A Detailed Guide to the Construction of Animal Models for Metabolic Diseases

Product Manager: Harrison Michael

I. Overview of Metabolic Disease Model Construction

Metabolic diseases, such as diabetes, obesity, non-alcoholic fatty liver disease (NAFLD), and atherosclerosis, are on the rise globally, posing a significant burden to public health. Animal models, as essential tools for uncovering the mechanisms of metabolic disorders and evaluating the efficacy and safety of drugs, have seen continuous advancements in their construction techniques, forming a relatively mature system.

The construction of animal models for metabolic diseases requires a comprehensive consideration of disease type, reproducibility, stability, operability, and ethical factors. This article systematically summarizes the mainstream methods for establishing animal models of metabolic diseases, common model types, and detailed experimental protocols for reference by researchers in the field of metabolic diseases.

II. Modeling Methods for Metabolic Disease Animal Models

Based on the induction methods and model characteristics, animal models for metabolic diseases can be classified into the following three categories:

1. Genetic Models (Congenital Models)

These models are constructed through gene mutations, spontaneous mutations, or gene editing techniques and are suitable for studying congenital metabolic abnormalities or metabolic diseases under genetic backgrounds.

·db/db mice: A classic model for type 2 diabetes, with a leptin receptor mutation leading to obesity and Ins resistance.

·ob/ob mice: Characterized by a deficiency in the leptin gene, resulting in severe obesity, hyperInsemia, and hyperglycemia.

·Zucker obese rats (fa/fa): With a leptin receptor mutation, they exhibit obesity, Ins resistance, and hyperlipidemia.

·ApoE⁻/⁻ mice, LDLR⁻/⁻ mice: Widely used in the study of hyperlipidemia and atherosclerosis.

2. Induced Models (Acquired Models)

These models induce metabolic abnormalities in animals through external means such as dietary intervention, drug injection, and surgical operations.

·STZ-induced diabetes model:

A single high dose (60–70 mg/kg) induces type 1 diabetes by destroying pancreatic β-cells;

Multiple low doses (30–40 mg/kg/day for 5 consecutive days) are used to create an autoimmune type 1 diabetes model.

·HFD-induced model:

Long-term feeding of a high-fat diet can induce obesity, Ins resistance, and NAFLD.

·HFD+STZ combined model:

This model mimics the pathogenesis of type 2 diabetes by first inducing Ins resistance with a high-fat diet and then damaging pancreatic β-cells with a low dose of STZ.

·Surgical models:

Methods such as partial pancreatectomy induce Ins secretion disorders, used for studying diabetes and pancreatic dysfunction.

3. Chemical or Toxicological Models

These models use specific chemicals or toxins to disrupt metabolic balance, simulating particular pathological conditions.

·MCD diet-induced NAFLD model: Lacking methionine and choline, it rapidly induces NASH without obesity.

·CDAA diet model: Deficient in choline and amino acids, it is suitable for studying the mechanisms of metabolic NASH.

·Pyruvate kinase inhibitor model: Used for studying diseases related to glucose metabolism disorders.

III. Introduction to Mainstream Metabolic Disease Models

IV. Detailed Experimental Protocols for Common Models

1. STZ-Induced Diabetes Model (Type 1)

Animals: Male C57BL/6J mice, 6–8 weeks old.

Reagent: STZ (dissolved in freshly prepared cold citrate buffer, pH 4.5).

Dose and method: A single intraperitoneal injection of STZ at 60 mg/kg.

Observation indicators: Monitor fasting blood glucose 3–7 days after injection; a model is considered successful if blood glucose levels exceed 16.7 mmol/L on two consecutive occasions.

Precautions:

·STZ should be prepared and used immediately to prevent degradation.

·Animals should be fasted for 12 hours before the experiment.

·Pay attention to the animals' water and nutritional supply after administration.

2. HFD+STZ-Induced Type 2 Diabetes Model

Animals: Male C57BL/6J mice, 6 weeks old.

Modeling process:

·Feed with a high-fat diet for 4 weeks to induce Ins resistance.

·Inject STZ (30–40 mg/kg, single or multiple low doses) in the 5th week.

·The model is considered successful if fasting blood glucose exceeds 11.1 mmol/L one week after injection.

Advantages: Combines Ins resistance and β-cell dysfunction, more closely resembling human type 2 diabetes.

Precautions:

·The fat content of the diet should be controlled between 45–60%.

·The timing and dose of STZ injection should be strictly controlled to avoid excessive damage.

3. High-Fat Diet-Induced NAFLD Model

Animals: C57BL/6J mice or SD rats, 6–8 weeks old.

Diet composition: Fat content 45%–60%, with some models adding fructose and cholesterol to enhance the phenotypic expression.

Feeding period: 12–20 weeks.

Detection indicators:

·Serum ALT, AST, TG.

·Liver HE staining, Oil Red O staining to observe fat deposition.

·Expression of inflammation and fibrosis-related genes in liver tissue.

4. MCD/CDAA Diet-Induced NASH Model

Animals: C57BL/6J mice, 8 weeks old.

Feed composition:

·MCD: Lacking methionine and choline.

·CDAA: Choline-deficient and rich in fatty acids.

Feeding period: 4–8 weeks.

Characteristics:

·Significant elevation of ALT/AST.

·Presence of inflammation, hepatocyte ballooning, and fibrosis.

·No weight gain, suitable for studying NASH mechanisms rather than the overall presentation of metabolic syndrome.

5. ApoE⁻/⁻ Atherosclerosis Model

Animals: ApoE gene knockout mice.

Diet composition: Western high-fat, high-cholesterol diet (containing 1.25% cholesterol).

Feeding period: 8–16 weeks.

Observation indicators:

·Aortic and cardiac tissue sections to detect plaque formation.

·Oil Red O staining.

·Lipid profile indicators: TC, LDL-C, HDL-C, etc.

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