Changes in laboratory markers of thrombotic risk early in the first trimester of pregnancy may be linked to an increase in estradiol and progesterone

BACKGROUND

Pregnant women are at increased risk of venous thrombosis compared to non-pregnant women. Epidemiological and laboratory data suggest that hypercoagulability begins in the first trimester but it is unknown exactly how early in pregnancy this develops. The mechanisms that result in a prothrombotic state may involve oestrogens and progestogens.

METHODS

Plasma samples were taken prior to conception and five times in early pregnancy, up to Day 59 gestation, from 22 women undergoing natural cycle in vitro fertilization, who subsequently gave birth at term following a normal pregnancy. Thrombin generation, free Protein S, Ddimer, Fibrinogen, factor VIII, estradiol and progesterone were measured. To counter inter-individual variability, the change in laboratory measurements between the pre-pregnant and pregnant state were measured over time.

RESULTS

Peak thrombin, Endogenous Thrombin Potential, Velocity Index and fibrinogen significantly increased, and free Protein S significantly decreased, from pre-pregnancy levels, by 32 days gestation. Ddimer and VIII significantly increased from pre-pregnancy levels by 59 days gestation. Estradiol significantly increased by Day 32 gestation with a non-significant increase of 67% by Day 24 gestation. Progesterone significantly increased by Day 32 gestation. Almost all laboratory markers of thrombosis correlated significantly with estradiol and progesterone.

CONCLUSION

Our work is the first to demonstrate that the prothrombotic state develops very early in the first trimester. Laboratory markers of hypercoagulability correlate significantly with estradiol and progesterone suggesting these are linked to the prothrombotic state of pregnancy. Clinicians should consider commencing thromboprophylaxis early in the first trimester in women at high thrombotic risk.

Coffee inhibition of CYP3A4 in vitro was not translated to a grapefruit-like pharmacokinetic interaction clinically

Grapefruit can augment oral medication bioavailability through irreversible (mechanism‐based) inhibition of intestinal CYP3A4. Supplementary data from our recent coffee–drug interaction clinical study showed some subjects had higher area under the plasma drug concentration ‐ time curve (AUC) and plasma peak drug concentration (Cmax) of the CYP3A4 probe felodipine compared to aqueous control. It was hypothesized that coffee might interact like grapefruit in responsive individuals. Beans from six geographical locations were consistently brewed into coffee that was separated chromatographically to a methanolic fraction for in vitro inhibition testing of CYP3A4 metabolism of felodipine at 1% coffee strength. The effect of simultaneous incubation and 10‐min preincubation with coffee fractions determined whether coffee had direct and mechanism‐based inhibitory activity. A subsequent five‐way randomized balanced controlled crossover clinical study evaluated the clinical pharmacokinetic interaction with single‐dose felodipine. Grapefruit juice, water, or three of the in vitro tested coffees were ingested at 300 mL alone 1 h before and then with felodipine. In vitro, all six coffees decreased felodipine metabolism for both simultaneous and preincubation exposure compared to corresponding control. Five coffees demonstrated mechanism‐based inhibition. Grapefruit increased felodipine AUC_0–8 (25 vs. 13 ng.h/mL, P < 0.001) and Cmax (5.8 vs. 2.7 ng/mL, P < 0.001) and decreased dehydrofelodipine/felodipine AUC_0–8 ratio (0.84 vs. 1.29, P < 0.001), while the three coffees caused no change in these parameters compared to water. Despite high in vitro potency of CYP3A4 inhibition, the coffees did not cause a clinical pharmacokinetic interaction possibly from insufficient amount of inhibitor(s) in coffee reaching intestinal CYP3A4 during the absorption phase of felodipine. The results of this study highlight the need for follow‐up clinical testing when in vitro results indicate the possibility of an interaction.

Coffee-Antihypertensive Drug Interaction: A Hemodynamic and Pharmacokinetic Study With Felodipine

OBJECTIVES

A period of abstinence from coffee to permit caffeine elimination appears to enable increased blood pressure on subsequent exposure. We hypothesized that this would offset the antihypertensive effect of the dihydropyridine calcium channel blocker felodipine.

METHODS

A randomized, single-dose, crossover study assessed hemodynamic and pharmacokinetic effects following 2 days without coffee and caffeine-containing foods. Consistently brewed black coffee (2×300ml), felodipine maximum recommended dose (10mg), and coffee plus felodipine were tested in middle-aged normotensive subjects.

RESULTS

Pretreatment plasma caffeine concentrations were unquantifiable. After coffee, blood pressure changes (mm Hg) averaged over study hours 1-4 were increased for brachial systolic (7.6, P < 0.001) and diastolic (4.9, P < 0.001) and aortic systolic (7.4, P < 0.001), pulse (3.0, P < 0.05) and augmentation (1.4, P < 0.05) relative to baseline. After coffee plus felodipine, they were higher for brachial systolic (4.0, P < 0.05) and diastolic (3.9, P < 0.001) and aortic systolic (4.6, P < 0.05) compared to felodipine alone. The pressor effects of coffee and its modulation by felodipine were variable among individuals. Coffee containing caffeine (127mg) caused maximum pressor effect. Caffeine and felodipine pharmacokinetics were similar for coffee and felodipine given alone or in combination indicating an interaction having a pharmacodynamic basis. Plasma felodipine concentration-diastolic blood pressure reduction relationship shifted with coffee such that doubling the felodipine concentration would eliminate the pressor effect. However, this may increase the risk of adverse drug events particularly during the timeframe without coffee.

CONCLUSION

Intermittent coffee ingestion might complicate hypertension diagnosis and management for many individuals.

Optogenetic apoptosis: light-triggered cell death

An optogenetic Bax has been designed that facilitates light-induced apoptosis. We demonstrate that mitochondrial recruitment of a genetically encoded light-responsive Bax results in the release of mitochondrial proteins, downstream caspase-3 cleavage, changes in cellular morphology, and ultimately cell death. Mutagenesis of a key phosphorylatable residue or modification of the C-terminus mitigates background (dark) levels of apoptosis that result from Bax overexpression. The mechanism of optogenetic Bax-mediated apoptosis was explored using a series of small molecules known to interfere with various steps in programmed cell death. Optogenetic Bax appears to form a mitochondrial apoptosis-induced channel analogous to that of endogenous Bax.

Micro-techniques for analysis of human adipose tissue fatty acid composition in dietary studies

BACKGROUND AND AIMS

Adipose tissue (AT) fatty acid (FA) composition is considered to be the gold standard long-term biomarker of dietary fatty acid intake. Typically this measurement is made directly from samples collected via large-needle-biopsy or incision. However, with growing interest in the role of AT in relation to health, ideally the fatty acid composition would be analysed along with other measurements, such as gene expression or histology, on a single AT sample. Here we assess alternative ways of obtaining AT for measuring FA composition, in some cases in conjunction with other measurements.

METHODS AND RESULTS

The FA composition of tissue obtained via different methods was compared to that of tissue collected via large-needle or surgical biopsy. Fatty acid composition was not significantly different in AT collected by small-needle mini-biopsy (n = 10), from an RNA 'lipid layer' (obtained during RNA extraction, 2 sites, n = 6 for each), or from cryosectioned tissue prepared for histology (n = 10). We also assessed the usefulness of the composition of plasma NEFA as a surrogate marker of subcutaneous AT (n = 58-80). Most FAs in plasma NEFA correlated strongly with those in AT (P < 0.05).

CONCLUSION

It is feasible to measure the FA composition of AT on very small amounts of tissue. Additionally, it is possible to measure FA composition on the lipid rich 'by-product' of AT samples undergoing RNA extraction for gene expression. Samples sectioned for histology are also suitable. This provides further opportunities for multidisciplinary collaborations that may lead to a better application of dietary biomarkers.

Endothelial FOS expression and pre-eclampsia

OBJECTIVE

To study gene expression profiles in human endothelial cells incubated with plasma from women who developed pre-eclampsia and women with normotensive pregnancies.

DESIGN

A case-control study.

SETTING

A longitudinal nested case-control study within three maternity units.

POPULATION

A mixed obstetric population attending maternity hospitals in Glasgow.

METHODS

Plasma was obtained at both 16 and 28 weeks of gestation from 12 women: six women subsequently developed pre-eclampsia (cases) and six women, matched for age, body mass index (BMI) and parity, remained normotensive (controls). Human umbilical vein endothelial cells (HUVECs) were incubated with plasma for 24 hour before RNA isolation.

MAIN OUTCOME MEASURES

Gene expression profiles were compared between the two gestational time points using Illumina(®) HumanHT-12 v4 Expression BeadChips. Differential mRNA expression observed in microarray experiments were validated using quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR), and gene networks were analysed using Ingenuity(®) pathway analysis.

RESULTS

There was a significant difference in the expression of 25 genes following incubation with plasma from controls, and an increase in the expression of 11 genes following incubation with plasma from cases, with no overlap between the two groups (false discovery rate, FDR < 0.05). There was a 3.74-fold (FDR < 0.001) increase in the expression of the c-Fos gene (FOS) when HUVECs were incubated with control plasma from 16 and 28 weeks of gestation, with no significant difference between the two time points with plasma from cases. Similar findings for FOS were obtained by qRT-PCR.

CONCLUSIONS

Plasma from women who subsequently develop pre-eclampsia appears to contain factors that lead to the dysregulation of FOS in endothelial cells during pregnancy. Reduced expression of c-Fos may lead to impaired vasculogenesis, and thereby contribute to the development of pre-eclampsia.

Hepatic organic anion transporting polypeptide transporter and thyroid hormone receptor interplay determines cholesterol and glucose homeostasis

The role of organic anion transporting polypeptides (OATPs), particularly the members of OATP1B subfamily, in hepatocellular handling of endogenous and exogenous compounds is an important and emerging area of research. Using a mouse model lacking Slco1b2, the murine ortholog of the OATP1B subfamily, we have demonstrated previously that genetic ablation causes reduced hepatic clearance capacity for substrates. In this study, we focused on the physiological function of the hepatic OATP1B transporters. First, we studied the influence of the Oatp1b2 deletion on bile acid (BA) metabolism, showing that lack of the transporter results in a significantly reduced expression of Cyp7a1, the key enzyme of BA synthesis, resulting in elevated cholesterol levels after high dietary fat challenge. Furthermore, Slco1b2-/- mice exhibited delayed clearance after oral glucose challenge resulting from reduced hepatic glucose uptake. In addition to increased hepatic glycogen content, Slco1b2-/- mice exhibited reduced glucose output after pyruvate challenge. This is in accordance with reduced hepatic expression of phosphoenolpyruvate carboxykinase (PEPCK) in knockout mice. We show that this phenotype is due to the loss of liver-specific Oatp1b2-mediated hepatocellular thyroid hormone entry, which then leads to reduced transcriptional activation of target genes of hepatic thyroid hormone receptor (TR), including Cyp7a1 and Pepck but also Dio1 and Glut2. Importantly, we assessed human relevance using a cohort of archived human livers in which OATP1B1 expression was noted to be highly associated with TR target genes, especially for glucose facilitating transporter 2 (GLUT2). Furthermore, GLUT2 expression was significantly decreased in livers harboring a common genetic polymorphism in SLCO1B1.

CONCLUSION

Our findings reveal that OATP1B-mediated hepatic thyroid hormone entry is a key determinant of cholesterol and glucose homeostasis.

Erythropoietin encapsulation in chitosan nanoparticles and kinetics of drug release

Recombinant human erythropoietin (rHu-EPO) is a glycoprotein, which is produced commercially from Chinese hamster ovary (CHO) cells. It is used for the therapy of renal anemia and chemotherapy-induced anemia in cancer patients. Recent evidence suggests that rHu-EPO exerts tissue protective effects via multiple mechanisms which include inhibition of apoptosis, promotion of angiogenesis and decreased inflammation. After intravenous (i.v.) injection, the blood concentration of rHu-EPO rapidly decreases due to proteolysis resulting in a relatively short half-life of 8.5 h, which necessitates regular dosing with intervals that do not exceed 7 days. It would be desirable to develop an encapsulated formulation providing controlled release of rHu-EPO to maintain therapeutic concentrations in plasma, and for potential tissue protective applications to maintain high local therapeutic concentrations in tissue while minimizing potential unwanted systemic effects such as polycythemia and platelet activation, both of which can predispose to intravascular thrombosis. Nanoparticle encapsulation of rHu-EPO can also allow for direct injection at sites of injury in specific tissues/organs, again minimizing systemic exposure of the drug. In this paper, we report the production of biopolymer nanoparticles by ionotropic gelation of chitosan with tripolyphosphate (TPP). The nanoparticle size distribution in aqueous solution was determined and rates of rHu-EPO release from chitosan-TPP nanoparticles were measured in PBS at 37°C. It was observed that almost 30% of the encapsulated rHu-EPO was released within the first 48 hours and thereafter a linear release profile was observed for up to 2 weeks. Total drug release over 15 days was 63% of the initial amount.

In vitro and in vivo assessment of renal drug transporters in the disposition of mesna and dimesna

Mesna and its dimer, dimesna, are coadministered for mitigation of ifosfamide- and cisplatin-induced toxicities, respectively. Dimesna is selectively reduced to mesna in the kidney, producing its protective effects. In vitro screens of uptake and efflux transporters revealed saturable uptake by renal organic anion transporters OAT1, OAT3, and OAT4. Efflux transporters breast cancer resistance protein; multidrug and toxin extrusion 1 (MATE1); multidrug resistance proteins MRP1, MRP2, MRP4, and MRP5; and P-glycoprotein (Pgp) significantly reduced dimesna accumulation. Further investigation demonstrated that renal apical efflux transporters MATE1, MRP2, and Pgp were also capable of mesna efflux. Administration of OAT inhibitor probenecid to healthy subjects significantly increased combined mesna and dimesna plasma exposure (91% ± 34%) while decreasing the renal clearance due to net secretion (67.0% ± 12.7%) and steady-state volume of distribution (45.2% ± 13.4%). Thus, the kidney represents a significant sink of total mesna, whereas function of renal drug transporters facilitates clearance in excess of glomerular filtration rate and likely the presence of active mesna in the urine. Loss of renal transporter function due to genetic variability or drug-drug interactions may decrease the efficacy of chemoprotectants, increasing the risk of ifosfamide- and cisplatin-induced toxicities.

Compensatory upregulation of the adenosine system following phenylephrine-induced hypertrophy in cultured rat ventricular myocytes

Adenosine has been shown to exert direct antihypertrophic effects on the heart, and plasma adenosine levels have been shown to be elevated in patients with heart failure. It has therefore been proposed that endogenously synthesized adenosine may function as a cardiac antihypertrophic factor. The present study was aimed to determine whether the adenosine system is altered in a potential adaptive manner following phenylephrine-induced hypertrophy in cultured neonatal rat ventricular myocytes. Phenylephrine produced significant hypertrophy as determined by cell size and atrial natriuretic peptide gene expression, which was accompanied by significantly increased gene and protein expression of adenosine A1, A2a, and A3 receptors. These effects and the hypertrophic response were prevented by the α1-adrenoceptor antagonist prazosin as well as pharmacological agonists for all adenosine receptor subtypes. The upregulation of adenosine receptors by phenylephrine was also abrogated by adenosine 5′-(α,β-methylene)diphosphate, an inhibitor of ectosolic 5′-nucleotidase. Moreover, phenylephrine significantly increased production of adenosine from myocytes in the presence of a nucleoside transport and adenosine deaminase inhibitor, the combination of which abrogated the hypertrophic effect of phenylephrine. The latter effect was reversed by adenosine receptor antagonists. Phenylephrine also produced a significant upregulation in expression levels of equilibrative nucleoside transporter 1 although expression levels of equilibrative nucleoside transporter 2 were unaffected. Taken together, our results suggest an adaptive upregulation of the adenosine system to phenylephrine-induced cardiomyocyte hypertrophy that serves to limit the hypertrophic effect of α1-adrenoceptor activation.

Erythrocytosis in offspring of mothers with Type 1 diabetes--are factors other than insulin critical determinants?

AIM

Maternal diabetes is associated with polycythaemia and thrombocytopaenia in the offspring; however, the relationship with fetal hormones is unknown. We assessed the association of maternal glycaemic control, birthweight and fetal hormones with haematological indices in pregnancies complicated by maternal diabetes.

METHODS

Prospective study using cord blood samples from 89 offspring of mothers with Type 1 diabetes (OT1DM) and 34 control offspring. Full blood count, insulin, leptin, adiponectin, cortisol, insulin-like growth factor 1 (IGF-1), insulin-like growth factor binding protein 3, intercellular adhesion molecule 1 and C-reactive protein were measured in the umbilical vein at birth.

RESULTS

Haematocrit was higher in OT1DM (OT1DM 0.55 +/- 0.17%, control offspring 0.51 +/- 0.06%; P = 0.02). The difference in platelets count was not statistically significant [OT1DM 214 x 10(9)/l (173-259); control offspring 253 x 10(9)/l (180-310), P = 0.06]. Maternal glycated haemoglobin (HbA(1c)) showed a moderate positive correlation with fetal haematocrit (r = 0.30, P = 0.02). Cord platelet counts were negatively associated with birthweight in OT1DM (r = -0.27, P = 0.01). In multivariate models, cord insulin was not associated with haematocrit, but cord leptin was negatively associated with platelets in control offspring (P < 0.001) and OT1DM (P = 0.046), with additional contributions from male sex (P = 0.08) in OT1DM, and IGF-1 (P = 0.04) and insulin (P = 0.04) in control offspring.

CONCLUSIONS

Fetal haematocrit is increased in response to diabetes in pregnancy and is related to maternal glycaemic control. Fetal hyperinsulinism, hyperleptinaemia or macrosomia, although readily demonstrable in this cohort, do not emerge as determinants of raised fetal haematocrit in OT1DM. Both increased birthweight and fetal leptin are negatively associated with platelet count.

Are elevated circulating intercellular adhesion molecule 1 levels more strongly predictive of diabetes than vascular risk? Outcome of a prospective study in the elderly

AIMS/HYPOTHESIS

The aim of this prospective study was to determine whether circulating intercellular adhesion molecule (ICAM) 1, as a potential surrogate of 'endothelial activation', is more strongly associated with risk of vascular events than with incident diabetes.

METHODS

We related baseline ICAM-1 levels to vascular events (866 CHD and stroke events in 5,685 participants) and incident diabetes (292 in 4,945 without baseline diabetes) in the elderly over 3.2 years of follow-up.

RESULTS

ICAM-1 levels correlated positively with triacylglycerol but negatively with LDL- and HDL-cholesterol. ICAM-1 levels were higher in those who developed diabetes (388.6 +/- 1.42 vs 369.4 +/- 1.39 ng/ml [mean+/-SD], p = 0.011) and remained independently associated with new-onset diabetes (HR 1.84, 95% CI 1.26-2.69, p = 0.0015 per unit increase in log[ICAM-1] after adjusting for classical risk factors and C-reactive protein). By contrast, ICAM-1 levels were not significantly (p = 0.40) elevated in those who had an incident vascular event compared with those who remained event-free, and corresponding adjusted risk associations were null (HR 0.98, 95% CI 0.80-1.22, p = 0.89) in analyses adjusted for other risk factors.

CONCLUSIONS/INTERPRETATION

We show that elevated ICAM-1 levels are associated with risk of incident diabetes in the elderly at risk, despite no association with incident cardiovascular disease risk. We suggest that perturbations in circulating ICAM-1 levels are aligned more towards diabetes risk.

Mesna for treatment of hyperhomocysteinemia in hemodialysis patients: a placebo-controlled, double-blind, randomized trial

BACKGROUND AND OBJECTIVES

Increased plasma total homocysteine is a graded, independent risk factor for the development of atherosclerosis and thrombosis. More than 90% of patients with end-stage renal disease have hyperhomocysteinemia despite vitamin supplementation. It was shown in previous studies that a single intravenous dose of mesna 5 mg/kg caused a drop in plasma total homocysteine that was significantly lower than predialysis levels 2 d after dosing. It was hypothesized 5 mg/kg intravenous mesna administered thrice weekly, before dialysis, for 8 wk would cause a significant decrease in plasma total homocysteine compared with placebo.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients with end-stage renal disease were randomly assigned to receive either intravenous mesna 5 mg/kg or placebo thrice weekly before dialysis. Predialysis plasma total homocysteine concentrations at weeks 4 and 8 were compared between groups by paired t test.

RESULTS

Mean total homocysteine at 8 wk in the placebo group was 24.9 micromol/L compared with 24.3 micromol/L in the mesna group (n = 22 [11 pairs]; mean difference 0.63). Interim analysis at 4 wk also showed no significant difference between mesna and placebo (n = 32 [16 pairs]; placebo 26.3 micromol/L, mesna 24.5 micromol/L; mean difference 1.88). Multivariable adjustments for baseline characteristics did not alter the analysis. Plasma mesna seemed to reach steady-state concentrations by 4 wk.

CONCLUSIONS

It is concluded that 5 mg/kg mesna does not lower plasma total homocysteine in hemodialysis patients and that larger dosages may be required.

Fetal corticotrophin-releasing hormone mRNA, but not phosphatidylserine-exposing microparticles, in maternal plasma are associated with factor VII activity in pre-eclampsia

BACKGROUND

Pre-eclampsia is associated with increased placental debris circulating in maternal plasma.

OBJECTIVES

This study related placental debris to maternal markers of coagulation and endothelial activation in pre-eclampsia.

PATIENTS/METHODS

Circulating fetal corticotrophin-releasing hormone (CRH) mRNA and phosphatidylserine (PS)-exposing microparticles were assayed in third trimester plasma from women with pre-eclampsia (n = 32) and controls (n = 32) matched for age, body mass index, parity, and gestational age at sampling. Markers of maternal hemostasis and endothelial function were assessed.

RESULTS

Fetal CRH mRNA levels were higher in pre-eclampsia [mean 0.75 (SD 2.77) CRH/glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA ratio] than in control pregnancies [0.20 (0.74), P = 0.014]. PS-exposing microparticle levels were not different between the groups. Women with pre-eclampsia had higher levels of tissue factor pathway inhibitor (TFPI), prothrombin F(1+2) fragment (F(1+2)), factor XIIa, soluble vascular cell adhesion molecule 1, von Willebrand factor and plasminogen activator inhibitor 1 than controls. Fetal CRH mRNA correlated with TFPI in pre-eclampsia and control groups (r = 0.38, P = 0.031, and r = 0.37, P = 0.039, respectively). Fetal CRH mRNA correlated with FVII activity (r = 0.43, P = 0.017) and PS-exposing microparticles correlated inversely with F(1+2) (r = -0.64, P < 0.001) in pre-eclampsia.

CONCLUSIONS

Placental debris, assessed by fetal CRH mRNA levels in maternal blood, is related to coagulation potential, i.e. FVII activity, but not to markers of coagulation or endothelial activation in pre-eclampsia.

Mesna as a nonvitamin intervention to lower plasma total homocysteine concentration: implications for assessment of the homocysteine theory of atherosclerosis

Elevated plasma total homocysteine is independently associated with atherosclerosis. Recent randomized trials show that vitamins lower total homocysteine but do not prevent cardiovascular events, suggesting the need for nonvitamin therapies to evaluate whether a causative relationship exists. Mesna (sodium 2-mercaptoethanesulfonate) is a thiol-containing drug capable of liberating homocysteine bound by disulfide bonds to proteins, facilitating its excretion. The effect of oral mesna on total homocysteine has not been evaluated and was the objective of this study. Eleven healthy volunteers received vehicle or 10 mg/kg mesna in random order, after which serial blood and urine samples were collected over 4 hours. Plasma total homocysteine decreased by 24.2% (P < .0001) following mesna. Urinary homocysteine excretion was significantly greater with mesna (3.9 +/- 2.4 mumol) compared to vehicle (0.4 +/- 0.1 mumol), P < .01. Oral mesna decreases plasma total homocysteine and is a potential nonvitamin treatment for assessing the homocysteine theory of atherosclerosis.

In vivo inhibition of growth of human tumor lines by flavonoid fractions from cranberry extract

Edible fruits and berries may serve as sources for novel anticancer agents, given that extracts of these foods have demonstrated cytotoxic activity against tumor cell lines. Semipurified, flavonoid-rich extracts of cranberry (Vaccinia macrocarpa) were shown previously to arrest proliferation of tumor cells and induce apoptosis. However, the ability of cranberry flavonoids to inhibit tumor growth in vivo has not been reported other than in a preliminary report. As model systems for testing this activity, human tumor cell lines representative of three malignancies were chosen: glioblastoma multiforme (U87), colon carcinoma (HT-29), and androgen-independent prostate carcinoma (DU145). A flavonoid-rich fraction 6 (Fr6) and a more purified proanthocyanidin (PAC)-rich fraction were isolated from cranberry presscake and whole cranberry, respectively, by column chromatography. Fr6 and PAC each significantly slowed the growth of explant tumors of U87 in vivo, and PAC inhibited growth of HT-29 and DU145 explants (P < 0.05), inducing complete regression of two DU145 tumor explants. Flow cytometric analyses of in vitro-treated U87 cells indicated that Fr6 and PAC could arrest cells in G1 phase of the cell cycle (P < 0.05) and also induce cell death within 24 to 48 h of exposure (P < 0.05). These results indicate the presence of a potential anticancer constituent in the flavonoid-containing fractions from cranberry extracts.

Reinstalling antitumor immunity by inhibiting tumor-derived immunosuppressive molecule IDO through RNA interference

Tumor-derived immune suppression is a major impediment to successful immune/gene cancer therapy. In the present study, we describe a novel strategy to disrupt tumor-derived immune suppression by silencing a tolerogenic molecule of tumor origin, IDO, using small interfering RNA (siRNA). Silencing of IDO in B16F10 cells in vitro using IDO-siRNA prevented catabolism of tryptophan and inhibited apoptosis of T cells. IDO-siRNA treatment of B16F10 cells in vitro inhibited subsequent growth, tumor formation, and the size of tumor formed, by those cells when transplanted into host mice. In vivo treatment of B16F10 tumor-bearing mice successfully postponed tumor formation time and significantly decreased tumor size. Furthermore, in vivo IDO-siRNA treatment resulted in recovery of T cells responses and enhancement of tumor-specific killing. Thus, silencing IDO may break tumor-derived immune suppression. These data indicate that RNA interference has potential to enhance cancer therapy by reinstalling anticancer immunity.

The Effect of Mesna on Plasma Total Homocysteine Concentration in Hemodialysis Patients

BACKGROUND

Plasma total homocysteine (tHcy) level is an independent risk factor for the development of atherosclerosis. The degree of risk in most of the population is decreased by using dietary vitamin supplementation; however, more than 90% of patients with end-stage renal disease have increased tHcy levels despite supplementation. Only a small fraction of tHcy is removed by hemodialysis because of extensive disulfide bonding to albumin. The objective of this study is to determine whether a single intravenous dose of mesna, a thiol-containing drug analogue of taurine, facilitates tHcy clearance during hemodialysis.

METHODS

Initial in vitro thiol exchange tests were performed with mesna in plasma from dialysis patients. Mesna, 300 micromol/L (49.2 mg/L), was incubated with plasma at 37 degrees C, and free homocysteine was measured at various times. In vivo, mesna activity was tested in 10 hemodialysis patients by administering 2.5 or 5.0 mg/kg of mesna intravenously at the beginning of a treatment cycle. Blood samples were drawn throughout dialysis, and plasma tHcy levels were compared with those obtained from a previous dialysis session in which mesna was not administered.

RESULTS

In vitro, mesna liberated 36.5% +/- 2.5% of protein-bound homocysteine in 30 minutes. In vivo, a single 2.5-mg/kg dose of mesna was ineffective; however, at 5.0 mg/kg, it caused a 55.2% +/- 3.9% decrease in plasma tHcy levels postdialysis compared with a 34.2% +/- 5.3% decrease with dialysis alone (P < 0.001).

CONCLUSION

Intravenous mesna causes a rapid decrease in plasma tHcy levels during hemodialysis.

Thiol exchange: An in vitro assay that predicts the efficacy of novel homocysteine lowering therapies

Elevated plasma total homocysteine (tHcy) is a risk factor for atherosclerosis. Hcy is 70-80% bound to albumin as a disulfide. Recent trials have evaluated ability of thiol-containing drugs to exchange with protein bound Hcy and consequently increase its renal clearance. The objective of this study was to develop an in vitro assay to predict the efficacy of thiol-containing drugs to lower tHcy in the clinical setting. The assay was used to test the effects of N-acetylcysteine (NAC), mesna, captopril, dimercaptosuccinic acid (DMSA), and penicillamine. Hcy was added in vitro to plasma of healthy subjects (n = 6) and equilibrated. Concentrations of thiol exchange agent were added and incubated at 37 degrees C. Aliquots were removed at selected intervals and free Hcy determined. Mesna, captopril, and NAC caused a concentration-dependent increase in free Hcy. Three-hundred micromolar mesna and captopril had a greater effect than equimolar NAC, increasing free Hcy by 33.9 +/- 5.0% and 32.0 +/- 2.6%, respectively compared to 22.3 +/- 2.4% for NAC, p < 0.001. Our in vitro results indicate that mesna, captopril, and NAC effectively exchange with covalently bound Hcy. This assay can act as screening tool for novel tHcy lowering therapies and should spare the expense of negative trials.

Cholesteryl ester transfer protein TaqIB variant, high-density lipoprotein cholesterol levels, cardiovascular risk, and efficacy of pravastatin treatment: individual patient meta-analysis of 13,677 subjects

BACKGROUND

Several studies have reported that the cholesteryl ester transfer protein (CETP) TaqIB gene polymorphism is associated with HDL cholesterol (HDL-C) levels and the risk of coronary artery disease (CAD), but the results are inconsistent. In addition, an interaction has been implicated between this genetic variant and pravastatin treatment, but this has not been confirmed.

METHODS AND RESULTS

A meta-analysis was performed on individual patient data from 7 large, population-based studies (each >500 individuals) and 3 randomized, placebo-controlled, pravastatin trials. Linear and logistic regression models were used to assess the relation between TaqIB genotype and HDL-C levels and CAD risk. After adjustment for study, age, sex, smoking, body mass index (BMI), diabetes, LDL-C, use of alcohol, and prevalence of CAD, TaqIB genotype exhibited a highly significant association with HDL-C levels, such that B2B2 individuals had 0.11 mmol/L (0.10 to 0.12, P<0.0001) higher HDL-C levels than did B1B1 individuals. Second, after adjustment for study, sex, age, smoking, BMI, diabetes, systolic blood pressure, LDL-C, and use of alcohol, TaqIB genotype was significantly associated with the risk of CAD (odds ratio=0.78 [0.66 to 0.93]) in B2B2 individuals compared with B1B1 individuals (P for linearity=0.008). Additional adjustment for HDL-C levels rendered a loss of statistical significance (P=0.4). Last, no pharmacogenetic interaction between TaqIB genotype and pravastatin treatment could be demonstrated.

CONCLUSIONS

The CETP TaqIB variant is firmly associated with HDL-C plasma levels and as a result, with the risk of CAD. Importantly, this CETP variant does not influence the response to pravastatin therapy.

Fetal cord plasma lipoprotein status in uncomplicated human pregnancies and in pregnancies complicated by pre-eclampsia and intrauterine growth restriction

Maternal lipids have been studied extensively in pre-eclampsia (PE) and intrauterine growth restriction (IUGR) but little is known about fetal lipids. We hypothesised that the maternal lipid perturbations in PE and IUGR pregnancies would result in similar alterations in the fetal lipid profile. We performed a cross-sectional case control study of maternal and fetal (delivery venous cord blood) lipid and lipoprotein concentrations in third trimester uncomplicated pregnancies (n = 81) and in pregnancies complicated by PE (n = 23) or IUGR (n = 17). In uncomplicated pregnancies, fetal log total cholesterol (TC), log triglyceride (TG) and high-density lipoprotein cholesterol (HDL-C) levels were significantly affected by mode of delivery. Fetal log TC (r = 0.37, P = 0.02), log TG (r = 0.34, P = 0.04) and TC/HDL-C ratio (r = 0.31, P = 0.05) were positively correlated with placental weight. Maternal TC (r = 0.35, P = 0.03) and LDL levels (r = 0.36, P = 0.02) were associated with fetal HDL-C levels. Maternal TC was significantly elevated in PE [mean 6.75 (standard deviation 1.14) mmol/L] compared to BMI-matched controls [5.94 (0.89) mmol/L P = 0.04]. In PE, fetal log TC [mean 0.36 (0.23) versus 0.11 (0.15) log mmol/L, P = 0.03], fetal log TG [-0.21 (0.32) versus -0.49 (0.26) log mmol/L, P = 0.02] and fetal TC/HDL-C ratio [3.64 (1.62) versus 1.80 (0.86), P = 0.001] were higher than in controls, after adjustment for mode of delivery. In IUGR, fetal log TG [-0.17 (0.35) versus -0.57 (0.10) log mmol/L, P = 0.01] was higher than controls, after adjustment for mode of delivery. There were no correlations between maternal and fetal lipid levels, or between fetal birth weight and either maternal or fetal lipids in the PE or IUGR groups. We conclude that although fetal lipids do not show a direct correlation with maternal lipids in PE or IUGR, these complications of pregnancy significantly impact upon fetal lipid levels possibly due to increased fetal stress or compromised placental lipid transport. Our findings are potentially pertinent to understanding the future cardiovascular health of the offspring.

Dimercaptosuccinic acid for the treatment of hyperhomocysteinemia in hemodialysis patients: a placebo-controlled, double-blind, randomized trial

BACKGROUND

Elevated total homocysteine (tHcy) levels may represent a potentially modifiable risk factor for cardiovascular disease in hemodialysis patients. Current therapies, including multivitamins, have been ineffective at normalizing homocysteine levels in this population; hence, new therapies are needed. There is increasing interest in the use of thiol pharmaceutical agents to displace homocysteine from albumin and improve its dialyzability. We designed a randomized, double-blind, placebo-controlled trial to determine the effect of prolonged administration of oral dimercaptosuccinic acid (DMSA) on plasma tHcy levels in vitamin-replete hemodialysis patients.

METHODS

Forty-four long-term stable dialysis patients were treated for a minimum of 4 weeks with a standard multivitamin, ensuring a vitamin-replete state, then matched on the basis of tHcy levels and randomly assigned as pairs to the administration of DMSA, 2.5 mg/kg/d, or identical placebo for 8 weeks. Multivitamins were continued for the duration of the trial.

RESULTS

Thirty-eight subjects (including 16 pairs) completed the trial. All important determinants of homocysteine level were balanced, and the only significant baseline difference was weight (P = 0.02). At 8 weeks, by paired analysis, there was no statistically significant difference in tHcy levels between the placebo and DMSA groups, at 21.2 micromol/L (2.87 mg/L) and 22.6 micromol/L (3.06 mg/L), respectively (mean difference, -1.4; 95% confidence interval, -5.3 to 2.5; P = 0.45). The same was true for unpaired and multivariable analyses.

CONCLUSION

This randomized placebo-controlled trial found that prolonged oral administration of the thiol DMSA had no impact on tHcy levels in hemodialysis patients. Additional strategies to test the homocysteine hypothesis in this population require investigation.

A flavonoid fraction from cranberry extract inhibits proliferation of human tumor cell lines

In light of the continuing need for effective anticancer agents, and the association of fruit and vegetable consumption with reduced cancer risk, edible plants are increasingly being considered as sources of anticancer drugs. Cranberry presscake (the material remaining after squeezing juice from the berries), when fed to mice bearing human breast tumor MDA-MB-435 cells, was shown previously to decrease the growth and metastasis of tumors. Therefore, further studies were undertaken to isolate the components of cranberry that contributed to this anticancer activity, and determine the mechanisms by which they inhibited proliferation. Using standard chromatographic techniques, a warm-water extract of cranberry presscake was fractionated, and an acidified methanol eluate (Fraction 6, or Fr6) containing flavonoids demonstrated antiproliferative activity. The extract inhibited proliferation of 8 human tumor cell lines of multiple origins. The androgen-dependent prostate cell line LNCaP was the most sensitive of those tested (10 mg/L Fr6 inhibited its growth by 50%), and the estrogen-independent breast line MDA-MB-435 and the androgen-independent prostate line DU145 were the least sensitive (250 mg/L Fr6 inhibited their growth by 50%). Other human tumor lines originating from breast (MCF-7), skin (SK-MEL-5), colon (HT-29), lung (DMS114), and brain (U87) had intermediate sensitivity to Fr6. Using flow cytometric analyses of DNA distribution (cell cycle) and annexin V-positivity (apoptosis), Fr6 was shown in MDA-MB-435 cells to block cell cycle progression (P < 0.05) and induce cells to undergo apoptosis (P < 0.05) in a dose-dependent manner. Fr6 is potentially a source of a novel anticancer agent.

Autonomic signs and dosing during the initial stages of clozapine therapy

BACKGROUND

Recent reports implicate clozapine in heart rate variability, QTc prolongation, torsade de pointes and sudden death at therapeutic doses, even in physically healthy patients. This study aims to examine whether autonomic (vital) signs are correlated with clozapine dose titration and blood levels of clozapine and nor-clozapine during clozapine therapy.

MATERIAL/METHODS

Thirty-seven consecutive patients with diagnosis of schizophrenia treated with clozapine were included in this prospective longitudinal study. The study was restricted to only the first 8 weeks of treatment. After obtaining informed consent, serum concentrations of clozapine and nor-clozapine were determined weekly at trough, as doses were administered q12h and adjusted according to clinical guidelines for clozapine use. Autonomic signs including BP (supine and erect), pulse (supine and erect) and temperature were monitored daily each morning before and one hour after the morning's dose of clozapine was administered.

RESULTS

We calculated analyses of covariance (ANCOVAs) to evaluate the changes in vital signs parameters, from baseline to week 8, with clozapine variables as covariates (i.e, the dose of clozapine, as well as the levels of serum clozapine and nor-clozapine). The blood pressure and pulse did not change significantly (p<0.01) from baseline to weeks 8. The temperature was inversely related to clozapine dose (p<0.003). Higher nor-clozapine to clozapine ratios were associated with higher BP measures (p=0.002). The magnitude of these relationships is weak (r<0.30).

CONCLUSIONS

There is a tendency to autonomic dysregulation during clozapine use. This has cardiac function implications, justifying cautious dose adjustment with frequent monitoring of vital signs.

Relative bioavailability and antioxidant potential of two coenzyme q10 preparations

Coenzyme Q10 (CoQ10) is synthesized by the human body and found in certain foods. Daily supplementation of CoQ10 could protect against heart disease but the bioavailability of CoQ10 supplements depends on the formulation taken. We compared the bioavailability and antioxidant properties of two commercial CoQ10 formulations, a commercial grade CoQ10 powder (commercial grade CoQ) and a new BT-CoQ10 BIO-TRANSFORMED (BT-CoQ10) obtained by fermentation of a soy-based, CoQ10-rich media with baker's yeast. Eleven healthy individuals participated in a randomized two-way crossover trial, with a 3-week washout period. Capsules containing 300 mg of either BT-CoQ10 or commercial grade CoQ10 were given daily for 1 week and multiple blood samples were taken for CoQ10, glutathione and glutathione peroxidase (GPx) determination. In 3 subjects, baseline plasma CoQ10 levels were lower prior to BT than prior to commercial grade CoQ treatment. In the remaining participants, ingestion of BT vs. commercial grade CoQ significantly increased maximum plasma CoQ10 concentration (+126%, p = 0.04) and tended to increase CoQ10 area under the curve from 0 to 24 h (+160%, p = 0.07). One week of treatment with each formulation increased plasma CoQ10 but did not alter plasma glutathione or GPx activity. The enhanced bioavailability of the BT product might be due to its predominantly reduced, hydrophilic membrane-complex form.

Monitoring clozapine: are fingerprick blood and plasma clozapine levels equivalent to arm venipuncture blood and plasma levels?

The objective of this pilot study was to determine whether fingerprick blood and plasma clozapine levels were equivalent to arm venipuncture blood and plasma levels for the purpose of therapeutic monitoring. A convenient sample of 10 outpatients from the Elgin Program of Assertive Community Treatment Team (PACT) participated in the study. Blood samples were obtained simultaneously from both the arm and finger in patients at steady state to measure clozapine levels. Each site provided a blood and plasma clozapine level, and they were compared. Clozapine levels from arm and finger sites were found to be equivalent in both blood and plasma. Although plasma clozapine levels were consistently greater than those in whole blood by a mean value of 27%, the plasma therapeutic threshold level (350-400 micro g/L) was considered an adequate target for monitoring. A fingerprick blood sample of 50 micro L was sufficient to measure clozapine levels accurately at steady state. We therefore concluded that fingerprick blood testing is as effective as the traditional arm venipuncture method in obtaining accurate clozapine levels. This procedure may provide certain benefits for the seriously mentally ill.

Relation of blood counts during clozapine treatment to serum concentrations of clozapine and nor-clozapine

OBJECTIVE

To determine the relation between serum clozapine and nor-clozapine levels and blood cell counts during clozapine treatment.

METHOD

We undertook a prospective longitudinal study of 37 consecutive patients with a diagnosis of schizophrenia treated with clozapine. We obtained informed consent and then determined serum concentrations of clozapine and nor-clozapine weekly. Clozapine was administered daily in divided doses given every 12 hours and adjusted according to clinical guidelines for its use. Samples for serum concentrations were taken at steady state, immediately before the next morning's dose, for 4 to 8 weeks. Complete blood counts (CBC), weight, and vital signs (that is, blood pressure, pulse, and temperature) were also monitored weekly before the morning's dose of clozapine was administered.

RESULTS

Analyses of variance showed no significant changes over the 8-week treatment course in the observed mean white blood count (WBC), red blood count (RBC), neutrophils, and lymphocytes counts, or in the hemoglobin and hematocrit. Only a few weak correlations (r < 0.21) were found between these hematological parameters and the measures of serum clozapine and nor-clozapine.

CONCLUSIONS

The mechanism of clozapine-induced hematotoxicity at the therapeutic dosage range is probably not by direct toxicity of clozapine or nor-clozapine to the blood cells or their precursors. The formation of the cytotoxic nitrenium compound from clozapine by neutrophils may be necessary.

Fruit juices inhibit organic anion transporting polypeptide-mediated drug uptake to decrease the oral availability of fexofenadine

OBJECTIVES

Our objective was to examine the effect of different fruits and their constituents on P-glycoprotein and organic anion transporting polypeptide (OATP) activities in vitro and on drug disposition in humans.

METHODS

P-glycoprotein-mediated digoxin or vinblastine efflux was determined in polarized epithelial cell monolayers. OATP-mediated fexofenadine uptake was measured in a transfected cell line. The oral pharmacokinetics of 120 mg fexofenadine was assessed with water, 25%-strength grapefruit juice, or normal-strength grapefruit, orange, or apple juices (1.2 L over 3 hours) in a randomized 5-way crossover study in 10 healthy subjects.

RESULTS

Grapefruit juice and segments and apple juice at 5% of normal strength did not alter P-glycoprotein activity. Grapefruit extract reduced transport. 6',7'-Dihydroxybergamottin had modest inhibitory activity (50% inhibitory concentration [IC(50)], 33 micromol/L). In contrast, grapefruit, orange, and apple juices at 5% of normal strength markedly reduced human OATP and rat oatp activity. 6',7'-Dihydroxybergamottin potently inhibited rat oatp3 and oatp1 (IC(50), 0.28 micromol/L). Other furanocoumarins and bioflavonoids also reduced rat oatp3 activity. Grapefruit, orange, and apple juices decreased the fexofenadine area under the plasma concentration-time curve (AUC), the peak plasma drug concentration (C(max)), and the urinary excretion values to 30% to 40% of those with water, with no change in the time to reach C(max), elimination half-life, renal clearance, or urine volume in humans. Change in fexofenadine AUC with juice was variable among individuals and inversely dependent on value with water.

CONCLUSIONS

Fruit juices and constituents are more potent inhibitors of OATPs than P-glycoprotein activities, which can reduce oral drug bioavailability. Results support a new model of intestinal drug absorption and mechanism of food-drug interaction.

Red wine-cisapride interaction: comparison with grapefruit juice

OBJECTIVES

Our objective was to compare the interactions of red wine and grapefruit juice with cisapride.

METHODS

The oral pharmacokinetics of cisapride, its norcisapride metabolite, and electrocardiographic QTc interval were determined over a 24-hour period after administration of cisapride 10 mg with 250 mL grapefruit juice, red wine (cabernet sauvignon), or water in a randomized 3-way crossover study in 12 healthy men.

RESULTS

The cisapride area under the concentration-time curve (AUC) and the maximum plasma drug concentration after single-dose administration (C(max)) with grapefruit juice were 151% (P <.01) and 168% (P <.001), respectively, of those with water. The increase in cisapride AUC and C(max) was variable among individuals; however, cisapride AUC and C(max) were enhanced by the same proportion. The time to reach maximum concentration after drug administration (t(max)) and the apparent elimination half-life (t((1/2)) for cisapride and the pharmacokinetics of norcisapride were not altered. Norcisapride/cisapride ratios were reduced. Cisapride AUC and C(max) with red wine were 115% (difference not statistically significant) and 107% (difference not statistically significant), respectively, of those with water. The cisapride t(max) was slightly longer. Cisapride t((1/2)) and norcisapride pharmacokinetics were not different. The norcisapride/cisapride ratio at cisapride C(max) was lower. One subject had a doubling in cisapride AUC and C(max) and a decrease in norcisapride/cisapride ratios with red wine and also had the largest interaction with grapefruit juice. QTc interval was unchanged in all treatment groups and individuals.

CONCLUSIONS

A single glass of grapefruit juice produced an individual-dependent variable increase in the systemic availability of cisapride by inhibition of intestinal cytochrome P450 3A4 (CYP3A4) activity. The identical volume of red wine caused only minor changes in cisapride pharmacokinetics despite some inhibition of CYP3A4 in most individuals. However, even this amount of red wine may cause a marked interaction similar to that for grapefruit juice in individuals with a preexisting high intestinal CYP3A4 content.

Pravastatin and the development of diabetes mellitus: evidence for a protective treatment effect in the West of Scotland Coronary Prevention Study

BACKGROUND

We examined the development of new diabetes mellitus in men aged 45 to 64 years during the West of Scotland Coronary Prevention Study.

METHODS AND RESULTS

Our definition of diabetes mellitus was based on the American Diabetic Association threshold of a blood glucose level of >/=7.0 mmol/L. Subjects who self-reported diabetes at baseline or had a baseline glucose level of >/=7.0 mmol/L were excluded from the analyses. A total of 5974 of the 6595 randomized subjects were included in the analysis, and 139 subjects became diabetic during the study. The baseline predictors of the transition from normal glucose control to diabetes were studied. In the univariate model, body mass index, log triglyceride, log white blood cell count, systolic blood pressure, total and HDL cholesterol, glucose, and randomized treatment assignment to pravastatin were significant predictors. In a multivariate model, body mass index, log triglyceride, glucose, and pravastatin therapy were retained as predictors of diabetes in this cohort.

CONCLUSIONS

We concluded that the assignment to pravastatin therapy resulted in a 30% reduction (P:=0.042) in the hazard of becoming diabetic. By lowering plasma triglyceride levels, pravastatin therapy may favorably influence the development of diabetes, but other explanations, such as the anti-inflammatory properties of this drug in combination with its endothelial effects, cannot be excluded with these analyses.

Grapefruit-felodipine interaction: effect of unprocessed fruit and probable active ingredients

OBJECTIVES

To determine whether unprocessed grapefruit can cause a drug interaction, whether the active ingredients are naturally occurring, and whether specific furanocoumarins or flavonoids are involved.

METHODS

The oral pharmacokinetics of felodipine and its dehydrofelodipine metabolite were determined after administration of felodipine 10 mg extended-release tablet with 250 mL commercial grapefruit juice, homogenized grapefruit segments, or extract of segment-free parts equivalent to one unprocessed fruit or water in a randomized four-way crossover study. Inhibition of recombinant CYP3A4 by furanocoumarins (bergamottin, 6',7'-epoxybergamottin, 6',7'-dihydroxybergamottin) and flavonoids (naringenin optical isomers) was determined. Furanocoumarin and naringenin precursor (naringin) concentrations were measured in each grapefruit treatment.

RESULTS

Felodipine AUC with commercial grapefruit juice, grapefruit segments, or grapefruit extract was on average 3-fold higher than that with water. Felodipine peak concentration was higher, but the half-life was unchanged. The dehydrofelodipine/felodipine AUC ratio was reduced. The furanocoumarins produced mechanism-based and competitive inhibition of CYP3A4. Bergamottin was the most potent mechanism-based inhibitor. Naringenin isomers produced only competitive inhibition. Bergamottin, 6',7'-dihydroxybergamottin, and naringin concentrations varied among grapefruit treatments but were sufficient to inhibit markedly in vitro CYP3A4 activity.

CONCLUSIONS

Unprocessed grapefruit can cause a drug interaction with felodipine. The active ingredients are naturally occurring in the grapefruit. Bergamottin is likely important in drug interactions with commercial grapefruit juice. 6',7'-Dihydroxybergamottin and naringin may be more important in grapefruit segments because they are present in higher concentrations. Any therapeutic concern for a drug interaction with commercial grapefruit juice should now be extended to include whole fruit and possibly confectioneries made from grapefruit peel.

HDL-cholesterol-raising effect of orange juice in subjects with hypercholesterolemia

BACKGROUND

Orange juice-a rich source of vitamin C, folate, and flavonoids such as hesperidin-induces hypocholesterolemic responses in animals.

OBJECTIVE

We determined whether orange juice beneficially altered blood lipids in subjects with moderate hypercholesterolemia.

DESIGN

The sample consisted of 16 healthy men and 9 healthy women with elevated plasma total and LDL-cholesterol and normal plasma triacylglycerol concentrations. Participants incorporated 1, 2, or 3 cups (250 mL each) of orange juice sequentially into their diets, each dose over a period of 4 wk. This was followed by a 5-wk washout period. Plasma lipid, folate, homocyst(e)ine, and vitamin C (a compliance marker) concentrations were measured at baseline, after each treatment, and after the washout period.

RESULTS

Consumption of 750 mL but not of 250 or 500 mL orange juice daily increased HDL-cholesterol concentrations by 21% (P: < 0.001), triacylglycerol concentrations by 30% (from 1.56 +/- 0.72 to 2.03 +/- 0.91 mmol/L; P: < 0.02), and folate concentrations by 18% (P: < 0.01); decreased the LDL-HDL cholesterol ratio by 16% (P: < 0.005); and did not affect homocyst(e)ine concentrations. Plasma vitamin C concentrations increased significantly during each dietary period (2.1, 3.1, and 3.8 times, respectively).

CONCLUSIONS

Orange juice (750 mL/d) improved blood lipid profiles in hypercholesterolemic subjects, confirming recommendations to consume >/=5-10 servings of fruit and vegetables daily.

Present and potential future use of gene therapy for the treatment of non-insulin dependent diabetes mellitus (Review)

This review describes the latest approaches towards using gene therapy as a treatment for non-insulin dependent diabetes mellitus (NIDDM; Type 2 diabetes). We examine attempts to directly deliver the insulin gene to non-beta-cells, to improve insulin secretion from existing beta-cells and to develop ex vivo approaches to implanting genetically modified cells. Future research into the pathology of non-insulin dependent diabetes, combined with the latest developments in gene delivery systems, may potentially make gene therapy an attractive alternative NIDDM treatment in the future.

Addition of arginine but not glycine to lysine plus methionine-enriched diets modulates serum cholesterol and liver phospholipids in rabbits

Previous experiments from our laboratory showed that in rabbits fed an amino acid diet corresponding to 30% casein, enrichment of the diet with L-lysine and L-methionine caused a marked increase in serum total and LDL cholesterol levels as well as a substantial body weight loss. Both effects were partially prevented by supplementation with L-arginine. The present studies were designed to extend this earlier observation by assessing the role of different dietary amino acids in modulation of cholesterolemic responses and body weights. In the first experiment, the original lysine and methionine-enriched diet was supplemented with glycine in an attempt to modify methionine metabolism, and thus to reduce body weight loss. In addition, the mechanism of action of lysine and methionine was investigated by quantitation of major liver phospholipids. The results showed that glycine addition had no effect on weight loss or hypercholesterolemia, nor did it alter plasma levels of homocyst(e)ine, an intermediate in methionine metabolism. However, enrichment of the diet with lysine and methionine (with or without glycine) significantly increased liver levels of phosphatidylcholine and the ratio of phosphatidylcholine to phosphatidylethanolamine, apparently through increased enzymatic conversion. These changes were consistent with higher lipoprotein levels and thus may explain the hypercholesterolemia. A second experiment showed that similar effects on body weights and serum cholesterol could be obtained by adding lysine and methionine to a diet containing amino acids equivalent to only 15% casein, or 15% intact casein. This approach is more physiologic and also reduces the expense of experiments designed to study the effects of lysine and methionine in more detail.

Corticosteroid pharmacokinetics in the inner ear fluids: an animal study followed by clinical application

OBJECTIVE

Autoimmune disease (e.g., Cogan syndrome) and other inflammatory inner ear diseases may ravage the labyrinth if not treated aggressively with antiinflammatory medication. Corticosteroids are the mainstay of treatment, yet, partly because of the existence of the blood-labyrinthine barrier, the ideal drug, dose, and route of administration are currently unknown.

STUDY DESIGN

In the present study, we established cochlear fluid pharmacokinetic profiles of hydrocortisone, methylprednisolone, and dexamethasone in the guinea pig following oral, intravenous, and topical (intratympanic) administration. High-performance liquid chromatography was used to determine the drug concentrations, and comparisons were made with simultaneous pharmacokinetic profiles from blood and cerebrospinal fluid.

RESULTS

Our findings demonstrated a much higher penetration of all three drugs into the cochlear fluids following topical application as compared with systemic administration, with methylprednisolone showing the best profile.

DISCUSSION

The results suggested that intratympanic administration of corticosteroids might be more efficacious while avoiding high blood levels and therefore the deleterious side effects of systemic use.

CLINICAL APPLICATION

Thirty-seven patients with various inner ear disorders causing sensorineural hearing loss were subsequently treated using intratympanic corticosteroids, 20 with dexamethasone, and 17 with methlyprednisolone. Patients with immune-mediated hearing losses showed the best results, with notable improvement also seen in several cases of a "sudden deafness." No benefit was seen in patients with cochlear hydrops or those with sudden deterioration of a preexisting hearing loss. Three patients developed a transient otitis media related to the treatments, easily controlled with antibiotics. There were no cases of treatment-induced hearing loss and no permanent tympanic membrane perforations.

CONCLUSIONS

Overall injection of intratympanic corticosteroids for the treatment of hearing loss in inner ear disorders appears to be both safe and highly effective for certain disorders. The concept of this technique is supported by animal experimental data. The findings from the present study warrant further clinical application and experimental investigation.

The cytotoxicity of clozapine metabolites: implications for predicting clozapine-induced agranulocytosis

BACKGROUND

Therapy of schizophrenia with clozapine is associated with the unpredictable development of severe neutropenia and agranulocytosis in 1% to 2% of patients. The mechanism of this effect is unknown but may involve reactive products of clozapine generated by either hepatic metabolism or oxidation by the peroxidase-peroxide system of activated neutrophils.

METHODS

Involvement of reactive metabolites was tested with in vitro cytotoxicity assays with use of peripheral blood mononuclear cells isolated from 3 groups of subjects: normal control subjects, patients with schizophrenia who tolerated clozapine therapy (control patients), and patients with schizophrenia in whom agranulocytosis developed while taking clozapine (patients with agranulocytosis). Cell viability was determined after incubations with clozapine and rat liver microsomes or clozapine and horseradish peroxidase-peroxide (HRP-H2O2).

RESULTS

In microsomal incubations, clozapine significantly increased the cell death in all groups: control subjects (8.8%+/-1.6%), control patients (7.4%+/-0.4%), and patients with agranulocytosis (9.1%+/-1.5%). However, differences between mean values were not statistically significant. In similar incubations with HRP-H2O2, clozapine significantly increased toxicity (P < .05) in cells from patients with agranulocytosis (22%+/-4.6%) compared with those from normal control subjects (7.7%+/-4.1%) or control patients (6.5%+/-4.4%).

CONCLUSIONS

These results suggest that both generating systems metabolized clozapine to toxic products. Some products may play a role in clozapine-induced agranulocytosis. Of diagnostic relevance is the observation the HRP-H2O2 produces significantly greater toxicity in cells from patients with agranulocytosis than in cells from control patients. Although the exact mechanism(s) of drug activation in vivo remains unclear, the bioactivation of clozapine by HRP-H2O2 may be a useful in vitro tool for predicting which patients are at risk for agranulocytosis before initiation of therapy.

Grapefruit juice-felodipine interaction: effect of naringin and 6',7'-dihydroxybergamottin in humans

OBJECTIVE

To test whether naringin or 6',7'-dihydroxybergamottin is a major active substance in grapefruit juice-felodipine interaction in humans.

METHODS

Grapefruit juice was separated by means of centrifugation and filtration into supernatant and particulate fractions, which were then assayed for naringin and 6',7'-dihydroxybergamottin. The effect of these fractions, grapefruit juice (containing comparable amounts of both fractions), and water on the pharmacokinetics of oral felodipine were assessed in 12 healthy men in a randomized, 4-way crossover study.

RESULTS

The amounts of naringin and 6',7'-dihydroxybergamottin in the supernatant fraction (148 mg and 1.85 mg) were greater than in the particulate fraction (7 mg and 0.60 mg). The area under the plasma concentration-time curve (AUC) and the peak concentration (Cmax) of felodipine were higher with supernatant fraction (81 nmol.h/L and 20 nmol/L), particulate fraction (117 nmol.h/L and 24 nmol/L), and grapefruit juice (130 nmol.h/L and 33 nmol/L) compared with water (53 nmol.h/L and 11 nmol/L). However, the supernatant fraction had a lower AUC for felodipine and a similar Cmax of felodipine relative to the particulate fraction. The supernatant fraction neither augmented the AUC of the primary metabolite dehydrofelodipine nor decreased the AUC ratio of dehydrofelodipine to felodipine compared with water. Individually the supernatant fraction consistently produced lower felodipine AUC and Cmax compared with grapefruit juice. In contrast, the particulate fraction had values ranging from more than grapefruit juice to less than supernatant fraction.

CONCLUSIONS

Naringin and 6',7'-dihydroxybergamottin are not the major active ingredients, although they may contribute to the grapefruit juice-felodipine interaction. The variable effect with the particulate fraction may result from erratic bioavailability of unidentified primary active substances. The findings show the importance of in vivo testing to determine the ingredients in grapefruit juice responsible for inhibition of cytochrome P450 3A4 in humans.

The effect of smoking on post-heparin lipoprotein and hepatic lipase, cholesteryl ester transfer protein and lecithin:cholesterol acyl transferase activities in human plasma

INTRODUCTION

Smoking is associated with dyslipidaemia, particularly raised plasma triglycerides and reduced high-density lipoprotein (HDL)-cholesterol and a delayed clearance of triglyceride in fat tolerance tests. The aim of this study was to investigate whether these phenomena could be explained by a reduced lipoprotein lipase activity in smokers.

METHODS

A group of 40 healthy individuals [plasma cholesterol 5.07 (SD 0.90) mmol L-1, plasma triglyceride 1.02 (SD 0.39) mmol L-1)] was studied to examine the effects of smoking on plasma enzyme activities, particularly post-heparin lipase activities. The group comprised 20 smokers and 20 non-smokers, who were matched for age, gender and body mass index (BMI).

RESULTS

Post-heparin lipoprotein lipase (LPL) activity [3.89 (SD 1.58) vs. 5.85 (SD 2.30) mumol free fatty acids (FFA) mL-1 h-1, P < 0.005], but not post-heparin hepatic lipase (HL) activity, was reduced in smokers. Plasma cholesteryl ester transfer protein (CETP) activity and lecithin: cholesterol acyl transferase (LCAT) activity were measured in a subgroup of 18 individuals, comprising nine smokers with nine matched non-smokers. There was no difference in CETP activities between two groups, but smokers had a significantly reduced plasma LCAT activity [112 (SD 23) vs. 152 (SD 24) nmol cholesterol mL-1 h-1, P < 0.005]. In both smokers (r=-0.53, P < 0.05) and non-smokers (r=-0.54, P < 0.05), HDL2 concentration was negatively associated with HL activity. In non-smokers, HDL3 concentration was negatively associated with CETP activity (r= -0.77, P < 0.05), whereas in smokers HDL3 concentration was negatively associated with LCAT activity (r= -0.78, P < 0.050).

CONCLUSION

It was shown by direct measurement that the activity of plasma post-heparin LPL is reduced in smokers, independently of age, gender and BMI. It is concluded that this enzyme perturbation associated with smoking may contribute to the development of the atherogenic lipoprotein phenotype seen in smokers.

Linkage between cholesterol 7alpha-hydroxylase and high plasma low-density lipoprotein cholesterol concentrations

Interindividual differences in plasma low-density lipoprotein cholesterol (LDL-C) levels reflect both environmental variation and genetic polymorphism, but the specific genes involved and their relative contributions to the variance in LDL-C are not known. In this study we investigated the relationship between plasma LDL-C concentrations and three genes with pivotal roles in LDL metabolism: the low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), and cholesterol 7alpha-hydroxylase (CYP7). Analysis of 150 nuclear families indicated statistically significant linkage between plasma LDL-C concentrations and CYP7, but not LDLR or APOB. Further sibling pair analyses using individuals with high plasma LDL-C concentrations as probands indicated that the CYP7 locus was linked to high plasma LDL-C, but not to low plasma LDL-C concentrations. This finding was replicated in an independent sample. DNA sequencing revealed two linked polymorphisms in the 5' flanking region of CYP7. The allele defined by these polymorphisms was associated with increased plasma LDL-C concentrations, both in sibling pairs and in unrelated individuals. Taken together, these findings indicate that polymorphism in CYP7 contributes to heritable variation in plasma LDL-C concentrations. Common polymorphisms in LDLR and APOB account for little of the heritable variation in plasma LDL-C concentrations in the general population.

Will routine therapeutic drug monitoring have a place in clozapine therapy?

Clozapine is an atypical antipsychotic medication with proven efficacy in the management of refractory schizophrenia. It is also recommended for patients who do not tolerate the extrapyramidal adverse effects of traditional antipsychotic medications. However, the therapeutic promise of clozapine has been limited by a higher incidence of agranulocytosis. Currently, plasma clozapine concentrations are not routinely used in clinical management. Therapeutic effects are monitored empirically during a 6 to 8 week titration period in which the dosage is raised to 300 to 450 mg/day. Clozapine nevertheless fulfils a number of criteria which make it a candidate for therapeutic monitoring. These include an identifiable therapeutic range, an unpredictable dose-concentration relationship between patients, a potential for clinically relevant pharmacokinetic interaction with other drugs and a high probability of patient noncompliance. The therapeutic threshold plasma concentration appears to be about 400 micrograms/L. Concentrations above 1000 micrograms/L increase the risk of adverse effects on the central nervous system (confusion, delirium and generalised seizures). There is no evidence to link increased concentrations of clozapine or its metabolite to the development of agranulocytosis. We conclude that therapeutic drug monitoring can play a useful role in the clinical management of patients treated with clozapine. The clinician is advised to primarily use clinical judgement during dosage escalation, but intermittent monitoring is recommended to quickly optimise a therapeutic dosage for each patient. At steady state, occasional measurements could be made when clinical signs indicate possible toxicity or lack of effect (possibly caused by a lack of compliance or drug interaction). Long term monitoring would, in our view, not be necessary.