Cold-induced growth arrest in gilthead sea bream Sparus aurata: metabolic reorganisation and recovery

Modulation of Pituitary Response by Dietary Lipids and Throughout a Temperature Fluctuation Challenge in Gilthead Sea Bream

“…Glucocorticoid receptor gr expression in sea bream has been suggested to be tissue specific and correlated to plasma cortisol levels [46]. This could not be the case in our pre-cold conditions, where a change in total dietary lipid of 4% did not prove to be a stressor condition [8,16]. As reported for pituitary modulation by amino acid supplementation [29], dietary lipids were also recognized as conditioning pituitary function by the expression of both the hormones and receptors studied.…”

“…In the case of gilthead sea bream, reducing dietary lipid before the cold season has been proposed to cope with liver affectations [4,[26][27][28]. We previously demonstrated that reducing dietary lipid from 18% to 14% resulted in a similar body weight, condition factor, SGR (0.86 ± 0.05 for D14 and 0.97 ± 0.05 for D18) and FCR (1.32 ± 0.02 for D14 and 1.33 ± 0.06 for D18) (data from [16]), with an improved redox status [8,16], suggesting a more efficient metabolism when sea bream have been fed a low lipid diet. The study of pituitary function during the pre-cold period showed that dietary lipid intake is capable of modifying pituitary expression of gh, tsh and both pomc hormones, together with that of the receptors trβ and gr.…”

“…Growth hormone actions are mediated by the Insulin growth factor 1 (IGF-1), which was not evaluated in relation to diet. Interestingly, however, the differences in expression between D14 and D18 are coincidental with changes in the activity of liver glucose-6-phosphate dehydrogenase (G6PDH) [16]. Although we have not analysed circulating GH, this hormone has been shown to be a potent regulator of the enzyme gene expression and activity in liver in silver sea bream (Sparus sarba), independently of IGF-1 [33,34].…”

“…Thus, although the changes in gene transcription at the pituitary level in relation to feed energy are important, it is not clear if they may result in altered hormone secretion and overall impact. To better elucidate the peripheral effects (growth and plasma markers) of dietary lipids proposed in the current trial, we performed a PCA analyses ( Figure 5) of body performance data, such as body weight, body length, condition factor and hepatosomatic index [8] together with relevant plasma metabolites markers such as glucose, lactate, and lipid fractions (NEFA and TAG) [16]. Similarly to thyroid hormone levels, we observed that both body parameters and plasma metabolites such as glucose, lactate or proteins did not show differences after overnight fasting for fish fed 18% or 14% dietary lipids [8,16], and resulting PCA did not discriminate between D14 or D18, differently to above-mentioned greater differences in pituitary expression.…”

“…The pituitary receptors selected were the glucocorticoid receptor (GR), and thyroid receptors (TRα and TRβ). Moreover, levels in plasma thyroid hormones T 3 and T 4 were also measured and taken in account together with known data on growth [8] and plasma metabolites [16] via principal components analyses (PCA).…”