Exercise Intensity Affects Acylated and Deacylated Ghrelin Levels in Humans Independent of Sex

Ghrelin circulates in acylated (AG) and deacylated (DAG) forms, which are known to have independent effects on glucose regulation, vascular health, and appetite. While acute exercise has been shown to affect ghrelin levels, data on the impact of exercise intensity on AG and DAG is sparse and primarily limited to males. PURPOSE: To investigate the effect of exercise intensity and sex on AG and DAG levels in untrained humans. METHODS: Four males (age: 44.5 ± 6.0y; BMI: 22.3 ± 0.61; VO2peak: 37.7 ± 5.8 mL/kg/min) and six females (age: 41.2 ± 6.0 y; BMI: 24.7 ± 5.5 kg/m2; VO2peak: 25.7 ± 5.0 mL/kg/min) completed a maximal graded cardiopulmonary cycle VO2peak/lactate threshold (LT) exercise test. This data was used to determine the exercise intensity on 3 subsequent randomized control or calorically matched cycle exercise bouts: a) CON, no exercise; b) MOD, the power output at LT; c) HIGH, the power output associated with 75% of the difference between LT and VO2peak. All visits occurred in the morning after an overnight fast. Blood was sampled at each visit at 0, 10, 20, 30, 40, 50, 60, 120, 150, and 180 minutes. Plasma AG and DAG were analyzed using ELISAs. Area under the curve (AUC) was calculated for AG (AGAUC) and DAG (DAGAUC) using the trapezoidal method. Two linear mixed models (1: AG, 2: DAG) were used to examine the ghrelin response to exercise, with subject as a random factor and sex and condition as fixed factors. Satterwaite’s approximation was utilized to determine significance. Data are reported as mean ± SE. RESULTS: The AG model found a significant main effect (p = 0.01) for condition, with lower AGAUC in HIGH (7,602 ± 1,996 min *AUC180) compared to MOD (12,876 ± 1,955 min *AUC180, p = 0.008) and CON (11,903 ± 1955 min *AUC180, p = 0.03). The DAG model also revealed a significant effect for condition (p = 0.01), with lower DAGAUC in HIGH (13,350 ± 2,463 min *AUC180) compared to MOD (19,900 ± 2,390 min *AUC180, p = 0.02) and CON (19,800 ± 2,390 min *AUC180, p = 0.03). There was no effect of sex or interaction of sex and condition on either model. CONCLUSION: Our data indicates exercise above LT decreases AG and DAG levels independent of sex. Additional data with a larger sample size is needed to fully elucidate the effect of exercise intensity and sex on AG and DAG. Funding: UVA School of Education and Human Development and NIDDK (5R01DK129510-02)