Differential regulation of brain microvessel transcriptome and brain metabolome by western and heart-healthy dietary patterns in Ossabaw pigs

Abstract

Diet is a potentially modifiable neurodegenerative disease risk factor. We studied the effects of a typical Western diet (WD; high in refined carbohydrates, cholesterol and saturated fat), relative to a heart-healthy diet (HHD; high in unrefined carbohydrates, polyunsaturated fat and fiber, and low in cholesterol) on brain microvessel transcriptomics and brain metabolomics of the temporal region in Ossabaw minipigs. Thirty-two pigs (16 male and 16 females) were fed a WD or HHD starting at the age of 4 months for a period of 6 months. The WD and HHD were isocaloric and had a similar macronutrient content but differed in macronutrient quality. Within each dietary group, half of the pigs also received atorvastatin. Relative to HHD-fed pigs, WD-fed pigs had 175 genes differentially expressed (fold change > 1.3, FDR < 0.05) by diet, 46 upregulated and 129 downregulated. Gene Set Enrichment Analysis identified 22 gene sets enriched in WD-fed pigs, comprising pathways related to inflammation, angiogenesis, and apoptosis, and 53 gene sets enriched in the HHD-fed pigs, including cell energetics, neurotransmission, and inflammation resolution pathways. Metabolite analysis showed enrichment in arginine, tyrosine, and lysine in WD-fed pigs, and ergothioneine and S-adenosyl methionine in HHD-fed pigs. Atorvastatin treatment did not affect gene expression. These results suggest a likely contribution of diet to brain pathologies characterized by neuroinflammation and neurodegeneration.

Keywords: Brain microvessels; Metabolomics; Neuroinflammation; Transcriptomics.

Fig. 1

GSEA analysis of differentially expressed genes by diet, grouped into gene sets with shared functions. The number of gene sets within each group is shown in parenthesis.

Fig. 2

GSEA pathways enriched in brain microvessels of WD-fed pigs. (A) Inflammation; (B) extracellular matrix; and (C) cell death. In each plot, the enrichment score for the given pathway is represented by the peak of the green line. The enrichment of individual genes in the pathway is represented by the vertical bars in the Ranked list metric and where they fall (red for the WD diet and blue for the HHD). The lower half of the ranked list metric displays the correlation of the individual genes with the phenotype.

Fig. 3

GSEA pathways enriched in brain microvessels of HHD-fed pigs. (A) Cell metabolism; (B) neurotransmission; (C) cell trafficking; and (D) immune functions. For each plot, the enrichment score for the given pathway is represented by the peak of the green line. The enrichment of individual genes in the pathway is represented by the vertical bars in the Ranked list metric and where they fall (red for the WD diet and blue for the HHD). The lower half of the ranked list metric displays the correlation of the individual genes with the phenotype.

Fig. 4

Primary metabolites and biogenic amines of brain temporal region. (A) sPLS-DA score plot of metabolites in the brain temporal region separating WD and HHD groups. (B) Heatmap of metabolites associated with WD and HHD; the more red colored the higher the abundance of the metabolite. The HHD showed a higher abundance of ergothioneine, S-adenosyl-methionine and L-cyteine-glutathione, while the WD showed higher abundance of arginine, tyrosine, lysine, betaine, and L-pipecolic acid.

Fig. 5

Brain temporal region complex lipids. (A) sPLS-DA score plot of lipid metabolites in the brain temporal region separating WD and HHD groups. (B) Heatmap of the top 20 lipids contributing to the separation of WD and HHD; triglycerides with longer chain and more unsaturated fatty acids are enriched in HHD relative to WD; phosphatidylcholines with 36 carbons, with varying levels of unsaturation, are also more prevalent in the HHD than WD.

Fig. 6

DIABLO integrated multi-omics analysis. The plots display the genes (purple) and metabolites/lipids (red) associated with differences in HHD and WD diets around the circle. The inner lines show positive (orange) and negative (black) correlations between each gene and each metabolite/lipid that have a correlation strength of 0.5 or greater, indicating strong correlation. The outer blue and orange lines represent the diet for which a given feature is elevated.