A simplified prediction model for end-stage kidney disease in patients with diabetes

This study aimed to develop a simplified model for predicting end-stage kidney disease (ESKD) in patients with diabetes. The cohort included 2549 individuals who were followed up at Kyushu University Hospital (Japan) between January 1, 2008 and December 31, 2018. The outcome was a composite of ESKD, defined as an eGFR < 15 mL min⁻¹ [1.73 m]⁻², dialysis, or renal transplantation. The mean follow-up was 5.6 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document}± 3.7 years, and ESKD occurred in 176 (6.2%) individuals. Both a machine learning random forest model and a Cox proportional hazard model selected eGFR, proteinuria, hemoglobin A1c, serum albumin levels, and serum bilirubin levels in a descending order as the most important predictors among 20 baseline variables. A model using eGFR, proteinuria and hemoglobin A1c showed a relatively good performance in discrimination (C-statistic: 0.842) and calibration (Nam and D’Agostino \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\chi$$\end{document}χ² statistic: 22.4). Adding serum albumin and bilirubin levels to the model further improved it, and a model using 5 variables showed the best performance in the predictive ability (C-statistic: 0.895, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\chi$$\end{document}χ² statistic: 7.7). The accuracy of this model was validated in an external cohort (n = 5153). This novel simplified prediction model may be clinically useful for predicting ESKD in patients with diabetes.

Intracellular Localization of Mycoplasma bovis in the Bronchiolar Epithelium of Experimentally Infected Calves

Lung tissues from calves infected experimentally with Mycoplasma bovis were examined by immunohistochemistry and electron microscopy. All inoculated calves had dark red areas of consolidation affecting both left and right lungs, which were characterized microscopically by subacute purulent bronchiolitis with hyperplasia of the surrounding lymphoid tissue. Immunohistochemically, M. bovis antigen was detected on the surface and inside the cytoplasm of bronchiolar epithelial cells in the pneumonic foci. The antigen was also found in the cytoplasm of phagocytes at the margin of bronchiolar exudates. Electron microscopically, numerous organisms were demonstrated in the immunohistochemically-positive sites. These findings suggest that M. bovis organisms adhere to the bronchiolar epithelium and at least some of them invade the epithelium.

Clinical usefulness of human serum nonmercaptalbumin to mercaptalbumin ratio as a biomarker for diabetic complications and disability in activities of daily living in elderly patients with diabetes

BACKGROUND

Oxidative stress may play an important role in the development of diabetic complications. The ratio of human nonmercaptalbumin (HNA; oxidized form) to human mercaptalbumin (HMA; reduced form) has attracted attention as an indicator for systemic redox states. In this study, we measured the ratio in elderly patients with diabetes and evaluated its association with diabetic complications and disability in activities of daily living (ADL disability).

METHODS

One hundred twenty-six elderly patients with diabetes, aged 70 years and older, under medical care at Yukuhashi Central Hospital from April 2018 to June 2018, were continuously recruited. HNA%, defined as HNA / (HNA + HMA) × 100, was measured by a high-performance liquid chromatography method. First, multivariate regression analysis was performed to evaluate which variables were significant determinants for HNA%. Next, to evaluate the association of HNA% with ADL disability, logistic regression analysis in various models was performed. Then we plotted the receiver operating characteristic (ROC) curve and calculated the under area the curve (AUC), sensitivity, and specificity in each model.

RESULTS

In elderly patients with diabetes, multiple regression analysis showed that serum bilirubin levels and albumin levels, both of which are major endogenous anti-oxidants, and chronic renal failure (or proliferative nephropathy) were significantly associated with HNA%, suggesting that HNA% may be a good biomarker for oxidative stress in those patients. We then evaluated the association of HNA% with ADL disability in various logistic regression models. Model using only HNA% showed that it was a significant determinant for ADL disability (OR 1.158, 95% CI 1.077-1.244, P < 0.001). Model using HNA% and age showed that both variables were significant determinants for ADL disability (OR 1.160, 95% CI 1.069-1.258, P < 0.001; OR 1.258, 95% CI 1.110-1.427, P < 0.001, respectively). ROC analysis showed that the AUC of HNA% alone was 0.765. The AUC of model using HNA% and age was further increased to 0.866.

CONCLUSIONS

HNA% was significantly associated with diabetic complications and ADL disability, thereby may be clinically useful as an oxidative stress marker in elderly patients with diabetes.

Serum bilirubin level is a strong predictor for disability in activities in daily living (ADL) in Japanese elderly patients with diabetes

Elderly patients with diabetes are at increased risk of frailty and disability in activities of daily living (ADL). Recent evidence has shown that oxidative stress is associated with these conditions. In this cross-sectional study, we aimed to assess whether serum level of bilirubin, a strong endogenous antioxidant, can predict ADL disability in elderly patients with diabetes. Forty elderly patients aged 70 years and older with diabetes and ADL disability and 158 elderly patients with diabetes and without ADL disability were continuously recruited. Multivariate logistic regression models showed that serum bilirubin level was a significant predictor for ADL disability. Receiver operating characteristic analysis showed that the area under the curve (AUC) of serum bilirubin level alone for ADL disability was 0.887 (95% CI 0.837–0.936, P < 0.001) and the cut-off value was 0.4 mg/dL (sensitivity = 88.0% and specificity = 65.0%). The predictive ability was further increased by the addition of age (AUC = 0.921) or addition of age, body mass index, red blood cell count, cerebrovascular disease and chronic renal failure (AUC = 0.953). In conclusion, low serum bilirubin level is a strong predictive biomarker for ADL disability in elderly patients with diabetes, and its clinical utility is suggested.

Immunohistochemical Localization of a Novel Peptide, Prostacyclin-Stimulating Factor (PSF), in Human Tissues

In a recent study, we purified and cloned a newly identified bioactive factor that stimulates prostacyclin (PGI2) production by vascular endothelial cells (ECs) using conditioned medium (CM) from cultured human diploid fibroblast cells. The present study was undertaken to clarify whether PSF is expressed in ECs and vascular smooth muscle cells (SMCs) of human tissues at a protein level. In an immunohistochemical study of seven human autopsy cases, all arteries in all lungs (n = 4) and kidneys (n = 6) examined stained positive to variable extents for PGI2-stimulating factor (PSF). PSF was predominantly expressed by SMCs in the media of small arteries. Staining for PSF was weaker in SMCs of aortic media (n = 3) and strong in SMCs of vaso vasorum (n = 3). PSF staining was also found in the SMCs of human bronchi (n = 4). Immunoblot analysis confirmed that PSF is present in CM from cultured bovine aortic SMCs.

Effect of Vitamin E on Platelet Aggregation in Diabetes Mellitus

Vitamin E is known to be an inhibitor of platelet prostaglandin production and aggregation. The rate of platelet aggregation induced by adenosine diphosphate was significantly increased in diabetics with proliferative retinopathy and the enhanced production of thromboxane B2, a stable metabolite of thromboxane A2, was demonstrated in those patients. On the other hand, vitamin E in platelets was significantly reduced in diabetics compared with age matched controls. In addition, it was shown that vitamin E content in platelets examined in diabetic and control subjects inversely correlated with both the rate of platelet aggregation and thromboxane B2 production during aggregation. It is suggested that the reduced vitamin E levels in diabetic platelets can contribute to the mechanisms of the enhanced platelet thromboxane production and aggregation which relate to the development of vascular complications.

Vitamin E Binds to Specific Binding Sites and Enhances Prostacyclin Production by Cultured Aortic Endothelial Cells

We evaluated the effect of d-α-tocopherol (vitamin E) on the production of prostacyclin (PGI2) by cultured bovine aortic endothelial cells. Vitamin E at physiological doses significantly enhanced the production of PGI2 by aortic endothelial cells when added to the culture simultaneously with histamine, the Ca2+ ionophore A23187 (A23187), plasma-derived serum (PDS), or arachidonic acid. This effect was found to occur in a time- and dose-dependent manner, and the maximal enhancement was produced by 9.28 µM of vitamin E for 1 h incubations. Significantly lower amounts of lipid peroxides were measured in endothelial cells stimulated by 10% PDS with 9.28 µM of vitamin E than in those stimulated without vitamin E for over 24 h, although the stimulation during the initial 1 to 12 h period did not have a significant effect on lipid peroxide formation in cultured aortic endothelial cells.

We also demonstrated that bovine aortic endothelial cells have specific binding sites for [3H]vitamin E that exhibited time- and temperature-dependent saturability. At 4° C, the nonspecific binding was 8–12% of the total binding, and the specific binding reached equilibrium by 2 h. Specific binding increased with the concentration of [3H]vitamin E and became saturated at concentrations between 1.5 µM and 2.0 µM per 2.0 × 105 cells. Raising the unlabeled vitamin E concentration from 97.7 nM to 1,000 µM reduced the specific binding of 2.0 µM [3H]vitamin E. The Scatchard plot of [3H]vitamin E binding to the endothelial cells shows two classes of binding sites: one with a high affinity {K a1 2.48 ± 0.32 × 107 NT-1, n = 6} and a low capacity {n 1 1.20 ± 0.34 × 107 sites/cell} and the other with a low affinity {K a2 1.18 ± 0.32 × 105 M–1} and a high capacity {n 2 3.39 ± 0.53 × 109 sites/cell}.

Our results suggest that the endothelial cells binding sites for vitamin E may play some roles in vascular homeostasis in vivo, and that vitamin E may prevent the development of atherosclerotic changes due in part to the enhancement of PGI2 production by the vascular wall and its action as an antioxidant in vascular endothelial cell.

Glucose Inhibits Prostacyclin Production by Cultured Aortic Endothelial Cells

A reduction in production of prostacyclin (PGI2) by the cells in the vascular wall may play a role in the pathogenesis of atherosclerosis in diabetic patients. The present study was undertaken to evaluate the effect of glucose on PGI2 production by endothelial cells in vitro. It was shown that PGI2 production by cultured bovine aortic endothelial cells was significantly reduced in the presence of a high concentration of glucose (300 mg/dl) compared with physiological concentrations of glucose (100 mg/ dl). In contrast, no reduction in PGI2 production was observed in cells cultured with equimolar mannitol, suggesting that glucose itself, rather than the effect of osmolality, inhibited PGI2 production by cultured endothelial cells.

In addition, a high concentration of glucose also inhibited the proliferation of cultured endothelial cells.

High-Sensitivity C-Reactive Protein in Japanese Patients with Type 2 Diabetes

OBJECTIVE

To assess the relationship between high-sensitivity (HS) C-reactive protein (CRP) and metabolic syndrome (MetS) or atherosclerosis and to assess effects of strict metabolic control on the degree of inflammation and MetS in patients with type 2 diabetes.

RESEARCH METHODS AND PROCEDURES

Four hundred thirteen patients with diabetes were enrolled in the cross-sectional study. Of these 413 patients, 161 patients were further admitted for 2.4 +/- 0.4 weeks (mean +/- SD) to investigate the change in HS-CRP or other parameters under strict metabolic control.

RESULTS

Log-transformed HS-CRP value (log HS-CRP) was strongly correlated with BMI (r = 0.448, p < 0.01). Log HS-CRP was also correlated with the presence of MetS or each component of MetS. Furthermore, a positive significant trend in HS-CRP levels was shown with an increasing number of MetS components (p < 0.05). Log HS-CRP showed a significant positive correlation with carotid artery intima-media thickness (IMT) (r = 0.152, p < 0.01). In multiple step-wise regression analysis, BMI, hemoglobin A(1c), right IMT, duration of diabetes, and triglyceride were selected as explanatory variables for log HS-CRP (R2 = 0.412). Under strict metabolic control, HS-CRP was significantly (p < 0.01) lower, together with lower levels of other markers for MetS. The change in HS-CRP was significantly correlated with the change in BMI (r = 0.161, p = 0.04).

DISCUSSION

In subjects with type 2 diabetes, HS-CRP levels are related to MetS and subclinical atherosclerosis. Strict weight management and metabolic control were associated with a reduction in HS-CRP levels, and changes in HS-CRP were related to changes in weight, supporting the hypothesis that lifestyle modification reduces inflammation and the risk of CHD.

Variation of fasting serum C-peptide level after admission in Japanese patients with type 2 diabetes mellitus

BACKGROUND

The aim of this study was to evaluate the variation of fasting serum C-peptide (S-CPR) levels, as a marker for endogenous insulin secretion after admission in Japanese patients with type 2 diabetes mellitus (T2DM).

METHODS

S-CPR levels together with other metabolic factors were measured in 234 T2DM patients twice: at the beginning and at the end of admission for the control of blood sugar levels. As a result, patients were classified into two groups according to their changes of S-CPR (DeltaS-CPR), which consisted of patients whose S-CPR levels had decreased (group D) and increased (group I) after admission.

RESULTS

Patients allocated to group I showed younger age, shorter duration of diabetes, and lower basal S-CPR level compared to group D. Conversely, patients in group D showed higher levels of high-sensitivity C-reactive protein (HS-CRP) and brachial-ankle pulse wave velocity compared to group I, suggesting patients in this group are prone to atherosclerosis. DeltaS-CPR was positively correlated with the change of body mass index, waist circumference, and triglycerides in group D. On the other hand, DeltaS-CPR was negatively correlated with the change of HS-CRP in group I, indicating residual beta-cell function could be recovered by the amelioration of inflammatory status in pancreatic islets.

CONCLUSIONS

It is plausible that Japanese T2DM patients could be classified according to the variation of S-CPR after admission. Evaluation of basal and the variation of S-CPR could provide advantageous information for the management of diabetes mellitus or related disorders.

Attenuated metabolic effect of waist measurement in Japanese female patients with type 2 diabetes mellitus

Waist circumference (WC) was measured in 200 Japanese patients with type 2 diabetes mellitus (T2DM: male 106, female 94, mean age 61 years old) who had been admitted in our hospital, and relationship with various risk factors to predict future cardiovascular disease (CVD) was analyzed. There was a positive and statistically significant trend in WC levels with an increasing number of CVD risk factors in male patients, whereas no significant trend of WC was observed in female patients. The receiver operator characteristic (ROC) curve for WC to predict the presence of two or more risk factors of CVD depicted greater area under the curve in male patients (0.732) than that in female patients (0.571). Apart from positive correlation with fasting serum C-peptide (S-CPR) and log-transformed high-sensitivity C-reactive protein (log HS-CRP) in both genders, WC was positively correlated with log-transformed triglyceride (log TG), systolic and diastolic blood pressure (SBP and DBP) and negatively with HDL-cholesterol (HDL-C) in male patients, whereas it was negatively correlated with HbA1c and fasting plasma glucose (FPG) in female patients. The change of WC after administration (DeltaWC) was correlated with DeltaS-CPR, DeltaLDL-C, DeltaSBP and DeltaDBP in male patients, while no relationship was observed in female patients. In conclusion, WC is a reliable marker to predict future CVD events at least in Japanese male, but not female patients with T2DM.

Indicators for the efficacy of pioglitazone before and during treatment in Japanese patients with type 2 diabetes

BACKGROUND

The aim of this study is to explore appropriate indicators for the efficacy of pioglitazone (Pio) before and during treatment of Japanese patients with type 2 diabetes mellitus (T2DM).

METHODS

Forty-eight Japanese patients with T2DM (22 men, 26 women, 60 +/- 2 years old) were enrolled and treated with 15 mg/day of Pio for 12 weeks. Before and after the treatment, various parameters were evaluated regarding the efficacy of Pio. Patients who had a reduction in hemoglobin A1c (HbA1c) of >1% after 12 weeks of treatment were defined as responders.

RESULTS

Twenty-two patients were classified as responders. In the responder group, age, fasting plasma glucose (FPG), and percentage female were significantly (P < 0.05) higher compared with the non-responder group. In logistic regression analysis, female sex and higher FPG were selected as explanatory variables for the efficacy of Pio. Furthermore, the change of HbA1c (DeltaHbA1c) was positively correlated with that of fasting C-peptide level (DeltaCPR) and log-transformed high-sensitivity C-reactive protein (Deltalog HS-CRP), and negatively correlated with that of high-density lipoprotein cholesterol (DeltaHDL-C) and log-transformed adiponectin (Deltalog AP). In multiple stepwise regression analysis, DeltaCPR, Deltalog HS-CRP, and Deltalog AP (or DeltaFPG) were selected as explanatory variables for DeltaHbA1c.

CONCLUSIONS

We concluded that Pio is likely to show favorable effects on blood glucose control especially in female patients with higher FPG levels. Administration of Pio ameliorates blood glucose control accompanied by the increase of AP and the decrease of CPR or HS-CRP, suggesting that Pio exerts its beneficial effects through the enhancement of AP, which leads to suppression of inflammation and amelioration of insulin resistance.

Genome-wide linkage analysis of type 2 diabetes mellitus reconfirms the susceptibility locus on 11p13–p12 in Japanese

Type 2 diabetes mellitus is a heterogeneous disorder, and the development of type 2 diabetes mellitus is associated with both insulin secretion defect and insulin resistance. The primary metabolic defect leading to type 2 diabetes mellitus has been thought to be varied among populations, especially in Japanese and Caucasians. Here, we have done the genome-wide scan for type 2 diabetes mellitus using 102 affected Japanese sib-pairs to identify the genetic factors predisposing to type 2 diabetes mellitus. Nonparametric linkage analysis showed one suggestive evidence for linkage to 11p13-p12 [D11S905: two-point maximum LOD score (MLS) of 2.89 and multipoint MLS of 2.32] and one nominally significant evidence for linkage to 6q15-q16 (D6S462: two-point MLS of 2.02). Interestingly, the 11p13-p12 region was reported to be a susceptibility locus for Japanese type 2 diabetes mellitus with suggestive evidence of linkage, and D11S905 was within 5 cM to D11S935 with the highest MLS in the previous linkage analysis reported. The only overlapped susceptibility region with suggestive evidence of linkage for Japanese type 2 diabetes mellitus was D11S935-D11S905 among the three reports including this study. These results taken together suggest that a susceptibility gene for type 2 diabetes mellitus in Japanese will reside in 11p13-p12.

Glucosamine-induced beta-cell dysfunction: a possible involvement of glucokinase or glucose-transporter type 2

INTRODUCTION

The mechanism for beta-cell dysfunction induced by glucosamine has not yet fully been investigated previously.

AIM

To investigate the effects of glucosamine on insulin release or gene expression related to glucose metabolism in rat islets cultured with glucosamine for 24 hours.

METHODOLOGY

After islets were cultured with glucosamine or diazoxide, we measured glucose- or arginine-induced insulin release by using radioimmunoassay (RIA) and gene expressions by semiquantitative polymerase/chain reaction.

RESULTS

Coculture with glucosamine inhibited 27 mmol/L glucose-induced insulin release with no effects on 20 mmol/L arginine-induced insulin release. Coculture with diazoxide did not restore the impaired glucose-induced insulin release. In glucosamine-cultured islets, glucose-transporter type 2 or glucokinase mRNA expression decreased, whereas hexokinase mRNA increased. Phosphofructokinase-A, pyruvate dehydrogenase E1alpha, or pyruvate carboxylase mRNA was not affected by the addition of glucosamine. Pancreatic and duodenal homeobox-1, preproinsulin, or p21 (induced by oxidative stress) mRNA expression did not change, whereas uncoupling protein 2 mRNA, which plays an important role in thermogenesis, decreased in glucosamine-cultured islets.

CONCLUSION

These data imply that glucosamine impairs glucose-induced insulin release probably through the inhibition of glucose metabolism.

Effects of biotin on glucotoxicity or lipotoxicity in rat pancreatic islets

Biotin (vitamin H) plays an important role as a cofactor in glucose or lipid metabolism. We showed that biotin potentiated glucose-induced insulin release in isolated rat islets, while biotin alone did not affect insulin release. Coculture with biotin in islets for 48 hours significantly enhanced glucose-induced insulin release or islet insulin content. Similarly, preproinsulin or pancreatic/duodenal homeobox-1 (PDX-1) mRNA was also enhanced in islets cultured with biotin for 48 hours. Furthermore, we measured effects of biotin on beta-cell function under glucotoxic or lipotoxic states. In islets cultured with high glucose or palmitate for 48 hours, glucose-induced insulin release or islet insulin content deteriorated. Coculture with biotin significantly restored glucose-induced insulin release or islet insulin content together with the restoration of preproinsulin or PDX-1 mRNA. We conclude that biotin exerts its beneficial effects on beta-cell dysfunction induced by glucose or free fatty acids probably through the enhancement of insulin biosynthesis.

Lysophosphatidylcholine inhibits the expression of prostacyclin stimulating factor in cultured vascular smooth muscle cells

We have cloned a prostacyclin (PGI2) stimulating factor (PSF), which stimulates PGI2 production by vascular endothelial cells. Previous study demonstrated the reduced PSF expression in the coronary arteries from the patients with ischemic heart disease. To clarify the mechanism of reduced PSF expression in atherosclerosis, we examined the effect of lysophosphatidylcholine (lysoPC), a main component of oxidized low density lipoprotein (LDL), on PSF expression in cultured vascular smooth muscle cells. LysoPC reduced PSF expression dose-dependently. Whereas neither phosphatidylcholine nor native LDL affects the PSF expression. Calphostin C, a protein kinase C (PKC) inhibitor, restored the reduction of PSF expression by lysoPC. These results suggest that lysoPC-induced reduction of PSF expression is mediated by PKC activation and is playing a role in the initiation and progression of atherosclerotic lesions.

Homology study of two polyhydroxyalkanoate (PHA) synthases from Pseudomonas aureofaciens

Recently, we have cloned and analyzed two polyhydroxyalkanoate (PHA) synthase genes (phaC1 and phaC2 in the pha cluster) from Pseudomonas aureofaciens. In this report, the deduced amino acid (AA) sequences of PHA synthase 1 and PHA synthase 2 from P. aureofaciens are compared with those from three other bacterial strains (Pseudomonas sp. 61-3, P. oleovorans and P. aeruginosa) containing the homologous pha cluster. The level of homology of either PHA synthase 1 or PHA synthase 2 was high with each enzyme from these three bacterial strains. Furthermore, multialignment of PHA synthase AA sequences implied that both enzymes of PHA synthase 1 and PHA synthase 2 were highly conserved in the four strains including P. aureofaciens.

Effects of bezafibrate on beta-cell function of rat pancreatic islets

Bezafibrate is an activator of peroxisome proliferator-activated receptors (PPAR) alpha. The present study was performed to investigate the effects of bezafibrate and the PPAR alpha activator, 4-Cholro-6-(2.3-xylidino)-2-pyrimidin-ylthio acetic acid (WY14643), on the beta-cell function of rat pancreatic islets in vitro. In islets cultured with 300 microM bezafibrate or WY14643 for 8 h, a low glucose concentration induced insulin release and increased the levels of mRNA for PPAR alpha, acyl CoA oxidase, carnitine palmitoyl transferase-1, pyruvate dehydrogenase E1 alpha or pyruvate carboxylase. In contrast, after a 48-h culture period, a high glucose concentration induced insulin release and islet insulin content, but decreased the levels of mRNA for glucose transporter-2 (GLUT-2), preproinsulin or pancreatic/duodenal homeobox-1. Diazoxide, the KATP channel opener, restored these responses. We conclude that bezafibrate enhances insulin release through the activation of PPAR alpha gene expression during a short culture period, whereas it may contribute to beta-cell dysfunction through the mechanism of "excessive stimulation" during longer culture periods.

The role of cyclic AMP in the pathogenesis of glucose desensitization in rat pancreatic islets

Adenosine-3',5'-cyclic monophosphate (cyclic AMP) promotes exocytosis of insulin in pancreatic beta cells. This study was performed to investigate the role of cyclic AMP in the pathogenesis of glucose desensitization in rat pancreatic islets. In islets cultured with high glucose for 48 hours, 27 mmol/L glucose-induced insulin release was markedly impaired, while 3.3 mmol/L glucose-or arginine-induced insulin release was enhanced, indicating glucose desensitization. Islet cyclic AMP content was 190% enhanced in high glucose-culture islets for 48 hours. In islets cultured with dibutyryl-cyclic AMP (dbcAMP) or 3-isobutyl methy-xanthine (IBMX), islet insulin content or 27 mmol/L glucose-induced insulin release was deteriorated. In contrast, 3.3 mmol/L glucose- or arginine-induced insulin release was increased, which was similar to glucose-desensitized islets. Wash-out of dbc AMP for the last 24 hours of the 48-hour culture period restored impaired high glucose-induced insulin release in the same manner as wash-out of high glucose. Diazoxide, the KATP channel opener, also restored impaired high glucose-induced insulin release from dbcAMP-cultured islets. The data suggest that enhancement of cyclic AMP in high glucose-culture islets may be one of the pathogenesis of glucose desensitization.

Effects of free fatty acids on beta-cell functions: a possible involvement of peroxisome proliferator-activated receptors alpha or pancreatic/duodenal homeobox

It is well known that acute administration of fatty acids enhances insulin release from beta cells, although chronic exposure to fatty acids inhibits insulin release (lipotoxicity). The mechanism for these reciprocal effects of fatty acids on insulin release remains to be elucidated. The present study was performed to investigate the effects of fatty acids on gene expression related to glucose metabolism or insulin biosynthesis. In islets cultured with palmitate for 8 hours, glucose-induced insulin release was enhanced together with increment of pyruvate carboxylase (PC) mRNA or peroxisome proliferator-activated receptors (PPAR)alpha. In contrast, by extending the culture period up to 48 hours, glucose-induced insulin release or islet insulin content was significantly impaired by the coexistence of palmitate. Concomitantly, PC, PPARalpha, GLUT-2, glucokinase (GK), preproinsulin, or pancreatic/duodenal homeobox-1 (PDX-1) mRNA were significantly suppressed in those islets cultured for 48 hours with palmitate. These data may imply that during short-term culture period palmitate promotes PPARalpha gene expression, which enhances PC mRNA expression leading to the enhancement of insulin release, whereas during long-term culture period, palmitate rather inhibits PPARalpha mRNA, which reduces PC mRNA expression. Furthermore, palmitate reduces GLUT-2, GK, or preproinsulin mRNA expression probably through the inhibition of PDX-1 mRNA.

Saturated non-esterified fatty acids stimulate de novo diacylglycerol synthesis and protein kinase c activity in cultured aortic smooth muscle cells

AIMS/HYPOTHESIS

Insulin resistance is linked with a cluster of multiple risk factors and excessive acceleration of atherosclerosis. The underlying mechanism is not, however, fully understood.

METHODS

To determine the link between insulin resistance and altered vascular function, we focused on the effect of various non-esterified fatty acids on diacylglycerol-protein kinase C pathway and mitogen-activated protein kinase activity in cultured aortic smooth muscle cells.

RESULTS

Incubation of the cells with saturated non-esterified fatty acids (200 micromol/l) for 24 h, such as palmitate or stearate, induced a significant increase in diacylglycerol concentrations by about fivefold or eightfold, respectively, whereas oleate induced a slight increase in diacylglycerol concentrations by 1.8-fold and arachidonate induced none. In addition, the increased diacylglycerol concentrations induced by palmitate were completely restored to control concentrations by triacsin C, acyl-CoA synthetase inhibitor. These results suggest that saturated non-esterified fatty acids may increase diacylglycerol concentrations through de novo pathway by stepwise acylation. In parallel with the increased diacylglycerol, incubation of the cells with saturated non-esterified fatty acids significantly induced the activation of protein kinase C and mitogen-activated protein kinase. The palmitate-induced increase in mitogen-activated protein kinase activity was restored to control concentrations by GF109203X (5 x 10(-7) mol/l), a specific protein kinase C inhibitor, suggesting a protein kinase C-dependent activation of mitogen-activated protein kinase.

CONCLUSION/INTERPRETATION

Saturated non-esterified fatty acids induced an increase in de novo diacylglycerol synthesis and subsequent activation of protein kinase C and mitogen-activated protein kinase in cultured aortic smooth muscle cells. This could contribute to the altered vascular functions in the insulin resistant state.

Chronic sulfonylurea treatment and hyperglycemia aggravate disproportionately elevated plasma proinsulin levels in patients with type 2 diabetes

It is established that disproportionately elevated plasma proinsulin levels occur in patients with Type 2 diabetes. In the present study, multivariate analysis was performed to determine what factors contributed to the disproportionately elevated plasma proinsulin levels in Japanese patients with Type 2 diabetes (n=276). Results from univariate analysis showed that both fasting proinsulin/C-peptide ratio and proinsulin/IRI ratio were approximately 2-fold higher in patients with Type 2 diabetes than those in healthy nondiabetic subjects (n=45). In patients with Type 2 diabetes, both proinsulin/C-peptide ratio and proinsulin/IRI ratio were significantly positively correlated with fasting plasma glucose level (FPG) and HbA1c. Neither proinsulin/C-peptide ratio nor proinsulin/IRI ratio was significantly correlated with BMI. Sulfonylurea-treated subjects had a significant elevation in both proinsulin/C-peptide ratio and proinsulin/IRI ratio compared with diet-treated subjects, whereas nonsulfonylurea hypoglycemic agent-treated subjects did not. Multivariate analysis confirmed that sulfonylurea treatment and FPG were significant determinants of both fasting proinsulin/C-peptide ratio (P=0.006 and P=0.030, respectively) and proinsulin/IRI ratio (P=0.003 and P=0.016, respectively) in patients with Type 2 diabetes. These results imply that disproportionate hyperproinsulinemia may reflect an excessive overwork of beta cells under chronic sulfonylurea treatment as well as hyperglycemia.

High glucose level and free fatty acid stimulate reactive oxygen species production through protein kinase C--dependent activation of NAD(P)H oxidase in cultured vascular cells

Recent studies have revealed that vascular cells can produce reactive oxygen species (ROS) through NAD(P)H oxidase, which may be involved in vascular injury. However, the pathological role of vascular NAD(P)H oxidase in diabetes or in the insulin-resistant state remains unknown. In this study, we examined the effect of high glucose level and free fatty acid (FFA) (palmitate) on ROS production in cultured aortic smooth muscle cells (SMCs) and endothelial cells (ECs) using electron spin resonance spectroscopy. Exposure of cultured SMCs or ECs to a high glucose level (400 mg/dl) for 72 h significantly increased the free radical production compared with low glucose level exposure (100 mg/dl). Treatment of the cells for 3 h with phorbol myristic acid (PMA), a protein kinase C (PKC) activator, also increased free radical production. This increase was restored to the control value by diphenylene iodonium, a NAD(P)H oxidase inhibitor, suggesting ROS production through PKC-dependent activation of NAD(P)H oxidase. The increase in free radical production by high glucose level exposure was completely restored by both diphenylene iodonium and GF109203X, a PKC-specific inhibitor. Exposure to palmitate (200 micromol/l) also increased free radical production, which was concomitant with increases in diacylglycerol level and PKC activity. Again, this increase was restored to the control value by both diphenylene iodonium and GF109203X. The present results suggest that both high glucose level and palmitate may stimulate ROS production through PKC-dependent activation of NAD(P)H oxidase in both vascular SMCs and ECs. This finding may be involved in the excessive acceleration of atherosclerosis in patients with diabetes and insulin resistance syndrome.

Retinal expression, regulation, and functional bioactivity of prostacyclin-stimulating factor

Prostacyclin-stimulating factor (PSF) acts on vascular endothelial cells to stimulate the synthesis of the vasodilatory molecule prostacyclin (PGI2). We have examined the expression, regulation, and hemodynamic bioactivity of PSF both in whole retina and in cultured cells derived from this tissue. PSF was expressed in all retinal cell types examined in vitro, but immunohistochemical analysis revealed PSF mainly associated with retinal vessels. PSF expression was constitutive in retinal pericytes (RPCs) but could be modulated in bovine retinal capillary endothelial cells (RECs) by cell confluency, hypoxia, serum starvation, high glucose concentrations, or inversely by soluble factors present in early vs. late retinopathy, such as TGF-beta, VEGF, or bFGF. In addition, RPC-conditioned media dramatically increased REC PGI2 production, a response inhibited by blocking PSF with a specific antisense oligodeoxynucleotide (ODN). In vivo, PGI2 increased retinal blood flow (RBF) in control and diabetic animals. Furthermore, the early drop in RBF during the initial weeks after inducing diabetes in rats, as well as the later increase in RBF, both correlated with levels of retinal PSF. RBF also responded to treatment with RPC-conditioned media, and this effect could be partially blocked using the antisense PSF ODN. We conclude that PSF expressed by ocular cells can induce PGI2, retinal vascular dilation, and increased retinal blood flow, and that alterations in retinal PSF expression may explain the biphasic changes in RBF observed in diabetes.

The meaning of serum levels of advanced glycosylation end products in diabetic nephropathy

It has been reported that advanced glycosylation end products (AGEs) play an important role in the development of diabetic complications. To evaluate the relationship between serum AGEs and diabetic nephropathy, we measured serum AGE levels in diabetic patients with normoalbuminuria (N), microalbuminuria (M), overt proteinuria (O), and hemodialysis (HD), non diabetic patients with nephropathy, and age-matched control subjects using the enzyme-linked immunosorbent assay (ELISA). Urine AGE levels were also measured in these subjects except group HD. Serum AGE levels in diabetic patients were not significantly higher than those in the normal subjects. When we compared serum AGE levels among various stages of diabetic nephropathy, groups O and HD had significantly higher serum AGE levels than the other groups. Serum AGE levels in group HD were almost 6-fold higher than those in groups N and M. In contrast, there were no significant differences in urinary AGE levels among any diabetic groups. As for the variables that determine serum AGE levels in diabetic patients, there was no significant correlation between serum AGEs and fasting blood glucose, hemoglobin A1c (HbA1c), or duration of diabetes. In contrast, serum AGEs showed a strong correlation with serum creatinine and an inverse correlation with creatinine clearance. To evaluate the relationship between serum AGEs and oxidative stress in diabetic nephropathy, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) and serum malondialdehyde (MDA), which are biological markers of total oxidative stress in vivo, were also examined. Both urinary 8-OHdG and serum MDA levels were significantly higher in diabetic patients with proteinuria versus those without proteinuria. However, there was no significant correlation between serum AGEs and urinary 8-OHdG or serum MDA levels in diabetic patients. These results suggest that the accumulation of serum AGEs in diabetic nephropathy may be mainly due to decreased removal in the kidney rather than increased production by high glucose levels or oxidative stress.

High incidence of silent myocardial ischemia in elderly patients with non insulin-dependent diabetes mellitus

The present study was designed to reveal the incidence of silent myocardial ischemia in asymptomatic elderly non-insulin-dependent diabetic (NIDDM) patients (aged over 60 years). As a first step screening, maximal treadmill exercise test was performed. Of 140 patients studied, 54 (38.6%) were unable or not expected to achieve diagnostic levels of exercise during treadmill testing. A positive exercise test was noted in 39 of 86 (45.3%) subjects. As a second step examination, dipyridamole thallium scintigraphy was performed for 93 subjects who exhibited a positive exercise test and could not perform a maximal exercise test. Abnormal perfusion pattern was found in 39 of 93 (41.9%), who were finally considered to have a silent myocardial ischemia. Coronary angiography was performed in 18 subjects with diagnosis of silent myocardial ischemia, who gave their consent. Significant coronary artery stenosis was in fact found in 17 of 18 (94.4%) subjects studied, confirming a very high positive predictive value of this diagnostic procedure. In conclusion, elderly NIDDM patients (aged over 60 years) had an extremely high prevalence (estimated 26.3%) of silent myocardial ischemia. This evidence suggests that early and intensive detection may be needed as a part of routine care for this group.

Subcutaneous or visceral adipose tissue expression of the PPARgamma gene is not altered in the fatty (fa/fa) Zucker rat

We cloned 537 basepairs (bp) of rat partial peroxisome proliferator-activated receptor gamma2 (PPARgamma2) cDNA and examined the effect of fasting or obesity on the expression of two isoforms of rat PPARgamma, gamma1 and gamma2, in either subcutaneous or mesenteric adipose tissue specimens using an RNase A protection assay. In Wistar rats, expression of both isoforms was dramatically reduced after 48 hours of fasting in the two fat tissue specimens. In comparing genetically obese (fa/fa) Zucker rats and lean control rats, no significant difference was observed in expression of the two isoforms in either type of adipose tissue. From these findings, we conclude that the adipose tissue level of rat PPARgamma depends on nutritional deprivation but is not closely associated with either obesity or insulin resistance in obese Zucker rats.

Oxidative stress measurement by in vivo electron spin resonance spectroscopy in rats with streptozotocin-induced diabetes

Enhanced oxidative stress in diabetic patients may contribute to the pathogenesis of diabetic angiopathy. We have recently developed a method to determine the electron spin resonance (ESR, electron paramagnetic resonance; EPR) of reactive oxygen species and free radicals in vivo, using the nitroxide derivative, carbamoyl-PROXYL as a probe. In this study, diabetes was induced in Wistar rats by streptozotocin (STZ) injection (65 mg/kg, body weight, intravenously). Two, 4, and 8 weeks later, the animals received carbamoyl-PROXYL (300 nmol/g, intravenously), and ESR was measured at the upper abdominal level at a frequency of 300 MHz. The intensity of the carbamoyl-PROXYL ESR signal decreased gradually after the injection, and the spin clearance rate was determined over the first 5 min. At all time points, the spin clearance rate was significantly greater in the diabetic rats than in control rats. Moreover, the spin clearance rate in the diabetic rats was significantly correlated with urinary malondialdehyde (MDA) levels, which serve as a marker for lipid peroxidation. Daily treatment with 4 units neutral protamin Hagedorn (NPH) insulin for 4 weeks reduced the spin clearance rate in the diabetic rats. Simultaneous injection of carbamoyl-PROXYL and superoxide dismutase reduced the spin clearance rate in the diabetic rats in a dose-dependent manner. Injection of the antioxidant alpha-tocopherol (40 mg/kg, intraperitoneally) for 2 weeks restored the spin clearance rate in the diabetic rats without concomitant glycaemic restoration. These results suggest that a diabetic state enhances the generation of free radicals in vivo, and that both glycaemic control and antioxidant treatment can reduce this oxidative stress. Non-invasive in vivo ESR measurement may be useful for evaluating oxidative stress in diabetes.

Reduced expression of a novel peptide, prostacyclin-stimulating factor, in the kidneys of streptozotocin-induced diabetic rats

Prostacyclin (PGI2) produced by vascular endothelial cells (ECs) is a potent vasoactive prostanoid involved in maintenance of vessel wall homeostasis. Reduced PGI2 synthesis by vascular ECs could be a mechanism of pathogenesis in the development of vascular lesions such as diabetic angiopathy. Recently, we purified and cloned a novel bioactive peptide, PGI2-stimulating factor (PSF), which stimulates PGI2 production by vascular ECs. PSF may act on vascular ECs in a paracrine and/or autocrine fashion to regulate PGI2 synthesis. Decreased PSF production in the vessel wall may result in an imbalance of prostanoid synthesis, leading to the development of vascular lesions such as diabetic angiopathy. Our immunohistochemical study demonstrated that PSF is located in vascular resident cells such as vascular smooth muscle cells (SMCs) and ECs, as well as in bronchial SMCs. Moreover, PSF mRNA was found to be expressed in various tissues in Wistar rats, particularly in the kidneys and lungs. The present study demonstrated that streptozotocin (STZ)-induced diabetic rats showed less PSF mRNA expression in the kidneys (PSF mRNA/28S rRNA ratio; STZ versus control; 1.7+/-0.2 versus 2.5+/-0.2, p < 0.05) and reduced immunohistochemical staining for PSF in arteries in the kidney. However, in the lungs, there were no changes in tissue PSF mRNA expression (STZ versus control; 10.9+/-0.9 versus 11.5+/-1.0, NS) or in the extent of PSF staining in bronchial SMCs of STZ-induced diabetic rats. These findings suggest that decreased expression of PSF in renal vessels of STZ-induced diabetic rats may cause an imbalance of prostanoid synthesis, leading to the development and progression of vascular damage in the kidney.

Effect of eicosapentaenoic acid on glucose-induced diacylglycerol synthesis in cultured bovine aortic endothelial cells

Hyperglycemia has been postulated to increase diacylglycerol (DAG) level through de novo synthesis pathway and subsequently activate protein kinase C (PKC) in vascular cells, possibly leading to vascular dysfunction associated with diabetes. In this study, we examined the effect of eicosapentaenoic acid (EPA) on high glucose-induced increase in DAG level in cultured aortic endothelial cells (ECs). In ECs, total DAG level was significantly increased in the cells cultured with high glucose levels (400 mg/dl) compared with the cells with normal glucose levels (100 mg/dl). The addition of EPA completely prevented high glucose-induced increase in total DAG level. In contrast, other common fatty acids such as palmitate and oleate significantly stimulated DAG syntheisis, although arachidonate did not affect it. High glucose level significantly stimulated the incorporation of 3H-palmitate into DAG, while it did not affect the incorporation of 3H-arachidonate into DAG. The addition of EPA completely prevented the high glucose-induced increase in 3H-palmitate incorporation into DAG, while it did not affect the 3H-arachidonate incorporation. These findings suggest that EPA can prevent high glucose induced-increase in DAG level in ECs, probably by specifically inhibiting de novo synthesis at the step of acylation. EPA may be one of the candidates for clinical agents normalizing activation of DAG-PKC pathway in diabetic vascular tissues and preventing vascular complications associated with diabetes.

Broad spectrum and mode of action of an antibiotic produced by Scytonema sp. TISTR 8208 in a seaweed-type bioreactor

A photobioreactor was constructed using anchored polyurethane foam strips (1 x 1 x 40 cm) fixed onto a stainless-steel ring to prevent flotation, as a biomass support material (BSM). This type of reactor was named a seaweed-type bioreactor. A filamentous cyanobacterium, Scytonema sp. TISTR 8208, which produces a novel cyclic dodecapeptide antibiotic, was immobilized in seaweed-type photobioreactor and cultivated with air containing 5% CO2 sparged at a gas flow rate of 250 mL/min under illumination at a light intensity of 200 mmol photon m-2 s-1. The antibiotic produced in the seaweed-type photobioreactor was purified by HPLC and examined regarding its spectrum and mode of action. The antibiotic effectively inhibited the growth of Gram-positive bacteria, pathogenic yeasts, and filamentous fungi, but it had only a weak effect on Gram-negative bacteria. Scanning electron micrograph analysis showed that the most characteristic change was swelling of the cells after exposure to the antibiotic. The antibiotic seems to alter the conformation of the microbial cell membrane, thereby changing its permeability, leading to osmotic shock.

Cloning and sequence analysis of the poly (3-hydroxyalkanoic acid)-synthesis genes of Pseudomonas acidophila

Pseudomonas acidophila can grow with CO2 as a sole carbon source by the possession of a recombinant plasmid that clones genes that confer chemolithoautotrophic growth ability derived from the H2-oxidizing bacterium Alcaligenes hydrogenophilus. H2-oxidizing bacteria produce poly(3-hydroxybutyric acid) (PHB) from CO2, but recombinant P. acidophila can produce the more useful biopolymer poly(3-hydroxyalkanoic acid) (PHA). In this study, the pha genes of P. acidophila were cloned and a sequence analysis was carried out. A gene library was constructed using the cosmid vector pVK102. A recombinant cosmid carrying the pha genes was selected by the complementation of a PHB-negative mutant of Alcaligenes eutrophus H16. The resulting recombinant cosmid pIK7 contained a 14.8-kb DNA insert. Subcloning was done. and the recombinant plasmid pEH74 was selected by hybridization with the A. eutrophus H16 pha genes. Escherichia coli possessing pEH74 produced PHB, indicating that pEH74 contained the pha genes of P. acidophila. The nucleotide sequences of the PHA-synthesis genes phaA (beta-ketothiolase), phaB (acetoacetyl-CoA reductase), and phaC (PHA synthase) in pEH74 were determined. The homologies of phaA, phaB, and phaC between P. acidophila and A. eutrophus H16 were 64.7, 76.1 and 56.6%, respectively.

High glucose induces alteration of gap junction permeability and phosphorylation of connexin-43 in cultured aortic smooth muscle cells

Gap junction is thought to have a crucial role in maintaining tissue homeostasis. We examined the effect of a high glucose level on gap junctional intercellular communication (GJIC) activity in cultured vascular smooth muscle cells (VSMCs) using the fluorescent dye transfer method. After a 48-h incubation with 22 mmol/l glucose (high glucose level), GJIC activity of VSMCs was significantly reduced compared with incubation with 5.5 mmol/l glucose (normal glucose level) (P < 0.05). Treatment of the cells with 12-O-tetradecanoylphorbol-13-acetate (TPA; 5 x 10(-8) mol/l), a protein kinase C (PKC) activator, for 1 h also reduced GJIC activity (P < 0.01). In addition, treatment of the cells with calphostin C, a specific PKC inhibitor, for 3 h completely restored the GJIC activity inhibited by the high glucose level. Western blot analysis showed that connexin 43 (Cx43), which is the major functional protein of gap junction, is present in multiphosphorylated forms: a nonphosphorylated form (P0) and phosphorylated forms (P1, P2, and P3). Incubation of VSMCs with a high glucose level significantly increased the density ratio of P3/P0 compared with a normal glucose level (P < 0.05). Similarly, treatment of the cells with TPA significantly increased the P3/P0 ratio compared with controls (P < 0.01). In addition, the increase in the P3/P0 density ratio induced by a high glucose level was restored to the control level by both staurosporine and calphostin C. These results suggest that the high glucose level induced the inhibition of GJIC activity in cultured VSMCs through excessive phosphorylation of Cx43, mediated by PKC activation. This may contribute to the development of the macroangiopathy associated with diabetes.

Increased mRNA expression of a novel prostacyclin-stimulating factor in human colon cancer

We recently cloned a prostacyclin (PGl2)-stimulating factor (PSF), which stimulates PGl2 production by cultured vascular endothelial cells. Immunohistochemistry and Northern blot analysis demonstrated that PSF was highly expressed in colon cancer sites compared with normal colon mucosa obtained from the same patient, as well as in cultured adenocarcinoma cell lines compared with cultured normal colon mucosal cell lines. Increased levels of the PSF protein were detected in the culture media of these adenocarcinoma cells compared with levels in the culture media of normal mucosal cells. These results suggest that PSF is closely associated with carcinogenesis of colon mucosa.

Effect of high glucose concentrations on prostacyclin-stimulating factor mRNA expression in cultured aortic smooth muscle cells

Prostacyclin (PGI2) is a potent vasoactive prostanoid regulating vascular tone. We recently purified and cloned a PGI2-stimulating factor (PSF), which stimulates PGI2 production by vascular endothelial cells (ECs). Previous study demonstrated that PSF is predominantly located in vascular smooth muscle cells (SMCs) and present in serum. PSF may act on vascular ECs to regulate PGI2 synthesis for maintaining vessel wall homeostasis. Decreased PSF production in the vessel wall may result in an imbalance of prostanoid synthesis, leading to the development of vascular lesions such as diabetic angiopathy. In the present study, to investigate the regulatory mechanisms of PSF gene expression, we examined the effect of high glucose concentrations on PSF mRNA expression in cultured bovine aortic SMCs. Expression of PSF mRNA was significantly decreased to 66+/-6% of control value (p < 0.01), when the glucose level was raised from 5.5 to 27.8 mmol/l. We also examined the effect of osmolarity on PSF mRNA expression by addition of an appropriate dose of mannitol to the culture medium. We confirmed that high glucose concentration itself reduced the expression of PSF mRNA and glucose had much more effect than the osmolarity control. The expression of PSF mRNA was significantly decreased to 72+/-5% of control value (p < 0.05) by a protein kinase C (PKC) activator, phorbol-12-myristate-13-acetate (PMA). The decreased expression of PSF mRNA in the presence of high glucose or PMA was restored by co-incubation with a PKC-specific inhibitor (GF109203X). These results suggest that PSF gene expression in vascular SMCs may be decreased via a specific effect of high glucose concentrations. High glucose-induced activation of PKC is suggested to participate partly in the regulation of PSF gene expression.

Prevention of diabetes-induced abnormal retinal blood flow by treatment with d-alpha-tocopherol

Hyperglycemia in diabetes mellitus has been shown to activate diacylglycerol (DAG)-protein kinase C (PKC) pathway in the vascular tissues, possibly altering vascular function. We have characterized the effects of vitamin E (d-alpha-tocopherol) on activation of PKC and DAG levels in retinal tissues of diabetic rats, and correlated its effects to retinal hemodynamics using video-based fluorescein angiography (VFA). Comparing streptozotocin-induced diabetic rats to controls, membranous PKC specific activities were increased by 71% (p < 0.05). Western blot analysis showed that the membranous PKC beta II isoform was significantly increased by 133 +/- 45% (p < 0.05). Intraperitoneal injection of d-alpha-tocopherol (40 mg/kg) every other day prevented the increases in membranous PKC specific activity and PKC beta II protein shown by immunoblots. Similar to PKC activities, total DAG levels were increased in the retina and were normalized by d-alpha-tocopherol treatment. Physiologically, abnormalities of retinal blood hemodynamics, as measured using VFA, which previously have been reported to be associated with increases of DAG and PKC levels in the diabetic rats, were prevented by d-alpha-tocopherol treatment in diabetic rats. The direct effect of d-alpha-tocopherol on total DAG and [3H]-palmitate incorporation into DAG were also examined using cultured bovine retinal endothelial cells (REC). Exposure of REC to 22 mM glucose for three days increased total DAG and [3H]-palmitate labeled DAG levels by 35 +/- 8% and 50 +/- 8%, respectively (p < 0.05). The presence of d-alpha-tocopherol (50 micrograms/ml) prevented the increase of both total DAG and [3H]-palmitate labeled DAG levels in cells exposed to 22 mM glucose. These findings suggested that the mechanism of the d-alpha-tocopherol's effect appears to be mediated by the normalization of the hyperglycemia-induced activation of the DAG-PKC pathway which leads to the normalization of abnormal retinal blood flow seen in diabetes mellitus.

A case of mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes associated with diabetes mellitus and hypothalamo-pituitary dysfunction

A 45-year-old woman with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) had muscular atrophy, severe cerebral and cerebellar atrophy, and cardiac hypertrophy. She also had diabetes mellitus treated with insulin, and sensorineural hearing loss. Ragged-red fibers were observed on muscle biopsy and an adenine to guanine transition mutation at position 3243 of her mitochondrial DNA was confirmed. Further investigations revealed that she also had hypothalamo-pituitary dysfunction. It appears that diabetes mellitus, hypothalamo-pituitary dysfunction, and the other abnormalities are all associated with mitochondrial dysfunction in this patient.

[Insulin secretin and resistance accompany immobilization of the aged patient]

Physical activity is known to increase glucose tolerance and insulin sensitivity. To examine the influence of physical inactivity on insulin sensitivity in aged people, insulin sensitivity and secretion was measured by using a two-step euglycemic glucose clamp, a glucagon tolerance test (GTT), an oral glucose tolerance test (OGGT) and urinary CPR excretion in 11 aged patients immobilized in bed for more than 12 weeks. The results were compared with those of nine healthy mobile aged controls. The muscle volume of the immobilized patients decreased by 20-25% compared with that of the controls, and insulin sensitivity decreased 50% in each step. These results mean that the immobilized patients had decreased insulin sensitivity and responsiveness, even when there was muscle atrophy. The glucose and insulin responses in both the GTT and OGTT showed that there was a slight decrease in the initial response of insulin in the immobilized patients and was in the controls compared with adolescent controls. There was no difference in the initial response of insulin between the immobilized patients and the aged controls. The ratio of impaired glucose tolerance in the OGTT was 4/11 of the immobilized patients and 3/9 of the controls. Total insulin secretion was increased and insulin sensitivity and responsiveness was decreased in the immobilized patients. This suggests that the decreased insulin sensitivity was compensated for increased by insulin secretion in the immobilized patients.

Immunohistochemical study of prostacyclin-stimulating factor (PSF) in the diabetic and atherosclerotic human coronary artery

Prostacyclin (PGI2) synthesis by vascular endothelial cells (ECs) decreases in diabetic subjects, possibly leading to the development of diabetic angiopathy, such as that seen in atherosclerosis. We recently found a novel bioactive peptide, prostacyclin-stimulating factor (PSF), which stimulates PGI2 synthesis by cultured aortic ECs. Our previous studies demonstrated that PSF is dominantly expressed by arterial smooth muscle cells (SMCs). In the present study, we found PSF to exist in the SMCs of human coronary arteries by means of immunohistochemical methods. Human coronary arteries obtained from autopsies were divided into four subgroups, with or without NIDDM and/or myocardial infarction. Immunostaining for PSF was performed by the avidin-biotin peroxidase complex method using a purified anti-PSF antibody, and the immunostaining for PSF was assessed semiquantitatively. PSF staining was markedly reduced in coronary arterial SMCs from patients with NIDDM and/or myocardial infarction. In addition, the effect of a high glucose culture on PSF mRNA expression and PSF production in bovine aortic SMCs was examined by immunocytochemical staining and both Western and Northern blot analyses. The immunostaining and immunoblot band for PSF also significantly decreased when bovine aortic SMCs were cultured with high concentrations of glucose. Furthermore, as compared with the SMCs cultured with a physiological glucose concentration, the density ratio of PSF mRNA to 28S rRNA expression significantly decreased when the SMCs were cultured with high concentrations of glucose. These results strongly suggest that the decreased PSF production may thus results in a decreased production of PGI2 in the coronary artery, thus leading to the development of both diabetic macroangiopathy and atherosclerosis.

Effect of acarbose on glucose intolerance in patients with non-insulin-dependent diabetes mellitus

We evaluated the effect of acarbose, an alpha-glucosidase inhibitor, on glucose intolerance in patients with non-insulin-dependent diabetes mellitus (NIDDM). Acarbose was given orally (300 mg/day) for 24 weeks to 20 NIDDM patients. Data in an oral glucose tolerance test (OGTT) were evaluated before and after 24 weeks of treatment using principal component analysis. Acarbose administration significantly reduced the postprandial plasma glucose level over 24 weeks of treatment. Principal component analysis suggested that the patients were separated into responders and non-responders. There was a significant improvement of fasting and postprandial glucose levels after 12 and 24 weeks in the responders, but not in the non-responders. Plasma glucose level following the OGTT improved significantly after 24 weeks of treatment in the responders (Hotelling T2 value = 47.098, P = 0.022500), but not in the non-responders. The immunoreactive insulin level did not change in either group. Results thus suggest that acarbose improved insulin resistance in some patients with NIDDM (responders as classified by principal component analysis).

Effect of beraprost sodium on the increased transendothelial permeation of albumin induced by high concentration of glucose

To determine whether a decrease in prostacyclin production is involved in the increase in endothelial permeability induced by a high concentration of glucose, we evaluated the effect of beraprost sodium, a stable prostacyclin analog, on the transendothelial permeation of albumin in cultured aortic cells. Permeation of albumin across an endothelial cell monolayer was significantly greater when the cells were cultured with a high concentration of glucose (400 or 800 mg/dl) than when they were cultured with 100 mg/dl glucose. No significant change in the permeation of albumin was observed when cells were cultured with 100 mg/dl glucose as compared with 100 mg/dl glucose plus 700 mg/dl mannitol. The addition of beraprost sodium to the culture medium completely restored the increase in the permeation of albumin brought about by 400 mg/dl glucose. These results suggest that increased transendothelial permeation of albumin by high glucose may be due in part to a decrease in prostacyclin production by the endothelial cells. Beraprost sodium may restore the endothelial barrier function affected by a high concentration of glucose.

Persistence of cyclopiazonic acid-induced endothelium-dependent vasodilatation in spontaneously hypertensive and streptozotocin-induced diabetic rats

We recently reported that cyclopiazonic acid (CPA) releases a novel endothelium-derived relaxing factor that is not prostacyclin, nitric oxide or endothelium-derived hyperpolarizing factor in rat mesenteric arterial bed. The acetylcholine-induced vasodilatation of the isolated mesenteric bed in spontaneously hypertensive rats (SHR) was not different from that in Wistar Kyoto rats (WKY), but it was significantly smaller in streptozotocin (STZ)-induced diabetic rats than in age-matched controls. The CPA-induced vasodilatation was not affected in SHR or in STZ-induced diabetic rats. These results suggest that the CPA-induced endothelium-dependent vasodilatation is resistant to the effects of diabetes.

Human diploid fibroblast cell culture medium contains a factor that increases cytosolic Ca2+ and stimulates prostaglandin synthesis by cultured bovine aortic endothelial cells

Previously, we demonstrated that conditioned medium (CM) from cultures of human diploid fibroblast cells contains a factor that stimulates the production of prostacyclin (PGI2) by cultured bovine aortic endothelial cells (BAEC). To study the mechanism by which CM stimulates PGI2 production, we measured the effect of removal of extracellular calcium (Ca2+) on the concentration of cytosolic Ca2+ and on the production of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), a stable metabolite of PGI2. The CM-induced production of 6-keto-PGF1 alpha was dependent on extracellular Ca2+ and did not require nascent protein synthesis. Application of CM to BAEC induced a transient increase in cytosolic Ca2+ concentration that was dependent on extracellular Ca2+. Bradykinin induced the production of 6-keto-PGF1 alpha by BAEC. However, bradykinin induced an increase in cytosolic Ca2+ concentration in the presence or absence of extracellular Ca2+. Voltage dependent Ca2+ channel blocker (verapamil, diltiazem) did not inhibit either the CM-induced increase in cytosolic Ca2+ or the production of 6-keto-PGF1 alpha by BAEC. These data suggest that CM increases the cytosolic Ca2+ concentration and stimulates PGI2 production by BAEC. The increase in cytosolic Ca2+ concentration occurred via the influx of extracellular Ca2+ independent of L-type Ca2+ channels blocked by verapamil or diltiazem.

Difference in serum-induced prostacyclin production by cultured aortic and capillary endothelial cells

Prostacyclin (PGl2) generated by vascular endothelial cells play an important role in the maintenance of vessel wall homeostasis. Human plasma-derived serum (PDS) stimulated PGl2 synthesis by both cultured bovine aortic endothelial cells (BAEC) and adrenal capillary endothelial cells (BCEC), but the PGl2 response of the latter cells was far smaller. When BAEC were cultured with a high concentration of glucose (400 mg/dl), the PGl2 synthesis induced by 20% PDS was significantly lower than in the culture with a physiological concentration of glucose (100 mg/dl) (258 +/- 45 pg/10(4) cells/h vs. 402 +/- 52 pg/10(4) cells/h, n = 4, P < 0.05). On the other hand, there was no significant difference in the PDS-induced PGl2 synthesis between BCEC cultured with high and physiological concentrations of glucose. Additionally, 10% PDS obtained from patients with non-insulin dependent diabetes mellitus (n = 6) stimulated significantly less PGl2 synthesis than that from healthy subjects (n = 4) in the case of both BAEC (133 +/- 27 pg/10(4) cells/h vs. 402 +/- 38 pg/10(4) cells/h, P < 0.05) and BCEC (72 +/- 15 pg/10(4) cells/h vs. 118 +/- 12 pg/10(4) cells/h, P < 0.05), with the difference in PGl2 synthesis being smaller for BCEC. These findings indicate that the PDS-induced PGl2 synthesis differs between cultured vascular endothelial cells from large and small vessels with the decrease in PGl2 by diabetic PDS and high glucose being more marked for BAEC than BCEC.

Elevated L-kynurenine level and its normalization by prednisolone in a patient with eosinophilia-myalgia syndrome

We report a L-tryptophan-induced case of eosinophilia-myalgia syndrome in a Japanese woman and describe the time course of changes in tryptophan metabolism observed during steroid therapy. She had taken 1.0 g of the implicated L-tryptophan daily. When admitted due to painful swelling of her extremities, eosinophil count was 22.3 x 10(9)/L. Before prednisolone treatment, her serum L-kynurenine level was 10.2 mumol/L, a level about three-fold higher than the normal value, while serum tryptophan level was abnormally low (23.1 mumol/L). On the 14th day of prednisolone treatment (40 mg daily), L-kynurenine was declined to 8.1 mumol/L and, concomitantly, L-tryptophan level increased to the normal range (51.0 mumol/L). Subsequently, on the 42nd day of therapy, serum L-kynurenine was normalized. In contrast, serum serotonin level was unchanged throughout the course of this therapy. Prednisolone dramatically reduced the elevated serum L-kynurenine with a reciprocal increase in serum L-tryptophan indicates that abnormal tryptophan metabolism, may play a role in the pathogenesis of eosinophilia myalgia syndrome, and that the observed effect of steroid treatment was due to suppression of elevated activity of indoleamine 2, 3-dioxygenase, a first rate-limiting enzyme of the kynurenine pathway.