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How does diet affect cardiac contractility?
Secondary Supervisor(s): Dr Mike Dodd
University of Registration: University of Birmingham
BBSRC Research Themes: Integrated Understanding of Health (Diet and Health)
Project Outline
Diet plays a critical role in maintaining overall health, with significant implications for cardiovascular function and disease prevention. Diet of low nutritional, high caloric content, has negative impacts on the body. It can lead to deposition of excess adipose tissue (as seen in obesity) and will change metabolism (e.g. insulin resistance seen in type 2 diabetes). Hence, through various pathways it negatively affects heart health. On the other hand, there is emerging evidence that some dietary components, such as unsaturated fatty acids found in Mediterranean diet, are beneficial to heart health.
In order to understand the effects of diet on the heart better, this project will develop a physiological human heart model and test variation of diet on it. It will make use of an emerging technology, called engineered heart tissue (EHT), which creates beating heart tissue from human stem cells. A particular novel aspect of the project is that the EHTs will be subjected to physical strain (pre- and after-load) as they would experience in a beating whole heart in a human (‘work loop model’).
Aims
Aim 1 will set up the work loop model for both atrial and ventricular EHTs and validate different mechanical strain profiles. We will optimise conditions to enable electro-mechanical coupling assessment of the atrial and ventricular EHTs. The biomechanical properties of the EHTs will be investigated via force[1]length and frequency relation protocols. Once force production has been stabilised, a stepwise stretch will be performed under isometric conditions to elicit a force-length relationship from physiological low to high preload levels. A series of cycle frequencies can also be applied to assess the force-frequency relationship at the optimal Length.
Aim 2 will investigate the effect of different fatty acid compositions on EHTs contractility in the work loop model - here we will use our expertise in cardiac cellular culture methodologies to determine the effects of different fatty acid mixes on EHTs contractile function and pharmacological responses (including beta blockers, sodium channel blockers, calcium channel blockers and potassium channel blockers). EHTs will be incubated with saturated, mono-unsaturated and poly-unsaturated medium and long chain fatty acids (including lauric, palmitic, oleic, stearic, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and linolenic acid) and contractile function will be assessed. Parallel metabolic assessment will identify whether different substrates shift the substrate preference of the EHTs.
Aim 3 will explore the effect of adipocytes/adipose tissue on EHTs contractility. Here we will use our expertise in cardiac cellular culture methodologies to determine the effects of adipocytes/adipose tissue secretome on EHTs contractile function and pharmacological responses (using the drugs from Aim2).
Initially, murine adipose tissue fragments (from mouse pericardial or inguinal subcutaneous adipose tissue) will be incubated in a DMEM-based culture medium to harvest the secreted proteome (i.e., the ‘secretome’). ‘Obese EHTs’ will be generated by incubating the EHTs in the presence of this ‘conditioned media’ and contractile function will be assessed.
An alternative approach for generating the ‘Obese EHTs’ will be done by inclusion of 3T3-L1 adipocytes in the EHT cellular mixture. The 3T3-L1 cell line is a well-established pre-adipose cell line that was developed from murine Swiss 3T3 cells. The student will determine optimal adipocyte-cardiomyocyte ratios for development of ‘obese EHT’”. EHTs will be created from cardiomyocyte-adipocyte incremental ratios (1:1 to 1:10) and contractile function will be assessed.
The successful project will give a detailed understanding how diet (good or bad) influences heart health with focus on cardiac electro-mechanical properties.
Techniques
Culture of induced pluripotent stem cells and differentiation into cardiac cells, Generation of 3D (co-)cultures in form of EHTs, Physiological electro[1]mechanical measurements in the work loop setup, Pharmacological interventions in vitro, Metabolic assessment of heart tissue, Molecular biology techniques (qPCR, western blotting), Confocal microscopy, Transferrable skills (presentations to different audiences, working in a team, time and project management etc.).