Lipoprotein(a) plasma concentrations after renal transplantation: a prospective evaluation after 4 years of follow-up

Relationship between lipoprotein(a) levels, cardiovascular outcomes and death in patients with chronic kidney disease: a systematic review of prospective studies

INTRODUCTION AND AIM

In the general population, high levels of lipoprotein(a) (Lp(a)) are an independent risk factor for atherosclerotic cardiovascular diseases. However, the information available in patients with chronic kidney disease (CKD) is less robust. The main objective of this updated systematic review of prospective studies was to analyze the association between elevated Lp(a) levels and cardiovascular outcomes or death in patients with CKD.

METHODS

The PRISMA guidelines were used to carry out this systematic review. Randomized clinical trials or prospective observational studies that evaluated the association between Lp(a) levels and cardiovascular outcomes or death in CKD patients were searched in the current literature.

RESULTS

Fifteen studies including 12,260 individuals were identified and considered eligible for this systematic review. In total, 14 prospective cohorts and one post-hoc analysis of a randomized clinical trial were analyzed. Eight studies evaluated hemodialysis patients, one study analyzed patients on peritoneal dialysis, while six studies evaluated subjects with different stages of CKD. Median follow-up duration ranged from 1 to 8.6 years. Our findings showed that elevated Lp(a) values were associated with a higher risk of cardiovascular events or death in most studies, despite adjusting for traditional risk factors.

CONCLUSION

The findings of this systematic review show that there is a positive association between Lp(a) levels and fatal and non-fatal cardiovascular events in patients with CKD.

Non-genetic influences on lipoprotein(a) concentrations

An elevated level of lipoprotein(a) [Lp(a)] is a genetically regulated, independent, causal risk factor for cardiovascular disease. However, the extensive variability in Lp(a) levels between individuals and population groups cannot be fully explained by genetic factors, emphasizing a potential role for non-genetic factors. In this review, we provide an overview of current evidence on non-genetic factors influencing Lp(a) levels with a particular focus on diet, physical activity, hormones and certain pathological conditions. Findings from randomized controlled clinical trials show that diets lower in saturated fats modestly influence Lp(a) levels and often in the opposing direction to LDL cholesterol. Results from studies on physical activity/exercise have been inconsistent, ranging from no to minimal or moderate change in Lp(a) levels, potentially modulated by age and the type, intensity, and duration of exercise modality. Hormone replacement therapy (HRT) in postmenopausal women lowers Lp(a) levels with oral being more effective than transdermal estradiol; the type of HRT, dose of estrogen and addition of progestogen do not modify the Lp(a)-lowering effect of HRT. Kidney diseases result in marked elevations in Lp(a) levels, albeit dependent on disease stages, dialysis modalities and apolipoprotein(a) phenotypes. In contrast, Lp(a) levels are reduced in liver diseases in parallel with the disease progression, although population studies have yielded conflicting results on the associations between Lp(a) levels and nonalcoholic fatty liver disease. Overall, current evidence supports a role for diet, hormones and related conditions, and liver and kidney diseases in modifying Lp(a) levels.

Managing cardiovascular disease risk in South Asian kidney transplant recipients

South Asians (SA) are at higher cardiovascular risk than other ethnic groups, and SA kidney transplant recipients (SA KTR) are no exception. SA KTR experience increased major adverse cardiovascular events both early and late post-transplantation. Cardiovascular risk management should therefore begin well before transplantation. SA candidates may require aggressive screening for pre-transplant cardiovascular disease (CVD) due to their ethnicity and comorbidities. Recording SA ethnicity during the pre-transplant evaluation may enable programs to better assess cardiovascular risk, thus allowing for earlier targeted peri- and post-transplant intervention to improve cardiovascular outcomes. Diabetes remains the most prominent post-transplant cardiovascular risk factor in SA KTR. Diabetes also clusters with other metabolic syndrome components including lower high-density lipoprotein cholesterol, higher triglycerides, hypertension, and central obesity in this population. Dyslipidemia, metabolic syndrome, and obesity are all significant CVD risk factors in SA KTR, and contribute to increased insulin resistance. Novel biomarkers such as adiponectin, apolipoprotein B, and lipoprotein (a) may be especially important to study in SA KTR. Focused interventions to improve health behaviors involving diet and exercise may especially benefit SA KTR. However, there are few interventional clinical trials specific to the SA population, and none are specific to SA KTR. In all cases, understanding the nuances of managing SA KTR as a distinct post-transplant group, while still screening for and managing each CVD risk factor individually in all patients may help improve the long-term success of all kidney transplant programs catering to multi-ethnic populations.

The role of lipoprotein (a) in chronic kidney disease

Lipoprotein (a) [Lp(a)] and its measurement, structure and function, the impact of ethnicity and environmental factors, epidemiological and genetic associations with vascular disease, and new prospects in drug development have been extensively examined throughout this Thematic Review Series on Lp(a). Studies suggest that the kidney has a role in Lp(a) catabolism, and that Lp(a) levels are increased in association with kidney disease only for people with large apo(a) isoforms. By contrast, in those patients with large protein losses, as in the nephrotic syndrome and continuous ambulatory peritoneal dialysis, Lp(a) is increased irrespective of apo(a) isoform size. Such acquired abnormalities can be reversed by kidney transplantation or remission of nephrosis. In this Thematic Review, we focus on the relationship between Lp(a), chronic kidney disease, and risk of cardiovascular events.

Lipoprotein(a) in clinical practice: New perspectives from basic and translational science

Elevated plasma concentrations of lipoprotein(a) (Lp(a)) are a causal risk factor for coronary heart disease (CHD) and calcific aortic valve stenosis (CAVS). Genetic, epidemiological and in vitro data provide strong evidence for a pathogenic role for Lp(a) in the progression of atherothrombotic disease. Despite these advancements and a race to develop new Lp(a) lowering therapies, there are still many unanswered and emerging questions about the metabolism and pathophysiology of Lp(a). New studies have drawn attention to Lp(a) as a contributor to novel pathogenic processes, yet the mechanisms underlying the contribution of Lp(a) to CVD remain enigmatic. New therapeutics show promise in lowering plasma Lp(a) levels, although the complete mechanisms of Lp(a) lowering are not fully understood. Specific agents targeted to apolipoprotein(a) (apo(a)), namely antisense oligonucleotide therapy, demonstrate potential to decrease Lp(a) to levels below the 30-50 mg/dL (75-150 nmol/L) CVD risk threshold. This therapeutic approach should aid in assessing the benefit of lowering Lp(a) in a clinical setting.

Lipoprotein (a): impact by ethnicity and environmental and medical conditions

Levels of lipoprotein (a) [Lp(a)], a complex between an LDL-like lipid moiety containing one copy of apoB, and apo(a), a plasminogen-derived carbohydrate-rich hydrophilic protein, are primarily genetically regulated. Although stable intra-individually, Lp(a) levels have a skewed distribution inter-individually and are strongly impacted by a size polymorphism of the LPA gene, resulting in a variable number of kringle IV (KIV) units, a key motif of apo(a). The variation in KIV units is a strong predictor of plasma Lp(a) levels resulting in stable plasma levels across the lifespan. Studies have demonstrated pronounced differences across ethnicities with regard to Lp(a) levels and some of this difference, but not all of it, can be explained by genetic variations across ethnic groups. Increasing evidence suggests that age, sex, and hormonal impact may have a modest modulatory influence on Lp(a) levels. Among clinical conditions, Lp(a) levels are reported to be affected by kidney and liver diseases.

Causes and consequences of lipoprotein(a) abnormalities in kidney disease

Lipoprotein(a) is one of the strongest genetically determined risk factors for cardiovascular disease, and patients with chronic kidney disease have major disturbances in lipoprotein(a) metabolism. Concentrations are increased and are influenced by glomerular filtration rate (GFR) and the amount of proteinuria. The reason for this elevation can be increased synthesis, as is the case for patients with nephrotic syndrome or those treated by peritoneal dialysis. In hemodialysis patients, a catabolic block is the reason for this elevation. The elevated concentrations might contribute to the tremendous cardiovascular risk in this particular population. In particular, the genetically determined small apolipoprotein(a) isoforms are associated with an increased risk for cardiovascular events and total mortality.

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.

Lipoprotein a: where are we now?

PURPOSE OF REVIEW

To provide an update of the literature describing the link between lipoprotein a and vascular disease.

RECENT FINDINGS

There is evidence that elevated plasma lipoprotein a levels are associated with coronary heart disease, stroke and other manifestations of atherosclerosis. Several mechanisms may be implicated, including proinflammatory actions and impaired fibrinolysis.

SUMMARY

Lipoprotein a potentially represents a useful tool for risk stratification in the primary and secondary prevention setting. However, there are still unresolved methodological issues regarding the measurement of lipoprotein a levels. Targeting lipoprotein a in order to reduce vascular risk is hampered by the lack of well tolerated and effective pharmacological interventions. Moreover, it has not yet been established whether such a reduction will result in fewer vascular events. The risk attributed to lipoprotein a may be reduced by aggressively tackling other vascular risk factors, such as low-density lipoprotein cholesterol.

Lipid management in chronic kidney disease, hemodialysis, and transplantation

Recent studies have shown the spectrum of dyslipidemia in patients who have chronic kidney disease (CKD) or end-stage renal disease to be different from that of the general population. This article discusses the pathophysiology of dyslipidemia in CKD, dialysis, and renal transplant patients, the therapeutic options, and their association with clinical outcomes. Whenever possible, comparisons are made to outcomes in the general population.

Kinetic studies of atherogenic lipoproteins in hemodialysis patients: do they tell us more about their pathology?

Patients with chronic kidney disease have one of the highest risks for atherosclerotic complications. Several large epidemiological studies described an opposite association of total and low density lipoprotein (LDL) cholesterol with cardiovascular complications and total mortality compared to the general population, a circumstance often called "reverse epidemiology." Many factors might contribute to this reversal such as interaction with malnutrition/inflammation, pronounced fluctuations of atherogenic lipoproteins during the course of renal disease, heterogeneity of lipoprotein particles with preponderance of remnant particles, and chemical modification of lipoproteins caused by the uremic environment. A vicious cycle has been suggested in uremia in which the decreased catabolism of atherogenic lipoproteins such as LDL, IDL and Lp(a) leads to their increased plasma residence time and further modification of these lipoproteins by oxidation, carbamylation, and glycation. Using stable isotope techniques, it has been shown recently that the plasma residence time of these particles is more than twice as long in hemodialysis patients as in nonuremic subjects. This reduced catabolism, however, is masked by the decreased production of LDL, resulting in near-normal plasma levels of LDL. The production rate of Lp(a) in hemodialysis patients is similar to that in controls which together with the doubled residence time results in elevated Lp(a) levels. An increased clearance of these altered lipoproteins via the scavenger receptors of macrophages leads to the transformation of macrophages into foam cells in the vascular wall and might contribute to the pronounced risk for cardiovascular complications of these patients. These observations suggest that the real danger of these particles is not reflected by the measured concentrations but by their metabolic qualities.

Effects of renal replacement therapy on plasma lipoprotein(a) levels

Patients with end-stage renal disease (ESRD) have significantly higher levels of lipoprotein(a) [Lp(a)] when compared to control populations. Elevated levels of Lp(a) may play a role in the high incidence of cardiovascular disease in ESRD. We conducted a prospective study to test the hypothesis that plasma levels of Lp(a) decline rapidly after renal transplantation proportional to the improvement in renal function, but are not affected by hemodialysis. All adults that initiated hemodialysis or received a renal transplant from our institution during a 10-month period were invited to participate in the study. Lp(a) levels were obtained immediately prior to the initiation of renal replacement therapy. In transplant recipients, repeat Lp(a) measures were done at 3 days, 5 days, 1 week, 2 weeks, 3 weeks and 4 weeks post-transplant. In hemodialysis patients, repeat Lp(a) measures were done after 3 months. We used a mixed effects model to analyze the effect of time, race and creatinine on Lp(a) after transplant. Lp(a) levels decreased rapidly after renal transplantation. Mean Lp(a) levels at 2 weeks were 35.3% lower than prior to transplantation. Each reduction of 50% in creatinine was associated with a 10.6% reduction in Lp(a) (p < 0.001). In contrast, there was no significant change in Lp(a) after initiation of hemodialysis. The rapid decrease of Lp(a) levels after renal transplantation provides support for a metabolic role of the kidney in Lp(a) catabolism and suggests that the increase in Lp(a) seen in chronic kidney disease is due to loss of functioning renal tissue.

Quo vadis haemapheresis. Current developments in haemapheresis

The techniques of haemapheresis originated in the development of centrifugal devices separating cells from plasma and later on plasma from cells. Subsequently membrane filtration was developed allowing for plasma-cell separation. The unspecificity of therapeutic plasma exchange led to the development of secondary plasma separation technologies being specific, semi-selective or selective such as adsorption, filtration or precipitation. In contrast on-line differential separation of cells is still under development. Whereas erythrocytapheresis, granulocytapheresis, lymphocytapheresis and stem cell apheresis are technically advanced, monocytapheresis may need further improvement. Also, indications such as erythrocytapheresis for the treatment of polycythaemia vera or photopheresis though being clinically effective and of considerable importance for an appropriate disease control are to some extent under debate as being either too costly or without sufficient understanding of the mechanism. Other forms of cell therapy are under development. Rheohaemapheresis as the most advanced technology of extracorporeal haemorheotherapy is a rapidly developing approach contributing to the treatment of microcirculatory diseases and tissue repair. Whereas the control of a considerable number of (auto-) antibody mediated diseases is beyond discussion, the indication of apheresis therapy for immune complex mediated diseases is quite often still under debate. Detoxification for artificial liver support advanced considerably during the last years, whereas conclusions on the efficacy of septicaemia treatment are debatable indeed. LDL-apheresis initiated in 1981 as immune apheresis is well established since 24 years, other semi-selective or unspecific procedures, allowing for the elimination of LDL-cholesterol among other plasma components are also being used. Correspondingly Lp(a) apheresis is available as a specific, highly efficient elimination procedure superior to techniques which also eliminate Lp(a). Quality control systems, more economical technologies as for instance by increasing automation, influencing the over-interpretation of evidence based medicine especially in patients with rare diseases without treatment alternative, more insight into the need of controlled clinical trials or alternatively improved diagnostic procedures are among others tools ways to expand the application of haemapheresis so far applied in cardiology, dermatology, haematology, immunology, nephrology, neurology, ophthalmology, otology, paediatrics, rheumatology, surgery and transfusion medicine.

Epidemiology, pathophysiology and therapeutic implications of lipoprotein(a) in kidney disease

Chronic kidney disease is associated with a tremendously increased risk for cardiovascular disease. Traditional risk factors for cardiovascular disease, however, show a diminished predictive power in these patients compared with the general population. This review provides an overview of lipoprotein(a), which is considered a nontraditional risk factor. The characteristic genetic and nongenetic changes of lipoprotein(a) in kidney disease are discussed and set into the context of risk prediction. In particular, genetically determined apolipoprotein(a) polymorphism is a powerful risk predictor for cardiovascular disease and total mortality in these patients. Finally, the limited interventional strategies available to lower lipoprotein(a) are considered.

Renal function and lipid metabolism in pregnant renal transplant recipients

OBJECTIVE

To estimate renal function and lipid metabolism in pregnant renal transplant recipients.

STUDY DESIGN

The study covered 64 women during the third trimester of pregnancy including 33 renal transplant recipients (the study group) and 31 healthy women (the control group). Serum concentrations of uric acid, urea, creatinine, electrolytes, total protein, albumin, acid-base balance and blood cell count were examined to assess renal function. Moreover, the levels of the following lipid metabolism parameters were estimated: (1) total lipids (TL), (2) total LDL fraction (TLDL), (3) total cholesterol (TCh), (4) free cholesterol (fCh), (5) free/total cholesterol (fCh/TCh) ratio, (6) phospholipids (PhL), (7) total cholesterol/phospholipids (fCh/PhL) ratio, (8) triglycerides (TG), (9) HDL-cholesterol (HDL-Ch), (10) LDL-cholesterol (LDL-Ch) and (11) LDL-Ch/HDL-Ch ratio. 'The effect of immunosuppressants (cyclosporine, prednisone and azathioprine) on serum lipid levels was estimated in the study group. The mean maternal age, gestational age and BMI did not differ in both groups.

RESULTS

Pregnant renal transplant recipients presented mild renal insufficiency during the third trimester resulting in the increase in serum level of uric acid (P<0.001), urea (P<0.001), creatinine (P<0.001), and Cl- (P<0.001). Proteinuria (1.19+/-1.9 g/24 h) leading to hypoproteinemia (P<0.001) and hypoalbuminemia (P<0.05) confirmed renal function impairment in the study group. Additionally, the diagnosis of renal insufficiency was supported by mild acidosis reflected by a drop in pH (P<0.001). standard HCO3- (P<0.001) and base excess (P<0.001). The women with renal grafts presented vital lipid metabolism disturbances illustrated by the elevated levels of: (1) TL by 72% (P<0.001), (2) TLDL by 21% (P<0.001), (3) TCh by 16% (P<0.001), (4) fCh by 34% (P<0.001), (5) fCh/TCh ratio by 21% (P<0.001), (6) PhL by 28% (P<0.001), (7) TG by 53% (P<0.001), (8) LDL-Ch by 13% (P<0.05) and (9) LDL-Ch/HDL-Ch ratio by 23% (P<0.001). No difference in HDL-Ch level between the two groups was found. Hyperlipidemia in pregnant kidney recipients was associated with immunosuppressive treatment and depended on cyclosporine treatment regimen. Treatment with azathioprine and prednisone was associated with elevated serum levels of examined lipids.

CONCLUSION

Serum lipid abnormalities are significantly influenced by the administered dosages of immunosuppressants.

Apolipoprotein(a) isoform-specific changes of lipoprotein(a) after kidney transplantation

The atherogenic lipoprotein(a) (Lp(a)) is significantly increased in patients with kidney disease. Some studies in hemodialysis patients described this increase to be dependent on the genetic apolipoprotein(a) (apo(a)) isoforms. Only patients who express high molecular weight (HMW) apo(a) isoforms but not those with low molecular weight (LMW) isoforms show a relative increase of Lp(a) when compared to healthy controls matched for apo(a) isoforms. However, this was not confirmed by all studies. We therefore prospectively investigated the changes of Lp(a) deriving from each apo(a) isoform in heterozygotes following kidney transplantation. Lp(a) concentrations were measured by ELISA. To calculate the isoform-specific concentrations and the changes of Lp(a) deriving from each isoform, we densitometrically scanned the apo(a) bands from immunoblots before and after transplantation in 20 patients expressing two apo(a) isoforms. Of these, 10 patients expressed both an LMW and an HMW apo(a) isoform. The other 10 patients expressed only HMW isoforms. Densitometric scanning of apo(a) bands and calculation of isoform-derived Lp(a) concentrations clearly demonstrated that the decrease of Lp(a) following kidney transplantation is caused by changes in the expression of HMW apo(a) isoforms. In some patients, we observed an almost complete disappearance of the HMW apo(a) isoform after transplantation. This study clearly demonstrates that the changes of Lp(a) plasma concentrations in kidney disease depend on the genetically determined size of apo(a). This provides evidence for an interaction of apo(a) genetic variability and kidney function on Lp(a) concentrations.

Association of kidney function with serum lipoprotein(a) level: the third National Health and Nutrition Examination Survey (1991-1994)

BACKGROUND

Elevated lipoprotein(a) (Lp[a]) levels have been observed in patients on dialysis therapy. However, few studies explored the relationship between kidney function and Lp(a) levels in patients with mild to moderate chronic kidney disease.

METHODS

We examined the association of estimated glomerular filtration rate (GFR) with Lp(a) level in 7,675 participants in the second phase of the Third National Health and Nutrition Examination Survey.

RESULTS

There was no association between Lp(a) level and estimated GFR in the overall sample (geometric mean, 10.4 mg/dL [95% confidence interval (CI), 9.2 to 11.8] in the group with a GFR of 90 to 149 mL/min/1.73 m2 versus 9.3 mg/dL [95% CI, 7.9 to 11.0] in the group with a GFR of 60 to 89 mL/min/1.73 m2 versus 12.1 mg/dL [95% CI, 9.0 to 15.9] in the group with a GFR of 15 to 59 mL/min/1.73 m2; P = 0.77 for linear trend) or non-Hispanic whites (geometric mean, 8.9 mg/dL [95% CI, 7.8 to 10.2] versus 8.5 mg/dL [95% CI, 7.1 to 10.2] versus 10.9 mg/dL [95% CI, 8.1 to 14.7]; P = 0.54 for linear trend). However, non-Hispanic blacks (geometric mean, 30.4 mg/dL [95% CI, 28.0 to 33.0] versus 35.2 mg/dL [95% CI, 31.4 to 39.4] versus 40.2 mg/dL [95% CI, 27.7 to 58.2]; P = 0.01 for linear trend) and Mexican Americans (geometric mean, 6.2 mg/dL [95% CI, 5.3 to 7.2] versus 7.4 mg/dL [95% CI, 6.4 to 8.5] versus 11.0 mg/dL [95% CI, 5.7 to 20.3]; P = 0.04 for linear trend) showed modestly, but significantly, greater Lp(a) levels with lower GFRs. In a weighed quantile regression model adjusted for age, sex, and race, a lower GFR was associated with greater 95th percentile serum Lp(a) values in the overall sample and non-Hispanic whites and with greater median Lp(a) levels in Mexican Americans.

CONCLUSION

In a cross-section of the US population, a low GFR is associated with only moderately greater Lp(a) levels, and this association may differ by race-ethnicity.

Cardiovascular disease after renal transplantation

Cardiovascular disease is a major hazard limiting the life expectancy of renal transplant recipients and the most frequent cause of late allograft loss. Patients with renal disease have usually been exposed for both traditional, and for them unique, risk factors over a prolonged period of time and may carry the burden of advanced atherosclerotic disease already at the time of transplantation. The observed survival benefit of transplantation is probably from elimination of the numerous uremia-related risk factors. However, immunosuppressive therapy and the chronic inflammatory state, together with genetic susceptibility and not infrequently impaired renal function, may bring about new potentially atherogenic conditions. Metabolic risk factors may jeopardize both patient and graft survival. Several observational studies provide evidence for the negative impact of preexisting metabolic abnormalities on long-term outcomes. Identification of modifiable cardiovascular risk factors may enable risk reduction also in renal transplant recipients. Results of ongoing intervention trials are awaited. The observed improvement of patient survival after renal transplantation during the past decade may reflect the increasing awareness and more optimal care of patients throughout the course of renal 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.

Impact of apolipoprotein(a) phenotypes on long-term renal transplant survival

The long-term success of renal transplantation is limited because of chronic rejection (CR), which shows histologic parallels to atherosclerosis. Lipoprotein(a) [Lp(a)] is an independent risk factor for atherosclerosis, but its role in CR has not been investigated. Plasma levels of Lp(a) are determined mainly by the inherited isoform (phenotype) of apolipoprotein(a) [apo(a)] and show an inverse correlation with the molecular weight of apo(a). Apo(a) isoforms were identified in frozen sera of 327 patients who received a renal transplant during 1982 to 1992. Long-term graft survival in recipients with high molecular weight (HMW) or low molecular weight (LMW) apo(a) phenotypes were compared retrospectively. Mean (95% confidence interval) transplant survival was 12.8 yr (range, 11.9 to 13.6 yr) in patients with HMW and 11.9 yr (range, 10.8 to 13.1 yr) in patients with LMW apo(a) phenotypes (P = 0.2065). In patients who were 35 yr or younger at the time of transplantation, mean transplant survival was more than 3 yr longer in recipients with HMW apo(a) phenotypes compared with those with LMW apo(a) phenotypes (13.2 yr [range, 12.1 to 14.4 yr] versus 9.9 yr (range, 8.5 to 11.5 yr); P = 0.0156). In a Cox's proportional hazards regression model, the presence of LMW phenotypes-but not gender, immunosuppression, or HLA mismatches-in young patients was associated with a statistically significant risk of CR (P = 0.0434). These retrospective data indicate that young renal transplant recipients with LMW apo(a) phenotypes have a significantly shorter long-term graft survival, regardless of the number of HLA mismatches, gender, or immunosuppressive treatment.

Cardiovascular risk factors in kidney transplantation

Classical and non-classical cardiovascular risk factors are common after renal transplantation, and they are effectively associated with the development of cardiovascular disease. Despite the absence of large, controlled clinical trials examining the effect of prevention strategies, therapies should not be withheld from renal transplant recipients with significant risk factors, because their risk of developing cardiovascular disease is at least as high as that of the general population.