Lp(a) is not associated with diabetes but affects fibrinolysis and clot structure ex vivo

Beyond cholesterol-pleiotropic effects of lipoprotein apheresis

Cardiovascular disease is a leading cause of mortality worldwide, which is caused mainly by atherosclerosis, a chronic inflammatory disease of blood vessels. Therefore, atherosclerosis represents a complex disorder, which induces damage or imbalance on different levels: for example, genes, cytokines, lipoproteins, cells, vessels, and organs. Lipoprotein apheresis (LA) is a well-established extracorporeal treatment of severe hyperlipoproteinemia. In addition, LA may have simultaneously crucial effects on many other atherogenic factors during the treatments, for example, as vascular inflammation, rheology, mobilization of adult stem cells and gene expressions in blood or endothelial cells, which will be discussed in this short review. In addition, stable microRNAs besides tissues also appear in extracellular compartments, for example, vessels, involved in atherosclerotic processes, were found to be reduced by LA treatments. In summary, LA represents a complex therapeutic procedure, that provides an ideal tool for the treatment of complex disorders such as atherosclerosis.

Expert position statements: comparison of recommendations for the care of adults and youth with elevated lipoprotein(a)

PURPOSE OF REVIEW

Summarize recent recommendations on clinical management of adults and youth with elevated lipoprotein(a) [Lp(a)] who are at-risk of or affected by cardiovascular disease (CVD).

RECENT FINDINGS

There is ample evidence to support elevated Lp(a) levels, present in approximately 20% of the general population, as a causal, independent risk factor for CVD and its role as a significant risk enhancer. Several guidelines and position statements have been published to assist in the identification, treatment and follow-up of adults with elevated levels of Lp(a). There is growing interest in Lp(a) screening and strategies to improve health behaviors starting in youth, although published recommendations for this population are limited. In addition to the well established increased risk of myocardial infarction, stroke and valvular aortic stenosis, data from the coronavirus pandemic suggest adults with elevated Lp(a) may have a particularly high-risk of cardiovascular complications. Lp(a)-specific-lowering therapies are currently in development. Despite their inability to lower Lp(a), use of statins have been shown to improve outcomes in primary and secondary prevention.

SUMMARY

Considerable differences exist amongst published guidelines for adults on the use of Lp(a) in clinical practice, and recommendations for youth are limited. With increasing knowledge of Lp(a)'s role in CVD, including recent observations of COVID-19-related risk of cardiovascular complications, more harmonized and comprehensive guidelines for Lp(a) in clinical practice are required. This will facilitate clinical decision-making and help define best practices for identification and management of elevated Lp(a) in adults and youth.

Identification and analyses of inhibitors targeting apolipoprotein(a) kringle domains KIV-7, KIV-10, and KV provide insight into kringle domain function

Increased plasma concentrations of lipoprotein(a) (Lp(a)) are associated with an increased risk for cardiovascular disease. Lp(a) is composed of apolipoprotein(a) (apo(a)) covalently bound to apolipoprotein B of low-density lipoprotein (LDL). Many of apo(a)'s potential pathological properties, such as inhibition of plasmin generation, have been attributed to its main structural domains, the kringles, and have been proposed to be mediated by their lysine-binding sites. However, available small-molecule inhibitors, such as lysine analogs, bind unselectively to kringle domains and are therefore unsuitable for functional characterization of specific kringle domains. Here, we discovered small molecules that specifically bind to the apo(a) kringle domains KIV-7, KIV-10, and KV. Chemical synthesis yielded compound AZ-05, which bound to KIV-10 with a K_d of 0.8 μm and exhibited more than 100-fold selectivity for KIV-10, compared with the other kringle domains tested, including plasminogen kringle 1. To better understand and further improve ligand selectivity, we determined the crystal structures of KIV-7, KIV-10, and KV in complex with small-molecule ligands at 1.6-2.1 Å resolutions. Furthermore, we used these small molecules as chemical probes to characterize the roles of the different apo(a) kringle domains in in vitro assays. These assays revealed the assembly of Lp(a) from apo(a) and LDL, as well as potential pathophysiological mechanisms of Lp(a), including (i) binding to fibrin, (ii) stimulation of smooth-muscle cell proliferation, and (iii) stimulation of LDL uptake into differentiated monocytes. Our results indicate that a small-molecule inhibitor targeting the lysine-binding site of KIV-10 can combat the pathophysiological effects of Lp(a).

Potent reduction of plasma lipoprotein (a) with an antisense oligonucleotide in human subjects does not affect ex vivo fibrinolysis

It is postulated that lipoprotein (a) [Lp(a)] inhibits fibrinolysis, but this hypothesis has not been tested in humans due to the lack of specific Lp(a) lowering agents. Patients with elevated Lp(a) were randomized to antisense oligonucleotide [IONIS-APO(a)_Rx] directed to apo(a) (n = 7) or placebo (n = 10). Ex vivo plasma lysis times and antigen concentrations of plasminogen, factor XI, plasminogen activator inhibitor 1, thrombin activatable fibrinolysis inhibitor, and fibrinogen at baseline, day 85/92/99 (peak drug effect), and day 190 (3 months off drug) were measured. The mean ± SD baseline Lp(a) levels were 477.3 ± 55.9 nmol/l in IONIS-APO(a)_Rx and 362.1 ± 89.9 nmol/l in placebo. The mean± SD percentage change in Lp(a) for IONIS-APO(a)_Rx was -69.3 ± 12.2% versus -5.4 ± 6.9% placebo (P < 0.0010) at day 85/92/99 and -15.6 ± 8.9% versus 3.2 ± 12.2% (P = 0.003) at day 190. Clot lysis times and coagulation/fibrinolysis-related biomarkers showed no significant differences between IONIS-APO(a)_Rx and placebo at all time points. Clot lysis times were not affected by exogenously added Lp(a) at concentrations up to 200 nmol/l to plasma with very low (12.5 nmol/l) Lp(a) levels, whereas recombinant apo(a) had a potent antifibrinolytic effect. In conclusion, potent reductions of Lp(a) in patients with highly elevated Lp(a) levels do not affect ex vivo measures of fibrinolysis; the relevance of any putative antifibrinolytic effects of Lp(a) in vivo needs further study.

Insulin Resistance Index and Proatherogenic Lipid Indices in the Offspring of People with Diabetes

<b><i>Background:</i></b> Diabetes mellitus and cardiovascular diseases significantly contribute to medical morbidity and mortality worldwide, especially in developing countries like Nigeria. Insulin resistance, a characteristic finding of type 2 diabetics and their offspring, is associated with an abnormal lipid metabolism and cardiovascular disease. <b><i>Aims:</i></b> This study therefore aims to determine the pattern of lipid biomarkers of atherogenesis and their relationship with insulin resistance index in young people with a family history of diabetes mellitus. <b><i>Methods:</i></b> This is a cross-sectional study carried out among 150 apparently healthy young adults between 18 and 25 years of age, including 76 with a family history of diabetes mellitus in first- and/or second-degree relatives (YWFH) and 74 with no family history of diabetes mellitus (YWoFH). Anthropometric characteristics, insulin resistance index, plasma glucose, fasting lipid profile (plasma total cholesterol, triglycerides [TG], high-density lipoprotein cholesterol, low-density lipoprotein cholesterol), and serum levels of insulin, lipoprotein(a) [Lp(a)], apolipoprotein B (ApoB), apolipoprotein A-1 (ApoA-1), and ApoB/ApoA-1 ratios were compared in the 2 groups. Plasma glucose, total cholesterol, high-density cholesterol, and TG were measured using standard methods. The Friedewald equation was used to calculate low-density cholesterol. Serum insulin, Lp(a) levels, ApoB, and ApoA-1 were also measured using standard assays. The insulin resistance index was determined using homeostatic model assessment (HOMA). Statistical analysis was performed using SPSS version 20.0. Comparisons between variables were performed using the Mann-Whitney U test, and correlations between variables were performed using Spearman rank correlation coefficients. The level of significance was set at <i>p</i> &#x3c; 0.05. <b><i>Results:</i></b> Offspring of diabetics (YWFH) had a significantly higher median BMI (<i>p</i> = 0.015), waist-to-hip ratio (WHR; <i>p</i> = 0.002), insulin resistance index (<i>p</i> = 0.038), total cholesterol (<i>p</i> = 0.017), TG (<i>p</i> = 0.004), Lp(a) (<i>p</i> = 0.045), ApoB (<i>p</i> = 0.002), and ApoB/ApoA-1 ratio (<i>p</i> = 0.001) than the age-matched control group with no family history of diabetes mellitus (YWoFH). There was no correlation between the insulin resistance index and each of the lipid biomarkers of atherogenesis except Lp(a), with which it was negatively correlated. <b><i>Conclusion:</i></b> This study demonstrates that a positive family history of type 2 diabetes mellitus is associated with a higher insulin resistance index and elevated atherogenic lipid indices; thus, a positive family history of diabetes mellitus in first or second-degree relatives when the index person is not diabetic confirms a significant cardiovascular risk.

Serum Lipoprotein (a) Levels in Black South African Type 2 Diabetes Mellitus Patients

Lipoprotein (a) (Lp(a)) which is a low-density lipoprotein-like particle containing apo(a) is considered as an emergent cardiovascular risk factor. Type 2 diabetes mellitus (T2DM) is associated with a two- to threefold increase in the risk of cardiovascular disease (CVD). The aim of this study was to investigate the levels of Lp(a) in Black South African T2DM patients and its association with other metabolic factors. 67 T2DM patients and 48 healthy control participants were recruited for the cross-sectional study. The Lp(a) level was determined by ELISA and the result was analyzed using SPSS. The Lp(a) level in diabetics was found to be significantly increased (P = 0.001) when compared to the normal healthy group. In the diabetic group, the Lp(a) levels correlated significantly with the duration of diabetes (P = 0.008) and oxidized LDL (ox-LDL) levels (P = 0.03) and decreased total antioxidant capacity (P = 0.001). The third tertile of Lp(a) was significantly correlated with increased ox-LDL, C-reactive protein, and triglycerides and decreased total antioxidant capacity.

Effect of Two Lipoprotein (a)-Associated Genetic Variants on Plasminogen Levels and Fibrinolysis

Two genetic variants (rs3798220 and rs10455872) in the apolipoprotein (a) gene (LPA) have been implicated in cardiovascular disease (CVD), presumably through their association with lipoprotein (a) [Lp(a)] levels. While Lp(a) is recognized as a lipoprotein with atherogenic and thrombogenic characteristics, it is unclear whether or not the two Lp(a)-associated genetic variants are also associated with markers of thrombosis (i.e., plasminogen levels and fibrinolysis). In the present study, we genotyped the two genetic variants in 2919 subjects of the Old Order Amish (OOA) and recruited 146 subjects according to the carrier and noncarrier status for rs3798220 and rs10455872, and also matched for gender and age. We measured plasma Lp(a) and plasminogen levels in these subjects, and found that the concentrations of plasma Lp(a) were 2.62- and 1.73-fold higher in minor allele carriers of rs3798220 and rs10455872, respectively, compared with noncarriers (P = 2.04 × 10⁻¹⁷ and P = 1.64 × 10⁻⁶, respectively). By contrast, there was no difference in plasminogen concentrations between carriers and noncarriers of rs3798220 and rs10455872. Furthermore, we observed no association between carrier status of rs3798220 or rs10455872 with clot lysis time. Finally, plasminogen mRNA expression in liver samples derived from 76 Caucasian subjects was not significantly different between carriers and noncarriers of these two genetic variants. Our results provide further insight into the mechanism of action behind two genetic variants previously implicated in CVD risk and show that these polymorphisms are not major modulating factors for plasma plasminogen levels and fibrinolysis.

Association between lipoprotein(a) and nonalcoholic fatty liver disease among Korean adults

BACKGROUND

Lipoprotein(a) [Lp(a)] and nonalcoholic fatty liver disease (NAFLD) are risk factors for cardiovascular diseases. We investigated the relationship between Lp(a) concentrations and NAFLD among Korean adults.

METHODS

A total of 2242 nondiabetic subjects undergoing routine health screening examination were enrolled. Anthropometric and biochemical parameters, including Lp(a) were measured. NAFLD were assessed by ultrasonography. Adjusted Odds ratios for the presence of NAFLD according to Lp(a) tertiles were estimated using logistic regression.

RESULTS

Subjects were grouped according to the severity of NAFLD and Lp(a) concentrations. Lp(a) concentrations were decreased across the severity of NAFLD and the prevalence of NAFLD decreased with the Lp(a) tertiles. Compared with subjects in the lowest tertile of Lp(a), those in the highest tertile had higher total cholesterol and LDL-C concentrations and lower body mass index, blood pressure, fasting glucose, triglyceride, ALT, and HOMA-IR concentrations. In the logistic regression analysis after adjusting for multiple risk factors, the relationship between Lp(a) concentrations and the presence of NAFLD remained significant. However, this association was attenuated after adjusting for insulin resistance.

CONCLUSIONS

Lp(a) was inversely associated with the presence of NAFLD, but it was not an independent risk factor for NAFLD among Korean adults.