Normotriglyceridemic Subjects Research Articles

Differences in peripheral blood mononuclear cell gene expression and triglyceride composition in lipoprotein subclasses in plasma triglyceride responders and non-responders to omega-3 supplementation

BackgroundIntake of the marine omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) reduces fasting triglyceride (TG) levels and may thereby lower cardiovascular disease risk. However, there are large inter-individual differences in the TG-lowering effect of omega-3 supplementation. Genotype differences partly explain this variation, but gene-environment interactions leading to gene expression differences may also be important. In this study, we aimed to investigate baseline differences and differences in the change in peripheral blood mononuclear cell (PBMC) gene expression and lipoprotein subclass TG levels between TG responders and non-responders to omega-3 fatty acid supplementation.MethodsIn a previous randomized controlled trial, healthy normotriglyceridemic subjects (n = 35, 71% women) received 1.6 g EPA + DHA/day for 7 weeks. In this exploratory sub-study, we defined TG responders as subjects having a TG reduction beyond the 20% day-to-day variation and non-responders as having a TG change between − 20% and + 20% after omega-3 supplementation. PBMC gene expression was measured using microarray, and lipoprotein subclasses were measured using nuclear magnetic resonance spectroscopy.ResultsEight subjects were defined as responders with a median TG reduction of 37%, and 16 subjects were defined as non-responders with a median TG change of 0%. At baseline, responders had higher TG levels in two of four high-density lipoprotein (HDL) subclasses and 909 gene transcripts (p ≤ 0.05) were differentially expressed compared to non-responders. During the intervention, the plasma TG reduction among responders was reflected in TG reductions in four of six different very low-density lipoprotein subclasses and three of four different HDL subclasses. Compared to non-responders, the expression of 454 transcripts was differentially altered in responders (p ≤ 0.05). Pathway analyses revealed that responders had altered signaling pathways related to development and immune function. In addition, two of the top 10 enriched pathways in responders compared to non-responders were related to lysophosphatidic acid signaling.ConclusionTG responders and non-responders to omega-3 supplementation have different lipoprotein subclass and PBMC gene expression profiles at baseline and different lipoprotein subclass and PBMC gene expression responses to omega-3 supplementation. These gene expression differences may partially explain the variability in TG response observed after omega-3 supplementation.Graphical abstractBased on free images from Servier Medical Art (Creative Commons Attribution License) and image from www.colourbox.com.

A promoter variant of the APOA5 gene increases atherogenic LDL levels and arterial stiffness in hypertriglyceridemic patients.

Hypertriglyceridemia is recognized as an independent risk factor for coronary artery disease. The apolipoprotein A5 gene (APOA5) is a key regulator of triglyceride levels. We aimed to evaluate the associations of single nucleotide polymorphisms (SNPs) in APOA5, including -1131T>C and c.553G>T, with hypertriglyceridemia, apoA5 concentrations, atherogenic LDL cholesterol levels, and arterial stiffness in hypertriglyceridemic patients. The study population included 599 hypertriglyceridemic patients (case) and 1,549 untreated normotriglyceridemic subjects (control). We genotyped two APOA5 variants, -1131T>C (rs662799) and c.553G>T (rs2075291). The frequencies of the CC genotype of -1131T>C (0.165) and the T allele of c.553G>T (0.119) were significantly higher in hypertriglyceridemic patients than in normotriglyceridemic subjects (0.061 and 0.070, respectively; all p<0.001). In the control and case groups, both the -1131T>C and c.553G>T variants were associated with higher triglyceride and lower HDL cholesterol levels. Controls with the -1131CC variant had lower apoA5 concentrations than controls with the -1131TT variant. Similar effects of the -1131T>C variant on apoA5 were observed in the cases. In the hypertriglyceridemic group, the -1131T>C variant was associated with a smaller LDL particle size, higher levels of oxidized LDL and malondialdehyde, and higher brachial-ankle pulse wave velocity. The -1131T>C and c.553G>T polymorphisms were associated with hypertriglyceridemia in the study population, but only the -1131T>C polymorphism directly affected apoA5 concentrations. Hypertriglyceridemic patients carrying the APOA5 -1131T>C polymorphism exhibited increased atherogenic LDL levels and arterial stiffness, probably due to an effect of the -1131T>C polymorphism on apoA5 concentrations.

Rare and common variants in LPL and APOA5 in Thai subjects with severe hypertriglyceridemia: A resequencing approach

Severe hypertriglyceridemia usually results from a combination of genetic and environmental factors. Few data exist on the genetics of severe hypertriglyceridemia in Asian populations. To examine the genetic variants of 3 candidate genes known to influence triglyceride metabolism, LPL, APOC2, and APOA5, which encode lipoprotein lipase, apolipoprotein C-II, and apolipoprotein A-V, respectively, in a large group of Thai subjects with severe hypertriglyceridemia. We identified sequence variants of LPL, APOC2, and APOA5 by sequencing exons and exon-intron junctions in 101 subjects with triglyceride levels ≥ 10mmol/L (886mg/dL) and compared with those of 111 normotriglyceridemic subjects. Six different rare variants in LPL were found in 13 patients, 2 of which were novel (1 heterozygous missense variant: p.Arg270Gly and 1 frameshift variant: p.Asp308Glyfs*3). Four previously identified heterozygous missense variants in LPL were p.Ala98Thr, p.Leu279Val, p.Leu279Arg, and p.Arg432Thr. Collectively, these rare variants were found only in the hypertriglyceridemic group but not in the control group (13% vs 0%, P<.0001). One common variant in APOA5 (p.Gly185Cys, rs2075291) was found at a higher frequency in the hypertriglyceridemic group compared with the control group (25% vs 6%, respectively, P<.0005). Altogether, rare variants in LPL or APOA5 and/or the common APOA5 p.Gly185Cys variant were found in 37% of the hypertriglyceridemic group vs 6% in the controls (P=3.1×10(-8)). No rare variant in APOC2 was identified. Rare variants in LPL and a common variant in APOA5 were more commonly found in Thai subjects with severe hypertriglyceridemia. A common p.Gly185Cys APOA5 variant, in particular, was quite prevalent and potentially contributed to hypertriglyceridemia in this group of patients.

Hypertriglyceridemic subjects exhibit an accumulation of small dense chylomicron particles in the fasting state

AimNormocholesterolemic subjects with elevated fasting plasma triglycerides are at increased risk of atherosclerosis through mechanisms that are not yet delineated. We hypothesized that elevated plasma triglyceride is associated with increased vascular exposure to pro-atherogenic lipoprotein remnants. To test this hypothesis, the abundance, and size distribution of chylomicron particles were determined in individuals with and without hypertriglyceridemia. MethodsTwelve hypertriglyceridemic subjects (HTG group, triglyceride concentration ≥1.7 mmol/L) and twelve normotriglyceridemic subjects (NTG group) matched for age and gender were studied. The distribution of chylomicron particles was assessed by determining the fasting concentration of apo B-48 in serum lipoprotein fractions with Svedberg flotation rates of (Sf) > 400, Sf 20–400 and Sf < 20. ResultsThe total concentration of apo B-48 in subjects with HTG was almost twice that observed in NTG controls with ∼80% of the increase residing in the Sf < 20 fraction (HTG: 8.7 ± 1.0 μg/mL vs NTG: 5.0 ± 0.6 μg/mL; P = 0.016). Significantly greater concentrations of apo B-48 were also observed in the less dense Sf 20–400 (HTG: 1.1 ± 0.2 μg/mL vs NTG: 0.4 ± 0.07 μg/mL; P < 0.001) and the Sf > 400 (HTG: 1.1 ± 0.3 μg/mL vs NTG: 0.3 ± 0.04 μg/mL; P < 0.001) fractions. An accumulation of triglyceride was also observed across all lipoprotein fractions in HTG subjects compared to NTG (Sf 400 & Sf 20–400: P < 0.001 and Sf < 20: P = 0.013). ConclusionNormocholesterolemic, moderately hypertriglyceridemic subjects are at increased atherogenic risk due to greater apo B-48 concentration in the small, dense lipoprotein fraction.

Effect of DHA-rich fish oil on PPARγ target genes related to lipid metabolism in type 2 diabetes: A randomized, double-blind, placebo-controlled clinical trial

The beneficial effects of omega-3 polyunsaturated fatty acids on lipid levels are well documented. However, the related molecular mechanisms are widely unknown. Omega-3 polyunsaturated fatty acids are natural ligand for peroxisome proliferator-activated receptor γ (PPARγ). The aim of this study was to evaluate the effect of docosahexaenoic acid (DHA)-rich fish oil supplementation on modulation of some PPARγ-responsive genes related to lipid metabolism. Patients with type 2 diabetes were randomly assigned to consume either DHA-rich fish oil (containing 2400 mg/d fish oil; DHA: 1450 mg and eicosapentaenoic acid: 400 mg) or placebo for 8 weeks. Lipid profile and glycemic control parameters as well as the gene expression of PPARγ, liver x receptor-a, ATP-binding cassette A1, and CD36 in peripheral blood mononuclear cells were measured at baseline and after 8 weeks. DHA-rich fish oil supplementation resulted in decreased triglycerides (TG) level compared with placebo group, independently of the baseline value of TG (all patients (P = .003), hypertriglyceridemic subjects (P = .01), and normotriglyceridemic subjects (P = .02)). Moreover, a higher reduction in TG level was observed in hypertriglyceridemic subjects, comparing to normotriglyceridemic subjects with DHA-rich fish oil supplementation (P = .01). Other lipid parameters as well as the expression of PPARγ, liver x receptor-a, ATP-binding cassette A1, and CD36 were not affected by DHA-rich fish oil supplementation. Only in hypertriglyceridemic subjects, DHA-rich fish oil supplementation upregulated CD36 expression, compared with the placebo group (P = .01). DHA-rich fish oil supplementation for 8 weeks increased CD36 expression in hypertriglyceridemic subjects, which might result to higher reduction in TG level, comparing with normotriglyceridemic subjects. However, this finding should be investigated in further studies.

Relationship between food and nutrient intake and the risk of hypertriglyceridemia in Vietnamese women residing in Bavi: the Korean Genome and Epidemiology Study (KoGES)

The purpose of this study is to investigate the proportion and associated risk factors of hypertriglyceridemia in rural Vietnamese women. Research data were collected as part of the Korean Genome and Epidemiology Study (KoGES). A cross-sectional study of 957 Vietnamese women in their 20 to 30s was conducted in rural areas of Bavi, Vietnam. Subjects were classified as hypertriglyceridemic (serum TG ≥ 150 mg/dL). Demographic, socio-economic details, anthropometric measurements, and blood profiles were recorded. The proportion of hypertriglyceridemic subjects was 22.0%, and the mean age of hypertriglyceridemics subjects was older than that of normo-triglyceridemic subjects (p ＜ 0.05). In hypertriglyceridemic subjects, height, HDL-cholesterol, and LDL-cholesterol were significantly lower, compared to subjects with normo-triglyceridemia, while weight, body mass index, waist hip ratio, body fat %, blood pressure, fasting blood sugar, total cholesterol, and atherogenic index were higher, compared to those with normo-triglyceridemia. Intake of cereal and cereal products, total plant food, and cereal/potato fiber in subjects with hypertriglyceridemia was significantly higher, compared to normo-triglyceridemic subjects. Hypertriglyceridemic subjects had a significantly lower intake of animal calcium and retinol than normo-triglyceridemic subjects. Significant positive relationships were observed between the prevalence of hypertriglyceridemia and consumption of total plant food [OR (95% CI) for the highest tertile, compared to the lowest: 1.764 (1.131-2.750); p for trend = 0.008] and crude fiber [OR (95% CI) for the highest tertile compared to the lowest: 1.651 (1.092-2.497); p for trend = 0.027]. In addition, a significant inverse rela tionship was observed between the prevalence of hypertriglyceridemia and cholesterol intake [OR (95% CI) for the highest tertile, compared to the lowest: 0.601 (0.400-0.901); p for trend = 0.012]. These findings may provide basic data for use by policymakers and dieticians in future development of nutrition and health programs to encourage healthier eating habits, and to prevent hypertriglyceridemia advancing cardiovascular disease in rural Vietnamese women. (Korean J Nutr 2013; 46(1): 15 ~ 25)

Impaired Hepatic Ketogenesis in Moderately Obese Men With Hypertriglyceridemia

BackgroundSeveral studies suggest that increased nonesterified fatty acid flux and increased de novo lipogenesis may contribute to hypertriglyceridemia, but few studies have examined fatty acid oxidation as a factor.RationaleEndogenous hypertriglyceridemia...

Low adiponectin levels in primary hypertriglyceridemic male patients

Background and aims Adiponectin is an adipokine highly and specifically expressed by adipose cells with antiatherogenic and antiinflammatory activities. The aim of the present study was to evaluate plasma adiponectin concentration in patients with primary hypertriglyceridemia and its relationship with metabolic parameters. Methods and results Male patients with primary hypertriglyceridemia and without the metabolic syndrome ( n = 22) were compared with normotriglyceridemic individuals ( n = 25). Plasma adiponectin concentration was measured by standardised enzyme-linked immunosorbent assay. Body mass index, waist circumference, glucose, insulin and non-esterified fatty acid levels, lipoprotein profile, and CETP activity were evaluated. Adiponectin levels were significantly decreased in hypertriglyceridemic patients in comparison with normotriglyceridemic subjects (4292 ± 1717 vs. 6939 ± 3249 ng/ml, p < 0.005, respectively). Adiponectin was negatively associated with glucose ( r = − 0.44, p < 0.01), insulin ( r = − 0.37, p < 0.01), HOMA ( r = − 0.40, p < 0.01), triglycerides ( r = − 0.36, p < 0.01), VLDL-C ( r = − 0.34, p < 0.05), and CETP ( r = − 0.47, p < 0.001). Positive and significant correlations were observed with QUICKI ( r = 0.49, p < 0.001) and HDL-C ( r = 0.33, p < 0.05). In the multiple linear regression analysis, considering waist circumference, QUICKI, Log-triglycerides, HDL-C, and CETP as independent variables, Log-adiponectin showed a positive correlation with QUICKI, with an r 2 = 0.229 and p < 0.001. Therefore, the independent variable QUICKI explained the 23% of the variance in Log-adiponectin concentration. Conclusions We found low adiponectin levels in a population of primary hypertriglyceridemic men without the metabolic syndrome and an independent relationship between adiponectin concentration and insulin resistance. A reduction in insulin sensitivity and its impact on adiponectin concentration could be linked to high non-esterified fatty acid levels, increased triglyceride synthesis in the liver and impaired catabolism of triglyceride-rich lipoproteins.

One Common Polymorphism of Cholesteryl Ester Transfer Protein Gene in Iranian Subjects With and Without Primary Hypertriglyceridemia

Primary hypertriglyceridemia is considered to be a major risk factor for pancreatitis, atherosclerosis and coronary heart disease. Cholesteryl ester transfer protein gene polymorphisms known to be associated with changes in lipid levels. This study was performed by using polymerase chain reaction and restriction fragment length polymorphisms. Genotype distribution and allelic frequencies of polymorphism were determined and compared in primary hypertriglyceridemic and normotriglyceridemic subjects. The results showed that plasma cholesteryl ester transfer protein activity was significantly higher in primary hypertriglyceridemia than in controls (p = 0.001). In this study all individuals with B2B2 genotype had lower plasma cholesteryl ester transfer protein activity, higher high-density lipoprotein than B1B1 and B1B2 genotypes, whereas triglyceride was significantly decreased in this genotype. The genotype and allelic frequencies for this polymorphism differed significantly between primary hypertriglyceridemic patients and controls (p = 0.014 and p = 0.027, respectively). In both groups, CETP Taq 1B polymorphism (presence of B2 allele) correlated significantly with HDL-C (r = 0.207 and 0.300 in control and patient groups, respectively) and CETP activity (r = -0.193 for controls and r = -0.132 for patients). Taq 1B polymorphism of cholesteryl ester transfer protein gene was associated with changes in lipids profile and plasma cholesteryl ester transfer protein activity in the selected population.

Effects of marine n-3 fatty acid supplementation on lipoprotein subclasses measured by nuclear magnetic resonance in subjects with type II diabetes

To measure effects of fish oil supplements on lipoprotein subclasses by nuclear magnetic resonance (NMR) in subjects with type II diabetes and relate them to insulin sensitivity. Two-armed, parallel, placebo-controlled, randomized. Normotriglyceridemic subjects with type II diabetes without insulin treatment were given either fish oil (n=12, median intake 5.9 g/day total n-3 fatty acids (FA) (1.8 g 20:5n-3, 3.0 g 22:6n-3)) or corn oil (n=14, 8.5 g/day 18:2n-6 FA). Size and concentration of lipoproteins subclasses were measured by NMR, insulin sensitivity by hyperinsulinemic, isoglycemic clamps. After 9 weeks, there were differences between those treated with fish and corn oil with respect to very low-density lipoprotein (VLDL) size (median -15 vs +0.6%, P=0.001), particle concentrations of large VLDL (-99 vs -4.1%, P=0.041) and small high-density lipoprotein (HDL) (-12 vs +10%, P=0.051). Compared with corn oil fish oil tended to increase HDL size and small low-density lipoprotein (LDL) concentration (P=0.063 and 0.068, respectively, for differences between groups). There was no effect on oxidized LDL. Insulin sensitivity (glucose utilization) decreased in the fish oil group compared with the corn oil group (P=0.049). The decrease in insulin sensitivity did not correlate with the effects on lipoprotein subclasses. A high intake of n-3 FA exerts effects on several lipoprotein subclasses without obvious influence from changes in insulin sensitivity.

Non-HDL cholesterol versus Apolipoprotein B in the identification of dyslipidemic phenotypes associated with cardiovascular risk in type 2 diabetic dyslipoproteinemia

Summary Objective Few studies have compared non-HDL cholesterol (non-HDLc) and Apolipoprotein B (apoB) as markers of atherosclerotic risk. No such study has yet been undertaken in Asian-Indians who have a different lipid–lipoprotein profile than their Western counterparts. Our aim, therefore, was to evaluate the role of non-HDLc and apoB, as markers of all potentially atherogenic species, and to further assess as to which is the better index of the risk of cardiovascular disease (CVD) in type 2 diabetic subjects. Research design and methods Lipidic parameters, apoB and carotid mean intima–media thickness (IMT) were determined in the 95 diabetic subjects included in the study. Subjects were classified on the basis of apoB and triglyceride as well as non-HDLc and triglyceride levels. Agreement of the resultant phenotypes with IMT was assessed (correlation and concordance ( κ ) analysis), and the major contributor to the variance of IMT was determined using multistep linear regression. Results HyperapoB was the most prevalent lipoproteic abnormality. The correlation between apoB and non-HDLc was strong in the whole cohort ( r = 0.60, p r = 0.67, p κ = 0.490, p κ = 0.403, p κ = 0.598, p κ = 0.481, p κ = 0.387, p κ = 0.043, p = NS). Further apoB was a better predictor of IMT in all the subgroups as well as the whole cohort ( R 2 = 0.378, β -coefficient = 0.002) as compared to non-HDLc ( R 2 change = 0.030, β -coefficient = 0.0017). Conclusions Non-HDLc and apoB are equivalent atherogenic markers of cardiovascular risk in hypertriglyceridemic diabetic subjects, but apoB is a better index of the risk of cardiovascular disease in normotriglyceridemic subjects. Thus, measurement of apoB might be helpful in identification of a subgroup of apparently normolipidemic subjects who have hyperapoB and thus stand increased cardiovascular risk.

Triglyceride-rich lipoproteins from hypertriglyceridemic subjects induce a pro-inflammatory response in the endothelium: Molecular mechanisms and gene expression studies

Triglyceride-rich lipoproteins (TGRLs) are a cardiovascular risk factor and induce endothelial dysfunction. In the present study we investigated the effects of TGRLs from type IV hyperlipidemic and normolipidemic subjects on endothelial activation focusing on the effects on intracellular pathways and gene expression. A total of 54 subjects, 30 hypertriglyceridemic (triglyceride (TG) levels 284+/-101 mg/dl) and 23 normotriglyceridemic (TG levels 109+/-40 mg/dl) were enrolled as lipoprotein donors. TGRLs were isolated from hypertriglyceridemic (H-TGRL) and normotriglyceridemic (N-TGRL) subjects. RNA from human endothelial cells incubated with N-TGRL or H-TGRL was prepared for cDNA microarray analyses. Western blotting was used to study intracellular signaling pathways. Regulated genes were further studied with real-time PCR, immunofluorescence and FACS. Furthermore, a protein/DNA array and chromatin-immunoprecipitation were used to identify transcription factors involved in the observed effects. Both N-TGRL and H-TGRL activated ERK1/2 and p38 MAPK. However, there were differences in the pattern of upregulated target genes between the two types of lipoproteins in HUVECs and/or HAECs: PAI-1, VCAM-1, ELAM-1 and MCP-1 were upregulated by both N-TGRL and H-TGRL, while PECAM-1, IL-6 and ADAMTs1 were selectively upregulated by H-TGRL. Chromatin immunoprecipitation analysis demonstrated the involvement of transcription factors NF-kB and CREB in the activation of these genes. These results support the possible involvement of hypertriglyceridemic TGRLs in endothelial dysfunction via induction of a pro-inflammatory and pro-thrombotic state.

Insulin resistance and postprandial triglyceride levels in primary renal disease

Background Renal failure is associated with a range of metabolic abnormalities including insulin resistance and dyslipidemia. We examined the role of creatinine clearance (CrCl) and body composition in the development of insulin resistance in patients with primary renal disease and a variable degree of renal failure. We also determined the effect of a high-fat meal on postprandial triglyceride levels in a subgroup of these patients. Methods Forty-four patients with primary renal disease (men, 25; women, 19; age, 21-75 years) were compared to 44 controls matched for age, sex, and body composition. Renal biochemistry, plasma glucose, insulin, lipids, and nonesterified fatty acids were measured in the fasting state. Insulin sensitivity was calculated using the Homeostasis Model Assessment for Insulin Resistance (HOMA-R), and pancreatic beta-cell secretory capacity by HOMA- β. Fourteen normotriglyceridemic subjects from each group consumed an 80-g fat meal to examine their postprandial metabolic response. Results Although there was no significant difference between HOMA-R for the controls and the entire patient group ( P = .06), HOMA-R was significantly higher in patients with CrCl less than 60 mL/min than those with CrCl greater than 60 mL/min or control subjects ( P < .01 for each pair). Exponential analysis of the relationship between CrCl and HOMA-R and - β showed a line of best fit that was superior to that obtained by linear regression analysis ( P < .01 and P < .005, respectively). HOMA-R in renal patients was correlated with several parameters of body composition, including central fat (kilogram) ( P < .005). There was no difference in body fat parameters or HOMA-R for the patient and control subgroups undergoing a fat meal challenge. However, the patient subgroup showed a greater postprandial incremental rise in plasma triglycerides compared to controls ( P < .02). Conclusion Patients with renal disease exhibit metabolic features typically associated with the metabolic syndrome. Insulin resistance increased with decline in renal function and was significantly higher in patients with CrCl less than 60 mL/min compared to subjects with CrCl greater than 60 mL/min or carefully matched controls. Renal patients also showed significant postprandial hypertriglyceridemia.

The lipoprotein lipase gene HindIII polymorphism is associated with lipid levels in early-onset type 2 diabetic patients

Lipoprotein lipase (LPL) plays a central role in triglyceride metabolism, and the LPL gene T495G HindIII polymorphism has been associated with variations in lipid levels and heart disease in Caucasians with the more common H+ allele being associated with adverse lipid profiles and increased risk of CHD. We investigated this polymorphism in 785 Chinese subjects with varying components of the metabolic syndrome, including 61.4% with early-onset type 2 diabetes (age at diagnosis ≤ 40 years), and 167 healthy control subjects using a polymerase chain reaction (PCR)-based restriction fragment length polymorphism (RFLP) method. The allele and genotype frequencies were similar in the patients and control subjects. When grouped above or below standard cutoffs for triglyceride levels, the H+ allele was more frequent in hypertriglyceridemic than that in normotriglyceridemic subjects in the total population (81.5% v 76.1%) and early-onset type 2 diabetics (84.4% v 77.4%, both P <.05). Moreover, H+H+ carriers had significantly higher plasma triglyceride and lower high-density lipoprotein (HDL)-cholesterol levels when compared to subjects with the H- allele in the total population, and in patients with early-onset diabetics (both P <.05). In the total population and the early-onset diabetic patients, this relationship was confined to males when gender was considered. We conclude that the H+ allele of the LPL gene HindIII polymorphism is associated with higher plasma triglyceride and lower HDL-cholesterol levels in Chinese patients with early-onset diabetes. Copyright 2003, Elsevier Science (USA). All rights reserved.

Mean platelet volume as an indicator of platelet activation: methodological issues

Background: Mean platelet volume (MPV) is increased in patients at high risk for athero-thrombotic diseases. Thus, an elevated MPV may be a risk marker for platelet activation. Methods: Healthy subjects with normal triglyceride (TG) levels (90 - 6 mg/dl; n = 40) or mild hypertriglyceridemia (161 - 79 mg/dl; n = 32) were studied. MPV was measured in fasting blood samples before and after stimulation with collagen (10 w g/ml), and exposure to 4 or 37°C. Samples from the normotriglyceridemic subjects were tested again 4 h after consuming a high-fat drink. Results: Collagen and exposure to 4°C increased MPV, whereas incubation at 37°C lowered MPV regardless of TG level. There was no significant difference in unstimulated MPV between the fasting and the fed states in the normotriglyceridemic subjects (both 7.2 - 0.1 fl; mean - SEM), nor between the latter group and hypertriglyceridemic subjects (7.0 - 0.1 fl). There was a significant negative relation between MPV and fasting TG level. Conclusions: This study suggests that MPV response to low-dose collagen may be a useful indicator of platelet propensity to activation. Further studies are warranted to correlate MPV with classical platelet aggregation tests and with the use of platelet-active drugs.

Moderate intake of n−3 fatty acids is associated with stable erythrocyte resistance to oxidative stress in hypertriglyceridemic subjects

The important triacylglycerol-lowering capacity of n-3 fatty acids is counterbalanced by their inherent sensitivity to oxidation. Inconsistent results about the latter have been reported in hypertriglyceridemic individuals. After incorporation into cell membranes, n-3 fatty acids may alter membrane-related functions. In view of the distinct composition of hypertriglyceridemic membranes and the prooxidant status in this condition, it can be surmised that cell enrichment with the oxidizable n-3 fatty acids will be associated with an increased hemolytic process. We sought to evaluate the effect of fish oil consumption on n-3 fatty acid incorporation into erythrocyte membranes and subsequent ex vivo oxidative-stress-induced hemolysis in normotriglyceridemic and hypertriglyceridemic subjects. Sixteen normotriglyceridemic and 12 hypertriglyceridemic subjects were given 6 g fish oil/d for 8 wk. Blood samples were collected before and 4 and 8 wk after treatment. Resistance to 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced hemolysis was assayed in fresh erythrocyte suspensions, and erythrocyte samples were stored at -70 degrees C for later analysis of cholesterol, hemoglobin, fatty acids, vitamin E, and glutathione peroxidase activity. Fish oil supplementation induced n-3 fatty acid incorporation in normotriglyceridemic and hypertriglyceridemic erythrocyte membranes without decreasing their resistance to AAPH. n-3 Fatty acids significantly protected normotriglyceridemic but not hypertriglyceridemic erythrocytes against hemolysis. In normotriglyceridemic subjects only, the higher resistance to hemolysis correlated with changes in cell vitamin E. Although they exhibit a high susceptibility to oxidation, n-3 fatty acids may preserve membrane integrity and represent an added benefit in the treatment of hypertriglyceridemic patients.

Impaired glucose tolerance without hypertriglyceridemia does not enhance postprandial lipemia.

Postprandial lipemia has been thought to be one of risk factors for coronary heart disease, and enhances in potential patients for atherosclerotic disease. Patients with impaired glucose tolerance (IGT) often show hypertriglyceride, which is caused by enhanced portprandial lipemia. Therefore, postprandial lipemia in patients with IGT and without hypertriglyceridemia has not been cleared. We have examined the levels of plasma triglyceride and chylomicron remnants after a high fat meal load (1250 kcal, 40% fat and 420 mg cholesterol) in 13 normotriglyceridemic subjects with IGT and 10 controls with normal glucose tolerance (NGT). Chylomicron remnants were evaluated as remnant-like particles (RLP) that were not bound to an immunoaffinity gel mixture containing apo A-I and apo B-100 monoclonal antibody. RLP cholesterol levels 4 hours after the fat load were significantly lower in IGT subjects than in NGT subjects. Increase of RLP cholesterol after the fat meal load only significantly correlated with increase of insulin during the first 30 min after a 75 g oral glucose tolerance test, but not fasting lipid, insulinogenic index and HOMA-R (homeostasis model) in all subjects. These results suggest that postprandial response does not enhance in IGT subjects, and may associate with early-phase insulin secretion and without insulin resistance in normotriglyceridemic men with IGT or NGT.

Alterations in the main steps of reverse cholesterol transport in male patients with primary hypertriglyceridemia and low HDL-cholesterol levels

Hypertriglyceridemia is a complex pathological entity strongly connected to low HDL-C levels but controversially related to the risk of coronary artery disease. In this study, we evaluated the main steps of the antiatherogenic pathway called reverse cholesterol transport in a group of patients with primary hypertriglyceridemia and low HDL-C levels in comparison to normotriglyceridemic subjects with or without hypoalphalipoproteinemia. In patients with primary hypertriglyceridemia, low HDL-C levels were accompanied by decreased apo A-I and apo A-II concentrations. These reductions were manifested by a selective reduction in LpA-I:A-II particles. In addition, apo C-III Lp non B was found to be elevated and HDL lipid percentage composition showed a triglyceride enrichment and cholesterol depletion. The capacity of serum samples from hypertriglyceridemic patients to promote cellular cholesterol efflux was reduced, as evidenced by using two different cellular models, Fu5AH and J774 cells. This impaired cholesterol efflux promotion was also corroborated by incubations of isolated HDL fractions with Fu5AH cells. Lecithin:cholesterol acyltransferase (LCAT) activity, the driving force of reverse cholesterol transport, showed a tendency towards lower values in hypertriglyceridemic patients, but this difference was not statistically significant. Additionally, cholesteryl ester transfer protein (CETP) activity was increased in this group of patients. Therefore, hypertriglyceridemia was found to induce quantitative and qualitative alterations in HDL and its subclasses and, consequently, in some steps of reverse cholesterol transport. The abnormalities found in this antiatherogenic pathway and its promoters could constitute a possible connection between hypertriglyceridemia and atherosclerosis.

Upregulation of macrophage lipoprotein lipase in patients with type 2 diabetes: role of peripheral factors.

Atherosclerosis is the major complication of diabetes. Accumulating evidence indicates that lipoprotein lipase (LPL) produced by macrophages in the vascular wall may favor the development of atherosclerosis by promoting lipid accumulation within the lesion. We previously demonstrated that high glucose stimulates in vitro murine and human macrophage LPL production. In this study, we measured macrophage LPL mRNA expression, immunoreactive mass, and activity in normotriglyceridemic subjects with type 2 diabetes. Monocytes isolated from healthy control subjects and patients with type 2 diabetes were differentiated into macrophages in RPMI medium containing 20% autologous serum. After 5 days in culture, macrophage LPL mRNA expression, mass, and activity were determined. Macrophages of diabetic patients cultured in their own sera showed a significant increase in LPL mRNA levels, mass, and activity compared with macrophages of control subjects. Differentiation of macrophages of diabetic patients in sera obtained from control subjects significantly reduced these anomalies. Conversely, culturing macrophages of control subjects in sera of diabetic patients significantly increased LPL mass and activity in these cells. Besides LPL overproduction, macrophages of diabetic patients exhibited an increase in basal and LPL-induced tumor necrosis factor (TNF)-alpha release. TNF-alpha alterations were reduced by exposing these cells to sera of control subjects. Overall, these data demonstrate that macrophages of diabetic patients overexpress LPL and TNF-alpha and that peripheral factors dysregulated in diabetes are, at least in part, responsible for these alterations.

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.