title: The expression of selected genes linked to metabolic homeostasis in obese pansteatitis-suffering Mozambique tilapia, Oreochromis mossambicus (Peters).
abstract: The Oreochromis mossambicus (Peters) population inhabiting Lake Loskop, South Africa, is characterized by a high incidence of obesity and pansteatitis. We investigated potential links between the impaired health of Lake Loskop O. mossambicus and the endocrine system by assessing the expression of selected genes associated with the thyroid and adrenal endocrine axes as well as peroxisome proliferator-activated receptor gamma (pparg). Moreover, contaminant-induced thyroid and/or metabolic modulation in Lake Loskop water was evaluated using juvenile O. mossambicus in laboratory exposures. The expression of thyroid hormone receptor alpha (thra) and type 2 deiodinase (dio2) was higher in Lake Loskop O. mossambicus than fish from another population, suggesting a degree of thyroid disruption. The altered gene expression may be a consequence, rather than cause of obesity. Expression of dio2 and pparg was higher in juvenile O. mossambicus exposed to unfiltered compared to filtered lake water, and our data suggest fasting as causative factor. Micro-organism abundance can therefore be a confounding factor in studies applying molecular markers to test for thyroid modulation by environmental waters. Pansteatitis was not a significant source of variance in the expression of any of the genes investigated, suggesting that the disease is not associated with disrupted endocrine signalling.
authors.affiliation: Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa.
authors.forename: J C
authors.initials: JC
authors.lastname: Truter
authors.affiliation: Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa.
authors.forename: J H
authors.initials: JH
authors.lastname: van Wyk
authors.affiliation: CSIR Natural Resources and the Environment, Stellenbosch, South Africa.|Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa.
authors.forename: P J
authors.initials: PJ
authors.lastname: Oberholster
authors.affiliation: Department of Genetics, Stellenbosch University, Stellenbosch, South Africa.
authors.forename: A-M
authors.initials: AM
authors.lastname: Botha
authors.affiliation: Department of Biodiversity, University of Limpopo, Sovenga, South Africa.
authors.forename: W J
authors.initials: WJ
authors.lastname: Luus-Powell
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D005393:Fish Diseases / Q000209:etiology / Q000235:genetics*; D006706:Homeostasis; D060106:Lakes / Q000737:chemistry; D016014:Linear Models; D008659:Metabolic Diseases / Q000150:complications / Q000235:genetics / Q000662:veterinary*; D008670:Metals / Q000032:analysis; D009765:Obesity / Q000150:complications / Q000235:genetics / Q000662:veterinary*; D010839:Phytoplankton / Q000145:classification; D013019:South Africa; D013231:Steatitis / Q000209:etiology / Q000235:genetics*; D058009:Stramenopiles / Q000145:classification; D017210:Tilapia / Q000235:genetics* / Q000378:metabolism
chemical_list: D008670:Metals
keywords: Lake Loskop; endocrine disruptors; fish; obesity; pollution; thyroid