Inflammatory biomarkers responses after acute whole body vibration in fibromyalgia

The aims of this study were 1) to characterize the intensity of the vibration stimulation in women diagnosed with fibromyalgia (FM) compared to a control group of healthy women (HW) matched by age and anthropometric parameters, and 2) to investigate the effect of a single session of whole body vibration (WBV) on inflammatory responses. Levels of adipokines, soluble tumor necrosis factor receptors (sTNFr1, sTNFr2), and brain-derived neurotrophic factor (BDNF) were determined by enzyme-linked immunosorbent assay. Oxygen consumption (VO2) was estimated by a portable gas analysis system, heart rate (HR) was measured using a HR monitor, and perceived exertion (RPE) was evaluated using the Borg scale of perceived exertion. Acutely mild WBV increased VO2 and HR similarly in both groups. There was an interaction (disease vs vibration) in RPE (P=0.0078), showing a higher RPE in FM compared to HW at rest, which further increased in FM after acute WBV, whereas it remained unchanged in HW. In addition, there was an interaction (disease vs vibration) in plasma levels of adiponectin (P=0.0001), sTNFR1 (P=0.000001), sTNFR2 (P=0.0052), leptin (P=0.0007), resistin (P=0.0166), and BDNF (P=0.0179). In conclusion, a single acute session of mild and short WBV can improve the inflammatory status in patients with FM, reaching values close to those of matched HW at their basal status. The neuroendocrine mechanism seems to be an exercise-induced modulation towards greater adaptation to stress response in these patients.

Protein turnover, amino acid requirements and recommendations for athletes and active populations

Skeletal muscle is the major deposit of protein molecules. As for any cell or tissue, total muscle protein reflects a dynamic turnover between net protein synthesis and degradation. Noninvasive and invasive techniques have been applied to determine amino acid catabolism and muscle protein building at rest, during exercise and during the recovery period after a single experiment or training sessions. Stable isotopic tracers (¹³C-lysine, ¹⁵N-glycine, ²H₅-phenylalanine) and arteriovenous differences have been used in studies of skeletal muscle and collagen tissues under resting and exercise conditions. There are different fractional synthesis rates in skeletal muscle and tendon tissues, but there is no major difference between collagen and myofibrillar protein synthesis. Strenuous exercise provokes increased proteolysis and decreased protein synthesis, the opposite occurring during the recovery period. Individuals who exercise respond differently when resistance and endurance types of contractions are compared. Endurance exercise induces a greater oxidative capacity (enzymes) compared to resistance exercise, which induces fiber hypertrophy (myofibrils). Nitrogen balance (difference between protein intake and protein degradation) for athletes is usually balanced when the intake of protein reaches 1.2 g·kg⁻¹·day⁻¹ compared to 0.8 g·kg⁻¹·day⁻¹ in resting individuals. Muscular activities promote a cascade of signals leading to the stimulation of eukaryotic initiation of myofibrillar protein synthesis. As suggested in several publications, a bolus of 15-20 g protein (from skimmed milk or whey proteins) and carbohydrate (± 30 g maltodextrine) drinks is needed immediately after stopping exercise to stimulate muscle protein and tendon collagen turnover within 1 h.

Effect of high-fat diets on body composition, lipid metabolism and insulin sensitivity, and the role of exercise on these parameters

Dietary fat composition can interfere in the development of obesity due to the specific roles of some fatty acids that have different metabolic activities, which can alter both fat oxidation and deposition rates, resulting in changes in body weight and/or composition. High-fat diets in general are associated with hyperphagia, but the type of dietary fat seems to be more important since saturated fats are linked to a positive fat balance and omental adipose tissue accumulation when compared to other types of fat, while polyunsaturated fats, omega-3 and omega-6, seem to increase energy expenditure and decrease energy intake by specific mechanisms involving hormone-sensitive lipase, activation of peroxisome proliferator-activated receptor α (PPARα) and others. Saturated fat intake can also impair insulin sensitivity compared to omega-3 fat, which has the opposite effect due to alterations in cell membranes. Obesity is also associated with impaired mitochondrial function. Fat excess favors the production of malonyl-CoA, which reduces GLUT4 efficiency. The tricarboxylic acid cycle and beta-oxidation are temporarily uncoupled, forming metabolite byproducts that augment reactive oxygen species production. Exercise can restore mitochondrial function and insulin sensitivity, which may be crucial for a better prognosis in treating or preventing obesity.

Training does not affect protein turnover in pre- and early pubertal female gymnasts

This study compared protein turnover in ten young female gymnasts [10.3 (0.5) years] engaged in regular intense physical training with ten age-matched controls [9.4 (0.6) years)]. Nitrogen flux ( Q), protein synthesis (PS), protein degradation (PD) and net protein turnover (NPB = PS-PD) were measured following a single oral dose of [(15)N]-glycine. The habitual dietary intake of each subject was assessed using a 7-day food record, with food portions being weighed before ingestion. The gymnasts had a low total energy intake which was unbalanced in the proportions of lipid, carbohydrate and protein. Protein flux was 7.19 (0.35) g.kg(-1).day(-1) in the gymnasts and 7.53 (0.81) g.kg(-1).day(-1) in the controls; protein synthesis was 6.06 (0.27) g.kg(-1).day(-1 )in the gymnasts and 6.53 (0.74) g.kg(-1).day(-1) in the controls; protein degradation was 5.45 (0.38) g.kg(-1).day(-1) in the gymnasts and 5.27 (0.74) g.kg(-1).day(-1) in the controls. All data are presented as means and standard errors of the mean (SEM). There were no statistical differences for protein flux, protein synthesis or protein degradation between the two groups. However, NPB was lower (-14%) in the trained gymnasts than in the control group ( P <0.05), which might be explained by a greater protein ingestion in the control group on the day of the protocol ( P <0.05). These results show that in pre- and early pubertal female gymnasts intense training does not exert a demonstrable effect on protein turnover.

Protein intake and nitrogen balance in male non-active adolescents and soccer players

Recommendations for the requirements for protein intake amount usually to 0.8-1.0 g x kg(-1) body mass x day(-1) in adolescents without any reference to the undertaking of acute exercise or to the training status. The present investigation intended to determine the nitrogen balance and protein intake in 8 healthy male non-active adolescents and 11 adolescent soccer players, both groups aged about 15 years. An assessment of nutrient intake was obtained by analysing 7 day food records collected by a questionnaire. Nitrogen excretion rate was determined and nitrogen balance was calculated from the mean daily protein intake and the urinary excretion. The results showed that the nutritional status of the two groups was similar. Nevertheless, we found that their diets were quite inappropriate in terms of the intakes of carbohydrate, some minerals (zinc, calcium, magnesium), vitamins (A, B6, D) and fibre. A positive nitrogen balance was observed from a mean protein intake of 1.57 g x kg(-1) body mass x day(-1) in these adolescents, whether they were non-active or athletes. Thus, the present investigation indicated that the growth and development in non-active adolescents and in adolescent soccer-players give rise to a need for a higher protein intake than is usually recommended. However, the higher protein requirements did not seem to be related only to the increased energy expenditure imposed by the exercise training in the soccer-player group.

Postexercise proteinuria in humans and its adrenergic component

BACKGROUND

Postexercise proteinuria is a common phenomenon depending on hypothetical mechanisms such as the hemodynamic system and its sympathetic component. To test this hypothesis we administrated an a2-adrenergic agonist (clonidine) in order to reduce the catecholamine response during exercise.

METHODS

Clonidine (300 mg) and a placebo, one week apart, were administrated randomly to nine healthy male subjects (23 yrs age) 2 hours prior to a maximal exercise test on bicycle ergometer. Blood samples and urine collections were obtained at rest and after exercise. Lactate in plasma, creatinine and albumin in plasma and urine were assayed and their clearances were calculated.

RESULTS

Postexercise lactate was identical under placebo and clonidine administration (10.1 +/- 1.0 versus 11.3 +/- 1.7 mmol.-1). It was observed that the clonidine treatment induced a lesser postexercise proteinuria (213 +/- 28 versus 298 +/- 55 mg.min-1) and albuminuria (71.8 +/- 16.3 versus 116.8 +/- 34.2 mg.min-1) when compared to the placebo test. The postexercise renal clearance of albumin did show a reduction of 40% under the influence of clonidine.

CONCLUSIONS

It may be argued that the catecholamines are partially acting on the mechanisms of the enhanced permeability of the glomerular membrane induced by strenuous exercise.

Adverse effects of creatine supplementation: fact or fiction?

The consumption of oral creatine monohydrate has become increasingly common among professional and amateur athletes. Despite numerous publications on the ergogenic effects of this naturally occurring substance, there is little information on the possible adverse effects of this supplement. The objectives of this review are to identify the scientific facts and contrast them with reports in the news media, which have repeatedly emphasised the health risks of creatine supplementation and do not hesitate to draw broad conclusions from individual case reports. Exogenous creatine supplements are often consumed by athletes in amounts of up to 20 g/day for a few days, followed by 1 to 10 g/day for weeks, months and even years. Usually, consumers do not report any adverse effects, but body mass increases. There are few reports that creatine supplementation has protective effects in heart, muscle and neurological diseases. Gastrointestinal disturbances and muscle cramps have been reported occasionally in healthy individuals, but the effects are anecdotal. Liver and kidney dysfunction have also been suggested on the basis of small changes in markers of organ function and of occasional case reports, but well controlled studies on the adverse effects of exogenous creatine supplementation are almost nonexistent. We have investigated liver changes during medium term (4 weeks) creatine supplementation in young athletes. None showed any evidence of dysfunction on the basis of serum enzymes and urea production. Short term (5 days), medium term (9 weeks) and long term (up to 5 years) oral creatine supplementation has been studied in small cohorts of athletes whose kidney function was monitored by clearance methods and urine protein excretion rate. We did not find any adverse effects on renal function. The present review is not intended to reach conclusions on the effect of creatine supplementation on sport performance, but we believe that there is no evidence for deleterious effects in healthy individuals. Nevertheless, idiosyncratic effects may occur when large amounts of an exogenous substance containing an amino group are consumed, with the consequent increased load on the liver and kidneys. Regular monitoring is compulsory to avoid any abnormal reactions during oral creatine supplementation.

Do regular high protein diets have potential health risks on kidney function in athletes?

Excess protein and amino acid intake have been recognized as hazardous potential implications for kidney function, leading to progressive impairment of this organ. It has been suggested in the literature, without clear evidence, that high protein intake by athletes has no harmful consequences on renal function. This study investigated body-builders (BB) and other well-trained athletes (OA) with high and medium protein intake, respectively, in order to shed light on this issue. The athletes underwent a 7-day nutrition record analysis as well as blood sample and urine collection to determine the potential renal consequences of a high protein intake. The data revealed that despite higher plasma concentration of uric acid and calcium, Group BB had renal clearances of creatinine, urea, and albumin that were within the normal range. The nitrogen balance for both groups became positive when daily protein intake exceeded 1.26 g.kg but there were no correlations between protein intake and creatinine clearance, albumin excretion rate, and calcium excretion rate. To conclude, it appears that protein intake under 2. 8 g.kg does not impair renal function in well-trained athletes as indicated by the measures of renal function used in this study

Effect of exogenous creatine supplementation on muscle PCr metabolism

31P NMR was used to assess the influence of two weeks creatine supplementation (21g x d(-1)) on resting muscle PCr concentration, on the rate of PCr repletion (R(depl)), and on the half-time of PCr repletion (t 1/2). Body mass (BM) and volume of body water compartments were also estimated by impedance spectroscopy. Fourteen healthy male subjects (20.8+/-1.9 y) participated in this double-blind study. PCr was measured using a surface coil placed under the calf muscle, at rest and during two exercise bout the duration of which was 1 min. They were interspaced by a recovery of 10 min. The exercises comprised of 50 plantar flexions-extensions against weights corresponding to 40% and 70% of maximal voluntary contraction (MVC), respectively. Creatine supplementation increased resting muscle PCr content by approximately 20% (P= 0.002). R(depl) was also increased by approximately 15% (P< 0.001) and approximately 10% (P = 0.026) during 40% and 70% MVC exercises, respectively. No change was observed in R(repl) and t1/2. BM and body water compartments were not influenced. These results indicate that during a standardized exercise more ATP is synthesized by the CK reaction when the pre-exercise level in PCr is higher, giving some support to the positive effects recorded on muscle performance.

Long-term oral creatine supplementation does not impair renal function in healthy athletes

PURPOSE

Oral creatine supplementation is widely used in sportsmen and women. Side effects have been postulated, but no thorough investigations have been conducted to support these assertions. It is important to know whether long-term oral creatine supplementation has any detrimental effects on kidney function in healthy population.

METHODS

Creatinine, urea, and plasma albumin clearances have been determined in oral creatine consumers (10 months to 5 yr) and in a control group.

RESULTS

There were no statistical differences between the control group and the creatine consumer group for plasma contents and urine excretion rates for creatinine, urea, and albumin. Clearance of these compounds did not differ between the two groups. Thus, glomerular filtration rate, tubular reabsorption, and glomerular membrane permeability were normal in both groups.

CONCLUSIONS

Neither short-term, medium-term, nor long-term oral creatine supplements induce detrimental effects on the kidney of healthy individuals.

Effects of training and creatine supplement on muscle strength and body mass

The purpose of this study was to test the effect of creatine supplement on the size of the extra- and intracellular compartments and on the increase of isokinetic force during a strength training-program. Twenty-five healthy male subjects (age 22.0+/-2.9 years) participated in this experiment. Seven subjects formed the control-group. They did not complete any training and did not have any dietary supplement. The eighteen other subjects were randomly divided into a creatine- (n = 8) and a placebo-group (n = 10). They were submitted to a controlled strength-training program for 42 days followed by a detraining period of 21 days. Creatine and placebo were given over a period of 9 weeks. The size of the body water compartments was assessed by bioimpedance spectroscopy and the isokinetic force was determined during a single squat by means of an isokinetic dynamometer. These measurements were completed beforehand, at the end of the training period, and after the determining period. Both placebo- and creatine-group increased the isokinetic force by about 6% after the training period, showing that creatine ingestion does not induce a higher increase of the force measured during a single movement. No change in body mass was observed in the control- and placebo-groups during the entire experiment period while the body mass of the creatine-group was increased by 2 kg (P < 0.001). This change can be attributed partially to an increase (P = 0.039) in the body water content (+1.11), and more specifically, to an increase (P < 0.001) in the volume of the inter-cellular compartment (+0.61). Nevertheless, the relative volumes of the body water compartments remained constant and therefore the gain in body mass cannot be attributed to water retention, but probably to dry matter growth accompanied with a normal water volume.

Endotoxaemia, production of tumour necrosis factor alpha and polymorphonuclear neutrophil activation following strenuous exercise in humans

To examine whether endotoxaemia accompanying long-term, strenuous physical exercise is involved in exercise-induced increase in plasma tumour necrosis factor alpha (TNF-alpha) concentration and polymorphonuclear neutrophil (PMN) activation, 14 male recreational athletes [mean age 28 (SEM 1) years] were studied. Exercise consisted of a 1.5-km river swim, a 40-km bicycle race, and a 10-km road race. Mean time to complete the race was 149.8 (SEM 4.8) min. The plasma concentrations of granulocyte myeloperoxidase (MPO) and TNF-alpha were significantly higher than baseline values immediately and 1 h after exercise (P<0.001). Both variables returned to pre-race levels the day after exercise. Marked, transient decreases in plasma concentrations of anti-lipopolysaccharide (LPS) immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies directed against a panel of selected smooth gram-negative LPS were observed after the race, reaching in most cases minimal values in the blood sample drawn immediately following the completion of the triathlon. There was no significant correlation between the magnitude of PMN activation, as assessed by the increase in plasma concentrations of MPO, and the humoral markers of endotoxaemia and TNF-alpha. An inverse, highly significant relationship between the increase in plasma TNF-alpha concentrations and the changes in circulating anti-LPS IgM antibodies concentrations was observed (r = -0.7; P<0.01). These findings suggest that exercise-induced endotoxaemia was involved in the release of TNF-alpha, that the magnitude of the TNF-alpha response to exercise was down-regulated by anti-LPS antibodies of the IgM class, and that the production of TNF-alpha and endotoxaemia did not seem to play a role in the activation of circulating PMN in the exercising subjects.

Possible in vivo tolerance of human polymorphonuclear neutrophil to low-grade exercise-induced endotoxaemia

To address the question of whether translocation of bacterial lipopolysaccharide (LPS) into the blood could be involved in the process of exercise-induced polymorphonuclear neutrophil (PMN) activation, 12 healthy male subjects who took part in a sprint triathlon (1.5 km river swim, 40 km bicycle race, 10 km road race) were studied. While there was no detectable amount of endotoxin in the blood samples drawn at rest, exercise was followed by the appearance of circulating endotoxin molecules at the end of competition in four subjects, and after one and 24 h recovery in three and seven athletes, respectively. The concentrations of plasma granulocyte myeloperoxidase ([MPO]), were significantly higher immediately after exercise and one hour later-than baseline values (P<0.001). This variable returned to pre-race levels the day after exercise, despite the presence of detectable amounts of LPS, at that time, in seven athletes. The absence of significant correlation (r=0.26; P=0.383) and temporal association between [MPO] and plasma endotoxin levels led us to conclude that endotoxaemia was not involved in the process of exercise-induced PMN degranulation observed in our subjects.

Effect of short-term creatine supplementation on renal responses in men

There is an increasing utilisation of oral creatine (Cr) supplementation among athletes who hope to enhance their performance but it is not known if this ingestion has any detrimental effect on the kidney. Five healthy men ingested either a placebo or 20 g of creatine monohydrate per day for 5 consecutive days. Blood samples and urine collections were analysed for Cr and creatinine (Crn) determination after each experimental session. Total protein and albumin urine excretion rates were also determined. Oral Cr supplementation had a significant incremental impact on arterial content (3.7 fold) and urine excretion rate (90 fold) of this compound. In contrast, arterial and urine Crn values were not affected by the Cr ingestion. The glomerular filtration rate (Crn clearance) and the total protein and albumin excretion rates remained within the normal range. In conclusion, this investigation showed that short-term oral Cr supplementation does not appear to have any detrimental effect on the renal responses of healthy men.

Evidence of differential renal dysfunctions during exercise in men

Post-exercise proteinuria is a common phenomenon in healthy subjects. Previous studies have used albumin (Alb) and beta 2-microglobulin (beta 2-m) molecules as representatives of high- and low-molecular-weight proteins. Recently, more specific markers of the human kidney proximal tubule have been used to identify the precise site of alterations. Active male subjects underwent two strenuous runs, one 400-m run and one 3000-m run. Urine was collected from the subjects before and after each event. Total protein (TP), Alb, alpha 1-microglobulin (alpha 1-m), beta 2-m, intestinal alkaline phosphatase (IAP), tissue-nonspecific alkaline phosphatase (TNAP) and N-acetyl-beta-D-glucosaminidase (NAG) were determined for each sample. The short-distance run (400 m) resulted in the largest increases (P < or = 0.05) in TP (31-fold), Alb (100-fold) and beta 2-m (164-fold) as compared to the long-distance run (3000-m). The alpha 1-m excretion rates were increased to a lesser extent by the exercises. The IAP activity was slightly increased (+90%) by the 400-m run while the TNAP and NAG activities showed a 6.8-fold and a 3.6-fold increase, respectively, after this event. Smaller increases were recorded for the long-distance run (P = 0.05). To conclude, the present investigation showed that: (1) post-exercise proteinuria is related to the absolute intensity of exercise; (2) the impairment of protein reabsorption is revealed better by changes in Alb and beta 2-m; (3) changes in TNAP and NAG activities could reveal biochemical modifications that occur in the proximal tubule, particularly at the S1-S2 segment.

Renal responses to exercise in heart and kidney transplant patients

There is a lack of information about renal responses in heart and kidney transplant patients after intense physical exercise. Eleven heart and ten kidney transplant recipients, as well as two control groups of healthy subjects, were given a maximum exercise test on a bicycle ergometer. One control group was also given a moderate load corresponding to the peak load of the kidney transplant group. Blood and urine samples were collected before and after exercise and assayed for lactate, creatinine, total protein, and albumin. The glomerular filtration rate remained stable at the end of exercise in the transplant patients, while there was a slight (17%) decrease in the control group. Albumin excretion rates after maximum exercise attained a mean of 237 micrograms.min-1 in the control group and a mean of 45 and 16 micrograms.min-1, respectively, in the heart and kidney groups. Postexercise proteinuria seemed to be related to the absolute intensity of the event, but kidney transplant patients showed a reduced effect as compared to heart transplant patients. We conclude that short-term, maximum exercise in heart and kidney transplant recipients is not detrimental to kidney function.

Some aspects of the acute phase response after a marathon race, and the effects of glutamine supplementation

Strenuous exercise may be associated with immune suppression. However, the underlying mechanism is not known. A decrease in the plasma level of glutamine, which is utilised at a high rate by cells of the immune system, and an increase in the plasma level of some cytokines may impair immune functions such as lymphocyte proliferation after prolonged, exhaustive exercise. In two separate studies of the Brussels marathon, using similar protocols, the time course of the changes in the plasma concentrations of some amino acids (glutamine, glutamate, alanine, tryptophan and branched chain amino acids), acute phase proteins and cytokines (interleukins IL-1 alpha, IL-2, IL-6, tumour necrosis factor type a) was measured in male athletes. The numbers of circulating leucocytes and lymphocytes were also measured. Amino acid and cytokine concentrations have not previously been measured concomitantly in marathon runners; the measurement of some of these parameters the morning after the marathon (16 h) is novel. Another novel feature is the provision of glutamine versus placebo to marathon runners participating in the second study. In both studies the plasma concentrations of glutamine, alanine and branched chain amino acids were decreased immediately after and 1 h after the marathon. Plasma concentrations of all amino acids returned to pre-exercise levels by 16 h after exercise. The plasma concentration of the complement anaphylotoxin C5a increased to abnormal levels after the marathon, presumably due to tissue damage activating the complement system. There was also an increase in plasma C-reactive protein 16 h after the marathon. The plasma levels of IL-1 alpha were unaffected by the exercise, while that of IL-2 was increased 16 h after exercise. Plasma IL-6 was increased markedly (approximately 45-fold) immediately after and at 1 h after exercise. Neopterine, a macrophage activation marker, was significantly increased post-exercise. There was a marked leucocytosis immediately after the marathon, which returned to normal 16 h later. At the same time there was a decrease in the number of T-lymphocytes, which was further reduced within 1 h to below pre-exercise levels. Glutamine supplementation, as administered in the second study, did not appear to have an effect upon lymphocyte distribution.

Postexercise proteinuria in childhood and adolescence

Postexercise proteinuria has been observed in healthy adults but there was a need for information in young individuals. Boys and girls (n = 170) from 6 to 18 years of age were submitted to maximal exercise by the 20-meter shuttle run test. Urine collection was made prior to and 30 min after completion of the run. Total protein, albumin, beta 2-microglobulin (beta 2-m), retinol-binding protein (RBP) and creatinine were determined on each sample. Resting values for total protein, albumin, beta 2-m and RBP excretion rates were within the normal range for each component with a progressive increase for total protein and albumin. The effect of exercise increased with age. Between the 6 and 9 year olds there was a gender difference in postexercise proteinuria, boys enhanced the excretion of macromolecules while girls did not show any increase by maximal exercise. The excretion rates of all protein components were related to the absolute intensity of exercise expressed as maximal speed (R between 0.86 and 0.90, p < 0.001). High- and low-molecular weight protein excretion gave evidence of increasing disturbances from the age of 9 to 18 years in boys and girls. These data clearly demonstrate that 1) postexercise proteinuria is present at maximal exercise from childhood to adolescence; 2) the magnitude of protein excretion is strictly related to the absolute intensity of exercise; 3) the glomerulus permeability and the tubular reabsorption process are both different in pre- and postpubertal children and adolescents.

Does glutamine have a role in reducing infections in athletes?

There is an increased risk of infections in athletes undertaking prolonged, strenuous exercise. There is also some evidence that cells of the immune system are less able to mount a defence against infections after such exercise. The level of plasma glutamine, an important fuel for cells of the immune system, is decreased in athletes after endurance exercise; this may be partly responsible for the apparent immunosuppression which occurs in these individuals. We monitored levels of infection in more than 200 runners and towers. The levels of infection were lowest in middle-distance runners, and highest in runners after a full or ultramarathon and in elite rowers after intensive training. In the present study, athletes participating in different types of exercise consumed two drinks, containing either glutamine (Group G) or placebo (Group P) immediately after and 2 h after exercise. They subsequently completed questionnaires (n = 151) about the incidence of infections during the 7 days following the exercise. The percentage of athletes reporting no infections was considerably higher in Group G (81%, n = 72) than in Group P (49%, n = 79, p < 0.001).

Influence of running different distances on renal glomerular and tubular impairment in humans

Strenuous exercise has been claimed to modify renal glomerular and tubular function, the relative involvement of the two sites being unknown. These changes may be assessed by the determination of plasma high and low molecular mass proteins. A group of 13 man performed five runs (100, 400, 800, 1,500, 3,000 m) at maximal speed. The excretion rates and renal clearances of creatinine, albumin (Alb), beta 2-microglobulin (beta 2-m) and retinol-binding protein (RBP) were determined before and after each run. The glomerular filtration rate remained stable during the shorter runs and declined by about 40% during the longer runs. The excretion rate for Alb rose from 10-fold above the basal value (6 micrograms.min-1) for the 100 m to 49-fold for the 800 m and then declined for distances up to 3,000 m. The beta 2-m and RBP had a lesser initial increase, 3.5-(rest 55 ng.min-1) and 7.6-(rest 116 ng.min-1) fold, respectively, for the 100 m run and thereafter showed a higher excretion rate than Alb for the 400 m and 800 m runs. The renal clearances of these high (Alb) and low molecular mass (beta 2-m and RBP) proteins followed the changes observed for excretion rates. There was a linear relationship (r2 = 0.996) between plasma lactate concentration and total protein excretion in the postexercise period when taking all five runs into consideration. Glomerular permeability was primarily affected by the 100-m run while the longer runs modified both the glomerular and the tubular sites. To conclude, the present study demonstrated a differential response of the kidney to strenuous exercise with respect to the intensity and duration of the events.

Kidney function during exercise in healthy and diseased humans. An update

Exercise induces profound changes in renal haemodynamics and protein excretion. The rate of ultrafiltration across the glomerular capillary is determined by the imbalance between the transcapillary hydraulic and colloid osmotic pressure gradients. Despite a major reduction in the renal plasma flow, the filtration fraction can double with maximal exercise, preserving the transfer of metabolites or substances through the glomerulus. Tubular processes and excretion rates are modified by exercise. Despite large increases in plasma lactate during strenuous exercise, renal excretion plays a limited role in lactate metabolism. Apparently, the mechanism of transcellular transport of lactate is saturated during severe exercise. Urea reabsorption is enhanced during prolonged exercise, and this process may act to limit the dehydration of an individual. As uric acid transport is also carrier-mediated, it appears that there is no saturation of the carrier system during prolonged exercise. Postexercise proteinuria is directly related to the intensity of exercise rather than to its duration. This excretion of excess proteins is a transient state with a half-time decay of about 1 hour. The increased clearance of plasma proteins suggests an increased glomerular permeability and a partial inhibition of tubular reabsorption. Studies suggest that exercise decreases the glomerular electrostatic barrier and facilitates transfer of macromolecules. Postexercise proteinuria appears to be age-dependent. Nephropathy is a common observation in the diabetic patient. In young and adult diabetic patients, exhaustive physical exercise does not provoke an enhanced dysfunction of the kidney to what is already found in healthy individuals. Heart and kidney transplant patients have a lesser postexercise proteinuria as compared with healthy individuals.

Urinary excretion of immunoglobulins and their subunits in human subjects before and after exercise

Immunoglobulins and their subunits in urines collected before and after exercise from healthy human subjects were studied. Quantitative analysis showed that only gamma A- and gamma G-immunoglobulins were excreted as whole molecules in normal urine, at a concentration of 0.35 and 1.70 micrograms/min., respectively. Exercise enhanced the excretion of both types of molecules. In some cases, gamma D-immunoglobulins were found in "exercise urine." Gel filtration on Sephadex G-150 showed that only gamma G-subunits were present in normal and in "exercise urine." The distribution of gamma G-subunits was not affected by exercise. The authors consider the importance of the present data in relation to renal physiology.

Urine protein excretion and swimming events

To determine total urinary protein, albumin (ALB), and beta 2-microglobulin (beta 2m) excretion rates in relation to different speeds, 12 males were studied while swimming distances of 100, 600, and 2,000 m at maximal speed. Venous blood lactate concentrations rose to 16.1, 11.6, and 4.5 mmol.l-1 after the 100, 600, and 2,000 m events, while plasma volumes were reduced by 11.3, 7.7, and 5.5%, respectively. ALB urine excretion increased to 110-120 micrograms.min-1 after the 100 and 600 m swims and to 56 micrograms.min-1 after 2,000 m (resting values: 9 micrograms.min-1). In the meantime, the beta 2m excretion rate increased 21 and 10 times the resting values, respectively, for the two shorter swims, with no change for the longer one. Progressive plasma volume reduction was associated with the increase of the protein excretion rate. As evidenced by the creatinine clearance, the glomerular filtration rate did not change for the 100 m swim but dropped by 23 and 35% for the 600 and 2,000 m ones, respectively. On the other hand, the ALB clearance increases were elevated for the three swims, while the beta 2m clearance increases were inversely related to the swimming speeds. The data showed a relationship between the rate of protein excretion and the speed of the swim, and the reduction of plasma volume. The findings could indicate a renal glomerular alteration, with an additional dysfunction of the tubular reabsorption process when the exercise load is high during swimming events.

Decreased plasma tryptophan concentration in major depression: relationship to melancholia and weight loss

Plasma total tryptophan (TRP) concentration was significantly lower in 31 patients with major depression compared to a healthy control group. The ratio of plasma TRP concentration to that of other branch chain amino acids (the TRP:BCAA ratio) was also decreased. Further analysis revealed that the decrease in plasma TRP and TRP:BCAA ratio was most apparent in patients with major depression and melancholia. Overall, women but not men had significantly decreased plasma tryptophan concentrations, perhaps because of a contributory effect of weight loss; this latter effect, however, could not be distinguished clearly from a diagnosis of melancholia. Our data suggest that in some depressed patients, reductions in plasma tryptophan availability may contribute to abnormalities in brain 5-hydroxytryptamine function.

Postexercise proteinuria in rowers

Exercise performance, glomerular filtration rate (GFR), and urinary filtration of proteins during static pool rowing and cycling to exhaustion were studied in trained rowers. The peak VO2 and heart rate were higher during rowing than during cycling. There was a reduction in plasma volume and an increase in lactate concentration after exercise; however, no significant difference was noted between rowing and cycling in either case. Postexercise proteinuria was increased 8 and 11 times, and albuminuria 25 and 20 times after rowing and cycling exercises, respectively. There was no difference between these exercises in terms of protein or albumin excretion. There was no change in postexercise GFR. Albumin clearance was increased 18 and 20 fold after rowing and cycling, respectively. A significant, but low correlation, r = 0.56, was noted between albumin excretion and postexercise blood lactate concentration. Thus, no difference in the effect on kidney response was found between static pool rowing and cycling to exhaustion in these athletes.

The influence of air-cushion shoes on post-exercise proteinuria

Fourteen trained males participated in three sets of progressive 1 min exercise till exhaustion comparing proteinuria after bicycling, treadmill running under barefoot and air-cushion shoe conditions. Venous lactate rose to about 11 moles.l-1 after the three bouts of exercise while total protein and albumin urinary excretion increased 7 (rest micrograms.min-1) and 19 (rest 11 micrograms.min-1) fold respectively. Creatinine clearance declined to 75% (88 ml.min-1) of the resting values for all three exercises. Albumin clearances increased from 0.24 microliter.min-1 at rest to 4.08 microliters.min-1 during the recovery period. None of the above values were statistically different while comparing the three protocols. On the contrary, plasma hemoglobin showed a significant rise with bare-footed-running (rest 10 mg.100 ml-1; exercise 21 mg.100 ml-1). The lack of hemoglobin in urine postulated that the renal threshold for excretion was not attained in the present conditions. The results indicate that haemolysis and repeated shocks on the foot sole do not lead to the urinary excretion of proteins induced by short-term progressive and exhaustive exercise in humans.

Renal protein excretion after exercise in man

Thirteen men were submitted to graded exhaustive cycle exercise to determine the kinetics of proteinuria in the recovery period. Venous blood samples were analysed for haematocrit, lactate, creatinine, total protein and albumin for 1 h following exercise. Urine samples were collected during a 3-h recovery period. Total protein, albumin, and creatinine levels were determined for these samples. Total protein and albumin urinary excretion increased to 581 and 315 micrograms min-1, respectively, at the end of the 1st h of recovery as compared to 42 and 15 micrograms.min-1 for resting values. Plasma volume returned to pre-exercise levels between 30 and 60 min after cessation of exercise, while urinary total protein and albumin content still remained above the resting values for the following 2 h. Both post-exercise urinary total protein and albumin excretion followed a logarithmic decline with the same half-life of 54 min, thus requiring about 4 h to regain resting values. The reduction of plasma volume and the degree of dehydration do not seem to be involved in the process. The present study indicates the delayed recovery of protein handling by the kidney, as compared with other biochemical parameters, and provides accurate information on the kinetics of post-exercise proteinuria.

Effects of inactivity and exercise on bone

Bone mass and muscular mass show a parallel evolution during growth, and parallel involution with age. However, the bone loss related to the withdrawal of oestrogens is independent of muscular waste. The extensive study of disuse osteoporosis shows that exercise without weightbearing cannot counteract the loss of bone mass provoked by bed rest or weightlessness. Physical training, even at low frequency (30 to 60 min/day, 2 or 3 days/week), can increase bone mass or reduce bone loss associated with age. This effect is even present when exercise is practised by very old people at a seemingly low level of muscular tension on bone. It is not known whether muscular exercise could be helpful in pathological osteopenia. Experiments in animals indicate a short-lived benefit of exercise practised during a definite growth period; the long term effect of physical training in humans, after cessation of such activity, has not been studied extensively. Equal distribution of tension on all parts of the skeleton is probably not mandatory to obtain a general effect of exercise on bone mass. It is assumed that muscular exercise acts through tension exerted on bone, but the exact mechanism is unknown, as are the specifications of effective exercise in terms of site of application, intensity, frequency and duration. Moreover, little is known about the expected synergy between exercise and occupational activity.

Indirect evidence of glomerular/tubular mixed-type postexercise proteinuria in healthy humans

Hypothetical mechanisms have been postulated to explain the presence of proteins in urine after severe exercise. Recently, it has been shown that several amino acids inhibit tubular protein reabsorption. Seven healthy men, hyperhydrated, were studied during a 2-min bicycle exercise at supramaximal load. The subjects were tested without or with lysine perfusion (0.4 g/kg body wt iv). In both testing conditions, blood lactate increased to 13.8 mmol/l. Total protein urinary excretion increased to 1.10 and 1.67 mg/min, without and with lysine perfusion, compared with 79 micrograms/min at rest. In the meantime, albumin excretion increased 48- and 74-fold, respectively, while beta 2-microglobulin excretion increased 97- and 1,043-fold compared with basal values. The renal clearance of albumin increased to 8.4 microliters/min without lysine and to 12.0 microliters/min with lysine perfusion (rest 0.18). beta 2-Microglobulin clearance increased to 10.0 and 39.3 ml/min, respectively (rest 0.05). These data clearly demonstrate that postexercise proteinuria is of mixed type after exhaustive short-term exertion. Both increased glomerular permeability and partial tubular reabsorption inhibition to proteins appear to be involved.

The influence of work intensity on postexercise proteinuria

Fifteen men were studied during 100 m, 400 m and 3,000 m runs at maximal speed to determine total urinary protein and albumin excretion rates in relation to different distances of running. Venous blood lactate rose to 7.5 mmol.l-1 after the 100 m and 3,000 m events, while reaching 12 mmol.l-1 after the 400 m dash. Total urinary protein excretion increased to 330, 1640 and 565 micrograms.min-1 after the 100 m, 400 m and 3,000 m runs respectively, as compared with basal values (70 micrograms.min-1). In the meantime, albumin excretion increased respectively by 5, 25 and 18 fold of the resting values. The renal clearance of albumin increased to 0.84, 5.62 and 3.35 microliter.min-1 after the three runs, as compared with a mean value of 0.19 microliter.min-1 at rest. Exponential relationships (r = 0.85) were recorded between post-exercise venous lactate and albumin, and total protein excretion. The present work illustrates the major influence of the intensity of exercise (anaerobic glycolytic component), rather than its duration, on the excretion rate of urinary proteins.

Influence of the degree of metabolic control on physical fitness in type I diabetic adolescents

Seventeen type I male diabetic adolescents and 17 control subjects matched for age, height, and weight were submitted to maximal exercise on a bicycle ergometer. The diabetic subjects were divided into two groups according to their degree of metabolic control using total glycosylated hemoglobin (HbA1): group 1, diabetics with HbA1 less than 8.5% (n = 9) and group 2, diabetics with HbA1 greater than 8.5% (n = 8). Oxygen uptake, pulmonary ventilation, and heart rate were recorded at rest and at maximal load. Glucose, lactate, and free fatty acids were determined in blood before and after exercise. Maximal work load and oxygen uptake were significantly lower in the two diabetic groups than in the healthy controls. An inverse relationship was observed between HbA1 concentration and the maximal work load (r = -0.63; P less than 0.01). It can be concluded that diabetic adolescents should obtain the best possible degree of metabolic control to improve their performances.

Metabolic implications during a 20-km run after heart transplantation

The aim of the present study was to evaluate a heart transplanted patient who ran a 20-km race 9 months after surgery. Thirty-six healthy male subjects were studied during the same run and served as control group. Biochemical variables were determined in blood and urine samples collected before and after the race. Post-exercise blood urea increased by 23% (P less than 0.05) in the control group but remained unchanged in the patient. Blood lactate increased far more in the transplanted patient (7.07 mmol/L) than in the control subjects (2.53 mmol/L). The exercise induced a 5.46- and 0.67-fold increase in creatine phosphokinase activity in the transplanted patient and control group, respectively. The creatinine and urea urinary excretion and clearance decreased by 40%-60% after exercise for all subjects. It may be concluded that the heart transplanted patient responded for most registered variables in the same way as normal subjects, but some differences occurred on the renal side due to the use of an immunosuppressive drug.

Postexercise proteinuria in humans. Facts and mechanisms

Strenuous exercise induces profound changes in renal hemodynamics and the protein content of urine. Postexercise proteinuria seems to be directly related to the intensity of exercise, rather than to its duration. The pattern of proteins identified in urine collected after exercise is different from normal physiological proteinuria. Immunochemical techniques demonstrate that postexercise proteinuria is of mixed glomerular-tubular type when heavy exercise is involved. The origin of proteinuria after light exercise seems to be preponderantly of glomerular type. Clearance of individual plasma proteins suggests an increased glomerular permeability and a partial tubular-reabsorption inhibition of macromolecules.

Exercise and renal function

Exercise induces profound changes in the renal haemodynamics and in electrolyte and protein excretion. Effective renal plasma flow is reduced during exercise. The reduction is related to the intensity of exercise and renal blood flow may fall to 25% of the resting value when strenuous work is performed. The combination of sympathetic nervous activity and the release of catecholamine substances is involved in this process. The reduction of renal blood flow during exercise produces a concomitant effect on the glomerular filtration rate, though the latter decreases relatively less than the former during exertion. However, the degree of hydration has an important influence on the glomerular filtration rate. An antidiuretic effect is observed during intense exercise. Changes in urine flow are dependent on the plasma antidiuretic hormone levels which are increased by intense exercise. Heavy exercise has an inhibitory effect on most electrolytes (Na, Cl, Ca, P). With potassium, however, most studies report that potassium excretion is not consistently affected by moderate to heavy exercise. Increased aldosterone production helps the body to maintain sodium by increasing its reabsorption from the filtered tubular fluid. Recent studies suggest that sympathetic stimulation may be involved during exercise. Strenuous work leads to an increased excretion of erythrocytes and leucocytes in urine. Cylindruria has been regularly found in postexercise urine in different sports. Postexercise proteinuria is a common phenomenon in humans. It seems to be directly related to the intensity of exercise, rather than to its duration. This excretion of proteins in urine is a transient state with a half-time of approximately 1 hour. Postexercise proteinuria has a pattern different from normal physiological proteinuria. Immunochemical techniques demonstrate that postexercise proteinuria is of the mixed glomerular-tubular type, the former being predominant. The increased clearance of plasma proteins suggests an increased glomerular permeability and a partial inhibition of tubular reabsorption of macromolecules. Haemoglobinuria and myoglobinuria may be observed under special exercise conditions. The degree of hydration appears to be important to reduce these abnormalities.

Biochemical changes in a 100 km run: free amino acids, urea, and creatinine

Free amino acids, urea, and creatinine were analyzed in venous blood and urine of 11 trained (28--81 years old) male subjects before, immediately after, and 1 day after a 100 km running competition. The urinary excretion per minute of all amino acids was lowered after the contest. The renal clearance of creatinine was reduced from 116 to 60 ml/min and the clearance of most amino acids was reduced to a similar extent. However, for the amino acids with a resting clearance under 1 ml/min (x), a high relative clearance ratio (y in % of x) was seen post-exercise: y = -92.3 (log10 x) +23.1, r = -0.83, showing that their high reabsorption capacity had been impaired. Serum concentrations of most free amino acids, including the branched-chain amino acids and alanine, were reduced to 35--85% of the pre-race values. The sulfur amino acids were elevated either at the end of (cystine, to 180%) or 24 h after (methionine, to 155%) the race. Urea production increased by 44% while creatinine production tended to decrease. The production of 3-methylhistidine remained unchanged. These findings are compatible with a stimulation of gluconegenesis at the expense of the amino acid pool without induction of muscle protein catabolism.

Biochemical changes in a 100 km run: proteins in serum and urine

Eleven male subjects took part in a 100 km running competition. Alterations in the total plasma protein and in ten individual plasma protein concentrations in blood and urine were measured prior to the run, immediately after and after 1 day of recovery. Five individual proteins showed a 7-10%, and lysozyme a 40%, increase in the plasma after the run. On the contrary, the haptoglobin concentration fell to 40% of its pre-race level. None of these variations were correlated with the plasma volume change. The present data showed a moderate hemolysis, as evidenced by plasma lysozyme and hemoglobin-haptoglobin binding. The urinary excretion of plasma proteins was slightly increased, especially albumin and alpha1-acid-glycoprotein. The renal clearance of plasma proteins revealed that the 100 km run induced a moderate increase of glomerular permeability without any signficant change in the tubular reabsorption process.

Lactate uptake by inactive forearm during progressive leg exercise

Eleven male subjects were studied during graded leg exercise from 60 to 270 W. Arterial and venous lactate concentrations were measured from the resting forearm during the exercise and recovery periods. Lactate concentration rose regularly during the work and declined slowly to basal levels after the exercise. The arteriovenous difference rapidly became positive during the exercise, indicating a net uptake of lactate by the nonexercising muscles. The uptake of lactate by the muscle correlated directly with the arterial concentration. After the 5th min of recovery, there was no longer any significant difference between arterial and venous lactate concentrations. It is concluded that 1) nonexercising muscles play a small role in the removal of lactate during exercise and 2) significant removal of lactate from the blood by nonexercising muscles stops soon after the cessation of exercise.

Renal glomerular and tubular impairment during strenuous exercise in young women

Creatinine, total protein, albumin and beta2-microglobulin were measured in the urine of fifteen healthy women before and after strenuous short-term exercise. The heavy intermittent load produced an increased urinary excretion of total protein, albumin and beta2-microglobulin, while creatinine was unaffected. The renal clearance of albumin and beta2-microglobulin showed very high values after stopping the exercise. However, 45 min after the end of exercise, total protein returned to initial values while albumin and beta2-microglobulin remained high. The urinary ratio between beta2-microglobulin and albumin is higher in urine collected after exercise than in normal proteinuria. This implies that post-exercise proteinuria is of glomerular and tubular origin.