Factors associated with lipoprotein(a) in chronic kidney disease

Causal effect of lipoprotein(a) level on chronic kidney disease of European ancestry: a two-sample Mendelian randomization study

INTRODUCTION

Chronic kidney disease is a growing health issue, and the options of prevention and therapy remain limited. Although a number of observational studies have linked higher Lp(a) [lipoprotein(a)] levels to the kidney impairment, the causal relationship remains to be determined. The purpose of this study was to assess the causal association between Lp(a) levels and CKD.

METHODS

We selected eight single-nucleotide polymorphisms (SNPs) significantly associated with Lp(a) levels as instrumental variables. Genome-wide association study (GWAS) from CKDGen consortium yielded the summary data information for CKD. We designed the bidirectional two-sample Mendelian randomization (MR) analyses. The estimates were computed using inverse-variance weighted (IVW), simple median, weighted median, and maximum likelihood. MR-Egger regression was used to detect pleiotropy.

RESULTS

Fixed-effect IVW analysis indicated that genetically predicted Lp(a) levels were associated with CKD significantly (odds ratio, 1.039; 95% CI, 1.009-1.069; p = 0.010). The SNPs showed no pleiotropy according to result of MR-Egger test. Results from sensitivity analyses were consistent. In the inverse MR analysis, random-effect IVW method showed CKD had no causal effect on the elevated Lp(a) (odds ratio, 1.154; 95% CI, 0.845-1.576; p = 0.367).

CONCLUSION

In this bidirectional two-sample MR analysis, the causal deteriorating effects of genetically predicted plasma Lp(a) levels on the risk of CKD were identified. On the contrary, there is no evidence to support a causal effect of CKD on Lp(a) levels.

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.

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.

Association of matrix γ-carboxyglutamic acid protein levels with insulin resistance and Lp(a) in diabetes: A cross-sectional study

AIMS

The risk of cardiovascular disease (CVD) and mortality is increased in patients with chronic kidney disease (CKD), with a background role of vascular calcification in the development of CVD also reported. Studies have demonstrated that high lipoprotein(a) (Lp(a)) levels accelerate the development of atherosclerolsis and are potentially involved in the vascular calcification. Matrix Gla Protein (MGP) seems to play an important role in vascular calcification. The aim of the study was to examine the potential association of MGP concentrations with Lp(a) and insulin resistance.

METHODS

The study involved 100patients divided in four groups: 25 with both CKD stage 4 and Type2 Diabetes (DM) (Group-A), 25 with CKD4 without DM (Group-B), 25 non uremic patients with DM (Group-C) and 25 healthy subjects (Group-D). Serum glucose, Lp(a), MGP, plasma HBA1c and insulin were measured in all patients. Insulin resistance was estimated by the homeostasis model assessment equation (HOMA-IR).

RESULTS

A significant positive linear association between MGP and Lp(a) levels (r=0.272, p=0.006) was noted, as well as between MGP and HOMA-IR levels (r=0.308, p=0.002). However, no significant linear association between Lp(a) and HOMA-IR levels was recorded. A similar positive association between MGP and insulin levels (r=0.204, p=0.042) was also found.

CONCLUSION

This study concluded that diabetes coexisting with renal disease leads to extreme vascular calcification expressed by elevated MGP levels, resulting in higher frequency of cardiovascular disease in comparison to CKD patients without diabetes. The detected Lp(a) and MGP association in CKD4 patients may also represent the key to the complicated mechanism of their coexisting accelerated atherosclerosis and vascular calcification.

Management of cardiovascular risk factors in patients with ANCA-associated vasculitis

OBJECTIVES

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is accompanied by increased cardiovascular (CV) risk. Treatment of AAV patients includes the management of conventional CV risk factors, primarily hypertension and hypercholesterolemia, while lipoprotein(a) (LP(a)) is an emerging potential target.

METHODS

We performed a multicenter, retrospective study in Germany. Patients were considered if they were between 18 and 90 years old and presented with AAV. Patients with arterial hypertension but no autoimmune disease were used as a control group (HTN reference group).

RESULTS

Compared to the reference group (n = 52), CV disease burden was significantly greater in patients with AAV (n = 53). Hypercholesterolemia was also more common in the AAV patients (71.7% vs 46.2% for the HTN; P = .008). Lipoprotein(a) levels were elevated in both groups, with 11.3% and 17.3% of the AAV and HTN groups, respectively, displaying a level above 0.6 g/l (P = .083). Guideline-recommended targets for low-density lipoprotein cholesterol and blood pressure levels were rarely met. According to Kidney Disease: Improving Global Outcomes guidelines, 72.5% of the patients with AAV should have been taking statins and/or ezetimibe for treatment of hyperlipidemia; however, only 24.3% of them were receiving such treatment. Blood pressure below ≤140/90 mmHg was reached in 78.6% of the patients with chronic kidney disease. However, for patients with chronic kidney disease and an albumin excretion rate of >30 mg/day, the recommended blood pressure is ≤130/80 mmHg, a value that was not reached in 65% of the AAV patients.

CONCLUSION

Patients with AAV are at high CV risk, but management of the associated risk factors is poor. In addition to improving the treatment of hypercholesterolemia and hypertension, lipoprotein(a) is a further potential target for reducing CV risk in individuals with AAV.

Plasma lipoprotein(a) predicts major cardiovascular events in patients with chronic kidney disease who undergo percutaneous coronary intervention

BACKGROUND

Chronic kidney disease (CKD) is associated with increased risk for cardiovascular disease. The predictive power of traditional risk factors for cardiovascular disease is diminished in patients with CKD. The serum level of lipoprotein(a) [Lp(a)] can be a risk factor for adverse events, but the clinical implications of Lp(a) in patients with CKD who have been treated by percutaneous coronary intervention (PCI) remain uncertain. We aimed to determine the role of Lp(a) on long-term outcomes in patients with CKD after PCI.

METHODS

We analyzed data from 904 patients with CKD among 3508 patients who underwent a first PCI between 1997 and 2011 at our institution. We divided patients into 2 groups [high (n=454) or low (n=450)] according to median levels of Lp(a). The primary outcome was a composite of all-cause death and acute coronary syndrome (ACS).

RESULTS

The baseline characteristics of the groups were similar and the median follow-up period was 4.7 years. Cumulative event-free survival was significantly worse for the group with high, than low Lp(a) (P=0.01). Multivariable analysis indicated a high Lp(a) level as an independent predictor of primary outcomes (hazard ratio, 1.35; 95% CI, 1.01-1.82; P=0.04).

CONCLUSIONS

A high Lp(a) value is associated with a poor prognosis after PCI for patients with CKD.

Relation of atherogenic lipoproteins with estimated glomerular filtration rate decline: a longitudinal study

BACKGROUND

Chronic kidney disease (CKD) is associated with dyslipidemia, but the role of atherogenic lipid fractions in CKD progression remains unclear. Here we assess whether baseline plasma levels of lipoprotein(a) [Lp(a)] and apolipoprotein C-III (apoC-III), causal cardiovascular (CV) risk factors being studied as therapeutic targets, are associated with decreasing estimated glomerular filtration rate (eGFR) over time.

METHODS

In the Penn Diabetes Heart Study (PDHS), a single-center observational cohort of type 2 diabetes patients without clinical CV disease or pre-existing CKD, we performed linear mixed effects modeling with incremental multivariable analysis to evaluate the effects of baseline plasma Lp(a) and apoC-III on the slope of eGFR over time for subjects with longitudinal data (N = 400).

RESULTS

Each two-fold higher plasma Lp(a) level was associated with an additional decline in eGFR by 0.50 mL/min/year in the fully adjusted model (p < 0.001). Baseline Lp(a) levels greater than the atherogenic cut-point of 30 mg/dL were associated with a decline in eGFR by 2.75 mL/min/year compared to 1.01 mL/min/year in subjects with baseline Lp(a) less than 30 mg/dL (p < 0.001). Although each two-fold higher apoC-III level was also associated with statistically significant decline in eGFR over time, as expected the association was attenuated after adjusting for baseline triglycerides, the key lipid intermediary regulated by apoC-III in circulation.

CONCLUSIONS

Elevated baseline plasma Lp(a) levels are associated with a decrease in eGFR over time independent of race, lipid medication use, and albuminuria, whereas elevated baseline apoC-III levels are associated with eGFR decline in a triglyceride-dependent fashion.

Plasma lipoprotein(a) levels are associated with mild renal impairment in type 2 diabetics independent of albuminuria

Background

CKD, an independent risk factor for CV disease, increases mortality in T2DM. Treating modifiable CV risk factors decreases mortality in diabetics with microalbuminuria, but the role of early CV prevention in diabetics with mild CKD by GFR criteria alone remains unclear. The purpose of this study was to probe whether T2DM patients with mild GFR impairment have atherogenic lipid profiles compared to diabetic counterparts with normal renal function.

Methods

In the Penn Diabetes Heart Study (PDHS), a single-center observational cohort of T2DM patients without clinical CVD, cross-sectional analyses were performed for directly measured lipid fractions in 1852 subjects with eGFR>60 mL/min/1.73 m² determined by the CKD-EPI equation (n = 1852). Unadjusted and multivariable analyses of eGFR association with log-transformed lipid parameters in incremental linear and logistic regression models (with eGFR 90 mL/min/1.73 m² as a cut-point) were performed.

Results

Mild GFR impairment (eGFR 60–90 mL/min/1.73 m², median urinary ACR 5.25 mg/g) was associated with higher log-transformed Lp(a) values (OR 1.17, p = 0.005) and with clinically atherogenic Lp(a) levels above 30 mg/dL (OR 1.35, p = 0.013) even after full adjustment for demographics, medications, metabolic parameters, and albuminuria. Logistic regression demonstrated a trend towards significance between worse kidney function and apoB (p = 0.17) as well as apoC-III (p = 0.067) in the fully adjusted model.

Conclusions

Elevated Lp(a) levels have a robust association with mild GFR impairment in type 2 diabetics independent of race, insulin resistance, and albuminuria.

Relation of serum lipids and lipoproteins with progression of CKD: The CRIC study

BACKGROUND AND OBJECTIVES

Hyperlipidemia is common in patients with CKD. The objective of this study was to evaluate whether measures of plasma lipids and lipoproteins predict progression of kidney disease in patients with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Prospective cohort study in adults (n=3939) with CKD aged 21-74 years recruited between 2003 and 2008 and followed for a median of 4.1 years. At baseline, total cholesterol, triglycerides, very-low-density lipoprotein cholesterol (VLDL-C), LDL cholesterol (LDL-C), HDL cholesterol (HDL-C), apoA-I , apoB, and lipoprotein(a) [Lp(a)] were measured. The outcomes were composite end point of ESRD or 50% decline in eGFR from baseline (rate of change of GFR).

RESULTS

Mean age of the study population was 58.2 years, and the mean GFR was 44.9 ml/min per 1.73 m(2); 48% of patients had diabetes. None of the lipid or lipoprotein measures was independently associated with risk of the composite end point or rate of change in GFR. However, there were significant (P=0.01) interactions by level of proteinuria. In participants with proteinuria<0.2 g/d, 1-SD higher LDL-C was associated with a 26% lower risk of the renal end point (hazard ratio [HR], 0.74; 95% confidence interval [95% CI], 0.59 to 0.92; P=0.01), and 1-SD higher total cholesterol was associated with a 23% lower risk of the renal end point (HR, 0.77; 95% CI, 0.62 to 0.96; P=0.02). In participants with proteinuria>0.2 g/d, neither LDL-C (HR, 0.98; 95% CI, 0.98 to 1.05) nor total cholesterol levels were associated with renal outcomes. Treatment with statins was reported in 55% of patients and was differential across lipid categories.

CONCLUSIONS

In this large cohort of patients with CKD, total cholesterol, triglycerides, VLDL-C, LDL-C, HDL-C, apoA-I, apoB, and Lp(a) were not independently associated with progression of kidney disease. There was an inverse relationship between LDL-C and total cholesterol levels and kidney disease outcomes in patients with low levels of proteinuria.

Association between serum lipids and survival in hemodialysis patients and impact of race

Despite the enormous cardiovascular disease epidemic among maintenance hemodialysis (MHD) patients, total hypercholesterolemia seems paradoxically to be associated with better survival. It was hypothesized that similar paradoxic associations also exist for serum LDL, HDL, and triglycerides. A 3-yr (July 2001 through June 2004) cohort of 15,859 MHD patients was studied in the United States from DaVita dialysis clinics where lipid profile was measured in at least 50% of all outpatients during a given calendar quarter. Cox proportional hazard models were adjusted for case mix and surrogates of malnutrition-inflammation complex. Both total and LDL hypercholesterolemia showed a paradoxic association with better survival. Hypertriglyceridemia (>200 mg/dl) also showed a similar trend, but serum HDL cholesterol did not have any clear association with survival. The association between a low serum LDL <70 mg/dl, which was prevalent among almost 50% of all MHD patients, and a higher all-cause death risk was robust to multivariate adjustment. In the subgroup analyses, these paradoxic associations persisted among most subgroups, although they tended to be stronger among hypoalbuminemic (<3.8 mg/dl) patients and those with a lower dietary protein intake (<1 g/kg per d). However, in black patients, a high serum LDL (>100 mg/ml) was associated with adjusted cardiovascular death hazard ratio of 1.94 (95% confidence interval 1.12 to 2.38; P = 0.02). Despite inverse associations between hyperlipidemia and survival, black MHD patients with high LDL show almost two-fold increase in cardiovascular death risk. Although these associations may not be causal, they call into question whether specific subgroups of dialysis patients are better targets for cholesterol-lowering therapy.