Adipose tissue plays a central role in metabolic and immune regulation, with adipocytes serving not only as energy storage cells but also as active participants in inflammatory signaling. Chronic low-grade inflammation in obesity is closely linked to the dysregulated secretion of pro-inflammatory adipokines such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6). These cytokines are key mediators in insulin resistance and metabolic syndrome. Glycine, the simplest amino acid, has emerged as a potential modulator of inflammation due to its cytoprotective, immunomodulatory, and anti-inflammatory properties. Recent studies have indicated that glycine can suppress the activation of the NF-κB pathway—a master regulator of inflammation—particularly in response to TNF-α stimulation in adipocytes. However, the precise molecular mechanism by which glycine exerts this effect remains unclear.
This study aimed to investigate whether glycine acts as a competitive antagonist at the TNF receptor, specifically targeting TNFR1 (Tnfrsf1a), to inhibit downstream inflammatory signaling in differentiated 3T3-L1 adipocytes.Cytokeratin 19 Antibody Epigenetics We first confirmed the expression of both glycine receptors (GlyRs) and TNF receptors in these cells using RT-qPCR. Among the five known GlyR subunits (Glra1–4, Glrb), Glrb was found to be the most abundantly expressed, suggesting a dominant role in glycine-mediated signaling. Similarly, TNFR1 (Tnfrsf1a) exhibited higher expression levels than TNFR2 (Tnfrsf1b), indicating its likely significance in TNF-α responses.PSMG2 Antibody Cancer
To determine the functional involvement of these receptors, we employed siRNA-mediated gene silencing to knock down either Glrb or Tnfrsf1a.PMID:35178802 Transfection efficiency was validated via confocal microscopy using a luciferase reporter system, confirming successful delivery and expression knockdown. Following transfection, cells were treated with 10 mM glycine alone, 5 ng/mL TNF-α alone, or pre-treated with glycine before TNF-α stimulation (Gly/TNF) or vice versa (TNF/Gly). mRNA expression levels of TNF-α, IL-6, and adiponectin were analyzed by qRT-PCR, while protein concentrations were measured using ELISA.
Our results demonstrated that glycine significantly reduced both mRNA and protein levels of TNF-α and IL-6 in control cells. However, when Tnfrsf1a was silenced, glycine lost its inhibitory effect on TNF-α and IL-6 expression, indicating that TNFR1 is essential for glycine’s anti-inflammatory action. In contrast, silencing Glrb had minimal impact on glycine’s ability to suppress cytokine production, suggesting that the glycine receptor subunit Glrb is not primarily responsible for this modulation. Interestingly, glycine treatment increased adiponectin mRNA levels in control cells, a beneficial adipokine associated with improved insulin sensitivity, although this effect was diminished upon Tnfrsf1a knockdown.
Molecular docking analysis further supported the hypothesis that glycine can bind directly to the TNFR1 ligand-binding domain. The predicted binding pose of glycine shared key interaction sites with the known inhibitor IV703, including hydrogen bonds with SER72, HIS66, and LYS32, as well as van der Waals interactions with ALA62, LEU67, and PHE60. Although glycine showed lower binding affinity compared to IV703, its structural compatibility suggests partial antagonism at the TNFR1 site.
These findings collectively indicate that glycine functions as a competitive antagonist at the TNF-α receptor (TNFR1), thereby preventing TNF-α from initiating NF-κB activation and subsequent pro-inflammatory cytokine release. This mechanism offers a novel insight into how an endogenous amino acid like glycine may regulate adipose tissue inflammation, potentially contributing to improved metabolic outcomes in conditions such as obesity and type 2 diabetes. Future studies should explore the therapeutic implications of glycine supplementation in inflammatory metabolic diseases, particularly through targeted modulation of TNFR1 signaling.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com