The Impact of Cardiac Lipotoxicity on Cardiac Function and Mirnas Signature in Obese and Non-Obese Rats with Myocardial Infarction

Abstract

Cardiac lipotoxicity is involved in the cardiac functional consequences associated with obesity. Therefore, the aim of this study was to explore whether changes in the mitochondrial lipid cardiac profile could reflect differences in cardiac function and structure in obese and non-obese rats with myocardial infarction (MI). Whether these changes can also be reflected in a specific plasma miRNA signature as markers of cardiac damage was also evaluated. Rats were fed with either standard (3.5% fat) or high fat diet (35% fat) for 6 weeks before the induction of MI and sacrificed 4 weeks later. MI showed cardiac lipotoxicity independently of the presence of obesity, although obese and non-obese rats did not present the same cardiac lipid profile at mitochondrial level. Several cardiac lipid species in mitochondria, including cardiolipins and triglycerides, were associated with myocardial fibrosis, with mitochondrial triglyceride levels being independently associated with it; this supports that lipotoxicity can affect cardiac function. MI down-regulated plasma levels of miRNA 15b-5p and 194-5p in obese and non-obese animals, which were associated with cardiac function, mitochondrial lipids and myocardial fibrosis, with miRNA 15b-5p levels being independently associated with cardiac fibrosis. This could support that lipotoxicity could affect heart function by modulating plasma miRNAs.

Figure 1

Impact of MI on cardiac echocardiographic parameters and interstitial fibrosis in non-obese and obese rats. (A) Septum interventricular thickening (IVST); (B) Posterior wall thickening (PWT); (C) Left ventricular ejection fraction (LVEF); (D) shortening fraction (SF); (E) E-wave and A-wave ratio (E/A); (F) Quantification of collagen volume fraction (CVF) and representative microphotographs of myocardial sections staining with picrosirius red examined by light microscopy (magnification 40x) in control rats (CT), or rats submitted to MI fed a standard (AMI) or a high fat diet (HFD-AMI). Bar graphs represent the mean ± SEM. of 8–10 animals. *P < 0.05; **P < 0.01; ***P < 0.001 vs control group. ^†P < 0.05; ^††P < 0.01 vs AMI group.

Figure 2

Impact of MI on total and mitochondrial triglycerides and protein levels in heart from non-obese and obese rats. Cardiac levels of (A) total triglycerides (TGs), (B) mitochondrial triglycerides. Protein expression of (C) carnitine palmitoyl transferase 1 (CPT1A), (D) Fatty acid translocase (FAT), (E) adipose triglyceride lipase (ATGL) and (F) diacylglycerol transferase 1 (DAGT1) in control rats (CT), or rats submitted to MI fed a standard (AMI) or a high fat diet (HFD-AMI). Bar graphs represent the mean ± SEM. of 8–10 animals normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH). *P < 0.05; **P < 0.01; ***P < 0.001 vs control group. ^† < 0.05; ^††P < 0.01; ^†††P < 0.001 vs AMI group.

Figure 3

Impact of MI on mitochondrial lipid species in heart from non-obese and obese rats. Cardiac levels of (A) total phospholipids (PL); (B) diacyl phosphatidylcholine (PC); (C) diacyl phosphatidylethanolamine (PE); (D) Lysophosphatidylcholine (Lyso-PC) and (E) Lysophosphatidylethanolamine (Lyso-PE) in control rats (CT), or rats submitted to MI fed a standard (AMI) or a high fat diet (HFD-AMI). Bar graphs represent the mean ± SEM. of 8–10 animals normalized to CT group. *P < 0.05; ***P < 0.001 vs control group; ^††P < 0.01, ^†††P < 0.001 vs AMI group.

Figure 4

Impact of MI on mitochondrial cardiolipins and ceramide species in heart from non-obese and obese rats. Cardiac levels of (A) total cardiolipins; (B) cardiolipins enriched with linoleic acid; (C) cardiolipins enriched with arachidonic acid (20:4), (D) cardiolipins enriched with docosahexaenoic acid (22:6), (E) Total ceramides and (F) ceramides enriched with docosanoic acid (22:0). Bar graphs represent the mean ± SEM. of 8–10 animals normalized to CT group. *P < 0.05; ***P < 0.001 vs control group. ^†P < 0.05; ^††P < 0.01vs AMI group.

Figure 5

Impact of MI on plasma-derived microRNAs from non-obese and obese rats. Plasma levels of (A) microRNA (mRNA) 15b-5p; (B) mRNA 194–5p; (C) mRNA 19a-3p; (D) mRNA 144-5p; (E) mRNA 301a-3p; (F) miRNA1260a and (G) mRNA let7f-5p in control rats (CT), or rats submitted to MI fed a standard (AMI) or a high fat diet (HFD-AMI). Bar graphs represent the mean ± SEM. of 8–10 animals normalized to CT group. *P < 0.05; **P < 0.01; ***P < 0.001 vs control group. P < 0.05; ^††P < 0.01; ^†††P < 0.001 vs AMI group.