Sex differences are evident in vascular mitochondrial function; however, the impact of sex on microvascular bioenergetics has never been studied. We investigated the bioenergetics of freshly isolated mouse brain microvessels (BMVs) from young mice (6-8 wk). Oxygen consumption rate and extracellular acidification rates of BMVs were measured using Agilent Seahorse XFe24 analyzer. The real-time ATP rate assay showed reduced total ATP production with contributions from both glycolysis and oxidative phosphorylation (OxPhos) in BMVs from females compared with males. The mitochondrial stress test revealed lower basal respiration and ATP production in BMVs of females versus males. The glycolytic rate assay indicated reduced basal glycolysis and proton efflux rate (PER) in females, with no sex differences in basal PER and post-2-DG acidification. Mito fuel flex test found no differences in fuel substrate utilization. Measurements using homogenates of BMVs confirmed lower ATP levels in females, with no sex differences in citrate synthase activity or key mitochondrial protein/mRNA levels. Ex vivo oxygen-glucose deprivation followed by reoxygenation (OGD/R) of mouse BMVs displayed significantly reduced mitochondrial respiratory function as well as glycolytic activity in females versus males. However, OGD/R paradoxically increased lactate dehydrogenase release, a marker of cellular injury, from male BMVs but has no effect on female BMVs. Thus, female BMVs exhibited decreased mitochondrial respiratory and glycolytic function compared with males, despite similar substrate utilization for energy production. In young mice, the sex-dependent differences in OxPhos and glycolysis may increase the vulnerability of the microvasculature to OGD/R injury in males and vasoprotection in females.NEW & NOTEWORTHY Impact of sex on microvascular bioenergetics has never been studied. We measured oxygen consumption rates and extracellular acidification rates in mouse brain microvessels using Agilent Seahorse XFe24 analyzer. For the first time, we observed decreased mitochondrial respiratory and glycolytic function in brain microvessels of female mice compared with male mice. These sex-dependent differences in glycolysis and oxidative phosphorylation may increase the vulnerability/protection of the microvasculature to vascular cell injury.

Most complex V subunits are nuclear encoded and so far, were not found in association with recognized Mendelian disorders. ATP5PO is a candidate gene for complex V mitochondrial disease. It encodes the oligomycin sensitivity-conferring protein (OSCP), an essential component of the "stalk" region that links the F1 and F0 domains of the ATP synthase complex. We report a 4-month-old girl, born at 35 weeks' gestation to a consanguineous couple via cesarean section due to fetal growth restriction and antenatal echocardiographic findings of moderate biventricular hypertrophy. At birth, she required intubation, ventilation, and surfactant therapy. The patient experienced intermittent hyperlactatemia, apneic spells, encephalopathy, axial hypotonia, and abnormal neonatal reflexes. She passed away at 4 months of age, and whole-exome sequencing revealed a homozygous splice variant (c.87 + 3A > G; p?) in ATP5PO. This gene was reported as a candidate gene, where additional evidence is needed to establish whether there is a relationship between this gene variant and human disease. So far and to our best knowledge, only four cases with a pathogenic variant in this gene have been reported. Mitochondrial respiratory chain analysis performed on fibroblasts revealed reduced ATPase enzyme activity with approximately 35% of the mean enzyme activity observed in the control reference range, with a decreased enzyme activity ratio relative to citrate synthase. These results suggest that isolated complex V enzyme deficiency is associated with the homozygous VUS identified in the ATP5PO gene in this patient and provide further functional support that ATP5PO is involved in complex V assembly and function.

Small colony variants (SCVs) of Staphylococcus aureus (S. aureus) are associated with persistent infections and poor clinical outcomes. The mechanisms driving stable SCV formation remain poorly understood, particularly concerning metabolic adaptations. This study explores the in-host evolutionary dynamics of S. aureus and identifies a novel genetic determinant linked to SCV formation. To investigate the genetic mutations and phenotypic adaptations underlying SCV formation, with a focus on the role of a novel mutation in the sufB gene, which is critical for Fe-S cluster biosynthesis. Sequential isolates from a patient with recurrent infections were analyzed using whole-genome sequencing, antimicrobial susceptibility testing, and functional assays. The phylogenetic relationship of the isolates was determined, and specific mutations were identified. Functional assays included aconitase and glutamate synthase activity measurements, ATP level quantification, reactive oxygen species (ROS) production, and biofilm formation assays. In vivo pathogenesis was assessed using a murine catheter infection model. A novel frameshift mutation in sufB was identified, disrupting Fe-S cluster biosynthesis and impairing the TCA cycle and electron transport chain, leading to reduced ATP and ROS production. This metabolic reprogramming promoted stable SCV formation, characterized by slow growth, enhanced tolerance to antibiotics and neutrophil-mediated killing, and persistent inflammation in vivo. Restoration of sufB reversed these phenotypes, confirming its pivotal role in SCV-associated persistence. sufB is a novel genetic determinant of stable SCV formation through Fe-S cluster deficiency, driving metabolic shifts that enhance immune evasion and chronic infection. Our findings highlight antibiotic stewardship and suggest potential therapeutic strategies for managing persistent SCV-associated infections.

Complex V of the mitochondrial oxidative phosphorylation system is an ATP synthase that plays a pivotal role in the cell's energy transduction. Mutations in genes encoding the multiple protein subunits that constitute complex V cause severe metabolic and neurodegenerative diseases. We present here three complementary assays to assess Complex V activity and assembly in peripheral blood mononuclear cells (PBMCs). The assays involve spectrophotometric and in-gel activity measurements, cytochemical assessment of the mitochondrial transmembrane electrochemical gradient (∆Ѱm) to determine if the enzyme acts forward as an ATP synthase or in reverse as an ATPase, and western blot analysis of clear native gels to evaluate Complex V assembly. The whole process can be performed with 2 × 106 PBMCs isolated from ~2 ml of blood. Our study suggests that PBMCs can serve as a platform for small-scale, minimally invasive investigations of patients suspected of Complex V deficiency or in biomarker research of mitochondrial function.

The mitochondrial DNA (mtDNA) genes MT-ATP6 and MT-ATP8 encode for subunits α and 8 (A6L) of the adenosine triphosphate synthase complex. Pathogenetic variants in MT-ATP6/8 cause incurable mitochondrial syndromes encompassing a wide spectrum of clinical features including ataxia, motor and language developmental delay, deafness, retinitis pigmentosa, and Leigh pattern in brain MRI. Typically, higher levels of mtDNA variants lead to more severe symptomatology although even individuals with similar mtDNA mutational loads exhibit high clinical variability. Hence, the establishment of potential therapeutics is currently challenging. In this article, we present an international multicenter study designed to provide a retrospective natural history of patients with MT-ATP6/8 deficiency and to identify primary and secondary end points for future clinical trials. Clinical, biochemical, and molecular genetics data of patients with genetically confirmed MT-ATP6/8 defects were collected and analyzed from Italian, German, US, and Spain national reference centers through ethical committee-approved mitochondrial patients' national registries or local programs. A cohort of 111 patients, 98 unreported, were analyzed (55 male, 56 female). Patients had infantile-onset disease (<1 year) in 44% of cases, pediatric-onset (≥1 year and ≤12 years) in 36%, and late-onset (>12 years) in 20%. Kaplan-Meier analysis showed a significant difference (p value = 0.0349) in the survival of infantile and pediatric patients compared with adult patients, although only 8% of patients were not alive at the last follow-up. The CNS was the most frequently affected tissue (93%), followed by the muscle (75%), eye (46%), and heart (18%). Brain MRI showed isolated Leigh-like lesions (58%), Leigh-like lesions and cortical and/or cerebellar atrophy (15%), isolated cerebellar atrophy (10%), and other lesions (21%). At the last follow-up, 11% of patients were wheelchair-bound. Metabolic acidosis or acute deterioration complicated the clinical course in ≅55% of early-onset patients. Molecular genetics studies identified 26 pathogenic variants (6 of them novel). Reduced citrulline levels and increased alanine and lactate levels were reported in 56%, 49%, and 71% of patients, respectively, suggesting their role as potential biomarkers. Our results define a more accurate classification based on the age at onset for MT-ATPase deficiency and provide fundamental clinical and biochemical data for disease management.