Acetone Breath in an Unconscious Patient

Molecular Explanation of the 3 Main Causes

Detection of acetone in the breath suggests:

• increased ketone body production

• usually due to severe carbohydrate deficiency or inability to use glucose.

The three classic causes are:

1. Long-term starvation

2. Diabetes mellitus

3. Alcoholism

What are ketone bodies?

Ketone bodies are produced in the liver from excess acetyl-CoA.

Main ketone bodies:

• acetoacetate

• β-hydroxybutyrate

• acetone

Acetone is volatile and is exhaled in breath.

1. Long-Term Starvation

During starvation:

• blood glucose falls

• insulin decreases

• glucagon increases

This shifts metabolism into a catabolic state.

Early starvation (first 10–18 h)

Main energy source:

• glycogenolysis

Liver glycogen becomes depleted after about:

• 10–18 hours.

After glycogen depletion

The liver increases:

• gluconeogenesis

using:

• amino acids

• lactate

• glycerol

At the same time:

• adipose tissue increases lipolysis

• fatty acid oxidation rises.

Why ketone bodies increase

Fatty acid oxidation generates large amounts of:

• acetyl-CoA

When acetyl-CoA exceeds TCA cycle capacity:

Ketone bodies become major fuels for:

• brain

• muscle

after prolonged fasting.

Acetone breath

At high ketone levels:

• acetoacetate spontaneously forms acetone

Acetone is exhaled:

• producing fruity/acetone breath.

2. Diabetes Mellitus

In:

• Type 1 Diabetes

there is:

• absolute insulin deficiency

In severe uncontrolled diabetes:

• cells cannot effectively utilize glucose

• body behaves as if it is starving.

So metabolism resembles starvation despite high blood glucose.

Metabolic consequences

↓ Insulin + ↑ Glucagon

causes:

• lipolysis

• fatty acid oxidation

• ketogenesis

Diabetic ketoacidosis (DKA)

Large ketone production causes:

• metabolic acidosis

• dehydration

• acetone breath

• unconsciousness in severe cases.

3. Alcoholism

Ethanol metabolism occurs mainly in the liver.

Two oxidation reactions produce large amounts of:

• NADH

Both reactions generate:

• NADH

Effect of excess NADH

High NADH shifts reactions toward:

Why this causes ketoacidosis

Oxaloacetate is needed for:

• gluconeogenesis

• TCA cycle function.

When oxaloacetate becomes depleted:

• gluconeogenesis decreases

• acetyl-CoA cannot efficiently enter TCA cycle

So acetyl-CoA is diverted into:

• ketone body synthesis.

Result:

• alcoholic ketoacidosis

• acetone breath

• hypoglycemia.

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