Jens Juul Holst: The Discovery of GLP-1 for Diabetes and Obesity Treatment

The Incretin Hypothesis and Early Discoveries

• 💡 Jens Juul Holst's research began with observing hypoglycemia in post-surgery patients after meals, hypothesizing an insulin-stimulating hormone from the gut, an incretin.
• 🔬 Initial work identified glicentin, a peptide resembling glucagon, which was part of the larger proglucagon molecule.
• 🔑 Graeme Bell's molecular cloning in 1983 revealed that proglucagon contained two additional glucagon-like stretches, providing crucial information for further investigation.

Unveiling GLP-1's Potent Effects

• 🎯 Researchers isolated and purified the "real" GLP-1 from gut extracts, discovering it was a powerful stimulator of insulin secretion from the pancreas.
• 🧠 GLP-1 was later proven to be responsible for the hypoglycemia observed in patients and also inhibited glucagon secretion, which is often elevated in type 2 diabetes.
• 🍽️ Beyond glucose regulation, GLP-1 was found to inhibit gastric acid secretion, pancreatic secretion, and gastric emptying, with its actions involving the brain.
• 🍎 Crucially, GLP-1 also demonstrated an ability to inhibit appetite and food intake in humans, opening doors for obesity treatment.

Advancing Diabetes Treatment

• 📈 Early clinical studies, including a 1993 collaboration, showed that GLP-1 infusion could normalize blood glucose in patients with severe type 2 diabetes.
• ✅ A 2002 study further confirmed that continuous subcutaneous GLP-1 infusion significantly improved blood glucose, insulin secretion, insulin sensitivity, and even body weight in long-standing type 2 diabetes patients.

Overcoming Challenges and Developing Therapies

• ⚠️ A major challenge was GLP-1's extremely short half-life of only 2 minutes in circulation, due to rapid breakdown by the DPP4 enzyme.
• 💊 The discovery that DPP4 inhibitors could prevent this breakdown led to the development of successful oral diabetes medications like sitagliptin (Januvia), approved in 2006.
• 🚀 Inspired by GLP-1's effects, Novo Nordisk developed liraglutide (Victoza), a long-acting GLP-1 analog with a 12-hour half-life, becoming a superior anti-diabetic agent.
• ✨ A second-generation, weekly version, semaglutide, proved even more effective, leading to significant weight loss (up to 18%) and preventing complications, establishing effective treatments for both obesity and diabetes.