Effects of graded amounts (0–50 g) of dietary fat on postprandial lipemia and lipoproteins in normolipidemic adults

Abstract

Eight normolipidemic males ingested on separate days and in a random order five mixed meals containing 0, 15, 30, 40, or 50 g fat. Fasting and postprandial blood samples were obtained for 7 h and chylomicrons and lipoproteins were isolated. The nonfat and 15-g fat meals did not generate noticeable postprandial variations except for HDL phospholipids (P < 0.05). The serum and chylomicron triacylglycerol responses obtained after the meals correlated positively with the amount of fat ingested and peaked after 2-3 h. Serum free cholesterol and phospholipids increased and esterified cholesterol decreased postprandially in a dose-response manner. At the same time, triacylglycerol-rich-lipoprotein triacylglycerols, esterified cholesterol, LDL free cholesterol, HDL triacylglycerols, phospholipids, and free cholesterol increased whereas LDL and HDL esterified cholesterol decreased when the amount of ingested fat increased. The data showed that increasing the amount of fat in the usual range of ingestion (0-50 g) led to stepwise increases in the postprandial rise of chylomicron and serum triacylglycerols and induced marked changes in serum lipoproteins postprandially. The existence of a no-effect level of dietary fat (15 g) on postprandial lipemia and lipoproteins in healthy adults was shown.

Methodology for studying postprandial lipid metabolism

“…As compared with a control test meal or another test meal, the studied component will be incorporated in the experimental test meal. This will make possible to evaluate the effect of the studied component on the amplitude and/or kinetics of the postprandial lipid response in subjects with normal metabolic homeostasis (Cara et al, 1992;Zampelas et al, 1994a, b;Murphy et al, 1995;Dubois et al, 1998;Roche et al, 1998a, b;Fielding et al, 2000;Harbis et al, 2001Harbis et al, , 2004van Wijk et al, 2001;Sauvant et al, 2003;Jackson et al, 2005).…”

“…Some studies have been performed with increasing doses of dietary fat to determine how meal-fat size impacts on metabolic capacity in normal subjects (Cohen et al, 1988;Dubois et al, 1994Dubois et al, , 1998Murphy et al, 1995). The data revealed that (i) very low (5 g) or low doses (15 g) of dietary triglycerides do not significantly increase triglyceridaemia postprandially, (ii) moderate doses (30-50 g) cause dosedependent increases in postprandial triglyceridaemia and (iii) very high doses (80 g and above) exaggerate postprandial triglyceridaemia but with a tendency for triglycerides to show a plateaux and less clear dose dependence than with more moderate fat loads (see Table 2 for summary).…”

“…Chylomicrons are classically floated on the top of a plasma sample in the form of a cloudy layer after a short ultracentrifugation at moderate speed (Dubois et al, 1994(Dubois et al, , 1998. Then in a second run, VLDL can be floated after adjusting plasma sample density to 1.006 and ultracentrifugation for several hours at moderate/high speed.…”

“…Because all classes of lipoproteins are interrelated, every kind of lipoprotein can be altered postprandially (Patsch et al, 1983;Weintraub et al, 1987;Cohn et al, 1988a, b;Karpe et al, 1993Karpe et al, , 1995Dubois et al, 1994Dubois et al, , 1998. If the full pattern of lipoprotein parameters, including LDL and HDL particles, is required, these can be separated from plasma samples by a more prolonged ultracentrifugation and components assayed (triglycerides, cholesterol and phospholipidsapolipoproteins).…”

Effect of prior exercise on lipemia after a meal of moderate fat content

“…In fact, with the exception of Murphy et al (2000), who employed a diet providing 47% of energy from fat over the course of 1 day, all studies on the effect of exercise on postprandial lipemia have used test meals containing 60-93% of energy as fat, or 1.0-1.5 g/kg body mass (Maruhama et al, 1977;Schlierf et al, 1987;Klein et al, 1992;Aldred et al, 1994;Hardman & Aldred, 1995;Tsetsonis & Hardman, 1996a, b;Tsetsonis et al, 1997;Gill et al, 1998Gill et al, , 2001aGill et al, , b, 2002Hardman et al, 1998;Herd et al, 1998Herd et al, , 2000Herd et al, , 2001Zhang et al, 1998;Malkova et al, 1999;Gill & Hardman, 2000;Thomas et al, 2001;Petitt et al, 2003). Since the lipemic response to a fat meal is expected and has been shown to be positively related to the amount of fat ingested (Dubois et al, 1998), one could claim that exercise might not have a significant effect on lipemia after a meal of moderate fat content. Figure 2 Postprandial plasma kinetics of four TG acyl groups exhibiting two distinct patterns, that is, either an early peak (left) or a late peak (right).…”