P2rx7 congenic mouse model insulin tolerance testing

PRIMARY OUTCOME

insulin sensitivity

EXPECTED OUTCOMES

## Expected Outcomes ### Primary Outcomes 1. **Impaired insulin sensitivity:** P2rx7 congenic mice show 20-40% higher glucose AUC during ITT vs 129SvJ controls 2. **Altered IL-1β:** P2X7 variation may affect NLRP3 inflammasome activation and IL-1β release 3. **Tissue-specific P2rx7 expression:** Higher expression in immune cells, adipose tissue vs muscle ### Secondary Outcomes - Fasting insulin levels may differ between genotypes - Body weight and fat mass differences possible - Lipid profile alterations (triglycerides, free fatty acids) ### Null Result Interpretation - If no phenotype at 10-12 weeks, examine aged mice (24 weeks) - May need high-fat diet challenge to unmask metabolic phenotype - Verify P2rx7 polymorphism functional significance (Calcium influx assay)

SUCCESS CRITERIA

## Success Criteria ### Primary - [ ] ≥8 animals/group complete ITT with full 120-min glucose curve - [ ] Baseline glucose similar between groups (no significant difference) - [ ] Control mice show ≥30% glucose reduction from baseline (assay validity) - [ ] Glucose AUC significantly different between congenic and control (p < 0.05) ### Secondary - [ ] P2rx7 expression confirmed in WAT, muscle, liver by qPCR - [ ] Terminal insulin measured (fasting state) - [ ] Inflammatory markers (IL-1β, IL-6) quantified in plasma ### Technical Quality Gates - [ ] Glucometer calibrated, quality control strips used - [ ] Duplicate glucose measurements (CV < 5%) - [ ] Insulin dose appropriate for 129 strain (avoid hypoglycemia) - [ ] Blinded analysis of glucose curves - [ ] Genotype confirmed for all animals post-study

PROTOCOL

## Protocol: P2rx7 Congenic Mouse Model Insulin Tolerance Testing ### Study Design Metabolic characterization of P2rx7 congenic mice (C57BL/6J P2rx7 allele on 129SvJ background) to assess the impact of P2X7 receptor variation on insulin sensitivity and glucose homeostasis. ### Animals and Breeding 1. Congenic mice: C57BL/6J-P2rx7 allele introgressed onto 129SvJ background (N≥10 generations) 2. Control: 129SvJ background mice with endogenous P2rx7 3. Groups: - Male and female P2rx7 congenic (n=10-12 per sex) - Age-matched 129SvJ controls (n=10-12 per sex) 4. Age: 10-12 weeks (young adult) for initial metabolic phenotyping 5. Optional: aged cohort (24 weeks) if young mice show no phenotype ### Metabolic Cages (Baseline) 1. Single-housing 48 hours prior to tests 2. Measure: - Food intake (automated cages) - Water intake - Energy expenditure (if equipped) - Locomotor activity (infrared beams) ### Insulin Tolerance Test (ITT) 1. Fasting: 4-6 hours (food removed at 8 AM, test at 12-2 PM) 2. Baseline blood glucose (tail vein, glucometer) 3. Intraperitoneal insulin injection: - Human insulin (0.5 U/kg for 129 background) - 129 mice are insulin-sensitive, adjust dose if needed 4. Blood glucose measurement at: 0, 15, 30, 45, 60, 90, 120 minutes post-injection 5. Calculate area under the curve (AUC) for glucose decline ### Glucose Tolerance Test (GTT) - Optional 1. Overnight fast (16 hours) 2. Baseline glucose 3. Glucose injection (2 g/kg IP) 4. Glucose measurement at 0, 15, 30, 60, 90, 120 minutes 5. Calculate AUC for glucose clearance ### Plasma Analysis 1. At sacrifice (terminal bleed): - Insulin (ELISA) - Glucose (direct measurement) - Lipids: triglycerides, free fatty acids - Inflammatory markers: IL-1β, IL-6 (P2X7 involved in inflammation) ### Tissue Collection 1. Epididymal white adipose tissue (WAT) 2. Gastrocnemius muscle 3. Liver 4. Store at -80°C or process for: - qPCR: P2rx7 expression, inflammatory genes, insulin signaling genes - Western blot: pAKT, total AKT, GLUT4 translocation ### Controls - **Genetic control:** 129SvJ mice with endogenous P2rx7 - **Baseline control:** Same mice before insulin challenge - **Technical replicates:** Duplicate glucose measurements per time point - **Sex differences:** Analyze males and females separately initially ### Expected Outcomes 1. **Impaired insulin sensitivity:** P2rx7 congenic mice may show reduced glucose clearance (higher glucose AUC) 2. **Altered inflammatory phenotype:** P2X7 variation affects IL-1β processing/release 3. **Tissue-specific effects:** Differential P2rx7 expression in WAT vs muscle 4. **Sex-specific:** Possible sex differences in metabolic phenotype ### Success Criteria - [ ] ≥8/10 animals per group complete ITT with full glucose curve - [ ] Baseline glucose not significantly different between groups - [ ] Insulin response: ≥30% decrease in glucose from baseline in control mice (confirms assay validity) - [ ] Significant difference in glucose AUC between P2rx7 congenic and control - [ ] P2rx7 expression validated in target tissues by qPCR - [ ] Terminal insulin levels measured and reported

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