Kidney as modulator and target of "good/bad" HDL

Urinary Protein-Biomarkers Reliably Indicate Very Early Kidney Damage in Children With Alport Syndrome Independently of Albuminuria and Inflammation

Introduction

Alport syndrome (AS) is a hereditary type IV collagen disease. It starts shortly after birth, without clinical symptoms, and progresses to end-stage kidney disease early in life. The earlier therapy starts, the more effectively end-stage kidney disease can be delayed. Clearly then, to ensure preemptive therapy, early diagnosis is an essential prerequisite.

Methods

To provide early diagnosis, we searched for protein biomarkers (BMs) by mass spectrometry in dogs with AS stage 0. At this very early stage, we identified 74 candidate BMs. Of these, using commercial enzyme-linked immunosorbent assays (ELISAs), we evaluated 27 in dogs and 28 in children, 50 with AS and 104 healthy controls.

Results

Most BMs from blood appeared as fractions of multiple variants of the same protein, as shown by their chromatographic distribution before mass spectrometry. Blood samples showed only minor differences because ELISAs rarely detect disease-specific variants. However, in urine , several proteins, individually or in combination, were promising indicators of very early and preclinical kidney injury. The BMs with the highest sensitivity and specificity were collagen type XIII, hyaluronan binding protein 2 (HABP2), and complement C4 binding protein (C4BP).

Conclusion

We generated very strong candidate BMs by our approach of first examining preclinical AS in dogs and then validating these BMs in children at early stages of disease. These BMs might serve for screening purposes for AS before the onset of kidney damage and therefore allow preemptive therapy.

Apolipoprotein A-I attenuates peritoneal fibrosis associated with peritoneal dialysis by inhibiting oxidative stress and inflammation

Apolipoprotein A-I (apoA-I), 90% of which is present in high-density lipoprotein (HDL), is the main constituent of HDL, has anti-inflammatory and anti-oxidant properties, and has received extensive attention in anti-atherosclerosis. Yet little is known about apoA-I 's role in peritoneal dialysis. In this study, by analyzing PD patients (n = 81), we found that decreased apoA/HDL-C ratio is significantly associated with rapid decline in peritoneal function. Further studies were performed in animal experiments to determine the ascendancy of apolipoprotein A-I mimetic peptide (D-4F) on peritoneum, we found that D-4F administration reduced peritoneal fibrosis and peritoneal endothelial mesenchymal transformation (EMT) induced by high glucose peritoneal dialysate, such as N-cadherin, Fibronectin, Vimentin, and α-smooth muscle actin (α-SMA) expression decreased. In mechanism, D-4F can significantly inhibit Smad2/3 phosphorylation, which is the major pathway leading to fibrosis. Furthermore, D-4F treatment inhibited NADPH oxidase and thiobarbituric acid reactive substances (TBARS) expression, increased the activity of certain enzymes, such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Finally, treatment with D-4F inhibits the expression of interleukins-6(IL-6), Interleukin-1β(IL-1β), and tumor necrosis factor-α(TNF-α). Taken together, based on the above research evidence, apoA-I and its peptide mimic may regulate the oxidative stress, TGF- β1/Smads signaling pathway and inflammatory response to reduce peritoneal fibrosis due to peritoneal dialysis.

Biokinetics, radiopharmacokinetics and estimation of the absorbed dose in healthy organs due to Technetium-99m transported in the core and on the surface of reconstituted high-density lipoprotein nanoparticles

The development of rHDL-radionuclide theragnostic systems requires evaluation of the absorbed doses that would be produced in healthy tissues and organs at risk. Technetium-99m is the most widely used radionuclide for diagnostic imaging, therefore, the design of theragnostic reconstituted high density-lipoprotein (rHDL) nanosystems labeled with Technetium-99m offers multiple possibilities.

OBJECTIVE

To determine the biokinetics, radiopharmacokinetics and estimate the absorbed doses induced in healthy organs by Technetium-99m transported in the core and on the surface of rHDL.

METHODS

Biokinetic and radiopharmacokinetic models of rHDL/[99mTc]Tc-HYNIC-DA (Technetium-99m in the core) and [99mTc]Tc-HYNIC-rHDL (Technetium-99m on the surface) were calculated from their ex vivo biodistribution in healthy mice. Absorbed doses were estimated by the MIRD formalism using OLINDA/EXM and LMFIT softwares.

RESULTS

rHDL/[99mTc]Tc-HYNIC-DA and [99mTc]Tc-HYNIC-rHDL show instantaneous absorption in kidney, lung, heart and pancreas, with slower absorption in spleen. rHDL/[99mTc]Tc-HYNIC-DA is absorbed more slowly in the intestine, while [99mTc]Tc-HYNIC-rHDL is absorbed more slowly in the liver. The main target organ for rHDL/[99mTc]Tc-HYNIC-DA, which is hydrophobic in nature, is the liver, whereas the kidney is for the more hydrophilic [99mTc]Tc-HYNIC-rHDL. Assuming that 925 MBq (25 mCi) of Technetium-99m, carried in the core or on the surface of rHDL, are administered, the maximum tolerated doses for the organs of greatest accumulation are not exceeded.

CONCLUSION

Theragnostic systems based on 99mTc-labeled rHDL are safe from the dosimetric point of view. The dose estimates obtained can be used to adjust the 99mTc-activity to be administered in future clinical trials.

Values of Donor Serum Lipids and Calcium in Predicting Graft Function after Kidney Transplantation: A Retrospective Study

OBJECTIVE

Delayed graft function (DGF) and early graft loss of renal grafts are determined by the quality of the kidneys from the deceased donor. As "non-traditional" risk factors, serum biomarkers of donors, such as lipids and electrolytes, have drawn increasing attention due to their effects on the postoperative outcomes of renal grafts. This study aimed to examine the value of these serum biomarkers for prediction of renal graft function.

METHODS

The present study consecutively collected 306 patients who underwent their first single kidney transplantation (KT) from adult deceased donors in our center from January 1, 2018 to December 31, 2019. The correlation between postoperative outcomes [DGF and abnormal serum creatinine (SCr) after 6 and 12 months] and risk factors of donors, including gender, age, body mass index (BMI), past histories, serum lipid biomarkers [cholesterol, triglyceride, high-density lipoprotein (HDL) and low-density lipoprotein (DL)], and serum electrolytes (calcium and sodium) were analyzed and evaluated.

RESULTS

(1) Donor age and pre-existing hypertension were significantly correlated with the incidence rate of DGF and high SCr level (≥2 mg/dL) at 6 and 12 months after KT (P<0.05); (2) The donor's BMI was significantly correlated with the incidence rate of DGF after KT (P<0.05); (3) For serum lipids, merely the low level of serum HDL of the donor was correlated with the reduced incidence rate of high SCr level at 12 months after KT [P<0.05, OR (95% CI): 0.425 (0.202-0.97)]; (4) The serum calcium of the donor was associated with the reduced incidence rate of high SCr level at 6 and 12 months after KT [P<0.05, OR (95% CI): 0.184 (0.045-0.747) and P<0.05, OR (95% CI): 0.114 (0.014-0.948), respectively].

CONCLUSION

The serum HDL and calcium of the donor may serve as predictive factors for the postoperative outcomes of renal grafts after KT, in addition to the donor's age, BMI and pre-existing hypertension.

Engineered rHDL Nanoparticles as a Suitable Platform for Theranostic Applications

Reconstituted high-density lipoproteins (rHDLs) can transport and specifically release drugs and imaging agents, mediated by the Scavenger Receptor Type B1 (SR-B1) present in a wide variety of tumor cells, providing convenient platforms for developing theranostic systems. Usually, phospholipids or Apo-A1 lipoproteins on the particle surfaces are the motifs used to conjugate molecules for the multifunctional purposes of the rHDL nanoparticles. Cholesterol has been less addressed as a region to bind molecules or functional groups to the rHDL surface. To maximize the efficacy and improve the radiolabeling of rHDL theranostic systems, we synthesized compounds with bifunctional agents covalently linked to cholesterol. This strategy means that the radionuclide was bound to the surface, while the therapeutic agent was encapsulated in the lipophilic core. In this research, HYNIC-S-(CH2)3-S-Cholesterol and DOTA-benzene-p-SC-NH-(CH2)2-NH-Cholesterol derivatives were synthesized to prepare nanoparticles (NPs) of HYNIC-rHDL and DOTA-rHDL, which can subsequently be linked to radionuclides for SPECT/PET imaging or targeted radiotherapy. HYNIC is used to complexing 99mTc and DOTA for labeling molecules with 111, 113mIn, 67, 68Ga, 177Lu, 161Tb, 225Ac, and 64Cu, among others. In vitro studies showed that the NPs of HYNIC-rHDL and DOTA-rHDL maintain specific recognition by SR-B1 and the ability to internalize and release, in the cytosol of cancer cells, the molecules carried in their core. The biodistribution in mice showed a similar behavior between rHDL (without surface modification) and HYNIC-rHDL, while DOTA-rHDL exhibited a different biodistribution pattern due to the significant reduction in the lipophilicity of the modified cholesterol molecule. Both systems demonstrated characteristics for the development of suitable theranostic platforms for personalized cancer treatment.

Cell transcriptomic atlas of the non-human primate Macaca fascicularis

Studying tissue composition and function in non-human primates (NHPs) is crucial to understand the nature of our own species. Here we present a large-scale cell transcriptomic atlas that encompasses over 1 million cells from 45 tissues of the adult NHP Macaca fascicularis. This dataset provides a vast annotated resource to study a species phylogenetically close to humans. To demonstrate the utility of the atlas, we have reconstructed the cell-cell interaction networks that drive Wnt signalling across the body, mapped the distribution of receptors and co-receptors for viruses causing human infectious diseases, and intersected our data with human genetic disease orthologues to establish potential clinical associations. Our M. fascicularis cell atlas constitutes an essential reference for future studies in humans and NHPs.

Albumin Uptake and Processing by the Proximal Tubule: Physiologic, Pathologic and Therapeutic Implications

For nearly 50 years the proximal tubule (PT) has been known to reabsorb, process, and either catabolize or transcytose albumin from the glomerular filtrate. Innovative techniques and approaches have provided insights into these processes. Several genetic diseases, nonselective PT cell defects, chronic kidney disease (CKD), and acute PT injury lead to significant albuminuria, reaching nephrotic range. Albumin is also known to stimulate PT injury cascades. Thus, the mechanisms of albumin reabsorption, catabolism, and transcytosis are being reexamined with the use of techniques that allow for novel molecular and cellular discoveries. Megalin, a scavenger receptor, cubilin, amnionless, and Dab2 form a nonselective multireceptor complex that mediates albumin binding and uptake and directs proteins for lysosomal degradation after endocytosis. Albumin transcytosis is mediated by a pH-dependent binding affinity to the neonatal Fc receptor (FcRn) in the endosomal compartments. This reclamation pathway rescues albumin from urinary losses and cellular catabolism, extending its serum half-life. Albumin that has been altered by oxidation, glycation, or carbamylation or because of other bound ligands that do not bind to FcRn traffics to the lysosome. This molecular sorting mechanism reclaims physiological albumin and eliminates potentially toxic albumin. The clinical importance of PT albumin metabolism has also increased as albumin is now being used to bind therapeutic agents to extend their half-life and minimize filtration and kidney injury. The purpose of this review is to update and integrate evolving information regarding the reabsorption and processing of albumin by proximal tubule cells including discussion of genetic disorders and therapeutic considerations.

HDL Composition, Heart Failure, and Its Comorbidities

Although research on high-density lipoprotein (HDL) has historically focused on atherosclerotic coronary disease, there exists untapped potential of HDL biology for the treatment of heart failure. Anti-oxidant, anti-inflammatory, and endothelial protective properties of HDL could impact heart failure pathogenesis. HDL-associated proteins such as apolipoprotein A-I and M may have significant therapeutic effects on the myocardium, in part by modulating signal transduction pathways and sphingosine-1-phosphate biology. Furthermore, because heart failure is a complex syndrome characterized by multiple comorbidities, there are complex interactions between heart failure, its comorbidities, and lipoprotein homeostatic mechanisms. In this review, we will discuss the effects of heart failure and associated comorbidities on HDL, explore potential cardioprotective properties of HDL, and review novel HDL therapeutic targets in heart failure.

Predictive nomogram model for major adverse kidney events within 30 days in sepsis patients with type 2 diabetes mellitus

BACKGROUND

In sepsis patients, Type 2 Diabetes Mellitus (T2DM) was associated with an increased risk of kidney injury. Furthermore, kidney damage is among the dangerous complications, with a high mortality rate in sepsis patients. However, the underlying predictive model on the prediction of major adverse kidney events within 30 days (MAKE30) in sepsis patients with T2DM has not been reported by any study.

METHODS

A total of 406 sepsis patients with T2DM were retrospectively enrolled and divided into a non-MAKE30 group (261 cases) and a MAKE30 group (145 cases). In sepsis patients with T2DM, univariate and multivariate logistic regression analyses were conducted to identify independent predictors of MAKE30. Based on the findings of multivariate logistic regression analysis, the corresponding nomogram was constructed. The nomogram was evaluated using the calibration curve, Receiver Operating Characteristic (ROC) curve, and decision curve analysis. A composite of death, new Renal Replacement Therapy (RRT), or Persistent Renal Dysfunction (PRD) comprised MAKE30. Finally, subgroup analyses of the nomogram for 30-day mortality, new RRT, and PRD were performed.

RESULTS

In sepsis patients with T2DM, Mean Arterial Pressure (MAP), Platelet (PLT), cystatin C, High-Density Lipoprotein (HDL), and apolipoprotein E (apoE) were independent predictors for MAKE30. According to the ROC curve, calibration curve, and decision curve analysis, the nomogram model based on those predictors had satisfactory discrimination (AUC = 0.916), good calibration, and clinical application. Additionally, in sepsis patients with T2DM, the nomogram model exhibited a high ability to predict the occurrence of 30-day mortality (AUC = 0.822), new RRT (AUC = 0.874), and PRD (AUC = 0.801).

CONCLUSION

The nomogram model, which is available within 24 hours after admission, had a robust and accurate assessment for the MAKE30 occurrence, and it provided information to better manage sepsis patients with T2DM.

Multifaced Roles of HDL in Sepsis and SARS-CoV-2 Infection: Renal Implications

High-density lipoproteins (HDLs) are a class of blood particles, principally involved in mediating reverse cholesterol transport from peripheral tissue to liver. Omics approaches have identified crucial mediators in the HDL proteomic and lipidomic profile, which are involved in distinct pleiotropic functions. Besides their role as cholesterol transporter, HDLs display anti-inflammatory, anti-apoptotic, anti-thrombotic, and anti-infection properties. Experimental and clinical studies have unveiled significant changes in both HDL serum amount and composition that lead to dysregulated host immune response and endothelial dysfunction in the course of sepsis. Most SARS-Coronavirus-2-infected patients admitted to the intensive care unit showed common features of sepsis disease, such as the overwhelmed systemic inflammatory response and the alterations in serum lipid profile. Despite relevant advances, episodes of mild to moderate acute kidney injury (AKI), occurring during systemic inflammatory diseases, are associated with long-term complications, and high risk of mortality. The multi-faceted relationship of kidney dysfunction with dyslipidemia and inflammation encourages to deepen the clarification of the mechanisms connecting these elements. This review analyzes the multifaced roles of HDL in inflammatory diseases, the renal involvement in lipid metabolism, and the novel potential HDL-based therapies.

Association of High-Density Lipoprotein Cholesterol With GFR Decline in a General Nondiabetic Population

Introduction

Although lower high-density lipoprotein cholesterol (HDL-C) levels are considered a risk factor for cardiovascular disease (CVD), experimental evidence suggest that aging, inflammation, and oxidative stress may remodel HDL-C, leading to dysfunctional HDL-C. Population studies on HDL-C and loss of the glomerular filtration rate (GFR) reported inconsistent results, but they used inaccurate estimates of the GFR and may have been confounded by comorbidity.

Methods

We investigated the association of HDL-C levels with risk of GFR loss in a general population cohort; the participants were aged 50-62 years and did not have diabetes, CVD, or chronic kidney disease (CKD) at baseline. The GFR was measured using iohexol-clearance at baseline (n=1627) and at the follow-up (n=1324) after a median of 5.6 years. We also investigated any possible effect modification by low-grade inflammation, physical activity, and sex.

Results

Higher HDL-C levels were associated with steeper GFR decline rates and increased risk of rapid GFR decline (>3 ml/min per 1.73 m² per year) in multivariable adjusted linear mixed models and logistic regression (-0.64 ml/min per 1.73 m² per year [95% CI -0.99, -0.29; P < 0.001] and odds ratio 2.7 [95% CI 1.4, 5.2; P < 0.001] per doubling in HDL-C). Effect modifications indicated a stronger association between high HDL-C and GFR loss in physically inactive persons, those with low-grade inflammation, and men.

Conclusion

Higher HDL-C levels were independently associated with accelerated GFR loss in a general middle-aged nondiabetic population.

Relationship of Para and Perirenal Fat and High-Density Lipoprotein and Its Function in Patients with Type 2 Diabetes Mellitus

BACKGROUND

Para and perirenal fat is a fat pad surrounding the kidneys. Recent studies showed the association between para and perirenal fat and cardiovascular diseases including atherosclerosis and hypertension. We aimed to assess the relationship between para-perirenal ultrasonographic fat thickness and serum high-density lipoprotein (HDL) level and cholesterol efflux capacity of HDL in patients with type 2 diabetes mellitus (T2DM).

METHODS

We recruited 58 subjects with T2DM and collected anthropometric indices including height, weight, waist circumference, and other clinical data. Para-perirenal ultrasonographic fat thickness (PUFT) was measured via ultrasound. Serum lipid profile and other metabolic indices were determined as well. Correlation analysis and regression analysis were performed to analyze the relationship between PUFT and HDL level and cholesterol efflux capacity in all patients and subgroups.

RESULTS

Patients with higher PUFT have lower serum HDL level but increased cholesterol efflux capacity. Further analysis showed that PUFT negatively correlated with the serum HDL level in all patients, with no difference in groups divided by body mass index (BMI). In addition, PUFT was positively correlated with cholesterol efflux capacity in all patients. Multiple stepwise regression analysis showed an independent association of PUFT and serum HDL level and cholesterol efflux capacity.

CONCLUSIONS

PUFT is closely correlated with the serum HDL level and cholesterol efflux capacity in patients with T2DM.

Lipoprotein modulation of proteinuric renal injury

High-density lipoprotein (HDL) and its main protein, apolipoprotein AI (apoAI), have established benefits in various cells, but whether these cytoprotective effects of HDL pertain to renal cells is unclear. We investigated the in vitro consequences of exposing damaged podocytes to normal apoAI, HDL, and apoAI mimetic (L-4F), and the in vivo effects of L-4F on kidney and atherosclerotic injury in a podocyte-specific injury model of proteinuria. In vitro, primary mouse podocytes were injured by puromycin aminonucleoside (PAN). Cellular viability, migration, production of reactive oxygen species (ROS), apoptosis, and the underlying signaling pathway were assessed. In vivo, we used a proteinuric model, Nphs1-hCD25 transgenic (NEP25⁺) mice, which express human CD25 on podocytes. Podocyte injury was induced by using immunotoxin (LMB2) and generated a proteinuric atherosclerosis model, NEP25⁺:apoE^-/- mice, was generated by mating apoE-deficient (apoE^-/-) mice with NEP25⁺ mice. Animals received L-4F or control vehicle. Renal function, podocyte injury, and atherosclerosis were assessed. PAN reduced podocyte viability, migration, and increased ROS production, all significantly lessened by apoAI, HDL, and L-4F. L-4F attenuated podocyte apoptosis and diminished PAN-induced inactivation of Janus family protein kinase-2/signal transducers and activators of transcription 3. In NEP25⁺ mice, L-4F significantly lessened overall proteinuria, and preserved podocyte expression of synaptopodin and cell density. Proteinuric NEP25⁺:apoE^-/- mice had more atherosclerosis than non-proteinuric apoE^-/- mice, and these lesions were significantly decreased by L-4F. Normal human apoAI, HDL, and apoAI mimetic protect against podocyte damage. ApoAI mimetic provides in vivo beneficial effects on podocytes that culminate in reduced albuminuria and atherosclerosis. The results suggest supplemental apoAI/apoAI mimetic may be a novel candidate to lessen podocyte damage and its complications.