Monoterpene phenolic compound thymol promotes browning of 3T3-L1 adipocytes.

PURPOSE: Appearance of brown-like adipocytes within white adipose tissue depots (browning) is associated with improved metabolic phenotypes, and thus a wide variety of dietary agents that contribute to browning of white adipocytes are being studied. The aim of this study was to assess the browning effect of thymol, a dietary monoterpene phenolic compound, in 3T3-L1 white adipocytes. METHODS: Thymol-induced fat browning was investigated by determining expression levels of brown fat-specific genes and proteins by real-time RT-PCR and immunoblot analysis, respectively. Moreover, the molecular mechanism underlying the fat-browning effect of thymol was investigated by determining expression levels of key players responsible for browning in the presence of kinase inhibitors. RESULTS: Thymol promoted mitochondrial biogenesis and enhanced expression of a core set of brown fat-specific markers as well as increased protein levels of PPARγ, PPARδ, pAMPK, pACC, HSL, PLIN, CPT1, ACO, PGC-1α, and UCP1, suggesting its possible role in browning of white adipocytes, augmentation of lipolysis, fat oxidation, and thermogenesis, and reduction of lipogenesis. Increased expression of UCP1 and other brown fat-specific markers by thymol was tightly coordinated with activation of ß3-AR as well as AMPK, PKA, and p38 MAPK. CONCLUSION: Our findings suggest that 3T3-L1 is a potential cell model for screening browning agents. Thymol plays multiple modulatory roles in the form of inducing the brown-like phenotype as well as enhancing lipid metabolism. Thus, thymol may be explored as a potentially promising food additive for prevention of obesity.

Chrysin induces brown fat-like phenotype and enhances lipid metabolism in 3T3-L1 adipocytes.

OBJECTIVES: Many studies have to do with promising therapeutic phytochemicals such as flavonoids to treat obesity and related complications, and a number of dietary compounds have been proposed as tools for increasing energy expenditure and decreasing fat accumulation in mammals. Here, we show that the flavonoid chrysin induces browning of 3T3-L1 adipocytes via enhanced expression of brown fat-specific genes and proteins as well as enhances lipid metabolism. METHODS: Chrysin-induced fat browning was investigated by determining expression levels of brown fat-specific genes and proteins by real-time polymerase chain reaction and immunoblot analysis, respectively. RESULTS: Chrysin enhanced expression of brown fat-specific markers and increased protein levels of peroxisome proliferator-activated receptor (PPAR)α, PPARγ, PPARδ, phosphorylated AMP-activated protein kinase (p-AMPK), phosphorylated acetyl-CoA carboxylase, hormone sensitive lipase, perilipin, carnitine palmitoyltransferase 1, acyl-coenzyme A oxidase 1, peroxisome proliferator-activated receptor-1 alpha (PGC-1α), and uncoupling protein 1 (UCP-1), suggesting its possible role in augmentation of lipolysis, fat oxidation, and thermogenesis as well as reduction of lipogenesis. Increased expression of UCP-1 and other brown fat-specific markers was possibly mediated by chrysin-induced activation of AMPK based on the fact that inhibition of AMPK by dorsomorphin abolished expression of PR domain-containing 16, UCP-1, and PGC-1α while the activator 5-aminoimidazole-4-carboxamide ribonucleotide elevated expression of these brown marker proteins. CONCLUSION: Our findings suggest that chrysin plays a dual modulatory role in the form of inducing the brown-like phenotype as well as enhancing lipid metabolism and thus may be explored as a potentially promising food additive for prevention of obesity.

Proteomic identification of fat-browning markers in cultured white adipocytes treated with curcumin.

We previously reported that curcumin induces browning of primary white adipocytes via enhanced expression of brown adipocyte-specific genes. In this study, we attempted to identify target proteins responsible for this fat-browning effect by analyzing proteomic changes in cultured white adipocytes in response to curcumin treatment. To elucidate the role of curcumin in fat-browning, we conducted comparative proteomic analysis of primary adipocytes between control and curcumin-treated cells using two-dimensional electrophoresis combined with MALDI-TOF-MS. We also investigated fatty acid metabolic targets, mitochondrial biogenesis, and fat-browning-associated proteins using combined proteomic and network analyses. Proteomic analysis revealed that 58 protein spots from a total of 325 matched spots showed differential expression between control and curcumin-treated adipocytes. Using network analysis, most of the identified proteins were proven to be involved in various metabolic and cellular processes based on the PANTHER classification system. One of the most striking findings is that hormone-sensitive lipase (HSL) was highly correlated with main browning markers based on the STRING database. HSL and two browning markers (UCP1, PGC-1α) were co-immunoprecipitated with these markers, suggesting that HSL possibly plays a role in fat-browning of white adipocytes. Our results suggest that curcumin increased HSL levels and other browning-specific markers, suggesting its possible role in augmentation of lipolysis and suppression of lipogenesis by trans-differentiation from white adipocytes into brown adipocytes (beige).

Curcumin induces brown fat-like phenotype in 3T3-L1 and primary white adipocytes.

Recent advances have been made in the understanding of pharmacological and dietary agents that contribute to browning of white adipose tissue in order to combat obesity by promoting energy expenditure. Here, we show that curcumin induces browning of 3T3-L1 and primary white adipocytes via enhanced expression of brown fat-specific genes. Curcumin-induced browning in white adipocytes was investigated by determining expression levels of brown adipocyte-specific genes/proteins by real-time reverse transcriptase polymerase chain reaction, immunoblot analysis and immunocytochemical staining. Curcumin increased mitochondrial biogenesis, as evidenced by transmission electronic microscopic detection and enhanced expression of proteins involved in fat oxidation. Cucurmin also increased protein levels of hormone-sensitive lipase and p-acyl-CoA carboxylase, suggesting its possible role in augmentation of lipolysis and suppression of lipogenesis. Increased expression of UCP1 and other brown adipocyte-specific markers was possibly mediated by curcumin-induced activation of AMP-activated protein kinase (AMPK) based on the fact that inhibition of AMPK by dorsomorphin abolished expression of PRDM16, UCP1 and peroxisome proliferator-activated receptor gamma co-activator 1-alpha while the activator 5-Aminoimidazole-4-carboxamide ribonucleotide elevated expression of these brown marker proteins. Our findings suggest that curcumin plays a dual modulatory role in inhibition of adipogenesis as well as induction of the brown fat-like phenotype and thus may have potential therapeutic implications for treatment of obesity.

Differential protein expression in white adipose tissue from obesity-prone and obesity-resistant mice in response to high fat diet and anti-obesity herbal medicines.

BACKGROUND: One of the most interesting issues in obesity research is why certain humans are obesity-prone (OP) while others are obesity-resistant (OR) upon exposure to a high-calorie diet. However, the pathways responsible for these phenotypic differences are still largely unknown. METHODS: In order to discover marker molecules determining susceptibility and/or resistance to obesity in response to high fat diet (HFD) or anti-obesity herbal medicine (TH), we conducted comparative proteomic analysis of white adipose tissue (WAT) from OP, OR, as well as TH-treated mice. RESULTS: OP mice fed HFD gained approximately 33% more body weight than OR mice, and TH significantly reduced body weight gain in HFD-fed mice by 30%. These mice were further subjected to proteomic analysis using two-dimensional electrophoresis (2-DE) combined with matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS). Proteomic data revealed 59 spots that were differentially regulated from a total of 1,045 matched spots, and 57 spots of these were identified as altered WAT proteins between OP and OR mice by peptide mass finger printing. Interestingly, 45 proteins were similarly regulated in OR mice in response to TH treatment. Of these, 10 proteins have already been recognized in the context of obesity; however, other proteins involved in obesity susceptibility or resistance were identified for the first time in the present study. CONCLUSION: Our results suggest that TH actively contributed to body weight reduction in HFD-fed obese mice by altering protein regulation in WAT, and it was also found that TH-responsive proteins can be used as potent molecules for obesity treatment.