The multi-nutrient model uses a set of parameters to describe metabolic processes and their regulation. These parameters control rates of metabolic reactions, insulin secretion and action, and nutrient oxidation. Below is a comprehensive list of all model parameters with their descriptions.
| Parameter Name | Default Value | Units | Description |
|---|---|---|---|
| Energy Expenditure & Insulin Secretion | |||
| v_energy | 7 | μmol min-1 gBW-1 | Energy expenditure (ATP production rate) |
| I_max | 0.2 | ng mL-1 min-1 | Maximal insulin secretion rate |
| h | 3.4 | dimensionless | Hill coefficient for insulin secretion |
| C | 16 | mM | Half-maximal glucose concentration for insulin secretion |
| Insulin Inhibition & Activation Constants | |||
| K_i_lipolysis | 0.4 | ng mL-1 | Inhibition constant for insulin action on lipolysis (Ki = 1.0 × I₀). Higher values indicate weaker insulin inhibition of lipolysis. |
| K_i_ketogenesis | 0.04 | ng mL-1 | Inhibition constant for insulin action on ketogenesis (Ki = 0.1 × I₀). Higher values indicate weaker insulin inhibition of ketogenesis. |
| K_a_glycolysis | 4.0 | ng mL-1 | Activation constant for insulin action on glycolysis (Ka = 10 × I₀). Higher values indicate weaker insulin activation of glycolysis. |
| K_i_glycogenolysis | 4.0 | ng mL-1 | Inhibition constant for insulin action on glycogenolysis (Ki = 10 × I₀). Higher values indicate weaker insulin inhibition of glycogenolysis. |
| Metabolic Rate Constants | |||
| k_glycolysis | 0.0303 | min-1 | Rate constant for glycolysis (vglycolysis / ([G₀] × VG)) |
| k_lactate | 0.0782 | min-1 | Rate constant for lactate production (vlactate / ([G₀] × VG)) |
| k_glucose | 0.00736 | min-1 | Rate constant for glucose uptake (vglucose / ([G₀] × VG)) |
| k_fatty_acids | 0.0415 | min-1 | Rate constant for fatty acid uptake (vfatty acids / ([L₀] × VL)) |
| k_3HB | — | min-1 | Rate constant for 3HB (ketone) oxidation (v3HB / ([K₀] × VK)) |
| k_lipolysis | 0.0500 | min-1 | Rate constant for lipolysis (vlipolysis / ([F₀] × VF)) |
| k_reesterification | 0.0330 | min-1 | Rate constant for reesterification (vreesterification / ([L₀] × VL)) |
| k_ketogenesis | 0.00745 | min-1 | Rate constant for ketogenesis (vketogenesis / ([F₀] × VF)) |
| k_gluconeogenesis | 0.0193 | min-1 | Rate constant for gluconeogenesis (vgluconeogenesis / ([K₀] × VK)) |
| V_glycogenolysis | 56 | nmol min-1 gBW-1 | Maximal rate of glycogen breakdown (steady state flux) |
| Infusion Rates (for Clamp Experiments) | |||
| R_insulin | 0.0 | ng mL-1 min-1 | Insulin infusion rate (for clamp experiments) |
| R_lactate | 0.0 | mM min-1 | Lactate infusion rate (for clamp experiments) |
| R_glucose | 0.0 | mM min-1 | Glucose infusion rate (for clamp experiments) |
| R_fatty_acids | 0.0 | mM min-1 | Fatty acid infusion rate (for clamp experiments) |
| R_3HB | 0.0 | mM min-1 | 3HB (ketone) infusion rate (for clamp experiments) |
| Insulin Action Switches (On/Off) | |||
| insulin_action_lipolysis | True | boolean | Toggle insulin's inhibitory action on lipolysis (True = active, False = inactive) |
| insulin_action_glycolysis | True | boolean | Toggle insulin's activating action on glycolysis (True = active, False = inactive) |
| insulin_action_glycogenolysis | True | boolean | Toggle insulin's inhibitory action on glycogenolysis (True = active, False = inactive) |
| insulin_action_ketogenesis | True | boolean | Toggle insulin's inhibitory action on ketogenesis (True = active, False = inactive) |