Lipoprotein(a)

Increase of serum lipoprotein (a), an adverse effect of growth hormone treatment

A number of reports show that high endogenous, or therapeutic administration of human growth hormone (hGH) cause an increase of serum lipoprotein a, Lp(a). Being thrombogenic Lp(a) is an independent risk factor of atherosclerotic cardiovascular disease (ASCVD). Hence, it is hypothesized that the recently reported association between childhood hGH treatment and cardiovascular morbidity is probably due to the GH effect on Lp(a) synthesis. It is therefore suggested to determine serum Lp(a) levels before and during hGH treatment in children and adults.

Relationship between lipoprotein(a) and spontaneous recanalization of infarct-related arteries in the early phase of acute myocardial infarction

BACKGROUND

Lipoprotein(a) (Lp[a]) is known to inhibit the fibrinolysis system and promote thrombus formation.

HYPOTHESIS

We retrospectively investigated the influences of Lp(a) on infarct-related artery patency in the early phase of acute myocardial infarction (AMI).

METHODS

In 144 patients with ST-segment elevation, myocardial, coronary angiography (CAG) was performed within 12 h of the onset of symptoms. Subjects were divided into 2 groups according to the thrombolysis in myocardial infarction (TIMI) grade, Group I (TIMI 0-1, n = 94) versus Group II (TIMI 2-3, n = 50). The Gensini score and 0- to 3-vessel disease score estimated the severity and extent of coronary artery disease (CAD), respectively. Lp(a), lipid profile and c-reactive protein (CRP) were measured before any medications including thrombolytics were given.

RESULTS

The Lp(a) level was higher in Group I than in Group II. There was a weak correlation between Lp(a) level and Gensini score. By multivariate logistic regression analysis, a Lp(a) level was a predictor of infarct-related artery patency in the early phase of AMI. There were no significant differences in the location of the infarct-related arteries, extent of CAD, time from pain to CAG, number of risk factors, and hs-CRP values between the 2 groups.

CONCLUSION

The Lp(a) level was significantly higher in patients with persistent occlusion compared with those with spontaneous recanalization of infarct-related arteries in the early phase of AMI.

Relationship between plasma lipoprotein (a), apolipoprotein (a) phenotypes, and other coronary heart disease risk factors in a Melbourne South Asian population

BACKGROUND

High plasma lipoprotein(a) [Lp(a)] level is a strong and important risk factor for cardiovascular disease (CVD). Small-sized apolipoprotein(a) [apo(a)] isoforms (F, B, S1, and S2) are inversely correlated with the high levels of Lp(a) in plasma and significantly associated with CVD. Although the effects of apo(a) phenotypes and various risk factors on Lp(a) status in South Asian population may have been studied in other countries, there are no reports involving these risk factors in Australia.

METHODS AND RESULTS

Factors contributing to variation in Lp(a) were surveyed in 402 (216 males and 186 females) South Asian Melburnians. There was a negative relationship between low alcohol beer per day and Lp(a) in men (P < 0.05). Approximately 21% of the variance of Lp(a) concentration in men and 6% in women were explained by age. Age was positively associated with Lp(a) concentrations in men but negatively in women. The most commonly occurring phenotype was apo(a) S3. In this phenotype, Lp(a) concentrations ranged from non-detectable to 811 mg/l. After adjusting for age, an inverse correlation was observed between Lp(a) concentration and apo(a) phenotypes (P < 0.01).

CONCLUSIONS

Although Lp(a) has been reported to be genetically determined, there are clearly other factors contributing to variations in Lp(a) concentrations in a South Asian population.

The Effects of Haemodialysis and Peritoneal Dialysis on Serum Lipoprotein(a) and C-Reactive Protein Levels

Elevated serum lipoprotein(a) is an independent risk factor for coronary artery disease, and C-reactive protein (CRP) is a general and cardiovascular marker in haemodialysis patients. We studied lipoprotein(a) and CRP levels in 48 haemodialysis and 24 continuous ambulatory peritoneal dialysis (CAPD) patients and 20 healthy individuals, after a 12 h fast. Serum lipoprotein(a) levels were elevated in 31.3%, 66.7% and 5% of haemodialysis and CAPD patients and control subjects, respectively. The difference between all groups was significant. Serum CRP levels were high in 43.8%, 58.4% and 5% of haemodialysis and CAPD patients, and healthy subjects, respectively. The mean serum CRP level was significantly different between all groups. Both protein levels were higher in CAPD patients than haemodialysis patients, suggesting that CAPD patients should be more closely monitored for coronary artery disease.

Lipid profile during rhGH therapy in pediatric renal transplant patients

To evaluate the effect of recombinant human growth hormone (rhGH) treatment on the lipid profile of pediatric renal transplant patients, we studied nine children treated with rhGH for 1 yr and a control group of 12 untreated patients matched in terms of age, renal transplant function and post-transplant follow-up. The levels of lipoprotein (a [Lp(a)], cholesterol, triglycerides, apolipoprotein A (APO A) and apolipoprotein B (APO B), and the APO B/APO A ratio, were determined at baseline and after 6 and 12 months of follow-up. RhGH therapy had no effect on cholesterol, triglycerides or apolipoproteins. Mean serum Lp(a) levels increased from 6.7 +/- 5.7 mg/dL at baseline to 11.8 +/- 10.7 after 6 months (p = 0.018) and 13.6 +/- 15.1 after 12 months of rhGH treatment (p = 0.04), but did not change in the control group. Lp(a) is a risk factor for cardiovascular morbidity, and increased Lp(a) levels may be a side-effect of rhGH treatment in renal transplant patients. Although long-term follow-up of a large number of patients is needed to establish the duration and extent of the effects of rhGH treatment on Lp(a) levels in transplanted children, serum Lp(a) levels should be carefully monitored in those receiving rhGH therapy.

The elevated plasma lipoprotein(a) concentrations in preeclampsia do not precede the development of the disorder

We sought to determine whether maternal plasma lipoprotein(a) [Lp(a)] levels are elevated in the second trimester, before the development of preeclampsia and other obstetrical complications, in women at risk. In the first part of the study (cross-sectional), plasma concentrations of Lp(a) were compared among 16 women with preeclampsia, 35 normotensive pregnant women and 18 healthy nonpregnant women. In the second part (nested case-control), blood samples were collected prospectively from 82 women at risk of preeclampsia, at 14-24 weeks of gestation, and Lp(a) levels were compared between those in whom preeclampsia or other obstetrical complications developed and those in whom they did not. In the cross-sectional study, plasma concentrations of Lp(a) were significantly higher in women with preeclampsia than in normotensive pregnant and healthy nonpregnant women (41 +/- 31 vs. 24 +/- 16 and 15 +/- 10 mg/dl, respectively; P=.001). Of the 82 women in the second part of the study, 9 (11%) developed preeclampsia and 19 (23%) had complications such as intrauterine growth restriction, preterm delivery and fetal or neonatal loss. There were no differences in plasma Lp(a) concentrations between the women with preeclampsia and those without complications, though Lp(a) levels were significantly higher in women with other complications than in those with either preeclampsia or uncomplicated pregnancies (40 +/- 29 vs. 17 +/- 13 or 28 +/- 18 mg/dl, respectively; P=.05). In conclusion, elevated plasma levels of Lp(a), associated with clinically established preeclampsia, are not detected before the appearance of the disorder in pregnant women at risk.

Lipoprotein (a) levels in normal pregnancy and in pregnancy complicated with pre-eclampsia

Lipoprotein (a) (Lp(a)) is recognised as a risk factor for arterial and venous thrombosis, a property which may relate to its structural similarity to plasminogen. Pregnancy is associated with a hypofibrinolytic state. Elevated Lp(a) may influence fibrinolysis and have an unfavourable role in pregnancy outcome. In this study alterations in plasma Lp(a) concentrations during normal pregnancy was examined, in a detailed longitudinal investigation, in ten women together with changes in other lipid parameters. In addition, Lp(a) concentrations were examined in subjects with pre-eclampsia (n=10) relative to matched controls (n=10), since it has recently been reported that a substantial increase in circulating Lp(a) occurs in this disorder. Lp(a) concentration increased steadily in normal pregnancy between 10 and 35 weeks with a doubling of the median value from 14.5 to 27.0 mg/dl (P=0.01). A significant increase in Lp(a) values was observed in all subjects with increasing gestation (median rise 190%, range 117-340%). This increase was intermediate to those seen in plasma triglyceride and cholesterol. No significant difference in Lp(a) values was observed in subjects with pre-eclampsia, compared with matched normal pregnancy controls (median 14 mg/dl [IQR 4.7-69.0] in pre-eclampsia vs 20 mg/dl [9.0-56. 3] in controls; P=0.57), at a median gestation of 32 weeks. In conclusion, there is a 2-fold increase in Lp(a) during normal pregnancy, which may influence fibrinolysis. Circulating Lp(a) is not significantly elevated in women with pre-eclampsia, and thus is unlikely to play a role in the pathophysiology of this disorder.

Interaction of the protein C/protein S anticoagulant system, the endothelium and pregnancy

Normal pregnancy is associated with significant changes in haemostasis, lipid metabolism and endothelial function. This suggests that maternal adaptation in these systems is required for successful pregnancy outcome. A number of acquired and heritable prothrombotic abnormalities are associated with complications in pregnancy. A common feature of these abnormalities is their ability to alter endothelial function or the protein C/protein S system and increase thrombin generation. In this review the normal function of the endothelium and the protein C/protein S system is detailed. The changes which characterize normal and complicated pregnancies are outlined and the evidence for the impact of heritable and acquired disorders of the protein C/protein S system on pre-eclampsia and fetal loss are discussed.

Treatment of obese subjects with the oral growth hormone secretagogue MK-677 affects serum concentrations of several lipoproteins, but not lipoprotein(a)

Obesity is associated with blunted GH secretion and an unfavorable lipoprotein pattern. The objective of this study was to investigate the effects of treatment with the oral GH secretagogue MK-677 on lipoproteins in otherwise healthy obese males. The study was randomized, double blind, and parallel. Twenty-four obese males, aged 18-50 yr, with body mass index greater than 30 kg/m2 and waist/hip ratio above 0.95 were treated with 25 mg MK-677 (n = 12) or placebo (n = 12) daily for 8 weeks. MK-677 treatment did not significantly change serum lipoprotein(a) [Lp(a)] levels. Serum apolipoprotein A-I and E (apoA-I and apoE) were increased at 2 weeks (P < 0.001 and P < 0.01 vs. placebo, respectively), but were not changed at study end. Serum total cholesterol and low density lipoprotein (LDL) cholesterol (LDL-C) levels were not significantly changed by MK-677 treatment. Serum high density lipoprotein (HDL) cholesterol (HDL-C) was increased at 2 weeks of MK-677 treatment (P < 0.01 vs. placebo), but not at 8 weeks. The LDL-C/HDL-C ratio was reduced after 8 weeks of MK-677 treatment (P < 0.05 vs. placebo). Mean LDL particle diameter was decreased at 2 weeks (P < 0.05 vs. placebo), but was unchanged compared with baseline values at 8 weeks (P = NS vs. placebo). The level of serum triglycerides was increased at 2 (P < 0.05 vs. placebo), but not at 8, weeks. Lipoprotein lipase activity in abdominal and gluteal sc adipose tissue was not affected by active treatment. In conclusion, treatment with the oral GH secretagogue MK-677 affected circulating lipoproteins. The effects on serum apoA-1, apoE, triglycerides, and mean LDL particle diameter were transient. At study end, the LDL-C/HDL-C ratio was decreased. MK-677 treatment did not significantly affect serum Lp(a) concentrations at the present dose and administration protocol.

Current insights into the "antiphospholipid" syndrome: clinical, immunological, and molecular aspects

Advances in defining the target antigen(s) for the autoantibodies in the APS highlight the inadequacies of the current classification of these autoantibodies into anticardiolipin and LA antibodies. The discovery that beta 2GPI is the target antigen for the autoantibodies detected in solid-phase immunoassays has opened a number of areas of research linking these autoantibodies to atherogenesis and thrombus formation. Although the role of beta 2GPI in the regulation of blood coagulation in unclear, current evidence suggests that anti-beta 2GPI antibodies interfere with its "normal" role and appear to promote a procoagulant tendency. The expansion of research in this area and the diversity of the clinical manifestations of patients with APS have resulted in the inclusion of molecular biologists and pharmaceutical companies joining immunologists, hematologists, rheumatologists, obstetricians, neurologists, vascular surgeons, and protein and lipid biochemists in attempting to understand the pathophysiology of this condition. Although the published literature may result in conflicting results and introduce new controversies, developing standardized laboratory methods and extrapolation of in vitro experimental results to the vivo situation will advance our understanding of the regulation of the immune system and its interaction with normal hemostatic mechanisms. Since the authors' last review in 1991, the study and understanding of the pathophysiology of APS have evolved from lipid biochemistry to molecular techniques that may eventually provide specific therapies for the clinical manifestations of this condition. Although current treatment has improved the morbidity associated with this condition, especially in improving pregnancy outcomes, future therapies, as outlined in this review, may specifically address the biological abnormalities and have fewer side effects. Better diagnostic tools, such as magnetic resonance imaging with perfusion studies, will allow the study of the true incidence and prevalence of vascular flow changes/tissue ischemia and infarction associated with aPL antibodies and help determine treatment and prophylaxis for APS patients. APS is still the only hypercoagulable condition where both arterial and venous beds can be affected independently or in the same individual.

Increased serum lipoprotein(a) concentrations after growth hormone (GH) treatment in patients with isolated GH deficiency

Fourteen post-pubertal subjects (11 male, 3 female) with isolated growth hormone (GH) deficiency were treated with a low dose (0.125 U/kg for the first 4 weeks and thereafter 0.25 U/kg/week) daily sc GH injection for 1 year. Fasting blood samples were collected at entry into the study and subsequently at 3 monthly intervals for estimation of serum cholesterol, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol and lipoprotein(a) [Lp(a)]. Serum Lp(a) increased progressively during the treatment period (by analysis of variance) and was 41% higher at 12 months (P < 0.02) despite the fact that five patients showed little or no change. There was no significant change in any of the other lipid fractions. These observations are of concern as Lp(a) is an independent risk factor for cardiovascular disease and should introduce a cautionary note into the enthusiastic efforts to offer GH replacement to all GH deficient adults.

Lipoprotein(a) is not elevated in non-diabetic microalbuminuric subjects. A longitudinal study of lipoprotein(a) concentrations and apolipoprotein(a) size isoforms

Microalbuminuric non-diabetic subjects have an increased risk of cardiovascular disease which is not explained by standard risk factors. In diabetic patients, microalbuminuria is associated with increased lipoprotein(a) concentrations. We have determined lipoprotein(a) concentrations and duplicate measures of albumin excretion rate, on two occasions separated by around 3 years, in 125 Europid subjects aged 40-75 years without hypertension or glucose intolerance and in 49 offspring aged 15-40 years. The apolipoprotein(a) isoform size, the major genetic determinant of lipoprotein(a) concentration, was also determined. There were no differences in lipoprotein(a) concentration between the 42 subjects who were microalbuminuric on either or both samples at screening (median 9.4 mg/dl, 20th and 80th percentiles 2.6 and 46.3 mg/dl) and the 79 who had been normoalbuminuric at both collections (median 10.9 mg/dl, 20th and 80th percentiles 2.9 and 53.0 mg/dl; P = 0.58). Lipoprotein(a) concentrations were not significantly different between subjects with or without microalbuminuria at recell (P = 0.55) or between those with or without microalbuminuria classified by mean albumin excretion rate in either collection (P = 0.24 and P = 0.73, respectively). There were no significant relationships between albumin excretion rate as a continuous variable and lipoprotein(a) concentration, or between changes in the two variables over 3 years. The microalbuminuric and normoalbuminuric subjects had similar distributions of size isoforms. There were also no differences in lipoprotein(a) concentration or isoform distribution between offspring of microalbuminuric and of normoalbuminuric subjects. In conclusion, we found no evidence that microalbuminuric subjects with normal blood pressure and normal glucose tolerance have elevated concentrations of lipoprotein(a) to explain their increased cardiovascular risk.

Elevated serum lipoprotein(a) in subclinical hypothyroidism

OBJECTIVES

Asymptomatic lymphocytic thyroiditis and subclinical hypothyroidism are associated with increased risk for coronary artery disease. The present study aimed at evaluating serum lipoprotein(a)(Lp(a)), measured as apo(a), and other lipid parameters in 32 subjects with asymptomatic subclinical hypothyroidism.

SUBJECTS

Thirty-two Chinese subjects with asymptomatic subclinical hypothyroidism were compared to 96 age and sex-matched healthy controls.

RESULTS

Subclinical hypothyroid patients had higher (P < 0.005) apo(a), total triglyceride (TG), total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) but lower (P < 0.05) high density lipoprotein cholesterol (HDL-C) levels compared with sex and age-matched controls (apo(a) 296 (48-1650) vs 182 (19-1952 U/l), geometric mean (range); TG 1.86 +/- 0.94 vs 1.33 +/- 0.74 mmol/l (mean +/- SD); TC 6.10 +/- 1.17 vs 5.42 +/- 1.13 mmol/l; LDL-C 4.10 +/- 1.00 vs 3.49 +/- 0.96 mmol/l; HDL-C 1.15 +/- 0.40 vs 1.34 +/- 0.40 mmol/l, respectively). APo A-I and apo B were also higher than controls (1.96 +/- 0.48 vs 1.48 +/ 0.29 g/l and 1.44 +/- 0.42 vs 1.05 +/- 0.29 g/l, respectively). Total cholesterol/HDL ratio and LDL/HDL ratio were also elevated in these subjects (5.77 +/- 1.96 vs 4.28 +/- 1.19 and 3.89 +/- 1.41 vs 2.79 +/- 0.97, respectively, both P < 0.0005). Individual analysis revealed that 16 (50%) subjects had hyperlipoproteinaemia (TC > 5.2 mmol/l in 10; TC > 5.2 mmol/l and TG > 2.3 mmol in six) as compared to 21(20.8%) in the control group (P < 0.005). Subjects with TSH > or = 11.0 mIU/l had significantly higher TC/HDL and LDL/HDL ratios. A significant correlation was observed between TSH levels and TC/HDL ratios (r = 0.455, P < 0.01).

CONCLUSIONS

Subclinical hypothyroidism is associated not only with elevated LDL-cholesterol levels and low HDL-cholesterol levels but also with elevated lipoprotein (a). This may further increase the risk development of atherosclerosis.

Effect of testosterone enanthate on serum lipoproteins in man

Sixty-three normal Caucasian men were administered intramuscular testosterone enanthate (TE) 200 mg i.m. weekly for 12 months as part of a male contraceptive trial. This dose of TE caused a 2.5-fold increase in trough serum testosterone concentrations. High density lipoprotein cholesterol (HDL-C) was significantly depressed from pretreatment concentration of 1.19 +/- 0.04 nmol/l to 1.03 +/- 0.04 mmol/l after 12 weeks of treatment, and remained suppressed for the duration of treatment (p < 0.001). There were no changes in serum concentration of total cholesterol (TC), low density lipoprotein cholesterol (LDL-C) or triglycerides (TG) during treatment, but the concentrations of TC and LDL-C were depressed at three months post-treatment. There was a sustained elevation in LDL-C:HDL-C ratio during TE treatment (p < 0.005), from 3.41 +/- 0.15 pretreatment to 3.88 +/- 0.19 after 12 weeks of TE treatment. Sex hormone binding globulin (SHBG), but not testosterone (T) or estradiol (E2), was significantly associated with HDL-C (r = 0.83, p = 0.001). Lipoprotein (a) (Lp(a)) was measured in a subgroup of 33 men: serum concentration fell from 187 +/- 45 mg/l pretreatment to 140 +/- 35 mg/l after 16 weeks of TE treatment (p < 0.01).

Immunohistochemical detection of lipoprotein(a) in the wall of placental bed spiral arteries in normal and severe preeclamptic pregnancies

In normal pregnancy trophoblast invades the spiral arteries and produces the physiological fibrinoid degeneration of the vessel wall. In pre-eclampsia, physiological change is restricted and pathological change develops in the non-invaded arteries, including acute atherosis. This study was undertaken to determine if lipoprotein(a) [Lp(a)], which is associated with atherogenesis is present in the wall of spiral arteries that have undergone physiological and pathological change. One hundred and sixteen spiral arteries were examined from 18 normal and 24 severe pre-eclamptic pregnancies. Lp(a) was detected in all atherotic and necrotic lesions, in 57% of spiral arteries with medical disorganization or hyperplasia, and in 45% of those with physiological change. When Lp(a) was detected differences were found in the amount seen: it was most in atherosis, less in necrosis, less still in medical change, and least in physiological change. For the same vascular change generally more Lp(a) was detected in the pre-eclamptic group than in the normal group. The detection of Lp(a) helps to distinguish physiological fibrinoid from atherotic and necrotic fibrinoid. Many atherotic and necrotic areas initially overlooked using standard histology were highlighted using immunohistochemistry. Atherosis can develop in spiral arteries that have been invaded by trophoblast. In those with pre-eclampsia, atherosis was found in 56% of decidual but only in 8% of myometrial spiral arteries. Small areas of necrosis were common in physiologically changed arteries from normal pregnancies.

Serum lipids and apolipoproteins and their relationship with macrovascular disease in type 1 diabetes

In order to examine the relationship between serum lipids and apolipoproteins and macrovascular disease in patients with Type 1 diabetes mellitus, 50 patients with Type 1 diabetes mellitus attending the diabetic clinics at St Mary's and St Charles' Hospitals, London were recruited into a cross-sectional study. B-mode ultrasound was used to measure intima-media thickness and define an arterial ultrasound score for each patient as a non-invasive indicator of atherosclerotic change. Intima-medial (i-m) thickness was significantly higher in those subjects with clinical evidence of macrovascular disease compared to those without macrovascular disease (0.865 +/- 0.191 vs 0.695 +/- 0.162 mm, p = 0.0038). In the study group there were significant correlations between i-m thickness and age (r = 0.65, p < 0.01), total serum cholesterol (r = 0.32, p < 0.01), and serum fibrinogen (r = 0.43, p < 0.01) but no other lipid or apolipoprotein variable. When i-m thickness was corrected for age there were significant correlations with total cholesterol (r = 0.43, p < 0.01) and LDL-cholesterol (r = 0.42, p < 0.01). Whereas total and LDL-cholesterol and serum fibrinogen concentrations were related to the extent of atherosclerotic disease by ultrasound techniques, there was no relationship with high density lipoprotein (HDL) or subfraction cholesterol concentrations. HDL-cholesterol may not be a useful marker for cardiovascular disease in Type 1 diabetes.

Lipoprotein(A): physiologic function, association with atherosclerosis, and effects of lipid-lowering drug therapy

OBJECTIVE

To review the structure and physiologic function of lipoprotein(a) [Lp(a)], review the association of Lp(a) with the development of atherosclerosis, and to critically evaluate the current literature regarding the effects of lipid-lowering drug therapy on Lp(a) serum concentrations.

DATA SOURCES

English language clinical and animal studies, abstracts, and review articles pertaining to Lp(a).

STUDY SELECTION AND DATA EXTRACTION

Relevant human and animal studies examining Lp(a)'s role in atherosclerosis and the effect of drug therapy on Lp(a) serum concentrations.

DATA SYNTHESIS

Possible physiologic functions and potential atherogenic mechanisms of Lp(a) are discussed. Evidence supporting the association of Lp(a) with atherosclerosis is presented. Studies evaluating the effects of lipid-lowering drug therapy on Lp(a) concentrations are reviewed and critiqued.

CONCLUSIONS

Lp(a) concentrations are correlated with the risk of atherosclerotic vascular disease (AVD) in both animals models and human studies. Drug therapies that have produced a consistent reduction in Lp(a) concentration include niacin alone or in combination with a bile acid sequestrant or neomycin. However, additional, larger studies are needed to evaluate the ability of drug therapies to specifically reduce elevated Lp(a) concentrations. Preliminary information suggests that reduction in Lp(a) concentrations may be associated with atherosclerotic plaque regression. Although drugs are available to lower Lp(a), one cannot conclude that lowering of Lp(a) is warranted until clinical trials demonstrating beneficial effects have been published.

Reduced serum lipoprotein(a) levels in patients with primary biliary cirrhosis

Lipoprotein(a) (Lp(a)) is a unique lipoprotein, elevated serum levels of which are independently associated with an increased risk of coronary heart disease (CHD). Primary biliary cirrhosis (PBC) is often associated with high serum cholesterol, itself a risk factor for CHD. Despite this, patients with PBC are thought to have a lower than expected incidence of CHD. We hypothesised that this may be related to low serum levels of Lp(a) in PBC patients. This was investigated by collecting fasting blood samples from 42 patients with PBC, 39 age- and sex-matched subjects with non-PBC liver disease and 432 community control subjects. Serum was analysed for total cholesterol, triglycerides, high density lipoprotein (HDL) cholesterol and apolipoproteins A1 and B (apo A1 and apo B). Lp(a) was measured by an enzyme-linked immunosorbent assay (ELISA) technique. There was a significant reduction of Lp(a) concentrations in the PBC group compared with the healthy controls (median value 28.5 mg/l vs. 75.0 mg/l, P < 0.005) and between the non-PBC liver disease group (median value 52.0 mg/l) and control group (P = 0.001). Within both the liver disease and PBC patient groups there were significant negative correlations between Lp(a) levels and bilirubin (R = -0.564, P < 0.001 and R = -0.395, P = 0.010 respectively). This preliminary study has demonstrated reduced Lp(a) levels in PBC patients which may be a contributory factor to explain a possible cardioprotective effect in such patients, despite elevated LDL cholesterol levels.

Lipoprotein(a) plasma concentrations associated with lipolytic activities in eight kindreds with familial combined hyperlipidemia and normolipidemic subjects

The relationship between lipoprotein(a) [Lp(a)] and metabolism of triglyceride-rich lipoproteins (TRL) was studied in 58 untreated patients with familial combined hyperlipidemia (FCH) from eight different kindreds, 17 spouse controls, and 17 unrelated controls. Lp(a) plasma concentrations were not significantly different between FCH subjects (343 +/- 61 mg/L, mean +/- SEM) and controls (249 +/- 52 mg/L). In FCH, log-transformed Lp(a) levels correlated positively with postheparin lipoprotein lipase ([LPL] r = .61, P = .0002) and hepatic lipase ([HL] r = .46, P = .008) activities and total plasma cholesterol level (r = .30, P = .03). In controls, Lp(a) correlated with LPL (r = .50, P = .04) and total plasma cholesterol level (r = .51, P = .003). In eight FCH patients, treatment with the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor simvastatin resulted in significantly increased mean LPL activities and plasma Lp(a) concentrations. In three of these FCH patients, repeated measurements during 1 year demonstrated that changes in Lp(a) concentrations were paralleled by similar changes in LPL activity, but not HL activity. The observed correlation between postheparin plasma lipolytic activities and Lp(a) plasma concentrations suggests a connection between the metabolism of TRL and Lp(a).

Evidence of persistent measles virus infection in Crohn's disease

Transmission electron microscopy was used to examine the microvasculature of perfusion-fixed tissues from Crohn's disease and control patients. Paramyxovirus-like particles, and inclusions consisting of condensations of nucleocapsid, in giant cells and endothelium at foci of vascular injury were identified in all 9 Crohn's disease patients. Tissues from patients with Crohn's disease were also examined by either in situ hybridisation (n = 10) or immunohistochemistry (n = 15), and compared to inflammatory and noninflammatory controls (n = 22). Hybridisation for measles virus N-protein genomic RNA was positive in all cases of Crohn's disease localising to foci of granulomatous vasculitis and lymphoid follicles. Positive immunohistochemical staining for measles virus nucleocapsid protein was positive in 13 of 15 patients with Crohn's disease, localising to foci of granulomatous inflammation. Hybridisation for measles virus RNA was positive in a minority of control intestinal tissues; viral inclusions were not seen ultrastructurally. Immunostaining was negative in control cases of intestinal tuberculosis. These observations suggest that measles virus is capable of causing persistent infection of the intestine and that Crohn's disease may be caused by a granulomatous vasculitis in response to this virus.

Lipoprotein (a) as an independent risk factor for myocardial infarction in patients with common hypercholesterolaemia

AIMS

To examine whether lipoprotein (a) (Lp(a)) increases the risk of myocardial infarction (MI) in patients with common hypercholesterolaemia.

METHODS

15 middle aged men with common hypercholesterolaemia (mean serum low density lipoprotein (LDL) cholesterol 4.94 mmol/l, SD 1.0) and a history of MI were selected consecutively from referrals to a lipid clinic. A control group that had not sustained an MI and with similar age, sex, cigarette smoking and blood pressure characteristics was also selected from the same clinic. Serum cholesterol, triglyceride, LDL cholesterol, high density lipoprotein cholesterol, apolipoproteins AI and B and Lp(a) were measured in both groups. Lp(a) was assayed by immunoturbidity.

RESULTS

The serum concentration of Lp(a) was significantly higher in patients with MI (geometric mean 0.64 (95% confidence interval 0.36 to 1.14) v 0.30 (0.21 to 0.42) g/l, p = 0.02), but there were no significant differences in other variables. Stepwise logistic regression analysis showed that Lp(a) was the only significant predictor of MI (p < 0.02). The odds ratio of MI (adjusted for age, smoking, blood pressure and apolipoprotein B) for an Lp(a) of > 0.57 g/l was 16.5, 95% confidence interval 2.3 to 125.4 (p = 0.001).

CONCLUSION

In middle aged men with common hypercholesterolaemia the serum concentration of Lp(a) is a powerful and independent risk factor for MI. Lp(a) should probably be routinely measured in all patients referred to a lipid clinic.

Growth hormone treatment of growth hormone-deficient adults results in a marked increase in Lp(a) and HDL cholesterol concentrations

The effects of growth hormone treatment of adults with adult-onset pituitary insufficiency on lipoproteins and apolipoproteins were investigated. Nine patients, one women and eight men (age range, 34-58 years), who had been treated for pituitary tumors were studied. They had complete pituitary insufficiency with a duration of at least 1 year. All patients received replacement therapy with thyroid hormones, glucocorticoids, and gonadal steroids. The study had a double-blind, placebo-controlled, crossover design for active treatment with recombinant human growth hormone (0.25-0.5 units/kg per week s.c. given each evening) for 6 months. Fasting serum levels of cholesterol; triglycerides; high density lipoprotein and low density lipoprotein cholesterol; apolipoproteins A-I, B, and E; and lipoprotein (a) were measured before and after 6 and 26 weeks of treatment. Lipoprotein (a) concentrations increased markedly during treatment and were about twice as high compared with pretreatment levels. Serum cholesterol and low density lipoprotein cholesterol concentrations were decreased after 6 weeks of treatment, but levels had returned to pretreatment levels after 26 weeks. High density lipoprotein cholesterol concentrations increased during treatment and were significantly higher than pretreatment levels after 26 weeks of treatment. Serum triglyceride concentrations did not change significantly, but in two patients with marked hypertriglyceridemia, growth hormone treatment resulted in a marked decrease. Serum concentrations of apolipoproteins A-I, B, and E did not change significantly, but changes in apolipoprotein A-I and B concentrations were in parallel to those observed for high density lipoprotein cholesterol and low density lipoprotein cholesterol, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipoprotein(a) and accelerated coronary artery disease in cardiac transplant recipients

High concentrations of serum lipoprotein(a) (Lp(a)) are associated with an increased risk of atherosclerotic vascular disease in the nontransplanted population. However, its relation with accelerated coronary artery disease (CAD) in cardiac transplant recipients has not been reported. We measured serum Lp(a) in 130 cardiac transplant recipients undergoing routine follow-up, which included annual coronary angiography. The median Lp(a) concentration in 33 patients with CAD was 71 mg/dl, which was significantly higher than the corresponding value of 22 mg/dL in the 97 patients without CAD (p = 0.0006). Multivariant analysis showed the serum Lp(a) value to be a higher significant risk factor for CAD irrespective of the other factors included in the regression analysis. Thus a high concentration of serum Lp(a) is an important, independent risk factor for the development of accelerated CAD in transplant recipients.

Differential effects of transdermal estradiol and sequential progestogens on impedance to flow within the uterine arteries of postmenopausal women

OBJECTIVE

To investigate the relationship between estradiol (E2), progestogen, and impedance to blood flow in the uterine artery.

SUBJECTS

Twelve postmenopausal women treated for two cycles with transdermal E2, 0.05 mg/d, with either norethindrone acetate, 0.7 mg, or medroxyprogesterone acetate, 10 mg added sequentially.

MEASUREMENTS

Transvaginal ultrasonography and color flow imaging were used to measure the pulsatility index in the uterine arteries before and during the E2-only and combined E2/progestogen phases.

RESULTS

The mean pulsatility index fell to 53% of its pretreatment value within 12 days E2 administration (P < or = 0.0001) and was 66% of its pretreatment value in the combined phase (P < 0.005). Similar changes were seen in cycle 2. Time since menopause was correlated with the pretreatment pulsatility index (r = 0.674, P < 0.05) and change in pulsatility index on treatment (r = 0.856, P < 0.001).

CONCLUSION

Gonadal hormones have a profound effect on arterial tone in postmenopausal women; this action may help explain some of the beneficial effects of estrogen on arterial disease risk.

Lipoprotein risk factors in vegetarian women of Indian descent are unrelated to dietary intake

Dietary intakes, anthropometric indices and plasma lipoprotein and alpha-tocopherol concentrations were measured in premenopausal vegetarian women of Indian descent (n = 22) and in white women of European descent consuming either mixed (n = 22) or vegetarian diets (n = 18). The Indian women were shorter in height than the white women and had a higher proportion of body fat. Energy intakes were lower in the Indian women, both in absolute terms and per kg body weight. The proportion of energy derived from saturated fatty acids was lower and that from polyunsaturated fatty acids was greater in both Indian and white vegetarians compared with the subjects on mixed diets. Intakes of dietary fibre and vitamins C and E were higher in the white vegetarians compared with the other groups. Plasma concentrations of total and LDL cholesterol and apolipoprotein B and the ratio of apolipoprotein B/apolipoprotein AI were lower and HDL and HDL2 cholesterol, alpha-tocopherol concentrations and the ratio of alpha-tocopherol/cholesterol were greater in the white vegetarian group than in the other groups. Total plasma cholesterol was associated with measures of truncal obesity, especially subscapular skinfold thickness and the percentage energy derived from saturated fatty acids. Plasma concentrations of apo(a) were higher and those of HDL and HDL2 cholesterol and sex hormone binding globulin (SHBG) were lower in the Indian vegetarian women compared with both groups of white women. No relationship could be found between apo(a), HDL and HDL2 cholesterol concentration and nutrient intake but HDL and HDL2 were negatively associated with the proportion of body fat and apo(a) weakly with subscapular skinfold thickness.(ABSTRACT TRUNCATED AT 250 WORDS)