Acylspermidines are conserved mitochondrial sirtuin-dependent metabolites

Sirtuins are NAD+-dependent enzymes that regulate metabolism and stress responses by deacylating proteins. Despite their importance, the specific acyl groups removed and their metabolic consequences remain unclear. Prior research has shown that sirtuins modify proteins by removing acyl groups, but the downstream metabolites and their biological roles are not fully understood. This gap motivated a re-examination of mitochondrial sirtuin biochemistry using metabolomics. The field lacks detailed characterization of the metabolites produced by sirtuin activity. No prior work had resolved the downstream fate of acyl groups after sirtuin action. This uncertainty drove the use of untargeted comparative metabolomics to explore new sirtuin-dependent metabolites. The study aimed to bridge the gap between sirtuin enzymatic activity and its metabolic outcomes. This approach allows for the discovery of novel metabolites that may influence sirtuin-related phenotypes.

The study aimed to identify and characterize metabolites downstream of mitochondrial sirtuins, specifically focusing on the role of acyl groups in sirtuin activity. The researchers sought to determine whether specific acyl groups are consistently removed by sirtuins across species and how these metabolites affect biological processes. The motivation was to clarify the enzymatic function of sirtuins and their impact on metabolism and lifespan. The study also aimed to test whether acylspermidines are conserved across species and whether they influence cell proliferation and longevity. By using comparative metabolomics, the researchers hoped to uncover new insights into sirtuin-dependent metabolic pathways. The goal was to expand the understanding of sirtuin activity beyond protein deacylation to include downstream metabolite formation. This work addresses a key question in sirtuin biology: how do sirtuins influence metabolism through their enzymatic products? The findings could help annotate sirtuin functions in vivo and provide new targets for further investigation.

The researchers used untargeted comparative metabolomics to analyze metabolite profiles in C. elegans, mouse, and human samples. They first focused on SIR-2.3 in C. elegans and identified N-glutarylspermidines as downstream metabolites. The team then conducted targeted analysis of N-acylspermidines in multiple species to assess conservation. They used mass spectrometry to detect and quantify acylspermidines in different organisms. The study compared the enzymatic activity of SIRT5 in mammalian cell lines with SIR-2.3 in C. elegans. The researchers tested whether SIRT5 could generate N-succinylspermidines and N-glutarylspermidines. They also examined the effects of N-glutarylspermidines on C. elegans lifespan and mammalian cell proliferation. The methods combined biochemical assays with metabolomic profiling to link sirtuin activity to specific metabolites.

The strongest finding was the identification of N-glutarylspermidines as downstream metabolites of SIR-2.3 in C. elegans. The study showed that SIR-2.3 functions as a lysine deglutarylase, removing glutaryl groups from proteins. Targeted analysis revealed a diverse range of N-acylspermidines in C. elegans, mouse, and human metabolomes. N-succinylspermidines and N-glutarylspermidines were also observed downstream of mammalian SIRT5 in two cell lines. The results confirmed that SIRT5 activity leads to the formation of these acylspermidines. The study found that N-glutarylspermidines negatively affect C. elegans lifespan and mammalian cell proliferation. The data suggest that acylspermidines are conserved metabolites across species. These findings support the role of sirtuins in generating acylspermidines that influence biological processes.

The study concludes that N-acylspermidines are conserved metabolites downstream of mitochondrial sirtuins. The authors propose that these metabolites facilitate the annotation of sirtuin enzymatic activities in vivo. The findings suggest that sirtuins remove glutaryl and succinyl groups, leading to the formation of acylspermidines. The study shows that N-glutarylspermidines adversely affect C. elegans lifespan and mammalian cell proliferation. The results support the idea that sirtuins influence biological processes through their downstream metabolites. The authors suggest that acylspermidines may contribute to sirtuin-dependent phenotypes. The study does not claim that acylspermidines are essential for sirtuin function, but they are significant in their effects. The findings provide a new perspective on sirtuin activity and its metabolic consequences.