DFA: Linoleic Acid (LA) and Intermediate Health Outcomes (2011)


Kusunoki M, Tsutsumi K, Nakayama M, et al. Relationship between serum concentrations of saturated fatty acids and unsaturated fatty acids and the moemeostasis model insulin-resistance index in Japanese patients with typt 2 diabetes mellitus. J Med Invest. 2007, 54 (3-4): 243-247. PMID: 17878672.

PubMed ID: 17878672
Study Design:
Cross-Sectional Study
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To study the relationship between the serum concentrations of saturated and unsatruated fatty acids and the homeostasis model insulin resistance index in Japanese patients with type 2 diabetes mellitus.

Inclusion Criteria:
  • Patients with type 2 diabetes
  • Attended the outpatient clinic of Aichi Medical University Hospital, Aichi, Japan
  • Signed informed consent
  • Followed treatment of hypoglycemic agents or dietetic therapy or both for two to three years.
Exclusion Criteria:

Exclusion criteria were not listed in the article. 

Description of Study Protocol:
  • Recruitment: Patient population (out-patient clinic) in Aichi Medical University Hospital
  • Design: Cross-sectional survey
  • Blinding used (if applicable): Not mentioned
  • Statistical analysis: Correlation analysis was performed by Spearman's test. P-values less than 0.05 were considered significant. Mean age and standard deviation were reported. BMI average and standard deviation were also reported.
Data Collection Summary:
  • Timing of measurements: After following either a drug or a dietary routine or both for two to three years, blood samples were taken from the 93 patients in this study
  • Dependent variables: Serum concentrations of various fatty acids
  • Independent variables: Dietary therapy or hypoglycemic agents (pioglitazone, sulfonylurea or alpha-glucosidase inhibitor) or both 
  • Control variables: Middle-aged adults of normal body size.
Description of Actual Data Sample:
  • Initial N: 93 (70 males, 23 females)
  • Attrition (final N): Same as above
  • Age: Average of 54 years with a standard deviation of 11 years
  • Ethnicity: Japanese
  • Location: Aichi Medical University Hospital, Aichi, Japan.
Summary of Results:

Key Findings

  • The fasting serum glucose levels in the diabetic population were 135±43mg per dL. Insulin levels were 8.61±8.05uU per ml and HOMA-R were 2.91±2.75.
  • The correlations between serum SFA concentrations and HOMA-R were significant:and positively correlated, as listed below:
    • Lauric acid, myristic acid, palmitic acid and stearic acid. 
  • The correlations between the serum MUFA concentrations and HOMA-R were significant and positively correlated, as listed below:
    • Palmitoleic acid, oleic acid and erucic acid.
  • The correlations between the serum PUFA concentrations and HOMA-R were signficant and positively correlated, as listed below:
    • Eicosadienoic acid, dihomo-y-linolenic acid, docosatetraenoic acid and docosapentaenoic acid.

Other Findings

No sex differences were noted for the fasting serum glucose levels, insulin levels, HOMA-R or FFA levels.

Author Conclusion:
  • Some PUFA as well as some SFA were positively correlated with HOMA-R. In other words, the intake of those fatty acids aggravates insulin resistance.
  • These results indicate that the intake of dietary fatty acids must be well balanced in diabetic patients because it is not always true that refraining from SFA is proper advice. Nor is it always true that increasing PUFA is always helpful for diabetic patients. 
Funding Source:
University/Hospital: Aichi Medical University Hospital
Reviewer Comments:
  • This study did not have a control group
  • The authors did not state any of their research limitations or study restrictions
  • The authors did not describe the dose of the medicine that was used among the diabetic patient population, nor did they describe the type of dietary therapy
  • Additionally, there were no details provided regarding how vigorously the diet therapy was taught or implemented
  • Some of the patients followed both therapies and there were no details provided on that note
  • No before blood measurements
  • No intra-experimental blood measurements: Only a one-time blood test after the two- to three-year study period ended
  • No health information was provided on the patients
  • No exercise information was provided on each patient.
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? 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? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
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.) No
  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? ???
  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? 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? 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.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? No
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? No
  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? N/A
  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? 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? No
  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? ???
  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? ???
  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)? N/A
  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? No
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? N/A
  10.2. Was the study free from apparent conflict of interest? Yes