Consequences of one-week creatine supplementation on creatine and creatinine levels in athletes 'serum and urine

We explored the washout period of creatine (Cr) after repeated ingestions of high doses of exogenous Cr. Ten athletes ingested daily, in a randomized double-blind study design, 30 g of exoge- nous Cr (n = 5, Cr-group) or a placebo (n = 5, Pl-group). Serum and urine samples were collected 1) before supplementation (BEFO- RE), 2) after one week Cr supplementation (AFTER), and 3) one week later without supplementation (LATER). The Cr and crea- tinine (Crn) concentrations in serum (sCr, sCrn) and in multiple spots urine (uCr, uCrn) were measured. We observed a significant rise (p < 0.01) in sCr, uCr and sCrn between BEFORE and AFTER supplementation in Cr-group, as well as a significant difference between Cr-group and Pl-group. Body weight increased signifi- cantly (+1.5 kg), but relative body fat (%fat) was unchanged. After the washout period in LATER Cr-group, sCr and uCr decreased to low residual values. No loss of body weight occurred during thisperiod. In contrast, sCrn and uCrn returned to baseline values. In conclusion, regular uptake of high doses of exogenous Cr affects both Cr and Crn concentrations in serum (sCr: 14 folds; sCrn: 1.2 folds) and urine (uCr: 140 folds; uCrn: 1.5 folds). An abuse of Cr is therefore mostly spilled over in urine. Surprise drug tests, such as doping controls, happening during the period of Cr supplementa- tion can reveal an important increase in Cr and Crn concentrations, although subjects stopped suddenly Cr loading. The discernible effect of Cr supplementation on these values disappeared within one week.

A high-fructose diet impairs basal and stress-mediated lipid metabolism in healthy male subjects.

The effects of a 7 d high-fructose diet (HFrD) or control diet on lipid metabolism were studied in a group of six healthy lean males. Plasma NEFA and beta-hydroxybutyrate concentrations, net lipid oxidation (indirect calorimetry) and exogenous lipid oxidation (13CO2 production) were monitored in basal conditions, after lipid loading (olive oil labelled with [13C]triolein) and during a standardised mental stress. Lactate clearance and the metabolic effects of an exogenous lactate infusion were also monitored. The HFrD lowered plasma concentrations of NEFA and beta-hydroxybutyrate as well as lipid oxidation in both basal and after lipid-loading conditions. In addition, the HFrD blunted the increase in plasma NEFA and exogenous lipid oxidation during mental stress. The HFrD also increased basal lactate concentrations by 31.8 %, and lactate production by 53.8 %, while lactate clearance remained unchanged. Lactate infusion lowered plasma NEFA with the control diet, and net lipid oxidation with both the HFrD and control diet. These results indicate that a 7 d HFrD markedly inhibits lipolysis and lipid oxidation. The HFrD also increases lactate production, and the ensuing increased lactate utilisation may contribute to suppress lipid oxidation.

Clinal variation in a brown lemur (Eulemur spp.) hybrid zone: Combining morphological, genetic and climatic data to examine stability.

Studies of hybrid zones can inform our understanding of reproductive isolation and speciation. Two species of brown lemur (Eulemur rufifrons and E. cinereiceps) form an apparently stable hybrid zone in the Andringitra region of south-eastern Madagascar. The aim of this study was to identify factors that contribute to this stability. We sampled animals at 11 sites along a 90-km transect through the hybrid zone and examined variation in 26 microsatellites, the D-loop region of mitochondrial DNA, six pelage and nine morphological traits; we also included samples collected in more distant allopatric sites. Clines in these traits were noncoincident, and there was no increase in either inbreeding coefficients or linkage disequilibrium at the centre of the zone. These results could suggest that the hybrid zone is maintained by weak selection against hybrids, conforming to either the tension zone or geographical selection-gradient model. However, a closer examination of clines in pelage and microsatellites indicates that these clines are not sigmoid or stepped in shape but instead plateau at their centre. Sites within the hybrid zone also occur in a distinct habitat, characterized by greater seasonality in precipitation and lower seasonality in temperature. Together, these findings suggest that the hybrid zone may follow the bounded superiority model, with exogenous selection favouring hybrids within the transitional zone. These findings are noteworthy, as examples supporting the bounded superiority model are rare and may indicate a process of ecologically driven speciation without geographical isolation.

Changes in sleeping and basal energy expenditure and substrate oxidation induced by short term thyroxin administration in man.

The present study was designed to explore the thermogenic effect of thyroid hormone administration and the resulting changes in nitrogen homeostasis. Normal male volunteers (n = 7) received thyroxin during 6 weeks. The first 3-week period served to suppress endogenous thyroid secretion (180 micrograms T4/day). This dose was doubled for the next 3 weeks. Sleeping energy expenditure (respiratory chamber) and BMR (hood) were measured by indirect calorimetry, under standardized conditions. Sleeping heart rate was continuously recorded and urine was collected during this 12-hour period to assess nitrogen excretion. The changes in energy expenditure, heart rate and nitrogen balance were then related to the excess thyroxin administered. After 3 weeks of treatment, serum TSH level fell to 0.15 mU/L, indicating an almost complete inhibition of the pituitary-thyroid axis. During this phase of treatment there was an increase in sleeping EE and sleeping heart rate, which increased further by doubling the T4 dose (delta EE: +8.5 +/- 2.3%, delta heart rate +16.1 +/- 2.2%). The T4 dose, which is currently used as a substitutive dose, lead to a borderline hyperthyroid state, with an increase in EE and heart rate. Exogenous T4 administration provoked a significant increase in urinary nitrogen excretion averaging 40%. It is concluded that T4 provokes an important stimulation of EE, which is mostly mediated by an excess protein oxidation.

Bolus injections of synthetic atrial natriuretic peptide in patients with chronic renal failure or nephrotic syndrome.

The diuretic and natriuretic responses to exogenous synthetic atrial natriuretic peptide (ANP) were evaluated in patients with chronic renal failure (CRF) or nephrotic syndrome (NS). Patients were studied after an oral water load (8 ml/kg in CRF and 20 ml/kg in NS patients). A short intravenous bolus of either a placebo or ANP was administered when urine output was stable. In each group of patients, three doses of ANP were injected at 24 h intervals, i.e., 1.0, 1.5, and 2.0 micrograms/kg in the CRF and 1.0, 1.5, and 3.0 micrograms/kg in the NS group. Blood pressure and heart rate were monitored throughout the study and urinary volume and electrolyte excretion were measured every 20 min up to 3 h after the bolus. An acute and transient fall in blood pressure was observed immediately after the ANP injection. It was more pronounced in CRF than in NS patients. In CRF patients, ANP caused only a slight increase in urinary volume (13.5-44% over baseline) but a significant increase in urinary sodium excretion (45-114% over baseline). In NS patients, significant increases in both urine volume (60-105%) and sodium excretion (149-248%) were also found. In these latter patients, the renal response to ANP appeared to be better preserved. The hemodynamic and renal changes induced by ANP occurred mainly during the first 20 min following the ANP administration, when the peak plasma ANP levels were obtained. However, no clear dose-response effect could be evidenced in either group with the three doses of ANP chosen in this study.

METABOLIC EFFECTS OF DIETARY PROTEINS

SUMMARY :Non-alcoholic fatty liver disease (NAFLD) is characterized by an elevated intra- hepatocellular lipid (IHCL) concentration (> 5%). The incidence of NAFLD is frequently increased in obese patients, and is considered to be the hepatic component of the metabolic syndrome. The metabolic syndrome, also characterized by visceral obesity, altered glucose homeostasis, insulin resistance, dyslipidemia, and high blood pressure, represents actually a major public health burden. Both dietary factors and low physical activity are involved in the development of the metabolic syndrome. ln animals and healthy humans, high-fat or high-fructose diets lead to the development of several features of the metabolic syndrome including increased intrahepatic lipids and insulin resistance. ln contrast the effects of dietary protein are less well known, but an increase in protein intake has been suggested to exert beneficial effects by promoting weight loss and improving glucose homeostasis in insulin-resistant patients. Increased postprandial thermogenesis and enhanced satiety after protein ingestion may be both involved. The effects of dietary protein on hepatic lipids have been poorly investigated in humans, but preliminary studies in rodents have shown a reduction of hepatic lipids in carbohydrate fed rats and in obese rats. ln this context this work aimed at investigating the metabolic effects of dietary protein intake on hepatic lipid metabolism and glucose homeostasis in humans. The modulation by dietary proteins of exogenous lipid oxidation, net lipid oxidation, hepatic beta-oxidation, triglycerides concentrations, whole-body energy expenditure and glucose tolerance was assessed in the fasting state and in postprandial states. Measurements of IHCL were performed to quantify the amount of triglycerides in the liver. ln an attempt to cover all these metabolic aspects under different point of views, these questions were addressed by three protocols involving various feeding conditions. Study I addressed the effects of a 4-day hypercaloric high-fat high-protein diet on the accumulation of fat in the liver (IHCL) and on insulin sensitivity. Our findings indicated that a high protein intake significantly prevents intrahepatic fat deposition induced by a short- term hypercaloric high-fat diet, adverse effects of which are presumably modulated at the liver level.These encouraging results led us to conduct the second study (Study ll), as we were also interested in a more clinical approach to protein administration and especially if increased protein intakes might be of benefit for obese patients. Therefore the effects of one-month whey protein supplementation on IHCL, insulin sensitivity, lipid metabolism, glucose tolerance and renal function were assessed in obese women. Results showed that whey protein supplementation reduces hepatic steatosis and improves the plasma lipid profile in obese patients, without adverse effects on glucose tolerance or creatinine clearance. However since patients were fed ud-libitum, it remains possible that spontaneous carbohydrate and fat intakes were reduced due to the satiating effects of protein. The third study (Study lll) was designed in an attempt to deepen our comprehension about the mechanisms involved in the modulation of IHCL. We hypothesized that protein improved lipid metabolism and, therefore, we evaluated the effects of a high protein meal on postprandial lipid metabolism and glucose homeostasis after 4-day on a control or a protein diet. Our results did not sustain the hypothesis of an increased postprandial net lipid oxidation, hepatic beta oxidation and exogenous lipid oxidation. Four days on a high-protein diet rather decreased exogenous fat oxidation and enhanced postprandial triglyceride concentrations, by impairing probably chylomicron-TG clearance. Altogether the results of these three studies suggest a beneficial effect of protein intake on the reduction in lHCL, and clearly show that supplementation of proteins do not reduce IHCL by stimulating lipid metabolism, e.g. whole body fat oxidation, hepatic beta oxidation, or exogenous fat oxidation. The question of the effects of high-protein intakes on hepatic lipid metabolism is still open and will need further investigation to be elucidated. The effects of protein on increased postprandial lipemia and lipoproteins kinetics have been little investigated so far and might therefore be an interesting research question, considering the tight relationship between an elevation of plasmatic TG concentrations and the increased incidence of cardiovascular diseases.Résumé :La stéatose hépatique non alcoolique se caractérise par un taux de lipides intra-hépatiques élevé, supérieur à 5%. L'incidence de la stéatose hépatique est fortement augmentée chez les personnes obèses, ce qui mène à la définir comme étant la composante hépatique du syndrome métabolique. Ce syndrome se définit aussi par d'autres critères tels qu'obésité viscérale, altération de l'homéostasie du glucose, résistance à l'insuline, dyslipidémie et pression artérielle élevée. Le syndrome métabolique est actuellement un problème de santé publique majeur.Tant une alimentation trop riche et déséquilibrée, qu'une faible activité physique, semblent être des causes pouvant expliquer le développement de ce syndrome. Chez l'animal et le volontaire sain, des alimentations enrichies en graisses ou en sucres (fructose) favorisent le développement de facteurs associés au syndrome métabolique, notamment en augmentant le taux de lipides intra-hépatiques et en induisant le développement d'une résistance à l'insuline. Par ailleurs, les effets des protéines alimentaires sont nettement moins bien connus, mais il semblerait qu'une augmentation de l'apport en protéines soit bénéfique, favorisant la perte de poids et l'homéostasie du glucose chez des patients insulino-résistants. Une augmentation de la thermogenese postprandiale ainsi que du sentiment de satiété pourraient en être à l'origine.Les effets des protéines sur les lipides intra-hépatiques chez l'homme demeurent inconnus à ce jour, cependant des études préliminaires chez les rongeurs tendent à démontrer une diminution des lipides intra hépatiques chez des rats nourris avec une alimentation riche en sucres ou chez des rats obèses.Dans un tel contexte de recherche, ce travail s'est intéressé à l'étude des effets métaboliques des protéines alimentaires sur le métabolisme lipidique du foie et sur l'homéostasie du glucose. Ce travail propose d'évaluer l'effet des protéines alimentaires sur différentes voies métaboliques impliquant graisses et sucres, en ciblant d'une part les voies de l'oxydation des graisses exogènes, de la beta-oxydation hépatique et de l'oxydation nette des lipides, et d'autre part la dépense énergétique globale et l'évolution des concentrations sanguines des triglycérides, à jeun et en régime postprandial. Des mesures des lipides intra-hépatiques ont aussi été effectuées pour permettre la quantification des graisses déposées dans le foie.Dans le but de couvrir l'ensemble de ces aspects métaboliques sous différents angles de recherche, trois protocoles, impliquant des conditions alimentaires différentes, ont été entrepris pour tenter de répondre à ces questions. La première étude (Etude I) s'est intéressée aux effets d'u.ne suralimentation de 4 jours enrichie en graisses et protéines sur la sensibilité à l'insuline et sur l'accumulation de graisses intra-hépatiques. Les résultats ont démontré que l'apport en protéines prévient l'accumulation de graisses intra-hépatiques induite par une suralimentation riche en graisses de courte durée ainsi que ses effets délétères probablement par le biais de mécanismes agissant au niveau du foie. Ces résultats encourageants nous ont conduits à entreprendre une seconde étude (Etude ll) qui s'intéressait à l'implication clinique et aux bénéfices que pouvait avoir une supplémentation en protéines sur les graisses hépatiques de patients obèses. Ainsi nous avons évalué pendant un mois de supplémentation l'effet de protéines de lactosérum sur le taux de graisses intrahépatiques, la sensibilité à l'insuline, la tolérance au glucose, le métabolisme des graisses et la fonction rénale chez des femmes obèses. Les résultats ont été encourageants; la supplémentation en lactosérum améliore la stéatose hépatique, le profil lipidique des patientes obèses sans pour autant altérer la tolérance au glucose ou la clairance de la créatinine. L'effet satiétogene des protéines pourrait aussi avoir contribué à renforcer ces effets. La troisième étude s'est intéressée aux mécanismes qui sous-tendent les effets bénéfiques des protéines observés dans les 2 études précédentes. Nous avons supposé que les protéines devaient favoriser le métabolisme des graisses. Par conséquent, nous avons cherché a évaluer les effets d'un repas riche en protéines sur la lipémie postprandiale et l'homéostasie glucidique après 4 jours d'alimentation contrôlée soit isocalorique et équilibrée, soit hypercalorique enrichie en protéines. Les résultats obtenus n'ont pas vérifié l'hypothèse initiale ; ni une augmentation de l'oxydation nette des lipides, ni celle d'une augmentation de la béta-oxydation hépatique ou de l'oxydation d'un apport exogène de graisses n'a pu étre observée. A contrario, il semblerait même plutôt que 4 jours d'a]irnentation hyperprotéinée inhibent le métabolisme des graisses et augmente les concentrations sanguines de triglycérides, probablement par le biais d'une clairance de chylornicrons altérée. Globalement, les résultats de ces trois études nous permettent d'attester que les protéines exercent un effet bénéfique en prévenant le dépot de graisses intra-hépatiques et montrent que cet effet ne peut être attribué à une stimulation du métabolisme des lipides via l'augmentation des oxydations des graisses soit totales, hépatiques, ou exogènes. La question demeure en suspens à ce jour et nécessite de diriger la recherche vers d'autres voies d'exploration. Les effets des protéines sur la lipémie postprandiale et sur le cinétique des lipoprotéines n'a que peu été traitée à ce jour. Cette question me paraît néanmoins importante, sachant que des concentrations sanguines élevées de triglycérides sont étroitement corrélées à une incidence augmentée de facteurs de risque cardiovasculaire.

Training in hypoxia fails to further enhance endurance performance and lactate clearance in well-trained men and impairs glucose metabolism during prolonged exercise.

The aim of this study was to investigate the synergistic effects of endurance training and hypoxia on endurance performance in normoxic and hypoxic conditions (approximately 3000 m above sea level) as well as on lactate and glucose metabolism during prolonged exercise. For this purpose, 14 well-trained cyclists performed 12 training sessions in conditions of normobaric hypoxia (HYP group, n = 7) or normoxia (NOR group, n = 7) over 4 weeks. Before and after training, lactate and glucose turnover rates were measured by infusion of exogenous lactate and stable isotope tracers. Endurance performance was assessed during incremental tests performed in normoxia and hypoxia and a 40 km time trial performed in normoxia. After training, performance was similarly and significantly improved in the NOR and HYP groups (training, P < 0.001) in normoxic conditions. No further effect of hypoxic training was found on markers of endurance performance in hypoxia (training x hypoxia interaction, n.s.). In addition, training and hypoxia had no significant effect on lactate turnover rate. In contrast, there was a significant interaction of training and hypoxia (P < 0.05) on glucose metabolism, as follows: plasma insulin and glucose concentrations were significantly increased; glucose metabolic clearance rate was decreased; and the insulin to glucagon ratio was increased after training in the HYP group. In conclusion, our results show that, compared with training in normoxia, training in hypoxia has no further effect on endurance performance in both normoxic and hypoxic conditions or on lactate metabolic clearance rate. Additionally, these findings suggest that training in hypoxia impairs blood glucose regulation in endurance-trained subjects during exercise.

Vascular Effects of RWJ-676070, a Selective Combined V-1a/V-2 Vasopressin Receptor Antagonist

In recent years, several vasopressin antagonists have been developed that block V-1 receptors either selectively or nonselectively.(1,2) To date, one combined V-1/V-2 antagonist (primarily a V-2 antagonist, as determined on the basis of human receptor binding data), conivaptan, has been approved for the treatment of euvolemic hyponatremia.(3,4) We have previously shown that the vascular properties of a vasopressin V-1 antagonist can be investigated safely and reliably in healthy subjects. We used the measurement of skin blood flow after intradermic injection of exogenous arginine vasopressin on a skin area prevasodilated with calcitonin gene-related peptide (CGRP).(3,5) This technique enables the documentation of the dose-dependent effects of vasopressin or vasopressin antagonists. In this study, we have characterized the V-1a pharmacodynamic profile of increasing doses of RWJ-676070, a new orally active dual V-1a/V-2 receptor antagonist, in healthy subjects.(5)

The biomechanic origin of sprint performance enhancement after one-week creatine supplementation.

In order to test whether an improvement of maximal sprinting speed after creatine (Cr) supplementation was due to the increase of stride frequency (SF), stride length (SL) or both, 7 subjects ran 4 consecutive sprints after 1 week of placebo or Cr supplementation. SF and SL were assessed by a triaxial accelerometer. Compared to the placebo, Cr induced an increase of running speed (+1.4% p < 0.05) and SF (+1.5%, p < 0.01), but not of SL. The drop in performance following repeated sprints was partially prevented by Cr. In conclusion, exogenous Cr enhanced sprinting performance by increasing SF. This result may be related to the recent findings of shortening in muscular relaxation time after Cr supplementation.

Critical role for the alpha-1B adrenergic receptor at the sympathetic neuroeffector junction.

The alpha-1 adrenergic receptors (alpha(1)ARs) are critical in sympathetically mediated vasoconstriction. The specific role of each alpha(1)AR subtype in regulating vasoconstriction remains highly controversial. Limited pharmacological studies suggest that differential alpha(1)AR responses may be the result of differential activation of junctional versus extrajunctional receptors. We tested the hypothesis that the alpha(1B)AR subtype is critical in mediating sympathetic junctional neurotransmission. We measured in vivo integrated cardiovascular responses to a hypotensive stimulus (induced via transient bilateral carotid occlusion [TBCO]) in alpha(1B)AR knockout (KO) mice and their wild-type (WT) littermates. In WT mice, after dissection of the carotid arteries and denervation of aortic baroreceptor buffering nerves, TBCO produced significant pressor and positive inotropic effects. Both responses were markedly attenuated in alpha(1B)AR KO mice (change systolic blood pressure 46+/-8 versus 11+/-2 mm Hg; percentage change in the end-systolic pressure-volume relationship [ESPVR] 36+/-7% versus 12+/-2%; WT versus KO; P<0.003). In vitro alpha(1)AR mesenteric microvascular contractile responses to endogenous norepinephrine (NE; elicited by electrical field stimulation 10 Hz) was markedly depressed in alpha(1B)AR KO mice compared with WT (12.4+/-1.7% versus 21.5+/-1.2%; P<0.001). In contrast, responses to exogenous NE were similar in alpha(1B)AR KO and WT mice (22.4+/-7.3% versus 33.4+/-4.3%; NS). Collectively, these results demonstrate a critical role for the alpha(1B)AR in baroreceptor-mediated adrenergic signaling at the vascular neuroeffector junction. Moreover, alpha(1B)ARs modulate inotropic responses to baroreceptor activation. The critical role for alpha(1B)AR in neuroeffector regulation of vascular tone and myocardial contractility has profound clinical implications for designing therapies for orthostatic intolerance.

Effects of nonhypotensive endotoxemia in conscious rats: role of prostaglandins.

A nonhypotensive dose of endotoxin was administered to normal conscious rats to evaluate the vascular and humoral effects of endotoxemia per se. Mean blood pressure and heart rate remained stable during the 45 min infusion of Escherichia coli endotoxin (0.01 mg/min). However, a marked increase in plasma renin activity (4.2 +/- 0.48 vs. 30.2 +/- 6 ng.ml-1.h-1, mean +/- SE, P less than 0.01), plasma epinephrine (0.112 +/- 0.04 vs. 1.71 +/- 0.5 ng/ml, P less than 0.01), and plasma norepinephrine (0.269 +/- 0.028 vs. 1.3 +/- 0.2 ng/ml, P less than 0.001) was observed during infusion in endotoxin-treated rats when compared with the vehicle-treated animals. In addition, the blood pressure response to exogenous norepinephrine was significantly reduced during nonhypotensive endotoxemia. Significant changes in regional blood flow distribution, as assessed by radiolabeled microspheres, were observed in endotoxemic rats; in particular a decrease in renal blood flow (7.39 +/- 0.43 vs. 5.97 +/- 0.4 ml.min-1.g-1, P less than 0.05) and an increase in coronary blood flow (5.01 +/- 0.38 vs. 6.44 +/- 0.33 ml.min-1.g-1, P less than 0.01) were found. The role of prostaglandins in the vascular and humoral alterations induced by nonhypotensive endotoxemia was also examined. Pretreatment with indomethacin (5 mg) prevented the increase in plasma renin activity as well as plasma catecholamine levels. On the contrary, the decreased vascular reactivity and the reduction in renal blood flow observed during endotoxemia were not affected by prostaglandin synthesis inhibition. Thus significant vascular and humoral changes have been found during endotoxemia even in absence of hypotension.(ABSTRACT TRUNCATED AT 250 WORDS)

Farnesol-induced apoptosis in Candida albicans is mediated by Cdr1-p extrusion and depletion of intracellular glutathione.

Farnesol is a key derivative in the sterol biosynthesis pathway in eukaryotic cells previously identified as a quorum sensing molecule in the human fungal pathogen Candida albicans. Recently, we demonstrated that above threshold concentrations, farnesol is capable of triggering apoptosis in C. albicans. However, the exact mechanism of farnesol cytotoxicity is not fully elucidated. Lipophilic compounds such as farnesol are known to conjugate with glutathione, an antioxidant crucial for cellular detoxification against damaging compounds. Glutathione conjugates act as substrates for ATP-dependent ABC transporters and are extruded from the cell. To that end, this current study was undertaken to validate the hypothesis that farnesol conjugation with intracellular glutathione coupled with Cdr1p-mediated extrusion of glutathione conjugates, results in total glutathione depletion, oxidative stress and ultimately fungal cell death. The combined findings demonstrated a significant decrease in intracellular glutathione levels concomitant with up-regulation of CDR1 and decreased cell viability. However, addition of exogenous reduced glutathione maintained intracellular glutathione levels and enhanced viability. In contrast, farnesol toxicity was decreased in a mutant lacking CDR1, whereas it was increased in a CDR1-overexpressing strain. Further, gene expression studies demonstrated significant up-regulation of the SOD genes, primary enzymes responsible for defense against oxidative stress, with no changes in expression in CDR1. This is the first study describing the involvement of Cdr1p-mediated glutathione efflux as a mechanism preceding the farnesol-induced apoptotic process in C. albicans. Understanding of the mechanisms underlying farnesol-cytotoxicity in C. albicans may lead to the development of this redox-cycling agent as an alternative antifungal agent.

Pre- and postsynaptic effects of SKF64139, a phenylethanolamine N-methyltransferase inhibitor, in conscious normotensive rats

We investigated in conscious normotensive rats the effect of SKF64139 (2 mg i.v.), a potent phenylethanolamine N-methyltransferase (PNMT) inhibitor, on blood pressure responses to norepinephrine (40, 80, and 160 ng i.v.); methoxamine (2.5, 5 and 10 micrograms i.v.), a directly active sympathomimetic agent that is not taken up by adrenergic nerves; and tyramine (20, 40, and 80 micrograms i.v.), an indirectly acting sympathomimetic amine. The pressor effect of norepinephrine was not changed by 2 mg of SKF64139, while those of methoxamine and tyramine were significantly reduced. The dose-response curve to exogenous norepinephrine was also evaluated following blockade of norepinephrine uptake in the nerve endings using 0.25 mg desipramine i.v. This dose of desipramine had no effect on blood pressure increase induced by methoxamine. In rats pretreated with the neuronal uptake inhibitor desipramine in a dose that did not affect alpha-adrenoceptors, SKF64139 significantly decreased the pressor responses to norepinephrine. Increasing the dose of SKF64139 to 8 mg i.v. resulted in a significant fall in base-line blood pressure and in a blunted blood pressure response to norepinephrine. These data demonstrate that in vivo the PNMT inhibitor SKF64139 blocks alpha-adrenoceptors and inhibits neuronal uptake. The alpha-adrenoceptor blocking properties of SKF65139 are masked by simultaneous blockade of norepinephrine uptake when agonists with affinity for the uptake system are used. These findings need to be taken into account when interpreting cardiovascular effects of the PNMT inhibitor SKF64139.

Acute creatine ingestion in human: consequences on serum creatine and creatinine concentrations.

The aim of the study was to explore the effect of an acute dose of creatine (Cr) ingestion on serum Cr and serum creatinine (Crn) concentrations. Sixteen healthy subjects ingested a single dose of Cr (20 g) followed by the measurement of serum Cr and Crn concentration for 3 h up to a maximum of 6 h (n=6). In response to Cr ingestion a large rise in serum Cr concentration was observed (by 50 folds) occurring approximately 2 1/2h after the ingestion (peak value of 2.17 +/- 0.66 mmol x l(-1)). We also found a moderate but significant rise in serum Crn concentration averaging 13 % after 3 h (peak value at 99.5 +/- 10.5 micromol x l(-1)). A dose response curve obtained in two case studies, in whom different doses of Cr were ingested (0, 2.5, 5, 10, 15, 20 g and 0, 10, 20, 30 g), showed that serum Cr concentration as well as the peak time increased linearly with Cr ingestion. In addition, acute Crn ingestion (5 g) resulted in a substantial increase in serum Crn concentration (by 10 folds) but led to a minor rise in serum Cr concentration (by 2 folds). These results suggest that when acute doses of Cr are ingested in humans, the degree of conversion of exogenous Cr to Crn in the stomach and the gut can be considered as negligible following the first 6 h of ingestion. However, further studies are required to explore the prolonged effect of Cr on Crn metabolism.

BCL9 is an essential component of canonical Wnt signaling that mediates the differentiation of myogenic progenitors during muscle regeneration.

Muscle stem cells and their progeny play a fundamental role in the regeneration of adult skeletal muscle. We have previously shown that activation of the canonical Wnt/beta-catenin signaling pathway in adult myogenic progenitors is required for their transition from rapidly dividing transient amplifying cells to more differentiated progenitors. Whereas Wnt signaling in Drosophila is dependent on the presence of the co-regulator Legless, previous studies of the mammalian ortholog of Legless, BCL9 (and its homolog, BCL9-2), have not revealed an essential role of these proteins in Wnt signaling in specific tissues during development. Using Cre-lox technology to delete BCL9 and BCL9-2 in the myogenic lineage in vivo and RNAi technology to knockdown the protein levels in vitro, we show that BCL9 is required for activation of the Wnt/beta-catenin cascade in adult mammalian myogenic progenitors. We observed that the nuclear localization of beta-catenin and downstream TCF/LEF-mediated transcription, which are normally observed in myogenic progenitors upon addition of exogenous Wnt and during muscle regeneration, were abrogated when BCL9/9-2 levels were reduced. Furthermore, reductions of BCL9/9-2 inhibited the promotion of myogenic differentiation by Wnt and the normal regenerative response of skeletal muscle. These results suggest a critical role of BCL9/9-2 in the Wnt-mediated regulation of adult, as opposed to embryonic, myogenic progenitors.