Jung Tak Park

Red blood cell distribution width is an independent predictor of mortality in acute kidney injury patients treated with continuous renal replacement therapy

BACKGROUND A potential independent association was recently demonstrated between high red blood cell distribution width (RDW) and the risk of all-cause mortality in patients with cardiovascular disease, although the mechanism remains unclear. However, there have been no reports on the relationship between RDW and mortality in acute kidney injury (AKI) patients treated with continuous renal replacement therapy (CRRT). In this study, we assessed whether RDW was associated with mortality in AKI patients on CRRT treatment in the intensive care unit (ICU). METHODS We enrolled 470 patients with AKI who were treated with CRRT at the Yonsei University Medical Center ICU from August 2007 to September 2009 in this study. We performed a retrospective analysis of demographic, biochemical parameters and patient outcomes. Following CRRT treatment, 28-day all-cause mortality was evaluated. RESULTS At the initiation of CRRT treatment, RDW level was significantly correlated with white blood cell count, hemoglobin (Hb) and total cholesterol. Patients with high RDW levels exhibited significantly higher 28-day mortality rates than patients with low RDW levels (P < 0.01). Baseline RDW level, Sequential Organ Failure Assessment (SOFA) score, low mean arterial pressure (MAP) and low cholesterol levels were independent risk factors for mortality. In multivariate Cox proportional hazard analyses, RDW at CRRT initiation was an independent predictor for 28-day all-cause mortality after adjusting for age, gender, MAP, Hb, albumin, total cholesterol, C-reactive protein and SOFA score. CONCLUSION Our study demonstrates that RDW could be an additive predictor for all-cause mortality in AKI patients on CRRT treatment in the ICU.

TGF-β Induces Acetylation of Chromatin and of Ets-1 to Alleviate Repression of miR-192 in Diabetic Nephropathy

Acetylation of chromatin and Ets-1 contributes to induction of miR-192, a microRNA involved in kidney pathogenesis. Kidney Fibrosis Through Acetylation Epigenetic changes alter gene expression and can induce pathogenesis. MicroRNA-192 (miR-192) mediates the transcription of genes involved in kidney fibrosis in response to high glucose–induced signaling by TGF-β (transforming growth factor–β). Kato et al. found that in basal conditions, Ets-1 was bound to chromatin upstream of miR-192 and suppressed its expression in murine kidney mesangial cells. After treatment with high glucose or TGF-β, Ets-1 was acetylated in an Akt- and p300-dependent manner and dissociated from miR-192. Although Ets-1 was dispensable for transiently increased expression of miR-192, Ets-1 deficiency in mice or murine mesangial cells prevented the sustained expression of miR-192 in response to TGF-β. Activation of p300 and acetylation of Ets-1 and of histone H3 at lysines 9 and 14 were increased in diabetic db/db mice compared with wild-type mice, suggesting that alleviation of Ets-1 repression may contribute to diabetic nephropathy. MicroRNAs (miRNAs), such as miR-192, mediate the actions of transforming growth factor–β1 (TGF-β) related to the pathogenesis of diabetic kidney diseases. We found that the biphasic induction of miR-192 expression by TGF-β in mouse renal glomerular mesangial cells initially involved the Smad transcription factors, followed by sustained expression that was promoted by acetylation of the transcription factor Ets-1 and of histone H3 by the acetyltransferase p300, which was activated by the serine and threonine kinase Akt. In mesangial cells from Ets-1–deficient mice or in cells in which Ets-1 was knocked down, basal amounts of miR-192 were higher than those in control cells, but sustained induction of miR-192 by TGF-β was attenuated. Furthermore, inhibition of Akt or ectopic expression of dominant-negative histone acetyltransferases decreased p300-mediated acetylation and Ets-1 dissociation from the miR-192 promoter and prevented miR-192 expression in response to TGF-β. Activation of Akt and p300 and acetylation of Ets-1 and histone H3 were increased in glomeruli from diabetic db/db mice compared to nondiabetic db/+ mice, suggesting that this pathway may contribute to diabetic nephropathy. These findings provide insight into the regulation of miRNAs through signaling-mediated changes in transcription factor activity and in epigenetic histone acetylation under normal and disease states.

Regulation of Inflammatory Phenotype in Macrophages by a Diabetes-Induced Long Noncoding RNA

The mechanisms by which macrophages mediate the enhanced inflammation associated with diabetes complications are not completely understood. We used RNA sequencing to profile the transcriptome of bone marrow macrophages isolated from diabetic db/db mice and identified 1,648 differentially expressed genes compared with control db/+ mice. Data analyses revealed that diabetes promoted a proinflammatory, profibrotic, and dysfunctional alternatively activated macrophage phenotype possibly via transcription factors involved in macrophage function. Notably, diabetes altered levels of several long noncoding RNAs (lncRNAs). Because the role of lncRNAs in diabetes complications is unknown, we further characterized the function of lncRNA E330013P06, which was upregulated in macrophages from db/db and diet-induced insulin-resistant type 2 diabetic (T2D) mice, but not from type 1 diabetic mice. It was also upregulated in monocytes from T2D patients. E330013P06 was also increased along with inflammatory genes in mouse macrophages treated with high glucose and palmitic acid. E330013P06 overexpression in macrophages induced inflammatory genes, enhanced responses to inflammatory signals, and increased foam cell formation. In contrast, small interfering RNA–mediated E330013P06 gene silencing inhibited inflammatory genes induced by the diabetic stimuli. These results define the diabetic macrophage transcriptome and novel functional roles for lncRNAs in macrophages that could lead to lncRNA-based therapies for inflammatory diabetes complications.

Preservation of Renal Function by Thyroid Hormone Replacement Therapy in Chronic Kidney Disease Patients with Subclinical Hypothyroidism

CONTEXT Subclinical hypothyroidism is not a rare condition, but the use of thyroid hormone to treat subclinical hypothyroidism is an issue of debate. OBJECTIVE This study was undertaken to investigate the impact of thyroid hormone therapy on the changes in estimated glomerular filtration rate (eGFR) in subclinical hypothyroidism patients with stage 2-4 chronic kidney disease. PATIENTS A total of 309 patients were included in the final analysis. MAIN OUTCOME MEASURE The changes in eGFR over time were compared between patients with and without thyroid hormone replacement therapy using a linear mixed model. Kaplan-Meier curves were constructed to determine the effect of thyroid hormone on renal outcome, a reduction of eGFR by 50%, or end-stage renal disease. The independent prognostic value of subclinical hypothyroidism treatment for renal outcome was ascertained by multivariate Cox regression analysis. RESULTS Among the 309 patients, 180 (58.3%) took thyroid hormone (treatment group), whereas 129 (41.7%) did not (nontreatment group). During the mean follow-up duration of 34.8 ± 24.3 months, the overall rate of decline in eGFR was significantly greater in the nontreatment group compared to the treatment group (-5.93 ± 1.65 vs. -2.11 ± 1.12 ml/min/yr/1.73 m(2); P = 0.04). Moreover, a linear mixed model revealed that there was a significant difference in the rates of eGFR decline over time between the two groups (P < 0.01). Kaplan-Meier analysis also showed that renal event-free survival was significantly lower in the nontreatment group (P < 0.01). In multivariate Cox regression analysis, thyroid hormone replacement therapy was found to be an independent predictor of renal outcome (hazard ratio, 0.28; 95% CI, 0.12-0.68; P = 0.01). CONCLUSION Thyroid hormone therapy not only preserved renal function better, but was also an independent predictor of renal outcome in chronic kidney disease patients with subclinical hypothyroidism.

FOG2 Protein Down-regulation by Transforming Growth Factor-β1-induced MicroRNA-200b/c Leads to Akt Kinase Activation and Glomerular Mesangial Hypertrophy Related to Diabetic Nephropathy

Background: The mechanism of TGF-β1-induced Akt kinase activation in diabetic nephropathy (DN) is not fully elucidated. Results: FOG2 down-regulation by TGF-β1-induced miR-200b/c activates Akt, which leads to glomerular mesangial hypertrophy. Conclusion: FOG2 and miR-200b/c are novel modulators of TGF-β1-induced Akt activation in glomerular mesangial cells. Significance: These results reveal new mediators of TGF-β1 actions related to the pathogenesis of DN. Glomerular hypertrophy is a hallmark of diabetic nephropathy. Akt kinase activated by transforming growth factor-β1 (TGF-β) plays an important role in glomerular mesangial hypertrophy. However, the mechanisms of Akt activation by TGF-β are not fully understood. Recently, miR-200 and its target FOG2 were reported to regulate the activity of phosphatidylinositol 3-kinase (the upstream activator of Akt) in insulin signaling. Here, we show that TGF-β activates Akt in glomerular mesangial cells by inducing miR-200b and miR-200c, both of which target FOG2, an inhibitor of phosphatidylinositol 3-kinase activation. FOG2 expression was reduced in the glomeruli of diabetic mice as well as TGF-β-treated mouse mesangial cells (MMC). FOG2 knockdown by siRNAs in MMC activated Akt and increased the protein content/cell ratio suggesting hypertrophy. A significant increase of miR-200b/c levels was detected in diabetic mouse glomeruli and TGF-β-treated MMC. Transfection of MMC with miR-200b/c mimics significantly decreased the expression of FOG2. Conversely, miR-200b/c inhibitors attenuated TGF-β-induced decrease in FOG2 expression. Furthermore, miR-200b/c mimics increased the protein content/cell ratio, whereas miR-200b/c inhibitors abrogated the TGF-β-induced increase in protein content/cell. In addition, down-regulation of FOG2 by miR-200b/c could activate not only Akt but also ERK, which was also through PI3K activation. These data suggest a new mechanism for TGF-β-induced Akt activation through FOG2 down-regulation by miR-200b/c, which can lead to glomerular mesangial hypertrophy in the progression of diabetic nephropathy.

An increase in red blood cell distribution width from baseline predicts mortality in patients with severe sepsis or septic shock.

IntroductionA potential independent association was recently demonstrated between high red blood cell distribution width (RDW) and the risk of all-cause mortality in critically ill patients, although the mechanism underlying this relationship remains unclear. Little is known about the impact changes in RDW may have on survival in critically ill patients. Therefore, we investigated the prognostic significance of changes in RDW during hospital stay in patients with severe sepsis or septic shock.MethodsWe prospectively enrolled 329 patients who were admitted to the emergency department (ED) and received a standardized resuscitation algorithm (early-goal directed therapy) for severe sepsis or septic shock. The relationship between the changes in RDW during the first 72 hours after ED admission and all-cause mortality (28-day and 90-day) were analyzed by categorizing the patients into four groups according to baseline RDW value and ΔRDW72hr-adm (RDW at 72 hours – RDW at baseline).ResultsThe 28-day and 90-day mortality rates were 10% and 14.6%, respectively. Patients with increased RDW at baseline and ΔRDW72hr-adm >0.2% exhibited the highest risks of 28-day and 90-day mortality, whereas the patients with normal RDW level at baseline and ΔRDW72hr-adm ≤0.2% (the reference group) had the lowest mortality risks. For 90-day mortality, a significantly higher mortality risk was observed in the patients whose RDW increased within 72 hours of ED admission (normal RDW at baseline and ΔRDW72hr-adm >0.2%), compared to the reference group. These associations remained unaltered even after adjusting for age, sex, Sequential Organ Failure Assessment (SOFA) score, Charlson Comorbidity Index, renal replacement therapy, albumin, hemoglobin, lactate, C-reactive protein and infection sites in multivariable models.ConclusionsWe found that an increase in RDW from baseline during the first 72 hours after hospitalization is significantly associated with adverse clinical outcomes. Therefore, a combination of baseline RDW value and an increase in RDW can be a promising independent prognostic marker in patients with severe sepsis or septic shock.

Transforming Growth Factor β1 (TGF-β1) Enhances Expression of Profibrotic Genes through a Novel Signaling Cascade and MicroRNAs in Renal Mesangial Cells

Background: The mechanism by which TGF-β1 down-regulates miR-130b to promote diabetic nephropathy (DN) remains unclear. Results: TGF-β1 initiates a signaling cascade, including NF-YC, RIK, miR-130b, and TGF-βR1, in mesangial cells to up-regulate profibrotic genes related to DN pathogenesis. Conclusion: A novel pathway involving microRNAs and the host gene can augment mesangial fibrosis. Significance: The reno-protective effects of miR-130b could be exploited for DN treatment. Increased expression of transforming growth factor-β1 (TGF-β1) in glomerular mesangial cells (MC) augments extracellular matrix accumulation and hypertrophy during the progression of diabetic nephropathy (DN), a debilitating renal complication of diabetes. MicroRNAs (miRNAs) play key roles in the pathogenesis of DN by modulating the actions of TGF-β1 to enhance the expression of profibrotic genes like collagen. In this study, we found a significant decrease in the expression of miR-130b in mouse MC treated with TGF-β1. In parallel, there was a down-regulation in miR-130b host gene 2610318N02RIK (RIK), suggesting host gene-dependent expression of this miRNA. TGF-β receptor 1 (TGF-βR1) was identified as a target of miR-130b. Interestingly, the RIK promoter contains three NF-Y binding sites and was regulated by NF-YC. Furthermore, NF-YC expression was inhibited by TGF-β1, suggesting that a signaling cascade, involving TGF-β1-induced decreases in NF-YC, RIK, and miR-130b, may up-regulate TGF-βR1 to augment expression of TGF-β1 target fibrotic genes. miR-130b was down-regulated, whereas TGF-βR1, as well as the profibrotic genes collagen type IV α 1 (Col4a1), Col12a1, CTGF, and PAI-1 were up-regulated not only in mouse MC treated with TGF-β1 but also in the glomeruli of streptozotocin-injected diabetic mice, supporting in vivo relevance. Together, these results demonstrate a novel miRNA- and host gene-mediated amplifying cascade initiated by TGF-β1 that results in the up-regulation of profibrotic factors, such as TGF-βR1 and collagens associated with the progression of DN.

Epigenetic Modifications in the Pathogenesis of Diabetic Nephropathy

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease. Diabetic vascular complications such as DN can progress despite subsequent glycemic control, suggesting a metabolic memory of previous exposure to hyperglycemia. Diabetes profoundly impacts transcription programs in target cells through activation of multiple signaling pathways and key transcription factors leading to aberrant expression of pathologic genes. Emerging evidence suggests that these factors associated with the pathophysiology of diabetic complications and metabolic memory also might be influenced by epigenetic mechanisms in chromatin such as DNA methylation, histone lysine acetylation, and methylation. Key histone modifications and the related histone methyltransferases and acetyltransferases have been implicated in the regulation of inflammatory and profibrotic genes in renal and vascular cells under diabetic conditions. Advances in epigenome profiling approaches have provided novel insights into the chromatin states and functional outcomes in target cells affected by diabetes. Because epigenetic changes are potentially reversible, they can provide a window of opportunity for the development of much-needed new therapies for DN in the future. In this review, we discuss recent developments in the field of epigenetics and their relevance to diabetic vascular complications and DN pathogenesis.

Small RNA sequencing reveals microRNAs that modulate angiotensin II effects in vascular smooth muscle cells

Background: Role of microRNAs in angiotensin II-mediated vascular smooth muscle cell (VSMC) dysfunction is unclear. Results: Angiotensin II up-regulates miR-132 in VSMC. miR-132 induces MCP-1 partly via targeting PTEN, activates CREB, and regulates genes related to cell-cycle and motility. Conclusion: miR-132/212 is a novel modulator of Ang II actions. Significance: miRNAs may serve as new drug targets for Ang II-mediated cardiovascular diseases. Angiotensin II (Ang II)-mediated vascular smooth muscle cell dysfunction plays a critical role in cardiovascular diseases. However, the role of microRNAs (miRNAs) in this process is unclear. We used small RNA deep sequencing to profile Ang II-regulated miRNAs in rat vascular smooth muscle cells (VSMC) and evaluated their role in VSMC dysfunction. Sequencing results revealed several Ang II-responsive miRNAs, and bioinformatics analysis showed that their predicted targets can modulate biological processes relevant to cardiovascular diseases. Further studies with the most highly induced miR-132 and miR-212 cluster (miR-132/212) showed time- and dose-dependent up-regulation of miR-132/212 by Ang II through the Ang II Type 1 receptor. We identified phosphatase and tensin homolog (PTEN) as a novel target of miR-132 and demonstrated that miR-132 induces monocyte chemoattractant protein-1 at least in part via PTEN repression in rat VSMC. Moreover, miR-132 overexpression enhanced cyclic AMP-response element-binding protein (CREB) phosphorylation via RASA1 (p120 Ras GTPase-activating protein 1) down-regulation, whereas miR-132 inhibition attenuated Ang II-induced CREB activation. Furthermore, miR-132 up-regulation by Ang II required CREB activation, demonstrating a positive feedback loop. Notably, aortas from Ang II-infused mice displayed similar up-regulation of miR-132/212 and monocyte chemoattractant protein-1, supporting in vivo relevance. In addition, microarray analysis and reverse transcriptase-quantitative PCR validation revealed additional novel miR-132 targets among Ang II-down-regulated genes implicated in cell cycle, motility, and cardiovascular functions. These results suggest that miR132/212 can serve as a novel cellular node to fine-tune and amplify Ang II actions in VSMC.

Renal outcomes in patients with type 2 diabetes with or without coexisting non-diabetic renal disease

AIMS We sought not only to determine the independent predictors of non-diabetic renal disease (NDRD) but also to investigate the impact of NDRD on renal outcomes in patients with type 2 diabetes who underwent renal biopsy and were followed-up longitudinally. METHODS The present study was conducted by reviewing the medical records of 119 type 2 diabetic patients who underwent renal biopsy at Yonsei University Health System from January 1988 to December 2008. RESULTS Renal biopsy findings declared that 43 patients (36.1%) had diabetic nephropathy alone, 12 (10.1%) had NDRD superimposed on diabetic nephropathy, and 64 (53.8%) had only NDRD. On multivariate analysis, the absence of diabetic retinopathy, higher hemoglobin levels, and shorter duration of diabetes were independent predictors of NDRD in these patients. During the follow-up period, end-stage renal disease (ESRD) developed in 33 patients (27.7%). On multivariate Cox regression, higher serum creatinine levels, higher systolic blood pressure, longer duration of diabetes, and the presence of diabetic nephropathy were identified as significant independent predictors of ESRD. When the presence of diabetic retinopathy was included in the multivariate model, higher serum creatinine levels, higher systolic blood pressure, and the presence of retinopathy were shown to be independent predictors of ESRD. CONCLUSIONS Since diabetic patients with NDRD have significantly better renal outcomes compared to patients with biopsy-proven diabetic nephropathy, it is important to suspect, identify, and manage NDRD as early as possible, especially in type 2 diabetic patients with short duration of diabetes and those without diabetic retinopathy or anemia.