The substance P receptor (NK1R) was localized to specific heart neurons and coronary vessel smooth muscle cells in rats, and long-term diabetes significantly altered NK1R gene expression in different heart chambers.
53 weeksDuration of diabetes at which significant NK1R gene expression changes were observed in the rat heart
What the researchers found
NK1R protein was localized by immunofluorescence to the surface of some intracardiac neurons and smooth muscle cells of coronary vessels. Quantitative RT-PCR showed NK1R mRNA was present in all four heart chambers, with the highest levels in the left atrium.
Laser capture microdissection revealed NK1R mRNA in some intracardiac neurons but not in cardiomyocytes or coronary smooth muscle cells, suggesting post-transcriptional regulation in smooth muscle cells.
In long-term diabetes (53 weeks post-induction), NK1R mRNA was significantly downregulated in the right atrium and upregulated in the right ventricle, indicating chamber-specific dysregulation of neuropeptide receptor expression in diabetic cardiomyopathy.
Why it matters
Diabetic cardiomyopathy is a major cause of heart failure in diabetes patients, and its mechanisms are incompletely understood. The finding that diabetes alters substance P receptor expression in specific heart chambers suggests that disrupted neuropeptide signaling may contribute to diabetic heart disease. Understanding these molecular changes could identify new therapeutic targets for preventing or treating cardiac complications of diabetes.
How the study worked
The researchers used multiple techniques to characterize NK1R in the rat heart: western blot to detect NK1R protein in separate heart compartments, immunofluorescence with peptide preabsorption controls for tissue localization, quantitative RT-PCR for mRNA abundance across heart chambers, and laser capture microdissection to isolate and test specific cell types (neurons, cardiomyocytes, smooth muscle cells). Long-term diabetic rats were studied at 53 weeks post-diabetes induction.
What this study cannot tell us
This is a rat study, and the findings may not directly translate to human hearts. The sample sizes for laser capture microdissection experiments are not specified, and NK1R mRNA was only detected in 'some samples' of intracardiac neurons. The study only examined one timepoint in diabetes (53 weeks), so the temporal progression of receptor changes is unknown. The functional consequences of the observed NK1R expression changes were not tested.
How to read the evidence
This is a basic science animal study using multiple molecular biology techniques to characterize receptor localization and expression. The methodology is rigorous for a preclinical study, but there is no clinical or therapeutic component.
When this study was published
Published in 2018, this study provides foundational data on substance P receptor localization in the heart that remains relevant to ongoing research in neuropeptide cardiology and diabetic heart disease.
The bigger picture
Substance P and the tachykinin neuropeptide family play diverse roles in cardiovascular function, including vasodilation, inflammation, and cardiac nerve signaling. This study adds important detail about where exactly the NK1R receptor sits in the heart and how chronic metabolic disease alters its expression. As the connection between neuropeptides and cardiac disease becomes clearer, peptide receptor modulation may emerge as a new therapeutic strategy for diabetic cardiomyopathy.
Questions still open
- What are the functional consequences of NK1R downregulation in the right atrium and upregulation in the right ventricle during diabetes?
- Could NK1R antagonists or substance P analogs be therapeutic in diabetic cardiomyopathy?
- Do similar NK1R expression changes occur in human hearts with long-term diabetes?
Common questions
What does substance P do in the heart?
Why would diabetes change a neuropeptide receptor in the heart?
Read the original research
Substance P Receptor in the Rat Heart and Regulation of Its Expression in Long-Term Diabetes.
Frontiers in physiology, 9, 918
Citation
Chottova Dvorakova, Magdalena; Mistrova, Eliska; Paddenberg, Renate; Kummer, Wolfgang; Slavikova, Jana. (2018). Substance P Receptor in the Rat Heart and Regulation of Its Expression in Long-Term Diabetes.. Frontiers in physiology, 9, 918. https://doi.org/10.3389/fphys.2018.00918