Effects of dietary fish oil on serum lipids and VLDL kinetics in hyperlipidemic apolipoprotein E*3-Leiden transgenic mice

Omega-3 Fatty Acids Effects on Inflammatory Biomarkers and Lipid Profiles among Diabetic and Cardiovascular Disease Patients: A Systematic Review and Meta-Analysis

The purpose of this systematic review and meta-analysis was to investigate omega-3 fatty acids’ influence on 12 inflammatory biomarkers—LDL, HDL, total cholesterol, TG, HbA1c, Apo AI, Apo AII, Apo B, CRP, TNF-α, glucose, and fasting blood glucose among diabetic and cardiovascular disease (CVD) patients. We searched articles in six database engines, and 16 of the 696 articles reviewed met the inclusion criteria. Among these, lipid and inflammatory biomarkers investigated commonly included total cholesterol (11 studies), LDL, and TG (10 studies each). Overall, omega-3 was associated with a significant reduction in Apo AII among diabetic patients, as compared to different controls (−8.0 mg/dL 95% CI: −12.71, −3.29, p = 0.0009), triglycerides (−44.88 mg/dL 95% CI: −82.6, −7.16, p < 0.0001), HDL (−2.27 mg/dL 95% CI: −3.72, −0.83, p = 0.002), and increased fasting blood glucose (16.14 mg/dL 95% CI: 6.25, 26.04, p = 0.001). Omega-3 also was associated with increased LDL among CVD patients (2.10 mg/dL 95% CI: 1.00, 3.20, p = 0.0002). We conclude that omega-3 fatty acids may be associated with lower inflammatory biomarkers among diabetic and cardiovascular patients. Clinicians should be aware of these potential benefits; however, it is essential to recommend that patients consult with clinicians before any omega-3 intake.

ATP-citrate lyase (ACLY) in lipid metabolism and atherosclerosis: An updated review

ATP citrate lyase (ACLY) is an important enzyme linking carbohydrate to lipid metabolism by generating acetyl-CoA from citrate for fatty acid and cholesterol biosynthesis. Mendelian randomization of large human cohorts has validated ACLY as a promising target for low-density-lipoprotein-cholesterol (LDL-C) lowering and cardiovascular protection. Among current ACLY inhibitors, Bempedoic acid (ETC-1002) is a first-in-class, prodrug-based direct competitive inhibitor of ACLY which regulates lipid metabolism by upregulating hepatic LDL receptor (LDLr) expression and activity. ACLY deficiency in hepatocytes protects from hepatic steatosis and dyslipidemia. In addition, pharmacological inhibition of ACLY by bempedoic acid, prevents dyslipidemia and attenuates atherosclerosis in hypercholesterolemic ApoE^-/- mice, LDLr^-/- mice, and LDLr^-/- miniature pigs. Convincing data from clinical trials have revealed that bempedoic acid significantly lowers LDL-C as monotherapy, combination therapy, and add-on with statin therapy in statin-intolerant patients. More recently, a phase 3 CLEAR Harmony clinical trial ("Safety and Efficacy of Bempedoic Acid to Reduce LDL Cholesterol") has shown that bempedoic acid reduces the level of LDL-C in hypercholesterolemic patients receiving guideline-recommended statin therapy with a good safety profile. Hereby, we provide a updated review of the expression, regulation, genetics, functions of ACLY in lipid metabolism and atherosclerosis, and highlight the therapeutic potential of ACLY inhibitors (such as bempedoic acid, SB-204990, and other naturally-occuring inhibitors) to treat atherosclerotic cardiovascular diseases. It must be pointed out that long-term large-scale clinical trials in high-risk patients, are warranted to validate whether ACLY represent a promising therapeutic target for pharmaceutic intervention of dyslipidemia and atherosclerosis; and assess the safety and efficacy profile of ACLY inhibitors in improving cardiovascular outcome of patients.

Effects of chocolate supplementation on metabolic and cardiovascular parameters in ApoE3L mice fed a high-cholesterol atherogenic diet

SCOPE

Dietary intake of cocoa and/or chocolate has been suggested to exhibit protective cardiovascular effects although this is still controversial. The aim of this study was to investigate the effects of chocolate supplementation on metabolic and cardiovascular parameters.

METHODS AND RESULTS

Four groups of ApoE*3Leiden mice were exposed to the following diet regimens. Group 1: cholesterol-free control diet (CO). Group 2: high-dose (1.0% w/w) control cholesterol (CC). Group 3: CC supplemented chocolate A (CCA) and Group 4: CC supplemented chocolate B (CCB). Both chocolates differed in polyphenol and fiber content, CCA had a relatively high-polyphenol and low-fiber content compared to CCB. Mice fed a high-cholesterol diet showed increased plasma-cholesterol and developed atherosclerosis. Both chocolate treatments, particularly CCA, further increased plasma-cholesterol and increased atherosclerotic plaque formation. Moreover, compared to mice fed a high-cholesterol diet, both chocolate-treated groups displayed increased liver injury. Mice on high-cholesterol diet had elevated plasma levels of sVCAM-1, sE-selectin and SAA, which was further increased in the CCB group. Similar effects were observed for renal inflammation markers.

CONCLUSION

The two chocolate preparations showed unfavorable, but different effects on cardiometabolic health in E3L mice, which dissimilarities may be related to differences in chocolate composition. We conclude that discrepancies reported on the effects of chocolate on cardiometabolic health may at least partly be due to differences in chocolate composition.

Combined therapy of dietary fish oil and stearoyl-CoA desaturase 1 inhibition prevents the metabolic syndrome and atherosclerosis

BACKGROUND

Stearoyl-CoA desaturase 1 (SCD1) is a critical regulator of energy metabolism and inflammation. We have previously reported that inhibition of SCD1 in hyperlipidemic mice fed a saturated fatty acid (SFA)-enriched diet prevented development of the metabolic syndrome, yet surprisingly promoted severe atherosclerosis. In this study we tested whether dietary fish oil supplementation could prevent the accelerated atherosclerosis caused by SCD1 inhibition.

METHODS AND RESULTS

LDLr(-/-), ApoB(100/100) mice were fed diets enriched in saturated fat or fish oil in conjunction with antisense oligonucleotide (ASO) treatment to inhibit SCD1. As previously reported, in SFA-fed mice, SCD1 inhibition dramatically protected against development of the metabolic syndrome, yet promoted atherosclerosis. In contrast, in mice fed fish oil, SCD1 inhibition did not result in augmented macrophage inflammatory response or severe atherosclerosis. In fact, the combined therapy of dietary fish oil and SCD1 ASO treatment effectively prevented both the metabolic syndrome and atherosclerosis.

CONCLUSIONS

SCD1 ASO treatment in conjunction with dietary fish oil supplementation is an effective combination therapy to comprehensively combat the metabolic syndrome and atherosclerosis in mice.

Orally administered eicosapentaenoic acid reduces and stabilizes atherosclerotic lesions in ApoE-deficient mice

Accumulating evidence demonstrates that dietary intake of n-3 polyunsaturated fatty acids (PUFAs) is associated with reduced incidence of cardiovascular events. However, the molecular mechanisms by which n-3 PUFAs prevent atherosclerosis are not fully understood. Here, we examined the effect of eicosapentaenoic acid (EPA), a major n-3 PUFA, on the pathogenesis of atherosclerosis in ApoE-deficient mice. Five-week-old ApoE-deficient male mice were fed on western-type diet supplemented with 5% (w/w) EPA (EPA group, n=7) or not (control group, n=5) for 13 weeks. An analysis of the fatty acid composition of liver homogenates revealed a marked increase of the n-3 PUFA content in the EPA group (n-3/n-6 ratio: 0.20+/-0.01 vs. 2.5+/-0.2, p<0.01). En face Sudan IV staining of the aorta and oil red O-staining of the aortic sinus revealed that EPA significantly suppressed the development of atherosclerotic lesions. We also observed anti-atherosclerotic effects of EPA in LDL-receptor-deficient mice. The lesions of the EPA group contained more collagen (19.6+/-2.4% vs. 32.9+/-3.9%, p<0.05) and smooth muscle cells (1.3+/-0.2% vs. 3.6+/-0.8%, p<0.05) and less macrophages (32.7+/-4.1% vs. 14.7+/-2.0%, p<0.05). Pretreatment with EPA attenuated the up-regulation of VCAM-1, ICAM-1 and MCP-1 in HUVECs as well as the expression of MMP-2 and MMP-9 in macrophage-like cells induced by TNF-alpha. The anti-inflammatory effects of EPA were abrogated when the expression of peroxisome proliferator-activated receptor alpha (PPARalpha) was suppressed. EPA may potentially reduce and stabilize atherosclerotic lesions through its anti-inflammatory effects.

Fenofibrate increases HDL-cholesterol by reducing cholesteryl ester transfer protein expression

In addition to efficiently decreasing VLDL-triglycerides (TGs), fenofibrate increases HDL-cholesterol levels in humans. We investigated whether the fenofibrate-induced increase in HDL-cholesterol is dependent on the expression of the cholesteryl ester transfer protein (CETP). To this end, APOE*3-Leiden (E3L) transgenic mice without and with the human CETP transgene, under the control of its natural regulatory flanking regions, were fed a Western-type diet with or without fenofibrate. Fenofibrate (0.04% in the diet) decreased plasma TG in E3L and E3L.CETP mice (-59% and -60%; P < 0.001), caused by a strong reduction in VLDL. Whereas fenofibrate did not affect HDL-cholesterol in E3L mice, fenofibrate dose-dependently increased HDL-cholesterol in E3L.CETP mice (up to +91%). Fenofibrate did not affect the turnover of HDL-cholesteryl ester (CE), indicating that fenofibrate causes a higher steady-state HDL-cholesterol level without altering the HDL-cholesterol flux through plasma. Analysis of the hepatic gene expression profile showed that fenofibrate did not differentially affect the main players in HDL metabolism in E3L.CETP mice compared with E3L mice. However, in E3L.CETP mice, fenofibrate reduced hepatic CETP mRNA (-72%; P < 0.01) as well as the CE transfer activity in plasma (-73%; P < 0.01). We conclude that fenofibrate increases HDL-cholesterol by reducing the CETP-dependent transfer of cholesterol from HDL to (V)LDL, as related to lower hepatic CETP expression and a reduced plasma (V)LDL pool.

Response of apolipoprotein E*3‐Leiden transgenic mice to dietary fatty acids: combining liver proteomics with physiological data

Dietary fatty acids have a profound impact on atherosclerosis, but mechanisms are not fully understood. We studied the effects of a saturated fat diet supplemented with fish oil, trans10,cis12 conjugated linoleic acid (CLA), or elaidic acid on lipid and glucose metabolism and liver protein levels of APOE*3 Leiden transgenic mice, a model for lipid metabolism and atherosclerosis. Fish oil lowered plasma and liver cholesterol and triglycerides, plasma free fatty acids, and glucose but increased plasma insulin. CLA lowered plasma cholesterol but increased plasma and liver triglycerides, plasma beta-hydroxybutyrate, and insulin. Elaidic acid lowered plasma and liver cholesterol. Proteomics identified significant regulation of 65 cytosolic and 8-membrane proteins. Many of these proteins were related to lipid and glucose metabolism, and to oxidative stress. Principal component analysis revealed that fish oil had a major impact on cytosolic proteins, and elaidic acid on membrane proteins. Correlation analysis between physiological and protein data revealed novel clusters of correlated variables, among which a metabolic syndrome cluster. The combination of proteomics and physiology gave new insights in mechanisms by which these dietary fatty acids regulate lipid metabolism and related pathways, for example, by altering protein levels of long-chain acyl-CoA thioester hydrolase and adipophilin in the liver.

Understanding hyperlipidemia and atherosclerosis: lessons from genetically modified apoe and ldlr mice

Hyperlipidemia is the most important risk factor for atherosclerosis, which is the major cause of cardiovascular disease. The etiology of hyperlipidemia and atherosclerosis is complex and governed by multiple interacting genes. However, mutations in two genes have been shown to be directly involved, i.e., the low-density lipoprotein receptor (LDLR) and apolipoprotein E (ApoE). Genetically modified mouse models have been instrumental in elucidating the underlying molecular mechanisms in lipid metabolism. In this review, we focus on the use of two of the most widely used mouse models, ApoE- and LDLR-deficient mice. After almost a decade of applications, it is clear that each model has unique strengths and drawbacks when carrying out studies of the role of additional genes and environmental factors such as nutrition and lipid-lowering drugs. Importantly, we elaborate on mice expressing mutant forms of APOE, including the

Absence of an atheroprotective effect of the garlic powder printanor in APOE*3-Leiden transgenic mice

Numerous animal studies have reported that garlic can protect against atherosclerosis. However, a comparable number of studies do not support this observation. This contradiction may result from differences in study design, use of different animal models, and use of different garlic formulations and preparations. Here, we investigated the effect of the chemically well-characterized and production-controlled garlic powder printanor on atherosclerosis in the APOE*3-Leiden transgenic mouse, a mouse model well suited for evaluating anti-atherosclerotic properties of drugs and food components under human-like conditions. APOE*3-Leiden mice were fed a Western diet supplemented with either 5 or 50 g kg(-1) printanor. As a reference, the commercially available fermented garlic kyolic was included (1.6 g kg(-1) diet). Treatment with printanor demonstrated reduced body weight, coinciding with increased feces production and fecal fatty acids excretion. Printanor and kyolic treatment did not affect plasma lipids, markers of inflammation (serum amyloid A, serum-soluble intercellular adhesion molecule-1, and blood-leukocytes tumor necrosis factor-alpha (TNFalpha) production) and vascular activation (plasma von Willebrand factor (vWF)). As analyzed after 28 weeks of treatment, printanor and kyolic did not affect atherosclerotic lesion type, area or composition. Under conditions relevant to the human situation, the well-characterized and production-controlled garlic powder printanor does not display hypolipidemic, anti-inflammatory or anti-atherosclerotic properties.

A fish oil diet does not reverse insulin resistance despite decreased adipose tissue TNF-alpha protein concentration in ApoE-3*Leiden mice

Dietary interventions with fish oil have been found to protect against the development of high-fat diet-induced insulin resistance and to decrease the expression of tumor necrosis factor (TNF)-alpha. However, the effect of fish oil administration on preexisting insulin resistance is subject to debate. In the present study, we examined the mechanism by which fish oil affects preexisting insulin resistance. High fat diet-induced insulin-resistant ApoE*3-Leiden transgenic mice were treated for 10 wk as follows: 1) high fat diet (control group), 2) high fat diet with 3 g/100 g fish oil and 3) high fat diet but food intake restricted to 75% of the ad libitum food intake. We measured plasma glucose, insulin, free fatty acids (FFA) and triglyceride (TG) levels throughout the study. After the 10-wk dietary intervention period we performed hyperinsulinemic euglycemic analyses and measured insulin sensitivity and FFA turnover. Furthermore, we then determined the VLDL-TG production rate and TNF-alpha protein expression in white adipose tissue (WAT). Compared with control mice, the insulin sensitivity of mice treated with fish oil was not affected, whereas it was improved (P < 0.05) for energy-restricted mice. FFA turnover was unaffected in both fish oil-treated and energy-restricted mice. Compared with controls, hepatic VLDL-TG production was lower (P < 0.05) with fish oil feeding but greater with energy restriction (P < 0.05). Interestingly, the level of TNF-alpha protein in WAT was lower (P < 0.05) in both groups. We conclude that partial replacement of saturated fat by fish oil does not improve preexisting high fat diet-induced insulin resistance, although it lowers TNF-alpha protein levels in WAT.

Well-characterized garlic-derived materials are not hypolipidemic in APOE*3-Leiden transgenic mice

Garlic is reported to have beneficial effects on risk factors associated with cardiovascular disease, including normalization of plasma lipid levels. However, numerous studies do not support this beneficial effect of garlic on plasma lipids. This contradiction may result from the use of different garlic-derived materials, experimental designs, and/or animal models. The present study investigated the hypolipidemic effect of garlic-derived materials in APOE*3-Leiden mice, a model well suited for drug and dietary intervention studies of hyperlipidemia. APOE*3-Leiden mice were fed a garlic-derived sulfur-rich compound, either allicin (0.29 g.L drinking water(-1)) or diallyldisulfide (0.27 g.kg diet(-1)), or powdered garlic, of either the kwai (42 g.kg diet(-1)) or morado (42 g.kg diet(-1)) variety. The amounts of garlic-derived materials supplied allowed free intake of allicin or allicin equivalents (diallyldisulfide, kwai, or morado) at 44 mg.kg body wt(-1).d(-1). Mice were fed a nonpurified diet for 4 wk, followed by a Western diet for 8 wk, both supplemented with the garlic-derived materials. These diets had no consistent effect on plasma lipids and did not affect lipoprotein profiles, which are markers for whole-body cholesterol synthesis and intestinal sterol absorption. The current data indicate that the postulated effects of garlic on cardiovascular disease are not caused via modulation of plasma lipid levels.

Omega-3 triglycerides modify blood clearance and tissue targeting pathways of lipid emulsions

Omega-3-rich (n-3) triglycerides (TG) are increasingly recognized as having modulating roles in many physiological and pathological conditions. We questioned whether the catabolism of lipid emulsions would be changed after enrichment with fish oil (n-3) TG as compared to enrichment with omega-6-rich soy oil (n-6) TG. Phospholipid-stabilized emulsions of n-3 TG and n-6 TG were labeled with [(3)H]cholesteryl oleoyl ether and administered by bolus injection to wild-type (WT) mice, mice lacking the low-density lipoprotein receptor (LDL-R) (LDL-R -/-), and apolipoprotein E (apoE) knockout mice (apoE -/-). The effects of exogenous apoE, heparin, Triton WR 1339, and lactoferrin on catabolism of emulsions were also assayed. n-3 TG emulsions were cleared faster from blood and had different extrahepatic tissue targeting compared to n-6 TG emulsions. In apoE -/- and LDL-R -/- mice, blood clearance of n-6 TG emulsions slowed with decreased liver uptake, but no changes were observed in n-3 TG emulsion clearance and tissue uptake compared to WT mice. In WT mice, addition of exogenous apoE to the emulsion increased liver uptake of n-6 TG emulsions but had no impact on n-3 TG emulsions. Pre-injection of heparin increased and Triton WR 1339 and lactoferrin decreased blood clearance of n-6 TG emulsions with little or no effect on n-3 TG emulsions. Liver uptake of n-6 TG emulsions increased after heparin injection and decreased after Triton WR 1339 injection, but uptake of n-3 TG emulsions was not changed. These data show that the catabolism of n-3 TG emulsions and the catabolism of n-6 TG emulsions occur via very different mechanisms. Removal of chylomicron-sized n-6 TG emulsions is modulated by lipoprotein lipase (LPL), apoE, LDL-R, and lactoferrin-sensitive pathways. In contrast, clearance of chylomicron-sized n-3 TG emulsions relies on LPL to a very minor extent and is independent of apoE, LDL-R, and lactoferrin-sensitive pathways.

Dietary vegetable oil and wood derived plant stanol esters reduce atherosclerotic lesion size and severity in apoE*3-Leiden transgenic mice

The hypolipidemic and anti-atherosclerotic effects of vegetable oil- and wood-based dietary plant stanol esters were compared in female apoE*3-Leiden transgenic mice at relevant plasma cholesterol levels. The plant stanol esters derived from vegetable oil (sitostanol 65.7%, campestanol 30.1%) had different contents of sitostanol and campestanol than the plant stanol esters derived from wood (sitostanol 87.6%, campestanol 9.5%) or from a mixture of vegetable oil and wood (sitostanol 73.0%, campestanol 24.7%). The mice (10 per group) received for 38 weeks a control diet or diets containing 1.0% (w/w) plant stanol esters derived from either vegetable oil, wood or a mixture of both. Vegetable oil (-46%), wood (-42%) and vegetable oil/wood (-51%) plant stanol esters decreased the plasma cholesterol levels (P<0.0001) by reducing the cholesterol content in plasma very low density-, intermediate density- and to a lesser extent in low density-lipoprotein. Plant stanol ester feeding did not change plasma triglyceride levels. Dietary plant stanol esters reduced the atherosclerotic lesion area by 91+/-13% (vegetable oil), 97+/-4% (wood) and 78+/-34% (vegetable oil/wood) (P<0.0001) and the severity from regular intimal fatty streaks/mild plaques (on average type 2--3 lesions) in controls to individual intimal foam cells (<type 1 lesions) in the treatment groups (P<0.0001). Plant stanol esters had no effect on adherence of monocytes to the vessel wall. Feeding of plant stanol esters dramatically reduced, independent of its sources, the extent and severity of atherosclerotic lesions, by decreasing VLDL-, IDL- and to a lesser extent LDL-cholesterol in apoE*3-Leiden transgenic mice.

Dietary plant stanol esters reduce VLDL cholesterol secretion and bile saturation in apolipoprotein E*3-Leiden transgenic mice

Dietary plant stanols lower serum cholesterol levels in humans and in hyperlipidemic rodents, mainly by inhibition of the intestinal cholesterol absorption. We used female apolipoprotein E*3-Leiden transgenic mice to investigate the consequences of this effect on serum lipid levels and hepatic lipid metabolism. Five groups of 6 or 7 mice received for 9 weeks a diet containing 0.25% cholesterol and 0.0%, 0.25%, 0.5%, 0.75%, or 1.0% (wt/wt) plant stanols (sitostanol 88% [wt/wt], campestanol 10% [wt/wt]) esterified to fatty acids. Compared with the control diet, plant stanol ester treatment dose-dependently reduced serum cholesterol levels by 10% to 33% (P<0.05), mainly in very low density lipoproteins (VLDLs), intermediate density lipoproteins, and low density lipoproteins. Furthermore, 1.0% of the dietary plant stanols significantly decreased the liver contents of cholesteryl esters (-62%), free cholesterol (-31%), and triglycerides (-38%) but did not change the hepatic VLDL-triglyceride and VLDL-apolipoprotein B production rates. However, plant stanol ester feeding significantly decreased the amounts of cholesteryl esters and free cholesterol incorporated in nascent VLDLs by 72% and 30%, respectively, resulting in a net 2-fold decreased VLDL cholesterol output. Liver mRNA levels of low density lipoprotein receptors, 3-hydroxy-3-methylglutaryl coenzyme A synthase, cholesterol 7alpha-hydroxylase, and sterol 27-hydroxylase were not changed by plant stanol ester feeding. Nevertheless, the serum lathosterol-to-cholesterol ratio was significantly increased by 23%, indicating that dietary plant stanol esters increased whole-body cholesterol synthesis. Plant stanol esters also significantly decreased the cholesterol saturation index in bile by 55%. In conclusion, in apolipoprotein E*3-Leiden transgenic mice, plant stanol ester feeding dose-dependently lowered serum cholesterol levels as a result of a reduced secretion of VLDL cholesterol. This was caused by a decreased hepatic cholesterol content that also resulted in a lowered biliary cholesterol output, indicative of a reduced lithogenicity of bile in these mice.

Acyl-CoA:cholesterol acyltransferase inhibitor avasimibe reduces atherosclerosis in addition to its cholesterol-lowering effect in ApoE*3-Leiden mice

BACKGROUND

The present study investigated whether the ACAT inhibitor avasimibe can reduce atherogenesis independently of its cholesterol-lowering effect in ApoE*3-Leiden mice.

METHODS AND RESULTS

Two groups of 15 female ApoE*3-Leiden mice were put on a high-cholesterol (HC) diet; 1 group received 0.01% (wt/wt) avasimibe mixed into the diet. The HC diet resulted in a plasma cholesterol concentration of 18.7+/-2.6 mmol/L. Addition of avasimibe lowered plasma cholesterol by 56% to 8.1+/-1.2 mmol/L, caused mainly by a reduction of and composition change in VLDL and LDL. In a separate low-cholesterol (LC) control group, plasma cholesterol was titrated to a level comparable to that of the avasimibe group (10.3+/-1.4 mmol/L) by lowering the amount of dietary cholesterol. After 22 weeks of intervention, atherosclerosis in the aortic root area was quantified. Treatment with avasimibe resulted in a 92% reduction of lesion area compared with the HC control group. Compared with the LC control, avasimibe reduced lesion area by 78%. After correction for the slight difference in cholesterol exposure between the LC control and avasimibe groups, the effect of avasimibe on lesion area (73% reduction) remained highly significant. In addition, monocyte adherence to the endothelium, free cholesterol accumulation, and lesion severity were reduced by avasimibe treatment.

CONCLUSIONS

Treatment with avasimibe potently lowered plasma cholesterol levels in ApoE*3-Leiden mice and considerably reduced atherosclerotic lesion area in addition to its cholesterol-lowering effect. Because monocyte adherence to the endothelium and lesion severity were also reduced by avasimibe, treatment with avasimibe may result in higher plaque stability and therefore a reduced risk of plaque rupture.

Effect of n-3 fatty acids on the composition and binding properties of lipoproteins in hypertriglyceridemic patients

BACKGROUND

Treatment of hyperlipidemic patients with fish oil results in an increase in plasma LDL cholesterol despite a marked decrease in the LDL precursor, VLDL.

OBJECTIVE

We studied the relation between VLDL composition and LDL concentrations.

DESIGN

Fourteen hypertriglyceridemic patients were treated with encapsulated fish oil (containing 1.45 g eicosapentaenoic acid and 1. 55 g docosahexaenoic acid/d) for 4 wk. Venous blood samples were collected before and after treatment. Eleven normolipidemic subjects served as a control group.

RESULTS

Fish oil effectively lowered plasma lipid and apolipoprotein (apo) E concentrations in the hypertriglyceridemic patients, whereas apo B concentrations increased. The lipid and apolipoprotein content of VLDL decreased, whereas LDL cholesterol and LDL apo B increased. Fractionation of VLDL by heparin-affinity chromatography showed that before treatment hypertriglyceridemic patients had more VLDL in the 0.05-mol NaCl/L subfraction and less in the 0.20-mol/L subfraction than did control subjects (P < 0.05), whereas the subfraction distribution pattern was normalized after fish-oil treatment. Nevertheless, plasma concentrations of the 0.05-mol NaCl/L subfraction were decreased and those of the 0.20-mol/L subfraction were increased in hypertriglyceridemic patients after fish-oil treatment (P < 0.05). Fish-oil treatment both enhanced VLDL binding and lowered LDL binding to fibroblasts.

CONCLUSION

Treatment of hypertriglyceridemic patients with fish oil caused differential effects on VLDL subfractions and decreased LDL binding to fibroblast receptors, which may have contributed to the paradoxical increase in LDL-cholesterol concentrations.

Lack of predictability of classical animal models for hypolipidemic activity: a good time for mice?

Hypolipidemic drugs that are efficacious in man are not always active in classical animal models of dyslipidemia. Inhibitors of HMG-CoA reductase (statins) do not lower plasma cholesterol in rats, but yet this species was alone in providing activity for fibrate-type drugs. Nicotinic acid possesses many desirable features with regard to clinical use, but most of these actions are lacking in rats and monkeys. The metabolism of low density lipoproteins in hamsters is widely thought to be similar to that in humans, yet neither statins or fibrates lower plasma lipids in these species. With the advent of mouse models expressing specific human genes (or disruption of genes) it is now possible to re-examine the effect of established drugs and to characterize new hypolipidemic compounds with respect to site and mechanism of action. Drug responses observed in humans are now being seen in such mouse models (e.g. HDL elevation with fenofibrate in mice with the human apo A-I gene). Moreover, mice are now being screened for compounds that lower plasma (human) Lp(a), or lower plasma cholesterol in the absence of LDL receptors. It is proposed that these new genetic mouse models may afford a more focused examination of drug action and provide, for new compounds, better prediction of the human response.