Diet-Induced Obese Male Mice Treated with a Rationally Designed P450 8B1 Inhibitor for 28 Days Successfully Increased CDCA to CA Ratios but Lacked Improved Glucose Tolerance and Body Weight
Authors: Sosa Fernando , Jia U-Ter Aondo , Chung Eunhee 
Published: May 2023

Altering the bile acid composition by inhibiting cytochrome P450 8B1 enzyme (CYP8B1) activity results in a decrease in the production of cholic acid (CA, 12α-hydroxylated bile acids) while increasing chenodeoxycholic acid (CDCA). Previous studies have shown that knocking out the Cyp8b1 gene in mice protects against diet-induced obesity and improves glucose tolerance and fat deposition in the liver. The objective of this study was to test the hypothesis that the inhibition of P450 8B1 enzyme activity with a rationally designed small molecule drug would alleviate diet-induced obesity and improve metabolic health. Male C57BL/6J mice (8-10 weeks old) were fed a high-fat and high sucrose (HF) diet over 10 weeks. When mice in the HF group were obese and developed glucose intolerance, half of the mice were treated with P450 8B1 inhibitor (HF/D), and the other half were treated with vehicle (HF/V, 20% β-hydroxypropyl cycolodextrin in the PBS). Mice fed a low fat and low sucrose diet treated with vehicle were used as a reference control (LF/V). Mice in the HF/D group were treated with 100 mg/kg/day, while mice in the vehicle groups (HF/V and LF/V) were administered with the same volume of vehicle. All mice were treated at the same time each morning by oral gavage for 28 days. Bodyweight and food intake were measured weekly. Glucose (GTT)- and insulin tolerance (ITT) tests were conducted before treatment and after treatment. Stool samples were extracted to measure the amount of CDCA and CA by high-resolution mass spectrometry. We found that the HF/D group did not have altered body weight, food intake, and fat composition compared to the HF/V group for the duration of the treatment (28 days). In addition, the HF/D group did not show any improvement in GTT and ITT during the 28 days of treatment. Despite these results related to body weight, GTT, and ITT, the stool samples from the HF/D group generally had a larger ratio of CDCA to CA compared to the HF/V group (CDCA/CA ratios for HF/D vs. HF/V were: 5.5, 9.4, 2.7, 4.1, 3.3 vs. 0.5, 1.5, 2.2, 8.4), suggesting that the inhibition of P450 8B1 did occur in the HFD group. The lipid droplet in the liver also decreased in some mice treated in the HF/D group. Our results suggest that a newly designed inhibitor that has a higher affinity towards the P450 8B1 enzyme relative to our originally designed inhibitor may reduce fatty liver diseases by modifying bile acid composition more effectively. Alternatively, future studies are warranted where the HF mice will be treated for a duration longer than 28 days to check whether the CDCA/CA ratio matches the physiological alterations including body weight and glucose homeostasis. This study was supported by the National Institute of Health [NIH, NIGMS, grant GM125603] to E. Chung This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.