-
1.
Increase of plasma erythroferrone levels during high-altitude exposure: A sub-analysis of the TOP OF HOMe study.
Emrich, IE, Scheuer, A, Wagenpfeil, S, Ganz, T, Heine, GH
American journal of hematology. 2021;(5):E179-E181
-
2.
Effect of carbohydrate-protein supplementation on endurance training adaptations.
Alghannam, AF, Templeman, I, Thomas, JE, Jedrzejewski, D, Griffiths, S, Lemon, J, Byers, T, Reeves, S, Gonzalez, JT, Thompson, D, et al
European journal of applied physiology. 2020;(10):2273-2287
-
-
Free full text
-
Abstract
PURPOSE To examine the influence of post-exercise protein feeding upon the adaptive response to endurance exercise training. METHODS In a randomised parallel group design, 25 healthy men and women completed 6 weeks of endurance exercise training by running on a treadmill for 30-60 min at 70-75% maximal oxygen uptake (VO2max) 4 times/week. Participants ingested 1.6 g per kilogram of body mass (g kg BM-1) of carbohydrate (CHO) or an isocaloric carbohydrate-protein solution (CHO-P; 0.8 g carbohydrate kg BM-1 + 0.8 g protein kg BM-1) immediately and 1 h post-exercise. Expired gas, blood and muscle biopsy samples were taken at baseline and follow-up. RESULTS Exercise training improved VO2max in both groups (p ≤ 0.001), but this increment was not different between groups either in absolute terms or relative to body mass (0.2 ± 0.2 L min-1 and 3.0 ± 2 mL kg-1 min-1, respectively). No change occurred in plasma albumin concentration from baseline to follow-up with CHO-P (4.18 ± 0.18 to 4.23 ± 0.17 g dL-1) or CHO (4.17 ± 0.17 to 4.12 ± 0.22 g dL-1; interaction: p > 0.05). Mechanistic target of rapamycin (mTOR) gene expression was up-regulated in CHO-P (+ 46%; p = 0.025) relative to CHO (+ 4%) following exercise training. CONCLUSION Post-exercise protein supplementation up-regulated the expression of mTOR in skeletal muscle over 6 weeks of endurance exercise training. However, the magnitude of improvement in VO2max was similar between groups.
-
3.
Serum endotoxin, gut permeability and skeletal muscle metabolic adaptations following a short term high fat diet in humans.
Bowser, SM, McMillan, RP, Boutagy, NE, Tarpey, MD, Smithson, AT, Osterberg, KL, Neilson, AP, Davy, BM, Davy, KP, Hulver, MW
Metabolism: clinical and experimental. 2020;:154041
Abstract
BACKGROUND Our previous work demonstrated that a short-term high fat diet (HFD) increased fasting serum endotoxin, altered postprandial excursions of serum endotoxin, and led to metabolic and transcriptional responses in skeletal muscle in young, healthy male humans. PURPOSE The purpose of the present study was to determine if a short-term high fat diet: 1) increases intestinal permeability and, in turn, fasting endotoxin concentrations and 2) decreases postprandial skeletal muscle fat oxidation. METHODS Thirteen normal weight young adult males (BMI 23.1 ± 0.8 kg/m2, age 22.2 ± 0.4 years) were fed a control diet (55% carbohydrate, 30% fat, 9% of which was saturated, 15% protein) for two weeks, followed by 5 days of an isocaloric HFD (30% carbohydrate, 55% fat, 25% of which was saturated, 15% protein, isocaloric to the control diet). Intestinal permeability (via four sugar probe test) was assessed in the fasting state. Both before and after the HFD, a high fat meal challenge (HFM, 820 kcal, 25% carbohydrate, 63% fat, 26% of which was saturated, and 12% protein) was administered. After an overnight fast, blood samples were collected before and every hour for 4 h after the HFM to assess endotoxin, and other serum blood measures. Muscle biopsies were obtained from the vastus lateralis before and 4 h after the HFM in order to assess substrate oxidation (glucose, fatty acid and pyruvate) using radiolabeled techniques. Insulin sensitivity was assessed via intravenous glucose tolerance test. Intestinal permeability, blood samples and muscle biopsies were assessed in the same manner before and following the HFD. MAIN FINDINGS Intestinal permeability was not affected by HFD (p > 0.05), but fasting endotoxin increased two fold following the HFD (p = 0.04). Glucose oxidation and fatty acid oxidation in skeletal muscle homogenates significantly increased after the HFM before the HFD (+97%, and +106% respectively) but declined after the HFM following 5 days of the HFD (-24% and +16% respectively). Fatty acid suppressibility of pyruvate oxidation increased significantly after the HFM (+32%) but this physiological effect was abolished following 5 days of the HFD (+7%). Insulin sensitivity did not change following the HFD. CONCLUSION These findings demonstrate that in healthy young men, consuming an isocaloric HFD for 5 days increases fasting endotoxin, independent of changes in gut permeability. These changes in endotoxin are accompanied by a broad effect on skeletal muscle substrate metabolism including increases in postprandial fat oxidation. Importantly, the latter occurs independent of changes in body weight and whole-body insulin sensitivity.
-
4.
Adaptations in Mitochondrial Enzymatic Activity Occurs Independent of Genomic Dosage in Response to Aerobic Exercise Training and Deconditioning in Human Skeletal Muscle.
Fritzen, AM, Thøgersen, FB, Thybo, K, Vissing, CR, Krag, TO, Ruiz-Ruiz, C, Risom, L, Wibrand, F, Høeg, LD, Kiens, B, et al
Cells. 2019;(3)
Abstract
Mitochondrial DNA (mtDNA) replication is thought to be an integral part of exercise-training-induced mitochondrial adaptations. Thus, mtDNA level is often used as an index of mitochondrial adaptations in training studies. We investigated the hypothesis that endurance exercise training-induced mitochondrial enzymatic changes are independent of genomic dosage by studying mtDNA content in skeletal muscle in response to six weeks of knee-extensor exercise training followed by four weeks of deconditioning in one leg, comparing results to the contralateral untrained leg, in 10 healthy, untrained male volunteers. Findings were compared to citrate synthase activity, mitochondrial complex activities, and content of mitochondrial membrane markers (porin and cardiolipin). One-legged knee-extensor exercise increased endurance performance by 120%, which was accompanied by increases in power output and peak oxygen uptake of 49% and 33%, respectively (p < 0.01). Citrate synthase and mitochondrial respiratory chain complex I⁻IV activities were increased by 51% and 46⁻61%, respectively, in the trained leg (p < 0.001). Despite a substantial training-induced increase in mitochondrial activity of TCA and ETC enzymes, there was no change in mtDNA and mitochondrial inner and outer membrane markers (i.e. cardiolipin and porin). Conversely, deconditioning reduced endurance capacity by 41%, muscle citrate synthase activity by 32%, and mitochondrial complex I⁻IV activities by 29⁻36% (p < 0.05), without any change in mtDNA and porin and cardiolipin content in the previously trained leg. The findings demonstrate that the adaptations in mitochondrial enzymatic activity after aerobic endurance exercise training and the opposite effects of deconditioning are independent of changes in the number of mitochondrial genomes, and likely relate to changes in the rate of transcription of mtDNA.
-
5.
Low skeletal muscle capillarization limits muscle adaptation to resistance exercise training in older adults.
Moro, T, Brightwell, CR, Phalen, DE, McKenna, CF, Lane, SJ, Porter, C, Volpi, E, Rasmussen, BB, Fry, CS
Experimental gerontology. 2019;:110723
-
-
Free full text
-
Abstract
OBJECTIVES Adequate muscle perfusion supports the transport of nutrients, oxygen and hormones into muscle fibers. Aging is associated with a substantial decrease in skeletal muscle capillarization, fiber size and oxidative capacity, which may be improved with regular physical activity. The aim of this study was to investigate the relationship between muscle capillarization and indices of muscle hypertrophy (i.e. lean mass; fiber cross sectional area (CSA)) in older adults before and after 12 weeks of progressive resistance exercise training (RET). DESIGN Interventional study SETTING AND PARTICIPANTS 19 subjects (10 male and 9 female; 71.1 ± 4.3 years; 27.6 ± 3.2 BMI) were enrolled in the study and performed a whole body RET program for 12 weeks. Subjects where then retrospectively divided into a LOW or HIGH group, based on their pre-RET capillary-to-fiber perimeter exchange index (CFPE). Physical activity level, indices of capillarization (capillaries-to-fiber ratio, C:Fi; CFPE index and capillary-to-fiber interface, LC-PF index), muscle hypertrophy, muscle protein turnover and mitochondrial function were assessed before and after RET. RESULTS Basal capillarization (C:Fi; CFPE and LP-CF index) correlates with daily physical activity level (C:Fi, r = 0.57, p = 0.019; CFPE index, r = 0.55, p = 0.024; LC-PF index, r = 0.56, p = 0.022) and CFPE and LC-PF indices were also positively associated with oxidative capacity (respectively r = 0.45, p = 0.06; r = 0.67, p = 0.004). Following RET, subjects in the HIGH group underwent hypertrophy with significant improvements in muscle protein synthesis and muscle fiber CSA (p < 0.05). However, RET did not promote muscle hypertrophy in the LOW group, but RET significantly increased muscle capillary density (p < 0.05). CONCLUSION/IMPLICATIONS Muscle fiber capillarization before starting an exercise training program may be predictive of the muscle hypertrophic response to RET in older adults. Increases in muscle fiber size following RET appear to be blunted when muscle capillarization is low, suggesting that an adequate initial capillarization is critical to achieve a meaningful degree of muscle adaptation to RET.
-
6.
Resistance training does not induce uniform adaptations to quadriceps.
Mangine, GT, Redd, MJ, Gonzalez, AM, Townsend, JR, Wells, AJ, Jajtner, AR, Beyer, KS, Boone, CH, La Monica, MB, Stout, JR, et al
PloS one. 2018;(8):e0198304
Abstract
Resistance training may differentially affect morphological adaptations along the length of uni-articular and bi-articular muscles. The purpose of this study was to compare changes in muscle morphology along the length of the rectus femoris (RF) and vastus lateralis (VL) in response to resistance training. Following a 2-wk preparatory phase, 15 resistance-trained men (24.0 ± 3.0 y, 90.0 ± 13.8 kg, 174.9 ± 20.7 cm) completed pre-training (PRE) assessments of muscle thickness (MT), pennation angle (PA), cross-sectional area (CSA), and echo-intensity in the RF and VL at 30, 50, and 70% of each muscle's length; fascicle length (FL) was estimated from respective measurements of MT and PA within each muscle and region. Participants then began a high intensity, low volume (4 x 3-5 repetitions, 3min rest) lower-body resistance training program, and repeated all PRE-assessments after 8 weeks (2 d ∙ wk-1) of training (POST). Although three-way (muscle [RF, VL] x region [30, 50, 70%] x time [PRE, POST]) repeated measures analysis of variance did not reveal significant interactions for any assessment of morphology, significant simple (muscle x time) effects were observed for CSA (p = 0.002) and FL (p = 0.016). Specifically, average CSA changes favored the VL (2.96 ± 0.69 cm2, p < 0.001) over the RF (0.59 ± 0.20 cm2, p = 0.011), while significant decreases in average FL were noted for the RF (-1.03 ± 0.30 cm, p = 0.004) but not the VL (-0.05 ± 0.36 cm, p = 0.901). No other significant differences were observed. The findings of this study demonstrate the occurrence of non-homogenous adaptations in RF and VL muscle size and architecture following 8 weeks of high-intensity resistance training in resistance-trained men. However, training does not appear to influence region-specific adaptations in either muscle.
-
7.
Noninvasive measurement of gastric accommodation by means of pertechnetate SPECT: limiting radiation dose without losing image quality.
Bennink, RJ, van den Elzen, BD, Kuiken, SD, Boeckxstaens, GE
Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2004;(1):147-52
Abstract
UNLABELLED The gastric accommodation response to a meal is impaired in conditions such as functional dyspepsia. At present, a barostat study is the gold standard to assess fundic relaxation in response to a meal. However, this method is invasive and possibly induces artifacts as a result of positive intraluminal balloon pressure. A noninvasive scintigraphic test has been developed to measure gastric accommodation in humans. The aim of this study was to refine this method, increasing the imaging time span and limiting the radiation dose applied without losing image quality, so that repeated measurements within 1 subject are possible without increasing radiation risk. METHODS Thirteen healthy volunteers without gastrointestinal symptoms were recruited from a student population. Each volunteer had previously undergone a barostat study. After an overnight fast, volunteers were scanned twice on separate days after intravenous injection of 200 MBq (99m)Tc-pertechnetate. On 1 occasion, volunteers were pretreated with a proton pump inhibitor. Thirty minutes after injection, sequential, 7-min SPECT scans (72 views, 10 s/view, 128 matrix) were acquired on a dual-head gamma-camera system before and up to 2 h after ingestion of a test meal. After reconstruction (filtered backprojection, ramp-Butterworth filter; order, 10; cutoff, 0.45 Nyquist), fundus volume was calculated semiautomatically by means of a threshold voxel volume tool. RESULTS Limiting injection dose from 370-740 MBq to 200 MBq (99m)Tc-pertechnetate resulted in good-quality images, with high target-to-background ratio up to 150 min after injection. This represents a significant dose reduction, from 4.6-9.3 to 2.5 mSv. There was no significant difference between SPECT fundic volumes or accommodation response with or without proton pump inhibitor pretreatment. Volume kinetics were similar to those with barostat studies, but gastric volumes were inferior. CONCLUSION Refining the methodology yields an improved noninvasive test for the assessment of gastric accommodation without unnecessarily increasing radiation burden. This technique enables repeated and serial measurement of gastric accommodation to a test meal, a process that is potentially useful for characterization and follow-up of dyspeptic patients with and without drug intervention.
-
8.
Adaptations in human muscle sarcoplasmic reticulum to prolonged submaximal training.
Green, HJ, Ballantyne, CS, MacDougall, JD, Tarnopolsky, MA, Schertzer, JD
Journal of applied physiology (Bethesda, Md. : 1985). 2003;(5):2034-42
Abstract
In this study, we employed single-leg submaximal cycle training, conducted over a 10-wk period, to investigate adaptations in sarcoplasmic reticulum (SR) Ca(2+)-regulatory proteins and processes of the vastus lateralis. During the final weeks, the untrained volunteers (age 21.4 +/- 0.3 yr; means +/- SE, n = 10) were exercising 5 times/wk and for 60 min/session. Analyses were performed on tissue extracted by needle biopsy approximately 4 days after the last training session. Compared with the control leg, the trained leg displayed a 19% reduction (P < 0.05) in homogenate maximal Ca(2+)-ATPase activity (192 +/- 11 vs. 156 +/- 18 micromol. g protein(-1). min(-1)), a 4.3% increase (P < 0.05) in pCa(50), defined as the Ca(2+) concentration at half-maximal activity (6.01 +/- 0.05 vs. 6.26 +/- 0.07), and no change in the Hill coefficient (1.75 +/- 0.15 vs. 1.76 +/- 0.21). Western blot analysis using monoclonal antibodies (7E6 and A52) revealed a 13% lower (P < 0.05) sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) 1 in trained vs. control in the absence of differences in SERCA2a. Training also resulted in an 18% lower (P < 0.05) SR Ca(2+) uptake and a 26% lower (P < 0.05) Ca(2+) release. It is concluded that a downregulation in SR Ca(2+) cycling in vastus lateralis occurs with aerobic-based training, which at least in the case of Ca(2+) uptake can be explained by reduction in Ca(2+)-ATPase activity and SERCA1 protein levels.
-
9.
Randomised controlled trial of postnatal sodium supplementation in infants of 25-30 weeks gestational age: effects on cardiopulmonary adaptation.
Hartnoll, G, Bétrémieux, P, Modi, N
Archives of disease in childhood. Fetal and neonatal edition. 2001;(1):F29-32
-
-
Free full text
-
Abstract
BACKGROUND It has previously been shown that, in preterm babies, routine sodium supplementation from 24 hours after birth is associated with increased risk of oxygen dependency and persistent expansion of the extracellular compartment. OBJECTIVE To explore whether this is mediated by a delayed fall in pulmonary artery pressure (PAP). Postnatal changes in PAP, estimated as the ratio of time to peak velocity to right ventricular ejection time, corrected for heart rate (TPV:RVET(c)), were compared in preterm infants who received routine sodium supplements that were either early or delayed. METHODS Infants were randomised, stratified according to sex and gestation, to receive a sodium intake of 4 mmol/kg/day starting either from 24 hours after birth or when a weight loss of 6% of birth weight was achieved. Echocardiographic assessment was made on the day of delivery (day 0), and on days 1, 2, 7, and 14. Babies with congenital heart disease were excluded. RESULTS There was no difference between the two groups in TPV:RVET(c) measured sequentially after birth. On within group testing, when compared with values at birth, the ratio was higher by day 3 in the early supplemented group, suggesting a more rapid fall in PAP compared with the late supplemented group, in whom a significant fall did not occur until day 14. CONCLUSIONS The timing of sodium supplementation after preterm birth does not appear to affect the rate of fall in PAP as measured by the TPV:RVET(c) ratio. The previous observation linking routine sodium supplementation from 24 hours after birth with increased risk of continuing oxygen requirement therefore does not appear to be mediated by a delayed fall in PAP. Instead, the increased risk of continuing oxygen requirement is likely to be a direct consequence of persistent expansion of the extracellular compartment and increased pulmonary interstitial fluid, resulting from a sodium intake that exceeded sodium excretory capacity. This adds further weight to the view that clinical management, in this case the timing of routine sodium supplementation, should be individually tailored and delayed until the onset of postnatal extracellular volume contraction, marked clinically by weight loss.