Abstract: FR-PO596

Expression of Hepatic Cytochrome P450 Drug-Metabolizing Enzymes in a Mouse Model of Diabetic Nephropathy

Session Information

Category: Diabetes

  • 501 Diabetes Mellitus and Obesity: Basic - Experimental

Authors

  • Fang, Cheng Jay, Western University, London, Ontario, Canada
  • Burger, Dylan, Kidney Research Centre, Ottawa, Ontario, Canada
  • Holterman, Chet E., Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
  • Kennedy, Chris R., Kidney Research Centre, Ottawa, Ontario, Canada
  • Thibodeau, Jean-Francois, ProMetic BioSciences Inc., Laval, Quebec, Canada
  • Urquhart, Brad, Western University, London, Ontario, Canada
Background

Out of 420 million diabetics, over a third will develop diabetic nephropathy. Studies in chronic kidney disease have demonstrated decreased expression of hepatic cytochrome P450 (CYP) drug-metabolizing enzymes. With polypharmacy in diabetic patients, diabetic kidney disease may lead to adverse drug reactions as a result of altered drug pharmacokinetics due to unexpected changes in CYP expression. This study evaluates the expression and metabolic activity of CYP3A11 and CYP2C29, mouse orthologues of human CYP3A4 and CYP2C9 in a mouse model of drug-induced diabetic nephropathy, as well as in a CYP3A4/PXR-humanized (TgCYP3A4/hPXR) mouse model.

Methods

Male C57BL/6 mice were treated with 50 mg/kg of streptozotocin (STZ; n = 7) intraperitoneally for 5 consecutive days. Control mice (n = 8) were injected with sodium acetate. After 16 weeks, blood glucose and kidney function (eGFR, urinary albumin-to-creatinine ratio (UACR)) were measured. Mouse livers were isolated for real-time PCR analysis and Western blot to determine CYP mRNA and protein expression. Activity of microsomes was assessed by metabolism of probe drugs (midazolam, testosterone) using liquid chromatography coupled to mass spectrometry (LC-MS).

Results

The UACR for STZ-treated mice was 667.3 µg/g compared to 145.5 µg/g in controls (P < 0.001). Similarly, eGFR was increased in STZ mice (20.2 mL/min/g body weight) compared to controls (10.2 mL/min/g body weight; P < 0.001). STZ-treated mice had higher plasma glucose (30.9 mM) compared to controls (6.4 mM; P < 0.001). Cyp3a11 mRNA expression showed a decreasing trend in diabetic nephropathy mice (-44%, P = 0.10) compared to control mice. Cyp2c29 mRNA expression was not significantly different in STZ mice compared to control.

Conclusion

Increased UACR, eGFR, and glucose are strong indicators of diabetic nephropathy, indicating reliability of the drug-induced diabetic mouse model. The same treatment is currently being used in studies investigating the impact of diabetic nephropathy on TgCYP3A4/hPXR mice. A decreasing trend in Cyp3a11 expression indicates possible down-regulation in diabetic nephropathy. Future directions will increase the sample size and evaluate hepatic differences caused by diabetic nephropathy by metabolomics in an effort to elucidate potential regulators of CYP expression.

Funding

  • Government Support - Non-U.S.