Differential effects of saturated and monounsaturated fatty acids on postprandial lipemia and incretin responses in healthy subjects

Abstract

Background: Elevations of postprandial triacylglycerol-rich plasma lipoproteins and suppressions of HDL-cholesterol concentrations are considered potentially atherogenic. Long-term studies have shown beneficial effects of monounsaturated fatty acids (eg, oleic acid) on fasting lipid and lipoprotein concentrations in humans. A direct stimulatory effect of oleic acid on the secretion of glucagon-like peptide 1 (GLP-1) was shown in animal studies. Objective: We compared the postprandial responses of glucose, insulin, fatty acids, triacylglycerol, gastric inhibitory polypeptide (GIP), and GLP-1 to test meals rich in saturated and monounsaturated fatty acids. Design: Ten young, lean, healthy persons ingested 3 meals: an energy-free soup consumed with 50 g carbohydrate (control meal), the control meal plus 100 g butter, and the control meal plus 80 g olive oil. Triacylglycerol and retinyl palmitate responses were measured in total plasma, in a chylomicron-rich fraction, and in a chylomicron-poor fraction. Results: No significant differences in glucose, insulin, or fatty acid responses to the 2 fat-rich meals were seen. Plasma triacylglycerol responses were highest after the butter meal, with chylomicron triacylglycerol rising 2.5-5-fold. Retinyl palmitate responses were higher and more prolonged after the butter meal than after the control and olive oil meals, whereas both postprandial HDL-cholesterol concentrations and GLP-1 and GIP responses were higher after the olive oil meal than after the butter meal. Conclusions: Olive oil induced lower triacylglycerol concentrations and higher HDL-cholesterol concentrations than butter, without eliciting differences in concentrations of glucose, insulin, or fatty acids. Furthermore, olive oil induced higher concentrations of GLP-1 and GIP than did butter, which may point to a relation between fatty acid composition, incretin responses, and triacylglycerol metabolism in the postprandial phase.

Methodology for studying postprandial lipid metabolism

“…To summarize the important number of studies performed (reviewed by Williams, 1997;Roche et al, 1998a;Thomsen et al, 1999;Mekki et al, 2002), short or medium dietary fatty acids lower postprandial lipid response by mostly entering the portal route instead of chylomicron secretion. Dairy fats contain significant amounts of short-and medium-chain fatty acids.…”

“…Dairy fats contain significant amounts of short-and medium-chain fatty acids. Most studies have shown that saturated, monounsaturated and n-6 polyunsaturated fatty acids (PUFAs) do not generally elicit markedly different postprandial lipid responses (de Bruin et al, 1993;Lichtenstein et al, 1993;Tholstrup et al, 2001;Mekki et al, 2002), while some studies report exacerbated (Thomsen et al, 1999) or reduced (Mekki et al, 2002) responses after intake of saturated butter fat. More recently, studies that have measured changes in different lipoprotein subfractions have revealed important differences with lipemic responses being of the order saturated fatty acid (SFA)4monounsaturated fatty acid (MUFA)4PUFA (Jackson et al, 2002a, b;Jackson et al, 2005).…”

Interaction between specific fatty acids, GLP-1 and insulin secretion in humans

“…Some conflicting data on the type of dietary fatty acids and their effects on insulin secretion are available from meal and dietary intervention studies. In humans, no differences in insulin responses were found after meals [39,40] or longterm diets [41], which were high in monounsaturated or saturated fatty acids. Some studies have reported greater stimulation of insulin secretion after diets high in saturated fatty acids in subjects with Type II diabetes [42] and normal rats [43] but others have reported a more pronounced effect with polyunsaturated fatty acids [44].…”

“…This could be the result of a slower intestinal absorption of saturated fatty acids [51]. After a mixed meal, the plasma GLP-1 increase has also been shown to be more pronounced with the presence of olive oil than palm oil or butter in healthy humans [39]. Also, in vitro, oleic acid is a stronger stimulator of GLP-1 secretion than saturated fatty acids [52].…”

Lower glucose-dependent insulinotropic polypeptide (GIP) response but similar glucagon-like peptide 1 (GLP-1), glycaemic, and insulinaemic response to ancient wheat compared to modern wheat depends on processing

“…The potential role of GLP-1 in the regulation of appetite and food intake (Flint et al, 1998;Gutzwiller et al, 1999) and the potential role of GLP-1 and GIP of lipid metabolism (Thomsen et al, 1999) have been investigated recently. A positive correlation between the postprandial GIP response and the subjective satiety sensation was observed in healthy normal weight subjects (Raben et al, 1996).…”