Seminar by Tetsuhiro Hatakeyama and Sosuke Ito

Living organisms optimize their survivability through evolutionary processes. In particular, intracellular metabolic systems are rationally regulated to maximize the cellular growth rate. Correspondingly, the field of microeconomics investigates the behavior of individuals assumed to act rationally to maximize their utility. Therefore, microeconomics can be applied to analyze the metabolic strategies of cells. Toward this end, we developed a microeconomics-based theory of cellular metabolism by precisely mapping the regulation of metabolic systems onto the theory of consumer choice in microeconomics. As a representative example, we focus on overflow metabolism, a seemingly wasteful strategy in which cells utilize fermentation instead of the more energetically efficient respiration (so-called Warburg effect in cancer). To resolve this apparent contradiction, we formulate overflow metabolism as an optimization problem of the allocation of carbon fluxes under the guidance of microeconomic theory. Accordingly, we demonstrate that overflow metabolism corresponds to Giffen behavior in economics, the strange consumer behavior by which greater amounts of goods are consumed as their price increases. We reveal the general conditions required for both overflow metabolism and Giffen goods: trade-off and complementarity, i.e., the impossibility of substitution for different goods, among multiple objectives. Based on the correspondence with Giffen behavior, a counterintuitive response of metabolism against the leakage and degradation of intermediate metabolites, which corresponds to the change in the price of a consumer good, is predicted. Overall, this demonstration highlights that application of microeconomics to metabolic systems will offer new predictions and potentially new paradigms for both biology and economics.

Reference: Yamagishi and Hatakeyama. bioRxiv 613166

Biochemical reaction in a cell is stochastic, and it requires the thermodynamic cost. To discuss thermodynamic cost of biochemical reaction, we use the theory of stochastic thermodynamics.

We here talk about our recent studies of stochastic thermodynamics [1,2]. We obtain a kind of thermodynamic speed limits, which is a classical counter part of the quantum speed limit.

Our result implies a trade-off relationship between speed and the thermodynamic cost; The faster speed of a transition is, the more thermodynamic cost is needed. 

In this talk, we illustrate our result for a simple model of enzyme reaction. We also discuss a geometric interpretation of our result, because our result can be derived from a technique of differential geometry called "information geometry”. 

[1] Sosuke Ito, Physical Review Letters 121, 030605 (2018). 

[2] Sosuke Ito and Andreas Dechant, arXiv preprint ariXiv:1810.06832 (2018).