LEPTIN STIMULATES HEPATIC GROWTH HORMONE RECEPTOR EXPRESSION: POSSIBLE ROLE IN ENHANCING GH-MEDIATED ANABOLIC PROCESSES IN FISH
-
1
North Carolina State University, Department of Biology, United States
Growth hormone (GH) exerts much of its anabolic actions through binding cytokine receptors (GHRs) and stimulating production of insulin-like growth factors (IGFs). Leptin is an anorexigenic hormone produced by adipocytes and that circulates in proportion to lipid deposition in mammals. Its regulation of the GH-IGF system, particularly GHRs, is poorly understood. Virtually nothing is known of leptin control of the GH-IGF axis in fishes. In hybrid striped bass (HSB, Morone chrysops x M. saxatilis) and many other vertebrates, fasting leads to a hepatic GH resistant state whereby elevated GH secretion is accompanied by declines in hepatic expression of GHR1, GHR2, IGF-1, and IGF-2 and low growth rate. Upon refeeding, HSB undergo a robust compensatory growth response, characterized by an alleviation of the GH resistant state, increase or overcompensation in expression of hepatic IGFs and GHRs, and growth that exceeds normal rates. We cloned and characterized the leptin gene in HSB and show there is likely only one form of leptin that is produced predominantly in the liver. Human recombinant leptin acutely inhibits appetite in HSB. HSB hepatic leptin mRNA levels decline during fasting and increase with refeeding, paralleling gene expression patterns observed with the GHRs and IGFs. This suggests the hormone may modulate GHRs and IGF expression under different metabolic states. To assess leptin regulation of hepatic GHRs, a primary cell culture system was established and validated for HSB hepatocytes. Leptin increased GHR1 and GHR2 gene expression by as much as 6-fold in HSB hepatocytes. The dose-dependent response occurred as early as 8 hours, and lasted for as long as 24 hours with the highest (50 nM) concentration. Additionally, leptin stimulated IGF-1 gene expression in hepatocytes over 24-hr incubation. The results suggest that leptin may promote anabolic processes in vertebrates through stimulation of hepatic GHRs and IGF-1 expression.
Keywords:
anabolic,
feeding,
Growth Hormone,
hybrid striped bass,
IGF-I,
Leptin,
Metabolism,
Morone saxatilis
Conference:
NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology, Ann Arbor, United States, 13 Jul - 16 Jul, 2011.
Presentation Type:
Invited Symposium
Topic:
Metabolism and feeding
Citation:
Borski
RJ,
Won
ET and
Baltzegar
DA
(2011). LEPTIN STIMULATES HEPATIC GROWTH HORMONE RECEPTOR EXPRESSION: POSSIBLE ROLE IN ENHANCING GH-MEDIATED ANABOLIC PROCESSES IN FISH.
Front. Endocrinol.
Conference Abstract:
NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology.
doi: 10.3389/conf.fendo.2011.04.00111
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
20 Jul 2011;
Published Online:
09 Aug 2011.
*
Correspondence:
Prof. Russell J Borski, North Carolina State University, Department of Biology, Raleigh, NC, 27695, United States, rjb@ncsu.edu