Mitochondrial respiration defects in lymphoblast cell lines from patients with Dravet syndrome.

Abstract

Objective: Dravet syndrome (DS) is a developmental and epileptic encephalopathy with early life intractable seizures and lifelong comorbidities. There is growing evidence linking energy metabolism to DS, from mitochondrial respiration deficits in skeletal muscle and fibroblasts from children with DS to responsiveness to ketogenic diets. Lymphoblast cell lines (LCLs) have revealed metabolic alterations in neurological disorders, suggesting their utility for studying systemic bioenergetics. In this pilot study, we used LCLs from patients with DS to evaluate energy metabolism.

Methods: LCLs were established from eight children with DS (DS-LCLs) and sex-/age-matched controls (control-LCLs). Extracellular flux analysis measured glycolytic function, mitochondrial respiration, and fatty acid oxidation (FAO). High-resolution respirometry was used to determine sites of mitochondrial respiration defects. Mitochondrial content and membrane potential were analyzed using high-content screening methods.

Results: DS-LCLs exhibit impaired bioenergetics, characterized by deficiencies in mitochondrial respiration with 25% lower baseline and adenosine triphosphate-linked respiration. Similarly, maximal mitochondrial capacity was 26% lower, leading to a 40% decrease in respiratory reserves. They exhibit a metabolic shift toward FAO, indicated by increased endogenous fatty acid utilization to counter cellular stress. Mitochondrial oxygen flux was impaired, with greatest deficiency in complex I, and reduced complex II activity. Leak respiration, mitochondrial content, membrane potential, and glycolytic function were unaffected.

Significance: LCLs from patients with DS reveal reduced mitochondrial respiratory capacity. These preliminary findings may enhance our understanding of energy metabolism in DS pathogenesis. Beyond helping identify new therapies, this model may noninvasively serve as a surrogate for evaluating metabolic function throughout a patient's life.