Regular Physical Activity Influences Plasma Ghrelin Concentration in Adolescent Girls

Serum sclerostin concentration is associated with specific adipose, muscle and bone tissue markers in lean adolescent females with increased physical activity

OBJECTIVES

Sclerostin is an important regulator of bone mass involving the Wnt/β-catenin signalling pathway. Relatively few studies have investigated the relationships of circulating sclerostin levels with adiposity-related and muscle-related biochemical factors in individuals with increased energy metabolism. The aim of this study was to investigate the associations of circulating sclerostin with adipokines, myokines, osteokines and body composition values in lean adolescent females with increased physical activity.

METHODS

A total of 73 adolescent females who were physically active and aged 14-18 years old participated in the study. Sclerostin, leptin, resistin, tumour necrosis factor (TNF)-α, interleukin (IL)-6, irisin, osteocalcin, C-terminal telopeptide of type I collagen (CTx), insulin-like growth factor (IGF)-1 and insulin were obtained from fasting blood samples. Body composition was measured by dual-energy X-ray absorptiometry (DXA) and analyzed for body fat mass, lean body mass, bone mineral content and muscle mass.

RESULTS

Serum sclerostin (117.9 ± 60.3 pg/mL) was correlated with age, age at menarche, body fat, muscle mass, training activity, leptin, TNF-α, irisin, osteocalcin, CTx and IGF-1. Multivariate linear regression analysis demonstrated that fat mass (β = 0.434; p = 0.001), leptin (β = -0.308; p = 0.015), irisin (β = 0.227; p = 0.024) and CTx (β = 0.290; p = 0.031) were the most important predictors of serum sclerostin concentration.

CONCLUSIONS

Bone-derived sclerostin is associated with specific adipokine, myokine and osteokine values in lean adolescent females with increased physical activity. These results suggest that the interactions between bone, adipose and muscle tissues could also be associated with circulating sclerostin concentrations.

Differences in the Postprandial Release of Appetite-Related Hormones Between Active and Inactive Men

Active, as opposed to inactive, individuals are able to adjust their energy intake after preloads of different energy contents. The mechanisms responsible for this remain unknown. This study examined differences in plasma concentration of appetite-related hormones in response to breakfasts of different energy contents, between active and inactive men. Sixteen healthy nonobese (body mass index = 18.5-27 kg/m²) adult males (nine active and seven inactive) participated in this study. Participants were given a high-energy (570 kcal) or a low-energy (205 kcal) breakfast in a random order. Subjective feelings of appetite and plasma concentrations of active ghrelin, active glucagon-like peptide-1, total peptide YY (PYY), cholecystokinin, and insulin were measured in fasting and every 30 min up to 2.5 hr, in response to both breakfasts. Mixed analysis of variance (fat mass [in percentage] as a covariate) revealed a higher concentration of active ghrelin and lower concentration of glucagon-like peptide-1, and cholecystokinin after the low-energy breakfast (p < .001 for all). Postprandial concentration of PYY was greater after the high energy compared with the low energy, but for inactive participants only (p = .014). Active participants had lower postprandial concentrations of insulin than inactive participants (p < .001). Differences in postprandial insulin between breakfasts were significantly lower in active compared with inactive participants (p < .001). Physical activity seems to modulate the postprandial plasma concentration of insulin and PYY after the intake of breakfasts of different energy contents, and that may contribute, at least partially, to the differences in short-term appetite control between active and inactive individuals.

Role of Relative Malnutrition in Exercise Hypogonadal Male Condition

OBJECTIVE

Exercise hypogonadal male condition is a well-recognized condition in women but much less understood in men. The aim of this case report is to highlight exercise-induced hypogonadotropic hypogonadism in a male who recovered with lifestyle modifications.

METHODS

We report a case of an adolescent male who developed hypogonadotropic hypogonadism secondary to excessive exercise and malnutrition that was followed up for a year without exogenous testosterone supplementation. Informed consent was obtained from the patient for his information to be used in a manuscript submitted to a journal.

RESULTS

An 18-yr-old adolescent male presented to the clinic with symptoms of fatigue and low endurance, low libido, and lack of morning erections. At the time of his presentation, he was running about 60 miles per week for school cross-country team in addition to cross training with kickboxing. Physical examination was remarkable for low body mass index of 19 kg·m but was otherwise normal. Biochemical workup confirmed hypogonadotropic hypogonadism and a mild pancytopenia. Other pituitary laboratory values and MRI of the brain were unremarkable. Bone marrow biopsy performed for anemia showed features consistent with malnutrition. With a working diagnosis of exercise hypogonadal male condition, he was advised to reduce the frequency and intensity of his exercise and increase calorie intake. Cell counts and testosterone levels normalized, and his symptoms resolved without any further interventions.

CONCLUSION

Significant reversible hypogonadism can develop after intensive and prolonged exercise. One of the mechanisms of hypogonadism in endurance athletes performing intensive exercise could be relative malnutrition. Further studies to evaluate the role of nutrition and body mass index in male endurance athletes presenting with hypogonadism are needed to identify the underlying mechanism of this condition.

Increased sclerostin and preadipocyte factor-1 levels in prepubertal rhythmic gymnasts: associations with bone mineral density, body composition, and adipocytokine values

SUMMARY

Rhythmic gymnastics as high-impact bone loading sport has positive effects on bone mineralization in prepubertal years. Sclerostin and preadipocyte factor-1 (Pref-1) are hormones that inhibit bone formation. The present study demonstrates that these hormones are higher in gymnasts, and gymnasts present higher bone mineral density (BMD) as compared to controls.

INTRODUCTION

Rhythmic gymnasts (RG) start their heavy trainings already in prepuberty and despite of low body fat mass (FM) and hypoleptinemia, their BMD is higher than in non-trained normal girls. The specific role of sclerostin and Pref-1, which are the inhibitors of bone formation, in bone development is not well understood. The impact of sclerostin and Pref-1 levels on BMD, body composition, and adipocytokine values was studied in prepubertal RG and untrained controls (UC).

METHODS

Sixty-four 9-10-year-old girls were divided into RG (n = 32) and UC (n = 32) groups. Bone mineral and body composition values were measured by dual-energy X-ray absorptiometry and bone age by X-ray. Sclerostin, Pref-1, leptin, and adiponectin levels were measured from fasting blood samples.

RESULTS

Sclerostin (RG 19.8 ± 6.3 pmol/l; UC 15.8 ± 5.4 pmol/l) and Pref-1 (RG 1.6 ± 1.0 ng/ml; UC 1.1 ± 0.5 ng/ml) were higher (p < 0.05) in RG compared with UC. Sclerostin was related to adiponectin (r = 0.41; p < 0.05) in UC. No relationship was found between sclerostin and Pref-1 with BMD values in prepubertal RG and age-matched UC groups.

CONCLUSIONS

Sclerostin and Pref-1 levels are higher in RG compared to UC girls. Specific physical activity pattern seen in prepubertal RG has a beneficial effect on bone mineralization despite increased levels of hormones that inhibit bone formation.

Adipocytokine and ghrelin levels in relation to bone mineral density in prepubertal rhythmic gymnasts entering puberty: a 3-year follow-up study

PURPOSE

To investigate changes in bone mineral density (BMD) in rhythmic gymnasts (RG) entering puberty and their age-matched untrained controls (UC) over the 36-month period, and associations with leptin, adiponectin and ghrelin over this period.

METHODS

Whole body (WB), lumbar spine (LS) and femoral neck (FN) BMD, WB bone mineral content (BMC), and leptin, adiponectin and ghrelin were measured in 35 RG and 33 UC girls at baseline and at 12-month intervals over the next 3 years. The change over the 36 months was calculated (∆ score).

RESULTS

The pubertal development over the next 36 months was slower in RG compard to UC, while there was no difference in bone age development between the groups. BMD at all sites was higher in RG in comparison with UC at every measurement point. ∆LS BMD and ∆FN BMD, but not ∆WB BMD and ∆WB BMC, were higher in RG compared with UC. None of the measured hormones at baseline or their ∆ scores correlated with ∆BMD and ∆BMC in RG. Baseline fat free mass correlated with ∆WB BMD and ∆WB BMC in RG, while baseline leptin was related to ∆WB BMC, ∆WB BMD and ∆LS BMD in UC.

CONCLUSIONS

Measured baseline hormones and their ∆ scores did not correlate with increases in bone mineral values in RG entering puberty. Although the pubertal development in RG was slower than in UC, high-intensity training appeared to increase BMD growth and counterbalance negative effects of slow pubertal develpment, lower fat mass and leptin in RG.

Do swimming exercises induce anthropometric changes in adolescents?

The aim of this study was to evaluate the influence of regular participation in school swimming lessons on anthropometric variables and postural defect occurrence in junior high school students. An intervention group (n = 116) and a control group (n = 114) of boys and girls aged 13.4 ± 0.3 years had an equal physical education obligatory course requirement at school, with the intervention group additionally participating in swimming class once a week for 2 years. Anthropometric variables were recorded in both groups 3 times between autumn 2006 and 2008, and a clinical examination was conducted twice during this same period of time. Students from the intervention group had lower body mass than their peers in the control group at the end of the course (ANOVA, P < 0.05). The differences in body height and body mass index between the groups were insignificant. In swimming students, the correction in scoliosis was more distinct than in the control group (P < 0.05 by chi-squared test). The groups did not differ significantly in occurrence of other postural defects. Regular participation in standard swimming education at school did not have much effect on postural defects in adolescents. A special program of corrective water exercises should be applied to the school physical education syllabus.

Cross-sectional associations between physical activity and selected coronary heart disease risk factors in young adults. The Cardiovascular Risk in Young Finns Study

OBJECTIVE

Physical activity (PA) may reduce the risk of coronary heart disease (CHD) by inducing beneficial changes in several risk factors. We studied the associations between PA and a range of risk markers of CHD in young adults.

METHODS AND RESULTS

We measured serum lipoproteins, oxidized LDL, adipokines, inflammatory markers, metabolic markers, and arginine metabolites in 2,268 individuals (age 24-39 y). Participants were asked frequency, duration, and intensity of PA in leisure time. In addition, commuting to work was assessed. In both sexes, PA was inversely associated with waist circumference (all P < 0.0001). After controlling for sex, age, and waist circumference, PA was directly associated with HDL-cholesterol and apolipoprotein A1, and inversely with heart rate, smoking, oxidized LDL, apolipoprotein B, insulin, glucose, C-reactive protein, leptin, L-arginine, and phospholipase A2 activity (all P < 0.05).

CONCLUSION

These population-based data are consistent with the idea that the beneficial effects of PA on CHD risk are mediated by favorable influences on several risk factors, as judged by independent relations to markers of lipoprotein metabolism, glucose metabolism, and inflammation. These associations reflect beneficial effects on cardiovascular health in both sexes and may offer mechanistic insights for the inverse association between PA and CHD.

The effect of three-month pre-season preparatory period and short-term exercise on plasma leptin, adiponectin, visfatin, and ghrelin levels in young female handball and basketball players

OBJECTIVE

The aim of the study was to assess the effect of a 3-month pre-season preparatory period and shortterm moderate aerobic exercise and intensive fitness and speed exercise on adipokine and ghrelin levels in young female handball and basketball players.

MATERIALS AND METHODS

Fifty healthy young female professional basketball and handball players were enrolled into the study before the opening of the season (after a 2-month holiday with no training or dietary restrictions). Serum estradiol and plasma leptin, adiponectin, visfatin, and ghrelin levels were determined at the beginning and the end of a 3-month period of moderate aerobic training. Plasma adipokines and ghrelin levels were additionally assessed after 2 h of moderate aerobic exercise or after intensive fitness and speed exercise training.

RESULTS

Long-term moderate aerobic exercise was followed by a significant decrease in plasma ghrelin and leptin levels (921±300 vs 575±572 pg/ml, p<0.001 and 16.4±15.6 vs 11.8±16.3 ng/ml, p<0.01, respectively); plasma adiponectin and visfatin remained unchanged. No changes were observed in plasma ghrelin and leptin levels after short-term moderate aerobic exercise or after intensive fitness and speed exercise. Plasma visfatin concentration increased significantly after short-term moderate aerobic exercise (22.1±8.7 vs 27.6±9.0 ng/ml, p<0.001), whilst adiponectin increased after intensive fitness and speed exercise (16.7±7.8 vs 21.0±9.8 μg/ml, p<0.001).

CONCLUSIONS

Regular moderate aerobic training in preparation for the match season is followed by a decline in circulating leptin and ghrelin levels even in athletes without body weight changes. Short-term intensive fitness and moderate aerobic exercise seem to modulate the production of different adipokines.

Plasma adipocytokine and ghrelin levels in relation to bone mineral density in prepubertal rhythmic gymnasts

The aim of the present study was to investigate possible differences in plasma adipocytokine and ghrelin levels and body composition parameters in prepubertal rhythmic gymnasts (RG) and untrained controls (UC), and to examine the relationships of bone mineral density (BMD) with hormonal status in prepubertal children with different physical activity patterns. Eighty-nine 7- to 9-year-old girls participated in the study (RG, n = 46; UC, n = 43). Body composition and BMD were measured by dual-energy X-ray absorptiometry. Bone maturity was estimated by using a radiograph of the nondominant hand. The measured whole-body, lumbar spine (LS), and femoral neck (FN) BMD values were significantly higher (P < 0.05) in gymnasts than in controls. In addition, RG presented significantly lower and higher values (P < 0.05) for leptin and ghrelin concentrations, respectively, in comparison with UC. No differences were observed for adiponectin levels between the studied groups. No relationships between measured BMD values with leptin and ghrelin were observed even after adjustment for age and fat mass (FM) in RG. Whole-body and LS BMD values were significantly correlated with leptin after controlling for age and FM (r = 0.32, P < 0.05) in UC. Femoral neck BMD remained significantly correlated with ghrelin after adjusting for age and FM (r = -0.4, P < 0.05) in UC. No relationships were found between measured BMD values and adiponectin even after controlling for age and FM values in both groups. In conclusion, although all measured BMD values were significantly higher in RG, plasma adipocytokine and ghrelin concentrations were not directly related to bone mineralization in prepubertal RG in contrast to UC.

Growth hormone is positively associated with surrogate markers of bone turnover during puberty

BACKGROUND

Puberty is characterized by increases in growth hormone (GH) and insulin-like growth factor-1 (IGF-1) and the pubertal growth spurt. Bone formation and resorption also increase, consistent with increased bone metabolism.

OBJECTIVE

To determine the relationship between pubertal bone metabolism, GH and IGF-1. We hypothesized that bone turnover peaks at the time of greatest pubertal GH secretion.

DESIGN AND SUBJECTS

Subjects included 86 girls and boys, 9-17 years-old (BMI 10th-90th percentiles). Because higher endogenous GH secretion is associated with a higher nadir following oral glucose, we used the GH nadir following a 2-h OGTT as indicative of GH status. Fasting serum IGF-1, aminoterminal propeptide of type 1 procollagen (P1NP) and carboxy-terminal collagen crosslinks (CTX) were obtained. Subjects were grouped per expected timing of peak growth. Group 1: Tanner 1 girls and Tanner 1-2 boys (period preceding peak growth), Group 2: Tanner 2-3 girls and Tanner 3-4 boys (period of peak growth) and Group 3: Tanner 4-5 girls and Tanner 5 boys (period following peak growth).

RESULTS

GH peaked at mid-puberty (Group 2) and IGF-1 in late puberty (Group 3). P1NP and CTX were highest in mid-puberty compared with early and late puberty (P = 0·0009 and 0·006 in girls and P = 0·005 and 0·04 in boys). GH, but not IGF-1, correlated with P1NP (r = 0·46 in both genders, P ≤ 0·008) and CTX (r = 0·37 and 0·38, P = 0·04 and 0·02 in girls and boys, respectively). Similarly, on regression modelling, GH (but not IGF-1) predicted both bone turnover markers in both genders.

CONCLUSION

GH is strongly associated with pubertal bone metabolism, independent of systemic IGF-1 in girls and boys.

Peripheral signals of energy homeostasis as possible markers of training stress in athletes: a review

The importance of physical exercise in regulating energy balance and ultimately body mass is widely recognized. There have been several investigative efforts in describing the regulation of the energy homeostasis. Important in this regulatory system is the existence of several peripheral signals that communicate the status of body energy stores to the hypothalamus including leptin, adiponectin, ghrelin, interleukin-6, interleukin-1β, and tumor necrosis factor-α--different cytokines and other peptides that affect energy homeostasis. In certain circumstances, all these peripheral signals may be used to reveal the condition of the athlete as the result of several months of prolonged exercise training. These hormone and cytokine concentrations characterize a physical stress condition in which different hormone and cytokine responses are apparently linked to changes in physical performance. The possibility to use these peripheral signals as markers of training stress (and possible overreaching/overtraining) in elite athletes should be considered. These measured hormone and cytokine levels could also be used to characterize the physical stress of single exercise session, as the hormone and cytokine response to exercise may actually be a response to the concurrent energy deficit. In summary, different peripheral signals of energy homeostasis may be sensitive to changes in specific training stress and may be useful for predicting the onset of possible overreaching/overtraining in athletes.

Plasma visfatin and adiponectin concentrations in physically active adolescent girls: relationships with insulin sensitivity and body composition variables

The purpose of this study was to evaluate the associations of visfatin and adiponectin concentrations with insulin resistance and body composition in regularly physically active pubertal girls. In 129 girls, aged 13-15 years (pubertal stages 3-5), visfatin, adiponectin, insulin resistance measured by homeostasis model assessment (HOMA), and body composition measured by dual-energy X-ray absorptiometry were evaluated. Visfatin concentration was related to HOMA and overall adiposity (body mass index, fat mass) markers, whereas adiponectin concentration was related to overall adiposity (fat mass), central adiposity (trunk fat) and fat free mass values. These relationships remained significant (p < 0.05) after adjusting for pubertal stage. Visfatin was independently related to body mass index (beta = 0.936; p = 0.0001) and HOMA (beta = 0.444; p = 0.039) indices, whereas adiponectin was independently related to fat free mass (beta = 0.889; p = 0.003) and trunk fat (beta = -0.468; p = 0.042) values. In conclusion, visfatin could be related to insulin resistance and overall adiposity indices, whereas adiponectin was related to different body composition values in regularly physically active pubertal girls.

Adipocytokines and bone mineral density in adolescent female athletes

AIM

 To evaluate the relationships of visfatin, adiponectin and leptin with bone mineral density (BMD) and bone mineral content (BMC) in adolescent female athletes with different training patterns.

METHODS

This study involved 170 healthy 13-15-year-old girls divided into six groups based on activity: sport games (i.e. basketball, volleyball, badminton) (n=49), track sprint (n=24), rhythmic gymnastics (n=23), swimming (n=24), cross-country skiing (n=17) and sedentary controls (n=33). BMD and BMC at femoral neck and lumbar spine (L2-L4) were measured using dual-energy X-ray absorptiometry. Visfatin, adiponectin, leptin, insulin and glucose were measured, and the insulin resistance index was calculated using homeostasis model assessment.

RESULTS

There were no relationships found between visfatin concentrations and bone mineral parameters in adolescent female athletes or controls. Adiponectin was inversely correlated to BMD and BMC of femoral neck and lumbar spine (r=-0.47-0.62) in the swimmer group only, but after adjustments for age, height and body mass these associations disappeared. Leptin concentrations correlated with bone mineral parameters even after adjusting for age, height and body mass (r=0.42-0.63) in the gymnast group only.

CONCLUSION

We may conclude that after adjustment, leptin is the only adipokine of those measured that correlates to femoral neck and lumbar spine BMD and femoral neck BMC in the rhythmic gymnast group.

The influence of physical activity on ghrelin and IGF-1/IGFBP-3 levels in children and adolescents with type 1 diabetes mellitus

OBJECTIVES

The aim of the study was to determine the influence of regular physical activity on ghrelin and IGF-1/IGFBP-3 levels during a diabetes camp.

METHODS

Twenty-eight children and adolescents (14 boys; mean age 12.1 yr) with type 1 diabetes mellitus (T1DM, mean duration of diabetes 4.8 yr) attending a 2-wk diabetes camp that features increased regular physical activities have been studied. Serum levels of ghrelin (total and acylated), growth hormone (GH), insulin-like growth factor-1 (IGF-1), insulin-like growth factor-bindng protein-3 (IGFBP-3) and insulin were measured in fasting state on day 1 and day 14. Improvement of metabolic control was documented by haemoglobin A1c (HbA1c). Glucose levels and insulin doses were determined daily.

RESULTS

Mean insulin dosage decreased from 0.87 to 0.78 U/kg/d, mean HbA1c levels decreased from 8.6 to 8.3%, but the changes were not statistical. There was a significant decline in total ghrelin. IGFBP-3 and IGF-1 decreased also significantly. Total basal ghrelin was inversely related to the change in IGFBP-3.

CONCLUSIONS

We hypothesize an association between ghrelin and metabolic control in T1DM. Higher ghrelin levels might be associated with poor metabolic control. The dynamic of IGFBP-3 levels appears to be under the influence of basal ghrelin concentrations in T1DM.

Interpretation and application of bone turnover markers in children and adolescents

PURPOSE OF REVIEW

To assess recent research findings on various biochemical bone turnover markers and to assess their use in monitoring bone growth in children and adolescents.

RECENT FINDINGS

There are very few recent studies that investigate various serum and urine analytes that reflect bone formation and resorption to monitor bone health during longitudinal growth. In infants and young children, the measurement of bone markers in serum is suggested because of the practical difficulties associated with urine collection and by the circadian and intraindividual variation in urinary markers. During the prepubertal growth, bone turnover values are similar in age-matched boys and girls. The increase in different bone turnover markers coincides with the pubertal growth spurt. This starts later in boys and the increase in bone turnover markers also occurs later, is greater and lasts longer when compared with girls. Recent studies demonstrated that bone size increases and bone turnover decreases until mid-twenties.

SUMMARY

More than one bone formation and resorption marker should be measured to monitor longitudinal growth and bone mineral accrual, because sensitivities and predictive values of single markers are still poor. It is important to find new and more sensitive markers that could better characterize linear growth.

The relationships among bone health, insulin-like growth factor-1 and sex hormones in adolescent female athletes

The aim of this study was to determine the relationships of bone mineral density (BMD) and content (BMC) with insulin-like growth factor-1 (IGF-1), IGF-binding protein-3 (IGFBP-3) and estradiol in pubertal female athletes. The participants were 170 healthy adolescent girls (13-15 years) who participated in competitive extramural athletic programs, i.e., sports games (n = 49), track sprinting (n = 24), rhythmic gymnastics (n = 23), swimming (n = 24) and cross-country skiing (n = 17). The control group (n = 33) consisted of girls who took part only in compulsory physical education classes at school. The whole-body BMD and femoral neck and lumbar spine BMD and BMC were measured using DXA, and the volumetric BMD was calculated. Venous blood samples to determine the concentration of IGF-1, IGFBP-3 and estradiol were drawn after an overnight fasting. After adjusting for age, body height and body mass, the relationships among BMD variables, IGF-1 and the IGF-1/IGFBP-3 molar ratio remained significant only in the rhythmic gymnast group. BMDs at the femoral neck and lumbar spine were also related to estradiol levels (r = 0.45-0.60; p < 0.05) only in the rhythmic gymnast group. No relationships were found among the measured BMD, IGF axis and estradiol in other athletic groups. Only BMC at the femoral neck remained associated with the IGF-1/IGFBP-3 molar ratio in the rhythmic gymnast group after adjusting for age, body height and body mass. Stepwise multiple regression analysis indicated that IGF-1 and estradiol together explained 42.6% (R(2) x 100) of total variance in the femoral neck BMD and IGF-1 alone 35.4% (R(2) x 100) of the total variance in the femoral neck BMC only in the rhythmic gymnast group. We conclude that femoral neck and lumbar spine BMD correlated with IGF-1, IGF-1/IGFBP-3 molar ratio and estradiol in rhythmic gymnasts. No relationships were found between bone parameters and the hormones used in other athletic groups.

Maturity-related differences in physical activity among 10- to 12-year-old girls

Besides environmental and psycho-social factors explaining the variation in physical activity levels during adolescence, some evidence suggests that biological processes are involved in regulating habitual daily physical activity and energy expenditure. The purpose of this study was to examine the influence of biological maturity status on physical activity. Chronological age, standing height, sitting height, and body mass were measured cross-sectionally in 268 girls, aged 9.5 to 11.5 years. Biological maturity groups (Early, Average, Late) were created according to estimated age at peak-height-velocity (estAPHV). Habitual physical activity was determined with a pedometer (Yamax Digiwalker SW-200) over a 7-day period. Differences in steps/day across maturity groups were examined by ANCOVA, controlling separately for time the pedometer was worn, leg length, and body mass. Mean pedometer steps/day was 10,822 +/- 2,639. As expected, body size varied by maturity status (e.g., early > average > late). Significant maturity group differences were found with early maturing girls showing lower activity levels compared to average or late maturers. These differences remained after controlling for time the pedometer was worn and leg length; however, the differences were no longer significant when controlling for body mass. The results suggest that biological maturity status influences physical activity levels in girls between 10 and 12 years of age but the relationship is not independent of body mass. Further research is needed to establish the complex inter-relationships among adiposity, biological maturation, and energy expenditure during puberty.

Bone metabolism markers and ghrelin in boys at different stages of sexual maturity

AIM

To examine the relationship of the markers of bone formation (procollagen type I N-terminal propeptide [PINP]) and bone resorption (type I carboxyterminal telopeptide [ICTP]) with bone mineral content (BMC), bone mineral density (BMD), ghrelin and testosterone in boys during puberty.

METHODS

Sixty boys were divided in three groups (20 boys in each) based on the pubertal stage (G1, I; G2-G3, II; G4-G5, III). Fasting PINP, ICTP, ghrelin and testosterone were measured. Total body BMD, lumbar BMD, lumbar apparent volumetric BMD (BMAD) and BMC were measured by DXA.

RESULTS

PINP and ICTP values peaked at the beginning of puberty (Group II). Ghrelin was lower in Groups II and III compared to less mature boys. PINP and ICTP correlated with each other and were associated with lumbar BMAD in total group of boys. Relationships of PINP and ICTP with total BMD, total BMC and lumbar spine BMD in Group I were observed. PINP and ICTP were also correlated with testosterone in Group II and with lumbar spine BMAD in Group III.

CONCLUSION

These data suggest that testosterone stimulates PINP and ICTP in early puberty, while ghrelin has no direct influence on bone turnover markers in boys at different stages of puberty.

Longitudinal Development of Physical and Performance Parameters during Biological Maturation of Young Male Swimmers

The aim of the study was to examine the development of specific physical, physiological, and biomechanical parameters in 29 young male swimmers for whom measurements were made three times for two consecutive years. During the 400-m front-crawl swimming, the energy cost of swimming, and stroking parameters were assessed. Peak oxygen consumption (VO2 peak) was assessed by means of the backward-extrapolation technique recording VO2 during the first 20 sec. of recovery period after a maximal trial of 400-m distance. Swimming performance at different points of physical maturity was mainly related to the increases in body height and arm-span values from physical parameters, improvement in sport-specific VO2 peak value from physiological characteristics, and improvement in stroke indices on biomechanical parameters. In addition, biomechanical factors characterised best the 400-m swimming performance followed by physical and physiological factors during the 2-yr. study period for the young male swimmers.

Effect of pubertal development and physical activity on plasma ghrelin concentration in boys

The aim of the present study was to assess the influence of regular physical activity on plasma ghrelin concentration in pre-pubertal and pubertal boys. In addition, the impact of ghrelin concentration on bone mineral density (BMD) was examined. In total, 56 healthy schoolboys aged between 10 and 16 yr were divided into the swimming (no.=28) and the control (no.=28) groups. The subjects were matched by age and body mass index (BMI), generating 9 matched pairs in pubertal group I (Tanner stage 1), 11 pairs in group II (Tanner stages 2 and 3), and 8 pairs in group III (Tanner stages 4 and 5). Swimmers in pubertal groups II and III had significantly (both p<0.05) higher mean ghrelin levels than the controls (group II: 1126.8+/-406.0 vs 868.3+/-411.2 pg/ml; group III: 1105.5+/-337.5 vs 850.8+/-306.0 pg/ml, respectively), whereas no difference was seen in the pubertal group I (1230.8+/-386.0 vs 1272.7+/-424.4 pg/ml). Ghrelin was the most important hormonal determinant for total BMD and lumbar apparent volumetric BMD (BMAD) (R2=27.2% and R2=19.8%, respectively) in swimmers, whereas in control boys, plasma IGF-I was the most important hormonal predictor accounting for 41.8% of the variability of total BMD and 20.4% of the variability of lumbar BMAD. In conclusion, ghrelin concentration decreased during puberty in physically inactive boys, while in regularly physically active boys it remained relatively unchanged. Ghrelin appears to be an important hormonal predictor for BMD in physically active boys, while BMD is mostly determined by IGF-I in physically inactive boys.

Acylated ghrelin and leptin in adolescent athletes with amenorrhea, eumenorrheic athletes and controls: a cross-sectional study

OBJECTIVES

Neuroendocrine factors may predict which athletes develop amenorrhea and which athletes remain eugonadal. Specifically, ghrelin and leptin have been implicated in regulation of GnRH secretion, with ghrelin having inhibitory and leptin, facilitatory effects. We hypothesized that adolescent athletes with amenorrhea (AA) would have higher ghrelin and lower leptin levels than eumenorrheic athletes (EA) and would predict levels of gonadal steroids.

DESIGN

Cross-sectional.

SUBJECTS AND MEASUREMENTS

We enrolled 58 girls, 21 AA, 19 EA and 18 nonathletic controls 12-18 years old. Fasting blood was drawn for active ghrelin, leptin, E(2) and testosterone. Athletes were > 85% of ideal body weight for age based on body mass index (BMI).

RESULTS

AA girls had lower BMI than EA and controls (P = 0.003). Log ghrelin was higher in AA than in EA and controls (P < 0.0001), and remained higher after controlling for BMI Z-scores. Leptin was lower in AA than in the other groups (P < 0.0001), however, the differences did not persist after controlling for BMI Z-scores. Testosterone was lower in AA than in EA and controls (P = 0.002) and log E(2) trended lower in AA (P = 0.07). We observed inverse associations of log active ghrelin with testosterone (P = 0.01), and positive associations of leptin with testosterone and log E(2) (P = 0.02 and 0.009).

CONCLUSION

Higher ghrelin levels, even after controlling for BMI, and lower leptin in AA compared with EA and controls, and their inverse and positive associations, respectively, with gonadal steroids suggest endocrine perturbations that may explain why hypogonadism occurs in some but not all athletes.

Effects of endurance exercise on the reproductive system of men: the "exercise-hypogonadal male condition"

An increasing number of investigative research studies point to participation in endurance exercise training as having significant detrimental effects upon reproductive hormonal profiles in men. Specifically, men chronically exposed to this type of exercise training exhibit persistently reduced basal (resting-state) free and total testosterone concentrations without concurrent LH elevations. Men displaying these symptoms have been deemed to exhibit the "exercise-hypogonadal male condition". The exact physiological mechanism inducing the reduction of testosterone in these men is currently unclear, but is postulated to be a dysfunction (or perhaps a readjustment) within the hypothalamic-pituitary-testicular regulatory axis. The potential exists for the reduced testosterone concentrations within exercise-hypogonadal men to be disruptive and detrimental to some anabolic-androgenic testosterone- dependent physiological processes. Findings on this point are limited, but do suggest spermatogenesis problems may exist in some cases. Alternatively, reductions in circulating testosterone concentrations could have cardiovascular protective effects and thus be beneficial to the health of these men. Present evidence suggests the exercise-hypogonadal condition is limited to men who have been persistently involved in chronic endurance exercise training for an extended period time (i.e., years), and it is not a highly prevalent occurrence (although, a thorough epidemiological investigation on the topic is lacking in the literature). Many questions regarding the male reproductive endocrine adaptive process to exercise training still remain unanswered, necessitating the need for much further investigation on the topic, especially with respect to the exercise-hypogonadal condition.