Cardiac health: Study links lower iron-transport protein to heart disease

Lower levels of serotransferrin, the blood protein that transports iron through the body, are an early indicator of coronary artery disease (CAD) and can help identify heart conditions earlier than routine clinical diagnoses, say scientists.

Iron deficiency is prevalent among patients with CAD, a common cardiovascular condition characterised by narrowing of the coronary arteries due to atherosclerosis, primarily caused by plaque or fatty deposits. An analysis of blood serum proteins by Delhi's CSIR-Institute of Genomics and Integrative Biology (IGIB) has revealed the critical role of serotransferrin in identifying cardiac disease.

"Serotransferrin may have value as an early diagnostic marker, meaning it could potentially help identify CAD earlier than routine clinical diagnosis," said Sagarika Biswas, corresponding author on the study.

A deeper understanding of how CAD develops is crucial for developing effective diagnostics and therapeutics, the IGIB researchers said. Serotransferrin presents a potential avenue for investigation, and exploring its related molecular and cellular processes may help shed light on CAD progression and identify new treatment targets.

"Of 197 differentially expressed proteins, serotransferrin (TF), an iron transporter, showed downregulation in samples from CAD patients compared to healthy," the authors wrote in the study published in the journal Acta Cardiologica.

The study, involving 50 CAD patients and 40 healthy people, also showed an increased level of the cardiac marker 'troponin I' among those affected by the heart disorder, demonstrating an inverse relationship with serotransferrin levels. Troponin I is a specialised protein present in heart muscle cells, which leaks into the bloodstream following damage or injury.

"TF protein was significantly associated with CAD progression and inversely correlated with cTnI (troponin I), suggesting it could be a potential therapeutic target pending further molecular and clinical investigation," the authors said.

Longitudinal studies would be required to estimate the duration in years before which serotransferrin could help identify CAD, explained Biswas, former distinguished chief scientist and professor at CSIR-IGIB's department of integrative and functional biology.

The study linked reduced levels of serotransferrin with the inflammatory environment created due to damage in the inner lining of arteries, which triggers an immune response against accumulated fatty deposits.
According to Biswas, worsening ischaemia — local anaemia due to reduced blood flow caused by narrowed or blocked vessels — and tissue injury can increase troponin I, whereas inflammatory and metabolic stress may suppress serotransferrin expression or availability in CAD.

Further, levels of serotransferrin can reflect iron status in an individual. "In standard iron studies, transferrin saturation below 20% is commonly taken as evidence of iron deficiency, meaning less than 20% of transferrin's binding sites are occupied by iron," Biswas said.
Transferrin refers to the family of iron-binding proteins, while serotransferrin is a subtype found in blood serum and plasma.  

"Serotransferrin is an iron-transport protein, so a lower level suggests reduced iron-binding and transport capacity. The protein may contribute to the functional iron deficiency component of CAD by limiting plasma iron transport, but the study did not quantify its contribution as a percentage," Biswas said.