Long-term prognostic value of trimethylamine N-oxide in community-based adults and patients with coronary heart disease

Background

Trimethylamine N-oxide (TMAO) is an amine oxide generated by gut microbial metabolism. Emerging evidence suggests pro-atherosclerotic and pro-inflammatory properties of TMAO; however, the clinical utility of circulating TMAO in risk stratification is uncertain.

Purpose

We prospectively assessed relationships of plasma TMAO with long-term risk of all-cause, cardiovascular (CV) and non-CV mortality in community-dwelling adults and patients with coronary heart disease.

Methods

By Cox modelling, risk-associations were examined in the Hordaland Health Study (HUSK; 6393 community-based adults) and the Western Norway Coronary Angiography Cohort (WECAC; 4132 patients with suspected chronic coronary syndrome).

Results

Median follow-up time was 11.0 and 10.3 years in HUSK and WECAC, respectively. Following adjustments for established CV risk factors in HUSK, the HRs (95% CIs) comparing the 4th vs. 1st TMAO-quartile were 1.11 (0.88–1.40), 0.97 (0.65–1.46) and 1.17 (0.88–1.54) for all-cause, CV and non-CV mortality, respectively. Corresponding risk estimates in WECAC were 1.07 (0.86–1.32), 1.16 (0.83–1.62) and 1.02 (0.77–1.34). Similar results were observed in patients with angiographically significant coronary artery disease and patients with reduced left ventricular ejection fraction.

Conclusion

Plasma TMAO was not predictive of long-term all-cause, CV or non-CV mortality in patients with or without established coronary heart disease. This large-scale study does not support a role of TMAO for patient risk stratification in primary or secondary prevention.

Funding Acknowledgement

Type of funding sources: None.

Circulating trimethyllysine predicts total and cardiovascular mortality in patients with and without coronary heart disease

Background

The carnitine precursor trimethyllysine (TML) is associated with the microbiota-derived metabolite trimethylamine N-oxide (TMAO) and predicts future cardiovascular events in patients with established coronary heart disease (CHD).

Purpose

To examine circulating TML as a predictor of total and cardiovascular mortality in two independent cohorts of subjects with or without CHD.

Methods

By Cox regression modelling, risk associations were examined in 6393 subjects in the community-based Hordaland Health Study (HUSK). A replication study was performed among 4117 patients undergoing coronary angiography for suspected stable angina pectoris in the Western Norway Coronary Angiography Cohort (WECAC).

Results

During a median follow-up of 10.9 years in the HUSK-cohort, 884 (13.8%) subjects died, of whom 287 from cardiovascular causes. After adjustments for traditional cardiovascular risk factors, the hazard ratio (HR) (95% CI) for total mortality comparing the 4th vs. 1st TML-quartile was 1.66 (1.31–2.10, p<0.001). Particularly strong associations were observed with cardiovascular mortality (HR [95% CI] 2.04 [1.32–3.15, p=0.001]). Corresponding risk estimates in the WECAC-cohort (median follow-up of 10.3 years) were 1.35 (1.10–1.66, p=0.004) for total and 1.45 (1.06–1.98, p=0.02) for cardiovascular mortality. Additional adjustments for plasma TMAO did not materially influence the risk estimates in either cohort, and no effect modification by TMAO was observed.

Conclusions

Circulating TML is associated with increased risk of total and cardiovascular mortality in both subjects with and without CHD.

Funding Acknowledgement

Type of funding sources: None.

Proton magnetic resonance spectroscopy of cerebrospinal fluid in neurodegenerative disease: indication of glial energy impairment in Huntington chorea, but not Parkinson disease

Metabolite levels in cerebrospinal fluid from patients with Parkinson disease or Huntington chorea were compared with the levels in healthy controls using proton magnetic resonance spectroscopy. No significant differences were found for any metabolite measured in cerebrospinal fluid from patients with Parkinson disease compared to controls. Slight but significantly reduced levels of both lactate and citrate, however, were found in cerebrospinal fluid from patients with Huntington chorea compared to controls. This suggests possible impairment of both glycolysis and tricarboxylic acid cycle function. The reduction in lactate found in the present study may reflect neuronal loss. The decrease in citrate supports the theory of mitochondrial dysfunction in the brain of patients with Huntington chorea, but also suggests that there may be an important astrocytic component in this disease. If so, it would certainly have implications for neuronal function.

Quantitative EEG in acute mountain sickness

OBJECTIVES

To investigate if the EEG response at moderate altitude may predict a person's tolerance to acute mountain sickness (AMS).

MATERIALS AND METHODS

Frequency analysis (QEEG) of tape-recorded ambulatory EEG was performed in 6 climbers during a mountaineering expedition to 7546 m above sea level. The QEEG response in climbers, measured at sea level, at 4500 m, and at 1800 m 1-4 days after maximal altitude exposure, was compared to the change observed during consecutive sea level recordings in 10 control subjects.

RESULTS

Three climbers experienced slight (grade 1) AMS symptoms both at 4500 m and at maximal altitude exposure (Group 1). Three other climbers (Group 2) had no symptoms at 4500 m, but they developed AMS (grades 1, 2, or 3) at maximal altitude. Alpha amplitudes were higher at 4500 m in group 1 climbers, while it was lower in group 2 climbers compared to the sea level recording. Significant time x group interactions in ANOVA were found for delta (P = 0.005), theta (P = 0.001) and alpha (P = 0.001) amplitude, indicating that QEEG amplitudes decreased significantly at high altitude in group 2 climbers.

CONCLUSION

The QEEG response to moderate hypobaric hypoxia is not uniform, but the direction of QEEG amplitude change, particularly in the alpha band, may possibly predict the risk of developing AMS.

Neuron-specific enolase concentrations in serum and cerebrospinal fluid in patients with no previous history of neurological disorder

Studies of cerebrospinal fluid (CSF) concentrations of neuron-specific enolase (NSE) in patients with neurological lesions indicate a quantitative relation between the degree of cell damage in the central nervous system (CNS) and the concentration of this CNS-specific protein. We collected serum and CSF from 63 males and 24 females undergoing various surgical procedures in spinal anaesthesia. The patients had no actual or previous history of neurological disease. The mean value of NSE in serum was 7.1 +/- 3.6 micrograms/L. NSE concentrations in CSF demonstrated age- and sex-dependency, with an increase with age from 21 to 84 years and significantly higher levels in males than in females. Therefore, age- and sex-matched reference values have to be used when NSE is evaluated in CSF in patients with different neurological disorders.

Large peripheral cystic schwannomas. Two case reports and a review

Two patients presented with benign cystic schwannomas, which originated from the brachial plexus and the sciatic nerve, respectively. The tumours were single, egg-shaped growths that were excised completely without damage to the nerve. Histopathological examination confirmed the diagnosis of encapsulated, cystic, benign schwannomas. Preoperative magnetic resonance imaging provided useful information and is recommended in the evaluation of peripheral nerve tumours.

[Chordoma. An unusual cause of cauda equina syndrome]

Acute cauda equina syndrome caused by a chordoma in the third lumbar vertebra is presented as a case report. This combination has not previously been described.

A Quick Method To Determine Subsidence, Reservoir Compaction, and In-Situ Stress Induced by Reservoir Depletion

Summary

This paper provides a quick method to determine subsidence, compaction, and in-situ stress induced by pore-pressure change. The method is useful for a reservoir whose Young's modulus is less than 20% or greater than 150% of the Young's modulus of the surrounding formation (where the conventional uniaxial strain assumption may not hold). In this work, a parameter study was conducted to find groups of parameters controlling the in-situ stress, subsidence, and compaction. These parameter groups were used to analyze the numerical calculation results generated by a three-dimensional (3D), general, nonlinear, finite-element model (FEM). The procedure and a set of figures showing how to calculate the in-situ stress, subsidence, and compaction induced by pore-pressure changes are provided. Example problems are also included to prevent confusion on sign convention and units. This work showed that Geertsma's results, which are based on no modulus contrast between cap and reservoir rocks, should be extended to simulate more closely "real" reservoirs, which generally have distinct property differences between the cap and reservoir rocks. Highly porous and high-pressure North Sea reservoirs and tight sand formations surrounded by soft shale often fall into this category. The application is intended for sand-production control, casing buckling problems, design of hydraulic fracturing jobs, subsidence, and estimation of PV and formation damage resulting from permeability reduction during hydrocarbon production.

Introduction

The in-situ stress induced by pore-pressure change usually has been calculated on the assumption that a rock deforms uniaxially without inducing strain along the horizontal direction. The amount of subsidence was calculated by Geertsma, with the strain nuclei method. These calculations assume that a reservoir is thin, that its depth is reasonably great, and that its rigidity is close to that of the confining formation. However, statistics of field measurements has shown that many hydrocarbon reservoirs are thick or shallow or have elastic moduli that are significantly different from those of confining formations. For example, North Sea reservoirs often have static Young's moduli that are orders of magnitude smaller than those of the surrounding rocks before they are compacted because of hydrocarbon production, although the dynamic Young's modulus calculated from sonic logs may give only three to six times modulus contrast. Some tight formations in the U.S. also have rock several times more rigid than surrounding shale. When a hydraulic fracture, a sand-control process. a subsidence-control operation, or an evaluation of formation damage resulting from permeability reduction is conducted in such a reservoir, accurate information on the in-situ stress, reservoir compaction, or subsidence induced by pore-pressure changes helps in designing such operations. This work does not use or develop new mathematical techniques, but emphasizes two important issues. First, the common practice in the oil industry is to calculate PV compressibility, reservoir compaction, and in-situ stress change on the basis of reservoir-rock property data. However, this work emphasizes that some reservoirs also require the caprock property data to evaluate these quantities. Second, a quick method to evaluate PV compressibility, reservoir compaction, in-situ stress change, and subsidence has not been published previously. Although techniques to calculate these values are available, they require long times to run sophisticated simulation models. The purpose of this work is to provide a method for quick estimation of in-situ stress, compaction, and subsidence for a reservoir having simple geometry. A quick estimation of these values is often sufficient during the reservoir development stage because accurate reservoir descriptions are not available. Such a crude estimation is essential because the decisions on downhole and surface facility designs are made during the early stages of reservoir development.

After more accurate reservoir descriptions are collected, however, we recommend that the 3D FEM be used for this work to get a better evaluation. The model can handle various complex problems, such as multilayer problems with heterogeneous rock properties, inclined reservoirs, irregular reservoirs, nonuniform pore pressure, nonlinear properties of rock, hysteresis effect of cyclic loading, and nonuniform reservoir pressure.

Assumptions and Calculation Methods

The in-situ stress is decomposed into two parts-original in-situ stress and-in-situ stress induced by pore-pressure change.

................................ (1a) and ............................ (1b) where K is the stress-ratio coefficient affected by rock grain shape, grain-size distribution, sedimentation process, present Poisson's ratio, tectonic force, temperature, and pore pressure. Delta sigma and delta sigma are in-situ stress components induced by pore-pressure change. If the pore-pressure change occurs over several years, we can reasonably assume that rock deforms elastically during the period. In addition, if the pore-pressure change is reasonably small and the state of stress is not far from hydrostatic-i.e., a small deviatoric stress-then a linear elastic deformation is a good approximation. Hence, a linear elastic deformation is assumed in this work for the calculation of delta sigma and delta sigma induced by the pore-pressure change. A disk-shaped reservoir is assumed for the present calculation as shown in Fig. 1. Although the moduli of the reservoir and the surrounding formation may vary within each formation, uniform moduli are assumed within both structures, respectively. The reservoir is located at depth D below the surface and its radius and height are r and h, respectively. More complex reservoir geometries require that data be entered directly into the 3D FEM used for the present calculations. Fig. 2 shows the finite-element meshes used for this work. The upper surface is free from a traction force, and the bottom surface is fixed to the rigid base rock. Infinite elements were used for the outer boundary. The hatched section is the reservoir and has elastic moduli different from those of surrounding formations. The pore pressure of the reservoir section is reduced to calculate the deformations and stress change of the reservoir and surrounding formations. Test runs were conducted for a well with and without a casing cemented to the borehole.

JPT

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