Large-scale Metabolomic Profiling Identifies Novel Biomarkers for Incident Coronary Heart Disease

Analyses of circulating metabolites in large prospective epidemiological studies could lead to improved prediction and better biological understanding of coronary heart disease (CHD). We performed a mass spectrometry-based non-targeted metabolomics study for association with incident CHD events in 1,028 individuals (131 events; 10 y. median follow-up) with validation in 1,670 individuals (282 events; 3.9 y. median follow-up). Four metabolites were replicated and independent of main cardiovascular risk factors [lysophosphatidylcholine 18∶1 (hazard ratio [HR] per standard deviation [SD] increment = 0.77, P-value<0.001), lysophosphatidylcholine 18∶2 (HR = 0.81, P-value<0.001), monoglyceride 18∶2 (MG 18∶2; HR = 1.18, P-value = 0.011) and sphingomyelin 28∶1 (HR = 0.85, P-value = 0.015)]. Together they contributed to moderate improvements in discrimination and re-classification in addition to traditional risk factors (C-statistic: 0.76 vs. 0.75; NRI: 9.2%). MG 18∶2 was associated with CHD independently of triglycerides. Lysophosphatidylcholines were negatively associated with body mass index, C-reactive protein and with less evidence of subclinical cardiovascular disease in additional 970 participants; a reverse pattern was observed for MG 18∶2. MG 18∶2 showed an enrichment (P-value = 0.002) of significant associations with CHD-associated SNPs (P-value = 1.2×10⁻⁷ for association with rs964184 in the ZNF259/APOA5 region) and a weak, but positive causal effect (odds ratio = 1.05 per SD increment in MG 18∶2, P-value = 0.05) on CHD, as suggested by Mendelian randomization analysis. In conclusion, we identified four lipid-related metabolites with evidence for clinical utility, as well as a causal role in CHD development.     

The role of tubulin in the mitochondrial metabolism and arrangement in muscle cells

Tubulin, a well-known component of the microtubule in the cytoskeleton, has an important role in the transport and positioning of mitochondria in a cell type dependent manner. This review describes different functional interactions of tubulin with cellular protein complexes and its functional interaction with the mitochondrial outer membrane. Tubulin is present in oxidative as well as glycolytic type muscle cells, but the kinetics of the in vivo regulation of mitochondrial respiration in these muscle types is drastically different. The interaction between VDAC and tubulin is probably influenced by such factors as isoformic patterns of VDAC and tubulin, post-translational modifications of tubulin and phosphorylation of VDAC. Important factor of the selective permeability of VDAC is the mitochondrial creatine kinase pathway which is present in oxidative cells, but is inactive or missing in glycolytic muscle and cancer cells. As the tubulin-VDAC interaction reduces the permeability of the channel by adenine nucleotides, energy transfer can then take place effectively only through the mitochondrial creatine kinase/phosphocreatine pathway. Therefore, closure of VDAC by tubulin may be one of the reasons of apoptosis in cells without the creatine kinase pathway. An important question in tubulin regulated interactions is whether other proteins are interacting with tubulin. The functional interaction may be direct, through other proteins like plectins, or influenced by simultaneous interaction of other complexes with VDAC.     

Formation of highly organized intracellular structure and energy metabolism in cardiac muscle cells during postnatal development of rat heart

Adult cardiomyocytes have highly organized intracellular structure and energy metabolism whose formation during postnatal development is still largely unclear. Our previous results together with the data from the literature suggest that cytoskeletal proteins, particularly βII-tubulin, are involved in the formation of complexes between mitochondria and energy consumption sites. The aim of this study was to examine the arrangement of intracellular architecture parallel to the alterations in regulation of mitochondrial respiration in rat cardiomyocytes during postnatal development, from 1 day to 6 months.     

24S,25-Epoxycholesterol in mouse and rat brain

24S,25-Epoxycholesterol is formed in a shunt of the mevalonate pathway that produces cholesterol. It is one of the most potent known activators of the liver X receptors and can inhibit sterol regulatory element-binding protein processing. Until recently analysis of 24S,25-epoxycholesterol at high sensitivity has been precluded by its thermal lability and lack of a strong chromophore. Here we report on the analysis of 24S,25-epoxycholesterol in rodent brain where its level was determined to be of the order of 0.4–1.4 μg/g wet weight in both adult mouse and rat. For comparison the level of 24S-hydroxycholesterol in brain of both rodents was of the order of 20 μg/g, while that of cholesterol in mouse was 10–20 mg/g. By exploiting knockout mice for the enzyme oxysterol 7α-hydroxylase (Cyp7b1) we show that this enzymes is important for the subsequent metabolism of the 24S,25-epoxide.     

IgG antibodies to Lewis type 2 antigens in serum of H. pylori-infected and noninfected blood donors of different Lewis(a,b) blood-group phenotype

Individuals of the Le(b+)/secretor phenotype revealed a stronger natural immune response to Le(x) and Le(y) epitopes irrespective of Helicobacter pylori serologic status. In contrast, H. pylori-infected Le(b-) type individuals showed a significantly higher proportion of strong responders to Le(x) antigen compared with the H. pylori-uninfected subgroup. The data suggest that the immune response to Lewis type 2 determinants is related to both the H. pylori serologic status and the Le(a,b) phenotype of the host.     

Structure–function relationships in feedback regulation of energy fluxes in vivo in health and disease: Mitochondrial Interactosome

The aim of this review is to analyze the results of experimental research of mechanisms of regulation of mitochondrial respiration in cardiac and skeletal muscle cells in vivo obtained by using the permeabilized cell technique. Such an analysis in the framework of Molecular Systems Bioenergetics shows that the mechanisms of regulation of energy fluxes depend on the structural organization of the cells and interaction of mitochondria with cytoskeletal elements. Two types of cells of cardiac phenotype with very different structures were analyzed: adult cardiomyocytes and continuously dividing cancerous HL-1 cells. In cardiomyocytes mitochondria are arranged very regularly, and show rapid configuration changes of inner membrane but no fusion or fission, diffusion of ADP and ATP is restricted mostly at the level of mitochondrial outer membrane due to an interaction of heterodimeric tubulin with voltage dependent anion channel, VDAC. VDAC with associated tubulin forms a supercomplex, Mitochondrial Interactosome, with mitochondrial creatine kinase, MtCK, which is structurally and functionally coupled to ATP synthasome. Due to selectively limited permeability of VDAC for adenine nucleotides, mitochondrial respiration rate depends almost linearly upon the changes of cytoplasmic ADP concentration in their physiological range. Functional coupling of MtCK with ATP synthasome amplifies this signal by recycling adenine nucleotides in mitochondria coupled to effective phosphocreatine synthesis. In cancerous HL-1 cells this complex is significantly modified: tubulin is replaced by hexokinase and MtCK is lacking, resulting in direct utilization of mitochondrial ATP for glycolytic lactate production and in this way contributing in the mechanism of the Warburg effect. Systemic analysis of changes in the integrated system of energy metabolism is also helpful for better understanding of pathogenesis of many other diseases.