Distinct biomarker roles for HbA1c and glycated albumin in patients with type 2 diabetes on hemodialysis

Current updates on metabolites and its interlinked pathways as biomarkers for diabetic kidney disease: A systematic review

Diabetic kidney disease (DKD) is a major microvascular complication of diabetes mellitus (DM) that poses a serious risk as it can lead to end-stage renal disease (ESRD). DKD is linked to changes in the diversity, composition, and functionality of the microbiota present in the gastrointestinal tract. The interplay between the gut microbiota and the host organism is primarily facilitated by metabolites generated by microbial metabolic processes from both dietary substrates and endogenous host compounds. The production of numerous metabolites by the gut microbiota is a crucial factor in the pathogenesis of DKD. However, a comprehensive understanding of the precise mechanisms by which gut microbiota and its metabolites contribute to the onset and progression of DKD remains incomplete. This review will provide a summary of the current scenario of metabolites in DKD and the impact of these metabolites on DKD progression. We will discuss in detail the primary and gut-derived metabolites in DKD, and the mechanisms of the metabolites involved in DKD progression. Further, we will address the importance of metabolomics in helping identify potential DKD markers. Furthermore, the possible therapeutic interventions and research gaps will be highlighted.

Novel clinical relationships between time in range and microangiopathies in people with type 2 diabetes mellitus on hemodialysis

AIMS/HYPOTHESIS

We investigated associations among glucose time in range (TIR, 70-180 mg/dL), glycemic markers and prevalence of diabetic microangiopathy in people with diabetes undergoing hemodialysis (HD).

METHODS

A total of 107 people with type 2 diabetes undergoing HD (HbA_1c 6.4 %; glycated albumin [GA] 20.6 %) using continuous glucose monitoring were analyzed in this observational and cross-sectional study.

RESULTS

HbA_1c and GA levels significantly negatively correlated with TIR, and positively correlated with time rate of hyperglycemia, but not with time rate of hypoglycemia. TIR of 70 % corresponded to HbA_1c of 6.5 % and GA of 21.2 %. The estimated HbA_1c level corresponding to TIR of 70 % in this study was lower than that previously reported in people with diabetes without HD. The prevalence of diabetic neuropathy was not significantly different between people with TIR ≥ 70 % and those with TIR < 70 % (P = 0.1925), but the prevalence of diabetic retinopathy in people with TIR ≥ 70 % was significantly lower than in those with TIR < 70 % (P = 0.0071).

CONCLUSION/INTERPRETATION

TIR correlated with HbA_1c and GA levels in people with type 2 diabetes on HD. Additionally, a higher TIR resulted in a lower rate of diabetic retinopathy.

RESEARCH IN CONTEXT

What is already known about this subject? What is the key question? What are the new findings? How might this impact on clinical practice in the foreseeable future?

[Alternative strategies to the use of glycosylated hemoglobin in monitoring the glycemic status of diabetic patients with end-stage renal disease]

BACKGROUND

Diabetes mellitus (DM) is one of the leading causes of end-stage renal disease. Glycosylated hemoglobin (HbA1c) is the recommended glycemic marker to achieve an optimal glycemic control that is essential to prevent comorbidities associated with the disease. However, in patients on haemodialysis (HD) this marker has important limitations, this reason has led us to search alternative markers such as glycosylated albumin (AG), labile fraction of glycosylated hemoglobin (LHbA1c) or glycation indices.

PATIENTS AND METHODS

We enrolled 47 patients in HD, 23 with DM, obtaining samples for the determination of de AG, HbA1c y LHbA1c. Glycation indices, which allow estimated the HbA1c using glucose, AG or LHbA1c, were calculated including a control group composed of 75 diabetic patients without kidney disease.

RESULTS

Diabetic patients in HD had significantly higher mean values than patients without DM for glucose [160 (44) vs 96 (12)mg/dL], HbA1c [6,4 (1,0) vs 4,9 (0,3)%], AG [16,0 (5,1) vs 12,9 (1,6)%] and LHbA1c [2,0 (0,3) vs 1,7 (0,2)%]. HbA1c calculated using glycation indices was significantly higher than measured in all HD patients, regardless of the marker used for the estimation.

CONCLUSIONS

The glycemic markers evaluated (glucose, AG and LHbA1c), could reflect a possible underestimation of the real glycemic state by HbA1c because of the limitations of this marker in HD patients. The use of alternative markers, knowing their limitations, could improve the monitoring of patients on HD and, therefore, reduce the risk of developing DM2 complications.

Can the Use of Continuous Glucose Monitoring Improve Glycemic Control in Patients with Type 1 and 2 Diabetes Receiving Dialysis?

BACKGROUND

Hemoglobin A1c (HbA1c) is an unreliable glycemic marker in the dialysis population, and alternative methods of glycemic monitoring should be considered. Continuous glucose monitoring (CGM) measures interstitial glucose, an indirect measure of plasma glucose, and allows for estimating mean sensor glucose, glucose variability, and time in ranges. Thus, CGM provides a more nuanced picture of glycemic variables than HbA1c, which only informs about average glucose and not variation in glucose or hypoglycemia.

SUMMARY

In non-dialysis patients with type 1 and type 2 diabetes, CGM metrics are increasingly used to estimate glycemic control and are associated with improvements in glucose levels. Although a clear link has not yet been established between some CGM variables and the development of late diabetic complications, CGM use could be an important step forward in improving glycemic control in patients receiving dialysis. The ability to detect and prevent hypoglycemia while optimizing glucose levels could be particularly valuable. However, long-term CGM use has not been evaluated in the dialysis population, and the practical burden and cost associated with CGM use may be a limitation. We discuss the strengths and limitations of using CGM in the dialysis population with type 1 and type 2 diabetes.

KEY MESSAGES

CGM circumvents the pitfalls of HbA1c in dialysis patients and provides detailed measures of the mean sensor glucose, glucose variability, and time in ranges. Guidelines recommend a minimum of 50% time spent in the target range (3.9-10.0 mmol/L) and less than 1% below range (<3.9 mmol/L) for patients receiving dialysis but remain to be evaluated in the dialysis population. CGM can be a valuable tool in reducing overall glucose levels and variations while detecting hypoglycemia, but the practical burden of CGM use and cost may be a limitation.

Evaluation of the relationship between hemodialysis-related glycemic variability and hormonal profiles in patients with type 2 diabetes on hemodialysis: a pilot study

Background

The number of dialysis patients with diabetes is currently increasing in Japan and a similar proportion worldwide. It was suggested that approximately 20% of these patients had hypoglycemia after dialysis session and most of these hypoglycemia were unconscious. Furthermore, it was suggested that glucose variabilities induced by hemodialysis may be related to insulin and insulin-counter hormones, such as glucagon, adrenocorticotropic hormone (ACTH), and cortisol and growth hormone, but conclusive evidence has not still been obtained.

Methods

We investigated in detail the glucose and hormonal profiles in 7 patients with type 2 diabetes on hemodialysis (all male, HbA1c 6.8 ± 2.1%, glycated albumin 24.7 ± 10.2%). All participants were attached continuous glucose monitoring (iPro2®). Blood glucose level, C-peptide immunoreactivity, plasma glucagon, ACTH, cortisol and growth hormone were measured by 7 points blood tests at before breakfast, after breakfast (predialysis), 2 h and 4 h after starting dialysis, after lunch and before/after dinner on the dialysis day and 6 points at before/after each meal on the non-dialysis day, and these relationship with blood glucose dynamics were examined. The meal contents were set to the indicated energy amount, and the same menu was served daily for breakfast, lunch, and dinner on dialysis and non-dialysis days of this study period. In addition, the start time of lunch on non-dialysis day was the same as the start time of lunch on the dialysis day.

Results

Serum C-peptide level was significantly increased by taking breakfast and lunch on the hemodialysis day, significantly decreased during hemodialysis, and was significantly lower before and after lunch on the hemodialysis day than on the non-hemodialysis day. Plasma glucagon level significantly decreased during hemodialysis and that before lunch on hemodialysis day was significantly lower than on non-hemodialysis day. ACTH, cortisol, and growth hormone did not show any changes related to hemodialysis.

Conclusions

It was suggested that C-peptide and glucagon play an important role in hemodialysis-related glycemic variabilities in patients with type 2 diabetic hemodialysis.

Trial registration UMIN Clinical Trial Registry (Registration Number UMIN000018707). Registered 18 August 2015, https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi?function=brows&action=brows&type=summary&language=J&recptno=R000021647.

Predictive value of the glycated albumin versus glycosylated hemoglobin in follow-up of glucose homeostasis in hemodialysis-maintained type-2 diabetic patients

Objectives. Markers for glucose control in hemodialysis patients (HDP) are debated. Glycosylated hemoglobin (HbA1c%) relies on the stable red blood cell survival. Albumin turnover is faster than hemoglobin. Glycated albumin (GA%) may be used as an index of short-term glycemic control. The predictive value of GA% versus HbA1c% in monitoring the glucose homeostasis in type-2 diabetic HDP is studied. Methods. Forty type-2 diabetic HDP and 20 healthy non diabetic subjects matched age and sex as a control group were included. Calculation of body mass index and Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) and urea reduction ratio were done. Glycosylated hemoglobin, glycated albumin, fasting blood glucose, insulin, total lipid, kidney and liver functions tests, hepatitis markers, electrolytes, complete blood count, and international normalized ratio were performed. Patients were followed up after 6 months. Results. The study showed that GA% is more sensitive than HbA1c%, but less specific in the follow-up of the glucose homeostasis in type-2 diabetic HDP. Diagnostic accuracy is higher in HbA1c% than in GA%. HOMA-IR is superior regarding the sensitivity and the diagnostic accuracy. Conclusion. The present data show that GA% is more sensitive than HbA1c% and has more diagnostic accuracy in the follow-up of the glucose homeostasis in type-2 diabetic HDP.

Hemoglobin A1c and Fructosamine Evaluated in Patients with Type 2 Diabetes Receiving Peritoneal Dialysis Using Long-Term Continuous Glucose Monitoring

INTRODUCTION

Shortened erythrocyte life span and erythropoietin-stimulating agents may affect hemoglobin A1c (HbA1c) levels in patients receiving peritoneal dialysis (PD). We compared HbA1c with interstitial glucose measured by continuous glucose monitoring (CGM) in patients with type 2 diabetes receiving PD.

METHODS

Fourteen days of CGM (Ipro2, Medtronic) were performed in 23 patients with type 2 diabetes receiving PD and in 23 controls with type 2 diabetes and an estimated glomerular filtration rate over 60 mL/min/1.73 m2. Patients were matched on gender and age (±5 years). HbA1c (mmol/mol), its derived estimate of mean plasma glucose (eMPGA1c) (mmol/L), and fructosamine (µmol/L) were measured at the end of the CGM period and compared with the mean sensor glucose (mmol/L) from CGM.

RESULTS

In the PD group, mean sensor glucose was 0.98 (95% con-fidence interval (CI): 0.43-1.54) mmol/L higher than the eMPGA1c compared with the control group (p = 0.002) where glucose levels were nearly identical (-0.05 (95% CI: -0.35-0.25) mmol/L). A significant association was found between fructosamine and mean sensor glucose using linear regression with no difference between slopes (p = 0.89) or y-intercepts (p = 0.28).

DISCUSSION/CONCLUSION

HbA1c underestimates mean plasma glucose levels in patients with type 2 diabetes receiving PD. However, the clinical significance of this finding is undetermined. Fructosamine seems to more accurately reflect glycemic status. CGM or fructosamine could complement HbA1c to increase the accuracy of glycemic monitoring in the PD population.

The Accuracy of Hemoglobin A1c and Fructosamine Evaluated by Long-Term Continuous Glucose Monitoring in Patients with Type 2 Diabetes Undergoing Hemodialysis

INTRODUCTION

The accuracy of hemoglobin A1c (HbA1c) as a glycemic marker in patients with type 2 diabetes (T2D) receiving hemodialysis (HD) remains unknown. To assess accuracy, we compared HbA1c and fructosamine levels with interstitial glucose measured by continuous glucose monitoring (CGM) in patients with T2D receiving HD.

METHODS

Thirty patients in the HD group and 36 patients in the control group (T2D and an estimated glomerular filtration rate >60 mL/min/1.73 m2) completed the study period of 17 weeks. CGM (Ipro2®, Medtronic) was performed 5 times for periods of up to 7 days (with 4-week intervals) during a 16-week period. HbA1c (mmol/mol), the estimated mean plasma glucose from HbA1c (eMPGA1c [mmol/L]) and fructosamine (μmol/L) was measured at week 17 and compared with mean sensor glucose levels from CGM.

FINDINGS

In the HD group, mean sensor glucose was 1.4 mmol/L (95% confidence interval [CI]: 1.0-1.8) higher than the eMPGA1c, whereas the difference for controls was 0.1 mmol/L (95% CI: -0.1-[0.4]; p < 0.001). Adjusted for mean sensor glucose, HbA1c was lower in the HD group (-7.3 mmol/mol, 95% CI: -10.0-[-4.7]) than in the control group (p < 0.001), with no difference detected for fructosamine (p = 0.64).

DISCUSSION

HbA1c evaluated by CGM underestimates plasma glucose levels in patients receiving HD. The underestimation represents a clinical challenge in optimizing glycemic control in the HD population. Fructosamine is unaffected by the factors affecting HbA1c and appears to be more accurate for glycemic monitoring. CGM or fructosamine could thus complement HbA1c in obtaining more accurate glycemic control in this patient group.

A Novel Substrate-Inspired Fluorescence-Based Albumin Detection Improves Assessment of Clinical Outcomes in Hemodialysis Patients Receiving a Nursing Nutrition Intervention

Background

Albumin level does not precisely reflect nutritional status. We aimed to investigate the impact of a nutrition intervention on hemodialysis patients by use of fluorescence-based plasma albumin (FPA) detection.

Material/Methods

Eighty patients underwent maintenance hemodialysis for more than half a year and had a mean albumin <3.5 g/dL for over 3 months. The subjects were randomly divided into either a Control Group (CG) or an Intervention Group (IG). The IG received nutritional supplementation, and the CG group received routine nutritional support for 12 months. FPA and plasma albumin (PA) concentrations were measured. The fluorescence probe 1,3-Dichloro-7-hydroxy-9,9-dimethyl-2(9H)-acridone methyl biphenyl benzoate was used in FPA detection. Quality of life was estimated using WHOQOL-BREF (Quality of Life Scale developed through the World Health Organization), the 36-Item Short-Form Survey (SF-36), and the 6-minute walking test (6MWT).

Results

After a 6-month and a 12-month intervention, PA and FPA concentrations increased, and the increase in FPA concentration was higher than that of PA in the IG group (P<0.05). Comparatively, the parameters of quality of life and 6MWT were improved in the IG group (P<0.05) but there were only minor changes in the CG group (P>0.05). There is an obvious association between the changes in FPA concentration and the parameters of quality of life and 6MWT but not PA.

Conclusions

Use of the fluorescence probe improves the detection sensitivity of plasma albumin and provides a potential method to assess clinical outcomes in hemodialysis patients.

Flash Glucose Monitoring to Assess Glycemic Control and Variability in Hemodialysis Patients: The GIOTTO Study

Background: Flash glucose monitoring (FGM) is a technology with considerable differences compared to continuous glucose monitoring (CGM), but it has been scarcely studied in hemodialysis patients. Thus, we aimed assessing the performance of FGM in such patients by comparison to self-monitoring of blood glucose (SMBG). We will also focus on estimation of glycemic control and variability, and their relationships with parameters of glucose homeostasis.

Methods: Thirty-one patients (20 with type 2 diabetes, T2DM, 11 diabetes-free, NODM) collected readings by FGM and SMBG for about 12 days on average. Readings by FGM and SMBG were compared by linear regression, Clarke error grid, and Bland-Altman analyses. Several indices of glycemic control and variability were computed. Ten patients also underwent oral glucose tolerance test (OGTT) for assessment of insulin sensitivity/resistance and insulin secretion/beta-cell function.

Results: Flash glucose monitoring and SMBG readings showed very good agreement in both T2DM and NODM (on average, 97 and 99% of readings during hemodialysis in A+B Clarke regions, respectively). Some glycemic control and variability indices were similar by FGM and SMBG (p = 0.06–0.9), whereas others were different (p = 0.0001–0.03). The majority of control and variability indices were higher in T2DM than in NODM, according to both FGM and SMBG (p = 0.0005–0.03). OGTT-based insulin secretion was inversely related to some variability indices according to FGM (R < −0.72, p < 0.02).

Conclusions: Based on our dataset, FGM appeared acceptable for glucose monitoring in hemodialysis patients, though partial disagreement with SMBG in glycemic control/variability assessment needs further investigations.

Hemodialysis-Related Glycemic Disarray Proven by Continuous Glucose Monitoring; Glycemic Markers and Hypoglycemia

OBJECTIVE

There is a high risk of asymptomatic hypoglycemia associated with hemodialysis (HD) using glucose-free dialysate; therefore, the inclusion of glucose in the dialysate is believed to prevent intradialytic hypoglycemia. However, the exact glycemic fluctuation profiles and frequency of asymptomatic hypoglycemia using dialysates containing >100 mg/dL glucose have not been determined.

RESEARCH DESIGN AND METHODS

We evaluated the glycemic profiles of 98 patients, 68 of whom were men, with type 2 diabetes undergoing HD (HbA_1c 6.4 ± 1.2%; glycated albumin 20.8 ± 6.8%) with a dialysate containing 100, 125, or 150 mg/dL glucose using continuous glucose monitoring.

RESULTS

Sensor glucose level (SGL) showed a sustained decrease during HD, irrespective of the dialysate glucose concentration, and reached a nadir that was lower than the dialysate glucose concentration in 49 participants (50%). Twenty-one participants (21%) presented with HD-related hypoglycemia, defined by an SGL <70 mg/dL during HD and/or between the end of HD and their next meal. All these hypoglycemic episodes were asymptomatic. Measures of glycemic variability calculated using the SGL data (SD, coefficient of variation, and range of SGL) were higher and time below range (<70 mg/dL) was lower in participants who experienced HD-related hypoglycemia than in those who did not, whereas time in range between 70 and 180 mg/dL, time above range (>180 mg/dL), HbA_1c, and glycated albumin of the two groups were similar.

CONCLUSIONS

Despite the use of dialysate containing 100-150 mg/dL glucose, patients with diabetes undergoing HD experienced HD-related hypoglycemia unawareness frequently. SGL may fall well below the dialysate glucose concentration toward the end of HD.

Assessment of the accuracy of an intermittent-scanning continuous glucose monitoring device in patients with type 2 diabetes mellitus undergoing hemodialysis (AIDT2H) study

FreeStyle Libre has been approved for use in patients undergoing hemodialysis (HD) in Japan, unlike Europe and the United States; however, evidence regarding its accuracy in such patients is sparse. Forty‐one participants with type 2 diabetes undergoing HD were recruited. The overall mean absolute relative difference and mean absolute difference were 23.4% and 33.9 mg/dL, respectively. Sensor glucose levels and capillary glucose levels were significantly correlated (r = 0.858, P < .01), although the sensor glucose levels were significantly lower than the capillary glucose levels. The accuracy of FreeStyle Libre in patients undergoing HD became deteriorated with the days of usage. The percentage of sensor results in Zones A and B in the consensus error grid analysis and in the Clarke error grid analysis were 99.7% and 99.0%, respectively. Its insufficient accuracy necessitates adjunct usage of FreeStyle Libre with self‐monitoring of blood glucose in patients undergoing HD.

CGMS and Glycemic Variability, Relevance in Clinical Research to Evaluate Interventions in T2D, a Literature Review

Glycemic variability (GV) appears today as an integral component of glucose homeostasis for the management of type 2 diabetes (T2D). This review aims at investigating the use and relevance of GV parameters in interventional and observational studies for glucose control management in T2D. It will first focus on the relationships between GV parameters measured by continuous glucose monitoring system (CGMS) and glycemic control and T2D-associated complications markers. The second part will be dedicated to the analysis of GV parameters from CGMS as outcomes in interventional studies (pharmacological, nutritional, physical activity) aimed at improving glycemic control in patients with T2D. From 243 articles first identified, 63 articles were included (27 for the first part and 38 for the second part). For both analyses, the majority of the identified studies were pharmacological. Lifestyle studies (including nutritional and physical activity-based studies, N-AP) were poorly represented. Concerning the relationships of GV parameters with those for glycemic control and T2D related-complications, the standard deviation (SD), the coefficient of variation (CV), the mean blood glucose (MBG), and the mean amplitude of the glycemic excursions (MAGEs) were the most studied, showing strong relationships, in particular with HbA1c. Regarding the use and relevance of GV as an outcome in interventional studies, in pharmacological ones, SD, MAGE, MBG, and time in range (TIR) were the GV parameters used as main criteria in most studies, showing significant improvement after intervention, in parallel or not with glycemic control parameters' (HbA1c, FBG, and PPBG) improvement. In N-AP studies, the same results were observed for SD, MAGE, and TIR. Despite the small number of N-AP studies addressing both GV and glycemic control parameters compared to pharmacological ones, N-AP studies have shown promising results on GV parameters and would require more in-depth work. Evaluating CGMS-GV parameters as outcomes in interventional studies may provide a more integrative dimension of glucose control than the standard postprandial follow-up. GV appears to be a key component of T2D dysglycemia, and some parameters such as MAGE, SD, or TIR could be used routinely in addition to classical markers of glycemic control such as HbA1c, fasting, or postprandial glycemia.

Reduced erythrocyte lifespan measured by chromium-51 in patients with type 2 diabetes undergoing long-term hemodialysis

INTRODUCTION

A reduced erythrocyte lifespan potentially explains the low hemoglobin A1c values found in hemodialysis patients. However, data supporting this notion in patients with type 2 diabetes is unclear. We evaluated the erythrocyte lifespan in patients with type 2 diabetes undergoing long-term hemodialysis and investigated potential predictors of erythrocyte lifespan.

METHODS

Long-term hemodialysis patients with type 2 diabetes and type 2 diabetes patients without nephropathy (estimated glomerular filtration rate > 60 mL/min/1.73 m² ) were included. The erythrocyte lifespan was measured using chromium-51 (⁵¹ Cr)-labeled erythrocytes. Blood radiotracer activity was measured six to nine times over a period of 3-5 weeks to determine the erythrocyte lifespan of each patient. Biochemical markers were obtained five times over 16 weeks and associated with the erythrocyte lifespan.

FINDINGS

Type 2 diabetes patients undergoing hemodialysis (N = 13) had a significantly shorter median erythrocyte lifespan of 49.7 (interquartile range [IQR] = 44.1-58.6) days compared with 64.2 (IQR = 62.6-83.5) days in the control group (N = 10) (P ˂ 0.001) with a difference between medians of 14.5 (95% confidence interval = 8.1-38.8) days. In the hemodialysis group, no association could be detected between the erythrocyte lifespan and markers of hemolysis, level of inflammation, or urea.

DISCUSSION

A reduced erythrocyte lifespan was detected in type 2 diabetes patients undergoing long-term hemodialysis. This may contribute to the reduced hemoglobin A1c values observed in the type 2 diabetic hemodialysis population. An association could not be detected between the erythrocyte lifespan and biochemical markers of hemolysis or inflammation.

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.

Comparison of accuracy between flash glucose monitoring and continuous glucose monitoring in patients with type 2 diabetes mellitus undergoing hemodialysis

INTRODUCTION

We evaluated the accuracy and clinical utility of flash glucose monitoring (FGM) in comparison with continuous glucose monitoring (CGM) and self-monitoring blood glucose (SMBG) in patients with type 2 diabetes (T2D) undergoing hemodialysis (HD).

METHODS

Simultaneous FGM (FreeStyle LibrePro), CGM (iPro2) and SMBG were performed on 13 T2D research subjects.

RESULTS

There were good overall correlations between SMBG and FGM (64.7% and 30.8% within the A and B of Parkes Error Grid, respectively) and between SMBG and CGM (87.9% and 11.0% within the A and B, respectively). However, during HD, correlations between SMBG and FGM were only 49.7% and 37.2% within the A and B, respectively, while correlations of SMBG and CGM were 72.8% and 22.2% within the A and B, respectively. The percentage of FGM not in Zone A + B was more than 4 times higher than for CGM. The overall mean absolute relative difference (MARD) for FGM was 18.2%, this significantly higher than 11.2% for CGM. During HD, MARD for FGM was 22.8%, significantly higher than 15.0% for CGM.

CONCLUSION

FGM has good clinical agreement in T2D patients undergoing HD. However, the accuracy of FGM relative to SMBG was worse than that of CGM.

Continuous Glucose Monitoring and Use of Alternative Markers To Assess Glycemia in Chronic Kidney Disease

OBJECTIVE

In chronic kidney disease, glycated albumin and fructosamine have been postulated to be better biomarkers of glycemic control than HbA_1c. We evaluated the accuracy, variability, and covariate bias of three biomarkers (HbA_1c, glycated albumin, and fructosamine) compared with continuous glucose monitoring (CGM)-derived measurement of glycemia across estimated glomerular filtration rate (eGFR) in type 2 diabetes.

RESEARCH DESIGN AND METHODS

A prospective cohort study was conducted of 104 participants with type 2 diabetes, 80 with eGFR <60 mL/min/1.73 m² (not treated with dialysis) and 24 frequency-matched control subjects with eGFR ≥60 mL/min/1.73 m². Participants wore a blinded CGM for two 6-day periods separated by 2 weeks, with blood and urine collected at the end of each CGM period. HbA_1c, glycated albumin, and fructosamine were measured by high-performance liquid chromatographic, enzymatic, and colorimetric nitroblue tetrazolium methods, respectively.

RESULTS

Within-person biomarker values were strongly correlated between the two CGM periods (r = 0.92-0.95), although no marker fully captured the within-person variability of mean CGM glucose. All markers were similarly correlated with mean CGM glucose (r = 0.71-77). Compared with mean CGM glucose, glycated albumin and fructosamine were significantly biased by age, BMI, serum iron concentration, transferrin saturation, and albuminuria; HbA_1c was underestimated in those with albuminuria.

CONCLUSIONS

Glycated albumin and fructosamine were not less variable than HbA_1c at a given mean CGM glucose level, with several additional sources of bias. These results support measuring HbA_1c to monitor trends in glycemia among patients with eGFR <60 mL/min/1.73 m². Direct measurements of glucose are necessary to capture short-term variability.

Oxidised Met147 of human serum albumin is a biomarker of oxidative stress, reflecting glycaemic fluctuations and hypoglycaemia in diabetes

Oxidative stress has been linked to a number of chronic diseases, and this has aroused interest in the identification of clinical biomarkers that can accurately assess its severity. We used liquid chromatography-high resolution mass spectrometry (LC-MS) to show that oxidised and non-oxidised Met residues at position 147 of human serum albumin (Met¹⁴⁷) can be accurately and reproducibly quantified with stable isotope-labelled peptides. Met¹⁴⁷ oxidation was significantly higher in patients with diabetes than in controls. Least square multivariate analysis revealed that glycated haemoglobin (HbA_1c) and glycated albumin (GA) did not significantly influence Met¹⁴⁷ oxidation, but the GA/HbA_1c ratio, which reflects glycaemic excursions, independently affected Met¹⁴⁷ oxidation status. Continuous glucose monitoring revealed that Met¹⁴⁷ oxidation strongly correlates with the standard deviation of sensor glucose concentrations and the time spent with hypoglycaemia or hyperglycaemia each day. Thus, glycaemic variability and hypoglycaemia in diabetes may be associated with greater oxidation of Met¹⁴⁷. Renal function, high-density lipoprotein-cholesterol and serum bilirubin were also associated with the oxidation status of Met¹⁴⁷. In conclusion, the quantification of oxidised and non-oxidised Met¹⁴⁷ in serum albumin using our LC-MS methodology could be used to assess the degree of intravascular oxidative stress induced by hypoglycaemia and glycaemic fluctuations in diabetes.

Molecular form and concentration of serum α2-macroglobulin in diabetes

α₂-Macroglobulin is a highly abundant serum protein involved in the development of atherosclerosis and cardiac hypertrophy. However, its circulating molecular form and exact concentrations in human health/diseases are not known. Blue native-polyacrylamide gel electrophoresis of human serum was used to confirm the native conformation of α₂-macroglobulin. We created an enzyme-linked immunosorbent assay suitable for quantifying its circulating molecular form and undertook a cross-sectional study to measure its serum levels in 248 patients with diabetes mellitus and 59 healthy volunteers. The predominant circulating molecular form of α₂-macroglobulin was the tetramer, whereas its dimer was detectable in patients with high serum levels of α₂-macroglobulin. The serum α₂-macroglobulin concentration was not associated with glycated hemoglobin or any other glycemic variable as evaluated from 48-h continuous glucose monitoring, but showed close correlation with left ventricular posterior wall thickness, carotid artery intima-media thickness, urinary albumin:creatinine ratio (ACR) and brachial–ankle pulse wave velocity (baPWV). Multivariate analysis revealed only the ACR and baPWV to be independent variables influencing serum levels of α₂-macroglobulin. Thus, an increased ACR and baPWV are associated with higher serum concentrations of α₂-macroglobulin, and the latter may contribute to the mechanism by which albuminuria increases the risk of developing cardiovascular diseases.

The clinical usefulness of glycated albumin in patients with diabetes and chronic kidney disease: Progress and challenges

Prolonged hyperglycemia leads to a non-enzymatic glycation of proteins, and produces Amadori products, such as glycated albumin (GA) and glycated hemoglobin (HbA1c). The utility of HbA1c in the setting of chronic kidney disease (CKD) may be problematic since altered lifespan of red blood cells, use of iron and/or erythropoietin therapy, uremia and so on. Therefore, as an alternative marker, GA has been suggested as a more reliable and sensitive glycemic index in patients with CKD. In addition to the mean plasma glucose concentration, GA also reflects postprandial plasma glucose and glycemic excursion. Besides, with a half-life of approximately 2-3 weeks, GA may reflect the status of blood glucose more rapidly than HbA1c. GA is also an early precursor of advanced glycation end products (AGEs), which cause alterations in various cellular proteins and organelles. Thus, high GA levels may correlate with adverse outcomes of patients with CKD. In this review, the clinical usefulness of GA was discussed, including a comparison of GA with HbA1c, the utility and limitations of GA as a glycemic index, its potential role in pathogenesis of diabetic nephropathy and the correlations between GA levels and outcomes, specifically in patients with diabetes and CKD.

Glycated Albumin Versus HbA1c in the Evaluation of Glycemic Control in Patients With Diabetes and CKD

INTRODUCTION

It is inaccurate to assess blood glucose with glycated hemoglobin (HbA1c) in patients with diabetes and chronic kidney disease (CKD), and whether glycated albumin (GA) is better than HbA1c in these patients remains unclear.

METHODS

We searched PubMed, Embase, Web of Science, Scopus, the Cochrane Library, and MEDLINE to July 2017 for studies that investigated the correlation between GA or HbA1c and the average glucose levels (AG) relevant to this theme. Statistical analysis was performed using RevMan5.3 and Stata12.0. The outcome was the correlation coefficient between GA or HbA1c and AG. For the first time, we made a comparison of GA and HbA1c in different CKD stages.

RESULTS

A total of 24 studies with 3928 patients were included. Early stages of CKD refer to CKD stage 1 to 3. Advanced CKD refer to CKD stage 4 and 5 including patients receiving dialysis. The meta-analysis suggested that in early stages of CKD, the pooled R between GA and AG was 0.61 (95% CI = 0.49-0.73) and 0.71 (95% CI = 0.55-0.87) for HbA1c (P > 0.05). In advanced CKD patients, the pooled R between GA and AG was 0.57 (95% CI = 0.52-0.62), and 0.49 (95% CI = 0.45-0.52) for HbA1c (P = 0.0001).

CONCLUSION

GA is superior to HbA1c in assessing blood glucose control in diabetes patients with advanced CKD.

Dietary black-grained wheat intake improves glycemic control and inflammatory profile in patients with type 2 diabetes: a randomized controlled trial

Introduction

Although black-grained wheat (BGW) is recognized as a nutritional food for humans in China, it has yet to be utilized well for industrial applications, which can be attributed to the limited research data available on its health benefits. Thus, the hypothesis was tested that a daily substitution of BGW for a partial staple food would improve glycemia and inflammatory profile of type 2 diabetes mellitus (T2DM) patients by a randomized controlled trial.

Materials and methods

A total of 120 patients were randomly divided between control group (diet control and nutritional education) and BGW group (daily substitution of BGW for a partial staple food).

Results

Based on the significant difference between BGW and control groups (P<0.05), the primary outcomes were that BGW treatment in diet resulted in a significant lowering of glycated albumin (GA, 18.05 to 16.06 mmol/L) level in T2DM patients after a 5-week intervention, and this treatment regimen was much more efficient than the strategy of diet control alone. In addition, BGW supplementation prevented the increase in tumor necrosis factor (TNF)-α and interleukin (IL)-6 induced by T2DM. There were no significant differences in blood glucose, glycated hemoglobin or insulin levels between the 2 groups. The subgroup analyses of the BGW daily intake showed that, except the TNF-α, significant improvements in GA and IL-6 were observed when the BGW intake dose was >69 g/day.

Conclusion

These findings support the hypothesis that BGW may improve glycemia and the inflammatory profile in T2DM patients.

Glycated albumin and its variability as an indicator of cardiovascular autonomic neuropathy development in type 2 diabetic patients

BACKGROUND

We investigated whether glycated albumin (GA) and its variability are associated with cardiovascular autonomic neuropathy (CAN) and further compared their associations with glycated hemoglobin (HbA1c).

METHODS

This retrospective longitudinal study included 498 type 2 diabetic patients without CAN. CAN was defined as at least two abnormal results in parasympathetic tests or presence of orthostatic hypotension. The mean, standard deviation (SD), and coefficient of variance (CV) were calculated from consecutively measured GA (median 7 times) and HbA1c levels (median 8 times) over 2 years. Logistic regression analysis was used to compare the associations between CAN and GA- or HbA1c-related parameters. Receiver operating characteristic (ROC) curve analysis was used to compare the predictive power for CAN between GA- and HbA1c-related parameters.

RESULTS

A total of 53 subjects (10.6%) developed CAN over 2 years. The mean, SD, and CV of GA or HbA1c were significantly higher in subjects with CAN. Higher mean GA and GA variability were associated with the risk of developing CAN, independent of conventional risk factors and HbA1c. In ROC curve analysis, the SD and CV of GA showed higher predictive value for CAN compared to the SD and CV of HbA1c, whereas the predictive value of mean GA did not differ from that of mean HbA1c. The mean, SD, and CV of GA showed additive predictive power to detect CAN development along with mean HbA1c.

CONCLUSIONS

Higher serum GA and its variability are significantly associated with the risk of developing CAN. Serum GA might be a useful indicator for diabetic complications and can enhance HbA1c's modest clinical prediction for CAN.

Identification and quantification of plasma free salusin-β, an endogenous parasympathomimetic peptide

Salusin-β is an endogenous parasympathomimetic proatherosclerotic peptide. Salusin-β was initially predicted from bioinformatic analyses and later immunologically detected in human biofluids. However, elucidation of salusin-β bioactivity has faced enormous challenges because of its unique physicochemical characteristics that cause it to strongly adhere to laboratory apparatus materials. In the strictest sense, the discovery of bioactive peptides is not complete until their exact native sequences have been confirmed in the peripheral circulation. In this study, we determined the plasma molecular form and levels of free salusin-β to determine its pathophysiological significance. Ultra-high-yield enrichment and preseparation of non-tryptic human plasma was followed by LC-MS/MS, and full-length salusin-β and seven different endogenous fragment sequences were identified. We established a new ELISA that specifically detects plasma free salusin-β without cross-reacting with any of its identified endogenous fragments. Free salusin-β levels exhibited a profound early morning nadir and rapidly decreased in response to parasympathetic nervous augmentation. Our technical advance in plasma native peptide analysis successfully identified a hard-to-detect bioactive peptide, salusin-β, together with its formerly unrecognized fragments, and further suggests that conventional immunological measurements of target peptides may not be fully representative.

Methionine sulfoxides in serum proteins as potential clinical biomarkers of oxidative stress

Oxidative stress contributes to the pathophysiology of a variety of diseases, and circulating biomarkers of its severity remains a topic of great interest for researchers. Our peptidomic strategy enables accurate and reproducible analysis of circulating proteins/peptides with or without post-translational modifications. Conventional wisdom holds that hydrophobic methionines exposed to an aqueous environment or experimental handling procedures are vulnerable to oxidation. However, we show that the mass spectra intensity ratio of oxidized to non-oxidized methionine residues in serum tryptic proteins can be accurately quantified using a single drop of human serum and give stable and reproducible results. Our data demonstrate that two methionine residues in serum albumin (Met-111 and Met-147) are highly oxidized to methionine sulfoxide in patients with diabetes and renal failure and in healthy smokers versus non-smoker controls. This label-free mass spectrometry approach to quantify redox changes in methionine residues should facilitate the identification of additional circulating biomarkers suitable for predicting the development or progression of human diseases.