Human oral pharmacokinetics of 4-hydroxy isoleucine and dosage simulation studies for predicting its pharmacodynamics in diabetes

Abstract

Introduction: 4-hydroxy isoleucine (4-HIL), a potent glucose-lowering agent and insulin secretagogue, is widely available in nutraceutical market as fenugreek seed extract formulations. This study aims to elucidate the oral pharmacokinetics (PK) of 4-HIL in healthy human volunteers to standardize its dose and dosing regimen, ensuring its potential for effective diabetes management.

Methodology: Twelve healthy volunteers received a single oral administration of 150 mg of 4-HIL as fenugreek seed extract tablets. Caplillary blood samples were collected at various time points within 24 h and plasma levels of 4-HIL were quantified using liquid chromatography-tandem mass spectrometry. In vitro studies on 4-HIL pharmacodynamics, derived from the literature, were used to calculate the half-minimal effective concentration (EC50). PK assessments based on compartmental modelling and dosage simulation studies were conducted using PKsolver and ModVizPOP, respectively. The PK simulation included three distinct dosage regimens (150 mg thrice daily, 225 mg twice daily, or 450 mg once daily) to evaluate EC50 level attainment.

Results: The best-fit was observed with a two-compartmental model, with maximum 4-HIL plasma concentration (Concentration maximum, 2.42 ± 0.61 µg/mL) observed at 0.5 h (Time maximum). The derived mean EC50 of 4-HIL, needed to reduce blood glucose, was 1.50 ± 0.31 µg/mL. The PK simulation study indicated that daily intake of 450 mg 4-HIL in all three tested dosing regimens had maintained EC50 levels more than 18 h for glucose-lowering effects.

Conclusion: The optimal 4-HIL dose of 450 mg/day up to three divided dosing regimens has proven effective and hence may be considered for future diabetic trials.

Keywords: 4-hydroxy isoleucine; diabetes; dosing regimen; fenugreek; pharmacokinetics; simulation.

Figure 1

(a) Observed time versus concentration plot of 4-hydroxy isoleucine (4-HIL) after oral intake of a single 150 mg tablet of fenugreek seed extract in healthy volunteers (n = 12), (b) Total ion chromatogram of 4-HIL, (c) Time versus blood glucose levels following single oral administration of 150 mg 4-HIL from baseline up to 2 h, (d) Predicted time versus concentration plot of 4-HIL showing best fit with observed values in cumulative two-compartmental pharmacokinetic model obtained using PKsolver ver. 2.0. *P < 0.05 and **P < 0.01. 4-HIL: 4-hydroxy isoleucine

Figure 2

Simulation of 4-hydroxy isoleucine (4-HIL) three different dosing regimens based on the pharmacokinetic parameter derived from two-compartmental models. Levels of 4HIL following the consumption of 150 mg three times a day for 1 week in 1000 subjects in central (a) and peripheral compartment (b-d) indicates 4HIL levels following administration of 225 mg twice daily for 1 week in 1000 subjects in central and peripheral compartments, respectively. Similarly, (e and f) illustrate the 450 mg once daily for 1 week in 1000 subjects in central and peripheral (tissue) compartments, respectively. The horizontal line at 1.5 µg/mL shows the EC₅₀ required for 4-HIL to induce its glucose lowering effect. 4-HIL: 4-hydroxy isoleucine