In vivo kinetic studies to further understand pathogenesis of abnormal lipoprotein metabolism in chronic kidney disease

Association of Renal Function and Statin Therapy with Lipoprotein(a) in Patients with Type 2 Diabetes

AIM

A high level of serum lipoprotein(a) [Lp(a)] is associated with kidney disease development in patients with type 2 diabetes (T2DM). Recent studies have suggested that statins may affect serum levels of Lp(a). However, the statin effect is not well-defined in patients with T2DM with kidney dysfunction. This retrospective study aimed to investigate the relevance of kidney dysfunction and statin therapy to Lp(a) in patients with T2DM.

METHODS

Japanese patients with T2DM (n=149, 96 men and 53 women) were divided into two groups: statin users (n=79) and non-statin users (n=70). Multiple logistic regression analyses were performed with Lp(a) as the objective variable and estimated glomerular filtration rate (eGFR), hemoglobin A1c, age, gender, and body mass index as the explanatory variables.

RESULTS

Lp(a) serum levels were higher in statin users than in non-statin users (P=0.022). Multivariate regression analysis results showed an inverse correlation of eGFR to log Lp(a) in all patients (P=0.009) and in non-statin users (P=0.025), but not in statin users. In a multiple logistic regression analysis for median Lp(a), there was an inverse association between eGFR and Lp(a) level (odds ratio, 0.965; 95% confidence interval, 0.935-0.997; P=0.030) in non-statin users as well as in all participants, but not in statin users.

CONCLUSIONS

The present study suggests that a high Lp(a) level in patients with T2DM, except in statin users, is significantly associated with decreased eGFR, indicating that the increased Lp(a) levels under statin therapy might diminish the relationship between Lp(a) and eGFR.

Dyslipidemia in diabetic kidney disease classified by proteinuria and renal dysfunction: A cross-sectional study from a regional diabetes cohort

AIMS/INTRODUCTION

Diabetic kidney disease (DKD) exacerbates dyslipidemia and increases the incidence of atherosclerotic cardiovascular disease. DKD is a concept that includes typical diabetic nephropathy and an atypical phenotype without proteinuria. We investigated dyslipidemia in different DKD phenotypes that have not been fully studied.

MATERIALS AND METHODS

Fasting plasma was obtained from 1,073 diabetes patients enrolled in the regional diabetes cohort (ViNA cohort). Non-proteinuric and proteinuric DKD were defined as an estimated glomerular filtration rate <60 mL/min/1.73 m² in the absence or presence of urinary albumin-to-creatinine ratio >300 mg/g. Novel lipid risk factors, low-density lipoprotein (LDL) triglyceride (TG) and small dense LDL cholesterol were measured using our established homologous assay.

RESULTS

The proportion of atherosclerotic cardiovascular disease patients was higher in non-proteinuric DKD and even higher in proteinuric DKD than in non-DKD. Increased estimated glomerular filtration rate grade and albuminuric stage were independently correlated with higher TG, TG-rich lipoprotein cholesterol and apolipoprotein CIII. Therefore, proteinuric DKD had the highest of these levels. Small dense LDL cholesterol and LDL-TG were higher in the proteinuria without renal dysfunction group in the lipid-lowering drug-free subset. Lipoprotein(a) was higher in DKD regardless of proteinuria.

CONCLUSIONS

Proteinuria was associated with an atherogenic subspecies of LDL, whereas renal dysfunction was associated with increased lipoprotein(a). Proteinuria and renal dysfunction independently exacerbated TG-rich lipoprotein-related dyslipidemia. This is in good agreement with the results of large-scale clinical studies in which proteinuria and renal dysfunction synergistically increased the risk of atherosclerotic cardiovascular disease in populations with diabetes.

Lipoprotein (a) and the Risk of Chronic Kidney Disease in Hospitalized Japanese Patients

Objective Lipoprotein (a), or Lp (a), has been shown to be associated with the development of chronic kidney disease (CKD) in populations of various ethnicities. This study aimed to investigate the association between serum Lp (a) and CKD in Japanese patients. Methods A total of 6,130 subjects who underwent a serum Lp (a) level assessment for any reason (e.g. any type of surgery requiring prolonged bed rest or risk factors for atherosclerosis, such as hypertension or diabetes) were retrospectively investigated at Kanazawa University Hospital from April 2004 to March 2014. Of these, 1,895 subjects were excluded because of the lack of clinical data. Subjects were assessed for Lp (a), low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, hypertension, diabetes, smoking, body mass index (BMI), coronary artery disease (CAD), and CKD (stage ≥3). Results When the study subjects were divided into quartiles of Lp (a) levels, significant trends were observed with regard to the presence of CKD (p = 2.7×10^-13). A multiple regression analysis showed that Lp (a) was significantly associated with CKD [odds ratio (OR), 1.12; 95% confidence interval (CI), 1.08-1.17; p = 1.3×10^-7, per 10 mg/dL], independent of other classical risk factors, including age, gender, BMI, hypertension, diabetes, smoking, LDL cholesterol, and triglycerides. Under these conditions, Lp (a) was significantly associated with CAD (OR = 1.11, 95% CI = 1.06-1.16; p = 1.7×10^-6, per 10 mg/dL), independent of other risk factors. Conclusion Serum Lp (a) was associated with CKD, independent of other classical risk factors in a Japanese population.

Triglyceride to high-density lipoprotein cholesterol ratio is associated with increased mortality in older patients on peritoneal dialysis

BACKGROUND

The triglyceride (TG) to high-density lipoprotein cholesterol (HDL-C) ratio (TG/HDL-C) has been suggested as a simple method to identify unfavorable cardiovascular (CV) outcomes in the general population. The aim of this study was to investigate the association between the TG/HDL-C ratio and all-cause and CV mortality in peritoneal dialysis (PD) patients.

METHODS

We retrospectively analyzed patients on PD from November 1, 2005, to February 28, 2017, with a follow-up period lasting until May 31, 2017. The main outcomes were all-cause and CV mortality.

RESULTS

Among the 973 PD patients, the mean age was 49.67 ± 14.58 (y). During a median follow-up period of 27.2 months (IQR = 13.4-41.5 months), 229 (23.5%) patients died, with 120 (12.3%) dying as a result of CV diseases. The median serum TG/HDL-C ratio was 1.11 (IQR = 0.71-1.80). In a multivariate Cox regression analysis, patients with higher TG/HDL-C ratio levels (tertile 3) had a higher incidence of CV mortality (adjusted HR = 2.12; 95% CI: 1.21-3.72; P = 0.009) and all-cause mortality (adjusted HR = 2.08; 95% CI: 1.37-3.14; P = 0.001) compared to patients in tertile 1. These associations persisted after excluding the patients who have already taken lipid-lowering medications. For older patients (> 60 years), each 1-unit higher baseline TG/HDL-C level was associated with a 48% (95% CI: 1.06-2.07; P = 0.021) increased risk of all-cause mortality and a 59% (95% CI: 1.03-2.45; P = 0.038) increased risk of CV mortality; however, this association was not observed in patients ≤60 years of age.

CONCLUSIONS

A higher serum TG/HDL-C ratio was an independent predictor of all-cause and CV mortality in PD patients. Furthermore, an elevated TG/HDL-C ratio was significantly associated with higher all-cause and CV mortality in older PD patients.

The influence of hemodialysis on FibroTest parameters

Chronic hepatitis C viral infection is an important cause of morbidity and mortality in patients with end-stage renal disease treated with hemodialysis. Liver fibrosis represents a main determinant of liver disease prognosis and clinical management, and its assessment by liver biopsy can decide treatment allocation. Although liver biopsy is the gold standard for staging liver fibrosis, it is an invasive procedure associated with complications that are more prevalent in patients with end-stage renal disease. FibroTest represents a surrogate marker of fibrosis which evaluates the levels of apolipoprotein A1, total bilirubin, haptoglobin, gamma-glutamyltransferase and α2-macroglobulin, generating a score that indicates the level of fibrosis. Discrepancies were observed in clinical practice between FibroTest score and histopathological findings. The aim of this study was to evaluate how hemodialysis influences the level of each FibroTest parameter and the final score. The systematic literature review conducted by us suggests that hemodialysis induces a reduction in apolipoprotein A1, haptoglobin and bilirubin levels, with an increase in gamma-glutamyltransferase and alpha-2-macroglobulin levels. In conclusion, hemodialysis modifies the levels of FibroTest parameters, suggesting that it may also have an impact on the accuracy of liver fibrosis assessment in hemodialysis patients.

Apolipoprotein B/apolipoprotein A1 ratio and mortality among incident peritoneal dialysis patients

BACKGROUND

To investigate the association between the ratio of apolipoprotein B (apo B) / apolipoprotein A1 (apo A1) with all-cause mortality and cardiovascular events in peritoneal dialysis (PD) patients.

METHODS

Eight hundred and sixty incident PD patients were enrolled from November 1, 2005, to February 28, 2017, and followed until May 31, 2017. Outcomes were all-cause mortality and cardiovascular events. Associations between the apo B/apo A1 ratio with all-cause mortality and cardiovascular events were evaluated using multivariable-adjusted Cox models.

RESULTS

Of the 860 patients, the mean age was 49.9 ± 14.5 years, 57.6% were men, and 19.3% were diabetic patients. The median apo B/apo A1 ratio was 0.65 (range: 0.22-2.24). During a median follow-up period of 27 months (interquartile range, 13 - 41 months), 202 deaths, and 145 cardiovascular events were recorded. After adjustment for age, sex, body mass index, diabetes, cardiovascular disease, systolic blood pressure, total Kt/V, estimated glomerular filtration rate, hemoglobin level, neutrophil to lymphocyte ratio and albumin, triglyceride, and cholesterol, as well as the use of lipid-lowering agents, the highest apo B/apo A1 ratio tertile was significantly associated with a hazard ratio for all-cause mortality of 1.60 (95% CI: 1.02 to 2.49, P = 0.040) and for cardiovascular events of 2.04 (95% CI: 1.21 to 3.44, P = 0.008).

CONCLUSION

An increased apo B/apo A1 ratio was independently associated with all-cause mortality and cardiovascular events in PD patients.

Associations among apolipoproteins, oxidized high-density lipoprotein and cardiovascular events in patients on hemodialysis

Apolipoproteins are associated with survival among patients on hemodialysis (HD), but these associations might be influenced by dysfunctional (oxidized) high-density lipoprotein (HDL). We assessed associations among apolipoproteins and oxidized HDL, mortality and cardiovascular disease (CVD) events in patients on HD. This prospective observational study examined 412 patients on prevalent HD. Blood samples were obtained before dialysis at baseline to measure lipids, apolipoproteins, oxidized LDL, oxidized HDL, high-sensitivity C-reactive protein (hs-CRP) and interleukin (IL)-6 at baseline, and HDL-C and hs-CRP were measured 12 months later. Patients were then prospectively followed-up (mean, 40 months) and all-cause mortality and composite CVD events were analyzed. Associations between variables at baseline and clinical outcome were assessed by Cox proportional hazards modeling (n = 412) and Cox hazards modeling with a time-varying covariate with HDL-C and hs-CRP (n = 369). Quartiles of apolipoproteins and oxidized HDL were not associated with all-cause mortality. However, Cox proportional hazards models with quartiles of each variable adjusted for confounders and hs-CRP or IL-6 identified apolipoprotein (apo)B-to-apoA-I ratio (apoB/apoA-I) and oxidized HDL, but not apoA-I or apoA-II, as independent risk factors for composite CVD events. These associations were confirmed by Cox proportional hazards modeling with time-varying covariates for hs-CRP. ApoB/apoA-I was independently associated with composite CVD events in 1-standard deviation (SD) increase-of-variables models adjusted for the confounders, oxidized HDL and hs-CRP. However, these associations disappeared from the model adjusted with IL-6 instead of hs-CRP, and oxidized HDL and IL-6 were independently associated with composite CVD events. Findings resembled those from Cox proportional hazards modeling using time-varying covariates with HDL-C adjusted with IL-6. In conclusion, both oxidized HDL and apoB/apoA-I might be associated with CVD events in patients on prevalent HD, while associations of apoB/apoA-I with CVD events differed between models of apoB/apoA-I quartiles and 1-SD increases, and were influenced by IL-6.

Residual Cardiovascular Risk in Chronic Kidney Disease: Role of High-density Lipoprotein

Although reducing low-density lipoprotein-cholesterol (LDL-C) levels with lipid-lowering agents (statins) decreases cardiovascular disease (CVD) risk, a substantial residual risk (up to 70% of baseline) remains after treatment in most patient populations. High-density lipoprotein (HDL) is a potential contributor to residual risk, and low HDL-cholesterol (HDL-C) is an established risk factor for CVD. However, in contrast to conventional lipid-lowering therapies, recent studies show that pharmacologic increases in HDL-C levels do not bring about clinical benefits. These observations have given rise to the concept of dysfunctional HDL where increases in serum HDL-C may not be beneficial because HDL loss of function is not corrected by or even intensified by the therapy. Chronic kidney disease (CKD) increases CVD risk, and patients whose CKD progresses to end-stage renal disease (ESRD) requiring dialysis are at the highest CVD risk of any patient type studied. The ESRD population is also unique in its lack of significant benefit from standard lipid-lowering interventions. Recent studies indicate that HDL-C levels do not predict CVD in the CKD population. Moreover, CKD profoundly alters metabolism and composition of HDL particles and impairs their protective effects on functions such as cellular cholesterol efflux, endothelial protection, and control of inflammation and oxidation. Thus, CKD-induced perturbations in HDL may contribute to the excess CVD in CKD patients. Understanding the mechanisms of vascular protection in renal disease can present new therapeutic targets for intervention in this population.