Roles of plasma leptin and resistin in novel subgroups of type 2 diabetes driven by cluster analysis.

BACKGROUND: A novel classification has been introduced to promote precision medicine in diabetes. The current study aimed to investigate the relationship between leptin and resistin levels with novel refined subgroups in patients with type 2 diabetes mellitus (T2DM). METHODS: The k-means analysis was conducted to cluster 541 T2DM patients into the following four subgroups: mild obesity-related diabetes (MOD), severe insulin-deficient diabetes (SIDD), severe insulin-resistant diabetes (SIRD) and mild age-related diabetes (MARD). Individuals meeting the exclusion criteria were eliminated, the data for 285 patients were analyzed. Characteristics were determined using various clinical parameters. Both the leptin and resistin levels were determined using enzyme-linked immunosorbent assay. RESULTS: The highest levels of plasma leptin were in the MOD group with relatively lower levels in the SIDD and SIRD groups (P < 0.001). The SIRD group had a higher resistin concentration than the MARD group (P = 0.024) while no statistical significance in resistin levels was found between the SIDD and MOD groups. Logistic regression demonstrated that plasma resistin was associated with a higher risk of diabetic nephropathy (odds ratios (OR) = 2.255, P = 0.001). According to receiver operating characteristic (ROC) curves, the area under the curve (AUC) of resistin (0.748, 95% CI 0.610-0.887) was significantly greater than that of HOMA2-IR (0.447, 95% CI 0.280-0.614) (P < 0.05) for diabetic nephropathy in the SIRD group. CONCLUSIONS: Leptin levels were different in four subgroups of T2DM and were highest in the MOD group. Resistin was elevated in the SIRD group and was closely related to diabetic nephropathy.

Pancreas deficiency modifies bone development in the ovine fetus near term.

Hormones have an important role in the regulation of fetal growth and development, especially in response to nutrient availability in utero. Using micro-CT and an electromagnetic three-point bend test, this study examined the effect of pancreas removal at 0.8 fraction of gestation on the developing bone structure and mechanical strength in fetal sheep. When fetuses were studied at 10 and 25 days after surgery, pancreatectomy caused hypoinsulinaemia, hyperglycaemia and growth retardation which was associated with low plasma concentrations of leptin and a marker of osteoclast activity and collagen degradation. In pancreatectomized fetuses compared to control fetuses, limb lengths were shorter, and trabecular (Tb) bone in the metatarsi showed greater bone volume fraction, Tb thickness, degree of anisotropy and porosity, and lower fractional bone surface area and Tb spacing. Mechanical strength testing showed that pancreas deficiency was associated with increased stiffness and a greater maximal weight load at fracture in a subset of fetuses studied near term. Overall, pancreas deficiency in utero slowed the growth of the fetal skeleton and adapted the developing bone to generate a more compact and connected structure. Maintenance of bone strength in growth-retarded limbs is especially important in a precocial species in preparation for skeletal loading and locomotion at birth.

The interaction of ASIC1a and ERS mediates nerve cell apoptosis induced by insulin deficiency.

Diabetes-related brain complications are the most serious complications of terminal diabetes. The increasing evidence have showed that the predisposing factor is not only hyperglycemia, but also insulin deficiency. In this study, we demonstrated that insulin deficiency was involved in the apoptosis of nerve cells, and it was related to the interaction between acid-sensitive ion channel 1a (ASIC1a) and endoplasmic reticulum stress (ERS). By silencing C/EBP homologous protein (CHOP) and ASIC1a, the pro-apoptotic effect of insulin deficiency on NS20y cells was relieved. Further research found that the binding of CHOP and C/EBPα was increased in the nucleus of cells cultured without insulin, and C/EBPα was competitively inhibited as a negative regulator of ASIC1a, which further increased the ERS and lead to neuronal apoptosis. In summary, ERS and ASIC1a play an important role in neurological damage caused by insulin deficiency. Our finding may lead to new ideas and treatment of diabetes-related brain complications.

Caracterización clínico epidemiológica de la diabetes mellitus tipo 1 en pediatría, Hospital Mario Catarino Rivas / Epidemiological Clinical characterization of diabetes mellitus type 1 in pediatrics, Mario Catarino Rivas Hospital

Antecedentes: Diabetes Mellitus (DM) se consi- dera una enfermedad metabólica con hiperglu- cemia de forma crónica, causada por un déficit parcial o total en la secreción o acción de la in- sulina. El 70-90% de DM1 tienen base autoin- mune. Objetivo: Describir las características clí- nico- epidemiológicas de Diabetes Mellitus I en Pediatría del Hospital Mario Catarino Rivas, San Pedro Sula, Cortés, en el período comprendido entre junio de 2017 - junio de 2019. Pacientes y métodos: Estudio cuantitativo, descriptivo, observacional, realizado en pacientes menores de 18 años que reunieron criterios de inclusión. Los datos se recolectaron mediante encuesta. Re- sultados: El grupo de edad más frecuente fue el escolar de 6-12 años en 49%. Mas frecuente en mujeres en 51%, 29% de los pacientes estudiados presentaron sedentarismo, 17% dislipidemias y sobrepeso, diagnosticadas en el debut de la enfer- medad. Los síntomas más frecuentes fueron po- lifagia en 44%, poliuria en 21%. Conclusiones: Las características socio-demográficas del grupo poblacional estudiado fueron las siguientes, el sexo más afectado fue el femenino y el grupo de edad más frecuente los escolares que se encuen- tran cursando la primaria, la mayoría de los pa- cientes estudiados no presentaban enfermedades asociadas, mientras que solo unos pocos presen- taban sobrepeso y dislipidemias asociado a Dia- betes Mellitus tipo I, se observó un predominio del debut sintomático asociado con la triada de polifagia, polidipsia y poliuria, además visión borrosa y pérdida de peso...(AU)

Acute insulin deprivation results in altered mitochondrial substrate sensitivity conducive to greater fatty acid transport.

Type 1 and type 2 diabetes are both tightly associated with impaired glucose control. Although both pathologies stem from different mechanisms, a reduction in insulin action coincides with drastic metabolic dysfunction in skeletal muscle and metabolic inflexibility. However, the underlying explanation for this response remains poorly understood, particularly since it is difficult to distinguish the role of attenuated insulin action from the detrimental effects of reactive lipid accumulation, which impairs mitochondrial function and promotes reactive oxygen species (ROS) emission. We therefore utilized streptozotocin to examine the effects of acute insulin deprivation, in the absence of a high-lipid/nutrient excess environment, on the regulation of mitochondrial substrate sensitivity and ROS emission. The ablation of insulin resulted in reductions in absolute mitochondrial oxidative capacity and ADP-supported respiration and reduced the ability for malonyl-CoA to inhibit carnitine palmitoyltransferase I (CPT-I) and suppress fatty acid-supported respiration. These bioenergetic responses coincided with increased mitochondrial-derived H2O2 emission and lipid transporter content, independent of major mitochondrial substrate transporter proteins and enzymes involved in fatty acid oxidation. Together, these data suggest that attenuated/ablated insulin signaling does not affect mitochondrial ADP sensitivity, whereas the increased reliance on fatty acid oxidation in situations where insulin action is reduced may occur as a result of altered regulation of mitochondrial fatty acid transport through CPT-I.

Update on Diabetes Mellitus and Glucose Metabolism Alterations in Prader-Willi Syndrome.

PURPOSE OF REVIEW: This review summarizes our current knowledge on type 2 diabetes mellitus (T2DM) and glucose metabolism alterations in Prader-Willi syndrome (PWS), the most common syndromic cause of obesity, and serves as a guide for future research and current best practice. RECENT FINDINGS: Diabetes occurs in 10-25% of PWS patients, usually in adulthood. Severe obesity is a significant risk factor for developing of T2DM in PWS. Paradoxically, despite severe obesity, a relative hypoinsulinemia, without the expected insulin resistance, is frequently observed in PWS. The majority of PWS subjects with T2DM are asymptomatic and diabetes-related complications are infrequent. Long-term growth hormone therapy does not adversely influence glucose homeostasis in all ages, if weight gain does not occur. Early intervention to prevent obesity and the regular monitoring of glucose levels are recommended in PWS subjects. However, further studies are required to better understand the physiopathological mechanisms of T2DM in these patients.

Efficacy and safety of dulaglutide in patients with absolute insulin deficiency.

OBJECTIVE: While dulaglutide has been approved inpatients with type 2 diabetes (T2DM) in combination with insulin, it has not been studied in insulin-deficient patients, not whether they have type 1 diabetes (T1DM) or T2DM. The aim of this study is to assess the efficacy and safety of dulaglutide 0.75 mg/once weekly (QW) in patients with absolute insulin deficiency (n=10). SUBJECTS AND RESULTS: Significant reductions of HbA1c (9.30±1.03% to 8.61±1.21%; p<0.02) and body mass index (BMI; 23.61±3.95 to 23.41±4.24; p<0.02) levels were observed at 3 months with the addition of dulaglutide to the existing pharmacotherapy. However, in all the patients, post-meal C-peptide levels remained undetectable. One patient had gastrointestinal adverse events and discontinue dulaglutide within the first month. One patient was a non-responder, who had little if any changes in HbA1c levels at 3 months. CONCLUSIONS: The results indicate that dulaglutide is effective in patients with T1DM or T2DM with absolute insulin deficiency, though gastrointestinal adverse events might be of concern. The improvements in glycemic control could not be due to enhanced insulin secretion, but may be as a result of a combination of the other effects of glucagon like peptide 1 (GLP-1), such as postprandial glucagon suppression, delayed gastric emptying, and weight loss.

Hematopoietic stem cell transplantation recovers insulin deficiency in type 1 diabetes mellitus associated with IPEX syndrome.

Immune dysregulation, polyendocrinopathy, enteropathy, and X-linked (IPEX) syndrome is an autoimmune disorder caused by the dysfunction of FOXP3, which leads to regulatory T-(Treg) cell dysfunction and subsequently autoimmunity including type 1 diabetes mellitus (T1D). Presently, allogeneic hematopoietic stem cell transplantation (HSCT) is a potential curative therapy for IPEX syndrome, but not for T1D. Generally, after complete loss of pancreatic ß-cells, HSCT cannot improve the prognosis of T1D. Here, we report the case of a 16-year-old adolescent with late-onset of FOXP3 R347H mutation associated IPEX syndrome with T1D, where insulin dependency was ameliorated following HSCT. This patient with insulin-dependent diabetes mellitus required insulin dosage of 1.28 U/kg/day for 1 month before HSCT. Although the results of glucose homeostasis before HSCT revealed impaired insulin secretion and low ΔC-peptide immunoreactivity (CPR, 1.0 ng/mL), the patient withdrew insulin infusion and remained euglycemic at 15 months after HSCT, and had normal ß-cell function with improved ΔCPR (3.4 ng/mL) at 20 months after HSCT. The present case suggests that HSCT for T1D-associated IPEX syndrome improves Treg deficiency and prevents elimination of ß-cells. We speculate that the period from the onset of T1D to HSCT could affect the therapeutic efficacy for T1D with IPEX, and early intervention with HSCT before or immediately after the onset of DM can rescue ß-cells and remit T1D completely. Our study elaborates not only the therapeutic strategy for T1D with IPEX, but also the pathogenic mechanism in general T1D.

Insulin deficiency and intranasal insulin alter brain mitochondrial function: a potential factor for dementia in diabetes.

Despite the strong association between diabetes and dementia, it remains to be fully elucidated how insulin deficiency adversely affects brain functions. We show that insulin deficiency in streptozotocin-induced diabetic mice decreased mitochondrial ATP production and/or citrate synthase and cytochrome oxidase activities in the cerebrum, hypothalamus, and hippocampus. Concomitant decrease in mitochondrial fusion proteins and increased fission proteins in these brain regions likely contributed to altered mitochondrial function. Although insulin deficiency did not cause any detectable increase in reactive oxygen species (ROS) emission, inhibition of monocarboxylate transporters increased ROS emission and further reduced ATP production, indicating the causative roles of elevated ketones and lactate in counteracting oxidative stress and as a fuel source for ATP production during insulin deficiency. Moreover, in healthy mice, intranasal insulin administration increased mitochondrial ATP production, demonstrating a direct regulatory role of insulin on brain mitochondrial function. Proteomics analysis of the cerebrum showed that although insulin deficiency led to oxidative post-translational modification of several proteins that cause tau phosphorylation and neurofibrillary degeneration, insulin administration enhanced neuronal development and neurotransmission pathways. Together these results render support for the critical role of insulin to maintain brain mitochondrial homeostasis and provide mechanistic insight into the potential therapeutic benefits of intranasal insulin.-Ruegsegger, G. N., Manjunatha, S., Summer, P., Gopala, S., Zabeilski, P., Dasari, S., Vanderboom, P. M., Lanza, I. R., Klaus, K. A., Nair, K. S. Insulin deficiency and intranasal insulin alter brain mitochondrial function: a potential factor for dementia in diabetes.

Aggravation of diabetes, and incompletely deficient insulin secretion in a case with type 1 diabetes-resistant human leukocyte antigen DRB1*15:02 treated with nivolumab.

Anti-programmed cell death-1 (PD-1) antibody therapy induces various adverse effects, especially in the endocrine system. Several cases of acute-onset insulin-dependent diabetes after anti-PD-1 antibody therapy have been reported. Many of these cases have a susceptible human leukocyte antigen (HLA) genotype for type 1 diabetes, possibly suggesting that HLA might be involved in the onset of diabetes with anti-PD-1 therapy. We describe an atypical case of hyperglycemia after anti-PD-1 antibody administration. A 68-year-old Japanese man with pancreatic diabetes and steroid diabetes was given nivolumab three times for chemoresistant adenocarcinoma of the lung. On day 5 after the third infusion of nivolumab, he had hyperglycemia (blood glucose 330 mg/dL and hemoglobin A1c 8.0%) without ketosis and with incompletely deficient insulin secretion. The patient had both type 1 diabetes susceptible (HLA-A*24:02 and -DRB1*09:01) and resistant (HLA-DRB1*15:02) HLA genotypes. These HLA genotypes differ from those previously reported in anti-PD-1 antibody-induced diabetes, and might have influenced the preservation of insulin secretion after nivolumab administration in the present case.

Insulin-Deficient Mouse ß-Cells Do Not Fully Mature but Can Be Remedied Through Insulin Replacement by Islet Transplantation.

Insulin receptor (IR) insufficiency in ß-cells leads to impaired insulin secretion and reduced ß-cell hyperplasia in response to hyperglycemia. Selective IR deficiency in ß-cells in later embryological development may lead to compensatory ß-cell hyperplasia. Although these findings suggest insulin signaling on the ß-cell is important for ß-cell function, they are confounded by loss of signaling by the insulinlike growth factors through the IR. To determine whether insulin itself is necessary for ß-cell development and maturation, we performed a characterization of pancreatic islets in mice with deletions of both nonallelic insulin genes (Ins1-/-Ins2-/-). We immunostained neonatal Ins1-/-Ins2-/- and Ins1+/+Ins2+/+ pancreata and performed quantitative polymerase chain reaction on isolated neonatal islets. Insulin-deficient islets had reduced expression of factors normally expressed in maturing ß-cells, including muscoloaponeurotic fibrosarcoma oncogene homolog A, homeodomain transcription factor 6.1, and glucose transporter 2. Ins1-/-Ins2-/-ß-cells expressed progenitor factors associated with stem cells or dedifferentiated ß-cells, including v-myc avian myolocytomatosis viral oncogene lung carcinoma derived and homeobox protein NANOG. We replaced insulin by injection or islet transplantation to keep mice alive into adulthood to determine whether insulin replacement was sufficient for the completed maturation of insulin-deficient ß-cells. Short-term insulin glargine (Lantus®) injections partially rescued the ß-cell phenotype, whereas long-term replacement of insulin by isogenic islet transplantation supported the formation of more mature ß-cells. Our findings suggest that tightly regulated glycemia, insulin species, or other islet factors are necessary for ß-cell maturation.

Kinetics of functional beta cell mass decay in a diphtheria toxin receptor mouse model of diabetes.

Functional beta cell mass is an essential biomarker for the diagnosis and staging of diabetes. It has however proven technically challenging to study this parameter during diabetes progression. Here we have detailed the kinetics of the rapid decline in functional beta cell mass in the RIP-DTR mouse, a model of hyperglycemia resulting from diphtheria toxin induced beta cell ablation. A novel combination of imaging modalities was employed to study the pattern of beta cell destruction. Optical projection tomography of the pancreas and longitudinal in vivo confocal microscopy of islets transplanted into the anterior chamber of the eye allowed to investigate kinetics and tomographic location of beta cell mass decay in individual islets as well as at the entire islet population level. The correlation between beta cell mass and function was determined by complementary in vivo and ex vivo characterizations, demonstrating that beta cell function and glucose tolerance were impaired within the first two days following treatment when more than 50% of beta cell mass was remaining. Our results illustrate the importance of acquiring quantitative functional and morphological parameters to assess the functional status of the endocrine pancreas.

Metabolic effects of insulin in a human model of ketoacidosis combining exposure to lipopolysaccharide and insulin deficiency: a randomised, controlled, crossover study in individuals with type 1 diabetes.

AIMS/HYPOTHESIS: Diabetic ketoacidosis (DKA) is often caused by concomitant systemic inflammation and lack of insulin. Here we used an experimental human model to test whether and how metabolic responses to insulin are impaired in the early phases of DKA with a specific focus on skeletal muscle metabolism. METHODS: Nine individuals with type 1 diabetes from a previously published cohort were investigated twice at Aarhus University Hospital using a 120 min infusion of insulin (3.0/1.5 mU kg-1 min-1) after an overnight fast under: (1) euglycaemic conditions (CTR) or (2) hyperglycaemic ketotic conditions (KET) induced by an i.v. bolus of lipopolysaccharide and 85% reduction in insulin dosage. The primary outcome was insulin resistance in skeletal muscle. Participants were randomly assigned to one of the two arms at the time of screening using www.randomizer.org . The study was not blinded. RESULTS: All nine volunteers completed the 2 days and are included in the analysis. Circulating concentrations of glucose and 3-hydroxybutyrate increased during KET (mean ± SEM 17.7 ± 0.6 mmol/l and 1.6 ± 0.2 mmol/l, respectively), then decreased after insulin treatment (6.6 ± 0.7 mmol/l and 0.1 ± 0.07 mmol/l, respectively). Prior to insulin infusion (KET vs CTR) isotopically determined endogenous glucose production rates were 17 ± 1.7 µmol kg-1 min-1 vs 8 ± 1.3 µmol kg-1 min-1 (p = 0.003), whole body phenylalanine fluxes were 2.9 ± 0.5 µmol kg-1 min-1 vs 3.1 ± 0.4 µmol kg-1 min-1 (p = 0.77) and urea excretion rates were 16.9 ± 2.4 g/day vs 7.3 ± 1.7 g/day (p = 0.01). Insulin failed to stimulate forearm glucose uptake and glucose oxidation in KET compared with CTR (p < 0.05). Glycogen synthase phosphorylation was impaired in skeletal muscle. CONCLUSIONS/INTERPRETATION: In KET, hyperglycaemia is primarily driven by increased endogenous glucose production. Insulin stimulation during early phases of DKA is associated with reduced glucose disposal in skeletal muscle, impaired glycogen synthase function and lower glucose oxidation. This underscores the presence of muscle insulin resistance in the pathogenesis of DKA. Trial registration www.clinicaltrials.gov (ID number: NCT02157155). Funding This work was funded by the Danish Council for Strategic Research (grant no. 0603-00479B).

Insulin deficiency results in reversible protein kinase A activation and tau phosphorylation.

Alzheimer's disease (AD) is a highly prevalent multifactorial disease for which Diabetes Mellitus (DM) is a risk factor. Abnormal phosphorylation and aggregation of tau is a key hallmark of AD. In animal models, DM induces or exacerbates the phosphorylation of tau, suggesting that DM may influence the risk at AD by directly facilitating tau pathology. Previously we reported that tau phosphorylation induced in response to metabolic stress is reversible. Since identification and understanding of early players in tau pathology is pivotal for therapeutic intervention, we here investigated the mechanism underlying tau phosphorylation in the diabetic brain and its potential for reversibility. To model DM we used streptozotocin-treatment to induce insulin deficiency in rats. Insulin depletion leads to increased tau phosphorylation in the brain and we investigated the activation status of known tau kinases and phosphatases in this model. We identified protein kinase A (PKA) as a tau kinase activated by DM in the brain. The potential relevance of this signaling pathway to AD pathogenesis is indicated by the increased level of active PKA in temporal cortex of early stage AD patients. Our data indicate that activation of PKA and tau phosphorylation are associated with insulin deficiency per se, rather than the downstream energy deprivation. In vitro studies confirm that insulin deficiency results in PKA activation and tau phosphorylation. Strikingly, both active PKA and induced tau phosphorylation are reversed upon insulin treatment in the steptozotocin animal model. Our data identify insulin deficiency as a direct trigger that induces the activity of the tau kinase PKA and results in tau phosphorylation. The reversibility upon insulin treatment underscores the potential of insulin as an early disease-modifying intervention in AD and other tauopathies.

CD4+ T cell-dominant insulitis in acute-onset Type 1 diabetes mellitus associated with intraductal papillary mucinous adenoma.

The loss of insulin-producing pancreatic ß-cells in Type 1 diabetes mellitus (DM) is presumably the result of a T cell-mediated process. In general, CD8+ T cells are the predominant lymphocytes in the insulitis lesions, and CD4+ T cell-dominant insulitis is very rare. We present a case of a 72-year-old woman presented with excessive thirst and a 3-month history of weight loss. She was in a state of ketosis, and her plasma glucose concentration and HbA1c value were elevated. Moreover, anti-islet autoantibodies were positive, thus acute-onset Type 1 DM was diagnosed. At the time of diagnosis, a tumour was detected in the pancreas; total pancreatectomy was carried out 2 months later. The pathological diagnosis was intraductal papillary mucinous adenoma. Immunohistochemical staining of a sample of non-tumorous pancreatic tissue revealed 13 insulitis lesions infiltrated by both CD4+ and CD8+ T cells, and interestingly there were more CD4+ T cells than CD8+ T cells in the lesions. Moreover, B cells and macrophages had also infiltrated the lesions, and these two cell frequencies were both positively correlated with CD4+ as well as CD8+ T cell frequencies. This was a rare case with acute-onset Type 1 DM characterized by CD4+ T cell-dominant insulitis. Proinflammatory cytokines that can promote ß-cell apoptosis or CD8+ T cell function are reported to be secreted from CD4+ T cells. Thus, together with B cells and macrophages, CD4+ T cell-associated immune responses may have, directly and/or indirectly, played a role in the pathogenesis of the Type 1 DM in this patient.

Serine 302 Phosphorylation of Mouse Insulin Receptor Substrate 1 (IRS1) Is Dispensable for Normal Insulin Signaling and Feedback Regulation by Hepatic S6 Kinase.

Constitutive activation of the mammalian target of rapamycin complex 1 and S6 kinase (mTORC1→ S6K) attenuates insulin-stimulated Akt activity in certain tumors in part through "feedback" phosphorylation of the upstream insulin receptor substrate 1 (IRS1). However, the significance of this mechanism for regulating insulin sensitivity in normal tissue remains unclear. We investigated the function of Ser-302 in mouse IRS1, the major site of its phosphorylation by S6K in vitro, through genetic knock-in of a serine-to-alanine mutation (A302). Although insulin rapidly stimulated feedback phosphorylation of Ser-302 in mouse liver and muscle, homozygous A302 mice (A/A) and their knock-in controls (S/S) exhibited similar glucose homeostasis and muscle insulin signaling. Furthermore, both A302 and control primary hepatocytes from which Irs2 was deleted showed marked inhibition of insulin-stimulated IRS1 tyrosine phosphorylation and PI3K binding after emetine treatment to raise intracellular amino acids and activate mTORC1 → S6K signaling. To specifically activate mTORC1 in mouse tissue, we deleted hepatic Tsc1 using Cre adenovirus. Although it moderately decreased IRS1/PI3K association and Akt phosphorylation in liver, Tsc1 deletion failed to cause glucose intolerance or promote hyperinsulinemia in mixed background A/A or S/S mice. Moreover, Tsc1 deletion failed to stimulate phospho-Ser-302 or other putative S6K sites within IRS1, whereas ribosomal S6 protein was constitutively phosphorylated. Following acute Tsc1 deletion from hepatocytes, Akt phosphorylation, but not IRS1/PI3K association, was rapidly restored by treatment with the mTORC1 inhibitor rapamycin. Thus, within the hepatic compartment, mTORC1 → S6K signaling regulates Akt largely through IRS-independent means with little effect upon physiologic insulin sensitivity.

An Indirect Action Contributes to C-Fos Induction in Paraventricular Hypothalamic Nucleus by Neuropeptide Y.

Neuropeptide Y (NPY) is a well-established orexigenic peptide and hypothalamic paraventricular nucleus (PVH) is one major brain site that mediates the orexigenic action of NPY. NPY induces abundant expression of C-Fos, an indicator for neuronal activation, in the PVH, which has been used extensively to examine the underlying NPY orexigenic neural pathways. However, PVH C-Fos induction is in discordance with the abundant expression of NPY receptors, a group of inhibitory Gi protein coupled receptors in the PVH, and with the overall role of PVH neurons in feeding inhibition, suggesting a mechanism of indirect action. Here we showed that the ability of NPY on C-Fos induction in the PVH was blunted in conditions of insulin deficiency and fasting, a condition associated with a high level of NPY and a low level of insulin. Moreover, insulin insufficiency blunted C-Fos induction in the PVH by fasting-induced re-feeding, and insulin and NPY induced c-Fos induction in the same group of PVH neurons. Finally, NPY produced normal C-Fos induction in the PVH with disruption of GABA-A receptors. Thus, our results revealed that PVH C-Fos induction by NPY is mediated by an indirect action, which is at least partially mediated by insulin action, but not GABA-A receptors.

Sustained intraocular VEGF neutralization results in retinal neurodegeneration in the Ins2(Akita) diabetic mouse.

Current therapies that target vascular endothelial growth factor (VEGF) have become a mainstream therapy for the management of diabetic macular oedema. The treatment involves monthly repeated intravitreal injections of VEGF inhibitors. VEGF is an important growth factor for many retinal cells, including different types of neurons. In this study, we investigated the adverse effect of multiple intravitreal anti-VEGF injections (200 ng/µl/eye anti-mouse VEGF164, once every 2 weeks totalling 5-6 injections) to retinal neurons in Ins2(Akita) diabetic mice. Funduscopic examination revealed the development of cotton wool spot-like lesions in anti-VEGF treated Ins2(Akita) mice after 5 injections. Histological investigation showed focal swellings of retinal nerve fibres with neurofilament disruption. Furthermore, anti-VEGF-treated Ins2(Akita) mice exhibited impaired electroretinographic responses, characterized by reduced scotopic a- and b-wave and oscillatory potentials. Immunofluorescent staining revealed impairment of photoreceptors, disruptions of synaptic structures and loss of amacrine and retinal ganglion cells in anti-VEGF treated Ins2(Akita) mice. Anti-VEGF-treated WT mice also presented mild amacrine and ganglion cell death, but no overt abnormalities in photoreceptors and synaptic structures. At the vascular level, exacerbated albumin leakage was observed in anti-VEGF injected diabetic mice. Our results suggest that sustained intraocular VEGF neutralization induces retinal neurodegeneration and vascular damage in the diabetic eye.

Degradation of extracellular chondroitin sulfate delays recovery of network activity after perturbation.

Chondroitin sulfate proteoglycans (CSPGs) are widely studied in vertebrate systems and are known to play a key role in development, plasticity, and regulation of cortical circuitry. The mechanistic details of this role are still elusive, but increasingly central to the investigation is the homeostatic balance between network excitation and inhibition. Studying a simpler neuronal circuit may prove advantageous for discovering the mechanistic details of the cellular effects of CSPGs. In this study we used a well-established model of homeostatic change after injury in the crab Cancer borealis to show first evidence that CSPGs are necessary for network activity homeostasis. We degraded CSPGs in the pyloric circuit of the stomatogastric ganglion with the enzyme chondroitinase ABC (chABC) and found that removal of CSPGs does not influence the ongoing rhythm of the pyloric circuit but does limit its capacity for recovery after a networkwide perturbation. Without CSPGs, the postperturbation rhythm is slower than in controls and rhythm recovery is delayed. In addition to providing a new model system for the study of CSPGs, this study suggests a wider role for CSPGs, and perhaps the extracellular matrix in general, beyond simply plastic reorganization (as observed in mammals) and into a foundational regulatory role of neural circuitry.

Geniposide attenuates insulin-deficiency-induced acceleration of ß-amyloidosis in an APP/PS1 transgenic model of Alzheimer's disease.

Our previous studies have shown that geniposide plays an essential role in glucose-stimulated insulin secretion from pancreatic ß cells and also antagonizesAß1-42-induced cytotoxicity examined using a primary cortical neuron assay. However, the mechanism by which geniposide appears to regulate insulin signaling in the brain is presently not well understood. In this study, we administered streptozotocin (STZ) to induce insulin-deficiency in an AD transgenic mouse model, and investigated the effects of geniposide on the ß-amyloidogenic processing of amyloid precursor protein (APP) using in vitro and in vivo models. Our results indicate that treatment with STZ (90 mg/kg, i.p., once daily for two consecutive days) induced significant reduction in peripheral and brain insulin levels in both wild-type and APP/PS1 transgenic mice. Administration of geniposide for 4 weeks significantly decreased the concentrations of cerebral ß-amyloid peptides (Aß1-40 and Aß1-42) in STZ-treated AD mice. Further experiments showed that geniposide up-regulated the protein levels of ß-site APP cleaving enzyme (BACE1) and insulin-degrading enzyme (IDE), and decreased the protein levels of ADAM10 when examined using a primary cultured cortical neuron assay and in STZ-induced AD mice. Meanwhile, geniposide also directly enhanced the effects of insulin by reducing Aß1-42 levels in primary cultured cortical neurons. Taken together, our findings provide a mechanistic link between diabetes and AD, and is consistent with the notion that geniposide might play an important role on APP processing via enhancing insulin signaling and may convey a therapeutic benefit in AD.