Autophagy: emerging therapeutic target for diabetic nephropathy

Deletion of IRE1α in podocytes exacerbates diabetic nephropathy in mice

Protein misfolding in the endoplasmic reticulum (ER) of podocytes contributes to the pathogenesis of glomerular diseases. Protein misfolding activates the unfolded protein response (UPR), a compensatory signaling network. We address the role of the UPR and the UPR transducer, inositol-requiring enzyme 1α (IRE1α), in streptozotocin-induced diabetic nephropathy in mice. Diabetes caused progressive albuminuria in control mice that was exacerbated in podocyte-specific IRE1α knockout (KO) mice. Compared to diabetic controls, diabetic IRE1α KO mice showed reductions in podocyte number and synaptopodin. Glomerular ultrastructure was altered only in diabetic IRE1α KO mice; the major changes included widening of podocyte foot processes and glomerular basement membrane. Activation of the UPR and autophagy was evident in diabetic control, but not diabetic IRE1α KO mice. Analysis of human glomerular gene expression in the JuCKD-Glom database demonstrated induction of genes associated with the ER, UPR and autophagy in diabetic nephropathy. Thus, mice with podocyte-specific deletion of IRE1α demonstrate more severe diabetic nephropathy and attenuation of the glomerular UPR and autophagy, implying a protective effect of IRE1α. These results are consistent with data in human diabetic nephropathy and highlight the potential for therapeutically targeting these pathways.

Crosstalk between autophagy and insulin resistance: evidence from different tissues

Insulin is a critical hormone that promotes energy storage in various tissues, as well as anabolic functions. Insulin resistance significantly reduces these responses, resulting in pathological conditions, such as obesity and type 2 diabetes mellitus (T2DM). The management of insulin resistance requires better knowledge of its pathophysiological mechanisms to prevent secondary complications, such as cardiovascular diseases (CVDs). Recent evidence regarding the etiological mechanisms behind insulin resistance emphasizes the role of energy imbalance and neurohormonal dysregulation, both of which are closely regulated by autophagy. Autophagy is a conserved process that maintains homeostasis in cells. Accordingly, autophagy abnormalities have been linked to a variety of metabolic disorders, including insulin resistance, T2DM, obesity, and CVDs. Thus, there may be a link between autophagy and insulin resistance. Therefore, the interaction between autophagy and insulin function will be examined in this review, particularly in insulin-responsive tissues, such as adipose tissue, liver, and skeletal muscle.

Actin cytoskeletal reorganization is involved in hyperosmotic stress-induced autophagy in tubular epithelial cells

Tubular epithelial cells are routinely exposed to severe changes in osmolarity. Although the autophagic activity of cells is an indispensable process to maintain cellular homeostasis and respond to stressors, the effect of hyperosmotic stress on autophagic activity in tubular epithelial cells remains unknown. The aim of this study was to determine the effect of hyperosmotic stress on autophagy in rat kidney tubular epithelial cells focusing on the role of actin and microtubule cytoskeletons. Normal rat kidney (NRK)-52E cells exposed to mannitol-induced hyperosmotic stress. As a result, NRK-52E cells showed elevated protein levels of the autophagosome marker LC3-II, indicating enhancement of the autophagic flux. Hyperosmotic stress also transiently decreased cell volume and caused the reorganization of actin and microtubule cytoskeletal structures in NRK-52E cells. The inhibition of the actin cytoskeleton reorganization by cytochalasin D impaired the increase in the levels of LC3-II; however, disassembly of the microtubules following treatment with nocodazole did not affect the increase. These results indicate that hyperosmotic stress can induce autophagy mediated by the reorganization of the actin cytoskeleton in tubular epithelial cells.

Role of renal tubular programed cell death in diabetic kidney disease

The pathogenic mechanism of diabetic kidney disease (DKD) is involved in various functions; however, its inadequate characterisation limits the availability of effective treatments. Tubular damage is closely correlated with renal function and is thought to be the main contributor to the injury observed in early DKD. Programed cell death (PCD) occurs during the biological development of the living body. Accumulating evidence has clarified the fundamental role of abnormalities in tubular PCD during DKD pathogenesis. Among PCD types, classical apoptosis, autophagic cell death, and pyroptosis are the most studied and will be the focus of this review. Our review aims to elucidate the current knowledge of the mechanism of DKD and the potential therapeutic potential of drugs targeting tubular PCD pathways in DKD.

Tangshenning Attenuates High Glucose-Induced Podocyte Injury via Restoring Autophagy Activity through Inhibiting mTORC1 Activation

Diabetic nephropathy (DN) is a microvascular complication of diabetes mellitus (DM) and the most common cause of death in diabetic patients. DN progression is associated with podocyte damage due to reduced autophagy caused by mTORC1 activation. Tangshenning (TSN) has been shown to reduce proteinuria, protect renal function, and reduce podocyte damage. Still, the effect of TSN on the autophagic activity of podocytes remains unclear. Herein, in vitro experiments using a high glucose-induced podocyte injury model were performed. Results showed that TSN treatment enhanced the weakened nephrin expression and autophagic activity of podocytes and inhibited the mTORC1 pathway (p-mTOR, mTOR, p-p70S6K, p70S6K, ULK1, and 4EBP1) under high glucose conditions. Furthermore, the mTORC1 activator (siRNA-TSC2) partially inhibited the above beneficial effects of TSN, suggesting that mTORC1 was the target of TSN to regulate autophagy. In summary, TSN reduces podocyte damage induced by high glucose via inhibiting mTORC1 pathway and downstream targets and restoring podocyte autophagy.

Alteration of autophagy-related protein 5 (ATG5) levels and Atg5 gene expression in diabetes mellitus with and without complications

BACKGROUND

Autophagy is a catabolic mechanism that involves lysosomal-dependent degradation of unnecessary intracellular components and responsible for normal cellular homeostasis. Autophagy pathway and its key participant ATG5/LC3 are associated with several pathologies such as diabetes mellitus and its complications.

METHODS

Levels and expression of autophagy key components ATG5 and LC3B were analyzed in both human model and murine tissues. One hundred and twenty human subjects were divided into four groups: Healthy (control), diabetes mellitus without complications, diabetic nephropathy, and diabetic retinopathy. Additionally, we used kidneys from WT healthy and diabetic nephropathy mice. Lysate derived from human peripheral blood mononuclear cells and murine renal cortex lysates were subjected to western blot and immunohistochemical analysis.

RESULTS

Western blot and immunohistochemical analysis demonstrate that ATG5 protein levels were significantly decreased in diabetes mellitus, diabetic nephropathy (DN), and diabetic retinopathy patients versus healthy controls and in DN mice compared to healthy mice (0.65 ± 0.04; 1.15 ± 0.13 A.U. units, respectively). Quantification of staining area (%) of ATG5 mice tissue expression also decreased in DN versus healthy mice (4.42 ± 1.08%; 10.87 ± 1.01%, respectively).

LC3B LEVELS AND EXPRESSION

Significant reduction in peripheral blood mononuclear cells in diabetic patients (with or without complications) vs. healthy controls. Renal LC3B levels were lower in DN versus healthy mice (0.36 ± 0.03; 0.68 ± 0.07 A.U. units). Renal LC3B staining quantification revealed significant reduction in DN versus healthy mice (1.7 ± 0.23%; 8.56 ± 1.7%).

CONCLUSION

We conclude that ATG5, as well as LC3B, are down regulated in diabetic patients with or without complications. This diminution contributes to deficiencies in the autophagy process.

Endoplasmic Reticulum Stress in Diabetic Nephrology: Regulation, Pathological Role, and Therapeutic Potential

Recent progress has been made in understanding the roles and mechanisms of endoplasmic reticulum (ER) stress in the development and pathogenesis of diabetic nephropathy (DN). Hyperglycemia induces ER stress and apoptosis in renal cells. The induction of ER stress can be cytoprotective or cytotoxic. Experimental treatment of animals with ER stress inhibitors alleviated renal damage. Considering these findings, the normalization of ER stress by pharmacological agents is a promising approach to prevent or arrest DN progression. The current article reviews the mechanisms, roles, and therapeutic aspects of these findings.

The Role of Non-coding RNAs in Diabetic Nephropathy-Related Oxidative Stress

Diabetic nephropathy (DN) is one of the main complications of diabetes and the main cause of diabetic end-stage renal disease, which is often fatal. DN is usually characterized by progressive renal interstitial fibrosis, which is closely related to the excessive accumulation of extracellular matrix and oxidative stress. Non-coding RNAs (ncRNAs) are RNA molecules expressed in eukaryotic cells that are not translated into proteins. They are widely involved in the regulation of biological processes, such as, chromatin remodeling, transcription, post-transcriptional modification, and signal transduction. Recent studies have shown that ncRNAs play an important role in the occurrence and development of DN and participate in the regulation of oxidative stress in DN. This review clarifies the functions and mechanisms of ncRNAs in DN-related oxidative stress, providing valuable insights into the prevention, early diagnosis, and molecular therapeutic targets of DN.

Yiqi Jiedu Huayu Decoction Alleviates Renal Injury in Rats With Diabetic Nephropathy by Promoting Autophagy

Diabetic nephropathy (DN), a common microvascular complication of diabetes, is one of the main causes of end-stage renal failure (ESRD) and imposes a heavy medical burden on the world. Yiqi Jiedu Huayu decoction (YJHD) is a traditional Chinese medicine formula, which has been widely used in the treatment of DN and has achieved stable and reliable therapeutic effects. However, the mechanism of YJHD in the treatment of DN remains unclear. This study aimed to investigate the mechanism of YJHD in the treatment of DN. Sprague-Dawley rats were randomly divided into a normal control group, a diabetic group, an irbesartan group, and three groups receiving different doses of YJHD. Animal models were constructed using streptozotocin and then treated with YJHD for 12 consecutive weeks. Blood and urine samples were collected during this period, and metabolic and renal function was assessed. Pathological kidney injury was evaluated according to the kidney appearance, hematoxylin-eosin staining, Masson staining, periodic-acid Schiff staining, periodic-acid Schiff methenamine staining, and transmission electron microscopy. The expression levels of proteins and genes were detected by immunohistochemistry, western blotting, and real-time qPCR. Our results indicate that YJHD can effectively improve renal function and alleviate renal pathological injury, including mesangial matrix hyperplasia, basement membrane thickening, and fibrosis. In addition, YJHD exhibited podocyte protection by alleviating podocyte depletion and morphological damage, which may be key in improving renal function and reducing renal fibrosis. Further study revealed that YJHD upregulated the expression of the autophagy-related proteins LC3II and Beclin-1 while downregulating p62 expression, suggesting that YJHD can promote autophagy. In addition, we evaluated the activity of the mTOR pathway, the major signaling pathway regulating the level of autophagy, and the upstream PI3K/Akt and AMPK pathways. YJHD activated the AMPK pathway while inhibiting the PI3K/Akt and mTOR pathways, which may be crucial to its promotion of autophagy. In conclusion, our study shows that YJHD further inhibits the mTOR pathway and promotes autophagy by regulating the activity of the PI3K/Akt and AMPK pathways, thereby improving podocyte injury, protecting renal function, and reducing renal fibrosis. This study provides support for the application of and further research into YJHD.

Autophagy in diabetic nephropathy: a review

Diabetes mellitus (DM) is the leading cause of end stage renal disease. 40% of the patients worldwide will require replacement therapy after 20 years of DM worldwide. Early-stage diabetic nephropathy is characterized by hyperfiltration related to hypeglycemia-induced afferent artery vasodilatation with micro-and macroalbuminuria. Later on, proteinuria with arterial hypertension may appear, culminating in glomerular filtration rate (GFR) decline and end stage renal disease. Forty percent of diabetic patients develop microvascular and macrovascular complications, with increased risk among patients with genetic predisposition, such as Haptoglobin 2-2 phenotype. The most frequent complications in the daily clinical practice are diabetic kidney disease, diabetic retinopathy and vascular disease, such as coronary artery disease and stroke. Various pathways are involved in the pathogenesis of diabetic kidney disease. Chronic systemic inflammation and the inflammatory response, such as increased circulating cytokines (Interleukins), have been recognized as main players in the development and progression of diabetic kidney disease. DM is also associated with increased oxidative stress, and alterations in carbohydrate, lipid and protein metabolism. Overexpression of the renin-angiotensin-aldosterone system (RAAS) in the kidney, the vitamin D-Vitamin D receptor-klotho axis, and autophagy. Differences in the ATG5 protein levels or ATG5 gene expression involved in the autophagy process have been associated with diabetic complications such as diabetic kidney disease. Under normal blood glucose level, autophagy is an important protective mechanism in renal epithelial cells, including podocytes, proximal tubular, mesangial and endothelial cells. Down regulation of the autophagic mechanism, as in hyperglycemic condition, can contribute to the development and progression of diabetic kidney disease.

Paecilomyces cicadae-fermented Radix astragali activates podocyte autophagy by attenuating PI3K/AKT/mTOR pathways to protect against diabetic nephropathy in mice

Radix astragali, a medicinal material for tonifying Chinese Qi, has widely been used for the treatment of Kidney disease in China and East Asia, especially in reducing the apoptosis of glomerular podocytes. Paecilomyces Cicadidae is a medicinal and edible fungus. In recent years, the application of traditional Chinese medicine (TCM) in solid-state fermentation of edible and medicinal fungi has become a hot issue. Fermentation is a special method to change the properties of TCM. Therefore, the potential roles and molecular mechanisms on podocytes of solid-state fermentation products of Radix astragali and Paecilomyces cicadidae (RPF) in diabetic nephropathy (DN) were studied. In vivo, the effect of RPF and Radix astragali on DN in mice was evaluated by detecting the biochemical indexes of blood and urine, renal function and podocyte integrity. In vitro, the expression of podocyte marker protein, autophagy marker protein and PI3K/AKT/mTOR signaling pathway protein were detected by Western blotting using a high glucose-induced podocyte injury model. The results showed that RPF had a significant alleviative effect on DN mice. RPF can significantly reduce urine protein, serum creatinine, and blood nitrogen urea in DN mice. Morphological analysis showed that RPF could improve kidney structure of DN and reduce the apoptosis of podocytes, and the effect was better than Radix astragali. In vitro results indicated that RPF could enhance autophagy and protect podocytes by inhibiting the PI3K/AKT/mTOR signaling pathway. In summary, RPF has better effect on delaying the development of DN than Radix astragali. RPF enhances autophagy in podocytes and delays DN probably by inhibiting the PI3K/AKT/mTOR signaling pathway.

Liver X receptor activation induces podocyte injury via inhibiting autophagic activity

Podocyte injury plays a key role in the occurrence and development of kidney diseases. Decreased autophagic activity in podocyte is closely related to its injury and the occurrence of proteinuria. Liver X receptors (LXRs), as metabolic nuclear receptors, participate in multiple pathophysiological processes and express in several tissues, including podocytes. Although the functional roles of LXRs in the liver, adipose tissue and intestine are well established; however, the effect of LXRs on podocytes function remains unclear. In this study, we used mouse podocytes cell line to investigate the effects of LXR activation on podocytes autophagy level and related signaling pathway by performing Western blotting, RT-PCR, GFP-mRFP-LC3 transfection, and immunofluorescence staining. Then, we tested this effect in STZ-induced diabetic mice. Transmission electron microscopy and immunohistochemistry were employed to explore the effects of LXR activation on podocytes function and autophagic activity. We found that LXR activation could inhibit autophagic flux through blocking the formation of autophagosome in podocytes in vitro which was possibly achieved by affecting AMPK, mTOR, and SIRT1 signaling pathways. Furthermore, LXR activation in vivo induced autophagy suppression in glomeruli, leading to aggravated podocyte injury. In summary, our findings indicated that activation of LXRs induced autophagy suppression, which in turn contributed to the podocyte injury.

Role of autophagy in Puromycin Aminonucleoside-induced podocyte apoptosis

Objective: The aim of our study is to investigate the relationship between podocyte autophagy and apoptosis induced by Puromycin Aminonucleoside (PAN) and to clarify its mechanism.Methods: Podocytes were cultured in vitro. The apoptosis rates of each group were detected using flow cytometry. The expression of LC3-II protein and changes in distribution were detected through laser scanning confocal microscope, and the western blot protocol was employed for detection of protein expression of LC3-II. The autophagosomes were detected by transmission electron microscopy.Results: In this study, We found that autophagosome increased followed by apoptosis after podocyte injury. Furthermore, we conformed that the activation of autophagy could inhibit the apoptosis to alleviate the injury of podocyte at an early stage.Conclusions: Autophagy occurred earlier before apoptosis and autophagy mediated podocyte apoptosis induced by PAN. These findings indicate that autophagy may become a novel therapeutic target for the treatment of podocyte injury and proteinuria in the future.

Connexin 43‑autophagy loop in the podocyte injury of diabetic nephropathy

The reduction of podocyte injury is a key strategy in controlling proteinuria, which is the main early clinical manifestation of diabetic nephropathy (DN). Impaired autophagic flux is the primary mechanism responsible for podocyte injury in DN. The aim of the present study was to elucidate the effect of connexin 43 (Cx43) on impaired autophagic flux in podocyte injury and to explore its molecular mechanism of action in DN. Sprague‑Dawley rats were administered streptozocin (STZ) to construct a DN animal model. Podocytes were incubated in media containing either buffer or high glucose (HG; 30 mM) for variable time periods. The podocytes were then examined and the mechanism of injury was investigated using an Annexin V/PI assay, immunofluorescence staining, western blotting, and RNA interference. In vivo, STZ‑induced DN rats with or without Cx43 knockdown were established to observe the role of Cx43 in autophagic flux and podocyte injury. We observed that HG induced podocyte injury, accompanied by increases in Cx43 expression and impaired autophagic flux, as evidenced by the accumulation of LC3II/LC3I and p62. Interestingly, the silencing of Cx43 expression ameliorated autophagic flux impairment and reduced podocyte injury via suppression of the mammalian target of rapamycin pathway. Furthermore, impaired autophagic flux also blocked the degradation of Cx43. In vitro studies indicated that higher numbers of Annexin V/PI‑positive podocytes, impaired autophagic flux and increased Cx43 expression were observed in HG‑induced podocyte injury relative to the control group. The pathogenic effect of Cx43 on impaired autophagic flux and podocyte injury was also confirmed by Cx43 knockdown. The present study provided preliminary evidence indicating that the interdependence of Cx43 and impaired autophagic flux represents a novel mechanism of podocyte injury in DN. Hence, the Cx43‑autophagy loop is a potentially relevant therapeutic target for the treatment of DN.

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.

Dilemmas and challenges in apolipoprotein L1 nephropathy research

PURPOSE OF REVIEW

The purpose of this mini-review is to highlight some unresolved questions and controversies in the evolving story of apolipoprotein L1 (APOL1) nephropathy.

RECENT FINDINGS

We highlight studies that introduce complexity in unraveling the mechanisms whereby APOL1 risk variant alleles cause disease. These include studies which support a possible protective role for the APOL1 GO nonrisk ancestral allele, and studies which explore the initiating events that may trigger other downstream pathways mediating APOL1 cellular injury. We also review studies that reconcile the perplexing findings regarding APOL1 anionic or cationic conductance, and pH dependency, and also studies that attempt to characterize the 3-dimensional structure of APOL1 C-terminal in APOL1 variants, as well as that of the serum resistance-associated protein. We also attempt to convey new insights from in-vivo and in-vitro models, including studies that do not support the differential toxicity of APOL1 renal risk variants and recapitulate the clinical variability of individuals at genotypic risk.

SUMMARY

Along with major progress that had been achieved in the field of APOL1 nephropathy, controversies and enigmatic issues persist. It remains to be determined which of the pathways which have been demonstrated to mediate cell injury by ectopically expressed APOL1 risk variants in cellular and organismal models are relevant to human disease and can pave the way to potential therapy.

PGRN acts as a novel regulator of mitochondrial homeostasis by facilitating mitophagy and mitochondrial biogenesis to prevent podocyte injury in diabetic nephropathy

Mitochondrial dysfunction is considered as a key mediator in the pathogenesis of diabetic nephropathy (DN). Therapeutic strategies targeting mitochondrial dysfunction hold considerable promise for the treatment of DN. In this study, we investigated the role of progranulin (PGRN), a secreted glycoprotein, in mediating mitochondrial homeostasis and its therapeutic potential in DN. We found that the level of PGRN was significantly reduced in the kidney from STZ-induced diabetic mice and patients with biopsy-proven DN compared with healthy controls. In DN model, PGRN-deficient mice aggravated podocyte injury and proteinuria versus wild-type mice. Functionally, PGRN deficiency exacerbated mitochondrial damage and dysfunction in podocytes from diabetic mice. In vitro, treatment with recombinant human PGRN (rPGRN) attenuated high glucose-induced mitochondrial dysfunction in podocytes accompanied by enhanced mitochondrial biogenesis and mitophagy. Inhibition of mitophagy disturbed the protective effects of PGRN in high glucose-induced podocytotoxicity. Mechanistically, we demonstrated that PGRN maintained mitochondrial homeostasis via PGRN-Sirt1-PGC-1α/FoxO1 signaling-mediated mitochondrial biogenesis and mitophagy. Finally, we provided direct evidence for therapeutic potential of PGRN in mice with DN. This study provides new insights into the novel role of PGRN in maintaining mitochondrial homeostasis, suggesting that PGRN may be an innovative therapeutic strategy for treating patients with DN.

Mitochondrial dysfunction in diabetic kidney disease

Although diabetic kidney disease (DKD) is the most common cause of end-stage kidney disease worldwide, the pathogenic mechanisms are poorly understood. There is increasing evidence that mitochondrial dysfunction contributes to the development and progression of DKD. Because the kidney is the organ with the second highest oxygen consumption in our body, it is distinctly sensitive to mitochondrial dysfunction. Mitochondrial dysfunction contributes to the progression of chronic kidney disease irrespective of underlying cause. More importantly, high plasma glucose directly damages renal tubular cells, resulting in a wide range of metabolic and cellular dysfunction. Overproduction of reactive oxygen species (ROS), activation of apoptotic pathway, and defective mitophagy are interlinked mechanisms that play pivotal roles in the progression of DKD. Although renal tubular cells have the highest mitochondrial content, podocytes, mesangial cells, and glomerular endothelial cells may all be affected by diabetes-induced mitochondrial injury. Urinary mitochondrial DNA (mtDNA) is readily detectable and may serve as a marker of mitochondrial damage in DKD. Unfortunately, pharmacologic modulation of mitochondrial dysfunction for the treatment of DKD is still in its infancy. Nonetheless, understanding the pathobiology of mitochondrial dysfunction in DKD would facilitate the development of novel therapeutic strategies.

STAT3 phosphorylation mediates high glucose-impaired cell autophagy in an HDAC1-dependent and -independent manner in Schwann cells of diabetic peripheral neuropathy

Schwann cells are the main supportive cells of the peripheral nerves. Schwann cells suffer inhibition of autophagy under hyperglycemia treatment in diabetic peripheral neuropathy (DPN). However, the exact mechanism is still not fully elucidated. We first observed the decrease of autophagy markers (LC3-II/LC3-I, P62) in the sciatic nerves of diabetic mice vs. normal mice, accompanied with the loss of myelinated nerve fibers and abnormal myelin sheath. In line with this, LC3-II/LC3-I and P62 were also significantly reduced in high glucose-treated rat Schwann cell 96 (RSC96) cells compared with normal glucose-treated cells. Furthermore, we found that trichostatin A [an inhibitor of histone deacetylase (HDAC)] evidently improved LC3-II/LC3-I in high glucose-treated RSC96 cells, without an effect on P62 expression. Again, HDAC1 and HDAC5 were revealed to be increased in RSC96 cells stimulated with high glucose. Inhibition of HDAC1 but not HDAC5 by small hairpin RNA vector enhanced LC3-II/LC3-I in high glucose-cultured RSC96 cells. In addition, LC3-II conversion regulators [autophagy-related protein (Atg)3, Atg5, and Atg7] were detected in high glucose-treated and HDAC1-knockdown RSC96 cells, and Atg3 was proven to be the key target of HDAC1. The presuppression of Atg3 offset the improvement of LC3-II/LC3-I resulting from HDAC1 inhibition in high glucose-treated RSC96 cells. The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway was activated in RSC96 cells treated with high glucose, which was indicated by increased STAT3 phosphorylation. Blocking STAT3 phosphorylation by chemical inhibitor AG490 induced HDAC1 down-regulation followed by increases in Atg3 and LC3-II/LC3-I. Interestingly, we also found that AG490 treatment enhanced P62 expression in high glucose-stimulated RSC96 cells. Taken together, our findings demonstrate that hyperglycemia inhibits LC3-II/LC3-I in an HDAC1-Atg3-dependent manner and decreases P62 expression in an HDAC-independent manner via the JAK-STAT3 signaling pathway in the Schwann cells of DPN.-Du, W., Wang, N., Li, F. Jia, K., An, J., Liu, Y., Wang, Y., Zhu, L., Zhao, S. Hao, J. STAT3 phosphorylation mediates high glucose-impaired cell autophagy in an HDAC1-dependent and -independent manner in Schwann cells of diabetic peripheral neuropathy.

Role of sirtuin-1 in diabetic nephropathy

Diabetic nephropathy (DN) is a research priority for scientists around the world because of its high prevalence and poor prognosis. Although several mechanisms have been shown to be involved in its pathogenesis and many useful drugs have been developed, the management of DN remains challenging. Increasing amounts of evidence show that silent information regulator 2 homolog 1 (sirtuin-1), a nicotinamide adenine dinucleotide (NAD+)–dependent protein deacetylase, plays a crucial role in the pathogenesis and development of DN. Clinical data show that gene polymorphisms of sirtuin-1 affect patient vulnerability to DN. In addition, upregulation of sirtuin-1 attenuates DN in various experimental models of diabetes and in renal cells, including podocytes, mesangial cells, and renal proximal tubular cells, incubated with high concentrations of glucose or advanced glycation end products. Mechanistically, sirtuin-1 has its renoprotective effects by modulating metabolic homeostasis and autophagy, resisting apoptosis and oxidative stress, and inhibiting inflammation through deacetylation of histones and the transcription factors p53, forkhead box group O, nuclear factor-κB, hypoxia-inducible factor-1α, and others. Furthermore, some microRNAs have been implicated in the progression of DN because they target sirtuin-1 mRNA. Several synthetic drugs and natural compounds have been identified that upregulate the expression and activity of sirtuin-1, which protects against DN. The present review will summarize advances in knowledge regarding the role of sirtuin-1 in the pathogenesis of DN. The available evidence implies that sirtuin-1 has great potential as a clinical target for the prevention and treatment of diabetes.

Supplementation of Abelmoschus manihot Ameliorates Diabetic Nephropathy and Hepatic Steatosis by Activating Autophagy in Mice

Diabetic nephropathy (DN) is a diabetic complication marked by albuminuria and a decline of the glomerular filtration rate. Diabetic kidneys are defective in the autophagy process and mitochondrial function and their enhancement of activity alleviates the pathology. In this paper, we developed a mouse model of DN by a combined treatment of a high-fat diet and streptozotocin after unilateral nephrectomy and supplementation with flower or leaf extracts of Abelmoschus manihot (AM) were tested. The preventive effects of the extracts on DN pathology and changes on autophagy and mitochondrial proteins were investigated. DN mice showed a significant increase in fasting blood glucose, plasma creatinine, blood urea nitrogen, and urinary albumin levels. Periodic acid–Schiff and Sirius red staining of the diabetic kidney presented a significant change in glomerular and tubular structures that was associated with podocyte loss and fibrotic protein accumulation. These changes were attenuated by AM extract treatment in DN mice. In addition, hepatic injury, proinflammatory cytokines, and lipid accumulation were decreased by AM extracts in DN mice. As a protective mechanism, AM extracts significantly increased the expression of proteins by regulating autophagy and mitochondrial dynamics, which potentially prevented the kidney and liver from accumulating pathogenic proteins and dysfunctional mitochondria, which alleviated the progression of DN.

Energy restriction in renal protection

Energy restriction (ER) has been widely studied as a novel intervention, and its ability to prolong life has been fully demonstrated. For example, ER can significantly extend the lifespans of model flies, worms, rodents and other mammals. The role of ER in renal protection has also been elucidated. In preclinical studies, adjusting total energy intake or consumption of specific nutrients has prophylactic or therapeutic effects on ageing-related kidney disease and acute and chronic kidney injury. Amino acid restriction has gradually attracted attention. ER mimetics have also been studied in depth. The protective mechanisms of ER and ER mimetics for renal injury include increasing AMP-activated protein kinase and sirtuin type 1 (Sirt1) levels and autophagy and reducing mammalian target of rapamycin, inflammation and oxidative stress. However, the renal protective effect of ER has mostly been investigated in rodent models, and the role of ER in patients cannot be determined due to the lack of large randomised controlled trials. To protect the kidney, the mechanism of ER must be thoroughly researched, and more accurate diet or drug interventions need to be identified.

APOL1: The Balance Imposed by Infection, Selection, and Kidney Disease

Chronic kidney disease (CKD) affects millions of people and constitutes a major health and financial burden worldwide. People of African descent are at an increased risk of developing kidney disease, which is mostly explained by two variants in the Apolipoprotein L1 (APOL1) gene that are found only in people of west African origin. It is hypothesized that these variants were genetically selected due to the protection they afford against African sleeping sickness, caused by the parasite Trypanosoma brucei. Targeting mutant APOL1 could have substantial therapeutic potential for treating kidney disease. In this review, we will describe the intriguing interplay between microbiology, genetics, and kidney disease as revealed in APOL1-associated kidney disease, discuss APOL1-induced cytotoxicity and its therapeutic implications.

High glucose induces apoptosis via upregulation of Bim expression in proximal tubule epithelial cells

Diabetic nephropathy is the primary cause of end-stage renal disease. Apoptosis of tubule epithelial cells is a major feature of diabetic nephropathy. The mechanisms of high glucose (HG) induced apoptosis are not fully understood. Here we demonstrated that, HG induced apoptosis via upregulating the expression of proapoptotic Bcl-2 homology domain 3 (BH3)-only protein Bim protein, but not bring a significant change in the baseline level of autophagy in HK2 cells. The increase of Bim expression was caused by the ugregulation of transcription factors, FOXO1 and FOXO3a. Bim expression initiates BAX/BAK-mediated mitochondria-dependent apoptosis. Silence of Bim by siRNA in HK2 cells prevented HG-induced apoptosis and also sensitized HK2 cells to autophagy during HG treatment. The autophagy inhibitor 3-MA increased the injury in Bim knockdown HK2 cells by retriggering apoptosis. The above results suggest a Bim-independent apoptosis pathway in HK2 cells, which normally could be inhibited by autophagy. Overall, our results indicate that HG induces apoptosis via up-regulation of Bim expression in proximal tubule epithelial cells.

Acute Kidney Injury and Progression of Diabetic Kidney Disease

Diabetic kidney disease, commonly termed diabetic nephropathy (DN), is the most common cause of end-stage kidney disease (ESKD) worldwide. The characteristic histopathology of DN includes glomerular basement membrane thickening, mesangial expansion, nodular glomerular sclerosis, and tubulointerstitial fibrosis. Diabetes is associated with a number of metabolic derangements, such as reactive oxygen species overproduction, hypoxic state, mitochondrial dysfunction, and inflammation. In the past few decades, our knowledge of DN has advanced considerably although much needs to be learned. The traditional paradigm of glomerulus-centered pathophysiology has expanded to the tubule-interstitium, the immune response and inflammation. Biomarkers of proximal tubule injury have been shown to correlate with DN progression, independent of traditional glomerular injury biomarkers such as albuminuria. In this review, we summarize mechanisms of increased susceptibility to acute kidney injury in diabetes mellitus and the roles played by many kidney cell types to facilitate maladaptive responses leading to chronic and end-stage kidney disease.

Autophagy in diabetic kidney disease: regulation, pathological role and therapeutic potential

Diabetic kidney disease, a leading cause of end-stage renal disease, has become a serious public health problem worldwide and lacks effective therapies. Autophagy is a highly conserved lysosomal degradation pathway that removes protein aggregates and damaged organelles to maintain cellular homeostasis. As important stress-responsive machinery, autophagy is involved in the pathogenesis of various diseases. Emerging evidence has suggested that dysregulated autophagy may contribute to both glomerular and tubulointerstitial pathologies in kidneys under diabetic conditions. This review summarizes the recent findings regarding the role of autophagy in the pathogenesis of diabetic kidney disease and highlights the regulation of autophagy by the nutrient-sensing pathways and intracellular stress signaling in this disease. The advances in our understanding of autophagy in diabetic kidney disease will facilitate the discovery of a new therapeutic target for the prevention and treatment of this life-threatening diabetes complication.

Live or Let Die: Is There any Cell Death in Podocytes?

Ultimately, the common final pathway of any glomerular disease is podocyte effacement, podocyte loss, and, eventually, glomerular scarring. There has been a long-standing debate on the underlying mechanisms for podocyte depletion, ranging from necrosis and apoptosis to detachment of viable cells from the glomerular basement membrane. However, this debate still continues because additional pathways of programmed cell death have been reported in recent years. Interestingly, viable podocytes can be isolated out of the urine of proteinuric patients easily, emphasizing the importance of podocyte detachment in glomerular diseases. In contrast, detection of apoptosis and other pathways of programmed cell death in podocytes is technically challenging. In fact, we still are lacking direct evidence showing, for example, the presence of apoptotic bodies in podocytes, leaving the question unanswered as to whether podocytes undergo mechanisms of programmed cell death. However, understanding the mechanisms leading to podocyte depletion is of particular interest because future therapeutic strategies might interfere with these to prevent glomerular scarring. In this review, we summarize our current knowledge on podocyte cell death, the different molecular pathways and experimental approaches to study these, and, finally, focus on the mechanisms that prevent the onset of programmed cell death.

APOL1 Nephropathy: A Population Genetics and Evolutionary Medicine Detective Story

Common DNA sequence variants rarely have a high-risk association with a common disease. When such associations do occur, evolutionary forces must be sought, such as in the association of apolipoprotein L1 (APOL1) gene risk variants with nondiabetic kidney diseases in populations of African ancestry. The variants originated in West Africa and provided pathogenic resistance in the heterozygous state that led to high allele frequencies owing to an adaptive evolutionary selective sweep. However, the homozygous state is disadvantageous and is associated with a markedly increased risk of a spectrum of kidney diseases encompassing hypertension-attributed kidney disease, focal segmental glomerulosclerosis, human immunodeficiency virus nephropathy, sickle cell nephropathy, and progressive lupus nephritis. This scientific success story emerged with the help of the tools developed over the past 2 decades in human genome sequencing and population genomic databases. In this introductory article to a timely issue dedicated to illuminating progress in this area, we describe this unique population genetics and evolutionary medicine detective story. We emphasize the paradox of the inheritance mode, the missing heritability, and unresolved associations, including cardiovascular risk and diabetic nephropathy. We also highlight how genetic epidemiology elucidates mechanisms and how the principles of evolution can be used to unravel conserved pathways affected by APOL1 that may lead to novel therapies. The APOL1 gene provides a compelling example of a common variant association with common forms of nondiabetic kidney disease occurring in a continental population isolate with subsequent global admixture. Scientific collaboration using multiple experimental model systems and approaches should further clarify pathomechanisms further, leading to novel therapies.

Apelin involved in progression of diabetic nephropathy by inhibiting autophagy in podocytes

Podocyte autophagy dysfunction has been reported to be responsible for the progression of diabetic nephropathy (DN), however, the factors contributed to autophagy dysfunction in type 2 diabetes are not fully understood. Among promoting factors in DN, an adipokine, apelin, had been showed to trigger podocyte dysfunction. Therefore, it is hypothesized that apelin, which is increased in plasma in type 2 diabetes, lead to podocyte apoptosis through inhibiting podocyte autophagy, which resulted in podocyte dysfunction followed by DN. KkAy mice (diabetic mice) and cultured podocytes (MPC5 cells and native podocytes) were treated with high glucose (HG) and apelin or its antagonist F13A. Renal function, podocyte autophagy, podocyte apoptosis and corresponding cell signaling pathways in podocytes were detected. The results showed that apelin aggravated the renal dysfunction and foot process injuries in kkAy mice, which is positively correlated to podocyte apoptosis and negatively correlated to podocyte autophagy. Apelin induced podocyte apoptosis and inhibited podocyte autophagy in both normal glucose and HG conditions while F13A reversed these effects. Investigations by western blot found that apelin inhibits podocyte autophagy through ERK-, Akt- and mTOR-dependent pathways. In conclusion, increased apelin concentration in plasma inhibited podocyte autophagy, which would lead to podocyte apoptosis and renal dysfunction in diabetes. These effects would contribute to the progression of DN.

Autophagy Protects against Palmitic Acid-Induced Apoptosis in Podocytes in vitro

Autophagy is a highly conserved degradation process that is involved in the clearance of proteins and damaged organelles to maintain intracellular homeostasis and cell integrity. Type 2 diabetes is often accompanied by dyslipidemia with elevated levels of free fatty acids (FFAs). Podocytes, as an important component of the filtration barrier, are susceptible to lipid disorders. The loss of podocytes causes proteinuria, which is involved in the pathogenesis of diabetic nephropathy. In the present study, we demonstrated that palmitic acid (PA) promoted autophagy in podocytes. We further found that PA increased the production of reactive oxygen species (ROS) in podocytes and that NAC (N-acetyl-cysteine), a potent antioxidant, significantly eliminated the excessive ROS and suppressed autophagy, indicating that the increased generation of ROS was associated with the palmitic acid-induced autophagy in podocytes. Moreover, we also found that PA stimulation decreased the mitochondrial membrane potential in podocytes and induced podocyte apoptosis, while the inhibition of autophagy by chloroquine (CQ) enhanced palmitic acid-induced apoptosis accompanied by increased ROS generation, and the stimulation of autophagy by rapamycin (Rap) remarkably suppressed palmitic acid-induced ROS generation and apoptosis. Taken together, these in vitro findings suggest that PA-induced autophagy in podocytes is mediated by ROS production and that autophagy plays a protective role against PA-induced podocyte apoptosis.

Repression of miR-217 protects against high glucose-induced podocyte injury and insulin resistance by restoring PTEN-mediated autophagy pathway

Podocyte damage is the initial hallmark of diabetic nephropathy (DN), leading to the increasing morbidity and mortality in diabetic patients. Recent researches have corroborated the critical roles of miRNAs in the pathological progression of DN. Here, elevation of miR-217 was verified in high glucose (HG)-stimulated podocytes. Moreover, blocking miR-217 expression antagonized HG-induced cell injury by attenuating the adverse role of HG on cell viability and inhibiting ROS levels and cell apoptosis. Simultaneously, miR-217 repression restored HG-disrupted insulin resistance by elevating glucose uptake and nephrin expression, an essential component for insulin-induced glucose uptake. Mechanism assay substantiated the defective autophagy in HG-treated podocytes, which was resumed by miR-217 cessation. Importantly, suppressing autophagy pathway with 3-MA alleviated the protective roles of miR-217 down-regulation in podocyte injury and insulin resistance. Luciferase reporter analysis confirmed that PTEN was a target of miR-217 in podocytes. Additionally, blocking PTEN expression restrained autophagy restoration in miR-217-decreased cells. Furthermore, PTEN down-regulation attenuated the beneficial role of miR-217 suppression in HG-induced injury and insulin resistance. Together, this study manifests that miR-217inhibition can protectively antagonize HG-induced podocyte damage and insulin resistance by restoring the defective autophagy pathway via targeting PTEN, representing a novel and promising therapeutic target against diabetic nephropathy.

Anti-fibrotic effects of valproic acid: role of HDAC inhibition and associated mechanisms

Tissue injuries and pathological insults produce oxidative stress, genetic and epigenetic alterations, which lead to an imbalance between pro- and anti-fibrotic molecules, and subsequent accumulation of extracellular matrix, thereby fibrosis. Various molecular pathways play a critical role in fibroblasts activation, which promotes the extracellular matrix production and accumulation. Recent reports highlighted that histone deacetylases (HDACs) are upregulated in various fibrotic disorders and play a central role in fibrosis, while HDAC inhibitors exert antifibrotic effects. Valproic acid is a first-line anti-epileptic drug and a proven HDAC inhibitor. This review provides the current research and novel insights on antifibrotic effects of valproic acid in various fibrotic conditions with an emphasis on the possible strategies for treatment of fibrosis.

Autophagy and Tubular Cell Death in the Kidney

Many common renal insults such as ischemia and toxic injury primarily target the tubular epithelial cells, especially the highly metabolically active proximal tubular segment. Tubular epithelial cells are particularly dependent on autophagy to maintain homeostasis and respond to stressors. The pattern of autophagy in the kidney has a unique spatial and chronologic signature. Recent evidence has shown that there is complex cross-talk between autophagy and various cell death pathways. This review specifically discusses the interplay between autophagy and cell death in the renal tubular epithelia. It is imperative to review this topic because recent discoveries have improved our mechanistic understanding of the autophagic process and have highlighted its broad clinical applications, making autophagy a major target for drug development.

Autophagy in renal diseases

Autophagy is the cell biology process in which cytoplasmic components are degraded in lysosomes to maintain cellular homeostasis and energy production. In the healthy kidney, autophagy plays an important role in the homeostasis and viability of renal cells such as podocytes and tubular epithelial cells and of immune cells. Recently, evidence is mounting that (dys)regulation of autophagy is implicated in the pathogenesis of various renal diseases, and might be an attractive target for new renoprotective therapies. In this review, we provide an overview of the role of autophagy in kidney physiology and kidney diseases.

Role of autophagy and histone deacetylases in diabetic nephropathy: Current status and future perspectives

The prevalence of diabetes and its complications is increasing at an alarming rate in both developed and deve1oping nations. The emerging evidences highlighted that both genetic and epigenetic mechanisms including histone modifications play a significant role in the pathogenesis of diabetic nephropathy (DN). Histone deacetylases (HDACs) and acetylation are involved in the regulation of autophagy as well as pathogenesis of DN. Both HDACs and histone acetyltransferases (HATs) play a key role in chromatin remodeling and affect the transcription of various genes involved in the cellular homeostasis, apoptosis, immunity and angiogenesis. Further, HDAC inhibitors are exert the renoprotective effects in DN and other diabetic complications. Thus, the cellular acetylation plays a crucial role in the regulation of autophagy and can be explored as a new therapeutic target for the treatment of DN. This review aimed to delineate the role of HDACs and associated molecular signaling/pathways in the regulation of autophagy with an emphasis on promising targets for the treatment of DN.

Autophagy downregulation contributes to insulin resistance mediated injury in insulin receptor knockout podocytes in vitro

It is unknown whether autophagy activity is altered in insulin resistant podocytes and whether autophagy could be a therapeutic target for diabetic nephropathy (DN). Here we used shRNA transfection to knockdown the insulin receptor (IR) gene in cultured human immortalized podocytes as an in vitro insulin resistant model. Autophagy related proteins LC3, Beclin, and p62 as well as nephrin, a podocyte injury marker, were assessed using western blot and immunofluorescence staining. Our results show that autophagy is suppressed when podocytes lose insulin sensitivity and that treatment of rapamycin, an mTOR specific inhibitor, could attenuate insulin resistance induced podocytes injury via autophagy activation. The present study deepens our understanding of the role of autophagy in the pathogenesis of DN.

The renoprotective role of autophagy activation in proximal tubular epithelial cells in diabetic nephropathy

With intensive investigations recently, autophagy is hoped to be a potential therapeutic target to prevent or alleviate diabetic nephropathy (DN). Our previous study revealed that lipotoxicity participated in epithelial-to-mesenchymal transition (EMT) of proximal tubular epithelial cells (PTECs) under diabetic conditions. Based on evidences that autophagy and lipid metabolism are closely related, we investigated autophagy under diabetic conditions and how it contributed in the lipotoxicity and EMT. In high-glucose-cultured PTECs, we found that Beclin1 and LC3-II were elevated, while p62 was decreased. These results indicate that autophagy activity was elevated under diabetic conditions. Autophagy deficiency induced by autophagy inhibitors, chloroquine diphosphate (CQ) and 3-Methyladenine (3-MA), and by Atg5 siRNA transfection exacerbated lipid accumulation and EMT. This supports that the elevated autophagy activity acts as a renoprotective response under diabetic conditions. Treatment of rapamycin, which is a mammalian target of rapamycin (mTOR) receptor-specific inhibitor and a known autophagy activator, attenuated high-glucose-induced lipid accumulation and EMT. The Atg5 silence counteracted the protective effect of rapamycin. The present study deepens our understanding of the role of autophagy in DN, suggesting a complex interplay of autophagy, metabolic pathways, lipotoxicity and EMT.

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.

Diabetic Kidney Disease: Pathophysiology and Therapeutic Targets

Diabetes is a worldwide epidemic that has led to a rise in diabetic kidney disease (DKD). Over the past two decades, there has been significant clarification of the various pathways implicated in the pathogenesis of DKD. Nonetheless, very little has changed in the way clinicians manage patients with this disorder. Indeed, treatment is primarily centered on controlling hyperglycemia and hypertension and inhibiting the renin-angiotensin system. The purpose of this review is to describe the current understanding of how the hemodynamic, metabolic, inflammatory, and alternative pathways are all entangled in pathogenesis of DKD and detail the various therapeutic targets that may one day play a role in quelling this epidemic.

Trehalose, an mTOR independent autophagy inducer, alleviates human podocyte injury after puromycin aminonucleoside treatment

Glomerular diseases are commonly characterized by podocyte injury including apoptosis, actin cytoskeleton rearrangement and detachment. However, the strategies for preventing podocyte damage remain insufficient. Recently autophagy has been regarded as a vital cytoprotective mechanism for keeping podocyte homeostasis. Thus, it is reasonable to utilize this mechanism to attenuate podocyte injury. Trehalose, a natural disaccharide, is an mTOR independent autophagy inducer. It is unclear whether trehalose alleviates podocyte injury. Therefore, we investigated the efficacy of trehalose in puromycin aminonucleoside (PAN)-treated podocytes which mimic cell damage in minimal change nephrotic syndrome in vitro. Human conditional immortalized podocytes were treated with trehalose with or without PAN. Autophagy was investigated by immunofluorescence staining for LC3 puncta and Western blotting for LC3, Atg5, p-AMPK, p-mTOR and its substrates. Podocyte apoptosis and necrosis were evaluated by flow cytometry and by measuring lactate dehydrogenase activity respectively. We also performed migration assay to examine podocyte recovery. It was shown that trehalose induced podocyte autophagy in an mTOR independent manner and without reactive oxygen species involvement. Podocyte apoptosis significantly decreased after trehalose treatment, while the inhibition of trehalose-induced autophagy abolished its protective effect. Additionally, the disrupted actin cytoskeleton of podocytes was partially reversed by trehalose, accompanying with less lamellipodias and diminished motility. These results suggested that trehalose induced autophagy in human podocytes and showed cytoprotective effects in PAN-treated podocytes.

Rodent animal models: from mild to advanced stages of diabetic nephropathy

Diabetic nephropathy (DN) is a secondary complication of both type 1 and type 2 diabetes, resulting from uncontrolled high blood sugar. 30-40% of diabetic patients develop DN associated with a poor life expectancy and end-stage renal disease, causing serious socioeconomic problems. Although an exact pathogenesis of DN is still unknown, several factors such as hyperglycemia, hyperlipidemia, hypertension and proteinuria may contribute to the progression of renal damage in diabetic nephropathy. DN is confirmed by measuring blood urea nitrogen, serum creatinine, creatinine clearance and proteinuria. Clinical studies show that intensive control of hyperglycemia and blood pressure could successfully reduce proteinuria, which is the main sign of glomerular lesions in DN, and improve the renal prognosis in patients with DN. Diabetic rodent models have traditionally been used for doing research on pathogenesis and developing novel therapeutic strategies, but have limitations for translational research. Diabetes in animal models such as rodents are induced either spontaneously or by using chemical, surgical, genetic, or other techniques and depicts many clinical features or related phenotypes of the disease. This review discusses the merits and demerits of the models, which are used for many reasons in the research of diabetes and diabetic complications.