Dan Nemet

Body composition and its components in preterm and term newborns: A cross-sectional, multimodal investigation

A prospective, cross‐sectional, observational study in preterm and term infants was performed to compare multimodal measurements of body composition, namely, limb ultrasound, bone quantitative ultrasound, and dual X‐ray absorptiometry (DXA). One hundred and two preterm and term infants appropriate for gestational age were enrolled from the newborn nursery and neonatal intensive care unit. Infants were included when they were medically stable, in an open crib, on full enteral feeds and within 1 week of anticipated discharge. Correlations among the various measurements of body composition were performed using standard techniques. A comparison between preterm infant (born at 28–32 weeks) reaching term to term‐born infants was performed. Limb ultrasound estimates of cross‐sectional areas of lean and fat tissue in a region of tissue (i.e., the leg) were remarkably correlated with regional and whole‐body estimates of fat‐free mass and fat obtained from DXA suggesting the potential usefulness of muscle ultrasound as an investigative tool for studying aspects of body composition in this fragile population. There was a weak but significant correlation between quantitative ultrasound measurements of bone strength and DXA‐derived bone mineral density (BMD). Preterm infants reaching term had significantly lower body weight, length, head circumference, muscle and fat cross‐sectional area, bone speed of sound, whole‐body and regional lean body mass, fat mass, and BMD compared to term‐born infants. Current postnatal care and nutritional support in preterm infants is still unable to match the in‐utero environment for optimal growth and bone development. The use of relatively simple bedside, noninvasive body composition measurements may assist in understanding how changes in different components of body composition early in life affect later growth and development. Am. J. Hum. Biol. 2010.

Exercise, caloric restriction, and systemic oxidative stress.

Background In humans, the main sources of reactive oxygen species (ROS), the molecules causing oxidative stress, are mitochondrial superoxide ions and neutrophil-derived oxidative radicals. Circulating antioxidants contribute to the protection against oxidative stress. Although the formation of ROS and secretion of antioxidants are independently regulated by exercise and diet, little is known about their combined effect. We hypothesized that relatively brief, intense exercise training may reduce systemic oxidation via an intrinsic mechanism, independent of changes in circulating antioxidants and of neutrophil-derived enzymes (as may be caused by concomitant caloric restriction). Methods Nineteen volunteers exercised for 7 days, 3 hours/day at 75% of oxygen uptake. Caloric intake was either 110% of caloric expenditure (high calorie, n = 10) or 75% of caloric expenditure (low calorie, n = 9). Blood samples for F2-isoprostanes, catalase, myeloperoxidase (MPO), interleukin-x (IL-x), white blood cells (WBCs), and other metabolic variables were taken at baseline, at the end of training, and 1 week after completion of the study. Results Serum F2-isoprostanes (μg/mL), markers of lipid peroxidation, were similarly reduced after 7 days of exercise in the high-calorie (from 35 ± 4 to 27 ± 2) and low-calorie (from 35 ± 3 to 24 ± 2) groups. Similar reductions were observed in IL-x concentrations. Conversely, no change was observed in circulating concentrations of the antioxidant catalase. Whereas total WBCs and neutrophil counts were significantly reduced in the low-calorie group only, no difference in neutrophil-derived MPO was measured between groups. Conclusion A significant reduction in systemic oxidation may occur relatively early during intense exercise training in healthy young men, independent of caloric intake. The potential contribution to these effects of circulating antioxidants and neutrophil-derived oxidative enzymes will require further investigation.

Effects of laboratory versus field exercise on leukocyte subsets and cell adhesion molecule expression in children

Abstract. In adults, exercise is a powerful and natural stimulator of immune cells and adhesion molecules. Far less is known about these exercise responses during childhood and whether or not exercise in real-life activities of healthy children might influence immune responses. We compared laboratory exercise (10×2xa0min periods of heavy, constant intensity, cycle ergometer exercise with 1xa0min rests between exercise in nine subjects, aged 9–15xa0years) with field exercise (90xa0min soccer practice in nine different subjects, aged 9–11xa0years). Blood was sampled before both protocols, 5xa0min after the 30xa0min laboratory protocol, and 10–15xa0min after the 90xa0min field protocol. Both field and laboratory exercise protocols led to significant (P<0.05) increases in granulocytes, monocytes, and all lymphocyte subpopulations. The mean (SEM) increases were similar for the two protocols except for the significantly greater increase in laboratory compared with field protocols for natural killer cells [142xa0(39)% vs 12xa0(16)%, P<0.001] and monocytes [64xa0(22)% vs 32xa0(19)%, P<0.001]. Both protocols significantly influenced adhesion molecules (such as CD54) which have not been previously studied in children. However, the adhesion molecule CD8+CD62L– increased to a significantly (P<0.001) greater extent in the laboratory [101xa0(25)%] versus field [34xa0(25)%] protocol. Finally, the density of CD62L on lymphocytes significantly decreased with laboratory exercise but showed no change in the field protocol [–20xa0(3)% vs –3xa0(3)%, P<0.001]. The rapid and substantial immune response in both laboratory and field protocols suggests that exercise stimulation of the immune system occurs commonly in the real lives of children and may play a role in their overall immune status.

Inflammatory and growth mediators in growing preterm infants.

Little is understood about the optimal balance between IGF-I and antagonistic inflammatory mediators, such as IL-6, in growing preterm infants. Using a prospective cohort study, we investigated the relationship between postnatal growth of preterm infants and key growth and inflammatory mediators. We studied 51 stable, growing preterm infants (mean gestational age: 27.8 +/- 0.4 weeks, mean birth weight: 1,032.8 +/- 50.6 g). IL-6 and IL-1ra (reflecting stress/ inflammation) and IGF-I and GHBP (reflecting anabolic activity and GH sensitivity) were measured at enrollment and discharge using ELISA. During the observation period (mean 6.1 +/- 0.34 weeks) there was a significant increase in weight (1,396 +/- 81 g, p < 0.0001). IGF-I increased from 46.6 +/- 4.1 to 88.7 +/- 5.2 ng/ml (p < 0.001). In contrast, IL-6 decreased from 9.5 +/- 1.0 to 2.3 +/- 0.34 pg/ml (p <0.001) and IL-1ra from 6,042 +/- 362 to 4,851 +/- 365 ng/ml (p = 0.007). GHBP increased from 65.8 +/- 6.7 to 82.5 +/- 7.9 ng/ml (p = 0.003). IL-6 was inversely correlated with IGF-I (p < 0.001). In addition, a multiple regression model showed IGF-I levels correlated positively and IL-6 levels inversely with various parameters of growth. Growth in preterm infants is characterized by increases in IGF-I and GHBP with simultaneous decreases in IL-6 and IL-1ra. Efforts to optimally balance inflammatory and growth mediators may benefit somatic growth in infants very early in life.

The Effects of Exercise on Body Weight and Circulating Leptin in Premature Infants

OBJECTIVE: To assess the effect of daily movements on weight gain, serum leptin, and insulin-like growth factor I (IGF-I) in premature infants.STUDY DESIGN: Twenty very-low-birth-weight premature infants were matched and randomized to a daily movement (n=10) and control groups (n=10). Daily movement consisted of passive range of motion with gentle compression of both the upper and lower extremities 5 days per week for 4 weeks.RESULTS: Daily movements led to a significant increase in weight gain (784±51 vs 608±26 g in movements and controls, respectively, p<0.02), and to a significant increase in leptin (0.60±0.19 vs 0.13±0.06 ng/ml in movements and controls, respectively, p<0.05). Changes in body weight correlated with changes in serum leptin (r=0.48, p<0.03). IGF-I also increased following daily movements (18.8±4.1 vs 9.2±4.1 ng/ml in movements and controls, respectively); however, this increase was not statistically significant.CONCLUSION: A relatively brief range of motion daily movement intervention was associated with greater weight gain and increased leptin levels in very-low-birth-weight premature infants. This may suggest that at least part of the daily movements associated with increase in body weight resulted from an increase in adipose tissue.

13 – Exercise and Lung Function in Child Health and Disease

Abstract Exercise in children is not merely play; rather, it is a critical environmental and physiological perturbation that has a profound effect on growth and development in health and disease. In this chapter, we review fundamental knowledge focused on how the growing child adapts to the physiological stress of exercise with a particular focus on respiratory disease. Cardiopulmonary exercise testing (CPET) remains the most widely used approach for precise measurement of respiratory and cardiovascular fitness in children and adults. Essential diagnostic uses of CPET in asthma, cystic fibrosis, and lung disease of prematurity are reviewed. Children at high altitude, particularly those with chronic lung disease, are at risk for exercise impairment, and the mechanisms responsible for these challenges are identified. We present new information regarding an increasingly diagnosed syndrome that limits exercise performance in adolescents, exercise-induced laryngeal obstruction. Finally, we set the stage for the next phase of discovery in exercise research in children, namely linking exercise to genomic, epigenetic, proteomic, and metabolomic technologies that will, hopefully, advance our understanding of exercise as a biomarker and therapeutic adjunct in child health.

Gait Pattern, Impact to the Skeleton and Postural Balance in Overweight and Obese Children: A Review

The article reviews the biomechanical factors that may cause overweight/obese children to reduce their level of physical activity, while increasing their risk of overuse injuries and exercise-related pain. Recommendations would be to screen those children for any gait or postural impairments before they join any exercise program, and to provide them with specific gait treatments and/or physical exercise programs, in order to decrease their risk for future musculoskeletal injuries and pain.