Regorafenib has been approved for second-line treatment of hepatocellular carcinoma (HCC) following sorafenib failure, but resistance to targeted therapy remains a major challenge. Enhancing the therapeutic sensitivity of HCC cells to regorafenib is crucial for improving treatment outcomes. This study aims to elucidate the role of PRMT5 in HCC and its impact on regorafenib sensitivity. Specifically, it focuses on the regulatory relationship between PRMT5 and RPL14, investigating their influence on DNA damage repair and drug resistance mechanisms in HCC.

IgG4-related diseases are fibroinflammatory disorders affecting multiple organs, with autoimmune pancreatitis (AIP) being a common manifestation. Steroid therapy is effective in inducing remission but has complex effects on glucose metabolism. Diabetes occurs in 40% to 80% of AIP patients, and steroids can worsen glucose tolerance, although some studies suggest they may improve pancreatic endocrine function. An 81-year-old man with elevated IgG4 levels and imaging findings consistent with AIP initially declined treatment. His condition worsened, leading to poor glycemic management and referral to our hospital. Imaging confirmed AIP and tests showed impaired insulin and glucagon secretion. He was diagnosed with pancreatic diabetes secondary to IgG4-related AIP. Initially, intensive insulin therapy was administered, but within 3 months, both insulin and glucagon secretion declined significantly in the arginine-stimulation test, necessitating steroid therapy with prednisolone (35 mg/day) for the AIP. The high dose of steroid treatment enhanced both insulin and glucagon secretion capacities but gradually declined with dose tapering. On the other hand, although steroid therapy poses a temporary risk of hyperglycemia, it likely prevented further deterioration of pancreatic endocrine function.

Arginine metabolism in tumors is often shunted into the pathway producing pro-tumor and immune suppressive polyamines (PAs), while downmodulating the alternative nitric oxide (NO) synthesis pathway. Aiming to correct arginine metabolism in tumors, arginine deprivation therapy and inhibitors of PA synthesis have been developed. Despite some therapeutic advantages, these approaches have often yielded severe side effects, making it necessary to explore an alternative strategy. We previously reported that supplementing sepiapterin (SEP), the endogenous precursor of tetrahydrobiopterin (BH the essential NO synthase cofactor), could correct arginine metabolism in tumor cells and tumor-associated macrophages (TAMs) and induce their metabolic and phenotypic reprogramming. We saw that oral SEP treatment effectively suppressed the growth of HER2-positive mammary tumors in animals. SEP also has no reported dose-dependent toxicity in clinical trials for metabolic disorders. In the present study, we tested our hypothesis that a long-term administration of SEP to individuals susceptible to HER2-positive mammary tumor would protect them against tumor occurrence.

Aquaglyceroporins such as aquaporin-3 (AQP3) and its bacterial homologue GlpF facilitate water and glycerol permeation across lipid bilayers. X-ray crystal structures of GlpF showed open pore conformations, and AQP3 has also been predicted to adopt this conformation. Here we present cryo-electron microscopy structures of rat AQP3 and GlpF in different narrowed pore conformations. In n-dodecyl-β-D-maltopyranoside detergent micelles, aromatic/arginine constriction filter residues of AQP3 containing Tyr212 form a 2.8-Å diameter pore, whereas in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) nanodiscs, Tyr212 inserts into the pore. Molecular dynamics simulation shows the Tyr212-in conformation is stable and largely suppresses water permeability. AQP3 reconstituted in POPC liposomes exhibits water and glycerol permeability, suggesting that the Tyr212-in conformation may be altered during permeation. AQP3 Y212F and Y212T mutant structures suggest that the aromatic residue drives the pore-inserted conformation. The aromatic residue is conserved in AQP7 and GlpF, but neither structure exhibits the AQP3-like conformation in POPC nanodiscs. Unexpectedly, the GlpF pore is covered by an intracellular loop, but the loop is flexible and not primarily related to the GlpF permeability. Our findings illuminate the unique AQP3 conformation and structural diversity of aquaglyceroporins.

To explore the mechanism of β-hydroxybutyric acid (β-HB) mediated β-hydroxybutyrylation in glucose-6-phosphate dehydrogenation (G6PDX) on reducing the damage of podocyte induced by high glucose. Mouse podocytes (MPC-5) were stimulated with high glucose to establish a podocyte injury model of diabetic nephropathy. The cells were divided into three groups: the control group, the high glucose group (stimulated with 30 mmol/L glucose for 48 hours), and the high glucose+β-HB group (stimulated with 30 mmol/L glucose plus 20 mmol/L β-HB for 48 hours). The content of β-HB, cell viability, and the expressions of podocin, Wilms tumor protein 1 (WT-1), and synaptopodin in MPC-5 cells of each group were measured. Liquid chromatography-tandem mass spectrometry was employed to screen for potential protein sites undergoing β-hydroxybutyrylation, and the expression of G6PDX was detected. A mutant vector was transfected to mutate the lysine at position 432 of G6PDX to arginine. The cells were then divided into three groups: the high glucose group (stimulated with 30 mmol/L glucose for 48 hours), the high glucose+β-HB group (stimulated with high glucose and 20 mmol/L β-HB for 48 hours), and the high glucose+β-HB+site mutation group (subjected to high glucose, β-HB, and transfection of a plasmid for lysine site mutation). The cell viability and G6PDX expression in each subgroup were determined. Compared with the control group, the cell viability in the high glucose group was significantly decreased (34.8%±2.8% vs 100.0%±8.5%, <0.001). In contrast, the cell viability in the high glucose+β-HB group was significantly higher than that in the high glucose group (72.7%±1.9% vs 34.8%±2.8%, <0.001). Moreover, β-HB could ameliorate podocyte injury induced by high glucose, as evidenced by the increased expressions of podocin (0.63±0.02 vs 0.39±0.03, <0.001), WT-1 (0.75±0.04 vs 0.50±0.03, <0.001), and synaptopodin (0.74±0.02 vs 0.56±0.02, <0.001). Liquid chromatography-tandem mass spectrometry analysis revealed an increased β-hydroxybutyrylation modification of the lysine at position 432 of G6PDX after β-HB treatment (fold change>1.5). The results of Western blotting (0.68±0.05 vs 0.38±0.01, <0.001), PCR (0.70±0.10 vs 0.15±0.03, <0.001), and immunofluorescence all indicated an upregulation of G6PDX expression. After the site mutation, the restoration of cell viability under β-HB treatment was restricted (171.7%±7.1% vs 259.7%±14.6%, 0.001). Additionally, the results of Western blotting (1.43±0.04 vs 2.22±0.09, <0.001) and PCR (2.33±0.16 vs 3.60±0.34, <0.001) showed a decrease in G6PDX expression compared with that with simple β-HB treatment. β-HB mediated β-hydroxybutyrylation of G6PDX can alleviate podocyte injury induced by high glucose.

Advanced glycation end products (AGEs) are dietary risk factors formed through the non-enzymatic glycation of reducing sugars with proteins, lipids, and other compounds. Siraitia grosvenorii polysaccharide (SGP) exhibits strong antioxidant activity and holds potential as a natural inhibitor of glycation. This study aims to investigate the anti-glycation activity and mechanisms of SGP, providing a theoretical basis for the anti-glycation effects of SGP. The results demonstrated that SGP inhibited the formation of AGEs during biscuit baking in a food matrix. In the bovine serum albumin-fructose (BSA-Fru) model, SGP reduced the formation of AGEs by chelating metal ions. SGP, Fru, and BSA were found to share the same binding sites, enabling SGP to compete with Fru for the aspartic acid 108 and arginine 144 binding sites on BSA, thereby directly inhibiting AGEs formation. In the Caco-2 cell model, SGP alleviated N-ε- (Carboxymethyl)-l-lysine (CML)-induced damage by reducing oxidative stress and regulating metabolic pathways, including the glycine-serine-threonine metabolism pathway, glyoxylate and dicarboxylate metabolism pathway, and the tricarboxylic acid (TCA) cycle. In summary, SGP not only serves as a natural inhibitor of in vitro AGEs formation but also alleviates intestinal barrier damage. This study provides a theoretical foundation for developing SGP as a functional food additive.

In this study, we examined the effects of arginine (L-ArgHCl) on ultrafiltration performance, a process with practical significance for not only research but also pharmaceutical applications. Specifically, we assessed the yield and filtration rate of ultrafiltration using rabbit and goat polyclonal antibodies (neutral to basic isoelectric points) as well as model proteins, BSA (acidic) and lysozyme (basic). When a 1 mg/mL protein solution was concentrated approximately 10-fold using a standard commercially available centrifugal ultrafiltration device, the addition of L-ArgHCl significantly improved yield at near-neutral buffer pH. The observed order of improvement was: 20 mM L-ArgHCl > 100 mM L-ArgHCl ≈ 0.5 M NaCl > no addition. A similar trend was observed with BSA, whereas lysozyme achieved slightly higher yields at 100 mM L-ArgHCl. In a 40-fold concentration of rabbit polyclonal antibody from 1 mg/mL, 20 mM L-ArgHCl enhanced yield at pH 6 and 7, but had minimal or no effect at pH 7.5. Notably, at pH 8, high yields were achieved without arginine. L-ArgHCl also accelerated the concentration rate at all pH levels, with greater enhancements observed at higher arginine concentrations. These findings suggest that L-ArgHCl mitigates protein precipitation and solubility loss by reducing protein-protein interactions and nonspecific binding to the ultrafiltration membrane. At pH 8, the increased surface charge of the antibody reduced hydrophobicity, further improving solubility. In summary, the addition of L-ArgHCl, particularly near pH 7, effectively enhanced ultrafiltration performance. This provides a practical strategy for improving protein concentration processes.

Cryopreservation of boar semen is widely applied in the conservation of genetic resources and animal breeding to enhance the utilization efficiency of superior boars. However, accurately identifying individuals with good freezing tolerance in boar sperm remains challenging. In this study, based on the differences in sperm motility before and after cryopreservation from 328 boars, we selected six boars each from the Duroc, Landrace, and Large White breeds, and categorized them into poor freezability ejaculates (PFE) and good freezability ejaculates (GFE) groups for sperm metabolomic analysis. A total of 1288 metabolites were identified using both positive and negative ion modes. There were 148 differentially expressed metabolites between the GFE and PFE groups, which were enriched in pathways such as alanine, aspartate and glutamate metabolism; arginine biosynthesis; D-amino acid metabolism; histidine metabolism; beta-alanine metabolism; citrate cycle (TCA cycle); pantothenate and CoA biosynthesis; and pyruvate metabolism. Further analysis, including ROC curve evaluation, identified seven potential biomarkers for sperm cryopreservation. Argininosuccinic acid, asparagine, L-aspartate, fumarate, D-ornithine, DL-serine and histidine were tightly interconnected in a series of amino acids metabolism. In conclusion, our findings imply that differences in certain amino acid biosynthetic pathways contribute to the variations in freezing tolerance of boar sperm.

Arginine has been a mainstay in biological formulation development for decades. To date, the way arginine modulates protein stability has been widely studied and debated. Here, we employed a hydrophobic polymer to decouple hydrophobic effects from other interactions relevant to protein folding. While existing hypotheses for the effects of arginine can generally be categorized as either direct or indirect, our results indicate that direct and indirect mechanisms of arginine co-exist and oppose each other. At low concentrations, arginine was observed to stabilize hydrophobic polymer folding a sidechain-dominated direct mechanism, while at high concentrations, arginine stabilized polymer folding a backbone-dominated indirect mechanism. Upon introducing partially charged polymer sites, arginine destabilized polymer folding. Further, we found arginine-induced destabilization of a model virus similar to direct-mechanism destabilization of the charged polymer and concentration-dependent stabilization of a model protein similar to the indirect mechanism of hydrophobic polymer stabilization. These findings highlight the modular nature of the widely used additive arginine, with relevance in the information-driven design of stable biological formulations.