Harnessing the Therapeutic Potential of Ginsenoside Rd for Activating SIRT6 in Treating a Mouse Model of Nonalcoholic Fatty Liver Disease.

Nonalcoholic fatty liver disease (NAFLD) is a prevalent global condition and a common precursor to liver cancer, yet there is currently no specific medication available for its treatment. Ginseng, renowned for its medicinal and dietary properties, has been utilized in NAFLD management, although the precise underlying mechanism remains elusive. To investigate the effectiveness of ginsenoside Rd, we employed mouse and cell models to induce NAFLD using high-fat diets, oleic acid, and palmitic acid. We explored and confirmed the specific mechanism of ginsenoside Rd-induced hepatic steatosis through experiments involving mice with a liver-specific knockout of SIRT6, a crucial protein involved in metabolic regulation. Our findings revealed that administration of ginsenoside Rd significantly reduced the inflammatory response, reactive oxygen species (ROS) levels, lipid peroxide levels, and mitochondrial stress induced by oleic acid and palmitic acid in primary hepatocytes, thereby mitigating excessive lipid accumulation. Moreover, ginsenoside Rd administration effectively enhanced the mRNA content of key proteins involved in fatty acid oxidation, with a particular emphasis on SIRT6 and its target proteins. We further validated that ginsenoside Rd directly binds to SIRT6, augmenting its deacetylase activity. Notably, we made a significant observation that the protective effect of ginsenoside Rd against hepatic disorders induced by a fatty diet was almost entirely reversed in mice with a liver-specific SIRT6 knockout. Our findings highlight the potential therapeutic impact of Ginsenoside Rd in NAFLD treatment by activating SIRT6. These results warrant further investigation into the development of Ginsenoside Rd as a promising agent for managing this prevalent liver disease.

Microglia Sirt6 modulates the transcriptional activity of NRF2 to ameliorate high-fat diet-induced obesity.

BACKGROUND: Microglia play a pivotal role in neuroinflammation, while obesity triggers hypothalamic microglia activation and inflammation. Sirt6 is an important regulator of energy metabolism in many peripheral tissues and hypothalamic anorexic neurons. However, the exact mechanism for microglia Sirt6 in controlling high-fat diet-induced obesity remain unknown. METHODS: Microglia Sirt6 expression levels under various nutritional conditions were measured in the hypothalamus of mice. Also, microglia Sirt6-deficient mice were provided various diets to monitor metabolic changes and hypothalamic inflammatory response. Besides, RNA-seq and Co-IP of microglia with Sirt6 alterations were conducted to further investigate the detailed mechanism by which Sirt6 modulated microglia activity. RESULTS: We found that Sirt6 was downregulated in hypothalamic microglia in mice given a high-fat diet (HFD). Additionally, knockout of microglia Sirt6 exacerbated high-fat diet-induced hypothalamic microglial activation and inflammation. As a result, mice were more prone to obesity, exhibiting a decrease in energy expenditure, impaired glucose tolerance, insulin and leptin resistance, and increased food intake. In vitro, Sirt6 overexpression in BV2 cells displayed protective effects against oleic acid and palmitic acid treatment-derived inflammatory response. Mechanically, Sirt6 deacetylated and stabilised NRF2 to increase the expression of anti-oxidative genes and defend against reactive oxygen species overload. Pharmacological inhibition of NRF2 eliminated the beneficial modulating effects of Sirt6 on microglial activity. CONCLUSION: Collectively, our results revealed that microglial Sirt6 was a primary contributor of microglial activation in the central regulation of obesity. Thus, microglial Sirt6 may be an important therapeutic target for obesity.

Bushen-Yizhi formula exerts neuroprotective effect via inhibiting excessive mitophagy in rats with chronic cerebral hypoperfusion.

ETHNOPHARMACOLOGICAL RELEVANCE: Bushen-Yizhi formula (BSYZ), a traditional Chinese medicine (TCM) prescription widely used in treating mental retardation and neurodegenerative diseases with kidney deficiency, has been reported to attenuate oxidative stress-related neuronal apoptosis. Chronic cerebral hypoperfusion (CCH) is considered to be related to cognitive and emotional disorders. However, it remains to be clarified that the effect of BSYZ on CCH and its underlying mechanism. AIM OF THE STUDY: In the present study, we aimed to investigate the therapeutic effects and underlying mechanisms of BSYZ on CCH- injured rats based on the domination of oxidative stress balance and mitochondrial homeostasis through inhibiting abnormal excessive mitophagy. MATERIALS AND METHODS: The in vivo rat model of CCH was established by bilateral common carotid artery occlusion (BCCAo), while the in vitro PC12 cell model was exposed to oxygen-glucose deprivation/reoxygenation (OGD/R) condition, and a mitophagy inhibitor (chloroquine) by decreasing autophagosome-lysosome fusion was used as reverse validation in vitro. The protective role of BSYZ on CCH-injured rats was measured by open field test, morris water maze test, analysis of amyloid fibrils and apoptosis, and oxidative stress kit. The expression of mitochondria-related and mitophagy-related proteins was evaluated by Western blot, immunofluorescence, JC-1 staining assay and Mito-Tracker Red CMXRos assay. The components of BSYZ extracts were identified by HPLC-MS. The molecular docking studies were used to investigate the potential interactions of characteristic compounds in BSYZ with lysosomal membrane protein 1 (LAMP1). RESULTS: Our result indicated that BSYZ improved the cognition and memory abilities of the BCCAo rats by diminishing the occurrence of apoptosis and abnormal amyloid deposition accumulation, suppressing oxidative stress damage for abnormal excessive mitophagy activation in the hippocampus. Moreover, in OGD/R-damaged PC12 cells, BSYZ drug serum treatment substantially enhanced the PC12 cell viability and suppressed intracellular reactive oxygen species (ROS) accumulation for protecting against oxidative stress, along with the improvement of mitochondrial membrane activity and lysosomal proteins. Our studies also showed that inhibiting of autophagosome-lysosome fusion to generate autolysosomes by using chloroquine abrogated the neuroprotective effects of BSYZ on PC12 cells regarding the modulation of antioxidant defence and mitochondrial membrane activity. Furthermore, the molecular docking studies supported the direct bindings between lysosomal associated membrane protein 1 (LAMP1) and compounds in BSYZ extract to inhibit excessive mitophagy. CONCLUSION: Our study demonstrated that BSYZ played a neuroprotective role in rats with CCH and reduced neuronal oxidative stress via promoting the formation of autolysosomes to inhibit abnormal excessive mitophagy.