Renal tubular function affects glycosuria-related urinary excretion of 1,5-anhydroglucitol

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.

Evaluation of 1,5-anhydro-d-glucitol in clinical and forensic urine samples

Because of the lack of characteristic morphological findings post mortem diagnosis of diabetes mellitus and identification of diabetic coma can be complicated. 1,5-Anhydroglucitol (1,5-AG), the 1-deoxy form of glucose, competes with glucose for renal reabsorption. Therefore low serum concentrations of 1,5-AG, reflect hyperglycemic excursions over the prior 1-2 weeks in diabetic patients. Next to clinical applications determination of 1,5-AG can also be used in forensic analysis. To investigate the elimination of 1,5-AG, a liquid chromatographic-mass spectrometric method for the determination of 1,5-AG and creatinine in urine was developed and validated according to international guidelines. To evaluate ante mortem concentrations of 1,5-AG spot urine samples of 30 healthy subjects, 46 type 1 and 46 type 2 diabetic patients were analyzed. 1,5-AG urine concentrations of diabetic patients were significantly (p<0.001) lower (mean: 1.54μg/ml, n=92) compared to concentrations of healthy subjects (mean: 4.76μg/ml, n=30) which led to the idea that 1,5-AG urine concentrations post mortem might help in the interpretation of a diabetic coma post mortem. Urine of 47 deceased non-diabetics, 37 deceased diabetic and 9 cases of diabetic coma were measured. Comparison of blood and urine 1,5-AG concentrations in clinic samples (linear, R²=0.13) and forensic samples (linear, R²=0.02) showed no correlation. Urinary levels of 1,5-AG in deceased diabetic (mean 6.9μg/ml) and in non-diabetic patients (mean 6.3μg/ml) did not show a significant difference (p=0.752). However, urinary 1,5-AG concentrations in deceased due to diabetic coma (mean: 1.7μg/ml) were significantly lower than in non-diabetic (mean: 6.3μg/ml, p=0.039) and lower than in diabetic cases (mean: 4.7μg/ml, p=0.058). The determination of a reliable cut-off for the differentiation of diabetic to diabetic coma cases was not possible. Normalization of urinary 1,5-AG concentrations with the respective creatinine concentrations did not show any gain of information. In clinical (serum) and forensic blood samples a significant difference between all groups could be detected (p<0.05). Comparison of blood and urine 1,5-AG concentrations in clinical samples (linear, R²=0.13) and forensic samples (linear, R²=0.02) showed no correlation.

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.

Evaluation of 1,5-anhydroglucitol as a marker for glycemic variability in patients with type 2 diabetes mellitus

1,5-anhydroglucitol (1,5-AG) has been suggested as a marker for short-term glycemic control and postprandial hyperglycemia. However, the role of 1,5-AG in glycemic variability has not been established. The aim of this study was to demonstrate the usefulness of 1,5-AG as a marker for glycemic variability in patients with type 2 diabetes. Sixty patients with type 2 diabetes were enrolled, and a continuous glucose monitoring system (CGMS) was applied for 72 h. Continuous overlapping net glycemic action (CONGA), mean amplitude of glycemic excursion (MAGE), and mean of the daily differences (MODD) were calculated for the assessment of glycemic variability and compared with 1,5-AG. Urinary 8-iso prostaglandin F2α (8-isoPGF2α) was measured to assess oxidative stress. 1,5-AG was correlated with fasting blood glucose, HbA1c, postprandial area under the curve for glucose above 180 mg/dL (AUC-180), and mean post-meal maximum glucose (MPMG). However, 1,5-AG did not show significant correlation with CONGA-1, MAGE, and MODD (R = -0.053, P = 0.689; R = -0.148, P = 0.259; R = -0.123, P = 0.350). In patients with HbA1c ≤ 8.0% (n = 35), 1,5-AG was significantly correlated with HbA1c, mean glucose, postprandial AUC-180, and MPMG. However, in patients with HbA1c > 8.0% (n = 25), 1,5-AG did not show correlation with any glycemic markers. Oxidative stress measured as urine 8-isoPGF2α showed positive correlations with CONGA-1, MAGE, AUC-180, postprandial AUC-180, and MPMG only in men. However, 1,5-AG did not correlate with oxidative stress. Our data suggested a limited usefulness of 1,5-AG in estimating glycemic variability and oxidative stress. 1,5-AG was able to represent mean glucose and postprandial hyperglycemia only in well-controlled diabetic patients.

Serum 1,5-anhydroglucitol is associated with diabetic retinopathy in Type 2 diabetes

AIMS

To determine whether there is a relationship between 1,5-anhydroglucitol (1,5-AG), a marker of postprandial hyperglycaemia and glycaemic variability, and the presence of diabetic retinopathy and albuminuria in patients with Type 2 diabetes.

METHODS

Five hundred and sixty-seven patients with Type 2 diabetes (serum creatinine < 133 μmol/l), who were enrolled in the Seoul Metro-City Diabetes Prevention Program (SMC-DPP), were cross-sectionally assessed by multivariate logistic regression analysis.

RESULTS

After controlling for age, sex, binary HbA(1c) levels, duration of diabetes, triglyceride, systolic blood pressure, smoking status, history of hypertension and dyslipidaemia, and the use of angiotensin-converting enzyme inhibitor/angiotensin receptor blocker medication, the odds ratios (95% CI) of diabetic retinopathy were 2.86 (1.12-7.25) for the first (lowest) quartile of 1,5-anhydroglucitol, 2.87 (1.25-6.61) for the second quartile and 0.88 (0.35-2.22) for the third quartile compared with the fourth quartile (P for trend = 0.010). Conversely, the associations between 1,5-anhydroglucitol and clinical albuminuria were non-significant after adjustment. Subjects with low 1,5-anhydroglucitol (< 10.0 μg/ml) were more likely to experience diabetic retinopathy than those with high 1,5-anhydroglucitol (≥ 10.0 μg/ml) under moderate glucose control (HbA(1c) < 8%, 64 mmol/mol) and there were no significant differences in the prevalence of diabetic retinopathy between the subgroup with HbA(1c) < 8% (64 mmol/mol) and low 1,5-anhydroglucitol and the subgroup with HbA(1c) ≥ 8% (64 mmol/mol).

CONCLUSIONS

1,5-Anhydroglucitol levels show close associations with diabetic retinopathy, especially among patients under moderate glucose control, but not with albuminuria. These results suggest that 1,5-anhydroglucitol might be a complementary marker for targeting higher risk group.

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.

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.

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.

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.