Impact Of Obesity, Insulin Sensitivity, Exercise Intensity, And Sex On Ghrelin Release With Acute Exercise

The hormone ghrelin exists in 2 isoforms, acylated (AG) and deacylated (DAG), and has systemic metabolic effects, including regulation of body weight and glucose metabolism. Ghrelin dysregulation is common in adults with obesity and/or diabetes and exercise has been shown to influence its release. However, few data examine the relationship among obesity, insulin sensitivity (IS), and acute exercise of differing intensity in untrained males and females. PURPOSE: To examine the effects of obesity (BMI > 30) and IS (Masuda Index >4.3) on ghrelin during acute exercise. METHODS: Sixteen lean adults (14IS/9F; Age: 38.4 ± 11.2 y.; BMI: 22.4 ± 1.7 kg/m2; VO2peak: 31.2 ± 6.0 ml/kg/min) and 13 adults with obesity (4IS/8F; Age: 37.9 ± 9.8 y.; BMI: 33.7 ± 2.3 kg/m2; VO2peak: 21.7 ± 4.4 ml/kg/min) completed a maximal exercise test on a cycle ergometer. Lactate threshold (LT) and VO2peak were used to set intensities for 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): rest. IS was determined by an oral glucose tolerance test. Blood samples obtained from an indwelling catheter every 10 min for the first hr, and every 30 min for last 2 hr during experimental visits were used to measure total ghrelin (TG), AG, and DAG. Linear mixed models were used to determine ghrelin response to exercise, with participant as the random factor and obesity status, IS, sex, time, and condition as fixed factors. RESULTS: Overall, ghrelin (TG, AG, DAG) was decreased in HIGH v CON (p < 0.001), and there was an interaction effect for obesity, sex, and condition (p < 0.001-0.027). In IS subjects, ghrelin (TG, AG, DAG) was decreased during HIGH v CON (p < 0.001), regardless of sex and obesity. Females, regardless of obesity status, had decreased AG and TG in HIGH v CON (p < 0.001-0.0162). Lean males had reduced DAG and TG in HIGH v CON (p < 0.001). CONCLUSIONS: Obesity, IS, exercise intensity, and sex influence ghrelin responses to acute exercise, with lean adults and females having suppressed ghrelin release with high intensity exercise. Moreover, IS individuals, regardless of obesity status, appear to have reduced ghrelin levels with high intensity exercise.