Abstract
Bilirubin levels in obese humans and rodents have been shown to be lower than in their lean counterparts. Some studies have proposed that the glucuronyl UGT1A1 enzyme that clears bilirubin from the blood increases in the liver with obesity. UGT1A1 clearance of bilirubin allows more conjugated bilirubin to enter the intestine, where it is catabolized into urobilin, which can be then absorbed via the hepatic portal vein. We hypothesized that when bilirubin levels are decreased, the urobilin increases in the plasma of obese humans, as compared to lean humans. To test this, we measured plasma levels of bilirubin and urobilin, body mass index (BMI), adiposity, blood glucose and insulin, and HOMA IR in a small cohort of obese and lean men and women. We found that bilirubin levels negatively correlated with BMI and adiposity in obese men and women, as compared to their lean counterparts. Contrarily, urobilin levels were positively associated with adiposity and BMI. Only obese women were found to be insulin resistant based on significantly higher HOMA IR, as compared to lean women. The urobilin levels were positively associated with HOMA IR in both groups, but women had a stronger linear correlation. These studies indicate that plasma urobilin levels are associated with obesity and its comorbidities, such as insulin resistance.
Document Type
Article
Publication Date
1-2023
Digital Object Identifier (DOI)
https://doi.org/10.3390/antiox12010170
Funding Information
This work was supported by the National Institutes of Health R01DK121797 (T.D.H.J.). The sample collection was supported by the Center for Clinical and Translational Science (CCTS) grant UL1TR001998 at the University of Kentucky. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Repository Citation
Kipp, Zachary A.; Xu, Mei; Bates, Evelyn A.; Lee, Wang-Hsin; Kern, Philip A.; and Hinds, Terry D. Jr., "Bilirubin Levels Are Negatively Correlated with Adiposity in Obese Men and Women, and Its Catabolized Product, Urobilin, Is Positively Associated with Insulin Resistance" (2023). Markey Cancer Center Faculty Publications. 304.
https://uknowledge.uky.edu/markey_facpub/304
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Notes/Citation Information
© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).