XPR1 Mediates the Pancreatic ß-Cell Phosphate Flush.

Glucose-stimulated insulin secretion is the hallmark of the pancreatic ß-cell, a critical player in the regulation of blood glucose concentration. In 1974, the remarkable observation was made that an efflux of intracellular inorganic phosphate (Pi) accompanied the events of stimulated insulin secretion. The mechanism behind this "phosphate flush," its association with insulin secretion, and its regulation have since then remained a mystery. We recapitulated the phosphate flush in the MIN6m9 ß-cell line and pseudoislets. We demonstrated that knockdown of XPR1, a phosphate transporter present in MIN6m9 cells and pancreatic islets, prevented this flush. Concomitantly, XPR1 silencing led to intracellular Pi accumulation and a potential impact on Ca2+ signaling. XPR1 knockdown slightly blunted first-phase glucose-stimulated insulin secretion in MIN6m9 cells, but had no significant impact on pseudoislet secretion. In keeping with other cell types, basal Pi efflux was stimulated by inositol pyrophosphates, and basal intracellular Pi accumulated following knockdown of inositol hexakisphosphate kinases. However, the glucose-driven phosphate flush occurred despite inositol pyrophosphate depletion. Finally, while it is unlikely that XPR1 directly affects exocytosis, it may protect Ca2+ signaling. Thus, we have revealed XPR1 as the missing mediator of the phosphate flush, shedding light on a 45-year-old mystery.

Insulin Modulates Inflammatory Cytokine Release in Acute Stages and Augments Expression of Adhesion Molecules and Leukocytes in Lungs on Chronic Stages of Paracoccidioidomycosis.

Type 1 diabetesmellitus (T1D) is caused by partial destruction of the insulin-producing beta cells in the pancreas and is a major issue for public health care worldwide. Reduced or impaired immunological responses, which render patients more susceptible to infections, have been observed in T1D, and this dysfunction is often related to a lack of insulin in the blood. Paracoccidioidomycosis is an important systemic mycosis endemic in Latin America. To evaluate the effects of T1D on this fungal infection and the modulatory effects of insulin, we induced diabetes in C57Bl/6 male mice (alloxan, 60 mg/kg), infected the mice (Pb18, 1 x 106 cells), and treated the mice with neutral protamine Hagedorn (NPH) insulin (2 IU/600 mg/dL blood glucose). Twenty-four hours after infection, infected diabetic mice showed reduced secretion of interferon (IFN)-γ and interleukine (IL)-12 p70 compared to infected nondiabetic controls. On the 45th day of infection, infected diabetic mice presented higher IFN-γ levels, a higher tumor necrosis factor (TNF)-α:IL-10 ratio, and lower adhesion molecule expression levels than nondiabetic mice. In the in vitro experiments, alveolar macrophages from diabetic animals showed reduced phagocytic activity compared to those from control animals at 4, 12, and 24 h. In infected diabetic mice, treatment with insulin restored IL-12 p70 levels at 24 h of infection, reduced IFN-γ levels and the TNF-α:IL-10 ratio at 45 days, and restored vascular cell adhesion molecule (VCAM)-1 expression in pulmonary blood vessels, and this treatment reduced the diminished phosphorylation of extracellular signal-regulated kinases (ERK) and increased nuclear factor-kappa-B(iκb)-α and jun amino-terminal kinases (JNK) p46 levels in infected nondiabetic mice. In addition, insulin promoted increased phagocytic activity in the alveolar macrophages of diabetic mice. These data suggest that T1D mice are more susceptible to Pb18 infection and that insulin modulates this inflammation in diabetic mice by augmenting the expression of adhesion molecules and leukocytes in the lungs and by reducing chronic inflammation.

Inositol hexakisphosphate kinase 1 is a metabolic sensor in pancreatic ß-cells.

Diphosphoinositol pentakisphosphate (IP7) is critical for the exocytotic capacity of the pancreatic ß-cell, but its regulation by the primary instigator of ß-cell exocytosis, glucose, is unknown. The high Km for ATP of the IP7-generating enzymes, the inositol hexakisphosphate kinases (IP6K1 and 2) suggests that these enzymes might serve as metabolic sensors in insulin secreting ß-cells and act as translators of disrupted metabolism in diabetes. We investigated this hypothesis and now show that glucose stimulation, which increases the ATP/ADP ratio, leads to an early rise in IP7 concentration in ß-cells. RNAi mediated knock down of the IP6K1 isoform inhibits both glucose-mediated increase in IP7 and first phase insulin secretion, demonstrating that IP6K1 integrates glucose metabolism and insulin exocytosis. In diabetic mouse islets the deranged ATP/ADP levels under both basal and glucose-stimulated conditions are mirrored in both disrupted IP7 generation and insulin release. Thus the unique metabolic sensing properties of IP6K1 guarantees appropriate concentrations of IP7 and thereby both correct basal insulin secretion and intact first phase insulin release. In addition, our data suggest that a specific cell signaling defect, namely, inappropriate IP7 generation may be an essential convergence point integrating multiple metabolic defects into the commonly observed phenotype in diabetes.

Insulina modula o fenótipo de células imunes na inflamação alérgica pulmonar, aumentando a resistência pulmonar de camundongos diabéticos / Insulin modulates immune cell phenotype in pulmonary allergic inflammation, increasing the pulmonary resistance of diabetic and healthy mice

Dados mostram que o aparecimento do diabetes mellitus (DM), em pacientes previamente asmáticos, diminui os sintomas da asma, enquanto a insulina agrava a asma. Devido a dados na literatura e por dados prévios do nosso grupo, o presente estudo teve como objetivo avaliar o efeito modulatório da insulina na inflamação alérgica pulmonar em camundongos diabéticos e saudáveis. Camundongos machos dibéticos BALB/c (aloxana, 50mg/kg, iv, 10 dias) foram sensibilizados com ovalbumina (OVA, 20 µg e Al (OH)3, 2 mg) 10 dias após a injeção de aloxana e uma dose reforço foi dada, após 12 dias da primeira de sensibilização, após 6 dias da dose reforço, os animais foram expostos a nebulização durante 7 dias com solução de OVA (1mg/mL) ou solução salina (SAL). Animais diabéticos foram tratados com doses múltiplas de Protamine Hagedorn Neutro (NPH) 2UI e 1UI, respectivamente, por via subcutânea 12 horas antes do desafio com OVA (às 19h) e 1UI (às 7h) 2h antes de cada desafio com OVA. Os animais não diabéticos receberam 1UI de insulina, pela mesma via 2h antes de cada desafio (às 7h), 24h após o último desafio, realizaram-se as seguintes análises: a) expressão de proteína quinase p38, proteína quinase regulada por sinais extracelulares 1 e 2 (ERK 1/2), proteína quinase ativada por estresse ou c-jun NH2- terminal (JNK) , transdutor de sinal e ativador de transcrição 3 (STAT 3) e transdutor de sinal e ativador de transcrição 6 (pSTAT 6) no homogenato de pulmão; b) perfil de imunoglobulinas presentes no soro; c) concentrações de interleucina (IL) IL-4, IL-5, IL-10, IL-13, fator de necrose tumoral alfa (TNF-α), fator de crescimento endotelial vascular (VEGF), fator de crescimento transformador beta (TGF-ß) e interferon-gamma IFN-γ em homogenato de pulmão; d) migração celular em fluído do lavado broncoalveolar (LBA); e) perfil de células imunes na medula óssea, pulmão, timo e baço; f) mecânica pulmonar por BUXCO e FlexiVent. Em comparação com camundongos não diabéticos desafiados com OVA, os animais diabéticos desafiados com OVA mostraram diminuição em: ERK 1, ERK 2, JNK (fosfo54), JNK / SAPK, STAT3, pSTAT6 estava ausente; concentração da imunoglobulinas IgE, IgG1; perfil de citocinas Th2 como IL-4, IL-5, IL-13, TNF-α, VEGF, TGF-ß; infiltrado inflamatório e) ausência de eosinofilia no LBA; células T, células B e eosinófilos na medula óssea, pulmão, timo e baço, e hiper-reatividade das vias aéreas. O tratamento com insulina restaubeleceu todos os parâmetros estudados. Portanto, sugerem que a insulina modula a inflamação alérgica pulmonar tardia em camundongos diabéticos

Data show that the onset of diabetes mellitus (DM) in previously asthmatic patients decreases asthma symptoms while insulin worsens asthma. Due to data in the literature and previous data from our group, the present study aimed to evaluate the modulatory effect of insulin on pulmonary allergic inflammation in diabetic and healthy mice. Ovalbumin (OVA, 20 µg and Al (OH)3, 2 mg) were sensitized at 10 days after alloxan injection and a booster dose was given , after 12 days of the first sensitization, after 6 days of booster dose, the animals were exposed to nebulization for 7 days with OVA solution (1mg / mL) or saline solution (SAL). Diabetic animals were treated with multiple doses of Protamine Hagedorn Neutral (NPH) 2UI and 1UI, respectively, subcutaneously 12 hours prior to challenge with OVA (at 7pm) and 1UI (at 7h) 2h before each challenge with OVA. Non-diabetic animals received 1UI of insulin, via the same route 2h before each challenge (at 7h), 24h after the last challenge, the following analyzes were performed: a) expression of protein kinase p38, protein kinase regulated by extracellular signals 1 and 2 (ERK 1/2), stress-activated or c-jun NH2-terminal protein kinase (JNK), signal transducer and transcriptional activator 3 (STAT 3) and signal transducer and transcriptional activator 6 (pSTAT 6) in the lung homogenate; b) profile of immunoglobulins present in serum; c) concentrations of interleukin (IL) IL-4, IL-5, IL-10, IL-13, tumor necrosis factor alpha (TNF-α), vascular endothelial growth factor (VEGF), transforming TGF-ß) and interferon-gamma IFN-γ in lung homogenate; d) cell migration in bronchoalveolar lavage fluid (BAL); e) profile of immune cells in the bone marrow, lung, thymus and spleen; f) Pulmonary mechanics by BUXCO and FlexiVent. In contrast to non-diabetic mice challenged with OVA, diabetic animals challenged with OVA showed decrease in: ERK 1, ERK 2, JNK (phospho54), JNK / SAPK, STAT3, pSTAT6 was absent; IgE immunoglobulin levels, IgG1; profile of Th2 cytokines such as IL-4, IL-5, IL-13, TNF-α, VEGF, TGF-ß; inflammatory infiltrate e) absence of eosinophilia in BAL; T cells, B cells and eosinophils in the bone marrow, lung, thymus and spleen, and airway hyperreactivity. The insulin treatment restored all parameters studied. Therefore, they suggest that insulin modulates late pulmonary allergic inflammation in diabetic mice