Hemoglobin Structure Changes in Type 2 Diabetes: How High HbA1c Affects Red Blood Cell Function
Diabetes affects over 400 million people worldwide, and by 2040, that number could jump to 642 million. For people with type 2 diabetes, keeping HbA1c (a marker of long-term blood sugar control) below 7% is key to avoiding complications like heart disease or nerve damage. But what happens when HbA1c climbs above that target? A 2020 study by researchers from the Islamia University of Bahawalpur, Pakistan, and the University of Texas at Austin explored how high HbA1c levels alter the structure of hemoglobin (Hb)—the protein in red blood cells that carries oxygen—and what that means for diabetic health.
What the Study Investigated
Hemoglobin is critical to red blood cell function: its structure determines how well it binds to oxygen and moves through tiny blood vessels (capillaries). The researchers wanted to know: Does high HbA1c (a sign of persistent high blood sugar) change hemoglobin’s structure, and if so, how?
To find out, they studied three groups:
- Group N (20 healthy controls): HbA1c <6% (normal range).
- Group A (25 type 2 diabetes patients): HbA1c between 6–7% (good glycemic control).
- Group B (28 type 2 diabetes patients): HbA1c ≥9% (poor glycemic control).
They used Fourier-transform infrared (FTIR) spectroscopy—a lab technique that analyzes molecular structures by measuring how they absorb infrared light—to compare hemoglobin from each group. They also created a “hyperglycemic erythrocyte model” (red blood cells exposed to high glucose in a lab) to test how glucose directly affects hemoglobin.
Key Findings: High HbA1c Alters Hemoglobin and Red Blood Cells
The study uncovered two critical changes in people with poorly controlled diabetes (HbA1c ≥9%):
1. Red Blood Cells Lose Their Shape and Flexibility
Normal red blood cells are oval and flexible, letting them squeeze through narrow capillaries. But in Group B (high HbA1c), erythrocytes (red blood cells) became almost circular and less deformable. This rigidity could slow blood flow in small vessels—one reason diabetes raises the risk of vascular complications like retinopathy (eye damage) or neuropathy (nerve damage).
2. Hemoglobin’s Secondary Structure Shifts: Alpha-Helix to Beta-Sheet
Hemoglobin’s function depends on its secondary structure—the folds (alpha-helices) and sheets (beta-sheets) that give the protein its shape. The researchers found:
- In healthy people (Group N), hemoglobin has more alpha-helices (tight, spring-like folds) that keep it stable and functional.
- In Group B (high HbA1c), alpha-helix content decreased significantly, while beta-sheet content increased.
This shift matters because beta-sheets are linked to protein misfolding—a process seen in diseases like Alzheimer’s and type 2 diabetes. When hemoglobin’s alpha-helices turn into beta-sheets, the protein unfolds, loses stability, and may work less efficiently.
Why This Matters for Type 2 Diabetes
The study’s results connect high blood sugar to structural changes in hemoglobin—and those changes could drive diabetic complications:
- Oxygen Binding: Unfolded hemoglobin may have less affinity for oxygen, meaning red blood cells can’t deliver oxygen to tissues as well.
- Red Blood Cell Flexibility: Rigid erythrocytes (from hemoglobin changes) struggle to move through capillaries, reducing blood flow to organs.
- Complication Risk: The shift to beta-sheets may increase protein aggregation (clumping), which is linked to inflammation and vascular damage—key drivers of diabetes-related heart disease, kidney disease, and vision loss.
What the Researchers Concluded
The team found that HbA1c levels above 9% are linked to significant hemoglobin structural changes—while patients with good control (HbA1c 6–7%) showed minimal differences from healthy people. They also noted that FTIR spectroscopy, which is not yet used clinically for diabetes, could be a powerful tool to detect early structural changes in hemoglobin—potentially helping doctors spot complications before they become severe.
The Study Details
This research was led by Farah Andleeb (Biophotonics Research Group, Islamia University of Bahawalpur; Biomedical Engineering Department, University of Texas at Austin) and colleagues from Govt Sadiq College Women University Bahawalpur and Bahawal Victoria Hospital. It was published in the Chinese Medical Journal in 2020 with ethical approval from the Pakistan Medical Research Council.
Read the original study: doi.org/10.1097/CM9.0000000000000801
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