Lipidomic profiling of chylomicron triacylglycerols in response to high fat meals.

Using lipidomic methodologies the impact that meal lipid composition and metabolic syndrome (MetS) exerts on the postprandial chylomicron triacylglycerol (TAG) response was examined. Males (9 control; 11 MetS) participated in a randomised crossover trial ingesting two high fat breakfast meals composed of either dairy-based foods or vegetable oil-based foods. The postprandial lipidomic molecular composition of the TAG in the chylomicron-rich (CM) fraction was analysed with tandem mass spectrometry coupled with liquid chromatography to profile CM TAG species and targeted TAG regioisomers. Postprandial CM TAG concentrations were significantly lower after the dairy-based foods compared with the vegetable oil-based foods for both control and MetS subjects. The CM TAG response to the ingested meals involved both significant and differential depletion of TAG species containing shorter- and medium-chain fatty acids (FA) and enrichment of TAG molecular species containing C16 and C18 saturated, monounsaturated and diunsaturated FA. Furthermore, there were significant changes in the TAG species between the food TAG and CM TAG and between the 3- and 5-h postprandial samples for the CM TAG regioisomers. Unexpectedly, the postprandial CM TAG concentration and CM TAG lipidomic responses did not differ between the control and MetS subjects. Lipidomic analysing of CM TAG molecular species revealed dynamic changes in the molecular species of CM TAG during the postprandial phase suggesting either preferential CM TAG species formation and/or clearance.

The fiber and/or polyphenols present in lingonberries null the glycemic effect of the sugars present in the berries when consumed together with added glucose in healthy human volunteers.

This study was undertaken on the broad hypothesis that lingonberry (Vaccinium vitis-idaea L.) has potential to reduce postprandial glycemic and lipemic response. More specifically, 2 postprandial crossover studies with healthy normal-weight male subjects were conducted to study the influence of commercial lingonberry powder on postprandial glycemia and lipemia. The test meals contained fat-free yoghurt with either glucose (50 g) or triacylglycerols (35 g) with or without (control) the lingonberry powder. The lingonberry powder provided the meals with a known amount of fiber and a known amount and composition of sugars, and it was a rich source of polyphenols. Postprandial glucose, insulin, and triacylglycerol responses were analyzed. There were no significant differences in the postprandial glucose concentration between the meals in the glycemia trial despite the fact that the lingonberry meal contained more glucose and fructose. When the meal did not contain added sugar but, instead, added triacylglycerol, no glycemia or lipemia-lowering effect was detected. On the contrary, there were indications of higher glycemic and insulinemic effect after the lingonberry meal. The results of this study indicate that the fibers and/or polyphenols present in lingonberries null the glycemic effect of the sugars present in the berries when consumed together with added glucose. By contrast, the lingonberry powder did not affect the postprandial lipemic response.

Positional distribution of decanoic acid: effect on chylomicron and VLDL TAG structures and postprandial lipemia.

Although medium-chain FA (MCFA) are mainly absorbed via the portal venous system, they are also incorporated into chylomicron TAG; therefore, the positional distribution of MCFA in TAG is likely to affect their metabolic fate. We studied chylomicron and VLDL TAG structures, as well as the magnitude of postprandial lipemia, after two oral fat loads containing decanoic acid (10:0) predominantly at the sn-1(3),2 (MML) or at the sn-1,3 positions (MLM) of TAG in a randomized, double-blind, crossover clinical trial with 10 healthy, normal-weight volunteers. An MS-MS method was used to analyze TAG regioisomers. The position of decanoic acid in chylomicron TAG reflected its position in the TAG ingested, and TAG with none, one, two, or three decanoic acid residues were detected after ingestion of both fats. More (P < 0.05) 30:0 and 38:1 TAG (acyl carbons:double bonds) and fewer 46:5, 54:5, and 54:4 TAG were found in chylomicrons after ingestion of MML than after MLM. The VLDL TAG composition did not differ between the fat loads but did change (P < 0.05) 2 to 6 h after ingestion of both fats. No statistical differences were seen between the fat loads in areas under the plasma, chylomicron, or VLDL TAG response curves or in FFA concentrations. Thus, the positional distribution of MCFA in TAG affects their metabolic fate, but the magnitude of postprandial lipemia does not seem to be dependent on the positional distribution of MCFA in the ingested fat.

Chylomicron and VLDL TAG structures and postprandial lipid response induced by lard and modified lard.

Alterations in chylomicron and VLDL TAG and the magnitude of postprandial lipemia were studied in healthy volunteers after two meals of equal FA composition but different TAG FA positional distribution. Molecular level information of individual lipoprotein TAG regioisomers was obtained with a tandem MS method. The incremental area under the response curve of VLDL TAG was larger (P = 0.021) after modified lard than after lard. In plasma TAG, the difference did not quite reach statistical significance (P = 0.086). In general, there were less TAG with palmitic acid in the sn-2 position and more TAG with oleic acid in the sn-2 position in chylomicrons than in fat ingested. From 1.5 to 8 h postprandially, the proportion of individual chylomicron TAG was constant or influenced by TAG M.W. VLDL TAG regioisomerism was similar regardless of the positional distribution of fat ingested. Significant alterations were seen in VLDL TAG FA, in M.W. fractions, and in individual regioisomers with respect to time. The TAG sn-14:0-18:1-18:1 + sn-18:1-18:1-14:0, sn-16:0-16:1-18:1 + sn-18:1-16:1-16:0, and sn-16:1-18:1-18:1 + sn-18:1-18:1-16:1 decreased (P < 0.05); and sn-16:0-16:0-18:2 + sn-18:2-16:0-16:0, sn-16:0-16:0-18:1 + sn-18:1-16:0-16:0, sn-16:0-18:1-16:0, and sn-16:0-18:1-18:2 + sn-18:2-18:1-16:0 increased (P < 0.05) after both meals. In conclusion, positional distribution of TAG FA was found to affect postprandial lipid metabolism in healthy normolipidemic subjects.

Triacylglycerol molecular weight and to a lesser extent, fatty acid positional distribution, affect chylomicron triacylglycerol composition in women.

Postprandial composition of chylomicron triacylglycerols (TAG) and their clearance may be affected by the molecular weight of TAG, their fatty acid (FA) combinations and the positional distribution of FA in TAG. Delayed postprandial TAG clearance is a risk factor for cardiovascular disease. However, due to the complexity of traditional analysis methods, the composition of individual TAG molecules is frequently overlooked. In this study, chylomicron TAG molecular weight distribution and regioisomerism were followed in 10 healthy female volunteers after two fat loads with identical FA composition but different positional distributions (palm oil and transesterified palm oil). An efficient tandem mass spectrometric method of analysis was applied. During the 6-h observation period, the relative concentrations of TAG with 48:2 [48 acyl carbons and 2 double bonds (ACN:DB)], 50:3 and 50:2 decreased, whereas the proportions of 48:0 (tripalmitin), 52:3 and 54:4 remained constant and the proportion of 54:3 (triolein) increased (P < 0.05). The existence of seven regioisomers containing palmitic, oleic and linoleic acids in different sn-positions was studied. The amount of 1,3-dipalmitoyl-2-oleoyl-sn-glycerol was less (P < 0.05) 1.5 h postprandially than at 2-5 h after palm oil, and less (P < 0.05) at 1.5 h than at 2-6 h after transesterified palm oil. This may be an indication of a loss of palmitic acid in the gut. Taken together, TAG molecular weight composition and to a lesser extent, positional distribution, seem to affect the rates of chylomicron TAG clearance in humans.