The role of chronic muscle (in)activity on carnosine homeostasis: a study with spinal-cord injured athletes

To examine the role of chronic (in)activity on muscle carnosine (MCarn) and how chronic (in)activity affects MCarn responses to β-alanine supplementation in spinal-cord injured athletes, sixteen male athletes with paraplegia were randomized (2:1 ratio) to receive β-alanine (n=11) or placebo (PL, n=5). They consumed 6.4 g‧d-1 of β-alanine or PL for 28 days. Muscle biopsies of the active deltoid and the inactive vastus lateralis (VL) were taken before and after supplementation. MCarn in the VL was also compared with the VL of a group of individuals without paraplegia (n=15). MCarn was quantified in whole muscle and in pools of individual fibers by High-performance Liquid Chromatography. MCarn was higher in chronically inactive VL vs. well-trained deltoid (32.0±12.0 vs. 20.5±6.1 mmol‧kg-1 DM; p=0.018). MCarn was higher in inactive vs. active VL (32.0±12.0 vs. 21.2±7.5 mmol‧kg-1 DM; p=0.011). In type-I fibers, MCarn was significantly higher in the inactive VL than in the active deltoid (38.3±4.7 vs. 27.3±11.8 mmol‧kg-1 DM, p=0.014). MCarn increased similarly between inactive VL and active deltoid in the β-alanine group (VL: 68.9±55.1%, p=0.0002; deltoid: 90.5±51.4%, p<0.0001), with no changes in the PL group. MCarn content was higher in the inactive VL than in the active deltoid and the active VL, but this is probably a consequence of fiber type shift (type I to type II) that occurs with chronic inactivity. Chronically inactive muscle showed an increase in MCarn after BA supplementation equally to the active muscle, suggesting that carnosine accretion following β-alanine supplementation is not influenced by muscle inactivity

Oxydation de l’ADN par l’oxygène moléculaire singulet, protection par des polyamines et conséquences biologiques

Les lésions de l'ADN causées par 1O2 ainsi que leurs conséquences biologiques ont été étudiées. Pour cela une source chimique ayant la propriété de produire uniquement de l ’oxygène moléculaire singulet (1O2), durant la thermodissociation d'un endoperoxyde soluble dans l'eau, le 3,3'-(1,4- naphthylidène)dipropionate (NDPO2), sans intermédiaires réactifs ou produits secondaires, a été utilisée. L’analyse de la mobilité électrophorétique de l'ADN simple brin ou double brin sur gel d'agarose, a permis de mesurer des coupures franches simples et doubles brin lors du traitement de l'ADN avec 1O2 généré par NDPO2. La prévention de ces lésions de l'ADN (coupures franches simples) par des biomolécules a été recherchée. Les polyamines, spermine et spermidine, se sont montrées efficaces. Les conséquences létales et mutagènes de ces lésions ont été démontrées après introduction des plasmides dans des bactéries ou cellules de mammifères. Une importante augmentation de la fréquence de mutation en fonction de la concentration du NDPO2 a été observée dans les plasmides de simple et double brin après introduction dans des cellules COS7 de singe. Ceci suggère l’existence d’un processus de réparation d’ADN endommagé par 1O2 qui produit des erreurs dans les cellules de mammifères. Le spectre de mutation révèle que 98% des mutations impliquent les paires de base G:C. La haute capacité mutagène est attribuée au grand nombre de lésions des guanines de l'ADN. Cela suggère que les résidus de guanine sont la cible de 1O2 et que ces lésions causent directement les mutations

Structural characterization of diastereoisomeric ethano adducts derived from the reaction of 2'-deoxyguanosine with trans,trans-2,4-decadienal

Background levels of exocyclic DNA adducts have been detected in rodent and human tissues. Several studies have focused on bifunctional electrophiles generated from lipid peroxidation as one of the endogenous sources of these lesions. We have previously shown that the reaction of 2'-deoxyguanosine (dGuo) with trans,trans-2,4-decadienal (DDE), a highly cytotoxic aldehyde generated as a product of lipid peroxidation in cell membranes, results in the formation of a number of different base derivatives. Three of these derivatives have been fully characterized as 1,N-2-etheno-2'-deoxyguanosine adducts. In the present work, four additional adducts, designated A3-A6, were isolated from in vitro reactions by reversed-phase HPLC and fully characterized on the basis of spectroscopic measurements. Adducts A3-A6 are four diastereoisomeric 1,N-2-hydroxyethano-2'-deoxyguanosine derivatives possessing a carbon side chain with a double bond and a hydroxyl group. The systematic name of these adducts is 6-hydroxy3-(2'-deoxy-beta-D-erythro-pentafuranosyl)-7-((E)-1-hydroxy-oct-2-enyl)-3,5,6,7-tetrahydro-imidazo- [1,2-a]purin-9-one. The proposed reaction mechanism yielding adducts A3-A6 involves DDE epoxidation at C2, followed by nucleophilic addition of the exocyclic amino group of dGuo to the C1 of the aldehyde and cyclization, via nucleophilic attack, on the C2 epoxy group by N-1. The formation of adducts A1-A6 has been investigated in acidic, neutral, and basic pH in the presence of H2O2 or tent-butyl hydroperoxide. Neutral conditions, in the presence of H2O2, have favored the formation of adducts A1 and A2, with minor amounts of A3-A6, which were prevalent under basic conditions. These data indicate that DDE can modify DNA bases through different oxidative pathways involving its two double bonds. It is important to structurally characterize DNA base derivatives induced by alpha,beta-unsaturated aldehydes so that the genotoxic risks associated with the lipid peroxidation process can be assessed

Quenching of singlet molecular oxygen by natural furan diterpenes

Singlet molecular oxygen O-2((1) Delta(g)) is a reactive oxygen species capable of damaging biological molecules and triggering oxidative stress, The quenching of this species by naturally occurring furans was measured using O-2((1) Delta(g)) from two different sources: (1) the thermal decomposition of 1,4-dimethylnaphthalene endoperoxide (1,4-DMNO2); (2) tetraphenylporphyrin sulphonate photosensitization. Four furan diterpenes were isolated from alcoholic extracts of Sucupira branca (Pterodon sp,, Leguminosae) seeds, which are used for the treatment of rheumatic diseases, suggesting anti-inflammatory activity. Using time-resolved near-IR (NIR) emission after photosensitization, the overall (physical + chemical) O-2((1) Delta(g)) quenching rate constants by these compounds were found to be of the order of 10(8) M-1 s(-1), with the exception of the conjugated furan diterpenes 3,5,6-trimethoxy-7,8-furano-3',4'-methylenedioxy-2 '',3 ''-flavane and 3,4,5,6-tetramethoxy-7,8-furano-2 '',3 ''-flavane for which 20-fold lower values were observed, These lower values are attributed to the conjugation of the furan moiety with the aromatic ring, which prevents (2 + 4) cycloaddition of O-2((1) Delta(g)) to the furan ring, Although the non-conjugated furans exhibit a low scavenging effect on lipid peroxidation in microsomes, their high O-2((1) Delta(g)) quenching constant may minimize the extent of tissue damage associated with the inflammatory process. (C) 1997 Elsevier Science S.A.384170016917

Increased SOD1 association with chromatin, DNA damage, p53 activation, and apoptosis in a cellular model of SOD1-linked ALS

Mutations in the gene encoding cytosolic Cu,Zn-superoxide dismutase (SOD1) have been linked to familial amyotrophic lateral sclerosis (FALS). However the molecular mechanisms of motor neuron death are multi-factorial and remain unclear. Here we examined DNA damage, p53 activity and apoptosis in SH-SY5Y human neuroblastoma cells transfected to achieve low-level expression of either wild-type or mutant Gly(93)-->Ala (G93A) SOD1, typical of FALS. DNA damage was investigated by evaluating the levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) and DNA strand breaks. Significantly higher levels of DNA damage, increased p53 activity, and a greater percentage of apoptotic cells were observed in SH-SY5Y cells transfected with G93A SOD1 when compared to cells overexpressing wild-type SOD1 and untransfected cells. Western blot, FACS, and confocal microscopy analysis demonstrated that G93A SOD1 is present in the nucleus in association with DNA. Nuclear G93A SOD1 has identical superoxide dismutase activity but displays increased peroxidase activity when compared to wild-type SOD1. These results indicate that the G93A mutant SOD1 association with DNA might induce DNA damage and trigger the apoptotic response by activating p53. This toxic activity of mutant SOD1 in the nucleus may play an important role in the complex mechanisms associated with motor neuron death observed in ALS pathogenesis

Kinetics of muscle carnosine decay after β-alanine supplementation: a 16-week washout study

Purpose: To describe the kinetics of carnosine washout in human skeletal muscle over 16 weeks. Methods: Carnosine washout kinetics were studied in fifteen young, physically-active omnivorous men randomly assigned to take 6.4 g·d-1 of β-alanine (n=11) or placebo (PL, n=4) for 8 weeks. Muscle carnosine content (M-Carn) was determined before (PRE), immediately after (POST) and 4, 8, 12 and 16 weeks after supplementation. High-intensity exercise tests were performed at these same time points. Linear and exponential models were fitted to the washout data and the leave-one-out method was used to select the model with the best fit for M-Carn decay data. Repeated measures correlation analysis was used to assess the association between changes in M-Carn and changes in performance. Results: M-Carn increased from PRE to POST in the β-alanine group only (+91.1±29.1%; PL:+0.04±10.1%; p<0.0001). M-Carn started to decrease after cessation of β-alanine supplementation and continued to decrease until week 16 (POST4:+59±40%; POST8:+35±39%; POST12:+18±32%; POST16:-3±24% of PRE M-Carn). From week 12 onwards, M-Carn was no longer statistically different from PRE. Both linear and exponential models displayed very similar fit and could be used to describe carnosine washout, although the linear model presented a slightly better fit. The decay in M-Carn was mirrored by a similar decay in high-intensity exercise tolerance; M-Carn was moderately and significantly correlated with TWD (r=0.505; p=0.032) and TTE (r=0.72; p<0.001). Conclusion: Carnosine washout takes 12-16 weeks to complete, and it can be described either by linear or exponential curves. Changes in M-Carn appear to be mirrored by changes in high-intensity exercise tolerance. This information can be used to optimise β-alanine supplementation strategies