Estimation of daily minimum energy expenditure in free-moving rats and mice

Population Semiphysiologic Kinetic Modeling and Simulation of Plasma Triglyceride Levels After Soybean Oil-Based Intravenous Lipid Emulsion Administration in Rats

BACKGROUND

Soybean oil-based intravenous lipid emulsion (SO-ILE) has clinical utility as an energy source and in lipid rescue therapy. However, an excessive infusion rate of SO-ILE in routine use and in lipid rescue therapy may cause serious side effects. There is little information about plasma triglyceride (TG) kinetics following SO-ILE administration. The present study aimed to develop a population semiphysiologic kinetic model of TG and to predict the TG kinetics even at extremely high concentrations in rats.

MATERIALS AND METHODS

TG concentration profiles after intravenous bolus (0.1, 0.25, 0.5, 1.0, 1.5, and 2.0 g/kg) or infusion (3.0 g/kg/h for 1 hour) of SO-ILE to rats were analyzed by a kinetic model constructed with 4 pathways: apolipoprotein acquisitions, zero-order catabolism, first-order uptake to storage sites, and zero-order secretion from storage sites. The developed model was subjected to internal and external validation.

RESULTS

Plasma TG concentrations appeared to decline in a biphasic manner with nonlinear TG kinetics. The developed kinetic model was well validated and found to accurately predict the external validation data.

CONCLUSIONS

The proposed kinetic model accurately described TG concentrations after SO-ILE administration at various infusion rates, including a lipid rescue regimen. The maximum acceptable infusion rate of SO-ILE in routine use should correspond to the maximum velocity of the apolipoprotein acquisition: 0.619 g/kg/h in rats. The prediction of TG kinetics at extremely high concentrations will provide useful information for lipid rescue therapy.

PPARgamma coactivator 1beta/ERR ligand 1 is an ERR protein ligand, whose expression induces a high-energy expenditure and antagonizes obesity

A well balanced body energy budget controlled by limitation of calorie uptake and/or increment of energy expenditure, which is typically achieved by proper physical exercise, is most effective against obesity and diabetes mellitus. Recently, peroxisome proliferator-activated receptor (PPAR) gamma, a member of the nuclear receptor, and its cofactors have been shown to be involved in lipid metabolism and in the control of energy expenditure. Here we show that PPARgamma coactivator 1 (PGC-1) beta functions as ERRL1 (for ERR ligand 1), which can bind and activate orphan ERRs (estrogen receptor-related receptors) in vitro. Consistently, PGC-1beta/ERRL1 transgenic mice exhibit increased expression of the medium-chain acyl CoA dehydrogenase, a known ERR target and a pivotal enzyme of mitochondrial beta-oxidation in skeletal muscle. As a result, the PGC-1beta/ERRL1 mice show a state similar to an athlete; namely, the mice are hyperphagic and of elevated energy expenditure and are resistant to obesity induced by a high-fat diet or by a genetic abnormality. These results demonstrate that PGC-1beta/ERRL1 can function as a protein ligand of ERR, and that its level contributes to the control of energy balance in vivo, and provide a strategy for developing novel antiobesity drugs.