@article{33392,
abstract = {{Abstract
Context
The effects of energy-balanced bed rest on metabolic flexibility have not been thoroughly examined.
Objective
We investigated the effects of 21 days of bed rest, with and without whey protein supplementation, on metabolic flexibility while maintaining energy balance. We hypothesized that protein supplementation mitigates metabolic inflexibility by preventing muscle atrophy.
Design and Setting
Randomized crossover longitudinal study conducted at the German Aerospace Center, Cologne, Germany.
Participants and Interventions
Ten healthy men were randomly assigned to dietary countermeasure or isocaloric control diet during a 21-day bed rest.
Outcome Measures
Before and at the end of the bed rest, metabolic flexibility was assessed during a meal test. Secondary outcomes were glucose tolerance by oral glucose tolerance test, body composition by dual energy X-ray absorptiometry, ectopic fat storage by magnetic resonance imaging, and inflammation and oxidative stress markers.
Results
Bed rest decreased the ability to switch from fat to carbohydrate oxidation when transitioning from fasted to fed states (i.e., metabolic inflexibility), antioxidant capacity, fat-free mass (FFM), and muscle insulin sensitivity along with greater fat deposition in muscle (P < 0.05 for all). Changes in fasting insulin and inflammation were not observed. However, glucose tolerance was reduced during acute overfeeding. Protein supplementation did not prevent FFM loss and metabolic alterations.
Conclusions
Physical inactivity triggers metabolic inflexibility, even when energy balance is maintained. Although reduced insulin sensitivity and increased fat deposition were observed at the muscle level, systemic glucose intolerance was detected only in response to a moderately high-fat meal. This finding supports the role of physical inactivity in metabolic inflexibility and suggests that metabolic inflexibility precedes systemic glucose intolerance.
}},
author = {{Rudwill, Floriane and O’Gorman, Donal and Lefai, Etienne and Chery, Isabelle and Zahariev, Alexandre and Normand, Sylvie and Pagano, Allan F and Chopard, Angèle and Damiot, Anthony and Laurens, Claire and Hodson, Leanne and Canet-Soulas, Emmanuelle and Heer, Martina and Meuthen, Petra Frings and Bühlmeier, Judith and Baecker, Natalie and Meiller, Laure and Gauquelin-Koch, Guillemette and Blanc, Stéphane and Simon, Chantal and Bergouignan, Audrey}},
issn = {{0021-972X}},
journal = {{The Journal of Clinical Endocrinology & Metabolism}},
keywords = {{Biochemistry (medical), Clinical Biochemistry, Endocrinology, Biochemistry, Endocrinology, Diabetes and Metabolism}},
number = {{5}},
pages = {{1910--1920}},
publisher = {{The Endocrine Society}},
title = {{{Metabolic Inflexibility Is an Early Marker of Bed-Rest–Induced Glucose Intolerance Even When Fat Mass Is Stable}}},
doi = {{10.1210/jc.2017-02267}},
volume = {{103}},
year = {{2018}},
}
@article{33399,
author = {{Bühlmeier, Judith and Frings-Meuthen, Petra and Remer, Thomas and Maser-Gluth, Christiane and Stehle, Peter and Biolo, Gianni and Heer, Martina}},
issn = {{0021-972X}},
journal = {{The Journal of Clinical Endocrinology & Metabolism}},
keywords = {{Biochemistry (medical), Clinical Biochemistry, Endocrinology, Biochemistry, Endocrinology, Diabetes and Metabolism}},
number = {{12}},
pages = {{4789--4797}},
publisher = {{The Endocrine Society}},
title = {{{Alkaline Salts to Counteract Bone Resorption and Protein Wasting Induced by High Salt Intake: Results of a Randomized Controlled Trial}}},
doi = {{10.1210/jc.2012-2857}},
volume = {{97}},
year = {{2012}},
}
@article{27728,
abstract = {{
Context:
Whether prepubertal glucocorticoid status impacts on the timing of puberty is not clear.
Objective:
The objective of the study was to examine the relationship between prepubertal glucocorticoid status and early or late pubertal markers, independent of adrenarchal and nutritional status.
Design and Participants:
Prospective cohort study of healthy Caucasian children (n = 111, 56 boys) who provided both 24-h urine samples and weighed dietary records 1 and 2 yr before the start of pubertal growth spurt [age at take-off (ATO)].
Measurements:
Major urinary glucocorticoid and androgen metabolites determined by gas chromatography-mass spectrometry analysis were summed to assess daily overall cortisol (ΣC21) and adrenal androgen secretion; urinary free cortisol and cortisone measured by RIA were summed (UFF+UFE) as an indicator of potentially bioactive free glucocorticoids.
Main Outcomes:
The main outcomes included ATO, age at peak height velocity, age at menarche/voice break, ages at Tanner stage 2 for breast (girls) and genital (boys) development, and pubic hair.
Results:
In girls ΣC21, but not UFF+UFE, was associated with pubertal markers after adjusting for overall adrenal androgen, urinary nitrogen, and body fat. Girls with higher ΣC21 (fourth quartile) reached ATO 0.7 yr (P = 0.01) and menarche 0.9 yr later (P = 0.006) than girls with lower ΣC21 (first quartile). The ΣC21 tended to be also positively associated with age at Tanner stage 2 for breast (P = 0.1), Tanner stage 2 for pubic hair (P = 0.1), and age at peak height velocity (P = 0.06). In boys, neither the ΣC21 nor UFF+UFE was related to pubertal timing.
Conclusion:
An individually higher prepubertal glucocorticoid secretion level, even in physiological range, appears to delay early and late pubertal timing of healthy girls, particularly their onset of pubertal growth spurt and menarche.
}},
author = {{Shi, Lijie and Wudy, Stefan A. and Buyken, Anette and Maser-Gluth, Christiane and Hartmann, Michaela F. and Remer, Thomas}},
issn = {{0021-972X}},
journal = {{The Journal of Clinical Endocrinology & Metabolism}},
pages = {{E891--E898}},
title = {{{Prepubertal Glucocorticoid Status and Pubertal Timing}}},
doi = {{10.1210/jc.2010-2935}},
year = {{2011}},
}
@article{27723,
author = {{Remer, Thomas and Shi, Lijie and Buyken, Anette and Maser-Gluth, Christiane and Hartmann, Michaela F. and Wudy, Stefan A.}},
issn = {{0021-972X}},
journal = {{The Journal of Clinical Endocrinology & Metabolism}},
pages = {{3002--3009}},
title = {{{Prepubertal Adrenarchal Androgens and Animal Protein Intake Independently and Differentially Influence Pubertal Timing}}},
doi = {{10.1210/jc.2009-2583}},
year = {{2010}},
}
@article{27762,
author = {{Kratz, Mario and von Eckardstein, Arnold and Fobker, Manfred and Buyken, Anette and Posny, Nicole and Schulte, Helmut and Assmann, Gerd and Wahrburg, Ursel}},
issn = {{0021-972X}},
journal = {{The Journal of Clinical Endocrinology & Metabolism}},
pages = {{5008--5014}},
title = {{{The Impact of Dietary Fat Composition on Serum Leptin Concentrations in Healthy Nonobese Men and Women}}},
doi = {{10.1210/jc.2002-020496}},
year = {{2002}},
}