Circadian mutant mice with obesity and metabolic syndrome are resilient to cardiovascular disease

Reitz CJ, Alibhai FJ, de Lima-Seolin BG, Nemec-Bakk A, Khaper N, Martino TA. Circadian mutant mice with obesity and metabolic syndrome are resilient to cardiovascular disease. Am J Physiol Heart Circ Physiol 319: H1097-H1111, 2020. First published September 28, 2020; doi:10.1152/ajpheart.00462.2020.-Obesity and metabolic syndrome commonly underlie cardiovascular disease. Clock▵19/▵19 mice fed a normal diet develop obesity and metabolic syndrome; however, it is not known whether they develop or are resilient to cardiovascular disease. We found that Clock▵19/▵19 mice do not develop cardiac dysfunction, despite their underlying conditions. Moreover, in contrast to wild-type controls fed a high-fat diet (HFD), Clock▵19/▵19 HFD mice still do not develop cardiovascular disease. Indeed, Clock▵19/▵19 HFD mice have preserved heart weight despite their obesity, no cardiomyocyte hypertrophy, and preserved heart structure and function, even after 24 wk of a HFD. To determine why Clock▵19/▵19 mice are resilient to cardiac dysfunction despite their underlying obesity and metabolic conditions, we examined global cardiac gene expression profiles by microarray and bioinformatics analyses, revealing that oxidative stress pathways were involved. We examined the pathways in further detail and found that 1) SIRT-dependent oxidative stress pathways were not directly involved in resilience; 2) 4-hydroxynonenal (4-HNE) increased in wild-type HFD but not Clock▵19/▵19 mice, suggesting less reactive oxygen species in Clock▵19/▵19 mice; 3) cardiac catalase (CAT) and glutathione peroxidase (GPx) increased, suggesting strong antioxidant defenses in the hearts of Clock▵19/▵19 mice; and 4) Pparc was upregulated in the hearts of Clock▵19/▵19 mice; this circadian-regulated gene drives transcription of CAT and GPx, providing a molecular basis for resilience in the Clock▵19/▵19 mice. These findings shed new light on the circadian regulation of oxidative stress and demonstrate an important role for the circadian mechanism in resilience to cardiovascular disease.