Physiology & Biochemistry · patient case question
In poorly controlled diabetes, ketone bodies are produced from the breakdown of:
Patient case: A Diabetic Who Does Not Check His Sugar
Patient: 56-year-old male
Chief Complaint: Broken tooth, wants it fixed.
Background: Type 2 diabetes for nine years. When asked about his blood glucose he says he does not test it and has not seen his physician in over a year. Reports increasing thirst and getting up at night to urinate.
Medications: Metformin — admits he is inconsistent with it
Vital Signs: BP 138/86 mmHg · HR 82 bpm · RR 16 · T 98.6°F
Findings: Generalized gingival inflammation with bleeding on probing, multiple 5–6 mm pockets, dry mucosa, and a fractured cusp on #14.
Show answer and explanation
Correct answer: B. Lipids (fatty acids)
- A. Carbon dioxide is a metabolic end product, not a substrate for synthesis.
- B. CORRECT. Without adequate insulin, cells cannot take up glucose, so the body switches to LIPOLYSIS. Free fatty acids are released from adipose tissue, travel to the liver and undergo beta-oxidation to acetyl-CoA. When acetyl-CoA production overwhelms the capacity of the citric acid cycle, the excess is diverted into KETOGENESIS, producing acetoacetate, beta-hydroxybutyrate and acetone. Acetone is volatile and exhaled — hence the characteristic fruity or acetone breath odour.
- C. Some amino acids are ketogenic (leucine, lysine), but they are a minor contributor. The dominant substrate is fatty acid.
- D. Glucose is what the cells cannot access. Its metabolism yields pyruvate and then acetyl-CoA, but ketogenesis in diabetes is driven by fat, not carbohydrate.
Note: This is why diabetic KETOACIDOSIS is a complication of HYPERglycaemia, not hypoglycaemia — and it is the trap this recall item was built around.
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