Growth hormone improves bioenergetics and decreases catecholamines in postinfarct rat hearts

The aims of this study were to examine, in vivo, the effects of GH treatment on myocardial energy metabolism, function, morphology, and neurohormonal status in rats during the early postinfarct remodeling phase. Myocardial infarction (MI) was induced in male Sprague Dawley rats. Three different groups were studied: MI rats treated with saline (n = 7), MI rats treated with GH (MI + GH; n = 11; 3 mg/kg x day), and sham-operated rats (sham; n = 8). All rats were investigated with 31P magnetic resonance spectroscopy and echocardiography at 3 days after MI and 3 weeks later. After 3 weeks treatment with GH, the phosphocreatine/ATP ratio increased significantly, compared with the control group (MI = 1.69 +/- 0.09 vs. MI + GH = 2.42 +/- 0.05, P < 0.001; sham = 2.34 +/- 0.08). Treatment with GH significantly attenuated an increase in left ventricular end systolic volume and end diastolic volume. A decrease in ejection fraction was prevented in GH-treated rats (P < 0.05 vs. MI). Myocardial and plasma noradrenaline levels were significantly lower in MI rats treated with GH. These effects were accompanied by normalization of plasma brain natriuretic peptide levels (sham = 124.1 +/- 8.4; MI = 203.9 +/- 34.7; MI + GH = 118.3 +/- 8.4 ng/ml; P < 0.05 vs. MI). In conclusion, GH improves myocardial energy reserve, preserves left ventricular function, and attenuates pathologic postinfarct remodeling in the absence of induction of left ventricular hypertrophy in postinfarct rats. The marked decrease in myocardial content of noradrenaline, after GH treatment, may protect myocardium from adverse effects of catecholamines during postinfarct remodeling.     

Cardioprotective effects of growth hormone-releasing hormone agonist after myocardial infarction

Whether the growth hormone (GH)/insulin-like growth factor 1(IGF-1) axis exerts cardioprotective effects remains controversial; and the underlying mechanism(s) for such actions are unclear. Here we tested the hypothesis that growth hormone-releasing hormone (GHRH) directly activates cellular reparative mechanisms within the injured heart, in a GH/IGF-1 independent fashion. After experimental myocardial infarction (MI), rats were randomly assigned to receive, during a 4-week period, either placebo (n = 14), rat recombinant GH (n = 8) or JI-38 (n = 8; 50 µg/kg per day), a potent GHRH agonist. JI-38 did not elevate serum levels of GH or IGF-1, but it markedly attenuated the degree of cardiac functional decline and remodeling after injury. In contrast, GH administration markedly elevated body weight, heart weight, and circulating GH and IGF-1, but it did not offset the decline in cardiac structure and function. Whereas both JI-38 and GH augmented levels of cardiac precursor cell proliferation, only JI-38 increased antiapoptotic gene expression. The receptor for GHRH was detectable on myocytes, supporting direct activation of cardiac signal transduction. Collectively, these findings demonstrate that within the heart, GHRH agonists can activate cardiac repair after MI, suggesting the existence of a potential signaling pathway based on GHRH in the heart. The phenotypic profile of the response to a potent GHRH agonist has therapeutic implications.     

Growth hormone prolongs survival in experimental postinfarction heart failure

OBJECTIVES: We evaluated the effects of growth hormone (GH) on survival in experimental heart failure (HF). BACKGROUND: Growth hormone has been beneficial in various models of experimental HF. Whether GH also affects HF progression and survival is not known. METHODS: A total of 119 rats with moderate myocardial infarction were randomized to receive either GH (3.5 mg/kg every other day) or placebo for 28 days. Treatment was initiated one month after coronary ligation; the follow-up lasted 13 months. In the surviving animals, Doppler echocardiography and closed-chest Millar left ventricular (LV) catheterization were performed. Apoptosis, collagen volume fraction, and capillary density in the LV zone remote from infarction were measured. The early effects of GH on apoptosis were also assessed in a subgroup of eight infarcted rats, treated as specified earlier and euthanized at one month. RESULTS: Survival rate was 68% in GH-treated rats and 48% in the placebo group (p = 0.0377). Growth hormone had no effect on myocardial architecture, systolic function, and sarcoplasmatic reticulum calcium ATPase-2 messenger ribonucleic acid. Growth hormone improved LV relaxation; this was associated with a 50% reduction in collagen volume fraction and a 27% increase in capillary density. Growth hormone reduced the apoptotic index by 50% at one month and by 33% at 13 months. CONCLUSIONS: Growth hormone prolonged survival of rats with postinfarction HF. This effect was associated with marked attenuation of cardiomyocyte apoptosis and pathologic interstitial remodeling in the surviving myocardium and enhanced LV relaxation.     

p38 mitogen-activated protein kinase inhibition improves cardiac function and attenuates left ventricular remodeling following myocardial infarction in the rat

OBJECTIVES: The aim of this study was to examine the effect of the p38 mitogen-activated protein kinase (MAPK) inhibitor, RWJ-67657 (RWJ), on left ventricular (LV) dysfunction and remodeling post-myocardial infarction (MI) in rats. BACKGROUND: p38 MAPK signaling has been implicated in the progression of chronic heart failure. METHODS: From day 7 post-MI (coronary artery ligation), rats received either RWJ (50 mg/day, by gavage, n = 8, MI+RWJ) or vehicle (by gavage, n = 8, MI+V) for 21 days. Echocardiography was performed on day 6, before the commencement of treatment, and on day 27. In vivo hemodynamic measurements were made on day 28. Sham-operated rats served as controls. RESULTS: The LV end-diastolic pressure and lung/body weight ratio were reduced, whereas the maximum rate of rise of LV pressure was increased towards sham levels in MI+RWJ compared with MI+V. Baseline echocardiographic studies demonstrated uniform LV remodeling and dysfunction in MI rats. Fractional shortening (FS) further deteriorated in MI+V, whereas FS was preserved in MI+RWJ. Progressive LV dilation and infarct expansion observed in MI+V were inhibited in MI+RWJ. MI+RWJ also demonstrated increased myocyte hypertrophy in the peri-infarct and non-infarct zones, and reduced myocardial collagen and alpha-smooth muscle actin (SMA) immunoreactivity compared with MI+V. The antifibrotic effects of RWJ in vivo may reflect direct effects on cardiac fibroblasts, because RWJ attenuated transforming growth factor beta-1-stimulated collagen synthesis and alpha-SMA expression in isolated cardiac fibroblasts. RWJ also protected cultured myocytes from hydrogen peroxide-induced apoptosis. CONCLUSIONS: RWJ-67657 treatment post-MI had beneficial effects on LV remodeling and dysfunction, supporting a key role for p38 MAPK in pathologic cell signaling in these processes and its inhibition as a novel therapy.     

心肌梗死大鼠左心室收缩与舒张功能的改变及其影响因素

目的 探讨心肌梗死大鼠左心室收缩和舒张功能的改变、以及心室重构对心室舒缩功能的影响.材料和方法结扎Wistar大鼠左冠状动脉、制成心肌梗死模型,6周后测定左室心肌力学指标,心肌胶原含量、血浆及心肌的血管紧张素Ⅱ(Aug Ⅱ)浓度.结果 心肌梗死组与对照组比较,LVPSP、+dp/dt_(max)、dp/dt_(max)绝对值及V_(max)明显降低(P<0.01),LVEDP增加(P<0.01),T值延长(P<0.01),MAP无差异.心肌梗死组与对照组比较、心肌羟脯氨酸和心肌胶原含量明显增高(P均0.01),心肌AngⅡ含量明显升高(P<0.01)、血浆AngⅡ浓度无显著差异.结论 心肌梗死后左室收缩与舒张　功能明显降低,同时出现心肌细胞的肥大和纤维细胞的增生以及间质纤维化、后者可进一步导致和加重心脏泵血功能的异常.     

Effect of beta-blockers on cardiac function and calcium handling protein in postinfarction heart failure rats

OBJECTIVES: The normal expression of Ca2+-handling protein is critical for efficient myocardial function. The present study was designed to test the hypothesis that beta-blocker treatment may attenuate left ventricular (LV) remodeling and cardiac contractile dysfunction in the failing heart, which may be associated with alterations of Ca2+-handling protein METHODS: We investigated the change of LV remodeling and function in a rat model of heart failure due to myocardial infarction (MI) with or without carvedilol (30 mg/kg/d) or metoprolol (60 mg/kg/d) treatment for 6 weeks (n = 9 in the MI plus carvedilol group, and n = 8 in every other group). The expression of messenger RNA and proteins of sarcoplasmic reticulum Ca2+-adenosine triphosphatase (SERCA) and phospholamban in cardiomyocytes of all rats were also measured RESULTS: There was significant LV remodeling and cardiac contractile dysfunction in MI rats. The messenger RNA and protein expression of SERCA were down-regulated (p < 0.01), but the expression of phospholamban messenger RNA and protein were up-regulated (p < 0.01) in MI rats compared to sham-operated rats. After the treatment with beta-blockers, LV remodeling and function were clearly improved. Carvedilol was better in attenuating the weight of the LV and the relative weight of the right ventricle than metoprolol (p < 0.05). beta-Blockers restored the low expression of SERCA (p < 0.05) but showed no effect on phospholamban expression (p > 0.05). Moreover, carvedilol induced a more significant improvement of SERCA expression than metoprolol (p < 0.05) CONCLUSIONS: Beta-blockers are effective in preventing LV remodeling and cardiac contractile dysfunction in the failing heart. The molecular mechanism may be related to normalization of SERCA expression.     

Growth hormone induces myocardial expression of creatine transporter and decreases plasma levels of IL-1beta in rats during early postinfarct cardiac remodeling.

Growth hormone has been proposed as a potential new therapeutic agent for treatment of myocardial infarction (MI) and congestive heart failure (CHF). The purpose of this study was to evaluate the effects of GH on: (a) myocardial expression of creatine transporter (CreaT) during early postinfarct remodeling, (b) myocardial levels of total creatine (TCr) and adenine pool (TAN) and (c) plasma levels of inflammatory cytokines interleukin-1beta (IL-1beta), tumor-necrosis-factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in rat model of postinfarct cardiac remodeling. Myocardial infarction (MI) was induced by ligation of the left coronary artery in male Sprague-Dawley rats (200-250 g). Three different groups were studied: MI rats treated with GH (n=11) (3 mg/kg/day), MI rats treated with saline (n=10), and sham operated rats (n=7). In the myocardium from GH treated rats the level of mRNA CreaT expression was significantly increased (p<0.01). There was no difference in TCr between the rats with MI and sham-operated rats. Treatment with GH had no effect on TCr. GH had no effect on TAN in left ventricle. All three groups had similar levels of IL-6 and TNF-alpha in plasma. In the rats with MI, treatment with GH normalized the levels of IL-1beta (p<0.05). In conclusion GH increased the expression of CreaT and decreased levels of plasma IL-1beta during postinfarct remodeling in rats. These mechanisms may be responsible for the previously reported beneficial effects of GH on myocardial energy metabolism and preservation of cardiac function in the settings of postinfarct remodeling and CHF.     

Long-term caspase inhibition ameliorates apoptosis, reduces myocardial troponin-I cleavage, protects left ventricular function, and attenuates remodeling in rats with myocardial infarction

OBJECTIVES: This study was designed to evaluate whether in vivo caspase inhibition can prevent myocardial contractile protein degradation, improve myocardial function, and attenuate ventricular remodeling. BACKGROUND: Apoptosis is thought to play an important role in the development and progression of heart failure (HF) after a myocardial infarction (MI). However, it is not known whether inhibiting apoptosis can attenuate left ventricular (LV) remodeling and minimize systolic dysfunction. METHOD: A 28-day infusion of caspase inhibitor (n = 12) or vehicle (n = 9) was administered to rats immediately after an anterior MI. In addition, five sham-operated rats given the caspase inhibitor were compared with 17 untreated sham-operated animals to study effects in non-MI rats. Left ventricular function, remodeling parameters, and hemodynamics were studied four weeks later. Myocardial caspase 3 activation and troponin-I contractile protein cleavage were studied in the non-infarct, remote LV myocardium using Western blots. Apoptosis was assessed using immunohistochemistry for activated caspase-positive cells as well as the TUNEL method. Collagen volume was estimated using morphometry. RESULTS: Caspase inhibition reduced myocardial caspase 3 activation. This was accompanied by less cleavage of troponin-I, an important component of the cardiac contractile apparatus, and fewer apoptotic cardiomyocytes. Furthermore, caspase inhibition reduced LV-weight-to-body-weight ratio, decreased myocardial interstitial collagen deposition, attenuated LV remodeling, and better preserved LV systolic function after MI. CONCLUSIONS: Caspase inhibition, started soon after MI and continued for four weeks, preserves myocardial contractile proteins, reduces systolic dysfunction, and attenuates ventricular remodeling. These findings may have important therapeutic implications in post-MI HF.     

Additive improvement of left ventricular remodeling and neurohormonal activation by aldosterone receptor blockade with eplerenone and ACE inhibition in rats with myocardial infarction

OBJECTIVES: We investigated the effects of the aldosterone blocker eplerenone alone and in combination with angiotensin-converting enzyme (ACE) inhibition on ventricular remodeling in rats with left ventricular (LV) dysfunction after extensive myocardial infarction (MI). BACKGROUND: Adding an aldosterone antagonist to ACE inhibition reduces mortality and morbidity in heart failure. METHODS: Starting 10 days after MI, rats were treated with placebo, eplerenone (100 mg/kg/day), the ACE inhibitor trandolapril (0.3 mg/kg/day), or a combination of both for nine weeks. RESULTS: Both monotherapies attenuated the rise in LV end-diastolic pressure (LVEDP) and LV end-diastolic volume (LVEDV) compared with placebo, whereas combined treatment further attenuated LVEDP and LVEDV, significantly improved LV function and reduced plasma norepinephrine levels. The time constant of LV pressure isovolumic decay (tau) was prolonged in placebo MI rats, significantly shortened by eplerenone, and normalized by eplerenone/trandolapril. Increased collagen type I gene expression and collagen content in the noninfarcted LV myocardium from MI placebo rats was attenuated by trandolapril, but almost completely prevented by eplerenone and eplerenone/trandolapril. The addition of eplerenone to ACE inhibition prevented sarcoplasmic-reticulum calcium ATPase downregulation and the increases in LV gene expression of beta-MHC and atrial natriuretic factor more effectively than either monotherapy. Furthermore, combination treatment attenuated the increase in myocardial angiotensin II type 1 receptor expression and increased phosphorylated endothelial nitric oxide synthase protein levels. CONCLUSIONS: The aldosterone blocker eplerenone improved LV remodeling in rats with LV dysfunction after extensive MI. Combination therapy with an ACE inhibitor substantially potentiates this effect by a complementary prevention of LV fibrosis, cardiac hypertrophy, and molecular alterations.     

辛伐他汀对家兔心肌梗死后心室重构及心功能的影响

目的研究辛伐他汀对家兔心肌梗死后(MI)心室重构及心功能的影响。方法家兔20只采用结扎冠状动脉左前降支的方法建立急性心肌梗死模型,随机分MI组(10只)和辛伐他汀组(10只)。MI组术后不给任何处理和干预,辛伐他汀干预组在MI术后3d口服辛伐他汀(10mg.kg-1.d-1)10周。术前和术后10周进行超声心动图检查。术后10周进行有创血液动力学测定,而后摘取心脏称重。取两组家兔左心室进行HE染色,做组织细胞学检查。结果10周后辛伐他汀组家兔左室重量、左室舒张期末径、左室收缩期末径、左房直径及左室舒张期末压显著低于MI组,射血分数、缩短分数明显高于MI组(P<0.05)。HE染色辛伐他汀组与MI组比较,心肌细胞变性坏死明显减轻,炎性细胞浸润减少,间质纤维化减轻,非梗死区心肌细胞的代偿性肥大增生较MI组为低。结论辛伐他汀能够改善心肌梗死后家兔心室重构和心功能。     

Growth hormone replacement attenuates diastolic dysfunction and cardiac angiotensin II expression in senescent rats

We tested the hypothesis that long-term growth hormone (GH) replacement in aged rats would preserve diastolic function and attenuate left ventricular remodeling associated with normal aging. Male Brown Norway x F344 rats were randomized to receive twice daily injections of porcine GH (200 microg/injection, subcutaneous) or saline from 24 to 30 months of age. Adult rats (6- to 9-months old) received saline injections throughout the study. Thirty-month-old, saline-treated rats exhibited low levels of insulin-like growth factor 1 (IGF-1), impaired diastolic left ventricular filling (Doppler), increased cardiac angiotensin II (Ang II), reduced plasma Ang II, and increased cardiac collagen. GH administration in old rats restored IGF-1 and diastolic indices to values comparable to those of adults. These effects were associated with reduced cardiac Ang II and attenuations in cardiac collagen. Age-related decreases in GH and IGF-1 may contribute to the decline in diastolic function of aging, in part through alterations in renin-angiotensin system-mediated ventricular remodeling.     

胰岛素对大鼠心肌梗死后心室重构和心脏功能的影响及其机制

目的:探讨胰岛素对大鼠心肌梗死(MI)后心室重构和心脏功能的影响及其机制。方法: 80只成年雄性Sprague-Dawley大鼠行冠状动脉左前降支(LAD)结扎制备MI模型,随机分为5组:即假手术(Sham)组(n=20)、生理盐水对照(MI+NS)组(n=20)、胰岛素治疗(MI+Ins)组(n=20)、肿瘤坏死因子α(TNF-α)拮抗剂益赛普治疗(MI+En)组(n=10)及Ins+En治疗(MI+Ins+En)组(n=10)。用ELISA法检测各组大鼠在MI后1周和4周时,心肌及血清TNF-α的水平。超声心动图测定各组大鼠左室射血分数(EF)、缩短分数(FS)和左心室舒张末内径(LVEDD)、左心室收缩末内径(LVESD)、经右颈总动脉插管测定血压(BP)、左室舒张压(LVDP)和最大左室舒张压/收缩压变化速率(±LVdp/dtmax）。结果: 大鼠MI后心肌中TNF-α增加,Ins治疗可明显降低大鼠心肌中TNF-α的含量(P<0.05,n=6)。Ins治疗组大鼠EF、FS、LVDP和±LVdp/dtmax均明显高于对照组(P<0.05,n=10),LVESD明显低于对照组(P<0.05,n=10)。与单独En治疗组相比,Ins+En治疗组大鼠EF、FS、LVDP和±LVdp/dtmax明显升高、LVESD明显降低(P<0.05,n=10)。结论: Ins可抑制MI后心室的扩张,改善心脏功能,但其机制不依赖于抑制心肌TNF-α的产生。     

Effects of Growth Hormone Following Chronic Angiotensin-converting Enzyme Inhibition in Chronic Heart Failure: Their Relation to Infarct Size

Growth hormone (GH) has been attracted as a possible adjunctive treatment for severe heart failure. However, its treatment effects have been still controversial. To assess severity of basal cardiac disease states in which GH might be effective, we analyzed the relation of treatment effects of GH following chronic angiotensin-converting enzyme (ACE) inhibition on cardiac function and structures to infarct size in rat model of chronic heart failure after myocardial infarction. One day after coronary occlusion, rats were randomized to either an ACE inhibitor, temocapril (T) (80 mg/L in drinking water) or placebo for 12 weeks. The animals received concomitant recombinant human (rh) GH (2 mg/kg/day, SC) (T + GH) or vehicle during the final 2 weeks. Compared with the T group, the T + GH group with large MI had smaller increments of left ventricular (LV) dP/dt _max (0 vs 17%) and cardiac output (9 vs 49%), less improvement of LV relaxation (tau) (–3 vs 29%) and systemic vascular resistance (8 vs 29%), and a greater increase in LV end-diastolic pressure (123 vs –5%) than did the T + GH group with moderate MI. In the T + GH group when compared with the T group, these functional alterations were associated with a 12% reduction in the LV capillary density and a 21% increase in hydroxyproline contents in rats with large MI, whereas a 12% increase in the density and similar collagen contents were found in rats with moderate MI. Thus, prominent beneficial cardiovascular effects of the additive short-term, high-dose GH to chronic high-dose ACE inhibition were obtained in rats with moderate MI, whereas little additional benefit or even detrimental effects of GH were found in rats with large MI. The present study may provide an insight into the therapeutic strategy of GH given late after MI in the presence of chronic ACE inhibition in congestive heart failure.     

Induction of myocardial hypertrophy after coronary ligation in rats decreases ventricular dilatation and improves systolic function.

BACKGROUND. Previous studies have shown that hypertrophy of surviving myocytes after myocardial infarction (MI) is limited. Progressive ventricular dilatation after MI may occur when compensatory hypertrophy cannot restore left ventricular (LV) wall stress to normal. METHODS AND RESULTS. To test whether induction of additional myocyte hypertrophy might prevent pathological LV remodeling after large MI, we administered 2-tetradecylglycidic acid (TDGA) 20 mg/kg/day to sham-operated (n = 12) and MI (n = 10) rats for 10 days, beginning the third day after infarction. We have previously shown that chronic inhibition of long-chain fatty acid oxidation with TDGA in rats results in myocardial hypertrophy without any apparent impairment of LV systolic function. When compared with untreated MI rats (n = 9), we found that TDGA-treated MI rats had increases in LV weight/body wt, myocyte cross-sectional area, and peak developed LV pressure during abrupt aortic occlusion. MI rats treated with TDGA had lower LV end-diastolic pressures and smaller end-diastolic volumes, whereas stroke volume was maintained. The ex vivo passive LV pressure-volume relation was shifted toward the pressure axis compared with untreated infarct rats. In sham-operated rats, TDGA caused increases in LV weight/body wt, myocyte size, peak developed LV pressure, cardiac index, and stroke volume index, and a shift of the passive LV pressure-volume relation toward the pressure axis. CONCLUSIONS. Induction of myocardial hypertrophy with an inhibitor of long-chain fatty acid oxidation retarded the process of LV dilatation and produced beneficial effects on systolic function after large myocardial infarction. These data support the hypothesis that inadequate hypertrophy of residual myocardium after infarction may contribute to LV dilatation and the development of congestive heart failure.     

Reconstituted high-density lipoprotein attenuates postinfarction left ventricular remodeling in rats

Since little is known about the effects of reconstituted high-density lipoprotein (rHDL) in left ventricular (LV) remodeling, these effects were examined in rats after acute myocardial infraction (MI). Sixteen male Wistar rats were randomly divided into three groups: Sham-operated (n=6), and MI rats that received a permanent ligation around the proximal left coronary artery and infusions of placebo (MI group, n=5) or rHDL (containing as apolipoproteinA-I 6mg/kg) administered intravenously (MI+rHDL group, n=5). rHDL was infused once a week for 4 weeks. In addition, in vitro assays were performed to examine the effect of rHDL. The MI+rHDL group showed a significant increase in LV ejection fraction (EF) between weeks 1 and 4, a decrease in LV end-systolic diameter, compared with the progressive deterioration of LV size and function in the MI group. In addition, the MI+rHDL group showed a significant decrease in fibrotic area of MI in LV compared to that in the MI group, while there were no significant increases in capillary density or cell size in LV in the MI+rHDL group. Interestingly, the MI+rHDL group showed a significant activation of retinoblastoma and ERK (extracellular-signal-regulated kinase) but not cleaved caspase-3, p38 MAPK or Jun N-terminal kinase. rHDL suppressed H(2)O(2)-induced arrest of cell growth in myocytes. This effect was blocked by PD98059, an ERK inhibitor. In conclusions, rHDL-promoted cell survival has beneficial morphological effects that help to prevent LV remodeling and improve function after MI, and may prevent arrest of cell growth through ERK pathway in myocytes.     

Gender differences in postinfarction left ventricular remodeling.

OBJECTIVE: Previous studies suggest that gender affects the adaptive responses of the heart to some forms of cardiac overload. It is unknown whether gender influences left ventricular (LV) remodeling after myocardial infarction (MI). METHODS: We performed transthoracic echocardiographic-Doppler examinations in age-matched male (n = 17) and female (n = 16) rats before, and 1 and 6 weeks after transmural MI or sham surgery. RESULTS: Following large MI (male = 45 +/- 1% LV circumference vs. female = 48 +/- 4%, p = NS), both male and female rats developed progressive LV dilatation. Infarctions caused a similar degree of global and regional LV systolic dysfunction in males and females. Male rats had significant increases in the thickness of the noninfarcted posterior wall by 6 weeks after MI. However, posterior wall thickness did not change in the infarcted female rats. Average myocyte diameter in the noninfarcted region of the heart was also greater in male than female MI rats. The combination of increased cavity size with little change in wall thickness resulted in a greater decline in relative wall thickness in the female rats compared to the males. Male rats with MI showed progressively restricted LV diastolic filling as assessed by transmitral Doppler recordings. Female rats had less of an increase in the ratio of early to late transmitral velocities and less of an increase in the E wave deceleration rate after MI. CONCLUSIONS: Female rats showed a different pattern of LV remodeling than males with less of an increase in thickness of the noninfarcted portions of the left ventricle than males, but comparable LV cavity enlargement and systolic dysfunction. Despite similar infarct size, females developed less pronounced abnormalities of LV diastolic filling. We hypothesize that the gender-related differences in postinfarction LV remodeling may contribute to the different LV filling patterns, and might ultimately relate to differences in clinical outcome.     

Usefulness of serial assessment of B-type natriuretic peptide, troponin I, and C-reactive protein to predict left ventricular remodeling after acute myocardial infarction (from the REVE-2 study)

Left ventricular (LV) remodeling after myocardial infarction (MI) indicates a high risk of heart failure and death. However, LV remodeling is difficult to predict, and limited information is available on the association of cardiac biomarkers with LV remodeling. Our aim was to study the association of B-type natriuretic peptide (BNP), cardiac troponin I (cTnI), and C-reactive protein with LV remodeling after MI. We designed a prospective multicenter study including 246 patients with a first anterior Q-wave MI. Serial echocardiographic studies were performed at hospital discharge and 3 months and 1 year after MI; quantitative analysis was performed at a core echocardiographic laboratory. Blood samples for determination of BNP, cTnI, and C-reactive protein levels were obtained at hospital discharge and the 1-month, 3-month, and 1-year follow up visits. One-year echocardiographic follow-up was obtained in 226 patients. End-diastolic volume increased from 52.3 ± 13.8 ml/m(2) at baseline to 62.3 ± 18.4 ml/m(2) at 1 year (p <0.0001); LV remodeling (>20% increase in end-diastolic volume) was observed in 87 patients (38%). At baseline, we found significant univariate relations between LV remodeling and the 3 biomarkers. During follow-up, high BNP levels and persistently detectable levels of cTnI were associated with LV remodeling. In multivariate analysis, none of the 3 biomarkers at baseline was independently predictive of LV remodeling. In contrast, during follow-up, high BNP and positive cTnI were independently associated with LV remodeling. In conclusion, circulating cardiac biomarkers may reflect pathophysiologic processes implicated in LV remodeling after MI. Determination of BNP and cTnI during follow-up can help refine risk stratification.     

Targeted overexpression of growth hormone by adenoviral gene transfer preserves myocardial function and ventricular geometry in ischemic cardiomyopathy

BACKGROUND: Post-infarction heart failure is characterized by progressive left ventricular dilatation and wall thinning, with both systolic and diastolic cardiac dysfunction. Human growth hormone (GH) stimulates cardiac hypertrophy when secreted in excess and directly enhances cardiomyocyte contractile function. We hypothesized that local myocardial overexpression of GH could prevent ventricular remodeling and heart failure following myocardial infarction (MI) in rats. METHODS AND RESULTS: Rats underwent ligation of the left anterior descending coronary artery with direct intramyocardial injection of adenovirus encoding human GH (n = 8) or null virus as control (n = 8). Six weeks following MI, Adeno-GH treated animals had significant preservation of both systolic and diastolic cardiac function compared to Null animals (maximum dP/dt GH 2927 +/- 83 vs Null 1622 +/- 159 mmHg/sec, p < 0.001; minimum dP/dt -2409 +/- 82 vs -1195 +/- 179 mmHg/sec, p < 0.01). GH animals had improved ventricular geometry with decreased chamber dilatation (13.2 +/- 0.13 vs 14.4+/-0.15 mm, p < 0.001) and increased wall thickness (2.02 +/- 0.10 vs 1.28 +/- 0.07 mm, p < 0.001), and this was associated with advantageous myocardial hypertrophy with increased cardiomyocyte fiber size. Local myocardial overexpression of GH protein was seen in Adeno-GH animals, while serum levels of human GH were undetectable after 6 weeks. CONCLUSIONS: Treatment with Adeno-GH following MI resulted in reduced ventricular dilatation, increased local myocardial hypertrophy, and preservation of both systolic and diastolic cardiac function. No significant systemic exposure to growth hormone transgene was observed. The induction of regional hypertrophy is a novel approach to treating heart failure, and may be useful to treat or prevent post-infarction ischemic cardiomyopathy.     

Gender-Based Differences in Cardiac Remodeling and ILK Expression after Myocardial Infarction

Background

Gender can influence post-infarction cardiac remodeling.

Objective

To evaluate whether gender influences left ventricular (LV) remodeling and integrin-linked kinase (ILK) after myocardial infarction (MI).

Methods

Female and male Wistar rats were assigned to one of three groups: sham, moderate MI (size: 20-39% of LV area), and large MI (size: ≥40% of LV area). MI was induced by coronary occlusion, and echocardiographic analysis was performed after six weeks to evaluate MI size as well as LV morphology and function. Real-time RT-PCR and Western blot were used to quantify ILK in the myocardium.

Results

MI size was similar between genders. MI resulted in systolic dysfunction and enlargement of end-diastolic as well as end-systolic dimension of LV as a function of necrotic area size in both genders. Female rats with large MI showed a lower diastolic and systolic dilatation than the respective male rats; however, LV dysfunction was similar between genders. Gene and protein levels of ILK were increased in female rats with moderate and large infarctions, but only male rats with large infarctions showed an altered ILK mRNA level. A negative linear correlation was evident between LV dimensions and ILK expression in female rats with large MI.

Conclusions

Post-MI ILK expression is altered in a gender-specific manner, and higher ILK levels found in females may be sufficient to improve LV geometry but not LV function.     

Early intervention with a potent endothelin-A/endothelin-B receptor antagonist aggravates left ventricular remodeling after myocardial infarction in rats

Intervention with selective endothelin (ET)A receptor antagonists within 24 h after myocardial infarction (MI) in rats has been reported to aggravate left ventricular (LV) remodeling. In contrast, beneficial effects are reported when initiation of treatment is delayed 7 days or more after MI. However, bosentan, a mixed ET_A/ET_B receptor antagonist with low affinity for the ET receptors, has been shown to exert beneficial effects independent of the time point of initiation of treatment after MI. The aim of the present study was to investigate to what extent early intervention with a mixed ET_A/ET_B receptor antagonist with higher affinity at the ET receptors (SB 209670) would also exert beneficial effects on postinfarction LV remodeling. After ligation of the left coronary artery, rats were randomized to treatment with SB 209670 (6.25 mg·kg⁻¹ SC b.i.d., n = 10) or vehicle (n = 12) for 26 days, starting 48 h after MI. Treatment with SB 209670 adversely affected the postinfarction remodeling process causing further dilatation of the LV (LV end-diastolic diameter: 10.4 ± 0.5 vs 9.1 ± 0.2 mm; LV end-systolic diameter: 8.5 ± 0.4 vs 7.2 ± 0.2 mm, P < 0.05). However, SB 209670 did not significantly affect infarct size, compensatory cardiac hypertrophy, nor the myocardial mRNA levels of procollagen type I and III, and prolyl 4-hydroxylase and lysyl oxidase, 2 important enzymes affecting collagen secretion, stability and functionality. In addition, SB 209670 had no significant effects on LV collagen cross-linking or extent of fibrosis. Thus, our data demonstrate that early intervention with a potent, mixed ET_A/ET_B receptor antagonist after MI may promote dilatation of the LV without significant alterations of infarct size and extracellular matrix composition. Our data support the notion that the timing of initiation of ET receptor antagonism after MI is critical and that potent ET receptor antagonists may be harmful during the first few days after MI. Received: 1 September 2001, Returned for revision: 13 September 2001, Revision received: 6 December 2001, Accepted: 21 December 2001