Lower plasma melatonin levels predict worse long-term survival in pulmonary arterial hypertension

Background

Exogenous melatonin has been reported to be beneficial in the treatment of pulmonary hypertension (PH) in animal models. Multiple mechanisms may be involved, with melatonin exerting anti-oxidant and anti-inflammatory effects, as well as inducing vasodilation and cardio-protection. However, endogenous levels of melatonin in treatment-naïve pulmonary arterial hypertension (PAH) patients and their clinical significance are still unknown.

Methods and results

Plasma levels of endogenous melatonin were measured by liquid chromatography-tandem mass spectrometry in treatment-naïve PAH patients (n=43) and healthy controls (n=111). Melatonin levels were higher in PAH patients when compared with controls (Median 118.9 [IQR 109.3–147.7] versus 108.0 [102.3–115.2] pM, P<0.001) (Figure 1A). The overall mortality was 26% (11/43) during a median long-term follow-up of 42 [IQR: 32–58] months. When PAH patients were stratified into 4 groups according to the quartiles of melatonin levels, the mortality from below 1st quartile to above 4th quartile was 55% (6/11), 10% (1/10), 0% (0/12), and 40% (4/10), respectively (Figure 1B). Kaplan-Meier analysis further showed that patients with melatonin levels below the 1st quartile (<109.3 pM) had a worse long-term survival than patients with melatonin levels above the 1st quartile (Mean survival times were 46 [95% CI: 30–65] versus 68 [58–77] months, Log-rank, p=0.026) (Figure 1C).

Conclusion

Endogenous melatonin levels were increased in treatment-naïve PAH patients, and lower levels of melatonin were associated with worse long-term survival in patient with PAH, however, whether exogenous melatonin supplements may be effective as a therapeutic strategy in human PAH remains to be established.

Figure 1

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): This work was supported by the China Scholarship Council (201606230252) as well as the Netherlands CardioVascular Research Initiative: an initiative with support of the Dutch Heart Foundation (CVON2014-11, RECONNECT), and German Center for Cardiovascular Research (DZHK81Z0600207). Instrumentation support was received from AB Sciex, ltd. for LC-MS/MS analyses performed in this study.

Different tryptophan-kynurenine metabolism profiles in human pulmonary arterial hypertension and animal models of pulmonary hypertension

Background

De novo NAD+ synthesis through the tryptophan-kynurenine (TK) metabolism was recognized as an important pathway in improving mitochondrial function and survival of injury or apoptotic cells, which are key processes involved in the pathogenesis of pulmonary arterial hypertension (PAH). Although abnormal TK metabolism has been reported in human PAH, the difference between human and animal models of pulmonary hypertension (PH) are currently unknown.

Objective

Determine and compare TK metabolism profiles in plasma from human PAH and 3 animal models of PH.

Methods

Human plasma was collected from treatment naïve patients with PAH (n=43) and healthy controls (n=111). Animal plasma was collected from 3 animal models of PH and corresponding controls, including monocrotaline (MCT) induced PH in rat (n=7, control n=6), Sugen + hypoxia (SuHx) induced PH in rat (n=5, control n=6), and pulmonary vein banding (PVB) induced PH in swine (n=7, control n=6). TK metabolites were determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Results

TK metabolism was altered in the plasma from of PAH compared to healthy controls (Figure 1A). Lower tryptophan (0.8 fold vs Control, p<0.0001), maintained 3-hydroxyanthranilic acid, and higher kynurenine, 3-hydroxykynurenine, anthranilic acid, and quinolinic acid (1.5, 2.6, 2.0, 2.6 fold vs Control, respectively, p all<0.0001) were seen in the plasma from human PAH. In the rat SuHx-PH model, kynurenine (0.7 fold, p<0.01) and quinolinic acid (0.5 fold, p<0.001) were lower, while 3-hydroxyanthranilic acid (4.3 fold, p<0.001) was higher in PH compared to control (Figure 1B). However, the TK metabolism was unaltered in MCT-PH model in rat (Figure 1C), and PVB-PH model in swine (Figure 1D).

Conclusions

TK metabolism was altered in the plasma from human PAH. The TK metabolism profiles were different among 3 animal models of PH, but did not mimic the profile in human PAH. Further research is required to determine the mechanism(s) behind the abnormal TK metabolism in human PAH as well as whether these mechanisms relate to disease onset or progression.

Figure 1

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): This work was supported by the China Scholarship Council (201606230252) as well as the Netherlands CardioVascular Research Initiative: an initiative with support of the Dutch Heart Foundation (CVON2014-11, RECONNECT), and German Center for Cardiovascular Research (DZHK81Z0600207). Instrumentation support was received from AB Sciex, ltd. for LC-MS/MS analyses performed in this study.

Pseudo CT Estimation using Patch-based Joint Dictionary Learning

Magnetic resonance (MR) simulators have recently gained popularity; it avoids the unnecessary radiation exposure associated with Computed Tomography (CT) when used for radiation therapy planning. We propose a method for pseudo CT estimation from MR images based on joint dictionary learning. Patient-specific anatomical features were extracted from the aligned training images and adopted as signatures for each voxel. The most relevant and informative features were identified to train the joint dictionary learning-based model. The well-trained dictionary was used to predict the pseudo CT of a new patient. This prediction technique was validated with a clinical study of 12 patients with MR and CT images of the brain. The mean absolute error (MAE), peak signal-to-noise ratio (PSNR), normalized cross correlation (NCC) indexes were used to quantify the prediction accuracy. We compared our proposed method with a state-of-the-art dictionary learning method. Overall our proposed method significantly improves the prediction accuracy over the state-of-the-art dictionary learning method. We have investigated a novel joint dictionary Iearning- based approach to predict CT images from routine MRIs and demonstrated its reliability. This CT prediction technique could be a useful tool for MRI-based radiation treatment planning or attenuation correction for quantifying PET images for PET/MR imaging.

A resource-utilization way of the waste printed circuit boards to prepare silicon carbide nanoparticles and their photocatalytic application

A resource-utilization strategy of the waste PCBs was developed: preparation of high value-added silicon carbide (SiC) nanoparticles using the waste PCBs as both silica and carbon precursors. The preparation process contained three optimized steps: acid wash pretreatment with 3 mol L^-1 nitric acid at 60 °C for 96 h, low-temperature pyrolysis at 500 °C to allow the epoxy resin to decompose into carbon, and high-temperature pyrolysis at 1600 °C (in situ carbothermal reduction) to gain pure SiC nanoparticles. The pseudo first-order reaction rate constant (k) of the p-n heterojunction of SiC/TiO₂ towards the photocatalytic degradation of methylene blue was 0.0219 min^-1, 3.42 and 3.98 times that of TiO₂ and no acid washed-SiC/TiO₂, respectively.