Serum neurotrophic factor levels in children with specific learning disorder

Objective: Evidence suggests that interactions of neurobiologic, genetic and environmental factors play role in etiology of specific learning disorder (SLD), but the definite mechanisms underlying SLD remain mostly unknown. Neurotrophic factors have important roles in nervous system such as neurogenesis, neuronal migration and neuroplasticity and possible role of neurotrophic factors have implicated in the the pathophysiology of various neurodevelopmental disorders. However, to our knowledge, there are no previous studies investigating the role of neurotrophic factors in SLD. The aim of this study was to investigate whether serum levels of brain derived neurotrophic factor (BDNF), glial derived neurotrophic factor (GDNF), nerve growth factor (NGF) and neurotrophin-3 (NT-3) in children with SLD differ from healthy controls and to evaluate relations between neurotrophic factor levels and clinical features of SLD. Methods: 44 patients with diagnosis of SLD and 44 controls consisting of healthy volunteers between ages of 7-12 were included in this study. SLD diagnosis was supported by SLD clinical observation battery in addition to the DSM based interview. All participants were screened for psychiatric disorders using the Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version, DSM-5 and IQ levels of all participants were evaluated using the Wechsler Intelligence Scale for Children-Revised. Parents completed sociodemographic questionnaire and Conners' Parent Rating Scale-Revised Short (CPRS-RS). 5-8 ml venous blood samples are obtained from both groups and neurotrophic factor levels were measured with ELISA using commercial human ELISA kits. Results: Serum BDNF, NGF and NT-3 levels of SLD patients were significantly higher than those of the controls. Serum GDNF levels were significantly different between mild and severe SLD groups classified according to DSM-5 criteria and serum GDNF levels were lower in severe SLD group. There was also significant correlation between severity of reading disorder and serum GDNF levels, serum GDNF levels were lower in children whose reading speed were slower. Conclusions: Our findings suggest that neurotrophic factors might play a role in the pathophysiology of SLD. The elevation of serum levels of BDNF, NGF and NT-3 might be a compensatory attempt at neuroprotection against neurodevelopmental impairment. Further studies are necessary to confirm the relationship between neurotrophic factors and SLD.