Vitamin C modulates the metabolic and cytokine profiles, alleviates hepatic endoplasmic reticulum stress, and increases the life span of Gulo−/− mice

Abstract

Suboptimal intake of dietary vitamin C (ascorbate) increases the risk of several chronic diseases but the exact metabolic pathways affected are still unknown. In this study, we examined the metabolic profile of mice lacking the enzyme gulonolactone oxidase (Gulo) required for the biosynthesis of ascorbate. Gulo−/− mice were supplemented with 0%, 0.01%, and 0.4% ascorbate (w/v) in drinking water and serum was collected for metabolite measurements by targeted mass spectrometry. We also quantified 42 serum cytokines and examined the levels of different stress markers in liver. The metabolic profiles of Gulo−/− mice treated with ascorbate were different from untreated Gulo−/− and normal wild type mice. The cytokine profiles of Gulo−/− mice, in return, overlapped the profile of wild type animals upon 0.01% or 0.4% vitamin C supplementation. The life span of Gulo−/− mice increased with the amount of ascorbate in drinking water. It also correlated significantly with the ratios of serum arginine/lysine, tyrosine/phenylalanine, and the ratio of specific species of saturated/unsaturated phosphatidylcholines. Finally, levels of hepatic phosphorylated endoplasmic reticulum associated stress markers IRE1α and eIF2α correlated inversely with serum ascorbate and life span suggesting that vitamin C modulates endoplasmic reticulum stress response and longevity in Gulo−/− mice.

Preventive Effects of Vitamin C on Diethylnitrosamine-induced Hepatotoxicity in Smp30 Knockout Mice

“…In this study, the final stage of HCC was not detected because the experimental period was limited to 17 weeks in consideration of the short lifespan of Smp30 KO mice (30). The SMP30 protein is responsible for the synthesis of Lgulonic acid to L-gulono-γ-lactone, the enzyme of the last step of the vitamin C conversion pathway (31)(32)(33). Therefore, Smp30 KO mice, which are unable to synthesize vitamin C, are used as a unique model to investigate the physiological functions of vitamin C in vivo (9).…”

Serum vitamin C levels modulate the lifespan and endoplasmic reticulum stress response pathways in mice synthesizing a nonfunctional mutant WRN protein

“…Blood was drawn at 10 AM by cardiac puncture and exsanguination under anesthesia at the age of 4 mo and processed (21). Ascorbic acid in serum was measured with the ferric reducing ascorbate assay kit from BioVision Research Products (Mountain View, CA, USA).…”

“…Total liver protein extracts were prepared as described elsewhere (21). Total endoplasmic reticulum (ER) fractions from mouse livers were obtained with an ER Enrichment Assay Kit (Novus Biologicals, Burlington, ON, Canada) according to the manufacturer's protocol.…”

“…Western blot analyses were performed as described in Aumailley et al (21). When indicated, immunoblots were probed with the following antibodies: rabbit polyclonal antibodies raised against the eukaryotic translation initiation factor 2-a kinase 3…”

“…We examined the effect of 0.01 and 0.4% (w/v) ascorbate supplementation in drinking water on Wrn Dhel/Dhel /Gulo 2/2 mice. A 0.4% ascorbate supplementation has been shown to significantly extend the lifespan of Wrn Δhel/Δhel mice (21).…”