Sex-Specific Mitochondrial Bioenergetics Differences in Heart and Kidney Cortex

Abstract

Rationale: Mitochondrial bioenergetics of different tissues have been studied widely, but their sex-specific differences have not been systematically studied. The goal of this study was therefore to investigate the sex-specific differences in mitochondrial respiration (oxygen consumption rate; OCR) and membrane potential (Δψ) in the heart and kidney cortex and to explore underlying mechanisms responsible for any observed differences. Methods: Mitochondria were isolated from adult male and female Sprague-Dawley rat heart and kidney cortex and were used to study their bioenergetics responses. Three different substrate combinations, namely, pyruvate+malate (PM), glutamate+malate (GM), and succinate in the presence of complex I inhibitor rotenone (SR) were used. This was followed by two different ADP addition protocols to determine how different substrates influence mitochondrial OCR and Δψ to ADP perturbations during oxidative phosphorylation (OxPhos) in male and female heart and kidney cortex. In one, a single saturated dose of ADP, while in the other, sequentially increasing doses of ADP were added to mitochondria in the presence of different substrates. Mitochondrial OCR was measured using a dual chamber Oroboros Oxygraph-2k Instrument and Δψ was measured using a spectrofluorometer and rhodamine-123 dye. From these measurements, OCR and Δψ alterations under different respiratory states and as functions of added ADP concentration were determined for different substrates and for both male and female rats. Results: Male and female mitochondria exhibited distinct respiratory patterns in the kidney cortex and heart with different substrates. In the kidney cortex, male mitochondria showed significantly higher OCR than female mitochondria when fueled with PM or SR. However, no significant sex differences in the OCR were observed when GM were used as substrates. In contrast, heart mitochondria exhibited negligible sex differences in the OCR for PM and SR, but significant differences emerged with GM, where female mitochondria displayed higher OCR than their male counterparts. Interestingly, sex-specific variations of Δψ in ADP-stimulated respiration were not apparent for either tissue or substrate when a single saturated dose of ADP was used. Instead, a trend similar to the OCR emerged when ADP was administered in gradually increasing concentrations. Conclusion: Heart and kidney cortex mitochondrial Δψ for males and females did not differ conclusively with the two ADP addition protocols. However, there were significant differences in the OCR of mitochondria from the heart and kidney cortex of males and females, depending on the respiratory substrate utilized. Males were found to have enhanced OCR in the kidney cortex, whereas females exhibited higher OCR in the heart. These observed sex-specific differences in the OCR could be attributed to differential regulation of mitochondrial metabolic pathways by respiratory substrates and sex hormones. NIH R01-HL151587. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.