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OBJECTIVE Intestinal lipoprotein production has recently been shown to be increased in insulin resistance, but it is not known whether it is regulated by insulin in humans. Here, we investigated the effect of acute hyperinsulinemia on intestinal (and hepatic) lipoprotein production in six healthy men in the presence and absence of concomitant suppression of plasma free fatty acids (FFAs). RESEARCH DESIGN AND METHODS Each subject underwent the following three lipoprotein turnover studies, in random order, 4–6 weeks apart: 1) insulin and glucose infusion (euglycemic-hyperinsulinemic clamp) to induce hyperinsulinemia, 2) insulin and glucose infusion plus Intralipid and heparin infusion to prevent the insulin-induced suppression of plasma FFAs, and 3) saline control. RESULTS VLDL1 and VLDL2-apoB48 and -apoB100 production rates were suppressed by 47–62% by insulin, with no change in clearance. When the decline in FFAs was prevented by concomitant infusion of Intralipid and heparin, the production rates of VLDL1 and VLDL2-apoB48 and -apoB100 were intermediate between insulin and glucose infusion and saline control. CONCLUSIONS This is the first demonstration in humans that intestinal apoB48-containing lipoprotein production is acutely suppressed by insulin, which may involve insulin's direct effects and insulin-mediated suppression of circulating FFAs.

We reported earlier that dietary cinnamon extract (CE) improves systemic insulin sensitivity and dyslipidemia by enhancing insulin signaling. In the present study, we have examined the effects of CE on several biomarkers including plasma levels of adipose-derived adipokines, and the potential molecular mechanisms of CE in epididymal adipose tissue (EAT). In Wistar rats fed a high-fructose diet (HFD) to induce insulin resistance, supplementation with a CE (Cinnulin PF ® , 50 mg/kg daily) for 8 weeks reduced blood glucose, plasma insulin, triglycerides, total cholesterol, chylomicron-apoB48, VLDL-apoB100, and soluble CD36. CE also inhibited plasma retinol binding protein 4 (RBP4) and fatty acid binding protein 4 (FABP4) levels. CE-induced increases in plasma adiponectin were not significant. CE did not affect food intake, bodyweight, and EAT weight. In EAT, there were increases in the insulin receptor ( IR) and IR substrate 2 ( IRS2) mRNA, but CE-induced increases in mRNA expression of IRS1, phosphoinositide-3-kinase, AKT1, glucose transporters 1 and 4 , and glycogen synthase 1 expression and decreased trends in mRNA expression of glycogen synthase kinase 3β were not statistically significant. CE also enhanced the mRNA levels of ADIPOQ, and inhibited sterol regulatory element binding protein-1c mRNA levels. mRNA and protein levels of fatty acid synthase and FABP4 were inhibited by CE and RBP4, and CD36 protein levels were also decreased by CE. These results suggest that CE effectively ameliorates circulating levels of adipokines partially mediated via regulation of the expression of multiple genes involved in insulin sensitivity and lipogenesis in the EAT.

We have reported previously that a cinnamon extract (CE), high in type A polyphenols, prevents fructose feeding-induced decreases in insulin sensitivity and suggested that improvements of insulin sensitivity by CE were attributable, in part, to enhanced insulin signaling. In this study, we examined the effects of CE on postprandial apolipoprotein (apo) B-48 increase in fructose-fed rats, and the secretion of apoB48 in freshly isolated intestinal enterocytes of fructose-fed hamsters. In an olive oil loading study, a water-soluble CE (Cinnulin PF, 50 mg/kg body weight, orally) decreased serum triglyceride (TG) levels and the over production of total- and TG-rich lipoprotein-apoB48. In ex vivo (35)S labeling study, significant decreases were also observed in apoB48 secretion into the media in enterocytes isolated from fructose-fed hamsters. We also investigated the molecular mechanisms of the effects of CE on the expression of genes of the insulin signaling pathway [insulin receptor (IR), IR substrate (IRS)1, IRS2 and Akt1], and lipoprotein metabolism [microsomal TG transfer protein (MTP), sterol regulatory element-binding protein (SREBP1c) in isolated primary enterocytes of fructose-fed hamsters, using quantitative real-time polymerase chain reaction. The CE reversed the expression of the impaired IR, IRS1, IRS2 and Akt1 mRNA levels and inhibited the overexpression of MTP and SREBP1c mRNA levels of enterocytes. Taken together, our data suggest that the postprandial hypertriglycerides and the overproduction of apoB48 can be acutely inhibited by a CE by a mechanism involving improvements of insulin sensitivity of intestinal enterocytes and regulation of MTP and SREBP1c levels. We present both in vivo and ex vivo evidence that a CE improves the postprandial overproduction of intestinal apoB48-containing lipoproteins by ameliorating intestinal insulin resistance and may be beneficial in the control of lipid metabolism.

In eukaryotes mRNA transcripts are extensively processed by different post-transcriptional events such as alternative splicing and RNA editing in order to generate many different mRNAs from the same gene, increasing the transcriptome and then the proteome diversity. The most frequent RNA editing mechanism in mammals involves the conversion of specific adenosines into inosines by the ADAR family of enzymes. This editing event can alter the sequence and the secondary structure of RNA molecules, with consequences for final proteins and regulatory RNAs. Alteration in RNA editing has been connected to tumor progression and many other important human diseases. Analysis of many editing sites in various cancer types is expected to provide new diagnostic and prognostic markers and might contribute to early detection of cancer, the monitoring of response to therapy, and to the detection of minimal residual disease.

Sixteen hyperlipidemic men were enrolled in a randomized, placebo-controlled, double-blind, cross-over study to evaluate the effect of ezetimibe 10 mg and simvastatin 40 mg, coadministered and alone, on the in vivo kinetics of apolipoprotein (apo) B-48 and B-100 in humans. Subjects underwent a primed-constant infusion of a stable isotope in the fed state. The coadministration of simvastatin and ezetimibe significantly reduced plasma concentrations of cholesterol (−43.0%), LDL-C (−53.6%), and triglycerides (−44.0%). Triglyceride-rich lipoproteins (TRL) apoB-48 pool size (PS) was significantly decreased (−48.9%) following combination therapy mainly through a significant reduction in TRL apoB-48 production rate (PR) (−38.0%). The fractional catabolic rate (FCR) of VLDL and LDL apoB-100 were significantly increased with all treatment modalities compared with placebo, leading to a significant reduction in the PS of these fractions. We also observed a positive correlation between changes in TRL apoB-48 PS and changes in TRL apoB-48 PR (r = 0.85; P < 0.0001) with combination therapy. Our results indicate that treatment with simvastatin plus ezetimibe is effective in reducing plasma TRL apoB-48 levels and that this effect is most likely mediated by a reduction in the intestinal secretion of TRL apoB-48. Our study also indicated that the reduction in LDL-C concentration following combination therapy is mainly driven by an increase in FCR of apoB-100 containing lipoproteins.

Atorvastatin and rosuvastatin at maximal doses are both highly effective in lowering low-density lipoprotein cholesterol (LDL-C) and triglyceride (TG) levels. Rosuvastatin has been shown to be more effective than atorvastatin in lowering LDL-C, small dense LDL-C and in raising high-density lipoprotein (HDL) and its subclasses. Intestinal lipoproteins containing apolipoprotein (apo) B-48 are also thought to be atherogenic particles. Our purpose in this study was to compare the effects of daily oral doses of atorvastatin 80 mg/day and rosuvastatin 40 mg/day over a 6-week period on serum apo B-48 (a marker of intestinal lipoproteins) and remnant lipoprotein cholesterol (RemL-C) levels (a marker of partially metabolized lipoproteins of both intestinal and liver origin), using novel direct assays in 270 hyperlipidemic men and women. Both atorvastatin and rosuvastatin caused significant (p < 0.0001) and similar median decreases in TG (−33.0%, −27.6%), RemL-C (−58.7%, −61.5%), and apoB-48 (−37.5%, −32.1%) as compared to baseline. Our findings utilizing a specific immunoassay and a fairly large number of subjects extend prior studies indicating that statins significantly lower apolipoprotein B containing lipoproteins of both intestinal and liver origin. © 2008 Elsevier Ireland Ltd. All rights reserved.

We have previously reported that the obesity-associated proinflammatory cytokine, TNF-alpha, stimulates the overproduction of intestinal apolipoprotein (apo) B48 containing lipoproteins. In the current study, we have evaluated whether a water-soluble cinnamon extract [CE (Cinnulin PF)] attenuates the dyslipidemia induced by TNF-alpha in Triton WR-1339 treated hamsters, and whether CE inhibits the oversecrection of apoB48-induced by TNF-alpha in enterocytes in a 35S labeling study. In vivo, oral treatment of Cinnulin PF (50 mg per kg BW), inhibited the postprandial overproduction of apoB48-containing lipoproteins and serum triglyceride levels. In ex vivo 35S labeling studies, CE (10 and 20 microg/ml) inhibited the oversecretion of apoB48 induced by TNF-alpha treated enterocytes into the media. To determine the molecular mechanisms, TNF-alpha treated primary enterocytes isolated from chow-fed hamsters, were incubated with CE (10 microg/ml), and the expression of the inflammatory factor genes, IL1-beta, IL-6, and TNF-alpha, insulin signaling pathway genes, insulin receptor (IR), IRS1, IRS2, phosphatidylinositol 3-kinase (PI3-K), Akt1 and phosphatase and tensin homology (PTEN), as well as the key regulators of lipid metabolism, cluster of differentiation (CD)36, microsomal triglyceride transfer protein (MTTP), and sterol regulatory element binding protein (SREBP)-1c were evaluated. Quantitative real-time PCR assays showed that CE treatment decreased the mRNA expression of IL-1beta, IL-6 and TNF-alpha, improved the mRNA expression of IR, IRS1, IRS2, PI3K and Akt1, inhibited CD36, MTTP, and PTEN, and enhanced the impaired SREBP-1c expression in TNF-alpha treated enterocytes. These data suggest that a water extract of cinnamon reverses TNF-alpha-induced overproduction of intestinal apoB48 by regulating gene expression involving inflammatory, insulin, and lipoprotein signaling pathways. In conclusion, Cinulin PF improves inflammation related intestinal dyslipidemia.

It is well established that leptin increases the sensitivity of carbohydrate metabolism to the effects of insulin. Leptin and insulin also have potent effects on lipid metabolism. However, the effects of leptin on the regulation of liver lipid metabolism by insulin have not been investigated. The current study addressed the effects of leptin on insulin-regulated hepatic very low-density lipoprotein (VLDL) metabolism in vivo in rats. A 90-min hyperinsulinemic/euglycemic clamp (4 mU/kg x min(-1)) reduced plasma VLDL triglyceride (TG) by about 50% (P < 0.001 vs. saline control). Importantly, a leptin infusion (0.2 microg/kg x min(-1)) in combination with insulin reduced plasma VLDL-TG by about 80% (P < 0.001 vs. insulin alone). These effects did not require altered skeletal muscle lipoprotein lipase activity but did include differential effects of insulin and leptin on liver apolipoprotein (apo) B and TG metabolism. Thus, insulin decreased liver and plasma apoB100/B48 levels (approximately 50%, P < 0.01), increased liver TGs (approximately 20%, P < 0.05), and had no effect on fatty acid oxidation. Conversely, leptin decreased liver TGs (approximately 50%, P < 0.01) and increased fatty acid oxidation (approximately 50%, P < 0.01) but had no effects on liver or plasma apoB levels. Importantly, the TG-depleting and prooxidative effects of leptin were maintained in the presence of insulin. We conclude that leptin additively increases the suppressive effects of insulin on hepatic and systemic VLDL metabolism by stimulating depletion of liver TGs and increasing oxidative metabolism. The net effect of the combined actions of insulin and leptin is to decrease the production and TG content of VLDL particles.

Chlordecone (CD) is one of many banned organochlorine (OC) insecticides that are widespread persistent organic pollutants. OC insecticides alter lipid homeostasis in rodents at doses that are not neurotoxic or carcinogenic. Pretreatment of mice or rats with CD altered tissue distribution of a subsequent dose of [(14)C]CD or [(14)C]cholesterol (CH). Nuclear receptors regulate expression of genes important in the homeostasis of CH and other lipids. In this study, we report that CD suppresses in vitro reporter systems for human liver X receptors (LXRs) and activates those for human farnesoid X receptor (FXR), pregnane X receptor (PXR) and estrogen receptor alpha (ERalpha) in a concentration-dependent manner (0-50 muM). Consistent with human PXR activation in vitro, three days after a single dose of CD (15 mg/kg) hepatic microsomal CYP3A11 protein increases in C57BL/6 mice. CD decreases hepatic CH ester content without altering total CH concentration. Apolipoprotein A-I (apoA-I) contents of hepatic lipoprotein-rich and microsomal fractions of CD-treated mice are higher than controls. There is a significant reduction in non-high density lipoprotein CH but not apolipoprotein B-48/100 (apoB-48/100) in plasma from CD-treated mice after a 4 h fast. At 14 days after 15 mg CD/kg apoA-I and apoB-100 proteins but not CYP3A11 protein in hepatic microsomes are similar to controls. This work indicates that altered CH homeostasis is a mode of OC insecticide action of relevance after a single dose. This at least partially explains altered CH tissue distribution in CD-pretreated mice.

Backgroud Hypertriglyceridaemia, a consistent feature of dyslipidaemia in the metabolic syndrome (MetS), is related to the extent of abdominal fat mass and altered adipocytokine secretion. We determined the effect of weight loss by dietary restriction on markers of triglyceride-rich lipoprotein (TRL) metabolism and plasma adipocytokines. Design Thirty-five men with MetS participated in a 16 week randomized controlled dietary intervention study. Apolipoprotein (apo) C-III, apoB-48, remnant-like particle (RLP)-cholesterol, total adiponectin, high-molecular weight (HMW) adiponectin, and retinol-binding protein-4 (RBP-4) concentrations were measured using immunoassays. Results Compared with weight maintenance (n = 15), weight loss (n = 20) significantly decreased body weight, plasma insulin, triglycerides, total cholesterol, low-density lipoprotein (LDL)-cholesterol and lathosterol (P

Objective— Lipin 1 controls fatty acid metabolism in the nucleus as a transcriptional regulator and in the cytosol as an enzyme catalyzing the penultimate step in phosphoglycerol triacylglyceride (TAG) synthesis. We sought to evaluate the effects of lipin 1 on hepatic TAG synthesis and secretion by gain-of-function and loss-of-function approaches. Methods and Results— Rates of TAG synthesis were not impaired in hepatocytes isolated from adult lipin 1–deficient ( fld ) mice and were actually increased in 14-day-old fld mice. Additionally, compared to littermate controls, VLDL-TAG secretion rates were markedly increased in fld mice of both ages. Lipin 1 overexpression did not alter TAG synthesis rates but significantly suppressed VLDL-TAG secretion. The lipin 1-mediated suppression of VLDL-TAG secretion was linked to the peptide motif mediating its transcriptional-regulatory effects. However, the expression of candidate genes required for VLDL assembly and secretion was unaltered by lipin 1 activation or deficiency. Finally, the hepatic expression of lipin 1 was diminished in obese insulin-resistant mice, whereas adenoviral-mediated overexpression of lipin 1 in liver of these mice inhibits VLDL-TAG secretion and improves hepatic insulin signaling. Conclusions— Collectively, these studies reveal new and unexpected effects of lipin 1 on hepatic TAG metabolism and obesity-related hepatic insulin resistance.

The atherogenicity of chylomicron remnants has been discussed. We examined whether serum apoB48 level is associated with the presence of carotid plaque in type 2 diabetic patients.Forty type 2 diabetic patients (21 males and 19 females, 52.8+/-11.8 years old; mean+/-S.D.) were divided into two groups by the presence or absence of carotid plaque. The diurnal change of serum apoB48 level was measured by enzyme-linked immunosorbent assay.Fasting serum apoB48 level was higher in the subjects with carotid plaque than those without (6.5+/-3.8vs. 4.1+/-1.9 microg/ml, p=0.01). Age- and gender-adjusted analysis showed that the presence of carotid plaque was associated with fasting apoB48 (OR 1.43; 95% CI, 1.07-2.09, p=0.04) and triglyceride (OR 1.14; 95% CI, 1.02-1.32, p=0.04) levels. In normal LDL-cholesterol (140 mg/dl) subjects, the presence of carotid plaque was associated with fasting apoB48 level (OR 2.16; 95% CI, 1.22-5.32, p=0.04), but not associated with fasting triglyceride level (OR 1.11; 95% CI, 0.99-1.30, p=0.13).Serum apoB48 level was strongly associated with the presence of carotid plaque in type 2 diabetic patients.

Dietary triacylglycerols are absorbed by enterocytes and packaged in the endoplasmic reticulum (ER) in the intestinal specific lipoprotein, the chylomicron, for export into mesenteric lymph. Chylomicrons exit the ER in an ER-to-Golgi transport vesicle, the pre-chylomicron transport vesicle (PCTV), which is the rate-limiting step in the transit of chylomicrons across the cell. Here, we focus on potential mechanisms of control of the PCTV-budding step from the intestinal ER. We incubated intestinal ER with intestinal cytosol and ATP to cause PCTV budding. The budding reaction was inhibited by 60 nM of the PKC inhibitor Gö 6983, suggesting the importance of PKCzeta in the generation of PCTV. Immunodepletion of PKCzeta from the cytosol and the use of washed ER greatly inhibited the generation of PCTVs, but was restored following the addition of recombinant PKCzeta. Intestinal ER incubated with intestinal cytosol and [gamma-(32)P]ATP under conditions supporting the generation of PCTVs showed the phosphorylation of a 9-kDa band following autoradiography. The phosphorylation of this protein correlated with the generation of PCTVs but not the formation of protein vesicles and was inhibited by depletion of PKCzeta. Phosphorylation of the 9-kDa protein was restored following the addition of recombinant PKCzeta. The association of the 9-kDa protein with proteins that are important for PCTV budding was phosphorylation dependent. We conclude that PKCzeta activity is required for PCTV budding from intestinal ER, and is associated with phosphorylation of a 9-kDa protein that might regulate PCTV budding.

Overweight and obesity is one of the risk factors for developing CVD. At present, very little is known about the acute effects of dietary fibre on lipids, glucose and insulin, resting energy expenditure and diet-induced thermogenesis in overweight and obese individuals. This study examined the postprandial metabolic effects of dietary fibre in overweight and obese men. Ten overweight and obese men consumed a mixed meal accompanied by either a high-fibre or low-fibre supplement on two separate visits, in a random order, 1 week apart. Two isoenergetic breakfast meals with similar composition were consumed by ten overweight/obese men. The meals contained either a low (3 g) or high (15 g) amount of fibre, low-fibre meal (LFM) and high-fibre meal (HFM) respectively. Analysis was carried out using paired t test and ANOVA. Serum TAG incremental area under the curve during 6 h of the postprandial period was significantly lower after the consumption of HFM compared with LFM. At the first hour of the postprandial period, plasma apo B48 concentration after consumption of HFM was significantly lower compared with LFM. The resting energy expenditure and diet-induced thermogenesis after both meals was similar during 6 h of the postprandial period. Collectively, these findings suggest that a single acute dose of dietary fibre in the form of psyllium supplement can decrease arterial exposure to TAG and modify chylomicron responses in the postprandial period.

Background ApoB-48 is a major apolipoprotein secreted by the small intestine and is the main constitutive apolipoprotein in chylomicrons (CM). In the past, presence of apoB-48 in human aortic atherosclerotic plaques has not been detected. Methods A newly developed apoB-48 ELISA together with an HPLC fractionation technique, were applied to investigate the presence of apoB-48 (CM) in aortic atherosclerotic plaques. The atherosclerotic plaques were obtained from aortae of sudden cardiac death cases. Total cholesterol, triglycerides (TG), apoB-100 and apoB-48 were measured in the aortic plaques extracts. Results HPLC analysis of plaques extracts monitored by cholesterol revealed mainly particle sizes of CM and very low density lipoproteins (VLDL) in the d > 1.006 fractions. The plaques extracts were monitored by apoB-48 and apoB-100 ELISA. There were no TG peaks in any lipoprotein fraction extracted from the plaques except as free glycerol. ApoB-100 was detected in VLDL particles and in LDL sizes. In contrast, apoB-48 was detected in particles of CM, VLDL and LDL sizes. Further, in postmortem plasma, apo B-48 was detected in particles sizes of HDL or smaller and the Western blot analysis could not show any 250 kDa molecular weight (MW) protein in the plaque extracts, but smaller and broader MW staining were observed at 20–150 kDa. Conclusion Hitherto there has been lack of an appropriate assay to measure apoB-48 in plaques. Our investigations show that apoB-48 is present in atherosclerotic plaques with denatured or degraded structure. This is the first report describing presence of apoB-48 in human atherosclerotic plaques.

The metabolic syndrome is a group of disorders including obesity, insulin resistance, atherogenic dyslipidemia, hyperglycemia, and hypertension. To date, few animal models have been described to recapitulate the phenotypes of the syndrome. In this study, we generated and characterized two lines of triple-knockout mice that are deficient in either apolipoprotein E (Apoe−/−) or low-density lipoprotein receptor (Ldlr−/−) and express no leptin (Lepob/ob) or apolipoprotein B-48 but exclusively apolipoprotein B-100 (Apob100/100). These two lines are referred to as Apoe triple-knockout-Apoe 3KO (Apoe−/−Apob100/100Lepob/ob) and Ldlr triple-knockout-Ldlr 3KO (Ldlr−/−Apob100/100Lepob/ob) mice. Both lines develop obesity, hyperinsulinemia, hyperlipidemia, hypertension, and atherosclerosis. However, only Apoe 3KO mice are hyperglycemic and glucose intolerant and are more obese than Ldlr 3KO mice. To evaluate the utility of these lines as pharmacological models, we treated both with leptin and found that leptin therapy ameliorated most metabolic derangements. Leptin was more effective in improving glucose tolerance in Ldlr 3KO than Apoe 3KO animals. The reduction of plasma cholesterol by leptin in Ldlr 3KO mice can be accounted for by its suppressive effect on food intake. However, in Apoe 3KO mice, leptin further reduced plasma cholesterol independently of its effect on food intake, and this improvement correlated with a smaller plaque lesion area. These effects suggest a direct role of leptin in modulating VLDL levels and, likewise, the lesion areas in VLDL-enriched animals. These two lines of mice represent new models with features of the metabolic syndrome and will be useful in testing therapies targeted for combating the human condition.

Apolipoprotein (apo) B48 is a structural protein of chylomicrons. Fasting serum levels of apoB48 suggest the presence of small number of remnant chylomicron particles which are thought to be an atherogenic lipoprotein. In view of the high incidence of coronary heart disease (CHD) in patients with diabetic nephropathy, we decided to measure the plasma apoB48 level in type 2 diabetics with diabetic nephropathy at various stages to ascertain how apoB48 relates to the progression of diabetic nephropathy. Patients with type 2 diabetes (n=105) were stratified into four groups: normo-albuminuria, micro-albuminuria, overt-proteinuria, and patients with end-stage renal disease (ESRD) receiving hemodialysis. Age-matched-diabetic hypertensive patients (n=24) and non-diabetic ESRD patients on hemodialysis (n=47) were also enrolled. Plasma triglyceride (TG) levels rose as diabetic nephropathy progressed to overt-proteinuria. No further elevation in TG was observed in diabetic ESRD, however, and the TG levels were normal in non-diabetic ESRD. A similar pattern was observed for remnant-like particle-cholesterol (RLP-C). In contrast to the changes observed for TG and RLP-C, the levels of apoB48 increased steadily as the diabetic nephropathy progressed (control, 3.7; normo, 5.7; micro, 6.9; overt, 10.6 mg/l, respectively). ApoB48 peaked in the diabetic ESRD (19 mg/l) and was also markedly elevated in non-diabetic ESRD (10.1mg/l). The apoB48/TG and apoB48/total-apoB ratios were substantially elevated in both diabetic and non-diabetic ESRD. These results are the first to demonstrate remarkable elevations of plasma apoB48 in patients with both diabetic and non-diabetic ESRD. The remarkably high level of apoB48 in diabetic ESRD seems to be attributable to dyslipidemia induced by both diabetic nephropathy and ESRD.

Background and aim The −250G/A promoter polymorphism of the hepatic lipase gene has been associated with changes in the activity of the enzyme. We investigated whether this polymorphism modifies the postprandial response of triacylglycerol-rich lipoproteins (TRL) in young normolipemic males. Methods and results Fifty-one healthy apolipoprotein (apo) E3/E3 male volunteers (30 G/G and 21 carriers of the A allele) underwent a vitamin A fat-loading test and blood samples were drawn every hour until the 6th, and every 2 h and 30 min until the 11th. Total plasma cholesterol and triacylglycerols (TG), as well as cholesterol, TG and retinyl palmitate (RP) in TRL, isolated by ultracentrifugation, were determined. Carriers of the A allele showed a higher response (P = 0.008), a higher area under the curve (AUC; P = 0.022) and a lower RP peak time (P = 0.029) in small TRL during the postprandial response, as well as a lower peak time in total plasma TG levels (P = 0.034) and large TRL-TG (P = 0.033) than subjects who were homozygous for the G allele. Conclusion Our data indicate that the presence of the A allele in the −250G/A promoter polymorphism of the hepatic lipase gene is associated with a higher postprandial lipemic response.

The specific impact of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors and fibrates on the in vivo metabolism of apolipoprotein (apo) B has not been systematically investigated in patients with type 2 diabetes mellitus with high plasma triglyceride (TG) levels. Therefore, the objective of this 2-group parallel study was to examine the differential effects of a 6-week treatment with atorvastatin or fenofibrate on in vivo kinetics of apo B-48 and B-100 in men with type 2 diabetes mellitus with marked hypertriglyceridemia. Apolipoprotein B kinetics were assessed at baseline and at the end of the intervention using a primed constant infusion of [5,5,5-D(3)]-l-leucine for 12 hours in the fed state. Fenofibrate significantly decreased plasma TG levels with no significant change in plasma low-density lipoprotein cholesterol (LDL-C) and apo B levels. On the other hand, atorvastatin significantly reduced plasma levels of TG, LDL-C, and apo B. After treatment with fenofibrate, very low-density lipoprotein (VLDL) apo B-100 pool size (PS) was decreased because of an increase in the fractional catabolic rate (FCR) of VLDL apo B-100. No significant change was observed in the kinetics of LDL apo B-100. Moreover, fenofibrate significantly decreased TG-rich lipoprotein (TRL) apo B-48 PS because of a significant increase in TRL apo B-48 FCR. After treatment with atorvastatin, VLDL and IDL apo B-100 PSs were significantly decreased because of significant elevations in the FCR of these subfractions. Low-density lipoprotein apo B-100 PS was significantly lowered because of a tendency toward decreased LDL apo B-100 production rate (PR). Finally, atorvastatin reduced TRL apo B-48 PS because of a significant decrease in the PR of this subfraction. These results indicate that fenofibrate increases TRL apo B-48 as well as VLDL apo B-100 clearance in men with type 2 diabetes mellitus with marked hypertriglyceridemia, whereas atorvastatin increases both VLDL and IDL apo B-100 clearance and decreases TRL apo B-48 and LDL apo B-100 PR.

Aim: We investigated postprandial changes of apolipoprotein (apo) B48 in type 2 diabetics at different stages of diabetic nephropathy in order to explore non-traditional lipid abnormalities in diabetic nephropathy.Methods: Twenty-two healthy controls and 56 type 2 diabetics with normoalbuminuria (NA), microalbuminuria (MA), and overt albuminuria (OA) were enrolled. Blood samples were taken at 0, 1, 2, 4, 6 h after the ingestion of Test meal A (460 Kcal, 18 g fat). The maximal increase of triglyceride (TG) was 40% above baseline in controls and 17% above baseline in diabetics. The incremental area under the curve (iAUC) of TG, however, was comparable among controls and diabetics with NA, MA, and OA. The maximal increase of apoB48 was 92% above baseline in controls and 56-88% above baseline in diabetics. Apo B48-iAUC was significantly higher in diabetics than in controls, and diabetics with OA exhibited the highest apoB48-iAUC among the diabetic subgroups. Small dense low-density lipoprotein-cholesterol (LDL-C) was elevated in diabetic nephropathy, and apoB48-iAUC was positively associated with the level of sd-LDL-C.Conclusions: ApoB48 is a sensitive marker for postprandial lipemia, a condition which is significantly increased in diabetic nephropathy and associated with an increase of potent atherogenic sd- LDL particles.

Chylomicrons produced by the human gut contain apolipoprotein (apo) B48, whereas very-low-density lipoproteins made by the liver contain apo B100. To study how these molecules function during lipid absorption, we examined the process as it occurs in apobec-1 knockout mice (able to produce only apo B100; KO) and in wild-type mice (of which the normally functioning intestine makes apo B48, WT). Using the lymph fistula model, we studied the process of lipid absorption when animals were intraduodenally infused with a lipid emulsion (4 or 6 μmol/h of triolein). KO mice transported triacylglycerol (TG) as efficiently as WT mice when infused with the lower lipid dose; when infused with 6 μmol/h of triolein, however, KO mice transported significantly less TG to lymph than WT mice, leading to the accumulation of mucosal TG. Interestingly, the size of lipoprotein particles from both KO and WT mice were enlarged to chylomicron-size particles during absorption of the higher dose. These increased-size particles produced by KO mice were not associated with increased apo AIV secretion. However, we found that the gut of the KO mice secreted fewer apo B molecules to lymph (compared with WT), during both fasting and lipid infusion, leading us to conclude that the KO gut produced fewer numbers of TG-rich lipoproteins (including chylomicron) than the wild-type animals. The reduced apo B secretion in KO mice was not related to reduced microsomal triglyceride transfer protein lipid transfer activity. We propose that apo B48 is the preferred protein for the gut to coat chylomicrons to ensure efficient chylomicron formation and lipid absorption.

We have previously reported that plasma levels of remnant-like lipoprotein particles (RLP) significantly increased in sudden cardiac death cases with and without coronary atherosclerosis. In this study we have elucidated the major subset of proatherogenic RLP, containing both apoB-48 and apoB-100-carrying remnants, in plasma of SCD and control death cases. One hundred and sixty seven Japanese cases of sudden cardiac death and 78 cases of control death underwent autopsy within 12h after death were studied. Heart weight was 9.2% higher in SCD cases than controls (P

Nine hypercholesterolemic and hypertriglyceridemic subjects were enrolled in a randomized, placebo-controlled, double-blind, crossover study to test the effect of atorvastatin 20 mg/day and 80 mg/day on the kinetics of apolipoprotein B-100 (apoB-100) in triglyceride-rich lipoprotein (TRL), intermediate density lipoprotein (IDL), and LDL, of apoB-48 in TRL, and of apoA-I in HDL. Compared with placebo, atorvastatin 20 mg/day was associated with significant reductions in TRL, IDL, and LDL apoB-100 pool size as a result of significant increases in fractional catabolic rate (FCR) without changes in production rate (PR). Compared with the 20 mg/day dose, atorvastatin 80 mg/day caused a further significant reduction in the LDL apoB-100 pool size as a result of a further increase in FCR. ApoB-48 pool size was reduced significantly by both atorvastatin doses, and this reduction was associated with nonsignificant increases in FCR. The lathosterol-campesterol ratio was decreased by atorvastatin treatment, and changes in this ratio were inversely correlated with changes in TRL apoB-100 and apoB-48 PR. No significant effect on apoA-I kinetics was observed at either dose of atorvastatin. Our data indicate that atorvastatin reduces apoB-100- and apoB-48-containing lipoproteins by increasing their catabolism and has a dose-dependent effect on LDL apoB-100 kinetics. Atorvastatin-mediated changes in cholesterol homeostasis may contribute to apoB PR regulation.

Patients with type 2 diabetes have high levels of triglyceride-rich lipoproteins (TRLs), including apolipoprotein B-48 (apoB-48)-containing TRLs of intestinal origin, but the mechanism leading to overaccumulation of these lipoproteins remains to be fully elucidated. Therefore, the objective of this study was to examine the in vivo kinetics of TRL apoB-48 and VLDL, intermediate density lipoprotein (IDL), and LDL apoB-100 in type 2 diabetic subjects (n = 11) and nondiabetic controls (n = 13) using a primed-constant infusion of l-[5,5,5-D(3)]leucine for 12 h in the fed state. Diabetic subjects had significantly higher fasting glycemia, higher fasting insulinemia, higher plasma triglyceride, and lower HDL-cholesterol levels than controls. Compared with controls, diabetic subjects had increased TRL apoB-48, VLDL apoB-100, and IDL apoB-100 pool sizes as a result of increased production rates (PRs) and reduced fractional catabolic rates of these lipoprotein subfractions. Furthermore, multiple linear regression analyses revealed that the diabetic/control status was an independent predictor of TRL apoB-48 PR and represented nearly 35% of its variance. These results suggest that the overaccumulation of TRLs seen in patients with type 2 diabetes is attributable to increased PRs of both intestinally derived apoB-48-containing lipoproteins and TRL apoB-100 of hepatic origin and to decreased catabolism of these subfractions.

Apolipoprotein A5 (APOA5) plays an important role in plasma triacylglycerol (TG) homeostasis. Five polymorphisms (1131TC, c.-3AG, c.56CG, IVS3+476GA, and c.1259TC) in the APOA5 gene define three common haplotypes (APOA5*1, APOA5*2, and APOA5*3) in Caucasian individuals. Our aim was to determine whether these haplotypes could modulate the postprandial response in young healthy males.Eighty-eight APO E3/3 volunteers [67 with (-1131T and 56C) APOA5*1 haplotype, 12 with (-1131C and 56C) APOA5*2 haplotype, and nine with (-1131T and 56G) APOA5*3 haplotype] underwent a fat load test consisting of the consumption of 1 g of fat per kilogram body weight and 60,000 IU vitamin A. Blood samples were taken at time 0, at every hour until the sixth hour, and at every 2.5 h until the 11th hour. Total plasma cholesterol (C) and TG, and C, TG, apolipoprotein B-100, apolipoprotein B-48, and retinyl palmitate in lipoprotein fractions were determined.Subjects with the APOA5*2 and APOA5*3 haplotypes had a higher area under the curve of total plasma TG (P = 0.03), large TG-rich lipoprotein (TRL)-TG (P = 0.02), small TRL-TG (P = 0.04), small TRL-C (P = 0.04), large TRL-C (P = 0.03), and small apolipoprotein B100 (P = 0.04) than subjects with the APOA5*1 haplotype.Our findings show that the presence of the APOA5*2 and APOA5*3 haplotypes in the APOA5 gene is associated with a higher postprandial response that could be involved in the higher risk of coronary heart disease associated with the 56G and -1131C alleles.

Familial hypobetalipoproteinemia (FHBL) is an autosomal codominantly inherited disorder of lipoprotein metabolism characterized by decreased plasma concentrations of low-density lipoprotein-cholesterol and apolipoprotein (apo) B. We examined the effect of truncated apoB variants (apoB-48) causing FHBL on postprandial triglyceride-rich lipoprotein (TRL) metabolism.A standardized oral fat load was given after a 12-h fast to six heterozygous [apoB-6.9 (n=3), apoB-25.8 (n=1), apoB-40.3 (n=2)] FHBL subjects and 10 normolipidemic controls. Plasma was obtained every 2 h for 10 h. Large TRLs [containing chylomicrons (CM)] and small TRLs (containing CM remnants) were isolated by ultracentrifugation. Compared with controls, FHBL subjects had significantly decreased fasting plasma cholesterol (2.3+/-0.5 vs. 4.8+/-0.5 mmol/liter), triglyceride (0.4+/-0.3 vs. 1.5+/-0.5 mmol/liter), low-density lipoprotein-cholesterol (0.6+/-0.4 vs. 3.0+/-0.5 mmol/liter), and apoB (0.22+/-0.05 vs. 0.95+/-0.14 g/liter) concentrations (all P0.001). The postprandial incremental area under the curve in FHBL subjects was decreased for large TRL-triglyceride (-61%; P0.005), small TRL-cholesterol (-86%; P0.001), and small TRL-triglyceride (-86%; P0.001) relative to controls. Multicompartmental modeling analysis showed that the delay time of apoB-48 was shorter and that apoB-48 production was decreased in FHBL subjects compared with controls.We have demonstrated that heterozygous FHBL subjects with apoB truncations shorter than apoB-48, and therefore only a single fully-functional apoB-48 allele, have decreased TRL production but normal postprandial TRL particle clearance.

Aim: Postprandial lipaemia is a significant contributor to the development of dyslipidaemia and cardiovascular disease, which has more recently been shown as a potential risk factor for obesity and pre-diabetes. Clinically however, the diagnosis of early insulin-resistance remains confounded due to the fact that aberrations in lipid metabolism are not often readily identified using classic indicators of hypercholesterolemia (i.e. LDL). Methods: In this study, we assessed the metabolism of apolipoprotein-B48 (apoB48)-containing lipoproteins in an animal model of obesity and insulin-resistance, the JCR:LA-cp rat. The contribution of lipoproteins from the intestine was assessed by measuring plasma apoB48 concentration in the postprandial period following an oral fat load. Plasma apoB48 was measured by improved enhanced chemiluminescent detection and other biochemical parameters measured by established analysis. Results: Fasting concentrations of plasma apoB48, postprandial apoB48 area under the curve (AUC), as well as incremental-AUC (iAUC), were all significantly greater in the obese phenotype compared to lean controls. Fasting apoB48 correlated significantly with apoB48-iAUC, triglyceride (TG)-iAUC and insulin-iAUC. In addition, there was a highly significant association with fasting insulin and the postprandial ratio of TG:apoB48, a relationship not often detected in humans during insulin-resistance. Conclusions/interpretation: We conclude that the JCR:LA-cp rat can be used as a model of postprandial lipemia to explore chylomicron metabolism during the onset and development of insulin-resistance, including the increased cardiovascular complications of the metabolic syndrome.

There is growing evidence suggesting intestinal insulin resistance and overproduction of apolipoprotein (apo) B48-containing chylomicrons in insulin-resistant states. In the current study, we investigated the potential role of the inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) in the development of insulin resistance and aberrant lipoprotein metabolism in the small intestine in a Syrian golden hamster model. TNF-alpha infusion decreased whole-body insulin sensitivity, based on in vivo euglycemic clamp studies in chow-fed hamsters. Analysis of intestinal tissue in TNF-alpha-treated hamsters indicated impaired phosphorylation of insulin receptor-beta, insulin receptor substrate-1, Akt, and Shc and increased phosphorylation of p38, extracellular signal-related kinase-1/2, and Jun NH(2)-terminal kinase. TNF-alpha infusion also increased intestinal production of total apoB48, triglyceride-rich lipoprotein apoB48, and serum triglyceride levels in both fasting and postprandial (fat load) states. The effects of TNF-alpha on plasma apoB48 levels could be blocked by the p38 inhibitor SB203580. Ex vivo experiments using freshly isolated enterocytes also showed TNF-alpha-induced p38 phosphorylation and intestinal apoB48 overproduction, effects that could be blocked by SB203580. Interestingly, TNF-alpha increased the mRNA and protein mass of intestinal microsomal triglyceride transfer protein without altering apoB mRNA levels. Enterocytes were found to have detectable levels of both TNF-alpha receptor types (p55 and p75), and antibodies against either of the two TNF-alpha receptors partially blocked the stimulatory effect of TNF-alpha on apoB48 production and p38 phosphorylation. In summary, these data suggest that intestinal insulin resistance can be induced in hamsters by TNF-alpha infusion, and it is accompanied by intestinal overproduction of apoB48-containing lipoproteins. TNF-alpha-induced stimulation of intestinal lipoprotein production appears to be mediated via TNF-alpha receptors and the p38 mitogen-activated protein kinase pathway.

Reduced white adipose tissue (WAT) LPL activity delays plasma clearance of TG-rich lipoproteins (TRLs). We reported the secretion of apoC-I, an LPL inhibitor, from WAT ex vivo in women. Therefore we hypothesized that WAT-secreted apoC-I associates with reduced WAT LPL activity and TRL clearance. WAT apoC-I secretion averaged 86.9 ± 31.4 pmol/g/4 h and 74.1 ± 36.6 pmol/g/4 h in 28 women and 11 men with BMI ≥27 kg/m(2), respectively, with no sex differences. Following the ingestion of a (13)C-triolein-labeled high-fat meal, subjects with high WAT apoC-I secretion (above median) had delayed postprandial plasma clearance of dietary TRLs, assessed from plasma (13)C-triolein-labeled TGs and apoB48. They also had reduced hydrolysis and storage of synthetic (3)H-triolein-labeled ((3)H)-TRLs in WAT ex vivo (i.e., in situ LPL activity). Adjusting for WAT in situ LPL activity eliminated group differences in chylomicron clearance; while adjusting for plasma apoC-I, (3)H-NEFA uptake by WAT, or body composition did not. apoC-I inhibited in situ LPL activity in adipocytes in both a concentration- and time-dependent manner. There was no change in postprandial WAT apoC-I secretion. WAT apoC-I secretion may inhibit WAT LPL activity and promote delayed chylomicron clearance in overweight and obese subjects. We propose that reducing WAT apoC-I secretion ameliorates postprandial TRL clearance in humans.

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.

Cyclocarya paliurus (CP; qing qian liu), which is used as an herbal tea in China, has been confirmed to have therapeutic effects on hyperlipidemia and obesity, and therefore it is widely consumed to prevent metabolic diseases such as hyperlipidemia and diabetes. In this study, we investigated the preventive effects of CP on obesity and hyperlipidemia, as well as the underlying mechanisms involved in intestinal secretion of apolipoprotein (apo) B48. Sprague–Dawley rats were fed a high-fat diet (HFD) and with or without various concentrations of an ethanol extract of CP (CPE; 2, 4, or 8 g·(kg body mass)–1) administered by gavage for 8 weeks. From the results we see that CPE dose-dependently blocked increases in body mass, and decreased food utilization as well as visceral fat mass. Decreased serum levels of total cholesterol, triglycerides, and low density lipoprotein cholesterol, and elevated levels of high density lipoprotein cholesterol, as well as lowered levels of total cholesterol and triglycerides in the liver were also noticed in CPE-treated rats. Magnetic resonance images indicated that the abnormal fat storage induced by the HFD was obviously suppressed by CPE. In addition, ELISA analysis showed reduced fasting serum apoB48 in the CPE treatment groups. Based on the above results, CPE shows a promising preventive effect on obesity and hyperlipidemia, partially through suppressing intestinal apoB48 overproduction.

Background and aims The postprandial situation is a pro-inflammatory condition most likely linked to the development of atherosclerosis. We evaluated the relationship between apolipoprotein (apo) B48 and fasting and postprandial leukocyte activation markers. Methods Leukocyte activation markers and apo B48 were determined in 80 subjects with and without coronary artery disease (CAD). Twelve healthy subjects underwent an oral fat loading test (up to 8 h). Results Fasting apo B48 was significantly higher in patients with CAD (n = 47, 8.1 ± 5.2 mg/L) than in subjects without CAD (n = 33, 5.9 ± 3.9 mg/L, p = 0.022). Fasting apo B48 and triglycerides correlated positively with fasting monocyte CD11b and neutrophil CD66b expression. Plasma apo B48 and leukocyte activation markers increased after an oral fat load. No correlations were found between fasting or postprandial triglycerides and postprandial leukocyte activation markers. We observed no correlations between postprandial apo B48 and postprandial neutrophil CD11b or CD66b expression. Conclusion This study suggests that chylomicron remnants may be responsible for postprandial leukocyte activation in the circulation. The postprandial chylomicron response may be a stronger mediator of postprandial inflammation than postprandial triglyceridemia.

Individuals with metabolic syndrome and frank type 2 diabetes are at increased risk of atherosclerotic cardiovascular disease, partially due to the presence of lipid and lipoprotein abnormalities. In these conditions, the liver and intestine overproduce lipoprotein particles, exacerbating the hyperlipidemia of fasting and postprandial states. Incretin-based, antidiabetes therapies (i.e., glucagon-like peptide [GLP]-1 receptor agonists and dipeptidyl peptidase-4 inhibitors) have proven efficacy for the treatment of hyperglycemia. Evidence is accumulating that these agents also improve fasting and postprandial lipemia, the latter more significantly than the former. In contrast, the gut-derived peptide GLP-2, cosecreted from intestinal L cells with GLP-1, has recently been demonstrated to enhance intestinal lipoprotein release. Understanding the roles of these emerging regulators of intestinal lipoprotein secretion may offer new insights into the regulation of intestinal lipoprotein assembly and secretion and provide new opportunities for devising novel strategies to attenuate hyperlipidemia, with the potential for cardiovascular disease reduction.

Objective To evaluate plasma apolipoprotein B (ApoB)-48 concentrations among Korean diabetic subjects with normal to moderately high levels of low-density-lipoprotein cholesterol (LDL-C). Methods This multicenter, cross-sectional study included subjects with LDL-C levels between 100 and 160mg/dL who had not been treated with a lipid-lowering agent for over 6weeks prior to baseline. Blood tests to assess lipid-profile parameters were conducted in both fasting and postprandial states. This study compared ApoB-48 and other lipid-profile parameters in diabetic and nondiabetic subjects. Results Of the 93 subjects enrolled, 88 (42 diabetic; 46 nondiabetic) completed the study. Significantly higher mean incremental area under curve (0–6h; iAUC 0–6h ) of postprandial ApoB-48 levels was noted among diabetic subjects than nondiabetic subjects ( p =0.0078). The mean postprandial ApoB-48 peak level was higher in diabetic subjects; however, the difference was not statistically significant. The fasting ApoB-48 level was similar in both groups: 5.9 (3.5) in diabetics and 7.3 (5.8) in nondiabetics ( p =0.18). The iAUC 0–6h of postprandial total cholesterol (TC), triglyceride (TG), LDL-C, non–high-density-lipoprotein cholesterol (non-HDL-C), ApoB-100, and remnant cholesterol was similar in both groups. The ApoB-48 level was moderately correlated with TG and non-HDL-C for both groups ( p Conclusion Without lipid-lowering treatment, the postprandial increment in ApoB-48 level was significantly higher in Korean diabetic subjects compared with nondiabetic subjects, irrespective of similar LDL-C levels.

Factors influencing the concentration of apolipoprotein B48 (apo B48) at fasting and post-prandial time frames are still being elucidated. This study assesses some possible contributing factors including the presence of type 2 diabetes and gender using an established enzyme-linked immunosorbent assay (ELISA) method. Apo B48 and triglyceride (TG) levels were measured before and for two, four and six hours post-prandially in 49 poorly controlled participants with type 2 diabetes and in 60 apparently healthy participants (controls). Apo B48 levels in the control participants increased post-prandially, peaking at four hours (14.81 ± 7.72 μg/mL) with similar responses demonstrated in TG concentrations. Post-prandial apo B48 levels were significantly higher in male control participants as demonstrated by apo B48 area under the curve (AUC); similar responses were also confirmed in triglyceride AUC. Post-prandial apo B48 concentrations in control participants correlated with HOMA-IR (P0.05). Apo B48 continued to increase throughout the six hours in participants with type 2 diabetes (17.73 ± 13.46 μg/mL), when levels were significantly greater than in the control participants (13.04 ± 7.67 μg/mL) (P0.05) despite a decrease in accompanying TG levels in participants with type 2 diabetes. Using an ELISA method, this study demonstrated that gender, insulin resistance (as evidenced by HOMA-IR) and diabetes status influence serum apo B48 levels. These effects were only apparent post-prandially.

Background: Postprandial lipemia is a risk factor for cardiovascular disease. The potential impacts of the type/nature of dietary protein on postprandial lipemia and associated dysregulations have been insufficiently investigated. Objective: We investigated the postprandial effect of including in a high-fat meal some milk protein fractions that markedly differ in their physicochemical properties and composition [either casein (CAS), whey protein (WHE), or a-lactalbumin-enriched whey protein (LAC)]. Methods: The protein fractions were incorporated as 15% energy in a high-fatmeal in a W3-period, crossover postprandial study of 10 healthy overweight men with an elevated waist circumference (>94 cm). We measured postprandial changes in plasma lipids, amino acids, glucose, and oxidative stress markers, vascular function (using pulse contour analysis), and low-grade inflammation (using plasma markers). We also characterized in vitro the meal structures, including the size of the fat globule, and possible changes during digestion. Results: The type of protein did not affect postprandial plasma glucose, amino acids, insulin, or nonesterified fatty acids, but, compared with WHE and LAC, which did not differ, CAS markedly reduced postprandial triglycerides (TGs), achieving a 22 +/- 10% reduction in the 6-h area under the curve (P < 0.05). Similar trends were shown for plasma chylomicrons [apolipoprotein (apo) B-48; P < 0.05]. However, there were no significant differences between the meals regarding postprandial oxidative stress (plasma hydroperoxides and malondialdehyde), endothelial dysfunction (salbutamol-induced changes in pulse contour analysis), or low-grade inflammation. In vitro studies showed that when the pH of the meal decreased to stomach pH values, the reduction in the solubility of casein resulted in a phase separation between fat and protein, whereas the proteins in the other meals remained suspended with fat globules. Conclusion: In healthy overweight men, casein has specific physical interactions with fat that affect postprandial TGs, leading to the formation of fewer chylomicrons or an increase in chylomicron clearance. This trial was registered at clinicaltrials. gov as NCT00931151.

Familial hypobetalipoproteinemia is a codominant disorder characterized by low plasma levels of low-density lipoprotein cholesterol and apolipoprotein B (apoB), which in similar to 50% of the cases is due to mutations in APOB gene. In most cases, these mutations cause the formation of truncated apoBs of various sizes, which have a reduced capacity to bind lipids and form lipoprotein particles. Here, we describe 2 children with severe hypobetalipoproteinemia found to be homozygous for novel APOB gene mutations. The first case (HBL-201) was an asymptomatic 13-year-old boy incidentally found to have slightly elevated serum transaminases associated with hepatic steatosis. He was homozygous for a truncated apoB (2211 amino acids, apoB-48.74) whose size is similar to that of wild-type apoB-48 (2152 amino acids) produced by the intestine. ApoB-48.74 is expected to be incorporated into chylomicrons in the intestine but might have a reduced capacity to form secretion-competent very low-density lipoprotein in the liver. The second patient (HBL-96) was a 6-month-old girl suspected to have abetalipoproteinemia, for the presence of chronic diarrhea, failure to thrive, extremely severe hypobetalipoproteinemia, and low plasma levels of vitamin E and vitamin A. She was homozygous for a nonsense mutation (Gln513*) resulting in a short truncated apoB (apoB-11.30), which is not secreted into the plasma. In this patient, the impaired chylomicron formation is responsible for the severe clinical manifestations and growth retardation. In homozygous familial hypobetalipoproteinemia, the capacity of truncated apoBs to form chylomicrons is the major factor, which affects the severity of the clinical manifestations. (C) 2015 National Lipid Association. All rights reserved.

Dysbetalipoproteinemia (dysb) and familial hypercholesterolemia (FH) are two genetic disorders giving rise to severe disturbances of lipid homeostasis and premature atherosclerosis. The co-occurrence of both metabolic abnormalities is very rare and is estimated to affect 1 individual per 2,500,000 in the general population. However, the relative contribution of these two dyslipidemias to the combined lipoprotein phenotype is unknown. The two objectives of this study were (1) to compare the in vivo kinetics of triglyceride-rich lipoprotein (TRL) apolipoprotein (apo) B48, VLDL, IDL and LDL apo B100 as well as plasma apo A-l labelled with a stable isotope (l-(5,5,5-D3) leucine) in two subjects presenting both heterozygous FH and dysbetalipoproteinemia (FH+/dysb+), in six FH heterozygotes and in five normolipidemic controls, and (2) to examine the impact of a 6-week treatment with micronized fenofibrate 200 mg/d on apolipoprotein kinetics in FH+/dysb+. As compared with FH heterozygotes and controls, the two FH+/dysb+ subjects showed elevated TRL apo B48 and VLDL, IDL apo B100 pool sizes (PS) mainly due to lower fractional catabolic rates (FCR). Moreover, as compared with FH heterozygotes, FH+/dysb+ subjects presented lower LDL apo B100 PS due to a higher FCR. Pool size, FCR and production rate (PR) of apo A-l were higher in FH+/dysb+ subjects than in FH heterozygotes. In FH+/dysb+ subjects, fenofibrate treatment was associated with a decreased TRL apo B48 PS (-52 and -61%), VLDL apo B100 (-61 and -63%) and IDL apo B100 (-37 and -16%) and an increased FCR of TRL apo B48 (10 and 67%), VLDL apo B100 (123 and 57%) and IDL apo B100 (29 and 10%). Fenofibrate also increased LDL apo B100 PS (3 and 57%) due to an increase in PR (80 and 26%) but had divergent effects on LDL apo B100 FCR. These results indicate that the coexistence of dysbetalipoproteinemia and heterozygous FH results in a mixed lipoprotein phenotype that is intermediate between the two pure phenotypes and that fenofibrate treatment partially reverses lipoprotein abnormalities, mostly through changes in PR and FCR of apo B48- and B100-containing lipoproteins.

We aimed to identify mechanisms by which apolipoprotein B-48 (apoB-48) could have an atherogenic role by simultaneously studying the metabolism of postprandial apoB-48 and apoB-100 lipoproteins. The kinetics of apoB-48 and apoB-100, each in four density subfractions of VLDL and intermediate density lipoprotein (IDL), were studied by stable isotope labeling in a constantly fed state with half-hourly administration of almond oil in five postmenopausal women. A non-steady-state, multicompartmental model was used. Despite a much lower production rate, VLDL and IDL apoB-48 shared a similar secretion pattern with apoB-100: both were directly secreted into all fractions with similar percentage mass distributions. Fractional catabolic rates (FCRs) of apoB-48 and apoB-100 were similar in VLDL and IDL. We identified a fast turnover compartment of light VLDL that had a residence time of

Background Obese, insulin-resistant individuals have raised levels of intestinal and hepatic lipoproteins. Insulin decreases the production of hepatic lipoproteins in vivo and so this study aimed to investigate whether an acute hyperinsulinaemic, euglycaemic clamp could correct fasting and post-prandial dyslipidaemia. Subjects and methods In a randomized, cross-over design, post-prandial lipaemia was compared in subjects infused either with insulin to achieve a steady-state concentration of 100 mU L−1 or with saline. Nine obese (Body Mass Index > 26 kg m−2; waist : hip > 1·0) insulin-resistant (Homeostatic Model Assessment score > 2·0) male subjects were given an oral fat load 3 h after the infusions began, and sampling continued for 6 h. Plasma apoB-48, triglyceride and nonesterified fatty acid (NEFA) were measured hourly. Results Average steady-state serum insulin levels during the hyperinsulinaemic clamp were 123 ± 4·4 mU L−1. A paired analysis showed no net effect of insulin on post-prandial chylomicron metabolism when calculated as the (apoB-48) incremental area under the curve (IAUC). However, there was a trend towards a delay in the apoB-48 peak, consistent with possible changes in the rates of chylomicron biogenesis, lipolysis and/or clearance. Similarly, post-prandial lipaemia (depicted as triglyceride IAUC) was similar for subjects infused with insulin or saline, but the peak post-prandial response was delayed during insulin infusion. The NEFA were rapidly decreased by 83% after 3 h of insulin infusion. Conclusions In obesity and insulin resistance, short-term changes in plasma insulin do not appreciably exert a regulatory effect on exogenously-derived post-prandial lipoproteins. The data suggest that hyperchylomicronaemia in insulin-resistant subjects is a result of chronic aberrations in insulin-mediated regulation of post-prandial lipid metabolism.

Objective— We investigated the role of adipocyte differentiation-related protein (ADRP) in triglyceride turnover and in the secretion of very low–density lipoprotein (VLDL) from McA-RH7777 cells and primary rat hepatocytes. Methods and Results— An increase in the expression of ADRP increased triglyceride accumulation in cytosolic lipid droplets and prevented the incorporation of fatty acids into secretable triglycerides, thereby reducing the secretion of triglycerides as well as of apolipoprotein B-100 (apoB-100) and apoB-48 VLDL. The ability of ADRP to block the secretion of apoB-100 VLDL1 decreased with increasing quantities of fatty acids in the medium, indicating a saturable process and emphasizing the importance of sequestering of fatty acids for the effect of ADRP on VLDL secretion. Knockdown (small interfering RNA) of ADRP decreased the pool of cytosolic lipid droplets but increased only the secretion of apoB-48 VLDL1. Additionally, there was an increased flow of fatty acids into β-oxidation. Conclusions— ADRP is essential for the accumulation of triglycerides in cytosolic lipid droplets. An increase in ADRP prevents the formation of VLDL by diverting fatty acids from the VLDL assembly pathway into cytosolic triglycerides, whereas a decrease of the protein increases the sorting of fatty acids to β-oxidation and promotes the secretion of apoB-48 VLDL1.

Emerging evidence underscores the important role of the small intestine in the pathogenesis of dyslipidaemia in insulin resistance and type 2 diabetes. We therefore tested the hypothesis that n-3 fatty acids improve the various events governing intra-enterocyte lipid transport in Psammomys obesus gerbils, a model of nutritionally induced metabolic syndrome.Experiments were carried out on Psammomys obesus gerbils that were assigned to an isocaloric control diet and a diet rich in fish oil for 6 weeks.Increased dietary intake of fish oil lowered body weight and improved hyperglycaemia and hyperinsulinaemia. It simultaneously decreased de novo intestinal lipogenesis and lipid esterification of the major lipid classes, e.g. triglycerides, phospholipids and cholesteryl esters, particularly in insulin-resistant and diabetic animals. Accordingly, lessened activity of monoacylglycerol and diacylglycerol acyltransferase was recorded. As assessed in cultured jejunal explants incubated with either [(14)C]-oleic acid or [(35)S]-methionine, fish oil feeding resulted in diminished triglyceride-rich lipoprotein assembly and apolipoprotein (apo) B-48 biogenesis, respectively. The mechanisms did not involve apo B-48 transcription or alter the gene expression and activity of the critical microsomal triglyceride transfer protein. Rather, the suppressed production of apo B-48 by n-3 fatty acids was associated with intracellular proteasome-mediated posttranslational downregulation in insulin-resistant and diabetic animals.Our data highlight the beneficial impact of n-3 fatty acids on adverse effects of the metabolic syndrome and emphasise their influence on intestinal lipid transport, an effect which may limit postprandial lipaemia and the risk of atherosclerosis.

Objectives— Whereas postprandial hyperlipidemia is a well-described feature of insulin-resistant states and type 2 diabetes, no previous studies have examined intestinal lipoprotein production rates (PRs) in relation to hyperinsulinemia or insulin resistance in humans. Methods and Results— Apolipoprotein B-48 (apoB-48)–containing lipoprotein metabolism was examined in the steady-state fed condition with a 15-hour primed constant infusion of [D3]- l -leucine in 14 nondiabetic men with a broad range of body mass index (BMI) and insulin sensitivity. To examine the relationship between indices of insulin resistance and intestinal lipoprotein PR data were analyzed in 2 ways: by correlation and by comparing apoB-48 PRs in those whose fasting plasma insulin concentrations were above or below the median for the 14 subjects studied (60 pmol/L). ApoB-48 PR was significantly higher in hyperinsulinemic, insulin-resistant subjects (1.73±0.39 versus 0.88±0.13 mg/kg per day; P r =0.558; P =0.038), despite great heterogeneity in apoB-48 kinetic parameters, particularly among the obese subjects. There was no significant difference in clearance of apoB-48 between the 2 groups, nor was there a significant correlation between apoB-48 fractional clearance rate and fasting insulin or homeostasis model assessment-insulin resistance. Conclusions— These are the first human data to conclusively demonstrate that intestinal apoB-48–containing triglyceride-rich lipoprotein PR is increased in hyperinsulinemic, insulin-resistant humans. Intestinal lipoprotein particle overproduction is a newly described feature of insulin resistance in humans.

Background Moderate red wine has been shown to reduce cardiovascular disease (CVD) risk, however the effects on certain CVD risk factors are unclear. In this study we have investigated the effects of dealcoholised red wine (DRW) and full-complement red wine (RW) on several cardiovascular risk factors in mildly hypercholesterolaemic postmenopausal women. Objectives To elucidate whether the chronic consumption of red wine polyphenols improves risk factors associated with CVD in hypercholesterolaemic postmenopausal women. Design Forty-five hypercholesterolaemic postmenopausal women were randomly assigned to consume 400 mL/day of either water, DRW or RW for 6 weeks following a 4-week washout. Fasting measures of lipids, lipoproteins, insulin and glucose were taken at 0 and 6 weeks. Results DRW consumption had no effect of fasting concentrations of lipids, lipoproteins, insulin and glucose. However, chronic consumption of RW significantly reduced fasting LDL cholesterol concentrations by 8% and increased HDL cholesterol concentrations by 17% in hypercholesterolaemic postmenopausal women. Conclusions Collectively, regular consumption of full-complement red wine reduces CVD risk by improving fasting lipid levels in hypercholesterolaemic postmenopausal women. This study uniquely demonstrated the LDL cholesterol-lowering effects of red wine in individuals at high CVD risk, which has not previously been shown.

Objectives— Experiments in cells and animal models show that lipoprotein lipase (LpL) bound to apolipoprotein (apo)B lipoproteins enhances their uptake by receptor mediated pathways. It is unknown whether this pathway is important in humans. Methods and Results— ApoB lipoproteins with LpL were isolated from normal subjects after oral fat loading by immunoaffinity chromatography and were further separated into apoB100 and apoB48 lipoproteins. Postprandially, apoB lipoproteins with LpL had significantly greater increases (4- to 10-fold) and faster rates of clearance (5- to 8-fold) percentage-wise than those without LpL. apoB lipoproteins with LpL had enhanced clearance regardless of whether they also contained apoE. LpL was particularly important for the clearance of apoB48 lipoproteins, of which 25% (range, 11% to 31%) could be removed from circulation together with LpL during the postprandial state. apoB lipoproteins with LpL were larger in size and were enriched in triglyceride, cholesterol, and apoE compared with those without LpL. However, neither size nor apoE content explained the faster clearance rates of LpL-containing lipoproteins. Conclusion— Plasma LpL may act like an apolipoprotein to enhance the clearance of apoB lipoproteins in humans, a mechanism particularly important for intestinal lipoproteins in the postprandial state.

Serum levels of intestinal alkaline phosphatase (IAP), a protein implicated in transcellular transport of chylomicrons, vary among ABO blood groups. In rat enterocytes, IAP is associated with chylomicron secretion, but the rat expresses only blood group A. It is not known whether chylomicron secretion may be affected in humans who express multiple blood group types. Serum samples from 40 healthy subjects were obtained after overnight fast and 3h after a high-fat meal, and assayed for IAP and apolipoprotein B-48 (apoB-48), both proteins exclusive to intestine, although only apoB-48 is found in chylomicrons. The two proteins were greater in subjects without blood antigen A (B and O) than in those with this antigen (A and AB); 2.4- and 4.7-fold for IAP and 1.5- and 2.0-fold for apoB-48 before and after the meal, respectively. Moreover, IAP and apoB-48 levels were strongly correlated in the subjects with the secretor phenotype (r > 0.81). These results indicate that IAP is strongly involved in chylomicron formation and fatty acid metabolism might change among ABO blood type. In addition, ABO blood type classification in apoB-48 measurement would improve the diagnostic value in the evaluation of metabolic syndrome.

The ability of human postprandial triacylglycerol-rich lipoproteins (TRLs), isolated after meals enriched in saturated fatty acids (SFAs), n-6 PUFAs, and MUFAs, to inhibit the uptake of 125I-labeled LDL by the LDL receptor was investigated in HepG2 cells. Addition of TRLs resulted in a dose-dependent inhibition of heparin-releasable binding, cell-associated radioactivity, and degradation products of 125I-labeled LDL (P < 0.001). SFA-rich Svedberg flotation rate (Sf) 60-400 resulted in significantly greater inhibition of cell-associated radioactivity than PUFA-rich particles (P = 0.016) and total uptake of 125I-labeled LDL compared with PUFA- and MUFA-rich particles (P < 0.02). Normalization of the apolipoprotein (apo)E but not apoC-III content of the TRLs removed the effect of meal fatty acid composition, and addition of an anti-apoE antibody reversed the inhibitory effect of TRLs on the total uptake of 125I-labeled LDL. Real time RT-PCR showed that the SFA-rich Sf 60-400 increased the expression of genes involved in hepatic lipid synthesis (P < 0.05) and decreased the expression of the LDL receptor-related protein 1 compared with MUFAs (P = 0.008). In conclusion, these findings suggest an alternative or additional mechanism whereby acute fat ingestion can influence LDL clearance via competitive apoE-dependent effects of TRL on the LDL receptor.

Serum lipoproteins (LP) are increasingly being recognized as dual purpose molecules that contribute to both cholesterol homeostasis and host innate defense. In fact, very low LP levels are associated with increased risk of bacterial infection in critically ill patients. In this respect, we reported that apolipoprotein B100 (apoB100), the 4536 amino acid structural protein of very low density lipoprotein (VLDL) produced by the liver, limits Staphylococcus aureus pathogenesis. S. aureus uses quorum-sensing (QS) via the accessory gene regulator (agr) operon and an autoinducing peptide (AIP) to coordinate expression of over 200 virulence genes. ApoB100 prevents agr activation by binding and sequestering secreted AIP. Importantly, human serum LP are produced not only by the liver, but are also produced by enterocytes, in the form of chylomicrons, during uptake of dietary lipids. In contrast to apoB100 in VLDL, human enterocytes use apoB48, the N-terminal 2152 amino acids (48%) of apoB100, as the structural component of chylomicrons. Interestingly, enteral feeding of critically ill patients has been associated with decreased risk of infectious complications, suggesting chylomicrons could contribute to host innate defense in critically ill patients when serum LP production by the liver is limited during the acute phase response. Therefore, we hypothesized that apoB48 would be sufficient to antagonize S. aureus QS. As expected, isolated apoB48-LP bound immobilized AIP and antagonized agr-signaling. ApoB48- and apoB100-LP inhibited agr activation with IC50s of 3.5 and 2.3 nM, respectively, demonstrating a conserved AIP binding site. Importantly, apoB48-LP antagonized QS, limited morbidity and promoted bacterial clearance in a mouse model of S. aureus infection. This work demonstrates that both naturally occurring forms of apolipoprotein B can antagonize S. aureus QS, and may suggest a previously unrecognized role for chylomicrons and enterocytes in host innate defense against S. aureus QS-mediated pathogenesis.