In depth profiling of dihydrolipoamide dehydrogenase deficiency in primary patients fibroblasts reveals metabolic reprogramming secondary to mitochondrial dysfunction

Dihydrolipoamide dehydrogenase (DLD) deficiency is an autosomal recessive disorder characterized by a functional disruption in several critical mitochondrial enzyme complexes, including pyruvate dehydrogenase and α-ketoglutarate dehydrogenase. Despite DLD's pivotal role in cellular energy metabolism, detailed molecular and metabolic consequences of DLD deficiency (DLDD) remain poorly understood. This study represents the first in-depth multi-omics analysis, specifically metabolomic and transcriptomic, of fibroblasts derived from a DLD-deficient patient compound heterozygous for a common Ashkenazi Jewish variant (c.685G > T) and a novel North African variant (c.158G > A). The investigation reveals significant metabolic disruptions that distinguish the cellular phenotype of DLDD from other metabolic disorders and healthy controls. Employing a range of cellular and molecular techniques, including live-cell imaging, mitochondrial activity assays, immunofluorescence, transcriptomics and metabolomic analysis, we compared DLDD fibroblasts with fibroblasts from glycogen storage disease type 1 A (GSD1a) patients and healthy controls (HC) subjects. Our metabolomics analysis identified significant alterations in mitochondrial metabolism, particularly reduced glycine cleavage, altered one carbon metabolism and serine catabolism. Transcriptome profiling highlighted dysregulation in genes associated with metabolic stress and mitochondrial dysfunction. Our findings highlight reduced mitochondrial activity and respiratory capacity in DLDD fibroblasts, similar to observations in GSD1a fibroblasts. This multi-omics approach not only advances our understanding of the pathophysiology of DLDD, but also illustrates the potential for developing targeted diagnostics and therapeutic strategies.