Optimal Dietary Fat Pattern to Prevent Cardiovascular Disease Among Type 2 Diabetes

Effects of Fatty Acid Composition Ratios of Oral Fatty Loads on the Dynamic Metabolism of Postprandial Lipid and Triglyceride-Rich Lipoproteins in Chinese NIDDM Out-Patients

Cardiovascular complications are the leading cause of death among type 2 diabetic patients. Postprandial triglyceride-rich lipoproteins (ppTRLs) are atherogenic. Dietary fatty acid quality, that is, dietary fatty acid composition is related to atherogenesis. However, to date, the overall influence of dietary fatty acid compositions on lipids in different subfractions of ppTRLs still remains unknown among Chinese diabetic patients. This paucity of evidence may limit the establishment of optimal recommendation of dietary fatty acid composition for type 2 diabetes. We have 2 hypotheses:

1. Different dietary fatty acid compositions lead to differential overall responses of lipids in four subfractions of ppTRLs over postprandial 6 h.
2. One dietary fatty acid composition will be identified as anti-atherogenesis for future study as it can improve atherogenic ppTRLs.

Atherosclerosis is the leading cause of death and disability among patients with type 2 diabetes mellitus. These patients characteristically have hypertriglyceridemia, high VLDL and low HDL-cholesterol in the fasting status. During day-time hours, most individuals are in a postprandial state and the composition of postprandial lipoproteins may play a more important role on metabolic outcome than fasting levels. Postprandial triglyceride-rich lipoproteins (ppTRLs) are atherogenic, and longer residence time and higher concentrations of chylomicron and VLDL remnants in the circulation are significant predictors of coronary heart disease (CHD). Abnormal postprandial lipemia is highly prevalent in diabetic patients, even in individuals with a normal fasting triglyceride concentration. It has been suggested that diabetes mellitus is associated with decreased catabolism of chylomicron remnants, prolonged residence of chylomicron and VLDL remnants in the circulation. Therefore, a diet with favorable effects on ppTRLs should be useful to prevent atherosclerosis among type 2 diabetes patients.

It is well known that dietary saturated fatty acids (SFA) increase the risk for CHD while monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) decrease the risk for CHD via the modification of fasting lipids. Since all dietary sources of fat are composed of a combination of SFA, MUFA nad PUFA, it is best to characterize dietary fats as ratio of SFA:MUFA:PUFA. In fact, the SFA:MUFA:PUFA ratio in any given region or population is relatively homogeneous due to common food sources, food accessibility, food preparation and processing, dietary culture and tradition. For example, dietary fatty acid compositions (SFA:MUFA:PUFA) obtained directly or derived from existing national/regional reports are: 1:1.7:0.4 in Greece,1:1.0:0.5 in USA, and 1:1.5:1 in the mainland of China. Our research showed that the composition was 1:1.7:1.2 among type 2 diabetic patients in Guangzhou, a city in Southern China(10). To date, the overall influence of dietary fatty acid compositions on lipids in different subfractions of ppTRLs still remains unclear. This paucity of evidence may limit the establishment of optimal recommendation of dietary fatty acid composition for type 2 diabetes.

We designed three fat loads with specific fatty acid composition based on our previous study and current nutrition knowledge, and aimed at elucidating the influence of these dietary fatty acid compositions on the overall response of lipids in ppTRLs over postprandial 6 h.Based on the result, we will identify on one dietary fatty acid compositions, which can improve atherogenic ppTRLs and thus may be recommended for diabetic patients, for future large-scale research.

Inclusion Criteria:

• Type 2 diabetes;
• Types and doses of antidiabetic agents had been unchanged for four weeks before the postprandial study;
• Nonsmokers;
• No prior cardiovascular disease, hepatic and renal diseases, or other diseases influencing fat absorption;
• No previous history of gastro-enteral surgery;
• Dietary fat provided energy less than 35% in last two weeks;
• No use of medications or vitamins known to affect plasma lipids;
• Ability to hold hypoglycemic drugs on the day of the study until postprandial tests are completed;
• Ability to provide verbal informed consent to participate.

Exclusion Criteria:

• Females with menstrual cycles