Project description:The brown seaweed Laminaria digitata is a novel feedstuff for weaned piglets. It can help prevent dysbiosis in addition to improve overall health and performance. However, it has a recalcitrant cell wall that is not easily digested by the piglet digestive system. Alginate lyase has promising effects for the supplementation of in vivo diets in order to address this issue. The objective of this study is to evaluate the effect of 10% dietary Laminaria digitata inclusion and alginate lyase supplementation on the hepatic proteome and metabolome of weaned piglets in a physiological study. The diets caused incipient differences on the metabolome of piglets, with the proteome having the most significant changes. Feeding seaweed provided a source of n-3 PUFA that accumulated in the liver, signalling for increased fatty acid oxidation (FABP, ACADSB, ALDH1B1). This contributed at least in part to reduce oxidative stability of the tissue, demanding the higher abundance of GST to maintain it. Reactive oxygen species possibly damaged proteins, which caused hepatocytes to increase proteasome activity (LAPTM4B, PSMD4), recycling their amino acids. Providing alginate lyase to the diet increased the number of differentially abundant proteins, including GBE1 and LDHC that contributed to the maintenance of circulating glucose through mobilization of glycogen stores and branched chain amino acids. Enzymatic supplementation enhanced the baseline effects of feeding seaweed alone.
Project description:Laminaria digitata is a brown seaweed with prebiotic properties that has the potential to improve the response of weaned piglets to nutritional stress. However, its cell wall polysaccharides are not digested by the endogenous enzymes of monogastric animals. Alginate lyase has shown promise in degrading them under in vitro conditions. The objective of this study is to evaluate the effect of a 10% incorporation of L. digitata, and alginate lyase supplementation on the ileum proteome and metabolome, in a hypothesis generating approach. Control piglets increased the use of glucose as an enteric source of energy, demonstrated by the higher abundance of PKLR and PCK2 proteins and the lower concentration of glucose found in the tissue. Furthermore, seaweed inclusion promoted an increased abundance of proteins related with improved enterocyte structural integrity (ACTBL2, CRMP1, FLII, EML2 and MYLK), peptidase activity (NAALADL1, CAPNS1) and anti-inflammatory activity (C3), demonstrating improved intestinal function. Coherently, they lowered the abundance of apoptosis (ERN2) and proteolytic (DPP4) proteins. Alginate lyase supplementation seems to magnify the baseline effects of feeding the seaweed alone, by increasing the number of differential proteins in the same pathways, possibly as a consequence of increased intracellular nutrient release.
Project description:Seaweeds may represent immunostimulants that could be used as health-promoting fish feed components thereby offering an alternative for the use of antibiotics. This study was performed to gain insights into the immunomodulatory effects of dietary seaweeds in Atlantic salmon. Specifically tested were 10% inclusion levels of Laminaria digitata (SW1) and a commercial blend of seaweeds (Oceanfeed®) (SW2) against a fishmeal based control diet (FMC). Differences between groups were assessed in growth, feed conversion ratio (FCR) and blood parameters hematocrit (Hct) and hemoglobin (Hb). After a LPS challenge of fish representing each of the three groups, RNAseq was performed on head kidneys to determine transcriptomic differences in response to the immune activation, to our knowledge for the first time in fish in this context. Atlantic salmon fed with dietary seaweeds showed slightly higher FCRs and more homogenous growth but in general no major differences in performance in comparison with fishmeal fed fish. RNAseq resulted in ~154 million reads which were mapped against a NCBI Salmo salar reference and against a de novo assembled Salmo salar reference for analyses of expression of immune genes and ontology of immune processes among the 87,600 cDNA contigs. The dietary seaweeds provoked a more efficient immune response which involved more efficient identification of the infection site, and processing and presentation of antigens. More specifically, chemotaxis and the chemokine-mediated signaling pathway with involvement of genes such as C-C motif chemokine 19 were improved and the defense response to Gram-positive bacterium reduced. The predicted integrin alpha-2-like gene had by far the highest up-regulated expression and may therefore represent a key marker gene of the LPS immune response in salmonids. Specific Laminaria digita effects included reduction of the cytokine-mediated signalling pathway as indicated by the cytokine macrophage migration inhibitory factor, and interferon-gamma-mediated signalling as indicated by STAT1 and the gamma-interferon-inducible lysosomal thiol reductase precursor. Highly upregulated and specific for this diet was the expression of Major histocompatibility complex class I-related gene protein. The commercial blend of seaweeds caused more differential expression than Laminaria digita and improved immune processes such as receptor-mediated endocytosis, inflammatory response, cell adhesion and response to lipopolysaccharide. Particularly expression of many important immune receptors was up-regulated illustrating increased responsiveness. NF-kappa-B inhibitor alpha is an important gene that marked the difference between both seaweed diets as Laminaria digita inhibits the production of this cytokine while the blend of seaweeds stimulates it. It can be concluded that replacing fishmeal partly with seaweeds such as Laminaria digita can have important modulatory effects on the immune capacity of Atlantic salmon resulting in a more efficient immune response.