Patients with primary mitochondrial oxidative phosphorylation (OxPhos) defects present with fatigue and multi-system disorders, are often lean, and die prematurely, but the mechanistic basis for this clinical picture remains unclear. By integrating data from 17 cohorts of patients with mitochondrial diseases (n = 690) we find evidence that these disorders increase resting energy expenditure, a state termed hypermetabolism. We examine this phenomenon longitudinally in patient-derived fibroblasts from multiple donors. Genetically or pharmacologically disrupting OxPhos approximately doubles cellular energy expenditure. This cell-autonomous state of hypermetabolism occurs despite near-normal OxPhos coupling efficiency, excluding uncoupling as a general mechanism. Instead, hypermetabolism is associated with mitochondrial DNA instability, activation of the integrated stress response (ISR), and increased extracellular secretion of age-related cytokines and metabokines including GDF15. In parallel, OxPhos defects accelerate telomere erosion and epigenetic aging per cell division, consistent with evidence that excess energy expenditure accelerates biological aging. To explore potential mechanisms for these effects, we generate a longitudinal RNASeq and DNA methylation resource dataset, which reveals conserved, energetically demanding, genome-wide recalibrations. Taken together, these findings highlight the need to understand how OxPhos defects influence the energetic cost of living, and the link between hypermetabolism and aging in cells and patients with mitochondrial diseases.

Aging is a process of progressive change. To develop biological models of aging, longitudinal datasets with high temporal resolution are needed. Here we report a multi-omics longitudinal dataset for cultured primary human fibroblasts measured across their replicative lifespans. Fibroblasts were sourced from both healthy donors (n = 6) and individuals with lifespan-shortening mitochondrial disease (n = 3). The dataset includes cytological, bioenergetic, DNA methylation, gene expression, secreted proteins, mitochondrial DNA copy number and mutations, cell-free DNA, telomere length, and whole-genome sequencing data. This dataset enables the bridging of mechanistic processes of aging as outlined by the “hallmarks of aging”, with the descriptive characterization of aging such as epigenetic age clocks. Here we focus on bridging the gap for the hallmark mitochondrial metabolism. Our dataset includes measurement of healthy cells, and cells subjected to over a dozen experimental manipulations targeting oxidative phosphorylation (OxPhos), glycolysis, and glucocorticoid signaling, among others. These experiments provide opportunities to test how cellular energetics affect the biology of cellular aging. All data are publicly available at our webtool: https://columbia-picard.shinyapps.io/shinyapp-Lifespan_Study/

Aging is a process of progressive change. In order to develop biological models of aging, longitudinal datasets with high temporal resolution are needed. Here we report a multi-omic longitudinal dataset for cultured primary human fibroblasts measured across their replicative lifespans. Based on the accelerated nature of epigenetic aging in vitro, these longitudinal data are equivalent to ~40 years of follow-up sampling at a frequency of every ~3 years. Fibroblasts were sourced from both healthy donors (n=6) and individuals with lifespan-shortening mitochondrial disease (n=3). The dataset includes cytological (cell size, morphology), bioenergetic (energy expenditure, derived ATP synthesis rates), epigenetic (DNA methylation), gene expression (RNA sequencing), secreted proteins, mitochondrial DNA (mtDNA) copy number and mutations, cell-free DNA, telomere length, and whole-genome sequencing data. This dataset enables the bridging of mechanistic processes of aging as outlined by the “hallmarks of aging”, with the descriptive characterization of aging provided by epigenetic clocks and other metrics. Here we focus on bridging the gap for the hallmark mitochondrial metabolism. Our dataset includes measurement of healthy cells replicating through senescence without intervention, as well as cells subjected to over a dozen experimental manipulations targeting oxidative phosphorylation (OxPhos), glycolysis, and glucocorticoid signaling, among others. These experiments provide opportunities to test how cellular energetics affect the biology of cellular aging. All data are publicly available at our webtool: https://columbia-picard.shinyapps.io/shinyapp-Lifespan_Study/

Patients with primary mitochondrial diseases present with fatigue and multi-system disease, are often lean, and die prematurely, but the mechanistic basis for this clinical picture remains unclear. Integrating data from 17 cohorts of patients with mitochondrial diseases (n=690), we find that clinical mitochondrial disorders increase resting energy expenditure, a state termed hypermetabolism. In a longitudinal cellular model of primary patient-derived fibroblasts from multiple donors, we show that genetic and pharmacological disruptions of oxidative phosphorylation (OxPhos) similarly trigger increased energy consumption in a cell-autonomous manner, despite near-normal OxPhos coupling efficiency. Hypermetabolism was associated with mtDNA instability, activation of the integrated stress response, increased extracellular secretion of age-related cytokines and metabokines including GDF15, as well as an accelerated rate of telomere erosion and epigenetic aging, and a reduced Hayflick limit. Finally, we generate a longitudinal RNASeq and DNA methylation resource dataset, which reveals conserved, energetically demanding, genome-wide recalibrations to OxPhos dysfunction. Hypermetabolism, or the increased energetic cost of living in mitochondrial diseases, has important biological and clinical implications.

Stress triggers energy-dependent, anticipatory responses that promote survival, a phenomenon termed allostasis. However, the chronic activation of allostatic responses results in allostatic load (AL) and in the maladaptive state known as allostatic overload. Epidemiological studies show that allostatic load predicts physical and cognitive decline, as well as earlier mortality; yet the manifestations of allostatic load and overload at the cellular level remain unclear. To define the energetic cost and potential detrimental effects of prolonged cellular allostatic load, we developed a longitudinal model of chronic glucocorticoid stress in primary human fibroblasts. Results replicated in three healthy donors demonstrated that chronic stress robustly increased cellular basal energy consumption by 62%. This hypermetabolic state relied on a bioenergetic shift away from glycolysis towards mitochondrial oxidative phosphorylation (OxPhos), supported by an upregulation of mitochondrial biogenesis and increased mitochondrial DNA (mtDNA) density. As in humans where chronic stress accelerates biological aging, chronic allostatic load altered extracellular cytokine and cell-free DNA, caused mtDNA instability, increased the rate of epigenetic aging based on DNA methylation clocks, accelerated telomere shortening, and reduced lifespan (i.e., Hayflick limit). Pharmacological blockade of mitochondrial nutrients uptake normalized OxPhos activity but exacerbated hypermetabolism, which further accelerated telomere shortening and reduced cellular lifespan. Together, these results highlight the increased energetic cost of cellular allostatic load and suggests a mechanism for the transduction of chronic stress into accelerated cellular aging to be examined in humans.