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Allen AA, Pierce AT, Dauchy RT, Voros GB, Dobek GL. Influence of Light Phase Exposure to LED Lighting on Circadian Levels of Neuroendocrine Hormones in Sprague-Dawley Rats. J Am Assoc Lab Anim Sci 2022; 61:333-343. [PMID: 35738839 PMCID: PMC9674009 DOI: 10.30802/aalas-jaalas-21-000123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 01/13/2022] [Accepted: 05/02/2022] [Indexed: 01/03/2023]
Abstract
Light and lighting protocols of animal research facilities are critically important to the outcomes of biomedical research that uses animals. Previous studies from our laboratory showed that the wavelength (color) of light in animal housing areas affects the nocturnal melatonin signal that temporally coordinates circadian rhythms in rodents. Here, we tested the hypothesis that exposure to LED light enriched in the blue-appearing portion (460-480 nm) of the visible spectrum during the light phase (bLAD) influences circadian concentrations of select neuroendocrine hormones in adolescent Sprague-Dawley rats. Male and female rats (4 to 5 wk old) were housed on a novel IVC system under a 12L:12D in either cool-white fluorescent (control, n = 72) or bLAD (experimental, n = 72) lighting. Every third day, body weight and food and water consumption were measured. On Day 30, rats were anesthetized with ketamine/xylazine and terminal collection of arterial blood was performed to quantify serum concentrations of melatonin, corticosterone, insulin, and glucose at 6 circadian time points (0400, 0800, 1200, 1600, 2000, 2400). As compared with male and female rats housed under cool white fluorescent (CWF) lighting, rats in bLAD lighting showed a 6-fold higher peak in dark phase serum melatonin (P < 0.05). Effects on serum corticosterone were sex dependent, as CWF and bLAD females had significantly higher corticosterone levels than did CWF and bLAD males, respectively. CWF and bLAD females had significantly higher serum glucose overall as compared with males. However, serum insulin was not affected by sex (M or F) or lighting conditions (CWF or bLAD). These data show that housing Sprague-Dawley rats under bLAD lighting conditions increases circadian peaks of melatonin without increasing serum levels of corticosterone, glucose or insulin, indicating less variation of circadian cycling of key neuroendocrine hormones in bLAD-exposed rats.
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Key Words
- blad, blue-enriched light-emitting diode light-at-day
- cwf, cool white fluorescent
- hpa, hypothalamic-pituitary-adrenal
- ip, intraperitoneal
- iprgc, intrinsically photosensitive retinal ganglion cell
- ivc, individual ventilated caging
- led, light-emitting diode
- lx, lux
- rht, retinohypothalamic tract
- scn, suprachiasmic nucleus
- spd, spectral power distribution
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Affiliation(s)
- Alexis A Allen
- Comparative Medicine, Tulane University, New Orleans, LA, United States;,
| | - Amy T Pierce
- Comparative Medicine, Tulane University, New Orleans, LA, United States
| | - Robert T Dauchy
- Structural & Cellular Biology, Tulane University, New Orleans, LA, United States
| | - George B Voros
- Comparative Medicine, Tulane University, New Orleans, LA, United States
| | - Georgina L Dobek
- Comparative Medicine, Tulane University, New Orleans, LA, United States
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Vauthier V, Roujeau C, Chen P, Sarkis C, Migrenne S, Hosoi T, Ozawa K, Rouillé Y, Foretz M, Mallet J, Launay JM, Magnan C, Jockers R, Dam J. Endospanin1 affects oppositely body weight regulation and glucose homeostasis by differentially regulating central leptin signaling. Mol Metab 2017; 6:159-72. [PMID: 28123946 DOI: 10.1016/j.molmet.2016.10.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 10/21/2016] [Accepted: 10/27/2016] [Indexed: 01/05/2023] Open
Abstract
The hypothalamic arcuate nucleus (ARC) is a major integration center for energy and glucose homeostasis that responds to leptin. Resistance to leptin in the ARC is an important component of the development of obesity and type 2 diabetes. Recently, we showed that Endospanin1 (Endo1) is a negative regulator of the leptin receptor (OBR) that interacts with OBR and retains the receptor inside the cell, leading to a decreased activation of the anorectic STAT3 pathway. Endo1 is up-regulated in the ARC of high fat diet (HFD)-fed mice, and its silencing in the ARC of lean and obese mice prevents and reverses the development of obesity. OBJECTIVE Herein we investigated whether decreased Endo1 expression in the hypothalamic ARC, associated with reduced obesity, could also ameliorate glucose homeostasis accordingly. METHODS We studied glucose homeostasis in lean or obese mice silenced for Endo1 in the ARC via stereotactic injection of shRNA-expressing lentiviral vectors. RESULTS We observed that despite being leaner, Endo1-silenced mice showed impaired glucose homeostasis on HFD. Mechanistically, we show that Endo1 interacts with p85, the regulatory subunit of PI3K, and mediates leptin-induced PI3K activation. CONCLUSIONS Our results thus define Endo1 as an important hypothalamic integrator of leptin signaling, and its silencing differentially regulates the OBR-dependent functions.
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Key Words
- ARC, arcuate nucleus
- BW, body weight
- CD, chow diet
- DIO, diet-induced obesity
- Diabetes
- Endo1, Endospanin1
- GTT, glucose tolerance test
- HFD, high fat diet
- Insulin
- LIF, leukemia inhibitory factor
- Leptin receptor
- OB-RGRP/Endospanin1
- OBR, leptin receptor
- Obesity
- PLA, proximity ligation assay
- T2D, type 2 diabetes
- ip, intraperitoneal
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Ballantyne LL, Sin YY, Al-Dirbashi OY, Li X, Hurlbut DJ, Funk CD. Liver-specific knockout of arginase-1 leads to a profound phenotype similar to inducible whole body arginase-1 deficiency. Mol Genet Metab Rep 2016; 9:54-60. [PMID: 27761413 DOI: 10.1016/j.ymgmr.2016.10.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 10/05/2016] [Indexed: 12/27/2022] Open
Abstract
Arginase-1 (Arg1) converts arginine to urea and ornithine in the distal step of the urea cycle in liver. We previously generated a tamoxifen-inducible Arg1 deficient mouse model (Arg1-Cre) that disrupts Arg1 expression throughout the whole body and leads to lethality ≈ 2 weeks after gene disruption. Here, we evaluate if liver-selective Arg1 loss is sufficient to recapitulate the phenotype observed in global Arg1 knockout mice, as well as to gauge the effectiveness of gene delivery or hepatocyte transplantation to rescue the phenotype. Liver-selective Arg1 deletion was induced by using an adeno-associated viral (AAV)-thyroxine binding globulin (TBG) promoter-Cre recombinase vector administered to Arg1 “floxed” mice; Arg1fl/fl). An AAV vector expressing an Arg1-enhanced green fluorescent protein (Arg1-eGFP) transgene was used for gene delivery, while intrasplenic injection of wild-type (WT) C57BL/6 hepatocytes after partial hepatectomy was used for cell delivery to “rescue” tamoxifen-treated Arg1-Cre mice. The results indicate that liver-selective loss of Arg1 (> 90% deficient) leads to a phenotype resembling the whole body knockout of Arg1 with lethality ≈ 3 weeks after Cre-induced gene disruption. Delivery of Arg1-eGFP AAV rescues more than half of Arg1 global knockout male mice (survival > 4 months) but a significant proportion still succumb to the enzyme deficiency even though liver expression and enzyme activity of the fusion protein reach levels observed in WT animals. Significant Arg1 enzyme activity from engrafted WT hepatocytes into knockout livers can be achieved but not sufficient for rescuing the lethal phenotype. This raises a conundrum relating to liver-specific expression of Arg1. On the one hand, loss of expression in this organ appears to be both necessary and sufficient to explain the lethal phenotype of the genetic disorder in mice. On the other hand, gene and cell-directed therapies suggest that rescue of extra-hepatic Arg1 expression may also be necessary for disease correction. Further studies are needed in order to illuminate the detailed mechanisms for pathogenesis of Arg1-deficiency.
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Taher J, Baker CL, Cuizon C, Masoudpour H, Zhang R, Farr S, Naples M, Bourdon C, Pausova Z, Adeli K. GLP-1 receptor agonism ameliorates hepatic VLDL overproduction and de novo lipogenesis in insulin resistance. Mol Metab 2014; 3:823-33. [PMID: 25506548 PMCID: PMC4264039 DOI: 10.1016/j.molmet.2014.09.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 09/07/2014] [Accepted: 09/11/2014] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND/OBJECTIVES Fasting dyslipidemia is commonly observed in insulin resistant states and mechanistically linked to hepatic overproduction of very low density lipoprotein (VLDL). Recently, the incretin hormone glucagon-like peptide-1 (GLP-1) has been implicated in ameliorating dyslipidemia associated with insulin resistance and reducing hepatic lipid stores. Given that hepatic VLDL production is a key determinant of circulating lipid levels, we investigated the role of both peripheral and central GLP-1 receptor (GLP-1R) agonism in regulation of VLDL production. METHODS The fructose-fed Syrian golden hamster was employed as a model of diet-induced insulin resistance and VLDL overproduction. Hamsters were treated with the GLP-1R agonist exendin-4 by intraperitoneal (ip) injection for peripheral studies or by intracerebroventricular (ICV) administration into the 3rd ventricle for central studies. Peripheral studies were repeated in vagotomised hamsters. RESULTS Short term (7-10 day) peripheral exendin-4 enhanced satiety and also prevented fructose-induced fasting dyslipidemia and hyperinsulinemia. These changes were accompanied by decreased fasting plasma glucose levels, reduced hepatic lipid content and decreased levels of VLDL-TG and -apoB100 in plasma. The observed changes in fasting dyslipidemia could be partially explained by reduced respiratory exchange ratio (RER) thereby indicating a switch in energy utilization from carbohydrate to lipid. Additionally, exendin-4 reduced mRNA markers associated with hepatic de novo lipogenesis and inflammation. Despite these observations, GLP-1R activity could not be detected in primary hamster hepatocytes, thus leading to the investigation of a potential brain-liver axis functioning to regulate lipid metabolism. Short term (4 day) central administration of exendin-4 decreased body weight and food consumption and further prevented fructose-induced hypertriglyceridemia. Additionally, the peripheral lipid-lowering effects of exendin-4 were negated in vagotomised hamsters implicating the involvement of parasympathetic signaling. CONCLUSION Exendin-4 prevents fructose-induced dyslipidemia and hepatic VLDL overproduction in insulin resistance through an indirect mechanism involving altered energy utilization, decreased hepatic lipid synthesis and also requires an intact parasympathetic signaling pathway.
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Affiliation(s)
- Jennifer Taher
- Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, ON, Canada
| | - Christopher L. Baker
- Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada
| | - Carmelle Cuizon
- Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada
| | - Hassan Masoudpour
- Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada
| | - Rianna Zhang
- Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada
| | - Sarah Farr
- Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, ON, Canada
| | - Mark Naples
- Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada
| | - Celine Bourdon
- Physiology and Experimental Medicine, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada
| | - Zdenka Pausova
- Physiology and Experimental Medicine, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada
| | - Khosrow Adeli
- Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, ON, Canada
- Corresponding author. Molecular Structure and Function, The Hospital for Sick Children, 555 University Ave, Atrium Room 3652, Toronto, ON M5G 1X8, Canada. Tel.: +1 416 813 8682; fax: +1 416 813 6257.
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Chandarana K, Gelegen C, Irvine EE, Choudhury AI, Amouyal C, Andreelli F, Withers DJ, Batterham RL. Peripheral activation of the Y2-receptor promotes secretion of GLP-1 and improves glucose tolerance. Mol Metab 2013; 2:142-52. [PMID: 24049729 DOI: 10.1016/j.molmet.2013.03.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 03/04/2013] [Accepted: 03/05/2013] [Indexed: 12/15/2022] Open
Abstract
The effect of peptide tyrosine-tyrosine (PYY) on feeding is well established but currently its role in glucose homeostasis is poorly defined. Here we show in mice, that intraperitoneal (ip) injection of PYY3-36 or Y2R agonist improves nutrient-stimulated glucose tolerance and enhances insulin secretion; an effect blocked by peripheral, but not central, Y2R antagonist administration. Studies on isolated mouse islets revealed no direct effect of PYY3-36 on insulin secretion. Bariatric surgery in mice, enterogastric anastomosis (EGA), improved glucose tolerance in wild-type mice and increased circulating PYY and active GLP-1. In contrast, in Pyy-null mice, post-operative glucose tolerance and active GLP-1 levels were similar in EGA and sham-operated groups. PYY3-36 ip increased hepato-portal active GLP-1 plasma levels, an effect blocked by ip Y2R antagonist. Collectively, these data suggest that PYY3-36 therefore acting via peripheral Y2R increases hepato-portal active GLP-1 plasma levels and improves nutrient-stimulated glucose tolerance.
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Key Words
- AUC, area under the curve
- CNS, central nervous system
- DPP-4, di-peptidyl peptidase-4
- EGA, entero-gastric anastomosis
- GLP-1
- Glucose homeostasis
- HFD, high-fat diet
- ICV, intracerebroventricular
- IPGTT, intraperitoneal glucose tolerance test
- PYY
- PYY, peptide tyrosine–tyrosine
- T2DM, type 2 diabetes mellitus
- WT, wild-type
- Y2-receptor
- Y2R, Y2-receptor
- aCSF, artificial cerebrospinal fluid
- active GLP-1, glucagon-like peptide-1(7-36)amide
- ip, intraperitoneal
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Affiliation(s)
- Keval Chandarana
- Centre for Obesity Research, Department of Medicine, University College London, Rayne Institute, 5 University Street, WC1E 6JJ, London, UK
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