Cytochrome P450 1b1 (Cyp1b1) participates in embryogenesis and is expressed in endothelia, fibroblasts and adipocytes. Genes involved in liver fatty acid metabolism are remarkably affected by deletion of Cyp1b1 in mice, despite only minimal expression in hepatocytes. Two gene clusters, distinguished by responses to dietary fat, are both suppressed by Cyp1b1 deletion and regulated by PPAR? Preliminary data that indicates that Cyp1b1 participates in the generation of endogenous PPAR? ligands will be explored further. Cyp1b1 deletion also suppresses diet-induced obesity and non-alcoholic hepatic steatosis. The increased liver fatty acid metabolism may be associated with decreased oxidative stress, as indicated by improved insulin sensitivity. Cyp1b1 may, therefore, be an unexpected contributor to Type 2 diabetes. Many dietary flavanoids are potent inhibitors of Cyp1b1. Select Cyp1b1 inhibitors, including natural compounds, may have therapeutic value for diabetes. Human Cyp1b1 suppression also enhances liver adenomas, consistent with a role in developmental processes. The proposed research compares the liver gene expression, metabolism responses and adiposity changes in WT and Cyp1b1-ko mice administered low fat/high carbohydrate or high fat/low carbohydrate diets. The goal is to determine how hepatocytes can be indirectly affected by Cyp1b1 metabolism in other cell types, particularly the endothelia of liver sinusoids and adipose tissue. The expression of Cyp1b1 in non-parenchymal liver cells and in fetal liver will be characterized. In order to define the site and timing of Cypb1 intervention, we have introduced a Floxed Cyp1b1 allele into mice. This will ultimately provide the means for controlled Cyp1b1 deletions in mice. We will use this defining set of liver and adipose responses to determine the effectiveness of Cyp1b1 deletions specifically targeted to endothelia by Tie2-Cre. We have shown that Cyp1b1 deletion affects the functions of endothelial cells and suppresses angiogenesis in vivo. Cyp1b1 deletion may cause these adult changes through active participation of Cyp1b1 in the fetal liver development that imprints adult liver regulation. Cre-targeting of Floxed Cyp1b1 will be activated through a tamoxifen-dependent promoter at selected times during development, in order to test whether this early expression contributes to the general deletion effects. Metabolomic studies using 2D-NMR and mass spectrometry analyses on, respectively, liver and serum extracts will focus on establishing that Cyp1b1 deletion increases mitochondrial fatty acid oxidation and glycogen synthesis, while lowering oxidative stress. The roles of PPAR? and PPAR? loss in these liver gene changes of Cyp1b1-ko mice will be tested by comparisons to effects of deleting these PPAR genes in mouse liver. Serum markers applicable to clinical studies will be used in probing these liver changes.

Public Health Relevance

Loss of Cytochrome P450 1B1 (CYP1B1) in humans is linked to Glaucoma and Liver tumors. CYP1B1 variants are common in humans. We find that CYP1B1 losses can counter obesity and improve insulin sensitivity. These studies address how CYP1B1 deletion remarkably increases liver fat oxidation and glycogen synthesis through suppression of PPAR?activity. The pathway offers therapeutic possibilities, including through dietary compounds that bind to CYP1B1.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
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Xenobiotic and Nutrient Disposition and Action Study Section (XNDA)
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Serrano, Jose
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University of Wisconsin Madison
Anatomy/Cell Biology
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United States
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