At a glance

◇Carob powder extract significantly reduces body weight and visceral fat weight and suppresses fatty liver in obese animal models. 

◇Underlying mechanism of the transcriptional repression of 3T3-L1 elucidated. 

Summary

Associate Professor Akiko Kojima, Graduate School of Human Life Science, Osaka City University, and graduate student Kasumi Fujita (at the time of the research, currently working at OISYS Co., Ltd.), and Associate Professor Toshio Norikura, Department of Nutrition, Aomori University of Health and Welfare, and Professor Shigenori Kumazawa, Department of Food and Nutritional Sciences, University of Shizuoka, have clarified that carob powder extract, which is used as an alternative to cocoa and coffee powder, has anti-obesity effects at the cellular and animal levels. 

Research outline

The accumulation of visceral fat is known to induce diabetes, dyslipidemia, hypertension, and other diseases, leading to arteriosclerosis and serious diseases such as myocardial and cerebral infarction. In this study, the research team aimed to discover a new method to prevent obesity by studying the anti-obesity effect of carob powder extract and its underlying mechanism. 

In an experiment using obese model mice, the weight of mice fed a high-fat diet for 52 days increased significantly, while the weight and visceral fat weight of mice fed a similar diet partnered with carob powder extract decreased significantly. Furthermore, fatty liver was suppressed and the size of adipocytes (fat cells), which make up fatty tissue, was significantly reduced (Fig. 1). 

 To clarify the anti-obesity mechanism of carob powder extract, the team studied 3T3-L1 preadipocytes and found that carob powder extract significantly reduced intracellular fat accumulation by inhibiting glycerol 3-phosphate dehydrogenase (GPDH) activity - the rate-limiting enzyme for fat synthesis. This indicates that carob powder extract inhibits the differentiation of 3T3-L1 preadipocytes into adipocytes (Fig. 2).

To further elucidate this mechanism, the team measured the expression levels of the transcription factors C/EBPβ, PPARγ, and C/EBPα, which are master regulators of 3T3-L1 preadipocyte differentiation into adipocytes, at the gene and protein levels. Carob powder extract had no effect on the change in the expression of the C/EBPβ gene, which is expressed immediately after differentiation, while it significantly reduced the amount of C/EBPβ protein. Furthermore, PPARγ and C/EBPα, which are induced by C/EBPβ protein, were both reduced in gene and protein levels by carob powder extract, indicating that a decrease in GPDH activity was induced (Fig. 3).

These results indicate that the anti-obesity effect of carob powder extract is based on the regulation of fat synthesis by controlling the amount of post-transcriptional C/EBPβ protein. 

For the future 

Carob powder has been used as a substitute for cocoa and coffee powder. Based on the new physiological effects found through this study, carob powder is expected to be developed into a food product that can help prevent lifestyle-related diseases. Furthermore, it is expected to lead to the development of research on the transcription factor cascade in adipocyte differentiation. 

Publication Information

Date of Publication: March 8, 2021

Journal name: PLOS ONE 

Paper Title: Carob pod polyphenols suppress the differentiation of adipocytes through posttranscriptional regulation of C/EBPb

Authors: Kasumi Fujita¹, Toshio Norikura², Isao Matsui-Yuasa¹, Shigenori Kumazawa³, Sari Honda³, Takumi Sonoda⁴ and Akiko Kojima-Yuasa^1*
1 Department of Food and Human Health Sciences, Graduate School of Human Life Science, Osaka City University.
² Department of Nutrition, Aomori University of Health and Welfare, Aomori.
³ Department of Food and Nutritional Sciences, University of Shizuoka, Shizuoka.
⁴ TAISHO TECHNOS, Co., Ltd., Tokyo.
^*: corresponding author 

Paper URL: https://doi.org/10.1371/journal.pone.0248073 

 Funding information

Grant-in-Aid for Scientific Research (C) (15K00832) and joint research funding from TAISHO TECHNOS, Co.