Abstract
BackgroundThe dramatic increase in obesity-related diseases emphasizes the need to elucidate the cellular and molecular mechanisms underlying fat metabolism. To investigate how natural substances influence lipolysis and adipogenesis, we determined the effects of White Tea extract on cultured human subcutaneous preadipocytes and adipocytes.MethodsFor our in vitro studies we used a White Tea extract solution that contained polyphenols and methylxanthines. Utilizing cultured human preadipocytes we investigated White Tea extract solution-induced inhibition of triglyceride incorporation during adipogenesis and possible effects on cell viability. In vitro studies on human adipocytes were performed aiming to elucidate the efficacy of White Tea extract solution to stimulate lipolytic activity. To characterize White Tea extract solution-mediated effects on a molecular level, we analyzed gene expression of essential adipogenesis-related transcription factors by qRT-PCR and determined the expression of the transcription factor ADD1/SREBP-1c on the protein level utilizing immunofluorescence analysis.ResultsOur data show that incubation of preadipocytes with White Tea extract solution significantly decreased triglyceride incorporation during adipogenesis in a dose-dependent manner (n = 10) without affecting cell viability (n = 10). These effects were, at least in part, mediated by EGCG (n = 10, 50 μM). In addition, White Tea extract solution also stimulated lipolytic activity in adipocytes (n = 7). Differentiating preadipocytes cultivated in the presence of 0.5% White Tea extract solution showed a decrease in PPARγ, ADD1/SREBP-1c, C/EBPα and C/EBPδ mRNA levels. Moreover, the expression of the transcription factor ADD1/SREBP-1c was not only decreased on the mRNA but also on the protein level.ConclusionWhite Tea extract is a natural source that effectively inhibits adipogenesis and stimulates lipolysis-activity. Therefore, it can be utilized to modulate different levels of the adipocyte life cycle.
Highlights
The dramatic increase in obesity-related diseases emphasizes the need to elucidate the cellular and molecular mechanisms underlying fat metabolism
Quantification was achieved using the 2-ΔΔCt method which calculates the relative changes in gene expression of the target normalized to an endogenous reference (GAPDH) and relative to a calibrator that serves as the control group
Effect of White Tea extract solution on ADD1/SREBP-1c protein expression Since our results (Figure 1A–D) indicated a White Teamediated reduction of triglyceride accumulation during adipogenesis we investigated the underlying mechanism of action in more detail
Summary
The dramatic increase in obesity-related diseases emphasizes the need to elucidate the cellular and molecular mechanisms underlying fat metabolism. The rising incidence of obesity-associated disorders including cardiovascular diseases and diabetes constitutes a growing problem. Due to this increase in obesity-related diseases, cellular and molecular processes underlying fat metabolism have been studied extensively in recent years [1,2]. Adipose tissue represents a dynamic endocrine organ that is present throughout the body forming different contiguous or non-contiguous depots [1,3]. The formation of mature adipocytes from precursor fat cells designated as preadipocytes is termed the adipocyte life cycle [4,5,6] It includes proliferation of preadipocytes, fat cell differentiation (adipogenesis), lipolytic-activity as well as apoptosis of preadipocytes or mature adipocytes
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