Modeling disease progression and rosiglitazone intervention in type 2 diabetic Goto-Kakizaki rats

Population Pharmacokinetic/Pharmacodynamic Analysis of the Glucokinase Activator PB201 in Healthy Volunteers and Patients with Type 2 Diabetes Mellitus: Facilitating the Clinical Development of PB201 in China

PB201 is an orally active, partial glucokinase activator targeting both pancreatic and hepatic glucokinase. As the second glucokinase activator studied beyond phase I, PB201 has demonstrated promising glycemic effects as well as favorable pharmacokinetic (PK) and safety profiles in patients with type 2 diabetes mellitus (T2DM). This study aims to develop a population PK/pharmacodynamic (PD) model for PB201 using the pooled data from nine phase I/II clinical trials conducted in non-Chinese healthy volunteers and a T2DM population and to predict the PK/PD profile of PB201 in a Chinese T2DM population. We developed the PK/PD model using the non-linear mixed-effects modeling approach. All runs were performed using the first-order conditional estimation method with interaction. The pharmacokinetics of PB201 were well fitted by a one-compartment model with saturable absorption and linear elimination. The PD effects of PB201 on reducing the fasting plasma glucose and glycosylated hemoglobin levels in the T2DM population were described by indirect response models as stimulating the elimination of fasting plasma glucose, where the production of glycosylated hemoglobin was assumed to be stimulated by fasting plasma glucose. Covariate analyses revealed enhanced absorption of PB201 by food and decreased systemic clearance with ketoconazole co-administration, while no significant covariate was identified for the pharmacodynamics. The population PK model established for non-Chinese populations was shown to be applicable to the Chinese T2DM population as verified by the PK data from the Chinese phase I study. The final population PK/PD model predicted persistent and dose-dependent reductions in fasting plasma glucose and glycosylated hemoglobin levels in the Chinese T2DM population receiving 50/50 mg, 100/50 mg, and 100/100 mg PB201 twice daily for 24 weeks independent of co-administration of metformin. Overall, the proposed population PK/PD model quantitatively characterized the PK/PD properties of PB201 and the impact of covariates on its target populations, which allows the leveraging of extensive data in non-Chinese populations with the limited data in the Chinese T2DM population to successfully supported the waiver of the clinical phase II trial and facilitate the optimal dose regimen design of a pivotal phase III study of PB201 in China.

Rosiglitazone Does Not Show Major Hidden Cardiotoxicity in Models of Ischemia/Reperfusion but Abolishes Ischemic Preconditioning-Induced Antiarrhythmic Effects in Rats In Vivo

Clinical observations are highly inconsistent with the use of the antidiabetic rosiglitazone regarding its associated increased risk of myocardial infarction. This may be due to its hidden cardiotoxic properties that have only become evident during post-marketing studies. Therefore, we aimed to investigate the hidden cardiotoxicity of rosiglitazone in ischemia/reperfusion (I/R) injury models. Rats were treated orally with either 0.8 mg/kg/day rosiglitazone or vehicle for 28 days and subjected to I/R with or without cardioprotective ischemic preconditioning (IPC). Rosiglitazone did not affect mortality, arrhythmia score, or infarct size during I/R. However, rosiglitazone abolished the antiarrhythmic effects of IPC. To investigate the direct effect of rosiglitazone on cardiomyocytes, we utilized adult rat cardiomyocytes (ARCMs), AC16, and differentiated AC16 (diffAC16) human cardiac cell lines. These were subjected to simulated I/R in the presence of rosiglitazone. Rosiglitazone improved cell survival of ARCMs at 0.3 μM. At 0.1 and 0.3 μM, rosiglitazone improved cell survival of AC16s but not that of diffAC16s. This is the first demonstration that chronic administration of rosiglitazone does not result in major hidden cardiotoxic effects in myocardial I/R injury models. However, the inhibition of the antiarrhythmic effects of IPC may have some clinical relevance that needs to be further explored.

Semi-Mechanism-Based Pharmacokinetic-Toxicodynamic Model of Oxaliplatin-Induced Acute and Chronic Neuropathy

Oxaliplatin (L-OHP) is widely prescribed for treating gastroenterological cancer. L-OHP-induced peripheral neuropathy is a critical toxic effect that limits the dosage of L-OHP. An ideal chemotherapeutic strategy that does not result in severe peripheral neuropathy but confers high anticancer efficacy has not been established. To establish an optimal evidence-based dosing regimen, a pharmacokinetic-toxicodynamic (PK-TD) model that can characterize the relationship between drug administration regimen and L-OHP-induced peripheral neuropathy is required. We developed a PK-TD model of L-OHP for peripheral neuropathy using Phoenix^® NLME™ Version 8.1. Plasma concentration of L-OHP, the number of withdrawal responses in the acetone test, and the threshold value in the von Frey test following 3, 5, or 8 mg/kg L-OHP administration were used. The PK-TD model consisting of an indirect response model and a transit compartment model adequately described and simulated time-course alterations of onset and grade of L-OHP-induced cold and mechanical allodynia. The results of model analysis suggested that individual fluctuation of plasma L-OHP concentration might be a more important factor for individual variability of neuropathy than cell sensitivity to L-OHP. The current PK-TD model might contribute to investigation and establishment of an optimal dosing strategy that can reduce L-OHP-induced neuropathy.

Population Pharmacokinetic-Pharmacodynamic Modeling of 5-Fluorouracil for Toxicities in Rats

BACKGROUND AND OBJECTIVES

Myelosuppression is a dose-limiting toxicity of 5-fluorouracil (5-FU). Predicting the inter- and intra-patient variability in pharmacokinetics and toxicities of 5-FU may contribute to the individualized medicine. This study aimed to establish a population pharmacokinetic-pharmacodynamic model that could evaluate the inter- and intra-individual variability in the plasma 5-FU concentration, 5-FU-induced body weight loss and myelosuppression in rats.

METHOD

Plasma 5-FU concentrations, body weight loss, and blood cell counts in rats following the intravenous administration of various doses of 5-FU for 4 days were used to develop the population pharmacokinetic-pharmacodynamic model.

RESULTS

The population pharmacokinetic model consisting of a two-compartment model with Michaelis-Menten elimination kinetics successfully characterized the individual and population predictions of the plasma concentration of 5-FU and provided credible parameter estimates. The estimates of inter-individual variability in maximal rate of saturable metabolism and residual variability were 8.1 and 22.0%, respectively. The population pharmacokinetic-pharmacodynamic model adequately described the individual complete time-course of alterations in body weight loss, erythrocyte, leukocyte, and lymphocyte counts in rats treated with various doses of 5-FU. The inter-individual variability of the drug effects in the pharmacodynamic model for body weight loss was 82.6%, which was relatively high. The results of the present study suggest that not only individual fluctuations in the 5-FU concentration but also the cell sensitivity would affect the onset and degree of 5-FU-induced toxicity.

CONCLUSION

This population pharmacokinetic-pharmacodynamic model could evaluate the inter- and intra-individual variability in drug-induced toxicity and guide the assessments of novel anticancer agents in drug development.

The Spectrum of Mechanism-Oriented Models and Methods for Explanations of Biological Phenomena

Developing and improving mechanism-oriented computational models to better explain biological phenomena is a dynamic and expanding frontier. As the complexity of targeted phenomena has increased, so too has the diversity in methods and terminologies, often at the expense of clarity, which can make reproduction challenging, even problematic. To encourage improved semantic and methodological clarity, we describe the spectrum of Mechanism-oriented Models being used to develop explanations of biological phenomena. We cluster explanations of phenomena into three broad groups. We then expand them into seven workflow-related model types having distinguishable features. We name each type and illustrate with examples drawn from the literature. These model types may contribute to the foundation of an ontology of mechanism-based biomedical simulation research. We show that the different model types manifest and exert their scientific usefulness by enhancing and extending different forms and degrees of explanation. The process starts with knowledge about the phenomenon and continues with explanatory and mathematical descriptions. Those descriptions are transformed into software and used to perform experimental explorations by running and examining simulation output. The credibility of inferences is thus linked to having easy access to the scientific and technical provenance from each workflow stage.

Influence of the pharmacokinetic profile on the plasma glucose lowering effect of the PPARγ agonist pioglitazone in Wistar fatty rats

Although the mechanism of action for peroxisome proliferator-activated receptor gamma (PPARγ) agonists has been extensively explored, the impact of the pharmacokinetic (PK) profile on the pharmacodynamic (PD) effects of PPARγ agonists has not been elucidated in detail. The importance of the PK profile of PPARγ agonist was evaluated for its PD effect based on population PK/PD analysis. Pioglitazone hydrochloride, the PPARγ agonist, was administered orally to Wistar fatty rats once a day (q.d.) or once every other day (q.2d.) as double the amount for the q.d.

TREATMENT

The plasma glucose lowering effect was selected as a surrogate PD effect for an anti-diabetic effect. The model fitting was conducted using the non-linear mixed effect modeling (NONMEM) method. The indirect response model described well the plasma glucose concentration-time profile. The q.d. treatment showed a stronger impact on the plasma glucose lowering effect than did the q.2d.

TREATMENT

The results of PK/PD modeling suggested that the sensitivity (i.e. EC₅₀ ) between each group was comparable. On the other hand, the time above the effective concentration in the q.d. treatment group was longer than that in the q.2d. treatment group. The simulation of various dose regimens suggested that the much longer exposure duration within the effective level showed a stronger plasma glucose lowering effect, even with identical exposure to pioglitazone in the plasma. The PK/PD analysis clarified that the PK profile affected the pharmacological response and that continuous exposure at an appropriate effective level would be efficient for the anti-diabetic effect of the PPARγ agonist.

Translational mixed-effects PKPD modelling of recombinant human growth hormone - from hypophysectomized rat to patients

BACKGROUND AND PURPOSE

We aimed to develop a mechanistic mixed-effects pharmacokinetic (PK)-pharmacodynamic (PD) (PKPD) model for recombinant human growth hormone (rhGH) in hypophysectomized rats and to predict the human PKPD relationship.

EXPERIMENTAL APPROACH

A non-linear mixed-effects model was developed from experimental PKPD studies of rhGH and effects of long-term treatment as measured by insulin-like growth factor 1 (IGF-1) and bodyweight gain in rats. Modelled parameter values were scaled to human values using the allometric approach with fixed exponents for PKs and unscaled for PDs and validated through simulations relative to patient data.

KEY RESULTS

The final model described rhGH PK as a two compartmental model with parallel linear and non-linear elimination terms, parallel first-order absorption with a total s.c. bioavailability of 87% in rats. Induction of IGF-1 was described by an indirect response model with stimulation of kin and related to rhGH exposure through an Emax relationship. Increase in bodyweight was directly linked to individual concentrations of IGF-1 by a linear relation. The scaled model provided robust predictions of human systemic PK of rhGH, but exposure following s.c. administration was over predicted. After correction of the human s.c. absorption model, the induction model for IGF-1 well described the human PKPD data.

CONCLUSIONS

A translational mechanistic PKPD model for rhGH was successfully developed from experimental rat data. The model links a clinically relevant biomarker, IGF-1, to a primary clinical end-point, growth/bodyweight gain. Scaling of the model parameters provided robust predictions of the human PKPD in growth hormone-deficient patients including variability.

Application of a Systems Pharmacology-Based Placebo Population Model to Analyze Long-Term Data of Postmenopausal Osteoporosis

Osteoporosis is a progressive bone disease characterized by decreased bone mass resulting in increased fracture risk. The objective of this investigation was to test whether a recently developed disease systems analysis model for osteoporosis could describe disease progression in a placebo-treated population from the Early Postmenopausal Intervention Cohort (EPIC) study. First, we qualified the model using a subset from the placebo arm of the EPIC study of 222 women who had similar demographic characteristics as the 149 women from the placebo arm of the original population. Second, we applied the model to all 470 women. Bone mineral density (BMD) dynamics were changed to an indirect response model to describe lumbar spine and total hip BMD in this second population. This updated disease systems analysis placebo model describes the dynamics of all biomarkers in the corresponding datasets to a very good approximation; a good description of an individual placebo response will be valuable for evaluating treatments for osteoporosis.

Modeling and design of challenge tests: Inflammatory and metabolic biomarker study examples

Given the complexity of pharmacological challenge experiments, it is perhaps not surprising that design and analysis, and in turn interpretation and communication of results from a quantitative point of view, is often suboptimal. Here we report an inventory of common designs sampled from anti-inflammatory, respiratory and metabolic disease drug discovery studies, all of which are based on animal models of disease involving pharmacological and/or patho/physiological interaction challenges. The corresponding data are modeled and analyzed quantitatively, the merits of the respective approach discussed and inferences made with respect to future design improvements. Although our analysis is limited to these disease model examples, the challenge approach is generally applicable to the vast majority of pharmacological intervention studies. In the present five Case Studies results from pharmacodynamic effect models from different therapeutic areas were explored and analyzed according to five typical designs. Plasma exposures of test compounds were assayed by either liquid chromatography/mass spectrometry or ligand binding assays. To describe how drug intervention can regulate diverse processes, turnover models of test compound-challenger interaction, transduction processes, and biophase time courses were applied for biomarker response in eosinophil count, IL6 response, paw-swelling, TNFα response and glucose turnover in vivo. Case Study 1 shows results from intratracheal administration of Sephadex, which is a glucocorticoid-sensitive model of airway inflammation in rats. Eosinophils in bronchoalveolar fluid were obtained at different time points via destructive sampling and then regressed by the mixed-effects modeling. A biophase function of the Sephadex time course was inferred from the modeled eosinophil time courses. In Case Study 2, a mouse model showed that the time course of cytokine-induced IL1β challenge was altered with or without drug intervention. Anakinra reversed the IL1β induced cytokine IL6 response in a dose-dependent manner. This Case Study contained time courses of test compound (drug), challenger (IL1β) and cytokine response (IL6), which resulted in high parameter precision. Case Study 3 illustrates collagen-induced arthritis progression in the rat. Swelling scores (based on severity of hind paw swelling) were used to describe arthritis progression after the challenge and the inhibitory effect of two doses of an orally administered test compound. In Case Study 4, a cynomolgus monkey model for lipopolysaccharide LPS-induced TNFα synthesis and/or release was investigated. This model provides integrated information on pharmacokinetics and in vivo potency of the test compounds. Case Study 5 contains data from an oral glucose tolerance test in rats, where the challenger is the same as the pharmacodynamic response biomarker (glucose). It is therefore convenient to model the extra input of glucose simultaneously with baseline data and during intervention of a glucose-lowering compound at different dose levels. Typically time-series analyses of challenger- and biomarker-time data are necessary if an accurate and precise estimate of the pharmacodynamic properties of a test compound is sought. Erosion of data, resulting in the single-point assessment of drug action after a challenge test, should generally be avoided. This is particularly relevant for situations where one expects time-curve shifts, tolerance/rebound, impact of disease, or hormetic concentration-response relationships to occur.

The effect of duodenojejunostomy and sleeve gastrectomy on type 2 diabetes mellitus and gastrin secretion in Goto-Kakizaki rats

BACKGROUND

Bariatric surgery is a highly effective treatment of type 2 diabetes in patients with morbid obesity. The weight-loss independent improvement of glycemic control observed after these procedures has led to the discussion whether bariatric surgery can be introduced as treatment for type 2 diabetes in patients with a body mass index < 35 kg/m(2). We have studied the effects of two bariatric procedures on type 2 diabetes and on gastrointestinal hormone secretion in a lean diabetic animal model.

METHODS

Male Goto-Kakizaki rats, 17-18 weeks old, were randomized into three groups: duodenojejunostomy (DJ), sleeve gastrectomy (SG), or sham operation. During 36 postoperative weeks we evaluated body weight, fasting blood glucose, glucose tolerance, insulin, HbA1c, glucagon-like peptide 1, cholesterol parameters, triglycerides, total ghrelin, and gastrin.

RESULTS

Oral glucose tolerance was significantly improved for both DJ and SG at four weeks after surgery (p < 0.05). At the 34th postoperative week, SG had significantly lower area under the curve during oral glucose tolerance test compared to sham (p = 0.007). SG had significantly lower HbA1c compared to sham at 12 weeks; (mean ± SEM) 4.3 ± 0.1 % versus 5.2 ± 0.3 % (p < 0.05) and compared to both DJ and sham 34 weeks after surgery [median (75 %;25 %)] 5.2 (6.0; 4.3) % versus 7.0 (7.5; 6.7) % and 7.3 (7.6; 6.7) % (p = 0.009). Serum gastrin levels were markedly elevated for SG compared to DJ and sham; 188.0 (318.0; 121.0) versus 77.5 (114.0; 58.0) and 68.0 (90.0; 59.5) pmol/L (p = 0.004) at six weeks and 192.0 (587.8; 110.8) versus 65.5 (77.0; 59.0) and 69.5 (113.0; 55.5) (p = 0.001) 36 weeks after surgery.

CONCLUSION

Sleeve gastrectomy induces hypergastrinemia, lowers HbA1c, and improves glycemic control in Goto-Kakizaki rats. Sleeve gastrectomy is superior to duodenojejunostomy as treatment of type 2 diabetes mellitus in this animal model.

Rosiglitazone enhances apolipoprotein M (Apom) expression in rat's liver

Apolipoprotein M (APOM) has been suggested as a vasculoprotective constituent of high density lipoprotein (HDL), which plays a crucial role behind the mechanism of HDL-mediated anti-atherosclerosis. Previous studies demonstrated that insulin resistance could associate with decreased APOM expressions. In agreement with our previous reports, here, we further confirmed that the insulin sensitivity was also reduced in rats treated with high concentrations of glucose; such effect could be reversed by administration of rosiglitazone, a peroxisome proliferator-activated receptor-γ (PPARγ). The present study shows that Apom expression is significantly affected by either rosiglitazone or hyperglycemia alone without cross interaction with each other, which indicates that the pathway of Apom expression regulating by hyperglycemia might be differed from that by rosiglitazone. Further study indicated that hyperglycemia could significantly inhibit mRNA levels of Lxrb (P=0.0002), small heterodimer partner 1 (Shp1) (P<0.0001), liver receptor homologue-1 (Lrh1) (P=0.0012), ATP-binding cassette transporter 1 (Abca1) (P=0.0012) and Pparb/d (P=0.0043). Two-way ANOVA analysis demonstrated that the interactions between rosiglitazone and infusion of 25% glucose solution on Shp1 (P=0.0054) and Abca1 (4E, P=0.0004) mRNA expression was statistically significant. It is concluded that rosiglitazone could increase Apom expression, of which the detailed mechanism needs to be further investigated. The downregulation of Apom by hyperglycemia might be mainly through decreasing expression of Pparg and followed by inhibiting Lxrb in rats.

Rosiglitazone improves insulin sensitivity and baroreflex gain in rats with diet-induced obesity

Obesity decreases baroreflex gain (BRG); however, the mechanisms are unknown. We tested the hypothesis that impaired BRG is related to the concurrent insulin resistance, and, therefore, BRG would be improved after treatment with the insulin-sensitizing drug rosiglitazone. Male rats fed a high-fat diet diverged into obesity-prone (OP) and obesity-resistant (OR) groups after 2 weeks. Then, OP and OR rats, as well as control (CON) rats fed a standard diet, were treated daily for 2 to 3 weeks with rosiglitazone (3 or 6 mg/kg) or its vehicle by gavage. Compared with OR and CON rats, conscious OP rats exhibited reductions in BRG (OP, 2.9 ± 0.1 bpm/mm Hg; OR, 4.0 ± 0.2 bpm/mm Hg; CON, 3.9 ± 0.2 bpm/mm Hg; P < 0.05) and insulin sensitivity (hyperinsulinemic euglycemic clamp; OP, 6.8 ± 0.9 mg/kg · min; OR, 22.2 ± 1.2 mg/kg · min; CON, 17.7 ± 0.8 mg/kg · min; P < 0.05), which were well correlated (r(2) = 0.49; P < 0.01). In OP rats, rosiglitazone dose-dependently improved (P < 0.05) insulin sensitivity (12.8 ± 0.6 mg/kg · min at 3 mg/kg; 16.0 ± 1.5 mg/kg · min at 6 mg/kg) and BRG (3.8 ± 0.4 bpm/mm Hg at 3 mg/kg; 5.3 ± 0.7 bpm/mm Hg at 6 mg/kg). However, 6 mg/kg rosiglitazone also increased BRG in OR rats without increasing insulin sensitivity, disrupted the correlation between BRG and insulin sensitivity (r(2) = 0.08), and, in OP and OR rats, elevated BRG relative to insulin sensitivity (analysis of covariance; P < 0.05). Moreover, in OP rats, stimulation of the aortic depressor nerve, to activate central baroreflex pathways, elicited markedly reduced decreases in heart rate and arterial pressure, but these responses were not improved by rosiglitazone. In conclusion, diet-induced obesity impairs BRG via a central mechanism that is related to the concurrent insulin resistance. Rosiglitazone normalizes BRG, but not by improving brain baroreflex processing or insulin sensitivity.