Decreased plasma levels of lipoprotein(a) in patients with hypertriglyceridemia

Reduced lipoprotein (a) in patients with severe hypertriglyceridaemia

OBJECTIVE

To investigate the relationship between plasma lipoprotein (a) (Lp[a]) and lipid profiles in patients with severe hypertriglyceridaemia (HTG).

METHODS

This case-control study undertook a retrospective chart review of patients from the Lipid Genetics Clinic at London Health Sciences Centre in Ontario, Canada. Plasma Lp(a) was compared between patients with severe HTG and healthy normolipidaemic control subjects. Severe HTG was defined by plasma triglycerides (TG) ≥ 10 mmol/l. Pairwise correlations between Lp(a), TG, apolipoprotein B (apo B) and non-high-density lipoprotein cholesterol (non-HDL-C) were evaluated.

RESULTS

This study reviewed 4400 patients and identified 154 patients with severe HTG, which were compared with 272 control subjects. The median Lp(a) was significantly lower in patients with severe HTG compared with control subjects (5.0 versus 10.2 mg/dl, respectively). No correlation was observed between Lp(a) and TG or non-HDL-C. Lp(a) and apo B were modestly correlated in patients with severe HTG (r = 0.235) and control subjects (r = 0.175). There were no significant differences between the genetic subgroups of patients with severe HTG.

CONCLUSIONS

Patients with severe HTG have lower plasma Lp(a) than normolipidaemic control subjects. The basis for this relationship is not immediately apparent but is hypothesis-generating and warrants further investigation.

Frequency of lipoprotein(a) testing and its levels in Pakistani population

BACKGROUND

Lipoprotein(a) [Lp(a)] is a highly atherogenic particle identified as an independent risk factor for the development of atherosclerotic cardiovascular disease (ASCVD). This study aimed to investigate the frequency of Lp(a) testing and the incidence of elevated Lp(a) levels in the Pakistani population.

METHODS

For this observational study, Lp(a) and lipid profile data from five years (June 2015 to October 2020) were acquired from the electronic patient records of a diagnostic laboratory with a countrywide network. The association of age and total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), non-HDL, and triglyceride (TG) levels with two thresholds for Lp(a), that is, <30 mg/dL and ≥30 mg/dL, was calculated using the Kruskal-Wallis test, while the association between Lp(a) levels and lipid variables was calculated using Spearman correlation.

RESULTS

For five years, 1060 tests were conducted, averaging 212 tests per year. Of these, 37.2% showed Lp(a) levels above 30 mg/dL. No significant differences were observed in the results between males and females. However, younger individuals displayed significantly higher Lp(a) levels. Additionally, there was only a weak correlation between the Lp(a) levels and other lipid variables.

CONCLUSION

Despite being recognized as a risk factor for ASCVD in the Pakistani population, only a small proportion of the large population underwent Lp(a) testing. Moreover, a significant proportion of the population exceeded this threshold.

Association between lipoprotein (a) and risk of atherosclerotic cardiovascular disease events among maintenance hemodialysis patients in Beijing, China: a single-center, retrospective study

BACKGROUND

Serum lipoprotein(a) [Lp(a)] is an independent risk factor for atherosclerotic cardiovascular disease (ASCVD) in the general population, its association with ASCVD incidence in Chinese maintenance hemodialysis (MHD) patients remains unclear. We aimed to evaluate the relationship between Lp(a) levels and ASCVD incidence among MHD patients in Beijing, China.

METHODS

This retrospective, observational cohort study included MHD patients at Beijing Tongren Hospital from January 1, 2013 to December 1, 2020, and followed until December 1,2023. The primary outcome was ASCVD occurrence. Kaplan-Meier survival analysis was used to evaluate ASCVD-free survival in MHD patients, with stratification based on Lp(a) levels. Cox regression analyses were conducted to assess the association between Lp(a) levels and the occurrence of ASCVD.

RESULTS

A total of 265 patients were enrolled in the study. The median follow-up period were 71 months.78 (29.4%) participants experienced ASCVD events, and 118 (47%) patients died, with 58 (49.1%) deaths attributed to ASCVD. Spearman rank correlation analyses revealed positive correlations between serum Lp(a) levels and LDL-c levels, and negative correlations with hemoglobin, triglyceride, serum iron, serum creatinine, and albumin levels. Multivariate Cox regression analysis showed that Lp(a) levels ≥ 30 mg/L, increased age, decreased serum albumin levels, and a history of diabetes mellitus were significantly associated with ASCVD incidence.

CONCLUSIONS

This study demonstrated an independent and positive association between serum Lp(a) levels and the risk of ASCVD in MHD patients, suggesting that serum Lp(a) could potentially serve as a clinical biomarker for estimating ASCVD risk in this population.

Association between hepatic steatosis and lipoprotein(a) levels in non-alcoholic patients: A systematic review

BACKGROUND AND OBJECTIVES

It is well known that lipid abnormalities exist in the context of non-alcoholic fatty liver disease (NAFLD). The association between lipoprotein(a) [Lp(a)] levels and NAFLD is poorly understood. The main objective of the present study was to assess the association between Lp(a) levels and NAFLD.

METHODS

This systematic review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (PROSPERO CRD42023392526). A literature search was performed to detect studies that evaluated the association between Lp(a) levels, NAFLD and steatohepatitis (NASH).

RESULTS

Ten observational studies, including 40,045 patients, were identified and considered eligible for this systematic review. There were 9266 subjects in the NAFLD groups and 30,779 individuals in the respective control groups. Five studies evaluated patients with NAFLD (hepatic steatosis was associated with lower Lp(a) levels in four studies, while the remaining showed opposite results). Two studies evaluating NASH patients showed that Lp(a) levels were not different compared to controls. However, the increment of Lp(a) levels was correlated with liver fibrosis in one of them. In addition, one study analyzed simultaneously patients with NAFLD and NASH, showing a neutral result in NAFLD patients and a positive relationship in NASH patients. Two studies that included patients with the new definition of metabolic-associated fatty liver disease (MAFLD) also showed neutral results.

CONCLUSION

Although there could be an association between Lp(a) levels and hepatic steatosis, the results of the studies published to date are contradictory and not definitive.

Influence of triglyceride concentration in lipoprotein (a) as a function of dyslipidemia

BACKGROUND

Recently, an inverse relationship between the blood concentration of lipoprotein(a) (Lp(a)) and triglycerides (TG) has been demonstrated. The larger the VLDL particle size, the greater the presence of VLDL rich in apoliprotein E and in subjects with the apoE2/E2 genotype, the lower Lp(a) concentration. The mechanism of this inverse association is unknown. The objective of this analysis was to evaluate the Lp(a)-TG association in patients treated at the lipid units included in the registry of the Spanish Society of Atherosclerosis (SEA) by comparing the different dyslipidemias.

PATIENTS AND METHODS

Five thousand two hundred and seventy-five subjects ≥18 years of age registered in the registry before March 31, 2023, with Lp(a) concentration data and complete lipid profile information without treatment were included.

RESULTS

The mean age was 53.0 ± 14.0 years, with 48% women. The 9.5% of subjects (n = 502) had diabetes and the 22.4% (n = 1184) were obese. The median TG level was 130 mg/dL (IQR 88.0-210) and Lp(a) 55.0 nmol/L (IQR 17.9-156). Lp(a) concentration showed a negative association with TG concentration when TG values exceeded 300 mg/dL. Subjects with TG > 1000 mg/dL showed the lowest level of Lp(a), 17.9 nmol/L, and subjects with TG < 300 mg/dL had a mean Lp(a) concentration of 60.1 nmol/L. In subjects without diabetes or obesity, the inverse association of Lp(a)-TG was especially important (p < 0.001). The median Lp(a) was 58.3 nmol/L in those with TG < 300 mg/dL and 22.0 nmol/L if TG > 1000 mg/dL. No association was found between TG and Lp(a) in subjects with diabetes and obesity, nor in subjects with familial hypercholesterolemia. In subjects with multifactorial combined hyperlipemia with TG < 300 mg/dL, Lp(a) was 64.6 nmol/L; in the range of 300-399 mg/dL of TG, Lp(a) decreased to 38. 8 nmol/L, and up to 22.3 nmol/L when TG > 1000 mg/dL.

CONCLUSIONS

Our results show an inverse Lp(a)-TG relationship in TG concentrations > 300 mg/dL in subjects without diabetes, obesity and without familial hypercholesterolemia. Our results suggest that, in those hypertriglyceridemias due to hepatic overproduction of VLDL, the formation of Lp(a) is reduced, unlike those in which the peripheral catabolism of TG-rich lipoproteins is reduced.

Triglyceride Metabolism Modifies Lipoprotein(a) Plasma Concentration

BACKGROUND

Lipoprotein(a) (Lp(a)) is a significant cardiovascular risk factor. Knowing the mechanisms that regulate its concentration can facilitate the development of Lp(a)-lowering drugs. This study analyzes the relationship between triglycerides (TGs) and Lp(a) concentrations, cross-sectionally and longitudinally, and the influence of the number and composition of TG-rich lipoproteins, and the APOE genotype.

METHODS

Data from Aragon Workers Health Study (AWHS) (n = 5467), National Health and Nutrition Examination Survey III phase 2 (n = 3860), and Hospital Universitario Miguel Servet (HUMS) (n = 2079) were used for cross-sectional TG and Lp(a) relationship. Lp(a) intrasubject variation was studied in AWHS participants and HUMS patients with repeated measurements. TG-rich lipoproteins were quantified by nuclear magnetic resonance in a subsample from AWHS. Apolipoproteins B and E were quantified by Luminex in very low-density lipoprotein (VLDL) isolated by ultracentrifugation, from HUMS samples. APOE genotyping was carried in AWHS and HUMS participants. Regression models adjusted for age and sex were used to study the association.

RESULTS

The 3 studies showed an inverse relationship between TG and Lp(a). Increased VLDL number, size, and TG content were associated with significantly lower Lp(a). There was an inverse association between the apoE concentration in VLDL and Lp(a). No significant association was observed for apolipoprotein (apo)B. Subjects carrying the apoE2/E2 genotype had significantly lower levels of Lp(a).

CONCLUSION

Our results show an inverse relationship Lp(a)-TG. Subjects with larger VLDL size have lower Lp(a), and lower values of Lp(a) were present in patients with apoE-rich VLDL and apoE2/E2 subjects. Our results suggest that bigger VLDLs and VLDLs enriched in apoE are inversely involved in Lp(a) plasma concentration.

Effect of bariatric surgery on plasma levels of oxidised phospholipids, biomarkers of oxidised LDL and lipoprotein(a)

BACKGROUND

Obesity is associated with adverse cardiovascular outcomes and this is improved following bariatric surgery. Oxidised phospholipids (OxPL) are thought to reflect the pro-inflammatory effects of lipoprotein(a) [Lp(a)], and both are independent predictors of cardiovascular disease.

OBJECTIVE

Our study sought to determine the impact of bariatric surgery on OxPL, biomarkers of oxidised LDL (OxLDL) and Lp(a).

METHODS

This is a prospective, observational study of 59 patients with severe obesity undergoing bariatric surgery. Blood samples were obtained prior to surgery and at 6 and 12 months after. Sixteen patients attending the tertiary medical weight management clinic at the same centre were also recruited for comparison. Lipid and metabolic blood parameters, OxLDL, OxPL on apolipoprotein B-100 (OxPL-apoB), IgG and IgM autoantibodies to MDA-LDL, IgG and IgM apoB-immune complexes and Lp(a) were measured.

RESULTS

Reduction in body mass index (BMI) was significant following bariatric surgery, from median 48 kg/m2 at baseline to 37 kg/m2 at 6 months and 33 kg/m2 at 12 months. OxPL-apoB levels decreased significantly at 12 months following surgery [5.0 (3.2-7.4) to 3.8 (3.0-5.5) nM, p = 0.001], while contrastingly, Lp(a) increased significantly [10.2 (3.8-31.9) to 16.9 (4.9-38.6) mg/dl, p = 0.002]. There were significant post-surgical decreases in IgG and IgM biomarkers, particularly at 12 months, while OxLDL remained unchanged.

CONCLUSIONS

Bariatric surgery results in a significant increase in Lp(a) but reductions in OxPL-apoB and other biomarkers of oxidised lipoproteins, suggesting increased synthetic capacity and reduced oxidative stress. These biomarkers might be clinically useful to monitor physiological effects of weight loss interventions.

Measuring the contribution of Lp(a) cholesterol towards LDL-C interpretation

BACKGROUND

Lipoprotein(a) [Lp(a)] is a pro-atherogenic and pro-thrombotic LDL-like particle recognized as an independent risk factor for cardiovascular disease (CVD). The cholesterol within Lp(a) (Lp(a)-C) contributes to the reported LDL-cholesterol (LDL-C) concentration by nearly all available methods. Accurate LDL-C measurements are critical for identification of genetic dyslipidemias such as familial hypercholesterolemia (FH). FH diagnostic criteria, such as the Dutch Lipid Clinic Network (DLCN) criteria, utilize LDL-C concentration cut-offs to assess the likelihood of FH. Therefore, failure to adjust for Lp(a)-C can impact accurate FH diagnosis and classification, appropriate follow-up testing and treatments, and interpretation of cholesterol-lowering treatment efficacy.

OBJECTIVE

In this study, we use direct Lp(a)-C measurements to assess the potential misclassification of FH from contributions of Lp(a)-C to reported LDL-C in patient samples submitted for advanced lipoprotein profiling.

METHODS

A total of 31,215 samples submitted for lipoprotein profiling were included. LDL-C was measured by beta quantification or calculated by one of three equations. Lp(a)-C was measured by quantitative lipoprotein electrophoresis. DLCN LDL-C cut-offs were applied to LDL-C results before and after accounting for Lp(a)-C contribution.

RESULTS

Lp(a)-C was detected in 8665 (28%) samples. A total of 940 subjects were reclassified to a lower DLCN LDL-C categories; this represents 3% of the total patient series or 11% of subjects with measurable Lp(a)-C.

CONCLUSION

Lp(a)-C is present in a significant portion of samples submitted for advanced lipid testing and could cause patient misclassification when using FH diagnostic criteria. These misclassifications could trigger inappropriate follow-up, treatment, and cascade testing for suspected FH.

Lipoprotein(a) in atherosclerosis: from pathophysiology to clinical relevance and treatment options

Lipoprotein(a) (Lp(a)) was discovered more than 50 years ago, and a decade later, it was recognized as a risk factor for coronary artery disease. However, it has gained importance only in the past 10 years, with emergence of drugs that can effectively decrease its levels. Lp(a) is a low-density lipoprotein (LDL) with an added apolipoprotein(a) attached to the apolipoprotein B component via a disulphide bond. Circulating levels of Lp(a) are mainly genetically determined. Lp(a) has many functions, which include proatherosclerotic, prothrombotic and pro-inflammatory roles. Here, we review recent data on the role of Lp(a) in the atherosclerotic process, and treatment options for patients with cardiovascular diseases. Currently 'Proprotein convertase subtilisin/kexin type 9' (PCSK9) inhibitors that act through non-specific reduction of Lp(a) are the only drugs that have shown effectiveness in clinical trials, to provide reductions in cardiovascular morbidity and mortality. The effects of PCSK9 inhibitors are not purely through Lp(a) reduction, but also through LDL cholesterol reduction. Finally, we discuss new drugs on the horizon, and gene-based therapies that affect transcription and translation of apolipoprotein(a) mRNA. Clinical trials in patients with high Lp(a) and low LDL cholesterol might tell us whether Lp(a) lowering per se decreases cardiovascular morbidity and mortality.KEY MESSAGESLipoprotein(a) is an important risk factor in patients with cardiovascular diseases.Lipoprotein(a) has many functions, which include proatherosclerotic, prothrombotic and pro-inflammatory roles.Treatment options to lower lipoprotein(a) levels are currently scarce, but new drugs are on the horizon.

Elevated Llpoprotein(A) and Fibrinogen Serum Levels Increase the Cardiovascular Risk in Continuous Ambulatory Peritoneal Dialysis Patients

Objective

To analyze the relationship between lipoprotein(a) [Lp(a)] and fibrinogen as potential cardiovascular risk factors in patients on continuous ambulatory peritoneal dialysis (CAPD).

Patients

A total of 47 uremic patients receiving CAPD, 21 with coronary artery disease (CAD), 26 without CAD.

Measurements

Lp(a) levels were determined by an immunoradiometric assay. Since Lp(a) serum concentrations vary depending on the size, apoprotein(a) [apo(a)] isoforms were determined (Westernblot). Fibrinogen was quantified according to Clauss.

Results

The mean Lp(a) serum concentration was 43 ± 5 mg/dL (SEM) (median 33 mg/dL) in CAPD patients and 21 ± 2 mg/dL (8 mg/dL) in controls (p < 0.01). Patients with low molecular weight apo(a) isoforms exhibited substantially elevated Lp(a) levels when compared with patients with high molecular isoforms (p < 0.01). In addition, we found elevated fibrinogen levels in the CAPD patients (538 ± 61 mg/dL) compared with healthy controls (288 ± 46 mg/dL). Twenty-one CAPD patients (45%) were suffering from CAD. Patients with CAD had higher Lp(a) levels (54 ± 5 mg/dL vs 34 ± 4 mg/dL) as well as higher fibrinogen concentrations (628 ± 59 mg/dL vs 459 ± 46 mg/dL). Furthermore, a positive correlation between the fibrinogen levels and the Lp(a) serum concentration was observed (r = 0.45, p = 0.01).

Conclusion

We suggest that elevated Lp(a) levels are influenced by the allelic variation of the apo(a) isoform. In addition to the typical dyslipidemia found in CAPD patients, high levels of Lp(a) and fibrinogen may contribute to the elevated risk of coronary artery disease and other cardiovascular complications.

Lipoprotein (a): structure, pathophysiology and clinical implications

The chemical structure of lipoprotein (a) is similar to that of LDL, from which it differs due to the presence of apolipoprotein (a) bound to apo B100 via one disulfide bridge. Lipoprotein (a) is synthesized in the liver and its plasma concentration, which can be determined by use of monoclonal antibody-based methods, ranges from < 1 mg to > 1,000 mg/dL. Lipoprotein (a) levels over 20-30 mg/dL are associated with a two-fold risk of developing coronary artery disease. Usually, black subjects have higher lipoprotein (a) levels that, differently from Caucasians and Orientals, are not related to coronary artery disease. However, the risk of black subjects must be considered. Sex and age have little influence on lipoprotein (a) levels. Lipoprotein (a) homology with plasminogen might lead to interference with the fibrinolytic cascade, accounting for an atherogenic mechanism of that lipoprotein. Nevertheless, direct deposition of lipoprotein (a) on arterial wall is also a possible mechanism, lipoprotein (a) being more prone to oxidation than LDL. Most prospective studies have confirmed lipoprotein (a) as a predisposing factor to atherosclerosis. Statin treatment does not lower lipoprotein (a) levels, differently from niacin and ezetimibe, which tend to reduce lipoprotein (a), although confirmation of ezetimibe effects is pending. The reduction in lipoprotein (a) concentrations has not been demonstrated to reduce the risk for coronary artery disease. Whenever higher lipoprotein (a) concentrations are found, and in the absence of more effective and well-tolerated drugs, a more strict and vigorous control of the other coronary artery disease risk factors should be sought.

Examination of adhesion molecules, homocysteine and hs-CRP in patients with polygenic hypercholesterolemia and isolated hypertriglyceridemia

BACKGROUND

Increased levels of selectins, adhesion molecules, hs-CRP and homocysteine are considered important as indicators of atherosclerosis. There is a significant amount of evidence that high LDL-C levels are a risk factor for coronary artery disease, whereas the relevance of isolated triglycerides is controversial. The present study aims to compare the levels of homocysteine, hs-CRP, E-selectin, sP-selectin, VCAM-1, ICAM-1 in patients with isolated hypertriglyceridemia and polygenic hypercholesterolemia.

METHODS

The following three groups were formed: polygenic hypercholesterolemia group (n=30), isolated hypertriglyceridemia group (n=30) and control group (n=30). These three groups were matched in terms of BMI, waist circumference and gender. Plasma high sensitive CRP, homocysteine, sVCAM-1, sICAM-1, sP-selectin, sE-Selectin levels of patients in these three groups were measured.

RESULTS

In the present study, mean values for sE-selectin, sVCAM-1 and sICAM-1 in the polygenic hypercholesterolemia group were significantly higher than in the other two groups (p<0.001). Homocysteine and hs-CRP levels were higher in the polygenic hypercholesterolemia group, compared to the isolated hypertriglyceridemia group (p=0.019, p<0.001; respectively) and the control group (p<0.001, p<0.001; respectively). Comparison of patients with hypertriglyceridemia to individuals in the control group did not yield a significant difference in terms of sE-selectin, sP-selectin, sVCAM-1, sICAM and homocysteine (p>0.05), where as the hs-CRP value was significantly higher in patients with isolated hypertriglyceridemia compared to the control group (p=0.001).

CONCLUSION

The increase of adhesion molecules, homocysteine and hs-CRP in polygenic hypercholesterolemia subjects compared to the isolated hypertriglyceridemia group reflects their high cardiovascular risk.

Effect of Fenofibrate on Lipoprotein(a) in Hypertriglyceridemic Patients

We investigated the effect of fenofibrate on lipoprotein(a)levels in hypertriglyceridemic patients and the parameters relating to its effect. Patients with a triglyceride level >/=300 mg/dL or with a triglyceride level >/=200 mg/dL and a high density lipoprotein cholesterol level </=40 mg/dL were treated either with 200 mg of fenofibrate(Fenofibrate group, n = 56) or with general measures (Control group,n = 56). Lipid and lipoprotein levels were measured at baseline and 2 months. Baseline lipoprotein(a) levels were negatively correlated with triglyceride (r = 20.30, P = 0.001) and alanine aminotransferase levels (r = 20.24, P = 0.012). Fenofibrate therapy increased lipoprotein(a) level from 9.4 6 10.6 to 15.6 6 17.5 mg/dL (P = 0.000). The more triglyceride levels decreased, the more lipoprotein(a) levels increased in all subjects (r = 20.46, P = 0.000) and in Control (r =20.35, P = 0.008) and Fenofibrate groups (r = 20.35, P = 0.008). Fenofibrate elevated lipoprotein(a) level greater in patients with a normal liver function. When Fenofibrate group was divided into two subgroups according to the degree of percentage change in lipoprotein(a) level, change in triglyceride level and alanine aminotransferase level were independent predictors by forward logistic regression analysis. In summary, fenofibrate therapy increases lipoprotein(a) level,and this elevation is associated with change in triglyceride level and liver function.

A prospective study of lipoprotein(a) and risk of coronary heart disease among women with type 2 diabetes

AIMS

We examined the association between lipoprotein (Lp)(a) and CHD among women with type 2 diabetes.

METHODS

Of 32,826 women from the Nurses' Health Study who provided blood at baseline, we followed 921 who had a confirmed diagnosis of type 2 diabetes.

RESULTS

During 10 years of follow-up (6,835 person-years), we documented 122 incident cases of CHD. After adjustment for age, smoking, BMI, glycosylated HbA(1)c, triglycerides (TGs), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and other cardiovascular risk factors, the relative risk (RR) comparing extreme quintiles of Lp(a) was 1.95 (95% CI 1.07-3.56). The association was not appreciably altered after further adjustment for apolipoprotein B(100) or several inflammatory biomarkers. Increasing levels of Lp(a) were associated with lower levels of TGs. The probability of developing CHD over 10 years was higher among diabetic women with substantially higher levels of both Lp(a) (>1.07 micromol/l) and TGs (>2.26 mmol/l) than among diabetic women with lower levels (22 vs 10%, p log-rank test=0.049). Diabetic women with a higher level of only Lp(a) or TGs had a similar (14%) risk. In a multivariate model, diabetic women with higher levels of Lp(a) and TGs had an RR of 2.46 (95% CI 1.21-5.01) for developing CHD, as compared with those with lower levels of both biomarkers (p for interaction=0.413). The RRs for women with a higher level of either Lp(a) (RR=1.22, 95% CI 0.77-1.92) or TGs (RR=1.39, 95% CI 0.78-2.42) were comparable.

CONCLUSIONS/INTERPRETATION

Increased levels of Lp(a) were independently associated with risk of CHD among diabetic women.

Does Lipoprotein(a) Inhibit Elastolysis in Abdominal Aortic Aneurysms?

PURPOSE

to test the hypothesis that there is a negative association between serum levels of lipoprotein(a) (Lp(a)) and elastin-derived peptides (EDP) as well as matrix metalloproteinase (MMP)-9 activation in the aneurysm wall in patients with asymptomatic abdominal aortic aneurysms (AAA).

MATERIAL AND METHODS

from 30 patients operated for asymptomatic AAAs, preoperative serum samples and AAA biopsies were collected. Lp(a) (mg/L) and EDP (ng/ml) in serum were measured by enzyme linked immunosorbent assays. MMP-9 activity (arbitrary units) in the AAA wall was measured by gelatin zymography and the ratio: active MMP-9/total MMP-9 were calculated.

RESULTS

there was a significant negative correlation (Spearman's rho) between serum levels of Lp(a) and EDP (r= -0.707, p<0.001), as well as the share of activated MMP-9 (r= -0.461, p=0.01) in the AAA wall.

CONCLUSION

this preliminary study indicate that Lp(a) inhibit elastolysis in asymptomatic AAA.

Influence of lipoprotein(a) on restenosis after femoropopliteal percutaneous transluminal angioplasty in Type 2 diabetic patients

OBJECTIVE

The influence of vascular morphology and metabolic parameters including lipoprotein(a) (Lp(a)) on restenosis after peripheral angioplasty has been compared in Type 2 diabetes (DM) vs. non-diabetic patients (ND).

RESEARCH DESIGN AND METHODS

The clinical course and risk profile of 132 (54 DM vs. 78 ND) patients with peripheral arterial occlusive disease (PAD) were observed prospectively following femoropopliteal angioplasty (PTA). Clinical examination, oscillometry, ankle brachial blood pressure index (ABI) and the toe systolic blood pressure index (TSPI) were used during follow-up. Duplex sonography and reangiography were also used to verify suspected restenosis or reocclusion.

RESULTS

At the time of intervention patients with DM had a lower median Lp(a) of 9 vs. 15 mg/dl (P < 0.01) in patients without diabetes. Recurrence within 1 year after PTA occurred in 25 diabetic (= 46%, Lp(a) 12 mg/dl) and 30 non-diabetic (= 38%, Lp(a) 48 mg/dl) patients. DM patients with 1 year's patency had a median Lp(a) of 7 vs. 11 mg/dl in non-diabetic patients (P < 0.05). However, 12 months after angioplasty Lp(a) correlated negatively with the ABI (r = -0.44, P < 0.01) in diabetic and in non-diabetic patients (r = -0.20, P < 0.05). The probability of recurrence after PTA continuously increased with higher levels of Lp(a) in each subgroup of patients.

CONCLUSIONS

Our data indicate that Lp(a) is generally lower in those with peripheral arterial occlusive disease and Type 2 diabetes than in non-diabetic individuals. The increased risk for restenosis with rising levels of Lp(a) is set at a lower Lp(a) in diabetes and may be more harmful for diabetic patients.

Differential influence of LDL cholesterol and triglycerides on lipoprotein(a) concentrations in diabetic patients

OBJECTIVE

To evaluate the relationship between plasma lipid profiles and lipoprotein(a) [Lp(a)] concentrations in diabetic patients, taking into account the Lp(a) phenotype.

RESEARCH DESIGN AND METHODS

We included 191 consecutive diabetic outpatients (69 type 1 and 122 type 2 diabetic patients) in a cross-sectional study Serum Lp(a) was determined by enzyme-linked immunosorbent assay, and Lp(a) phenotypes were assessed by SDS-PAGE followed by immunoblotting. The statistical methods included a stepwise multiple regression analysis using the Lp(a) serum concentration as the dependent variable. The lipid profile consisted of total cholesterol, HDL cholesterol, LDL cholesterol, corrected LDL cholesterol, triglycerides, and apolipoproteins AI and B.

RESULTS

In the multiple regression analysis, LDL cholesterol (positively) and triglycerides (negatively) were independently related to the Lp(a) concentration, and they explained the 6.6 and 7.8% of the Lp(a) variation, respectively. After correcting LDL cholesterol, the two variables explained 3.8 and 6.4% of the Lp(a) variation, respectively. In addition, we observed that serum Lp(a) concentrations were significantly lower in patients with type IV hyperlipidemia (mean 1.0 mg/dl [range 0.5-17], n = 16) than in normolipidemic patients (6.5 mg/dl [0.5-33.5], n = 117) and in type II hyperlipidemic patients (IIa 15.5 mg/dl [3.5-75], n = 13; IIb 9 mg/dl [1-80], n = 45); P < 0.001 by analysis of variance.

CONCLUSIONS

Lp(a) concentrations were directly correlated with LDL cholesterol and negatively correlated with triglyceride levels in diabetic patients. Therefore, our results suggest that the treatment of diabetic dyslipemia may indirectly affect Lp(a) concentrations.

Quantification of lipoprotein(a) and apolipoprotein(a) in plasma and lipoprotein fractions in the hypertriglyceridemic state

Lipoprotein(a) [Lp(a)] is a risk factor for coronary heart disease (CHD) in particular in association with high low density lipoprotein (LDL) cholesterol concentrations. Hypertriglyceridemia on the other hand has been found to be associated with low Lp(a) values. This observation could be confirmed in 851 patients of the outpatient lipid clinic. Lp(a) median levels were 2.7-fold higher in patients with triglycerides below 200 mg/dl as compared with patients expressing triglyceride levels above 200 mg/dl (19 vs 7 mg/dl, P < 0.0001). In contrast to these data apolipoprotein(a) [apo(a)] has been detected in triglyceride-rich lipoproteins (TRL). To find out whether the presence of apo(a) in TRL is determined by the concentration of these particles, apo(a) concentrations were measured in TRL in fasting plasma of ten hypertriglyceridemic patients and ten normal controls with Lp(a) serum levels above 25 mg/dl. The apo(a) concentration in TRL did not show statistically significant differences between controls and patients (2.0+/-0.9 vs 1.8+/-1.6 mg/dl). In the second part of the study apo(a) levels in TRL were measured before and after fat feeding in eight healthy volunteers. Again no significant differences were observed in the apo(a) concentrations of the d < 1.006 a ml fraction before and after fat feeding (1.03+/-1.06 vs 0.81+/-0.63 mg/dl). In summary, this study fails to show an association of apo(a) with TRL for different states of hypertriglyceridemia. This negative finding is shown for constant particle numbers but might not be true if the particle number in TRL increases.

Lipoprotein (a) level in the population in Taiwan: relationship to sociodemographic and atherosclerotic risk factors

To examine the lipoprotein(a) (Lp(a)) level in the Taiwanese population and its association with cardiovascular risk factors, 1703 men and 1899 women aged 35 years and above were enrolled in a community-based study cohort established between 1990 and 1991. The distributions of Lp(a) levels were skewed to the right, and females were more likely than males to have Lp(a) levels greater than 30 mg/dl (14.3% versus 11.6%, P < 0.05). The Lp(a) level increased with age. Socioeconomic status did not seem to have consistent influence on the level of Lp(a). Smoking and alcohol use also had no effect on Lp(a) levels. Multivariate analysis indicated that older age and high level of low-density-lipoprotein cholesterol corresponded to an elevated Lp(a) level, while hypertriglyceridemia, low high-density-lipoprotein cholesterol level, obesity and high insulin resistance corresponded to a lower Lp(a) level. In univariate analysis, hyperinsulinemia was negatively associated with Lp(a) level (-0.107, P < 0.01) only in males. In females, use of oral contraceptive lowered Lp(a) levels, but menopause did not change Lp(a) levels. We also found that different correlation patterns existed for selected coagulation profiles between sexes. There was a significant correlation between Lp(a) and fibrinogen levels in males (0.154, P < 0.001) but not in females (0.007, P > 0.05). These data provided clues for investigating atherosclerotic risk factors and coagulation parameters for the Taiwanese population.

Lipoprotein (a) phenotype distribution in a population of bypass patients and its influence on lipoprotein (a) concentration

A case control study was undertaken to compare the distribution of apolipoprotein (a) phenotypes in patients suffering from atherosclerosis and undergoing coronary bypass surgery with the distribution observed in adequately selected controls. Cases differed from controls for triglycerides (1.90 +/- 0.88 mmol l-1 and 1.16 +/- 0.79 mmol l-1, P < 0.0001, respectively), HDL cholesterol (1.15 +/- 0.34 mmol l-1 and 1.69 +/- 0.42 mmol l-1, P < 0.0001, respectively), apolipoprotein AI (1.31 +/- 0.24 g l-1 and 1.70 +/- 0.29 g l-1, P < 0.0001, respectively) and lipoprotein a (Lp(a)) (0.32 +/- 0.30 g l-1 and 0.19 +/- 0.20 g l-1, P < 0.0001, respectively). The apolipoprotein (a) phenotypes were distributed differently in cases and controls (chi 2 = 25.26, P < 0.0001) with a lower percentage of isoforms of larger size and a higher percentage of isoforms of smaller size in patients. The Lp(a) concentration remained significantly higher in patients than in controls for most of the phenotypes, suggesting that both a high Lp(a) concentration and a different apolipoprotein (a) size distribution could be involved in the development of atherosclerosis in this population. In addition, patients exhibiting the highest Lp(a) concentrations had higher levels of LDL cholesterol and apolipoprotein B than patients exhibiting the lowest Lp(a) concentrations. This feature was not observed in controls. By contrast, controls with the highest Lp(a) concentration had significantly higher triglyceride levels than controls with the lowest Lp(a) concentration. This feature was not observed in patients. Our results indicate that patients undergoing bypass surgery have higher Lp(a) concentrations than controls, this increase being not completely explained by the difference in apolipoprotein (a) phenotype distribution. The high Lp(a) concentration seems to be associated with different lipid profiles in patients than in controls.

Lipoprotein (a) concentrations in patients with various dyslipidaemias

Although the genetic background is the most important determinant of lipoprotein (a) (Lp(a)) concentration other factors, such as coexistent dyslipidaemia, could modify its levels. We undertook the present study to examine the serum Lp(a) concentration in various dyslipidaemias and to reveal any correlation of serum Lp(a) concentration with the other lipid parameters in a large group of dyslipidaemic Greek patients. A total of 242 patients followed as outpatients in our lipid clinic were studied. The patients were stratified into four main groups. Patients with cholesterol levels greater than 5.17 mmol/L but normal triglycerides were regarded as hypercholesterolaemic (n=85), patients with triglycerides greater than 2.25 mmol/L but normal cholesterol levels as hypertriglyceridaemic (n=51), patients with both increased cholesterol and triglyceride levels as having mixed hyperlipidaemia (n=62), and finally patients with decreased (<0.90 mmol/L) high-density lipoprotein (HDL) cholesterol but normal cholesterol and triglyceride levels as having primary hypoalphalipoproteinaemia (n=44). Hypercholesterolaemic patients exhibited the highest serum Lp(a) levels, while hypertriglyceridaemic patients exhibited the lowest. Patients with mixed hyperlipidaemia had intermediate serum Lp(a) concentration, which was significantly higher than that of hypertriglyceridaemic patients but significantly lower than that of hypercholesterolaemic patients. Interestingly, patients with low serum HDL-cholesterol levels presented with low serum Lp(a) concentration similar to that of hypertriglyceridaemic patients. In hypercholesterolaemic patients no correlation was found between serum total and low-density lipoprotein (LDL) cholesterol nor apolipoprotein B (apoB) levels and Lp(a) concentration. On the contrary, in hypertriglyceridaemic patients an inverse correlation was observed between serum triglycerides and Lp(a) concentration. After dividing the hypertriglyceridaemic patients into one group with elevated (>1.3 g/L) serum apoB levels (n=32) and another group with normal apoB levels (n=19), we found that the median serum Lp(a) concentration was three times higher in hyperapoB patients compared to patients with normal apoB levels. We conclude that serum Lp(a) levels are different in various types of primary hyperlipidaemia and are modulated according to the type of lipid elevation.

Corticotropin increases the receptor-specific uptake of native low-density lipoprotein (LDL)--but not of oxidized LDL and native or oxidized lipoprotein(a) [Lp(a)]--in HEPG2 cells: no evidence for Lp(a) catabolism via the LDL-receptor

To understand the interaction of corticotropin (ACTH) and lipid catabolism, we analyzed the influence of ACTH on receptor-mediated lipoprotein uptake and compared the uptake and degradation of human native (N-LDL) and oxidized (Ox-LDL) low-density lipoprotein and native (N-Lp(a)) and oxidized (Ox-Lp(a)) lipoprotein(a) by human hepatoma (HepG2) cells. The receptor affinity of N-LDL, Ox-LDL, N-Lp(a), and Ox-Lp(a) was comparable (Kd, 33, 13, 24, and 13 micrograms/mL medium), whereas the maximum degradative capacity was 10.5-fold higher in N-LDL (Vmax, 1,978 ng/mg cell protein) compared with Ox-LDL (189 ng/mg). In N-LDL, it was 4.5-fold higher than in N-Lp(a) (442 ng/mg) and eightfold higher than in Ox-Lp(a) (246 ng/mg) (P < .05). Addition of ACTH to the cell cultures increased receptor-specific degradation of N-LDL by 44% (2,866 v 1,978 ng/mg, P < .05), whereas changes in Ox-LDL, N-Lp(a), and Ox-Lp(a) showed no significant increase. No differences in uptake specificity were observed with or without ACTH. In addition, a 12-hour preincubation of liver cells with LDL increased Lp(a) uptake by 40% to 50% with (411 v 620 ng/mg) and without (393 v 558 ng/mg) ACTH administration. These data indicate that ACTH elevates receptor-specific uptake of N-LDL, but only to a low extent versus Ox-LDL, N-Lp(a), or Ox-Lp(a). These results support the hypothesis that catabolism of oxidized lipoproteins and Lp(a) through the LDL receptor pathway is only a minor route of lipid metabolism, whereas LDL receptor activity itself can be stimulated by ACTH.

Association of Lp(a) rather than integrally-bound apo(a) with triglyceride-rich lipoproteins of human subjects

The majority of apolipoprotein (a) [apo(a)] in plasma is characteristically associated with Lipoprotein (a) [Lp(a)], having a buoyant density (1.05-1.08 g/ml) intermediate between low density lipoproteins (LDL) and high density lipoproteins (HDL). In the fed (postprandial) state or in the presence of fasting (endogenous) hypertriglyceridemia, a small proportion of plasma apo(a) is found in the density < 1.006 g/ml fraction of plasma, associated with larger and less dense triglyceride-rich lipoproteins (TRL). In order to further characterize the presence of apo(a) in ultracentrifugally-separated TRL (UTC-TRL), this lipoprotein fraction was isolated from plasma obtained in the fed state (three hours after an oral fat load) from healthy normolipidemic subjects (Lp(a): 38 +/- 8 mg/dl (mean +/- S.E.), n = 4) and also from plasma obtained after an overnight fast from hypertriglyceridemic patients (plasma TG: 8.16 +/- 2.00 mmol/l, Lp(a): 41 +/- 3 mg/dl, n = 18). Apo(a) in 3 h-postprandial UTC-TRL (5 +/- 2% of total plasma apo(a)) and in hypertriglyceridemic UTC-TRL (8 +/- 2% total apo(a)) was separable by electrophoresis and/or gel chromatography (FPLC) from the majority of UTC-TRL lipid. Apo(a) in UTC-TRL fractions had slow pre-beta electrophoretic mobility and was isolated in a lipoprotein size-range smaller than VLDL and larger than LDL, consistent with it being Lp(a). Recentrifugation of UTC-TRL resulted in the majority of apo(a) being recovered in the density > 1.006 g/ml fraction. Addition of proline to plasma samples before ultracentrifugation (final concentration: 0.1 M) substantially reduced the amount of Lp(a) in UTC-TRL. TRL separated from plasma by FPLC contained less apo(a) (2-5% of total plasma apo(a)), but this apo(a) was also readily dissociable from TRL lipid, had slow pre-beta electrophoretic mobility, and was associated with a lipoprotein with the size of Lp(a). Our data suggest that apo(a) in the TRL fraction of subjects with postprandial triglyceridemia or endogenous hypertriglyceridemia is not an integral component of plasma VLDL or chylomicrons, but represents the presence of non-covalently bound Lp(a).

Interrelationship of triglyceride-rich lipoproteins, serum lipoprotein (a) concentration and apolipoprotein(a) size

At present, the biochemical mechanisms underlying lipoprotein(a) (Lp(a)) metabolism are not fully understood. We analysed sera from 202 patients with atherosclerotic disease and 109 healthy subjects as a control group to investigate the possible relationship between triglyceride-rich lipoproteins (TRL) and serum lipoprotein(a) levels. To assess the influence of apolipoprotein (apo) (a) isoforms on the Lp(a)-TRL association, the apo(a) phenotypes of 177 patients and 95 controls were included in the analysis. Patients with atherosclerotic disease showed triglyceride levels almost within the normal range. There was no significant correlation between serum Lp(a) levels and triglyceride concentrations, or between Lp(a) and TRL levels in either group. When a subset of subjects from each group with serum triglycerides above 1.7 mmol l-1 was considered, a significant negative correlation between lipid concentration of very low density lipoproteins (VLDL) and serum Lp(a) levels was found only in patients. Control subjects with triglyceride levels under or over 1.7 mmol l-1 showed similar median Lp(a) levels (0.06 gl-1), in contrast to atherosclerotic patients, in whom median Lp(a) concentration was higher in the subset with serum triglycerides under 1.7 mmol l-1 than in those with triglyceride concentration above this value (0.16 vs. 0.13 gl-1). When patients with triglyceride concentrations above 1.7 mmol l-1 were classified into quartiles according to VLDL lipid concentration, subjects with the highest quartiles showed the lowest Lp(a) median levels. Despite the dependence of the Lp(a) concentration on apo(a) size isoforms, we found no effect of apo(a) genetic polymorphism on triglyceride levels or on TRL concentrations. We conclude that the variation in TRL metabolism may constitute a source of variation in serum Lp(a) concentrations that is independent of the genetically determined apo(a) molecule size.

Intraindividual variations in lipoprotein (a) levels and factors related to these changes

Lp(a) levels are genetically determined and remain stable without major changes throughout lives. However, when an individual's Lp(a) levels are observed over a one-year period, they show spontaneous variation. The rate of intraindividual variation in Lp(a) was observed in 16 patients with hypertension, hyperlipidemia and/or glucose intolerance in a chronic stable state who regularly visited the hospital clinic once a month, at least 10 times during the year, and in whom a total of 42 blood and clinical chemistry tests including serum lipids, Lp(a) and apoproteins were performed. The rate of annual intraindividual variation of Lp(a) averaged out as 16.6%. The rate was 18.8% for isoform S4 (n = 10), 18.6% for S3 (n = 3), and although small in number of subjects, other isoforms showed minor variation rates. There was a significant negative correlation between the rate of variation (y%) and LP(a) level (xmg/dl) r = -0.605, p < 0.05, y = -0.461 x +29.8). Therefore, when Lp(a) was high, the rate of variation (SD%) was low. This was consistent with the finding that the rates of variation were low for isoforms S2, S3S4 and F, whose molecular weights were low, accompanied by high Lp(a) levels. On the other hand, when the relationship between Lp(a) level and the amount of variation (SD mg/dl) was examined, there was no correlation between the two, since the amounts of variation were almost constant at a level of 3.8 mg/dl, regardless of Lp(a) level. The annual variation of Lp(a) level was found to be related to three groups of factors based on comparison of the variations among WHO phenotypes of hyperlipidemias, univariate correlation analysis with the clinical parameters tested, and multivariate analysis: the first group of factors was related to structure and metabolism of very low-density lipoprotein such as triglycerides, phospholipids, apo C-II, C-III, E, A-II and uric acid; the second group was related to thrombosis centering on platelets; and the third group involved those in the acute phase reactions represented by 1 hr and 2 hr erythrocyte sedimentation rates.

Lipoprotein (a) in patients with hyperlipidaemia

Lipoprotein (a) [Lp(a)] is an atherogenic lipoprotein which is similar in structure to, but metabolically distinct from, LDL. Factors modulating plasma Lp(a) concentrations are poorly understood. We hypothesized that patients with hyperlipidaemia have elevated Lp(a) levels and determined the phenotype, concentration and distribution of Lp(a) in a group of hyperlipidaemic patients (n = 107) compared with a control group (n = 128). Lp(a) concentrations were significantly increased in the hyperlipidaemic patients (mean, 34 +/- 4 mg dL-1; median, 19 mg dL-1) as compared with the controls (20 +/- 3 mg dL-1; 9 mg dL-1) (P < 0.01). Interestingly, after dividing the patients into one group with elevated cholesterol (> 200 mg dL-1) (n = 44) and another group with elevated triglycerides (> 200 mg dL-1) (n = 51) we found that Lp(a) concentrations were 2.3-fold higher in the high cholesterol patients (mean, 45 +/- 5; median, 41 mg dL-1) compared to the high triglyceride subjects (20 +/- 4; 8 mg dL-1) (P < 0.01). Furthermore, a negative correlation between triglyceride and Lp(a) plasma concentrations was found in patients exhibiting triglyceride levels > 300 mg dL-1 (r = -0.41, P = 0.04, n = 36) and with triglycerides > 400 mg dL-1 (r = -0.52, P = 0.03, n = 17). These data indicate that plasma Lp(a) concentrations are elevated in hyperlipidaemia if the patients have high cholesterol levels, whereas Lp(a) is normal to low in patients with elevated triglycerides.(ABSTRACT TRUNCATED AT 250 WORDS)