Multidisciplinary metabolomics approach reveals meglutol as an important bioactive metabolite in tempe, an Indonesian traditional fermented food
Laboratory of Bioresource Engineering, Fukusaki Lab
Marvin Nathanael Iman
Chapter 1: General Introduction
Tempe is an Indonesian traditional fermented food made from soybean, well-known for its high nutritional and functional contents. Tempe is considered a functional food owing to its many health benefits beyond basic nutrition. While there has been extensive research conducted on the functionality of tempe, previous efforts to understand its effects have predominantly focused on the overall bioactivity of tempe, e.g., overall antioxidant capacity, lacking specific identification of the bioactive metabolites responsible for these effects. Alternatively, certain studies have solely concentrated on a limited set of well-studied bioactive components, such as soy isoflavones or bioactive peptides, without comprehensively exploring the entire tempe metabolome. Although these studies are valuable and insightful, a comprehensive investigation into the metabolome of tempe would offer significant advantages by ensuring that potential bioactive compounds are not overlooked. This research aims to profile the bioactive components of tempe using a comprehensive metabolomics-based techniques. Furthermore, we aim to characterize the bioactive components of tempe using a nutritional epidemiological analysis and investigate the improvement of tempe’s bioactive components using a raw material substitution strategy.
Chapter 2: GC-MS and LC-MS-based identification of bioactive metabolites in tempe, an Indonesian traditional fermented food
A comprehensive investigation was conducted to explore the bioactive metabolites in soybean tempe using metabolomics-based approaches. The study employed a combination of widely-targeted GC-MS, untargeted LC-MS, and targeted HPLC-PDA-MS analyses to perform comprehensive metabolome profiling. This approach successfully identified 16 bioactive metabolites in samples of soybean, germinated soybean, and soybean tempe. The identified bioactive metabolites consist of 12 well-characterized soy isoflavones daidzin, glycitin, genistin, malonyl daidzin, malonyl genistin, malonyl glycitin, acetyl daidzin, acetyl genistin, acetyl glycitin, daidzein, glycitein, genistein, as well as 3,4-dihydroxybenzoic acid, 3-hydroxyanthranillic acid, 3-hydroxy-3-methylglutaric acid (meglutol), and 4-aminobutyric acid (GABA). Notably, this study highlights the presence of a hypolipidemic bioactive metabolite, 3-hydroxy-3-methylglutaric acid (meglutol), in tempe for the first time. Meglutol
is a hypolipidemic agent naturally found in some food sources. Despite this, studies on meglutol’s health benefits and its relation with food are currently very limited. For these reasons, in the next few chapters further characterization of meglutol’s health benefits, as well as meglutol in food are explored.
Chapter 3: Population-based examination of plasma 3-hydroxy-3-methylglutaric acid (meglutol) and cardiometabolic risk
To provide a thorough characterization of meglutol's bioactive potential, its association with cardiovascular risk is examined through epidemiological analyses involving two well-characterized cohorts, the Boston Puerto Rican Health Study (BPHRS) and the San Juan Overweight Adult Longitudinal Study (SOALS). Meta-analysis involving these two cohorts reveals a significant association between lower baseline plasma meglutol concentration (per 1-SD) and decreased LDL-C concentration (β [SE]: -5.5 [1.6, P = 0.0005). The results presented in this chapter are the first epidemiological evidence of the LDL-lowering effect of meglutol. Furthermore, following stratifications of the constructed models, these associations were found to be stronger in metabolically-compromised groups, including patients with type-2 diabetes, high BMI levels, and patients taking lipid-lowering medication.
Chapter 4: Optimization of meglutol concentrations in tempe using raw material substitutions
While the meglutol’s hypolipidemic properties have been highlighted in Chapter 3, there is a limited body of research on meglutol in the context of food. This chapter provides a comprehensive exploration of meglutol in relation to food. A survey of the meglutol concentrations in various foods previously documented to contain meglutol are reported. Tempe was found to contains significantly higher meglutol levels compared to other known meglutol-containing foods. Building upon this finding, the modulation of meglutol through tempe fermentation was investigated. Furthermore, raw material substitution strategies to optimize meglutol concentrations in tempe were explored. Significant increases in meglutol levels in soybean, edamame, white bean, red kidney bean, and green pea following tempe fermentation were observed. Notably, green pea tempe exhibited the highest concentration of meglutol at 21.8±4.6 mg/100g, which is over ten times higher than that found in regular soybean.
Chapter 5: Conclusion and future perspectives
This research employed metabolomics-based techniques to investigate and analyze bioactive metabolites in tempe. The primary objectives include profiling the bioactive metabolites, characterizing their bioactive properties, and optimizing them using principles of food engineering. First, 16 bioactive metabolites in tempe were identified through the use of metabolomics-based bioactive metabolite profiling. Notably, 3-hydroxy-3-methylglutaric acid (meglutol) was highlighted as a promising bioactive metabolite with hypolipidemic properties. Characterization of meglutol’s hypolipidemic properties were provided by through population-based study involving a meta-analysis of two well-characterized cohorts. Finally, meglutol concentrations in foods were explored. Tempe, particularly green pea tempe, was highlighted to be a potential meglutol-rich functional food. The findings of this research shed light on the promising potential of meglutol as a food-based alternative for controlling LDL-C levels.
List of publication:
Marvin N. Iman, Rafidha Irdiani, Della Rahmawati, Eiichiro Fukusaki, Sastia P. Putri: Improvement of the functional value of green soybean (edamame) using germination and tempe fermentation: a comparative metabolomics study, J. Biosci. Bioeng., [Accepted May 2023]. (Expected publication date: 2023).