l-Arginine and allopurinol supplementation attenuates inflammatory mediators in human osteoblasts-osteoarthritis cells

A novel conductometric biosensor based on hybrid organic/inorganic recognition element for determination of L-arginine

A highly accurate conductometric biosensor for determination of L-arginine (L-arg) in the real samples with the complex sample matrices was developed by co-immobilization of arginase, urease and the ammonium-sensitive zeolite clinoptilolite (Clt). The biosensors with different mutual arrangements of the enzyme component and zeolite on the sensitive surface of the gold interdigitated electrodes were studied and compared. The studies showed that the biosensor containing the primary layer of Clt deposited on the electrode surface followed by arginase and urease co-immobilized as the secondary layer has the most advantageous analytical characteristics compared to the biosensors based on other configurations of the bioselective membrane. In particular, for this biosensor they were as follows: sensitivity 9.61 ± 0.01 μS/mM, limit of detection 5 μM, linear range 0-280 μM and dynamic range 0-15 mM. The biosensor demonstrated high operational stability and storage stability. The effect of solution parameters (pH, ionic strength and buffer capacity) on the biosensor sensitivity was studied. Finally, we used the developed biosensor for quantification of L-arg in the food samples. The results of the biosensor analysis were compared with the control method (ion chromatography). The data of the biosensor method demonstrated high correlation with the reference data (R = 0.96).

The role of metabolites in the progression of osteoarthritis: Mechanisms and advances in therapy

Osteoarthritis (OA) is a progressive degenerative disease affected by many factors, and there is currently no effective treatment. In recent years, the latest progress in metabolomics in OA research has revealed several metabolic pathways and new specific metabolites involved in OA. Metabolites play significant roles in the identification and management of OA. This review looks back on the development history of metabolomics and the progress of this technology in OA as well as its potential clinical applications. It summarizes the applications of metabolites in the field of OA and future research directions. This understanding will advance the identification of metabolic treatment goals for OA.

The translational potential of this article

The development of metabolomics offers possibilities for the treatment of OA. This article reviews the relationship between metabolites associated with chondrocytes and OA. Selectively altering these three metabolic pathways and their associated metabolites may hold great potential as new focal points for OA treatment.

Novel insights into the role of metabolic disorder in osteoarthritis

Osteoarthritis (OA) is a prevalent condition that affects individuals worldwide and is one of the leading causes of disability. Nevertheless, the underlying pathological mechanisms of OA remain inadequately understood. Current treatments for OA include non-drug therapies, pharmacological interventions, and surgical procedures. These treatments are mainly focused on alleviating clinical manifestations and improving patients' quality of life, but are not effective in limiting the progression of OA. The detailed understanding of the pathogenesis of OA is extremely significant for the development of OA treatment. Metabolic syndrome has become a great challenge for medicine and public health, In recent years, several studies have demonstrated that the metabolic syndrome and its individual components play a crucial role in OA. Consequently, this review summarizes the mechanisms and research progress on how metabolic syndrome and its components affect OA. The aim is to gain a deeper understanding of the pathogenesis of OA and explore effective treatment strategies.

Bridging biomimetic and bioenergetics scaffold: Cellulose-graphene oxide-arginine functionalized aerogel for stem cell-mediated cartilage repair

The avascular nature of cartilage tissue limits inherent regenerative capacity to counter any damage and this has become a substantial burden to the health of individuals. As a result, there is a high demand to repair and regenerate cartilage. Existing tissue engineering approaches for cartilage regeneration typically produce either microporous or nano-fibrous scaffolds lacking the desired biological outcome due to lack of biomimetic dual architecture of microporous construct with nano-fibrous interconnected structures like the native cartilage. Most of these scaffolds also fail to suppress ROS generation and provide sustained bioenergetics to cells, resulting in the loss of metabolic activity under avascular microenvironment of cartilage. A dual architecture microporous construct with nano-fibrous interconnected network of cellulose aerogel reinforced with arginine-coated graphene oxide (CNF-GO-Arg aerogel) was developed for cartilage regeneration. The designed dual-architectured CNF-GO-Arg aerogel using dual ice templating assembly demonstrates 80 % strain recovery ability under compression. The release of Arginine from CNF-GO-Arg aerogel supported 41 % reduction in intracellular ROS activity and promoted chondrogenic differentiation of hMSCs by shifting mitochondrial bioenergetics towards oxidative phosphorylation indicated by JC-1 dye staining. Overall developed CNF-GO-Arg aerogel provided multifunctionality via biomimetic morphology, cellular bioenergetics, and suppressed ROS generation to address the need for regeneration of cartilage.

Causal association of genetically determined plasma metabolites with osteoarthritis: a two-sample Mendelian randomization study

Background

We aimed to elucidate the causal relationship between plasma metabolites and the vulnerability to Osteoarthritis (OA), encompassing both hip OA and knee OA.

Methods

We conducted a two-way two-sample Mendelian randomization (MR) analysis to investigate the association of 1,400 plasma metabolites with OA. The Inverse Variance Weighted (IVW) model served as the primary two-sample MR Analysis method, with supplementary analysis using the Weighted Median (WM) and MR Egger methods. To ensure the robustness of our findings, sensitivity analyses were performed, incorporating Cochran's Q test, MR-Egger intercept test, MR-PRESSO, and Leave-One-Out analyses. To validate the identified metabolites, we utilized the Steiger test and linkage disequilibrium score regression.

Results

A total of 94 plasma metabolites were associated with osteoarthritis, with 60 associated with hip OA and 106 associated with knee OA. IVW analysis revealed that tryptophan levels showed the strongest positive association with hip OA (OR [95% CI]: 1.119 [1.024, 1.223]), while X-24757 levels exhibited the highest positive association with knee osteoarthritis (OR [95% CI]: 1.095 [1.032, 1.162]). Ethylparaben sulfate levels were found to have the greatest positive association with hip OA (OR [95% CI]: 1.118 [1.015, 1.231]). Notably, the plasma metabolite X-2475 showed a strong robust random effect across all three types of osteoarthritis. Metabolic pathway analysis revealed that the pathogenesis of osteoarthritis in the hip was mediated by acetylarginine, specifically in four important metabolic pathways: ethanol degradation (p = 0.044), amino sugar metabolism (p = 0.090), fatty acid biosynthesis (p = 0.095), and aspartate metabolism (p = 0.097816).

Conclusion

There is a significant association between tryptophan levels and the risk of hip OA, as well as X-24757 levels and the risk of knee osteoarthritis. Additionally, X-24757 levels are also linked to the risk of hip OA. Moreover, this study has identified four crucial metabolic pathways in hip osteoarthritis, which are all regulated by acetylarginine. These findings provide valuable insights into potential biomarkers for OA and highlight potential pathways for its prevention and clinical intervention.

Preparation and evaluation of a novel alginate-arginine-zinc ion hydrogel film for skin wound healing

In this paper, the mixed solution of sodium alginate (SA) and arginine (Arg) was dried into a film and then crosslinked with zinc ion to form sodium alginate-arginine-zinc ion (SA-Arg-Zn²⁺) hydrogel for skin wound dressings. SA-Arg-Zn²⁺ hydrogel had higher swelling ability, which was beneficial to absorbing wound exudate. Moreover, it exhibited antioxidant activity and strong inhibition against E. coli and S. aureus, and had no obvious cytotoxicity to NIH 3T3 fibroblasts. Compared with other dressings utilized in rat skin wound, SA-Arg-Zn²⁺ hydrogel showed better wound healing efficacy and the wound closure ratio reached to 100 % on the 14th day. The result of Elisa test indicated that SA-Arg-Zn²⁺ hydrogel down-regulated the expression of inflammatory factors (TNF-α and IL-6) and promoted the growth factor levels (VEGF and TGF-β₁). Furthermore, H&E staining results confirmed that SA-Arg-Zn²⁺ hydrogel could reduce wound inflammation and accelerate re-epithelialization, angiogenesis and wound healing. Therefore, SA-Arg-Zn²⁺ hydrogel is an effective and innovative wound dressing, moreover, the preparation technique is simple and feasible for industrial application.

Causality of genetically determined metabolites and metabolic pathways on osteoarthritis: a two-sample mendelian randomization study

BACKGROUND

Osteoarthritis (OA) is one of the most prevalent musculoskeletal diseases and is the leading cause of pain and disability in the aged population. However, the underlying biological mechanism has not been fully understood. This study aims to reveal the causal effect of circulation metabolites on OA susceptibility.

METHODS

A two-sample Mendelian Randomization (MR) analysis was performed to estimate the causality of GDMs on OA. A genome-wide association study (GWAS) of 486 metabolites was used as the exposure, whereas 8 different OA phenotypes, including any-site OA (All OA), knee and/or hip OA (knee/hip OA), knee OA, hip OA, spine OA, finger and/or thumb OA (hand OA), finger OA, thumb OA, were set the outcomes. Inverse-variance weighted (IVW) was used for calculating causal estimates. Methods including weight mode, weight median, MR-egger, and MR-PRESSO were used for the sensitive analysis. Furthermore, metabolic pathway analysis was performed via the web-based Metaconflict 4.0. All statistical analyses were performed in R software.

RESULTS

In this MR analysis, a total of 235 causative associations between metabolites and different OA phenotypes were observed. After false discovery rate (FDR) correction and sensitive analysis, 9 robust causative associations between 7 metabolites (e.g., arginine, kynurenine, and isovalerylcarnitine) and 5 OA phenotypes were finally identified. Additionally, eleven significant metabolic pathways in 4 OA phenotypes were identified by metabolic pathway analysis.

CONCLUSION

The finding of our study suggested that identified metabolites and metabolic pathways can be considered useful circulating metabolic biomarkers for OA screening and prevention in clinical practice, and can also serve as candidate molecules for future mechanism exploration and drug target selection.

Therapeutic Liquid Formulations Based on Low Transition Temperature Mixtures for the Incorporation of Anti-Inflammatory Drugs

Most nonsteroidal anti-inflammatory drugs (NSAIDs) present poor aqueous solubility, impairing their efficiency in physiological media. In this context, Low Transition Temperature Mixtures (LTTMs) are a promising platform to overcome drugs' poor solubility, forming therapeutic liquid formulations. In this work, the LTTMs of citric acid:L-arginine:water (C:A:W) and glycerol:sorbitol (G:S) were studied in terms of their features and assessed in terms of their ability to increase the solubility of six NSAIDs in physiological media. The physicochemical properties of LTTMs were characterized by state-of-art techniques commonly used for these systems. The cytotoxicity of G:S was also evaluated in L929 mouse fibroblasts and the viscosity, polarity, and pH properties of the studied mixtures were related to the solubility of NSAIDs. The pH and polarity were the parameters that most influenced the drugs' solubility. Ibuprofen, naproxen, ketoprofen, indomethacin, and flurbiprofen did not present any solubility improvement in the formulations tested. However, concentrated mixtures of C:A:W or G:S in the physiologic-mimicked media (PBS) rendered a celecoxib solubility 4 and 5 times higher than PBS, respectively. These therapeutic liquid formulations of celecoxib in C:A:W or G:S can be a promising tool to increase celecoxib's therapeutic efficiency in local applications.

Iron induces insulin resistance in cardiomyocytes via regulation of oxidative stress

Iron overload is associated with various pathological changes which contribute to heart failure. Here, we examined mechanisms via which iron alters cardiomyocyte insulin sensitivity. Treatment of primary adult and neonatal cardiomyocytes as well as H9c2 cells with iron decreased insulin sensitivity determined via Western blotting or immunofluorescent detection of Akt and p70S6K phosphorylation and glucose uptake. Using CellROX deep red or DCF-DA probes we also observed that iron increased generation of reactive oxygen species (ROS), and that pretreatment with the superoxide dismutase mimetic MnTBAP reduced ROS production and attenuated iron-induced insulin resistance. SKQ1 and allopurinol but not apocynin reduced iron-induced ROS suggesting mitochondria and xanthine oxidase contribute to cellular ROS in response to iron. Western blotting for LC3-I, LC3-II and P62 levels as well as immunofluorescent co-detection of autophagosomes with Cyto-ID and lysosomal cathepsin activity indicated that iron attenuated autophagic flux without altering total expression of Atg7 or beclin-1 and phosphorylation of mTORC1 and ULK1. This conclusion was reinforced via protein accumulation detected using Click-iT HPG labelling after iron treatment. The adiponectin receptor agonist AdipoRon increased autophagic flux and improved insulin sensitivity both alone and in the presence of iron. We created an autophagy-deficient cell model by overexpressing a dominant-negative Atg5 mutant in H9c2 cells and this confirmed that reduced autophagy flux correlated with less insulin sensitivity. In conclusion, our study showed that iron promoted a cascade of ROS production, reduced autophagy and insulin resistance in cardiomyocytes.