EET intervention on Wnt1, NOV, and HO-1 signaling prevents obesity-induced cardiomyopathy in obese mice

Abstract

We have previously reported that epoxyeicosatrienoic acid (EET) has multiple beneficial effects on vascular function; in addition to its antiapoptotic action, it increases insulin sensitivity and inhibits inflammation. To uncover the signaling mechanisms by which EET reduces cardiomyopathy, we hypothesized that EET infusion might ameliorate obesity-induced cardiomyopathy by improving heme oxygenase (HO)-1, Wnt1, thermogenic gene levels, and mitochondrial integrity in cardiac tissues and improved pericardial fat phenotype. EET reduced levels of fasting blood glucose and proinflammatory adipokines, including nephroblastoma overexpressed (NOV) signaling, while increasing echocardiographic fractional shortening and O consumption. Of interest, we also noted a marked improvement in mitochondrial integrity, thermogenic genes, and Wnt 1 and HO-1 signaling mechanisms. Knockout of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) in EET-treated mice resulted in a reversal of these beneficial effects including a decrease in myocardial Wnt1 and HO-1 expression and an increase in NOV. To further elucidate the effects of EET on pericardial adipose tissues, we observed EET treatment increases in adiponectin, PGC-1α, phospho-AMP-activated protein kinase, insulin receptor phosphorylation, and thermogenic genes, resulting in a "browning" pericardial adipose phenotype under high-fat diets. Collectively, these experiments demonstrate that an EET agonist increased Wnt1 and HO-1 signaling while decreasing NOV pathways and the progression of cardiomyopathy. Furthermore, this report presents a portal into potential therapeutic approaches for the treatment of heart failure and metabolic syndrome. The mechanism by which EET acts on obesity-induced cardiomyopathy is unknown. Here, we describe a previously unrecognized function of EET infusion that inhibits nephroblastoma overexpressed (NOV) levels and activates Wnt1, hence identifying NOV inhibition and enhanced Wnt1 expression as novel pharmacological targets for the prevention and treatment of cardiomyopathy and heart failure.Listen to this article's corresponding podcast at http://ajpheart.physiology.org/content/early/2017/05/31/ajpheart.00093.2017.

Cardioprotective Heme Oxygenase‐1‐PGC1α Signaling in Epicardial Fat Attenuates Cardiovascular Risk in Humans as in Obese Mice

“…In the present report, we describe signaling pathways in the epicardial fat of patients with overweight or obesity and coronary disease that correspond to pathways that we have previously described in epicardial fat of an obese mouse model. In addition, we describe adverse signaling expression pathways in the epicardial fat of overweight humans with vascular disease that are significantly more prominent than those found in visceral fat, another observation in concert with that seen in our mouse model . This suggests that the accumulation of inflammatory cytokines and chemokines in epicardial fat has a significantly greater toxic effect on the heart than those emanating from visceral fat, both in humans and mice.…”

“…This study provides the first evidence for a difference in activity of HO‐1‐PGC1α between epicardial fat and visceral fat and demonstrates for the first time that these signaling pathways previously described in the mouse appear to be active in human epicardial fat as well. Stimulation of HO‐1‐PGC1α in the mouse is associated with significant improvement in the ejection fraction of the hearts of mice with obesity and diabetic cardiomyopathy . Hence, the current observations open the way toward additional human studies that may further elucidate these pathways and consequently lead to novel targets for the treatment both of obesity itself and its related cardiomyopathy syndromes.…”

“…TaqMan Fast Universal PCR Master Mix (2×) on a 7500 HT Fast Real‐Time PCR System (Applied Biosystems) was used to perform real‐time PCR. Specific TaqMan Gene Expression Assay probes (Thermo Fisher Scientific, Waltham, Massachusetts) for mouse HO‐1, PGC1α, NOV, mitofusin 2 (MFN2), tumor necrosis factor (TNF‐α), IL4, PRDM16, adiponectin, and GAPDH were used as previously described .…”

“…Five target housekeeping genes (β‐actin, GAPDH, LDHA, NONO , and PPIH ) enable normalization of data. The following genes were analyzed in both epicardial and visceral adipose tissue : for preadipocyte cell markers, ADIPOQ, LEP, HOXC8/9, TBX1, TMEM26, UCP1, CIDEA, PRDM16, SLC7A10 , and P2RX5 ; for proliferation, CCND1, PROKR1, LYRM1, FTO, SLC2A4, PDGFA, IL4, IGF1, FGF5, MAPK1/3 , and TNFSF10 ; for differentiation and adipogenesis, PPARG, CEBPA/B, KLF2/5/15, SOCS1/3, INSR, DLK1, ADD1 , and SREBF1 ; for extracellular matrix and cytoskeleton, MMP1/2/3, FAP, DPP4, TGFB1, COL1A1/2 , and SMAD2/4 ; for lipid metabolism, FABP5/7, LBP, LPL, PLIN2, ACSL1, and LIPC ; for obesity, MC4R, UCP3, ADRB2/3, POMC, FFAR4 , and CARTPT ; and for liposarcoma, FUS, MDM2, HMGA2, DDIT3, CDK4, EWSR1, DES, and VIM .…”

“…Induction of NOV increased adipose tissue deposition, enhanced cholesterol, and increased insulin resistance and sleep apnea . In particular, epicardial fat is a distinct source of adipokines, reactive oxygen species (ROS), and inflammatory cytokines, and it has been tied to significant cardiac remodeling because of a decrease in the levels of heme oxygenase 1 (HO‐1) and peroxisome proliferator‐activated receptor (PPAR) gamma coactivator 1‐alpha (PGC1α) . HO‐1 is regarded as the first line of defense against oxidative stress given that oxidative stress is a strong inducer of HO, which comprises both an inducible and a constitutive form (HO‐1 and HO‐2, respectively) and catalyzes the oxidative degradation of heme into iron, biliverdin, and carbon monoxide (CO).…”