Cardiomyocyte Aldose Reductase Causes Heart Failure and Impairs Recovery from Ischemia

<div><p>Aldose reductase (AR), an enzyme mediating the first step in the polyol pathway of glucose metabolism, is associated with complications of diabetes mellitus and increased cardiac ischemic injury. We investigated whether deleterious effects of AR are due to its actions specifically in cardiomyocytes. We created mice with cardiac specific expression of human AR (hAR) using the α–myosin heavy chain (MHC) promoter and studied these animals during aging and with reduced fatty acid (FA) oxidation. hAR transgenic expression did not alter cardiac function or glucose and FA oxidation gene expression in young mice. However, cardiac overexpression of hAR caused cardiac dysfunction in older mice. We then assessed whether hAR altered heart function during ischemia reperfusion. hAR transgenic mice had greater infarct area and reduced functional recovery than non-transgenic littermates. When the hAR transgene was crossed onto the PPAR alpha knockout background, another example of greater heart glucose oxidation, hAR expressing mice had increased heart fructose content, cardiac fibrosis, ROS, and apoptosis. In conclusion, overexpression of hAR in cardiomyocytes leads to cardiac dysfunction with aging and in the setting of reduced FA and increased glucose metabolism. These results suggest that pharmacological inhibition of AR will be beneficial during ischemia and in some forms of heart failure.</p> </div

Cardiac dysfunction is observed at an earlier age in MHC-hAR/<i>Ppara^−/−</i> mice.

<p>(<b>A</b>) Representative echocardiographic images of LVD in the mice (age = 7 months). (<b>B–D</b>) Echocardiography showed increased LVDs, LVDd and FS in MHC-hAR/<i>Ppara^−/−</i> mice. FS, fractional shortening; LVDs, left ventricular end-systolic dimension. Data are shown as mean ± SD. *P<0.05 and ^§P<0.001 versus littermate controls.</p

Increased cardiac fibrosis, apoptosis and ROS in MHC-hAR/<i>Ppara</i>^−/− mice.

<p>(<b>A</b>) Cardiac fibrosis was detected using Masson's trichrome stain (original magnification, ×100) (<b>B</b>) Cardiac ventricular tissues were stained for DNA fragmentation by TUNEL protocol (original magnification, ×200). Apoptotic cardiomyocytes containing fragmented nuclear chromatin exhibited dark brown nuclear staining (arrows). (<b>C</b>) Histological analysis of heart tissues using dihydroethidium staining to detect ROS (original magnification, ×100).</p

Cardiac fructose content and proteins expression in MHC-hAR<i>/Ppara^−/−</i> mice.

<p>(<b>A</b>) Representative Western blot images of hAR, PPAR α, PDK4 and BAX proteins in the heart from all the groups of mice studied. IgG bands are shown as control. (<b>B</b>) Cardiac fructose content (nmol/mg protein) in MHC-hAR/<i>Ppara</i>^−/− mice are compared to those in MHC-hAR mice. Data are shown as mean ± SD (n = 5–7). *P<0.05 versus littermate controls.</p

Cardiac ceramide in MHC-hAR/<i>Ppara</i>^−/− mice.

<p>(<b>A</b>) Total ceramide and (<b>B</b>) individual ceramide species. Ceramide species data represent the content of each FA as a percentage of total ceramide and are shown as mean ± SD (n = 6–8 per group). *P<0.05, ^#P<0.01 and ^§P<0.001 versus littermate controls. ^a P<0.05 and ^bP<0.01 versus MHC-hAR/<i>Ppara^−/−</i> mice.</p

Construct and hAR protein expression in MHC-hAR mice.

<p>(<b>A</b>) hAR construct design employed in this study is presented. The α-MHC promoter was used to drive hAR cDNA expression. The construct scheme indicate exons that are numbered (black boxes) along with poly(A) site (PA). (<b>B</b>) Cardiac-specific hAR expression are presented for. Western blotting was performed in 3-month-old MHC-hAR male mice using polyclonal human AR antibody. Total protein (30 µg) from adipose, heart, muscle and liver tissues of MHC-hAR and their littermate controls was analyzed. GAPDH antibody is shown as a control.</p

Cardiac dysfunction and reduced FAO related mRNA expression with aging in MHC-hAR mice.

<p>13 month old mice were used in these studies. (<b>A</b>) The heart to body weight ratio was increased in MHC-hAR mice (n = 9–12). (<b>B and C</b>) Echocardiographic measurements showed increased left ventricular systolic dimension and reduced fractional shortening with age in MHC-hAR mice. (<b>D</b>) MHC-hAR transgene altered cardiac FA and glucose oxidation gene expression in mice. FS, fractional shortening; LVDs, left ventricular end-systolic dimension. Data are shown as mean ± SD. *P<0.05, ^#P<0.01, and ^§P<0.001 versus littermate controls.</p