PCSK9 and syndecan-1 in renal disease-related dyslipidemia

Liver is the primary organ for clearance of triglyceride-rich remnant lipoproteins (TRL) via LDL receptor (LDLR), ), LDLR-related protein-1 (LRP1) and syndecan-1. Elevated plasma TRL due to reduced liver clearance is a major cause of dyslipidemia, cardiovascular disease and mortality in chronic kidney disease (CKD). Although substantial effort has been put into understanding the molecular mechanisms underlying dyslipidemia in CKD and development of novel therapies, dyslipidemia related to CKD still remains a huge challenge. Recently, heparan sulfate proteoglycans (HSPG) has been reported to facilitate LDLR degradation by proprotein convertase subtilisin kexin type-9 (PCSK9). In this thesis, we have investigated i) the effects of CKD on primary hepatic lipoprotein receptors (LDLR, LRP1 and syndecan-1); ii) the interaction of PCSK9 and hepatic HSPGs in connection to plasma lipids and iii) whether lipid lowering therapies are associated with reductions in plasma PCSK9 and syndecan-1 and clinical outcomes. The studies reported in this thesis provide novel insights into the mechanisms underlying dyslipidemia in renal diseases that involve increased hepatic HSPG interaction with PCSK9 leading to reduced clearance of TRL. At present, where current cholesterol-lowering strategies to treat dyslipidemia in CKD are still insufficient, studies present in this thesis suggest that PCSK9 inhibition can be beneficial in improving lipid levels in CKD. Further, our study opens new venues for future development of cost-effective heparin mimetics as PCSK9 inhibitors

Prevention of Triglyceridemia by (Non-)Anticoagulant Heparin(oids) Does Not Preclude Transplant Vasculopathy and Glomerulosclerosis

Background: In renal transplantation, chronic transplant dysfunction (CTD) is associated with increased PCSK9 and dyslipidemia. PCSK9 is an enzyme that increases plasma cholesterol levels by downregulating LDLR expression. We recently showed increased PCSK9–syndecan-1 interaction in conditions of proteinuria and renal function loss. Treatment with heparin(oids) might be a therapeutic option to improve dyslipidemia and CTD. We investigated the effects of (non-)anticoagulant heparin(oids) on serum lipids, syndecan-1 and PCSK9 levels, and CTD development. Methods: Kidney allotransplantation was performed from female Dark Agouti to male Wistar Furth recipients. Transplanted rats received daily subcutaneous injections of saline, unfractionated heparin, and RO-heparin or NAc-heparin (2 mg heparin(oid)/kg BW) until sacrifice after 9 weeks of treatment. Results: Saline-treated recipients developed hypertension, proteinuria, and loss of creatinine clearance (all p < 0.05 compared to baseline), along with glomerulosclerosis and arterial neo-intima formation. Saline-treated recipients showed significant increase in plasma triglycerides (p < 0.05), borderline increase in non-HDLc/HDLc (p = 0.051), and ∼10-fold increase in serum syndecan-1 (p < 0.05), without significant increase in serum PCSK9 at 8 weeks compared to baseline. Heparin and non-anticoagulant RO-heparin administration in transplanted rats completely prevented an increase in triglycerides compared to saline-treated recipients at 8 weeks (both p < 0.05). Heparin(oids) treatment did not influence serum total cholesterol (TC), plasma syndecan-1 and PCSK9 levels, creatinine clearance, proteinuria, glomerulosclerosis, and arterial neo-intima formation, 8 weeks after transplantation. Combining all groups, increased syndecan-1 shedding was associated with TC (r = 0.5; p = 0.03) and glomerulosclerosis (r = 0.53; p = 0.021), whereas the non-HDLc/HDLc ratio was associated with the neo-intimal score in the transplanted kidneys (r = 0.65; p < 0.001). Conclusion: Prevention of triglyceridemia by (non-)anticoagulant heparin(oids) neither influenced PCSK9/syndecan-1 nor precluded CTD, which however did associate with the shedding of lipoprotein clearance receptor syndecan-1 and the unfavorable cholesterol profile

Proteinuria converts hepatic heparan sulfate to an effective proprotein convertase subtilisin kexin type 9 enzyme binding partner:a historical appraisal of its origins and conceptual evolution

International audienc

Novel aspects of PCSK9 and lipoprotein receptors in renal disease-related dyslipidemia

Chronic kidney disease (CKD) is a global health problem with a profound impact on quality of life. Cardiovascular disease is established as a major cause of morbidity and mortality in patients with CKD. Dyslipidemia is frequently observed in CKD patients, suggesting a causal relation between dyslipidemia and cardiovascular disease in CKD patients. Currently, lipid-lowering drugs such as statins, are the primary choice for lipid lowering therapy in high-risk populations. Despite many studies showing CVD risk reduction with statins, CVD still remains the leading cause of the death in CKD. This underscores the need for new therapeutic approaches to reduce cardiovascular risk in CKD patients. Reduced lipoprotein lipase activity, increased very low-density lipoprotein production, increased proprotein convertase subtilisin kexin type 9 (PCSK9) expression and loss of hepatic heparan sulfate proteoglycans (HSPG) syndecan-1 have been associated with CKD-related dyslipidemia. Low-density lipoprotein receptor (LDLR), low-density lipoprotein receptor-related protein 1 (LRP-1) and syndecan-1, are the most important hepatic receptors for lipoprotein clearance. However, their contributions to the pathogenesis of dyslipidemia and cardiovascular disease in CKD remain unclear. Interestingly, in CKD, increased plasma lipid levels are associated with elevated levels of PCSK9. This promotes the proteolysis of LDLR, suggesting a role for PCSK9 in CKD-associated dyslipidemia. Fully humanized monoclonal antibodies targeting PCSK9 have been approved by the US Food and Drug Administration and the European Medicines Agency as lipid lowering treatment for patients with hypercholesterolemia. In CKD sub-group analysis, ODYSSEY COMBO I and ODYSSEY COMBO II studies demonstrated strong reduction in LDL-C by alirocumab compared to placebo and ezetimibe and when added to statins. However, their efficacy in reducing plasma TG is controversial. Therefore, further research work is need for a detailed analysis on efficacy and safety of PCSK9 antibodies in CKD groups. Interestingly, novel findings on PCSK9 interaction with HSPG might shed new insight on altered lipid metabolism in CKD. In this review, we discuss various aspects of lipoprotein metabolism and hepatic lipoprotein receptor signaling pathways along with the concept of renal disease-related dyslipidemia. Furthermore, this review highlights the drawbacks of current lipid-lowering therapies and proposes novel approaches for lipid management in CKD

High sodium diet converts renal proteoglycans into pro-inflammatory mediators in rats

International audienceBACKGROUND:High dietary sodium aggravates renal disease by affecting blood pressure and by its recently shown pro-inflammatory and pro-fibrotic effects. Moreover, pro-inflammatory modification of renal heparan sulfate (HS) can induce tissue remodeling. We aim to investigate if high sodium intake in normotensive rats converts renal HS into a pro-inflammatory phenotype, able to bind more sodium and orchestrate inflammation, fibrosis and lymphangiogenesis.METHODS:Wistar rats received a normal diet for 4 weeks, or 8% NaCl diet for 2 or 4 weeks. Blood pressure was monitored, and plasma, urine and tissue collected. Tissue sodium was measured by flame spectroscopy. Renal HS and tubulo-interstitial remodeling were studied by biochemical, immunohistochemical and qRT-PCR approaches.RESULTS:High sodium rats showed a transient increase in blood pressure (week 1; p<0.01) and increased sodium excretion (p<0.05) at 2 and 4 weeks compared to controls. Tubulo-interstitial T-cells, myofibroblasts and mRNA levels of VCAM1, TGF-β1 and collagen type III significantly increased after 4 weeks (all p<0.05). There was a trend for increased macrophage infiltration and lymphangiogenesis (both p = 0.07). Despite increased dermal sodium over time (p<0.05), renal concentrations remained stable. Renal HS of high sodium rats showed increased sulfation (p = 0.05), increased L-selectin binding to HS (p<0,05), and a reduction of sulfation-sensitive anti-HS mAbs JM403 (p<0.001) and 10E4 (p<0.01). Hyaluronan expression increased under high salt conditions (p<0.01) without significant changes in the chondroitin sulfate proteoglycan versican. Statistical analyses showed that sodium-induced tissue remodeling responses partly correlated with observed HS changes.CONCLUSION:We show that high salt intake by healthy normotensive rats convert renal HS into high sulfated pro-inflammatory glycans involved in tissue remodeling events, but not in increased sodium storage

General parameters.

<p>General parameters.</p

Correlations between sodium excretion (as a measure of sodium intake) and changes in HS (A), changes in HS and tubulo-interstitial remodeling (B), sodium excretion and tubulo-interstitial remodeling (C) and correlations of sodium excretion with tubulo-interstitial remodeling after partial correction for changes in HS (D).

<p>Correlations between sodium excretion (as a measure of sodium intake) and changes in HS (A), changes in HS and tubulo-interstitial remodeling (B), sodium excretion and tubulo-interstitial remodeling (C) and correlations of sodium excretion with tubulo-interstitial remodeling after partial correction for changes in HS (D).</p

PAS staining of kidney of a control rat (left) and high salt fed rat (right).

<p>No apparent fibrosis was observed upon high salt feeding, however, we noted quite some accumulation of tubulo-interstitial cells (arrows) in the high salt kidneys. Scale bar represents 50 μm.</p

High dietary salt induced hyaluronan accumulation and apparent loss of versican.

<p>High dietary sodium increased hyaluronan especially in the cortico-medullary region (top), whereas versican tended to be reduced in the same areas (bottom). Scale bar represents 50 μm. Statistical differences between groups (N = 5/group) were tested using the Kruskall-Wallis test. *p<0.05; **p<0.01; ***p<0.0001.</p