Evolutionary structural and functional conservation of an ortholog of the GLUT2 glucose transporter gene (SLC2A2) in zebrafish

In mammals, GLUT2 plays an essential role in glucose homeostasis. From an evolutionary perspective, relatively little is known about the biology of GLUT2, or other GLUTs, in nonmammalian vertebrates. Here, we have conducted studies to functionally characterize GLUT2 in zebrafish. First, we cloned the zebrafish ortholog of GLUT2 (zfGLUT2) encoding a protein of 504 amino acids with high-sequence identity to other known vertebrate GLUT2 proteins. The zfGLUT2 gene consists of 11 exons and 10 introns, spanning 20 kb and mapping to a region of chromosome 2 that exhibits conserved synteny with human chromosome 3. When expressed in Xenopus oocytes, zfGLUT2 transported 2-deoxyglucose (2-DG) with similar affinity than mammalian GLUT2 ( Km of 11 mM). Transport of 2-DG was competed mostly by d-fructose and d-mannose and was inhibited by cytochalasin B. During early development, zfGLUT2 expression was detected already at 10 h postfertilization and remained elevated in 5-day larvae, when it was clearly localized to the liver and intestinal bulb. In the adult, zfGLUT2 expression was highest in testis, brain, skin, kidney, and intestine, followed by liver and muscle. In the intestine, zfGLUT2 transcripts were detected in absorptive enterocytes, and its mRNA levels were altered by fasting and refeeding, suggesting that its expression in the intestine may be regulated by the nutritional status. These results indicate that the structure and function of GLUT2 has been remarkably well conserved during vertebrate evolution and open the way for the use of zebrafish as a model species in which to study the biology and pathophysiology of GLUT2.

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Regulation of glucose transporter-specific mRNA levels in rat adipose cells with fasting and refeeding. Implications for in vivo control of glucose transporter number.

Journal of Clinical Investigation ◽

10.1172/jci113859 ◽

1989 ◽

Vol 83 (1) ◽

pp. 199-204 ◽

Cited By ~ 42

Author(s):

B B Kahn ◽

S W Cushman ◽

J S Flier

Keyword(s):

Glucose Transporter ◽

Mrna Levels ◽

Fasting And Refeeding ◽

Adipose Cells ◽

Specific Mrna

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Recovery of glucose-induced insulin secretion in a rat model of NIDDM is not accompanied by return of the B-cell GLUT2 glucose transporter

Diabetes ◽

10.2337/diabetes.41.10.1320 ◽

1992 ◽

Vol 41 (10) ◽

pp. 1320-1327 ◽

Cited By ~ 5

Author(s):

C. Chen ◽

B. Thorens ◽

S. Bonner-Weir ◽

G. C. Weir ◽

J. L. Leahy

Keyword(s):

Insulin Secretion ◽

B Cell ◽

Rat Model ◽

Glucose Transporter ◽

Glut2 Glucose Transporter

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Faculty Opinions recommendation of NMR structures of two designed proteins with high sequence identity but different fold and function.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1124240.581386 ◽

2008 ◽

Author(s):

H Jane Dyson ◽

Gira Bhabha

Keyword(s):

High Sequence Identity ◽

Sequence Identity ◽

Nmr Structures ◽

Designed Proteins ◽

And Function

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Glucolipotoxicity and GLP-1 secretion

BMJ Open Diabetes Research & Care ◽

10.1136/bmjdrc-2020-001905 ◽

2021 ◽

Vol 9 (1) ◽

pp. e001905

Author(s):

Jung-Hee Hong ◽

Dae-Hee Kim ◽

Moon-Kyu Lee

Keyword(s):

Glucose Transporter ◽

Cell Function ◽

Nicotinamide Adenine Dinucleotide Phosphate ◽

Mrna Levels ◽

Dependent Manner ◽

Gene Expressions ◽

Simultaneous Treatment ◽

L Cells ◽

Triglyceride Accumulation

IntroductionThe concept of glucolipotoxicity refers to the combined, deleterious effects of elevated glucose and/or fatty acid levels.Research design and methodsTo investigate the effects of chronic glucolipotoxicity on glucagon-like peptide-1-(7-36) amide (GLP-1) secretion, we generated glucolipotoxic conditions in human NCI-H716 enteroendocrine cells using either 5 or 25 mM glucose with or without 500 µM palmitate for 72 hours. For in vivo study, we have established a chronic nutrient infusion model in the rat. Serial blood samples were collected for 2 hours after the consumption of a mixed meal to evaluate insulin sensitivity and β-cell function.ResultsChronic glucolipotoxic conditions decreased GLP-1 secretion and the expressions of pCREB, pGSK3β, β-catenin, and TCF7L2 in NCI-H716 cells. Glucolipotoxicity conditions reduced glucose transporter expression, glucose uptake, and nicotinamide-adenine dinucleotide phosphate (NADPH) levels in L-cells, and increased triglyceride accumulation. In contrast, PPARα and ATP levels were reduced, which correlated well with decreased levels of SUR1 and Kir6.2, cAMP contents and expressions of pCAMK2, EPAC and PKA. We also observed an increase in reactive oxygen species production, UCP2 expression and Complex I activity. Simultaneous treatment with insulin restored the GLP-1 secretion. Glucolipotoxic conditions decreased insulin secretion in a time-dependent manner in INS-1 cells, which was recovered with exendin-4 cotreatment. Glucose and SMOFlipid infusion for 6 hours decreased GLP-1 secretion and proglucagon mRNA levels as well as impaired the glucose tolerance, insulin and C-peptide secretion in rats.ConclusionThese results provide evidence for the first time that glucolipotoxicity could affect GLP-1 secretion through changes in glucose and lipid metabolism, gene expressions, and proglucagon biosynthesis and suggest the interrelationship between glucolipotoxicities of L-cells and β-cells which develops earlier than that of L-cells.

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Spinal Cord Injury Increases Pro-inflammatory Cytokine Expression in Kidney at Acute and Sub-chronic Stages

Inflammation ◽

10.1007/s10753-021-01507-x ◽

2021 ◽

Author(s):

Shangrila Parvin ◽

Clintoria R. Williams ◽

Simone A. Jarrett ◽

Sandra M. Garraway

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Inflammatory Response ◽

Inflammatory Cytokine ◽

Cardiovascular Health ◽

Mrna Levels ◽

Post Injury ◽

Cord Injury ◽

And Function ◽

The Impact

Abstract— Accumulating evidence supports that spinal cord injury (SCI) produces robust inflammatory plasticity. We previously showed that the pro-inflammatory cytokine tumor necrosis factor (TNF)α is increased in the spinal cord after SCI. SCI also induces a systemic inflammatory response that can impact peripheral organ functions. The kidney plays an important role in maintaining cardiovascular health. However, SCI-induced inflammatory response in the kidney and the subsequent effect on renal function have not been well characterized. This study investigated the impact of high and low thoracic (T) SCI on C-fos, TNFα, interleukin (IL)-1β, and IL-6 expression in the kidney at acute and sub-chronic timepoints. Adult C57BL/6 mice received a moderate contusion SCI or sham procedures at T4 or T10. Uninjured mice served as naïve controls. mRNA levels of the proinflammatory cytokines IL-1β, IL-6, TNFα, and C-fos, and TNFα and C-fos protein expression were assessed in the kidney and spinal cord 1 day and 14 days post-injury. The mRNA levels of all targets were robustly increased in the kidney and spinal cord, 1 day after both injuries. Whereas IL-6 and TNFα remained elevated in the spinal cord at 14 days after SCI, C-fos, IL-6, and TNFα levels were sustained in the kidney only after T10 SCI. TNFα protein was significantly upregulated in the kidney 1 day after both T4 and T10 SCI. Overall, these results clearly demonstrate that SCI induces robust systemic inflammation that extends to the kidney. Hence, the presence of renal inflammation can substantially impact renal pathophysiology and function after SCI.

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Restoration of Noradrenergic Function in Parkinson’s Disease Model Mice

ASN NEURO ◽

10.1177/17590914211009730 ◽

2021 ◽

Vol 13 ◽

pp. 175909142110097

Author(s):

Kui Cui ◽

Fan Yang ◽

Turan Tufan ◽

Muhammad U. Raza ◽

Yanqiang Zhan ◽

...

Keyword(s):

Parkinson’S Disease ◽

Parkinson's Disease ◽

Transcription Factors ◽

Disease Model ◽

Neuronal Loss ◽

Mrna Levels ◽

Gene Therapies ◽

Protein Levels ◽

Dopaminergic Systems ◽

And Function

Dysfunction of the central noradrenergic and dopaminergic systems is the primary neurobiological characteristic of Parkinson’s disease (PD). Importantly, neuronal loss in the locus coeruleus (LC) that occurs in early stages of PD may accelerate progressive loss of dopaminergic neurons. Therefore, restoring the activity and function of the deficient noradrenergic system may be an important therapeutic strategy for early PD. In the present study, the lentiviral constructions of transcription factors Phox2a/2b, Hand2 and Gata3, either alone or in combination, were microinjected into the LC region of the PD model VMAT2 Lo mice at 12 and 18 month age. Biochemical analysis showed that microinjection of lentiviral expression cassettes into the LC significantly increased mRNA levels of Phox2a, and Phox2b, which were accompanied by parallel increases of mRNA and proteins of dopamine β-hydroxylase (DBH) and tyrosine hydroxylase (TH) in the LC. Furthermore, there was considerable enhancement of DBH protein levels in the frontal cortex and hippocampus, as well as enhanced TH protein levels in the striatum and substantia nigra. Moreover, these manipulations profoundly increased norepinephrine and dopamine concentrations in the striatum, which was followed by a remarkable improvement of the spatial memory and locomotor behavior. These results reveal that over-expression of these transcription factors in the LC improves noradrenergic and dopaminergic activities and functions in this rodent model of PD. It provides the necessary groundwork for the development of gene therapies of PD, and expands our understanding of the link between the LC-norepinephrine and dopamine systems during the progression of PD.

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DBC1 (Deleted in Breast Cancer 1) modulates the stability and function of the nuclear receptor Rev-erbα

Biochemical Journal ◽

10.1042/bj20121085 ◽

2013 ◽

Vol 451 (3) ◽

pp. 453-461 ◽

Cited By ~ 26

Author(s):

Claudia C. S. Chini ◽

Carlos Escande ◽

Veronica Nin ◽

Eduardo N. Chini

Keyword(s):

Breast Cancer ◽

Nuclear Receptor ◽

Clock Genes ◽

Mrna Levels ◽

Protein Levels ◽

The Stability ◽

And Function ◽

Interfering Rna ◽

In Cells

The nuclear receptor Rev-erbα has been implicated as a major regulator of the circadian clock and integrates circadian rhythm and metabolism. Rev-erbα controls circadian oscillations of several clock genes and Rev-erbα protein degradation is important for maintenance of the circadian oscillations and also for adipocyte differentiation. Elucidating the mechanisms that regulate Rev-erbα stability is essential for our understanding of these processes. In the present paper, we report that the protein DBC1 (Deleted in Breast Cancer 1) is a novel regulator of Rev-erbα. Rev-erbα and DBC1 interact in cells and in vivo, and DBC1 modulates the Rev-erbα repressor function. Depletion of DBC1 by siRNA (small interfering RNA) in cells or in DBC1-KO (knockout) mice produced a marked decrease in Rev-erbα protein levels, but not in mRNA levels. In contrast, DBC1 overexpression significantly enhanced Rev-erbα protein stability by preventing its ubiquitination and degradation. The regulation of Rev-erbα protein levels and function by DBC1 depends on both the N-terminal and C-terminal domains of DBC1. More importantly, in cells depleted of DBC1, there was a dramatic decrease in circadian oscillations of both Rev-erbα and BMAL1. In summary, our data identify DBC1 as an important regulator of the circadian receptor Rev-erbα and proposes that Rev-erbα could be involved in mediating some of the physiological effects of DBC1.

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