The PI3K/p-Akt signaling pathway participates in calcitriol ameliorating podocyte injury in DN rats

Dapagliflozin attenuates AKI to CKD transition in diabetes by activating SIRT3/PGC1-α signaling and alleviating aberrant metabolic reprogramming

BACKGROUND

Patients with diabetes are prone to acute kidney injury (AKI) with a high mortality rate, poor prognosis, and a higher risk of progression to chronic kidney disease than non-diabetic patients.

METHODS

Streptozotocin (STZ)-treated type 1 and db/db type 2 diabetes model were established, AKI model was induced in mice by ischemia-reperfusion injury(IRI). Mouse proximal tubular cell cells were subjected to high glucose and hypoxia-reoxygenation in vitro. Transcriptional RNA sequencing was performed for clustering analysis and target gene screening. Renal structural damage was determined by histological staining, whereas creatinine and urea nitrogen levels were used to measure renal function.

RESULTS

Deteriorated renal function and renal tissue damage were observed in AKI mice with diabetic background. RNA sequencing showed a decrease in fatty acid oxidation (FAO) pathway and an increase in abnormal glycolysis. Treatment with Dapa, Sitagliptin(a DPP-4 inhibitor)and insulin reduced blood glucose levels in mice, and improved renal function. However, Dapa had a superior therapeutic effect and alleviated aberrant FAO and glycosis. Dapa reduced cellular death in cultured cells under high glucose hypoxia-reoxygenation conditions, alleviated FAO dysfunction, and reduced abnormal glycolysis. RNA sequencing showed that SIRT3 expression was reduced in diabetic IRI, which was largely restored by Dapa intervention. 3-TYP, a SIRT3 inhibitor, reversed the renal protective effects of Dapa and mediated abnormal FAO and glycolysis in mice and tubular cells.

CONCLUSION

Our study provides experimental evidence for the use of Dapa as a means to reduce diabetic AKI by ameliorating metabolic reprogramming in renal tubular cells.

Nutritional Strategies against Diabetic Nephropathy: Insights from Animal Studies and Human Trials

Diabetic nephropathy (DN), defined as continuously elevated urinary albumin and a diminished estimated glomerular filtration rate, is a serious complication of both type 1 diabetes and type 2 diabetes and is the main cause of end-stage kidney disease. Patients with end-stage renal disease require chronic kidney dialysis and/or a kidney transplantation. Research highlights the role of diet in modulating specific signaling pathways that are instrumental in the progression of DN. Nutrient-sensitive pathways, affected by nutritional compounds and dietary components, offer a novel perspective on the management of DN by influencing inflammation, oxidative stress, and nutrient metabolism. Animal models have identified signaling pathways related to glucose metabolism, inflammation responses, autophagy, and lipid metabolism, while human population studies have contributed to the clinical significance of designing medical and nutritional therapies to attenuate DN progression. Here, we will update recent progress in research into the renoprotective or therapeutic effects of nutritional compounds, and potential nutrition-modulated pathways.

Study on the mechanism of inhibition of Escherichia coli by Polygonum capitatum based on network pharmacology and molecular docking technology: A review

This study aims to analyze the effective components of Polygonum capitatum (PC) inhibiting Escherichia coli based on network pharmacology methods and predict its molecular mechanism of action. PC compounds and targets were collected from the TCMSP database, Swiss Target Prediction, and the literature. E coli targets were searched using the GeneCards database. The targets of E coli and the targets of the active ingredients of PC were taken as intersections to obtain the intersecting targets. The resulting overlapping targets were uploaded to the STRING database to construct the protein interaction network diagram of E coli target inhibition. The key targets for the inhibitory effect of PC on E coli were obtained. Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed by uploading key targets into the DAVID database. The results showed that there were 50 targets for PC to inhibit E coli. Among them, there are 5 core targets, mainly including AKT1, TNF, EGFR, JUN, and ESR1. A total of 196 gene ontology functional analysis results and 126 Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis results were obtained. These include cellular response to cadmium-ion, cellular response to reactive oxygen species, pathways in cancer, prostate cancer, and PI3K-Akt signaling pathway. Molecular docking results indicate that Lutedin, Hirsutin, Flazin, and Ellagic acid in PC have high affinity for the target genes AKT1, TNF, MAPK3 and EGFR. PC exerts its inhibitory effect on E coli through multi-targets and multi-pathways, which provides a new basis for the new use of PC as an old medicine.

Exploring the mechanism of Jingshen Xiaoke decoction in treating T2DM mice based on network pharmacology and molecular docking

BACKGROUND

Jingshen Xiaoke decoction (JS) was prepared by studying the classic prescriptions of famous scholars in the past dynasties to prevent and treat diabetes. The related mechanism of JS against hyperlipidemia has yet to be revealed.

OBJECTIVE

To investigate the mechanism of action of JS in treating diabetes mellitus by using bioinformatics methods.

METHODS

A database was used to search the active ingredients and targets of the JS and targets for type 2 diabetes mellitus (T2DM). The protein interaction between the intersection targets, and the constructed the PPI network diagram was analyzed using the STRING database. Furthermore, the gene annotation tool DAVID was used to enrich the intersecting targets for the Gene ontology (GO) function and Kyoto encyclopedia of genes and genomes (KEGG) signaling pathway. Finally, Maestro software was used for molecular docking to verify the binding ability of the active ingredients to the core target genes.

RESULTS

A total of 45 active ingredients in JS were screened out corresponding to 239 effective targets, of which 64 targets were potential targets for treating T2DM. The analysis of PPI network diagram analysis revealed that the ingredients' active components are quercetin, β-sitosterol, stigmasterol, luteolin, and 7-Methoxy-2-methyl isoflavone. GO functional enrichment analysis indicated 186 biological processes (BP), 23 molecular functions (MF) and 13 cellular components (CC). KEGG pathway enrichment analysis revealed the enrichment of 59 signal pathways. The molecular docking results demonstrated that the active ingredients and core targets had a good docking affinity with a binding activity less than -7 kcal/mol. Finally, the western blotting illustrated that JS could up-regulate the liver PI3K/AKT-signaling pathway.

CONCLUSION

JS can regulate glucolipid metabolism, reduce the inflammatory response, improve insulin resistance and modulate the immune response through PI3K/AKT signaling pathway treating of T2DM and its complications effects.

A review on the hypoglycemic effect, mechanism and application development of natural dietary polysaccharides

Diabetes mellitus (DM) as one chronic metabolic disease was greatly increased over recent decades. The major agents treating diabetes have noticeable side effects as well as the tolerability problems. The bioactive dietary polysaccharides from abundant natural resources exhibit good hypoglycemic effect with rare adverse effects, which might serve as a candidate to prevent and treat diabetes. However, the correlations between the hypoglycemic mechanism of polysaccharides and their structure were not mentioned in several studies, what's more, most of the current hypoglycemic studies on polysaccharides were based on in vitro and in vivo experiments, and there was a lack of knowledge about the effects in human clinical trials. The aim of this review is to discuss recent literature about the variety of dietary polysaccharides with hypoglycemic activity, as well the mechanism of action and the structure-function relationship are highlighted. Meanwhile, the application of dietary polysaccharides in functional foods and clinical medicine are realized with an in-depth understanding. So as to promote the exploration of dietary polysaccharides in low glycemic healthy foods or clinical medicine to prevent and treat diabetes.

Bisdemethoxycurcumin suppresses the progression of atherosclerosis and VSMC-derived foam cell formation by promoting lipophagy

Vascular smooth muscle cells (VSMCs) are one of the sources of foam cells in atherosclerosis. However, the mechanism of VSMC-derived foam cell formation remain largely unknown. Bisdemethoxycurcumin (BDMC) is considered to possess diverse pharmacological properties, including anti-inflammation and anti-oxidation. However, the effects of BDMC on atherosclerosis remain unclear. Here, we established an in vitro foam cell model by culturing VSMCs with oxidized low-density lipoprotein (ox-LDL). The results show that BDMC reduced lipid droplets in ox-LDL-stimulated VSMCs. In addition, BDMC promotes autophagy by suppressing PDK1/Akt/mTOR signaling pathway. In vivo, BDMC alleviates inflammatory responses and lipid accumulation in in apoe-/- mice. Above all, the results from the present study suggested that BDMC may be used as a therapeutic agent for the prevention and treatment of atherosclerosis.

Sweroside attenuates podocyte injury and proteinuria in part by activating Akt/BAD signaling in mice

In this study, we investigated the effects of sweroside on podocyte injury in diabetic nephropathy (DN) mice and elucidated its molecular mechanisms. We conducted in vivo experiments using a C57BL/6 mice model of DN to explore the effects of sweroside on proteinuria and podocyte injury in DN mice. In in vitro experiments, conditionally immortalized mouse podocytes were treated with high glucose and sweroside, and the protective effects of sweroside on podocyte injury were analyzed. In vitro, Akt/BAD pathways were detected using gene siRNA silencing assays and found to be involved in the protective roles of sweroside in high glucose-mediated podocyte injury. In vivo, sweroside significantly decreased albuminuria in DN mice (p < 0.01). periodic acid-Schiff staining showed that sweroside alleviated the glomerular volume and mesangium expansion in DN mice. Consistently, western blot and reverse transcription-polymerase chain reaction analyses showed that the profibrotic molecule expression in the glomeruli declined in sweroside-treated DN mice. Immunofluorescent results showed that sweroside preserved nephrin and podocin expression, and transmission electron microscopy showed that sweroside attenuated podocyte injury. In DN mice, sweroside decreased podocyte apoptosis, and increased nephrin, podocin expression and decreased desmin and HIF1α expression. These results confirmed that sweroside ameliorated albuminuria, glomerulomegaly, and glomerulosclerosis in these mice. Experiments in vitro revealed that sweroside improved HG-induced podocyte injury and apoptosis. Sweroside stimulated activation of the Akt/BAD pathway and upregulated Bcl-2-associated death promoter (BAD) and p-Akt. Overall, sweroside protected podocytes from injury and prevented the progression of DN, providing a novel strategy for the treatment of DN.

Protective Mechanism of Fagopyrum esculentum Moench. Bee Pollen EtOH Extract Against Type II Diabetes in a High-Fat Diet/Streptozocin-Induced C57BL/6J Mice

Bee pollen is known as a natural nutrient storehouse and plays a key role in many biological processes. Based on the preliminary separation, identification, and characterization of the main active components of Fagopyrum esculentum Moench. bee pollen (FBP), the protective effects of F. esculentum bee pollen extract (FBPE) on high-fat-diet (HFD) and streptozocin (STZ) induced type II diabetes mellitus (T2DM) was evaluated in this study. The results revealed that FBPE contains 10 active compounds mainly including luteolin (9.46 g/kg), resveratrol (5.25 g/kg), kaemferol (3.67 g/kg), etc. The animal experiment results showed that FBPE could improve HFD-STZ induced T2DM mice. Moreover, the underlying mechanism of the above results could be: (i) FBPE could reduce the inflammation related to phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathway, and (ii) the gut microbiota remodeling. The results of correlation analysis showed Candidatus Arthromitus and SMB53 indicated positive correlations to tumor necrosis factor-α (TNF-α); Coprococcus, Ruminocossus, and Odoribacteraceae reported negative correlations to transforming growth factor-β (TGF-β). That FBPE has an outstanding ability to improve T2DM and could be used as a kind of potential functional food for the prevention of T2DM.

Association between Vitamin D Status and Mortality among Adults with Diabetic Kidney Disease

OBJECTIVE

Emerging evidence demonstrates that vitamin D status contributes to the incidence of diabetic kidney disease (DKD). However, the causal relationships between vitamin D and mortality among individuals with DKD are inconclusive. Our study is aimed at exploring the relationship between serum 25-hydroxyvitamin D (25(OH)D) concentrations and mortality among adults with DKD. Research Design and Methods. Our study included 1,202 adult participants with DKD from the National Health and Nutrition Examination Survey (NHANES) 2001-2014. Cox and competing-risks regression were used to estimate hazard ratios (HRs) and 95% CIs for associations between 25(OH)D concentrations and survival.

RESULTS

The overall mean serum 25(OH)D concentration was 55.9 ± 26.3. Vitamin D deficiency (25(OH)D < 50 nmol/l), insufficiency group (50 ≤ 25(OH)D < 75 nmol/l), and sufficiency group (25(OH)D ≥ 75 nmol/l) were observed in 552 (45.9%), 409 (34.0%), and 241 (20.0%) participants, respectively. Higher levels of vitamin D were significantly associated with improved all-cause and nonaccident- and malignant neoplasm-cause mortality among individuals with DKD after adjusting for the potential confounding factors.

CONCLUSIONS

We observed widespread vitamin D deficiency or insufficiency in DKD patients. Higher 25(OH)D values were significantly correlated with lower risk of mortality after adjusting for confounding variables.

Vitamin D/vitamin D receptor/Atg16L1 axis maintains podocyte autophagy and survival in diabetic kidney disease

OBJECTIVE

To investigate the effect of vitamin D/vitamin D receptor (VDR)/Atg16L1 signaling on podocyte autophagy and survival in diabetic nephropathy.

METHODS

Diabetic rat models were induced by intraperitoneal injection of streptozotocin (STZ) (60 mg/kg) and treated with and without gavage of 0.1 μg/kg/d active vitamin D3 (aVitD3; 1,25- OH vitamin D3) and kidney tissues assessed by histopathology and immunohistochemistry. The murine podocyte cell line MPC-5 was cultured under hyperglycemic conditions in the absence or presence of 100 nmol/L calcitriol to investigate podocyte injury and autophagy. Cell survival rates were analyzed using Cell Counting Kit-8 (CCK-8) assays and the numbers of autophagosomes were determined after transduction with the mRFP-GFP-LC3 autophagy reporter construct. The expression of autophagy-related proteins (LC3-II, beclin-1, Atg16L1) and podocyte-related proteins (nephrin, podocin, synaptopodin, and desmin) was determined by Western blotting.

RESULTS

VDR expression and autophagy were decreased in diabetic nephropathy. Calcitriol treatment repressed renal injury in rat diabetic kidneys and reduced high glucose-induced damage to cultured podocytes. Mechanistically, Atg16L1 was identified as a functional target of VDR, and siRNA-mediated knockdown of VDR and Atg16L1 blocked the protective effects of aVitD3 against podocyte damage.

CONCLUSION

Autophagy protects podocytes from damage in DN and is modulated by VitD3/VDR signaling and downstream regulation of Atg16L1 expression.

1,25(OH)2D3 Mitigates Oxidative Stress-Induced Damage to Nucleus Pulposus-Derived Mesenchymal Stem Cells through PI3K/Akt Pathway

Intervertebral disc degeneration (IVDD) is one of the main causes of low back pain. The local environment of the degenerated intervertebral disc (IVD) increases oxidative stress and apoptosis of endogenous nucleus pulposus-derived mesenchymal stem cells (NPMSCs) and weakens its ability of endogenous repair ability in degenerated IVDs. A suitable concentration of 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) has been certified to reduce oxidative stress and cell apoptosis. The current study investigated the protective effect and potential mechanism of 1,25(OH)₂D₃ against oxidative stress-induced damage to NPMSCs. The present results showed that 1,25(OH)₂D₃ showed a significant protective effect on NPMSCs at a concentration of 10⁻¹⁰ M for 24 h. Protective effects of 1,25(OH)₂D₃ were also exhibited against H₂O₂-induced NPMSC senescence, mitochondrial dysfunction, and reduced mitochondrial membrane potential. The Annexin V/PI apoptosis detection assay, TUNEL assay, immunofluorescence, western blot, and real-time quantitative polymerase chain reaction assay showed that pretreatment with 1,25(OH)₂D₃ could alleviate H₂O₂-induced NPMSC apoptosis, including the apoptosis rate and the expression of proapoptotic-related (Caspase-3 and Bax) and antiapoptotic-related (Bcl-2) proteins. The intracellular expression of p-Akt increased after pretreatment with 1,25(OH)₂D₃. However, these protective effects of 1,25(OH)₂D₃ were significantly decreased after the PI3K/Akt pathway was inhibited by the LY294002 treatment. In vivo, X-ray, MRI, and histological analyses showed that 1,25(OH)₂D₃ treatment relieved the degree of IVDD in Sprague–Dawley rat disc puncture models. In summary, 1,25(OH)₂D₃ efficiently attenuated oxidative stress-induced NPMSC apoptosis and mitochondrial dysfunction via PI3K/Akt pathway and is a promising candidate treatment for the repair of IVDD.

Pueraria lobata root polysaccharide alleviates glucose and lipid metabolic dysfunction in diabetic db/db mice

CONTEXT

Pueraria lobata (Willd.) Ohwi (Fabaceae) root extract can lower blood glucose levels; however, whether Pueraria lobata root polysaccharide (PLP) possesses these effects is still unknown.

OBJECTIVE

This study evaluates the therapeutic effect of PLP on diabetic metabolic syndrome.

MATERIALS AND METHODS

The db/m mice were assigned to normal control group (NC), db/db mice were divided into four groups randomly (n = 8). The db/db mice received rosiglitazone (10 mg/kg BW) or PLP (100 or 200 mg/kg BW) via oral gavage for 6 weeks. Afterward, blood glucose, insulin, and glycogen content were assayed, and insulin tolerance test (ITT), oral glucose tolerance test (OGTT) were performed. Glucose and lipid metabolism-related parameters and gene expression levels were assayed by ELISA and RT-PCR, respectively.

RESULTS

After treatment with HPLP, the values of body weight, epididymal fat, subcutaneous fat, fasting blood glucose, insulin, and HOMA-IR decreased to 45.89 ± 1.66 g, 1.65 ± 0.14 g, 1.97 ± 0.16 g, 14.84 ± 1.52 mM, 9.35 ± 0.98 mU/L, and 5.56 ± 1.26, respectively; the levels of TG, TC, LDL-C, and FFA decreased to 1.67 ± 0.11 mmol/L, 6.23 ± 0.76 mmol/L, 1.29 ± 0.07 mmol/L, and 1.71 ± 0.16 mmol/L, respectively. HPLP down-regulated PEPCK, G6PC, FOXO1, SREBP-1, and ACC mRNA expression (p < 0.01), and up-regulated GS, Akt2, PI3K, GLUT2, PPARα, and LDLR mRNA expression in the liver (p < 0.01).

DISCUSSION AND CONCLUSION

PLP exerts antidiabetic effects via activating the PI3K/AKT signalling pathway, thus improving insulin resistance, glucose, and lipid metabolism in db/db mice. Thus, PLP may be considered as a potential antidiabetic agent in clinical therapy.

MicroRNA 1228 Mediates the Viability of High Glucose-Cultured Renal Tubule Cells through Targeting Thrombospondin 2 and PI3K/AKT Signaling Pathway

AIM

The present study aimed to elucidate the potential function of microRNA 1228 (miR-1228) on the high glucose (HG)-damaged human renal proximal tubule cells (HK-2) and the underlying mechanism.

METHODS

The datasets GSE47185 and GSE51674 were downloaded from the Gene Expression Omnibus database for mining differently expressed mRNAs and miRNAs, respectively. Bioinformatics online tools were applied to predict the binding sites between miR-1228 and thrombospondin 2 (THBS2), which was confirmed by dual-luciferase assay. Real-time quantitative polymerase chain reaction was used to detect the mRNA level of miR-1228/THBS2. Western blot was used to detect the protein level of THBS2 and the PI3K/AKT signaling pathway-associated markers. HK-2 cells were cultured in HG (30 mM) to mimic hyperglycemia. Cell counting kit 8 and flow cytometry assays were utilized to determine the cell proliferation and apoptosis.

RESULTS

The expression of THBS2 was significantly upregulated in diabetic nephropathy (DN) based on bioinformatics tools and identified as a direct target of miR-1228. miR-1228 was downregulated in DN and HG-damaged HK-2 cells. HG notably reduced HK-2 cell proliferation. This negative effect was attenuated by transfecting with an miR-1228 mimic and aggravated by transfecting with an miR-1228 inhibitor. However, under basal condition, there was no significant effect on the HK-2 cell proliferation among blank control, mimic, and inhibitor groups. Overexpression of THBS2 abolished the elevating effect of the miR-1228 mimic on the HG-damaged HK-2 cell proliferation, while restored the inhibitory effects of the miR-1228 mimic on the cell apoptosis. On the contrary, the suppressive effects on the proliferation and the enhancive effects on the apoptosis by silencing miR-1228 in HK-2 cells stimulated with HG can be weakened by recommendation of THBS2 small interference RNAs. Furthermore, we also found that HG significantly enhanced the phosphorylation levels of PI3K and AKT. In terms of overexpression and knockdown experiments, Western blot analysis further revealed that miR-1228 inhibited the activation of the PI3K/AKT signaling pathway in HG-damaged HK-2 cells by regulating THBS2.

CONCLUSION

The findings illustrated that miR-1228 improved survivability and inhibited apoptosis in HK-2 cells stimulated with HG partly by restraining the activation of the PI3K/AKT signaling pathway.

Total Flavones of Abelmoschus manihot Ameliorates Podocyte Pyroptosis and Injury in High Glucose Conditions by Targeting METTL3-Dependent m6A Modification-Mediated NLRP3-Inflammasome Activation and PTEN/PI3K/Akt Signaling

Background: The total flavones of Abelmoschus manihot (TFA), a compound that is extracted from Abelmoschus manihot, has been widely used in China to reduce podocyte injury in diabetic kidney disease (DKD). However, the mechanisms underlying the therapeutic action of this compound have yet to be elucidated. Podocyte pyroptosis is characterized by activation of the NLRP3 inflammasome and plays an important role in inflammation-mediated diabetic kidneys. Regulation of the PTEN/PI3K/Akt pathway is an effective strategy for improving podocyte damage in DKD. Previous research has also shown that N6-methyladenosine (m6A) modification is involved in DKD and that m6A-modified PTEN regulates the PI3K/Akt pathway. In this study, we investigated whether TFA alleviates podocyte pyroptosis and injury by targeting m6A modification-mediated NLRP3-inflammasome activation and PTEN/PI3K/Akt signaling. Methods: We used MPC-5 cells under high glucose (HG) conditions to investigate the key molecules that are involved in podocyte pyroptosis and injury, including activation of the NLRP3 inflammasome and the PTEN/PI3K/Akt pathway. We detected alterations in the levels of three methyltransferases that are involved in m6A modification. We also investigated changes in the levels of these key molecules in podocytes with the overexpression or knockdown of methyltransferase-like (METTL)3. Results: Analysis showed that TFA and MCC950 protected podocytes against HG-induced pyroptosis and injury by reducing the protein expression levels of gasdermin D, interleukin-1β, and interleukin-18, and by increasing the protein expression levels of nephrin, ZO-1, WT1 and podocalyxin. TFA and 740Y-P inhibited activation of the NLRP3 inflammasome via the PI3K/Akt pathway by inhibiting the protein levels of NIMA-related kinase7, NLRP3, ASC, and caspase-1, and by increasing the protein expression levels of p-PI3K and p-Akt. TFA improved pyroptosis and injury in HG-stimulated podocytes by regulating METTL3-dependent m6A modification. Conclusion: Collectively, our data indicated that TFA could ameliorate pyroptosis and injury in podocytes under HG conditions by adjusting METTL3-dependent m6A modification and regulating NLRP3-inflammasome activation and PTEN/PI3K/Akt signaling. This study provides a better understanding of how TFA can protect podocytes in DKD.

Vitamin D/VDR Protects Against Diabetic Kidney Disease by Restoring Podocytes Autophagy

OBJECTIVE

The present study is to investigate the effect of vitamin D/Vitamin D Receptor (VDR) signaling on podocyte autophagy in diabetic nephropathy.

METHODS

Kidney tissue sections from patients with diabetic nephropathy and nontumor kidney were checked under electronic microscope and VDR immunohistochemistry. Diabetic rat models were induced by intraperitoneal injection of streptozotocin (STZ) (60 mg/kg). Calcitriol treatment was achieved by gavage at dose of 0.1μg/kg/d. Blood, urine and kidney tissue specimens were used for serum, urine biochemistry, histopathology and molecular biology testing. Podocyte cell line MPC-5 was cultured under hyperglycaemic conditions in the absence or presence of 100 nmol/L calcitriol to investigate podocyte injury and autophagy.

RESULTS

VDR and autophagosomes in podocytes were significantly decreased in renal biopsy from patients with diabetic nephropathy, compared to healthy kidney tissue. Rats with STZ treatment developed typical diabetic kidney disease with low VDR expression. Calcitriol, the active form of vitamin D, could activate VDR and attenuate diabetic nephropathy including proteinuria and glomerular sclerosis. Calcitriol treatment also alleviated the podocyte foot process fusion, reduced podocyte injury marker desmin and preserved slit diaphragms proteins in diabetic nephropathy. Reduced LC3II/I, Beclin-1 and elevated p62 in renal homogenate and reduced autophagosomes and LC3II in podocytes indicated podocytes autophagy impairment in diabetic nephropathy. Whereas calcitriol treatment restored podocyte autophagy activities. In cultured podocytes, the protective effect of calcitriol against high glucose induced podocyte injury could be abated by autophagy inhibitor chloroquine.

CONCLUSION

Our study delivered the evidence that calcitriol/VDR signaling attenuated diabetic nephropathy and podocytes injury by restoring podocytes autophagy. This finding may have potential implication for exploring protective mechanisms of calcitriol/VDR in diabetic nephropathy.

Modified Linggui Zhugan Decoction () Ameliorates Glycolipid Metabolism and Inflammation via PI3K-Akt/mTOR-S6K1/AMPK-PGC-1 α Signaling Pathways in Obese Type 2 Diabetic Rats

OBJECTIVE

To investigate the protective effects of modified Linggui Zhugan Decoction (, MLZD), a traditional Chinese medicine formula, on obese type 2 diabetes mellitus (T2DM) rats.

METHODS

Fifty Sprague-Dawley rats were randomly divided into 5 groups by a random number table, including normal, obese T2DM (ob-T2DM), MLZD low-dose [MLDZ-L, 4.625 g/(kg·d)], MLZD middle-dose [MLD-M, 9.25 g/(kg·d) ] and MLZD high-dose [MLD-H, 18.5 g/(kg·d)] groups, 10 rats in each group. After 4-week intervention, blood samples and liver, pancreas, muscle tissues were collected to assess the insulin resistance (IR), blood lipid, adipokines and inflammation cytokines. The alteration of phosphatidylinositol 3 kinase (PI3K)-protein kinase B (PKB or Akt)/the mammalian target of rapamycin (mTOR)-ribosome protein subunit 6 kinase 1 (S6K1 )/AMP-activated protein kinase (AMPK)-peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1 α) pathways were also studied.

RESULTS

MLZD dose-dependently reduced fasting blood glucose, fasting insulin, homeostasis model of assessment for IR index and increased insulin sensitive index compared with ob-T2DM rats (P<0.05). Similarly, total cholesterol, triglyceride, low-density lipoprotein cholesterol and free fatty acids were also decreased compared with ob-T2DM rats after 4-week treatment (P<0.05 or P<0.01). Improvements in adipokines and inflammatory cytokines were observed with a raised level of adiponectin and a reduced level of leptin, resistin, tumor necrosis factor-α and interleukin-6 (P<0.05 or P<0.01). MLZD regulated the PI3K-Akt/mTOR-S6K1/AMPK-PGC-1 α pathways and restored the tissue structure of liver and pancreas (P<0.05 or P<0.01).

CONCLUSIONS

MLZD ameliorated glycolipid metabolism and inflammation, which may be attributed to the regulation of PI3K-Akt/mTOR-S6K1/AMPK-PGC-1 α pathways.

sPLA2-IB and PLA2R mediate insufficient autophagy and contribute to podocyte injury in idiopathic membranous nephropathy by activation of the p38MAPK/mTOR/ULK1ser757 signaling pathway

Secretory phospholipase A2 group IB (sPLA2-IB) and M-type phospholipase A2 receptor (PLA2R) are closely associated with proteinuria in idiopathic membranous nephropathy (IMN). Podocytes constitute an important component of glomerular filtration, and high basal autophagy is indispensable for podocyte function. The current study aimed to analyze the relationship between sPLA2-IB and podocyte autophagy in IMN and determine whether sPLA2-IB mediates abnormal autophagy regulation in podocytes. The serum sPLA2-IB level and podocyte autophagy were detected, and clinical data were collected from IMN patients with different proteinuria levels. Then, the effects of sPLA2-IB on autophagy signaling pathways were evaluated in cultured human podocytes treated with sPLA2-IB, rapamycin, p38 inhibition, and PLA2R-siRNA in vitro. We found that IMN patients with nephrotic-range proteinuria have a significantly higher level of sPLA2-IB and fewer autophagosomes than those with non-nephrotic-range proteinuria. In vitro sPLA2-IB-induced insufficient autophagy in podocytes and promoted podocyte injury via activation of the mTOR/ULK1^ser757 signaling pathway. Moreover, inhibition of p38 MAPK evidently abrogated sPLA2-IB-induced autophagy and the activation of mTOR/ULK1^ser757 . Additionally, PLA2R silencing demonstrated that sPLA2-IB-induced abnormal autophagy was also PLA2R-dependent. In conclusion, the results revealed that sPLA2-IB downregulated autophagy and contributed to podocyte injury via PLA2R though activation of the p38MAPK/mTOR/ULK1^ser757 signaling pathway.

MYDGF attenuates podocyte injury and proteinuria by activating Akt/BAD signal pathway in mice with diabetic kidney disease

AIMS/HYPOTHESIS

Myeloid-derived growth factor (MYDGF), mainly secreted by bone marrow-derived cells, has been known to promote glucagon-like peptide-1 production and improve glucose/lipid metabolism in mouse models of diabetes, but little is known about the functions of MYDGF in diabetic kidney disease (DKD). Here, we investigated whether MYDGF can prevent the progression of DKD.

METHODS

In vivo experiments, both loss- and gain-of-function strategies were used to evaluate the effect of MYDGF on albuminuria and pathological glomerular lesions. We used streptozotocin-treated Mydgf knockout and wild-type mice on high fat diets to induce a model of DKD. Then, albuminuria, glomerular lesions and podocyte injury were evaluated in Mydgf knockout and wild-type DKD mice treated with adeno-associated virus-mediated Mydgf gene transfer. In vitro and ex vivo experiments, the expression of slit diaphragm protein nephrin and podocyte apoptosis were evaluated in conditionally immortalised mouse podocytes and isolated glomeruli from non-diabetic wild-type mice treated with recombinant MYDGF.

RESULTS

MYDGF deficiency caused more severe podocyte injury in DKD mice, including the disruption of slit diaphragm proteins (nephrin and podocin) and an increase in desmin expression and podocyte apoptosis, and subsequently caused more severe glomerular injury and increased albuminuria by 39.6% compared with those of wild-type DKD mice (p < 0.01). Inversely, MYDGF replenishment attenuated podocyte and glomerular injury in both wild-type and Mydgf knockout DKD mice and then decreased albuminuria by 36.7% in wild-type DKD mice (p < 0.01) and 34.9% in Mydgf knockout DKD mice (p < 0.01). Moreover, recombinant MYDGF preserved nephrin expression and inhibited podocyte apoptosis in vitro and ex vivo. Mechanistically, the renoprotection of MYDGF was attributed to the activation of the Akt/Bcl-2-associated death promoter (BAD) pathway.

CONCLUSIONS/INTERPRETATION

The study demonstrates that MYDGF protects podocytes from injury and prevents the progression of DKD, providing a novel strategy for the treatment of DKD. Graphical abstract.

LncRNA CCAT1 functions as apoptosis inhibitor in podocytes via autophagy inhibition

Podocyte apoptosis importantly contributes to various kidney diseases. Long noncoding RNAs Colon cancer‐associated transcript‐1 (CCAT‐1) has been demonstrated for a critical role in cell proliferation. In the present study, the relationship between CCAT1 and popdocyte impairment, and the underlying mechanism was investigated. Podocytes were isolated from mice and then treated with tumor necrosis factor‐α to simulate podocyte injury. After developed CCAT1 overexpression or knockdown, cell viabilities were determined with the CCK‐8 assay, apoptosis was examined with Flow cytometry, the autophagy was observed by Western blot. Furthermore, phosphorylated PI3K and Akt expressions were examined. We found that after CCAT1 overexpression, the cell viability was significantly increased, apoptosis was significantly decreased, and autophagy was significantly inhibited, which was indicated by induced P62, LC3B‐I and decreased LC3B‐II. In addition, CCAT1 overexpression induced the levels of phosphorylated PI3K and Akt. With Rap treatment, these effects by CCAT1 were reversed. Furthermore, the results contrary to the effects by CCAT1 overexpression were presented after CCAT1 knockdown, and this was inhibited by 3‐MA. Taken together, our results suggested that CCAT1 induction critically participated in apoptosis inhibition in podocytes through autophagy inhibition via increasing PI3K/Akt signaling. This might act as a promising therapeutic intervention for renal diseases associated with podocyte apoptosis.

Whole transcriptome analysis of diabetic nephropathy in the db/db mouse model of type 2 diabetes

Whole-transcriptome analysis using RNA sequencing (RNA-seq) affords broader insights about gene expression regulatory networks in diabetic nephropathy (DN). To better explore the molecular basis of DN, kidney tissue from db/db DN model mice and control mice were submitted to RNA-seq analysis. Thousands of long noncoding RNAs (lncRNAs) and messenger RNAs (mRNAs) were found to be significantly differentially expressed in the DN group relative to the control group. To research the regulatory mechanism of these lncRNAs and mRNAs, the integrated co-expression networks were constructed for 322 mRNAs and 27 lncRNAs that revealed significantly correlated expression patterns in DN. The potential roles of these co-expressed mRNAs were classified by Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analyses. The co-expression networks involved 27 lncRNAs interacting with 38 key mRNAs related to metabolic processes, including ND4/4L, Ndufa2/5, Ndufb4/7, Ndufs3, Uqcrc1, Aco2, Alad, Alas1, Alpl, Atp5j2, Coq5, Coq6, Cth, and CytB, all of which are highly related to encoding subunits of the mitochondrial complexes. Thus, mitochondrial dysfunction could result in renal function decline in DN. Seven dysregulated lncRNAs and nine dysregulated mRNAs in the DN model were confirmed by quantitative real-time polymerase chain reaction. The lncRNA-mRNA co-expression network provides novel evidence to support the contention that metabolic changes are associated with metabolic reprogramming in the kidneys, and that these changes play a critical role during the progression of DN.

miRNA-214 suppresses oxidative stress in diabetic nephropathy via the ROS/Akt/mTOR signaling pathway and uncoupling protein 2

In the present study, the function of microRNA (miR)-214 on diabetic nephropathy (DN) and diabetes of proximal tubular cells was investigated. Reverse transcription-quantitative polymerase chain reaction was used measure the expression of miR-214 in rats with DN and ELISA was performed to measure oxidative stress and ROS levels. Results indicated that miR-214 expression in the peripheral blood was significantly decreased in rats with DN. The in vitro model of DN indicated that miR-214 upregulation significantly decreased oxidative stress and reactive oxygen species (ROS) levels, but significantly increased uncoupling protein 2 (UCP2), phosphorylated (p)-Akt and p-mammalian target of rapamycin (mTOR) protein expression levels. The administration of genipin, a UCP2 inhibitor, significantly attenuated the effects of miR-214 upregulation on oxidative stress in the in vitro DN model by regulating ROS, Akt and mTOR protein expression levels. Notably, Akt inhibitor suppressed p-Akt protein expression and attenuated the effects of miR-214 upregulation on oxidative stress in the in vitro DN model. Collectively, these data suggest that miR-214 regulates diabetes through a ROS/Akt/mTOR signaling pathway by UCP2 in proximal tubular cells.

Ramipril can alleviate the accumulation of renal mesangial matrix in rats with diabetic nephropathy by inhibiting insulin-like growth factor-1

Purpose

To investigate the impact of Ramipril (RAM) on the expressions of insulin-like growth factor-1 (IGF-1) and renal mesangial matrix (RMM) in rats with diabetic nephropathy (DN).

Methods

The Sprague Dawley rats were divided into normal control (NC) group (n = 12), DN group (n = 11), and DN+RAM group (n = 12). The ratio of renal weight to body weight (RBT), fasting blood glucose (FBG), HbA1c, 24-h urine protein (TPU), blood urea nitrogen (BUN), creatinine (Cr), renal pathological changes, the levels of IGF-1, fibronectin (FN), type IV collagen (Col-IV), and matrix metalloproteinases (MMP)-2 were compared among the groups.

Results

Compared with NC group, the RBT, FBG, HbA1c, TPU, BUN, Cr, and RMM in DN group were significantly increased (P < 0.05), the IGF-1, FN, and Col-IV were significantly upregulated (P < 0.05), while MMP was significantly downregulated (P < 0.05). Compared with DN group, the indexes except for the FBG and HbA1c in DN+RAM group were significantly improved (P < 0.05), among which IGF-1 exhibited significant positive correlation with TPU(r=0.937), FN(r=0.896) and Col-IV(r=0.871), while significant negative correlation with MMP-2 (r=-0.826) (P<0.05).

Conclusion

RAM may protect the kidneys by suppressing IGF-1 and mitigating the accumulation of RMM.

Ginseng Total Saponin Attenuates Podocyte Apoptosis Induced by Diabetic Conditions Through the Recovery of CD2-Associated Protein

CD2-associated protein (CD2AP), an adaptor protein, plays several important roles in podocyte function, linking slit diaphragms to actin-based cytoskeleton and sending survival signals. Here, we investigated whether ginseng total saponin (GTS) had a protective role in the changes of podocyte CD2AP protein and podocyte apoptosis under in vitro diabetic conditions. Conditionally immortalized mouse podocytes cultured with normal glucose (5 mM) or high glucose (30 mM) and with or without advanced glycosylation end products were treated with GTS. We found that CD2AP co-localized with the F-actin fibers in podocyte cytoplasm using confocal imaging; however, diabetic conditions caused the podocytes to diminish and conglomerate CD2AP stainings in the peripheral cytoplasm, which were recovered by GTS. Diabetic conditions also suppressed CD2AP protein levels at 6 and 24 h in western blotting. These phenotypical changes of CD2AP protein were mitigated by GTS. Diabetic conditions also induced podocyte apoptosis at 24 h, which were attenuated by GTS. These findings provide a novel mechanism that diabetic conditions induce quantitative and qualitative changes of podocyte CD2AP protein and apoptosis, which would be restored by GTS.

Antidiabetic activity of a polysaccharide-protein complex from Asian Clam (Corbicula fluminea) in streptozotoxin-induced diabetic rats and its underlying mechanism

Antidiabetic activity of a polysaccharide-protein complex from Asian Clam (Corbicula fluminea) in streptozotoxin-induced diabetic rats and its underlying mechanism.

TUG1 knockdown enhances adriamycin cytotoxicity by inhibiting glycolysis in adriamycin-resistant acute myeloid leukemia HL60/ADR cells

Taurine-upregulated gene 1 (TUG1) has been reported as an oncogenic long non-coding RNA (lncRNA) in acute myeloid leukemia (AML). Nevertheless, the roles and molecular mechanism of TUG1 in drug resistance of AML cells are still unclear. Glycolysis level was evaluated by detecting glucose consumption and lactate production. qRT-PCR and Western blot were performed to detect TUG1, hexokinase2 (HK2) and pyruvate kinase isoenzyme M2 (PKM2) expressions. Adriamycin (ADR) cytotoxicity and apoptosis were assessed by MTT assay and flow cytometry, respectively. The changes of the protein kinase B (Akt) pathway were determined by Western blot analysis of phosphorylated-Akt (p-Akt) (ser473) and Akt. Our results showed that glycolysis was increased in HL60/ADR cells, as evidenced by the elevated glucose consumption and lactate production, as well as the increased HK2 and PKM2 expressions at mRNA and protein levels. TUG1 was up-regulated in HL60/ADR cells and TUG knockdown inhibited glycolysis. TUG1 knockdown enhanced ADR-induced cytotoxicity and apoptosis in HL60/ADR cells. TUG1 knockdown inhibited the Akt pathway and activation of the Akt pathway by 740Y-P attenuated the effects of TUG1 knockdown on ADR-induced cytotoxicity and apoptosis, as well as glycolysis in HL60/ADR cells. Taken together, TUG1 knockdown enhances adriamycin cytotoxicity in HL60/ADR cells via inhibiting the glycolysis by inactivating the Akt pathway.

Taurine-upregulated gene 1 (TUG1) has been reported as an oncogenic long non-coding RNA (lncRNA) in acute myeloid leukemia (AML).

Vitamin D protects against diabetic nephropathy: Evidence-based effectiveness and mechanism

Vitamin D has been suggested to harbor multiple biological activities, among them the potential of vitamin D in the protection of diabetic nephropathy (DN) has attracted special attention. Both animal studies and clinical trials have documented an inverse correlation between low vitamin D levels and DN risk, and supplementation with vitamin D or its active derivatives has been demonstrated to improve endothelial cell injury, reduce proteinuria, attenuate renal fibrosis, and resultantly retard DN progression. Vitamin D exerts its pharmacological effects primarily via vitamin D receptor, whose activation inhibits the renin-angiotensin system, a key culprit for DN under hyperglycemia. The anti-DN benefit of vitamin D can be enhanced when administrated in combination with angiotensin converting enzyme inhibitors or angiotensin II receptor blockers. Mechanistic studies reveal that pathways relevant to inflammation participate in the pathogenesis of DN, however, consumption of vitamin D-related products negatively regulates inflammatory response at multiple levels, indicated by inhibiting macrophage infiltration, nuclear factor-kappa B (NF-κB) activation, and production of such inflammatory mediators as transforming growth factor-β(TGF-β), monocyte chemoattractant protein 1(MCP-1), and regulated upon activation normal T cell expressed and secreted protein(RANTES). The robust anti-inflammatory property of vitamin D-related products allows them with a promising renoprotective therapeutic option for DN. This review summarizes new advances in our understanding of vitamin D-related products in the DN management.

Proteinuric Kidney Diseases: A Podocyte's Slit Diaphragm and Cytoskeleton Approach

Proteinuric kidney diseases are a group of disorders with diverse pathological mechanisms associated with significant losses of protein in the urine. The glomerular filtration barrier (GFB), comprised of the three important layers, the fenestrated glomerular endothelium, the glomerular basement membrane (GBM), and the podocyte, dictates that disruption of any one of these structures should lead to proteinuric disease. Podocytes, in particular, have long been considered as the final gatekeeper of the GFB. This specialized visceral epithelial cell contains a complex framework of cytoskeletons forming foot processes and mediate important cell signaling to maintain podocyte health. In this review, we will focus on slit diaphragm proteins such as nephrin, podocin, TRPC6/5, as well as cytoskeletal proteins Rho/small GTPases and synaptopodin and their respective roles in participating in the pathogenesis of proteinuric kidney diseases. Furthermore, we will summarize the potential therapeutic options targeting the podocyte to treat this group of kidney diseases.

Inhibition of LY294002 in retinal neovascularization via down-regulation the PI3K/AKT-VEGF pathway in vivo and in vitro

AIM

To investigate the effects of the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 on retinal neovascularization (RNV) in the oxygen-induced retinopathy (OIR) mouse model and human umbilical vein endothelial cells (HUVECs).

METHODS

C57BL/6J mice were randomly divided into normoxia-control, OIR-control and LY294002 treatment groups. LY294002 or phosphate-buffered solution was intraperitoneally injected daily into mouse pups from P6 to P9 in LY294002 treatment group or OIR-control group. Morphological and pathological changes in RNV, as well as expression levels of PI3K, serine-threonine kinase (AKT) and vascular endothelial growth factor (VEGF) were observed. HUVECs treating with LY294002 were exposed to hypoxia; the expression of PI3K, AKT and VEGF were examined by Western blot and RT-PCR analyses.

RESULTS

Compared with the OIR-control group, LY294002 significantly inhibit RNV. Adenosine diphosphatase (ADPase) staining and hematoxylin and eosin staining indicated that the clock hour scores of neovascularization and the nuclei of pre-retinal neovascular cells in the LY294002 treatment group were clearly less than those in the OIR-control group (1.41±0.52 vs 6.20±1.21; 10.50±1.58 vs 22.25±1.82, both P<0.05). Intravitreal injection of LY294002 (in the LY294002 treatment group) markedly decreased PI3K/AKT-VEGF expression compared with the OIR-control group by immunohistochemistry, Western blotting and RT-PCR (all P<0.05). In HUVECs treated with hypoxia, expression of PI3K, AKT and VEGF were downregulated in the hypoxia-LY294002 group (all P<0.05).

CONCLUSION

The PI3K inhibitor LY294002 can inhibit RNV by downregulating PI3K, AKT, and VEGF expression in vivo and in vitro. LY294002 may provide an effective method for preventing retinopathy of prematurity (ROP).

Silencing of PAQR3 suppresses extracellular matrix accumulation in high glucose-stimulated human glomerular mesangial cells via PI3K/AKT signaling pathway

Progestin and AdipoQ Receptor 3 (PAQR3), a member of the PAQR family, was involved in multiple biological processes, including tumorigenesis, cholesterol homeostasis, autophagy, obesity, insulin sensitivity and energy metabolism. However, the role of PAQR3 in diabetic nephropathy is still unclear. Therefore, in this study, we investigated the effects of PAQR3 on cell proliferation and extracellular matrix (ECM) accumulation in human glomerular mesangial cells (MCs) cultured under high glucose (HG), and explored the underlying mechanism. Our results demonstrated that HG significantly up-regulated the expression of PAQR3 in human MCs. In addition, knockdown of PAQR3 efficiently suppressed MC proliferation and ECM production in HG-stimulated MCs. Furthermore, knockdown of PAQR3 markedly reversed HG-induced PI3K/AKT activation in MCs. In summary, our present study demonstrated that knockdown of PAQR3 suppressed HG-induced the proliferation and ECM accumulation in human MCs, via inhibiting the PI3K/AKT signaling pathway. Thus, PAQR3 may be a potential therapeutic target for the treatment of diabetic nephropathy.

The protective effect of the EP2 receptor on TGF-β1 induced podocyte injury via the PI3K / Akt signaling pathway

Transforming growth factor β1 (TGF-β1) plays a central role in chronic kidney diseases. TGF-β1 induction causes podocyte injury, which results in proteinuria and renal failure. However, the effect of the prostaglandin E2 /E-prostanoid receptor (EP2) on TGF-β1-induced podocyte injury remains unknown. Previous studies have shown that phosphoinositide 3-OH kinase (PI3K)/Akt is widespread in cells, and is vital for the regulation of cell proliferation, differentiation, apoptosis and metabolism. In this study, we cultured immortalized mouse podocytes in vitro in different groups: control group; TGF-β1 (5ng/ml) group; EP2 agonist Butaprost treatment (10⁻⁷, 10⁻⁶, or 10^-5mol/L) +TGF-β1 group; EP2 antagonist AH6809 treatment (10⁻⁷, 10⁻⁶, or 10^-5mol / L) + TGF-β1 group. We found that compared with the control group, proliferation of podocytes in the TGF-β1 group significantly decreased and apoptosis increased. Expression of cAMP decreased, whereas PGE2 increased. Meanwhile, expressions of nephrin, podocin and CD2AP mRNA and protein were dramatically downregulated, activated caspase-3 was increased, and activated PI3K/Akt activity were depressed. Butaprost intervention promoted podocyte proliferation with reduced apoptosis. Conversely, AH6809 intervention led to opposite results (P<0.05). Our findings suggested that EP2 agonist protects podocytes by increasing expression of cAMP, which creates feedback of inhibiting PGE2 expression. This causes the interaction of nephrin, podocin and CD2AP resulting the inhibition of apoptosis induced by activation of the PI3K / Akt signaling pathway.

Higher maternal vitamin D concentrations are associated with longer leukocyte telomeres in newborns

Gestational vitamin D insufficiency is related with increased risks of various diseases and poor health outcomes later in life. Telomere length at birth or early in life is known to be a predictor of individual health. Both vitamin D and telomere length are related with various health conditions, and vitamin D concentrations are associated with leukocyte telomere lengths in women. We investigated the association between maternal vitamin D concentrations and newborn leukocyte telomere lengths. This cross-sectional study included 106 healthy pregnant women without adverse obstetric outcomes and their offspring. We examined the maternal age, weight before pregnancy, health behaviours, and nutritional intakes, along with each newborn's sex and birthweight, and we measured maternal height, telomere length, total white blood cell count, and glycosylated haemoglobin as covariates. Pearson's correlation coefficients were calculated to evaluate the relationship between the baseline variables and newborn leukocyte telomere lengths. To confirm that there was an independent association between newborn leukocyte telomere lengths and maternal vitamin D concentrations, we performed a stepwise multiple linear regression analysis. Newborn leukocyte telomere lengths correlated positively with maternal leukocyte telomere lengths (r = .76, p < .01), maternal 25-hydroxyvitamin D concentrations (r = .72, p < .01), maternal energy intakes (r = .22, p = .03), and newborn body weights (r = .51, p < .01). In the multivariate model, newborn leukocyte telomere lengths were associated with maternal vitamin D concentrations (β = .33, p < .01). These findings suggest that the maternal vitamin D concentration during pregnancy may be a significant determinant of the offspring's telomere length.

Vitamin D Receptor: A Novel Therapeutic Target for Kidney Diseases

BACKGROUND

Kidney disease is a serious problem that adversely affects human health, but critical knowledge is lacking on how to effectively treat established chronic kidney disease. Mounting evidence from animal and clinical studies has suggested that Vitamin D Receptor (VDR) activation has beneficial effects on various renal diseases.

METHODS

A structured search of published research literature regarding VDR structure and function, VDR in various renal diseases (e.g., IgA nephropathy, idiopathic nephrotic syndrome, renal cell carcinoma, diabetic nephropathy, lupus nephritis) and therapies targeting VDR was performed for several databases.

RESULT

Included in this study are the results from 177 published research articles. Evidence from these papers indicates that VDR activation is involved in the protection against renal injury in kidney diseases by a variety of mechanisms, including suppression of RAS activation, anti-inflammation, inhibiting renal fibrogenesis, restoring mitochondrial function, suppression of autoimmunity and renal cell apoptosis.

CONCLUSION

VDR offers an attractive druggable target for renal diseases. Increasing our understanding of VDR in the kidney is a fertile area of research and may provide effective weapons in the fight against kidney diseases.

Vitamin D3 ameliorates podocyte injury through the nephrin signalling pathway

Renal podocytes form the main filtration barrier possessing unique phenotype maintained by proteins including podocalyxin and nephrin, which are modulated in pathological conditions. In diabetic nephropathy (DN), podocytes become structurally and functionally compromised. Nephrin, a structural backbone protein of the slit diaphragm, acts as regulator of podocyte intracellular signalling with renoprotective role. Vitamin D₃ through its receptor, VDR, provides renal protection in DN but limited data exist about its effect on podocytes. In this study, we used isolated rat glomeruli to assess podocalyxin and nephrin expression after treatment with the 1,25‐dihydroxyvitamin D₃ analogue paricalcitol in the presence of normal and diabetic glucose levels. The role of 1,25‐dihydroxyvitamin D₃ (calcitriol) and its analogue, paricalcitol, on podocyte morphology and survival was also investigated in the streptozotocin (STZ)‐diabetic animal model. In our ex vivo model, glomeruli exhibited high glucose‐mediated down‐regulation of podocalyxin, and nephrin, while paricalcitol reversed the high glucose‐induced decrease of nephrin and podocalyxin expression. Paricalcitol treatment enhanced VDR expression and promoted VDR and RXR co‐localization in the nucleus. Our data also indicated that hyperglycaemia impaired survival of cultured glomeruli and suggested that the implemented nephrin down‐regulation was reversed by paricalcitol treatment, initiating Akt signal transduction which may be involved in glomerular survival. Our findings were further verified in vivo, as in the STZ‐diabetic animal model, calcitriol and paricalcitol treatment resulted in significant amelioration of hyperglycaemia and restoration of nephrin signalling, suggesting that calcitriol and paricalcitol may provide molecular bases for protection against loss of the permselective renal barrier in DN.

Vitamin D3 Partly Antagonizes Advanced-Glycation Endproducts-Induced NFκB Activation in Mouse Podocytes

BACKGROUND/AIMS

We have previously shown that advanced glycation-endproducts (AGEs) induced NFκB activation in differentiated mouse podocytes. This NFκB activation may contribute to the progression of renal disease and mediation of fibrosis by various mechanisms. This study was undertaken to test whether this detrimental response may be reversed by vitamin D3 or its analogue paricalcitol.

METHODS

Differentiated mouse podocytes were challenged with glycated bovine serum albumin (AGE-BSA), or non-glycated control BSA (in the presence or absence of various concentrations of vitamin D3 (decostriol, 1α,25-dihydroxyvitamin D3)) or its active analog paricalcitol. Quantitative mRNA expressions were measured by real-time PCR, whereas protein expressions were determined by Western blotting followed by densitometry. Cytoplasmic and nuclear protein expression of the NFκB subunit p65 (Rel A) were determined by Western blotting. Furthermore, the ratio of phosphorylated to non-phosphorylated IκB-α was measured using specific antibodies. Electrophoretic mobility shift assays and a capture ELISA assay were used to assess NFκB transactivation in vitro. In addition, NFκB transactivation was also monitored in HEK-NFκBIA reporter cells using live cell luminometry.

RESULTS

Podocytes expressed the receptor for vitamin D. The vitamins did not suppress receptor for AGEs (RAGE) expression; instead, they rather upregulated RAGE. Although vitamin D3 and paricalcitol partly and differentially modified some of the studied parameters, both hormones inhibited AGE-BSA-induced NFκB transactivation, presumably by various mechanisms including the upregulation of IκB-α protein, keeping NFκB sequestered in an inactive state in the cytoplasm.

CONCLUSION

Vitamin D3 or its analog paricalcitol partly prevented AGE-mediated NFκB activation, an important feature of diabetic nephropathy (DN). Whether this in vitro finding is of clinical relevance to prevent/treat DN requires further studies.

Blood glucose fluctuation accelerates renal injury involved to inhibit the AKT signaling pathway in diabetic rats

Blood glucose fluctuation is associated with diabetic nephropathy. However, the mechanism by which blood glucose fluctuation accelerates renal injury is not fully understood. The aim of the present study was to assess the effects of blood glucose fluctuation on diabetic nephropathy in rats and investigate its underlying mechanism. Diabetes in the rats was induced by a high sugar, high-fat diet, and a single dose of STZ (35 mg/kg)-injected intraperitoneally. Unstable blood sugar models were induced by subcutaneous insulin injection and intravenous glucose injection alternately. Body weight, glycosylated hemoglobin A1c (HbAlc), blood urea nitrogen (BUN), serum creatinine (Scr), and Creatinine clearance (Ccr) were assessed. T-SOD activity and MDA level were measured by assay kit. Change in renal tissue ultrastructure was observed by light microscopy and electron microscopy. Phosphorylated ser/thr protein kinase (p-AKT) (phosphor-Ser473), phosphorylated glycogen synthase kinase-3 beta (p-GSK-3β) (phosphor-Ser9), Bcl-2-associated X protein (BAX), B cell lymphoma/leukemia 2 (BCL-2), and cleaved-cysteinyl aspartate-specific proteinase-3 (caspase-3) levels were detected by immunohistochemistry and Western blot. We observed that BUN and Scr were increased in diabetic rats, and Ccr was decreased. Furthermore, blood glucose fluctuations could exacerbate the Ccr changes. Renal tissue ultrastructure was also seriously injured by glucose variability in diabetic rats. In addition, glucose fluctuation increased the oxidative stress of renal tissue. Moreover, fluctuating blood glucose decreased p-AKT level and BCL-2, and increased p-GSK-3β, BAX, cleaved-caspase-3 levels, and ratio of BAX/BCL-2 in the kidneys of diabetic rats. In conclusion, these results suggest that blood glucose fluctuation accelerated renal injury is due, at least in part to its oxidative stress promoting and inhibiting the AKT signaling pathway in diabetic rats.

New Pathogenic Concepts and Therapeutic Approaches to Oxidative Stress in Chronic Kidney Disease

In chronic kidney disease inflammatory processes and stimulation of immune cells result in overproduction of free radicals. In combination with a reduced antioxidant capacity this causes oxidative stress. This review focuses on current pathogenic concepts of oxidative stress for the decline of kidney function and development of cardiovascular complications. We discuss the impact of mitochondrial alterations and dysfunction, a pathogenic role for hyperuricemia, and disturbances of vitamin D metabolism and signal transduction. Recent antioxidant therapy options including the use of vitamin D and pharmacologic therapies for hyperuricemia are discussed. Finally, we review some new therapy options in diabetic nephropathy including antidiabetic agents (noninsulin dependent), plant antioxidants, and food components as alternative antioxidant therapies.

The differential effects of 1,25-dihydroxyvitamin D3 on Salmonella-induced interleukin-8 and human beta-defensin-2 in intestinal epithelial cells

Salmonellosis or Salmonella, one of the most common food-borne diseases, remains a major public health problem worldwide. Intestinal epithelial cells (IECs) play an essential role in the mucosal innate immunity of the host to defend against the invasion of Salmonella by interleukin (IL)-8 and human β-defensin-2 (hBD-2). Accumulated research has unravelled important roles of vitamin D in the regulation of innate immunity. Therefore, we investigated the effects of 1,25-dihydroxyvitamin D3 (1,25D3) on Salmonella-induced innate immunity in IECs. We demonstrate that pretreatment of 1,25D3 results in suppression of Salmonella-induced IL-8 but enhancement of hBD-2, either protein secretion and mRNA expression, in IECs. Furthermore, 1,25D3 enhanced Salmonella-induced membranous recruitment of nucleotide oligomerization domain (NOD2) and its mRNA expression and activation of protein kinase B (Akt), a downstream effector of phosphoinositide 3-kinase (PI3K). Inhibition of the PI3K/Akt signal counteracted the suppressive effect of 1,25D3 on Salmonella-induced IL-8 expression, while knock-down of NOD2 by siRNA diminished the enhanced hBD-2 expression. These data suggest differential regulation of 1,25D3 on Salmonella-induced IL-8 and hBD-2 expression in IECs via PI3K/Akt signal and NOD2 protein expression, respectively. Active vitamin D-enhanced anti-microbial peptide in Salmonella-infected IECs protected the host against infection, while modulation of proinflammatory responses by active vitamin D prevented the host from the detrimental effects of overwhelming inflammation. Thus, active vitamin D-induced innate immunity in IECs enhances the host's protective mechanism, which may provide an alternative therapy for invasive Salmonella infection.

Wnt/β-catenin signalling and podocyte dysfunction in proteinuric kidney disease

Podocytes are unique, highly specialized, terminally differentiated cells that are integral components of the kidney glomerular filtration barrier. Podocytes are vulnerable to a variety of injuries and in response they undergo a series of changes ranging from hypertrophy, autophagy, dedifferentiation, mesenchymal transition and detachment to apoptosis, depending on the nature and extent of the insult. Emerging evidence indicates that Wnt/β-catenin signalling has a central role in mediating podocyte dysfunction and proteinuria. Wnts are induced and β-catenin is activated in podocytes in various proteinuric kidney diseases. Genetic or pharmacologic activation of β-catenin is sufficient to impair podocyte integrity and causes proteinuria in healthy mice, whereas podocyte-specific ablation of β-catenin protects against proteinuria after kidney injury. Mechanistically, Wnt/β-catenin controls the expression of several key mediators implicated in podocytopathies, including Snail1, the renin-angiotensin system and matrix metalloproteinase 7. Wnt/β-catenin also negatively regulates Wilms tumour protein, a crucial transcription factor that safeguards podocyte integrity. Targeted inhibition of Wnt/β-catenin signalling preserves podocyte integrity and ameliorates proteinuria in animal models. This Review highlights advances in our understanding of the pathomechanisms of Wnt/β-catenin signalling in mediating podocyte injury, and describes the therapeutic potential of targeting this pathway for the treatment of proteinuric kidney disease.

1,25-Dihydroxyvitamin D₃ Promotes High Glucose-Induced M1 Macrophage Switching to M2 via the VDR-PPARγ Signaling Pathway

Macrophages, especially their activation state, are closely related to the progression of diabetic nephropathy. Classically activated macrophages (M1) are proinflammatory effectors, while alternatively activated macrophages (M2) exhibit anti-inflammatory properties. 1,25-Dihydroxyvitamin D₃ has renoprotective roles that extend beyond the regulation of mineral metabolism, and PPARγ, a nuclear receptor, is essential for macrophage polarization. The present study investigates the effect of 1,25-dihydroxyvitamin D₃ on macrophage activation state and its underlying mechanism in RAW264.7 cells. We find that, under high glucose conditions, RAW264.7 macrophages tend to switch to the M1 phenotype, expressing higher iNOS and proinflammatory cytokines, including TNFα and IL-12. While 1,25-dihydroxyvitamin D₃ significantly inhibited M1 activation, it enhanced M2 macrophage activation; namely, it upregulated the expression of MR, Arg-1, and the anti-inflammatory cytokine IL-10 but downregulated the M1 markers. However, the above effects of 1,25-dihydroxyvitamin D₃ were abolished when the expression of VDR and PPARγ was inhibited by VDR siRNA and a PPARγ antagonist. In addition, PPARγ was also decreased upon treatment with VDR siRNA. The above results demonstrate that active vitamin D promoted M1 phenotype switching to M2 via the VDR-PPARγ pathway.