The effects of dietary arachidonic acid on bone in flatfish larvae: the last but not the least of the essential fatty acids

Abstract

SummaryFlatfish can provide a reliable model to study developmental disorders in bone tissues occurring during morphogenesis in response to nutritional imbalances. To date, most studies dealing with the effect of dietary essential fatty acids (EFA) on skeletogenesis in fish have focused their investigation on the role of docohexanoic (22:6nÀ3, DHA) and eicosapentaenoic (20:5n-3, EPA) acids, but only a few have focused on investigating the effects of arachidonic acid (20:4n-6, ARA) on bone during fish larval development. Bone development and composition at larval stage have been demonstrated to be highly sensitive to dietary levels of EFA, in particular the EPA and ARA acids, both precursors for highly bioactive eicosanoids presenting opposite effects on bone metabolism. Since fish are not able to synthesize EFA, they need to obtain them from the diet. However, dietary imbalances in EPA and ARA in flatfish larvae may disrupt bone formation and osteoblast differentiation in skeletal tissues, leading to the incidence of skeletal deformities, reduced mineralization and problems of bone remodelling in the cranial region associated with impaired eye migration. These anomalies in skeletal structures are one of the most important factors that affect flatfish larval quality and hamper their production. Thus, we have reviewed the current state of knowledge about the effects of dietary ARA contents on skeletogenesis in Senegalese sole (Solea senegalensis), one of the main flatfish species cultured in Europe. Their larval quality still suffers for a high incidence of skeletal anomalies induced by dietary imbalances during metamorphosis.

Arachidonic acid matters

“…76 In another study, the amount of 4.5% TFA of dietary ARA during Artemia feeding period promoted proper skeletogenesis of Senegalese sole larvae. 92 The effects of dietary ARA on morphogenesis and bone in Senegalese sole have been reviewed by Boglino et al 178,179 In Atlantic cod larvae, high ARA + vitamin A (6.0% TFA + 12.0 μg g À1 ) resulted in significantly less mineralized bones in larvae of similar size (29 DPH), 85 but in zebrafish ARA enhanced turnover of the dermal skeleton, mediated by matrix metalloproteinases. 180 All these results evidenced the complicated effects of ARA on skeletogenesis depending on fish species and development stage; however, the currently available limited information precludes from any possible speculation about the biological mechanisms behind these observed phenomena.…”

The effect of dietary arachidonic acid (ARA) on growth performance, fatty acid composition and expression of ARA metabolism-related genes in larval half-smooth tongue sole (Cynoglossus semilaevis)

“…ARA can be converted to a number of compounds, including PG, thromboxanes, hydroxyeicosatetraenoic acids and LT ( 31 ) , which are very active even at low physiological concentrations and play an important role during larval development ( 7 ) . It has been demonstrated that bone development and composition at the larval stage are highly sensitive to the dietary concentration of ARA ( 54 ) . In addition, fish larvae possess a high growth rate ( 55 ) , which indicates that metabolism in this stage is active; thus, tongue sole larvae appear to be more sensitive to ARA nutrition than juvenile tongue sole are.…”

Influence of salinity and linoleic or α-linolenic acid based diets on ontogenetic development and metabolism of unsaturated fatty acids in pike perch larvae (Sander lucioperca)

“…Salinity and dietary ALA/LA ratio may thus influence C20 EPA, DHA and ARA synthesis with possible implications for effects on prostaglandin eicosanoid activity, a group of active hormonelike agents formed from C20 EFA. Their transitory nature fits them to an important role in modulating rapid physiological responses to stimuli while imbalances may impair skeletogenesis during early stages of larval development (Boglino et al, 2014). Successful production of pikeperch juveniles is constrained by the high incidence of skeletal anomalies (Kestemont et al, 2015) and salinity markedly affected the occurrence of skeletal abnormalities in other fishes (Lall and Lewis-McCrea, 2007).…”