Objectives: Lipid metabolism in the liver plays an important role in the development and progression of liver disease. ER is an organelle that plays an important role in intracellular lipid metabolism, and when ER stress occurs, abnormal lipid metabolism occurs. S-adenosylmethionine (SAMe) is a metabolite of methionine and is known to have various functions including antioxidant properties. In this study, we aimed to determine whether SAMe could affect lipid metabolism by helping to alleviate ER stress in the liver.

Prohibitin 1 (PHB1) plays an important role in maintaining liver health and function. The PHB1 level is decreased in patients with various liver diseases. In this study, liver cancer was induced in liver-specific Phb1 knock-out mice, which were then subjected to hepatic gene and metabolomic analysis. The reduced expression of mRNA expression level of Phb1 induced down-regulation of cholesterol and lipid metabolism. This result was confirmed in a cell model. The expression of Hmgcr and Srebp2 in normal cells decreased when they were treated with cholesterol. In HepG2 cells in which the expression of Phb1 was lowered using siPhb1, the mRNA expression of Hmgcr and Srebp2 also decreased when the cells were treated with cholesterol. Furthermore, in the Phb1 knock-out group, the expression of Fasn and Srebp1 related to lipid metabolism increased but the expression of Ldlr decreased. The expression of Cat and Gpx in cells increased when the expression of Phb1 decreased. Altogether, a decreased expression of Phb1 induces down-regulation of cholesterol- and lipid metabolism-related genes and cholesterol homeostasis is not achieved, particularly in a cholesterol-rich environment. The decrease in Phb1 expression causes excessive oxidative stress in cholesterol and lipid metabolism. Therefore, maintaining a normal level of PHB1 expression is crucial for maintaining cholesterol homeostasis in the liver. Thus, PHB1 may become an important target for non-alcoholic fatty liver disease and lipid metabolism in the future.

Prohibitin 1 (Phb1) is a pleiotropic protein, located mainly in the mitochondrial inner membrane and involved in the regulation of cell proliferation and the stabilization of mitochondrial protein. Acetaminophen (APAP) is one of the most commonly used over-the-counter analgesics worldwide. However, at high dose, the accumulation of N-acetyl-p-benzoquinone imine (NAPQI) can lead to APAP-induced hepatotoxicity. In this study, we sought to understand the regulation of mRNA expression in relation to APAP and GSH metabolism by Phb1 in normal mouse AML12 hepatocytes. We used two different Phb1 silencing levels: high-efficiency (HE, >90%) and low-efficiency (LE, 50-60%). In addition, the siRNA-transfected cells were further pretreated with 0.5 mM of S-adenosylmethionine (SAMe) for 24 h before treatment with APAP at different doses (1-2 mM) for 24 h. The expression of APAP metabolism-related and antioxidant genes such as Cyp2e1 and Ugt1a1 were increased during SAMe pretreatment. Moreover, SAMe increased intracellular GSH concentration and it was maintained after APAP treatment. To sum up, Phb1 silencing and APAP treatment impaired the metabolism of APAP in hepatocytes, and SAMe exerted a protective effect against hepatotoxicity by upregulating antioxidant genes.

Non-alcoholic fatty liver disease and type 2 diabetes are representing symptoms of metabolic syndrome, which is often accompanied with hepatic fat accumulation and insulin resistance. Since liver is the major site of glucose and lipid metabolism, this study aimed to understand the effects of SCAAs and BCAAs supplementations on glucose and lipid metabolism in HepG2 cells. These cells were pretreated with SAMe, betaine, taurine, and BCAA for 24 h, followed by treatments of a high concentration of glucose (50 mM) or palmitic acid (PA, 0.5 mM) for 48 h to simulate high-glucose and high-fat environments. Pretreatment of BCAA and SCAAs inhibited the fat accumulation. At the transcriptional level, glucose and PA treatment led to significant increase of mRNA gluconeogenic enzyme. The mRNA expression level of GLUT2 was decreased by 20% in the SAMe-treated group and inhibited glucose synthesis by reducing the level of gluconeogenic enzyme. After SAMe or BCAA pretreatment, the mRNA expression of lipogenic enzymes was decreased. The PPAR-γ expression was increased after BCAA pretreatment, but SAMe not only downregulated the expression of PPAR-γ, but also inhibited the expression of ChREBP approximately 20% and SREBP-1c decreased by about 15%. Taken together, the effect of SAMe on glucose and lipid metabolism is significant especially on inhibiting hepatic lipogenesis and gluconeogenesis under the metabolic syndrome environment.

Isoquercitrin, a flavonoid glycoside found in various plants, has demonstrated antioxidant, anti-inflammatory, and anticancer properties. However, its hepatoprotective effects and underlying mechanisms against oxidative liver injury remain unclear. In this study, we evaluated the antioxidant and hepatoprotective effects of isoquercitrin using integrated in silico, in vitro, and in vivo approaches. HepG2 cells exposed to arachidonic acid (AA) and iron exhibited oxidative stress-induced apoptosis, which was significantly attenuated by isoquercitrin treatment, as evidenced by increased cell viability and reduced apoptosis-related protein alterations. Isoquercitrin decreased reactive oxygen species (ROS) generation and preserved mitochondrial function in a dose-dependent manner. Molecular docking and Western blot analyses revealed that isoquercitrin activates the LKB1/AMPK pathway, increasing phosphorylation of AMPK and its downstream target ACC, thereby modulating energy metabolism and reducing oxidative stress. This activation was LKB1 dependent, as confirmed in LKB1-deficient HeLa cells. Additionally, isoquercitrin modulated the YAP signaling pathway in hepatic cells. In vivo, isoquercitrin protected mice against carbon tetrachloride-induced liver injury, reducing serum ALT and AST levels and improving histopathological features. These findings suggest that isoquercitrin exerts hepatoprotective effects by activating the LKB1/AMPK pathway and modulating metabolic enzymes, highlighting its potential as a therapeutic agent against oxidative liver damage.

The increasing demand for multi-ingredient dietary supplements (MIDS), driven by diverse consumer health needs, has introduced analytical challenges in product testing and quality control. These challenges stem from complex ingredient interactions, formulation variability, and the diverse physicochemical properties of the individual components. To examine these issues and explore practical solutions, this study employed semi-structured focus group interviews with 33 industry professionals and 10 analytical experts from academic and industry. Professionals reported major obstacles including the degradation or loss of trace components, interferences among ingredients, analytical difficulties with specific dosage forms, and the lack of standardized testing protocols. To mitigate these challenges, professionals reported implementing various combination strategies including substituting problematic raw materials and modifying analytical instruments and pretreatment procedures, in order to improve test reproducibility. These measures were developed internally and varied significantly across companies, reflecting the absence of a unified analytical framework for MIDS testing. Building on these insights, the analytical experts proposed systematic improvements including developing matrix-specific pretreatment protocols and optimized extraction strategies as well as regulatory harmonization to enhance analytical reliability and reproducibility. These findings provide critical insights into current field practices and inform the development of standardized methodologies for the analysis and quality assurance of MIDS.

Objectives: Lipid metabolism in the liver plays an important role in the development and progression of liver disease. ER is an organelle that plays an important role in intracellular lipid metabolism, and when ER stress occurs, abnormal lipid metabolism occurs. S-adenosylmethionine (SAMe) is a metabolite of methionine and is known to have various functions including antioxidant properties. In this study, we aimed to determine whether SAMe could affect lipid metabolism by helping to alleviate ER stress in the liver.

Prohibitin 1 (PHB1) plays an important role in maintaining liver health and function. The PHB1 level is decreased in patients with various liver diseases. In this study, liver cancer was induced in liver-specific Phb1 knock-out mice, which were then subjected to hepatic gene and metabolomic analysis. The reduced expression of mRNA expression level of Phb1 induced down-regulation of cholesterol and lipid metabolism. This result was confirmed in a cell model. The expression of Hmgcr and Srebp2 in normal cells decreased when they were treated with cholesterol. In HepG2 cells in which the expression of Phb1 was lowered using siPhb1, the mRNA expression of Hmgcr and Srebp2 also decreased when the cells were treated with cholesterol. Furthermore, in the Phb1 knock-out group, the expression of Fasn and Srebp1 related to lipid metabolism increased but the expression of Ldlr decreased. The expression of Cat and Gpx in cells increased when the expression of Phb1 decreased. Altogether, a decreased expression of Phb1 induces down-regulation of cholesterol- and lipid metabolism-related genes and cholesterol homeostasis is not achieved, particularly in a cholesterol-rich environment. The decrease in Phb1 expression causes excessive oxidative stress in cholesterol and lipid metabolism. Therefore, maintaining a normal level of PHB1 expression is crucial for maintaining cholesterol homeostasis in the liver. Thus, PHB1 may become an important target for non-alcoholic fatty liver disease and lipid metabolism in the future.

Prohibitin 1 (Phb1) is a pleiotropic protein, located mainly in the mitochondrial inner membrane and involved in the regulation of cell proliferation and the stabilization of mitochondrial protein. Acetaminophen (APAP) is one of the most commonly used over-the-counter analgesics worldwide. However, at high dose, the accumulation of N-acetyl-p-benzoquinone imine (NAPQI) can lead to APAP-induced hepatotoxicity. In this study, we sought to understand the regulation of mRNA expression in relation to APAP and GSH metabolism by Phb1 in normal mouse AML12 hepatocytes. We used two different Phb1 silencing levels: high-efficiency (HE, >90%) and low-efficiency (LE, 50-60%). In addition, the siRNA-transfected cells were further pretreated with 0.5 mM of S-adenosylmethionine (SAMe) for 24 h before treatment with APAP at different doses (1-2 mM) for 24 h. The expression of APAP metabolism-related and antioxidant genes such as Cyp2e1 and Ugt1a1 were increased during SAMe pretreatment. Moreover, SAMe increased intracellular GSH concentration and it was maintained after APAP treatment. To sum up, Phb1 silencing and APAP treatment impaired the metabolism of APAP in hepatocytes, and SAMe exerted a protective effect against hepatotoxicity by upregulating antioxidant genes.