Monia Zaouali

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.

Growth factor concentrations and their placental mRNA expression are modulated in gestational diabetes mellitus: possible interactions with macrosomia

BackgroundGestational diabetes mellitus (GDM) is a form of diabetes that occurs during pregnancy. GDM is a well known risk factor for foetal overgrowth, termed macrosomia which is influenced by maternal hypergycemia and endocrine status through placental circulation. The study was undertaken to investigate the implication of growth factors and their receptors in GDM and macrosomia, and to discuss the role of the materno-foeto-placental axis in the in-utero regulation of foetal growth.Methods30 women with GDM and their 30 macrosomic babies (4.75 ± 0.15 kg), and 30 healthy age-matched pregnant women and their 30 newborns (3.50 ± 0.10 kg) were recruited in the present study. Serum concentrations of GH and growth factors, i.e., IGF-I, IGF-BP3, FGF-2, EGF and PDGF-B were determined by ELISA. The expression of mRNA encoding for GH, IGF-I, IGF-BP3, FGF-2, PDGF-B and EGF, and their receptors, i.e., GHR, IGF-IR, FGF-2R, EGFR and PDGFR-β were quantified by using RT-qPCR.ResultsThe serum concentrations of IGF-I, IGF-BP3, EGF, FGF-2 and PDGF-B were higher in GDM women and their macrosomic babies as compared to their respective controls. The placental mRNA expression of the growth factors was either upregulated (FGF-2 or PDGF-B) or remained unaltered (IGF-I and EGF) in the placenta of GDM women. The mRNA expression of three growth factor receptors, i.e., IGF-IR, EGFR and PDGFR-β, was upregulated in the placenta of GDM women. Interestingly, serum concentrations of GH were downregulated in the GDM women and their macrosomic offspring. Besides, the expression of mRNAs encoding for GHR was higher, but that encoding for GH was lower, in the placenta of GDM women than control women.ConclusionsOur results demonstrate that growth factors might be implicated in GDM and, in part, in the pathology of macrosomia via materno-foeto-placental axis.

IGFBP-3, a sensitive marker of physical training and overtraining

Objective: To investigate the response of the somatotrope axis (insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3)) to intense exercise in relation to tiredness. Methods: The study involved 11 rugby players who completed a questionnaire intended to evaluate fitness or, conversely, overtraining and who agreed to plasma samples being taken before and after an international rugby match. Results: The main finding of our study is that we observed strong negative correlations between IGF-1 (r = 0.652) and IGFBP-3 (r = 0.824) levels and the overtraining state estimated using the French Society of Sport Medicine questionnaire. In particular, there was a fall (of up to 25%) in IGFBP-3 levels after the match in the more fatigued subjects compared to an increase (of up to 40%) in fit subjects. Conclusions: A fall in IGFBP-3 in response to an intense bout of exercise may represent an index of tiredness in highly trained sportsmen, as indicated by the scores obtained from the overtraining questionnaire.

Ramadan fasting and the GH/IGF-1 axis of trained men during submaximal exercise.

Aims: The aim of this study was to explore possible changes in body composition, blood glucose regulation, plasma growth hormone (GH), insulin-like growth factor 1 (IGF-1), insulin-like growth factor-binding protein-3 (IGFBP-3), and insulin concentrations of trained athletes in response to the intermittent fasting and dehydration of Ramadan observance. Methods: Nine trained male rugby players (age 19 ± 2 years, height 1.78 ± 0.74 m) were tested 3 times: before Ramadan (C), at the end of the first week (R1), and during the fourth week (R2). They performed a progressive cycle ergometer test at each visit. The work rate was increased in 6-min stages corresponding to 20, 30, 40, 50 and 60% of &Wdot; max. Substrate oxidation was evaluated by indirect calorimetry. On each occasion, substrate and plasma hormone concentrations were measured at rest and at the end of the exercise. Results: Ramadan fasting induced a significant decrease in body mass and body fat (R2 vs. C, p < 0.001). Plasma concentrations of glucose, insulin, GH, IGF-1 and IGFBP-3 did not change significantly between C and R2, either at rest or following exercise. Conclusion: Ramadan fasting induces positive changes in body composition without disturbing glucose regulation or activity of the GH/IGF-1 system.

The A allele of cluster of differentiation 36 (CD36) SNP 1761667 associates with decreased lipid taste perception in obese Tunisian women.

Recent studies have suggested that excessive intake of dietary fat is associated with obesity. Some obese subjects have been reported to exhibit high thresholds for the gustatory detection of lipids via lipid receptors, such as cluster of differentiation 36 (CD36). We studied lingual detection thresholds for emulsions containing oleic acid in obese Tunisian women (n 203) using a three-alternative forced choice (3-AFC) method. Genotyping of the TNF-α (rs1800629), IL-6 (rs1800795) and CD36 (rs1761667) genes was performed to associate with lipid taste perception thresholds. The CD36 genotype distribution was as follows: GG (n 42), AG (n 102) and AA (n 59). Women with the CD36 GG genotype exhibited oral detection thresholds for oleic acid that were more than three times lower than those with the CD36 AA genotype. The present study confirms a high threshold of gustatory fat detection in obese women with the CD36 AA genotype, but there is no significant association with the IL-6 and TNF-α gene polymorphisms.

Bone mineral density of young boy soccer players at different pubertal stages: relationships with hormonal concentration.

OBJECTIVES To examine the effects of soccer in relation with the hormonal concentration, on the bone mass of young Tunisian players at different pubertal stages. METHODS Two groups of 152 young boys (age: 13.3+/-0.9 years) participated in this study: (1) 91 soccer players, and (2) 61 non-athletic boys used as control subjects. The bone mineral density (BMD) and the bone mineral content (BMC) were measured by dual-energy X-ray absorptiometry (DXA). Pubertal stages were assessed, and serum concentrations of insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3), growth hormone (GH) and the total testosterone were measured. RESULTS The BMD and BMC for whole body, lumbar spine, femoral neck, pelvis and lower limbs were higher in soccer players than in controls (p<0.001). In early puberty, the soccer players also exhibited significantly greater BMD and BMC in the whole body and in weight-bearing bones compared with the controls (p<0.001). However, there was no intersubject variability due to puberty in either BMD or BMC. The pubescent soccer players had significantly higher hormonal concentrations of IGF-1 and IGFBP-3 than their counterpart controls (p<0.05). Moreover, the whole body BMD was significantly (p<0.001) correlated with GH, IGF-1 and IGFBP-3 but not with the testosterone concentrations. CONCLUSION The soccer participation of boys is generally associated with the improvement of their bone mass which is mainly marked at early and late puberty. The relationships between somatotropic axis hormones and BMD of the players may be linked to the parallel development of these two parameters during puberty.

Placental infiltration of inflammatory markers in gestational diabetic women.

Gestational diabetes mellitus (GDM) is pathology of glucose intolerance during pregnancy. It is influenced by maternal hyperglycemia and insulinemia through placental circulation. The study was undertaken to investigate the implication of pro-inflammatory factors in the placenta of GDM women. Thirty GDM women have delivered macrosomic babies, and 30 healthy age-matched pregnant women have delivered non macrosomic babies, were recruited in the study. The mRNAs encoding for IL-6, TLR4, TGF-β, CD68, CD14, EMR-1, CCL2, TCR-α, T-bet, GATA-3, leptin and adiponectin were quantified in placental samples by using RT-qPCR. The mRNA expression of the pro-inflammatory factors, i.e., IL-6, TLR4 and TGF-β, was increased in GDM placenta. The mRNA expression of markers of infiltration of macrophage, i.e., CD68, CD14 and EMR-1, was higher in the GDM placenta than the control placenta. The expression of mRNA of TCR-α, an indicator of T-cell infiltration, was significantly higher in the GDM placenta. Interestingly, the expression of mRNA of GATA-3, an indicator of Th2 phenotype differentiation, was unregulated in the GDM placenta. Leptin and adiponectin mRNAs were also significantly increased in the placenta of the GDM group. Our results revealed that there is an increase of inflammation in the GDM placenta which might be involved, in part, in the pathogenesis of macrosomia.

Inflammation and impaired endothelium-dependant vasodilatation in non obese women with gestational diabetes mellitus: preliminary results

BackgroundTo evaluate whether abnormal endothelial function, a common finding in gestational diabetes mellitus (GDM) pregnancies, can be explained by inflammatory cytokines.MethodsForearm skin blood flow (FSBF), into response to acetylcholine (Ach) (endothelium-dependent vasodilatation), were measured in 24 pregnant control subjects and 28 gestational diabetes mellitus (GDM) women, in the third trimester of gestation. A fasting glycemic and lipidic panel was obtained, and inflammatory cytokines (TNF-α and IL-6) and adiponectin were determined.ResultsFSBF is significantly reduced in GDM group compared with control subjects (344.59 ± 57.791 vs.176.38 ± 108.52, P < 0.05). Among all subjects, FSBF showed a strong negative correlation with TNF-α and IL-6 (r = −0.426, P < 0.0001 and r = −0.564, P < 0.0001, respectively) and positive correlation with adiponectin (r = 0.468, P < 0.0001).ConclusionsEndothelial function, an early marker of macrovascular disease, is present in non-obese pregnancies complicated by GDM. This alteration seems to be directly related to inflammatory status, which may represent a patho-physiological link between GDM and type 2 diabetes and, later on, metabolic syndrome.

Short-Term Lower-Body Plyometric Training Improves Whole-Body BMC, Bone Metabolic Markers, and Physical Fitness in Early Pubertal Male Basketball Players

The effects of a 9-week lower-body plyometric training program on bone mass, bone markers and physical fitness was examined in 51 early pubertal male basketball players divided randomly into a plyometric group (PG: 25 participants) and a control group (CG: 26 participants). Areal bone mineral density (aBMD), bone mineral content (BMC), and bone area (BA) in the whole body, L2-L4 vertebrae, and in total hip, serum levels of osteocalcin (Oc) and C-terminal telopeptide fragment of Type I collagen (CTx), jump, sprint and power abilities were assessed at baseline and 9 weeks. Group comparisons were done by independent students t-test between means and analyses of (ANOVA) and covariance (ANCOVA), adjusting for baseline values. PG experienced a significant increase in Oc (p < .01) and all physical fitness except for the 5-jump test. However, there was no improvement in aBMD, BMC and BA in any measured site, except in whole body BMC of the PG. A positive correlation was observed between percentage increase (Δ%) of physical fitness and those of (Oc) for the PG. In summary, biweekly sessions of lower body plyometric training program were successful for improving whole body BMC, bone formation marker (Oc) and physical fitness in early pubertal male basketball players.

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.