Sexual dimorphism in hepatic gene expression and the response to dietary carbohydrate manipulation in the zebrafish (Danio rerio)

Abstract

In this study, we tested for the presence of sexual dimorphism in the hepatic transcriptome of the adult zebrafish and examined the effect of long term manipulation of dietary carbohydrate on gene expression in both sexes. Zebrafish were fed diets comprised of 0%, 15%, 25%, or 35% carbohydrate from the larval stage through sexual maturity, then sampled for hepatic tissue, growth, proximate body composition, and retention efficiencies. Using Affymetrix microarrays and qRT-PCR, we observed substantial sexual dimorphism in the hepatic transcriptome. Males upregulated genes associated with oxidative metabolism, carbohydrate metabolism, energy production, and amelioration of oxidative stress, while females had higher expression levels of genes associated with translation. Restriction of dietary carbohydrate (0% diet) significantly affected hepatic gene expression, growth performance, retention efficiencies of protein and energy, and percentages of moisture, lipid, and ash. The response of some genes to dietary manipulation varied by sex; with increased dietary carbohydrate, males up-regulated genes associated with oxidative metabolism (e.g. hadhβ) while females up-regulated genes associated with glucose phosphorylation (e.g. glucokinase). Our data support the use of the zebrafish model for the study of fish nutritional genomics, but highlight the importance of accounting for sexual dimorphism in these studies.

Dietary Protein Source Influence on Body Size and Composition in Growing Zebrafish

“…Thus, we cannot formally exclude the possibility that manipulation of the dietary carbohydrate content also influences the measures growth outcomes, 34 although previous findings would suggest that dietary carbohydrate does not affect growth outcomes at those levels. 35 Diets with similar carbohydrate content and protein content but different protein sources (see Tables 1 and 2: SOY vs. CAS) still exhibited significant differences in multiple growth outcomes, most likely attributable to the protein source contribution to the individual diets.…”

Effect of starvation on transcriptomes of brain and liver in adult female zebrafish (Danio rerio)

“…For example, expression of hexokinase IV (hex4; aka glucokinase) significantly decreased in livers of starved zebrafish. This gene is inducible by feeding and available dietary carbohydrates in many fish species, including zebrafish (49). Similarly, hepatic expression and activity of HEX4 decreased in gilthead sea bream undergoing starvation or reduced rations (7).…”

“…For each tissue, RNA pools were selected for microarray analysis so that each biological replicate came from a different tank. Microarrays were hybridized at the Washington State University-University of Idaho Center for Reproductive Biology Genomics Core Facility (Pullman, WA) by methods described elsewhere (49). Briefly, for each array, up to 10 g of total RNA was converted to cDNA and then to biotinylated cRNA in vitro with the GeneChip expression 3Ј amplification one-cycle target labeling kit (Affymetrix).…”

“…Data for brain and liver were normalized and analyzed separately because variances of expression differed considerably between the tissues. The microarray data were filtered with two criteria (49). First, probe sets were eliminated if they were not classified as present in at least 75% of the microarrays from one treatment (control or starved) with PMA calls.…”

“…The zebrafish is an important model organism for the study of development and is now emerging as a model organism in other fields, including behavioral, physiological, and nutritional genomics (42,49,76). Despite its importance as a developmental and genomic model organism, our understanding of the nutritional physiology of the zebrafish remains very limited.…”