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

Diabetes mellitus in chronic kidney disease: Biomarkers beyond HbA1c to estimate glycemic control and diabetes-dependent morbidity and mortality

Diabetes mellitus (DM) is the leading cause of chronic kidney disease (CKD). Optimal glycemic control contributes to improved outcomes in patients with DM, particularly for microvascular damage, but blood glucose levels are too variable to provide an accurate assessment and instead markers averaging long-term glycemic load are used. The most established glycemic biomarker of long-term glycemic control is HbA1c. Nevertheless, HbA1c has pitfalls that limit its accuracy to estimate glycemic control, including the presence of altered red blood cell survival, hemoglobin glycation and suboptimal performance of HbA1c assays. Alternative methods to evaluate glycemic control in patients with DM include glycated albumin, fructosamine, 1-5 anhydroglucitol, continuous glucose measurement, self-monitoring of blood glucose and random blood glucose concentration measurements. Accordingly, our aim was to review the advantages and pitfalls of these methods in the context of CKD.

Serum Metabolomic Alterations Associated with Proteinuria in CKD

BACKGROUND AND OBJECTIVES

Data are scarce on blood metabolite associations with proteinuria, a strong risk factor for adverse kidney outcomes. We sought to investigate associations of proteinuria with serum metabolites identified using untargeted profiling in populations with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using stored serum samples from the African American Study of Kidney Disease and Hypertension (AASK; n=962) and the Modification of Diet in Renal Disease (MDRD) study (n=620), two rigorously conducted clinical trials with per-protocol measures of 24-hour proteinuria and GFR, we evaluated cross-sectional associations between urine protein-to-creatinine ratio and 637 known, nondrug metabolites, adjusting for key clinical covariables. Metabolites significantly associated with proteinuria were tested for associations with CKD progression.

RESULTS

In the AASK and the MDRD study, respectively, the median urine protein-to-creatinine ratio was 80 (interquartile range [IQR], 28-359) and 188 (IQR, 54-894) mg/g, mean age was 56 and 52 years, 39% and 38% were women, 100% and 7% were black, and median measured GFR was 48 (IQR, 35-57) and 28 (IQR, 18-39) ml/min per 1.73 m2. Linear regression identified 66 serum metabolites associated with proteinuria in one or both studies after Bonferroni correction (P<7.8×10-5), 58 of which were statistically significant in a meta-analysis (P<7.8×10-4). The metabolites with the lowest P values (P<10-27) were 4-hydroxychlorthalonil and 1,5-anhydroglucitol; all six quantified metabolites in the phosphatidylethanolamine pathway were also significant. Of the 58 metabolites associated with proteinuria, four were associated with ESKD in both the AASK and the MDRD study.

CONCLUSIONS

We identified 58 serum metabolites with cross-sectional associations with proteinuria, some of which were also associated with CKD progression.

PODCAST

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Beyond self-monitored plasma glucose and HbA1c: the role of non-traditional glycaemic markers in gestational diabetes mellitus

Strict glycaemic management is the cornerstone of metabolic control in gestational diabetes mellitus (GDM). Current monitoring standards involve self-monitoring plasma glucose (SMBG) and haemoglobin A1c (HbA1c). However, both have important limitations. SMBG only reflects instantaneous blood glucose and the inconvenience of self-collecting blood frequently results in poor compliance. HbA1c provides information on blood glucose levels from the previous 2 to 3 months and it is influenced by iron-deficient states, common during pregnancy. There is an urgent need for new shorter-term glycaemic markers, as glycated albumin, fructosamine or 1,5-anhydroglucitol. Glycated albumin seems especially interesting as it provides information on blood glucose levels over the foregoing 2-3 weeks and it is not influenced by iron deficiency or the dilutional anaemia of pregnancy. Fructosamine has a precise and inexpensive measurement and it is not affected by haemoglobin characteristics. This review further discusses the potential value of these non-traditional indicators of glycaemic control in patients with GDM, outlining their possible future applications.

Effect of renal function on serum concentration of 1,5-anhydroglucitol in type 2 diabetic patients in chronic kidney disease stages I-III: A comparative study with HbA1c and glycated albumin

BACKGROUND

1,5-Anhydroglucitol (1,5-AG) is a new blood glucose control marker reflecting temporary glucose elevations. However, 1,5-AG is of limited value in patients with advanced renal insufficiency. The aim of the present study was to assess the correlation between 1,5-AG levels and renal function in patients with earlier stages of nephropathy compared with another two markers of diabetes control, namely HbA1c and glycated albumin (GA).

METHODS

The following parameters were measured in 377 patients with type 2 diabetes: HbA1c, serum concentrations of 1,5-AG, GA and creatinine, hemoglobin, urinary albumin/creatinine ratio, and urinary excretion of α1 -microglobulin (A1M). Estimated glomerular filtration rate (eGFR) was calculated according to the Cockgroft-Gault formula.

RESULTS

There was a negative correlation between 1,5-AG and renal function (r = -0.18; P < 0.001). Concentrations of 1,5-AG were, on average, 27.2% lower in patients with glomerular hyperfiltration (eGFR >120 mL/min) compared with patients with moderate renal impairment (eGFR 30-59 mL/min; P = 0.016). In contrast, HbA1c, GA levels and urinary A1M excretion did not differ between the two patient groups. The mean age of patients with eGFR 30-59 mL/min was substantially higher than that of patients with glomerular hyperfiltration (P < 0.001). Thus, an age-related change in the renal glucose threshold could be the reason for the observed correlation between 1,5-AG and renal function.

CONCLUSIONS

In clinical practice, age and renal function must be taken into consideration when interpreting 1,5-AG levels, even in the absence of advanced renal impairment.

Indicators of glycemic control in patients with gestational diabetes mellitus and pregnant women with diabetes mellitus

Recently, it has become clear that mild abnormal glucose tolerance increases the incidence of perinatal maternal-infant complications, and so the definition and diagnostic criteria of gestational diabetes mellitus (GDM) have been changed. Therefore, in patients with GDM and pregnant women with diabetes mellitus, even stricter glycemic control than before is required to reduce the incidence of perinatal maternal-infant complications. Strict glycemic control cannot be attained without an indicator of glycemic control; this review proposes a reliable indicator. The gold standard indicator of glycemic control in patients with diabetes mellitus is hemoglobin A1c (HbA1c); however, we have demonstrated that HbA1c does not reflect glycemic control accurately during pregnancy because of iron deficiency. It has also become clear that glycated albumin, another indicator of glycemic control, is not influenced by iron deficiency and therefore might be a better indicator of glycemic control in patients with GDM and pregnant women with diabetes mellitus. However, large-population epidemiological studies are necessary in order to confirm our proposal. Here, we outline the most recent findings about the indicators of glycemic control during pregnancy including fructosamine and 1,5-anhydroglucitol.

1,5-Anhydroglucitol and glycated albumin in glycemia

The main purpose of treating diabetes is to prevent the onset and the progression of diabetic chronic complications. Since the mechanism of onset of chronic complications is still not well understood, the main strategy to achieve this purpose is to bring the plasma glucose level in diabetic patients as close as possible to that in healthy subjects and try to maintain good glycemic control over the long term. Glycated hemoglobin (HbA1c), glycated albumin (GA), fructosamine, and 1,5-anhydroglucitol (1,5 AG) are used for evaluating glycemic control. At present, HbA1c is widely used as a gold standard index for glycemic control in clinical practice. While HbA1c reflects the long-term glycemic control state (for the past 1-2 months), it does not accurately reflect glycemic control in the clinical state in which glycemic control improves or deteriorates in the short-term. It is also known that HbA1c in patients with hematological disorders such as anemia and variant hemoglobin shows an abnormal value. In addition, HbA1c mainly reflects the mean plasma glucose but does not reflect the postprandial plasma glucose. On the other hand, GA and 1,5-AG reflect intermediate- or short-term glycemic control and are not influenced by hemoglobin metabolism. While 1,5-AG is known to reflect the postprandial plasma glucose, it was shown recently that GA also reflects the postprandial plasma glucose. This chapter summarizes the measurement methods, usage methods, evidence, and problems concerning such indices for glycemic control.

Glycemic control indicators in patients with neonatal diabetes mellitus

Neonatal diabetes mellitus (NDM) is a type of diabetes mellitus caused by genetic abnormality which develops in insulin dependent state within 6 mo after birth. HbA1c is widely used in clinical practice for diabetes mellitus as the gold standard glycemic control indicator; however, fetal hemoglobin (HbF) is the main hemoglobin in neonates and so HbA1c cannot be used as a glycemic control indicator in NDM. Glycated albumin (GA), another glycemic control indicator, is not affected by HbF. We reported that GA can be used as a glycemic control indicator in NDM. However, it was later found that because of increased metabolism of albumin, GA shows an apparently lower level in relation to plasma glucose in NDM; measures to solve this problem were needed. In this review, we outlined the most recent findings concerning glycemic control indicators in neonates or NDM.

1,5-Anhydroglucitol in diabetes mellitus

The measure of glycated hemoglobin (HbA1c) concentration is the gold standard of glycemic control index in diabetes management and is well known as a marker for diabetes complications. However, HbA1c level neither accurately reflect glucose fluctuations, nor does it provide a clear indication of glycemic control in recent days or weeks. HbA1c concentration measurement can be confounded in patients with anemia, hemoglobinopathy, liver disease, or renal impairment. 1,5-Anhydroglucitol (1,5-AG) structurally resembles glucose. It can be influenced by diet or medication, gender and race, especially severe renal disease and various pathological conditions. Most notably, 1,5-AG level is reflective of short-term glucose status, postprandial hyperglycemia, and glycemic variability which are not captured by HbA1c assay. 1,5-AG may suggest an alternative index of subtypes of diabetes and a warning sign of diabetes complications. This review provides an overview of our current understanding of the role of 1,5-AG marker in diabetes. However, further investigations on the associations between this glycemic marker and diabetes complications are needed.

Serum 1,5-anhydroglucitol concentrations are a reliable index of glycemic control in type 2 diabetes with mild or moderate renal dysfunction

OBJECTIVE

To assess the relationship between 1,5-anhydroglucitol (AG) levels, which are a marker of glycemic control, and stages of chronic kidney disease (CKD).

RESEARCH DESIGN AND METHODS

This was a cross-sectional study with 269 subjects with type 2 diabetes who were divided into four groups based on estimated glomerular filtration rate (eGFR) using Modification of Diet in Renal Disease (eGFR(MDRD)) formula: 57 in control, 111 in CKD stages 1-2, 78 in stage 3, and 23 in stages 4-5.

RESULTS

The study groups differed significantly with respect to 1,5-AG and fasting plasma glucose (FPG), age, duration of diabetes, blood pressure, HDL, and percentage of antihypertension or antidyslipidemia medication use. Stepwise multivariate regression analyses showed that 1,5-AG levels in the control group, the CKD stages 1-2 group, and the CKD stage 3 group could be explained by HbA(1c), age, duration of diabetes, FPG, and antihypertension medication. However, eGFR(MDRD) was the only independent determinant of 1,5-AG levels in CKD stages 4-5. Logarithmic transformed 1,5-AG values (ln[1,5-AG]) had significant inverse correlations with HbA(1c) and FPG levels for CKD stages 1-2 and CKD stage 3 (all P < 0.001). However, associations between ln(1,5-AG) and HbA(1c) or FPG were insignificant for CKD stages 4-5 (P = 0.274 and P = 0.080, respectively).

CONCLUSIONS

This study demonstrated that 1,5-AG levels do not appear to be influenced by mild or moderate renal dysfunction, suggesting it is a reliable glycemic marker in type 2 diabetes with CKD stages 1-3.

Plasma 1,5 anhydroglucitol levels, a measure of short-term glycaemia: assay assessment and lower levels in diabetic vs. non-diabetic subjects

An assay of plasma 1,5-anhydroglucitol was evaluated. Assay CVs, effects of four plasma freeze-thaw cycles, glucose up to 80 mmol/L and triglycerides up to 20 mmol/L were acceptable. 1,5-anhydroglucitol levels were significantly lower in diabetic vs. non-diabetic subjects and correlated inversely with renal function, but not with HbA1c.

Evaluation of serum 1,5 anhydroglucitol levels as a clinical test to differentiate subtypes of diabetes

OBJECTIVE

Assignment of the correct molecular diagnosis in diabetes is necessary for informed decisions regarding treatment and prognosis. Better clinical markers would facilitate discrimination and prioritization for genetic testing between diabetes subtypes. Serum 1,5 anhydroglucitol (1,5AG) levels were reported to differentiate maturity-onset diabetes of the young due to HNF1A mutations (HNF1A-MODY) from type 2 diabetes, but this requires further validation. We evaluated serum 1,5AG in a range of diabetes subtypes as an adjunct for defining diabetes etiology.

RESEARCH DESIGN AND METHODS

1,5AG was measured in U.K. subjects with: HNF1A-MODY (n = 23), MODY due to glucokinase mutations (GCK-MODY, n = 23), type 1 diabetes (n = 29), latent autoimmune diabetes in adults (LADA, n = 42), and type 2 diabetes (n = 206). Receiver operating characteristic curve analysis was performed to assess discriminative accuracy of 1,5AG for diabetes etiology.

RESULTS

Mean (SD range) 1,5AG levels were: GCK-MODY 13.06 microg/ml (5.74-29.74), HNF1A-MODY 4.23 microg/ml (2.12-8.44), type 1 diabetes 3.09 microg/ml (1.45-6.57), LADA 3.46 microg/ml (1.42-8.45), and type 2 diabetes 5.43 (2.12-13.23). Levels in GCK-MODY were higher than in other groups (P < 10(-4) vs. each group). HNF1A-MODY subjects showed no difference in unadjusted 1,5AG levels from type 2 diabetes, type 1 diabetes, and LADA. Adjusting for A1C revealed a difference between HNF1A-MODY and type 2 diabetes (P = 0.001). The discriminative accuracy of unadjusted 1,5AG levels was 0.79 for GCK-MODY versus type 2 diabetes and 0.86 for GCK-MODY versus HNF1A-MODY but was only 0.60 for HNF1A-MODY versus type 2 diabetes.

CONCLUSIONS

In our dataset, serum 1,5AG performed well in discriminating GCK-MODY from other diabetes subtypes, particularly HNF1A-MODY. Measurement of 1,5AG levels could inform decisions regarding MODY diagnostic testing.

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.

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.

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.

Plasma anhydro-D-glucitol (1,5-AG) as an indicator of hyperglycaemic excursions in pregnant women with diabetes

AIMS

To evaluate the use of the plasma 1,5-anhydro-d-glucitol (1,5-AG) level as a possible marker for glucose excursions in pregnant women with diabetes.

METHODS

The study group consisted of 55 pregnant women with diabetes (gestational diabetes mellitus-GDM, n = 28 or pre-gestational diabetes mellitus -PGDM, n = 27), without hepatic or renal insufficiency, gestational age range 5-38 weeks. In each patient, 24-h glucose profile, glycated haemoglobin and 1,5-AG plasma levels were measured. Mean blood glucose (MBG) and M-value (by Schlichtkrull) were calculated. MBG, M-value and maximal daily glycaemia (MxG) were used as indexes of daily glycaemic excursions.

RESULTS

A significant correlation was found between the 1,5-AG plasma level and MxG [r = (-0.3)] and between the 1,5-AG level and M-value [r = (-0.36)]. There was no association between the 1,5-AG level and gestational age. Multivariate regression analysis, with 24-h glucose profile, gestational age and MxG as independent variables, showed that MxG was the main parameter determining the 1,5-AG plasma level [beta = (-0.68)]. The M-value, the coefficient of glucose fluctuations, also determined the 1,5-AG level but with lower statistical power [beta = (0.41)]. No statistical differences were found in the group with HbA(1c) < 6% or > 6% for 1,5-AG and M-value, while MBG was higher in poorly controlled patients (HbA(1c) > 6%).

CONCLUSIONS

The plasma 1,5-AG level may be a useful marker of daily glucose excursion in pregnant women with diabetes, as an adjunct to HbA(1c) monitoring.

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.