Sex hormones and lipoprotein(a) concentration

Lipoprotein(a): Are we ready for large-scale clinical trials?

Cardiovascular diseases (CVD) are currently the most important disease threatening human health, which may be due to the high incidence of risk factors including hyperlipidemia. With the deepening of research on lipoprotein, lipoprotein (a) [Lp(a)] has been shown to be an independent risk factor for atherosclerotic cardiovascular diseases and calcified aortic valve stenosis and is now an unaddressed "residual risk" in current CVD management. Accurate measurement of Lp(a) concentration is the basis for diagnosis and treatment of high Lp(a). This review summarized the Lp(a) structure, discussed the current problems in clinical measurement of plasma Lp(a) concentration and the effects of existing lipid-lowering therapies on Lp(a).

The effect of tibolone treatment on apolipoproteins and lipoprotein (a) concentrations in postmenopausal women: A meta-analysis of randomized controlled trials

OBJECTIVE

Tibolone is a synthetic steroid with estrogenic, androgenic and progestogenic properties that is used as hormone replacement therapy (HRT) in postmenopausal women. Treatment with tibolone has been demonstrated to lead to changes of the lipid profile, including alterations in lipoprotein (a) and apolipoprotein levels. Hence, we conducted the present meta-analysis of randomized controlled trials (RCTs) to assess the effect of tibolone treatment on apolipoproteins and lipoprotein (a) values in postmenopausal women.

METHODS

Several databases (Cochrane Library, PubMed/Medline, Scopus, and Google Scholar) were searched for English-language manuscripts published up to September 2023 that scrutinized the effects of tibolone administration on apolipoprotein A-I (ApoA-I), apolipoprotein A-II (ApoA-II), apolipoprotein B (ApoB), and lipoprotein (a) in postmenopausal women. The results were reported as the weighted mean difference (WMD) with a 95% confidence interval (CI), generated using a random-effects model.

RESULTS

Finally, 12 publications with 13 RCT arms were included in the current meta-analysis. The overall results from the random-effects model demonstrated a notable reduction in ApoA-I (n = 9 RCT arms, WMD: -34.96 mg/dL, 95 % CI: -42.44, -27.48, P < 0.001) and lipoprotein (a) (n = 12 RCT arms, WMD: -7.49 mg/dl, 95 % CI: -12.17, -2.81, P = 0.002) after tibolone administration in postmenopausal women. However, treatment with tibolone did not impact ApoA- II (n = 4 RCT arms, WMD: 1.32 mg/dL, 95 % CI: -4.39, 7.05, P = 0.64) and ApoB (n = 9 RCT arms, WMD: -2.68 mg/dL, 95 % CI: -20.98, 15.61, P = 0.77) values. In the subgroup analyses, we noticed a notable decrease in lipoprotein (a) levels when tibolone was prescribed to females aged < 60 years (WMD: -10.78 mg/dl) and when it was prescribed for ≤ 6 months (WMD: -15.69 mg/dl).

CONCLUSION

The present meta-analysis of RCTs highlighted that treatment with tibolone reduces lipoprotein (a) and apolipoprotein A-I levels in postmenopausal women. As the decrease in serum lipids' concentrations is associated with a decrease in the risk of cardiovascular disease (CVD), treatment with tibolone could be a suitable therapy for postmenopausal women with elevated CVD risk.

Sex-Specific Differences in Lipoprotein Production and Clearance

Therapeutic approaches to reduce atherogenic lipid and lipoprotein levels remain the most effective and assessable strategies to prevent and treat cardiovascular disease. The discovery of novel research targets linked to pathways associated with cardiovascular disease development has enhanced our ability to decrease disease burden; however, residual cardiovascular disease risks remain. Advancements in genetics and personalized medicine are essential to understand some of the factors driving residual risk. Biological sex is among the most relevant factors affecting plasma lipid and lipoprotein profiles, playing a pivotal role in the development of cardiovascular disease. This minireview summarizes the most recent preclinical and clinical studies covering the effect of sex on plasma lipid and lipoprotein levels. We highlight the recent advances in the mechanisms regulating hepatic lipoprotein production and clearance as potential drivers of disease presentation. We focus on using sex as a biological variable in studying circulating lipid and lipoprotein levels.

Plasma Lipoprotein(a) Levels in Polycystic Ovary Syndrome: A Systematic Review and Meta-analysis

INTRODUCTION

The polycystic ovary syndrome (PCOS) may represent an important model of lipid alterations. Lipoprotein(a) [Lp(a)] has emerged as a new marker of cardiovascular risk.

AIM

The main objective of this meta-analysis was to analyze the available evidence on Lp(a) levels in patients with PCOS compared to a control group.

METHODS

This meta-analysis was performed according to PRISMA guidelines. A literature search was performed to detect studies that have quantified Lp(a) levels in women with PCOS compared to a control group. The primary outcome was Lp(a) levels expressed in mg/dL. Random effects models were used.

RESULTS

Twenty-three observational studies including 2,337 patients were identified and considered eligible for this meta-analysis. In the overall analysis, the quantitative analysis showed that patients with PCOS have a higher Lp(a) levels (SMD: 1.1 [95% CI: 0.7 to 1.4]; I²=93%) compared to the control group. The results were similar in the analysis of the subgroups of patients according to body mass index (normal weight group: SMD: 1.2 [95% CI: 0.5 to 1.9], I²=95%; overweight group: SMD: 1.2 [95% CI: 0.5 to 1.8], I²=89%). Sensitivity analysis showed that the results were robust.

CONCLUSIONS

This meta-analysis shows that women with PCOS had higher levels of Lp(a) compared to healthy women used as a control group. These findings were observed in both overweight and non-overweight women.

Lipoprotein(a) distribution and its association with carotid arteriopathy in the Chinese population

BACKGROUND AND AIMS

The distribution of lipoprotein(a) [Lp(a)] has not been well-studied in a large population in China. The relationship between Lp(a) and carotid atherosclerosis remains undefined. In this study, we aimed to investigate the distribution of Lp(a) levels and to assess their association with carotid arteriopathy in China.

METHODS

In this cross-sectional study, 411,634 adults with Lp(a) measurements from 22 health check-up centers were used to investigate Lp(a) distribution in China. Among participants with Lp(a) data, carotid ultrasound was performed routinely at seven health check-up centers covering 75,305 subjects. Carotid intima-media thickness (cIMT) and carotid plaque were used as surrogate biomarkers of carotid arteriopathy. The multivariate logistic regression model was applied to evaluate the association of increased Lp(a) levels with carotid arteriopathy.

RESULTS

The distribution of Lp(a) concentrations was right-skewed, with a median concentration of 10.60 mg/dL. The proportions of Lp(a) levels ≥30 mg/dL and ≥50 mg/dL were 16.75% and 7.10%, respectively. The median Lp(a) level was higher in females individuals in northern China, and increased with age. Spearman's analysis revealed weak correlations between the Lp(a) concentration as a continuous variable and other lipid profiles. The multiple logistic regression analysis showed that participants with Lp(a) levels ≥50 mg/dL had an increased risk of cIMT ≥1.0 mm (OR = 1.138, 95% CI, 1.071-1.208) and carotid plaque (OR = 1.296, 95% CI, 1.219-1.377) compared with those with Lp(a) levels <50 mg/dL.

CONCLUSIONS

This is the first study of the Lp(a) distribution in a large population in China. Our findings revealed a positive association between elevated Lp(a) levels (≥50 mg/dL) and increased prevalence of carotid atherosclerosis, which implies an increased risk of cardiovascular disease in the future.

Circulating levels of PCSK9, ANGPTL3 and Lp(a) in stage III breast cancers

Background / synopsis

Cholesterol and lipids play an important role in sustaining tumor growth and metastasis in a large variety of cancers. ANGPTL3 and PCSK9 modify circulating cholesterol levels, thus availability of lipids to peripheral cells. Little is known on the role, if any, of circulating lipid-related factors such as PCSK9, ANGPTL3 and lipoprotein (a) in cancers.

Objective/purpose

To compare circulating levels of PCSK9, ANGPTL3, and Lp(a) in women with stage III breast cancer versus women with premalignant or benign breast lesions.

Methods

Twenty-three plasma samples from women diagnosed with a stage III breast cancer (ductal, lobular or mixed) were matched for age with twenty-three plasma samples from women bearing premalignant (stage 0, n = 9) or benign (n = 14) breast lesions. The lipid profile (Apo B, total cholesterol, HDL cholesterol and triglycerides levels) and Lp(a) were measured on a Roche Modular analytical platform, whereas LDL levels were calculated with the Friedewald formula. ANGPTL3 and PCSK9 plasma levels were quantitated by ELISA. All statistical analyses were performed using SAS software version 9.4.

Results

PCSK9 levels were significantly higher in women with stage III breast cancer compared to age-matched counterparts presenting a benign lesion (95.9 ± 27.1 ng/mL vs. 78.5 ± 19.3 ng/mL, p < 0.05, n = 14). Moreover, PCSK9 levels positively correlated with breast disease severity (benign, stage 0, stage III) (Rho = 0.34, p < 0.05, n = 46). In contrast, ANGPTL3 and Lp(a) plasma levels did not display any association with breast disease status and lipids did not correlate with disease severity.

Conclusion

In this small cohort of 46 women, PCSK9 levels tended to increase with the severity of the breast disease. Given that PCSK9 plays an important role in maintaining cholesterolemia, and a potential role in tumor evasion, present results warrant further investigation into a possible association between PCSK9 levels and breast cancer severity in larger cohorts of women.

Understanding the ins and outs of lipoprotein (a) metabolism

PURPOSE OF REVIEW

This review summarizes our current understanding of the processes of apolipoprotein(a) secretion, assembly of the Lp(a) particle and removal of Lp(a) from the circulation. We also identify existing knowledge gaps that need to be addressed in future studies.

RECENT FINDINGS

The Lp(a) particle is assembled in two steps: a noncovalent, lysine-dependent interaction of apo(a) with apoB-100 inside hepatocytes, followed by extracellular covalent association between these two molecules to form circulating apo(a).The production rate of Lp(a) is primarily responsible for the observed inverse correlation between apo(a) isoform size and Lp(a) levels, with a contribution of catabolism restricted to larger Lp(a) isoforms.Factors that affect apoB-100 secretion from hepatocytes also affect apo(a) secretion.The identification of key hepatic receptors involved in Lp(a) clearance in vivo remains unclear, with a role for the LDL receptor seemingly restricted to conditions wherein LDL concentrations are low, Lp(a) is highly elevated and LDL receptor number is maximally upregulated.

SUMMARY

The key role for production rate of Lp(a) [including secretion and assembly of the Lp(a) particle] rather than its catabolic rate suggests that the most fruitful therapies for Lp(a) reduction should focus on approaches that inhibit production of the particle rather than its removal from circulation.

Association Between Atopic Dermatitis, Asthma, and Serum Lipids: A UK Biobank Based Observational Study and Mendelian Randomization Analysis

Background

Both atopic diseases and dysregulation of serum lipids (SLs) add to significant health burden, but evidences about their association are inconsistent.

Objective

This work is to evaluate the association between asthma/atopic dermatitis (AD) and SLs and investigate the potential causal relationship.

Methods

A large-scale cross-sectional study based on the UK Biobank (UKB) and then examined the casual relationships between SLs with asthma/AD based on a Mendelian randomization (MR) analysis.

Results

A total of 502,505 participants were included in analysis. After full adjustment, AD was associated with lower TG (β = −0.006; 95%CI, −0.010 to −0.002; P = 0.006), lower LDL (β = −0.004; 95%CI, −0.006 to −0.002, P < 0.001), and lower TC (β = −0.004; 95%CI, −0.005 to −0.002; P < 0.001) but insignificantly correlated to HDL (P = 0.794). Asthma was also inversely correlated to TG (β = −0.005; 95%CI, = −0.007 to −0.003; < 0.001), LDL (β = −0.003; 95%CI, −0.004 to −0.002; P < 0.001), and TC (β = −0.002; 95%CI, −0.003 to −0.002; P < 0.001), but was positively correlated to HDL (β = 0.004; 95%CI, 0.003 to 0.005; P < 0.001), respectively. In subsequent MR analysis, both allergic diseases and asthma showed a protective effect on TC. Allergic diseases, asthma, and AD all showed a negative effect on LDL.

Conclusion

Collectively, we identify a protective causal effect of allergic diseases on serum lipids, as well as a potentially positive association of HDL with asthma. Owing to the largest sample size and the application of IVs in causal inference, this study will provide a robust evidence for the management of asthma and AD and the prevention of dyslipidemia.

Lipoprotein (a) as a treatment target for cardiovascular disease prevention and related therapeutic strategies: a critical overview

Advances in several fields of cardiovascular (CV) medicine have produced new treatments (e.g. to treat dyslipidaemia) that have proven efficacy in terms of reducing deaths and providing a better quality of life. However, the burden of CV disease (CVD) remains high. Thus, there is a need to search for new treatment targets. Lipoprotein (a) [Lp(a)] has emerged as a potential novel target since there is evidence that it contributes to CVD events. In this narrative review, we present the current evidence of the potential causal relationship between Lp(a) and CVD and discuss the likely magnitude of Lp(a) lowering required to produce a clinical benefit. We also consider current and investigational treatments targeting Lp(a), along with the potential cost of these interventions.

A Review of Analytical Methods for the Determination of Tibolone: Pharmacokinetics and Pharmaceutical Formulations Analysis and Application in Doping Control

Background:

Tibolone is a synthetic steroid commercialized by Organon under the brand name Livial (Org OD14), which is used in hormone therapy for menopause management and treatment of postmenopausal osteoporosis. Tibolone is defined as a selective tissue estrogenic activity regulator (STEAR) demonstrating tissue-specific effects on several organs such as brain, breast, urogenital tract, endometrium, bone and cardiovascular system.

Aims:

This work aims to (1) present an overview of important published literature on existing methods for the analysis of tibolone and/or its metabolites in pharmaceutical formulations and biological fluids and (2) to conduct a critical comparison of the analytical methods used in doping control, pharmacokinetics and pharmaceutical formulations analysis of tibolone and its metabolites.

Results and conclusions:

The major analytical method described for the analysis of tibolone in pharmaceutical formulations is High Pressure Liquid Chromatography (HPLC) coupled with ultraviolet (UV) detection, while Liquid Chromatography (LC) or Gas Chromatography (GC) used in combination with Mass Spectrometry (MS) or tandem mass spectrometry (MS/MS) is employed for the analysis of tibolone and/or its metabolites in biological fluids.

Lipoprotein(a) the Insurgent: A New Insight into the Structure, Function, Metabolism, Pathogenicity, and Medications Affecting Lipoprotein(a) Molecule

Lipoprotein(a) [Lp(a)], aka “Lp little a”, was discovered in the 1960s in the lab of the Norwegian physician Kåre Berg. Since then, we have greatly improved our knowledge of lipids and cardiovascular disease (CVD). Lp(a) is an enigmatic class of lipoprotein that is exclusively formed in the liver and comprises two main components, a single copy of apolipoprotein (apo) B-100 (apo-B100) tethered to a single copy of a protein denoted as apolipoprotein(a) apo(a). Plasma levels of Lp(a) increase soon after birth to a steady concentration within a few months of life. In adults, Lp(a) levels range widely from <2 to 2500 mg/L. Evidence that elevated Lp(a) levels >300 mg/L contribute to CVD is significant. The improvement of isoform-independent assays, together with the insight from epidemiologic studies, meta-analyses, genome-wide association studies, and Mendelian randomization studies, has established Lp(a) as the single most common independent genetically inherited causal risk factor for CVD. This breakthrough elevated Lp(a) from a biomarker of atherosclerotic risk to a target of therapy. With the emergence of promising second-generation antisense therapy, we hope that we can answer the question of whether Lp(a) is ready for prime-time clinic use. In this review, we present an update on the metabolism, pathophysiology, and current/future medical interventions for high levels of Lp(a).

Looking at Lp(a) and Related Cardiovascular Risk: from Scientific Evidence and Clinical Practice

PURPOSE OF REVIEW

A considerable body of data from genetic and epidemiological studies strongly support a causal relationship between high lipoprotein(a) [Lp(a)] levels, and the development of atherosclerosis and cardiovascular disease. This relationship is continuous, unrelated to Lp(a) threshold, and independent of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol levels. Unfortunately, the mechanism(s) through which Lp(a) promotes atherosclerosis are not clarified yet. Suggested hypotheses include: an increased Lp(a)-associated cholesterol entrapment in the arterial intima followed by inflammatory cell recruitment, abnormal upload of proinflammatory oxidized phospholipids, impaired fibrinolysis by inhibition of plasminogen activation, and enhanced coagulation, through inhibition of the tissue factor pathway inhibitor. This review is aimed at summarizing the available evidence on the topic.

RECENT FINDINGS

There are two clinical forms, isolated hyperlipidemia(a) [HyperLp(a)] with acceptable LDL-C levels (< 70 mg/dL), and combined elevation of Lp(a) and LDL-C in plasma. To date, no drugs that selectively decrease Lp(a) are available. Some novel lipid-lowering drugs can lower Lp(a) levels, but to a limited extent, as their main effect is aimed at decreasing LDL-C levels. Significant Lp(a) lowering effects were obtained with nicotinic acid at high doses. However, adverse effects apart, nicotinic acid is no longer prescribed and available in Europe for clinical use, after European Agency of Medicines (EMA) ban. The only effective therapeutic option for now is Lipoprotein Apheresis (LA), albeit with some limitations. Lastly, it is to be acknowledged that the body of evidence confirming that reducing plasma isolated elevation of Lp(a) brings cardiovascular benefit is still insufficient. However, the growing bulk of clinical, genetic, mechanistic, and epidemiological available evidence strongly suggests that Lp(a) is likely to be the smoking gun.

Establishing age and sex dependent upper reference limits for the plasma lipoprotein (a) in a Chinese health check-up population and according to its relative risk of primary myocardial infarction

BACKGROUND

Though lipoprotein (a) (Lp (a)) has been considered as a risk factor for coronary artery disease, there is a lack of cutoff values of Lp (a) for Chinese Han ethnicity.

METHODS

We included 1 population for health check-ups. Lp (a) percentile distributions were analyzed and its cutoff for Chinese Han ethnicity was also proposed according to the its relative risk of myocardial infarction.

RESULTS

Lp (a) distributions differed between sexes, and were highly skewed towards low concentrations with a long tail towards the highest ones. The relative risks of elevated Lp (a) concentrations for myocardial infarction had an inflection in Chinese Han ethnic at the 8th decile, corresponding to 167 mg/l, where the risk was prone to be increased. In terms of Lp (a) median concentrations, per higher age quantile (5-y interval) was associated with a significant increase of 3.2 mg/l and females were on average 19.75 mg/l higher than males with a significant difference.

CONCLUSIONS

We proposed Lp (a) < 170 mg/l after rounding as cut-off values for Chinese Han ethnicity. Effects of age and sex on Lp (a) concentrations were also noted. Prospective validation of these cutoff values is critically important in Chinese Han ethnicity.

[Clinical significance of and treatment options for increased lipoprotein(a)]

Lipoprotein(a) has been shown to be associated with an increased incidence of cardiovascular diseases for decades. However, only recent research revealed more about its physiological function and its role in the development of cardiovascular diseases. The authors summarize the physiological role of lipoprotein(a), causes and treatment of elevated lipoprotein(a) level, and the association between lipoprotein(a) and cardiovascular diseases.

Reproductive toxicity of nanoscale graphene oxide in male mice

In the past few years, much work has been performed to explore the biomedical applications and toxicity of nano-graphene and its derivatives. However, the reproductive toxicity of those carbon nanomaterials has been rarely studied. In this study, we report on the male reproductive toxicity of nanoscale graphene oxide (GO) using a mouse model. The results showed that the adult male mice injected with high dosages of GO (25 mg/kg mouse) via the tail vein exhibited normal sex hormone secretion and retained normal reproductive activity. All untreated female mice mated with the GO-treated male mice could produce healthy pups. There were no significant differences in pup numbers, sex ratio, weights, pup survival rates or pup growth over time between the GO-treated and control groups. Furthermore, these GO-treated male mice could produce a second, third, fourth and even fifth litter of healthy offspring when they lived with the untreated female mice. The testicular and epididymal histology as well as the activities of several important epididymal enzymes including α-glucosidase, lactate dehydrogenase, glutathione peroxidase and acid phosphatase were not affected by GO treatment. In addition, no damaging effects were seen at high dose rates of GO (total 300 mg/kg male mouse, 60 mg/kg every 24 h for 5 days) via intra-abdominal injection. Thus, GO showed very low or nearly no toxicity for male reproduction. This work will greatly enable future investigations of GO nanosheets for in vivo biomedical applications.

Lipoprotein(a) metabolism: potential sites for therapeutic targets

Lipoprotein(a) [Lp(a)] resembles low-density lipoprotein (LDL), with an LDL lipid core and apolipoprotein B (apoB), but contains a unique apolipoprotein, apo(a). Elevated Lp(a) is an independent risk factor for coronary and peripheral vascular diseases. The size and concentration of plasma Lp(a) are related to the synthetic rate, not the catabolic rate, and are highly variable with small isoforms associated with high concentrations and pathogenic risk. Apo(a) is synthesized in the liver, although assembly of apo(a) and LDL may occur in the hepatocytes or plasma. While the uptake and clearance site of Lp(a) is poorly delineated, the kidney is the site of apo(a) fragment excretion. The structure of apo(a) has high homology to plasminogen, the zymogen for plasmin and the primary clot lysis enzyme. Apo(a) interferes with plasminogen binding to C-terminal lysines of cell surface and extracellular matrix proteins. Lp(a) and apo(a) inhibit fibrinolysis and accumulate in the vascular wall in atherosclerotic lesions. The pathogenic role of Lp(a) is not known. Small isoforms and high concentrations of Lp(a) are found in healthy octogenarians that suggest Lp(a) may also have a physiological role. Studies of Lp(a) function have been limited since it is not found in commonly studied small mammals. An important aspect of Lp(a) metabolism is the modification of circulating Lp(a), which has the potential to alter the functions of Lp(a). There are no therapeutic drugs that selectively target elevated Lp(a), but a number of possible agents are being considered. Recently, new modifiers of apo(a) synthesis have been identified. This review reports the regulation of Lp(a) metabolism and potential sites for therapeutic targets.

Lipoprotein(a): resurrected by genetics

Plasma lipoprotein(a) [Lp(a)] is a quantitative genetic trait with a very broad and skewed distribution, which is largely controlled by genetic variants at the LPA locus on chromosome 6q27. Based on genetic evidence provided by studies conducted over the last two decades, Lp(a) is currently considered to be the strongest genetic risk factor for coronary heart disease (CHD). The copy number variation of kringle IV in the LPA gene has been strongly associated with both Lp(a) levels in plasma and risk of CHD, thereby fulfilling the main criterion for causality in a Mendelian randomization approach. Alleles with a low kringle IV copy number that together have a population frequency of 25-35% are associated with a doubling of the relative risk for outcomes, which is exceptional in the field of complex genetic phenotypes. The recently identified binding of oxidized phospholipids to Lp(a) is considered as one of the possible mechanisms that may explain the pathogenicity of Lp(a). Drugs that have been shown to lower Lp(a) have pleiotropic effects on other CHD risk factors, and an improvement of cardiovascular endpoints is up to now lacking. However, it has been established in a proof of principle study that lowering of very high Lp(a) by apheresis in high-risk patients with already maximally reduced low-density lipoprotein cholesterol levels can dramatically reduce major coronary events.