Recent Publications of BIIC Members

Subscribe to Recent Publications of BIIC Members feed Recent Publications of BIIC Members
NCBI: db=pubmed; Term=Gray JP OR Heart E OR Zarrouki B OR Corkey BE OR Bonner-Weir S OR Urano F OR Cline GW OR Sharp GW OR Holz GG OR Weir GC OR Kulkarni RN OR Tornheim K OR Kibbey RG OR Fonseca SG OR Straub SG OR Jetton TL OR Poitout V OR Prentki M
Updated: 2 days 10 hours ago

Maternal uniparental disomy of chromosome 4 and homozygous novel mutation in the WFS1 gene in a paediatric patient with Wolfram syndrome.

Thu, 07/16/2015 - 07:49
Related Articles

Maternal uniparental disomy of chromosome 4 and homozygous novel mutation in the WFS1 gene in a paediatric patient with Wolfram syndrome.

Diabetes Metab. 2015 Jul 10;

Authors: Papadimitriou DT, Manolakos E, Bothou C, Zoupanos G, Papoulidis I, Orru S, Skarmoutsos F, Delides A, Bakoula C, Papadimitriou A, Urano F

PMID: 26169481 [PubMed - as supplied by publisher]

β-arrestin recruitment and biased agonism at free fatty acid receptor 1.

Mon, 07/13/2015 - 04:52

β-arrestin recruitment and biased agonism at free fatty acid receptor 1.

J Biol Chem. 2015 Jul 8;

Authors: Mancini A, Bertrand G, Vivot K, Carpentier É, Tremblay C, Ghislain J, Bouvier M, Poitout V

Abstract
FFAR1/GPR40 is a seven-transmembrane domain receptor (7TMR) expressed in pancreatic β-cells and activated by free fatty acids (FFAs). Pharmacological activation of GPR40 is a strategy under consideration to increase insulin secretion in type 2 diabetes (T2D). GPR40 is known to signal predominantly via the heterotrimeric G proteins Gq/11. However, 7TMRs can also activate functionally distinct G protein-independent signaling via β-arrestins. Further, G protein- and β-arrestin-based signaling can be differentially modulated by different ligands, thus eliciting ligand-specific responses ("biased agonism"). Whether GPR40 engages β-arrestin-dependent mechanisms and is subject to biased agonism is unknown. Using BRET-based biosensors for real-time monitoring of cell signaling in living cells, we detected a ligand-induced GPR40:β-arrestin interaction, with the synthetic GPR40 agonist TAK-875 being more effective than palmitate or oleate in recruiting β-arrestins 1 and 2. Conversely, TAK-875 acted as a partial agonist of Gq/11-dependent GPR40 signaling relative to both FFAs. Pharmacological blockade of Gq activity decreased FFA-induced insulin secretion. In contrast, knockdown or genetic ablation of β-arrestin 2 in an insulin-secreting cell line and mouse pancreatic islets, respectively, uniquely attenuated TAK-875's insulinotropic activity, thus providing functional validation of the biosensor data. Collectively, these data reveal that in addition to coupling to Gq/11, GPR40 is functionally linked to a β-arrestin 2-mediated insulinotropic signaling axis. These observations expose previously unrecognized complexity for GPR40 signal transduction and may guide the development of biased agonists showing improved clinical profile in T2D.

PMID: 26157145 [PubMed - as supplied by publisher]

Phenotypic characterization of MIP-CreERT1Lphi mice with transgene-driven islet expression of human growth hormone.

Mon, 07/13/2015 - 04:52

Phenotypic characterization of MIP-CreERT1Lphi mice with transgene-driven islet expression of human growth hormone.

Diabetes. 2015 Jul 7;

Authors: Oropeza D, Jouvet N, Budry L, Campbell JE, Bouyakdan K, Lacombe J, Perron G, Bergeron V, Neuman JC, Brar HK, Fenske RJ, Meunier C, Sczelecki S, Kimple ME, Drucker DJ, Screaton RA, Poitout V, Ferron M, Alquier T, Estall JL

Abstract
There is growing concern over confounding artifacts associated with β-cell-specific Cre-recombinase transgenic models, raising questions about their general usefulness in research. The inducible β-cell-specific transgenic (MIP-CreERT(1Lphi)) mouse was designed to circumvent many of these issues and we investigated whether this tool effectively addressed concerns of ectopic expression and disruption of glucose metabolism. Recombinase activity was absent from the CNS using a reporter line and high-resolution microscopy. Despite increased pancreatic insulin content, MIP-CreERT mice on chow diet exhibited normal ambient glycaemia, glucose tolerance, insulin sensitivity, and appropriate insulin secretion in response to glucose in vivo and in vitro. However, MIP-CreERT mice on different genetic backgrounds were protected from high-fat/STZ-induced hyperglycemia that was accompanied by increased insulin content and islet density. Ectopic human growth hormone (hGH) was highly expressed in MIP-CreERT islets independent of tamoxifen administration. Circulating insulin levels remained similar to WT controls, whereas STZ-associated increases in α-cell number and serum glucagon were significantly blunted in MIP-CreERT(1Lphi) mice, possibly due to paracrine effects of hGH-induced serotonin expression. These studies reveal important new insight into the strengths and limitations of the MIP-CreERT mouse line for β-cell research.

PMID: 26153246 [PubMed - as supplied by publisher]

Compensatory Islet Response to Insulin Resistance Revealed by Quantitative Proteomics.

Fri, 07/10/2015 - 03:00

Compensatory Islet Response to Insulin Resistance Revealed by Quantitative Proteomics.

J Proteome Res. 2015 Jul 7;

Authors: El Ouaamari A, Zhou J, Liew CW, Shirakawa J, Dirice E, Gedeon N, Kahraman S, De Jesus DF, Bhatt S, Kim JS, Clauss TR, Camp DG, Smith RD, Qian WJ, Kulkarni RN

Abstract
Compensatory islet response is a distinct feature of the pre-diabetic insulin resistant state in humans and rodents. To identify alterations in the islet proteome that characterize the adaptive response, we analyzed islets from five-month-old male control, high-fat diet fed (HFD) or obese ob/ob mice by LC-MS(/MS) and quantified ~1,100 islet proteins (at least two peptides) with a false discovery rate <1%. Significant alterations in abundance were observed for ~350 proteins between groups. A majority of alterations were common to both models, and the changes of a subset of ~40 proteins and 12 proteins were verified by targeted quantification using selected reaction monitoring and Western blots, respectively. The insulin resistant islets in both groups exhibited reduced expression of proteins controlling energy metabolism, oxidative phosphorylation, hormone processing, and secretory pathways. Conversely, an increased expression of molecules involved in protein synthesis and folding suggested effects in endoplasmic reticulum stress response, cell survival, and proliferation in both insulin resistant models. In summary, we report a unique comparison of the islet proteome that is focused on the compensatory response in two insulin resistant rodent models that are not overtly diabetic. These data provide a valuable resource of candidate proteins to the scientific community to undertake further studies aimed at enhancing β-cell mass in patients with diabetes. The data are available via the MassIVE repository, with accession MSV000079093.

PMID: 26151086 [PubMed - as supplied by publisher]

Multiple approaches for increasing the immunogenicity of an epitope-based anti-HIV vaccine.

Fri, 07/10/2015 - 03:00

Multiple approaches for increasing the immunogenicity of an epitope-based anti-HIV vaccine.

AIDS Res Hum Retroviruses. 2015 Jul 6;

Authors: Rosa DS, Ribeiro SP, Fonseca SG, Almeida RR, Santana VC, Apostólico JS, Kalil JE, Cunha-Neto E

Abstract
The development of a highly effective vaccine against the human immunodeficiency virus (HIV) will likely be based on rational vaccine design since traditional vaccine approaches had failed so far. In the last years, an understanding of what type of immune response is protective against infection and/or disease facilitated vaccine design. T-cell based vaccines against HIV have the goal of limiting both transmission and disease progression by inducing broad and functionally relevant T cell responses. In this context, CD4+ T cells play a direct cytotoxic role and are also important for generation and maintenance of functional CD8+ T and B cell responses. The use of MHC-binding algorithms has allowed the identification of novel CD4+ T cell epitopes that could be used in vaccine design, the so-called epitope-driven vaccine design. Epitope-based vaccines have the ability to focus the immune response on highly antigenic, conserved epitopes that are fully recognized by the target population. We have recently mapped a set of conserved multiple HLA-DR-binding HIV-1 CD4 epitopes and observed IFN-γ producing CD4+ T cells when we tested these peptides in PBMC from HIV-infected individuals. We then designed multiepitopic DNA vaccines that induced broad and polyfunctional T cell responses in immunized mice. In this review we will focus on alternative strategies to increase the immunogenicity of an epitope-based vaccine against HIV infection.

PMID: 26149745 [PubMed - as supplied by publisher]

Multi-Wavelength Photoacoustic Visualization of High Intensity Focused Ultrasound Lesions.

Fri, 07/10/2015 - 03:00

Multi-Wavelength Photoacoustic Visualization of High Intensity Focused Ultrasound Lesions.

Ultrason Imaging. 2015 Jul 5;

Authors: Gray JP, Dana N, Dextraze KL, Maier F, Emelianov S, Bouchard RR

Abstract
High intensity focused ultrasound (HIFU) thermal therapies are limited by deficiencies in existing image-guidance techniques. Previous studies using single-wavelength photoacoustic (PA) imaging have demonstrated that HIFU lesions generate contrast with respect to native tissues but have not sufficiently assessed lesion extent. The purpose of this study is to demonstrate feasibility of characterization of in vitro HIFU ablation lesion dimensions using 3D multi-wavelength PA imaging. Fresh porcine cardiac and liver tissue samples were embedded in agar phantoms and ablated using a 2.5 MHz small-animal HIFU system. Both 2D and 3D multi-wavelength photoacoustic-ultrasonic (PAUS) scans were performed in the near-infrared (NIR) range to characterize the change in the absorption spectrum of tissues following ablation and were compared to stained gross pathology to assess treatment margins and lesion extent. Comprehensive 2D multi-wavelength PA imaging yielded a spectrum in ablated tissue that did not display the characteristic local maximum in the optical absorption spectrum of deoxy-hemoglobin (Hb) near 760 nm. Two-dimensional tissue characterization map (TCM) images reconstructed from 3D TCM volumes reliably characterized lesion area and showed >70% area agreement with stained gross pathology. In addition, tissue samples were heated via water bath and concurrently interrogated with 2D PAUS imaging. PA signal exhibited an initial amplitude increase across all wavelengths, corresponding to an initial temperature increase, before then exhibiting a spectral change. This study suggests that multi-wavelength PA imaging has potential to obtain accurate characterization of HIFU lesion extent and may be better suited to guide HIFU ablation therapies during clinical treatments than single-wavelength methods.

PMID: 26149314 [PubMed - as supplied by publisher]

IRE1 prevents endoplasmic reticulum membrane permeabilization and cell death under pathological conditions.

Sat, 06/27/2015 - 21:15
Related Articles

IRE1 prevents endoplasmic reticulum membrane permeabilization and cell death under pathological conditions.

Sci Signal. 2015;8(382):ra62

Authors: Kanekura K, Ma X, Murphy JT, Zhu LJ, Diwan A, Urano F

Abstract
The endoplasmic reticulum (ER) has emerged as a critical regulator of cell survival. IRE1 is a transmembrane protein with kinase and RNase activities that is localized to the ER and that promotes resistance to ER stress. We showed a mechanism by which IRE1 conferred protection against ER stress-mediated cell death. IRE1 signaling prevented ER membrane permeabilization mediated by Bax and Bak and cell death in cells experiencing ER stress. Suppression of IRE1 signaling triggered by its kinase activity led to the accumulation of the BH3 domain-containing protein Bnip3, which in turn triggered the oligomerization of Bax and Bak in the ER membrane and ER membrane permeabilization. Consequently, in response to ER stress, cells deficient in IRE1 were susceptible to leakage of ER contents, which was associated with the accumulation of calcium in mitochondria, oxidative stress in the cytosol, and ultimately cell death. Our results reveal a role for IRE1 in preventing a cell death-initializing step that emanates from the ER and provide a potential target for treating diseases characterized by ER stress, including diabetes and Wolfram syndrome.

PMID: 26106220 [PubMed - in process]

Ophthalmologic correlates of disease severity in children and adolescents with Wolfram syndrome.

Sat, 06/27/2015 - 21:15
Related Articles

Ophthalmologic correlates of disease severity in children and adolescents with Wolfram syndrome.

J AAPOS. 2014 Oct;18(5):461-465.e1

Authors: Hoekel J, Chisholm SA, Al-Lozi A, Hershey T, Tychsen L, Washington University Wolfram Study Group

Abstract
PURPOSE: To describe an ophthalmic phenotype in children at relatively early stages of Wolfram syndrome.
METHODS: Quantitative ophthalmic testing of visual acuity, color vision, automated visual field sensitivity, optic nerve pallor and cupping, and retinal nerve fiber layer (RNFL) thickness assessed by optical coherence tomography (OCT) was performed in 18 subjects 5-25 years of age. Subjects were also examined for presence or absence of afferent pupillary defects, cataracts, nystagmus, and strabismus.
RESULTS: Subnormal visual acuity was detected in 89% of subjects, color vision deficits in 94%, visual field defects in 100%, optic disk pallor in 94%, abnormally large optic nerve cup:disk ratio in 33%, thinned RNFL in 100%, afferent pupillary defects in 61%, cataracts in 22%, nystagmus in 39%, and strabismus in 39% of subjects. RNFL thinning (P < 0.001), afferent pupillary defects (P = 0.01), strabismus (P = 0.04), and nystagmus (P = 0.04) were associated with more severe disease using the Wolfram United Rating Scale.
CONCLUSIONS: Children and adolescents with Wolfram syndrome have multiple ophthalmic markers that correlate with overall disease severity. RNFL thickness measured by OCT may be the most reliable early marker.

PMID: 25439303 [PubMed - indexed for MEDLINE]

An acetate-specific GPCR, FFAR2, regulates insulin secretion.

Thu, 06/18/2015 - 13:48
Related Articles

An acetate-specific GPCR, FFAR2, regulates insulin secretion.

Mol Endocrinol. 2015 Jun 15;:me20151007

Authors: Priyadarshini M, Villa SR, Fuller M, Wicksteed B, Mackay CR, Alquier T, Poitout V, Mancebo H, Mirmira RG, Gilchrist A, Layden BT

Abstract
G protein-coupled receptors (GPCRs) have been well described to contribute to the regulation of glucose-stimulated insulin secretion (GSIS). The short chain fatty acid (SCFA)-sensing GPCR, Free Fatty Acid Receptor 2 (FFAR2), is expressed in pancreatic β cells, and in rodents, its expression is altered during insulin resistance. Thus, we explored the role of FFAR2 in regulating GSIS. First, assessing the phenotype of wild type (WT) and Ffar2(-/-) mice in vivo, we observed no differences with regard to glucose homeostasis on normal or high fat diet, with a marginally significant defect in insulin secretion in Ffar2(-/-) mice during hyperglycemic clamps. In ex vivo insulin secretion studies, we observed diminished GSIS from Ffar2(-/-) islets relative to WT islets under high glucose conditions. Further, in the presence of acetate, the primary endogenous ligand for FFAR2, we observed FFAR2-dependent potentiation of GSIS, while FFAR2-specific agonists resulted in either potentiation or inhibition of GSIS, which we found to result from selective signaling through either Gαq/11 or Gαi/o, respectively. Lastly, in ex vivo insulin secretion studies of human islets, we observed that acetate and FFAR2 agonists elicited different signaling properties at human FFAR2 than at mouse FFAR2. Taken together, our studies reveal that FFAR2 signaling occurs by divergent G-protein pathways that can selectively potentiate or inhibit GSIS in mouse islets. Further, we have identified important differences in the response of mouse and human FFAR2 to selective agonists, and suggest these differences warrant consideration in the continued investigation of FFAR2 as a novel type 2 diabetes target.

PMID: 26075576 [PubMed - as supplied by publisher]

Rp-cAMPS Prodrugs Reveal the cAMP Dependence of First-Phase Glucose-Stimulated Insulin Secretion.

Fri, 06/12/2015 - 09:59
Related Articles

Rp-cAMPS Prodrugs Reveal the cAMP Dependence of First-Phase Glucose-Stimulated Insulin Secretion.

Mol Endocrinol. 2015 Jun 10;:me20141330

Authors: Schwede F, Chepurny OG, Kaufholz M, Bertinetti D, Leech CA, Cabrera O, Zhu Y, Mei F, Cheng X, Manning Fox JE, MacDonald PE, Genieser HG, Herberg FW, Holz GG

Abstract
cAMP-elevating agents such as the incretin hormone glucagon-like peptide-1 potentiate glucose-stimulated insulin secretion (GSIS) from pancreatic β-cells. However, a debate has existed since the 1970s concerning whether or not cAMP signaling is essential for glucose alone to stimulate insulin secretion. Here, we report that the first-phase kinetic component of GSIS is cAMP-dependent, as revealed through the use of a novel highly membrane permeable para-acetoxybenzyl (pAB) ester prodrug that is a bioactivatable derivative of the cAMP antagonist adenosine-3',5'-cyclic monophosphorothioate, Rp-isomer (Rp-cAMPS). In dynamic perifusion assays of human or rat islets, a step-wise increase of glucose concentration leads to biphasic insulin secretion, and under these conditions, 8-bromoadenosine-3',5'-cyclic monophosphorothioate, Rp-isomer, 4-acetoxybenzyl ester (Rp-8-Br-cAMPS-pAB) inhibits first-phase GSIS by up to 80. Surprisingly, second-phase GSIS is inhibited to a much smaller extent (≤20%). Using luciferase, fluorescence resonance energy transfer, and bioluminescence resonance energy transfer assays performed in living cells, we validate that Rp-8-Br-cAMPS-pAB does in fact block cAMP-dependent protein kinase activation. Novel effects of Rp-8-Br-cAMPS-pAB to block the activation of cAMP-regulated guanine nucleotide exchange factors (Epac1, Epac2) are also validated using genetically encoded Epac biosensors, and are independently confirmed in an in vitro Rap1 activation assay using Rp-cAMPS and Rp-8-Br-cAMPS. Thus, in addition to revealing the cAMP dependence of first-phase GSIS from human and rat islets, these findings establish a pAB-based chemistry for the synthesis of highly membrane permeable prodrug derivatives of Rp-cAMPS that act with micromolar or even nanomolar potency to inhibit cAMP signaling in living cells.

PMID: 26061564 [PubMed - as supplied by publisher]

SGLT-2 inhibition and glucagon: Cause for alarm?

Fri, 06/12/2015 - 09:59
Related Articles

SGLT-2 inhibition and glucagon: Cause for alarm?

Trends Endocrinol Metab. 2015 Jun 6;

Authors: Kibbey RG

Abstract
Recent studies raised the alarm that the inhibition of sodium-coupled glucose transporter type-2 in humans increases endogenous glucose production rates by an unclear mechanism. Surprisingly, a potential explanation may be linked directly to the alpha-cell. Is this a mechanistic spoiler or an added benefit?

PMID: 26059706 [PubMed - as supplied by publisher]

The Intra- or Extracellular Redox State Was Not Affected by a High vs. Low Glycemic Response Diet in Mice.

Wed, 06/03/2015 - 02:51
Related Articles

The Intra- or Extracellular Redox State Was Not Affected by a High vs. Low Glycemic Response Diet in Mice.

PLoS One. 2015;10(6):e0128380

Authors: Kleckner AS, Wong S, Corkey BE

Abstract
A low glycemic response (LGR) vs. high glycemic response (HGR) diet helps curtail the development of obesity and diabetes, though the mechanisms are unknown. We hypothesized that consumption of a HGR vs. a LGR diet would lead to a more oxidized circulating redox state and predicted that a HGR diet would increase fat accumulation, reduce insulin sensitivity, and impair metabolic acclimation to a high fat diet in a mouse model. Hence, male C57BL/6 mice consumed a HGR or LGR diet for 16 weeks and a subset of the mice subsequently consumed a high fat diet for 4 weeks. We found that body mass increased at a faster rate for those consuming the HGR diet. Percent body fat was greater and percent lean mass was lesser in the HGR group starting at 12 weeks. However, the groups did not differ in terms of glucose tolerance at week 14 and metabolic parameters (respiratory exchange ratio, heat production, activity) at weeks 4 or 15. Moreover, mice on either diet did not show differences in metabolic acclimation to the high fat leg of the study. At the termination of the study, the groups did not differ in terms of redox pairs (lactate/pyruvate and β-hydroxybutyrate/acetoacetate) or thioredoxin reductase activity in blood. Also, total and oxidized glutathione levels and lipid peroxidation were similar in blood and liver. Correlations between baseline measures, longitudinal parameters, environmental conditions, and terminal metrics revealed that individual mice have innate propensities to metabolic regulation that may be difficult to perturb with diet alone; for example, starting mass correlated negatively with energy expenditure 4 weeks into the study and total hepatic glutathione at the end of the study. In conclusion, these data suggest that the mechanism by which HGR carbohydrates contributes to obesity is not via prolonged oxidation of the circulating redox state.

PMID: 26030878 [PubMed - in process]

Human β-Cell Proliferation and Intracellular Signaling: Part 3.

Sun, 05/24/2015 - 21:25
Related Articles

Human β-Cell Proliferation and Intracellular Signaling: Part 3.

Diabetes. 2015 Jun;64(6):1872-85

Authors: Stewart AF, Hussain MA, García-Ocaña A, Vasavada RC, Bhushan A, Bernal-Mizrachi E, Kulkarni RN

Abstract
This is the third in a series of Perspectives on intracellular signaling pathways coupled to proliferation in pancreatic β-cells. We contrast the large knowledge base in rodent β-cells with the more limited human database. With the increasing incidence of type 1 diabetes and the recognition that type 2 diabetes is also due in part to a deficiency of functioning β-cells, there is great urgency to identify therapeutic approaches to expand human β-cell numbers. Therapeutic approaches might include stem cell differentiation, transdifferentiation, or expansion of cadaver islets or residual endogenous β-cells. In these Perspectives, we focus on β-cell proliferation. Past Perspectives reviewed fundamental cell cycle regulation and its upstream regulation by insulin/IGF signaling via phosphatidylinositol-3 kinase/mammalian target of rapamycin signaling, glucose, glycogen synthase kinase-3 and liver kinase B1, protein kinase Cζ, calcium-calcineurin-nuclear factor of activated T cells, epidermal growth factor/platelet-derived growth factor family members, Wnt/β-catenin, leptin, and estrogen and progesterone. Here, we emphasize Janus kinase/signal transducers and activators of transcription, Ras/Raf/extracellular signal-related kinase, cadherins and integrins, G-protein-coupled receptors, and transforming growth factor β signaling. We hope these three Perspectives will serve to introduce these pathways to new researchers and will encourage additional investigators to focus on understanding how to harness key intracellular signaling pathways for therapeutic human β-cell regeneration for diabetes.

PMID: 25999530 [PubMed - in process]

Size- and shape-dependent foreign body immune response to materials implanted in rodents and non-human primates.

Thu, 05/21/2015 - 18:29
Related Articles

Size- and shape-dependent foreign body immune response to materials implanted in rodents and non-human primates.

Nat Mater. 2015 Jun;14(6):643-51

Authors: Veiseh O, Doloff JC, Ma M, Vegas AJ, Tam HH, Bader AR, Li J, Langan E, Wyckoff J, Loo WS, Jhunjhunwala S, Chiu A, Siebert S, Tang K, Hollister-Lock J, Aresta-Dasilva S, Bochenek M, Mendoza-Elias J, Wang Y, Qi M, Lavin DM, Chen M, Dholakia N, Thakrar R, Lacík I, Weir GC, Oberholzer J, Greiner DL, Langer R, Anderson DG

Abstract
The efficacy of implanted biomedical devices is often compromised by host recognition and subsequent foreign body responses. Here, we demonstrate the role of the geometry of implanted materials on their biocompatibility in vivo. In rodent and non-human primate animal models, implanted spheres 1.5 mm and above in diameter across a broad spectrum of materials, including hydrogels, ceramics, metals and plastics, significantly abrogated foreign body reactions and fibrosis when compared with smaller spheres. We also show that for encapsulated rat pancreatic islet cells transplanted into streptozotocin-treated diabetic C57BL/6 mice, islets prepared in 1.5-mm alginate capsules were able to restore blood-glucose control for up to 180 days, a period more than five times longer than for transplanted grafts encapsulated within conventionally sized 0.5-mm alginate capsules. Our findings suggest that the in vivo biocompatibility of biomedical devices can be significantly improved simply by tuning their spherical dimensions.

PMID: 25985456 [PubMed - in process]

Forced Hepatic Over-expression of CEACAM1 Curtails Diet-induced Insulin Resistance.

Fri, 05/15/2015 - 13:05
Related Articles

Forced Hepatic Over-expression of CEACAM1 Curtails Diet-induced Insulin Resistance.

Diabetes. 2015 May 13;

Authors: Al-Share QY, DeAngelis AM, Lester SG, Bowman TA, Ramakrishnan SK, Abdallah SL, Russo L, Patel PR, Kaw MK, Raphael CK, Kim AJ, Heinrich G, Lee AD, Kim JK, Kulkarni RN, Philbrick WM, Najjar SM

Abstract
CEACAM1 regulates insulin sensitivity by promoting hepatic insulin clearance. Liver-specific inactivation or global null-mutation of Ceacam1 impairs hepatic insulin extraction to cause chronic hyperinsulinemia, resulting in insulin resistance and visceral obesity. We herein investigated whether diet-induced insulin resistance implicates changes in hepatic CEACAM1. We report that feeding C57/BL6J mice a high-fat diet reduced hepatic CEACAM1 levels by >50% beginning at 21 days, causing hyperinsulinemia, insulin resistance and elevation in hepatic triacylglycerol content. Conversely, liver-specific inducible CEACAM1 expression prevented hyperinsulinemia and markedly limited insulin resistance as well as hepatic lipid accumulation that was induced by prolonged high-fat intake. This was partly mediated by increased hepatic β-fatty acid oxidation and energy expenditure. The data demonstrate that high-fat diet reduced hepatic CEACAM1 expression and that over-expressing CEACAM1 in liver curtailed diet-induced metabolic abnormalities by protecting hepatic insulin clearance.

PMID: 25972571 [PubMed - as supplied by publisher]

Chronic Exposure to Excess Nutrients Left-shifts the Concentration Dependence of Glucose-stimulated Insulin Secretion in Pancreatic β-Cells.

Sun, 05/03/2015 - 06:17

Chronic Exposure to Excess Nutrients Left-shifts the Concentration Dependence of Glucose-stimulated Insulin Secretion in Pancreatic β-Cells.

J Biol Chem. 2015 May 1;

Authors: Erion KA, Berdan CA, Burritt NE, Corkey BE, Deeney JT

Abstract
Hyperinsulinemia (HI) is elevated plasma insulin at basal glucose. Impaired glucose tolerance is associated with HI, though the exact cause and effect relationship remains poorly defined. We tested the hypothesis that HI can result from an intrinsic response of the β-cell to chronic exposure to excess nutrients, involving a shift in the concentration dependency of glucose- stimulated insulin secretion (GSIS). INS-1 (832/13) cells were cultured in either a physiological (4 mM) or high (11 mM) glucose concentration with or without concomitant exposure to oleate. Isolated rat islets were also cultured with or without oleate. A clear hypersensitivity to sub-maximal glucose concentrations was evident in INS-1 cells cultured in excess nutrients such that the 25% of maximal (S0.25) GSIS was significantly reduced in cells cultured in 11 mM glucose (S0.25 = 3.5 mM) and 4 mM glucose with oleate (S0.25 = 4.5 mM) compared to 4 mM glucose alone (S0.25 = 5.7 mM). The magnitude of the left shift was linearly correlated with intracellular lipid stores in INS-1 cells (r2 = 0.97). We observed no significant differences in the dose responses for glucose stimulation of respiration, NAD(P)H autofluoresence or Ca2+ responses between left and right-shifted β-cells. However, a left-shift in the sensitivity of exocytosis to Ca2+ was documented in permeabilized INS-1 cells cultured in 11 versus 4 mM glucose (S0.25 = 1.1 and 1.7 μM, respectively). Our results suggest the sensitivity of exocytosis to triggering is modulated by a lipid component , the levels of which are influenced by the culture nutrient environment.

PMID: 25934392 [PubMed - as supplied by publisher]

Differential mobility spectrometry: a valuable technology for analyzing challenging biological samples.

Sun, 05/03/2015 - 06:17
Related Articles

Differential mobility spectrometry: a valuable technology for analyzing challenging biological samples.

Bioanalysis. 2015 Apr;7(7):853-6

Authors: Campbell JL, Le Blanc JY, Kibbey RG

PMID: 25932519 [PubMed - in process]

High-level Gpr56 expression is dispensable for the maintenance and function of hematopoietic stem and progenitor cells in mice.

Sun, 04/05/2015 - 17:25
Related Articles

High-level Gpr56 expression is dispensable for the maintenance and function of hematopoietic stem and progenitor cells in mice.

Stem Cell Res. 2015 Feb 18;14(3):307-322

Authors: Rao TN, Marks-Bluth J, Sullivan J, Gupta MK, Chandrakanthan V, Fitch SR, Ottersbach K, Jang YC, Piao X, Kulkarni RN, Serwold T, Pimanda JE, Wagers AJ

Abstract
Blood formation by hematopoietic stem cells (HSCs) is regulated by a still incompletely defined network of general and HSC-specific regulators. In this study, we analyzed the role of G-protein coupled receptor 56 (Gpr56) as a candidate HSC regulator based on its differential expression in quiescent relative to proliferating HSCs and its common targeting by core HSC regulators. Detailed expression analysis revealed that Gpr56 is abundantly expressed by HSPCs during definitive hematopoiesis in the embryo and in the adult bone marrow, but its levels are reduced substantially as HSPCs differentiate. However, despite enriched expression in HSPCs, Gpr56-deficiency did not impair HSPC maintenance or function during steady-state or myeloablative stress-induced hematopoiesis. Gpr56-deficient HSCs also responded normally to physiological and pharmacological mobilization signals, despite the reported role of this GPCR as a regulator of cell adhesion and migration in neuronal cells. Moreover, Gpr56-deficient bone marrow engrafted with equivalent efficiency as wild-type HSCs in primary recipients; however, their reconstituting ability was reduced when subjected to serial transplantation. These data indicate that although GPR56 is abundantly and selectively expressed by primitive HSPCs, its high level expression is largely dispensable for steady-state and regenerative hematopoiesis.

PMID: 25840412 [PubMed - as supplied by publisher]

Revision of EN-14-1987, "Reprogramming mouse cells with a pancreatic duct phenotype to insulin-producing beta-like cells".

Sun, 04/05/2015 - 17:25
Related Articles

Revision of EN-14-1987, "Reprogramming mouse cells with a pancreatic duct phenotype to insulin-producing beta-like cells".

Endocrinology. 2015 Apr 2;:en20141987

Authors: Yamada T, Cavelti-Weder C, Caballero F, Lysy P, Guo L, Sharma A, Li W, Zhou Q, Bonner-Weir S, Weir GC

Abstract
Reprogramming technology has opened the possibility of converting one cell type into another by forced expression of transgenes. Transduction of adenoviral vectors encoding three pancreatic transcription factors, Pdx1, Ngn3 and MafA, into mouse pancreas results in direct reprogramming of exocrine cells to insulin-producing beta-like cells. We hypothesized that cultured adult pancreatic duct cells could be reprogrammed to become insulin-producing beta cells by adenoviral-mediated expression of this same combination of factors. Exocrine were isolated from adult MIP-GFP transgenic mice to allow new insulin-expressing cells to be detected by GFP fluorescence. Cultured cells were transduced by an adenoviral vector carrying a polycistronic construct Ngn3/Pdx1/MafA/mCherry (Ad-M3C) or mCherry sequence alone (Ad-C) as a control vector. In addition, the effects of GLP-1 receptor agonist, exendin-4, on the reprogramming process were examined. GFP+ cells appeared 2 days after Ad-M3C transduction; the reprogramming efficiency was 8.6 ± 2.6 % by day 4 after transduction. Ad-M3C also resulted in increased expression of beta cell markers insulin 1 and 2, with enhancement by exendin-4. Expression of other beta cell markers, neuroD and GLP-1R, were also significantly up-regulated. The amount of insulin release into the media and insulin content of the cells were significantly higher in the Ad-M3C transduced cells; this too was enhanced by exendin-4. The transduced cells did not secrete insulin in response to increased glucose, indicating incomplete differentiation to beta cells. Thus, cultured murine adult pancreatic cells with a duct phenotype can be directly reprogrammed to insulin-producing beta-like cells by adenoviral delivery of three pancreatic transcription factors.

PMID: 25836667 [PubMed - as supplied by publisher]

The extracellular redox state modulates mitochondrial function, gluconeogenesis, and glycogen synthesis in murine hepatocytes.

Thu, 04/02/2015 - 14:23
Related Articles

The extracellular redox state modulates mitochondrial function, gluconeogenesis, and glycogen synthesis in murine hepatocytes.

PLoS One. 2015;10(3):e0122818

Authors: Nocito L, Kleckner AS, Yoo EJ, Jones Iv AR, Liesa M, Corkey BE

Abstract
Circulating redox state changes, determined by the ratio of reduced/oxidized pairs of different metabolites, have been associated with metabolic diseases. However, the pathogenic contribution of these changes and whether they modulate normal tissue function is unclear. As alterations in hepatic gluconeogenesis and glycogen metabolism are hallmarks that characterize insulin resistance and type 2 diabetes, we tested whether imposed changes in the extracellular redox state could modulate these processes. Thus, primary hepatocytes were treated with different ratios of the following physiological extracellular redox couples: β-hydroxybutyrate (βOHB)/acetoacetate (Acoc), reduced glutathione (GSH)/oxidized glutathione (GSSG), and cysteine/cystine. Exposure to a more oxidized ratio via extracellular βOHB/Acoc, GSH/GSSG, and cysteine/cystine in hepatocytes from fed mice increased intracellular hydrogen peroxide without causing oxidative damage. On the other hand, addition of more reduced ratios of extracellular βOHB/Acoc led to increased NAD(P)H and maximal mitochondrial respiratory capacity in hepatocytes. Greater βOHB/Acoc ratios were also associated with decreased β-oxidation, as expected with enhanced lipogenesis. In hepatocytes from fasted mice, a more extracellular reduced state of βOHB/Acoc led to increased alanine-stimulated gluconeogenesis and enhanced glycogen synthesis capacity from added glucose. Thus, we demonstrated for the first time that the extracellular redox state regulates the major metabolic functions of the liver and involves changes in intracellular NADH, hydrogen peroxide, and mitochondrial respiration. Because redox state in the blood can be communicated to all metabolically sensitive tissues, this work confirms the hypothesis that circulating redox state may be an important regulator of whole body metabolism and contribute to alterations associated with metabolic diseases.

PMID: 25816337 [PubMed - in process]

Pages