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.

alpha-Dicarbonyls increase in the postprandial period and reflect the degree of hyperglycemia

OBJECTIVE

Chronic hyperglycemia is known to increase tissue glycation and diabetic complications, but controversy exists regarding the independent role of increased postprandial glucose excursions. To address this question, we have studied the effect of postprandial glycemic excursions (PPGEs) on levels of methylglyoxal (MG) and 3-deoxyglucosone (3-DG), two highly reactive precursors of advanced glycation end products (AGEs).

RESEARCH DESIGN AND METHODS

We performed 4-month crossover studies on 21 subjects with type 1 diabetes and compared the effect of premeal insulin lispro or regular insulin on PPGEs and MG/3-DG excursions. PPGE was determined after standard test meal (STMs) and by frequent postprandial glucose monitoring. HbA1c and postprandial MG and D-lactate were measured by HPLC, whereas 3-DG was determined by gas chromatography/mass spectroscopy.

RESULTS

Treatment with insulin lispro resulted in a highly significant reduction in PPGEs relative to the regular insulin-treated group (P = 0.0005). However, HbA1c levels were similar in the two groups, and no relationship was observed between HbA1c and PPGE (P = 0.93). Significant postprandial increases in MG, 3-DG, and D-lactate occurred after the STM. Excursions of MG and 3-DG were highly correlated with levels of PPGE (R = 0.55, P = 0.0002 and R = 0.61, P = 0.0004; respectively), whereas a significant inverse relationship was seen between PPGE and D-lactate excursions (R = 0.40, P = 0.01). Conversely, no correlation was observed between HbAlc and postprandial MG, 3-DG, or D-lactate levels.

CONCLUSIONS

Increased production of MG and 3-DG occur with greater PPGE, whereas HbA1c does not reflect these differences. Reduced PPGE also leads to increased production of D-lactate, indicating a role for increased detoxification in reducing MG levels. The higher postprandial levels of MG and 3-DG observed with greater PPGE may provide a partial explanation for the adverse effects of glycemic lability and support the value of agents that reduce glucose excursions.

DYN 12, a small molecule inhibitor of the enzyme amadorase, lowers plasma 3-deoxyglucosone levels in diabetic rats

3-Deoxyglucosone (3DG) is a highly reactive alpha-dicarbonyl sugar and potent protein cross-linker that is important in the formation of advanced glycation end products (AGEs), which have been postulated to lead to the development of diabetic complications. (1) Reducing 3DG levels in diabetics is a potentially effective therapy to slow the development of diabetic complications. Standard biochemical methods were used to isolate, identify, and characterize the enzyme responsible for the production of 3DG, in order to develop an effective therapeutic agent against this target. We have purified and characterized Amadorase, a fructosamine-3-kinase, and demonstrated both in vitro and in vivo that it is responsible for the production of 3-deoxyglucosone (3DG). A small molecule inhibitor of Amadorase, DYN 12, significantly lowered plasma levels of 3DG in diabetic (by 46%, p = 0.0116) and normal (by 43%, p = 0.0024) rats. These data are the first indications that it is possible to significantly reduce 3DG production in diabetics and thus possibly reduce the development of diabetic complications.

Insulin tolerance during endotoxic shock in 10-day-old rats

PURPOSE

The purpose was to investigate insulin tolerance during endotoxic shock in 10-day-old rats.

MATERIALS AND METHODS

[(14)C]Deoxy-glucose (2DG) with or without insulin (1 unit/kg) was injected to 10-day-old and 6-week-old rats 3 h after an injection of endotoxin (lipopolysaccharide: LPS). Plasma concentrations of glucose and 2DG were serially measured for 45 min. Gluconeogenesis was measured in hepatocytes isolated from control and endotoxic 10-day-old rats to evaluate effects of insulin on gluconeogenesis.

RESULTS

In endotoxic 10-day-old rats, plasma glucose concentration at 45 min was 48 +/- 3% (P < 0.05) of value at 0 min, and when insulin was injected with 2DG, it was 29 +/- 4% (P < 0.05) after insulin injection. Plasma 2DG disappearance was enhanced by insulin injection in the control (t(1/2) = 17.9 vs 20.5 min, P < 0.05), but not in the endotoxic rats (t(1/2) = 17.9 vs 18.4 min), indicating the presence of insulin tolerance in septic rats. Insulin decreased gluconeogenesis (P < 0.05) in hepatocytes from both control and endotoxic 10-day-old rats. In endotoxic 6-week-old rats, plasma glucose concentration was decreased to 46 +/- 10% at 45 min and further decreased to 38 +/- 4% (P < 0.05) by insulin injection. Plasma 2DG disappearance was enhanced by insulin injection in the control (t(1/2) = 11.8 vs 17.4 min, P < 0.05) and in the septic rats (t(1/2) = 14.8 vs 12.2 min). However, the enhancement of plasma 2DG disappearance by insulin was less (P < 0.05) in the septic rats than in the control, confirming reports of other investigators which showed insulin tolerance in septic shock.

CONCLUSION

Although hepatocytes from endotoxic rats retained insulin sensitivity, insulin tolerance which was evaluated by 2DG disappearance occurred during septic shock in newborn rats.

Central, but not peripheral, glucose-sensing mechanisms mediate glucoprivic suppression of pulsatile luteinizing hormone secretion in the sheep

Changes in glucose availability are proposed to modulate pulsatile GnRH secretion, and at least two anatomical sites, the liver and hindbrain, may serve as glucose sensors. The present study determined the relative importance of these putative glucose-sensing areas in regulating pulsatile LH secretion in the sheep. Our approach was to administer the antimetabolic glucose analog, 2-deoxy-D-glucose (2DG) into either the hepatic portal vein or the fourth ventricle in gonadectomized females in which LH pulse frequency was high. In the first study, a catheter was placed in the ileocolic vein to determine the effects of local injection of 2DG into the hepatic portal system on the release of LH. After monitoring the pattern of LH secretion for 4 h, 2DG (250 mg/kg) was infused (500 microl/min) into the liver for 2 h. For comparison, animals were also given the same dose of 2DG into a jugular vein for 2 h. Administration of 2DG into either the hepatic portal or jugular vein reduced LH pulse frequency to the same extent. Infusion of the lower dose (50 mg/kg) locally into the hepatic portal vein did not affect plasma LH profiles. Collectively, these results are interpreted to indicate that the liver does not contain special glucose-sensing mechanisms for the glucoprivic suppression of LH pulses. In the second study, 2DG (5 mg/kg) was infused (50 l/min) for 30 min into the fourth ventricle or lateral ventricle. During the subsequent 4-h sampling period, pulsatile LH secretion was significantly suppressed, but there was no significant difference in LH pulse frequency between sites of infusion. Peripheral 2DG concentrations were not detectable after either fourth or lateral ventricle infusions, indicating that the 2DG had acted centrally to suppress LH pulses. Plasma cortisol concentrations increased more in animals infused with 2DG into the fourth ventricle than in those infused into the lateral ventricle, suggesting that 2DG infused into lateral ventricle is transported caudally into the fourth ventricle and acts within the area surrounding the fourth ventricle. Overall, these findings suggest that an important glucose-sensing mechanism is located circumventricularly in the fourth ventricle. Moreover, the liver does not appear to play an important role in detecting glucoprivic action of 2DG to suppress pulsatile LH secretion.

The brain response to 2-deoxy glucose is blocked by a glial drug

Two brain regions - the basomedial hypothalamus and area postrema (AP) - react to changes in circulating glucose levels by altering feeding behavior and the secretion of pituitary and non-pituitary hormones. The precise identity of cells responding to glucose in these regions is uncertain. The recent detection of high-capacity glucose transporter proteins in astrocytes in these areas has suggested that astrocytes may play a role in glucose sensing by the brain. To test this hypothesis, rats were injected with either saline or methionine sulfoximine (MS), a compound that produces alterations in carbohydrate and glutamate metabolism in astrocytes. Eighteen hours later, rats were injected with either saline or 2-deoxy glucose (2-DG) and brain sections were stained to demonstrate 2-DG-activated neurons immunoreactive for Fos protein. MS-treated rats showed a 70% reduction in numbers of Fos+ neurons in the AP region (p<0.05). Also, specialized, Gomori+ astrocytes were particularly abundant in both glucose sensitive regions and showed a distribution identical to that reported for high-capacity glucose transporter proteins. These data suggest that specialized astrocytes influence the glucose-sensing function of the brain.

Epalrestat, an aldose reductase ihibitor, reduces the levels of Nepsilon-(carboxymethyl)lysine protein adducts and their precursors in erythrocytes from diabetic patients

OBJECTIVE

To clarify the role of the polyol pathway in the intracellular formation of advanced glycation end products in human tissues, we examined the effects of epalrestat, an aldose reductase inhibitor, on the level of Nepsilon-(carboxymethyl)lysine (CML) along with 3-deoxyglucosone (3-DG) and triosephosphates in erythrocytes from diabetic patients. Plasma thiobarbituric acid-reactive substances (TBARS) were also determined as indicators of oxidative stress.

RESEARCH DESIGN AND METHODS

Blood samples were collected from 12 nondiabetic volunteers, 38 untreated type 2 diabetic patients, and 16 type 2 diabetic patients who had been treated with 150 mg epalrestat/day. Blood samples were also collected from 14 of the untreated type 2 diabetic patients before and after the administration of epalrestat for 2 months. The amount of erythrocyte CML was determined by a competitive enzyme-linked immunosorbent assay, and 3-DG was measured by high-performance liquid chromatography

RESULTS

In diabetic patients not treated with epalrestat, the erythrocyte CML level was significantly elevated above levels seen in nondiabetic individuals (49.9 +/- 5.0 vs. 31.0 +/- 5.2 U/g protein, P < 0.05) and was significantly lower in patients receiving epalrestat (33.1 +/- 3.8 U/g protein, P < 0.05). Similar results were observed with 3-DG. The treatment of patients with epalrestat for 2 months significantly lowered the level of erythrocyte CML (46.2 +/- 5.6 at baseline vs. 34.4 +/- 5.0 U/g protein, P < 0.01) along with erythrocyte 3-DG (P < 0.05), triosephosphates (P < 0.05), fructose (P < 0.05), sorbitol (P < 0.05), and plasma TBARS (P < 0.05) without changes in plasma glucose and HbA(1c) levels. A positive correlation was evident between the erythrocyte CML and sorbitol (r = 0.49, P < 0.01) or fructose (r = 0.40, P < 0.05) levels in diabetic patients.

CONCLUSIONS

The results indicate that epalrestat administration lowers CML and associated variables and that polyol metabolites are correlated with CML in the erythrocytes of diabetic patients. The observed results suggest that aldose reductase activity may play a substantial role in the intracellular formation of CML in the mediation of reactive intermediate metabolites and oxidative stress.

The influence of traditional Chinese herbal drugs on serum 1, 5-anhydroglucitol levels

The serum concentration of 1,5-anhydroglucitol (1,5-AG), a polyol which originates mainly in the diet, is used in Japan as a new marker for glycemia. To evaluate the potential interference of 1, 5-AG measurements by traditional Chinese medicines (Kampo), we examined the 1,5-AG content in 32 types of concentrated dosage forms of Kampo using high performance liquid chromatography (HPLC). The 32 types of Kampo were the most frequently used in Japan, two of which, Ninjin-yoei-to (7030 microg/g dry weight) and Kami-kihi-to (6700 microg/g dry weight), contained large amounts of 1,5-AG. Six others contained small amounts of 1,5-AG. Both Ninjin-yoei-to and Kami-kihi-to contain the same ingredient, Polygalae radix, which is a crude form of polygalitol (1,5-AG). To confirm the effects of these Kampo medicines on the serum levels of 1,5-AG, we administered Ninjin-yoei-to (7.5 g/day) for 8 weeks to 18 patients with Type 2 diabetes mellitus (Type 2 DM). The serum level of 1,5-AG increased from 9.8+/-8.9 to 28.1+/-17.5 microg/ml by week 8. Hemoglobin A1c (HbA1c) had not changed by week 8. Thus, an abnormal serum 1,5-AG level may be present in patients taking Kampo which contains Polygalae radix.

Enzyme electrochemical preparation of a 3-keto derivative of 1,5-anhydro-D-glucitol using glucose-3-dehydrogenase

A novel enzymatic organic synthesis was reported, utilizing glucose-3-dehydrogenase (G3DH) and its regeneration via electrochemical methods. We combined the water-soluble G3DH prepared from a marine bacterium, Halomonas sp. alpha-15, and electron mediator with the electrode system in order to regenerate the enzyme. Using this system, the conversion of 1,5-anhydro-D-glucitol (1,5AG), a diabetes marker in human blood, was investigated. The final yield of the product, 3-keto anhydroglucitol (3-ketoAG), which was identified by 13C nuclear magnetic resonance, was 82% based on the initial amount of 1,5AG. The electrochemical yield of the reaction proceeded almost stoichiometrically. The electrochemical conversion rate of 1,5AG was 1.24 mmol/(L.h), and the electrochemical yield of 1,5AG consumption was 80%, whereas that for 3-ketoAG was 60%.

Nonradioisotope assay of glucose uptake activity in rat skeletal muscle using enzymatic measurement of 2-deoxyglucose 6-phosphate in vitro and in vivo

We investigated a nonradioisotope method for the evaluation of glucose uptake activity using enzymatic measurement of 2-deoxyglucose 6-phosphate (2DG6P) content in isolated rat soleus muscle in vitro and in vivo. The 2DG6P content in isolated rat soleus muscle after incubation with 2-deoxyglucose (2DG) was increased in a dose-dependent manner by insulin (ED(50) = 0.6 mU/ml), the maximum response being about 5 times that of the basal content in vitro. This increment was completely abolished by wortmannin (100 nM), with no effect on basal 2DG6P content. An insulin-mimetic compound, vanadium, also increased 2DG6P content in a dose-dependent manner. In isolated soleus muscle of Zucker fa/fa rats, well known as an insulin-resistant model, insulin did not increase 2DG6P content. The 2DG6P content in rat soleus muscle increased after 2DG (3 mmol/kg) injection in vivo, and conversely, the 2DG concentration in plasma was decreased in a dose-dependent manner by insulin (ED(50) = 0.11 U/kg). The maximum response of the accumulation of 2DG6P in soleus muscle was about 4 times that of the basal content. This method could be useful for evaluating glucose uptake (transport plus phosphorylation) activity in soleus muscle in vitro and in vivo without using radioactive materials.

Pancreatic fate of 6-deoxy-6-[125I]iodo-D-glucose: in vivo experiments

The fate of 6-deoxy-6-[125I]iodo-D-glucose (6-DIG), injected intravenously, was compared in control rats and animals that had received streptozotocin and were then treated with insulin or not. In the control rats, the measurement of plasma radioactivity suggested that, after an initial and rapid (up to min 10) distribution phenomenon (Kvalue: 12.2 x 10(-2) min(-1)), the clearance of the iodinated hexose occurred mainly by glomerular filtration (K value: 0.2 x 10(-2) min(-1)). Three minutes after the injection of 6-DIG, the radioactive content of muscle, liver, and pancreas, relative to the paired value in blood, was lower in untreated diabetic rats than in control animals. In the case of muscle and liver, such a difference was no longer observed when the treatment of the diabetic rats by insulin resulted in restoration of normoglycemia. In the pancreas, however, the radioactive content, whether expressed relative to the paired blood or liver value, remained significantly lower in the insulin-treated diabetic rats than in the control animals. No significant difference between control and diabetic rats, in terms of pancreatic radioactivity, was observed 10 min after the injection of 6-DIG. These findings indicate that advantage can be taken from the vastly different time course for 6-DIG uptake by pancreatic acinar and islet cells, as recently documented in vitro, to label preferentially the endocrine moiety of the pancreatic gland shortly after 6-DIG injection.

Fate of 6-deoxy-6-[123I]iodo-D-glucose in normal and diabetic rats

The D-glucose analog 6-deoxy-6-¿123Iĭodo-D-glucose (6-DIG) was recently proposed as a potential tracer for the in vivo characterization of D-glucose transport in distinct cell types. In this study, the validity of such a proposal was investigated in both control and streptozotocin-induced diabetic rats. 6-DIG was injected intravenously in either control or diabetic rats. The fate of 6-DIG was assessed by scintigraphy of the injected animals, blood and urine sampling, and measurement of tissue radioactivity at the time of sacrifice, 140 min after 6-DIG injection. The half-life for 6-DIG in plasma and its accumulation in kidney and urinary bladder indicated that it was mainly eliminated from the body by glomerular filtration. The urinary elimination of 6-DIG was accelerated, however, in the polyuric diabetic rats. Bile formation also apparently contributed to the clearance of 6-DIG. Its uptake by liver, heart and muscles yielded values lower than blood concentration. The usefulness of 6-DIG as a tracer for D-glucose transport in selected organs in the perspective of clinical application, e.g. by single photon emission computed tomography, requires further investigations.

The coupling of 5-oxo-eicosanoid receptors to heterotrimeric G proteins

5-Oxo-eicosatetraenoic acid (5-oxoETE) stimulated human neutrophil (PMN) and eosinophil chemotaxis, PMN hexose uptake, and PMN membrane GTP/GDP exchange. Pertussis toxin (PT), a blocker of heterotrimeric G proteins (GP), completely inhibited these responses, but proved far less effective on the same responses when elicited by leukotriene B4, C5a, FMLP, platelet-activating factor, IL-8, or RANTES chemotactic factors. 5-OxoETE also specifically bound to the membrane preparations that conducted GTP/GDP exchange. This binding was down-regulated by GTPgammaS, but not ADPgammaS, and displaced by 5-oxoETE analogues, but not by leukotriene B4, lipoxin A4, or lipoxin B4. Finally, PMN expressed PT-sensitive GP alphaiota2 and PT-resistant GP alphaq/11- and alpha13-chains; eosinophils expressed only alphai2 and alphaq/11. We conclude that 5-oxoETE activates granulocytes through a unique receptor that couples preferentially to PT-sensitive GP. The strict dependency of this putative receptor on PT-sensitive GP may underlie the limited actions of 5-oxoETE, compared with other CF, and help clarify the complex relations between receptors, GP, cell signals, and cell responses.

Serum concentration and renal handling of 1,5-anhydro-D-glucitol in patients with chronic renal failure

We measured serum and urinary 1,5-anhydro-D-glucitol (1,5-AG) during a glucose tolerance test (GTT) in patients with chronic renal failure (CRF) and compared the fractional excretion of 1,5-AG (FEAG) with that of diabetes mellitus (DM) patients and healthy controls. The mean serum 1,5-AG in CRF patients [60 +/- 23(SE) mumol/L] was significantly lower than in controls (155 +/- 7 mumol/L) in spite of a normal glycaemia. The levels in the CRF group were similar to those in the DM group. During GTT, the blood glucose profile in the CRF group was not significantly different from that of the control group, and urinary glucose excretion was negligible. However, FEAG was significantly higher in CRF patients than in controls. These data suggest that serum 1,5-AG in patients with CRF decreases due to a decrease in 1,5-AG reabsorption, independently of glucose excretion, and that serum and/or urinary 1,5-AG can be a useful marker for renal tubular dysfunction because the 1,5-AG reabsorption system is more vulnerable than the glucose reabsorption system.

Gas chromatographic-mass spectrometric analysis of erythrocyte 3-deoxyglucosone in hemodialysis patients

The erythrocyte levels of 3-deoxyglucosone (3-DG) were measured by a selected ion monitoring method of gas chromatography-chemical ionization mass spectrometry using [13C6]-3-DG as an internal standard. Because the erythrocyte levels of 3-DG measured after deproteinization using ethanol were 18 times higher than those using ultrafiltration, we used ethanol deproteinization for measurement of total 3-DG in the erythrocytes. The concentration of 3-DG was significantly elevated in hemodialysis (HD) patients compared with healthy subjects. Although HD treatment could remove the erythrocyte 3-DG efficiently, its post-HD levels were still elevated compared with the healthy subjects.

Economic evaluation of alternative indicators for screening for diabetes mellitus

BACKGROUND

the optimal indicator for screening for diabetes mellitus without relying on fasting conditions was clarified.

METHODS

the subjects were 891 men ages 26 through 80 years (48.5 +/- 8.5). The objectives of this study were (1) to elucidate the efficacy of 1,5-anhydroglucitol (1,5-AG), glycosylated hemoglobin, and fructosamine (FRA) as screening tests for non-insulin-dependent diabetes mellitus (NIDDM) or for impaired glucose tolerance (IGT) and (2) to perform an economic evaluation for each indicator. The efficacy of each indicator was evaluated by drawing the receiver operating characteristic curves and calculating the areas under these curves (AUCs). An original model was developed for the pur pose of cost-effectiveness analysis.

RESULTS

each indicator was evaluated as a screening test for NIDDM alone and for both IGT and NIDDM. The AUCs of 1,5-AG and fasting plasma glucose were the largest in the case of the detection of NIDDM alone and the detection of both IGT and NIDDM, respectively. FRA was, however, the most cost-effective in Japan.

CONCLUSION

using equations, we indicated the equi librium points at which the cost-effectiveness ratios of each indicator intersected in order to generalize the results. By calculating the appropriate-actual ratios of costs for each indicator, we could ascertain the optimal indicator for each country.

Plasma 1,5-anhydroglucitol concentrations are influenced by variations in the renal threshold for glucose

AIMS

Measurement of serum 1,5-anhydroglucitol (1,5AG) concentrations has been proposed as an alternative to HbA1c as both a marker of diabetic glycaemic control and as a screening test for diabetes. The sugar competes with glucose for renal tubular reabsorption, so hyperglycaemia leads to reduced serum 1,5AG concentrations through increased urinary loss. This study has sought to establish whether plasma 1,5AG can be influenced by not only hyperglycaemia, but by variations in renal threshold for glucose.

METHODS

Thirty-eight pregnant women (median age 30 years, range 20-43) found to be normoglycaemic after a 75-g carbohydrate load had plasma 1,5AG and urine glucose measured.

RESULTS

Using multivariate analysis, the presence and degree of detectable glycosuria at 2 h post glucose load was strongly predictive of a low plasma 1,5AG concentration (P=0.0012) independently of fasting plasma glucose (P=0.96), 2 h glucose (P=0.029), subject age (P=0.97) and gestation (P=0.36). Thus, when matched for plasma glucose areas under the glucose load curve, 16 glycosuric subjects had significantly lower 1,5AG concentrations compared to 16 nonglycosuric ones (median 1,5AG 46 micromol/l (IQR 30-56) vs. 72 micromol/l (IQR 55-79, P=0.017).

CONCLUSIONS

People with the same glucose tolerance may demonstrate variable plasma 1,5AG concentrations depending on their renal threshold for glucose. This inherent characteristic is likely to limit the usefulness of the test when monitoring or screening for diabetes.

Increase in three alpha,beta-dicarbonyl compound levels in human uremic plasma: specific in vivo determination of intermediates in advanced Maillard reaction

Methylglyoxal (MGO), glypxal (GO) and 3-deoxyglucosone (3-DG) are reactive alpha,beta-dicarbonyl intermediates in advanced Maillard reaction, which form advanced glycation and oxidation end products (AGEs) by reaction with both lysine and arginine residues in protein. We measured these three dicarbonyl compound levels in human plasma to estimate the relationship between accumulation of alpha, beta-dicarbonyl compounds and AGE formation reactions in uremia and diabetes in human plasma by a highly selective and specific assay, electrospray ionization liquid chromatography mass spectrometry (ESI/LC/MS). We show that 3-DG and MGO levels are significantly higher in uremia and diabetes compared with age-matched healthy controls. Only the GO level in uremic plasma is significantly higher compared to diabetes and healthy controls. In both diabetic and uremic patients, these dicarbonyl compounds promote AGE accumulation in vivo, and especially in uremic patients, increased accumulation of GO could result from accelerating oxidative stress.

Metformin reduces systemic methylglyoxal levels in type 2 diabetes

Methylglyoxal (MG) is a reactive alpha-dicarbonyl that is thought to contribute to diabetic complications either as a direct toxin or as a precursor for advanced glycation end products. It is produced primarily from triose phosphates and is detoxified to D-lactate (DL) by the glyoxalase pathway. Because guanidino compounds can block dicarbonyl groups, we have investigated the effects of the diamino biguanide compound metformin and of hyperglycemia on MG and its detoxification products in type 2 diabetes. MG and DL were measured by high-performance liquid chromatography in plasma from 57 subjects with type 2 diabetes. Of these subjects, 27 were treated with diet, sulfonylureas, or insulin (nonmetformin), and 30 were treated with metformin; 28 normal control subjects were also studied. Glycemic control was determined by HbA1c. MG was significantly elevated in diabetic subjects versus the normal control subjects (189.3 +/- 38.7 vs. 123.0 +/- 37 nmol/l, P = 0.0001). MG levels were significantly reduced by high-dosage (1,500-2,500 mg/day) metformin (158.4 +/- 44.2 nmol/l) compared with nonmetformin (189.3 +/- 38.7 nmol/l, P = 0.03) or low-dosage (< or = 1,000 mg/day) metformin (210.98 +/- 51.0 nmol/l, P = 0.001), even though the groups had similar glycemic control. Conversely, DL levels were significantly elevated in both the low- and high-dosage metformin groups relative to the nonmetformin group (13.8 +/- 7.7 and 13.4 +/- 4.6 vs. 10.4 +/- 3.9 micromol/l, P = 0.03 and 0.06, respectively). MG correlated with rising HbA1c levels (R = 0.4, P = 0.03, slope = 13.2) in the nonmetformin subjects but showed no increase with worsening glycemic control in the high-dosage metformin group (R = 0.0004, P = 0.99, slope = 0.02). In conclusion, MG is elevated in diabetes and relates to glycemic control. Metformin reduces MG in a dose-dependent fashion and minimizes the effect of worsening glycemic control on MG levels. To the extent that elevated MG levels lead to their development, metformin treatment may protect against diabetic complications by mechanisms independent of its antihyperglycemic effect.

Limitations to exercise- and maximal insulin-stimulated muscle glucose uptake

The hypothesis of this investigation was that insulin and muscle contraction, by increasing the rate of skeletal muscle glucose transport, would bias control so that glucose delivery to the sarcolemma (and t tubule) and phosphorylation of glucose intracellularly would exert more influence over glucose uptake. Because of the substantial increases in blood flow (and hence glucose delivery) that accompany exercise, we predicted that glucose phosphorylation would become more rate determining during exercise. The transsarcolemmal glucose gradient (TSGG; the glucose concentration difference across the membrane) is inversely related to the degree to which glucose transport determines the rate of glucose uptake. The TSGG was determined by using isotopic methods in conscious rats during euglycemic hyperinsulinemia [Ins; 20 mU/(kg. min); n = 7], during treadmill exercise (Ex, n = 6), and in sedentary, saline-infused rats (Bas, n = 13). Rats received primed, constant intravenous infusions of trace 3-O-[3H]methyl-D-glucose and [U-14C]mannitol. Then 2-deoxy-[3H]glucose was infused for the calculation of a glucose metabolic index (Rg). At the end of experiments, rats were anesthetized, and soleus muscles were excised. Total soleus glucose concentration and the steady-state ratio of intracellular to extracellular 3-O-[3H]methyl-D-glucose (which distributes on the basis of the TSGG) were used to calculate ranges of possible glucose concentrations ([G]) at the inner and outer sarcolemmal surfaces ([G]im and [G]om, respectively). Soleus Rg was increased in Ins and further increased in Ex. In Ins, total soleus glucose, [G]om, and the TSGG were decreased compared with Bas, while [G]im remained near 0. In Ex, total soleus glucose and [G]im were increased compared with Bas, and there was not a decrease in [G]om as was observed in Ins. In addition, accumulation of intracellular free 2-deoxy-[3H]glucose occurred in soleus in both Ex and Ins. Taken together, these data indicate that, in Ex, glucose phosphorylation becomes an important limitation to soleus glucose uptake. In Ins, both glucose delivery and glucose phosphorylation influence the rate of soleus glucose uptake more than under basal conditions.

Accumulation of carbonyls accelerates the formation of pentosidine, an advanced glycation end product: carbonyl stress in uremia

Advanced glycation end product (AGE) formation is related to hyperglycemia in diabetes but not in uremia, because plasma AGE levels do not differ between diabetic and nondiabetic hemodialysis patients. The mechanism of this phenomenon remains elusive. Previously, it was suggested that elevation of AGE levels in uremia might result from the accumulation of unknown AGE precursors. The present study evaluates the in vitro generation of pentosidine, a well identified AGE structure. Plasma samples from healthy subjects and nondiabetic hemodialysis patients were incubated under air for several weeks. Pentosidine levels were determined at intervals by HPLC assay. Pentosidine rose to a much larger extent in uremic than in control plasma. Pentosidine yield, i.e., the change in pentosidine level between 0 and 4 wk divided by 28 d, averaged 0.172 nmol/ml per d in uremic versus 0.072 nmol/ml per d in control plasma (P < 0.01). The difference in pentosidine yield between uremic and control plasma was maintained in samples ultrafiltrated through a filter with a 5000-Da cutoff value and fortified with human serum albumin (0.099 versus 0.064 nmol/ml per d; P < 0.05). Pentosidine yield was higher in pre- than in postdialysis plasma samples (0.223 versus 0.153 nmol/ml per d; P < 0.05). These results suggest that a large fraction of the pentosidine precursors accumulated in uremic plasma have a lower than 5000 Da molecular weight. Addition of aminoguanidine and OPB-9195, which inhibit the Maillard reaction, lowered pentosidine yield in both uremic and control plasma. When ultrafiltrated plasma was exposed to 2,4-dinitrophenylhydrazine, the yield of hydrazones, formed by interaction with carbonyl groups, was markedly higher in uremic than in control plasma. These observations strongly suggest that the pentosidine precursors accumulated in uremic plasma are carbonyl compounds. These precursors are unrelated to glucose or ascorbic acid, whose concentration is either normal or lowered in uremic plasma. They are also unrelated to 3-deoxyglucosone, a glucose-derived dicarbonyl compound whose level is raised in uremic plasma: Its addition to normal plasma fails to increase pentosidine yield. This study reports an elevated level of reactive carbonyl compounds ("carbonyl stress") in uremic plasma. Most have a lower than 5000 Da molecular weight and are thus partly removed by hemodialysis. Their effect on pentosidine generation can be inhibited by aminoguanidine or OPB-9195. Carbonyl stress might contribute to AGE modification of proteins and thus to clinically relevant complications of uremia.

Diverse effects of mild and potent goitrogens on blood-brain barrier nutrient transport

Populations living in goitre endemic areas consume foods rich in a variety of goitrogens of different potencies and some are severely hypothyroid. Recently we observed in Wistar/NIN rats that chronic feeding of KSCN to dams produced only a moderate hypothyroidism and decreased the transport of 2-deoxy-D-glucose (2-DG) across the blood-brain barrier (BBB) in the offspring. The present studies were conducted to assess whether severe hypothyroidism would have greater effect on BBB nutrient transport. It has now been observed that weaning the pups of KSCN fed dams on to KSCN diet for four weeks had no further effect either on their thyroid status or the BBB 2-DG transport. However, feeding KSCN to rats through two generations produced somewhat severe hypothyroidism in F2 pups than that in F1 pups. Interestingly, unlike in F1 pups, the BBB transport of all the three nutrients tested (2-DG, Leu and Tyr) was significantly decreased in F2 pups, albeit to a small extent (10-15%). On the other hand the potent goitrogen: methyl mercaptoimidazole (MMI) even on short term feeding to pregnant dams produced very severe hypothyroidism in the offspring [Serum T4:0.55+/-0.09 microg/dl vs 4.96+/-0.85 in controls]. Surprisingly, the BBB transport of 2-DG, Leu, Tyr and also sucrose, the background marker, was significantly increased in these pups (20-30%). The diverse effects of goitrogen-induced moderate and severe hypothyroidism observed here on the BBB nutrient transport probably suggest different mechanisms for iodine deficiency disorders of different aetiologies and hence the need for discrete approaches for their management.

Insulin-like growth factors - insulin-like growth factor binding protein axis and diabetic control in insulin-dependent diabetes mellitus

There is some evidence that insulin-like growth factors (IGFs) and/or IGF binding proteins (IGFBPs) (IGF-IGFBP axis) may be involved in glucose metabolism. The purpose of this study was to investigate the relationship between the IGF-IGFBP axis and diabetic control in subjects with insulin-dependent diabetes mellitus (IDDM). Thirty-nine subjects with IDDM without major complications (age: 5.8-30.3 years, 13 males and 26 females) participated in this study. In all subjects, the free form of IGF-I (free IGF-I), the total IGF-I (total IGF-I: free plus complexed form of IGF-I) and IGFBP-3 in serum or plasma were measured. The Z-scores of free IGF-I, total IGF-I, and IGFBP-3 were calculated. In 18 young adults with IDDM (age 18.0-30.3 years, 5 males and 13 females), IGFBP-1 in serum was also measured. In all subjects, the diabetic control parameters such as blood glucose (BS) (momentary control), 1,5-anhydro-D-glucitol (1,5 AG) (Ultrashort-term), fructosamine (short term), and glycosylated hemoglobin (HbA1) (long-term) were measured. None of the Z scores for free IGF-I, total IGF-I or IGFBP-3 had a significant correlation with BS. In young adults, IGFBP-I was correlated with BS (r=0.57, P<0.005). None of the Z scores for free IGF-I, total IGF-I or IGFBP-3 had a significant correlation with 1,5 AG, fructosamine or HbA1. In young adults, IGFBP-1 did not correlate with 1,5 AG, fructosamine or HbA1. These data suggested that the IGF-IGFBP axis did not reflect diabetic control in subjects with IDDM under treatment.

Serum 1,5-anhydro-D-glucitol levels in liver cirrhosis

We studied the serum 1,5-anhydro-D-glucitol (AG) levels, a marker of glycemic control, in liver cirrhotic patients who had no evidence of glycosuria in 24-h urine samples in order to clarify the effects of impaired liver function on serum AG metabolism. We showed first that serum AG concentrations were significantly lower in cirrhotic patients than in age- and sex-matched healthy controls (17.6+/-1.6 vs 26.3+/-1.7 microg/ml, P<0.05). Moreover, serum AG levels were found to be positively correlated with both serum cholinesterase and albumin levels. The observations indicate that serum AG levels were decreased in liver cirrhosis, especially in cases of severely reduced hepatic functions, suggesting the possibility of altered AG synthesis in liver cirrhosis.