Mitochondrial Functional Capacity Is Impaired in Angiotensin II-Infused Mice and Not Recovered by Metformin

Background: The pathophysiological mechanisms of Abdominal Aortic Aneurysm (AAA) are not elucidated. Alterations in mitochondrial function, such as a reduction in oxidative phosphorylation (OXPHOS), have been observed at genome level and functionally in vascular smooth muscle cells. Metformin reduces AAA development and growth in diabetic patients, but the precise mechanisms are not known. In this paper we aim to demonstrate the feasibility of measuring mitochondrial functional capacity ex vivo in intact murine aneurysmal tissue and confirm a decrease in OXPHOS, and to determine if the protective effect of metformin on AAA is mediated by mitochondrial function. Methods: AAA was induced in ApoE KO mice by administration of angII (1000 ng/kg/min) through osmotic minipumps. Metformin was administered in drinking water at a dose of 100 mg/kg/day. The abdominal aorta was isolated in situ and mitochondrial functional capacity was analyzed ex vivo in whole permeabilized tissue by high-resolution respirometry. Results: Mitochondrial respiration was successfully measured ex vivo in whole aneurysmal tissue. Mitochondrial function was impaired in angII-treated mice, with decreased fold change in Complex I and Complex I+II oxygen consumption, relative to basal levels. Complex II oxygen consumption was also decreased in angII-treated mice. Rescue treatment of mice with metformin did not affect or restore mitochondrial function. Conclusions: Mitochondrial function can be evaluated in murine whole aneurysmal tissue, providing a method for a physiological approach to the study of mitochondrial function in AAA. Mitochondrial function is impaired in AAA. However, rescue treatment with metformin is not sufficient to recover mitochondrial function and seems not to be the mechanism behind prevention of aneurysm.