Supplementation of Oocytes by Microinjection with Extra Copies of mtDNA Alters Metabolite Profiles and Interactions with Expressed Genes in a Tissue-Specific Manner

Abstract

Mitochondrial DNA (mtDNA) supplementation can rescue poor oocyte quality and overcome embryonic arrest. Here, we investigated a series of sexually mature pigs generated through autologous and heterologous mtDNA supplementation. Brain, liver and heart tissues underwent metabolite profiling using gas chromatography-mass spectrometry and gene expression analysis through RNA-seq. They were then assessed for mRNA-metabolite interactions. The comparison between overall mtDNA supplemented and control pigs revealed that mtDNA supplementation reduced the lipids stearic acid and elaidic acid in heart tissue. However, heterologous mtDNA supplemented-derived pigs exhibited lower levels of abundance of metabolites when compared with autologous-derived pigs. In the brain, these included mannose, mannose 6-phosphate and fructose 6-phosphate. In the liver, maltose and cellobiose, and in the heart, glycine and glutamate were affected. mRNA-metabolite pathway analysis revealed a correlation between malate and CS, ACLY, IDH2 and PKLR in the liver and glutamate and PSAT1, PHGDH, CDO1 and ANPEP in the heart. Our outcomes demonstrate that mtDNA supplementation, especially heterologous supplementation, alters the metabolite and transcriptome profiles of brain, liver, and heart tissues. This is likely due to the extensive resetting of the balance between the nuclear and mitochondrial genomes in the preimplantation embryo, which induces a series of downstream effects.

Keywords: brain; gene expression; heart; liver; metabolic pathways; metabolite profile; mtDNA; mtDNA supplementation.

Figure 1

Schematic diagram of carbohydrate (A) and protein (B) metabolism in offspring brain. Red font indicates differentially relatively abundant compounds for the comparison between heterologous and autologous mtDNA-supplemented pigs.

Figure 2

Schematic diagram of starch and sucrose (A) and carbohydrate–protein (B) metabolism in offspring liver. Red font indicates differentially relatively abundant compounds for the comparison between heterologous and autologous mtDNA-supplemented pigs.

Figure 3

Schematic diagram of protein metabolism in offspring heart. Red font indicates differentially relatively abundant compounds for the comparison between heterologous and autologous mtDNA-supplemented pigs.

Figure 4

RNA–metabolite network analyses for liver (A) and heart (C) derived from heterologous compared to autologous mtDNA-supplemented pigs. Schematic diagram of pyruvate metabolism/citrate cycle (TCA cycle) in liver tissue (B) and glycine, serine and threonine metabolism/glutathione metabolism/cysteine and methionine metabolism in heart tissue (D). In A and C, the blue boxes indicate compounds and blue circles indicate mRNA. In C and D, circles and red font indicate compounds and blocks and green font indicate mRNA. Red and blue arrows indicate upregulated and downregulated gene expression in heterologous compared to autologous mtDNA-supplemented cohorts, respectively.