Total and LDL-cholesterol levels in the plasma of zebrafish fed a low or a high cholesterol diet. Boxplots show the total cholesterol (A) and LDL-cholesterol (B) levels (mg dL⁻¹) in the plasma of zebrafish fed either a control (CT) diet or a high cholesterol (HC) diet for a period of 12 weeks. Black dots inside each box indicate the mean values of the corresponding groups. * indicates p < 0.05 and • indicates p < 0.1.

Total and LDL-cholesterol levels in the plasma of zebrafish fed glucans or simvastatin. Boxplots show total cholesterol (A) and LDL-cholesterol (B) levels (mg dL⁻¹) in the plasma of zebrafish fed high cholesterol (HC) diet or HC diet supplemented with either algal glucan (AG) or oat glucan (OG) or simvastatin (SS), for a period of 12 weeks. Black dots inside each box indicate the mean values of the corresponding groups. ^**indicates p < 0.01 and * indicates p < 0.05.

KEGG pathways and GO terms that were enriched in zebrafish fed a high cholesterol diet. (A) Significantly altered KEGG pathways in the high cholesterol diet (HC) group, based on the altered genes in the HC group compared to the low cholesterol (CT) diet group. Each treatment group consisted of at least five biological replicates. (B) Chord diagram showing the link between the enriched GO terms and the associated genes that were detected as downregulated in the HC vs. CT group comparison. Genes that were considered for the enrichment analyses are shown on the left half of the circle. The gradient color bar intensity varies with the Log₂ fold change.

Network showing the link between enriched GO terms and the associated genes that were upregulated in zebrafish fed the high cholesterol (HC) diet compared to the control (CT) diet. Genes that were considered for the enrichment are written near the red circles. The gradient color bar intensity varies with the adjusted p value (Benjamini-Hochberg method) for each GO term. Node size of each GO term increases with the number of mapped genes.

Genes and GO terms that were regulated in zebrafish fed the algal glucan diet. (A) Differentially expressed genes obtained by comparing the algal glucan group (AG) with the high cholesterol (HC) group (|Log2 fold-change| ≥ 1, q-value < 0.05). (B) Bar plot showing enriched GO terms in the AG group, based on genes that were upregulated in the AG group compared to the HC group. Bar colors represent the gene count. For both analyses, each treatment group consisted of at least five biological replicates.

GO terms that were altered in zebrafish fed the oat glucan diet. (A) Chord diagram showing the link between enriched GO terms and the associated upregulated genes in the oat glucan (OG) group compared to the high cholesterol diet (HC) group. Genes that were considered for the enrichment are shown on the left half of the circle. The gradient color bar intensity varies with the Log₂ fold change. (B) Enriched GO terms in the OG group. Only the non-redundant GO terms are marked in the bubble plot, and the analysis was performed using the genes that were downregulated in the OG group compared to the HC group. The color of the circles ranging from green to red indicates the order of adjusted p value (0.01–0.049). Circle sizes are proportional to the gene count.

Molecular effects of the oat glucan and simvastatin supplemented diets. (A) KEGG pathways that were altered in zebrafish fed the oat glucan (OG) diet. The enrichment analyses were performed by considering the differentially expressed genes in the OG fed zebrafish compared to the fish fed the high cholesterol (HC) diet. (B) Enriched GO terms in simvastatin fed (SS) group. Only the non-redundant GO terms are marked in the bubble plot, and the analysis was performed using the genes that were downregulated in the SS group compared to the HC group. The color of the circles ranging from green to red indicates the order of adjusted p value. Circle sizes are proportional to the gene number. (C) KEGG pathways that were altered in zebrafish fed simvastatin. The enrichment analyses were performed by considering the differentially expressed genes in the SS group compared to the HC group. Each treatment group consisted of at least five biological replicates.

Venn diagram showing the total number of genes that were affected by the experimental diets. The pink ellipse includes the genes that were downregulated in the HC group compared to the CT group. Green, yellow and gray ellipses include genes that were upregulated (compared to the HC group) in the AG, OG and SS groups, respectively. Thirteen (2 + 11), 30 (2 + 5 + 11 + 12) and 38 genes (12 + 15 + 11) that were downregulated in the HC group were upregulated in the AG, OG and SS groups, respectively.

Lipid accumulation in the liver of zebrafish fed four experimental diets. (A) Representative images of the liver of zebrafish. Scale bar = 50 μm. Boxplots show average size (B) and average number (C) of vacuoles in the liver of fish fed high cholesterol (HC) diet or HC diet supplemented with either algal glucan (AG) or oat glucan (OG) or simvastatin (SS), for a period of 12 weeks. Black dots inside each box indicate the mean values of the corresponding groups. * indicates p < 0.05 and • indicates p < 0.1. Each treatment group consisted of eight biological replicates.

Micromorphology and feature indices of the intestine of the zebrafish. Representative images (A) from the different study groups. Scale bar = 100 μm. Boxplots show average villi length (B), lamina propria width (C), submucosa thickness (D) and tunica muscularis thickness (E) in the mid intestine of the fish fed experimental diets for a period of 12 weeks. Black dots inside each box indicate the mean values of the corresponding groups. ** indicates p < 0.01, * indicates p < 0.05, and • indicates p < 0.1. Each treatment group consisted of eight biological replicates.

Verification of the expression of selected genes from the transcriptomic data. (A) Relative expression of 7 selected genes in the intestine of the zebrafish. CT, fish fed low cholesterol; HC, fish fed high cholesterol; AG, fish fed algal glucan; OG, fish fed oat glucan; SS, fish fed simvastatin. n = 5. *** indicate p < 0.001, ** indicates p < 0.01, * indicates p < 0.05, and • indicates p < 0.1. Each treatment group consisted of five biological replicates. (B) Correlation between the normalized counts from the RNA-Seq data and relative gene expression from the qPCR data.