Lipoprotein modulation of proteinuric renal injury

HDL and chronic kidney disease

Low HDL-cholesterol (HDL-C) concentrations are a typical trait of the dyslipidemia associated with chronic kidney disease (CKD). In this condition, plasma HDLs are characterized by alterations in structure and function, and these particles can lose their atheroprotective functions, e.g., the ability to promote cholesterol efflux from peripheral cells, anti-oxidant and anti-inflammatory proprieties and they can even become dysfunctional, i.e., exactly damaging. The reduction in plasma HDL-C levels appears to be the only lipid alteration clearly linked to the progression of renal disease in CKD patients. The association between the HDL system and CKD development and progression is also supported by the presence of genetic kidney alterations linked to HDL metabolism, including mutations in the APOA1, APOE, APOL and LCAT genes. Among these, renal disease associated with LCAT deficiency is well characterized and lipid abnormalities detected in LCAT deficiency carriers mirror the ones observed in CKD patients, being present also in acquired LCAT deficiency. This review summarizes the major alterations in HDL structure and function in CKD and how genetic alterations in HDL metabolism can be linked to kidney dysfunction. Finally, the possibility of targeting the HDL system as possible strategy to slow CKD progression is reviewed.

Post-Stroke Administration of L-4F Promotes Neurovascular and White Matter Remodeling in Type-2 Diabetic Stroke Mice

Patients with type 2 diabetes mellitus (T2DM) exhibit a distinct and high risk of ischemic stroke with worse post-stroke neurovascular and white matter (WM) prognosis than the non-diabetic population. In the central nervous system, the ATP-binding cassette transporter member A 1 (ABCA1), a reverse cholesterol transporter that efflux cellular cholesterol, plays an important role in high-density lipoprotein (HDL) biogenesis and in maintaining neurovascular stability and WM integrity. Our previous study shows that L-4F, an economical apolipoprotein A member I (ApoA-I) mimetic peptide, has neuroprotective effects via alleviating neurovascular and WM impairments in the brain of db/db-T2DM stroke mice. To further investigate whether L-4F has neurorestorative benefits in the ischemic brain after stroke in T2DM and elucidate the underlying molecular mechanisms, we subjected middle-aged, brain-ABCA1 deficient (ABCA1-B/-B), and ABCA1-floxed (ABCA1fl/fl) T2DM control mice to distal middle cerebral artery occlusion. L-4F (16 mg/kg, subcutaneous) treatment was initiated 24 h after stroke and administered once daily for 21 days. Treatment of T2DM-stroke with L-4F improved neurological functional outcome, and decreased hemorrhage, mortality, and BBB leakage identified by decreased albumin infiltration and increased tight-junction and astrocyte end-feet densities, increased cerebral arteriole diameter and smooth muscle cell number, and increased WM density and oligodendrogenesis in the ischemic brain in both ABCA1-B/-B and ABCA1fl/fl T2DM-stroke mice compared with vehicle-control mice, respectively (p < 0.05, n = 9 or 21/group). The L-4F treatment reduced macrophage infiltration and neuroinflammation identified by decreases in ED-1, monocyte chemoattractant protein-1 (MCP-1), and toll-like receptor 4 (TLR4) expression, and increases in anti-inflammatory factor Insulin-like growth factor 1 (IGF-1) and its receptor IGF-1 receptor β (IGF-1Rβ) in the ischemic brain (p < 0.05, n = 6/group). These results suggest that post-stroke administration of L-4F may provide a restorative strategy for T2DM-stroke by promoting neurovascular and WM remodeling. Reducing neuroinflammation in the injured brain may contribute at least partially to the restorative effects of L-4F independent of the ABCA1 signaling pathway.

Preprocedural Lp(a) level and ApoB/ApoA-Ι ratio and the risk for contrast-induced acute kidney injury in patients undergoing emergency PCI

BACKGROUND

High serum Lipoprotein(a) (Lp(a)) level and Apolipoprotein B/Apolipoprotein AΙ (ApoB/ApoA-Ι) ratio are risk factors for cardiovascular disease and kidney disease and have been found to be correlated with the prevalence and prognosis of various kidney diseases. However, it is not clear whether the serum Lp(a) level and ApoB/ApoA-Ι ratio pre-PCI are correlated with the prevalence of contrast-induced acute kidney injury (CI-AKI).

METHODS

A total of 931 participants undergoing emergency PCI from July 2018 to July 2020 were included. According to whether the serum creatinine concentration was higher than the baseline concentration (by ≥25% or ≥ 0.5 mg/dL) 48-72 h after contrast exposure, these participants were divided into a CI-AKI group (n = 174) and a non-CI-AKI group (n = 757). Serum Lp(a), ApoA-Ι and ApoB concentration were detected in the patients when they were admitted to hospital, and the ApoB/ApoA-Ι ratio was calculated. Logistic regression and restricted cubic spline analyses were used to explore the correlation between the Lp(a) concentration or the ApoB/ApoA-Ι ratio and the risk of CI-AKI.

RESULTS

Among the 931 participants undergoing emergency PCI, 174 (18.69%) participants developed CI-AKI. Compared with the non-CI-AKI group, the Lp(a) level and ApoB/ApoA-Ι ratio pre-PCI in the CI-AKI group were significantly higher (P < 0.05). The incidence of CI-AKI was positively associated with the serum Lp(a) level and ApoB/ApoA-Ι ratio pre-PCI in each logistic regression model (P < 0.05). After adjusting for all the risk factors included in this study, restricted cubic spline analyses found that the Lp(a) level and the ApoB/ApoA-Ι ratio before PCI, within certain ranges, were positively associated with the prevalence of CI-AKI.

CONCLUSION

High Lp(a) levels and high ApoB/ApoA-Ι ratios before PCI are potential risk factors for CI-AKI.

High-Density Lipoproteins in Kidney Disease

Decades of epidemiological studies have established the strong inverse relationship between high-density lipoprotein (HDL)-cholesterol concentration and cardiovascular disease. Recent evidence suggests that HDL particle functions, including anti-inflammatory and antioxidant functions, and cholesterol efflux capacity may be more strongly associated with cardiovascular disease protection than HDL cholesterol concentration. These HDL functions are also relevant in non-cardiovascular diseases, including acute and chronic kidney disease. This review examines our current understanding of the kidneys’ role in HDL metabolism and homeostasis, and the effect of kidney disease on HDL composition and functionality. Additionally, the roles of HDL particles, proteins, and small RNA cargo on kidney cell function and on the development and progression of both acute and chronic kidney disease are examined. The effect of HDL protein modification by reactive dicarbonyls, including malondialdehyde and isolevuglandin, which form adducts with apolipoprotein A-I and impair proper HDL function in kidney disease, is also explored. Finally, the potential to develop targeted therapies that increase HDL concentration or functionality to improve acute or chronic kidney disease outcomes is discussed.

Association between monocyte count to high-density lipoprotein cholesterol ratio and mortality in patients undergoing peritoneal dialysis

BACKGROUND AND AIMS

Previous studies had demonstrated that elevated monocyte count to high-density lipoprotein cholesterol ratio (MHR), a novel marker of inflammation, was associated with higher cardiovascular events and mortality in patients with pre-dialysis chronic kidney disease, diabetes, and coronary heart disease. However, the association between MHR and mortality in patients undergoing peritoneal dialysis (PD) has received little attention. The aim of this study was to investigate the association between MHR and all-cause and cardiovascular mortality in PD patients.

METHODS AND RESULTS

In this single center retrospective cohort study, PD patients who had catheter insertion in our PD center from January 1, 2006 to December 31, 2016 were enrolled. All patients were divided into three groups according to the tertiles of baseline MHR levels and followed up until December 31, 2018. The associations of MHR levels with all-cause and cardiovascular mortality were assessed by using Cox proportional hazards models. Of 1584 patients, mean age was 46.02 ± 14.65 years, 60.1% were male, and 24.2% had diabetes. The mean MHR level was 0.39 ± 0.23. During a median follow up time of 45.6 (24.6-71.8) months, 349 patients died, and 181 deaths were caused by cardiovascular disease. After adjusting for confounders, the highest MHR tertile was significantly associated with all-cause and cardiovascular mortality with a hazard ratio of 1.43 (95%CI = 1.06-1.93, P = 0.019), 1.54 (95%CI = 1.01-2.35, P = 0.046), respectively.

CONCLUSION

Higher MHR level was an independent risk factor for all-cause and cardiovascular mortality in PD patients.

Kidney injury-mediated disruption of intestinal lymphatics involves dicarbonyl-modified lipoproteins

Kidney disease affects intestinal structure and function. Although intestinal lymphatics are central in absorption and remodeling of dietary and synthesized lipids/lipoproteins, little is known about how kidney injury impacts the intestinal lymphatic network, or lipoproteins transported therein. To study this, we used puromycin aminoglycoside-treated rats and NEP25 transgenic mice to show that proteinuric injury expanded the intestinal lymphatic network, activated lymphatic endothelial cells and increased mesenteric lymph flow. The lymph was found to contain increased levels of cytokines, immune cells, and isolevuglandin (a highly reactive dicarbonyl) and to have a greater output of apolipoprotein AI. Plasma levels of cytokines and isolevuglandin were not changed. However, isolevuglandin was also increased in the ileum of proteinuric animals, and intestinal epithelial cells exposed to myeloperoxidase produced more isolevuglandin. Apolipoprotein AI modified by isolevuglandin directly increased lymphatic vessel contractions, activated lymphatic endothelial cells, and enhanced the secretion of the lymphangiogenic promoter vascular endothelial growth factor-C by macrophages. Inhibition of isolevuglandin synthesis by a carbonyl scavenger reduced intestinal isolevuglandin adduct level and lymphangiogenesis. Thus, our data reveal a novel mediator, isolevuglandin modified apolipoprotein AI, and uncover intestinal lymphatic network structure and activity as a new pathway in the crosstalk between kidney and intestine that may contribute to the adverse impact of kidney disease on other organs.

Urinary apolipoprotein AI in children with kidney disease

BACKGROUND

Although high-density lipoprotein (HDL) modulates many cell types in the cardiovascular system, little is known about HDL in the kidney. We assessed urinary excretion of apolipoprotein AI (apoAI), the main protein in HDL.

METHODS

We enrolled 228 children with various kidney disorders and 40 controls. Urinary apoAI, albumin, and other markers of kidney damage were measured using ELISA, apoAI isoforms with Western blot, and renal biopsies stained for apoAI.

RESULTS

Patients followed in nephrology clinic had elevated urinary apoAI vs. controls (median 0.074 μg/mg; interquartile range (IQR) 0.0160-0.560, vs. 0.019 μg/mg; IQR 0.004-0.118, p < 0.001). Patients with tubulopathies, renal dysplasia/congenital anomalies of the kidney and urogenital tract, glomerulonephritis, and nephrotic syndrome (NS) in relapse had the greatest elevations (p ≤ 0.01). Patients with NS in remission, nephrolithiasis, polycystic kidney disease, transplant, or hypertension were not different from controls. Although all NS in relapse had higher apoAI excretion than in remission (0.159 vs. 0.0355 μg/mg, p = 0.01), this was largely driven by patients with focal segmental glomerulosclerosis (FSGS). Many patients, especially with FSGS, had increased urinary apoAI isoforms. Biopsies from FSGS patients showed increased apoAI staining at proximal tubule brush border, compared to diffuse cytoplasmic distribution in minimal change disease.

CONCLUSIONS

Children with kidney disease have variably increased urinary apoAI depending on underlying disease. Urine apoAI is particularly elevated in diseases affecting proximal tubules. Kidney disease is also associated with high molecular weight (HMW) apoAI isoforms in urine, especially FSGS. Whether abnormal urinary apoAI is a marker or contributor to renal disease awaits further study.