Ann Saada

Mitochondrial dysfunction contributes to diabetic cardiomyopathy, yet how genetic predisposition and diet interact to reshape cardiac metabolism in diabetic and prediabetic states remains unclear. The Cohen diabetic rat model, comprising diabetes-resistant (CDr) and diabetes-sensitive (CDs) strains, provides a unique platform to dissect this interplay. Here, we present an integrative global proteomic and bioenergetic characterization of cardiac tissue from CDr and CDs rats fed either a regular or a diabetogenic diet. Proteomic pathway mapping revealed downregulation of cytochrome c oxidase (CcO) subunits, strain-dependent rewiring of fatty-acid oxidation pathways, and CcO subunits switch from “heart-type” to “liver-type” isoforms in the sensitive strain. These changes were accompanied by impaired mitochondrial respiration, ATP depletion, and disruption of mitochondrial quality-control mechanisms, together with increased accumulation of tyrosine 304 phosphorylation of cytochrome c oxidase subunit I, indicative of inflammation-driven regulatory inhibition in a diet-specific manner. These findings establish an understanding of how genetic susceptibility and diet contribute to cardiac mitochondrial dysfunction in the Cohen diabetic rat model.

Ethoxyquin (EQ) is a synthetic antioxidant historically used as a preservative in animal feed, but was recently banned as a feed ingredient in food-producing animals due to human health concerns. Nevertheless, EQ was reported to have a neuroprotective effect, ameliorating the side effects of anti-cancer chemotherapy and increasing ATP content in animal models. As the effect of EQ has not been investigated in humans, we aimed to examine its effect of primary fibroblasts derived from controls and patients with confirmed mitochondrial dysfunction. To this end, we incubated primary fibroblasts from patients with mitochondrial respiratory chain complex 1 (C1) deficiency, cytochrome-c-oxidase (COX) deficiency, and a genetic form of Parkinson’s disease (PD). Although EQ did not alter ATP production, it significantly increased oxygen consumption and improved energy status in C1 and COX cells, decreased ROS production in COX, PD, and control cells, while maintaining or increasing mitochondrial content. Our results indicate that EQ has the potential to improve some mitochondrial functions in patients’ cells without any apparent negative effects. Nevertheless, as EQ is controversial and clinical studies are lacking, the use of this compound and its derivatives remains uncertain.

Dihydrolipoamide dehydrogenase (DLD) deficiency (MIM #246900) is a rare autosomal recessive mitochondrial disorder caused by pathogenic variants in the DLD gene, which encodes the E3 subunit common to multiple mitochondrial enzyme complexes, including pyruvate dehydrogenase (PDHc) and α-ketoglutarate dehydrogenase (αKGDHc). Although genotype–phenotype correlations have been described, the precise bioenergetic consequences of DLD dysfunction remain poorly defined. Here, we applied high-resolution respirometry using a novel single-run protocol that allows simultaneous assessment of mitochondrial respiratory capacity and, critically, distinguishing between PDHc- and αKGDHc-linked respiration within the same assay. Fibroblasts from six genetically confirmed DLD-deficient patients with distinct pathogenic variants and clinical severities exhibited a consistent reduction in maximal and complex I-linked respiration. The most severe cases (c.1436A>T; p.D479V) showed combined PDHc and αKGDHc impairment, whereas milder genotypes displayed isolated PDHc dysfunction. This mechanistic distinction likely underlies the variable clinical response to ketogenic therapy, which depends on intact αKGDHc function. Analysis of the mitochondrial mass and mtDNA copy number revealed no global reduction, indicating intrinsic enzymatic dysfunction as the primary defect. Collectively, this study defines a reproducible bioenergetic signature of DLD deficiency and introduces an integrated one-run diagnostic strategy for delineating enzyme-specific mitochondrial defects, providing a framework for mechanistic and therapeutic investigations.

Supplementary Figure S3 shows that targeting the IL-6-pSTAT-HNF4a pathway preserves liver metabolism and restricts BC growth

Supplementary Table S6 lists the genes regulated by HNF4a

Supplementary Extended Data 1 describes the FACS gating startegy

Supplementary Figure S2 demonstrates the infiltration of mature innate immune cells to the liver during breast carcinogenesis

Supplementary Table S2 lists the antibodies used for western blots

Supplementary Table S4 lists the antibodies used for FACS

Supplementary Table S5 lists the antibodies used for CyTOF