scholarly journals Preptin, another peptide product of the pancreatic β-cell, is osteogenic in vitro and in vivo

2007 ◽  
Vol 292 (1) ◽  
pp. E117-E122 ◽  
Author(s):  
J. Cornish ◽  
K. E. Callon ◽  
U. Bava ◽  
M. Watson ◽  
X. Xu ◽  
...  
Keyword(s):  
Bone Mass ◽  
Map Kinases ◽  
Cell Number ◽  
Dependent Manner ◽  
Pancreatic Β Cell ◽  
Hepatitis C Infection ◽  
Β Cell ◽  
High Bone Mass

Several hormones that regulate nutritional status also impact on bone metabolism. Preptin is a recently isolated 34-amino acid peptide hormone that is cosecreted with insulin and amylin from the pancreatic β-cells. Preptin corresponds to Asp69-Leu102 of pro-IGF-II. Increased circulating levels of a pro-IGF-II peptide complexed with IGF-binding protein-2 have been implicated in the high bone mass phenotype observed in patients with chronic hepatitis C infection. We have assessed preptin's activities on bone. Preptin dose-dependently stimulated the proliferation (cell number and DNA synthesis) of primary fetal rat osteoblasts and osteoblast-like cell lines at periphysiological concentrations (>10−11 M). In addition, thymidine incorporation was stimulated in murine neonatal calvarial organ culture, likely reflecting the proliferation of cells from the osteoblast lineage. Preptin did not affect bone resorption in this model. Preptin induced phosphorylation of p42/p44 MAP kinases in osteoblastic cells in a dose-dependent manner (10−8-10−10 M), and its proliferative effects on primary osteoblasts were blocked by MAP kinase kinase inhibitors. Preptin also reduced osteoblast apoptosis induced by serum deprivation, reducing the number of apoptotic cells by >20%. In vivo administration of preptin increased bone area and mineralizing surface in adult mice. These data demonstrate that preptin, which is cosecreted from the pancreatic β-cell with amylin and insulin, is anabolic to bone and may contribute to the preservation of bone mass observed in hyperinsulinemic states such as obesity.

scholarly journals Amylin inhibits bone resorption while the calcitonin receptor controls bone formation in vivo

2004 ◽  
Vol 164 (4) ◽  
pp. 509-514 ◽  
Author(s):  
Romain Dacquin ◽  
Rachel A. Davey ◽  
Catherine Laplace ◽  
Régis Levasseur ◽  
Howard A. Morris ◽  
...  
Keyword(s):  
Bone Resorption ◽  
Bone Formation ◽  
Bone Mass ◽  
Dependent Manner ◽  
Calcitonin Receptor ◽  
Low Bone Mass ◽  
High Bone Mass ◽  
High Bone

Amylin is a member of the calcitonin family of hormones cosecreted with insulin by pancreatic β cells. Cell culture assays suggest that amylin could affect bone formation and bone resorption, this latter function after its binding to the calcitonin receptor (CALCR). Here we show that Amylin inactivation leads to a low bone mass due to an increase in bone resorption, whereas bone formation is unaffected. In vitro, amylin inhibits fusion of mononucleated osteoclast precursors into multinucleated osteoclasts in an ERK1/2-dependent manner. Although Amylin +/− mice like Amylin-deficient mice display a low bone mass phenotype and increased bone resorption, Calcr +/− mice display a high bone mass due to an increase in bone formation. Moreover, compound heterozygote mice for Calcr and Amylin inactivation displayed bone abnormalities observed in both Calcr +/− and Amylin +/− mice, thereby ruling out that amylin uses CALCR to inhibit osteoclastogenesis in vivo. Thus, amylin is a physiological regulator of bone resorption that acts through an unidentified receptor.

scholarly journals Intermittent-Hypoxia-Induced Autophagy Activation Through the ER-Stress-Related PERK/eIF2α/ATF4 Pathway is a Protective Response to Pancreatic β-Cell Apoptosis

2018 ◽  
Vol 51 (6) ◽  
pp. 2955-2971 ◽  
Author(s):  
Shuling Song ◽  
Jin Tan ◽  
Yuyang Miao ◽  
Zuoming Sun ◽  
Qiang  Zhang
Keyword(s):  
Er Stress ◽  
Signaling Pathway ◽  
Cell Apoptosis ◽  
Intermittent Hypoxia ◽  
Autophagic Vacuole ◽  
Pancreatic Β Cell ◽  
Β Cell ◽  
Protective Response

Background/Aims: Intermittent hypoxia (IH) causes apoptosis in pancreatic β-cells, but the potential mechanisms remain unclear. Endoplasmic reticulum (ER) stress, autophagy, and apoptosis are interlocked in an extensive crosstalk. Thus, this study aimed to investigate the contributions of ER stress and autophagy to IH-induced pancreatic β-cell apoptosis. Methods: We established animal and cell models of IH, and then inhibited autophagy and ER stress by pharmacology and small interfering RNA (siRNA) in INS-1 cells and rats. The levels of biomarkers for autophagy, ER stress, and apoptosis were evaluated by immunoblotting and immunofluorescence. The number of autophagic vacuoles was observed by transmission electron microscopy. Results: IH induced autophagy activation both in vivo and in vitro, as evidenced by increased autophagic vacuole formation and LC3 turnover, and decreased SQSTM1 level. The levels of ER-stress-related proteins, including GRP78, CHOP, caspase 12, phosphorylated (p)-protein kinase RNA-like ER kinase (PERK), p-eIF2α, and activating transcription factor 4 (ATF4) were increased under IH conditions. Inhibition of ER stress with tauroursodeoxycholic acid or 4-phenylbutyrate partially blocked IH-induced autophagy in INS-1 cells. Furthermore, inhibition of PERK with GSK2606414 or siRNA blocked the ERstress-related PERK/eIF2α/ATF4 signaling pathway and inhibited autophagy induced by IH, which indicates that IH-induced autophagy activation is dependent on this signaling pathway. Promoting autophagy with rapamycin alleviated IH-induced apoptosis, whereas inhibition of autophagy with chloroquine or autophagy-related gene (Atg5 and Atg7) siRNA aggravated pancreatic β-cell apoptosis caused by IH. Conclusion: IH induces autophagy activation through the ER-stress-related PERK/eIF2α/ATF4 signaling pathway, which is a protective response to pancreatic β-cell apoptosis caused by IH.

Honokiol protects pancreatic β cell against high glucose and intermittent hypoxia-induced injury by activating Nrf2/ARE pathway in vitro and in vivo

2018 ◽  
Vol 97 ◽  
pp. 1229-1237 ◽  
Author(s):  
Chen-guang Li ◽  
Chang-lin Ni ◽  
Min Yang ◽  
Yun-zhao Tang ◽  
Zhu Li ◽  
...  
Keyword(s):  
High Glucose ◽  
Intermittent Hypoxia ◽  
Pancreatic Β Cell ◽  
Β Cell

scholarly journals Extracellular Signal-Regulated Kinases Phosphorylate Mitogen-Activated Protein Kinase Phosphatase 3/DUSP6 at Serines 159 and 197, Two Sites Critical for Its Proteasomal Degradation

2005 ◽  
Vol 25 (2) ◽  
pp. 854-864 ◽  
Author(s):  
Sandrine Marchetti ◽  
Clotilde Gimond ◽  
Jean-Claude Chambard ◽  
Thomas Touboul ◽  
Danièle Roux ◽  
...  
Keyword(s):  
Map Kinases ◽  
Fluorescent Protein ◽  
Proteasomal Degradation ◽  
Mitogen Activated Protein Kinase ◽  
Dependent Manner ◽  
Double Mutation ◽  
Extracellular Signal ◽  
Mitogen Activated Protein

ABSTRACT Mitogen-activated protein (MAP) kinase phosphatases (MKPs) are dual-specificity phosphatases that dephosphorylate phosphothreonine and phosphotyrosine residues within MAP kinases. Here, we describe a novel posttranslational mechanism for regulating MKP-3/Pyst1/DUSP6, a member of the MKP family that is highly specific for extracellular signal-regulated kinase 1 and 2 (ERK1/2) inactivation. Using a fibroblast model in which the expression of either MKP-3 or a more stable MKP-3-green fluorescent protein (GFP) chimera was induced by tetracycline, we found that serum induces the phosphorylation of MKP-3 and its subsequent degradation by the proteasome in a MEK1 and MEK2 (MEK1/2)-ERK1/2-dependent manner. In vitro phosphorylation assays using glutathione S-transferase (GST)-MKP-3 fusion proteins indicated that ERK2 could phosphorylate MKP-3 on serines 159 and 197. Tetracycline-inducible cell clones expressing either single or double serine mutants of MKP-3 or MKP-3-GFP confirmed that these two sites are targeted by the MEK1/2-ERK1/2 module in vivo. Double serine mutants of MKP-3 or MKP-3-GFP were more efficiently protected from degradation than single mutants or wild-type MKP-3, indicating that phosphorylation of either serine by ERK1/2 enhances proteasomal degradation of MKP-3. Hence, double mutation caused a threefold increase in the half-life of MKP-3. Finally, we show that the phosphorylation of MKP-3 has no effect on its catalytic activity. Thus, ERK1/2 exert a positive feedback loop on their own activity by promoting the degradation of MKP-3, one of their major inactivators in the cytosol, a situation opposite to that described for the nuclear phosphatase MKP-1.

scholarly journals Increased Bone Mass in Mice Lacking the Adipokine Apelin

Endocrinology ◽  
2013 ◽  
Vol 154 (6) ◽  
pp. 2069-2080 ◽  
Author(s):  
Lalita Wattanachanya ◽  
Wei-Dar Lu ◽  
Ramendra K. Kundu ◽  
Liping Wang ◽  
Marcia J. Abbott ◽  
...  
Keyword(s):  
Bone Mass ◽  
Bone Cells ◽  
Physiological Role ◽  
In Vitro Study ◽  
Maximum Effect ◽  
Dependent Manner ◽  
Primary Mouse ◽  
Skeletal Homeostasis

Abstract Adipose tissue plays an important role in skeletal homeostasis, and there is interest in identifying adipokines that influence bone mass. One such adipokine may be apelin, a ligand for the Gi-G protein-coupled receptor APJ, which has been reported to enhance mitogenesis and suppress apoptosis in MC3T3-E1 cells and primary human osteoblasts (OBs). However, it is unclear whether apelin plays a physiological role in regulating skeletal homeostasis in vivo. In this study, we compared the skeletal phenotypes of apelin knockout (APKO) and wild-type mice and investigated the direct effects of apelin on bone cells in vitro. The increased fractional cancellous bone volume at the distal femur was observed in APKO mice of both genders at 12 weeks of age and persisted until the age of 20. Cortical bone perimeter at the femoral midshaft was significantly increased in males and females at both time points. Dynamic histomorphometry revealed that APKO mice had increased rates of bone formation and mineral apposition, with evidences of accelerated OB proliferation and differentiation, without significant alteration in osteoclast activity. An in vitro study showed that apelin increased proliferation of primary mouse OBs as well as suppressed apoptosis in a dose-dependent manner with the maximum effect at 5nM. However, it had no effect on the formation of mineralized nodules. We did not observed significantly altered in osteoclast parameters in vitro. Taken together, the increased bone mass in mice lacking apelin suggested complex direct and paracrine/endocrine effects of apelin on bone, possibly via modulating insulin sensitivity. These results indicate that apelin functions as a physiologically significant antianabolic factor in bone in vivo.

Regulation of mouse placental lactogen secretion by factors secreted from the pituitary in vitro

1996 ◽  
Vol 134 (1) ◽  
pp. 123-127 ◽  
Author(s):  
Masaaki Yamaguchi ◽  
Akira Miyake
Keyword(s):  
Conditioned Medium ◽  
Northern Blot Analysis ◽  
Cell Number ◽  
Placental Lactogen ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
Placental Cells ◽  
A Cell

Yamaguchi M. Miyake A. Regulation of mouse placental lactogen secretion by factors secreted from the pituitary in vitro. Eur J Endocrinol 1996;134:123–7. ISSN 0804–4643 The effect of factors secreted from the pituitary on mouse placental lactogen I (mPL-I) and mPL-II secretion in vitro was examined. Co-culture of mouse placental cells from day 7 of pregnancy with the pituitary cells of the mother significantly stimulated mPL-I secretion but did not regulate mPL-II secretion. The effect on mPL-I secretion was dependent on the number of pituitary cells. The conditioned medium of pituitary cells also significantly stimulated mPL-I secretion but did not regulate mPL-II secretion. The stimulatory effect of mPL-I secretion was dependent on the volume of the conditioned medium. The number of cells containing mPL-I assessed by immunocytochemistry was increased by the co-culture in a cell number-dependent manner. Northern blot analysis for mPL-I indicated that treatment of placental cells with the pituitary-conditioned medium results in an increase of mPL-I gene expression. These findings suggest that factors secreted from the pituitary directly regulate mPL-I secretion, but not mPL-II secretion, before midpregnancy in vivo. Masaaki Yamaguchi, Department of Obstetrics and Gynecology. Osaka University Medical School, 2-2 Yamadaoka, Suita. Osaka 565, Japan

scholarly journals Neuron Regeneration and Proliferation Effects of Danshen and Tanshinone IIA

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Jui-Lung Shen ◽  
Yueh-Sheng Chen ◽  
Jing-Ying Lin ◽  
Yun-Chen Tien ◽  
Wen-Huang Peng ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Schwann Cell ◽  
Schwann Cells ◽  
Map Kinases ◽  
Mapk Signaling ◽  
Tanshinone Iia ◽  
Dependent Manner ◽  
Neuron Regeneration

This study evaluates the proliferative effects of danshen and its monomer extract, tanshinone IIA, on Schwann cell proliferation. A piece of silicone rubber was guided across a 15-mm gap in the sciatic nerve of a rat. This nerve gap was then filled with different concentrations of danshen (0–100 mg/mL). The results showed that danshen increased the expressions of uPA, cyclin D1, E and ERK, JNK, and P38 MAP kinases via the FGF-2 signaling pathway in a dose-dependent manner. RSC96, Schwann cells were also administered with danshen (0, 20, 40, 60, 80, and 100 μg/mL) and tanshinone IIA (0, 2, 4, 6, 8, and 10 μg/mL). In lower concentrations, danshen and tanshinone IIA exhibited an apparent effect on Schwann cells. Similar effects were also demonstrated in the FGF-2-uPA regulating cascade and cell cycle proliferative protein results. Schwann cell migration was elevated as well. We used MAPK-signaling chemical inhibitors and identified the proliferative effects of danshen and tanshinone IIA as MAPK-signaling dependent. The results from thein vitrosystems indicate that danshen and tanshinone IIA can be used to induce Schwann cell proliferation, andin vivoresults potentially suggest that danshen and tanshinone IIA might enhance neuron regeneration.

scholarly journals Identification of PCIF1, a POZ Domain Protein That Inhibits PDX-1 (MODY4) Transcriptional Activity

2004 ◽  
Vol 24 (10) ◽  
pp. 4372-4383 ◽  
Author(s):  
Aihua Liu ◽  
Biva M. Desai ◽  
Doris A. Stoffers
Keyword(s):  
Late Onset ◽  
Dependent Manner ◽  
Gene Promoters ◽  
Transactivation Domain ◽  
Β Cells ◽  
Β Cell ◽  
C Terminus ◽  
Domain Protein

ABSTRACT Hox factors are evolutionarily conserved homeodomain-containing transcription factors that activate and repress gene expression in a precise temporally and spatially regulated manner during development and differentiation. Pancreatic-duodenal homeobox 1 (PDX-1) is a Hox-type protein that is a critical requirement for normal pancreas development and for proper differentiation of the endocrine pancreas. In humans, PDX-1 gene mutation causes pancreatic agenesis and early- and late-onset type 2 diabetes. PDX-1 consists of an N-terminal transactivation domain, a homeodomain responsible for DNA binding and nuclear localization, and a conserved C terminus that is mutated in human diabetes but whose function is poorly understood. We have identified a novel POZ domain protein, PDX-1 C terminus-interacting factor 1 (PCIF1)/SPOP, that interacts with PDX-1 both in vitro and in vivo. PCIF1 is localized to the nucleus in a speckled pattern, and coexpression of PDX-1 alters the subnuclear distribution of PCIF1. Functionally, PCIF1 inhibits PDX-1 transactivation of established target gene promoters in a specific and dose-dependent manner that requires critical amino acids in the PDX-1 C terminus. PCIF1 is expressed in adult pancreatic insulin-producing β cells, and overexpression of PCIF1 inhibits the rat insulin 1 and rat insulin 2 promoters in the MIN6 insulinoma β cell line. The coexpression of PCIF1 with PDX-1 in β cells and the ability of PCIF1 to repress PDX-1 transactivation suggest that modulation of PDX-1 function by PCIF1 may regulate normal β cell differentiation.

scholarly journals In vivo evaluation of GG2–GG1/A2 element activity in the insulin promoter region using the CRISPR–Cas9 system

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hirofumi Noguchi ◽  
Chika Miyagi-Shiohira ◽  
Takao Kinjo ◽  
Issei Saitoh ◽  
Masami Watanabe
Keyword(s):  
Promoter Region ◽  
In Vivo Studies ◽  
Pancreatic Β Cell ◽  
Β Cell ◽  
In Vivo Evaluation ◽  
Specific Expression ◽  
Insulin Promoter ◽  
Element Activity

AbstractThe insulin promoter is regulated by ubiquitous as well as pancreatic β-cell-specific transcription factors. In the insulin promoter, GG2–GG1/A2–C1 (bases − 149 to − 116 in the human insulin promoter) play important roles in regulating β-cell-specific expression of the insulin gene. However, these events were identified through in vitro studies, and we are unaware of comparable in vivo studies. In this study, we evaluated the activity of GG2–GG1/A2 elements in the insulin promoter region in vivo. We generated homozygous mice with mutations in the GG2–GG1/A2 elements in each of the Ins1 and Ins2 promoters by CRISPR–Cas9 technology. The mice with homozygous mutations in the GG2–GG1/A2 elements in both Ins1 and Ins2 were diabetic. These data suggest that the GG2–GG1/A2 element in mice is important for Ins transcription in vivo.

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