Abstract
A mechanism-based model was developed to describe the effects of methylprednisolone (MPL), circadian rhythms, and the glucose/free fatty acid (FFA)/insulin system on leptin and adiponectin expression in white adipose tissue in rats. Fifty-four normal Wistar rats received 50 mg/kg MPL intramuscularly and were sacrificed at various times. An additional set of 54 normal Wistar rats were sacrificed at 18 time points across the 24-h light/dark cycle and served as controls. Measurements included plasma MPL, glucocorticoid receptor (GR) mRNA, leptin mRNA, adiponectin mRNA, plasma leptin, adiponectin, glucose, FFA, and insulin. MPL pharmacokinetics was described by a two-compartment model with two absorption components. All measured plasma markers and mRNA expression exhibited circadian patterns except for adiponectin and were described by Fourier harmonic functions. MPL caused significant down-regulation in GR mRNA with the nadir occurring at 5 h. MPL disrupted the circadian patterns in plasma glucose and FFA by stimulating their production. Plasma glucose and FFA subsequently caused an increase in plasma insulin. Furthermore, MPL disrupted the circadian patterns in leptin mRNA expression by stimulating its production. This rise was closely followed by an increase in plasma leptin. Both leptin mRNA and plasma leptin peaked at 12 h after MPL and eventually returned back to their circadian baselines. MPL and insulin had opposing effects on adiponectin mRNA expression and plasma adiponectin, which resulted in biphasic pharmacodynamic profiles. This small systems model quantitatively describes, integrates, and provides additional insights into various factors controlling adipokine gene expression.
Footnotes
This work was supported by the National Institutes of Health National Institute of General Medical Sciences [Grant GM24211].
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.111.179960.
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ABBREVIATIONS:
- SCN
- suprachiasmatic nucleus
- FFA
- free fatty acids
- GR
- glucocorticoid receptor
- MPL
- methylprednisolone
- PK/PD
- pharmacokinetics/pharmacodynamics
- QRT-PCR
- quantitative real-time reverse transcription-polymerase chain reaction
- FAM
- 5-carboxyfluorescein
- CV
- coefficient of variation
- IDR
- indirect response.
- Received January 25, 2011.
- Accepted March 10, 2011.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
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