title: Lipid droplets fusion in adipocyte differentiated 3T3-L1 cells: a Monte Carlo simulation.
abstract: Several human worldwide diseases like obesity, type 2 diabetes, hepatic steatosis, atherosclerosis and other metabolic pathologies are related to the excessive accumulation of lipids in cells. Lipids accumulate in spherical cellular inclusions called lipid droplets (LDs) whose sizes range from fraction to one hundred of micrometers in adipocytes. It has been suggested that LDs can grow in size due to a fusion process by which a larger LD is obtained with spherical shape and volume equal to the sum of the progenitors' ones. In this study, the size distribution of two populations of LDs was analyzed in immature and mature (5-days differentiated) 3T3-L1 adipocytes (first and second populations, respectively) after Oil Red O staining. A Monte Carlo simulation of interaction between LDs has been developed in order to quantify the size distribution and the number of fusion events needed to obtain the distribution of the second population size starting from the first one. Four models are presented here based on different kinds of interaction: a surface weighted interaction (R2 Model), a volume weighted interaction (R3 Model), a random interaction (Random model) and an interaction related to the place where the LDs are born (Nearest Model). The last two models mimic quite well the behavior found in the experimental data. This work represents a first step in developing numerical simulations of the LDs growth process. Due to the complex phenomena involving LDs (absorption, growth through additional neutral lipid deposition in existing droplets, de novo formation and catabolism) the study focuses on the fusion process. The results suggest that, to obtain the observed size distribution, a number of fusion events comparable with the number of LDs themselves is needed. Moreover the MC approach results a powerful tool for investigating the LDs growth process.
authors.affiliation: Department of Neurological and Movement Sciences, University of Verona, Strada Le Grazie 8, 37134 Verona, Italy; Department of Computer Science, University of Verona, Strada Le Grazie 15, 37134 Verona, Italy. Electronic address: federico.boschi@univr.it.
authors.forename: Federico
authors.initials: F
authors.lastname: Boschi
authors.affiliation: Department of Medicine, Geriatric Section, University of Verona, Piazzale Stefani 1, 37126 Verona, Italy.
authors.forename: Vanni
authors.initials: V
authors.lastname: Rizzatti
authors.affiliation: Department of Medicine, Geriatric Section, University of Verona, Piazzale Stefani 1, 37126 Verona, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Zamboni
authors.affiliation: Department of Neurological and Movement Sciences, University of Verona, Strada Le Grazie 8, 37134 Verona, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Sbarbati
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000502:physiology*; D000465:Algorithms; D000818:Animals; D002454:Cell Differentiation; D003198:Computer Simulation; D002479:Inclusion Bodies / Q000378:metabolism; D050356:Lipid Metabolism; D008055:Lipids / Q000032:analysis; D051379:Mice; D008954:Models, Biological; D009010:Monte Carlo Method
chemical_list: D008055:Lipids
keywords: 3T3-L1; Adipocyte; Fat; Lipid droplet; Monte Carlo simulation; Triglycerides accumulation