Proteomic Signals in Pre-COPD Phenotypes

> Research explainer: This briefing examines verified primary research published 54 days before the briefing date. It is not a same-day research update and does not provide medical advice.

Evidence

This research explainer examines a study published on 2026-07-01. In the COPDGene cohort analysis, investigators studied tobacco-exposed individuals with preserved spirometry (TEPS), defining two mutually exclusive lung-volume phenotypes from CT-derived supine volumes: elevated total lung capacity (TLC) without elevated FRC/TLC, and elevated functional residual capacity-to-TLC ratio (FRC/TLC) without elevated TLC. [pmid:41776818]

Plasma proteomics were measured at the study’s 5-year follow-up visit with SomaScan v4.0. The platform comprised 4,979 aptamers mapping to 4,776 unique human proteins, and the proteomic analysis included 1,959 TEPS participants. Models adjusted for demographic characteristics, smoking status and burden, blood-cell counts, FEV1 percent predicted, and study site as described by the authors. [pmid:41776818]

The elevated-TLC phenotype differed from the low-COPD-risk reference group in 310 proteins: 165 were reported as upregulated and 145 as downregulated. The elevated-FRC/TLC phenotype differed from that reference group in 22 proteins. Direct comparison of the two pre-COPD phenotypes identified 269 differentially expressed proteins, with 116 upregulated and 153 downregulated in elevated FRC/TLC relative to elevated TLC. [pmid:41776818]

For longitudinal outcomes, 1,232 participants had relevant follow-up data. Over a mean 5.3 years, spirometric COPD developed in 17% of pre-COPD TEPS (133 of 761) and 8% of low-risk TEPS (37 of 471); the adjusted odds ratio was 2.51 (95% CI, 1.69–3.75; P<.001). Within the pre-COPD subgroups, elevated FRC/TLC showed greater observed progression to GOLD stage 2 or higher (adjusted odds ratio, 2.90; 95% CI, 1.62–5.18; P<.001) and PRISm (adjusted odds ratio, 3.29; 95% CI, 1.41–7.69; P=.005) than the comparison pre-COPD subgroup. [pmid:41776818]

Reported differential proteins included soluble receptor for advanced glycation end products, insulin-like growth factor-binding protein, and zymogen granule membrane protein 16. Pathway-enrichment modeling highlighted immune signaling, cellular trafficking, and apoptotic pathways. [pmid:41776818]

Analysis — Phenotype-specific proteomic separation

The central contribution is not a single protein marker, but the separation of two lung-volume-defined phenotypes into markedly different circulating-protein patterns. The elevated-TLC group had 310 proteins differing from the low-risk group, whereas the elevated-FRC/TLC group had 22; the 269-protein contrast between the two phenotypes further indicates that grouping them under one pre-COPD label can obscure biological heterogeneity. [pmid:41776818]

The longitudinal findings give that molecular separation clinical context within this cohort. Pre-COPD TEPS as a combined group had higher observed odds of spirometric COPD than the low-risk reference group, and the elevated-FRC/TLC phenotype had greater observed odds of later GOLD stage 2 or higher and PRISm than the other pre-COPD phenotype. These associations align with the study’s interpretation that lung-volume phenotypes capture differing trajectories, while they do not establish that any measured protein drives those trajectories. [pmid:41776818]

For proteomics research, the results make the reported proteins useful candidates for replication studies, phenotype refinement, and mechanistic investigation. They do not support treating soluble receptor for advanced glycation end products, insulin-like growth factor-binding protein, zymogen granule membrane protein 16, or the pathway signals as stand-alone diagnostic, prognostic, or treatment-selection biomarkers. The study used a broad aptamer-based plasma assay and statistical modeling; validation in independent populations and assessment of prospective biomarker performance would be required before any clinical interpretation. [pmid:41776818]

Limitations

This was an observational analysis of COPDGene data, so its adjusted associations cannot demonstrate causality between lung-volume phenotype, plasma proteins, pathways, and later respiratory outcomes. [pmid:41776818]

Proteomics were collected at visit 2 rather than established as a prospective clinical test, and the source does not report validated diagnostic thresholds, clinical utility, or biomarker performance for individual proteins. [pmid:41776818]

The population consisted of current or former smokers with preserved spirometry; applicability to never-smokers and populations with different characteristics is not established by this source. CT-derived supine TLC and FRC were adjusted and stratified because validated reference equations for these CT lung volumes were lacking, which also bounds interpretation of the phenotype definitions. [pmid:41776818]

Finally, pathway enrichment is a modeled interpretation of the observed protein differences. It supports hypotheses about immune signaling, trafficking, and apoptosis in these phenotypes, but it does not prove that those pathways cause COPD or determine an individual outcome. [pmid:41776818]