Spontaneous Diabetes Mellitus Models

Model Introduction

Spontaneous diabetes models refer to models of diabetes and its complications that occur naturally due to genetic factors such as gene mutations or chromosomal aberrations, without human intervention. This category mainly includes NOD mice, Insulin-2 Akita mice, KK-Ay mice, and BB rats. The core principles involve autoimmune destruction of pancreatic islet cells, proteotoxicity caused by insulin gene mutations, and metabolic disorders induced by specific gene introductions. These models can effectively simulate the natural occurrence and progression of human diabetic nephropathy (DN).

Research Applications

These models are primarily used to simulate the pathophysiological changes of human Type 1 and Type 2 diabetes and their renal complications:

1. Type 1 Diabetes Research: NOD mice and BB rats are commonly used to simulate autoimmune insulin-dependent diabetes mellitus (IDDM).
2. Type 2 Diabetes Research: KK-Ay mice, characterized by severe obesity and hyperglycemia, are widely used in the study of renal injury in Type 2 diabetes.
3. Complications Research: In addition to diabetes research, Akita mice can be used to explore complications such as hypertension and heart failure.

Key Points of Experimental Design

Since these models are spontaneous, experimental designs are mainly based on observations of the natural disease course across different strains, requiring no specific drug induction or surgical intervention:

1. NOD Mice: Pancreatic inflammation typically appears at 4–5 weeks of age, diabetes develops at 24–30 weeks, and progression to DN occurs around 37 weeks.
2. Insulin-2 Akita Mice: Significant hyperglycemia and albuminuria can be observed as early as 4 weeks of age.
3. KK-Ay Mice: Significant segmental glomerular sclerosis and related changes in biochemical indicators can be observed at 20 weeks of age.
4. BB Rats: The disease course is relatively long, usually requiring observation up to 18 months.
5. Husbandry Costs: These models are difficult to breed and maintain, resulting in higher costs.

Key Monitoring Indicators

1. Biochemical Indicators:
   • Blood glucose levels, Glycated hemoglobin (HbA1c).
   • Urinary protein excretion rate, albuminuria, urinary protein-to-creatinine ratio (UPCR).
   • Glomerular filtration rate (GFR).
2. Pathological Indicators:
   • Pancreas: Pancreatic inflammatory response, reduction in pancreatic β-cell mass.
   • Kidney: Glomerular hypertrophy, mesangial cell proliferation, mesangial matrix expansion, thickening of the glomerular capillary basement membrane, increased extracellular matrix (ECM), and glomerulosclerosis (e.g., segmental sclerosis).
3. Molecular Markers:
   • Localization and expression of Advanced Glycation End-products (AGEs) and Transforming Growth Factor-β (TGF-β) in the glomerular mesangial area.
4. Other Physical Signs:
   • Body weight (e.g., severe obesity in KK-Ay mice), blood pressure (e.g., hypertension in Akita mice).