Mainly most of monosaccharides; like fructose & galactose; and firstly of course is glucose; are automatically; non – enzymatically & rapidly bind to haemoglobin; as long as they existed in blood stream, and however, glucose binding is less than fructose by (13%) & for galactose with (21%), thus, this made it clear the cause of considering glucose is the main source of energy rather than these two latter as a monosaccharide. (Recuperado et al, 2021).

     Glycation is the phrase used to describe of attachment of sugars to haemoglobin, for this, HbA1c; as mostly called; is in fact a measure of component of haemoglobin of “Beta – N – 1 – deoxy – fructosyl” part, in order to investigate presence of excessive sugar particles in plasma. (Patel et al, 2021).

    There is a limitation for this test which is linked due to life span of red blood corpuscles of 4 months; hence; it is done to perform three – months measurement control & monitoring for diabetic people as a “Glycemic Control”, as long as its level is normal for ordinary individuals, but if it increases due to presence of glycated fragments in blood stream, it would give an indication about poor control for diabetes mellitus patients, because the fragments are in a predictable criteria, in addition to association with nephropathy, cardiovascular disturbances, neuropathy & retinopathy. (Lee et al, 2022).

      In another way, glycated Hb may cause damage by atherosclerotic formation of plaque by inflammation, while by another route, molecules of Hb are clumping to each other & to release “Quadric – Ferric – Hb”; Fe⁺⁴ - Hb, into the sub – endothelium of veins & arteries in order to increase its permeability to defending cells, and by this way, loss of ferric ions will continue by excitation of Fe⁺² through Fe⁺³ to the abnormal “Ferryl – Hb”; Fe⁺⁴ - Hb. (Deo et al, 2021).

Figure (1): Glycosylation and formation of HbA1c. Labpedia,net (Dr. Riaz Ahmed, 2020).

     Proteins glycation occurs frequently, and it is non – enzymatically if it was with Hb by condensation reaction between N – terminal of β – chain & glucose; by further reactions; it gives glucose molecules to attach to red blood corpuscles when it is in a high level. (Wu et al, 2021).

        Whenever plasma glucose levels are with high ranges, and hyperglycaemia takes place more often, the more glycation occur & gives higher readings during testing of HbA1c; for thus; and due to increased level of glucose during COVID – 19; HbA1c became undependable as monitoring score for patients of DM or as an alarm test for pre – diabetic people. (Alesci et al, 2022).

References

--------------

1-  Alesci, A., Nicosia, N., Fumia, A., Giorgianni, F., Santini, A. and Cicero, N., 2022. Resveratrol and Immune Cells: A Link to Improve Human Health. Molecules, 27(2), p.424.

2- Deo, S., Sundaram, V., Sheikh, M.A., Sahadevan, J., Selvaganesan, P., Madan Mohan, S.K., Rubelowsky, J., Elgudin, Y., Josephson, R., Davierwala, P.M. and Cmolik, B., 2021. Pre-operative glycaemic control and long-term survival in diabetic patients after coronary artery bypass grafting. European Journal of Cardio-Thoracic Surgery, 60(5), pp.1169-1177.

3- Lee, S.L., Wu, L.M., Chou, Y.Y., Lai, F.C. and Lin, S.Y., 2022. Developing the Chinese version problem areas in diabetes-teen for measuring diabetes distress in adolescents with type 1 diabetes. Journal of Pediatric Nursing.

4- Patel, A.J., Klek, S.P., Peragallo-Dittko, V., Goldstein, M., Burdge, E., Nadile, V., Ramadhar, J., Islam, S. and Rothberger, G.D., 2021. Correlation of hemoglobin A1c and outcomes in patients hospitalized with COVID-19. Endocrine Practice, 27(10), pp.1046-1051.

5- Recuperado, A., Da Milla, C., Goldy, H., American Diabetes Association, 2021. Understanding A1C A1C does it all. Recuperado et al, p11.

6- Riaz, A.M., 2020. Biochemistry. Labpedia.net

7- Wu, L., Fang, C., Zhang, L., Yuan, W., Yu, X. and Lu, H., 2021. Integrated strategy for discovery and validation of glycated candidate biomarkers for hemodialysis patients with cardiovascular complications. Analytical Chemistry, 93(10), pp.4398-4407.