Effect of hypoalbuminemia on the increased serum cholesteryl ester transfer protein concentration in children with idiopathic nephrotic syndrome

Effect of high density lipoprotein cholesterol (HDL-C) on renal outcome in patients with nephrotic syndrome complicated with steroid-induced diabetes mellitus(SIDM)

OBJECTIVE

We aimed to investigate the renal prognosis of patients with idiopathic nephrotic syndrome (INS) complicated with steroid-induced diabetes mellitus (SIDM), the association of high-density lipoprotein cholesterol (HDL-C) before glucocorticoid treatment with renal prognosis, and the risk for persistent diabetes among patients with INS who had withdrawn from steroid therapy.

MATERIALS AND METHODS

We retrospectively analyzed 239 patients with INS complicated with SIDM at the National Clinical Research Center of Kidney Diseases, Jinling Hospital, from January 2008 to December 2019. The primary endpoint was the composite renal outcome defined as the development of end-stage renal disease (ESRD) or a 50% decrease in estimated glomerular filtration rate (eGFR) for more than 24 months after glucocorticoid withdrawal. The secondary endpoint was persistent diabetes, defined as fulfilling the criteria for diagnosing diabetes or using antidiabetic medications for at least 24 months after glucocorticoid withdrawal.

RESULTS

After glucocorticoid withdrawal for over 24 months, 35 (14.6%) patients reached the composite renal endpoint: end-stage renal disease (n = 14) or a 50% decrease in eGFR (n = 21). Before glucocorticoid therapy, a level of HDL-C greater than 1.45 mmol/L worsened renal survival in patients with INS complicated with SIDM. The log₁₀ the level of HDL-C before glucocorticoid treatment was an independent risk factor for the renal outcome. A prediction model was generated: Hazard ratio (renal outcome) = 0.94 * hypertension before glucocorticoid therapy + 2.29 * log₁₀ level of HDL-C before glucocorticoid treatment + 0.90 * the grade of interstitial tubule injury (AUROC, 0.75; 95% CI, 0.63 to 0.87; P < 0.01). Meanwhile, a level of fasting plasma glucose (FPG) before glucocorticoid treatment greater than 5.2 mmol/L enhanced the likelihood of persistent diabetes for at least 24 months after glucocorticoid withdrawal.

CONCLUSIONS

Increased level of HDL-C before glucocorticoid therapy was independently associated with a higher risk for renal outcome and thus may be useful in the renal prognosis of patients with INS complicated with SIDM.

Kidney and lipids: novel potential therapeutic targets for dyslipidemia in kidney disease?

INTRODUCTION

Altered lipid distribution and metabolism may lead to the development and/or progression of chronic kidney disease (CKD). Dyslipidemia is a major risk factor for CKD and increases the risk of cardiovascular events and mortality. Therefore, lipid-lowering treatments may decrease cardiovascular risk and prevent death.

AREAS COVERED

Key players involved in regulating lipid accumulation in the kidney; contribution of lipids to CKD progression, lipotoxicity, and mitochondrial dysfunction in kidney disease; recent therapeutic approaches for dyslipidemia.

EXPERT OPINION

The precise mechanisms for regulating lipid metabolism, particularly in kidney disease, are poorly understood. Guidelines for lipid-lowering therapy for CKD are controversial. Several hypolipemic therapies are available, but compared to others, statin therapy is the most common. No clinical trial has evaluated the efficacy of proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) in preventing cardiovascular events or improving kidney function among patients with CKD or kidney transplant recipients. Attractive alternatives, such as PCSK9-small interfering RNA (siRNA) molecules or evinacumab are available. Additionally, several promising agents, such as cyclodextrins and the FXR/TGR5 dual agonist, INT-767, can improve renal lipid metabolism disorders and delay CKD progression. Drugs targeting mitochondrial dysfunction could be an option for the treatment of dyslipidemia and lipotoxicity, particularly in renal diseases.

HDL and Kidney Diseases

Serum lipid profiles, as well as HDL can be altered in patients with kidney diseases. There are various types of kidney diseases, including nephrotic syndrome and chronic kidney disease. In patients with nephrotic syndrome, plasma levels of HDL cholesterol and ApoA-I were within or below the normal limits. The HDL cholesterol: total cholesterol ratio decreased compared to healthy individuals. In patients with chronic kidney disease (CKD), reverse cholesterol transport function of HDL is impaired, and CKD also affects the composition and function of HDL. Cardiovascular disease (CVD) is the severe complication of CKD. Furthermore, HDL might also be a potential target for the prevention of cardiovascular complications associated with CKD.

Systematic interaction of plasma albumin with the efficacy of chemotherapeutic drugs

Albumin, as the most abundant plasma protein, plays an integral role in the transport of a variety of exogenous and endogenous ligands in the bloodstream and extravascular spaces. For exogenous drugs, especially chemotherapeutic drugs, binding to and being delivered by albumin can significantly affect their efficacy. Meanwhile, albumin can also bind to many endogenous ligands, such as fatty acids, with important physiological significance that can affect tumor proliferation and metabolism. In this review, we summarize how albumin with unique properties affects chemotherapeutic drugs efficacy from the aspects of drug outcome in blood, toxicity, tumor accumulation and direct or indirect interactions with fatty acids, plus application of albumin-based carriers for anti-tumor drug delivery.

IL-13-driven alterations in hepatic cholesterol handling contributes to hypercholesterolemia in a rat model of minimal change disease

Circulating factors have been implicated in the pathogenesis of minimal change disease (MCD), and may have direct effects on cholesterol metabolism. This study investigated the pathogenesis of hypercholesterolemia in an IL-13 overexpression rat model of MCD prior to the onset of proteinuria, so as to establish the direct contribution of IL-13, especially with regard to hepatic cholesterol handling. In this model of MCD, the temporal relationship between hypercholesterolemia and proteinuria was first identified. Plasma proprotein convertase subtilisin/kexin type 9 (Pcsk9) and liver ATP-binding cassette sub-family G member 5 (Abcg5) were measured using ELISA. Liver Ldlr and liver X receptor alpha (Lxra) were quantified with Western blot. Abcg5-mediated cholesterol efflux in IL-13-stimulated rat primary hepatocytes was measured using taurocholate as cholesterol acceptor. The role of Lxra was validated using a luciferase assay in Lxre-luciferase-transfected IL-13-stimulated hepatocytes. IL-13-transfected rats developed hypercholesterolemia prior to proteinuria, with 35% of rats hypercholesterolemic but only 11% proteinuric by Day 20 (P = 0.04). These pre-proteinuric hypercholesterolemic rats showed elevations in total and LDL-cholesterol, but not hypertriglyceridemia or hepatic steatosis. The hypercholesterolemia was associated with increased hepatic Pcsk9 synthesis and enhanced circulating Pcsk9 levels, which correlated strongly with plasma total cholesterol (r = 0.73, P&lt;0.001). The hypercholesterolemia was also contributed by decreased Abcg5 expression and activity, due to reduced Lxra expression. Lxra expression correlated with plasma total cholesterol levels (r = −0.52, P = 0.01), and overexpression of pLxra in rat hepatocytes abrogated the IL-13-mediated down-regulation of Lxre-driven gene expression. In conclusion, we have shown that IL-13 induced changes in hepatic cholesterol handling in a cytokine-induced rat model of MCD, resulting in hypercholesterolemia which can precede the onset of proteinuria.

Disorders of lipid metabolism in nephrotic syndrome: mechanisms and consequences

Nephrotic syndrome results in hyperlipidemia and profound alterations in lipid and lipoprotein metabolism. Serum cholesterol, triglycerides, apolipoprotein B (apoB)-containing lipoproteins (very low-density lipoprotein [VLDL], immediate-density lipoprotein [IDL], and low-density lipoprotein [LDL]), lipoprotein(a) (Lp[a]), and the total cholesterol/high-density lipoprotein (HDL) cholesterol ratio are increased in nephrotic syndrome. This is accompanied by significant changes in the composition of various lipoproteins including their cholesterol-to-triglyceride, free cholesterol-to-cholesterol ester, and phospholipid-to-protein ratios. These abnormalities are mediated by changes in the expression and activities of the key proteins involved in the biosynthesis, transport, remodeling, and catabolism of lipids and lipoproteins including apoproteins A, B, C, and E; 3-hydroxy-3-methylglutaryl-coenzyme A reductase; fatty acid synthase; LDL receptor; lecithin cholesteryl ester acyltransferase; acyl coenzyme A cholesterol acyltransferase; HDL docking receptor (scavenger receptor class B, type 1 [SR-B1]); HDL endocytic receptor; lipoprotein lipase; and hepatic lipase, among others. The disorders of lipid and lipoprotein metabolism in nephrotic syndrome contribute to the development and progression of cardiovascular and kidney disease. In addition, by limiting delivery of lipid fuel to the muscles for generation of energy and to the adipose tissues for storage of energy, changes in lipid metabolism contribute to the reduction of body mass and impaired exercise capacity. This article provides an overview of the mechanisms, consequences, and treatment of lipid disorders in nephrotic syndrome.

HDL abnormalities in nephrotic syndrome and chronic kidney disease

Normal HDL activity confers cardiovascular and overall protection by mediating reverse cholesterol transport and through its potent anti-inflammatory, antioxidant, and antithrombotic functions. Serum lipid profile, as well as various aspects of HDL metabolism, structure, and function can be profoundly altered in patients with nephrotic range proteinuria or chronic kidney disease (CKD). These abnormalities can, in turn, contribute to the progression of cardiovascular complications and various other comorbidities, such as foam cell formation, atherosclerosis, and/or glomerulosclerosis, in affected patients. The presence and severity of proteinuria and renal insufficiency, as well as dietary and drug regimens, pre-existing genetic disorders of lipid metabolism, and renal replacement therapies (including haemodialysis, peritoneal dialysis, and renal transplantation) determine the natural history of lipid disorders in patients with kidney disease. Despite the adverse effects associated with dysregulated reverse cholesterol transport and advances in our understanding of the underlying mechanisms, safe and effective therapeutic interventions are currently lacking. This Review provides an overview of HDL metabolism under normal conditions, and discusses the features, mechanisms, and consequences of HDL abnormalities in patients with nephrotic syndrome or advanced CKD.

Nephrotic syndrome causes upregulation of HDL endocytic receptor and PDZK-1-dependent downregulation of HDL docking receptor

BACKGROUND

Nephrotic syndrome (NS) is associated with dysregulation of lipid/lipoprotein metabolism and impaired high-density lipoprotein (HDL)-mediated reverse cholesterol transport and atherosclerosis. HDL serves as vehicle for transport of surplus lipids from the peripheral tissues for disposal in the liver via two receptors: (i) scavenger receptor class B type I (SR-BI) which serves as a docking receptor, enabling HDL to unload its lipid cargo and return to circulation to repeat the cycle, and (ii) beta chain ATP synthase which serves as the endocytic receptor mediating removal and catabolism of lipid-poor HDL. SR-BI abundance is regulated by PDZ-containing kidney protein 1 (PDZK1), a multifunctional protein, which prevents SRB-1 degradation at the post-translational level. This study explored the effect of NS on hepatic expression of these important molecules.

METHODS

Gene expression, protein abundance and immunohistological appearance of the above proteins were measured in the liver of rats with puromycin-induced NS and control rats.

RESULTS

The nephrotic animals exhibited severe proteinuria, hypoalbuminemia, hypercholesterolemia, hypertriglyceridemia, reduced HDL/total cholesterol ratio, normal glomerular filtration rate, significant upregulation of the endocytic HDL receptor messenger RNA (mRNA) and protein (P < 0.005) and significant reduction of SR-BI protein (P < 0.002) despite its normal mRNA abundance. The reduction in SR-BI protein abundance in NS animals was accompanied by parallel reductions in PDZK1 mRNA (P = 0.02) and protein abundance (P = 0.012).

CONCLUSIONS

NS results in elevation of hepatic HDL endocytic receptor and deficiency of HDL docking receptor. The latter is associated with and, in part, mediated by downregulation of PDZK1. Together, these abnormalities can increase catabolism and diminish recycling of HDL and contribute to the defective reverse cholesterol/lipid transport in NS.

Rationale for albumin infusions

PURPOSE OF REVIEW

To describe the metabolism and function of albumin, and to scrutinize the evidence that infusion of albumin may be beneficial in disease. To explain why albumin infusion does not improve clinical outcome in most disease states, studied.

RECENT FINDINGS

Albumin acts as a binding protein and an oncotic agent. However, albumin may also act as an extracellular scavenger, which leads to oxidation of albumin. It is likely that this compromises its function and it is possible that this drives its degradation. In disease, these useful processes are accelerated leading to rapid ageing of the molecule.Albumin infusion does not improve clinical outcome despite increasing oncotic pressure in chronic disease. It is not superior to nonprotein colloids or electrolyte solutions in acute hypovolemia with one or two exceptions (liver failure, possibly cerebral infarction). One potential explanation is that pharmaceutical albumin does not have the oxidative qualities that freshly synthesized albumin has.

SUMMARY

Albumin infusion has not proven to achieve clinical benefit in many acute and chronic disease states with a few exceptions in acute hypovolemia (e.g. postparacentesis). Future studies should reveal whether infusion of freshly synthesized nonoxidized albumin is of greater clinical benefit.