Effect of Lipoprotein(a) on the Diagnosis of Familial Hypercholesterolemia: Does It Make a Difference in the Clinic?

BACKGROUND

Diagnostic tools for familial hypercholesterolemia (FH) rely on estimation of LDL cholesterol concentration. However, routine measurement or calculation of LDL cholesterol concentration using the Friedewald equation contains a cholesterol contribution from lipoprotein(a) [Lp(a)]. We investigated whether Lp(a) influences the phenotypic diagnosis of FH by commonly used clinical criteria.

METHODS

A cohort of 907 adult index patients attending a clinic were studied. The Dutch Lipid Clinic Network (DLCN) and Simon Broome (SB) diagnostic criteria were estimated before and after adjusting LDL cholesterol concentration for the cholesterol content (30%) of Lp(a). Diagnostic reclassification rates and area under the ROC (AUROC) curves in predicting an FH mutation were also compared.

RESULTS

Seventy-four patients defined by DLCN criteria (8.2%) and 207 patients defined by SB criteria (22.8%) were reclassified to “unlikely” FH after adjusting LDL cholesterol for Lp(a) cholesterol. The proportion of FH patients defined by DLCN (probable/definite) and SB (possible/definite) criteria decreased significantly in patients with increased Lp(a) (>0.5 g/L; n = 330) after Lp(a) cholesterol adjustment (P < 0.01). The overall reclassification rate was significantly higher in patients with Lp(a) concentration >1.0 g/L (P < 0.001). The AUROC curve for LDL cholesterol concentration ≥191 mg/dL (≥5.0 mmol/L), DLCN criteria, and SB criteria in predicting an FH mutation increased significantly after adjustment (P < 0.001). There was no significant difference in AUROC curve before and after Lp(a) cholesterol adjustment at an LDL cholesterol concentration ≥251 mg/dL (≥6.5 mmol/L).

CONCLUSIONS

Adjusting LDL cholesterol concentration for Lp(a) cholesterol improves the diagnostic accuracy of DLCN and SB criteria, especially with Lp(a) >1.0 g/L and LDL cholesterol <251 mg/dL (<6.5 mmol/L). Lp(a) should be measured in all patients suspected of having FH.

Fractional turnover of apolipoprotein(a) and apolipoprotein B-100 within plasma lipoprotein(a) particles in statin-treated patients with elevated and normal Lp(a) concentration

CONTEXT

Lipoprotein(a) [Lp(a)] is a highly atherogenic lipoprotein characterized by apolipoprotein(a) [apo(a)] covalently bounded to apoB-100 (apoB). However, the metabolism of apo(a) and apoB within plasma Lp(a) particles in patients on statins remains unclear.

METHODS

The kinetics of Lp(a)-apo(a) and Lp(a)-apoB were determined in 20 patients with elevated Lp(a) (≥0.8 g/L; n = 10) and normal Lp(a) (≤0.3 g/L; n = 10) using stable isotope techniques and compartmental modeling. Plasma apo(a) concentration was measured using liquid chromatography-mass spectrometry. All patients were on statin therapy and were studied in the fasting state.

RESULTS

The fractional catabolic rate (FCR) of Lp(a)-apo(a) was not significantly different from that of Lp(a)-apoB in statin-treated patients with elevated or normal Lp(a) (P > 0.05 in both). Lp(a)-apo(a) FCR was significantly correlated with Lp(a)-apoB in patients with elevated and normal Lp(a) concentrations (r = 0.970 and r = 0.979, respectively; all P < 0.001) with Lin's concordance test showing substantial agreement between the FCRs of Lp(a)-apo(a) and Lp(a)-apoB in patients with elevated and normal Lp(a) concentrations (r_c = 0.978 and r_c = 0.966, respectively).

CONCLUSION

Our data indicate that the apo(a) and apoB proteins within Lp(a) particles have similar FCR and are therefore tightly coupled as an Lp(a) holoparticle in statin-treated patients with elevated and normal Lp(a) concentrations.

Lipoprotein (a) and Low-density lipoprotein apolipoprotein B metabolism following apheresis in patients with elevated lipoprotein(a) and coronary artery disease

BACKGROUND

Lipoprotein apheresis effectively lowers lipoprotein(a) [Lp(a)] and low-density lipoprotein (LDL) by approximately 60%-70%. The rebound of LDL and Lp(a) particle concentrations following lipoprotein apheresis allows the determination of fractional catabolic rate (FCR) and hence production rate (PR) during non-steady state conditions. We aimed to investigate the kinetics of Lp(a) and LDL apolipoprotein B-100 (apoB) particles in patients with elevated Lp(a) and coronary artery disease undergoing regular apheresis.

PATIENTS AND METHODS

A cross-sectional study was carried out in 13 patients with elevated Lp(a) concentration (>500 mg/L) and coronary artery disease. Lp(a) and LDL-apoB metabolic parameters, including FCR and PR were derived by the fit of a compartment model to the Lp(a) and LDL-apoB concentration data following lipoprotein apheresis.

RESULTS

The FCR of Lp(a) was significantly lower than that of LDL-apoB (0.39 [0.31, 0.49] vs 0.57 [0.46, 0.71] pools/day, P = 0.03) with no significant differences in the corresponding PR (14.80 [11.34, 19.32] vs 15.73 [11.93, 20.75] mg/kg/day, P = 0.80). No significant associations were observed between the FCR and PR of Lp(a) and LDL-apoB.

CONCLUSIONS

In patients with elevated Lp(a), the fractional catabolism of Lp(a) is slower than that of LDL-apoB particles, implying that different metabolic pathways are involved in the catabolism of these lipoproteins. These findings have implications for new therapies for lowering apolipoprotein(a) and apoB to prevent atherosclerotic cardiovascular disease.

Comparative aspects of the care of familial hypercholesterolemia in the "Ten Countries Study"

BACKGROUND

There is a lack of information on the health care of familial hypercholesterolemia (FH).

OBJECTIVE

The objective of this study was to compare the health care of FH in countries of the Asia-Pacific region and Southern Hemisphere.

METHODS

A series of questionnaires were completed by key opinion leaders from selected specialist centers in 12 countries concerning aspects of the care of FH, including screening, diagnosis, risk assessment, treatment, teaching/training, and research; the United Kingdom (UK) was used as the international benchmark.

RESULTS

The estimated percentage of patients diagnosed with the condition was low (overall <3%) in all countries, compared with ∼15% in the UK. Underdetection of FH was associated with government expenditure on health care (ϰ = 0.667, P < .05). Opportunistic and systematic screening methods, and the Dutch Lipid Clinic Network criteria were most commonly used to detect FH; genetic testing was infrequently used. Noninvasive imaging of coronary calcium and/or carotid plaques was underutilized in risk assessment. Patients with FH were generally not adequately treated, with <30% of patients achieving guideline recommended low-density lipoprotein cholesterol targets on conventional therapies. Treatment gaps included suboptimal availability and use of lipoprotein apheresis and proprotein convertase subtilsin-kexin type 9 inhibitors. A deficit of FH registries, training programs, and publications were identified in less economically developed countries. The demonstration of cost-effectiveness for cascade screening, genetic testing, and specialized treatments were significantly associated with the availability of subsidies from the health care system (ϰ = 0.571-0.800, P < .05).

CONCLUSION

We identified important gaps across the continuum of care for FH, particularly in less economically developed countries. Wider implementation of primary and pediatric care, telehealth services, patient support groups, education/training programs, research activities, and health technology assessments are needed to improve the care of patients with FH in these countries.

Comparative Effects of PCSK9 (Proprotein Convertase Subtilisin/Kexin Type 9) Inhibition and Statins on Postprandial Triglyceride-Rich Lipoprotein Metabolism

Supplemental Digital Content is available in the text.

Objective—

Inhibition of PCSK9 (proprotein convertase subtilisin/kexin type 9) and statins are known to lower plasma LDL (low-density lipoprotein)-cholesterol concentrations. However, the comparative effects of these treatments on the postprandial metabolism of TRLs (triglyceride-rich lipoproteins) remain to be investigated.

Approach and Results—

We performed a 2-by-2 factorial trial of the effects of 8 weeks of subcutaneous evolocumab (420 mg every 2 weeks) and atorvastatin (80 mg daily) on postprandial TRL metabolism in 80 healthy, normolipidemic men after ingestion of an oral fat load. We evaluated plasma total and incremental area under the curves for triglycerides, apo (apolipoprotein)B-48, and VLDL (very-LDL)-apoB-100. We also examined the kinetics of apoB-48 using intravenous D3-leucine administration, mass spectrometry, and multicompartmental modeling. Atorvastatin and evolocumab independently lowered postprandial VLDL-apoB-100 total area under the curves (P<0.001). Atorvastatin, but not evolocumab, reduced fasting plasma apoB-48, apoC-III, and angiopoietin-like 3 concentrations (P<0.01), as well as postprandial triglyceride and apoB-48 total area under the curves (P<0.001) and the incremental area under the curves for plasma triglycerides, apoB-48, and VLDL-apoB-100 (P<0.01). Atorvastatin also independently increased TRL apoB-48 fractional catabolic rate (P<0.001) and reduced the number of apoB-48–containing particles secreted in response to the fat load (P<0.01). In contrast, evolocumab did not significantly alter the kinetics of apoB-48.

Conclusions—

In healthy, normolipidemic men, atorvastatin decreased fasting and postprandial apoB-48 concentration by accelerating the catabolism of apoB-48 particles and reducing apoB-48 particle secretion in response to a fat load. Inhibition of PCSK9 with evolocumab had no significant effect on apoB-48 metabolism.

A Comparative Analysis of Phenotypic Predictors of Mutations in Familial Hypercholesterolemia

CONTEXT

The gold standard for diagnosing familial hypercholesterolemia (FH) is identification of a causative pathogenic mutation. However, genetic testing is expensive and not widely available.

OBJECTIVE

To compare the validity of the Dutch Lipid Clinic Network (DLCN), Simon Broome (SB), Make Early Diagnosis to Prevent Early Deaths (MEDPED), and American Heart Association (AHA) criteria in predicting an FH-causing mutation.

DESIGN, SETTING, AND PATIENTS

An adult cohort of unrelated patients referred to a lipid clinic for genetic testing.

MAIN OUTCOME MEASURES

Odds ratio (OR), area under the curve (AUC), sensitivity, and specificity.

RESULTS

A pathogenic FH-causing mutation was detected in 30% of 885 patients tested. Elevated low-density lipoprotein (LDL) cholesterol and personal or family history of tendon xanthomata were independent predictors of a mutation (OR range 5.3 to 16.1, P < 0.001). Prediction of a mutation for the DLCN and SB definite and MEDPED criteria (ORs 9.4, 11.7, and 10.5, respectively) was higher than with the AHA criteria (OR 4.67). The balance of sensitivity and specificity was in decreasing order DLCN definite (Youden Index 0.487), MEDPED (0.457), SB definite (0.274), and AHA criteria (0.253), AUC being significantly higher with DLCN definite and MEDPED than other criteria (P < 0.05). Pretreatment LDL cholesterol and tendon xanthomata had the highest AUC in predicting a mutation.

CONCLUSIONS

The DLCN, SB, and MEDPED criteria are valid predictors of an FH-causing mutation in patients referred to a lipid clinic, but concordance between these phenotypic criteria is only moderate. Use of pretreatment LDL cholesterol and tendon xanthomata alone may be particularly useful for deciding who should be genetically tested for FH.

Blunt Abdominal Trauma with Left Kidney Dropped into Lower Retroperitoneal Cavity: A Case Report and Literature Review

Blunt abdominal injury with kidney laceration is not unusually seen in high-energy traffic accident. It can present with no symptoms and yet lead to fatal complications. High-grade lacerations of kidney (American Association for the Surgery of Trauma [AAST] grade IV to V) will show up with contrast extravasation and disrupted kidney/pelvicalyceal system morphology in computed tomography (CT). However, it is rare to see kidney dislocation from retroperitoneal space because of the presence of the Gerota's fascia. We present a case of a 16-year-old boy suffering from traffic accident with blunt truncal/abdominal injury. The contrast CT of abdomen revealed that his left kidney was dislocated from the original retroperitoneal space and sagged to the lower retroperitoneal cavity. We performed emergency left nephrectomy. He recovered well and there was no complication noted after the surgical intervention. We also review the literature of kidney laceration regarding diagnosis and treatment. (Hong Kong j.emerg.med. 2016;24:176-179)

Nutrition and physical activity in the prevention and treatment of sarcopenia: systematic review

This systematic review summarizes the effect of combined exercise and nutrition intervention on muscle mass and muscle function. A total of 37 RCTs were identified. Results indicate that physical exercise has a positive impact on muscle mass and muscle function in subjects aged 65 years and older. However, any interactive effect of dietary supplementation appears to be limited.

INTRODUCTION

In 2013, Denison et al. conducted a systematic review including 17 randomized controlled trials (RCTs) to explore the effect of combined exercise and nutrition intervention to improve muscle mass, muscle strength, or physical performance in older people. They concluded that further studies were needed to provide evidence upon which public health and clinical recommendations could be based. The purpose of the present work was to update the prior systematic review and include studies published up to October 2015.

METHODS

Using the electronic databases MEDLINE and EMBASE, we identified RCTs which assessed the combined effect of exercise training and nutritional supplementation on muscle strength, muscle mass, or physical performance in subjects aged 60 years and over. Study selection and data extraction were performed by two independent reviewers.

RESULTS

The search strategy identified 21 additional RCTs giving a total of 37 RCTs. Studies were heterogeneous in terms of protocols for physical exercise and dietary supplementation (proteins, essential amino acids, creatine, β-hydroxy-β-methylbuthyrate, vitamin D, multi-nutrients, or other). In 79% of the studies (27/34 RCTs), muscle mass increased with exercise but an additional effect of nutrition was only found in 8 RCTs (23.5%). Muscle strength increased in 82.8% of the studies (29/35 RCTs) following exercise intervention, and dietary supplementation showed additional benefits in only a small number of studies (8/35 RCTS, 22.8%). Finally, the majority of studies showed an increase of physical performance following exercise intervention (26/28 RCTs, 92.8%) but interaction with nutrition supplementation was only found in 14.3% of these studies (4/28 RCTs).

CONCLUSION

Physical exercise has a positive impact on muscle mass and muscle function in healthy subjects aged 60 years and older. The biggest effect of exercise intervention, of any type, has been seen on physical performance (gait speed, chair rising test, balance, SPPB test, etc.). We observed huge variations in regard to the dietary supplementation protocols. Based on the included studies, mainly performed on well-nourished subjects, the interactive effect of dietary supplementation on muscle function appears limited.

Effect of omega-3 fatty acid supplementation on arterial elasticity in patients with familial hypercholesterolaemia on statin therapy

BACKGROUND AND AIMS

Increased arterial stiffness is closely linked with raised blood pressure that contributes substantially to enhanced risk of coronary heart disease in high risk individuals with familial hypercholesterolaemia (FH). Omega-3 fatty acid (ω3-FA) supplementation has been demonstrated to lower blood pressure in subjects with a high cardiovascular disease risk. Whether ω3-FA supplementation improves arterial stiffness in FH subjects, on background statin therapy, has yet to be investigated.

METHOD AND RESULTS

We carried out an 8-week randomized, crossover intervention trial to test the effect of 4 g/d ω3-FA supplementation (46% eicosapentaenoic acid and 38% docosahexaenoic acid) on arterial elasticity in 20 adults with FH on optimal cholesterol-lowering therapy. Large and small artery elasticity were measured by pulse contour analysis of the radial artery. ω3-FA supplementation significantly (P < 0.05 in all) increased large artery elasticity (+9%) and reduced systolic blood pressure (-6%) and diastolic blood pressure (-6%), plasma triglycerides (-20%), apoB concentration (-8%). In contrast, ω3-FAs had no significant effect on small artery elasticity. The change in large artery elasticity was not significantly associated with changes in systolic blood pressure or plasma triglyceride concentration.

CONCLUSIONS

ω3-FA supplementation improves large arterial elasticity and arterial blood pressure independent of statin therapy in adults with FH.

CLINICAL TRIAL REGISTRATION

https://www.clinicaltrials.com/NCT01577056.

Recent explanatory trials of the mode of action of drug therapies on lipoprotein metabolism

PURPOSE OF REVIEW

Dysregulated lipoprotein metabolism leads to increased plasma concentrations of atherogenic lipoproteins. We highlight the findings from recent studies of the effect of lipid-regulating therapies on apolipoprotein metabolism in humans employing endogenous labelling with stable isotopically labelled isotopomers.

RECENT FINDINGS

Fish oil supplementation and niacin treatment both reduce fasting and postprandial triglyceride levels by decreasing the hepatic secretion of VLDL-apoB-100 (apoB) and apoB-48-containing chylomicron particles in obese and/or type 2 diabetes. Niacin also lowers plasma LDL-apoB and Lp(a) levels by increasing catabolism of LDL-apoB and decreasing secretion of Lp(a), respectively. In subjects with hypercholesterolaemia, inhibition of cholesteryl ester transfer protein raises apoA-I and lowers apoB by decreasing and increasing the catabolism of HDL-apoA-I and LDL-apoB, respectively. Antisense oligonucleotides directed at apoB mRNA lowers plasma LDL-cholesterol and apoB chiefly by increasing the catabolism and decreasing the secretion of LDL-apoB in healthy subjects. That apoB ASO treatment does not lower hepatic secretion in humans is unexpected and merits further investigation.

SUMMARY

Kinetic studies provide mechanistic insight into the mode of action of lipid lowering therapies and lipoprotein disorders. Understanding the mode of action of new drugs in vivo is important to establish their effective use in clinical practice.

ω-3 Fatty Acid Ethyl Esters Diminish Postprandial Lipemia in Familial Hypercholesterolemia

CONTEXT

Impaired postprandial chylomicron metabolism induces hypertriglyceridemia and may increase the risk of atherosclerotic cardiovascular disease. Omega-3 fatty acid ethyl ester (ω-3 FAEE) supplementation decreases plasma triglycerides. However, its effect on postprandial chylomicron metabolism in familial hypercholesterolemia (FH) has not yet been investigated.

OBJECTIVE

We aimed to examine the effect of ω-3 FAEE supplementation on postprandial responses in plasma triglycerides, very-low-density lipoprotein (VLDL) apolipoprotein B (apoB)-100, and apoB-48 in FH patients receiving standard cholesterol-lowering treatment.

DESIGN, SETTING, AND PATIENTS

We carried out an 8-week open-label, randomized, crossover intervention trial to test the effect of oral supplementation with 4 g/d ω-3 FAEE (46% eicosapentaenoic acid and 38% docosahexaenoic acid) on postprandial triglyceride, VLDL-apoB-100, and apoB-48 responses in FH patients after ingestion of an oral fat load.

OUTCOMES MEASURES

Plasma total and incremental triglyceride, VLDL-apoB-100, and apoB-48 0- to 10-hour area under the curve (AUC).

RESULTS

ω-3 FAEE supplementation significantly (P < .05 in all) reduced concentrations of fasting plasma triglyceride (-20%), apoB (-8%), VLDL-apoB-100 (-26%), and apoB-48 (-36%); as well as systolic blood pressure (-6%) and diastolic blood pressure (-6%). Postprandial triglyceride and VLDL-apoB-100 total AUCs (-19% and -26%, respectively; P < .01) and incremental AUCs (-18% and -35%, respectively; P < .05), as well as postprandial apoB-48 total AUC (-30%; P < .02) were significantly reduced by ω-3 FAEE supplementation.

CONCLUSION

Supplementation with ω-3 FAEEs improves postprandial lipemia in FH patients receiving standard care; this may have implications for further reducing atherosclerotic cardiovascular disease in this high-risk patient group.

Triglyceride-rich lipoprotein metabolism in women: roles of apoC-II and apoC-III

BACKGROUND

Experimental data suggest that apolipoprotein (apo) C-II and C-III regulate triglyceride-rich lipoprotein (TRL) metabolism, but there are limited studies in humans. We investigated the metabolic associations of TRLs with apoC-II and apoC-III concentrations and kinetics in women.

MATERIAL AND METHODS

The kinetics of plasma apoC-II, apoC-III and very low-density lipoprotein (VLDL) apoB-100 and triglycerides were measured in the postabsorptive state using stable isotopic techniques and compartmental modelling in 60 women with wide-ranging body mass index (19·5-32·9 kg/m(2) ).

RESULTS

Plasma apoC-II and apoC-III concentrations were positively associated with the concentrations of plasma triglycerides, VLDL1 - and VLDL2 -apoB-100 and triglyceride (all P < 0·05). ApoC-II production rate (PR) was positively associated with VLDL1 -apoB-100 concentration, VLDL1 triglyceride concentration and VLDL1 triglyceride PR, while apoC-II fractional catabolic rate (FCR) was positively associated with VLDL1 triglyceride FCR (all P < 0·05). No significant associations were observed between apoC-II and VLDL2 apoB-100 or triglyceride kinetics. ApoC-III PR, but not FCR, was positively associated with VLDL1 triglyceride, and VLDL2 -apoB-100 and triglyceride concentrations (all P < 0·05). No significant associations were observed between apoC-III and VLDL-apoB-100 and triglyceride kinetics. In multivariable analysis, including homoeostasis model assessment score, menopausal status and obesity, apoC-II concentration was significantly associated with plasma triglyceride, VLDL1 -apoB-100 and VLDL1 triglyceride concentrations and PR. Using the same multivariable analysis, apoC-III was significantly associated with plasma triglyceride and VLDL1 - and VLDL2 -apoB-100 and triglyceride concentrations and FCR.

CONCLUSIONS

In women, plasma apoC-II and apoC-III concentrations are regulated by their respective PR and are significant, independent determinants of the kinetics and plasma concentrations of TRLs.

Effect of niacin on triglyceride-rich lipoprotein apolipoprotein B-48 kinetics in statin-treated patients with type 2 diabetes

AIM

To investigate the effects of extended-release (ER) niacin on apolipoprotein B-48 (apoB-48) kinetics in statin-treated patients with type 2 diabetes (T2DM).

METHODS

A total of 12 men with T2DM were randomized to rosuvastatin or rosuvastatin plus ER niacin for 12 weeks and then crossed to the alternate therapy. Postprandial metabolic studies were performed at the end of each treatment period. D3-leucine tracer was administered as subjects consumed a high-fat liquid meal. ApoB-48 kinetics were determined using stable isotope tracer kinetics with fractional catabolic rates (FCRs) and secretion rates derived using a non-steady-state compartmental model. Area-under-the-curve (AUC) and incremental AUC (iAUC) for plasma triglyceride and apoB-48 were also calculated over the 10-h period after ingestion of the fat meal.

RESULTS

In statin-treated patients with T2DM, apoB-48 concentration was lower with ER niacin (8.24 ± 1.98 vs 5.48 ± 1.14 mg/l, p = 0.03) compared with statin alone. Postprandial triglyceride and apoB-48 AUC were also significantly lower on ER niacin treatment (-15 and -26%, respectively; p < 0.05), without any change to triglyceride and apoB-48 iAUC. ApoB-48 secretion rate in the basal state (3.21 ± 0.34 vs 2.50 ± 0.31 mg/kg/day; p = 0.04) and number of apoB-48-containing particles secreted in response to the fat load (1.35 ± 0.19 vs 0.84 ± 0.12 mg/kg; p = 0.02) were lower on ER niacin. ApoB-48 FCR was not altered with ER niacin (8.78 ± 1.04 vs 9.17 ± 1.26 pools/day; p = 0.79).

CONCLUSIONS

ER niacin reduces apoB-48 concentration by lowering fasting and postprandial apoB-48 secretion rate. This effect may be beneficial for lowering atherogenic postprandial lipoproteins and may provide cardiovascular disease risk benefit in patients with T2DM.

Effects of extended-release niacin on the postprandial metabolism of Lp(a) and ApoB-100-containing lipoproteins in statin-treated men with type 2 diabetes mellitus

OBJECTIVE

The effects of extended-release niacin (ERN; 1-2 g/d) on the metabolism of lipoprotein(a) (Lp(a)) and apolipoprotein (apo) B-100-containing lipoproteins were investigated in 11 statin-treated white men with type 2 diabetes mellitus in a randomized, crossover trial of 12-weeks duration.

APPROACH AND RESULTS

The kinetics of Lp(a) and very low-density lipoprotein (VLDL), intermediate-density lipoprotein, and low-density lipoprotein (LDL) apoB-100 were determined following a standardized oral fat load (87% fat) using intravenous administration of D3-leucine, gas chromatography-mass spectrometry, and compartmental modeling. ERN significantly decreased fasting plasma total cholesterol, LDL cholesterol, and triglyceride concentrations. These effects were achieved without significant changes in body weight or insulin resistance. ERN significantly decreased plasma Lp(a) concentration (-26.5%) and the production rates of apo(a) (-41.5%) and Lp(a)-apoB-100 (-32.1%); the effect was greater in individuals with elevated Lp(a) concentration. ERN significantly decreased VLDL (-58.7%), intermediate-density lipoprotein (-33.6%), and LDL (-18.3%) apoB-100 concentrations and the corresponding production rates (VLDL, -49.8%; intermediate-density lipoprotein, -44.7%; LDL, -46.1%). The number of VLDL apoB-100 particles secreted increased in response to the oral fat load. Despite this, total VLDL apoB-100 production over the 10-hour postprandial period was significantly decreased with ERN (-21.9%).

CONCLUSIONS

In statin-treated men with type 2 diabetes mellitus, ERN decreased plasma Lp(a) concentrations by decreasing the production of apo(a) and Lp(a)-apoB-100. ERN also decreased the concentrations of apoB-100-containing lipoproteins by decreasing VLDL production and the transport of these particles down the VLDL to LDL cascade. Our study provides further mechanistic insights into the lipid-regulating effects of ERN.

Menopausal Status and Abdominal Obesity Are Significant Determinants of Hepatic Lipid Metabolism in Women

Background

Android fat distribution (abdominal obesity) is associated with insulin resistance, hepatic steatosis, and greater secretion of large very low‐density lipoprotein (VLDL) particles in men. Since abdominal obesity is becoming increasingly prevalent in women, we aimed to investigate the relationship between android fat and hepatic lipid metabolism in pre‐ and postmenopausal women.

Methods and Results

We used a combination of stable isotope tracer techniques to investigate intrahepatic fatty acid synthesis and partitioning in 29 lean and 29 abdominally obese women (android fat/total fat 0.065 [0.02 to 0.08] and 0.095 [0.08 to 0.11], respectively). Thirty women were premenopausal aged 35 to 45 and they were matched for abdominal obesity with 28 postmenopausal women aged 55 to 65. As anticipated, abdominal obese women were more insulin resistant with enhanced hepatic secretion of large (404±30 versus 268±26 mg/kg lean mass, P<0.001) but not small VLDL (160±11 versus 142±13). However, postmenopausal status had a pronounced effect on the characteristics of small VLDL particles, which were considerably triglyceride‐enriched (production ratio of VLDL₂‐ triglyceride:apolipoprotein B 30±5.3 versus 19±1.6, P<0.05). In contrast to postmenopausal women, there was a tight control of hepatic fatty acid metabolism and triglyceride production in premenopausal women, whereby oxidation (r_s=−0.49, P=0.006), de novo lipogenesis (r_s=0.55, P=0.003), and desaturation (r_s=0.48, P=0.012) were closely correlated with abdominal obesity‐driven large VLDL‐triglyceride secretion rate.

Conclusions

In women, abdominal obesity is a major driver of hepatic large VLDL particle secretion, whereas postmenopausal status was characterized by increased small VLDL particle size. These data provide a mechanistic basis for the hyperlipidemia observed in postmenopausal obesity.

Association of Plasma Ceramides and Sphingomyelin With VLDL apoB-100 Fractional Catabolic Rate Before and After Rosuvastatin Treatment

INTRODUCTION

The objective of the study was to examine post hoc associations between plasma sphingolipids and lipoprotein kinetics in men with the metabolic syndrome after rosuvastatin treatment.

MATERIALS AND METHODS

Plasma sphingolipid profiling, determined by tandem mass spectrometry, was performed in a randomized, double-blind, triple-crossover trial (n = 12) of 5-week treatment periods with placebo or rosuvastatin (10 or 40 mg/d) with 2-week washouts between treatments.

RESULTS AND DISCUSSION

Baseline plasma ceramides were associated with very low-density lipoprotein (VLDL) apolipoprotein (apo)-B-100 concentration (r = 0.58, P < .05) and inversely with VLDL apoB-100 fractional catabolic rate (FCR; r = -0.67, P = .02). Posttreatment changes with rosuvastatin (40 mg/d) in plasma ceramides were inversely associated with VLDL apoB-100 FCR (r = -0.62, P = .03) independent of changes in plasma triglycerides, cholesterol, and low-density lipoprotein-cholesterol. By contrast, baseline and postrosuvastatin treatment plasma sphingomyelin levels were not associated with apoB-100 kinetics. Plasma ceramides and sphingomyelin were not associated with the kinetics or concentrations of high-density lipoprotein apoA-I, and low-density lipoprotein apoB. In the metabolic syndrome, the ability of rosuvastatin to increase VLDL apoB-100 FCR may reflect ceramide-specific mechanistic actions and/or sphingolipid exchange.

Dose-dependent effects of rosuvastatin on the plasma sphingolipidome and phospholipidome in the metabolic syndrome

CONTEXT

Statins are effective cholesterol-lowering agents that reduce cardiovascular disease risk but also have pleiotropic effects that may extend to other lipid classes.

OBJECTIVE

The purpose of this article was to investigate, in a post hoc analysis, the dose-dependent effects of rosuvastatin on plasma sphingolipids and phospholipids in men with the metabolic syndrome.

METHODS

Subjects (n = 12) were studied in a randomized, double-blind, triple-crossover trial of a 5-week treatment period with placebo or rosuvastatin (10 or 40 mg/day) with 2-week washouts between treatments. Plasma sphingolipid profiling was determined by liquid chromatography electrospray ionization-tandem mass spectrometry.

RESULTS

Rosuvastatin at 10 mg/d (R10) and 40 mg/d (R40) significantly (all P < .001 unless stated otherwise) lowered plasma cholesterol (-34% and -42% [% change with R10 and with R40, respectively]), low-density lipoprotein cholesterol (-49% and -57%) and triglyceride (-24%, P =.03 and -42%) concentrations. Compared with placebo, R10 and R40 significantly decreased the plasma levels of total sphingolipids including those of ceramide (-33% and -37%), sphingomyelin (-27% and -31%), monohexosylceramide (-40% and -47%), dihexosylceramide (-31% and -34%), and trihexosylceramide (-29% and -31%), and GM3 gangliosides (-29% and -26%), lysophosphatidylcholine (-32% and -37%), alkylphosphatidylcholine (-19% and -19%), phosphatidylcholine (-17% and -19%), alkenylphosphatidylcholine (plasmalogen) (-20% and -22%), alkylphosphatidylethanolamine (-20%, P =.008 and -24%, P =.02), alkenylphosphatidylethanolamine (plasmalogen) (-24%, P =.003 and -23%, P =.007), phosphatidylglycerol (-24%, P =.07, -31%, P =.046), and phosphatidylinositol (-34% and -40%). No significant changes were found with phosphatidylethanolamine and phosphatidylserine. Significant dose effects were found with the majority of the plasma sphingolipids, whereas only phosphatidylcholine, lysophosphatidylcholine, alkylphosphatidylcholine, alkenylphosphatidylcholine (plasmalogen), and phosphatidylinositol had significant dose effects. Similar changes were found with plasma sphingolipids when results were normalized to the total phosphatidylcholine concentration.

CONCLUSIONS

Rosuvastatin dose-dependently lowers plasma sphingolipids and phospholipids, independent of low-density lipoprotein lowering, in men with the metabolic syndrome.

Association between skeletal muscle fat content and very-low-density lipoprotein-apolipoprotein B-100 transport in obesity: effect of weight loss

AIMS

Ectopic deposition of fat in skeletal muscle is a feature of metabolic syndrome, but its specific association with very-low-density lipoprotein (VLDL)-apolipoprotein (apo) B-100 metabolism remains unclear.

METHODS

We examined the association between skeletal muscle fat content and VLDL-apoB-100 kinetics in 25 obese subjects, and the responses of these variables to weight loss. The fat contents of liver, abdomen and skeletal muscle were determined by magnetic resonance imaging, and VLDL-apoB-100 kinetics were assessed using stable isotope tracers.

RESULTS

In obese subjects who were insulin sensitive (homeostasis model assessment, HOMA, score ≤ 2.6, n = 12), skeletal muscle fat content was significantly associated with hepatic fat content (r = 0.636), energy intake (r = 0.694), plasma triglyceride (r = 0.644), apoB-100 (r = 0.529), glucose (r = 0.622), VLDL-apoB-100 concentrations (r = 0.860), VLDL-apoB-100 fractional catabolic rate (FCR; r = -0.581) and VLDL-apoB-100 secretion rate (r = 0.607). These associations were not found in obese subjects who were insulin resistant (HOMA score >2.6, n = 13). Of these 25 subjects, 10 obese subjects underwent a 16-week weight loss program. The low-fat diet achieved significant reduction (p < 0.05) in body weight, visceral and subcutaneous fat areas, liver and skeletal muscle fat, energy intake, triglyceride, insulin, HOMA score, VLDL-apoB100 concentrations and VLDL-apoB100 secretion rate. The percentage reduction of skeletal muscle fat with weight loss was significantly associated with the corresponding changes in VLDL-apoB100 concentration (r = 0.770, p = 0.009) and VLDL-apoB-100 secretion (r = 0.682, p = 0.030).

CONCLUSIONS

Skeletal muscle fat content is associated with VLDL-apoB-100 transport. Weight loss lowers skeletal muscle fat and VLDL-apoB-100 secretion.

Effect of ω-3 fatty acid ethyl esters on apolipoprotein B-48 kinetics in obese subjects on a weight-loss diet: a new tracer kinetic study in the postprandial state

CONTEXT

Dysregulated chylomicron metabolism may account for hypertriglyceridemia and increased risk of cardiovascular disease in obese subjects. Supplementation with ω-3 fatty acid ethyl ester (FAEE) decreases plasma triglyceride. However, its effect on postprandial chylomicron metabolism in obese subjects on a weight-loss diet has not yet been investigated.

OBJECTIVE

We aimed to examine the effect of ω-3 FAEE supplementation on apolipoprotein (apo) B-48 kinetics in obese subjects on a weight-loss diet.

DESIGN, SETTING, AND PATIENTS

We carried out a 12-week, randomized trial of a hypocaloric diet plus 4 g/d ω-3 FAEE supplementation (46% eicosapentaenoic acid and 38% docosahexaenoic acid) (n = 13) compared with a hypocaloric diet alone (n = 12) on postprandial apoB-48 kinetics in obese subjects after ingestion of an oral load. The apoB-48 kinetics were determined using stable isotope tracer kinetics and multicompartmental modeling.

OUTCOMES MEASURES

We evaluated plasma total and incremental apoB-48 0- to 10-hour area under the curves (AUCs) as well as apoB-48 secretion and fractional catabolic rate.

RESULTS

Weight loss with or without ω-3 FAEE supplementation significantly reduced body weight, total fat mass, homeostasis model assessment score, fasting triglyceride concentration, postprandial triglyceride AUC, and increased plasma high-density lipoprotein cholesterol concentration (P < .05 in all). Compared with weight loss alone, weight loss plus ω-3 FAEE significantly (all P < .05) decreased fasting triglyceride (-11%), apoB-48 (-36%) concentrations, postprandial triglyceride (-21%), and apoB-48 (-22%) total AUCs, as well as incremental postprandial triglyceride AUCs (-32%). The ω-3 FAEE also significantly decreased apoB-48 secretion in the basal state, without a significant effect during the postprandial period (3-6 hours). The fractional catabolic rate of apoB-48 increased with both interventions with no significant independent effect of ω-3 FAEE supplementation.

CONCLUSION

Addition of ω-3 FAEE supplementation to a moderate weight-loss diet in obese subjects can significantly improve chylomicron metabolism by independently decreasing the secretion of apoB-48.

Atorvastatin plus omega-3 fatty acid ethyl ester decreases very-low-density lipoprotein triglyceride production in insulin resistant obese men

AIM

To test the effect of atorvastatin (ATV) and ATV plus ω-3 FAEEs on VLDL-TG metabolism in obese, insulin resistant men.

METHODS

We carried out a 6-week randomized, placebo-controlled study to examine the effect of ATV (40 mg/day) and ATV plus ω-3 FAEEs (4 g/day) on VLDL-TG metabolism in 36 insulin resistant obese men. VLDL-TG kinetics were determined using d5 -glycerol, gas chromatography-mass spectrometry and compartmental modelling.

RESULTS

Compared with the placebo, ATV significantly decreased VLDL-TG concentration (-40%, p < 0.001) by increasing VLDL-TG fractional catabolic rate (FCR) (+47%, p < 0.01). ATV plus ω-3 FAEEs lowered VLDL-TG concentration to a greater degree compared with placebo (-46%, p < 0.001) or ATV monotherapy (-13%, p = 0.04). This was achieved by a reduction in VLDL-TG production rate (PR) compared with placebo (-32%, p = 0.008) or ATV (-20%, p = 0.03) as well as a reciprocal increase in VLDL-TG FCR (+42%, p < 0.05) compared with placebo.

CONCLUSION

In insulin resistant, dyslipidaemic, obese men, ATV improves VLDL-TG metabolism by increasing VLDL-TG FCR. The addition of 4 g/day ω-3 FAEE to statin therapy provides further TG-lowering by lowering VLDL-TG PR.

The metabolic and pharmacologic bases for treating atherogenic dyslipidaemia

Dyslipoproteinaemia is a cardinal feature of the metabolic syndrome that accelerates atherosclerosis. It is characterized by high plasma concentrations of triglyceride-rich and apolipoprotein (apo) B-containing lipoproteins, with depressed high-density lipoprotein (HDL) and increased small dense low-density lipoprotein (LDL) particle concentrations. Dysregulation of lipoprotein metabolism in the metabolic syndrome may be due to a combination of overproduction of very-low density lipoprotein (VLDL) apoB, decreased catabolism of apoB-containing particles, and increased catabolism of HDL apoA-I particles. These abnormalities are due to a global metabolic effect of insulin resistance and visceral obesity. Lifestyle modifications (dietary restriction and increased exercise) and pharmacological treatments favourably alter lipoprotein transport by decreasing the hepatic secretion of VLDL-apoB and the catabolism of HDL apoA-I, as well as by increasing the clearance of LDL-apoB. The safety and tolerability of combination drug therapy based on statins is important and merits further investigation. There are several pipeline therapies for correcting triglyceride-rich lipoprotein and HDL metabolism. However, their clinical efficacy, safety and cost-effectiveness remain to be demonstrated.

Origin and therapy for hypertriglyceridaemia in type 2 diabetes

Hypertriglyceridaemia (HTG) is a risk factor for cardiovascular disease (CVD) in type 2 diabetes and is caused by the interaction of genes and non-genetic factors, specifically poor glycaemic control and obesity. In spite of statin treatment, residual risk of CVD remains high in type 2 diabetes, and this may relate to HTG and atherogenic dyslipidemia. Treatment of HTG emphasises correcting secondary factors and adverse lifestyles, in particular, diet and exercise. Pharmacotherapy is also required in most type 2 diabetic patients. Statins are the first-line therapy to achieve recommended therapeutic targets of plasma low-density lipoprotein cholesterol and non-high-density lipoprotein cholesterol. Fibrates, ezetimibe and n-3 fatty acids are adjunctive treatment options for residual and persistent HTG. Evidence for the use of niacin has been challenged by non-significant CVD outcomes in two recent large clinical trials. Further investigation is required to clarify the use of incretin-based therapies for HTG in type 2 diabetes. Extreme HTG, with risk of pancreatitis, may require insulin infusion therapy or apheresis. New therapies targeting HTG in diabetes need to be tested in clinical endpoint trials. The purpose of this review is to examine the current evidence and provide practical guidance on the management of HTG in type 2 diabetes.

Effect of Niacin on High-Density Lipoprotein Apolipoprotein A-I Kinetics in Statin-Treated Patients With Type 2 Diabetes Mellitus

Objective—

To investigate the effect of extended-release (ER) niacin on the metabolism of high-density lipoprotein (HDL) apolipoprotein A-I (apoA-I) in men with type 2 diabetes mellitus on a background of optimal statin therapy.

Approach and Results—

Twelve men with type 2 diabetes mellitus were recruited for a randomized, crossover design trial. Patients were randomized to rosuvastatin or rosuvastatin plus ER niacin for 12 weeks and then crossed over to the alternate therapy after a 3-week washout period. Metabolic studies were performed at the end of each treatment period. HDL apoA-I kinetics were measured after a standardized liquid mixed meal and a bolus injection of d3-leucine for 96 hours. Compartmental analysis was used to model the data. ER niacin significantly decreased plasma triglyceride, plasma cholesterol, non-HDL cholesterol, low-density lipoprotein cholesterol, and apoB (all P <0.05) and significantly increased HDL cholesterol and apoA-I concentrations ( P <0.005 and P <0.05, respectively). ER niacin also significantly increased HDL apoA-I pool size (6088±292 versus 5675±305 mg; P <0.001), and this was attributed to a lower HDL apoA-I fractional catabolic rate (0.33±0.01 versus 0.37±0.02 pools/d; P <0.005), with no significant changes in HDL apoA-I production (20.93±0.63 versus 21.72±0.85 mg/kg per day; P =0.28).

Conclusions—

ER niacin increases HDL apoA-I concentration in statin-treated subjects with type 2 diabetes mellitus by lowering apoA-I fractional catabolic rate. The effect on HDL metabolism was independent of the reduction in plasma triglyceride with ER niacin treatment. Whether this finding applies to other dyslipidemic populations remains to be investigated.

Plasma apolipoprotein B-48 transport in obese men: a new tracer kinetic study in the postprandial state

CONTEXT

The mechanisms responsible for impaired chylomicron metabolism have not been adequately investigated in obese subjects.

OBJECTIVE

We aimed to compare apolipoprotein (apo) B-48 kinetics in obese and lean men by developing a new model to describe the kinetics of apoB-48 particles in the postprandial state.

DESIGN, SETTING, AND PATIENTS

Seven obese and 13 age-matched lean men were given an oral fat load. apoB-48 tracer to tracee ratios were measured after intravenous d3-leucine administration using gas chromatography-mass spectrometry. Kinetic parameters were derived using a multicompartmental model.

OUTCOMES MEASURES

Plasma total and incremental apoB-48 0-10 hour areas under the curve as well as apoB-48 secretion and fractional catabolic rate.

RESULTS

Compared with lean men, fasting plasma triglyceride (+148%) and apoB-48 (+110%) concentrations as well as plasma total and incremental triglycerides (+184% and +185%, respectively) and apoB-48 (+182% and 224%, respectively) areas under the curve were significantly higher in obese men (P<.05 for all). The obese men also had significantly (P<.05 for all) higher secretion rates of apoB-48 in the fasted state (+145%) as well as at 3 hours (+70%), 4 hours (+82%), 5 hours (+82%), 6 hours (+76%), and 8 hours (+61%) in response to the fat load. This was associated with a greater number of apoB-48-containing particles secreted over the 10-hour study period in the obese men, compared with lean men (+125%, P<.01). The fractional catabolic rate of apoB-48 was significantly lower in the obese men compared with the lean men (-33%, P<.05) CONCLUSION: We demonstrate that postprandial hypertriglyceridemia in central obesity relates to an overproduction and impaired catabolism of apoB-48-containing lipoproteins. These findings are based on a new, physiologically relevant, kinetic model, which describes the non-steady-state postprandial metabolism of apoB-48.

Supplementation with n3 fatty acid ethyl esters increases large and small artery elasticity in obese adults on a weight loss diet

Increased arterial stiffness is associated with enhanced risk of cardiovascular disease in obese individuals. Whether n3 fatty acid ethyl ester (FAEE) supplementation improves arterial stiffness in obese participants on a weight loss diet has not yet been investigated. The objective of the study was to carry out a 12-wk randomized, single-blind trial to test the effect of a 25% energy deficit weight loss diet alone (WL) (n = 12) or WL plus 4 g/d Omacor (46% EPA and 38% DHA) supplementation (WL+FAEE) (n = 13) on arterial elasticity in obese adults. Large (C1) and small artery elasticity (C2) were measured by pulse contour analysis of the radial artery. WL alone reduced (P < 0.05 in all) body weight (-3%), waist circumference (-4%), systolic (-3%) and diastolic (-3%) blood pressures, cardiac output (-4%), plasma TG concentration (-25%), and the homeostasis model assessment (HOMA) score (-12%) and increased plasma HDL cholesterol (+9%) and adiponectin (+18%) concentrations. However, WL alone did not alter C1 and C2. The WL+FAEE intervention significantly reduced body weight (-4%), waist circumference (-4%), systolic (-8%) and diastolic (-5%) blood pressures, pulse pressure (-5%), heart rate (-8%), plasma TG concentration (-36%), and HOMA score (-12%) and increased stroke volume (+3%), plasma HDL cholesterol (+6%) and adiponectin concentrations (+28%), and C1 (+20%) and C2 (+22%) artery elasticity. The changes in systolic blood pressure, heart rate, plasma TGs, C1, and C2 were significantly greater in the WL+FAEE group than in the WL group. Supplementation with n3 FAEEs improves C1 and C2 independently of weight loss in obese adults.

Effect of fenofibrate and atorvastatin on VLDL apoE metabolism in men with the metabolic syndrome

We examined the effects of fenofibrate and atorvastatin on very low density lipoprotein (VLDL) apolipoprotein (apo)E metabolism in the metabolic syndrome (MetS). We studied 11 MetS men in a randomized, double-blind, crossover trial. VLDL-apoE kinetics were examined using stable isotope methods and compartmental modeling. Compared with placebo, fenofibrate (200 mg/day) and atorvastatin (40 mg/day) decreased plasma apoE concentrations (P < 0.05). Fenofibrate decreased VLDL-apoE concentration and production rate (PR) and increased VLDL-apoE fractional catabolic rate (FCR) compared with placebo (P < 0.05). Compared with placebo, atorvastatin decreased VLDL-apoE concentration and increased VLDL-apoE FCR (P < 0.05). Fenofibrate and atorvastatin had comparable effects on VLDL-apoE concentration. The increase in VLDL-apoE FCR with fenofibrate was 22% less than that with atorvastatin (P < 0.01). With fenofibrate, the change in VLDL-apoE concentration was positively correlated with change in VLDL-apoB concentration, and negatively correlated with change in VLDL-apoB FCR. In MetS, fenofibrate and atorvastatin decreased plasma apoE concentrations. Fenofibrate decreased VLDL-apoE concentration by lowering VLDL-apoE production and increasing VLDL-apoE catabolism. By contrast, atorvastatin decreased VLDL-apoE concentration chiefly by increasing VLDL-apoE catabolism. Our study provides new insights into the mechanisms of action of two different lipid-lowering therapies on VLDL-apoE metabolism in MetS.

Apolipoprotein B-100 and apoA-II kinetics as determinants of cellular cholesterol efflux

CONTEXT

Cellular cholesterol efflux is a key step in reverse cholesterol transport and may depend on the metabolism of apolipoprotein (apo) B-100, apoA-I, and apoA-II.

OBJECTIVE

We examined the associations between cholesterol efflux and plasma concentrations and kinetics of very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and low-density lipoprotein (LDL)-apoB-100, high-density lipoprotein (HDL)-apoA-I, and HDL-apoA-II in men. DESIGN, SUBJECTS, AND METHODS: Thirty men were recruited from the community with a wide range of body mass index. The capacity of plasma and HDL to efflux cholesterol was measured ex vivo. Apolipoprotein kinetics were measured using stable isotope techniques and multicompartmental modeling.

RESULTS

Cholesterol efflux to whole plasma was correlated with plasma levels of cholesterol, triglyceride, apoB-100, insulin, cholesteryl ester transfer protein, and lecithin-cholesterol acyltransferase, body mass index and waist circumference (P < 0.05 in all). Cholesterol efflux was inversely correlated with the fractional catabolic rate (FCR) of VLDL (r = -0.728), IDL (r = -0.662), and LDL-apoB-100 (r = -0.479) but positively correlated with the FCR (r = 0.438) and production rate (r = 0.468) of HDL-apoA-II. In multiple regression analysis, the concentration and FCR of VLDL-apoB-100 (β-coefficient = 0.708 and -0.518, respectively) and IDL-apoB-100 (β-coefficient = 0.354 and -0.447, respectively) were independent predictors of cholesterol efflux. The association of cholesterol efflux with apoB-100 metabolism was diminished after removal of apoB-100-containing lipoproteins from plasma prior to efflux. All associations, except for cholesteryl ester transfer protein, were lost when cholesterol efflux to isolated HDL was tested.

CONCLUSIONS

The plasma concentration and kinetics of apoB-100-containing lipoproteins are significant predictors of the capacity of whole plasma to effect cellular cholesterol efflux.

Postprandial dyslipidaemia and diabetes: mechanistic and therapeutic aspects

PURPOSE OF REVIEW

There has been a resurgence of interest in the role of triglyceride-rich lipoproteins in the development of atherosclerosis and cardiovascular disease, and this is particularly relevant to diabetes mellitus and the postprandial state.

RECENT FINDINGS

Recent evidence suggests that insulin resistance in diabetes induces postprandial dyslipidemia by increasing the enterocytic production of chylomicrons and their remnant particles, but an impaired clearance capacity is also involved. Postprandial dyslipidaemia in diabetes induces oxidative stress, inflammation and endothelial dysfunction and this may be compounded by dysglycaemia. New guidelines for managing hypertriglyceridaemia in diabetes have been published, first-line therapies being improved glycaemic control, treatment of other secondary causes of dyslipidaemia and statin therapy, followed by judicious use of fibrates, n-3 fatty acids or niacin. A new role for incretin-based therapies in regulating dyslipidaemia has been identified.

SUMMARY

Postprandial dyslipidaemia is a pivotal mechanism whereby diabetes can induce and accelerate atherosclerosis. Regulating the plasma concentrations of triglyceride-rich lipoproteins may decrease the cardiovascular complications of diabetes. The mechanisms of action of incretin-based treatments on dyslipidaemia and endothelial dysfunction need further investigation. The efficacy of new therapies targeted at postprandial dysmetabolism in diabetes need to be confirmed, against best current levels of care, in clinical endpoint trials.

Apolipoprotein A-II: evaluating its significance in dyslipidaemia, insulin resistance, and atherosclerosis

Reduced HDL cholesterol, commonly found in subjects with obesity and type 2 diabetes, is associated with increased risk of cardiovascular disease (CVD). ApoA-II, a constituent apolipoprotein of certain HDL particles, plays an important role in the regulation of cholesterol efflux, HDL remodelling, and cholesteryl ester uptake via its interactions with lipid transfer proteins, lipases, and cellular HDL receptors. Recent studies have linked apoA-II directly with triglyceride and glucose metabolism. Most of the data are, however, derived from cellular systems and transgenic animal models. Direct evidence from human studies is scarce. Clinical studies demonstrate that apoA-II is a strong predictor of risk for CVD. There is no evidence, however, that selective therapeutic modification of apoA-II impacts on atherosclerosis and clinical outcomes. More research is required to investigate further the significance of apoA-II in clinical medicine.

Abstract 322: Effect of Atorvastatin on Very-Low-Density Lipoprotein Triglyceride Kinetics in Obese Men

Background Hypertriglyceridemia is a risk factor for cardiovascular disease. Atorvastatin effectively decreases plasma and VLDL triglyceride concentrations in humans, but the mechanism of action is unknown. This study examined the effect of atorvastatin on VLDL triglyceride (VLDL-TG) metabolism in obese men.

Hypothesis: Atorvastatin decreases VLDL-TG concentrations by increasing VLDL-TG catabolism.

Methods: 25 obese men (mean ± SEM: age 52 ± 3 years, BMI 34.5 ± 1.4 kg/m 2 , plasma triglyceride 1.9 ± 0.1 mmol/L, HDL cholesterol 1.00 ± 0.05 mmol/L) were studied in a two-arm parallel group study design. Eligible subjects entered a 3 week run-in dietary stabilizing period at the end of which they were randomized to a 6 week treatment period of either atorvastatin 40 mg/day (ATV) or placebo. VLDL-TG kinetics were examined using stable isotope methods and compartmental modelling.

Results: ATV decreased plasma TG, VLDL apoB and VLDL apoC-III concentrations compared with placebo (p<0.05). Compared with placebo, ATV decreased VLDL-TG concentration ( ATV vs. placebo) (-40% vs. +2%, p<0.01) and increased VLDL-TG fractional catabolic rate (FCR; +54 % vs. -7%, p<0.01). ATV did not alter VLDL-TG production rate. Change in VLDL-TG concentration was positively correlated with change in VLDL apoB (r = 0.81, p<0.01) and VLDL apoC-III (r = 0.65, p=0.02) concentrations, and negatively correlated with VLDL-TG FCR (r = -0.54, p=0.05). Change in VLDL-TG FCR was negatively correlated with VLDL apoC-III, but this failed to reach statistical significance (r = -0.53, p=0.06).

Conclusions: In obese men, ATV decreased plasma and VLDL-TG concentrations chiefly by increasing VLDL-TG catabolism, with no appreciable effect on VLDL-TG synthesis. Our data suggest that reduction in apoC-III concentration with ATV may explain, in part, the increase in VLDL-TG catabolism.

Postprandial lipoprotein metabolism in familial hypercholesterolemia: thinking outside the box

Familial hypercholesterolemia (FH) is a dominantly inherited disorder principally due to mutations in the low-density lipoprotein (LDL) receptor that classically cause markedly elevated plasma LDL cholesterol concentrations and premature coronary heart disease (CHD). However, elevated plasma LDL cholesterol alone does not fully account for the increase or variation in risk of CHD. We propose a hypothetical model for the role of postprandial dyslipoproteinemia based on the overproduction and decreased catabolism of triglyceride-rich lipoproteins, which may be a consequence of LDL receptor deficiency. Expression of postprandial dyslipoproteinemia in FH may also depend on the type of pathogenic gene variants and on coexistent conditions, particularly obesity and insulin resistance. Further research is required to investigate our model proposed and to test whether treating postprandial dyslipoproteinemia decreases CHD risk in FH incremental to standard therapy.

Mechanism of action of a peroxisome proliferator-activated receptor (PPAR)-delta agonist on lipoprotein metabolism in dyslipidemic subjects with central obesity

CONTEXT

Dyslipidemia increases the risk of cardiovascular disease in obesity. Peroxisome proliferator-activated receptor (PPAR)-δ agonists decrease plasma triglycerides and increase high-density lipoprotein (HDL)-cholesterol in humans.

OBJECTIVE

The aim of the study was to examine the effect of GW501516, a PPAR-δ agonist, on lipoprotein metabolism. Design, Setting, and Intervention: We conducted a randomized, double-blind, crossover trial of 6-wk intervention periods with placebo or GW501516 (2.5 mg/d), with 2-wk placebo washout between treatment periods.

PARTICIPANTS

We recruited 13 dyslipidemic men with central obesity from the general community.

MAIN OUTCOME MEASURES

We measured the kinetics of very low-density lipoprotein (VLDL)-, intermediate-density lipoprotein-, and low-density lipoprotein (LDL)-apolipoprotein (apo) B-100, plasma apoC-III, and high-density lipoprotein (HDL) particles (LpA-I and LpA-I:A-II).

RESULTS

GW501516 decreased plasma triglycerides, fatty acid, apoB-100, and apoB-48 concentrations. GW501516 decreased the concentrations of VLDL-apoB by increasing its fractional catabolism and of apoC-III by decreasing its production rate (P < 0.05). GW501516 reduced VLDL-to-LDL conversion and LDL-apoB production. GW501516 increased HDL-cholesterol, apoA-II, and LpA-I:A-II concentrations by increasing apoA-II and LpA-I:A-II production (P < 0.05). GW501516 decreased cholesteryl ester transfer protein activity, and this was paralleled by falls in the triglyceride content of VLDL, LDL, and HDL and the cholesterol content of VLDL and LDL.

CONCLUSIONS

GW501516 increased the hepatic removal of VLDL particles, which might have resulted from decreased apoC-III concentration. GW501516 increased apoA-II production, resulting in an increased concentration of LpA-I:A-II particles. This study elucidates the mechanism of action of this PPAR-δ agonist on lipoprotein metabolism and supports its potential use in treating dyslipidemia in obesity.

Apolipoprotein A-II and adiponectin as determinants of very low-density lipoprotein apolipoprotein B-100 metabolism in nonobese men

Data from cellular systems and transgenic animal models suggest a role of apolipoprotein (apo) A-II in the regulation of very low-density lipoprotein (VLDL) metabolism. However, the precise mechanism whereby apoA-II regulates VLDL metabolism remains to be elucidated in humans. In this study, we examined the associations between the kinetics of high-density lipoprotein (HDL)-apoA-II and VLDL-apoB-100 kinetics, and plasma adiponectin concentrations. The kinetics of HDL-apoA-II and VLDL-apoB-100 were measured in 37 nonobese men using stable isotope techniques. Plasma adiponectin concentration was measured using immunoassays. Total plasma apoA-II concentration was positively associated with HDL-apoA-II production rate (PR) (r = 0.734, P < .01); both were positively associated with plasma triglyceride concentration (r = 0.360 and 0.369, respectively) and VLDL-apoB-100 PR (r = 0.406 and 0.427, respectively), and inversely associated with plasma adiponectin concentration (r = -0.449 and -0.375, respectively). Plasma adiponectin was inversely associated with plasma triglyceride concentration (r = -0.327), VLDL-apoB-100 concentration (r = -0.337), and VLDL-apoB-100 PR (r = -0.373). In multiple regression models including waist circumference and plasma insulin, plasma adiponectin concentration was an independent determinant of total plasma apoA-II concentration (β-coefficient = -0.508, P = .001) and HDL-apoA-II PR (β-coefficient = -0.374, P = .03). Conversely, total plasma apoA-II concentration (β-coefficient = 0.348, P = .047) and HDL-apoA-II PR (β-coefficient = -0.350, P = .035) were both independent determinants of VLDL-apoB-100 PR. However, these associations were not independent of plasma adiponectin. Variation in HDL apoA-II production, and hence total plasma apoA-II concentration, may exert a major effect on VLDL-apoB-100 production. Plasma adiponectin may also contribute to the variation in VLDL-apoB-100 production partly by regulating apoA-II transport.

Plasma apolipoprotein C-III metabolism in patients with chronic kidney disease

Moderate chronic kidney disease (CKD) (defined by an estimated glomerular filtration rate of 30-60 ml/min) is associated with mild hypertriglyceridemia related to delayed catabolism of triglyceride-rich lipoprotein particles. Altered apolipoprotein C-III (apoC-III) metabolism may contribute to dyslipidemia in CKD. To further characterize the dyslipidemia of CKD, we investigated the kinetics of plasma apoC-III in 7 nonobese, nondiabetic, non-nephrotic CKD subjects and 7 age- and sex-matched healthy controls, using deuterated leucine ([5, 5, 5, ²H₃]leucine), gas chromatography-mass spectrometry, and multicompartmental modeling. Compared with controls, CKD subjects had higher concentrations of plasma and VLDL triglycerides and plasma and VLDL apoC-III (P < 0.05). The increased plasma apoC-III concentration was associated with a decreased apoC-III fractional catabolic rate (FCR) (1.21 ± 0.15 vs. 0.74 ± 0.12 pools/day, P = 0.03). There were no differences between apoC-III production rates of controls and those of CKD subjects. In CKD subjects, plasma apoC-III concentration was significantly and negatively correlated with apoC-III FCR (r = -0.749, P = 0.05) but not with apoC-III production rate. Plasma apoC-III concentration was positively correlated with plasma and VLDL triglycerides and VLDL apoB concentrations and negatively correlated with VLDL apoB FCR (P < 0.05 for all). ApoC-III FCR was negatively correlated with plasma and VLDL triglycerides and VLDL apoB concentration and positively correlated with VLDL apoB FCR (P < 0.05 for all). Altered plasma apoC-III metabolism is a feature of dyslipidemia in moderate CKD. Modification of apoC-III catabolism may be an important therapeutic target for reducing cardiovascular disease risk in moderate CKD.

Effect of laparoscopic sleeve gastrectomy on elevated C-reactive protein and atherogenic dyslipidemia in morbidly obese patients

OBJECTIVES

To examine the effect of weight loss by laparoscopic sleeve gastrectomy (LSG) on plasma hs-CRP and lipid profiles in morbidly obese patients.

DESIGN AND METHODS

A mean follow-up of 9 months in 37 patients.

RESULTS

A mean weight loss of 35 kg decreased plasma hs-CRP, glucose, HbA1c, triglycerides, cholesterol, non-HDL-cholesterol, and increased HDL-cholesterol. The percentage reduction of BMI was significantly associated with changes in plasma hs-CRP.

CONCLUSIONS

Weight loss by LSG improves inflammation and dyslipidemia.

The relationship between acid-suppressing drugs and phytobezoar formation: a retrospective analysis and discussion of phytobezoar formation

OBJECTIVES

Although phytobezoars are a rare cause of gastrointestinal obstruction, they are most commonly found in patients with previous gastric surgery. It is well known that predisposing factors of phytobezoar formation are ingestion of fruits containing soluble tannin, presence of dilute hydrochloric acid in the stomach, and gastric stasis or delayed emptying. We investigated whether intake of acid-suppressing drugs that neutralize gastric acidity or inhibit gastric acid secretion to constitute a hypo-acidic condition, increases the risk of phytobezoar formation.

MATERIALS AND METHODS

Between September 1992 and October 2008, 32 patients (24 male and 8 female) with gastrointestinal phytobezoars were diagnosed either surgically or endoscopically at the Tri-Service General Hospital, Taipei, Republic of China. The data were collected from hospital records and analyzed retrospectively.

RESULTS

Eighteen (56.25%) of all patients had previous gastric surgery and 6 (42.9%) of the 14 patients who had not undergone surgery had diabetes mellitus. The majority of admissions were during winter and spring (between October and March) (P < 0.01) and none of the patients had taken acid-suppressing drugs during the 6 months before detection of gastrointestinal phytobezoars.

CONCLUSIONS

In our study, intake of acid-suppressing drugs did not increase the risk of phytobezoar formation in patients with normal gastric motility. Moreover, we believe that the major factor in phytobezoar formation is gastric stasis or delayed emptying, which sufficiently prolongs the retention period of materials in the stomach, while dilute hydrochloric acid is a minor factor.

The effect of fenofibrate on HDL cholesterol and HDL particle concentration in postmenopausal women on tibolone therapy

BACKGROUND

Low high-density lipoprotein (HDL) cholesterol and particle concentration are risk factors for coronary heart disease in women. Tibolone lowers HDL cholesterol and HDL particle concentration, an effect that could be reversed by the peroxisome proliferator-activator receptor-α agonist fenofibrate.

OBJECTIVE

To assess the effects of fenofibrate on plasma HDL particles in postmenopausal women taking tibolone therapy.

DESIGN AND PARTICIPANTS

Randomized crossover study conducted in a women's health clinic. Fourteen postmenopausal women taking tibolone 2.5 mg daily for menopausal symptoms were randomized to either fenofibrate 160 mg daily or no treatment for 8 weeks, followed by a 3-week wash-out for fenofibrate and then crossed over to alternate therapy for another 8 weeks. The main outcome measure was changes in plasma HDL cholesterol concentration, apoA-I and apoA-II, LpA-I and LpA-I-A-II.

RESULTS

After 8 weeks of fenofibrate therapy, there was no change in HDL cholesterol, 1.13 ± 0.06 v 1.16 ± 0.06 mmol/l (P = 0.47) or apoA-I, 1.19 ± 0.05 v 1.20 ± 0.05 g/l (P = 0.23). LpA-I fell significantly 0.35 ± 0.03 v 0.29 ± 0.02 (P = 0.02) but there was a rise in apoA-II, 0.35 ± 0.01 v 0.39 ± 0.01 g/l (P = 0.01). There was a significant fall in total cholesterol, triglycerides, low-density lipoprotein cholesterol and apoB.

CONCLUSION

In women taking tibolone, fenofibrate increases plasma apoA-II concentration and effects a redistribution of HDL subfractions but does not correct tibolone-induced changes in HDL cholesterol or HDL particle concentration. The mechanism and significance of this require further investigation.

Fenofibrate concomitantly decreases serum proprotein convertase subtilisin/kexin type 9 and very-low-density lipoprotein particle concentrations in statin-treated type 2 diabetic patients

AIM

Diabetic dyslipidaemia, characterized by hypertriglyceridaemia as a result of elevated serum very-low-density lipoprotein (VLDL) concentrations, contributes to the increased risk of cardiovascular disease (CVD) in type 2 diabetes (T2DM). Proprotein convertase subtilisin/kexin type 9 (PCSK9) may play a role in regulating VLDL metabolism. We investigated the effect of fenofibrate on serum PCSK9 and VLDL particle concentrations in T2DM patients already receiving statin therapy.

METHODS

In a double-blind randomized crossover study, 15 statin-treated T2DM patients (63 +/- 8 years, body mass index (BMI) 29 +/- 3 kg/m(2)) were treated with fenofibrate (145 mg/day) or matching placebo for 12 weeks. Serum PCSK9 concentrations were measured by immunoassay. VLDL particle concentration and size were determined by nuclear magnetic resonance spectroscopy.

RESULTS

Fenofibrate decreased serum triglycerides (-23%), VLDL-triglycerides (-51%), total cholesterol (-11%), LDL-cholesterol (-16%), apolipoprotein B-100 (-16%), apolipoprotein C-III (-20%) and PCSK9 (-13%) concentrations compared with placebo (p < 0.05). Fenofibrate also decreased serum concentrations of large (-45%), medium (-66%) and small VLDL (-67%) particles (p < 0.05), without altering VLDL particle size. Serum PCSK9 reduction correlated with decreases in total (r = 0.526, p = 0.044) and small (r = 0.629, p = 0.021) VLDL particle concentrations.

CONCLUSIONS

Fenofibrate concomitantly decreased serum PCSK9 and VLDL particle concentrations in statin-treated T2DM patients. These findings support a mechanistic link between PCSK9 and VLDL metabolism, possibly through an effect of PSK9 on VLDL receptor degradation.