L-Theanine Extends the Lifespan of Caenorhabditis elegans by Reducing the End Products of Advanced Glycosylation

Abstract

L-theanine, a non-protein amino acid naturally occurring in tea leaves, is recognized for its antioxidant, anti-inflammatory, and neuroprotective properties. Despite its known benefits, the mechanisms by which L-theanine influences lifespan extension remain poorly understood. This study investigated the effects of L-theanine on the lifespan of Caenorhabditis elegans and explored the underlying mechanisms. Our findings indicate that L-theanine significantly diminishes the accumulation of advanced glycation end products (AGEs), which are biomarkers closely linked to aging and age-related diseases. Through an AGE-level analysis, we observed that L-theanine, when administered during early adulthood, notably extended the lifespan of Caenorhabditis elegans under both normal and high-glucose-induced stress conditions. L-theanine enhanced the lifespan under typical conditions and provided protective effects against high-glucose-induced stress. A further analysis demonstrated that L-theanine extends the lifespan of Caenorhabditis elegans by modulating the DAF-2/DAF-16 insulin-like signaling pathway and reducing the accumulation of advanced glycation end products (AGEs). In summary, this study identified L-theanine as a potential anti-aging intervention that extends the lifespan by reducing AGE accumulation and regulating insulin-like signaling pathways. These findings provide new insights for developing anti-aging strategies and lay the groundwork for further research on the potential benefits of L-theanine in mammals. Future studies could explore the molecular mechanisms, test L-theanine in mammalian models, and assess the long-term side effects.

Keywords: Caenorhabditis elegans; L-theanine; advanced glycation end products (AGEs); insulin-like signaling; lifespan extension.

Figure 1

Effects of L-theanine (L) on lifespan phenotypes of C. elegans. (A) Control (Ctrl) group and 10 μM L-theanine group; n ≥ 60 in each group. Group with 2% glucose and group with 2% glucose plus 10 μM L-theanine; n ≥ 60 in each group. All groups were tested with N2 strains. (B–D) show effects on body bending, head thrashing, pharyngeal pumping for Ctrl, L 10 μM, 2% glucose, and 2% glucose + L10 μM groups. Each test involved 10 nematodes, with results replicated more than three times to ensure reliability. Statistical significance between experimental groups was determined using t-tests, with a p-value of <0.05 considered significant.

Figure 2

L-theanine reduces AGE accumulation in C. elegans under high-glucose conditions. (A) Fluorescence imaging at day 5, showing the DAPI, bright, and merged fluorescence levels across the four groups, with each group having n = 10. (B) Quantitative analysis between groups, analyzed using t-tests with a p-value < 0.05 indicating significant differences. (C) ELISA measurements used to quantify the AGE levels across the different treatment groups in C. elegans. Each bar represents the mean AGE concentration, with the error bars indicating the standard deviation; the statistical significance was determined by a t-test.

Figure 3

L-theanine reduces the gst-4 expression in C. elegans under high-glucose conditions. (A) Fluorescence imaging was performed on day 5, showing the GFP, bright, and merged fluorescence levels across the three groups, with each group consisting of n = 10 worms. (B) A quantitative analysis was conducted to compare the groups, with the statistical significance determined using a t-test, and a p-value of <0.05 indicating significant differences.

Figure 4

L-theanine regulates the lifespan and AGE accumulation via the daf-2/daf-16 pathway. (A) Control group (N2), 10 μM L-theanine group (N2), daf-2 mutant group, and daf-2 mutant with 10 μM L-theanine group, with each group consisting of n = 60. (B) A quantitative analysis between the different groups was performed using a t-test, with a p-value of <0.05 indicating significant differences. For the fluorescence analysis, 8–10 representative C. elegans from each group were selected for presentation.