Leptin: clue to poor appetite in oxygen-starved fish.
Hypoxia is the most widespread deleterious consequence of eutrophication and has become a major cause of fishery decline. One feature of chronic exposure to hypoxia in fish is inhibition of feeding. In this study, we investigated if the gene that encodes the appetite-suppressing hormone leptin is regulated by hypoxia in zebrafish (Danio rerio). Exposure of adult zebrafish to hypoxic conditions (1+/-0.2 mg O(2) L(-1)) for 4 and 10 days significantly increased leptin-a (zlep-a) mRNA levels in the liver. To evaluate the role of hypoxia-inducible factor 1 (HIF-1) in regulating zlep-a expression, zebrafish embryos were exposed to cobalt chloride (CoCl(2), a HIF-1 inducer) and overexpressed with HIF-1alpha mRNA. Both CoCl(2) treatment and HIF-1alpha overexpression markedly increased zlep-a expression in developing embryos, indicating the possible involvement of HIF-1 in zlep-a regulation. In vivo promoter analysis indicated that zlep-a promoter activity is found in the muscle fibers of zebrafish embryos and enhanced by CoCl(2). This is the first report to show that leptin gene expression in fish is regulated by hypoxia possibly via the involvement of HIF-1.
Chu
Daniel Ling Ho
DL
Department of Biology and Chemistry, City University of Hong Kong, Kowloon, Hong Kong Special Administrative Region, People's Republic of China.
Li
Vincent Wai Tsun
VW
Yu
Richard Man Kit
RM
D000818:Animals; D005786:Gene Expression Regulation / Q000235:genetics; D000860:Hypoxia / Q000235:genetics / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D020738:Leptin / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015027:Zebrafish / Q000235:genetics / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D020738:Leptin; D012333:RNA, Messenger; D029961:Zebrafish Proteins