Combined transcriptomics and proteomics analysis unveiled the impact of vitamin C in modulating specific mitochondrial protein abundance in the mouse liver.
Vitamin C (ascorbate) is a crucial antioxidant and an essential cofactor of biosynthetic and regulatory enzymes. Unlike humans, mice can synthesize vitamin C thanks to the key enzyme gulonolactone oxidase (Gulo). In the present study, we used the Gulo-/- mouse model, which cannot synthesize their own ascorbate to determine the impact of this vitamin on both the transcriptomics and proteomics profiles in the liver. The study included Gulo-/- mouse groups treated with either sub-optimal or optimal vitamin C concentrations in drinking water. We found a distinctive difference in the mRNA and protein profiles as a function of sex between all the mouse groups. Despite this sexual dimorphism, Spearman correlation analyses were conducted to divulge which transcripts and proteins correlated with hepatic vitamin C concentrations in both females and males. Such analysis on transcriptomics data from females and males revealed changes in a wide array of biological processes involved in glucose, lipid, steroid, and glutathione metabolisms as well as in acute-phase response. Furthermore, although several proteins of the mitochondrial complex III significantly correlated with vitamin C concentrations, their corresponding transcripts did not correlate with vitamin C in both females and males. Thus, this side-by-side comparison between transcriptome and proteome supported the view that post-transcriptional processes play a major role in the regulation of cellular respiration in the liver upon vitamin C deficiency. Our findings suggest that transcriptome profiling alone provides an incomplete picture of molecular changes associated with vitamin C deficiency in the liver of mice and examination of changes in protein abundances is essential to unveil variations that are not transcriptionally regulated. Overall design: RNA-seq analyses were performed on the liver of 4 months old mice. Groups of mice included: 3 Gulo-/- males and 3 Gulo-/- females treated with 0.4% vitamin C (weight/volume of L-ascorbate) in drinking water since weaning until the age of 4 months (3 MGL40 and 3 FGL40); Gulo-/- males and females treated with 0.05% vitamin C (weight/volume of L-ascorbate) in drinking water since weaning until the age of 4 months (3 MGL05 and 3 FGL05); Gulo-/- males and females treated with 0.01% vitamin C (weight/volume of L-ascorbate) in drinking water since weaning until the age of 4 months (3 MGL01 and 3 FGL01); a fourth cohort of Gulo-/- mice was treated with 0.4% ascorbate until the age of three months at which point ascorbate was then removed from drinking water for four weeks (3 MGL00) and 3 FGL00); a fifth cohort of Gulo-/- mice were treated with 0.4% ascorbate from weaning until the age of two months at which point ascorbate was removed from drinking water for one month. Then ascorbate was added back (0.4%) to drinking water until the mice reached the age of four months (3 MGLR40 and 3 FGLR40); finally, wild type control (Gulo+/+) mice were maintained in the same room with no ascorbate supplementation in drinking water and were used as our normal reference cohort (3 MWT00 and 3 FWT00).