Lipoprotein(a) and Atherosclerotic Cardiovascular Disease, the Impact of Available Lipid-Lowering Medications on Lipoprotein(a): An Update on New Therapies

OBJECTIVE

To review evidence of existing and new pharmacological therapies for lowering lipoprotein(a) (Lp[a]) concentrations and their impact on clinically relevant outcomes.

METHODS

We searched for literature pertaining to Lp(a) and pharmacological treatments in PubMed. We reviewed articles published between 1963 and 2020.

RESULTS

We found that statins significantly increased Lp(a) concentrations. Therapies that demonstrated varying degrees of Lp(a) reduction included ezetimibe, niacin, proprotein convertase subtilisin/kexin type 9 inhibitors, lipoprotein apheresis, fibrates, aspirin, hormone replacement therapy, antisense oligonucleotide therapy, and small interfering RNA therapy. There was limited data from large observational studies and post hoc analyses showing the potential benefits of these therapies in improving cardiovascular outcomes.

CONCLUSION

There are multiple lipid-lowering agents currently being used to treat hyperlipidemia that also have a Lp(a)-lowering effect. Two RNA therapies specifically targeted to lower Lp(a) are being investigated in phase 3 clinical trials and, thus far, have shown promising results. However, evidence is lacking to determine the clinical relevance of reducing Lp(a). At present, there is a need for large-scale, randomized, controlled trials to evaluate cardiovascular outcomes associated with lowering Lp(a).

Evaluation of the chylomicron-TG to VLDL-TG ratio for type I hyperlipoproteinemia diagnostic

BACKGROUND

The aim of this study is to confirm the diagnostic performance of the Chylomicron to very low-density lipoproteins triglycerides (CM/VLDL-TG) ratio, the triglycerides to cholesterol ratio (TG/TC) and a dichotomic rule including the tryglycerides to apolipoprotein B (TG/APOB) ratio for the presence of Type I hyperlipoproteinemia (HPLI) in patients with severe hypertriglyceridemia (sHTG) that were at high risk for familial chylomicronemia syndrome (FCS).

METHODS

Two cohorts (derivation and validation) of patients with sHTG were included in the study. Anthropometric, clinical, biochemical and genetic data were obtained. The CM/VLDL-TG, TG/TC and TG/APOB ratios were calculated. Finally, a diagnostic performance study was developed to establish sensitivity, specificity and cut-offs by a ROC curve analysis in the derivation cohort as well as agreement and predictive values in the validation cohort.

RESULTS

Patients with FCS in both cohorts showed an earlier presence in pancreatitis, greater number of acute pancreatitis episodes and lower BMI. FCS patients also showed higher ratios of CM/VLDL-TG, TG/TC and TG/APOB ratios, whereas their HDL-C, LDL-C and APOB levels were lower than in non-FCS patients. Sensitivity and agreement were low for both the TG/TC and TG/APOB ratios, although predictive values were good. The CM/VLDL-TG ratio showed greatest sensitivity, specificity, agreement and predictive values for cut-off of 3.8 and 4.5.

CONCLUSIONS

Our results suggest that in subjects at high risk of FCS a total serum TG/TC ratio or TG/APOB ratio are feasible to initially screen for HLPI; however, a CM/VLDL-TG ratio ≥4.5 is a better diagnostic criterion for HPLI.

Modern prevalence of the Fredrickson-Levy-Lees dyslipidemias: findings from the Very Large Database of Lipids and National Health and Nutrition Examination Survey

INTRODUCTION

Five decades ago, Fredrickson, Levy, and Lees (FLL) qualitatively characterized clinical dyslipidemias with specific implications for cardiovascular and non-cardiovascular morbidity and mortality. They separated disorders of elevated cholesterol and triglycerides into five phenotypes (types I-V) based on their lipoprotein profile. Although clinicians generally consider them rare entities, modern FLL prevalence may be greater than previously reported.

MATERIAL AND METHODS

We performed a cross-sectional analysis in 5,272 participants from the 2011-2014 National Health and Nutrition Examination Survey and 128,506 participants from the Very Large Database of Lipids study with complete, fasting lipid profiles. We used a validated algorithm to define FLL phenotypes employing apolipoprotein B, total cholesterol, and triglycerides.

RESULTS

Overall prevalence of FLL phenotypes was 33.9%. FLL prevalence in the general population versus clinical lipid database was: type I (0.05 vs. 0.02%), type IIa (3.2 vs. 3.9%), type IIb (8.0 vs. 10.3%), type III (2.0 vs. 1.7%), type IV (20.5 vs. 24.1%), and type V (0.15 vs. 0.13%). Those aged 40-74 years had a higher overall prevalence compared to other age groups (p < 0.001) and men had overall higher prevalence than women (p < 0.001). Those with diabetes (51.6%) or obese BMI (49.0%) had higher prevalence of FLL phenotypes compared to those without diabetes (31.3%; p < 0.001) and normal BMI (18.3%; p < 0.001).

CONCLUSIONS

FLL phenotypes are likely far more prevalent than appreciated in clinical practice, in part due to diabetes and obesity epidemics. Given the prognostic and therapeutic importance of these phenotypes, their identification becomes increasingly important in the era of precision medicine.

Severe hypertriglyceridemia presenting as eruptive xanthomatosis

Eruptive xanthomatosis is described as the sudden eruption of erythematous yellow papules in the presence of hypertriglyceridemia, often associated with serum triglyceride levels above 2000 mg/dl. Severe hypertriglyceridemia can be caused by primary genetic mutations, secondary chronic diseases, or a combination of both. Uncontrolled diabetes mellitus is a known risk factor. It is imperative for physicians to be aware of eruptive xanthomatosis as a warning sign for severe hypertriglyceridemia due to the underlying risk for the potentially fatal complication of acute pancreatitis. Herein, we discuss a case of a 52-year-old man with uncontrolled diabetes mellitus who presented with eruptive xanthomata and a triglyceride level of 7157 mg/dl, the highest recorded value in the absence of acute pancreatitis, with a remarkable response to drug therapy. A review of the literature is included to discuss the clinical relevance and appropriate treatment of this disease entity.

[Hyperlipoprotienemias and (not only) atherosclerosis: fragments from history and present]

The examples from the history, as well as the recent view, clearly demonstrate a great change in the perception of hyperlipoprotienemias and dyslipidemias (HLP and DLP) at the end of 20th and at the beginning of 21st century. Our aim is not a complex overview about HLP and DLP. We just want to describe the changing position and importance of these diseases in clinical medicine. We will touch cardiology, angiology, but also diabetology, hepatology and gastroenterology (pancreas). HLP and DLP, which started as a research topic in laboratory became clinically interesting as risk factors of atherosclerosis. They are understood as epidemic occurrence diseases, also in connection with metabolic syndrome. However, some of them, e.g. familial chylomicronemia or homozygous familial hypercholesterolemia fulfill criteria of rare diseases.

Whole-exome sequencing reveals GPIHBP1 mutations in infantile colitis with severe hypertriglyceridemia

Severe congenital hypertriglyceridemia (HTG) is a rare disorder caused by mutations in genes affecting lipoprotein lipase (LPL) activity. Here we report a 5-week-old Hispanic girl with severe HTG (12,031 mg/dL, normal limit 150 mg/dL) who presented with the unusual combination of lower gastrointestinal bleeding and milky plasma. Initial colonoscopy was consistent with colitis, which resolved with reduction of triglycerides. After negative sequencing of the LPL gene, whole-exome sequencing revealed novel compound heterozygous mutations in GPIHBP1. Our study broadens the phenotype of GPIHBP1-associated HTG, reinforces the effectiveness of whole-exome sequencing in Mendelian diagnoses, and implicates triglycerides in gastrointestinal mucosal injury.

Adipocyte triglyceride turnover is independently associated with atherogenic dyslipidemia

BACKGROUND

Inappropriate storage of fatty acids as triglycerides in adipocytes and their removal from adipocytes through lipolysis and subsequent oxidation may cause the atherogenic dyslipidemia phenotype of elevated apolipoprotein B levels and subsequent hypertriglyceridemia. We tested whether turnover of triglycerides in fat cells was related to dyslipidemia.

METHODS AND RESULTS

The age of triglycerides (reflecting removal) and triglyceride storage in adipocytes was determined under free living conditions by measuring incorporation of atmospheric (14)C into these lipids within the adipocytes in 47 women and 26 men with a large interindividual variability in body mass index. Because limited (14)C data were available, triglyceride age was also determined in 97 men and 233 women by using an algorithm based on adipocyte lipolysis, body fat content, waist-to-hip ratio, and insulin sensitivity. This cohort consisted of nonobese subjects since obesity per se is related to all components in the algorithm. Triglyceride turnover (age and storage) was compared with plasma levels of apolipoproteins and lipids. Plasma levels of apolipoprotein B and triglycerides were positively related to triglyceride age in adipocytes, when measured directly using radiocarbon analyses (r=0.45 to 0.47; P<0.0001). This effect was independent of subject age, waist circumference measures, and insulin sensitivity (partial r=0.29 to 0.45; P from 0.03 to <0.0001). Triglyceride storage showed no independent correlation (partial r=0.02 to 0.11; P=0.42 to 0.91). Algorithm-based values for adipocyte removal of triglycerides were positively associated with plasma triglycerides and apolipoprotein B (r=0.44 to 0.45; P<0.0001) and (also positively) with the inflammation status of adipose tissue (r=0.39 to 0.47; P<0.05). These correlations were statistically independent of subject age and observed in men and women as well as in lean and overweight subjects when subgroups were examined separately.

CONCLUSIONS

Decreased removal of adipocyte triglycerides (as indicated by a high triglyceride age in fat cells) is independently associated with circulating apolipoprotein B and triglycerides. This suggests a hitherto unknown role of triglyceride turnover in adipocytes for the development and/or maintenance of atherogenic dyslipidemia.

Palmar xanthoma-an indicator of a more sinister problem

Multiple palmar xanthomas may often be seen first by the hand surgeon. One such case presented to us in the hand clinic. Further investigations revealed the presence of a more sinister metabolic problem of type III hyperlipoproteinemia. We discuss the details of this case and review relevant literature on the subject.

The clinical effect and tolerability of ezetimibe in high-risk patients managed in a specialty cardiovascular risk reduction clinic

INTRODUCTION

Ezetimibe (EZ) is a selective cholesterol absorption inhibitor approved for use in Canada. The effect and tolerability of EZ among patients was evaluated in the clinical setting of a specialty cardiovascular risk reduction clinic at the University of Alberta Hospital, Edmonton, Alberta. patients and

METHODS

All patients 18 years of age or older who were prescribed EZ were included, unless they failed to take EZ for a minimum of two weeks, did not have baseline and on-EZ low-density lipoprotein cholesterol (LDL-C) levels, or had concomitant lipid-lowering drugs or dosages changed within one month of starting EZ.

RESULTS

Eighty-four patients (mean age 57.9 years) were included. By Framingham risk calculation, 71.4% were found to be high-risk patients, 13.1% moderate-risk patients and 15.5% low-risk patients; 66.7% of patients had prior cardiovascular events. On EZ, the mean reductions were: total cholesterol level 1.11 mmol/L (16.5%); LDL-C level 1.01 mmol/L (22.3%); high-density lipoprotein cholesterol level 0.06 mmol/L (4.6%); and ratio of total cholesterol level to high-density lipoprotein cholesterol level 0.68 mmol/L (12.8%); all were statistically significant (P<0.001). Results were similar when stratified by primary (n=28) versus secondary (n=56) prevention. Patients on EZ monotherapy (n=34) had mean LDL-C reductions of 1.03 mmol/L (20.5%) compared with 1.19 mmol/L (30.1%) or 0.95 mmol/L (22.5%), where EZ was added to low-dose or high-dose statins (P<0.01 for all). On EZ, 30 patients (35.7%) achieved previously unattainable target LDL-C levels. Four patients discontinued the drug due to side effects.

CONCLUSIONS

EZ is safe and effective in high-risk patients treated in the clinical setting of a cardiovascular risk reduction clinic. A mean LDL-C reduction of 1 mmol/L (20% to 30%) in all patient subgroups is consistent with previous clinical trial results. The significant reduction in LDL-C (mean 22.5%) observed in the EZ plus high-dose statin subgroup provides clinical evidence for use of this medication beyond published studies.

Recurrent acute pancreatitis in a patient with type IIb hyperlipoproteinemia: a case report and review of the literature in Korea

Hyperlipidemia is a rare cause of pancreatitis. It has been believed that free fatty acids released from hydrolyzed serum chylomicrons or triglycerides and chylomicrons induce hyperlipidemic pancreatitis by damaging acinar cells and capillaries. Type I, IV or V hyperlipidemic (Fredrickson's classification) pancreatitides have distinctive features of increased and heightened serum chylomicron and triglyceride levels. In contrast, type IIb hyperlipidemia usually doesn't have increased chylomicrons. It is a dominant inherited genetic disorder and doesn't manifest the subjective symptom before combining vascular complications such as coronary artery disease. Only a few cases of type IIb hyperlipidemic pancreatitis have been reported. We experienced a male patient with recurrent hyperlipidemic pancreatitis combined with type IIb hyperlipidemia. We present the case report and a review of the literature of hyperlipidemic pancreatitis, especially cases in Korea.

Clinical efficacy of the direct assay method using polymers for serum high density lipoprotein cholesterol

The clinical efficacy and accuracy of the homogeneous assay method for the serum high density lipoprotein (HDL)-cholesterol determination were evaluated. The principle is as follows: low density lipoproteins (LDL) and very low density lipoproteins (VLDL) were coated by polymers and polyanion to be blocked from cholesterol esterase and cholesterol oxidase. The reaction of these enzymes for HDL cholesterol was enhanced with a detergent, and HDL cholesterol was selectively measured. Both within-run (n = 3, 20 times) and between-run (n = 3, 7 days) CVs were < 2%. The repeated freezing and thawing (4 times) of three distinct sera resulted in no changes of HDL cholesterol values. Additions of lipid emulsion (Triglyceride = 100 mg/dl) and free bilirubin (20 mg/dl) gave no effect. Linearity was found up to 300 mg/dl. Increases in HDL cholesterol values by the addition of VLDL (total cholesterol (TC) = 300 mg/dl) or LDL (TC = 300 mg/dl) to the tested sera were < 0.5%. The correlation coefficient of the new method with a precipitation method was 0.995 (n = 64). HDL-C values for patients with hyperlipidemia (Type IIa, IIb, or III, IV, and V) by this method were comparable with those obtained by the precipitation method. From these results, we concluded that the new method meets the requirements for accuracy, precision, ease of handling massive samples, and was clinically useful.