Hyun Wha Chung

Long-Term Treatment of Glucagon-Like Peptide-1 Analog Exendin-4 Ameliorates Diabetic Nephropathy through Improving Metabolic Anomalies in db/db Mice

Glucagon-like peptide-1 (GLP-1) is a gut incretin hormone and is a new clinically available class of agents for improving of insulin resistance in both animals and humans with type 2 diabetes. These studies aimed to determine whether long-term treatment with a long-acting GLP-1 analog, exendin-4, delayed the progression of diabetes. Male db/db mice and db/m mice at 8 wk of age were treated with exendin-4 for 8 wk, whereas the control db/db mice received only vehicle. Urinary albumin excretion was significantly decreased in db/db mice that were treated with 1 nmol/kg exendin-4 compared with those in db/db mice that were treated with 0.5 nmol/kg exendin-4 and control db/db mice (P < 0.005). Intraperitoneal glucose tolerance test was improved in db/db mice that were treated with 1 nmol/kg exendin-4 compared with other groups (P < 0.05). Despite this, fasting blood glucose, glycated hemoglobin, and creatinine concentrations were not significantly different among db/db mice. Renal histology studies further demonstrated that glomerular hypertrophy, mesangial matrix expansion, TGF-beta1 expression, and type IV collagen accumulation and associated glomerular lipid accumulation were significantly decreased in db/db mice that were treated with 1 nmol/kg exendin-4. Furthermore, there were fewer infiltrating inflammatory cells and apoptotic cells in the glomeruli of db/db mice that were treated with 1 nmol/kg exendin-4 compared with those in the other groups accompanied by an increase in the renal immunoreactivity of peroxisome proliferator-activated receptor alpha and GLP-1 receptor-positive cells and a decrease in 24-h urinary 8-hydroxy-deoxyguanosine levels (P < 0.01, respectively) along with decreases in lipid content. Taken together, exendin-4 treatment seems to ameliorate diabetic nephropathy together with improvement of the metabolic anomalies. These results suggest that exendin-4 could provide a therapeutic role in diabetic nephropathy that results from type 2 diabetes.

Peroxisome proliferator-activated receptor-α activator fenofibrate prevents high-fat diet-induced renal lipotoxicity in spontaneously hypertensive rats

We investigated the effects of a high-fat (HF) diet and peroxisome proliferator-activated receptor (PPAR)-α activation on the intrarenal lipotoxicity associated with the renin–angiotensin system (RAS) and oxidative stress using spontaneously hypertensive (SHR) rats. Male SHR and Wistar–Kyoto (WKY) rats at 8 weeks of age were fed either a normal-fat diet or an HF diet without or with fenofibrate treatment for 12 weeks. Severe intrarenal lipid accumulation was noted in the SHR rats fed an HF diet than in WYK rats fed an HF diet (P<0.05). This lipid accumulation was associated with a 70% decrease in renal PPARα expression in SHR rats, whereas an HF diet increased the expression of PPARα in WKY rats by threefold. An HF diet also activated intrarenal, not systemic, RAS and induced oxidative stress associated with reduced nitric oxide (NO) bioavailability. By contrast, fenofibrate attenuated weight gain, fat mass and insulin resistance. Fenofibrate recovered HF diet-induced decreases in intrarenal PPARα expression and fat accumulation, and abolished intrarenal RAS activation and oxidative stress in SHR–HF animals (P<0.01). These activities conferred protection against increased blood pressure (BP), glomerulosclerosis and renal inflammation. Intrarenal free fatty acid and triglyceride concentrations were positively correlated with angiotensin II (γ=0.63, 0.36) and 24-h urinary 8-hydroxy-deoxyguanosine (γ=0.36, 0.39), and negatively correlated with PPARα contents (γ=−0.47, −0.44; P<0.05). An HF diet-induced lipotoxicity by depletion of intrarenal PPARα aggravated BP and renal inflammation as a result of intrarenal RAS activation and oxidative stress. Therefore, intervention with PPARα activators can effectively prevent diet-induced renal lipotoxicity in hypertensive rats.

High-fat diet-induced renal cell apoptosis and oxidative stress in spontaneously hypertensive rat are ameliorated by fenofibrate through the PPARα–FoxO3a–PGC-1α pathway

BACKGROUND The peroxisome proliferator-activated receptor-α (PPARα) is a lipid-sensing transcriptional factor that has a role in gluco-oxidative stress and lipotoxicity. Forkhead box O (FoxO)s and peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1α are also known to regulate cell metabolism, cell cycle arrest, apoptosis and oxidative stress during stressful conditions. We evaluated whether PPARα-FoxOs-PGC-1α signaling in overfed spontaneously hypertensive rats (SHR) has a protective role in the kidney. METHODS Male SHR and Wistar-Kyoto rats (WKY) fed a high-fat diet (HFD) received treatment with fenofibrate, PPARα agonist or tempol, antioxidants for 12 weeks and were evaluated about the PPARα-FoxOs-PGC-1α pathway. RESULTS The SHRs with an HFD had an elevated systolic pressure, plasma insulin, free fatty acid (FFA) and triglyceride (TGs) levels, and they had induced glucose intolerance as well as albuminuria, glomerular expansion and renal inflammation. An HFD caused the accumulation of intra-renal FFA and TGs and this was related to a decrease in the PPARα expression, the activation of phosphatidylinositol 3-kinase (PI3K)-Akt, phosphorylation of FoxO3a and decreases in the PGC-1α and estrogen-related receptor (ERR)-1α expressions, which suppressed the superoxide dismutase (SOD2) and Bcl-2 expressions and led to increases in oxidative stress and the number of apoptotic renal cells. Interestingly, administering fenofibrate or tempol to the HFD-induced SHRs reversed all of the renal phenotypes by increasing the PPARα expression with concomitant inactivation of the PI3K-Akt pathway, dephosphorylation of FoxO3a and activation of PGC-1α-ERR-1α signaling, and this all resulted in ameliorating the oxidative stress and apoptotic cell death. CONCLUSION Our results demonstrated that PPARα agonists or antioxidants are associated with improvement of the circulating FFA and TGs levels and this prevents HFD-induced renal lipotoxicity and hypertension by the activation of PPARα and its downstream signals of both FoxO3a and PGC-1α.

Tempol or candesartan prevents high-fat diet-induced hypertension and renal damage in spontaneously hypertensive rats

BACKGROUND Obesity has been strongly associated with the development and aggravation of hypertension and chronic kidney disease. To date, the systemic renin-angiotensin system (RAS) has been known to involve in obesity-induced tissue damage and hypertension. However, the intrarenal mechanism whereby obesity induces and aggravates hypertension and renal disease remains poorly understood. Therefore, we investigated the role of intrarenal RAS and oxidative stress in diet-induced hypertension and renal inflammation in spontaneously hypertensive rats (SHR) fed a high-fat diet. METHODS Male SHR and Wistar-Kyoto rats (WKY) were divided into eight groups: normal-fat diet-fed WKY (WKY-NF), high-fat diet-fed WKY (WKY-HF), high-fat diet-fed tempol-treated WKY (WKY-HF/T), high-fat diet-fed candesartan-treated WKY (WKY-HF/C), normal-fat diet-fed SHR (SHR-NF), high-fat diet-fed SHR (SHR-HF), high-fat diet-fed tempol-treated SHR (SHR-HF/T) and high-fat diet-fed candesartan-treated SHR (SHR-HF/C). After 12 weeks of treatment, haemodynamic measurements and histological assessment of the kidney were performed. RESULTS At the end of week 12, the high-fat fed SHR gained more body weight, their systolic blood pressure was further elevated and glucose intolerance induced. There was no significant difference in the insulin resistance index, serum lipid profile, plasma renin activity and serum aldosterone levels according to diet. However, the high-fat diet resulted in increases in immunohistochemical stains of renin and angiotensin II in the kidney. The real-time PCR also demonstrated significant increases in mRNA levels of renin, angiotensinogen and angiotensin-converting enzyme in the kidney, reflecting enhanced activation of the intrarenal RAS, which findings were also shown by Western blot analysis for renin and angiotensin II type 1 receptor. The expression of ED-1, osteopontin and TGF-beta1 in the renal cortex were prominently enhanced in the SHR-HF group with the increased intrarenal lipid concentrations and oxidative stress. Administration of tempol or candesartan in the high-fat diet-induced SHR inhibited the elevation of the systolic blood pressure, intrarenal lipid concentrations, oxidative stress and the degree of renal inflammation to the levels of, or more than, the SHR-NF with no differences in the body weight and periepididymal fat weight, compared to those in the SHR-HF group without such treatment. CONCLUSIONS Our study suggests that a high-fat diet induces fatty kidneys, aggravation of blood pressure and renal inflammation in the SHR. Blockade of oxidative stress by tempol or of RAS by candesartan ameliorates the increase in blood pressure and renal inflammation and improves intrarenal lipid accumulation. Therefore, antioxidants or angiotensin receptor blockers can prevent diet-induced hypertension and renal inflammation in hypertensive rats.

Vascular Endothelial Growth Factor Inhibition by dRK6 Causes Endothelial Apoptosis, Fibrosis, and Inflammation in the Heart via the Akt/eNOS Axis in db/db Mice

OBJECTIVE Vascular endothelial growth factor (VEGF), which is associated with the stimulation of angiogenesis and collateral vessel synthase, is one of the crucial factors involved in cardiac remodeling in type 2 diabetes. RESEARCH DESIGN AND METHODS We investigated VEGF inhibition by dRK6 on the heart in an animal model of type 2 diabetes. Male db/db and db/m mice either were treated with dRK6 starting at 7 weeks of age for 12 weeks (db/db-dRK6 and db/m-dRK6) or were untreated. RESULTS Cardiac dysfunction and hypertrophy were noted by echocardiogram and molecular markers in the db/db-dRK6 mice. The presence of diabetes significantly suppressed the expression of VEGF receptor (VEGFR)-1 and VEGFR-2, phospho-Akt, and phospho-endothelial nitric oxide synthase (eNOS) in the heart. In db/db-dRK6 mice, dRK6 completely inhibited VEGFR-2, phospho-Akt, and phospho-eNOS expression, whereas no effect on VEGFR-1 was observed. Cardiac fibrosis, microvascular scarcity associated with an increase in apoptotic endothelial cells, and inflammation were prominent, as well as increase in antiangiogenic growth factors. Cardiac 8-hydroxy-deoxyguanine and hypoxia-inducible factor-1α expression were significantly increased. No such changes were found in the other groups, including the db/m-dRK6 mice. The number of apoptotic human umbilical vein endothelial cells was increased by dRK6 in a dose-dependent manner only at high glucose concentrations, and this was associated with a decrease in phospho-Akt and phospho-eNOS related to oxidative stress. CONCLUSIONS Our results demonstrated that systemic blockade of VEGF by dRK6 had deleterious effects on the heart in an animal model of type 2 diabetes; dRK6 induced downregulation of the VEGFR-2 and Akt-eNOS axis and enhancement of oxidative stress.

Long-term blockade of vascular endothelial growth factor receptor-2 aggravates the diabetic renal dysfunction associated with inactivation of the Akt/eNOS-NO axis

BACKGROUND Diabetic nephropathy is characterized by abnormal angiogenesis, and this is driven by several factors, including hyperglycaemia and ischaemia. We investigated the role of vascular endothelial growth factor receptor-2 (VEGFR-2) blockade and its effects on diabetic nephropathy. METHODS Male db/db and db/m mice received long-term treatment with dRK6, an arginine-rich anti-VEGF hexapeptide, for 12 weeks or short-term treatment for only the first 4 weeks, starting from 8 weeks of age. RESULTS The urinary albuminuria and VEGF excretion varied according to the duration of diabetes, and the urinary VEGF levels were strongly correlated with the levels of albuminuria. Diabetes increased the VEGFR-2 expression in the kidneys. At the end of the 12-week study, compared with the db/db control mice, the db/db mice with long-term dRK6 treatment, which selectively inhibited VEGFR-2, had more albuminuria, related to weak nephrin signalling and advanced renal phenotypes, which were associated with hypoxia-oxidative stress, and an increased number of apoptotic endothelial cells. Interestingly, these changes were related to a decrease in phospho-Akt/eNOS-NO bioavailability. On the in vitro study, dRK6 increased the number of apoptotic human umbilical vein endothelial cells (HUVECs) in the high glucose media by blocking phospho-Akt/eNOS-NO signalling, and this was related to the increased oxidative stress. The short-term inhibition of VEGFR-2 neither improved the albuminuria nor the renal phenotype induced by diabetes. CONCLUSIONS Long-term selective blockade of VEGFR-2 by dRK6 had deleterious renal effects, and this was associated with downregulation of the Akt/eNOS-NO axis in db/db mice. Short-term VEGFR-2 blockade did not improve the renal phenotypes and the albuminuria. These findings suggest that VEGF-A-VEGFR-2 inhibition, regardless of how long it may be, does not ameliorate diabetic nephropathy in type 2 diabetes.

Late Referral to a Nephrologist Increases the Risk of Uremia-Related Cardiac Hypertrophy in Patients on Hemodialysis

Background: The prognosis and outcome of patients with end-stage renal disease are related to the quality of predialysis care and the timing of referral. Late referral (LR) has been correlated with more frequent hospital admissions, malnutrition and cardiovascular mortality after hemodilaysis (HD) is started. Methods: We investigated the effects of LR on cardiac hypertrophy, uremia-related metabolic risk factors and mortality in patients on HD. A baseline echocardiography was performed in 119 patients on HD, 67 of whom were early referrals (ER, referred more than 3 months before the start of HD) and 52 were LR (referred less than 3 months before the start of HD; median (range): 22.5 (4–120) vs. 1.0 (0–3) months, respectively). Results: The survival curves showed a higher mortality rate in the LR patients than in the ER patients (log rank, p = 0.004). More patients in the LR group died of cardiovascular disease compared to the ER patients (p = 0.04). The plasma levels of albumin were significantly lower (p < 0.05), and the intact parathyroid hormone (iPTH) and log C-reactive protein (log CRP) were significantly higher in the LR patients compared to the ER patients (p < 0.05 and p < 0.001, respectively). The LR patients, especially nonsurvivors, showed greater impairment of systolic cardiac function and more concentric left ventricular hypertrophy (LVH) than ER patients, as determined by interventricular septal thickness (p < 0.001), left ventricular posterior wall thickness (p < 0.001), relative wall thickness (p = 0.02), and the left ventricular mass index (LVMi, p < 0.001). Interestingly, the duration of the pre-HD treatment, after referral, was positively associated with the plasma albumin (r = 0.229; p = 0.01) and negatively associated with the log CRP (r = –0.350; p < 0.001), iPTH (r = –0.309; p = 0.001) and LVMi (r = –0.268; p = 0.004). Multiple linear regression analysis also demonstrated that the log CRP and iPTH as well as the LR were independently associated with LVMi in the HD patients (p < 0.05). Conclusions: The results of this study demonstrated that the LR HD patients were at an increased risk for more cardiovascular related mortality, severe concentric LVH and systolic dysfunction accompanied by inflammatory and malnutrition indices, as well as with increased iPTH levels. In the LR patients, the more severe LVH associated with severe inflammatory indices, as well as the higher iPTH levels, may be one of the causes of LR-related mortality.

Safety and Efficacy of a Quinolone-Based Regimen for Treatment of Tuberculosis in Renal Transplant Recipients

BACKGROUND Rifampin (RFP) is a first-line antituberculosis drug, but it increases the risk of acute rejection (AR) in transplant recipients. This study evaluated whether quinolone (QNL) can replace RFP in renal transplant recipients with tuberculosis. METHODS One hundred nine patients with active tuberculosis were included. Patients consisted of RFP (n = 91) and QNL (n = 18) groups based on the initial treatment regimen. Patients with RFP-associated adverse effects were subdivided into RFP-maintenance (RFP-M; n = 18) and QNL-conversion (QNL-C; n = 8) groups. Clinical outcomes were compared between groups. RESULTS The incidence of AR was higher in the RFP group than in the QNL group (24.2% vs 5.6%). The QNL group showed significantly higher 10-year graft survival rates than the RFP group (88.1% vs 66.5%; P = .022). The QNL-C group showed significantly higher 10-year graft survival rates than the RFP-M group (87.5% vs 27.8%; P = .011). The rate of complete functional recovery after AR was higher in the QNL-C group than in the RFP-M group (50% vs 22.2%). CONCLUSIONS A QNL-based regimen may be safe and effective for treatment of tuberculosis and may lower the risk of graft failure in renal transplant recipients.

Acute renal failure presenting as a granulomatous interstitial nephritis due to cryptococcal infection

On admission the physical examination showed a body temperature of 37.81C, the blood pressure was 110/ 70mmHg, the pulse rate was 110 beats/min, and the respiratory rate was 28 breaths/min. There were no signs or symptoms indicating a neurological disorder. There was no palpable regional lymphadenopathy or abnormally pigmented skin lesions. Coarse inspiratory crackles were audible bilaterally over the basal lung fields. The abdomen was flat and soft without organomegaly. However, tenderness was noted at both costovertebral angles. In addition, there was pitting edema of both lower legs. The urine dipstick test was positive for protein (2 þ), with leukocyturia and microscopic hematuria on microscopic examination; the 24-h urine collection had 810mg of protein. The other biochemical values are summarized in Table 1. All viral markers were negative, including hepatitis B surface antigen, hepatitis C antibody, cytomegalovirus immunoglobulin M antibody, herpes simplex immunoglobulin M antibody, human immunodeficiency virus (HIV), and hantavirus antibody. An initial chest X-ray showed no active lung lesions, except for fibrocalcified opacities at both upper lung fields. The renal ultrasound revealed enlargement of both kidneys with normal corticomedullary differentiation, suggesting acute renal parenchymal disease.

The Impact of the Aortic Pulse Wave Velocity on the Cardiovascular Outcomes of Hemodialysis Patients

The aims of our study were to identify the risk factors for an increased aortic pulse wave velocity (AoPWV) and to assess the impact of the AoPWV on the cerebro-cardiovascular (CV) outcomes of hemodialysis (HD) patients. Seventy two HD patients were included, and the AoPWV, the echocardiography and the biochemical parameters were measured. After dividing the patients into tertiles according to the AoPWV values, we defined the low, the middle and the high AoPWV groups. The patients in the high AoPWV group showed a significantly higher age and high-sensitivity C-reactive protein level, a greater prevalence of diabetes and statin use, left ventricular hypertrophy, average pulse pressure (PP), AoPWV and left ventricular mass index and a lower serum albumin level than those in the low AoPWV group (p<0.05). On multivariate regression analysis of the AoPWV, age and the average PP were independently related to the AoPWV (p<0.05). On the multivariate Cox analysis for CV outcomes, the AoPWV and the average PP remained significant independent predictors of CV events. Our data suggest that an increased AoPWV is an independent predictor for the CV outcomes of HD patients.