Osamu Igawa

Uricosuric Action of Losartan via the Inhibition of Urate Transporter 1 (URAT 1) in Hypertensive Patients

BACKGROUND The angiotensin receptor blocker losartan inhibited urate transporter 1 (URAT1) according to in vitro experiments. However, it is still unknown whether the inhibitory effect of losartan on URAT1 contributes to its uricosuric action in humans. METHODS Thirty-two patients with hypertension and nine patients with idiopathic renal hypouricemia (five with and four without hypertension) were enrolled for this study. Hypertensive patients were prescribed oral losartan (50 mg/day, n = 16) or candesartan (8 mg/day, n = 16). Before and after 1-month treatment, the serum concentration of urate (Sur) and creatinine (Scr), and the clearance value of urate (Cur) and creatinine (Ccr) were determined. Clearance studies using the URAT1 inhibitor benzbromarone (100 mg/day) or losartan (50 mg/day) loading test were also performed in these patients. RESULTS Blood pressure (BP) significantly decreased in the patients treated with either losartan or candesartan. Losartan significantly reduced Sur, which was associated with a concomitant increase in the Cur/Ccr ratio, whereas candesartan did not alter these parameters. In hypertensive patients with loss-of-function mutation of URAT1, losartan did not alter either Sur or Cur/Ccr, nor did benzbromarone. The lack of effect of URAT1 inhibitors on renal excretion of urate was independent of the renal function of hypouricemic patients. On the other hand, both losartan and benzbromarone increased Cur/Ccr ratio in hypertensive patients harboring the wild URAT1 gene, regardless of the presence of hypouricemia. CONCLUSIONS These findings suggested that losartan inhibited URAT1 and thereby it lowered Sur levels in hypertensive patients.

Uric Acid-Lowering Treatment With Benzbromarone in Patients With Heart Failure A Double-Blind Placebo-Controlled Crossover Preliminary Study

Background— Hyperuricemia is common in chronic heart failure (CHF), and it is a strong independent marker of prognosis. Upregulated xanthine oxidase (XO) activity and impaired renal excretion have been shown to account for increased serum uric acid (UA) levels in CHF. Therapeutic interventions with allopurinol to reduce UA levels by XO inhibition have been shown to be beneficial. Discussions are ongoing whether UA itself is actively involved or it is a mere marker of upregulated XO activity within CHF pathophysiology. Therefore, the aim of this study was to test the effect of lowering UA by uricosuric treatment without XO inhibition on hemodynamic and metabolic characteristics of CHF. Impaired renal excretion of UA was taken into account. Methods and Results— Serum UA (SUA), urinary UA (uUA) excretion, and renal clearance test for UA (ClUA) were measured in 82 patients with CHF. SUA was significantly increased compared with controls of similar age (control, 5.45±0.70 mg/dL; New York Heart Association I, 6.48±1.70 mg/dL; New York Heart Association II, 7.34±1.94 mg/dL; New York Heart Association III, 7.61±2.11 mg/dL; P <0.01). Patients with CHF showed lower uUA excretion and ClUA. On multivariate analysis, insulin, brain natriuretic peptide ( P <0.01), and creatinine levels ( P =0.05) showed independent correlation with SUA. The treatment effect of the uricosuric agent benzbromarone was tested in 14 patients with CHF with hyperuricemia in a double-blind, placebo-controlled, randomized crossover study design. Benzbromarone significantly decreased SUA ( P <0.01). Brain natriuretic peptide, left ventricular ejection fraction, and dimensions in echocardiographic assessment did not change after benzbromarone therapy. In contrast, fasting insulin (placebo, 18.8±8.9 μU/mL; benzbromarone, 11.0±6.2 μU/mL; P <0.05), homeostasis model assessment of insulin resistance index (placebo, 5.4±2.6; benzbromarone, 3.0±1.7; P <0.05), and tumor necrosis factor-α (placebo, 2.59±0.63 pg/mL; benzbromarone, 2.14±0.51 pg/mL; P <0.05) improved after benzbromarone, and the changes in tumor necrosis factor-α levels were correlated with reduction of SUA ( P <0.05). Conclusions— These results show that UA lowering without XO inhibition may not have an effect on hemodynamic impairment in CHF pathophysiology. To the extent that these data are correct, this finding suggests that upregulated XO activity rather than UA itself is actively involved in hemodynamic impairment in CHF. Clinical Trial Registration— clinical trials.gov. Identifier: [NCT00422318][1]. Received March 26, 2009; accepted November 3, 2009. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT00422318&atom=%2Fcirchf%2F3%2F1%2F73.atomBackground—Hyperuricemia is common in chronic heart failure (CHF), and it is a strong independent marker of prognosis. Upregulated xanthine oxidase (XO) activity and impaired renal excretion have been shown to account for increased serum uric acid (UA) levels in CHF. Therapeutic interventions with allopurinol to reduce UA levels by XO inhibition have been shown to be beneficial. Discussions are ongoing whether UA itself is actively involved or it is a mere marker of upregulated XO activity within CHF pathophysiology. Therefore, the aim of this study was to test the effect of lowering UA by uricosuric treatment without XO inhibition on hemodynamic and metabolic characteristics of CHF. Impaired renal excretion of UA was taken into account. Methods and Results—Serum UA (SUA), urinary UA (uUA) excretion, and renal clearance test for UA (ClUA) were measured in 82 patients with CHF. SUA was significantly increased compared with controls of similar age (control, 5.45±0.70 mg/dL; New York Heart Association I, 6.48±1.70 mg/dL; New York Heart Association II, 7.34±1.94 mg/dL; New York Heart Association III, 7.61±2.11 mg/dL; P<0.01). Patients with CHF showed lower uUA excretion and ClUA. On multivariate analysis, insulin, brain natriuretic peptide (P<0.01), and creatinine levels (P=0.05) showed independent correlation with SUA. The treatment effect of the uricosuric agent benzbromarone was tested in 14 patients with CHF with hyperuricemia in a double-blind, placebo-controlled, randomized crossover study design. Benzbromarone significantly decreased SUA (P<0.01). Brain natriuretic peptide, left ventricular ejection fraction, and dimensions in echocardiographic assessment did not change after benzbromarone therapy. In contrast, fasting insulin (placebo, 18.8±8.9 &mgr;U/mL; benzbromarone, 11.0±6.2 &mgr;U/mL; P<0.05), homeostasis model assessment of insulin resistance index (placebo, 5.4±2.6; benzbromarone, 3.0±1.7; P<0.05), and tumor necrosis factor-&agr; (placebo, 2.59±0.63 pg/mL; benzbromarone, 2.14±0.51 pg/mL; P<0.05) improved after benzbromarone, and the changes in tumor necrosis factor-&agr; levels were correlated with reduction of SUA (P<0.05). Conclusions—These results show that UA lowering without XO inhibition may not have an effect on hemodynamic impairment in CHF pathophysiology. To the extent that these data are correct, this finding suggests that upregulated XO activity rather than UA itself is actively involved in hemodynamic impairment in CHF. Clinical Trial Registration—clinicaltrials.gov. Identifier: NCT00422318.

Appropriate Use of Nasal Continuous Positive Airway Pressure Decreases Elevated C-Reactive Protein in Patients With Obstructive Sleep Apnea

BACKGROUND C-reactive protein (CRP) is an important risk factor for cardiovascular disease. Furthermore, it has been reported that levels of CRP are increased in patients with obstructive sleep apnea (OSA). The aim of this study was to examine the effects of long-term therapy with nasal continuous positive airway pressure (nCPAP) on CRP levels and to investigate whether compliance with nCPAP therapy more effectively attenuated markers of systemic inflammation in patients with OSA. METHODS AND RESULTS Fifty-five patients (mean [+/- SEM] age, 55 +/- 2 years; 44 male patients, 11 female patients) with newly diagnosed moderate-to-severe OSA (apnea-hypopnea index > 20 events/h) were studied before and after 6 months of nCPAP treatment. There was a significant reduction in CRP levels after nCPAP therapy (before nCPAP therapy, 0.23 +/- 0.03 mg/dL; after nCPAP therapy, 0.17 +/- 0.02 mg/dL; p < 0.01). Additionally, we divided these patients into two groups based on adherence to nCPAP therapy. A group of patients using nCPAP > 4 h/d and > 5 d/wk were designated as the good compliance group. The decrease in CRP concentration was significant (before nCPAP therapy, 0.23 +/- 0.04 mg/dL; after nCPAP therapy, 0.16 +/- 0.03 mg/dL; p < 0.05) in the good compliance group but not in the poor compliance group (before nCPAP therapy, 0.24 +/- 0.05 mg/dL; after nCPAP therapy, 0.20 +/- 0.05 mg/dL; p = 0.21). Furthermore, we divided those patients into a high CRP group (>/= 0.2 mg/dL) and a normal CRP group (< 0.2 mg/dL) before nCPAP therapy. The significant decrease in CRP levels in the good compliance group was evident only in those patients with an initially elevated CRP level (before nCPAP therapy, 0.48 +/- 0.08 mg/dL; after nCPAP therapy, 0.29 +/- 0.06 mg/dL; p < 0.05). CONCLUSION Appropriate use of nCPAP in patients with OSA may be required to decrease elevated CRP levels, with possible implications for cardiovascular morbidity and mortality.

Ubiquitin-Proteasome System Impairment Caused by a Missense Cardiac Myosin-binding Protein C Mutation and Associated with Cardiac Dysfunction in Hypertrophic Cardiomyopathy

The ubiquitin-proteasome system is responsible for the disappearance of truncated cardiac myosin-binding protein C, and the suppression of its activity contributes to cardiac dysfunction. This study investigated whether missense cardiac myosin-binding protein C gene (MYBPC3) mutation in hypertrophic cardiomyopathy (HCM) leads to destabilization of its protein, causes UPS impairment, and is associated with cardiac dysfunction. Mutations were identified in Japanese HCM patients using denaturing HPLC and sequencing. Heterologous expression was investigated in COS-7 cells as well as neonatal rat cardiac myocytes to examine protein stability and proteasome activity. The cardiac function was measured using echocardiography. Five novel MYBPC3 mutations -- E344K, DeltaK814, Delta2864-2865GC, Q998E, and T1046M -- were identified in this study. Compared with the wild type and other mutations, the E334K protein level was significantly lower, it was degraded faster, it had a higher level of polyubiquination, and increased in cells pretreated with the proteasome inhibitor MG132 (50 microM, 6 h). The electrical charge of its amino acid at position 334 influenced its stability, but E334K did not affect its phosphorylation. The E334K protein reduced cellular 20 S proteasome activity, increased the proapoptotic/antiapoptotic protein ratio, and enhanced apoptosis in transfected Cos-7 cells and neonatal rat cardiac myocytes. Patients carrying the E334K mutation presented significant left ventricular dysfunction and dilation. The conclusion is the missense MYBPC3 mutation E334K destabilizes its protein through UPS and may contribute to cardiac dysfunction in HCM through impairment of the ubiquitin-proteasome system.

Uric Acid-Lowering Treatment With Benzbromarone in Patients With Heart FailureCLINICAL PERSPECTIVE

Background— Hyperuricemia is common in chronic heart failure (CHF), and it is a strong independent marker of prognosis. Upregulated xanthine oxidase (XO) activity and impaired renal excretion have been shown to account for increased serum uric acid (UA) levels in CHF. Therapeutic interventions with allopurinol to reduce UA levels by XO inhibition have been shown to be beneficial. Discussions are ongoing whether UA itself is actively involved or it is a mere marker of upregulated XO activity within CHF pathophysiology. Therefore, the aim of this study was to test the effect of lowering UA by uricosuric treatment without XO inhibition on hemodynamic and metabolic characteristics of CHF. Impaired renal excretion of UA was taken into account. Methods and Results— Serum UA (SUA), urinary UA (uUA) excretion, and renal clearance test for UA (ClUA) were measured in 82 patients with CHF. SUA was significantly increased compared with controls of similar age (control, 5.45±0.70 mg/dL; New York Heart Association I, 6.48±1.70 mg/dL; New York Heart Association II, 7.34±1.94 mg/dL; New York Heart Association III, 7.61±2.11 mg/dL; P <0.01). Patients with CHF showed lower uUA excretion and ClUA. On multivariate analysis, insulin, brain natriuretic peptide ( P <0.01), and creatinine levels ( P =0.05) showed independent correlation with SUA. The treatment effect of the uricosuric agent benzbromarone was tested in 14 patients with CHF with hyperuricemia in a double-blind, placebo-controlled, randomized crossover study design. Benzbromarone significantly decreased SUA ( P <0.01). Brain natriuretic peptide, left ventricular ejection fraction, and dimensions in echocardiographic assessment did not change after benzbromarone therapy. In contrast, fasting insulin (placebo, 18.8±8.9 μU/mL; benzbromarone, 11.0±6.2 μU/mL; P <0.05), homeostasis model assessment of insulin resistance index (placebo, 5.4±2.6; benzbromarone, 3.0±1.7; P <0.05), and tumor necrosis factor-α (placebo, 2.59±0.63 pg/mL; benzbromarone, 2.14±0.51 pg/mL; P <0.05) improved after benzbromarone, and the changes in tumor necrosis factor-α levels were correlated with reduction of SUA ( P <0.05). Conclusions— These results show that UA lowering without XO inhibition may not have an effect on hemodynamic impairment in CHF pathophysiology. To the extent that these data are correct, this finding suggests that upregulated XO activity rather than UA itself is actively involved in hemodynamic impairment in CHF. Clinical Trial Registration— clinical trials.gov. Identifier: [NCT00422318][1]. Received March 26, 2009; accepted November 3, 2009. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT00422318&atom=%2Fcirchf%2F3%2F1%2F73.atomBackground—Hyperuricemia is common in chronic heart failure (CHF), and it is a strong independent marker of prognosis. Upregulated xanthine oxidase (XO) activity and impaired renal excretion have been shown to account for increased serum uric acid (UA) levels in CHF. Therapeutic interventions with allopurinol to reduce UA levels by XO inhibition have been shown to be beneficial. Discussions are ongoing whether UA itself is actively involved or it is a mere marker of upregulated XO activity within CHF pathophysiology. Therefore, the aim of this study was to test the effect of lowering UA by uricosuric treatment without XO inhibition on hemodynamic and metabolic characteristics of CHF. Impaired renal excretion of UA was taken into account. Methods and Results—Serum UA (SUA), urinary UA (uUA) excretion, and renal clearance test for UA (ClUA) were measured in 82 patients with CHF. SUA was significantly increased compared with controls of similar age (control, 5.45±0.70 mg/dL; New York Heart Association I, 6.48±1.70 mg/dL; New York Heart Association II, 7.34±1.94 mg/dL; New York Heart Association III, 7.61±2.11 mg/dL; P<0.01). Patients with CHF showed lower uUA excretion and ClUA. On multivariate analysis, insulin, brain natriuretic peptide (P<0.01), and creatinine levels (P=0.05) showed independent correlation with SUA. The treatment effect of the uricosuric agent benzbromarone was tested in 14 patients with CHF with hyperuricemia in a double-blind, placebo-controlled, randomized crossover study design. Benzbromarone significantly decreased SUA (P<0.01). Brain natriuretic peptide, left ventricular ejection fraction, and dimensions in echocardiographic assessment did not change after benzbromarone therapy. In contrast, fasting insulin (placebo, 18.8±8.9 &mgr;U/mL; benzbromarone, 11.0±6.2 &mgr;U/mL; P<0.05), homeostasis model assessment of insulin resistance index (placebo, 5.4±2.6; benzbromarone, 3.0±1.7; P<0.05), and tumor necrosis factor-&agr; (placebo, 2.59±0.63 pg/mL; benzbromarone, 2.14±0.51 pg/mL; P<0.05) improved after benzbromarone, and the changes in tumor necrosis factor-&agr; levels were correlated with reduction of SUA (P<0.05). Conclusions—These results show that UA lowering without XO inhibition may not have an effect on hemodynamic impairment in CHF pathophysiology. To the extent that these data are correct, this finding suggests that upregulated XO activity rather than UA itself is actively involved in hemodynamic impairment in CHF. Clinical Trial Registration—clinicaltrials.gov. Identifier: NCT00422318.

Interleukin-6 and tumor necrosis factor-α levels increase in response to maximal exercise in patients with chronic heart failure

Abstract Chronic heart failure (CHF) is characterized by the activation of neurohormones and cytokines. Strenuous exercise causes activation of both systems but the effect of acute bouts of exercise on cytokines is not known in patients with CHF. This study determined whether maximal exercise induces activation of cytokines in CHF. Plasma interleukin-6 (IL-6), tumor necrosis factor (TNF)-α, epinephrine, norepinephrine, and atrial and brain natriuretic peptides (ANP and BNP) were determined before and after symptom-limited cardiopulmonary exercise testing in 80 patients with CHF (LVEF=38±1%, peak V O 2 =18.8±0.5 ml/min/kg) and age-matched 33 controls. Resting IL-6 (Controls vs. CHF: 1.3±0.2 vs. 2.5±0.3 pg/ml, P P r =0.34 and r =0.35, respectively) with logplasma norepinephrine, and were negatively correlated ( r =−0.39 and r =−0.32, respectively) with peak V O 2 . Maximal exercise increased IL-6 and TNF-α both in controls and CHF (all P r =0.63, P r =0.57, P =0.0006) in controls, but not in CHF. ΔTNF-α correlated with ΔANP ( r =0.28, P =0.01) only in CHF. In summary, cytokine activation at rest was associated with high plasma norepinephrine and exercise intolerance. Maximal exercise caused increases in IL-6 and TNF-α concentrations. Sympathetic activation seems to be important for the IL-6 increase during exercise in controls. In CHF, changes in ANP during exercise were associated with the exercise-induced increase in TNF-α, but still unknown mechanisms are involved for the cytokine activation during exercise.

Augmented response in plasma brain natriuretic peptide to dynamic exercise in patients with left ventricular dysfunction and congestive heart failure

Abstract. Kato M, Kinugawa T, Ogino K, Endo A, Osaki S, Igawa O, Hisatome I, Shigemasa C (Tottori University Faculty of Medicine, Yonago, Japan). Augmented response in plasma brain natriuretic peptide to dynamic exercise in patients with left ventricular dysfunction and congestive heart failure. J Intern Med 2000; 248: 309–315.

Mitochondrial DNA deletion associated with the reduction of adenine nucleotides in human atrium and atrial fibrillation

Background Structural changes in the number, size, and shape of mitochondria (mt) have been observed in the atrial muscles of patients with atrial fibrillation (AF) and of animals with rapid atrial pacing, however, it is not known whether the mitochondrial function is impaired in human atrium with AF.

Age-related BM-MNC dysfunction hampers neovascularization.

Although ischemia-induced neovascularization is reportedly impaired with aging, the effect of aged-bone marrow mononuclear cells (BM-MNCs) on neovascularization has not been investigated. The neovascularization capacity of BM-MNCs obtained from 8-week-old mice (young) was compared to those obtained from 18-month-old mice (old), both in vivo and in vitro. Neovascularization in ischemic limbs was significantly impaired in old mice. Whereas transplantation of young BM-MNCs significantly improved blood perfusion, tissue capillary density, and vascular endothelial growth factor (VEGF) production in transplanted ischemic limbs, no such effects were observed with old BM-MNCs. Old BM-MNCs also showed a significant impairment of in vitro VEGF production and migratory capacity in response to VEGF. The number of Dil/lectin-positive cells was significantly lower in old mice, but there was no difference in the number of AC133(+)/CD34(+) and CD34(+)/VEGF-R2(+) positive cells between young and old BM-MNCs. Transplantation of young BM-MNCs improved neovascularization and VEGF production in the ischemic limbs of old recipients, with results that were similar to those obtained in young recipients. These results indicate that the neovascularization capacity of transplanted BM-MNCs is impaired with aging. However, aging does not hamper the revitalization of neovascularization in the murine host in response to transplantation of young BM-MNCs.

Reciprocal Control of hERG Stability by Hsp70 and Hsc70 With Implication for Restoration of LQT2 Mutant Stability

Rationale: The human ether-a-go-go–related gene (hERG) encodes the &agr; subunit of the potassium current IKr. It is highly expressed in cardiomyocytes and its mutations cause long QT syndrome type 2. Heat shock protein (Hsp)70 is known to promote maturation of hERG. Hsp70 and heat shock cognate (Hsc70) 70 has been suggested to play a similar function. However, Hsc70 has recently been reported to counteract Hsp70. Objective: We investigated whether Hsc70 counteracts Hsp70 in the control of wild-type and mutant hERG stability. Methods and Results: Coexpression of Hsp70 with hERG in HEK293 cells suppressed hERG ubiquitination and increased the levels of both immature and mature forms of hERG. Immunocytochemistry revealed increased levels of hERG in the endoplasmic reticulum and on the cell surface. Electrophysiological studies showed increased IKr. All these effects of Hsp70 were abolished by Hsc70 coexpression. Heat shock treatment of HL-1 mouse cardiomyocytes induced endogenous Hsp70, switched mouse ERG associated with Hsc70 to Hsp70, increased IKr, and shortened action potential duration. Channels with disease-causing missense mutations in intracellular domains had a higher binding capacity to Hsc70 than wild-type channels and channels with mutations in the pore region. Knockdown of Hsc70 by small interfering RNA or heat shock prevented degradation of mutant hERG proteins with mutations in intracellular domains. Conclusions: These results indicate reciprocal control of hERG stability by Hsp70 and Hsc70. Hsc70 is a potential target in the treatment of LQT2 resulting from missense hERG mutations.