Exercise training during normobaric hypoxic confinement does not alter hormonal appetite regulation

Abstract

Background: Both exposure to hypoxia and exercise training have the potential to modulate appetite and induce beneficial metabolic adaptations. The purpose of this study was to determine whether daily moderate exercise training performed during a 10-day exposure to normobaric hypoxia alters hormonal appetite regulation and augments metabolic health.

Methods: Fourteen healthy, male participants underwent a 10-day hypoxic confinement at ∼ 4000 m simulated altitude (FIO2 = 0.139 ± 0.003%) either combined with daily moderate intensity exercise (Exercise group; N = 8, Age = 25.8 ± 2.4 yrs, BMI = 22.9 ± 1.2 kg · m(-2)) or without any exercise (Sedentary group; N = 6 Age = 24.8 ± 3.1 yrs, BMI = 22.3 ± 2.5 kg · m(-2)). A meal tolerance test was performed before (Pre) and after the confinement (Post) to quantify fasting and postp randial concentrations of selected appetite-related hormones and metabolic risk markers. 13C-Glucose was dissolved in the test meal and 13CO2 determined in breath samples. Perceived appetite ratings were obtained throughout the meal tolerance tests.

Results: While body mass decreased in both groups (-1.4 kg; p = 0.01) following the confinement, whole body fat mass was only reduced in the Exercise group (-1.5 kg; p = 0.01). At Post, postprandial serum insulin was reduced in the Sedentary group (-49%; p = 0.01) and postprandial plasma glucose in the Exercise group (-19%; p = 0.03). Fasting serum total cholesterol levels were reduced (-12%; p = 0.01) at Post in the Exercise group only, secondary to low-density lipoprotein cholesterol reduction (-16%; p = 0.01). No differences between groups or testing periods were noted in fasting and/or postprandial concentrations of total ghrelin, peptide YY, and glucagon-like peptide-1, leptin, adiponectin, expired 13CO2 as well as perceived appetite ratings (p>0.05).

Conclusion: These findings suggest that performing daily moderate intensity exercise training during continuous hypoxic exposure does not alter hormonal appetite regulation but can improve the lipid profile in healthy young males.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. Study protocol and meal tolerance test outline.

The meal tolerance test (MTT) was performed in the morning, one day before (Day -1) and just prior to exiting the 10-day confinement (morning of Day +1). FIO2, Fraction of inspired oxygen; VAS, Visual analogue scale for perceived appetite rating; AIR, Exhaled air sampling for determination of 13C isotope; MET, Blood sampling for determination of metabolic markers: total ghrelin, peptide YY, Glucagon-like peptide-1 and insulin at all samplings and leptin, adiponectin, free fatty acids, triacylglycerols, cholesterol, and catecholamines during fasting samplings only; GLU, Blood sampling for plasma glucose concentration determination.

Figure 2. Total ghrelin and peptide YY (PYY) kinetics during the meal tolerance test in both Exercise (A, C) and Sedentary (B, D) group, respectively.

The meal tolerance test (MTT) was performed before (Pre; closed circles) and after (Post; open squares) the confinement. Two-way repeated measures ANOVA analysis, followed by a Tukey's HSD post hoc test; # indicates significant differences compared to fasting values (# p<0.05; ## p<0.01). Values are mean ± SEM.

Figure 3. Glucagon-like peptide-1 (GLP-1) and insulin kinetics during the meal tolerance test in Exercise (A, C) and Sedentary (B, D) group, respectively.

The meal tolerance test (MTT) was performed before (Pre; closed circles) and after (Post; open squares) the confinement. Two-way repeated measures ANOVA analysis, followed by a Tukey's HSD post hoc test; # indicates significant differences compared to fasting values (# p<0.05; ## p<0.01). * indicates significant differences compared to Pre values (p<0.05). Values are mean ± SEM.

Figure 4. Composite satiety scores before (Fast) and at 30-min intervals throughout the meal tolerance test for both Exercise (A) and Sedentary group (B).

One-way repeated measures ANOVA followed by Tukey's HSD post hoc test; # indicates significant differences compared to fasting values (p<0.05). Values are mean ± SEM.

Figure 5. Plasma glucose kinetics and atom percent excess (APE) of expired CO2 isotopic enrichment changes during the meal tolerance test in Exercise (A, C) and Sedentary group (B, D), respectively.

The meal tolerance test (MTT) was performed before (Pre; closed circles) and after (Post; open squares) the confinement. Two-way repeated measures ANOVA followed by Tukey's HSD post hoc test; ## indicates significant differences compared to fasting values (p<0.01). * indicates significant differences compared to Pre values (p<0.05). Values are mean ± SEM.

Figure 6. Fasting total cholesterol (A) and low-density lipoprotein cholesterol (LDL-C) levels in both Exercise and Sedentary group before (Pre), following the first 24-hrs of confinement (Day 2) and immediately after the confinement (Post).

One-way repeated measures ANOVA followed by Tukey's HSD post hoc test; # indicates significant differences compared to Pre (# p<0.05; ## p<0.01). * indicates significant differences compared to the Sedentary group (p<0.05). Values are mean ± SEM.