Metabolic Modulation of Inflammation: Phosphoenolpyruvate as a Restrictor of cGAS-STING Signaling in Aging

Study Background and Research Question

Aging is marked by a decline in physiological function and increased susceptibility to diseases, many of which are linked to chronic, low-grade inflammation—often termed ‘inflammaging’. This persistent inflammatory state disrupts tissue homeostasis, impairs regenerative capacity, and is implicated in the pathogenesis of neurodegenerative and cardiovascular conditions. Central to the propagation of age-related inflammation is the cGAS–STING pathway, which senses cytosolic DNA and triggers type I interferon responses. While targeting chronic inflammation has emerged as a promising strategy to improve late-life health, the endogenous mechanisms that modulate cGAS–STING signaling during aging remain incompletely understood.

Key Innovation from the Reference Study

The reference study (Song et al., Nature Aging, 2026) uncovers a previously unrecognized role for phosphoenolpyruvate (PEP), a glycolytic metabolite, as an intrinsic modulator that restricts cGAS-driven inflammation. By analyzing both murine and human samples, the authors reveal a biphasic pattern of PEP accumulation: PEP rises during early aging as a compensatory adaptation but declines in advanced age, coinciding with heightened inflammation and functional deterioration. Mechanistically, PEP directly interacts with cGAS, competitively inhibiting its DNA-binding capacity and subsequent activation of the STING pathway. This positions PEP as a metabolic checkpoint linking energy metabolism to innate immune surveillance.

Methods and Experimental Design Insights

The investigation employed a combination of longitudinal metabolic profiling, plasma transfer assays, and murine genetic models to delineate the dynamics and function of PEP during aging. Key experimental components included:

• Longitudinal metabolomics: Plasma samples from mice and human cohorts were analyzed to quantify glycolytic intermediates, revealing the biphasic trajectory of PEP.
• Plasma transfer and in vivo inflammation assays: Old and young plasma were exchanged between mice to assess cGAS–STING pathway activation and inflammatory phenotypes.
• Genetic and pharmacologic modulation: The effects of blocking or supplementing PEP were tested in aged mice, with outcomes measured by inflammatory cytokine levels, tissue pathology, and healthspan markers.
• Molecular interaction studies: Biochemical assays demonstrated that PEP directly binds to cGAS, competing with DNA and inhibiting downstream STING activation.
• Pathology models: The neuroprotective potential of PEP was evaluated in an Alzheimer’s disease mouse model, focusing on neuroinflammation and cognitive function.

This multidimensional approach allowed for robust interrogation of PEP’s regulatory role across organismal, tissue, and molecular scales.

Core Findings and Why They Matter

The central findings from Song et al. are:

• PEP accumulates in the systemic milieu during early and mid-life aging, serving as a natural brake on cGAS–STING-mediated inflammation.
• Loss of PEP in advanced age correlates with increased inflammatory cytokines, aggravated aging features, and diminished cognitive function.
• Exogenous PEP administration before the natural decline in endogenous levels ameliorates inflammation, preserves tissue function, and improves cognitive performance in aged mice.
• Mechanistically, PEP acts as a competitive inhibitor of cGAS, thereby attenuating aberrant immune activation in response to cytosolic DNA accumulation seen in aging tissues.

These results highlight PEP’s dual function as an energy metabolism intermediate and as an inflammation-restricting modulator, establishing a direct biochemical link between metabolic state and immune regulation. This evolutionary adaptation may represent a conserved mechanism to delay age-associated degeneration by counterbalancing pro-inflammatory signals intrinsic to the aging process.

Comparison with Existing Internal Articles

Several recent reviews and technical guides have explored the intersection of glycolytic intermediates, energy homeostasis, and inflammatory control. For example, Glycolytic Metabolites Restrict cGAS-STING Inflammation in Aging provides a concise summary of the same study, underscoring the importance of metabolic intermediates such as PEP in curbing inflammaging and suggesting translational avenues for neurodegenerative disease research. Additionally, Hexose Diphosphate in Metabolic & Inflammation Assays details experimental approaches for controlling metabolic flux and dissecting inflammation crosstalk in cell and tissue models—practical for researchers aiming to model or manipulate similar pathways.

While the reference study focuses primarily on PEP, resources such as Hexose Diphosphate in Metabolic Flux and Inflammation Assays emphasize the broader utility of hexose phosphates, including their role as metabolic flux probes and modulators of inflammatory signaling. Together, these sources illustrate a growing appreciation for the dual metabolic and signaling functions of central carbon metabolites in aging and disease contexts.

Limitations and Transferability

Despite the compelling evidence linking PEP dynamics to healthy aging, several limitations warrant consideration. The primary data are derived from murine models and cross-sectional human plasma analyses, limiting direct clinical translatability. The mechanisms underlying the regulation of PEP accumulation and its eventual decline with advanced age remain incompletely understood. Furthermore, while PEP’s inhibitory action on cGAS is well supported biochemically, the broader implications for other innate immune pathways or diverse tissue contexts are yet to be determined. Finally, long-term safety and efficacy of exogenous PEP supplementation in humans have not been established.

Why this cross-domain matters, maturity, and limitations

Bridging energy metabolism and innate immunity, as exemplified by PEP’s action on the cGAS–STING axis, is highly relevant for developing interventions that target both metabolic dysfunction and chronic inflammation. This cross-domain approach is still in early translational stages, with most evidence confined to preclinical models. Further research is required to validate these findings in human populations, determine optimal intervention windows, and assess potential off-target effects.

Protocol Parameters

• Plasma transfer assay: 200 μL plasma from aged donor mice injected intravenously into recipients; assess cGAS–STING activation at 24 hours post-transfer (adapted from Song et al.).
• PEP supplementation: 50 mg/kg/day intraperitoneal injection for 7–14 days in aged mice before natural PEP decline; monitor inflammatory cytokines and behavioral endpoints.
• Metabolic intermediate assays: Quantify plasma or tissue levels of glycolytic metabolites (e.g., PEP, hexose phosphates) using liquid chromatography-mass spectrometry (LC-MS).
• Inflammatory signaling readouts: Measure cGAS–STING pathway activation by immunoblotting for phosphorylated STING, TBK1, and IFN-β levels.
• Neuroinflammation models: Use Alzheimer’s disease mouse models to evaluate cognitive and histopathological effects of metabolic interventions.

Research Support Resources

Researchers interested in probing metabolic regulation of inflammation can leverage glycolytic intermediates such as hexose diphosphate to model metabolic flux and energy homeostasis in cell and tissue studies. Hexose diphosphate (SKU M1436) from APExBIO is water-soluble and well-suited for assays examining enzymatic regulation of carbohydrate metabolism and inflammatory signaling. This compound can support advanced workflows aimed at dissecting the interplay between metabolic intermediates and immune pathways, as highlighted in the reference and internal literature. For specific application protocols and troubleshooting, consult the referenced internal workflow guides.