Induction of salivary nerve growth factor by Yogic breathing: a randomized controlled trial

Abstract

Nerve growth factor (NGF), a trophic factor involved in the development, maintenance, and survival of the peripheral nervous system and the cholinergic neurons of the central nervous system, is significantly reduced in Alzheimer's Disease (AD) patients (Aloe et al., 2012). Particularly basal forebrain complex (BFC) neurons are highly affected in AD patients. NGF protects BFC neurons in experimental trauma models and in age-associated cholinergic decline. Therefore, administration of NGF is investigated as a therapeutic option for AD patients (Aloe et al., 2012). NGF therapy is limited by hyperalgesia, limited bioavailability, and use of invasive methods including intracranial injection of adeno-associated virus-based gene delivery vector, which constitutively expresses human NGF. In this context, non-pharmacological modes of treatment such as meditation and Yoga have been considered as alternative approaches to treat neurological disorders. Yogic breathing (YB, also called Pranayama) is a collection of techniques to regulate breathing voluntarily. YB induces a strong relaxation response via vagal and parasympathetic stimulation (Jerath et al., 2006). Such responses are causally linked to rapid changes in gene expression, particularly to those genes controlling stress, inflammation, and metabolism. Saliva is a known source of NGF, and incidentally, Yoga and relaxation stimulate salivation. Saliva (0.75–1.5 L/day in humans) contains numerous biologically active molecules to be potentially useful as diagnostic markers and as therapeutic clues. Salivary secretion regulates the digestive, nervous, immune, and respiratory systems. We conducted a pilot study to investigate whether YB could potentially stimulate salivary expression of NGF in cognitively normal healthy volunteers. This could serve as a model for future studies in AD patients.