Abstract 81: Absence of Macrophage microRNA-155 Affects Cardiac Metabolic and Inflammatory Remodeling Following Diabesotension and Protects Against Development of Heart Failure

Abstract

The co-existence of diabetes, obesity, hypertension - diabesotension - is a major burden in western societies and often culminates into heart failure (HF). Diabesotension is associated with a chronic status of low-grade inflammation, involving macrophage infiltration into adipose and cardiac tissues, local activation of inflammatory pathways and concomitant insulin-resistance. We showed that the microRNA miR-155 is a powerful modulator of hypertension-induced cardiac inflammation and HF. Here we hypothesize that absence of miR-155 in macrophages protects against adipose tissue and cardiac inflammation during diabesotension and thereby prevents insulin resistance and cardiac dysfunction. Male C57Bl/6J mice received a bone marrow transplantation of miR-155 WT (n=30) or miR-155 KO (n=30) donors with same genetic background. High fat (HFD; n=22/gr) or chow diet (n=8/gr) was given for 20 weeks. An HFD subgroup was subjected to pressure overload by angiotensin II (1.5mg/kg/d) for 4 weeks (HFD+PO; n=12/gr). Glycaemia, glucose tolerance test, cardiac MRI were performed after 16 and/or 20 weeks. Organs were stored for histology, RNA and FACS analysis. After 16 weeks of HFD, body weight (+11% WT; +14% KO; p<0.05) and glycaemia (+16% WT; +18% KO; p<0.05) increased compared to chow diet animals in both genotypes, confirming the status of obesity and pre-diabetes. Absence of macrophage miR-155 protected HFD-mice from glucose intolerance (at T15: WT 25.08; KO 18.15 mmol/L; p<0.05), suggesting that adipose tissue macrophages might contribute to insulin resistance. In addition, HFD+PO caused mild systolic dysfunction in WT but not in miR-155 KO animals compared to control (ejection fraction: -19% WT, p<0.05; -7% KO, n.s.). While cardiac interstitial fibrosis was not affected by absence of macrophage miR-155, cardiac CD45-positive leukocyte infiltration upon HFD+PO was abrogated. HFD+PO-induced cardiac expression of two PPAR-dependent metabolic genes, angiopoietin-like 4 and uncoupling protein 3, is repressed in the absence of macrophage miR-155. Our data suggest that macrophage miR-155 plays a role in the development of insulin resistance and cardiac dysfunction, possibly by affecting local immune cell function and metabolic programming.