Gene expression throughout a vertebrate's embryogenesis

Abstract Background Describing the patterns of gene expression during embryonic development has broadened our understanding of the processes and patterns that define morphogenesis. Yet gene expression patterns have not been described throughout vertebrate embryogenesis. This study presents statistical analyses of gene expression during all 40 developmental stages in the teleost Fundulus heteroclitus using four biological replicates per stage. Results Patterns of gene expression for 7,000 genes appear to be important as they recapitulate developmental timing. Among the 45% of genes with significant expression differences between pairs of temporally adjacent stages, significant differences in gene expression vary from as few as five to more than 660. Five adjacent stages have disproportionately more significant changes in gene expression (> 200 genes) relative to other stages: four to eight and eight to sixteen cell stages, onset of circulation, pre and post-hatch, and during complete yolk absorption. The fewest differences among adjacent stages occur during gastrulation. Yet, at stage 16, (pre-mid-gastrulation) the largest number of genes has peak expression. This stage has an over representation of genes in oxidative respiration and protein expression (ribosomes, translational genes and proteases). Unexpectedly, among all ribosomal genes, both strong positive and negative correlations occur. Similar correlated patterns of expression occur among all significant genes. Conclusions These data provide statistical support for the temporal dynamics of developmental gene expression during all stages of vertebrate development

Contribution of Social Isolation, Restraint, and Hindlimb Unloading to Changes in Hemodynamic Parameters and Motion Activity in Rats

The most accepted animal model for simulation of the physiological and morphological consequences of microgravity on the cardiovascular system is one of head-down hindlimb unloading. Experimental conditions surrounding this model include not only head-down tilting of rats, but also social and restraint stresses that have their own influences on cardiovascular system function. Here, we studied levels of spontaneous locomotor activity, blood pressure, and heart rate during 14 days under the following experimental conditions: cage control, social isolation in standard rat housing, social isolation in special cages for hindlimb unloading, horizontal attachment (restraint), and head-down hindlimb unloading. General activity and hemodynamic parameters were continuously monitored in conscious rats by telemetry. Heart rate and blood pressure were both evaluated during treadmill running to reveal cardiovascular deconditioning development as a result of unloading. The main findings of our work are that: social isolation and restraint induced persistent physical inactivity, while unloading in rats resulted in initial inactivity followed by normalization and increased locomotion after one week. Moreover, 14 days of hindlimb unloading showed significant elevation of blood pressure and slight elevation of heart rate. Hemodynamic changes in isolated and restrained rats largely reproduced the trends observed during unloading. Finally, we detected no augmentation of tachycardia during moderate exercise in rats after 14 days of unloading. Thus, we concluded that both social isolation and restraint, as an integral part of the model conditions, contribute essentially to cardiovascular reactions during head-down hindlimb unloading, compared to the little changes in the hydrostatic gradient

A new leptin-mediated mechanism for stimulating fatty acid oxidation A pivotal role for sarcolemmal FAT/CD36

International audienceLeptin stimulates fatty acid oxidation in muscle and heart; but, the mechanism by which these tissues provide additional intracellular fatty acids for their oxidation remains unknown. We examined, in isolated muscle and cardiac myocytes, whether leptin, via AMP-activated protein kinase (AMPK) activation, stimulated fatty acid translocase (FAT/CD36)-mediated fatty acid uptake to enhance fatty acid oxidation. In both mouse skeletal muscle and rat cardiomyocytes, leptin increased fatty acid oxidation, an effect that was blocked when AMPK phosphorylation was inhibited by adenine 9-β-D-arabinofuranoside or Compound C. In wild-type mice, leptin induced the translocation of FAT/CD36 to the plasma membrane and increased fatty acid uptake into giant sarcolemmal vesicles and into cardiomyocytes. In muscles of FAT/CD36-KO mice, and in cardiomyocytes in which cell surface FAT/CD36 action was blocked by sulfo-N-succinimidyl oleate, the leptin-stimulated influx of fatty acids was inhibited; concomitantly, the normal leptin-stimulated increase in fatty acid oxidation was also prevented, despite the normal leptin-induced increase in AMPK phosphorylation. Conversely, in muscle of AMPK kinase-dead mice, leptin failed to induce the translocation of FAT/CD36, along with a failure to stimulate fatty acid uptake and oxidation. Similarly, when siRNA was used to reduce AMPK in HL-1 cardiomyocytes, leptin failed to induce the translocation of FAT/CD36. Our studies have revealed a novel mechanism of leptin-induced fatty acid oxidation in muscle tissue; namely, this process is dependent on the activation of AMPK to induce the translocation of FAT/CD36 to the plasma membrane, thereby stimulating fatty acid uptake. Without increasing this leptin-stimulated, FAT/CD36-dependent fatty acid uptake process, leptin-stimulated AMPK phosphorylation does not enhance fatty acid oxidation. © 2017 The Author(s); published by Portland Press Limited on behalf of the Biochemical Society

應有部分的拋棄與歸屬

Recently, fatty acid transport across the plasma membrane has been shown to be a key process that contributes to the regulation of fatty acid metabolism in the heart. Since AMP kinase activation by 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) stimulates fatty acid oxidation, as well as the expression of selected proteins involved with energy provision, we examined (a) whether AICAR induced the expression of the fatty acid transporters FABPpm and FAT/CD36 in cardiac myocytes and in perfused hearts and (b) the signaling pathway involved. Incubation of cardiac myocytes with AICAR increased the protein expression of the fatty acid transporter FABPpm after 90 min (+27%, P <0.05) and this protein remained stably overexpressed until 180 min. Similarly, FAT/CD36 protein expression was increased after 60 min (+38%, P <0.05) and remained overexpressed thereafter. Protein overexpression, which occurred via transcriptional mechanisms, was dependent on the AICAR concentration, with optimal induction occurring at AICAR concentrations 1-5 mM for FABPpm and at 2-8 mM for FAT/CD36. The AICAR (2 h, 2 mM AICAR) effects on FABPpm and FAT/CD36 protein expression were similar in perfused hearts and in cardiac myocytes. AICAR also induced the plasmalemmal content of FAT/CD36 (+49%) and FABPpm (+42%) (P <0.05). This was accompanied by a marked increase in the rate of palmitate transport (2.5 fold) into giant sarcolemmal vesicles, as well as by increased rates of palmitate oxidation in cardiac myocytes. When the AICAR-induced AMPK phosphorylation was blocked, neither FAT/CD36 nor FABPpm were overexpressed, nor were palmitate uptake and oxidation increased. This study has revealed that AMPK activation stimulates the protein expression of both fatty acid transporters, FAT/CD36 and FABPpm in (a) time- and (b) dose-dependent manner via (c) the AMPK signaling pathway. AICAR also (d) increased the plasmalemmal content of FAT/CD36 and FABPm, thereby (e) increasing the rates of fatty acid transport. Thus, activation of AMPK is a key mechanism regulating the expression as well as the plasmalemmal localization of fatty acid transporters

Physical performance level in sarcomeric mitochondria creatine kinase knockout mouse model throughout ageing

International audiencePurpose: The objective of the present study was to establish the role of sarcomeric mitochondrial creatine kinase (Mt-CK) in muscle energy output during exercise in a murine model of ageing (the Mt-CK knock-out mouse, Mt-CK-/-).Methods: Three age groups of Mt-CK-/- mice and control male mice (6, 9, and 18 months of age) underwent incremental treadmill running tests. The maximum speed (Vpeak) and maximal oxygen consumption (VO2 peak) values were recorded. Urine samples were analyzed using metabolomic techniques. The skeletal muscle (quadriceps) expression of proteins involved in mitochondria biogenesis, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1 alpha) and dynamin-related GTPase mitofusin 2 (Mnf2) were quantified.Results: The VO(2)peak (normalized to heart weight: HW) of 18-month-old (mo) Mt-CK-/- mice was 27% (p < 0.001) lower than in 18-mo control mice. The VO(2)peak/HW ratio was 29% (p < 0.001) lower in 18-mo Mt-CK-/- mice than in 6-mo (p < 0.001) and 32% (p < 0.001) than 9-mo Mt-CK-/- mice. With a 0 degrees slope, Vpeak was 10% (p < 0.05) lower in 18-mo Mt-CK-/- mice than in 6-mo Mt-CK-/- mice but did not differ when comparing the 18-mo and 6-mo control groups. The skeletal muscles weight normalized on body weight in 6-mo Mt-CK-/- were 13 to 14% (p < 0.001, p < 0.05) lower versus the 6-mo control, in addition, the presence of branched-chain amino acids in the urine of 6-mo Mt-CK-/- mice suggests an imbalance in protein turnover (catabolism rather than anabolism) but we did not observe any age-related differences. The expression of PGC-1 alpha and Mnf2 proteins in the quadriceps showed that age-related effects were more prominent than genotype effects.Conclusion: The present study showed ageing is potentialized by Mt-CK deficiency with regard to VO(2)peak, Vpeak and mitochondrial protein expression. Our results support that Mt-CK-/- mice undergo physiological adaptations, enabling them to survive and to perform as well as wild-type mice. Furthermore, it is possible that these adaptations in Mt-CK-/- mice have a high energy cost and might trigger premature ageing