Proteomic Analyses of Cysteine Redox in High-Fat-Fed and Fasted Mouse Livers: Implications for Liver Metabolic Homeostasis

Intensive
oxidative stress occurs during high-fat-diet-induced
hepatic fat deposition, suggesting a critical role for redox signaling
in liver metabolism. Intriguingly, evidence shows that fasting could
also result in redox-profile changes largely through reduced oxidant
or increased antioxidant levels. However, a comprehensive landscape
of redox-modified hepatic substrates is lacking, thereby hindering
our understanding of liver metabolic homeostasis. We employed a proteomic
approach combining iodoacetyl tandem mass tag and nanoliquid chromatography
tandem mass spectrometry to quantitatively probe the effects of high-fat
feeding and fasting on in vivo redox-based cysteine modifications.
Compared with control groups, ∼60% of cysteine residues exhibited
downregulated oxidation ratios by fasting, whereas ∼94% of
these ratios were upregulated by high-fat feeding. Importantly, in
fasted livers, proteins exhibiting diminished cysteine oxidation were
annotated in pathways associated with fatty acid metabolism, carbohydrate
metabolism, insulin, peroxisome proliferator-activated receptors,
and oxidative respiratory chain signaling, suggesting that fasting-induced
redox changes targeted major metabolic pathways and consequently resulted
in hepatic lipid accumulation.