PubMed Health⌕ Search

Biomedical subjects

Dan M Cooper

Publications and source records attributed to Dan M Cooper.

At least 19 recordsLinked to original sources
PubMed2026

The effect of sex and endurance exercise training on the incretin signaling pathway in 17 rat tissues.

Incretin-based pharmacotherapies, particularly glucagon-like peptide-1 (GLP-1) receptor agonists, have transformed the treatment of type 2 diabetes, with demonstrated benefits across multiple organ systems. Their success has driven the investigation of related gut-derived hormones, most prominently dual GLP-1/glucose-dependent insulinotropic polypeptide (GIP) receptor agonists, but extend to other targets with similar metabolic functions. For this class of drugs, the extent to which organ health improvements are secondary to improved systemic glycemic control versus direct tissue signaling remains unclear, partly because receptor availability across tissues is poorly annotated. We leveraged data from the Molecular Transducers of Physical Activity Consortium to annotate incretin receptor expression across 17 tissues in Fischer 344 rats and the Genotype-Tissue Expression Portal for human-level receptor expression. Furthermore, given the role of exercise in the preservation of muscle mass during weight loss, we analyzed the effects of 1, 2, 4, or 8 wk of treadmill exercise training on incretin-related signaling at the epigenetic, transcript, and protein levels. Endurance training elicited sex- and tissue-specific changes in incretin receptor expression, including downregulation of Gcgr across brown adipose, adrenal glands, and white adipose tissue (WAT). Training-induced Gipr regulation occurred in the adrenal glands, brain cortex, and hippocampus. Collectively, these findings contribute to the map of incretin receptor biology and identify exercise-responsive regulatory axes that may underlie synergistic effects of exercise and incretin-based therapies on weight management and metabolic health.NEW & NOTEWORTHY This study provides the first multiomic, multitissue description of incretin signaling receptor expression and regulation in response to endurance exercise training. We identify time point and sex-specific changes in incretin signaling across tissues, highlighting training effects on Gcgr, Gipr, and Sctr regulation in the adrenals, WAT, and brain. These findings help establish an exercise-responsive incretin signaling axis that may identify interactions from incretin-based therapies and exercise-based lifestyle interventions.

Animals↗
PubMed2026

Endurance training attenuates acute exercise-induced monocyte transcriptomic responses in adolescents: sex-specific molecular adaptations.

Circulating monocytes contribute to atherogenesis and vascular dysfunction. Although clinical cardiovascular disease presents in adulthood, its biological origins often begin in youth and differ substantially between females and males. Twelve males and nine females (13-17 yr) completed an acute exercise protocol consisting of 10, 2-min cycling bouts at 70% of maximal work rate interspersed with 1-min rest intervals, performed before and after an 8-wk supervised endurance training intervention with brief supplementary strength work (60 min/session, 3 sessions/wk). Blood was collected before and immediately after each exercise challenge. Peripheral blood monocytes were isolated, and whole transcriptome RNA sequencing (RNA-seq) was performed. Before training, acute exercise induced a markedly greater monocyte transcriptomic response in females compared with males [5,135 vs. 567 differentially expressed transcripts, false discovery rate (FDR) < 0.1]. Pathway analyses identified vascular function-related pathways in males, whereas females showed enrichment of pathways related to adipose tissue cross talk and oxidative metabolism. Following training, the acute transcriptomic response was markedly attenuated in both sexes (165 transcripts in males and 94 in females, FDR < 0.1), representing an &#x223c;98% reduction in females and a &#x223c;70% reduction in males relative to pre-training responses. These findings reveal sex-specific monocyte responses to acute exercise in youth and suggest that endurance exercise alters immune transcriptional responsiveness in pathways relevant to vascular and cardiovascular health.NEW & NOTEWORTHY Acute exercise induced a markedly greater monocyte transcriptomic response in female adolescents than in males. Females showed activation of pathways related to adipose tissue signaling and oxidative metabolism, whereas males exhibited vascular-function pathways. Following exercise training, the monocyte transcriptomic response to acute exercise was substantially attenuated in both sexes. These findings identify sex-specific immune transcriptional responses to exercise during adolescence with potential implications for cardiovascular health.

Humans↗
PubMed2006

Effect of rhIL-6 infusion on GH-->IGF-I axis mediators in humans.

Exercise leads to simultaneous increases in mediators signaling apparently antagonistic functional responses such as growth factors and inflammatory mediators. The aim of the present study was to demonstrate the physiological effect of IL-6 on circulating components of the growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis. Twelve men (ages 26 +/- 2 yr) were divided into two groups (n = 6 in each group), receiving either albumin or recombinant human (rh) IL-6 infusion. IL-6 was infused via an antecubital vein, and a contralateral antecubital vein was used for blood sampling. The IL-6 dose was chosen to reach plasma levels of IL-6 characteristic of intense exercise (5 microg/h, for 3 h, resulting in plasma levels of 100 pg/ml). Blood samples for GH, GH binding protein, IGF-I, and IGF binding protein (IGFBP)-1 and -3 were collected at baseline, 30 min, and 1, 2, 3, 4, 5, and 8 h after the beginning of the rhIL-6 infusion. IL-6 levels increased only in the rhIL-6-infused group (P < 0.0005) and returned to baseline after the infusion was stopped. IL-6 infusion led to a significant increase in GH, peaking 1 h after the beginning of infusion (P < 0.001). A decrease in total IGF-I levels was noted only in the rhIL-6-infused group (P < 0.027). An initial decrease in IGFBP-1 levels was noted in both groups during infusion (P < 0.03). Following the initial decrease, there was a significant increase in IGFBP-1 levels only in the IL-6-infused participants, peaking at 2 after the infusion cessation (P < 0.001). IL-6 infusion had no effect on GH binding protein, IGFBP-3, and acid-labile subunit levels. rhIL-6 levels similar to the levels found after strenuous exercise induced a typical exercise-associated GH-->IGF-I axis response (increase GH, decreased IGF-I, and elevated IGFBP-1). The results suggest that IL-6 plays a role in the GH-->IGF-I response to intense exercise.

Adult↗
PubMed2006

Exercise-induced bronchoconstriction alters airway nitric oxide exchange in a pattern distinct from spirometry.

Exhaled nitric oxide (NO) is altered in asthmatic subjects with exercise-induced bronchoconstriction (EIB). However, the physiological interpretation of exhaled NO is limited because of its dependence on exhalation flow and the inability to distinguish completely proximal (large airway) from peripheral (small airway and alveolar) contributions. We estimated flow-independent NO exchange parameters that partition exhaled NO into proximal and peripheral contributions at baseline, postexercise challenge, and postbronchodilator administration in steroid-naive mild-intermittent asthmatic subjects with EIB (24-43 yr old, n = 9) and healthy controls (20-31 yr old, n = 9). The mean +/- SD maximum airway wall flux and airway diffusing capacity were elevated and forced expiratory flow, midexpiratory phase (FEF(25-75)), forced expiratory volume in 1 s (FEV(1)), and FEV(1)/forced vital capacity (FVC) were reduced at baseline in subjects with EIB compared with healthy controls, whereas the steady-state alveolar concentration of NO and FVC were not different. Compared with the response of healthy controls, exercise challenge significantly reduced FEV(1) (-23 +/- 15%), FEF(25-75) (-37 +/- 18%), FVC (-12 +/- 12%), FEV(1)/FVC (-13 +/- 8%), and maximum airway wall flux (-35 +/- 11%) relative to baseline in subjects with EIB, whereas bronchodilator administration only increased FEV(1) (+20 +/- 21%), FEF(25-75) (+56 +/- 41%), and FEV(1)/FVC (+13 +/- 9%). We conclude that mild-intermittent steroid-naive asthmatic subjects with EIB have altered airway NO exchange dynamics at baseline and after exercise challenge but that these changes occur by distinct mechanisms and are not correlated with alterations in spirometry.

Adaptation, Physiological↗
PubMed2006

Reduced tetanus antibody titers in overweight children.

Under-nutrition impairs immune responses, but far less is known about the impact of over-nutrition, such as obesity, on the response to vaccines. We measured the effect of childhood overweight status on inflammatory mediators, circulating immunoglobulins and tetanus antibodies in fifteen overweight children (BMI > 85 age-adjusted percentile) and 15 age-matched normal weight controls. Fitness was measured by a progressive ramp type exercise test. Lean body mass (LBM) and fat mass were determined by DXA. Tumor necrosis factor-a (TNF-a), interleukin-6 (IL-6), interleukin-1 beta (IL-1beta) and interleukin-1 receptor antagonist (IL-1ra) were used to assess the inflammatory status; and circulating immunoglobulins (IgM, IgA, IgG and IgG subclasses) and specific IgG titer to tetanus were used to assess humoral immunity. Overweight children had higher LBM and percent fat mass, and lower peak VO2 normalized to body weight. IL-6 was significantly higher in the obese children (2.6 +/- 0.3 vs. 1.3 +/- 0.3 pg/ml, in overweight and normal weight children, respectively; p < 0.05). No significant differences were found in TNF-a, IL-1beta and IL-1ra between the groups. No significant differences were found in immunoglobulin levels (IgM, IgA, IgG and IgG subclasses) between the groups. Anti-tetanus IgG antibodies were significantly lower in the overweight children compared to normal weight controls (2.4 +/- 0.6 vs. 4.2 +/- 0.5 IU/ml, in overweight and normal weight children, respectively; p < 0.05). The reduced specific antibody response to tetanus in obese children and adolescent might be due to mechanical factors such as lower relative vaccination dose, or reduced absorption from the injection site due to increased adipose tissue, or related to reduce immune response due to the chronic low grade inflammation expressed by the higher levels of IL-6.

Adolescent↗
PubMed2006

Impaired motor control in patients with benign focal epilepsy of childhood.

Upper extremity motor function was quantitatively assessed in 6 children (age 7-11 years) treated with antiepileptic drugs for benign focal epilepsies of childhood and compared with that of 30 age-matched normal children. Both motor performance and adaptation to perturbing mechanical constraints imposed by a robotic device were significantly impaired in children with benign focal epilepsies of childhood. Our findings thus question whether certain "benign" epilepsies are truly benign and whether pharmacologic treatment might contribute to motor impairment.

Anticonvulsants↗
PubMed2006

Exercise, caloric restriction, and systemic oxidative stress.

BACKGROUND: In humans, the main sources of reactive oxygen species (ROS), the molecules causing oxidative stress, are mitochondrial superoxide ions and neutrophil-derived oxidative radicals. Circulating antioxidants contribute to the protection against oxidative stress. Although the formation of ROS and secretion of antioxidants are independently regulated by exercise and diet, little is known about their combined effect. We hypothesized that relatively brief, intense exercise training may reduce systemic oxidation via an intrinsic mechanism, independent of changes in circulating antioxidants and of neutrophil-derived enzymes (as may be caused by concomitant caloric restriction). METHODS: Nineteen volunteers exercised for 7 days, 3 hours/day at 75% of oxygen uptake. Caloric intake was either 110% of caloric expenditure (high calorie, n=10) or 75% of caloric expenditure (low calorie, n=9). Blood samples for F2-isoprostanes, catalase, myeloperoxidase (MPO), interleukin-x (IL-x), white blood cells (WBCs), and other metabolic variables were taken at baseline, at the end of training, and 1 week after completion of the study. RESULTS: Serum F2-isoprostanes (microg/mL), markers of lipid peroxidation, were similarly reduced after 7 days of exercise in the high-calorie (from 35+/-4 to 27+/-2) and low-calorie (from 35+/-3 to 24+/-2) groups. Similar reductions were observed in IL-x concentrations. Conversely, no change was observed in circulating concentrations of the antioxidant catalase. Whereas total WBCs and neutrophil counts were significantly reduced in the low-calorie group only, no difference in neutrophil-derived MPO was measured between groups. CONCLUSION: A significant reduction in systemic oxidation may occur relatively early during intense exercise training in healthy young men, independent of caloric intake. The potential contribution to these effects of circulating antioxidants and neutrophil-derived oxidative enzymes will require further investigation.

Adolescent↗
PubMed2005

Reduced exercise-associated response of the GH-IGF-I axis and catecholamines in obese children and adolescents.

Obesity blunts catecholamine and growth hormone (GH) responses to exercise in adults, but the effect of obesity on these exercise-associated hormonal responses in children is unclear. Therefore, the aim of the present study was to asses the effect of childhood obesity on the counterregulatory hormonal response to acute exercise. Twenty-five obese children (Ob; body mass index > 95%), and 25 age, gender, and maturity-matched normal-weight controls (NW) participated in the study. Exercise consisted of ten 2-min bouts of constant-cycle ergometry above the anaerobic threshold, with 1-min rest intervals between each bout. Pre-, post-, and 120-min postexercise blood samples were collected for circulating components of the GH-IGF-I axis and catecholamines. There were no differences in peak exercise heart rate, serum lactate, and peak O2 uptake normalized to lean body mass between the groups. Obesity attenuated the GH response to exercise (8.9 +/- 1.1 vs. 3.4 +/- 0.7 ng/ml in NW and Ob participants, respectively; P < 0.02). No significant differences in the response to exercise were found for other components of the GH-IGF-I axis. Obesity attenuated the catecholamine response to exercise (epinephrine: 52.5 +/- 12.7 vs. 18.7 +/- 3.7 pg/ml, P < 0.02; norepinephrine: 479.5 +/- 109.9 vs. 218.0 +/- 26.0 pg/ml, P < 0.04; dopamine: 17.2 +/- 2.9 vs. 3.5 +/- 1.9 pg/ml, P < 0.006 in NW and Ob, respectively). Insulin levels were significantly higher in the obese children and dropped significantly after exercise in both groups. Despite the elevated insulin levels and the blunted counterregulatory response, none of the participants developed hypoglycemia. Childhood obesity was associated with attenuated GH and catecholamine response to acute exercise. These abnormalities were compensated for, so that exercise was not associated with hypoglycemia, despite increased insulin levels in obese children.

Adolescent↗
PubMed2005

Constitutive pro- and anti-inflammatory cytokine and growth factor response to exercise in leukocytes.

Leukocytosis following exercise is a well-described phenomenon of stress/inflammatory activation in healthy humans. We hypothesized that, despite this increase in circulating inflammatory cells, exercise would paradoxically induce expression of both pro- and anti-inflammatory cytokines and growth factors within these cells. To test this hypothesis, 11 healthy adult men, 18-30 yr old, performed a 30-min bout of heavy cycling exercise; blood sampling was at baseline, end-exercise, and 60 min into recovery. The percentage of leukocytes positive for intracellular cytokines and growth factors and mean fluorescence intensity was obtained by flow cytometry. Proinflammatory cytokines (IL-1alpha, IL-2, IFN-gamma, and TNF-alpha), a pleiotropic cytokine (IL-6), and anti-inflammatory cytokines and growth factors [IL-4, IL-10, growth hormone (GH), and IGF-I] were examined. Median fluorescence intensity was not affected by exercise; however, we found a number of significant changes (P < 0.05 by mixed linear model and modified t-test) in the numbers of circulating cells positive for particular mediators. The pattern of expression reflected both pro- and anti-inflammatory functions. In T-helper lymphocytes, TNF-alpha, but also IL-6, and IL-4 were significantly increased. In monocytes, both IFN-gamma and IL-4 increased. B-lymphocytes positive for GH and IGF-I increased significantly. GH-positive granulocytes also significantly increased. Collectively, these observations indicate that exercise primes an array of pro- and anti-inflammatory and growth factor expression within circulating leukocytes, perhaps preparing the organism to effectively respond to a variety of stressors imposed by exercise.

Adolescent↗
PubMed2005

Effect of muscle fatigue on internal model formation and retention during reaching with the arm.

The motor system adapts to novel dynamic environments by forming internal models that predict the muscle forces needed to move skillfully. The goal of this study was to determine how muscle fatigue affects internal model formation during arm movement and whether an internal model acquired while fatigued could be recalled accurately after rest. Twelve subjects adapted to a viscous force field applied by a lightweight robot as they reached to a target. They then reached while being resisted by elastic bands until they could no longer touch the target. This protocol reduced the strength of the muscles used to resist the force field by approximately 20%. The bands were removed, and subjects adapted again to the viscous force field. Their adaptive ability, quantified by the amount and time constant of adaptation, was not significantly impaired following fatigue. The subjects then rested, recovering approximately 70% of their lost force-generation ability. When they reached in the force field again, their prediction of the force field strength was different than in a nonfatigued state. This alteration was consistent with the use of a higher level of effort than normally used to counteract the force field. These results suggest that recovery from fatigue can affect recall of an internal model, even when the fatigue did not substantially affect the motor system's ability to form the model. Recovery from fatigue apparently affects recall because the motor system represents internal models as a mapping between effort and movement and relies on practice to recalibrate this mapping.

Adaptation, Physiological↗
PubMed2005

Hormonal effect on psoriasis in pregnancy and post partum.

OBJECTIVES: To investigate prospectively how psoriasis fluctuates in pregnancy and post partum and to correlate hormone levels in pregnancy (progesterone and estrogens) with psoriatic change. DESIGN: Psoriatic body surface area (BSA) in pregnant patients with psoriasis (study group) and nonpregnant, menstruating patients with psoriasis (control group) were assessed 5 times over a year. Hormone levels (progesterone and estrogens) were measured in the study group and correlated with change in BSA. SETTING: University-affiliated obstetric and dermatology clinics. PATIENTS: Forty-seven pregnant patients in the psoriasis group and 27 nonpregnant, menstruating patients in the control group. RESULTS: During pregnancy, 55% of the patients reported improvement, 21% reported no change, and 23% reported worsening. However, post partum, only 9% of patients reported improvement, 26% reported no change, and 65% reported worsening. Psoriatic BSA decreased significantly from 10 to 20 weeks' gestation (P<.001) compared with controls, whereas BSA increased significantly by 6 weeks post partum (P = .001) compared with controls. In patients with 10% or greater psoriatic BSA who reported improvement (n = 16; mean BSA, 40%), lesions decreased by 83.8% during pregnancy. There were significant or near significant correlations between improvement in BSA and estradiol (P = .009, r = 0.648), estriol (P = .06, r = 0.491), and the ratio of estrogen to progesterone (P = .006, r = 0.671). CONCLUSION: High levels of estrogen correlated with improvement in psoriasis, whereas progesterone levels did not correlate with psoriatic change.

Adult↗
PubMed2005

Breath ethanol and acetone as indicators of serum glucose levels: an initial report.

BACKGROUND: Many volatile organic compounds are present in exhaled breath and may represent by-products of endogenous biological processes. Ethanol is produced via alcoholic fermentation of glucose by gut bacteria and yeast, while acetone derives from oxidations of free fatty acids, influenced by glucose metabolism. We hypothesized that the integrated analysis of breath ethanol and acetone would provide a good approximation of the blood glucose profile during a glucose load. METHODS: We collected simultaneous exhaled breath gas, ambient air, and serum glucose and insulin samples from 10 healthy volunteers at baseline and during an oral glucose tolerance test (OGTT) (ingestion of 75 g of glucose followed by 120 min of sampling). Gas samples were analyzed by gas chromatography/mass spectrometry. RESULTS: Mean glucose values displayed a typical OGTT pattern (rapid increase, peak values at 30-60 min, and gradual return to near baseline by 120 min). Breath ethanol displayed a similar pattern early in the test, with peak values at 30 min; this was followed by a fast return to basal levels by 60 min. Breath acetone decreased progressively below basal levels, with lowest readings obtained at 120 min. A multiple regression analysis of glucose, ethanol, and acetone was used to estimate glucose profiles that correlated with measured glucose values with an average individual correlation coefficient of 0.70, and not lower than 0.41 in any subject. CONCLUSION: The integrated analysis of multiple exhaled gases may serve as a marker of blood glucose levels. Further studies are needed to assess the usefulness of this method in different populations.

Acetone↗
PubMed2004

Effects of exercise on gene expression in human peripheral blood mononuclear cells.

Exercise leads to increases in circulating levels of peripheral blood mononuclear cells (PBMCs) and to a simultaneous, seemingly paradoxical increase in both pro- and anti-inflammatory mediators. Whether this is paralleled by changes in gene expression within the circulating population of PBMCs is not fully understood. Fifteen healthy men (18-30 yr old) performed 30 min of constant work rate cycle ergometry (approximately 80% peak O2 uptake). Blood samples were obtained preexercise (Pre), end-exercise (End-Ex), and 60 min into recovery (Recovery), and gene expression was measured using microarray analysis (Affymetrix GeneChips). Significant differential gene expression was defined with a posterior probability of differential expression of 0.99 and a Bayesian P value of 0.005. Significant changes were observed from Pre to End-Ex in 311 genes, from End-Ex to Recovery in 552 genes, and from Pre to Recovery in 293 genes. Pre to End-Ex upregulation of PBMC genes related to stress and inflammation [e.g., heat shock protein 70 (3.70-fold) and dual-specificity phosphatase-1 (4.45-fold)] was followed by a return of these genes to baseline by Recovery. The gene for interleukin-1 receptor antagonist (an anti-inflammatory mediator) increased between End-Ex and Recovery (1.52-fold). Chemokine genes associated with inflammatory diseases [macrophage inflammatory protein-1alpha (1.84-fold) and -1beta (2.88-fold), and regulation-on-activation, normal T cell expressed and secreted (1.34-fold)] were upregulated but returned to baseline by Recovery. Exercise also upregulated growth and repair genes such as epiregulin (3.50-fold), platelet-derived growth factor (1.55-fold), and hypoxia-inducible factor-I (2.40-fold). A single bout of heavy exercise substantially alters PBMC gene expression characterized in many cases by a brisk activation and deactivation of genes associated with stress, inflammation, and tissue repair.

Adolescent↗
PubMed2004

Probing the impact of axial diffusion on nitric oxide exchange dynamics with heliox.

Exhaled nitric oxide (NO) is a potential noninvasive index of lung inflammation and is thought to arise from the alveolar and airway regions of the lungs. A two-compartment model has been used to describe NO exchange; however, the model neglects axial diffusion of NO in the gas phase, and recent theoretical studies suggest that this may introduce significant error. We used heliox (80% helium, 20% oxygen) as the insufflating gas to probe the impact of axial diffusion (molecular diffusivity of NO is increased 2.3-fold relative to air) in healthy adults (21-38 yr old, n = 9). Heliox decreased the plateau concentration of exhaled NO by 45% (exhalation flow rate of 50 ml/s). In addition, the total mass of NO exhaled in phase I and II after a 20-s breath hold was reduced by 36%. A single-path trumpet model that considers axial diffusion predicts a 50% increase in the maximum airway flux of NO and a near-zero alveolar concentration (Ca(NO)) and source. Furthermore, when NO elimination is plotted vs. constant exhalation flow rate (range 50-500 ml/s), the slope has been previously interpreted as a nonzero Ca(NO) (range 1-5 ppb); however, the trumpet model predicts a positive slope of 0.4-2.1 ppb despite a zero Ca(NO) because of a diminishing impact of axial diffusion as flow rate increases. We conclude that axial diffusion leads to a significant backdiffusion of NO from the airways to the alveolar region that significantly impacts the partitioning of airway and alveolar contributions to exhaled NO.

Adult↗
PubMed2004

A controlled evaluation of a school-based intervention to promote physical activity among sedentary adolescent females: project FAB.

PURPOSE: To evaluate the effect of a school-based intervention designed to increase physical activity among sedentary adolescent females. METHODS: Sedentary adolescent females were assigned to a control (n = 22) or intervention (n = 25) group based on school attended. Students at the intervention school enrolled in a special physical education class. All participants completed clinical and behavioral assessments at baseline and after 4 months. Physiological tests included cardiovascular fitness (VO(2) peak via bicycle ergometer), body composition (via dual x-ray absorptiometer; DEXA), and body mass index (BMI). Psychosocial assessments included a physical activity recall, report of lifestyle activity, and self-efficacy, perceived barriers, social support, and enjoyment related to physical activity. Data were analyzed using repeated measures analyses of variance (ANOVAs) for continuous variables, and logistic regression for hard activity (scored as a dichotomous variable). RESULTS: The intervention had a significant effect on cardiovascular fitness (p =.017), lifestyle activity (p =.005), and light (p =.023), moderate (p =.007), and hard (p =.006) activity. All changes were in a direction that favored the intervention. There was no effect of the intervention on psychosocial factors related to exercise. CONCLUSIONS: A school-based intervention targeting sedentary adolescent females can increase physical activity and prevent a decline in cardiovascular fitness. Moreover, the effect of the intervention generalized to lifestyle activity.

Adolescent↗
PubMed2004

Cytokines and growth factors during and after a wrestling season in adolescent boys.

PURPOSE: Brief periods of aerobic exercise training lead to reductions, rather then the expected increases in circulating IGF-I. We hypothesized that intense exercise training in adolescents initially leads to simultaneous increases in proinflammatory cytokines and decreases in activity of the GH/IGF-I axis; and that as exercise training proceeds, levels of proinflammatory cytokines become reduced, and a rebound in IGF-I ensues leading to the higher IGF-I levels. METHOD: To test this, we evaluated the GH/IGF-I axis and levels of inflammatory cytokines (IL-6, TNF-alpha, IL-1beta, IL-1ra), body composition, and fitness in 13 healthy adolescent boys (mean age 15.9 +/- 0.3 yr) over the course of a high-school wrestling season. Subjects were tested preseason, midseason (6 wk), peak season (12-14 wk), and 4 wk postseason. RESULTS: No significant weight loss was noted throughout the season. During the wrestling season (mid and peak) both total (P < 0.046) and free (P < 0.002) IGF-I levels decreased, whereas proinflammatory cytokines (IL-1ra, P < 0.005; IGFBP-1, P < 0.013; and IGFBP-2, P < 0.025) increased. GHBP (P < 0.018) levels also decreased during the season. In the postseason, there were significant increases in GHBP, and free and total IGF-I, whereas proinflammatory cytokines decreased. CONCLUSIONS: An initial catabolic-type hormonal response occurs with intense exercise training in adolescents. This is followed by a rebound in circulating growth factors when the period of heavy training ceases.

Adolescent↗