Large lipoproteins are excluded from the arterial wall in diabetic cholesterol-fed rabbits

Advances in targeting LDL cholesterol: PCSK9 inhibitors and beyond

There is a direct relationship between the duration and level of exposure to low density lipoprotein cholesterol (LDL-C) levels over one's lifespan and cardiovascular events. Early treatment to lower elevated LDL-C is crucial for better outcomes with multiple therapies currently available to reduce atherogenic lipoproteins. Statins remain the foundation of LDL-C lowering therapy as one of the most cost-effective drugs to reduce atherosclerotic events (ASCVD) and mortality. Nonetheless, LDL-driven goal attainment remains suboptimal globally, highlighting a considerable need for non-statin therapies to address residual risk related to statin intolerance, non-adherence, and inherited lipoprotein disorders. LDL-C lowering interventions beyond statins include ezetimibe, PCSK9 monoclonal antibodies, inclisiran and bempedoic acid with specific guideline recommendations as to when to consider each. For patients with homozygous familial hypercholesterolemia requiring more advanced therapy, lomitapide and evinacumab are available, providing mechanisms that are not LDL receptor dependent. Lipoprotein apheresis remains an effective option for clinical familial hypercholesterolemia as well as elevated lipoprotein (a). There are investigational therapies being explored to add to our current armamentarium including CETP inhibitors, a third-generation PCSK9 inhibitor (small recombinant fusion protein oral PCSK9 inhibitor) and gene editing which aims to directly restore or disrupt genes of interest at the DNA level. This article is a brief review of the pharmacotherapy options beyond statins for lowering LDL-C and their impact on ASCVD risk reduction. Our primary aim is to guide physicians on the role these therapies play in achieving appropriate LDL-C goals, with an algorithm of when to consider each based on efficacy, safety and outcomes.

Modification of lipoprotein metabolism and function driving atherogenesis in diabetes

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease, characterized by raised blood glucose levels and impaired lipid metabolism resulting from insulin resistance and relative insulin deficiency. In diabetes, the peculiar plasma lipoprotein phenotype, consisting in higher levels of apolipoprotein B-containing lipoproteins, hypertriglyceridemia, low levels of HDL cholesterol, elevated number of small, dense LDL, and increased non-HDL cholesterol, results from an increased synthesis and impaired clearance of triglyceride rich lipoproteins. This condition accelerates the development of the atherosclerotic cardiovascular disease (ASCVD), the most common cause of death in T2DM patients. Here, we review the alteration of structure, functions, and distribution of circulating lipoproteins and the pathophysiological mechanisms that induce these modifications in T2DM. The review analyzes the influence of diabetes-associated metabolic imbalances throughout the entire process of the atherosclerotic plaque formation, from lipoprotein synthesis to potential plaque destabilization. Addressing the different pathophysiological mechanisms, we suggest improved approaches for assessing the risk of adverse cardiovascular events and clinical strategies to reduce cardiovascular risk in T2DM and cardiometabolic diseases.

Predictive utility of remnant cholesterol in atherosclerotic cardiovascular disease

PURPOSE OF REVIEW

Remnant cholesterol (RC) is the cholesterol carried in lipoproteins derived from the catabolism of chylomicrons and very low-density lipoproteins. Evidence supporting the causal relationship of RC with atherosclerotic cardiovascular disease (ASVD) is accumulating rapidly. The number of impactful contributions to this field are increasing and provide a pathophysiological insight into the current residual cardiovascular risk beyond low-density cholesterol (LDL)-cholesterol (LDL-C). They also raise the question of whether RC should be used in prediction models and become the target of new therapeutic interventions. The intent of this review is to highlight the recent advances on the role of RC in atherogenesis and the validation of RC as a predictor of ASVD.

RECENT FINDINGS

Numerous prospective and retrospective cohorts helped validate a significant causal relationship of RC with various forms of ASVD, independent of LDL-C. A recent large Mendelian randomization study reinforced the existence of this relationship and showed that the risk of atherosclerotic events was driven nearly entirely by a direct effect of RC.

SUMMARY

Both available and accumulating evidence suggest that a lifelong reduction in RC could translate into a substantial reduction in ASVD risk. The data support a revision of current guidelines to incorporate RC as an independent risk factor for ASVD. We propose that early screening of RC should be implemented and that RC lowering should become the target of future drug developments.

New approaches to triglyceride reduction: Is there any hope left?

Triglycerides play a crucial role in the efficient storage of energy in the body. Mild and moderate hypertriglyceridemia (HTG) is a heterogeneous disorder with significant association with atherosclerotic cardiovascular disease (ASCVD), including myocardial infarction, ischemic stroke, and peripheral artery disease and represents an important component of the residual ASCVD risk in statin treated patients despite optimal low-density lipoprotein cholesterol reduction. Individuals with severe HTG (>1,000 mg/dL) rarely develop atherosclerosis but have an incremental incidence of acute pancreatitis with significant morbidity and mortality. HTG can occur from a combination of genetic (both mono and polygenic) and environmental factors including poor diet, low physical activity, obesity, medications, and diseases like insulin resistance and other endocrine pathologies. HTG represents a potential target for ASCVD risk and pancreatitis risk reduction, however data on ASCVD reduction by treating HTG is still lacking and HTG-associated acute pancreatitis occurs too rarely to effectively demonstrate treatment benefit. In this review, we address the key aspects of HTG pathophysiology and examine the mechanisms and background of current and emerging therapies in the management of HTG.

Use of therapeutic plasma exchange to remove lipoprotein X in a patient with vanishing bile duct syndrome presenting with cholestasis, pseudohyponatremia, and hypercholesterolemia: A case report and review of literature

INTRODUCTION

Lipoprotein X (Lp-X) is an abnormal lipoprotein found in multiple disease conditions, including liver dysfunction and cholestasis. High Lp-X concentrations can interfere with some laboratory testing that may result in spurious results. The detection of Lp-X can be challenging, and there is currently a lack of consensus regarding the management of Lp-X other than treating the underlying disease.

CASE PRESENTATION

A 42-year-old female with Hodgkin's lymphoma treated with dexamethasone, high dose cytarabine and cisplatin and vanishing bile duct syndrome confirmed by liver biopsy presented with cholestasis, pseudohyponatremia (sodium, 113 mmol/L; reference range 136-146 mmL/L; serum osmolality, 303 mOsm/kg), and hypercholesterolemia (> 2800 mg/dL, reference range < 200 mg/dL). Lp-X was confirmed by lipoprotein electrophoresis (EP). Although she did not manifest any specific signs or symptoms, therapeutic plasma exchange (TPE) was initiated based on laboratory findings of extreme hypercholesterolemia, spuriously abnormal serum sodium, and HDL values, and the potential for short- and long-term sequelae such as hyperviscosity syndrome, xanthoma, and neuropathy. During the hospitalization, she was treated with four 1.0 plasma volume TPE over 6 days using 5% albumin for replacement fluid. After the first TPE, total cholesterol (TC) decreased to 383 mg/dL and sodium was measured at 131 mmol/L. The patient was transitioned into outpatient maintenance TPE to eliminate the potential of Lp-X reappearance while the underlying disease was treated. Serial follow-up laboratory testing with lipoprotein EP showed the disappearance of Lp-X after nine TPEs over a 10-week period.

LITERATURE REVIEW

There are seven and four case reports of Lp-X treated with TPE and lipoprotein apheresis (LA), respectively. While all previous case reports showed a reduction in TC levels, none had monitored the disappearance of Lp-X after completing a course of therapeutic apheresis.

CONCLUSION

Clinicians should have a heightened suspicion for the presence of abnormal Lp-X in patients with cholestasis, hypercholesterolemia, and pseudohyponatremia. Once Lp-X is confirmed by lipoprotein EP, TPE should be initiated to reduce TC level and remove abnormal Lp-X. Most LA techniques are not expected to be beneficial since Lp-X lacks apolipoprotein B. Therefore, we suggest that inpatient course of TPE be performed every other day until serum sodium, TC and HDL levels become normalized. Outpatient maintenance TPE may also be considered to keep Lp-X levels low while the underlying disease is treated. Serum sodium, TC, and HDL levels should be monitored while on maintenance TPE.

The chylomicron saga: time to focus on postprandial metabolism

Since statins have had such tremendous therapeutic success over the last three decades, the field of atherosclerosis has become somewhat LDL-centric, dismissing the relevance of triglycerides (TG), particularly chylomicrons, in atherogenesis. Nonetheless, 50% of patients who take statins are at risk of developing atherosclerotic cardiovascular disease (ASCVD) and are unable to achieve their goal LDL-C levels. This residual risk is mediated, in part by triglyceride rich lipoproteins (TRL) and their remnants. Following his seminal investigation on the subject, Zilversmit proposed that atherosclerosis is a postprandial event in 1979 (1-4). In essence, the concept suggests that remnant cholesterol-rich chylomicron (CM) and very-low density lipoprotein (VLDL) particles play a role in atherogenesis. Given the foregoing, this narrative review addresses the most recent improvements in our understanding of postprandial dyslipidemia. The primary metabolic pathways of chylomicrons are discussed, emphasizing the critical physiological role of lipoprotein lipase and apoCIII, the importance of these particles' fluxes in the postprandial period, their catabolic rate, the complexities of testing postprandial metabolism, and the role of angiopoietin-like proteins in the partition of CM during the fed cycle. The narrative is rounded out by the dysregulation of postprandial lipid metabolism in insulin resistance states and consequent CVD risk, the clinical evaluation of postprandial dyslipidemia, current research limits, and potential future study directions.

Nonlinear connection between remnant cholesterol and stroke risk: evidence from the China health and retirement longitudinal study

OBJECTIVE

The evidence on the relationship between remnant cholesterol (RC) and stroke remains controversial. Therefore, this study aimed to explore the relationship between RC and stroke risk in a Chinese population of middle-aged and elderly individuals.

METHODS

The present study included 10067 Chinese subjects of middle-aged and elderly individuals. The connection between RC and incident stroke was investigated using the multivariate Cox proportional hazards regression model, several sensitivity analyses, generalized additive models, and smoothed curve fitting.

RESULTS

A total of 1180 participants with stroke were recorded during the follow-up period. The multivariate Cox proportional hazards regression model identified a positive connection between RC and stroke risk (hazard ratio (HR) = 1.087, 95% confidence interval (CI): 1.001-1.180). In addition, the current study discovered a nonlinear connection between RC and incident stroke, and the point of inflection for RC was 1.78 mmol/L. The risk of stroke increased by 25.1% with each unit increase in RC level when RC was < 1.78 mmol/L (HR:1.251, 95%CI: 1.089-1.437, P = 0.0015). The results were not affected by sensitivity tests.

CONCLUSION

The current study showed a positive and nonlinear connection between RC and stroke risk in a middle-aged and elderly Chinese population. These findings provided new information to help researchers better understand the relationship between RC levels and incident stroke.

Hypertriglyceridemia-Associated Pancreatitis: New Concepts and Potential Mechanisms

BACKGROUND

Triglycerides are a major source of energy, while high plasma triglycerides are a risk factor for various diseases and premature death. Severely elevated plasma triglycerides are a well-established cause of acute pancreatitis with high mortality, likely due to the presence of elevated levels of chylomicrons and large very low-density lipoproteins in plasma. As markedly elevated levels of these very large lipoproteins are not generally found in mild to moderate hypertriglyceridemia, this was previously not regarded as a cause or marker of increased risk of acute pancreatitis. However, mild to moderate hypertriglyceridemia may identify individuals who at a later timepoint develop severe hypertriglyceridemia and acute pancreatitis.

CONTENT

We describe measurement of plasma triglycerides and studies on plasma triglycerides and risk of acute pancreatitis. Further, we summarize current European and American guidelines for the prevention of acute pancreatitis and, finally, the potential for future prevention of acute pancreatitis through lowering of plasma triglycerides.

SUMMARY

Recent observational and genetic studies indicate that mild to moderate hypertriglyceridemia is causally related to increased risk of acute pancreatitis, most likely as a marker of future severe hypertriglyceridemia. Current guidelines do not mention individuals with mild to moderate hypertriglyceridemia, even though newer evidence suggests an unmet medical need. Treatment could include plasma triglyceride-lowering therapy targeting the pathway for lipoprotein lipase as the main triglyceride degrading enzyme in plasma. Angiopoietin-like 3 and apolipoproteinC-III are inhibitors of lipoprotein lipase, and blocking of these 2 inhibitors is showing promising results in relation to marked triglyceride-lowering and could perhaps be used to prevent acute pancreatitis in the future.

Triglycerides revisited: is hypertriglyceridaemia a necessary therapeutic target in cardiovascular disease?

Despite the atherosclerotic cardiovascular disease (ASCVD) risk reduction achieved by low-density lipoprotein cholesterol (LDL-C) lowering therapy, residual ASCVD risk still exists. Previous epidemiological studies have suggested high plasma triglyceride (TG) levels as a risk factor or risk marker for ASCVD independent of LDL-C levels. In this review, we highlighted the underlying pathophysiology of hypertriglyceridaemia, the mechanistic action of therapeutic agents, the interpretation of conflicting results on recent clinical trials, and the present options for primary and secondary prevention. The benefits of fibrates-induced reduction in TG and increase in high-density lipoprotein cholesterol might outweigh the disadvantages of increasing LDL-C levels in primary prevention. In secondary CVD prevention, using eicosapentaenoic acid without docosahexaenoic acid, in addition to statins, will be beneficial. This comprehensive review may prove useful for the development of novel approaches that target hypertriglyceridaemia in future.

Proteomics Analysis of Lipid Metabolism and Inflammatory Response in the Liver of Rabbits fed on a High Cholesterol Diet

In this study, we aimed to analyze the proteomics of the liver in rabbits on a high cholesterol diet (HCD). We randomly divided New Zealand white rabbits into the normal diet group and the HCD group. We established the atherosclerosis model and measured plasma cholesterol and triglycerides. The model was successfully established using ultrasound examination and histopathological staining of the intima of aorta and liver of the two groups of rabbits. The differential proteins in the rabbit liver were analyzed using Tandem Mass Tags proteomic analysis technology. Finally, we used western blot to verify the reliability of proteomics. The results showed that compared with the control group, the serum lipid levels of rats in the HCD group was significantly increased, and the pathological sections showed the formation of atherosclerotic plaques in the aorta, inflammation, and adipose lesions in the liver. Proteomic analysis of the liver revealed 149 differences in HCD-expressed protein, which is mainly involved in inflammation and regulation of lipid and sugar metabolism. In addition, we verified differentially expressed liver proteins in the HCD group using western blot. We found that HCD caused lipid accumulation, abnormal glucose metabolism, and inflammatory response in the liver.

Interventional hepatic apoC-III knockdown improves atherosclerotic plaque stability and remodeling by triglyceride lowering

Apolipoprotein C-III (apoC-III) is a critical regulator of triglyceride metabolism and correlates positively with hypertriglyceridemia and cardiovascular disease (CVD). It remains unclear if therapeutic apoC-III lowering reduces CVD risk and if the CVD correlation depends on the lipid-lowering or antiinflammatory properties. We determined the impact of interventional apoC-III lowering on atherogenesis using an apoC-III antisense oligonucleotide (ASO) in 2 hypertriglyceridemic mouse models where the intervention lowers plasma triglycerides and in a third lipid-refractory model. On a high-cholesterol Western diet apoC-III ASO treatment did not alter atherosclerotic lesion size but did attenuate advanced and unstable plaque development in the triglyceride-responsive mouse models. No lesion size or composition improvement was observed with apoC-III ASO in the lipid-refractory mice. To circumvent confounding effects of continuous high-cholesterol feeding, we tested the impact of interventional apoC-III lowering when switching to a cholesterol-poor diet after 12 weeks of Western diet. In this diet switch regimen, apoC-III ASO treatment significantly reduced plasma triglycerides, atherosclerotic lesion progression, and necrotic core area and increased fibrous cap thickness in lipid-responsive mice. Again, apoC-III ASO treatment did not alter triglyceride levels, lesion development, and lesion composition in lipid-refractory mice after the diet switch. Our findings suggest that interventional apoC-III lowering might be an effective strategy to reduce atherosclerosis lesion size and improve plaque stability when lipid lowering is achieved.

The Remnant Lipoprotein Hypothesis of Diabetes-Associated Cardiovascular Disease

Both type 1 and type 2 diabetes are associated with an increased risk of atherosclerotic cardiovascular disease (CVD). Research based on human-first or bedside-to-bench approaches has provided new insights into likely mechanisms behind this increased risk. Although both forms of diabetes are associated with hyperglycemia, it is becoming increasingly clear that altered lipoprotein metabolism also plays a critical role in predicting CVD risk in people with diabetes. This review examines recent findings indicating that increased levels of circulating remnant lipoproteins could be a missing link between diabetes and CVD. Although CVD risk associated with diabetes is clearly multifactorial in nature, these findings suggest that we should increase efforts in evaluating whether remnant lipoproteins or the proteins that govern their metabolism are biomarkers of incident CVD in people living with diabetes and whether reducing remnant lipoproteins will prevent the increased CVD risk associated with diabetes.

Elevated plasma triglyceride concentration and risk of adverse clinical outcomes in 1.5 million people: a CALIBER linked electronic health record study

BACKGROUND

Assessing the spectrum of disease risk associated with hypertriglyceridemia is needed to inform potential benefits from emerging triglyceride lowering treatments. We sought to examine the associations between a full range of plasma triglyceride concentration with five clinical outcomes.

METHODS

We used linked data from primary and secondary care for 15 M people, to explore the association between triglyceride concentration and risk of acute pancreatitis, chronic pancreatitis, new onset diabetes, myocardial infarction and all-cause mortality, over a median of 6-7 years follow up.

RESULTS

Triglyceride concentration was available for 1,530,411 individuals (mean age 56·6 ± 15·6 years, 51·4% female), with a median of 1·3 mmol/L (IQR: 0.9.to 1.9). Severe hypertriglyceridemia, defined as > 10 mmol/L, was identified in 3289 (0·21%) individuals including 620 with > 20 mmol/L. In multivariable analyses, a triglyceride concentration > 20 mmol/L was associated with very high risk for acute pancreatitis (Hazard ratio (HR) 13·55 (95% CI 9·15-20·06)); chronic pancreatitis (HR 25·19 (14·91-42·55)); and high risk for diabetes (HR 5·28 (4·51-6·18)) and all-cause mortality (HR 3·62 (2·82-4·65)) when compared to the reference category of ≤ 1·7 mmol/L. An association with myocardial infarction, however, was only observed for more moderate hypertriglyceridaemia between 1.7 and 10 mmol/L. We found a risk interaction with age, with higher risks for all outcomes including mortality among those ≤ 40 years compared to > 40 years.

CONCLUSIONS

We highlight an exponential association between severe hypertriglyceridaemia and risk of incident acute and chronic pancreatitis, new diabetes, and mortality, especially at younger ages, but not for myocardial infarction for which only moderate hypertriglyceridemia conferred risk.

Hypertriglyceridemia: A Neglected Risk Factor for Ischemic Stroke?

Hypertriglyceridemia is caused by defects in triglyceride metabolism and generally manifests as abnormally high plasma triglyceride levels. Although the role of hypertriglyceridemia may not draw as much attention as that of plasma cholesterol in stroke, plasma triglycerides, especially nonfasting triglycerides, are thought to be correlated with the risk of ischemic stroke. Hypertriglyceridemia may increase the risk of ischemic stroke by promoting atherosclerosis and thrombosis and increasing blood viscosity. Moreover, hypertriglyceridemia may have some protective effects in patients who have already suffered a stroke via unclear mechanisms. Therefore, further studies are needed to elucidate the role of hypertriglyceridemia in the development and prognosis of ischemic stroke.

Coronary Heart Disease Risk Associated with Primary Isolated Hypertriglyceridemia; a Population-Based Study

Background Hypertriglyceridemia is associated with increased risk of coronary heart disease but the association is often attributed to concomitant metabolic abnormalities. We investigated the epidemiology of primary isolated hypertriglyceridemia (PIH) and associated cardiovascular risk in a population-based setting. Methods and Results We identified adults with at least one triglyceride level ≥500 mg/dL between 1998 and 2015 in Olmsted County, Minnesota. We also identified age- and sex-matched controls with triglyceride levels <150 mg/dL. There were 3329 individuals with elevated triglyceride levels; after excluding those with concomitant hypercholesterolemia, a secondary cause of high triglycerides, age <18 years or an incomplete record, 517 patients (49.4±14.0 years, 72.0% men) had PIH (triglyceride 627.6±183.6 mg/dL). The age- and sex-adjusted prevalence of PIH in adults was 0.80% (0.72-0.87); the diagnosis was recorded in 60%, 46% were on a lipid-lowering medication for primary prevention and a triglyceride level <150 mg/dL was achieved in 24.1%. The association of PIH with coronary heart disease was attenuated but remained significant after adjustment for demographic, socioeconomic, and conventional cardiovascular risk factors (hazard ratio [HR], 1.53; 95% CI, 1.06-2.20; P= 0.022). There was no statistically significant association between PIH and cerebrovascular disease (HR, 1.06; 95% CI, 0.65-1.73, P= 0.813), peripheral artery disease (HR, 1.27; 95% CI, 0.43-3.75; P= 0.668), or the composite end point of all 3 (HR, 1.28; 95% CI, 0.92-1.80; P=0.148) in adjusted models. Conclusions PIH was associated with incident coronary heart disease events (although there was attenuation after adjustment for conventional risk factors), supporting a causal role for triglycerides in coronary heart disease. The condition is relatively prevalent but awareness and control are low.

Low-density lipoproteins cause atherosclerotic cardiovascular disease: pathophysiological, genetic, and therapeutic insights: a consensus statement from the European Atherosclerosis Society Consensus Panel

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Exploring the causal roles of circulating remnant lipid profile on cardiovascular and cerebrovascular diseases: Mendelian randomization study

Background

Causal evidence of circulating lipids especially the remnant cholesterol with cardiovascular and cerebrovascular disease (CVD) is lacking. This research aimed to explore the causal roles of extensive lipid traits especially the remnant lipids in CVD.

Methods

Two-sample Mendelian randomization (TSMR) analysis was performed based on large-scale meta-analysis datasets in European ancestry. The causal effect of 15 circulating lipid profiles including 6 conventional lipids and 9 remnant lipids on coronary heart disease (CHD) and ischemic stroke (IS), as well as the subtypes, was assessed.

Results

Apolipoprotein B (Apo B), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and triglyceride (TG) were still important risk factors for CHD and myocardial infarction (MI) but not for IS. Apo B is the strongest which increased the CHD and MI risk by 44% and 41%, respectively. The odds ratios (ORs) of total TG on CHD and MI were 1.25 (95% confidence interval [CI], 1.13–1.38) and 1.24 (95% CI, 1.11–1.38), respectively. A one standard deviation difference increased TG in medium very-low-density lipoproteins (M.VLDL.TG), TG in small VLDL (S.VLDL.TG), TG in very small VLDL (XS.VLDL.TG), TG in intermediate-density lipoproteins (IDL.TG), TG in very large HDL (XL.HDL.TG), and TG in small HDL (S.HDL.TG) particles also robustly increased the risk of CHD and MI by 9–28% and 9–27%, respectively. TG in very/extremely large VLDL (XXL.VLDL.TG and XL.VLDL.TG) were insignificant or even negatively associated with CHD (in multivariable TSMR), and negatively associated with IS as well.

Conclusion

The remnant lipids presented heterogeneity and two-sided effects for the risk of CHD and IS that may partially rely on the particle size. The findings suggested that the remnant lipids were required to be intervened according to specific components. This research confirms the importance of remnant lipids and provides causal evidence for potential targets for intervention.

Relative effect of hypertriglyceridemia on non-HDLC and apolipoprotein B as cardiovascular disease risk markers

BACKGROUND

Non-high density lipoprotein cholesterol (non-HDLC) represents the cholesterol in triglyceride-rich lipoproteins (TRL) and low-density lipoproteins (LDL). Apolipoprotein B (apoB) reflects the number of TRL and LDL particles. In hypertriglyceridemia (HTG), there is triglyceride (TG) enrichment of TRLs, and also a substantial increase of cholesterol in larger TRLs that considerably augments the non-HDLC value. Therefore, in HTG, non-HDLC could increase disproportionately with respect to apoB.

OBJECTIVE

We aimed to compare the relative effect of the full range of mild, moderate, and severe HTG on the status of non-HDLC and apoB as cardiovascular disease (CVD) risk markers.

METHODS

Analysis of lipid profile data from 4347 patients in a Lipid Clinic cohort with baseline fasting lipid profiles documented prior to starting lipid-lowering medications. The correlation between non-HDLC and apoB was assessed in intervals of increasing TG. Non-HDLC and apoB were analyzed at each TG level using comparative CVD risk equivalent categories and assessed for divergence and discordance.

RESULTS

With increasing TG levels: (1) the correlation between non-HDLC and apoB diminished progressively, (2) non-HDLC levels increased continuously, whereas apoB levels plateaued after an initial increase up to TG of ~ 4.0-5.0 mmol/L (~354-443 mg/dL), (3) there was divergence in the stratification of non-HDLC and apoB into CVD risk equivalent categories.

CONCLUSIONS

Non-HDLC and apoB should not be viewed as interchangeable CVD risk markers in the presence of severe HTG. This has never been tested. With increasing HTG severity, discordance between non-HDLC and apoB can cause clinically important divergence in CVD risk categorization.

Comparison of calculated remnant lipoprotein cholesterol levels with levels directly measured by nuclear magnetic resonance

BACKGROUND

Remnant cholesterol (RC) can partly explain the residual risk in atherosclerotic cardiovascular disease (ASCVD). A consensus method of measuring RC levels has not been established yet. In clinical practice, RC levels are usually calculated from the standard lipid profile, which are not true RC. Nuclear magnetic resonance (NMR) can measure RC levels directly. This study aimed to characterize RC at fasting and non-fasting states in more details and establish the performance of calculated RC and NMR-measured RC.

METHODS

Blood samples at fasting state and at 2 h and 4 h postprandial states were collected in 98 subjects. Lipid parameters including total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), subfractions 3, 4, and 5 of very low-density lipoprotein cholesterol (VLDL3-C, VLDL4-C, and VLDL5-C, respectively), and intermediate-density lipoprotein cholesterol (IDL-C) were measured by enzymatic method and NMR. RC levels calculated from the standard lipid profile or measured by NMR were referred here as RCe or RCn.

RESULTS

The RCe and RCn levels were different, but both of them increased after a meal (P < 0.05), especially at 4 h postprandial state. Low correlations were found between RCe and RCn in the 1st, 2nd, and 3rd quartiles of TG, but RCn showed great correlation with RCe in the highest quartile regardless of the fasting or non-fasting state (R = 0.611, 0.536, and 0.535 for 0 h, 2 h, and 4 h, respectively). However, across the 2nd and 3rd quartiles, RCe levels were nearly close to RCn levels. RCe levels tended to overestimate RCn levels in the 1st quartile of TGe levels with median differences of 0.23(- 0.13, 0.63) and underestimate RCn levels with median differences of - 0.23(- 0.33, 0.07) in the highest quartile of TGe levels.

CONCLUSIONS

RC calculated from the standard lipid profile as TC minus LDL-C minus HDL-C is different from the NMR-measured RC. According to different TG levels, RC could overestimate or underestimate the actual RC level. Developing a consensus clinical method to measure RC levels is necessary, so that results from different studies and platforms can be more directly compared.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR1900020873. Registered in 21 January 2019 - Retrospectively registered.

A Diet Rich in Saturated Fat and Cholesterol Aggravates the Effect of Bacterial Lipopolysaccharide on Alveolar Bone Loss in a Rabbit Model of Periodontal Disease

Increasing evidence connects periodontitis with a variety of systemic diseases, including metabolic syndrome, atherosclerosis, and non-alcoholic fatty liver disease (NAFLD). The proposal of this study was to evaluate the role of diets rich in saturated fat and cholesterol in some aspects of periodontal diseases in a lipopolysaccharide (LPS)-induced model of periodontal disease in rabbits and to assess the influence of a periodontal intervention on hyperlipidemia, atherosclerosis, and NAFLD progression to non-alcoholic steatohepatitis. Male rabbits were maintained on a commercial standard diet or a diet rich in saturated fat (3% lard w/w) and cholesterol (1.3% w/w) (HFD) for 40 days. Half of the rabbits on each diet were treated 2 days per week with intragingival injections of LPS from Porphyromonas gingivalis. Morphometric analyses revealed that LPS induced higher alveolar bone loss (ABL) around the first premolar in animals receiving standard diets, which was exacerbated by the HFD diet. A higher score of acinar inflammation in the liver and higher blood levels of triglycerides and phospholipids were found in HFD-fed rabbits receiving LPS. These results suggest that certain dietary habits can exacerbate some aspects of periodontitis and that bad periodontal health can contribute to dyslipidemia and promote NAFLD progression, but only under certain conditions.

Delayed postprandial TAG peak after intake of SFA compared with PUFA in subjects with and without familial hypercholesterolaemia: a randomised controlled trial

Postprandial hypertriacylglycerolaemia is associated with an increased risk of developing CVD. How fat quality influences postprandial lipid response is scarcely explored in subjects with familial hypercholesterolaemia (FH). The aim of this study was to investigate the postprandial response of TAG and lipid sub-classes after consumption of high-fat meals with different fat quality in subjects with FH compared with normolipidaemic controls. A randomised controlled double-blind cross-over study with two meals and two groups was performed. A total of thirteen hypercholesterolaemic subjects with FH who discontinued lipid-lowering treatment 4 weeks before and during the study, and fourteen normolipidaemic controls, were included. Subjects were aged 18-30 years and had a BMI of 18·5-30·0 kg/m2. Each meal consisted of a muffin containing 60 g (70 E%) of fat, either mainly SFA (40 E%) or PUFA (40 E%), eaten in a random order with a wash-out period of 3-5 weeks between the meals. Blood samples were collected at baseline (fasting) and 2, 4 and 6 h after intake of the meals. In both FH and control subjects, the level of TAG and the largest VLDL sub-classes peaked at 2 h after intake of PUFA and at 4 h after intake of SFA. No significant differences were found in TAG levels between meals or between groups (0·25≤P≤0·72). The distinct TAG peaks may reflect differences in the postprandial lipid metabolism after intake of fatty acids with different chain lengths and degrees of saturation. The clinical impact of these findings remains to be determined.

Triglycerides and triglyceride-rich lipoproteins in the development and progression of atherosclerosis

PURPOSE OF REVIEW

In this review, we intend to show the heterogenicity of the triglyceride group, including the triglyceride-rich lipoproteins and its subparticles, apolipoproteins, and its role in atherogenesis through epidemiological and genetic studies, observing the association of these various components and subclasses with subclinical atherosclerosis and cardiovascular events. Also, we reevaluated the moment of blood collection for the triglyceride measurement and its repercussion in atherosclerosis. Finally, we present the current scenario and new insights about the pharmacologic treatment of hypertriglyceridemia.

RECENT FINDINGS

Recent studies have been observed, a correlation between cardiovascular disease and triglyceride components (as apolipoproteins A-V, C-I, C-III) as well as proteins involved in the metabolism pathway, such as the angiopoietin-like proteins. Also, the triglyceride-rich lipoproteins, also known as remnants, were recently associated with atherogenesis. Another important topic addressed is about nonfasting triglyceride level, which has been postulated as a better predictor of cardiovascular events than fasting collection.

SUMMARY

Regarding hypertriglyceridemia treatment, the drug therapy was updated, as the omega-3 polyunsaturated fatty acids were tested in primary prevention as eicosapentaenoic acid and docosahexaenoic acid combination resulted in no benefit, whereas the administration of icosapent ethyl in secondary prevention and high-risk patients showed a robust decrease of the cardiovascular outcomes.

The Forgotten Lipids: Triglycerides, Remnant Cholesterol, and Atherosclerotic Cardiovascular Disease Risk

Atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of death worldwide. Low-density lipoprotein cholesterol (LDL-C) is a well-established mediator of atherosclerosis and a key target for intervention for the primary and secondary prevention of ASCVD. However, despite substantial reduction in LDL-C, patients continue to have recurrent ASCVD events. Hypertriglyceridemia may be an important contributor of this residual risk. Observational and genetic epidemiological data strongly support a causal role of triglycerides (TGs) and the cholesterol content within triglyceride-rich lipoproteins (TGRLs) and/or remnant cholesterol (RC) in the development of ASCVD. TGRLs are composed of hepatically derived very low-density lipoprotein and intestinally derived chylomicrons. RC is the cholesterol content of all TGRLs and plasma TGs serve as a surrogate measure of TGRLs and RC. Although lifestyle modification remains the cornerstone for management of hypertriglyceridemia, many novel drugs are in development and have shown impressive efficacy in lowering TG levels. Several ongoing, randomized controlled trials are underway to examine the impact of these novel agents on ASCVD outcomes. In this comprehensive review, we provide an overview of the biology, epidemiology, and genetics of TGs and ASCVD; we discuss current and novel TG-lowering therapies under development.

Lipoprotein-X fifty years after its original discovery

AIMS

To review the formation, catabolism, and the possible atherogenic properties of Lp-X.

DATA SYNTHESIS

The conversion of cholesterol to bile acids is regulated by several mechanisms including cholesterol 7 alpha hydroxylase, fibroblast growth factor 19, and farnesoid X receptors. During cholestasis these mechanisms are altered and there is an accumulation of bile acids and cholesterol in plasma. The hypercholesterolemia observed in cholestasis is due to the presence of an anomalous lipoprotein called lipoprotein-X (Lp-X). Lp-X is a lipoprotein rich in phospholipid and free cholesterol present in plasma of patients with cholestasis and, with some variations, in patients with lecithin-cholesterol-acyl-transferase deficiency (LCAT), and after lipid infusion. Lp-X is formed from a bile lipoprotein moving to the blood vessels where it incorporates small quantities of triglycerides, apo-C and esterified cholesterol and becomes a "mature" Lp-X. The activity of the phosphatidilcholine canalicular transporter Mdr2 P-glycoprotein (homologous to the human ABCB4) is essential for LpX appearance, since its suppression abolishes Lp-X formation. However, the concentration of Lp-X in plasma is determined also by the degree of the cholestasis, the residual liver function, and the LCAT deficiency. The Lp-X catabolism seems to be mediated by the reticuloendothelial system and possibly the kidney.

CONCLUSIONS

Lp-X might be considered a defense mechanism against the toxic effect of free cholesterol in cholestasis. The frequency of cardiovascular events in patients affected by primary biliary cholangitis, in whom the Lp-X is present in high concentration, are not increased. Further studies could now clarify the remaining open questions on the role of Lp-X in the dyslipidemia of cholestasis.

Nonfasting versus fasting lipid profile for cardiovascular risk prediction

Before 2009 essentially all societies, guidelines, and statements required fasting before measuring a lipid profile for cardiovascular risk prediction. This was mainly due to the increase seen in triglycerides during a fat tolerance test. However, individuals eat much less fat during a normal day and nonfasting triglycerides have been shown to be superior to fasting in predicting cardiovascular risk. Lipids and lipoproteins only change minimally in response to normal food intake: in four large prospective studies, maximal mean changes were +0.3 mmol/L (26 mg/dL) for triglycerides, -0.2 mmol/L (8 mg/dL) for total cholesterol, -0.2 mmol/L (8 mg/dL) for LDL cholesterol, and -0.1 mmol/L (4 mg/dL) for HDL cholesterol. Further, in 108,602 individuals from the Copenhagen General Population Study in random nonfasting samples, the highest versus the lowest quartile of triglycerides, total cholesterol, LDL cholesterol, remnant cholesterol, non-HDL cholesterol, lipoprotein(a), and apolipoprotein B were all associated with higher risk of both ischaemic heart disease and myocardial infarction. Finally, lipid-lowering trials using nonfasting blood samples for assessment of lipid levels found that reducing levels of nonfasting lipids reduced the risk of cardiovascular disease. To date there is no sound scientific evidence as to why fasting should be superior to nonfasting when evaluating a lipid profile for cardiovascular risk prediction. Indeed, nonfasting samples rather than fasting samples have many obvious advantages. First, it would simplify blood sampling in the laboratory. Second, it would benefit the patient, avoiding the inconvenience of fasting and therefore needing to have blood drawn early in the day. Third, for individuals with diabetes, the risk of hypoglycaemia due to fasting would be minimised. Many countries are currently changing their guidelines towards a consensus on measuring a lipid profile for cardiovascular risk prediction in the nonfasting state, simplifying blood sampling for patients, laboratories, and clinicians worldwide.

Which Lipids Should Be Analyzed for Diagnostic Workup and Follow-up of Patients with Hyperlipidemias?

PURPOSE OF REVIEW

To summarize and discuss the clinical use of lipid and apolipoprotein tests in the settings of diagnosis and therapeutic follow-up of hyperlipidemia.

RECENT FINDINGS

The joint consensus panel of the European Atherosclerosis Society (EAS) and the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) recently produced recommendations on the measurement of atherogenic lipoproteins, taking into account the strengths and weaknesses of analytical and clinical performances of the tests. Total cholesterol, triglycerides, HDL cholesterol, LDL cholesterol, and calculated non-HDL cholesterol (= LDL + remnant cholesterol) constitute the primary lipid panel for hyperlipidemia diagnosis and cardiovascular risk estimation. LDL cholesterol is the primary target of lipid-lowering therapies. Non-HDL cholesterol or apolipoprotein B should be used as secondary therapeutic target in patients with mild-to-moderate hypertriglyceridemia, 2-10 mmol/l (175-880 mg/dl). Lipoprotein (a) is included in LDL cholesterol and should be measured at least once in all patients at cardiovascular risk, including to explain poor response to statin treatment.

Statin Effects on Metabolic Profiles: Data From the PREVEND IT (Prevention of Renal and Vascular End-stage Disease Intervention Trial)

BACKGROUND

Statins lower cholesterol by inhibiting HMG-CoA reductase, the rate-limiting enzyme of the metabolic pathway that produces cholesterol and other isoprenoids. Little is known about their effects on metabolite and lipoprotein subclass profiles. We, therefore, investigated the molecular changes associated with pravastatin treatment compared with placebo administration using a nuclear magnetic resonance-based metabolomics platform.

METHODS AND RESULTS

We performed metabolic profiling of 231 lipoprotein and metabolite measures in the PREVEND IT (Prevention of Renal and Vascular End-stage Disease Intervention Trial) study, a placebo-controlled randomized clinical trial designed to test the effects of pravastatin (40 mg once daily) on cardiovascular risk. Metabolic profiles were assessed at baseline and after 3 months of treatment. Pravastatin lowered low-density lipoprotein cholesterol (change in SD units [95% confidence interval]: -1.01 [-1.14, -0.88]), remnant cholesterol (change in SD units [95% confidence interval]: -1.03 [-1.17, -0.89]), and apolipoprotein B (change in SD units [95% confidence interval]: -0.98 [-1.11, -0.86]) with similar effect magnitudes. In addition, pravastatin globally lowered levels of lipoprotein subclasses, with the exception of high-density lipoprotein subclasses, which displayed a more heterogeneous response pattern. The lipid-lowering effect of pravastatin was accompanied by selective changes in lipid composition, particularly in the cholesterol content of very-low-density lipoproteinparticles. In addition, pravastatin reduced levels of several fatty acids but had limited effects on fatty acid ratios.

CONCLUSIONS

These randomized clinical trial data demonstrate the widespread effects of pravastatin treatment on lipoprotein subclass profiles and fatty acids.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT03073018.

Low-density lipoproteins cause atherosclerotic cardiovascular disease. 1. Evidence from genetic, epidemiologic, and clinical studies. A consensus statement from the European Atherosclerosis Society Consensus Panel

Aims

To appraise the clinical and genetic evidence that low-density lipoproteins (LDLs) cause atherosclerotic cardiovascular disease (ASCVD).

Methods and results

We assessed whether the association between LDL and ASCVD fulfils the criteria for causality by evaluating the totality of evidence from genetic studies, prospective epidemiologic cohort studies, Mendelian randomization studies, and randomized trials of LDL-lowering therapies. In clinical studies, plasma LDL burden is usually estimated by determination of plasma LDL cholesterol level (LDL-C). Rare genetic mutations that cause reduced LDL receptor function lead to markedly higher LDL-C and a dose-dependent increase in the risk of ASCVD, whereas rare variants leading to lower LDL-C are associated with a correspondingly lower risk of ASCVD. Separate meta-analyses of over 200 prospective cohort studies, Mendelian randomization studies, and randomized trials including more than 2 million participants with over 20 million person-years of follow-up and over 150 000 cardiovascular events demonstrate a remarkably consistent dose-dependent log-linear association between the absolute magnitude of exposure of the vasculature to LDL-C and the risk of ASCVD; and this effect appears to increase with increasing duration of exposure to LDL-C. Both the naturally randomized genetic studies and the randomized intervention trials consistently demonstrate that any mechanism of lowering plasma LDL particle concentration should reduce the risk of ASCVD events proportional to the absolute reduction in LDL-C and the cumulative duration of exposure to lower LDL-C, provided that the achieved reduction in LDL-C is concordant with the reduction in LDL particle number and that there are no competing deleterious off-target effects.

Conclusion

Consistent evidence from numerous and multiple different types of clinical and genetic studies unequivocally establishes that LDL causes ASCVD.

Chylomicronemia risk factors ranked by importance for the individual and community in 108 711 women and men

BACKGROUND

Hypertriglyceridemia prevalence is increasing as more individuals become obese, and chylomicronemia risk factors for the individual and community have not been described previously.

OBJECTIVE

To describe chylomicronemia risk factors in the general population for individuals and community.

METHODS

A total of 108 711 individuals from the Copenhagen General Population Study were grouped as unlikely chylomicronemia (nonfasting triglycerides <2 mmol L^-1 (177 mg dL^-1 )), possible chylomicronemia (2-4.99 mmol L^-1 (177-442 mg dL^-1 )), probable chylomicronemia (5-9.99 mmol L^-1 (443-885 mg dL^-1 )) and definite chylomicronemia (≥10 mmol L^-1 (≥ 886 mg dL^-1 )). Relative risk (RR) from Poisson regression ranked dichotomized chylomicronemia risk factors for individuals, and population attributable fractions (PAF) for the community: type 2 diabetes, alcohol intake, obesity, fat intake, hypothyroidism, kidney function, education, sedentary lifestyle, menopause and hormone replacement (women).

RESULTS

For women and men, chylomicronemia was unlikely in 81% and 64%, possible in 18% and 33%, probable in 1% and 3% and definite in 0.03% and 0.14%, respectively. For the individual, the three top-ranked risk factors for probable/definite versus unlikely chylomicronemia in women were type 2 diabetes (RR: 4.21; 95% confidence interval: 3.30-5.36), menopause (RR: 3.74; 2.62-5.36) and obesity (RR: 3.44; 2.81-4.21). Corresponding top-ranked risk factors in men were obesity (RR: 3.86; 3.46-4.30), type 2 diabetes (RR: 1.88; 1.61-2.19) and reduced kidney function (RR: 1.86; 1.48-2.34). For the community, top-ranked risk factors in women were menopause (PAF: 63%), obesity (PAF: 29%) and type 2 diabetes (PAF: 15%). Corresponding top-ranked risk factors in men were obesity (PAF: 29%), type 2 diabetes (PAF: 6.4%) and sedentary lifestyle (PAF: 6.0%).

CONCLUSIONS

Obesity and type 2 diabetes were the most important modifiable chylomicronemia risk factors in women and men, both for the individual and community. This could influence chylomicronemia prevention and help design randomized trials aimed at reducing triglycerides.

Clinical features and outcomes of severe, very severe, and extreme hypertriglyceridemia in a regional health service

BACKGROUND

Comprehensive data on severe hypertriglyceridemia (HTG) in the general population setting are limited and of importance due to the increase in metabolic risk factors and novel therapies under development.

OBJECTIVE

To investigate contributing causes and outcomes of severe to extreme HTG.

METHODS

Regional database retrospectively analyzed for subjects with severe HTG. Adverse outcomes were investigated in correlation to HTG severity, with follow-up initiating at first documentation of HTG > 1000 mg/dL.

RESULTS

A total of 3091 subjects with severe (peak triglycerides 1000-1999 mg/dL; n = 2590), very severe (2000-2999 mg/dL; n = 369), and extreme (≥3000 mg/dL; n = 132) HTG were identified. Mean age was 48 ± 12 years; 73% males. Obesity (48%) and diabetes (62%) were main contributing factors. During follow-up (median 101 months), 4.7% subjects had pancreatitis, 4.7% myocardial infarction, and 6% stroke. Compared with severe HTG, the multivariate-adjusted hazard ratio for pancreatitis was 3.22 (95% confidence interval 2.21-4.70) for individuals with very severe HTG and 5.55 (3.53-8.71) for those with extreme HTG, P < .0001. In contrast, the extent of HTG severity at these levels was not associated with worse cardiovascular outcomes or death. Most subjects (81%) achieved triglyceride levels <500 mg/dL, associated with lower risk for developing pancreatitis but not myocardial infarction or stroke.

CONCLUSIONS

Severity of HTG is closely related to cardiometabolic conditions, with a stepwise increase in the risk for pancreatitis, particularly if not attaining reduced triglyceride levels during the follow-up. In contrast, whereas mild-to-moderate HTG is a known established cardiovascular risk factor, very severe and extreme HTG may not further increase the risk for myocardial infarction, stroke, or mortality.

New medications targeting triglyceride-rich lipoproteins: Can inhibition of ANGPTL3 or apoC-III reduce the residual cardiovascular risk?

Remarkably good results have been achieved in the treatment of atherosclerotic cardiovascular diseases (CVD) by using statin, ezetimibe, antihypertensive, antithrombotic, and PCSK9 inhibitor therapies and their proper combinations. However, despite this success, the remaining CVD risk is still high. To target this residual risk and to treat patients who are statin-intolerant or have an exceptionally high CVD risk for instance due to familial hypercholesterolemia (FH), new therapies are intensively sought. One pathway of drug development is targeting the circulating triglyceride-rich lipoproteins (TRL) and their lipolytic remnants, which, according to the current view, confer a major CVD risk. Angiopoietin-like protein 3 (ANGPTL3) and apolipoprotein C-III (apoC-III) are at present the central molecular targets for therapies designed to reduce TRL, and there are new drugs emerging that suppress their expression or inhibit the function of these two key proteins. The medications targeting these components are biological, either human monoclonal antibodies or antisense oligonucleotides. In this article, we briefly review the mechanisms of action of ANGPTL3 and apoC-III, the reasons why they have been considered promising targets of novel therapies for CVD, as well as the current status and the most important results of their clinical trials.

Advances in lipid-lowering therapy through gene-silencing technologies

New treatment opportunities are emerging in the field of lipid-lowering therapy through gene-silencing approaches. Both antisense oligonucleotide inhibition and small interfering RNA technology aim to degrade gene mRNA transcripts to reduce protein production and plasma lipoprotein levels. Elevated levels of LDL, remnant lipoproteins, and lipoprotein(a) all cause cardiovascular disease, whereas elevated levels of triglyceride-rich lipoproteins in some patients can cause acute pancreatitis. The levels of each of these lipoproteins can be reduced using gene-silencing therapies by targeting proteins that have an important role in lipoprotein production or removal (for example, the protein products of ANGPTL3, APOB, APOC3, LPA, and PCSK9). Using this technology, plasma levels of these lipoproteins can be reduced by 50-90% with 2-12 injections per year; such dramatic reductions are likely to reduce the incidence of cardiovascular disease or acute pancreatitis in at-risk patients. The reported adverse effects of these new therapies include injection-site reactions, flu-like symptoms, and low blood platelet counts. However, newer-generation drugs are more efficiently delivered to liver cells, requiring lower drug doses, which leads to fewer adverse effects. Although these findings are promising, robust evidence of cardiovascular disease reduction and long-term safety is needed before these gene-silencing technologies can have widespread implementation. Before the availability of such evidence, these drugs might have roles in patients with unmet medical needs through orphan indications.

A Renewed Focus on the Association Between Thyroid Hormones and Lipid Metabolism

Thyroid dysfunction, manifesting as either overt or subclinical hypothyroidism, negatively affects lipid metabolism: this leads to hypercholesterolemia which progressively increases the risk for cardiovascular disease and, potentially, mortality. Hypercholesterolemia in hypothyroidism is mainly due to a reduction in low-density lipoprotein (LDL) receptor activity, this accompanied by concomitant diminishing control by triiodothyronine (T3) of sterol regulatory element-binding protein 2 (SREBP-2), which modulates cholesterol biosynthesis by regulating rate-limit degrading enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA) activity. Recently, 3,5-diiodothyronine (T2), a natural thyroid hormone derivative, was found to repress the transcription factor carbohydrate-response element-binding protein (ChREBP) and also to be involved in lipid catabolism and lipogenesis, though via a different pathway than that of T3. While thyroid hormone could therapeutically reverse the dyslipidemic profile commonly occurring in hypothyroidism, it should be borne in mind that the potency of the effects may be age-and sex-dependent. Thyroid hormone administration possibly also sustains and enhances the efficacy of hypolipidemic drugs, such as statins, ezetimibe and proprotein convertase subtilisin/kexin type 9 (PCSK9), in patients with dyslipidemia and hypothyroidism.

A Test in Context: Lipid Profile, Fasting Versus Nonfasting

Fasting for >8 h, as previously required for lipid profiles, normally only occurs a few hours before breakfast. By contrast, the nonfasting state predominates most of a 24-h cycle and better captures atherogenic lipoprotein levels. Plasma contains atherogenic lipoproteins of hepatic origin in the fasting state and additionally those of intestinal origin in the nonfasting state. Maximal mean changes for random, nonfasting versus fasting levels are +26 mg/dl for triglycerides, -8 mg/dl for total cholesterol, -8 mg/dl for low-density lipoprotein cholesterol, +8 mg/dl for remnant cholesterol, and -8 mg/dl for non-high-density lipoprotein cholesterol; lipoprotein(a), apolipoprotein B, and high-density lipoprotein cholesterol are largely unaffected. For patients, laboratories, and clinicians alike, nonfasting lipid profiles represent a simplification without negative implications for prognostic, diagnostic, and therapeutic options for cardiovascular disease prevention. Several societies' guidelines and statements in Denmark, the United Kingdom, Europe, Canada, Brazil, and the United States endorse nonfasting lipid profiles.

Animal models of atherosclerosis

Atherosclerosis is a significant cause of morbidity and mortality globally. Many animal models have been developed to study atherosclerosis, and permit experimental conditions, diet and environmental risk factors to be carefully controlled. Pathophysiological changes can be produced using genetic or pharmacological means to study the harmful consequences of different interventions. Experiments using such models have elucidated its molecular and pathophysiological mechanisms, and provided platforms for pharmacological development. Different models have their own advantages and disadvantages, and can be used to answer different research questions. In the present review article, different species of atherosclerosis models are outlined, with discussions on the practicality of their use for experimentation.

Nonfasting Mild-to-Moderate Hypertriglyceridemia and Risk of Acute Pancreatitis

IMPORTANCE

Severe hypertriglyceridemia is associated with increased risk of acute pancreatitis. However, the threshold above which triglycerides are associated with acute pancreatitis is unclear.

OBJECTIVE

To test the hypothesis that nonfasting mild-to-moderate hypertriglyceridemia (177-885 mg/dL; 2-10 mmol/L) is also associated with acute pancreatitis.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study examines individuals from the Copenhagen General Population Study in 2003 to 2015 and the Copenhagen City Heart Study initiated in 1976 to 1978 with follow-up examinations in 1981 to1983, 1991 to 1994, and in 2001 to 2003. Median follow-up was 6.7 years (interquartile range, 4.0-9.4 years); and includes 116 550 individuals with a triglyceride measurement from the Copenhagen General Population Study (n = 98 649) and the Copenhagen City Heart Study (n = 17 901). All individuals were followed until the occurrence of an event, death, emigration, or end of follow-up (November 2014), whichever came first.

EXPOSURES

Plasma levels of nonfasting triglycerides.

MAIN OUTCOMES AND MEASURES

Hazard ratios (HRs) for acute pancreatitis (n = 434) and myocardial infarction (n = 3942).

RESULTS

Overall, 116 550 individuals were included in this study (median [interquartile range] age, 57 [47-66] years). Compared with individuals with plasma triglyceride levels less than 89 mg/dL (<1 mmol/L), the multivariable adjusted HRs for acute pancreatitis were 1.6 (95% CI, 1.0-2.6; 4.3 events/10 000 person-years) for individuals with triglyceride levels of 89 mg/dL to 176 mg/dL (1.00 mmol/L-1.99 mmol/L), 2.3 (95% CI, 1.3-4.0; 5.5 events/10 000 person-years) for 177 mg/dL to 265 mg/dL (2.00 mmol/L-2.99 mmol/L), 2.9 (95% CI, 1.4-5.9; 6.3 events/10 000 person-years) for 366 mg/dL to 353 mg/dL (3.00 mmol/L-3.99 mmol/L), 3.9 (95% CI, 1.5-10.0; 7.5 events/10 000 person-years) for 354 mg/dL-442 mg/dL (4.00 mmol/L-4.99 mmol/L), and 8.7 (95% CI, 3.7-20.0; 12 events/10 000 person-years) for individuals with triglyceride levels greater than or equal to 443 mg/dL (≥5.00 mmol/L) (trend, P = 6 × 10-8). Corresponding HRs for myocardial infarction were 1.6 (95% CI, 1.4-1.9; 41 events/10 000 person-years), 2.2 (95% CI, 1.9-2.7; 57 events/10 000 person-years), 3.2 (95% CI, 2.6-4.1; 72 events/10 000 person-years), 2.8 (95% CI, 2.0-3.9; 68 events/10 000 person-years), and 3.4 (95% CI, 2.4-4.7; 78 events/10 000 person-years) (trend, P = 6 × 10-31), respectively. The multivariable adjusted HR for acute pancreatitis was 1.17 (95% CI, 1.10-1.24) per 89 mg/dL (1 mmol/L) higher triglycerides. When stratified by sex, age, education, smoking, hypertension, statin use, study cohort, diabetes, body mass index (calculated as weight in kilograms divided by height in meters squared), alcohol intake, and gallstone disease, these results were similar with no statistical evidence of interaction.

CONCLUSIONS AND RELEVANCE

Nonfasting mild-to-moderate hypertriglyceridemia from 177 mg/dL (2 mmol/L) and above is associated with high risk of acute pancreatitis, with HR estimates higher than for myocardial infarction.

Discrepant association of serum C-3 epimer of 25-hydroxyvitamin D versus non-epimeric 25-hydroxyvitamin D with serum lipid levels

Background

Low vitamin D status has been associated with a number of chronic diseases. For dyslipidemia, vitamin D deficiency has been associated with higher low density lipoprotein-cholesterol (LDL-C) in a number of studies, but with inconsistent results in clinical trials. The purpose of the present study is to explore the relative importance of 3-epi-25-hydroxyvitamin D (25(OH)D) as compared with the non-epimeric form in relation to serum lipid.

Method

This study used data from 1068 randomly selected volunteers in the Thai 4^th National Health Examination Survey (NHES IV). Serum 25(OH)D₂, 25(OH)D₃, 3-epi-25(OH)D₂ and 3-epi-25(OH)D₃ were analyzed by liquid chromatography–tandem mass spectrometry.

Results

There was no association between serum total 25(OH)D and serum LDL-C. However, circulating 3-epi-25(OH)D₃ was negatively related to serum LDL-C (r = −0.077, P <0.05), while no such association was found for non-epimeric 25(OH)D₃ (r =0.030, P = 0.33). On the other hand, both 3-epi-25(OH)D₃ (r = 0.175, P <0.001) and non-epimeric 25(OH)D₃ (r = 0.142, P <0.001) were positively related to serum triglyceride (TRIG) levels. In multiple linear regression models with age, gender, body mass index , urban residence, education, hypertension and education as covariates, it was found that 3-epi-25(OH)D₃ was independently associated with serum LDL-C (beta = −0.12, P <0.01), while non-epimeric 25(OH)D₃ was positively related to LDL-C (beta = 0.13, P = 0.002). For TRIG, there were positive association with 3-epi-25(OH)D₃ (beta = 0.27, P <0.001) and negative association with non-epimeric 25(OH)D₃ (beta = − 0.10, P = 0.011) independent of age, gender, urban resident and education.

Conclusions

There is a discrepant association of 25(OH)D levels with serum lipids according to 25(OH)D epimeric forms.

Rabbit models for the study of human atherosclerosis: from pathophysiological mechanisms to translational medicine

Laboratory animal models play an important role in the study of human diseases. Using appropriate animals is critical not only for basic research but also for the development of therapeutics and diagnostic tools. Rabbits are widely used for the study of human atherosclerosis. Because rabbits have a unique feature of lipoprotein metabolism (like humans but unlike rodents) and are sensitive to a cholesterol diet, rabbit models have not only provided many insights into the pathogenesis and development of human atherosclerosis but also made a great contribution to translational research. In fact, rabbit was the first animal model used for studying human atherosclerosis, more than a century ago. Currently, three types of rabbit model are commonly used for the study of human atherosclerosis and lipid metabolism: (1) cholesterol-fed rabbits, (2) Watanabe heritable hyperlipidemic rabbits, analogous to human familial hypercholesterolemia due to genetic deficiency of LDL receptors, and (3) genetically modified (transgenic and knock-out) rabbits. Despite their importance, compared with the mouse, the most widely used laboratory animal model nowadays, the use of rabbit models is still limited. In this review, we focus on the features of rabbit lipoprotein metabolism and pathology of atherosclerotic lesions that make it the optimal model for human atherosclerotic disease, especially for the translational medicine. For the sake of clarity, the review is not an attempt to be completely inclusive, but instead attempts to summarize substantial information concisely and provide a guideline for experiments using rabbits.

Use of Mouse Models in Atherosclerosis Research

Cardiovascular disease is the major cause of death in most developed nations and the social and economic burden of this disease is quite high. Atherosclerosis is a major underlying basis for most cardiovascular diseases including myocardial infarction and stroke. Genetically modified mouse models, particularly mice deficient in apoprotein E or the LDL receptor, have been widely used in preclinical atherosclerosis studies to gain insight into the mechanisms underlying this pathology. This chapter reviews several mouse models of atherosclerosis progression and regression as well as the role of immune cells in disease progression and the genetics of murine atherogenesis.

Triglycerides and cardiovascular disease

After the introduction of statins, clinical emphasis first focussed on LDL cholesterol-lowering, then on the potential for raising HDL cholesterol, with less focus on lowering triglycerides. However, the understanding from genetic studies and negative results from randomised trials that low HDL cholesterol might not cause cardiovascular disease as originally thought has now generated renewed interest in raised concentrations of triglycerides. This renewed interest has also been driven by epidemiological and genetic evidence supporting raised triglycerides, remnant cholesterol, or triglyceride-rich lipoproteins as an additional cause of cardiovascular disease and all-cause mortality. Triglycerides can be measured in the non-fasting or fasting states, with concentrations of 2-10 mmol/L conferring increased risk of cardiovascular disease, and concentrations greater than 10 mmol/L conferring increased risk of acute pancreatitis and possibly cardiovascular disease. Although randomised trials showing cardiovascular benefit of triglyceride reduction are scarce, new triglyceride-lowering drugs are being developed, and large-scale trials have been initiated that will hopefully provide conclusive evidence as to whether lowering triglycerides reduces the risk of cardiovascular disease.

Low Nonfasting Triglycerides and Reduced All-Cause Mortality: A Mendelian Randomization Study

BACKGROUND

Increased nonfasting plasma triglycerides marking increased amounts of cholesterol in remnant lipoproteins are important risk factors for cardiovascular disease, but whether lifelong reduced concentrations of triglycerides on a genetic basis ultimately lead to reduced all-cause mortality is unknown. We tested this hypothesis.

METHODS

Using individuals from the Copenhagen City Heart Study in a mendelian randomization design, we first tested whether low concentrations of nonfasting triglycerides were associated with reduced all-cause mortality in observational analyses (n = 13 957); second, whether genetic variants in the triglyceride-degrading enzyme lipoprotein lipase, resulting in reduced nonfasting triglycerides and remnant cholesterol, were associated with reduced all-cause mortality (n = 10 208).

RESULTS

During a median 24 and 17 years of 100% complete follow-up, 9991 and 4005 individuals died in observational and genetic analyses, respectively. In observational analyses compared to individuals with nonfasting plasma triglycerides of 266–442 mg/dL (3.00–4.99 mmol/L), multivariably adjusted hazard ratios for all-cause mortality were 0.89 (95% CI 0.78–1.02) for 177–265 mg/dL (2.00–2.99 mmol/L), 0.74 (0.65–0.84) for 89–176 mg/dL (1.00–1.99 mmol/L), and 0.59 (0.51–0.68) for individuals with nonfasting triglycerides &lt;89 mg/dL (&lt;1.00 mmol/L). The odds ratio for a genetically derived 89-mg/dL (1-mmol/L) lower concentration in nonfasting triglycerides was 0.50 (0.30–0.82), with a corresponding observational hazard ratio of 0.87 (0.85–0.89). Also, the odds ratio for a genetically derived 50% lower concentration in nonfasting triglycerides was 0.43 (0.23–0.80), with a corresponding observational hazard ratio of 0.73 (0.70–0.77).

CONCLUSIONS

Genetically reduced concentrations of nonfasting plasma triglycerides are associated with reduced all-cause mortality, likely through reduced amounts of cholesterol in remnant lipoproteins.

Relaxation of porcine retinal arterioles exposed to hypercholesterolemia in vivo is modified by hepatic LDL-receptor deficiency and diabetes mellitus

Metabolic disturbances in diabetes mellitus include changes in the type and concentration of lipids in the blood plasma which may contribute to the development of diabetic retinopathy. This disease is characterized by changes in retinal blood flow secondary to changes in the tone of retinal arterioles which is regulated by compounds such as adenosine, adenosine triphosphate (ATP), the glutamate agonist N-methyl-d-aspartate (NMDA) and prostaglandin E2 (PGE2). However, the relation between increased plasma low density lipoprotein (LDL) and tone regulation in retinal resistance vessels has not been studied in detail. Twelve male and nine female Yucatan minipigs overexpressing a gain-of-function mutant (D374Y) of the human gene PCSK9 that blocks LDL transport into the liver and twelve wild-type males were studied. The animals were fed a cholesterol rich diet from the age of 60 days, followed by induction of diabetes mellitus in twelve of the transgenic animals. The animals were sacrificed at a mean age of 51 weeks (range 26-60 weeks), followed by inspection and histological examination of retinal vessels, and examination of the changes in vascular tone induced by adenosine, ATP, NMDA and PGE2. In the transgenic pigs without diabetes mellitus ATP-induced relaxation was reduced in isolated arterioles, and a whitish infiltration in an arteriole was observed in 4/8 (50%) of the animals, whereas these changes were not found in the other groups. Histological examination of one of the infiltrations showed staining with Oil Red O representing foamy cells sub-endothelially in the vascular wall indicating atheromatosis. Adenosine, ATP and PGE2 induced a significant concentration-dependent relaxation of retinal arterioles in all groups. The presence of perivascular retinal tissue had no effect on the relaxing effect of adenosine, but increased the relaxing effect of ATP and PGE2 in the two transgenic animal groups, whereas NMDA had no significant effect on vascular tone in any of the groups. Relaxation of porcine retinal arterioles exposed to hypercholesterolemia in vivo is modified by hepatic LDL-receptor deficiency and diabetes mellitus. This suggests that transgenic animal models are suitable for studying the influence of systemic diseases on retinal vascular function.