Triheptanoin Alleviates Ventricular Hypertrophy and Improves Myocardial Glucose Oxidation in Rats With Pressure Overload

OBJECTIVE

Cardiac hypertrophy is characterized by changes in substrate utilization and activity of the Krebs cycle. We assessed the effects of triheptanoin, an odd-chain fat that might support the Krebs cycle, on cardiac metabolism and function in a model of cardiac hypertrophy.

METHODS AND RESULTS

Rats were subjected to aortic banding (AoB) to induce pressure overload (PO). Starting at 1 week after AoB, rats were blindly fed a control diet or a special diet containing triheptanoin at 7% (T7 group) or 30% (T30 group) of total energy value. Six weeks after AoB, echocardiography revealed attenuated hypertrophy and improved diastolic function of the left ventricle. Isolated working heart perfusion showed similar cardiac power, fatty acid oxidation, substrate preference, and insulin response among groups. However, cardiac glucose oxidation (GO) was increased in the T30 group compared with the T7 and control groups. Blood levels of the odd-chain ketone body beta-hydroxypentanoate confirmed adequate bioavailability of triheptanoin. Importantly, they were directly proportional to cardiac GO.

CONCLUSIONS

Treatment with triheptanoin-enriched diet reduces ventricular hypertrophy and improves diastolic function in rats with PO, which is associated with enhanced cardiac GO. The results suggest targeting supplementation of the Krebs cycle to approach ventricular and metabolic remodeling in cardiac hypertrophy.

Adrenergic Repression of the Epigenetic Reader MeCP2 Facilitates Cardiac Adaptation in Chronic Heart Failure

Supplemental Digital Content is available in the text.

In chronic heart failure, increased adrenergic activation contributes to structural remodeling and altered gene expression. Although adrenergic signaling alters histone modifications, it is unknown, whether it also affects other epigenetic processes, including DNA methylation and its recognition.

[Density equalizing mapping of obesity: analysis of a global epidemic]

Obesity is a chronic disease whose origin is determined by genetic factors as well as environmental influences. The prevalence has rapidly increased worldwide in the recent decades. This paper evaluated the research on obesity in the period of 1900 - 2009 in the ISI "Web of Science" by Thomson Reuters. For this purpose scientometric methods were used and the results were graphically illustrated by "Density Equalizing Map Projections". From 1900 till 2009 94.987 published items are the basis for the present qualitative and quantitative data analysis. The publication rates show an exponential growth indicating a pronounced research activity. Concerning the country comparison the United States has the highest number of publications and citations, the highest modified h-index and most academic institutions. This manuscript shows the first comprehensive scientometric data on obesity. In this research area, the United States is a leader and is located at the center of global collaborations.

Self-gated cardiac Cine MRI of the rat on a clinical 3 T MRI system

The ability to perform small animal functional cardiac imaging on clinical MRI scanners may be of particular value in cases in which the availability of a dedicated high field animal MRI scanner is limited. Here, we propose radial MR cardiac imaging in the rat on a whole-body clinical 3 T scanner in combination with interspersed projection navigators for self-gating without any additional external triggering requirements for electrocardiogram (ECG) and respiration. Single navigator readouts were interspersed using the same TR and a high navigator frequency of 54 Hz into a radial golden-angle acquisition. The extracted navigator function was thresholded to exclude data for reconstruction from inhalation phases during the breathing cycle, enabling free breathing acquisition. To minimize flow artifacts in the dynamic cine images a center-out half echo radial acquisition scheme with ramp sampling was used. Navigator functions were derived from the corresponding projection navigator data from which both respiration and cardiac cycles were extracted. Self-gated cine acquisition resulted in high-quality cardiac images which were free of major artifacts with spatial resolution of up to 0.21 × 0.21 × 1.00 mm(3) and a contrast-to-noise ratio (CNR) of 21 ± 3 between the myocardium and left ventricle. Self-gated golden ratio based radial acquisition successfully acquired cine images of the rat heart on a clinical MRI system without the need for dedicated animal ECG equipment.

Mitochondrial reactive oxygen species production and respiratory complex activity in rats with pressure overload-induced heart failure

We investigated the impact of cardiac reactive oxygen species (ROS) during the development of pressure overload-induced heart failure. We used our previously described rat model where transverse aortic constriction (TAC) induces compensated hypertrophy after 2 weeks, heart failure with preserved ejection fraction at 6 and 10 weeks, and heart failure with systolic dysfunction after 20 weeks. We measured mitochondrial ROS production rates, ROS damage and assessed the therapeutic potential of in vivo antioxidant therapies. In compensated hypertrophy (2 weeks of TAC) ROS production rates were normal at both mitochondrial ROS production sites (complexes I and III). Complex I ROS production rates increased with the appearance of diastolic dysfunction (6 weeks of TAC) and remained high thereafter. Surprisingly, maximal ROS production at complex III peaked at 6 weeks of pressure overload. Mitochondrial respiratory capacity (state 3 respiration) was elevated 2 and 6 weeks after TAC, decreased after this point and was significantly impaired at 20 weeks, when contractile function was also impaired and ROS damage was found with increased hydroxynonenal. Treatment with the ROS scavenger α-phenyl-N-tert-butyl nitrone or the uncoupling agent dinitrophenol significantly reduced ROS production rates at 6 weeks. Despite the decline in ROS production capacity, no differences in contractile function between treated and untreated animals were observed. Increased ROS production occurs early in the development of heart failure with a peak at the onset of diastolic dysfunction. However, ROS production may not be related to the onset of contractile dysfunction.

The E-wave deceleration rate E/DT outperforms the tissue Doppler-derived index E/e' in characterizing lung remodeling in heart failure with preserved ejection fraction

Background

Diastolic dysfunction in heart failure with preserved ejection fraction (HFpEF) may result in pulmonary congestion and lung remodeling. We evaluated the usefulness of major diastolic echocardiographic parameters and of the deceleration rate of early transmitral diastolic velocity (E/DT) in predicting lung remodeling in a rat model of HFpEF.

Methods and Results

Rats underwent aortic banding (AoB) to induce pressure overload (PO). Left ventricular hypertrophy fully developed 2 weeks after AoB. At 4 and 6 weeks, the lung weight-to-body weight ratio (LW/BW), a sensitive marker for pulmonary congestion and remodeling, dramatically increased despite preserved fractional shortening, indicating the presence of HFpEF. The time course of LW/BW was well reflected by E/DT, by the ratio of early to late transmitral diastolic velocity (E/A) and the deceleration time of E (DT), but not by the ratio of transmitral to mitral annular early diastolic velocity (E/e'). In agreement, the best correlation with LW/BW was found for E/DT (r = 0.76; p<0.0001), followed by E/A (r = 0.69; p<0.0001), DT (r = −0.62; p<0.0001) and finally E/e' (r = 0.51; p<0.001). Furthermore, analysis of receiver-operating characteristic curves for the prediction of increased LW/BW revealed excellent area under the curve values for E/DT (AUC = 0.98) and DT (AUC = 0.95), which are significantly higher than that of E/e' (AUC = 0.82). In a second approach, we also found that the new parameter E/DT correlated well with right ventricular weight index and echocardiographic measures of right ventricular systolic function.

Conclusions

The novel parameter E/DT outperforms the tissue Doppler index E/e' in detecting and monitoring lung remodeling induced by pressure overload. The results may provide a handy tool to point towards secondary lung disease in HFpEF and warrant further clinical investigations.

Glucagon-like peptide-1 reduces contractile function and fails to boost glucose utilization in normal hearts in the presence of fatty acids

GLP-1 and exendin-4, which are used as insulin sensitizers or weight reducing drugs, were shown to improve glucose uptake in the heart. However, the direct effects of GLP-1 or exendin-4 on normal hearts in the presence of fatty acids, the main cardiac substrates, have never been investigated. We therefore assessed the effects of GLP-1 or exendin-4 on myocardial glucose uptake (GU), glucose oxidation (GO) and cardiac performance (CP) under conditions of fatty acid utilization.

METHODS AND RESULTS

Rat hearts were perfused with only glucose (5 mM) or glucose (5 mM) plus oleate (0.4 mM) as substrates for 60 min. After 30 min, GLP-1 or exendin-4 (0.5 nM or 5 nM) was added. In the absence of oleate, GLP-1 increased both GU and GO. Exendin-4 increased GO but showed no effect on GU. Neither GLP-1 nor exendin-4 affected CP. However, when oleate was present, GLP-1 failed to stimulate glucose utilization and exendin-4 even decreased GU. Furthermore, now GLP-1 reduced CP. In contrast to prior reports, this negative inotropic effect could not be blocked by the protein kinase A inhibitor H-89. We then measured myocardial GO and CP in rats receiving a 4-week GLP-1 infusion. Interestingly, this chronic treatment resulted in a significant reduction in both GO and CP.

CONCLUSIONS

Under the influence of oleate, GLP-1 reduces contractile function and fails to stimulate glucose utilization in normal hearts. Exendin-4 may acutely reduce cardiac glucose uptake but not contractility. We suggest advanced investigation of heart function and metabolism in patients treating with these peptides.