Sophie Lemoine-Morel

Catecholamines and Obesity: Effects of Exercise and Training

Excess body fat in obese individuals can affect the catecholamine response to various stimuli. Indeed, several studies report lower plasma catecholamine concentrations in obese subjects compared with nonobese subjects in response to submaximal or maximal exercise. This low catecholamine response reflects decreased sympathetic nervous system (SNS) activity. Although the relationship between the SNS and obesity is not well established, some authors have suggested that low SNS activity may contribute to the development of obesity. A decreased catecholamine response could affect α- and β-adrenoceptor sensitivity in adipose tissue, reducing lipolysis and increasing fat stores. Few studies have examined the effects of obesity on the plasma catecholamine response at rest and during exercise in adolescents. It is interesting to note that the effects of age, sex, and degree of obesity and the impact of very intense exercise on the catecholamine response have not yet been well examined. Moreover, the hormonal concentrations measured in the majority of obesity studies did not take into account plasma volume changes. This methodological factor can also undoubtedly influence plasma catecholamine results.

Fat Mass Localization Alters Fuel Oxidation during Exercise in Normal Weight Women.

PURPOSE Abdominal and lower body fat mass tissues exhibit particular metabolic profiles at rest and during exercise. However, data are missing in normal weight women during exercise. The purpose of this study was to investigate the effect of low (LA/LB) and high (HA/LB) abdominal to lower body (A/LB) fat mass ratio on metabolic and hormonal responses during exercise in premenopausal normal weight women. METHODS After preliminary testing (V˙O2max and body composition assessment), substrate oxidation (RER, lipid, and carbohydrate oxidation rates), metabolic response (glycerol, free fatty acids, and glucose), and hormonal response (insulin, growth hormone, atrial natriuretic peptide, adrenaline, and noradrenaline) were determined during exercise (45 min at 65% of V˙O2max) in 21 premenopausal normal weight women (10 HA/LB women vs 11 LA/LB women). RESULTS Waist circumference was significantly higher in HA/LB women compared with LA/LB women (P < 0.01). No difference in other anthropometric characteristics, V˙O2max, and resting blood values was observed between the two groups. LA/LB subjects exhibited greater lipid oxidation rates compared with HA/LB women during exercise (P < 0.01). This occurred with lower plasma insulin (P < 0.05) and glucose (P < 0.05) concentrations and higher plasma free fatty acids (P < 0.05), glycerol (P < 0.05), growth hormone (P < 0.05), and atrial natriuretic peptide levels (P < 0.01) during exercise in the LA/LB group compared with the HA/LB group. CONCLUSIONS The present study demonstrated that LA/LB women exhibited an increase in whole-body lipid mobilization and use during exercise compared with HA/LB counterparts. This greater reliance on lipid as fuel metabolism during exercise could be explained by substrate availability and metabolic and hormonal responses. It appeared that LA/LB women exhibited greater metabolic flexibility during an exercise bout of 45 min at 65% of V˙O2max on cycle ergometer.

Catecholamine Response to Exercise in Obese, Overweight, and Lean Adolescent Boys

INTRODUCTION The aim of this study was to examine the effect of body fat percentage on the plasma catecholamine response to a cycling sprint test (CST) in sedentary adolescent boys. METHODS In this study, 31 adolescent boys (9 obese (% body fat = 31.0% ± 3.0%), 11 overweight (% body fat = 24.0% ± 1.6%), and 11 lean (% body fat = 16.0% ± 1.9%)), matched for peak oxygen consumption, completed a CST consisting of six 6-s maximal sprints with 2 min of passive rest between each repetition. Performance of each subject was determined as the mean power output (PO(mean)) developed during the CST. Plasma lactate, epinephrine, and norepinephrine concentrations were determined successively at rest, after a 10-min warm-up, immediately after the CST, and after 20 min of passive recovery. RESULTS Although groups were not different in age, height, or peak oxygen consumption (mL·kg(-1) fat-free mass·min(-1)), maximal epinephrine concentration was significantly (P < 0.05) higher in lean vs obese and was negatively correlated to body fat percentage (r = -0.60, P < 0.05). Maximal norepinephrine values were higher in lean versus overweight and obese, and a negative relationship was found between maximal norepinephrine concentration and body fat percentage (r = -0.60, P < 0.05). Maximal lactate concentration was higher in lean versus overweight and obese (14.7 ± 3.3, 10.4 ± 2.7, and 10.2 ± 2.5 mM in lean, overweight, and obese, respectively). A significant relationship was also obtained between maximal norepinephrine and maximal epinephrine values with both maximal lactate concentration (r = 0.60 and r = 0.60, P < 0.05, respectively) and PO(mean) (r = 0.65 and r = 0.6, P < 0.05). CONCLUSIONS Our results show that the catecholamine response to a CST was affected by body fat percentage, with reduced epinephrine and norepinephrine values in overweight and obese adolescents.

Beneficial effects of an intradialytic cycling training program in patients with end-stage kidney disease.

In chronic kidney disease (CKD), oxidative stress (OS) plays a central role in the development of cardiovascular diseases. This pilot program aimed to determine whether an intradialytic aerobic cycling training protocol, by increasing physical fitness, could reduce OS and improve other CKD-related disorders such as altered body composition and lipid profile. Eighteen hemodialysis patients were randomly assigned to either an intradialytic training (cycling: 30 min, 55%-60% peak power, 3 days/week) group (EX; n = 8) or a control group (CON; n = 10) for 3 months. Body composition (from dual-energy X-ray absorptiometry), physical fitness (peak oxygen uptake and the 6-minute walk test (6MWT)), lipid profile (triglycerides (TG), total cholesterol, high-density lipoprotein, and low-density lipoprotein (LDL)), and pro/antioxidant status (15-F2α-isoprostanes (F2-IsoP) and oxidized LDL in plasma; superoxide dismutase, glutathione peroxidase, and reduced/oxidized glutathione in erythrocytes) were determined at baseline and 3 months later. The intradialytic training protocol did not modify body composition but had significant effects on physical fitness, lipid profile, and pro/antioxidant status. Indeed, at 3 months: (i) performance on the 6MWT was increased in EX (+23.4%, p < 0.001) but did not change in CON, (ii) plasma TG were reduced in EX (-23%, p < 0.03) but were not modified in CON, and (iii) plasma F2-IsoP concentrations were lower in EX than in CON (-35.7%, p = 0.02). In conclusion, our results show that 30 min of intradialytic training, 3 times per week for 3 months, are enough to exert beneficial effects on the most sensitive and reliable marker of lipid peroxidation (IsoP) while improving CKD-associated disorders (lipid profile and physical fitness). Intradialytic aerobic cycling training represents a useful and easy strategy to reduce CKD-associated disorders. These results need to be confirmed with a larger randomized study.

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.

Effects of Acute Supramaximal Cycle Exercise on Plasma FFA Concentration in Obese Adolescent Boys

Aims The aims of the present study are 1) to evaluate the free fatty acid (FFA) profile and 2) to determine the relative anaerobic and aerobic contributions to total energy consumption during repeated supramaximal cycling bouts (SCE) in adolescent boys with different body weight statuses. Materials and Methods Normal-weight (NW), overweight (OW), and obese (OB) adolescent boys (n =15 per group) completed a SCE sessions consisted of 6 x 6s maximal sprints with 2 min of passive rest between each repetition. Plasma FFA levels were determined at rest, immediately after a 10 min warm-up, and immediately at the end of SCE. The anaerobic and aerobic contributions (%) were measured via repeated SCE bouts. Insulin resistance was calculated using the homoeostatic model assessment (HOMA-IR) index. Results The FFA concentrations measured immediately after SCE were higher in the OB group than in the OW and NW (p<0.01 and p<0.01, respectively) groups. Moreover, the anaerobic contributions to SCE were significantly lower in obese adolescents (p<0.01) and decreased significantly during the 2nd, 3rd and 4th repetitions. The FFA levels were significantly associated with the HOMA-IR index and aerobic contribution among adolescent boys (r=0.83 and r=0.91, respectively, p<0.01). Conclusion In contrast to the NW and OW groups, there is an increase in lipid mobilization and sift to aerobic energy metabolism during SCE in the OB group.

Plasma volume variation with exercise: a crucial consideration for obese adolescent boys

Previous studies have demonstrated that considerable plasma volume variations (ΔPV) occur during and after exposure to different environmental and physiological conditions. Such changes have an important effect on plasma concentration of metabolite values. Currently, no study has examined ΔPV in individuals with different body weight status and used ΔPV to correct plasma solute values. The aims of this study were to assess (i) the effect of body weight status on ΔPV and (ii) the impact of these variations on lactate ([La]) and glucose ([Glu]) concentrations in normal-weight, overweight, and obese adolescent boys. Participants performed a cycling sprint test at their maximal power output. ΔPV were calculated using 2 methods, and both lactate and glucose concentrations were compared using total circulating values (T) and corrected values (cr) for ΔPV: [La]T vs. [La]cr and [Glu]T vs. [Glu]cr. Following exercise, ΔPV values decreased significantly from rest value and were higher in obese compared with overweight and normal-weight boys (p < 0.01). Moreover, ΔPV were correlated with body weight status (r = 0.85; p < 0.05). While [La]T and [Glu]T differed among the groups, no difference persisted when these values were corrected for ΔPV. The differences between total circulating and corrected values were significant. The impact of body weight status on ΔPV and thus on various plasma measures in response to exercise is important and should be considered in further studies.

Exercise per se masks oral contraceptive-induced postprandial lipid mobilization

Because of their hormonal content, oral contraceptives may alter lipolytic activity under resting or exercise conditions in women. The aim of the present study was to compare lipid mobilization in a postprandial state at rest and during exercise in oral contraceptive users (OC+) versus nonusers (OC-). The metabolic (glucose, glycerol, free fatty acids) and hormonal (insulin, atrial natriuretic peptide (ANP), growth hormone, insulin-like growth factor-1 (IGF-1), and catecholamines) concentrations were determined in 11 OC+ (monophasic low-dose oral contraceptives) and 10 OC- during a resting and an exercise session (45 min at 65% maximal oxygen consumption). Results were expressed as plasma concentrations and area under the concentration versus time curve values. ANP concentrations were higher in OC+ compared with OC- women at baseline (p = 0.04). Plasma concentrations of glycerol (p = 0.04), free fatty acids (p = 0.04), ANP (p = 0.02), and noradrenaline (p = 0.04) were higher in OC+ compared with OC- when both sessions were pooled. The plasma growth hormone, IGF-1, and adrenaline concentrations were not significantly different between the 2 groups. When the effect of exercise was isolated to overcome food intake and daytime variations (exercise per se using the area under the curve), no difference was observed between groups for all metabolic and hormonal variables. Overall, oral contraceptives increased lipid mobilization in the postprandial state, but this effect was blunted when lipolytic activity was stimulated by exercise per se. Oral contraceptive-induced greater lipolytic mobilization could be partly explained by greater ANP levels in OC users.

Food group preferences and energy balance in moderately obese postmenopausal women subjected to brisk walking program

The objective of the study was to examine the effects of a 16-week walking program on food group preferences and energy balance of sedentary, moderately obese (body mass index, 29-35 kg/m(2)), postmenopausal Caucasian women, aged 60 ± 5 years old. One hundred and fifty-six volunteers were subjected to 3 sessions/week of 45 min of walking at 60% of heart rate reserve. Total energy intake (TEI) and food group preferences (3-day dietary record), total energy expenditure (TEE, 3-day physical activity diary), cardiorespiratory fitness (2-km walking test), anthropometry, and body composition (bioelectrical impedance) were measured before and after walking. Data were statistically analyzed using an ANOVA with repeated measures on 1 factor (time). The modest increase in TEE of 151 ± 24 kcal/day (p < 0.0001) leads to body weight, fat mass losses, and waist girth reduction (p < 0.0001). TEI remained unchanged despite a slight decrease in carbohydrate intake and a minor increase in protein intake (p < 0.05). Analysis of food records revealed a decreased consumption of fruits (p < 0.05) and sweet and fatty foods (p < 0.01), but an increase in oil consumption (p < 0.0001) after walking. Women with the highest body weight loss showed the greatest reduction in the consumption of fruits, sugar, sweet foods, and fatty foods (p < 0.05). Women with the greatest fat mass loss showed the highest decrease in fatty food intake (p < 0.05). In conclusion, although our walking program changed some food group consumption patterns, body weight loss was primarily because of the increased TEE.