Solid-State Characterization of Different Crystalline Forms of Sitagliptin.

Sitagliptin is an inhibitor of the enzyme dipeptidyl peptidase-4, used for the treatment of type 2 diabetes mellitus. The crystal structure of active pharmaceutical solids determines their physical and chemical properties. The polymorphism, solvates and hydrates can influence the free energy, thermodynamic parameters, solubility, solid-state stability, processability and dissolution rate, besides directly affecting the bioavailability. Thus, the physicochemical characterization of an active pharmaceutical ingredient is required to guarantee the rational development of new dosage forms. In this context, we describe herein the solid-state characterization of three crystalline forms of sitagliptin: sitagliptin phosphate monohydrate, sitagliptin phosphate anhydrous and sitagliptin base form. The investigation was carried out using differential scanning calorimetry (DSC), thermogravimetry (TG)/derivative thermogravimetry (DTG), spectroscopic techniques, X-ray powder diffraction (XRPD) and morphological analysis by scanning electron microscopy. The thermal analysis revealed that during the dehydration of sitagliptin phosphate monohydrate (Tpeak = 134.43 °C, ΔH = -1.15 J g-1) there is a characteristic crystalline transition event, which alters the physicochemical parameters of the drug, such as the melting point and solubility. The crystalline behavior of sitagliptin base form differs from that of sitagliptin phosphate monohydrate and sitagliptin phosphate anhydrous, mainly with regard to the lower temperature of the fusion event. The melting point (Tpeak) values obtained were 120.29 °C for sitagliptin base form, 206.37 °C for sitagliptin phosphate monohydrate and 214.92 °C for sitagliptin phosphate anhydrous. In relation to the thermal stability, sitagliptin phosphate monohydrate and sitagliptin phosphate anhydrous showed a slight difference; however, both are more thermostable than the base molecule. Therefore, through this study it was possible to establish the most suitable crystalline form of sitagliptin for the development of a safe, effective and appropriate pharmaceutical dosage form.

Debriefing as an opportunity to develop emotional competence in health profession students: faculty, be prepared! / Debriefing como uma oportunidade de desenvolver competência emocional em estudantes da área da saúde: docentes, preparem-se!

AIMS: In this article, we want to share our perspective on how simulation sessions could contribute to change reality, building a safe environment in which facilitators can role-modeling students to develop emotional competence. Noteworthy, acknowledging and legitimating emotions are also essential components of creating a safe environment for students. We also intend to stress how faculty development programs are essential to guarantee that facilitators will be prepared to accomplish this new learning goal, and how different cultural contexts can influence the process. METHODS: In this narrative review, we will focus on the importance of emotions. Emotions in the context of learning but also learners' emotions from the viewpoint of teachers, and teachers' emotions in the context of faculty development. RESULTS: Simulation in medical education is becoming increasingly important. Advances in technology give many opportunities to simulate almost anything you want, with high fidelity and enhanced reality. It creates the possibility of bringing the complexity of real clinical tasks to a controlled simulated environment. While performing these complex simulated tasks, students experience several and sometimes distinct emotions: the emotions of patients and their families, the emotions of the multi-professional team members, and their own emotions, as learners and as future health professionals. Unfortunately, the formal curricula of the majority of medical schools do not address the importance of emotional competence specifically, and students end with the general impression that emotions are mainly negative, and must be avoided and kept at a safe distance. However, there are plenty of data showing how emotions can influence learning and decision-making, and how important it is to create awareness of and modulate them to guarantee the safeguard of patients' interests. CONCLUSIONS: Emotions directly affect several dimensions of clinical work, such as communication, decision-making, teamwork, and leadership. We hope that including dealing with emotions as a natural goal of the learning activities in the health professions can catalyze the reconciliation between the technical and emotional aspects of clinical practice.

OBJETIVOS: Neste artigo, pretendemos compartilhar nossa perspectiva em relação a como a simulação pode ajudar a transformar a realidade, construindo um ambiente seguro em que os facilitadores das sessões de simulação sejam os modelos em que os estudantes podem se espelhar para desenvolver competência emocional. Vale ressaltar que reconhecer e dar legitimidade às emoções é passo essencial para a criação de um ambiente seguro para os estudantes. Também pretendemos reforçar como os programas de capacitação docente são fundamentais para garantir que os facilitadores estarão preparados para atingir esse novo objetivo de aprendizagem, e como contextos culturais diferentes podem influenciar esse processo. MÉTODOS: Nesta revisão narrativa, nos concentraremos na importância das emoções. Emoções no contexto da aprendizagem, mas também emoções dos aprendizes do ponto de vista dos professores, e emoções dos professores no contexto do desenvolvimento do corpo docente. RESULTADOS: A simulação está se tornando cada vez mais importante na educação médica. Os avanços tecnológicos permitem simular praticamente qualquer situação, com alta fidelidade e realidade. Isso cria a possibilidade de trazer a complexidade de situações clínicas reais para um ambiente simulado e controlado. Ao executar essas simulações de alta complexidade, os estudantes experimentam várias e diferentes emoções: as emoções dos pacientes e de suas famílias, as emoções dos membros da equipe, e as suas próprias emoções, como estudantes e como futuros profissionais da saúde. Infelizmente, a grade curricular formal da maioria das escolas médicas não aborda especificamente a importância de desenvolver competência emocional, e os estudantes acabam com a impressão geral de que as emoções são basicamente negativas, e que devem ser evitadas e mantidas a uma distância de segurança. No entanto, vários estudos mostram como as emoções influenciam o aprendizado e a tomada de decisões, e como é importante estar consciente delas e modulá-las de uma forma que garanta a salvaguarda dos interesses dos pacientes. CONCLUSÕES: As emoções afetam diretamente várias dimensões do trabalho clínico, como comunicação, tomada de decisão, trabalho em equipe e liderança. Esperamos que tratar das emoções como meta natural das atividades de aprendizagem nas profissões da saúde oportunize catalisar a reconciliação entre os aspectos técnicos e emocionais da prática clínica.

Suspected infection in afebrile patients: Are they septic?

We prospectively evaluated afebrile patients admitted to an emergency department (ED), with suspected infection and only tachycardia or tachypnea.The white blood cell count (WBC) was obtained, and patients were considered septic if leukocyte count was >12,000 µL-1 or <4000 µL-1 or with >10% of band forms. Clinical data were collected to examine whether sepsis could be predicted.Seventy patients were included and 37 (52.86%) met sepsis criteria. Self-measured fever showed an odds ratio (OR) of 5.936 (CI95% 1.450-24.295; P = 0.0133) and increased pulse pressure (PP) showed an OR of 1.405 (CI95% 1.004-1.964; P = 0.0471) on multivariate analysis. When vital signs were included in multivariate analysis, the heart rate showed an OR of 2.112 (CI95% 1.400-3.188; P = 0.0004). Self-measured fever and mean arterial pressure <70 mm Hg had high positive likelihood ratios (3.86 and 2.08, respectively). The nomogram for self-measured fever showed an increase of sepsis chance from 53% (pretest) to approximately 80% (post-test).The recognition of self-measured fever, increased PP, and the intensity of heart rate response may improve sepsis recognition in afebrile patients with tachycardia or tachypnea. These results are important for medical assessment of sepsis in remote areas, crowded and low-resourced EDs, and low-income countries, where WBC may not be readily available.

Translational research into gut microbiota: new horizons on obesity treatment: updated 2014.

Obesity is currently a pandemic of worldwide proportions affecting millions of people. Recent studies have proposed the hypothesis that mechanisms not directly related to the human genome could be involved in the genesis of obesity, due to the fact that, when a population undergoes the same nutritional stress, not all individuals present weight gain related to the diet or become hyperglycemic. The human intestine is colonized by millions of bacteria which form the intestinal flora, known as gut flora. Studies show that lean and overweight human may present a difference in the composition of their intestinal flora; these studies suggest that the intestinal flora could be involved in the development of obesity. Several mechanisms explain the correlation between intestinal flora and obesity. The intestinal flora would increase the energetic extraction of non-digestible polysaccharides. In addition, the lipopolysaccharide from intestinal flora bacteria could trigger a chronic sub-clinical inflammatory process, leading to obesity and diabetes. Another mechanism through which the intestinal flora could lead to obesity would be through the regulation of genes of the host involved in energy storage and expenditure. In the past five years data coming from different sources established causal effects between intestinal microbiota and obesity/insulin resistance, and it is clear that this area will open new avenues of therapeutic to obesity, insulin resistance and DM2.

Translational research into gut microbiota: new horizons on obesity treatment: updated 2014

Obesity is currently a pandemic of worldwide proportions affecting millions of people. Recent studies have proposed the hypothesis that mechanisms not directly related to the human genome could be involved in the genesis of obesity, due to the fact that, when a population undergoes the same nutritional stress, not all individuals present weight gain related to the diet or become hyperglycemic. The human intestine is colonized by millions of bacteria which form the intestinal flora, known as gut flora. Studies show that lean and overweight human may present a difference in the composition of their intestinal flora; these studies suggest that the intestinal flora could be involved in the development of obesity. Several mechanisms explain the correlation between intestinal flora and obesity. The intestinal flora would increase the energetic extraction of non-digestible polysaccharides. In addition, the lipopolysaccharide from intestinal flora bacteria could trigger a chronic sub-clinical inflammatory process, leading to obesity and diabetes. Another mechanism through which the intestinal flora could lead to obesity would be through the regulation of genes of the host involved in energy storage and expenditure. In the past five years data coming from different sources established causal effects between intestinal microbiota and obesity/insulin resistance, and it is clear that this area will open new avenues of therapeutic to obesity, insulin resistance and DM2.

A simplified ultrasound-based edema score to assess lung injury and clinical severity in septic patients.

BACKGROUND: Lung ultrasound (US) is an excellent tool to assess lung edema in a myriad of different clinical situations. We hypothesized that lung US might also be a good prognostic and management instrument in septic patients, regardless of disease severity. METHODS: This was a prospective observational cohort study at an urban academic emergency department (ED). Inclusion criteria were as follows: septic patients, at least 18 years old, admitted at the ED of a tertiary hospital. A simplified lung edema scoring system (SLESS) was developed, and 6 thoracic regions were evaluated. Four different lung US patterns were considered, from normal aeration to total consolidation. To evaluate disease severity, the SLESS was compared with the Mortality in Emergency Department Sepsis Score and the third version of the Simplified Acute Physiology Score scoring systems. Aiming to assess the effect of the lung edema in the gas exchange, the SLESS was compared with the Pao2/fraction of inspired oxygen ratio. RESULTS: Sixty-one patients were enrolled in a 3-month period. The SLESS had a good correlation with the Mortality in Emergency Department Sepsis Score and Simplified Acute Physiology Score (r = 0.53 and r = 0.55, respectively; P < .001 for both) and a negative correlation with the Pao2/fraction of inspired oxygen ratio (r = -0.62; P < .001). The SLESS also showed correlation with the respiratory rate (r = 0.45; P = .0003). The odds ratio for death related to the SLESS was 1.370 (95% confidence interval, 1.109-1.691; P = .0035). CONCLUSION: The SLESS is an easy and practical scoring system. It might be a useful tool to predict severity of disease in sepsis patients. The SLESS might also be able to be correlated with the oxygen exchange.

Modulation of double-stranded RNA-activated protein kinase in insulin sensitive tissues of obese humans.

OBJECTIVE: The double-stranded RNA-dependent protein kinase (PKR) was recently implicated in regulating molecular integration of nutrient- and pathogen-sensing pathways in obese mice. However, its modulation in human tissues in situations of insulin resistance has not been investigated. The present study was performed to first determine the tissue expression and phosphorylation levels of PKR in the liver, muscle, and adipose tissue in obese humans, and also the modulation of this protein in the adipose tissue of obese patients after bariatric surgery. DESIGN AND METHODS: Eleven obese subjects who were scheduled to undergo Roux-en-Y Gastric Bypass Procedure participated in this study. Nine apparently healthy lean subjects as a control group were also included. RESULTS: Our data show that PKR is activated in liver, muscle, and adipose tissue of obese humans and, after bariatric surgery, there is a clear reduction in PKR activation accompanied by a decrease in protein kinase-like endoplasmic reticulum kinase, c-Jun N-terminal kinase, inhibitor of kappa ß kinase, and insulin receptor substrate-1 serine 312 phosphorylation in subcutaneous adipose tissue from these patients. CONCLUSION: Thus, it is proposed that PKR is an important mediator of obesity-induced insulin resistance and a potential target for the therapy.

Targeted disruption of inducible nitric oxide synthase protects against aging, S-nitrosation, and insulin resistance in muscle of male mice.

Accumulating evidence has demonstrated that S-nitrosation of proteins plays a critical role in several human diseases. Here, we explored the role of inducible nitric oxide synthase (iNOS) in the S-nitrosation of proteins involved in the early steps of the insulin-signaling pathway and insulin resistance in the skeletal muscle of aged mice. Aging increased iNOS expression and S-nitrosation of major proteins involved in insulin signaling, thereby reducing insulin sensitivity in skeletal muscle. Conversely, aged iNOS-null mice were protected from S-nitrosation-induced insulin resistance. Moreover, pharmacological treatment with an iNOS inhibitor and acute exercise reduced iNOS-induced S-nitrosation and increased insulin sensitivity in the muscle of aged animals. These findings indicate that the insulin resistance observed in aged mice is mainly mediated through the S-nitrosation of the insulin-signaling pathway.

Translational research into gut microbiota: new horizons in obesity treatment.

Obesity is a pandemic which has been rapidly developing for three decades. When a population is submitted to the same nutritional stress, some individuals are less susceptible to diet-induced weight gain and hyperglycemia. This observation suggests that other mechanisms are involved which are not directly related to the human genome. The human gut contains an immense number of microorganisms, collectively known as the microbiota. Evidence that gut microbiota composition can differ between obese and lean humans has led to the speculation that gut microbiota can participate in the pathophysiology of obesity. Different mechanisms have been proposed to explain the link between gut flora and obesity. The first mechanism consists in the role of the gut microbiota to increase energy extraction from indigestible dietary polysaccharides. The second, consists in the role of gut flora to modulate plasma lipopolysaccharide levels which triggers chronic low-grade inflammation leading to obesity and diabetes. A third mechanism proposes that gut microbiota may induce regulation of host genes that modulate how energy is expended and stored. However, further studies are needed to clarify a number of issues related to the relationship between the gut microbiota and obesity.

Translational research into gut microbiota: new horizons in obesity treatment / Pesquisa translacional em microbiota intestinal: novos horizontes no tratamento da obesidade

Obesity is a pandemic which has been rapidly developing for three decades. When a population is submitted to the same nutritional stress, some individuals are less susceptible to diet-induced weight gain and hyperglycemia. This observation suggests that other mechanisms are involved which are not directly related to the human genome. The human gut contains an immense number of microorganisms, collectively known as the microbiota. Evidence that gut microbiota composition can differ between obese and lean humans has led to the speculation that gut microbiota can participate in the pathophysiology of obesity. Different mechanisms have been proposed to explain the link between gut flora and obesity. The first mechanism consists in the role of the gut microbiota to increase energy extraction from indigestible dietary polysaccharides. The second, consists in the role of gut flora to modulate plasma lipopolysaccharide levels which triggers chronic low-grade inflammation leading to obesity and diabetes. A third mechanism proposes that gut microbiota may induce regulation of host genes that modulate how energy is expended and stored. However, further studies are needed to clarify a number of issues related to the relationship between the gut microbiota and obesity.

A obesidade é uma pandemia que afeta milhões de pessoas em todo o mundo. Quando uma população é submetida ao mesmo estresse nutricional, alguns indivíduos são menos suscetíveis ao ganho de peso induzido pela dieta e à hiperglicemia. Essa observação sugere que outros mecanismos não diretamente relacionados ao genoma humano estejam envolvidos. O intestino humano é colonizado por milhões de bactérias, que coletivamente constituem a flora comensal normal. A evidência de que a composição da flora intestinal pode ser diferente em humanos magros e obesos levou à especulação de que a flora intestinal pode participar na fisiopatologia da obesidade. Diferentes mecanismos foram propostos para tentar explicar a correlação entre flora intestinal e obesidade. O primeiro mecanismo consiste no papel da flora intestinal na extração de energia de polissacarídeos não digeríveis. O segundo mecanismo envolve a modulação dos níveis de lipopolissacarídeo pela flora intestinal, o que desencadeia uma inflamação crônica subclínica que acarreta obesidade e diabetes. Um terceiro mecanismo propõe que a flora intestinal pode induzir a regulação de genes do hospedeiro que modulam como a energia é gasta e armazenada. Entretanto, estudos adicionais são necessários para estabelecer o papel da flora intestinal no desenvolvimento da obesidade.

Physico-chemical solid-state characterization of omeprazole sodium: thermal, spectroscopic and crystallinity studies.

The physical characterization of active pharmaceutical substances is crucial to the successful development of the final drug product. The different solid forms and variations in the degree of crystallinity can lead to significantly different physical and chemical properties, including color, morphology, stability, dissolution and bioavailability. In the case of omeprazole sodium (OMS), its chemical structures contain a specific number of water molecules (hydrate). The behavior of pharmaceutical hydrates has become the object of increasing attention over the past decade, primarily due to the potential impact of hydrates on the development process and dosage form performance. The present study was designed to characterize and evaluate the crystallinity of omeprazole sodium, dehydrated omeprazole sodium (DOMS) and omeprazole free base (OM) using a variety of techniques including thermal analysis (thermogravimetry/derivative thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC)), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). Furthermore, an NMR spectroscopy study was also carried out to clarify the conformation and crystal structure.

Acute physical exercise reverses S-nitrosation of the insulin receptor, insulin receptor substrate 1 and protein kinase B/Akt in diet-induced obese Wistar rats.

Early evidence demonstrates that exogenous nitric oxide (NO) and the NO produced by inducible nitric oxide synthase (iNOS) can induce insulin resistance. Here, we investigated whether this insulin resistance, mediated by S-nitrosation of proteins involved in early steps of the insulin signal transduction pathway, could be reversed by acute physical exercise. Rats on a high-fat diet were subjected to swimming for two 3 h-long bouts, separated by a 45 min rest period. Two or 16 h after the exercise protocol the rats were killed and proteins from the insulin signalling pathway were analysed by immunoprecipitation and immunoblotting. We demonstrated that a high-fat diet led to an increase in the iNOS protein level and S-nitrosation of insulin receptor beta (IR beta), insulin receptor substrate 1 (IRS1) and Akt. Interestingly, an acute bout of exercise reduced iNOS expression and S-nitrosation of proteins involved in the early steps of insulin action, and improved insulin sensitivity in diet-induced obesity rats. Furthermore, administration of GSNO (NO donor) prevents this improvement in insulin action and the use of an inhibitor of iNOS (L-N6-(1-iminoethyl)lysine; L-NIL) simulates the effects of exercise on insulin action, insulin signalling and S-nitrosation of IR beta, IRS1 and Akt. In summary, a single bout of exercise reverses insulin sensitivity in diet-induced obese rats by improving the insulin signalling pathway, in parallel with a decrease in iNOS expression and in the S-nitrosation of IR/IRS1/Akt. The decrease in iNOS protein expression in the muscle of diet-induced obese rats after an acute bout of exercise was accompanied by an increase in AMP-activated protein kinase (AMPK) activity. These results provide new insights into the mechanism by which exercise restores insulin sensitivity.

Loss-of-function mutation in Toll-like receptor 4 prevents diet-induced obesity and insulin resistance.

Obesity is associated with insulin resistance and a state of abnormal inflammatory response. The Toll-like receptor (TLR)4 has an important role in inflammation and immunity, and its expression has been reported in most tissues of the body, including the insulin-sensitive ones. Because it is activated by lipopolysaccharide and saturated fatty acids, which are inducers of insulin resistance, TLR4 may be a candidate for participation in the cross-talk between inflammatory and metabolic signals. Here, we show that C3H/HeJ mice, which have a loss-of-function mutation in TLR4, are protected against the development of diet-induced obesity. In addition, these mice demonstrate decreased adiposity, increased oxygen consumption, a decreased respiratory exchange ratio, improved insulin sensitivity, and enhanced insulin-signaling capacity in adipose tissue, muscle, and liver compared with control mice during high-fat feeding. Moreover, in these tissues, control mice fed a high-fat diet show an increase in IkappaB kinase complex and c-Jun NH(2)-terminal kinase activity, which is prevented in C3H/HeJ mice. In isolated muscles from C3H/HeJ mice, protection from saturated fatty acid-induced insulin resistance is observed. Thus, TLR4 appears to be an important mediator of obesity and insulin resistance and a potential target for the therapy of these highly prevalent medical conditions.

[Insulin and angiotensin II signaling pathways cross-talk: implications with the association between diabetes mellitus, arterial hypertension and cardiovascular disease]. / Cross-talk das vias de sinalização de insulina e angiotensina II: implicações com a associação entre diabetes mellitus e hipertensão arterial e doença cardiovascular.

Insulin (Ins) and angiotensin II (AII) play pivotal roles in the control of two vital and closely related systems: the metabolic and the circulatory, respectively. A failure in the proper action of each of these hormones results, to a variable degree, in the development of two highly prevalent and commonly overlapping diseases--diabetes mellitus (DM) and hypertension (AH). In recent years, a series of studies has revealed a tight connection between the signal transduction pathways that mediate Ins and AII actions in target tissues. This molecular cross-talk occurs at multiple levels and plays an important role in phenomena that range from the action of anti-hypertensive drugs to cardiac hypertrophy and energy acquisition by the heart. At the extracellular level, the angiotensin-converting enzyme controls AII synthesis but also interferes with Ins signaling through the proper regulation of AII and the accumulation of bradykinin. At an early intracellular level, AII, acting through JAK-2/IRS-1/PI3-kinase, JNK and ERK, may induce the serine phosphorylation and inhibition of key elements of the Ins-signaling pathway. Finally, by inducing the expression of the regulatory protein SOCS-3, AII may impose a late control on the Ins signal. This review will focus on the main advances obtained in this field and will discuss the implications of this molecular cross-talk in the common clinical association between DM and AH.

Cross-talk das vias de sinalização de insulina e angiotensina II: implicações com a associação entre diabetes mellitus e hipertensão arterial e doença cardiovascular / Insulin and angiotensin II signaling pathways cross-talk: implications with the association between diabetes mellitus, arterial hypertension and cardiovascular disease

Insulina (Ins) e Angiotensina II (AII) são fundamentais no controle de dois sistemas vitais e inter-relacionados: o metabólico e o cardiocirculatório, respectivamente. A disfunção de qualquer um desses hormônios pode levar ao desenvolvimento de duas doenças de alta prevalência, muitas vezes concomitantes e, talvez, com fisiopatologia integrada - diabetes mellitus (DM) e hipertensão arterial (HA). Vários estudos mostram que os sistemas de sinalização intracelular de Ins e AII estão conectados e influenciam um ao outro. Esta comunicação molecular ocorre em diferentes etapas da sinalização celular e é importante para vários fenômenos fisiológicos, desde o desenvolvimento de hipertrofia cardíaca e aquisição de energia pelo coração, até a ação de drogas anti-hipertensivas. No nível extracelular, a enzima de conversão de angiotensina regula a síntese de AII e o acúmulo de bradicinina, e ambos desempenham papel regulador sobre a sinalização de Ins. No nível intracelular, a interação dos sinais de Ins e AII ocorre em dois momentos distintos. Inicialmente, em etapas mais precoces da sinalização celular, a AII, atuando através da cascata JAK-2/IRS-1/PI3-quinase, JNK e ERK, provoca a fosforilação em serina e a conseqüente inibição de elementos-chave da via de sinalização da Ins. Finalmente, a AII induz a expressão da proteína regulatória SOCS-3, que impõe um controle mais tardio sobre o sinal de Ins. Esta revisão discute os avanços mais recentes neste campo e a importância dessa interação molecular na fisiopatologia e na associação clínica de DM e HA.

Insulin (Ins) and angiotensin II (AII) play pivotal roles in the control of two vital and closely related systems: the metabolic and the circulatory, respectively. A failure in the proper action of each of these hormones results, to a variable degree, in the development of two highly prevalent and commonly overlapping diseases - diabetes mellitus (DM) and hypertension (AH). In recent years, a series of studies has revealed a tight connection between the signal transduction pathways that mediate Ins and AII actions in target tissues. This molecular cross-talk occurs at multiple levels and plays an important role in phenomena that range from the action of anti-hypertensive drugs to cardiac hypertrophy and energy acquisition by the heart. At the extracellular level, the angiotensin-converting enzyme controls AII synthesis but also interferes with Ins signaling through the proper regulation of AII and the accumulation of bradykinin. At an early intracellular level, AII, acting through JAK-2/IRS-1/PI3-kinase, JNK and ERK, may induce the serine phosphorylation and inhibition of key elements of the Ins-signaling pathway. Finally, by inducing the expression of the regulatory protein SOCS-3, AII may impose a late control on the Ins signal. This review will focus on the main advances obtained in this field and will discuss the implications of this molecular cross-talk in the common clinical association between DM and AH.

Targeted disruption of iNOS prevents LPS-induced S-nitrosation of IRbeta/IRS-1 and Akt and insulin resistance in muscle of mice.

We have previously demonstrated that the insulin resistance associated with inducible nitric oxide synthase (iNOS) induction in two different models of obesity, diet-induced obesity and the ob/ob mice, is mediated by S-nitrosation of proteins involved in insulin signal transduction: insulin receptor beta-subunit (IRbeta), insulin receptor substrate 1(IRS-1), and Akt. S-nitrosation of IRbeta and Akt impairs their kinase activities, and S-nitrosation of IRS-1 reduces its tissue expression. In this study, we observed that LPS-induced insulin resistance in the muscle of wild-type mice, as demonstrated by reduced insulin-induced tyrosine phosphorylation of IRbeta and IRS-1, reduced IRS-1 expression and reduced insulin-induced serine phosphorylation of Akt. This resistance occurred in parallel with enhanced iNOS expression, which was accompanied by S-nitrosation of IRbeta/IRS-1 and Akt. In the muscle of iNOS(-/-) mice, we did not observe enhanced iNOS expression or any S-nitrosation of IRbeta/IRS-1 and Akt after LPS treatment. Moreover, insulin resistance was not present. The preservation of insulin-induced tyrosine phosphorylation of IRbeta and IRS-1, of IRS-1 protein expression, and of insulin-induced serine phosphorylation of Akt observed in LPS-treated iNOS(-/-) mice strongly suggests that the insulin resistance induced by LPS is iNOS mediated, probably through S-nitrosation of proteins of early steps of insulin signaling.

S-nitrosation of the insulin receptor, insulin receptor substrate 1, and protein kinase B/Akt: a novel mechanism of insulin resistance.

Evidence demonstrates that exogenous nitric oxide (NO) and the NO produced by inducible nitric oxide synthase (iNOS) can induce insulin resistance in muscle. Here, we investigated whether this insulin resistance could be mediated by S-nitrosation of proteins involved in early steps of the insulin signal transduction pathway. Exogenous NO donated by S-nitrosoglutathione (GSNO) induced in vitro and in vivo S-nitrosation of the insulin receptor beta subunit (IRbeta) and protein kinase B/Akt (Akt) and reduced their kinase activity in muscle. Insulin receptor substrate (IRS)-1 was also rapidly S-nitrosated, and its expression was reduced after chronic GSNO treatment. In two distinct models of insulin resistance associated with enhanced iNOS expression-diet-induced obesity and the ob/ob diabetic mice-we observed enhanced S-nitrosation of IRbeta/IRS-1 and Akt in muscle. Reversal of S-nitrosation of these proteins by reducing iNOS expression yielded an improvement in insulin action in both animal models. Thus, S-nitrosation of proteins involved in insulin signal transduction is a novel molecular mechanism of iNOS-induced insulin resistance.

Molecular and functional resistance to insulin in hypothalamus of rats exposed to cold.

Insulin and leptin act in the hypothalamus, providing robust anorexigenic signals. The exposure of homeothermic animals to a cold environment leads to increased feeding, accompanied by sustained low levels of insulin and leptin. In the present study, the initial and intermediate steps of the insulin-signaling cascade were evaluated in the hypothalamus of cold-exposed Wistar rats. By immunohistochemistry, most insulin receptor (IR) and insulin receptor substrate-2 (IRS-2) immunoreactivity localized to the arcuate nucleus. Basal levels of tyrosine phosphorylation of IR and IRS-2 were increased in cold-exposed rats compared with rats maintained at room temperature. However, after an acute, peripheral infusion of exogenous insulin, significantly lower increases of IR and IRS-2 tyrosine phosphorylation were detected in the hypothalamus of cold-exposed rats. Insulin-induced association of p85/phosphatidylinositol 3-kinase with IRS-2, Ser473 phosphorylation of Akt, and tyrosine phosphorylation of ERK was significantly reduced in the hypothalamus of cold-exposed rats. To test the hypothesis of functional impairment of insulin signaling in the hypothalamus, intracerebroventricularly cannulated rats were acutely treated with insulin, and food ingestion was measured over a period of 12 h. Cold-exposed animals presented a significantly lower insulin-induced reduction in food consumption compared with animals maintained at room temperature. Hence, the present studies reveal that animals exposed to cold are resistant, both at the molecular and the functional level, to the actions of insulin in the hypothalamus.