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

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.

Predictive value of procalcitonin in chronic allograft dysfunction in kidney transplant recipients

The present study was designed to determine the potential role of circulating procalcitonin (PCT) in predicting chronic allograft dysfunction (CAD) in kidney transplant recipients (KTRs). A total of 87 KTRs were retrospectively analyzed and divided into a CAD and a non-CAD (normal renal function) group. Clinical features and inflammatory markers were compared between the groups, including PCT, white blood cell count, C-reactive protein, neutrophil percentage (N%) and lipoprotein(a) [Lp(a)], and the receiver operating characteristic (ROC) curve for CAD prediction was plotted. Univariate and multivariate logistic regression analyses were used to analyze the relevant risk factors for CAD. The results indicated that i) the values of these indicators in the CAD group, including the male ratio, years after transplantation, PCT, N% and Lp(a), were significantly higher than those in the non-CAD group, while the body mass index, aspartate aminotransferase, high-density lipoprotein and low-density lipoprotein were significantly lower; ii) PCT and Lp(a) were able to predict CAD with an area under the ROC curve of 0.893 and 0.770, respectively; iii) multivariate logistic regression analysis of factors influencing CAD in KTRs suggested that elevated PCT was an independent risk factor. In KTRs, PCT was identified as a potential biomarker for predicting CAD.

Ankle-arm blood pressure monitoring does not correlate with serum lipoprotein a in renal transplant recipients

OBJECTIVE

Lipoprotein a [Lp(a)] is a strong biochemical risk factor that predicts posttransplant atherosclerosis. In this study we measured the ankle to arm blood pressure index (AAI) as a predictor of clinical atherosclerosis and assessed its relationship to serum Lp(a) values among 60 renal transplant recipients.

MATERIALS AND METHODS

After measuring the AAI in a recumbent position, biochemical factors including cholestrol, triglyceride, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and Lp(a) were measured by commercial kits in 60 renal transplant and 30 healthy subjects. Results were analyzed using SPSS.

RESULTS

Lp(a) concentrations were significantly higher among transplant recipients compared with the control group (P < .05). AAI was similar between the kidney transplant recipients and controls, showing no significant correlation of Lp(a) concentration with AAI.

CONCLUSION

Increased serum Lp(a) in renal transplant recipients, a potent biochemical risk factor for atherosclerosis, was not associated with abnormal AAI.

Relation of apolipoprotein(a) size to alzheimer's disease and vascular dementia

Lipoprotein(a) [Lp(a)] level is a newly established vascular risk factor which has been suggested to play a role in dementia. However, the majority of Lp(a) cell-to-cell interactions are mediated by its specific apolipoprotein(a) [apo(a)] moiety. This suggests that the size polymorphism of apo(a) may be of importance in conveying the Lp(a)-related risk. Specifically, we postulated that variation in apo(a) isoform size may lead to increased risk of vascular dementia (VaD), Alzheimer's disease (AD), stroke, or all three of them. Under a case-control design we compared Lp(a) plasma levels and the distribution of apo(a) phenotypes in groups of subjects consisting of 50 VaD patients, 162 sporadic AD patients, 95 non-demented stroke patients (NDS), and 105 normal controls. The prevalence of small-sized apo(a) isoforms in the VaD group was significantly higher than that in the stroke and normal control groups, with an odds ratio of 5.29 (95% CI 2.24-12.49, p = 0.0001) for the development of VaD for individuals with at least one apo(a) isoform of low molecular weight (LMW). Furthermore, the possession of at least one small-sized apo(a) isoform significantly increased the risk of AD to 1.92 (95% CI 1.02-3.61, p = 0.0434). Our results demonstrate that possession of at least one LMW apo(a) isoform is significantly associated with dementia and specifically offer new evidence of a strong association between the lipoprotein system and post-stroke dementia.

Using value of information analysis to inform publicly funded research priorities

INTRODUCTION

The purpose of this article is to demonstrate the application and feasibility of using value of information analysis to help set priorities for research as part of the UK National Health Service (NHS) Health Technology Assessment Programme. Probabilistic decision analysis and value of information methods were applied to a research topic under consideration by the National Coordinating Centre for Health Technology Assessment (NCCHTA), in the UK. The case study presented considers whether long-term, low-dose antibacterial treatment of recurrent urinary tract infections (UTIs) in children is effective and cost effective compared with short-term antibacterial therapy.

METHODS

A probabilistic decision-analytic model was developed, within which evidence from published sources was synthesised. Eight subgroups were considered and defined in terms of sex and presence of vesico-ureteral reflux (VUR). Costs were assessed from an NHS perspective, and benefits were expressed as quality-adjusted life-years (QALYs). Simulation methods were used to determine the probability that alternative therapies would be cost effective at a range of threshold values that the NHS may attach to an additional QALY. Value of information analysis was used to quantify the cost of uncertainty associated with the decision about which therapy to adopt, which indicates the maximum value of future research. The feasibility and practicality of using value of information methods to help inform research prioritization was evaluated.

RESULTS

At a threshold value for an additional QALY of 30,000 pound , long-term antibacterial treatment may be regarded as cost effective for all eight patient groups. There was, however, substantial uncertainty surrounding the choice of antibacterial.

DISCUSSION/CONCLUSION

The use of value of information methods was feasible and could inform research prioritization for the NHS. In the context of this specific decision faced by the NHS, the results show that long-term low-dose antibacterials for preventing recurrent UTIs may be cost effective, based on current evidence. However, the analysis suggests that further primary research with longer follow-up may be worthwhile, particularly for girls with no VUR.

High urine sIL-6R as a predictor of late graft failure in renal transplant recipients

BACKGROUND

Chronic allograft nephropathy is an important cause of late renal transplant failure. Although numerous studies on cytokines have been carried out, the pathogenetic role of cytokines in chronic renal allograft nephropathy remains unclear.

METHODS

In a retrospective study, the authors compared posttransplant plasma and urine cytokine levels (interleukin [IL]-1alpha, IL-1beta, soluble [s] IL-1 receptor [R] antagonist [A], IL-2, sIL-2R, IL-3, IL-4, IL-6, sIL-6R, IL-10, tumor necrosis factor-alpha, transforming growth factor-beta2, and interferon-gamma) in 34 matched pairs of patients with or without late graft failure and in 50 matched pairs with either normal or increased serum creatinine levels and continued stable graft function.

RESULTS

Twelve and 6 months before late graft failure, urine levels of sIL-6R were significantly increased (P=0.003 and P=0.01, respectively). Serum creatinine levels were not associated with increased urine sIL-6R.

CONCLUSION

High urine sIL-6R appears to be predictive of late graft failure in renal transplant recipients.

Lipoprotein(a): still an enigma?

PURPOSE OF REVIEW

Lipoprotein(a) belongs to the class of the most atherogenic lipoproteins. Despite intensive research - in the last year more than 80 papers have been published on this topic - information is still lacking on the physiological function of lipoprotein(a) and the site of its catabolism. Important advances have been made in the knowledge of these points, which may have some therapeutic implications.

RECENT FINDINGS

The association of high lipoprotein(a) values with an increase in risk for coronary events has been documented in further prospective studies. This increased risk may relate to recent findings that apolipoprotein(a) is produced in situ within the vessel wall. In addition, lipoprotein(a) binds and inactivates the tissue factor pathway inhibitor and induces plasminogen activator inhibitor type 2 expression in monocytes. A new antisense oligonucleotide strategy has been proposed which efficiently inhibits apolipoprotein(a) expression in vitro and in vivo. Apolipoprotein(a), however, suppresses angiogenesis and thus may interfere with the infiltration of tumor cells. Finally, the enzymatic activity leading to the formation of apolipoprotein(a) fragments in plasma and their catabolism have been further elucidated.

SUMMARY

We are still far away from understanding the pathways involved in lipoprotein(a) catabolism, and the physiological function of this lipoprotein. Recent findings, however, provide new insight into pathomechanisms in patients with increased lipoprotein(a) related to hemostasis, which may serve as a basis for designing new treatment strategies.