Diet, Immunity, and Microbiota Interactions: An Integrative Analysis of the Intestine Transcriptional Response and Microbiota Modulation in Gilthead Seabream (Sparus aurata) Fed an Essential Oils-Based Functional Diet.

Essential oils (EOs) are promising alternatives to chemotherapeutics in animal production due to their immunostimulant, antimicrobial, and antioxidant properties, without associated environmental or hazardous side effects. In the present study, the modulation of the transcriptional immune response (microarray analysis) and microbiota [16S Ribosomal RNA (rRNA) sequencing] in the intestine of the euryhaline fish gilthead seabream (Sparus aurata) fed a dietary supplementation of garlic, carvacrol, and thymol EOs was evaluated. The transcriptomic functional analysis showed the regulation of genes related to processes of proteolysis and inflammatory modulation, immunity, transport and secretion, response to cyclic compounds, symbiosis, and RNA metabolism in fish fed the EOs-supplemented diet. Particularly, the activation of leukocytes, such as acidophilic granulocytes, was suggested to be the primary actors of the innate immune response promoted by the tested functional feed additive in the gut. Fish growth performance and gut microbiota alpha diversity indices were not affected, while dietary EOs promoted alterations in bacterial abundances in terms of phylum, class, and genus. Subtle, but significant alterations in microbiota composition, such as the decrease in Bacteroidia and Clostridia classes, were suggested to participate in the modulation of the intestine transcriptional immune profile observed in fish fed the EOs diet. Moreover, regarding microbiota functionality, increased bacterial sequences associated with glutathione and lipid metabolisms, among others, detected in fish fed the EOs supported the metabolic alterations suggested to potentially affect the observed immune-related transcriptional response. The overall results indicated that the tested dietary EOs may promote intestinal local immunity through the impact of the EOs on the host-microbial co-metabolism and consequent regulation of significant biological processes, evidencing the crosstalk between gut and microbiota in the inflammatory regulation upon administration of immunostimulant feed additives.

Unveiling the effect of dietary essential oils supplementation in Sparus aurata gills and its efficiency against the infestation by Sparicotyle chrysophrii.

A microencapsulated feed additive composed by garlic, carvacrol and thymol essential oils (EOs) was evaluated regarding its protective effect in gills parasitized by Sparicotyle chrysophrii in Sparus aurata. A nutritional trial (65 days) followed by a cohabitation challenge with parasitized fish (39 days) were performed. Transcriptomic analysis by microarrays of gills of fish fed the EOs diet showed an up-regulation of genes related to biogenesis, vesicular transport and exocytosis, leukocyte-mediated immunity, oxidation-reduction and overall metabolism processes. The functional network obtained indicates a tissue-specific pro-inflammatory immune response arbitrated by degranulating acidophilic granulocytes, sustained by antioxidant and anti-inflammatory responses. The histochemical study of gills also showed an increase of carboxylate glycoproteins containing sialic acid in mucous and epithelial cells of fish fed the EOs diet, suggesting a mucosal defence mechanism through the modulation of mucin secretions. The outcomes of the in vivo challenge supported the transcriptomic results obtained from the nutritional trial, where a significant reduction of 78% in the abundance of S. chrysophrii total parasitation and a decrease in the prevalence of most parasitic developmental stages evaluated were observed in fish fed the EOs diet. These results suggest that the microencapsulation of garlic, carvacrol and thymol EOs could be considered an effective natural dietary strategy with antiparasitic properties against the ectoparasite S. chrysophrii.

Cyclooxygenase 2-Regulated Genes an Alternative Avenue to the Development of New Therapeutic Drugs for Colorectal Cancer.

Colorectal cancer (CRC) is one of the most common and recurrent types of cancer, with high mortality rates. Several clinical trials and meta-analyses have determined that the use of pharmacological inhibitors of cyclooxygenase 2 (COX-2), the enzyme that catalyses the rate-limiting step in the synthesis of prostaglandins (PG) from arachidonic acid, can reduce the incidence of CRC as well as the risk of recurrence of this disease, when used together with commonly used chemotherapeutic agents. These observations suggest that inhibition of COX-2 may be useful in the treatment of CRC, although the current drugs targeting COX-2 are not widely used since they increase the risk of health complications. To overcome this difficulty, a possibility is to identify genes regulated by COX-2 activity that could give an advantage to the cells to form tumors and/or metastasize. The modulation of those genes as effectors of COX-2 may cancel the beneficial effects of COX-2 in tumor transformation and metastasis. A review of the available databases and literature and our own data have identified some interesting molecules induced by prostaglandins or COX-2 that have been also described to play a role in colon cancer, being thus potential pharmacological targets in colon cancer. Among those mPGES-1, DUSP4, and 10, Programmed cell death 4, Trop2, and many from the TGFß and p53 pathways have been identified as genes upregulated in response to COX-2 overexpression or PGs in colon carcinoma lines and overexpressed in colon tumor tissue. Here, we review the available evidence of the potential roles of those molecules in colon cancer in the context of PG/COX signaling pathways that could be critical mediators of some of the tumor growth and metastasis advantage induced by COX-2. At the end, this may allow defining new therapeutic targets/drugs against CRC that could act specifically against tumor cells and would be effective in the prevention and treatment of CRC, lacking the unwanted side effects of COX-2 pharmacological inhibitors, providing alternative approaches in colon cancer.

Zebrafish as a Model to Screen the Potential of Fatty Acids in Reproduction.

Sperm quality is an important topic in general health, chemotherapy, and gamete preservation technology. Fatty acid (FA) composition of membranes, which is influenced by the diet, plays key roles in sperm biology and quality. Dietary supplementation with natural products can be used as a technique to screen potential agents to protect, modify, and recover sperm quality. In this study, zebrafish (male [♂-ZF] and female [♀-ZF]) were fed a single cultivar olive oil (OO) bioencapsulated in Artemia. OO-treated ♂-ZF had higher (p < 0.05) sperm density and motility compared to the Artemia nauplii (AN). A significant difference was also observed in follicle abundance at different stages of gametogenesis, and a nonsignificant increase in total fecundity between OO-treated ♀-ZF and the AN, although in OO-treated ♀-ZF, mature follicles had a smaller diameter. A higher fertility rate (FR) was observed in OO-treated pairs compared to the other groups. Hatching in the OO-treated fish was accelerated, although no significant differences could be found in terms of hatching rate (HR) and embryo/larval survival rate (SR). These findings in FR, HR, and SR were also confirmed in male and female replacement mating trials. Taken together, this study shows that altering the FA ratios in the diet has a clear impact on several reproductive parameters in the zebrafish, adding new information about the nutritional requirement of this model species.

Dietary Fatty Acid Metabolism is Affected More by Lipid Level than Source in Senegalese Sole Juveniles: Interactions for Optimal Dietary Formulation.

This study analyses the effects of dietary lipid level and source on lipid absorption and metabolism in Senegalese sole (Solea senegalensis). Juvenile fish were fed 4 experimental diets containing either 100 % fish oil (FO) or 25 % FO and 75 % vegetable oil (VO; rapeseed, linseed and soybean oils) at two lipid levels (~8 or ~18 %). Effects were assessed on fish performance, body proximate composition and lipid accumulation, activity of hepatic lipogenic and fatty acid oxidative enzymes and, finally, on the expression of genes related to lipid metabolism in liver and intestine, and to intestinal absorption, both pre- and postprandially. Increased dietary lipid level had no major effects on growth and feeding performance (FCR), although fish fed FO had marginally better growth. Nevertheless, diets induced significant changes in lipid accumulation and metabolism. Hepatic lipid deposits were higher in fish fed VO, associated to increased hepatic ATP citrate lyase activity and up-regulated carnitine palmitoyltransferase 1 (cpt1) mRNA levels post-prandially. However, lipid level had a larger effect on gene expression of metabolic (lipogenesis and ß-oxidation) genes than lipid source, mostly at fasting. High dietary lipid level down-regulated fatty acid synthase expression in liver and intestine, and increased cpt1 mRNA in liver. Large lipid accumulations were observed in the enterocytes of fish fed high lipid diets. This was possibly a result of a poor capacity to adapt to high dietary lipid level, as most genes involved in intestinal absorption were not regulated in response to the diet.

Dietary lecithin source affects growth potential and gene expression in Sparus aurata larvae.

Soybean lecithin (SBL), used as a phospholipid source in larval fish diets, may compromise growth and survival in marine species, and affect gene expression, due to differences in fatty acid composition relative to marine lecithins (ML). The potential of SBL as a phospholipid source in gilthead seabream microdiets as compared to ML was evaluated. Two stocking densities were tested in order to exacerbate possible dietary effects: 5 and 20 larvae L(-1). Larvae reflected dietary fatty acid profiles: linoleic acid was higher, whereas eicosapentaenoic and arachidonic acids were lower in SBL fed groups than in ML fed larvae. Highest stocking density decreased survival, and led to elevated saturates and lower docosahexaenoic acid levels in polar lipid. Muscle histology observations showed hindered growth potential in SBL fed larvae. Despite similar cortisol levels between treatments, higher glucocorticoid receptor (GR), as well as hormone-sensitive lipase (HSL) mRNA levels in SBL fed groups revealed a role for fatty acids in gene regulation. Further analysed genes suggested these effects were independent from the hypothalamus-pituitary-interrenal axis control and the endocannabinoid system. Cyclooxygenase-2 and gluconeogenesis seemed unaffected. For the first time in fish, a link between dietary lecithin nature and HSL gene transcription, perhaps regulated through GR fatty acid-induced activation, is suggested. Enhanced lipolytic activity could partly explain lower growth in marine fish larvae when dietary ML is not provided.