Developmental changes in hepatic antioxidant capacity are age-and sex-dependent

External Evaluation of Population Pharmacokinetic Models of Busulfan in Chinese Adult Hematopoietic Stem Cell Transplantation Recipients

Objective: Busulfan (BU) is a bi-functional DNA-alkylating agent used in patients undergoing hematopoietic stem cell transplantation (HSCT). Over the last decades, several population pharmacokinetic (pop PK) models of BU have been established, but external evaluation has not been performed for almost all models. The purpose of the study was to evaluate the predictive performance of published pop PK models of intravenous BU in adults using an independent dataset from Chinese HSCT patients, and to identify the best model to guide personalized dosing.

Methods: The external evaluation methods included prediction-based diagnostics, simulation-based diagnostics, and Bayesian forecasting. In prediction-based diagnostics, the relative prediction error (PE%) was calculated by comparing the population predicted concentration (PRED) with the observations. Simulation-based diagnostics included the prediction- and variability-corrected visual predictive check (pvcVPC) and the normalized prediction distribution error (NPDE). Bayesian forecasting was executed by giving prior one to four observations. The factors influencing the model predictability, including the impact of structural models, were assessed.

Results: A total of 440 concentrations (110 patients) were obtained for analysis. Based on prediction-based diagnostics and Bayesian forecasting, preferable predictive performance was observed in the model developed by Huang et al. The median PE% was -1.44% which was closest to 0, and the maximum F₂₀ of 57.27% and F₃₀ of 72.73% were achieved. Bayesian forecasting demonstrated that prior concentrations remarkably improved the prediction precision and accuracy of all models, even with only one prior concentration.

Conclusion: This is the first study to comprehensively evaluate published pop PK models of BU. The model built by Huang et al. had satisfactory predictive performance, which can be used to guide individualized dosage adjustment of BU in Chinese patients.

Nutritional impact of mycotoxins in food animal production and strategies for mitigation

Mycotoxins are toxic secondary metabolites produced by filamentous fungi that are commonly detected as natural contaminants in agricultural commodities worldwide. Mycotoxin exposure can lead to mycotoxicosis in both animals and humans when found in animal feeds and food products, and at lower concentrations can affect animal performance by disrupting nutrient digestion, absorption, metabolism, and animal physiology. Thus, mycotoxin contamination of animal feeds represents a significant issue to the livestock industry and is a health threat to food animals. Since prevention of mycotoxin formation is difficult to undertake to avoid contamination, mitigation strategies are needed. This review explores how the mycotoxins aflatoxins, deoxynivalenol, zearalenone, fumonisins and ochratoxin A impose nutritional and metabolic effects on food animals and summarizes mitigation strategies to reduce the risk of mycotoxicity.

Effect of GSTA1 Variants on Busulfan-Based Conditioning Regimen Prior to Allogenic Hematopoietic Stem-Cell Transplantation in Pediatric Asians

Busulfan is widely used as a chemotherapy treatment before hematopoietic stem-cell transplantation (HSCT). However, the response of busulfan is highly variable and unpredictable, whereby the pharmacogenetic interference of glutathione S-transferase (GST) has strong evidence in Caucasians and some adult Asians but not in pediatric Asian patients. This study was aimed at investigating the associations of GST genetic polymorphisms with variations in the pharmacokinetic (PK) properties of busulfan in pediatric Asian patients. This retrospective cohort study recruited 92 pediatric patients. The polymorphism of GSTA1 was genotyped by Sanger sequencing, and GSTM1 and GSTP1 were genotyped by real-time PCR. Drug concentration and PK estimation were identified using an LC-MS/MS method and a noncompartmental model. Statistical analysis was performed by R software. Out of 92 patients, 48 (53%) were males, the mean age was 8.4 ± 5.12 years old, and the average weight was 26.52 ± 14.75 kg. The allele frequencies of GSTA1*B and of GSTM1 and GSTP1* deletions were 16.9%, 68.5%, and 21.2%, respectively. Patients with GSTA1*B had a statistically significant impact on the PK of busulfan, whereas those with GSTM1 and GSTP1 did not (p > 0.05). The carriers of GSTA1*B showed a significant difference compared to noncarriers in terms of t1/2 (for first dose: 161.9 vs. 134.3 min, p = 0.0016; for second dose: 156.1 vs. 129.8, p = 0.012), CL (88.74 vs. 124.23 mL/min, p = 0.0089), Cmax (4232.6 vs. 3675.5 ng/mL, p = 0.0021), and AUC (5310.6 vs. 4177.1 µM/min, p = 0.00033). The augmentation of AUC was around 27.1% in patients carrying the GSTA1*B variant. The GSTA1 polymorphism was significantly associated with variations of the pharmacokinetic properties of busulfan treatment in pediatric Asian patients.

Impact of dietary supplementation with olive and thyme phenols on alpha-tocopherol concentration in the muscle and liver of adult Wistar rats

A preliminary study to evaluate the effect of dietary supplementation with olive phenols (oleuropein, hydroxytyrosol and secoiridoids), thyme phenols and a combination of these (5 mg per kg rat weight per day) on the α-tocopherol concentrations in the muscle and liver of healthy adult Wistar rats over 21 days was conducted. In addition, the excretion of α-tocopherol through the faeces was examined. The results demonstrated that the diet supplemented with some phenolic compounds of olive and thyme increased α-tocopherol (P < 0.05) in the liver of female rats, although the α-tocopherol content in the diet of all groups was identical. In addition, a synergic effect between the olive phenols and thyme was observed. Therefore, our study indicates a protective effect of olive and thyme phenols supplemented in the diet on α-tocopherol, resulting in a higher concentration of endogenous α-tocopherol in the rat liver.

Complexity of vitamin E metabolism

Bioavailability of vitamin E is influenced by several factors, most are highlighted in this review. While gender, age and genetic constitution influence vitamin E bioavailability but cannot be modified, life-style and intake of vitamin E can be. Numerous factors must be taken into account however, i.e., when vitamin E is orally administrated, the food matrix may contain competing nutrients. The complex metabolic processes comprise intestinal absorption, vascular transport, hepatic sorting by intracellular binding proteins, such as the significant α-tocopherol-transfer protein, and hepatic metabolism. The coordinated changes involved in the hepatic metabolism of vitamin E provide an effective physiological pathway to protect tissues against the excessive accumulation of, in particular, non-α-tocopherol forms. Metabolism of vitamin E begins with one cycle of CYP4F2/CYP3A4-dependent ω-hydroxylation followed by five cycles of subsequent β-oxidation, and forms the water-soluble end-product carboxyethylhydroxychroman. All known hepatic metabolites can be conjugated and are excreted, depending on the length of their side-chain, either via urine or feces. The physiological handling of vitamin E underlies kinetics which vary between the different vitamin E forms. Here, saturation of the side-chain and also substitution of the chromanol ring system are important. Most of the metabolic reactions and processes that are involved with vitamin E are also shared by other fat soluble vitamins. Influencing interactions with other nutrients such as vitamin K or pharmaceuticals are also covered by this review. All these processes modulate the formation of vitamin E metabolites and their concentrations in tissues and body fluids. Differences in metabolism might be responsible for the discrepancies that have been observed in studies performed in vivo and in vitro using vitamin E as a supplement or nutrient. To evaluate individual vitamin E status, the analytical procedures used for detecting and quantifying vitamin E and its metabolites are crucial. The latest methods in analytics are presented.

The Ontogeny and Population Variability of Human Hepatic NADPH Dehydrogenase Quinone Oxido-Reductase 1 (NQO1)

The NADPH dehydrogenase quinone oxido-reductase 1 (NQO1) enzyme is an antioxidant and metabolic enzyme that performs two electron reduction of quinones and other chemicals. Based on the physiologic role(s) of NQO1, we hypothesized that expression and activity of this enzyme would vary with age and other demographic variables. Cytosols from 117 archived human livers were investigated for changes in NQO1 with age, sex, obesity, and ethnicity. Protein expression but not activity of NQO1 was weakly negatively correlated with age (Spearman r = -0.2, P = 0.03). No sex differences were observed for either protein expression or activity and for ethnicity; Caucasians had greater NQO1 activity than Asians (P < 0.05). Overweight children had statistically significantly higher NQO1 activity as compared with ideal weight children (P < 0.05) although this difference was not observed in adults. These findings establish that NQO1 is approximately as active in children as adults. However, modeled NQO1 clearance (both allometric and physiologically based pharmacokinetics) predicted maturation at 23 to 26 years. This is almost certainly an overestimate, with error in the model resulting from a small sample size and inability to scale for age-related changes in hepatic cellularity and/or cytosolic protein content, and indicates a delay in reaching maximum clearance through the NQO1 pathway that is affected by physiologic development as much, or more than, biochemical development. Obesity may increase hepatic NQO1 activity in children, which is likely a protective mechanism in oxidative stress, but may also have significant implications for drug and chemical disposition in obese children.

Influence of glutathione S-transferase gene polymorphisms on busulfan pharmacokinetics and outcome of hematopoietic stem-cell transplantation in thalassemia pediatric patients

Hematopoietic stem-cell transplantation (HSCT) is currently the only curative therapeutic option for the treatment of thalassemia. In spite of the high cure rate, HSCT can lead to life-threatening adverse events in some patients. Busulfan (Bu) is a key component of the conditioning regimen prior to HSCT. Inter-individual differences in Bu pharmacokinetics (PK) are hypothesized to influence Bu efficacy and toxicity. Since Bu is mainly metabolized by glutathione S-transferase (GST), we investigated the relationship of GSTA1 and GSTM1 genotypes with first-dose PK and HSCT outcomes in 44 children with thalassemia intermedia and thalassemia major. All children received a myeloablative conditioning regimen with IV Bu. Association analysis revealed a relationship between GSTA169C>T (or haplotype *A/*B) and first Bu dose PK that was dependent on sex and Pesaro risk classification (PRC). Among female patients and patients with PRC I-II, homozygous individuals for the GSTA1T-69 allele defining haplotype *B, had higher Bu exposure and lower clearance (P⩽0.01). Association with HSCT outcomes showed that patients with the GSTM1 null genotypes had higher occurrence of regimen-related toxicity (P=0.01). These results suggest that GST genotypes could be useful to tailor the first Bu dose accordingly to improve HSCT outcome.

Application of elderly donor for liver transplantation

Recently, much more attention has been paid on application of elderly donor due to the shortage of organs. Although liver quality of elderly donors may be sub-optimal comparing with that from younger donors, primary non-function of a liver graft is a rare event. On the other hand, long-term graft and recipient survival for usage of elderly grafts has become a major concern and focus of research. Many transplant centers have changed the upper limit of donor age from previous 50 to 70 or even 75-year-old and achieved good graft function. Although some scholars believed that liver transplant using elderly grafts was associated with high probability of delayed liver function recovery, graft loss and hepatitis C recurrence, reports from several transplant centers document that long-term survival of grafts and recipients may be significantly improved through certain screening of donors and recipients before transplant. In conclusion, it is very important and relatively safe to use grafts from elderly donors to expand the donor pool. However, elderly donors and corresponding recipients must be carefully selected before transplant. The long-term effect of advanced age on grafts and recipients need to be evaluated through a comprehensive and long-term in-depth observation.

Serum superoxide dismutase activity in acute and chronic paediatric liver diseases

BACKGROUND AND STUDY AIMS

Measuring serum superoxide dismutase (SOD) levels in infants and children having acute or chronic liver disease of different aetiologies, and correlating these levels with disease aetiology in an attempt to clarify the role of SOD as an antioxidant in these diseases.

PATIENTS AND METHODS

We prospectively enrolled 58 infants and children and divided them into four groups: Group I, 24 patients with surgical cholestasis; group II, 11 patients with medical cholestasis; group III, nine patients with autoimmune chronic hepatitis; and group IV, 14 patients with viral hepatitis. Forty healthy age- and sex-matched children served as controls. Serum SOD activity was measured in all patients and controls using spectrophotometry.

RESULTS

The level of SOD showed a statistically significant increase in patients with medical cholestasis compared to healthy controls (p<0.0001). SOD activity of other groups showed no significant difference compared to controls.

CONCLUSIONS

Significantly increased serum SOD in infants and children with medical cholestasis is probably consequent to its increase in liver tissue in response to the liberation of reactive oxygen species. This suggests that products of free radical reactions might be involved in the pathogenesis and/or progression of medical cholestasis, and that SOD might attempt to minimise the liver injury.

Serum oxidant and antioxidant status following an all-out 21-km run in adolescent runners undergoing professional training--a one-year prospective trial

This study investigated the 1-year longitudinal effect of professional training in adolescent runners on redox balance during intense endurance exercise. Changes in selected serum oxidant and antioxidant status in response to a 21-km running time trial in 10 runners (15.5 ± 1.3 years) undergoing professional training were evaluated twice in 12 months (pre- and post-evaluation). Venous blood samples were collected immediately before and 4-h following the 21-km run for analysis of serum concentrations of thiobarbituric acid-reactive substances (TBARS), xanthine oxidase (XO), catalase (CAT), reduced glutathione (GSH), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC). In pre-evaluation trial, serum TBARS and SOD decreased after the 21-km run (p < 0.05) while XO, GSH, CAT and TAOC were unchanged. In post-evaluation trial, serum TBARS and SOD decreased, whereas XO and CAT increased post-exercise (p < 0.05). Furthermore, pre-exercise serum T-AOC, post-exercise serum XO, CAT, T-AOC (p < 0.05), and GSH (p = 0.057) appeared to be higher than the corresponding pre-evaluation values. The current findings suggest that a professional training regime in adolescent runners is not likely to jeopardize the development of their antioxidant defense. However, uncertainties in the maintenance of redox balance in runners facing increased exercise-induced oxidative stress as a consequence of training-induced enhancement of exercise capacity await further elucidation.

Bone marrow cell transcripts from Fanconi anaemia patients reveal in vivo alterations in mitochondrial, redox and DNA repair pathways

Fanconi anaemia (FA) is a genetic cancer predisposition disorder associated with cytogenetic instability, bone marrow failure and a pleiotropic cellular phenotype, including low thresholds of responses to oxidative stress, cross-linking agents and selected cytokines. This study was aimed at defining the scope of abnormalities in gene expression using the publicly available FA Transcriptome Consortium (FTC) database (Gene Expression Omnibus, 2009 and publicly available as GSE16334). We evaluated the data set that included transcriptomal analyses on RNA obtained from low-density bone marrow cells (BMC) from 20 patients with FA and 11 healthy volunteers, by seeking to identify changes in expression of over 22,000 genes, including a set of genes involved in: (i) bioenergetic pathways; (ii) antioxidant activities; (iii) response to stress and metal-chelating proteins; (iv) inflammation-related cytokines and (v) DNA repair. Ontological analysis of genes expressed at magnitudes of 1.5-fold or greater demonstrated significant suppression of genes in the categories of (i) energy metabolism; (ii) antioxidant activities; and (iii) stress and chelating proteins. Enhanced expression was found for 16 of 26 genes encoding inflammatory cytokines. A set of 20 of 21 transcripts for DNA repair activities were down-regulated; four of these transcripts related to type II topoisomerase. The data provide evidence for alterations in gene regulation of bioenergetic activities, redox-related activities, stress and metal-chelating proteins, and of some selected DNA repair activities in patients with FA.

The effect of weight loss on pediatric nonalcoholic Fatty liver disease

This study evaluated the effect of weight loss on pediatric nonalcoholic fatty liver disease (NAFLD). Subjects included 81 overweight NAFLD patients referred to two pediatric gastroenterologists from 2000 to 2010. Data on subjects were obtained from review of medical charts. The effect of weight loss was assessed at 1–4 months, 5–8 months, 9–12 months, and beyond one year as the change in weight, BMI z-score (for age-and-sex), and alanine aminotransferase and the relationship between the change in body weight and BMI z-score, and the change in alanine aminotransferase. Subjects were mostly obese (99%), male (86%), and Asian (63%) and had median age of 14.1 (11.2–16.2) years and alanine aminotransferase of 105 (78–153) U/L at referral. Alanine aminotransferase decreased 32 ± 66 (P = 0.016), 30 ± 65 (P = 0.134), 37 ± 75 (P = 0.0157), and 45 ± 69 (P = 0.014) for subjects with follow-up data at 1–4 months (n = 47), 5–8 months (n = 26), 9–12 months (n = 19), and beyond one year (n = 19), respectively. During these time periods, neither was body weight (−0.2 to +7.1 kg) or BMI z-score (−0.12 to −0.05) significantly reduced, nor were changes in these variables associated with the change in alanine aminotransferase. These findings suggest that weight and BMI z-score may not be sufficient indicators of treatment response in pediatric NAFLD patients.

Liver disease among children in Hawai'i diagnosed with metabolic syndrome

The purpose of this study was to evaluate the prevalence of and factors related to liver disease among children in Hawai'i with metabolic syndrome. The medical charts of children diagnosed with metabolic syndrome by an outpatient endocrinologist between January 2000 and December 2010 were reviewed. Liver disease prevalence was estimated based on serum alanine aminotransferase (ALT) levels, which were then assessed for associations with demographic (age, gender, ethnicity), anthropometric (body mass index), biochemical (fasting blood glucose, hemoglobin A1c, triglycerides, and total, LDL- and HDL-cholesterol), and clinical (blood pressure) characteristics of subjects. Serum ALT was available for 167 of the 195 subjects. The proportion of subjects with liver disease (105/167 [63%]) was greater than many traditional features of metabolic syndrome including hypertriglyceridemia (73/177 [41%]), hypertension (37/194 [19%]) and hyperglycemia (37/170 [22%]). Serum ALT values were positively associated with age (P=.030), and liver disease was more common among boys than girls (62/91 [68%] vs 43/76 [57%]), although this difference was not statistically significant (P=.123). There was a significant difference in liver disease across ethnicities (P=.029), and appeared to be more common in children with Pacific Islander surnames (14/16 [88%]), and less common in children with Hispanic surnames (7/20 [35%]). Diastolic blood pressure was the only obesity-related disease parameter associated with serum ALT after adjusting for age and gender (P=.018). In conclusion, liver disease was common among children diagnosed with metabolic syndrome in Hawai'i. Age, gender, and ethnicity may be important determinants of liver disease risk, and should be investigated further.