CARD9 knockout ameliorates myocardial dysfunction associated with high fat diet-induced obesity

J Mol Cell Cardiol. 2016 Mar;92:185-95. doi: 10.1016/j.yjmcc.2016.02.014. Epub 2016 Feb 17.

Abstract

Obesity is associated with chronic inflammation which plays a critical role in the development of cardiovascular dysfunction. Because the adaptor protein caspase recruitment domain-containing protein 9 (CARD9) in macrophages regulates innate immune responses via activation of pro-inflammatory cytokines, we hypothesize that CARD9 mediates the pro-inflammatory signaling associated with obesity en route to myocardial dysfunction. C57BL/6 wild-type (WT) and CARD9(-/-) mice were fed normal diet (ND, 12% fat) or a high fat diet (HFD, 45% fat) for 5months. At the end of 5-month HFD feeding, cardiac function was evaluated using echocardiography. Cardiomyocytes were isolated and contractile properties were measured. Immunofluorescence was performed to detect macrophage infiltration in the heart. Heart tissue homogenates, plasma, and supernatants from isolated macrophages were collected to measure the concentrations of pro-inflammatory cytokines using ELISA kits. Western immunoblotting analyses were performed on heart tissue homogenates and isolated macrophages to explore the underlying signaling mechanism(s). CARD9 knockout alleviated HFD-induced insulin resistance and glucose intolerance, prevented myocardial dysfunction with preserved cardiac fractional shortening and cardiomyocyte contractile properties. CARD9 knockout also significantly decreased the number of infiltrated macrophages in the heart with reduced myocardium-, plasma-, and macrophage-derived cytokines including IL-6, IL-1β and TNFα. Finally, CARD9 knockout abrogated the increase of p38 MAPK phosphorylation, the decrease of LC3BII/LC3BI ratio and the up-regulation of p62 expression in the heart induced by HFD feeding and restored cardiac autophagy signaling. In conclusion, CARD9 knockout ameliorates myocardial dysfunction associated with HFD-induced obesity, potentially through reduction of macrophage infiltration, suppression of p38 MAPK phosphorylation, and preservation of autophagy in the heart.

Keywords: Autophagy; Diabetes; Heart disease; Inflammation; Myocardial dysfunction; Obesity.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • CARD Signaling Adaptor Proteins / biosynthesis
  • CARD Signaling Adaptor Proteins / genetics*
  • Cardiomyopathies
  • Diet, High-Fat
  • Heart Failure / genetics*
  • Heart Failure / pathology
  • Humans
  • Inflammation / genetics*
  • Inflammation / metabolism
  • Inflammation / pathology
  • Insulin Resistance / genetics
  • Mice
  • Mice, Knockout
  • Microtubule-Associated Proteins / biosynthesis
  • Microtubule-Associated Proteins / genetics
  • Myocardium / metabolism
  • Myocardium / pathology
  • Myocytes, Cardiac / metabolism
  • Myocytes, Cardiac / pathology
  • Obesity / genetics*
  • Obesity / metabolism
  • Obesity / pathology
  • Signal Transduction / genetics
  • Transcription Factor TFIIH
  • Transcription Factors / biosynthesis
  • p38 Mitogen-Activated Protein Kinases / biosynthesis
  • p38 Mitogen-Activated Protein Kinases / genetics

Substances

  • CARD Signaling Adaptor Proteins
  • Card9 protein, mouse
  • Gtf2h1 protein, mouse
  • Map1lc3b protein, mouse
  • Microtubule-Associated Proteins
  • Transcription Factors
  • Transcription Factor TFIIH
  • p38 Mitogen-Activated Protein Kinases