Project description:Purpose: Our previous study has confirmed that reduction of SIRT3 expression is a main factor contributing to salt-induced hepatic inflammtion. Here we sought to investigate whether salt-induced SIRT3 reduction was related to epigenetic modification. Methods: 6-week-old male wild-type mice were fed with high salt diet (HSD, containing 8% NaCl) or normal salt diet (NSD, containing 0.4% NaCl) for 4 months. And then their liver tissues were removed and subjected to bilsulfate-seq. Results: Through bisulfate-seq, we did not observe any change in DNA methylation in the CpG island of Sirt3 gene promoter region. Conclusions: Salt-induced SIRT3 reduction is not related to DNA methylation on SIRT3 gene promoter.
Project description:Purpose: Although clinical evidence suggests that high salt intake is associated with NAFLD, the underlying mechanism remains elusive. We sought to investigate whether salt-induced inflammation in liver is dependent on SIRT3 reduction. Methods: 6-week-old male SIRT3 knockout or their wild-type littermates were fed with high salt diet (HSD, containing 8% NaCl) or normal salt diet (NSD, containing 0.4% NaCl) for 4 months. And then their liver tissues were removed and total RNA was extracted to perform RNA sequencing. Results: 1850 differentially upregulated expressed genes were identified when comparing HSD group (HSD1, HSD2) to NSD group (NSD WT1, NSD2). Meanwhile, 1246 differentially upregulated expressed genes in response to SIRT3 knockout were determined (each group containing 3 samples). we observed that the common genes upregulated by both HSD and knockout of SIRT3 were enriched in immune system, including Tnf, Ccl2, etc. In addition, the common genes upregulated by knockout of SIRT3 in both NSD and HSD group were still enriched in the immune system. Conclusions: Through RNA-seq, we determined that HSD-induced hepatic inflammtion was highly similar to the effect of SIRT3 knockout, suggesting that reduction of SIRT3 expression is the main reason leading to salt-induced hepatic inflammation.
Project description:Purpose: Our previous study has confirmed that reduction of SIRT3 expression is a main factor contributing to salt-induced hepatic inflammtion. Here we sought to investigate whether salt-induced SIRT3 reduction was related to epigenetic modification. Methods: 6-week-old male SIRT3 knockout or their wild-type littermates were fed with high salt diet (HSD, containing 8% NaCl) or normal salt diet (NSD, containing 0.4% NaCl) for 4 months. And then their liver tissues were removed and subjected to ChIP-seq using antibodies against H3K27ac (ab4729), H3K4me1 (ab8895), H3K9ac (39917) and H3 (ab1791). Results: Through ChIP-seq, we observed the enrichment of H3K27ac was increased on the promoters of Sirt3 and some pro-inflammatory genes, including Ccl2, Tnf and Il6, after high salt loading. However, neither H3K4me1 nor H3K9ac displayed such phenomunum. In addition, those genes containing increased H3K27ac level in response to high salt were mainly enriched in metabolism and inflammatory pathways. And knockout of SIRT3 mainly affected genes related to AMP-activated protein kinase (AMPK) and insulin signaling pathways. Conclusions: Salt-induced SIRT3 reduction is related to the epigenetic regulation, especially H3K27ac.
Project description:Tumor cells exhibit aberrant metabolism characterized by high glycolysis even in the presence of oxygen. This metabolic reprogramming, known as the Warburg effect, provides tumor cells with the substrates and redox potential required for the generation of biomass. Here, we show that the mitochondrial NAD-dependent deacetylase SIRT3 is a crucial regulator of the Warburg effect. SIRT3 loss promotes a metabolic profile consistent with high glycolysis required for anabolic processes in vivo and in vitro. Mechanistically, SIRT3 mediates metabolic reprogramming independently of mitochondrial oxidative metabolism and through HIF1a, a transcription factor that controls expression of key glycolytic enzymes. SIRT3 loss increases reactive oxygen species production, resulting in enhanced HIF1a stabilization. Strikingly, SIRT3 is deleted in 40% of human breast cancers, and its loss correlates with the upregulation of HIF1a target genes. Finally, we find that SIRT3 overexpression directly represses the Warburg effect in breast cancer cells. In sum, we identify SIRT3 as a regulator of HIF1a and a suppressor of the Warburg effect. RNA isolated from brown adipose tissue of SIRT3 WT and KO mice. 5 wild-type samples and 5 SIRT3 KO samples
Project description:SIRT3 is a member of the Sir2 family of NAD+-dependent protein deacetylases that promotes longevity in many organisms. The processed, short form of SIRT3 is a well-established mitochondrial protein whose deacetylase activity regulates various metabolic processes. However, the presence of full-length (FL) SIRT3 in the nucleus and its functional importance remains controversial. Our previous studies demonstrated that nuclear FL-SIRT3 functions as a histone deacetylase and is transcriptionally repressive when artificially recruited to a reporter gene. Here, we report that nuclear FL-SIRT3 is subjected to rapid degradation upon cellular stress, including oxidative stress and UV-irradiation, whereas the mitochondrial, processed form is unaffected. FL-SIRT3 degradation is mediated by the ubiquitin-proteasome pathway, at least partially through the E3 activity of SKP2. Finally, we show by chromatin immunoprecipitation that some target genes of nuclear SIRT3 are derepressed upon the degradation of SIRT3 caused by stress stimuli. Thus, SIRT3 exhibits a previously unappreciated role in the nucleus modulating the expression of some stress-related and nuclear-encoded mitochondrial genes. ChIP-seq with a SIRT3 antibody in untreated, UV-irradiated, and stable SIRT3 knockdown (KD) U2OS cells
Project description:SIRT3 is a NAD+-dependent mitochondrial protein deacetylase participating in the regulation of central metabolism and mitochondrial proteostasis. SIRT3 is downregulated in clear cell renal cell carcinoma (ccRCC), a main type of renal cancers, but the function of SIRT3 in tumorigenesis and development of ccRCC remains unknown. In this study, we established a SIRT3 overexpressed cell line to explore the changes of proteomics and metabolomics regulated by SIRT3 expression. Both the results of quantitative proteomics, metabolomics and acetylome showed overexpression of SIRT3 increased mitochondrial biogenesis and reversed the mitochondrial dysfunctions in ccRCC. We found SIRT3 could increase the activity of TFAM through modulation of TFAM transcription, degradation and acetylation level. The acetylation of TFAM K154 decreased while TFAM protein expression increased after SIRT3 overexpression. Further study revealed that SIRT3 could bind with TFAM, and decrease the acetylation of TFAM, promoting TFAM activity in mitochondrial biogenesis. Overall, our results present a new mechanism of SIRT3 in regulating mitochondrial functions, and the downregulation of SIRT3 in ccRCC lowers the activity of TFAM, subsequently inhibits the transcription of mitochondrial genes and mitochondrial biogenesis.