Liver-Specific Bmal1 Deletion in Mice Increases Aortic Stiffness and Alters Age-Dependent Vascular Remodeling

Circadian rhythms are important in cardiovascular physiology. The circadian clock gene Bmal1 is critical for vascular homeostasis. We previously showed that hepatocyte-specific Bmal1 deletion (HBK) in the liver alters perivascular adipose tissue-mediated vascular function in young adult mice, suggesting cross-talk between the liver and vasculature. We hypothesized that liver-specific Bmal1 deletion leads to aortic stiffness and vascular disease in young (4- to 6-month old) and middle-aged (8- to 11-month old) mice. Studies were performed in male flox control and HBK young and middle-aged mice. Aortic stiffness, measured by pulse wave velocity, was significantly elevated in young and middle-aged HBK mice compared to flox control mice (Young; Flox: 1.84 ± 0.1 m/s; HBK: 2.9 ± 0.2 m/s; n = 5, Middle-aged; Flox: 1.93 ± 0.2 m/s; HBK: 3.25 ± 0.5 m/s; n = 7-8, Genotype: p < 0.01). Aortas and plasma were collected at ZT2 for histological analysis and metabolite measurements, respectively. Aortic wall thickness, measured with CellSens software, was significantly higher in middle-aged flox controls compared to young flox controls, yet was similar between young HBK and middle-aged HBK mice (Young; Flox: 57.9 ± 2.0 µm; HBK: 57.9 ± 1.5 µm; n = 5, Middle-aged; Flox: 70.0 ± 2.3 µm; HBK: 58.8 ± 2.3 µm; n = 4-5, Genotype: p < 0.01, Age: p = 0.02, Interaction: p = 0.02). Picrosirius red (PSR)-stained aortic sections were examined to assess collagen content with ImageJ software. Aortic wall collagen content was significantly increased in both groups of HBK mice compared to age-matched flox control mice (% PSR per area, Young; Flox: 61.0% ± 2.5%, HBK: 67.8% ± 0.8%; n=5, Middle-aged; Flox: 59.7 ± 4.0%; HBK: 73.2 ± 3.3%; n = 3-5, Genotype: p < 0.01). The number of TUNEL stained apoptotic cells was significantly higher in both young and middle-aged HBK mice aortas compared to flox controls (Flox: 224 ± 56.1; HBK: 408 ± 20.8; n=5, Middle-aged; Flox: 191 ± 74.2; HBK: 298 ± 70.7; n = 4-5, Genotype: p = 0.02). Aortic sections were stained with the oxidative stress marker vascular 4-hydroxynonenal (4-HNE), a measure of lipid peroxidation. MetaMorph software analysis revealed significantly increased 4-HNE content in HBK mice compared to flox control mice (% 4-HNE per area, Young; Flox 6.5% ± 0.7%, HBK 8.4% ± 0.8%; n=4-5, Middle-aged; Flox: 5.2 ± 0.4%; HBK: 9.2 ± 1.0%; n = 3-5, Genotype: p < 0.01). In plasma, the oxidative stress marker, 8-hydroxy-2’-deoxyguanosine (8-OHdG), a DNA damage product, was not different between genotypes. These data suggest that altered age-dependent vascular remodeling in HBK mice may contribute to aortic stiffness leading to cardiovascular disease. P01HL136267 to JSP, R21AA026906 to SMB, and AHA 856877 to PP This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.