Postprandial behavior of plasma squalene and non-cholesterol sterols in men with varying cholesterol absorption

BACKGROUND

The purpose of this study was to investigate, whether low vs. high absorption of cholesterol affects the postprandial lipid clearance (squalene as the surrogate marker) and postprandial cholesterol metabolism evaluated with plasma levels of cholesterol absorption (cholestanol and plant sterols) and synthesis markers (desmosterol and lathosterol).

METHODS

Fifteen normo- or mildly hypercholesterolemic men were divided into low or high cholesterol absorbers on the basis of plasma cholestanol to cholesterol ratio and they volunteered to an oral fat load test containing fat 35 g/m(2) body surface.

RESULTS

Plasma squalene to cholesterol ratio did not differ between the groups throughout the postprandial follow-up of 8 h. The level differences in the plasma absorption and synthesis markers seen at baseline remained between the groups, so that in high absorbers the absorption markers remained high and synthesis markers low throughout the postprandial follow-up. The postprandial response curves of desmosterol (p<0.05) and lathosterol (p=0.052) to cholestanol decreased linearly in the low, but not in the high absorbers.

CONCLUSIONS

Low vs. high absorption of cholesterol does not affect the first 8-h postprandial lipid clearance. The metabolic profile of cholesterol is maintained postprandially. The postprandial decrease in cholesterol synthesis differs in low vs. high absorbers especially through the desmosterol pathway.

Ester percentages of plant sterols and cholesterol in chylomicrons and VLDL of humans with low and high sterol absorption

Ester percentages of cholesterol and non-cholesterol sterols were measured in chylomicrons and very low density lipoproteins (VLDL) in 15 subjects. Our hypothesis was that in humans, in contrast to animal experiments, plant sterols in chylomicrons are esterified similarly to cholesterol. In fact, the mean ester percentage of chylomicron sitosterol (approximately 40%), but not of campesterol ( approximately 51%), was lower than that of cholesterol (approximately 54%) in the whole study population. In high cholesterol absorbers (high serum total campesterol, > or = 2.8 mmol/mol of cholesterol), the ester percentages of sitosterol and other non-cholesterol sterols were similar to that of cholesterol in chylomicrons, and the percentages tended to be higher than those in low absorbers. In contrast to chylomicrons, the ester percentages of sterols in VLDL tended to be lower in the high than low absorbers. In conclusion, percentages of plant sterol esters are not consistently lower than those of cholesterol in chylomicrons.

Postprandial lipemic response is modified by the polymorphism at codon 54 of the fatty acid-binding protein 2 gene

Polymorphism of the fatty acid-binding protein 2 (FABP2) gene has been shown to affect the affinity of intestinal FABP for fatty acids. This could cause changes in postprandial triglyceride metabolism. In the present study, postprandial lipemia was studied in normotriglyceridemic subjects with genetic variation in the FABP2 gene. Oral fat-loading tests were performed in 8 subjects homozygous for the Thr-encoding allele at codon 54 of the FABP2 gene and in 7 subjects homozygous for the Ala-encoding allele (wild type). There were no significant differences between these 2 groups in age, body mass index, fasting plasma triglyceride and cholesterol levels, or fasting glucose and insulin levels. The increase of plasma triglyceride concentration after the fat test meal was significantly greater in subjects who were homozygous for the Thr-54 allele (area under the response curve, 4.27+/-1.31 versus 2.49+/-1.18 mmol/L x h-1, P=0.04). The difference was seen in both chylomicron (2.51+/-0. 98 versus 1.41+/-0.74 mmol/L x h-1, P=0.03) and very low-density lipoprotein triglycerides (1.57+/-0.77 versus 0.99+/-0.40 mmol/L x h-1, P=0.04). Postprandial triglyceride response correlated with fasting triglycerides in the Ala-54 homozygotes (r=0.79, P=0.05) but not in the Thr-54 homozygotes (r=0.09), who showed a strong correlation between triglyceride and insulin responses (r=0.83, P=0. 02). With reservations related to a small number of subjects studied, these results indicate that the Thr-encoding allele of the FABP2 gene is associated with increased postprandial lipemia. The lipemic response was associated with postprandial insulin response, suggesting that in the Thr-54 homozygotes, altered postprandial lipemia may also modify insulin action or vice versa.

Fish diet, fish oil and docosahexaenoic acid rich oil lower fasting and postprandial plasma lipid levels

OBJECTIVE

The present study was carried out to clarify the effects of fish diet, fish oil and docosahexaenoic acid (DHA) rich oil on fasting and postprandial lipid levels in healthy male students.

DESIGN

The study was a randomized single-blind study with a control and three study groups.

SETTING

The study was carried out in the Departments of Physiology and Clinical Nutrition of University of Kuopio.

SUBJECTS

Healthy male volunteers were recruited for the study from the university student population. Fifty-nine subjects entered and 55 completed the study.

INTERVENTIONS

For 15 weeks the subjects in the fish diet group ate 4.3 +/- 0.5 fish containing meals per week and those in the fish oil and DHA-oil groups ate 4 g oil per day. Fish diet provided 0.38 +/- 0.04 g eicosapentaenoic acid (EPA) and 0.67 +/- 0.09 g DHA, fish oil 1.33 g EPA and 0.95 g DHA and DHA-oil (EPA-free) 1.68 g DHA per day.

RESULTS

Fasting plasma triglyceride levels decreased in all test groups in 14 weeks when compared to the control group (P < 0.05). Total plasma cholesterol levels did not change but the HDL2/HDL3-cholesterol ratio increased in all test groups by over 50% (P < 0.05). The postprandial total and chylomicron triglyceride responses, measured as areas under the response curve, were lowered in 15 weeks by the fish diet and fish oil (P < 0.05), the same tendency (P < 0.1) being seen in DHA-oil group.

CONCLUSIONS

These results show that both fasting and postprandial triglyceride concentrations can be decreased with moderate intakes of long-chain n-3 fatty acids either from a fish diet or fish oil and that also pure DHA has a hypotriglyceridemic effect.