Urolithin A (UA), an intestinal metabolite of ellagic acid, exhibits significant anti-inflammatory activity. Concurrently, Tumor necrosis factor α (TNF-α) serves as a pivotal inflammatory factor, and induces insulin resistance. This study aims to investigate the ameliorative effect of UA on TNF-α-induced insulin resistance and elucidate its underlying molecular mechanism. Methods and results: Through Western Blot (WB), glucose uptake, and immunocytochemistry (ICC) experiments, it was observed that UA significantly alleviated TNF-α-induced insulin resistance in C2C12 cells. Surface plasmon resonance (SPR) and molecular docking experiments validated the binding of UA to TNF-α with an affinity of 9.626×10^-5M, t which demonstrated UA could directly bind to TNF-α and inhibiting its downstream signaling. These results suggested a potential monoclonal antibody-like mechanism of UA to inhibit TNF-α-induced insulin resistance. Furthermore, we also found the  the substantial inhibitory effect of UA on LPS-induced pro-inflammatory polarization in RAW264.7 cells using WB and ICC experiments. In type 2 diabetes mellitus (T2DM) mouse models, OGTT, ITT, Elisa, WB, and RT-PCR experiments revealed that UA could effectively reduce blood glucose levels and serum concentrations of TNF-α and insulin while enhancing insulin signaling pathway transmission in muscle tissues and upregulating the expression of relevant genes for glycogen synthesis. Additionally, analysis of the intestinal microbiota showed that UA intervention markedly reshaped the composition and structure of the microbial community, reduced the elevated Firmicutes/Bacteroidetes ratio and increased the relative abundance of beneficial genera such as Akkermansia, Dubosiella, and Kurthia, as well as the key species Akkermansia muciniphila, thereby ameliorating HFD/STZ-induced dysbiosis and promoting the functional homeostasis of the intestinal ecosystem in T2DM. Conclusion: UA could directly bind to TNF-α and inhibit its downstream signaling, suggesting a potential monoclonal antibody-like mechanism. UA also exerted inhibitory effects on TNF-α-induced insulin resistance by specifically binding to TNF-α in C2C12 myotubes. We also found that UA could significantly improve insulin resistance, enhanced insulin signaling pathway transmission in muscle tissues, and improved intestinal microbiota dysbiosis.

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disorder that has long been hampered by limited treatment efficacy and significant side effects. Tumor necrosis factor-α (TNF-α) plays a pivotal role in RA pathogenesis by binding to its receptor (TNFR) and activating the downstream nuclear factor-kappa B (NF-κB) signaling pathway, which promotes the transcription of pro-inflammatory genes and perpetuates disease progression. Blocking the TNF-α–TNFR interaction thus represents a promising therapeutic strategy for RA. In this study, we identified a natural compound, 1-norbetulonic acid (DOCA), that disrupts the binding between TNF-α and TNFR, leading to therapeutic benefits in RA. Our results show that DOCA inhibits TNF-α-induced activation of the NF-κB pathway in human fibroblast-like synoviocytes and MH7A cells, and prevents nuclear translocation of the p65 subunit. Notably, DOCA demonstrated significant therapeutic efficacy in a mouse model of RA. Together, these findings support the hypothesis that DOCA alleviates RA by blocking TNF-α–TNFR signaling, underscoring its potential as a natural product-derived inhibitor of this interaction and highlighting a viable approach for the discovery of TNF-α/TNFR-targeted natural therapeutics.

Keratinocyte proliferation delay was a prominent clinical manifestation of diabetes, significantly impeding the wound healing process in diabetic mice. The potential therapeutic role of (−)-epigallocatechin gallate (EGCG) has been recognized due to its ability to enhance wound healing under diabetic conditions, but the underlying mechanism remained unclear. This study elucidates that EGCG expedited wound healing in diabetic mice by accelerating re-epithelialization and collagen deposition. Remarkably, we observed that EGCG promotes epidermal cell proliferation and enhances wound healing process in diabetic mice. We also discovered an overexpression of the Notch pathway in the epidermal cells of diabetic mice. Interestingly, EGCG effectively suppresses this overexpressed Notch pathway, suggesting a targeted mechanism for its therapeutic effects. Furthermore, the experiments with human immortalized keratinocytes (HaCaT) confirmed that high glucose levels activated the Notch signaling pathway, which was subsequently inhibited by EGCG treatment. In conclusion, our study reveals that EGCG improves wound healing in streptozotocin (STZ)-induced diabetic mice by targeting the Notch pathway in epidermal cells. These findings offered novel insights into therapeutic strategies for diabetic wounds and highlight EGCG as a promising candidate for treating chronic wounds.

Tumor necrosis factor-α (TNF-α) is a key player in the pathogenesis of rheumatoid arthritis (RA) and considered a promising target for therapeutic drug development. Activation of the nuclear factor-kappa B (NF-κB) pathway upon TNF-α binding to its receptor is crucial for progression of RA. Stephanine (SA), an isoquinoline aporphine-type alkaloid recently identified in Stephania plants, exhibits anti-inflammatory properties, but its underlying mechanisms of action are unknown at present. In this study, we explored whether SA could ameliorate RA through inhibition of the NF-κB signaling pathway in association with TNF-α activity. Our experiments revealed a binding affinity (K_D) of SA for TNF-α of 2.934 × 10⁻⁶ mol/L. Additionally, SA at a concentration of 10 μmol/L effectively hindered the binding of TNF-α to its receptors tumor necrosis factor receptor 1 (TNFR1) and TNFR2. In vitro, SA prevented TNF-α-induced death of L929 cells and blocked NF-κB activation triggered by TNF-α in 293-TNF-α responsive, as well as human fibroblast-like synoviocytes (HFLS) and human RA fibroblast-like synoviocytes (MH7A) cell lines. Furthermore, in a collagen-induced arthritis (CIA) mouse model, SA alleviated the symptoms of RA through suppression of NF-κB signaling. Our collective findings support the therapeutic efficacy of SA, a natural compound targeting TNF-α, in the management of RA.

Excessive osteoclastogenesis-mediated osteoporosis has been recognized as a global health concern. Candidate compounds derived from medicinal plants or functional foods are promising to treat osteoporosis due to their high safety and efficiency. (−)-Epigallocatechin-3-gallate (EGCG) is the most abundant and biologically active polyphenol in green tea. It can inhibit osteoclastogenesis in vitro by blocking receptor activator of nuclear factor (NF) -κB (RANK) signaling pathways. This study used the ovariectomized (OVX) mouse model to estimate the therapeutic effect of EGCG on osteoporosis and verified the molecular mechanism in vivo. The results revealed that EGCG significantly inhibited the OVX-induced body weight gain. Moreover, no adverse effects were observed on blood glucose, histomorphological features, weights, as well as indices of liver and kidney in OVX mice. EGCG could significantly ameliorate bone loss in OVX mice by inhibiting osteoclastogenesis. This effect was evidenced by the reduced number of osteoclasts and the increased trabecular bone area in the femurs. Moreover, EGCG inhibited the activities of c-telopeptide of type I collagen (CTX-I) and tartrate-resistant acid phosphatase 5b (TRACP-5b) and strengthened bone gla protein (BGP) and procollagen I N-terminal peptide (PINP) activities in OVX mice. Mechanistically, EGCG significantly downregulated the expression of osteoclastogenesis-related marker genes and proteins, including nuclear factor of activated T cells, cytoplasmic 1 (NFATc1), c-Fos, tartrate-resistant acid phosphatase (TRAP), c-Src, and cathepsin K. In addition, the phosphorylation levels of p65, c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase 1/2 (ERK1/2), p38, and protein kinase B (AKT) were significantly suppressed in OVX mice. It was found that EGCG could alleviate OVX-induced bone loss in mice by suppressing osteoclastogenesis by blocking the NF-κB, mitogen-activated protein kinase (MAPK), and AKT signaling pathways. EGCG has the potential to prevent and treat osteoclast-related diseases such as osteoporosis.

Moringa oleifera have laxative effects, but their active compositions and mechanisms are not very clear thus far. To this end, we systematically explored the active components and mechanism of M. oleifera leaves in relieving constipation by using the slow transit constipation (STC) mouse model and network pharmacology. The results of animal experiments showed that M. oleifera aqueous extract (MOA) had good laxative activity, and its 70% alcohol soluble part (ASP) also showed significant laxative activity (P < 0.01). Network pharmacological prediction results suggested that L-phenylalanine (Phe) was the key compound of ASP, and it might relieve constipation through tachykinin receptor 1 (TACR1) and three kinds of adrenergic receptors, including α_1A (ADRA1A), α_2A (ADRA2A), and α_2B (ADRA2B). Further animal experiment results showed that Phe significantly promoted gastrointestinal motility. Phe may relieve STC by enhancing the release of substance P (SP) and upregulating the mRNA expression of TACR1 in the ileum. Importantly, Phe may also promote intestinal movement by downregulating the mRNA expression of ADRA2A and ADRA2B and upregulating the mRNA expression of Calm and the mRNA and protein expression of myosin light chain 9 in the ileum, thereby activating the G protein-coupled receptor-myosin light chain signaling pathway. These results lay a foundation for the application of M. oleifera and Phe in constipation.

Epidemiological studies have demonstrated that a range of metabolic diseases, particularly type 2 diabetes and obesity, have reached epidemic proportions. These chronic conditions not only diminish the equality of life for individuals but also impose significant financial burdens on families and healthcare systems. While various therapeutic medications can effectively manage the progression of these diseases, they often come with adverse side effects. In contrast, natural products and their metabolites, such as ellagic acid (EA) and urolithins derived from a variety of plant species, have gained attention for their wide-ranging biological activities, diverse classes, and minimal side effects. Emerging research suggests that EA and urolithins may offer promising therapeutic effects in the treatment of metabolic disorders. This review aims to provide a comprehensive overview of the therapeutic effects and associated signaling pathways of EA and its metabolite urolithins in various metabolic diseases, offering valuable insights for their clinical applications and the potential development of novel food and medicine homologous therapies.