Dietary vegetable oils do not alter the intestine transcriptome of gilthead sea bream (Sparus aurata), but modulate the transcriptomic response to infection with Enteromyxum leei

Abstract

BackgroundStudies conducted with gilthead sea bream (Sparus aurata L.) have determined the maximum dietary replacement of fish meal and oil without compromising growth or product quality. The present study aimed to analyze the effect of the nutritional background on fish health and fish fed plant protein-based diets with fish oil (FO diet) or a blend of vegetable oils (66VO diet) were exposed for 102 days to the intestinal myxosporean parasite Enteromyxum leei, and the intestine transcriptome was analyzed with a customized oligo-microarray of 7,500 annotated genes.ResultsInfection prevalence was high and similar in the two diet groups, but the outcome of the disease was more pronounced in fish fed the 66VO diet. No differences were found in the transcriptome of both diet control groups, whereas the number of differentially expressed genes in infected groups was considerable. K-means clustering of these differentially expressed genes identified four expression patterns that reflected the progression of the disease with the magnitude of the fold-change being higher in infected 66VO fish. A positive correlation was found between the time of infection and the magnitude of the transcriptional change within the 66VO group, being higher in early infected animals. Within this diet group, a strong up-regulation of many components of the immune specific response was evidenced, whereas other genes related to complement response and xenobiotic metabolism were down-regulated.ConclusionsThe high replacement of fish oil by vegetable oils in practical fish feeds did not modify the intestine transcriptome of gilthead sea bream, but important changes were apparent when fish were exposed to the myxosporean E. leei. The detected changes were mostly a consequence rather than a cause of the different disease progression in the two diet groups. Hence, the developed microarray constitutes an excellent diagnostic tool to address changes associated with the action of intestinal pathogens, but lacks a prognostic value to predict in advance the different susceptibility of growing fish to the current pathogen.

Dietary oils mediate cortisol kinetics and the hepatic mRNA expression profile of stress-responsive genes in gilthead sea bream (Sparus aurata) exposed to crowding stress. Implications on energy homeostasis and stress susceptibility

“…Certainly, the advent of microarray gene expression technology has revealed a wide range of stress-responsive genes in response to a number of aquaculture stressors (Aluru and Vijayan, 2009). In particular for gilthead sea bream (Calduch-Giner et al, 2010), the microarray gene expression profiling of crowding stress underscores three major steps leading to i) rapid enhancement of energy supply, ii) strong activation of tissue repair and remodeling processes and iii) re-establishment of redox balance with increased scavenging of reactive oxygen species (ROS) and a general decline of ROS production. Such temporal gene expression pattern was exemplified herein by the strong activation 24 h after stressor disturbance of the cell-tissue repair response that assists mitochondria and ER protein-folding and misfolding.…”

“…At that point, three replicates from each dietary group (9-10 kg/m 3 ) remained undisturbed (control fish), whereas the remaining replicate was used as a donor tank of stressed fish, according to the protocol conducted in previous studies (Calduch-Giner et al, 2010;Saera-Vila et al, 2009b) and summarized in Fig. 1.…”

“…Hence, in gilthead sea bream, the replacement of fish oil with vegetable oils is highly feasible when the theoretical requirements in essential fatty acids for normal growth are met by diet, but this dietary intervention allows a faster disease progression when fish are challenged with the intestinal parasite Enteromyxum leei (Estensoro et al, 2011;Calduch-Giner et al, 2012). Stress responsiveness and susceptibility are also nutritionally regulated, and a recent gilthead sea bream study highlights that the magnitude and persistence of high plasma cortisol levels after crowding exposure are dependent on the source of dietary oils (Ganga et al, 2011).…”

“…Thus, the present study addressed this complex issue in combination with the hepatic gene expression profiling of a set of 31 stress-responsive genes, selected as markers of lipid and lipoprotein metabolism, antioxidant defence system, cell-tissue repair mechanims, xenobiotic metabolism and stress transcriptional regulation. This set of markers was derived from a previous study underlying the liver microarray gene expression profiling of gilthead sea bream after crowding exposure (Calduch-Giner et al, 2010). Additional markers were identified by BLAST-searches for metabolic-and stress-relevant genes in the updated transcriptomic database of gilthead sea bream (www.nutrigroup-iats.org/seabreamdb).…”

“…The coefficient of variation intra-and interassay was lower than 8% and 12%, respectively. Plasma glucose levels were measured by the glucose oxidase method (Thermo Electron, Louisville, CO, USA) as reported elsewhere as described earlier (Calduch-Giner et al, 2003). Briefly, RT reactions were conveniently diluted and the equivalent of 660 pg of total input RNA was used in a 25 µL volume for each PCR reaction.…”