The Effect of High- and Moderate-intensity Endurance Training on Some Anabolic/Catabolic Osteokines in Old Male Wistar Rats

Bone-related osteokines are crucial for bone function and metabolic response to physical activity. The present study aimed to shed light on the effect of different intensities of continuous and interval endurance training on the serum levels of some osteokines that are associated with wingless-related integration site (WNT) signaling pathway and Receptor Activator of Nuclear Factor (NF)-κB Ligand (RANKL) in old male Wistar rats.

A total of 24 old male Wistar rats (mean age: 23 months, mean weight: 437.93 g) were randomly assigned to three groups: interval endurance-training group (n=8), continuous endurance-training group (n=8), and control group (n=8). The continuous and interval training interventions comprised 8 weeks of treadmill exercise, 5 days a week. The continuous endurance-training group started to exercise at 60% of velocity at maximal oxygen uptake (vVO2max) for 16 min during the first week. It continued with 70% of vVO2max for 45 min from the fourth week onward. In contrast, the interval endurance-training group switched on exercise with 40%-80% of vVO2max from the first week and persisted with 30%-110% of vVO2max from the fourth week onward. As the exercise bout was completed, the enzyme-linked immunosorbent assay was applied to measure the study dependent variables. Statistical analysis was further performed using 1-way analysis of variance, considering the significance level of P≤0.05.

The study results demonstrated a significant difference in the levels of Oteoprotegerin (OPG) (P=0.036) and RANKL (P=0.001) in the experimental (namely, interval and continuous training) groups compared with the controls following the exercise bout. However, the level of sclerostin was not significantly changed (P=0.549).

High-intensity endurance training in the RANKL/OPG and WNT pathways decreased sclerostin and RANKL levels, but this decrease was significant at the RANKL level. It was effective with regard to the intensities of different types of endurance exercise.