The research team, working with streptozotocin-induced diabetic C57BL/6J mice, set out to address a critical unmet need. Diabetes mellitus causes severe complications that increase mortality rates, and diabetic neuropathy—one of the most common adverse outcomes—disrupts the reflex and sensory pathways that regulate gastric and intestinal function. Among the resulting gastrointestinal neuropathy complications, diabetic gastroparesis stands out for its poor prognosis and persistent symptoms. Regenerative medicine is drawing attention as a possible therapeutic option, but it remains experimental. The investigators therefore pursued two parallel goals: identifying potential biomarkers of diabetic gastroparesis in exhaled volatile organic compounds, and evaluating whether modulating Nav1.8-expressing neuronal activity through chemogenetics could alleviate the symptoms of delayed gastric emptying.

To establish the disease model, six-week-old male mice received intraperitoneal injections of streptozotocin at 110 mg/kg for two consecutive days after a six-hour fast. Diabetes induction was confirmed by tail-vein blood glucose measurements at seven days after the last injection, with animals included only if levels reached 300 mg/dl or higher. Eleven weeks after diabetes induction, the acetaminophen absorption test revealed significantly decreased plasma acetaminophen levels at every time point in diabetic mice, indicating delayed liquid-phase gastric emptying. Western blotting of stomach tissue showed significantly lower expression of c-Kit, a marker of interstitial cells of Cajal whose loss is a common finding in diabetic gastroparesis and is crucial for maintaining gastrointestinal motility through pacemaker activity. Heme oxygenase-1, an indicator of oxidative stress with cytoprotective properties, was elevated in the early stage of diabetes but showed no significant difference at the time point when delayed gastric emptying developed, consistent with previous studies in non-obese diabetic rodent models. Additional analyses confirmed that the gastroparesis phenotype was not attributable to age-related maturation and was absent at the early diabetic stage, emerging only in association with prolonged diabetes.

The breath volatilomics component of the study represents a genuinely novel angle. Breath volatile organic compounds reflect specific biological conditions because they are produced throughout the body and influenced by metabolic status, the gut microbiome, medications, the external environment, and diet. While previous studies have used breath tests to assess gastroparesis, they primarily focused on the non-radioactive carbon isotope 13C rather than on analyzing exhaled VOCs, and few studies have examined breath VOC analysis in mouse models. The researchers built a custom sampling device consisting of a mouse stabilizer made from a tip-cut 50 ml Falcon tube with a PTFE disc, connected to a pre-cleaned PTFE bag filled with one liter of VOC-free synthetic air. After thirty minutes of breath collection, 750 ml of concentrated breath was pumped onto a Bio-monitoring adsorbent tube at 200 ml/min and stored at −20 °C. Gas chromatography–mass spectrometry with thermal desorption then identified the compounds, with a compound accepted only if its retention time was under twenty minutes, its mass spectra matched the NIST 17 library, and its coefficient of agreement exceeded 80.

The statistical screening produced striking results. Partial least squares discriminant analysis clearly separated diabetic from non-diabetic breath profiles, and volcano plots identified 1-butanol and 2-ethylhexan-1-ol as statistically significant compounds, both elevated in diabetic mice with |log2 fold change| ≥ 1.0 and P < 0.05. Notably, 1-butanol was higher in diabetic mice at both three and twelve weeks after diabetes induction. As the mice aged, 1-butanol levels declined markedly in non-diabetic controls but persisted at elevated levels in diabetic animals, resulting in a more pronounced distinction following gastroparesis onset. Enrichment analysis indicated that fatty alcohols, monoterpenoids, carboxylic acids, and benzoyl derivatives comprised the largest proportions of detected breath VOCs, with alkanes and carbonyl compounds representing the majority overall. These findings suggest that 1-butanol in the breath is associated with diabetes itself and with the gastroparesis that develops in later stages.

On the therapeutic front, the team turned to Nav1.8, a voltage-gated sodium channel subtype encoded by the SCN10A gene in humans. This channel is expressed in small and medium diameter neurons of the nodose ganglion, dorsal root ganglion, and trigeminal ganglion, and in roughly seventy-five percent of nodose ganglion neurons. Vagal and spinal endings expressing Nav1.8 have been distinctly observed in the gastrointestinal mucosa and myenteric plexus. A previous case report described severe progressive gastroparesis in a female patient with SCN10A mutations, and genetic polymorphisms of SCN10A are closely associated with functional dyspepsia. To test whether modulating these neurons could control gastrointestinal motility, the researchers crossed Nav1.8-cre mice with ROSA26-LSL-hM3Dq mice, generating chemogenetic activation lines in which designer receptors exclusively activated by designer drugs could be triggered by clozapine N-oxide injection.

The results were compelling. In both diabetic and non-diabetic groups, mice with diabetes exhibited lower plasma acetaminophen concentrations, consistent with delayed gastric emptying. But diabetic mice with the Nav1.8 activation construct showed significantly higher plasma acetaminophen levels after clozapine N-oxide injection, reaching levels comparable to non-diabetic controls. A similar enhancement appeared in the non-diabetic activation group as well. Chemogenetic activation was confirmed by increased numbers of c-Fos-positive cells in the lateral septal nucleus, bed nucleus of the stria terminalis, amygdala, and paraventricular nucleus of the hypothalamus. To corroborate these findings, the team used the IVIS Spectrum system with intragastric gavage of IVISense GastroIntestinal 750, a fluorescence probe. Diabetic mice with activated Nav1.8-expressing neurons showed a significantly higher gastric emptying rate than diabetic controls without the construct. Collectively, these results suggested that stimulation of Nav1.8-expressing neurons enhances gastric emptying and may mitigate the manifestations of diabetic gastroparesis.

The breath analysis after neuronal activation revealed an equally important pattern. Regardless of the presence or absence of diabetes, styrene was enriched, and four other substances—2,4-dimethyl-1-heptene, 4-methylheptane, 1-butanol, and 2,4-dimethyl-1-decene—were detected at lower levels in both activation groups following stimulation of Nav1.8-expressing neurons. Most notably, 1-butanol, the most prominent compound discriminating diabetic from non-diabetic mice, was significantly decreased after activation, with diabetic activation mice showing significantly lower concentrations than diabetic controls. There were no changes in VOC levels caused by the drug itself. The team then built classification models using VOCs with variable importance in projection scores greater than 1.0, excluding exogenous compounds such as styrene. Univariate receiver operating characteristic analyses revealed strong performance, with area under the curve values of 0.859 for 2,4-dimethyl-1-heptene and 0.825 for 4-methylheptane. A multivariate model combining both VOCs was validated by a permutation test with one thousand iterations, achieving an empirical P value of 0.021. Because the different breath VOC patterns likely reflect physiological changes associated with improved gastric motility, these models could serve as tools for tracking treatment outcomes.

The study carries important limitations that the authors acknowledge. The streptozotocin-induced model mimics type 1 diabetes complications, given that gastroparesis prevalence in type 1 diabetes is more than fivefold higher than in type 2 diabetes, but the pathophysiological mechanisms underlying gastroparesis in type 2 diabetes may differ. Nav1.8 is expressed in both vagal and spinal afferents, complicating precise manipulation in humans, and further studies are required to identify which afferent pathways are critical for regulating gastric motility. The activation of these neurons may also have effects beyond improving gastric emptying, and the study was conducted exclusively in male mice, limiting generalizability to females. The term treatment in this context refers to short-term symptomatic relief rather than modification of the underlying disease. Despite these caveats, the breath VOCs detected are also known constituents of human breath, suggesting that corresponding compounds can be detected in human biological samples.

Looking ahead, the researchers emphasize that robust quantification methods using standardized reference compounds and defined normal and pathological ranges will be crucial for clinical application. A comprehensive human breath database for diabetes must be established before bedside use. The findings imply that Nav1.8-expressing neuron-driven enhancement of afferent pathways can promote gastric emptying even in the absence of diabetes, suggesting that selectively targeting these neurons may represent a therapeutic strategy with broader applicability for functional dyspepsia and other conditions associated with delayed gastric emptying, while minimizing adverse off-target effects. The work also opens the possibility of developing medical devices that use electrical stimulation of Nav1.8-expressing neurons to enhance gastric motility in patients with gastroparesis. For a disorder whose prognosis has generally been poor, this convergence of breath-based diagnostics and neuronal neuromodulation offers a genuinely fresh path forward.

Subject of Research: Breath volatile organic compound biomarkers and Nav1.8-expressing neuron activation in diabetic gastroparesis

Article Title: Breath volatiles reflect diabetic gastroparesis and its recovery by activating Nav1.8-expressing neurons in mice

Article References: Hwang, S., Kim, E., Lee, S., Lee, D., Park, M., Lee, H.-S., Chung, H., & Kwon, O. (2026). Breath volatiles reflect diabetic gastroparesis and its recovery by activating Nav1.8-expressing neurons in mice. Experimental &amp; Molecular Medicine, 58(9), 3214-3225. https://doi.org/10.1038/s12276-026-01824-x

Image Credits: AI Generated

DOI: 10.1038/s12276-026-01824-x

Keywords: diabetic gastroparesis, breath volatilomics, volatile organic compounds, Nav1.8, SCN10A, chemogenetics, gastric emptying, diabetic neuropathy, 1-butanol, biomarkers, Breath, volatiles