Altered xanthine oxidase and N-acetyltransferase activity in obese children

Hemin and iron increase synthesis and trigger export of xanthine oxidoreductase from hepatocytes to the circulation

We recently reported a previously unknown salutary role for xanthine oxidoreductase (XOR) in intravascular heme overload whereby hepatocellular export of XOR to the circulation was identified as a seminal step in affording protection. However, the cellular signaling and export mechanisms underpinning this process were not identified. Here, we present novel data showing hepatocytes upregulate XOR expression/protein abundance and actively release it to the extracellular compartment following exposure to hemopexin-bound hemin, hemin or free iron. For example, murine (AML-12 cells) hepatocytes treated with hemin (10 μM) exported XOR to the medium in the absence of cell death or loss of membrane integrity (2.0 ± 1.0 vs 16 ± 9 μU/mL p < 0.0001). The path of exocytosis was found to be noncanonical as pretreatment of the hepatocytes with Vaculin-1, a lysosomal trafficking inhibitor, and not Brefeldin A inhibited XOR release and promoted intracellular XOR accumulation (84 ± 17 vs 24 ± 8 hemin vs 5 ± 3 control μU/mg). Interestingly, free iron (Fe2+ and Fe3+) induced similar upregulation and release of XOR compared to hemin. Conversely, concomitant treatment with hemin and the classic transition metal chelator DTPA (20 μM) or uric acid completely blocked XOR release (p < 0.01). Our previously published time course showed XOR release from hepatocytes likely required transcriptional upregulation. As such, we determined that both Sp1 and NF-kB were acutely activated by hemin treatment (∼2-fold > controls for both, p < 0.05) and that silencing either or TLR4 with siRNA prevented hemin-induced XOR upregulation (p < 0.01). Finally, to confirm direct action of these transcription factors on the Xdh gene, chromatin immunoprecipitation was performed indicating that hemin significantly enriched (∼5-fold) both Sp1 and NF-kB near the transcription start site. In summary, our study identified a previously unknown pathway by which XOR is upregulated via SP1/NF-kB and subsequently exported to the extracellular environment. This is, to our knowledge, the very first study to demonstrate mechanistically that XOR can be specifically targeted for export as the seminal step in a compensatory response to heme/Fe overload.

Pharmacokinetics of obese adults: Not only an increase in weight

Obesity is a pathophysiological state defined by a body mass index > 30 kg/m2 and characterized by an adipose tissue accumulation leading to an important weight increased. Several pathologies named comorbidities such as cardiovascular disease, type 2 diabetes and cancer make obesity the fifth cause of death in the world. Physiological changes impact the four main phases of pharmacokinetics of some drugs and leads to an inappropriate drug-dose. For absorption, the gastrointestinal transit is accelerated, and the gastric empty time is shortened, that can reduce the solubilization and absorption of some oral drugs. The drug distribution is probably the most impacted by the obesity-related changes because the fat mass (FM) increases at the expense of the lean body weight (LBW), leading to an important increase of the volume of distribution for lipophilic drugs and a low or moderately increase of this parameter for hydrophilic drugs. This modification of the distribution may require drug-dose adjustments. By various mechanisms, the metabolism and elimination of drugs are impacted by obesity and should be considered as similar or lower than that non-obese patients. To better understand the necessary drug-dose adjustments in obese patients, a narrative review of the literature was conducted to highlight the main elements to consider in the therapeutic management of adult obese patients.

Malondialdehyde as an independent predictor of body mass index in adolescent girls

Background: Given the fact that the studies that examined oxidative stress in relation to obesity that included late adolescents are scarce and show inconclusive results we aimed to investigate a wide spectrum of nitro-oxidative stress biomarkers i.e., malondialdehyde (MDA), xanthine oxidase (XO), xanthine oxidoreductase (XOD), xanthine dehydrogenase (XDH), advanced oxidation protein products (AOPP) and nitric oxide products (NOx), as well as an antioxidative enzyme, i.e., catalase (CAT) in relation with obesity in the cohort of adolescent girls ages between 16 and 19 years old. Methods: A total of 59 teenage girls were included in this cross-sectional study. Binary logistic regression analysis was performed to examine possible associations between biochemical and nitro-oxidative stress markers and body mass index (BMI). Results: There were not significant differences between oxidative stress markers between normal weight and overweight/obese girls (i.e., AOPP, XOD, XO, XDH) and CAT, except for MDA (p<0.001) and NOx (p=0.010) concentrations which were significantly higher in overweight/obese adolescent girls. Positive associations were evident between BMI and high sensitivity C-reactive protein (hsCRP) (OR=2.495), BMI and uric acid (OR=1.024) and BMI and MDA (OR=1.062). Multivariable binary regression analysis demonstrated significant independent associations of BMI and hsCRP (OR=2.150) and BMI and MDA (OR=1.105). Even 76.3% of the variation in BMI could be explained with this Model. Conclusions: Inflammation (as measured with hsCRP) and oxidative stress (as determined with MDA) independently correlated with BMI in teenage girls.

Chemotherapy and Anticancer Drugs Adjustment in Obesity: A Narrative Review

BACKGROUND

Obese individuals have higher rates of cancer incidence and cancer- related mortality. The worse chemotherapy outcomes observed in this subset of patients are multifactorial, including the altered physiology in obesity and its impact on pharmacokinetics, the possible increased risk of underdosing, and treatment-related toxicity.

AIMS

The present review aimed to discuss recent data on physiology, providing just an overall perspective and pharmacokinetic alterations in obesity concerning chemotherapy. We also reviewed the controversies of dosing adjustment strategies in adult and pediatric patients, mainly addressing the use of actual total body weight and ideal body weight.

METHODS

This narrative review tried to provide the best evidence to support antineoplastic drug dosing strategies in children, adolescents, and adults.

RESULTS

Cardiovascular, hepatic, and renal alterations of obesity can affect the distribution, metabolism, and clearance of drugs. Anticancer drugs have a narrow therapeutic range, and variations in dosing may result in either toxicity or underdosing. Obese patients are underrepresented in clinical trials that focus on determining recommendations for chemotherapy dosing and administration in clinical practice. After considering associated comorbidities, the guidelines recommend that chemotherapy should be dosed according to body surface area (BSA) calculated with actual total body weight, not an estimate or ideal weight, especially when the intention of therapy is the cure.

CONCLUSION

The actual total body weight dosing appears to be a better approach to dosing anticancer drugs in both adults and children when aiming for curative results, showing no difference in toxicity and no limitation in treatment outcomes compared to adjusted doses.

Development and Evaluation of a Virtual Population of Children with Obesity for Physiologically Based Pharmacokinetic Modeling

BACKGROUND AND OBJECTIVE

While one in five children in the USA are now obese, and more than three-quarters receive at least one drug during childhood, there is limited dosing guidance for this vulnerable patient population. Physiologically based pharmacokinetic modeling can bridge the gap in the understanding of how pharmacokinetics, including drug distribution and clearance, changes with obesity by incorporating known obesity-related physiological changes in children. The objective of this study was to develop a virtual population of children with obesity to enable physiologically based pharmacokinetic modeling, then use the novel virtual population in conjunction with previously developed models of clindamycin and trimethoprim/sulfamethoxazole to better understand dosing of these drugs in children with obesity.

METHODS

To enable physiologically based pharmacokinetic modeling, a virtual population of children with obesity was developed using national survey, electronic health record, and clinical trial data, as well as data extracted from the literature. The virtual population accounts for key obesity-related changes in physiology relevant to pharmacokinetics, including increased body size, body composition, organ size and blood flow, plasma protein concentrations, and glomerular filtration rate. The virtual population was then used to predict the pharmacokinetics of clindamycin and trimethoprim/sulfamethoxazole in children with obesity using previously developed physiologically based pharmacokinetic models.

RESULTS

Model simulations predicted observed concentrations well, with an overall average fold error of 1.09, 1.24, and 1.53 for clindamycin, trimethoprim, and sulfamethoxazole, respectively. Relative to children without obesity, children with obesity experienced decreased clindamycin and trimethoprim/sulfamethoxazole weight-normalized clearance and volume of distribution, and higher absolute doses under recommended pediatric weight-based dosing regimens.

CONCLUSIONS

Model simulations support current recommended weight-based dosing in children with obesity for clindamycin and trimethoprim/sulfamethoxazole, as they met target exposure despite these changes in clearance and volume of distribution.

Independent and joint associations of body mass index, waist circumference, waist-height ratio and their changes with risks of hyperuricemia in middle-aged and older Chinese individuals: a population-based nationwide cohort study

Background

Previous reports regarding the predictive power of adiposity indices remain inconsistent, and longitudinal studies on this top are limited. The associations of hyperuricemia risk with changes in obesity status, as well as the joint effects of baseline adiposity indices and body adiposity change on hyperuricemia risk are not fully elucidated. This study aimed to explore the independent and joint associations of baseline adiposity indicators and body adiposity change with hyperuricemia risk among middle-aged and older population in China.

Methods

A total of 2895 participants aged ≥ 45 years from the baseline survey of the China Health and Retirement Longitudinal Study were followed up for 4 years. Anthropometric parameters (weight, height, and waist circumference) and serum uric acid were obtained using standard devices. Adjusted odds ratio and 95% confidential interval were calculated to estimate the associations between predictor variables and hyperuricemia risk using multivariate logistic regression.

Results

Of the 2895 participants, 293 (10.12%) cases of hyperuricemia were identified. Increased baseline body mass index (BMI), waist circumference, and waist-height ratio (WHtR) were significantly associated with higher risks of hyperuricemia. A slightly greater but non-significant area under the curve value was observed for waist circumference (0.622) than for BMI (0.611) and WHtR (0.614) (P = 0.447). Compared to subjects with stable adiposity status, participants with weight loss of ≥ 4 kg or waist circumference loss of ≥ 6 cm had a 56% or 55% lower risk of hyperuricemia, and those with weight gain of > 4 kg had a 1.62-fold higher risk of hyperuricemia. Compared to those without obesity, participants with incident or persistent obesity were more likely to develop hyperuricemia. Additionally, regardless of stable or increased weight/waist circumference during follow-up, individuals with obesity at baseline had a higher risk of incident hyperuricemia.

Conclusion

This study demonstrates that BMI, waist circumference, and WHtR equally predict the development of hyperuricemia, and weight loss and waist circumference reduction are favorable in preventing hyperuricemia.

How much does fat mass change affect serum uric acid levels among apparently clinically healthy Korean men?

Objective:

The aim of this study was to examine the impact of fat mass alteration on serum uric acid (SUA) levels in apparently clinically healthy men.

Methods:

We evaluated 27,387 men who consecutively underwent health check ups between 2015 and 2017. We assessed the likelihood of achieving a SUA level of <0.41 mmol/L and compared the SUA levels according to fat mass changes.

Results:

Compared with those without fat mass change (the reference group), the odds ratios (95% confidence interval) of achieving a SUA level of <0.41 mmol/L for fat mass decreases of ⩾2.5, 1.5–2.5, and 0.5–1.5 kg were 1.63 (1.45–1.82), 1.19 (1.06–1.34), and 1.07 (0.97–1.18), respectively, while those for a fat mass increase of ⩾2.5, 1.5–2.5, and 0.5–1.5 kg were 0.71 (0.64–0.78), 0.87 (0.79–0.97), and 0.95 (0.86–1.04), respectively. The corresponding beta-coefficients of SUA levels (mmol/L) were –0.26 [–0.29–(–0.23)], –0.12 [–0.16–(–0.09)], and –0.09 [–0.12–(–0.06)] for fat mass decreases of ⩾2.5, 1.5–2.5, and 0.5–1.5 kg, respectively. Every 1-kg fat mass reduction was associated with 9% increased odds of achieving the target SUA level. The multivariate SUA level difference per 1-kg fat mass gain was 2.97 µmol/L. Similar levels of association persisted among the prespecified subgroups.

Conclusion:

We quantitatively demonstrated that fat mass reduction contributes to a clinically relevant decrease in SUA levels and a significant increase in the likelihood of achieving target SUA levels. Our findings may help to provide clear clinical guidance on fat mass alteration to reduce SUA levels in patients with hyperuricemia.

The effect of obesity, macronutrients, fasting and nutritional status on drug-metabolizing cytochrome P450s: a systematic review of current evidence on human studies

BACKGROUND

Cytochrome P450s (CYPs) are a class of hemoproteins involved in drug metabolism. It has been reported that body composition, proportion of dietary macronutrients, fasting and nutritional status can interfere with the activity of drug-metabolizing CYPs.

OBJECTIVES

The present systematic review was conducted to summarize the effect of obesity, weight reduction, macronutrients, fasting and malnutrition on the CYP-mediated drug metabolism.

METHODS

PubMed (Medline), Scopus, Embase and Cochrane Library databases and Google Scholar were searched up to June 2020 to obtain relevant studies. The PRISMA guidelines were employed during all steps. Two reviewers independently extracted the information from the included studies. Studies investigating CYPs activity directly or indirectly through pharmacokinetics of probe drugs, were included. Increase in clearance (CL) or decrease in elimination half-life (t½) and area under the curve (AUC) of probe drugs were considered as increase in CYPs activity.

RESULTS

A total of 6545 articles were obtained through searching databases among which 69 studies with 126 datasets fully met the inclusion criteria. The results indicated that obesity might decrease the activity of CYP3A4/5, CYP1A2 and CYP2C9 and increase the activity of CYP2E1. The effect of obesity on CYP2D6 is controversial. Also, weight loss increased CYP3A4 activity. Moreover, CYP1A2 activity was decreased by high carbohydrate diet, increased by high protein diet and fasting and unchanged by malnutrition. The activity of CYP2C19 was less susceptible to alterations compared to other CYPs.

CONCLUSION

The activity of drug-metabolizing CYPs are altered by body composition, dietary intake and nutritional status. This relationship might contribute to drug toxicity or reduce treatment efficacy and influence cost-effectiveness of medical care.

Toward precision medicine in pediatric population using cytochrome P450 phenotyping approaches and physiologically based pharmacokinetic modeling

The activity of drug-metabolizing enzymes (DME) shows high inter- and intra-individual variability. Genetic polymorphisms, exposure to drugs, and environmental toxins are known to significantly alter DME expression. In addition, the activity of these enzymes is highly age-dependent due to maturation processes that occur during development. Currently, there is a vast choice of phenotyping methods in adults using exogenous probes to characterize the activity of these enzymes. However, this can hardly be applied to children since it requires the intake of non-therapeutic xenobiotics. In addition, sampling may be challenging in the pediatric population for a variety of reasons: limited volume (e.g., blood), inappropriate sampling methods for age (e.g., urine), and metric requiring invasive or multiple blood samples. This review covers the main existing methods that can be used in the pediatric population to determine DME activity, with a particular focus on cytochrome P450 enzymes. Less invasive tools are described, including phenotyping using endogenous probes. Finally, the potential of pediatric model-informed precision dosing using physiologically based pharmacokinetic modeling is discussed.

Body mass index is independently associated with xanthine oxidase activity in overweight/obese population

PURPOSE

The pathophysiological mechanism of the relationship between xanthine oxidase (XO) activity and obesity has not been completely elucidated. Since inflammation and oxidative stress are regarded as key determinants of enlarged adipose tissue, we aimed to investigate the association between oxidative stress (as measured with XO activity), inflammation [as measured with high-sensitivity C-reactive protein (hsCRP)] and obesity [as measured with body mass index (BMI)]. In addition, we wanted to examine whether hsCRP itself plays an independent role in XO activity increase or it is only mediated through obesity.

METHODS

A total of 118 overweight/obese volunteers (mean age 54.76 ± 15.13 years) were included in the current cross-sectional study. Anthropometric, biochemical parameters, and blood pressure were obtained.

RESULTS

Significant differences between age, BMI, waist circumference, concentrations of uric acid and hsCRP, as well as xanthine dehydrogenase (XDH) activities were evident among XO tertile groups. Multiple linear regression analysis revealed that BMI (beta = 0.241, p = 0.012) and XDH (beta = - 0.489, p < 0.001) are the independent predictors of XO activity (R²-adjusted = 0.333), whereas hsCRP lost its independent role in XO activity prediction.

CONCLUSION

Obesity (as determined with increased BMI) is an independent predictor of high XO activity in overweight/obese population.

LEVEL OF EVIDENCE

Level V: cross-sectional descriptive study.

Effects of short-term saffron (Crocus sativus L.) intake on the in vivo activities of xenobiotic metabolizing enzymes in healthy volunteers

Crocus sativus L., a perennial plant grown mainly around the Mediterranean and Iran, has many medicinal properties including anti-inflammatory, anti-depressive and cancer preventing properties. Aqueous herbal extracts may affect the activity of Phase I and II enzymes involved in xenobiotic metabolism. The present study was designed to determine whether C. sativus infusion alters the activity of CYP1A2, CYP2A6, XO and NAT2 enzymes in humans. Thirty-four healthy volunteers consumed infusion prepared from C. sativus stigmata for six days. Enzyme phenotyping was assessed in saliva and urine using caffeine metabolite ratios as follows: CYP1A2: 17X/137Χ (saliva) and CYP1A2: (AFMU+1U+1X)/17U, CYP2A6: 17U/(17U + 17X), XO: 1U/(1U+1X) and NAT2: AFMU/(AFMU+1U+1X) (urine). Following C. sativus intake, CYP1A2 index was reduced by ∼13.7% in saliva (before: 0.51 ± 0.22, after: 0.44 ± 0.14; p = 0.002) and ∼6.0% in urine (before: 3.81 ± 1.20, after: 3.58 ± 0.92; p = 0.054). CYP1A2 index was significantly reduced only in males (saliva, before: 0.65 ± 0.22, after: 0.51 ± 0.16; p = 0.0001; urine, before: 4.53 ± 1.19, after: 4.03 ± 0.87; p = 0.017) suggesting sexual dimorphism in CYP1A2 inhibition. There was no effect of C. sativus intake on CYP2A6, XO or NAT2 indices. Short-term consumption of C. sativus infusion is unlikely to result in significant herb-drug interactions involving the enzymes studied, with the exception of potential herb-CYP1A2 substrate interaction in males.

Body Mass Index as a Determinant of Systemic Exposure to Gallotannin Metabolites during 6-Week Consumption of Mango (Mangifera indica L.) and Modulation of Intestinal Microbiota in Lean and Obese Individuals

SCOPE

This human clinical pilot trial investigated pharmacokinetics of gallotannin-metabolites and modulation of intestinal microbiota in healthy lean and obese individuals after 6 weeks of daily mango consumption.

METHODS AND RESULTS

Participants are divided into three groups: Lean Mango (LM: n = 12; BMI = 22.9 kg m^-2 ), Obese Mango (OM: n = 9; BMI = 34.6 kg m^-2 ), and Lean Control (LC: n = 11; BMI = 22.1 kg m^-2 ). LM and OM consumed 400 g of mango per day for 6 weeks. LC consumed mango only on Days 0 and 42. After 6 weeks, LM experienced increased systemic exposure (AUC_0-8h ) to gallotannin-metabolites, 1.4-fold (p = 0.043). The greatest increase is 4-O-methyl-gallic acid, 3.3-fold (p = 0.0026). Cumulative urinary excretion of gallotannin-metabolites significantly increased in LM and OM, but not LC. For OM, qPCR data show increased levels of tannase-producing Lactococcus lactis and decreased levels of Clostridium leptum and Bacteroides thetaiotaomicron, bacteria associated with obesity. LM experienced an increased trend of fecal levels of butyric (1.3-fold; p = 0.09) and valeric acids (1.5-fold; p = 0.056). Plasma endotoxins showed a decreased trend in LM and OM.

CONCLUSION

Continuous mango intake significantly increased systemic exposure to gallotannin- metabolites and induced an increased trend for fecal short-chain fatty acids in lean but not obese individuals. This pharmacokinetic discrepancy may result in BMI-associated reduced gallotannin-derived health benefits.

Effect of Diabetes Mellitus on the Pharmacokinetics and Pharmacodynamics of Tuberculosis Treatment

Diabetes mellitus (DM) and tuberculosis (TB) are two common diseases with increasing geographic overlap and clinical interactions. The effect of DM and hemoglobin A1c (HbA1c) values on the pharmacokinetics (PK) and pharmacodynamics (PD) of anti-TB drugs remains poorly characterized. Newly diagnosed TB patients with and without DM starting fixed-dose, thrice-weekly treatment underwent sampling for PK assessments (predose and 0.5, 2, and 6 h postdose) during the intensive and continuation phases of treatment. The effect of DM and HbA1c values on the maximum concentration (C _max) of rifampin, isoniazid, and pyrazinamide and the association between drug concentrations and microbiologic and clinical outcomes were assessed. Of 243 patients, 101 had DM. Univariate analysis showed significant reductions in the C _max of pyrazinamide and isoniazid (but not rifampin) with DM or increasing HbA1c values. After adjusting for age, sex, and weight, DM was associated only with reduced pyrazinamide concentrations (adjusted geometric mean ratio = 0.74, P = 0.03). In adjusted Cox models, female gender (adjusted hazards ratio [aHR] = 1.75, P = 0.001), a lower smear grade with the Xpert assay (aHR = 1.40, P < 0.001), and the pyrazinamide C _max (aHR = 0.99, P = 0.006) were independent predictors of sputum culture conversion to negative. Higher isoniazid or rifampin concentrations were associated with a faster time to culture conversion in patients with DM only. A pyrazinamide C _max above the therapeutic target was associated with higher unfavorable outcomes (treatment failure, relapse, death) (odds ratio = 1.92, P = 0.04). DM and higher HbA1c values increased the risk of not achieving therapeutic targets for pyrazinamide (but not rifampin or isoniazid). Higher pyrazinamide concentrations, though, were associated with worse microbiologic and clinical outcomes. DM status also appeared to influence PK-PD relationships for isoniazid and rifampin.

Impact of obesity and overweight on DNA stability: Few facts and many hypotheses

Health authorities are alarmed worldwide about the increase of obesity and overweight in the last decades which lead to adverse health effects including inflammation, cancer, accelerated aging and infertility. We evaluated the state of knowledge concerning the impact of elevated body mass on genomic instability. Results of investigations with humans (39 studies) in which DNA damage was monitored in lymphocytes and sperm cells, are conflicting and probably as a consequence of heterogeneous study designs and confounding factors (e.g. uncontrolled intake of vitamins and minerals and consumption of different food types). Results of animal studies with defined diets (23 studies) are more consistent and show that excess body fat causes DNA damage in multiple organs including brain, liver, colon and testes. Different molecular mechanisms may cause genetic instability in overweight/obese individuals. ROS formation and lipid peroxidation were found in several investigations and may be caused by increased insulin, fatty acid and glucose levels or indirectly via inflammation. Also reduced DNA repair and formation of advanced glycation end products may play a role but more data are required to draw firm conclusions. Reduction of telomere lengths and hormonal imbalances are characteristic for overweight/obesity but the former effects are delayed and moderate and hormonal effects were not investigated in regard to genomic instability in obese individuals. Increased BMI values affect also the activities of drug metabolizing enzymes which activate/detoxify genotoxic carcinogens, but no studies concerning the impact of these alterations of DNA damage in obese individuals are available. Overall, the knowledge concerning the impact of increased body weight and DNA damage is poor and further research is warranted to shed light on this important issue.

Higher chlorzoxazone clearance in obese children compared with nonobese peers

AIMS

To test the in vivo activity of Cytochrome P450 (CYP) 2E1 in obese children vs. nonobese children, aged 11-18 years. Secondly, whether the activity of CYP2E1 in these patients is associated with NALFD, diabetes or hyperlipidaemia.

METHODS

Seventy children were divided into groups by body mass index (BMI) standard deviation score (SDS). All children received 250 mg oral chlorzoxazone (CLZ) as probe for CYP2E1 activity. Thirteen blood samples and 20-h urine samples were collected per participant.

RESULTS

Obese children had an increased oral clearance and distribution of CLZ, indicating increased CYP2E1 activity, similar to obese adults. The mean AUC_0-∞ value of CLZ was decreased by 46% in obese children compared to nonobese children. The F was was increased twofold in obese children compared to nonobese children, P < 0.0001. Diabetic biomarkers were significantly increased in obese children, while fasting blood glucose and Hba1c levels were nonsignificant between groups. Liver fat content was not associated with CLZ Cl.

CONCLUSION

Oral clearance of CLZ was increased two-fold in obese children vs. nonobese children aged 11-18 years. This indicates an increased CYP2E1 activity of clinical importance, and dose adjustment should be considered for CLZ.

Oxidative stress and immunosenescence in spleen of obese mice can be reversed by 2-hydroxyoleic acid

NEW FINDINGS

What is the central question of this study? Evidence is growing for the link between obesity, immune dysfunction and oxidative stress, but it is still not known how the properties and functions of the spleen and splenic leucocytes are affected. What is the main finding and its importance? Obesity led to premature immunosenescence, manifested as oxidative stress and changes in leucocyte functions in mouse spleen. The oleic acid derivative 2-hydroxyoleate and, to a lesser extent, a combination of eicosapentaenoic and docosahexaenoic acids could reverse most of the observed alterations, suggesting a potential therapeutic tool for obesity-related immune dysfunction and redox imbalance. We aimed to investigate the effects of obesity on oxidative stress and leucocyte function in the mouse spleen and to assess whether supplementation with 2-hydroxyoleic acid (2-OHOA) or n-3 polyunsaturated fatty acids (PUFAs) could reverse those effects. Female ICR/CD1 mice (8 weeks old, n = 24) received an obesogenic diet (22% fat for 4 weeks and 60% fat for 14 weeks). After 6 weeks, mice were divided into the following three groups (n = 8 per group): no supplementation; 2-OHOA supplementation (1500 mg kg^-1 of diet); and n-3 PUFA supplementation (eicosapentaenoic acid and docosahexaenoic acid, 1500 + 1500 mg kg^-1 of diet). Eight mice were fed the standard diet for the whole duration of the study (control group). At the end of the experiment, the following variables were assessed in spleens: levels of reduced (GSH) and oxidized glutathione (GSSG), GSH/GSSG, xanthine oxidase activity, lipid peroxidation, lymphocyte chemotaxis, natural killer activity and mitogen (concanavalin A and lipopolysaccharide)-induced lymphocyte proliferation. Obese animals presented higher GSSG levels (P = 0.003), GSSG/GSH ratio (P = 0.013), lipid peroxidation (P = 0.004), xanthine oxidase activity (P = 0.015) and lymphocyte chemotaxis (P < 0.001), and lower natural killer activity (P = 0.003) and proliferation in response to concanavalin A (P < 0.001) than control mice. 2-Hydroxyoleic acid totally or partly reversed most of the changes (body weight, fat content, GSSG levels, GSH/GSSG, lipid peroxidation, chemotaxis and proliferation, all P < 0.05), whereas n-3 PUFAs reversed the increase in xanthine oxidase activity (P = 0.032). In conclusion, 2-OHOA or, to a lesser extent, n-3 PUFAs could ameliorate the oxidative stress and alteration of leucocyte function in the spleens of obese mice. Our findings support a link between obesity and immunosenescence and suggest a potential therapeutic tool for obesity-related immune dysfunction.

Pediatric Cytochrome P450 Activity Alterations in Nonalcoholic Steatohepatitis

Variable drug responses depend on individual variation in the activity of drug-metabolizing enzymes, including cytochrome P450 enzymes (CYP). As the most common chronic liver disease in children and adults, nonalcoholic steatohepatitis (NASH) has been identified as a source of significant interindividual variation in hepatic drug metabolism. Compared with adults, children present age-related differences in pharmacokinetics and pharmacodynamics. The purpose of this study was to determine the impact of fatty liver disease severity on the activity of a variety of CYP enzymes in children and adolescents. Healthy and nonalcoholic fatty liver disease pediatric subjects aged 12-21 years inclusive received an oral cocktail of four probe drugs: caffeine (CYP1A2, 100 mg), omeprazole (CYP2C19, 20 mg), losartan (CYP2C9, 25 mg), and midazolam (CYP3A4, 2 mg). Venous blood and urine were collected before administration and 1, 2, 4, and 6 hours after administration. Concentrations of the parent drugs and CYP-specific metabolites were quantified in plasma and urine using liquid chromatography with tandem mass spectrometry. In plasma, the decreased metabolic area under the curve (AUC) ratio, defined as the metabolite AUC to parent AUC, of omeprazole indicated significant decreases of CYP2C19 (P = 0.002) enzymatic activities in NASH adolescents, while the urine analyses did not show significant differences and were highly variable. A comparison between the present in vivo pediatric studies and a previous ex vivo study in adults indicates distinct differences in the activities of CYP1A2 and CYP2C9. These data demonstrate that pediatric NASH presents an altered pattern of CYP activity and NASH should be considered as a confounder of drug metabolism for certain CYP enzymes. These differences could lead to future investigations that may reveal unexpected variable drug responses that should be considered in pediatric dosage recommendations.

Weight Loss, Xanthine Oxidase, and Serum Urate Levels: A Prospective Longitudinal Study of Obese Patients

OBJECTIVE

The mechanisms by which weight loss decreases serum uric acid (SUA) levels are poorly known. We aimed to investigate the role played by xanthine oxidase (XOD), metabolic status, and low-grade inflammation in decreased SUA levels induced by weight loss in obese patients.

METHODS

Data were from a series of consecutive patients with severe obesity involved in a bariatric surgery program. Measurements of body composition and biologic samples were obtained before surgery and 6 months after surgery.

RESULTS

Among the 154 patients (mean ± SD age 41.0 ± 12.3 years, body mass index [BMI] 47.8 ± 7.2 kg/m(2) , 81% female), the mean ± SD weight loss at 6 months was 31.3 ± 7.8 kg. Reduction in SUA levels was modest (-10%): 4.98 ± 1.21 mg/dl at 6 months versus 5.52 ± 1.33 mg/dl at baseline (P < 0.001). The decrease in SUA levels was greatest (-18%) in hyperuricemic patients (n = 48). In these patients, circulating XOD activity decreased with weight loss (P < 0.0001). Multiple linear regression analysis revealed decreased SUA levels associated with decreased triglyceride levels (P = 0.0001) and BMI (P = 0.02) but not XOD activity, adipokine levels (leptin and adiponectin), insulin resistance, or levels of inflammatory variables (interleukin 6, orosomucoid, fibrinogen, and high-sensitivity C-reactive protein).

CONCLUSION

In obese patients, weight loss was associated with a decrease in both SUA levels and XOD activity. Our findings suggest that reduced SUA levels are not mediated by decreased XOD activity or improved insulin resistance but could be partly due to a reduction in triglyceride levels.

Weight Loss Mediated Reduction in Xanthine Oxidase Activity and Uric Acid Clearance in Adolescents with Severe Obesity

BACKGROUND

Increased xanthine oxidase (XO) activity and uric acid levels are known to be associated with obesity and hypertension; however, it is not known if obesity is directly responsible for these associations in youth. This study investigated the effect of weight loss on XO activity, uric acid, and their relationship to blood pressure change in obese youth to provide greater insight on how obesity increases cardiovascular risk.

METHODS

This was an ancillary study in which 16 adolescents (mean age 15 ± 2 years) received meal replacement therapy over a period of four weeks. Outcomes measured at baseline and after intervention included weight, blood pressure, XO activity, plasma uric acid, uric acid clearance, and creatinine clearance.

RESULTS

After the meal replacement intervention, participants experienced reductions in body weight (109.2 ± 16 kg vs. 105.2 ± 14 kg, p < 0.0001) and BMI (38.7 ± 4 kg vs. 37.4 ± 3 kg, p < 0.0001). Plasma XO activity was reduced by 9.8% (p = 0.016). Uric acid clearance was decreased by 39% (p = 0.006). SBP (systolic blood pressure) and plasma uric acid concentrations were reduced but did not achieve statistical significance (p = 0.34 and 0.38, respectively). DBP (diastolic blood pressure) was unchanged (p = 0.86). No significant relationships were found between changes in blood pressure and changes in either XO activity or plasma uric acid levels.

CONCLUSION

Weight loss led to decreases in uric acid production by lowering XO activity and decreases in uric acid clearance by reducing glomerular filtration (GF) and increasing reabsorption. Changes in XO activity and uric acid levels did not correlate with changes in blood pressure.

Gaps in Drug Dosing for Obese Children: A Systematic Review of Commonly Prescribed Emergency Care Medications

PURPOSE

Approximately 1 of 6 children in the United States is obese. This has important implications for drug dosing and safety because pharmacokinetic (PK) changes are known to occur in obesity due to altered body composition and physiologic mechanisms. Inappropriate drug dosing in an emergency setting can limit therapeutic efficacy and increase drug-related toxic effects for obese children. Few systematic reviews examining PK properties and drug dosing in obese children have been performed.

METHODS

We identified 25 emergency care drugs from the Strategic National Stockpile and Acute Care Supportive Drugs List and performed a systematic review for each drug in 3 study populations: obese children (2-18 years of age), normal weight children, and obese adults (aged >18 years). For each study population, we first reviewed a drug's Food and Drug Administration label and then performed a systematic literature review. From the literature, we extracted drug PK data, biochemical properties, and dosing information. We then reviewed data in 3 age subpopulations (2-7 years, 8-12 years, and 13-18 years) for obese and normal weight children and by route of drug administration (intramuscular, intravenous, oral, and inhaled). If sufficient PK data were not available by age and route of administration, a data gap was identified.

FINDINGS

Only 2 of 25 emergency care drugs (8%) contained dosing information on the Food and Drug Administration label for obese children and adults compared with 22 of 25 (88%) for normal weight children. We found no sufficient PK data in the literature for any of the emergency care drugs in obese children. Sufficient PK data were found for 7 of 25 emergency care drugs (28%) in normal weight children and 3 of 25 (12%) in obese adults.

IMPLICATIONS

Insufficient information exists to guide dosing in obese children for any of the emergency care drugs reviewed. This knowledge gap is alarming, given the known PK changes that occur in the setting of obesity. Future clinical trials examining the PK properties of emergency care medications in obese children should be prioritized.

Dispelling dogma and misconceptions regarding the most pharmacologically targetable source of reactive species in inflammatory disease, xanthine oxidoreductase

Xanthine oxidoreductase (XOR), the molybdoflavin enzyme responsible for the terminal steps of purine degradation in humans, is also recognized as a significant source of reactive species contributory to inflammatory disease. In animal models and clinical studies, inhibition of XOR has resulted in diminution of symptoms and enhancement of function in a number of pathologies including heart failure, diabetes, sickle cell anemia, hypertension and ischemia-reperfusion injury. For decades, XOR involvement in pathologic processes has been established by salutary outcomes attained from treatment with the XOR inhibitor allopurinol. This has served to frame a working dogma that elevation of XOR-specific activity is associated with enhanced rates of reactive species generation that mediate negative outcomes. While adherence to this narrowly focused practice of designating elevated XOR activity to be "bad" has produced some benefit, it has also led to significant underdevelopment of the processes mediating XOR regulation, identification of alternative reactants and products as well as micro-environmental factors that alter enzymatic activity. This is exemplified by recent reports: (1) identifying XOR as a nitrite reductase and thus a source of beneficial nitric oxide ((•)NO) under in vivo conditions similar to those where XOR inhibition has been assumed an optimal treatment choice, (2) describing XOR-derived uric acid (UA) as a critical pro-inflammatory mediator in vascular and metabolic disease and (3) ascribing an antioxidant/protective role for XOR-derived UA. When taken together, these proposed and countervailing functions of XOR affirm the need for a more comprehensive evaluation of product formation as well as the factors that govern product identity. As such, this review will critically evaluate XOR-catalyzed oxidant, (•)NO and UA formation as well as identify factors that mediate their production, inhibition and the resultant impact on inflammatory disease.

Dapsone and body mass index in subjects with multibacillary leprosy

BACKGROUND

The physiological changes in obese subjects can modify the pharmacokinetic profiles of drugs influencing the therapeutic efficacy.

METHODS

In this study, the authors compare plasma dapsone trough levels of multibacillary leprosy subjects stratified by body mass index (BMI) to evaluate if obesity plays a significant role on drug levels. The relationship between drug levels and BMI was also determined. Dapsone was measured by high-performance liquid chromatography and BMI based on World Health Organization criteria.

RESULTS

At steady state, the median plasma dapsone trough level was significantly lower in obesity class 2 group, when compared with other groups, but they were similar between normal weight and preobesity groups. A weak association between drug levels and BMI was observed.

CONCLUSIONS

Obesity promotes a significant reduction in plasma dapsone trough levels of subjects with multibacillary leprosy with a weak association between drug levels and BMI.

The challenge of obesity in paediatric leukaemia treatment: it is not just size that matters

In the last two decades, tremendous advances have been made in the treatment of acute lymphocytic leukaemia (ALL) in children with 5 year 'cure' rates in excess of 90%. The maintenance of remission is due, in part, to individualisation of therapy which must consider age, body size, genetic constitution and the impact of disease on drug disposition and action. This review, focused on treatment of ALL and one of the therapeutic mainstays, 6-mercaptopurine, illustrates the importance of obesity as a modulating factor in dose individualisation.

Plasma level of hypoxanthine/xanthine as markers of oxidative stress with different stages of obstructive sleep apnea syndrome

BACKGROUND AND OBJECTIVES

Tissue hypoxia due to repeated apneas among patients of obstructive sleep apnea syndrome (OSAS) leads to cumulative oxidative stress. It is established that an increased plasma level of hypoxanthine/xanthine may serve as a criterion of tissue hypoxia. We presumed that plasma levels of hypoxan.thine/xanthine might be high among patients of OSAS due to oxidative stress. Nobody studied this relationship earlier. The aim of this study was to estimate their plasma levels as markers of hypoxia.

DESIGN AND SETTINGS

This case-control study was performed for a period of 1-year including patients re.ferred to a tertiary care hospital, New Delhi, India.

MATERIALS AND METHODS

It was a case-control study. A total of 43 patients of OSAS, diagnosed by overnight polysomnography (PSG), were included in the study. Age- and sex-matched 43 subjects in whom the presence of OSAS was not confirmed by overnight PSG were enrolled as healthy controls. The severity of disease was classified on the basis of apnea-hypopnea index (AHI). Out of 43 patients, 9 were moderate and 14 were severe. None was with mild OSAS. The venous blood sample was collected in the morning after PSG. Hematological and biochemical assays were also performed. Plasma levels of hypoxanthine/xanthine were measured by fluorometric analysis (normal laboratory reference < 2.00 mmol/L). Data collected was analyzed statistically by SPSS version 14.0, student unpaired t test, chi-square test, Mann-Whitney U test, and Pearson correlation coefficient.

RESULTS

The mean plasma level of hypoxanthine/xanthine in patients of OSAS was found to be 5.4 (5.1) mmol/L, and in controls it was 1.2 (0.4) mmol/L. A statistically significant (P=.000) difference was found be.tween both groups. Among patients, a positive correlation between hypoxanthine/xanthine levels with age, AHI, and serum triglyceride levels was observed. The joint explanatory power of these significant factors was found to be 59.6% (P < .001).

CONCLUSION

Plasma levels of xanthine/hypoxanthine were significantly elevated in patients of OSAS, and these were positively correlated with age, serum triglyceride levels, AHI, and severity of the disease.

Impaired vascular KATP function attenuates exercise capacity in obese zucker rats

OBJECTIVE

Obese subjects exhibit decreased exercise capacity (VO2max ). We have shown that vascular KATP channel mediates arteriolar dilation to muscle contraction. We hypothesize that exercise capacity is decreased in obesity due to impaired vascular KATP function.

METHODS

The VO2max was measured in LZR and OZR by treadmill running before and following treatment with the KATP blocker glibenclamide i.p. One week later, the spinotrapezius muscle was prepared for in vivo microscopy. Arcade arteriolar diameters were measured following muscle contraction or application of the KATP opener cromakalim before and after glibenclamide application. In additional animals, LZR and OZR were treated with apocynin for five weeks. VO2max and arteriolar dilation experiments were repeated.

RESULTS

The OZR exhibited decreased VO2max , functional and cromakalim-induced vasodilation as compared with LZR. Glibenclamide had no effect on VO2max and functional vasodilation in OZR, but significantly inhibited responses in LZR. Vascular superoxide levels and NADPH oxidase activity were increased in OZR, but reduced in apocynin-treated OZR. Apocynin increased the VO2max , functional and cromakalim-induced vasodilation in OZR with no effect in LZR.

CONCLUSIONS

Exercise capacity is dependent on vascular KATP channel function. The reduced exercise capacity in OZR appears to be due in part to superoxide-mediated impairment in vascular KATP function.

Xanthine oxidase and cardiovascular risk in obese children

BACKGROUND

Pathological mechanisms of how childhood obesity leads to increased risk of cardiovascular disease (CVD) are not fully characterized. Oxidative-stress-related enzymes, such as xanthine oxidase (XO), have been linked to obesity, endothelial dysfunction, and CVD in adults, but little is known about this pathway in children. The aim of this study was to determine whether differential XO activity is associated with endothelial dysfunction, CVD risk factors, or cytokine levels.

METHODS

Fasting plasma samples were obtained from obese (BMI ≥ 95th percentile; n = 20) and age- and gender-matched healthy weight (BMI > 5th and < 85th percentile; n = 22) children and adolescents (mean age, 12 ± 3 years) to quantify XO activity. In addition, fasting cholesterol, insulin, glucose, blood pressure, endothelial function, and cytokine levels were assessed.

RESULTS

We observed a 3.8-fold increase in plasma XO activity in obese, compared to healthy weight, children (118 ± 21 vs. 31 ± 9  nU/mg of protein; p < 0.001). Plasma XO activity was correlated with BMI z-score (r = 0.41), waist circumference (r = 0.41), high-density lipoprotein cholesterol (r = -0.32), oxidized low-density lipoprotein (r = 0.57), adiponectin (r = -0.53), and monocyte chemotactic protein-1 (r = -0.59).

CONCLUSION

XO activity is highly elevated in obese children and correlates with CVD risk factors, suggesting that XO may play a role in increasing cardiovascular risk early in life in the context of obesity.

Pharmacokinetics of Antimicrobials in Obese Children

INTRODUCTION

Childhood obesity is common and results in substantial morbidity. The most commonly prescribed drugs in obese children are antibiotics. However, physiologic changes associated with childhood obesity can alter antibiotic pharmacokinetics and optimal body size measures to guide dosing in his population are ill defined. This combination can result in therapeutic failures or drug-related toxicities. This review summarizes pharmacokinetic information for antibiotics in obese children and implications for dosing.

METHODS

We conducted a comprehensive literature search of PubMed, EMBASE, and International Pharmaceutical Abstracts to identify pharmacokinetic studies of antimicrobial agents in obese children. We included the following search terms: obesity, pharmacokinetics, pharmacodynamics, drug toxicity, dosing, anti-infective agents, antiviral agents, and antifungal agents.

RESULTS

We identified four pharmacokinetic studies of antibiotics in obese children: one for cefazolin and tobramycin, one for gentamicin, and two for vancomycin. Only the cefazolin/tobramycin trial was prospective. The drugs studied differ in their tissue and body water distribution characteristics. Two of the studies (tobramycin and gentamicin) reported pharmacokinetic differences and required dosing modifications in obese children.

DISCUSSION

The lack of pharmacokinetic studies in obese children is pronounced. The scarcity of pharmacokinetic data limits the ability to predict drug disposition using drug physicochemical properties and impedes a rational approach to selection of appropriate body size measures for dosing. Given this knowledge gap, additional trials in obese children are urgently needed and is a public health concern.

CONCLUSION

Pharmacokinetic studies of antimicrobials in obese children are desperately needed to guide dosing and avoid therapeutic failures or unwanted toxicities.

Impact of obesity on drug metabolism and elimination in adults and children

The prevalence of obesity in adults and children is rapidly increasing across the world. Several general (patho)physiological alterations associated with obesity have been described, but the specific impact of these alterations on drug metabolism and elimination and its consequences for drug dosing remains largely unknown. In order to broaden our knowledge of this area, we have reviewed and summarized clinical studies that reported clearance values of drugs in both obese and non-obese patients. Studies were classified according to their most important metabolic or elimination pathway. This resulted in a structured review of the impact of obesity on metabolic and elimination processes, including phase I metabolism, phase II metabolism, liver blood flow, glomerular filtration and tubular processes. This literature study shows that the influence of obesity on drug metabolism and elimination greatly differs per specific metabolic or elimination pathway. Clearance of cytochrome P450 (CYP) 3A4 substrates is lower in obese as compared with non-obese patients. In contrast, clearance of drugs primarily metabolized by uridine diphosphate glucuronosyltransferase (UGT), glomerular filtration and/or tubular-mediated mechanisms, xanthine oxidase, N-acetyltransferase or CYP2E1 appears higher in obese versus non-obese patients. Additionally, in obese patients, trends indicating higher clearance values were seen for drugs metabolized via CYP1A2, CYP2C9, CYP2C19 and CYP2D6, while studies on high-extraction-ratio drugs showed somewhat inconclusive results. Very limited information is available in obese children, which prevents a direct comparison between data obtained in obese children and obese adults. Future clinical studies, especially in children, adolescents and morbidly obese individuals, are needed to extend our knowledge in this clinically important area of adult and paediatric clinical pharmacology.