Abdelkarim Zbidi

Review on leptin and adiponectin responses and adaptations to acute and chronic exercise

Leptin and adiponectin represent two newly discovered adipose tissue derived hormones; that are both associated with health status and glucose and free fatty acid (FFA) metabolism. Moreover, acute and chronic exercises affect body composition, carbohydrate and lipid metabolism. It is thus interesting to evaluate the effects of physical exercise and training on leptin and adiponectin levels. It seems that leptin concentration is not modified after short-term exercise (<60 min) or exercise that generates an energy expenditure lower than 800 kcal. Leptin levels decrease after long-term exercise (≥60 min) stimulating FFA release, or after exercise that generates energy expenditure higher than 800 kcal. Adiponectin concentration presents a delayed increase (30 min) after short-term intense exercise (<60 min) performed by trained athletes. For adiponectin, limited data suggest that adiponectin concentration presents a delayed increase (30 min) after short-term intense exercise (<60 min) performed by trained athletes. It seems that adiponectin concentrations do not change in response to long-term exercise (≥60 min). Short-term training (<12 weeks) and long-term training (≥12 weeks) show contrasting results regarding leptin and adiponectin. Most training studies which improve fitness levels and affect body composition could decrease leptin and increase adiponectin concentrations.

Changes in six-minute walking distance during pulmonary rehabilitation in patients with COPD and in healthy subjects

Background: The six-minute walking distance (6MWD) test has demonstrated validity and reliability to assess changes in functional capacity following pulmonary rehabilitation in patients with chronic obstructive lung disease. However, no attempt has been made to establish an iterative measurement of 6MWD during the overall period of pulmonary rehabilitation. Therefore, the aim of this study was to evaluate the impact of a twelve-week rehabilitation program on the iterative weekly measurement of 6MWD in chronic obstructive pulmonary disease (COPD) patients and healthy subjects. Methods: Twenty-six patients with COPD and nine age-matched healthy subjects were studied. Measurements were taken at baseline and after twelve weeks except for the 6MWD. The exercise measurements included a six-minute walking test (6MWT) and an incremental exercise test. Oxygen saturation, heart rate, and dyspnea will be monitored during all these tests. Results: At baseline there were significant differences between groups, except in age, body mass index, and oxygen saturation. After 12 weeks, there was no significant change in lung function in patients with COPD and healthy subjects. The 6MWD, peak oxygen uptake V̇O2peak and anaerobic threshold increased significantly after training in both groups (P < 0.01). The averaged trace of the 6MWD of patients with COPD and healthy subjects was followed-up respectively by a logarithmic and linear fitting. 6MWD showed a plateau after eight weeks in patients with COPD, however, it increased continually overall in healthy subjects. Conclusion: Both patients with COPD and healthy subjects demonstrated functional responses to training but with somewhat different patterns in quality of the improvement of the 6MWD.

Factors affecting the development of lung function in Tunisian children.

We undertook to evaluate the impacts of morphology at birth, physical activity, anthropometric, socioeconomic and environmental factors on lung function in healthy Tunisian children. Pulmonary function parameters were measured with a Minato portable spirometer in a randomized population of 756 healthy children (388 males and 368 females) aged between 6 and 16. The morphology at birth, the gestational age, the physical activity, the socioeconomic status, the type of habitation, and the environmental factors were all assessed by a standard questionnaire. Using univariate analysis, we found that: (1) morphometric parameters (height, weight, maximal inspiratory, and expiratory perimeter), as well as sex were highly associated with pulmonary function parameters; (2) Height at birth showed strong significant relations with FVC, FEV1, and FEV1/FVC; (3) lung function parameters were influenced by physical training of our children, socioeconomic status, indoor pollution, and passive smoking; and (4) we did not observe any association between the gestational age and the weight at their birth and lung function parameters. Using a general linear model analysis, morphometric parameters, age, sex, type of heating, and maximal inspiratory and expiratory perimeters had significant relation with respiratory parameters. In our population of healthy Tunisian children, the main predictive factors of the pulmonary development were the morphological factors such as height, weight, maximal inspiratory, and expiratory thoracic perimeter, sex and age, and the environmental conditions such as type of heating but not morphology at birth, physical activity, or socioeconomic status. Am. J.Hum. Biol., 2008.

Effect of hyperthermia and physical activity on circulating growth hormone

The aim of this study was to differentiate the effects of hyperthermia and physical activity on circulating growth hormone (GH) secretion. Nine healthy volunteer adults performed two 40 min exercise trials and two 50 min passive standing trials. The exercise was performed in either thermo-neutral (N-Ex: air temperature 18 degrees C, air humidity 40%, and wet bulb globe temperature (WBGT) 17.7 degrees C) or hot environmental conditions (H-Ex: air temperature 33 degrees C, air humidity 30%, and WBGT 34.6 degrees C). The passive exposure trials were also performed in either a comfortable (N-P: air temperature 18 degrees C, air humidity 40%, and WBGT 17.7 degrees C) or a hot climatic chamber (H-P: air temperature 40 degrees C, air humidity 100%, and WBGT 97.1 degrees C). Plasma GH, plasma volume (PV), tympanic temperature (Tty), and body mass loss (BML) were measured before and after each trial. The decrease in PV was significantly higher during H-Ex and H-P sessions than during N-Ex and N-P sessions. Comparisons showed significantly lower BML in the N-Ex session (1.5% +/- 0.3%) than in the H-Ex and H-P sessions (2.1% +/- 0.3% and 1.9% +/- 0.2%, respectively) (p < 0.001). The rise in Tty was significantly higher during the H-P session (2.9 +/- 0.4 degrees C) (p < 0.001) when compared with the other sessions. Plasma GH concentration increased significantly during all the trials, particularly during the H-Ex session (45 +/- 7 ng.mL-1) (p < 0.01). Both exercise and heat exposure, separately, are sufficient to increase significantly the plasma GH concentration, and their combined effect induced a highly synergistic rise in GH.

Circadian leptin, insulin and cortisol rhythms in obese subjects

Abstract The recent discovery of leptin, the product of the “ob” gene has greatly advanced the understanding of body adiposity and energy balance regulation. Serum leptin levels follow a circadian rhythm, which seems to be regulated predominantly by insulin increases levels and the circadian rhythm of cortisol. The aims of this study were to: (1) determine the effect of obesity on leptin 24 hours pattern; (2) determine the biological rhythm of leptin, insulin and cortisol. Thirteen subjects (10 women, three men) participated in this study. Serum samples were drawn at four hour intervals for a total of 24 hours. Leptin showed diurnal rhythmicity with peaks at 04.00 h (91.7±12.9 ng/ml) and troughs at 12.00 h (73.1±9.7 ng/ml). There was a strong association between leptin levels and BMI (r = 0.34; p < 0.001). The high levels of leptin may contribute to leptin resistance in obesity. Our data show the negative correlation over time between leptin and cortisol (r = −0.28, p = 0.005), and we demonstrate also that leptin and insulin are not correlated over time.

Effect of training status on adiponectin concentrations

AbstractObjectiveThe purpose of this investigation was to analyse the effect of sub-maximal acute exercise at different intensities on plasma adiponectin and insulin concentrations in trained and untrained subjects.MethodsSeven trained (TR) and eight untrained (UTR) subjects participated in this study. Subjects performed two submaximal cycling exercises of 20 min each: moderate and heavy. The intensity of the exercises was respectively at 60% and 80% of maximal oxygen consumption (

Leptin, its implication in physical exercise and training: a short review.

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Effect of Energy Expenditure and Training Status on Leptin Response to Sub-Maximal Cycling

O2max). Blood samples were obtained before, at the end, and after 30, 60 and 90 min of recovery.ResultsAdiponectin concentrations were unchanged after both exercises and during recovery in TR and UTR. Insulin concentrations were significantly lowered (p<0.05 and p<0.01) at the end and during recovery in both protocols and groups. The comparison between groups indicated that TR presented lower control adiponectin and insulin concentrations than UTR during the moderate and the heavy exercise: −51.62%, p<0.05 and −43.33%, p<0.05, respectively for adiponectin and −35.29%, p<0.05 and −35.11%, p<0.05, respectively for insulin. Rest adiponectin levels during the heavy exercise were significantly related to