Urinary levels of neurotrophic factors (NGF and BDNF) in patients with detrusor overactivity

Abstract

Overactive bladder refers to a group of urinary symptoms involving urinary urgency accompanied by pollakiuria or day time and nocturnal enuresis. Urodynamic testing is the gold standard for diagnosing the most frequent form of overactive bladder that is detrusor overactivity. Neurotrophins (nerve growth factor – NGF, brain-derived neurotrophic factor – BDNF, neurotrophin 3 – NT-3, and neurotrophin 4 – NT-4) are proteins secreted by the nervous system, found in many tissues, including bladder cells. They are bound by two types of receptors: low- and high-affinity receptors, two of which, i.e. tropomyosin receptor kinase A (TrkA) and p75 receptor, are located in the epithelial cells of the urinary bladder. The detrusor muscle was shown to secrete NGF in response to stretching of the urinary bladder. In addition, numerous studies have shown an increase in the urinary levels of NGF and BDNF in patients with overactive bladder and their decrease after the introduction of anticholinergic therapy. Therefore, the assessment of urinary levels of neurotrophins NGF and BDNF seems to be useful as a potential biomarker of detrusor overactivity. Unfortunately, the sensitivity of these parameters in the diagnosis of detrusor overactivity is low due to the possible overlapping of other conditions, especially bladder pain syndrome, which affects mainly adults. Additionally, previous studies have been conducted in small groups of patients, therefore studies in a larger population are needed. Confirming the usefulness of these biomarkers in the future opens the opportunity to replace the urodynamic test with the analysis of urinary markers, which would significantly simplify diagnosis and increase patient’s comfort.