Correlations of growth hormone (GH) and insulin-like growth factor I (IGF-I): effects of exercise and abuse by athletes

Apelin/APJ signaling in IGF-1-induced acute mitochondrial and antioxidant effects in spontaneously hypertensive rat myocardium

IGF-1 and apelin are released in response to exercise training with beneficial effects. Previously we demonstrated that a swimming routine is effective to convert pathological into physiological cardiac hypertrophy, and that IGF-1 improves contractility and the redox state, in spontaneously hypertensive rats (SHR). Now, we hypothesize that the apelinergic pathway is involved in the cardioprotective effects of IGF-1 in the SHR. We assessed the redox state and mitochondrial effects of IGF-1 or apelin in the presence/absence of AG1024 or ML221 [pharmacological antagonists of IGF1 (IGF1R) and apelin (APJ) receptors, respectively] in SHR isolated cardiomyocytes or perfused hearts. Acute IGF-1 (10 nmol/L) significantly: -reduced H2O2 production (IGF-1:62 ± 6; control:100 ± 8.1, %), -increased the activity of superoxide dismutase (IGF-1:193 ± 17, control: 100 ± 13,%), -prevented H2O2-induced ΔΨm loss (TMREF10min/F0 min: IGF-1:0.93 ± 0.017, control: 0.72 ± 0.029), -reduced mitochondrial permeability transition pore (mPTP) opening estimated by the calcium retention capacity (nmol/mg protein, IGF-1:251 ± 34, control:112 ± 5), and -increased P-AMPK (IGF-1:129 ± 0.9, control: 100 ± 2%) and P-AKT (IGF-1:143 ± 17 control:100 ± 6, %). These effects were suppressed not only by the antagonism of IGF1R but also of APJ. Moreover, IGF-1 significantly increased APJ (IGF-1:198 ± 29 control:100 ± 15,%) and apelin mRNAs (IGF-1:251 ± 48, control:100 ± 6,%). On the other hand, an equipotent dose of exogenous apelin (50 nmol/L) emulated IGF-1 effects being cancelled by the antagonism of APJ however not by AG1024. IGF-1/IGF1R stimulates the apelinergic pathway, improving the redox balance and mitochondria status in the pathologically hypertrophied myocardium of the SHR.

Na+/H+ exchanger and cardiac hypertrophy

Reactive cardiac hypertrophy (CH) is an increase in heart mass in response to hemodynamic overload. Exercise-induced CH emerges as an adaptive response with improved cardiac function, in contrast to pathological CH that represents a risk factor for cardiovascular health. The Na⁺/H⁺ exchanger (NHE-1) is a membrane transporter that not only regulates intracellular pH but also intracellular Na⁺ concentration. In the scenario of cardiovascular diseases, myocardial NHE-1 is activated by a variety of stimuli, such as neurohumoral factors and mechanical stress, leading to intracellular Na⁺ overload and activation of prohypertrophic cascades. NHE-1 hyperactivity is intimately linked to heart diseases, including ischemia-reperfusion injury, maladaptive CH and heart failure. In this review, we will present evidence to support that the NHE-1 hyperactivity constitutes a "switch on/off" for the pathological phenotype during CH development. We will also discuss some classical and novel strategies to avoid NHE-1 hyperactivity, and that are therefore worthwhile to improve cardiovascular health.

Comparison and validation of ELISA assays for plasma insulin-like growth factor-1 in the horse

Insulin-like growth factor-1 (IGF-1) plays several important physiological roles, and IGF-related pathways have been implicated in developmental osteochondral disease and endocrinopathic laminitis. This factor is also a downstream marker of growth hormone activity and its peptide mimetics. Unfortunately, previously used assays for measuring equine IGF-1 (radioimmunoassays and ELISAs) are no longer commercially available, and many of the kits on the market give poor results when used on horse samples. The aim of the present study was to compare three different ELISA assays (two human and one horse-specific). Plasma samples from six Standardbreds, six ponies and six Andalusians were used. The human IGF-1 ELISA kit from Immunodiagnostic Systems (IDS) proved to be the most accurate and precise of the three kits; the other two assays gave apparently much lower concentrations, with poor recovery of spiked recombinant human IGF-1 and unacceptably poor intra-assay coefficients of variation (CV). The IDS assay gave an intra-assay CV of 3.59 % and inter-assay CV of 7.31%. Mean percentage recovery of spiked IGF-1 was 88.82%, and linearity and dilutional parallelism were satisfied. The IGF-1 plasma concentrations were 123.21 ±8.24 ng/mL for Standardbreds, 124.95 ±3.69 ng/mL for Andalusians and 174.26 ±1.94 ng/mL for ponies. Therefore of the three assays assessed, the IGF-1 ELISA manufactured by IDS was the most suitable for use with equine plasma samples and may have many useful applications in several different research areas. However, caution should be used when comparing equine studies where different analytical techniques and assays may have been used to measure this growth factor.

Illicit drugs and cardiac arrhythmias in athletes

The current management of athletes with cardiac arrhythmias has become complicated by the widespread use of illicit drugs, which can be arrhythmogenic.

The World Anti-Doping Agency annually updates a list of prohibited substances and methods banned by the International Olympic Committee that includes different classes of substances namely, anabolic androgenic steroids, hormones and related substances, β2-agonists, diuretics, stimulants, narcotics, cannabinoids, glucocorticosteroids, alcohol, β-blockers and others. Almost all illicit drugs may cause, through a direct or indirect arrhythmogenic effect, a wide range of cardiac arrhythmias (focal or reentry type, supraventricular and/or ventricular) that can even be lethal and which are frequently sport activity related.

A large use of illicit drugs has been documented in competitive athletes, but the arrhythmogenic effect of specific substances is not precisely known. Precipitation of cardiac arrhythmias, particularly in the presence of a latent electrophysiologic substrate including some inherited cardiomyopathies, at risk of sudden death or due to long-term consumption of the substances, should raise the suspicion that illicit drugs may be a possible cause and lead cardiologists to investigate carefully this relationship and appropriately prevent the clinical consequences.

Use and Effectiveness of Performance-Enhancing Substances

The use and effects of selected performance-enhancing drugs and nutritional supplements are reviewed. Recent sports medicine studies are mostly double blind and placebo controlled but contain relatively small sample sizes. Their data appear reliable and are reported in reputable journals. Definitions and methods used in sports medicine are provided to enhance the understanding of this literature. The use of performance-enhancing substances is probably under-reported. Anabolic-androgenic steroids are reportedly used in 0% to 1% of women, 0.5% to 3% of high school girls, 1% to 5% of men, 1% to 12% of high school boys, and up to 67% of some groups of elite athletes. The use of combinations of performance-enhancing substances is common. Carbohydrate loading, adequate protein intake, creatine, blood doping, and erythropoietin (epoetin alfa) appear to enhance performance. Anabolic-androgenic steroids enhance performance, but health risks limit their use. Growth hormones and β2 -selective adrenergic agonists may enhance performance, but additional studies are needed. Androstenedione, caffeine, amphetamines, and nonprescription sympathomimetics do not appear to enhance performance. Performance-enhancing drugs have shown some benefit in diseased patients with malnutrition and/or decreases in physical ability. Pharmacists and other health care providers have opportunities to improve the understanding, use, and monitoring of performance-enhancing substances.

Neurotrophins and cognitive functions in T1D compared with healthy controls: effects of a high-intensity exercise

Exercise is known to have beneficial effects on cognitive function. This effect is greatly favored by an exercise-induced increase in neurotrophic factors, such as brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1), especially with high-intensity exercises (HIE). As a complication of type 1 diabetes (T1D), a cognitive decline may occur, mostly ascribed to hypoglycaemia and chronic hyperglycaemia. Therefore, the purpose of this study was to examine the effects of acute HIE on cognitive function and neurotrophins in T1D and matched controls. Ten trained T1D (8 males, 2 females) participants and their matched (by age, sex, fitness level) controls were evaluated on 2 occasions after familiarization: a maximal test to exhaustion and an HIE bout (10 intervals of 60 s at 90% of their maximal wattage followed by 60 s at 50 W). Cognitive tests and analyses of serum BDNF, IGF-1, and free insulin were performed before and after HIE and following 30 min of recovery. At baseline, cognitive performance was better in the controls compared with the T1D participants (p < 0.05). After exercise, no significant differences in cognitive performance were detected. BDNF levels were significantly higher and IGF-1 levels were significantly lower in T1D compared with the control group (p < 0.05) at all time points. Exercise increased BDNF and IGF-1 levels in a comparable percentage in both groups (p < 0.05). In conclusion, although resting levels of serum BDNF and IGF-1 were altered by T1D, comparable increasing effects on BDNF and IGF-1 in T1D and healthy participants were found. Therefore, regularly repeating acute HIE could be a promising strategy for brain health in T1D.

Low-intensity resistance training with blood flow restriction improves vascular endothelial function and peripheral blood circulation in healthy elderly people

PURPOSE

The present study aimed to investigate the effects of low-intensity resistance training with blood flow restriction (BFR resistance training) on vascular endothelial function and peripheral blood circulation.

METHODS

Forty healthy elderly volunteers aged 71 ± 4 years were divided into two training groups. Twenty subjects performed BFR resistance training (BFR group), and the remaining 20 performed ordinary resistance training without BFR. Resistance training was performed at 20 % of each estimated one-repetition maximum for 4 weeks. We measured lactate (Lac), norepinephrine (NE), vascular endothelial growth factor (VEGF) and growth hormone (GH) before and after the initial resistance training. The reactive hyperemia index (RHI), von Willebrand factor (vWF) and transcutaneous oxygen pressure in the foot (Foot-tcPO2) were assessed before and after the 4-week resistance training period.

RESULTS

Lac, NE, VEGF and GH increased significantly from 8.2 ± 3.6 mg/dL, 619.5 ± 243.7 pg/mL, 43.3 ± 15.9 pg/mL and 0.9 ± 0.7 ng/mL to 49.2 ± 16.1 mg/dL, 960.2 ± 373.7 pg/mL, 61.6 ± 19.5 pg/mL and 3.1 ± 1.3 ng/mL, respectively, in the BFR group (each P < 0.01). RHI and Foot-tcPO2 increased significantly from 1.8 ± 0.2 and 62.4 ± 5.3 mmHg to 2.1 ± 0.3 and 68.9 ± 5.8 mmHg, respectively, in the BFR group (each P < 0.01). VWF decreased significantly from 175.7 ± 20.3 to 156.3 ± 38.1 % in the BFR group (P < 0.05).

CONCLUSIONS

BFR resistance training improved vascular endothelial function and peripheral blood circulation in healthy elderly people.

Obesity, growth hormone and exercise

Growth hormone (GH) is regulated, suppressed and stimulated by numerous physiological stimuli. However, it is believed that obesity disrupts the physiological and pathological factors that regulate, suppress or stimulate GH release. Pulsatile GH has been potently stimulated in healthy subjects by both aerobic and resistance exercise of the right intensity and duration. GH modulates fuel metabolism, reduces total fat mass and abdominal fat mass, and could be a potent stimulus of lipolysis when administered to obese individuals exogenously. Only pulsatile GH has been shown to augment adipose tissue lipolysis and, therefore, increasing pulsatile GH response may be a therapeutic target. This review discusses the factors that cause secretion of GH, how obesity may alter GH secretion and how both aerobic and resistance exercise stimulates GH, as well as how exercise of a specific intensity may be used as a stimulus for GH release in individuals who are obese. Only five prior studies have investigated exercise as a stimulus of endogenous GH in individuals who are obese. Based on prior literature, resistance exercise may provide a therapeutic target for releasing endogenous GH in individuals who are obese if specific exercise programme variables are utilized. Biological activity of GH indicates that this may be an important precursor to beneficial changes in body fat and lean tissue mass in obese individuals. However, additional research is needed including what molecular GH variants are acutely released and involved at target tissues as a result of different exercise stimuli and what specific exercise programme variables may serve to stimulate GH in individuals who are obese.

Immunoreactive and bioactive growth hormone responses to resistance exercise in men who are lean or obese

It has been suggested that obese individuals have a blunted growth hormone (GH) response to spontaneous and stimulated GH secretion. The present study was designed to examine the effects of a high-volume, whole body acute resistance exercise (RE) protocol on immunoreactive GH (iGH), bioactive GH (bGH), and GH-binding protein (GHBP) in sedentary lean and obese men. Nine obese (mean ± SD: 20.8 ± 2.1 yr old, 177.0 ± 4.1 cm height, 108.7 ± 15.9 kg body mass, 37.6 ± 5.29% body fat) and nine lean (20.1 ± 2.1 yr old, 177.8 ± 8.7 cm height, 71.7 ± 5.8 kg body mass, 14.7 ± 3.54% body fat) men completed an acute RE protocol (6 exercises, 3 sets of 10 repetitions at 85–95% of 10 repetitions maximum with 120- and 90-s rest periods), and blood samples were collected before, at the midpoint, and immediately after exercise and during recovery (+50, +70, and +110). In contrast to prior studies, which examined acute responses to cardiovascular exercise protocols, groups did not differ in iGH response to the exercise stimulus. However, bGH concentrations overall were significantly lower in the obese than the lean participants ( P < 0.001). Additionally, obese individuals had significantly higher GHBP concentrations ( P < 0.001). Results suggest that obese and lean sedentary men performing a high-volume, whole body acute RE protocol demonstrate similar increases in iGH. Blunted bGH and elevated GHBP concentrations are indicative of altered GH activity associated with obesity. Prior research findings of blunted iGH response may be attributable to RE protocols not equated on relative intensity or volume. These results underscore the complexity of pituitary biology and its related mechanisms and may have implications for exercise prescription in the treatment of obesity.

Doping and musculoskeletal system: short-term and long-lasting effects of doping agents

Doping is a problem that has plagued the world of competition and sports for ages. Even before the dawn of Olympic history in ancient Greece, competitors have looked for artificial means to improve athletic performance. Since ancient times, athletes have attempted to gain an unfair competitive advantage through the use of doping substances. A Prohibited List of doping substances and methods banned in sports is published yearly by the World Anti-Doping Agency. Among the substances included are steroidal and peptide hormones and their modulators, stimulants, glucocorticosteroids, β₂-agonists, diuretics and masking agents, narcotics, and cannabinoids. Blood doping, tampering, infusions, and gene doping are examples of prohibited methods indicated on the List. Apart from the unethical aspect of doping, as it abrogates fair-play's principle, it is extremely important to consider the hazards it presents to the health and well-being of athletes. The referred negative effects for the athlete's health have to do, on the one hand, by the high doses of the performance-enhancing agents and on the other hand, by the relentless, superhuman strict training that the elite or amateur athletes put their muscles, bones, and joints. The purpose of this article is to highlight the early and the long-lasting consequences of the doping abuse on bone and muscle metabolism.

Detection of GH abuse in sport: Past, present and future

Due to its considered performance enhancing effects, human growth hormone (hGH) is abused as a doping agent in sport. Its misuse also carries potentially serious side effects to a person's health. Consequently, hGH and its releasing factors are prohibited in sport, as established in the Prohibited List which is updated and published yearly by the World Anti-Doping Agency (WADA). In order to fight the menace that hGH doping poses to the spirit of sport and to the health of athletes, the sport movement and the anti-doping authorities, initially led by the International Olympic Committee (IOC) and later by WADA, have put substantial efforts into developing tests for its detection. Currently, a primary analytical approach, the isoform differential immunoassay, has been implemented in WADA-accredited laboratories. In parallel, a second, indirect approach for the detection of hGH abuse, based on the quantification of hGH-associated biological markers, has been developed. The final aim is to combine both methodologies to improve the sensitivity and expand the time window to detect doping with hGH. In addition, novel analytical procedures, based on proteomic and genomic technologies as well as the use of mass spectrometry-based methods of detection, are being investigated for future application in hGH anti-doping tests.

Salivary free insulin-like growth factor-i levels: effects of an acute physical exercise in athletes

BACKGROUND/AIMS

The offer of human saliva IGF-I (sIGF-I) measurement in athletes investigation is a new proposal. The aim was to investigate the physical exercise effect on sIGF-I and explore plasma free IGF-I relation.

MATERIALS AND METHODS

Saliva and blood were collected from well-trained athletes, investigated immediately before and at the end of a physical exercise test.

RESULTS

sIGF-I was significantly increased at the end of the physical exercise. The plasma free IGF-I concentrations did not demonstrate any difference. The saliva total protein level (sTP) was also significantly increased. A positive correlation between sTP and sIGF-I, was observed, both before and after physical exercise, and between salivary and plasma free IGF-I only after physical exercise. The salivary free IGF-I level significantly increased after physical exercise, moreover a correlation with the plasma levels exists in post-exercise condition.

CONCLUSION

The physical exercise affects sIGF-I as well as the sTP. The correlation between plasma and salivary free IGF-I levels only in post-exercise condition suggests further studies to investigate the effects of different type and duration of physical exercise. The comparison with other salivary biochemical parameter investigation would also further increase comprehension on the role of salivary IGF-I.

Effects of two different types of exercise on GH/IGF axis in athletes. Is the free/total IGF-I ratio a new investigative approach?

BACKGROUND

Human growth hormone (hGH) responds to bouts of exercise by increasing, while the insulin-like growth factor-I (IGF-I) responses are conflicting.

METHODS

Twenty well-trained male cyclists completed a brief duration exercise (A: warm up+increasing workload until exhaustion, lasting 25 min) and a medium duration exercise (B: warm up+70-80%VO(2 max)+increasing workload until exhaustion, lasting 40 min). The immunoreactivity of plasma hGH, the IGF-I in its total and free fraction were measured before and at the end of the exercise, and the free/total IGF-I ratio response to the two cycling exercise bouts was examined.

RESULTS

Both A and B demonstrated increased hGH (from 77+/-122 to 544+/-327 and 28+/-68 to 369+/-276 pmol/l respectively) and total IGF-I (from 67+/-10 to 70+/-10 and 55+/-14 to 61+/-15 nmol/l respectively). The free IGF-I was decreased only in A (from 0.38+/-0.16 to 0.32+/-0.14 nmol/l). Both A and B demonstrated a decreased free/total IGF-I ratio (from 0.57+/-0.30 to 0.46+/-0.22 and 0.61+/-0.37 to 0.52+/-0.29).

CONCLUSION

Brief and medium duration physical exercise influences the hGH, the total and free IGF-I concentrations. The free/total IGF-I ratio was also influenced and it might be related to the GH/IGF system. Its investigation might be a way of studying the training condition.

Enzyme-linked immunosorbent assays for insulin-like growth factor-I using six-histidine tag fused proteins

The fusion proteins of insulin-like growth factor-I (IGF-I) and six-histidine tag (IGF-I-6H, 6H-IGF-I-6H) were cloned, expressed, purified and renatured, with their immunoreaction properties and biological activities intact. The binding kinetics between these fusion proteins and anti-IGF-I antibody or anti-6H antibody were studied using surface plasmon resonance (SPR). Two enzyme-linked immunosorbent assay (ELISA) modes, which proved feasible in the measurement of human serum samples, were used to detect IGF-I with the help of the six-histidine tagged proteins. Furthermore, combining the production technique of the six-histidine tagged fusion protein with the competitive sandwich ELISA mode, using an enzyme labeled anti-6H antibody as a tracer, can be a universal immunochemical method to quantitate other polypeptides or proteins.

Low-Intensity Exercise, Vascular Occlusion, and Muscular Adaptations

The study investigated the effects of low-intensity exercise on muscular fitness when combined with vascular occlusion. Nineteen college male and female students performed two sets of a 5-min step exercise using a 12-inch bench three times per week for 5 weeks. During the step exercise, blood flow to one leg was restricted (vascular occlusion) with a blood pressure cuff, while the other leg was not occluded. Muscular strength of the occluded leg was significantly increased over the nonoccluded leg (p < 0. 05). Muscular endurance and muscle mass were improved after 5 weeks of training (p < 0.05); however, the changes between the two legs were not significantly different (p > 0.05). Exercise with vascular occlusion has the potential to be an alternative form of training to promote muscular strength.

Expression and characterization of insulin growth factor-I-enhanced green fluorescent protein fused protein as a tracer for immunoassay

The insulin-like growth factor-I (IGF-I) is an important polypeptide hormone under investigation for body metabolism study and for doping detection. Here, we describe for the first time the expression of a recombinant fusion protein of IGF-I and the enhanced green fluorescent protein (EGFP). The genetic fusion approach enables preparation of conjugates with 1:1 stoichiometry and homogeneous structure. The fused protein (EGFP-IGF-I) was expressed as a soluble protein in cytoplasm of Escherichia coli and its fluorescence and immunoreaction properties were thoroughly characterized. Finally, we demonstrated the utility of the EGFP-IGF-I fusion protein for the fluorescence immunoassay of IGF-1. The linear range of the assay is 1.6 x 10(-8) to 2.0 x 10(-6) M with a detection limit of 1.6 x 10(-8) M. To our knowledge, this is the first time that EGFP has been used as a quantitative label in a fusion protein to develop a quantitative assay for IGF-I. Furthermore, the use of genetically engineered fusion proteins, which combine peptide hormones with fluorescent protein, can lead to a new labeling approach to a number of bioanalytical applications.

Dietas vegetarianas e desempenho esportivo

As evidências atuais apontam benefícios da dieta vegetariana para a saúde humana. Contudo, a partir da adoção de práticas vegetarianas mais restritivas, confirmam-se os riscos à saúde. As dietas vegetarianas são caracterizadas pelo elevado consumo de carboidratos, fibras, magnésio, potássio, folato e antioxidantes, podendo apresentar deficiências em aminoácidos e ácidos graxos essenciais, cálcio, zinco, ferro e cobalamina. Pesquisas experimentais em humanos indicam que vegetarianos e não-vegetarianos apresentam capacidade aeróbica semelhante. Em relação ao desempenho em atividades de força e potência muscular, as pesquisas são escassas, mas as existentes não apontam diferenças significativas. Situações de risco cardiovascular têm sido confirmadas, devido ao provável quadro de hiperhomocisteinemia, em decorrência da baixa ingestão de cobalamina. As dietas vegetarianas são isentas de creatina, o que resulta em estoques musculares mais baixos nessa população. Possivelmente ocorrem alterações hormonais e metabólicas em resposta às dietas vegetarianas, como baixos níveis de testosterona e androstenediona. A função imune parece não ser prejudicada. Dessa forma, a prática de dietas vegetarianas apresenta-se compatível com a prática esportiva cotidiana, desde que bem planejada para evitar deficiências nutricionais.

Growth hormone 1 (GH1) gene and performance and post-race rectal temperature during the South African Ironman triathlon

BACKGROUND

Some studies have suggested that the insertion allele of the ACE gene is associated with endurance performance, including the Ironman triathlon. It is possible that this association is due to genetic linkage between the ACE I/D locus and the T/A variant in intron 4 of the neighbouring GH1 gene. The A variant is associated with lower levels of growth hormone production. Growth hormone has multiple effects, especially on metabolism during exercise and recovery from exercise. Its production during exercise has also been shown to stimulate sweat rate and heat loss.

OBJECTIVE

To determine whether the GH1 gene is associated with the performance and/or post-race rectal temperatures of competitors in the South African Ironman triathlon.

METHODS

A total of 169 of the fastest finishing white male triathletes who completed the 2000 and/or 2001 South African Ironman triathlon and 155 control subjects were genotyped for the T/A variant in the GH1 gene. Post-race rectal temperature was also determined in 103 of these triathletes.

RESULTS

There was no significant difference in the frequency of this polymorphism in the GH1 gene when the fastest finishing triathletes were compared with the control subjects. Post-race rectal temperatures were, however, significantly higher in those triathletes with an AA genotype (mean (SD) 37.7 (0.8) degrees C) compared with those with a TT genotype (37.2 (0.8) degrees C) (p = 0.019).

CONCLUSIONS

The T/A polymorphism in intron 4 of the GH1 gene was not associated with performance of the fastest finishers of the South African Ironman triathlon. Post-race rectal temperatures were, however, significantly higher in the fastest finishing athletes, who were homozygous for a GH1 genotype associated with lower growth hormone production.

Growth hormone isoforms, segments/fragments: Does a link exist with multifunctionality?

Understanding the relationship between growth hormone (GH) structure (its molecular fragments) and function via interaction with single or multiple receptors is of particular importance in clinical diagnostics and physiologic biochemistry. Direct and indirect actions of GH are numerous ranging from carbohydrate and lipid metabolism to growth effects at muscle and vessels. To this end, we have focused on the influence of physical exercise on GH synthesis and release into the circulation. Physical exercise is a physiological condition to which GH multifunctionality is inextricably linked and is thus important physiologically and pathologically. This review describes the potential human GH fragments with respect to protein hormone multifunctionality and the molecular regions of potential action. The intent of the review is to highlight human GH fragments and hypothesize their potential physiologic role. GH fragmentation is also reviewed in relation to the effects of physical exercise and hormone multifunctionality.

Growth hormone abuse: methods of detection

In the past two decades, growth hormone (GH) has been considered as a performance-enhancing drug in the sport world, certainly favoured by the awareness that there is not yet an approved method for detecting its abuse. Because resting or random measurements of plasma GH concentrations per se are meaningless, new methods have been devised to evaluate plasma levels of GH-sensitive substances that are more stable, and hence detectable, than the hormone itself. This review discusses some of the most recently proposed approaches, including a diagnostic algorithm, based on the timed application of different tests, which, collectively, would have a high diagnostic capability.

Combined evaluation of resting IGF-I, N-terminal propeptide of type III procollagen (PIIINP) and C-terminal cross-linked telopeptide of type I collagen (ICTP) levels might be useful for detecting inappropriate GH administration in athletes: a preliminary report

OBJECTIVE

To verify whether combined measurements of GH-dependent parameters might be useful in detecting exogenous recombinant GH (rGH) administration in male athletes from different disciplines.

METHODS

Sixty-six athletes (control group) were sampled for the evaluation of resting IGF-I, N-terminal propeptide of type III procollagen (PIIINP) and telopeptide type I collagen (ICTP). Cut-off values (mean + 2 SD) for IGF-I, PIIINP and ICTP were calculated and arbitrary scores (1.5, 2.0) were assigned to abnormal parameters. By using the sum of individual parameter scores, positive (> or = 3) or negative (< 3) scores were obtained. In addition, a subgroup of six athletes was treated for 3 weeks with rGH (0.09 IU/kg body weight, 6 days/week) and was similarly evaluated at the end of the 1st, 2nd and 3rd week (i.e. 18 samples).

RESULTS

Abnormal IGF-I, or PIIINP or ICTP levels were found, respectively, in one, two and four subjects (1.5-6.1%) of the control group (in the younger athletes); only one 19-year-old subject of this group obtained a positive score. Abnormal IGF-I, PIIINP and ICTP levels were found in 61.1-66.7% samples of the treated group. Positive cases were 3/6 at the 1st and 2nd week and 6/6 at the 3rd week. The sensitivity of the screening approach was 50-100% (at the 1st-2nd and 3rd week, respectively) and specificity was 98.5%.

CONCLUSION

This 'first level' screening test is safe, acceptable and relatively inexpensive. Further additional investigations of 'second level' (i.e. GH secretory profile, GH response to a GH-releasing peptide) can be retained to validate or exclude rGH administration or for the early diagnosis of infrequent endogenous GH hypersecretion.

Popular sports supplements and ergogenic aids

This article reviews the evidence-based ergogenic potential and adverse effects of 14 of the most common products in use by recreational and elite athletes today. Both legal and prohibited products are discussed. This is an aggressively marketed and controversial area of sports medicine worldwide. It is therefore prudent for the clinician to be well versed in the more popular supplements and drugs reputed to be ergogenic in order to distinguish fact from fiction.Antioxidants, proteins and amino acids are essential components of diet, but additional oral supplementation does not increase endurance or strength. Caffeine is ergogenic in certain aerobic activities. Creatine is ergogenic in repetitive anaerobic cycling sprints but not running or swimming. Ephedrine and pseudoephedrine may be ergogenic but have detrimental cardiovascular effects. Erythropoietin is ergogenic but increases the risk of thromboembolic events. beta-Hydroxy-beta-methylbutyrate has ergogenic potential in untrained individuals, but studies are needed on trained individuals. Human growth hormone and insulin growth factor-I decrease body fat and may increase lean muscle mass when given subcutaneously. Pyruvate is not ergogenic. The androgenic precursors androstenedione and dehydroepiandrosterone have not been shown to increase any parameters of strength and have potentially significant adverse effects. Anabolic steroids increase protein synthesis and muscle mass but with many adverse effects, some irreversible. Supplement claims on labels of product content and efficacy can be inaccurate and misleading.

Abuse of recombinant human growth hormone: studies in two different dog models

The search for inappropriately high growth hormone (GH) titers in plasma has been widely used to detect GH abuse, despite many shortcomings especially related to the pulsatile nature of GH secretion. Hence, the need for new anti-doping strategies. In the present study dogs were used to evaluate the ability of recombinant human GH (rhGH) to affect canine GH (cGH) release ensuing after somatostatin (SS) infusion withdrawal (SSIW) - a purported stimulus for the release of endogenous GH-releasing hormone (GHRH) - or the cGH response to administration of a GH-releasing peptide (GHRP). In the SSIW experiments, 8 beagle dogs of either gender (4-6 years old) were given a subcutaneous bolus injection of physiological saline (0.1 ml/kg) or, alternatively, rhGH (0.2 IU/kg s.c.) 60 min before the starting a continuous infusion of SS (4 microg/kg g h i.v.) of 1.5 h duration. In the dogs given a saline bolus, SSIW was followed by a 'rebound' rise in plasma cGH levels. In contrast, in dogs which had received the bolus injection of rhGH, the cGH rise elicited by SSIW was completely abrogated. In the set of experiments with a GHRP challenge, 13 dogs of either gender (3-12 years old) received the following treatment schedule at least 15 days apart: (1) a single bolus injection of rhGH (0.2 IU/kg s.c.); (2) rhGH (0.05 IU/kg s.c.) daily for 12 days; (3) rhGH (0.2 IU/kg s.c.) on alternate days for 12 days, and (4) rhGH (0.2 IU/kg s.c.) daily for 12 days. For each treatment schedule, before treatment, during treatment (24 h from the previous rhGH injection) and 1, 5 and 10 days after treatment, all dogs received an intravenous injection of a GHRP, EP51216 (125 microg/kg). In all treatments under baseline conditions, a single injection of EP51216 elicited an abrupt rise in plasma cGH. Twenty-four hours after the injection of an acute bolus of rhGH, the C(max) and AUC(0-90) of the GHRP-stimulated cGH response were significantly lower than the baseline cGH response. Five days later, there was a trend in the C(max) and AUC(0-90) towards complete restoration of the original values. One, 5 and 10 days after the end of the daily treatment with rhGH (0.05 IU/kg s.c.), no significant changes in the GHRP-stimulated cGH responses vs. the baseline GH response were recorded. In contrast, treatment with rhGH at a dose of 0.2 IU/kg s.c., on either alternate or daily administration, markedly reduced the GHRP-stimulated cGH responses evaluated after 3 and 5 rhGH injections. One day after the last rhGH injection, the EP51216-stimulated cGH response was still significantly reduced when compared with that present under baseline conditions. Five and 10 days following termination of rhGH treatment on alternate days, no significant differences in the C(max) and AUC(0-90) of the cGH responses to EP51216 were present. Differently, following the end of daily rhGH treatment, a marked inhibition in the C(max) of the cGH response to EP51216 was still present at 1 and 5 days, though not at 10 days. In conclusion, these studies show that a single administration of rhGH can abrogate the cGH response ensuing SSIW or acute stimulation by a GHRP. The inhibitory effect of rhGH on the cGH response to GHRP is present even 5 days after termination of a short-lived treatment with rhGH at a dose (0.2 IU/kg) which, in the dog, is undoubtedly lower than that used in humans for doping purposes. Extrapolation of these preclinical results to humans may pave the way for the development of a new rhGH anti-doping test.

Influence of Acute Exercise on Urinary Protein, Creatinine, Insulin-Like Growth Factor-I (IGF-I) and IGF Binding Protein-3 Concentrations in Children

Insulin-like growth factor-I (IGF-I) is a polypeptide hormone and present in human urine. Insulin-like growth factor binding protein-3 (IGFBP-3) is the major form of binding protein in human circulation and functions as a carrier for IGF-I. Our goal was to determine the effects of volleyball exercise on the concentrations of urine protein, creatinine, IGF-I, and IGFBP-3 in children and to find out whether these effects differ between boys and girls. Volunteer children (13 females and 14 males), aged 10-13 years old were included in this work. Weight and height of the subjects were measured, and urine samples of their were collected before and after 2 hours of exercise. Urinary protein, creatinine, IGF-I and IGFBP-3 levels were analysed. Urinary protein, creatinine and IGF-I concentrations were increased after two hours of exercise wheres urinary IGFBP-3 concentrations did not change. In addition, no statistically significant difference in all parameters analysed was observed between boys and girls of similar age and body mass index.

Urinary insulin-like growth factor I in athletes, before and after physical exercise, and in sedentary subjects

BACKGROUND

Insulin-like growth factor I (IGF-I), like growth hormone (GH), is excreted in urine in a smaller fraction than the concentration found in blood. Exercising subjects undergo post-exercise proteinuria. The present work aims to propose a method for urinary IGF-I analysis (uIGF-I) by defining urinary concentration in sedentary individuals and athletes before and after strenuous exercise.

METHODS

Urine samples were collected from 30 sedentary healthy male individuals during the morning and from 30 well-trained cyclists, before and after a competition of about 3 h (150 km). uIGF-I was measured in undiluted acidified urine by radioimmunoassay (RIA) method using a purified polyclonal rabbit antibody, human 125I-IGF-I and a second anti-rabbit antiserum. The acidification of the urine samples and the excess of IGF-II addition in the incubation medium of the assay were used to dissociate the binding and to block the interference from IGF binding proteins (IGFBPs). Urinary growth hormone (uGH), total protein (utPr) and creatinine (ucr) concentrations were also measured by immunoradiometric assay (IRMA), colorimetric and capillary electrophoresis methods, respectively.

RESULTS

The analysis range was 0-2500 ng/l (0-327 pmol/l), the intra- and inter-assay coefficients of variations (CVs) ranged from 2.3% to 7.8%, respectively. The detection limit was 0.6 pg/tube. The uIGF-I/creatinine (cr) ratio in healthy subjects was 70 +/- 8 pg/mg cr. The uIGF-I/creatinine ratio (pg/mg cr) was different (p<0.001) in athletes before vs. after competition 93 +/- 27 vs. 136 +/- 13. Athletes' [uIGF-I/total proteins] ratio (ng/mg tPr) before and post-exercise was 2.3 +/- 0.5 and 2.5 +/- 0.3, respectively.

CONCLUSIONS

uIGF-I assay appears to be an effective way of monitoring IGF-I excretion. In the cyclists, in the pre-exercise state, uIGF-I was comparable with that measured in sedentary healthy individuals. In the cyclists, after strenuous exercise, the increased uIGF-I/cr and uGH/cr ratios suggested a relation with the post-exercise proteinuria. In conclusion, proteinuria physiologically obtained, such as post-exercise proteinuria, might be a new approach in IGF-I system investigation.

Insulin-like growth factor-I and neurogenesis in the adult mammalian brain

In most brain regions of highly developed mammals, the majority of neurogenesis is terminated soon after birth. However, new neurons are continually generated throughout life in the subventricular zone and the dentate gyrus of the hippocampus. Insulin-like growth factor-I (IGF-I) is a polypeptide hormone that has demonstrated effects on these progenitor cells. IGF-I induces proliferation of isolated progenitors in culture, as well as affecting various aspects of neuronal induction and maturation. Moreover, systemic infusion of IGF-I increases both proliferation and neurogenesis in the adult rat hippocampus, and uptake of serum IGF-I by the brain parenchyma mediates the increase in neurogenesis induced by exercise. Neurogenesis in the adult brain is regulated by many factors including aging, chronic stress, depression and brain injury. Aging is associated with reductions in both hippocampal neurogenesis and IGF-I levels, and administration of IGF-I to old rats increases neurogenesis and reverses cognitive impairments. Similarly, stress and depression also inhibit neurogenesis, possibly via the associated reductions in serotonin or increases in circulating glucocorticoids. As both of these changes have the potential to down regulate IGF-I production by neural cells, stress may inhibit neurogenesis indirectly via downregulation of IGF-I. In contrast, brain injury stimulates neurogenesis, and is associated with upregulation of IGF-I in the brain. Thus, there is a tight correlation between IGF-I and neurogenesis in the adult brain under different conditions. Further studies are needed to clarify whether IGF-I does indeed mediate neurogenesis in these situations.