Folic acid prevents cardiac dysfunction and reduces myocardial fibrosis in a mouse model of high-fat diet-induced obesity

In the obese and diabetic heart, an imbalance between fatty acid uptake and fatty acid oxidation (FAO) promotes the development of cardiac lipotoxicity. We previously showed that cardiac specific deletion of acetyl CoA carboxylase 2 (ACC2) was effective in increasing myocardial FAO while maintaining normal cardiac function and energetics. In this study, we tested the hypothesis that ACC2 deletion in an adult heart would prevent the cardiac lipotoxic phenotype in a mouse model of diet-induced obesity. ACC2 flox/flox (CON) and ACC2 flox/flox-MerCreMer+ (iKO) after tamoxifen injection were subjected to a high fat diet (HFD) for 24 weeks. HFD induced similar body weight gain and glucose intolerance in CON and iKO. In isolated Langendorff-perfused heart experiments, HFD feeding increased FAO 1.6-fold in CON mice which was increased to 2.5-fold in iKO mice compared with CON on chow diet. Fractional shortening was significantly decreased in CON-HFD (32.8±2.8% vs. 39.2±3.2%, p< 0.05, n=5-6), but preserved in iKO-HFD mice (42.8±2.3%, vs. 38.5±1.4%, n=6), compared to respective chow fed controls. Diastolic function, assessed by E’/A’ ratio using tissue Doppler imaging, was significantly decreased in CON-HFD mice (1.11±0.08 vs. 0.91±0.09, p<0.05 n=5-6), while no difference was observed in iKO-HFD compared to iKO-chow (1.10±0.03 vs. 1.09±0.04, n=6). Heart weight /Tibia length ratio was significantly higher in CON than iKO mice after HFD feeding (7.19±0.22 vs. 6.47±0.28, p<0.05, n=6). Furthermore, HFD induced mitochondria super complex II, III and V instability, which was attenuated in iKO-HFD mice. These data indicate that elevated myocardial FAO per se does not cause the development of cardiac dysfunction in obese animals. In fact, enhancing FAO via ACC2 deletion prevents HFD induced cardiac dysfunction and attenuates pathological hypertrophy. These effects may be mediated, in part, by maintenance of mitochondrial integrity. Taken together, our findings suggest that promoting cardiac FAO is an effective strategy to resist the development of cardiac lipotoxicity during diet-induced obesity.

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Minor role of mature adipocyte mineralocorticoid receptor in high-fat diet-induced obesity

Journal of Endocrinology ◽

10.1530/joe-18-0314 ◽

2018 ◽

Vol 239 (2) ◽

pp. 229-240 ◽

Cited By ~ 4

Author(s):

A Feraco ◽

A Armani ◽

R Urbanet ◽

A Nguyen Dinh Cat ◽

V Marzolla ◽

...

Keyword(s):

Adipose Tissue ◽

Mouse Model ◽

High Fat Diet ◽

Mineralocorticoid Receptor ◽

Metabolic Effects ◽

Minor Role ◽

High Fat ◽

Mature Adipocyte ◽

Diet Induced Obesity ◽

Significant Difference

Obesity is a major risk factor that contributes to the development of cardiovascular disease and type 2 diabetes. Mineralocorticoid receptor (MR) expression is increased in the adipose tissue of obese patients and several studies provide evidence that MR pharmacological antagonism improves glucose metabolism in genetic and diet-induced mouse models of obesity. In order to investigate whether the lack of adipocyte MR is sufficient to explain these beneficial metabolic effects, we generated a mouse model with inducible adipocyte-specific deletion of Nr3c2 gene encoding MR (adipo-MRKO). We observed a significant, yet not complete, reduction of Nr3c2 transcript and MR protein expression in subcutaneous and visceral adipose depots of adipo-MRKO mice. Notably, only mature adipocyte fraction lacks MR, whereas the stromal vascular fraction maintains normal MR expression in our mouse model. Adipo-MRKO mice fed a 45% high-fat diet for 14 weeks did not show any significant difference in body weight and fat mass compared to control littermates. Glucose and insulin tolerance tests revealed that mature adipocyte MR deficiency did not improve insulin sensitivity in response to a metabolic homeostatic challenge. Accordingly, no significant changes were observed in gene expression profile of adipogenic and inflammatory markers in adipose tissue of adipo-MRKO mice. Moreover, pharmacological MR antagonism in mature primary murine adipocytes, which differentiated ex vivo from WT mice, did not display any effect on adipokine expression. Taken together, these data demonstrate that the depletion of MR in mature adipocytes displays a minor role in diet-induced obesity and metabolic dysfunctions.

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