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Balaž M, Ukropcova B, Kurdiova T, Vlcek M, Surova M, Krumpolec P, Vanuga P, Gašperíková D, Klimeš I, Payer J, Wolfrum C, Ukropec J. Improved adipose tissue metabolism after 5-year growth hormone replacement therapy in growth hormone deficient adults: The role of zinc-α2-glycoprotein. Adipocyte 2015; 4:113-22. [PMID: 26167410 DOI: 10.4161/21623945.2014.973772] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 09/14/2014] [Accepted: 10/02/2014] [Indexed: 01/17/2023] Open
Abstract
Growth hormone (GH) supplementation therapy to adults with GH deficiency has beneficial effects on adipose tissue lipid metabolism, improving thus adipocyte functional morphology and insulin sensitivity. However, molecular nature of these effects remains unclear. We therefore tested the hypothesis that lipid-mobilizing adipokine zinc-α2-glycoprotein is causally linked to GH effects on adipose tissue lipid metabolism. Seventeen patients with severe GH deficiency examined before and after the 5-year GH replacement therapy were compared with age-, gender- and BMI-matched healthy controls. Euglycemic hyperinsulinemic clamp was used to assess whole-body and adipose tissue-specific insulin sensitivity. Glucose tolerance was determined by oGTT, visceral and subcutaneous abdominal adiposity by MRI, adipocyte size morphometrically after collagenase digestion, lipid accumulation and release was studied in differentiated human primary adipocytes in association with GH treatment and zinc-α2-glycoprotein gene silencing. Five-year GH replacement therapy improved glucose tolerance, adipose tissue insulin sensitivity and reduced adipocyte size without affecting adiposity and whole-body insulin sensitivity. Adipose tissue zinc-α2-glycoprotein expression was positively associated with whole-body and adipose tissue insulin sensitivity and negatively with adipocyte size. GH treatment to adipocytes in vitro increased zinc-α2-glycoprotein expression (>50%) and was paralleled by enhanced lipolysis and decreased triglyceride accumulation (>35%). Moreover, GH treatment improved antilipolytic action of insulin in cultured adipocytes. Most importantly, silencing zinc-α2-glycoprotein eliminated all of the GH effects on adipocyte lipid metabolism. Effects of 5-year GH supplementation therapy on adipose tissue lipid metabolism and insulin sensitivity are associated with zinc-α2-glycoprotein. Presence of this adipokine is required for the GH action on adipocyte lipid metabolism in vitro.
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Key Words
- ACC1, acetyl-CoA carboxylase 1
- BSA, bovine serum albumin
- DGAT, diacylglycerol acyltransferase
- DMEM, Dulbecco's Modified Eagle Medium
- EHC, euglycemic hyperinsulinemic clamp
- FABP4, fatty acid binding protein 4
- FAS, fatty acid synthase
- FBS, fetal bovine serum
- FFA, free fatty acids
- GAPDH, glyceraldehyde-3-phosphate dehydrogenase
- GH, growth hormone
- GHD, growth hormone deficiency
- GLUT4, glucose transporter 4
- HSL, hormone sensitive lipase
- IGF-1, insulin-like growth factor 1
- IRS1, insulin receptor substrate 1
- MRI, magnetic resonance imaging
- PPARGC1A, peroxisome proliferator-activated receptor 1 gamma coactivator 1 α
- RPL13A, ribosomal protein L13a
- TG, triglycerides
- ZAG, zinc-α2-glycoprotein.
- adipocyte size
- adipose tissue
- glucose tolerance
- growth hormone deficiency
- growth hormone replacement therapy
- insulin sensitivity
- lipolysis
- oGTT, oral glucose tolerance test
- rhGH, recombinant human growth hormone
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Rojas JM, Bruinstroop E, Printz RL, Alijagic-Boers A, Foppen E, Turney MK, George L, Beck-Sickinger AG, Kalsbeek A, Niswender KD. Central nervous system neuropeptide Y regulates mediators of hepatic phospholipid remodeling and very low-density lipoprotein triglyceride secretion via sympathetic innervation. Mol Metab 2015; 4:210-21. [PMID: 25737956 PMCID: PMC4338317 DOI: 10.1016/j.molmet.2015.01.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 12/29/2014] [Accepted: 01/09/2015] [Indexed: 12/26/2022] Open
Abstract
OBJECTIVE Elevated very low-density lipoprotein (VLDL)-triglyceride (TG) secretion from the liver contributes to an atherogenic dyslipidemia that is associated with obesity, diabetes and the metabolic syndrome. Numerous models of obesity and diabetes are characterized by increased central nervous system (CNS) neuropeptide Y (NPY); in fact, a single intracerebroventricular (icv) administration of NPY in lean fasted rats elevates hepatic VLDL-TG secretion and does so, in large part, via signaling through the CNS NPY Y1 receptor. Thus, our overarching hypothesis is that elevated CNS NPY action contributes to dyslipidemia by activating central circuits that modulate liver lipid metabolism. METHODS Chow-fed Zucker fatty (ZF) rats were pair-fed by matching their caloric intake to that of lean controls and effects on body weight, plasma TG, and liver content of TG and phospholipid (PL) were compared to ad-libitum (ad-lib) fed ZF rats. Additionally, lean 4-h fasted rats with intact or disrupted hepatic sympathetic innervation were treated with icv NPY or NPY Y1 receptor agonist to identify novel hepatic mechanisms by which NPY promotes VLDL particle maturation and secretion. RESULTS Manipulation of plasma TG levels in obese ZF rats, through pair-feeding had no effect on liver TG content; however, hepatic PL content was substantially reduced and was tightly correlated with plasma TG levels. Treatment with icv NPY or a selective NPY Y1 receptor agonist in lean fasted rats robustly activated key hepatic regulatory proteins, stearoyl-CoA desaturase-1 (SCD-1), ADP-ribosylation factor-1 (ARF-1), and lipin-1, known to be involved in remodeling liver PL into TG for VLDL maturation and secretion. Lastly, we show that the effects of CNS NPY on key liporegulatory proteins are attenuated by hepatic sympathetic denervation. CONCLUSIONS These data support a model in which CNS NPY modulates mediators of hepatic PL remodeling and VLDL maturation to stimulate VLDL-TG secretion that is dependent on the Y1 receptor and sympathetic signaling to the liver.
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Key Words
- AGPAT, 1-acyl-glycerol-3-phosphate acyltransferase
- ARF-1, ADP-ribosylation factor-1
- ApoB, apolipoprotein B
- CNS, central nervous system
- Cyto, cytoplasmic
- DAG, diacylglycerol
- DGAT, diacylglycerol acyltransferase
- ER, endoplasmic reticulum
- FFA(s), free fatty acid(s)
- GAPDH, glyceraldehyde 3-phosphate dehydrogenase
- HDAC-1, histone deacetylase-1
- Lipin-1
- NE, norepinephrine
- NPY Y1 receptor
- NPY, neuropeptide Y
- Nuc, nuclear
- PA, phosphatidic acid
- PAP-1, phosphatidic acid phosphatase-1
- PF, pair-fed
- PL, phospholipid
- PLD, phospholipase D
- POMC, proopiomelanocortin
- Phospholipid
- RPL13A, ribosomal protein L13a
- RT-PCR, real-time PCR
- SCD-1, stearoyl-CoA desaturase-1
- SNS, sympathetic nervous system
- Sham, sham-denervation
- Sx, sympathetic denervation
- Sympathetic denervation
- TG, triglyceride
- Triglyceride
- VLDL
- VLDL, very low-density lipoprotein
- Veh, vehicle
- ZF, Zucker fatty
- ad-lib, ad-libitum
- icv, intracerebroventricular
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Affiliation(s)
- Jennifer M. Rojas
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Eveline Bruinstroop
- Department of Endocrinology and Metabolism, Laboratory of Endocrinology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Richard L. Printz
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Aldijana Alijagic-Boers
- Department of Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Science, Amsterdam, The Netherlands
| | - Ewout Foppen
- Department of Endocrinology and Metabolism, Laboratory of Endocrinology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Maxine K. Turney
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Leena George
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Annette G. Beck-Sickinger
- Institute of Biochemistry, Faculty of Bioscience, Pharmacy and Psychology, Leipzig University, Leipzig, Germany
| | - Andries Kalsbeek
- Department of Endocrinology and Metabolism, Laboratory of Endocrinology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
- Department of Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Science, Amsterdam, The Netherlands
| | - Kevin D. Niswender
- Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville, TN, United States
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, United States
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, United States
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