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- González Henríquez, J J, et al.
(author)
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A new equation to estimate temperature-corrected PaCO2 from PET CO2 during exercise in normoxia and hypoxia.
- 2015
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In: Scandinavian Journal of Medicine & Science in Sports. - : Wiley. - 1600-0838 .- 0905-7188. ; 26:9, s. 1045-1051
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Journal article (peer-reviewed)abstract
- End-tidal PCO2 (PET CO2 ) has been used to estimate arterial pressure CO2 (Pa CO2 ). However, the influence of blood temperature on the Pa CO2 has not been taken into account. Moreover, there is no equation validated to predict Pa CO2 during exercise in severe acute hypoxia. To develop a new equation to predict temperature-corrected Pa CO2 values during exercise in normoxia and severe acute hypoxia, 11 volunteers (21.2 ± 2.1 years) performed incremental exercise to exhaustion in normoxia (Nox, PI O2 : 143 mmHg) and hypoxia (Hyp, PI O2 : 73 mmHg), while arterial blood gases and temperature (ABT) were simultaneously measured together with end-tidal PCO2 (PET CO2 ). The Jones et al. equation tended to underestimate the temperature corrected (tc) Pa CO2 during exercise in hypoxia, with greater deviation the lower the Pa CO2 tc (r = 0.39, P < 0.05). The new equation has been developed using a random-effects regression analysis model, which allows predicting Pa CO2 tc both in normoxia and hypoxia: Pa CO2 tc = 8.607 + 0.716 × PET CO2 [R(2) = 0.91; intercept SE = 1.022 (P < 0.001) and slope SE = 0.027 (P < 0.001)]. This equation may prove useful in noninvasive studies of brain hemodynamics, where an accurate estimation of Pa CO2 is needed to calculate the end-tidal-to-arterial PCO2 difference, which can be used as an index of pulmonary gas exchange efficiency.
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- PÉREZ-SUÁREZ, I, et al.
(author)
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LEPTIN RECEPTOR MOLECULAR VARIANTS ARE DIFFERENTLY REGULATED BY EXERCISE AND ENERGY DEFICIT IN HUMAN SKELETAL MUSCLE
- 2014
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Conference paper (peer-reviewed)abstract
- IntroductionLeptin signals in skeletal muscles through pathways which share some steps with the insulin and IGF1. We have recently shown that LEPR (OBR-170) is increased in the dominant arm of tennis players 1 and is reduced in deltoid and vastus lateralis (VL) of obese compared to control subjects 2. The aim of this study was to determine whether exercise up-regulates the protein abundance and phosphorylation status of the different molecular variations of the LEPR (OBR-170, 128, 98A or 98B) in human skeletal muscle. We hypothesized that exercise will up-regulate leptin signaling in skeletal muscle. MethodsFifteen overweight men underwent three experimental phases: pre-test (PRE); caloric restriction (3.2 Kcal/kg body Wt/d) + exercise (45min unilateral arm cranking/d + 8h walking/d) for 4 days (CRE); and control isoenergetic diet + reduced exercise for 3 days (CD). During CRE, the diet consisted solely of whey protein (PRO, n=8) or sucrose (SU, n=7) (0.8 g/kg body Wt/d). Muscle biopsies (135 biopsies in all) were obtained from the trained and untrained deltoid, and VL, after 12h fast at PRE, and end of CRE and CD. The molecular variants of LEPR (OBR-170, 128, 98A and 98B) were determined by western blot and LEPR mRNA by PCR. ResultsSerum leptin was reduced by ~60% following CRE and CD (P<0.05). LEPRs were more abundant in arm than leg muscles. LEPR mRNA was increased in exercised muscles after CRE. OBR-170 was reduced after CRE and CD only in the control arm (P<0.05). OBR-128 was increased after CD in exercised extremities (P<0.05). OBR-98A was increased after CRE in trained arm, and after CD in legs (P<0.05). However, OBR-98B was increased after CRE and CD in both arms and exercised extremities (P<0.05), being these effects more pronounced in the PRO group (P<0.05). After CD, LEPR mRNA returned to basal levels while LEPR expression was increased in all muscles (P<0.05). The fraction of LEPR activated (Tyr1141 phosphorylated) was reduced in arms but not in leg muscles. LEPR phosphorylation was correlated with JAK2 (upstream) and STAT3 (downstream) phosphorylation (r=0.67-0.89, P<0.05). DiscussionCaloric restriction seems to reduce the abundance of LEPR, but this effect varies depending on specific molecular variants of the receptor. The reduction of LEPR is partly counteracted by exercise, likely contributing to increase muscle leptin sensitivity. Whey protein ingestion facilitates these effects. Resuming normal food ingestion after a period of severe energy deficit is accompanied by increased expression LEPR in skeletal muscle.
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