Type 2 Diabetes

What is Type 2 Diabetes?

Type 2 diabetes (T2D) is a chronic metabolic disease in which the body becomes resistant to insulin’s effects and gradually loses the ability to produce enough insulin to compensate. It affects over 400 million people worldwide and is a leading cause of cardiovascular disease, kidney failure, blindness, and amputation.

Key concept: Type 2 diabetes is the primary approved indication for GLP-1 receptor agonists and dual agonists, making it central to understanding metabolic peptide research.

Pathophysiology

The progression:

1. Insulin resistance develops — Cells respond poorly to insulin
2. Compensatory hyperinsulinemia — Pancreas makes more insulin
3. β-cell stress — Overworked β-cells begin to fail
4. Hyperglycemia — Blood sugar rises as insulin production falls
5. Overt diabetes — A1C ≥6.5% or fasting glucose ≥126 mg/dL

Diagnosis Criteria

Test	Diabetes Threshold
Fasting plasma glucose	≥126 mg/dL
2-hour OGTT	≥200 mg/dL
A1C	≥6.5%
Random glucose	≥200 mg/dL (with symptoms)

Type 2 vs Type 1 Diabetes

Feature	Type 2	Type 1
Cause	Insulin resistance + β-cell dysfunction	Autoimmune β-cell destruction
Onset	Usually adults (increasingly children)	Usually children/young adults
Prevalence	~90-95% of diabetes	~5-10% of diabetes
Insulin	Initially present (often elevated)	Absent from diagnosis
Weight	Often overweight/obese	Variable
Treatment	Lifestyle + oral/injectable meds	Insulin required

GLP-1 Agonists in Type 2 Diabetes

GLP-1 receptor agonists are now first-line therapy for many patients:

Medication	Brand (T2D)	A1C Reduction
Semaglutide	Ozempic	~1.5-2.0%
Tirzepatide	Mounjaro	~2.0-2.6%
Liraglutide	Victoza	~1.0-1.5%
Dulaglutide	Trulicity	~1.0-1.6%
Exenatide	Byetta, Bydureon	~0.8-1.5%

Why Peptides Work in T2D

GLP-1 and dual agonists address multiple T2D mechanisms:

Effect	Benefit in T2D
Glucose-dependent insulin	Reduces hypoglycemia risk
Glucagon suppression	Lowers hepatic glucose output
Weight loss	Improves insulin sensitivity
β-cell preservation	May slow disease progression
Appetite reduction	Addresses driver of insulin resistance

Landmark Clinical Trials

Trial	Medication	Key Finding
SUSTAIN 1-10	Semaglutide	Superior to comparators
SURPASS 1-5	Tirzepatide	Superior to semaglutide 1 mg
LEADER	Liraglutide	Cardiovascular benefit
SELECT	Semaglutide	CV benefit in obesity

Beyond Glycemic Control

Modern T2D treatment targets multiple outcomes:

Target	Medications with Benefit
A1C reduction	All GLP-1 agonists
Cardiovascular protection	Semaglutide, liraglutide, dulaglutide
Weight management	Semaglutide, tirzepatide
Kidney protection	Semaglutide (FLOW trial)

Complications of T2D

Complication	Affected System
Retinopathy	Eyes
Nephropathy	Kidneys
Neuropathy	Nerves
Cardiovascular disease	Heart, blood vessels
Foot ulcers/amputation	Lower extremities

Treatment Guidelines (2025-2026)

Current guidelines recommend:

1. Lifestyle intervention for all patients
2. Metformin as initial pharmacotherapy (usually)
3. GLP-1 agonist or SGLT2 inhibitor added early, especially with CVD, heart failure, or kidney disease
4. Dual agonists (tirzepatide) increasingly used first-line

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This entry is for educational purposes only. Type 2 diabetes management should be individualized by a healthcare provider.