Acute alcohol consumption induces oxidative stress, triggers inflammation, and disrupts the immunity balance in the heart. L-theanine (LTA) possesses antioxidant, anti-inflammatory, and immune-regulating properties. This study aimed to investigate the effects of LTA on acute alcoholic heart injury in C57BL/6J mice, which were administered varying doses of LTA followed by a single high dose of edible alcohol. The findings demonstrated that LTA mitigated acute alcoholic heart injury by maintaining immune balance, enhancing antioxidant enzyme activity, and reducing indicators of heart injury and inflammation in the mice. RNA-seq and qPCR analysis revealed that LTA intervention down-regulated key mRNAs related to T cell receptor, Th1/Th2 cell differentiation, and Th17 cell differentiation signaling pathways activated by acute alcohol intake. LTA regulated the expression levels of key proteins involved in T cell receptor and helper T cell differentiation signaling pathways, thereby maintaining the Th1/Th2 and Th17/Treg cell balance. Non-targeted metabolomic analyses indicated that LTA increased the levels of beneficial metabolites in the hearts of the mice. These results provide evidence for the preventive effects of LTA on acute alcoholic heart injury.

Strategies altering dietary nutrients composition, such as the addition of appropriate essential amino acids or phytochemicals, is effective in addressing the adverse effects of heat stress (HS) under rising temperatures. The new food ingredient L-theanine (LTA), a natural non-protein amino acid found in tea, shows promising effect in alleviating HS. However, systematic studies underlying LTA mitigating HS are lacking. Here, we evaluated the mechanisms by which LTA alleviates HS both in vivo and in vitro. The results showed that LTA suppressed HS-induced decreases in cell viability, antioxidant enzyme activity, mitochondrial membrane potential and ATP content. It reduced reactive oxygen species levels and apoptosis in heat-stressed BRL-3A cells. In addition, LTA affected the expression of heat shock proteins, ribosomal proteins and apoptosis-relate genes during HS and HS recovery process. Similar results were observed in heat-stressed rats. Mechanistically, the alleviating effect of LTA on HS may be mediated by heat shock factor 1 (Hsf1). Specifically, in the initiation of HS, LTA promoted the binding of Hsf1 to the promoter of heat shock protein family H member 1 (Hsph1), which facilitated Hsph1 transcription and accelerated the response to HS. Following the end of HS treatment, LTA repressed the expression of Hsph1, thus restoring intracellular homeostasis. Taken together, these results suggest that LTA is effective in regulating the transcription of Hsph1 via Hsf1, thereby mitigating HS-induced hepatic injury. This provides scientific evidence that drinking tea is helpful in preventing HS and LTA is a promising anti-HS phytochemical deserves further development.

Dark tea (containing Eurotium cristatum) and black tea have hypoglycemic effects. The black brick tea with fungal growth is obtained from black tea by adding E. cristatum, followed by steaming, pressing, fungal growth, and drying. However, the hypoglycemic effects of black brick tea are still unexplored. Here, we used black brick tea with fungal growth and black tea as raw materials to study their hypoglycemic effects in a hyperglycemic mice model. Both these types of black tea could lower the content of blood glucose and increase the content of hepatic glycogen by upregulating the proteins and mRNA expression of phosphatidylinositol-4,5-bisphosphate3-kinase, glycogen synthase, protein kinase B and phosphoinositide-dependent protein kinase-1 and downregulating the protein and mRNA expression of glycogen synthase kinase 3β. These regulatory steps were followed by high activities of glutathione peroxidase and superoxide dismutase and low content of malondialdehyde. These teas can promote blood glucose transport and absorption by upregulating the protein and mRNA expression of insulin receptor substrate-1 and glucose transporter-2 and stimulate glycolysis by upregulating the protein and mRNA expression of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 2. Our study suggests that the black brick tea was more effective than the black tea in terms of hypoglycemic.