HKDC1 Is a Novel Hexokinase Involved in Whole-Body Glucose Use

In a recent genome-wide association study, hexokinase domain-containing protein 1, or HKDC1, was found to be associated with gestational glucose levels during 2-hour glucose tolerance tests at 28 weeks of pregnancy. Because our understanding of the mediators of gestational glucose homeostasis is incomplete, we have generated the first transgenic mouse model to begin to understand the role of HKDC1 in whole-body glucose homeostasis. Interestingly, deletion of both HKDC1 alleles results in in utero embryonic lethality. Thus, in this study, we report the in vivo role of HKDC1 in whole-body glucose homeostasis using a heterozygous-deleted HKDC1 mouse model (HKDC1+/−) as compared with matched wild-type mice. First, we observed no weight, fasting or random glucose, or fasting insulin abnormalities with aging in male and female HKDC1+/− mice. However, during glucose tolerance tests, glucose levels were impaired in both female and male HKDC1+/− mice at 15, 30, and 120 minutes at a later age (28 wk of age). These glucose tolerance differences also existed in the female HKDC1+/− mice at earlier ages but only during pregnancy. And finally, the impaired glucose tolerance in HKDC1+/− mice was likely due to diminished whole-body glucose use, as indicated by the decreased hepatic energy storage and reduced peripheral tissue uptake of glucose in HKDC1+/− mice. Collectively, these data highlight that HKDC1 is needed to maintain whole-body glucose homeostasis during pregnancy but also with aging, possibly through its role in glucose use.

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MiR-206 is expressed in pancreatic islets and regulates glucokinase activity

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00510.2015 ◽

2016 ◽

Vol 311 (1) ◽

pp. E175-E185 ◽

Cited By ~ 20

Author(s):

Manjula Vinod ◽

Jay V. Patankar ◽

Vinay Sachdev ◽

Saša Frank ◽

Wolfgang F. Graier ◽

...

Keyword(s):

Glucose Tolerance ◽

Pancreatic Islets ◽

Glucose Homeostasis ◽

Posttranscriptional Regulation ◽

Germ Line ◽

In Silico Analysis ◽

Liver Glycogen ◽

Whole Body ◽

The Metabolic Syndrome

Glucose homeostasis is a complex indispensable process, and its dysregulation causes hyperglycemia and type 2 diabetes mellitus. Glucokinase (GK) takes a central role in these pathways and is thus rate limiting for glucose-stimulated insulin secretion (GSIS) from pancreatic islets. Several reports have described the transcriptional regulation of Gck mRNA, whereas its posttranscriptional mechanisms of regulation, especially those involving microRNAs (miR), are poorly understood. In this study, we investigated the role of miR-206 as a posttranscriptional regulator of Gck. In addition, we examined the effects of miR-206 on glucose tolerance, GSIS, and gene expression in control and germ line miR-206 knockout (KO) mice fed either with chow or high-fat diet (HFD). MiR-206 was found in Gck-expressing tissues and was differentially altered in response to HFD feeding. Pancreatic islets showed the most profound induction in the expression of miR-206 in response to HFD. Chow- and HFD-fed miR-206KO mice have improved glucose tolerance and GSIS but unaltered insulin sensitivity. In silico analysis of Gck mRNA revealed a conserved 8-mer miR-206 binding site. Hence, the predicted regulation of Gck by miR-206 was confirmed in reporter and GK activity assays. Concomitant with increased GK activity, miR-206KO mice had elevated liver glycogen content and plasma lactate concentrations. Our findings revealed a novel mechanism of posttranscriptional regulation of Gck by miR-206 and underline the crucial role of pancreatic islet miR-206 in the regulation of whole body glucose homeostasis in a murine model that mimics the metabolic syndrome.

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Critical Role of Egr Transcription Factors in Regulating Insulin Biosynthesis, Blood Glucose Homeostasis, and Islet Size

Endocrinology ◽

10.1210/en.2012-1064 ◽

2012 ◽

Vol 153 (7) ◽

pp. 3040-3053 ◽

Cited By ~ 21

Author(s):

Isabelle Müller ◽

Oliver G. Rössler ◽

Christine Wittig ◽

Michael D. Menger ◽

Gerald Thiel

Keyword(s):

Transcription Factors ◽

Glucose Tolerance ◽

Transgenic Mice ◽

Glucose Homeostasis ◽

Insulin Biosynthesis ◽

Β Cells ◽

Pancreatic Β Cells ◽

Islet Size

Expression of early growth response protein (Egr)-1, a protein of the Egr family of zinc finger transcription factors, is stimulated in glucose-treated pancreatic β-cells and insulinoma cells. The purpose of this study was to elucidate the role of Egr transcription factors in pancreatic β-cells in vivo. To overcome the problem associated with redundancy of functions between Egr proteins, conditional transgenic mice were generated expressing a dominant-negative mutant of Egr-1 in pancreatic β-cells. The Egr-1 mutant interferes with DNA binding of all Egr proteins and thus impairs the biological functions of the entire Egr family. Expression of the Egr-1 mutant reduced expression of TGFβ and basic fibroblast growth factor, known target genes of Egr-1, whereas the expression of Egr-1, Egr-3, Ets-like gene-1 (Elk-1), and specificity protein-3 was not changed in the presence of the Egr-1 mutant. Expression of the homeobox protein pancreas duodenum homeobox-1, a major regulator of insulin biosynthesis, was reduced in islets expressing the Egr-1 mutant. Accordingly, insulin mRNA and protein levels were reduced by 75 or 25%, respectively, whereas expression of glucagon and somatostatin was not altered after expression of the Egr-1 mutant in β-cells. Glucose tolerance tests revealed that transgenic mice expressing the Egr-1 mutant in pancreatic β-cells displayed impaired glucose tolerance. In addition, increased caspase-3/7 activity was detected as a result of transgene expression, leading to a 20% decrease of the size of the islets. These results show that Egr proteins play an important role in controlling insulin biosynthesis, glucose homeostasis, and islet size of pancreatic β-cells in vivo.

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Reduced expression of TCF7L2 in adipocyte impairs glucose tolerance associated with decreased insulin secretion, incretins levels and lipid metabolism dysregulation in male mice

10.1101/2020.05.18.102384 ◽

2020 ◽

Cited By ~ 1

Author(s):

Marie-Sophie Nguyen-Tu ◽

Aida Martinez-Sanchez ◽

Isabelle Leclerc ◽

Guy A. Rutter ◽

Gabriela da Silva Xavier

Keyword(s):

Insulin Secretion ◽

Lipid Metabolism ◽

Glucose Tolerance ◽

Impaired Glucose Tolerance ◽

Glucose Homeostasis ◽

Knockout Mice ◽

Male Mice ◽

Glucose Stimulated Insulin Secretion

AbstractTranscription factor 7-like 2 (TCF7L2) is a downstream effector of the Wnt/beta-catenin signalling pathway and its expression is critical for adipocyte development. The precise role of TCF7L2 in glucose and lipid metabolism in adult adipocytes remains to be defined. Here, we aim to investigate how changes in TCF7L2 expression in mature adipocytes affect glucose homeostasis. Tcf7l2 was selectively ablated from mature adipocytes in C57BL/6J mice using an adiponectin promoter-driven Cre recombinase to recombine alleles floxed at exon 1 of the Tcf7l2 gene. Mice lacking Tcf7l2 in mature adipocytes displayed normal body weight. Male mice exhibited normal glucose homeostasis at eight weeks of age. Male heterozygote knockout mice (aTCF7L2het) exhibited impaired glucose tolerance (AUC increased 1.14 ± 0.04 -fold, p=0.03), as assessed by intraperitoneal glucose tolerance test, and changes in fat mass at 16 weeks (increased by 1.4 ± 0.09-fold, p=0.007). Homozygote knockout mice exhibited impaired oral glucose tolerance at 16 weeks of age (AUC increased 2.15 ± 0.15-fold, p=0.0001). Islets of Langerhans exhibited impaired glucose-stimulated insulin secretion in vitro (decreased 0.54 ± 0.13-fold aTCF7L2KO vs control, p=0.02), but no changes in in vivo glucose-stimulated insulin secretion. Female mice in which one or two alleles of the Tcf7l2 gene was knocked out in adipocytes displayed no changes in glucose tolerance, insulin sensitivity or insulin secretion. Plasma levels of glucagon-like peptide-1 and gastric inhibitory polypeptide were lowered in knockout mice (decreased 0.57 ± 0.03-fold and 0.41 ± 0.12-fold, p=0.04 and p=0.002, respectively), whilst plasma free fatty acids and Fatty Acid Binding Protein 4 circulating levels were increased by 1.27 ± 0.07 and 1.78 ± 0.32-fold, respectively (p=0.05 and p=0.03). Mice with biallelic Tcf7l2 deletion exposed to high fat diet for 9 weeks exhibited impaired glucose tolerance (p=0.003 at 15 min after glucose injection) which was associated with reduced in vivo glucose-stimulated insulin secretion (decreased 0.51 ± 0.03-fold, p=0.02). Thus, our data indicate that loss of Tcf7l2 gene expression in adipocytes leads to impairments on metabolic responses which are dependent on gender, age and nutritional status. Our findings further illuminate the role of TCF7L2 in the maintenance of glucose homeostasis.

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Abstract 1216: The Cardioactive Peptide Apelin Increases Adipocyte Glucose Uptake and is Necessary for the Maintenance of Systemic Insulin Sensitivity

Circulation ◽

10.1161/circ.116.suppl_16.ii_247 ◽

2007 ◽

Vol 116 (suppl_16) ◽

Author(s):

Patrick Yue ◽

Tomoko Asagami ◽

Ramendra K Kundu ◽

Yin-Gail Yee ◽

Alexander J Glassford ◽

...

Keyword(s):

Insulin Sensitivity ◽

Glucose Tolerance ◽

Glucose Uptake ◽

Embryonic Stem ◽

Peptide Hormone ◽

Wild Type ◽

Glucose Levels ◽

Glucose Tolerance Tests

Background : Apelin, a peptide hormone with unique cardioactive properties, is also an adipokine, secreted by adipocytes in response to insulin. However, the overall effect of apelin on insulin sensitivity remains largely uncharacterized. Methods : For in vitro experiments, 3T3L1 cells were differentiated into adipocytes over 8 days, with apelin (1 microM) added daily to the media. Cells were then treated with insulin (100 nM; n = 5) for 30 minutes and incubated with 2-[ 3 H]-deoxyglucose. Glucose incorporation was then measured by scintillation counting. For in vivo experiments (n = 4 all studies), apelin-deficient (KO) mice were created by homologous recombination in embryonic stem cells. At age 7 weeks, insulin and glucose tolerance tests, as well as an enzyme immunosorbent assay for insulin, were performed after a 6-hour fast. The mice were then scanned by computed tomography using a GE eXplore RS MicroCT system, and visceral adipose content was determined with MicroView software. Upon sacrifice 1 week later, visceral adipocytes were isolated via collagenase digestion, exposed to insulin, and assessed for glucose uptake as above. Results : Because apelin is upregulated by insulin in adipocytes, we measured glucose uptake in differentiated 3T3L1 cells chronically dosed with apelin. Though no differences were observed in basal uptake, insulin-induced uptake was increased versus control (p < 0.05). To further investigate the role of apelin in vivo , we assessed for insulin resistance in apelin KO mice. At 8 weeks of age, apelin KOs were heavier than age-matched wild type controls (25 vs. 22 g; p < 0.05). Though fasting glucose levels were not significantly different between groups, insulin levels were increased in the KOs (895 vs. 477 pg/microL; p < 0.05). In addition, both insulin and glucose tolerance tests were significantly abnormal in the KOs compared to wild type. Moreover, visceral fat volume was greater in the KOs (274 vs. 248 mm 3 /g body weight; p < 0.05). Finally, insulin-stimulated uptake was reduced (p < 0.05). Conclusions : Apelin is necessary for the proper maintenance of glucose homeostasis. Furthermore, apelin potentiates insulin-induced glucose uptake in adipocytes, suggesting a possible mechanism for its insulin sensitizing effects.

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The effect of fat removal on glucose tolerance is depot specific in male and female mice

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00649.2006 ◽

2007 ◽

Vol 293 (4) ◽

pp. E1012-E1020 ◽

Cited By ~ 42

Author(s):

Haifei Shi ◽

April D. Strader ◽

Stephen C. Woods ◽

Randy J. Seeley

Keyword(s):

Adipose Tissue ◽

Glucose Tolerance ◽

Glucose Homeostasis ◽

Male And Female ◽

Female Mice ◽

Glucose Levels ◽

Dietary Condition ◽

Fat Removal ◽

Glucose Tolerance Tests ◽

Males And Females

Energy is stored predominately as lipid in white adipose tissue (WAT) in distinct anatomical locations, with each site exerting different effects on key biological processes, including glucose homeostasis. To determine the relative contributions of subcutaneous and visceral WAT on glucose homeostasis, comparable amounts of adipose tissue from abdominal subcutaneous inguinal WAT (IWAT), intra-abdominal retroperitoneal WAT (RWAT), male gonadal epididymal WAT (EWAT), or female gonadal parametrial WAT (PWAT) were removed. Gonadal fat removal in both male and female chow-fed lean mice resulted in lowered glucose levels across glucose tolerance tests. Female lean C57BL/6J mice as well as male and female lean FVBN mice significantly improved glucose tolerance, indicated by decreased areas under glucose clearance curves. For the C57BL/6J mice maintained on a high-fat butter-based diet, glucose homeostasis was improved only in female mice with PWAT removal. Removal of IWAT or RWAT did not affect glucose tolerance in either dietary condition. We conclude that WAT contribution to glucose homeostasis is depot specific, with male gonadal EWAT contributing to glucose homeostasis in the lean state, whereas female gonadal PWAT contributes to glucose homeostasis in both lean and obese mice. These data illustrate both critical differences among various WAT depots and how they influence glucose homeostasis and highlight important differences between males and females in glucose regulation.

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The role of resistance to inhibitors of cholinesterase 8b in the control of heart rate

Physiological Genomics ◽

10.1152/physiolgenomics.00157.2020 ◽

2021 ◽

Vol 53 (4) ◽

pp. 150-159

Author(s):

Sonia Sebastian ◽

Muriel Nobles ◽

Elena Tsisanova ◽

Andreas Ludwig ◽

Patricia B. Munroe ◽

...

Keyword(s):

Heart Rate ◽

Genome Wide Association Study ◽

Sinoatrial Node ◽

Chronotropic Response ◽

Genome Wide ◽

Heterologous System ◽

Stimulatory G Protein ◽

Electrocardiographic Intervals

We have assessed the role of ric-b8 in the control of heart rate after the gene was implicated in a recent genome-wide association study of resting heart rate. We developed a novel murine model in which it was possible to conditionally delete ric-8b in the sinoatrial (SA) node after the addition of tamoxifen. Despite this, we were unable to obtain homozygotes and thus studied heterozygotes. Haploinsufficiency of ric-8b in the sinoatrial node induced by the addition of tamoxifen in adult animals leads to mice with a reduced heart rate. However, other electrocardiographic intervals (e.g., PR and QRS) were normal, and there was no apparent arrhythmia such as heart block. The positive chronotropic response to isoprenaline was abrogated, whereas the response to carbachol was unchanged. The pacemaker current If(funny current) has an important role in regulating heart rate, and its function is modulated by both isoprenaline and carbachol. Using a heterologous system expressing HCN4, we show that ric-8b can modulate the HCN4 current. Overexpression of ric-8b led to larger HCN4 currents, whereas silencing ric-8b led to smaller currents. Ric-8b modulates heart rate responses in vivo likely via its actions on the stimulatory G-protein.

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Major role of iron uptake systems in the intrinsic extra-intestinal virulence of the genus Escherichia revealed by a genome-wide association study

10.1101/712034 ◽

2019 ◽

Cited By ~ 4

Author(s):

Marco Galardini ◽

Olivier Clermont ◽

Alexandra Baron ◽

Bede Busby ◽

Sara Dion ◽

...

Keyword(s):

Association Study ◽

Iron Uptake ◽

Genome Wide Association Study ◽

Opportunistic Pathogen ◽

Genome Wide Association ◽

E Coli ◽

Genome Wide ◽

A Genome

AbstractThe genus Escherichia is composed of several species and cryptic clades, including E. coli, which behave as a vertebrate gut commensal, but also as an opportunistic pathogen involved in both diarrheic and extra-intestinal diseases. To characterize the genetic determinants of extra-intestinal virulence within the genus, we carried out an unbiased genome-wide association study (GWAS) on 370 commensal, pathogenic and environmental strains representative of the Escherichia genus phylogenetic diversity and including E. albertii (n=7), E. fergusonii (n=5), Escherichia clades (n=32) and E. coli (n=326), tested in a mouse model of sepsis. We found that the high-pathogenicity island (HPI), a ∼35 kbp gene island encoding the yersiniabactin siderophore, is highly associated with death in mice, surpassing other associated genetic factors also related to iron uptake, such as the aerobactin and the sitABCD operons. We validated the association in vivo by deleting key components of the HPI in E. coli strains in two phylogenetic backgrounds, and found that virulence is correlated in E. coli with growth in the presence of various stressors including several antimicrobials, which hints at collateral sensitivities associated with intrinsic virulence. This study points to the major role of iron capture systems in the extra-intestinal virulence of the genus Escherichia and the collateral effects on cell growth of such systems.

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STUDIES IN CONGENITAL GENERALIZED LIPODYSTROPHY (SEIP-BERARDINELLI SYNDROME)

Acta Endocrinologica ◽

10.1530/acta.0.0720475 ◽

1973 ◽

Vol 72 (3) ◽

pp. 475-494 ◽

Cited By ~ 21

Author(s):

Svein Oseid

Keyword(s):

Insulin Resistance ◽

Glucose Tolerance ◽

Normal Glucose Tolerance ◽

Juvenile Form ◽

Congenital Generalized Lipodystrophy ◽

Glucose Levels ◽

Normal Glucose ◽

Glucose Tolerance Tests ◽

The One ◽

Adipose Organ

ABSTRACT Six cases of congenital generalized lipodystrophy have been studied at different ages from infancy to adolescence with regard to glucose tolerance, insulin secretion, and insulin sensitivity. During the first few years of life there is normal glucose tolerance. The fasting immuno-reactive insulin (IRI) levels are either slightly elevated or normal. The IRI response to glucose is exaggerated and prolonged, at least from the third year of life. Some degree of insulin resistance is already present in infancy. From the age of 8–10 years glucose tolerance decreases rapidly. The fasting IRI levels are usually grossly elevated, while fasting plasma glucose levels are only moderately elevated or normal. The IRI responses to oral and iv administered glucose, and to tolbutamide are exaggerated; the insulinogenic indices are high. Cortisone primed glucose tolerance tests become abnormal. Insulin resistance is marked, and increases with age. After cessation of growth at approximately 12 years of age, frank diabetes with fasting hyperglycaemia and diabetic glucose tolerance curves developed in the one patient followed beyond this age. Her fasting IRI was increased, but there was a poor IRI response to glucose stimulation, suggesting a partial exhaustion of the β-cells. Her initial IRI response to tolbutamide was still good, but not as brisk as in the younger patients. This type of diabetes is quite different from the juvenile form, and also from the diabetes of older age. It may be causally related to the lack of an adequate adipose organ necessary for the disposal of excesses of glucose, or possibly related to another anti-insulin mechanism.

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Gpr1 is an active chemerin receptor influencing glucose homeostasis in obese mice

Journal of Endocrinology ◽

10.1530/joe-14-0069 ◽

2014 ◽

Vol 222 (2) ◽

pp. 201-215 ◽

Cited By ~ 52

Author(s):

Jillian L Rourke ◽

Shanmugam Muruganandan ◽

Helen J Dranse ◽

Nichole M McMullen ◽

Christopher J Sinal

Keyword(s):

Adipose Tissue ◽

Glucose Homeostasis ◽

Stromal Vascular Fraction ◽

Tolerance Test ◽

Glucose Levels ◽

Brown Adipose ◽

Elevated Glucose ◽

And Function ◽

G Protein Coupled

Chemerin is an adipose-derived signaling protein (adipokine) that regulates adipocyte differentiation and function, immune function, metabolism, and glucose homeostasis through activation of chemokine-like receptor 1 (CMKLR1). A second chemerin receptor, G protein-coupled receptor 1 (GPR1) in mammals, binds chemerin with an affinity similar to CMKLR1; however, the function of GPR1 in mammals is essentially unknown. Herein, we report that expression of murineGpr1mRNA is high in brown adipose tissue and white adipose tissue (WAT) and skeletal muscle. In contrast to chemerin (Rarres2) andCmklr1,Gpr1expression predominates in the non-adipocyte stromal vascular fraction of WAT. Heterozygous and homozygousGpr1-knockout mice fed on a high-fat diet developed more severe glucose intolerance than WT mice despite having no difference in body weight, adiposity, or energy expenditure. Moreover, mice lackingGpr1exhibited reduced glucose-stimulated insulin levels and elevated glucose levels in a pyruvate tolerance test. This study is the first, to our knowledge, to report the effects ofGpr1deficiency on adiposity, energy balance, and glucose homeostasisin vivo. Moreover, these novel results demonstrate that GPR1 is an active chemerin receptor that contributes to the regulation of glucose homeostasis during obesity.

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