The Vestibular System: A Newly Identified Regulator of Bone Homeostasis Acting Through the Sympathetic Nervous System

Abstract

The vestibular system is a small bilateral structure located in the inner ear, known as the organ of balance and spatial orientation. It senses head orientation and motion, as well as body motion in the three dimensions of our environment. It is also involved in non-motor functions such as postural control of blood pressure. These regulations are mediated via anatomical projections from vestibular nuclei to brainstem autonomic centers and are involved in the maintenance of cardiovascular function via sympathetic nerves. Age-associated dysfunction of the vestibular organ contributes to an increased incidence of falls, whereas muscle atrophy, reduced physical activity, cellular aging, and gonadal deficiency contribute to bone loss. Recent studies in rodents suggest that vestibular dysfunction might also alter bone remodeling and mass more directly, by affecting the outflow of sympathetic nervous signals to the skeleton and other tissues. This review will summarize the findings supporting the influence of vestibular signals on bone homeostasis, and the potential clinical relevance of these findings.

Editorial: The Vestibular System in Cognitive and Memory Processes in Mammalians

“…Ideas are emerging on the cerebral benefits of vestibular stimulation which might even spread beyond the brain. For example, recent studies report that the vestibular organ can influence bone and muscle remodeling (Vignaux et al, 2015 ), help synchronize circadian rhythms (Fuller et al, 2002 ; Martin et al, 2015 ), and regulate vegetative and postural blood pressure (Normand et al, 1997 ; Yates et al, 2014 ).…”

Fat and Bone: Where are We Now?

“…Our understanding of neuronal control has extended from the sympathetic nervous system [14] to the parasympathetic and sensory nervous systems [15,16]. Abnormalities in the central nervous system such as vestibular dysfunction may also indirectly affect bone mass [17]. The role of the central nervous system in bone metabolism and the specific role of adiponectin in skeletal metabolism are addressed in this issue.…”

Impaired Vestibular Function and Low Bone Mineral Density: Data from the Baltimore Longitudinal Study of Aging

“…The vestibular system sends projections to autonomic nervous system centers including brainstem medullary and pontine nuclei (Balaban 1999;Luxon and Pagarkar 2013;Holstein et al 2014). Moreover, the effect of vestibular ablation on bone mineral density seen in rats was abrogated by the concurrent administration of a sympathetic antagonist and in beta receptor knockout mice (Denise et al 2009;Vignaux et al 2013;Vignaux et al 2014;Vignaux et al 2015). Interestingly, the changes in bone mineral density following vestibular lesion in rodents were limited to the weight-bearing lower extremity bones (Levasseur et al 2004;Denise et al 2009;Vignaux et al 2013;Vignaux et al 2014).…”

“…Recent studies in animals have found that experimentally induced loss of vestibular function leads to decreases in bone mineral density, possibly through effects mediated by the sympathetic nervous system (Levasseur et al 2004;Denise et al 2009;Vignaux et al 2014;Vignaux et al 2015). Although these studies reported no difference in physical activity between control and vestibular-deafferented mice, physical activity level may play an important role as a mediator and/or confounder of the association between vestibular function and BMD.…”

“…A recent qualitative study found patients with vestibular impairments report decreased physical activity (Harun et al 2016), while another study found decreased gait speed in older adults which may in part be due to changes in saccular function (Layman et al 2015). The vestibular system is an evolutionarily ancient sensor of gravitational force, and it has been hypothesized that vestibular input is essential for the development of appropriate bone architecture in the direction of gravity (Vignaux et al 2013;Vignaux et al 2015). In addition, there is evidence that spinal scoliosis and other disorders of postural alignment are often accompanied by impaired vestibular function in both animals and humans (Lambert et al 2013).…”