Yung-Chien Hsu

MicroRNA-29a Promotion of Nephrin Acetylation Ameliorates Hyperglycemia-Induced Podocyte Dysfunction

Podocyte dysfunction is a detrimental feature in diabetic nephropathy, with loss of nephrin integrity contributing to diabetic podocytopathy. MicroRNAs (miRs) reportedly modulate the hyperglycemia-induced perturbation of renal tissue homeostasis. This study investigated whether regulation of histone deacetylase (HDAC) actions and nephrin acetylation by miR-29 contributes to podocyte homeostasis and renal function in diabetic kidneys. Hyperglycemia accelerated podocyte injury and reduced nephrin, acetylated nephrin, and miR-29a levels in primary renal glomeruli from streptozotocin-induced diabetic mice. Diabetic miR-29a transgenic mice had better nephrin levels, podocyte viability, and renal function and less glomerular fibrosis and inflammation reaction compared with diabetic wild-type mice. Overexpression of miR-29a attenuated the promotion of HDAC4 signaling, nephrin ubiquitination, and urinary nephrin excretion associated with diabetes and restored nephrin acetylation. Knockdown of miR-29a by antisense oligonucleotides promoted HDAC4 action, nephrin loss, podocyte apoptosis, and proteinuria in nondiabetic mice. In vitro, interruption of HDAC4 signaling alleviated the high glucose-induced apoptosis and inhibition of nephrin acetylation in podocyte cultures. Furthermore, HDAC4 interference increased the acetylation status of histone H3 at lysine 9 (H3K9Ac), the enrichment of H3K9Ac in miR-29a proximal promoter, and miR-29a transcription in high glucose-stressed podocytes. In conclusion, hyperglycemia impairs miR-29a signaling to intensify HDAC4 actions that contribute to podocyte protein deacetylation and degradation as well as renal dysfunction. HDAC4, via epigenetic H3K9 hypoacetylation, reduces miR-29a transcription. The renoprotective effects of miR-29a in diabetes-induced loss of podocyte integrity and renal homeostasis highlights the importance of post-translational acetylation reactions in podocyte microenvironments. Increasing miR-29a action may protect against diabetic podocytopathy.

Hyperuricemia as an independent risk factor of chronic kidney disease in middle-aged and elderly population.

Introduction:Hyperuricemia in the general population remains controversial, in terms of it being considered a risk factor for chronic kidney disease (CKD). Within this context, we evaluated the effects of hyperuricemia on renal function in older Taiwanese adults. Methods:From January 2002 to December 2006, we conducted a community-based medical screening program involving 31,331 subjects older than 40 years. According to the National Kidney Foundation guidelines, stage 3 to 5 patients with CKD were included for analysis. Age, body mass index, systolic blood pressure, fasting plasma glucose, triglyceride, cholesterol and proteinuria were considered potential confounders. Results:Participants with hyperuricemia tended to have higher systolic blood pressure, sugar levels, body mass index, and cholesterol and triglyceride levels but lower estimated glomerular filtration rate (eGFR) levels; eGFR negatively correlated with serum uric acid level. By using multiple logistic regression models before and after adjusting for any confounding factors, we noted that participants with hyperuricemia had a 4.036-fold (odds ratios = 4.036) and 3.649-fold (odds ratios = 3.649) increased risk for CKD, respectively, compared with the control group. We used multiple linear regression analysis to examine the association of serum uric acid level and eGFR at different stages of CKD; significance was found only in participants with stage 3 CKD and not in participants with stages 4 or 5. Conclusions:Hyperuricemia is an independent risk factor for CKD in middle-aged and elderly Taiwanese adults. Thus, an effective screening program that identifies people with hyperuricemia is warranted.

Sustained Wnt/β-catenin signaling rescues high glucose induction of transforming growth factor-β1-mediated renal fibrosis.

Introduction:Although diabetic nephropathy is attributable to transforming growth factor-&bgr;1 (TGF-&bgr;1) overproduction in glomer-ular mesangial cells, the biological role of Wnt/&bgr;-catenin signaling in controlling high glucose-induced TGF-&bgr;1 has not yet been elucidated. Methods:This study found that sustained Wnt/&bgr;-catenin signaling was required to protect glomerular mesangial cells from high glucose induction of TGF-&bgr;1-mediated fibrosis using in vitro and in vivo diabetic models. Results:High glucose down-regulated the Wnt signaling associated with increased TGF-&bgr;1 and fibronectin messenger RNA expression in glomerular mesangial cells. Restoring Wnt4, Wnt5a and cytosolic &bgr;-catenin levels by transfecting Wnt4, Wnt5a and stable &bgr;-catenin alleviated the stimulatory effect of high glucose on c-Jun mediated TGF-&bgr;1 fibrosis. Transfection of kinase-active glycogen synthase kinase-3&bgr; (GSK-3&bgr;) also abrogated high glucose promotion of nuclear c-Jun levels, TGF-&bgr;1 and fibronectin messenger RNA expression in mesangial cells. Pharmacological modulation of GSK-3&bgr;&bgr; and &bgr;&bgr;-catenin signaling by recombinant Wnt5a or GSK-3&bgr; inhibitor (BIO or LiCl) suppressed high glucose promotion of TGF-&bgr;1-mediated fibrosis. Exogenous BIO and SB216763 alleviated TGF-&bgr;1-mediated fibrogenic expression in the kidneys of diabetic rats. Immunohistochemistry showed that GSK-3&bgr; inhibitor significantly reversed the diabetic attenuation of TGF-&bgr;1 and c-Jun coinciding with fibronectin immunoreactivity within glomeruli. Immunofluorescence demonstrated that cells within the glomeruli restored &bgr;-catenin expression after BIO and SB216763 treatment in cells within diabetic glomeruli colocalized with fragmented nuclei by 4′,6-diamidino-2-phenylindole staining. Conclusions:Sustained Wnt signaling reduced c-Jun-dependent TGF-&bgr;1-mediated fibronectin accumulation in mesangial cells. These findings suggest that modulation of Wnt signaling is a viable alternative strategy to rescue the TGF-&bgr;1-mediated fibrotic signaling pathway in diabetic renal injury.

Hypertriglyceridemia: an independent risk factor of chronic kidney disease in Taiwanese adults.

Background:The prevalence and incidence of chronic kidney disease (CKD) are relatively high in Taiwanese patients than in patients of other countries, particularly in the older age groups. Dyslipidemia in patients with CKD has been recognized as a risk factor for disease progression but the role of triglycerides (TGs) remains controversial. With this regard, we evaluated the effects of hypertriglyceridemia on renal function in Taiwanese adults (aged ≥40 years). Methods:From January 2002 to December 2006, we conducted a community-based medical screening program in Chiayi County with 18,422 subjects (aged ≥40 years). The CKD was defined as an estimated glomerular filtration rate of <60 mL min 1.73 m2. Age, body mass index, systolic blood pressure, fasting plasma glucose, and serum total cholesterol were considered as potential confounders. Result:The CKD was prevalent in 24.2% of the middle-aged and elderly population. By using multiple logistic regression models, we determined that old age and elevated levels of body mass index, systolic blood pressure, fasting plasma glucose, and cholesterol were associated with CKD. The adjusted odds ratios of CKD in participants with serum TG ≧200 mg/dL was 1.901 (95% confidence interval: 1.07–3.36; P < 0.05) and in participants with serum TG > 500 mg/dL it increased to 2.205 (1.33–3.64, P < 0.05). Conclusion:Hypertriglyceridemia is an independent risk factor for CKD in Taiwanese adults. Thus, an effective screening program that identifies people with hypertriglyceridemia is warranted.

Curcumin Rescues Diabetic Renal Fibrosis by Targeting Superoxide-Mediated Wnt Signaling Pathways

ABSTRACT The purposes of this study were to investigate whether curcumin can weaken diabetic nephropathy by modulating both oxidative stress and renal injury from Wnt signaling mediation. Wnt5a/&bgr;‐catenin depression and induction of superoxide synthesis are associated with high glucose (HG) induced transforming growth factor (TGF)‐&bgr;1 and fibronectin expression in mesangial cells. Curcumin resumes HG depression of Wnt/&bgr;‐catenin signaling and alleviates HG induction of superoxide, TGF‐&bgr;1 and fibronectin expression in renal mesangial cell. Exogenous curcumin alleviated urinary total proteinuria and serum superoxide level in diabetic rats. Based on laser‐captured microdissection for quantitative real‐time polymerase chain reaction, it was found that diabetes significantly increased TGF‐&bgr;1 and fibronectin expression in line with depressed Wnt5a expression. Curcumin treatment reduced the TGF‐&bgr;1 and fibronectin activation and the inhibiting effect of diabetes on Wnt5a/&bgr;‐catenin expression in renal glomeruli. Immunohistochemistry showed that curcumin treatment significantly reduced 8‐hydroxy‐2′‐deoxyguanosine, TGF‐&bgr;1 and fibronectin, and was in line with the restoration of the suppressed Wnt5a expression immunoreactivities in glomeruli of diabetic rats. Curcumin alleviated extracellular matrix accumulation in diabetic nephropathy by not only preventing the diabetes‐mediated superoxide synthesis but also resuming downregulation of Wnt/&bgr;‐catenin signaling. These findings suggest that regulation of Wnt activity by curcumin is a feasible alternative strategy to rescue diabetic renal injury.

Hyperuricemia Is an Independent Risk Factor for New Onset Micro-Albuminuria in a Middle-Aged and Elderly Population: A Prospective Cohort Study in Taiwan

Background Hyperuricemia is now regarded as a risk factor for cardiovascular disease. Micro-albuminuria is associated with increased risk for cardiovascular disease and chronic kidney disease. We hypothesized that elevated serum uric acid (UA) is associated with development of micro-albuminuria in the general population. Methodology/Principal Findings We conducted a community-based prospective cohort study. A total of 1862 subjects from southern Taiwan, all older than 40 years, were screened and 993 of these participants without micro-albuminuria were followed for 4 years. Urinary albumin-to-creatinine ratio was measured two times per year. A multiple linear regression model indicated that serum UA was independently associated with ln(ACR) after adjustment for 8 factors (age, sex, and 6 metabolic metrics) (β = 0.194, p<0.01). Logistic regression analysis indicated that each 1 mg/dL increase of UA was associated with a 1.42-fold increased risk of micro-albuminuria after adjustment for the same 8 factors (OR = 1.42, 95% CI: 1.27–1.59, p<0.01). A Cox regression model using subjects with serum UA less than 5 mg/dL as reference group indicated higher hazard ratios (HRs) only found in subjects with serum UA more than 7 mg/dL (HR = 3.54, 95% CI: 2.11–5.93, p<0.01) and not in subjects with serum UA of 5 to 7 mg/dL (HR = 1.30, 95% CI: 0.82–2.07, p = 0.15). Conclusion Hyperuricemia is significantly associated with micro-albuminuria in middle-aged and elderly males and females from a general population in Taiwan. Elevated serum UA is an independent predictor for development of micro-albuminuria in this population.

Cannabinoid receptor 1 disturbance of PPARγ2 augments hyperglycemia induction of mesangial inflammation and fibrosis in renal glomeruli.

Intensive fibrosis in the glomerular microenvironment is a prominent feature of diabetic nephropathy. Cannabinoid receptor 1 (CB1R) reportedly mediates diabetes-induced renal injury. However, studies on the molecular events underlying CB1R promotion of renal dysfunction are limited. This study is undertaken to investigate whether CB1R signaling via Ras or PPARγ pathway regulates mesangial fibrosis in diabetic kidneys. In streptozotocin-induced diabetic rats, hyperglycemia induced glomerular hypertrophy and fibrosis in association with increased IL-1β, fibronectin, and CB1R expressions and reduced PPARγ2 signaling. CB1R transgenic mice gained kidney weight, and renal glomeruli strongly displayed IL-1β and fibrotic matrices. Disruption of CB1R by antisense oligonucleotides or inverse agonist AM251 restored PPARγ2 signaling and reduced the promotional effects of hyperglycemia on the expression of fibrogenic transcription factor c-Jun, inflammation regulator SOCS3, proinflammatory cytokines, and accumulation of fibrotic matrix. PPARγ agonist rosiglitazone reduced the hyperglycemia-mediated enhancement of CB1R signaling, inflammation, and glomerular fibrosis in diabetic animals. In vitro, CB1R antagonism restored PPARγ2 action and reduced the promotional effects of high glucose on Ras, ERK, c-Jun, SOCS3 signaling, IL-1β, and fibronectin expression in renal mesangial cells. Activation of PPARγ2 reduced the high glucose-induced CB1R expression in mesangial cells. Taken together, CB1R signaling contributes to the hyperglycemia disturbance of PPARγ2 signaling and increases inflammatory cytokine secretion and fibrotic matrix deposition in renal glomeruli. CB1R mediates the hyperglycemia-induced inflammation and fibrosis in mesangial cells by regulating Ras, ERK, and PPARγ2 signaling. CB1R blockade has a therapeutic potential to reduce the deleterious actions of hyperglycemia on renal glomerular integrity.Key messageHyperglycemia increases glomerular fibrosis, inflammation, and CB1R signaling.CB1R signaling promotes fibrosis and inflammation of renal tissue.Loss of CB1R function alleviates diabetes-mediated renal deterioration.PPARγ agonist decreases CB1R expression in diabetic renal glomeruli.Ras and ERK mediated CB1R promotion of fibrosis matrix deposition in mesangial cells.

Induction of Proteinuria by Cannabinoid Receptors 1 Signaling Activation in CB1 Transgenic Mice

Abstract:Proteinuria is not only a sign of kidney damage but is also involved in the progression of renal disease as an independent pathologic factor. Although patients with mutated type 1 cannabinoid receptors (CB1) polymorphism are associated with renal microvascular damage, the biologic role of CB1 signaling in proteinuria remains uncharacterized till now. Herein, we investigate whether CB1 participates in glomerular proteinuria in CB1 transgenic mice and treatment with CB1 agonist WIN55212-2 rat, neither of which are diabetic models. The CB1 transgenic mice and rats treated with CB1 agonist WIN55212-2 had higher kidney weight and urinary protein concentrations but not blood glucose levels compared with the wild-type group. A combination of laser-capture microsdissection, quantitative reverse transcription–polymerase chain reaction, immunoblotting and immunohistochemical validation revealed that CB1 transgenic mice and rats treated with CB1 agonist WIN55212-2 had higher vascular endothelial growth factor (VEGF) expression in renal glomeruli than that of the wild-type group. Geneticorpharmacological activation of CB1 by transgenic CB1 mice or treatment with WIN55212-2 reduced nephrin expression in the renal glomeruli compared with that of the wild-type group in the glomerular mesanglium. Taken together, CB1 transgenic mice and rats treated with CB1 agonist WIN55212-2 induced proteinuria with upregulation of CB1 resulting in impaired nephrin expression, by inducing excess VEGF reaction in the renal glomeruli. Genetic and pharmacological manipulation of CB1 signaling revealed VEGF-dependent nephrin depression of glomerulopathy. Controlling CB1 activity can be used an alternative strategy for sustaining renal function in the presence of CB1 activation.

Protective effects of miR-29a on diabetic glomerular dysfunction by modulation of DKK1/Wnt/β-catenin signaling

Dysregulation of specific microRNAs or Wnt/β-catenin signaling pathway is critically implicated in the pathogenesis of various renal diseases. However, the relationship between microRNAs and Wnt/β-catenin signaling in diabetes-induced glomerular sclerosis remains unknown. Here, we found that decreased miR-29a expression and attenuated Wnt/β-catenin signaling were concomitantly detected in glomeruli of streptozotocin-induced diabetic mice. Gain of miR-29a function in diabetic mice substantially increased the expression of β-catenin and blocked the expressions of profibrotic gene markers, including DKK1 (a Wnt antagonist), TGF-β1 and fibronectin, in glomerular mesangium. Moreover, in the normal mice treated with miR-29a inhibitor, renal fibrosis was induced with an attenuated Wnt/β-catenin signaling activity. Consistently, the constructed miR-29a transgenic mice that supported sustained Wnt/β-catenin signaling had the ability to block the expressions of profibrotic genes after induction of diabetes. We also demonstrated that miR-29a acts as a positive regulator of Wnt/β-catenin signaling in cultured mesangial cells and functions to protect cell apoptosis and fibrosis. Importantly, we showed that activation of Wnt/β-catenin signaling in cultured mesangial cells by transfecting the β-catenin (Δ45) mutant or by a GSK-3β inhibitor reversely upregulated miR29a. Our findings suggest that the reciprocal relationship between miR-29a and DKK1/Wnt/β-catenin signaling may play an important part in protecting renal fibrogenesis.

Nitric oxide donors rescue diabetic nephropathy through oxidative-stress- and nitrosative-stress-mediated Wnt signaling pathways

The role of the renal nitric oxide (NO) system in the pathophysiology of diabetic nephropathy constitutes a very challenging and fertile field for future investigation. The purpose of the present study was to investigate whether NO donors can attenuate diabetic renal fibrosis and apoptosis through modulating oxidative‐ and nitrosative‐stress, and Wnt signaling using in vivo diabetic models.