Hemoglobin structure at higher levels of hemoglobin A1C in type 2 diabetes and associated complications

Characterization of Hemoglobin Variants by Capillary Electrophoresis, UV-Vis, and FTIR Spectroscopy

Hemoglobinopathies, hereditary disorders affecting the structure or production of hemoglobin, were detected by routine HbA1c measurements by capillary electrophoresis (CE) at the University Hospital Motol, Prague. The potential of ultraviolet-visible (UV-Vis) and Fourier-transform infrared (FTIR) spectroscopy for the detection and characterization of hemoglobinopathies was investigated. FTIR spectra were recorded with a very high resolution (0.5 cm-1) with 128 scans. The broad amide I peak, located at 1700-1600 cm-1, can be formed by superimposition of the conformational structures of hemoglobin. These secondary protein structures were subjected to mathematical analysis. The application of band narrowing techniques, followed by curve fitting and integration processes, provided the basis for the quantitative estimation of protein secondary structure. As a result, unambiguous differences in UV-Vis spectra among patients with presumably normal hemoglobin, an HbC or a hemoglobin S/hemoglobin G (HbS/HbG)-Philadelphia variant could not be demonstrated. However, FTIR spectra indicated slight differences in α-helix, β-turns, β-sheet, or random coil secondary hemoglobin structures for these mutations. In the spectral wavenumber range of 950-850 cm-1, there were some obvious FTIR differences at specific wavenumbers between patients with normal hemoglobin and those with the HbC variant. Further investigations are needed with a sufficient number of hemoglobin variants to elucidate the potency of FTIR spectroscopy for the characterization of hemoglobinopathies.

Extrapolation study for determining the time since injury in a rat subcutaneous hematoma model utilizing ATR-FTIR spectroscopy

The determination of the time of an injury has been a major problem in forensic science due to the lack of objective, reliable and portable methods. In this study, a subcutaneous hemorrhage model in rats was established over six days, and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy coupled with chemometrics was used to determine the time since injury. Initial principal component analysis (PCA) showed variance among hematoma sites. Subsequently, spectral data were acquired to establish a dependable partial least square (PLS) regression model with predictive abilities. The root mean square error of cross-validation (RMSECV) and the root mean square error of prediction (RMSEP) values produced by a genetic algorithm (GA) were 0.64 d (R2 = 0.88) and 0.57 d (R2 = 0.90), respectively. Few variables were involved in the model, and significantly better results were obtained in comparison to the conventional full-spectrum PLS model. In combination with the results of variable importance in projection (VIP) scores, all components, including proteins, nucleic acids and phospholipids, provided inferences regarding the samples at different time points; additionally, amide I and II bands represented the secondary structure of proteins and provided the largest contribution. Based on our preliminary study, the combination of swift and nondamaging ATR-FTIR spectroscopy with chemometrics could prove to be an advantageous approach for gauging the age of an injury in the forensic field.

Evaluation of Red Blood Cell Indices for Prediction of Glycemic Control in People Living with Type 2 Diabetes

Background

Achieving target glycemic control in people living with diabetes lessens most of the diabetes-related complications and hemoglobin A1C is the gold standard test for assessing the long-term glycemic control. However, the expensive cost, and its limited access are problematic for routine use in developing countries, demanding an urgent alternative solution. Hence, this study aimed to assess the potential of red blood cell indices in predicting glycemic control among people living with type 2 diabetes at Dilla University Hospital.

Methods

A cross-sectional study was conducted among 207 participants with type 2 diabetes. Red blood cell indices were compared between the poor and good glycemic control groups using the t-test. Performance of red cell indices in discriminating poor glycemic control was assessed using receiver operating characteristic analysis.

Results

The prevalence of poor glycemic control among the participants was 91.8%. Higher mean hemoglobin (p=0.002) and mean corpuscular hemoglobin (p=0.015) was found in the good glycemic control group. An inverse correlation was also observed between hemoglobin A1C and mean corpuscular hemoglobin (r=-0.158; P=0.023). The area under the curve to discriminate poor glycemic control from good was statistically significant for hemoglobin, hematocrit, and mean corpuscular hemoglobin. However, hemoglobin had the highest discrimination ability at a cutoff ≤14.8 g/dL; area under the curve was 0.738 (P=0.001), sensitivity, specificity, and positive predictive value were 68.95%, 82.35%, and 97.77%, respectively.

Conclusion

This study revealed that hemoglobin can potentially be used to assess glycemic control among people with type 2 diabetes but the interpretation needs to be cautious.

Evaluation of Red Blood Cell Parameters as a Biomarker for Long-Term Glycemic Control Monitoring Among Type 2 Diabetic Patients in Southwest Ethiopia: A Cross-Sectional Study

OBJECTIVE

The main aim of this study was to assess red blood cell parameters as a biomarker for long-term glycemic monitoring among T2 DM patients.

METHODS

Facility-based cross-sectional study through a consecutive sampling technique was conducted among 124 T2 DM patients at the chronic illness follow-up clinic of Jimma Medical Center (JMC) from July 27 to August 31, 2020. A structured questionnaire was used to collect socio-demographic and clinical-related data. Five milliliters of the blood specimen were collected from each eligible T2 DM patient. Glycated hemoglobin (HbA1c) and red blood cell parameters were determined by Cobas 6000 and DxH 800 fully automated analyzers, respectively. Data were entered into EpiData software version 3.1 and exported to SPSS 25 version for analysis. Independent t-test and Pearson's correlation coefficient were used to address the research questions. A P-value <0.05 was considered statistically significant.

RESULTS

The mean age of study participants was 51.84± 11.6 years. Moreover, 60.5% of T2 DM patients were in poor glycemic control. There was a significant mean difference between good and poor glycemic controlled T2 DM patients in red blood cell count (4.79±0.5 vs 4.38±0.8), hemoglobin (14.13±1.4 vs 13.60±1.6), mean corpuscular volume (89.52±4.7 vs 92.62±7.5), mean corpuscular hemoglobin (29.63±1.6 vs 30.77±2.9), and red cell distribution width (13.68±1.1 vs 14.63±1.2) respectively. Red blood cell count was inversely correlated (r=-0.280, p=0.002) with HbA1c while mean corpuscular volume (r=0.267, p=0.003), mean corpuscular hemoglobin (r=0.231, p=0.010), and red cell distribution width (r= 0.496, p=0.000) were positively correlated with level of HbA1c.

CONCLUSION

Red cell count, mean corpuscular volume, mean corpuscular hemoglobin, and red cell distribution width could be useful indicators to monitor the glycemic status of T2 DM patients instead of HbA1c, though large prospective studies should be considered.

Ion Mobility Mass Spectrometry Analysis of Oxygen Affinity-Associated Structural Changes in Hemoglobin

Hemoglobin (Hb) is a major oxygen-transporting protein with allosteric properties reflected in the structural changes that accompany binding of O₂. Glycated hemoglobin (GHb), which is a minor component of human red cell hemolysate, is generated by a nonenzymatic reaction between glucose and hemoglobin. Due to the long lifetime of human erythrocytes (∼120 days), GHb is widely used as a reliable biomarker for monitoring long-term glucose control in diabetic patients. Although the structure of GHb differs from that of Hb, structural changes relating to the oxygen affinity of these proteins remain incompletely understood. In this study, the oxygen-binding kinetics of Hb and GHb are evaluated, and their structural dynamics are investigated using solution small-angle X-ray scattering (SAXS), electrospray ionization mass spectrometry equipped with ion mobility spectrometry (ESI-IM-MS), and molecular dynamic (MD) simulations to understand the impact of structural alteration on their oxygen-binding properties. Our results show that the oxygen-binding kinetics of GHb are diminished relative to those of Hb. ESI-IM-MS reveals structural differences between Hb and GHb, which indicate the preference of GHb for a more compact structure in the gas phase relative to Hb. MD simulations also reveal an enhancement of intramolecular interactions upon glycation of Hb. Therefore, the more rigid structure of GHb makes the conformational changes that facilitate oxygen capture more difficult creating a delay in the oxygen-binding process. Our multiple biophysical approaches provide a better understanding of the allosteric properties of hemoglobin that are reflected in the structural alterations accompanying oxygen binding.