HbA1c Formation Research Articles

6656 Frequently sampled HbA1c Shows Low-Sodium, High-Carbohydrate Rice Diet To Be Effective in Type 2 Diabetes

Abstract Disclosure: F.A. Neelon: None. S. Sanoff: None. P. Lin: None. Hemoglobin and glucose react to form HbA1c, which persists until red blood cells (RBCs) are removed from circulation. Since RBCs survive approximately 122 days, HbA1c is usually measured at intervals of months to years, but more frequent measurement can illuminate changes in blood glucose (BG). We used Beach’s equation for the kinetics of HbA1c formation, to construct graphical depictions of how HbA1c should decline over the 122 days after a drop from constantly high to constantly normal BG levels. As part of routine patient care (not an experimental protocol), we measured HbA1c at 2-4-week intervals in a convenience sample of 10 patients (one of whom was evaluated on 2 occasions) with Type 2 diabetes, obesity, and elevated HbA1c who attended the now defunct Rice Diet Program (RDP) in Durham, NC. All were fed 3 meals/day, comprising 800-1000 kcal of rice, fruits, grains, and vegetables (70-90% carbohydrates) and 300 mg of sodium. Two patients were initially taking insulin; 1, glipizide; and 1, sitagliptin, exenatide, metformin; all hypoglycemic agents were eventually discontinued, and none added. Mean initial HbA1c of 9.7% (range, 8.3-11.7) fell to a mean of 6.2% (range 5.3-8.4) after a mean of 82 days (range, 41-139). Variability in final HbA1c values reflects, at least in part, variable duration of voluntary residence at the RDP. In 9 patients, HbA1c declined in close accordance with the course predicted for complete normalization of blood glucose from the very start of the diet; in 1 patient, HbA1c declined slowly for 25 days, after which the rate increased to near that for complete normalization of BG. Plots of Hb1c values extrapolate back through the point of origin, implying normalization of BG occurs within days of starting the RDP, and is maintained thereafter. Data from frequent measurement of HbA1c show: 1) Normalization of BG occurs almost immediately upon dietary restriction, implying that hyperglycemia in Type 2 diabetes is driven by daily calorie excess, not by accumulated calorie excess (ie, obesity). 2) Contrary to some misperceptions, a high-carbohydrate, sodium- and calorie-restricted diet is not deleterious to ― and may actually benefit ― glucose control in Type 2 diabetes. Presentation: 6/3/2024

A-070 A fully automated HbA1c Assay on the DxC 500 AU Clinical Chemistry Analyser

Abstract Background Diabetes mellitus is a condition characterized by hyperglycemia resulting from the body’s inability to use blood glucose for energy. In Type-1 diabetes, the pancreas no longer makes insulin and blood glucose cannot enter the cells to be used for energy. In Type-2 diabetes, the pancreas does not make enough insulin or the body is unable to use insulin correctly. According to the World Health Organization (WHO), 422 million adults were living with diabetes globally in 2014 with an estimated 1.6 million deaths directly associated with diabetes annually. HbA1c is the major species of glycohemoglobin in human blood. HbA1c formation occurs through a non-enzymatic reaction, called glycation, which occurs between glucose and the n-terminal valine of the hemoglobin â-chain of HbA. A Schiff base intermediate product is formed, which rearranges to form a stable ketoamine in an irreversible reaction. The rate of glycation is proportional to the glucose concentration in the bloodstream and is an accurate reflection of average blood glucose over a period of eight to twelve weeks. HbA1c testing is recommended for the diagnosis of diabetes by the International Expert Committee (IEC), the American Diabetes Association (ADA), and the WHO, who recommended a diagnostic threshold of = 6.5% ( = 48 mmoL/moL) HbA1c and a range for pre-diabetes of 5.7%–6.4% (39–46 mmoL/moL) HbA1c. Methods The HbA1c Advanced assay on the DxC 500 AU* utilizes automatic sample pre-treatment, has batch and random access capability. No manual pre-treatment of the whole blood sample or additional washing steps are required. Firstly the red blood cells are hemolyzed automatically, total hemoglobin and glycated hemoglobin are then measured colorimetrically and immunoturbidimetrically respectively. Results Precision studies were conducted according to CLSI EP15-A3. Commercial controls and four native K2 EDTA whole blood samples ranging from 5.1% to 12.0% HbA1c, were run twice daily, over twenty days using three lots of reagent on three DxC500AU Clinical Chemistry analyzers at a single site. Repeatability ranged from 0.86% to 1.44% CV and Total Precision ranged from 1.55% to 2.43% CV. Linearity studies were conducted according to CLSI EP06-A, and verified an analytical measuring range of 4.0%–15.0% (NGSP) and 20–140 mmol/mol (IFCC). Method comparison and bias estimation was evaluated using CLSI EP09-A3. K2 EDTA patient samples (n = 150) across the analytical range were run vs a Secondary Reference method and yielded a slope of 1.031, intercept −0.147% HbA1c, correlation coefficient R = 0.997 for Weighted Deming regression, and slope 1.000 and intercept 0.06% HbA1c for Passing Bablok regression. Interference studies carried out demonstrated no significant interference from common endogenous interferences, a large panel of drugs, common Hb variants (HbC, HbD, HbE, HbA2 and HbS) and cross reactants (HbA0, HbA1a+b, acetylated hemoglobin, carbamylated hemoglobin, glycated hemoglobin, glycated albumin and labile HbA1c). Conclusion The HbA1c Advanced assay on the DxC 500 AU is a precise and accurate assay, requiring no manual pretreatment and can be used for monitoring and diagnosing diabetes. *Pending clearance by the United States Food and Drug Administration and achievement of CE compliance. Not currently available for in vitro diagnostic use.

Optimization of trial duration to predict long-term HbA1c change with therapy: A pharmacometrics simulation-based evaluation.

Glycated hemoglobin (HbA1c) is the main biomarker of diabetes drug development. However, because of its delayed turnover, trial duration is rarely shorter than 12 weeks, and being able to predict long-term HbA1c with precision using data from shorter studies would be beneficial. The feasibility of reducing study duration was therefore investigated in this study, assuming a model-based analysis. The aim was to investigate the predictive performance of 24- and 52-week extrapolations using data from up to 4, 6, 8 or 12 weeks, with six previously published pharmacometric models of HbA1c. Predictive performance was assessed through simulation-based dose-response predictions and model averaging (MA) with two hypothetical drugs. Results were consistent across the methods of assessment, with MA supporting the results derived from the model-based framework. The models using mean plasma glucose (MPG) or nonlinear fasting plasma glucose (FPG) effect, driving the HbA1c formation, showed good predictive performance despite a reduced study duration. The models, using the linear effect of FPG to drive the HbA1c formation, were sensitive to the limited amount of data in the shorter studies. The MA with bootstrap demonstrated strongly that a 4-week study duration is insufficient for precise predictions of all models. Our findings suggest that if data are analyzed with a pharmacometric model with MPG or FPG with a nonlinear effect to drive HbA1c formation, a study duration of 8 weeks is sufficient with maintained accuracy and precision of dose-response predictions.

Effects of Ethanol Extract of Rosa damascene on HbA1c Level and NF-κB Expression in Diabetic Rats

Diabetes mellitus (DM) is a chronic hyperglycemic that can cause complications in several organs. It could lead glycosylated hemoglobin or HbA1c formation which has ability undergo further changes into Advanced Glycation End Products (AGEs) and stimulate activation of transcription factors such as nuclear factor kappa B (NF-κB). Some studies showed that anthocyanin has antioxidant and anti-inflammatory activity and it has been found Rosa damascene contain high level of anthocyanin. Total anthocyanin content was 0.459 ± 0.003 mg/L. The aim of this study was to investigate inhibitory effect of R. damascena extract on HbA1c levels and NF-κB activation in diabetic rats. Male wistar rats (n=24) were divided into 6 groups as normal control (KN), streptozotocin-induced diabetic control (KP), diabetic treated with R. damascene (P1, P2, P3; 250, 500 and 1000 mg/kg/d respectively) and diabetic treated with metformin (KM; 500 mg/kg/d). This was carried out for 28 days. The inhibition mode of R. damascene extract was examined by measuring HbA1c levels and expression of NFκB by immunohistochemistry. The results showed p values ​​> 0.05 for HbA1c and p < 0.05 for NFκB. From immunohistochemical staining, it seen the expression of NFκB was low in treated group (P1, P2, P3 and KM) compared with KP. Thus, oral administration of R. damascene extract for 28 days could not reduce HbA1c levels, but can supress NFκB expression.

Effects of Iron Deficiency Anaemia on HbA1c Levels in Non-Diabetics and Diabetics

Background: Iron deficiency anaemia is one of the most common anaemia striking in our country. The level up to which blood sugar level is regulated is measured by HbA1c. HbA1c represents sugar level in the blood for 120 days. HbA1c could be dependent upon an assemblage of factors like variants of haemoglobinopathies, haemolytic anaemia, other deficiency anaemia, acute loss of blood, uraemia, and pregnancy. Thus, it is crucial to determine the role of HbA1c in iron deficiency anemia in diabetics and non-diabetics before treating the patients.
 Methods: Total of 58 articles were collected and based on our study objective total of 19 articles were included in this study. Iron deficiency anaemia, HbA1c, diabetics and non-diabetics has been added in pub med advanced searches and Google scholar. Original articles which compare the correlation between these two were taken. All the information was gathered from original and review articles. Articles which were qualified for review, their inclusion criteria, exclusion criteria, quality of assessment and data collections were taken into consideration. Structure of heme particle, basic mechanism of HbA1c formation in RBCs is elaborated. Review articles which were taken include RCT, retrospective analysis and observational studies. The results were all compared and concluded of each articles. Basic mechanism of formation of HbA1c in RBCs is shown. Also necessary conclusions were derived from each study.
 Results: In a wide range of studies, HbA1c was found to be raised in IDA. After iron supplements, studies showed a decrease in HbA1c. Our study showed there is a need to correct anemia in diabetic patients before starting treatment.
 Conclusions: Strict HbA1c control is not a prerequisite and prior anaemia correction should be done. Nevertheless, a study which will be conducted in representative population matching to the prevalence and incident of disease in our country also which should be interventional is required for the highest correction value of HbA1c in DM and NDM population.

Effect of Citrullus colocynthis Extract on Glycated Hemoglobin Formation (In Vitro).

Diabetes mellitus (DM) is typically a disorder of carbohydrate, fat, and protein metabolism. It develops due to a lack of or loss associated with insulin and/or resistance to insulin. Regarding complications of chemical substance use, drugs with few complications and high-reliability tannins are needed. This study aimed to determine the effect and mechanism of action of Citrullus colocynthis extract on the formation of glycated hemoglobin (HbA1c). A solution containing hemoglobin and glucose was incubated for 1, 2, 3, 4, 30, and 60 days by adding Citrullus colocynthis extract or glutathione. Quantitative measurement of HbA1c was performed using ion-exchange chromatography. Data were analyzed using ANOVA and two-way repeated measures test. A p<0.05 was considered statistically significant. The Citrullus colocynthis extract in hyperglycemic conditions and with increasing time reduced the formation of HbA1c and thus inhibited the production of glycated proteins. By increasing the time and after initiation of reaction of extract concentrations (0, 0.1, 0.3, 0.5, and 1 g/dL), presently, there was a significant decrease in the formation of HbA1C compared to those in the control group (p<0.05). The decrease in glycation has been dose dependent. Therefore, Citrullus colocynthis could directly reduce the formation of HbA1c.

A labile form of hemoglobin A1c is higher in African-American youth with type 1 diabetes compared to Caucasian patients at similar glucose levels.

Hemoglobin A1c (HbA1c) levels are higher in African-American (AA) individuals compared to Caucasians (EA) even after adjustment for blood glucose levels. To better understand the mechanism of this disparity we examined the relationship of an unstable (labile) form of HbA1c (L-HbA1c) with race and glucose. Samples for HbA1c were collected from pediatric patients self-identified as either AA (15F, 12M, age 13.4 ± 3.5 years) or EA (22F, 30M, age 14.6 ± 3.4 years) with type 1 diabetes at the time of a clinic visit. Clinic HbA1c (HbA1c) was performed by immunoassay. L-HbA1c equaled the difference in the HbA1c fraction by dynamic capillary isoelectric focusing before and after incubation in a low pH buffer. A capillary glucose (Clinic-BG) was measured at clinic visit. Mean blood glucose (MBG) was calculated from the last 30 days of the patient's glucose meter data. The influence of race on L-HbA1c was assessed in a multiple variable regression model adjusted for Clinic-BG. The groups were similar for age and duration of diabetes. L-HbA1c was correlated with Clinic-BG, MBG, and HbA1c. The mean levels of L-HbA1c, HbA1c, MBG, but not Clinic-BG were higher in AA patients compared to EA. After adjustment for Clinic-BG, L-HbA1c was still higher in AA (2.8 ± 0.7% AA vs 2.1 ± 0.7% EA, P < .0001). L-HbA1c is correlated with Clinic-BG. At any given level of Clinic-BG, AA patients have higher levels of L-HbA1c than EA. This preliminary study suggests that early factors prior to the formation of stable HbA1c may contribute to the observed glucose-independent racial disparity.

Insights into the Progression of Labile Hb A1c to Stable Hb A1c via a Mechanistic Assessment of 2,3-Bisphosphoglycerate Facilitation of the Slow Nonenzymatic Glycation Process

Nonenzymatic glycation (NEG) of human hemoglobin (Hb A) consists of initial non covalent, reversible steps involving glucose and amino acid residues, which may also involve effector reagent(s) in the formation of labile Hb A1c (the conjugate acid of the Schiff base). Labile Hb A1c can then undergo slow, largely irreversible, formation of stable Hb A1c (the Amadori product). Stable Hb A1c is measured to assess diabetic progression after labile Hb A1c removal. This study aimed to increase the understanding of the distinctions between labile and stable Hb A1c from a mechanistic perspective in the presence of 2,3-bisphosphoglycerate (2,3-BPG). 2,3-Bisphosphoglycerate is an effector reagent that reversibly binds in the Hb A1c pocket and modestly enhances overall NEG rate. The deprotonation of C2 on labile Hb A1c in the formation of the Amadori product was previously proposed to be rate-limiting. Computational chemistry was used here to identify the mechanism(s) by which 2,3-BPG facilitates the deprotonation of C2 on labile Hb A1c. 2,3-Bisphosphoglycerate is capable of abstracting protons on C2 and the α-nitrogen of labile Hb A1c and can also deprotonate water and/or amino acid residues, therefore preparing these secondary reagents to deprotonate labile Hb A1c. Parallel reactions not leading to an Amadori product were found that include formation of the neutral Schiff base, dissociation of glucose from the protein, and cyclic glycosylamine formation. These heretofore under appreciated parallel reactions may help explain both the selective removal of labile from stable Hb A1c and the slow rate of NEG.

Average glucose from hemoglobin A1c for altered red blood cell lifetimes: Predictions based on a model for hemoglobin A1c formation

BackgroundA model for hemoglobin A1c (HbA1c) formation was used to predict the relationship between average glucose (AG) and %HbA1c under conditions of altered red blood cell lifetime (RCL). MethodsUsing a kinetic mass balance model for formation of HbA1c in red blood cells as a function of age (time in circulation), whole blood %HbA1c vs. glucose was calculated based on the nonlinear distribution of red blood cells as a function of age across RCL. ResultsModel calculations provided a close fit to the standard relationship of estimated average glucose to %HbA1c for normal RCL (r>0.999). Results for altered RCL were calculated assuming simple time-scale compression or expansion of the distribution of red blood cells as a function of RCL. For a given %HbA1c, the operative average glucose needed to have achieved a given %HbA1c was predicted to be altered by RCL according to average glucose×RCL=constant. ConclusionsModel calculations estimate the extent to which standard reporting of AG vs. HbA1c underestimates or overestimates AG under conditions of altered RCL. Conditions of altered RCL may often be operative in patients with certain hemoglobin variants.

Prevention of advanced glycation end-products formation in diabetic rats through beta-cell modulation by Aegle marmelos

BackgroundAlthough the anti-diabetic activity of Aegle marmelos (AM) is known, however, its anti-glycation activity is not reported yet. In this study, we have investigated its anti-glycation activity under in vitro and in vivo conditions and determined possible mechanism(s) in streptozotocin-induced diabetic rats.MethodsEffective dose of AM (400 mg/kg) was administrated orally to diabetic rats for 42 days. Thereafter, blood glucose, serum insulin, HbA1c, antioxidant status, and advanced glycation end-products (AGEs) were measured. AGEs and its receptor (RAGE) in kidney were analyzed by immunohistochemistry and immunoblotting. Additionally, pancreatic sections were co-stained for insulin and glucagon and images were acquired using NIKON TE2000E fluorescence microscopy.ResultsOral administration of AM extract resulted in a significant increase in serum insulin by better functioning of β-cell and preserving pancreatic β-cell integrity in diabetic rats. Treatment of AM extract significantly (p = 0.000) prevented the formation of HbA1c in the diabetic rats (8.20 ± 0.18% vs. 11.92 ± 0.59%). The circulatory AGEs level found in diabetic rat was significantly (p = 0.002) attenuated by AM treatment (0.66 ± 0.05 mg/ml vs. 1.18 ± 0.19 mg/ml). AM treatment also reduced AGEs accumulation around Bowman’s capsule and in tubular basement membrane around arteries in diabetic rat kidney. The accumulation of RAGE was very similar to that of AGEs in diabetic rats and RAGE accumulation was also prevented by AM treatment. The extract showed potent antioxidant activity both under in vitro and in vivo systems. Eugenol, one of the active constituent of AM fruit extract, showed acute blood glucose-lowering activity in diabetic rats and enhanced glucose-stimulated insulin secretion from mice islets.ConclusionAM extract prevents AGEs formation by modulating β-cell function, and eugenol may play important role in preventing complications of diabetes in this rat model.

Whole Blood Donation Affects the Interpretation of Hemoglobin A1c.

IntroductionSeveral factors, including changed dynamics of erythrocyte formation and degradation, can influence the degree of hemoglobin A1c (HbA1c) formation thereby affecting its use in monitoring diabetes. This study determines the influence of whole blood donation on HbA1c in both non-diabetic blood donors and blood donors with type 2 diabetes.MethodsIn this observational study, 23 non-diabetic blood donors and 21 blood donors with type 2 diabetes donated 475 mL whole blood and were followed prospectively for nine weeks. Each week blood samples were collected and analyzed for changes in HbA1c using three secondary reference measurement procedures.ResultsTwelve non-diabetic blood donors (52.2%) and 10 (58.8%) blood donors with type 2 diabetes had a significant reduction in HbA1c following blood donation (reduction >-4.28%, P < 0.05). All non-diabetic blood donors with a normal ferritin concentration predonation had a significant reduction in HbA1c. In the non-diabetic group the maximum reduction was -11.9%, in the type 2 diabetes group -12.0%. When eligible to donate again, 52.2% of the non-diabetic blood donors and 41.2% of the blood donors with type 2 diabetes had HbA1c concentrations significantly lower compared to their predonation concentration (reduction >-4.28%, P < 0.05).ConclusionPatients with type 2 diabetes contributing to whole blood donation programs can be at risk of falsely lowered HbA1c. This could lead to a wrong interpretation of their glycemic control by their general practitioner or internist.

A Biochemistry Question-Guided Derivation of a Potential Mechanism for HbA1c Formation in Diabetes Mellitus Leading to a Data-Driven Clinical Diagnosis

A unique homework exercise with a related clinical case study has been designed as a tool for teaching applied biochemistry. Within the framework of the homework exercise, students derive a mechanism for the covalent attachment of glucose to hemoglobin. This process is critical to understand both nonenzymatic glycation and the molecular basis of diabetes mellitus. The homework exercise teaches first-principles using a data-driven, question-guided approach. The accompanying case study contextualizes the principles derived by students into a tangible clinical application. In the case study, students interpret analytical chemistry data from a clinical setting for a diabetic patient and must make conclusions on the best control and treatment for the patient. To make the proper clinical assessment, students must understand the mechanistic principles regarding nonenzymatic glycation of proteins that they learned in the homework exercise. Overall, the homework exercise and the case study tether together principles from organic chemistry (electrophiles/nucleophiles, Brønsted–Lowry acid–base theory, thermodynamics, blood glucose concentration, and cation exchange column chromatography) with those from biochemistry (covalent and noncovalent interactions, lock and key vs induced fit paradigms, and organic chemistry mechanisms for nonenzymatic formation of hemoglobin HbA1c and carbamylated hemoglobin, CHb) into a practical and tangible medical application.

One HbA1c Measurement Does Not Tell the Whole Story – 5 Case Studies

Hemoglobin A1c is produced by an interaction between intracellular glucose and hemoglobin. This is a dynamic process, because glucose values vary and RBCS have a limited lifespan. Hemoglobin A1c testing is performed to monitor glycemic control in patients with diabetes mellitus. The ADA recommends testing HbA1c twice a year in patients with good control, and more often in patients who do not meet their goals. MLS/CLS students are required to have an understanding of the relationship between HbA1c, plasma glucose and time. Case studies are valuable teaching tools to illustrate the dynamic nature of HbA1c formation. This work shows 4 months of serial HbA1c and glucose measurements in 5 individuals with type 2 diabetes mellitus. A stepwise increase or decrease of HbA1c is seen in subjects who have a change in their glycemic control, illustrating why one HbA1c result does not tell the whole story. ABBREVIATIONS:eAG - estimated average glucose, ADA - American Diabetes Association, HbA1c - Hemoglobin A1c

In vitro determination of hemoglobin A1c for diabetes diagnosis and management: technology update

In vitro determination of hemoglobin A1c for diabetes diagnosis and management: technology update Emma English,1 Elise T Milosevich,1 W Garry John2 1School of Medicine, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom; 2Department of Clinical Biochemistry, Norfolk and Norwich University Hospital, Norwich, United Kingdom Abstract: It is fascinating to consider the analytical improvements that have occurred since glycated hemoglobin was first used in routine clinical laboratories for diabetes monitoring around 1977; at that time methods displayed poor precision, there were no calibrators or material with assayed values for quality control purposes. This review outlines the major improvements in hemoglobin A1c (HbA1c) measurement that have occurred since its introduction, and reflects on the increased importance of this hemoglobin fraction in the monitoring of glycemic control. The use of HbA1c as a diagnostic tool is discussed in addition to its use in monitoring the patient with diabetes; the biochemistry of HbA1c formation is described, and how these changes to the hemoglobin molecule have been used to develop methods to measure this fraction. Standardization of HbA1c is described in detail; the development of the IFCC Reference Measurement Procedure for HbA1c has enabled global standardization to be achieved which has allowed global targets to be set for glycemic control and diagnosis. The importance of factors that may interfere in the measurement of HbA1c are highlighted. Keywords: glycated hemoglobin, HbA1c, IFCC

Ebselen exhibits glycation‐inhibiting properties and protects against osmotic fragility of human erythrocytes in vitro

Diabetic status is associated with an increase on oxidative stress markers in humans and animal models. We have investigated the in vitro effects of high concentrations of glucose on the profile of oxidative stress and osmotic fragility of blood from control and diabetic patients; we considered whether its antioxidant properties could afford some protection against glucose-induced osmotic fragility, and whether ebselen could act as an inhibitor of hemoglobin glycation. Raising blood glucose to 5-100 mmol/L resulted in a concentration-dependent increase of glycated hemoglobin (HbA1c; P < 0.001) and thiobarbituric acid reactive species (TBA-RS) content (P < 0.004). Non-protein SH groups (NPSH) also increased significantly as the concentration of glucose increased up to 30 mmol/L (P < 0.001). The osmotic fragility was more pronounced in blood of uncontrolled diabetic patients than in these non-diabetic subjects. Ebselen significantly reduced the glucose-induced increase in osmotic fragility and inhibited HbA1c formation (P < 0.0001). These results indicate that blood from patients with uncontrolled diabetes are more sensitive to osmotic shock than from patients with controlled diabetes and control subjects in relation to increased production of free radicals in vivo.

Glucose and Hemoglobin A1c

Glucose, a monosaccharide, is the primary source of energy for the human body. It is used by the liver and other cells for energy or stored as glycogen for later use. The level of glucose in the bloodstream is regulated by 2 pancreatic hormones, insulin and glucagon. Insulin is released when glucose levels rise. Insulin acts by increasing glycogenesis, lipogenesis, and glycolysis, causing a decrease of glucose in the bloodstream. Glucagon is released when glucose levels fall, causing the liver to release stored glucose (glycogen) into the bloodstream (glycogenolysis), thereby increasing the level of glucose in the bloodstream. Hemoglobin A1c (HbA1c), also called glycosylated hemoglobin, is a hemoglobin compound produced when glucose reacts with the amino group on a hemoglobin molecule forming a ketoamine. The glucose molecule is attached to one or both N-terminal valines of the β-polypeptide chains of normal adult hemoglobin.1 The HbA1c formation is proportional to the blood glucose concentrations. Because the average red blood cell life is approximately 120 days, the glycosylated hemoglobin level reflects the average blood glucose level during the previous 2 to 3 months. Glucose testing is used to determine if an individual has hyperglycemia or hypoglycemia. A high fasting glucose level (≥126 mg/dL) and/or a high HbA1c level (>6.5%) might indicate that an individual has diabetes mellitus. HbA1c is a reliable method of monitoring long-term diabetes mellitus control; it determines the average blood glucose level of an individual during a period of approximately 3 months. Normal values range from 4.0% to 6.0%. Results of a study2 have shown the strong linear relationship between average blood glucose levels and HbA1c levels. Current American Diabetes mellitus Association guidelines recommend that a HbA1c test be performed at least twice yearly on patients who are meeting treatment … [↵][1]* To whom correspondence should be addressed. E-mail: vfreeman{at}utmb.edu [1]: #xref-corresp-1-1

A Model‐Based Approach to Predict Longitudinal HbA1c, Using Early Phase Glucose Data From Type 2 Diabetes Mellitus Patients After Anti‐Diabetic Treatment

Predicting late phase outcomes from early-phase findings can help inform decisions in drug development. If the measurements in early-phase differ from those in late phase, forecasting is more challenging. In this paper, we present a model-based approach for predicting glycosylated hemoglobin (HbA1c) in late phase using glucose and insulin concentrations from an early-phase study, investigating an anti-diabetic treatment. Two previously published models were used; an integrated glucose and insulin (IGI) model for meal tolerance tests and an integrated glucose-red blood cell-HbA1c (IGRH) model predicting the formation of HbA1c from the average glucose concentration (Cg,av ). Output from the IGI model was used as input to the IGRH model. Parameters of the IGI model and drug effects were estimated using data from a phase1 study in 59 diabetic patients receiving various doses of a glucokinase activator. Cg,av values were simulated according to a Phase 2 study design and used in the IGRH model for predictions of HbA1c. The performance of the model-based approach was assessed by comparing the predicted to the actual outcome of the Phase 2 study. We have shown that this approach well predicts the longitudinal HbA1c response in a 12-week study using only information from a 1-week study where glucose and insulin concentrations were measured.

Hemoglobin A1c in Diabetes: Panacea or Pointless?

Glycation is the nonenzymatic attachment of a monosaccharide to amino groups of proteins. The reaction has been recognized for many years in the food industry, where it is known as browning (also termed the Maillard reaction) and is responsible for the formation of commonly ingested items, such as toast. In patients with diabetes, glucose accumulation results in enhanced glycation of many proteins, both in tissues (e.g., the lens) and in the blood. Of these, glycated hemoglobin (GHb) is by far the most frequently measured in patient care. Hemoglobin (Hb) in healthy adults consists predominantly of HbA, which has 2α- and 2β-chains. Glucose can attach to several amino acid residues in these chains. HbA1c is formed when glucose attaches specifically to the NH2-terminal valine of the β-chain. Formation of HbA1c is essentially irreversible, and its concentration in the blood depends on both the life span of the red blood cell (RBC), which averages ∼120 days, and the blood glucose concentration. Because the rate of formation of HbA1c is directly proportional to the concentration of glucose in the blood, HbA1c represents integrated values for glucose over the preceding 8 to 12 weeks (Table 1). View this table: TABLE 1 Selected attributes of HbA1c Initially described 57 years ago (1), GHb was first reported to be increased in patients with diabetes in the late 1960s (2). The clinical value of GHb was soon realized and the American Diabetes Association (ADA) began encouraging the routine measurement of GHb in all patients with diabetes (3). The fundamental role of GHb in diabetes was accentuated by the publication in 1993 of the Diabetes Control and Complications Trial (DCCT) (4). The study, which compared intensive to conventional insulin therapy in patients with type 1 diabetes, documented a direct relationship between blood glucose concentrations …

Hemoglobin Glycation Rate Constant in Non-diabetic Individuals

The objectives were as follows: (1) estimating mean value of the overall hemoglobin glycation rate constant (k); (2) analyzing inter-individual variability of k; (3) verifying ability of the hemoglobin A1c (HbA1c) formation model to predict changes of HbA1c during red blood cells cultivation in vitro and to reproduce the clinical data. The mean k estimated in a group of 10 non-diabetic subjects was equal to 1.257 ± 0.114 × 10(-9) L mmol(-1) s(-1). The mean k was not affected by a way of estimation of glycemia. The mean k differed less than 20% from values reported earlier and it was almost identical to the mean values calculated on basis of the selected published data. Analysis of variability of k suggests that inter-individual heterogeneity of HbA1c formation is limited or rare. The HbA1c mathematical model was able to predict changes of HbA1c in vitro resulting from different glucose levels and to reproduce a linear relationship of HbA1c and average glucose obtained in the A1C-Derived Average Glucose Study. This study demonstrates that the glycation model with the same k value might be used in majority of individuals as a tool supporting interpretation of HbA1c in different clinical situations.

Cranberry Phytochemicals Inhibit Glycation of Human Hemoglobin and Serum Albumin by Scavenging Reactive Carbonyls

The objective of this study was to investigate the inhibitory effects of cranberry phytochemicals on protein glycation. Cranberries were purified to yield a sugar‐free powder, which was fractionated into ethyl acetate fraction and water fraction. Water fraction was separated into water fraction‐I, II, and III. Antiglycation activities were tested using glycated hemoglobin (HbA1c), human serum albumin (HSA) ‐glucose, and HSA‐methylglyoxal assays. Cranberry powder and its fractions significantly inhibited the formation of HbA1c by 41.7–81.9 %. The concentrations of cranberry phytochemicals required to inhibit 50% of albumin glycation (EC50) in HSA‐glucose assay was lower than aminoguanidine except for water fraction‐I. The cranberry powder and fractions inhibited glycation of HSA by methylglyoxal. Cranberry phytochemicals scavenged 21.6–89.3% methylglyoxal within 6 hours. Fractions enriched with procyanidins showed higher antiglycation activities. Epicatechin, the constituent unit of procyanidins, were incubated with methylglyoxal and glyoxal at pH 7.4. Five adducts were detected and their structures were tentatively identified using HPLC‐ESI‐MSn. In conclusion, cranberry phytochemicals inhibited glycation of human hemoglobin and serum albumin by scavenging reactive carbonyls. This research is supported in part by Ocean Spray Cranberries, Inc.