Mechanism-Based Pharmacokinetic Model for the Deglycosylation Kinetics of 20(S)-Ginsenosides Rh2.

Aim: The 20(S)-ginsenoside Rh2 (Rh2) is being developed as a new antitumor drug. However, to date, little is known about the kinetics of its deglycosylation metabolite (protopanoxadiol) (PPD) following Rh2 administration. The aim of this work was to 1) simultaneously characterise the pharmacokinetics of Rh2 and PPD following intravenous and oral Rh2 administration, 2) develop and validate a mechanism-based pharmacokinetic model to describe the deglycosylation kinetics and 3) predict the percentage of Rh2 entering the systemic circulation in PPD form. Methods: Plasma samples were collected from rats after the I.V. or P.O. administration of Rh2. The plasma Rh2 and PPD concentrations were determined using HPLC-MS. The transformation from Rh2 to PPD, its absorption, and elimination were integrated into the mechanism based pharmacokinetic model to describe the pharmacokinetics of Rh2 and PPD simultaneously at 10 mg/kg. The concentration data collected following a 20 mg/kg dose of Rh2 was used for model validation. Results: Following Rh2 administration, PPD exhibited high exposure and atypical double peaks. The model described the abnormal kinetics well and was further validated using external data. A total of 11% of the administered Rh2 was predicted to be transformed into PPD and enter the systemic circulation after I.V. administration, and a total of 20% of Rh2 was predicted to be absorbed into the systemic circulation in PPD form after P.O. administration of Rh2. Conclusion: The developed model provides a useful tool to quantitatively study the deglycosylation kinetics of Rh2 and thus, provides a valuable resource for future pharmacokinetic studies of glycosides with similar deglycosylation metabolism.

Predicting the Drug-Drug Interaction Mediated by CYP3A4 Inhibition: Method Development and Performance Evaluation.

The prediction of drug-drug interactions (DDIs) plays critical roles for the estimation of DDI risk caused by inhibition of CYP3A4. The aim of this paper is to develop a physiologically based pharmacokinetic (PBPK)-DDI model for prediction of the DDI co-administrated with ketoconazole in humans and evaluate the predictive performance of the model. The pharmacokinetic and biopharmaceutical properties of 35 approved drugs, as victims, were collected for the development of a PBPK model, which were linked to the PBPK model of ketoconazole for the DDI prediction. The PBPK model of victims and ketoconazole were validated by matching actual in vivo pharmacokinetic data. The predicted results of DDI were compared with actual data to evaluate the predictive performance. The percentage of predicted ratio of AUC (AUCR), Cmax (CmaxR), and Tmax (TmaxR) was 75%, 69%, and 91%, respectively, which were within the twofold threshold (range, 0.5-2.0×) of the observed values. Only 3% of the predicted AUCRs are obviously underestimated. After integration of the reported fraction of metabolism (fm) into the PBPK-DDI model for limited four cases, the model-predicted AUCRs were improved from the twofold range of the observed AUCRs to the 90% confidence interval. The developed method could reasonably predict drug-drug interaction with a low risk of underestimation. The present accuracy of the prediction was improved compared with that of static mechanistic models. The evaluation of predictive performance increases the confidence using the model to evaluate the risk of DDIs co-administrated with ketoconazole before the in vivo DDI study.

The incidence and analysis of ipsilateral occult hernia in patients undergoing hernia repair: a single institution retrospective study of 1066 patients.

BACKGROUND: Misdiagnosis or failure to intraoperatively detect occult hernia in the inguinal region can lead to the recurrence of postoperative hernia and the appearance of local pain symptoms, which affect the patient's quality of life and make it difficult to reperform hernia repair. METHODS: This study included 1066 inguinal hernia patients who underwent surgical treatment at Shanghai Tongren Hospital between January 2016 and October 2018 to investigate ipsilateral occult hernia epidemiology, to analyze the characteristics of ipsilateral occult hernias with regards to patient age, gender, classification and anatomical site, and to explore the superiority and inferiority of the expert hernia surgeons/ non-expert hernia surgeons group and of operation methods in finding occult inguinal hernias. RESULTS: The incidence of ipsilateral occult hernia in the surgical population was 8.26%. Ipsilateral occult hernia included indirect inguinal hernia, direct inguinal hernia, femoral hernia, obturator hernia, and spigelian hernia, among which the highest incidence was direct inguinal hernia (4.11%), followed by indirect inguinal hernia (2.45%). There was no difference in the incidence of ipsilateral occult hernia between males and females, but there were significant differences in the incidence of ipsilateral occult hernia, which decreased gradually with increasing age in patients younger than 70 years-old; there was no difference in incidence in patients over 70 years-old. There were significant differences in the incidence of ipsilateral occult hernia in the bilateral inguinal region between direct and femoral hernia, with the higher incidence found on the right side; in contrast, there was no difference in the incidence of indirect inguinal hernia in the bilateral inguinal region. There was no difference in the ability of experienced physicians to detect ipsilateral occult inguinal hernias, either professionally or by surgery. CONCLUSIONS: Ipsilateral occult inguinal hernia has a higher incidence in patients with inguinal hernia, especially older patients; therefore, it is necessary for experienced surgeons to carefully detect for possible occult hernia during the operation and in elderly patients.

Function of ghrelin and ghrelin receptors in the network regulation of gastric motility.

Numerous previous studies have demonstrated that ghrelin promotes gastric motility when administered peripherally. This effect appears to be regulatory but not directly stimulatory, and therefore may involve a number of complex mechanisms. In the periphery, ghrelin may affect gastric motility through intercellular networks among interstitial cells of Cajal, myenteric nerve cells and smooth muscle cells. The aim of the present study was to investigate the effects and possible mechanisms underlying this hypothesis. The effects of ghrelin on the contraction force of gastric antrum smooth muscle strips of rats were studied in the presence or absence of carbachol (CCh), [D­Lys3]­GHRP­6, atropine, tetrodotoxin (TTX) and nimodipine in vitro. The expression of ghrelin receptors (GHS­Rs) on different cell types in gastric muscle layers was observed by means of immunofluorescence. Ghrelin enhanced smooth muscle strip contraction induced by CCh, but when CCh was absent, this effect was eliminated. Atropine and nimodipine eradicated the muscle strip contraction enhanced by ghrelin, while [D­Lys3]­GHRP­6 was only able to partly block this effect and TTX had no effect on muscle strip contraction. It was identified that ghrelin had no effect on the contractive rhythm of the strips. GHS­R1s were located differentially depending on the cell type, including myenteric nerve cells, interstitial cells of Cajal and smooth muscle cells. In conclusion the present study demonstrated that ghrelin may act as an adjuvant to regulate gastric smooth muscle contraction induced by CCh through GHS­R1s, which are expressed on myenteric nerve cells, Cajal cells and smooth muscle cells. Ghrelin may exert its effects by influencing the functional status of different cell types in the gastric muscle layer to subsequently enhance the contractive effect of cholinergic neurotransmitters and enhance gastric motility.

Gastric motility in ghrelin receptor knockout mice.

The aim of this study was to investigate the effects and possible mechanisms of ghrelin receptor (GHS-R) deficiency on gastric motility in GHS-R deficient (Ghsr-/-) mice. Ghsr-/- and control (Ghsr+/+) mice were genotyped by PCR. The percentage of gastric emptying (GE%) was calculated following the intraperitoneal adminis-tration of ghrelin. In vitro, the contractile response of smooth muscle strips to ghrelin and electrical field stimulation (EFS) and the intraluminal pressure change of isolated stomach to carbachol were observed in an organ bath. The staining of nerve cells in the gastric muscle layer was performed by immunofluorescence. Delayed gastric emptying was observed in the Ghsr-/- mice; ghrelin enhanced the GE% in the Ghsr+/+ mice but had no effect on the GE% in the Ghsr-/- mice. In vitro, the response of the strips to ghrelin and EFS and the intraluminal pressure change to cabarchol was reduced in the Ghsr-/- mice. GHS-Rs were predominantly expressed on nerve cells in gastric muscle layers. The number of nerve cells was observed to be decreased in the Ghsr-/- mice. The delayed gastric emptying may relate to the loss of GHS-Rs and the reduction in the number of nerve cells in the gastric muscle layers of the GHS-R-deficient mice.

[Growth hormone secretagogue participates in two-way regulation of the motility of small intestinal smooth muscle in rats].

OBJECTIVE: To investigate the effect of growth hormone secretagogue(ghrelin) on the contraction and relaxation of small intestinal smooth muscle in rats and its mechanism. METHODS: Twenty-four vagotomized rats were injected intraperitoneally with different concentrations of ghrelin (0, 20, 40, 80 µg/kg). The small intestinal transit were observed. The effect of ghrelin(0.01, 0.1, 0.5, 1.0 µmol/L) on the contraction and relaxation of rat small intestinal smooth muscle strips was observed in vitro in the presence of carbachol(50 nmol/L), the locations of ghrelin receptors(GHS-R1a) on different cells in small intestinal muscle layers were detected by immunofluorescence. RESULTS: With the increase of concentrations, ghrelin elevated the percentage of small intestinal transit[(25.4±1.0)%, (33.7±1.9)%, (39.3±2.4)%, (44.7±2.1)%] in a dose-dependent manner, and the differences were statistically significant among groups(P<0.05). Ghrelin could also enhance the contraction [(67.0±2.4)%,(149.5±3.3)%, (187.1±4.7)%, (213.5±3.4)%] and relaxation[(35.3±1.1)%, (62.9±3.8)%, (79.6±2.7)%, (94.6±2.2)%] of smooth muscle strips mediated by Cch in a dose-dependent manner, and the differences were statistically significant among groups(P<0.05). Immunofluorescence revealed that ghrelin receptors mainly located on membrane of the nerve cells in the muscle layers, while no receptors were observed on membrane of the smooth muscle cells. CONCLUSION: Ghrelin may enhance the effect of the contraction and relaxation of the rat small intestinal smooth muscle mediated by cholinergic neurotransmitters by activating the nerve cells in the enteric plexus.

Down-regulation of ghrelin receptors in the small intestine delays small intestinal transit in vagotomized rats.

Vagal nerve injury may occur in esophageal and gastric surgeries. The aim of this study was to observe the effects of ghrelin on small intestinal motility upon vagal nerve injury and the possible co-relationship between changes in ghrelin receptor expression in the small intestine and delayed small intestinal transit after vagotomy. The effects of intraperitoneal administration of ghrelin (20, 40 and 80 µg/kg) and the ghrelin receptor antagonist [D-Lys3]-GHRP-6 (1.5 µmol/kg) on small intestinal transit were studied in control and vagotomized rats in vivo. The effects of ghrelin (0.01, 0.1, 0.5, 1.0 and 2.0 µmol/l) on the contraction force of smooth muscle strips from the jejunum were studied in the presence or absence of carbachol (50 nmol/l) and [D-Lys3]-GHRP-6 (10 µmol/l) in vitro. Ghrelin receptor expression was assessed in intestinal muscle layers by means of Western blotting. The results indicated that ghrelin dose-dependently increased small intestinal transit in the control and model rats. In addition, ghrelin enhanced smooth muscle strip contraction induced by carbachol. Ghrelin receptor antagonist [D-Lys3]-GHRP-6 blocked the effect of ghrelin. Ghrelin receptor expression in the small intestinal muscle layers was down-regulated in the vagotomized rats. Down-regulation of growth hormone secretagogue receptor 1a in small intestinal muscle layers, which affected the function of ghrelin, may be one of the mechanisms behind delayed small intestinal transit after vagotomy.

[Effect of the expression of ghrelin receptors on the postoperative underpowered small intestinal motility in rats].

OBJECTIVE: To investigate the effect of the expression of ghrelin receptors on the postoperative small intestine dysmotility in rat models. METHODS: The effect of different concentrations of ghrelin (0, 0.01, 0.1, 0.5, 1.0 µmol/L) on the contraction of smooth muscle strips of rat small intestine in the presence or absence of carbachol was observed in vitro. End-to-side anastomosis was performed in the study group and sham controls were used. The expression of ghrelin receptors(GHS-R1a) in small intestine muscle layers was detected by immunohistochemistry and Western blot. RESULTS: In vitro, ghrelin enhanced the contraction of smooth muscle strips in the presence of carbachol, and the differences in contraction induced by different concentrations of ghrelin(0.1, 0.5, 1.0 µmol/L) were statistically significant [(223±18)%, (245±22)%, (264±25)%, P<0.01]. Immunohistochemistry study showed that GHS-R1a mainly located in the muscular layer of the bowel wall. The expression of GHS-R1a in the circular and longitudinal muscle was significantly weaker than that in the control group. The expression of ghrelin receptors after surgery was down-regulated in the study group, which was lower than that in the control group(0.51±0.02 vs. 0.71±0.01, P<0.01). CONCLUSION: Down regulation of ghrelin receptors in small intestine muscle layers may contribute to the occurrence of small intestine dysmotility after intestinal surgery.