VLDL TG Research Articles

GLP-1 attenuates intestinal fat absorption and chylomicron production via vagal afferent nerves originating in the portal vein

Background/ObjectiveGLP-1R agonists have been shown to reduce fasting and postprandial plasma lipids, both of which are independent risk factors for the development of cardiovascular disease. However, how endogenous GLP-1 – which is rapidly degraded – modulates intestinal and hepatic lipid metabolism is less clear. A vagal gut-brain-axis originating in the portal vein has been proposed as a possible mechanism for GLP-1’s anti-lipemic effects. Here we sought to examine the relationship between vagal GLP-1 signalling and intestinal lipid absorption and lipoprotein production. MethodsSyrian golden hamsters or C57BL/6 mice received portal vein injections of GLP-1(7-36), and postprandial and fasting plasma TG, TRL TG, or VLDL TG were examined. These experiments were repeated during sympathetic blockade, and under a variety of pharmacological or surgical deafferentation techniques. In addition, hamsters received nodose ganglia injections of a GLP-1R agonist or antagonist to further probe the vagal pathway. Peripheral studies were repeated in a novel GLP-1R KO hamster model and in our diet-induced hamster models of insulin resistance. ResultsGLP-1(7-36) site-specifically reduced postprandial and fasting plasma lipids in both hamsters and mice. These inhibitory effects of GLP-1 were investigated via pharmacological and surgical denervation experiments and found to be dependent on intact afferent vagal signalling cascades and efferent changes in sympathetic tone. Furthermore, GLP-1R agonism in the nodose ganglia resulted in markedly reduced postprandial plasma TG and TRL TG, and fasting VLDL TG and this nodose GLP-1R activity was essential for portal GLP-1s effect. Notably, portal and nodose ganglia GLP-1 effects were lost in GLP-1R KO hamsters and following diet-induced insulin resistance. ConclusionOur data demonstrates for the first time that portal GLP-1 modulates postprandial and fasting lipids via a complex vagal gut–brain–liver axis. Importantly, loss or interference with this signalling axis via surgical, pharmacological, or dietary intervention resulted in the loss of portal GLP-1s anti-lipemic effects. This supports emerging evidence that native GLP-1 works primarily through a vagal neuroendocrine mechanism.

Dietary N-Carbamylglutamate (NCG) alleviates liver metabolic disease and hepatocyte apoptosis by suppressing ERK1/2-mTOR-S6K1 signal pathway via promoting endogenous arginine synthesis in Japanese seabass (Lateolabrax japonicus)

N-Carbamylglutamate (NCG), an analogue of N-acetylglutamate (NAG), can promote the synthesis of endogenous Arginine (Arg) in mammals, but not well studied in fish. This study was conducted to investigate the capacity of Arg endogenous synthesis by NCG, and the effects of various dietary NCG doses on growth performance, hepatic health and underlying nutrient regulation metabolism on ERK1/2-mTOR-S6K1 signaling pathway in Japanese seabass (Lateolabrax japonicus). Four experimental diets were prepared with NCG supplement levels of 0 (N0), 360 (N360), 720 (N720) and 3600 (N3600) mg/kg, in which N360 was at the maximum recommended level authorized by MOA, China in fish feed, and the N720 and N3600 levels were 2 and 10-fold of N360, respectively. Each diet was fed to 6 replicates with 30 Japanese seabass (initial body weight, IBW = 11.67 ± 0.02 g) in each tank. The results showed that the dietary NCG supplementation had no significant effects on the SGR and morphometric parameters of Japanese seabass, but 360–720 mg/kg NCG inclusion promoted PPV, while the 10-fold (3600 mg/kg) overdose of NCG had remarkably negative effects with significantly reduced feed efficiency, PPV and LPV. We found that Japanese seabass can utilize 360–720 mg/kg NCG to synthesis Arg to improve the amino acid metabolism by increasing plasma Arg and up-regulating intestinal ASL gene expression. Increased plasma GST and decreased MDA indicated the improved antioxidant response. Dietary NCG inclusion decreased plasma IgM and down-regulated the mRNA levels of inflammation (TNF-α and IL8), apoptosis (caspase family) and fibrosis (TGF-β1) related genes in the liver. The immunofluorescence examination revealed significantly decreased hepatic apoptosis and necrosis signals in the NCG groups. The ameliorated liver function and histological structure were closely related to the improved lipid metabolism parameters with decreased plasma VLDL and hepatic TG and NEFA accumulation, down-regulated fatty acid and cholesterol synthesis and simultaneously increased lipolysis gene mRNA levels, which regulated by inhibiting phosphorylation of ERK1/2-mTOR-S6K1 signaling pathway. Consuming 3600 mg/kg of dietary NCG is not safe for Japanese seabass culturing with the significantly increased FCR and decreased protein and lipid retention, and reduced plasma ALB. Accordingly, the observed efficacy and safety level of dietary NCG in the diet of Japanese seabass is 720 mg/kg.

Abstract 405: Utility of Very Low-density Lipoprotein Cholesterol to Total Triglyceride Ratio (VLDL-C/TG) and Non-VLDL TG to Quantify Remnant Lipoprotein Cholesterol (RLP-C): The Very Large Database of Lipids Study 7C

Background: RLP-C is comprised of atherogenic triglyceride- (TG-) rich lipoproteins, commonly defined as the sum of intermediate-density lipoprotein cholesterol (IDL-C) and very low-density lipoprotein cholesterol remnants (VLDL 3 -C). In clinical practice, the VLDL-C/TG ratio is used to diagnose type III dyslipidemia, a primary lipoprotein disorder characterized by high levels of RLP-C. Methods: Serum lipids of 556,307 U.S. adults with TG ≥130 mg/dL were analyzed by ultracentrifugation (VAP, Atherotech, Birmingham, AL). We estimated TG content in VLDL (VLDL-TG) as the product of VLDL-C and validated variable TG/VLDL-C factors. Non-VLDL-TG was then calculated as total TG minus VLDL-TG, for which negative values represented the presence of RLP-C. We examined the relationship of non-VLDL-TG to 1000 quantiles of VLDL-C/TG ratio. We defined a VLDL-C/TG ratio cutpoint for presence of RLP-C based on the quantile at which median non-VLDL-TG≤0. Results: We found median non-VLDL-TG≤0 at VLDL-C/TG = 0.18 (Figure) . There were 174,907 adults who did not meet diagnostic criteria for type III dyslipidemia (VLDL-C/TG 0.18 to <0.30), whose levels of RLP-C and non-VLDL-TG levels were 37 (31-46) and -20 (-40 to -8) mg/dL, respectively. A total of 1,550 adults met classical diagnostic criteria for type III dyslipidemia (VLDL-C/TG ≥0.3), whose plasma levels of RLP-C and non-VLDL-TG levels were 80 (67-101) and -187 (-290 to -129) mg/dL, respectively. Conclusion: A threshold of VLDL-C/TG ≥0.18 correlates with the accumulation of RLP-C in plasma. If validated in future studies, these findings will improve identification of individuals who are at greater risk for atherosclerotic disease.

PET Measurements of Organ Metabolism: The Devil Is in the Details.

Abnormalities in myocardial fatty acid (FA) metabolism, which are primarily driven by an increase in plasma FAs delivered to the heart, play a central role in the pathogenesis of the cardiomyopathic processes associated with obesity, insulin resistance, and diabetes (1). Moreover, the prevalence and magnitude of the cardiovascular complications of these diseases, such as left ventricular hypertrophy, heart failure, and ischemic heart disease, are typically more pronounced in women compared with men (2,3). Thus, it is tempting to speculate that the sex differences in myocardial FA metabolism may be contributory to this interaction. Evidence to support this notion has come from studies using positron emission tomography (PET), which because of its inherent quantitative capabilities and diversity of metabolic radiotracers is the most commonly used imaging method to measure organ metabolism. PET studies using the FA radiotracer 1-11C-palmitate have recently shown that myocardial FA uptake and oxidation are higher in obese women compared with men and that this sex disparity appears to become more pronounced when one transitions to obesity with concurrent type 2 diabetes (4,5). However, myocardial FA metabolism is dependent on the plasma delivery of FA from nonesterified FA (NEFA) bound to albumin as well as those incorporated into triglyceride (TG), either as chylomicrons (CM-TG) or VLDLs (VLDL-TG). Fatty acids bound to TGs are made available to the myocardium via their release by lipoprotein lipase located on the capillary endothelium. Measuring this contribution of TG-extracted FAs destined for metabolism is important because it represents a major source of FAs from dietary intake (DFA) and evidence suggesting that the source of extracted FAs may impact their metabolic fate in tissue (6,7). To date, the PET method described above to measure myocardial FA metabolism relies on intravenous administration of FA radiotracers and …

Exercise training alters VLDL TG and apoB metabolism in men with non-alcoholic liver disease (NAFLD)

Exercise training alters VLDL TG and apoB metabolism in men with non-alcoholic liver disease (NAFLD)

Ten weeks of aerobic training does not result in persistent changes in VLDL triglyceride turnover or oxidation in healthy men.

Very low density lipoprotein triglyceride (VLDL-TG) and free fatty acids (FFA) constitute a substantial proportion of human energy supply both at rest and during exercise. Exercise acutely decreases VLDL-TG concentration, and VLDL-TG clearance is increased after an exercise bout. However, the effects of long-term training are not clear. The aim was to investigate long-term effects of training by direct assessments of VLDL-TG and palmitate kinetics and oxidation in healthy lean men (n=9) at rest, before and after a 10-week training program, compared with a non-training control group (n=9). VLDL-TG kinetics were assessed by a primed constant infusion of [1-14C]VLDL-TG, and VLDL-TG oxidation by specific activity (14CO2) in expired air. The metabolic study days were placed 60-72 h after the last exercise bout. Palmitate kinetics and oxidation were assessed by a 2 h constant infusion of [9,10-(3)H]palmitate. In the training group (n=9), maximal oxygen uptake increased significantly by ≈20% (P<0.05), and the insulin sensitivity (assessed by the hyperinsulinemic-euglycemic clamp) improved significantly (P<0.05). Despite these metabolic improvements, no changes were observed in VLDL-TG secretion, clearance, or oxidation or in palmitate kinetics. We conclude that 10 weeks of exercise training did not induce changes in VLDL-TG and palmitate kinetics in healthy lean men.

Contribution of very low-density lipoprotein triglyceride fatty acids to postabsorptive free fatty acid flux in obese humans

ObjectiveIn the fasting state, plasma free fatty acids (FFA) are thought to derive almost exclusively from adipose tissue lipolysis. However, there are mixed reports as to whether the spillover of fatty acids (FA) from very low-density lipoprotein triglyceride (VLDL–TG) hydrolysis contributes significantly to the plasma FFA pool. Because substantial VLDL–TG fatty acid spillover into the plasma FFA pool would profoundly impact the interpretation of isotope dilution measures of FFA flux, we investigated the contribution of VLDL–TG spillover to plasma FFA appearance. Materials/MethodsEighteen obese adults (15 women) participated in these studies. Each volunteer received a primed, continuous infusion of their own ex-vivo labeled ([1-14C]triolein) VLDL–TG and a continuous infusion of [U-13C]oleate (8nmol·kg fat free mass−1·min−1) to measure VLDL–TG and FFA rate of appearance (Ra), respectively. The presence of 14C-oleate in the plasma FFA–oleate pool was used to calculate the contribution of spillover from VLDL–TG–oleate to the plasma FFA–oleate Ra. ResultsThe spillover rate of VLDL–TG–oleate into plasma FFA–oleate was 6±2μmol/min (7%±2% of [14C]oleate from VLDL–TG) and FFA–oleate flux was 240±61μmol/min. Thus, only 3%±1% of total plasma FFA–oleate appearance could be accounted for by VLDL–TG spillover. ConclusionThe contribution of VLDL–TG spillover to the total plasma FFA pool is negligible and will not materially affect the interpretation of FFA flux measures as an index of adipose tissue lipolysis.

Acute changes in lipoprotein subclasses during exercise

ObjectiveLipids are important substrates for oxidation in the basal fasting state and during exercise. Studies have demonstrated beneficial changes in lipoprotein subclass composition the day after an exercise bout. However, the acute effect of exercise on TG concentration and lipoprotein subclass composition remains unclear. Materials/MethodsSixteen lean, healthy individuals (8 men and 8 women) were recruited (age 20–30years, BMI<25kg/m2). The subjects were studied during basal fasting conditions as well as during and after 90min of cycling at 50% of VO2peak. Lipoprotein subclass composition was measured with 1H NMR spectroscopy. ResultsDuring exercise, LDL and HDL particle concentration increased significantly (p<0.05) despite lower total TG concentration. In addition, exercise resulted in a shift towards smaller VLDL particles in men (p<0.05), but VLDL–TG concentration was unaltered. ConclusionsAcute exercise induces beneficial changes in lipoprotein subclass composition. These changes are similar to the effects of exercise training.

Effect of a high bicarbonate mineral water on fasting and postprandial lipemia in moderately hypercholesterolemic subjects: a pilot study

BackgroundDuring postprandial state, TG concentration is increasing and HDL cholesterol decreasing, leading to a transitory pro-atherosclerotic profile. Previous studies have reported that bicarbonate water improve postprandial lipemia. The objective of this study was to analyze the effect of a strongly bicarbonated mineral water on lipoprotein levels during fasting and postprandial state.MethodsA controlled, randomised, double-blind cross-over design was conducted in 12 moderately hypercholesterolemic subjects after a daily ingestion of 1.25 L of mineral (SY) or low mineral water during eight weeks separated by a one week wash-out period. Blood samples were collected in first visit to the hospital (V1) before water consumption (referent or SY) and in a second visit (V2) after eight week water consumption period. The effect of the consumed water was studied in fasting and in postprandial state during ingestion of a meal and 0.5 L of water.ResultsComparison of data between V1 and V2 after SY consumption showed a significant decrease in triglyceridemia (23%), VLDL TG (31%) and tendency to a decrease of VLDL cholesterol (p = 0.066) at fasting state. Whatever the consumed water during postprandial state, the measurement of total areas under curves did not show a significant difference. No difference was observed between SY and referent water consumption for measured parameters at fasting and postprandial state.ConclusionWhen subjects consumed SY we showed a decrease of their basal TG and VLDLTG. The unexpected absence of effect of high mineralized water on postprandial lipemia, probably related to experimental conditions, is discussed in the discussion section.

Omega 3 Fatty Acids Promote Macrophage Reverse Cholesterol Transport in Hamster Fed High Fat Diet

The aim of this study was to investigate macrophage reverse cholesterol transport (RCT) in hamster, a CETP-expressing species, fed omega 3 fatty acids (ω3PUFA) supplemented high fat diet (HFD). Three groups of hamsters (n = 6/group) were studied for 20 weeks: 1) control diet: Control, 2) HFD group: HF and 3) HFD group supplemented with ω3PUFA (EPA and DHA): HFω3. In vivo macrophage-to-feces RCT was assessed after an intraperitoneal injection of 3H-cholesterol-labelled hamster primary macrophages.Compared to Control, HF presented significant (p<0.05) increase in body weight, plasma TG (p<0.01) and cholesterol (p<0.001) with an increase in VLDL TG and in VLDL and LDL cholesterol (p<0.001).Compared to HF, HFω3 presented significant decrease in body weight. HFω3 showed less plasma TG (p<0.001) and cholesterol (p<0.001) related to a decrease in VLDL TG and HDL cholesterol respectively and higher LCAT activity (p<0.05) compared to HF. HFω3 showed a higher fecal bile acid excretion (p<0.05) compared to Control and HF groups and higher fecal cholesterol excretion (p<0.05) compared to HF. This increase was related to higher gene expression of ABCG5, ABCA1 and SR-B1 in HFω3 compared to Control and HF groups (<0.05) and in ABCG1 and CYP7A1 compared to HF group (p<0.05). A higher plasma efflux capacity was also measured in HFω3 using 3H- cholesterol labeled Fu5AH cells.In conclusion, EPA and DHA supplementation improved macrophage to feces reverse cholesterol transport in hamster fed HFD. This change was related to the higher cholesterol and fecal bile acids excretion and to the activation of major genes involved in RCT.

Effect of cholesterol on lipogenesis and VLDL–TG assembly and secretion in goose primary hepatocytes

To investigate how cholesterol induces hepatocytic steatosis, we investigated the effect of cholesterol on hepatic lipogenesis and the assembly and secretion of very-low-density lipoprotein-triglycerides (VLDL-TGs) in goose primary hepatocytes. We found that cholesterol at 20 μg/ml increased the concentrations of extracellular VLDL, intracellular cholesterol, and intracellular TGs, while cholesterol at 30 μg/ml had a reduced effect (p < 0.05). Additionally, cholesterol at 20 μg/ml, but not at 10 or 30 μg/ml, increased the extracellular TG concentration. Cholesterol increased the fatty acid synthase (FAS) enzyme activity in a dose-dependent manner. Incubation with cholesterol increased the mRNA level of genes involved in lipogenesis, including sterol regulatory element-binding proteins (SREBPs), FAS, acetyl-CoA carboxylase-α (ACCα), and liver X receptors. The mRNA level of the acyl-CoA: diacylglycerol acyltransferase 1 (DGAT1) gene changed in response to cholesterol treatment in a dose-dependent manner. Similar to the regulation of extracellular VLDL and intracellular TG accumulation, the mRNA levels of the microsomal triglyceride transfer protein, forkhead box O1, and DGAT2 increased with treatment with 10 or 20 μg/ml of cholesterol, but decreased with treatment with 30 μg/ml of cholesterol (p < 0.05). Cholesterol had no evident effect on the mRNA level of the apolipoprotein B gene. Incubation with cholesterol at 20 and 30 μg/ml increased the nuclear SREBP-1 protein level (p < 0.05) and the binding affinity of the nuclear SREBP-1 to ACCα SRE probes. In conclusion, cholesterol not only activates the transcription of genes involved in fatty acid synthesis and TG accumulation, but also activates the transcription of genes involved in the assembly and secretion of VLDL-TG in goose primary hepatocytes.

Algal Docosahexaenoic Acid Affects Plasma Lipoprotein Particle Size Distribution in Overweight and Obese Adults1–3

Fish oils containing both EPA and DHA have been shown to have beneficial cardiovascular effects, but less is known about the independent effects of DHA. This study was designed to examine the effects of DHA on plasma lipid and lipoprotein concentrations and other biomarkers of cardiovascular risk in the absence of weight loss. In this randomized, controlled, double-blind trial, 36 overweight or obese adults were treated with 2 g/d of algal DHA or placebo for 4.5 mo. Markers of cardiovascular risk were assessed before and after treatment. In the DHA-supplemented group, the decrease in mean VLDL particle size (P ≤ 0.001) and increases in mean LDL (P ≤ 0.001) and HDL (P ≤ 0.001) particle sizes were significantly greater than changes in the placebo group. DHA supplementation also increased the concentrations of large LDL (P ≤ 0.001) and large HDL particles (P = 0.001) and decreased the concentrations of small LDL (P = 0.009) and medium HDL particles (P = 0.001). As calculated using NMR-derived data, DHA supplementation reduced VLDL TG (P = 0.009) and total TG concentrations (P = 0.006). Plasma IL-10 increased with DHA supplementation to a greater extent than placebo (P = 0.021), but no other significant changes were observed in glucose metabolism, insulin sensitivity, blood pressure, or markers of inflammation with DHA. In summary, DHA supplementation resulted in potentially beneficial changes in some markers of cardiometabolic risk, whereas other markers were unchanged.

Effect of conjugated linoleic acid (CLA) on lipid profile and liver histology in laboratory rats fed high-fructose diet

The objective of the study was to assess the effect of CLA on serum lipid profile, plasma malondialdehyde and liver histology in Wistar rats fed high-fructose diet. Eighteen rats were randomly assigned to three experimental groups and fed for the next 21 days. The experimental diets were: I, Control; II, Fructose (63.2% of fructose); and III, CLA + Fructose (1% CLA and 63.2% of fructose). The experimental treatments had no effect on body weight of the rats. The LDL + VLDL cholesterol, TG and liver weight were significantly increased in animals fed Fructose. MDA concentrations were significantly increased in rats fed Fructose diet but CLA + Fructose diet had no effect on this marker. In the same line, the histological examination of the livers showed a series of morphological alterations, notably hepatic steatosis in animals fed high-fructose diet. No signs of the steatosis in rats fed CLA + Fructose diet were observed. In conclusion, CLA in high-fructose diet, decreases serum LDL + VLDL and TG and plasma MDA concentrations as well as liver weight and liver cholesterol, thus opposing the effects of high-fructose diet and showing a potential antiatherogenic effect. Similarly, dietary CLA fed at 1% level (w/w) in high-fructose diet, prevented steatosis observed histologically in livers of rats fed high-fructose diets.

Capillary isotachophoresis study of lipoprotein network sensitive to apolipoprotein E phenotype. 2. ApoE and apoC-III relations in triglyceride clearance

The plasma (P), VLDL (V) triglyceride and apoB (B) clearance rates were measured both as 'mass' clearance (k (1)) and 'within the particle' clearance in three patient groups (E33, E23 and E34 phenotypes) at heparin-induced lipolysis in vivo. The lipid (C)- and apoE (E)-specific lipoprotein profiles both before and after heparin were followed by capillary isotachophoresis. The displacement of apoE by exogenous apoC-III at plasma titration in vitro was measured as well. The phenotype-sensitive lipoprotein networks were constructed based on an established set of metabolic rules. The k (1)(V) values did not differ between the three groups, but the lower k (1)(P) values showed significant differences. The k (1)(P) values for E33 and E23 groups were twofold higher compared to E34. A twofold increase in the rate constant for VLDL triglyceride clearance within the particle in E34 group compared to E23 reflected the inhibition of lipolysis by apoE2. For E33 group, (i) the k (1)(V) value was negatively correlated to the size of non-displaceable apoE pool in 2E lipoprotein and to the maximal apoE sorbtion capacity for 2E and 3E lipoproteins; (ii) the k (1)(P) value was not associated to the apoE binding parameters; (iii) the k (1)(V) value was positively correlated to the 4C level and the magnitude of apoC-III removal from VLDL particle; (iv) the k (1)(P) value was positively correlated to the content of apoE, while negatively with apoC-III, in VLDL remnants. For E34 group, the k (1)(V) value was positively correlated to 11C and 1-7C pool levels. Lipolysis- and receptor-mediated TG runways seem to be mostly balanced in E33 group, and VLDL TG clearance may be controlled by HDL through apoE dissociation from VLDLs and apolipoprotein accumulation within 'fast' HDLs at lipolysis.

Lipoprotein separation in a novel iodixanol density gradient, for composition, density, and phenotype analysis

Separation of lipoproteins by traditional sequential salt density floatation is a prolonged process ( approximately 72 h) with variable recovery, whereas iodixanol-based, self-generating density gradients provide a rapid ( approximately 4 h) alternative. A novel, three-layered iodixanol gradient was evaluated for its ability to separate lipoprotein fractions in 63 subjects with varying degrees of dyslipidemia. Lipoprotein cholesterol, triglycerides, and apolipoproteins were measured in 21 successive iodixanol density fractions. Iodixanol fractionation was compared with sequential floatation ultracentrifugation. Iodixanol gradient formation showed a coefficient of variation of 0.29% and total lipid recovery from the gradient of 95.4% for cholesterol and 84.7% for triglyceride. Recoveries for VLDL-, LDL-, and HDL-cholesterol, triglycerides, and apolipoproteins were approximately 10% higher with iodixanol compared with sequential floatation. The iodixanol gradient effectively discriminated classic lipoproteins and their subfractions, and there was evidence for improved resolution of lipoproteins with the iodixanol gradient. LDL particles subfractionated by the gradient showed good correlation between density and particle size with small, dense LDL (<25.5 nm) separated in fractions with density >1.028 g/dl. The new iodixanol density gradient enabled rapid separation with improved resolution and recovery of all lipoproteins and their subfractions, providing important information with regard to LDL phenotype from a single centrifugation step with minimal in-vitro modification of lipoproteins.

Th-P15:17 Abnormal in vivo metabolism of apoB and VLDL TG associated with two sibling cases of sitosterolemia

Th-P15:17 Abnormal in vivo metabolism of apoB and VLDL TG associated with two sibling cases of sitosterolemia

Surfactant-Based Homogeneous Assay for the Measurement of Triglyceride Concentrations in VLDL and Intermediate-Density Lipoprotein

Existing studies have demonstrated the clinical significance of triglyceride content in VLDL (VLDL-TG) and intermediate-density lipoprotein (IDL-TG). We developed a homogeneous assay protocol to directly measure VLDL-TG. Possible reagents and conditions for measuring VLDL-TG were comprehensively tested, and the "best" combination was determined. Healthy persons were instructed to consume a fatty meal after 15-h overnight fasting. Serum VLDL-TG + IDL-TG concentrations were measured using the proposed method. Patients with serum LDL-cholesterol concentrations > or = 3.62 mmol/L (140 mg/dL) were administered simvastatin at a daily dose of 5 mg, and serum VLDL-TG concentrations were then measured. The combination of 2 nonionic surfactants played an important role in differentiating VLDL and IDL from other lipoproteins, probably via specific interactions with phospholipids and apolipoproteins. The regression line of the proposed method (y) and the ultracentrifugal assay (x) was: y = 0.98x + 0.31 mmol/L (r = 0.98; n = 73; P < 0.05). The difference between postprandial total TG and VLDL-TG concentrations was statistically significant (P < 0.05). After 8 weeks of therapy with simvastatin, total TG and LDL-cholesterol concentrations were 13.6% and 26.3% lower, respectively (P < 0.05), whereas VLDL-TG did not show any significant decrease. Our homogeneous method can measure TG content in VLDL and IDL.

A rapid single-step centrifugation method for determination of HDL, LDL, and VLDL cholesterol, and TG, and identification of predominant LDL subclass

Determination of the circulating levels of plasma lipoproteins HDL, LDL, and VLDL is critical in the assessment of risk of coronary heart disease. More recently it has become apparent that the LDL subclass pattern is a further important diagnostic parameter. The reference method for separation of plasma lipoproteins is ultracentrifugation. However, current methods often involve prolonged centrifugation steps and use high salt concentrations, which can modify the lipoprotein structure and must be removed before further analysis. To overcome these problems we have now investigated the use of rapid self-generating gradients of iodixanol for separation and analysis of plasma lipoproteins. A protocol is presented in which HDL, LDL, and VLDL, characterized by electron microscopy and agarose gel electophoresis, separate in three bands in a 2.5 h centrifugation step. Recoveries of cholesterol and TG from the gradients were close to 100%. The distribution profiles of cholesterol and TG in the gradient were used to calculate the concentrations of individual lipoprotein classes. The values correlated with those obtained using commercial kits for HDL and LDL cholesterol. The position of the LDL peak in the gradient and its shape varied between plasma samples and was indicative of the density of the predominant LDL class. The novel protocol offers a rapid, reproducible and accurate single-step centrifugation method for the determination of HDL, LDL, and VLDL cholesterol, and TG, and identification of LDL subclass pattern.—Sawle, A., M. K. Higgins, M. P. Olivant, and J. A. Higgins. A rapid single-step centrifugation method for determination of HDL, LDL, and VLDL cholesterol, and TG, and identification of predominant LDL subclass.

Reduced HDL particle size as an additional feature of the atherogenic dyslipidemia of abdominal obesity

Reduced plasma HDL cholesterol concentration has been associated with an increased risk of coronary heart disease. However, a low HDL cholesterol concentration is usually not observed as an isolated disorder because this condition is often accompanied by additional metabolic alterations. The objective of this study was to document the relevance of assessing HDL particle size as another feature of the atherogenic dyslipidemia found among subjects with visceral obesity and insulin resistance. For that purpose, an average HDL particle size was computed by calculating an integrated HDL particle size using nondenaturing 4-30% gradient gel electrophoresis. Potential associations between this average HDL particle size versus morphometric and metabolic features of visceral obesity were examined in a sample of 238 men. Results of this study indicated that HDL particle size was a significant correlate of several features of an atherogenic dyslipidemic profile such as increased plasma TG, decreased HDL cholesterol, high apolipoprotein B, elevated cholesterol/HDL cholesterol ratio, and small LDL particles as well as increased levels of visceral adipose tissue (AT) (0.33 < or = absolute value of r < or = 0.61, P < 0.0001). Thus, men with large HDL particles had a more favorable plasma lipoprotein-lipid profile compared with those with smaller HDL particles. Furthermore, men with large HDL particles were also characterized by reduced overall adiposity and lower levels of visceral AT as well as reduced insulinemic-glycemic responses to an oral glucose load. In conclusion, small HDL particle size appears to represent another feature of the high TG- low HDL cholesterol dyslipidemia found in viscerally obese subjects characterized by hyperinsulinemia.

Apolipoprotein C-III deficiency accelerates triglyceride hydrolysis by lipoprotein lipase in wild-type and apoE knockout mice

Previous studies with hypertriglyceridemic APOC3 transgenic mice have suggested that apolipoprotein C-III (apoC-III) may inhibit either the apoE-mediated hepatic uptake of TG-rich lipoproteins and/or the lipoprotein lipase (LPL)-mediated hydrolysis of TG. Accordingly, apoC3 knockout (apoC3−/−) mice are hypotriglyceridemic. In the present study, we attempted to elucidate the mechanism(s) underlying these phenomena by intercrossing apoC3−/− mice with apoE−/− mice to study the effects of apoC-III deficiency against a hyperlipidemic background. Similar to apoE+/+apoC3−/− mice, apoE−/−apoC3−/− mice exhibited a marked reduction in VLDL cholesterol and TG, indicating that the mechanism(s) by which apoC-III deficiency exerts its lipid-lowering effect act independent of apoE. On both backgrounds, apoC3−/− mice showed normal intestinal lipid absorption and hepatic VLDL TG secretion. However, turnover studies showed that TG-labeled emulsion particles were cleared much more rapidly in apoC3−/− mice, whereas the clearance of VLDL apoB, as a marker for whole particle uptake by the liver, was not affected. Furthermore, it was shown that cholesteryl oleate-labeled particles were also cleared faster in apoC3−/− mice. Thus the mechanisms underlying the hypolipidemia in apoC3−/− mice involve both a more efficient hydrolysis of VLDL TG as well as an enhanced selective clearance of VLDL cholesteryl esters from plasma.In summary, our studies of apoC3−/− mice support the concept that apoC-III is an effective inhibitor of VLDL TG hydrolysis and reveal a potential regulating role for apoC-III with respect to the selective uptake of cholesteryl esters.