Mathematical Modelling and Quasi-Steady-State Approximations of Lipolysis on Lipid Droplets

Fatty acids (FAs) are crucial for the production of adenosine triphosphates, synthesis of biological membranes, thermogenesis, and signal transduction. Animals and humans store FAs in the form of water-insoluble triglycerides (TGs) within cytosolic lipid droplets of specialised fat cells called adipocytes, but also in other cell types. Biochemically, a TG molecule is composed of three FAs esterified to a glycerol backbone. In a cascade of enzymatic reactions, these FAs are released in a process called hydrolysis. However, in a recent paper, a system of ODE rate equations based on mass-action and Michaelis-Menten reaction kinetics, showed that a biochemical process called transacylation can also play a significant role in the whole lipolytic machinery.

In this talk, we propose a chemical reaction network that incorporates both hydrolysis and transacylation and derive a single system based only on mass-action law (MAL) that describes the reaction rates of chemical concentrations in both processes. With a suitable choice of scaling parameters, we nondimensionalise the system and derive a reduced model via quasi-steady-state approximation (QSSA). We end with a qualitative analysis and some numerical examples of both MAL and QSSA systems.