Effects of estrogen and estrus cycle on pharmacokinetics, absorption, and disposition of genistein in female Sprague-Dawley rats

Pharmacokinetics and Safety of Mitragynine in Beagle Dogs

Mitragynine is the most abundant psychoactive alkaloid derived from the leaves of Mitragyna speciosa (kratom), a tropical plant indigenous to regions of Southeast Asia. Mitragynine displays a moderate affinity to opioid receptors, and kratom is often self-prescribed to treat pain and/or opioid addiction. The purpose of this study was to investigate the safety and pharmacokinetic properties of mitragynine in the dog. Single dose oral (5 mg/kg) and intravenous (0.1 mg/kg) pharmacokinetic studies of mitragynine were performed in female beagle dogs. The plasma concentrations of mitragynine were measured using ultra-performance liquid chromatography coupled with a tandem mass spectrometer, and the pharmacokinetic properties were analyzed using non-compartmental analysis. Following intravenous administration, mitragynine showed a large volume of distribution (V_d, 6.3 ± 0.6 L/kg) and high clearance (Cl, 1.8 ± 0.4 L/h/kg). Following oral mitragynine dosing, first peak plasma (C_max, 278.0 ± 47.4 ng/mL) concentrations were observed within 0.5 h. A potent mu-opioid receptor agonist and active metabolite of mitragynine, 7-hydroxymitragynine, was also observed with a C_max of 31.5 ± 3.3 ng/mL and a T_max of 1.7 ± 0.6 h in orally dosed dogs while its plasma concentrations were below the lower limit of quantification (1 ng/mL) for the intravenous study. The absolute oral bioavailability of mitragynine was 69.6%. Administration of mitragynine was well tolerated, although mild sedation and anxiolytic effects were observed. These results provide the first detailed pharmacokinetic information for mitragynine in a non-rodent species (the dog) and therefore also provide significant information for allometric scaling and dose predictions when designing clinical studies.

Flavoured water consumption alters pharmacokinetic parameters and increases exposure of erlotinib and gefitinib in a preclinical study using Wistar rats

Background

Erlotinib (ERL) and Gefitinib (GEF) are considered first line therapy for the management of non-small cell lung carcinoma (NSCLC). Like other tyrosine kinase inhibitors (TKIs), ERL and GEF are mainly metabolized by the cytochrome P450 (CYP450) CYP3A4 isoform and are substrates for transporter proteins with marked inter-/intra-individual pharmacokinetic (PK) variability. Therefore, ERL and GEF are candidates for drug-drug and food-drug interactions with a consequent effect on drug exposure and/or drug-related toxicities. In recent years, the consumption of flavoured water (FW) has gained in popularity. Among multiple ingredients, fruit extracts, which might constitute bioactive flavonoids, can possess an inhibitory effect on the CYP450 enzymes or transporter proteins. Therefore, in this study we investigated the effects of different types of FW on the PK parameters of ERL and GEF in Wistar rats.

Methods

ERL and GEF PK parameters in different groups of rats after four weeks consumption of different flavours of FW, namely berry, peach, lime, and pineapple, were determined from plasma drug concentrations using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).

Results

Data indicated that tested FWs altered the PK parameters of both ERL and GEF differently. Lime water had the highest impact on most of ERL and GEF PK parameters, with a significant increase in C_max (95% for ERL, 58% for GEF), AUC_0-48 (111% for ERL, 203% for GEF), and AUC_0-∞ (200% for ERL, 203% for GEF), along with a significant decrease in the apparent oral clearance of both drugs (65% for ERL, 67% for GEF). The order by which FW affected the PK parameters for ERL and GEF was as follows: lime > pineapple > berry > peach.

Conclusion

The present study indicates that drinking FW could be of significance in rats receiving ERL or GEF. Our results indicate that the alteration in PKs was mostly recorded with lime, resulting in an enhanced bioavailability, and reduced apparent oral clearance of the drugs. Peach FW had a minimum effect on the PK parameters of ERL and no significant effect on GEF PKs. Accordingly, it might be of clinical importance to evaluate the PK parameters of ERL and GEF in human subjects who consume FW while receiving therapy.

Genistein stimulates jejunum chloride secretion via an Akt-mediated pathway in intact female mice

Background/Aims

We have previously shown that daily subcutaneous injections with the naturally occurring phytoestrogen genistein (600 mg genistein/kg body weight/day, 600G) results in a significantly increased basal intestinal chloride, Cl⁻, secretion (I_sc, a measure of transepithelial secretion) in intact C57BL/6J female mice after 1-week of treatment, compared to controls (DMSO vehicle injected). Removal of endogenous estrogen via ovariectomy (OVX) had no effect on the 600G-mediated increase in basal I_sc.

Methods

Given the estrogen-like characteristics of genistein, we compared the effects of daily estradiol (E2) injections (10 mg E2/kg body weight/day, 10E2) on basal I_sc in intact and OVX mice. In intact mice, 10E2 was without effect on basal I_sc, however, in OVX mice, 10E2 significantly increased basal I_sc (mimicked 600G). The goal of the current study was to characterize the intracellular signaling pathways responsible for mediating 600G- or 10E2-stimulated increases in basal I_sc in intact female or OVX mice.

Results

We measured total protein expression in isolated segments of jejunum using western blot from the following six groups of mice; intact or OVX with; 600G, 10E2 or control. The proteins of interest were: Akt, p-Akt, p-PDK1, p-PTEN, p-c-Raf, p-GSK-3β, rap-1 and ERK1/2. All blots were normalized to GAPDH levels (n = 6–18/group).

Conclusion

These data suggest that the presence of the endogenous sex steroid, estrogen, modifies the intracellular signaling pathway required to mediate Cl⁻ secretion when the intestine is exposed to exogenous 600G or E2. These studies may have relevance for designing pharmacological tools for women with intestinal chloride secretory dysfunctions.

Ovariectomy lowers urine levels of unconjugated (+)-catechin, (–)-epicatechin, and their methylated metabolites in rats fed grape seed extract

Steroid hormones modulate expression of enzymes that metabolize xenobiotics, including dietary supplements. Half of the human population undergoes menopause, yet the effect of this age-related loss of ovarian steroid hormones on the metabolism of dietary supplements has yet to be determined. Grape seed extract (GSE) is a dietary supplement comprised of monomeric and oligomeric catechins and has health benefits in models of age-related diseases. We hypothesized that surgically-induced loss of ovarian hormones would increase methylation, glucuronidation, and/or sulfation of the grape seed polyphenols (+)-catechin and (–)-epicatechin. Fourteen-week-old spontaneously hypertensive rats (SHRs) were ovariectomized (OVX) or sham-OVX. At 17 weeks of age, SHRs were gavaged with vehicle (water) or GSE (300 mg/kg body weight) once daily for 6 days. Urinary excretion of (+)-catechin, (–)-epicatechin, and their metabolites was analyzed by liquid chromatography-mass spectrometry. Although total urinary output of (+)-catechin, (–)-epicatechin, and their methylated metabolites was unaffected by OVX, the amounts of (+)-catechin, (–)-epicatechin and their methylated metabolites that were not conjugated with glucuronic acid or sulfate were lowered by OVX. Specifically, urine from OVX SHRs administered GSE contained 30% higher proportions (91.8% vs. 62.3%) of glucuronidated (+)-catechin and (–)-epicatechin and glucuronidated methyl (+)-catechin and methyl (–)-epicatechin than urine from sham-OVX SHRs. However, there were no differences in urinary levels of total methylated or sulfated catechins in OVX SHRs. This is the first quantitative characterization of metabolites of grape seed polyphenols in a model of menopause; it indicates that ovariectomy causes either an increase in expression and/or activity of select uridine 5′-diphospho-glucuronosyltransferase(s).