Pregnenolone and dexamethasone, modulators of cytochrome P450-3A, not increase but reduce urinary alpha-CEHC excretion in rats

Analysis and Prediction of Subway Tunnel Surface Subsidence Based on Internet of Things Monitoring and BP Neural Network

With the acceleration of the urban development process and the rapid growth of China's population, the subway has become the first choice for people to travel, and the urban underground space has been continuously improved. The subway construction has become the focus of urban underground space development in the 21st century. During the construction of subway tunnels, the problem of surface settlement will inevitably be caused, and the problem of surface settlement will have a certain safety impact on the safe use of surface buildings. The impact of surface construction is predicted, so as to select the best construction technology and avoid the problem of surface subsidence to the greatest extent. On the basis of analyzing the principle of surface subsidence, this paper studies the optimal control strategy and process of subsidence in subway tunnel engineering. The research results of the article show the following. (1) The two sections of the pebble soil layer have basically the same subsidence trend. Among them, the first section has a larger settlement amplitude and both sides are steeper. The second section is mainly cobble clay soil. The pebble layer has good mechanical properties. If it can be well filled, its stability will be improved. The comparative analysis of the two sections shows that with the increase of the soil cover thickness, the maximum subsidence at the surface gradually decreases. The reason is that when the stratum loss is the same, the greater the soil cover thickness, the greater the settlement width. Sections 2 and 3 of a single silty clay have relatively close settlement laws, and the settlement changes on both sides of the tunnel are similar. (2) The surface subsidence caused by the excavation of the side hole accounts for more than 50% of the total surface subsidence, and the width of the settlement tank after the excavation of the side hole is increased by 8–10 meters compared with the excavation of the middle hole. (3) The prediction error of the BP neural network model proposed in this paper is the lowest among the four models, whether it is the prediction of the cumulative maximum surface subsidence or the location of the cumulative maximum surface subsidence, and the average relative error of the cumulative maximum surface subsidence is 3.27%, the root mean square error is 3.87, the average relative error of the location of the cumulative maximum surface subsidence is 7.96%, and the root mean square error is 21.06. In the prediction process of the cumulative maximum surface subsidence, the prediction error value of the Elman neural network is relatively large, and the GRNN generalized neural network and RBF neural network have no significant changes; in the process of predicting the position where the cumulative maximum surface subsidence occurs, the prediction error value of RBF neural network is maximum.

Testosterone represses urinary excretion of the alpha-tocopherol metabolite alpha-carboxymethylhydroxychroman in rats

In rats, plasma and tissue concentrations of α-tocopherol, a predominant form of vitamin E in mammals, are known to differ between the sexes. In order to examine sex differences in α-tocopherol metabolism, we investigated urinary excretion of the α-tocopherol metabolite α-carboxymethylhydroxychroman (α-CEHC) using Wistar rats. First, we measured α-CEHC in urine of 9-week-old male and female rats in basal and α-tocopherol-administered conditions. We observed that female rats excrete significantly more α-CEHC than male rats via urine. This sex difference was observed in matured 9-week-old rats but not in premature 3-week-old rats, suggesting that the difference may relate to sex hormones. In order to confirm this, we examined the effect of ovariectomy and orchiectomy on female and male rats, respectively. The results of castration clearly demonstrated that orchiectomy enhanced urinary excretion of α-CEHC, supporting the hypothesis that testosterone repressed α-tocopherol metabolism. We then administered testosterone propionate to orchiectomized rats and observed down-regulation of α-CEHC excretion. Taken together, these results indicate that testosterone represses the metabolism and urinary excretion of α-tocopherol in rats. This is the first report to show a sex-dependent difference in urinary excretion rate of an α-tocopherol metabolite and contributes to the understanding of vitamin E metabolism.

Mechanisms for the prevention of vitamin E excess

The liver is at the nexus of the regulation of lipoprotein uptake, synthesis, and secretion, and it is the site of xenobiotic detoxification by cytochrome P450 oxidation systems (phase I), conjugation systems (phase II), and transporters (phase III). These two major liver systems control vitamin E status. The mechanisms for the preference for α-tocopherol relative to the eight naturally occurring vitamin E forms largely depend upon the liver and include both a preferential secretion of α-tocopherol from the liver into the plasma for its transport in circulating lipoproteins for subsequent uptake by tissues, as well as the preferential hepatic metabolism of non-α-tocopherol forms. These mechanisms are the focus of this review.

Elevation of tissue α-tocopherol levels by conjugated linoleic acid in C57BL/6J mice is not associated with changes in vitamin E absorption or α-carboxyethyl hydroxychroman production

OBJECTIVE

Conjugated linoleic acid (CLA) decreases adipose mass and increases vitamin E levels in the liver and adipose tissue in mice. The aim of the present study was to examine the mechanism by which CLA alters vitamin E levels in tissues and antioxidant activity in mice.

METHODS

C57BL/6J mice were divided into three groups and fed 5% lipid as soybean oil alone (control group), 4% soybean oil supplemented with 1% CLA (CLA group), or 5% lipid with a vitamin E supplement (VE group) for 4 wk.

RESULTS

The CLA and VE diets resulted in a significant increase in the α-tocopherol concentration in all tissues examined, i.e., the liver, kidney, testis, spleen, heart, lung, and adipose tissue (P < 0.05). Levels of thiobarbituric acid-reactive substances in the kidney, testis, heart, lung, and adipose tissue were lower in the CLA and VE groups than in the control group (P < 0.05). CLA did not alter the absorption rate of vitamin E or α-carboxyethyl hydroxychromans levels in the liver and plasma. The CLA diet induced a significant increase in α-tocopherol transfer protein and mRNA levels in the liver. CLA resulted in a decrease in catalase and glutathione peroxidase activities and peroxisome proliferator α mRNA levels but had no effect on levels of mRNAs for other nuclear transcription factors in the liver.

CONCLUSION

The increase in vitamin E status in CLA-fed mice is not due to altered absorption and metabolism of vitamin E but might be related to the induction of α-tocopherol transfer protein expression in the liver. The regulation of the activities of catalase and glutathione peroxidase by CLA is not mediated by vitamin E accumulation in the liver.

Effects of Oxidized Frying Oil on Proteins Related to alpha-Tocopherol Metabolism in Rat Liver

An oxidized frying oil (OFO) diet has been reported to induce an increase in lipid peroxidation and a reduction in vitamin E status in animal tissues. This study was performed to investigate how vitamin E metabolism is influenced by OFO. Male Wistar rats were divided into three groups, a control group (CO) and two OFO-fed groups (OF and OFE). The diet of the OFE group was supplemented with an extra 50 mg/kg of alpha-tocopherol acetate and thus contained twice as much vitamin E as that of the OF group. After six weeks on these diets, liver alpha-tocopherol levels in the OF group were the significantly lowest among the three groups. Excretion of the alpha-tocopherol metabolite, alpha-carboxyethyl hydroxychroman (alpha-CEHC) in the urine was significantly lower in the OF group than in the other two groups. There were no significant differences in protein levels of alpha-tocopherol transfer protein (alpha-TTP) and multidrug resistance protein among the three groups. Protein levels of cytochrome P450 monooxygenase (CYP) 3A, CYP4A, and catalase were markedly increased in both groups on the OFO diet. This suggests that an OFO diet may interfere with medicine metabolism and needs further investigation.

Effects of pregnenolone-16alpha-carbonitrile on vitamin E status and protein levels of antioxidant enzymes in male rats fed a vitamin E-supplemented diet

The aim of this study was to evaluate the effects of the administration of pregnenolone-16alpha-carbonitrile (PCN), an inducer of the cytochrome P450 3A gene in rats, on vitamin E status and antioxidant enzyme protein levels in rats fed a vitamin E-supplemented diet. Two groups of male Wistar rats were fed for 3 weeks with a basal diet containing 50 ppm of alpha-tocopherol or the same diet containing 10 times more alpha-tocopherol. In the final 3 days, each group was divided into two subgroups which were given a single daily intraperitoneal injection of PCN at 75 mg/kg (groups PCN and PCN+VE) or DMSO (groups DS and DS+VE). PCN treatment alone significantly reduced the alpha-tocopherol content of the liver and plasma and this effect was prevented by supplementation with 10-fold more alpha-tocopherol. alpha-Tocopherol levels in the kidneys, lung, heart, and testes were significantly higher in both vitamin E-supplemented groups than in the control groups. TBARS levels in the liver and lung were significantly increased in both PCN-treated groups, as shown by two-way ANOVA analysis. PCN also caused a significant reduction in protein levels of catalase and glutathione peroxidase (GPx) in both groups. Dietary vitamin E supplementation caused a decrease in liver protein levels of GPx and superoxide dismutase, but not catalase, in both groups and protected against PCN-induced lipid peroxidation, which was caused by CYP3A induction and a reduction in antioxidant enzyme levels.

Metabolomics reveals a novel vitamin E metabolite and attenuated vitamin E metabolism upon PXR activation

Pregnane X receptor (PXR) is an important nuclear receptor xenosensor that regulates the expression of metabolic enzymes and transporters involved in the metabolism of xenobiotics and endobiotics. In this study, ultra-performance liquid chromatography (UPLC) coupled with electrospray time-of-flight mass spectrometry (TOFMS), revealed altered urinary metabolomes in both Pxr-null and wild-type mice treated with the mouse PXR activator pregnenolone 16alpha-carbonitrile (PCN). Multivariate data analysis revealed that PCN significantly attenuated the urinary vitamin E metabolite alpha-carboxyethyl hydroxychroman (CEHC) glucuronide together with a novel metabolite in wild-type but not Pxr-null mice. Deconjugation experiments with beta-glucuronidase and beta-glucosidase suggested that the novel urinary metabolite was gamma-CEHC beta-D-glucoside (Glc). The identity of gamma-CEHC Glc was confirmed by chemical synthesis and by comparing tandem mass fragmentation of the urinary metabolite with the authentic standard. The lower urinary CEHC was likely due to PXR-mediated repression of hepatic sterol carrier protein 2 involved in peroxisomal beta-oxidation of branched-chain fatty acids (BCFA). Using a combination of metabolomic analysis and a genetically modified mouse model, this study revealed that activation of PXR results in attenuated levels of the two vitamin E conjugates, and identification of a novel vitamin E metabolite, gamma-CEHC Glc. Activation of PXR results in attenuated levels of the two vitamin E conjugates that may be useful as biomarkers of PXR activation.