The effect of eight-week high intensity interval training (HIIT) and caffeine consumption on glycogen synthase expression and hepatic glycogen levels in diabetic rats

Diabetes is a common metabolic disease that leads to impaired hepatic glycogen synthesis. The present study investigates the effect of eight weeks of intense intermittent exercise (HIIT) and caffeine consumption on glycogen synthase (GYS2) expression and liver glycogen levels in diabetic rats.

In an experimental clinical-intervention study, 50 streptozotocin-induced diabetic rats were divided into 5 equal groups of control (C), diabetic (D), supplemental diabetic (D + CAF), diabetic with exercise (D + T), supplement and exercise (D + CAF + T). The training program consisted of eight weeks, 5 sessions per week (6 to 12 2-minute sessions with an intensity of 85-90% of the maximum speed) and 70 mg/kg of caffeine were injected five days a week. After anesthesia, liver tissue was extracted and the expression levels of (GYS2) and liver glycogen were assessed. Data analysis was performed by independent t-test and two-way ANOVA at a significant level of (P<0.05).

Induction of diabetes significantly reduced hepatic glycogen and GYS2 expression (P<0.001). Also, caffeine consumption (P<0.01) and HIIT (P=0.024) both significantly increased GYS2, which had a greater effect of caffeine with a 44% effect size. Also, HIIT (P=0.529) and caffeine (P=0.761) neither alone, nor in combination (P=0.12) caused a significant increase in hepatic glycogen.

According to results, it is possible to suggest HIIT and caffeine consumption as an effective intervention to improve (GYS2) expression. However, a clear statement requires further research in this area.