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Effects of long-term restricted feeding on plasma leptin, hepatic leptin expression and leptin receptor expression in juvenile Atlantic salmon (Salmo salar L.)
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Comparative Physiology. (Jämförande fiskfysiologi)
Muséum National d’Histoire Naturelle, Paris Cedex 05, France.
Göteborg universitet.
Göteborg universitet.
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2012 (English)In: General and Comparative Endocrinology, ISSN 0016-6480, E-ISSN 1095-6840, Vol. 175, no 1, 92-99 p.Article in journal (Refereed) Published
Abstract [en]

Leptin is a pleiotropic hormone and plays a key role in body weight regulation, energy homeostasis and lipid store utilization in mammals. In this study, we investigated the effect of feed-restriction on leptin genes (lepa1 and lepa2), leptin receptor (lepr) gene expression and plasma leptin levels in juvenile Atlantic salmon parr. Feed restriction was performed from late April to mid-June, in order to gain insight into the role of the leptin system in energy balance regulation and adiposity in juvenile salmon. A significant increase in lepa1 expression as well as higher levels of plasma leptin was found in feed-restricted fish in June compared to fully fed controls, while lepa2 gene expression decreased in both groups during the treatment period. Lepa2 was, however significantly higher in the feed-restricted group in June. Leptin receptor expression was up regulated during the period of enhanced growth and lipid deposition in the fully fed control, indicating a seasonal effect on the receptor expression in the brain. Both lepa1 and lepa2 genes very mainly expressed in the liver in juvenile salmon, while lepr was expressed in the brain but showed also considerable expression in various peripheral tissues. The study provides evidence that the leptin system is sensitive to the metabolic status of the fish as both season and restricted feeding affect lepa1 and lepa2 gene expression in the liver and brain leptin receptor expression, however, for lepa1 expression and leptin plasma level in an opposite way as that observed in the mammalian system.

Place, publisher, year, edition, pages
2012. Vol. 175, no 1, 92-99 p.
National Category
Zoology
Research subject
Biology with specialization in Comparative Physiology
Identifiers
URN: urn:nbn:se:uu:diva-166581DOI: 10.1016/j.ygcen.2011.10.001ISI: 000299065800012PubMedID: 22019478OAI: oai:DiVA.org:uu-166581DiVA: diva2:476902
Funder
Formas, 2010-03-11
Available from: 2012-01-12 Created: 2012-01-12 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Role of leptin in energy balance and sexual maturation in male Atlantic salmo (Salmo salar L.) parr
Open this publication in new window or tab >>Role of leptin in energy balance and sexual maturation in male Atlantic salmo (Salmo salar L.) parr
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Uppsala: Department of Organismal Biology, Uppsala University, 2012. 25 p.
Keyword
leptin, leptin receptor, sexual maturation, restricted feeding, Atlantic salmon
National Category
Zoology
Research subject
Biology with specialization in Comparative Physiology
Identifiers
urn:nbn:se:uu:diva-190203 (URN)
Presentation
2012-06-14, Seminar room 05:1021, Evolutionsbiologiskt centrum,Norbyvägen 18A, Uppsala, 10:00 (English)
Opponent
Supervisors
Funder
Formas, 221-2006-1534
Available from: 2013-01-10 Created: 2013-01-07 Last updated: 2013-01-10Bibliographically approved
2. Regulation of Leptin by Sexual Maturation and Energy Status in Male Atlantic Salmon (Salmo salar L.) Parr
Open this publication in new window or tab >>Regulation of Leptin by Sexual Maturation and Energy Status in Male Atlantic Salmon (Salmo salar L.) Parr
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Leptin is a peripheral adiposity signal and a key hormone in energy balance regulation in mammals, acting as a link between nutritional status and the endocrine reproductive axis. If this is also the role of leptin in fish is not fully understood. This thesis investigates how different components of the leptin system are affected by sexual maturation and seasonal changes in energy balance in male Atlantic salmon (Salmo salar L.) parr under fully fed and feed-restricted conditions. Moreover, the role of sex steroids as being one of the possible mechanisms by which sexual maturation interacts with leptin is explored.

The salmon leptin-a genes, lepa1 and lepa2, were expressed mainly in liver and the leptin receptor (lepr) in brain and ubiquitously in peripheral tissues. Seasonal characterization of the lepa genes and lepr during the growth and reproductive season in one-year old males showed that hepatic lepa1 and lepa2 mRNA levels and plasma leptin levels were down-regulated concomitantly with an increase in weight and body fat. Feed restriction up-regulated hepatic leptin, and pituitary lepr expression as well as plasma leptin levels. Correlation between leptin levels and body lipid stores were either lacking or negative. These findings show that leptin and lepr are sensitive to changes in energy balance, but that leptin might not reflect adiposity in juvenile salmon.

Hepatic lepa1 and lepa2, and testicular lepr expression increased during mid- to late spermatogenesis in early maturing males. This up-regulation was preceded by rapid gonadal growth and elevated pituitary follicle-stimulating hormone gene expression levels, whereas peak leptin levels coincided with peak pituitary luteinizing hormone expression and the presence of running milt in the testes. The sex steroids testosterone (T), 11-ketotestosterone and 17-β estradiol stimulated lepa1 and lepa2 gene expression in Atlantic salmon hepatocytes in vitro differentially depending on developmental stage. T was also able to stimulate hepatic lepa1 and pituitary lepa1 and lepr gene expression in immature male salmon in vivo. These results suggest that leptin plays a role in male fish reproduction during later stages of the maturational process and that the elevation of leptin expression during spermatogenesis could be caused by androgen stimulation.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 54 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1151
Keyword
Leptin, leptin receptor, Atlantic salmon, Salmo salar, sexual maturation, puberty, energy balance, hepatocytes, sex steriods
National Category
Biological Sciences
Research subject
Biology with specialization in Comparative Physiology
Identifiers
urn:nbn:se:uu:diva-223462 (URN)978-91-554-8956-4 (ISBN)
Public defence
2014-06-10, Lindahlsalen, Evolutionary Biology Center, Norbyvägen 18A, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2014-05-20 Created: 2014-04-21 Last updated: 2014-06-30

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Trombley, SusanneSchmitz, Monika

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