PDM: Prediabetes (2013)

Citation:

Melton CE, Tucker PS, Fisher-Wellman KH, Schilling BK, Bloomer RJ. Acute exercise does not attenuate postprandial oxidative stress in prediabetic women. Phys Sportsmed. 2009; 37(1): 27-36.

PubMed ID: 20048485
 
Study Design:
Randomized Crossover Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To investigate the effects of a single bout of aerobic exercise compared with a no-exercise control condition using a crossover design on post-prandial oxidative stress in a sample of obese prediabetic individuals.

Inclusion Criteria:
  • Provided both verbal and written consent
  • Obese (body mass index higher than 30kg/m2) prediabetic women, defined as having fasting blood glucose of 100 to 125mg per dL
  • Only women were recruited to keep the sample homogenous
  • Non-smoking
  • Reported no use of medications including oral contraceptives or nutritional supplements.
Exclusion Criteria:

Not described.

Description of Study Protocol:

Recruitment

Obese women with a body mass index higher than 30kg/mwith a fasting blood glucose of 100 to 125mg per dL.

Design

Randomized crossover trial.

Blinding Used

Implied with measurements.

Intervention

  • Subjects consumed a high-fat meal with and without a session of aerobic exercise 15 minutes preceding the meal (45-minute duration, 65% heart rate reserve)
  • Subjects were assigned to either consume the test meal with or without first performing a single bout of exercise. Under exercise conditions, the initial (pre-meal) fasting blood sample was obtained before the exercise bout in an attempt to control for any transient increase in RONS due to exercise, which may have influenced our chosen biomarkers at the pre-meal collection time if the sample was obtained immediately after the completion of the exercise. The aerobic exercise was performed on a cycle ergometer after intake of a test meal and blood sampling.
  • Exercise sessions lasted 45 minutes and was performed at an intensity equal to 65% heart rate reserve. Heart rate was continuously observed via Polar heart rate monitors and participants were encouraged by research assistants to maintain the precise heart rate during the entire session.
  • For the test meal, subjects reported to the lab in the morning (6:00 a.m. to 10:00 a.m.) after a 10-hour overnight fast. Subjects only reported to the lab in the early follicular phase of the menstrual cycle because circulating estrogen is lowest at this time. A pre-meal blood sample was collected after a 10-minute rest period and participants consumed the test meal within 15 minutes followed by consumption of the test meal. The meal consisted of a milkshake made with a combination of whole milk, ice cream and heavy whipping cream.

Statistical Analysis

  • Outcome variables were analyzed using a 2x5 [(condition-exercise/no exercise)x(time)] repeated measures analysis of variance (ANOVA)
  • Time of main effects were analyzed using Tukey's post hoc tests
  • Dietary and physical activity data were analyzed using a T-test
  • All analyses were performed using JMP statistical software version 4.0.3
  • Statistical significance was set at P≤0.05.
  • Data are presented as mean ±SEM.

 

Data Collection Summary:

Timing of Measurements

Measurements made pre-meal and post-meal.

Dependent Variables

  • A maximal GXT was conducted to determine aerobic capacity (VO2 max) using a Lode Excalibur Sports cycle ergometer, while expired gases were collected via facemask and analyzed using a SensorMedics Vmax 229 metabolic system to determine maximal oxygen consumption (VO2)
  • The test continued until the participant could no longer continue because of fatigue (rpms drop below 50)
  • Before and during the GXT, heart rate was continuously monitored via electrocardiographic (ECG) tracings using a SensorMedics Max-1ECG unit
  • Blood pressure was monitored and the Borg scale of exertion was used to monitor participants' level of perceived work
  • Participants were allowed an active cool-down period for several minutes until their heart rate fell below 120 beats per minute or stabilized
  • Blood triglycerides and oxidative stress biomarkers: Venous blood samples were taken from participants' forearm veins via needle and EDTA containing pre-meal at one, two, four and six hours post-meal. Blood was processed immediately and stored in multiple aliquots at -80 degrees Celsius until analyzed.
  • Antioxidant capacity was measured in plasma using the Trolox equivalent  antioxidant capacity assay and procedures outlined by the reagent provider intra-assay coefficient of variation (CV)=5.3%
  • Xanthine oxidase and hydrogen peroxide were measured in plasma using the Amplex Red reagent method
  • Malondialdehyde (MDA) was measured in plasma
  • Blood triglycerides, glucose, total cholesterol and high-density lipoprotein (HDL) were assayed using serum according to standard enzymatic procedures
  • Total, HDL, and LDL cholesterol were measured in pre-meal samples only and used for simply description. The CV for the lipid and glucose assays was less than 5%. Assays were performed in duplicate on first thaw.

Independent Variables

  • Subjects consumed a high-fat meal with and without a session of aerobic exercise 15 minutes preceding the meal (45-minute duration, 65% heart rate reserve)
  • Subjects were assigned to either consume the test meal with or without first performing a single bout of exercise. Under exercise conditions, the initial (pre-meal) fasting blood sample was obtained before the exercise bout in an attempt to control for any transient increase in RONS due to exercise, which may have influenced our chosen biomarkers at the pre-meal collection time if the sample was obtained immediately after the completion of the exercise. The aerobic exercise was performed on a cycle ergometer after intake of a test meal and blood sampling.
  • Exercise sessions lasted 45 minutes and were performed at an intensity equal to 65% heart rate reserve. Heart rate was continuously observed via Polar heart rate monitors and participants were encouraged by research assistants to maintain the precise heart rate during the entire session.
  • For the test meal, subjects reported to the lab in the morning (6:00 a.m. to 10:00 a.m.) after a 10-hour overnight fast. Subjects only reported to the lab in the early follicular phase of the menstrual cycle because circulating estrogen is lowest at this time. A pre-meal blood sample was collected after a 10-minute rest period and participants consumed the teat meal within 15 minutes followed by consumption of the test meal. The meal consisted of a milkshake made with a combination of whole milk, ice cream and heavy whipping cream.

Control Variables

  • Participants were asked not to perform any strenuous physical tasks 48 hours before the GXT
  • Participants were asked to maintain their normal diet and activity and to record these variables on data forms in the seven days before the test meal. Dietary records were reviewed with each participants upon return, then analyzed for total dietary energy, protein, carbohydrate, fat and a variety of antioxidant micronutrients.
  • Activity records were reviewed with each participant upon return to enhance accuracy of reporting and entry.
Description of Actual Data Sample:
  • Initial N: 16 women
  • Attrition (final N): 16 women
  • Age: Mean age 30±3 years
  • Other relevant demographics: Mean total cholesterol 191±13mg per dL
  • Anthropometrics: Mean body mass index 32±2kg/m2
  • Location: Helsinki, Finland.
Summary of Results:

Key Findings

  • No interaction or condition main effects were noted (P>0.05).
  • Time main effects were noted for XO, H2O2, MDA and TAG (P<0.0001) with values higher from 1 to 6 hours postmeal compared with premeal and for TEAC (P=0.05) with values lower at 4 hours postmeal.
  • Glucose remained relatively unchanged (P>0.05).
  • Anthropometric and blood pressure outcomes were not reported.

 

 

 

Author Conclusion:

The results of this study showed that acute exercise performed at the intensity and duration of the present study, does not influence post-prandial TAG and oxidative stress in obese prediabetic women. Such women may require a great volume of exercise for measurable effects.

Funding Source:
University/Hospital: University of Memphis
Reviewer Comments:
  • Small sample size and only women studied. 
  • Short duration of study. 
  • The authors noted that the prediabetic status of these participants may have influenced the findings.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? No
2. Was the selection of study subjects/patients free from bias? No
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? No
  2.4. Were the subjects/patients a representative sample of the relevant population? No
  3. Were study groups comparable? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
  4. Was method of handling withdrawals described? Yes
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
  5. Was blinding used to prevent introduction of bias? Yes
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
  6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? ???
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? ???
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? ???
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? ???
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
  7. Were outcomes clearly defined and the measurements valid and reliable? ???
7. Were outcomes clearly defined and the measurements valid and reliable? ???
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? ???
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? ???
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
  8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
  9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
  10. Is bias due to study's funding or sponsorship unlikely? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes