A tRNA synthase in metabolic control: Leucyl-tRNA synthetase 1 (LARS1), which covalently couples leucine to its cognate transfer RNAs (tRNAs), appears to have broader roles in the control of leucine metabolism. The enzyme also serves as a leucine sensor for the mechanistic target of rapamycin complex 1 (mTORC1), which regulates protein synthesis, metabolism, autophagy, and cell growth. Yoon et al. show that in cells deprived of glucose, LARS1 is phosphorylated by Unc-51 like autophagy activating kinase 1 (see the Perspective by Lehman and Abraham). This phosphorylation decreases leucine binding to LARS1 and, in turn, should decrease translation, reduce activation of mTORC1, and perhaps free up leucine for use in the generation of adenosine triphosphate in glucose-starved cells. Science , this issue p. 205 ; see also p. 146

The Westernized diet has been associated with the pathogenesis of metabolic diseases, whereas a Korean diet has been reported to exert beneficial effects on health in several studies. However, the effects of Western and Korean diets on the gut microbiome and host metabolome are unclear. To examine the diet-specific effects on microbiome and metabolome, we conducted a randomized crossover clinical trial of typical Korean diet (TKD), typical American diet (TAD), and recommended American diet (RAD). The trial involved a 4-week consumption of an experimental diet followed by a 2-week interval before diet crossover. 16S rRNA sequencing analysis identified 16, 10, and 14 differential bacteria genera specific to TKD, RAD, and TAD, respectively. The Firmucutes-Bacteroidetes ratio was increased by TKD. Nuclear magnetic resonance metabolome profiling revealed that TKD enriched branched chain amino acid metabolism, whereas ketone body metabolism was evident in RAD and TAD. Microbiome and metabolome responses to the experimental diets varied with individual enterotypes. These findings provide evidence that the gut microbiome and host metabolome rapidly respond to different cultural diets. The findings will inform clarification of the diet-related communication networks of the gut microbiome and host metabolome in humans.

Lentinula edodes (shiitake) is a popular nutritious edible mushroom with a desirable aroma and flavor. Traditional cultivation of L. edodes on beds of logs has been replaced by cultivation on sawdust, but the effects of cultivation changes on L. edodes mushrooms have not been well characterized. We determined the metabolic profile, bioactive compounds, and antioxidant capacity in L. edodes grown on log or sawdust substrates. Metabolic profiles of L. edodes extracts were determined by ¹H nuclear magnetic resonance (NMR) and ultra-performance liquid chromatography to quadrupole time-of-flight mass spectrometry. Principal component analysis score plots from ¹H NMR analysis showed clear differences between samples. Concentrations of primary metabolites, especially amino acids, generally decreased in L. edodes grown on logs compared to sawdust. Phenolic compounds showed variations in concentration depending on the cultivation method. Bioactive compounds and their antioxidant capacity were analyzed spectrophotometrically. L. edodes cultivated on logs had high concentrations of bioactive compounds with strong antioxidant capacity compared to L. edodes cultivated on sawdust. Thus, the concentration of primary metabolites was high in L. edodes grown on sawdust, which produces a high growth rate. In contrast, log-cultivated L. edodes, which were similar to wild mushrooms, had high levels of bioactive compounds and high antioxidant capacity. This information is useful for determining optimal cultivation conditions for nutritional and medicinal uses of L. edodes mushrooms.

Codonopsis lanceolata (C. lanceolata) has been commonly utilized as a therapeutic plant in traditional medicine. In this study, we examined variations in metabolites in C. lanceolata roots grown in different regions using ultra-high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS). Multivariate analysis showed that the metabolite profiles of plants grown in Hoengseong and Jeongseon were more similar to each other than to that of C. lanceolata grown in Jeju. Most primary metabolites were present at higher levels in C. lanceolata grown in Jeju. In contrast, C. lanceolata grown in Hoengseong and Jeongseon had high levels of secondary metabolites such as phenylpropanoids and triterpenoid saponins, respectively. In addition, the bioactive compound content and antioxidant capacity of in C. lanceolata grown in Hoengseong and Jeongseon were observed to be higher than those of C. lanceolata grown in Jeju. This study suggests that metabolomics is an effective approach to investigate the difference of metabolite profiling in C. lanceolata from different geographical origins, and is useful for evaluating its pharmacological potential.