Changes in erythrocyte membrane phospholipid composition induced by physical training and physical exercise

Insight into the Molecular Mechanism of Surface Interactions of Phosphatidylcholines─Langmuir Monolayer Study Complemented with Molecular Dynamics Simulations

Mutual interactions between components of biological membranes are pivotal for maintaining their proper biophysical properties, such as stability, fluidity, or permeability. The main building blocks of biomembranes are lipids, among which the most important are phospholipids (mainly phosphatidylcholines (PCs)) and sterols (mainly cholesterol). Although there is a plethora of reports on interactions between PCs, as well as between PCs and cholesterol, their molecular mechanism has not yet been fully explained. Therefore, to resolve this issue, we carried out systematic investigations based on the classical Langmuir monolayer technique complemented with molecular dynamics simulations. The studies involved systems containing 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) analogues possessing in the structure one or two polar functional groups similar to those of DPPC. The interactions and rheological properties of binary mixtures of DPPC analogues with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and cholesterol were compared with reference systems (DPPC/POPC and DPPC/cholesterol). This pointed to the importance of the ternary amine group in PC/cholesterol interactions, while in PC mixtures, the phosphate group played a key role. In both cases, the esterified glycerol group had an effect on the magnitude of interactions. The obtained results are crucial for establishing structure-property relationships as well as for designing substitutes for natural lipids.

Effect of Different Exercise Training Modalities on Fasting Levels of Oxylipins and Endocannabinoids in Middle-Aged Sedentary Adults: A Randomized Controlled Trial

This study aimed to investigate the effects of different exercise training programs on fasting plasma levels of oxylipins, endocannabinoids (eCBs), and eCBs-like molecules in middle-aged sedentary adults. A 12-week randomized controlled trial was conducted using a parallel group design. Sixty-five middle-aged adults (40-65 years old) were randomly assigned to: (a) no exercise (control group), (b) concurrent training based on international physical activity recommendations (PAR group), (c) high-intensity interval training (HIIT group), and (d) HIIT together with whole-body electromyostimulation (HIIT + EMS group). Plasma levels of oxylipins, eCBs, and eCBs-like molecules were determined in plasma samples before and after the intervention using targeted lipidomics. Body composition was assessed through dual-energy X-ray absorptiometry, and dietary intake through a food frequency questionnaire and three nonconsecutive 24-hr recalls. The physical activity recommendations, HIIT, and HIIT-EMS groups showed decreased plasma levels of omega-6 and omega-3-derived oxylipins, and eCBs and eCBs-like molecules after 12 weeks (all Δ ≤ -0.12; all p < .05). Importantly, after Bonferroni post hoc corrections, the differences in plasma levels of omega-6 and omega-3 oxylipins were not statistically significant compared with the control group (all p > .05). However, after post hoc corrections, plasma levels of anandamide and oleoylethanolamide were increased in the physical activity recommendations group compared with the control group (anandamide: Δ = 0.05 vs. -0.09; oleoylethanolamide: Δ = -0.12 vs. 0.013, all p ≤ .049). In conclusion, this study reports that a 12-week exercise training intervention, independent of the modality applied, does not modify fasting plasma levels of omega-6 and omega-3 oxylipins, eCBs, and eCBs-like molecules in middle-aged sedentary adults.

ISSFAL Official Statement Number 6: The importance of measuring blood omega-3 long chain polyunsaturated fatty acid levels in research

A statement on measuring blood omega-3 long chain polyunsaturated fatty acid levels was developed and edited based on input from ISSFAL members and accepted by vote of the ISSFAL Board of Directors. Summary of Statement: Omega-3 long chain polyunsaturated fatty acid (n-3 LCPUFA) levels at baseline and post-intervention should be assessed and reported in future research to evaluate the efficacy of n-3 LCPUFA supplementation: b ecause; 1. there are numerous factors that affect n-3 LCPUFA levels in humans as described in the systematic literature review [1]; 2. assessing intake of n-3 LCPUFA from the diet and/or supplements is not sufficient to accurately determine n-3 LCPUFA levels in humans; 3. some studies do not provide sufficient doses of n-3 LCPUFA to produce a significant impact on bloodstream/organ content and there is substantial variability in the uptake of n-3 LPCUFA into tissues between individuals. In secondary analyses, clinical trials should consider the influence of fatty acid status (baseline, endpoint and change from baseline to endpoint) on the outcome variables.

Impact of ApoE Polymorphism and Physical Activity on Plasma Antioxidant Capability and Erythrocyte Membranes

The allele epsilon 4 (ε4) of apolipoprotein E (ApoE) is the strongest genetic risk factor for Alzheimer's disease (AD). ApoE protein plays a pivotal role in the synthesis and metabolism of amyloid beta (Aβ), the major component of the extracellular plaques that constitute AD pathological hallmarks. Regular exercise is an important preventive/therapeutic tool in aging and AD. Nevertheless, the impact of physical exercise on the well-being of erythrocytes, a good model of oxidative stress and neurodegenerative processes, remains to be investigated, particularly depending on ApoE polymorphism. Herein, we evaluate the oxidative status, Aβ levels, and the membrane's composition of erythrocytes in a cohort of human subjects. In our hands, the plasma antioxidant capability (AOC), erythrocytes membrane fluidity, and the amount of phosphatidylcholine (PC) were demonstrated to be significantly decreased in the ApoE ε4 genotype and non-active subjects. In contrast, erythrocyte Aβ content and lipid peroxidation increased in ε4 carriers. Regular physical exercise was associated with an increased plasma AOC and membrane fluidity, as well as to a reduced amount of erythrocytes Aβ. Altogether, these data highlight the influence of the ApoE genotype on erythrocytes' well-being and confirm the positive impact of regular physical exercise.

Non-dietary factors associated with n-3 long-chain PUFA levels in humans - a systematic literature review

Numerous health benefits are attributed to the n-3 long-chain PUFA (n-3 LCPUFA); EPA and DHA. A systematic literature review was conducted to investigate factors, other than diet, that are associated with the n-3 LCPUFA levels. The inclusion criteria were papers written in English, carried out in adult non-pregnant humans, n-3 LCPUFA measured in blood or tissue, data from cross-sectional studies, or baseline data from intervention studies. The search revealed 5076 unique articles of which seventy were included in the qualitative synthesis. Three main groups of factors potentially associated with n-3 LCPUFA levels were identified: (1) unmodifiable factors (sex, genetics, age), (2) modifiable factors (body size, physical activity, alcohol, smoking) and (3) bioavailability factors (chemically bound form of supplements, krill oil v. fish oil, and conversion of plant-derived α-linolenic acid (ALA) to n-3 LCPUFA). Results showed that factors positively associated with n-3 LCPUFA levels were age, female sex (women younger than 50 years), wine consumption and the TAG form. Factors negatively associated with n-3 LCPUFA levels were genetics, BMI (if erythrocyte EPA and DHA levels are &lt;5·6 %) and smoking. The evidence for girth, physical activity and krill oil v. fish oil associated with n-3 LCPUFA levels is inconclusive. There is also evidence that higher ALA consumption leads to increased levels of EPA but not DHA. In conclusion, sex, age, BMI, alcohol consumption, smoking and the form of n-3 LCPUFA are all factors that need to be taken into account in n-3 LCPUFA research.

Oxidative stress, lipid peroxidation indexes and antioxidant vitamins in long and middle distance athletes during a sport season

BACKGROUND

The main objective of this study was to observe any changes and possible adaptations produced in MDA and antioxidants vitamins on plasma and erythrocytes in endurance male athletes among an athletic season (12 months).

METHODS

Twenty three long and middle distance male athletes participated in this study. Basal MDA on plasma and antioxidant vitamins in plasma and erythrocytes were measured at four moments along the season (0, 3, 6 and 9 months). Fatty acid concentrations in erythrocytes were obtained to determine lipid peroxidation indexes.

RESULTS

In plasma, vitamin C suffered significant decreases at 3 and 6 months compared with the begin (P<0.01), and an increase at 9 months, compared with 3 months. On the other hand, vitamin A level was significantly lower at 9 months compared with the other periods (P<0.01 compared with 0 and 6 months; P<0.05 compared with 3 months). In erythrocytes, significant decreases were observed in vitamin E among the season at 6 months and an increase from 6 to 9 months (P<0.05). Vitamin A suffers a significant decrease in both for competitive periods, at 3 and 9 months, compared with the beginning of the season. The most of changes in lipid peroxidation indexes were produced along the firsts 3 months.

CONCLUSIONS

1) Physical training improves the antioxidant systems in order to reduce lipid peroxidation in trained athletes along the season; 2) PUFA/SFA ratios seem more reliable than MDA to observe oxidative stress.

Cell-derived microparticles after exercise in individuals with G6PD Viangchan

Glucose-6-phospate dehydrogenase (G6PD) deficient cells are sensitive to oxidative damage leading to the formation of microparticles (MPs). Therefore, we examined the concentration of MPs and changes in the antioxidant balance after an acute strenuous exercise (SEx) and moderate-intensity exercise (MEx). Eighteen healthy females (18-24 years) with G6PD normal and eighteen age-matched females with G6PD Viangchan (871G>A) were tested by running on a treadmill at their maximal oxygen uptake for SEx and at 75% of their maximal heart rate for MEx. It was found that SEx triggered the release of total microparticles (TTMPs) above baseline levels and remained significantly higher 45 minutes after the exercise in G6PD normal individuals. However, SEx-induced increase in TTMPs was significantly higher in G6PD Viangchan as compared to G6PD normal. In contrast, MEx did not to alter the release of TTMPs in both G6PD normal and Viangchan. Moreover, TTMPs concentrations were inversely correlated with G6PD activity (r =-0.82, P <  0.05) but positively correlated with MDA concentrations (r = 0.74, P <  0.05). Using cell specific antibodies, we determined that MPs were mainly derived from platelets and erythrocytes. Altogether, the present study indicates that G6PD Viangchan may participate in MEx without higher MPs concentration and oxidative stress compared with G6PD normal.

Effects of a TASER® conducted energy weapon on the circulating red-blood-cell population and other factors in Sus scrofa

In previous studies hematocrit has been consistently increased in an anesthetized animal model after exposures to TASER(®) conducted energy weapons (CEWs). In the present study we analyzed changes in blood cell counts and red blood cell membrane proteins following two 30-s applications of a TASER C2 device (which is designed for civilian use). Hematocrit increased significantly from 33.2 ± 2.4 (mean ± SD) to 42.8 ± 4.6 % immediately after CEW exposure of eleven pigs (Sus scrofa). Red blood cell count increased significantly from 6.10 ± 0.55 × 10(12)/L to 7.45 ± 0.94 × 10(12)/L, and mean corpuscular volume increased significantly from 54.5 ± 2.4 fl to 57.8 ± 2.6 fl. Mean corpuscular hemoglobin concentration decreased significantly from 20.5 ± 0.7 to 18.5 ± 0.6 mM. Thirty protein spots (from two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis, selected for detailed comparison) exhibited greater densities 30-min post-exposure compared with pre-exposure values. A greater number of echinocytes were observed following CEW exposure. On the basis of these results it appears that, during the strong muscle contractions produced by TASER CEWs, a specific population of red blood cells (RBCs) may be released from the spleen or other reservoirs within the body. The total time of CEW exposure in the present study was relatively long compared with exposures in common law-enforcement scenarios. Despite statistically significant changes in red blood cell counts (and other measures directly related to RBCs), the alterations were short-lived. The transient nature of the changes would be likely to counteract any potentially detrimental effects.

Phospholipid composition of plasma and erythrocyte membranes in animal species by 31P NMR

The aim of this study was to provide basal values of phospholipid (PL) composition in different animal species by 31P NMR analysis using detergents. This fast and accurate method allowed a quantitative analysis of PLs without any previous separation. Plasma and erythrocyte membrane PLs were investigated in mammals (pig, cow, horse). Moreover, for the first time, the composition of plasma PLs in avian (chicken and ostrich) was performed by 31P NMR. Significant qualitative and quantitative interspecies differences in plasma PL levels were found. Phosphatidilcholine (PC) and sphingomyelin (SPH) levels were significantly higher (P < 0.001) in chicken plasma than all the other species tested. In erythrocytes, cow PC and phosphatidylcholine diarachidoyl were significantly lower (P < 0.001) than for pigs and horses, whereas pig PC presented intermediate values among cows and horses. Inorganic phosphate and 2,3-diphosphoglycerate levels were also significantly different between the species under investigation. The [SPH/total PLs] molar ratios in erythrocytes confirmed interspecies differences in phospholipid composition while the PC/SPH molar ratios could be related to a distinct erythrocyte flexibility and aggregability. Diet and nutrition may contribute primarily to the interspecies differences in plasma PL amounts detected. Significant differences between chicken plasma PC and SPH levels and those of the other animal species could be ascribed to a fat metabolism specific to egg production.

Docosahexaenoic acid in red blood cells of women of reproductive age is positively associated with oral contraceptive use and physical activity

Optimal intake of the long-chain n-3 polyunsaturated fatty acid (PUFA) docosahexaenoic acid (DHA) and proper balance between intake of n-6 PUFA and n-3 PUFA are important for human health. Considerable evidence exists to show that DHA has a marked benefit during pregnancy. Lifestyle factors can affect the biosynthesis of DHA from dietary precursors, incorporation into membranes and degradation. The purpose of this study was to investigate the PUFA composition of red blood cells (RBCs) from women (n=40) in reproductive age, and how it is affected by diet and other lifestyle factors. Of all the lifestyle factors tested oral contraceptive use and physical activity were the ones correlated with DHA in RBCs, after adjustment for DHA intake. The findings indicate that oral contraceptive use and physical activity have a positive impact on the DHA status, as assessed by RBC level, of women in reproductive age.

Effects of phosphatidylserine supplementation on exercising humans

Phosphatidylserine (PtdSer) is a ubiquitous phospholipid species that is normally located within the inner leaflet of the cell membrane. PtdSer has been implicated in a myriad of membrane-related functions. As a cofactor for a variety of enzymes, PtdSer is thought to be important in cell excitability and communication. PtdSer has also been shown to regulate a variety of neuroendocrine responses that include the release of acetylcholine, dopamine and noradrenaline. Additionally, PtdSer has been extensively demonstrated to influence tissue responses to inflammation. Finally, PtdSer has the potential to act as an effective antioxidant, especially in response to iron-mediated oxidation. The majority of the available research that has investigated the effects of PtdSer supplementation on humans has concentrated on memory and cognitive function; patients experiencing some degree of cognitive decline have traditionally been the main focus of investigation. Although investigators have administered PtdSer through intravenous and oral routes, oral supplementation has wider appeal. Indeed, PtdSer is commercially available as an oral supplement intended to improve cognitive function, with recommended doses usually ranging from 100 to 500 mg/day. The main sources that have been used to derive PtdSer for supplements are bovine-cortex (BC-PtdSer) and soy (S-PtdSer); however, due to the possibility of transferring infection through the consumption of prion contaminated brain, S-PtdSer is the preferred supplement for use in humans. Although the pharmacokinetics of PtdSer have not been fully elucidated, it is likely that oral supplementation leads to small but quantifiable increases in the PtdSer content within the cell membrane.A small number of peer-reviewed full articles exist that investigate the effects of PtdSer supplementation in the exercising human. Early research indicated that oral supplementation with BC-PtdSer 800 mg/day moderated exercise-induced changes to the hypothalamo-pituitary-adrenal axis in untrained participants. Subsequently, this finding was extended to suggest that S-PtdSer 800 mg/day reduced the cortisol response to overtraining during weight training while improving feeling of well-being and decreasing perceived muscle soreness. However, equivocal findings from our laboratory might suggest that the dose required to undertake this neuroendocrine action may vary between participants.Interestingly, recent findings demonstrating that short-term supplementation with S-PtdSer 750 mg/day improved exercise capacity during high-intensity cycling and tended to increase performance during intermittent running might suggest an innovative application for this supplement. With the findings from the existing body of literature in mind, this article focuses on the potential effects of PtdSer supplementation in humans during and following exercise.

Erythrocyte Adaptation to Oxidative Stress in Endurance Training

BACKGROUND

We tested the hypothesis that endurance training may reduce exercise oxidative stress damage on erythrocytes.

METHODS

Fifteen subjects performed a standardized endurance exercise at 75% of maximal oxygen consumption weekly during a 19-week training period. Blood samples taken before and after exercise were analyzed by Fourier transform-infrared (FT-IR) spectrometry to determine exercise-induced change in plasma concentrations and erythrocyte IR absorptions.

RESULTS

Training first induced a stabilization of plasma concentration changes during exercise (unchanged for glucose, increased for lactate, triglycerides, glycerol, and fatty acids), whereas erythrocyte phospholipid alterations remained elevated (p <0.05). Further, training reduced the exercise-induced erythrocyte lactate content increase (nuC-O; p <0.05) and phospholipid alterations (nuC-H(n) and nuP=O; p <0.05) during exercise. These changes paralleled the decrease of exercise-induced hemoconcentration (p <0.05) and plasma lactate increase (p <0.05).

CONCLUSIONS

These correlated changes between plasma and erythrocyte parameters suggest that endurance training reduces erythrocyte susceptibility to oxidative stress.

Haemolysis caused by alterations of α- and β-spectrin after 10 to 35 min of severe exercise

The pathophysiology of exercise related haemolysis is not thoroughly understood. We investigated whether exercise related haemolysis (1) is associated with alterations of red blood cell (RBC) membrane proteins similar to those found in inherited anaemic diseases, (2) can be induced with a non-running exercise mode, (3) is related to exercise intensity, and (4) coincides with indicators of oxidative stress. In ten triathletes [median (P25/P75-percentiles) age: 28.0 (26.3/28.5) years, height: 1.84 (1.78/1.87) m, body mass: 78.5 (74.8/80.8) kg, maximal oxygen uptake: 60.0 (57.3/64.8) ml kg(-1) min(-1)], haptoglobin, alpha- and beta-spectrin bands, malondialdehyde (MDA) and H2O2-induced chemiluminescence (H2O2-Chem) were determined immediately pre- and post-both, a 35 min low intensity and a high intensity cycling exercise [240 (218/253) vs 290 (270/300) W, P<0.05) requiring similar amounts of metabolic energy [28.3 (25.9/29.9) vs 24.9 (18.4/30.5) kJ kg(-1), P>0.05]. At high exercise intensity haptoglobin [1.10 (0.81/2.53) vs 1.01 (0.75/2.00) g l(-1)] decreased (P<0.05) whilst MDA [2.80 (2.65/3.20) vs 3.13 (2.78/3.31) nmol ml(-1)] and H2O2-Chem [29.70 (22.55/37.10) vs 37.25 (35.20/52.63) rel. U min] increased (P<0.05), coinciding with the disappearance of the spectrin bands in six out of ten gels. No corresponding changes were found at low intensity exercise. Ten to 35 min of non-running exercise in a regularly used intensity domain causes intra-vascular haemolysis associated with alterations in the RBC membrane proteins similar to those found after in vitro oxidative stress and in inherited anaemic diseases like Sphaerocytosis and Fanconi's anaemia.

Exercise-induced oxidative stress leads hemolysis in sedentary but not trained humans

Intravascular hemolysis is one of the most emphasized mechanisms for destruction of erythrocytes during and after physical activity. Exercise-induced oxidative stress has been proposed among the different factors for explaining exercise-induced hemolysis. The validity of oxidative stress following exhaustive cycling exercise on erythrocyte damage was investigated in sedentary and trained subjects before and after antioxidant vitamin treatment (A, C, and E) for 2 mo. Exercise induced a significant increase in thiobarbituric acid-reactive substance and protein carbonyl content levels in sedentary subjects and resulted in an increase of osmotic fragility and decrease in deformability of erythrocytes, accompanied by signs for intravascular hemolysis (increase in plasma hemoglobin concentration and decrease in haptoglobulin levels). Administration of antioxidant vitamins for 2 mo prevented exercise-induced oxidative stress (thiobarbituric acid-reactive substance, protein carbonyl content) and deleterious effects of exhaustive exercise on erythrocytes in sedentary subjects. Trained subjects' erythrocyte responses to exercise were different from those of sedentary subjects before antioxidant vitamin treatment. Osmotic fragility and deformability of erythrocytes, plasma hemoglobin concentration, and haptoglobulin levels were not changed after exercise, although the increased oxidative stress was observed in trained subjects. After antioxidant vitamin treatment, functional and structural parameters of erythrocytes were not altered in the trained group, but exercise-induced oxidative stress was prevented. Increased percentage of young erythrocyte populations was determined in trained subjects by density separation of erythrocytes. These findings suggest that the exercise-induced oxidative stress may contribute to exercise-induced hemolysis in sedentary humans.

Effects of exercise on the fatty-acid composition of blood and tissue lipids

This article reviews the effects of acute and chronic exercise on the fatty-acid composition of animal and human tissues (plasma, skeletal muscle, heart, adipose tissue, liver, artery and erythrocytes), as reported in 68 studies spanning four decades. The most consistently observed effect has been an increase in the relative amount of unsaturated, especially monounsaturated, non-esterified fatty acids in plasma of both animals and humans after acute exercise. Chronic exercise seems to increase the proportion of polyunsaturated fatty acids and omega6 fatty acids, while decreasing the proportion of monounsaturated fatty acids in animal and human adipose tissue. Additionally, chronic exercise seems to decrease the relative amount of unsaturated fatty acids in liver lipids of animals and humans. There is no consensus regarding the effect of exercise on the fatty-acid composition of lipids in any other tissue. In general, the effects of exercise are independent of nutrition and, regarding skeletal muscle, muscle fibre type. The available literature shows that, in addition to modifying the concentrations of animal and human tissue lipids, exercise also changes their fatty-acid profile. Unfortunately, the available studies are so much divided among exercise models, species and biological samples that a cohesive picture of the plasticity of the fatty-acid pattern of most tissues toward exercise has not emerged. Future studies should focus on determining the fatty-acid profile of separate lipid classes (rather than total lipids) in separate subcellular fractions (rather than whole tissues), examining tissues and organs on which no data are available and exploring the mechanisms of the exercise-induced changes in fatty-acid composition.

Effects of mild aerobic physical exercise on membrane fluidity of erythrocytes in essential hypertension

1. The present study was undertaken to investigate the effects of aerobic physical exercise on membrane function in mild essential hypertension. 2. Hypertensive patients were divided into an exercise group (n = 8) and a non-exercise (control) group (n = 8). Physical exercise within the intensity of the anaerobic threshold level was performed twice a week for 6 months. Membrane fluidity of erythrocytes was examined by means of electron paramagnetic resonance (EPR) and spin-labelling methods before and after the trial period in both groups. 3. After physical exercise, blood pressure decreased significantly. 4. Compared with the non-exercise group, in the exercise group both the order parameter (S) and the peak height ratio (ho/h-1) in the EPR spectra of erythrocytes were significantly reduced (S, 0.717 +/- 0.004 vs 0.691 +/- 0.008, respectively (n = 8), P < 0.05; ho/h-1, 5.38 +/- 0.06 vs 4.89 +/- 0.06, respectively (n = 8), P < 0.05). These findings indicated that exercise increased membrane fluidity and improved the membrane microviscosity of erythrocytes. 5. There was no direct correlation between blood pressure reduction and the exercise-induced increase in membrane fluidity of erythrocytes. 6. In the non-exercise (control) group, blood pressure and membrane fluidity were not changed after a 6 month follow-up period. 7. The results show that aerobic physical exercise increased erythrocyte membrane fluidity and improved the rigidity of cell membranes in hypertensive patients. The improvement of rheological properties of erythrocytes may explain, in part, the cellular mechanisms for the beneficial effects of physical exercise in hypertension.

Exercise-induced oxidative stress affects erythrocytes in sedentary rats but not exercise-trained rats

Oxidant stress is one of the factors proposed to be responsible for damaged erythrocytes observed during and after exercise. The impact of exertional oxidant stress after acute exhaustive treadmill running on erythrocyte damage was investigated in sedentary (Sed) and exercise-trained (ET) rats treated with or without antioxidant vitamins C and E. Exhaustive exercise led to statistically significant increments in the levels of thiobarbituric acid-reactive substance (TBARS) and H2O2-induced TBARS in Sed rats and resulted in functional and structural alterations in erythrocytes (plasma hemoglobin concentrations, methemoglobin levels, and rise in osmotic fragility of erythrocytes with decrease in erythrocyte deformability). Administration of antioxidant vitamin for 1 mo before exhaustive exercises prevented lipid peroxidation (TBARS, H2O2-induced TBARS) in Sed rats without any functional or structural alterations in erythrocytes. Parameters indicating erythrocyte lipid peroxidation and deterioration after exhaustive exercise in rats trained regularly with treadmill running for 1 mo were not different from those in Sed controls. Erythrocyte lipid peroxidation (TBARS) increased in exhausted-ET rats compared with ET controls; however, the plasma hemoglobin, methemoglobin levels, and erythrocyte osmotic fragility and deformability did not differ. Exhaustive exercise-induced lipid peroxidation in ET rats on antioxidant vitamin treatment was prevented, whereas functional and structural parameters of erythrocytes were not different from those of the ET controls. We conclude that exertional oxidant stress contributed to erythrocyte deterioration due to exercise in Sed but not in ET rats.

Effects of growth hormone treatment on red cell plasma membrane fatty acid constituents in hypopituitary adults

The effects of replacement with recombinant human GH (hGH) on red cell plasma membrane fatty acid and cholesterol constituents were assessed in nine adult patients with growth hormone deficiency. They were treated with hGH in a dose of 0.125 U.kg-1.wk-1 for four weeks and at 0.25 U.kg-1.wk-1 thereafter for an overall mean duration 13.5 +/- 3.9 months (mean +/- SD). The relative proportions of the various phospholipid fatty acid constituents and the proportion of cholesterol in the phospholipid bilayer were assayed every six months. At the end of the study, the percentage of arachadonic acid (20:4) in membrane phospholipid was found to rise by an average of 3.7% (P < 0.05) and there appeared to be a nonsignificant trend showing an increase in highly unsaturated fatty acids, namely linoleate (18:2) and gamma linolenic acid (18:3) and a corresponding decrease in unsaturated fatty acids, namely palmitate (16:0) and stearate (18:0) and monounsaturated fatty acids such as palmitoleic acid (16:1), oleic acid (18:1) and oleic acid isomer (18:1 iso). In addition, the proportion of cholesterol in the plasma membrane i.e. the cholesterol/phospholipid ratio was found to decrease by 0.84% (P < 0.05). There was a significant increase in HbAlc from 4.85 +/- 0.51 to 4.94 +/- 0.45% (P < 0.01) by the end of the study.

Exercise performance, red blood cell deformability, and lipid peroxidation: effects of fish oil and vitamin E

Previous studies have indicated that fish oil supplementation increases red blood cell (RBC) deformability, which may improve exercise performance. Exercise alone, or in combination with an increase in fatty acid unsaturation, however, may enhance lipid peroxidation. Effects of a bicycle time trial of approximately 1 h on RBC characteristics and lipid peroxidation were, therefore, studied in 24 trained cyclists. After 3 wk of fish oil supplementation (6 g/day), without or with vitamin E (300 IU/day), trial performance, RBC characteristics, and lipid peroxidation were measured again. RBC deformability appeared to decrease during endurance exercise. After correction for hemoconcentration, plasma total tocopherol concentrations decreased by 0.77 micromol/l (P = 0. 012) or 2.9% and carotenoid concentrations by 0.08 micromol/l (P = 0. 0008) or 4.5%. Endurance exercise did not affect the lag time and rate of in vitro oxidation of low-density lipoproteins (LDLs), but the maximum amount of conjugated dienes formed decreased by 2.1 +/- 1.0 micromol/mmol LDL cholesterol (P = 0.042) or 1.2%. Fish oil supplementation with and without vitamin E did not affect RBC characteristics or exercise performance. Both supplements decreased the rate of LDL oxidation, and fish oil supplementation with vitamin E delayed oxidation. The amount of dienes, however, was not affected. The supplements also did not change effects of exercise. We conclude that the changes observed during endurance exercise may indicate increased oxidative stress, but further research is necessary to confirm this. Fish oil supplementation does not improve endurance performance, but it also does not cause or augment changes in antioxidant levels or LDL oxidation during exercise.

Exercise, training and red blood cell turnover

Endurance training can lead to what has been termed 'sports anaemia'. Although under normal conditions, red blood cells (RBCs) have a lifespan of about 120 days, the rate of aging may increase during intensive training. However, RBC deficiency is rare in athletes, and sports anaemia is probably due to an expanded plasma volume. Cycling, running and swimming have been shown to cause RBC damage. While most investigators measure indices of haemolysis (for example, plasma haemoglobin or haptoglobin), RBC removal is normally an extravascular process that does not involve haemolysis. Attention is now turning to cellular indices (such as antioxidant depletion, or protein or lipid damage) that may be more indicative of exercise-induced damage. RBCs are vulnerable to oxidative damage because of their continuous exposure to oxygen and their high concentrations of polyunsaturated fatty acids and haem iron. As oxidative stress may be proportional to oxygen uptake, it is not surprising that antioxidants in muscle, liver and RBCs can be depleted during exercise. Oxidative damage to RBCs can also perturb ionic homeostasis and facilitate cellular dehydration. These changes impair RBC deformability which can, in turn, impede the passage of RBCs through the microcirculation. This may lead to hypoxia in working muscle during single episodes of exercise and possibly an increased rate of RBC destruction with long term exercise. Providing RBC destruction does not exceed the rate of RBC production, no detrimental effect to athletic performance should occur. An increased rate of RBC turnover may be advantageous because young cells are more efficient in transporting oxygen. Because most techniques examine the RBC population as a whole, more sophisticated methods which analyse cells individually are required to determine the mechanisms involved in exercise-induced damage of RBCs.

Exercise-induced hypoxaemia in master athletes: effects of a polyunsaturated fatty acid diet

Exercise-induced hypoxaemia (EIH) has been associated with an oxygen diffusion limitation. Because polyunsaturated fatty acids (PUFA) administration can modify cell membrane fluidity, we hypothesized that the importance of EIH could be reduced after a 6-week PUFA diet. Resting pulmonary functions and a maximal cycling test were performed before and after the diet, in eight master athletes -48 (SD 6 years)-. The partial pressure of O2 in arterial blood (PaO2), alveolar ventilation (VA) and ideal alveolar-arterial oxygen partial pressure difference (P(Ai-a) O2) were obtained at each exercise intensity. The extent of EIH at maximal exercise was significantly lower after PUFA [PaO2-17.2 (SEM 1.9) vs -12.9 (SEM 2.2)]. Before PUFA, VA accounted for 50% of the variance in the fall in P (Ai-a) for intensities below 80% maximal oxygen uptake (VO2max) and P(Ai-a)O2 for 60% between 70% and 100% VO2max. After PUFA, the reduction in EIH was highly correlated (r2 = 0.85; P < 0.001) to resulting changes in P(Ai-a)O2 and resting pulmonary diffusing capacity (DLCO)/VA but not with changes in ideal alveolar partial pressure of oxygen. The improvement in EIH following PUFA could be related to an increase in alveolar-arterial oxygen conductance following improved pulmonary diffusion.