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Synaptotagmin 4 Regulates Pancreatic β Cell Maturation by Modulating the Ca Sensitivity of Insulin Secretion Vesicles.
Huang C, Walker EM, Dadi PK, Hu R, Xu Y, Zhang W, Sanavia T, Mun J, Liu J, Nair GG, Tan HYA, Wang S, Magnuson MA, Stoeckert CJ, Hebrok M, Gannon M, Han W, Stein R, Jacobson DA, Gu G
(2018) Dev Cell 45: 347-361.e5
MeSH Terms: Animals, Biological Transport, Calcium, Cell Differentiation, Female, Gene Expression Regulation, Glucose, Humans, Hypoglycemic Agents, Insulin, Insulin Secretion, Insulin-Secreting Cells, Male, Mice, Mice, Knockout, Sweetening Agents, Synaptotagmins
Show Abstract · Added April 17, 2018
Islet β cells from newborn mammals exhibit high basal insulin secretion and poor glucose-stimulated insulin secretion (GSIS). Here we show that β cells of newborns secrete more insulin than adults in response to similar intracellular Ca concentrations, suggesting differences in the Ca sensitivity of insulin secretion. Synaptotagmin 4 (Syt4), a non-Ca binding paralog of the β cell Ca sensor Syt7, increased by ∼8-fold during β cell maturation. Syt4 ablation increased basal insulin secretion and compromised GSIS. Precocious Syt4 expression repressed basal insulin secretion but also impaired islet morphogenesis and GSIS. Syt4 was localized on insulin granules and Syt4 levels inversely related to the number of readily releasable vesicles. Thus, transcriptional regulation of Syt4 affects insulin secretion; Syt4 expression is regulated in part by Myt transcription factors, which repress Syt4 transcription. Finally, human SYT4 regulated GSIS in EndoC-βH1 cells, a human β cell line. These findings reveal the role that altered Ca sensing plays in regulating β cell maturation.
Copyright © 2018 Elsevier Inc. All rights reserved.
3 Communities
3 Members
0 Resources
17 MeSH Terms
α Cell Function and Gene Expression Are Compromised in Type 1 Diabetes.
Brissova M, Haliyur R, Saunders D, Shrestha S, Dai C, Blodgett DM, Bottino R, Campbell-Thompson M, Aramandla R, Poffenberger G, Lindner J, Pan FC, von Herrath MG, Greiner DL, Shultz LD, Sanyoura M, Philipson LH, Atkinson M, Harlan DM, Levy SE, Prasad N, Stein R, Powers AC
(2018) Cell Rep 22: 2667-2676
MeSH Terms: Adolescent, Adult, Animals, Case-Control Studies, Cellular Reprogramming, Child, Diabetes Mellitus, Type 1, Female, Gene Expression Regulation, Glucagon, Glucagon-Secreting Cells, Humans, Insulin Secretion, Insulin-Secreting Cells, Male, Mice, Middle Aged, Phenotype, Tissue Donors, Transcription Factors, Young Adult
Show Abstract · Added March 8, 2018
Many patients with type 1 diabetes (T1D) have residual β cells producing small amounts of C-peptide long after disease onset but develop an inadequate glucagon response to hypoglycemia following T1D diagnosis. The features of these residual β cells and α cells in the islet endocrine compartment are largely unknown, due to the difficulty of comprehensive investigation. By studying the T1D pancreas and isolated islets, we show that remnant β cells appeared to maintain several aspects of regulated insulin secretion. However, the function of T1D α cells was markedly reduced, and these cells had alterations in transcription factors constituting α and β cell identity. In the native pancreas and after placing the T1D islets into a non-autoimmune, normoglycemic in vivo environment, there was no evidence of α-to-β cell conversion. These results suggest an explanation for the disordered T1D counterregulatory glucagon response to hypoglycemia.
Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.
0 Communities
3 Members
0 Resources
21 MeSH Terms
Cytokine-mediated changes in K channel activity promotes an adaptive Ca response that sustains β-cell insulin secretion during inflammation.
Dickerson MT, Bogart AM, Altman MK, Milian SC, Jordan KL, Dadi PK, Jacobson DA
(2018) Sci Rep 8: 1158
MeSH Terms: Adult, Animals, Calcium, Female, Gene Expression Regulation, Glucose, Humans, Insulin, Insulin Secretion, Insulin-Secreting Cells, Interferon-gamma, Interleukin-1beta, Ion Transport, Islets of Langerhans, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Potassium, Potassium Channels, Tandem Pore Domain, Primary Cell Culture, RNA, Messenger, Sarcoplasmic Reticulum Calcium-Transporting ATPases, Tissue Culture Techniques, Tumor Necrosis Factor-alpha
Show Abstract · Added February 7, 2018
Cytokines present during low-grade inflammation contribute to β-cell dysfunction and diabetes. Cytokine signaling disrupts β-cell glucose-stimulated Ca influx (GSCI) and endoplasmic reticulum (ER) Ca ([Ca]) handling, leading to diminished glucose-stimulated insulin secretion (GSIS). However, cytokine-mediated changes in ion channel activity that alter β-cell Ca handling remain unknown. Here we investigated the role of K currents in cytokine-mediated β-cell dysfunction. K currents, which control the termination of intracellular Ca ([Ca]) oscillations, were reduced following cytokine exposure. As a consequence, [Ca] and electrical oscillations were accelerated. Cytokine exposure also increased basal islet [Ca] and decreased GSCI. The effect of cytokines on TALK-1 K currents were also examined as TALK-1 mediates K by facilitating [Ca] release. Cytokine exposure decreased KCNK16 transcript abundance and associated TALK-1 protein expression, increasing [Ca] storage while maintaining 2 phase GSCI and GSIS. This adaptive Ca response was absent in TALK-1 KO islets, which exhibited decreased 2 phase GSCI and diminished GSIS. These findings suggest that K and TALK-1 currents play important roles in altered β-cell Ca handling and electrical activity during low-grade inflammation. These results also reveal that a cytokine-mediated reduction in TALK-1 serves an acute protective role in β-cells by facilitating increased Ca content to maintain GSIS.
0 Communities
1 Members
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25 MeSH Terms
Glucocorticoids Reprogram β-Cell Signaling to Preserve Insulin Secretion.
Fine NHF, Doig CL, Elhassan YS, Vierra NC, Marchetti P, Bugliani M, Nano R, Piemonti L, Rutter GA, Jacobson DA, Lavery GG, Hodson DJ
(2018) Diabetes 67: 278-290
MeSH Terms: 11-beta-Hydroxysteroid Dehydrogenase Type 1, Animals, Biomarkers, Calcium Channels, Calcium Signaling, Cell Differentiation, Corticosterone, Cortisone, Cyclic AMP, Glucocorticoids, Glucose, Humans, Hydrocortisone, Insulin, Insulin Secretion, Insulin-Secreting Cells, Kinetics, Mice, Inbred Strains, Mice, Knockout, Tissue Culture Techniques
Show Abstract · Added December 6, 2017
Excessive glucocorticoid exposure has been shown to be deleterious for pancreatic β-cell function and insulin release. However, glucocorticoids at physiological levels are essential for many homeostatic processes, including glycemic control. We show that corticosterone and cortisol and their less active precursors 11-dehydrocorticosterone (11-DHC) and cortisone suppress voltage-dependent Ca channel function and Ca fluxes in rodent as well as in human β-cells. However, insulin secretion, maximal ATP/ADP responses to glucose, and β-cell identity were all unaffected. Further examination revealed the upregulation of parallel amplifying cAMP signals and an increase in the number of membrane-docked insulin secretory granules. Effects of 11-DHC could be prevented by lipotoxicity and were associated with paracrine regulation of glucocorticoid activity because global deletion of 11β-hydroxysteroid dehydrogenase type 1 normalized Ca and cAMP responses. Thus, we have identified an enzymatically amplified feedback loop whereby glucocorticoids boost cAMP to maintain insulin secretion in the face of perturbed ionic signals. Failure of this protective mechanism may contribute to diabetes in states of glucocorticoid excess, such as Cushing syndrome, which are associated with frank dyslipidemia.
© 2017 by the American Diabetes Association.
0 Communities
1 Members
0 Resources
20 MeSH Terms
Shared Genetic Control of Brain Activity During Sleep and Insulin Secretion: A Laboratory-Based Family Study.
Morselli LL, Gamazon ER, Tasali E, Cox NJ, Van Cauter E, Davis LK
(2018) Diabetes 67: 155-164
MeSH Terms: Adiposity, Adult, Blood Glucose, Brain, Electroencephalography, Female, Glucose Tolerance Test, Humans, Insulin, Insulin Secretion, Male, Middle Aged, Pedigree, Sleep
Show Abstract · Added November 29, 2017
Over the past 20 years, a large body of experimental and epidemiologic evidence has linked sleep duration and quality to glucose homeostasis, although the mechanistic pathways remain unclear. The aim of the current study was to determine whether genetic variation influencing both sleep and glucose regulation could underlie their functional relationship. We hypothesized that the genetic regulation of electroencephalographic (EEG) activity during non-rapid eye movement sleep, a highly heritable trait with fingerprint reproducibility, is correlated with the genetic control of metabolic traits including insulin sensitivity and β-cell function. We tested our hypotheses through univariate and bivariate heritability analyses in a three-generation pedigree with in-depth phenotyping of both sleep EEG and metabolic traits in 48 family members. Our analyses accounted for age, sex, adiposity, and the use of psychoactive medications. In univariate analyses, we found significant heritability for measures of fasting insulin sensitivity and β-cell function, for time spent in slow-wave sleep, and for EEG spectral power in the delta, theta, and sigma ranges. Bivariate heritability analyses provided the first evidence for a shared genetic control of brain activity during deep sleep and fasting insulin secretion rate.
© 2017 by the American Diabetes Association.
0 Communities
2 Members
0 Resources
14 MeSH Terms
Synergistic Modulation of Inflammatory but not Metabolic Effects of High-Fat Feeding by CCR2 and CX3CR1.
Zhang H, Hinkle CC, O'Neill SM, Shi J, Caughey J, Lynch E, Lynch G, Gerelus M, Tsai ASD, Shah R, Ferguson JF, Ahima RS, Reilly MP
(2017) Obesity (Silver Spring) 25: 1410-1420
MeSH Terms: Animals, Body Composition, CX3C Chemokine Receptor 1, Diet, High-Fat, Female, Glucose Intolerance, Inflammation, Insulin, Insulin Resistance, Insulin Secretion, Macrophages, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Obesity, Receptors, CCR2, Weight Gain
Show Abstract · Added April 2, 2019
OBJECTIVE - The purpose of the study was to explore the impact of dual targeting of C-C motif chemokine receptor-2 (CCR2) and fractalkine receptor (CX3CR1) on the metabolic and inflammatory consequences of obesity induced by a high-fat diet (HFD).
METHODS - C57BL/6J wild-type, Cx3cr1 , Ccr2 , and Cx3cr1 Ccr2 double-knockout male and female mice were fed a 45% HFD for up to 25 weeks starting at 12 weeks of age.
RESULTS - All groups gained weight at a similar rate and developed a similar degree of adiposity, hyperglycemia, glucose intolerance, and impairment of insulin sensitivity in response to HFD. As expected, the circulating monocyte count was decreased in Ccr2 and Cx3cr1 Ccr2 mice but not in Cx3cr1 mice. Flow cytometric analysis of perigonadal adipose tissue of male, but not female, mice revealed trends to lower CD11c+MGL1- M1-like macrophages and higher CD11c-MGL1+ M2-like macrophages as a percentage of CD45+F4/80+CD11b+ macrophages in Cx3cr1 Ccr2 mice versus wild-type mice, suggesting reduced adipose tissue macrophage activation. In contrast, single knockout of Ccr2 or Cx3cr1 did not differ in their adipose macrophage phenotypes.
CONCLUSIONS - Although CCR2 and CX3CR1 may synergistically impact inflammatory phenotypes, their joint deficiency did not influence the metabolic effects of a 45% HFD-induced obesity in these model conditions.
© 2017 The Obesity Society.
0 Communities
1 Members
0 Resources
MeSH Terms
Osteopontin activates the diabetes-associated potassium channel TALK-1 in pancreatic β-cells.
Dickerson MT, Vierra NC, Milian SC, Dadi PK, Jacobson DA
(2017) PLoS One 12: e0175069
MeSH Terms: Aged, Animals, Calcium Signaling, Diabetes Mellitus, Type 2, Female, Glucose, HEK293 Cells, Humans, Insulin, Insulin Secretion, Insulin-Secreting Cells, Membrane Potentials, Mice, Knockout, Osteopontin, Potassium, Potassium Channels, Tandem Pore Domain
Show Abstract · Added November 13, 2017
Glucose-stimulated insulin secretion (GSIS) relies on β-cell Ca2+ influx, which is modulated by the two-pore-domain K+ (K2P) channel, TALK-1. A gain-of-function polymorphism in KCNK16, the gene encoding TALK-1, increases risk for developing type-2 diabetes. While TALK-1 serves an important role in modulating GSIS, the regulatory mechanism(s) that control β-cell TALK-1 channels are unknown. Therefore, we employed a membrane-specific yeast two-hybrid (MYTH) assay to identify TALK-1-interacting proteins in human islets, which will assist in determining signaling modalities that modulate TALK-1 function. Twenty-one proteins from a human islet cDNA library interacted with TALK-1. Some of these interactions increased TALK-1 activity, including intracellular osteopontin (iOPN). Intracellular OPN is highly expressed in β-cells and is upregulated under pre-diabetic conditions to help maintain normal β-cell function; however, the functional role of iOPN in β-cells is poorly understood. We found that iOPN colocalized with TALK-1 in pancreatic sections and coimmunoprecipitated with human islet TALK-1 channels. As human β-cells express two K+ channel-forming variants of TALK-1, regulation of these TALK-1 variants by iOPN was assessed. At physiological voltages iOPN activated TALK-1 transcript variant 3 channels but not TALK-1 transcript variant 2 channels. Activation of TALK-1 channels by iOPN also hyperpolarized resting membrane potential (Vm) in HEK293 cells and in primary mouse β-cells. Intracellular OPN was also knocked down in β-cells to test its effect on β-cell TALK-1 channel activity. Reducing β-cell iOPN significantly decreased TALK-1 K+ currents and increased glucose-stimulated Ca2+ influx. Importantly, iOPN did not affect the function of other K2P channels or alter Ca2+ influx into TALK-1 deficient β-cells. These results reveal the first protein interactions with the TALK-1 channel and found that an interaction with iOPN increased β-cell TALK-1 K+ currents. The TALK-1/iOPN complex caused Vm hyperpolarization and reduced β-cell glucose-stimulated Ca2+ influx, which is predicted to inhibit GSIS.
0 Communities
1 Members
0 Resources
16 MeSH Terms
SIRT4 Is a Lysine Deacylase that Controls Leucine Metabolism and Insulin Secretion.
Anderson KA, Huynh FK, Fisher-Wellman K, Stuart JD, Peterson BS, Douros JD, Wagner GR, Thompson JW, Madsen AS, Green MF, Sivley RM, Ilkayeva OR, Stevens RD, Backos DS, Capra JA, Olsen CA, Campbell JE, Muoio DM, Grimsrud PA, Hirschey MD
(2017) Cell Metab 25: 838-855.e15
MeSH Terms: Amidohydrolases, Amino Acid Sequence, Animals, Carbon-Carbon Ligases, Glucose, HEK293 Cells, Homeostasis, Humans, Insulin, Insulin Resistance, Insulin Secretion, Leucine, Lysine, Metabolic Flux Analysis, Mice, Inbred C57BL, Mice, Knockout, Mitochondrial Proteins, Models, Molecular, Phylogeny, Sirtuins
Show Abstract · Added April 18, 2017
Sirtuins are NAD-dependent protein deacylases that regulate several aspects of metabolism and aging. In contrast to the other mammalian sirtuins, the primary enzymatic activity of mitochondrial sirtuin 4 (SIRT4) and its overall role in metabolic control have remained enigmatic. Using a combination of phylogenetics, structural biology, and enzymology, we show that SIRT4 removes three acyl moieties from lysine residues: methylglutaryl (MG)-, hydroxymethylglutaryl (HMG)-, and 3-methylglutaconyl (MGc)-lysine. The metabolites leading to these post-translational modifications are intermediates in leucine oxidation, and we show a primary role for SIRT4 in controlling this pathway in mice. Furthermore, we find that dysregulated leucine metabolism in SIRT4KO mice leads to elevated basal and stimulated insulin secretion, which progressively develops into glucose intolerance and insulin resistance. These findings identify a robust enzymatic activity for SIRT4, uncover a mechanism controlling branched-chain amino acid flux, and position SIRT4 as a crucial player maintaining insulin secretion and glucose homeostasis during aging.
Copyright © 2017 Elsevier Inc. All rights reserved.
0 Communities
1 Members
0 Resources
20 MeSH Terms
β-arrestin-2 is an essential regulator of pancreatic β-cell function under physiological and pathophysiological conditions.
Zhu L, Almaça J, Dadi PK, Hong H, Sakamoto W, Rossi M, Lee RJ, Vierra NC, Lu H, Cui Y, McMillin SM, Perry NA, Gurevich VV, Lee A, Kuo B, Leapman RD, Matschinsky FM, Doliba NM, Urs NM, Caron MG, Jacobson DA, Caicedo A, Wess J
(2017) Nat Commun 8: 14295
MeSH Terms: Animals, Calcium-Calmodulin-Dependent Protein Kinase Type 2, Cell Line, Cell Line, Tumor, Diet, High-Fat, Gene Expression, Humans, Insulin, Insulin Secretion, Insulin-Secreting Cells, Islets of Langerhans, Mice, Inbred C57BL, Mice, Knockout, Mice, Transgenic, Signal Transduction, beta-Arrestin 2
Show Abstract · Added November 13, 2017
β-arrestins are critical signalling molecules that regulate many fundamental physiological functions including the maintenance of euglycemia and peripheral insulin sensitivity. Here we show that inactivation of the β-arrestin-2 gene, barr2, in β-cells of adult mice greatly impairs insulin release and glucose tolerance in mice fed with a calorie-rich diet. Both glucose and KCl-induced insulin secretion and calcium responses were profoundly reduced in β-arrestin-2 (barr2) deficient β-cells. In human β-cells, barr2 knockdown abolished glucose-induced insulin secretion. We also show that the presence of barr2 is essential for proper CAMKII function in β-cells. Importantly, overexpression of barr2 in β-cells greatly ameliorates the metabolic deficits displayed by mice consuming a high-fat diet. Thus, our data identify barr2 as an important regulator of β-cell function, which may serve as a new target to improve β-cell function.
0 Communities
2 Members
0 Resources
16 MeSH Terms
ERAD-icating mutant insulin promotes functional insulin secretion.
Moore DJ
(2017) Sci Transl Med 9:
MeSH Terms: Endoplasmic Reticulum, Endoplasmic Reticulum-Associated Degradation, Insulin, Insulin Secretion, Proinsulin, Protein Folding
Show Abstract · Added January 20, 2017
Overexpression of a chaperone protein liberates functional insulin from a misfolded mutant partner to improve insulin secretion.
Copyright © 2017, American Association for the Advancement of Science.
0 Communities
1 Members
0 Resources
6 MeSH Terms