Among the several determinants of bone health, emerging evidence focused on the influence of bone marrow metabolism. The topic is addressed in human studies involving both healthy subjects and participants with different pathological conditions, particularly those associated with altered adipose tissue metabolism. The main perturbation of bone marrow metabolism that was found to significantly and negatively impact bone health was the increase in the adipose tissue content within the bone marrow. This evidence translates in a clinically relevant increase in fracture risk in conditions associated with augmented bone marrow adipose tissue, such as insulin resistance and diabetes.
Ojala et al. conducted an interesting study analyzing bone marrow metabolism in terms of glucose and free fatty acids uptake both at baseline and in response to exercise training in subjects with insulin resistance. The use of positron emission tomography allowed authors to identify glucose and free fatty acids uptake in different skeletal regions. As expected, they found impairment in the bone marrow uptake of both glucose and free fatty acids in association with the presence of insulin resistance, as well as differences in the bone marrow metabolism at different skeletal sites. The most important result was the observation that a 2-week exercise-training program was successful in reversing the abnormal bone marrow metabolism. Glucose uptake stimulated by insulin increased and fatty acids uptake decreased after exercise intervention not only in subjects with insulin resistance but also in healthy participants.
Notwithstanding the limited number of subjects studied, results from this study provide interesting cues on an important topic, namely the role of exercise training in the management of metabolic bone disease. The impact of exercise intervention on bone health is indeed not fully and specifically included in clinical guidelines and neither frequently nor adequately recommended in clinical practice. This point could be certainly explained by the lack of robust evidence detailing specific types of efficacious exercise interventions in patients with osteoporosis and fractures, particularly those with concomitant conditions affecting other metabolic pathways. As fragility fractures represent a relevant proportion of the global burden of metabolic disease such as diabetes and obesity, research studies suggesting training programs targeting both weight loss, glucose, but also bone metabolism will definitely impact clinical management of such conditions. The evaluation of bone marrow metabolism, that represents one of the “trait d’union” between adipose tissue and bone metabolism, needs to be included in such studies, as well as long term data.
Among the undoubted several beneficial effects of exercise in our life, those on the bone marrow metabolism may represent a new way of preserving skeletal health.