title: Mathematical model of metabolism and electrophysiology of amino acid and glucose stimulated insulin secretion: in vitro validation using a β-cell line.
abstract: We integrated biological experimental data with mathematical modelling to gain insights into the role played by L-alanine in amino acid-stimulated insulin secretion (AASIS) and in D-glucose-stimulated insulin secretion (GSIS), details important to the understanding of complex β-cell metabolic coupling relationships. We present an ordinary differential equations (ODEs) based simplified kinetic model of core metabolic processes leading to ATP production (glycolysis, TCA cycle, L-alanine-specific reactions, respiratory chain, ATPase and proton leak) and Ca(2+) handling (essential channels and pumps in the plasma membrane) in pancreatic β-cells and relate these to insulin secretion. Experimental work was performed using a clonal rat insulin-secreting cell line (BRIN-BD11) to measure the consumption or production of a range of important biochemical parameters (D-glucose, L-alanine, ATP, insulin secretion) and Ca(2+) levels. These measurements were then used to validate the theoretical model and fine-tune the parameters. Mathematical modelling was used to predict L-lactate and L-glutamate concentrations following D-glucose and/or L-alanine challenge and Ca(2+) levels upon stimulation with a non metabolizable L-alanine analogue. Experimental data and mathematical model simulations combined suggest that L-alanine produces a potent insulinotropic effect via both a stimulatory impact on β-cell metabolism and as a direct result of the membrane depolarization due to Ca(2+) influx triggered by L-alanine/Na(+) co-transport. Our simulations indicate that both high intracellular ATP and Ca(2+) concentrations are required in order to develop full insulin secretory responses. The model confirmed that K(+) ATP channel independent mechanisms of stimulation of intracellular Ca(2+) levels, via generation of mitochondrial coupling messengers, are essential for promotion of the full and sustained insulin secretion response in β-cells.
authors.affiliation: School of Biomolecular and Biomedical Sciences, University College Dublin, Dublin, Ireland. manuela.salvucci@gmail.com
authors.forename: Manuela
authors.initials: M
authors.lastname: Salvucci
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Neufeld
authors.forename: Philip
authors.initials: P
authors.lastname: Newsholme
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000596:Amino Acids / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D027682:Cation Transport Proteins / Q000378:metabolism; D002460:Cell Line; D055724:Electrophysiological Phenomena / Q000187:drug effects*; D005947:Glucose / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D051381:Rats; D013549:Sweetening Agents / Q000494:pharmacology*
chemical_list: D000596:Amino Acids; D027682:Cation Transport Proteins; D007328:Insulin; D013549:Sweetening Agents; D000251:Adenosine Triphosphatases; C022761:potassium transporting ATPase; D005947:Glucose; D002118:Calcium