Effect Of Acute Exercise Intensity On Ghrelin Levels In Untrained Adults

Ghrelin is a peptide hormone that affects hunger, energy intake, and growth hormone secretion. Ghrelin circulates in two isoforms: acyl ghrelin (AG) and deacylated ghrelin (DAG). Acute exercise is associated with ghrelin suppression, yet most data is in young, trained males and only AG is measured. PURPOSE: To investigate the effects of exercise intensity on ghrelin (total ghrelin [TG], AG, DAG) in untrained males and females. METHODS: Eight males (age: 42.3 ± 10.9 y.; BMI: 26.6 ± 5.7 kg/m2; VO2peak: 30.7 ± 8.7 ml/kg/min) and eight females (age: 35.3 ± 11.1 y.; BMI: 24.3 ± 4.7 kg/m2; VO2peak: 27.7 ± 5.7 ml/kg/min) completed a maximal cardiopulmonary exercise test on a cycle ergometer to obtain VO2peak and lactate threshold (LT). Maximal testing data was used to determine the intensity of subsequent randomized, calorically matched exercise conditions – moderate intensity (MOD): power output at LT; high intensity (HIGH): power output at 75% of difference between VO2peak and LT; and control (CON): no exercise. Blood samples were obtained via an IV catheter at baseline, every 10 minutes for the first hour post-exercise, and at 30-minute increments for the last 2 hours of each session to measure TG, AG, DAG, and lactate (LAC). Area under the curve (AUC) was calculated for ghrelin isoforms and lactate using the trapezoidal method. Separate linear mixed models (one for each isoform) were used to determine ghrelin response to exercise – participant was the random factor; sex and condition were fixed factors. Estimated marginal means (EMM) estimated means adjusted for factors in each model. RESULTS: TGAUC, AGAUC, and DAGAUC models identified a main effect for condition with lower levels following the HIGH exercise compared to MOD and CON (p < 0.01). There was an interaction for condition and sex in the TGAUC and AGAUC models (TG: p = 0.04; AG: p < 0.05), where females had higher levels. For LACAUC, there was a main effect for condition such that HIGH was greater than MOD and CON (p < 0.0001). Moreover, LACAUC was inversely related to TGAUC and DAGAUC (p < 0.05). CONCLUSIONS: Exercise above LT transiently suppressed ghrelin levels, and sex may affect this response. Lactate contributes to the exercise-induced reduction of ghrelin. UVA School of Education and Human Development and NIH NIDDK (R01 DK129510)