Population Pharmacokinetics of Topiramate in Patients with Epilepsy Using Nonparametric Modeling

BACKGROUND

Topiramate (TPM) is used for the treatment of various epileptic seizures and the prevention of migraine. This study aimed to develop a population pharmacokinetic model and identify covariates that influence TPM behavior in patients with epilepsy in Kuwait.

METHODS

Data were collected retrospectively from 108 patients (2 years old and above) with epilepsy who were treated with oral TPM and 174 TPM blood samples from 3 hospitals in Kuwait from 2009 to 2016. Data were randomly divided into 2 groups for model development and validation. The population pharmacokinetic model was built using the nonparametric modeling algorithm (Pmetrics). The model was evaluated internally through the visual predictive check method and externally using a new data set.

RESULTS

A 1-compartment model with first-order elimination fitted the data well. Covariates showing a significant effect on the elimination rate constant were renal function and coadministration of carbamazepine (CBZ). The mean estimated clearance was 2.11 L/h; this was 50% higher for patients coadministered with CBZ. Age and sex were essential covariates for the volume of distribution (V). The visual predictive check of the final model could predict the measured concentrations. External validation further confirmed the favorable predictive performance of the model with low bias and imprecision for predicting the concentration in a particular population.

CONCLUSIONS

TPM elimination was increased with CBZ coadministration and was affected by renal function. Meanwhile, age and sex were the main predictors for V. The predictive performance of the final model proved to be valid internally and externally.

Copper-Fructose Interactions: A Novel Mechanism in the Pathogenesis of NAFLD

Compelling epidemiologic data support the critical role of dietary fructose in the epidemic of obesity, metabolic syndrome and nonalcoholic fatty liver disease (NAFLD). The metabolic effects of fructose on the development of metabolic syndrome and NAFLD are not completely understood. High fructose intake impairs copper status, and copper-fructose interactions have been well documented in rats. Altered copper-fructose metabolism leads to exacerbated experimental metabolic syndrome and NAFLD. A growing body of evidence has demonstrated that copper levels are low in NAFLD patients. Moreover, hepatic and serum copper levels are inversely correlated with the severity of NAFLD. Thus, high fructose consumption and low copper availability are considered two important risk factors in NAFLD. However, the causal effect of copper-fructose interactions as well as the effects of fructose intake on copper status remain to be evaluated in humans. The aim of this review is to summarize the role of copper-fructose interactions in the pathogenesis of the metabolic syndrome and discuss the potential underlying mechanisms. This review will shed light on the role of copper homeostasis and high fructose intake and point to copper-fructose interactions as novel mechanisms in the fructose induced NAFLD.

Effects of fructose-containing sweeteners on fructose intestinal, hepatic, and oral bioavailability in dual-catheterized rats

Objective

Fructose is commonplace in Western diets and is consumed primarily through added sugars as sucrose or high fructose corn syrup. High consumption of fructose has been linked to the development of metabolic disorders, such as cardiovascular diseases. The majority of the harmful effects of fructose can be traced to its uncontrolled and rapid metabolism, primarily within the liver. It has been speculated that the formulation of fructose-containing sweeteners can have varying impacts on its adverse effects. Unfortunately, there is limited data supporting this hypothesis. The objective of this study was to examine the impact of different fructose-containing sweeteners on the intestinal, hepatic, and oral bioavailability of fructose.

Methods

Portal and femoral vein catheters were surgically implanted in male Wistar rats. Animals were gavaged with a 1 g/kg carbohydrate solution consisting of fructose, 45% glucose/55% fructose, sucrose, glucose, or water. Blood samples were then collected from the portal and systemic circulation. Fructose levels were measured and pharmacokinetic parameters were calculated.

Results

Compared to animals that were gavaged with 45% glucose/55% fructose or sucrose, fructose-gavaged animals had a 40% greater fructose area under the curve and a 15% greater change in maximum fructose concentration in the portal circulation. In the systemic circulation of fructose-gavaged animals, the fructose area under the curve was 17% and 24% higher and the change in the maximum fructose concentration was 15% and 30% higher than the animals that received 45% glucose/55% fructose or sucrose, respectively. After the oral administration of fructose, 45% glucose/55% fructose, and sucrose, the bioavailability of fructose was as follows: intestinal availability was 0.62, 0.53 and 0.57; hepatic availability was 0.33, 0.45 and 0.45; and oral bioavailability was 0.19, 0.23 and 0.24, respectively.

Conclusions

Our studies show that the co-ingestion of glucose did not enhance fructose absorption, rather, it decreased fructose metabolism in the liver. The intestinal, hepatic, and oral bioavailability of fructose was similar between 45% glucose/55% fructose and sucrose.

High-Fructose Corn-Syrup-Sweetened Beverage Intake Increases 5-Hour Breast Milk Fructose Concentrations in Lactating Women

This study determined the effects of consuming a high-fructose corn syrup (HFCS)-sweetened beverage on breast milk fructose, glucose, and lactose concentrations in lactating women. At six weeks postpartum, lactating mothers (n = 41) were randomized to a crossover study to consume a commercially available HFCS-sweetened beverage or artificially sweetened control beverage. At each session, mothers pumped a complete breast milk expression every hour for six consecutive hours. The baseline fasting concentrations of breast milk fructose, glucose, and lactose were 5.0 ± 1.3 µg/mL, 0.6 ± 0.3 mg/mL, and 6.8 ± 1.6 g/dL, respectively. The changes over time in breast milk sugars were significant only for fructose (treatment × time, p < 0.01). Post hoc comparisons showed the HFCS-sweetened beverage vs. control beverage increased breast milk fructose at 120 min (8.8 ± 2.1 vs. 5.3 ± 1.9 µg/mL), 180 min (9.4 ± 1.9 vs. 5.2 ± 2.2 µg/mL), 240 min (7.8 ± 1.7 vs. 5.1 ± 1.9 µg/mL), and 300 min (6.9 ± 1.4 vs. 4.9 ± 1.9 µg/mL) (all p < 0.05). The mean incremental area under the curve for breast milk fructose was also different between treatments (14.7 ± 1.2 vs. -2.60 ± 1.2 µg/mL × 360 min, p < 0.01). There was no treatment × time interaction for breast milk glucose or lactose. Our data suggest that the consumption of an HFCS-sweetened beverage increased breast milk fructose concentrations, which remained elevated up to five hours post-consumption.

Insights into the Hexose Liver Metabolism-Glucose versus Fructose

High-fructose intake in healthy men is associated with characteristics of metabolic syndrome. Extensive knowledge exists about the differences between hepatic fructose and glucose metabolism and fructose-specific mechanisms favoring the development of metabolic disturbances. Nevertheless, the causal relationship between fructose consumption and metabolic alterations is still debated. Multiple effects of fructose on hepatic metabolism are attributed to the fact that the liver represents the major sink of fructose. Fructose, as a lipogenic substrate and potent inducer of lipogenic enzyme expression, enhances fatty acid synthesis. Consequently, increased hepatic diacylglycerols (DAG) are thought to directly interfere with insulin signaling. However, independently of this effect, fructose may also counteract insulin-mediated effects on liver metabolism by a range of mechanisms. It may drive gluconeogenesis not only as a gluconeogenic substrate, but also as a potent inducer of carbohydrate responsive element binding protein (ChREBP), which induces the expression of lipogenic enzymes as well as gluconeogenic enzymes. It remains a challenge to determine the relative contributions of the impact of fructose on hepatic transcriptome, proteome and allosterome changes and consequently on the regulation of plasma glucose metabolism/homeostasis. Mathematical models exist modeling hepatic glucose metabolism. Future models should not only consider the hepatic adjustments of enzyme abundances and activities in response to changing plasma glucose and insulin/glucagon concentrations, but also to varying fructose concentrations for defining the role of fructose in the hepatic control of plasma glucose homeostasis.

Chronic Fructose Ingestion as a Major Health Concern: Is a Sedentary Lifestyle Making It Worse? A Review

Obesity contributes to metabolic abnormalities such as insulin resistance, dyslipidemia, hypertension, and glucose intolerance, all of which are risk factors associated with metabolic syndrome. The growing prevelance of metabolic syndrome seems to be an end result of our current lifestyle which promotes high caloric, high-fat foods and minimal physical activity, resulting in a state of positive energy balance. Increased adiposity and physical inactivity may represent the beginning of the appearance of these risk factors. Understanding the metabolic and cardiovascular disturbances associated with diet and exercise habits is a crucial step towards reducing the risk factors for metabolic syndrome. Although considerable research has been conducted linking chronic fructose ingestion to the increased prevalence of obesity and metabolic syndrome risk factors, these studies have mainly been performed on animals, and/or in a post-absorptive state. Further, the magnitude of the effect of fructose may depend on other aspects of the diet, including the total amount of carbohydrates and fats in the diet and the overall consumption of meals. Therefore, the overall aim of this review paper is to examine the effects of a diet high in fructose on postprandial lipidemia, inflammatory markers and glucose tolerance, all risk factors for diabetes and cardiovascular disease. Moreover, an objective is to investigate whether increased physical activity can alter such effects.

Lactase Non-Persistence Genotyping: Comparison of Two Real-Time PCR Assays and Assessment of Concomitant Fructose/Sorbitol Malabsorption Rates

BACKGROUND

Genetic testing is a standard technique for the diagnosis of primary adult-type hypolactasia, also referred to as lactase non-persistence. The aim of this study was to compare the lactase gene (LCT) C/T-13910 polymorphism genotyping results of two commercially available real-time (RT)-PCR assays in patients referred to our outpatient clinic for primary lactose malabsorption testing. Furthermore, concomitant conditions of fructose/sorbitol malabsorption were assessed.

METHODS

Samples obtained from 100 patients were tested in parallel using the LCT T-13910C ToolSet for Light Cycler (Roche, Rotkreuz, Switzerland) and the LCT-13910C>T RealFast Assay (ViennaLab Diagnostics GmbH, Vienna, Austria). Additionally, patients were also screened for the presence of fructose/sorbitol malabsorption by functional hydrogen (H2)/methane (CH4) breath testing (HMBT). Cohen's Kappa (κ) was used to calculate the agreement between the two genotyping methods. The exact Chi-Square test was performed to compare fructose/sorbitol HMBT with LCT genotyping results.

RESULTS

Twenty-one (21.0%) patients had a LCT C/C-13910 genotype suggestive of lactase non-persistence, and 79 (79.0%) patients were identified with either a LCT T/C-13910 or T/T-13910 genotype (i.e., lactase persistence). In all genotype groups, concordance between the two RT-PCR assays was 100%. Cohen's κ demonstrated perfect observed agreement (p < 0.001, κ = 1). Fructose and sorbitol malabsorption was observed in 13/100 (13.0%) and 25/100 (25.0%) individuals, respectively.

CONCLUSIONS

Both RT-PCR assays are robust and reliable LCT genotyping tools in a routine clinical setting. Concomitant fructose and/or sorbitol malabsorption should be considered in individuals with suspected lactase-non-persistence. However, standardization of clinical interpretation of laboratory HMBT results is required.

Boron neutron capture synovectomy (BNCS) as a potential therapy for rheumatoid arthritis: boron biodistribution study in a model of antigen-induced arthritis in rabbits

Boron neutron capture synovectomy (BNCS) is explored for the treatment of rheumatoid arthritis (RA). The aim of the present study was to perform boron biodistribution studies in a model of antigen-induced arthritis (AIA) in female New Zealand rabbits, with the boron carriers boronophenylalanine (BPA) and sodium decahydrodecaborate (GB-10) to assess the potential feasibility of BNCS for RA. Rabbits in chronic phase of AIA were used for biodistribution studies employing the following protocols: intra-articular (ia) (a) BPA-f 0.14 M (0.7 mg (10)B), (b) GB-10 (5 mg (10)B), (c) GB-10 (50 mg (10)B) and intravenous (iv), (d) BPA-f 0.14 M (15.5 mg (10)B/kg), (e) GB-10 (50 mg (10)B/kg), and (f) BPA-f (15.5 mg (10)B/kg) + GB-10 (50 mg (10)B/kg). At different post-administration times (13-85 min for ia and 3 h for iv), samples of blood, pathological synovium (target tissue), cartilage, tendon, muscle, and skin were taken for boron measurement by inductively coupled plasma mass spectrometry. The intra-articular administration protocols at <40 min post-administration both for BPA-f and GB-10, and intravenous administration protocols for GB-10 and [GB-10 + BPA-f] exhibited therapeutically useful boron concentrations (>20 ppm) in the pathological synovium. Dosimetric estimations suggest that BNCS would be able to achieve a therapeutically useful dose in pathological synovium without exceeding the radiotolerance of normal tissues in the treatment volume, employing boron carriers approved for use in humans. Radiobiological in vivo studies will be necessary to determine the actual therapeutic efficacy of BNCS to treat RA in an experimental model.

[Does medication abuse in patients with chronic migraine influence the effectiveness of preventive treatment with topiramate?]

INTRODUCTION

Patients with chronic migraine (CM) and medication abuse are difficult to treat, and have a greater tendency towards chronification and a poorer quality of life than those with other types of headache.

AIM

To evaluate whether the presence of medication abuse lowers the effectiveness of topiramate.

PATIENTS AND METHODS

A series of patients with CM were grouped according to whether they met abuse criteria or not. They were advised to stop taking the drug that they were abusing. Treatment was adjusted to match their crises and preventive treatment with topiramate was established from the beginning. The number of days with headache and intense migraine in the previous month and at four months of treatment was evaluated.

RESULTS

In all, 262 patients with CM criteria were selected and 167 (63.7%) of them fulfilled abuse criteria. In both groups there was a significant reduction in the number of days with headache/month and number of migraine attacks/month at the fourth month of treatment with topiramate. The percentage of reduction in the number of days with headache/month in CM without abuse was 59.3 ± 36.1%, and with abuse, 48.7 ± 41.7% (p = 0.0574). The percentage of reduction in the number of days with intense migraine/month in CM without abuse was 61.2%, and with abuse, 50% (p = 0.0224). Response rate according to the number of days with headache/month in CM without abuse was 69%, and with abuse, 57%. Response rate according to the number of intense migraines/month in CM without abuse was 76.8%, and in CM with abuse, 61% (p = 0.0097).

CONCLUSIONS

Topiramate was effective in patients with CM with and without medication abuse, although effectiveness is lower in the latter case.

Pharmacokinetic interactions between topiramate and pioglitazone and metformin

OBJECTIVE

To investigate potential drug-drug interactions between topiramate and metformin and pioglitazone at steady state.

METHODS

Two open-label studies were performed in healthy adult men and women. In Study 1, eligible participants were given metformin alone for 3 days (500 mg twice daily [BID]) followed by concomitant metformin and topiramate (titrated to 100mg BID) from days 4 to 10. In Study 2, eligible participants were randomly assigned to treatment with pioglitazone 30 mg once daily (QD) alone for 8 days followed by concomitant pioglitazone and topiramate (titrated to 96 mg BID) from days 9 to 22 (Group 1) or to topiramate (titrated to 96 mg BID) alone for 11 days followed by concomitant pioglitazone 30 mg QD and topiramate 96 mg BID from days 12 to 22 (Group 2). An analysis of variance was used to evaluate differences in pharmacokinetics with and without concomitant treatment; 90% confidence intervals (CI) for the ratio of the geometric least squares mean (LSM) estimates for maximum plasma concentration (Cmax), area under concentration-time curve for dosing interval (AUC12 or AUC24), and oral clearance (CL/F) with and without concomitant treatment were used to assess a drug interaction.

RESULTS

A comparison to historical data suggested a modest increase in topiramate oral clearance when given concomitantly with metformin. Coadministration with topiramate reduced metformin oral clearance at steady state, resulting in a modest increase in systemic metformin exposure. Geometric LSM ratios and 90% CI for metformin CL/F and AUC12 were 80% (75%, 85%) and 125% (117%, 134%), respectively. Pioglitazone had no effect on topiramate pharmacokinetics at steady state. Concomitant topiramate resulted in decreased systemic exposure to pioglitazone and its active metabolites, with geometric LSM ratios and 90% CI for AUC24 of 85.0% (75.7%, 95.6%) for pioglitazone, 40.5% (36.8%, 44.6%) for M-III, and 83.8% (76.1%, 91.2%) for M-IV, respectively. This effect appeared more pronounced in women than in men. Coadministration of topiramate with metformin or pioglitazone was generally well tolerated by healthy participants in these studies.

CONCLUSIONS

A modest increase in metformin exposure and decrease in topiramate exposure was observed at steady state following coadministration of metformin 500 mg BID and topiramate 100mg BID. The clinical significance of the observed interaction is unclear but is not likely to require a dose adjustment of either agent. Pioglitazone 30 mg QD did not affect the pharmacokinetics of topiramate at steady state, while coadministration of topiramate 96 mg BID with pioglitazone decreased steady-state systemic exposure to pioglitazone, M-III, and M-IV. While the clinical consequence of this interaction is unknown, careful attention should be given to the routine monitoring for adequate glycemic control of patients receiving this concomitant therapy. Concomitant administration of topiramate with metformin or pioglitazone was generally well tolerated and no new safety concerns were observed.

Vague effects of chronic topiramate administration on maximal electroshock-induced seizures in mice

BACKGROUND

Almost all experimental studies evaluating interactions between antiepileptic and non-antiepileptic drugs are based on their single administration, whereas epileptic patients require chronic pharmacotherapy. Herein, we attempted to figure out whether single and repeated administration of topiramate leads to the same anticonvulsant and undesired effects.

METHODS

Experiments were conducted in the model of maximal electroshock in mice. Motor coordination was evaluated in the chimney test. Brain concentrations of topiramate were determined by high-performance liquid chromatography and triple quadrupole mass spectrometry.

RESULTS

The anticonvulsant activity of topiramate administered once or twice a day for 7 days did not significantly differ from the respective effect of topiramate given acutely in a single injection. However, calculating of 50% effective doses for topiramate applied in 14-days protocol (once or two times a day) was impossible. The antiepileptic administered at the dose range of 80-150 mg/kg did not offer protection in more than 50% of mice. This phenomenon cannot be attributed to pharmacokinetic events, because there were no significant differences between plasma and brain concentrations of topiramate after its acute and chronic administration. Topiramate (150 mg/kg) did not affect motor performance in mice.

CONCLUSIONS

Maximal electroshock in mice does not seem to be an appropriate seizure model to test anticonvulsant effects of chronic topiramate.

Pharmacokinetics of BPA in gliomas with ultrasound induced blood-brain barrier disruption as measured by microdialysis

The blood-brain barrier (BBB) can be transiently disrupted by focused ultrasound (FUS) in the presence of microbubbles for targeted drug delivery. Previous studies have illustrated the pharmacokinetics of drug delivery across the BBB after sonication using indirect visualization techniques. In this study, we investigated the in vivo extracellular kinetics of boronophenylalanine-fructose (BPA-f) in glioma-bearing rats with FUS-induced BBB disruption by microdialysis. After simultaneous intravenous administration of BPA and FUS exposure, the boron concentration in the treated brains was quantified by inductively coupled plasma mass spectroscopy. With FUS, the mean peak concentration of BPA-f in the glioma dialysate was 3.6 times greater than without FUS, and the area under the concentration-time curve was 2.1 times greater. This study demonstrates that intracerebral microdialysis can be used to assess local BBB transport profiles of drugs in a sonicated site. Applying microdialysis to the study of metabolism and pharmacokinetics is useful for obtaining selective information within a specific brain site after FUS-induced BBB disruption.

Effekte von Topiramat bei Patienten mit Epilepsie und intellektueller Beeinträchtigung

There is little knowledge about the effects of topiramate in intellectually impaired epileptic patients. This open prospective study compares seizure frequencies during a 3-month period of topiramate add-on therapy (after 3 months of titration) compared with a 3-month baseline period. An intention-to-treat analysis was made on the first 24 consecutive topiramate-treated adult patients (residents of the Bethel epilepsy centre, therapy-resistant epilepsy, intellectual impairment of different degrees, one half with neurological deficits). The responder rate (at least a 50% reduction in seizure frequency) was 37.5%. One patient became completely seizure-free during post-evaluation (up to 24 months). Efficacy was not different between different epileptic syndromes or seizure types (case number too small). Responders had topiramate dosages above 200 mg/day and serum concentrations above 2.2 micrograms/ml. Six patients (25%) experienced serious neuropsychiatric complications such as confusion and severe deceleration of thinking and acting, up to complete helplessness (at topiramate dosages from 50 mg/day to 900 mg/day and serum concentrations from 2.2 micrograms/ml to 8.0 micrograms/ml). Preexisting brain damage may enhance the risk of unwanted central nervous effects.

[Fructose transporter in yeasts]

Study of hexoses transporter started with discovery of galactose permease in Saccharomyces cerevisiae. Glucose, fructose and mannose assimilation is assumed by numerous proteins encoded by different genes. To date over 20 hexoses transporters, belonging to Sugar Porter family and to Major Facilitator Superfamily, were known. Genome sequence analysis of Candida glabrata, Kluyveromyces lactis, Yarrowia lipolytica, S. cerevisaie and Debaryomyces hansenii reveled potential presence of 17-48 sugar porter proteins. Glucose transporters in S. cerevisiae have been already characterized. In this paper, hexoses transporters, responsible for assimilation of fructose by cells, are presented and compared. Fructose specific transporter are described for yeasts: Zygosaccharomyces rouxii, Zygosaccharomyces bailli, K. lactis, Saccharomyces pastorianus, S. cerevisiae winemaking strain and for fungus Botritys cinerea and human (Glut5p). Among six yeasts transporters, five are fructose specific, acting by facilitated diffusion or proton symport. Yeasts monosaccharides transporter studies allow understanding of sugars uptake and metabolism important aspects, even in higher eukaryotes cells.

The low FODMAP diet improves gastrointestinal symptoms in patients with irritable bowel syndrome: a prospective study

BACKGROUND AND AIM

Current treatment for irritable bowel syndrome (IBS) is suboptimal. Fermentable oligo-, di-, mono-saccharides and polyols (FODMAPs) may trigger gastrointestinal symptoms in IBS patients. Our aim was to determine whether a low FODMAP diet improves symptoms in IBS patients.

METHODS

Irritable bowel syndrome patients, who had performed hydrogen/methane breath testing for fructose and lactose malabsorption and had received dietary advice regarding the low FODMAP diet, were included. The effect of low FODMAP diet was prospectively evaluated using a symptom questionnaire. Furthermore, questions about adherence and satisfaction with symptom improvement, dietary advice and diet were assessed.

RESULTS

Ninety patients with a mean follow up of 15.7 months were studied. Most symptoms including abdominal pain, bloating, flatulence and diarrhoea significantly improved (p < 0.001 for all). 75.6%, 37.8% and 13.3% of patients had fructose, lactose malabsorption or small intestinal bacterial overgrowth respectively. Fructose malabsorption was significantly associated with symptom improvement (abdominal pain odds ratio (OR) 7.09 [95% confidence interval (CI) 2.01-25.0], bloating OR 8.71 (95% CI 2.76-27.5), flatulence OR 7.64 (95% CI 2.53-23.0) and diarrhoea OR 3.39 (95% CI 1.17-9.78), p < 0.029 for all). Most patients (75.6%) were adherent to the diet, which was associated with symptom improvement (abdominal pain, bloating, flatulence and diarrhoea all significantly associated with adherence, r > 0.27, p < 0.011). Most patients (72.1%) were satisfied with their symptoms.

CONCLUSIONS

The low FODMAP diet shows efficacy for IBS patients. The current strategy of breath testing and dietary advice provides a good basis to understand and adhere to the diet.

Effects of fructose vs glucose on regional cerebral blood flow in brain regions involved with appetite and reward pathways

IMPORTANCE

Increases in fructose consumption have paralleled the increasing prevalence of obesity, and high-fructose diets are thought to promote weight gain and insulin resistance. Fructose ingestion produces smaller increases in circulating satiety hormones compared with glucose ingestion, and central administration of fructose provokes feeding in rodents, whereas centrally administered glucose promotes satiety.

OBJECTIVE

To study neurophysiological factors that might underlie associations between fructose consumption and weight gain.

DESIGN, SETTING, AND PARTICIPANTS

Twenty healthy adult volunteers underwent 2 magnetic resonance imaging sessions at Yale University in conjunction with fructose or glucose drink ingestion in a blinded, random-order, crossover design.

MAIN OUTCOME MEASURES

Relative changes in hypothalamic regional cerebral blood flow (CBF) after glucose or fructose ingestion. Secondary outcomes included whole-brain analyses to explore regional CBF changes, functional connectivity analysis to investigate correlations between the hypothalamus and other brain region responses, and hormone responses to fructose and glucose ingestion.

RESULTS

There was a significantly greater reduction in hypothalamic CBF after glucose vs fructose ingestion (-5.45 vs 2.84 mL/g per minute, respectively; mean difference, 8.3 mL/g per minute [95% CI of mean difference, 1.87-14.70]; P = .01). Glucose ingestion (compared with baseline) increased functional connectivity between the hypothalamus and the thalamus and striatum. Fructose increased connectivity between the hypothalamus and thalamus but not the striatum. Regional CBF within the hypothalamus, thalamus, insula, anterior cingulate, and striatum (appetite and reward regions) was reduced after glucose ingestion compared with baseline (P < .05 significance threshold, family-wise error [FWE] whole-brain corrected). In contrast, fructose reduced regional CBF in the thalamus, hippocampus, posterior cingulate cortex, fusiform, and visual cortex (P < .05 significance threshold, FWE whole-brain corrected). In whole-brain voxel-level analyses, there were no significant differences between direct comparisons of fructose vs glucose sessions following correction for multiple comparisons. Fructose vs glucose ingestion resulted in lower peak levels of serum glucose (mean difference, 41.0 mg/dL [95% CI, 27.7-54.5]; P < .001), insulin (mean difference, 49.6 μU/mL [95% CI, 38.2-61.1]; P < .001), and glucagon-like polypeptide 1 (mean difference, 2.1 pmol/L [95% CI, 0.9-3.2]; P = .01).

CONCLUSION AND RELEVANCE

In a series of exploratory analyses, consumption of fructose compared with glucose resulted in a distinct pattern of regional CBF and a smaller increase in systemic glucose, insulin, and glucagon-like polypeptide 1 levels.

Macro- and microdistributions of boron drug for boron neutron capture therapy in an animal model

BACKGROUND

The boron concentration (BC) in the blood, rather than in normal tissue, is often used as the reference to calculate the BC in tumor for boron neutron capture therapy (BNCT). The aims of this study were to justify whether BC in the blood is equal to that of normal tissue, and to verify the macro- and microdistributions of boron in tumor.

MATERIALS AND METHODS

BALB/c nude mice bearing SAS human oral carcinoma xenografts were intravenously injected with 400 mg/kg of boronophenylalanine (BPA). Macro- and microdistributions of boron in the tumor were assayed with (18)F-fluoro-L-boronophenylalanine-fructose (FBPA-Fr)/micro-positron-emission tomography (PET) and alpha track autoradiography, respectively.

RESULTS

The BCs assayed from the blood, normal tissue and tumor varied even on sampling at the same time points post-BPA administration. The ratio of BC in normal tissue to that in blood, i.e. N/B ratio, remains about 1.31 at 30 to 45 min post-BPA administration. Furthermore, (18)F-FBPA-Fr/micro-PET imaging and autoradiography also showed heterogeneous boron distribution in the tumor.

CONCLUSION

The heterogeneous distribution of boron in the tumor is a limiting factor for the precise calculation of BC in the tumor. Here we suggest that the N/B ratio could be used to calculate the true BC in the tumor and in normal tissue for BNCT. (18)F-FBPA-Fr/PET imaging is useful to justify the N/B ratio for BNCT treatment.

Effects of high-fructose corn syrup and sucrose on the pharmacokinetics of fructose and acute metabolic and hemodynamic responses in healthy subjects

It is unclear whether high-fructose corn syrup (HFCS), which contains a higher amount of fructose and provides an immediate source of free fructose, induces greater systemic concentrations of fructose as compared with sucrose. It is also unclear whether exposure to higher levels of fructose leads to increased fructose-induced adverse effects. The objective was to prospectively compare the effects of HFCS- vs sucrose-sweetened soft drinks on acute metabolic and hemodynamic effects. Forty men and women consumed 24 oz of HFCS- or sucrose-sweetened beverages in a randomized crossover design study. Blood and urine samples were collected over 6 hours. Blood pressure, heart rate, fructose, and a variety of other metabolic biomarkers were measured. Fructose area under the curve and maximum concentration, dose-normalized glucose area under the curve and maximum concentration, relative bioavailability of glucose, changes in postprandial concentrations of serum uric acid, and systolic blood pressure maximum levels were higher when HFCS-sweetened beverages were consumed as compared with sucrose-sweetened beverages. Compared with sucrose, HFCS leads to greater fructose systemic exposure and significantly different acute metabolic effects.

Hypoglycemic health benefits of D-psicose

Diabetes is an emerging health problem worldwide. The incidence of type 2 diabetes has dramatically increased and is expected to increase more rapidly in the future. Most patients with type 2 diabetes suffer from obesity and diabetes-related complications, including cardiovascular disease and hepatic steatosis. It has been proposed that simple sugar consumption is one of the major risk factors in the development of diabetes. Hence, the replacement of sugars with a low glycemic response would be an effective strategy to prevent type 2 diabetes. Accumulating evidence demonstrates that D-psicose, which has 70% the sweetness of sucrose and no calories, is a functional sugar exerting several health benefits preventing the development of diabetes. Although D-psicose presents in small amounts in natural products, a recent new technique using biocatalyst sources enables large-scale D-psicose production. More importantly, several clinical and animal studies demonstrated that D-psicose has hypoglycemic, hypolipidemic, and antioxidant activities, which make it an ideal candidate for preventing diabetes and related health concerns. This review will summarize the protective effects of D-psicose against type 2 diabetes and its complications, suggesting its potential benefits as a sucrose substitute.

[Pharmacotherapy of epilepsy: the use of topiramate in initial and additional treatment]

Topiramate (topamax) is an antiepileptic drug of the new generation that was first registered and introduced in clinical practice in 1995. Due to its effective clinical properties, the drug is used widely all over the world including Russia where it has been using since 1999. Topamax is a principally new antiepileptic drug (AED) with the unique mechanism of action, favorable pharmacokinetics, high efficacy and safety. During its existence, it is widely accepted as an AED of first choice for additional and initial treatment of many forms of epilepsy in children over 2 years old and adults including old patients of both sexes. The drug can be successfully used as monotherapy and as well as polytherapy in treatment of most severe and "catastrophic" epilepsies resistant to any previous treatment.

Clinical effects and toxicokinetic evaluation following massive topiramate ingestion

Topiramate is used to treat a variety of neurologic and psychiatric diseases due to its benign safety profile. Data regarding the toxicity and toxicokinetics of topiramate in acute overdose are limited. A case of massive, acute ingestion resulting in the highest reported topiramate level is presented, including toxicokinetic evaluation. A 37-year-old woman presented with coma unresponsive to naloxone following topiramate ingestion. She had normal vital signs without respiratory depression. She was intubated for airway protection, given 3.5 mg lorazepam IV for facial and neck muscle twitching, and transferred to our facility. No additional sedation was required for 18 h on the ventilator. Following mental status improvement, the patient was extubated. Confusion, dysarthria, and imbalance resolved over the next 2 days. Nonanion gap metabolic acidosis persisted for 3 days. Peak serum topiramate level was 356.6 microg/ml (reference range, 5-20 microg/ml). Massive topiramate ingestion led to prolonged coma with normal vital signs and nonanion gap metabolic acidosis. Coma of this severity has not been previously reported. Serum half-life, which has not been studied after overdose, was 16 h. Despite the large ingestion and significant presenting symptoms, the patient recovered fully with supportive intensive care alone. Massive acute topiramate ingestion may lead to nonanion gap metabolic acidosis and prolonged coma which resolves with intensive supportive care. Toxicokinetic data following large, suicidal ingestion of topiramate were similar to previously published pharmacokinetic information.

Pharmacokinetic interaction study between eslicarbazepine acetate and topiramate in healthy subjects

OBJECTIVE

Combination therapy is frequently required in the management of epilepsy. The primary objective of this study was to investigate the pharmacokinetic interaction between eslicarbazepine acetate (ESL) 1200 mg once daily and topiramate (TPM) 200 mg once daily in healthy subjects.

METHODS

Multiple-dose, open-label, one-sequence study in two parallel groups of 16 healthy male volunteers. After an 8-day treatment with ESL (Group A) or TPM (Group B), ESL and TPM were co-administered for 19 days. A bioequivalence approach based on a within-subject comparison was used to investigate a potential drug-drug interaction. End/start of treatment geometric mean ratios (GMR, %) and 90% confidence intervals (90% CI) were calculated for maximum plasma concentration (C(max)) and area under the plasma concentration-time curve over the dosing interval at steady-state (AUC(ss)) of eslicarbazepine (ESL major active metabolite), R-licarbazepine (ESL minor active metabolite) and TPM at Day 8 and Day 27.

RESULTS

In Group A, eslicarbazepine GMR (90% CI) was 86.79% (81.06%; 92.94%) for C(max) and 92.70% (89.21%; 96.32%) for AUC(ss). In Group B, TPM GMR (90% CI) was 81.50% (77.48%; 85.89%) for C(max) and 81.81% (79.69%; 84.00%) for AUC(ss). The 90% CI of eslicarbazepine C(max) and AUC(ss) fell within the pre-specified bioequivalence range (80.00%; 125.00%), allowing it to be concluded that the extent of systemic exposure to eslicarbazepine was unaffected by the concomitant administration of TPM. The 90% CI for topiramate AUC(ss) was borderline in relation to the pre-specified bioequivalence range and topiramate C(max) fell outside the pre-specified bioequivalence range. Therefore, the extent of systemic exposure to TPM following co-administration with ESL was not formally bioequivalent to the extent of systemic exposure to TPM when TPM was administered alone. However, there was no difference between TPM elimination half-life following TPM co-administered with ESL and TPM administered alone (24.0 and 24.3 h, respectively). The bioavailability of R-licarbazepine was essentially bioequivalent. Two subjects discontinued due to adverse events. No clinical interaction appeared to be present in terms of adverse events when both drugs were given concomitantly.

CONCLUSION

Concomitant administration of eslicarbazepine acetate 1200 mg once daily and topiramate 200 mg once daily showed no significant change in exposure to eslicarbazepine but an 18% decrease in exposure to topiramate, most likely caused by a reduced bioavailability of topiramate. No dose adjustment is required.

Review of topiramate for the treatment of epilepsy in elderly patients

Individuals over 65 years of age experience the new onset of seizures at a prevalence rate of roughly twice that of younger adults. Differences in physiology, need of concomitant medications, and liability for cognitive deficits in this population, make the choice of anticonvulsant drugs especially important. This paper reviews topiramate (TPM), a treatment for many types of seizures, with the above risks in mind. In particular, we discuss efficacy and pharmacokinetics with emphasis on the older patient, and adverse events in both the younger and older adult. With most studies of TPM-induced cognitive deficits having been performed in younger adults and volunteers, we discuss the implications for the older adult. Even in studies of younger individuals, up to 50% discontinue TPM because of intolerable cognitive deficits. Most studies find specific declines in working memory and verbal fluency. In conclusion, we give recommendations for use of this antiepileptic drug in this population.

Failure of d-psicose absorbed in the small intestine to metabolize into energy and its low large intestinal fermentability in humans

Experiments with rats have produced data on the metabolism and energy value of d-psicose; however, no such data have been obtained in humans. The authors assessed the availability of d-psicose absorbed in the small intestine by measuring carbohydrate energy expenditure (CEE) by indirect calorimetry. They measured the urinary excretion rate by quantifying d-psicose in urine for 48 hours. To examine d-psicose fermentation in the large intestine, the authors measured breath hydrogen gas and fermentability using 35 strains of intestinal bacteria. Six healthy subjects participated in the CEE test, and 14 participated in breath hydrogen gas and urine tests. d-Psicose fermentation subsequent to an 8-week adaptation period was also assessed by measuring hydrogen gas in 8 subjects. d-Psicose absorbed in the small intestine was not metabolized into energy, unlike glucose, because CEE did not increase within 3 hours of d-psicose ingestion (0.35 g/kg body weight [BW]). The accumulated d-psicose urinary excretion rates were around 70% for 0.34, 0.17, and 0.08 g/kg BW of ingested d-psicose. Low d-psicose fermentability was observed in intestinal bacteria and breath hydrogen gas tests, in which fructooligosaccharide (0.34, 0.17, and 0.08 g/kg BW) was used as a positive control because its available energy is known to be 8.4 kJ/g. Based on the results of the plot of breath hydrogen concentration vs calories ingested, the energy value of d-psicose was expected to be less than 1.6 kJ/g. Incremental d-psicose fermentability subsequent to an adaptation period was not observed.

Retention rates of new antiepileptic drugs in localization-related epilepsy: a single-center study

OBJECTIVES

We evaluated long-term retention rates of newer antiepileptic drugs (AED) in adults with localization-related epilepsy retrospectively.

METHODS

We estimated retention rates by Kaplan-Meier method in all 222 patients (age > or = 16) with localization-related epilepsy exposed to new AED at the Tampere University Hospital.

RESULTS

There were 141 patients exposed to lamotrigine, 78 to levetiracetam, 97 to topiramate, 68 to gabapentin, and 69 to tiagabine. Three-year retention rate for lamotrigine was 73.5%, levetiracetam 65.4%, topiramate 64.2%, gabapentin 41.7%, and tiagabine 38.2%. The most common cause for withdrawal of these AED was lack of efficacy.

CONCLUSIONS

Our study suggests that there are clinically significant differences among gabapentin, lamotrigine, levetiracetam, tiagabine, and topiramate as treatment for focal epilepsy in everyday practice. Gabapentin and tiagabine seem to be less useful than the other three AED. Furthermore, our study supports the value of retention rate studies in assessing outcome of the drugs in clinical practice.

New antiepileptic drugs in pediatric epilepsy

New antiepileptic drugs (AEDs), introduced since 1993, provide more diverse options in the treatment of epilepsy. Despite the equivalent efficacy and better tolerability of these drugs, more than 25% of patients remain refractory to treatment. Moreover, the issues for pediatric patients are different from those for adults, and have not been addressed in the development and application of the new AEDs. Recently published evidence-based treatment guidelines have helped physicians to choose the most reasonable AED, although they cannot fully endorse new AEDs because of the lack of well-designed, randomized controlled trials. We review the mechanisms of action, pharmacokinetic properties, adverse reactions, efficacy, and tolerability of eight new AEDs (felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, topiramate, vigabatrin, and zonisamide), focusing on currently available treatment guidelines and expert opinions regarding pediatric epilepsy.

Molecular pharmacodynamics, clinical therapeutics, and pharmacokinetics of topiramate

Topiramate (TPM; TOPAMAX) is a broad-spectrum antiepileptic drug (AED) that is approved in many world markets for preventing or reducing the frequency of epileptic seizures (as monotherapy or adjunctive therapy), and for the prophylaxis of migraine. TPM, a sulfamate derivative of the naturally occurring sugar D-fructose, possesses several pharmacodynamic properties that may contribute to its clinically useful attributes, and to its observed adverse effects. The sulfamate moiety is essential, but not sufficient, for its pharmacodynamic properties. In this review, we discuss the known pharmacodynamic and pharmacokinetic properties of TPM, as well as its various clinically beneficial and adverse effects.

A highly conserved hydrophobic motif in the exofacial vestibule of fructose transporting SLC2A proteins acts as a critical determinant of their substrate selectivity

The substrate specificity of the facilitated hexose transporter, GLUT, family, (gene SLC2A) is highly varied. Some appear to be able to translocate both glucose and fructose, while the ability to handle 2-deoxyglucose and galactose does not necessarily correlate with the other two hexoses. It has become generally accepted that a central substrate binding/translocation site determines which hexoses can be transported. However, a recent study showed that a single point mutation of a hydrophobic residue in GLUTs 2, 5 & 7 removed their ability to transport fructose without affecting the kinetics of glucose permeation. This residue is in the 7th transmembrane helix, facing the aqueous pore and lies close to the opening of the exofacial vestibule. This study expands these observations to include the other class II GLUTs (9 & 11) and shows that a three amino acid motif (NXI/NXV) appears to be critical in determining if fructose can access the translocation mechanism. GLUT11 can also transport fructose, but it has the motif DSV at the same position, which appears to function in the same manner as NXI and when all three residues are replaced with NAV fructose transport lost. These results are discussed in relation to possible roles for hydrophobic residues lining the aqueous pore at the opening of the exofacial vestibule. Finally, the possibility that the translocation binding site may not be the sole determinant of substrate specificity for these proteins is examined.

Lack of Pharmacokinetic Interaction of Levetiracetam on Carbamazepine, Valproic Acid, Topiramate, and Lamotrigine in Children with Epilepsy

PURPOSE

To determine whether levetiracetam (LEV) affects plasma concentrations of carbamazepine, valproic acid, topiramate, and lamotrigine in children with epilepsy.

METHODS

The potential for interaction of LEV with other antiepileptic drugs (AEDs) was assessed using plasma drug levels obtained in a randomized placebo-controlled phase III trial of adjunctive LEV in children receiving one or two concomitant AEDs. Multiple plasma AED levels at baseline and during adjunctive treatment with LEV or placebo were compared by repeated measures analysis of covariance and mean concentration ratios (treatment/baseline) were estimated with their 90% confidence intervals (CI).

RESULTS

The study population included 187 children receiving any concomitant AED alone or in combination. The geometric mean concentrations at baseline and during LEV treatment were carbamazepine 8.4 microg/ml versus 8.1 microg/ml (coefficient of variation, CV = 30%; n = 35); valproic acid 83.8 versus 82.5 microg/ml (CV = 38%; n = 23); topiramate 7.3 versus 7.2 microg/ml (CV = 82%; n = 28); lamotrigine 8.2 versus 7.7 microg/ml (CV = 62%; n = 22). For each AED, the mean concentration ratios (LEV/baseline) and their 90% CIs showed that AED concentrations were unaffected by concomitant LEV administration. No differences were observed between LEV and placebo.

CONCLUSIONS

LEV does not affect plasma concentrations of carbamazepine, valproic acid, topiramate, or lamotrigine in children with epilepsy.

Fructose malabsorption may be gender dependent and fails to show compensation by colonic adaptation

Fructose malabsorption is linked to gastrointestinal and other unusual symptoms. Polymers of fructose are also recognized prebiotics. While some prebiotics can self-adapt when consumed regularly (resulting in decreased breath hydrogen and symptoms), we wondered whether self-adaptation occurs with basic fructose. We evaluated 90 subjects (61 females). Each completed a diet questionnaire and underwent a fructose challenge. Breath hydrogen and quantified symptom scores were recorded. Group comparisons for sum of breath hydrogen and total symptom scores were evaluated with the Mann-Whitney U test. Spearman's correlation coefficient and chi(2) or Fisher's exact test were used as appropriate. Malabsorption occurred in 29 patients (32.2%) and low-grade symptoms without malabsorption in 30 (33%). Women complained of symptoms more frequently (p = 0.04) and exhibited more fructose malabsorption (p = 0.0527). Breath hydrogen correlated with symptoms (r = 0.516, p = 0.0037). Adaptation with increasing pretest fructose intake was absent. We conclude that gender may influence fructose malabsorption and there is no adaptation to regular consumption.

PET/CT with Gluc-Lys-([(18)F]FP)-TOCA: correlation between uptake, size and arterial perfusion in somatostatin receptor positive lesions

PURPOSE

Somatostatin receptor (sstr) positive tumours vary widely in uptake of radiolabelled somatostatin (sst) analogues. This study determinates variability in lesion uptake of the glycosylated sst analogon N(alpha)-(1-deoxy-D-fructosyl)-N(epsilon)-(2-[(18)F]fluoropropionyl)-Lys(0)-Tyr(3)-octreotate (Gluc-Lys([(18)F]FP)-TOCA) and correlates it with lesion size and arterial perfusion as measured on computed tomography (CT).

METHODS

Ten patients with metastasized neuroendocrine carcinomas were investigated with positron emission tomography PET/CT (Biograph 16, Siemens, Germany). Lesion standardized uptake values (SUVs) were determined at approximately 50 min post tracer injection according to a 60% isocontour volume of interest around each lesion. Lesion size and enhancement in the arterial phase (hounsfield units, HUs) were derived from CT.

RESULTS

114 lesions in the upper abdomen had a correlate on both, PET and CT. Variability in lesion SUVs was high (SUV(mean) 22 +/- 13). Intraindividually, there was a sigmoid positive correlation between lesion SUV and lesion diameter indicating partial volume effects. Residual variability in lesions > or =3 cm (> or =2.5 cm) ranged down to about half (third) of the maximum lesion uptake and remained unexplained by partial volume effects. No correlation with measured HU in the arterial phase was found, neither intraindividually nor interindividually.

CONCLUSION

Partial volume effects were a major source of intraindividual variability in tumour tracer uptake. Lesions below 2.5 to 3 cm should thus be used with caution when performing dose calculations. In larger lesions residual variability in uptake must be considered; it may be due to variable sstr2 expression on the tumours' cell surfaces.

Effects of sucromalt on postprandial responses in human subjects

BACKGROUND/OBJECTIVE

To compare postprandial responses elicited by sucromalt, a nutritive sweetener produced by treating a blend of sucrose and corn syrup with an enzyme from Leuconostoc mesenteroides, with those after 42% of high-fructose corn syrup (HFCS), and to see if the reduced responses after sucromalt could be accounted for by carbohydrate malabsorption.

SUBJECT AND METHODS

Three experiments were performed in separate groups of normal subjects studied after overnight fasts using double-blind, randomized, cross-over designs. HFCS was used as the control because it contained a similar amount of fructose as sucromalt. Experiment 1 (n = 10): plasma glucose and insulin were measured after 50 g sucromalt and 50 g HFCS. Experiment 2 (n = 10): metabolic profiles were measured after 80 g HFCS, 80 g sucromalt or 56 g fructose/glucose blend plus 24 g inulin. Experiment 3 (n = 20): the glycaemic indices of sucromalt and HFCS were determined.

RESULTS

Mean glucose and insulin responses after sucromalt were 66 and 62%, respectively, of those after HFCS (P < 0.05). The inulin treatment, used to mimic the effects of carbohydrate malabsorption, elicited higher breath hydrogen (H2), lower glucose and insulin responses, and a significantly earlier rise in serum free fatty acids (FFA) than those of HFCS (all P < 0.05). Sucromalt elicited no rise in breath H2, and delayed falls in glucose and insulin, and a delayed rebound of FFA compared to HFCS (all P < 0.05).

CONCLUSIONS

The reduced glucose and insulin responses elicited by sucromalt are not explained by malabsorption and are more likely related to differences in either rate of digestion and absorption or postabsorptive handling by body.

Truncated AUCs in the assessment of the bioequivalence of topiramate, a long half-life drug

This study was conducted in order to assess the bioequivalence of two tablet formulations containing topiramate (CAS 97240-79-4), 25 mg. Twenty-four healthy volunteers were enrolled in an open-label, randomised, crossover, 2 periods x 2 sequences, with a minimum washout period of 21 days, single dose study. Blood samples were collected prior to study drug administration and 0.167, 0.333, 0.500, 0.667, 1.00, 1.33, 1.67, 2.00, 2.50, 3.00, 4.00, 6.00, 8.00, 12.0, 24.0, 48.0, 96.0, 144, 192, and 264 h post-dose in each period. Plasma levels of topiramate from the 23 subjects who completed the study, were determined by high-pressure liquid chromatography with tandem mass detection, HPLC/MS/MS (lower limit of quantification 9.98 ng/mL). Pharmacokinetic parameters used for bioequivalence assessment (AUC(last), AUC(inf) and C(max)) were determined from the plasma concentration data using non-compartmental analysis. Mean +/- standard deviation elimination half-life for the reference formulation was 84.18 +/- 14.61h whereas for the test formulation it was 80.82 +/- 11.50h. The 90% Confidence Intervals (90 CI) were 98.00-111.35% for C(max), 98.44-103.76% for AUC(last) and 96.61-103.00% for AUC(inf), that is, within the ranges defined in the protocol for acceptance of bioequivalence. The 90 CIs obtained for the truncated AUCs were as follows: 100.27-105.32% for AUC0-48, 99.28-104.62% for AUC0-48, 99.13-104.56% for AUC0-96, 95.67-104.82% for AUC0-144, and 100.04-103.76% for AUC0-192. Both analysed formulations are bioequivalent irrespective of whether the conventional or truncated AUC approach is used. This study demonstrated that topiramate can be viewed as a long half-life drug and that the truncated AUC ap proach could be considered for bioequivalence assessment.

Ability of the normal human small intestine to absorb fructose: evaluation by breath testing

BACKGROUND & AIMS

Fructose consumption is increasing, and its malabsorption causes common gastrointestinal symptoms. Because its absorption capacity is poorly understood, there is no standard method of assessing fructose absorption. We performed a dose-response study of fructose absorption in healthy subjects to develop a breath test to distinguish normal from abnormal fructose absorption capacity.

METHODS

In a double-blind study, 20 healthy subjects received 10% solutions of 15, 25, and 50 g of fructose and 33% solution of 50-g fructose on 4 separate days at weekly intervals. Breath samples were assessed for hydrogen (H2) and methane (CH4) during a period of 5 hours, and symptoms were recorded.

RESULTS

No subject tested positive with 15 g. Two (10%) tested positive with 25 g fructose but were asymptomatic. Sixteen (80%) tested positive with 50 g (10% solution), and 11 (55%) had symptoms. Breath H2 was elevated in 13 (65%), CH4 in 1 (5%), and both in 2 (10%). Twelve (60%) tested positive with 50 g (33% solution), and 9 (45%) experienced symptoms. The area under the curve for H2 and CH4 was higher (P < .01) with 50 g compared with lower doses. There were no gender differences.

CONCLUSIONS

Healthy subjects have the capacity to absorb up to 25 g fructose, whereas many exhibit malabsorption and intolerance with 50 g fructose. Hence, we recommend 25 g as the dose for testing subjects with suspected fructose malabsorption. Breath samples measured for H2 and CH4 concentration at 30-minute intervals and for 3 hours will detect most subjects with fructose malabsorption.

Global transcriptional analysis of Streptococcus mutans sugar transporters using microarrays

The transport of carbohydrates by Streptococcus mutans is accomplished by the phosphoenolpyruvate-phosphotransferase system (PTS) and ATP-binding cassette (ABC) transporters. To undertake a global transcriptional analysis of all S. mutans sugar transporters simultaneously, we used a whole-genome expression microarray. Global transcription profiles of S. mutans UA159 were determined for several monosaccharides (glucose, fructose, galactose, and mannose), disaccharides (sucrose, lactose, maltose, and trehalose), a beta-glucoside (cellobiose), oligosaccharides (raffinose, stachyose, and maltotriose), and a sugar alcohol (mannitol). The results revealed that PTSs were responsible for transport of monosaccharides, disaccharides, beta-glucosides, and sugar alcohol. Six PTSs were transcribed only if a specific sugar was present in the growth medium; thus, they were regulated at the transcriptional level. These included transporters for fructose, lactose, cellobiose, and trehalose and two transporters for mannitol. Three PTSs were repressed under all conditions tested. Interestingly, five PTSs were always highly expressed regardless of the sugar source used, presumably suggesting their availability for immediate uptake of most common dietary sugars (glucose, fructose, maltose, and sucrose). The ABC transporters were found to be specific for oligosaccharides, raffinose, stachyose, and isomaltosaccharides. Compared to the PTSs, the ABC transporters showed higher transcription under several tested conditions, suggesting that they might be transporting multiple substrates.

Safety and efficacy of anticonvulsants in elderly patients with psychiatric disorders: oxcarbazepine, topiramate and gabapentin

Few controlled studies are available to guide the clinician in treating potentially assaultive elderly individuals with psychiatric disorders. Safety concerns limit the use of benzodiazepines and antipsychotic medications in the elderly individual, making anticonvulsants an attractive alternative. This paper reviews three specific anticonvulsants for this purpose: gabapentin, oxcarbazepine and topiramate, describing safety and efficacy in elderly patients with severe agitation from psychosis or dementia. Gabapentin, renally excreted, with a half-life of 6.5-10.5 h, may cause ataxia. Oxcarbazapine, hepatically reduced, may cause hyponatremia, and topiramate may cause significant cognitive impairment. Nonetheless, these are important medications to consider in the treatment of agitation.

Potential genetic causes of heterogeneity of treatment effects

Nongenetic biologic and lifestyle-related factors, including age, sex, hepatic/renal function, diet/exercise practices, illness severity, smoking, and alcohol consumption habits can account for the heterogeneity of treatment effects (HTE). However, even when these factors are taken into account, considerable variation remains unexplained and could potentially be attributable to genetic differences between patients. Drug response may be dictated by variation in genes involved in both pharmacokinetic (PK) (absorption, distribution, metabolism, excretion [ADME]) and pharmacodynamic (PD) (receptors, ion channels, enzymes, immune system) pathways. Functional variants of the ADME genes can result in patients being poor, intermediate, efficient, or ultrarapid metabolizers of specific agents, thereby affecting efficacy and/or susceptibility to adverse drug reaction and necessitating individualized dosing. A well-documented example of ADME gene variation is the debrisoquine polymorphism, which is characterized by markedly different metabolism of numerous commonly prescribed drugs based on variants of the cytochrome P450 2D6 gene. Variants of genes regulating PD pathways cause altering of drug target pathways, which may affect efficacy in a more pronounced manner. Examples of gene variants affecting PD pathways include those coding for dopamine metabolism, synthesis, and transport. These gene variants may act independently, in combination with each other, and/or in combination with PK genes to affect drug response, for example to antipsychotic medications. Increased understanding of a patient's genotype and its corresponding effect on drug response would be useful to the practicing clinician in choosing an effective drug and in optimizing the dose in a timely manner.

Eucalyptus leaf extract inhibits intestinal fructose absorption, and suppresses adiposity due to dietary sucrose in rats

Sucrose is more lipogenic than starch, and the extreme ingestion of sucrose induces adiposity and obesity. The aim of this study was to examine the effect of the eucalyptus (Eucalyptus globulus) leaf extract (ELE) on adiposity due to dietary sucrose in rats. In addition, in this study, the effect of ELE on intestinal fructose absorption was also examined. Rats were fed a high-sucrose diet (75 % in calorie base) with or without ELE (10 g/kg diet) for 5 weeks. Body weight was lower in the rats receiving ELE than in the controls (342 (sd 37·9)v. 392 (sd 26·0) g (n7);P<0·05). Furthermore, ELE resulted in decreases in the triacylglycerol concentrations in the plasma (1·44 (sd 0·448)v.2·79 (sd 0·677) mmol/l (n7);P<0·05) and liver (19·1 (sd 5·07)v.44·1 (sd 16·28) μmol/g (n7);P<0·05). In contrast, ELE did not show any significant effects in the rats fed a starch diet. When rats were orally given ELE 10 min before fructose administration, the intestinal fructose absorption, which was examined by measuring the elevated concentration of fructose in the portal vein at 30 min after the fructose administration, was significantly inhibited in a dose-dependent manner. Furthermore, in rats fed a high-fructose diet, the plasma and hepatic triacylglycerol concentrations were significantly decreased by ELE. These results indicate that ELE, which inhibits the intestinal fructose absorption, can suppress adiposity in rats that ingest large amounts of sucrose or fructose.

Isobolographic analysis of interaction between drugs with nonparallel dose-response relationship curves: a practical application

The objective of this study was to characterize the anticonvulsant and acute adverse-effect potentials of topiramate (TPM) and gabapentin (GBP)-two second-generation antiepileptic drugs administered alone and in combination in the maximal electroshock (MES)-induced seizures and chimney test in mice. The anticonvulsant and acute adverse effects of the combination of TPM with GBP at the fixed ratio of 1:1 were determined using the type I isobolographic analysis for nonparallel dose-response relationship curves (DRRCs). To ascertain any pharmacokinetic contribution to the observed interaction between TPM and GBP, total brain concentrations of both drugs were determined. The isobolographic analysis of interaction for TPM and GBP, whose DRRCs were not parallel in both MES and chimney tests, was accompanied with a presentation of all required calculations allowing the determination of lower and upper lines of additivity. The isobolographic analysis revealed that TPM combined with GBP at the fixed-ratio combination of 1:1 interacted supraadditively (synergistically) in terms of suppression of MES-induced seizures, and simultaneously, the combination produced additive interaction with respect to motor coordination impairment (adverse effects) in the chimney test. The evaluation of pharmacokinetic characteristics of interaction for the combination of TPM with GBP revealed that neither TPM nor GBP affected their total brain concentrations in experimental animals, and thus, the observed interaction in the MES test was pharmacodynamic in nature. In conclusion, the combination of TPM with GBP, because of supraadditivity in the MES test and additivity in terms of motor coordination impairment in the chimney test as well as lack of pharmacokinetic interactions between drugs, fulfilled the criterion of a favorable combination, worthy of recommendation in further clinical practice.

Sodium, ammonium, calcium, and magnesium forms of zeolite Y for the adsorption of glucose and fructose from aqueous solutions

The kinetics of adsorption by sodium, ammonium, calcium and magnesium forms of zeolite Y from aqueous solutions containing 25% w/v of either one or an equimolar mixture of glucose (G) and fructose (F) have been studied batch-wise at 50 degrees C. The adsorption of aqueous pure G was fast, while that of aqueous pure F depended on the cationic form, approaching that of G on the Mg-Y, and slowing down in the sequence of Mg2+ > NH4+ > Ca2+ > Na+ of the cations. The adsorption behavior from solutions containing both G and F indicated significant hindering effects of F on G on Na-Y. Na-Y and Mg-Y did not exhibit rate-based selectivity, while Ca-Y an NH4-Y adsorbed G faster than F. Addition of CaCl2 to the mixture of Ca-Y and aqueous solution of G and F improved the separation, by hindering the adsorption of F. Addition of NH4Cl to the mixture of the sugar solution and NH4-Y, on the other hand, had a negative effect on the separation. NH4-Y was found to be desorbing about 30% of the adsorbed sugars and this value was found to be around 50% for Ca-Y. Re-adsorption experiments resulted in similar or somewhat higher percentages of amounts adsorbed compared to adsorption on fresh samples. Both NH4-Y and Ca-Y were found to be re-adsorbing around 50% of the sugars they adsorbed on fresh samples.

Pharmacokinetic and pharmacodynamic interactions of aminophylline and topiramate in the mouse maximal electroshock-induced seizure model

The aim of this study was to determine the influence of acute (single) and chronic (twice daily for 14 consecutive days) treatments with aminophylline (theophylline(2).ethylenediamine) on the anticonvulsant potential of topiramate (a broad-spectrum antiepileptic drug) in the mouse maximal electroshock-induced seizure model. Additionally, the effects of acute and chronic administration of aminophylline on the adverse effect potential of topiramate were assessed in the chimney test (motor performance). To evaluate pharmacokinetic characteristics of interaction between topiramate and aminophylline, total brain concentrations of topiramate and theophylline were estimated with fluorescence polarization immunoassay technique. Results indicate that aminophylline in non-convulsive doses of 50 and 100 mg/kg (i.p.), both in acute and chronic experiments, markedly attenuated the anticonvulsant potential of topiramate by raising its ED(50) value against maximal electroconvulsions. Aminophylline at a lower dose of 25 mg/kg did not affect significantly the ED(50) value of topiramate in the acute experiment, but the drug markedly increased the ED(50) value of topiramate during the chronic treatment in mice. Only, aminophylline at 12.5 mg/kg, in both acute and chronic experiments, did not affect the antielectroshock action of topiramate in mice. Moreover, aminophylline at a dose of 100 mg/kg had no impact on the adverse effect potential of topiramate in the chimney test. Pharmacokinetic evaluation of total brain concentrations of topiramate and theophylline revealed that topiramate significantly increased total brain theophylline concentrations following both acute and chronic applications of aminophylline. Conversely, aminophylline did not alter total brain concentrations of topiramate in mice. Based on this preclinical study, one can conclude that aminophylline attenuated the antiseizure action of topiramate in the mouse maximal electroshock-induced seizure model and the observed interaction between drugs was both pharmacokinetic and pharmacodynamic in nature.

[An association between the FABP2 gene polymorphism and efficacy of valproates]

To search for association between the 163G>A polymorphism of the fatty acid binding protein 2 (FABP2) gene and intracellular transport of the valproic acid in the small intestines, 168 patients with different forms of epilepsy, aged from 1 to 89 years, and different illness duration have been studied. The patients received valproates (127 patients) and topiramate (41 patients) as a monotherapy. It has been shown that the 163G>A (Ala54Thr) polymorphism exerts an influence on effective dose of the valproic acid but not of topiramate.

Fructose malabsorption in Thai adult

Fructose malabsorption has not been well-defined in Thai populations but there has been increasing consumption of fructose-fortified drinks.

OBJECTIVES

To assess the incidence of fructose malabsorption and intolerance in Thai normal subjects as well as the facilitating effect of glucose on fructose absorption.

METHODS

Twenty-five gram of fructose was ingested by 77 subjects (37 men, 40 women; mean age 26 and 31 y, range 20-50 y and 21-50 y for men and women, respectively). Measurement of breath-H(2) levels after fructose ingestion in each subject up to 2 h was performed. Those who showed fructose malabsorption were later given 25 g of each glucose and fructose and second tests of breath-H(2) tests were done.

RESULTS

Fructose malabsorption was found in eleven females with a significant rise in average breath-H(2) level at 30, 60, 90, and 120 min (p< 0.001), whereas none of the males had an abnormal breath-H(2) test. Only 1 of the 11 females with increased breath H(2) had gastrointestinal symptoms. In all the fructose malabsorbers, excess breath-H(2) reverted to normal when the fructose solution was mixed and administered with 25 g glucose (p< 0.001).

CONCLUSION

The incidence rate of fructose malabsorption was 11 of 77 subjects but these were female. One of the 11 had gastrointestinal symptoms. It was found that an equal amount of glucose would abolish fructose malabsorption.

A 4-wk high-fructose diet alters lipid metabolism without affecting insulin sensitivity or ectopic lipids in healthy humans

BACKGROUND

High fructose consumption is suspected to be causally linked to the epidemics of obesity and metabolic disorders. In rodents, fructose leads to insulin resistance and ectopic lipid deposition. In humans, the effects of fructose on insulin sensitivity remain debated, whereas its effect on ectopic lipids has never been investigated.

OBJECTIVE

We assessed the effect of moderate fructose supplementation on insulin sensitivity (IS) and ectopic lipids in healthy male volunteers (n = 7).

DESIGN

IS, intrahepatocellular lipids (IHCL), and intramyocellular lipids (IMCL) were measured before and after 1 and 4 wk of a high-fructose diet containing 1.5 g fructose . kg body wt(-1) . d(-1). Adipose tissue IS was evaluated from nonesterified fatty acid suppression, hepatic IS from suppression of hepatic glucose output (6,6-2H2-glucose), and muscle IS from the whole-body glucose disposal rate during a 2-step hyperinsulinemic euglycemic clamp. IHCL and IMCL were measured by 1H magnetic resonance spectroscopy.

RESULTS

Fructose caused significant (P < 0.05) increases in fasting plasma concentrations of triacylglycerol (36%), VLDL-triacylglycerol (72%), lactate (49%), glucose (5.5%), and leptin (48%) without any significant changes in body weight, IHCL, IMCL, or IS. IHCL were negatively correlated with triacylglycerol after 4 wk of the high-fructose diet (r = -0.78, P < 0.05).

CONCLUSION

Moderate fructose supplementation over 4 wk increases plasma triacylglycerol and glucose concentrations without causing ectopic lipid deposition or insulin resistance in healthy humans.

Gabapentin synergistically interacts with topiramate in the mouse maximal electroshock seizure model: an isobolographic analysis

The anticonvulsant effects produced by topiramate (TPM) and gabapentin (GBP)--two second-generation antiepileptic drugs, in numerous fixed-ratio combinations of 8:1, 4:1, 2:1, 1:1, 1:2, 1:4 and 1:8 were examined by isobolographic analysis in the mouse maximal electroshock seizure (MES) model. Results indicate that the combinations of TPM and GBP at the fixed-ratios of 2:1, 1:1, 1:2, 1:4 and 1:8 resulted in supra-additive (synergistic) interaction against MES-induced seizures. Moreover, the combinations of TPM and GBP (at their median effective doses) did not affect motor performance of animals challenged with the chimney test and had no impact on neuromuscular tone in the grip-strength test. Additionally, GBP had no impact on total brain TPM concentrations, and simultaneously, TPM did not alter brain GBP concentrations, indicating that the interaction between drugs was pharmacodynamic in nature. In conclusion, supra-additive interaction of TPM with GBP against MES-induced seizures, lack of motor coordination and neuromuscular tone impairments as well as lack of pharmacokinetic interactions between TPM and GBP in preclinical study, strongly support the combined application of both antiepileptic drugs in patients with refractory partial epilepsy.

Topiramate and its clinical applications in epilepsy

Topiramate, a derivative of the monosaccharide d-fructose, has shown a wide spectrum of antiepileptic efficacy in both animal models and clinical trials. Multiple putative mechanisms of action include voltage-sensitive sodium channel blockade, calcium channel inhibition, increase of potassium conductance, GABA-mediated chloride current increment, glutamate-mediated neurotransmission inhibition and carbonic anhydrase isoenzyme inhibition. In general, the clinical response is maintained in the long-term. The most common side effects include somnolence, fatigue, headache, psychomotor slowing, confusion, difficulty with memory, impaired concentration and attention, speech and language problems and weight loss. If slowly titrated and used at a low-to-medium dosage, it is well tolerated and offers a valid therapeutic option, the relevance of which is comparable to that of the most widely used 'old' antiepileptic drugs. As it is not yet wholly clear which specific epilepsy syndromes may benefit most from topiramate with respect to other drugs, more accurate indications for initial monotherapy would require syndrome-oriented trials and more clinical experience.

Gluc-Lys([18F]FP)-TOCA PET in patients with SSTR-positive tumors: biodistribution and diagnostic evaluation compared with [111In]DTPA-octreotide

A recently developed (18)F-labeled PET tracer for somatostatin receptor (sstr) imaging, N(alpha)-(1-deoxy-D-fructosyl)-N(epsilon)-(2-[(18)F]fluoropropionyl)-Lys(0)-Tyr(3)-octreotate (Gluc-Lys([(18)F]FP)-TOCA), was evaluated in patients with sstr-positive tumors by assessing the pharmacokinetics, biodistribution, and diagnostic performance in comparison with [(111)In]DTPA-octreotide.

METHODS

Twenty-five patients with different sstr-positive tumors were included in the study and were injected with 105 +/- 50 MBq Gluc-Lys([(18)F]FP)-TOCA. PET was performed up to 120 min with 2 different dynamic imaging protocols. Tracer kinetics in tumors and nontumor tissues and tumor-to-background ratios were described by region-of-interest analysis and standardized uptake values (SUVs). In 16 patients, sstr scintigraphy with [(111)In]DTPA-octreotide was performed (whole-body scans and SPECT). Two independent experts on PET and gamma- camera scans performed lesion counts.

RESULTS

Gluc-Lys([(18)F]FP)-TOCA showed a fast and intense tumor accumulation as well as a rapid clearance from blood serum (biexponential elimination, with the half-lives of the initial and the terminal elimination phase calculated as t(1/2)(1) = 2.3 +/- 1.3 min and t(1/2)(2) = 26.4 +/- 14.6 min, respectively). Tumor-to-background ratios at 16 +/- 9 min and 34 +/- 12 min were as high as 80% and 90% (% of maximum ratios), respectively. Tumors showed high SUVs ranging from 13.7 +/- 2.3 (tumors in lung) up to 26.9 +/- 15.4 (abdominal tumors). Tracer distribution within tumor and nontumor tissues was stable up to 120 min (except spleen). No significant bowel activity was observed. Comparison of 29 tumors located in the liver showed a mean tumor-to-background ratio of 5.3 +/- 2.6 for Gluc-Lys([(18)F]FP)-TOCA vs. 4.6 +/- 3.3 for [(111)In]DTPA-octreotide (P = 0.24). Visual image analysis revealed a significantly higher number of lesions (factor of 2.4) and improved interobserver correlation (r = 0.99 vs. 0.86) for PET.

CONCLUSION

Gluc-Lys([(18)F]FP)-TOCA PET allows a fast, high- contrast imaging of sstr-positive tumors. The biokinetics and diagnostic performance of Gluc-Lys([(18)F]FP)-TOCA are superior to [(111)In]DTPA-octreotide and-as far as can be derived from the literature-comparable with [(68)Ga]-DOTA-d Phe(1)-Tyr(3)-octreotide ([(68)Ga]DOTATOC).

Brain Homocarnosine and Seizure Control of Patients Taking Gabapentin or Topiramate

PURPOSE

To assess the relation between seizure control and brain homocarnosine and gamma-aminobutyric acid (GABA) levels of patients with complex partial seizures taking gabapentin (GBP) or topiramate (TPM) as adjunctive therapy.

METHODS

In vivo measurements of GABA and homocarnosine were made of a 14-cc volume in the occipital cortex by using (1)H spectroscopy with a 2.1-Tesla magnetic resonance spectrometer and an 8-cm surface coil. Poor seizure control was defined as more recent seizures than the median for the two groups of patients studied.

RESULTS

Homocarnosine levels were higher in patients with better seizure control than in those with poor control. No differences were found in the intracellular GABA levels between the patients who responded to GBP or TPM compared with those who did not.

CONCLUSIONS

In the visual neocortex, which is remote from the presumed seizure-onset zone, higher homocarnosine levels were associated with better seizure control in the patients taking GBP or TPM as adjunctive therapy; elevated intracellular GABA levels appeared to offer no additional protection.

Clinical experience with topiramate dosing and serum levels in patients with epilepsy

OBJECTIVE

To investigate the relevance of serum topiramate (TPM) levels (SL) monitoring in the clinical management of epileptic patients.

METHODS

Twenty-seven patients with different epileptic syndromes on TPM therapy were studied. TPM was used as add-on in 26 patients, only in one as monotherapy de novo; one case changed from TPM as add-on to TPM monotherapy. The mean follow-up time was 11 months. TPM SL were measured by fluorescence polarization immunoassay.

RESULTS

We analyzed the TPM SL in 43 samples from 27 patients. Mean TPM dose was 3.9mg/kg, mean TPM SL 13.43mumol/l. The mean level to dose ratio (LDR) was 3.63mumol/l/mg/kg. Four patients became seizure-free, all with TPM dosages lower than the mean. Eleven patients had at least 50% seizure reduction. The comedication with enzyme-inducing AED significantly reduced TPM SL and LDR. On the other hand, the influence of valproic acid (VPA) on TPM LDR was not univocal. Indeed, patients younger than 15 years showed SL values lower than the adults did, although not significant.

CONCLUSION

We could not detect a direct relationship between high TPM SL and efficacy neither between high TPM SL and tolerability. However, the data we collected seem to favour the hypothesis that high TPM dosage and SL might be associated to a greater probability to reduce seizure severity.