Molecular alterations compromising key metabolic pathways are poorly understood in sporadic frontotemporal lobar degeneration with TDP-43 pathology (sFTLD-TDP). Whole-transcriptome array, RT-qPCR validation, gel electrophoresis, and Western blotting, and mitochondrial electron transport chain (ETC) activity were comparatively examined in frontal cortex (area 8) of 16 sFTLD-TDP cases and 14 controls. Assessment of 111 genes by RT-qPCR showed deregulation of 81 genes linked to neurotransmission and synapses, neuronal architecture, cytoskeleton of axons and dendrites, vesicle trafficking, purines, mitochondria, and energy metabolism in sFTLD-TDP. Western blotting studies disclosed downregulation of several mitochondrial subunits encoded by genomic DNA and MTCO1 encoded by the mitochondrial DNA. Mitochondrial ETC activity of complexes I, IV, and V was decreased in sFTLD-TDP. These findings provide robust information about downregulation of genes involved in vital biochemical pathways and in synaptic neurotransmission which may help to increase understanding about the biochemical substrates of clinical manifestations in sFTLD-TDP. Key Words: Energy metabolism, Frontotemporal lobar degeneration, Mitochondria, Neurotransmission, Purines, Synapses, TDP43.