An enzymatic method for the measurement of glycated albumin in biological samples

A comprehensive review on fructosyl peptide oxidase as an important enzyme for present hemoglobin A1c assays

Glycated proteins are generated by binding of glucose to the proteins in blood stream through a nonenzymatic reaction. Hemoglobin A1c (HbA1c) is a glycated protein with glucose at the N-terminal of β-chain. HbA1c is extensively used as an indicator for assessing the blood glucose concentration in diabetes patients. There are different conventional clinical methods for the detection of HbA1c. However, enzymatic detection method has newly obtained great attention for its high precision and cost-effectiveness. Today, fructosyl peptide oxidase (FPOX) plays a key role in the enzymatic measurement of HbA1c, and different companies have marketed HbA1c assay systems based on FPOX. Recent investigations show that FPOX could be used in assaying HbA1 without requiring HbA1c primary digestion. It could also be applied as a biosensor for HbA1c detection. In this review, we have discussed the recent improvements of FPOX properties, different methods of FPOX purification, solubility, and immobilization, and also the use of FPOX in HbA1c biosensors.

Exploring glycated sites in human serum albumin: impact of sample processing techniques on detection and analysis

Glycation and the subsequent formation of advanced glycation end products (AGEs) disrupt and impair the physiological functions of proteins. This study presents a comprehensive glycation site mapping of human serum albumin (HSA) utilizing liquid chromatography-tandem mass spectrometry (LC-MS/MS). Both in vitro glycation experiments and patient samples were investigated, exploring various enzymes, processing techniques, and their impacts on glycation site detection. A pilot study was conducted, analyzing sixteen serum samples, which spanned from healthy individuals to severe diabetic patients (with HbA1c values ranging from 5.7% to 18.1%). The aim was to comprehend the progression of glycation on various sites of HSA with increasing levels of glycation. Their glycated albumin levels (GA) spanned from 19.7% to 62.3%. Trypsin-mediated proteolytic digestion unveiled 12 glycation sites through direct in-solution digestion of whole serum. However, isolating albumin from serum enabled the identification of a higher number of glycation sites in each sample compared to direct serum digestion. Boronate affinity chromatography facilitated the segregation of less glycated albumin (LGA) from the more glycated albumin (MGA) fraction. Subsequent proteolytic digestion of both LGA and MGA samples revealed similar glycation sites. The MGA fraction exhibited a greater number of identified glycation sites, thereby elucidating which sites are particularly prone to glycation in highly glycated albumin samples. Changes in relative glycation levels were noted in the tryptic digests of albumin samples following the sample enrichment steps, as opposed to direct in-solution digestion of whole serum. Two enzymes, trypsin and Glu-C, were evaluated for efficacy in sequence coverage and glycation site analysis of HSA, with trypsin demonstrating superior efficiency over Glu-C.

Association between glycated albumin and adverse outcomes in patients with heart failure

AIMS/INTRODUCTION

Diabetes mellitus is a traditional risk factor for heart failure (HF), and glycated albumin (GA) is a marker to assess short-term glycemic control. Whether GA has prognostic significance in patients with HF remains unclear.

MATERIALS AND METHODS

A total of 717 patients with HF were enrolled in the prospective cohort study. Patients were grouped by the normal upper limit of GA (17%). Kaplan-Meier analysis and Cox proportional hazards regression were used to evaluate the association between GA and prognosis.

RESULTS

During a mean follow-up of 387 days, 232 composite endpoint events of hospitalization for HF or all-cause death occurred. Kaplan-Meier analysis showed a higher rate of adverse events in the higher GA group (GA >17%; log-rank test P < 0.001). GA was an independent predictor of adverse events, both as a continuous variable (per 1% change: hazard ratio [HR] 1.03, 95% confidence interval [CI] 1.00-1.06, P = 0.030) and as a categorical variable (GA >17%: HR 1.36, 95% CI 1.03-1.80, P = 0.032). Restricted cubic splines showed a linear association between GA and adverse events (P for non-linearity = 0.231). There was no significant difference in adverse outcome risk between those with diabetes and GA ≤17% and those without diabetes, whereas the prognosis was worse in those with diabetes and GA >17% (HR 1.56, 95% CI 1.16-2.11, P = 0.004). Compared to the group with normal levels of GA and glycated hemoglobin, the group with GA >17% and glycated hemoglobin >6.5% had a higher risk of adverse events (HR 1.49, 95% CI 1.06-2.10, P = 0.022).

CONCLUSIONS

GA was an independent predictor of HF prognosis. Combining GA and glycated hemoglobin might improve the predictive power of adverse outcomes in patients with HF.

Limitations of glycated albumin standardization when applied to the assessment of diabetes patients

OBJECTIVES

Glycated albumin (GA) has potential value in the management of people with diabetes; however, to draw meaningful conclusions between clinical studies it is important that the GA values are comparable. This study investigates the standardization of the Norudia Glycated Albumin and Lucica Glycated Albumin-L methods.

METHODS

The manufacturer reported imprecision was verified by performing CLSI-EP15-A3 protocol using manufacturer produced controls. The Japanese Clinical Chemistry Reference Material (JCCRM)611-1 was measured 20 times to evaluate the accuracy of both methods. GA was also measured in 1,167 patient samples and results were compared between the methods in mmol/mol and %.

RESULTS

Maximum CV for Lucica was ≤0.6 % and for Norudia ≤1.8 % for control material. Results in mmol/mol and % of the JCCRM611-1 were within the uncertainty of the assigned values for both methods. In patient samples the relative difference in mmol/mol between the two methods ranged from -10.4 % at a GA value of 183 mmol/mol to +8.7 % at a GA value of 538 mmol/mol. However, the relative difference expressed in percentage units ranged from of 0 % at a GA value of 9.9 % to +1.7 % at a GA value of 30 %.

CONCLUSIONS

The results in mmol/mol between the two methods for the patient samples were significantly different compared to the results in %. It is not clear why patient samples behave differently compared to JCCRM611-1 material. Valuable lessons can be learnt from comparing the standardization process of GA with that of HbA1c.

Development of a glycated albumin sensor employing dual aptamer-based extended gate field effect transistors

Glycated albumin (GA), defined as the percentage of serum albumin glycation, is a mid-term glycemic control marker for diabetes. The concentrations of both glycated human serum albumin (GHSA) and total human serum albumin (HSA) are required to calculate GA. Here, we report the development of a GA sensor employing two albumin aptamers: anti-GHSA aptamer which is specific to GHSA and anti-HSA aptamer which recognizes both glycated and non-glycated HSA. We combine these aptamers with extended gate field effect transistors (EGFETs) to realize GA monitoring without the need to pretreat serum samples, and therefore suitable for point of care and home-testing applications. Using anti-GHSA aptamer-immobilized electrodes and EGFETs, we measured GHSA concentrations between 0.1-10 μM within 20 min. The sensor was able to measure GHSA concentration in the presence of BSA for a range of known GA levels (5-29%). With anti-HSA aptamer-immobilized electrodes and EGFETs, we measured total HSA concentrations from 1-17 μM. Furthermore, GHSA and total HSA concentrations of both healthy and diabetic-level samples were determined with GHSA and HSA sensors. The measured GHSA and total HSA concentrations in three samples were used to determine respective GA percentages, and our calculations agreed with GA levels determined by reference methods. Thus, we developed simple and rapid dual aptamer-based EGFET sensors to monitor GA through measuring GHSA and total HSA concentration, without the need for sample pretreatment, a mandatory step in the current standard of enzymatic GA monitoring.

Estimation of mean erythrocyte age using HbA1c or HbA1c/glycated albumin for evaluation of anemia severity

BACKGROUND

Hemoglobin A1c (HbA1c) levels are low in patients with hemolytic anemia, as HbA1c reflects mean erythrocyte age (MRBC ). Erythrocyte creatine (EC) is a hemolytic indicator that also reflects MRBC . We previously reported an equation for estimating MRBC using EC (EC-MRBC ).

AIMS

In this study, EC-MRBC was compared to the HbA1c level expressed in the International Federation of Clinical Chemistry and Laboratory Medicine units (iA1c) and to the iA1c/glycated albumin (GA) ratio to estimate MRBC .

METHODS

This study included 238 subjects, including patients with hemolytic anemia and/or type 2 diabetes mellitus (T2DM).

RESULTS

In non-diabetic individuals, both iA1c and iA1c/GA showed a strong positive correlation with EC-MRBC (p < 0.0001). The equations to estimate iA1c-MRBC and iA1c/GA-MRBC derived from the regression equations between EC-MRBC and iA1c, and EC-MRBC and iA1c/GA in nondiabetic individuals were 1.45 × iA1c and 20.0 × iA1c/GA, respectively. iA1c-MRBC and iA1c/GA-MRBC in non-diabetic individuals without hemolytic anemia were 57.6 ± 4.0 and 57.1 ± 6.4 days, respectively, and iA1c/GA-MRBC in T2DM patients without hemolytic anemia was 56.0 ± 8.8 days.; no significant difference was seen in the comparisons.

CONCLUSIONS

The MRBC can be estimated using iA1c or iA1c/GA in non-diabetic individuals, and iA1c/GA in T2DM patients.

Protein glycation in diabetes mellitus

Diabetes mellitus is the ninth leading cause of mortality worldwide. It is a complex disease that manifests as chronic hyperglycemia. Glucose exposure causes biochemical changes at the proteome level as reflected in accumulation of glycated proteins. A prominent example is hemoglobin A1c (HbA1c), a glycated protein widely accepted as a diabetic indicator. Another emerging biomarker is glycated albumin which has demonstrated utility in situations where HbA1c cannot be used. Other proteins undergo glycation as well thus impacting cellular function, transport and immune response. Accordingly, these glycated counterparts may serve as predictors for diabetic complications and thus warrant further inquiry. Fortunately, modern proteomics has provided unique analytic capability to enable improved and more comprehensive exploration of glycating agents and glycated proteins. This review broadly covers topics from epidemiology of diabetes to modern analytical tools such as mass spectrometry to facilitate a better understanding of diabetes pathophysiology. This serves as an attempt to connect clinically relevant questions with findings of recent proteomic studies to suggest future avenues of diabetes research.

Glycated albumin and post-transplant diabetes mellitus in kidney transplant recipients

BACKGROUND

Post-transplant diabetes mellitus is one of the most important cardiovascular risk factors after solid organ transplantation. Factors other than hyperglycaemia found in patients post-transplant, affect the level of haemoglobin A_1c (HbA_1c), and new markers of hyperglycaemia are needed. Our aim was to establish a 95% reference interval for glycated albumin in kidney transplant recipients, and to compare glycated albumin concentrations to the diagnostic criteria for diabetes mellitus post-transplant using oral glucose tolerance test and HbA_1c.

METHODS

A total of 341 non-diabetic kidney transplant recipients aged ≥18 years who underwent an oral glucose tolerance test at 8 weeks and 1 year after transplantation were included. Glycated albumin was determined by liquid chromatography coupled with tandem mass spectrometry.

RESULTS

The 95% reference interval for glycated albumin was 8.2 (90% CI: 7.2-8.5) to 12.8% (90% CI: 12.2-13.5) which is not significantly different from our laboratory's 95% reference interval for persons without diabetes. At both 8 weeks and 1 year after transplantation, 35 patients (10.3%) fulfilled one, two or all three diagnostic criteria for diabetes mellitus. One year after transplantation, eight additional patients had glycated albumin concentration >12.8%.

CONCLUSION

Our findings are in accordance with the notion that kidney transplant recipients form glycation end products like normal controls as estimated by glycated albumin and HbA_1c. Further studies should address glycated albumin as a supplemental tool for the diagnosis of post-transplant diabetes mellitus in kidney transplant recipients.

Development of a high-performance liquid chromatographic glycated albumin assay using finger-prick blood samples

BACKGROUND

Home blood glucose monitoring can be effective for the self-management of diabetic patients. Hemoglobin A1c (HbA1c) is a widely used marker that reflects the average blood glucose within 1-2 months but does not sensitively respond to behavioral changes. Self-monitoring of blood glucose, continuous glucose monitoring, and flush glucose monitoring are sensitive; however, the cost and invasiveness of these tests prevent their widespread use. We focused on glycated albumin (GA), which reflects the average blood glucose levels over 1-2 weeks, and established a GA measurement method for self-sampling, finger-prick blood, which may be submitted for testing through postal service to receive weekly results.

METHODS

A high-performance liquid chromatography assay was established to measure GA levels in finger-prick blood samples from 103 diabetic patients and the results were compared with venous blood measurements using an enzymatic method. Furthermore, conditions for sending blood samples by mail were evaluated. Under these conditions, samples from 27 healthy and 32 patient volunteers sent through postal service were compared with samples stored in the laboratory.

RESULTS

GA levels were measured in samples containing > 20 μg albumin, which resulted in a CV less than 0.3%. The correlation between the GA levels of finger-prick blood measured using HPLC and the GA levels of venous blood measured using the enzymatic method was R² = 0.988 with the slope ∼ 1.0, suggesting that the two were nearly equivalent. GA levels were stable for four days at 30 °C and two days at 37 °C. Mail-delivered samples exhibited a high correlation with samples that were not sent (R² > 0.99).

CONCLUSIONS

We established a method to measure GA levels in self-sampled, finger-prick blood sent through postal service in Japan. The method is applicable for weekly feedback of GA levels, which is potentially useful for motivating behavioral changes. In addition to markers such as HbA1c and blood glucose, GA can be used as a marker for assessing dietary and physical activities. This study highlighted the importance of GA monitoring by developing a suitable measurement method for weekly monitoring of GA levels.

Predicting the response to SGLT-2 inhibitors as add-on therapy to multiple day injection insulin with glycated albumin: a pilot study

BACKGROUND

Achieving optimal glycemic targets is the main therapeutic goal in patients with type 2 diabetes (T2D) mellitus. HbA1c is the reference biomarker for monitoring glycemic control; however, in specific conditions affecting erythrocyte turnover or in patients on multiple daily injection (MDI) insulin regimens, the determination of glycated albumin (GA) may be preferable. Sodium-glucose cotransporter-2 (SGLT-2) inhibitors represent a novel class of antidiabetic drugs that lower plasma glucose concentrations quickly, with insulin-independent mechanisms. Herein, we explored the role of GA in predicting the short-term response to SGLT-2 inhibitors as add-on to MDI insulin.

METHODS

Sixteen patients with long-standing, poorly controlled T2D on MDI insulin starting an SGLT-2 inhibitor were subjected to plasma GA and HbA1c measurements at 30 days intervals for up to 3 months in order to examine the temporal changes of these glycemic biomarkers.

RESULTS

At the end of the study, grossly coincident with the life span of erythrocytes, a significant decrease in median HbA1c was observed, (from 8.7 [range: 8.2-9.3%] at baseline to 7.2 [range: 7.0-7.9%]), with the advantage of less insulin dose requirements. However, significant, and incremental reductions in median GA determinations could be already evident after 30 days (-3.5 [range: -7.5, -2.5%]) and 60 days (-6.4 [range: -10.5, -4.7%]) from the start of SGLT-2 inhibitor treatment and persisted for up to 3 months (-8.6 [range: -12.1, 6.1%]). The decrements of HbA1c observed at the 3-month visit were highly correlated with the concurrent absolute reductions of plasma GA (ρ=0.550, P=0.027), whereas a borderline significance could be demonstrated with reference to reductions in plasma GA at 30 and 60 days.

CONCLUSIONS

Although limited by the small number of participants, these preliminary findings suggest that GA, rather than HbA1c, could represent a useful and reliable biomarker in T2D to monitor the early glucose-lowering effects of antidiabetic drugs with rapid onset of action, such as SGLT-2 inhibitors and MDI insulin.

Effect of Iron Deficiency Anemia on Glycated Albumin Levels: A Comparative Study in Nondiabetic Subjects with Iron Deficiency Anemia

Objective Glycated hemoglobin A1c (HbA1c), used for monitoring glycemia control, is altered in iron deficiency anemia (IDA). Glycated albumin (GA) is considered an alternate biomarker to HbA1c. However, effect of IDA on GA needs to be studied.

Materials and Methods Thirty nondiabetic cases with IDA and 30 healthy controls were included. Fasting plasma glucose (FPG), creatinine, urea, albumin, total protein, ferritin, iron, unsaturated iron binding capacity, hemoglobin (Hb), HbA1c, complete hemogram, and GA were estimated. Transferrin saturation and total iron binding capacity (TIBC) were calculated. Statistical analysis was done using unpaired two-tailed t-test/Mann–Whitney U-test and Pearson's correlation/Spearman-rank correlation, as appropriate.

Results Total protein, albumin, Hb, iron, ferritin, and transferrin saturation were significantly lower while FPG, GA, TIBC, and HbA1c were significantly higher in cases compared to controls. HbA1C and GA have a significant negative correlation with iron, transferrin saturation, and ferritin. Significant negative correlations of GA with albumin (r = –0.754; p < 0.001) and Hb (r = –0.435; p = 0.001) and that of HbA1c with albumin (r = –0.271; p = 0.03) and Hb (r = –0.629; p  < 0.001) while significant positive correlation of Hb with albumin (r = 0.395; p = 0.002) and HbA1c with FPG (r = 0.415; p = 0.001) were observed.

Conclusion Low albumin levels increase plasma protein glycation, including albumin. Hence, elevated GA levels indicate false elevation of GA in scenario of lowered albumin observed in IDA, similar to HbA1c. Thus, using GA in diabetes mellitus with IDA should be avoided or used with caution to prevent potentially inappropriate treatment intensification and risk of hypoglycemia.

Serum glycated albumin is associated with in-stent restenosis in patients with acute coronary syndrome after percutaneous coronary intervention with drug-eluting stents: An observational study

Background

Previous studies have confirmed the predicted value of serum glycated albumin (GA) in atherosclerotic cardiovascular disease. However, the relationship between GA and the development of in-stent restenosis (ISR) after drug-eluting stent (DES) implantation has not been verified in patients with acute coronary syndrome (ACS).

Materials and methods

In this study, 797 patients diagnosed with ACS who underwent re-coronary angiography more than 6 months after the first successful DES-based percutaneous coronary intervention (PCI) were eventually included. Patients were categorized into two groups based on the median GA levels of 14.94%. Moreover, multivariate logistic regression analysis models and the net reclassification improvement and integrated differentiation improvement risk models were constructed to assess the relationship between the GA and DES-ISR in patients with ACS.

Results

The GA was significantly associated with an increased risk of DES-ISR, upon adjusting for confounding factors (as nominal variate: OR 1.868, 95% CI 1.191-2.932, P = 0.007; as continuous variate: OR 1.109, 95% CI 1.040-1.183, P = 0.002). The addition of GA to a baseline risk model had an incremental effect on the predictive value for DES-ISR (AUC: GA vs. baseline model, 0.714 vs. 0.692, comparison P = 0.017; category-free net reclassification improvement (NRI) 0.080, P = 0.035; integrated discrimination improvement (IDI) 0.023, P < 0.001).

Conclusion

GA level was significantly associated with a high risk of DES-ISR in patients with ACS treated with PCI. Moreover, the addition of the GA to a baseline risk model has an incremental effect on the predictive potential for DES-ISR.

Biomarkers in Diabetes Mellitus

Diabetes mellitus (DM) is a chronic metabolic disease characterized by hyperglycemia that occurs as a result of impaired insulin secretion and/or insulin effect, or both of these factors. The fact that the disease has both individual and social dimensions makes it important to detect as early as possible and make the necessary lifestyle changes. For this purpose, it becomes necessary to develop fast, effortless, cheap, and reliable methods for diagnosis. We discussed which biochemical markers should enter routine use according to their sensitivity and specificity among the biochemical markers that have been used and are still being studied. In this chapter, we explored some methods that may be used as biomarkers and discussed advantages and pitfalls for each.

Analyzation of the binding mechanism and the isoelectric point of glycated albumin with self-assembled, aptamer-conjugated films by using surface plasmon resonance

Glycated albumin(GA), a biomarker which has great potential to replace glycated hemoglobin in the diagnosis and treatment of diabetes, is being extensively studied by scientists, especially in preventive medicine. Aptamers, as novel probes, have attracted much attention due to their high specificity, wide storage conditions, and simple preparation. However, the interaction mechanism between GA and its aptamer is still unclear, hindering the progress of diabetic aptamer sensors into clinical testing. In this study, the interaction mechanism between GA and its aptamer was evaluated for the first time using surface plasmon resonance by changing the pH value, salt concentration and temperature. The successful preparation of the sensor chip is proved by the water contact angle, Atomic Force Microscope, and the X-ray photoelectron spectroscopy. This study shows that the pH can greatly affect the formation of a complex from the interaction between the aptamer and GA. The interaction mechanism between GA aptamer and GA was caused by electrostatic force. Otherwise, this is the first time to detect protein isoelectric point (pI) using SPR. This study provides an important reference for researchers of aptamer sensors from the perspective of detection environment, and promotes the use of aptamer sensors to the clinic.

Analytical performances of a glycated albumin assay that is traceable to standard reference materials and reference range determination

BACKGROUND

Glycated albumin (GA) is an intermediate-term marker for monitoring glycemic control (preceding 2-3 weeks) in patients with diabetes mellitus. We evaluated the performance of Lucica Glycated Albumin-L, a new GA assay that is traceable to standard reference materials and determined the reference range in healthy subjects without diabetes.

METHODS

The performance and reference range studies were conducted in accordance with Clinical and Laboratory Standards Institute (CLSI) Guidelines. The traceability was established using reference material recommended by the Japan Society of Clinical Chemistry (JSCC).

RESULTS

The coefficient of variation (CV) of overall repeatability, within-laboratory precision, and overall reproducibility values of GA values were not more than 2.6%, 3.3%, and 1.6%, respectively, among laboratories. The GA values showed good linearity from 173 to 979 mmol/mol (9.4%-54.9%) across the assay range. The GA reference range in 262 healthy subjects was between 183 and 259 mmol/mol (9.9%-14.2%) while that of subjects with diabetes was 217-585 mmol/mol (11.8-32.6%). The reagent was stable for 2 months on the bench at room temperature. The limits of blank, detection, and qualification were 6.9, 7.9, and 9.7 μmol/L for GA concentration, and 3.8, 7.0, and 21.8 μmol/L for albumin concentration, respectively. Hemoglobin slightly affected the assay, while other classical interfering substances had no significant impact.

CONCLUSIONS

The present GA assay shows comparable performance to current clinical assays and could be used for intermediate-term monitoring of glycemic control in diabetes patients.

Prognostic implication of serum glycated albumin for patients with non-ST-segment elevation acute coronary syndrome undergoing percutaneous coronary intervention

Background

It has been demonstrated that glycated albumin (GA) is significantly associated with diabetes complications and mortality. However, among patients diagnosed with non-ST-elevation acute coronary syndrome (NSTE-ACS) administered percutaneous coronary intervention (PCI), the predictive value of GA for poor prognosis is unclear.

Methods

This study eventually included 2247 NSTE-ACS patients in Beijing Anzhen Hospital, Capital Medical University in January-December 2015 who received PCI. All patients were followed up until death or for 48 months post-discharge. The primary endpoint was major adverse cardio-cerebral events (MACCEs), including all-cause death, non-fatal myocardial infarction, ischemia-induced revascularization and non-fatal ischemic stroke.

Results

In total, 547 (24.3%) MACCEs were recorded during the follow-up period. Upon adjusting for potential confounders, GA remained an important risk predictor of MACCEs (As nominal variate: hazard ratio [HR] 1.527, 95% confidence interval [CI] 1.236–1.886, P < 0.001; As continuous variate: HR 1.053, 95% CI 1.027–1.079, P < 0.001). GA addition significantly enhanced the predictive ability of the traditional risk model (Harrell’s C-index, GA vs. Baseline model, 0.694 vs. 0.684, comparison P = 0.002; continuous net reclassification improvement (continuous-NRI) 0.085, P = 0.053; integrated discrimination improvement (IDI) 0.007, P = 0.020).

Conclusion

GA is highly correlated with poor prognosis in NSTE-ACS patients undergoing PCI, suggesting that it may be a major predictive factor of adverse events among these individuals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01446-3.

Monitoring gestational diabetes at the point-of-care via dual glycated albumin lateral flow assays in conjunction with a handheld reader

A dual assay cartridge was developed and used in conjunction with a handheld reader for sensing % glycated albumin to monitor gestational diabetes at home.

Correlation between hyperglycemia and glycated albumin with retinopathy of prematurity

To determine the association between hyperglycemia, glycated albumin (GlyA) and retinopathy of prematurity (ROP). Prospective study of all infants under ROP screening from March 2017 to July 2019. All demographic, clinical and laboratory data were collected. Glucose was measured at birth and every 8 h for the first week and serum GlyA was evaluated at birth, 1st, 2nd and 4th weeks after birth. Reference range for GlyA was obtained. Univariate logistic regression was used to examine risk factors for ROP followed by multivariate regression. A total of 152 infants were included in the study. Median gestational age was 30 weeks and median birth weight 1240 g. Thirty-three infants (21.7%) had ROP. Hyperglycemia was present in 24 (72.7%) infants diagnosed with any ROP versus 6 (0.05%) in those without ROP. Median GlyA at birth, 1st, 2nd and 4th and respective reference ranges were 8.50% (6.00-12.65), 8.20% (5.32-11.67), 8.00% (5.32-10.00) and 7.90% (5.30-9.00) respectively. After multivariate logistic regression, hyperglycemia but not GlyA, remained a significant risk factor for ROP overpowering the other recognized risk factors (Exp (B) 28.062, 95% CI for Exp(B) 7.881-99.924 p < 0.001). In our cohort, hyperglycemia but not GlyA, remained a significant risk factor for ROP overpowering the other recognized risk factors.

Glycated albumin as a biomarker for diagnosis of diabetes mellitus: A systematic review and meta-analysis

BACKGROUND

Glycated albumin (GA), the non-enzymatic glycation product of albumin in plasma, became a glycemic marker in the beginning of the 21st century. The assay is not affected by hemoglobin levels and reflects the glycemic status over a shorter period as compared to HbA1c measurements. Thus, GA may contributes as an intermediate glucose index in the current diabetes mellitus (DM) diagnostic system.

AIM

To search and summarize the available data on glycated albumin measurements required for the diagnosis of diabetes mellitus.

METHODS

Databases, including PubMed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials (CENTRAL), among others, were systematically searched. The Quality Assessment of Diagnostic Accuracy Studies-2 tool was applied for the assessment of quality, and the bivariate model was used to pool the sensitivity and specificity. The hierarchical summary receiver operator characteristic curves (HSROC) model was utilized to estimate the summary receiver operating characteristics curve (SROC). Sensitivity analysis was performed to investigate the association of the study design and patient characteristics with the test accuracy and meta-regression to find the source of heterogeneity.

RESULTS

Three studies regarding gestational diabetes mellitus (GDM) and a meta-analysis of 16 non-GDM studies, comprising a total sample size of 12876, were included in the work. Results reveal that the average cut-off values of GA reported for the diagnosis of GDM diagnosis was much lower than those for non-GDM. For non-GDM cases, diagnosing DM with a circulating GA cut-off of 14.0% had a sensitivity of 0.766 (95%CI: 0.539, 0.901), specificity of 0.687 (95%CI: 0.364, 0.894), and area under the curve of 0.80 (95%CI: 0.76, 0.83) for the SROC. The estimated SROC at different GA cut-off values for non-GDM exhibited that the average location parameter lambda of 16 non-GDM studies was 2.354 (95%CI: 2.002, 2.707), and the scale parameter beta was -0.163 (95%CI: -0.614, 0.288). These non-GDM studies with various thresholds had substantial heterogeneity, which may be attributed to the type of DM, age, and body mass index as possible sources.

CONCLUSION

Glycated albumin in non-DM exhibits a moderate diagnostic accuracy. Further research on the diagnostic accuracy of GA for GDM and combinational measurements of GA and other assays is suggested.

Factors associated with glycated albumin in adults without diabetes

Background and aims

Glycated albumin is a glycemic marker useful in short-term monitoring and in situations when a glycated hemoglobin test is not reliable. This study aims to evaluate glycated albumin levels and its associated factors in normoglycemic adults from Southern Brazil.

Method

136 individuals, without diabetes or pre-diabetes, were included in this cross-sectional study. Levels of glycated albumin, glycated hemoglobin, and other biochemical markers were measured.

Results

Glycated albumin levels ranged from 11.1% to 17.5% (2.5^th and 97.5^th percentiles). Glycated albumin/glycated hemoglobin ratio was 2.8±0.2. Glycated albumin did not differ according to gender and age groups. However, in overweight individuals, levels of glycated albumin and glycated albumin/glycated hemoglobin ratio were lower and weakly and negatively correlated with body mass index.

Conclusions

Glycated albumin levels in Brazilians were similar to those previously described in other populations. Glycated albumin seems to be irrespective of gender or age, but weakly correlated with weight. These aspects should be taken into account in the interpretation of glycated albumin results.

The effect of ambient ozone on glucose-homoeostasis: A prospective study of non-diabetic older adults in Beijing

OBJECTIVE

To investigate potential effects of short- and medium-term exposure to low levels of ozone (O3) on glucose-homeostasis in non-diabetic older adults.

METHODS

166 non-diabetic, older participants in Beijing were deemed eligible to partake in this longitudinal population-based study. Observations were recorded on three separate occasions from November 2016 up until January 2018. Concentrations of outdoor O3 were monitored throughout the study period. Biomarkers indicative of glucose-homeostasis, including fasting blood glucose, insulin, HbAlc, glycated albumin percentage (glycated albumin/albumin), HOMA-IR and HOMA-B were measured at 3 sessions. A linear mixed effects model with random effects was adopted to quantify the effect of O3 across a comprehensive set of glucose-homeostasis markers.

RESULTS

Short-term O3 exposure positively associated with increased fasting blood glucose, insulin, HOMA-IR and HOMA-B. The effect on glucose occurred at 3-, 5-, 6- and 7-days, although the largest effect manifested on 6-days (5.6%, 95% CI: 1.4, 9.9). Significant associations with both insulin and HOMA-IR were observed on the 3- and 4-days. For HOMA-B, positive associations were identified from 3- to 7-days with estimates ranging from 40.0% (95% CI: 2.3, 91.5) to 83.1% (95% CI: 25.3, 167.5). Stratification suggests that women may be more susceptible to short-term O3 exposure. There does not appear to be a significant association between O3 and glucose-homeostasis in medium-term exposures.

CONCLUSIONS

In this study, we found that O3 exposure is at least partially associated with type II diabetes in older adults with no prior history of this condition. O3 therefore appears to be a potential risk factor, which is a particular concern when we consider the rise in global concentrations. Evidence also suggests that women may be more susceptible to short-term O3 exposure although we are not quite sure why. Future research may look to investigate this phenomenon further.

Glycated Hemoglobin and Methods for Its Point of Care Testing

Glycated hemoglobin (HbA1c) is a product of the spontaneous reaction between hemoglobin and elevated glucose levels in the blood. It is included among the so-called advanced glycation end products, of which is the most important for the clinical diagnosis of diabetes mellitus, and it can serve as an alternative to glycemia measurement. Compared to the diagnosis of diabetes mellitus by glycemia, the HbA1c level is less influenced by a short-term problem with diabetes compensation. Mass spectroscopy and chromatographic techniques are among the standard methods of HbA1c level measurement. Compared to glycemia measurement, there is lack of simple methods for diabetes mellitus diagnosis by means of the HbA1c assay using a point-of-care test. This review article is focused on the surveying of facts about HbA1c and its importance in diabetes mellitus diagnosis, and surveying standard methods and new methods suitable for the HbA1c assay under point-of-care conditions. Various bioassays and biosensors are mentioned and their specifications are discussed.

Development of an Interdigitated Electrode-Based Disposable Enzyme Sensor Strip for Glycated Albumin Measurement

Glycated albumin (GA) is an important glycemic control marker for diabetes mellitus. This study aimed to develop a highly sensitive disposable enzyme sensor strip for GA measurement by using an interdigitated electrode (IDE) as an electrode platform. The superior characteristics of IDE were demonstrated using one microelectrode of the IDE pair as the working electrode (WE) and the other as the counter electrode, and by measuring ferrocyanide/ferricyanide redox couple. The oxidation current was immediately reached at the steady state when the oxidation potential was applied to the WE. Then, an IDE enzyme sensor strip for GA measurement was prepared. The measurement of fructosyl lysine, the protease digestion product of GA, exhibited a high, steady current immediately after potential application, revealing the highly reproducible measurement. The sensitivity (2.8 nA µM⁻¹) and the limit of detection (1.2 µM) obtained with IDE enzyme sensor strip were superior compared with our previously reported sensor using screen printed electrode. Two GA samples, 15 or 30% GA, corresponding to healthy and diabetic levels, respectively, were measured after protease digestion with high resolution. This study demonstrated that the application of an IDE will realize the development of highly sensitive disposable-type amperometric enzyme sensors with high reproducibility.

Estimation of the hemoglobin glycation rate constant

In a previous study, a method of obtaining mean erythrocyte age ([Formula: see text]) from HbA1c and average plasma glucose (AG) was proposed. However, the true value of the hemoglobin glycation constant ([Formula: see text] dL/mg/day), required for this model has yet to be well characterized. Another study also proposed a method of deriving [Formula: see text] from erythrocyte creatine (EC). Utilizing these formulae, this study aimed to determine a more accurate estimate of [Formula: see text]. One hundred and seven subjects including 31 patients with hemolytic anemia and 76 subjects without anemia were included in this study. EC and HbA1c data were analyzed, and [Formula: see text] using HbA1c, AG and the newly-derived constant, [Formula: see text] were compared to [Formula: see text] using traditional [Formula: see text] in three patients whose data were taken from previous case studies. A value of [Formula: see text] dL/mg/day was determined for [Formula: see text]. [Formula: see text] using HbA1c, AG and [Formula: see text] were found to no be significantly different (paired t-test, [Formula: see text]) to [Formula: see text] using traditional [Formula: see text]. [Formula: see text] enables the estimation of [Formula: see text] from HbA1c and AG.

Dansyl–NA3 conjugates for glycoprotein detection through fluorescent tagging and native gel electrophoresis

An aldehyde-reactive fluorophore has been prepared that can afford the fluorescent detection of serum glycoproteins by native gel electrophoresis.

Soluble Receptor for Advanced Glycation End Products and Its Forms in COVID-19 Patients with and without Diabetes Mellitus: A Pilot Study on Their Role as Disease Biomarkers

The receptor for advanced glycation end products (RAGE), a well-known player of diabetes mellitus (DM)-related morbidities, was supposed to be involved in coronavirus disease-19 (COVID-19), but no data exist about COVID-19, DM, and the soluble RAGE (sRAGE) forms. We quantified total sRAGE and its forms, the endogenously secretory esRAGE and the membrane-cleaved cRAGE, in COVID-19 patients with and without DM and in healthy individuals to explore how COVID-19 may affect these molecules and their potential role as biomarkers. Circulating sRAGE and esRAGE were quantified by enzyme-linked-immunosorbent assays. cRAGE was obtained by subtracting esRAGE from total sRAGE. sRAGE, esRAGE, cRAGE, and the cRAGE/esRAGE ratio did not differ between DM and non-DM patients and had the same trend when compared to healthy individuals. Levels of total sRAGE, cRAGE, and cRAGE/esRAGE ratio were upregulated, while esRAGE was downregulated. The lack of difference between DM and non-DM COVID-19 patients in the levels of sRAGE and its forms supports the hypothesis that in COVID-19 the RAGE system is modulated regardless of glycemic control. Identifying how sRAGE and its forms associate to COVID-19 prognosis and the potential of RAGE as a therapeutic target to control inflammatory burden seem of relevance to help treatment of COVID-19.

Nanoselenium effect on growth performance, carcass traits, antioxidant activity, and immune status of broilers

A 42-day comparative study was conducted to assess the impact of nanoselenium to other selenium sources on performance, antioxidant activity, immunity, and carcass traits in broilers. Ross 308 (n = 156) 1-day-old broiler chicks, with average initial body weight of 45.80 ± 0.35, were randomly allocated to 4 groups. The first group (G1) fed the basal diet without selenium supplementation. The second group (G2), the third group (G3), and the fourth group (G4) were supplemented with dietary selenium at the level of 0.3 mg kg^-1 diet in the form of sodium selenite, seleno-methionine, and nanoselenium, respectively. The results revealed significant improvement on most of the performance parameters of nanoselenium at the level of 0.3 mg kg^-1 diet (P < 0.05). Nanoselenium and seleno-methionine achieved the best dressing %, spleen index %, and thymus index %. Concerning to internal organ indices, none of these indices was significantly affected by any selenium sources (P < 0.05). Glutathione peroxidase (GSH-PX) activity and malondialdehyde (MDA) content were not significantly affected by different selenium sources among all experimental groups. Serum interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) showed significant (P < 0.05) decrease in nanoselenium supplemented group compared with other groups. In case of serum IL-10 level, a significant (P < 0.05) increase was reported in nanoselenium supplemented group followed by G3 then G2. There were no statistical differences in the serum alanine transaminase, aspartate transaminase, total protein, albumin concentration, serum creatinine level, and uric acid concentration levels among all experimental groups. It is concluded that nano selenium can be a useful and better source of selenium for broilers.

Electrochemical Immunoassay for Determination of Glycated Albumin using Nanozymes

We developed a new nanozyme-based electrochemical immunoassay method for the monitoring of glycated albumin (GA) known to reflect short-term glycaemic levels. For this study, we synthesized urchin-like Pt nanozymes (uPtNZs) and applied them to colorimetric and electrochemical assays for sensitive determination of GA in total human serum albumin (tHSA) using 3,3',5,5'-tetramethylbenzidine (TMB) and thionine as substrates, respectively. The uPtNZs showed peroxidase-mimic activity in the presence of hydrogen peroxide. Boronic acid (BA)-agarose bead was used to capture GA through specific cis-diol interactions. uPtNZs were modified with GA antibody (GA-Ab) to form sandwich complexes with GA/BA-agarose bead. The amount of Ab-uPtNZ/GA/BA-agarose bead complex increased with increasing percentage of GA in 50 mg/mL tHSA. The colorimetric assay exhibited linearity from 0.02 to 10% (10 µg/mL - 5 mg/mL) GA with an LOD of 0.02% (9.2 µg/mL). For electrochemical assay, GA was detected from 0.01 to 20% (5 µg/mL - 10 mg/mL) with an LOD of 0.008% (3.8 µg/mL). The recovery values of measured GA in human plasma samples were from 106 to 107%. These results indicate that electrochemical assay using uPtNZs is a promising method for determining GA.

Critical discrepancy in blood glucose control levels evaluated by glycated albumin and estimated hemoglobin A1c levels determined from a flash continuous glucose monitoring system in patients with type 2 diabetes on hemodialysis

We aimed to investigate if estimated hemoglobin A1c (eHbA1c) levels determined using a flash continuous glucose monitoring system could be an indicator of glycemic control status in hemodialysis patients with diabetes. Hemodialysis patients with type 2 diabetes were recruited. eHbA1c levels were measured using the FreeStyle Libre Flash Glucose Monitoring System^®. A total of 18 hemodialysis patients with diabetes were included in the study. The eHbA1c^GA – calculated based on glycated albumin level, and body mass index and serum hemoglobin concentration were also included in the formula – was higher than the eHbA1c in most patients. Furthermore, the eHbA1c^GA – eHbA1c values were >2% in all patients with body mass index <18.5 kg/m²; the maximal value was 4.1%. This study shows that eHbA1c can be used as a reliable indicator for evaluating glycemic control and avoiding hypoglycemia in hemodialysis patients with diabetes, particularly those with decreased body mass index.

Individualized Correction of the Interference of Hemolysis on Glycated Albumin Determined by the Ketamine Oxidase Method

OBJECTIVE

To investigate the effect of hemolysis on glycated albumin (GA) levels, as determined by the ketamine oxidase method.

METHODS

GA levels and the hemolysis index were determined in nonhemolyzed serum and hemolyzed serum from corresponding patients. We developed an equation to correct the interference of hemolysis on GA, using multiple regression analysis.

RESULTS

The degree of hemolysis was negatively correlated with GA levels (R2 = 0.9500). A correction equation for GA (corrected GA = 2.703 × OD of hemolysis + 1.044 × measured GA -0.906) can revert GA concentrations of hemolyzed specimens to values that were not significantly different from the GA concentration of corresponding nonhemolyzed specimens. The bias of GA concentrations before and after correction was statistically significantly different (P <.01).

CONCLUSIONS

Our results indicate that the level of GA measured through the ketamine oxidase method is negatively affected by hemolysis. The individualized correction of GA results provides increased accuracy in hemolyzed specimens.

Glycation ratio determination through simultaneous detection of human serum albumin and glycated albumin on an advanced lateral flow immunoassay sensor

Glycated albumin synthesized in a non-enzymatic reaction with high glucose levels in human plasma is a long-term biomarker for understanding average glucose levels over the past few weeks. Glycated albumin level determination requires an enzymatic assay involving an expensive, complicated, and laborious process, including the specific hydrolysis of albumin and the oxidation of glycated amino acids. In this study, we developed two advanced lateral flow immunoassays (LFIAs) for the simultaneous determination of total human serum albumin and glycated albumin concentrations using a colorimetric signal. Additionally, through a sequential reaction on our advanced LFIA, the selectivity of glycated albumin was improved. We quantified both HSA and GA with wide detection ranges of 1 ng mL^-1-1 mg mL^-1 and 0.5 μg mL^-1-3.6 mg mL^-1, respectively. Various serum samples with different glycation ratios were analyzed using this sensor and demonstrated a reasonable recovery range. This indicated that our platform could directly determinate the glycation ratio of various samples, and therefore, be applicable in point-of-care glucose status monitoring.

Circulating Irisin and esRAGE as Early Biomarkers of Decline of Metabolic Health

A decline in metabolic health may take place before observing any alteration in the levels of the traditional metabolic markers. New indicators of metabolic derangement are therefore compelling. Irisin is a myokine with important metabolic functions. The role of irisin as a metabolic biomarker in humans has not been fully established yet. We quantified plasma irisin and esRAGE in 106 apparently healthy individuals and we performed a cluster analysis to evaluate their associations with metabolic profile. Plasma levels of various traditional markers of metabolic risk (i.e., glucose and lipid levels) were all within the ranges of normality. We identified two clusters of individuals. Compared to cluster 2, individuals in cluster 1 had higher irisin levels, a metabolic profile shifted toward the limits of the reference ranges and lower esRAGE levels. The traditional metabolic blood tests seem not to be enough to identify a metabolic decline early. Irisin increase and esRAGE decrease may reflect a metabolic derangement at the beginning of its development. The role of these molecules as early biomarkers of decline of metabolic health seems an interesting topic to be further explored.

Modification of reduced graphene/Au-aptamer to develop an electrochemical based aptasensor for measurement of glycated albumin

Herein, an electrochemical label-free biosensor designed for the detection of glycated albumin (GA) using reduced graphene oxide/Au nanoparticles (RGO/AuNPs) modified by anti-GA aptamer. For fast and simple modification of the electrode, the aptamer chain was thiolated. Transition electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) techniques were used to the characterization of synthesized materials. Structural analysis of nanomaterials shows that graphene sheets were synthesized very fine by average thickness of 2.5 nm and Au nanoparticles distributed on the surface of graphene sheets uniformly. Cyclic voltammetry (CV) square wave voltammetry (SWV) and impedance spectroscopy (EIS) were used to electrochemical study of the decorated electrode. Electrochemical studies described the potential of fabricated rGO/AuNPs-aptamer electrode to selectively determine GA properly in buffer solution at the range of 2-10 μg mL^-1 by the detection limit of 0.07 μg. mL^-1 for GA.

Inverse association of fat mass, but not lean mass, with glycated albumin in hemodialysis patients with or without diabetes mellitus

Background: Glycated albumin (GA), which is independent of anemia and/or use of erythropoiesis-stimulating agents, might provide a more precise measure than glycated hemoglobin (HbA1c) in hemodialysis patients. The present study examines whether body composition is associated with GA besides glycemic control in hemodialysis patients.

Methods: This study included 90 hemodialysis patients with diabetes mellitus (DM) and 86 hemodialysis patients without DM. We examined blood parameters after an overnight fast and body fat and lean mass using dual X-ray absorptiometry 21–24 h after completing the dialysis session.

Results: The mean body mass index (BMI) was 22.0 kg/m². BMI and truncal fat mass were significantly higher, and total fat mass tended to be higher in hemodialysis patients with DM than in those without DM. GA exhibited inverse correlations with BMI, total lean mass, total fat mass, and truncal fat mass in hemodialysis patients with and without DM; however, there was a lack of correlation with total lean mass in patients without DM. In multiple regression analysis including total fat mass and total lean mass simultaneously as independent variables, total fat mass (with DM: β = –0.322, p = .006) (without DM: β = –0.391, p < .001), but not total lean mass, in addition to log fasting plasma glucose, emerged as an independent factor associated with GA in hemodialysis patients with and without DM. When total fat mass was replaced with truncal fat mass (with DM: β = –0.311, p = .007) (without DM: β = –0.396, p < .001), the association remained significant and independent with GA in both patient groups.

Conclusions: Higher total fat mass, particularly truncal fat mass, might be associated with lower GA levels, beside glycemic control, in hemodialysis patients with or without DM.

HbA1c adjusted by erythrocyte creatine is a useful glycemic control indicator in patients with hemolysis

OBJECTIVES

HbA1c shows low in patients with hemolysis, whereas glycated albumin (GA) is not affected by hemolysis. Therefore, the GA/HbA1c ratio reflects hemolysis in diabetic patients with hemolysis. Erythrocyte creatine (EC) is an indicator of hemolysis that reflects the mean erythrocyte age. The aim of this study was to examine whether HbA1c adjusted by EC accurately reflected glycemic control in patients with hemolysis.

MATERIALS AND METHODS

A total of 238 individuals, consisting of 131 diabetic patients and 107 non-diabetic subjects, and consisting of 42 patients with hemolysis, and 196 subjects without hemolysis were selected for the study. HbA1c expressed in the IFCC units (iA1c) as well as in the NGSP units (A1C) were used. From the fact that EC and the GA/iA1c ratio showed a significant positive correlation, a formula for iA1c adjusted by EC (ECadj-iA1c) was created from a regression equation between EC and the GA/iA1c ratio.

RESULTS

Significant correlations were observed between the GA/iA1c ratio and various hemolytic indicators but not between the GA/ECadj-iA1c ratio and those hemolytic indicators. The GA/iA1c ratio in individuals with hemolysis was significantly higher than in individuals without hemolysis, while no significant differences were observed in the GA/ECadj-iA1c ratio between the groups. Further, iA1c concentrations in non-diabetic patients with hemolysis were significantly lower than in the non-diabetic subjects without hemolysis, whereas ECadj-iA1c and GA concentrations showed no significant difference between the two groups.

CONCLUSIONS

These results suggested that ECadj-iA1c accurately reflected glycemic control in patients with hemolysis.

Hemolysis causes a decrease in HbA1c level but not in glycated albumin or 1,5-anhydroglucitol level

HbA1c has been widely used as a glycemic control indicator or as a diagnostic indicator for diabetes mellitus. However, HbA1c is affected by the erythrocyte life span and, therefore, shows falsely low values in hemolytic patients. Erythrocyte creatine (EC) is a sensitive hemolytic marker that reflects the mean erythrocyte age. In the present study, the relationships of HbA1c, glycated albumin (GA), and 1,5-anhydroglucitol (1,5-AG) with different hemolytic markers, including EC, were investigated in non-diabetic individuals. A total of 43 non-diabetic individuals whose complete blood count and reticulocytes were measured via medical examinations were included in this study (28 individuals with hemolysis and 15 individuals without hemolysis). Those with suspected diabetes mellitus based on medical history, low 1,5-AG values, or had comorbid liver and renal diseases were excluded from this study. HbA1c, GA, 1,5-AG, and various hemolytic markers were measured to examine the correlation of the glycemic control indicators with the various hemolytic markers. A significant correlation was observed between GA and 1,5-AG but not between HbA1c and GA or 1,5-AG. Significant correlations were observed between HbA1c values and various hemolytic markers (reticulocytes, haptoglobin, and EC) but not between GA or 1,5-AG values and those hemolytic markers. HbA1c, but not with GA and 1,5-AG, showed significant correlations with the hemolytic markers. These results suggested that HbA1c does not reflect the glycemic control accurately in hemolytic patients, while GA and 1,5-AG values are not affected by mean erythrocyte age and, therefore, accurately reflect the glycemic control.

Multiple Glycation Sites in Blood Plasma Proteins as an Integrated Biomarker of Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is one of the most widely spread metabolic diseases. Because of its asymptomatic onset and slow development, early diagnosis and adequate glycaemic control are the prerequisites for successful T2DM therapy. In this context, individual amino acid residues might be sensitive indicators of alterations in blood glycation levels. Moreover, due to a large variation in the half-life times of plasma proteins, a generalized biomarker, based on multiple glycation sites, might provide comprehensive control of the glycemic status across any desired time span. Therefore, here, we address the patterns of glycation sites in highly-abundant blood plasma proteins of T2DM patients and corresponding age- and gender-matched controls by comprehensive liquid chromatography-mass spectrometry (LC-MS). The analysis revealed 42 lysyl residues, significantly upregulated under hyperglycemic conditions. Thereby, for 32 glycation sites, biomarker behavior was demonstrated here for the first time. The differentially glycated lysines represented nine plasma proteins with half-lives from 2 to 21 days, giving access to an integrated biomarker based on multiple protein-specific Amadori peptides. The validation of this biomarker relied on linear discriminant analysis (LDA) with random sub-sampling of the training set and leave-one-out cross-validation (LOOCV), which resulted in an accuracy, specificity, and sensitivity of 92%, 100%, and 85%, respectively.

Glycated serum proteins: High in pancreatic cancer and low in preeclampsia

Glycated serum protein (GSP, measured as serum fructosamine concentration in μmol/L) is a product of glycation reaction between glucose and serum proteins in the blood circulation. GSP is used along with blood glucose, glycated hemoglobin (HbA1c), and glycated albumin as indicators of glycemic control for diabetic patients. However, a systematic comparison of the GSP levels in different types of human diseases has not been reported. In this study, 62,698 clinical lab test results of GSP levels in patients with 61 clinically defined diseases over the past 5 years in our hospital were retrieved and compared to that of 1861 clinical lab test results in healthy individuals. Based on the mean (SD), median, and p (-Log₁₀p) values, we found that patients with type 2 diabetes, hepatic encephalopathy, pancreatic cancer, healthy individuals >65 years old, and cerebral arteriosclerosis had significantly (p<0.05, -Log₁₀p>1.30) increased whereas patients with 49/61 diseases including preeclampsia, nephrotic syndrome, sepsis, lupus erythematous, and leukemia had significantly decreased GSP levels compared to that of healthy controls. Among the 61 diseases, type 2 diabetes and leukemia had the highest -Log₁₀p values (>274) and lupus erythematous, nephrotic syndrome, and gastric cancer had -Log₁₀p values >140. Revealing the molecular mechanisms especially those underlying the decreased GSP levels in most of human diseases might make GSP levels serve more clinical purposes in future.

Usefulness of hemoglobin A1c and glycated albumin measurements for insulinoma screening: an observational case-control study

Background

Insulinoma represents hypoglycemia as a predominant symptom; the autonomic symptoms may be resolved by chronically recurrent hypoglycemia resulting in the persistence of non-specific symptoms alone. Therefore, it has been estimated that there are many patients in whom the disease takes longer to diagnose and has remained undiagnosed. Although some parameters exist for the definitive diagnosis of the disease, there are currently no indices for early screening. Indices of glycemic control, hemoglobin A1c (HbA1c), and glycated albumin (GA) may be useful for the screening of patients with insulinoma having chronic hypoglycemia because the values become low in such a condition. Because there are no articles that have reported the point, we examine the effective cutoff values of HbA1c and GA for the diagnosis of insulinoma in the present study.

Methods

In a multicenter cross-sectional study, 31 patients with insulinoma were included for comparison with 120 control subjects with normal glucose tolerance based on 75 g oral glucose tolerance tests whose characteristics were matched to the patients. The primary outcomes were optimal cutoff values of HbA1c and GA for the screening of insulinoma.

Results

HbA1c was significantly lower in the insulinoma group at 4.7 ± 0.4% compared to the healthy control group at 5.7 ± 0.3% (p < 0.001), and GA was significantly lower in the insulinoma group at 11.6 ± 1.8% compared to the healthy control group at 14.5 ± 1.0% (p < 0.001). According to a receiver operating characteristic (ROC) analysis, optimal cutoff values of HbA1c and GA for the diagnosis of insulinoma were 5.0 and 12.4%, respectively. Area under the curve values of HbA1c and GA were 0.970 and 0.929, respectively, showing no significant difference (p = 0.399).

Conclusions

In the present study, HbA1c and GA values in patients with insulinoma were significantly lower compared to the healthy controls, and effective cutoff values for screening were shown in the diagnosis of insulinoma for the first time. HbA1c and GA can be useful indices for insulinoma screening. Because malignant insulinoma have a similar diagnostic process to that of benign insulinoma, these could be useful for malignant insulinoma.

Update on biomarkers of glycemic control

Attaining and maintaining good glycemic control is a cornerstone of diabetes care. The monitoring of glycemic control is currently based on the self-monitoring of blood glucose (SMBG) and laboratory testing for hemoglobin A1c (HbA1c), which is a surrogate biochemical marker of the average glycemia level over the previous 2-3 mo period. Although hyperglycemia is a key biochemical feature of diabetes, both the level of and exposure to high glucose, as well as glycemic variability, contribute to the pathogenesis of diabetic complications and follow different patterns in type 1 and type 2 diabetes. HbA1c provides a valuable, standardized and evidence-based parameter that is relevant for clinical decision making, but several biological and analytical confounders limit its accuracy in reflecting true glycemia. It has become apparent in recent years that other glycated proteins such as fructosamine, glycated albumin, and the nutritional monosaccharide 1,5-anhydroglucitol, as well as integrated measures from direct glucose testing by an SMBG/continuous glucose monitoring system, may provide valuable complementary data, particularly in circumstances when HbA1c results may be unreliable or are insufficient to assess the risk of adverse outcomes. Long-term associations of these alternative biomarkers of glycemia with the risk of complications need to be investigated in order to provide clinically relevant cut-off values and to validate their utility in diverse populations of diabetes patients.

Shortened mean erythrocyte age in female patients with type 2 diabetes mellitus

BACKGROUND

The hyperglycemic state is known to shorten the erythrocyte life span. Erythrocyte creatine (EC) reflects the mean erythrocyte age and is useful as an indicator of hemolysis. Here, we studied the relationship between EC and glycemic control indicators [HbA1c or glycated albumin (GA)] in non-diabetic subjects and diabetic patients.

METHODS

This study included 119 patients with type 2 diabetes mellitus (T2DM) and 76 non-diabetic subjects matched by sex and age. We studied the relationships between EC and HbA1c or GA in patients with T2DM and non-diabetic subjects.

RESULTS

Erythrocyte creatine in T2DM patients was significantly higher than that in non-diabetic subjects, and the ratio of high EC levels (>1.8 μmol/g Hb) in T2DM patients was significantly higher as well. Furthermore, female EC was significantly higher than male EC, and the ratio of high EC levels in females was significantly higher than in the males as well. While male EC had no significant correlation with HbA1c or GA, female EC had significant positive correlations with both. Male EC had no significant difference between T2DM patients and non-diabetic subjects, while the EC in female patients with T2DM was significantly higher than in female non-diabetic subjects.

CONCLUSIONS

The significant positive correlations of EC with HbA1c and GA in female patients with T2DM suggested that the mean erythrocyte age decreased in female diabetic patients with poor glycemic control.

Usefulness of glycated albumin as a biomarker for glucose control and prognostic factor in chronic kidney disease patients on dialysis (CKD-G5D)

In chronic kidney disease patients on dialysis (CKD-G5D) accurate assessment of glycemic control is vital to improve their outcome and survival. The best glycemic marker for glucose control in these patients is still debated because several clinical and pharmacological factors may affect the ability of the available biomarkers to reflect the patient's glycemic status properly. This review discusses the role of glycated albumin (GA) both as a biomarker for glucose control and as a prognostic factor in CKD-G5D; it also looks at the pros and cons of GA in comparison to the other markers and its usefulness in hemodialysis and peritoneal dialysis.