Abstract Background Loeys-Dietz syndrome (LDS) is a rare, autosomal-dominant connective tissue disorder caused by mutations in genes encoding proteins of the transforming growth factor beta (TGF-β) signaling pathway. The condition can lead to the development of severe vascular abnormalities, such as aneurysms or aortic dissections 1. Emerging evidence suggests that endothelial dysfunction, particularly impaired mitochondrial bioenergetics, may contribute directly to maladaptive vascular remodeling, chronic inflammation, and weakening of the aortic wall, thereby promoting aneurysm formation in LDS 2,3. Purpose This study aimed to assess endothelial function in patients with LDS and to isolate and establish primary cultures of aortic endothelial cells (ECs) to test the effects of sodium-glucose co-transporter SGLT2 inhibitors (SGLT2i) on mitochondrial function and energy metabolism. Methods Three patients with LDS and pathogenic variants in SMAD3, TGFβ1 and TGFβR2 genes who qualified for cardiac surgery due to aortic dilation were included in this study (Figure 1A). The flow-mediated skin fluorescence technique 4 assessed vascular endothelial function by measuring the reactive hyperemia response (RHR), which is related to the production of nitric oxide in blood vessels as a result of occlusion-induced hyperemia (Figure 1B). ECs were isolated from the ascending aorta of these patients using magnetic beads. Flow cytometry was used to assess the purity of ECs. Mitochondria distribution and actin cytoskeleton organization were visualized using immunofluorescence microscopy. Mitochondrial function and the effects of 24-hour treatment with SGLT2i (dapagliflozin and empagliflozin) were determined using the Seahorse Flex metabolic analyzer 5. Results Patients with LDS demonstrated endothelial dysfunction, as evidenced by lower RHR values than those of healthy controls (Figure 1C). After isolation, ECs revealed high purity (98-99%) and exhibited a preserved cytoskeletal network and perinuclear mitochondrial clustering (Figure 2A-D). There were no changes in mitochondrial respiration parameters between the 1st and 3rd passage of ECs isolated from Patient 1 (Figure 2E). However, the mitochondrial function assay performed at the 3rd passage in all three patients demonstrated a beneficial response to empagliflozin (Figure 2F). A particularly notable effect was observed on basal and ATP-linked respiration. Conclusions We demonstrated endothelial dysfunction in patients with Loeys-Dietz syndrome. Functional analyses of primary aortic endothelial cells revealed that empagliflozin improved mitochondrial function. These findings support the role of endothelial mitochondrial dysfunction in early mechanisms driving aortic aneurysm formation in LDS and suggest that targeting endothelial bioenergetics may offer a promising therapeutic approach. Further research is needed to clarify these mechanisms and guide future diagnostic and treatment strategies.Endothelial dysfunction in LDS.For image description, please refer to the figure legend and surrounding text. Primary endothelial cell bioenergetics.For image description, please refer to the figure legend and surrounding text.
Knapczyk et al. (Fri,) studied this question.