Cellular cholesterol transport proteins in diabetic nephropathy

HSPA8 dampens SCAP/INSIG split and SREBP activation by reducing PKR-mediated INSIG phosphorylation

Lipid accumulation in renal tubules is a major determinant of diabetic kidney disease (DKD), and activation of SREBPs plays a central role in this process. Our study aims to explore whether HSPA8, a molecular chaperone, is the master regulator of INSIG/SREBPs function in DKD. Here, we show that tubular epithelial cell (TEC)-specific knockout of HSPA8 upregulates the phosphorylation of INSIG1 and INSIG2, which disrupts the interaction between INSIG proteins and SCAP, leading to SREBP activation. TEC-specific overexpression of HSPA8 restrains these changes. INSIG1/2 can be phosphorylated by protein kinase R (PKR), while HSPA8 recognizes PKR and recruits the E3 ubiquitin ligase to promote PKR ubiquitination and degradation. Under temporary hyperglycemic stimulation, SREBP1 transcriptionally activates HSPA8 expression. Conversely, persistent hyperglycemia reduces HSPA8 levels via promoting NF-κB-mediated transcriptional inhibition of HSPA8. Collectively, these findings indicate that the molecular chaperone HSPA8 serves as a negative feedback regulator of SREBPs, lipogenesis, and DKD development.

The association of fasting triglyceride variability with renal dysfunction and proteinuria in medical checkup participants

BACKGROUND

The association between the variability of triglyceride (TG) and chronic kidney disease (CKD) progression remains unclear. We examined whether intraindividual variability in fasting TG was associated with the exacerbation of CKD.

METHODS

We conducted a retrospective and observational study. 18,339 participants, who went through medical checkups and had checked their estimated glomerular filtration rate (eGFR) and semi-quantitative proteinuria by urine dipstick every year since 2017 for 4 years were registered. Variability in fasting TG was determined using the standard deviation (SD), and maximum minus minimum difference (MMD) between 2017 and 2021. The primary end point for the analysis of eGFR decline was eGFR < 60 mL/min/1.73 m2. The secondary end point for the analysis of proteinuria was the incidence of proteinuria ≥ ( ±) by urine dipstick.

RESULTS

The renal survival was lower in the higher-SD, and higher-MMD groups than in the lower-SD, and lower-MMD groups, respectively (log-rank test p < 0.001, and < 0.001, respectively). Lower SD and lower MMD were significantly associated with renal survival in the adjusted model (hazard ratio (HR), 1.12; 95% confidence intervals (CI), 1.04-1.21, and HR, 1.13; 95% CI 1.05-1.23, respectively). The non-incidence of proteinuria was lower in the higher-SD, and higher-MMD groups than in the lower-SD, and lower-MMD groups, respectively (log-rank test p < 0.001 and < 0.001, respectively).

CONCLUSION

Fasting TG variability was associated with CKD progression in participants who went through medical checkups.

High-Density Lipoprotein in Patients with Diabetic Kidney Disease: Friend or Foe?

High-density lipoprotein (HDL) exhibits multiple metabolic protective functions, such as facilitating cellular cholesterol efflux, antioxidant, anti-inflammatory, anti-apoptotic and anti-thrombotic properties, showing antidiabetic and renoprotective potential. Diabetic kidney disease (DKD) is considered to be associated with high-density lipoprotein cholesterol (HDL-C). The hyperglycemic environment, non-enzymatic glycosylation, carbamylation, oxidative stress and systemic inflammation can cause changes in the quantity and quality of HDL, resulting in reduced HDL levels and abnormal function. Dysfunctional HDL can also have a negative impact on pancreatic β cells and kidney cells, leading to the progression of DKD. Based on these findings, new HDL-related DKD risk predictors have gradually been proposed. Interventions aiming to improve HDL levels and function, such as infusion of recombinant HDL (rHDL) or lipid-poor apolipoprotein A-I (apoA-I), can significantly improve glycemic control and also show renal protective effects. However, recent studies have revealed a U-shaped relationship between HDL-C levels and DKD, and the loss of protective properties of high levels of HDL may be related to changes in composition and the deposition of dysfunctional particles that exacerbate damage. Further research is needed to fully elucidate the complex role of HDL in DKD. Given the important role of HDL in metabolic health, developing HDL-based therapies that augment HDL function, rather than simply increasing its level, is a critical step in managing the development and progression of DKD.

Lipid homeostasis in diabetic kidney disease

Lipid homeostasis is crucial for proper cellular and systemic functions. A growing number of studies confirm the importance of lipid homeostasis in diabetic kidney disease (DKD). Lipotoxicity caused by imbalance in renal lipid homeostasis can further exasperate renal injury. Large lipid deposits and lipid droplet accumulation are present in the kidneys of DKD patients. Autophagy plays a critical role in DKD lipid homeostasis and is involved in the regulation of lipid content. Inhibition or reduction of autophagy can lead to lipid accumulation, which in turn further affects autophagy. Lipophagy selectively recognizes and degrades lipids and helps to regulate cellular lipid metabolism and maintain intracellular lipid homeostasis. Therefore, we provide a systematic review of fatty acid, cholesterol, and sphingolipid metabolism, and discuss the responses of different renal intrinsic cells to imbalances in lipid homeostasis. Finally, we discuss the mechanism by which autophagy, especially lipophagy, maintains lipid homeostasis to support the development of new DKD drugs targeting lipid homeostasis.

Bioactivities of morroniside: A comprehensive review of pharmacological properties and molecular mechanisms

Morroniside (MOR) is an iridoid glycoside and the main active principle of the medicinal plant, Cornus officinalis Sieb. This phytochemical is associated with numerous health benefits due to its antioxidant properties. The primary objective of the present study was to assess the pharmacological effects and underlying mechanisms of MOR, utilizing published data obtained from literature databases. Data collection involved accessing various sources, including PubMed/Medline, Scopus, Science Direct, Google Scholar, Web of Science, and SpringerLink. Our findings demonstrate that MOR can be utilized for the treatment of several diseases and disorders, as numerous studies have revealed its significant therapeutic activities. These activities encompass anti-inflammatory, antidiabetic, lipid-lowering capability, anticancer, trichogenic, hepatoprotective, gastroprotective, osteoprotective, renoprotective, and cardioprotective effects. MOR has also shown promising benefits against various neurological ailments, including Alzheimer's disease, Parkinson's disease, spinal cord injury, cerebral ischemia, and neuropathic pain. Considering these therapeutic features, MOR holds promise as a lead compound for the treatment of various ailments and disorders. However, further comprehensive preclinical and clinical trials are required to establish MOR as an effective and reliable therapeutic agent.

Lipid metabolism disorder in diabetic kidney disease

Diabetic kidney disease (DKD), a significant complication associated with diabetes mellitus, presents limited treatment options. The progression of DKD is marked by substantial lipid disturbances, including alterations in triglycerides, cholesterol, sphingolipids, phospholipids, lipid droplets, and bile acids (BAs). Altered lipid metabolism serves as a crucial pathogenic mechanism in DKD, potentially intertwined with cellular ferroptosis, lipophagy, lipid metabolism reprogramming, and immune modulation of gut microbiota (thus impacting the liver-kidney axis). The elucidation of these mechanisms opens new potential therapeutic pathways for DKD management. This research explores the link between lipid metabolism disruptions and DKD onset.

Mechanisms and efficacy of traditional Chinese herb monomers in diabetic kidney disease

Diabetic kidney disease (DKD) is a serious complication of diabetes and is the primary cause of end-stage renal disease. Current treatment strategies primarily focus on the inhibition of the renin-angiotensin-aldosterone system and the attainment of blood glucose control. Although current medical therapies for DKD have been shown to delay disease progression and improve long-term outcomes, their efficacy is limited and they may be restricted in certain cases, particularly when hyperkalemia is present. Traditional Chinese medicine (TCM) treatment has emerged as a significant complementary approach for DKD. TCM monomers, derived from various Chinese herbs, have been found to modulate multiple therapeutic targets and exhibit a broad range of therapeutic effects in patients with DKD. This review aims to summarize the mechanisms of action of TCM monomers in the treatment of DKD, based on findings from clinical trials, as well as cell and animal studies. The results of these investigations demonstrate the potential effective use of TCM monomers in treating or preventing DKD, offering a promising new direction for future research in the field. By providing a comprehensive overview of the mechanisms and efficacy of TCM monomers in DKD, this review highlights the potential of these natural compounds as alternative therapeutic options for improving outcomes in patients with DKD.

Designing nanodiscs as versatile platforms for on-demand therapy

Nowadays, there has been an increasing utilization of nanomedicines for disease treatment. Nanodiscs (NDs) have emerged as a novel platform technology that garners significant attention in biomedical research and drug discovery. NDs are nanoscale phospholipid bilayer discs capable of incorporating membrane proteins and lipids within a native-like environment. They are assembled using amphiphilic biomacromolecular materials, such as apolipoprotein A1 or membrane scaffold proteins (MSPs), peptides, and styrene-maleic acid polymers (SMAs). NDs possess well-defined sizes and shapes, offering a stable, homogeneous, and biologically relevant environment for studying membrane proteins and lipids. Their unique properties have made them highly desirable for diverse applications, including cancer immunotherapy, vaccine development, antibacterial and antiviral therapy, and treating Alzheimer's disease (AD) and diabetes-related conditions. This review discusses the classifications, advantages, and applications of NDs in disease therapy.

Tubular deficiency of ABCA1 augments cholesterol- and Na+-dependent effects on systemic blood pressure in male mice

Dyslipidemia, with changes in plasma membrane (PM) composition, is associated with hypertension, while rising PM cholesterol induces Na+ channel activity. We hypothesize that ablation of renal tubular ABCA1, a cholesterol efflux protein, leads to cholesterol- and Na+-dependent changes in blood pressure (BP). Transgenic mice (TgPAX8rtTA;tetO-Cre/+) expressing a doxycycline (dox)-inducible CRE recombinase were bred with mice expressing floxed ABCA1 to generate renal tubules deficient in ABCA1 (ABCA1FF). Tail-cuff systolic BP (SBP) was measured in mice on specific diets. Immunoblotting was performed on whole and PM protein lysates of kidney from mice completing experimental diets. Cortical PM of ABCA1FF showed reduced ABCA1 (60 ± 28%; n = 10, P < 0.05) compared with wild-type littermates (WT; n = 9). Tail-cuff SBP of ABCA1FF (n = 11) was not only greater post dox, but also during cholesterol or high Na+ feeding (P < 0.05) compared with WT mice (n = 15). A Na+-deficient diet abolished the difference, while 6 wk of cholesterol diet raised SBP in ABCA1FF compared with mice before cholesterol feeding (P < 0.05). No difference in α-ENaC protein abundance was noted in kidney lysate; however, γ-ENaC increased in ABCA1FF mice versus WT mice. In kidney membranes, NKCC2 abundance was greater in ABCA1FF versus WT mice. Cortical lysates of ABCA1FF mouse kidneys expressed less renin and angiotensin I receptor than WT mouse kidneys. Furosemide injection induced a greater diuretic effect in ABCA1FF (n = 7; 45.2 ± 8.7 µL/g body wt) versus WT (n = 7; 33.1 ± 6.9 µL/g body wt; P < 0.05) but amiloride did not. Tubular ABCA1 deficiency induces cholesterol-dependent rise in SBP and modest Na+ sensitivity of SBP, which we speculate is partly related to Na+ transporters and channels.NEW & NOTEWORTHY Cholesterol has been linked to greater Na+ channel activity in kidney cells, which may predispose to systemic hypertension. We showed that when ABCA1, a protein that removes cholesterol from tissues, is ablated from mouse kidneys, systemic blood pressure is greater than normal mice. Dietary cholesterol further increases blood pressure in transgenic mice, whereas low dietary salt intake reduced blood pressure to that of normal mice. Thus, we speculate that diseases and pharmaceuticals that reduce renal ABCA1 expression, like diabetes and calcineurin inhibitors, respectively, contribute to the prominence of hypertension in their clinical presentation.

To Explore the Putative Molecular Targets of Diabetic Nephropathy and their Inhibition Utilizing Potential Phytocompounds

BACKGROUND

This review critically addresses the putative molecular targets of Diabetic Nephropathy (DN) and screens effective phytocompounds that can be therapeutically beneficial, and highlights their mechanistic modalities of action.

INTRODUCTION

DN has become one of the most prevalent complications of clinical hyperglycemia, with individual-specific variations in the disease spectrum that leads to fatal consequences. Diverse etiologies involving oxidative and nitrosative stress, activation of polyol pathway, inflammasome formation, Extracellular Matrix (ECM) modifications, fibrosis, and change in dynamics of podocyte functional and mesangial cell proliferation adds up to the clinical complexity of DN. Current synthetic therapeutics lacks target-specific approach, and is associated with the development of inevitable residual toxicity and drug resistance. Phytocompounds provides a vast diversity of novel compounds that can become an alternative therapeutic approach to combat the DN.

METHODS

Relevant publications were searched and screened from research databases like GOOGLE SCHOLAR, PUBMED and SCISEARCH. Out of 4895 publications, the most relevant publications were selected and included in this article.

RESULT

This study critically reviews over 60 most promising phytochemical and provides with their molecular targets, that can be of pharmacological significance in context to current treatment and concomitant research in DN.

CONCLUSION

This review highlights those most promising phytocompounds that have the potential of becoming new safer naturally-sourced therapeutic candidates and demands further attention at clinical level.

Oxidative Stress Induced by Lipotoxicity and Renal Hypoxia in Diabetic Kidney Disease and Possible Therapeutic Interventions: Targeting the Lipid Metabolism and Hypoxia

Oxidative stress, a hallmark pathophysiological feature in diabetic kidney disease (DKD), arises from the intricate interplay between pro-oxidants and anti-oxidants. While hyperglycemia has been well established as a key contributor, lipotoxicity emerges as a significant instigator of oxidative stress. Lipotoxicity encompasses the accumulation of lipid intermediates, culminating in cellular dysfunction and cell death. However, the mechanisms underlying lipotoxic kidney injury in DKD still require further investigation. The key role of cell metabolism in the maintenance of cell viability and integrity in the kidney is of paramount importance to maintain proper renal function. Recently, dysfunction in energy metabolism, resulting from an imbalance in oxygen levels in the diabetic condition, may be the primary pathophysiologic pathway driving DKD. Therefore, we aim to shed light on the pivotal role of oxidative stress related to lipotoxicity and renal hypoxia in the initiation and progression of DKD. Multifaceted mechanisms underlying lipotoxicity, including oxidative stress with mitochondrial dysfunction, endoplasmic reticulum stress activated by the unfolded protein response pathway, pro-inflammation, and impaired autophagy, are delineated here. Also, we explore potential therapeutic interventions for DKD, targeting lipotoxicity- and hypoxia-induced oxidative stress. These interventions focus on ameliorating the molecular pathways of lipid accumulation within the kidney and enhancing renal metabolism in the face of lipid overload or ameliorating subsequent oxidative stress. This review highlights the significance of lipotoxicity, renal hypoxia-induced oxidative stress, and its potential for therapeutic intervention in DKD.

Kidney lipid dysmetabolism and lipid droplet accumulation in chronic kidney disease

Chronic kidney disease (CKD) is a global health problem with rising incidence and prevalence. Among several pathogenetic mechanisms responsible for disease progression, lipid accumulation in the kidney parenchyma might drive inflammation and fibrosis, as has been described in fatty liver diseases. Lipids and their metabolites have several important structural and functional roles, as they are constituents of cell and organelle membranes, serve as signalling molecules and are used for energy production. However, although lipids can be stored in lipid droplets to maintain lipid homeostasis, lipid accumulation can become pathogenic. Understanding the mechanisms linking kidney parenchymal lipid accumulation to CKD of metabolic or non-metabolic origin is challenging, owing to the tremendous variety of lipid species and their functional diversity across different parenchymal cells. Nonetheless, multiple research reports have begun to emphasize the effect of dysregulated kidney lipid metabolism in CKD progression. For example, altered cholesterol and fatty acid metabolism contribute to glomerular and tubular cell injury. Newly developed lipid-targeting agents are being tested in clinical trials in CKD, raising expectations for further therapeutic development in this field.

Renal ectopic lipid deposition in rats with early-stage diabetic nephropathy evaluated by the MR mDixon-Quant technique: association with the expression of SREBP-1 and PPARα in renal tissue

BACKGROUND

Renal ectopic lipid deposition (ELD) plays a significant role in the development of diabetic nephropathy (DN). This study aimed to use the magnetic resonance (MR) mDixon-Quant technique to evaluate renal ELD and its association with the expression of sterol regulatory element binding protein 1 (SREBP-1) and peroxisome proliferator-activated receptor alpha (PPARα) in renal tissue.

METHODS

Seventy male Sprague-Dawley (SD) rats were randomly divided into experimental (n=50) and control groups (n=20). A high-fat diet combined with low-dose streptozotocin (STZ) was administered to the experimental group to establish a type 2 diabetes mellitus (T2DM) model. The rats received renal mDixon-Quant scans and blood lipid and histopathological examinations in batches after the T2DM model was established. According to the histopathological findings, the included rats were stratified into control and early DN groups. Renal fat fraction (FF), blood lipid level, the ratio of the integrated optical density of intracellular lipid droplets and the total area of all the cells (IOD/TAC), and the expression of SREBP-1 and PPARɑ in renal tissue were analyzed.

RESULTS

Compared to the controls, renal FF, IOD/TAC, the expression of SREBP-1 in renal tissue, and serum total cholesterol (TC), triglyceride (TG) and low-density lipoprotein (LDL) levels were higher in the early DN group, while the expression of PPARɑ in renal tissue and the high-density lipoprotein (HDL) level were lower (all P values <0.001). Renal FF gradually increased with the progression of disease [r=0.810 (95% CI: 0.675-0.928), P<0.001]. Positive correlations between renal FF and each of the following: TC, TG, LDL, IOD/TAC, and the expression of SREBP-1 [r=0.479 (95% CI: 0.353-0.640, P=0.012), 0.576 (95% CI: 0.283-0.842, P=0.002), 0.441 (95% CI: 0.305-0.606, P=0.021), 0.911 (95% CI: 0.809-0.964, P<0.001) and 0.800 (95% CI: 0.640-0.910, P<0.001), respectively] and negative correlations between renal FF and each of the following: HDL and the expression of PPARɑ [r=-0.611 (95% CI: -0.809 to -0.469, P=0.001) and -0.748 (95% CI: -0.886 to -0.585, P<0.001), respectively] were found.

CONCLUSIONS

Renal lipid deposition evaluated by the MR mDixon-Quant technique is associated with the blood lipid level, histological fat quantification, and the expression of SREBP-1 and PPARɑ in renal tissue. The renal FF value might serve as a biomarker for better understanding of renal lipid metabolism in early-stage DN.

Correlation between different levels and patterns of dyslipidemia and glomerular filtration rate in patients with type 2 diabetes: A cross-sectional survey of a regional cohort

BACKGROUND

Due to the high cardiovascular risk in patients with diabetic nephropathy, more attention should be paid to lipid levels and dyslipidemia in these patients. The current study investigated the association between single and mixed dyslipidemia patterns, estimated glomerular filtration rate (eGFR), and different chronic kidney disease (CKD) stages.

METHODS

This cross-sectional study evaluated 4059 patients with type 2 diabetes (T2D). TG, TC, LDL-C, and HDL-C were measured. Non-HDL-C and AIP were calculated. We estimated eGFR using the CKD-EPI equation.

RESULTS

With the progression of the kidney failure stage, mean levels of TG, LDL-C, non-HDL-C, and AIP decreased. HDL-C levels decreased with the advance of the CKD stage in men but did not change significantly in women. The prevalence of single dyslipidemia, including high LDL-C and high non-HDL-C, decreased with the advancing CKD stage. The prevalence of mixed dyslipidemia patterns, including high AIP and high LDL-C, high AIP and high non-HDL-C, showed a significant downward tendency. TG and AIP levels were negatively, and HDL-C levels were positively correlated with eGFR after adjusting for the risk factors. Also, CKD stage 3 was positively related to the risk of high TG and low HDL-C.

CONCLUSION

This study shows that blood lipids decreased with the progression of renal failure in patients with T2D. However, after adjustment, TG and AIP levels had negative, and HDL-C levels had a positive correlation with eGFR, which could be consistent with the hypothesis that eGFR decreases with increasing TG or AIP levels or decreasing HDL-C levels.

Hypertriglyceridemia is associated with decline of estimated glomerular filtration rate and risk of end-stage kidney disease in a real-word Italian cohort: Evidence from the TG-RENAL Study

BACKGROUND

This analysis investigated the role of hypertriglyceridemia on renal function decline and development of end-stage kidney disease (ESKD) in a real-world clinical setting.

METHODS

A retrospective analysis using administrative databases of 3 Italian Local Health Units was performed searching patients with at least one plasma triglyceride (TG) measurement between 2013 and June 2020, followed-up until June 2021. Outcome measures included reduction in estimated glomerular filtration rate (eGFR) ≥30% from baseline and ESKD onset. Subjects with normal (normal-TG), high (HTG) and very high TG levels (vHTG) (respectively <150 mg/dL, 150-500 mg/dL and >500 mg/dL) were comparatively evaluated.

RESULTS

Overall 45,000 subjects (39,935 normal-TGs, 5,029 HTG and 36 vHTG) with baseline eGFR of 96.0 ± 66.4 mL/min were considered. The incidence of eGFR reduction was 27.1 and 31.1 and 35.1 per 1000 person-years, in normal-TG, HTG and vHTG subjects, respectively (P<0.01). The incidence of ESKD was 0.7 and 0.9 per 1000 person-years, in normal-TG and HTG/vHTG subjects, respectively (P<0.01). Univariate and multivariate analyses revealed that HTG subjects had a risk of eGFR reduction or ESKD occurrence (composite endpoint) increased by 48% compared to normal-TG subjects (adjusted OR:1.485, 95%CI 1.300-1.696; P<0.001). Moreover, each 50 mg/dL increase in TG levels resulted in significantly greater risk of eGFR reduction (OR:1.062, 95%CI 1.039-1.086 P<0.001) and ESKD (OR:1.174, 95%CI 1.070-1.289, P = 0.001).

CONCLUSIONS

This real-word analysis in a large cohort of individuals with low-to-moderate cardiovascular risk suggests that moderate-to-severe elevation of plasma TG levels is associated with a significantly increased risk of long-term kidney function deterioration.

Artesunate targets cellular metabolism to regulate the Th17/Treg cell balance

INTRODUCTION

Metabolic reprogramming is one of the important mechanisms of cell differentiation, and different cells have different preferences for energy sources. During the differentiation of naive CD4 + T cells into Th17 and Treg cells, these cells show specific energy metabolism characteristics. Th17 cells depend on enhanced glycolysis, fatty acid synthesis, and glutaminolysis. In contrast, Treg cells are dependent on oxidative phosphorylation, fatty acid oxidation, and amino acid depletion. As a potent antimalarial drug, artesunate has been shown to modulate the Th17/Treg imbalance and regulate cell metabolism.

METHODOLOGY

Relevant literatures on ART, cellular metabolism, glycolysis, lipid metabolism, amino acid metabolism, CD4 + T cells, Th17 cells, and Treg cells published from January 1, 2010 to now were searched in PubMed database.

CONCLUSION

In this review, we will highlight recent advances in which artesunate can restore the Th17/Treg imbalance in disease states by altering T-cell metabolism to influence differentiation and lineage selection. Data from the current study show that few studies have focused on the effect of ART on cellular metabolism. ART can affect the metabolic characteristics of T cells (glycolysis, lipid metabolism, and amino acid metabolism) and interfere with their differentiation lineage, thereby regulating the balance of Th17/Treg and alleviating the symptoms of the disease.

Urinary RBP as an Independent Predictor of Renal Outcome in Diabetic Nephropathy

Background

Renal tubular impairment is prevalent in diabetic nephropathy (DN) and the histological severity predicted renal outcome. Biomarkers of tubular injury also increased in the urine of DN patients. The retrospective study aimed to assess the prognostic value of clinically widely applied urinary tubular injury markers, retinol-binding protein (RBP), β2-microglobulin (β2-MG) and N-acetyl-β-D-glucosaminidase (NAG) in DN.

Method

A total of 305 patients with biopsy-proven DN were enrolled. The baseline urine total protein and components including albumin, IgG, RBP, β2-MG and NAG were retrieved from medical records. The primary outcome was end stage renal disease (ESRD). Cox proportional hazard analysis and restricted cubic splines were performed to evaluate the association of parameters with ESRD. Nomograms were constructed and concordance index (C-index) was used to measure the prediction ability.

Result

The levels of urinary RBP, β2-MG and NAG were positively correlated with the severity of interstitial fibrosis and tubular atrophy (IFTA). Positive correlations were also observed among β2-MG, NAG and mesangial expansion. Urinary RBP was not correlated with any glomerular lesions. Urinary RBP, β2-MG and NAG were risk factors for ESRD in hazard analysis with adjustment for age, gender and body mass index (BMI). The hazard ratios increased with the increment of baseline levels. In the multivariate Cox model including serum creatinine (SCr), total urinary protein, urinary albumin, urinary IgG and the tubular injury biomarkers, urinary RBP (with every g/mol.Cr increase: HR 1.06, 95% CI 1.03-1.10, p =0.001) remained as an independent risk factor for ESRD in DN patients. Patients were divided by the medium value of urinary RBP into the low RBP and high RBP groups. Survival analysis showed that significantly more patients in the high RBP progressed to ESRD compared to those in the low RBP group (p =0.02) when urinary total protein was less than 3.5 g/g. The C-index of the nomogram incorporating age, gender, BMI, SCr and total urine protein was 0.757. The value increased to 0.777 after adding urinary RBP to the model.

Conclusions

Urinary RBP excretion was only correlated with the severity of IFTA and independently predicted ESRD in DN patients.

Nanodisc delivery of liver X receptor agonist for the treatment of diabetic nephropathy

Dyslipidemia is recognized to be an important contributor to the progression of diabetic nephropathy (DN), leading to lipoprotein dysregulation, excessive mesangium expansion as well as inflammation in the glomeruli. Thus, dual targeting of abnormal cholesterol metabolism and inflammatory responses of mesangial cells represents an alternative approach for DN treatment. Herein, we sought to develop a renal-targeting therapeutic strategy for diabetic nephropathy by modifying synthetic high-density lipoprotein (sHDL) nanodiscs with a kidney targeting ligand (KT peptide) and encapsulating a liver X receptor (LXR) agonist in the modified sHDL. LXR agonists delivered by sHDL can facilitate the removal of excessive lipids from mesangial cells, ameliorate inflammation and restore normal renal function. Overall, our data suggests that our optimized KT-targeted sHDL/TO nanodiscs (KT-sHDL/TO) generate potent therapeutic efficacy not only by more efficient cholesterol efflux, but also by suppressing mesangial cell proliferation. Most importantly, in a DN murine model, KT-sHDL/TO ameliorated dyslipidemia and inflammation superior to blank sHDL and non-targeting sHDL/TO formulations, showing promise for future clinical translation in DN treatment.

[Dysfunctional high-density lipoproteins in diabetes mellitus]

The risk of cardiovascular disease (CVD) in persons with type 2 diabetes mellitus (DM2) increases two to four times. One of the main factors increasing cardiovascular risk is dyslipidemia, which includes abnormalities in all lipoproteins, including high-density lipoproteins (HDL). The development of DM2 is accompanied not only by a decrease in the level of HDL, but also by significant changes in their structure. This leads to the transformation of native HDL into so-called dysfunctional or diabetic HDL, which loses their antiatherogenic, cardioprotective, anti-inflammatory and anti-diabetic properties. In poorly controlled diabetes mellitus HDL can not only lose its beneficial functions, but also acquire proatherogenic, proinflammatory ones. Diabetic HDL can contribute to the accumulation of such unfavorable qualities as increased proliferation, migration, and invasion of cancer cells. Given that HDL, in addition to participation in cholesterol transport, performs important regulatory functions in the body, there is reason to assume that structural modifications of HDL (oxidation, glycation, triglyceride enrichment, loss of HDL-associated enzymes, etc.) are one of the causes of vascular complications of diabetes.

Plasma Calcium and Phosphorus Levels and Cardiovascular Disease Risks in Egyptian Type 2 Diabetic Patients

Background: Cardiovascular complication of diabetes is considered an important issue that needs deep investigations. The levels of plasma calcium (Ca) and phosphorus (P) have been implicated as having an association to cardiovascular diseases. AIM: The objective of the present research was to study the plasma levels of both Ca and P and their association to the atherogenic ratio; total cholesterol: high density lipoprotein-cholesterol and the plasma albumin in male and female patients with type 2-diabetes. The interrelation between anthropometric parameters represented by body mass index (BMI), waist circumference and waist/hip ratio with Ca and P were studied. Also, the association between plasma Ca and P with their dietary intake were investigated. Subjects and METODS: Thirty-one type 2-diabetic male and female patients participated in the study, in addition of ten healthy subjects. Biochemical parameters, anthropometric measurements and nutrients′ intake were assessed. Biochemical parameters include plasma Ca, P, lipid profile, albumin, liver function tests and creatinine. RESULTS: Plasma Ca levels of female patients of BMI> 30 kg/m2 demonstrated significant increase compared to the control group.  All male and female patients showed significant increase in plasma P compared to the control group. Glycosylated hemoglobin of male and females showed significant high values compared to the control group except for diabetic male of BMI>30 kg/m2 that showed insignificant increase. No significant changes in plasma TG and LDL-C levels were noticed compared to the control.  Plasma TC of patients showed significant high levels compared to the control group. The levels of HDL-C of patients were significantly lower than that of the control. The ratios of TC/HDL-C diabetic patients either male or female and whatever their BMI were significantly higher than that of the control. No significant changes in plasma activities of ALT and AST and bilirubin levels were observed among the different groups including the control.  Plasma albumin levels demonstrated significant reduction compared to the control group whatever their sexes or BMI. Plasma creatinine levels of the different diabetic groups showed insignificant change from the control group except for the male group of BMI<30 kg/m2 that showed significant elevation. In male, plasma Ca showed significant negative correlation with albumin and positive correlation with creatinine and dietary vitamin D. In female, a significant positive correlation was noticed between plasma and dietary P while a negative correlation was observed between plasma Ca and dietary iron. CONCLUSION: Elevated of plasma P together with reduced plasma albumin and elevated TC/HDL-C may reflect an association of plasma P to CVD in male and female diabetic subjects while high plasma Ca might predict CVD in only female diabetic patients of BMI > 30 kg/m2.

Cholesterol Metabolism in Chronic Kidney Disease: Physiology, Pathologic Mechanisms, and Treatment

High plasma levels of lipids and/or lipoproteins are risk factors for atherosclerosis, nonalcoholic fatty liver disease (NAFLD), obesity, and diabetes. These four conditions have also been identified as risk factors leading to the development of chronic kidney disease (CKD). Although many pathways that generate high plasma levels of these factors have been identified, most clinical and physiologic dysfunction results from aberrant assembly and secretion of lipoproteins. The results of several published studies suggest that elevated levels of low-density lipoprotein (LDL)-cholesterol are a risk factor for atherosclerosis, myocardial infarction, coronary artery calcification associated with type 2 diabetes, and NAFLD. Cholesterol metabolism has also been identified as an important pathway contributing to the development of CKD; clinical treatments designed to alter various steps of the cholesterol synthesis and metabolism pathway are currently under study. Cholesterol synthesis and catabolism contribute to a multistep process with pathways that are regulated at the cellular level in renal tissue. Cholesterol metabolism may also be regulated by the balance between the influx and efflux of cholesterol molecules that are capable of crossing the membrane of renal proximal tubular epithelial cells and podocytes. Cellular accumulation of cholesterol can result in lipotoxicity and ultimately kidney dysfunction and failure. Thus, further research focused on cholesterol metabolism pathways will be necessary to improve our understanding of the impact of cholesterol restriction, which is currently a primary intervention recommended for patients with dyslipidemia.

Cholesterol-induced toxicity: An integrated view of the role of cholesterol in multiple diseases

High levels of cholesterol are generally considered to be associated with atherosclerosis. In the past two decades, however, a number of studies have shown that excess cholesterol accumulation in various tissues and organs plays a critical role in the pathogenesis of multiple diseases. Here, we summarize the effects of excess cholesterol on disease pathogenesis, including liver diseases, diabetes, chronic kidney disease, Alzheimer's disease, osteoporosis, osteoarthritis, pituitary-thyroid axis dysfunction, immune disorders, and COVID-19, while proposing that excess cholesterol-induced toxicity is ubiquitous. We believe this concept will help broaden the appreciation of the toxic effect of excess cholesterol, and thus potentially expand the therapeutic use of cholesterol-lowering medications.

Effects of periostin deficiency on kidney aging and lipid metabolism

Periostin plays a crucial role in fibrosis, which is involved in kidney aging. A few studies have shown that lipid metabolism is involved in kidney aging. We investigated the role of periostin in lipid metabolism during kidney aging. Renal function, fibrosis, and inflammatory markers were studied using urine, blood, and tissue samples from wild-type (WT) C57BL/6 mice and Postn-null mice of 2 and 24 months of age. Lipids were quantitatively profiled using liquid chromatography-tandem mass spectrometry in the multiple reaction monitoring mode. Renal function was worse and tubular atrophy/interstitial fibrosis, periostin expression, and inflammatory and fibrotic markers were more severe in aged WT mice than in young WT mice. In aged Postn-null mice, these changes were mitigated. Thirty-five differentially regulated lipids were identified. Phosphatidylcholines, cholesteryl ester, cholesterol, ceramide-1-phosphate, and CCL5 expression were significantly higher in aged WT mice than in aged Postn-null mice. Particularly, linoleic acid, linolenic acid, arachidonic acid, and docosahexaenoic acid differed strongly between the two groups. Lysophosphatidylcholine acyltransferase 2, which converts lysophosphatidylcholine to phosphatidylcholine, was significantly higher in aged WT mice than in aged Postn-null mice. Periostin expression in the kidneys increased with age, and periostin ablation delayed aging. Changes in lipids and their metabolism were found in Postn-null mice. Further research on the precise mechanisms of and relationships between lipid expression and metabolism, kidney aging, and periostin expression is warranted.

Morroniside Promotes PGC-1α-Mediated Cholesterol Efflux in Sodium Palmitate or High Glucose-Induced Mouse Renal Tubular Epithelial Cells

Lipid deposition is an etiology of renal damage caused by lipid metabolism disorder in diabetic nephropathy (DN). Thus, reducing lipid deposition is a feasible strategy for the treatment of DN. Morroniside (MOR), an iridoid glycoside isolated from the Chinese herb Cornus officinalis Sieb. et Zucc., is considered to be an effective drug in inhibiting oxidative stress, reducing inflammatory response, and countering apoptosis. To explore the protective mechanism of MOR in attenuating renal lipotoxicity in DN, we investigated the effect of MOR on an in vitro model of lipid metabolism disorder of DN established by stimulating mouse renal tubular epithelial cells (mRTECs) with sodium palmitate (PA) or high glucose (HG). Oil Red O and filipin cholesterol staining assays were used to determine intracellular lipid accumulation status. Results revealed that PA or HG stimulation inhibited the expressions of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), liver X receptors (LXR), ATP-binding cassette subfamily A member 1 (ABCA1), ABCG1, and apolipoprotein E (ApoE) in mRTECs as evidenced by western blot and quantitative real-time PCR, resulting in increased intracellular lipid deposition. Interestingly, MOR upregulated expressions of PGC-1α, LXR, ABCA1, ABCG1, and ApoE, thus reducing cholesterol accumulation in mRTECs, suggesting that MOR might promote cholesterol efflux from mRTECs via the PGC-1α/LXR pathway. Of note, silencing PGC-1α reversed the promotive effect of MOR on PA- or HG-induced cellular cholesterol accumulation. In conclusion, our results suggest that MOR has a protective effect on mRTECs under high lipid or high glucose conditions, which may be related to the promotion of intracellular cholesterol efflux mediated by PGC-1α.

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.

New insights into renal lipid dysmetabolism in diabetic kidney disease

Lipid dysmetabolism is one of the main features of diabetes mellitus and manifests by dyslipidemia as well as the ectopic accumulation of lipids in various tissues and organs, including the kidney. Research suggests that impaired cholesterol metabolism, increased lipid uptake or synthesis, increased fatty acid oxidation, lipid droplet accumulation and an imbalance in biologically active sphingolipids (such as ceramide, ceramide-1-phosphate and sphingosine-1-phosphate) contribute to the development of diabetic kidney disease (DKD). Currently, the literature suggests that both quality and quantity of lipids are associated with DKD and contribute to increased reactive oxygen species production, oxidative stress, inflammation, or cell death. Therefore, control of renal lipid dysmetabolism is a very important therapeutic goal, which needs to be archived. This article will review some of the recent advances leading to a better understanding of the mechanisms of dyslipidemia and the role of particular lipids and sphingolipids in DKD.

Epigenetic changes related to glucose metabolism in type 1 diabetes after BCG vaccinations: A vital role for KDM2B

BACKGROUND

A recent epigenome-wide association study of genes associated with type 2 diabetics (T2D), used integrative cross-omics analysis to identify 22 abnormally methylated CpG sites associated with insulin and glucose metabolism. Here, in this epigenetic analysis we preliminarily determine whether the same CpG sites identified in T2D also apply to type 1 diabetes (T1D). We then determine whether BCG vaccination could correct the abnormal methylation patterns, considering that the two diseases share metabolic derangements.

METHODS

T1D (n = 13) and control (n = 8) subjects were studied at baseline and then T1D subjects studied yearly for 3 years after receiving BCG vaccinations in a clinical trial. In this biomarker analysis, methylation patterns were evaluated on CD4+ T-lymphocytes from baseline and yearly blood samples using the human Illumina Methylation EPIC Bead Chip. Methylation analysis combined with mRNA analysis using RNAseq.

RESULTS

Broad but not complete overlap was observed between T1D and T2D in CpG sites with abnormal methylation. And in the three-year observation period after BCG vaccinations, the majority of the abnormal methylation sites were corrected in vivo. Genes of particular interest were related to oxidative phosphorylation (CPT1A, LETM1, ABCG1), to the histone lysine demethylase gene (KDM2B), and mTOR signaling through the DDIT4 gene. The highlighted CpG sites for both KDM2B and DDIT4 genes were hypomethylated at baseline compared to controls; BCG vaccination corrected the defect by hypermethylation.

CONCLUSIONS

Glycolysis is regulated by methylation of genes. This study unexpectedly identified both KDM2B and DDIT4 as genes controlling BCG-driven re-methylation of histones, and the activation of the mTOR pathway for facilitated glucose transport respectively. The BCG effect at the gene level was confirmed by reciprocal mRNA changes. The DDIT4 gene with known inhibitory role of mTOR was re-methylated after BCG, a step likely to allow improved glucose transport. BCGs driven methylation of KDM2B's site should halt augmented histone activity, a step known to allow cytokine activation and increased glycolysis.

Antidiabetic and Renoprotective Effects of Coffea arabica Pulp Aqueous Extract through Preserving Organic Cation Transport System Mediated Oxidative Stress Pathway in Experimental Type 2 Diabetic Rats

Coffea arabica pulp (CP) is a by-product of coffee processing. CP contains polyphenols that have exhibited beneficial effects, including antioxidant and lipid-lowering effects, as well as enhanced insulin sensitivity, in in vitro and in vivo models. How polyphenols, as found in CP aqueous extract (CPE), affect type 2 diabetes (T2D) has not been investigated. Thus, the present study examined the potential antidiabetic, antioxidant, and renoprotective effects of CPE-rich polyphenols, using an experimental model of T2D in rats induced by a high-fat diet and a single low dose of streptozotocin. The T2D rats received either 1000 mg/kg body weight (BW) of CPE, 30 mg/kg BW of metformin (Met), or a combination treatment (CPE + Met) for 3 months. Plasma parameters, kidney morphology and function, and renal organic transport were determined. Significant hyperglycemia, hypertriglyceridemia, insulin resistance, increased renal lipid content and lipid peroxidation, and morphological kidney changes related to T2D were restored by both CPE and CPE + Met treatments. Additionally, the renal uptake of organic cation, ³H-1-methyl-4-phenylpyridinium (MPP⁺), was reduced in T2D, while transport was restored by CPE and CPE + Met, through an up-regulation of antioxidant genes and protein kinase Cα deactivation. Thus, CPE has antidiabetic and antioxidant effects that potentially ameliorate kidney function in T2D by preserving renal organic cation transport through an oxidative stress pathway.

Protein convertase subtilisin/kexin type 9 biology in nephrotic syndrome: implications for use as therapy

Low-density lipoprotein cholesterol (LDL-C) levels almost constantly increased in patients with nephrotic syndrome (NS). Protein convertase subtilisin/kexin type 9 (PCSK9) [accelerates LDL-receptor (LDL-R) degradation] is overexpressed by liver cells in NS. Their levels, correlated inversely to LDL-R expression and directly to LDL-C, seem to play a central role in hypercholesterolaemia in NS. Hypersynthesis resulting from sterol regulatory element-binding protein dysfunction, hyperactivity induced by c-inhibitor of apoptosis protein expressed in response to stimulation by tumour necrosis factor-α produced by damaged podocytes and hypo-clearance are the main possible mechanisms. Increased LDL-C may damage all kidney cell populations (podocytes, mesangial and tubular cells) in a similar manner. Intracellular cholesterol accumulation produces oxidative stress, foam cell formation and apoptosis, all favoured by local inflammation. The cumulative effect of cellular lesions is worsened proteinuria and kidney function loss. Accordingly, NS patients should be considered high risk and treated by lowering LDL-C. However, there is still not enough evidence determining whether lipid-lowering agents are helpful in managing dyslipidaemia in NS. Based on good efficacy and safety proved in the general population, therapeutic modulation of PCSK9 via antibody therapy might be a reasonable solution. This article explores the established and forthcoming evidence implicating PCSK9 in LDL-C dysregulation in NS.

Paclitaxel Ameliorates Palmitate-Induced Injury in Mouse Podocytes

Background

Palmitate, a common saturated free fatty acid, is increased in patients with diabetic nephropathy (DN). Excessive palmitate in kidney is known to cause proteinuria and fibrosis. Several studies have demonstrated that paclitaxel has anti-fibrotic and anti-inflammatory effects on kidney disease. However, whether paclitaxel can relieve podocyte injury is unclear.

Material/Methods

Immortalized mouse podocytes were used as an in vitro system. Palmitate was used to induce podocyte injury. Podocytes were divided into 4 groups: bovine serum albumin, palmitate, palmitate+1 nM paclitaxel, and palmitate+5 nM paclitaxel. The effects of paclitaxel on palmitate-induced podocyte injury were analyzed by western blot and real-time PCR. Intracellular reactive oxygen species (ROS) generation and podocyte cytoskeletons were analyzed using CM-H2DCF-DA and phalloidin staining.

Results

Paclitaxel restored downregulated expression of nephrin and synaptopodin and upregulated VEGF expression after injury induced by palmitate. Remarkably, palmitate-induced actin cytoskeleton rearrangement in podocytes was repaired by paclitaxel. Four endoplasmic reticulum stress markers, ATF-6α, Bip, CHOP, and spliced xBP1, were significantly increased in palmitate-treated podocytes compared with control podocytes. Such increases were decreased by paclitaxel treatment. Palmitate-induced ROS generation was ameliorated by paclitaxel. Elevated Nox4 expression was also improved by paclitaxel. Paclitaxel alleviated the expression levels of the antioxidant molecules, Nrf-2, HO-1, SOD-1, and SOD-2. The paclitaxel effects were accompanied by inhibition of the inflammatory cytokines, MCP-1, TNF-α, TNF-R2, and TLR4, as well as attenuation of the apoptosis markers, Bax, Bcl-2, and Caspase-3. Furthermore, paclitaxel suppressed the palmitate-induced fibrosis molecules, fibronectin and TGF-β1.

Conclusions

This study suggests that paclitaxel could be a therapeutic agent for treating palmitate-induced podocyte injury in DN.

Identification and characterization of anti-diabetic principle in Senna alata (Linn.) flower using alloxan-induced diabetic male Wistar rats

ETHNO-PHARMACOLOGICAL RELEVANCE

The age-long folkloric use of Senna alata flower (SAF) was recently substantiated with scientific evidence. However, the study did not account for the anti-diabetic principle(s) in SAF.

AIM OF THE STUDY

The study aimed to identify and characterize the bioactive principle(s) responsible for the anti-diabetic activity in SAF.

MATERIALS AND METHODS

Ninety-one male Wistar rats were used for the two phases of this study. In phase 1, forty-two of these were allotted into six groups (A-F) of seven rats each. Animals in group A received distilled water while those in groups B-F were made diabetic by treatment with 150 mg/kg body weight (b.w.) of alloxan. Group B received 0.5 mL of distilled water; C, D and E were treated each with 75 mg/kg b.w. of ethyl acetate, n-butanol and aqueous residual fractions of SAF, while F received 2.5 mg/kg b.w. of glibenclamide. In the second phase, forty-nine rats were assigned into seven groups (A-G) of seven rats each. Group A received distilled water. Animals in Groups B-G were also made diabetic by alloxan treatment. B received 0.5 mL of distilled water; C, D, E and F were treated with 5.77, 25.96, 15.40, 27.87 mg/kg b.w (equivalent dose of 75 mg/kg b.w.) of sub-fractions obtained from the ethyl acetate fraction of SAF respectively whereas G received 2.5 mg/kg b.w. of glibenclamide. Fasting blood glucose (FBG), serum lipids, albumin, globulin, liver glycogen, urine ketone, hexokinase and glucose-6-phosphate dehydrogenase activities, α-glucosidase and α-amylase inhibitory activities and cardiac function indices were evaluated using standard methods. Compounds D, E and F isolated from ethyl acetate sub-fraction B were evaluated for in vitro anti-diabetic activity. The structure of the anti-diabetic compound was identified using FTIR, ¹H-NMR, ¹³C-NMR, HCOSY, HSQC and HMBC. Data were subjected to Analysis of Variance and Duncan Multiple Range Test at p < 0.05.

RESULTS

Alloxan treatment increased the levels of FBG, total cholesterol, LDL-cholesterol, VLDL-cholesterol, urine ketone and cardiac function indices and reduced the levels of globulin, albumin, HDL-cholesterol, globulin, liver glycogen, hexokinase and glucose-6-phosphate dehydrogenase activities. Ethyl acetate fraction and sub-fraction B reversed the level and/or activities of these biochemical indices to levels and/or activities that compared favourably with the distilled water treated non-diabetic animals. Of the three compounds (D, E and F) that were obtained from the sub-fraction B, compound E which was Emodin (1, 3, 8-trihydroxy-6-methylanthraquinone) produced the highest α-glucosidase and α-amylase inhibitory activities.

CONCLUSION

Emodin is one of the bioactive constituents present in Senna alata flower.

Interaction between high-density lipoproteins and inflammation: Function matters more than concentration!

High-density lipoprotein (HDL) plays an important role in lipid metabolism and especially contributes to the reverse cholesterol transport pathway. Over recent years it has become clear that the effect of HDL on immune-modulation is not only dependent on HDL concentration but also and perhaps even more so on HDL function. This review will provide a concise general introduction to HDL followed by an overview of post-translational modifications of HDL and a detailed overview of the role of HDL in inflammatory diseases. The clinical potential of HDL and its main apolipoprotein constituent, apoA-I, is also addressed in this context. Finally, some conclusions and remarks that are important for future HDL-based research and further development of HDL-focused therapies are discussed.

Novel therapeutic agents for the treatment of diabetic kidney disease

INTRODUCTION

Diabetic kidney disease (DKD) involves multifaceted pathophysiology which increases the risk of cardiorenal events and mortality. Conventional therapy is limited to renin-angiotensin aldosterone system inhibition and management of hyperglycemia and hypertension. Recent clinical trials have demonstrated promising nephroprotective effects of antihyperglycemic agents thus modifying guideline treatment recommendations for type 2 diabetic patients with chronic kidney disease.

AREAS OF COVERED

Relevant studies and clinical trials were searched via PubMed and clinicaltrials.gov through August 2020. Authors offer an update on clinical evidence regarding nephroprotective effects and side effects of sodium-glucose-cotransporter-2 (SGLT2) inhibitors, glucagon-like-peptide-1 (GLP1) agonists and dipeptidylpeptidase-4 (DPP4) inhibitors. They discuss the potential benefits of novel therapy targeting DKD pathogenic processes including inflammation, oxidative stress, fibrosis, and vasoconstriction shown in early phases of clinical trials and offer an opinion on key challenges and directions for future progress.

EXPERT OPINION

SGLT2 inhibitors are the most promising agents for DKD and improving cardiorenal outcomes. Mineralocorticoid-receptor antagonists and janus kinase inhibitors are also promising investigational therapies that target oxidative stress, nitric oxide synthesis, and inflammation. Novel therapeutic targets and the identification of clinically useful biomarkers may provide future therapies that detect early stages of DKD enabling a slower kidney function decline.

Atherogenic dyslipidemia and diabetic nephropathy

Chronic kidney disease is associated with altered lipid metabolism and lipid accumulation. Although it is though that hyperlipemia is a consequence of kidney dysfunction, several lines of evidence support that hyperlipidemia may contribute to the onset and progression of kidney disease, also in diabetes. This review describes the results of recent observational studies supporting the concept that glucose is only partly responsible for kidney damage onset, while a cluster of factors, including hypertriglyceridemia and low HDL-cholesterol, could play a relevant role in inducing onset and progression of DKD. We also report the results of randomized clinical trials investigating in type 2 diabetic patients the role of drug improvement of hypertriglyceridemia on renal outcomes. Finally, we discuss putative mechanisms linking hyperlipidemia (i.e. hypertriglyceridemia or low HDL cholesterol) with kidney disease.

Lipotoxicity and Diabetic Nephropathy: Novel Mechanistic Insights and Therapeutic Opportunities

Lipotoxicity is characterized by the ectopic accumulation of lipids in organs different from adipose tissue. Lipotoxicity is mainly associated with dysfunctional signaling and insulin resistance response in non-adipose tissue such as myocardium, pancreas, skeletal muscle, liver, and kidney. Serum lipid abnormalities and renal ectopic lipid accumulation have been associated with the development of kidney diseases, in particular diabetic nephropathy. Chronic hyperinsulinemia, often seen in type 2 diabetes, plays a crucial role in blood and liver lipid metabolism abnormalities, thus resulting in increased non-esterified fatty acids (NEFA). Excessive lipid accumulation alters cellular homeostasis and activates lipogenic and glycogenic cell-signaling pathways. Recent evidences indicate that both quantity and quality of lipids are involved in renal damage associated to lipotoxicity by activating inflammation, oxidative stress, mitochondrial dysfunction, and cell-death. The pathological effects of lipotoxicity have been observed in renal cells, thus promoting podocyte injury, tubular damage, mesangial proliferation, endothelial activation, and formation of macrophage-derived foam cells. Therefore, this review examines the recent preclinical and clinical research about the potentially harmful effects of lipids in the kidney, metabolic markers associated with these mechanisms, major signaling pathways affected, the causes of excessive lipid accumulation, and the types of lipids involved, as well as offers a comprehensive update of therapeutic strategies targeting lipotoxicity.

Roles of pattern recognition receptors in diabetic nephropathy

Diabetic nephropathy (DN) is currently the most common complication of diabetes. It is considered to be one of the leading causes of end-stage renal disease (ESRD) and affects many diabetic patients. The pathogenesis of DN is extremely complex and has not yet been clarified; however, in recent years, increasing evidence has shown the important role of innate immunity in DN pathogenesis. Pattern recognition receptors (PRRs) are important components of the innate immune system and have a significant impact on the occurrence and development of DN. In this review, we classify PRRs into secretory, endocytic, and signal transduction PRRs according to the relationship between the PRRs and subcellular compartments. PRRs can recognize related pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs), thus triggering a series of inflammatory responses, promoting renal fibrosis, and finally causing renal impairment. In this review, we describe the proposed role of each type of PRRs in the development and progression of DN.

Metabolic effects of RUBCN/Rubicon deficiency in kidney proximal tubular epithelial cells

Macroautophagy/autophagy is a lysosomal degradation system which plays a protective role against kidney injury. RUBCN/Rubicon (RUN domain and cysteine-rich domain containing, Beclin 1-interacting protein) inhibits the fusion of autophagosomes and lysosomes. However, its physiological role in kidney proximal tubular epithelial cells (PTECs) remains uncertain. In the current study, we analyzed the phenotype of newly generated PTEC-specific rubcn-deficient (KO) mice. Additionally, we investigated the role of RUBCN in lipid metabolism using isolated rubcn-deficient PTECs. Although KO mice exhibited sustained high autophagic flux in PTECs, they were not protected from acute ischemic kidney injury. Unexpectedly, KO mice exhibited hallmark features of metabolic syndrome accompanied by expanded lysosomes containing multi-layered phospholipids in PTECs. RUBCN deficiency in cultured PTECs promoted the mobilization of phospholipids from cellular membranes to lysosomes via enhanced autophagy. Treatment of KO PTECs with oleic acid accelerated fatty acids transfer to mitochondria. Furthermore, KO PTECs promoted massive triglyceride accumulation in hepatocytes (BNL-CL2 cells) co-cultured in transwell, suggesting accelerated fatty acids efflux from the PTECs contributes to the metabolic syndrome in KO mice. This study shows that sustained high autophagic flux by RUBCN deficiency in PTECs leads to metabolic syndrome concomitantly with an accelerated mobilization of phospholipids from cellular membranes to lysosomes. Abbreviations: ABC: ATP binding cassette; ACADM: acyl-CoA dehydrogenase medium chain; ACTB: actin, beta; ATG: autophagy related; AUC: area under the curve; Baf: bafilomycin A₁; BAT: brown adipose tissue; BODIPY: boron-dipyrromethene; BSA: bovine serum albumin; BW: body weight; CAT: chloramphenicol acetyltransferase; CM: complete medium; CPT1A: carnitine palmitoyltransferase 1a, liver; CQ: chloroquine; CTRL: control; EGFP: enhanced green fluorescent protein; CTSD: cathepsin D; EAT: epididymal adipose tissue; EGFR: epidermal growth factor receptor; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; FA: fatty acid; FBS: fetal bovine serum; GTT: glucose tolerance test; HE: hematoxylin and eosin; HFD: high-fat diet; I/R: ischemia-reperfusion; ITT: insulin tolerance test; KAP: kidney androgen regulated protein; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LD: lipid droplet; LRP2: low density lipoprotein receptor related protein 2; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MAT: mesenteric adipose tissue; MS: mass spectrometry; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; NDRG1: N-myc downstream regulated 1; NDUFB5: NADH:ubiquinone oxidoreductase subunit B5; NEFA: non-esterified fatty acid; OA: oleic acid; OCT: optimal cutting temperature; ORO: Oil Red O; PAS: Periodic-acid Schiff; PFA: paraformaldehyde; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; PPARA: peroxisome proliferator activated receptor alpha; PPARGC1A: PPARG coactivator 1 alpha; PTEC: proximal tubular epithelial cell; RAB7A: RAB7A, member RAS oncogene family; RPS6: ribosomal protein S6; RPS6KB1: ribosomal protein S6 kinase B1; RT: reverse transcription; RUBCN: rubicon autophagy regulator; SAT: subcutaneous adipose tissue; SFC: supercritical fluid chromatography; SQSTM1: sequestosome 1; SREBF1: sterol regulatory element binding transcription factor 1; SV-40: simian virus-40; TFEB: transcription factor EB; TG: triglyceride; TS: tissue specific; TUNEL: terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling; UN: urea nitrogen; UQCRB: ubiquinol-cytochrome c reductase binding protein; UVRAG: UV radiation resistance associated; VPS: vacuolar protein sorting; WAT: white adipose tissue.

Renal Lipid Metabolism and Lipotoxicity in Diabetes

The pathogenesis of diabetic kidney disease is a complex process caused by both glucotoxicity and lipotoxicity due to lipid accumulation. In cases of diabetic animals, lipid deposition is found in both tubular and glomerular portions of the kidneys, which are the major sites of diabetic nephropathy lesions. The aim of this review was to provide insights into the mechanisms that lead to the development of renal lipid accumulation and the effects of renal lipotoxicity in the diabetic condition. An increased number of lipogenic genes and a decreased number of lipid oxidation genes are also detected in diabetic kidneys, both of which lead to lipid accumulation. The induction of oxidative stress, inflammation, fibrosis and apoptosis caused by lipid accumulation and lipid metabolites is called lipotoxicity. Renal lipotoxicity due to derangement in lipid metabolism may be a pathogenic mechanism leading to diabetic nephropathy and renal dysfunction.

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

The strong inverse relationship between low levels of high-density lipoproteins (HDLs) and atherosclerotic cardiovascular disease (CVD) led to the designation of HDL as the "good" cholesterol. The atheroprotection is thought to reflect HDL's capacity to efflux cholesterol from macrophages, followed by interaction with other lipoproteins in the plasma, processing by the liver and excretion into bile. However, pharmacologic increases in HDL-C levels have not led to expected clinical benefits, giving rise to the concept of dysfunctional HDL, in which increases in serum HDL-C are not beneficial due to lost or altered HDL functions and transition to "bad" HDL. It is now understood that the cholesterol in HDL, measured by HDL-C, is neither a marker nor the mediator of HDL function, including cholesterol efflux capacity. It is also understood that besides cholesterol efflux, HDL functionality encompasses many other potentially beneficial functions, including antioxidant, anti-inflammatory, antithrombotic, anti-apoptotic, and vascular protective effects that may be critical protective pathways for various cells, including those in the kidney parenchyma. This review highlights advances in our understanding of the role kidneys play in HDL metabolism, including the effects on levels, composition, and functionality of HDL particles, particularly the main HDL protein, apolipoprotein AI (apoAI). We suggest that normal apoAI/HDL in the glomerular filtrate provides beneficial effects, including lymphangiogenesis, that promote resorption of renal interstitial fluid and biological particles. In contrast, dysfunctional apoAI/HDL activates detrimental pathways in tubular epithelial cells and lymphatics that lead to interstitial accumulation of fluid and harmful particles that promote progressive kidney damage.

ATP-binding cassette A1 deficiency causes cardiolipin-driven mitochondrial dysfunction in podocytes

Fibroblasts from patients with Tangier disease carrying ATP-binding cassette A1 (ABCA1) loss-of-function mutations are characterized by cardiolipin accumulation, a mitochondrial-specific phospholipid. Suppression of ABCA1 expression occurs in glomeruli from patients with diabetic kidney disease (DKD) and in human podocytes exposed to DKD sera collected prior to the development of DKD. We demonstrated that siRNA ABCA1 knockdown in podocytes led to reduced oxygen consumption capabilities associated with alterations in the oxidative phosphorylation (OXPHOS) complexes and with cardiolipin accumulation. Podocyte-specific deletion of Abca1 (Abca1fl/fl) rendered mice susceptible to DKD, and pharmacological induction of ABCA1 improved established DKD. This was not mediated by free cholesterol, as genetic deletion of sterol-o-acyltransferase-1 (SOAT1) in Abca1fl/fl mice was sufficient to cause free cholesterol accumulation but did not cause glomerular injury. Instead, cardiolipin mediates ABCA1-dependent susceptibility to podocyte injury, as inhibition of cardiolipin peroxidation with elamipretide improved DKD in vivo and prevented ABCA1-dependent podocyte injury in vitro and in vivo. Collectively, we describe a pathway definitively linking ABCA1 deficiency to cardiolipin-driven mitochondrial dysfunction. We demonstrated that this pathway is relevant to DKD and that ABCA1 inducers or inhibitors of cardiolipin peroxidation may each represent therapeutic strategies for the treatment of established DKD.

Tangshen Formula Attenuates Diabetic Nephropathy by Promoting ABCA1-Mediated Renal Cholesterol Efflux in db/db Mice

The commonly prescribed Tangshen Formula (TSF) is a traditional Chinese formulation that has been shown to reduce plasma lipid metabolism and proteinuria and improve the estimated glomerular filtration rate (eGFR) in patients with diabetic kidney disease. This study investigated the underlying mechanism whereby TSF regulates renal lipid accumulation and ameliorates diabetic renal injuries in spontaneous diabetic db/db mice and in vitro in sodium palmitate (PA)-stimulated and Abca1-SiRNA-transfected mouse tubular epithelial cells (mTECs). The results revealed that TSF treatment significantly ameliorated the renal injuries by lowering urinary albumin excretion and improving renal tissue injuries in diabetic (db/db) mice. Interestingly, the treatment with TSF also resulted in decreased cholesterol levels in the renal tissues of db/db mice, which was associated with increased expression of the peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α), the Liver X receptors (LXR), and ATP-binding cassette subfamily A member 1 (ABCA1), suggesting that TSF might attenuate diabetic kidney injury via a mechanism associated with improving cholesterol efflux in the diabetic kidney. This was investigated in vitro in mTECs, and the results showed that TSF reduced the PA-stimulated cholesterol accumulation in mTECs. Mechanistically, the addition of TSF was capable of reversing PA-induced downregulation of PGC-1α, LXR, and ABCA1 expression and cholesterol accumulation in mTECs, suggesting that TSF might act the protection via the PGC-1α-LXR-ABCA1 pathway to improve the cholesterol efflux in the renal tissues of db/db mice. This was further confirmed by silencing ABCA1 to block the promotive effect of TSF on cholesterol efflux in vitro. In conclusion, TSF might ameliorate diabetic kidney injuries by promoting ABCA1-mediated renal cholesterol efflux.

Dysfunctional HDL in diabetes mellitus and its role in the pathogenesis of cardiovascular disease

Coronary artery disease, the leading cause of death in the developed and developing countries, is prevalent in diabetes mellitus with 68% cardiovascular disease (CVD)-related mortality. Epidemiological studies suggested inverse correlation between HDL and CVD occurrence. Therefore, low HDL concentration observed in diabetic patients compared to non-diabetic individuals was thought to be one of the primary causes of increased risks of CVD. Efforts to raise HDL level via CETP inhibitors, Torcetrapib and Dalcetrapib, turned out to be disappointing in outcome studies despite substantial increases in HDL-C, suggesting that factors beyond HDL concentration may be responsible for the increased risks of CVD. Therefore, recent studies have focused more on HDL function than on HDL levels. The metabolic environment in diabetes mellitus condition such as hyperglycemia-induced advanced glycation end products, oxidative stress, and inflammation promote HDL dysfunction leading to greater risks of CVD. This review discusses dysfunctional HDL as one of the mechanisms of increased CVD risks in diabetes mellitus through adversely affecting components that support HDL function in cholesterol efflux and LDL oxidation. The dampening of reverse cholesterol transport, a key process that removes cholesterol from lipid-laden macrophages in the arterial wall, leads to increased risks of CVD in diabetic patients. Therapeutic approaches to keep diabetes under control may benefit patients from developing CVD.

Exendin-4 Ameliorates Lipotoxicity-induced Glomerular Endothelial Cell Injury by Improving ABC Transporter A1-mediated Cholesterol Efflux in Diabetic apoE Knockout Mice

ATP-binding cassette transporter A1 (ABCA1), which promotes cholesterol efflux from cells and inhibits inflammatory responses, is highly expressed in the kidney. Research has shown that exendin-4, a glucagon-like peptide-1 receptor (GLP-1R) agonist, promotes ABCA1 expression in multiple tissues and organs; however, the mechanisms underlying exendin-4 induction of ABCA1 expression in glomerular endothelial cells are not fully understood. In this study we investigated the effect of exendin-4 on ABCA1 in glomerular endothelial cells of diabetic kidney disease (DKD) and the possible mechanism. We observed a marked increase in glomerular lipid deposits in tissues of patients with DKD and diabetic apolipoprotein E knock-out (apoE^-/-) mice by Oil Red O staining and biochemical analysis of cholesterol. We found significantly decreased ABCA1 expression in glomerular endothelial cells of diabetic apoE^-/- mice and increased renal lipid, cholesterol, and inflammatory cytokine levels. Exendin-4 decreased renal cholesterol accumulation and inflammation and increased cholesterol efflux by up-regulating ABCA1. In human glomerular endothelial cells, GLP-1R-mediated signaling pathways (e.g. Ca²⁺/calmodulin-dependent protein kinase, cAMP/PKA, PI3K/AKT, and ERK1/2) were involved in cholesterol efflux and inflammatory responses by regulating ABCA1 expression. We propose that exendin-4 increases ABCA1 expression in glomerular endothelial cells, which plays an important role in alleviating renal lipid accumulation, inflammation, and proteinuria in mice with type 2 diabetes.

Human SR-BI and SR-BII Potentiate Lipopolysaccharide-Induced Inflammation and Acute Liver and Kidney Injury in Mice

The class B scavenger receptors BI (SR-BI) and BII (SR-BII) are high-density lipoprotein receptors that recognize various pathogens, including bacteria and their products. It has been reported that SR-BI/II null mice are more sensitive than normal mice to endotoxin-induced inflammation and sepsis. Because the SR-BI/II knockout model demonstrates multiple immune and metabolic disorders, we investigated the role of each receptor in the LPS-induced inflammatory response and tissue damage using transgenic mice with pLiv-11-directed expression of human SR-BI (hSR-BI) or human SR-BII (hSR-BII). At 6 h after i.p. LPS injection, transgenic hSR-BI and hSR-BII mice demonstrated markedly higher serum levels of proinflammatory cytokines and 2- to 3-fold increased expression levels of inflammatory mediators in the liver and kidney, compared with wild-type (WT) mice. LPS-stimulated inducible NO synthase expression was 3- to 6-fold higher in the liver and kidney of both transgenic strains, although serum NO levels were similar in all mice. Despite the lower high-density lipoprotein plasma levels, both transgenic strains responded to LPS by a 5-fold increase of plasma corticosterone levels, which were only moderately lower than in WT animals. LPS treatment resulted in MAPK activation in tissues of all mice; however, the strongest response was detected for hepatic extracellular signal-regulated protein kinase 1 and 2 and kidney JNK of both transgenic mice. Histological examination of hepatic and renal tissue from LPS-challenged mice revealed more injury in hSR-BII, but not hSR-BI, transgenic mice versus WT controls. Our findings demonstrate that hSR-BII, and to a lesser extent hSR-BI, significantly increase LPS-induced inflammation and contribute to LPS-induced tissue injury in the liver and kidney, two major organs susceptible to LPS toxicity.

High density lipoprotein and metabolic disease: Potential benefits of restoring its functional properties

Background

High density lipoproteins (HDLs) are thought to be atheroprotective and to reduce the risk of cardiovascular disease (CVD). Besides their antioxidant, antithrombotic, anti-inflammatory, anti-apoptotic properties in the vasculature, HDLs also improve glucose metabolism in skeletal muscle.

Scope of the review

Herein, we review the functional role of HDLs to improve metabolic disorders, especially those involving insulin resistance and to induce regression of CVD with a particular focus on current pharmacological treatment options as well as lifestyle interventions, particularly exercise.

Major conclusions

Functional properties of HDLs continue to be considered important mediators to reverse metabolic dysfunction and to regress atherosclerotic cardiovascular disease. Lifestyle changes are often recommended to reduce the risk of CVD, with exercise being one of the most important of these. Understanding how exercise improves HDL function will likely lead to new approaches to battle the expanding burden of obesity and the metabolic syndrome.

Genome-wide peripheral blood transcriptome analysis of Arab female lupus and lupus nephritis

Systemic lupus erythematosus (lupus) is a genetically heterogeneous autoimmune disorder with an obscure etiology. With 92-94% of human genes exhibiting alternative splicing, gaining insights to such events may lead to better diagnostics. Herein, we explored the genome-wide peripheral blood transcriptome of lupus and its severe form lupus-nephritis (LN) compared to healthy controls (HC). Age/gender/ethnically-matched Arab females were tested using high-density arrays and statistical analysis was carried out using appropriate software. Analysis revealed 15 splice variants that are differentially expressed between lupus/HC and 99 variants between LN/HC (p ≤ 0.05, SI> or ≤ 0.5, Benjamin Hochberg-False discovery rate correction). Comparison between LN/lupus revealed 7 variants that significantly differed in expression. Pathway analysis of differentially spliced-genes postulated 11 significant pathways in lupus and 12 in LN (p<0.05). Analysis of peripheral blood transcriptome possibly revealed signature causative genes that are alternatively spliced, signifying their clinical relevance. Present study is the first to reveal the significance of alternative variants in lupus and LN.