bluuebunny/crossref_metadata_2025 huggingface dataset:
GnRH Increases c-Fos Half-Life Contributing to Higher FSHβ Induction
Authors: Reddy Gaddameedi R. , Xie Changchuan , Lindaman Lacey L. , Coss Djurdjica
Published: December 2012

GnRH is a potent hypothalamic regulator of gonadotropin hormones, LH and FSH, which are both expressed within the pituitary gonadotrope and are necessary for the stimulation of gametogenesis and steroidogenesis in the gonads. Differential regulation of LH and FSH, which is essential for reproductive fitness, is achieved, in part, through the varying of GnRH pulse frequency. However, the mechanism controlling the increase in FSH during the periods of low GnRH has not been elucidated. Here, we uncover another level of regulation by GnRH that contributes to differential expression of the gonadotropins and may play an important role for the generation of the secondary rise of FSH that stimulates folliculogenesis. GnRH stimulates LHβ and FSHβ subunit transcription via induction of the immediate early genes, Egr1 and c-Fos, respectively. Here, we determined that GnRH induces rapidly both Egr1 and c-Fos, but specifically decreases the rate of c-Fos degradation. In particular, GnRH modulates the rate of c-Fos protein turnover by inducing c-Fos phosphorylation through the ERK1/2 pathway. This extends the half-life of c-Fos, which is normally rapidly degraded. Confirming the role of phosphorylation in promoting increased protein activity, we show that a c-Fos mutant that cannot be phosphorylated by GnRH induces lower expression of the FHSβ promoter than wild-type c-Fos. Our studies expand upon the role of GnRH in the regulation of gonadotropin gene expression by highlighting the role of c-Fos posttranslational modification that may cause higher levels of FSH during the time of low GnRH pulse frequency to stimulate follicular growth.
Induction of 11β-HSD 1 and Activation of Distinct Mineralocorticoid Receptor- and Glucocorticoid Receptor-Dependent Gene Networks in Decidualizing Human Endometrial Stromal Cells
Authors: Kuroda Keiji , Venkatakrishnan Radha , Salker Madhuri S. , Lucas Emma S. , Shaheen Fozia , Kuroda Masako , Blanks Andrew , Christian Mark , Quenby Siobhan , Brosens Jan J.
Published: December 2012

The actions of glucocorticoids at the feto-maternal interface are not well understood. Here, we show that decidualization of human endometrial stromal cells (HESCs) in response to progesterone and cAMP signaling is associated with a strong induction of 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) expression and enzyme activity. Decidualization also triggered a gradual decrease in glucocorticoid receptor (GR) expression and reciprocal increase in mineralocorticoid receptor (MR) levels. Gene expression profiling of differentiating HESCs after small interfering RNA (siRNA)-mediated knockdown of either GR or MR identified 239 and 167 significantly regulated genes, respectively. Interestingly, GR-repressed genes were enriched for Krüppel-associated box domain containing zinc-finger proteins, transcriptional repressors involved in heterochromatin formation. In agreement, GR knockdown was sufficient to enhance trimethylated H3K9 levels in decidualizing cells. Conversely, we identified several MR-dependent genes implicated in lipid droplet biogenesis and retinoid metabolism. For example, the induction in differentiating HESCs of DHRS3, encoding a highly conserved enzyme that catalyzes the oxidation/reduction of retinoids and steroids, was enhanced by aldosterone, attenuated in response to MR knockdown, and abolished upon treatment with the MR antagonist RU26752. Furthermore, we demonstrate that decidualization is associated with dynamic changes in the abundance and distribution of cytoplasmic lipid droplets, the formation of which was blocked by RU26752. In summary, progesterone drives local cortisol biosynthesis by decidual cells through induction of 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1), leading to transcriptional regulation of distinct GR and MR gene networks involved in epigenetic programming and lipid and retinoid metabolism, respectively.
First synthesis of chloroformylphosphane complexes
Authors: Nesterov Vitaly , Heurich Tobias , Streubel Rainer
Published: December 2012

An approach to novel P-functional chloroformylphosphane complexes is described using the synthetic potential of lithium/halogeno phosphinidenoid tungsten(0) complexes. Similarly to transition-metal-free chloroformylphosphanes, the obtained complexes tend to eliminate CO via P–C bond cleavage to give the corresponding P-chlorophosphane complex derivatives. Nevertheless, this method allowed the isolation of the first complex derivatives, which will open new synthetic perspectives in organophosphorus chemistry.
Multiple bonds between lead atoms and short bonds between transition metals
Authors: Nagase Shigeru
Published: December 2012

The heaviest analogues of alkynes are investigated to realize a short triple bond between Pb atoms. For a short double bond between Pb atoms, the Pb2 molecule stabilized by dative N-heterocyclic carbenes is investigated. For unsupported and supported short bonds between transition metals, two-coordinate transition-metal and bicyclic four-membered ring complexes are investigated.
Cisplatin-related drugs for nongenomic targets: Forcing the reactivity with nucleobases
Authors: De Pascali Sandra Angelica , Muscella Antonella , Marsigliante Santo , Bottone Maria Grazia , Bernocchi Graziella , Fanizzi Francesco Paolo
Published: December 2012

The products obtained by forcing the reaction with nucleosides (guanosine, Guo, and adenosine, Ado) of potential anticancer drugs for nongenomic targets [PtCl(O,O'-acac)(L)] (L = dimethyl sulfoxide, DMSO; dimethyl sulfide, DMS), closely related to their very powerful organometallic analogues [Pt(O,O'-acac)(γ-acac)(L)], have been studied. [PtCl(O,O'-acac)(L)] and [Pt(O,O'-acac)(γ-acac)(L)] complexes were reported unreactive toward nucleobases. Aquo species [Pt(O,O'-acac)H2O(L)]+, obtained from [PtCl(O,O'-acac)(L)] by Ag+ driven coordinated Cl– removal, gave access to [Pt(O,O'-acac)(L)(nucleoside)]+ ([Pt(O,O'-acac)(DMSO)(Guo)]+, [Pt(O,O'-acac)(DMS)(Guo)]+, [Pt(O,O'-acac)(DMSO)(Ado)]+). The effect of the chelate oxygen donor acac (with respect to a chelate diammine), the role of the sulfur ligand (DMSO, DMS), and the influence of the purinic nucleoside itself on the coordinated Guo or Ado dynamic motions in [Pt(O,O'-acac)(L)(nucleoside)]+ complexes have been investigated by NMR spectroscopy. Interestingly, a slow rotation of nucleobase around the Pt–N(7) bond with formation of two rotamers was observed already at room temperature only in the case of [Pt(O,O'-acac)(DMSO)(Guo)]+. On the other hand, no hindered rotation at room temperature was detected in the analogous [Pt(O,O'-acac)(DMS)(Guo)]+ and [Pt(O,O'-acac)(DMSO)(Ado)]+ complexes. Data suggest that rotation of the nucleoside in [Pt(O,O'-acac)(L)(nucleoside)]+ is very different with respect to the analogous [Pt(diammine)(L)(nucleoside)]2+ systems, due to specific interactions between the acac chelate ligand, the DMSO, and the nucleobase.
Protein Domain Histochemistry (PDH)
Authors: Nollau Peter , Wolters-Eisfeld Gerrit , Mortezai Naghmeh , Kurze Anna-Katharina , Klampe Birgit , Debus Annegret , Bockhorn Maximilian , Niendorf Axel , Wagener Christoph
Published: December 2012

Specialized protein domains bind to posttranslational modifications (PTMs) of proteins, such as phosphorylation or glycosylation. When such PTM-binding protein domains are used as analytical tools, the functional states of cells and tissues can be determined with high precision. Here, we describe the use of recombinant CLEC10A (CD301), a human glycoreceptor of the C-type lectin family, for the detection of ligands in sections from formalin-fixed, paraffin-embedded normal and cancerous mammary tissues. A construct, in which part of the carbohydrate recognition domain (CRD) was deleted, was used as a negative control. In comparison to normal mammary glands, a pronounced staining of tumor tissues was observed. Because the construct with the truncated CRD did not show any tissue staining, the binding of the wild-type glycoreceptor can be attributed to its carbohydrate recognition domain. To distinguish our novel approach from immunohistochemistry, we propose the designation “protein domain histochemistry” (PDH).
Evidence for a Role of Proline and Hypothalamic Astrocytes in the Regulation of Glucose Metabolism in Rats
Authors: Arrieta-Cruz Isabel , Su Ya , Knight Colette M. , Lam Tony K.T. , Gutiérrez-Juárez Roger
Published: December 2012

The metabolism of lactate to pyruvate in the mediobasal hypothalamus (MBH) regulates hepatic glucose production. Because astrocytes and neurons are functionally linked by metabolic coupling through lactate transfer via the astrocyte-neuron lactate shuttle (ANLS), we reasoned that astrocytes might be involved in the hypothalamic regulation of glucose metabolism. To examine this possibility, we used the gluconeogenic amino acid proline, which is metabolized to pyruvate in astrocytes. Our results showed that increasing the availability of proline in rats either centrally (MBH) or systemically acutely lowered blood glucose. Pancreatic clamp studies revealed that this hypoglycemic effect was due to a decrease of hepatic glucose production secondary to an inhibition of glycogenolysis, gluconeogenesis, and glucose-6-phosphatase flux. The effect of proline was mimicked by glutamate, an intermediary of proline metabolism. Interestingly, proline’s action was markedly blunted by pharmacological inhibition of hypothalamic lactate dehydrogenase (LDH) suggesting that metabolic flux through LDH was required. Furthermore, short hairpin RNA–mediated knockdown of hypothalamic LDH-A, an astrocytic component of the ANLS, also blunted the glucoregulatory action of proline. Thus our studies suggest not only a new role for proline in the regulation of hepatic glucose production but also indicate that hypothalamic astrocytes are involved in the regulatory mechanism as well.
Fetal PGC-1α Overexpression Programs Adult Pancreatic β-Cell Dysfunction
Authors: Valtat Bérengère , Riveline Jean-Pierre , Zhang Ping , Singh-Estivalet Amrit , Armanet Mathieu , Venteclef Nicolas , Besseiche Adrien , Kelly Daniel P. , Tronche François , Ferré Pascal , Gautier Jean-François , Bréant Bernadette , Blondeau Bertrand
Published: December 2012

Adult β-cell dysfunction, a hallmark of type 2 diabetes, can be programmed by adverse fetal environment. We have shown that fetal glucocorticoids (GCs) participate in this programming through inhibition of β-cell development. Here we have investigated the molecular mechanisms underlying this regulation. We showed that GCs stimulate the expression of peroxisome proliferator–activated receptor-γ coactivator-1α (PGC-1α), a coregulator of the GCs receptor (GR), and that the overexpression of PGC-1α represses genes important for β-cell development and function. More precisely, PGC-1α inhibited the expression of the key β-cell transcription factor pancreatic duodenal homeobox 1 (Pdx1). This repression required the GR and was mediated through binding of a GR/PGC-1α complex to the Pdx1 promoter. To explore PGC-1α function, we generated mice with inducible β-cell PGC-1α overexpression. Mice overexpressing PGC-1α exhibited at adult age impaired glucose tolerance associated with reduced insulin secretion, decreased β-cell mass, and β-cell hypotrophy. Interestingly, PGC-1α expression in fetal life only was sufficient to impair adult β-cell function whereas β-cell PGC-1α overexpression from adult age had no consequence on β-cell function. Altogether, our results demonstrate that the GR and PGC-1α participate in the fetal programming of adult β-cell function through inhibition of Pdx1 expression.
Kinetics of Saturated, Monounsaturated, and Polyunsaturated Fatty Acids in Humans
Authors: Nelson Robert H. , Mundi Manpreet S. , Vlazny Danielle T. , Smailovic Almira , Muthusamy Kalpana , Almandoz Jaime P. , Singh Ekta , Jensen Michael D. , Miles John M.
Published: December 2012

Plasma free fatty acid (FFA) kinetics in humans are often measured with only one tracer. In study 1, healthy volunteers received infusions of [U-13C]linoleate, [U-13C]oleate, and [U-13C]palmitate during continuous feeding with liquid meals low (n = 12) and high (n = 5) in palmitate and containing three labeled fatty acids to measure FFA appearance and fractional spillover of lipoprotein lipase–generated fatty acids. Study 2 used an intravenous lipid emulsion to increase FFA concentrations during infusion of linoleate and palmitate tracers. In study 1, there were no differences in spillover of the three fatty acids for the low-palmitate meal, but linoleate spillover was greater than oleate or palmitate for the high-palmitate meal. In studies 1 and 2, clearance was significantly greater for linoleate than for the other FFAs. There was a negative correlation between clearance and concentration for each fatty acid in the two studies. In study 1, concentration and spillover correlated positively for oleate and palmitate but negatively for linoleate. In conclusion, linoleate spillover is greater than that of other fatty acids under some circumstances. Linoleate clearance is greater than that of palmitate or oleate, indicating a need for caution when using a single FFA to infer the behavior of all fatty acids.
Rac1 Is a Novel Regulator of Contraction-Stimulated Glucose Uptake in Skeletal Muscle
Authors: Sylow Lykke , Jensen Thomas E. , Kleinert Maximilian , Mouatt Joshua R. , Maarbjerg Stine J. , Jeppesen Jacob , Prats Clara , Chiu Tim T. , Boguslavsky Shlomit , Klip Amira , Schjerling Peter , Richter Erik A.
Published: December 2012

In skeletal muscle, the actin cytoskeleton-regulating GTPase, Rac1, is necessary for insulin-dependent GLUT4 translocation. Muscle contraction increases glucose transport and represents an alternative signaling pathway to insulin. Whether Rac1 is activated by muscle contraction and regulates contraction-induced glucose uptake is unknown. Therefore, we studied the effects of in vivo exercise and ex vivo muscle contractions on Rac1 signaling and its regulatory role in glucose uptake in mice and humans. Muscle Rac1-GTP binding was increased after exercise in mice (∼60–100%) and humans (∼40%), and this activation was AMP-activated protein kinase independent. Rac1 inhibition reduced contraction-stimulated glucose uptake in mouse muscle by 55% in soleus and by 20–58% in extensor digitorum longus (EDL; P < 0.01). In agreement, the contraction-stimulated increment in glucose uptake was decreased by 27% (P = 0.1) and 40% (P < 0.05) in soleus and EDL muscles, respectively, of muscle-specific inducible Rac1 knockout mice. Furthermore, depolymerization of the actin cytoskeleton decreased contraction-stimulated glucose uptake by 100% and 62% (P < 0.01) in soleus and EDL muscles, respectively. These are the first data to show that Rac1 is activated during muscle contraction in murine and human skeletal muscle and suggest that Rac1 and possibly the actin cytoskeleton are novel regulators of contraction-stimulated glucose uptake.
The Suprachiasmatic Nucleus Controls Circadian Energy Metabolism and Hepatic Insulin Sensitivity
Authors: Coomans Claudia P. , van den Berg Sjoerd A.A. , Lucassen Eliane A. , Houben Thijs , Pronk Amanda C.M. , van der Spek Rianne D. , Kalsbeek Andries , Biermasz Nienke R. , Willems van Dijk Ko , Romijn Johannes A. , Meijer Johanna H.
Published: December 2012

Disturbances in the circadian system are associated with the development of type 2 diabetes mellitus. Here, we studied the direct contribution of the suprachiasmatic nucleus (SCN), the central pacemaker in the circadian system, in the development of insulin resistance. Exclusive bilateral SCN lesions in male C57Bl/6J mice, as verified by immunochemistry, showed a small but significant increase in body weight (+17%), which was accounted for by an increase in fat mass. In contrast, mice with collateral damage to the ventromedial hypothalamus and paraventricular nucleus showed severe obesity and insulin resistance. Mice with exclusive SCN ablation revealed a loss of circadian rhythm in activity, oxygen consumption, and food intake. Hyperinsulinemic–euglycemic clamp analysis 8 weeks after lesioning showed that the glucose infusion rate was significantly lower in SCN lesioned mice compared with sham-operated mice (−63%). Although insulin potently inhibited endogenous glucose production (−84%), this was greatly reduced in SCN lesioned mice (−7%), indicating severe hepatic insulin resistance. Our data show that SCN malfunctioning plays an important role in the disturbance of energy balance and suggest that an absence of central clock activity, in a genetically intact animal, may lead to the development of insulin resistance.
Fecal Microbiota Composition Differs Between Children With β-Cell Autoimmunity and Those Without
Authors: de Goffau Marcus C. , Luopajärvi Kristiina , Knip Mikael , Ilonen Jorma , Ruohtula Terhi , Härkönen Taina , Orivuori Laura , Hakala Saara , Welling Gjalt W. , Harmsen Hermie J. , Vaarala Outi
Published: December 2012

The role of the intestinal microbiota as a regulator of autoimmune diabetes in animal models is well-established, but data on human type 1 diabetes are tentative and based on studies including only a few study subjects. To exclude secondary effects of diabetes and HLA risk genotype on gut microbiota, we compared the intestinal microbiota composition in children with at least two diabetes-associated autoantibodies (n = 18) with autoantibody-negative children matched for age, sex, early feeding history, and HLA risk genotype using pyrosequencing. Principal component analysis indicated that a low abundance of lactate-producing and butyrate-producing species was associated with β-cell autoimmunity. In addition, a dearth of the two most dominant Bifidobacterium species, Bifidobacterium adolescentis and Bifidobacterium pseudocatenulatum, and an increased abundance of the Bacteroides genus were observed in the children with β-cell autoimmunity. We did not find increased fecal calprotectin or IgA as marker of inflammation in children with β-cell autoimmunity. Functional studies related to the observed alterations in the gut microbiome are warranted because the low abundance of bifidobacteria and butyrate-producing species could adversely affect the intestinal epithelial barrier function and inflammation, whereas the apparent importance of the Bacteroides genus in development of type 1 diabetes is insufficiently understood.
Failure of the Adaptive Unfolded Protein Response in Islets of Obese Mice Is Linked With Abnormalities in β-Cell Gene Expression and Progression to Diabetes
Authors: Chan Jeng Yie , Luzuriaga Jude , Bensellam Mohammed , Biden Trevor J. , Laybutt D. Ross
Published: December 2012

The normal β-cell response to obesity-associated insulin resistance is hypersecretion of insulin. Type 2 diabetes develops in subjects with β-cells that are susceptible to failure. Here, we investigated the time-dependent gene expression changes in islets of diabetes-prone db/db and diabetes-resistant ob/ob mice. The expressions of adaptive unfolded protein response (UPR) genes were progressively induced in islets of ob/ob mice, whereas they declined in diabetic db/db mice. Genes important for β-cell function and maintenance of the islet phenotype were reduced with time in db/db mice, whereas they were preserved in ob/ob mice. Inflammation and antioxidant genes displayed time-dependent upregulation in db/db islets but were unchanged in ob/ob islets. Treatment of db/db mouse islets with the chemical chaperone 4-phenylbutyric acid partially restored the changes in several β-cell function genes and transcription factors but did not affect inflammation or antioxidant gene expression. These data suggest that the maintenance (or suppression) of the adaptive UPR is associated with β-cell compensation (or failure) in obese mice. Inflammation, oxidative stress, and a progressive loss of β-cell differentiation accompany diabetes progression. The ability to maintain the adaptive UPR in islets may protect against the gene expression changes that underlie diabetes development in obese mice.
BDNF Action in the Brain Attenuates Diabetic Hyperglycemia via Insulin-Independent Inhibition of Hepatic Glucose Production
Authors: Meek Thomas H. , Wisse Brent E. , Thaler Joshua P. , Guyenet Stephan J. , Matsen Miles E. , Fischer Jonathan D. , Taborsky Gerald J. , Schwartz Michael W. , Morton Gregory J.
Published: December 2012

Recent evidence suggests that central leptin administration fully normalizes hyperglycemia in a rodent model of uncontrolled insulin-deficient diabetes by reducing hepatic glucose production (HGP) and by increasing glucose uptake. The current studies were undertaken to determine whether brain-derived neurotrophic factor (BDNF) action in the brain lowers blood glucose in uncontrolled insulin-deficient diabetes and to investigate the mechanisms mediating this effect. Adult male rats implanted with cannulas to either the lateral cerebral ventricle or the ventromedial hypothalamic nucleus (VMN) received either vehicle or streptozotocin to induce uncontrolled insulin-deficient diabetes. Three days later, animals received daily intracerebroventricular or intra-VMN injections of either BDNF or its vehicle. We found that repeated daily intracerebroventricular administration of BDNF attenuated diabetic hyperglycemia independent of changes in food intake. Instead, using tracer dilution techniques during a basal clamp, we found that BDNF lowered blood glucose levels by potently suppressing HGP, without affecting tissue glucose uptake, an effect associated with normalization of both plasma glucagon levels and hepatic expression of gluconeogenic genes. Moreover, BDNF microinjection directly into the VMN also lowered fasting blood glucose levels in uncontrolled insulin-deficient diabetes, but this effect was modest compared with intracerebroventricular administration. We conclude that central nervous system BDNF attenuates diabetic hyperglycemia via an insulin-independent mechanism. This action of BDNF likely involves the VMN and is associated with inhibition of glucagon secretion and a decrease in the rate of HGP.
Genetic and Molecular Insights Into the Role of PROX1 in Glucose Metabolism
Authors: Lecompte Sophie , Pasquetti Gianni , Hermant Xavier , Grenier-Boley Benjamin , Gonzalez-Gross Marcela , De Henauw Stephan , Molnar Denes , Stehle Peter , Béghin Laurent , Moreno Luis A. , Amouyel Philippe , Dallongeville Jean , Meirhaeghe Aline
Published: December 2012

Genome-wide association studies have shown that the rs340874 single nucleotide polymorphism (SNP) in PROX1 is a genetic susceptibility factor for type 2 diabetes. We conducted genetic and molecular studies to better understand the role of PROX1 in type 2 diabetes. We assessed the impact of the whole common genetic variability of PROX1 (80 SNPs) on type 2 diabetes–related biochemical traits in the HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) study (n = 1,155). Three SNPs (rs340838, rs340837, and rs340836) were significantly associated with fasting plasma insulin levels (P ≤ 0.00295). We evaluated the impact of nine PROX1 SNPs (the three insulin-associated SNPs plus six SNPs in strong linkage disequilibrium) on luciferase reporter gene expression. The insulin-lowering alleles of rs340874, rs340873, and rs340835 were associated with lower luciferase activity in MIN6 and HepG2 cells (except for rs340874, which was in HepG2 cells only). Electrophoretic mobility shift assays indicated that specific nuclear protein bindings occur at the three SNPs in HepG2 cells, with allele-binding differences for rs340874. We also showed that the knockdown of Prox1 expression by small interfering RNAs in INS-1E cells resulted in a 1.7-fold reduction in glucose-stimulated insulin secretion. All together, we propose that reduced expression of PROX1 by cis-regulatory variants results in altered β-cell insulin secretion and thereby confers susceptibility to type 2 diabetes.
Mutations in HNF1A Result in Marked Alterations of Plasma Glycan Profile
Authors: Thanabalasingham Gaya , Huffman Jennifer E. , Kattla Jayesh J. , Novokmet Mislav , Rudan Igor , Gloyn Anna L. , Hayward Caroline , Adamczyk Barbara , Reynolds Rebecca M. , Muzinic Ana , Hassanali Neelam , Pucic Maja , Bennett Amanda J. , Essafi Abdelkader , Polasek Ozren , Mughal Saima A. , Redzic Irma , Primorac Dragan , Zgaga Lina , Kolcic Ivana , Hansen Torben , Gasperikova Daniela , Tjora Erling , Strachan Mark W.J. , Nielsen Trine , Stanik Juraj , Klimes Iwar , Pedersen Oluf B. , Njølstad Pål R. , Wild Sarah H. , Gyllensten Ulf , Gornik Olga , Wilson James F. , Hastie Nicholas D. , Campbell Harry , McCarthy Mark I. , Rudd Pauline M. , Owen Katharine R. , Lauc Gordan , Wright Alan F.
Published: December 2012

A recent genome-wide association study identified hepatocyte nuclear factor 1-α (HNF1A) as a key regulator of fucosylation. We hypothesized that loss-of-function HNF1A mutations causal for maturity-onset diabetes of the young (MODY) would display altered fucosylation of N-linked glycans on plasma proteins and that glycan biomarkers could improve the efficiency of a diagnosis of HNF1A-MODY. In a pilot comparison of 33 subjects with HNF1A-MODY and 41 subjects with type 2 diabetes, 15 of 29 glycan measurements differed between the two groups. The DG9-glycan index, which is the ratio of fucosylated to nonfucosylated triantennary glycans, provided optimum discrimination in the pilot study and was examined further among additional subjects with HNF1A-MODY (n = 188), glucokinase (GCK)-MODY (n = 118), hepatocyte nuclear factor 4-α (HNF4A)-MODY (n = 40), type 1 diabetes (n = 98), type 2 diabetes (n = 167), and nondiabetic controls (n = 98). The DG9-glycan index was markedly lower in HNF1A-MODY than in controls or other diabetes subtypes, offered good discrimination between HNF1A-MODY and both type 1 and type 2 diabetes (C statistic ≥0.90), and enabled us to detect three previously undetected HNF1A mutations in patients with diabetes. In conclusion, glycan profiles are altered substantially in HNF1A-MODY, and the DG9-glycan index has potential clinical value as a diagnostic biomarker of HNF1A dysfunction.
Nogo-A Downregulation Improves Insulin Secretion in Mice
Authors: Bonal Claire B. , Baronnier Delphine E. , Pot Caroline , Benkhoucha Mahdia , Schwab Martin E. , Lalive Patrice H. , Herrera Pedro L.
Published: December 2012

Type 2 diabetes (T2D) is characterized by β-cell dysfunction and the subsequent depletion of insulin production, usually in a context of increased peripheral insulin resistance. T2D patients are routinely treated with oral antidiabetic agents such as sulfonylureas or dipeptidyl peptidase-4 antagonists, which promote glucose- and incretin-dependent insulin secretion, respectively. Interestingly, insulin secretion may also be induced by neural stimulation. Here we report the expression of Nogo-A in β-cells. Nogo-A is a membrane protein that inhibits neurite outgrowth and cell migration in the central nervous system. We observed that Nogo-A–deficient mice display improved insulin secretion and glucose clearance. This was associated with a stronger parasympathetic input and higher sensitivity of β-cells to the cholinergic analog carbachol. Insulin secretion was also improved in diabetic db/db mice treated with neutralizing antibody against Nogo-A. Together, these findings suggest that promoting the vagal stimulation of insulin secretion through the selective inhibition of Nogo-A could be a novel therapeutic approach in T2D.
EphA5-EphrinA5 Interactions Within the Ventromedial Hypothalamus Influence Counterregulatory Hormone Release and Local Glutamine/Glutamate Balance During Hypoglycemia
Authors: Szepietowska Barbara , Zhu Wanling , Czyzyk Jan , Eid Tore , Sherwin Robert S.
Published: December 2012

Activation of β-cell EphA5 receptors by its ligand ephrinA5 from adjacent β-cells has been reported to decrease insulin secretion during hypoglycemia. Given the similarities between islet and ventromedial hypothalamus (VMH) glucose sensing, we tested the hypothesis that the EphA5/ephrinA5 system might function within the VMH during hypoglycemia to stimulate counterregulatory hormone release as well. Counterregulatory responses and glutamine/glutamate concentrations in the VMH were assessed during a hyperinsulinemic-hypoglycemic glucose clamp study in chronically catheterized awake male Sprague-Dawley rats that received an acute VMH microinjection of ephrinA5-Fc, chronic VMH knockdown, or overexpression of ephrinA5 using an adenoassociated viral construct. Local stimulation of VMH EphA5 receptors by ephrinA5-Fc or ephrinA5 overexpression increased, whereas knockdown of VMH ephrinA5 reduced counterregulatory responses during hypoglycemia. Overexpression of VMH ephrinA5 transiently increased local glutamate concentrations, whereas ephrinA5 knockdown produced profound suppression of VMH interstitial fluid glutamine concentrations in the basal state and during hypoglycemia. Changes in ephrinA5/EphA5 interactions within the VMH, a key brain glucose-sensing region, act in concert with islets to restore glucose homeostasis during acute hypoglycemia, and its effect on counterregulation may be mediated by changes in glutamate/glutamine cycling.
Permanent Neonatal Diabetes inINSC94Y Transgenic Pigs
Authors: Renner Simone , Braun-Reichhart Christina , Blutke Andreas , Herbach Nadja , Emrich Daniela , Streckel Elisabeth , Wünsch Annegret , Kessler Barbara , Kurome Mayuko , Bähr Andrea , Klymiuk Nikolai , Krebs Stefan , Puk Oliver , Nagashima Hiroshi , Graw Jochen , Blum Helmut , Wanke Ruediger , Wolf Eckhard
Published: December 2012

Mutations in the insulin (INS) gene may cause permanent neonatal diabetes mellitus (PNDM). Ins2 mutant mouse models provided important insights into the disease mechanisms of PNDM but have limitations for translational research. To establish a large animal model of PNDM, we generated INSC94Y transgenic pigs. A line expressing high levels of INSC94Y mRNA (70–86% of wild-type INS transcripts) exhibited elevated blood glucose soon after birth but unaltered β-cell mass at the age of 8 days. At 4.5 months, INSC94Y transgenic pigs exhibited 41% reduced body weight, 72% decreased β-cell mass (−53% relative to body weight), and 60% lower fasting insulin levels compared with littermate controls. β-cells of INSC94Y transgenic pigs showed a marked reduction of insulin secretory granules and severe dilation of the endoplasmic reticulum. Cataract development was already visible in 8-day-old INSC94Y transgenic pigs and became more severe with increasing age. Diabetes-associated pathological alterations of kidney and nervous tissue were not detected during the observation period of 1 year. The stable diabetic phenotype and its rescue by insulin treatment make the INSC94Y transgenic pig an attractive model for insulin supplementation and islet transplantation trials, and for studying developmental consequences of maternal diabetes mellitus.
Electrical Stimuli Release ATP to Increase GLUT4 Translocation and Glucose Uptake via PI3Kγ-Akt-AS160 in Skeletal Muscle Cells
Authors: Osorio-Fuentealba Cesar , Contreras-Ferrat Ariel E. , Altamirano Francisco , Espinosa Alejandra , Li Qing , Niu Wenyan , Lavandero Sergio , Klip Amira , Jaimovich Enrique
Published: December 2012

Skeletal muscle glucose uptake in response to exercise is preserved in insulin-resistant conditions, but the signals involved are debated. ATP is released from skeletal muscle by contractile activity and can autocrinely signal through purinergic receptors, and we hypothesized it may influence glucose uptake. Electrical stimulation, ATP, and insulin each increased fluorescent 2-NBD-Glucose (2-NBDG) uptake in primary myotubes, but only electrical stimulation and ATP-dependent 2-NBDG uptake were inhibited by adenosine-phosphate phosphatase and by purinergic receptor blockade (suramin). Electrical stimulation transiently elevated extracellular ATP and caused Akt phosphorylation that was additive to insulin and inhibited by suramin. Exogenous ATP transiently activated Akt and, inhibiting phosphatidylinositol 3-kinase (PI3K) or Akt as well as dominant-negative Akt mutant, reduced ATP-dependent 2-NBDG uptake and Akt phosphorylation. ATP-dependent 2-NBDG uptake was also inhibited by the G protein βγ subunit-interacting peptide βark-ct and by the phosphatidylinositol 3-kinase-γ (PI3Kγ) inhibitor AS605240. ATP caused translocation of GLUT4myc-eGFP to the cell surface, mechanistically mediated by increased exocytosis involving AS160/Rab8A reduced by dominant-negative Akt or PI3Kγ kinase-dead mutants, and potentiated by myristoylated PI3Kγ. ATP stimulated 2-NBDG uptake in normal and insulin-resistant adult muscle fibers, resembling the reported effect of exercise. Hence, the ATP-induced pathway may be tapped to bypass insulin resistance.
G6PC2: A Negative Regulator of Basal Glucose-Stimulated Insulin Secretion
Authors: Pound Lynley D. , Oeser James K. , O’Brien Tracy P. , Wang Yingda , Faulman Chandler J. , Dadi Prasanna K. , Jacobson David A. , Hutton John C. , McGuinness Owen P. , Shiota Masakazu , O’Brien Richard M.
Published: December 2012

Elevated fasting blood glucose (FBG) is associated with increased risk for the development of type 2 diabetes and cardiovascular-associated mortality. Genome-wide association studies (GWAS) have linked polymorphisms in G6PC2 with variations in FBG and body fat, although not insulin sensitivity or glucose tolerance. G6PC2 encodes an islet-specific, endoplasmic reticulum–resident glucose-6-phosphatase catalytic subunit. A combination of in situ perfused pancreas, in vitro isolated islet, and in vivo analyses were used to explore the function of G6pc2 in mice. G6pc2 deletion had little effect on insulin sensitivity and glucose tolerance, whereas body fat was reduced in female G6pc2 knockout (KO) mice on both a chow and high-fat diet, observations that are all consistent with human GWAS data. G6pc2 deletion resulted in a leftward shift in the dose-response curve for glucose-stimulated insulin secretion (GSIS). As a consequence, under fasting conditions in which plasma insulin levels were identical, blood glucose levels were reduced in G6pc2 KO mice, again consistent with human GWAS data. Glucose-6-phosphatase activity was reduced, whereas basal cytoplasmic calcium levels were elevated in islets isolated from G6pc2 KO mice. These data suggest that G6pc2 represents a novel, negative regulator of basal GSIS that acts by hydrolyzing glucose-6-phosphate, thereby reducing glycolytic flux.
Dietary Proteins Contribute Little to Glucose Production, Even Under Optimal Gluconeogenic Conditions in Healthy Humans
Authors: Fromentin Claire , Tomé Daniel , Nau Françoise , Flet Laurent , Luengo Catherine , Azzout-Marniche Dalila , Sanders Pascal , Fromentin Gilles , Gaudichon Claire
Published: December 2012

Dietary proteins are believed to participate significantly in maintaining blood glucose levels, but their contribution to endogenous glucose production (EGP) remains unclear. We investigated this question using multiple stable isotopes. After overnight fasting, eight healthy volunteers received an intravenous infusion of [6,6-2H2]-glucose. Two hours later, they ingested four eggs containing 23 g of intrinsically, uniformly, and doubly [15N]-[13C]–labeled proteins. Gas exchanges, expired CO2, blood, and urine were collected over the 8 h following egg ingestion. The cumulative amount of dietary amino acids (AAs) deaminated over this 8-h period was 18.1 ± 3.5%, 17.5% of them being oxidized. The EGP remained stable for 6 h but fell thereafter, concomitantly with blood glucose levels. During the 8 h after egg ingestion, 50.4 ± 7.7 g of glucose was produced, but only 3.9 ± 0.7 g originated from dietary AA. Our results show that the total postprandial contribution of dietary AA to EGP was small in humans habituated to a diet medium-rich in proteins, even after an overnight fast and in the absence of carbohydrates from the meal. These findings question the respective roles of dietary proteins and endogenous sources in generating significant amounts of glucose in order to maintain blood glucose levels in healthy subjects.
Congenital Hyperinsulinism Caused by Hexokinase I Expression or Glucokinase-Activating Mutation in a Subset of β-Cells
Authors: Henquin Jean-Claude , Sempoux Christine , Marchandise Joelle , Godecharles Sebastien , Guiot Yves , Nenquin Myriam , Rahier Jacques
Published: December 2012

Congenital hyperinsulinism causes persistent hypoglycemia in neonates and infants. Most often, uncontrolled insulin secretion (IS) results from a lack of functional KATP channels in all β-cells or only in β-cells within a resectable focal lesion. In more rare cases, without KATP channel mutations, hyperfunctional islets are confined within few lobules, whereas hypofunctional islets are present throughout the pancreas. They also can be cured by selective partial pancreatectomy; however, unlike those with a KATP focal lesion, they show clinical sensitivity to diazoxide. Here, we characterized in vitro IS by fragments of pathological and adjacent normal pancreas from six such cases. Responses of normal pancreas were unremarkable. In pathological region, IS was elevated at 1 mmol/L and was further increased by 15 mmol/L glucose. Diazoxide suppressed IS and tolbutamide antagonized the inhibition. The most conspicuous anomaly was a large stimulation of IS by 1 mmol/L glucose. In five of six cases, immunohistochemistry revealed undue presence of low-Km hexokinase-I in β-cells of hyperfunctional islets only. In one case, an activating mutation of glucokinase (I211F) was found in pathological islets only. Both abnormalities, attributed to somatic genetic events, may account for inappropriate IS at low glucose levels by a subset of β-cells. They represent a novel cause of focal congenital hyperinsulinism.
Stimulation of Autophagy Improves Endoplasmic Reticulum Stress–Induced Diabetes
Authors: Bachar-Wikstrom Etty , Wikstrom Jakob D. , Ariav Yafa , Tirosh Boaz , Kaiser Nurit , Cerasi Erol , Leibowitz Gil
Published: December 2012

Accumulation of misfolded proinsulin in the β-cell leads to dysfunction induced by endoplasmic reticulum (ER) stress, with diabetes as a consequence. Autophagy helps cellular adaptation to stress via clearance of misfolded proteins and damaged organelles. We studied the effects of proinsulin misfolding on autophagy and the impact of stimulating autophagy on diabetes progression in Akita mice, which carry a mutation in proinsulin, leading to its severe misfolding. Treatment of female diabetic Akita mice with rapamycin improved diabetes, increased pancreatic insulin content, and prevented β-cell apoptosis. In vitro, autophagic flux was increased in Akita β-cells. Treatment with rapamycin further stimulated autophagy, evidenced by increased autophagosome formation and enhancement of autophagosome–lysosome fusion. This was associated with attenuation of cellular stress and apoptosis. The mammalian target of rapamycin (mTOR) kinase inhibitor Torin1 mimicked the rapamycin effects on autophagy and stress, indicating that the beneficial effects of rapamycin are indeed mediated via inhibition of mTOR. Finally, inhibition of autophagy exacerbated stress and abolished the anti-ER stress effects of rapamycin. In conclusion, rapamycin reduces ER stress induced by accumulation of misfolded proinsulin, thereby improving diabetes and preventing β-cell apoptosis. The beneficial effects of rapamycin in this context strictly depend on autophagy; therefore, stimulating autophagy may become a therapeutic approach for diabetes.
Neighborhood Deprivation and Change in BMI Among Adults With Type 2 Diabetes
Authors: Stoddard Pamela J. , Laraia Barbara A. , Warton E. Margaret , Moffet Howard H. , Adler Nancy E. , Schillinger Dean , Karter Andrew J.
Published: December 2012

OBJECTIVE

To compare associations between neighborhood deprivation and measures of BMI change among adults with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Using data from the Kaiser Permanente Diabetes Study of Northern California (DISTANCE) survey, we estimated the association between neighborhood deprivation and two measures of BMI change over 3 years: 1) a continuous measure and 2) a categorical measure of clinically substantive BMI loss or gain (≥7% of baseline BMI) versus stable BMI. The sample included 13,609 adults.

RESULTS

On average, there was little change in BMI (−0.12, SD 3.07); 17.0 and 16.1% had clinically substantive BMI loss or gain, respectively, at follow-up. There was a positive association between neighborhood deprivation and BMI change for adults in the most versus least-deprived quartile of neighborhood deprivation (β = 0.22, P = 0.02) in adjusted models. In addition, relative to the least-deprived quartile (Q1), adults in more-deprived quartiles of neighborhood deprivation were more likely to experience either substantive BMI loss (Q2 relative risk ratio 1.19, 95% CI 1.00–1.41; Q3 1.20, 1.02–1.42; Q4 1.30, 1.08–1.55) or gain (Q2 1.25, 1.04–1.49; Q3 1.24, 1.04–1.49; Q4 1.45, 1.20–1.75).

CONCLUSIONS

Greater neighborhood deprivation was positively associated with BMI change among adults with diabetes as well as with clinically substantive BMI loss or gain. Findings stress the importance of allowing for simultaneous associations with both gain and loss in future longitudinal studies of neighborhood deprivation and weight change, which may be particularly true for studies of patients with diabetes for whom both weight loss and gain have health implications.
A Comparative Effectiveness Analysis of Three Continuous Glucose Monitors
Authors: Damiano Edward R. , El-Khatib Firas H. , Zheng Hui , Nathan David M. , Russell Steven J.
Published: December 2012

OBJECTIVE

To compare three continuous glucose monitoring (CGM) devices in subjects with type 1 diabetes under closed-loop blood glucose (BG) control.

RESEARCH DESIGN AND METHODS

Six subjects with type 1 diabetes (age 52 ± 14 years, diabetes duration 32 ± 14 years) each participated in two 51-h closed-loop BG control experiments in the hospital. Venous plasma glucose (PG) measurements (GlucoScout, International Biomedical) obtained every 15 min (2,360 values) were paired in time with corresponding CGM glucose (CGMG) measurements obtained from three CGM devices, the Navigator (Abbott Diabetes Care), the Seven Plus (DexCom), and the Guardian (Medtronic), worn simultaneously by each subject. Errors in paired PG–CGMG measurements and data reporting percentages were obtained for each CGM device.

RESULTS

The Navigator had the best overall accuracy, with an aggregate mean absolute relative difference (MARD) of all paired points of 11.8 ± 11.1% and an average MARD across all 12 experiments of 11.8 ± 3.8%. The Seven Plus and Guardian produced aggregate MARDs of all paired points of 16.5 ± 17.8% and 20.3 ± 18.0%, respectively, and average MARDs across all 12 experiments of 16.5 ± 6.7% and 20.2 ± 6.8%, respectively. Data reporting percentages, a measure of reliability, were 76% for the Seven Plus and nearly 100% for the Navigator and Guardian.

CONCLUSIONS

A comprehensive head-to-head-to-head comparison of three CGM devices for BG values from 36 to 563 mg/dL revealed marked differences in performance characteristics that include accuracy, precision, and reliability. The Navigator outperformed the other two in these areas.
Prospective Study of Serum Adiponectin and Incident Metabolic Syndrome
Authors: Kim Jang-Young , Ahn Song Vogue , Yoon Jin-Ha , Koh Sang-Baek , Yoon Junghan , Yoo Byung-Su , Lee Seung-Hwan , Park Jong-Ku , Choe Kyung-Hoon , Guallar Eliseo
Published: December 2012

OBJECTIVE

Increased adiponectin levels may play a protective role in the development of metabolic abnormalities, but prospective studies of the predictive value of serum adiponectin to identify individuals at high risk of new-onset metabolic syndrome are lacking. We investigated whether serum adiponectin predicts incident cases of the metabolic syndrome in a population-based longitudinal study.

RESEARCH DESIGN AND METHODS

A prospective cohort study was conducted of 2,044 adults (831 men and 1,213 women) aged 40–70 years without metabolic syndrome examined in 2005–2008 (baseline) and 2008–2011 (follow-up). Baseline serum adiponectin concentrations were measured by radioimmunoassay.

RESULTS

During an average of 2.6 years of follow-up, 153 men (18.4%) and 199 women (16.4%) developed metabolic syndrome. In multivariable-adjusted models, the odds ratio for incident metabolic syndrome comparing the highest with the lowest quartiles of adiponectin levels was 0.25 (95% CI 0.14–0.47) in men and 0.45 (0.28–0.74) in women. While serum adiponectin did not improve the area under the ROC curve for predicting new-onset metabolic syndrome based on information from metabolic syndrome components, the net reclassification improvement and the integrated discrimination improvement of prediction models including adiponectin were significantly higher compared with those of models not including adiponectin among men, with a significant difference between men and women (P = 0.001).

CONCLUSIONS

Increased adiponectin is an independent protective factor for incident metabolic syndrome in men and women, and it may have a clinical role in predicting new-onset metabolic syndrome among men.
Patterns of Insulin Concentration During the OGTT Predict the Risk of Type 2 Diabetes in Japanese Americans
Authors: Hayashi Tomoshige , Boyko Edward J. , Sato Kyoko Kogawa , McNeely Marguerite J. , Leonetti Donna L. , Kahn Steven E. , Fujimoto Wilfred Y.
Published: December 2012

OBJECTIVE

To examine whether the patterns of insulin concentration during the oral glucose tolerance test (OGTT) predict type 2 diabetes.

RESEARCH DESIGN AND METHODS

We followed 400 nondiabetic Japanese Americans for 10–11 years. Insulin concentrations at 30, 60, and 120 min during a 2-h 75-g OGTT at baseline were used to derive the following possible patterns of insulin: pattern 1 (30-min peak, higher insulin level at 60 than at 120 min), pattern 2 (30-min peak, lower or equal level at 60 vs. 120 min), pattern 3 (60-min peak); pattern 4 (120-min peak, lower level at 30 than at 60 min), and pattern 5 (120-min peak, equal or higher level at 30 vs. 60 min). Insulin sensitivity was estimated by homeostasis model assessment of insulin resistance (HOMA-IR) and Matsuda index. Insulin secretion was estimated by the insulinogenic index (IGI) [Δinsulin/Δglucose (30–0 min)] and disposition index (IGI/HOMA-IR).

RESULTS

There were 86 incident cases of type 2 diabetes. The cumulative incidence was 3.2, 9.8, 15.4, 47.8, and 37.5% for patterns 1, 2, 3, 4, and 5, respectively. Compared with pattern 1, patterns 4 and 5, characterized by a lasting late insulin response, were associated with significantly less insulin sensitivity as measured by the Matsuda index and lower early insulin response by the disposition index. The multiple-adjusted odds ratios of type 2 diabetes were 12.55 (95% CI 4.79–32.89) for pattern 4 and 8.34 (2.38–29.27) for pattern 5 compared with patterns 1 and 2. This association was independent of insulin secretion and sensitivity.

CONCLUSIONS

The patterns of insulin concentration during an OGTT strongly predict the development of type 2 diabetes.