Introduction 1 1 2 3 6 α α 7 1 8 6 7 9 10 11 11 7 12 2 13 14 N Materials and methods Animals n 2 2 15 Diets In vivo cardiac function 2 2 16 17 \documentclass[12pt]{minimal}
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\begin{document}$$ {\left( {\operatorname{FS} \% } \right)} = {\left[ {{{\left( {EDD - ESD} \right)}} \mathord{\left/  {\vphantom {{{\left( {EDD - ESD} \right)}} {\left. {EDD} \right)}}} \right.  \kern-\nulldelimiterspace} {\left. {EDD} \right)}} \right]} \times 100\%  $$\end{document} 3 3 \documentclass[12pt]{minimal}
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\begin{document}$$ {\left( {EF\% } \right)} = {\left[ {{{\left( {EDV - ESV} \right)}} \mathord{\left/  {\vphantom {{{\left( {EDV - ESV} \right)}} {EDV}}} \right.  \kern-\nulldelimiterspace} {EDV}} \right]} \times 100\%  $$\end{document} \documentclass[12pt]{minimal}
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\begin{document}$$ 1.05 \times {\left[ {{\left( {EDD + PWT + IVS} \right)}^{3}  - \operatorname{EDV} } \right]} $$\end{document} 18 Plasma and tissue determinations 2 Treatment of isolated cardiomyocytes 15 19 9 20 15 21 22 14 Glucose uptake, palmitate uptake and oxidation, and incorporation into intracellular lipid pools 3 14 15 14 14 2 14 9 Western blotting 9 13 2 23 2 Cardiac morphology and subcellular localisation of CD36 2 24 23 2 2 Statistical analysis n t t p Results HFD induces cardiac contractile dysfunction 1 p 1 1 1 p 1 p 1 p 1 p p 1 p 1 Table 1 In vivo cardiac characteristics of rats before and after 8 weeks on an HFD or a LFD   Start LFD HFD n n n Physiological parameters  Body weight (g) 295 ± 4 476 ± 8* 463 ± 8*  Left ventricular mass (mg) 637 ± 15 890 ± 18* 882 ± 32* LV diastolic parameters  Posterior wall thickness (mm) 1.63 ± 0.03 1.80 ± 0.07 1.71 ± 0.05  Lumen diameter (mm) 6.92 ± 0.07 7.55 ± 0.20* 7.68 ± 0.10*  Interventricular septum wall thickness (mm) 1.37 ± 0.03 1.67 ± 0.08* 1.54 ± 0.04*  Ventricular diameter (mm) 9.80 ± 0.06 10.86 ± 0.13* 10.89 ± 0.12* LV systolic parameters  Posterior wall thickness (mm) 2.93 ± 0.06 3.45 ± 0.12* 3.00 ± 0.08**  Lumen diameter (mm) 3.41 ± 0.10 3.32 ± 0.25 ,  Interventricular septum wall thickness (mm) 2.51 ± 0.05 2.85 ± 0.09* 2.67 ± 0.06  Ventricular diameter (mm) 8.81 ± 0.07 9.82 ± 0.12* 9.81 ± 0.10*  Fractional shortening (%) 50.8 ± 1.3 56.3 ± 2.4* ,  Ejection fraction (%) 87.5 ± 1.0 91.1 ± 1.4 , Data are means±SE p p Fig. 1 a closed circles n open circles n b  Insulin action, but not AMPK signalling, is impaired in HFD cardiomyocytes p 2 p p Table 2 Characteristics of rats after 10 weeks on a high- or low-fat diet   LFD HFD n n Body composition  Body weight at killing (g) 465 ± 5 472 ± 10  Heart weight (% body weight) 0.445 ± 0.007 0.431 ± 0.012  Liver weight (% body weight) 3.10 ± 0.07 3.02 ± 0.08  Perirenal fat pad weight (% body weight) 1.63 ± 0.08 2.43 ± 0.14* Plasma characteristics  Blood glucose (mmol/l) 5.50 ± 0.08 5.78 ± 0.08**  Plasma insulin (pmol/l) 269 ± 18 216 ± 16*** Data are means±SE p p p −1 -1 p 2 p p p Fig. 2 open bars filled bars Basal INS Oli n p p  13 25 p 3 p p Fig. 3 a c b d Basal INS Oli n p p  25 3 p HFD feeding results in increased CD36-mediated LCFA uptake p 4 p p 4 p p 4 4 p Fig. 4 a b c open bars filled bars Basal INS Oli n p p  4 p p p p 4 p p 4 p p 2 HFD induces cardiomyocyte hypertrophy and alters the subcellular localisation of CD36 5 p 3 p 5 3 Fig. 5 a b d c e b c d e Arrows Scale bar  Table 3 Cardiac morphology and subcellular localisation of CD36   LFD HFD n n Morphology 2 214 ± 3.5 276 ± 23* CD36 localisation  Sarcolemma   Saline (%) 61.7 ± 3 74.8 ± 1**   Insulin (%) 75.9 ± 4*** 78.2 ± 3  Cytoplasm   Saline (%) 38.3 ± 3 25.2 ± 1**   Insulin (%) 24.1 ± 4*** 21.8 ± 3 Data are means±SE p p p 4 2 5 p 3 5 HFD-induced CD36 redistribution to the sarcolemma precedes the onset of cardiac contractile dysfunction and associates with elevated basal phosphorylation of PKB/Akt p p p 1 6 5 Fig. 6 a b arrows scale bar c d open bars filled bars n p  26 5 6 p Discussion Here we report that HFD feeding induces cardiac contractile dysfunction in rats and that this is associated with a permanent relocation of CD36 to the sarcolemma. The continuous presence of CD36 at the sarcolemmal membrane results in enhanced rates of LCFA uptake and subsequent esterification. We propose that this contributes to a decrease in myocardial insulin action and the development of diabetes-related heart disease. In addition, we show that AMPK-mediated responses are not affected by the composition of the diet. A key observation in this study is that the alterations in cardiac contractile function in HFD hearts was associated with a continuous presence of CD36 at the sarcolemmal membrane. The present study provides the first morphological evidence for translocation of CD36 to the sarcolemmal membrane. Importantly, the amount of sarcolemmal CD36 closely correlated with enhanced LCFA uptake rates in isolated cardiomyocytes. The observation that SSO inhibited LCFA uptake in HFD cardiomyocytes to the same residual levels as measured in LFD cardiomyocytes provides further pharmacological evidence that the enhanced flux of LCFA in the heart of HFD-fed rats is a direct consequence of the relocalisation of CD36 to the sarcolemmal membrane. 27 28 9 22 9 22 9 26 10 14 26 11 26 9 2 13 2+ 29 1 30 2 2 12 31 32 33 31 34 35 36 2+ 37 38 1 2 8 39 40 33 35 41 2 13 We conclude that HFD feeding in rats induces cardiac contractile dysfunction, which is preceded by relocation of CD36 to the sarcolemma, and elevated basal levels of phosphorylated PKB/Akt. The continuous presence of CD36 at the sarcolemma contributes to enhanced rates of fatty acid uptake, resulting in myocardial triacylglycerol accumulation and accompanying insulin resistance. Collectively, these data suggest that alterations in the subcellular localisation of CD36 may contribute to the development of diabetes-related heart disease and that CD36 may be a therapeutic target to prevent cardiac dysfunction and the development of heart failure in diabetes. Electronic supplementary material Below is the link to the electronic supplementary material.
 ESM Table 1 Heart rate and blood pressure of rats after 10 weeks on an HFD or a LFD (PDF 22 kb)