Intermittent hypoxia induces premature adipose tissue senescence leading to cardiac remodeling

Abstract

Obstructive sleep apnea is a growing worldwide health problem. The landmark feature of OSA is a chronic intermittent hypoxia (CIH) responsible for multiple organ damages including heart diseases. CIH profoundly alters both visceral adipose tissue (VAT) and heart structures and functions, but little is known regarding their interactions in the context of CIH. We recently showed that VAT senescence drives myocardial alterations through the release of profibrotic factors in aged mice. Thus, we aim at demonstrating that CIH induces a premature vWAT senescent phenotype, responsible for subsequent heart dysfunction. In a first series of animals, ten-week old C57BL6 male mice ( n = 10/group) were exposed to 14 days CIH protocol (8 hours daily, 5–21% cyclic inspired oxygen fraction, 60 seconds per cycle). In another series, mice were submitted to VAT surgical lipectomy or sham-surgery ( n = 10/group) and then exposed to the same CIH protocol. VAT and heart were assessed by histology for fibrosis (Sirius red), cell hypertrophy (wheat-germ agglutinin) and reactive oxygen species (ROS) (4-HNE), and markers of senescence (p16, p21, p53), inflammation (CD68, Tnfa, Serpine1), fibrosis (Col1a1) and hypertrophy were also evaluated by RT-qPCR and western blot. CIH induced an increased macrophage infiltration in VAT, along with an increased expression of senescence markers, ROS production and gene expression of inflammatory and fibrogenic markers. This was associated with CIH-induced myocardial interstitial fibrosis and upregulation of profibrotic gene expression in myocardium. Interestingly, VAT lipectomy prevented CIH-induced myocardial fibrosis. Short-term exposure to CIH is sufficient to induce both VAT remodelling, characterized by oxidative stress, inflammation and fibrosis, and cardiac interstitial fibrosis that was prevented by VAT lipectomy. This strongly suggest a causal crosstalk between CIH-induced VAT senescence and cardiac remodeling.