Cardiac Col1a2 as a potential earl hub gene in obesity-induced maladaptive heart remodeling in DIO mice model

Introduction: Obesity cardiomyopathy refers to structural, functional, and metabolic abnormalities of the heart caused by obesity. Indeed, if untreated it can cause ventricular hypertrophy, diastolic dysfunction, and cardiac fibrosis in adulthood. The non-cardiac cells (non-CCs) play an important role in obesity-induced extracellular matrix (ECM) responses. ECM in normal heart is usually composed of type I collagen and controlled by Col1a2 gene. Under obesogenic stimuli, ECM reorganization driven by non-CCs leads to increased transforming growth factor-β (Tgf-β) activity, and cardiomyopathy with loss of cardiac function over time. Little is currently known about pro-fibrotic ECM reorganization and remodeling occurring in the early stage of adult age, between the second and third decade. Here, we investigated the role of Col1a2 expression gene from the heart of diet-induced obesity (DIO) mice, and their association with cardiac ECM rearrangement in the early stage of adulthood. Methods: Twelve six-week-old male C57BL/6N DIO-mice (Charles River Laboratories, Calco, Italy) were divided into two groups and fed for 20 weeks as follows: (1) normal chow diet (10% fat, CTR) and (2) high-fat (HF) diet (60% fat). At the age of 26 weeks (human beings age matched of 20-30 years) the mice were sacrificed through exposure to atmosphere saturation of carbon dioxide for 15 min. Hearts were collected, subdivided in two parts: 1) half-hearts were immediately snap-frozen in liquid nitrogen, and stored at −80° until genomic analysis and total collagen quantification analyses by quantitative Sircol assay for measurement of both acid-soluble and pepsin-soluble collagens. 2) the second half-hearts were fixed in 10% of formalin and d in paraffin to Masson’s Trichrome staining. The Italian Ministry of Health approved all animal procedures (Number 5AD83.N.G1Q). Results: Genomic results showed that in HF but not in CTR hearts, cardiac tissue starts to modify toward a pro-fibrotic ECM rearrangement. HF diet in DIO-mice aged matched to 20-30 years old humans, promotes ECM deposition, through Col1a2 gene up-regulation which positively correlates with Acta2 and Tgfb1 family genes, the main actors of tissue remodeling. Sircol analysis showed that HF cardiac biopsies presented higher collagen content than CTR hearts, although Masson’s trichrome staining showed no difference in HF and CTR groups. Conclusions: Our data highlight the role of Col1a2 in pro-fibrotic ECM rearrangement in HF DIO-heart with 6 months of age, suggesting that Col1a2 gene can be considered a hub gene of obesity induced ECM remodeling at the beginning of adulthood.