Angiotensin-converting enzyme inhibition improves cardiac fatty acid metabolism in patients with congestive heart failure

Clinical significance of 123I-BMIPP washout rate in patients with uncertain chronic heart failure

BACKGROUND

Recently, triglyceride deposit cardiomyovasculopathy (TGCV) with defective intracellular lipolysis was found to be a disease that causes heart failure. As a diagnostic criterion for TGCV, an Iodaine-123-β-methyl iodophenyl-pentadecanoic acid washout rate (BMIPP WOR) of < 10% is used, but its clinical significance in patients with heart failure remains to be clarified.

METHODS

In 62 hospitalized patients with chronic heart failure, ¹²³I-BMIPP myocardial single-photon emission computed tomography (SPECT) was performed predischarge state. The prevalence of TGCV was investigated. Subsequently, follow-up was conducted for ≥ 90 days (mean: 724.6 ± 392.7 days), and the association between the BMIPP WOR and cardiac events was examined, establishing all-cause mortality and admission due to heart failure as endpoints.

RESULTS

Of the 62 patients, the WOR was < 10% in 41 (66.1%). Of these, 26 (41.9%) were diagnosed with definite TGCV. Furthermore, cardiac events were noted in 12 patients (19.4%). Analysis with Cox proportional hazards models showed that the BMIPP WOR < 4.5% was a significant event-predicting factor [HR 4.29, 95% CI: 1.20-16.87; p = 0.0245]. On a Kaplan-Meier curve, the WOR was 4.5%; there was a significant difference in the incidence of events (p = 0.0298).

CONCLUSION

In the predischarge state of heart failure, ¹²³I-BMIPP myocardial SPECT was performed. In approximately 40% of the patients, a diagnosis of TGCV was made. The results suggested that the BMIPP WOR is useful for predicting the prognosis of chronic heart failure patients regardless of TGCV.

A "PET" area of interest: myocardial metabolism in human systolic heart failure

Myocardial substrate metabolism provides the energy needed for cardiac contraction and relaxation. The normal adult heart uses predominantly fatty acids (FAs) as its primary fuel source. However, the heart can switch and use glucose (and to a lesser extent, ketones, lactate, as well as endogenous triglycerides and glycogen), depending on the metabolic milieu and superimposed conditions. FAs are not a wholly better fuel than glucose, but they do provide more energy per mole than glucose. Conversely, glucose is the more oxygen-efficient fuel. Studies in animal models of heart failure (HF) fairly consistently demonstrate a shift away from myocardial fatty acid metabolism and toward glucose metabolism. Studies in humans are less consistent. Some show the same metabolic switch away from FA metabolism but not all. This may be due to differences in the etiology of HF, sex-related differences, or other mitigating factors. For example, obesity, insulin resistance, and diabetes are all related to an increased risk of HF and may complicate or contribute to its development. However, these conditions are associated with increased FA metabolism. This review will discuss aspects of human heart metabolism in systolic dysfunction as measured by the noninvasive, quantitative method-positron emission tomography. Continued research in this area is vital if we are to ameliorate HF by manipulating heart metabolism with the aim of increasing energy production and/or efficiency.

Beneficial effects of beta-blockers on left ventricular function and cellular energy reserve in patients with heart failure

Beta-blockers have been shown to improve left ventricular (LV) function in patients with heart failure. The aim of this study is to non-invasively assess, by means of in vivo 31P-magnetic resonance spectroscopy (31P-MRS), the effects of beta-blockers on LV cardiac phosphocreatine and adenosine triphosphate (PCr/ATP) ratio in patients with heart failure. Ten heart failure patients on full medical therapy were beta-blocked by either carvedilol or bisoprolol. Before and after 3 months of treatment, exercise testing, 2D echocardiography, MRS, New York Heart Association (NYHA) class, ejection fraction (EF), maximal rate-pressure product and exercise metabolic equivalent system (METS) were evaluated. Relative concentrations of PCr and ATP were determined by cardiac 31P-MRS. After beta-blockade, NYHA class decreased (from 2.2 ± 0.54 to 1.9 ± 0.52, P = 0.05), whereas EF (from 33 ± 7 to 44 ± 6%, P = 0.0009) and METS (from 6.74 ± 2.12 to 8.03 ± 2.39, P = 0.01) increased. Accordingly, the mean cardiac PCr/ATP ratio increased by 33% (from 1.48 ± 0.22 to 1.81 ± 0.48, P = 0.03). Beta-blockade-induced symptomatic and functional improvement in patients with heart failure is associated to increased PCr/ATP ratio, indicating preservation of myocardial high-energy phosphate levels.

Transcriptional changes associated with recovery from heart failure in the SHR

To identify biological pathways associated with myocardial recovery from heart failure (HF), gene profiling and gene set enrichment analysis (GSEA) were examined in left ventricle of spontaneously hypertensive rats with HF (SHR-F) with no treatment, following treatment with the angiotensin converting enzyme inhibitor captopril, and treatment with captopril combined with the short chain fatty acid derivative phenylbutyrate. Failing hearts demonstrated depressed left ventricular ejection fraction, while ventricular volume and mass increased. Captopril treatment alone prevented further deterioration but did not improve myocardial function; relatively few transcripts were differentially expressed relative to untreated SHR-F. Gene sets identified by GSEA as downregulated with captopril treatment compared to SHR-F group included those related to hypoxia and reactive oxygen species, while upregulated gene sets included G protein signaling. Treatment with phenylbutyrate alone did not improve survival (no animals in this group survived the 30 day treatment period), while phenylbutyrate combined with captopril increased survival and significantly improved cardiac function in vivo and in vitro. Normalized microarray data identified 780 genes that demonstrated a combined treatment effect of which 258 genes were modified with HF. Fatty acid metabolism and ion transport were among the most significantly upregulated pathways in the combined treatment group compared to untreated SHR with HF, whereas those related to oxidative stress, growth, inflammation, protein degradation, and TGF-beta signaling were downregulated. These findings demonstrate improved myocardial function and regression of cardiac hypertrophy, and identify many HF related gene sets altered with phenylbutyrate and captopril treatment, but not captopril alone. These results characterize gene sets associated with recovery from HF, and suggest that phenylbutyrate may be a potentially effective adjunctive treatment, together with captopril, by synergistically modulating pathways that contribute to restoration of contractile function of the failing SHR heart.

Long chain fatty acid uptake in vivo: comparison of [125I]-BMIPP and [3H]-bromopalmitate

Insulin resistance is characterized by increased metabolic uptake of fatty acids. Accordingly, techniques to examine in vivo shifts in fatty acid metabolism are of value in both clinical and experimental settings. Partially metabolizable long chain fatty acid (LCFA) tracers have been recently developed and employed for this purpose: [9,10-3H]-(R)-2-bromopalmitate ([3H]-BROMO) and [125I]-15-(rho-iodophenyl)-3-R,S-methylpentadecanoic acid ([125I]-BMIPP). These analogues are taken up like native fatty acids, but once inside the cell do not directly enter beta-oxidation. Rather, they become trapped in the slower processes of omega and alpha-oxidation. Study aims were to (1) simultaneously assess and compare [3H]-BROMO and [125I]-BMIPP and (2) determine if tracer breakdown is affected by elevated metabolic demands. Catheters were implanted in a carotid artery and jugular vein of Sprague-Dawley rats. Following 5 days recovery, fasted animals (5 h) underwent a rest (n = 8) or exercise (n = 8) (0.6 mi/h) protocol. An instantaneous bolus containing both [3H]-BROMO and [125I]-BMIPP was administered to determine LCFA uptake. No significant difference between [125I]-BMIPP and [3H]-BROMO uptake was found in cardiac or skeletal muscle during rest or exercise. In liver, rates of uptake were more than doubled with [3H]-BROMO compared to [125I]-BMIPP. Analysis of tracer conversion by TLC demonstrated no difference at rest. Exercise resulted in greater metabolism and excretion of tracers with approximately 37% and approximately 53% of [125I]-BMIPP and [3H]-BROMO present in conversion products at 40 min. In conclusion, [3H]-BROMO and [125I]-BMIPP are indistinguishable for the determination of tissue kinetics at rest in skeletal and cardiac muscle. Exercise preferentially exacerbates the breakdown of [3H]-BROMO, making [125I]-BMIPP the analogue of choice for prolonged (>30 min) experimental protocols with elevated metabolic demands.

The significance of 123I-BMIPP delayed scintigraphic imaging in cardiac patients

BACKGROUND

Earlier studies have not fully investigated the significance of radionuclide planar imaging in cardiac patients using the fatty acid analogue 123I-beta-methyl-iodophenylpentadecanoic acid (123I-BMIPP).

OBJECTIVES

This study was to clarify the effectiveness of 123I-BMIPP in assessing the heart-to-mediastinum ratio (H/M) and myocardial washout rate (WR) in patients with heart disease.

METHODS

Myocardial 123I-BMIPP imaging was performed in 33 patients (20 with chronic heart failure [CHF] and 13 with stable angina pectoris [AP]) and 11 control subjects. Myocardial 123I-BMIPP planner images were obtained 30 min (early image) and 4 h (delayed image) after tracer injection. The left ventricular ejection fraction (LVEF) was measured by quantitative gated single photon emission computed tomography. The concentration of plasma brain natriuretic peptide (BNP) was measured before the scintigraphic study.

RESULTS

(1) Delayed H/M was much lower in CHF than in AP (1.93 +/- 0.37 vs. 2.21 +/- 0.38, p < 0.05) and controls (vs. 2.47 +/- 0.38, p < 0.001). (2) The WR in CHF and AP were higher than the WR in controls (39.8 +/- 12.7% and 38.7 +/- 11.1 vs. 27.9 +/- 10.2%, p < 0.01 and p < 0.05, respectively). (3) In all subjects, LVEF was correlated with delayed H/M (r = 0.39, p < 0.01). And, the BNP was correlated with both the WR (r = 0.36, p < 0.05) and delayed H/M (r = - 0.29, p = 0.05).

CONCLUSION

These data strongly suggest that the delayed H/M and myocardial WR of 123I-BMIPP enhances the assessment of the myocardial fatty acid metabolism disorders in patients with heart disease in both masked and unmasked conditions.

Cardiac sympathetic denervation and ongoing myocardial damage for prognosis in early stages of heart failure

BACKGROUND

Iodine-123-metaiodobenzylguanidine ((123)I-MIBG) can assess cardiac sympathetic nervous function. Heart-type fatty acid binding protein (H-FABP) has been used as a marker of ongoing myocardial damage. The prognostic value of combination (123)I-MIBG imaging and H-FABP in heart failure is unknown.

METHODS AND RESULTS

We prospectively enrolled consecutive 104 patients with heart failure in whom we quantified (123)I-MIBG scintigraphy, simultaneously measured serum H-FABP and plasma brain natriuretic peptide (BNP) levels, and analyzed clinical outcomes. The multivariate Cox regression analysis revealed that augmented H-FABP level and decreased heart to mediastinum ratio of (123)I-MIBG at 240 minutes (delayed H/M ratio), but not BNP, were the independent predictors for cardiac events. The cutoff values for H-FABP and delayed H/M ratio were determined from the receiver operating characteristic curves as 5.2 ng/mL for H-FABP and 1.73 for delayed H/M ratio. The cardiac event rate was markedly higher in patients with both H-FABP and delayed H/M ratio of (123)I-MIBG was abnormal. Conversely, no cardiac events occurred in patients with both H-FABP level and delayed H/M ratio were normal.

CONCLUSION

H-FABP adds independent prognostic information to delayed H/M ratio of (123)I-MIBG imaging, and the combination of these approaches may improve the accuracy of prognostic determination in heart failure.

Effects of metabolic modulation by trimetazidine on left ventricular function and phosphocreatine/adenosine triphosphate ratio in patients with heart failure

AIMS

The addition of trimetazidine to standard treatment has been shown to improve left ventricular (LV) function in patients with heart failure. The aim of this study is to non-invasively assess, by means of in vivo 31P-magnetic resonance spectroscopy (31P-MRS), the effects of trimetazidine on LV cardiac phosphocreatine and adenosine triphosphate (PCr/ATP) ratio in patients with heart failure.

METHODS AND RESULTS

Twelve heart failure patients were randomized in a double-blind, cross-over study to placebo or trimetazidine (20 mg t.i.d.) for two periods of 90 days. At the end of each period, all patients underwent exercise testing, 2D echocardiography, and MRS. New York Heart Association (NYHA) class, ejection fraction (EF), maximal rate-pressure product, and metabolic equivalent system (METS) were evaluated. Relative concentrations of PCr and ATP were determined by cardiac 31P-MRS. On trimetazidine, NYHA class decreased from 3.04+/-0.26 to 2.45+/-0.52 (P = 0.005), whereas EF (34+/-10 vs. 39+/-10%, P = 0.03) and METS (from 7.44+/-1.84 to 8.78+/-2.72, P = 0.03) increased. The mean cardiac PCr/ATP ratio was 1.35+/-0.33 with placebo, but was increased by 33% to 1.80+/-0.50 (P = 0.03) with trimetazidine.

CONCLUSION

Trimetazidine improves functional class and LV function in patients with heart failure. These effects are associated to the observed trimetazidine-induced increase in the PCr/ATP ratio, indicating preservation of the myocardial high-energy phosphate levels.

Myocardial substrate metabolism in the normal and failing heart

The alterations in myocardial energy substrate metabolism that occur in heart failure, and the causes and consequences of these abnormalities, are poorly understood. There is evidence to suggest that impaired substrate metabolism contributes to contractile dysfunction and to the progressive left ventricular remodeling that are characteristic of the heart failure state. The general concept that has recently emerged is that myocardial substrate selection is relatively normal during the early stages of heart failure; however, in the advanced stages there is a downregulation in fatty acid oxidation, increased glycolysis and glucose oxidation, reduced respiratory chain activity, and an impaired reserve for mitochondrial oxidative flux. This review discusses 1) the metabolic changes that occur in chronic heart failure, with emphasis on the mechanisms that regulate the changes in the expression of metabolic genes and the function of metabolic pathways; 2) the consequences of these metabolic changes on cardiac function; 3) the role of changes in myocardial substrate metabolism on ventricular remodeling and disease progression; and 4) the therapeutic potential of acute and long-term manipulation of cardiac substrate metabolism in heart failure.

Prognostic value of elevated circulating heart-type fatty acid binding protein in patients with congestive heart failure

BACKGROUND

Heart-type fatty acid binding protein (H-FABP) is released into the circulation when the myocardium is injured and is a novel marker for the diagnosis of acute myocardial infarction. The purpose of the present study was to examine the clinical significance of increased serum H-FABP levels in patients with congestive heart failure.

METHODS AND RESULTS

Serum levels of H-FABP were measured in 179 patients admitted with congestive heart failure and 20 age-matched normal controls by using a sandwich enzyme-linked immunosorbent assay. Patients were prospectively followed during a mean follow-up period of 20 months with the end points of cardiac death and progressive heart failure requiring rehospitalization. Serum levels of H-FABP were higher in patients with congestive heart failure than in control subjects (5.7 +/- 4.8 ng/mL versus 2.7 +/- 0.8 ng/mL, P < .01) and increased with advancing NYHA class (P < .01). The cardiac event rate was markedly higher in patients with elevated H-FABP levels than in those with normal levels (43% versus 7%, P < .0001). Furthermore, the Cox multivariate proportional hazard analysis revealed that the elevated H-FABP level was the only independent predictor for cardiac events (chi2= 7.397, P < .01).

CONCLUSIONS

Elevation of H-FABP indicates latent and ongoing cardiomyocyte damage and identifies patients at high risk for future cardiac events in congestive heart failure.