Six Different Fat Tolerance Tests in Young, Healthy Subjects – Gender Dependent Postprandial Lipemia and Glucose

What is it about?

Saturated fat intake constitutes a major risk factor for the development of cardiovascular disease (CVD) by accelerating the atherosclerotic process through alterations in plasma lipoprotein and lipid levels (1-3). A meta-analysis including 262.000 subjects found a strong positive correlation between ischemic heart disease and postprandial lipemia (PPL), most strongly in triglyceride (TG) levels (4). The important physiological event appears to occur between two and 12 hours after the ingestion of food high in lipids like TG and TG-rich lipoproteins. The accelerated atherosclerotic process is thought to be effected by reduced lipid efflux from the vascular endothelial intima associated with postprandial TGs and lipoprotein levels (5-8). Most studies in CVD have applied fasting lipid and lipoprotein levels, which may not give the true picture of lifestyle intervention, and data from the postprandial state are scarce (3,5,6,8). Patients with CVD have higher non-fasting TG levels compared with normal, and TGs measured 2 to 4 hours postprandial show the strongest association with cardiac events in an 11-year follow-up study (9). Most individuals are hypertriglyceridemic after a moderate- or high-fat meal, which usually peaks four to six hours after the meal (7,10). In Western countries, TG levels are elevated most of the day due to high-fat diets rich in saturated fat and expose individuals to large amounts of atherogenic TGs-rich remnants particles and low HDL-C levels, contributing to lipid accumulation in the endothelium. Current recommendations, thus, prescribe a reduction in total fat, saturated fat in particular, which should be replaced by carbohydrate (11). However, monounsaturated fat may also be used as an alternative to saturated fat. Thus, clinical studies with high-fat diets rich in monounsaturated fatty acids (MUFAs) showed improved lipoprotein composition compared with the recommended high-carbohydrate diet in normal subjects and improved glycemic control in subjects with type 2 diabetes (12,13). Gender is known to affect the PPL; however, the etiology is uncertain (10,14,15). A negative association between estrogens and the postprandial lipoprotein lipase activity is well- described and will result in lower dissociation of TG to free fatty acids (FFA) from the postprandial TG-rich chylomicron and VLDL particles (10,16,17). This activity lowers FFA flux to target tissues and increases extracellular/vascular levels. Furthermore, BMI, age, and exercise influence PPL significantly but the effect in young, healthy subjects is less investigated (10,15,18,19). Different types of fatty acids influence PPL and glycemic responses differently, which is important for planning of diets of patients with higher CVD risk like diabetes, obesity, and hypercholesterolemia (20-22). Clinical studies of metabolic responses to various foods are important to improve health information strategies and recommendations; in concordance, standards for the methodology in studying postprandial lipid metabolism were suggested (23). Our aim was to evaluate the influence of fat type in meals by acute metabolic responses and their association with gender in a group of young healthy subjects. Therefore, we used six different mixtures of fats, i.e. saturated, mono-and polyunsaturated fat, and measured PPL and glycemia. Similarly, most studies are performed on both sexes in variety of ages. We were aware that baseline values between sexes vary; thus, we aimed at narrowing the age and weight span of the investigation to minimize the effect of these variables.

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