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Biomedical subjects

Xavier Leverve

Publications and source records attributed to Xavier Leverve.

At least 19 recordsLinked to original sources
PubMed2007

Emergency department visits caused by adverse drug events: results of a French survey.

BACKGROUND: Adverse drug events (ADEs) are a substantial cause of hospital admissions. However, little is known about the incidence, preventability and severity of ADEs resulting in emergency department visits. To address this issue, we conducted a prospective survey in emergency departments of French public hospitals. METHODS: This study was performed over two periods of 1 week each, one in June 1999 and one in December 1999, in emergency departments of five university hospitals and five general hospitals throughout France. All patients aged>or=15 years presenting with medical complaints were included in the study. Trauma patients, those with gynaecological conditions and those with alcohol intoxication or intentional drug poisoning were excluded from the study. Each patient was assessed by two local emergency physicians to determine whether the visit was the result of an ADE. All medical records were subsequently validated by an independent group of medical lecturers in iatrogenic disorders. RESULTS: Out of a total of 1937 patients consulting, 1562 were taking at least one drug during the previous week and were included for analysis; 328 (21%; 95% CI 19, 23) of these patients consulted an emergency physician because of an ADE. Patients with ADEs were older than those without (mean age 63.5 vs 54.8 years; p<0.0001). Furthermore, ADE patients were more likely to have a higher severity presentation than the non-ADE group (p=0.019). The number of drug exposures was significantly higher in patients with an ADE than in those without (mean number of medications 5.17 vs 3.82; p<0.0001). On multivariate analysis, only age and the number of medications taken were significantly associated with adverse events. In total, 410 drugs were incriminated in the occurrence of 328 ADEs. The most frequently incriminated drug classes were: (i) psychotropic agents (n=84; 20.5%); (ii) diuretics (n=48; 11.7%), anticoagulants (n=38; 9.3%) and other cardiovascular drugs (n=63; 15.4%); and (iii) analgesics, including NSAIDs (n=57; 13.9%). Preventability could be assessed in 280 of the 328 cases. In 106 cases (37.9%), the ADE was judged to be preventable. CONCLUSION: ADEs leading to emergency department visits are frequent, and many are preventable, confirming that there is a need to develop prevention strategies.

Adult↗
PubMed2006

Profound effects of the general anesthetic etomidate on oxidative phosphorylation without effects on their yield.

We investigated the effects of the general anesthetic Etomidate on oxidative phosphorylation in isolated rat liver mitochondria. The study of each electron transfer site shows that there is an inhibition: mainly at complex I but also, to a lesser extent, at complex III. Moreover, with succinate as substrate, the increase in non-phosphorylating respiration is accompanied by a decrease in DeltaPsi. However, this effect is not due to classical uncoupling of oxidative phosphorylation, since ADP addition at high Etomidate concentrations restores the transmembrane difference of electrical potential. Also, in the same range of Etomidate concentration, the ATP/O ratio is not significantly affected. In conclusion, the main effect of Etomidate is to decrease the oxidative phosphorylation rate without changing yield. The H(+) leak which appears under non-phosphorylating conditions becomes negligible in physiological conditions.

Adenosine Diphosphate↗
PubMed2005

Fat intake reverses the beneficial effects of low caloric intake on skeletal muscle mitochondrial H(2)O(2) production.

Food restriction is the most effective modulator of oxidative stress and it is believed that a reduction in caloric intake per se is responsible for the reduced generation of reactive oxygen species (ROS) by mitochondria. Hydrogen peroxide (H(2)O(2)) generation and oxygen consumption (O(2)) by skeletal muscle mitochondria were determined in a peculiar strain of rats (Lou/C) characterized by a self-low-caloric intake and a dietary preference for fat. These rats were fed either with a standard high-carbohydrate (HC) or a high-fat (HF) diet and the results were compared to those measured in Wistar rats fed a HC diet. H(2)O(2) production was significantly reduced in Lou/C rats fed a HC diet; this effect was not due to a lower O(2) consumption but rather to a decrease in rotenone-sensitive NADH-ubiquinone oxidoreductase activity and increased expression of uncoupling proteins 2 and 3. The reduced H(2)O(2) generation displayed by Lou/C rats was accompanied by a significant inhibition of permeability transition pore (PTP) opening. H(2)O(2) production was restored and PTP inhibition was relieved when Lou/C rats were allowed to eat a HF diet, suggesting that the reduced oxidative stress provided by low caloric intake is lost when fat proportion in the diet is increased.

Animals↗
PubMed2005

Effects of decreasing mitochondrial volume on the regulation of the permeability transition pore.

The permeability transition pore (PTP) is a Ca(2+)-sensitive mitochondrial inner membrane channel involved in several models of cell death. Because the matrix concentration of PTP regulatory factors depends on matrix volume, we have investigated the role of the mitochondrial volume in PTP regulation. By incubating rat liver mitochondria in media of different osmolarity, we found that the Ca(2+) threshold required for PTP opening dramatically increased when mitochondrial volume decreased relative to the standard condition. This shrinkage-induced PTP inhibition was not related to the observed changes in protonmotive force, or pyridine nucleotide redox state and persisted when mitochondria were depleted of adenine nucleotides. On the other hand, mitochondrial volume did not affect PTP regulation when mitochondria were depleted of Mg(2+). By studying the effects of Mg(2+), cyclosporin A (CsA) and ubiquinone 0 (Ub(0)) on PTP regulation, we found that mitochondrial shrinkage increased the efficacy of Mg(2+) and Ub(0) at PTP inhibition, whereas it decreased that of CsA. The ability of mitochondrial volume to alter the activity of several PTP regulators represents a hitherto unrecognized characteristic of the pore that might lead to a new approach for its pharmacological modulation.

Animals↗
PubMed2005

Dialyzer membrane permeability and survival in hemodialysis patients.

BACKGROUND: We previously showed that nutritional protein concentrations were predictive of outcome, whereas variables reflecting body composition and dialysis dose were not, in a 30-month prospective follow-up of 1,610 hemodialysis patients. Information on dialysis membrane and erythropoietin use had to be evaluated in an additional follow-up. METHODS: A subset of 650 patients from the initial cohort of 1,610 was analyzed for survival in a 2-year extension of follow-up. Detailed data were collected: demographics; cause of renal failure; time on dialysis therapy; type of membrane; erythropoietin treatment; body mass index (BMI); predialysis albumin, prealbumin, and bicarbonate levels; and outcome. Normalized protein catabolic rate (nPCR), dialysis adequacy, and lean body mass were computed from predialysis and postdialysis urea and creatinine values. RESULTS: Patient characteristics were age of 61 +/- 16 years, 58% men, BMI of 22.7 +/- 4.4 kg/m2 , time on dialysis therapy of 102 +/- 73 months, and 8.8% had diabetes. Dialysis parameters were duration of 247 +/- 31 minutes, Kt/V of 1.4 +/- 0.3, and nPCR of 1.2 +/- 0.3 g/kg/d. Albumin level was 3.73 +/- 0.53 g/dL (37.3 +/- 5.3 g/L), and prealbumin level was 31 +/- 8 mg/dL. The survival rate was 78.7% after 2 years. Survival was influenced by age, presence of diabetes, use of high-flux membrane, and serum albumin level, but not other variables, including Kt/V and prealbumin level. Two-year variations in values for urea, creatinine, and weight were predictive of survival in univariate, but not multivariate, analyses. CONCLUSION: In patients on dialysis therapy for a long period, better survival was observed when high-flux dialysis membranes were used.

Aged↗
PubMed2005

Lactate metabolism in acute uremia.

Lactate is a key metabolite that is produced by every cell and oxidized by most of them, provided that they do contain mitochondria. Its metabolism is connected to energetic homeostasis and the cellular redox state. It is well recognized as an indicator of severe outcome in severely ill patients, however, it is not a detrimental factor per se. Conversely, some recent data tend even to indicate a beneficial effect in several metabolic disorders. Although the liver has long been recognized as a key organ in lactate homeostasis, the kidney also plays a major role as a gluconeogenic organ significantly involved in the glucose-lactate cycle. In acute renal failure, sodium lactate is widely used as a buffer in replacement fluids because the anion (lactate - ) is metabolized and the cation (Na + ) remains, leading to decreased water dissociation and proton concentration. The metabolic disorders related to acute renal failure or associated with it, such as liver failure, may affect lactate metabolism, and therefore they are often regarded as limiting factors for the use of lactate-containing fluids in such patients. By investigating endogenous lactate production in severe septic patients with acute renal failure, we found that an acute exogenous load of lactate did not affect the basal endogenous lactate production and metabolism. This indicates that exogenous lactate is well metabolized even in patients suffering from acute renal failure and severe sepsis with a compromised hemodynamic status.

Acute Kidney Injury↗
PubMed2005

Effects of dopamine and norepinephrine on systemic and hepatosplanchnic hemodynamics, oxygen exchange, and energy balance in vasoplegic septic patients.

Dopamine is widely used to improve systemic and hepatosplanchnic hemodynamics and oxygenation during sepsis. However, some studies have suggest that norepinephrine may have beneficial effects on regional blood flow and metabolism, whereas dopamine might have deleterious effects related to redistribution of blood flow away from the intestinal mucosa or by decreasing directly the cell redox state. In 12 vasoplegic septic patients, we compared the effects of norepinephrine and dopamine on systemic and hepatosplanchnic hemodynamics, oxygenation, and energy metabolism. Catecholamines were administered in a crossover randomized order to maintain mean arterial pressure (MAP) at 80 mmHg. Hepatosplanchnic blood flow (Qspl) was determined using a continuous infusion of indocyanine green dye. Despite a similar MAP, the cardiac index was higher with dopamine than with norepinephrine (6.3 [5.3-7.3] vs. 4.3 [3.8-4.9] L.min.m) (P <0.001). Qspl was similar with both catecholamines, but the ratio of Qspl to cardiac output was significantly lower with dopamine (23.9% [17.5-33.5]) than with norepinephrine (33.5% [25.8-37]) (P <0.05). Although global O2 delivery and O2 consumption were higher with dopamine (782 [707-859] vs. 553 [512-629] mL.min.m, P <0.001 and 164 [134-192] vs. 128 [111-149] mL.min.m, P <0.001, respectively), hepatosplanchnic O2 delivery and consumption were not different. Hepatic lactate uptake was lower (0.47 [0.3-0.89] vs. 1.01 [0.69-1.34] mmol.min) (P <0.01), and hepatic venous lactate-to-pyruvate ratio was higher (15.3 [7.6-21.1] vs. 11.2 [6.6-15.1], P <0.05) with dopamine than with norepinephrine. In vasoplegic septic patients, maintaining mean arterial pressure, hepatosplanchnic hemodynamics, and oxygen exchange with dopamine requires a consequent increased cardiac output, which is responsible for an increased global oxygen demand when compared with norepinephrine. In addition, dopamine impairs the hepatic energy balance. Its position as a preferential treatment compared with norepinephrine in this context may therefore be questionable.

Adult↗
PubMed2005

Metformin prevents high-glucose-induced endothelial cell death through a mitochondrial permeability transition-dependent process.

Hyperglycemia-induced oxidative stress is detrimental for endothelial cells, contributing to the vascular complications of diabetes. The mitochondrial permeability transition pore (PTP) is an oxidative stress-sensitive channel involved in cell death; therefore, we have examined its potential role in endothelial cells exposed to oxidative stress or high glucose level. Metformin, an antihyperglycemic agent used in type 2 diabetes, was also investigated because it inhibits PTP opening in transformed cell lines. Cyclosporin A (CsA), the reference PTP inhibitor, and a therapeutic dose of metformin (100 micromol/l) led to PTP inhibition in permeabilized human microvascular endothelial cells (HMEC-1). Furthermore, exposure of intact HMEC-1 or primary endothelial cells from either human umbilical vein or bovine aorta to the oxidizing agent tert-butylhydroperoxide or to 30 mmol/l glucose triggered PTP opening, cytochrome c decompartmentalization, and cell death. CsA or metformin prevented all of these effects. The antioxidant N-acetyl-l-cysteine also prevented hyperglycemia-induced apoptosis. We conclude that 1) elevated glucose concentration leads to an oxidative stress that favors PTP opening and subsequent cell death in several endothelial cell types and 2) metformin prevents this PTP opening-related cell death. We propose that metformin improves diabetes-associated vascular disease both by lowering blood glucose and by its effect on PTP regulation.

Cell Death↗
PubMed2004

Metformin inhibits mitochondrial permeability transition and cell death: a pharmacological in vitro study.

Metformin, a drug widely used in the treatment of Type II diabetes, has recently received attention owing to new findings regarding its mitochondrial and cellular effects. In the present study, the effects of metformin on respiration, complex 1 activity, mitochondrial permeability transition, cytochrome c release and cell death were investigated in cultured cells from a human carcinoma-derived cell line (KB cells). Metformin significantly decreased respiration both in intact cells and after permeabilization. This was due to a mild and specific inhibition of the respiratory chain complex 1. In addition, metformin prevented to a significant extent mitochondrial permeability transition both in permeabilized cells, as induced by calcium, and in intact cells, as induced by the glutathione-oxidizing agent t-butyl hydroperoxide. This effect was equivalent to that of cyclosporin A, the reference inhibitor. Finally, metformin impaired the t-butyl hydroperoxide-induced cell death, as judged by Trypan Blue exclusion, propidium iodide staining and cytochrome c release. We propose that metformin prevents the permeability transition-related commitment to cell death in relation to its mild inhibitory effect on complex 1, which is responsible for a decreased probability of mitochondrial permeability transition.

Cell Death↗
PubMed2004

Opening of the mitochondrial permeability transition pore induces reactive oxygen species production at the level of the respiratory chain complex I.

We have investigated the consequences of permeability transition pore (PTP) opening on the rate of production of reactive oxygen species in isolated rat liver mitochondria. We found that PTP opening fully inhibited H(2)O(2) production when mitochondria were energized both with complex I or II substrates. Because PTP opening led to mitochondrial pyridine nucleotide depletion, H(2)O(2) production was measured again in the presence of various amounts of NADH. PTP opening-induced H(2)O(2) production began when NADH concentration was higher than 50 microm and reached a maximum at over 300 microm. At such concentrations of NADH, the maximal H(2)O(2) production was 4-fold higher than that observed when mitochondria were permeabilized with the channel-forming antibiotic alamethicin, indicating that the PTP opening-induced H(2)O(2) production was not due to antioxidant depletion. Moreover, PTP opening decreased rotenone-sensitive NADH ubiquinone reductase activity, whereas it did not affect the NADH FeCN reductase activity. We conclude that PTP opening induces a specific conformational change of complex I that (i) dramatically increases H(2)O(2) production so long as electrons are provided to complex I, and (ii) inhibits the physiological pathway of electrons inside complex I. These data allowed the identification of a novel consequence of permeability transition that may partly account for the mechanism by which PTP opening induces cell death.

Animals↗
PubMed2004

Influence of an orally effective SOD on hyperbaric oxygen-related cell damage.

In a prospective, double-blind, randomised placebo-controlled study, we tested the hypothesis that a new formulation consisting of wheat gliadin chemically combined with a vegetal (thus orally effective) preparation of superoxide dismutase (SOD) allows to prevent hyperbaric oxygen (HBO)-induced oxidative cell stress. Twenty healthy volunteers were exposed to 100% oxygen breathing at 2.5 ATA for a total of 60 min. DNA strand breaks (tail moments) were determined using the alkaline version of the comet assay. Whole blood concentrations of reduced (GSH) and oxidised (GSSG) glutathione and F2-isoprostanes, SOD, glutathione peroxidase (GPx) and catalase (Cat) activities and red cell malondialdehyde (MDA) content were determined. After HBO exposure the tail moment (p = 0.03) and isoprostane levels (p = 0.049) were significantly lower in the group that received the vegetal formulation. Neither SOD and Cat nor GSH and GSSG were significantly affected by this preparation or HBO exposure. By contrast, blood GPx activity, which tended to be lower in the SOD-group already before the HBO exposure (p = 0.076), was significantly lower afterwards (p = 0.045). We conclude that an orally effective SOD-wheat gliadin mixture is able to protect against DNA damage, which coincided with reduced blood isoprostane levels, and may therefore be used as an antioxidant.

Adult↗
PubMed2004

Glucose appearance in the peripheral circulation and liver glucose output in men after a large 13C starch meal.

BACKGROUND: Glucose absorption from starchy food has only been described with small amounts ingested ( approximately 20-75 g). OBJECTIVE: Our aim was to describe total plasma (Ra) and exogenous glucose (Ra(exo)) appearance, glucose release from the liver (HGP), and the metabolic response after ingestion of 5 g polished or parboiled rice/kg body mass. DESIGN: Gas exchange and urea excretion were monitored in 8 healthy subjects before (3.5 h) and after (8 h) ingestion of rice intrinsically labeled with (13)C; [6,6-(2)H(2)]glucose was infused for the measurement of Ra, Ra(exo), and HGP. RESULTS: Changes in plasma glucose, insulin, lactate, and free fatty acids and the increase in Ra(exo) and Ra ( approximately 200%) and the decrease in HGP ( approximately 90%) were not significantly different (P > 0.05) after ingestion of either rice. Glucose oxidation was not significantly different (111.6 +/- 8.2 compared with 89.0 +/- 11.3 g; P = 0.13), but fat oxidation was significantly lower (9.9 +/- 1.7 compared with 21.3 +/- 4.0 g; P < 0.05) after parboiled than after polished rice. The percentage of the glucose load that appeared in the circulation over 8 h was not significantly different after ingestion of polished (70.4 +/- 4.5%) or parboiled (63.8 +/- 2.0%) rice (P > 0.05). CONCLUSION: Although the starch in parboiled rice is less susceptible to digestion in vitro, exogenous glucose availability was not significantly different after ingestion of large amounts of polished or parboiled rice. Glucose absorption remains incomplete 8 h after ingestion of both types of rice.

Adult↗
PubMed2003

Nutritional regulation and role of peroxisome proliferator-activated receptor delta in fatty acid catabolism in skeletal muscle.

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors primarily involved in lipid homeostasis. PPARdelta displays strong expression in tissues with high lipid metabolism, such as adipose, intestine and muscle. Its role in skeletal muscle remains largely unknown. After a 24-h starvation period, PPARdelta mRNA levels are dramatically up-regulated in gastrocnemius muscle of mice and restored to control level upon refeeding. The rise of PPARdelta is accompanied by parallel up-regulations of fatty acid translocase/CD36 (FAT/CD36) and heart fatty acid binding protein (H-FABP), while refeeding promotes down-regulation of both genes. To directly access the role of PPARdelta in muscle cells, we forced its expression and that of a dominant-negative PPARdelta mutant in C2C12 myogenic cells. Differentiated C2C12 cells responds to 2-bromopalmitate or synthetic PPARdelta agonist by induction of genes involved in lipid metabolism and increment of fatty acid oxidation. Overexpression of PPARdelta enhanced these cellular responses, whereas expression of the dominant-negative mutant exerts opposite effects. These data strongly support a role for PPARdelta in the regulation of fatty acid oxidation in skeletal muscle and in adaptive response of this tissue to lipid catabolism.

Animals↗
PubMed2003

[Adverse drug effects observed at French admissions departments and emergency services (Prospective study of the National Educational Association for Teaching Therapeutics and proposals for preventive measures].

Various studies have shown that adverse drug events (ADE) are a substantial cause of hospital admissions. However, little is known about the incidence and severity of ADE resulting in hospital visits. To address this issue, we conducted a prospective survey in 10 primary care and emergency departments of French public hospitals. This study was performed over two periods of one week, one in June 1999 and one in December 1999, in primary care and emergency departments of five university hospitals and five general hospitals throughout France. Out of a total of 1,937 patients consulting, 1,562 were taking at least one drug during the previous week and were included for analysis according to the protocol. Altogether, 328 (21%; 95% confidence interval 19% to 23%) of these patients receiving at least one drug consulted because of an ADE. The sex ratio (M/F) was the same in both groups with or without ADE (1.04 vs 1.02, respectively, P = 0.83). Patients with ADE were older than those without (63.5 vs 54.8 years, P < 0.0001). Furthermore, ADR patients were more likely to have a higher severity score than no-ADE group (P = 0.019). The outcome seemed to be worse in patients with an ADE. The percentage of patients treated with 2 or more drugs and the number of drug exposures were significantly higher in patients with ADE than in those without (90.9% vs 75.0%, P < 0.0001, and 5.17 vs 3.82, P < 0.0001, respectively). The most frequent causes of visits for ADE-patients were digestive (n = 53, 16.2%), neurological (n = 52, 15.9%), cardiovascular (n = 49, 14.9%) and malaise (n = 49, 14.9%) events. In total, 410 drugs were incriminated in the occurrence of 328 ADE. The most frequently incriminated drug classes were (1) psychotropic agents, including anxiolytics and/or hypnotics, antidepressants and antipsychotics (n = 84, 20.5%), (2) diuretics (n = 48, 11.7%), (3) anticoagulants (n = 38, 9.3%), (4) other cardiovascular drugs (n = 63, 15.4%), and (5) analgesics, including non steroidal antiinflammatory agents (n = 57, 13.9%). The avoidability of ADE could be estimated by an external expert panel in 280 of the 328 cases. In 106 cases (37.9%), ADE was considered to be preventable because a contra-indication or a warning about drug use had not been respected.

Adult↗
PubMed2002

Position paper of the ESICM Working Group on Nutrition and Metabolism. Metabolic basis of nutrition in intensive care unit patients: ten critical questions.

The metabolic changes associated with critical illness involve several pathways acting at different steps of the utilization of nutritive substrates. The understanding of the role of these pathways and of their complex regulation has led to the development of new strategies for the metabolic and nutritional management of critically ill patients, including the development of new products for nutritional support. The rationale for changing the profile of nutritional support solutions by adding novel substrates is also discussed. This review focuses on the metabolic specificities of critically ill patients and also includes an analysis of the adequacy of tools to monitor the metabolic status and the adequacy of the nutritional support.

Critical Care↗