Clinical usefulness of serum 1,5-anhydroglucitol in monitoring glycaemic control

Racial and ethnic differences in mean plasma glucose, hemoglobin A1c, and 1,5-anhydroglucitol in over 2000 patients with type 2 diabetes

CONTENT

Recent studies have reported hemoglobin A(1c) (A1c) differences across racial/ethnic groups. Our diverse population allows for further investigation of potential differences in measurements of glycemia.

OBJECTIVES

Our objectives were to describe and explore baseline racial/ethnic differences in self-monitored plasma glucose profiles, A1c, and 1,5-anhydroglucitol (1,5-AG) in patients with type 2 diabetes enrolled in the Assessing DURAbility of Basal vs. Lispro Mix 75/25 Insulin Efficacy trial.

DESIGN, SETTING, PATIENTS

The trial enrolled 2094 patients with type 2 diabetes, ages 30-80 yr, from 11 countries.

MAIN OUTCOME MEASURES

Estimated mean plasma glucose (MPG), A1c, and 1,5-AG were compared among racial/ethnic groups before and after adjusting for factors affecting glycemia: age, sex, duration of diabetes, body mass index, and MPG.

RESULTS

Baseline estimated MPG +/- sd was 220.0 +/- 82.0 mg/dl, mean A1c was 9.0 +/- 1.3%, and 1,5-AG was 5.0 +/- 4.1microg/ml. Estimated MPG did not differ between Caucasian and non-Caucasian groups. A1c was higher in Hispanics (9.4 +/- 1.4%; P < 0.001), Asians (9.2 +/- 1.4%; P < 0.01), and patients of other racial/ethnic groups (9.7 +/- 1.5%; P < 0.001) compared with Caucasians (8.9 +/- 1.2%). Paradoxically, 1,5-AG was higher for Asian (5.7 +/- 4.6 microg/ml) and African patients (6.2 +/- 5.4 microg/ml) vs. Caucasians (4.9 +/- 3.9 microg/ml) (P < 0.01). After adjusting for factors affecting glycemia, A1c was higher (all P <or= 0.002) in Hispanics, Asians, Africans, and patients of other racial/ethnic groups, and 1,5-AG was higher in Asian and African patients (P < 0.001) vs. Caucasians.

CONCLUSIONS

There were differences in A1c and 1,5-AG, but not MPG, among racial/ethnic groups. Comparisons of glycemia across racial/ethnic groups using these parameters may be problematic due to inherent biological variability and methodological issues.

Dominant-negative mutant hepatocyte nuclear factor 1alpha induces diabetes in transgenic-cloned pigs

Pigs have been recognized as an excellent biomedical model for investigating a variety of human health issues. We developed genetically modified pigs that exhibit the apparent symptoms of diabetes. Transgenic cloned pigs carrying a mutant human hepatocyte nuclear factor 1alpha gene, which is known to cause the type 3 form of maturity-onset diabetes of the young, were produced using a combined technology of intracytoplasmic sperm injection-mediated gene transfer and somatic cell nuclear transfer. Although most of the 22 cloned offspring obtained died before weaning, four pigs that lived for 20-196 days were diagnosed as diabetes mellitus with nonfasting blood glucose levels greater than 200 mg/dl. Oral glucose tolerance test on a cloned pig also revealed a significant increase of blood glucose level after glucose loading. Histochemical analysis of pancreas tissue from the cloned pigs showed small and irregularly formed Langerhans Islets, in which poor insulin secretion was detected.

1,5-Anhydroglucitol reflects postprandial hyperglycemia and a decreased insulinogenic index, even in subjects with prediabetes and well-controlled type 2 diabetes

To examine the serum 1,5-anhydroglucitol (AG) levels as a surrogate measure of postprandial hyperglycemia (PPH) and insulin secretion in a wide range of hyperglycemia, we compared the relationship between the glycemic index during a 75g oral glucose tolerance test (OGTT) and the insulinogenic index and 1,5-AG according the overall glycemic state. Fasting serum 1,5-AG levels were lower in the type 2 diabetic group (18.0+/-7.0microg/mL) than in the normal glucose tolerance (NGT, 25.4+/-4.0microg/mL), impaired fasting glucose (IFG, 24.6+/-6.2microg/mL), and impaired glucose tolerance (IGT, 22.1+/-6.2microg/mL) groups and were clearly correlated with glycemic values from the OGTT. 120-min post-challenge plasma glucose (PPG(120)) emerged as an independent predictor for 1,5-AG levels after multiple linear regression analysis (beta=-0.554, P<0.001). Additionally, 1,5-AG levels were significantly correlated with PPG(120) in each quartile of A1C, and the coefficients increased with higher A1C quartiles. Subjects with low 1,5-AG levels had both increased insulin resistance and decreased insulin secretion. Decreased 1,5-AG levels are closely correlated with PPH and decreased insulin secretion capacity across a wide range of glycemia, even in relatively well-controlled diabetes.

1,5-anhydroglucitol monitoring in diabetes: a mass balance perspective

1,5-anhydroglucitol (AG) is a nonmetabolizable glucose analogue found in plasma due to ingestion. The normal steady-state concentration can be dramatically decreased by inhibition of tubular reabsorption during periods of hyperglycemia. For this reason, monitoring of AG has been plausibly advocated for detection of periodic glucosuric hyperglycemia. In this review, we examine the influence of variation in factors affecting both steady-state and transient changes in plasma AG. Among normals, the lower and upper limits of the plasma AG reference range vary by a factor of 5. Using a simplified mass balance model (a single compartment model with 3-6x larger-than-plasma volume of distribution), reasonable inter-individual variations of ingestion rate, glomerular filtration rate and fractional post-filtration reabsorption are each able to account for the wide range of normal, steady-state AG concentrations. In monitoring of changes in AG, inter-individual variations in the threshold for glucose excretion, volume of distribution and glomerular filtration rate are all likely to significantly affect correspondence of integral changes in AG to integral glucosuria/hyperglycemia. This combination of variables, affecting both steady-state and transient changes, is significantly confounding with respect to interpretation of serial plasma AG concentrations. Resolution of information content of AG monitoring is thus largely that of crossing simple characterization of deltas [+,0,-] for changes in AG concentration against the information content of hemoglobin A1c monitoring. Despite this limitation, AG monitoring can in principle provide information about glycemic control in the short term that is not apparent through monitoring of hemoglobin A1c alone. However, whether AG monitoring can lead to improved outcomes in diabetes management remains to be established.

Clinical application of 1,5-anhydroglucitol measurements in patients with hepatocyte nuclear factor-1alpha maturity-onset diabetes of the young

OBJECTIVE

1,5-anhydroglucitol (1,5-AG) is a short-term marker of metabolic control in diabetes. Its renal loss is stimulated in hyperglycemic conditions by glycosuria, which results in a lowered plasma concentration. As a low renal threshold for glucose has been described in hepatocyte nuclear factor-1alpha (HNF-1alpha) maturity-onset diabetes of the young (MODY), the 1,5-AG level may be altered in these patients. The purpose of this study was to assess the 1,5-AG levels in patients with HNF-1alpha MODY and in type 2 diabetic subjects with a similar degree of metabolic control. In addition, we aimed to evaluate this particle as a biomarker for HNF-1alpha MODY.

RESEARCH DESIGN AND METHODS

We included 33 diabetic patients from the Polish Nationwide Registry of MODY. In addition, we examined 43 type 2 diabetic patients and 47 nondiabetic control subjects. The 1,5-AG concentration was measured with an enzymatic assay (GlycoMark). Receiver operating characteristic (ROC) curve analysis was used to evaluate 1,5-AG as a screening marker for HNF-1alpha MODY.

RESULTS

The mean 1,5-AG plasma concentration in diabetic HNF-1alpha mutation carriers was 5.9 microg/ml, and it was lower than that in type 2 diabetic patients (11.0 microg/ml, P = 0.003) and in nondiabetic control subjects (23.9 microg/ml, P < 0.00005). The ROC curve analysis revealed 85.7% sensitivity and 80.0% specificity of 1,5-AG in screening for HNF-1alpha MODY at the criterion of <6.5 microg/ml in patients with an A1C level between 6.5 and 9.0%.

CONCLUSIONS

1,5-AG may be a useful biomarker for differential diagnosis of patients with HNF-1alpha MODY with a specific range of A1C, although this requires further investigation. However, the clinical use of this particle in diabetic HNF-1alpha mutation carriers for metabolic control has substantial limitations.

Guideline for management of postmeal glucose

An estimated 246 million people worldwide have diabetes. Diabetes is a leading cause of death in most developed countries, and is reaching epidemic proportions in many developing and newly industrialized nations. Poorly controlled diabetes is associated with the development of renal failure, vision loss, macrovascular diseases and amputations. Large controlled clinical trials have demonstrated that intensive treatment of diabetes can significantly decrease the development and/or progression of microvascular complications of diabetes. There appears to be no glycaemic threshold for reduction of diabetes complications; the lower the glycated haemoglobin (HbA1c), the lower the risk. The progressive relationship between plasma glucose levels and cardiovascular risk extends well below the diabetic threshold. Until recently, the predominant focus of therapy has been on lowering HbA1c levels, with a strong emphasis on fasting plasma glucose. Although control of fasting hyperglycaemia is necessary, it is usually insufficient to obtain optimal glycaemic control. A growing body of evidence suggests that reducing postmeal plasma glucose excursions is as important, or perhaps more important for achieving HbA1c goals. This guideline reviews the evidence on the harmful effects of elevated postmeal glucose and makes recommendations on its treatment, assessment and targets.

A novel fully enzymatic method for determining glucose and 1,5-anhydro-D-glucitol in serum of one cuvette

The aim of the study was to set up a novel fully enzymatic method for screening glucose and 1,5-anhydro-D-glucitol (1,5-AG) in one cuvette. We have determined glucose and 1,5-AG, based on glucokinase (GK) converting glucose to G6P, a compound that can be catalyzed ultimately into 6-PGA by G-6PD and its coenzyme NADP(+), and then calculated glucose concentration according to absorbance variety. Furthermore, pyranose oxidase was used to oxidize 1,5-AG with the formation of 1, 5-anhydro-fructose and H(2)O(2). Measurement was done according to Trinder's reaction principle. The mean within-run and day-to-day precision (CV) of this method for glucose was 0.88% and 1.4%, and also that for 1,5-AG was 1.05% and 1.94%, respectively. The mean recovery rate of two targets was 100.2% and 101.6%, respectively. The correlation (R(2)) between the results of 1,5-AG obtained with our proposed method (y) and those obtained with LanaAG method (x) was 0.999 (y=1.002x-0.675 micromol/l; n=86), and the correlation (R(2)) of glucose between the results obtained with our GK method (y) and those obtained with recommendatory hexokinase method (x) was 0.9999 (y=1.0043x+0.1229 mmol/l; n=86). The reference range (95%) of serological glucose and 1,5-AG was 3.7 to 5.7 mmol/l (4.70+/-0.51 mmol/l) and 83.1 to 240.7 micromol/l (161.9+/-40.2 micromol/l), respectively; and there was no difference with age and sex (P>0.05). This newly developed method was dependable and steady-going, with analysis automatization, and allows quicker and easier measurement of serum glucose and 1,5-AG in one identical reaction cuvette in-phase than previously described methods.

1,5-anhydroglucitol (GlycoMark) as a marker of short-term glycemic control and glycemic excursions

1,5-anhydroglucitol (1,5-AG) is a validated marker of short-term glycemic control. It is a metabolically inert polyol that competes with glucose for reabsorption in the kidneys. Otherwise stable levels of 1,5-AG are rapidly depleted as blood glucose levels exceed the renal threshold for glucosuria. 1,5-AG more accurately predicts rapid changes in glycemia than hemoglobin A1C (A1C) or fructosamine. It is also more tightly associated with glucose fluctuations and postprandial glucose. Thus, 1,5-AG may offer complementary information to A1C. This review will summarize the limitations of current methods of assessing glycemic control, assess the data to support 1,5-AG as a glycemic marker and highlight the scenarios by which 1,5-AG may fill the gap in assessing glycemic control.

Serum 1,5-anhydroglucitol (Glycomark) levels in children with and without type 1 diabetes mellitus

Postprandial hyperglycemia associated with diabetes is a risk factor for cardiovascular disease. Currently, glycated hemoglobin A(1c) (HgbA(1c)) and glycated protein fructosamine are not sensitive markers for acute and short-term hyperglycemia. 1,5-Anhydroglucitol (1,5-AG) (Glycomark; Tomen America, New York, NY, USA) is reported in adults with type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) as a marker for postmeal hyperglycemia. However, the reference ranges for 1,5-AG in normal children and children with T1DM are not known. We studied 1,5-AG levels in 10 control children (6 males and 4 females) and 10 children with T1DM (7 males and 3 females). The levels of 1,5-AG in the normal controls were higher than those in children with T1DM (24.60 +/- 3.99 microg/mL vs. 4.75 +/- 2.95 microg/mL; p < 0.0001). There were no gender differences noted. The 1,5-AG levels were negatively correlated with HgbA(1c) (r =-0.9366; p < 0.0001) and the peak postmeal plasma glucose concentrations (Pearson r =-7230; p = 0.0003). Our findings suggest that despite good glycemic control, postprandial glucose concentrations are elevated and that 1,5-AG showed a difference between controls and children with T1DM. The data are comparable with previous studies in normal adults and in those with T1DM and T2DM. They support the use of 1,5-AG concentrations, together with HgbA(1c), to evaluate therapy, especially to target postprandial hyperglycemia.

1,5-anhydroglucitol and postprandial hyperglycemia as measured by continuous glucose monitoring system in moderately controlled patients with diabetes

OBJECTIVE

Postprandial hyperglycemia is often inadequately assessed in diabetes management. Serum 1,5-anhydroglucitol (1,5-AG) drops as serum glucose rises above the renal threshold for glucose and has been proposed as a marker for postprandial hyperglycemia. The objective of this study is to demonstrate the relationship between 1,5-AG and postprandial hyperglycemia, as assessed by the continuous glucose monitoring system (CGMS) in suboptimally controlled patients with diabetes.

RESEARCH DESIGN AND METHODS

Patients with type 1 or type 2 diabetes and an HbA(1c) (A1C) between 6.5 and 8% with stable glycemic control were recruited from two sites. A CGMS monitor was worn for two consecutive 72-h periods. Mean glucose, mean postmeal maximum glucose (MPMG), and area under the curve for glucose above 180 mg/dl (AUC-180), were compared with 1,5-AG, fructosamine (FA), and A1C at baseline, day 4, and day 7.

RESULTS

1,5-AG varied considerably between patients (6.5 +/- 3.2 mug/ml [means +/- SD]) despite similar A1C (7.3 +/- 0.5%). Mean 1,5-AG (r = -0.45, P = 0.006) correlated with AUC-180 more robustly than A1C (r = 0.33, P = 0.057) or FA (r = 0.38, P = 0.88). MPMG correlated more strongly with 1,5-AG (r = -0.54, P = 0.004) than with A1C (r = 0.40, P = 0.03) or FA (r = 0.32, P = 0.07).

CONCLUSIONS

1,5-AG reflects glycemic excursions, often in the postprandial state, more robustly than A1C or FA. 1,5-AG may be useful as a complementary marker to A1C to assess glycemic control in moderately controlled patients with diabetes.

Evaluation of an assay for serum 1,5-anhydroglucitol (GlycoMark) and determination of reference intervals on the Hitachi 917 analyzer

BACKGROUND

1,5-Anhydroglucitol (1,5-AG) is a glucose analogue, which is decreased in hyperglycemic individuals. We report the technical performance of an assay (GlycoMark) on a chemistry analyzer, evaluation of analyte stability and determination of reference intervals for 1,5-AG in a non-diabetic US population.

METHODS

NCCLS protocols were followed to evaluate the reagent on a Hitachi 917 chemistry analyzer.

RESULTS

Intra- and interassay imprecision ranged from 1.3% to 3.8% and 0.79% to 3.7%, respectively. The assay was linear to 110 microg/ml. Interference from triglyceride, hemoglobin and bilirubin was <10% to concentrations of 12.6 mmol/l, 12.1 and 911.4 micromol/l, respectively. Correlation coefficients between lot numbers on the Hitachi 917 and between analyses on the Hitachi 917 and the Hitachi 7170 analyzers were >0.99. The lowest limit of detection was 0.49 microg/ml (mean+/-2 S.D.). 1,5-AG was stable at 4 degrees C for 7 days, at 22 degrees C for 5 days, at -80 degrees C for 14 days and for three freeze-thaw cycles at -80 degrees C. The US reference intervals (nonparametric 2.5th-97.5th percentiles) were 10.2-33.8 microg/ml (males) and 5.9-31.8 microg/ml (females).

CONCLUSIONS

The performance of the GlycoMark assay for the measurement of 1,5-AG was acceptable on the Hitachi 917 analyzer.

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.

1,5-Anhydroglucitol stimulates insulin release in insulinoma cell lines

Concentrations of 1,5-anhydroglucitol (1,5-AG), which is a major circulating polyol, decrease in patients with diabetes mellitus. In both insulinoma-derived RINr and MIN6 cells, 1,5-AG stimulated insulin release within the range of 0.03-0.61 mM in a dose-dependent manner. Insulin release was maximally stimulated by 1,5-AG to levels that reached 25% and 100% greater than that of control (1,5-AG-free group) in RINr and MIN6 cells, respectively. A physiological concentration of 1,5-AG stimulated insulin release after a 5-min incubation and this action was maintained for 60 min. In addition, at approximately 1/200 the concentration of glucose, 1,5-AG had additive action with 20 mM glucose. The action of 1,5-AG on insulin secretion with other types of saccharides and polyol was similarly additive. Mannnoheptulose and diazoxide suppressed the stimulative action of 1,5-AG on insulin release. The secretagogue action of 1,5-AG seemed to be independent on an increase in the intracellular content of cAMP and ATP. These results suggest that 1,5-AG can stimulate insulin secretion through a mechanism that completely differs from that of glucose.

Effects of an off-site walking program on energy expenditure, serum lipids, and glucose metabolism in middle-aged women

The present study aims to identify the effects of systematic walking on exercise energy expenditure (EEE) and blood profiles in middle-aged women. Fifty-two female nurse managers, aged 32 to 57 years (42.0 +/- 6.2), were randomly assigned to an intervention group (IG) and a control group (CG) for a 12-week study of the walking program. EEE was measured using a microelectronic device. Blood profiles were assessed before and after the walking program. The mean EEE (kcal/kg/d) in the IG and CG was 4.73 +/- 1.02 and 3.88 +/- 0.81 (P = 0.01), indicating an increase of 1.17 +/- 0.98 and 0.46 +/- 0.68 from baseline (P = 0.01), respectively. The mean change in high-density lipoprotein cholesterol in the IG and CG was 1.8 +/- 8.3 mg/dL and -2.9 +/- 7.0 mg/dL (P = 0.051); that in insulin was -4.5 +/- 7.5 microU/dL and -0.6 +/- 4.3 microU/dL (P = 0.046), respectively. These results show that systematic walking increases EEE and improves blood profiles.

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.

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.

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.

Transport of 1,5-anhydro-D-glucitol into insulinoma cells by a glucose-sensitive transport system

The uptake of 1,5-anhydro-D-glucitol (1,5-AG) occurs by passive mechanisms in cells or tissues that have passive glucose transporters. It is known that serum 1,5-AG concentrations are reduced in patients with diabetes mellitus. To elucidate the metabolism of this substance and its physiological role in pancreatic beta-cells, we assayed 1,5-AG transport in the insulinoma-derived cell lines, RINr and MIN6. Both cell lines showed an insulin-insensitive, concentration-dependent uptake of 1,5-AG with a saturation time of approximately 120 min, and most of the 1,5-AG in the cytoplasm was in the free form. A biphasic saturation curve was obtained using a wide range of 1,5-AG concentrations, suggesting that accumulation was mediated by a high affinity and a low affinity transporter. The high affinity transporter had a K(m) of 10.4 in RINr cells and 13.0 mM in MIN6 cells, and the low affinity transporter had a K(m)100 times, being much higher than the physiological concentrations of 1,5-AG. These results indicate that the 1,5-AG carrier system in insulinoma cells is distinct from that in either the somatic cells or renal tubular cells. These findings also suggest that a unique 1,5-AG transport system is present in pancreatic beta-cells.

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.

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.

Acute glucosuria after continuous glucocorticoid loading in the rat in vivo

We investigated the effects of the continuous infusion of various steroids in rats on renal tubular reabsorption of glucose in vivo to elucidate the pathogenesis of steroid-induced glucosuria. Urinary glucose excretion increased 60 min after administration of dexamethasone (2.38 mM). By 120 min, urinary excretion of glucose was three times higher in the dexamethasone group than in the control group (24.1 +/- 4.6 versus 72.4 +/- 16.7 micromol); the plasma level of glucose did not increase. Dexamethasone had no effect on the resorption of 1,5-anhydro-D-glucitol, which is a glucose-resembling polyol that is actively absorbed by the renal tubules as glucose. Neither estradiol nor progesterone increased urinary excretion of glucose. These findings suggest that continuous administration of a high-dose glucocorticoid selectively influences the glucose reabsorption system in the kidney.