Yasuhiro Sako

Effects of a new oral hypoglycaemic agent (CS-045) on metabolic abnormalities and insulin resistance in type 2 diabetes.

The effects of a thiazolidinedione antidiabetic agent (CS‐045) on diabetic metabolic abnormalities were studied in a double‐blind clinical trial. Fourteen patients with Type 2 diabetes were selected according to study criteria. Eight were treated with oral CS‐045 at 400 mg daily, and six were given placebo. A multi‐step, hyperinsulinaemic, euglycaemic clamp study, with simultaneous plasma free fatty acid study, and glucagon tolerance test were performed before and after administration of drug. Following 3 months of treatment with CS‐045, there were significant decreases in the mean levels of fasting plasma glucose (from 9.18 ± 0.95 to 7.78 ± 0.44 mmol l−1), postprandial plasma glucose (from 11.8 ± 1.23 to 10.36 ± 1.06 mmol l−1), and haemoglobin A1c (from 9.3 ± 0.4 to 6.8 ± 0.4%). Insulin sensitivity also improved (1st step: from 3.12 ± 0.33 to 4.70 ± 0.47 mg kg−1 min−1 (p < 0.01); 2nd step: from 5.61 ± 0.63 to 7.54 ± 0.58 mg kg−1 min−1 (p< 0.01); 3rd step: from 9.21 ± 0.67 to 11.10 ± 0.87 mg kg−1 min−1). The fasting free fatty acid level decreased significantly from 0.28 ± 0.04 to 0.22 ± 0.02 g l−1. The residual free fatty acid level (%) under insulin infusion clamp conditions decreased significantly from 63.7 ± 9.7 to 45.0 ± 9.2%. CS‐045 treatment was associated with decrease in total cholesterol, total triglycerides, and increase in HDL cholesterol. Basal C‐peptide immunoreactivity level decreased, but there was no change in the peak C‐peptide immunoreactivity value. None of these changes was observed in the placebo group. CS‐045 improved hyperglycaemia as well as insulin resistance. CS‐045 appears to have a different mode of hypoglycaemic action from that of the sulphonylureas.

A comparison of the handling and accuracy of syringe and vial versus prefilled insulin pen (FlexPen).

BACKGROUND To determine the preferable method for self-injecting insulin, we compared the handling, safety, and dose accuracy of a conventional disposable syringe and vial with FlexPen (Novo Nordisk A/S, Bagsvaerd, Denmark), a prefilled pen. METHODS Insulin therapy-naive healthcare professionals (HCPs) (n = 30), unfamiliar with insulin delivery, injected 10 U of insulin into a sponge pad using either a syringe and vial or the FlexPen, both with 30-gauge 8-mm needles, on day 1. The following day, they used the alternative method. They evaluated the handling of the two methods on device-specific questionnaires and compared overall preference on a third questionnaire. To evaluate dose accuracy, 30 insulin therapy-experienced HCPs and 20 insulin therapy-naive HCPs were asked to deliver 10 U of insulin using each method, and the amount discharged was weighed. RESULTS FlexPen was rated easier to use and overall more preferable than the syringe and vial by insulin therapy-naive HCPs (P < 0.001). The pen device was more accurate than the syringe and vial when used by experienced HCPs (mean +/- SD dose delivered, 9.91 +/- 0.11 U vs. 9.82 +/- 0.25 U, respectively; P < 0.001) and by insulin therapy-naive HCPs (9.91 +/- 0.12 U vs. 9.74 +/- 0.85 U; P < 0.001). CONCLUSIONS Insulin therapy-naive HCPs found FlexPen easier to handle and preferable to use compared to a conventional syringe and vial. Both insulin therapy-experienced and -naive HCPs were able to deliver insulin significantly more accurately with the FlexPen than with a syringe and vial (P < 0.001).

Effect of glibenclamide on pancreatic hormone release from isolated perifused islets of normal and cysteamine-treated rats

The effect of glibenclamide, a sulfonylurea agent, on islet hormone secretion, particularly on glucagon was studied using isolated perifused pancreatic islets of normal and cysteamine-treated rats. In normal rat islets, glibenclamide enhanced both insulin and somatostatin release in normoglycemic (50 mg/dL) and glucopenic (0 mg/dL) states, as well as under the condition of arginine stimulation. In contrast, glibenclamide stimulated glucagon release only transiently, then suppressed it in a sustaining manner in each state. In the cysteamine-treated islets, as expected, somatostatin concentrations in the perifusate remained unchanged during the infusion of arginine and/or glibenclamide. Under this condition, glibenclamide enhanced insulin release to the same extent as seen in normal islets, and again markedly inhibited glucagon release. These observations indicate that in isolated perifused rat pancreatic islets, glibenclamide suppresses glucagon secretion independently of D cell stimulation. It is concluded that glibenclamide may exert its inhibitory effect directly on A cell rather than through paracrine action of concomitant somatostatin release, and that the suppression of glucagon secretion by glibenclamide may, in part, contribute to the antidiabetogenic effect of this compound.

Glucosamine-induced β-cell Dysfunction : A Possible Involvement of Glucokinase or Glucose-transporter Type 2

Introduction The mechanism for &bgr;-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 E1&agr;, 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 bezafibrate on β-cell function of rat pancreatic islets

Abstract Bezafibrate is an activator of peroxisome proliferator-activated receptors (PPAR) α. The present study was performed to investigate the effects of bezafibrate and the PPAR α activator, 4-Cholro-6-(2.3-xylidino)-2-pyrimidin-ylthio acetic acid (WY14643), on the β-cell function of rat pancreatic islets in vitro. In islets cultured with 300 μM bezafibrate or WY14643 for 8 h, a low glucose concentration induced insulin release and increased the levels of mRNA for PPAR α, acyl CoA oxidase, carnitine palmitoyl transferase-1, pyruvate dehydrogenase E1 α 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 α gene expression during a short culture period, whereas it may contribute to β-cell dysfunction through the mechanism of “excessive stimulation” during longer culture periods.

Insulin Treatment Improves Relative Hypersecretion of Amylin to Insulin in Rats With Non-Insulin-Dependent Diabetes Mellitus Induced by Neonatal Streptozocin Injection

The dissociated release of insulin and amylin in the hyperglycemic state has been reported. This relative hypersecretion of amylin is thought to provide an important insight into how amylin aggregates to form islet amyloid deposits in non-insulin-dependent diabetes mellitus (NIDDM). The aim of the present study was to characterize the alterations of amylin hypersecretion in NIDDM with exacerbation or amelioration of diabetic control. For this purpose, neonatally streptozocin (nSTZ) diabetic rats were treated with dexamethasone (0.25 mg/kg) or Lente insulin (3 to 5 U/kg) daily for 14 days, and responses of amylin and insulin to 16.7 mmol/L glucose or 10 mmol/L arginine were evaluated in vitro using an isolated perfused pancreas system. nSTZ rats exhibited moderate elevations of plasma glucose compared with normal rats. In the isolated perfused pancreas, the molar ratio of secreted amylin to insulin in response to 16.7 mmol/L glucose by nSTZ pancreas (1.8% +/- 0.2%) was significantly greater than that of normal rat pancreas (1.2% +/- 0.1%). Plasma glucose levels in nSTZ rats (7.3 +/- 0.4 mmol/L) increased with dexamethasone treatment (17.8 +/- 1.1 mmol/L, P < .005) and decreased with insulin treatment (5.8 +/- 0.4 mmol/L, P < .05). The secreted amylin to insulin ratio in dexamethasone-treated nSTZ rats was significantly greater than that of the controls (P < .05). Moreover, insulin-treated nSTZ rats exhibited decreased amylin to insulin molar ratios compared with saline-treated nSTZ rats (P < .05), which had the same levels as normal rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of cilostazol, a phosphodiesterase inhibitor, on urinary excretion of albumin and prostaglandins in non-insulin-dependent diabetic patients.

Microalbuminuria is characteristic in diabetic nephropathy and is thought to be influenced by renal hemodynamics, especially by the metabolism of prostaglandins (PGs) in glomruli. To reduce urinary albumin excretion in patients with non-insulin-dependent diabetes mellitus (NIDDM), we administered 100 mg of cilostazol, a phosphodiesterase inhibitor, daily for 3 months. The urinary albumin index (UAI: microgram albumin/mg creatinine) decreased significantly after 3 months of administering cilostazol. Urinary excretions of thromboxane B2 (TXB2), a stable metabolite of thromboxane A2, decreased significantly after treatment. However, it had no effects on urinary excretions of PGE2 and 6-keto PGF1 alpha (6KF), a stable metabolite of prostacyclin. The ratio 6KF/TXB2 has been known to reflect the renal metabolism of PGs. In this study, urinary 6KF/TXB2 ratio increased significantly in parallel with a significant reduction of UAI. Cilostazol had no adverse effects on the control of blood glucose and lipids. In conclusion, cilostazol has a beneficial effect on UAI in patients with NIDDM by reducing renal production of TXB2., which increases 6KF/TXB2 ratio.

Effect of vitamin E on prostacyclin production from cultured aortic endothelial cells.

Vitamin E is known as a preventive agent against the development of atherosclerosis.1 On the other hand, prostacyclin (PGI2) generated by vascular endothelial cell is considered to play an important role to keep the homeostasis in vascular wall.2–4 The reduction of PGI2 production can be proposed as one of the possible causes of atherosclerosis. In our previous study, human plasma derived serum (PDS) showed a prostacyclin stimulatory activity (PSA) on cultured bovine aortic endothelial cells. Furthermore, the reduction of PSA in PDS was observed in diabetic rats and diabetic patients.5,6 Since PSA can be one of the key modulators to the development of vascular lesions, the present study was done to evaluate the effect of vitamin E on PSA when stimulated by PDS.

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 &bgr; 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.