Glucagon

How Glucagon Works

Glucagon raises blood glucose through several mechanisms:

1. Glycogenolysis - Breaks down glycogen stores in liver to release glucose
2. Gluconeogenesis - Stimulates liver to make new glucose from amino acids
3. Ketogenesis - Promotes ketone body production when glucose is low
4. Lipolysis - Stimulates fat breakdown for energy

Glucagon vs Insulin Balance

Condition	Insulin	Glucagon	Result
After eating	High	Low	Glucose stored
Fasting	Low	High	Glucose released
Exercise	Decreases	Increases	Fuel mobilized
Low blood sugar	Suppressed	Elevated	Emergency glucose release

Glucagon Structure

Glucagon is a 29-amino acid peptide:

• Produced from proglucagon (same precursor as GLP-1)
• Single chain, no disulfide bonds
• Secreted by pancreatic alpha cells

Glucagon in Diabetes

Type 1 Diabetes

• Alpha cell dysfunction common
• Impaired glucagon response to low blood sugar
• Increases hypoglycemia risk

Type 2 Diabetes

• Elevated glucagon levels
• Contributes to high blood sugar
• Alpha cells become resistant to insulin’s suppressive effect

Glucagon Receptor in Drug Development

GLP-1 Agonists (Indirect Effect)

• Suppress glucagon release
• Help lower blood sugar
• Work through GLP-1 receptor, not glucagon receptor

Glucagon Receptor Agonists (New Approach)

• Retatrutide - Triple agonist (GIP/GLP-1/Glucagon)
• Glucagon activity increases energy expenditure
• May enhance weight loss beyond GLP-1 alone
• Requires careful balance to avoid hyperglycemia

Why Add Glucagon Activity?

Seems counterintuitive for diabetes/obesity, but:

Effect	Benefit
Increased energy expenditure	More calories burned
Enhanced fat oxidation	Promotes fat loss
Satiety effects	May reduce appetite
Thermogenesis	Increases metabolic rate

The key is combining with GLP-1 to offset glucose-raising effects.

Emergency Glucagon Use

Glucagon is also an emergency medication:

• Indication: Severe hypoglycemia
• Administration: Injection or nasal spray
• Effect: Rapidly raises blood sugar
• Examples: Baqsimi (nasal), GlucaGen (injection)

Frequently Asked Questions

Why does the body need both insulin and glucagon?

They work as a balanced system. Insulin lowers blood sugar when it’s high (after eating); glucagon raises it when it’s low (fasting, exercise). This push-pull system maintains blood glucose in a narrow, healthy range.

Why would you want glucagon receptor activity in a diabetes drug?

While glucagon raises blood sugar, it also increases energy expenditure and fat burning. When combined with GLP-1 (which lowers blood sugar), the metabolic benefits of glucagon can be captured while GLP-1 offsets the glucose-raising effect.

Is GLP-1 related to glucagon?

Yes, they come from the same precursor molecule (proglucagon). In the pancreas, proglucagon is processed into glucagon. In the intestine, it’s processed into GLP-1. Despite shared origins, they have different—often opposite—effects on blood sugar.