Naoto Yokota

Plasma Concentration of Human Brain Natriuretic Peptide in Patients on Hemodialysis

The plasma concentration of immunoreactive human brain natriuretic peptide (ir-BNP) was measured in 40 patients on hemodialysis (HD) and in 12 healthy subjects. Immunoreactive human atrial natriuretic peptide (ir-ANP) was also measured. The mean (+/- SE) plasma ir-BNP concentration in the patients before HD (18.4 +/- 3.4 fmol/mL) was markedly higher than that in the control group (0.39 +/- 0.08 fmol/mL). The plasma ir-BNP level was significantly decreased by HD from 18.4 +/- 3.4 fmol/mL to 10.5 +/- 2.2 fmol/mL (P < 0.001), but the latter value was still higher than the upper limit of the normal range for our laboratory. There were significant correlations between the plasma ir-ANP level and the mean blood pressure before HD (P < 0.05) and between the HD-induced changes in plasma ir-ANP level and mean blood pressure (P < 0.001). These correlations were not observed between the plasma ir-BNP level and mean blood pressure. The plasma ir-BNP level correlated with the cardiothoracic ratio and this correlation was closer to that between the plasma ir-ANP level and cardiothoracic ratio. Ultrasound echocardiographic studies in 13 patients revealed that the pre-HD state of high cardiac output was correlated by HD in association with decreases in plasma ir-BNP and ir-ANP levels. Correlations were observed between the pre-HD ir-ANP level and the interventricular septal thickness index (r = 0.68, P < 0.05) and between the change in ir-BNP level and that in left atrial diameter (r = 0.806, P < 0.001). In conclusion, BNP levels were high in HD patients compared with the control subjects and were decreased during HD. In addition, BNP and ANP levels correlated with several parameters of volume change and cardiac status.

Plasma and Urine Levels of Uroguanylin, a New Natriuretic Peptide, in Nephrotic Syndrome

Uroguanylin, a new natriuretic peptide originally isolated from urine, stimulates the membrane guanylate cyclase C receptor. No information, however, is available on the plasma and urine levels of uroguanylin in nephrotic syndrome (NS), the state associated with sodium and water retention. Using a sensitive radioimmunoassay, we measured the plasma and urine concentrations of immunoreactive (ir-)uroguanylin in NS patients and compared them with those of patients with non-nephrotic glomerulonephritis. Plasma ir-uroguanylin, blood pressure and the cardiothoracic ratio were higher, and urine excretion of ir-uroguanylin was lower in the NS patients. Plasma ir-uroguanylin in the NS patients significantly decreased during remission as compared with findings on admission. There was a significant inverse correlation between the concentration of plasma ir-uroguanylin and that of serum total protein or albumin. Moreover, fluid retention in the NS patients was correlated with the changes in plasma ir-uroguanylin between admission and remission, indicative that the plasma concentration increases with the severity of the nephrotic state. Taking into account its potent natriuretic effect, these findings suggest that uroguanylin may function in the pathophysiological mechanism in NS.

Efficacy of alogliptin, a dipeptidyl peptidase-4 inhibitor, on glucose parameters, the activity of the advanced glycation end product (AGE) – receptor for AGE (RAGE) axis and albuminuria in Japanese type 2 diabetes

To examine the effects of alogliptin, a dipeptidyl peptidase‐4 inhibitor, on glucose parameters, the advanced glycation end product (AGE)‐receptor for AGE (RAGE) axis and albuminuria in Japanese type 2 diabetes patients.

One-year effectiveness and safety of open-label losartan/hydrochlorothiazide combination therapy in Japanese patients with hypertension uncontrolled with ARBs or ACE inhibitors

The long-term antihypertensive efficacy and safety of losartan/hydrochlorothiazide (HCTZ) combinations have not been appropriately evaluated in Japan. In this study, treated hypertensive patients taking angiotensin-receptor blocker (ARB) or angiotensin-converting enzyme inhibitor (ACEI) regimens not at blood pressure (BP) goals proposed by the Japanese Society of Hypertension (JSH) were switched to losartan/HCTZ combinations and followed for 1 year. Data analysis included 244 patients aged 64.5±10.7 years, 56% male, 27% with diabetes mellitus and 36% with dyslipidemia. Pre-switching BP 157±16/88±10 mm Hg promptly decreased and maintained a steady state, reaching 132±15/77±9 mm Hg (P<0.001) 1 year later. After 1 year of treatment, 50% of patients cleared the goals of the JSH guideline for systolic BP and 79% for diastolic BP. Patients with maximal doses of ARBs tended to show larger decreases in BP (159±11/90±10 to 128±10/75±8 mm Hg, P<0.001, n=32). Clinical and laboratory adverse events were reported for 29 patients (11%), but serious abnormalities were not observed. In particular, plasma levels of uric acid (UA) were well-maintained for 1 year, and significant decreases in UA were observed in patients with higher levels of UA (⩾7.0 mg dl−1). Losartan/HCTZ combinations showed strong and steady hypotensive abilities and acceptable safety and tolerability in patients currently not at BP goals with regimens including ARBs or ACEIs in Japan.

Plasma and urine levels of adrenomedullin and proadrenomedullin N-terminal 20 peptide in chronic glomerulonephritis

Proadrenomedullin N-terminal 20 peptide (PAMP) is a novel hypotensive peptide present in the precursor of adrenomedullin (AM), a vasodilative and natriuretic peptide. We examined the plasma and urinary levels of these peptides in patients with chronic glomerulonephritis (CGN). The mean plasma AM concentration of the patients with CGN did not differ from that of control subjects (4.17 +/- 0.17 v 3.87 +/- 0.21 fmol/mL, respectively), whereas urinary AM excretion was significantly less in the patients with CGN (5.96 +/- 0.95 v control, 8.93 +/- 1.02 fmol/mg of creatinine; P < 0.05). Plasma concentrations and urinary excretion of PAMP were significantly less for the patients with CGN compared with control subjects (0.91 +/- 0.08 v 1.23 +/- 0.20 fmol/mL; P < 0.05 and 25.0 +/- 3.0 v 35.0 +/- 3.6 fmol/mg of creatinine, respectively; P < 0. 05). The plasma AM concentration was negatively correlated with plasma renin activity (r = -0.58; P < 0.01) and aldosterone concentration (r = -0.40; P < 0.05). Urinary excretions of AM and PAMP showed significant correlations with urine excretion of sodium (r = 0.39; P < 0.05 and r = 0.49; P < 0.01, respectively). These findings suggest that AM and PAMP may have roles in the regulation of sodium in patients with CGN.

Increased plasma brain natriuretic peptide levels in DOCA-salt hypertensive rats: relation to blood pressure and cardiac concentration.

Four experimental groups of rats treated with (1) DOCA-salt, (2) DOCA or (3) salt, and (4) controls were used to study the participation of brain natriuretic peptide (BNP) in the development of hypertension. Plasma and cardiac tissue concentrations of BNP as well as atrial natriuretic peptide (ANP) were measured in each group by using radioimmunoassays specific to rat BNP or ANP. Plasma BNP levels in DOCA-salt hypertensive group were higher than those in control (p less than 0.01), salt (p less than 0.01) and DOCA (p less than 0.01) groups. A positive correlation was observed between plasma BNP levels and blood pressure (r = 0.70, p less than 0.001) and between plasma ANP levels and blood pressure (r = 0.62, p less than 0.001). Plasma BNP/ANP ratio increased parallel with elevation of blood pressure. Plasma BNP levels correlated negatively with atrial BNP concentration (r = -0.33, p less than 0.05), but positively with ventricular BNP (r = 0.76, p less than 0.001). Compared with controls, tissue BNP-45/gamma-BNP ratio in the DOCA-salt rats was lower in atrium, but higher in ventricle. Thus, in DOCA-salt hypertension atrial BNP decreased with exhaustion of stored BNP-45, while ventricular BNP increased as BNP-45 accumulated. These results suggest that BNP is a novel cardiac hormone, synthesized, processed and secreted in response to changes in blood pressure. BNP may play different roles in controlling blood pressure than those assumed by ANP.

Comparison of combination therapies, including the angiotensin receptor blocker olmesartan and either a calcium channel blocker or a thiazide diuretic, in elderly patients with hypertension

The blood pressure goals set for the treatment of hypertensive patients have been lowered in recent guidelines. To reduce blood pressure levels sufficiently, combination therapies are often needed, but there is little evidence about which combination should be chosen. The present study was carried out to compare the effects of combination therapies, including the angiotensin receptor blocker olmesartan and either a calcium channel blocker (CCB) or a thiazide diuretic, in elderly patients with hypertension. A total of 65 patients aged 65–85 years, with blood pressures of 140/90 mm Hg or higher for those taking antihypertensive medication or 160/100 mm Hg or higher for those not on medication, were randomly assigned to either the group treated with olmesartan plus a dihydropyridine CCB or the group treated with olmesartan plus a thiazide diuretic; 58 patients completed the treatment for 6 months. Systolic and diastolic blood pressures (SBP and DBP) were reduced during the treatment period in both the groups. The reductions in SBP at 1 and 6 months were significantly (P<0.05) greater in the CCB combination group than in the diuretic group (−29 vs. −18 mm Hg, respectively, at 1 month; −32 vs. −23 mm Hg, respectively, at 6 months). Despite greater reduction in SBP in the CCB group, the serum creatinine level and the estimated glomerular filtration rate (eGFR) remained unchanged, whereas in the diuretic group, creatinine was elevated (+0.06 mg per 100 ml, P<0.05) and eGFR was reduced (−4.5 ml min−1 per 1.73 m2). In addition, high-density lipoprotein cholesterol levels were reduced in the diuretic group (−5.0 mg per 100 ml, P<0.01). These results suggest that olmesartan plus a CCB is the preferable combination therapy in comparison with olmesartan plus a thiazide diuretic for elderly patients with hypertension.

Regional differences in hypertensive cardiovascular remodeling between fishing and farming communities in Japan.

BACKGROUND Effects of dietary n-3 polyunsaturated fatty acids (n-3 PUFA) intake on the cardiovascular system have been reported, and thus we hypothesized that the prevalence of hypertensive cardiovascular remodeling would be lower in a fishing than a farming community. METHODS We recruited 263 essential hypertensives from a fishing and 333 from a farming village; all subjects were ≥40 years (mean 73 years; 42% men). They were cross-sectionally examined for serum eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), asymmetric dimethylarginine (ADMA) levels, left ventricular mass index (LVMI), and common-carotid artery (CCA) and internal-carotid artery (ICA) intima-media thickness (IMT). RESULTS Compared to the patients in the farming village, those in the fishing village had higher serum EPA and DHA levels (63.3 vs.70.9 µg/ml, 137.2 vs.157.8 µg/ml) and lower ADMA levels (0.49 vs.0.47 nmol/ml; all P < 0.05). LVMI and both CCA-IMT and ICA-IMT levels were lower in the fishing than the farming village (113.2 vs.121.6 g/m(2), 0.88 vs.0.94 mm, 1.10 vs.1.17 mm: all P < 0.01) even after adjustment for age, sex, body mass index (BMI), duration of hypertensive medication, number of antihypertensive medications, and 24-h systolic blood pressure (SBP) level. The differences in LVMI and IMT levels between these communities also remained unchanged (all P < 0.01) after additional adjustment for the regional differences in EPA, DHA, and ADMA levels. A multivariable linear regression analysis showed that the difference in place of residence was independently associated with LVMI as well as with both CCA-IMT and ICA-IMT levels (all P < 0.01). CONCLUSION The prevalence of cardiovascular remodeling was significantly lower in patients in the fishing community than in those in the farming community. Further investigations are required to explain the mechanisms underlying this association.

Synergistic effect of chronic kidney disease and high circulatory norepinephrine level on stroke risk in Japanese hypertensive patients.

OBJECTIVE Evidence is now available about the association between chronic kidney disease (CKD) and stroke. However, less is known about the underlying mechanisms, and there is currently no reliable marker for identifying stroke-prone high-risk patients among CKD patients. METHODS A total of 514 hypertensive patients aged >50 years (mean, 72.3 years; 37% men) underwent 24-h BP monitoring and measurement of circulatory high-sensitivity C-reactive protein (hs-CRP) and norepinephrine at baseline. CKD was defined as eGFR<60 ml/min/1.73 m(2) using the Cockcroft-Gault equation. RESULTS AND CONCLUSION During an average of 41 months (1751 person-years), there were 43 stroke events. Compared with hypertensive patients without CKD, those with CKD (n=225) had higher levels of sleep systolic BP (SBP) (125 mmHg vs. 129 mmHg), circulatory hs-CRP (0.12 mg/L vs. 0.20 mg/L) and norepinephrine (332.2 pg/ml vs. 372.8 pg/ml; all P<0.05). On multivariable analysis, the hazard ratio (HR) (95% CI) for stroke in CKD vs. non-CKD was 2.7 (1.2-6.9) (P<0.05). CKD, as well as the baseline presence of silent cerebral infarction, sleep SBP increase, and high hs-CRP level (highest quartile: ≥0.42 mg/L) were independently and additively associated with stroke events; above all, there was a synergistic effect of CKD and high norepinephrine level (highest quartile: ≥538 pg/ml) on stroke risk (all P<0.05). Among hypertensive patients with CKD, those within the highest quartiles of norepinephrine had a greater stroke risk compared to those who were in the lower quartiles of norepinephrine (HR (95% CI): 2.2 (1.0-4.5); P=0.045). In conclusion, CKD is an independent predictor of stroke in Japanese hypertensive patients; in particular, hypertensive patients with CKD and a high norepinephrine level have a synergistically augmented stroke risk.

Evidence for participation of GCS1 in fertilization of the starlet sea anemone Nematostella vectensis: Implication of a common mechanism of sperm–egg fusion in plants and animals

It has been reported that GCS1 (Generative Cell Specific 1) is a transmembrane protein that is exclusively expressed in sperm cells and is essential for gamete fusion in flowering plants. The GCS1 gene is present not only in angiosperms but also in unicellular organisms and animals, implying the occurrence of a common or ancestral mechanism of GCS1-mediated gamete fusion. In order to elucidate the common mechanism, we investigated the role of GCS1 in animal fertilization using a sea anemone (Cnidaria), Nematostella vectensis. Although the existence of the GCS1 gene in N. vectensis has been reported, the expression of GCS1 in sperm and the role of GCS1 in fertilization are not known. In this study, we showed that the GCS1 gene is expressed in the testis and that GCS1 protein exists in sperm by in situ hybridization and proteomic analysis, respectively. Then we made four peptide antibodies against the N-terminal extracellular region of NvGCS1. These antibodies specifically reacted to NvGCS1 among sperm proteins on the basis of Western analysis and potently inhibited fertilization in a concentration-dependent manner. These results indicate that sperm GCS1 plays a pivotal role in fertilization, most probably in sperm-egg fusion, in a starlet sea anemone, suggesting a common gamete-fusion mechanism shared by eukaryotic organisms.