Effect of plant-based feed ingredients on osmoregulation in the Atlantic salmon lens

Abstract

Lenses of adult Atlantic salmon fed with a plant oil and plant protein-based diet (plant diet) were compared to lenses of fish fed a diet based on traditional marine ingredients (marine diet) with respect to biochemical composition and functionality ex vivo. After 12 months of feeding, plant diet-fed fish had smaller lenses with higher water contents and lower concentrations of histidine (His) and N-acetylhistidine (NAH) than fish fed with the marine diet. Cataract development in both dietary groups was minimal and no differences between the groups were observed. Lens fatty acid and lipid class composition differed minimally, although a significant increase in linoleic acid was observed. The lenses were examined for their ability to withstand osmotic disturbances ex vivo. Culture in hypoosmotic and hyperosmotic media led to increase and decrease of lens volume, respectively. Lenses from plant diet-fed fish were less resistant to swelling and shrinking, released less NAH into the culture medium, and accumulated His and NAH at higher rates than lenses from marine diet-fed fish. Culture in hypoosmotic medium resulted in higher cataract scores than in control and hyperosmotic medium. mRNA expression of selected genes, including glutathione peroxidase 4 and SPARC (secreted protein acidic and rich in cysteine), was affected by diet and osmotic treatment. It can be concluded that lenses of farmed Atlantic salmon are affected by the diet composition, both in biochemical composition and physiological functionality in relation to osmoregulation.

Adult triploid Atlantic salmon (Salmo salar) have higher dietary histidine requirements to prevent cataract development in seawater

“…It has also been shown that diet composition affects lens His and NAH accumulation rate and synthesis (Tröβe et al . ). However, although dietary requirements have been relatively well defined in diploids (NRC ), no work has to date been conducted in triploids specifically addressing dietary His requirements and correlation with occurrence of cataract.…”

“…), although Tröβe et al . () reported that utilization of NAH is more efficient in lens osmoregulation than efflux of other amino acids as a compensatory mechanism in such instances. Ploidy has been reported to affect amino acid levels as demonstrated in tench ( Tinca tinca ) (Buchtova et al .…”

“…The development of ex vivo culture techniques for the study of fish lens (Tröβe et al . ) allows the possibility for comparative studies between diploid and triploid cells and tissues. Specifically, osmotic homeostasis and/or gas diffusion gradients could be easily studied and may elucidate mechanistic effects of histidine between ploidy.…”

“…In particular, the aetiological importance of nutritional factors is supported by the increased prevalence of cataracts within the salmon industry following the removal of mammalian blood meal from the diet (Wall ; Tröβe et al . ). Blood meal was especially rich in the amino acid histidine (His), which can be supplemented in the diet.…”

Transcriptomic profiling of male European eel ( Anguilla anguilla ) livers at sexual maturity

“…In sea bream (Sparus auratus), mRNA levels of osteonectin are low in the liver and other soft tissues in comparison to hard tissues such as scales and bone (Redruello et al, 2005). However, SPARC expression (osteonectin) levels in the lenses of Atlantic salmon are influenced by diet (Tröβe et al, 2010) suggesting the regulation of this gene is linked with metabolism in fish.…”