Sirtuin 1 Protects the Mitochondria in Hepatocellular Carcinoma Cells via Suppressing Hypoxia-induced Factor-1 Alpha Expression

Background: We hypothesized that Sirtuin 1 (SIRT1) might attenuate the Warburg effect in tumor cells by modulating hypoxia-induced factor-1 alpha (HIF-1α) expression. This study aimed to explore the role and the underlying mechanism of SIRT1 in protecting the mitochondrial functions in hepatocellular carcinoma (HCC) cells. Methods: Quantitative real-time PCR and western blot analysis were conducted to determine gene expression in HCC cells. Co-immunoprecipitation (co-IP), chromatin immunoprecipitation (ChIP), and luciferase reporter assays were performed to examine DNA-protein interactions. Colony formation and MTT assays were carried out to explore the role of SIRT1 in HCC cell proliferation in vitro. PLC5 and Huh7 tumor xenografts were generated in mice to investigate the role of SIRT1–HIF-1α signaling in HCC development in vivo. Results: In different HCC cell lines, overexpression of SIRT1 promoted oxidative phosphorylation-associated gene expressions, ATP production, cell proliferation, and apoptotic protein expression while attenuating VEGF expression. In mice, overexpression of SIRT1 resulted in significant reductions in the weights of PLC5 and Huh7 tumor xenografts. Knockdown of SIRT1 exhibited opposite effects. Mechanistically, overexpression of SIRT1 promoted HIF-1α deacetylation, VHL-mediated HIF-1α degradation, and AMPK expression. Furthermore, SIRT1 interfered with the HIF-1α–c-Myc interaction to stimulate the transcription of a mitochondrial biogenesis enhancer mitochondrial transcription factor A (TFAM). Overexpression of HIF-1α completely reversed the effects of SIRT1.Conclusions: SIRT1 protects the mitochondria of HCC cells via suppressing HIF-1α expression, suggesting that SIRT1 may exert antitumor activity in HCC by reducing the Warburg effect.

Saikokeishikankyoto extract alleviates muscle atrophy in KKAy mice

Sarcopenic obesity is associated with increased visceral fat and decreased muscle mass, resulting in decreased insulin sensitivity, increased production of inflammatory cytokines, and oxidative stress. In this study, we first evaluated the effects of herbal medicines on the transcriptional activity of the Sirtuin 1 (sirt1) promoter in vitro as an indicator of their therapeutic effect. Our data suggested that hot water Saikokeishikankyoto (SKK) extracts increased sirt1 transcriptional activity in vitro, identifying it as a candidate therapeutic for evaluation in the KKAy type 2 diabetic obesity mouse model. These in vivo evaluations revealed that SKK treatment increased the wet weight and muscle fiber content in cross sections of the gastrocnemius muscle (GA) and restored motor function in these animals. In addition, SKK treatment reduced tumor necrosis factor-α (TNFα) expression in the sera and suppressed Atrogin1 and MuRF1 transcription in the GA samples. This treatment also increased sirt1 expression in these tissues. These results suggest that SKK inhibits skeletal muscle atrophy and improves motor function in KKAy mice by suppressing inflammation. In actual clinical practice, SKK is expected to inhibit muscle atrophy and improve motor dysfunction in sarcopenic obesity. Graphical abstract

Decreased Systemic and Airway Sirtuin 1 Expression in Adults With Bronchiectasis

Aim: Whether accelerated aging, reflected by sirtuin 1 (SIRT1) expression, is implicated in bronchiectasis remains largely unknown. We sought to determine the patterns of SIRT1 and other aging markers in systemic circulation and airways and their expression levels associated with bronchiectasis severity and exacerbation.Methods: We enrolled 132 patients with bronchiectasis and 50 healthy subjects in a prospective cohort study to profile aging markers in systemic circulation and recruited 36 patients with bronchiectasis and 32 disease controls (idiopathic pulmonary fibrosis or tumors) in a cross-sectional study to profile aging markers in bronchial epithelium of both large-to-medium and small airways. We profiled aging marker expression from peripheral blood mononuclear cells and enumerated the positively stained cells for detection of aging marker expression in bronchial epithelium.Results: Compared with healthy controls, the relative telomere length (median: 0.88 vs. 0.99, p = 0.009), SIRT1 (median: 0.89 vs. 0.99, p = 0.002), and Ku80 (median: 0.87 vs. 0.96, p < 0.001) expression levels were consistently lower in the peripheral blood mononuclear cells among patients with bronchiectasis and modestly discriminated patients with bronchiectasis from healthy controls. No remarkable changes in SIRT1, telomere length, or Ku70 were identified at onset of exacerbation. Within the bronchial epithelium, the percentage of positively stained cells was lower for SIRT1 (median: 25.1 vs. 57.2%, p < 0.05) and numerically lower for p16 (median: 40.0 vs. 45.1%) and p21 (median: 28.9 vs. 35.9%) in patients with bronchiectasis than in disease controls (p > 0.05).Conclusion: SIRT1 was downregulated in systemic circulation and bronchiectatic airways, which was independent of disease severity and lung function impairment.

IBF-R Regulates IRE1α Post-Translational Modifications and ER Stress in High-Fat Diet-Induced Obese Mice

Obesity is a global health issue linked to the heightened risk of several chronic diseases. Rhus verniciflua (RV) is a traditional food supplement used for a range of pharmacological effects such as antitumor, antioxidant, α-glucosidase inhibitory effects, hepatitis, and arthritis. Despite the traditional medicinal values, scientific evidence for its application in obesity is inadequate and unclear. Thus, this investigation was designed to evaluate the anti-obesity effects of IBF-R, an RV extract, using a high-fat diet (HFD) model. The study has six groups: chow diet group; chow diet with 80 mg/kg IBF-R; HFD group; IBF-R group with 20, 40, and 80 mg/kg. IBF-R supplementation significantly regulated the weight gain than the HFD fed mice. Further, IBF-R supplementation lowered the expressions of adipogenic transcription factors such as SREBP-1c, C/EBPα, FAS, and PPAR-γ in white adipose tissue (WAT) of diet-induced obese mice. In addition, IBF-R supplementation reduced the lipogenic gene expression while enhancing genes was related to fatty acid oxidation. Obesity is linked to redox-based post-translational modifications (PTMs) of IRE1α such as S-nitrosylation, endoplasmic reticulum (ER) stress, and chronic metabolic inflammation. The administration of IBF-R inhibits these PTMs. Notably, IBF-R administration significantly enhanced the expression of AMPK and sirtuin 1 in WAT of HFD-fed mice. Together, these findings reveal the IRE1α S-nitrosylation-inflammation axis as a novel mechanism behind the positive implications of IBF-R on obesity. In addition, it lays a firm foundation for the development of Rhus verniciflua extract as a functional ingredient in the food and pharmaceutical industries.

Therapeutic Effects of Sirtuin 1 Activator on Glaucoma Mice and the Regulation Mechanism of Mitogen-Activated Protein Kinase Pathway

The study focused on the therapeutic effects of resveratrol, sirtuin 1 (Sirt1) activator, on glaucoma, and its influence on mitogen-activated protein kinase (MAPK) pathway. Specifically, C57BL/6 mice were used and the glaucoma mouse model was established by intraperitoneal injection of N-methyl-D-aspartate (NMDA). According to different treatment methods, they were randomly rolled into 3 groups: control group (no treatment), model group (glaucoma mouse model), and resveratrol (Res) group (intraperitoneal injection of 20 mg/kg resveratrol solution on the basis of model group). The intraocular pressure was measured, and Sirt1 mRNA and protein expression was detected using reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. Subsequently, hematoxylin-eosin staining was used to observe histopathological morphology, the immunofluorescence labeling was used to identify retinal survival ganglia, and Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL) and Western blot were for apoptotic cells determination and the expression of c-Jun N-terminal kinase (JNK), extracellular regulated protein kinase (ERK), and p38 protein in mitogen-activated protein kinase (MAPK) pathway, respectively. The model group showed lower intraocular pressure, Sirt1 mRNA and protein expression, number of survival retinal ganglion cells (RGCs), and thinner retina versus the control group (P < 0.05), but number of apoptotic RGCs and the phosphorylation levels of the three kinds of protein were higher (P < 0.05), and it exhibited no notable difference from the Res group (P > 0.05). Also, compared with the control group, the number of survival RGCs in the Res group was reduced (P < 0.05), but no notable difference was noted in the retinal thickness, the number of apoptotic RGCs, and the phosphorylation levels of the three kinds of protein (P > 0.05). In conclusion, resveratrol, the Sirt1 activator, can inhibit RGCs apoptosis through the MAPK signaling pathway and improve the pathological manifestations of glaucoma animal models, thus playing a protective role of the retina.

Sirt1 Protects Against Hippocampal Atrophy and its Induced Cognitive Impairment in Middle-aged Mice

Background: Sirtuin 1 (Sirt1) is a recognized longevity gene and has been shown to be associated with aging and its related diseases. Hippocampal volume is considered to be the most sensitive brain imaging phenotype for cognition, but the effect of Sirt1 on hippocampal morphology during aging has not been reported. Results: Herein, we investigated the effect of conditional Sirt1 knockdown on hippocampal volume in middle-aged mice, as well as its cognitive function and the underlying molecular mechanisms. Brain structural magnetic resonance imaging (MRI) showed that adeno-associated virus (AAV) mediated hippocampal Sirt1 knockdown caused hippocampal atrophy in 8-month-old mice. Open field test (OFT) and Morris Water Maze (MWM) test revealed that hippocampal Sirt1 knockdown significantly weakened spatial learning and memory of mice without effect on anxiety and exploratory behavior. Western blotting analysis showed that p-tau levels were significantly increased while PSD95 levels were obviously reduced, indicating that hippocampal Sirt1 knockdown could activate tau pathology and synaptic damage.Conclusions: This work revealed that Sirt1 is an important protective gene against hippocampal atrophy and its induced cognitive impairment during aging, providing potential therapeutic targets for the prevention and intervention of aging-related neuropsychic diseases.

Salvianolic Acid B Activates Chondrocytes Autophagy and Reduces Chondrocyte Apoptosis in Obese Mice via the KCNQ1OT1/Mir-128-3p/SIRT1 Signaling Pathways

Purpose: Salvianolic acid B (Sal B) possesses strong anti-inflammatory and antioxidant activity. This study aims to explore the underlying mechanism of Sal B to improve the obesity-related osteoarthritis (OA). Methods: C57BL/6J male mice were fed with a standard diet, a high fat diet (HFD), or HFD with Sal B (25 mg/kg), and mouse body weights and osteoarticular inflammatory factor levels were examined. Mouse chondrogenic cell line ATDC5 were transfected with lncRNA KCNQ1 overlapping transcript 1 small hairpin RNA (KCNQ1OT1 shRNA), miR-128-3p mimic or Sirtuin-1 small interfering RNA (SIRT1 siRNA), then stimulated with Palmitic acid (PA) followed by the treatment of Sal B. Then, inflammatory response, apoptosis, and autophagy of ATDC5 cells in different groups were detected. Results: Sal B reduced body weight, decreased the levels of inflammatory markers, and improved cartilage damage in OA mice. KCNQ1OT1 was downregulated in OA mice and PA- stimulated ATDC5 cells. Sal B protected ATDC5 cells against PA-mediated inflammation, apoptosis, and the inhibition of autophagy, while knockdown of KCNQ1OT1 reversed these results. KCNQ1OT1 was found to be functioned as a ceRNA to bind and downregulate the expression of miR-128-3p that was upregulated in PA-induced cells. Furthermore, SIRT1 was verified as a target of miR-128-3p. MiR-128-3p overexpression reversed the effects of Sal B on inflammatory response, apoptosis, and autophagy in PA-stimulated cells, and knockdown of SIRT1 displayed similar results. Conclusion: Sal B exerted a chondroprotective effect by upregulating KCNQ1OT1, which indicates Sal B can used for a therapeutic agent in obesity-related OA.

A New Insight into an Alternative Therapeutic Approach to Restore Redox Homeostasis and Functional Mitochondria in Neurodegenerative Diseases

Neurodegenerative diseases are accompanied by oxidative stress and mitochondrial dysfunction, leading to a progressive loss of neuronal cells, formation of protein aggregates, and a decrease in cognitive or motor functions. Mitochondrial dysfunction occurs at the early stage of neurodegenerative diseases. Protein aggregates containing oxidatively damaged biomolecules and other misfolded proteins and neuroinflammation have been identified in animal models and patients with neurodegenerative diseases. A variety of neurodegenerative diseases commonly exhibits decreased activity of antioxidant enzymes, lower amounts of antioxidants, and altered cellular signalling. Although several molecules have been approved clinically, there is no known cure for neurodegenerative diseases, though some drugs are focused on improving mitochondrial function. Mitochondrial dysfunction is caused by oxidative damage and impaired cellular signalling, including that of peroxisome proliferator-activated receptor gamma coactivator 1α. Mitochondrial function can also be modulated by mitochondrial biogenesis and the mitochondrial fusion/fission cycle. Mitochondrial biogenesis is regulated mainly by sirtuin 1, NAD+, AMP-activated protein kinase, mammalian target of rapamycin, and peroxisome proliferator-activated receptor γ. Altered mitochondrial dynamics, such as increased fission proteins and decreased fusion products, are shown in neurodegenerative diseases. Due to the restrictions of a target-based approach, a phenotype-based approach has been performed to find novel proteins or pathways. Alternatively, plasma membrane redox enzymes improve mitochondrial function without the further production of reactive oxygen species. In addition, inducers of antioxidant response elements can be useful to induce a series of detoxifying enzymes. Thus, redox homeostasis and metabolic regulation can be important therapeutic targets for delaying the progression of neurodegenerative diseases.