Oxidative stress, resulting from an imbalance between oxidative and reductive processes, plays a pivotal role in aging and age-related diseases¹. The gut, a complex ecosystem, is particularly vulnerable to oxidative stress with age. Elevated levels of reactive oxygen species (ROS) and diminished antioxidant defenses compromise gut barrier integrity, alter the microbiota, and impair immune function², which contributes to gut dysfunction and diseases. Cysteine, an amino acid with a highly reactive thiol group, is particularly sensitive to oxidative stress. As ROS accumulate with age, cysteine modifications undergo reprogramming. However, the patterns of these modifications over time, their functional implications, and the key regulatory factors of oxidative stress and cysteine modifications remain poorly understood.

 To clarify these aspects, Xiao, Dai et al. developed a high-throughput pipeline that requires only 60 μg of protein per sample to efficiently quantify five cysteine redox states in Macaca fascicularis gut tissues. They found that these cysteine modifications exhibited distinct regional differences, with the descending colon found to be more susceptible to oxidative stress than the ascending colon. Through correlation analysis with transcriptomics, proteomics, and metabolomics, Xiao, Dai et al. identified several key cysteine sites involved in cellular regulation. Moreover, cellular experiments proved that modifications at these sites regulate ROS production, suggesting that cysteine oxidation not only reflects the level of oxidative stress but also imparts new functional roles to the proteins involved.

 Oxidative stress is tightly regulated by various mechanisms. Endogenous metabolites such as glutathione and vitamins play a crucial role in mitigating oxidative stress, suggesting that metabolic homeostasis may be key to regulating oxidative stress. However, our understanding of the metabolites involved in antioxidant defense remains limited. To explore this, Xiao, Dai et al. hypothesized that antioxidant metabolites would show a negative correlation with cysteine oxidation modifications, while pro-oxidant metabolites would show a positive correlation. They calculated the correlations between age-related metabolites and cysteine oxidation modifications and found that many metabolites, such as allantoin, N-acetyl alanine, and fumarate, were negatively correlated with oxidation levels, while metabolites like glycocholic acid and thiamine were positively associated. Cellular and animal experiments further demonstrated the effects of these metabolites on ROS levels, consistent with the analysis results.

 Calorie restriction is believed to extend lifespan. Xiao, Dai et al. found that calorie restriction significantly reversed the levels of a lot of cysteine oxidation modifications, suggesting that calorie restriction plays an important role in combating oxidative stress. Further research revealed that calorie restriction reversed the levels of numerous antioxidant metabolites, including lipids, vitamins, and the newly discovered antioxidant metabolites such as allantoin, N-acetyl alanine, and fumarate. However, calorie restriction did not show a consistent effect on proteins associated with gut aging³. These findings suggest that calorie restriction may delay aging through the regulation of metabolic reprogramming.

 In conclusion, Xiao, Dai et al. developed a cost-effective, high-throughput pipeline for analyzing cysteine oxidative modifications, emphasizing the role of metabolic regulation in oxidative stress.

Figure 1. Schematic of metabolic regulation of oxidative stress in the aging gut of non-human primates.

References

1. Finkel T, H. N. Oxidants, oxidative stress and the biology of ageing. Nature 408, 239-247 (2000).

2. Si, J. et al. The Aged Intestine: Performance and Rejuvenation. Aging Dis 12, 1693-1712 (2021).

3. Wang, X. et al. Age-, sex- and proximal-distal-resolved multi-omics identifies regulators of intestinal aging in non-human primates. Nat Aging 4, 414-433 (2024).