The metabolic syndrome in mice overexpressing neuropeptide Y in noradrenergic neurons
- Liisa Ailanen,
- Suvi T Ruohonen,
- Laura Vähätalo,
- Katja Tuomainen,
- Kim Eerola,
- Henriikka Salomäki-Myftari,
- Matias Röyttä,
- Asta Laiho,
- Markku Ahotupa,
- Helena Gylling and
- Eriika Savontaus⇑
- L Ailanen, Institute of Biomedicine and Turku Center for Disease Modelling, University of Turku, Turku, Finland
- S Ruohonen, Institute of Biomedicine and Turku Center for Disease Modelling , University of Turku, Turku, Finland
- L Vähätalo, Institute of Biomedicine and Turku Center for Disease Modelling, Turun Yliopisto, Turku, Finland
- K Tuomainen, Institute of Biomedicine and Turku Center for Disease Modelling, Turun Yliopisto, Turku, Finland
- K Eerola, Institute of Biomedicine and Turku Center for Disease Modelling, University of Turku, Turku, Finland
- H Salomäki-Myftari, Institute of Biomedicine and Turku Center for Disease Modelling, Turun Yliopisto, Turku, Finland
- M Röyttä, Pathology, University of Turku, Turku, Finland
- A Laiho, Turku Centre for Biotechnology, University of Turku, Turku, Finland
- M Ahotupa, Research Centre of Applied and Preventive Cardiovascular Medicine, University of Turku, Turku, Finland
- H Gylling, Internal Medicine, Helsingin Yliopisto Laaketieteellinen tiedekunta, Helsinki, Finland
- E Savontaus, Pharmacology, Drug Development and Therapeutics and Turku Center for Disease Modelling, University of Turku, Turku, Finland
- Correspondence: Eriika Savontaus, Email: eriika.savontaus{at}utu.fi
Abstract
A gain-of-function polymorphism in human neuropeptide Y (NPY) gene (rs16139) associates with metabolic disorders and earlier onset of type 2 diabetes (T2D). Similarly, mice overexpressing NPY in noradrenergic neurons (OE-NPYDBH) display obesity and impaired glucose metabolism. In this study, the metabolic syndrome -like phenotype was characterized and mechanisms of impaired hepatic fatty acid, cholesterol and glucose metabolism in pre-obese (2-month-old) and obese (4-7-month-old) OE-NPYDBH mice were elucidated. Susceptibility to T2D was assessed by subjecting mice to high caloric diet combined with low-dose streptozotocin. Contribution of hepatic Y1-receptor to the phenotype was studied using chronic treatment with a Y1-receptor antagonist, BIBO3304. Obese OE-NPYDBH mice displayed hepatosteatosis and hypercholesterolemia preceded by decreased fatty acid oxidation and accelerated cholesterol synthesis. Hyperinsulinemia in early obese state inhibited pyruvate- and glucose-induced hyperglycemia, and deteriation of glucose metabolism of OE-NPYDBH mice developed with aging. Furthermore, streptozotocin induced T2D only in OE-NPYDBH mice. Hepatic inflammation was not morphologically visible, but up-regulated hepatic anti-inflammatory pathways and increased 8-isoprostane combined with increased serum resistin and decreased interleukin 10 pointed to increased NPY-induced oxidative stress that may predispose OE-NPYDBH mice to insulin resistance. Chronic treatment with BIBO3304 did not improve the metabolic status of OE-NPYDBH mice. Instead, down-regulation of beta1-adrenoceptors suggests indirect actions of NPY via inhibition of sympathetic nervous system. In conclusion, changes in hepatic fatty acid, cholesterol and glucose metabolism favoring energy storage contribute to the development of NPY-induced metabolic syndrome, and the effect is likely mediated via changes in sympathetic nervous system activity.
- Received 20 May 2016
- Received in final form 28 March 2017
- Accepted 3 May 2017
- Accepted Preprint first posted online on 3 May 2017