Date of Award
Master of Science
Guoxun Chen, Ahmed Bettaieb
As obesity continues to grow and medical costs in the United States are estimated at $147 billion annually, novel ways to prevent and treat obesity are needed. One approach is to promote thermogenesis to improve energy balance by increasing the activities of thermogenic brown and beige adipocytes.
Naringenin, a citrus flavanone, has been shown to act as anti-inflammatory and lipid lowering agent as well as activate PPARgamma. However, it is unclear whether it can activate thermogenic activity in white adipocytes, i.e., promote formation of beige adipocytes. Indomethacin (INDO) is an FDA approved drug used to treat pain related to inflammation by inhibiting cyclooxygenase (COX). It has been demonstrated that INDO is a PPARgamma agonist and is protective against weight gain in mice fed a high fat and high sucrose diet. Whether INDO independently induces brown adipocyte differentiation has not been studied.
In this thesis, I investigated the effect of naringenin combined with isoproterenol, a beta- adrenergic receptor agonist on thermogenic activation of a common white adipocyte cell line, 3T3-L1. In addition, I investigated whether INDO induces brown adipocyte differentiation. 3T3- L1 cells were differentiated into mature adipocytes with a standard differentiation cocktail in the presence of naringenin and then stimulated with isoproterenol. While naringenin had little effect at the basal level, it significantly increased mRNA and protein expression of UCP-1 and PGC- 1alpha, browning marker genes. Moreover, naringenin increased mitochondrial DNA, which is indicative of increased mitochondrial biogenesis. The results suggest that in addition to increased UCP-1 expression, naringenin can promote up regulation of PGC-1alpha, leading to increased mitochondrial biogenesis in thermogenic activation of 3T3-L1.
To study the effects of INDO on brown adipocyte differentiation I differentiated brown preadipocytes in the presence of increasing doses of INDO using a modified differentiation protocol. INDO dose-dependently increased lipid accumulation and mRNA expression of brown specific marker genes PGC-1alpha, UCP-1 and PRDM16. Protein expression of PGC-1alpha and UCP-1 was confirmed by western analysis. Consistently, INDO dose-dependently increased mitochondrial biogenesis. Mechanistically, INDO increased PPAR responsive promoter activities. These results suggest that INDO may promote brown adipogenesis through activation of PPARgamma.
Kearns, Jamie Ann, "Beneficial effects of naringenin and indomethacin on white and brown adipocytes. " Master's Thesis, University of Tennessee, 2016.