Postprandial triglyceride is associated with fasting triglyceride and HOMA-IR in Korean subjects with Type 2 Diabetes
This paper is an in-depth review of an original empirical research study published in a peer reviewed journal. The paper will therefore focus on describing the research questions, subjects, sampling and research methods employed during the study, variables measured or observed and finally the conclusions of the study. My opinion on the study will be provided in the latter part of the paper.
“Postprandial triglyceride is associated with fasting triglyceride and HOMA-IR in Korean subjects with Type 2 Diabetes” was a study by Lee et al (2010) that was first published in the Diabetes and Metabolism Journal on March 14 2011.
/> The research question for this particular study was “what are the metabolic relation as well as the clinical implications of post-prandial triglyceridemia (TG) in Korean patients with type 2 diabetes following a low-fat diet?”
For this specific study, purposive non-random sampling was used to obtain the sample. In this case, the study participants’ had to satisfy a pre-designated inclusion criterion. A comprehensive analysis of the patients’ medical records was therefore done to identify the patients who were eligible for the study. The 639 study subjects selected were all Korean nationals who had to have been enrolled in the registry for diabetes at the Severance diabetes center in the period between July 2009 and August 2010. In addition, the subjects had to be first time visitors to the center who were having either diabetes complication work-ups done or were scheduled to undergo a standardized mixed-meal simulation test. All patients on insulin and/or steroid therapy or those who had thyroid disorders, severe kidney or liver disease, hematologic and malignant diseases were excluded from the study. The other group of patients who were excluded from the study was constituted by those who were either pregnant or heavy alcoholics.
Pertaining to the research method, the study was a cross sectional retrospective study in which the study participants were divided into two groups. Group I comprised of 539 patients (n=539) who had type 2 diabetes. Group II on the other hand had 100 (n=100) patients with impaired fasting blood glucose (IFG). The patients ingested a standardized liquid mixed-meal that was low in fat content (total 500Kcal, 17.5g protein, 17.5g fat and 68.5g carbohydrate) following which blood samples for glucose, insulin, C-peptide and TG analysis were collected at 0 (basal) and 90 (stimulated) minutes respectively. The authors then compared fasting and postprandial TG. In addition, they analyzed the association between postprandial TG and a number of demographic and metabolic parameters.
Statistical analysis was done using SPSS version 18.0. Data for normally distributed variables was given in terms of means ±standard deviation (SD) and median (25th and 75th percentile values). Mean and median values for the two groups were compared using either Mann-Whitney U-test or the unpaired Student’s t-test depending on which was appropriate. Correlation between continuous parameters was determined using Pearson’s correlation coefficient. Multiple linear regression analysis was done using a number of clinical and laboratory factors such as age, waist circumference, sex, glucose AC and HOMA-IR as the independent factors and postprandial TG as the dependent factor. For all the statistical procedures, an alpha level of 0.05 (α=0.05) was accepted as significant.
The variables measured in this particular study included anthropometric, laboratory and β-cell functional status. Waist circumference (WC) was obtained by placing the tape measure horizontally at the level of the umbilicus and asking the patient to exhale gently. BMI was calculated by dividing weight in kilograms by height in meters. Total cholesterol, blood urea nitrogen, plasma TG, HDL-C, AST, ALT, creatinine, LDL-C, serum insulin and C-peptide levels were the lab variables measured. Insulin sensitivity, pancreatic β-cell function and pancreatic β-cell secretary function were also calculated.
The authors of the study after analyzing the data concluded that fasting TG levels were strongly correlated with postprandial TG. The study also concluded that low fat meal diets have near identical effects on both fasting and postprandial TG in Korean patients with T2D. Further, the authors concluded that there was a stronger relationship between postprandial TG and insulin resistance measured by HOMA-IR than that of the latter with fasting TG amongst the Korean group of patients studied.
On my thoughts about the study, I liked the study for a number of reasons which I will outline. Firstly, it sought to address paucity in research whereby there existed a knowledge gap as far as metabolic and clinical implications of postprandial TG in Korean patients with T2D following a low fat standardized mixed meal simulation diet is concerned. The findings of this study therefore augment those from similar studies conducted amongst other populations. The other studies had concurred in their conclusions that non-fasting TG was more superior to fasting TG in its association with metabolic syndrome being strongly correlated with waist circumference and carotid IMT. Further, authors to these studies had postulated that postprandial TG is in its own right an independent risk factor for cardiovascular disease.
Secondly, the authors provided adequate and relevant background information to justify their study. The study design employed is also adequately described hence it is possible to replicate the study and thereby test the validity and reliability of the study findings. The size of the study sample on the other hand was adequate to impart power and significance to the study findings. Notably, confounding was controlled via conducting multiple regression analysis on both clinical and demographic variables. More importantly, multiple regression analysis enabled the authors to identify the association between the independent variables and the dependent variable (post-prandial TG) (Bates, 2009, p.4).
On the treatment of data, the statistical methods employed in performing the data analysis were appropriate for the data collected. For instance, Mann-Whitney’s U-test was used to compare the medians of the two groups. In this case, its use is justified since the Mann-Whitney U-test is normally used to compare continuous parameters of two independent populations with regard to a specified criterion which is at the least measured on an ordinal scale. Likewise, the Student’s T-test was used correctly in the comparison of means between the two independent groups that is groups I and II (Howell, 2010, p.542). The use of Pearson’s coefficient to help determine the relationship between continuous parameters was not only appropriate but necessary because the Spearman’s correlation coefficient would not have been applicable in this case. However, its use limited the significance of the correlation to only the variables whose correlation was computed (Howell, 2010, p.542).
Concerning the presentation of findings, the authors of the study presented the results of their study in a coherent manner using both descriptive statistics and figures. The use of mean, medians and statistical level of significance enhanced the comparison power of the findings between the two groups and with those from similar studies. The overall conclusions made by the authors were also in tandem with the data collected (Bates, 2009, p.27).
Regarding the aspects of the study I would have done differently, to confer more validity to the anthropometric measurements like the waist and hip circumference, I would have opted for a different approach whereby I would have obtained three measurements of each and then calculated their average.
In conclusion therefore, the empirical research study by Lee et al. (2010) explored some of the risk factors of metabolic syndrome that is fasting and post-prandial triglyceride levels amongst a population previously not studied. Further, the study findings elucidated on the metabolic and clinical implications of the two triglyceride levels on this population. My overall opinion on the study is that the authors of the study employed knowledge on research design, sampling methods as well as other aspects of research in an appropriate and fruitful manner.
Bates, R.A. (2009). Fast fundamentals: Research in organizations. In R.A. Swanson & E.F.
Holton (Ed.), Foundations and methods of inquiry (pp.3-27). Louisiana, LA: Berrett-
Howell, D.C. (2010). Fundamental statistics for the behavioral sciences (7th ed.). Belmont, CA:
Wadsworth Cengage Learning.
Lee, S.H., Lee, B.W., Won, H.K., Moon, J.H., Kim, K.J., Kang, E.S., Cha, B.S., Lee, H.C.
(2011). Postprandial triglyceride is associated with fasting triglyceride and HOMA-IR in
Korean subjects with type 2 diabetes. Diabetes Metab J., 35(4), 404-410.
Portney, L. & Watkins, M. P. (2009). Foundations of clinical research applications to practice.
Upper Saddle River, NJ: Prentice Hall Inc.