Efficacy and safety of once daily gliclazide (20 mg/day) compared with nateglinide

An open-label prospective cross-over trial was performed to compare the efficacy and safety of once daily low-dose gliclazide (20 mg/day) with that of nateglinide at the usual dosage (270 mg/day, 90 mg t.i.d.) in Japanese type 2 diabetics with relatively good glycemic control (HbA1c<7.0%). Eight patients received 20 mg/day of gliclazide and 16 received 270 mg/day of nateglinide. After at least 12 weeks of gliclazide or nateglinide therapy, the drugs were switched and treatment was continued for another 12 weeks. The final HbA1c value was modestly, but significantly, lower after gliclazide treatment than after nateglinide treatment (6.2% vs. 6.4%). However, symptoms related to hypoglycemia were significantly more common with gliclazide treatment than nateglinide treatment (7 vs. 0 cases), although there were no severe hypoglycemic events. While gliclazide acts as a free radical scavenger, there was no effect on parameters of oxidative stress such as malondialdehyde-modified low density lipoprotein and thiobarbituric acid-reactive substances at the low dosage tested. In conclusion, both drugs are reasonable options for early type 2 diabetes. Compared with the regular dose of nateglinide, 20 mg/day of gliclazide achieved modestly better glycemic control with an increased frequency of hypoglycemia in diabetic patients with relatively good glycemic control.

Circulating 1,5-anhydroglucitol levels in adult patients with diabetes reflect longitudinal changes of glycemia: a U.S. trial of the GlycoMark assay

OBJECTIVE

1,5-Anhydroglucitol (1,5AG) is a major circulating polyol arising primarily from ingestion and excreted competitively with glucose. Japanese studies have demonstrated reduced concentrations of 1,5AG in serum in hyperglycemic patients in comparison with euglycemic subjects and a gradual normalization of 1,5AG values for patients responding to antihyperglycemic therapies. In this first U.S. study, we assessed the ability of 1,5AG measurements to monitor glycemic control in a cohort of 77 patients with diabetes (22 with type 1 diabetes, 55 with type 2 diabetes) who presented with suboptimal glycemic control at baseline (defined as HbA(1c) >or=7%).

RESEARCH DESIGN AND METHODS

Each patient received therapies consisting of combinations of diabetes education, nutritional counseling, and addition or dose adjustment of various insulins or oral antihyperglycemic medications. Therapy was targeted to reduce mean HbA(1c) by >or=1.0% over the monitoring period. 1,5AG, HbA(1c), fructosamine, and random glucose measurements were performed at baseline and at 2, 4, and 8 weeks after the initiation of therapy.

RESULTS

1,5AG, fructosamine, and glucose values progressed significantly toward euglycemia by week 2 of monitoring (Wilcoxon's signed-rank test, P < 0.05), with median changes of 93, -7, and -13% for 1,5AG, fructosamine, and glucose, respectively. In contrast, HbA(1c) values did not respond significantly to therapy until week 4. On an individual patient basis, 89.6% of patients displayed longitudinal changes of 1,5AG from baseline to week 8 in concordance with HbA(1c). 1,5AG was also highly correlated with HbA(1c) and fructosamine (Spearman rho = -0.6459 and -0.6751, respectively; both P < 0.0001).

CONCLUSIONS

We conclude that 1,5AG responds sensitively and rapidly to changes in glycemia and monitors glycemic control in accordance with established markers.

Different effects of two alpha-glucosidase inhibitors, acarbose and voglibose, on serum 1,5-anhydroglucitol (1,5AG) level

Serum 1,5-anhydroglucitol (1,5AG) is a useful glycemic marker in the control of diabetes; however, treated with alpha-glucosidase inhibitors (alpha-GIs), acarbose (Aca) and voglibose (Vog), it tends to show the discrepancy between serum 1,5AG and related glucose levels. Twenty patients were randomly assigned to adding Aca or Vog to the current treatment. We measured serum 1,5AG levels and other parameters of diabetic control before, 2 and 4 weeks after the alpha-GI treatment. We also measured urinary 1,5AG levels using gas chromatography/mass spectrometry (GC/MS). Glycated albumin, Hb(A1c), and fasting plasma glucose (FPG) levels were significantly decreased after 2 and 4 weeks of treatment, and the changes were similar in the two groups. Despite the similar urinary excretion of 1,5AG and other glycemic parameters, serum 1,5AG level was significantly lower in the Aca group than in the Vog group (3.4+/-0.5 vs. 7.9+/-1.2 microg/ml, P<.005; mean+/-S.E.) at the period of 4 weeks. Even in the same glycemic level, the less increase of serum 1,5AG after treatment with Aca might be due to a reduction of intestinal 1,5AG absorption via inhibition of alpha-amylase that features Aca.

Postprandial plasma fructose level is associated with retinopathy in patients with type 2 diabetes

The aim of the present study was to investigate the association of fructose on microangiopathy in patients with diabetes. Postprandial plasma fructose concentrations and postprandial plasma glucose concentrations were simultaneously measured 3 times within a 24-hour period (2 hours after each meal) in 38 patients with type 2 diabetes that had been admitted to the hospital. The mean postprandial plasma fructose concentrations (MPPF) and the mean postprandial plasma glucose concentrations (MPPG) were calculated. Fructose was measured by gas chromatography-mass spectrometry (GCMS). Based solely on MPPF, we were able to divide the patients into three groups: the high MPPF (31.9 +/- 6.5 micromol/L) group (n = 12), the middle MPPF (21.2 +/- 1.8 micromol/L) group (n = 13), and the low MPPF (15.2 +/- 2.4 micromol/L) group (n = 13). Prevalence and degree of retinopathy and nephropathy were then evaluated in the 3 different groups. A significant correlation was observed in the prevalence of proliferative diabetic retinopathy (PDR) among the 3 MPPF groups (P =.024). The prevalence of PDR was higher in the high MPPF group (75.0%) than in the middle and low MPPF groups (23.1% and 38.5%, respectively). Although not significantly different statistically, the prevalence of all degrees of retinopathy showed a tendency to be higher in the high MPPF group (83.3%) than in the middle and low MPPF groups (46.2% and 46.2%, respectively) (P =.081). Nephropathy prevalence also showed a tendency to be higher in the high MPPF group (66.7%) than in the middle and low MPPF groups (38.5% and 30.8%, respectively), although the differences were not significant. The prevalence of clinical albuminuria was not significantly different among the 3 groups, but there was a tendency for it to be higher in the low MPPF group (30.8%) than in the high and middle MPPF groups (16.7% and 0%, respectively). No significant differences in glycemic indicators and mean duration of diabetes were observed among the 3 groups. The increased prevalence of retinopathy in the high MPPF group suggests that fructose is associated with retinopathy in patients with type 2 diabetes.

Effect of antidiabetic medications on microalbuminuria in patients with type 2 diabetes

The progression of diabetes and hypertension complications is associated with microalbuminuria. Intensive glycemic control prevents or retards microalbuminuria in patients with type 2 diabetes, but little is known about the respective benefits of different antidiabetic drugs. We studied the effect of gliclazide and pioglitazone on microalbuminuria in patients with type 2 diabetes. We excluded patients with very poor glycemic control (glycated hemoglobin [HbA(1c)] >10%), impaired liver function, nondiabetic renal diseases, and those whose urine contained red blood cells, hemoglobin, or casts. Each patient received the designated drug for 12 weeks and their body weight, blood pressure (BP), fasting plasma glucose (FPG), HbA(1c), lipids (triglycerides [TG], total, and high-density lipoprotein-cholesterol [HDL-C]), 1,5 anhidroglucitol (1,5-AG), immunoreactive insulin (IRI), and urinary albumin to creatinine ratio (UACR) were measured every month. The effects of the drugs were analyzed using 2-way repeated measures analysis of variance (ANOVA). The 2 groups of patients were well matched for age, duration of diabetes, retinal status, blood pressure, body mass index (BMI), IRI, FPG, HBA(1c), 1,5-AG, lipids, and UACR, as well as the use of antihypertensive drugs. After treatment, no significant differences were seen in drug efficacy between the 2 groups. Gliclazide and pioglitazone significantly reduced FPG (F = 26.0, P <.0001), HBA(1c) (F = 48.1, P <.0001), and total cholesterol (TC) levels (F = 3.5, P <.05). Decrements in these metabolic parameters were comparable between the groups. 1,5-AG increased in both groups (F = 27.5, P <.0001), and the increment was comparable in both groups. Gliclazide and pioglitazone significantly reduced UACR (F = 15.7, P <.0001) with a comparable decrement in both groups. No other variables changed significantly throughout the 12-week treatment. These results suggest that 12 weeks of treatment with gliclazide or pioglitazone are equally effective in reducing microalbuminuria with similar improvements in blood glucose and cholesterol levels, independent of their mechanisms of actions.

Hexokinase II overexpression improves exercise-stimulated but not insulin-stimulated muscle glucose uptake in high-fat-fed C57BL/6J mice

The aim of the present study was to determine the specific sites of impairment to muscle glucose uptake (MGU) in the insulin-resistant high-fat-fed, conscious C57BL/6J mouse. Wild type (WT) and hexokinase II overexpressing (HK(Tg)) mice were fed either a standard diet or high-fat diet and studied at 4 months of age. A carotid artery and jugular veins had catheters chronically implanted for sampling and infusions, respectively, and mice were allowed to recovery for at least 5 days. Mice were fasted for 5 h and underwent a hyperinsulinemic-euglycemic clamp or saline infusion for 120 min. Separate groups of mice were studied during 30-min sedentary or treadmill exercise periods. A bolus of 2-deoxy[(3)H]glucose was administered 25 min before the end of each study for determination of R(g), an index of tissue-specific glucose uptake. Fasting blood glucose was increased in high-fat compared with standard diet-fed WT (194 +/- 4 vs. 171 +/- 4 mg/dl) but not HK(Tg) (179 +/- 5 vs. 171 +/- 3 mg/dl) mice. High-fat feeding created hyperinsulinemia in both WT and HK(Tg) mice (58 +/- 8 and 77 +/- 15 micro U/ml) compared with standard diet-fed mice (21 +/- 2 and 20 +/- 1 micro U/ml). R(g) was not affected by genotype or diet during either saline infusion or sedentary conditions. HK II overexpression augmented insulin-stimulated R(g) in standard diet-fed but not high-fat-fed mice. Exercise-stimulated R(g) was impaired by high-fat feeding in WT mice, but this impairment was largely rectified in HK(Tg) mice. In conclusion, high-fat feeding impairs both insulin- and exercise-stimulated MGU, but only exercise-stimulated MGU was corrected by HK II overexpression.

Modulation of in vivo 3-deoxyglucosone levels

Fructoselysine 3-phosphate is synthesized in vivo by the recently discovered fructoseamine-3-kinase (F3K) from fructoselysine and ATP and decomposes to lysine, Pi and 3-deoxyglucosone (3DG). This pathway appears to dominate 3DG production in vivo, making it possible to modulate 3DG levels by stimulating or inhibiting the reaction. Present inhibitors are non-reacting substrate analogues with relatively high Ki values and can inhibit F3K sufficiently in vivo to reduce 3DG in diabetic rat plasma by approx. 50%. Stimulation of the F3K pathway by feeding glycated casein causes an increase of 10–20-fold in plasma levels of 3DG and 3-fold in kidney tubules. Consequences of this increase were studied in two systems: the Eker rat, a model of susceptible kidney tubules; and birth rates in two rat strains. In both cases substantial pathological effects were observed. In the Eker rats, an approx. 3-fold increase in kidney lesions was observed (P<0.00001). In both Fischer 344 and Sprague–Dawley rats, birth rates were reduced by 56% (P<0.0001) and 12% (P<0.015) respectively. These results suggest that inhibition of F3K is a promising new therapeutic target for diabetic complications, as well as other 3DG-dependent pathologies.

Diabetic ketoacidosis and its treatment increase plasma 3-deoxyglucosone

OBJECTIVES

Highly reactive dicarbonyl compounds are known to be increased by hyperglycemia, ketone bodies and lipid peroxidation. This study was carried out to investigate the effect of diabetic ketoacidosis (DKA) and its treatment on the plasma concentration of 3 deoxyglucosone (3-DG) one of the dicarbonyl compounds.

DESIGN AND METHODS

3-DG was measured in 7 children before, during and following correction of severe DKA. 3-DG was elevated before treatment (610 nmol/L +or/- 70) in comparison to baseline (120 h) (200 nmol/L+/or- 17) (p < 0.05). At 6 to 24 h into treatment 3-DG was further elevated (1080 nmol/L +or/- 80) in comparison to both pretreatment (p < 0.05) and baseline (p < 0.05).

CONCLUSION

3-DG is significantly elevated before the treatment of DKA and increases further during the treatment of DKA. The time course of the increase of 3-DG coincides with the time of progression of subclinical brain edema, which occurs in DKA.

Relation between serum 3-deoxyglucosone and development of diabetic microangiopathy

OBJECTIVE

3-Deoxyglucosone (3-DG), a highly reactive intermediate of the glycation reaction, has been suggested to contribute to the development of diabetes complications. To verify this hypothesis, we assessed the relation between serum 3-DG concentrations and the severity of diabetic microangiopathy in diabetic patients.

RESEARCH DESIGN AND METHODS

We conducted a high-performance liquid chromatography assay to determine the serum 3-DG concentrations of 110 diabetic patients with different degrees of severity of diabetic microangiopathy and 57 age-matched control subjects.

RESULTS

The fasting serum 3-DG level in diabetic patients was significantly (P < 0.001) higher than that in control subjects (353 +/- 110 vs. 199 +/- 53 nmol/l). The 3-DG levels were significantly (P < 0.001) elevated even in the diabetic patients showing normoalbuminuria (n = 62, 322 +/- 79 nmol/l) compared with control subjects. The 3-DG levels were further elevated in the patients with microalbuminuria (n = 30, 383 +/- 146 nmol/l) and overt proteinuria (n = 18, 410 +/- 100 nmol/l) (P = 0.027 and P < 0.001 vs. normoalbuminuria group, respectively). This phenomenon was basically reproduced in a category of retinopathy. Furthermore, the diabetic patients with low nerve conduction velocity showed a tendency to display higher 3-DG levels.

CONCLUSIONS

The present results show that the fasting serum 3-DG level is elevated in diabetic patients and that the patients with relatively higher 3-DG levels were prone to suffer from more severe complications, indicating a possible association of 3-DG with diabetic microangiopathy.

Usefulness of troglitazone administration to obese hyperglycaemic patients with near-normoglycaemia

AIMS

We assessed the effectiveness of 400 mg/day of troglitazone administered to hyperglycaemic patients with near-normoglycaemia who were obese and who had hyperinsulinaemia.

RESULTS

The area under the plasma glucose curve in oral glucose tolerance tests (OGTT) significantly decreased from 39.8 +/- 19.4-20.5 +/- 10.2 mg/dL. h and the area under the insulin-response curve from 31.8 +/- 22.5-12.2 +/- 5.7 microU/ml x h 4 months after the start of treatment. The level of HbA1c significantly improved from 6.6 +/- 0.2 to 6.3 +/- 0.2% (p < 0.05) by 1 month after administration, and that of serum 1,5-anhydroglucitol (1,5-AG) from 12.6 +/- 1.1-18.3 +/- 2.5 micro/ml (p < 0.05). In some cases, recovery of the first-phase insulin secretion was observed.

CONCLUSIONS

These findings suggest that the administration of this insulin sensitizer is useful in the treatment of obese Japanese subjects with borderline or mild diabetics accompanied by hyperinsulinaemia.

A novel NAD-dependent dehydrogenase, highly specific for 1,5-anhydro-D-glucitol, from Trichoderma longibrachiatum strain 11-3

A novel NAD-dependent dehydrogenase highly specific for 1,5-anhydro-D-glucitol (1,5-AG) was found in the cell extract of an imperfect fungus, Trichoderma longibrachiatum strain 11-3. This fungus used 1,5-AG as a sole carbon source for growth and transformed 1,5-AG into glucose. 1,5-AG dehydrogenase (AGH) was purified to homogeneity, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The molecular mass of the purified enzyme was estimated to be 36 and 141 kDa by SDS-PAGE and by gel filtration, respectively, suggesting that the enzyme was homotetrameric. The enzyme was highly specific for 1,5-AG and did not exhibit activity with any sugar or sugar alcohol tested in this study other than 1,5-AG. A linear relationship between the initial rate of the enzyme reaction and the concentration of 1,5-AG at the physiological level was observed. The presence of glucose in abundance did not interfere with the relationship. The optimum temperature for the enzyme reaction was 50 degrees C, and the enzyme was stable at temperatures up to 70 degrees C. These results suggested that AGH is a novel enzyme and is useful for specifically diagnosing diabetes mellitus.

Serum 1,5-anhydroglucitol (GlycoMark ): a short-term glycemic marker

1,5-Anhydroglucitol (1,5-AG), the 1-deoxy form of glucose, has been measured and used clinically in Japan for over a decade to monitor short-term glycemic control. Evaluation of glucose control otherwise requires measuring plasma glucose or glycated proteins whose levels reflect average glucose concentration over the half-life of the protein analyzed. Hemoglobin A1c measurements reflect blood glucose levels over that past 2-3 months, while fructosamine can be used to evaluate glycemic control over 10-14 days. In contrast, 1,5-AG levels in blood respond within 24 h as a result of glucose's competitive inhibition of 1,5-AG reabsorption in the kidney tubule. When glucose levels rise, even transiently, urinary loss of 1,5-AG occurs, and circulating levels fall. Because of changes in renal hemodynamics in normal pregnancies, 1,5-AG appears of limited usefulness in evaluation of gestational diabetes. However, the characteristics of 1,5-AG levels in patients with moderate to near-normal glycemic control suggest that it may be a valuable complement to frequent self-monitoring or continuous monitoring of plasma glucose to confirm stable glycemic control. Measurements performed daily or weekly in a given patient would suggest that overall glycemic control has been stable or improved if 1,5-AG levels are stable or increasing. If 1,5-AG levels fall, greater attention to glucose monitoring and both lifestyle and medical management could be prescribed to correct the glycemic excursions that would underlie such changes. The behavior of this analyte is different from all others used in the management of diabetes, creating potential opportunities for its use in clinical practice.

Clinical application of the serum 1,5-anhydroglucitol assay method using glucose 3-dehydrogenase

We attempted to develop a novel serum 1,5-anhydroglucitol (1,5-AG) assay kit using glucose 3-dehydrogenase (G3DH) from Halomonas sp. alpha-15 strain. The major advantages of this method are that the 1,5-AG detection requires a very small amount of G3DH, and the enzyme catalyzes a simple reaction. The analytical performances were acceptable for clinical use operated with a clinical automatic analyzer. The correlation with a commercial assay kit against sera of healthy volunteers was y=0.975x+0.008, r=0.993, Sylx=1.32 microg/mL. However, sham-negative specimens were observed in the validation of this method using specimens from hospital patients.

Plasma 3-deoxyglucosone elevation in chronic renal failure is associated with increased aldose reductase in erythrocytes

BACKGROUND

Serum concentrations of 3-deoxyglucosone (3DG), a highly reactive dicarbonyl compound, are elevated in uremic patients. Aldose reductase (AR) is an enzyme involved in both the detoxification of 3DG and producing precursors of 3DG.

METHODS

We examined the relationship between plasma 3DG and erythrocyte AR content in uremic patients. Patients were divided into three groups: (1) progressive renal disease without hemodialysis (HD; chronic renal failure [CRF] group), (2) patients without diabetes mellitus (DM) treated with maintenance HD (HD group), and (3) patients with DM treated with maintenance HD (DM-HD group). High-performance liquid chromatography was used to measure 3DG, and erythrocyte AR was measured by means of enzyme-linked immunosorbent assay.

RESULTS

Both 3DG and erythrocyte AR levels were significantly greater in the CRF, HD, and DM-HD groups than in healthy controls. These results did not change after HD sessions in the HD or DM-HD groups. Serum creatinine levels correlated with 3DG and erythrocyte AR levels in the control and CRF groups (3DG: r = 0.67; P < 0.001; erythrocyte AR: r = 0.71; P < 0.001). Both erythrocyte AR and 3DG levels then increased as renal function declined. A positive correlation was seen between 3DG and erythrocyte AR levels in all groups (r = 0.65; P < 0.001), and also between plasma osmolality and erythrocyte AR level (r = 0.46; P < 0.001).

CONCLUSION

Both erythrocyte AR and 3DG levels are increased in uremic patients, and these increases could possibly contribute to the development of uremic symptoms.

Rolipram depresses [(3)H]2-deoxyglucose uptake in mouse brain and heart in vivo

The effects of systemic administration of rolipram, a selective phosphodiesterase type 4 inhibitor, on [(3)H]2-deoxyglucose (DG) uptake in brain and peripheral tissues were examined. Rolipram significantly and dose-dependently decreased [(3)H]DG uptake in brain, heart and skeletal muscle. In contrast, the radioactivity concentrations in the plasma of rolipram-treated mice were significantly higher than those of control mice at all times after injection of the tracer. In the kinetic study, the initial uptake of [(3)H]DG in brain was decreased by rolipram, whereas no significant differences were observed in the uptake in heart and skeletal muscle. However, radioactivity concentrations in the brain, heart and skeletal muscle 30 min after the injection of [(3)H]DG were significantly lowered by rolipram to about 60%, 10% and 10% of control values, respectively. The uptake of [(13)N]ammonia in brain and heart of rolipram-treated mice was slightly decreased, which indicated that rolipram diminished both cerebral and cardiac blood flow. These results indicate that the phosphorylation process via hexokinase rather than the transport of [(3)H]DG might be depressed by rolipram. Together with the previous observations that inhibition of protein kinase A (PKA) markedly enhanced [(14)C]DG uptake in rat brain, these results indicate an important role of the cAMP/PKA systems in the regulation of glucose metabolism in the living brain as well as in peripheral tissues such as the heart and skeletal muscle.

Gas chromatographic-mass spectrometric determination of erythrocyte 3-deoxyglucosone in diabetic patients

To determine if the erythrocyte levels of 3-deoxyglucosone (3-DG) are increased in diabetic patients, and if they correlate with glycemic status, they were measured in diabetic patients without renal disease as well as in healthy subjects. The erythrocyte levels of 3-DG were measured by a selected ion monitoring method of gas chromatography-chemical ionization mass spectrometry using [(13)C(6)]-3-DG as an internal standard. The erythrocyte levels of 3-DG were significantly higher in diabetic patients than in healthy subjects. The erythrocyte concentration of 3-DG was significantly and positively correlated with HbA1c (r=0.84, P<0.001). However, no significant correlation could be found between erythrocyte 3-DG and age, onset age of diabetes, or duration of diabetes in our group of diabetic patients. In diabetes, the production of 3-DG in the erythrocytes is increased via the polyol pathway and/or the Maillard reaction due to hyperglycemia.

1,5-anhydro-D-glucitol: a novel marker of glucose excursions

In recent years a great deal of discussion has focused on postprandial hyperglycaemia as a risk factor for cardiovascular mortality. Routinely used parameters of metabolic control such as fasting plasma glucose (FPG) and HbA1c are not useful for determination of daily glucose excursions. 1,5-Anhydro-D-glucitol (1,5-AG) in human plasma has been proposed for several years as a short-term, retrospective marker of glycaemic control and seems to be the most suitable parameter for monitoring glucose excursions. The plasma level of 1,5-AG reflects acute episodes of hyperglycaemia more sensitively than HbA1c does and is correlated with FPG and postprandial hyperglycaemic peaks. The maximal glycaemic value observed in a patient ultimately determines the plasma 1,5-AG level. 1,5-AG could be helpful in detection of hyperglycaemic excursions, even in those patients with diabetes who self-monitor blood glucose and in those patients who are monitored routinely for FPG and HbA1c. In non-diabetic patients the plasma 1,5-AG level may serve as a screening marker for postprandial hyperglycaemia-associated cardiovascular risk.

Nicotinamide is not a substrate of the facilitative hexose transporter GLUT1

It has been proposed that GLUT1, a membrane protein that transports hexoses and the oxidized form of vitamin C, dehydroascorbic acid, is also a transporter of nicotinamide (Sofue, M., Yoshimura, Y., Nishida, M., and Kawada, J. (1992) Biochem. J. 288, 669-674). To ascertain this, we studied the transport of 2-deoxy-D-glucose, 3-O-methyl-D-glucose, and nicotinamide in human erythrocytes and right-side-out and inside-out erythrocyte membrane vesicles. The transport of nicotinamide was saturable, with a K(M) for influx and efflux of 6.1 and 6.2 mM, respectively. We found that transport of the hexoses was not competed by nicotinamide in both the erythrocytes and the erythrocyte vesicles. Likewise, the transport of nicotinamide was not affected by hexoses or by inhibitors of glucose transport such as cytochalasin B, genistein, and myricetin. On the other hand, nicotinamide blocked the binding of cytochalasin B to human erythrocyte membranes but did so in a noncompetitive manner. Using GLUT1-transfected CHO cells, we demonstrated that increased expression of GLUT1 was paralleled by a corresponding increase in hexose transport but that there were no changes in nicotinamide transport. Moreover, nicotinamide failed to affect the transport of hexoses in both control and GLUT1-transfected CHO cells. Therefore, our results indicates that GLUT1 does not transport nicotinamide, and we propose instead the existence of other systems for the translocation of nicotinamide across cell membranes.

A double-blind trial on the effects of atorvastatin on glycemic control in Japanese diabetic patients with hypercholesterolemia

A double-blind, placebo-controlled, parallel-group study was performed to determine whether atorvastatin, a new HMG-CoA reductase inhibitor, could effectively and safely reduce plasma LDL-cholesterol concentrations in Japanese patients with type-2 diabetes without influencing glycemic control. The subjects were patients with hypercholesterolemia (serum cholesterol concentration > or =5.7 mmol/l (220 mg/dl)) and stable glycemic control. The fasting concentrations of hemoglobin A(1C) (HbA(1C)), fructosamine, and 1,5-anhydroglucitol (1,5-AG) were measured as indices of glycemic control. Plasma lipid concentrations and the safety of the drug were also examined. Forty eligible patients in two groups of 20 each were administered atorvastatin (10 mg/day) or placebo. Neither atorvastatin nor placebo caused a significant change in HbA(1C), fructosamine, or 1,5-AG concentrations. Atorvastatin significantly reduced total cholesterol and LDL-cholesterol concentrations from baseline by 29.7% (p<0.0001) and 41.6% (p<0.0001), respectively. The incidence of clinical adverse events and that of abnormal changes in laboratory test values did not differ between the two groups. In this trial, atorvastatin effectively and safely reduced LDL-cholesterol concentrations in diabetic patients with hypercholesterolemia without influencing glycemic control. These findings are clinically important because there are many diabetic patients with hypercholesterolemia and such patients have a high risk of developing arteriosclerotic disease.

Post-load glucose measurements in oral glucose tolerance tests correlate well with 1,5-anhydroglucitol, an indicator of overall glycaemic state, in subjects with impaired glucose tolerance

Using both cross-sectional and longitudinal methods, we investigated the relationship between post-load serum glucose concentration in a 75 g oral glucose tolerance test (OGTT) and overall glycaemic state in subjects with impaired glucose tolerance (IGT). Glycaemic state was assessed by measuring glycated haemoglobin (HbA1c) and the serum concentration of 1,5-anhydroglucitol (1,5-AG). In the cross-sectional study, the concentration of 1,5-AG, while remaining within a normal range, was reduced to a degree proportional to the post-load glycaemic level. Although the correlation between HbA1c and post-load plasma glucose was relatively weak (r=0.281, P<0.001), a significant inverse correlation (r=-0.824, P<0.0001) was found between 1,5-AG and mean post-load plasma glucose concentration in 211 subjects with IGT. Fasting plasma glucose (r=-0.539, P<0.0001) and 2 h plasma glucose (r=-0.621, P<0.0001) were correlated with 1,5-AG less strongly than was post-load glycaemia. Both 1,5-AG and HbA1c were correlated weakly but significantly with the fasting insulin concentration. In the longitudinal study we measured 1,5-AG and mean post-load plasma glucose with an OGTT once yearly for 10 years in 15 subjects with IGT. Strong inverse correlations were seen between 1,5-AG and mean post-load plasma glucose in each subject (range of r values among subjects of -0.584 to -0.978). These findings suggest a close relationship between post-load plasma glucose concentration measured by OGTT and overall glycaemic state in subjects with IGT.

The predictive value of serum 1,5-anhydro-D-glucitol in pregnancies at increased risk of gestational diabetes mellitus and gestational impaired glucose tolerance

The objective of the study was to determine the efficacy of 1,5-anhydro-D-glucitol (1,5 AG) for the prediction of gestational diabetes and gestational impaired glucose tolerance (GIGT). One hundred and eighty-five pregnant women with epidemiological risk factors of gestational diabetes or GIGT underwent 75 g oral glucose tolerance test and plasma 1,5 AG assay at 26 to 28 weeks of gestation. There was no significant difference in plasma 1,5 AG either before or after an oral glucose load. The area under the receiver operator characteristic curve for 1,5 AG was only 0.485 which implies that 1,5 AG is a poor predictor of GIGT or gestational diabetes.