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Regional myocardial free fatty acid utilization following carvedilol therapy in patients with heart failure
ENDOTHELIN-1
IS EXAGGERATED
IN DIABETIC
BATS
Subodh Verma, Emi Arikawa, Sammy Lee & John H. McNeill. Faculty of Pharmaceutical Sciences, UBC, Vancouver, Canada We previously demonstrated that chronic endothelin (ET) receptor blockade (with bosentan) improved isolated working cardiac function in streptozotocin-diabetic rats. In an attempt to gain insight into the mechanism(s) underlying this effect, the present study examined the direct effects of ET-l on coronary arterial pressure in diabetic and control rat hearts treated with or without bosentan. Male Wistar rats were divided into control, control bosentan-treated, diabetic, and diabetic bosentan-treated groups. After 8 weeks of bosentan treatment (1 OOmg/kg/day), hearts were isolated and perfused, and coronary art&al pressure was measured in response to ET-l (SO and 100 DM). Additionallv. maximal coronarv blood bow (assessed with 1K5 M ade&ine) was measure; in isolated perfused hearts. The key observation from this study is that coronary reactivity to ET-l (assessed using coronary arterial pressure) was significantly higher in the diabetic group than in the control rats. This effect was normalized in diabetic rats chronically treated with bosentan. Maximal coronary vasodilation did not differ between the four groups. In conclusion, (a) the reactivity of ET-I is altered in the isolated perfused coronary vascular bed from diabetic rats and (a) chronic ET receptor blockade (with bosentan) restores this reactivity to control values. These observations provide a mechanism for the improvement in isolated working heart function observed following chronic bosentan treatment. (EA is a HSFC research trainee. SV is a Fellow
A180
METABOLIC PHENOTYPING OF THE DISEASED HEART USING %SUBSTRATES AND EX V/V0 PERFUSION IN THE WORKING MODE. Genevieve Vincent*, Maya Khalrallah, Bertrand Bouchard, Joanne K. Kelleher 8 Christine Des Roslers, Depts Biochemistry & Nutrition, CHUM Res. Ctr, Univ. Montrbal, Canada; Dept Physiology, GW Univ., USA. Although accelerated glycolysis is shown to be part of the metabolic phenotype expressed by the hypertrophied heart, less is known about the impact of hypertrophy on the activity of mitochondrial citric acid cycle (CAC) reactions. Methods: We have used ‘3C-mass isotopomer analysis by gas chromatography-mass spectrometry to assess pyruvate partitioning between decarboxylation (PDC) and carboxylation (PC) for mitochondrial citrate formation and efflux (reflected by citrate release rate) in spontaneously hvpertensive rat (SHR: 15 week-old) hearts. Wistar-Kvoto @KY) rats served as controls. ‘Working hearts were oerfused with 5.5 mM alucose. 8 nM insulin. 1 mM %-
iactate (Lac), 0.2 mM-‘3C3-p;ruvate (Pyr), and 50 &l carnitine. Results: Compared to WKY, SHR hearts showed significantly lower leff ventricular contractility, cardiac output, aortic and coronary flows, cardiac power (CP) and efficiency. This mechanical dysfunction was associated with the following metabolic perturbations (normalised to CP): an increase of [Lac + Pyr] and citrate release rates, and a decrease of [Lac + Pyr] uptake, PDClPC and PDClCAC flux ratios and CAC flux rate. Conclusion: Since SHR hearts release more citrate, suggesting that substrate supply for citrate synthesis exceeds citrate utilisation in the CAC, mitochondrial pyruvate oxidation appears to be restricted beyond the citrate synthase reaction. (Funded by the CIHR).
of MRC(Canada).)
REGIONALMYOCARDIALFREEFATTYACID UTlLlZATlONFOLLOWINGCARVEDILOLTHERAPYIN PATIENTS WITHHEARTFAILURE. TR.Wallhaus”, M.Taylor,DCRussell,TR. DeGrado,RJ.Nickles, CKStone.VeteransHospital-Madison WisconsinUSA
GLUCOSE OXIDATION RATES ARE LOW IN HYPERTROPHIED RAT HEARTS PERFUSED IN THE ABSENCE OF FATTY ACID. Richard Wambolt, Mark Grist, Hannah Parsons, Roger Brownsey, Michael Allard. UBC, Vancouver, B.C.
Changesin myocardialfree fatty acid utilizationfollowingbetablockadetreatmentin heartfailurepatientsmaybe an important mechanismfor their observedclinicalbenefits.We evaluated regional myocardialfree fatty acid utilization(FFAU)using positronemissiontomography(PET)and the fatty acidtracer 14(R,S)-[l*F]fluoro-6-thia-heptadecanoic acid(FTHA).Regional wallmotion(RWM)was assessedusingechocardiography in 8 patientswith stable NYHAClassIll ischemiccardiomyopathy (LVEF?;35%)beforeand 3 monthsafter carvediloltreatment. Echocardiographic andPETimagedatawereco-registered using a 16 segment model. RWM score (I-4) and change in wall motionscore(-1 to +2) were evaluated.Followingcatvedilol, mean uptake rates (Ki) for FTHAwere decreasedby 58% (19.3k2.6 to 8.2~0.63mMol/lOOg/min; pcO.005)and (FFAU) decreasedby 55% (21.5k3.0 to 9.7~0.80mL~100gm-~~min-1; pcO.005).RWMscoredecreasedsignificantly followingcarvedilol (2.4kO.2to 1.9iO.l; pcO.005).Regionaldecreasein FFAU determinedas a functionof changesin regionalwall motion demonstrateda similarreduction:ARWM-1 (60.5%decrease; p=O.38), ARWM0 (60.3%decrease,p
In the presence of high physiological levels of fatty acid, glycolysis (GLY) is accelerated in hypertrophied hearts but glucose oxidation (GO) is not. Thus, we determined the effect of removal of fatty acid from the pefisate on GO and GLY in isolated working hypertrophied (H, n=3-8)) and control (C, n=3-8) rat hearts. Hearts were perfused for 30min with 5SmM [53H/U-‘4C1-glucose, OSmM lactate and lOOrnU/L insulin in -tie presence (+Pal) or absence (-Pal) of 1.2mM Dalmitate. Glvcogen (GGN. umol/, drv wt\ and pyruvate dehydrog&& (PDHj ’ act&y d(mG/mg protein) was measured in hearts frozen at 30min. Heart function (Rate Pressure Product, mmHgmin-‘) was lower in H (27.2M.6) than C (32.ofo.6. ~~0.05) and was unaffect& by the gbsence oi‘palmitatk.^ ’ C+Pal C-Pal H+Pal H-Pal GLYl 2.8k0.2 6.6+0.lt 4.2%3* 6.4ti.3t GO1 0.4M.l 2.4*0.1t 0.4*0.1 1.2&0.1*t %GOz 15.7~kO.9 35.*1.2t 9.7ti.5 19.0&l .2*t GGN lloil.l 105k1.5’ 116*1.1* 105Zk3.5 1, lunol.min-‘lg dry wt. 2, (GO/GLY) x 100. *, vs. corresponding c. t,-vs. corresponding iPal, ~~0.05. DesDite lower GO. PDH activitv was hither in H than C &I the absence of palmitate (H, 2<1+1.1 vs. C, 17. lk1.8). These data unequivocally demonstrate that GO is limited in H and that alterations in PDH and GGN metabolism are not responsible.
IS EXAGGERATED
IN DIABETIC
BATS
Subodh Verma, Emi Arikawa, Sammy Lee & John H. McNeill. Faculty of Pharmaceutical Sciences, UBC, Vancouver, Canada We previously demonstrated that chronic endothelin (ET) receptor blockade (with bosentan) improved isolated working cardiac function in streptozotocin-diabetic rats. In an attempt to gain insight into the mechanism(s) underlying this effect, the present study examined the direct effects of ET-l on coronary arterial pressure in diabetic and control rat hearts treated with or without bosentan. Male Wistar rats were divided into control, control bosentan-treated, diabetic, and diabetic bosentan-treated groups. After 8 weeks of bosentan treatment (1 OOmg/kg/day), hearts were isolated and perfused, and coronary art&al pressure was measured in response to ET-l (SO and 100 DM). Additionallv. maximal coronarv blood bow (assessed with 1K5 M ade&ine) was measure; in isolated perfused hearts. The key observation from this study is that coronary reactivity to ET-l (assessed using coronary arterial pressure) was significantly higher in the diabetic group than in the control rats. This effect was normalized in diabetic rats chronically treated with bosentan. Maximal coronary vasodilation did not differ between the four groups. In conclusion, (a) the reactivity of ET-I is altered in the isolated perfused coronary vascular bed from diabetic rats and (a) chronic ET receptor blockade (with bosentan) restores this reactivity to control values. These observations provide a mechanism for the improvement in isolated working heart function observed following chronic bosentan treatment. (EA is a HSFC research trainee. SV is a Fellow
A180
METABOLIC PHENOTYPING OF THE DISEASED HEART USING %SUBSTRATES AND EX V/V0 PERFUSION IN THE WORKING MODE. Genevieve Vincent*, Maya Khalrallah, Bertrand Bouchard, Joanne K. Kelleher 8 Christine Des Roslers, Depts Biochemistry & Nutrition, CHUM Res. Ctr, Univ. Montrbal, Canada; Dept Physiology, GW Univ., USA. Although accelerated glycolysis is shown to be part of the metabolic phenotype expressed by the hypertrophied heart, less is known about the impact of hypertrophy on the activity of mitochondrial citric acid cycle (CAC) reactions. Methods: We have used ‘3C-mass isotopomer analysis by gas chromatography-mass spectrometry to assess pyruvate partitioning between decarboxylation (PDC) and carboxylation (PC) for mitochondrial citrate formation and efflux (reflected by citrate release rate) in spontaneously hvpertensive rat (SHR: 15 week-old) hearts. Wistar-Kvoto @KY) rats served as controls. ‘Working hearts were oerfused with 5.5 mM alucose. 8 nM insulin. 1 mM %-
iactate (Lac), 0.2 mM-‘3C3-p;ruvate (Pyr), and 50 &l carnitine. Results: Compared to WKY, SHR hearts showed significantly lower leff ventricular contractility, cardiac output, aortic and coronary flows, cardiac power (CP) and efficiency. This mechanical dysfunction was associated with the following metabolic perturbations (normalised to CP): an increase of [Lac + Pyr] and citrate release rates, and a decrease of [Lac + Pyr] uptake, PDClPC and PDClCAC flux ratios and CAC flux rate. Conclusion: Since SHR hearts release more citrate, suggesting that substrate supply for citrate synthesis exceeds citrate utilisation in the CAC, mitochondrial pyruvate oxidation appears to be restricted beyond the citrate synthase reaction. (Funded by the CIHR).
of MRC(Canada).)
REGIONALMYOCARDIALFREEFATTYACID UTlLlZATlONFOLLOWINGCARVEDILOLTHERAPYIN PATIENTS WITHHEARTFAILURE. TR.Wallhaus”, M.Taylor,DCRussell,TR. DeGrado,RJ.Nickles, CKStone.VeteransHospital-Madison WisconsinUSA
GLUCOSE OXIDATION RATES ARE LOW IN HYPERTROPHIED RAT HEARTS PERFUSED IN THE ABSENCE OF FATTY ACID. Richard Wambolt, Mark Grist, Hannah Parsons, Roger Brownsey, Michael Allard. UBC, Vancouver, B.C.
Changesin myocardialfree fatty acid utilizationfollowingbetablockadetreatmentin heartfailurepatientsmaybe an important mechanismfor their observedclinicalbenefits.We evaluated regional myocardialfree fatty acid utilization(FFAU)using positronemissiontomography(PET)and the fatty acidtracer 14(R,S)-[l*F]fluoro-6-thia-heptadecanoic acid(FTHA).Regional wallmotion(RWM)was assessedusingechocardiography in 8 patientswith stable NYHAClassIll ischemiccardiomyopathy (LVEF?;35%)beforeand 3 monthsafter carvediloltreatment. Echocardiographic andPETimagedatawereco-registered using a 16 segment model. RWM score (I-4) and change in wall motionscore(-1 to +2) were evaluated.Followingcatvedilol, mean uptake rates (Ki) for FTHAwere decreasedby 58% (19.3k2.6 to 8.2~0.63mMol/lOOg/min; pcO.005)and (FFAU) decreasedby 55% (21.5k3.0 to 9.7~0.80mL~100gm-~~min-1; pcO.005).RWMscoredecreasedsignificantly followingcarvedilol (2.4kO.2to 1.9iO.l; pcO.005).Regionaldecreasein FFAU determinedas a functionof changesin regionalwall motion demonstrateda similarreduction:ARWM-1 (60.5%decrease; p=O.38), ARWM0 (60.3%decrease,p
In the presence of high physiological levels of fatty acid, glycolysis (GLY) is accelerated in hypertrophied hearts but glucose oxidation (GO) is not. Thus, we determined the effect of removal of fatty acid from the pefisate on GO and GLY in isolated working hypertrophied (H, n=3-8)) and control (C, n=3-8) rat hearts. Hearts were perfused for 30min with 5SmM [53H/U-‘4C1-glucose, OSmM lactate and lOOrnU/L insulin in -tie presence (+Pal) or absence (-Pal) of 1.2mM Dalmitate. Glvcogen (GGN. umol/, drv wt\ and pyruvate dehydrog&& (PDHj ’ act&y d(mG/mg protein) was measured in hearts frozen at 30min. Heart function (Rate Pressure Product, mmHgmin-‘) was lower in H (27.2M.6) than C (32.ofo.6. ~~0.05) and was unaffect& by the gbsence oi‘palmitatk.^ ’ C+Pal C-Pal H+Pal H-Pal GLYl 2.8k0.2 6.6+0.lt 4.2%3* 6.4ti.3t GO1 0.4M.l 2.4*0.1t 0.4*0.1 1.2&0.1*t %GOz 15.7~kO.9 35.*1.2t 9.7ti.5 19.0&l .2*t GGN lloil.l 105k1.5’ 116*1.1* 105Zk3.5 1, lunol.min-‘lg dry wt. 2, (GO/GLY) x 100. *, vs. corresponding c. t,-vs. corresponding iPal, ~~0.05. DesDite lower GO. PDH activitv was hither in H than C &I the absence of palmitate (H, 2<1+1.1 vs. C, 17. lk1.8). These data unequivocally demonstrate that GO is limited in H and that alterations in PDH and GGN metabolism are not responsible.