Role of free radicals in Diabetes mellitus MCQs With Answer

Role of free radicals in Diabetes mellitus MCQs With Answer

Free radicals and oxidative stress play a central role in the pathogenesis and complications of diabetes mellitus. Excess glucose metabolism generates reactive oxygen species (ROS) and reactive nitrogen species (RNS) via mitochondrial dysfunction, NADPH oxidase activation, and glycation pathways, causing β-cell dysfunction, insulin resistance, lipid peroxidation, and protein damage. Understanding biomarkers (MDA, 8-OHdG), antioxidant defenses (SOD, catalase, glutathione peroxidase), and signaling pathways (PKC, NF-κB, Nrf2) helps B. Pharm students evaluate drug targets and antioxidant therapies. This focused set of MCQs emphasizes mechanisms, assays, and therapeutic implications to deepen pharmaceutical understanding. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which of the following best describes a free radical implicated in diabetes-related oxidative stress?

• Electron-deficient molecule with positive charge
• Species containing one or more unpaired electrons
• Stable ion that does not react with biomolecules
• Protein-bound carbohydrate adduct

Correct Answer: Species containing one or more unpaired electrons

Q2. Which reactive oxygen species is primarily produced by mitochondrial electron transport chain leakage?

• Hydrogen peroxide (H2O2)
• Superoxide anion (O2•−)
• Hydroxyl radical (•OH)
• Peroxynitrite (ONOO−)

Correct Answer: Superoxide anion (O2•−)

Q3. Persistent hyperglycemia increases free radical generation mainly through which pathway?

• Glycolysis upregulation only
• Polyol pathway flux and NADPH consumption
• Decreased hexosamine pathway flux
• Inhibition of glycation

Correct Answer: Polyol pathway flux and NADPH consumption

Q4. Which antioxidant enzyme catalyzes the conversion of superoxide to hydrogen peroxide?

• Glutathione peroxidase
• Catalase
• Superoxide dismutase (SOD)
• Thioredoxin reductase

Correct Answer: Superoxide dismutase (SOD)

Q5. Lipid peroxidation in diabetic patients is commonly assessed by measuring which biomarker?

• 8-OHdG (8-hydroxy-2′-deoxyguanosine)
• Malondialdehyde (MDA)
• Reduced glutathione (GSH)
• Catalase activity

Correct Answer: Malondialdehyde (MDA)

Q6. Advanced glycation end products (AGEs) exacerbate oxidative stress primarily by:

• Directly scavenging ROS
• Activating RAGE receptors and proinflammatory signaling
• Increasing insulin secretion
• Enhancing antioxidant enzyme expression

Correct Answer: Activating RAGE receptors and proinflammatory signaling

Q7. Which of the following is a reactive nitrogen species relevant to diabetic vascular damage?

• Nitric oxide (NO) only in its physiologic form
• Peroxynitrite (ONOO−)
• Hydrogen sulfide (H2S)
• Superoxide dismutase

Correct Answer: Peroxynitrite (ONOO−)

Q8. Beta-cell vulnerability to oxidative stress is high because pancreatic β-cells have:

• High levels of catalase and glutathione peroxidase
• Low antioxidant enzyme expression
• Excess mitochondrial biogenesis
• Overactive DNA repair mechanisms

Correct Answer: Low antioxidant enzyme expression

Q9. Which assay is used to measure oxidative DNA damage in diabetic patients?

• Thiobarbituric acid reactive substances (TBARS) for MDA
• 8-OHdG ELISA
• Glucose oxidase test
• Hemoglobin A1c measurement

Correct Answer: 8-OHdG ELISA

Q10. Activation of NADPH oxidase in diabetes leads to increased:

• Antioxidant capacity
• Generation of superoxide radicals
• Insulin receptor sensitivity
• Glycogen synthesis

Correct Answer: Generation of superoxide radicals

Q11. Glutathione peroxidase protects cells by:

• Reducing hydrogen peroxide to water using glutathione
• Generating superoxide radicals
• Cleaving advanced glycation end products
• Producing nitric oxide

Correct Answer: Reducing hydrogen peroxide to water using glutathione

Q12. Which transcription factor is a master regulator of cellular antioxidant response relevant in diabetes?

• NF-κB
• HIF-1α
• Nrf2
• AP-1

Correct Answer: Nrf2

Q13. Increased mitochondrial ROS in diabetes primarily contributes to insulin resistance by:

• Improving insulin receptor signaling
• Activating stress kinases and serine phosphorylation of IRS proteins
• Enhancing GLUT4 translocation
• Increasing pancreatic β-cell proliferation

Correct Answer: Activating stress kinases and serine phosphorylation of IRS proteins

Q14. Which therapeutic strategy targets oxidative stress in diabetes by boosting endogenous antioxidants?

• Use of NADPH oxidase activators
• Administration of Nrf2 activators (e.g., sulforaphane)
• AGE formation enhancers
• Inhibition of superoxide dismutase

Correct Answer: Administration of Nrf2 activators (e.g., sulforaphane)

Q15. Peroxynitrite formation requires reaction between:

• Hydrogen peroxide and hydroxyl radical
• Nitric oxide (NO) and superoxide (O2•−)
• Glutathione and catalase
• Reducing sugars and proteins

Correct Answer: Nitric oxide (NO) and superoxide (O2•−)

Q16. Which marker indicates protein oxidation in diabetic patients?

• Protein carbonyl content
• Serum insulin level
• Glycated hemoglobin (HbA1c) only
• Plasma glucose alone

Correct Answer: Protein carbonyl content

Q17. Chronic oxidative stress contributes to diabetic nephropathy by promoting:

• Podocyte protection and matrix degradation
• Glomerular basement membrane thickening and fibrosis
• Reduced mesangial expansion
• Improved renal blood flow

Correct Answer: Glomerular basement membrane thickening and fibrosis

Q18. Which dietary antioxidant directly scavenges free radicals and is studied in diabetes?

• Metformin
• Vitamin E (α-tocopherol)
• Insulin
• Sulfonylurea

Correct Answer: Vitamin E (α-tocopherol)

Q19. The hexosamine pathway contributes to oxidative stress in diabetes by:

• Decreasing O-GlcNAc modification of proteins
• Altering signaling and increasing ROS via protein modification
• Directly detoxifying ROS
• Enhancing catalase activity

Correct Answer: Altering signaling and increasing ROS via protein modification

Q20. Which cellular event links hyperglycemia to activation of protein kinase C (PKC) and oxidative stress?

• Decreased diacylglycerol (DAG) synthesis
• Increased DAG formation leading to PKC activation
• Reduced fatty acid oxidation only
• Enhanced insulin receptor tyrosine phosphorylation

Correct Answer: Increased DAG formation leading to PKC activation

Q21. Measurement of total antioxidant capacity in plasma primarily reflects:

• Only enzymatic antioxidants
• Combined effect of enzymatic and non-enzymatic antioxidants
• Glycated protein levels
• Insulin sensitivity directly

Correct Answer: Combined effect of enzymatic and non-enzymatic antioxidants

Q22. Which pharmacological agent has antioxidant effects in diabetes besides glucose-lowering action?

• Sulfonylureas exclusively
• Metformin via AMP-activated protein kinase (AMPK) activation and reduced ROS
• Insulin that increases ROS production only
• Thiazolidinediones that solely impair mitochondrial function

Correct Answer: Metformin via AMP-activated protein kinase (AMPK) activation and reduced ROS

Q23. Oxidative modification of low-density lipoprotein (LDL) in diabetes primarily leads to:

• Reduced atherogenesis
• Enhanced uptake by macrophages and foam cell formation
• Decreased endothelial dysfunction
• Improved lipid profiles without inflammation

Correct Answer: Enhanced uptake by macrophages and foam cell formation

Q24. Which enzyme regenerates reduced glutathione (GSH) from oxidized glutathione (GSSG)?

• Glutathione peroxidase
• Glutathione reductase
• Catalase
• Superoxide dismutase

Correct Answer: Glutathione reductase

Q25. Chronic inflammation in diabetes increases ROS production primarily through activation of:

• Insulin receptors
• Immune cells and inducible nitric oxide synthase (iNOS)
• Glycogen synthase only
• Adiponectin secretion

Correct Answer: Immune cells and inducible nitric oxide synthase (iNOS)

Q26. 8-Isoprostanes are reliable biomarkers of:

• Protein glycation
• Lipid peroxidation and oxidative stress in vivo
• Reduced glutathione levels only
• Insulin secretion rate

Correct Answer: Lipid peroxidation and oxidative stress in vivo

Q27. Which mitochondrial change is commonly observed in diabetic tissues contributing to ROS?

• Enhanced coupling efficiency and reduced ROS
• Electron transport chain dysfunction and increased electron leak
• Upregulated complex I activity only to decrease ROS
• Complete loss of mitochondrial DNA repair

Correct Answer: Electron transport chain dysfunction and increased electron leak

Q28. Antioxidant supplementation in diabetes has shown mixed clinical results primarily because:

• All antioxidants are harmful in diabetes
• Complexity of redox signaling and inappropriate dosing/timing
• Oxidative stress is not important in diabetes
• Biomarkers are fully standardized and always predictive

Correct Answer: Complexity of redox signaling and inappropriate dosing/timing

Q29. Which molecular event is a downstream consequence of ROS-mediated NF-κB activation in diabetes?

• Suppression of proinflammatory cytokines
• Increased transcription of TNF-α and IL-6
• Decreased adhesion molecule expression
• Promotion of insulin receptor sensitivity

Correct Answer: Increased transcription of TNF-α and IL-6

Q30. Targeting oxidative stress therapeutically in diabetes could involve all EXCEPT:

• Enhancing endogenous antioxidant enzyme expression
• Direct ROS scavengers
• Inhibiting NADPH oxidase activity
• Stimulating AGE formation

Correct Answer: Stimulating AGE formation

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