Intestinal apoB Research Articles

APOBEC1 mediated C-to-U RNA editing: target sequence and trans-acting factor contribution to 177 RNA editing events in 119 murine transcripts in-vivo.

Mammalian C-to-U RNA editing was described more than 30 yr ago as a single nucleotide modification in small intestinal Apob RNA, later shown to be mediated by the RNA-specific cytidine deaminase APOBEC1. Reports of other examples of C-to-U RNA editing, coupled with the advent of genome-wide transcriptome sequencing, identified an expanded range of APOBEC1 targets. Here we analyze the cis-acting regulatory components of verified murine C-to-U RNA editing targets, including nearest neighbor as well as flanking sequence requirements and folding predictions. RNA secondary structure of the editing cassette was associated with editing frequency and exhibited minimal free energy values comparable to small nuclear RNAs. We summarize findings demonstrating the relative importance of trans-acting factors (A1CF, RBM47) acting in concert with APOBEC1. Cofactor dominance was associated with editing frequency, with RNAs targeted by both RBM47 and A1CF edited at a lower frequency than RBM47-dominant targets. Using this information, we developed a multivariable linear regression model to predict APOBEC1 dependent C-to-U RNA editing efficiency, incorporating factors independently associated with editing frequencies based on 103 Sanger-confirmed editing sites, which accounted for 84% of the observed variance. This model also predicted a composite score for available human C-to-U RNA targets, which again correlated with editing frequency.

Effects of statins and exercise on postprandial lipoproteins in metabolic syndrome vs metabolically healthy individuals.

To determine if the combination of exercise and statin could normalize postprandial triglyceridaemia (PPTG) in hypercholesteraemic individuals. Eight hypercholesteraemic (blood cholesterol 182 ± 38 mg dL-1 ; low-density lipoprotein-cholesterol [LDL-c] 102 ± 32 mg dL-1 ) overweight (body mass index 30 ± 4 kg m-2 ) individuals with metabolic syndrome (MetS) were compared to a group of 8 metabolically healthy (MetH) controls (blood cholesterol 149 ± 23 mg dL-1 ; LDL-c 77 ± 23 mg dL-1 , and body mass index 23 ± 2 kg m-2 ). Each group underwent 2 PPTG tests, either 14 hours after a bout of intense exercise or without previous exercise. Additionally, MetS individuals were tested 96 hours after withdrawal of their habitual statin medication to study medication effects. A bout of exercise before the test meal did not reduce PPTG in MetS (P = .347), but reduced PPTG by 46% in MetH (413 ± 267 to 224 ± 142 mg dL-1 for 5 h incremental area under the curve; P = .02). In both trials (i.e., either after a bout of intense exercise or without previous exercise), statin withdrawal in MetS greatly increased PPTG (average 65%; P < .01), mean LDL-c (average 25%; P < .01), total cholesterol (average 16%; P < .01) and apolipoprotein (Apo) B48 (24%; P < .01), without interference from exercise. However, Apo B100 was not affected by statin withdrawal. Hypercholesteraemic MetS individuals (compared to MetH controls) fail to show an effect of exercise on reducing PPTG. However, chronic statin medication blunts the elevations in triglyceride after a fat meal (i.e., incremental area under the curve of PPTG) reducing their cardiovascular risk associated with their atherogenic dyslipidaemia. Statin decreases PPTG by reducing the secretion or accelerating the catabolism of intestinal Apo B48.

Atherogenic postprandial remnant lipoproteins—a causal lipoproteins for the initiation of obesity and atherosclerosis

: Oxidized low density lipoprotein (Ox-LDL) and chylomicron (CM) remnants were proposed previously as the most atherogenic lipoproteins which initiate and progress the coronary atherosclerosis as the causal lipoproteins. However, there are still controversies on these hypothesizes. Therefore, we propose a new hypothesis on postprandial remnant lipoproteins (RLP) which contain hepatic origin apoB100 and intestinal origin apoB48 in VLDL fraction. Plasma RLP-cholesterol (RLP-C) and RLP-triglyceride (RLP-TG) increased significantly after fat load associated with the increase of TG. Approximately above 80% of the increased TG after fat load is composed of TG in RLP. Postprandial RLP contained significantly greater apoB100 lipoprotein particles than apoB48 particles. Also most LPL in non-heparin plasma was found in RLP as RLP-LPL complex and found in circulation and incorporated in peripheral issues primarily for energy delivery as a ligand for VLDL receptor. Plasma LPL concentration and activity don’t increase in plasma after fat intake, therefore it may cause the insufficient hydrolysis of RLP. As the results, we observed the significant increase of RLP-TG concentration with large particle size as mostly VLDL remnants in postprandial plasma. Therefore, LPL concentration was inversely correlated with RLP-C and RLP-TG concentration in postprandial plasma. Increased postprandial TG associated with increased RLP having striking similarity with Ox-LDL has been shown as the risk of cardiovascular disease by large epidemiological studies. We have shown that VLDL remnants, not CM remnants, are the major atherogenic lipoproteins increased in postprandial plasma associated with insufficient LPL activity as the possible causal factor for the initiation of atherosclerosis. Therefore, overproduced RLP in postprandial plasma should be the initial target to be controlled as the initiator of atherosclerosis by choosing the kind of food intake and appropriate exercise, without using therapeutic drugs.

Postprandial lipid absorption in seven heterozygous carriers of deleterious variants of MTTP in two abetalipoproteinemic families

Abetalipoproteinemia, a recessive disease resulting from deleterious variants in MTTP (microsomal triglyceride transfer protein), is characterized by undetectable concentrations of apolipoprotein B, extremely low levels of low-density lipoprotein cholesterol in the plasma, and a total inability to export apolipoprotein B-containing lipoproteins from both the intestine and the liver. To study lipid absorption after a fat load and liver function in 7 heterozygous relatives from 2 abetalipoproteinemic families, 1 previously unreported. Both patients are compound heterozygotes for p.(Arg540His) and either c.708_709del p.(His236Glnfs*11) or c.1344+3_1344+6del on the MTTP gene. The previously undescribed patient has been followed for 22years with ultrastructure analyses of both the intestine and the liver. In these 2 families, 5 relatives were heterozygous for p.(Arg540His), 1 for p.(His236Glnfs*11) and 1 for c.1344+3_1344+6del. In 4 heterozygous relatives, the lipid absorption was normal independent of the MTTP variant. In contrast, in 3 of them, the increase in triglyceride levels after fat load was abnormal. These subjects were additionally heterozygous carriers of Asp2213 APOB in-frame deletion, near the cytidine mRNA editing site, which is essential for intestinal apoB48 production. Liver function appeared to be normal in all the heterozygotes except for one who exhibited liver steatosis for unexplained reasons. Our study suggests that a single copy of the MTTP gene may be sufficient for human normal lipid absorption, except when associated with an additional APOB gene alteration. The hepatic steatosis reported in 1 patient emphasizes the need for liver function tests in all heterozygotes until the level of risk is established.

Apobec1 complementation factor (A1CF) and RBM47 interact in tissue-specific regulation of C to U RNA editing in mouse intestine and liver.

Mammalian C to U RNA is mediated by APOBEC1, the catalytic deaminase, together with RNA binding cofactors (including A1CF and RBM47) whose relative physiological requirements are unresolved. Although A1CF complements APOBEC1 for in vitro RNA editing, A1cf–/– mice exhibited no change in apolipoproteinB (apoB) RNA editing, while Rbm47 mutant mice exhibited impaired intestinal RNA editing of apoB as well as other targets. Here we examined the role of A1CF and RBM47 in adult mouse liver and intestine, following deletion of either one or both gene products and also following forced (liver or intestinal) transgenic A1CF expression. There were minimal changes in hepatic and intestinal apoB RNA editing in A1cf–/– mice and no changes in either liver- or intestine-specific A1CF transgenic mice. Rbm47 liver-specific knockout (Rbm47LKO) mice demonstrated reduced editing in a subset (11 of 20) of RNA targets, including apoB. By contrast, apoB RNA editing was virtually eliminated (<6% activity) in intestine-specific (Rbm47IKO) mice with only five of 53 targets exhibiting C-to-U RNA editing. Double knockout of A1cf and Rbm47 in liver (ARLKO) eliminated apoB RNA editing and reduced editing in the majority of other targets, with no changes following adenoviral APOBEC1 administration. Intestinal double knockout mice (ARIKO) demonstrated further reduced editing (<10% activity) in four of five of the residual APOBEC1 targets identified in ARIKO mice. These data suggest that A1CF and RBM47 each function independently, yet interact in a tissue-specific manner, to regulate the activity and site selection of APOBEC1 dependent C-to-U RNA editing.

Antihyperlipidaemic effect of triterpenic acid-enriched fraction from Cyclocarya paliurus leaves in hyperlipidaemic rats

Context: Cyclocarya paliurus (Batal) Iljinskaja (Juglandaceae) is an edible and medicinal plant; the leaves are used in Chinese folkloric medicine to treat dyslipidaemia and diabetes.Objective: This study evaluates the antihyperlipidaemic potential of the triterpenic acid-enriched fraction (TAE) from C. paliurus and the underlying mechanism.Materials and methods: The hyperlipidaemic rats were induced by high fat diet for 6 weeks. After oral administration of TAE (200 and 400 mg/kg), the neutral fraction (150 and 300 mg/kg) and statin (4 mg/kg) to the hyperlipidaemic rats for 4 weeks, lipid profile and apolipoprotein (apoB48) level in plasma, and the expression levels of apoB48, microsomal triglyceride transfer protein (MTP), phosphorylation of mitogen-activated protein kinase (MAPK) and tumour necrosis factor α (TNF-α) in intestine were examined. The main constituents in the TAE were identified by HPLC-MS.Results: TAE administration (400 mg/kg) decreased the levels of atherogenic lipids in serum and liver (p < 0.05) and increased serum high-density lipoprotein cholesterol by 19.7%. Furthermore, TAE treatment (200 and 400 mg/kg) decreased plasma apoB48 level by 15.3 and 19.5%, downregulated intestinal apoB48 and MTP expression levels (p < 0.05), and inhibited TNF-α expression by 36.2 and 56.2% and the phosphorylation level of MAPK by 8.8 and 13.2%, respectively. HPLC analysis revealed the presence of pentacyclic- and tetracyclic-triterpene acids in TAE.Conclusion and discussion: These findings suggested that TAE possessed antihyperlipidaemic activity partially involved in the inhibitory effect on apoB48 overproduction, which may provide evidence about its potential role in ameliorating dyslipidaemia.

Vascular Disease Is Associated With the Expression of Genes for Intestinal Cholesterol Transport and Metabolism.

Intestinal cholesterol metabolism is important in influencing postprandial lipoprotein concentrations, and might be important in the development of vascular disease. This study evaluated associations between expression of intestinal cholesterol metabolism genes, postprandial lipid metabolism, and endothelial function/early vascular disease in human subjects. One hundred patients undergoing routine oesophago-gastro-duodenoscopy were recruited. mRNA levels of Nieman-Pick C1-like 1 protein (NPC1L1), ABC-G5, ABC-G8, ABC-A1, microsomal tissue transport protein (MTTP), and sterol-regulatory element-binding protein (SREBP)-2 were measured in duodenal biopsies using quantitative reverse transcription polymerase chain reaction. Postprandially, serum lipid and glycemic profiles were measured, endothelial function was assessed using fasting, and postprandial flow-mediated dilatation (FMD) and carotid intima-media thickness (IMT). Subjects were divided into those above and below the median value of relative expression of each gene, and results were compared between the groups. There were no between-group differences in demographic variables or classical cardiovascular risks. For all genes, the postprandial triglyceride incremental area under the curve was greater (P < 0.05) in the group with greater expression. Postprandial apolipoprotein B48 (ApoB48) levels were greater (P < 0.05) in groups with greater expression of NPC1L1, ABC-G8, and SREBP-2. For all genes, postprandial but not fasting FMD was lower (P < 0.01) in the group with greater expression. Triglyceride and ApoB48 levels correlated significantly with postprandial FMD. Carotid artery IMT was greater (P < 0.05) in groups with greater expression of MTTP, ABC-A1, and SREBP-2. Intestinal cholesterol metabolism gene expression is significantly associated with postprandial increment in triglycerides, intestinal ApoB48, and reduced postprandial FMD. Some genes were also associated with increased IMT. These findings suggest a role of intestinal cholesterol metabolism in development of early vascular disease.

Selective PPAR modulators (SPPARs) may fill the need for treatment of the atherogenic dyslipidemia of insulin resistance and type 2 diabetes: Can they reduce the associated cardiac risk?

Selective PPAR modulators (SPPARs) may fill the need for treatment of the atherogenic dyslipidemia of insulin resistance and type 2 diabetes: Can they reduce the associated cardiac risk?

Cyclocarya paliurus prevents high fat diet induced hyperlipidemia and obesity in Sprague-Dawley rats.

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.

Abstract 597: Nobiletin Reduces Intestinal Lipoprotein Production in LDL Receptor-Null Mice With Diet-Induced Insulin Resistance

Insulin resistant subjects display excessive postprandial lipemia (PPL), defined by overproduction of intestinal triglyceride (TG)-rich, apoB48-containing chylomicrons (CM), which contribute to atherogenesis. However, the regulation of intestinal lipoprotein secretion by insulin and the mechanisms underlying elevated CM production in insulin resistant states remain poorly understood. In mice, the citrus flavonoid nobiletin prevents diet-induced obesity, dyslipidemia, insulin resistance, hepatic steatosis and VLDL overproduction. In the present study, we sought to characterize the aberrant PPL response in mice with diet-induced insulin resistance and hypothesized that nobiletin treatment would correct this abnormal response by normalizing intestinal insulin signaling and TG metabolism. Ldlr-/- mice were fed a high-fat, cholesterol-containing (HFHC) diet (42% fat, 0.2% cholesterol), a HFHC diet plus 0.3% w/w nobiletin or chow for 8 weeks (n=8 per group). Compared to chow, HFHC-fed mice displayed elevated TG (3-fold) within intestinal tissue following a 6 hour fast, which was completely normalized by nobiletin. Fasting-refeeding studies revealed impaired FoxO1 phosphorylation, increased mTOR phosphorylation and elevated Srebp1c mRNA in the jejunum of HFHC-fed mice, indicating intestinal insulin resistance. These parameters were normalized by nobiletin. Measurement of plasma TG following an oral gavage of 150ul olive oil revealed a 3-fold elevation in the total TG area under the curve, which was prevented by nobiletin. Intestinal CM production was determined by injection of mice with poloxamer-407 to inhibit plasma TG-rich lipoprotein lipolysis followed by a gavage containing olive oil and 3H-triolein. Although plasma TG was higher at baseline in HFHC-fed mice, no difference in secretion rates of TG mass or TG radioactivity was observed compared to nobiletin-treated or chow-fed mice. However, secretion of apoB48 was elevated by 20% in HFHC-fed mice, whereas nobiletin decreased apoB48 secretion to levels observed in chow-fed mice. These results indicate that nobiletin prevents intestinal TG accumulation and apoB48 overproduction induced by a HFHC diet, in part, through correction of intestinal insulin resistance.

Abstract 672: Reduced "Egress" of Remnant Lipoproteins From Arterial Tissue Relative to LDL During Insulin Resistance May Explain a Preferential Role in Atherosclerosis Progression

INTRODUCTION: There is emerging epidemiological data that supports a causative role for remnant cholesterol in atherosclerotic and CVD progression. We have shown that hepatic (apoB100) and intestinal (apoB48) lipoproteins may have disparate ‘egress’ and retention properties. Additionally we have reported that insulin resistance (IR) increases the arterial atherogenic proteoglycans. However the underlying effects of this metabolic milieu on the comparative arterial retention of both low-density lipoproteins (LDL) and chylomicron-remnant lipoproteins (CM-R) towards arterial cholesterol deposition remain elusive. Aim: To determine the comparative arterial retention and ‘egress’ of LDL and CM-R in insulin resistant carotid vessels in JCR:LA-cp rats using an ex vivo perfusion approach. METHODS: For in vivo generation of Cy5-labeled CM-R, an intravenous injection of nascent chylomicrons obtained after intragastric intralipid infusion was given to eviscerated rabbits. Labeled CM-R were collected from the plasma after density centrifugation. Human LDL was commercially obtained and was labeled with Cy3. Carotid vessels of JCR-LA:cp IR rats were perfused with Cy5-labeled remnants simultaneously with Cy3-labeled LDL. Images were quantified using confocal microscopy. RESULTS: When equivalent number of CM-R and LDL particles were perfused, a significantly greater number of LDL particles were delivered to the vessel (9-fold) as compared to CM-R. However, after extensive washout (i.e retention) significantly fewer (55% decrease) LDL particles remained in the tissue. In contrast, we observed no difference in the retention of CM-R relative to delivery experiments (no washout) perhaps due to reduced ‘egress’. Despite the greater number of LDL particles retained compared to CM-R, we observed a greater than 1.5-fold increase in total mass of cholesterol associated with CM-R as compared to cholesterol associated with LDL. CONCLUSION: There is debate whether current changes to the US clinical guidelines to move away from plasma LDL-C as an effective predictor of CVD risk. This study suggests that due to disparate ‘egress’ and retention properties of LDL and CM-R there may be a disconnection between their plasma concentration and arterial accumulation.

MTP gene polymorphisms and postprandial lipemia in familial combined hyperlipidemia: Effects of treatment with atorvastatin

BackgroundThe microsomal triglyceride transfer protein (MTP) is involved in hepatic and intestinal apoB secretion. We studied the effect of the functional MTP−493G/T polymorphism on fasting and postprandial lipoproteins in patients with familial combined hyperlipidemia (FCH) before and after treatment with atorvastatin. MethodsEight FCH heterozygote carriers of the rare −493T allele were compared to 9 matched FCH homozygotes for the wild-type allele in a pilot study. Oral fat loading tests were carried out to measure triglycerides (TG) and apo B48 and B100 in the different fractions of triglyceride-rich lipoproteins (TRLs) before and after treatment with atorvastatin. ResultsBefore treatment, TG were similar between the −493T allele carriers and non-carriers. In the T-allele carriers, a trend was observed for increased postprandial apo B48 and B100 concentrations in Sf >400 and Sf 60–400 compared to non-carriers. After treatment, fasting and postprandial TG were significantly lowered in carriers of the T allele, but atorvastatin had no effect on postprandial TG in non-carriers. Atorvastatin resulted in similar reductions of apo B48 and B100 in TRLs in both groups. ConclusionThe MTP-493G/T polymorphism modulates postprandial apo B48 and apo B100 of TRLs in FCH. Atorvastatin decreases postprandial TG in T-allele carriers with FCH.

Metabolic Effects of Resistance Training with or without Caloric Restriction in Dynapenic/Obese Postmenopausal Women

s / Can J Diabetes 37 (2013) S13eS84 S24 Methods: Prediabetes and PCOS-prone and control rats were fed a diet supplemented with the insulin sensitizer metformin and the androgen receptor antagonist flutamide or a combination for 4 weeks. Plasma and intestinal lymph lipid and apoB-lipoprotein metabolism were assessed in the fasted and postprandial state following an oral lipid challenge. Results: Flutamide and combination treatments decreased fasting plasma apoB48 apoB100 and triglyceride concentrations. Metformin treatment alone had no effect on plasma lipids or apoB-lipoproteins, and postprandial lipids and apoB-lipoproteins were not modulated by treatments. Flutamide lowered lymphatic intestinal secretion of triglyceride, cholesterol and apoB48 in the fasted state, and flutamide and combination treatments reduced intestinal apoB48 secretion. Flutamide decreased the serum concentration of total testosterone and estradiol, but not free testosterone. Conclusion: Flutamide appears to independently attenuate circulating plasma apoB-lipoproteins of intestinal and hepatic origin, and reduces the secretion of apoB-lipoproteins into intestinal lymph. We are investigating further the mechanisms associated with testosterone-mediated regulation of these lipidogenic pathways via the androgen receptor.

High-Dose Resveratrol Treatment for 2 Weeks Inhibits Intestinal and Hepatic Lipoprotein Production in Overweight/Obese Men

Overproduction of hepatic apolipoprotein B (apoB)-100 containing very low-density lipoprotein particles and intestinal apoB-48 containing chylomicrons contributes to hypertriglyceridemia seen in conditions such as obesity and insulin resistance. Some, but not all, preclinical and clinical studies have demonstrated that the polyphenol resveratrol ameliorates insulin resistance and hypertriglyceridemia. Here, we assessed intestinal and hepatic lipoprotein turnover, in humans, after 2 weeks of treatment with resveratrol (1000 mg daily for week 1 followed by 2000 mg daily for week 2) or placebo. Eight overweight or obese individuals with mild hypertriglyceridemia were studied on 2 occasions, 4 to 6 weeks apart, after treatment with resveratrol or placebo in a randomized, double-blinded, crossover study. Steady-state lipoprotein kinetics was assessed in a constant fed state with a primed, constant infusion of deuterated leucine. Resveratrol treatment did not significantly affect insulin sensitivity (homeostasis model of assessment of insulin resistance), fasting or fed plasma triglyceride concentration. Resveratrol reduced apoB-48 production rate by 22% (P=0.007) with no significant effect on fractional catabolic rate. Resveratrol reduced apoB-100 production rate by 27% (P=0.02) and fractional catabolic rate by 26% (P=0.04). These results indicate that 2 weeks of high-dose resveratrol reduces intestinal and hepatic lipoprotein particle production. Long-term studies are needed to evaluate the potential clinical benefits of resveratrol in patients with hypertriglyceridemia, who have increased concentrations of triglyceride-rich lipoprotein apoB-100 and apoB-48. www.clinicaltrials.gov. Unique identifier: NCT01451918.

Octreotide promotes weight loss via suppression of intestinal MTP and apoB48 expression in diet-induced obesity rats

ObjectiveThe goal of this study was to investigate the effect of octreotide on the expression of intestinal fat absorption-associated apolipoproteinB48 (apoB48), microsomal triglyceride transfer protein (MTP) and apolipoproteinAIV (apoAIV) in a high-fat diet-induced obesity rat model. MethodsSprague–Dawley rats were placed into a control or high-fat diet group. Obese rats from the high-fat diet group were further divided into an obese group and an octreotide-treated group. Rats in the octreotide-treated group were subcutaneously injected with octreotide (40 μg/kg body weight) twice daily for 8 d. Body weight, fasting plasma glucose (FPG), fasting serum insulin, triglyceride (TG), total cholesterol (TC), and high density lipoprotein-cholesterol (HDL-C) were measured. Intestinal MTP, apoB48, and apoAIV expression levels were determined by real-time polymerase chain reaction, Western blot, or enzyme-linked immunosorbent assay analysis. ResultsWe found high-fat diet-induced obesity rats express more apoB, MTP, and apoAIV mRNA as well as apoB48 and MTP protein in the intestine than normal chow-fed rats. This observation occurred along with increased body weight, FPG, TG, TC, fasting serum insulin, and Homeostatic Model Assessment value. Octreotide intervention significantly decreased body weight and blood parameters, and down-regulated expression of apoB mRNA and apoB48 protein, as well as MTP mRNA and proteins. However, apoAIV mRNA was not significantly different between obese and octreotide-treated rats although it was decreased by 47%. ConclusionHigh-fat diet-induced obesity is associated with increased expression of apoB48, MTP, and apoAIV in the intestine. Octreotide intervention inhibited the overexpression of apoB48 and MTP, and consequently brought about reduced fat absorption and weight loss.

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.

Tu1751 Octreotide Promotes Weight Loss via Suppression of Intestinal MTP and ApoB48 Expression in Diet-Induced Obesity Rats

Tu1751 Octreotide Promotes Weight Loss via Suppression of Intestinal MTP and ApoB48 Expression in Diet-Induced Obesity Rats

ASSOCIATION OF APOLIPOPROTEIN B SUBFRACTIONS AND CORONARY ARTERY CALCIUM IN ASYMPTOMATIC PATIENTS WITH INTERMEDIATE CARDIOVASCULAR RISK

Apolipoprotein B (apoB) is an excellent risk predictor for cardiovascular events, but little is known about the intestinal apoB48 subtype compared with the hepatic apoB100 subtype. Coronary artery calcium (CAC) is an extremely specific tool to quantify subclinical atherosclerosis. This study aimed

Exon Skipping of Hepatic APOB Pre-mRNA With Splice-switching Oligonucleotides Reduces LDL Cholesterol In Vivo

Familial hypercholesterolemia (FH) is a genetic disorder characterized by extremely high levels of plasma low-density lipoprotein (LDL), due to defective LDL receptor-apolipoprotein B (APOB) binding. Current therapies such as statins or LDL apheresis for homozygous FH are insufficiently efficacious at lowering LDL cholesterol or are expensive. Treatments that target APOB100, the structural protein of LDL particles, are potential therapies for FH. We have developed a series of APOB-directed splice-switching oligonucleotides (SSOs) that cause the expression of APOB87, a truncated isoform of APOB100. APOB87, like similarly truncated isoforms expressed in patients with a different condition, familial hypobetalipoproteinemia, lowers LDL cholesterol by inhibiting very low-density lipoprotein (VLDL) assembly and increasing LDL clearance. We demonstrate that these "APO-skip " SSOs induce high levels of exon skipping and expression of the APOB87 isoform, but do not substantially inhibit APOB48 expression in cell lines. A single injection of an optimized APO-skip SSO into mice transgenic for human APOB resulted in abundant exon skipping that persists for >6 days. Weekly treatments generated a sustained reduction in LDL cholesterol levels of 34-51% in these mice, superior to pravastatin in a head-to-head comparison. These results validate APO-skip SSOs as a candidate therapy for FH.

Regulation of Intestinal Chylomicron Production by Glucagon-Like Peptides

Apolipoprotein B48 (apoB48)-containing triglyceride-rich lipoproteins are atherogenic and therefore it is important to understand factors that regulate their metabolism in the intestine. Insulin resistant states are associated with increased intestinal output of apo B48, but the mechanistic studies explaining this overproduction have relied heavily on models of diet-induced insulin resistance. There is evidence that glucagon-like peptide (GLP) secretion is diminished in insulin resistant and diabetic states, which may have implications for postprandial lipid secretion. This review presents a survey of studies on GLPs and intestinal lipoprotein metabolism, along with some insights into the net physiological significance of GLP action in postprandial lipoprotein metabolism. Studies with GLP-1 receptor agonists and dipeptidyl peptidase-IV inhibitors have indicated that GLP-1 in pharmacological and physiological doses can inhibit intestinal TRL production. On the other hand, GLP-2 has an acute stimulatory effect on intestinal apoB48 secretion. Modulating GLP action may serve as a strategy to improve postprandial dyslipidemia in insulin resistant states.