Endocrine Abstracts

Introduction: Besides the benefits of low-to-high intensity physical activity (PA) on metabolism, it is currently emerging that excessive PA can be deleterious with serious implications not only in muscle but also, bone remodeling. Despite recent findings remains still unclear and controversial, we hypothesize that exercise of impact, like mountain cycling, beyond influencing the metabolic and skeletal profile, represents an important model of profoundly changes in bone metabolism.

Methods: 55 participants (mean age 44.8±7.1 years old) of mountain cycling race (TransPortugal) were evaluated at the beginning/basal (M0) and 9-days post-race (M9). Anthropometric/body composition parameters, haematological and liver function were evaluated by conventional methods. Serum Irisin and plasma osteocalcin and IL-6 measurements were evaluated with ELISA (R&D systems and Phoenix Pharmaceuticals-Irisin). Statistical analyses included departure from normality and adequate parametric or non-parametric test to compare the means and the medians. The results were significant for P<0.05.

Results: In the metabolic point of view, we found that this strenuous exercise induced a significant decrease of fasting insulin, triglycerides, total-cholesterol, non-HDL cholesterol, LDL and an increase of glucose, creatinine, uric acid, HDL, HOMA-B (P<0.05). These results reflected the important modifications in muscle, being the myokine/adipokine, irisin, significantly decreased post-race (P=0.002). In terms of bone remodelling, although not statistically significant, osteocalcin was decreased post-race (P=0.154), yet the plasma IL-6, a cytokine involved in osteoclastic proliferation, was significantly increased post-race (P<0.0001).

Conclusions: Our preliminary results, revealed a possible regulation of osteocalcin in glucose and insulin metabolism, being the slowdown in bone formation observed, a prompt metabolic response of bone to the increased energy demands of the muscle.