Christophe Jacob

Catecholamines and the Effects of Exercise, Training and Gender

Stress hormones, adrenaline (epinephrine) and noradrenaline (norepinephrine), are responsible for many adaptations both at rest and during exercise. Since their discovery, thousands of studies have focused on these two catecholamines and their importance in many adaptive processes to different stressors such as exercise, hypoglycaemia, hypoxia and heat exposure, and these studies are now well acknowledged. In fact, since adrenaline and noradrenaline are the main hormones whose concentrations increase markedly during exercise, many researchers have worked on the effect of exercise on these amines and reported 1.5 to >20 times basal concentrations depending on exercise characteristics (e.g. duration and intensity). Similarly, several studies have shown that adrenaline and noradrenaline are involved in cardiovascular and respiratory adjustments and in substrate mobilization and utilization. Thus, many studies have focused on physical training and gender effects on catecholamine response to exercise in an effort to verify if significant differences in catecholamine responses to exercise could be partly responsible for the different performances observed between trained and untrained subjects and/or men and women. In fact, previous studies conducted in men have used different types of exercise to compare trained and untrained subjects in response to exercise at the same absolute or relative intensity. Their results were conflicting for a while.As research progressed, parameters such as age, nutritional and emotional state have been found to influence catecholamine concentrations. As a result, most of the recent studies have taken into account all these parameters. Those studies also used very well trained subjects and/or more intense exercise, which is known to have a greater effect on catecholamine response so that differences between trained and untrained subjects are more likely to appear. Most findings then reported a higher adrenaline response to exercise in endurance-trained compared with untrained subjects in response to intense exercise at the same relative intensity as all-out exercise. This phenomenon is referred to as the ‘sports adrenal medulla’. This higher capacity to secrete adrenaline was observed both in response to physical exercise and to other stimuli such as hypoglycaemia and hypoxia. For some authors, this phenomenon can partly explain the higher physical performance observed in trained compared with untrained subjects. More recently, these findings have also been reported in anaerobic-trained subjects in response to supramaximal exercise. In women, studies remain scarce; the results are more conflicting than in men and the physical training type (aerobic or anaerobic) effects on catecholamine response remain to be specified. Conversely, the works undertaken in animals are more unanimous and suggest that physical training can increase the capacity to secrete adrenaline via an increase of the adrenal gland volume and adrenaline content.

Activity, inactivity and quality of life among Lebanese adolescents

Background:  The aim of the present study was to investigate recent overweight and obesity prevalence rates for Lebanese adolescents, and to examine differences in physical activity, screen time (sum of time spent in front of TV, computer, and videogames), and health‐related quality of life (HRQOL) for the first time among normal, overweight, and obese adolescents.

Relative Importance of Lean Mass and Fat Mass on Bone Mineral Density in a Group of Lebanese Postmenopausal Women

The aim of this study was to determine the relative importance of lean mass and fat mass on bone mineral density (BMD) in a group of Lebanese postmenopausal women. One hundred ten Lebanese postmenopausal women (aged 65-84 yr) participated in this study. Age and years since menopause were recorded. Body weight and height were measured and body mass index (BMI) was calculated. Body composition (lean mass, fat mass, and fat mass percentage) was assessed by dual-energy X-ray absorptiometry (DXA). Bone mineral content (BMC) of the whole body (WB) and BMD of the WB, the lumbar spine (L1-L4), the total hip (TH), the femoral neck (FN), the ultra distal (UD) Radius, and the 1/3 Radius were measured by DXA. The expressions WB BMC/height and WB BMD/height were also used. Weight, BMI, fat mass, and lean mass were positively correlated to WB BMC, WB BMC/height, WB BMD/height, and to WB, L1-L4, TH, FN, UD Radius, and 1/3 Radius BMD. However, using multiple linear regression analyses, fat mass was more strongly correlated to BMC and to BMD values than lean mass after controlling for years since menopause. This study suggests that fat mass is a stronger determinant of BMC and BMD than lean mass in Lebanese postmenopausal women.

Exercise-induced oxidative stress in overweight adolescent girls: roles of basal insulin resistance and inflammation and oxygen overconsumption

Hypothesis:Basal insulin resistance (IR) and inflammation exacerbate post-exercise oxidative stress (OS) in overweight adolescent girls.Design:Cross-sectional study, effect of incremental ergocycle exercise until exhaustion on OS markers.Participants:Normal-weight (control) (n=17, body mass index (BMI): 20–24.2 kg/m2) and overweight adolescent girls (n=29, BMI: 24.1–36.6 kg/m2).Measurements:Dietary measurement, physical activity assessment (validated questionnaires), fat distribution parameters (by dual-energy X-ray absorptiometry and anthropometry) and maximal oxygen consumption ([Vdot ]O2peak). Blood assays include the following: (1) at fasting state: blood cell count, lipid profile, and IR parameters (leptin/adiponectin ratio (L/A), homeostasis model assessment of IR, insulin/glucose ratio; (2) before exercise: inflammation and OS markers (interleukin-6 (IL-6), C-reactive protein (CRP), myeloperoxidase (MPO), reduced glutathione/oxidized glutathione ratio (GSH/GSSG), 15 F2α-isoprostanes (F2-Isop), lipid hydroperoxides (ROOH), oxidized low-density lipoprotein (ox-LDL)) and antioxidant status (superoxide dismutase (SOD), glutathione peroxidase (GPX), vitamin C, α-tocopherol and β-carotene); and (3) after exercise: inflammation and OS markers.Results:At rest, overweight girls had a deteriorated lipid profile and significantly higher values of IR parameters and inflammation markers, compared with the control girls. These alterations were associated with a moderate rest OS state (lower GSH/GSSG ratio, α-tocopherol/total cholesterol (TC) ratio and GPX activity). In absolute values, overweight girls exhibited higher peak power output and oxygen consumption ([Vdot ]O2peak), compared with the control girls. Exercise exacerbated OS only in the overweight group (significant increase in F2-Isop, ROOH and MPO). As hypothesized, basal IR and inflammation state were correlated with the post-exercise OS. However, the adjustment of F2-Isop, ROOH and MPO variation per exercise [Vdot ]O2 variation canceled the intergroup differences.Conclusion:In overweight adolescent girls, the main factors of OS, after incremental exhaustive exercise, are not the basal IR and inflammation states, but oxygen overconsumption.

Bone mineral content and density in obese, overweight, and normal-weighted sedentary adolescent girls.

PURPOSE The aim of this study was to compare the whole body (WB) bone mineral content (BMC) and bone mineral density (BMD) in obese, overweight, and normal-weighted adolescent sedentary girls. METHODS This study included 17 obese, 27 overweight, and 21 normal-weighted adolescent (aged, 12-20) sedentary (practicing less than 2 hours of physical activity/week) girls. The three groups (obese, overweight, and normal) were matched for age and maturation index (years since menarche). BMC, bone mineral area (BMA), BMD, and body composition were assessed by dual-energy X-ray asborptiometry. Bone mineral apparent density (BMAD) was calculated for the WB. RESULTS Obese girls had higher BMC values than overweight and normal-weighted girls (p < .05 and p < .001, respectively). Overweight girls had higher BMC values than normal-weighted girls (p < .05). BMD values were not different among the three groups. However, obese and overweight girls had lower BMAD and higher BMC/height values in comparison with normal-weighted girls (p < .05). Finally, after adjustment for lean mass, BMC, BMA, BMD, and BMAD were not different among the three groups. CONCLUSION In this population, overweight and obesity are associated with higher BMC, BMC/height, and lower BMAD of the WB. This study suggests that BMD, BMC, BMA, and BMAD of the WB are not significantly different among the three groups (obese, overweight, and normal) after adjustment for lean mass. Therefore, our results suggest that the skeleton of the overweight and the obese girls adapts to the increased lean mass.

Influence of the weight status on bone mineral content and bone mineral density in a group of Lebanese adolescent girls

AIM The aim of this study was to determine the influence of being overweight on whole-body (WB) bone mineral content (BMC) and bone mineral density (BMD) in a group of Lebanese adolescent girls. METHODS This study included 32 overweight (BMI>25 kg/m2) adolescent girls (15.3+/-2.3 years old) and 24 maturation-matched (15.7+/-1.7 years old) controls (BMI<25 kg/m2). Bone mineral area (BMA), BMC, BMD at the WB and body composition (lean mass and fat mass) were assessed by dual-energy X-ray absorptiometry (DXA). Calculation of the ratio BMC/height and bone mineral apparent density (BMAD) were completed for the WB. RESULTS Expressed as crude values, BMA, BMC and the ratio BMC/height were higher in overweight adolescent girls compared to controls. After adjusting for body weight, there were no differences in BMC or in the ratio BMC/height between the two groups. However, BMA was lower in overweight girls compared to controls. After adjusting for either lean mass or fat mass, there were no significant differences between the two groups regarding these variables: BMC, BMA, BMD, BMC/height and BMAD. CONCLUSION This study suggests that the positive effect of overweight on BMC is due to body weight. In fact, the difference in BMC between the overweight and the control girls disappears after adjusting for body weight. In contrast, overweight girls have lower BMA compared to controls when values are adjusted to body weight.

Geometric Indices of Hip Bone Strength in Obese, Overweight, and Normal-Weight Adolescent Girls

The aim of this study was to compare hip bone strength indices in obese, overweight, and normal-weight adolescent girls using hip structure analysis (HSA). This study included 64 postmenarcheal adolescent girls (14 obese, 21 overweight, and 29 normal weight). The 3 groups (obese, overweight, and normal weight) were matched for maturity (years since menarche). Body composition and bone mineral density (BMD) of whole body, lumbar spine, and proximal femur were assessed by dual-energy X-ray absorptiometry (DXA). To evaluate hip bone strength, DXA scans were analyzed at the femoral neck (FN) at its narrow neck (NN) region, the intertrochanteric (IT), and the femoral shaft (FS) by the HSA program. Cross-sectional area and section modulus were measured from hip BMD profiles. Total hip BMD and FN BMD were significantly higher in obese and overweight girls in comparison with normal-weight girls (p < 0.05). However, after adjusting for weight, using a one-way analysis of covariance, there were no significant differences among the 3 groups regarding HSA variables. This study suggests that in obese and overweight adolescent girls, axial strength and bending strength indices of the NN, IT, and FS are adapted to the increased body weight.

Bone Mineral Content and Density in Overweight and Control Adolescent Boys

The aim of this study was to compare bone mineral content (BMC) and areal bone mineral density (aBMD) in overweight and control adolescent boys. This study included 27 overweight (body mass index [BMI] > 25 kg/m²) adolescent (17.1 ± 2.1 yr old) boys and 29 maturation-matched (16.7 ± 2.0 yr old) controls (BMI< 25 kg/m²). Bone mineral area (BMA), BMC, and aBMD were assessed by dual-energy X-ray absorptiometry (DXA) at the whole body (WB), lumbar spine (L2-L4), total hip (TH), femoral neck (FN), and left forearm (ultra distal [UD], mid Radius, 1/3 Radius, and total Radius). Body composition (lean mass, fat mass, and fat mass percentage) was assessed also by DXA. The expressions WB BMC/height, WB aBMD/height, and WB BMAD were used to adjust for WB bone size. WB BMC, WB BMC/height, WB BMA, L2-L4 aBMD, TH aBMD, FN aBMD, and UD aBMD were higher in overweight boys compared with controls (p < 0.05). However, WB BMAD was lower in overweight boys compared with controls (p < 0.05). After adjustment for weight, lean mass, or BMI, using a one-way analysis of covariance, there were no differences between the 2 groups (overweight and controls) regarding bone characteristics (BMC, BMA, aBMD, BMC/height, aBMD/height, and BMAD of the WB and aBMD of the lumbar spine; the TH; the FN; and the forearm). In conclusion, this study shows that after adjusting for weight, lean mass, or BMI, there are no differences between overweight and control adolescent boys regarding aBMD values.

Aerobic Training Suppresses Exercise-induced Lipid Peroxidation and Inflammation in Overweight/Obese Adolescent Girls

This study aimed to determine whether aerobic training could reduce lipid peroxidation and inflammation at rest and after maximal exhaustive exercise in overweight/obese adolescent girls. Thirty-nine adolescent girls (14-19 years old) were classified as nonobese or overweight/obese and then randomly assigned to either the nontrained or trained group (12-week multivariate aerobic training program). Measurements at the beginning of the experiment and at 3 months consisted of body composition, aerobic fitness (VO2peak) and the following blood assays: pre- and postexercise lipid peroxidation (15F2a-isoprostanes [F2-Isop], lipid hydroperoxide [ROOH], oxidized LDL [ox-LDL]) and inflammation (myeloperoxidase [MPO]) markers. In the overweight/ obese group, the training program significantly increased their fat-free mass (FFM) and decreased their percentage of fat mass (%FM) and hip circumference but did not modify their VO2peak. Conversely, in the nontrained overweight/obese group, weight and %FM increased, and VO2peak decreased, during the same period. Training also prevented exercise-induced lipid peroxidation and/or inflammation in overweight/obese girls (F2-Isop, ROOH, ox-LDL, MPO). In addition, in the trained overweight/obese group, exercise-induced changes in ROOH, ox-LDL and F2-Isop were correlated with improvements in anthropometric parameters (waist-to-hip ratio, %FM and FFM). In conclusion aerobic training increased tolerance to exercise-induced oxidative stress in overweight/obese adolescent girls partly as a result of improved body composition.

Bone mineral content and density in obese, overweight and normal weight adolescent boys.

AIM OF THE STUDY The aim of this study was to compare bone mineral content (BMC), bone mineral density (BMD) and bone mineral apparent density (BMAD) in obese, overweight and normal weight adolescent boys. METHODS & RESULTS This study included 23 obese, 19 overweight and 25 normal weight adolescents (aged 14-20 years) boys. The three groups (obese, overweight and normal weight) were matched for age and maturation index. Body composition, BMC and BMD were assessed by dual-energy X-ray absorptiometry (DXA). The expressions whole body (WB) BMC/height and WB BMD/height were used to adjust for WB bone size. BMAD was calculated for the WB. WB BMC, WB BMC/height, total hip (TH) BMD, femoral neck (FN) BMD and ultra distal (UD) radius BMD) were higher in obese and overweight boys in comparison to normal weight boys (p < 0.05). WB BMAD was lower in obese boys in comparison to overweight and normal weight boys (p < 0.05). After adjustment for either weight or lean mass, obese boys displayed lower WB BMC, WB BMC/height and WB BMD values in comparison to overweight and normal weight boys (p < 0.05). CONCLUSION This study suggests that WB BMC, WB BMC/height and WB BMD do not adapt to the increased body weight in obese adolescent boys.