The Decreased Expression of Peroxisome Proliferator-activated Receptors δ (PPARδ) is Reversed by Digoxin in the Heart of Diabetic Rats

Abstract

The present study is designed to investigate the role of peroxisome proliferator-activated receptors δ (PPARδ) in the action of digoxin in diabetic rats showing cardiac hypertrophy. We used Wistar rats to induce diabetes by injection of streptozotocin (STZ-rat) and examined the effect of digoxin on PPARδ expression in these hyperglycemic rats (STZ-rat) at 10 weeks later. We measured the changes of body weight, water intake, and food intake in three groups of age-matched rats; the vehicle treated normal control (Wistar rats), the vehicle treated STZ-rats, and the digoxin-treated STZ-rats. Cardiac output, heart rate, and blood pressure in addition to plasma insulin or glucose level were also determined. The mRNA and protein levels of PPARδ were measured using Northern and Western blotting, respectively. Cardiac output, heart rate, and blood pressure were markedly reduced while food intake, water intake, and blood glucose were raised in STZ-rats showing lower body weight and plasma insulin as compared with the vehicle-treated controls. After a 20-day of digoxin treatment, cardiac output was raised in STZ-rats but the diabetic parameters were not modified. The PPARδ expressions, both mRNA and protein, were markedly elevated in the hearts of STZ-rats by digoxin treatment. The related signals with PPARδ, such as carnitine palmitoyltransferase 1B (CPT1B), acetyl-coenzyme A, carboxylase alpha (ACC1), fatty acid synthase (FAS), and troponin I, were also raised. The increase of cardiac output by digoxin was reversed by the combined treatment with PPARδ antagonist GSK0660. Thus, we suggest a new finding that PPARδ is involved in digoxin induced cardiac inrotropic action.

Key words

digoxin - cardiac output - PPARδ - heart - diabetic rat

References

• 1 Saini-Chohan HK, Hatch GM. Biological actions and metabolism of currently used pharmacological agents for the treatment of congestive heart failure.  Curr Drug Metab. 2009;  10 206-219
• 2 Besch Jr HR, Watanabe AM. The positive inotropic effect of digitoxin: independence from sodium accumulation.  J Pharmacol Exp Ther. 1978;  207 958-965
• 3 Pervaiz MH, Dickinson MG, Yamani M. Is digoxin a drug of the past?.  Cleve Clin J Med. 2006;  73 821-824 826, 829–832 and passim
• 4 van Veldhuisen DJ, Man in ’ t Veld AJ, Dunselman PH, Lok DJ, Dohmen HJ, Poortermans JC, Withagen AJ, Pasteuning WH, Brouwer J, Lie KI. Doubleblind placebo-controlled study of ibopamine and digoxin in patients with mild to moderate heart failure: results of the Dutch Ibopamine Multicenter Trial (DIMT).  J Am Coll Cardiol. 1993;  22 1564-1573
• 5 Ahmed A, Pitt B, Rahimtoola SH, Waagstein F, White M, Love TE, Braunwald E. Effects of digoxin at low serum concentrations on mortality and hospitalization in heart failure: a propensity-matched study of the DIG trial.  Int J Cardiol. 2008;  123 138-146
• 6 Ohtsuki I, Morimoto S. Troponin: regulatory function and disorders.  Biochem Biophys Res Commun. 2008;  369 62-73
• 7 Metzger JM, Westfall MV. Covalent and noncovalent modification of thin filament action: the essential role of troponin in cardiac muscle regulation.  Circ Res. 2004;  94 146-158
• 8 Layland J, Solaro RJ, Shah AM. Regulation of cardiac contractile function by troponin I phosphorylation.  Cardiovasc Res. 2005;  66 12-21
• 9 Bootman MD, Berridge MJ. The elemental principles of calcium signaling.  Cell. 1995;  83 675-678
• 10 Yang Q, Li Y. Roles of PPARs on regulating myocardial energy and lipid homeostasis.  J Mol Med. 2007;  85 697-706
• 11 Issemann I, Green S. Activation of a member of the steroid hormone receptor superfamily by peroxisome proliferators.  Nature. 1990;  347 645-650
• 12 Cheng L, Ding G, Qin Q, Huang Y, Lewis W, He N, Evans RM, Schneider MD, Brako FA, Xiao Y, Chen YE, Yang Q. Cardiomyocyte-restricted peroxisome proliferator-activated receptor-delta deletion perturbs myocardial fatty acid oxidation and leads to cardiomyopathy.  Nat Med. 2004;  10 1245-1250
• 13 Cheng L, Ding G, Qin Q, Xiao Y, Woods D, Chen YE, Yang Q. Peroxisome proliferator-activated receptor deltam activates fatty acid oxidation in cultured neonatal and adult cardiomyocytes.  Biochem Biophys Res Commun. 2004;  313 277-286
• 14 Barish GD, Narkar VA, Evans RM. PPAR delta: a dagger in the heart of the metabolic syndrome.  J Clin Invest. 2006;  116 590-597
• 15 Kannel WB, Hjortland M, Castelli WP. Role of diabetes in congestive heart failure: the Framingham study.  Am J Cardiol. 1974;  34 29-34
• 16 Kannel WB, McGee DL. Diabetes and cardiovascular disease.  The Framingham study. J AMA. 1979;  241 2035-2038
• 17 Malmberg K, Ryden L. Myocardial infarction in patients with diabetes mellitus.  Eur Heart J. 1988;  9 259-264
• 18 Herlitz J, Malmberg K, Karlson BW, Ryden L, Hjalmarson A. Mortality and morbidity during a five-year follow-up of diabetics with myocardial infarction.  Acta Med Scand. 1988;  224 31-38
• 19 Poornima IG, Parikh P, Shannon RP. Diabetic cardiomyopathy: the search for a unifying hypothesis.  Circ Res. 2006;  98 596-605
• 20 An D, Rodrigues B. Role of changes in cardiac metabolism in development of diabetic cardiomyopathy.  Am J Physiol Heart Circ Physiol. 2006;  291 H1489-H1506
• 21 Yu BC, Chang CK, Ou HY, Cheng KC, Cheng JT. Decrease of peroxisome proliferator-activated receptor delta expression in cardiomyopathy of streptozotocin-induced diabetic rats.  Cardiovasc Res. 2008;  80 78-87
• 22 Fein FS, Kornstein LB, Strobeck JE, Capasso JM, Sonnenblick EH. Altered myocardial mechanics in diabetic rats.  Circ Res. 1980;  47 922-933
• 23 Fein FS, Strobeck JE, Malhotra A, Scheuer J, Sonnenblick EH. Reversibility of diabetic cardiomyopathy with insulin in rats.  Circ Res. 1981;  49 1251-1261
• 24 Shearer BG, Steger DJ, Way JM, Stanley TB, Lobe DC, Grillot DA, Iannone MA, Lazar MA, Willson TM, Billin AN. Identifi cation and characterization of a selective peroxisome proliferator-activated receptor beta/ delta (NR1C2) antagonist.  Mol Endocrinol. 2008;  22 523-529
• 25 Dimopoulos N, Watson M, Green C, Hundal HS. The PPARdelta agonist, GW501516, promotes fatty acid oxidation but has no direct effect on glucose utilisation or insulin sensitivity in rat L6 skeletal muscle cells.  FEBS Lett. 2007;  581 4743-4748
• 26 Tanaka T, Yamamoto J, Iwasaki S, Asaba H, Hamura H, Ikeda Y, Watanabe M, Magoori K, Ioka RX, Tachibana K, Watanabe Y, Uchiyama Y, Sumi K, Iguchi H, Ito S, Doi T, Hamakubo T, Naito M, Auwerx J, Yanagisawa M, Kodama T, Sakai J. Activation of peroxisome proliferator-activated receptor delta induces fatty acid beta-oxidation in skeletal muscle and attenuates metabolic syndrome.  Proc Natl Acadm Sci USA. 2003;  100 15924-15929
• 27 Dressel U, Allen TL, Pippal JB, Rohde PR, Lau P, Muscat GE. The peroxisome proliferatoractivated receptor beta/delta agonist, GW501516, regulates the expression of genes involved in lipid catabolism and energy uncoupling in skeletal muscle cells.  Mol Endocrinol. 2003;  17 2477-2493
• 28 Kobayashi T, Jin L, de Tombe PP. Cardiac thin filament regulation.  Pfl ugers Arch. 2008;  457 37-46
• 29 Liu X, Takeda N, Dhalla NS. Troponin I phosphorylation in heart homogenate from diabetic rat.  Biochim Biophys Acta. 1996;  1316 78-84
• 30 Messer AE, Jacques AM, Marston SB. Troponin phosphorylation and regulatory function in human heart muscle: dephosphorylation of Ser23/24 on troponin I could account for the contractile defect in end-stage heart failure.  J Mol Cell Cardiol. 2007;  42 247-259
• 31 Ayaz-Guner S, Zhang J, Li L, Walker JW, Ge Y. In vivo phosphorylation site mapping in mouse cardiac troponin I by high resolution top-down electron capture dissociation mass spectrometry: Ser22/23 are the only sites basally phosphorylated.  Biochemistry. 2009;  48 8161-8170
• 32 MacGowan GA, Evans C, Hu TC, Debrah D, Mullet S, Chen HH, McTiernan CF, Stewart AF, Koretsky AP, Shroff SG. Troponin I protein kinase C phosphorylation sites and ventricular function.  Cardiovasc Res. 2004;  63 245-255
• 33 Tate CA, Hyek MF, Taffet GE. The role of calcium in the energetics of contracting skeletal muscle.  Sports Med. 1991;  12 208-217
• 34 Li L, Desantiago J, Chu G, Kranias EG, Bers DM. Phosphorylation of phospholamban and troponin I in beta-adrenergic-induced acceleration of cardiac relaxation.  Am J Physiol Heart Circ Physiol. 2000;  278 H769-H779
• 35 Pi Y, Kemnitz KR, Zhang D, Kranias EG, Walker JW. Phosphorylation of troponin I controls cardiac twitch dynamics: evidence from phosphorylation site mutants expressed on a troponin I-null background in mice.  Circ Res. 2002;  90 649-656

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