Studies in humans show global changes in mRNA and protein expression occur in human skeletal muscle during bed rest. As microRNAs are important regulators of expression, we analysed the global microRNA expression changes in human muscle following 10 days of sustained bed rest, with the rationale that miRNAs play key roles in atrophy of skeletal muscle. We analysed expression of miRNA and selected target proteins before and after 10 days of bed rest in muscle biopsies obtained from 6 healthy males. 15 out of 152 miRNAs detected in human muscle tissue were differentially expressed and all of them with exception of two were downregulated. The downregulated miRNA include: miR206, a myomir involved in function and maintenance of skeletal muscle; miR23a, involved in insulin response and atrophy defence; and several members of the let7 family involved in cell cycle, cell differentiation and glucose homeostasis. Predicted gene targets of these miRNA are members of the MAPK, TNF receptor, ALK1, TGFbeta receptor and SMAD signalling pathways. All of these pathways were previously indicated to be involved in skeletal muscle response to physical inactivity. We also measured protein expression of selected miRNA targets and observed a decrease in HDAC4. Our data demonstrates that miRNAs in postural muscles are affected by sustained inactivity and unloading, as induced by prolonged bed rest, and hence are potentially involved in regulation of skeletal muscle adjustments to inactivity. We also propose new miRNAs involved in regulation of biological processes in adult human muscle.
COBISS.SI-ID: 27392551
The paper presents the effects of simulated planetary habitation on body mass and body composition. Our main finding was that hypoxia per se does not seem to influence body mass and composition modulation during inactivity. In addition, the obtained results indicate that confinement per se might also be an important factor contributing to the body composition modulation.
COBISS.SI-ID: 27184167
Recent studies are reviewed, concerning the in vivo wall stiffness of arteries and arterioles in healthy humans, and how these properties adapt to iterative increments or sustained reductions in local intravascular pressure. A novel technique was used, by which arterial and arteriolar stiffness were determined as changes in arterial diameter and flow, respectively, during graded increments in distending pressure in the blood vessels of an arm or a leg. Pressureinduced increases in diameter and flow were smaller in the lower leg than in the arm, indicating greater stiffness in the arteries/arterioles of the leg. A 5wk period of intermittent intravascular pressure elevations in one arm reduced pressure distension and pressureinduced flow in the brachial artery by about 50%. Conversely, prolonged reduction of arterial/arteriolar pressure in the lower body by 5 wks of sustained horizontal bedrest, induced threefold increases of the pressuredistension and pressureflow responses in a tibial artery. Thus, the wall stiffness of arteries and arterioles are plastic properties that readily adapt to changes in the prevailing local intravascular pressure. The discussion concerns mechanisms underlying changes in local arterial/arteriolar stiffness as well as whether stiffness is altered by changes in myogenic tone and/or wall structure. As regards implications, regulation of local arterial/arteriolar stiffness may facilitate control of arterial pressure in erect posture and conditions of exaggerated intravascular pressure gradients. That increased intravascular pressure leads to increased arteriolar wall stiffness also supports the notion that local pressure loading may constitute a prime mover in the development of vascular changes in hypertension.
COBISS.SI-ID: 27299623
This study aimed to scrutinize the hypothesis that moderate exercise alleviates chronic hypoxia induced oxidative stress. Our obtain results confirm the proposed hypothesis and show the ability of daily, moderate intensity exercise training to reduce the oxidative stress levels and improve redox equilibrium. These findings also have significant applied value, since moderate training can be used to blunt oxidative stress induced by health/disease related chronic hypoxic exposures as experienced by patients with pulmonary disease, obesity etc.
COBISS.SI-ID: 26881063