Blood Levels of 2 Proteins Seen as Possible Measure of Heart Health

Measuring blood levels of two proteins, N-terminal pro-brain natriuretic peptide (NT-proBNP) and troponin, may provide useful information about heart health in people with Friedreich’s ataxia (FA), a study suggests.

The study, “Significance of NT-proBNP and High-Sensitivity Troponin in Friedreich Ataxia,” was published in the Journal of Clinical Medicine.

FA affects the body in a myriad of ways. Some of the complications associated with FA, particularly those related to the nervous system, have been thoroughly characterized. Less is known about changes to the heart, even though cardiac disease is common in people with FA.

NT-proBNP and troponin are proteins commonly used in cardiology. NT-proBNP is released into the blood when heart muscle stretches, and is considered a marker of pressure within the heart. Troponin is released upon injury to heart cells, and is a marker of such injury.

“These two cardiac biomarkers could be useful for the evaluation of cardiac involvement in FA patients,” researchers with Sorbonne Université, in France, wrote.

Their study aimed to determine blood plasma levels of cardiac troponin T and NT-proBNP in adults with FA, and to investigate possible links with genetic markers or conventional echocardiographic parameters of cardiac involvement.

Researchers measured NT-proBNP and troponin levels in 85 patients (mean age 39, mean age at disease onset 17); 53 of them (62%) were wheelchair bound.

These patients underwent clinical assessments, including an evaluation of heart health. The researchers then looked for connections between marker levels and clinical features.

Threshold levels for NT-proBNP was placed at 125 nanograms (ng)/L,  and for troponin at 14 ng/L, based on data collected on the general population. Levels at or above these thresholds were considered high.

NT-proBNP levels were high in 12 FA patients, 14% of these 85 people. Troponin levels, available from 70 study participants, were high in 26 of them, or 33%.

Notably, previous research indicates that only about 1% of the general population has high troponin levels. The considerable prevalence of elevated troponin levels seen in this patient group has been seen in previous FA research.

These elevated troponin level might reflect ongoing subclinical heart cell injury, the investigator wrote, adding that the exact mechanism of injury is unclear.

Statistical models were also used to look for associations between levels of these blood markers and clinical features.

NT-proBNP levels were significantly associated with increased pressure in the heart, likely as a result of previous heart injury.

“Indeed, the highest plasma levels were observed in patients with previous heart failure or atrial fibrillation,” the researchers wrote. “Whereas NT-proBNP plasma levels appeared to be a marker of early cardiac involvement in Fabry’s disease, in Friedreich’s ataxia they seemed to increase in more severe patients with previous cardiac events, likely signifying the evolution of the cardiac disease.”

Troponin levels were significantly associated with septal wall thickness — that is, the thickness of the walls that divide the chambers of the heart.

Notably, troponin levels did not significantly associate with hypertrophy, which refers to the thickening of heart tissue, a predictor of heart disease. As such, “the biomarker could not replace the assessment of cardiac hypertrophy by echocardiography yet,” the researchers wrote.

In general, they found that NT-proBNP and troponin levels provided different information, remaining unclear whether combining the two yielded useful insights.

Six patients had high levels of both markers, including four with known cardiac problems (e.g., heart failure). The team suggested that the two without known cardiac issues could be at higher risk of such complications.

Neither NT-proBNP nor troponin were associated with neurological disease or with genetic markers.

This study had limitations, its scientists noted, including it being conducted at a single center in adults, and biomarkers levels were measured only once. As such, these results may not be applicable to all with FA, and more research is needed.

“Further larger collaborative studies are needed to confirm the range of plasma levels of NT-proBNP and [troponin] in FA patients and to define the place of these biomarkers in the management of FA patients,” the researchers wrote. “Serial measurements are needed to characterize the temporal course of the two biomarkers and their relations with the evolution of echocardiographic parameters and the underlying cardiac disease.”