γ-glutamylcysteine alleviates insulin resistance and hepatic steatosis by regulating adenylate cyclase and IGF-1R/IRS1/PI3K/Akt signaling pathways

The Role of Solute Carrier Family Transporters in Hepatic Steatosis and Hepatic Fibrosis

Solute carrier (SLC) family transporters are crucial transmembrane proteins responsible for transporting various molecules, including amino acids, electrolytes, fatty acids, and nucleotides. To date, more than fifty SLC transporter subfamilies have been identified, many of which are linked to the progression of hepatic steatosis and fibrosis. These conditions are often caused by factors such as non-alcoholic fatty liver disease and non-alcoholic steatohepatitis, which are major contributors to the global liver disease burden. The activity of SLC members regulates the transport of substrates across biological membranes, playing key roles in lipid synthesis and metabolism, mitochondrial function, and ferroptosis. These processes, in turn, influence the function of hepatocytes, hepatic stellate cells, and macrophages, thereby contributing to the development of hepatic steatosis and fibrosis. Additionally, some SLC transporters are involved in drug transport, acting as critical regulators of drug-induced hepatic steatosis. Beyond substrate transport, certain SLC members also exhibit additional functions. Given the pivotal role of the SLC family in hepatic steatosis and fibrosis, this review aimed to summarize the molecular mechanisms through which SLC transporters influence these conditions.

A computational model of the crosstalk between hepatocyte fatty acid metabolism and oxidative stress highlights the key enzymes, metabolites, and detoxification pathways in the context of MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD; formerly known as NAFLD) is a common liver disease worldwide and carries the risk of progressing to severe liver conditions, such as fibrosis and liver cancer. In the context of MASLD, evaluating fat accumulation in the liver and the subsequent production of oxidative stress is essential to understand the disease propagation. However, clinical studies using human patients to investigate the fat accumulation and the onset of oxidative stress in MASLD face ethical and technical challenges, highlighting the importance of alternative methods. To understand the relationship between fatty acid metabolism, lipid accumulation, oxidative stress generation, and antioxidant mechanisms in hepatocytes, we proposed a new mathematical model. The importance of this model lies in its ability to track the time-dependent changes in oxidative stress and glutathione concentration in response to the input of fatty acids. Furthermore, the model allows for the evaluation of the effects of altering the activity of the key enzymes involved in those mechanisms. Our model is anticipated to provide new insights into MASLD therapy strategies by identifying key pathways and predicting the effects of drug-induced changes in enzyme activity.

γ-Glutamylcysteine restores glucolipotoxicity-induced islet β-cell apoptosis and dysfunction via inhibiting endoplasmic reticulum stress

PURPOSE

The impaired function of islet β-cell is associated with the pathogenesis of type 2 diabetes mellitus (T2DM). γ-glutamylcysteine (γ-GC), an immediate precursor of glutathione (GSH), has antioxidant and neuroprotective functions. Its level has been reported to be down-regulated in hyperglycemia. However, whether γ-GC has a protective effect on islet β-cell dysfunction remains elusive. Recently, we explore the molecular mechanism by which γ-GC protects islet β-cell from glucolipotoxicity-induced dysfunction.

METHODS

In vivo mice models and in vitro cell models were established to examine the therapeutic effects and molecular mechanisms of γ-GC.

RESULTS

db mice develop impaired glucose-stimulated insulin secretion (GSIS) due to reduced islet number and damaged islet microstructure. Serious oxidative damage, apoptosis and lipid accumulation are also observed in β-cell stimulated by glucolipotoxicity. Mechanistic studies suggest that glucolipotoxicity inhibits PDX-1 nuclear translocation by inducing endoplasmic reticulum (ER) stress, which leads to impaired insulin (INS) secretion in β-cell. Nevertheless, γ-GC as an inhibitor of ER stress can alleviate the damage of islet microstructure in db mice. Importantly, γ-GC promotes INS gene expression and GSIS through driving nuclear translocation of PDX-1, thereby enhancing intracellular INS content. Moreover, treatment with γ-GC can also mitigate oxidative damage, apoptosis and lipid accumulation of β-cell, resulting in ameliorating islet β-cell dysfunction induced by glucolipotoxicity.

CONCLUSION

Our results support the use of γ-GC as an inhibitor of ER stress for prevention and treatment of T2DM in the future.

Exogenous Nucleotides Ameliorate Insulin Resistance Induced by Palmitic Acid in HepG2 Cells through the IRS-1/AKT/FOXO1 Pathways

Nucleotides (NTs) act as pivotal regulatory factors in numerous biological processes, playing indispensable roles in growth, development, and metabolism across organisms. This study delves into the effects of exogenous NTs on hepatic insulin resistance using palmitic-acid-induced HepG2 cells, administering interventions at three distinct dosage levels of exogenous NTs. The findings underscore that exogenous NT intervention augments glucose consumption in HepG2 cells, modulates the expression of glycogen-synthesis-related enzymes (glycogen synthase kinase 3β and glycogen synthase), and influences glycogen content. Additionally, it governs the expression levels of hepatic enzymes (hexokinase, phosphoenolpyruvate carboxykinase, and glucose-6-phosphatase). Moreover, exogenous NT intervention orchestrates insulin signaling pathway (insulin receptor substrate-1, protein kinase B, and forkhead box protein O1) and AMP-activated protein kinase (AMPK) activity in HepG2 cells. Furthermore, exogenous NT intervention fine-tunes the expression levels of oxidative stress-related markers (malondialdehyde, glutathione peroxidase, and NADPH oxidase 4) and the expression of inflammation-related nuclear transcription factor (NF-κB). Lastly, exogenous NT intervention regulates the expression levels of glucose transporter proteins (GLUTs). Consequently, exogenous NTs ameliorate insulin resistance in HepG2 cells by modulating the IRS-1/AKT/FOXO1 pathways and regulate glucose consumption, glycogen content, insulin signaling pathways, AMPK activity, oxidative stress, and inflammatory status.

LC-MS-Based Metabolomics Reveals the Mechanism of Protection of Berberine against Indomethacin-Induced Gastric Injury in Rats

Berberine is a natural isoquinoline alkaloid with low toxicity, which exists in a wide variety of medicinal plants. Berberine has been demonstrated to exhibit potent prevention of indomethacin-induced gastric injury (GI) but the related mechanism remains unclear. In the present study, liquid chromatography-mass spectrometry (LC-MS)-based metabolomics was applied for the first time to investigate the alteration of serum metabolites in the protection of berberine against indomethacin-induced gastric injury in rats. Subsequently, bioinformatics was utilized to analyze the potential metabolic pathway of the anti-GI effect of berberine. The pharmacodynamic data indicated that berberine could ameliorate gastric pathological damage, inhibit the level of proinflammatory factors in serum, and increase the level of antioxidant factors in serum. The LC-MS-based metabolomics analysis conducted in this study demonstrated the presence of 57 differential metabolites in the serum of rats with induced GI caused by indomethacin, which was associated with 29 metabolic pathways. Moreover, the study revealed that berberine showed a significant impact on the differential metabolites, with 45 differential metabolites being reported between the model group and the group treated with berberine. The differential metabolites were associated with 24 metabolic pathways, and berberine administration regulated 14 of the 57 differential metabolites, affecting 14 of the 29 metabolic pathways. The primary metabolic pathways affected were glutathione metabolism and arachidonic acid metabolism. Based on the results, it can be concluded that berberine has a gastroprotective effect on the GI. This study is particularly significant since it is the first to elucidate the mechanism of berberine's action on GI. The results suggest that berberine's action may be related to energy metabolism, oxidative stress, and inflammation regulation. These findings may pave the way for the development of new therapeutic interventions for the prevention and management of NSAID-induced GI disorders.

Biosynthesis of the antioxidant γ-glutamyl-cysteine with engineered Yarrowia lipolytica

The dipeptide γ-glutamylcysteine (γ-GC), the first intermediate of glutathione (GSH) synthesis, is considered as a promising drug to reduce or prevent plethora of age-related disorders such as Alzheimer and Parkinson diseases. The unusual γ-linkage between the two constitutive amino acids, namely cysteine and glutamate, renders its chemical synthesis particularly challenging. Herein, we report on the metabolic engineering of the non-conventional yeast Yarrowia lipolytica for efficient γ-GC synthesis. The yeast was first converted into a γ-GC producer by disruption of gene GSH2 encoding GSH synthase and by constitutive expression of GSH1 encoding glutamylcysteine ligase. Subsequently genes involved in cysteine and glutamate anabolism, namely MET4, CYSE, CYSF, and GDH1 were overexpressed with the aim to increase their intracellular availability. With such a strategy, a γ-GC titer of 464 nmol mg-1 protein (93 mg gDCW-1 ) was obtained within 24 h of cell growth.

Actinidia deliciosa Extract as a Promising Supplemental Agent for Hepatic and Renal Complication-Associated Type 2 Diabetes (In Vivo and In Silico-Based Studies)

Type 2 diabetes (T2D) is a chronic metabolic condition associated with obesity, oxidative stress-mediated inflammation, apoptosis, and impaired insulin signaling. The utilization of phytochemical therapy generated from plants has emerged as a promising approach for the treatment of diabetes and its complications. Kiwifruit is recognized for its substantial content of antioxidative phenolics. Therefore, this work aimed to examine the effect of Actinidia deliciosa (kiwi fruit) on hepatorenal damage in a high-fat diet (HFD) and streptozotocin (STZ)-induced T2D in rats using in vivo and in silico analyses. An increase in hepatic and renal lipid peroxidation was observed in diabetic rats accompanied by a decrease in antioxidant status. Furthermore, it is important to highlight that there were observable inflammatory and apoptotic responses in the hepatic and renal organs of rats with diabetes, along with a dysregulation of the phosphorylation levels of mammalian target of rapamycin (mTOR), protein kinase B (Akt), and phosphoinositide 3-kinase (PI3K) signaling proteins. However, the administration of kiwi extract to diabetic rats alleviated hepatorenal dysfunction, inflammatory processes, oxidative injury, and apoptotic events with activation of the insulin signaling pathway. Furthermore, molecular docking and dynamic simulation studies revealed quercetin, chlorogenic acid, and melezitose as components of kiwi extract that docked well with potential as effective natural products for activating the silent information regulator 1(SIRT-1) pathway. Furthermore, phenolic acids in kiwi extract, especially syringic acid, P-coumaric acid, caffeic acid, and ferulic acid, have the ability to inhibit the phosphatase and tensin homolog (PTEN) active site. In conclusion, it can be argued that kiwi extract may present a potentially beneficial adjunctive therapy approach for the treatment of diabetic hepatorenal complications.