EAL

PDM: Metabolic Syndrome (2013)

Citation:

Zhang JQ, Ji LL, Fretwell VS, Nunez G. Effect of exercise on postprandial lipemia in men with hypertriglyceridemia. Eur J Appl Physiol. 2006; 98(6): 575-582.

PubMed ID: 17006711

Study Design:

Randomized Crossover Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To investigate the effect of exercise intensities on post-prandial lipemia and insulin resistance in middle-aged men with metabolic syndrome. We hypothesized that exercising at a higher intensity would more effectively attenuate a fat-rich meal-induced post-prandial lipemia and reduce insulin resistance than low intensity.

Inclusion Criteria:

Sedentary males with metabolic syndrome
Provided informed consent
Characteristics of metabolic syndrome were:
- Fasting TG of 150mg per dL or more
- HOMA-IR more than 2.5
- BMI 30kg/m² or more
- Waist-to-hip ratio higher than 0.90
Based on the classification by the World Health Organization, the subjects had characteristics of metabolic syndrome.

Exclusion Criteria:

Not described.

Description of Study Protocol:

Design

Randomized crossover trial.

Blinding Used

Implied with measurements.

Intervention

Exercise trials: Each subject performed a control trial (no exercise) and three exercise trials at 40%, 60% and 70% of their VO₂_max. The order of the trials was randomized and there were one to two weeks wash-out period between the trials. All subjects had a fat-rich meal in each trial.
In the exercise trials, subjects jogged on a treadmill for one hour at a designated intensity 12 hours prior to a fat meal ingestion
The milkshake composed of a combination of 270ml of whipping cream and 65g of specialty ice cream with walnuts (980kcal, 100g fat, 17g carbohydrates and 3g protein).

Statistical Analysis

A two-way (trial x time) analysis of variance (ANOVA) with repeated-measures was performed to test the effects of exercise intensities on TG and insulin data
The magnitude of total TG response was also quantified as TG AUC score (the area score under TG concentration curve over an eight-hour period) according to the trapezoidal rule
TG AUC score is a conventional index indicating plasma TG response to a fat-meal intake
Data of TG AUC score, fasting glucose and HOMA-IR were analyzed using one-way ANOVA with repeated measures
An ANOVA with significant F ratios (P<0.05) was followed by Tukey post-hoc tests
SAS software was used to perform the analysis
All data are reported as means ±SE.

Data Collection Summary:

Timing of Measurements

At initial visit, body mass index (BMI), body composition and waist-to-hip ratio were measured
After the initial assessment, subjects performed a VO₂_max test
During each trial, blood samples were taken at zero hours (before the meal) and two, four, six and eight hours after the meal
There were one to two weeks wash-out period between the trials.

Dependent Variables

Post-prandial hypertriglyceridemia (PPL) and insulin resistance: Ten ml of blood were drawn for each sample and collected in a vacutainer containing EDTA. Blood samples were separated by centrifugation at 4° Celsius for 15 minutes at 2,000g. Plasma TG and cholesterol concentrations were measured enzymatically using diagnostic kits.
Plasma glucose levels were measured using a diagnostic kit
Insulin levels were analyzed using a radioimmunoassays
Total HDL-C was measured by precipitating apolipoprotein B-containing lipoproteins with heparin-MnCl₂
HOMA-IR was calculated using Microsoft Excel based HOMA-IR calculator provided by the Oxford Center for Diabetes, Endocrinology and Metabolism
The intra-assay coefficients of variation for TG, total cholesterol, HDL-C, glucose and insulin were 1.5%, 0.8%, 1.4%, 1.9% and 2.8% respectively
Body composition was assessed using the sum of three skin-fold measurements specific for males (chest, abdomen and thigh). The mean of three measurements at each site was used to estimate body density and percent body fat.

Independent Variables

Exercise trials: Each subject performed a control trial (no exercise) and three exercise trials at 40%, 60% and 70% of their VO₂_max
In the exercise trials, subjects jogged on a treadmill for one hour at a designated intensity 12 hours prior to a fat-meal ingestion
All subjects had a fat-rich meal in each trial. The milkshake composed of a combination of 270ml of whipping cream and 65g of specialty ice cream with walnuts (980kcal, 100g fat, 17g carbohydrates and 3g protein).

Description of Actual Data Sample:

Initial N:10 men
Attrition (final N): 10 men
Age: Mean age 40.1+2.2 years
Anthropometrics:
- Mean body mass index (kg/m²) 31.3±1.3
- Mean fasting triglycerides (mg per dL) 263±25
Location: San Antonio, Texas.

Summary of Results:

Key Findings

The fasting plasma glucose concentration in the 70% intensity was lower than the non-exercise control (P=0.004), whereas 40% and 60% intensities did not elicit such glucose-lowering effects
The TG AUC score in 40%T was 30% lower (P=0.003), 60%T was 31% lower (P=0.02) and 70%T was 39% lower (P=0.02) than control
There were no significant differences in the TG AUC scores among the exercise trials (P>0.05)
The insulin concentrations in both 60%T and 70%T were lower than Control (P<0.01), which did not differ from 40%T
HOMA-IR in both 60% T (P=0.041) and 70%T (P=0.002) were lower than Control but not different from 40% T (HOMA-IR: Control=3.05±0.40, 40%T=2.67±0.35, 60%T=2.49±0.31, 70%T=2.21±0.27).

Author Conclusion:

The results from this study demonstrate that exercising at 40, 60, or 70% VO₂ max prior to a fat-rich meal ingestion noticeably attenuates postprandial lipemia response in subjects with the metabolic syndrome. These findings suggest that for physically inactive individuals with metabolic syndrome exercising at low to moderate intensity may be sufficient to attenuate postprandial lipemia and increase insulin sensitivity, whereas higher intensity exercise may be needed to normalize blood glucose. These data may provide an exercise-oriented therapeutic measure to individuals with metabolic syndrome.

Funding Source:

Not-for-profit

American Heart Association grant # 0150795Y

Other non-profit:

Reviewer Comments:

Small sample size. Only men were studied.

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
	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
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
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
	2.2.	Were criteria applied equally to all study groups?	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
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
	3.2.	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
	3.4.	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
	3.6.	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
	4.1.	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
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	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
	5.1.	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
	5.3.	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
	5.5.	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?		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?	N/A
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	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
	6.6.	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
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		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
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	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
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	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
	8.1.	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
	8.3.	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
	8.5.	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
	8.7.	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
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes