Acute sucrose availability before and during high-intensity interval exercise modifies recovery-phase myonectin...

Myonectin is a nutrient-responsive myokine implicated in systemic lipid handling, yet whether acute carbohydrate availability modifies exercise-induced myonectin responses in postmenopausal obesity remains unclear. This randomized crossover study examined the effects of sucrose ingestion before and during high-intensity interval exercise (HIIT) on circulating myonectin and related metabolic-myokine responses in postmenopausal women with obesity.

Fifteen postmenopausal women with obesity completed two experimental trials in randomized order: sucrose ingestion before and during HIIT and a non-caloric control trial. Trials were separated by a 7-day washout period. Venous blood samples were obtained before exercise, immediately after exercise, and 2 h after exercise. Circulating myonectin was the primary outcome; glucose, insulin, free fatty acids, glycerol, lactate, and interleukin-6 were secondary outcomes used to characterize the accompanying metabolic and myokine environment. Linear mixed-effects models included condition, time, condition × time, period, and treatment sequence.

Significant condition × time interactions were observed for myonectin, glucose, insulin, free fatty acids, glycerol, lactate, and interleukin-6. Myonectin increased in both conditions, but the 2 h increase was greater following sucrose ingestion than control (between-condition difference: 0.543 ng/mL, 95% CI 0.346-0.741, p < 0.001). Sucrose produced higher glucose, insulin, and lactate responses, while attenuating free fatty acid and glycerol responses during early recovery. Although interleukin-6 increased in both trials, the 2 h interleukin-6 response was lower in the sucrose condition. No period or sequence effect was observed for myonectin.

Under a common HIIT stimulus, the sucrose condition was associated with a greater recovery-phase increase in circulating myonectin and distinct metabolic responses compared with the non-caloric control condition. Without non-exercise conditions or another carbohydrate comparator, these findings cannot establish an effect independent of exercise, an exercise × sucrose interaction, or specificity to sucrose. Circulating measurements also do not establish altered myonectin production or secretion.