EAL

DM: Prevention and Treatment of CVD (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To measure platelet aggregation of type 2 diabetics and healthy subjects against platelet aggregating factor (PAF), ADP, and arachidonic acid (AA) before and after a 4-week diet, containing meals of a Mediterranean-type diet offered from a fast-food Greek chain restaurant.

Inclusion Criteria:

type 2 diabetes
treated either by diet only or sulfonylureas and/or metformin

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment : not specified

Design

the diabetic subjects were randomized into two subgroups: group B and group C
both groups were treated with similar medication and maintained the same treatment during the study period
Group A (healthy subjects) and Group B followed a diet containing the chosen meals for 4 weeks
Group C was kept on the diet that they followed before entering the study
the intervention diets were planned to be isocaloric to the usual diet
no alcohol, additional medication, or heavy physical effort was allowed during the study period

Blinding used (if applicable): not used

Intervention (if applicable)

pre-study diet was 50-55% CHO, 20-25% fat, and 25% protein
intervention diet: 38±5% fat, 15±2% protein and 50±5% CHO
- subjects consumed meals that contained main dishes and salads from a Greek fast food chain: "Goody's"
- main dishes were tested in vitro for their ability to reduce PAF in washed rabbit platelets; the meals with the most potent anti-aggregating activity were chosen for the experimental diet
- the chosen fast-food meals were offered at breakfast and at lunch
- low-fat milk (<2%), bread, and feta cheese were included for breakfast
- between meals subjects ate a piece of fruit
- once a week subjects had a Greek legume soup

Statistical Analysis

comparison before and after the intervention period expressed as mean ± SD and analyzed using Wilcoxon sign rank test.
the Mann-Whitney test was performed in order to compare the EC₅₀ values of type 2 diabetics and healthy subjects before diet

Data Collection Summary:

Timing of Measurements: blood samples were obtained from all subjects before and after 4 weeks on the diet

Dependent Variables

platelet-rich plasma was isolated and the ability of platelets to aggregate towards PAF, ADP, and AA was tested
EC₅₀ (Equivalent Concentration for 50% aggregation), or the concentration of each of the aggregatory agents which induces 50% of maximum aggregation
total cholesterol, LDL, HDL, triglycerides
glucose, HbA1c
BMI

Independent Variables

dietary intake assessed by 3-day recall

Control Variables

Description of Actual Data Sample:

Initial N: 45 in intervention group: 25 men and 20 women ; 20 healthy age- and weight-matched control subjects (10 men and 12 women)

Attrition (final N): 45 in intervention (Groups B and C), 20 controls (Group A)

Age: 26-74, mean 56±15 years

Ethnicity: not specified

Other relevant demographics: mean HbA1c was below 7%; all women were postmenopausal. Controls were age and weight-matched.

Anthropometrics: mean wieght 77±9 kg

Location: Greece

Summary of Results:

Ability of main dishes to prevent platelet-aggregation

Fast food macaroni and cheese; chicken filet with lettuce, carrot, lemon, tomato, and mustard; a dish of black bread, feta cheese, black olives, tomato, and origanum; and a "pita burger classic" ( white bread pie, minced beef, onions, parsley, tomato, cucumber, yougurt and garlic had the most biological action against PAF.
The caesar salad and the chef salad had the most important biological action against PAF
The dishes exerting only a slight inhibition of PAF were: pastitsio, lentil soup, boiled chicken with rice, roast meat with potatoes, roast fish with potatoes, boiled root vegetables, and a salad of carrot and cabbage.

Effect on serum lipids and glycemic control

There was no significant difference in all the subjects before and after the diet period for cholesterol, LDL, HDL, triglycerides, glucose, HbA1c and BMI.

EC₅₀ values of type 2 diabetic and healthy subjects before and after diet intervention

Variables	EC₅₀ Before Diet	EC₅₀ after diet	P-value
Group A (healthy subjects) PAF x 10^-7 M	1.45±1.47	2.70±2.59	0.023
Group B (diabetic subjects)PAF x 10^-7 M	1.02±1.37	2.40±4.65	0.019
Group C PAF x 10^-7 M (Control diet)	0.774±0.522	0.831±0.500	0.285

Other Findings

The diet increased the EC₅₀ of ADP by 113%, p=0.010 in group A and 31% (p=0.004) in Group B.

Group C (usual diet) did not show any significant differences in PAF, ADP, or AA after the diet.

Author Conclusion:

PAF plays a critical role in atherosclerosis and may trigger the initiation of atherogenesis. The existence of PAF antoagonists in foodstuffs may contribute to the slowing down of the atherosclrotic process by improving platelet function.

In terms of its effects on platelet aggregation of type 2 diabetic subjects, a Mediterranean-type diet appears to antithrombotic, anti-inflammatory, and antiatherogenic.

Funding Source:

Reviewer Comments:

This study was interesting in that they tested 22 menu items in the laboratory for the antagonistic effect against PAF on washed rabbit platelets. They determined the diets of the study groups based on these results, making sure that the control Group C, consumed only those dishes with low activity.

Recruitment methods not specified, baseline characteristics between groups not discussed.

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?	No
2.	Was the selection of study subjects/patients free from bias?		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
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
3.	Were study groups comparable?		???
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	???
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	???
	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?	N/A
	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)?	No
	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?	N/A
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