The aim of this study was to investigate whether VO
max can be accurately measured in a respiration chamber. Thirty participants aged 23.4 ± 3.9 years with a wide range in VO
max were included. ...Participants performed four incremental cycle ergometer tests (VO
max) with a minimum of 5 days between tests. These tests consisted of one familiarization test with face mask, followed by two VO
max tests in the respiration chamber and one test with face mask in randomized order. Oxygen consumption and CO
production were measured continuously using Omnical (Maastricht University, the Netherlands) gas analysis system. The mean VO
max was 3634 ± 766 ml, which resulted in mean VO
max per lean body mass of 60.8 ± 8.0 ml/kg. Repeated respiration chamber tests showed a high concordance, and no significant differences were detected between tests (Lin's concordance correlation coefficient (Rc) = 0.99; ∆70 ± 302 ml/min; p = .38). There was high concordance between the mean VO
max from both respiration chamber tests and the mean face mask tests, and no significant difference (Rc = 0.99; ∆41 ± 173 ml/min; p = .22) was observed. The Bland-Altman plots showed no proportional bias between different tests. In conclusion, the respiration chamber has been found to be a valid and reproducible method for measuring VO
max. New research opportunities are possible in the respiration chamber, such as maximal exercise testing during 24-hour measurements.
AbstractObjectiveTo evaluate the performance of a UK based prediction model for estimating fat-free mass (and indirectly fat mass) in children and adolescents in non-UK settings.DesignIndividual ...participant data meta-analysis.Setting19 countries.Participants5693 children and adolescents (49.7% boys) aged 4 to 15 years with complete data on the predictors included in the UK based model (weight, height, age, sex, and ethnicity) and on the independently assessed outcome measure (fat-free mass determined by deuterium dilution assessment).Main outcome measuresThe outcome of the UK based prediction model was natural log transformed fat-free mass (lnFFM). Predictive performance statistics of R2, calibration slope, calibration-in-the-large, and root mean square error were assessed in each of the 19 countries and then pooled through random effects meta-analysis. Calibration plots were also derived for each country, including flexible calibration curves.ResultsThe model showed good predictive ability in non-UK populations of children and adolescents, providing R2 values of >75% in all countries and >90% in 11 of the 19 countries, and with good calibration (ie, agreement) of observed and predicted values. Root mean square error values (on fat-free mass scale) were <4 kg in 17 of the 19 settings. Pooled values (95% confidence intervals) of R2, calibration slope, and calibration-in-the-large were 88.7% (85.9% to 91.4%), 0.98 (0.97 to 1.00), and 0.01 (−0.02 to 0.04), respectively. Heterogeneity was evident in the R2 and calibration-in-the-large values across settings, but not in the calibration slope. Model performance did not vary markedly between boys and girls, age, ethnicity, and national income groups. To further improve the accuracy of the predictions, the model equation was recalibrated for the intercept in each setting so that country specific equations are available for future use.ConclusionThe UK based prediction model, which is based on readily available measures, provides predictions of childhood fat-free mass, and hence fat mass, in a range of non-UK settings that explain a large proportion of the variability in observed fat-free mass, and exhibit good calibration performance, especially after recalibration of the intercept for each population. The model demonstrates good generalisability in both low-middle income and high income populations of healthy children and adolescents aged 4-15 years.
In mammals, trait variation is often reported to be greater among males than females. However, to date, mainly only morphological traits have been studied. Energy expenditure represents the metabolic ...costs of multiple physical, physiological, and behavioral traits. Energy expenditure could exhibit particularly high greater male variation through a cumulative effect if those traits mostly exhibit greater male variation, or a lack of greater male variation if many of them do not. Sex differences in energy expenditure variation have been little explored. We analyzed a large database on energy expenditure in adult humans (1494 males and 3108 females) to investigate whether humans have evolved sex differences in the degree of interindividual variation in energy expenditure. We found that, even when statistically comparing males and females of the same age, height, and body composition, there is much more variation in total, activity, and basal energy expenditure among males. However, with aging, variation in total energy expenditure decreases, and because this happens more rapidly in males, the magnitude of greater male variation, though still large, is attenuated in older age groups. Considerably greater male variation in both total and activity energy expenditure could be explained by greater male variation in levels of daily activity. The considerably greater male variation in basal energy expenditure is remarkable and may be explained, at least in part, by greater male variation in the size of energy-demanding organs. If energy expenditure is a trait that is of indirect interest to females when choosing a sexual partner, this would suggest that energy expenditure is under sexual selection. However, we present a novel energetics model demonstrating that it is also possible that females have been under stabilizing selection pressure for an intermediate basal energy expenditure to maximize energy available for reproduction.
For the same BMI, South Asians have a higher body fat percentage than Caucasians. There might be differences in the fatty acid (FA) handling in adipose tissue when both ethnicities are exposed to ...high-fat overfeeding. The objective of the present study was to investigate the molecular adaptation in relation to FA metabolism in response to overfeeding with a high-fat diet (OHFD) in South Asian and Caucasian men. Ten South Asian men (BMI 18–29 kg/m2) and ten Caucasian men (BMI 22–33 kg/m2), matched for body fat percentage, aged 20–40 years were included. A weight-maintenance diet (30 % fat, 55 % carbohydrate and 15 % protein) was given for 3 d followed by 3 d of overfeeding (150 % energy requirement) with a high-fat diet (60 % fat, 25 % carbohydrate and 15 % protein) while staying in a respiration chamber. Before and after overfeeding, abdominal subcutaneous fat biopsies were taken. Proteins were isolated, analysed and quantified for short-chain 3-hydroxyacyl-CoA dehydrogenase (HADH), carnitine palmitoyl-transferase 1α (CPT1a), adipose TAG lipase, perilipin A (PLINA), perilipin B, lipoprotein lipase and fatty acid binding protein 4 using Western blotting. OHFD decreased the HADH level (P < 0·05) in Caucasians more than in Asians (P < 0·05), but the baseline and after intervention HADH level was relatively higher in Caucasians. The level of CPT1a decreased in South Asians and increased in Caucasians (P < 0·05). PLINA did not change with diet but the level was higher in South Asians (P < 0·05). The observed differences in HADH and PLINA levels as well as in CPT1a response may be important for differences in the long-term regulation of energy (fat) metabolism in these populations.
The aim of this study was to investigate whether VO2max can be accurately measured in a respiration chamber. Thirty participants aged 23.4 ± 3.9 years with a wide range in VO2max were included. ...Participants performed four incremental cycle ergometer tests (VO2max) with a minimum of 5 days between tests. These tests consisted of one familiarization test with face mask, followed by two VO2max tests in the respiration chamber and one test with face mask in randomized order. Oxygen consumption and CO2 production were measured continuously using Omnical (Maastricht University, the Netherlands) gas analysis system. The mean VO2max was 3634 ± 766 ml, which resulted in mean VO2max per lean body mass of 60.8 ± 8.0 ml/kg. Repeated respiration chamber tests showed a high concordance, and no significant differences were detected between tests (Lin's concordance correlation coefficient (Rc) = 0.99; ∆70 ± 302 ml/min; p = .38). There was high concordance between the mean VO2max from both respiration chamber tests and the mean face mask tests, and no significant difference (Rc = 0.99; ∆41 ± 173 ml/min; p = .22) was observed. The Bland‐Altman plots showed no proportional bias between different tests. In conclusion, the respiration chamber has been found to be a valid and reproducible method for measuring VO2max. New research opportunities are possible in the respiration chamber, such as maximal exercise testing during 24‐hour measurements.
Purpose
The effects of growth hormone (GH) treatment on linear growth and body composition have been studied extensively. Little is known about the GH effect on energy expenditure (EE). The aim of ...this study was to investigate the effects of GH treatment on EE in children, and to study whether the changes in EE can predict the height gain after 1 year.
Methods
Total EE (TEE), basal metabolic rate (BMR), and physical activity level (PAL) measurements before and after 6 weeks of GH treatment were performed in 18 prepubertal children (5 girls, 13 boys) born small for gestational age (
n
= 14) or with growth hormone deficiency (
n
= 4) who were eligible for GH treatment. TEE was measured with the doubly labelled water method, BMR was measured with an open-circuit ventilated hood system, PAL was assessed using an accelerometer for movement registration and calculated (PAL = TEE/BMR), activity related EE (AEE) was calculated AEE = (0.9 × TEE) − BMR. Height measurements at start and after 1 year of GH treatment were analysed. This is a 1-year longitudinal intervention study, without a control group for comparison.
Results
BMR and TEE increased significantly (resp. 5% and 7%). Physical activity (counts/day), PAL, and AEE did not change. 11 out of 13 patients (85%) with an increased TEE after 6 weeks of GH treatment had a good first-year growth response (∆height SDS > 0.5).
Conclusions
GH treatment showed a positive effect on EE in prepubertal children after 6 weeks. No effect on physical activity was observed. The increase in TEE appeared to be valuable for the prediction of good first-year growth responders to GH treatment.
Myotonic dystrophy type 1 (DM1) patients are at risk for metabolic abnormalities and commonly experience overweight and obesity. Possibly, weight issues result from lowered resting energy expenditure ...(EE) and impaired muscle oxidative metabolism.
This study aims to assess EE, body composition, and muscle oxidative capacity in patients with DM1 compared to age-, sex- and BMI-matched controls.
A prospective case control study was conducted including 15 DM1 patients and 15 matched controls. Participants underwent state-of-the-art methodologies including 24 h whole room calorimetry, doubly labeled water and accelerometer analysis under 15-days of free-living conditions, muscle biopsy, full body magnetic resonance imaging (MRI), dual-energy x-ray absorptiometry (DEXA), computed tomography (CT) upper leg, and cardiopulmonary exercise testing.
Fat ratio determined by full body MRI was significantly higher in DM1 patients (56 49-62 %) compared to healthy controls (44 37-52 % ; p = 0.027). Resting EE did not differ between groups (1948 1742-2146 vs (2001 1853-2425> kcal/24 h, respectively; p = 0.466). In contrast, total EE was 23% lower in DM1 patients (2162 1794-2494 vs 2814 2424-3310 kcal/24 h; p = 0.027). Also, DM1 patients had 63% less steps (3090 2263-5063 vs 8283 6855-11485 steps/24 h; p = 0.003) and a significantly lower VO2 peak (22 17-24 vs 33 26-39 mL/min/kg; p = 0.003) compared to the healthy controls. Muscle biopsy citrate synthase activity did not differ between groups (15.4 13.3-20.0 vs 20.1 16.6-25.8 μM/g/min, respectively; p = 0.449).
Resting EE does not differ between DM1 patients and healthy, matched controls when assessed under standardized circumstances. However, under free living conditions, total EE is substantially reduced in DM1 patients due to a lower physical activity level. The sedentary lifestyle of DM1 patients seems responsible for the undesirable changes in body composition and aerobic capacity.
Despite their good appetite, many females with Rett syndrome (RTT) meet the criteria for moderate to severe malnutrition. Although feeding difficulties may play a part in this, other constitutional ...factors such as altered metabolic processes are suspected. Irregular breathing is a common clinical feature, leading to chronic respiratory alkalosis or acidosis. We assumed that these changes in intracellular pH cause disturbances in the metabolic equilibrium, with important nutritional consequences. The study population consisted of a group of thirteen well-defined RTT girls with extended clinical, molecular and neurophysiological assessments. Despite normal levels of total dietary energy and protein intakes, malnutrition was confirmed based on significantly low fat-free mass index (FFMI) values. Biochemical screening of multiple metabolic pathways showed significantly elevated plasma creatine concentrations and increased urinary creatine/creatinine ratio in five RTT girls. Four girls, 10 years and older, were forceful breathers, one 13-year-old girl had an undetermined cardiorespiratory phenotype. An isolated increase of the urinary creatine/creatinine ratio was seen in two girls, a 9-year old forceful and a 4-year old feeble breather. Given that the young girls are feeble breathers and the older girls are forceful breathers, it is impossible to determine whether the elevated creatine concentrations are due to increasing age or cardiorespiratory phenotype. Furthermore, MeCP2 deficiency may cause epigenetic aberrations affecting the expression of the creatine-transporter gene, which is located at Xq28. Further studies are required to confirm these findings and to provide greater insight into the pathogenesis of the abnormal creatine metabolism in RTT.
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