Cheol Whee Park

Intravenous calcitriol regresses myocardial hypertrophy in hemodialysis patients with secondary hyperparathyroidism

To evaluate the response of circulating intact parathyroid hormone (iPTH) on myocardial hypertrophy in hemodialysis (HD) patients with secondary hyperparathyroidism (SHPT), echocardiographic and neurohormonal assessments were performed over a 15-week period in 15 HD patients with SHPT before and after calcitriol treatment and 10 HD control patients with SHPT not receiving calcitriol therapy. We prospectively studied a group of 15 patients with significantly elevated iPTH levels (iPTH >450 pg/mL) receiving calcitriol (2 microg after dialysis twice weekly). Clinical assessment, medication status, and biochemical and hematological measurements were performed once a month. Throughout the study, calcium carbonate levels were modified to maintain serum phosphate levels at less than 6 mg/dL, but body weight, antihypertensive medication, and ultrafiltration dose remained constant. In patients treated with calcitriol, an adequate reduction of iPTH levels was found (1,112 +/- 694 v 741 +/- 644 pg/mL; P < 0.05) without changes in values of serum ionized calcium (iCa++), phosphate, or hematocrit. Blood pressure (BP), cardiac output (CO), and total peripheral resistance (TPR) did not significantly change. After 15 weeks of treatment with calcitriol, M-mode echocardiograms showed pronounced reductions in interventricular wall thickness (13.9 +/- 3.6 v 12.8 +/- 3.10 mm; P = 0.01), left ventricular posterior wall thickness (12.5 +/- 2.4 v 11.3 +/- 1.8 mm; P < 0.05), and left ventricle mass index (LVMi; 178 +/- 73 v 155 +/- 61 g/m2; P < 0.01). However, in control patients, these changes were not found after the treatment period. In addition, sequential measurements of neurohormonal mediator levels in patients receiving calcitriol showed that plasma renin (18.5 +/- 12.7 v 12.3 +/- 11.0 pg/mL; P = 0.007), angiotensin II (AT II; 79.7 +/- 48.6 v 47.2 +/- 45.7 pg/mL; P = 0.001), and atrial natriuretic peptide (ANP; 16.6 +/- 9.7 v 12.2 +/- 4.4 pg/mL; P = 0.03) levels significantly decreased, whereas antidiuretic hormone (ADH), epinephrine, and norepinephrine levels did not change significantly. The percent change in LVMi associated with calcitriol therapy had a strong correlation with the percent change in iPTH (r = 0.52; P < 0.05) and AT II (r = 0.47; P < 0.05) levels. We conclude that the partial correction of SHPT with intravenous calcitriol causes a regression in myocardial hypertrophy without biochemical or hemodynamic changes, such as heart rate, BP, and TPR. The changes in plasma levels of iPTH and, secondarily, plasma levels of neurohormones (especially AT II) after calcitriol therapy may have a key role in attenuating ventricular hypertrophy in SHPT.

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.

Calcitriol regresses cardiac hypertrophy and QT dispersion in secondary hyperparathyroidism on hemodialysis.

Background: Sudden cardiac death is common in patients on hemodialysis (HD), and its rate is as high as 25% of all cardiac deaths associated with left ventricular hypertrophy (LVH) and secondary hyperparathyroidism. A prolonged QT interval on standard electrocardiography is related to an increase in sudden death in various patient groups. It is also well known that LVH has been noted in uremic patients with high parathyroid hormone levels. Methods: To evaluate the response of intravenous calcitriol treatment on the QT interval and LVH in HD patients with secondary hyperparathyroidism (intact parathyroid hormone, iPTH, >450 ng/ml), echocardiographic, electrocardiographic (ECG), and biochemical assessments were performed over a 15-week period in 25 HD patients before and after intravenous calcitriol treatment. We also evaluated 25 age-, sex-, HD duration-, and BMI-matched HD control patients with secondary hyperparathyroidism. Results: In patients receiving intravenous calcitriol, a significant reduction in iPTH levels (p < 0.05) and alkaline phosphatase levels (p < 0.01) was found without changes in values of serum calcium and ionized Ca2+, phosphorus, Na+, K+, Mg2+, hematocrit, blood pressure, or other hemodynamic changes. Echocardiograms showed significant decreases in the thickness of the interventricular septum (p < 0.05), left posterior wall thickness (p < 0.05), and left ventricle mass index (LVMi, p < 0.01). In addition, sequential ECG measurement in patients with calcitriol treatment showed significant reductions in QTcmax (QTmax interval corrected for heart rates, p < 0.01) and QTc dispersion (QT dispersion corrected for heart rates, p < 0.01). However, in the control patients, biochemical, hemodynamic, and ECG changes, as well as myocardial structural and functional changes were not seen. Multiple regression analysis in all patients indicated that iPTH and LVMi levels were independent predictors of QTcmax while the LVMi level was the only independent predictor of QTc dispersion (p < 0.05). Conclusions: Our study showed a significant correlation between LVMi and QT dispersion in HD patients with secondary hyperparathyroidism. Intravenous calcitriol treatment, to be used for the control of secondary hyperparathyroidism, was found to cause regression of myocardial hypertrophy and a reduction in the QTc interval and dispersion, without biochemical and hemodynamic changes. These findings suggest that an active vitamin D metabolite has a cardioprotective action in HD patients.

High glucose-induced intercellular adhesion molecule-1 (ICAM-1) expression through an osmotic effect in rat mesangial cells is PKC-NF-ϰB-dependent

AbstractsAims/hypothesis. Infiltration of mononuclear cells and glomerular enlargement accompanied by glomerular cell proliferation are very early characteristics of the pathophysiology of diabetes. To clarify the mechanism of early diabetic nephropathy, we measured [3H]-thymidine incorporation and cell numbers to show the influence of a high ambient glucose concentration and the osmotic effect on rat mesangial cell proliferation. We also measured the effect of high glucose on the expression of intercellular adhesion molecule-1 and vascular adhesion molecule-1 by flow cytometry and semiquantitative RT-PCR in mesangial cells and the adhesion of leukocytes to mesangial cells. Methods/results. Cells exposed to high d-glucose (30 mmol/l) caused an increase in [3H]-thymidine incorporation and cell numbers at 24 and 48 h and normalized at 72 h (p < 0.05), whereas these changes were not found in high mannitol (30 mmol/l), IL-1β, or TNFα-stimulated mesangial cells. Cells exposed to high-glucose (15, 30, or 60 mmol/l) or osmotic agents (l-glucose, raffinose and mannitol) showed that intercellular adhesion molecule-1 expression began to increase after 24 h, reached its maximum at 24 and 48 h and gradually decreased afterwards. The stimulatory effects of high glucose and high mannitol on mRNA expression were observed as early as 6 h and reached its maximum at 12 h. Up-regulation of ICAM-1 protein and mRNA was also found in IL-1-β and TNF-α-stimulated mesangial cells. Neither vascular adhesion molecule-1 protein nor mRNA expression was, however, affected by high glucose and high mannitol. Notably, the protein kinase C inhibitors calphostin C and staurosporine reduced high glucose- or high mannitol-induced intercellular adhesion molecule-1 mRNA expression and high glucose-induced proliferation. Furthermore, the NF-ϰB inhibitor N-tosyl-l-phenylalanine chloromethyl ketone reduced high glucose- or high mannitol-induced intercellular adhesion molecule-1 mRNA expression and high glucose-induced proliferation. Results showed that high glucose (15, 30 mmol/l) or high concentrations of osmotic agents remarkably increased the number of adherent leukocytes to mesangial cells (p < 0.01) compared with control cells (5 mmol/l d-glucose). Functional blocking of intercellular adhesion molecule-1 on mesangial cells with rat intercellular adhesion molecule-1 monoclonal antibody, calphostin C, staurosporine, or N-tosyl-l-phenylalanine chloromethyl ketone significantly inhibited high glucose- or high mannitol-induced increase in leukocyte adhesion (p < < 0.05). Conclusion/interpretation. These results suggest that high glucose can upregulate intercellular adhesion molecule-1 protein and mRNA expression but not vascular adhesion molecule-1 expression in mesangial cells and promote leukocyte adhesion through up-regulation of intercellular adhesion molecule-1 through osmotic effect, possibly depending on the protein kinase C nuclear factor-kappa B (PKC-NF-ϰB) pathway. High glucose itself can also promote mesangial cell proliferation through the PKC-NF-ϰB pathways. We conclude that hyperglycaemia in itself seems to be an important factor in the development of early diabetic nephropathy. [Diabetologia (2000) 43: 1544–1553]

The Oxford classification as a predictor of prognosis in patients with IgA nephropathy.

BACKGROUND In 2009, the Oxford classification was developed as a pathological classification system for immunoglobulin A nephropathy (IgAN) to predict the risk of disease progression. The aim of this retrospective study was to evaluate the clinical and pathologic relevance of the Oxford classification in Korean patients with a pathologic diagnosis of IgAN. PATIENTS AND METHODS We reviewed the renal pathology archives from January 2000 to December 2006 at Seoul St Marys Hospital in Korea and identified 273 patients, who were diagnosed as having IgAN. We enrolled 197 patients who were available for further clinicopathologic analysis. All cases of IgAN were categorized according to the WHO classification, the semiquantitative classification and the Oxford classification. These pathologic classifications were compared. The clinical and laboratory findings at the time of biopsy were compared with those at the end of the follow-up according to the Oxford classification. RESULTS When three pathologic classifications were compared, M1, S1, E1, T1 or T2 were associated with a higher score in the activity index. S1, T1 or T2 were associated with a higher score in the chronicity index and a higher grade in the WHO classification. The clinical and laboratory findings were compared according to the Oxford classification. At the time of biopsy, the proteinuria in patients with M1 was more than that of M0 (P = 0.035). At the end of follow-up, the number of antihypertensive drugs taken among patients with M1 was greater than that of patients with M0 (P = 0.001). At the time of biopsy, the proteinuria of patients with S1 was greater than that of S0 patients (P = 0.009). At the end of follow-up, the number of patients who received immunosuppressants was increased as the grade of T increased (P = 0.000). At the end point of the follow-up, the estimated glomerular filtration rate (eGFR) decreased as the grade of T increased (P = 0.008). The time-average proteinuria after adjusting the initial proteinuria increased significantly with increasing degree of T (P = 0.000). Levels of tubular atrophy/interstitial fibrosis were predictive for survival from end-stage renal disease or of having a 50% reduction of eGFR. CONCLUSION The pathologic variables of the Oxford classification correlated significantly with other classifications (the WHO classification and the semiquantitative classification). The Oxford classification is a simple method for predicting renal outcome and differentiating between active and chronic lesions. We suggest that the Oxford classification offers an advantage for determining treatment policy for patients with IgAN.

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.

Fenofibrate Improves Renal Lipotoxicity through Activation of AMPK-PGC-1α in db/db Mice

Peroxisome proliferator-activated receptor (PPAR)-α, a lipid-sensing transcriptional factor, serves an important role in lipotoxicity. We evaluated whether fenofibrate has a renoprotective effect by ameliorating lipotoxicity in the kidney. Eight-week-old male C57BLKS/J db/m control and db/db mice, divided into four groups, received fenofibrate for 12 weeks. In db/db mice, fenofibrate ameliorated albuminuria, mesangial area expansion and inflammatory cell infiltration. Fenofibrate inhibited accumulation of intra-renal free fatty acids and triglycerides related to increases in PPARα expression, phosphorylation of AMP-activated protein kinase (AMPK), and activation of Peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α)-estrogen-related receptor (ERR)-1α-phosphorylated acetyl-CoA carboxylase (pACC), and suppression of sterol regulatory element-binding protein (SREBP)-1 and carbohydrate regulatory element-binding protein (ChREBP)-1, key downstream effectors of lipid metabolism. Fenofibrate decreased the activity of phosphatidylinositol-3 kinase (PI3K)-Akt phosphorylation and FoxO3a phosphorylation in kidneys, increasing the B cell leukaemia/lymphoma 2 (BCL-2)/BCL-2-associated X protein (BAX) ratio and superoxide dismutase (SOD) 1 levels. Consequently, fenofibrate recovered from renal apoptosis and oxidative stress, as reflected by 24 hr urinary 8-isoprostane. In cultured mesangial cells, fenofibrate prevented high glucose-induced apoptosis and oxidative stress through phosphorylation of AMPK, activation of PGC-1α-ERR-1α, and suppression of SREBP-1 and ChREBP-1. Our results suggest that fenofibrate improves lipotoxicity via activation of AMPK-PGC-1α-ERR-1α-FoxO3a signaling, showing its potential as a therapeutic modality for diabetic nephropathy.

Age-Associated Molecular Changes in the Kidney in Aged Mice

Background. Aging is a multifactorial process characterized by a progressive decline in physiological function. Decreased kidney function is associated with cardiovascular disease and mortality. Therefore, increasing our insight into kidney aging by understanding the anatomic, physiologic, and pathologic changes of aging in the kidney is important to prevent disastrous outcomes in elderly people. Methods. Male two-, 12-, and 24-month-old C57/BL6 mice were used in this study. We measured histological change, oxidative stress, and aging-related protein expression in the kidneys. Results. Twenty-four-month-old mice displayed increased albuminuria. Creatinine clearance decreased with aging, although this was not statistically significant. There were increases in mesangial volume and tubulointerstitial fibrosis in 24-month-old mice. There were also increases in F4/80 expression and in apoptosis detected by TUNEL assay. Urine isoprostane excretion increased with aging and SOD1 and SOD2 were decreased in 24-month-old mice. Oxidative stress may be mediated by a decrease in Sirt1, PGC-1α, ERR-1α, and PPARα expression. Klotho expression also decreased. Conclusions. Our results demonstrate that Sirt1 was decreased with aging and may relate to changed target molecules including PGC-1α/ERR-1α signaling and PPARα. Klotho can also induce oxidative stress. Pharmacologically targeting these signaling molecules may reduce the pathologic changes of aging in the kidney.

Diabetic kidney disease: from epidemiology to clinical perspectives.

With worldwide epidemic of diabetes mellitus, diabetic nephropathy which is one of the major causes of microvascular complication has become a serious concern in Korea as well as the rest of the world. In view of its significance, there is an urgent and paramount need for proper managements that could either deter or slow the progression of diabetic nephropathy. Despite advances in care, ever increasing number of patients suffering from diabetic kidney disease and from end-stage renal disease implies that the current management is not adequate in many aspects. The reasons for these inadequacies compromise lack of early diagnosis, failure to intervene with timely and aggressive manner, and lack of understanding on the kind of interventions required. Another issue equally important for the adequate care of patients with diabetic nephropathy is an understanding of past, present and future epidemiology of diabetic nephropathy which serves, especially in Korea, as a material determining standard diagnosis and treatment and a national health-policy decision.

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.