Obesity is characterized by a state of chronic low-grade inflammation, primarily driven by the overproduction of pro-inflammatory adipokines such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) from hypertrophic adipocytes. TNF-α exerts its effects through two distinct receptors—TNFR1 (Tnfrsf1a) and TNFR2 (Tnfrsf1b)—with TNFR1 being the dominant mediator of inflammatory and apoptotic signaling. The activation of TNFR1 triggers complex downstream pathways, including NF-κB, JNK, and MAPK cascades, leading to the transcriptional upregulation of multiple inflammatory genes. Emerging evidence suggests that glycine, a simple amino acid with known cytoprotective and anti-inflammatory properties, may interfere with this cascade.
This study investigated whether glycine acts as a competitive antagonist at the TNFR1 receptor to inhibit TNF-α-induced inflammatory responses in differentiated 3T3-L1 adipocytes. Using siRNA-mediated gene silencing, we selectively knocked down either the TNFR1 (Tnfrsf1a) or the glycine receptor subunit β (Glrb). Following transfection, cells were treated with 5 ng/mL TNF-α alone, 10 mM glycine alone, or pre-treated with glycine before TNF-α exposure (Gly/TNF), or vice versa (TNF/Gly). mRNA expression levels of TNF-α, IL-6, and adiponectin were quantified by qRT-PCR, while protein concentrations were measured via ELISA.
In non-silenced control cells, glycine treatment significantly reduced both mRNA and protein levels of TNF-α and IL-6, while increasing adiponectin expression—a favorable shift associated with improved insulin sensitivity. However, when Tnfrsf1a was silenced, glycine lost its ability to suppress cytokine production. Notably, TNF-α stimulation still induced strong upregulation of TNF-α and IL-6 mRNA and protein in these cells, confirming that TNFR1 is essential for both TNF-α signaling and glycine’s inhibitory action. In contrast, Glrb knockdown had no significant effect on glycine’s anti-inflammatory efficacy, indicating that GlyR signaling is not required for this mechanism.
Importantly, glycine was most effective when administered prior to TNF-α stimulation (Gly/TNF), suggesting a prophylactic role in preventing receptor activation. This timing-dependent effect aligns with the hypothesis that glycine competes with TNF-α for binding to TNFR1. Molecular docking simulations supported this notion: glycine was predicted to bind within the ligand-binding domain of TNFR1, forming hydrogen bonds with SER72, HIS66, and LYS32, and engaging in van der Waals interactions with ALA62, LEU67, PHE60, and CYS73. While its binding affinity was lower than that of the reference inhibitor IV703, the spatial overlap with key residues involved in TNF-α recognition indicates that glycine can occupy the binding site and partially block ligand access.CLDN1 Protein web
Furthermore, the suppression of NF-κB activation by glycine—evidenced by reduced IκBα phosphorylation and diminished p65 nuclear translocation—was absent in Tnfrsf1a-silenced cells, reinforcing the necessity of functional TNFR1 for this effect.Cascaroside C MedChemExpress In contrast, cells with intact TNFR1 responded robustly to glycine, regardless of Glrb status.PMID:34661901
These findings demonstrate that glycine functions as a competitive antagonist at TNFR1 in adipocytes, directly interfering with TNF-α binding and thereby attenuating downstream inflammatory signaling. This mechanism provides a molecular explanation for glycine’s previously observed ability to reduce adipose tissue inflammation and improve metabolic parameters in obese models. Given that glycine levels are often depleted in metabolic disorders, dietary supplementation may offer a viable strategy to restore anti-inflammatory balance in adipose tissue.
In summary, glycine modulates inflammatory responses in 3T3-L1 adipocytes primarily through competitive inhibition of TNFR1, rather than via classical glycine receptor pathways. This insight opens new avenues for developing glycine-based interventions aimed at reducing inflammation and improving metabolic health in obesity and type 2 diabetes. Future studies should validate these findings in vivo and explore the translational potential of glycine as a natural therapeutic agent in inflammatory metabolic diseases.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