研究者詳細 - 伊藤　裕

論文 - 伊藤　裕

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Islet number rather than islet size is a major determinant of beta- and alpha-cell mass in humans

Kou, K., Saisho, Y., Sato, S., Yamada, T. and Itoh, H.

J Clin Endocrinol Metab 99 （ 5 ） 1733 - 40 2014年05月

ISSN 0021-972

OBJECTIVE: The objective of the study was to clarify the relative contribution of islet number and islet size to beta- and alpha-cell mass in humans. RESEARCH DESIGN AND METHODS: We obtained the pancreas at autopsy from 72 Japanese adults with no history of diabetes or pancreatitis (aged 47 +/- 12 years, body mass index 24.1 +/- 5.0 kg/m(2)). Pancreatic sections were stained for insulin or glucagon, and fractional beta-cell area (%BCA) and alpha-cell area (%ACA) were measured. Islet number and islet size as well as beta-cell turnover were also quantified. Glycosylated hemoglobin measured within 1 year prior to death was obtained in 38 individuals. RESULTS: There was considerable interindividual variation in islet density and mean islet size, with a significant negative correlation between the two (r = -0.25, P = .03). There were significant positive correlations between islet density and %BCA or %ACA (r = 0.63, P < .001, and r = 0.41, P = .001), whereas mean islet size correlated with neither of them. Islet density as well as %BCA, but not mean islet size, was negatively correlated with glycosylated hemoglobin (r = -0.37, P = .02, and r = -0.36, P = .03). CONCLUSION: The present study suggests that islet number rather than islet size is a major determinant of beta- and alpha-cell mass in humans. Interindividual difference in islet number may contribute to susceptibility to development of glucose intolerance.

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miR-34c attenuates epithelial-mesenchymal transition and kidney fibrosis with ureteral obstruction

Morizane, R., Fujii, S., Monkawa, T., Hiratsuka, K., Yamaguchi, S., Homma, K. and Itoh, H.

Sci Rep 4 4578 2014年04月

ISSN 2045-2322

micro RNAs (miRNAs) are small non-coding RNAs that act as posttranscriptional repressors by binding to the 3'-UTR of target mRNAs. On the other hand, mesenchymal-epithelial transition (EMT) and kidney fibrosis is a pathological process of chronic kidney disease (CKD), and its relationship to miRNAs is becoming recognized as a potential target for CKD therapies. To find new miRNAs involved in EMT, we examined miRNA expression in experimental models of EMT and renal epithelialization using microarray, and found that miR-34c attenuates EMT induced by TGF-beta in a mouse tubular cell line. To confirm the effects of miR-34c in vivo, we administered the precursor of miR-34c to mice with unilateral ureteral obstruction, and miR-34c decreased kidney fibrosis area and the expression of connective tissue growth factor, alpha-SMA, collagen type 1, collagen type 3 and fibronectin. In conclusion, our study showed miR-34c attenuates EMT and kidney fibrosis of mice with ureteral obstruction.

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Association between plasma triglycerides and high-density lipoprotein cholesterol and microvascular kidney disease and retinopathy in type 2 diabetes mellitus: a global case-control study in 13 countries

Sacks, F. M., Hermans, M. P., Fioretto, P., Valensi, P., Davis, T., Horton, E., Wanner, C., Al-Rubeaan, K., Aronson, R., Barzon, I., Bishop, L., Bonora, E., Bunnag, P., Chuang, L. M., Deerochanawong, C., Goldenberg, R., Harshfield, B., Hernandez, C., Herzlinger-Botein, S., Itoh, H., Jia, W., Jiang, Y. D., Kadowaki, T., Laranjo, N., Leiter, L., Miwa, T., Odawara, M., Ohashi, K., Ohno, A., Pan, C., Pan, J., Pedro-Botet, J., Reiner, Z., Rotella, C. M., Simo, R., Tanaka, M., Tedeschi-Reiner, E., Twum-Barima, D., Zoppini, G. and Carey, V. J.

Circulation 129 （ 9 ） 999 - 1008 2014年03月

ISSN 0009-7322

BACKGROUND: Microvascular renal and retinal diseases are common major complications of type 2 diabetes mellitus. The relation between plasma lipids and microvascular disease is not well established. METHODS AND RESULTS: The case subjects were 2535 patients with type 2 diabetes mellitus with an average duration of 14 years, 1891 of whom had kidney disease and 1218 with retinopathy. The case subjects were matched for diabetes mellitus duration, age, sex, and low-density lipoprotein cholesterol to 3683 control subjects with type 2 diabetes mellitus who did not have kidney disease or retinopathy. The study was conducted in 24 sites in 13 countries. The primary analysis included kidney disease and retinopathy cases. Matched analysis was performed by use of site-specific conditional logistic regression in multivariable models that adjusted for hemoglobin A1c, hypertension, and statin treatment. Mean low-density lipoprotein cholesterol concentration was 2.3 mmol/L. The microvascular disease odds ratio increased by a factor of 1.16 (95% confidence interval, 1.11-1.22) for every 0.5 mmol/L ( approximately 1 quintile) increase in triglycerides or decreased by a factor of 0.92 (0.88-0.96) for every 0.2 mmol/L ( approximately 1 quintile) increase in high-density lipoprotein cholesterol. For kidney disease, the odds ratio increased by 1.23 (1.16-1.31) with triglycerides and decreased by 0.86 (0.82-0.91) with high-density lipoprotein cholesterol. Retinopathy was associated with triglycerides and high-density lipoprotein cholesterol in matched analysis but not significantly after additional adjustment. CONCLUSIONS: Diabetic kidney disease is associated worldwide with higher levels of plasma triglycerides and lower levels of high-density lipoprotein cholesterol among patients with good control of low-density lipoprotein cholesterol. Retinopathy was less robustly associated with these lipids. These results strengthen the rationale for studying dyslipidemia treatment to prevent diabetic microvascular disease.

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Effect of single tablet of fixed-dose amlodipine and atorvastatin on blood pressure/lipid control, oxidative stress, and medication adherence in type 2 diabetic patients

Tanaka, M., Nishimura, R., Nishimura, T., Kawai, T., Meguro, S., Irie, J., Saisho, Y. and Itoh, H.

Diabetol Metab Syndr 6 56 2014年

ISSN 1758-5996

BACKGROUND: Oxidized low-density lipoprotein (LDL) plays central roles in the formation and progression of atherosclerotic lesions. Malondialdehyde (MDA)-modified LDL (MDA-LDL) is speculated to be generated as a result of oxidative stress in the human body. Because both amlodipine and atorvastatin have been reported to reduce oxidative stress, it is expected that both drugs would have a favorable influence to reduce oxidative stress. OBJECTIVE: The objective of this study was to investigate the effects of a single pill of amlodipine (5 mg)/atorvastatin (10 mg) on oxidative stress, blood pressure/lipid control and adherence to medication in patients with type 2 diabetes. METHODS: This combination tablet was administered to 29 patients (16 male), and MDA-LDL, blood pressure, lipid profile, renal/liver function, CPK, hs-CRP, adiponectin, BNP, and HbA1c were measured at baseline, 6, and 12 months, and baPWV and mean IMT were measured at baseline and 12 months. Medication adherence was examined using a questionnaire at 6 months. RESULTS: MDA-LDL was decreased significantly. LDL-C, TG, and Cr were significantly decreased at 6 and 12 months compared with baseline. eGFR was increased at 6 months, and urinary albumin/creatinine ratio was decreased at 12 months. BNP was decreased at 6 and 12 months, and adiponectin was increased at 12 months. Both mean IMT and baPWV were significantly decreased. The results of the questionnaire showed that 93% of patients were satisfied with this medication. No severe adverse event was observed. CONCLUSION: This combination tablet controlled both hypertension and dyslipidemia well in type 2 diabetic patients. The deceases in mean IMT and baPWV might suggest the improvement of atherosclerosis by this medication, which could be caused by the reduction of oxidative stress measured by MDA-LDL. In addition, this medication is expected to improve medication adherence.

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Lower beta cell function relates to sustained higher glycated albumin to glycated hemoglobin ratio in Japanese patients with type 2 diabetes

Saisho, Y., Tanaka, K., Abe, T., Kawai, T. and Itoh, H.

Endocr J 61 （ 2 ） 149 - 57 2014年

ISSN 0918-8959

The aim of this study was to clarify the relationship between baseline beta cell function and future glycated albumin (GA) to glycated hemoglobin ratio (GA/HbA1c) in patients with type 2 diabetes. In our retrospective cohort, 210 type 2 diabetic patients who had been admitted to our hospital and in whom HbA1c and GA had been measured at baseline and 2 years after admission were included in this study. Baseline beta cell function was assessed by postprandial C-peptide immunoreactivity index (PCPRI) during admission. With intensification of treatment during admission, HbA1c and GA were significantly decreased 1 year and 2 years after admission. While baseline HbA1c was not significantly correlated with HbA1c after 2 years, baseline GA/HbA1c was strongly correlated with GA/HbA1c after 2 years (r = 0.575, P <0.001). When the patients were divided into two groups according to median PCPRI, patients with low PCPRI showed higher GA/HbA1c both at baseline and after 2 years compared to those with high PCPRI. There was a significant negative correlation between PCPRI and GA/HbA1c after 2 years (r = -0.379, P <0.001). Multiple regression analysis revealed that PCPRI was an independent predictor of GA/HbA1c after 2 years. In conclusion, our findings suggest that lower beta cell function is associated with sustained higher GA/HbA1c ratio in patients with type 2 diabetes.

Effects of 16-week high-intensity interval training using upper and lower body ergometers on aerobic fitness and morphological changes in healthy men: a preliminary study

Osawa, Y., Azuma, K., Tabata, S., Katsukawa, F., Ishida, H., Oguma, Y., Kawai, T., Itoh, H., Okuda, S. and Matsumoto, H.

Open Access J Sports Med 5 257 - 65 2014年

ISSN 1179-1543

It is unclear whether combined leg and arm high-intensity interval training (HIIT) improves fitness and morphological characteristics equal to those of leg-based HIIT programs. The aim of this study was to compare the effects of HIIT using leg-cycling (LC) and arm-cranking (AC) ergometers with an HIIT program using only LC. Effects on aerobic capacity and skeletal muscle were analyzed. Twelve healthy male subjects were assigned into two groups. One performed LC-HIIT (n=7) and the other LC- and AC-HIIT (n=5) twice weekly for 16 weeks. The training programs consisted of eight to 12 sets of >90% VO2 (the oxygen uptake that can be utilized in one minute) peak for 60 seconds with a 60-second active rest period. VO2 peak, watt peak, and heart rate were measured during an LC incremental exercise test. The cross-sectional area (CSA) of trunk and thigh muscles as well as bone-free lean body mass were measured using magnetic resonance imaging and dual-energy X-ray absorptiometry. The watt peak increased from baseline in both the LC (23%+/-38%; P<0.05) and the LC-AC groups (11%+/-9%; P<0.05). The CSA of the quadriceps femoris muscles also increased from baseline in both the LC (11%+/-4%; P<0.05) and the LC-AC groups (5%+/-5%; P<0.05). In contrast, increases were observed in the CSA of musculus psoas major (9%+/-11%) and musculus anterolateral abdominal (7%+/-4%) only in the LC-AC group. These results suggest that a combined LC- and AC-HIIT program improves aerobic capacity and muscle hypertrophy in both leg and trunk muscles.

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Kidney specific protein-positive cells derived from embryonic stem cells reproduce tubular structures in vitro and differentiate into renal tubular cells

Morizane, R., Monkawa, T., Fujii, S., Yamaguchi, S., Homma, K., Matsuzaki, Y., Okano, H. and Itoh, H.

PLoS One 8 （ 6 ） e64843 2014年

ISSN 1932-6203

Embryonic stem cells and induced pluripotent stem cells have the ability to differentiate into various organs and tissues, and are regarded as new tools for the elucidation of disease mechanisms as well as sources for regenerative therapies. However, a method of inducing organ-specific cells from pluripotent stem cells is urgently needed. Although many scientists have been developing methods to induce various organ-specific cells from pluripotent stem cells, renal lineage cells have yet to be induced in vitro because of the complexity of kidney structures and the diversity of kidney-component cells. Here, we describe a method of inducing renal tubular cells from mouse embryonic stem cells via the cell purification of kidney specific protein (KSP)-positive cells using an anti-KSP antibody. The global gene expression profiles of KSP-positive cells derived from ES cells exhibited characteristics similar to those of cells in the developing kidney, and KSP-positive cells had the capacity to form tubular structures resembling renal tubular cells when grown in a 3D culture in Matrigel. Moreover, our results indicated that KSP-positive cells acquired the characteristics of each segment of renal tubular cells through tubular formation when stimulated with Wnt4. This method is an important step toward kidney disease research using pluripotent stem cells, and the development of kidney regeneration therapies.

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Plasma Antimicrobial Peptide LL-37 Level Is Inversely Associated with HDL Cholesterol Level in Patients with Type 2 Diabetes Mellitus

Meguro, S., Tomita, M., Katsuki, T., Kato, K., Oh, H., Ainai, A., Ito, R., Kawai, T., Itoh, H. and Hasegawa, H.

Int J Endocrinol 2014 703696 2014年

ISSN 1687-8337

Introduction. Relation between atherosclerosis and innate immunity has attracted attention. As the antimicrobial peptide, LL-37, could have an important role in atherosclerosis, we supposed that there could be a meaningful association of plasma LL-37 level with risk factors for cardiovascular disease in subjects with type 2 diabetes mellitus. Materials and Methods. We evaluated plasma LL-37 level and other clinical markers in Japanese subjects with type 2 diabetes mellitus (n = 133, 115 men and 18 women; age 64.7 +/- 11.5 years; HbA1c 8.1 +/- 1.6%). Plasma level of LL-37 was measured by ELISA. Results. Mean plasma LL-37 level was 71.2 +/- 22.3 ng/mL. Plasma LL-37 level showed significant correlations with HDL cholesterol (r = -0.450, P < 0.01), triglyceride (r = 0.445, P < 0.01), and high sensitive C-reactive protein (r = 0.316, P < 0.01) but no significant correlation with age, body mass index, HbA1c, estimated glomerular filtration rate, 25-hydroxyvitamin D, or vitamin D binding protein. Multiple linear regression analysis showed significant correlations of plasma LL-37 level with HDL cholesterol (beta = -0.411, P < 0.01) and high sensitive C-reactive protein (beta = 0.193, P < 0.05). Conclusion. Plasma LL-37 level was positively correlated with inflammatory markers and negatively correlated with HDL cholesterol in patients with type 2 diabetes mellitus.

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Basal-Supported Oral Therapy with Sitagliptin Counteracts Rebound Hyperglycemia Caused by GLP-1 Tachyphylaxis

Meguro, S., Kawai, T., Matsuhashi, T., Sano, M., Fukuda, K., Itoh, H. and Suzuki, Y.

Int J Endocrinol 2014 927317 2014年

ISSN 1687-8337

Introduction. Treatment with a glucagon-like peptide 1 (GLP-1) analog fails in some patients due to rebound hyperglycemia caused by tachyphylaxis (GLP-1 tachyphylaxis). We investigated the efficacy of basal-supported oral therapy (BOT) with insulin glargine and sitagliptin for counteracting GLP-1 tachyphylaxis. Materials and Methods. The subjects were 12 men and 3 women aged 59.9 +/- 10.0 years who had been treated with GLP-1 analogs. All of them had developed rebound hyperglycemia caused by GLP-1 tachyphylaxis. Their GLP-1 analog-based therapy was switched to BOT with insulin glargine plus sitagliptin and other medications. The primary outcomes were whether switching of therapy was associated with a change of hemoglobin A1c (HbA1c) and whether weight gain occurred. Results. Baseline HbA1c was 8.0 +/- 0.9%. It decreased to 7.3 +/- 0.9% at 3 months after switching (P < 0.01) and to 7.2 +/- 0.9% at 4 months (P < 0.05). Weight gain was 1.1 kg after 1 month (P < 0.01) and 2.3 kg after 5 months (P < 0.01). Conclusion. Switching to BOT with insulin glargine and sitagliptin improved glycemic control. The significant decrease of HbA1c demonstrated that this combination can counteract deterioration of glycemic control due to rebound hyperglycemia secondary to GLP-1 tachyphylaxis. However, weight gain remains a problem.

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Rho-kinase contributes to pressure-induced constriction of renal microvessels

Homma, K., Hayashi, K., Wakino, S., Tokuyama, H., Kanda, T., Tatematsu, S., Hasegawa, K., Fujishima, S., Hori, S., Saruta, T. and Itoh, H.

Keio J Med 63 （ 1 ） 1 - 12 2014年

ISSN 0022-9717

Renal afferent arterioles (AFF) regulate glomerular capillary pressure through two main mechanisms: the myogenic response (MYO) and tubuloglomerular feedback (TGF). Because Rho-kinase and nitric oxide synthase (NOS) are established factors that modulate vascular tone, we examined the role of these factors in pressure-induced AFF tone in Wistar-Kyoto rats and in spontaneously hypertensive rats (SHR) using an intravital CCD camera. Elevated renal perfusion pressure elicited marked AFF constriction that was partially inhibited by gadolinium, furosemide and fasudil, which inhibit MYO, TGF and Rho-kinase, respectively; however, this AFF constriction was completely blocked by combined treatment with fasudil+gadolinium or fasudil+furosemide. S-methyl-L-thiocitrulline (SMTC) partially reversed the fasudil-induced inhibition of TGF-mediated, but not that of MYO-mediated, AFF constriction. In SHR, the pressure-induced AFF response was enhanced, and MYO- and TGF-induced constriction were exaggerated. In the presence of gadolinium, SMTC partially mitigated the fasudil-induced inhibition of TGF-mediated AFF constriction. Immunoblot analyses demonstrated that both Rho-kinase activity and neuronal NOS were augmented in SHR kidneys. In conclusion, Rho-kinase contributes to MYO- and TGF-mediated AFF responses, and these responses are enhanced in SHR. Furthermore, neuronal NOS-induced nitric oxide modulates the TGF mechanism. This mechanism constitutes a target for Rho-kinase in TGF-mediated AFF constriction.

Ghrelin protects against renal damages induced by angiotensin-II via an antioxidative stress mechanism in mice

Fujimura, K., Wakino, S., Minakuchi, H., Hasegawa, K., Hosoya, K., Komatsu, M., Kaneko, Y., Shinozuka, K., Washida, N., Kanda, T., Tokuyama, H., Hayashi, K. and Itoh, H.

PLoS One 9 （ 4 ） e94373 2014年

ISSN 1932-6203

We explored the renal protective effects by a gut peptide, Ghrelin. Daily peritoneal injection with Ghrelin ameliorated renal damages in continuously angiotensin II (AngII)-infused C57BL/6 mice as assessed by urinary excretion of protein and renal tubular markers. AngII-induced increase in reactive oxygen species (ROS) levels and senescent changes were attenuated by Ghrelin. Ghrelin also inhibited AngII-induced upregulations of transforming growth factor-beta (TGF-beta) and plasminogen activator inhibitor-1 (PAI-1), ameliorating renal fibrotic changes. These effects were accompanied by concomitant increase in mitochondria uncoupling protein, UCP2 as well as in a key regulator of mitochondria biosynthesis, PGC1alpha. In renal proximal cell line, HK-2 cells, Ghrelin reduced mitochondria membrane potential and mitochondria-derived ROS. The transfection of UCP2 siRNA abolished the decrease in mitochondria-derived ROS by Ghrelin. Ghrelin ameliorated AngII-induced renal tubular cell senescent changes and AngII-induced TGF-beta and PAI-1 expressions. Finally, Ghrelin receptor, growth hormone secretagogue receptor (GHSR)-null mice exhibited an increase in tubular damages, renal ROS levels, renal senescent changes and fibrosis complicated with renal dysfunction. GHSR-null mice harbored elongated mitochondria in the proximal tubules. In conclusion, Ghrelin suppressed AngII-induced renal damages through its UCP2 dependent anti-oxidative stress effect and mitochondria maintenance. Ghrelin/GHSR pathway played an important role in the maintenance of ROS levels in the kidney.

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Postprandial serum C-peptide to plasma glucose ratio predicts future insulin therapy in Japanese patients with type 2 diabetes

Saisho, Y., Kou, K., Tanaka, K., Abe, T., Shimada, A., Kawai, T. and Itoh, H.

Acta Diabetol 50 （ 6 ） 987 - 8 2013年12月

ISSN 0940-5429

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Feasibility of regression of hypertension using contemporary antihypertensive agents

Sasamura, H., Nakaya, H., Julius, S., Tomotsugu, N., Sato, Y., Takahashi, F., Takeuchi, M., Murakami, M., Ryuzaki, M. and Itoh, H.

Am J Hypertens 26 （ 12 ） 1381 - 8 2013年12月

ISSN 0895-7061

BACKGROUND: Recently, we reported that transient treatment of genetically hypertensive rats with high-dose angiotensin receptor blocker (ARB) causes regression of established hypertension. In this study, we investigated whether treatment with candesartan or nifedipine controlled-release (CR) resulted in a sustained regression of hypertension in humans. METHODS: Patients aged 30 to 59 years with untreated stage 1 essential hypertension and a family history of hypertension were treated with the antihypertensive agents candesartan (n = 124) or nifedipine CR (n = 120). After 1 year of treatment (phase 1), the medications were tapered and discontinued (phase 2). During phase 2, home and office blood pressures were monitored for another year to assess posttreatment reoccurrence of stage 1 hypertension. RESULTS: In phase 1, after 1 year of treatment a similarly substantial BP decrease was seen in the candesartan (-24.5/16.1 mm Hg) and nifedipine (-26.8/18.0 mm Hg) groups. In phase 2 there was a substantial reoccurrence of hypertension; at the study end, only 1 patient was able to continue without antihypertensive medication. However, a Kaplan-Meier analysis revealed a significant delay of reoccurrence of hyper tension (P = 0.0001) in the candesartan group. CONCLUSIONS: One year of treatment with candesartan or nifedipine CR was not associated with marked regression of hypertension in humans at the standard doses used in this trial. However, withdrawal of candesartan was associated with a slightly longer delay before restarting medications. Further studies with larger doses of candesartan given over a longer time are required to determine whether such a regimen may induce sustainable and clinically relevant reversal of hypertension and alteration in its natural history.

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Renal tubular Sirt1 attenuates diabetic albuminuria by epigenetically suppressing Claudin-1 overexpression in podocytes

Hasegawa, K., Wakino, S., Simic, P., Sakamaki, Y., Minakuchi, H., Fujimura, K., Hosoya, K., Komatsu, M., Kaneko, Y., Kanda, T., Kubota, E., Tokuyama, H., Hayashi, K., Guarente, L. and Itoh, H.

Nat Med 19 （ 11 ） 1496 - 504 2013年11月

ISSN 1078-8956

Sirtuin 1 (Sirt1), a NAD(+)-regulated deacetylase with numerous known positive effects on cellular and whole-body metabolism, is expressed in the renal cortex and medulla. It is known to have protective effects against age-related disease, including diabetes. Here we investigated the protective role of Sirt1 in diabetic renal damage. We found that Sirt1 in proximal tubules (PTs) was downregulated before albuminuria occurred in streptozotocin-induced or obese (db/db) diabetic mice. PT-specific SIRT1 transgenic and Sirt1 knockout mice showed prevention and aggravation of the glomerular changes that occur in diabetes, respectively, and nondiabetic knockout mice exhibited albuminuria, suggesting that Sirt1 in PTs affects glomerular function. Downregulation of Sirt1 and upregulation of the tight junction protein Claudin-1 by SIRT1-mediated epigenetic regulation in podocytes contributed to albuminuria. We did not observe these phenomena in 5/6 nephrectomized mice. We also demonstrated retrograde interplay from PTs to glomeruli using nicotinamide mononucleotide (NMN) from conditioned medium, measurement of the autofluorescence of photoactivatable NMN and injection of fluorescence-labeled NMN. In human subjects with diabetes, the levels of SIRT1 and Claudin-1 were correlated with proteinuria levels. These results suggest that Sirt1 in PTs protects against albuminuria in diabetes by maintaining NMN concentrations around glomeruli, thus influencing podocyte function.

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Dietary protein decreases exercise endurance through rapamycin-sensitive suppression of muscle mitochondria

Mitsuishi, M., Miyashita, K., Muraki, A., Tamaki, M., Tanaka, K. and Itoh, H.

Am J Physiol Endocrinol Metab 305 （ 7 ） E776 - 84 2013年10月

ISSN 0193-1849

Loss of physical performance is linked not only to decreased activity in daily life but also to increased onset of cardiovascular diseases and mortality. A high-protein diet is recommended for aged individuals in order to preserve muscle mass; however, the regulation of muscle mitochondria by dietary protein has not been clarified. We investigated the long-term effects of a high-protein diet on muscle properties, focusing especially on muscle mitochondria. Mice were fed a high-protein diet from the age of 8 wk and examined for mitochondrial properties and exercise endurance at the ages of 20 and 50 wk. Compared with normal chow, a high-protein diet significantly decreased the amount of muscle mitochondria, mitochondrial activity, and running distance at 50 wk, although it increased muscle mass and grip power. Inhibition of TORC1-dependent signal pathways by rapamycin from 8 wk suppressed the decline in mitochondria and exercise endurance observed when mice were fed the high-protein diet in association with preserved AMPK activity. Collectively, these findings suggest a role for dietary protein as a suppressor of muscle mitochondria and indicate that the age-associated decline in exercise endurance might be accelerated by excessive dietary protein through rapamycin-sensitive suppression of muscle mitochondria.

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Change in beta-cell mass in Japanese nondiabetic obese individuals

Kou, K., Saisho, Y., Satoh, S., Yamada, T. and Itoh, H.

J Clin Endocrinol Metab 98 （ 9 ） 3724 - 30 2013年09月

ISSN 0021-972

AIM: The aim of this study was to clarify the change in beta-cell mass in Japanese obese individuals. METHODS: We obtained the pancreas at autopsy from 39 lean and 33 obese Japanese nondiabetic individuals (aged 47 +/- 13 vs 47 +/- 12 y, P = .83, body mass index 20.4 +/- 1.6 vs 28.5 +/- 3.9 kg/m(2), P < .01). Pancreatic sections were stained for insulin, and beta-cell area (%BCA) was measured as the fraction of the beta-cell area to the total pancreas area. beta-Cell mass was then calculated as the product of %BCA and estimated pancreas weight. beta-Cell replication and apoptosis were assessed by double staining for insulin and Ki67 and insulin and single-stranded DNA, respectively. The frequencies of insulin-positive duct cells and scattered beta-cells were assessed as the surrogate markers of beta-cell neogenesis. The alpha-cell area (%ACA) was also measured, and the %ACA to %BCA ratio was determined. RESULTS: There was no increase in beta-cell mass in obese individuals compared with lean individuals (0.6 +/- 0.4 vs 0.7 +/- 0.4 g, P = .12). beta-Cell replication, beta-cell neogenesis, and beta-cell apoptosis were not significantly increased in the presence of obesity. There was no significant difference in %ACA to %BCA ratio between obese and lean individuals (0.91 +/- 1.09 vs 0.75 +/- 0.51, P = .47). CONCLUSION: There was no increase in beta-cell mass and no detectable change in beta-cell turnover in Japanese obese individuals.

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Renal microcirculation and calcium channel subtypes

Homma, K., Hayashi, K., Yamaguchi, S., Fujishima, S., Hori, S. and Itoh, H.

Curr Hypertens Rev 9 （ 3 ） 182 - 6 2013年08月

ISSN 1573-4021

It has recently been reported that voltage-dependent Ca channel subtypes, e.g., L-, T-, N-, and P/Q-type, are expressed in renal arterioles and renal tubules, and the inhibition of these channels exerts various effects on renal microcirculation. For example, selective blockade of L-type Ca channels with nifedipine preferentially dilates the afferent arteriole and potentially induces glomerular hypertension. On the other hand, recently developed Ca channel blockers (CCBs) such as mibefradil and efonidipine block both T-type and L-type Ca channels and consequently dilate both afferent and efferent arterioles, leading to lowering of intraglomerular pressure. Interestingly, aldosterone has recently been recognized as a factor exacerbating renal diseases, and its secretion from adrenal gland is mediated by T-type Ca channels. Furthermore, T-type CCBs were shown to ameliorate renal dysfunction by suppressing inflammatory processes and renin secretion. On the basis of histological evaluations, N-type Ca channels are present in peripheral nerve terminals innervating both afferent and efferent arterioles. Further, it was suggested that N-type CCBs such as cilnidipine suppress renal arteriolar constriction induced by enhanced sympathetic nerve activity, thereby lowering intraglomerular pressure. Taken together, various Ca channel subtypes are present in the kidney and blockade of selective channels with distinct CCBs exerts diverse effects on renal microcirculation. Inhibition of T-type and N-type Ca channels with CCBs is anticipated to exert pleiotropic effects that would retard the progression of chronic kidney disease through modulation of renal hemodynamic and non-hemodynamic processes.

Effects of mitiglinide, a short-acting insulin secretagogue, on daily glycemic variability and oxidative stress markers in Japanese patients with type 2 diabetes mellitus

Kodani, N., Saisho, Y., Tanaka, K., Kawai, T. and Itoh, H.

Clin Drug Investig 33 （ 8 ） 563 - 70 2013年08月

ISSN 1173-2563

BACKGROUND AND OBJECTIVE: The objective of this study was to clarify the effects of mitiglinide on daily glycemic variability and oxidative stress markers in outpatients with type 2 diabetes mellitus that is insufficiently controlled by diet and/or non-insulin secretagogues. METHODS: We enrolled 24 patients with type 2 diabetes whose glycemic control had been suboptimal [i.e. glycosylated hemoglobin (HbA(1c)) >/= 6.9 %]. The patients were treated with mitiglinide 10 mg three times daily for 16 weeks. If their glycemic control was not improved at week 8, the dose of mitiglinide was increased to 20 mg three times daily. Daily glycemic variability was assessed by 7-point self-monitoring of blood glucose for 2 days, and standard deviation (SD), M value, and mean of daily differences(MODD) were calculated. Oxidative stress was assessed by oxidized low-density lipoprotein, pentosidine,urinary 8-iso-prostaglandin F2 alpha, and urinary 8-hydroxydeoxy guanosine. RESULTS: After 16 weeks of mitiglinide treatment, the HbA(1c) level was significantly decreased (mean +/- SD,7.4 +/- 0.7 to 6.8 +/- 0.5 %, P < 0.0001). Postprandial glucose excursion and glycemic variability were also significantly improved after mitiglinide treatment (all P < 0.05). The reductions in SD, M value, and MODD were 17, 50,and 48 %, respectively. There was a significant positive correlation between the change in HbA(1c) and change in SD during the study (r = 0.454, P = 0.03). There were no significant changes in oxidative stress markers. CONCLUSIONS: The present study supports the notion that mitiglinide improves postprandial glucose excursion and HbA(1c) level in patients with type 2 diabetes. In addition,we demonstrated that mitiglinide also effectively improves daily glycemic variability. The effect of mitiglinide on oxidative stress needs further investigation.

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The hydrolase DDAH2 enhances pancreatic insulin secretion by transcriptional regulation of secretagogin through a Sirt1-dependent mechanism in mice

Hasegawa, K., Wakino, S., Kimoto, M., Minakuchi, H., Fujimura, K., Hosoya, K., Komatsu, M., Kaneko, Y., Kanda, T., Tokuyama, H., Hayashi, K. and Itoh, H.

Faseb j 27 （ 6 ） 2301 - 15 2013年06月

ISSN 0892-6638

The role of dimethylarginine dimethylaminohydrolase 2 (DDAH2) in glucose metabolism is unknown. Here, we generated DDAH2 transgenic (Tg) mice. These mice had lower plasma glucose levels (60 min: 298+/-32 vs. 418+/-35 mg/dl; 120 min: 205+/-15 vs. 284+/-20 mg/dl) and higher insulin levels (15 min: 2.1+/-0.2 vs. 1.5+/-0.1 ng/ml; 30 min: 1.8+/-0.1 vs. 1.5+/-0.1 ng/ml) during intraperitoneal glucose tolerance tests when fed a high-fat diet (HFD) compared with HFD-fed wild-type (WT) mice. Glucose-stimulated insulin secretion (GSIS) was increased in Tg islets by 33%. Pancreatic asymmetrical dimethylarginine, nitric oxide, and oxidative stress levels were not correlated with improvements in insulin secretion in Tg mice. Secretagogin, an insulin vesicle docking protein, was up-regulated by 2.7-fold in Tg mice and in pancreatic MIN-6 cells overexpressing DDAH2. GSIS in MIN-6 cells was dependent on DDAH2-induced secretagogin expression. Pancreatic Sirt1, DDAH2, and secretagogin were down-regulated in HFD-fed WT mice by 70, 75, and 85%, respectively. Overexpression of Sirt1 overexpression by 3.9-fold increased DDAH2 and secretagogin expression in MIN-6 cells by 3.2- and 2.5-fold, respectively. DDAH2 overexpression improved GSIS in pancreas-specific Sirt1-deficient mice. In summary, the Sirt1/DDAH2/secretagogin pathway is a novel regulator of GSIS.

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Sema3A regulates bone-mass accrual through sensory innervations

Fukuda, T., Takeda, S., Xu, R., Ochi, H., Sunamura, S., Sato, T., Shibata, S., Yoshida, Y., Gu, Z., Kimura, A., Ma, C., Xu, C., Bando, W., Fujita, K., Shinomiya, K., Hirai, T., Asou, Y., Enomoto, M., Okano, H., Okawa, A. and Itoh, H.

Nature 497 （ 7450 ） 490 - 3 2013年05月

ISSN 0028-0836

Semaphorin 3A (Sema3A) is a diffusible axonal chemorepellent that has an important role in axon guidance. Previous studies have demonstrated that Sema3a(-/-) mice have multiple developmental defects due to abnormal neuronal innervations. Here we show in mice that Sema3A is abundantly expressed in bone, and cell-based assays showed that Sema3A affected osteoblast differentiation in a cell-autonomous fashion. Accordingly, Sema3a(-/-) mice had a low bone mass due to decreased bone formation. However, osteoblast-specific Sema3A-deficient mice (Sema3acol1(-/-) and Sema3aosx(-/-) mice) had normal bone mass, even though the expression of Sema3A in bone was substantially decreased. In contrast, mice lacking Sema3A in neurons (Sema3asynapsin(-/-) and Sema3anestin(-/-) mice) had low bone mass, similar to Sema3a(-/-) mice, indicating that neuron-derived Sema3A is responsible for the observed bone abnormalities independent of the local effect of Sema3A in bone. Indeed, the number of sensory innervations of trabecular bone was significantly decreased in Sema3asynapsin(-/-) mice, whereas sympathetic innervations of trabecular bone were unchanged. Moreover, ablating sensory nerves decreased bone mass in wild-type mice, whereas it did not reduce the low bone mass in Sema3anestin(-/-) mice further, supporting the essential role of the sensory nervous system in normal bone homeostasis. Finally, neuronal abnormalities in Sema3a(-/-) mice, such as olfactory development, were identified in Sema3asynasin(-/-) mice, demonstrating that neuron-derived Sema3A contributes to the abnormal neural development seen in Sema3a(-/-) mice, and indicating that Sema3A produced in neurons regulates neural development in an autocrine manner. This study demonstrates that Sema3A regulates bone remodelling indirectly by modulating sensory nerve development, but not directly by acting on osteoblasts.

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伊藤 裕

論文 - 伊藤 裕

伊藤　裕

論文 - 伊藤　裕