Association of Single Nucleotide Polymorphism in Transcription Factors Modulating Antioxidant Defense with Oxidative Stress Profile in Diabetic Patients

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By Dipak Ashok Kadam | Savitribai Phule Pune University

Type 2 Diabetes (T2D) is not just a disease of blood sugar; it is a complex metabolic disorder deeply intertwined with genetics and cellular stress. A groundbreaking thesis submitted to Savitribai Phule Pune University explores the genetic underpinnings of how diabetic patients fight off cellular damage.

This research dives deep into the Single Nucleotide Polymorphisms (SNPs) found in key transcription factors and antioxidant genes to determine if specific genetic variations make certain individuals more susceptible to oxidative stress. Below is a detailed breakdown of the topics and findings covered in this comprehensive study.

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1. The Link Between Hyperglycemia and Oxidative Stress

The thesis begins by establishing the fundamental problem in diabetes: Oxidative Stress (OS).

• The Mechanism: Persistent high blood sugar (hyperglycemia) leads to the overproduction of Reactive Oxygen Species (ROS).
• The Damage: When ROS exceeds the body’s ability to neutralize them, it leads to damage in DNA, lipids, and proteins.
• Complications: This oxidative stress is identified as a primary culprit behind diabetic complications, including neuropathy, retinopathy, and cardiovascular issues.

2. The Body’s Antioxidant Defense System

To combat oxidative stress, the human body utilizes a sophisticated defense system. The research focuses on two categories of defense:

• Antioxidant Molecules: Such as Glutathione (GSH), Bilirubin, and Uric Acid.
• Antioxidant Enzymes: Specifically Superoxide Dismutase (SOD), Catalase (CAT), and Heme Oxygenase-1 (HO-1).

3. Key Transcription Factors: Nrf2 and FoxO1

The study highlights that antioxidant enzymes don’t just appear; they are regulated by specific Transcription Factors (TFs). The thesis focuses on two critical TFs:

• Nrf2 (Nuclear factor erythroid 2-related factor 2): A master regulator that induces the expression of cytoprotective genes.
• FoxO1 (Forkhead box protein O1): Critical for cell differentiation, metabolism, and stress response.
  The Hypothesis: If the genes coding for these TFs (or the enzymes they regulate) have mutations (SNPs), the body’s defense system might fail, worsening diabetes.

4. Methodology: Analyzing the Indian Population

The research was conducted using a comparative study between 98 diabetic individuals and 90 non-diabetic controls from the Indian population. The methodology included:

• Biochemical Analysis: Measuring Fasting Blood Sugar (FBS), HbA1c, SOD, CAT activities, and Total Antioxidant Capacity (TAC).
• Genetic Sequencing: Using Next-Generation Sequencing (Illumina) and Sanger Sequencing to identify SNPs in Nrf2, FoxO1, HO-1, and the CAT promoter.
• In-Silico Analysis: Using computational tools (PolyPhen-2, SIFT, mutation3D) to predict how these genetic changes affect protein structure and stability.

5. Key Research Findings

A. Biochemical Profile

The study confirmed that diabetic patients had significantly lower antioxidant defenses. Specifically, the activity of Catalase (CAT) and Superoxide Dismutase (SOD) was reduced, leading to a depleted Total Antioxidant Capacity (TAC) compared to healthy individuals.

B. Genetic Variations (SNPs) Detected

The sequencing revealed a significant number of genetic variations:

• Nrf2: 34 SNPs/SNVs detected (8 novel).
• FoxO1: 34 SNPs/SNVs detected (8 novel).
• HO-1: 89 SNPs detected (all previously reported).
• CAT Promoter: 6 SNPs detected.

C. The Critical Role of the CAT Gene

The most significant finding of the thesis related to the Catalase (CAT) gene promoter:

• The allele T of SNP rs1001179 was significantly associated with decreased catalase activity in diabetic individuals.
• This suggests a genetic risk factor where this specific variation makes the antioxidant defense system less effective in diabetic patients.

D. In-Silico Predictions

Using advanced bioinformatics, the study predicted that certain novel mutations found in Nrf2 and FoxO1 (such as D588G in Nrf2 and D53A in FoxO1) could destabilize the proteins, potentially altering their function, though these did not show a direct statistical correlation with protein levels in this specific sample size.

6. Conclusion

This thesis provides the first report on the allele and haplotype diversity of Nrf2, FoxO1, and HO-1 genes in the Indian population regarding diabetes. While many polymorphisms were found, the study strongly highlights that oxidative stress is elevated in T2D and that specific genetic variations in the Catalase promoter may contribute to a weakened antioxidant defense, exacerbating the disease.

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