BDNF as potential biomarker of epilepsy severity and psychiatric comorbidity: pitfalls in the clinical population

Reduced Levels of Lacrimal Glial Cell Line-Derived Neurotrophic Factor (GDNF) in Patients with Focal Epilepsy and Focal Epilepsy with Comorbid Depression: A Biomarker Candidate

Our previous studies showed that in patients with brain diseases, neurotrophic factors in lacrimal fluid (LF) may change more prominently than in blood serum (BS). Since glial cell line-derived neurotrophic factor (GDNF) is involved in the control of neuronal networks in an epileptic brain, we aimed to assess the GDNF levels in LF and BS as well as the BDNF and the hypothalamic-pituitary-adrenocortical and inflammation indices in BS of patients with focal epilepsy (FE) and epilepsy and comorbid depression (FE + MDD) and to compare them with those of patients with major depressive disorder (MDD) and healthy controls (HC). GDNF levels in BS were similar in patients and HC and higher in FE taking valproates. GDNF levels in LF were significantly lower in all patient groups compared to controls, and independent of drugs used. GDNF concentrations in LF and BS positively correlated in HC, but not in patient groups. BDNF level was lower in BS of patients compared with HC and higher in FE + MDD taking valproates. A reduction in the GDNF level in LF might be an important biomarker of FE. Logistic regression models demonstrated that the probability of FE can be evaluated using GDNF in LF and BDNF in BS; that of MDD using GDNF in LF and cortisol and TNF-α in BS; and that of epilepsy with MDD using GDNF in LF and TNF-α and BDNF in BS.

Stress and Epilepsy: Towards Understanding of Neurobiological Mechanisms for Better Management

Stress has been identified as a major contributor to human disease and is postulated to play a substantial role in epileptogenesis. In a significant proportion of individuals with epilepsy, sensitivity to stressful events contributes to dynamic symptomatic burden, notably seizure occurrence and frequency, and presence and severity of psychiatric comorbidities [anxiety, depression, posttraumatic stress disorder (PTSD)]. Here, we review this complex relationship between stress and epilepsy using clinical data and highlight key neurobiological mechanisms including the hypothalamic-pituitary-adrenal (HPA) axis dysfunction, altered neuroplasticity within limbic system structures, and alterations in neurochemical pathways such as brain-derived neurotrophic factor (BNDF) linking epilepsy and stress. We discuss current clinical management approaches of stress that help optimize seizure control and prevention, as well as psychiatric comorbidities associated with epilepsy. We propose that various shared mechanisms of stress and epilepsy present multiple avenues for the development of new symptomatic and preventative treatments, including disease modifying therapies aimed at reducing epileptogenesis. This would require close collaborations between clinicians and basic scientists to integrate data across multiple scales, from genetics to systems biology, from clinical observations to fundamental mechanistic insights. In future, advances in machine learning approaches and neuromodulation strategies will enable personalized and targeted interventions to manage and ultimately treat stress-related epileptogenesis.