Allopurinol protects human glomerular endothelial cells from high glucose-induced reactive oxygen species generation, p53 overexpression and endothelial dysfunction

Recent advances in potential enzymes and their therapeutic inhibitors for the treatment of Alzheimer's disease

Alzheimer's disease (AD), a chronic neurodegenerative disease, is clinically characterized by loss of memory and learning ability among other neurological deficits. Amyloid plaques, hyperphosphorylated tau protein, and neurofibrillary tangles involve in AD etiology. Meanwhile, enzymes and their inhibitors have become the focus of research in AD treatment. In this review, the molecular mechanisms involved in the pathogenesis of AD were overviewed and various enzymes such as acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), β-secretase, γ-secretase, monoamine oxidase (MAO), and receptor of advanced glycation end products (RAGE) were highlighted as potential targets for AD treatment. Several hybrid molecules with essential substructures derived from various chemotypes have demonstrated desired pharmacological activity. It is envisioned that the development of new drugs that inhibit enzymes involved in AD is a future trend in the management of the disease.

Xanthine oxidoreductase inhibition ameliorates high glucose-induced glomerular endothelial injury by activating AMPK through the purine salvage pathway

Xanthine oxidoreductase (XOR) contributes to reactive oxygen species production. We investigated the cytoprotective mechanisms of XOR inhibition against high glucose (HG)-induced glomerular endothelial injury, which involves activation of the AMP-activated protein kinase (AMPK). Human glomerular endothelial cells (GECs) exposed to HG were subjected to febuxostat treatment for 48 h and the expressions of AMPK and its associated signaling pathways were evaluated. HG-treated GECs were increased xanthine oxidase/xanthine dehydrogenase levels and decreased intracellular AMP/ATP ratio, and these effects were reversed by febuxostat treatment. Febuxostat enhanced the phosphorylation of AMPK, the activation of peroxisome proliferator-activated receptor (PPAR)-gamma coactivator (PGC)-1α and PPAR-α and suppressed the phosphorylation of forkhead box O (FoxO)3a in HG-treated GECs. Febuxostat also decreased nicotinamide adenine dinucleotide phosphate oxidase (Nox)1, Nox2, and Nox4 expressions; enhanced superoxide dismutase activity; and decreased malondialdehyde levels in HG-treated GECs. The knockdown of AMPK inhibited PGC-1α-FoxO3a signaling and negated the antioxidant effects of febuxostat in HG-treated GECs. Despite febuxostat administration, the knockdown of hypoxanthine phosphoribosyl transferase 1 (HPRT1) also inhibited AMPK-PGC-1α-FoxO3a in HG-treated GECs. XOR inhibition alleviates oxidative stress by activating AMPK-PGC-1α-FoxO3a signaling through the HPRT1-dependent purine salvage pathway in GECs exposed to HG conditions.

Investigating the Anti-inflammatory Effect of Allopurinol on the Prevention of Prostate Cancer

Introduction Gout is a form of arthritis that arises from the accumulation of uric acid in the bloodstream. Allopurinol, a medication that reduces uric acid levels, has also been shown to have anti-inflammatory effects. Research in this area seems to have mixed results. Furthermore, limited research has examined the relationship between gout treated with Allopurinol and its possible protective factors against prostate cancer. The purpose of this study was to examine the relationship between Allopurinol use and prostate cancer, controlling for demographic and metabolic factors. Methods Information was collected from the National Health and Nutrition Examination Survey (NHANES) dataset of the Centers for Disease Control and Prevention (CDC). Logistic regression analysis was employed to establish the correlation between the usage of Allopurinol and the occurrence of prostate cancer while considering variables such as weight, hypertension, hyperlipidemia, race, educational level, and marital status. The research received approval from the review board of the Physician's Journal of Medicine. Results We found no significant association between Allopurinol use and prostate cancer, controlling for covariates. Age was found to have a positive association with prostate cancer. Marriage was found to have a negative association with prostate cancer. Conclusion The results of this study did not find a significant association between Allopurinol use and the risk of prostate cancer. However, this study adds to the limited body of research examining the relationship between gout, Allopurinol, and prostate cancer and suggests that further research is needed in this area. Overall, while Allopurinol has been shown to have anti-inflammatory effects and is used to treat gout, its use does not appear to have a significant impact on the risk of developing prostate cancer.

Dapagliflozin Prevents High-Glucose-Induced Cellular Senescence in Renal Tubular Epithelial Cells

Gliflozins are a new class of antidiabetic drugs with renoprotective properties. In cultures of primary human renal tubular epithelial cells (RPTECs) subjected to high-glucose conditions in the presence or absence of dapagliflozin, we evaluated cellular senescence pathways. High glucose increased sodium-glucose cotransporter-2 (SGLT-2) expression and glucose consumption, enhancing reactive oxygen species production. The latter induced DNA damage, ataxia telangiectasia mutated kinase (ATM), and p53 phosphorylation. Stabilized p53 increased the cell cycle inhibitor p21, resulting in cell cycle arrest and increasing the cellular senescence marker beta-galactosidase (GLB-1). RPTECs under high glucose acquired a senescence-associated secretory phenotype, which was detected by the production of IL-1β, IL-8, and TGF-β1. By decreasing SGLT-2 expression and glucose consumption, dapagliflozin inhibited the above pathway and prevented RPTEC senescence. In addition, dapagliflozin reduced the cell cycle inhibitor p16 independently of the glucose conditions. Neither glucose concentration nor dapagliflozin affected the epithelial-to-mesenchymal transition when assessed with α-smooth muscle actin (α-SMA). Thus, high glucose induces p21-dependent RPTEC senescence, whereas dapagliflozin prevents it. Since cellular senescence contributes to the pathogenesis of diabetic nephropathy, delineating the related molecular mechanisms and the effects of the widely used gliflozins on them is of particular interest and may lead to novel therapeutic approaches.

Hyperoxaluria Induces Endothelial Dysfunction in Preglomerular Arteries: Involvement of Oxidative Stress

Urolithiasis is a worldwide problem and a risk factor for kidney injury. Oxidative stress-associated renal endothelial dysfunction secondary to urolithiasis could be a key pathogenic factor, similar to obesity and diabetes-related nephropathy. The aim of the present study was to characterize urolithiasis-related endothelial dysfunction in a hyperoxaluria rat model of renal lithiasis. Experimental approach: Endothelial dysfunction was assessed in preglomerular arteries isolated from control rats and in which 0.75% ethylene glycol was administered in drinking water. Renal interlobar arteries were mounted in microvascular myographs for functional studies; superoxide generation was measured by chemiluminescence and mRNA and protein expression by RT-PCR and immunofluorescence, respectively. Selective inhibitors were used to study the influence of the different ROS sources, xanthine oxidase, COX-2, Nox1, Nox2 and Nox4. Inflammatory vascular response was also studied by measuring the RNAm expression of NF-κB, MCP-1 and TNFα by RT-PCR. Results: Endothelium-dependent vasodilator responses were impaired in the preglomerular arteries of the hyperoxaluric group along with higher superoxide generation in the renal cortex and vascular inflammation developed by MCP-1 and promoted by NF-κB. The xanthine oxidase inhibitor allopurinol restored the endothelial relaxations and returned superoxide generation to basal values. Nox1 and Nox2 mRNA were up-regulated in arteries from the hyperoxaluric group, and Nox1 and Nox2 selective inhibitors also restored the impaired vasodilator responses and normalized NADPH oxidase-dependent higher superoxide values of renal cortex from the hyperoxaluric group. Conclusions: The current data support that hyperoxaluria induces oxidative stress-mediated endothelial dysfunction and inflammatory response in renal preglomerular arteries which is promoted by the xanthine oxidase, Nox1 and Nox2 pathways.

TFPI2 suppresses the interaction of TGF-β2 pathway regulators to promote endothelial-mesenchymal transition in diabetic nephropathy

Endothelial–mesenchymal transition (EndMT) is an important source of myofibroblasts, but also contributes to the progression of diabetic nephropathy (DN). By several differential gene expression analyses from the Gene Expression Omnibus (GEO) database, the tissue factor pathway inhibitor 2 (TFPI2) gene, known as a tumor suppressor, was shown to be dysregulated in DN; however, the potential role and regulatory mechanism of TFPI2 in DN are unclear. Here, we found abnormal upregulation of TFPI2 in the renal cortex of diabetic mice, accompanied by impaired renal function. We also injected a single dose of adeno-associated virus (AAV)2 carrying shRNA targeting TFPI2 intravenously into these mice and found that knockdown of TFPI2 improved renal function and reduced renal fibrosis and cell apoptosis in experimental DN. Furthermore, hyperglycemia-induced EndMT was inhibited in the absence of TFPI2, as evidenced by increased expression of endothelial markers (VE-cadherin and CD31) and decreased expression of mesenchymal markers (α-SMA, desmin, and FSP-1). To further explore the mechanism in vitro, human renal glomerular endothelial cells (hRGECs) were incubated in the presence of high glucose or transforming growth factor beta (TGF-β)2. TFPI2 deficiency inhibited high glucose-induced cell apoptosis and TGF-β2-induced EndMT in hRGECs, while overexpression of TFPI2 had the opposite effects. Importantly, TGF-β2 is a crucial driver of EndMT, and we found that TFPI2 promoted TGF-β2/Smad signaling activation by interferring the interaction of TGF-β pathway regulators (SMURF2 with SMAD7). Our results show that TFPI2 regulates EndMT and the TGF-β2 signaling pathway and is a potential promoter of DN pathogenesis.

Superior effect of allopurinol compared to febuxostat on the retardation of chronic kidney disease progression

BACKGROUND

Although hyperuricemia is associated with chronic kidney disease, whether and how it should be managed for renoprotection remains debatable. Thus, we investigated whether allopurinol and febuxostat, the most frequently used urate-lowering treatments, have differential renoprotective effects on chronic kidney disease.

METHODS

Incident users of allopurinol and febuxostat were identified from two tertiary referral centers. One-to-one propensity score matching between the allopurinol and febuxostat groups was performed. Participants were followed up until the occurrence of clinical outcomes, urate-lowering agent discontinuation, mortality, or the end of the study period, whichever occurred first. The primary outcomes were a 30% decline in estimated glomerular filtration rate (eGFR) and end-stage renal disease. Differential trends of eGFR decline were estimated using a linear mixed-effects model.

RESULTS

Each group included 654 participants. Baseline eGFRs were 40.1 [26.6-57.3] and 39.1 [27.9-58.3] mL/min/1.73 m2 in the allopurinol and febuxostat group, respectively. Adjusted least square mean change in serum urate was -1.58 mg/dL [95% confidence interval (CI), -1.78 to -1.38] and -2.69 mg/dL (95% CI, -2.89 to -2.49) in the allopurinol and febuxostat groups, respectively. Despite lower serum urate levels, febuxostat was significantly more associated with a 30% decline in eGFR (hazard ratio 1.26; 95% CI 1.03-1.54) and end-stage renal disease (hazard ratio 1.91, 95% CI 1.42-2.58) than allopurinol. Annual eGFR decline in febuxostat users was estimated to be more rapid than in allopurinol users by 2.14 (standard error 0.71) mL/min/1.73 m2 per year.

CONCLUSIONS

Allopurinol demonstrated attenuation of chronic kidney disease progression and prevention of hypouricemia, compared to febuxostat. Because the treatment can be renoprotective, further studies on its effects on chronic kidney disease are required.

Role of asymptomatic hyperuricemia in the progression of chronic kidney disease and cardiovascular disease

Previous research has investigated whether hyperuricemia serves as an independent risk factor for cardiovascular and renal diseases. Hyperuricemia is defined as an abnormally high level of uric acid (UA; i.e., serum urate level > 6.8 mg/dL). Hyperuricemia has been considered a complication of chronic kidney disease (CKD). However, it seems to play a pathogenic role in the progression of renal diseases. There has been increasing focus on the link between hyperuricemia and CKD. The results of randomized controlled trials have implied independent associations between hyperuricemia and the progression of cardiovascular and renal morbidities. These associations may be mediated by renin-angiotensin system activation, nitric oxide synthase inhibition, and macrovascular/microvascular disease development. There remains controversy regarding the use of serum UA level as an indirect index of renal vascular disease. This literature review focuses on the role of asymptomatic hyperuricemia in the progression of CKD, as well as the association between hyperuricemia and cardiovascular disease. It also provides a general overview of the physiological metabolism of UA.

Cytoskeleton-associated protein 2 (CKAP2) is regulated by vascular endothelial growth factor and p53 in retinal capillary endothelial cells under high-glucose conditions

PURPOSE

We previously found the mutation frequency of cytoskeleton-associated protein 2 (CKAP2) was significantly increased in proliferative diabetic retinopathy (PDR) patients through whole exome sequencing. The present study was conducted to explore the expression and possible mechanism of CKAP2 in PDR patients and human retinal capillary endothelial cells (HRCECs) under high-glucose (HG) conditions.

METHODS

Expression of CKAP2 and p53 in the vitreous fluid and fibrovascular membrane (FVM) of PDR patients and HRCECs under HG conditions was observed. Cell proliferation, migration and tubule formation were assessed. Ranibizumab and siRNA transfection were used in the inhibition assay.

RESULTS

CKAP2 and p53 were significantly increased in the ocular tissues of PDR patients. HG combined with VEGF treatment significantly up-regulated expression of CKAP2 and p53 in HRCECs. Inhibition of CKAP2 attenuated the abilities of cell proliferation, migration and tube formation under HG conditions. Blocking VEGF or p53 significantly decreased CKAP2 expression, whereas inhibition of CKAP2 failed to alter the level of VEGF or p53.

CONCLUSIONS

CKAP2 is involved in the pathogenesis of PDR and regulated by VEGF and p53 under HG conditions.

Development of a novel NIR viscosity fluorescent probe for visualizing the kidneys in diabetic mice

Viscosity is an important parameter for evaluating cell health, and abnormal viscosity can cause a variety of intracellular organelle function disorders. The mitochondria are a key organelle in cells, and the viscosity of the mitochondria determines the state of the cell. In this work, we report a novel near-infrared fluorescent probe, referred to as NI-VD, that has a large Stokes-shift and a satisfactory response multiple. NI-VD can sensitively detect changes in cell viscosity in cells and tissues, and it can effectively avoid interference from the overlap of excitation and emission light. The fluorescence spectrum shows that NI-VD has maximum emission peaks at 730 nm, and the fluorescence intensity is amplified with an increase in the solution viscosity. The response from pure PBS solution to glycerol changes by 13-fold. After confirmation in a variety of cell and biological models, NI-VD can detect the changes in viscosity in mitochondria. Most importantly, this study is the first to visualize the differences between the kidneys of diabetic mice and normal mice. This approach is a new solution for the diagnosis and treatment of diabetic nephropathy.

The Role of Oxidative Stress in Hyperuricemia and Xanthine Oxidoreductase (XOR) Inhibitors

Uric acid is the end product of purine metabolism in humans. Hyperuricemia is a metabolic disease caused by the increased formation or reduced excretion of serum uric acid (SUA). Alterations in SUA homeostasis have been linked to a number of diseases, and hyperuricemia is the major etiologic factor of gout and has been correlated with metabolic syndrome, cardiovascular disease, diabetes, hypertension, and renal disease. Oxidative stress is usually defined as an imbalance between free radicals and antioxidants in our body and is considered to be one of the main causes of cell damage and the development of disease. Studies have demonstrated that hyperuricemia is closely related to the generation of reactive oxygen species (ROS). In the human body, xanthine oxidoreductase (XOR) catalyzes the oxidative hydroxylation of hypoxanthine to xanthine to uric acid, with the accompanying production of ROS. Therefore, XOR is considered a drug target for the treatment of hyperuricemia and gout. In this review, we discuss the mechanisms of uric acid transport and the development of hyperuricemia, emphasizing the role of oxidative stress in the occurrence and development of hyperuricemia. We also summarize recent advances and new discoveries in XOR inhibitors.

Metabolic Reprogramming of Vascular Endothelial Cells: Basic Research and Clinical Applications

Vascular endothelial cells (VECs) build a barrier separating the blood from the vascular wall. The vascular endothelium is the largest endocrine organ, and is well-known for its crucial role in the regulation of vascular function. The initial response to endothelial cell injury can lead to the activation of VECs. However, excessive activation leads to metabolic pathway disruption, VEC dysfunction, and angiogenesis. The pathways related to VEC metabolic reprogramming recently have been considered as key modulators of VEC function in processes such as angiogenesis, inflammation, and barrier maintenance. In this review, we focus on the changes of VEC metabolism under physiological and pathophysiological conditions.

Geniposide Improves Diabetic Nephropathy by Enhancing ULK1-Mediated Autophagy and Reducing Oxidative Stress through AMPK Activation

Diabetic nephropathy (DN) is a common pathological feature in patients with diabetes and the leading cause of end-stage renal disease. Although several pharmacological agents have been developed, the management of DN remains challenging. Geniposide, a natural compound has been reported for anti-inflammatory and anti-diabetic effects; however, its role in DN remains poorly understood. This study investigated the protective effects of geniposide on DN and its underlying mechanisms. We used a C57BL/6 mouse model of DN in combination with a high-fat diet and streptozotocin after unilateral nephrectomy and treated with geniposide by oral gavage for 5 weeks. Geniposide effectively improves DN-induced renal structural and functional abnormalities by reducing albuminuria, podocyte loss, glomerular and tubular injury, renal inflammation and interstitial fibrosis. These changes induced by geniposide were associated with an increase of AMPK activity to enhance ULK1-mediated autophagy response and a decrease of AKT activity to block oxidative stress, inflammation and fibrosis in diabetic kidney. In addition, geniposide increased the activities of PKA and GSK3β, possibly modulating AMPK and AKT pathways, efficiently improving renal dysfunction and ameliorating the progression of DN. Conclusively, geniposide enhances ULK1-mediated autophagy and reduces oxidative stress, inflammation and fibrosis, suggesting geniposide as a promising treatment for DN.

Allopurinol use and type 2 diabetes incidence among patients with gout: A VA retrospective cohort study

To assess the impact of allopurinol on diabetes in a retrospective cohort of Veterans' Affairs patients with gout.The New York Harbor VA computerized patient record system was searched to identify patients with an ICD-9 code for gout meeting at least 4 modified 1977 American Rheumatology Association gout diagnostic criteria. Patients were divided into subgroups based on >30 continuous days of allopurinol, versus no allopurinol. New diagnoses of diabetes, defined according to American Diabetes Association diagnostic criteria or clinical documentation explicitly stating a new diagnosis of diabetes, were identified during an observation period from January 1, 2000 through December 31, 2015.Six hundred six gout patients used allopurinol >30 continuous days, and 478 patients never used allopurinol. Over an average 7.9 ± 4.8 years of follow-up, there was no significant difference in diabetes incidence between the allopurinol and non-allopurinol groups (11.7/1000 person-years vs 10.0/1000 person-years, P = .27). A lower diabetes incidence in the longest versus shortest quartiles of allopurinol use (6.3 per 1000 person-years vs 19.4 per 1000 person-years, P<.0001) was attributable to longer duration of medical follow-up.In this study, allopurinol use was not associated with decreased diabetes incidence. Prospective studies may further elucidate the relationship between hyperuricemia, gout, xanthine oxidase activity, and diabetes, and the potential impact of gout treatments on diabetes incidence.

FOXO3a accumulation and activation accelerate oxidative stress-induced podocyte injury

Podocyte injury is the primary cause of glomerular injury in diabetic nephropathy (DN). Advanced oxidation protein products (AOPPs), the triggers and markers of oxidative stress in DN, have been linked to podocyte damage. However, the underlying mechanism is not yet clear. Here, we investigated the potential role of FOXO3a, a key transcription factor in the response to stress, in mediating AOPPs-induced podocyte injury. We found that FOXO3a expression was increased in the glomeruli of kidney biopsies from patients with DN and it was positively correlated with proteinuria. The serum from patients with DN significantly increased FOXO3a and its downstream genes FasL and Bim, thereby inducing the high level of cleaved caspase3 and the loss of nephrin and podocin expressions in podocytes. Blockade of AOPPs signaling by a neutralizing antibody against the receptor of advanced glycation end products (αRAGE) abolished the effect of DN serum on podocytes, confirming the pathogenic role of AOPPs in DN serum. Downregulation of FOXO3a decreased AOPPs-induced podocyte apoptosis and restored the levels of podocyte markers nephrin and podocin, and upregulation of FOXO3a exacerbated these changes in podocytes after AOPPs treatment. Furthermore, FOXO3a specifically activated proapoptotic genes in podocytes only in the presence of AOPPs. Mechanistically, AOPPs increased the FOXO3a protein levels by inhibiting their autophagic degradation in a ROS/mTOR-dependent manner. Moreover AOPPs activated the accumulated FOXO3a by maintaining FOXO3a in the nucleus, and this process was dependent on ROS-mediated AKT signaling deactivation. These studies suggest that FOXO3a plays a critical role in mediating AOPPs-induced podocyte injury and reveal a new mechanistic linkage of oxidative stress, FOXO3a activation and podocyte injury in DN.

Relationship between serum uric acid level and vascular injury markers in hemodialysis patients

PURPOSE

It has been reported that hyperuricemia causes vascular endothelial injury. Most hemodialysis patients present with hyperuricemia and also with vascular injury, resulting in cardiovascular diseases (CVD). However, the association of serum uric acid (sUA) with vascular injury markers in hemodialysis patients remains unclear. This study aimed to investigate this and discuss the mechanism by which uric acid causes vascular injury.

METHODS

We enrolled 48 Japanese maintenance hemodialysis patients without any history of CVD. The association between sUA level and three vascular injury markers (reactive hyperemia index [RHI], ankle-brachial index [ABI], and cardio ankle vascular index [CAVI]) was investigated by linear- and logistic regression analyses.

RESULTS

The median natural logarithm RHI (LnRHI) was 0.36. Linear regression analysis revealed a significant positive correlation between sUA level and LnRHI (β = 0.42, p = 0.001) in all patients. Moreover, a significant, strongly positive correlation was observed between sUA and LnRHI in patients who were treated with xanthine oxidase inhibitors (XOIs) (β = 0.75, p = 0.001). Further, the linear analysis showed a significant negative correlation between sUA level and CAVI in patients who were treated with XOIs (β = - 0.52, p = 0.049). sUA level was not significantly associated with ABI abnormality.

CONCLUSIONS

It is possible that a high level of sUA is significantly associated with better vascular endothelial function and condition of vascular tone in hemodialysis patients who were treated with XOIs. The findings suggest a significant paradox between sUA level and vascular endothelial function in hemodialysis patients; however, the opposite has been reported in patients without hemodialysis.

Xanthine Oxidase Inhibitor Febuxostat Exerts an Anti-Inflammatory Action and Protects against Diabetic Nephropathy Development in KK-Ay Obese Diabetic Mice

Hyperuricemia has been recognized as a risk factor for insulin resistance as well as one of the factors leading to diabetic kidney disease (DKD). Since DKD is the most common cause of end-stage renal disease, we investigated whether febuxostat, a xanthine oxidase (XO) inhibitor, exerts a protective effect against the development of DKD. We used KK-Ay mice, an established obese diabetic rodent model. Eight-week-old KK-Ay mice were provided drinking water with or without febuxostat (15 μg/mL) for 12 weeks and then subjected to experimentation. Urine albumin secretion and degrees of glomerular injury judged by microscopic observations were markedly higher in KK-Ay than in control lean mice. These elevations were significantly normalized by febuxostat treatment. On the other hand, body weights and high serum glucose concentrations and glycated albumin levels of KK-Ay mice were not affected by febuxostat treatment, despite glucose tolerance and insulin tolerance tests having revealed febuxostat significantly improved insulin sensitivity and glucose tolerance. Interestingly, the IL-1β, IL-6, MCP-1, and ICAM-1 mRNA levels, which were increased in KK-Ay mouse kidneys as compared with normal controls, were suppressed by febuxostat administration. These data indicate a protective effect of XO inhibitors against the development of DKD, and the underlying mechanism likely involves inflammation suppression which is independent of hyperglycemia amelioration.

Dietary Antioxidant Supplements and Uric Acid in Chronic Kidney Disease: A Review

Increased serum levels of uric acid have been associated with the onset and development of chronic kidney disease (CKD), cardiovascular disease, and mortality, through several molecular pathogenetic mechanisms, such as inflammation and oxidative stress. Oxidative stress is present even in the early stages of CKD, progresses parallelly with the deterioration of kidney function, and is even more exacerbated in end-stage renal disease patients undergoing maintenance hemodialysis. Although acting in the plasma as an antioxidant, once uric acid enters the intracellular environment; it behaves as a powerful pro-oxidant. Exogenous intake of antioxidants has been repeatedly shown to prevent inflammation, atherosclerosis and oxidative stress in CKD patients. Moreover, certain antioxidants have been proposed to exert uric acid-lowering properties. This review aims to present the available data regarding the effects of antioxidant supplements on both oxidative stress and uric acid serum levels, in a population particularly susceptible to oxidative damage such as CKD patients.

Salidroside and FG-4592 ameliorate high glucose-induced glomerular endothelial cells injury via HIF upregulation

Increasing research indicates that hyperglycemia plays a crucial role in the progression of diabetic nephropathy (DN); however, effective treatment for preventing or slowing DN progression are seriously lacking. Although salidroside (SAL) has been demonstrated to have a positive anti-diabetic effect, the cellular mechanisms remain unclear. FG-4592, a novel prolyl hydroxylase inhibitor, was used to regulate HIF-1α and HIF-2α expression. The present study aimed to explore the underlying mechanisms of SAL and FG-4592 on high glucose (HG)-induced rat glomerular endothelial cells (rGECs) injury. HG-cultured rGECs were used to induce a diabetic environment. An MTT assay, RT-qPCR, Western blot, flow cytometry, and immunofluorescent staining were performed to investigate the effects of SAL on HG-induced rGECs injury. FG-4592 and SAL protected rGECs against HG-induced injury by increasing cellular viability and reducing the cell apoptosis rate. SAL and FG-4592 downregulated PHD-2 expression and upregulated HIF-1α and HIF-2α expression. In conclusion, our findings suggest that SAL and FG-4592 ameliorate HG-induced rGEC injury by upregulating HIF expression, indicating that SAL and FG-4592 might be favorable for further DN-treatment.

XBP1 inhibits mesangial cell apoptosis in response to oxidative stress via the PTEN/AKT pathway in diabetic nephropathy

Diabetic nephropathy (DN) is a complication of diabetes mellitus (DM) that frequently results in renal disease, and is characterized by a variety of symptoms, including albuminuria. It has been shown that apoptosis of glomerular mesangial cells (MCs) can aggravate albuminuria and contribute to the development of diabetic glomerulosclerosis. Hence, determination of the mechanisms leading to MC apoptosis may help us gain insights into the pathogenesis of DN. As our understanding of the role of high glucose (HG) in MC apoptosis remains elusive, we explored the interplay between X-box binding protein 1 (XBP1) and MC apoptosis in this study. XBP1 was observed to be downregulated both in vivo and in vitro. Treatment of XBP1-overexpressing cells with HG resulted in a decrease of reactive oxygen species (ROS) and a suppression of cell apoptosis, concomitant with decreases in cleaved caspase-3 and Bax. Subsequent analyses demonstrated that XBP1 overexpression inhibited the expression of phosphatase and tensin homolog deleted on chromosome ten (PTEN) and enhanced the activation of AKT in MCs exposed to HG. In addition, XBP1-induced injuries in MC were reversed by overexpression of PTEN, and XBP1 inhibited apoptosis, which was mediated by the activated PTEN/AKT signaling pathway. Thus, our data indicate that XBP1 can activate the PTEN/AKT signaling pathway, thereby alleviating oxidative stress caused by HG or MC apoptosis. These findings suggest that XBP1 may have potential in the development of treatment methods for DN.

Klotho attenuates diabetic nephropathy in db/db mice and ameliorates high glucose-induced injury of human renal glomerular endothelial cells

Glomerular endothelial cell injury plays an important role in the development and progression of diabetic nephropathy (DN). The expression and function of klotho in glomerular endothelial cells remain unclear. Thus, this study aimed to investigate the expression and the functional role of klotho in DN progression in mice and in high glucose (HG)-induced cell injury of human renal glomerular endothelial cells (HRGECs) and the underlying mechanism. In this study, HRGECs were cultured with media containing HG to induce endothelial cell injury and db/db mice were used as DN model mice. Klotho was overexpressed or knocked down in HRECs to evaluate its role in HG-induced HRGECs injury. klotho-overexpressing adenovirus (rAAV-klotho) was injected into db/db mice via the tail vein to further validate the protective effect of klotho in DN. Decreased klotho expression was observed in DN patients, DN mice, and HG-exposed HRGECs. Furthermore, klotho overexpression significantly abolished the HG-induced HRGECs injury and activation of Wnt/β-catenin pathway and RAAS. In contrast, klotho knockdown exerted the opposite effects. Moreover, klotho attenuated diabetic nephropathy in db/db mice, which was also associated with inhibition of the Wnt/β-catenin pathway and RAAS. In conclusion, klotho attenuates DN in db/db mice and ameliorates HG-induced injury of HRGECs.

Local Mammary Glucose Supply Regulates Availability and Intracellular Metabolic Pathways of Glucose in the Mammary Gland of Lactating Dairy Goats Under Malnutrition of Energy

As glucose is the regulator of both the milk yield and mammary oxidative status, glucose supply is considered to play important nutritional and physiological role on mammary gland (MG) metabolism. However, inconsistent results were observed from different infusion methods to evaluate the effect of glucose on MG glucose metabolism. Thus, precise method should be developed to learn how availability and intracellular metabolic pathways of glucose in the MG are altered by the direct mammary glucose supply. In addition, limited information is available on the role of mammary glucose supply in milk synthesis in lactating ruminants under an energy-deficient diet. Direct glucose supply to the MG was implemented in the current study through the external pudendal artery infusion under an energy-deficient diet. Six doses of glucose (0, 20, 40, 60, 80, and 100 g/d) were infused through the external pudendal arteries, which is the main artery to the MG, to six lactating goats fed with basal diet meeting 81% energy requirement in a 6 × 6 Latin square design. Milk and lactose yields were both quadratically increased with increased glucose infusion, whereas the milk yield changed inconsistently with the increased energy balance (EB), indicating local glucose supply, rather than EB, improved milk production. Glucose fluxes in the MG were significantly increased and correlated with mammary plasma flow. However, the ratio of lactose yield to glucose absorbed by the MG was significantly decreased. The increased glucose fluxes in the MG and changed glucose-related metabolites in milk indicated that the glucose availability and intracellular metabolic pathways was regulated by local mammary glucose. Acute glycolysis consumed the superfluous glucose and induced accumulation of oxygen radicals in the MG during over-supplied glucose conditions. The present study provided insight to optimal glucose supply to the MG during the lactation.