Dietary schizophyllan reduces mitochondrial damage by activating SIRT3 in mice

Molecular and cellular regulatory roles of sirtuin protein

Sirtuins (SIRT) are unique posttranslational modification enzymes that utilize NAD + as co-substrate to remove acyl groups from lysine residues. SIRT act on variety of substrates and impact major metabolic process. All seven members of SIRT family are unique and targets wide range of cellular proteins in nucleus, cytoplasm, and mitochondria for post-translational modification by acetylation (SIRT1, 2, 3, and 5) or ADP-ribosylation (SIRT4 and 6). Each member of SIRT family is distinct. SIRT2 was first to be discovered that incited research on mammalian SIRT. Enzymatic activities of SIRT 4 are yet to be elucidated while only SIRT7 is localized in nucleoli that govern the transcription of RNA polymerase I. SIRT 5 and 6 exhibit weakest deacetylase activity. Out of all SIRT analogs, SIRT1 is identified as nutrient sensor. Increased expression of only SIRT3 is linked with longevity in humans. Since SIRT is regulated by the bioenergetic state of the cell, nutrition impacts it but very few studies about diet-mediated effect on SIRT are reported. The present review elaborates distribution, specific biological role and prominent effect of all SIRT on vital human tissue along with highlighting need to trace molecular mechanisms and identifying foods that may augment it beneficially.

Enhanced exopolysaccharide yield and antioxidant activities of Schizophyllum commune fermented products by the addition of Radix Puerariae

To increase the production of exopolysaccharides (EPS) and expand the application of Schizophyllum commune (S. commune) fermentation liquid, the traditional Chinese medicine Radix Puerariae (RP) with outstanding biological activity was selected as a culture additive to improve the EPS yield and enhance the antioxidant activity of fermented products from S. commune. The effects of three independent factors: A: initial pH (5.0-6.0), B: concentration of RP (10-14 g L-1), and C: inoculum size (8-12%, v/v) on the EPS yield were evaluated. The results of response surface methodology (RSM) showed that the optimal fermentation conditions were: A: 5.40, B: 12.80 g L-1, and C: 10.0%. The optimal yield of EPS was 8.41 ± 0.12 mg mL-1, which showed an insignificant (p > 0.05) difference with the predicted value (8.45 mg mL-1). The fermented supernatants cultured from RP-supplemented medium (SC-RP) or regular medium (SC) were collected for further study. FT-IR analysis of EPS-1 (purified from SC) and EPS-2 (purified from SC-RP) showed that their structures were consistent, indicating that the addition of RP did not affect the structure of schizophyllan (SPG). In addition, compared with SC, the in vitro antioxidant activities of SC-RP were significantly improved with ORAC values and FRAP values increasing by 11.56-fold and 14.69-fold, respectively. There was a significant correlation among the phenolic compounds, flavonoids, and antioxidant activity of SC-RP in this study. Besides, SC-RP was detected to contain more than 25 bioactive ingredients compared with that of SC, which may play a key role in its antioxidant activities. Thus, these results indicated that RP enhanced the yield of SPG and improved the antioxidant activity of the fermented products by S. commune. Accordingly, the fermentation liquid of S. commune with the addition of RP may have potential application in food, cosmetics, and pharmaceutical industries.

SIRT3 affects mitochondrial metabolic reprogramming via the AMPK-PGC-1α axis in the development of benign prostatic hyperplasia

BACKGROUND

Sirtuin 3 (SIRT3) has been reported to share an association with mitochondrial metabolic reprogramming. However, the molecular mechanism underlying is not well understood, especially in benign prostatic hyperplasia (BPH). Therefore, the purpose of this study was to research whether SIRT3 can affect the progression of BPH via the regulation of mitochondrial metabolic reprogramming.

METHODS

Following the development of a rat model of BPH using testosterone propionate (TP), we extracted prostate tissues from sham-operated and BPH rats. Subsequently, bioinformatics prediction was used to screen the genes differentially expressed in BPH. To verify the role played by SIRT3 in BPH, we injected AAV9-SIRT3 into rats, followed by TP treatment. Prostate epithelial cells (PEC) were treated with TP to assess the mitochondrial morphology, mitochondrial membrane potential, and expression of enzymes related to the oxidative phosphorylation pathway after SIRT3 expression alteration. Finally, we examined the expression of AMPK-PGC-1α pathway in tissues and cells.

RESULTS

SIRT3 was reduced in the prostate tissues of BPH rats. After overexpression of SIRT3, mitochondrial morphology was more stable in prostate tissues of BPH rats and in TP-treated PEC, with significant increases in mitochondrial membrane potential and in the expression of oxidative phosphorylation-related enzymes in the cytoplasm. Moreover, SIRT3 significantly activated the AMPK-PGC-1α signaling pathway, which maintained the stability of mitochondrial membrane potential as well as mitochondrial structure, thus alleviating the symptoms of BPH.

CONCLUSION

SIRT3 maintained the stability of mitochondrial membrane potential as well as mitochondrial structure by activating the AMPK-PGC-1α pathway, thereby alleviating the symptoms of BPH.

Sirtuins-Mediated System-Level Regulation of Mammalian Tissues at the Interface between Metabolism and Cell Cycle: A Systematic Review

Sirtuins are a family of highly conserved NAD+-dependent proteins and this dependency links Sirtuins directly to metabolism. Sirtuins' activity has been shown to extend the lifespan of several organisms and mainly through the post-translational modification of their many target proteins, with deacetylation being the most common modification. The seven mammalian Sirtuins, SIRT1 through SIRT7, have been implicated in regulating physiological responses to metabolism and stress by acting as nutrient sensors, linking environmental and nutrient signals to mammalian metabolic homeostasis. Furthermore, mammalian Sirtuins have been implicated in playing major roles in mammalian pathophysiological conditions such as inflammation, obesity and cancer. Mammalian Sirtuins are expressed heterogeneously among different organs and tissues, and the same holds true for their substrates. Thus, the function of mammalian Sirtuins together with their substrates is expected to vary among tissues. Any therapy depending on Sirtuins could therefore have different local as well as systemic effects. Here, an introduction to processes relevant for the actions of Sirtuins, such as metabolism and cell cycle, will be followed by reasoning on the system-level function of Sirtuins and their substrates in different mammalian tissues. Their involvement in the healthy metabolism and metabolic disorders will be reviewed and critically discussed.