by all participants. STAT-1 activation was increased in UC when compared to FAP and controls (P < 0.05). Higher levels of interferon (IFN)-gamma expression were observed in UC patients when compared to the control group (P < 0.05), but were similar to FAP. In contrast, cytokine signalling (SOCS-3) and interleukin (IL)-10 expression were similar in all groups (P > 0.05). These findings could explain the higher susceptibility to this inflammatory complication in UC when compared to FAP. A tendency towards increased levels of IFN-gamma and STAT-1 in patients with UC, even without clinical and endoscopic evidence of pouchitis, was observed; studying inflammatory activity in asymptomatic ileal pouches may help understanding of the pathogenesis of pouchitis.

The brain is the conductor: diet-induced inflammation overlapping physiological control of body mass and metabolism

Obesity is currently a worldwide pandemic. It affects more than 300 million humans and it will probably increase over the next 20 years. The consumption of calorie-rich foods is responsible for most of the obesity cases, but not all humans exposed to high-calorie diets develop the disease. This fact has prompted researchers to investigate the mechanisms linking the consumption of high-calorie diets to the generation of an imbalance between energy intake and expenditure. According to recent studies, the exposure to fat-rich diets induces an inflammatory response in the hypothalamic areas involved in the control of feeding and thermogenesis. The inflammatory process damages the neuronal circuitries that maintain the homeostatic control of the body's energy stores, therefore favoring body mass gain. This review will focus on the main advances obtained in this field.

Inflammatory response in a rat model of gastroschisis is associated with an increase of NF-kappaB

Babies with gastroschisis have high morbidity, which is associated with inflammatory bowel injury caused by exposure to amniotic fluid. The objective of this study was to identify components of the inflammatory response in the intestine and liver in an experimental model of gastroschisis in rats. The model was surgically created at 18.5 days of gestation. The fetuses were exposed through a hysterotomy and an incision at the right of the umbilicus was made, exposing the fetal bowel. Then, the fetus was placed back into the uterus until term. The bowel in this model had macro- and microscopic characteristics similar to those observed in gastroschisis. The study was conducted on three groups of 20 fetuses each: gastroschisis, control, and sham fetuses. Fetal body, intestine and liver weights and intestine length were measured. IL-1beta, IL-6, IL-10, TNF-alpha, IFN-gamma and NF-kappaB levels were assessed by ELISA. Data were analyzed statistically by ANOVA followed by the Tukey post-test. Gastroschisis fetuses had a decreased intestine length (means +/- SD, 125 +/- 25 vs 216 +/- 13.9; P < 0.005) and increased intestine weight (0.29 +/- 0.05 vs 0.24 +/- 0.04; P < 0.005). Intestine length correlated with liver weight only in gastroschisis fetuses (Pearson's correlation coefficient, r = 0.518, P = 0.019). There were no significant differences in the concentrations of IL-1beta, TNF-alpha or IFN-gamma in the intestine, whereas the concentration of NF-kappaB was increased in both the intestine and liver of fetuses with gastroschisis. These results show that the inflammatory response in the liver and intestine of the rat model of gastroschisis is accompanied by an increase in the amount of NF-kappaB in the intestine and liver.

Acute exercise reverses TRB3 expression in the skeletal muscle and ameliorates whole body insulin sensitivity in diabetic mice

AIM

TRB3 became of major interest in diabetes research when it was shown to interact with and inhibit the activity of Akt. Conversely, physical exercise has been linked to improved glucose homeostasis. Thus, the current study was designed to investigate the effects of acute exercise on TRB3 expression and whole body insulin sensitivity in obese diabetic mice.

METHODS

Male leptin-deficient (ob/ob) mice swam for two 3-h-long bouts, separated by a 45-min rest period. After the second bout of exercise, food was withdrawn 6 h before antibody analysis. Eight hours after the exercise protocol, the mice were submitted to an insulin tolerance test (ITT). Gastrocnemius muscle samples were evaluated for insulin receptor (IR) and IRS-1 tyrosine phosphorylation, Akt serine phosphorylation, TRB3/Akt association and membrane GLUT4 expression.

RESULTS

Western blot analysis showed that TRB3 expression was reduced in the gastrocnemius of leptin-deficient (ob/ob) mice submitted to exercise when compared with respective ob/ob mice at rest. In parallel, there was an increase in the insulin-signalling pathway in skeletal muscle from leptin-deficient mice after exercise. Furthermore, the GLUT4 membrane expression was increased in the muscle after the exercise protocol. Finally, a single session of exercise improved the glucose disappearance (K(ITT)) rate in ob/ob mice.

CONCLUSION

Our results demonstrate that acute exercise reverses TRB3 expression and insulin signalling restoration in muscle. Thus, these results provide new insights into the mechanism by which physical activity ameliorates whole body insulin sensitivity in type 2 diabetes.

Aspirin attenuates insulin resistance in muscle of diet-induced obese rats by inhibiting inducible nitric oxide synthase production and S-nitrosylation of IRbeta/IRS-1 and Akt

AIM/HYPOTHESIS

High-dose aspirin treatment improves fasting and postprandial hyperglycaemia in patients with type 2 diabetes, as well as in animal models of insulin resistance associated with obesity and sepsis. In this study, we investigated the effects of aspirin treatment on inducible nitric oxide synthase (iNOS)-mediated insulin resistance and on S-nitrosylation of insulin receptor (IR)-beta, IRS-1 and protein kinase B (Akt) in the muscle of diet-induced obese rats and also in iNos (also known as Nos2)-/- mice on high fat diet.

METHODS

Aspirin (120 mg kg-1 day-1 for 2 days) or iNOS inhibitor (L-NIL; 80 mg/kg body weight) were administered to diet-induced obese rats or mice and iNOS production and insulin signalling were investigated. S-nitrosylation of IRbeta/IRS-1 and Akt was investigated using the biotin switch method.

RESULTS

iNOS protein levels increased in the muscle of diet-induced obese rats, associated with an increase in S-nitrosylation of IRbeta, IRS-1 and Akt. These alterations were reversed by aspirin treatment, in parallel with an improvement in insulin signalling and sensitivity, as measured by insulin tolerance test and glucose clamp. Conversely, while aspirin reversed the increased phosphorylation of IkappaB kinase beta and c-Jun amino-terminal kinase, as well as IRS-1 serine phosphorylation in diet-induced obese rats and iNos -/- mice on high-fat diet, these alterations were not associated with the improvement of insulin action induced by this drug.

CONCLUSIONS/INTERPRETATION

Our data demonstrate that aspirin treatment not only reduces iNOS protein levels, but also S-nitrosylation of IRbeta, IRS-1 and Akt. These changes are associated with improved insulin resistance and signalling, suggesting a novel mechanism of insulin sensitisation evoked by aspirin treatment.

Reduction of hypothalamic protein tyrosine phosphatase improves insulin and leptin resistance in diet-induced obese rats

Protein tyrosine phosphatase (PTP1B) has been implicated in the negative regulation of insulin and leptin signaling. PTP1B knockout mice are hypersensitive to insulin and leptin and resistant to obesity when fed a high-fat diet. We investigated the role of hypothalamic PTP1B in the regulation of food intake, insulin and leptin actions and signaling in rats through selective decreases in PTP1B expression in discrete hypothalamic nuclei. We generated a selective, transient reduction in PTP1B by infusion of an antisense oligonucleotide designed to blunt the expression of PTP1B in rat hypothalamic areas surrounding the third ventricle in control and obese rats. The selective decrease in hypothalamic PTP1B resulted in decreased food intake, reduced body weight, reduced adiposity after high-fat feeding, improved leptin and insulin action and signaling in hypothalamus, and may also have a role in the improvement in glucose metabolism in diabetes-induced obese rats.

Differential expression of pro-inflammatory cytokines and a pro-apoptotic protein in pelvic ileal pouches for ulcerative colitis and familial adenomatous polyposis

BACKGROUND

Pouchitis after total rectocolectomy is among the most common complications of patients with ulcerative colitis (UC). However, its frequency is quite rare in patients with familial adenomatous polyposis (FAP). We evaluated the inflammatory and pro-apoptotic activity in endoscopically normal mucosa of the ileal pouch in patients with UC and FAP.

METHODS

Twenty patients (10 with UC and 10 with FAP) with "J" pouch after total proctocolectomy were studied as were 10 normal controls. Biopsies were obtained from the mucosa of the pouch of UC and FAP patients and from the normal ileum of controls. The expression levels of TNF-alpha, IL-1beta, IL-6, IL-8 and phospho-BAD were determined by immunoblotting. Activated NFkappaB was evaluated by immuno-precipitation and immunoblotting for IkappaB kinase beta.

RESULTS

Patients with UC had higher levels of IL-1beta, IL-6, IL-8 and TNF-alpha than patients with FAP. The level of TNF-alpha was higher in patients with UC than in patients with FAP; both patient groups had TNF-alpha levels higher than controls. Activation of NFkappaB was similar in all three groups. The expression of phospho-BAD was significantly lower in patients with FAP than in patients with UC.

CONCLUSIONS

As compared with patients with FAP, patients with UC presented increased levels of some pro-inflammatory cytokines, even in the absence of clinical or endoscopic signs of pouchitis. Patients with FAP presented lower levels of pro-inflammatory proteins and of phospho-BAD. These findings may explain the higher rates of progression to pouchitis in UC patients, which could correlate with mucosal atrophy that occurs in inflamed tissue.

L-glutamine supplementation induces insulin resistance in adipose tissue and improves insulin signalling in liver and muscle of rats with diet-induced obesity

AIMS/HYPOTHESIS

Diet-induced obesity (DIO) is associated with insulin resistance in liver and muscle, but not in adipose tissue. Mice with fat-specific disruption of the gene encoding the insulin receptor are protected against DIO and glucose intolerance. In cell culture, glutamine induces insulin resistance in adipocytes, but has no effect in muscle cells. We investigated whether supplementation of a high-fat diet with glutamine induces insulin resistance in adipose tissue in the rat, improving insulin sensitivity in the whole animal.

MATERIALS AND METHODS

Male Wistar rats received standard rodent chow or a high-fat diet (HF) or an HF supplemented with alanine or glutamine (HFGln) for 2 months. Light microscopy and morphometry, oxygen consumption, hyperinsulinaemic-euglycaemic clamp and immunoprecipitation/immunoblotting were performed.

RESULTS

HFGln rats showed reductions in adipose mass and adipocyte size, a decrease in the activity of the insulin-induced IRS-phosphatidylinositol 3-kinase (PI3-K)-protein kinase B-forkhead transcription factor box 01 pathway in adipose tissue, and an increase in adiponectin levels. These results were associated with increases in insulin-stimulated glucose uptake in skeletal muscle and insulin-induced suppression of hepatic glucose output, and were accompanied by an increase in the activity of the insulin-induced IRS-PI3-K-Akt pathway in these tissues. In parallel, there were decreases in TNFalpha and IL-6 levels and reductions in c-jun N-terminal kinase (JNK), IkappaB kinase subunit beta (IKKbeta) and mammalian target of rapamycin (mTOR) activity in the liver, muscle and adipose tissue. There was also an increase in oxygen consumption and a decrease in the respiratory exchange rate in HFGln rats.

CONCLUSIONS/INTERPRETATION

Glutamine supplementation induces insulin resistance in adipose tissue, and this is accompanied by an increase in the activity of the hexosamine pathway. It also reduces adipose mass, consequently attenuating insulin resistance and activation of JNK and IKKbeta, while improving insulin signalling in liver and muscle.

Non-effect of p22-phox −930A/G polymorphism on end-organ damage in Brazilian hypertensive patients

The p22-phox subunit is an essential component of NAD(P)H oxidase enzymatic complex, which is considered the major source of oxidative stress products in the cardiovascular system. The -930G allele of p22-phox has been associated with higher promoter activity, increased NAD(P)H oxidase-mediated oxidative stress and hypertension. We recently reported that left ventricular hypertrophy is accompanied by increased myocardial p22-phox expression in aortic-banded rats, suggesting that this protein might be involved in hypertensive cardiac hypertrophy.

Circulating ghrelin concentrations are lowered by intracerebroventricular insulin

AIMS/HYPOTHESIS

Ghrelin is a peptide that is mainly produced by the stomach and stimulates food intake, adiposity and weight gain. Previous studies have documented that plasma levels of ghrelin are reduced by insulin, but the mechanisms that mediate this effect are unclear.

METHODS

To determine whether phosphatidylinositol 3-kinase (PI(3)K) and/or mitogen-activated protein kinase (MAPK) are involved in this insulin action, we tested the intracerebroventricular (i.c.v.) effect of specific inhibitors of PI(3)K (LY294002 and wortmannin) and MAPK (PD98059 and UO126) on the insulin-mediated reduction of ghrelin levels in rats.

RESULTS

Intracerebroventricular treatment with insulin reduced ghrelin levels. Inhibition of PI(3)K specifically blocked the insulin-induced reduction in ghrelin concentration, whereas inhibition of MAPK had no effect on insulin-mediated actions. Moreover, pretreatment with i.c.v. PI(3)K inhibitors blocked the reduction of ghrelin levels after OGTT-induced hyperglycaemia and hyperinsulinaemia.

CONCLUSIONS/INTERPRETATION

These data demonstrate that changes in insulin action in the central nervous system regulate circulating ghrelin levels and that PI(3)K is a specific mediator of this action.

Increased expression of advanced glycation end-products and their receptor, and activation of nuclear factor kappa-B in lacrimal glands of diabetic rats

AIMS/HYPOTHESIS

To assess the involvement of the AGE-specific receptor (AGER, also known as RAGE) axis and nuclear factor kappa-B (NFKB, also known as NF-kappaB) activation in the development of lacrimal gland and tear film dysfunction in diabetes, the present study evaluated: (1) lacrimal gland and tear film alterations in diabetic rats; and (2) the expression of AGE, AGER and NFKB in ocular tissues of normoglycaemic and diabetic rats.

MATERIALS AND METHODS

Diabetes was induced in male Wistar rats with intravenous streptozotocin. Tear secretion parameters were measured and NFKB expression was evaluated in lacrimal glands of control and diabetic rats by western blot. Immunohistochemistry with confocal microscopy was used to assess AGE, AGER and NFKB expression in lacrimal glands of both groups.

RESULTS

Lacrimal gland weight and tear film volume were lower in diabetic than in control rats (p=0.01 and 0.02, respectively). IL1B and TNF concentrations in tears were higher in diabetic than in control rats (p=0.007 and 0.02, respectively). NFKB protein was identified in rat cornea, conjunctiva and lacrimal glands. AGE, AGER and NFKB expression were greater in lacrimal glands of diabetic than in those of control rats.

CONCLUSIONS/INTERPRETATION

Diabetes induces significant alterations in rat lacrimal gland structure and secretion. The higher expression of AGE, AGER and NFKB in lacrimal glands of diabetic rats suggests that these factors are involved in signalling and in subsequent inflammatory alterations related to dry eye in diabetes mellitus.

Effect of obesity on insulin signaling through JAK2 in rat aorta

Pathway specific resistance to insulin signaling through PI 3-kinase/Akt/eNOS associated with a normal or hyper-activated MAP kinase signaling in vascular tissues has recently been proposed as a candidate link between cardiovascular disease and insulin resistance. Growth stimulatory pathways other than ERK/MAP kinase, such as JAK/STAT have not yet been investigated in vessels of animal models of insulin resistance. Here we have examined whether insulin is able to activate JAK2/STAT pathway in rat aorta and also the regulation of this pathway in an animal model of obesity/insulin resistance. Our results demonstrate that insulin activates JAK2 tyrosine kinase activity in rat aorta in parallel with the activation of STAT3 and STAT5a/b. Moreover, it is shown that, in obese animals, JAK2/STAT and MAP kinase pathways are hyper-activated in response to insulin, which occurs in association with a reduced activation of PI 3-kinase/Akt pathway in aorta. The results of the present study suggest that, besides ERK/MAP kinase pathway, another potentially pro-atherogenic pathway, JAK2/STAT is hyper-activated in vessels in a state of insulin resistance and this phenomenon, in association with the inhibition of the PI 3-kinase/Akt pathway, may play an important role in the pathogenesis of cardiovascular diseases.

Short-term inhibition of peroxisome proliferator-activated receptor-gamma coactivator-1alpha expression reverses diet-induced diabetes mellitus and hepatic steatosis in mice

AIMS/HYPOTHESIS

The coactivator of nuclear receptors, peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) has been implicated in a series of events that contribute to the control of glucose metabolism. We have recently reported the use of a PGC-1alpha antisense oligonucleotide (PGC-1alphaAS) that inhibits up to 60% of PGC-1alpha expression in pancreatic islets, leading to increased insulin secretion. This oligonucleotide was used in this study to try to ameliorate diet-induced type 2 diabetes in a genetically predisposed mouse strain (Swiss mice).

MATERIALS AND METHODS

Glucose and insulin tolerance tests, euglycaemic-hyperinsulinaemic clamp, immunoprecipitation assays, immunoblotting assays and immunohistochemistry were used in this investigation.

RESULTS

Swiss mice became obese and overtly diabetic after 8 weeks of feeding with chow containing 24% saturated fat. One daily dose (1.0 nmol) of PGC-1alphaAS significantly reduced glucose and increased insulin blood levels without affecting food intake and body weight. These effects were accompanied by a reduced area under the glucose curve during an intraperitoneal glucose tolerance test, an increased constant of glucose decay (K(itt)) during an insulin tolerance test, and an increased glucose consumption rate during a euglycaemic-hyperinsulinaemic clamp. Moreover, mice treated with PGC-1alphaAS presented an outstanding reduction of macroscopic and microscopic features of hepatic steatosis. These effects were accompanied by reduced expression or function of a series of proteins involved in lipogenesis.

CONCLUSIONS/INTERPRETATION

PGC-1alpha is an attractive target for pharmacological therapeutics in type 2 diabetes mellitus and diet-induced hepatic steatosis.

Severe hypoleptinaemia associated with insulin resistance in patients with common variable immunodeficiency

OBJECTIVE

Common variable immunodeficiency (CVI) is a primary immunodeficiency syndrome characterized by impaired production of antibodies and recurrent infections. Delay in diagnosis leads to metabolic wastage and low body weight. Leptin, a hormone produced by white adipose tissue, modulates insulin action by signal transduction cross-talk and by direct action on pancreatic beta-cells. We hypothesized that patients with CVI might present a defective regulation of leptin production and insulin resistance.

PATIENTS

Thirteen CVI patients (39 +/- 11 years) under gammaglobulin replacement were evaluated in parallel with 13 gender-, age-, body weight- and body mass index (BMI)-matched healthy voluntaries, and with data from two large population series, the Bruneck and the Hoorn Studies.

MEASUREMENTS

Serum leptin and insulin levels, homeostasis model assessment - insulin resistance (HOMA-IR), body composition, haematological, biochemical and immunoglobulin measurements were obtained. Data were analysed by a one-way analysis of variance (anova) and by Pearson's rank analysis. The institutional ethics committee approved the study, and informed consent was obtained from patients and controls.

RESULTS

No differences were found between CVI and the control group when comparing gender distribution, age, body weight, BMI, waist/hip ratio, relative body fat and fasting glucose levels. Leptin levels were lower (P < 0.05) in CVI patients than in controls and lower than fasting leptin levels detected in a large population study. CVI patients' serum leptin levels did not correlate with BMI (r = 0.074, P = 0.8) and their high HOMA-IR indicated insulin resistance.

CONCLUSIONS

CVI patients are relatively hypoleptinaemic and insulin resistant, and their serum leptin levels are not correlated to their BMI.

Restoration of insulin secretion in pancreatic islets of protein-deficient rats by reduced expression of insulin receptor substrate (IRS)-1 and IRS-2

Autocrine and paracrine insulin signaling may participate in the fine control of insulin secretion. In the present study, tissue distribution and protein amounts of the insulin receptor and its major substrates, insulin receptor substrate (IRS)-1 and IRS-2, were evaluated in a model of impaired glucose-induced insulin secretion, the protein-deficient rat. Immunoblot and RT-PCR studies showed that the insulin receptor and IRS-2 expression are increased, whilst IRS-1 protein and mRNA contents are decreased in pancreatic islets of protein-deficient rats. Immunohistochemical studies revealed that the insulin receptor and IRS-1 and -2 are present in the great majority of islet cells; however, the greatest staining was localized at the periphery, suggesting a co-localization with non-insulin-secreting cells. Exogenous insulin stimulation of isolated islets promoted higher insulin receptor and IRS-1 and -2 tyrosine phosphorylation in islets from protein-deficient rats, as compared with controls. Moreover, insulin-induced IRS-1- and IRS-2-associated phosphatidylinositol 3-kinase activity are increased in islets of protein-deficient rats. The reduction of IRS-1 and IRS-2 protein expression in islets isolated from protein-deficient rats by the use of antisense IRS-1 or IRS-2 phosphorthioate-modified oligonucleotides partially restored glucose-induced insulin secretion. Thus, the impairment of insulin cell signaling through members of the IRS family of proteins in isolated rat pancreatic islets improves glucose-induced insulin secretion. The present data reinforced the role of insulin paracrine and autocrine signaling in the control of its own secretion.

Selective impairment of insulin signalling in the hypothalamus of obese Zucker rats

AIM/HYPOTHESIS

By acting in the brain, insulin suppresses food intake. However, little is known with regard to insulin signalling in the hypothalamus in insulin-resistant states.

METHODS

Western blotting, immunohistochemistry and polymerase chain reaction assays were combined to compare in vivo hypothalamic insulin signalling through the PI3-kinase and MAP kinase pathways between lean and obese Zucker rats.

RESULTS

Intracerebroventricular insulin infusion reduced food intake in lean rats to a greater extent than that observed in obese rats, and pre-treatment with PI3-kinase inhibitors prevented insulin-induced anorexia. The relative abundance of IRS-2 was considerably higher than that of IRS-1 in hypothalamus of both lean and obese rats. Insulin-stimulated phosphorylation of IR, IRS-1/2, the associations of PI 3-kinase to IRS-1/2 and phosphorylation of Akt in hypothalamus were decreased in obese rats compared to lean rats. These effects seem to be mediated by increased phosphoserine content of IR, IRS-1/2 and decreased protein levels of IRS-1/2 in obese rats. In contrast, insulin stimulated the phosphorylation of MAP kinase equally in lean and obese rats.

CONCLUSION/INTERPRETATION

This study provides direct measurements of insulin signalling in hypothalamus, and documents selective resistance to insulin signalling in hypothalamus of Zucker rats. These findings provide support for the hypothesis that insulin could have anti-obesity actions mediated by the PI3-kinase pathway, and that impaired insulin signalling in hypothalamus could play a role in the development of obesity in this animal model of insulin-resistance.

Peroxisome proliferator-activated receptor gamma coactivator-1-dependent uncoupling protein-2 expression in pancreatic islets of rats: a novel pathway for neural control of insulin secretion

AIMS/HYPOTHESIS

Sympathetic inputs inhibit insulin secretion through alpha2-adrenergic receptors coupled with Gi protein. High adrenergic tonus generated by exposure of homeothermic animals to cold reduces insulin secretion. In this study we evaluate the participation of UCP-2 in cold-induced regulation of insulin secretion.

METHODS

Static insulin secretion studies, western blotting and immunohistochemistry were used in this investigation.

RESULTS

Exposure of rats to cold during 8 days promoted 60% ( n=15, p<0.05) reduction of basal serum insulin levels concentration accompanied by reduction of the area under insulin curve during i.p. GTT (50%, n=15, p<0.05). Isolated islets from cold-exposed rats secreted 57% ( n=6, p<0.05) less insulin following a glucose challenge. Previous sympathectomy, partially prevented the effect of cold exposure upon insulin secretion. Islets isolated from cold-exposed rats expressed 51% ( n=6, p<0.5) more UCP-2 than islets from control rats, while the inhibition of UCP-2 expression by antisense oligonucleotide treatment partially restored insulin secretion of islets obtained from cold-exposed rats. Cold exposure also induced an increase of 69% ( n=6, p<0.05) in PGC-1 protein content in pancreatic islets. Inhibition of islet PGC-1 expression by antisense oligonucleotide abrogated cold-induced UCP-2 expression and partially restored insulin secretion in islets exposed to cold.

CONCLUSION/INTERPRETATION

Our data indicate that sympathetic tonus generated by exposure of rats to cold induces the expression of PGC-1, which participates in the control of UCP-2 expression in pancreatic islets. Increased UCP-2 expression under these conditions could reduce the beta-cell ATP/ADP ratio and negatively regulate insulin secretion.

Prolactin-signal transduction in neonatal rat pancreatic islets and interaction with the insulin-signaling pathway

During pregnancy, pancreatic islets undergo structural and functional changes in response to an increased demand for insulin. Different hormones, especially placental lactogens, mediate these adaptive changes. Prolactin (PRL) mainly exerts its biological effects by activation of the JAK2/STAT5 pathway. PRL also stimulates some biological effects via activation of IRS-1, IRS-2, PI 3-kinase, and MAPK in different cell lines. Since IRS-2 is important for the maintenance of pancreatic islet cell mass, we investigated whether PRL affects insulin-signaling pathways in neonatal rat islets. PRL significantly potentiated glucose-induced insulin secretion in islets cultured for 7 days. This effect was blocked by the specific PI 3-kinase inhibitor wortmannin. To determine possible effects of PRL on insulin-signaling pathways, fresh islets were incubated with or without the hormone for 5 or 15 min. Immunoprecipitation and immunoblotting with specific antibodies showed that PRL induced a dose-dependent IRS-1 and IRS-2 phosphorylation compared to control islets. PRL-induced increase in IRS-1/-2 phosphorylation was accompanied by an increase in the association with and activation of PI 3-kinase. PRL-induced IRS-2 phosphorylation and its association with PI 3-kinase did not add to the effect of insulin. PRL also induced JAK2, SHC, ERK1 and ERK2 phosphorylation in neonatal islets, demonstrating that PRL can activate MAPK. These data indicate that PRL can stimulate the IRSs/PI 3-kinase and SHC/ERK pathways in islets from neonatal rats.

Effects of age on elements of insulin-signaling pathway in central nervous system of rats

Insulin resistance is known to play a pivotal role in type 2 diabetes. Senile individuals, besides being prone to insulin resistance and, consequently, to type 2 diabetes, manifest diseases of the central nervous system (CNS) that may be influenced by disturbances of insulin signaling in the brain, such as memory impairment, Parkinson disease, and Alzheimer disease. We investigated the expression and response to insulin of elements involved in the insulin-signaling pathway in the forebrain cortex and cerebellum of rats ages 1 d to 60 wk. The protein content of insulin receptors and SRC homology adaptor protein (SHC) did not change significantly along the time frame analyzed. However, insulin-induced tyrosine phosphorylation of the insulin receptor and SHC, and the association of SHC/growth factor receptor binding protein-2 (GRB2) decreased significantly from d 1 to wk 60 of life in both types of tissues. Moreover, the expression of SH protein tyrosine phosphatase-2 (SHP2), a tyrosine phosphatase involved in insulin signal transduction and regulation of the insulin signal, decreased significantly with age progression, in both the forebrain cortex and the cerebellum of rats. Thus, elements involved in the insulin-signaling pathway are regulated at the expression and/or functional level in the CNS, and this regulation may play a role in insulin resistance in the brain.

Early steps of insulin action in the skin of intact rats

Insulin is an important regulator of growth and initiates its action by binding to its receptor, which undergoes tyrosyl autophosphorylation and further enhances its tyrosine kinase activity towards other intermediate molecules, including insulin receptor substrate 1, insulin receptor substrate 2, and Shc. Insulin receptor substrate proteins can dock various src-homology-2-domain-containing signaling proteins, such as the 85 kDa subunit of phosphatidylinositol 3 kinase and growth-factor-receptor-bound protein 2. The serine-threonine kinase is activated downstream to phosphatidylinositol 3 kinase. Shc protein has been shown to directly induce the association with growth-factor-receptor-bound protein 2 and downstream the activation of the mitogen-activated protein kinase. In this study we investigated insulin signal transduction pathways in skin of intact rats by immunoprecipitation and immunoblotting with specific antibodies, and also by immunohistochemistry with anti-insulin-receptor antibody. Our results showed that skin fragments clearly demonstrated the presence of insulin receptor in cell bodies of the epidermis and hair follicles and some faint staining was also detected in fibroblasts of the dermis. It was also observed that acute stimulation with insulin can induce tyrosyl phosphorylation of insulin receptor, that the insulin receptor substrates and Shc proteins serve as signaling molecules for insulin in skin of rats, and that insulin is able to induce association of insulin receptor substrate 1/phosphatidylinositol 3 kinase and Shc/growth-factor-receptor-bound protein 2 in this tissue, as well as phosphorylation of mitogen-activated protein kinase and serine-threonine kinase, demonstrating that proteins involved in early steps of insulin action are expressed in skin of intact rats and are quickly activated after insulin stimulation.

Isolation and characterization of a convulxin-like protein from Crotalus durissus collilineatus venom

A convulxin (Cvx)-like protein was isolated from Crotalus durissus collilineatus venom by a combination of molecular exclusion and reversed-phase HPLC chromatographies. The molecular mass of the Cvx-like protein in the absence and presence of DTT was 78 kDa and 12-13 kDa, respectively. The Cvx-like protein consisted of two nonidentical polypeptide chains (alpha and beta). The N-terminal amino-acid sequences of the alpha and beta subunits were GLHCPSDWYAYDGHCYKIFNEEMNWED and GFCCPSHWSSYSRYCYKFFSQEMNWEDAEK, respectively, with both subunits having a high content of Glu, Ser, Cys, and Asp. The Cvx-like protein showed high homology with other venom C-type lectins, but had low hemagglutinating activity on intact and trypsinized erythrocytes. The Cvx-like protein stimulated insulin receptor phosphorylation and potentiated insulin secretion from isolated islets in the presence of sub- (2.8 mM) or supra-physiological (16.7 mM) glucose concentrations. These results suggest that the increase in insulin secretion induced by Cvx-like protein may be mediated by a protein tyrosine kinase-dependent pathway and may involve other membrane receptors, such as GP VI or Scr family proteins.