Cadmium exposure affects the expression of genes involved in skeletogenesis and stress response in gilthead sea bream larvae.

Gilthead sea bream larvae (Sparus aurata) aged 47 days post hatching (dph) (11.6-12.8 mg in wet weight) were exposed to several sublethal concentrations of Cd(2+) (0.1, 5 and 10 mg/L) during 6 days in order to investigate the effects of this heavy metal on the expression of selected genes involved in detoxification (metallothionein-mt, glutathione peroxidase 1-gpx1), stress response (heat shock protein 70-hsp70, tumour necrosis factor α-tnfα) and ossification (osteocalcin-oc) processes. For this purpose, specimens of 47 dph were exposed first for 72 h from 0.1 to 20 mg/L of Cd(2+) in order to evaluate the median lethal concentration (LC(50)) for this metal, which was determined at 15.32 mg/L. Considering the results regarding the relative transcript levels of gpx1 and hsp70, Cd(2+) at any of the tested levels (0.1, 5 and 10 mg/L) did not induce oxidative stress in gilthead sea bream larvae, whereas relative transcript levels of mt were increased at 5 and 10 mg/L of Cd(2+) probably to detoxify this metal excess. Relative transcript levels of tnfα were not level dependent and were down-regulated in larvae exposed to 5 and 10 mg/L of Cd(2+). At those concentrations, transcript levels of oc were down-regulated suggesting a disruption in bone mineralization. Results from this study provided insights in some molecular mechanisms underlying Cd(2+)-induced toxicity in fish at early stages of development. This is the first study to show that cadmium contamination can depress oc expression in teleosts.

Molecular regulation of both dietary vitamin A and fatty acid absorption and metabolism associated with larval morphogenesis of Senegalese sole (Solea senegalensis).

The present study aimed to deepen the understanding of molecular mechanisms governing the absorption and metabolism of some nutrients, growth and development in larvae of Senegalese sole (Solea senegalensis) fed with Artemia enriched with Easy Selco (ES, INVE) or Aquagrow Gold (AGG, ABN), which mainly differed in their vitamin A (VA) content and fatty acid composition. The expression profile of genes involved in VA metabolism (crbp2, rbp, crabp1), lipid transport (i-fabp, l-fabp), nuclear receptors for VA and fatty acids (rarα1, rxrα, pparß), growth (igf1, igf2 and their receptor igf1r) and development (bgp) was analyzed at 22, 30 and 38 days post hatching. The main results suggested that the amount of VA absorbed by larvae is controlled at the intestinal level by crbp2 in both groups, preventing excessive accumulation of this vitamin in the target tissues. The stable expression of i-fabp in the ES group with age could cause an excessive fat accumulation in the intestine inducing, in turn, the steatosis found in the liver and vascular system of these specimens. In liver, the regulation of rbp and fabp expression reflected the status of the physiological functions demanding VA and lipids. The findings revealed that dietary composition induced different strategies for VA and lipid absorption and metabolism affecting, in turn, larval development, growth and health.