The aim of this study was to determine the chronic (≥72 h postexercise) effects of high-intensity interval training (HIIT) on postprandial lipemia and metabolic markers in healthy volunteers. Eight ...physically active young men (mean ± SD: age 22 ± 3 yr, height 1.77 ± 0.07 m, body mass 67.7 ± 6.2 kg) underwent two 6-h mixed-meal tolerance tests and resting vastus lateralis muscle biopsies before the first session and ≥72 h after the final session of 4 wk of HIIT 16 sessions in total; 10 × 60-s bouts of cycling at 90% maximal oxygen uptake (V̇o
), interspersed with 60-s intervals at 45% V̇o
. Arterialized and deep venous blood samples from across the forearm, brachial artery blood flow measurements, and whole-body indirect calorimetry data were obtained before, and at regular intervals for 6 h after, consumption of a standardized mixed meal. The main findings revealed that, when assessed ≥72 h postexercise, postprandial free fatty acid (FFA) uptake across the forearm was increased in response to exercise training (
= 0.025). However, 4 wk of HIIT did not alter fasting or postprandial circulating triglyceride concentrations or their tissue uptake, despite a 10.2% ± 7.7% improvement in V̇o
(
= 0.004). Protein content of adipose triglyceride lipase in the vastus lateralis at rest was reduced by 25% ± 21% (
= 0.01). Collectively, these findings suggest that 4 wk of HIIT enhances postprandial clearance of FFA when assessed ≥72 h postexercise but does not confer persisting (training) adaptations in postprandial triglyceridemia.
When assessed ≥72 h after the last exercise session, 4 wk of high-intensity interval training (HIIT) did not improve triglyceridemia but enhanced free fatty acid uptake into muscle with a concurrent reduction in skeletal muscle adipose triglyceride lipase protein content. This suggests that previously reported acute reductions in postprandial triglyceridemia following a single bout of HIIT do not translate to sustained improvements after 4 wk of HIIT, supporting the concept of frequent exercise for the maintenance of lipemic control.
Results from randomised controlled trials (RCTs) testing the effect of vitamin C supplementation on blood pressure (BP) have been inconsistent. This systematic review evaluated the effects of vitamin ...C supplementation on BP and included RCTs testing the effects of vitamin C supplementation alone, on systolic and diastolic BP in adult participants (≥18 years). Random-effect models were conducted to estimate the pooled effects of vitamin C supplementation on BP. A total of 20 studies with 890 participants were included. The median dose of vitamin C was 757.5 mg/d, the median duration was 6 weeks. Vitamin C supplementation was found to reduce systolic BP by -3.0 mmHg (95%CI: -4.7, -1.3 mmHg;
= 0.001). Subgroup analysis showed a more pronounced effect on systolic BP in patients with hypertension (-3.2 mmHg, 95%CI -5.2, -1.2 mmHg,
= 0.002) and diabetes (-4.6 mmHg, 95%CI -8.9, -0.3 mmHg,
= 0.03). Further research needs to evaluate the long-term effect of vitamin C on BP in populations with impaired cardio-metabolic health.
An inability to respond to nutrition could be implicated in low muscle mass in Crohn's disease. We aim to determine skeletal muscle metabolic response to feeding in Crohn's disease and healthy ...volunteers.
Twenty asymptomatic Crohn's disease participants (15.6 ± 0.5 yrs; BMI 20.6 ± 0.9 kg/m2); 9 with active disease (faecal calprotectin, 808 ± 225 ug/g and C-reactive protein, 2.2 ± 1.2 mg/dl), 11 in deep remission (faecal calprotectin, 61 ± 12 ug/g and C-reactive protein, 0.3 ± 0.2 mg/dl) and 9 matched healthy volunteers (16.0 ± 0.6 yrs; BMI 20.7 ± 0.6 kg/m2) were recruited. Participants had a dual energy X-ray absorptiometry scan, handgrip dynamometer test, wore a pedometer and completed a food diary. Arterialised hand and venous forearm blood samples were collected concurrently and brachial artery blood flow measured at baseline and every 20 min for 2 hrs after the ingestion of a standardised liquid meal. Net balance of branched chain amino acids (BCAA) and glucose were derived.
Controls had a positive mean BCAA balance. CD participants had an initial anabolic response to the meal, with increasing BCAA balance between t = 0 & t = 20, but returned to negative by t = 60. This was associated with reduced FFM z-scores in CD but not with insulin resistance or disease activity. Exploratory analyses suggest that negative postprandial BCAA response seen in CD is predominant in males (p = 0.049), with associated lower appendicular muscle mass (p = 0.034), higher muscle fatigue (p = 0.014) and reduced protein intake (p = 0.026).
The inability to sustain a positive protein balance postprandially could provide an explanation for the reduced muscle mass seen in CD. Further mechanistic studies will be needed to confirm these findings.
•A positive skeletal muscle protein balance is only seen in healthy controls.•Neutral protein balance and reduced FFM z-scores in CD.•No other differences in body composition or muscle physiology between CD & control.•Negative protein balance, lower muscle mass and function in male CD.
The optimal pattern of sedentarism displacement and mechanisms underlying its health effects are poorly understood. Therefore, the aim of this study was to quantify muscle-tendon adaptation in ...response to two different sedentarism displacement interventions and relate any adaptations to functional outcomes. Thirty-four older women (73±5yrs) underwent skeletal muscle-tendon size and functional assessments. Participants were randomly allocated to: Sedentary behavior fragmentation (SBF), Light intensity physical activity (LIPA), or Control groups. Measures were taken at weeks 0 and 8. Gait speed significantly increased (p=0.003), in both experimental groups (SBF: 0.06 ± 0.08m/s, 6±10%, LIPA: 0.06 ± 0.07m/s, 6±6%), but not control (-0.02 ± 0.12m/s, -2±9%). Accordingly, the relative change in Vastus Lateralis muscle volume, accounted for 30% (p=0.027), and 45% (p=0.0006) of the explained variance in the relative change in gait speed, for SBF and LIPA respectively. Gastrocnemius Medialis fascicle length changes were positively associated with gait speed changes, following LIPA exclusively (R
= 0.50, p=0.009). This is the first study to show SBF and LIPA are adequate loading in older women, with related muscle adaptation and clinically relevant gait speed improvements. Such adaptations appear similar irrespective of whether sedentarism displacement is prescribed in a single bout (LIPA) or in frequent micro-bouts (SBF).
Objective: To determine activity patterns and perceived barriers to exercise in ambulant people with neuromuscular disease compared with ambulatory controls.
Design: Prospective controlled parallel ...group design.
Setting: Outpatient clinic and community.
Subjects: Thirteen ambulatory people with neuromuscular disease and 18 ambulatory controls.
Main measures: Heart rates were recorded during sedentary activity and treadmill walking at various speeds to indicate activity threshold (flex heart rate), followed by ambulatory heart rate monitoring over two weekdays and one weekend day. The EPIC-Norfolk Physical Activity Questionnaire-2 and Barriers to Physical Activity and Disability Survey were completed.
Results: Participants with neuromuscular disease were less active than controls as estimated by both the EPIC-Norfolk Physical Activity Questionnaire-2, P<0.004, and the flex heart rate method, P<0.05. The number of perceived barriers was greater in the neuromuscular group, a mean of 7 (SD 4.2) barriers, compared with mean 3 (SD 2.1) barriers for controls, P<0.05. Specific barriers differed, with the barriers of `pain', `lack of energy' and `exercise is too difficult' showing the greatest discrepancy and being higher in the neuromuscular disease group.
Conclusion: Physical activity, as determined by two different methods, was less and barriers to exercise greater in people with neuromuscular disease compared with healthy controls. Specific barriers were different in the two groups. This information could assist in the design of achievable and effective exercise programmes for people with neuromuscular disease.
Adipokines have emerged as central mediators of insulin sensitivity and metabolism, in part due to the known association of obesity with metabolic syndrome disorders such as type 2 diabetes. Recent ...studies in rodents have identified the novel adipokine vaspin as playing a protective role in inflammatory metabolic diseases by functioning as a promoter of insulin sensitivity during metabolic stress. However, at present the skeletal muscle and adipose tissue expression of vaspin in humans is poorly characterised. Furthermore, the functional role of vaspin in skeletal muscle insulin sensitivity has not been studied. Since skeletal muscle is the major tissue for insulin-stimulated glucose uptake, understanding the functional role of vaspin in human muscle insulin signalling is critical in determining its role in glucose homeostasis. The objective of this study was to profile the skeletal muscle and subcutaneous adipose tissue expression of vaspin in humans of varying adiposity, and to determine the functional role of vaspin in mediating insulin signalling and glucose uptake in human skeletal muscle. Our data shows that vaspin is secreted from both human subcutaneous adipose tissue and skeletal muscle, and is more highly expressed in obese older individuals compared to lean older individuals. Furthermore, we demonstrate that vaspin induces activation of the PI3K/AKT axis, independent of insulin receptor activation, promotes GLUT4 expression and translocation and sensitises older obese human skeletal muscle to insulin-mediated glucose uptake.
Abstract Context Skeletal muscle plays a central role in the storage, synthesis, and breakdown of nutrients, yet little research has explored temporal responses of this human tissue, especially with ...concurrent measures of systemic biomarkers of metabolism. Objective To characterize temporal profiles in skeletal muscle expression of genes involved in carbohydrate metabolism, lipid metabolism, circadian clocks, and autophagy and descriptively relate them to systemic metabolites and hormones during a controlled laboratory protocol. Methods Ten healthy adults (9M/1F, mean ± SD age 30 ± 10 years; BMI 24.1 ± 2.7 kg·m−2) rested in the laboratory for 37 hours with all data collected during the final 24 hours (08:00–08:00 hours). Participants ingested hourly isocaloric liquid meal replacements alongside appetite assessments during waking before a sleep opportunity from 22:00 to 07:00 hours. Blood samples were collected hourly for endocrine and metabolite analyses, with muscle biopsies occurring every 4 hours from 12:00 to 08:00 hours the following day to quantify gene expression. Results Plasma insulin displayed diurnal rhythmicity peaking at 18:04 hours. Expression of skeletal muscle genes involved in carbohydrate metabolism (Name, Acrophase hours: GLUT4, 14:40; PPARGC1A, 16:13; HK2, 18:24) and lipid metabolism (FABP3, 12:37; PDK4, 05:30; CPT1B, 12:58) displayed 24-hour rhythmicity that reflected the temporal rhythm of insulin. Equally, circulating glucose (00:19 hours), nonesterified fatty acids (04:56), glycerol (04:32), triglyceride (23:14), urea (00:46), C-terminal telopeptide (05:07), and cortisol (22:50) concentrations also all displayed diurnal rhythmicity. Conclusion Diurnal rhythms were present in human skeletal muscle gene expression as well systemic metabolites and hormones under controlled diurnal conditions. The temporal patterns of genes relating to carbohydrate and lipid metabolism alongside circulating insulin are consistent with diurnal rhythms being driven in part by the diurnal influence of cyclic feeding and fasting.
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