Skeletal muscle ATP turnover by 31P magnetic resonance spectroscopy during moderate and heavy bilateral knee-extension

During constant-power high-intensity exercise, the expected increase in oxygen uptake (V̇O2) is supplemented by a V̇O2 slow component (V̇O2 sc ), reflecting reduced work efficiency, predominantly within the locomotor muscles. The intracellular source of inefficiency is postulated to be an increase in the ATP cost of power production (an increase in P/W). To test this hypothesis, we measured intramuscular ATP turnover with (31)P magnetic resonance spectroscopy (MRS) and whole-body V̇O2 during moderate (MOD) and heavy (HVY) bilateral knee-extension exercise in healthy participants (n = 14). Unlocalized (31)P spectra were collected from the quadriceps throughout using a dual-tuned ((1)H and (31)P) surface coil with a simple pulse-and-acquire sequence. Total ATP turnover rate (ATPtot) was estimated at exercise cessation from direct measurements of the dynamics of phosphocreatine (PCr) and proton handling. Between 3 and 8 min during MOD, there was no discernable V̇O2 sc (mean ± SD, 0.06 ± 0.12 l min(-1)) or change in [PCr] (30 ± 8 vs. 32 ± 7 mm) or ATPtot (24 ± 14 vs. 17 ± 14 mm min(-1); each P = n.s.). During HVY, the V̇O2 sc was 0.37 ± 0.16 l min(-1) (22 ± 8%), [PCr] decreased (19 ± 7 vs. 18 ± 7 mm, or 12 ± 15%; P < 0.05) and ATPtot increased (38 ± 16 vs. 44 ± 14 mm min(-1), or 26 ± 30%; P < 0.05) between 3 and 8 min. However, the increase in ATPtot (ΔATPtot) was not correlated with the V̇O2 sc during HVY (r(2) = 0.06; P = n.s.). This lack of relationship between ΔATPtot and V̇O2 sc , together with a steepening of the [PCr]-V̇O2 relationship in HVY, suggests that reduced work efficiency during heavy exercise arises from both contractile (P/W) and mitochondrial sources (the O2 cost of ATP resynthesis; P/O)

Ectopic lipid storage in non-alcoholic fatty liver disease is not mediated by impaired mitochondrial oxidative capacity in skeletal muscle

Background and Aims. Simple clinical algorithms including the Fatty Liver Index (FLI) and Lipid Accumulation Product (LAP) have been developed as a surrogate marker for Non-Alcoholic Fatty Liver Disease (NAFLD). These algorithms have been constructed using ultrasonography, a semi-quantitative method. This study aimed to validate FLI and LAP as measures of hepatic steatosis, as measured quantitatively by proton magnetic resonance spectroscopy (1H-MRS). Methods. Data were collected from 168 patients with NAFLD and 168 controls who had undergone clinical, biochemical and anthropometric assessment in the course of research studies. Values of FLI and LAP were determined, and assessed both as predictors of the presence of hepatic steatosis (liver fat >5.5 %) and of actual liver fat content, as measured by 1H MRS. The discriminative ability of FLI and LAP was estimated using the area under the Receiver Operator Characteristic curve (AUROC). Since FLI can also be interpreted as a predictive probability of hepatic steatosis, we assessed how well calibrated it was in our cohort. Linear regression with prediction intervals was used to assess the ability of FLI and LAP to predict liver fat content. Results. FLI and LAP discriminated between patients with and without hepatic steatosis with an AUROC of 0.79 (IQR= 0.74, 0.84) and 0.78 (IQR= 0.72, 0.83), although quantitative prediction of liver fat content was unsuccessful. Additionally, the algorithms accurately matched the observed percentages of patients with hepatic steatosis in our cohort. Conclusions. FLI and LAP may be used clinically, and for metabolic and epidemiological research, to identify patients with hepatic steatosis, but not as surrogates for liver fat content

The effects of neoadjuvant chemoradiotherapy and an in-hospital exercise training programme on physical fitness and quality of life in locally advanced rectal cancer patients (The EMPOWER Trial): Study protocol for a randomised controlled trial

Background: The standard treatment pathway for locally advanced rectal cancer is neoadjuvant chemoradiotherapy (CRT) followed by surgery. Neoadjuvant CRT has been shown to decrease physical fitness, and this decrease is associated with increased post-operative morbidity. Exercise training can stimulate skeletal muscle adaptations such as increased mitochondrial content and improved oxygen uptake capacity, both of which are contributors to physical fitness. The aims of the EMPOWER trial are to assess the effects of neoadjuvant CRT and an in-hospital exercise training programme on physical fitness, health-related quality of life (HRQoL), and physical activity levels, as well as post-operative morbidity and cancer staging. Methods/Design: The EMPOWER Trial is a randomised controlled trial with a planned recruitment of 46 patients with locally advanced rectal cancer and who are undergoing neoadjuvant CRT and surgery. Following completion of the neoadjuvant CRT (week 0) prior to surgery, patients are randomised to an in-hospital exercise training programme (aerobic interval training for 6 to 9 weeks) or a usual care control group (usual care and no formal exercise training). The primary endpoint is oxygen uptake at lactate threshold ( V · o 2 at δ L ) measured using cardiopulmonary exercise testing assessed over several time points throughout the study. Secondary endpoints include HRQoL, assessed using semi-structured interviews and questionnaires, and physical activity levels assessed using activity monitors. Exploratory endpoints include post-operative morbidity, assessed using the Post-Operative Morbidity Survey (POMS), and cancer staging, assessed by using magnetic resonance tumour regression grading. Discussion: The EMPOWER trial is the first randomised controlled trial comparing an in-hospital exercise training group with a usual care control group in patients with locally advanced rectal cancer. This trial will allow us to determine whether exercise training following neoadjuvant CRT can improve physical fitness and activity levels, as well as other important clinical outcome measures such as HRQoL and post-operative morbidity. These results will aid the design of a large, multi-centre trial to determine whether an increase in physical fitness improves clinically relevant post-operative outcomes

fMRI of thermal pain:effects of stimulus laterality and attention

Brain activity was studied by fMRI in 18 healthy subjects during stimulation of the thenar eminence of the hand with either warm (nonpainful, 40°C) or hot (painful, 46-49°C) stimuli using a contact thermode. Experiments were performed on the right and left hand independently and with two attentional contexts: subjects either attended to pain or attended to a visual global motion discrimination task (to distract them from pain). Group analysis demonstrated that attended warm stimulation of the right hand did not produce any significantly activated clusters. Painful thermal stimulation of either hand elicited significant activity over a large network of brain regions, including insula, inferior frontal gyrus, cingulate gyrus, secondary somatosensory cortex, cerebellum, and medial frontal gyrus (corrected P < 0.05). Insula activity was distributed along its anterior-posterior axis and depended on the hand stimulated and attentional context. In particular, activity within the posterior insula was contralateral to the site of stimulation, tested using regions of interest (ROI) analysis: significant side x site interaction (P = 0.001). With attention diverted from the painful stimulus bilateral anterior insula activity moved posteriorly to midinsula and decreased in extent (ROI analysis: significant main effect of attention (P = 0.03)). The role of the insula in thermosensation and attention is discussed

fMRI of thermal pain: Effects of stimulus laterality and attention

Brain activity was studied by fMRI in 18 healthy subjects during stimulation of the thenar eminence of the hand with either warm (nonpainful, 40°C) or hot (painful, 46–49°C) stimuli using a contact thermode. Experiments were performed on the right and left hand independently and with two attentional contexts: subjects either attended to pain or attended to a visual global motion discrimination task (to distract them from pain). Group analysis demonstrated that attended warm stimulation of the right hand did not produce any significantly activated clusters. Painful thermal stimulation of either hand elicited significant activity over a large network of brain regions, including insula, inferior frontal gyrus, cingulate gyrus, secondary somatosensory cortex, cerebellum, and medial frontal gyrus (corrected P < 0.05). Insula activity was distributed along its anterior–posterior axis and depended on the hand stimulated and attentional context. In particular, activity within the posterior insula was contralateral to the site of stimulation, tested using regions of interest (ROI) analysis: significant side × site interaction (P = 0.001). With attention diverted from the painful stimulus bilateral anterior insula activity moved posteriorly to midinsula and decreased in extent (ROI analysis: significant main effect of attention (P = 0.03)). The role of the insula in thermosensation and attention is discussed

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Averaged number of steps at Baseline (before NACRT)) and at 48±5 hours post-NACRT: lines link data-points (closed circles) for individual patients, and open circles show overall mean±SEM. Mean change (SEM) between baseline and post-NACRT is −1627(712) steps, p = 0.039.

<p>Averaged number of steps at Baseline (before NACRT)) and at 48±5 hours post-NACRT: lines link data-points (closed circles) for individual patients, and open circles show overall mean±SEM. Mean change (SEM) between baseline and post-NACRT is −1627(712) steps, p = 0.039.</p

³¹P MRS (k_PCr) and CPET (o₂ at _L and o₂ at Peak) data at Baseline (before NACRT)) and at 48±5 hours post-NACRT: lines link data-points (closed circles) for individual patients, and open circles show overall mean±SEM. Mean changes (SEM) between baseline and post-NACRT are for k_PCr −0.4(0.1) min⁻¹, p = 0.001; for o₂ at _L −2.4(0.7) ml.kg⁻¹.min⁻¹, p = 0.004; and for o₂ Peak −4.0(1.3) ml.kg⁻¹.min⁻¹, p = 0.011.

<p>³¹P MRS (k_PCr) and CPET (o₂ at _L and o₂ at Peak) data at Baseline (before NACRT)) and at 48±5 hours post-NACRT: lines link data-points (closed circles) for individual patients, and open circles show overall mean±SEM. Mean changes (SEM) between baseline and post-NACRT are for k_PCr −0.4(0.1) min⁻¹, p = 0.001; for o₂ at _L −2.4(0.7) ml.kg⁻¹.min⁻¹, p = 0.004; and for o₂ Peak −4.0(1.3) ml.kg⁻¹.min⁻¹, p = 0.011.</p

Showing flow of patients through the study protocol.

<p>Post-NACRT tests carried out within 48±5 hours of finishing NACRT period.</p