Janica Auluck - Searching for the Elusive Markers of Heart Failure

Heart failure is a common presentation of cardiovascular disease and half of all patients diagnosed with the condition die within five years of initial diagnosis.

In this article, Janica Auluck of the Department of Cancer Studies and Molecular Medicine describes her research which, using state of the art protein discovery methods and mass spectrometry techniques, aims to identify disease markers in blood to enable clinicians to make more accurate and timely decisions that ultimately improve disease management and consequently patient outcome. This personalised medicine approach should culminate in a significant increase in the survival rate of heart failure suffers.  

About My Research

Heart Failure Illustration
Illustration of Heart Failure - Image Courtesy of the National Institutes of Health
Proteomics is an approach that uses the proteins expressed by the genome to understand disease mechanisms and the role that proteins play in the pathology of disease. By studying the proteins expressed by patients in different disease states we can work out the differences in protein patterns between healthy patients and heart failure sufferers. These differences in proteins can then be used as a way of marking a disease state vs. a healthy state.

Although in theory this seems to be a clear task, blood contains over one million different types of proteins and the concentration of these proteins span 12 orders of magnitude. Approximately 22 proteins dominate 99% of the entire blood plasma masking the presence of lower abundant proteins that may play a role in the aetiology of heart failure. Therefore, highly sophisticated chemical and analytical techniques need to be applied to uncover these hidden markers in blood. 

Taking all of this into consideration the main research question for this project are:

  1. Can differences in protein concentrations be overcome using sophisticated protein separation and analysis methods?
  2. Do differences in the protein profiles of patients with and without heart failure exist?
  3. Can these proteins be successfully confirmed in a larger population of patients?
  4. And, if so, can the new proteins that have been identified be tested in clinical laboratories?

Research Approach

The project was broken down to the following key stages to help answer the research questions:

Searching

First, the large number of proteins and the varying concentrations had to be simplified using chemical methods. For this, special chemically constructed beads were mixed with plasma. The beads help overcome the large dynamic range of plasma by ‘equalizing’ the protein concentrations. In theory, the beads contain different shapes and sizes, so they act as bait for different proteins in plasma  that could be markers for heart failure.

Identifying

Mass spectrometry is used to further separate, detect, identify and quantify the protein markers to find heart failure markers in human plasma. This produces different protein signatures for each patient.

Confirming

To ensure the markers that are identified after plasma is treated with the beads and searched by mass spectrometry are truly there (thus ruling out false discovery). Bioinformatic computer programmes check the identified markers using various statistical models. The differences in the protein patterns of healthy and heart failure patients are determined.   

Applying

The proteins that are singled out by the process are individually confirmed in patient samples using techniques employed in clinical laboratories such as ELISA.  

Research Findings

Using the aforementioned methods and techniques, human plasma samples from three populations (healthy, heart failure survivors and heart failure non-survivors) were all tested and protein profiles of each group were established and markers for heart failure have been identified. 

We have found that testing different methods of removing the blood protein (markers) from the beads (the baits) we are able to obtain a greater amount of markers. These markers also seem to now be in a smaller concentration dynamic range so we no longer have low concentration proteins being masked by the higher concentration proteins. 

To date we have found that vast differences in the protein profiles of healthy and heart failure patients exist. We have used this information to help identify diagnostic and prognostic markers of heart failure using chemical beads and mass spectrometry methods.

After analysing 100s of samples 1170 blood proteins were identified of which 660 proteins were potential markers of heart failure. These markers were split into groups according to their molecular mechanisms and the proteins that were associated with the molecular process of heart failure were chosen for further studies upon statistical approval.
Potential Markers of Heart Failure

The chart displays the molecular processes of the proteins identified in heart failure patient groups. The proteins discovered in heart failure plasma feature in 21 different molecular processes. Proteins identified seem to predominantly feature in cellular and metabolic processes. Metabolites are the end products or necessary for metabolism. The number of protein identified in metabolic process in plasma indicates that metabolomic studies may elucidate further biomarkers for heart failure.

The protein were then whittled down using a series of statistical (Protein criteria: P<0.05 and >2 fold change between heart failure groups) and biological criteria to produce a list of 7 target proteins that all responded differently in different disease states.

One example of a protein that was chosen is Vitamin D binding protein. This protein was higher in heart failure survival patients than non-survivors. Vitamin D is thought to be protective in heart failure thus, a higher level of binding protein is expected in survivors. This finding lead to a spin-off study within the group looking at vitamin D in acute myocardial infarction patients.

In this study we have successfully been able to elucidate novel prognostic markers of heart failure using chemical bead and mass spectrometry methodology in human plasma.

The protein markers that have been identified have been shown to play a role in the pathogenesis of acute heart failure and therefore, are good candidate markers for further verification studies.

We have also identified the possibility of further metabolism studies as Figure 1 has identified metabolic proteins as one of the largest population of identifications from the analysis. Which means metabolism could play a big role in heart failure pathology.

These potential markers for acute heart failure can now:

  • Test our markers in a THOUSANDS of samples to confirm our findings are true
  • Test for our markers WORLDWIDE – the marker can be used in many countries
  • MOVE TEST TO CLINICAL LABS - The test can then be used like any other blood or urine test we send off to the hospital labs to help clinicians with prognosis and help TAILOR THERAPY according to the results

About Janica Auluck

Janica AuluckJanica Auluck is a research student working towards completion of her doctoral degree in the Department of Cancer Studies and Molecular Medicine. Janica's research is funded by the John and Lucille van Geest Foundation.

Janica is supervised by Dr Don Jones and Professor Leong Loke Ng.

Department of Cancer Studies and Molecular Medicine
University of Leicester
Leicester Royal Infirmary - Clinical Sciences Building
Leicester
LE2 7LX

Janica will present her work at the Festival of Postgraduate Research 27 June 2013 - see Janica's Festival poster.

The Festival is open to all members of the University community and the public - book your place here.

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