Fasting and postprandial apolipoprotein B-48 levels in healthy, obese, and hyperlipidemic subjects

Role of apolipoprotein B in the clinical management of cardiovascular risk in adults: An Expert Clinical Consensus from the National Lipid Association

This National Lipid Association (NLA) Expert Clinical Consensus provides an overview of the physiologic and clinical considerations regarding the role of apolipoprotein B (apoB) measurement to guide clinical care based on the available scientific evidence and expert opinion. ApoB represents the total concentration of atherogenic lipoprotein particles in the circulation and more accurately reflects the atherogenic burden of lipoproteins when compared to low-density lipoprotein cholesterol (LDL-C). ApoB is a validated clinical measurement that augments the information found in a standard lipoprotein lipid panel; therefore, there is clinical value in using apoB in conjunction with a standard lipoprotein lipid profile when assessing risk and managing lipid-lowering therapy (LLT). ApoB has been shown to be superior to LDL-C in risk assessment both before and during treatment with LLT. In individuals, there can be discordance between levels of LDL-C and apoB, as well as LDL-C and non-high-density lipoprotein cholesterol (non-HDL-C), despite high levels of population-wide correlation. When there is discordance between LDL-C and apoB, or LDL-C and non-HDL-C, atherosclerotic cardiovascular disease risk generally aligns better with apoB or non-HDL-C. Additionally, apoB can be used in tandem with standard lipoprotein lipid measurements to diagnose distinct lipoprotein phenotypes. ApoB testing can inform clinical prognosis and care, as well as enable family cascade screening, when an inherited lipoprotein syndrome is identified. The NLA and other organizations will continue to educate clinicians about the role of apoB measurement in improving clinical risk assessment and dyslipidemia management. An urgent need exists to improve access and reimbursement for apoB testing.

Interplay of Postprandial Triglyceride-Rich Lipoprotein Composition and Adipokines in Obese Adolescents

In the context of the alarming rise of infant obesity and its health implications, the present research aims to uncover disruptions in postprandial lipid metabolism and the composition of triglyceride-rich lipoproteins in obese adolescents. A double-blind, controlled clinical trial in the postprandial phase on 23 adolescents aged 12 to 16 years was carried out. Twelve participants were categorized as obese (BMI > 30 kg/m2 and percentile > 95) and 11 as normal-weight (BMI = 20-25 kg/m2, percentile 5-85). Blood samples were collected after a 12-h overnight fast and postprandially after consumption of a standardized breakfast containing olive oil, tomato, bread, orange juice, and skimmed milk. Obese adolescents exhibited elevated triglyceride concentrations in both fasting and postprandial states and higher TG/apo-B48 ratios, indicating larger postprandial triglyceride-rich lipoprotein (TRL) particle size, which suggests impaired clearance. Obese subjects also exhibited higher n-6 PUFA concentrations, potentially linked to increased TRL hydrolysis and the release of pro-inflammatory adipokines. In contrast, TRL from normal-weight individuals showed higher concentrations of oleic acid and DHA (n-3 PUFA), with possible anti-inflammatory effects. The results indicate an interplay involving postprandial TRL metabolism and adipokines within the context of adolescent obesity, pointing to potential cardiovascular implications in the future.

Identification of genetic drivers of plasma lipoprotein size in the Diversity Outbred mouse population

Despite great progress in understanding lipoprotein physiology, there is still much to be learned about the genetic drivers of lipoprotein abundance, composition, and function. We used ion mobility spectrometry to survey 16 plasma lipoprotein subfractions in 500 Diversity Outbred mice maintained on a Western-style diet. We identified 21 quantitative trait loci (QTL) affecting lipoprotein abundance. To refine the QTL and link them to disease risk in humans, we asked if the human homologs of genes located at each QTL were associated with lipid traits in human genome-wide association studies. Integration of mouse QTL with human genome-wide association studies yielded candidate gene drivers for 18 of the 21 QTL. This approach enabled us to nominate the gene encoding the neutral ceramidase, Asah2, as a novel candidate driver at a QTL on chromosome 19 for large HDL particles (HDL-2b). To experimentally validate Asah2, we surveyed lipoproteins in Asah2-/- mice. Compared to wild-type mice, female Asah2-/- mice showed an increase in several lipoproteins, including HDL. Our results provide insights into the genetic regulation of circulating lipoproteins, as well as mechanisms by which lipoprotein subfractions may affect cardiovascular disease risk in humans.

Circulating Apolipoprotein B-48 as a Biomarker of Parenteral Nutrition Dependence in Adult Patients with Short Bowel Syndrome

Short bowel syndrome (SBS) is a rare but serious condition that may lead to chronic intestinal failure. Citrulline concentrations are currently used to reflect the residual intestinal mass in patients with SBS, although this method has several limitations. In a cohort of patients with SBS, we quantified apolipoprotein B-48 (ApoB-48), which is exclusively synthesized by enterocytes and secreted associated with dietary lipids and investigated the relationship between ApoB-48 and clinical and biological data as well as PN dependence. A total of 51 adult patients were included, 36 of whom were PN-dependent. We found a robust positive correlation between circulating ApoB-48 and residual small bowel length, which was also found in the subgroup of patients with jejunocolic anastomosis. Fasting ApoB-48 levels were significantly lower in PN-dependent patients than in PN-weaned patients and negatively correlated with parenteral nutrition dependence. Our results suggest that ApoB-48 could be proposed as a marker of intestinal absorptive function and could be an interesting follow-up marker in patients with SBS.

The FGF21 analog pegozafermin in severe hypertriglyceridemia: a randomized phase 2 trial

Pegozafermin, a long-acting glycopegylated analog of human fibroblast growth factor 21, is in development for the treatment of severe hypertriglyceridemia (SHTG) and nonalcoholic steatohepatitis. Here we report the results of a phase 2, double-blind, randomized, five-arm trial testing pegozafermin at four different doses (n = 67; 52 male) versus placebo (n = 18; 12 male) for 8 weeks in patients with SHTG (triglycerides (TGs), ≥500 mg dl-1 and ≤2,000 mg dl-1). Treated patients showed a significant reduction in median TGs for the pooled pegozafermin group versus placebo (57.3% versus 11.9%, difference versus placebo -43.7%, 95% confidence interval (CI): -57.1%, -30.3%; P < 0.001), meeting the primary endpoint of the trial. Reductions in median TGs ranged from 36.4% to 63.4% across all treatment arms and were consistent regardless of background lipid-lowering therapy. Results for secondary endpoints included significant decreases in mean apolipoprotein B and non-high-density lipoprotein cholesterol concentrations (-10.5% and -18.3% for pooled doses compared to 1.1% and -0.6% for placebo (95% CI: -21.5%, -2.0%; P = 0.019 and 95% CI: -30.7%, -5.1%; P = 0.007, respectively), as well as a significant decrease in liver fat fraction for pooled treatment (n = 17) versus placebo (n = 6; -42.2% pooled pegozafermin, -8.3% placebo; 95% CI: -60.9%, -8.7%; P = 0.012), as assessed in a magnetic resonance imaging sub-study. No serious adverse events were observed to be related to the study drug. If these results are confirmed in a phase 3 trial, pegozafermin could be a promising treatment for SHTG (ClinicalTrials.gov registration: NCT0441186).

Evaluation of circulating miR-122, miR-30c and miR-33a levels and their association with lipids, lipoproteins in postprandial lipemia

AIMS

Postprandial lipemia is characterized by an increase in triglyceride-rich lipoproteins after fatty meals. MicroRNAs (miRs) play important roles in lipid and lipoprotein metabolism. The aim of this study was to determine relationship between levels of plasma miR expression and lipoprotein metabolism-related proteins in subjects with normal (NPR) and high postprandial response (HPR) in postprandial period.

MATERIALS AND METHODS

The oral fat tolerance test was applied to 22 individuals with NPR and 22 with HPR.

KEY FINDINGS

Increased expressions of miR-122 and miR-33a and miR-122/30c ratio and decreased miR-30c expression were observed in fasting and postprandial period of HPR compared with NPR. ROC curve analysis showed that miR-122/30c ratio is a good biomarker for postprandial lipemia (AUC: 0.97, p < 0.001). Levels of TG, MTTP, and Apo B-48 and chylomicron (CM) particle size were significantly higher in HPR than in NPR (p < 0.05). The miR-122/30c ratio at 2 h was positively correlated with CM particle size, and with TG, MTTP and Apo B-48 levels at 4th hour. miR-33a expression decreased in HPR and was negatively correlated with ABCA1 and Apo A-1 levels at 4th hour of the postprandial period in both groups.

SIGNIFICANCE

Increased miR-122 and decreased miR-30c expression levels in HPR may play critical roles in elevated or prolonged postprandial lipemia. The miR122/30c ratio exhibited good association with MTTP, Apo B-48 and TG levels, and with CM particle size, and may be a reliable marker for evaluating postprandial lipemia. miR-33a may also play a key role in decreased HDL-C in postprandial lipemia.

FTO Variant rs1421085 Associates With Increased Body Weight, Soft Lean Mass, and Total Body Water Through Interaction With Ghrelin and Apolipoproteins in Arab Population

Association studies have implicated single nucleotide polymorphisms (SNPs), particularly rs1421085, from the fat mass and obesity-associated (FTO) gene with body composition phenotypes, obesity, dietary intake, and physical activity in European, East Asian, and African populations. However, the impact of the rs1421085 variant has not been sufficiently tested in ethnic populations (such as Arabs) with high levels of obesity. Further, there is a lack of studies identifying biomarkers that interact with FTO. Therefore, we investigated the association of rs1421085 with obesity and body composition traits and metabolic biomarkers in Arab population. We genotyped rs1421085 SNP in 278 Arab individuals, where multiple biomarkers relating to obesity, inflammation, and other metabolic pathways were quantified. We performed genetic association tests under additive mode of inheritance using linear regression models and found association of rs1421085_C allele with higher levels of body weight, soft lean mass (SLM), and total body water. Examination (using linear regression models under dominant mode of inheritance) of correlation among biomarkers and interaction with genotypes at the variant revealed that measures of these three body composition traits were found mediated by interaction between carrier genotypes (TC+CC) and measures of ghrelin, ApoA1, and ApoB48. Lean body mass (LBM), to which SLM contributes, is an important determinant of physical strength and is a focal point in studies on sarcopenia. Low LBM is known to be associated with higher risk of cardiometabolic disorders. Thus, the finding on the FTO variant as a genetic determinant of SLM via interaction with ghrelin, ApoA1, and ApoB48 is important.

Incretin Hormones: The Link between Glycemic Index and Cardiometabolic Diseases

This review aimed to describe the potential mechanisms by which incretin hormones could mediate the relationship between glycemic index and cardiometabolic diseases. A body of evidence from many studies suggests that low glycemic index (GI) diets reduces the risk for type 2 diabetes and coronary heart disease. In fact, despite the extensive literature on this topic, the mechanisms underlying unfavorable effects of high GI foods on health remain not well defined. The postprandial and hormonal milieu could play a key role in the relationship between GI and cardiovascular risk. Incretin hormones, glucagon-like peptide1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), are important regulators of postprandial homeostasis by amplifying insulin secretory responses. Response of GIP and GLP-1 to GI have been studied more in depth, also by several studies on isomaltulose, which have been taken as an ideal model to investigate the kinetics of incretin secretion in response to foods’ GI. In addition, extrapancreatic effects of these incretin hormones were also recently observed. Emerging from this have been exciting effects on several targets, such as body weight regulation, lipid metabolism, white adipose tissue, cardiovascular system, kidney, and liver, which may importantly affect the health status.

[Clinical biochemistry methods in objectiva evalution of overeating foood of carnivores (meat)by a phylogenetically herbivorous homo sapiens (a patient).]

The abuse of food of carnivores (meat) by phylogeneticallyI herbivorous Homo sapiens (a patient) initiates atherosclerosis. Addressing biogenetic law of E. Haeckel that ontogeny recapitulates phylogeny (a universal anamnesis), we suggest a diagnostic technique that allows evaluation of the meat diet abuse by a herbivorous Homo sapiens. This technique is based on application of phylogenetic theory of general pathology to clinical practice. The degrees of objective evaluation of nonphysiological overeating of meat are: the first, an increase in the fast plasma content of oleic triglycerides palmitoyl-oleyl-palmitate (POP). The second, hyperglyceridemia + an increase in low density lipoprotein cholesterol (LDL-CL) content. The third, increased plasma content of apoС-III. The fourth, an increase in the concentration of apoВ-48. If electrophoregrams are analyzed and hyperlipoproteinemia (HLP) type is determined according to WHO classification, the first degree of meat overeating is not informative, the second, corresponds to type IV HLP; the third, to type IIb HLP, and the forth, to type V HLP, i.e, the patient diet consists practically of the food of carnivores. Hyperlipoproteinemia coincides with insulin resistance syndrome, hyperglycemia and hyperinsulinemia, which is based on blood increase of fatty acids in the form of polar unesterified fatty acids (UFA). According to phylogenetic theory of general pathology, in vivo cells do not internalize glucose if there is a possibility to internalize UFA. Preventive examination allows evaluation of disorders in the biological function of trophology (food consumption). Thus, the use of different methods in the analysis of this function offers evaluation of the effectiveness of diet therapy from the level of disorders when treatment was started.

Direct Versus Calculated LDL Cholesterol and C-Reactive Protein in Cardiovascular Disease Risk Assessment in the Framingham Offspring Study

BACKGROUND

Increases in circulating LDL cholesterol (LDL-C) and high-sensitivity C-reactive protein (hsCRP) concentrations are significant risk factors for cardiovascular disease (CVD). We assessed direct LDL-C and hsCRP concentrations compared to standard risk factors in the Framingham Offspring Study.

METHODS

We used stored frozen plasma samples (-80 °C) obtained after an overnight fast from 3147 male and female participants (mean age, 58 years) free of CVD at cycle 6 of the Framingham Offspring Study. Overall, 677 participants (21.5%) had a CVD end point over a median of 16.0 years of follow-up. Total cholesterol (TC), triglyceride (TG), HDL cholesterol (HDL-C), direct LDL-C (Denka Seiken and Kyowa Medex methods), and hsCRP (Dade Behring method) concentrations were measured by automated analysis. LDL-C was also calculated by both the Friedewald and Martin methods.

RESULTS

Considering all CVD outcomes on univariate analysis, significant factors included standard risk factors (age, hypertension, HDL-C, hypertension treatment, sex, diabetes, smoking, and TC concentration) and nonstandard risk factors (non-HDL-C, direct LDL-C and calculated LDL-C, TG, and hsCRP concentrations). On multivariate analysis, only the Denka Seiken direct LDL-C and the Dade Behring hsCRP were still significant on Cox regression analysis and improved the net risk reclassification index, but with modest effects. Discordance analysis confirmed the benefit of the Denka Seiken direct LDL-C method for prospective hard CVD endpoints (new-onset myocardial infarction, stroke, and/or CVD death).

CONCLUSIONS

Our data indicate that the Denka Seiken direct LDL-C and Dade Behring hsCRP measurements add significant, but modest, information about CVD risk, compared to standard risk factors and/or calculated LDL-C.

Large triglyceride-rich lipoproteins from fasting patients with type 2 diabetes activate platelets

AIMS

Type 2 diabetes (T2D) patients present with risk factors for atherothrombosis such as fasting hypertriglyceridaemia and platelet hyperactivity. Our study objective was to determine the effect of large triglyceride-rich lipoproteins (TGRL) from fasting T2D patients on platelet aggregation and, if any, to identify the signaling pathway involved.

METHODS

Large TGRL were isolated from the plasma of 25 T2D patients by ultracentrifugation (density < 1.000 g/mL). Platelets were isolated from healthy blood donors (HBD) and suspended in buffer, then preincubated in the presence or absence of TGRL and stimulated with either collagen or thrombin. Platelet aggregation and the arachidonic acid (AA) signaling pathway were studied.

RESULTS

Fasting T2D large TGRL were mostly of hepatic origin (apoB100/apoB48 ratio: 42 ± 7) and rich in triglycerides (TG/total apoB ratio: 4.2 ± 0.5), and able to potentiate agonist-stimulated platelet aggregation (collagen: +68%, P < 0.05; thrombin: +771%, P < 0.05). It should also be mentioned that TGRL from the plasma of HBD (n = 7) had no effect on platelet aggregation. In addition, T2D large TGRL increased thromboxane B₂ (TxB₂) concentration in platelets stimulated with either collagen (+34%, P < 0.05) or thrombin (+37%, P < 0.05) compared with platelets stimulated with either of these agonists without TGRL. Phosphorylation of p38 MAPK and cytosolic phospholipase A₂ (cPLA₂) was enhanced after incubation of platelets with T2D TGRL and thrombin (+87% and +32%, respectively, P < 0.05) compared with platelets incubated with thrombin only.

CONCLUSION

Large TGRL from fasting T2D patients may play a role in the development of atherothrombosis by increasing platelet aggregation and activating the platelet AA signaling pathway.

The biochemical and genetic diagnosis of lipid disorders

PURPOSE OF REVIEW

To examine recent advances in our knowledge on the diagnosis of lipid disorders.

RECENT FINDINGS

Fasting values above the 99th percentile for direct LDL-cholesterol (LDL-C), lipoprotein(a), and triglycerides are greater than 225 mg/dl, greater than 160 mg/dl, and greater than 500 mg/dl (>5.82, >394, and >5.65 mmol/l), respectively, whereas such values for plasma lathosterol, β-sitosterol, and cholestanol are greater than 8.0, 8.0, and 5.0 mg/l (>0.021, 0.019, and 0.013 mmol/l), respectively. Values below the first percentile for LDL-C are less than 40 mg/dl (<1.03 mmol/l) and for HDL-cholesterol (HDL-C) less than 25 mg/dl (<0.65 mmol/l) in men and less than 30 mg/dl (<0.78 mmol/l) in women, respectively. The above values can predispose to premature CVD, pancreatitis, neurologic disease, and kidney failure, and may be associated with monogenic lipid disorders. In the absence of secondary causes including diabetes or kidney, liver, or thyroid disease, consideration should be given to sequencing the following genes: ABCA1, ABCG5, ABCG8, APOA1, APOA5, APOB, APOC2, APOE, CETP, CYP27A1, GPIHBP1, LCAT, LDLR, LDLRAP1, LIPA, LIPC, LMF1, LPL, MTTP, PCSK9, SCARB1, and STAP1.

SUMMARY

Recent data indicate that secondary causes and a wider range of conditions need to be considered in identifying the underlying causes of hypercholesterolemia, hypertriglyceridemia, hyperalphalipoproteinemia, hypobetalipoproteinemia, and HDL deficiency. Identifying such disorders allows for a more precise assessment of prognosis and the formulation of optimal therapy.

Polymorphisms rs2167444 and rs508384 in the SCD1 Gene Are Linked with High ApoB-48 Levels and Adverse Profile of Cardiometabolic Risk Factors

Elevated plasma concentration of apolipoprotein B-48 (apoB-48) is an independent risk factor of cardiovascular disease. Stearoyl-CoA desaturase-1 (SCD1) is a rate-limiting lipogenic enzyme and a key regulator of fuel metabolism. The aim of this study was to analyse associations between clinical, biochemical, and genetic factors and different apoB-48 levels in subjects at increased cardiometabolic risk. We examined 220 subjects exhibiting at least one metabolic syndrome (MetS) component. In conjunction with basic clinical, anthropometric and laboratory measurements, we analysed various polymorphisms of stearoyl-CoA desaturase-1 (SCD1). Subjects were divided into two groups according to the median apoB-48 level: (1) high apoB-48 (≥ 7.9 mg/l, N = 112) and (2) low apoB-48 (< 7.9 mg/l, N = 108). Neither group differed significantly in anthropometric measures. High plasma apoB-48 levels were associated with increased systolic blood pressure (+3 %; P < 0.05), MetS prevalence (59.8 vs. 32.4 %; P < 0.001), small-dense LDL frequency (46.4 vs. 20.4 %; P < 0.001), triglycerides (+97 %; P < 0.001), non-HDLcholesterol (+27 %; P < 0.001), and lower concentrations of HDL-cholesterol (-11 %; P < 0.01). This group was further characterized by a higher HOMA-IR index (+54 %; P < 0.001) and increased concentrations of conjugated dienes (+11 %; P < 0.001) and oxidatively modified LDL (+ 38 %; P < 0.05). Lower frequencies of SCD1 minor genotypes (rs2167444, rs508384, P < 0.05) were observed in subjects with elevated plasma concentrations of apoB-48. Elevated plasma concentrations of apoB-48 are associated with an adverse lipid profile, higher systolic blood pressure, insulin resistance, and oxidative stress. Lower proportions of minor SCD1 genotypes (rs2167444, rs508384) implicate the role of genetic factors in the pathogenesis of elevated levels of apoB-48.

Recent Advances in Triacylglycerol Mobilization by the Gut

Dietary lipid absorption and lipoprotein secretion by the gut are important in maintaining whole-body energy homeostasis and have significant implications for health and disease. The processing of dietary lipids, including storage within and subsequent mobilization and transport from enterocyte cytoplasmic lipid droplets or other intestinal lipid storage pools (including the secretary pathway, lamina propria and lymphatics) and secretion of chylomicrons, involves coordinated steps that are subject to various controls. This review summarizes recent advances in our understanding of the mechanisms that underlie lipid storage and mobilization by small intestinal enterocytes and the intestinal lymphatic vasculature. Therapeutic targeting of lipid processing by the gut may provide opportunities for the treatment and prevention of dyslipidemia, and for improving health status.

The repeatability of the abbreviated (4-h) Oral Fat Tolerance Test and influence of prior acute aerobic exercise

PURPOSE

The Oral Fat Tolerance Test (OFTT) is regarded as a repeatable measure used to assess postprandial triglyceride (TAG) levels, with higher levels observed in cardio-metabolic disorders. Acute aerobic exercise intervention before OFTT reduces the TAG response, but the repeatability of this effect is unknown. The aim of this study was to determine the repeatability of the abbreviated 4-h OFTT with and without immediate prior aerobic exercise.

METHODS

On four separate days, healthy adult male participants underwent two 4-h OFTT (n = 10) and another two 4-h OFTT with 1-h of standardised moderate intensity aerobic exercise performed immediately before meal ingestion (n = 11). The OFTT meal composition included 75.4 g total fat, 21.7 g carbohydrate and 13.7 g protein. Venous blood was sampled at baseline and hourly up to 4 h after the OFTT meal ingestion, and TAG area under the curve (AUC) was calculated.

RESULTS

Nonparametric Bland-Altman analysis of 4-h TAG AUC revealed that 9 of 10 repeat measurements fell within ±15 % of the median TAG AUC for the OFTT. By contrast, two of 11 repeat measurements fell within ±15 % of the median TAG AUC for the OFTT undertaken with 1-h prior aerobic exercise.

CONCLUSIONS

The 4-h OFTT is a repeatable test of postprandial TAG responses in healthy men. However, aerobic exercise performed immediately before OFTT considerably increases the variability of TAG AUC. These findings have implications for interpretation of research studies investigating exercise intervention performed immediately before OFTT. Future studies should also investigate the repeatability of exercise performed 8-24 h before OFTT.

Update on the laboratory investigation of dyslipidemias

The role of the clinical laboratory is evolving to provide more information to clinicians to assess cardiovascular disease (CVD) risk and target therapy more effectively. Current routine methods to measure LDL-cholesterol (LDL-C), the Friedewald calculation, ultracentrifugation, electrophoresis and homogeneous direct methods have established limitations. Studies suggest that LDL and HDL size or particle concentration are alternative methods to predict future CVD risk. At this time there is no consensus role for lipoprotein particle or subclasses in CVD risk assessment. LDL and HDL particle concentration are measured by several methods, namely gradient gel electrophoresis, ultracentrifugation-vertical auto profile, nuclear magnetic resonance and ion mobility. It has been suggested that HDL functional assays may be better predictors of CVD risk. To assess the issue of lipoprotein subclasses/particles and HDL function as potential CVD risk markers robust, simple, validated analytical methods are required. In patients with small dense LDL particles, even a perfect measure of LDL-C will not reflect LDL particle concentration. Non-HDL-C is an alternative measurement and includes VLDL and CM remnant cholesterol and LDL-C. However, apolipoprotein B measurement may more accurately reflect LDL particle numbers. Non-fasting lipid measurements have many practical advantages. Defining thresholds for treatment with new measurements of CVD risk remain a challenge. In families with genetic variants, ApoCIII and lipoprotein (a) may be additional risk factors. Recognition of familial causes of dyslipidemias and diagnosis in childhood will result in early treatment. This review discusses the limitations in current laboratory technologies to predict CVD risk and reviews the evidence for emergent approaches using newer biomarkers in clinical practice.

Triterpenoids from Cyclocarya paliurus and their inhibitory effect on the secretion of apoliprotein B48 in Caco-2 cells

Five previously undescribed compounds including two triterpenoid aglycones, 3β,23-dihydroxy-1,12-dioxo-olean-28-oic acid and 3β,23,27-trihydroxy-1-oxo-olean-12-ene-28-oic acid, and three triterpenoid glucosides cyclocarioside L-N, along with 17 known compounds were isolated from a CH₃Cl-soluble extract of the leaves of Cyclocarya paliurus. Two 27-nor-triterpenoid glycosides were isolated from the genus for the first time. Furthermore, the characterized compounds were tested for the inhibitory effects on apoliprotein B48 secretion in Caco-2 cells. Seven triterpenoid aglycones together with four triterpenoid saponins significantly decreased the apoliprotein B48 oversecretion induced by oleic acid in Caco-2 cells.

Effects of a liquid high-fat meal on postprandial lipid metabolism in type 2 diabetic patients with abdominal obesity

Background

Postprandial lipemia and lipoprotein lipase (LPL) activity play crucial roles in the pathogenesis of accelerated atherosclerosis. This study aimed to evaluate the postprandial lipid metabolism after the ingestion of a liquid high-fat meal in type 2 diabetic patients with abdominal obesity, and determine if the PvuII polymorphisms of LPL influence their postprandial lipid responses.

Methods

Serum glucose, insulin, triglycerides (TG), total cholesterol (TC) and high density lipoprotein cholesterol (HDL-C) were measured in fasting and postprandial state at 0.5, 1, 2, 4, 6 and 8 h after a liquid high-fat meal in 51 type 2 diabetic patients with abdominal obesity, 31 type 2 diabetic patients without abdominal obesity and 39 controls. Their PvuII polymorphisms of LPL were tested in fasting.

Results

Type 2 diabetic patients with abdominal obesity had significantly higher postprandial areas under the curve (AUC) of glucose [least square mean difference (LSMD) = 30.763, 95% confidence interval (CI) = 23.071–38.455, F = 37.346, P < 0.05] and TC (LSMD = 3.995, 95% CI = 1.043–6.947, F = 3.681, P < 0.05) than controls. Postprandial AUCs for insulin, homeostasis model assessment-insulin resistance (HOMA-IR) and TG were higher (LSMD = 86.987, 95% CI = 37.421–136.553, F = 16.739, P < 0.05; LSMD = 37.456, 95% CI = 16.312–58.600, F = 27.012, P < 0.05; LSMD = 4.684, 95% CI = 2.662–6.705, F = 26.158, P < 0.05), whereas HDL-C AUC was lower (LSMD = −1.652, 95% CI = −2.685 – -0.620, F = 8.190, P < 0.05) in type 2 diabetic subjects with abdominal obesity than those without abdominal obesity. In type 2 diabetic patients with abdominal obesity, postprandial TG AUC was lower in P−/− than in P+/− (LSMD = −4.393, 95% CI = −9.278 – -0.491, F = 4.476, P < 0.05) and P+/+ (LSMD = −7.180, 95% CI = −12.319 – -2.014, F = 4.476, P < 0.05) phenotypes. Postprandial AUCs for glucose, insulin, HOMA-IR, TC and HDL-C were not different according to PvuII phenotypes.

Conclusions

Abdominal obesity exacerbates the postprandial lipid responses in type 2 diabetic patients, which partly explains the excess atherogenic risk in these patients. In addition, the presence of P+ allele could contribute to a greater postprandial TG increase in type 2 diabetic patients with abdominal obesity.

Trial registration

ChiCTR-IOR-16008435. Registered 8 May 2016.

The elevation of plasma concentrations of apoB-48-containing lipoproteins in familial hypercholesterolemia is independent of PCSK9 levels

BACKGROUND

Previous studies have reported high plasma concentrations of both intestinal apolipoprotein (apo) B-48-containing lipoproteins and PCSK9 in subjects with familial hypercholesterolemia (FH). However, the extent to which LDL receptor deficiency and PCSK9 levels influence plasma apoB-48 concentrations in humans remains to be fully characterized. The objective of the study was to assess the independent association between FH, PCSK9 concentrations and plasma apoB-48 levels in a large cohort of genetically defined FH heterozygotes (HeFH) and homozygotes (HoFH).

METHODS

A total of 118 HeFH, 6 HoFH, and 117 controls were included in the study. Plasma PCSK9 and apoB-48 concentrations were measured in the fasting state.

RESULTS

Plasma PCSK9 and apoB-48 levels were higher in FH subjects compared with controls (PCSK9: HoFH: 642.6 ± 246.9 vs. HeFH: 324.9 ± 119.8 vs.

CONTROLS

194.5 ± 65.9 ng/mL, P < 0.0001; apoB-48: HoFH: 14.71 ± 4.36 vs. HeFH: 6.55 ± 4.24 vs.

CONTROLS

3.03 ± 2.07 μg/mL; P < 0.0001). There were no correlations between apoB-48 and PCSK9 plasma levels in both controls (ρ = 0.06, P = 0.5) and HeFH subjects (ρ = 0.07, P = 0.4). Multiple linear regression analysis showed that the FH status was the only independent factor associated with apoB-48 levels, contributing to 28.7% of the variance (P < 0.0001).

CONCLUSIONS

These data indicate that the elevation in plasma apoB-48 levels associated with FH is independent of PCSK9 levels.

TRIAL REGISTRATION

NCT02225340 .

Effects of eicosapentaenoic acid and docosahexaenoic acid on cardiovascular disease risk factors: a randomized clinical trial

BACKGROUND

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the primary omega-3 fatty acids in fish oil, have been shown to reduce cardiovascular disease (CVD) risk.

OBJECTIVE

This study aimed to examine the independent effects of EPA and DHA on lipid and apolipoprotein levels, as well as on inflammatory biomarkers of CVD risk, using doses often used in the general population.

DESIGN

A blinded, randomized 6-week trial was performed in 121 healthy, normolipidemic subjects who received olive oil placebo 6g/d, EPA 600mg/d, EPA 1800mg/d, or DHA 600mg/d. The EPA was derived from genetically modified yeast.

RESULTS

The subjects tolerated the supplements well with no safety issues; and the expected treatment-specific increases in plasma EPA and DHA levels were observed. Compared to placebo, the DHA group had significant decreases in postprandial triglyceride (TG) concentrations (-20%, -52.2mg/dL, P=0.03), significant increases in fasting and postprandial low-density lipoprotein cholesterol (LDL-C) (+18.4%, 17.1mg/dL, P=0.001), with no significant changes in inflammatory biomarkers. No significant effects were observed in the EPA 600mg/d group. The high-dose EPA group had significant decreases in lipoprotein-associated phospholipase A2 concentrations (Lp-PLA₂) (-14.1%, -21.4ng/mL, P=0.003).

CONCLUSIONS

The beneficial effects of EPA 1800mg/d on CVD risk reduction may relate in part to the lowering of Lp-PLA₂ without adversely affecting LDL-C. In contrast, DHA decreased postprandial TG, but raised LDL-C. Our observations indicate that these dietary fatty acids have divergent effects on cardiovascular risk markers.

Effect of Pitavastatin Treatment on ApoB-48 and Lp-PLA₂ in Patients with Metabolic Syndrome: Substudy of PROspective Comparative Clinical Study Evaluating the Efficacy and Safety of PITavastatin in Patients with Metabolic Syndrome

BACKGROUND

Apolipoprotein (Apo) B-48 is an intestinally derived lipoprotein that is expected to be a marker for cardiovascular disease (CVD). Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) is a vascular-specific inflammatory marker and important risk predictor of CVD. The aim of this study was to explore the effect of pitavastatin treatment and life style modification (LSM) on ApoB-48 and Lp-PLA₂ levels in metabolic syndrome (MS) patients at relatively low risk for CVD, as a sub-analysis of a previous multi-center prospective study.

METHODS

We enrolled 75 patients with MS from the PROPIT study and randomized them into two treatment groups: 2 mg pitavastatin daily+intensive LSM or intensive LSM only. We measured the change of lipid profiles, ApoB-48 and Lp-PLA₂ for 48 weeks.

RESULTS

Total cholesterol, low density lipoprotein cholesterol, non-high density lipoprotein cholesterol, and ApoB-100/A1 ratio were significantly improved in the pitavastatin+LSM group compared to the LSM only group (P≤0.001). Pitavastatin+LSM did not change the level of ApoB-48 in subjects overall, but the level of ApoB-48 was significantly lower in the higher mean baseline value group of ApoB-48. The change in Lp-PLA₂ was not significant after intervention in either group after treatment with pitavastatin for 1 year.

CONCLUSION

Pitavastatin treatment and LSM significantly improved lipid profiles, ApoB-100/A1 ratio, and reduced ApoB-48 levels in the higher mean baseline value group of ApoB-48, but did not significantly alter the Lp-PLA₂ levels.

The expression of genes involved in jejunal lipogenesis and lipoprotein synthesis is altered in morbidly obese subjects with insulin resistance

The dyslipidemia associated with type 2 diabetes mellitus (T2DM) is an important risk factor for atherosclerotic cardiovascular disease. However, until now little attention has been paid to the role that the intestine might have. The aim of this research was to determine the relation between insulin resistance and intestinal de novo lipogenesis/lipoprotein synthesis in morbidly obese subjects and to study the effect of insulin on these processes. Jejunal mRNA expression of the different genes involved in the intestinal de novo lipogenesis/lipoprotein synthesis was analyzed in three groups of morbidly obese subjects: Group 1 with low insulin resistance (MO-low-IR), group 2 with high insulin resistance (MO-high-IR), and group 3 with T2DM and treatment with metformin (MO-metf-T2DM). In addition, intestinal epithelial cells (IECs) from MO-low-IR were incubated with different doses of insulin/glucose. In Group 2 (MO-high-IR), the jejunal mRNA expression levels of apo A-IV, ATP-citrate lyase (ACLY), pyruvate dehydrogenase (lipoamide) beta (PDHB), and sterol regulatory element-binding protein-1c (SREBP-1c) were significantly higher and acetyl-CoA carboxylase alpha (ACC1) and fatty-acid synthase lower than in Group 1 (MO-low-IR). In Group 3 (MO-metf-T2DM), only the ACLY and PDHB mRNA expressions were significantly higher than in Group 1 (MO-low-IR). The mRNA expression of most of the genes studied was significantly linked to insulin and glucose levels. The incubation of IEC with different doses of insulin and glucose produced a higher expression of diacylglycerol acyltransferase 2, microsomal triglyceride transfer protein, apo A-IV, SREBP-1c, and ACC1 when both, glucose and insulin, were at a high concentration. However, with only high insulin levels, there were higher apo A-IV, PDHB and SREBP-1c expressions, and a lower ACLY expression. In conclusion, the jejunum of MO-high-IR has a decreased mRNA expression of genes involved in de novo fatty-acid synthesis and an increase of genes involved in acetyl-CoA and lipoprotein synthesis. This effect is attenuated by metformin. In addition, the expression of most of the genes studied was found to be regulated by insulin.

The relationship of apolipoprotein B and very low density lipoprotein triglyceride with hyperuricemia and gout

INTRODUCTION

Gout results from an innate immune response to monosodium urate (MSU) crystals deposited in joints. Increased very low-density lipoprotein (VLDL) has been associated with gout. The apolipoprotein B (apo B), which is present on VLDL, regulates neutrophil response to MSU crystals and has been positively associated with gout. Furthermore, the gene (A1CF) encoding the complementation factor for the APOB mRNA-editing enzyme is associated with urate levels. However, the relationship of apo B and VLDL with gout and hyperuricaemia (HU) is still unclear. Therefore, we tested the association of VLDL and apo B with HU and with gout compared to HU.

METHODS

New Zealand European (n = 90) and Māori and Pacific Island (Polynesian) (n = 90) male gout case and control sample sets were divided into normouricaemia (NU), asymptomatic HU and gout groups. Size exclusion chromatography and enzyme-linked immunosorbant assay was used to measure VLDL and apo B. Multivariate logistic regression was used to assess the risk of gout and HU per unit change in VLDL and apo B.

RESULTS

Increased levels of VLDL triglycerides (Tg) were observed in the gout sample set compared to NU and HU in Europeans (P = 1.8 × 10(-6) and 1 × 10(-3), respectively), but only compared to NU in Polynesians (P = 0.023). This increase was driven by increased number of VLDL particles in the European participants and by the Tg-enrichment of existing VLDL particles in the Polynesian participants. Each mmol/L increase in VLDL Tg was significantly associated with gout in the presence of HU in Europeans, with a similar trend in Polynesians (OR = 7.61, P = 0.011 and 2.84, P = 0.069, respectively). Each μmol/L increase in total apo B trended towards decreased risk of HU (OR = 0.47; P = 0.062) and, conversely, with increased risk of gout compared to HU (OR = 5.60; P = 0.004).

CONCLUSIONS

Increased VLDL Tg is associated with the risk of gout compared to HU. A genetic approach should be taken to investigate the possibility for causality of VLDL in gout. Apolipoprotein B may have pleiotropic effects in determining HU and gout.

Effects of bariatric surgery on hepatic and intestinal lipoprotein particle metabolism in obese, nondiabetic humans

OBJECTIVE

The dyslipidemia of obesity and other insulin-resistant states is characterized by the elevation of plasma triglyceride-rich lipoproteins (TRL) of both hepatic (apoB-100-containing very low-density lipoprotein) and intestinal (apoB-48-containing chylomicrons) origin. Bariatric surgery is a well-established and effective modality for the treatment of obesity and is associated with improvements in several metabolic abnormalities associated with obesity, including a reduction in plasma triglycerides. Here, we have investigated the effect of bariatric surgery on TRL metabolism.

APPROACH AND RESULTS

Twenty-two nondiabetic, obese subjects undergoing bariatric surgery: sleeve gastrectomy (n=12) or gastric bypass (n=10) were studied. Each subject underwent 1 lipoprotein turnover study 1 month before surgery followed by a second study, 6 months after surgery, using established stable isotope enrichment methodology, in constant fed state. TRL-apoB-100 concentration was significantly reduced after sleeve gastrectomy, explained by a decrease (P<0.05) in TRL-apoB-100 production rate and an increase (P<0.05) in TRL-apoB-100 fractional catabolic rate. TRL-apoB-48 concentration was also significantly reduced after sleeve gastrectomy, explained by reduction in TRL-apoB-48 production rate (P<0.05). For gastric bypass, although TRL-apoB-100 concentration declined after surgery (P<0.01), without a significant decline in TRL-apoB-48, there was no significant change in either TRL-apoB-100 or TRL-apoB-48 production rate or fractional catabolic rate. The reduction in TRL-apoB-100 concentration was significantly associated with a reduction in plasma apoC-III in the pooled group of patients undergoing bariatric surgery.

CONCLUSIONS

This is the first human lipoprotein kinetic study to explore the mechanism of improvement of TRL metabolism after bariatric surgery. These effects may contribute to the decrease of cardiovascular mortality after surgery.

CLINICAL TRIAL REGISTRATION URL

http://www.ClinicalTrials.gov. Unique identifier: NCT01277068.

Exercise and dietary-mediated reductions in postprandial lipemia

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

Static and turnover kinetic measurement of protein biomarkers involved in triglyceride metabolism including apoB48 and apoA5 by LC/MS/MS

LC/MS quantification of multiple plasma proteins that differ by several orders of magnitude in concentration from a single sample is challenging. We present a strategy that allows the simultaneous determination of the concentration and turnover kinetics of higher and lower abundant proteins from a single digestion mixture. Our attention was directed at a cluster of proteins that interact to affect the absorption and interorgan lipid trafficking. We demonstrate that apos involved in TG metabolism such as apoC2, C3, E, and A4 (micromolar concentration), and apoB48 and apoA5 (single-digit nanomolar concentration) can be quantified from a single digestion mixture. A high degree of correlation between LC/MS and immunobased measurements for apoC2, C3, E, and B48 was observed. Moreover, apoA5 fractional synthesis rate was measured in humans for the first time. Finally, the method can be directly applied to studies involving nonhuman primates because peptide sequences used in the method are conserved between humans and nonhuman primates.

Ezetimibe prevents hepatic steatosis induced by a high-fat but not a high-fructose diet

Nonalcoholic fatty liver disease is the most frequent liver disease. Ezetimibe, an inhibitor of intestinal cholesterol absorption, has been reported to ameliorate hepatic steatosis in human and animal models. To explore how ezetimibe reduces hepatic steatosis, we investigated the effects of ezetimibe on the expression of lipogenic enzymes and intestinal lipid metabolism in mice fed a high-fat or a high-fructose diet. CBA/JN mice were fed a high-fat diet or a high-fructose diet for 8 wk with or without ezetimibe. High-fat diet induced hepatic steatosis accompanied by hyperinsulinemia. Treatment with ezetimibe reduced hepatic steatosis, insulin levels, and glucose production from pyruvate in mice fed the high-fat diet, suggesting a reduction of insulin resistance in the liver. In the intestinal analysis, ezetimibe reduced the expression of fatty acid transfer protein-4 and apoB-48 in mice fed the high-fat diet. However, treatment with ezetimibe did not prevent hepatic steatosis, hyperinsulinemia, and intestinal apoB-48 expression in mice fed the high-fructose diet. Ezetimibe decreased liver X receptor-α binding to the sterol regulatory element-binding protein-1c promoter but not expression of carbohydrate response element-binding protein and fatty acid synthase in mice fed the high-fructose diet, suggesting that ezetimibe did not reduce hepatic lipogenesis induced by the high-fructose diet. Elevation of hepatic and intestinal lipogenesis in mice fed a high-fructose diet may partly explain the differences in the effect of ezetimibe.

Fasting serum concentration of apolipoprotein B48 represents residual risks in patients with new-onset and chronic coronary artery disease

BACKGROUND

To identify new therapeutic targets for coronary artery disease (CAD), we investigated whether fasting serum concentration of apolipoprotein (apo) B48 could be a marker for CAD.

METHODS

Patients with CAD were divided into those with new-onset CAD [i.e., those receiving percutaneous coronary intervention (PCI) for the first time] and those with chronic CAD (i.e., those receiving follow-up coronary angiography). Fasting serum biochemical analyses were performed on admission and 6 months after the PCI.

RESULTS

On admission, serum LDL-C concentrations in patients with chronic CAD (n=138), presumably receiving statin treatment, were lower than in patients with new-onset CAD (n=50, p<0.02) or without CAD (n=71, p<0.001). Nevertheless, apoB48 was higher in CAD patients than in those without CAD (p<0.001). After adjusting for classic cardiovascular risk factors, multivariate logistic regression analyses showed apoB48 to be an independent predictor of coronary risk in new-onset or chronic CAD, irrespective of the LDL-C levels. Moreover, apoB48 was markedly increased during the follow-up period in CAD patients having new lesion progression after the prior PCI.

CONCLUSION

Fasting serum apoB48 concentration could be a marker of new onset as well as chronic CAD, and predict new lesion progression in secondary prevention.

Diagnosis and treatment of severe hypertriglyceridemia

Severe hypertriglyceridemia is associated with acute pancreatitis and can be a manifestation of lipoprotein lipase (LPL) deficiency. It is associated with a spectrum of disorders, ranging from heterozygous LPL deficiency allied with environmental factors to rare severe cases of homozygous LPL deficiency. The genes associated with reduced LPL activity include LPL, its cofactor apoC-2, a controlling protein apoA-5 and the LPL receptor GPI-HBP1. The effects of mutations are exacerbated by environmental factors such as diet, pregnancy and insulin resistance. Treatment of clinical LPL deficiency is by ultra-low-fat diet along with the use of fibrates, omega-3 fatty acids, niacin, statins and insulin-sensitizing therapies, depending on the extent of residual LPL activity. Novel therapies that target lipoprotein particle assembly through the antisense oligonucleotides or by interference with triglyceride-loading microsomal transport protein inhibitors offer new potential options for treating hypertriglyceridemia.

Effects of CETP inhibition on triglyceride-rich lipoprotein composition and apoB-48 metabolism

Cholesteryl ester transfer protein (CETP) facilitates the transfer of HDL cholesteryl ester to triglyceride-rich lipoproteins (TRL). This study aimed to determine the effects of CETP inhibition with torcetrapib on TRL composition and apoB-48 metabolism. Study subjects with low HDL cholesterol (<40 mg/dl), either untreated (n = 9) or receiving atorvastatin 20 mg daily (n = 9), received placebo for 4 weeks, followed by torcetrapib 120 mg once daily for the next 4 weeks. A subset of the subjects not treated with atorvastatin participated in a third phase (n = 6), in which they received torcetrapib 120 mg twice daily for an additional 4 weeks. At the end of each phase, all subjects received a primed-constant infusion of [5,5,5-(2)H(3)]L-leucine, while in the constantly fed state, to determine the kinetics of TRL apoB-48 and TRL composition. Relative to placebo, torcetrapib markedly reduced TRL CE levels in all groups (≥-69%; P < 0.005). ApoB-48 pool size (PS) and production rate (PR) decreased in the nonatorvastatin once daily (PS: -49%, P = 0.007; PR: -49%, P = 0.005) and twice daily (PS: -30%, P = 0.01; PR: -27%, P = 0.13) cohorts. In the atorvastatin cohort, apoB-48 PS and PR, which were already lowered by atorvastatin, did not change with torcetrapib. Our findings indicate that CETP inhibition reduced plasma apoB-48 concentrations by reducing apoB-48 production but did not have this effect in subjects already treated with atorvastatin.

The chronic effects of fish oil with exercise on postprandial lipaemia and chylomicron homeostasis in insulin resistant viscerally obese men

Background

Visceral obesity and insulin resistance are associated with a postprandial accumulation of atherogenic chylomicron remnants that is difficult to modulate with lipid-lowering therapies. Dietary fish oil and exercise are cardioprotective interventions that can significantly modify the metabolism of TAG-rich lipoproteins. In this study, we investigated whether chronic exercise and fish oil act in combination to affect chylomicron metabolism in obese men with moderate insulin resistance.

Methods

The single blind study tested the effect of fish oil, exercise and the combined treatments on fasting and postprandial chylomicron metabolism. Twenty nine men with metabolic syndrome were randomly assigned to take fish oil or placebo for four weeks, before undertaking an additional 12 week walking program. At baseline and at the end of each treatment, subjects were tested for concentrations of fasting apo B48, plasma lipids and insulin. Postprandial apo B48 and TAG kinetics were also determined following ingestion of a fat enriched meal.

Results

Combining fish oil and exercise resulted in a significant reduction in the fasting apo B48 concentration, concomitant with attenuation of fasting TAG concentrations and the postprandial TAG_IAUC response (p < 0.05). Fish oil by itself reduced the postprandial TAG response (p < 0.05) but not postprandial apo B48 kinetics. Individual treatments of fish oil and exercise did not correspond with improvements in fasting plasma TAG and apo B48.

Conclusion

Fish oil was shown to independently improve plasma TAG homeostasis but did not resolve hyper-chylomicronaemia. Instead, combining fish oil with chronic exercise reduced the plasma concentration of pro-atherogenic chylomicron remnants; in addition it reduced the fasting and postprandial TAG response in viscerally obese insulin resistant subjects.

Postprandial lipoprotein metabolism: VLDL vs chylomicrons

Since Zilversmit first proposed postprandial lipemia as the most common risk of cardiovascular disease, chylomicrons (CM) and CM remnants have been thought to be the major lipoproteins which are increased in the postprandial hyperlipidemia. However, it has been shown over the last two decades that the major increase in the postprandial lipoproteins after food intake occurs in the very low density lipoprotein (VLDL) remnants (apoB-100 particles), not CM or CM remnants (apoB-48 particles). This finding was obtained using the following three analytical methods; isolation of remnant-like lipoprotein particles (RLP) with specific antibodies, separation and detection of lipoprotein subclasses by gel permeation HPLC and determination of apoB-48 in fractionated lipoproteins by a specific ELISA. The amount of the apoB-48 particles in the postprandial RLP is significantly less than the apoB-100 particles, and the particle sizes of apoB-48 and apoB-100 in RLP are very similar when analyzed by HPLC. Moreover, CM or CM remnants having a large amount of TG were not found in the postprandial RLP. Therefore, the major portion of the TG which is increased in the postprandial state is composed of VLDL remnants, which have been recognized as a significant risk for cardiovascular disease.

Ezetimibe improves postprandial hyperlipemia and its induced endothelial dysfunction

OBJECTIVE

Postprandial hyperlipemia has been shown to impair endothelial function and contribute to the development of atherosclerosis. We investigated the association between postprandial lipid profiles and endothelial function, and we examined the effects of ezetimibe on postprandial hyperlipemia and lipemia-induced endothelial dysfunction.

METHODS

A randomized prospective trial in which 10 mg/day of ezetimibe was administered to 10 subjects for 4 weeks and not administered to 10 subjects (control group) was performed. Lipid profiles and endothelial function, assessed by brachial artery flow-mediated dilation (FMD) during a fasting state and at 2, 4, 6 and 8 h after an oral cookie loading test, were determined before and after treatment for 4 weeks.

RESULTS

In all subjects before treatment, the maximum reduction in postprandial %FMD was significantly correlated with the maximum increases in postprandial triglyceride (TG) (r=-0.499, P<0.05) and apolipoprotein B-48 (apoB-48) concentrations (r=-0.551, P<0.05). Ezetimibe treatment for 4 weeks significantly suppressed postprandial elevation in TG (area under the incremental curve, from 1419±594 to 968±32 1 mg h/dl, P<0.05), remnant lipoprotein cholesterol (from 66.9±27.6 to 38.9±15.4 mg h/dl, P<0.01) and apoB-48 (from 58.8±27.5 to 36.2±17.0 μg h/ml, P<0.05) concentrations, and postprandial endothelial dysfunction assessed by %FMD (maximum reduction in %FMD, from -2.6±1.1% to -1.2±0.8%, P<0.05), whereas no significant changes were observed in the control group.

CONCLUSION

Postprandial hyperlipemia is closely correlated with transient endothelial dysfunction. Ezetimibe improves postprandial hyperlipemia and its induced endothelial dysfunction.

Particle size of apoB-48 carrying lipoproteins in remnant lipoproteins isolated from postprandial plasma

BACKGROUND

Particle size of apoB-48 carrying lipoproteins in remnant-like lipoprotein particles (RLP) in postprandial plasma has not been well characterized.

METHODS

Plasma lipids, lipoproteins and apolipoproteins in 12 healthy subjects were analysed after an oral fat load. RLP isolated by immunoaffinity gel from plasma of a normolipidaemic and a hyperlipidaemic subject in four hours after an oral fat load was fractionated by high-performance liquid chromatography (HPLC) and monitored by total cholesterol (TC), triglycerides (TG), apoB-48 and apoB-100.

RESULTS

TC, low-density lipoprotein (LDL)-C and apoB did not change after an oral fat load, while TG, RLP-C, RLP-TG and apoB-48 increased significantly in postprandial plasma. HPLC profiles monitored by TC and TG revealed that major lipoproteins increased in RLP after an oral fat load was VLDL size particles. The percentage of RLP-TG in total TG and the ratio of RLP-TG/RLP-C were significantly increased in four hours after an oral fat load compared with the fasting state (P < 0.01). RLP in four hours after an oral fat load fractionated by HPLC and monitored by TC, TG, apoB-48 and apoB-100 revealed that VLDL size or smaller particles were the major lipoproteins.

CONCLUSIONS

ApoB-48 carrying lipoproteins in RLP isolated from a normolipidaemic and a hyperlipidaemic subject after an oral fat load showed a similar particle size with apoB-100 carrying VLDL remnants. Therefore, the most apoB-48 carrying particles found in postprandial RLP can be classified as CM remnants. The majority of remnants in the postprandial state were not CM remnants, but VLDL remnants.

Endothelial cells as targets for chylomicron remnants

Endothelial dysfunction is characterised by pro-inflammatory/pro-coagulant changes in the endothelium and supports leukocyte adhesion and transmigration, key steps in early atherogenesis. There is emerging evidence that triacylglycerol-rich lipoproteins (TGRLs) present in the circulation during the postprandial phase influence vascular inflammation but the specific contribution of the remnant lipoprotein component of TGRLs is largely unexplored and the mechanistic basis of their actions poorly defined. This article provides a brief overview of the evidence supporting direct actions of these particles on endothelial cells and highlights the importance of their fatty acid composition and oxidative state as determinants of their cellular actions.

Postprandial lipid and apolipoprotein responses following three consecutive meals associate with liver fat content in type 2 diabetes and the metabolic syndrome

OBJECTIVE

Liver fat is associated with dyslipidemia following a fat load. Previous studies demonstrated that alimentary fat is temporarily retained within enterocytes and mobilized by subsequently ingested nutrients. As this potentially contributes to cumulative postprandial hyperlipidemia, we assessed postprandial lipoprotein changes and their association with liver fat following 3 consecutive meals during a 24 h period in males with type 2 diabetes, and men with the metabolic syndrome (MetS).

METHODS

Plasma lipids were measured in 14 type 2 diabetic, 14 MetS and 14 healthy age-matched males, following a standardized breakfast (t=0 h), lunch (t=4 h) and diner (t=8 h). Blood samples were collected before and at t=2, 4, 6, 8, 12, 16, 20 and 24 h following breakfast. Liver fat was measured by proton magnetic resonance spectroscopy.

RESULTS

Type 2 diabetic (mean age 55 (4.2) years; HbA1c 7.2 (1.1)%) and MetS men had similar BMI, waist, blood pressure and triglycerides. 24 h-AUC triglycerides, ApoB, and cholesterol-rich-remnants, but not ApoB-48, differed significantly among groups (calculated by ANOVA, all P<0.05). Liver fat was independently associated with 24 h-AUC triglycerides, ApoB and cholesterol-rich-remnants (r=0.57, P<0.001, r=0.38, P=0.017; r=0.48, P=0.002, respectively), but not with 24 h-AUC ApoB-48 (r=0.22, P=0.18).

CONCLUSIONS

In type 2 diabetes and the MetS exposure to 3 consecutive meals produced exaggerated 24 h triglyceride, ApoB and cholesterol-rich-remnant concentrations, which were closely associated with liver fat. Instead, ApoB-48 peak was delayed in type 2 diabetes, but not related to liver fat. In addition to liver fat, other mechanisms, including local intestinal processes, determine atherogenic postprandial lipoprotein changes following 3 consecutive meals during 24 h.