A 45‑year‑old man has been diagnosed with type 2 diabetes mellitus and is prescribed metformin. (a) Explain the biochemical mechanism by which metformin lowers blood glucose. (b) Recommend two lifestyle modifications that should accompany the drug therapy. (c) Mention one common side effect of metformin and how it can be managed.
Answer
Metformin activates AMP‑activated protein kinase, reducing hepatic gluconeogenesis and increasing peripheral glucose uptake; lifestyle changes: regular moderate exercise and a diet low in refined carbohydrates; common side effect: gastrointestinal upset, managed by taking the drug with meals or using extended‑release formulation.
Step-by-step solution
- State that metformin belongs to the biguanide class and does not stimulate insulin secretion.
- Explain that metformin activates AMP‑activated protein kinase (AMPK) in liver and muscle cells.
- Describe how AMPK activation suppresses hepatic gluconeogenesis, decreasing glucose output.
- Mention that AMPK also enhances glucose transporter (GLUT4) translocation in muscle, increasing glucose uptake.
- Summarize that the net effect is lowered blood glucose without causing hypoglycaemia.
- List two lifestyle measures: (i) performing at least 150 minutes of moderate‑intensity aerobic exercise per week, and (ii) adopting a balanced diet rich in fibre, whole grains, and low in refined sugars.
- Identify the most frequent side effect: gastrointestinal disturbances such as nausea, diarrhoea, or abdominal discomfort.
- Suggest management: take metformin with meals, start with a low dose and titrate gradually, or switch to an extended‑release formulation to reduce GI symptoms.
Common mistake: Confusing metformin’s action with insulin secretion or ignoring the need for lifestyle changes
Concept tested: Metformin action and diabetes management
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