Intra-individual variations of fasting plasma lipids, apolipoproteins and postprandial lipemia in familial combined hyperlipidemia compared to controls

Postprandial plasma lipidome responses to a high-fat meal among healthy women

Postprandial lipemia consists of changes in concentrations and composition of plasma lipids after food intake, commonly presented as increased levels of triglyceride-rich lipoproteins. Postprandial hypertriglyceridemia may also affect high-density lipoprotein (HDL) structure and function, resulting in a net decrease in HDL concentrations. Elevated triglycerides (TG) and reduced HDL levels have been positively associated with risk of cardiovascular diseases development. Here, we investigated the plasma lipidome composition of 12 clinically healthy, nonobese and young women in response to an acute high-caloric (1135 kcal) and high-fat (64 g) breakfast meal. For this purpose, we employed a detailed untargeted mass spectrometry-based lipidomic approach and data was obtained at four sampling points: fasting and 1, 3 and 5 h postprandial. Analysis of variance revealed 73 significantly altered lipid species between all sampling points. Nonetheless, two divergent subgroups have emerged at 5 h postprandial as a function of differential plasma lipidome responses, and were thereby designated slow and fast TG metabolizers. Late responses by slow TG metabolizers were associated with increased concentrations of several species of TG and phosphatidylinositol (PI). Lipidomic analysis of lipoprotein fractions at 5 h postprandial revealed higher TG and PI concentrations in HDL from slow relative to fast TG metabolizers, but not in apoB-containing fraction. These data indicate that modulations in HDL lipidome during prolonged postprandial lipemia may potentially impact HDL functions. A comprehensive characterization of plasma lipidome responses to acute metabolic challenges may contribute to a better understanding of diet/lifestyle regulation in the metabolism of lipid and glucose.

Familial combined hyperlipidaemia/polygenic mixed hyperlipidaemia

Familial combined hyperlipidaemia (FCH) is the most prevalent form of familial hyperlipidaemia with a multigenic origin and a complex pattern of inheritance. In this respect, FCH is an oligogenic primary lipid disorder due to interaction of genetic variants and mutations with environmental factors. Patients with FCH are at increased risk of cardiovascular disease and often have other associated metabolic conditions. Despite its relevance in cardiovascular prevention, FCH is frequently underdiagnosed and very often undertreated. In this review, emphasis is placed on the most recent advances in FCH, in order to increase its awareness and ultimately contribute to improving its clinical control.

Familial combined hyperlipidemia: An overview of the underlying molecular mechanisms and therapeutic strategies

Among different types of dyslipidemia, familial combined hyperlipidemia (FCHL) is the most common genetic disorder, which is characterized by at least two different forms of lipid abnormalities: hypercholesterolemia and hypertriglyceridemia. FCHL is an important cause of cardiovascular diseases. FCHL is a heterogeneous condition linked with some metabolic defects that are closely associated with FCHL. These metabolic features include dysfunctional adipose tissue, delayed clearance of triglyceride-rich lipoproteins, overproduction of very low-density lipoprotein and hepatic lipids, and defect in the clearance of low-density lipoprotein particles. There are also some genes associated with FCHL such as those affecting the metabolism and clearance of plasma lipoprotein particles. Due to the high prevalence of FCHL especially in cardiovascular patients, targeted treatment is ideal but this necessitates identification of the genetic background of patients. This review describes the metabolic pathways and associated genes that are implicated in FCHL pathogenesis. We also review existing and novel treatment options for FCHL. © 2019 IUBMB Life, 71(9):1221-1229, 2019.

Diurnal triglyceridemia in relation to alcohol intake in men

Fasting and postprandial triglyceride concentrations largely depend on dietary and lifestyle factors. Alcohol intake is associated with triglycerides, but the effect of alcohol on diurnal triglyceridemia in a free living situation is unknown. During three days, 139 men (range: 18–80 years) measured their own capillary triglyceride (cTG) concentrations daily on six fixed time-points before and after meals, and the total daily alcohol intake was recorded. The impact of daily alcohol intake (none; low, <10 g/day; moderate, 10–30 g/day; high, >30 g/day) on diurnal triglyceridemia was analyzed by the incremental area under the cTG curve (∆cTG-AUC) reflecting the mean of the six different time-points. Fasting cTG were similar between the alcohol groups, but a trend of increased cTG was observed in men with moderate and high alcohol intake after dinner and at bedtime (p for trend <0.001) which persisted after adjustment for age, smoking and body mass index. The ∆cTG-AUC was significantly lower in males with low alcohol intake (3.0 ± 1.9 mmol·h/L) (n = 27) compared to males with no (7.0 ± 1.8 mmol·h/L) (n = 34), moderate (6.5 ± 1.8 mmol·h/L) (n = 54) or high alcohol intake (7.2 ± 2.2 mmol·h/L) (n = 24), when adjusted for age, smoking and body mass index (adjusted p value < 0.05). In males, low alcohol intake was associated with decreased diurnal triglyceridemia, whereas moderate and high alcohol intake was associated with increased triglycerides after dinner and at bed time.

Influence of metabolic syndrome superposition on familial combined hyperlipoproteinemia cardiovascular complication rate

INTRODUCTION

Familial combined hyperlipoproteinemia (FCHL) is a very common and aggressive genetic mixed hyperlipoproteinemia, with many features similar to that of the metabolic syndrome (MS). We aimed to evaluate whether the presence of the MS per se could account for a significant part of the elevated cardiovascular disease (CVD) risk associated with FCHL.

MATERIAL AND METHODS

A retrospective cross-sectional evaluation of MS features' influence on CVD prevalence in a large sample of adult Italian FCHL affected patients (64 familial clusters; 867 subjects) was carried out.

RESULTS

Age is associated with early cardiovascular complications, both in men (OR 1.08, 95% CI: 1.05-1.11, p < 0.0001) and in women (OR 1.09, 95% CI: 1.04-1.13, p = 0.0001). No MS component appears to be related to cardiovascular complications in men, whilst only low plasma high-density lipoprotein cholesterol (HDL-C) shows such a relation in women. Among non-MS parameters, only low-density lipoprotein cholesterol (LDL-C) and lipoprotein(a) (Lp(a)) plasma levels are significantly associated with early cardiovascular complications in male FCHL patients (LDL-C: OR 2.24, 95% CI: 1.02-4.91, p = 0.04; Lp(a): OR 4.64, 95% CI: 1.85-11.62, p = 0.001), but not in women (LDL-C: OR 1.83, 95% CI 0.53-6.34, p = 0.34; Lp(a): OR 3.65, 95% CI: 0.89-14.97, p = 0.07).

CONCLUSIONS

Our data support the hypothesis that MS is not associated with a higher prevalence of cardiovascular complications in FCHL affected subjects, probably because of the strongest risk increase associated with the FCHL itself.

Daytime triglyceride variability in men and women with different levels of triglyceridemia

BACKGROUND

Triglyceride (TG) levels measured in either the fasting or non-fasting state predict the risk of cardiovascular disease (CVD). Since CVD risk assessment is affected by variability in TG, the aim of the study was to investigate intra-individual variability of non-fasting TG.

METHODS

Capillary triglyceride (cTG) levels were measured in 246 free-living individuals at six time-points during the day on three separate occasions. Intra-individual variability in cTG was assessed by calculating the standard deviation of three measures at each time-point. Subjects were analyzed by gender and by fasting TG level.

RESULTS

In the fasting state, intra-individual variability was similar in males and females (0.28 and 0.35 mmol/l, respectively), but increased significantly in male but not in female subjects during the day, i.e., 0.28 to 0.69, and 0.35 to 0.36 mmol/l, resp. Subjects with higher fasting TG levels had greater absolute variability in both fasting and non-fasting TG.

CONCLUSIONS

The variability in non-fasting TG is greater in males and in individuals with higher levels of TG. Since greatest variability in non-fasting TG occurs very late in the day, it is unlikely to affect the assessment of CVD risk, which is based on a blood sample taken during daylight hours.

Postprandial lipoproteins and cardiovascular disease risk in diabetes mellitus

Diabetes mellitus is associated with increased risk for atherosclerotic cardiovascular disease (CVD). Recent prospective studies in healthy individuals suggest that the postprandial triglyceride (TG) level is a better independent predictor for assessing future CVD events than fasting TG levels. In contrast, results have been more controversial among diabetic patients, as some studies report a positive association between postprandial TG and CVD. This raises the issue of to what extent postprandial TG levels may be of predictive value in the diabetic population. One possibility impacting on the predictive power of postprandial TG in identifying CVD risk may be the presence of other risk factors, including alterations in lipid and lipoprotein metabolism, which could make it more difficult to identify the impact of postprandial lipemia on cardiovascular risk. The findings provide a challenge to develop a better approach to assess the impact of postprandial lipemia on CVD risk under diabetic conditions.

Novel aspects of postprandial lipemia in relation to atherosclerosis

Postprandial hyperlipidemia is considered to be a substantial risk factor for atherosclerosis. Interestingly, this concept has never been supported by randomized clinical trials. The difficulty lies in the fact that most interventions aimed to reduce postprandial lipemia, will also affect LDL-C levels. The atherogenic mechanisms of postprandial lipids and lipoproteins can be divided into direct lipoprotein-mediated and indirect effects; the latter, in part, by inducing an inflammatory state. Elevations in postprandial triglycerides (TG) have been related to the increased expression of postprandial leukocyte activation markers, up-regulation of pro-inflammatory genes in endothelial cells and involvement of the complement system. This set of events is part of the postprandial inflammatory response, which is one of the recently identified potential pro-atherogenic mechanisms of postprandial lipemia. Especially, complement component 3 levels show a close correlation with postprandial lipemia and are also important determinants of the metabolic syndrome. In clinical practice, fasting TG are frequently used as reflections of postprandial lipemia due to the close correlation between the two. The use of serial capillary measurements in an out-of-hospital situation is an alternative for oral fat loading tests. Daylong TG profiles reflect postprandial lipemia and are increased in conditions like the metabolic syndrome, type 2 diabetes and atherosclerosis. Studies are needed to elucidate the role of postprandial inflammation in atherogenesis and to find new methods in order to reduce selectively the postprandial inflammatory response. Future studies are needed to find new methods in order to reduce selectively the postprandial inflammatory response.

Five-year follow-up of waist circumference, insulin and ALT levels in familial combined hyperlipidaemia

FCHL (familial combined hyperlipidaemia), an entity with many features of the metabolic syndrome, is characterized by changes in cholesterol and triacylglycerol (triglyceride) phenotype over time. The present study was conducted to investigate the relationship of ALT (alanine aminotransferase) levels, used as a surrogate marker for the amount of hepatic fat, with the switch in triacylglycerol phenotype and the increased susceptibility to develop hypertriglyceridaemia in FCHL. BMI (body mass index), waist circumference and plasma triacylglycerols, insulin and ALT levels were measured in 145 FCHL family members and 54 spouses at baseline and after a 5-year follow-up. A switch from normotriglyceridaemia to hypertriglyceridaemia or vice versa, as observed in 22 of 145 FCHL family members, was associated with changes in plasma ALT levels (P=0.001), but not with insulin levels or waist circumference. At 5 years of follow-up, an intra-individual relationship was observed between waist circumference and plasma triacylglycerols, insulin and ALT levels. For each waist circumference, FCHL patients, but not their NL (normolipidaemic) relatives, exhibited higher triacylglycerol and insulin levels than spouses (P<0.001). Remarkably, both FCHL patients and the NL relatives had higher ALT levels for each waist circumference compared with spouses (P<0.001 for FCHL patients, and P=0.035 for NL relatives). In conclusion, the present study shows that the longitudinal relationship of abdominal obesity–ALT is more specific for all FCHL family members, i.e. patients and their NL relatives, than the relationship of abdominal obesity–triacylglycerols. Additionally, the association of ALT with the switch in triacylglycerol phenotype suggests a central role of the liver in the pathogenesis of FCHL.

Effects of a stanol-enriched diet on plasma cholesterol and triglycerides in patients treated with statins

BACKGROUND

Plant stanols have been recommended in combination with individualized dietary interventions to reduce plasma cholesterol concentrations. It is unclear whether plant stanols in combination with dietary guidance in patients already using optimal doses of statins will further reduce fasting and postprandial lipids compared with standard care.

STUDY DESIGN

This single-blind, randomized study investigated the effect of plant stanols in margarines, combined with a lipid-lowering dietary intervention, in patients already on lipid-lowering medications at maximal doses not reaching their target lipid levels. Nutrition education was based on the stages of change theory. The control group (which served as the standard care control group) was also taking optimal doses of statins. This group received a margarine without plant stanols and a leaflet with Dutch nutrition guidelines. Fasting lipids were measured once in venous samples and postprandial lipemia was assessed by self-measured triglycerides in an outpatient setting. All subjects were given a capillary triglyceride measuring device (Accutrend GCT, Roche Diagnostics, Mannheim, Germany) and were instructed to measure their capillary triglycerides at six fixed time-points throughout the day on three different days. The mean area under the triglyceride curve represented total daylong triglyceridemia, which has been shown to reflect postprandial triglyceridemia. Twenty patients were included, 11 in the intervention group and 9 in the control group.

RESULTS

In the plant stanol group, low-density lipoprotein cholesterol decreased significantly by 15.6% compared with a reduction of only 7.7% in the control group. The daylong triglyceridemia was similar in both groups at the beginning and at the end of the study, and no change was observed by the intervention.

CONCLUSION

Intensive dietary intervention with addition of plant stanols results in clinically relevant reduction of low-density lipoprotein cholesterol in patients optimally treated with statins, compared with similar patients on statins receiving only standard care. The use of a plant stanol-enriched margarine did not decrease postprandial triglyceridemia in these patients.

High doses of bifendate elevate serum and hepatic triglyceride levels in rabbits and mice: animal models of acute hypertriglyceridemia

AIM

To investigate the effects of bifendate on serum and hepatic lipids level in rabbits and mice.

METHODS

Animals were administered bifendate [powdered pill suspended in 0.5% sodium carboxymethylcellulose (CMC)] at increasing doses (0.25-1 g/kg, ig). Blood lipid and apolipoprotein levels were measured using commercially available assay kits.

RESULTS

The treatment of rabbits with a single dose of bifendate (0.3 g/kg) caused a time-dependent and biphasic change in serum triglyceride (TG) levels, with the value reaching a maximum (3-fold increase compared to the baseline value) between 24 and 36 h post-dosing. When mice were orally treated with bifendate (0.25-1 g/kg), serum TG levels increased by 39%-76% and 14%-39% at 24 and 48 h post-dosing, respectively. When given at daily doses of 0.25 and 1 g/kg for 4 d, bifendate increased serum TG levels (56%-79%), with concomitant elevations in apolipoprotein A-I and apolipoprotein B levels at 24 h after the last dosing. TG levels were also increased (11%-43%) in liver samples of mice receiving single or multiple doses of bifendate. However, bifendate treatment caused slight reductions in serum and hepatic total cholesterol levels (9%-13%). The hypertriglyceridemia induced by bifendate was ameliorated by fenofibrate but not inositol nicotinate treatment in mice.

CONCLUSION

The findings suggest that bifendate treatment at high oral doses can cause an acute elevation in serum and hepatic TG levels.

Efecto del género y de la obesidad en la lipemia posprandial en sujetos sanos normolipidémicos no diabéticos y sujetos con hiperlipemia familiar combinada

INTRODUCTION

A new method based on self-measurement of diurnal capillary triglycerides (TG) facilitates the study of postprandial lipemia (PL). The objectives of our study are: to evaluate the effect of gender and obesity on PL measured by self-determination of diurnal capillary TG with Accutrend GCT in normolipidemic non-diabetic subjects and subjects with familial combined hyperlipidemia (FCH).

MATERIAL AND METHODS

We studied 23 FCH subjects (10 males) and 45 normolipidemic non-diabetic subjects (29 males). All subjects self-determine 3 diurnal capillary TG profiles during a week.

RESULTS

In normolipidemic non diabetic subjects significantly higher diurnal TG profiles and area under the curve of TG (AUCTGc) (25.25 +/-9.09 vs 19.71 +/- 6.16 mmolh/l) were found in males compared to females. In FCH subjects these differences were not found and the AUCTGc correlated with BMI (r = 0.510, p < 0.05) and waist circumference (r = 0.453, p < 0.05). Obese subjects (BMI >or= 27 kg/m2) showed diurnal TG profiles and AUCTGc significantly higher than the non-obese.

DISCUSSION

Normolipidemic non diabetic females showed a lower PL compared to males, probably due to the effect of estrogens in PL metabolism. Obesity negatively influences PL in normolipidemic non diabetic subjects and subjects with FCH.

Determinantes de la lipemia posprandial medida como perfil diurno de triglicéridos en personas no diabéticas con normolipemia

BACKGROUND AND OBJECTIVE

We decided to evaluate the clinical and biochemical predictors of postprandial lipemia, measured as daylong capillarly triglycerides (TGc) profiles, in normolipidemic non diabetic subjects.

PATIENTS AND METHOD

We studied 76 normolipidemic non diabetic subjects (45 premenopausal females). Accutrend was used to measure daylong TGc profiles during 3 days in 6 previously standardized points: fasting, pre and 3 h after dinner and lunch and at bedtime. The area under the curve of TGc (AUC-TGc) was determined as expression of postprandial lipemia.

RESULTS

Males showed significantly higher AUC-TGc (26.20 [11.00] vs 19.12 [6.57] in females; p < 0.001). Obese showed significantly higher values of AUC-TGc (27.87 [12.47] vs 20.05 [7.04]; p < 0.01). The AUC-TGc correlated with: age (r = 0.242; p < 0.05), body mass index (r = 0.312; p < 0.01), waist circumference (r = 0.394; p < 0.01), fasting plasma triglyceride (r = 0.634; p < 0.001), fasting insulinemia (r = 0.485; p < 0.001) and fasting HOMA (r = 0.484; p < 0.001). The multivariate analysis showed that HOMA (regression coefficient: 0.352; p = 0.02) and waist circumference (regression coefficient: 0.4; p = 0.05) were independent predictors of the AUC-TGc.

CONCLUSIONS

Independent determinants of postprandial lipemia were waist circumference and HOMA.

Additive effects of the PPARgamma, APOE, and FABP-2 genes in increasing daylong triglycerides of normolipidemic women to concentrations comparable to those in men

BACKGROUND

Fasting and postprandial triglyceride (TG) concentrations vary considerably among individuals. TG metabolism is more efficient in women than in men, which may partly explain why females are protected against atherosclerosis. Our aim was to identify gender-specific genetic influences on fasting and postprandial TG concentrations under typical living conditions in healthy, lean, normolipidemic women.

METHODS

We studied 40 women and 48 men. Diurnal capillary TG profiles were calculated as the integrated area under the capillary TG curve averaged over 3 days. Genotypes of the FABP-2, HL, LPL, APOE, and PPARgamma genes and the APOC-III, APOC-III/A-IV intergenic region were determined.

RESULTS

Three genes (FABP-2, APOE, and PPARgamma) had a significant additive effect only in women. Mean TG concentrations were fourfold higher in women carriers of the PPARgamma wild-type allele (P = 0.044), threefold higher in carriers of the rare FABP-2 allele (P = 0.006), and fivefold higher in carriers of the E2 allele of the APOE gene (P = 0.037) than in noncarriers. None of these effects was observed in men. The presence of two or more of these adverse alleles increased TG concentrations in a dose-dependent manner. Women carriers of three adverse alleles had postprandial TG values comparable to those for men.

CONCLUSIONS

An adverse combination of common alleles of the FABP-2, APOE, and PPARgamma genes in women increases their TG concentrations to values comparable to those seen in men. Although this influence is not appreciable when studying fasting plasma TGs, it becomes apparent with use of a more sensitive index such as measurements made throughout the day.

Intra-individual fasting versus postprandial variation of biochemical markers of liver fibrosis (FibroTest) and activity (ActiTest)

BACKGROUND: Biochemical marker combinations, including alpha2-macroglobulin, haptoglobin, apolipoprotein A1, gamma-glutamyl transpeptidase, and total bilirubin (all part of FibroTest) plus alanine aminotransferase (all part of ActiTest), are being developed as alternatives to liver biopsy in patients with chronic hepatitis C and other various chronic liver diseases. Considering this premise, the primary aim of this study was to assess the impact of meal intake on FibroTest and ActiTest results. Such studies are very important for patients, as many clinical errors have been related to the absence of baseline evidence. RESULTS: Intra-individual variation was assessed for the 6 above components and for FibroTest and ActiTest, by measuring time dependent variations before and one hour after a standard meal in 64 subjects. These consisted of 29 healthy volunteers and 35 patients with chronic liver diseases. Meal intake had no significant impact on any of the six components, or on FibroTest or ActiTest, as assessed by repeated measure variance analyses (ANOVA all p > 0.90); the Spearman correlation coefficient ranged from 0.87 (total bilirubin) to 0.995 (gamma-glutamyl transpeptidase). The coefficients of variation (CV) between fasting and postprandial measurements fluctuated for the six components from 0.09 (apolipoprotein A1) to 0.14 (alpha2-macroglobulin), and from 0.09 for FibroTest to 0.13 for ActiTest. In contrast, meal intake had a significant impact on triglycerides (ANOVA p = 0.01, CV = 0.65) and glucose (ANOVA p = 0.04, CV = 0.31). As for the prediction of liver injury, the concordance between fasting and postprandial predicted histological stages and grades was almost perfect, both for FibroTest (kappa = 0.91, p < 0.001) and ActiTest (kappa = 0.80, p < 0.001). CONCLUSIONS: The intra-individual variation of biochemical markers was low, and it was shown that measurements of FibroTest, ActiTest and their components are not significantly modified by meal intake. This fact makes the screening of patients at risk of chronic liver diseases more convenient.

Rat model of familial combined hyperlipidemia as a result of comparative mapping

Total genome scan was carried out in 266 F2intercrosses from the Prague hypertriglyceridemic (HTG) rat that shares several clinical characteristics with human metabolic syndrome. Two loci for plasma triglycerides (TG) were localized on chromosome 2 (Chr 2) (LOD 4.4, 3.2). The first locus overlapped with the rat syntenic region of the human locus for the metabolic syndrome and for small, dense LDL, while the second overlapped with the syntenic region of another locus for small, dense LDL in humans by the comparative mapping approach. Loci for TG on rat Chr 13 (LOD 3.3) and Chr 1 (LOD 2.7) overlapped with the syntenic region of loci for human familial combined hyperlipidemia (FCHL) in Finnish and Dutch populations, respectively. The concordances of loci for TG localized in this study with previously reported loci for FCHL and its related phenotypes are underlying the generalized importance of these loci in dyslipidemia. These data suggest the close relationship between dyslipidemia in HTG rats and human FCHL, establishing a novel animal model for exploration of pathophysiology and therapy based on genomic determinants.

Early alterations in the postprandial VLDL1 apoB-100 and apoB-48 metabolism in men with strong heredity for type 2 diabetes

OBJECTIVES

To study the postprandial triglyceride-rich lipoprotein (TRL) metabolism, specifically the concentrations of very low-density lipoproteins (VLDL); from intestine (apoB-48) and liver (apoB-100), in men with normal fasting triglycerides but at increased risk of developing type 2 diabetes.

DESIGN

Cross-sectional study.

SUBJECTS AND SETTINGS

Sixteen healthy men with at least two first-degree relatives with type 2 diabetes were individually matched with 16 control subjects without known diabetes heredity for: age, body mass index, and fasting triglyceride level. They underwent an 8-h meal tolerance test (919 kcal, 51 g fat) during which lipoproteins were separated by density gradient ultracentrifugation. They were characterized by euglycaemic hyperinsulinaemic clamp, peak VO2, 7-day diet registration and computed tomography.

RESULTS

The relatives were, as expected, more insulin resistant than the controls and had increased concentration of postprandial VLDL1 particles (49% higher for VLDL1 apoB-48, P = 0.04 and 21% higher for VLDL1 apoB-100, P = 0.048). The elevation was related to insulin sensitivity, but not to lifestyle and body composition. Moreover, the concentration of postprandial triglycerides in VLDL1 fraction was inversely related to low-density lipoprotein (LDL) size in both relatives (rs = -0.60, P = 0.03) and controls (rs = -0.72, P = 0.004). There were no differences in the concentration of triglycerides or apoB-48 and apoB-100 particles in the other fractions (plasma, chylomicron or VLDL2).

CONCLUSION

Increased postprandial concentration of TRLs in the VLDL1 fraction seems to be present at an early stage in the development of diabetes and probably contributes to the excess risk of future coronary events in insulin-resistant men.

Lipaemia, Inflammation and Atherosclerosis

Atherosclerosis is the major cause of death in the world. Fasting and postprandial hyperlipidaemia are important risk factors for coronary heart disease (CHD). Recent developments have undoubtedly indicated that inflammation is pathophysiologically closely linked to atherogenesis and its clinical consequences. Inflammatory markers such as C-reactive protein (CRP), leucocyte count and complement component 3 (C3) have been linked to CHD and to hyperlipidaemia and several other CHD risk factors. Increases in these markers may result from activation of endothelial cells (CRP, leucocytes, C3), disturbances in adipose tissue fatty acid metabolism (CRP, C3), or from direct effects of CHD risk factors (leucocytes). It has been shown that lipoproteins, triglycerides, fatty acids and glucose can activate endothelial cells, most probably as a result of the production of reactive oxygen species. Similar mechanisms may also lead to leucocyte activation. Increases in triglycerides, fatty acids and glucose are common disturbances in the metabolic syndrome and are most prominent in the postprandial phase. People are in a postprandial state most of the day, and this phase is proatherogenic. Inhibition of the activation of leucocytes, endothelial cells, or both, is an interesting target for intervention, as activation is obligatory for adherence of leucocytes to the endothelium, thereby initiating atherogenesis. Potential interventions include the use of unsaturated long-chain fatty acids, polyphenols, antioxidants, angiotensin converting enzyme inhibitors and high-dose aspirin, which have direct anti-inflammatory and antiatherogenic effects. Furthermore, peroxisome proliferator activating receptor gamma (PPARgamma) agonists and statins have similar properties, which are in part independent of their lipid-lowering effects.

Daytime triglyceridemia in normocholesterolemic patients with premature atherosclerosis and in their first-degree relatives

Postprandial hypertriglyceridemia tested under metabolic ward conditions with unphysiological high fat loads has been reported in CAD patients and their relatives even in the presence of normal fasting lipids. It is unclear whether this also occurs in the daytime situation. Twenty-seven normocholesterolemic, non-obese and nondiabetic patients with premature coronary artery disease (CAD) and 56 first-degree relatives without CAD measured daytime capillary triglyceride profiles (TGc-AUC) as an estimate of postprandial lipemia. Fasting capillary triglycerides (TGc) were not significantly different between CAD index patients and their relatives (1.68 +/- 0.63 and 1.54 +/- 0.71 mmol/L, respectively). In contrast, daytime triglyceridemia was significantly higher in CAD patients (30.7 +/- 13.6 mmol. h/L) compared to their relatives (24.4 +/- 9.4 mmol. h/L) and this was also the case after correction for fasting TGc (7.24 +/- 7.41 and 2.79 +/- 6.89 mmol. h/L; P <.05). The best predictors of TGc-AUC by multiple regression analysis in CAD families were fasting TGc, systolic blood pressure, and high-density lipoprotein cholesterol (HDL-C), which are all components of the metabolic syndrome, explaining 65% of the variation. Since there were no major differences in nutritional intake between index patients and their relatives, this could not explain the differences Daytime triglyceridemia, measured under physiological conditions, is increased in patients with premature atherosclerosis and normal fasting TG levels, when compared to their non-CAD relatives. This study confirms previous observations using standardized oral fat loading tests and underlines the importance of postprandial hyperlipidemia in CAD.

Diurnal triglyceridaemia and insulin resistance in mildly obese subjects with normal fasting plasma lipids

OBJECTIVE

A novel method has been developed to study diurnal triglyceride (TG) profiles using repeated capillary self-measurements in an 'out-of-hospital' situation. We assessed the diurnal capillary TG (TGc) profile in males with mild obesity and evaluated the use of plasma and capillary TG as markers of insulin resistance.

DESIGN

Cross-sectional study.

SETTING AND SUBJECTS

Fifty-four lean (body mass index, BMI < 25 kg m-2) and 27 mildly obese (25 < BMI < 30 kg m-2), normolipidaemic males measured capillary TG concentrations on six fixed time-points over a 3-day period in an 'out-of-hospital' situation.

MAIN OUTCOME MEASURES

The total area under the TGc curve (TGc-AUC) and incremental area under the TGc curve (TGc-IAUC) were used as estimation of diurnal triglyceridaemia. Fasting blood samples were obtained once. Food intake was recorded by all participants.

RESULTS

Obese and lean subjects had comparable fasting capillary TG concentrations (1.37 +/- 0.40 mmol L-1 and 1.32 +/- 0.53 mmol L-1, respectively). However, during the day, obese subjects showed a greater TG increase, resulting in significantly higher TGc-AUC (27.1 +/- 8.4 and 23.0 +/- 6.3 mmol h-1 l-1, respectively; P < 0.05) and TGc-IAUC (7.9 +/- 5.8 and 4.6 +/- 6.6 mmolh-1 L-1, respectively; P < 0.05). The total group of 81 males was divided into quartiles based on fasting plasma TG, fasting capillary TG, TGc-AUC and TGc-IAUC. Amongst these variables, TGc-AUC was the only significant discriminator of subjects with high homeostasis model assessment (HOMA) (insulin resistance) compared with low HOMA (insulin sensitive). Overall, BMI was the strongest determinant of HOMA.

CONCLUSIONS

Diurnal TG profiles can be used to investigate postprandial lipaemia in both lean and mildly obese subjects and may help to detect subjects with an underlying disposition for hypertriglyceridaemia related to insulin resistance, i.e. the metabolic syndrome.

Fasting and daylong triglycerides in obesity with and without type 2 diabetes

Postprandial hypertriglyceridemia associated with insulin resistance is one of the cardiovascular risk factors in obesity and type 2 diabetes. It is not known whether diabetics have a more pronounced postprandial hypertriglyceridemia than obese subjects. Daylong triglyceridemia, representing postprandial lipemia, was determined in obese subjects with and without type 2 diabetes and in lean subjects. Nineteen type 2 diabetics (F/M: 7/12, body mass index [BMI]: 30.6 +/- 5.4 kg/m(2)), 45 obese nondiabetics (F/M: 16/29, BMI: 29.5 +/- 2.6 kg/m(2)) and 78 lean subjects (F/M: 28/50, BMI: 23.7 +/- 2.2 kg/m(2)) measured capillary triglycerides (TGc) during 3 days on 6 fixed time-points each day in an out-of-hospital situation. Daylong TGc profiles were calculated as mean integrated area under the TGc-curve (TGc-AUC). Fasting plasma TG were higher in diabetics and obese nondiabetics (1.81 +/- 0.79 and 1.77 +/- 0.80 mmol/L) compared with lean subjects (1.23 +/- 0.67 mmol/L, P <.001). TGc-AUC was similarly increased in both diabetics and obese nondiabetics (35.0 +/- 12.1 and 35.2 +/- 10.6 mmol.1 h/L) compared with lean controls (25.5 +/- 12.0 mmol.1 h/L, P <.001). Self-reported energy intake was not significantly different between the groups. Fasting TGc (r =.87, P <.001) and waist circumference (r =.51, P <.001) were the parameters best associated with TGc-AUC. Using stepwise multiple regression analysis, fasting TGc, BMI, total cholesterol, and high-density lipoprotein (HDL) cholesterol were the best predictors of TGc-AUC, explaining 77% of the variation. The cut-off level for "normal" TGc-AUC, calculated as the 75th percentile of TGc-AUC in lean subjects, was 30.7 mmol.1 h/L and corresponded with a fasting TGc of 1.8 mmol/L (eg, 1.6 mmol/L in plasma), calculated using univariate regression analysis. In conclusion, daylong triglyceridemia is similarly increased in diabetics and obese nondiabetics compared with lean subjects. Fasting TG and central obesity largely determine daylong triglyceridemia, independent of the presence of type 2 diabetes. Decreasing fasting plasma TG below 1.6 mmol/L could lead to a normalization of postprandial lipemia in obese subjects with and without diabetes.