Decreased postprandial response to a fat meal in normotriglyceridemic men with hypoalphalipoproteinemia

Exercise and dietary-mediated reductions in postprandial lipemia

Postprandial hyperlipemia produces long-term derangements in lipid/lipoprotein metabolism, vascular endothelial dysfunction, hypercoagulability, and sympathetic hyperactivity which are strongly linked to atherogenesis. The purpose of this review is to (1) provide a qualitative analysis of the available literature examining the dysregulation of postprandial lipid metabolism in the presence of obesity, (2) inspect the role of adiposity distribution and sex on postprandial lipid metabolism, and (3) examine the role of energy deficit (exercise- and/or energy restriction-mediated), isoenergetic low-carbohydrate diets, and omega-3 (n-3) fatty acid supplementation on postprandial lipid metabolism. We conclude from the literature that central adiposity primarily accounts for sex-related differences in postprandial lipemia and that aerobic exercise attenuates this response in obese or lean men and women to a similar extent through potentially unique mechanisms. In contrast, energy restriction produces only mild reductions in postprandial lipemia suggesting that exercise may be superior to energy restriction alone as a strategy for lowering postprandial lipemia. However, isoenergetic very low-carbohydrate diets and n-3 fatty acid supplementation reduce postprandial lipemia indicating that macronutrient manipulations reduce postprandial lipemia in the absence of energy restriction. Therefore, interactions between exercise/energy restriction and alterations in macronutrient content remain top priorities for the field to identify optimal behavioral treatments to reduce postprandial lipemia.

Postprandial lipemia in postmenopausal women with high fasting high-density lipoprotein cholesterol

BACKGROUND

Several groups of patients at high risk for cardiovascular disease have been found to show an exaggerated postprandial hypertriglyceridemia. Postprandial lipemia (PPL) therefore has been implicated as a potential additional risk factor that has been evading us. The purpose of this study was to test the effect of high fasting high-density lipoprotein cholesterol (HDL-C) levels on PPL in postmenopausal females.

METHODS

Oral fat tolerance test, as quantified by the areas under the curve (AUC) of triglyceride (TG) levels, was given to 3 groups: normal postmenopausal females (control), postmenopausal females with exceptionally high HDL-C and a familial history of longevity (longevity syndrome), and postmenopausal females that were heterozygotes of familial hypercholesterolemia (hFH) with exceptionally high HDL-C.

RESULTS

The PPL was not different between the control and longevity syndrome groups but was significantly higher in the hFH group; AUC (SD), in mg/dl/h; 749 (195), 882 (278) and 1244 (497) respectively, p=0.002. In linear regression analysis only fasting TG levels were a significant predictor of the AUC (Coefficient B = 11.779, p < 0.001).

CONCLUSIONS

In subjects with longevity syndrome the PPL is similar to controls, which means that high fasting HDL-C has not any beneficial influence on PPL. The fasting TG concentration is the main determinant of PPL. Furthermore, postmenopausal females with hFH have higher TG response postprandially, even in the case of high fasting HDL-C. Whether there is a threshold below or above, where HDL-C becomes a significant independent determinant of PPL is a question to be answered by future research.

Effect of 6 dietary fatty acids on the postprandial lipid profile, plasma fatty acids, lipoprotein lipase, and cholesterol ester transfer activities in healthy young men

BACKGROUND

There is increasing evidence that postprandial triacylglycerol-rich lipoproteins may be related to atherogenic risk.

OBJECTIVE

The objective was to investigate the effect of individual fatty acid intakes on postprandial plasma lipoprotein triacylglycerol and cholesterol concentrations, plasma fatty acids, and preheparin lipoprotein lipase and cholesterol ester transfer protein (CETP) activities.

DESIGN

Six test fats high (approximately 43% by wt) in stearic acid, palmitic acid, palmitic + myristic acid, oleic acid, elaidic acid (trans 18:1), and linoleic acid were produced by interesterification. After having fasted for 12 h, 16 healthy young men were served the individual test fats incorporated into meals (1 g fat/kg body wt) in random order on different days separated by washout periods. Blood samples were drawn before and 2, 4, 6, and 8 h after the meals.

RESULTS

Different responses to the test-fat meals were observed for plasma lipoprotein triacylglycerol and cholesterol concentrations, plasma fatty acid concentrations, and lipoprotein lipase and CETP activities (diet x time interaction: 0.001 < P < 0.05). Intake of the long-chain saturated fatty acids stearic and palmitic acids resulted in a relatively lower lipemic response than did intake of the unsaturated fatty acids, probably because the saturated fatty acids were absorbed less and at a lower rate; therefore, the lipemic response took longer to return to postabsorptive values.

CONCLUSIONS

Fatty acid chain length and degree of saturation appear to affect the extent and duration of lipemia and affect hepatic output indirectly. These effects may not be mediated via effects on lipoprotein lipase and CETP activities.

Double-blind controlled study on the effects of dietary diacylglycerol on postprandial serum and chylomicron triacylglycerol responses in healthy humans

OBJECTIVE

The effects of dietary diacylglycerol (DG) on postprandial lipemia in healthy humans were investigated.

METHODS

Forty normolipidemic male volunteers ingested fat emulsions containing either DG oil or triacylglycerol (TG) oil, at different doses: 10 g (n = 13), 20 g (n = 10) and 44 g (n = 17). Two test emulsions were given at seven-days intervals in random order. Fatty acid compositions of the test oils had been adjusted to be equal. Fasting and postprandial serum lipid concentrations in each group and plasma lipoprotein lipids in the 20 g-fat ingestion group were measured during the postprandial intervals.

RESULTS

When DG emulsion was ingested, serum TG concentrations were significantly lower (p < 0.05) in the late postprandial phase, i.e., 4 hours, 6 hours as compared to the TG emulsion. The magnitude of postprandial lipemia (the area bounded by the curve above the fasting concentration) after ingestion of 44 g-DG emulsion was significantly less than that of 44 g-TG emulsion (6.54 +/- 5.12 and 8.45 +/- 7.54 mmol x h/L, mean +/- SD, respectively). Chylomicron TG, cholesterol, and phospholipid concentrations at 4 hours after ingestion of DG emulsion were significantly lower (p < 0.05) than those after the ingestion of TG emulsion at the same time point. No marked differences were observed for VLDL, LDL and HDL lipids between the test emulsions.

CONCLUSION

In the usual range of fat intake (10-44 g), postprandial response after ingestion of DG emulsion was significantly less than that after ingestion of TG emulsion in healthy human subjects.

The genetic determinants of plasma cholesterol and response to diet

In general, risk factors for multifactorial disorders such as atherosclerosis and hyperlipidaemia show a continuous distribution in the population, and this is the result of both interaction between genetic variation at genetic loci, and genetic and environmental interaction. Therefore, the investigation of the genetics of intermediate phenotypes such as levels of plasma lipid traits is likely to be particularly informative. Once the genes involved in determining the levels of these phenotypes have been identified, it should be possible to use the information to obtain a better understanding of the way these genetic variations determine the clinical end points. In the population it will be possible to identify a number of polygenes that are having a small effect on determining the trait, but for a particular individual, or the relatives of that individual, only a subset of all these polygenes will determine the level of the trait and therefore the risk of developing the disorder. In general, mutations with a large effect on the trait are rare in the population, By contrast, polymorphisms with a small effect on the trait may be common, such as is found with the effect of the apoE alleles and variation at the apoB gene locus on lipid levels. In the field of hyperlipidaemia and atherosclerosis research, molecular techniques have already given a great deal of information on how specific sequence variations in some of the candidate genes are involved in determining levels of plasma apoproteins, lipoproteins and lipids. As more mutations and sequence variations are identified, this will not only aid our understanding of the underlying pathology, but should be useful for identifying individuals who are at risk of developing atherosclerosis because of their particular genotype or combination of genotypes.

Common variation in the gene for apolipoprotein B modulates postprandial lipoprotein metabolism: a hypothesis generating study

We have carried out a pilot study to examine the influence on postprandial lipid and lipoprotein metabolism of common genetic variation in the gene coding for apolipoprotein (apo) B, in a previously described group of 30 individuals who had survived a myocardial infarction (MI) before the age of 45 (normo (NTG)- and hypertriglyceridaemic (HTG) patients) and 11 age-matched healthy individuals. Postprandial lipid or lipoprotein levels were examined by genotypes in the three groups separately and after adjustment for fasting triglycerides (TG) in the whole group combined. For the signal peptide polymorphism in the apo B gene, individuals with one or more SP-24 alleles had a 38% smaller mean area under curve (AUC) (P = 0.06) for postprandial large chylomicron remnants and a 29% smaller mean AUC (P = 0.01) for large very low density lipoproteins (VLDLs) compared to individuals homozygous for the wild type SP-27 allele. Previously in this patient group, small chylomicron remnants (apo B-48 levels in the Sf 20-60 range) were found to relate significantly and positively to progression of coronary atherosclerosis suggesting that these lipoproteins are implicated in progression of atherosclerosis. For the apo B Val591-Ala polymorphism (Ag a1/d), individuals homozygous for the V591 allele had a 33% greater AUC for Sf 20-60 postprandial triglycerides (P = 0.006), with higher postprandial levels of both apo B-48- and apo B-100-containing lipoproteins in this fraction. This pilot study gives insight into the mechanisms of the previously reported associations between polymorphisms in the apo B gene and fasting plasma lipids and lipoproteins.

Evaluation of effects of unmodified niacin on fasting and postprandial plasma lipids in normolipidemic men with hypoalphalipoproteinemia

PURPOSE

The aim of this study was to define the effects of unmodified niacin on basal lipids and lipoproteins and on the plasma triglyceride response to a fatty meal--postprandial or alimentary lipemia--in individuals with low levels of high-density lipoprotein cholesterol (HDL-C) and normal fasting cholesterol and triglyceride concentrations (normolipidemic hypoalphalipoproteinemia, isolated low HDL-C).

PATIENTS AND METHODS

Twenty-eight normolipidemic men (total plasma cholesterol concentration [TC] < 230 mg/dL [< 6 mmol/L], plasma triglyceride [Tg] < 250 mg/dL [2.75 mmol/L]) with low plasma concentrations of HDL-C were randomly assigned to increasing doses of crystalline niacin (up to 3,000 mg/d) or no drug for 12 weeks, then crossed over to the alternate regimen. Outcome measures included changes in plasma lipoproteins and alimentary lipemia.

RESULTS

Fifteen participants completed the study. Mean baseline HDL-C +/- SD was 31.7 +/- 6.2 mg/dL (0.82 +/- 0.16 mmol/L). Mean baseline TC, plasma concentration of low-density lipoprotein cholesterol (LDL-C), and Tg were 192 +/- 29.4 mg/dL (4.97 +/- 0.76 mmol/L), 123 +/- 27 mg/dL (3.17 +/- 0.69 mmol/L), and 197 +/- 75 mg/dL (2.17 +/- 0.83 mmol/L), respectively. Unmodified niacin treatment resulted in significant (P < 0.001) reductions of 14% in TC (to 165 mg/dL, 4.26 mmol/L), 40% in Tg (to 119 mg/dL, 1.31 mmol/L), and 18% in LDL-C (to 101 mg/dL, 2.60 mmol/L) and significant increases of 30% in HDL-C (to 42 mg/dL, 1.07 mmol/L), 100% in HDL2 cholesterol (from 5 mg/dL to 9 mg/dL, 0.12 mmol/L to 0.24 mmol/L), and 21% in HDL3 cholesterol (from 27 mg/dL to 33 mg/dL, 0.70 mmol/L to 0.85 mmol/L). Unmodified niacin treatment reduced alimentary lipemia by 45% (P < 0.02).

CONCLUSIONS

Crystalline niacin effectively raises HDL-C, lowers LDL-C, and reduces alimentary lipemia in patients with isolated low HDL-C. However, many patients have difficulty tolerating the drug, and supervision may be required to sustain patient compliance and avoid toxicity.