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Feedback modeling of non-esterified fatty acids in obese Zucker rats after nicotinic acid infusions.
MedLine Citation:
PMID:  24114415     Owner:  NLM     Status:  Publisher    
This study investigates the impact of disease on nicotinic acid (NiAc)-induced changes in plasma concentrations of non-esterified fatty acids (NEFA). NiAc was given by constant intravenous infusion to normal Sprague-Dawley and obese Zucker rats, and arterial blood samples were taken for analysis of NiAc, NEFA, insulin and glucose plasma concentrations. The intravenous route was intentionally selected to avoid confounding processes, such as absorption, following extravascular administration. Data were analyzed using nonlinear mixed effects modeling (NONMEM, version VI). The disposition of NiAc in the normal rats was described by a two-compartment model with endogenous synthesis of NiAc and two parallel capacity-limited elimination processes. In the obese rats disposition was described by a one-compartment model with endogenous synthesis of NiAc and one capacity-limited elimination process. The plasma concentration of NiAc drove NEFA (R) turnover via an inhibitory drug-mechanism function acting on the formation of NEFA. NEFA turnover was described by a feedback model with a moderator distributed over a series of transit compartments, where the first compartment (M 1 ) inhibited the formation of R and the last compartment (M N ) stimulated the loss of R. All processes regulating plasma NEFA concentrations were assumed to be captured by the moderator function. Differences in the pharmacodynamic response of the two strains included, in the obese animals, an increased NEFA baseline, diminished rebound and post-rebound oscillation, and a more pronounced slowly developing tolerance during the period of constant drug exposure. The feedback model captured the NiAc-induced changes in NEFA response in both the normal and obese rats. Differences in the parameter estimates between the obese and normal rats included, in the former group, increases in R 0 , k in and p by 44, 41 and 78 %, respectively, and decreases in k out and γ by 64 and 84 %, respectively. The estimates of k tol and IC 50 were similar in both groups. The NiAc-NEFA concentration-response relationship at equilibrium was substantially different in the two groups, being shifted upwards and to the right, and being shallower in the obese rats. The extent of such shifts is important, as they demonstrate the impact of disease at equilibrium and, if ignored, will lead to erroneous dose predictions and, in consequence, poorly designed studies. The proposed models are primarily aimed at screening and selecting candidates with the highest potential of becoming a viable drug in man.
Christine Ahlström; Tobias Kroon; Lambertus A Peletier; Johan Gabrielsson
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-10-10
Journal Detail:
Title:  Journal of pharmacokinetics and pharmacodynamics     Volume:  -     ISSN:  1573-8744     ISO Abbreviation:  J Pharmacokinet Pharmacodyn     Publication Date:  2013 Oct 
Date Detail:
Created Date:  2013-10-11     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101096520     Medline TA:  J Pharmacokinet Pharmacodyn     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
CVMD iMed DMPK, AstraZeneca R&D Mölndal, Pepparedsleden 1, 43183, Mölndal, Sweden,
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