EAL

DM: Prevention and Treatment of CVD (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine the fatty acid composition of serum lipids fractions and to describe the lipid profile of type 2 diabetic patients with microalbuminuria following a standardized diet.

Inclusion Criteria:

type 2 diabetes diagnosis according to WHO guidelines
age<75 years
BMI <35
good compliance with diabetes treatment
triglyceride levels <4.52 mmol/l
urinary albumin excretion rate (UAER) < 200 microgram/min
normal liver and thyroid function
absence of urinary tract infections, other renal disease, and cardiac failure

Exclusion Criteria:

use of hypolipidemic agents

Description of Study Protocol:

Recruitment : subjects recruited from endocrine division of outpatient clinic

Design: Case-Control Study. Lipid profiles compared between normoalbuminuric and microalbuminuric patients.

Blinding used (if applicable): not applicable - lab tests

Intervention (if applicable)

2-month run-in period to achieve best possible metabolic control using diet, and oral hypoglycemic agents or insulin
patients were assessed a minimum of 4 weeks after the run-in period
followed American Diabetes Association guidelines
amount and source of protein not modified from subjects' usual diets
subjects given corn oil to prepare their food during experimental period
compliance assessed with 2-day weighed diet records and 24-h urinary nitrogen output at the end of the second and fourth week

Statistical Analysis

the characteristics of normoalbuminuric and microalbuminuric subjects were analyzed using the unpaired Student's t test, Mann-Whitney U test, chi-square tests or Fisher's exact test as appropriate
Pearson correlation coefficient was used for testing the relationships among the different fatty acids
multiple logistic regression analysis was performed with microalbuminuria as the dependent variable and possible associated factors were selected according to their significance (P< 0.10) in univariate analyses

Data Collection Summary:

Timing of Measurements

clinical evaluation at the end of the run-in period
fasting blood sample after at least 4 weeks on diet

Dependent Variables

HDL, HDL2, HDL3
total cholesterol
triglycerides
non-HDL cholesterol (diffference between total cholesterol and HDL)
LDL using Friedewald's formula
apolipoprotein B
fatty acids using thin-layer chromatography using a silica gel plate
plasma glucose level by glucose oxidase method
serum creatinine
HbA1c
fructosamine

Independent Variables

standardized diet and used corn oil for 4 weeks
compliance assessed through food records and urinalysis
genotype analysis of the amino acid variant (A54T) of the fatty acid-binding protein type 2 (FAPB2) gene

Control Variables

Description of Actual Data Sample:

Initial N: 72; 37 normoalbuminuric, 35 microalbuminuric; 49% men

Attrition (final N): 72

Age: 56.0±9.3 y for microalbuminuric group; no significant difference from normoalbuminuric group

Ethnicity: not specified

Other relevant demographics:

diabetes duration for microalbuminuric group; no significant difference from normoalbuminuric group
the microalbuminuric group was treated more often with insulin and presented signficantly higher HbA1c and fructosamine levels compared to the normoalbuminuric group

Anthropometrics: BMI 27.9±2.7 for microalbuminuric group; no significant difference from normoalbuminuric group

Location: Brazil

Summary of Results:

Serum lipid levels: no differences observed between groups for apolipoprotein B, total cholesterol, HDL cholesterol and fractions, LDL, non-HDL cholesterol, and triglycerides.

Fatty Acid Lipid Fractions in Microalbuminuria

Variables	Normoalbuminuriac	Microalbuminuric	P
Triglyceride Fraction
SFA	34.70±13.09	43.38±18.01	0.022
MUFA	31.20±13.21	31.83±13.37	0.840
PUFA	34.10±11.31	24.79±11.01	0.001
PUFA n-6	31.36±11.45	21.67±10.55	<0.0001
PUFA n-3	2.09±3.40	2.20±5.50	0.920
Cholesterol ester fraction
SFA	21.77±9.83	26.15±11.42	0.085
MUFA	17.25±10.20	17.92±12.08	0.799
PUFA	60.98±13.15	55.62±14.95	0.111
PUFA n-6	54.29±14.26	51.72±14.76	0.463
PUFA n-3	5.98±6.56	3.44±3.39	0.044
Phospholipid Fraction
SFA	54.23±14.13	57.29±16.48	0.406
MUFA	11.49±11.01	11.63±11.09	0.958
PUFA	34.28±11.93	30.74±12.85	0.236
PUFA n-6	31.94±10.77	28.44±11.79	.0199
PUFA n-3	1.93±1.89	1.87±1.44	0.876

Other Findings

In a multiple logistic regression analysis, the proportion of PUFA in the triglyceride fraction was the only factor associated with microalbuminuria ( P=0.019).

When the proportion of fatty acids was compared in different lipid fractions, we observed a significant positive correlation between triglyderice and phospholipid fractions regarding SFA (r=0.356; P=0.003) and PUFA content (r=0.566; P<0.001).

The genotype distribution of FAPB2 gene polymorphism was similar in both groups.

There were no significant differences in diet intake between groups.

Author Conclusion:

Type 2 patients with microalbuminuria presented lower levels of PUFA, especially of the n- family, in triglyceride fraction. Lower levels of PUFA in triglyceride fraction may represent a risk factor for cardiovascular disease and may contribute to the progression of renal disease in type 2 diabetic patients with microalbuminuria.

It is unlikely that the lower proportion of PUFA in the triglyceride fraction was due to decreased absorption of those fatty acids, because the proportion of each group showing polymorphism of the FABP2 gene was similar.

The differences in PUFA in the triglyceride fraction was not associated with diet composition, as there was no statistical difference in fatty acid composition of the diets.

Funding Source:

Reviewer Comments:

4-weeks of diet was not associated with the differences found in fatty acid composition of serum lipids.

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)	N/A

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?		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?	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)	N/A
	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.)	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.)	Yes
	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?		N/A
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	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%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	N/A
	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?	N/A
	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?	Yes
	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?	No
	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?	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
	9.1.	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